What is Compression: Definition and 632 Discussions
Lossless compression is a class of data compression algorithms that allows the original data to be perfectly reconstructed from the compressed data. By contrast, lossy compression permits reconstruction only of an approximation of the original data, though usually with greatly improved compression rates (and therefore reduced media sizes).
By operation of the pigeonhole principle, no lossless compression algorithm can efficiently compress all possible data. For this reason, many different algorithms exist that are designed either with a specific type of input data in mind or with specific assumptions about what kinds of redundancy the uncompressed data are likely to contain.
Lossless data compression is used in many applications. For example, it is used in the ZIP file format and in the GNU tool gzip. It is also often used as a component within lossy data compression technologies (e.g. lossless mid/side joint stereo preprocessing by MP3 encoders and other lossy audio encoders).
Lossless compression is used in cases where it is important that the original and the decompressed data be identical, or where deviations from the original data would be unfavourable. Typical examples are executable programs, text documents, and source code. Some image file formats, like PNG or GIF, use only lossless compression, while others like TIFF and MNG may use either lossless or lossy methods. Lossless audio formats are most often used for archiving or production purposes, while smaller lossy audio files are typically used on portable players and in other cases where storage space is limited or exact replication of the audio is unnecessary.
In "Introduction to Thermal Physics" - Schroeder, the derivation for adiabatic compression: V^\gamma P = \mbox{constant} is derived by assuming the compression is still slow enough to be quasistatic.
However, I'm still a bit confused with how slow is 'slow'.
Quasistatic compression needs...
A 2kg block is placed pushing against a spring. The spring is compressed and stores 10 joules of potential energy. The block remains attached to the spring as it oscillates on a frictionless track.
The mass experiences zero acceleration when the spring compression is __________
A. greatest...
Homework Statement
A compressed cylinder holds nitrogen gas at room temperature. How cold is the gas that is escaping from the cylinder?
T(cylinder) = 298 K
P(cylinder) = 1.034e7 Pa
n = 1
Homework Equations
PV = nRT
The Attempt at a Solution
So since I was not given either the volume of...
I know that when a metal is compressed its fermi energy is increased. I would attempt to explain this by saying, "as the volume has been decreased, so has the allowed number of particle in a 3D box states, thus as we have the same number of electrons and fewer allowed states, and the pauli...
Hello everyone
I'm quite confused here and would really appreciate help.
Consider a spring standing upright with a box on top of it. Now according to statics there are two forces acting on the spring: the weight of the box G and the support of the ground -F. But when we calcuate the...
Hi, if I'm using the 3d element, I'm wondering how to detect the tensil and compression for a known stress state? the hydrostatic pressure p has been used before, but i don't think it is correct to all the cases.
Excuse my ignorence here but as I understand you cannot compress water. Why not, is there not some space between any molecules, particularly following heating, that would allow compression? Assuming there isn`t then how is it we can compress a pure gas. Is the situation not the same?
Hi everyone. Hopefully this should be a relatively simple question here.
I'm running a compression test on my car and I am using a Bentley Manual (very good mechanical Bibles car people use that depict how to take apart the entire car) as a reference for the PSI I should be shooting for.
A...
Hi All,
I am currently researching required bolting torques for flanges on a large water pipeline, but my question relates to compression of compressed fibre gaskets.
I know that catalogues and vendors typically specify the percent compression under a specfic test stress, and also percent...
Homework Statement
A mass of 2.3 kg is dropped from a height of 4.82 meters above a vertical spring anchored at its lower end to the floor. If the spring constant is 20 N/cm, how far, to the nearest tenth of a cm, is the spring compressed?
answer is 34.1
Homework Equations
PE = mgh
KE =...
I have a general question about otto cycle. If we heat a gas with constant volume its temperature rise according to PV=mRT. However during Isentropic compression(delta Q and delta S is zero), the volume is becoming less and pressure is increasing but i don't know why the temperature should...
Homework Statement
the ball has a mass M and is fixed to a rod having a negligible mass and length L. If it's released from rest when theta=0, determine the angle theta at which the compression force in the rod becomes zero.
Homework Equations
A(tangent) = dv/dt = vdv/ds
A (normal) =...
1. Homework Statement
A 0.1kg is shot with a speed of 6m/s toward a 1.2kg spring gun( with spring constant of 0.4N/m). The spring gun is initially at rest with its spring relaxed. The spring gun is free to slide without friction on a horizontal table. The 0.1 kg mass compresses the spring to...
