Transitioning from Software Development to Engineering

Hello.



I graduated 1.5 years ago with a major in Computer Engineering. I have been programming since I was a young child so it seemed very natural for me to go into software development. Throughout my undergrad I focused on the easiest path to me (computer science classes were a breeze) while doing decently well in my engineering classes (electronics, digital systems, dynamics, mechanics of materials.) The engineering classes seemed very difficult.



During my internships I worked at huge engineering organizations (NASA, Lockheed, my school robotics lab) but I was always doing mostly software (C++, Java/Android, and C#.NET). My current job is as a web developer at a startup where I am about as far from hardware as I can get.



I don't see myself as much of a true "engineer", but more of an embedded software developer. I programmed the microcontroller (an Atmel XMEGA) for senior design and had a lot of fun. I loved writing low level routines for electronic devices like motor controllers, sensors and LCD screens. But I felt like I was at such a "hobbyist" level that I wasn't qualified for a real "embedded job".



I've never had the title "embedded engineer" and all I know is how to program a few very simple microcontrollers. What do I need to learn to be a well rounded "embedded software engineer"? Would a second degree that teaches me more about hardware and mechanics be helpful? Do I need to improve my CAD skills? Or should I be compiling linux kernels and writing device drivers for that? I just don't really know WHAT skills I would need or how to get them.

Indefinite integral problem

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



Evaluate the indefinite integral of x*cos(3x)^2



2. Relevant equations



Integration by parts: [itex]\int(udv)[/itex]= uv - [itex]\int(vdu)[/itex]



3. The attempt at a solution



Im having trouble finding the antiderivative of cos(3x)^2 (which I designated as dv when doing integration by parts). I keep getting (1/9)(sin(3x)^3) using the power and chain rules, but that's not correct.



Thanks!

Angular momentum vector

A bicycle is traveling North. The direction of the angular momentum vector of it's front wheel is?



I chose "North." The answer is West. Why?

thanks

Random question about cones and cylinders volume

A cone's volume with height ##x## and radius ##y## is ##1/3## of the volume of a cylinder with height ##x## and radius ##y##.I was trying to visualize it in my head and struggled a bit.Take a rectangle triangle with height ##x## and the other side of lenght ##y## which isn't the hypothenuse , then you get the cone if you rotates the triangle such that the two corners forming height ##x## rotates on themselves at the center , and you get the the rest of the cylinder if you rotates (from the same center) the triangle that would form a rectangle with the initial rectangle triangle.This means a rotation of a rectangle triangle where only one corner is rotating on itself at the center covers 2 times the volume of a rectangle triangle rotating such that two corners rotate on themselves at the center.



(Obviously I assume the triangle is filling the volume anywhere it goes during the rotation and I assume the rotation is complete)



So at the center of the rotation , in the first exemple constructing the cone the side ##x## is only "filling" the volume at the very center while it's filling all the curved area of the cylinder in the second exemple.I'm not exactly sure what I'm trying to accomplish here but I guess putting more rigor on this phenomenon in my mind would be a good start.



Any help?



thanks

k space sum to integral

How is it exactly i convert between a k-space sum an integral?

Assume that we have some macroscopic solid. Periodic boundary conditions leads to kx,ky,kz = 2π/L, so each k-space state fills a volume (2π/L)³ or has a density of V/(2π)³. To then count for instance the number of state with wavevector k<k0, what do you then do?

Intuitively I would multiply the volume of a cube of radius k0, but how does this translate into an integral exactly?

Harmonic Motion of Oscillating Particle

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

A particle moves along the x axis. It is moving initially at the position 0.280 m, moving with velocity 0.200 m/s and acceleration -0.450 m/s^2. Suppose it moves with constant acceleration for 4.10 s.





(a) Find the position of the particle after this time.



(b) Find its velocity at the end of this time interval.



We take the same particle and give it the same initial conditions as before. Instead of having a constant acceleration, it oscillates in simple harmonic motion for 4.10 s around the equilibrium position x = 0.

