What is Shm: Definition and 502 Discussions

The MIT Shared Memory Extension or MIT-SHM or XShm is an X Window System extension for exchange of image data between client and server using shared memory (/dev/shm). The mechanism only works when both pieces are on the same computer.
The basic capability provided is that of shared memory XImages. This is essentially a version of the ximage interface where the actual image data is stored in a SysV shared memory segment, and thus need not be transferred across the socket to the X server. For large images, use of this facility can result in some real performance increases.
Additionally, some implementations provide shared memory pixmaps. These are two-dimensional arrays of pixels in a format specified by the X server, where the image data is stored in the shared memory segment. Through use of shared memory pixmaps, it is possible to change the contents of these pixmaps without using any Xlib routines at all. Shared memory pixmaps can only be supported when the X server can use regular virtual memory for pixmap data; if the pixmaps are stored in the on-board memory of graphics hardware, an application will not be able to share them with the server.
In the 1.15 release of the X.org server the MIT-SHM extension gains two additional requests: 'X_ShmAttachFd' and 'X_ShmCreateSegment', to be able to pass shared memory through file descriptors from client to server and from server to client, reducing the number of copy operations further.

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  1. R

    Board the Boat When It's Within 10cm of the Dock

    A boat(1500kg) is on a lake exibiting SHM with an amp of 20cm bobbing on the waves. The boat takes 3.5s to make one complete up and down cycle. When the boat is at its highest point it is at the same level as the dock. You will only board the boat if it is within 10cm of the dock. How much...
  2. S

    How Does the Phase Angle in SHM Equations Affect Displacement and Energy?

    question 1) If a simple harmonic oscillation is described by the function x = A sin (wt + phi) would phi be the opposite of what it would be for a SHM described by the function x = A cos (wt + phi) I.e if the graph for for x = A sin (wt + phi) , when t = 0, x = +A. would phi be equal to pi...
  3. P

    Why is the Second Derivative Negative in SHM?

    Say you had a spring hanging vertically-- spring constant k. A mass m is attached to it and it's at its equilibrium position, b. Say, I decide to extend it (downward) such that its total extension distance from how it would be normally (without the mass) is x. Say I take the upward direction as...
  4. A

    SHM question and Current question.

    Hi guys, I'm stuck at this 2 questions for a while. :confused: 1. A mass suspended from a vertical spring is displaced vertically downwards by a distance A and released. It executes simple harmonic motion about its equilibrium position O. Given that time taken for the mass to move through...
  5. A

    How Does Increasing Mass Affect SHM Amplitude and Frequency?

    Hi everyone, I'm given a graph of the object's displacement and frequency and the object is executing SHM. The question asks what would the graph look like when the mass of the object is increased to lower the amplitude of the oscillation. Personally I think that the natural frequency...
  6. A

    SHM: Impulse applied to two masses connected by spring

    I've come across the following problem: Two otherwise isolated, equal masses m are at rest and connected by a spring with constant k. An impulse is applied to one of the masses along the direction of the spring connecting them. What happens? Qualitatively, I think that the force will both...
  7. M

    SHM in a horizontal plane: 4 springs

    a point mass is constrained to move in a horizontal plane and is attached to four fixed pegs by 4 light springs. The four pegs are arranged at the corners of a square of side root2*a. Each spring has a natural length of a/2 and a spring constant a. If the mass is displaced towards one corner...
  8. D

    SHM damping coefficient which envelope sign?

    Hi, I'll get right away to the point. I'm determining damping coefficients from motion sensor traces of a damped oscillator. I have gone through the standard procedure of taking natural logs of the sine wave peaks and drawing graphs etc, however what puzzles me is that the SIGN of the damping...
  9. K

    Calculating Time and Oscillations in Spring-Mass System | Beginner's Guide

    Hi, I've got a problem to solve, but I'm really new to this topic and I'm having a bit of trouble knowing where to start. Here's the question I'm working on: A mass = 1.5 kg attached to a spring with k=8 N/m on a horizontal surface with friction force -b(dx/dt) where b = -230g/s The...
  10. K

    Projectile & SHM: Solving a Physics Problem

    Hey i came across this physics problem in a uni textbook however i am stuck, Q: A 70.0kg circus performer is fired from a cannon that is elevated at an angle of 40.0' (degrees) above the horizontal. The cannon uses strong elastic bands to propel the performer, much in the same way that a...
  11. C

    Energy Loss in SHM: Piano Wire (262Hz) - Help Needed!

