Systems Definition and 1000 Threads

A system is a group of interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its environment, is described by its boundaries, structure and purpose and expressed in its functioning. Systems are the subjects of study of systems theory.

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  1. O

    Virtual Intertia in Power Systems

    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...
  2. A

    I Practicality of quantum communications systems

    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...
  3. I

    Engineering Energy systems engineering + business

    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.
  4. tomdodd4598

    I Physical eigenstates of systems of n particles of spins sᵢ?

    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...
  5. avito009

    How do animals have better immune systems than humans?

    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...
  6. S

    Anyone on PF involved in complex systems research?

    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...
  7. G

    Pulley systems and friction (simple or compound)

    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...
  8. Woa90210

    What was most helpful understanding Signals and Systems?

    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...
  9. navierstokes

    Courses Control for Aerospace Systems?

    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...
  10. S

    MHB Combined Buoyancy and Dynamics of Moving Mechanical Systems

    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...
  11. R

    Equivalent force couple systems at a point on a rigid body

    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" -...
  12. haushofer

    Entropy: second law for systems with zero input net energy

    Dear all, I'm trying to think about applying the second law of thermodynamics to a system which is not isolated, but has an energy flowing inwards and an equal (!) energy flowing outwards, such that the total energy does not change (total energy flux is zero). Can we still apply the second law...
  13. Ben S

    Thermodynamics - property relationship of 2 systems

    Homework Statement A pure substance is placed into two containers of the same volume. Container 1 has twice the mass of pure substance of Container 2. After the containers are shut and both reach thermal equilibrium with the surroundings, what do we know about: a) the pressure of Container 1...
  14. U

    Examples of systems which cannot receive work adiabatically?

    In Principles of General Thermodynamics, Hatsopoulus and Keenan (p 442) make the following claim: What, however, would be some physical examples of such a system?
  15. S

    What different types of on-grid solar systems are there?

    What different types of on-grid solar systems are there? I got asked this question but I don't know what makes on-grid solar systems different from each other. They are both tied to the grid / utility company. The only two types I can think of are rooftop solar system (for homes, offices...
  16. D

    I Complex Exponential solutions in time invariant systems

    Hi there! First Post :D In a recent CM module we've been looking at coupled oscillators and the role of time translational invariance in the description of such physical systems. I will present the statement that I am having trouble understanding and then continue to elaborate. In stating that...
  17. SuperDaniel

    Digital Control Systems Textbook

    Hi Guys, I need some material to update, or, better said, to reinforce my skills in Digital Control Systems. In the very beginning I thought on "Digital Control Systems by Benjamin C. Kuo", but, after think about this, I realized that, maybe, this is an oldie for this subject. Do you have any...
  18. faradayscat

    I Non-homogeneous systems with repeated eigenvalues

    Quick question, can you solve non-homogeneous systems with repeated eigenvalues the same ways? i.e. variation of parameters, undetermined coefficients, etc... would the fundamental matrix contain the solution with the generalized eigenvalue? Thanks!
  19. Square1

    Need help understanding pressure vs weather systems

    This is a subject that confuses me for a long time. Everywhere I go to get an understanding, I seem to run into the same explanations over and over which don't really do that much explaining. I find that only the basic elements of weather are explained, and overly basic examples that utilize...
  20. lfqm

    I Temperature in quantum systems

    Hi! These days I've been studying thermodynamics of quantum systems, and in so a very basic doubt come to me... I hope you guys can help me: When we study the usual hamiltonians of quantum mechanics (H-atom, harmonic oscillator, etc.)... Are these hamiltonians modeling the system at...
  21. M

    Engineering What Textbook Covers Design and Evaluation of Mechanical Systems?

    I'm looking for a textbook on designing mechanical systems with multiple machine components. I'd like to study both rigid and non rigid dynamic systems. I'm open to studying systems composed of any mechanical component. In particular, I'd like to learn 1. draw accurate Free Body(FBD) and...
  22. O

    A De Broglie Wavelength - Compound Particles, Particle Systems

    Can someone describe the physical processes which distinguish between separate and single particles when dealing with a collection of particles in the context of the De Broglie wavelength? The De Broglie wavelength is inversely proportional to the momentum of a "particle". Assume "separate"...
  23. U

    Particle accelerators safety systems

    Hello, I am looking for scientific articles about particle accelerators safety systems, that posted at scientific journals. The articles I'm looking for should be about safety while the operation of the accelerator, like monitoring the radiation that could be around - and the process that...
  24. S

    I Why are some systems defined with the name "variable mass"?