(c) Find the angular frequency of the oscillation. Hint: in SHM, a is proportional to x.



(d) Find the amplitude of the oscillation. Hint: use conservation of energy.



(e) Find its phase constant 0 if cosine is used for the equation of motion. Hint: when taking the inverse of a trig function, there are always two angles but your calculator will tell you only one and you must decide which of the two angles you need.



(f) Find its position after it oscillates for 4.10 s.



(g) Find its velocity at the end of this 4.10 s time interval.



2. Relevant equations

x(t) = A cos(wt + phi)

w = sqrt(k/m)

v = dx/dt = -w Asin(wt + phi)

Vmax = w A = sqrt(k/m) A

a = d^2x/dt^2 = -w^2 Acos(wt + phi)

T = 2pi sqrt(m/k)

f = 1/T

w = 2pi f







3. The attempt at a solution

found a to be -2.68 m

found b to be -1.65 m/s

can't figure out c-g please help :(

Can this diagram make any sense? [counts of alpha decay]

Hello all you physics folks,



this is my first post, so if I screw this up, go easy on me :)



Here's the problem I'm working on and that I simply can't get my head wrapped around:



I have a table of 10 values of counts per second (cps) of alpha decay of Americium-241, depending on the pressure ##p## inside a chamber, where at a distance of ##x_0 = 6## cm a detector is mounted.



I have to plot the cps...but not against the pressure, but a distance corresponding to that pressure at normal pressure levels (##p = 1 bar##). I am to use Boyle-Marriots law

$$

p \cdot V = p \cdot A \cdot x = const.

$$



Since the cross-section of the chamber ##A## can be considered constant, we have

$$

p \cdot x = const.

$$



But this means that for decreasing pressure the distances get longer (that makes sense), but when I plot ##p_i## vs ##x_i##, I get an increasing cps count for longer distances, which is pretty much the opposite of what we'd want...any idea where I made a mistake here? Do I have to modify the cps counts in any way?

LED/Photodiode advice

I am currently doing a university project looking into potentially energy saving ideas. The project has a 'novel' element to it, in that ideas don't have to be "new", but for example you can take an idea and apply it to a new environment.



I am looking specifically into lighting (as most do) and am trying to build on the idea of "intelligent street lighting" (see http://www.tvilight.com).

I was wondering if it would be possible to set up a photodiode/LED combination in the same unit, so that in one state it acts as photodiode, in the other as a light source.



Major problem I soon encountered (if it to be possible) was getting it from light source back to photodiode. The converse I believe could be triggered when the light received by photodiode fell below a critical level. This would not be possible for light source back to photodiode without another additional application (perhaps IR sensor?).



Any help is greatly appreciated.

How to calculate Fourier Transform of e^-a*|t|?

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

Calculate (from the definition, no tables allowed) the Fourier Transform of [itex]e^{-a*|t|}[/itex], where a > 0.



2. Relevant equations



Fourier Transform:



[itex]G(f) = \int_{-\infty}^{\infty} g(t)e^{-j\omega t} dt[/itex]



3. The attempt at a solution



I thought I'd break up the problem into the two cases of t (where it's negative and positive). However, when I calculated the portion where t > 0, I got:



[itex]

G(f) = \int_{0}^{\infty} e^{-at} e^{-j\omega t}dt = G(f) = \int_{0}^{\infty} e^{-(j\omega + a)t}dt = \frac{e^{-(j\omega + a)t}}{-(j\omega + a)}\bigg|_0^\infty = 0 - \frac{1}{-(j\omega + a)} = \frac{1}{j\omega + a}

[/itex]



Which is nowhere close to what WolframAlpha says the answer should be:



http://ift.tt/1mrJrHi



So I guess I'm confused on how I should even approach the problem. Any suggestions?

Quick ring question

Is (-x) * y = x * (-y) true for all rings?



It seems simple enough but I feel like * must be commutative when trying to prove this.

Not sure about finding velocity with this equation.

I need to find velocity when force, distance, and mass are known.