Homework Statement
A 700 g block is released from rest at height h0 above a vertical spring with spring constant k = 445 N/m and negligible mass. The block sticks to the spring and momentarily stops after compressing the spring 20.5 cm.
(a) How much work is done by the block on the...
Homework Statement
A massless hooksw law spring has a unstretched length of L, when a mass m is ploaced on it, and slowly lowered until the mass is at rest, the spring is queezed to a length of x. the mass is then dropped on the spring from a height of h, use energ methods
what is the...
This is my first time posting, but I've done quite a bit of reading around on here, and I admire your guys' intuition/skills for this stuff. Most of you appear to have a real knack for conceptualizing these problems, and I'm jealous ;).
Homework Statement
Two identical blocks, A and B, on...
Homework Statement An engineer creates a spring so that when an elevator falls from a height h, the spring constant k, only allows the elevator to reach an acceleration of 5g's. Let M be the total mass of the elevator and passengers. Solve for K
Homework Equations
F=-kx
1/2mv^2 + mgh + 1/2kh^2...
Homework Statement
Consider an adiabatic chemical reaction which results in the system being compressed. Assume an infinitely large surrounding.
Draw a pressure-volume plot for the process. Indicate the points corresponding to your final and initial volumes o the plot. Indicate at which...
Homework Statement
Block #1 (m=2.00 kg) traveling to the right at 5.00 m/s along a level frictionless surface collides elastically with block #2 (m=3.00 kg) attached to a massless spring of spring constant 275 N/m. Assume that block #2 was at rest before the collision.
(a) calculate the...
This is actually related to Thermodynamics but as it comes directly under the Mechanical field I'm asking it here and I invite all my fellow Mechanical Engineers and Physics Experts to answer this.
The question is : How does the Tempreature of a gas change (increase) when the gas is...
Homework Statement
Particle A and particle B are held together with a compressed spring between them. When they are released, the spring pushes them apart, and they then fly off in opposite directions, free of the spring. The mass of A is 5.00 times the mass of B, and the energy stored in the...
A 1.5kg object is held 1.2m above a spring with force constant 320N/m. The object is dropped on the spring how far does the object compress the spring?
Alright so what i did was mgh=0.5kx^2 but the answer is different from the book. I guess is when the object touches the spring, its exerting...
Hey ya,
Well, I have been having a difficult time finding the answer to this question, probably because I don't know the specific terminology. So here I am. I did not know exactly which forum category to put this in so...
I am building a small diving bell with a remote controlled camer...
Homework Statement
Suppose you compress an ideal gas to half its original volume, while also halving its absolute temperature. During this process, the pressure of the gas (a) halves (b) remains constant (c) doubles (d) x4
Homework Equations
PV=nRT
The Attempt at a Solution...
I have been trying to find out how to calculate a number of things in a system involving liquid and gas.
In the attached diagram there is a U-bend with gravity acting down on it. If one side is sealed with a plunger and the other side is filled with a fluid (L) we would end up with the...
Hi there.
I'm using the following equations as part of my physics research paper:
http://www.grc.nasa.gov/WWW/K-12/airplane/normal.html
The initial equation, concerning the half angle of the nose cone of the object, gives me a rather trivial answer at mach 1.5..
a > 0.199 (3sf)
Now...
Honestly I do not think automotive techs would know the answer to this question so being said from a physics stand point about the relationship between the high voltage spark on a spark plug and compression in a engine. I have had experiances where there was spark on the plugs but the engine...
An explosive liquid at temperature 300 K contains a spherical bubble of radius 5 mm, full of its vapour. When a mechanical shock to the liquid causes adiabatic compression of the bubble, what radius of the bubble is required for combustion of the vapour, given that the vapour ignites...
How compressed are the atoms black holes are made of? Is there a limit to how much you can compress matter?
It seems to me, the most you can compress matter would be until the individual subatomic particles are side by side touching each other.
Are black holes compressed more than that? Are...
I am interested in the fluid dynamics of a turbine engine that compresses its exhaust gasses along its centerline.
http://www.faqs.org/patents/app/20090067983
Any thoughts?
Homework Statement
A 6.0 kg box moving at 3.0 m/s on a horizontal, frictionless surface runs into a light spring of force constant 75N/cm. Use the work energy theorem to find the maximum compression of the spring.
