Systems Definition and 1000 Threads

I know that the Cascade Refrigeration Systems are more efficient than the normal Refrigeration Systems, but I still don't know why?

Hi. I am an undergrad student taking a course on dynamical systems. Our final assignment is to find and study a dynamic system (not necesarily mechanic, but chaotic, natually). I was wondering if there is experenced people in this community that could help me find an interesting system or...

Hi I have a bachelor in mathematics with a minor in physics, and my plan for the future is to move on to computational science and robotics. However, before I can do that, I need to work a few years due to bad personal finance. In my city, the easiest route is programming. I already knew...

Homework Statement How to show a block diagram can be simplified to a standard first order form for the diagram shown in the image attached and the question is shown in 1.a Homework Equations Standard first order form K/(1+tD) where K gain and t is time constant The Attempt at a Solution...

I was just wondering if the quantum Zeno effect can be applied to macroscopic systems. It's applies to microscopic systems such as atoms but how about macroscopic systems like the universe?

Could you recommend books which covers extensively numerical simulation of quantum system, such as hubbard model, ising model and discuss quantum monte carlo method? Ideally this is a book of condensed matter physics.

I wasn't sure into which category I should post this, so feel free to move it into a more appropriate place. As part of my work I'm solving a system of nonlinear equations, of a usual form: $$\vec{F}(\vec{X})=\begin{pmatrix}F_1(X_1, X_2, \cdots X_N) \\ F_2(\cdots) \\ \vdots \\...

I need websites or books that has quantum mechanical exercises in particular that finds the total angular momentum eigenvalues (for example two spin 1/2 systems). Do you know where I can train?

Hi, I would like to ask you for advice with a problem, I'm working on. I have a regular shape object (glass cylinder) in which is the 100W heat source. The heat source is ind the middle of cylinder and radiates heat uniformly throughout it’s height. Heat, of course, gradually moving into...

The hereditarily finite sets(a subclass of the Von Neumann universe) are an axiomatic model that corresponds to the usual axioms of set theory but with the axiom of infinity replaced by its negation(showing its independency from the other axioms of set theory). Some mathematicians (a minority)...

I'm trying to write some code to generate plausible star systems, but so far, I only have a main sequence star generator, and even with that I don't know how good the mass-radius relationships are. So, I'm coming here to ask for some formulas or pointers as to where I can go to find the math to...

Imagine that we have an intertial system F, and there is an electric charge Q at the origin. Obviously the field is symmetric and spherical in this reference system. Imagine another inertial system F' that is moving at constant speed v to the right respect to F, and at t=t'=0 both origins...

Homework Statement [/B] How are we able to go from the first line to the second line and then the second line to the third? Homework Equations Euler Identity: e^j(theta) = cos(theta) +jsin(theta) The Attempt at a Solution This problem is more about preliminary theory in my opinion so I tried...

So a spherically symmetric object, by Birkhoff's theorem, does not emit gravitational waves. Is this why we look to binaries, so that there is some rotation of the objects with respect to each other breaking the spherical symmetry? Or mainly because the gravitational radiation is much greater...

Homework Statement Design a lag-lead compensator for the system of Figure 9.37 so that the system will operate with 20% overshoot and a twofold reduction in settling time. Further, the compensated system will exhibit a tenfold improvement in steady-state error for a ramp input. Homework...

I have a recycle loop system: Please could someone give me a place to understand the theory behind it? What would be its purpose? Where would it be used? I've googled recycle loop systems but I can't find anything relevant, is it the same as a pressurized water reactor...

How can planets exist in star systems with two or three stars? Shouldn't the planets' orbits get severely disturbed by the other stars?

Homework Statement Homework Equations Momentum conservation and Energy conservation equations The Attempt at a Solution Ok First I translated the units, ##1000 \frac {kg} {min}=16.66\frac {kg} {s}## ##10\frac {km}...