    When middle C on a piano (frequency = 262Hz) is struck, the vibration of the piano string loses half its energy after 4s. (i) What is the decay time for the energy? (ii) What is the Q-factor for this piano wire? (iii) What is the fractional energy loss per cycle? SHM has been going great...
  12. G

    Solving Problems in Projectile Motion, SHM of Charge Ring & Electric Quadrapole

    i have a few problems that i was struggling with. Projectile motion: An electron is fired in an electric field E=-720j. Its launched with a velocity of 9550 m/s. if you want the x distance it travels to be 1.27mm, what are the two values of theta that will work? how long does it take...
  13. N

    Physics: Calculate x(t), T & Kinetic Energy, Find Force & Direction of Block

    A block of mass 0.5kg moving on a horizontal frictionless surface at 2.0 m/s collides with and sticks to a massless pan attached to the end of a horizontal ideal spring whose spring constan is 32 N/m. a) Determine the function for x(t), the displacement from equilibrium position as a function...
  14. W

    How Do You Solve the Damped Oscillator Equation Using Newton's Second Law?

    Using Newton's 2nd Law for a damped oscillator: ma = -kx - \alpha x which is a second order linear DE. To solve it we use the trial integrating factor e^{\lambda x} [/tex] to come to the root equation mx^2 + \alpha x + k = 0 where we can find our two solutions to be r_{1} \ and...
  15. G01

    Solving SHM Kinematics: Find the Period!

    Hi there I'm having a little trouble doing problems with SHM kinematics. I think its because I have yet to find a good method of solving them. I'll post one and show what I can do. Them I hope somone can help me find a good method to solving it.A 1 kg block oscillates on a spring with k= 20...
  16. D

    SHM MULTIPLE damping coefficents practical help

    Right, I'm about to open a big can of worms: I'm investigating eddy current damping of Simple Harmonic motion and I'm going to be investigating how the damping coefficient varies with various factors including the distance of the magnetic field (irrelevant, just informing). A "magnetic tunnel"...
  17. D

    Can a Pendulum-Spring System Achieve Linear Motion with Matching Periods?

    Hey, I have a debate that needs to be resolved. Here is the diagram of the problem and I will describe below: It is essentially a string that has a spring attached to the bottom with a weight of mass m attached to the spring. This is system is pulled back and released. Is it possible that...
  18. K

    2 questions (weightlessness and SHM)

    the acceleration of free fall of a satellite has a finite value so that an object at this position certainly has weight. making reference to the perception of weight by an observer, explain how astronauts inside this satellite arppear to be weightless. i thought weightlessness was when the...
  19. E

    Manipulating the TISE for a SHM

    Hi guys, hoping someone can help with this manipulation. I need to transform this: \frac{-\hbar^2}{2m}\frac{d^2}{dx^2}u(x) + \frac{1}{2}m\omega^2 x^2 u(x) = Eu(x) Into its dimensionless form: \frac{d^2}{dy^2}u(y) + (2\epsilon - y^2)u(y) = 0 I have the following info: E =...
  20. C

    How Does a Spring Attached to a Pivoting Rod Demonstrate Simple Harmonic Motion?

    I am working on a problem that has a few angles of approach. I am hoping to get at least that right before I waste too much more time. The problem is a slender, uniform, rigid rod is placed to pivot on its center, so that the rotation is taking place at the ends of the rod. then a spring...
  21. S

    Proving SHM in a System of Electric Charges

    Two postitive charges +Q are held at fixed distance d from each other. A particle of charge -q is placed at the mid point between them and given a small displacement y, on the line perpendicular to the line joining them and released. Show that hte particle described SHM of period...
  22. W

    Deriving Speed and Period of Rotating Disk System with Attached Small Disk

    A small thin disk of radius r and mass m is attached rigidly to the face of a second thin disk of radius R and mass M. The centre of the small disk is located at the edge of the large disk. The large disk is mounted on its centre of a frictionless axle. the assembly is rotated through a small...
  23. I

    SHM problem involving an applied force

    Hi, I need advice as to whether or not I solved this question correctly. I would really appreciate the feedback, etc... I really need to know if I did this right QA: A 2kg object is attached to a spring and placed on a horizontal smooth surface. A horizontal force of 20N is required to hold...
  24. D

    Please do not post multiple times on the same topic.

