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.
Imagine you are getting dressed in the morning and fastening a belt around your waste. You pull on the loose end of the belt, developing tension T throughout the length of the belt. Using this information, how can you determine the amount of compression the belt is applying to your waste?
I...
Question: A block of mass m and speed v collides with a spring, compressing it a distance deltaX. What is the compression of the spring if the mass of the block is halved and its speed is doubled?
I have no idea how to do this problem. If anyone can explain this to me it would be GREATLY...
How does the first law of thermodynamics apply to the Compression And expansion of a gas at constant temperature ?
If the gas is at a constant temperature and is being compressed, then
ΔQ = 0
ΔU = +
W(on the system) = +
Are those(^^) correct ?
The equation being :
ΔU = ΔQ +...
Homework Statement
a fluid undergoes a reversible adiabatic compression from .5 MPa, .2 m3 to .05 m3 according to the law PV1.3 = constant. determine the change in enthalpy, internal energy and work transfer during the process.
Homework Equations
P1V11.3 = P2V21.3
dH = T dS + V dP
dS = 0...
Hi again
I try to solve this by my own with little help from the net, but still I'm not sure if it's the correct!
Here is my work, and please someone tell me if I'm wrong, again. (x = 20,8 m ?)
Thanks
P.S. Here is the full problem http://i.minus.com/j8Fbhtd9CJtCQ.jpg
Hi,
I have got experimental data for a steel material for a cyclic test perfoemd in the following scenario:
0-1% Torsion followed by
0-1% strain Tension followed by
1-2% Torsion followed by
1% to 0 % compression followed by
2 to 3% torsion followed by
0 to -1% compression...
Homework Statement
The figure(Figure 1) shows a thermodynamic process followed by 150 mg of helium. Determine the pressure (in atm) at points 1, 2, and 3. Determine the temperature (in °C) at points 1, 2, and 3.
http://imgur.com/B7lwQ
n=.0375 mol
P1=3 atm
P2=1 atm
T1=971.85 k
T2=971.85 k...
An object with mass m1=0.4kg moves at v0=10 m/s toward a second object with mass m2 = 0.8kg. Attached to the second object is a spring with spring constant k = 200N/m, and natural length L0 = 0.1m. As the objects collide the spring is initially compressed. After compressing a maximum amount the...
I'm just trying to figure out a theory. Forget what you know about a reciprocating piston engine, and just dream with me for a second. Say a piston could just turn around and come back down the cylinder at ANYTIME in the stroke, would the fuel always burn most efficiently?
It's hard to...
Need help in determining the impact force strength of a door stop rubber. It is a urethane rubber formed in a triangular shape. I used a 50t press with a 2" round shaft to compress rubber product and it required 100 lbs of force to compress. I believe this worked out to 18.75 ft lbs to...
Hello,
for some reason I can't seem to be able to find this.
Suppose you have a elastic cylinder, a full cylindrical bar (not hollow), and you want to compress the two end faces (axial compression) together and find the stress in the axial direction...or strain.
I can't seem to be able...
A 0.50 kg block is pushed against a 400 N/m spring, compressing it 22 cm. When the block is released, it moves along a frictionless horizontal surface and then up an incline (which has friction). The angle of the incline is 37 degrees and the coefficient of kinetic friction is 0.25. Use the...
Homework Statement
Please check the enclosed figure.
Find the force of compression in the wire loop.
Magnetic field B is directed into the page and current i is flowing anti-clockwise. The radius of the wire loop is 'a'.
Homework Equations
\vec{F}=i\vec{l}\times\vec{B}
The...
i have calculated the coefficient of performance COP for both COP ideal and COP from p-h diagram. But the COP ideal i get is lower than the COP i calculated from p-h diagram. is it possible? please help :)
Homework Statement
Hi Guys, I am trying to solve a classic problem involves conservation energy, spring, compression, I got my attempt and answer and I think my step was correct but the answer is different with the solution, can anyone please have look for me, any suggestions will be really...
I am asked to rate a series of elastic collisions in order greatest time of max compression to least time of max compression for several vehicles with varying masses and velocities, which strike a spring with a spring constant k.
I can determine the Momentum of each case, as I am given...
