Physics Forums - Engineering, Comp Sci, & Technology Homework

Phase Diagram Composition Determination

sara06 — Sat, 25 May 2013 01:12:56 GMT

1. The problem statement, all variables and given/known data

Reference the Cu-Zr phase diagram. If you make the alloy CuZr and heat it to 300�C, what percentage of the material will be Cu10Zr7 and what percentage of the material will be CuZr2?

2. Relevant equations

Phase diagram attached.

3. The attempt at a solution

I used the lever rule. I called the alpha phase Cu10Zr7 and the beta phase CuZr2. In terms of atomic percent Zr, I have C0=0.5, Cα=0.41, and Cβ=0.665. Then the atomic percent alpha phase is (Cβ-C0)/(Cβ-Cα) which is 64.7 percent. The atomic percent beta is (C0-Cα)/(Cβ-Cα) which is 35.3 percent. So I have 64.7% Cu10Zr7 and 35.3% CuZr2.

Attached Images

Cu-Zr.jpg (69.5 KB)

Thermodynamics polytropic processes and work for them

mihalj — Fri, 24 May 2013 23:54:00 GMT

Hi, something is a bit confusing in regards to polytropic processes.Can anyone explain why boundary work in closed system for compressor is calculated as W = ∫pdV and polytropic process after integration is generally W = -(p2V2 - p1V1)/(1-n)...(numbers behind p and V are subscripts)...
When we talk about control volume, internally reversible process (isn't above one also reversible???) then work is defined as W = -∫Vdp and for polytropic process for compressor work is defined as W = -n*(p2V2-p1V1)/(n-1).
When I am supposed to use one way of calculation and when other? The results are not same. Aren't they same type of group as control volume compressor should behave during the process of compression as closed system (there is no constant add or removal of mass during compression).
Thanks in advance!

Determine the bending of a bar

Firben — Fri, 24 May 2013 16:09:06 GMT

1. The problem statement, all variables and given/known data
Hello, i have problem with the following:
Determine the bending of the free end of an adjacent bar. The bar have flexural rigidity EI

Picture:
http://s716.photobucket.com/user/Pit...tml?sort=3&o=0

2. Relevant equations

q = -dt/dx = -d^2M/dx^2 = d^2/dx^2(EI*d^2w/dx^2)

3. The attempt at a solution

x = 0; w = 0, d2/dx = 0
x = l, T=0, M=M0

I integrated 4 times and putted in those initialvalues but it didn't get my the correct answer.

The answer should be w = PL^3/(3EI)

Finding max force from (1 dimensional) energy curve as function of tim

sciencerocks — Fri, 24 May 2013 04:31:34 GMT

1. The problem statement, all variables and given/known data

Hi guys,

I just wanted to confirm I am doing this right. I have a graph of energy (Joules) vs. time (seconds). I need to get the force from this information. If I know the linear distance the object has traveled, can I use the work equation W= Force* Distance, and solve for force. Also I know this will give me average force, How do I find maximum force.

Thank you

2. Relevant equations

W=FD

3. The attempt at a solution

Integrate the curve to find the total energy, then use the formula above to find the force since I already know the distance, however this will only give me average force.

Circuit Analysis via Laplace Transforms :yuck:

Kevin2341 — Fri, 24 May 2013 03:22:54 GMT

Hi there, I have my final in my circuit analysis class tomorrow morning(at a community college, it feels like two semesters worth of content was covered in 18 weeks). Last week, the teacher went over LaPlace Transform analysis rather quickly, and then onto basic digital logic. I do not understand either topic, digital logic is a little more simple to understand.

does anyone have any online reading or good tutorial videos on this? I looked on youtube for it, but I didn't see any very helpful videos, they just started from the beginning and didn't give any context of where this stuff was coming from. My book is EXTREMELY vague. Absolutely no examples at all. My teacher did half of an example in class, and no one in my class understands what the heck is going on. I learned Laplace transforms in my differential equations class, and I understood it. But this stuff that we are asked to do now looks like poorly written Japanese in a Russian grammatical structure that is spoken with a heavy African accent to me.

(here is the fun part, as far as I know, not a single soul in my class understands it, as I talked with a good majority of them today, and no one knows what the hell to do!)

Is this textbook example incorrect?

kl055 — Fri, 24 May 2013 01:28:28 GMT

1. The problem statement, all variables and given/known data

2. Relevant equations

I got 4.5*10^22 /m^3 using the exact numbers that they used...

which gives 4.5*10^16 /cm^3

Is there some intermediate step which was not shown? ie. the numerical answer given by the equation is in some other unit which was converted to /m^3?
3. The attempt at a solution

Monte Carlo Python Plotting Question

clope023 — Thu, 23 May 2013 16:05:26 GMT

If this is better served in a section like Nuclear Engineering please let me know.