    I do not get why systems such as the rocket in space are defined as "variable mass" since the mass of the system is not varying. The equation used for such systems $$\sum F^{(E)}=\frac{d\vec{P}}{dt} \tag{1}$$ (sum of external forces on the system equals the change in momentum) holds true only...
  25. ErikZorkin

    I Eigenvalue degeneracy in real physical systems

    I understand this question is rather marginal, but still think I might get some help here. I previously asked a question regarding the so-called computable Universe hypothesis which, roughly speaking, states that a universe, such as ours, may be (JUST IN PRINCIPLE) simulated on a large enough...
  26. The Bill

    Analysis General texts on systems of partial differential equations?

    What are some good general textbooks on the properties and solution of systems of partial differential equations? I'm most interested in the general theory of vector and tensor valued PDEs like Maxwell's, Navier-Stokes, and the bulk equations governing elasticity and deformation of solids, etc...
  27. W

    Complex Loading Systems And Loaded Beams And Cylinders

    Hello this is my first post here so basically I've had my best crack at all the questions all I am really after is a bit or re assurance as to my answers and if any are wrong were I have gone wrong essentially. I've tried to include all my working out were possible. 1. Homework Statement The...
  28. D

    100um Core MM Fiber connected to 50um Core 10G SFP Module

    I have two systems that are approx. 300-400ft apart that I am connecting via a 10 Gig fiber connection. The fiber I am using is a 100um core MM fiber and the switches will be using a 50um core OM4 (4700 MHz*km) SFP module. Is there a way to find out what type of loss I should be expecting, is...
  29. B

    3 phase power systems: per unit with transformers

    Hey, I'm currently working a problem that looks like this: There's more to this problem, but I'm sure I can solve the rest of it, there are just things I'm uncertain about. Actually, it's only one thing I'm uncertain about. I'm looking through my notes, and when converting the voltage...
  30. John Pang

    Why Energy Flows Between Temperature-Different Systems

    Why energy flows from one system to another due to difference in temperature but not internal energy? The energy of the atoms of a system is only directly proportional to temperature. Same temperature doesn't mean same internal energy. However, I believed tgat heat is transferred through...
  31. RoboNerd

    Force Systems Multiple Choice Thread

    Homework Statement http://gpschools.schoolwires.net/cms/lib05/MI01000971/Centricity/Domain/272/Chapter%205%20MC%2013.pdf It is problem 22 on page 7 of the document: A block of mass M1 on a horizontal table is connected to a hanging block of mass M2 by a string that passes over a pulley, as...
  32. E

    A Understanding the Meaning of Splitting in Two-Level Systems

    Hi, I am trying to understand the meaning in two level system of splitting of the states due to high light intensity. the main question that I asked my self that if I had an atomic vapor and I excited the vapor in high intensity laser beam the levels will be split and I will observe Mollow...
  33. ltkach2015

    BIBO/Stable Systems: True/False Q&A on Homogenous & Particular Solutions

    ASSUMPTIONS: BIBO/stable systems NOTE: zero here does not mean the roots of the denominator in a transfer functionTRUE/FALSE -Please provide feedback- some answers are based on ODE example listed below 1/True) The Homogenous Solution is either zero or transient.; i.e. it can never be steady...
  34. D

    Matrices and Systems of Linear Equations

    Homework Statement Homework EquationsThe Attempt at a Solution No clue really. I went ahead and tried to simplify this by turnining it into an echelon matrix. But I am sort of stuck now, since I can't divide by -k because I don't know whether or not it is equal to 0?
  35. M

    Morehead State -- Space Systems Engineering MS

    Hi, I was just accepted to this program and was wondering if anyone has had any experience with it. It seems quite rigorous, but my main concern is that I know little of the school. The research looks quite interesting and I know that Kentucky is injecting large amounts of funding to the local...
  36. Jezza

    Div and curl in other coordinate systems

    My question is mostly about notation. I know the general definitions for divergence and curl, which can be derived from the divergence and Stokes' theorems respectively, are: \mathrm{div } \vec{E} \bigg| _P = \lim_{\Delta V \to 0} \frac{1}{\Delta V} \iint_{S} \vec{E} \cdot \mathrm{d} \vec{S}...
  37. navierstokes

    Control Systems of Turbomachinery?

