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. H

    Maximum exhaust velocity for a De Laval nozzle

    Here is what I did so far. First of all, at ##P_0## (the opposite end of the exit), I supposed ##u_0 = 0##. (Is it correct?) Hence, using Bernoulli's equation for a compressible gas. ##\frac{\gamma}{\gamma -1} \frac{P_0}{\rho_0} = \frac{u^2}{2} + \frac{\gamma}{\gamma -1} \frac{P}{\rho}##...
  2. L

    Calculating drag for high mach numbers

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  3. R

    Aerodynamics Monographs: Recent Advances in High Mach Subsonic Flight

    Summary:: I'm looking for recommendations of recent aerodynamics monographs which treat high Mach number subsonic (pre-transsonic) flight thoroughly. I'm looking for recommendations of recent aerodynamics monographs which treat high Mach number subsonic (pre-transsonic) flight thoroughly. I...
  4. Vin B

    Simulate mach reflection with mach stem generation using Ansys Fluent

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  5. theudster

    How to derive the reflected Mach number relationship?

    Hi, when learnig about reflected waves, I keep coming up with this equation; to calculate the reflected mach number (Mr). I can't seem to find the derivation for this and would appreciate your help Thank you
  6. PainterGuy

    Pressure felt by a piston, Mach number of speaker making the sound

    Hi, Once someone wrote the following to me in response to my query. My query was somewhat unrelated to it and I don't even have the copy of query anymore. The pressure felt by the piston at any time is the average component of momentum of a gas molecule that is normal to the piston times the...
  7. D

    What is the relationship between Mach number and compressibility in fluids?

    Homework Statement Hi, The below website states the definition of Mach number, which is a quantity that expresses how compressible a fluid is. https://physics.info/turbulence/ M = sqrt [ ( inertial resistance in the fluid ) / ( compressional resistance in the fluid ) ] = v / c...
  8. T

    I What is the difference between Mach cone and shock wave in aerodynamics?

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  9. T

    At supersonic speed, why does Mach number decrease?

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  10. R

    Multiphase flow with high Mach number

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  11. F

    Frame of reference (non inertial/inertial) in an Atwood Mach

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  12. J

    Would a reverse wing sweep be better for speeds above Mach 2

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  13. D

    I Why is there a sonic boom at Mach 1.5?

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  14. grandpa2390

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  15. MaxKang

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  16. G

    Solving Long Mach Nozzle Shape Problem for MBMS

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  17. C

    B How can we tell that "fictitious forces" are not real?

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  18. T

    Heat-shield for a Mach 30 missile at 10km for 10 seconds?

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  19. G

    If a person passes near me at Mach 2 speed would I see him?

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  20. C

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  21. K

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  22. evan-e-cent

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  23. RabbitWho

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  24. jk22

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  25. B

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  26. 8eou8elisi

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  27. S

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  28. A

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  29. J

    TI89 calculator solver in functions?

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  30. LaReina

    What is the Relationship Between Mach Number and Velocity in Compressible Flow?

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  31. M

    How/Why does the Mach principle define what is a 'direction'?

    I now have a general understanding of relativity but it threw up a few issues. I understand that there are no 'fixed' points of reference in the universe, which of course begs the question as to why inertia exists. The way I imagine it is if I am the only matter in the universe, then why should...
  32. N

    Low Mach Numbers: Incompressible flow or fluid

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  33. chasrob

    How Can a Superpowered Character Control Their Abilities to Avoid Catastrophe?

    Yep, half light speed or thereabouts; superhero story :). I'm writing a story about this fellow who gets super powers, including super speed. He can move, fly, at up to 100 000 miles per second. He can also move around at normal speed if he concentrates on what he's doing. Right after he...
  34. J

    What Is the Altitude of a Plane Traveling at Mach 2.5?

    Homework Statement A plane is traveling at Mach 2.5. An observer on the ground hears the sonic boom 1.0min after the plane passes directly overhead. What is the plane's altitude? Ignore the change in the speed of sound with the altitude. Homework Equations v=d/t 1/T= fThe Attempt at a...
  35. D

    Why Does a Projectile Create a Trailing Mach Cone?