The problem statement, all variables and given/known data

Simulate the projection of a radiation source onto the plane of a collimated detector. Check if said projection is circular.

The attempt at a solution

What I want to do is create a list of vector objects that will be 'moved' from their initial position to the final position at the plane of the detector. The source point is at the origin. The collimator entrance is 2mm (in the y-direction) away and the detector plane is 4mm (in the y-direction) away.
I want the final position of the vectors to be randomly distributed in the plane and check if the x and z elements of those vectors satisfy the equation of the circle with the radius of that circle being the radius of the circular collimator and then plot those positions. I want to be using vpython's vector class for some of the vector operations though if simple nested lists are just as good I will use those too. This is the code I have so far.

import numpy as np
import random
import matplotlib.pyplot as plt
from visual import vector
r = 2.5 #radius of collimator in mm
l = 50.8 #length of collimator in mm
n = 1000 #number of test points
lst = []
for i in range(n):
lst.append(vector(0,0,0)) #creates 1000 vectors at the origin
lst1 = []
rr = r*random.random()
for j in lst:
lst1.append(j + vector(rr, l, rr))
def toList(v):
return [v.x, v.y, v.z] #returns the components of the vector and places them in a list
lst2 = []
for k in lst1:
lst2.append(toList(k)) #places those list of vector components into another list
lst3 = []
for u in lst2:
lst3.append(u.pop())
# pop function removes and returns the last element in the list

At this point I have a list filled with a 1000 3 element lists, and I want to organize the x (0th elements) and z (2nd elements) components and put them in a 2d plot and then check if they satisfy the equation of the circle like so:

plt.plot(x,z,'o')
plt.show()
lst4 = []
lst5 = []
for v in lst3:
if v[0]**2 + v[2]**2 <= r**2:
lst4.append(v)
if v[0]**2 + v[2]**2 > r**2:
lst5.append(v)

So right now this where my logic takes me, am I on the right track? Are my commands right to do what I want to do? I appreciate any and all help, thanks very much.

full adder circuit using NAND v NOT, AND, OR v PLA logic

Bourbon daddy — Thu, 23 May 2013 12:18:47 GMT

I have designed a full adder circuit, first of all implementing NOT, AND, OR logic, then redesigned NAND logic and finally Programmable Logic Array.

I would like to talk evaluate my designs a little and need a bit of help.

When using NOT, AND, OR gates I used the following;

NOT x 3 = 1 chip
AND x 11 = 3 chips
OR x 5 = 2 chips

Total 6 chips required

Using NAND Logic, I think I originally used 40 NAND gates, but reduced it to 26, so 7 chips would be required.

PLA:

NOT x 3 = 1 chip
AND x 7 = 2 chips
OR x 2 = 1 chip

Total 4 chips required.

Obviously, PLA offers the best solution for this scenario regarding efficiency, cost, speed and reliability.

I was wondering if using just one type of chip, such as the NAND offers any benefits to using various types of chip(NOT, AND and OR). If not, am I right in thinking that in this situation, using NAND logic offers no benefits to this circuit over NOT, AND, OR logic.

Regards

Moment of a Couple, need help making sure answer is reasonable

torchflame — Thu, 23 May 2013 03:45:28 GMT

1. The problem statement, all variables and given/known data
Given the following structure, determine the value of F such that the resultant couple moment on the structure is 200 pound-feet clockwise.

I'm not looking for help here per se, just if this is a valid method of solution:
Because the moment of a couple is a free vector, it seems to me that the moments of the two couples can be placed at point B without any problem.
Then it would also make sense to me that: [itex]M_{\text{couple with F}}=F\cdot 2\sqrt{2}[/itex] pound-feet clockwise, and [itex]M_{\text{150 lb couple}}=600\sqrt{2}[/itex] pound-feet counterclockwise, which gives me that [itex]F\cdot 2\sqrt{2}-600\sqrt{2}=-200[/itex], which implies that [itex]F=229 \text{ lb}[/itex].
Is this a valid method of solution? It makes sense to me, but I'm not sure if it makes sense to anyone else.

probability with a normalized wave function

mreff555 — Thu, 23 May 2013 02:19:07 GMT

1. The problem statement, all variables and given/known data
So I have this normalized wave function

psi=sqrt(2/a) * sin^2(pi*x/a)

with limits of 0 and a.

I'm supposed to find the probability for a bunch of points if this form:

p(x=0.00a,x=0.002a)

2. Relevant equations

P(a,b)=int(psi^2)dx

3. The attempt at a solution

So, partially solving the integral, I'm stuck here:

(2/a) * [ (x/2) - (a/4pi) * sin(2*pi*x/a) ] between 0 and a

My first question. If I continue to solve the definate integral P=1. This is appearently not the correct answer. I know my calculus is right and I've verified it in wolfram alpha and octave.

