texts: Duplicate a sketch on a spiral like array of lines in solidworks

texts:
This one is gonna be hard for me to explain, but I hope you will get it
I have this sketch:

Each side of this part is half of it, to be easily duplicate / mirror / pattern
Important to note the both ends of this chain needs to be just the half (so in IRL can be connected to a round object and glued together)
This is how a full part looks (made from two half's) (sorry for the mass, mirroring it cause all this chaos):

And I want to duplicate 40~ times it to this shape that I created:

The reason for it to be a spiral and not a a round circle is so save space on the mold
some guidelines and restrictions:

each hinge need to be between 185-195 degrees, preferably as little as much variations (although necessary to achieve the spiral)
Need to retain the ability to change the length (125mm here) , width (17mm) and number of parts
ends need to be the half shaped
if you have another way that is more efficient then manually doing the spiral it will be amazing

Really hope that its clear enough, appreciate your help, thanks


texts: Impact of having flexible electrical hose buried into the reinforced concrete slab

texts:
Given:

a reinforced concrete two-way slab at about 160 mm (the edges are cantilevered between the concrete walls)
the electricians buried the flexible electrical hose into the slab (red lines in the image below) and then covered the tubes with mortar (the channel are about 30 mm depth)
the mortar is a light one (probably supporting about 4 MPa or even less) and it covers the hoses superficially (1 to 3 mm over the top of the tubes)
no rebars were cut
the structure is not based on beams (the slab is sustained by precast concrete walls)

How does this affect the structure resistance of the reinforced concrete slab?

Based on your experience / simulations, could you provide an empirical percent regarding the new load capacity based on the initial load capacity?

Edit:

I believe that the load on the slab looks similar to this (where the vertical should look similar to the horizontal, including the red spots):

where red & yellow are for a top bending and blue is for a bottom bending.

P.S.: My purpose is to have the following stack over the slab for the permanent load (240 kg / m2):

thin leveling screed => 40 kg / m2
heating floor system based on water and insulated panels => 20 kg / m2
sand-cement screed ~5 cm over the pipes (=> ~6.5 cm) => 145 kg / m2
adhesive + ceramic tiles => 35 kg / m2

at which a normal useful load is added.


texts: Why do these piers have a height miss-match?

texts: I found this image of 2 piers of a Grider bridge with varying height. By any change could this be part of the design? The bridge is supposed to be a flyover for traffic decongestion.


texts: Shape Functions of beam element with 3 nodes (quadratic element)

texts:
For a two node beam element there are four shape functions for four degree of freedom:

For a straight three node beam element how shape functions are?

Please note that beam is straight and not curved.


texts: Is having one large motor more efficient than having two motors half the size?

texts: I wanted to use multiple smaller motors to have the same strength as a large motor but spread out across a wider area. Is that as good as one large motor or is there some efficiency or power loss in doing that?


texts: Gear pump has backflow and does not stop forced flow

texts:
I have a "Micropump GB-P25.JVS.A" gear pump. I pump in the range between 100 and 500 ml/min up to a column about 10 cm above the pump level. The column is filled from the top and has a bottom outlet.

I have noticed lately that my pump allows the fluid to flow backwards when it is not on. I assume this is caused by the small pressure head caused in the column. The backflow is small, but it is there. This was not the case a couple of months ago.

Furthermore, one can forcefully pump the fluid from the inlet side of the pump using a syringe.

I suspect that either the gears or the O-ring are damaged.

Are there any other possibilities I might be missing?

How hard is it to change an O-ring of this kind of pump?

Are there any other possible fixes to the situation? I have attached check-valves before and after the pump, but I doubt this is the ideal solution.


texts: How to create a non uniform pressure load in MSC Patran

texts:
I need to simulate an external pressure load that varies sinusoidally along a circular arc. The sinusoidal variation is with arc length.

I know how to create a uniform pressure load in Patran but do not know how to create a non uniform pressure load. I can't seem to find any guides, tutorials or articles on it either.

If anyone knows how to do this or has a useful guide they could link, your help will be greatly appreciated.

I am using MSC Nastran/Patran student version 2017.0.1


texts:
I am trying to make an advanced car physics simulation for a game. What I need to do now is to calculate engine RPM in quite an accurate way. As the timesteps between calculations are very small (60 frames per second or 0.166667 ms) I can afford to use old frame data in a new frame so that's not a problem.

What I want to do is to calculate engine RPM. The values that I can access are:

Throttle $f_\mathrm{throttle}$ (a scalable float value between 0.0 and 1.0)
Clutch $f_\mathrm{clutch}$ (just like throttle - a scalable float)
Engine torque output $T_\mathrm{engine}$ based on torque curve (torque curve is lineary interpolated curve between RPM and Torque axis using RPM as input which returns torque as float output).
Wheel angular velocity $\omega_\mathrm{wheels}$ (a float value in rad/s, for drive wheels it is $T / I$, for free-rolling wheels it is $V/r$).

I need to calculate the engine rotation speed in revolutions per minute.


texts:
The deflection of the sector is assumed in the following form

But I don't know why they assumed G(θ) in the following form
and how to compute η.Can somebody help me? Thanks.


texts: How many controllers of output or state are available?

texts:
Im in daily basis see a lot of controller. Sliding mode PID. Fuzzy, adapttive. Controller based on lyapunov etc.

But how many are they that are actually in use in industry and when do we use them? If you want to drive a state to a certain set points what do you use? And output?


texts:
It is stated on here that:

Air-entraining admixtures cause small stable bubbles of air to form uniformly through a concrete mix. The bubbles are mostly below 1 mm diameter with a high proportion below 0.3 mm. The benefits of entraining air in the concrete include increased resistance to freeze-thaw degradation, increased cohesion (resulting in less bleed and segregation) and improved compaction in low-workability mixes.

This does not make sense to me. By introducing more voids into the concrete there are more paths of ingress for water which can then expand and crack the concrete.
Why do air entrainment admixtures improve the freeze-thaw resistance of concrete?


texts:
I'm studying a hydro-power project in high rise building.
given a 100 story building(3 meter per floor) with 2.5 cubic meter of water per floor DAILY with 1 or more tanks within the floors and turbine at the ground. goal is to have the highest output per day with the minimal size turbine to save on the turbine cost.
up until now I have few equations such as Potential Energy in a Tank or Reservoir
and output of hydro-power turbine.
I am missing a few equations and contents.
formula of Time to empty a water tank( does the height of the water tank from the floor effects it),I've some online but none of them were direct and straightforward.
does the water velocity formula exiting the tank of (2gh)^0.5 is based on the h of the tank or the ground?
In the formula of hydro-power output(Pth = ρqgh), I'm very focused on the Q. I calculate it based on va(velocity and cross section of pipe) but I don't understand how the flow rate(Q in litter/sec) in the pipe at the has nothing to do with the falling height(water head above ground).
please ignore the economical feasibility issues of the project.
thank you very much for the help


texts: How do you find the kinematic degrees of freedom of a mechanism?

texts:
In the above mechanism it is required to find the generalized coordinates to write equation of motion of the MDOF system. I just want to ask how do we actually approach such a problem? How to identify which kinematic degrees of freedom are relevant and independent?

The answer given in this particular case is 4. Two rotation of the pulleys, and two vertical motions of the masses B and C. Now how to visualize this? How do I methodically come to this conclusion? Again, is there any other combination possible?

All pulleys are massless and frictionless.


texts: Best balance of electrical and pneumatic control lines in CNC router table?

texts:
I'm building a 4' x 8' gantry-style CNC router table. The spindle motor uses pneumatics to power its draw bar (for automatic tool changes). There are three separate pneumatic supply lines that go to the spindle motor.

One is a constant air supply of low pressure that serves to blow debris out of the tool mount during tool changes. The other two are the "open" and "close" lines.

I can choose to place the electrically-actuated pneumatic valves and various pneumatic components on the base of the machine, on the gantry, or on the spindle mount itself.

In the first case, three pneumatic lines must run several meters to reach the spindle, but the bulk of the pneumatic hardware is kept off the moving parts of the machine (reducing vibration and moving mass).

In the last case, the electrical control lines have to be run, but the pneumatic control lines are shortened (except for the main supply line), and a number of valves and regulators have to be placed on the gantry carriage. The second case is similar, but the equipment is mounted to the gantry itself.

I'm leaning toward just running the three pneumatic lines the full distance and keeping as much equipment as possible off the moving parts of the machine. But I don't know if the long pneumatic lines will cause other problems, perhaps sluggishness due to the elasticity of the tubing (they're typical poly or PVC pneumatic tubing). Is this even a concern?


texts:
I have expanded steel mesh that I use to make garden cages:

I would like to know how much sunlight the mesh blocks.

I think I need to calculate the area that the mesh takes up (per square inch) and then from there I could calculate a percentage of sunlight blocked.

How can I calculate the area of the mesh?


texts: I hope this is the correct forum for temperature related question

texts: I have about (this is experimental) 0.75 to 1 liter of water. Ive found I can use 400W of power through peltiers to reduce water flowing through at 1L/minute from 32C to 20C in about 1 to 1.5 minutes through a 0.25 lpm flow rate tube that cools by absorbing 8C per minute (thus maintaining a roughly 20C temperature). There is also other power consumed by fans and voltage converters but for this I'm simply addressing the water temperature. I assumed at first this would be Wh (watt hours required) to achieve this but my pack DOD (depth of discharge) isn't holding up. I have calculated everything. Resistance, amps being pulled, voltage to meet temperature settings, temperature probed before and after cooling. Does anyone have a clue what I should expect from a 3s15p battery pack with 480Wh  and only feeding the peltiers 7.5v from a 11.1A source (forget the loss from regulators and fans...they are accounted for through a separate calculation and power source)


texts: Would a large dome structure prevent widespread effects of nuclear plant explosions?

texts:
In both the Fukushima and Chernobyl incidents, widespread contamination would have been prevented had both facilities been enclosed within a larger structure. While existing plant designs call for hardened structures for the reactor itself, they often don't contain secondary and support infrastructure (Fukushima) or are insufficient to contain more explosive incidents (Chernobyl).

I'm curious if existing plant designs could be augmented with the addition of a
large, non-hardened, dome structure that covers the entire plant. The dome would be able to contain escaped gasses simply by being hermetically sealed - and a sufficient distance between the dome and any potential sources of explosions means there's enough normal air to buffer and absorb the explosive shockwave, if any.

Such a structure could be built very cheaply - a geodesic hemisphere, for example, constructed of plastic links with inward-opening transparent plastic panels for natural light and ventilation. A fail-safe system would automatically close all panels to prevent the escape of unwanted gasses after an explosion.