Hey! So I have a raspberry pi that uses 5V/1.2A and a LCD monitor that uses 12v/0.2A. I would like to power both using a single wall power outlet. I found a power adapter that converts 100-240VAC/50-60Hz/1.2A to 12VDC/2A. I was wondering if it is as easy as cutting off the connector on the...

Homework Statement For each of the following, determine if the system is linear. If not, clearly state why not. (a) ##y''(t)+15y'(t)+sin(y(t)))=u(t)## (b) ##y''(t)-y'(t)+3y(t)=u'(t)+u(t)## (c) ##y'(t)=u(t)## and ##z'(t)=u(t)-z(t)-y(t)## Homework Equations None The Attempt at a Solution...

Homework Statement Deriving an s-domain equation for the following inputs a) &b) The Attempt at a Solution I understand how to derive the equation for an input with zero initial conditions (part a) but I'm not sure what to do when there are non-zero initial conditions (part b)

Looks like a lot of good stuff, I know what I’m doing this weekend! Summary document on SP 800-160: http://csrc.nist.gov/publications/nistbul/itlbul2016_12.pdf SP 800-160, Systems Security Engineering: http://dx.doi.org/10.6028/NIST.SP.800-160

Homework Statement I am having trouble solving systems of equations when they contain complex numbers. The context is circuit theory and phasors. For example, I am given this And the goal is to find I2 and Voc, which you can see the answers for. I just don't know how to manipulate the numbers...

Okay, so I've reached the Work Chapters in my textbook, and I've noticed some contradictions, especially in what consists (and what doesn't) an Isolated System, plus the external and/or applied forces. For example, in one of the "Speed Questions" it categorizes a single cube as a non-isolated...

Hi there. Excuse that I write it all in standard text but I don't know how to write it otherwise. I'll get right to the question and try to see if I understand the theory from the answer. Suppose we have a system of two electrons, one spin up and one spin down in a system with 3 possible...

Homework Statement In the drawing below, a rod of length L and mass M is pivoted a distance L/4 from one end. The pivot attaches the rod to a smooth horizontal table, allowing the rod to rotate frictionlessly in a horizontal plane (so that gravity does not affect the motion). The end furthest...

Homework Statement A 3.0kg mass is connected to a system of three springs, k1 = 100N/m, k2 = 80N/m, and k3 = 150N/m, as shown below. (a) Derive the relation between k1, k2, k3 and the equivalent spring constant of the three springs together. (b) If the mass is pulled 10cm from its equilibrium...

Homework Statement Consider the 3 following Scenarios: 1. 2. rms value of line voltage is 208 V Three equal impedances, 60 +j30 W each, are delta-connected to a 230-V rms, three-phase circuit. Another three equal impedances, 40 +j10 W are wye-connected across the same circuit at the same...

The transfer function of a linear system is known in the sinusoidal frequency domain. It is given in its final form as a complex function of the angular frequency ω (not jω ). How to obtain the step response? Thanks in advance.

If one wants to write about different worlds in his story, it isn't enough to just change a few things on the surface. Culture has to be different, different political systems usually means differences in economy too. An example from my universe: on the totalitarian planet, most people barely...

Chaos could appear in the system if there is some nonlinearity. My question is how to explain that there is no chaos in constant acceletating system s(t)=v_0t+\frac{at^2}{2} when equation is nonlinear? Why is important only that difference and differential equation be nonlinear. It confusing me.

Anyone know any good power electronics / power systems textbooks?

I have a few questions about earthing in electrical systems. 1) How can Earth be used as a "conductor"? I googled its resistance and it turns out that Earth resistance is not that large and it can be reliably used as a conductor. For example, I read it can be used as a return conductor in single...

In particular how does matter "clump" together to form stars and planets, and how do Galaxy/star systems form? For the latter question is the answer simply that near massive enough bodies, the spacetime curvature is significant enough that the geodesics within its vicinity are closed curves...