Once I figure out how to proceed I need to plug in these values which have a in them, not really sure how that is going to work out either.

Any suggestions?

How to calculate the diameter of a hydrocyclone?

Naicker2013 — Wed, 22 May 2013 22:40:36 GMT

A cyclone manufacturer provides a 2 inch diameter cyclone with an imperfection of 0.2
For a slurry of the size distribution listed below which is to have a cut-point of 200um, what will be the size distribution of the overflow product and the percentage feed solids to the overflow in the ideal situation?

I don't want the answer to that question. I want to know about the "2inch diameter cyclone". How do you work out the diameter of a hydrocyclone in general?

One shaft model

simlar — Wed, 22 May 2013 14:59:47 GMT

1. The problem statement, all variables and given/known data

Develop a one shaft model of a geared system if the moments of inertia of the gear elements are included.
The geared system consists of two discs with inertia J1 and J2 and rotation θ1 (anticlockwise) and θ4 (clockwise). The discs are connected by two shafts with stiffness K1 and K2 respectively. The shafts are connected by two gears with inertia J3 and J4, rotation θ2 (anticlockwise) and θ3 (clockwise) and radii r1 and r2.

2. Relevant equations

-The time derivative of the angular momentum is equal to the sum of torque acting on the body.

-Equation of motion with constant moment of inertia:

J[itex]\ddot{θ}[/itex]+Kθ=0

No slipping in the gear:

θ3=nθ2

n=r1/r2

3. The attempt at a solution

My strategy was to reduce the system to a system with only two degrees of freedom by some manipulation of the equations of motion.

The assumption was made that:

θ1≤θ2≤θ3≤θ4

I tried to make a one shaft model as I would have done in the case with massless gears. I constructed the equations of motion, from the FBD, for the geared system like this:

J1[itex]\ddot{θ}[/itex]1=K1(θ2-θ1)
J2[itex]\ddot{θ}[/itex]4=-K2(θ4-θ3)

Then I assumed that the gears move without slipping:

θ3=nθ2

n=r1/r2

To deal with the last degree of freedom I made a FBD for the gear, including contact forces and moments. I tried to include the inertia forces at this stage by assuming them have opposite direction to defined positive direction of rotation. From the FBD I got:

M1=F*r1-J3[itex]\ddot{θ}[/itex]2=K2(θ2-θ1)

M2=F*r2+J4[itex]\ddot{θ}[/itex]3=K2(θ4-nθ2)

where M1 is the torque in the first shaft and M2 is the torque in the second shaft.

Then I eliminated F from the above equations and found an expression for θ2.

But this is where I run in to trouble. At this stage in the massless gear problem there are only two degrees of freedom left and the system can be written as a single shaft model. But now there will be additional degrees of freedom from the gears, namely: [itex]\ddot{θ}[/itex]2 and [itex]\ddot{θ}[/itex]3.

I thought that one possibility could be to use the transmission ratio on the angular accelerations as well. But there would still be one degree of freedom to take care about after doing this.

What can be done to develop a one shaft model of the problem. Please let me know if I did any fundamental errors or if I'm on the right track.
Any help is greatly appreciated!

Solving for Vo in terms of Vs/Vx

eatsleep — Wed, 22 May 2013 11:28:31 GMT

http://imgur.com/xe52P30

2. Vx= Vs(R1/R1+R2), V=IR

3. I combined the 1k Ω and 5k Ω resistors then used voltage division to find Vx. I used Vx to find Vo which I found to be (5/18)Vx. I dont know where I can do KCL or KVL to solve for Vx.

incident question -- historical event with lack of ethics

k31453 — Wed, 22 May 2013 11:12:16 GMT

I have to Write a report outlining an historical event in which a lack of ethics has caused the injury or loss of life. You
should discuss the issues with reference to the Engineers Australia code of ethics.

i cant find any events !!! an any body help me out ?

RISC CPU question

fran1942 — Wed, 22 May 2013 06:32:57 GMT

Hello, I am having some trouble with the following set of questions.
I include them along with my answers.
Would anyone be able to confirm if I am correct here ?
Thanks kindly for any help.

Suppose a RISC machine uses overlapping register windows for passing parameters between procedures. The machine has 298 registers, and each register window has 22 registers, of which 10 are global registers and 10 are local registers. Answer the following:

a) How many registers would be available for use by input parameters?
My attempted answer: 1

b) How many registers would be available for use by output parameters?
My attempted answer: 1

c) How many register windows would be available for use?
My attempted answer: 13

d) By how much would the current window pointer (CWP) be incremented at each procedure call ?
My attempted answer: By 12.