There is some precedent for this, insofar as how's Chernobyl's reactor complex is now enclosed within the New Safe Confinement structure - except it's an ugly, opaque, and very expensive structure, constructed in a dangerous environment. Presumably my dome proposal could be built cheaply - and the cost/benefit of construction vs clean-up costs (multiplied by actuarial risk) make it a straight-forward decision - and given human penchant for safety theatre it would help "sell" nuclear power to the masses, but that is beyond the scope of my question.

So my engineering questions are:

How big would a dome or other enclosing structure have to be in order to enclose all of a plant's at-risk structures?
And wold the volume of air inside the dome be sufficient to buffer an explosion to eliminate the need to excessively harden or reinforce (and so, add weight) to the dome structure?
Assuming that all of the panels in the dome structure are capable of opening and used for ventilation, would that be sufficient to prevent a greenhouse effect?
In your opinion, is this proposal feasible or realistic?


texts: How to calculate the output power of engine exhaust

texts:
Apologize if probably this is duplicate question. But I have tried to search if someone have asked such this question.

I have a Honda engine, GX200, 196cc, with it's gross power is 6.5HP. I would like to make its exhaust to blow something. For that purpose, I need to modify the muffler to become something like shown by the picture below. But before I modify, I need to know how strong will be the blowing force right from the  exhaust output from the piston? Is any formula to calculate the force? That modification is intended to utilize it heat and its wind blowing.


texts: What are sectional views and cutting plane lines?

texts: I am a student in a Drafting 1 class and we are going over all of the section views (full, half, revolved, offset, etc.) and also all about the cutting planes and different ways for that and how to do them in Autocad. Anyways I'm reading from the book and I still don't understand it very well.  Could someone here explain it well?


texts:
I hope this is the right place to ask my question. I am conducting a feasibility study into whether or not it would be possible to tint a single region of a continuous piece of glass. Think of a single square in the centre of a much larger rectangular pane of glass. It is important that whatever process is applied to the glass that it is still a single continuous pane.

I have seen electrochromic glass, but the samples of these frames I've seen always tint the whole pane.

I'm trying to conduct a literature review of potential methods of tinting but this isnt my area and im not sure what to search.

TLDR;
Is it feasible to tint a small region of a much larger pane of glass via electrochromic  means or otherwise?


texts: Laser saturation and laser saturation intensity

texts: Can someone explain what is laser saturation and laser saturation intensity? I don't find a proper definition and it seems to me similar to steady state intensity.


texts: Analytical solution for wall eigenvalue analysis

texts:
I have a wall with the bottom end of it fixed to the ground. I want to derive from first principles the frequencies and mode shapes of the structure.

I know that I will need to start with the following formula:

$K-\omega^2M=0$

And I know how to do that for a cantilever column.

But wall is a different thing than column because it is an area element instead of a line element. And I don't know how to generate the correct expression for $K$ and $M$ for a continuum area element.

How to proceed with the analytical solution for wall eigenvalue analysis?

Note: I am not looking for a FEM solution.


texts: CSTR properties - What happens to conversion of products if I change the reactor size?

texts:
For example, initially this reactor is having a 2nd order reaction of $-ra=kaCa^2$ and it has a fractional conversion of 50% in a CSTR.

I replace it with something 1/6 as large. What happens to the conversion assuming everything else stays the same

Through theory, I know the conversion will decrease as its a smaller CSTR, but is there a way to calculate it using the formula - $fa = Fao - Fa1 / Fao$?


texts: Does a sinusoidal input voltage make a BLDC motor into a PMSM?

texts:
As the title says, does a sinusoidal input voltage make a BLDC motor nearly into a PMSM?

From Sensorless Trapezoidal Control of BLDC Motors, it follows that a BLDC motor has a trapezoidal back emf while a PMSM has sinusoidal back EMF. But if I use a sinusoidal commutation, will the back EMF of a BLDC motor still be trapezoidal?


texts: Artificial Intelligence in manufacturing machines

texts:
I am a researcher on robotics and AI, and wonder if traditional manufacturing machines, such as lathe, CNC, or grind use any kind of machine learning technique or algorithm. This algos are widely used in mobile robots.

I.e.: in a plant where there are some lathes, do they interact somehow between them? Do they adjust on the fly their parameters when machining a new piece? Or do lathes try to adjust to the parameters to the lathe that is performing the best? Kind of collaborative learning?

I did not find this kind of examples in industry yet, but I wonder if industry 4.0 is about implementing this kind of techniques.


texts: Design Input: Rotary motion to Linear motion, What system should I choose?

texts:
I am posting this here because of the multidisciplinary knowledge needed to tackle this issue.

Problem: I have to make an electromechanical device that is required to have controllable (downward) piston strokes, that can up to deliver 500N of force upon impact with a body. The piston's stroke length can be flexible, but it needs to deliver at least 500N when it hits something and go back up to its starting position.

The real difficulty: The first problem is meeting the required frequency of this operation. Each full cycle (starting position > travel down > strike > come back up) needs to happen at least twice a second (100 - 120 cycles per minute).

Work done so far: Basic math tells me that this should be doable with 200-300W of power accounting for losses. However, I have an electrical engineering background with very little mechanical/kinematics/dynamic loads knowledge.

I have a 1hp DC brushed motor, that's driven through PWM and I have control over the motor's operation. However, I would really appreciate some input on what kind of set up you would use to transfer the rotary motion to linear motion. The project has a $1000 budget and currently there are the following options:
1. Crank piston style (Rotor turns the crank connected to a linear shaft
2. Carry ball and screw system

Motor Specs: Operated at 24V, 5600RPM no load, 0.6Nm Torque.

I would gladly take any mathematical suggestion too! Theoretical analysis tends to get quite complex as the piston does not have to constantly move with 600N (No load to pull back) but only when it's on the downward stroke.


texts: Can I submerge a pneumatic cylinder in oil?

texts: I am looking for a linear pneumatic cylinder to raise and lower a fixed object. Everything will be submerged in oil (for electrical purposes). I am new to engineering and pneumatics in particular, and I don't know if I can completely submerge the cylinder without damaging it.


texts: Why do manufacturers still make aluminum kitchen utensils?

texts:
I noticed many kitchen utensils or stand mixer attachments are made with injected aluminum. Aluminum (~\$20/kg) is usually more expensive than stainless steel (~\$10/kg) and is not compatible with dishwashers.

For instance, I have a peeler made with anodized aluminum and a KitchenAid attachment with some aluminum parts that I cannot put in my dishwasher. I don't understand why engineers are still making such utensils in this material.

Is there any good reason for this?


texts: Did not understand this regarding angular velocity

texts:
It says $V\sin \alpha$ (component of velocity perpendicular to OP) is the cause of angular displacement. How is it?
if only $V\cos \alpha$ existed, we need not turn over head to always to look at a particle. What does this mean?
Also, Can we say that $V$ is the linear speed? Because that is the one tangential in direction.
How is $PQ = OP \cdot \Delta \theta$ ?


texts:
I am building a device to remind myself of keeping my spine straight.

I have a way to implement the "reminder" feature and the control package, but  I have not found a way to measure changes in curvature in a small form factor.

I thought about using a simple light encoder with a marked rod that slides through it, but that would make it much too large to stay hidden under clothes. Rotary encoders suffer from the same problem. Plus, to get a reliable value, I would need multiple individual sensors.

One way I can think of is using something similar to this and monitoring changes in pressure in the different tubes, but this seems unviable to me.

A perfect solution would be something directly implemented in the flexible surface... Some sort of flexible PCB based solution perhaps.

How can I detect changes in curvature?


texts: I am need to match DIN C15 steel with an Indian steel but I don't know the equivalent grade in the Indian standard. For example, DIN C40 steel is known as EN8 under the IS standard; similarly, what is the IS grade for C15 steel?


texts: What are the career implications of choosing a non-accredited postgraduate degree?

texts:
I am looking to complete a materials science/engineering-based Master's degree in the UK. Those which I have been looking at, particularly Leeds and Manchester, do not seem to be accredited by the IOM3 or other institutions.

I am interested in becoming chartered/incorporated in the future. If I were to complete an unaccredited course, what impact would the lack of accreditation have on my career prospects in the field of materials science/engineering?


texts:
I am currently designing a winch for a submersible vehicle and need to implement a self reversing screw shaft in it for ensuring proper spooling of the tether cable. It's also known as diamond screw shaft.

Is there any mechanical design handbook or guidelines from where i can get the design details for design of such a screw shaft ?

To know what is a self reversing screw, please refer to this link.


texts: Mechatronics Engineering is about Precision or intelligence?

texts:
i have Question that Mechatronics Engineering is all about Precision or intelligence , from precision i mean that to follow pattern precisely with precise time and from intelligence i mean making intelligent decisions based on input using image processing etc.
for example i google these Mechatronics keyword and i got these images

a) auto industry robotic arms manufacturing cars : https://i.imgur.com/gf4q8fK.jpg
so my Question is these auto industry robotic arms just follow precise pattern or they have cameras in them and they assemble or cut parts of cars based on what they see in camera added to them ( image processing ).
if no camera then it mean if car assembly is bit off from its position they could make mistake and could mess up things ?


texts: Why torsional warping does not occur for shafts with circular symmetry?

texts:
When we twist a shaft/beam/rod, shearing stresses are produced. The angle by which the end of the shaft rotates can be found as:

$${\displaystyle \theta ={\frac {TL}{GJ}}}$$

where $T$ is torque, $L$ is the length, $G$ the shear modulus, and $J$ a torsion constant depending on the geometry of the cross section. For circular cross section, $J$ equals the second moment of area. For non-circular shafts there is an effect called "warping" present where the cross sections don't remain planar during twisting; if we had a beam with a rectangular cross section and held it radially away from us and twisted it, the cross sections would bend towards us/away from us. Do I understand warping correctly?

But shafts with circular cross sections do not experience this. Planar cross sections remain planar, and deform only in 2D. Why is this?


texts: A friend and I were debating whether a biplane/propeller plane has a faster turning rate than jet aircraft. I argued that the propeller planes often do have better turning rates than jets, but I could not explain why. Does anyone know why this is?


texts: Force applied on board from bed of nails

texts:
For testing a new manufacturing process of PCBs in our company, we design 2 bed of nails. One bed will have about 80 nails while the other about 180.
Both beds will use the same fixture that will generate the force needed to attach the nails to the pads.

