Mach Definition and 80 Threads

Mach () is a kernel developed at Carnegie Mellon University by Richard Rashid and Avie Tevanian to support operating system research, primarily distributed and parallel computing. Mach is often mentioned as one of the earliest examples of a microkernel. However, not all versions of Mach are microkernels. Mach's derivatives are the basis of the operating system kernel in GNU Hurd and of Apple's XNU kernel used in macOS, iOS, iPadOS, tvOS, and watchOS.
The project at Carnegie Mellon ran from 1985 to 1994, ending with Mach 3.0, which is a true microkernel. Mach was developed as a replacement for the kernel in the BSD version of Unix, so no new operating system would have to be designed around it. Mach and its derivatives exist within a number of commercial operating systems. These include all using the XNU operating system kernel which incorporates an earlier non-microkernel Mach as a major component. The Mach virtual memory management system was also adopted in 4.4BSD by the BSD developers at CSRG, and appears in modern BSD-derived Unix systems, such as FreeBSD.
Mach is the logical successor to Carnegie Mellon's Accent kernel. The lead developer on the Mach project, Richard Rashid, has been working at Microsoft since 1991; he founded the Microsoft Research division. Another of the original Mach developers, Avie Tevanian, was formerly head of software at NeXT, then Chief Software Technology Officer at Apple Inc. until March 2006.

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  1. J

    Is this demonstration of the book from Ernst Mach correct?

    ¿Is this demonstration of the book from Ernst Mach correct? I am reading the book "The science of mechanics", Ernst mach. He is talking about the achievements of Christian huygens, and he wants to calculate the centripetal acceleration of a circular motion. As you can see in the image...
  2. S

    Plotting Mach number as a function of Area ratio

    Homework Statement A=0.1+x^2 in a convergent -divergent nozzle .I need to plot mach number as a function of x for isentropic flow across the nozzle. I know the A/A* as a function of Ma. But finding the opposite (Ma in terms of A/A*) from that equation did not seem to be that easy...
  3. P

    Quantum nature of the inertia and Mach principle

    The fundamental question about the nature of inertial mass is not solved up to now. Success of Newton's conception of physical force influencing on a separated body may be explained by the fact that the \emph{geometric counterpart to the force - acceleration in some inertial frame} was found...
  4. F

    TSFC vs Mach Number, Why does it increase?

    I have the Thrust Specific Fuel consumption plot for a turbofan engine versus the Mach Number. Until Mach = 1, the TSFC increases steadily for different flight altitude conditions (0 km...10 km, with the 0 km line on top and then 2km, 4 km etc). Can anyone tell me why TSFC increases with the...
  5. A

    How Might GR and Mach's Principle Explain Cosmic Redshift?

    ....This is just a concept I have been playing with for awhile... As my knowledge of GR is limited and my knowledge of Mach's principle is limited to its application to inertia I am going to use my own generalizations from them both. If my understanding or interpretation of either is wrong...
  6. J

    Finding the mach number of an aircraft

    A supersonic aircraft is flying parallel to the ground. When the aircraft is directly overhead, an observer sees a rocket fired from the aircraft. 10.4 s later the observer hears the sonic boom, followed 3.37 s later by the sound of the rocket engine. What is the mach number of the aircraft...
  7. G

    Is gravity the key to solving the twin paradox in general relativity?

    If the fixed stars/galaxies did not exist, would there be a twin paradox?
  8. J

    Calculate the mach number after an oblique shockwave

    I am trying to calculate the mach number after an oblique shockwave. The freestream mach number is 2.0 and the angle theta is 25 deg. But on the Theta-Beta-Mach Diagram the line Theta=25deg does not intersect the Mach=2 line. So this means that the angle has exceeded the maximum allowable theta...
  9. D

    What happened to the division of g in the Mach 3 force diagram problem?

    Here is an answer from a book of mine: From the force diagram we have N-mg=(\frac{mv^2}{R})e_r. The acceleration that the pilot feels is \frac{N}{m}=g+(\frac{mv^2}{R})e_r. I'm confused though; what happened to the g being divided by the last term as well?
  10. DaveC426913

    Verifying Mach 10+ Shocks in Shuttle Launch Exhaust

    My friend (whom I normally trust) told me something I did not know and would like to verify. We were watching a shuttle launch, talking about the main engines which, while much fainter than the boosters, can be seen in the right light...
  11. WCOLtd

    Is Mach's Principle incorporated into General Relativity?

    In this mock-up universe there exists two observers on a large disc of great mass, and there is a third observer a great distance away. In this scenario we take the observation of the spinning disc from the distant (third) observer. I was thinking about Special Relativity and Mach's Principle...
  12. R

    Supersonic Jet: Mach 3 at Altitude 20,000m - Shock Wave & Boom Times

    Homework Statement A supersonic jet traveling at Mach 3.00 at an altitude of 20,000 meters is directly over a person at a time t=0 as show in figure (see below). (a) At what time will the person encounter the the shock wave? (b) Where will the plane be when the "boom" is finally heard? (Assume...
  13. Cyrus

    Replacement blades for my Mach 3 razor

    I just bought a pack of replacement blades for my Mach 3 razor. It cost me $18.00...
  14. P

    Can a pilot hear engine > mach 1?

