# All Questions

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### “Transport Phenomena” (Bird, Stewart, Lightfoot) difference between edition 1 and 2 [closed]

What is the difference between Transport Phenomena first edition (1979) and second edition (2002)? Which one do you recommend to be bought, taking into account that I am a student and that the first ...
259 views

### Which type of Turbine (Pelton, Francis, etc.) is most suitable to be driven by high velocity forced-air jet?

Which type of turbine (Pelton, Kaplan, Francis, etc.) would be suitable and deliver the best efficiency when driven by a high velocity forced air jet of 125-200 mph through a nozzle of 2-2.5 inches ...
444 views

140 views

### Problem in an axial turbine

I am simulating an known as , using CFX as a solver. This turbine have 8 blades((360/8)=45 deg=pitch angle). Due to the circumferential symmetry, only one eight of the annulus has been computed, ...
140 views

### From strain to displacement in 3d

I got a question thats been bugging me for a while: Say that you're given a straight square beam (say one meter long), and you attach three strain gauges on each face. One at 0 degrees, one at 45 ...
160 views

### Virtual Work - Determining Relationships in deflections

I'm having problems understanding the worked answer for this problem: Here's part of the worked answer: I don't understand why $\delta_C = \dfrac{4}{9} \delta_A$ . Can you please explain that part ...
60 views

### Uniform values from different MEMS 3-axis accelerometers

I have to find a solution to uniform values on 3-axis accelerometers on different android devices. I mean, a device with a specific accelerometer, under the same acceleration, give me values for 3 ...
501 views

### Center of Pressure Line from Barefoot Scan (EMED)

I have raw data obtained from EMED barefoot scan containing a matrix of pressure sensors over about 70 frames. This totals 70 matrices that record a snapshot of the pressure over the duration of a ...
130 views

### Can somebody explain how this equation(based on conservation of mass of a fluid) came about?

This is taken from Versteeg and Malalasekhara CFD book. δx, δy, and δz are given as the dimensions of the sides of the fluid element under consideration along the three axes respectively. On the ...
116 views

### What could be the downsides of leaving twist-off bolt splines in the interior of exterior columns?

I have a project where the contractor is using ASTM F1852 Tension Control (twist-off) bolts. The project is outdoors and uses weathering steel and weathering fasteners. The main members are hollow ...
931 views

### Determine the range of values for a PI controller

This is a basic control theory question, since Control Theory is a part of applied mathematics but also of engineering I was unsure whether to ask this here. The question says: Given the transfer ...
2k views

### ANSYS Workbench/Mechanical: Automatically export chart?

I'm running a simple tensile test simulation for a single element. Under Results I made a Chart object with Stress vs Strain, which can be manually exported to a csv file by right clicking on the ...
947 views

### Why are creeks sometimes piped underground in urban areas?

I live in Melbourne, Australia and a lot of the creeks here have been diverted through underground storm water pipes. I guessed that this is because land is highly sought after for development, and a ...
544 views

### What is a non-equilibrium boundary layer?

I studied a manual of Ansys CFX about turbulence models and I came across the term "non equilibrium boundary layer". What does this term mean?
913 views

### Flow velocity in exhaust chimney - typical design value

I'm looking at a project where stationary CHP engines will be replaced, leaving as much of the infrastructure in place as possible. Current exhaust velocity in the chimney is ~42m/s and it will be a ...
121 views

### How can I get a quick 2B shine on grade 316 stainless steel?

I have a stainless steel (316) 2B finish strip. I tried buffing the material for a shiny surface but it takes lot of time to finish my production. So, I want to know if there is any chemical ...
63 views

### How does non-electrical ATEX apply to springs?

This question relates to the ATEX directive, which is the European regulation governing the design of products to be used in explosive atmospheres. In particular, I am asking about the part relating ...
294 views

### What is this kind of X-Y motorized system?

I'm wondering what the technical name is for this kind of stepper-motorized arrangement (a positioning system? an XY table?)? What is it typically used for? It appears to have two steppers as ...
39 views

### Analog addressing flat panel display

Cathode ray tubes (CRT) are analog addressing displays because you can light a point on its surface applying a continuous electric or magnetic field to deflect electrons beam. Virtually, there is no ...
1k views

### Arranging members within a truss efficiently

A wide variety of trusses exist for bridges and roofs. There are many different permutations when it comes to arranging the internal truss members. Depending on the direction, a diagonal member may be ...
233 views

### Measuring the distance to an object with RF resonance

Assume I put an RF antenna in front of an object (typically the face of someone sitting in a chair, so able to move about +/- 10cm in all directions) at a typical distance of 1m. If I consider the ...
107 views

### Schematic Reading - Fluid Control Limit Switch Question

Does limit switch LS1 remain pressed on until the piston moves to LS2?
1k views

### Increase static pressure

I have an application (a tube with parts in it) which needs a certain static pressure in it in order to contain a sustainable air flow. Unfortunately the fan I wanted to use in a push-configuration is ...
603 views

### Frame/truss problem with sliding joint

I'm supposed to be finding the reaction forces first but from the FBD of the entire truss where am I supposed to start. If I take the moment at A then I get 3 unknowns at Bx Dy and Dx. If I get the ...
1k views