Homework Equations
Wtotal=K2-K1
k1=1/2mv^2=27 J
The Attempt at a...
1) A 28.86 kg child bounces on a pogo stick. The pogo stick has a spring constant 18016 N/m. When the child makes a nice big bounce, she finds that at the bottom of the bounce she is accelerating upwards at 4.802 m/s2. How much is the spring compressed?
Given:
Mass of Child: 28.86kg
Spring...
A toy car with mass 0.043 kg is propelled by a spring with spring constant 92 N/m onto a track. The track contains a vertical loop of radius 0.15 m. Ignore any losses due to friction and use g = 10 m/s2. What is the minimum compression of the spring necessary for the car to complete the loop...
Hi,
I want to study magnetic compression theory.
I want to able to calculate and simulate how magnetic compression can store or give back energy from a circuit
Any differential equation are available for this ?
Any tutorial will be helpfull.
Thanks
Homework Statement
A block sliding along a horizontal frictionless surface with speed v collides with a spring and compresses it by 2.34 cm. What will be the compression if the same block collides with the spring at a speed of 4.00v?
Homework Equations
e=0.5mvSUP]2[/SUP] e= 0.5k*x2...
Homework Statement
A gas at an initial volume of 0.1 m^3, a pressure of 140 kN/m^2 and a temperture of 25 degrees is compressed to a pressure of 700kN/m^2 and a temerture of 60 degrees.
Determine its volume after compression?
Homework Equations
P1 × V1 = P2 × V2
T1...
Homework Statement
The engine of a Ferrari F355 F1 sports car takes in air at 20.0 *C and 1.00 atm and compresses it adiabatically to 0.0900 times the original volume. The air may be treated as an ideal gas with \gamma = 1.40.
Find Final Temp and Final Pressure
Homework Equations...
Hi
The source coding theorem says that one needs at least N*H bits to encode a message of length N and entropy H. This supposedly is the theoretical limit of data compression.
But is it? Or does it only apply to situations where only the frequency (probability) of a given symbol is known...
Homework Statement
Trying to calculate changes in psi and temperature with a known change of volume.
One cubic foot of air(14.7 psi) compressed to one tenth its original volume. 10:1 compression ratio.
Starting temp=70° F or 294° K
Homework Equations
Don't know the equasion. That is...
Homework Statement
Two carts of equal mass, m = 0.300 kg, are placed on a frictionless track that has a light spring of force constant k = 48.9 N/m attached to one end of it. The red cart is given an initial velocity of v0 = 3.13 m/s to the right, and the blue cart is initially at rest. If...
here is the problem
A package of mass 6 kg sits at the equator of an airless asteroid of mass 5.7e5 kg and radius 41 m, which is spinning so that a point on the equator is moving with speed 4 m/s. We want to launch the package in such a way that it will never come back, and when it is very far...
Homework Statement
A package of mass 5 kg sits at the equator of an airless asteroid of mass 6.3*10^5 kg and radius 48 m, which is spinning so that a point on the equator is moving with speed 2 m/s. We want to launch the package in such a way that it will never come back, and when it is very...
How much should a soccer ball be compressed between 2 objects for it to be safe for the soccer ball but also to maximize the friction between the ball and the objects. The values used for this should be the official circumference of 70 cm and a pressure of 13.5 psi.
Homework Statement
In a diesel engine, atmospheric air is quickly compressed to about 1/20 of its original volume. Estimate the temperature of the air after compression , and explain why a Diesel engine does not require spark plugs. Homework Equations
f/2*ln(T_f/T_i)=-ln(V_f/V_i)
The...
Homework Statement
Imagine some helium in a cylinder with initial volume of 1 liter and an initial pressure of 1 atm. Somehow the helium is made to expand to a final volume of 3 liters, in such a way that its pressure rises in diect proportion to its volume.
a) calculate the work done on...
Hi, I'm a newbie here.
I'm sorry if my questions are worded improperly or are too simple. I'm a chemist who hasn't had a physics class in over 20 years, so I'm a little rusty.
I have some questions on compression forces (and their propagation). I'm a battery chemist and have an electrolyte...
I found a long-time ago problem in helping archive here
The problem is about attaching a mass m to a massless rod which released at initial angle \theta_0 (measured from vertically axis), try to find the critical angle where the compression force change to tension force. Using Newtonian...