    A mass on a spring with a constant of 3.76 N/m vibrates, with its position given by the equation x = (4.55 cm) cos(3.70t rad/s). During the first cycle, for 0<t<1.70 s, when is the potential energy of the system changing most rapidly into kinetic energy? There are two solutions, enter both with...
  25. D

    Solve SHM Eqn Problem: Max Energy Transformation

    A mass on a spring with a constant of 3.76 N/m vibrates, with its position given by the equation x = (4.55 cm) cos(3.70t rad/s). During the first cycle, for 0<t<1.70 s, when is the potential energy of the system changing most rapidly into kinetic energy? There are two solutions, enter both with...
  26. P

    Elastic Potential Energy and SHM test

    Hello, I took a test on Simple Harmonic Motion today and the very last problem looked something like this: A simple harmonic oscillator has a total energy of E. (a) Detemine the kinetic and potential energies when the displacement is one half the amplitude. (b) For what value of the...
  27. B

    Understanding the Relationship between Frequency and Period in Physical Motion"

    Hi all, I have been studying for my physics final which is tomorrow for the past 9 hours..my brain hurts...sorry if this question is dumb I keep getting f=freq T=period mixed what is the difference between the two again in the physical sense (i.e. would the motion of pistons in a...
  28. S

    SHM of a Tuning Fork: Calculating Maximum Velocity and Acceleration

    Q: The prong of a tuning fork moves back and forth when it is set into vibration. The distance the prong moves between its extreme positions is 2.29 mm. If the frequency of the tuning fork is 440.2 Hz, what are the maximum velocity and the maximum acceleration of the prong? Assume SHM. I...
  29. P

    Calculating Maximum Acceleration in Simple Harmonic Motion

    A 29.0 kg block at rest on a horizontal frictionless air track is connected to the wall via a spring. The equilibrium position of the mass is defined to be at x=0. Somebody pushes the mass to the position x=.350 m, then let's go. The mass undergoes simple harmonic motion with a period of 3.50 s...
  30. K

    Odd equation relating to springs and SHM

    Well I am working on a lab report for 12th grade physics and my teacher has decided to throw a cuve ball at us. The lab is designed to determine the value of the force constant of a spring by measuring the number of oscillations a certain weight makes when on the end of the spring. To find k was...
  31. A

    Maximum Velocity When Doubling Amplitude & Period of SHM

    what happens to the maximum velocity if you double both Amplitude and period of a SHM? the equation is x(t) = A cos (wt + f) v(t) = -A w sin (wt + f) f is phase constant, w = angular velocity i know if i double A and T, the first part of the v(t) equation will be like: -2A *...
  32. C

    Uncovering the History of SHM: From Newton to Trig Functions

    I am wondering if anyone knows the history of the mathematical study of simple harmonic motion. Who first set up the equation: \frac{d^2X(t)}{dt^2} +\frac{k}{m} X(t) = 0 Was it Newton? Hooke? Did they know about uniqueness of solutions? The trig functions occupy such a cetral role...
  33. $

    SHM- differential Equations. Finding the constants of Integration from exp. data

    Hey guys, bit stuck here with this problem I have a differential equation for SHM here in the form x= A cos 10.7t + B sin 10.7t I need to find the constants of integration. w = 10.7 as above I don't have anything other than experimental data Time Second Distance / m 0...
  34. $

    How do you find the Damping Constant? (SHM)

    Hi guys, I am a bit stuck at the moment on this experiment I am doing. I am trying to model an oscillating spring mass which is being damped using air resistance and a circle piece of polystyrene. The equation of this will be in the form d^2y/dt^2 + Rdy/dx + ky/x = 0 I...
  35. S

    Calculating Intensity of Spherical Wave & Pendulum T - Confirm Correct Answers

    The intensity of a spherical wave is 21 W/m^2 at a distance 16 m away from a constantly emitting source. What will it be 3 m away? Using the formula I_2/I_1 = (r_1)^2/(r_2)^2 I got 588 W/m^2 0r 600. Correct? If the length of pendulum with T = 10 s were halved, what would be its...
  36. P