Which of the beds is more likely to break due to the force applied?


texts: Modelling radial Stiffness in Patran Usinf CBUSH Element

texts: I am currently working on a project using MSC Nastran and Patran trying to model only radial stiffness between two hollow cylinders. I have been able to idealize a connection which has both radial and axial stiffness in a cylindrical coordinate system using CBUSH elements. However when only radial stiffness is required I am encountering a fatal error due to excessive pivot ratios. I am wondering if it is possible to model radial stiffness only and if so how?


texts:
I would like to know how the pressure of a blast is measured when using a piezoelectric gauge as well as if this is the best way to measure the reflective wave from an explosion.

In better terms I guess would be maybe how does the sensor, sense, the passing pressure wave and what about it triggers it? Also I know there are other sensors out there that measures a different point of the wave and I would like to know how that differs from the pencil piezoelectric sensor.


texts: Why doesn't my pen ballpoint or nib emerge?

texts:
https://i.imgur.com/SfdRluq.mp4. This shows a working pen. How can I make the GIF show up?
When I rotate that silver part on the broken pen, the nib doesn't emerge.


texts: Why do cold formed sections buckle differently from hot finished?

texts: Above is a chart from a Eurocode handbook. It gives a correct buckling curve depending on cross section and its dimensions. I noticed that for hollow sections, the choice depends on whether the section is hot finished or cold formed. Why does it matter how the beam is manufactured? Shouldn't the buckling behavior depend just on cross section geometry and the material used? Why does it matter how the beam is made?


texts: Why is 3D printing with metals so uncommon?

texts: What are the differences between the processes of 3D printing with plastics versus metals? Why is metal such a problem? There are plenty of metals with low melting points. And AFAIK metal can be sprayed and directed in a number of ways such as with electric arcs and similar.


texts: Cost effective electronic packaging solution

texts:
What would be a cost effective environmentally friendly material to package a simple electronic circuit? The electronic circuit also need to be protected from moisture. The system will have a IP rated connector to provide power and support data communication. The product will be 60 x 40 x 20 mm in size.
The choices presented are PVC or ABS+PC for the outer shell. Potting material will be dispensed inside the enclosure protect from water or moisture seepage.
Are the above cost effective environmentally friendly solutions? If so why, if not what are other available options.

Reference:

A guide to the plastics used for Electronic Enclosures
Custom Potting Compounds


texts: How to determine the damping coefficient?

texts:
For a project using rotating voice coils motor in order to balance a system I need to determine the damping coefficient of these voice coils in order to insert it in a ADAMS model and analyse its performances.

Starting with the oscillation data obtained during a physical test on a mock-up, I used the Matlab tool vibration data in order to find the damping ratio of these voices coils. To find this value the vibrationdata tool makes a FFT and then a "Half-Power Bandwidth Curve fit" method...
At the end I got : damping ratio = 0.061, as well as the natural frequency $(f_n)$ 3.1Hz and the Q factor 5.8

As I was not sure about either to insert a damping coefficient or damping ratio value in my ADAMS model, I sent an email to MSC and they answered me "In Adams, bushing required the damping coefficient values, in the units as:
- newton-sec/meter
- newton-meter-sec/deg"

So, I have to calculate the damping_coefficient using the damping_ratio, natural frequency...

This is obtained using the expression : $$c = 2\,m\omega_n \times \text{(damping ratio)}$$
with $\omega_n = 2\pi f_n$

I get a certain value but I am totally not sure about the use of the mass $m$ in this expression as I want to get the damping coefficient of a rotating system...
Can I directly replace this mass by the mass inertia coefficient around which the system rotate ($I_{yy}$ for example from the Matrix)  ?
Or what else should I do ?
I would like to specify a damping coefficient in Translation in my ADAMS model...

On this awful drawing I just tried to sketch the two rotating voice coils in blacks with the magnets (right and left) rotating around the axis y... I would like to know what should I consider in term of mass or inertia to find the damping coefficient in the expression above.


texts: Definition of Mass in Multiple Mass Oscillators

texts:
In an exam on seismics and earthquake proof design I had a couple of days ago, there was a question on multiple mass oscillators in the form of a simply supported beam of length $L$, stiffness $EI$ and two point masses $M$ at the points $x_1=\frac{1}{3}L$ and $x_2=\frac{2}{3}L$.

Although I know, how to solve such a system, I was a bit confused about the unit of measurement of the mass.
Both "masses" featured a value of $M=1'000$ $kg\cdot s^2/m$. At first I thought it was a typo meant to be $[kg\cdot m/s^2]$, which I would have interpreted as $M$ representing a force, i.e. $M=m\cdot g$.
However this denotation appeared over and over again on this exam (and of recent years as well).
A classmate assumed, you had to multiply this "mass" $M$ with the readings from an accelerometer. This would make sense to me in regards to the units but not as a logical principle.
Why would you denote the mass-property of an object neither by its mass, nor by its weight?
Is anyone around here familiar with such a concept either in seismics or any other field?


texts: Structurally sound option for overhead storage platform in garage

texts:
I have an RV garage but no RV.  I'm considering building a platform 10ft above the floor.  The garage is 14 feet tall and the area that I want the platform is 16ft a 16ft.

The details are stopping me though.

I'm thinking that I'll use a 2x6 every 2 feet as the joists.  (see my picture attached.)  Would a,b,c,or d be better?

a: each joist runs the full length and is attached to a 2x6 that has already been attached to the wall

b: i split the joists in half and have a middle joist running perpendicular.

c: similar to a but the joists are connected directly to the wall studs rather than an intermediary 2x6

d: combination of b and c.

Maybe there's a better way, so I'm open to suggestions.

Are 2x6s strong even strong enough for this?

Photo attached to show what I mean.  The perspective view is to show how it fits in my garage.  There are 3 solid walls and 1 open.  I'm thinking that the open side will be where the joists are parallel to, (so each end of the main 8 joists will be connected to a solid wall)


texts:
I have the following system (at P and Q there is a ball joint; the length of L beam is l; the PB and PA forces are applied at l/2 and are known; Fz is not zero and is known):

The system has 0 degrees of freedom because each ball joint removes three degrees of freedom (6-2*3=0).
I replaced each ball joint with three unknown forces.

The problem is that the second cardinal equation along x gives:

$$-F_z \, l = 0$$

How can I solve the problem?

Thank you very much for your time.


texts: Correct terminology for 'putting instructions onto an FPGA'

texts:
In an introduction to field-programmable gate arrays (FPGAs) Sparkfun describes that FPGAs aren't really 'programmed' (see below for excerpt) even though this is often used in every day language.
If this is 'not entirely correct', what would be the correct terminology for putting instructions onto an FPGA, used by the experts in the field? I would presume FPGA's are 'flashed', but I'm not sure if 'configured' would be the right word since putting instructions onto an FPGA is literally changing the hardware.
(sorry if this is not the right platform to ask this, it's more of a meta-question for engineering)
Citation from the Sparkfun introduction Jan 2021:

But you aren’t writing a program. You are creating a circuit. You
don’t use programming languages to create circuits, you use hardware
description languages (HDLs).


texts:
If you consider a motor attached to a spur gearbox with a reduction ratio of say $r=50:1$ which is then back-driven so that the motor acts as a generator, what would be the effective moment of inertia of the system? If the motor has a rotor inertia of say $1*10^{-5} kgm^2$ and the gearbox has a mass inertia of $1*10^{-6} kgm^2$ would I be correct in calculating the overall inertia through

$I_{total}=r^2I_{rotor}+I_{gearbox}=0.025 kgm^2$


texts:
I'm trying to estimate the magnetic force which develops on a truss-like ferromagnetic structure (I want to estimate the motion of the object) in a uniform magnetic field, and I came to realize that I have a fundamental gap in my knowledge.
My question is: how do I calculate the magnetic force in a uniform magnetic field with magnitude $B$, related to a rod-like object with length $L$, diameter $d$, and mass $m$?
From what I could fathom so far, the force should be independent of the mass. It is mainly depended on the intensity of the field.
An initial guess is that the force should be independent of the mass. However, that cannot hold because then what happens if I take two masses and glue them together?


texts: Do gears make an electric motor bike more efficient?

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Electric motor bikes were sold initially on the idea that there would be lesser maintenance and it would remove the requirements of the gears.

Now, a lot of people like having a geared system. Some argue it makes it more efficient during cruise mode or high speeds. I want to understand if this is correct. Are there added benefits to having a gear system on an electric motor bike?

My hypothesis states that it is not dependent on the torque generated and has to do more with the load generated at the motor.

Edit: this is not a cycle. I'm talking about replacing IC engine powered two wheelers. No pedals. Not a cycle. No assisting. Purely run by the motor


texts: Which one is preferable? Multiple layers of reinforcements or one layer of reinforcement?

texts:
For RC beams, which one is preferable to be designed for construction? Is it multiple layer of reinforcements or one single layer? and why?

Eg. If the beam required 3T20, is it preferable one layer of 3T20 or multiple layers: 2T16+3t16?

Thanks


texts: How does Hysteresis in tires helps create friction?

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I am currently reading “Fundamentals Of Vehicle Dynamics” by Thomas D. Gillespie.

The author states how tires generate the required frictional forces for movement by 2 methods :

1)Hysteresis
2)Adhesion

It’s a no-brainier in understanding how adhesion can help generate friction. What I don’t understand however is how Hysteresis can help produce the same ?

What is the mechanism using which tires generate forces by stretching and un-stretching ? How does this work?


texts: How to attach a shell covering to a flat piece with clay as adhesive?

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I have a ceramic nozzle type structure sort of like this:

The outer casing is joined with clay material with the inner ceramic nozzle. What we do is, we attach the clay in the casing, put the nozzle in base and press the casing with the help of a air press. But the thing is, we are not getting uniformity in this. The outer diameter formed with the casing is irregular. Can someone help here?

SUGGESTED ONLY - PLEASE CHECK:

See Tundish nozzle - CASTING - here  = Ceramic nozzle inside outer shell - the ceramic IS attached to the base of a "Tundish" flow smoothing reservoir for molten steel which accepts molten steel from "ladles" and delivers it via these nozzles to molds.

The problem here is that the ceramic does not form smoothly against the outer shell when pressed,


texts: Inventor parts that move in sub-assembly won't move in main assembly

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So suppose I have 4 files.

Part 1
Part 2
Sub-assembly
Assembly

Now in sub-assembly, part1 and part 2 are "connected" to each other and there is an articulation.