Hi, I'm having some problems with this truss question that I have in my homework. So far this is my solutions. I worked out my solutions to the reaction forces but don't know if they're correct. The ...
141 views

### Crushing drink cans

I have a 15 pound weight that I use to crush 8.4 oz red bull cans. A metal barbell with a handle and 2 ends. Not 100% flat ends, but close to flat. About 12 inches from end to end. I hold the barbell ...
38k views

### How to determine the characteristic length in reynolds number calculations in general?

I understand that the reynolds number is given by the expression $Re=\frac{\rho v L}{\mu}$, where $\rho$ is the density, $v$ is the fluid velocity and $\mu$ is the dynamic viscosity. For any given ...
481 views

### What is the difference between being UL recognized and being UL listed?

A product can be UL recognized or UL listed. I understand that there is some difference between these two things, but I have never had a full and clear explanation of the difference. What is, in fact, ...
64 views

### Find optimal configuration for Stirling Engine

I'm trying to figure out the theoretical calculations for a Stirling Engine system so I can determine optimal piston size, optimal piston displacement and number of pistons. I want to calculate which ...
129 views

### Is there a way to obtain a circuit of some sort given a Nyquist plot?

I have some transfer functions and I was wondering if it would be possible to approximate this to an electric circuit equivalent. For example, given the Nyquist plot below, is it acceptable to ...
141 views

### How do I interpret the curing pressure of a composite from this data sheet?

A question asked about the necessary curing pressures for a composite resin in the autoclave. Looking through the corresponding datasheet (HexPly F155), I'm confused: Cure Procedure Apply ...
712 views

### How can I finish a round hole so it has 90 degree corners (flat bottom)?

I have a 10 mm depth x 5 cm length 99% Tungsten rod. How can I machine the described hole so that instead of having a bevel from the tip of the main drill-hole bit, it has a perfect 90 degree corner ...
150 views

### How do I determine plate thickness and anchor size for a 10-ton span supported by synthetic rope?

I am supporting 25,448 pounds over a series of cables, spaced 20' apart, over a span of approximately 424', left to right. The load is mostly in an area of the middle 10' of the span. I am using ...
52 views

### If my electronics are outdoors in a ventillated NEMA 4 enclosure, should I conformal coat my circuit boards?

I'm considering putting a circuit board in a ventilated NEMA 4 enclosure outdoors. I'm a little concerned about humidity and condensation inside the enclosure. Do I need to conformal coat my circuit ...
124 views

### How did Al-jazary's “castle clock” work?

My question is what are the ideas behind the complicated historical water clocks. According to wikipedia, modern versions of the historical water clock rely on the principle of the syphon. So I ask ...
453 views

### Gas cleaning in activated carbon filters - How much moisture is needed and why?

Biogas and sewage (typically around 60% CH4, rest CO2) gas is typically treated in activated carbon (ac) filters to remove H2S and siloxanes. The ac filters need a small amount of oxygen (>0,4%) to ...
881 views

### What screw for 2.0 mm plastic hole in housing

I'm thinking about using the Bopla UM 32009 housing for my product. It has little standoffs for attaching PCBs. These standoffs are made of plastic, and seem to be drilled (or molded?) to a diameter ...
347 views

### What is the accuracy of direct metal laser sintering (DMLS)?

They've printed jet engines with it that work after polishing. So how is the accuracy measured and how accurate is the DMLS process? I can't find the required info anywhere.
127 views

### What's the smallest pin-like hole I can machine into a piece of tungsten using a metal lathe and common carbide tools?

I am going to machine something out of a small 40mm long x 8mm diam tungsten rod. The majority will be hollowed out using a larger bit, but at the very tip, I need a small hole, the smaller the ...
6k views

### Is inviscid flow necessarily turbulent?

The Reynolds Number is defined as $Re = \frac{\rho v L}{\mu}$, where $\rho$ is the density, $v$ is the fluid velocity, $L$ is the characteristic length, and $\mu$ is the dynamic viscosity. By ...
206 views

### How to move a thin metal piece with a tiny string or anything else?

Recently I was experimenting with a metal piece, and I came across a challenge. A small piece of thin copper metal (5cm x 3cm x 0.2 cm) has to be pushed forward and to be rotated. The problem is how ...
798 views

### How do I calculate rolling resistance for tire on pavement?

First condition assuming perfect rolling, no slip, from what I understand is that the rolling resistance coefficient can be calculated as the displacement arm of the normal force the tire "feels", in ...
474 views

### BER peroformance of MPSK and MQAM in Rayleigh fading channel

I have a question regarding bit error rate (BER) performance over the Rayleigh channel. I observed BER performance over the AWGN channel using Simulink in MATLAB. I used to change the "SNR" parameter ...
4k views

### Difference between continuous wave laser and a pulsed laser

I understand the difference between the two in terms of how they function; one will release all of it's energy in small pulses with the other creates a constant stream of radiation. My question is ...
558 views

I am having trouble to calculate the differential equations of a simplified loading bridge. The system is build as shown in the picture below (just a sketch): If I use the Newton approach, I am ...

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