    I'm a sophomore of Mechanical Engineering, but I do like delving into more advanced subjects that I haven't seen in undergrad yet, and among those are fluid dynamics. I've made a little bit of research into turbomachinery (while looking for some classes that could interest me hereafter) and...
  38. ramzerimar

    Digital Systems class for a MechE

    Hey people, I need some help, preferably from the Electrical Engineers... Classes start next month and I'm stuck deciding some electives to take during my third mechanical engineering semester. Here's the thing: I decided to take some electives from the EE department so I have a good basis to...
  39. D

    Solving Systems of Linear Equations (Echelon Matrices)

    Homework Statement find the general solution of the given system of equations: http://puu.sh/ncKaS/57a333f5b9.png Homework Equations Row Echelon Operations The Attempt at a Solution http://puu.sh/ncKcm/3e2b2bd5ab.jpg The correct answer given is x = 1, y = 1, z = 2, w = −3 I have done...
  40. avorobey

    Work and forces in systems of many particles

    I'm reading Goldstein's "Classical Mechanics", first chapter, and am confused about what's going on in equations of forces and work in systems of particles. For example, Goldstein calculates work done by all the forces, external and internal, in evolving the system from state ##1## to state...
  41. Sisoeff

    B Relativity of simultaneity and the balance of the systems

    Hi everybody, Glad to be with you, in the most popular physics forums on the Internet. First of all, I'm not a physicist and the problem I hope to get the answer from you, is part of the work I'm writing in another field. To cut it short, I don't quite understand how the relativity of...
  42. Feodalherren

    Dynamic systems: two rotating disks interconnected by damper

    Homework Statement Homework EquationsThe Attempt at a Solution So I'm assuming my solution is just as valid as the one in the book, if not, can somebody explain to me why? I prefer my solution since they say that phi is a known function.
  43. Justice Hunter

    Exploring the Science of Feedback Loops in Social Media and Beyond

    So I'm trying to exploit the idea of audio feedback and applying it to different Sciences, The one I had in particular in mind is social media. But before I go hammering away at how to exploit it, I need a better understanding of how feedback actually works I believe that the way feedback in...
  44. S

    Understand Contravariant Transformations b/w Coordinate Systems

    I am trying to make sure that I have a proper understanding of contravariant transformations between coordinate systems. The contravariant transformation formula is: Vj = (∂yj/∂xi) * Vi where Vj is in the y- frame of reference and Vi is in the x-frame of reference. Einstein summation...
  45. M

    Brown dwarfs and close binary systems

    (I honestly don't know whether this is Intermediate or Advanced. I'm guessing the latter since I don't know the answers and I've done second year astrophysics, but maybe I'm just an idiot.) Let's say you've got a high mass (~60 Jupiter masses) brown dwarf in relatively close orbit around a true...
  46. J

    Applied Systems of 1st order PDEs with many independant variables?

    Does anyone know of any books or online resources that do a good job discussing systems of linear 1st order PDEs with several (more than 2) independent variables? I am not a mathematician, but can handle graduate level classical physics with the associated applied math. Analytical and...
  47. Charles Link

    Non-linear properties in linear systems

    Common sense would suggest that all observed properties in a linear system would likely be linear. The response of a pendulum to an impulse can be computed, and for multiple impulses, the individual solutions can be superimposed to obtain the resultant solution. Qualitatively however...
  48. charliebrown

    Engineering Mechanical engineering or computer systems engineering

    Hi everybody, I'm looking for some advice in what to do for choosing a career in a few weeks i'll be able to change my career path, I've recently applied for a career change in my school and next february 11 they'll tell me if my change of career is approved. it's very likely that i´ll obtain...
  49. K

    Engineering Book on Dynamics (Mechanical systems)

    I'm looking for a book that has problems and explanations (not necessarily background theory) about mechanical systems. Consider the picture below for reference. The idea is I want to get a hold of energy and impulse methods for solving problems like this, eventually the book would have a...
  50. srinaath

    Air conditioner compressor capacity control in VRF systems

    hi guys... am working on a variable refrigerant flow (VRF) type air conditioner. my aim is to change the capacity of the compressor based on load change. i can vary compressor capacity by using inverter...now my doubt is on what basis i should change compressor speed for muti evaporator...
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