Homework Statement
A 11 kg box slides 4.0 m down the frictionless ramp shown in the figure , then collides with a spring whose spring constant is 190 N/m. The angle of the ramp is 30°. What is the maximum compression of the spring?
Homework Equations
Ei=mgh
Ef=1/2kx^2
The Attempt...
Homework Statement
A model diesel C.I engine has a volumetric compression ratio of 18:1 and a cut*off ratio of 1.5:1?
The engine has a volumetric compression ratio of 18:1 and a cut*off ratio of
1.5:1.
If p1 = 1 bar and T1 = 27°C, determine the pressure and temperature
at each point in the...
Homework Statement
This is one of the questions in my materials engineering assignment.
1. Thermal shock is the focus of this problem. Note that the resistance to thermal shock of a material, “R”, is defined here as the temperature change required causing fracture: (σc*λ*(1-v))/(α*E)
Where...
Homework Statement
A 1.18 kg block slides across a horizontal surface directly toward a massless spring with spring constant 5,803 N/m. The surface is frictionless except for a rough patch of length 0.42 m that has coefficient of kinetic friction 0.367. The initial velocity of the block is...
Time Compression and Length Expansion are the opposite effects of Time Dilation and Length Contraction.
According to Lorentz, observation of time in another inertial reference frame is ALWAYS dilated.
But I read on some other forum that due to "Complex Lorentz Transformations", Time...
Hello. I need help with some thermo basics.
I can't understand the concept of constant volume compression/expansion. Please help me understand how it occurs.
Also, I am not clear on how pressure is an intensive property. To my understanding it IS a quantity dependent on system size (eg...
Homework Statement
A cylinder is filled with .1 moles of an ideal gas at STP, and a piston of mass 1.4Kg seals the gas in the cylinder with a frictionless seal, as shown in the figure below. The trapped column of gas has an initial height 2.4. The piston and cylinder are surrounded by air...
Consider a heat pump works on the vapor-compression refrigeration cycle with 0.2 kg/s of refrigerant-134a as the working fluid. The cycle is used to maintain a house at 26oC while absorbing heat from the outdoors at 3oC. R-134a enters the compressor at 200 kPa as a saturated vapor and leaves at...
Hey guys, I know this is a simple question but I'm not really sure how to do it.
Let's say we have a beam supported by two pins at both extremes.
There is a central load on the beam, so it will deflect in the direction of the load.
But we also have an axial force compressing the beam.
My...
Dear physics forum, I am doing an experiment on the vibrational behavior of beams and a question has come up that I can't answer. How does compression affect wave speed?
Brief overview of the experiment:
studying the change in vibrational behavior of a beam that is gradually tapered...
Homework Statement
A solid cylindrical bar 18.34 mm diameter and 180 mm long is welded to a hollow tube 18.34 mm internal diameter and 120 mm long to make a compound bar. Determine the external diameter of the tube in (mm) if when loaded with an axial force of 40 kN, the stress in the solid...
When there is a change in the volume of a gas either compression or expansion and if it is carried out in multi step or single step stages is the work W_{a\rightarrow{b}} = W_{a\rightarrow{c}} + W_{c\rightarrow{b}}
Homework Statement
Calculate a value of R, specific gas constant for air, from the values you have.
Also calculate the work done in the compression process.Homework Equations
Pv = RT
ρair = 1.2 kg/m^3The Attempt at a Solution
Have P,V and T data from an adiabatic compression. I think I need...
I'm currently learning about different types of compressional work. The book I'm using covers mostly just isothermal and adiabatic processes, which make sense. Isothermal being so slow that everything equilibriates while adiabatic is so fast that heat cannot escape.
However, the book briefly...
Assuming idealized springs under Hooke's Law:
A spring 1m in length, mounted on the ground, compresses 10cm under its own weight.
Next to it is a spring identical in material, construction, etc., but 2m long with twice the mass.
If I understand correctly, doubled weight alone would...
Homework Statement
Forum! I'm struggling on this one D:
any help would be greatly appreciated!
An elastic head-on collision, a 0.60kg cart moving 5.0m/s [W] collides with a 0.8-kg cart moving 2.0 m/s[E]
The collision is cushioned by a spring (k=1200N/m)
**Find the maximum compression...
Find the force of tension in the chain. Determine the force of compression in the support bar. Be sure to include a free body diagram as part of your solution.