Everything works well until I place my sub-assembly in my main assembly. When I do that, part1 and part 2 can't "move" anymore. How do I solve that problem??


texts: Force Transmission in Flexible Tools such as this tool

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In general, I want understand how the Power transmission in flexible tools works such as this flexible pick up tool in this link: https://www.youtube.com/watch?v=TLbCatz4Pnkv=q9AkmsTNLkY . Specifically, I want to find a model of the inside tool, that describe the relationship between the axial input force at the one end and the axial output force at the other end given a certain shape of the tool. I know, that the mechanical name of the flexible tool inside is called flexible multibody, but I fail to find useful resources, which describe a direct relationship between axial input force and axial output force. I tried looking for the datasheet of similar products, but I didn't find any useful information.
I would be more than thankful, if someone can provide me with a useful guidance.


texts: Tankless air compressor for electronics desoldering station

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I purchased a Weller WSD161V soldering station (similar to this one, at least with regards to the pneumatic system I'm about to describe -- sorry, I was unable to find a manual for my specific model on the internet) with a DSX80 desoldering iron.

This desoldering iron works like an automatic desoldering pump -- when pressing a button on the iron, it suctions the molten solder.

To work, it needs (as described on the link above) a 35 l/min supply of dry, oil-free, 58-87 psi (4-6 bar) compressed air. I recall reading somewhere that there is a venturi inside the soldering station which generates the vacuum for the pump.

Due to space and noise constraints, I decided to purchase a tankless air compressor -- specifically, the Einhell BT-AC-180. It is able to supply compressed air at a pressure of 8 bar, with a flow rate of 77 l/min at 4 bar and 63 l/min at 7 bar, so it should be plenty to supply my desoldering iron.

However, I have a couple of questions -- keep in mind my expertise is in electronics, and I have very little knowledge of pneumatic equipment:

The compressor doesn't appear to have any kind of pressure regulator. Since my desoldering system only consumes 35 l/min of air, which is well above what the compressor can supply even at a pressure of 8 bar, I understand the compressor should well be capable of supplying the full 8 bar to the desoldering system. This would be out of spec for the system, and I'm afraid it might blow some kind of safety valve inside it. Does there exist some kind of pressure regulator I can couple to the output of the compressor, which will drop pressure to the safe 4-6 bar range for the desoldering system?
In looking for such a system, I was told by a salesman at a compressor shop that if a tankless compressor's flow is impeded, their internal safety valve will blow, so there needs to be a path for the compressed air to get out at all times. I've learned not to take salesmen at their word, and in this particular case I'm inclined to believe this is wrong, because the compressor in question comes with some kind of pistol which can cut out the flow of air -- I guess the manufacturer wouldn't include such an accessory if it would cause the compressor's safety valve to blow out. Still, since I recently purchased this compressor, there's still time to return it to the dealer if it is unfit for my purpose. Is this compressor compatible with the desoldering system, or should I return it and go for a compressor with a tank?
The desoldering system calls for dry air, and I was told by a salesman that condensation is an issue with compressors -- at first I found it weird since compressing air should increase (not decrease) its temperature, but now I believe I understand the effect, which should be similar to a capillary tube in refrigeration systems: when the flow of air is restricted, its pressure drops and so does the temperature, which may then form condensation. The salesman said the solution to this is adding a filter to the compressor output. Is my understanding of the phenomenon correct? Will a filter solve the problem? What kind of filter should I look for?

Taking into account my complete lack of experience with pneumatic systems, any other tips on how to connect the system, what extra equipment to purchase, etc. are welcome.


texts: I’ve been trying to figure out what this connector is and everyone has no clue. There isn’t enough identifying information to find anything on google. All I see is a label “lwai”. It’s located in a panel with power outlets, rj45 jacks, and some audio jacks. I think I found that it might be related to some hvac system but I can’t find any description or picture that confirms that.


texts:
Logged in a little time ago i have a new question. So I am trying to mesh an arifoil geometry using ANSYS meshing. Airfoil number is NACA 84-M profile. Running  2-D simulation my main objective is to find a good enough mesh for a specific task, which has to do mainly with active flow control, using a tiny jet nozzle located at the top back of my airfoil section.
The outline of my airfoil sectin has been devided into 4 main sections.
Lower part
Upper front part
Jet nozzle part (only made of 2 points)
Upper back part (from jet nozzle through trailing edge of the airfoil)

Regarding my outter part of my flow domain i have used a C-type structured mesh seen below.

I left the nozzle spot and my main concern is the fact that i want to use a different face meshing for that specific spot. Trying to alter the number of cells due to the fact that the number should be enough to simulate flow phenomena.
    Shall I use different meshes for the bottom and both of the upper two sections of my geometry? (remeber that the hole airfoil has been bi-sected into 4 different categories, described previously).
    Total chord length has been dimensionalized. Points arranged in the range of [0 to 1]. So the total chord length is 1m, or 1mm, it doesnt play a role.
If you have many articles in consideration, please reply, anything should be much appreciated.
Thanks in advance!


texts: Euler buckling formula,triangular structure

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So I tried equating the sum of forces in the x,y and torque about $C$ to zero and found $B_x$ and $C_x$.

But how to find $B_y$ and $C_y$? I have 3 equations and 4 unknowns?


texts: Roskam Book equation of dry air density is not clear. I need explanation

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Preface:

Roskam in book "Airplane Aerodynamics and Performance" explains (in paragraph "1.1 ATMOSPHERIC FUNDAMENTALS"):

  To determne how water vapor affects air density, consider a given volume filled with a dry air and water vapor mixture. Dalton's law of partial pressures states that the obvious pressure, $p$, of the mixture equals the sum of the dry air pressure, $p_a$ and the water vapor pressure, $p_v$:

  $$p = p_a + p_v \qquad \mbox{(1.2)}$$

  Also, since the total mass of air inside the volume is equal to the sum of the dry air mass and the water vapor mass, the observed density of the mixture is given by:

  $$\rho = \rho_a + \rho_v \qquad \mbox{(1.3)}$$

  In Eqn. (1.3) it is also assumed that the distribution of masses of dry air and water vapor is uniform. By using the perfect gas law, $p=\rho g R T$, it is possible to show that the density of the mixture is given by:

  $$\rho=\frac{p-p_v}{gRT}+\frac{p_v}{gR_vT} = \frac{1}{gRT}\left( p-p_v\left( 1 - \frac{R}{R_v}\right)\right) \qquad \mbox{(1.4)}$$

  For water vapor or steam, $R_v$=85.89 ft/°R. It follows that $R < R_v$ so that second term in equation (1.4) is negative. Therefore, the density of a mixture of dry air and water vapor is less than that of dry air. Normally the effect of water vapor on air density is small. To illustrate this fact, assume that the observed temperature and pressure of a mixture of dry air and water vapor are 90 °F and 2116.2 lb/ft^2 respectively. If the relative humidity is 100%, the water vapor pressure can be found to be 100.6 lbs/ft^2. The density of the mixture then follows from Eqn (1.4) as:

  $$\rho =\frac{1}{53.35*32.17*549.7}(2116.2-100.6*0.379)=0.002203  \mbox{slug}/ft^3 \qquad \mbox{(1.5)}$$

  The corresponding dry air density is 0.002243 slugs/ft^3. The density reduction in this case is therefore only 1.8%.

Granted that in the equations above the term "R" is referred to dry air, in my opinion the sentence "The corresponding dry air density is 0.002243 slugs/ft^3" is not correct because in my calculation I found 0.002130 with the following calculation:
$$\begin{array}{}
\rho_a & =\frac{p_a}{gRT} \\
\rho_a & =\frac{p-p_v}{gRT} \\
\rho_a & =\frac{2116.2-100.6}{32.17*53.5*549.7} \\
\rho_a & =0.002130
\end{array}
$$

So, can someone explain if I'm wrong?


texts:
I have a quick question about the parallel axis theorem.

Let's say I have a box-like object rotated about the following pivot point

I was wondering, by applying the parallel axis theorem, would the moment of inertia about the pivot point be the following,

$$M = I_{cm} + M_d^2+M_h^2$$

where $I_{cm}$ is the moment of inertia about the box's centroid and $M$ is its mass.

Or, does the parallel axis theorem not hold true for two axis shifts?


texts: What is the type of bearing used on swivel base chairs?

texts:
I'm designing a chair from scratch and I'd like it to have a swivel base. For this my initial idea was to press fit a bearing (thrust bearing) in the shaft of the base and connect the seat by press fitting a small shaft through the middle.

But I'm having my doubts if this can handle the load of a person sitting on the chair.

Looking for a purpose built or better suited bearing for this.

Also opened to suggestions for a better way to build this.

Thanks


texts: How to calculate the volume capacity flow rate of a vertical pipe?

texts:
There is a rain pipe in a house. I want to know how many cubic meter rain water can flows through the given pipe in a minute. I need to know the maximum capacity of the pipe. In other words: How many liter water can pass through this pipe in one minute.

Data:
Pipe diameter: 70mm
Pipe length: 3000mm
Pipe angle: 90°
Height of the top hole: 3000mm
Height of the bottom hole: 0mm
Pipe material: Copper
Time: 1 minute
Fluid: Water

Can anyone describe me or suggest me an online tool to calculate that?


texts: Passivity in automatic control (Linear and nonlinear control)

texts:
The definition of passivity for control systems is:
$\langle y,u \rangle _T \geq 0 \: \: \: \forall T >0 \: \: \: \forall u$.
Considering  signals $u,y :[0,T] \rightarrow R^m$.

As I understand it, passivity is when the system is still stable and does not change the direction and lose stability. If we look at the vectors I understand that in the scalar multiplication $\cos\theta \geq 0$. Does that mean that the direction or phase doesn't change from positive to negative and why?

Another definition using the storage function is:

$$V(x(T)) \leq \int_0^Ty(t)u(t)dt + V(x(0)), \: \: \forall T > 0 $$

  Passivity idea: “Increase in stored energy ≤ Added energy”

How do I describe the passivity for a system in words without the storage function? I mean, what is passivity and why is it useful? In what way is it different from stability?


texts:
In a vibration measurement of a rotating blade, I have the following information. The vibration signal is measured using an ICP accelerometer which has the following specification

Measurement range: 50g
Sensitivity: 100 mV/g
max output voltage: ±5V
Broadband resolution: 100e-6g

The variance of the acquired signal is
$$var_{aq} = var_{acl} + var_{adc} + var_{sig} \approx 6.2e-4 g$$

$var_{acl}$ = variance of noise in the accelerometer
$var_{adc}$ = variance of the ADC noise (quantization, jitter)
$var_{sig}$ = variance of the vibration acceleration of the blade.

Assuming that $var_{acl} \approx \sqrt{\text{broadband noise of accelerometer}} = 1e-8 \text{g_rms}$.
From the specification sheet of the ADC, for the used input gain of 30db and sampling frequency = 51.2Hz, the $var_{adc} = 1e-12 \text{V_rms}$
Can anyone please help, how can I calculate the variance of vibration acceleration of the blade $var_{sig}$?


texts: Decision criterion if bolted joints are loaded concentrically or eccentrically

texts:
When dimensioning bolts I have to decide if the applied load is concentrically or eccentrically to the bolt axis (according to VDI 2230 but I think in other approaches too). But how do I decide and justify my decision for concentrically or eccentrically load?