I found this equation: Fd = (M/2)V^2



The process to solve it is put forth by using the metric system. It would be a great help to know if (and how) I can use the imperial system only with this equation.



I'd like to take you through the process put forth, to hopefully reveal to you where I'm faltering.



-----------------------------------



"Step ONE: Weigh the object to find Mass. All other resistance, such as bearing resistance, being negligible, is not accounted for here; and so the WORK done on the object equals its KINETIC ENERGY. If grams, convert to Kg by dividing by 1,000. If pounds, convert to Kg by multiplying by .45"



> I have a disc that weighs .8 oz, which converts to .02268 Kg



-----------------------------------



"Step TWO: Set equations for WORK and KINETIC ENERGY so they are equal.

WORK = FORCE x DISTANCE; KINETIC ENERGY = 1/2 the MASS of the object x its VELOCITY squared.

That is: F x D = (M/2) X V^2.

Enter measurements for FORCE, DISTANCE and MASS.

Example: FORCE = 2 Newtons, DISTANCE = 5 meters, MASS = 0.7kg.

Therefore: (2 N) x (5 m) = (0.7kg/2) x v^2 "



> I converted oz to kg above for "M".

> Next, I have .3 lbs of force being applied to the disc. (The disc, by the way, is a motor rotor and the force applied is the repelling force via interaction between the rotor magnet and the stator's electromagnet...) So I need to convert .3 lbs to Newtons. 1 lbf = 4.448 N, so .3 lbs = 1.3344 Newtons.

> Next, for distance I'm assuming it's the circumference of the disc. A 2.365" diameter disc x Pi = 7.428465" circumference. Seems logical now to convert inches to metric, to keep with the metric equation. 1" = .0254m, so 7.428465" x .0254m = .188683011 m



My numbers so far: (1.3344 N) x (.188683011 m) = (.02268 kg/2) x v^2



More confusion sets in, whereby this equation is for figuring velocity linearly, not radially (as I need it to be). Therefore, at the end I attach the resolve for converting m/s to RPM, which involves finding the circumference, which I just did in step TWO, and is why I'm not sure about this equation altogether. But I keep on with it....



-----------------------------------



"Step THREE: Multiply and divide to simplify the equation.

Example: (2 N)*(5 m) = (0.7 kg/2)*v^2

becomes 10 N*m = (0.35 kg)*v^2."



My numbers: (1.3344 N) x (.188683011 m) = (.02268 kg/2) x v^2

becomes .251779 N*m = (.01134 kg) x v^2



-----------------------------------



"Step FOUR: Divide the left side of the equation by the number on the right side of the equation to isolate v^2.

Example: 10 N*m = (0.35 kg)*v^2

becomes 28.6 N*m/kg = v^2."



My numbers: .251779 N*m = (.01134 kg) x v^2

becomes 22.2027.. N*m/kg = v^2



-----------------------------------



"Step FIVE: Take the square root of the number on the left side of the equation to find the velocity.

Example: 28.6 N*m/kg = v^2

The square root of 28.6 equals 5.3, so the velocity is 5.3 m/s."



My numbers: 22.2027.. N*m/kg = v^2

Square root of 22.20273.. = 4.71197.. m/s



-----------------------------------



Now, for converting meters per second to RPM: RPM = V/(Pi*D).



RPM = 4.71197.. / 7.428465"



RPM = .634313..



?????????????



Quite exhausting.

Any help on the matter, I am truly grateful.

Modern debates in evolution?

Google keeps giving me stuff about evolution vs creationism, but I'm curious about what debates are currently going on within the scientific community. Are there still things about evolution that scientists don't understand or agree upon? Links/sources would be greatly appreciated!

Entanglement and Simultaneity

Instantaneous action-at-a-distance (which is how we explain quantum entanglement) implies event-simultaneity, but we know (from SR) that an observer's "now" is dependent upon their velocity/reference frame.