    Finding x: Block Sliding on Spring SHM

    A block of mass m is attached to a horizontal spring with constant k. resting on top of this block is another block of mass m. a coefficient of static friction mu exists between the two blocks. now suppose the spring is initially at equilibrium length, and someone gives it a push. the block...
  37. G

    SHM with mass over pulley problem

    I am having a problem with this: One end of a light spring with force constant 100N/m is attached to a vertical wall. A light string is tied to the other end of the horizontal spring. The string changes from horizontal to vertical as it passes over a solid pulley of diameter 0.04m. The pulley...
  38. S

    Equilibrium of a Suspended Mass on a Spring: Understanding Potential Energy

    Say a mass is suspended vertically from a spring and is in equilibrium. What is its potential energy? I think its zero because while it has gravitational potential that would allow it to do work downwards, it also has potential energy from the spring upwards. So do these cancel out? It seems...
  39. H

    Understanding Oscillations in Coupled Pendulum Systems

    Dear friends this question is really annoying me .please. help me in understanding this question and the concepts involved in it. Two pendulums of equal length of bob of mass m are connected by a spring of spring constant k.find the frequency of oscillations.there are two conditions also...
  40. M

    Solving for Amplitude of a Brick on a Piston with SHM: Help Needed!

    I have no idea why I can not get this question, but here it is: A brick is resting atop a piston that is moving vertically with simple harmonic motion of period 1.19 s. At what amplitude will the brick separate from the piston? I know that once the acceleration is greater than that of...
  41. N

    Calculating Amplitude of Brick Separation from Piston with SHM

    A brick is resting atop a piston that is moving vertically with simple harmonic motion of period 1.08 s. At what amplitude will the brick separate from the piston? I came across this question reviewing for my test next Thursday. Anyway, I can calculate the angular frequency using the...
  42. G

    Does a Car Exhibit Simple Harmonic Motion?

    Can someone help me with this please? I think this moves with SHM (of a car), but I don't really know the principles of it very well. Thanks
  43. C

    How Does SHM Relate to Probability Distributions in Quantum Mechanics?

    Hey there. :smile: As part of our quantum assignment we;ve to also look at a simple classical oscillator (it's part b to a question about the one dimensional harmonic oscillator). Problem is, I can hardly remember a thing that isn't to do wih quantum! So any help here would be...
  44. S

    Pendulum & SHM: Exploring the Relationship and Limits of Simple Harmonic Motion

    Why is it that a simple pendulum only shows SHM at small angles close to the equilibrium position?
  45. C

    Basics of SHM (undamped, under-driven)

    My textbook says the an object undergoing undamped, under-driven harmonic motion (http://romano.physics.wisc.edu/lab/manual/img279.gif) does NOT have its maxima at the points where the displacement curve makes contact with the exponential envelope curve. How can this be the case?? Doesn't...
  46. C

    Solving the SHM Calculus Twister

    I saw this in an old, junior-level, classical mechanics textbook and haven't been able to figure it out. A particle undergoing simple harmonic motion has a velocity: \frac{dx_1}{dt} when the displacement is: x_1 and a velocity \frac{dx_2}{dt} when the displacement is...
  47. P

    Calculate Amplitude of SHM for Block Connected to Spring and Embedded Bullet

    A 35.0 kg block at rest on a horizontal frictionless table is connected to the wall via a spring with a spring constant k=25.0 N/m. A 3.60×10-2 kg bullet traveling with a speed of 490 m/s embeds itself in the block. What is the amplitude of the resulting simple harmonic motion? Okay. So If...
  48. N

    Centre of Mass & SHM: Help Understanding & Graphing

    Hi, I have a hard time trying to understand the Centre of Mass as well as the graphing for SHM. Please help. Thanks heaps.
  49. X

    What factor affects the rate of exponential decay in coupled pendulums?

    You have 2 pendulums attached to the same piece of horizontal string. One pendulum has a large mass, the other is small. They are both of the same length. The large pendulum is released from an amplitude and so the small pendulum resonates. The rate of exponential decay of the large...
  50. denian

    How Does Material Affect Resonance in Pendulum Oscillations?

    2 pendulum bobs X and Y have the same length and sixe. ( pendulum bob X is made from copper while Y -> polystyrene ) there is another pendulum Z with variable length ( Z -> lead ) when pendulum Z is set oscillating with frequency f each time at different length, pendulum X and Y will be...
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