    I understand why the leading edge of a projectile creates a Mach cone in front of which the air is undisturbed. But apparently the trailing edge of the projectile also creates its own Mach cone behind which the air is undisturbed. I don't understand why this is the case.
  36. PhysicoRaj

    Reaching Mach 1: Detecting Sonic Velocity in a Convergent Nozzle

    How do you know if a convergent nozzle has reached the exit velocity of mach 1? Suppose a convergent nozzle is connected to a blower, and gradually the blower air velocity is increased, would any phenomenon be helpful in detecting when the nozzle exit velocity is sonic, which can be heard or...
  37. S

    Air Molecules at Mach 1: Understanding Collisions and Net Velocity

    If molecules generally move at sound speed, given they are accelerated at Mach 1, does this mean there are less arbitrary collisions? or less collisions in general and more molecules move in the direction of mach 1 speed??
  38. chasrob

    Mach 6 at Low Altitude: Craft Skin, Booms & Visibility

    A cruise missile, small--say 10 feet long, making 4000 mph at 1 mile altitude- Would it make a boom loud enough to break windows? The smaller the craft, the less the boom, correct? Probably would be a tough one to answer; no aircraft I'm aware of is that small, making that kind of speed. The...
  39. S

    Exploring the Mach Principle: Books to Help You Understand

    some books mention one of a basis of GR is mach principle i study some text but i can't actually realize it please explain it for me or introduce some books to refer them thanks
  40. T

    Solving for shock wave angle using Mach and deflection angle

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  41. P

    Modern Philosophical Science Books(a very old example would be Mach)

    Einstein drew much of his inspiration for his reworkings of space and time from philosophical books such as those written by Ernst Mach. Are there any modern philosophical science books that focus on the dilemmas of today's physics (hopefully that are respectable and not completely wacky)...
  42. L

    Calculating Reflected Pressures in Mach Reflection Region

    Hello guys, I want to compute reflected pressures in Mach reflection region. In Mach reflection, let's just think about the reflected, incident and merged pressures (of Mach stem). You know, the merged pressure is created by coalescing the incident and reflected pressures. Assuming that all...
  43. S

    How Long Before Hearing a Sonic Boom from a Supersonic Plane at Mach 3?

    Homework Statement A supersonic plane flies at Mach 3 at an altitude of 20,000 m. A person on the ground sees the plane directly overhead. How much time passes the before she hears the sonic boom? Homework Equations f=fo(v+-vo/v-+vs) The Attempt at a Solution I don't really know...
  44. U

    Can mach number increase from 1.8 to 1.22 in Fanno flow?

    In a problem in our book, it says that the mach number in a constant area duct with friction (Fanno flow), the mach number increases from 1.8 to 1.22...however, from the Fanno line, its very clear that in the supersonic region, mach number always decreases along the flow...is there some kind of...
  45. W

    Is it possible to have a Mach number greater than 1 at the throat?

    I have a question on Gas Dynamics, we were going over a problem in class in which the problem asks to solve for the Mach number at the throat of a converging-diverging nozzle. I assumed that the Mach at the throat should be equal to 1 since the professor said it was impossible to have a Mach...
  46. W

    Is it possible to have a Mach number greater than 1 at the throat?

    I have a problem for my Gas Dynamics homework, in which the problem asks to solve for the Mach number at the throat of a converging-diverging nozzle. I assumed that the Mach at the throat should be equal to 1 since the professor said it was impossible to have a Mach number greater then 1 at...
  47. N

    What would happen when a jet travelling at Mach 10 experiences engine failure

    If a hypersonic jet (Mach 10) were to experience sudden engine failure at high altitude what would happen? Would it continue traveling forward, slowly decelerating and descending, thereby giving the pilot chance to attempt a controlled engine restart? Or would the jet experience catastrophic...
  48. A

    Flying at the Speed of Sound: What Would a Human Feel?

    If a human were to wear a jetpack and could fly at the speed of sound, what would he feel? Would he feel the sound waves piling up on his head? What would he hear? Inside supersonic aircraft he would hear nothing, and anyone outside would hear the pressure wave, but, what if his head is the...
  49. Bob3141592

    Inflation, Mach's Principle & the Early Universe

    As I understand it, somewhere close to the beginning of the universe, the universe experienced an inflationary phase when the space 'underneath' object began to expand faster than c, the speed of light. Since it wasn't the objects themselves that were expanding, there was no violation of the...
  50. R

    Flight Mach number in terms of fuel flow rate and other parameters

    I've posted on here in relation to an aerospace analysis project I'm doing. I'm stuck on one part of the project where I need to develop the performance envelope of the turbojet engine. 3 of the 9 plots that are required are Thrust vs. Mach number. On each of those plots I'll about 7 different...
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