Yet I made my decision if the axial load of a specific bolt (the working load is proportionally related to the bolts in the bolted joint) is concentrically or eccentrically to the bolt axis. My worry is that this decision criterion is to rigorous and my dimensioning of the bolt leads (always) to an overdesigned bolt.

Are there more decision criterion to consider?

Now I give some parameters which might be relevant – but mind the following list is not complete:

the material of the housing and cover (plastic or metal)
the thickness of the housing and cover
may be some parameters of a FEM simulation

bend of the considered bolt ($[N/mm^2]$ or $[°]$)

surfaces of the used materials

the coating
the roughness of material (caused by kind of production)

and more parameters…

And what are the thresholds of these parameters to say the load is concentrically or eccentrically?

I’m expecting a statement like: When the parameter A fulfils the following, then you can say that the applied load on the bolt is concentrically.

I’m glad to hear from your experiences how you decide if a bolt is loaded concentrically or eccentrically.

Many thanks in advance.


texts: Pipe seized to inaccessible coupling - how to attach a new pipe?

texts:
A friend of mine that doesn't use the internet much runs a commercial laundry. They use an old 'Manlove Tullis' laundry calendar (c. 1980) that looks like this:

(click to enlarge photos)

Essentially, it is a machine with 3 rollers (2 visible in the photo) on a hot plate. Garments (e.g. bedsheets) go in wet, and come out ironed flat, and dry.

The hot bed runs on steam fed by 6 pipes (2 for each roller) underneath the machine, coming from a big boiler.

A couple of days ago 1 of the pipes broke off/burst under the machine with wear & tear over the years; where the pipe is joined by a coupling to the hot bed.

It is possible that over the years with repeated super-heating and cooling some metal fatigue has crept in, or it became so brittle that it finally failed.

After allowing the machine and the pipes to cool down for a day, he went under the machine to try to fix it; but the pipe is seized to the [possibly brass] coupling. The coupling affixes to the hot bed and it appears it cannot be removed because it is both seized and in an inaccessible part of the machine. It is a 22mm coupling.

The pipe is steel, and could be cut off and a new one joined by welding it or something.

Underneath the machine, the working area is only 50cm in height at most, and it is 10ft x 15ft / 3m x 5m.

From how it's been explained to me, when you're under the machine lying on the floor; the actual pipe/coupling that needs removing is within a small cavity above you. Something like this:

The space is very limited and the angle very awkward; there are also some health & safety issues with operating a welding torch under there.

An additional coupling could be added, but this introduces another mode of failure.

He has just installed a copper stop end, temporarily, so that he can use the machine with 2 out of 3 rollers operating at 100% and 1 operating at 50%.

The boiler operates at 8 Bar / 115 PSI — therefore the laundry calendar also operates at 115 PSI. From reading online I understand that the pipework is more than adequate. It is also regularly inspected and serviced.

My question is:

How can we get this pipe and/or coupling off and a new one on?

The person I'm posting this question for is very knowledgeable on the subject, but for the first time I've seen, he's stuck here. Three engineers have been out on-site and don't know what to do.

One has said that "it either needs to be welded or a proper coupling added; but it cannot be cut off because it is inaccessible".


texts: Is the Spring Rate for a Belleville Spring Linear?

texts:
Belleville disc springs are usually spec'd with a free height, loaded height, and loaded force.  From this information you can calculate the average spring rate of a belleville spring.  However, what I would like to know if if the force is actually linear (or nearly linear).

I assume it is not, but don't know what curve the force might follow.  Is there an equation that can predict the force-curve (plot of force versus height) of a belleville spring given ID, OD, free height, and thickness?


texts:
I hope I'm asking this in the right place.
I have the following problem:

and am to calculate A,B & C so that the system is in static equilibrium.
I calculated A without too many problems.

My problem is with B & C

What I have done so far:

I realised that my placing my moment at the point ABF I can eliminate B as an unknown and solve for C.

I calculated the resultant for the diagonal part ($R_1=q_0\cdot l$) and for the vertical part ($R_2=\frac{q_0\cdot 2l}{2}=q_0\cdot l$).

I calculated the distances of $R_1$ and $R_2$ from my moment $M^{ABF}$ using the Pythagorean theory and set them both negative as they are turning my system in a mathematically negative direction.

The force C I added to my moment as $C\cdot 2l$.

My moment calculation is at this point:

$$\Sigma M^{ABF}=2l\cdot C-(\sqrt{(2l)^2+(2l)^2}+\frac{l}{2})\cdot R_1-\sqrt{(2l)^2+(\frac{2}{3}2l})^2\cdot R_2$$

My problem:
I don't know what to do with the moment $M$ which is at a distance of $l$ from $M^{ABF}$. I have tried adding as it is, adding it and multiplying by $l$, but both times the answer comes out wrong (I have a numerical answer).

I'm obviously doing something wrong but I don't know what.

In case it helps to have values:
$F=4q_0l$,  $M=2q_0l^2$,  $\alpha=45°$
$q_0=3kN/m$, $l=2m$


texts: Is Model order reduction good for complex models with a lot of contact points in them?

texts: we know that MOR ( or model order reduction ) is used to reduce the size of heavy FEM models. but if there are so many faces, edges of the part that are in contact with another part in the model or within itself, is it usefull or wise to use MOR ?


texts:
I want to make a smaller version of a revolving stage with rotation and lift.
But how do you combine those mechanism that creates a turntable and that rotates and lifts up at the same time? I know that you can use a slip ring, but how do you put that together to make a lift?

Also there are lots of tutorials about the lazy susan but no lift... Does anyone has a simular tutorial on how to make this?

And if you want to recycle an old printer which part could you use the best to make this rotating-lift up-turntable like a revolving stage?


texts: An animal's blood pressure and/or body movements can be used to generate a few mW of electrical energy. Can an RF transmitter which radiates 1 mW be detected by receivers (without any parabolic reflectors) on satellites? The receiver has to only detect the signal and power level, no data transfer is required. This could be used to locate the animal.


texts: How is calcium and aluminium wire feeding different from each other?

texts: How is Aluminum wire feeding different from that of Calcium wire feeding as far as the purpose is concerned also what I do not understand is what has wire feeding to do with the purpose and how are aluminum and calcium different with purpose?


texts: What angle - for a strut - provides the greatest vertical strength/support for a cantilever?

texts:
I want to affix a cantilever to wall. I will support the other end of the cantilever with a strut made of wood, that attaches to some point on the wall below the cantilever, as shown in this sketch (click for full resolution):

At what angle will the strut provide the greatest vertical strength/support for the free end of the cantilever?


texts:
I learned in high school science that everything has a hardness index, that metal has a relatively low hardness compared to many kinds of stones, and that something cannot be scratched by a substance that is less hard.

Then why does the disc on an angle grinder wear down? Why can't it be made of a substance that can stand up to metal?


texts:
I need a vacuum to provide 21" Hg but looking online many list an ultimate vacuum of 10Pa but 1"Hg = 3300Pa? I know I am missing something and just want to make sure I get it right. Thanks for the help!

http://www.ebay.com/itm/Single-Stage-4CFM-1-3HP-Rotary-Vane-Deep-Vacuum-Pump-HVAC-AC-Air-tool-R134-R410a-/371397348640?hash=item567901cd20:g:BHMAAOSwf-VWXedU


texts: Why would a column expand before accepting load through a narrow thunk?

texts:
Here's a column top which holds a driveway overbridge.

The column is a reinforced concrete cylinder with an inverse truncated cone on top - so it expands sideways at its top. The column top holds some narrow thunk and that thunk holds the driveway floor.

Note that the thunk cross section square is much, much smaller than the column top cross section square, so it looks like the column top is overbuilt and the top is too wide for no reason - the thunk could rest on the column top even if the column had no expansion.

Why would this design be used instead of a cylinder?


texts: 3D printed houses and energy efficiency in Germany

texts:
I have just learned that in Germany you wouldn't be able to print a house because of existing rules, especially regarding energy efficiency.

Isn't it possible to print an insulating inlayer to fulfil this standard?


texts: What is the need of having a separate flag as Auxiliary carry in microprocessor 8085?

texts:
My question is "what is the need of using auxiliary carry?"  I mean 'AC' flag is set when D3 generates a carry. Then why not different flags for D2 or D4?

Why suddenly we are treating D3 carry in a special way?


texts: finding a volume after non-isentropic expansion (constant heat approach)

texts:
Nitrogen (N2) in a piston cylinder device undergoes an expansion process from State 1, T1=500 K, V1=1.0 m3 to State 2, T2=700 K. If the specific entropy change (s2-s1) is 0.468 kJ/kgK for the process calculate the final volume, V2 in m3.
Use constant specific heats approach and when necessary, evaluate properties in average temperature.
I tried using $ s_2-s_1=C_v.ln(T_2/T_1)+ln(v_1/v_2)$ but the answer was wrong. I calculated 1.025 but the answer is 2.


texts: Transparent material which could withstand high temperatures

texts:
I am an fire safety engineer trying to build a fire model which I could use to demonstrate basic fire behavior in enclosures. In general, the model is a box (for example 0,3*0,3*0,2 m or larger) with one opening. Inside the box is the burner (gas burner or some material which burns).

At the university, we always used models built out of gypsum plaster. It was cheap, easy to connect and it could resist quite high temperatures (around 700 degrees Celsius).

Is there any kind of transparent material which could be used in such an application? If I understand correctly, the highest temperature which thermoplastics could withstand are about 270 degrees Celsius. Quartz glass is too brittle I think, and probably too hard to cut out.

Is there a material like this?  Or if there are multiple materials, which one(s) are least expensive?


texts: Determine the moment of inertia of a filled circular sector

texts:
Does anyone know how to determine the moment of inertia of the filled circular sector shown below?

Apparently I have to use $dA=r\ d\theta\ dr$, $y= r\sin(\theta)$ and end up getting $I_x=\frac{r^4}{8}(\alpha-\sin(\alpha))$

But I have no idea how they got that, I have never had this.
Could someone step by step explain how to get to $I_x$ with this question and how to integrate something that has two different differentials.


texts: Are the design load values in this floor determination table (span chart) inclusive or exclusive of the given floor weight (inherent dead load)?

texts:
So, I have been doing research into the use of Insulated Composite Concrete Forms (ICCFs) for small-scale construction, and that has led me to looking at the Rastra ICCF system, as it has been in production for a long time, is relatively well documented, and is versatile enough to answer a variety of building design needs; in particular, Rastra parts can not only be used to build walls, but horizontal assemblies (floors/ceilings/roofs) as well.