Now the only information given is a mass=20.4 kg and the angle 22 degrees.
If anyone could help me with this question, it would...
Find the force of tension in the chain. Determine the force of compression in the support bar. Be sure to include a free body diagram as part of your solution.
Now the only information given is a mass=20.4 kg and the angle 22 degrees.
If anyone could help me with this question, it would...
Homework Statement
http://img29.imageshack.us/img29/4386/prob1p.jpg The Attempt at a Solution
To answer the first question as to why the air needs to be refrigerated, I think it's because refrigerating the gas cause it to do work, so its enthalpy will decrease resulting in a decrease in...
Homework Statement
We have an ideal gas of N particles with mass m and temperature T and volume V.
a) Calculate \langle E_{kin} \rangle
We now reversibly compress the gas from volume V to V/2. During this compression heat Q is added, work W is done on the gas and the energy of the gas...
Homework Statement
A 740g quantity of an ideal gas undergoes a reversible isothermal compression at a temperature of 330 K. The compression reduces the volume of the gas from 0.40 m3 initially, to 0.32 m3 finally. The entropy change of the gas is equal to:
A) -43 J/K B) -150 J/K...
I have a system that looks like this:
The top part is a piston, whereas the bottom is a displacer.
I have looked at the Isothermal case for this system in a separate thread (https://www.physicsforums.com/showthread.php?t=553165)
But in short, the result was that the pressure of the system...
Homework Statement
Hello. I have some troubles with a truss problem. In fact i believe i have correctly identified the direction of the forces involved in the rods, but i cannot identify which rod is in compression or which is in tension. Are there any tips/rules to identify only with a force...
Homework Statement
Homework Equations
Work done by an ideal gas, isothermal process: W=n*R*T*ln(V_f / V_i)
Work, constant-pressure process: W=p*(V_f - V_i)
The Attempt at a Solution
I first tried plugging n=1, R=8.31, T=273.15, V_f=17.5 L, V_i=24 L into the first equation and it...
Homework Statement
A 4.63-kg ball of clay is thrown downward from a height of 2.69 m with a speed of 5.01 m/s onto a spring with k = 1610 N/m. The clay compresses the spring a certain maximum amount before momentarily stopping.
b) Find the total work done on the clay during the spring's...
I really need help on this question, I've tried asking several people but I still don't quite get it.
The formula for the work done on compressing/expanding an ideal gas is \int-pdV.
Now first of all - p denotes the internal pressure of the gas right?
If so, good so far.
Let us now assume...
Have already received excellent help in understanding this but might need a bit more.
Suppose we have a gas inside a cylinder with a piston in it. Now my teacher said that to compress the gas quasistatically we would need to press in the piston with a speed, that is slow compared to the speed...
hi
in school we talked about a process called "isochoric compression". i do not really know what they mean by that, since the word" isochoric" refers to a process that has always constant volume, whereas "compression" makes me think of a change in volume. is there anybody who can explain this...
Homework Statement
A 1 kg cart is at the top of a frictionless ramp as shown. It rolls down and makes an elastic collision with a stationary 3 kg cart at the bottom. The spring constant is 400 N/m. What is the maximum compression of the spring? How far up the ramp will the first cart travel...
Hi guys
I have a general query regarding Rubber O-rings.
For an application , say seal between 2 mating flanges of pipes ,with water pressure say about 10bars,
How exactly does the hardness of rubber effect the the sealing?
Is there a direct relation between hardness & strength ?
Can some...
Hi, I have a little problem understanding adiabatic compression.
Let me start with the definition of adiabatic process from wikipedia, "In thermodynamics, an adiabatic process or an isocaloric process is a thermodynamic process in which the net heat transfer to or from the working fluid is...
So, I'm launching foam balls using spinning wheels. The way it works is a sheet of polycarb is near the wheels. The ball is fed into the wheel and is compressed. The wheel turns and shoots the ball out.
My question is this. How should I calculate the output velocity of the ball? I know the...
If a sugar cube size piece of neutron star weighs as much as every vehicle in U.S.A, and H2 in the core of Jupiter has been compressed to a metalic version of itself, what then is the limit of compression? Can matter be compressed further than that of a neutron star?