Imagine that we have two observers, Scott and Sean, and two entangled particles. Scott and the two particles are onboard a starship while Sean is inside a nearby space station. Scott and the two entangled particles aboard the starship are moving through space at 99% of c, while Sean's space station is in a low geosynchronous orbit around the Earth (moving only slightly faster than the Earth's rotational speed; i.e., nowhere near c). Scott's starship quickly flies past Sean's space station. As they fly past each other, Scott remains at rest relative to the entangled particles, but Sean is in motion (at near light speed) relative to the entangled particles. As Scott flies past Sean, Scott checks the spin of one of the entangled particles, thereby "instantaneously" determining the spin of its entangled partner-particle, and Sean witnesses the events during the fly-by. Does the action-at-a-distance between the two entangled particles appear to be instantaneous to BOTH Scott AND Sean?

semiconductor diode (graph quesiton)

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





The current-voltage characteristic curve of a semiconductor diode as a function of temperature T is given by the equation: ##I = I_0(e^{|e|\Delta V / k_BT}-1)##

where e is the base of the natural logarithm.

|e| is the charge of an electron

k_B is the boltzmann's constant

and T is the absolute temperature.



Set up a spreadsheet to calculate I and R = ΔV/I for V = 0.400V to 0.600V at 0.005 V increments. Assume I_0 = 1.00nA. Scatterplot R versus ΔV for T = 280K, 300K, 320 K. Plot the temperatures.



2. Relevant equations



see above

3. The attempt at a solution



I don't get how you can set up a spreadsheet to calculate I….aren't we missing the value of T?

And if "T" is suppose to be the absolute temperature, wouldn't it be 0 K making the fraction undefined?

Help understanding the Friedmann equations?

Hello! I'm a senior at San Francisco State University, and I'm currently enrolled in a cosmology class. It's a GWAR class, meaning General Writing Assessment Requirement- I didn't expect much math. In fact, the first half of the class was basically an anthropology course, which is more in line with my interests. I was surprised when, come the second half of the coures, the 'paper' I was supposed to write was a long math explanation. I've taken three years worth of calculus plus a course on linear algebra and differential equations, so the math isn't what's difficult for me here. I believe my problem lies in understanding the concepts and variable in the equations. It seems there are a lot of different variables in the Friedmann equation that are a result of other equations, and some variables mean certain things about the universe, but getting any hard and fast information has been difficult. I'm coming to you all to see if you'll be able to provide to me an explanation of the use and composition of the Friedmann equation that I can understand. Here's the link to the paper I'm writing, so that you can see what I'm having questions about.



http://ift.tt/1ojeb1T



Any other help regarding what the assignment is asking would be appreciated as well, though hopefully I'll be able to work all of that out myself once I have a better understanding of this equation and its meaning. Thank you very much for your help.

Mass air flow through a nozzle at different upstream pressures

I'm interested in identifying mass airflow through a choked convergent or conical nozzle.



I've found some web info claiming that mass airflow through a nozzle becomes primarily a linear function of the inlet pressure, and doubling the inlet pressure doubles the flowrate.



Further research has led me to question the validity of the above statement, that velocity through the nozzle can not exceed the speed of sound in the pressurized medium, compressed air. That the increased density with increased upstream pressure will increase mass air flow, however given a sonic condition occurs at a lower velocity in the compressed air, mass flow doesn't increase in a linear fashion.



So, my question is: Which is it?

Calculate required valve diameter (Darcy-Weisbach)

I am planning to custom build a water tank into which a household washer should discharge it's used water. I have estimated that a tank holding 60 ltrs would be sufficient. This quantity should be released into the building's drainage system within about an hour because the system is old and has difficulty handling surges. My own difficulty is with calculating the required valve diameter. The advice I need is like, "use a 1/4" ball valve (and open it about half)".

Presuming that the draining velocity would be greater with the tank full, my purposes would be served if I could guarantee a maximum discharge rate of near 1 ltr per minute. It doesn't really matter how long the tank takes to drain fully as long as it isn't slower than the washer releases water. According to my research the most water-inefficient washer would use about 50 ltrs per wash which, in my experience, would take about an hour.

Thanks for the help!

Faustulus