However, the published documentation for Rastra ICCFs stops short of providing span charts for their use in horizontal assembly construction.  I contacted Rastra's technical support regarding this omission, and they sent me a PDF file that included the following drawing and determination-table (span chart) for Rastra floor systems using Trigon-type reinforcing girders and supplemental reinforcement laid in a bed of Rastra end elements, then finished with a concrete pour:

Most of this is clear enough (although I'm not sure how to get my paws on prefabricated reinforcing girders of the style they used, given that I'm across the pond from them); however, it does not answer one question for me: are the loads given across the top of the posted table inclusive or exclusive of the floor assembly's unit weight (inherent deadload)?


texts: Can I use the delay of different paths of a RAKE receiver for orthogonal channels. The idea is that if I have a square law detector for a packet of bits there will be no channel interference because the delay effectively acts as a pad of zeros. It's a technique that I want to use? If there are any papers on this I would greatly appreciate it.


texts: How to construct a weir for Volume flow measurement

texts:
A weir can be used to measure flow rate, from the known relationship between height of the water level above the weir crest, weir length and flow rate (assuming the water level downstream is below the weir crest). However, the flow coeffiecent depends on the conditions, among other things on wether the flow is aerated from below. In low flow conditions, the water flow may cling to the weir resulting in another flow coefficient.

According to the DWA-M 181 straight weirs can achieve a decent accuracy for flow ranges $Q_{max}/Q_{min}$ = 25 to 30, if the weir is built according to the ISO 1438. The crucial element is areation of the water jet, according to the DWA-M 181. What does ISO 1438 (or other similarly authoritative voices) say about straight weirs and how to build to achieve decent accuracy over a wide range?

the weir will be mounted into a rectangular concrete channel.

(Image source is the DWA-M 181 that mostly points to the ISO 1438)


texts: Are threads machined from high tensile steel more susceptible to damage?

texts:
I have an ASTM A311-04 1.25" diameter round 1050 steel bar that exhibits a tensile strength reading of 155,227 PSI. Normally, we receive material in the 13-133,000 PSI range. The bar is machined to a 5/8-18 UNF thread.

We have experienced instances where the threads of these machined parts get damaged when installing a prevailing torque nut. The nut is hand tightened and then driven tight with a pneumatic gun. Threads are being cracked off from the shaft during the installation of the prevailing torque nuts. This is a new phenomenon and seems to be centered around threads machined in steel that has this "high" tensile strength (155,227 PSI). The nuts and assembly process have been ruled out as root cause.

Could the material tensile strength create a situation where the threads become susceptible to damage? In tests, it appears as though the threads are being pulled off the shaft and getting embedded in the threads of the nut. The hardness is 33 HRC if that is of interest.


texts: Are cameras' CCDs just elaborate tiny solar cells?

texts: While watching How It's Made episode on CCDs, this just springed to my mind... I always though of CCDs as of some kind of alien technology. Only now I realized that it's just an array of silica crystals that, same that we use for generating power but all connected to CPU for processing. Is this correct?


texts: Question on the determinacy of frame structures

texts:
I have been working on a program to solve frame problems, and I have used the following formula for determining whether a frame is statically determinate:
$$RD=3m + r-3j-s,$$
where:

$m$ is the number of members,
$r$ is the number of support reactions,
$j$ the number of joints, and
$s$ the number of equations of condition.

The structure is:

unstable if $0<RD$,
determinate if $RD=0$, and
statically indeterminate if $RD<0$.

It seems to work, for the most part, but I came across a problem that is deemed to be statically indeterminate by this method, which nevertheless can be solved using only the sum of forces and moments. The frame is as follows:

For the frame above, $RD=3$, so the frame is supposedly statically indeterminate. However, it can be solved by first solving te support reactions, then solving for the normal and shear forces of each member (8 variables using 8 equations from nodes A, B, C, and D) and then using these to solve for the internal moments. Is the method I used to determine determinacy invalid?


texts: Hardening leads to a material being more brittle.However I can't understand what is strain hardening or strain hardening exponent.Please explain why hardening leads to brittleness also in this answer itself.I would be happy to get a detailed answer of this.


texts: Why aren't gravity batteries everywhere?

texts:
The problem of energy storage, especially with regard to renewables, remains unsolved. Or at least there do not seem to be any popular solutions.

Why not gravity batteries?

I love the idea, and they look like a beautiful and effective approach to the problem. The low-tech, simple principles grant it so many different region-taylored forms. Many of these designs could easily be low-cost. I could go on.

Are there some shortcomings that I am missing here?
I asked this same question to the physics stack exchange, but I don't feel satisfied as to why they aren't more commonplace in renewable energy storage applications.


texts: I have a shaft with splines on it that I want to create a drawing for in Solidworks because I may need to have this specific spline replicated on a part in the future. Does anyone have any documentation on how to identify a spline? Or possibly a table of standard splines used in industry based off of shaft size?


texts:
When an ideal gas with constant specific heat is throttled adiabatically, with negligible changes in kinetic and potential energies:

(a): ∆h = 0, ∆T = 0
(b): ∆h =0, ∆S > 0

The answer is supposed to be (b).

Please explain why answer (a) is wrong and (b) is correct.


texts: can we run rotary compressor of Air conditioner with different frequency level ?

texts:
I am working on split type AC compressor. I actually want to know, if i changed the frequency of the compressor to run on different power level, will it affect the life of the compressor. My actual work to run the Compressor with different power level. I will use VDF ( variable frequency drive) to change the frequency of compressor and it will take different power with respect to the frequency.
can you tell me that all rotary compressor is designed for a specific frequency. ?


texts: Does anybody have information on how to refurbish an old laser rod (alexandrite or Nd Yag)? )

texts: With usage, old laser rods eventually will need maintenance by cleaning and refurbishing it. Does anyone know how this is done?


texts: Root locus: ambiguity on which branch goes where?

texts:
I could not find a Controls Stackexchange, I hope this is the right place, otherwise I would be glad to post it in the appropriate section. My question concerns the root locus method.

Given a plant with some transfer function that I want to control with gain, I would arrive to such an equation,
$$1 + \frac{K}{s(s+0.5)(s^2 + a s + 4)} = 0,$$
where $a$ is a given constant (think $1$ for example), and $K$ is a gain I will be able to choose. I want to draw the root locus by hand to have a rough idea.

I place my poles, the root locus on the real axis, count the branches (four go to infinity, no zeros), find the centroid then asymptotes, find the breakouts on the real axis, find the intersection of the root locus with the imaginary axis and find the the angle of departure from the two complex poles.

Once I have done this, for $a$ close to $\frac 12$, I find myself with a departure angle which is close to $-90^\circ$ (for the upper pole), that is "downwards". This seems ambiguous regarding which asymptote the branch leaving from the upper complex pole will eventually reach. I attach two plots to the post with values of $a = 0.5 \pm 0.1$: $a = 0.49$ and $a = 0.51$.

Obviously now that I look at the plots, I can tell which branch goes where, and using some criterion like "if the branch leaving the complex pole goes to the right, it will go on the right asymptote, and vice versa", you would indeed get the right answer. My question is,

  Is there a general way to tell which branch goes to which asymptote?


texts: What happens at the other side of the piston?

texts: In a standard 4 stroke vertical internal combustion engine, Does the downward piston movement compress gas below it? If so, does it affect efficiency?


texts: How do I add the nodes' IDs and locations that are situated on a helix in space to a set in ADPL?

texts:
I have a beam structure in the form of a Helix. How do I add the nodes positioned on this helix using ANSYS APDL ?

I need to add the locations and IDs in separte sets.


texts: Will helium gas lift more weight in air when it is spread over large volume compared to equal weight heavily compressed small volume?

texts:
Is it possible for a weather balloons filled with helium gas to lift the weight of itself and a helium tank(highest psi possible) which can fit the volume of the lifting gas in it?

Assuming a typical weather ballon material is used as the ascending vehicle would the balloon with the helium pumped back in the tank fall down to the earths surface?

P.S. In water the weight as well as the surface area for that weight determine its buoyancy - ships etc. A 5tons of dense block steel would sink in water but spread around over wide enough area it should float instead.

Wouldn't the same thing apply to the difference between a helium gas filling the  larger volume of the balloon vs the high pressure compact volume storage vessel?


texts: Matching Output of Two Old Ring Compressors using Larger Single Unit

texts:
Disclaimer: I am new in the design of any fluid systems, however the selection of these units is critical for the electrical design I am responsible for this system, so please excuse me if my approach is naive. We are running the system @ 480V 60Hz

We have an application where we are using Fuji Ring Compressors (https://americas.fujielectric.com/files/Fuji%20Electric%20VFC90.pdf) in a vacuum mode to hold aluminum panels up with vacuum belts. The outlet of the ring compressor goes into 3 chambers connected to the belt track. The belts have holes along the middle which provide enough suction force to hold up the panel. This method has proven to be successful in the past but we are expanding the number of belts, and would like to avoid simply adding more ring compressors (we would need 9 more units to expand the system in the same way, and we are short on space). What I am investigating is if we can use a larger compressor to match the outputs of two of these old units. This is the highest capactiy model that Fuji can offer in the same range (https://americas.fujielectric.com/wp-content/uploads/2017/05/VFB2000-7Wa-Single-Stage-Ring-Compressor.pdf).

My approach was to look at this from a black box perspective, and for now not worry about the force required to hold the panels, figuring out # of holes covering etc, since I know the singular ring compressor could handle it. My thought is that since the pressure is inversely proportional to area, I can simply compare the outlets of the units and the pressure they can supply at a given airflow. So I imagine a y-connector at the 4" outlet of the larger VFB unit splitting into two 3" lines representing two of the VFC units. If the vacuum generated at the end of those two 3" lines was greater than then what the VFC's could output, I can use the singular VFB unit.

The old VFC units have a 3" diameter outlet for an area of ~7.07 inches^2. The new VFB units have a 4" diameter outlet for an area of ~12.57 inches^2. If I am trying to match the output of two VFC units, I double the areas for those and compare the ratio (14.14/12.57 = 1.125). At any given point on the Flowrate/Pressure curves given in the datasheet, the pressure supplied by the VFB is greater than that ratio multiplied by the pressure supplied by the VFC by about 10-15%. I also anticipate less head loss in the lines because running one 4" line and splitting it should be more efficient then two 3" lines.

I still want to do the analysis back to the force required to hold panel, and required pressure at each vacuum hole etc, but I want to know if my idea is even remotely feasible before I spend too much time investigating. My main concern is the drop in vacuum flow at each hole, but I am not sure if this is a concern if I satisfy the vacuum requirements.