    Can a pilot hear engine > mach 1? Can a the pilot of an airplane hear the engine when he is traveling greater then the speed of sound? part 2: Can the pilot of airplane 1 hear the engine of airplane 2 which is traveling right behind him, both traveling at the same speed, and both greater...
  15. MathematicalPhysicist

    Mach zhender interforometer (round 2).

    problem statement two questions from my exam about MZI. in the attached file there's a picture of the settings while the dots there represent the machines that keep give photons. the questions in both of the settings is what percentage of the photons from the machines both get to A, both get...
  16. M

    UFO-Inspired Future Spacecraft: Faster Than Mach 4?

    Hi don't know if I am in the right area but i have a random question about future spacecraft and the speed they travel. the rumor of ufo's are known the be a flat sphere shape, why don't the people who design the future jets try designing the shape a little bit like a ufo instead of make the...
  17. O

    Was Mach's Principle Correct All Along?

    It is always convenient to raise something you don't quite understand to the status of a Principle. Mach's Principle seems to be a case in point; over the years it has greatly puzzled many Physicists and Philosophers. It certainly still puzzles me. Perhaps this forum can dispel some of my...
  18. S

    Mach Value64: Calculate Jet Speed after 41s at 12ms2

    Homework Statement If the temperature is 12 degrees and a jet accelerates at rest at 12ms2 for 41s, then what is the Mach value for the jet at the end of 41 seconds Homework Equations mach#=vovs speed of sound equation The Attempt at a Solution v=12degrees a=12ms2 v=339,08ms...
  19. S

    Calculating Speed of Military Airplane at Mach 2.00

    Homework Statement A military airplane can travel at mach 2.00 What is the speed in km/h at sea level and at 0 degress Homework Equations mach number=speed of object/speed of sound The Attempt at a Solution speed of object=speed of sound divided by mach number 322meters per...
  20. S

    Calculating Mach Number of Aircraft at Sea Level

    Homework Statement What is the mach number if an aircraft traveling at sea level at 0 degrees with a speed of A)1140km/h b)900.0km/ the answers are 0.995 abd 0.753 in order. I Cant get those. Homework Equations mach number=speed of object/speed of sound The Attempt at a Solution...
  21. Q

    What causes a sonic boom when traveling at Mach 1+?

    Here's a problem that's been bugging me. We know that we get sonic booms because of the Doppler effect since, for an example, the jetplane over takes the soundwaves that it emits some time ago because it is travels faster than the speed of sound. The overlapping of new sound waves it produce...
  22. M

    Mach Number as a Function of Area Ratio

    Hi there, I have an assignment in my Gas Dynamics class where were supposed to compute the flow inside a nozzle given stagnation pressure, temperature and area ratio (throat to exit). I am 80% sure this is given a choked condition. Anyways, we have charts to find the Mach number as a function...
  23. M

    Zero Mach number lift coefficient

    I have some aerodynamics homework to finish up, and I am not really sure how to do one part. Question is: What is the corresponding zero Mach number lift coefficient I can't find an equation in my book or anything. Can someone maybe shed some light? My first two questions were to...
  24. O

    Bullets from a Jet Fighter Mach 3.2

    :confused: A gentlemen on another site, not related to physics stated the following: [moderator removed personal information of third: indeed something that is inappropriate without consent] Bullet speed is relative. A .22 long rifle compared to the .22-250 is a great example. The SR-71...
  25. L

    Entanglement and the Mach principle

    Has anyone read something related? Thanks to point me to such papers, and to express your ideas or knowledge. The Mach principle aknowledges that a "frame of inertia" can only be conceived with respect to the whole bulk of nearby universe. That is to say that physics frame of reference is...
  26. C

    How Do Compressor Blades Exceed the Speed of Sound Without Loss of Performance?

    Ok, so a prop is an airfoil that spins and as such is subject to limitations that severly hamper performance as it approaches the speed of sound correct? But how do spinning compressor wheels like in a jet engine or a turbocharger not succumb to the same effects even when their blades would...
  27. B

    Mach 1 Torpedoes - Supercavitating Projectiles Underwater

    I am curious here, does anyone know anything about supercavitating projectiles underwater, I was told by a friend that the USSR developed torpedoes capable of going mach1 by means of this effect. Does this really happen or is it possible in theory? He offered no mathematicl basis for this claim...
  28. M

    Where Can I Find Advanced Scramjet Theory Online?

    There's a scramjet trying to achieve a velocity of Mach 10; it will do the flight on Monday, trying to improve the actual record of Mach 7. I hope it can achieve it. Here's an article http://www.newscientist.com/news/news.jsp?id=ns99996658
  29. N

    Mach space in The Fabric of the Cosmos

    I have been reading about Mach space in Dr. Brian Greene's recent book, "The Fabric of the Cosmos", and must admit I am somewhat confused. This is not Dr. Greene's fault, I am sure. I was hoping for some clarification here. I will try to summarize what I found in Dr. Greene's book. Mach...
  30. I

    2000 Ford Mustang Mach 460 system

    I'm trying to find out if anyone knows anything about installing aftermarket speakers into a ford mustang convertible. It's a 2000 and has the Mach 460 sound system. My main concern is with increasing the bass. I've read that the car outputs 460 watts to 4 subwoofers. does this mean that an...
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