This is with regard to 2 boxes of different masses that are stacked on top of each other and pushed at a constant velocity across a table that has friction. One of the sentences is right: "When the boxes move at a constant speed, there is no change in momentum. This means that the boxes are an...

Homework Statement Determine the maximum velocity attainable by a vehicle with the following conditions: RWD 6% grade Weight = 20 kN CG is 1.25 m behind front axle and 0.5 m above ground level. Wheel base is 2.8 m. Effective rolling radius of wheel = 30 cm Coefficient of aerodynamic drag =...

Homework Statement Determine the maximum velocity attainable by a vehicle with the following conditions: RWD 6% grade Weight = 20 kN CG is 1.25 m behind front axle and 0.5 m above ground level. Wheel base is 2.8 m. Effective rolling radius of wheel = 30 cm Coefficient of aerodynamic drag =...

Homework Statement A particle of mass m moves along the x–axis under the influence of force ##F_x=-ax+bx^3## , where a and b are known positive constants. (a) Find, and sketch, the particle's potential energy, taking U(0) = 0 (b) Identify and classify all equilibrium points (c) Find the...

Homework Statement Determine the maximum mass of the lamp that the cord system can support so that no single cord develops a tension exceeding 350 N Homework Equations The Attempt at a Solution F(x)=0; F(ED)cos30 - F(CD)= 0 F(y)=0; F(ED)sin30 - W F(ED)= 2W F(CD)= 1.73205W F(X)=0...

Hi again PF. I recently came across the term "virtual inertia" when reading about photovoltaics and power converters (DC/DC, DC/AC etc.). Article: http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6953370, not sure if people are able to view the article, I have access via university library...

Some years ago there was a news announcement about a quantum commlink between Beijing and Shanghai, more recently a few weeks ago there was the announcement of the first ever quantum communication satellite. I've done some looking but I haven't found any analysis about whether or not this is...

so I ill be going into my first year of energy systems engineering but I would really love to develop my own business surrounding things like biofuels and wind farming , i was just wondering what prospects are their to develop a business or if there are any sort of ideas around that field.

I am relatively well versed when it comes to systems of spin, or doing the maths for them at least, but am unsure whether all of the {L2, Lz, (other required quantum numbers)} basis eigenstates for a general system of n particles of spins si, where si is the spin of the ith particle, can...

Animals get wet in the rain and still don't fall sick, how is that?. Let's take a stray dog. I have noticed that a dogs nose keeps running and he has to breathe though the mouth. So his immune system has some flaws. Can a human being become so immune just like animals? Tarzan had good imunity...

Hi everyone! I have been perusing PF for some time, and what's struck me is how little discussion there has about research in complex systems & complexity, such as the research conducted in places like the Santa Fe Institute or the Center for the Study of Complex Systems at the University of...

This is a two part question: 1. With a simple pulley system using one pulley - say 10000 kg on each side - the ability to pull either one up or down to change the position is theoretically just the friction on the system and any extra length of rope on one side? 2. Would it be more work lost...

Hey guys! This is my first day on the forum so, hey! I'm a third year electrical engineering student and I'm really having some trouble with Signals and Systems so I want to know what helped other people understand it so that maybe I could try some of their methods. What were your biggest...

Hi, MechE student here! I've become quite interested in control theory recently, and I've been studying it a lot. I thought about specializing myself in this field, but also, I want to work with aerospace. The problem is that control engineering looks like a EE field, and I fear that I wouldn't...

Hi All, So glad to have come across this amazing site and resource. I am a mature student completing an engineering degree with the Open University and I am after some guidance and help with creating a way to plot forces from a moving mechanical system. The images on the attached drawing are...

Homework Statement Attached is a pdf of the assignment problems, I'm looking at problem 1 under the "Try" section. It shows a rod attached to a wall bracket on the left, with a force applied on the right side. I'm also including a link to the solution, it's under "Problem 3.83" -...