Thanks for any help and I would be glad to offer more information.


texts: Is this function common in PID controllers?

texts:
I'm reading some old microcontroller code for a PID algorithm. There's a strange function (to me) that seems to work like this:

$output = \frac{1}{n}input + \frac{n-1}{n}previous\_output$

The value $n$ varies.

Over several iterations, it will eventually output a value very close to the input, but sudden jumps in the input create a lag that takes a few cycles to catch up.

This function is used in multiple places, for instance:

it's used on the setpoint when calculating the error - the current process variable is subtracted from f(setpoint) (where 'f' is the function I described above) instead of the true setpoint. This seems to produce a weighted set point, where the weight is inversely proportional to the rate of change - is that correct?
it's also used in another component of the PID when comparing the true error to the previous value. The previous value is put through this function, instead of using the true previous value. In this case, it's harder to understand it's purpose.

Is this a common function used in PID controllers? I haven't found a description that quite seems to explain this, but if it might be a case of just not knowing the right keyword to search for.


texts: Find location of resultant of forces without using moments

texts:
I am trying to solve the problem below without using moments. To find the resultant force is simply a  matter of adding the force components together, but I cannot find any method of finding a location of the resultant without using moments. Is there any other way?

The problems is from Hartog's Mechanics.

Edit: This page explains how to solve it using moments: http://www.leancrew.com/mechanics/problem006.html


texts:
I want to set up steel truck fenders production line, but have no idea how to do that. Something like this picture.

Edit1:
I have two plans to form final curved shape , using a hydraulic press or using a customized rolling machine .
Final products must have no riples .


texts: Determining the Steady Discharge Between Two Reservoirs

texts:
A uniform pipeline, $5km$ in length, $100mm$ in diameter and with a
  roughness size of $0.03mm$, conveys water between two reservoirs.

  The difference in water level between the reservoirs is $50m$.

  In addition to the entry loss of $0.5\frac{v^2}{2g}$, a valve produces
  a head loss of $10\frac{v^2}{2g}$.

  Determine the steady discharge
  between the reservoirs.

I know that the first stage should be to find a value for velocity $v$ using the Colebrook-White Formula:$$v=-2\sqrt{2gDs_{f}}log(\frac{k_{s}}{3.7D}+\frac{2.51u}{D\sqrt{2gDs_{f}}})$$

where $v=$ velocity, $g= 9.81$ m/s, $D=0.1$, $s_{f}=0.01$, $k_{s}=0.03$ x $10^{-3}$ and $u=1$ x $10^{-6}$.

Subbing these values in, I get velocity $v=2.312$ m/s (3 d.p.).

Now I assume I need to sum the entry and head losses $h_{l}$  $$h_{l}=0.5\frac{2.312^2}{2\times 9.81}+10\frac{2.312^2}{2\times 9.81}=2.861m$$

Now adjust $h$ to get $h_{f}=50-2.861=47.139$

Then find a new value for $s_{f}=47.139/5000=9.4278\times 10^{-3}$

And finally recalculate for $v$ using the Colebrook-White Formula:$$v=-2\sqrt{2gDs_{f}}log(\frac{k_{s}}{3.7D}+\frac{2.51u}{D\sqrt{2gDs_{f}}})$$

where $v=$ velocity, $g= 9.81$ m/s, $D=0.1$, $s_{f}=9.4278\times 10^{-3}$, $k_{s}=0.03$ x $10^{-3}$ and $u=1$ x $10^{-6}$.

Subbing these values in, I get velocity $v=2.240$ m/s (3 d.p.).

Now recalculating $$h_{l}=0.5\frac{2.240^2}{2\times 9.81}+10\frac{2.240^2}{2\times 9.81}=2.685m$$

$h_{l}+h_{f}=2.685+47.139=49.82\approx 50m$ which is sufficiently accurate to be acceptable.

Since $Q=vA \implies Q=2.240\times 0.05^{2}\pi=0.01759$ $m^{3}/s$

Have I answered this correctly? Thanks!


texts: I'm working on a small project where an armature is actuated by a servo via a couple feet of tendon. The servo+tendon needs to be able to pull about 5-10 lbs. There will be springs at the endpoints to allow some flexibility and shock absorption, so I don't need the tendon to incorporate much flexibility of its own. What's the appropriate type of wire to use for the tendon? Should I use Nylon? Or stranded steel? I see a lot of projects using tendons, but I don't see much description of what's the best material to use to avoid snapping and breakage.


texts:
I am studying for the FE exam and have come across a question regarding calculating cancer risk.  I'm fairly certain that the answer provided has typos, but I'm not 100% sure.  Here is the question:

A carcinogen is in drinking water at a concentration of 0.01 mg/L.  The cancer risk of 30 years of adult (75 kg) exposure, given a cancer slope factor of 0.80 [mg/(kg*day)]^-1, is most nearly:

I understand that the chronic daily intake equation is CDI = [(Concentration)(Ingestion Rate)(Exposure Frequency)(Exposure Duration)]/[(Body Weight)(Averaging Time)]

Here are my issues with solution provided:

The ingestion rate is 2.3 L/day.  That wasn't given in the question, and the standard ingestion rate anyways given by the EPA is 2 L/day.  How did they come up with this number?  Is it likely just a typo?
For "Averaging Time", they have multiplied 75*365...shouldn't it be 30*365 since the question states that it is 30 years of exposure??


texts:
When an infrastructure project is complete, the professional team has to prepare drawings representing the infrastructure, as it was completed in the end. All on-site changes and deviations from designs are incorporated in these drawings. This is very important particularly to services which are difficult to locate once they have been covered, like pipelines and under ground power lines.

In the past we would mark/label these drawings "as built". Now we have been informed that we should change that to "as recorded", because "as built" implies that the drawings are a perfect representation of what in fact has been built. By using the phrase "as recorded", any liability / responsibility for incorrect drawings becomes unclear.

What is the proper term to use?  And to what extent is the person preparing the "as built" drawings responsible for inaccuracies?


texts: What propulsion method: Franky Zapata hoverboard

texts: Looking for the answer to what kind of engine provides the thrust on the French hoverboard on which its inventor, Franky Zapata, recently crossed the English Channel, I find the same phrase repeated everywhere: it's a "turbine engine". Exactly what is it? A turbojet? A turbofan? A turboprop? It is fuelled by paraffin (kerosene). Is all the thrust produced by propellers in a ducted fan configuration or does exhaust gas contribute?


texts: I want to know the function of counterweights on crankshaft. I heard it is to able the piston to go back up, to repeat the explosion stroke. But doesnt the piston on one cylinder goes back up because the piston in other cylinder is pushed down? This makes the first cylinder go down and up.


texts: How to calculate permittivity for higher frequencies?

texts:
In many books the permittivity of a material is only listed as dielectric constant for one or a couple of frequencies. 1 kHz is used often (for example in the Plastics Technology Handbook, 4th ed, ISBN-13: 978-0-8493-7039-7), but I'm looking for the permittivity for a frequency at least 2000 times higher (2-4 GHz).

How does one calculate the permittivity of a material for a higher frequency? Is the dielectric constant still useful here?


texts: Ansys multiphysics import deformed mesh to HFSS

texts:
I want to run a coupled simulation in Ansys - RF heating and deformation of waveguide. Pictures of project layout and settings are here.

I calculated RF fields and surface losses in HFSS; imported them to steady-state thermal, calculated temperature of the waveguide; calculated structure deformation in static structural. Now what is needed is to run this problem until it converges. But for some reason HSFF does not import calculated deformed mesh from static structural. What else should I do to make it import mesh? Can I then use feedback iterator to automatically recalculate this problem?


texts: What is the distance at which the triangular UDL is acting on in this problem?

texts:
I'm working on the statics problem below:

I'm tasked to draw the shear and bending moment diagram for the frame. I'm trying to work out the reactions and I'm taking the moment about pin E.Here's my working so far:
$$\Sigma M_E=0$$
$$(10)(5)-100-(2*10)(\frac{1}{2}*10+5)+(10)(15)-100-(\frac{30}{\sqrt{2}})+(0.5*5*4)(\frac{1}{3}*5)+A_y(20)=0$$
My question here is, for the triangular UDL, is the distance one-third or two thirds? My lecturer did a similar problem and he said that the distance is two thirds but I don't quite get why it is two thirds. Someone help.


texts:
I want to break a blade as it attempts to cut into a piece of metal.

If the metal in question was vibrating rapidly or with a significant amount of force, would the blade break in attempt to cut through the metal?

Going on, would the same concept work on bolt-cutters, effectively breaking the blade on them?

If metal will not break in this instance, but may bend, would this be an applicable concept if such a vibrating force were used on a bicycle U-Lock in order to combat bolt cutters? In essence, would it be an effective deterrent as far as bending the metal in the bolt cutter blades, rendering it useless against the U-Lock?

I'm tying to think about potential concepts that could be applied to bike locks in order to mitigate potential theft.


texts: Why can't we predict turbulence deterministically?

texts: As far as I've researched, turbulence has a chaotic nature that can't truly be predicted or analyzed. If we took into account all viscous and inertial forces, air resistance, fluid density, etc., why couldn't we predict it?


texts: What is meant by the rotation capacity of a cross section?

texts:
I'm reading about classification of beam cross sections here.
It is said:

The ratio of the ultimate rotation to the yield rotation is called the rotation capacity
of the section. The yield and the plastic moments together with the rotation capacity of
the cross-section are used to classify the sections.

I understand the concept of yield moment, it is the moment at which the extreme fiber of the cross section reaches the yield. But the page also talks about yield rotation. Rotation of what? I understand that we normally measure the rotation of the ends of the beam, but here it is supported rigidly at the ends, so what rotation are we measuring here?
If we thought about a simply supported beam so we could measure the rotation of the end, isn't the yield rotation a property of the beam, rather than the cross section? If the beam is longer, wouldn't the required rotation (to make the critical cross section reach yield) probably be smaller, making the yield rotation dependent on the whole beam rather than just cross section?


texts: Thevenin equivalent impedance in laplace domain

texts: I can't understand why $Z_{th}$ doesn't include $3\ \Omega$ resistance.


texts:
Hello I am hoping someone can share their knowledge I encountered a problem on a recent project at a site I visited. They are encountering enormous amounts of waste copper wire which they are sending away to scrap.

My background is in the mining sector and I wanted to know what the process is to get copper wire into granulated copper and the wire armor and insulation in separate containers.

I know from research that a grinder will break up the cables. My main confusion is within separation of the copper/metals and insulation. Is this achieved used hydrocyclones, magnetic separation, vibration screens or flotation cells (only because a YouTube video appeared to mention this).

Just to confirm I am specifically asking how they separate the different materials as in https://youtu.be/ZKN5MtrY5Cg


texts:
What is the type of and principle of operation of the fitting connector circled in this photo:

There are a few other similar joints depicted.

It looks like this connector is tightened "circumferentially" as a hoop, possibly / probably over the top of the mating flanges of the two fittings. So that makes the fitting ends universal but its not obvious how it would provide reaction against the pressure at the joint.

(Contrast to the bolted flanges just below the circled area - its more obvious that they press the fittings together, maybe with a gasket, which would resist internal pressure forcing the joint apart).

Note: photo snippet from What is this plumbing apparatus?


texts: What is a good method (equation) for locally refining a 1D grid at each end?

texts:
I have a grid that I plan to discretize in 1D. It extends from 0 to L using N nodes, and I need to refine it at each end. I plan to have something that looks as follows:

I have tried the to specify these two parameters:

growth rate (r)
initial node spacing (dx1)

Then the x points are calculated in a series such as the following:

x(i) = dx1 * r ^ x(i-1)

This works fine if I know N, and specify r and dx1. But ideally, I would need r and dx1 to be functions of N to properly scale the grid when N increases. I.e. with N = 10, r should be about 1.7 but when N = 100, r should be about 1.1 to have the same "shape". Similar problem with dx1. Anyone know how to make those two parameters functions of N that will scale with it?


texts:
I am attempting to figure out why a laser layout tool I have is drifting over time. It was designed with a small adjustment mechanism that relies on a spring to apply pressure to a fulcrum that rotates the entire laser. A screw is used to apply and release pressure on the spring thus moving the laser very small amounts left and right.

I am getting a drift in the lasers horizontal position of about 1/2inch at 100 feet over the course of several hours. I am doing this test at night and there is about a 15 degree Fahrenheit temperature from when I start the test to when it is complete.

I made a Sketch-Up model of the device and determined that 5 micron change in position (at the end of the fulcrum) is all it would take to move the laser 1/2 inch at 100ft.

My question is it possible that my spring is expanding and contracting 5 microns with a 15 degree temperature change?

I am not an engineer and am looking for some speculation just to rule in or rule out the general possibility.

The spring looks similar to this:

The diameter of the entire spring is about 1/4 inch. The diameter of the coiled metal wire is about 1/6 inch. The spring length is about 1/2" uncompressed. It consists of about 8 loops.

I do not know the metal it is made of, speculation on different scenarios would be helpful as, again, I'm just trying to rule in or out the possibility.


texts: What is the difference between W, S, I, H sections?

texts: W and H sections look pretty much the same. S and I sections have their flanges rounded. What difference does this rounding make, why would an S-section be used instead of W-section for example?


texts: Difference between the tailboard and boot lid.

texts:
What is difference between the tailboard and the bood lid? Can you show me where each part is?

Thanks for help.


texts: Effect of bad weather on P2P Communication or Broadcasting?

texts:
I stop receiving TV signals whenever their is cloud cover outside. On the other hand I have never had any such problems with my internet connection or GPS system. I cannot understand why and how often (or easily) these different technologies get affected by bad weather conditions.

So my question(s) would be:

How often and why does satellite broadcasting get affected due to weather conditions?
How often and why does point-to-point (using satellites) get affected?
How often and why does point-to-point (using line of sight) get affected?

By how often I mean how much worse weather conditions have to be for communication to be affected.


texts:
I'm trying to run a simulation about crack progation using XFEM.
In particular, I have a 2D case where I'm representing a composite material composed of matrix plus a single fiber. I would like to underline the crack propagation path derived by the difference in toughness between the matrix and the composite.

I'm attaching a figure to better clarify the starting point.

The problem is that, before running the simulation, Abaqus displays the warning "ABAQUS CRACK DOMAIN CONTAINS INVALID ELEMENT SHAPE" and, if i try to run the simulation, the error "ABAQUS SIM DATABASE FILE CANNOT BE OPENED" appears.
I tried to change the mesh geometry as suggested in other topics but nothing changed.

Is this due to the fact that in general this approach can not be used with this type of material with a discontinuity (the fiber) inside?
Actually my real need is to simulate a case with a lot of fibers inside, not just one (see attached picture 2).
Thank you all for the kind attention.


texts: Final temperature of an isolated vessel - Thermodynamics

texts:
8) Consider an inextensible tank of 10 m3 of volume, isolated by an adiabatic
wrap. The tank contains nitrogen at 2 bar and 300 K. This tank is connected to a piping by which more N2 (at 300 K) is added to the tank until the internal pressure reaches 8 bar. At this moment, the admission valve between the tank and the piping is closed.

What is the final system temperature?

(Resposta: T = 381,8 K)

I seriously can't seem to get this answer right. I can calculate the number of mols in the initial state, but how do I calculate the final number of N2 mols (and then the temperature)?

Also, I'm not that used to concept of adding a gas (at 300 K) to more gas at 300 K and the temperature increasing. Can you explain it to me?


texts: How do I calculate the velocity of the piston?

texts:
I have a system with a motor connected to the trapezoidal lead screw. The lead screw is connected to the tube which is connected to the piston. The piston has to pump 1000cc oil against a pressure of 20 bar into the bladder.

Well , first I found out the force on the piston at 200m which is 10054 N. I calculated the torque considering 20 bar+1000 Pa of extra pressure to push the oil into the bladder at 20 bar. The resulting torque was calculated as 12.6 Nm (this seems a lot to me and hence asked the question on this forum).
Once I know the RPM of the motor, I can calculate the piston velocity (using stroke length ,lead and RPM)

Is this approach correct? Am I doing something wrong? If not, then which motor should I use?

Piston diameter: 80 mm
Pitch of the screw: 3mm
Lead angle: ø = 9.38˚
Helix angle: α = 6.8˚
Time to pump the oil into the bladder at 20 bar: 12s ± 3s (This can increase        but I am trying to keep it as low as possible)
The orifice diameter is 17.77mm


texts: Is it possible to determine tip-speed ratio from rotor geometry?

texts: Let's say I have the geometry of the rotor: the number of blades, the airfoils that make up each blade, their position, chord length and their twist angle. Would it be possible to use this information to determine the tip-speed ratio?


texts: What is the difference between NIL and hot embossing?

texts: NIL (Nanoimprint lithography) and hot embossing seem to mean the same thing in many instances. Is hot embossing a subset technique of NIL? Or are they completely different methods?


texts: Infinitesimal Strain Tensor in Cylindrical Coordinates

texts:
How can  I obtain the below formulas of infinitesimal strain in cylindrical coordinates using matrix calculation given the first formula? I find it hard to study them because I still don't know how to derive them.
$$
\epsilon_{ij}=\frac{1}{2}\left(u\otimes\nabla+\nabla\otimes u\right)\\
\,\\
\begin{align}
u\otimes\nabla
&=\begin{bmatrix}u_r\\u_{\vartheta}\\u_z\end{bmatrix}\begin{bmatrix}\dfrac{\partial}{\partial r}&\dfrac{1}{r}\dfrac{\partial}{\partial\vartheta}&\dfrac{\partial}{\partial z}\end{bmatrix}\\\\
&=\begin{bmatrix}\dfrac{\partial U_r}{\partial r}&\dfrac{1}{r}\dfrac{\partial U_r}{\partial\vartheta}&\dfrac{\partial U_r}{\partial z}\\\\\dfrac{\partial U_{\vartheta}}{\partial r}&\dfrac{1}{r}\dfrac{\partial U_{\vartheta}}{\partial\vartheta}&\dfrac{\partial U_{\vartheta}}{\partial z}\\\\\dfrac{\partial U_z}{\partial r}&\dfrac{1}{r}\dfrac{\partial U_z}{\partial\vartheta}&\dfrac{\partial U_z}{\partial z}\end{bmatrix}\end{align}
$$
Above, I show my try in deriving the first part of the tensor, but I didn't know how to derive the second part.
\begin{align}
     \varepsilon_{ij} &= \frac{1}{2} (U_{i,j} + U_{j,i})\\
    \varepsilon_{rr} & = \cfrac{\partial u_r}{\partial r} \\
    \varepsilon_{\theta\theta} & = \cfrac{1}{r}\left(\cfrac{\partial u_\theta}{\partial \theta} + u_r\right) \\
    \varepsilon_{zz} & = \cfrac{\partial u_z}{\partial z} \\
    \varepsilon_{r\theta} & = \cfrac{1}{2}\left(\cfrac{1}{r}\cfrac{\partial u_r}{\partial \theta} + \cfrac{\partial u_\theta}{\partial r}- \cfrac{u_\theta}{r}\right) \\
    \varepsilon_{\theta z} & = \cfrac{1}{2}\left(\cfrac{\partial u_\theta}{\partial z} + \cfrac{1}{r}\cfrac{\partial u_z}{\partial \theta}\right) \\
    \varepsilon_{zr} & = \cfrac{1}{2}\left(\cfrac{\partial u_r}{\partial z} + \cfrac{\partial u_z}{\partial r}\right)
  \end{align}


texts: Why does it take so long to restart a nuclear power plant?

texts:
I have heard a couple of times that an operating nuclear power plant which was shut down (non-emergency; e.g. for a regular check) needs over 24 hours (up to 72 hours?) to get up running again.

Why does it take that long?


texts: Mechanical/electronic chalkboard cleaning device to replace the conventional duster to clean the chalkboard

texts:
The chalk board duster which is used by teachers to wipe the chalkboard seems very agonizing for them. What new mechanical/electronic devices can be devised to replace conventional chalkboard duster which can be easily operated by teachers. Please suggest product design approach for such new cleaning device. Thanks
ps:  I am not allowed to replace chalkboard to whiteboard


texts: How do I calculate the gear ratio to lift a weight at a constant speed?

texts: I have an 80 g·cm motor with a rotational frequency of 15,000 rpm. I want to lift a weight of 2 kg at a speed of 0.5 m/s. How do I calculate the gear ratio required?


texts: How progressive scan televisions works in depth?

texts:
I'm trying to understand in depth the behavior of progressive scan TV monitors (LCD/LED - Digital Television). From what we already know, the tv's screen scans the image row by row (as rolling shutter cameras does), sequentially from top to bottom. However, I would like to know a basic time schedule that can help me answer the following questions:

What is the definition of the duration of the scanning of one row, and how is it related to the response time of the screen?
Does the scanning of one frame happens before the previous frame scan ends? In other words, Does this scanning occurs in an overlapped manner between consecutive frames? Or there is a wait time between consecutive frames, so the screens holds one frame during a short amount of time before starting the transition to the next frame. In this case, what is the definition of that time?.