HDTenEightyP/NetNews huggingface dataset:
From: weemba@sagi.wistar.upenn.edu (Matthew P Wiener)
Newsgroups: sci.math
Subject: Re: When's a proposition provable w/ choice indep. of choice?
Keywords: Axiom of Choice, logic, set theory, intuitionism, constructionism, nonstandard analysis
Date: 15 Nov 92 18:50:27 GMT
Reply-To: weemba@sagi.wistar.upenn.edu (Matthew P Wiener)
Organization: The Wistar Institute of Anatomy and Biology
In-reply-to: pruss@math.ubc.ca (Alexander Pruss)

In article <1e3qvjINN3ul@iskut.ucs.ubc.ca>, pruss@math (Alexander Pruss) writes:
>       Are there any ways of judging whether a proposition is in some way
>independent of the axiom of choice, without trying to prove/disprove it
>without Choice?  The application would be to take a proposition which is
>proved with the axiom of choice, and be able to assert that it holds even
>without the axiom of choice, without going through the proof.

Yes--it's a notion called "absoluteness".  The only case I've seen of
the above was an invocation of model-theoretical results that depended
on GCH, and the claim that the final result itself did not need it.

>[...]  A similar but stricter question is whether there is any guideline
>for determining if a proposition of a certain form being provable in
>ordinary set theory is thence constructively provable. [...]

The easy result, which you realized yourself, is that all first order
statements about the positive integers are absolute.  (Meaning that
all quantifiers are for integers.)  A step beyond is the realization
that an existential second-order quantifier over sets of the integers
preserves absoluteness upwards.  That is, given a purely first-order
statement, quantified by "there exists a function f:N->N" or something
like that, if its true in a small model, it will be true in a larger
model.

The canonical choice of "small model" is Goedel's constructible universe
L.  Since L models AC, anything proven in L that is absolute upward is
true without assuming AC.  This kind of diagram chasing, where truth and
not elements is what gets kicked around, bugs some people, so it's worth
realizing that all that's done is the search for the quantifier witness
is done via the time-honored method of looking for a particular kind of
witness.  In this case, one that's part of a well-ordered universe.

Things get exciting though.  Shoenfield has an absoluteness theorem
which state that the first non-obviosity here also works.  If you have
a statement "there exists f, for all g,h <1o arithmetic>", then it too
will be absolute between L and V.  So any use of choice is redundant
for such a statement also.

See Jech SET THEORY for the precise statement and proof.
-- 
-Matthew P Wiener (weemba@sagi.wistar.upenn.edu)
From: mmm@cup.portal.com (Mark Robert Thorson)
Newsgroups: sci.aeronautics
Subject: Re: AERO-CAR??
Date: Sat, 21 Nov 92 18:43:35 PST
Organization: The Portal System (TM)

There was an article in _Smithsonian_ magazine on this, about five years ago.
The one which was most successful was produced in small numbers back in
the 1950's.  I believe it was a pusher design, and that it used some sort
of unorthodox system to transfer power to the propellor.  This was its
main weakness, because it made the plane a maintenance hog.

One of these planes was used for short time by a Seattle radio station
to report on traffic conditions.  One of the people who flew in it
said it was fun to honk the horn at seagulls.

Note that I referred to _Smithsonian_ above.  This is their regular
magazine, not the one published by the National Air and Space Museum.
Newsgroups: sci.aeronautics
From: vkochend@nyx.cs.du.edu (vance kochenderfer)
Subject: Re: Boomerangs
X-Disclaimer: Nyx is a public access Unix system run by the University
	of Denver for the Denver community.  The University has neither
	control over nor responsibility for the opinions of users.
Organization: Nyx, Public Access Unix at U. of Denver Math/CS dept.
Distribution: usa
Date: Wed, 18 Nov 92 01:46:56 GMT

In article <1992Nov17.170857.15462@athena.mit.edu> brndlfly@athena.mit.edu (Matthew T Velazquez) writes:
>vkochend@nyx.cs.du.edu (vance kochenderfer) writes:
>
>> Of course, the boomerang will not develop any lift from the frictionless
>> air and will simply travel in a straight line as it falls to the ground.
>
>Friction has very little to do with lift.  The only purpose friction serves is
>to make an engineer ruin a perfectly good airplane by putting an engine on it.
>:o)#
>

Actually, I was oversimplifying.  Of course, the boomerang will generate
lift from the pressure difference.  It will travel in some sort of
a quasi-circular path, but remember that the atmosphere is not moving
with the same speed as the train.  It will probably return close to the
point from which it was thrown.  But I still want to get some frictionless
air.  It would make my design project so much easier.

Vance "you could try Slick 50, I guess" Kochenderfer
Virginia Tech                     |        "You are growing tiresome."
vkochend@nyx.cs.du.edu            |                       -Dieter
Newsgroups: sci.aeronautics
From: natelson@ernie.Princeton.EDU (Douglas Natelson)
Subject: thermodynamic model of air
Originator: news@nimaster
Organization: Princeton University
Distribution: sci.aeronautics
Date: Sat, 21 Nov 1992 03:33:30 GMT

Hi.

I'm interested in a thermodynamic model of air over the following 
range:

	Pressure: 2e-4 atm to ~10000 atm
	Temperature:  100 K to 2500 K

outside the vapor dome.  I've already got William Reynolds' 1979
model from his book _Thermodynamic_Properties_in_SI_, and I'm
looking for others.

Specifically, I'd like h(rho,T), P(rho,T), s(rho,T) if possible.

Any help would be appreciated, especially FORTRAN code, if 
available.

			Thanks.

			Douglas Natelson
			natelson@phoenix.princeton.edu

Newsgroups: sci.aeronautics
From: lcardina@nhgs.vak12ed.edu (Loretta A. Cardinale)
Subject: NASA Select
Organization: Virginia's Public Education Network (Hampton)
Date: Wed, 18 Nov 92 22:15:55 GMT

NASA SELECT TELEVISION

NASA Select Television is now available for viewing at the 
NASA Teacher Resource Centers.  In addiiton to live mission 
coverage, NASA Select offers informational and educational 
programming on space and related topics.  The station is now 
available in the Teacher Resource Center at the Air & Space 
Center in Hampton.  Programs may be taped and cover topics 
such as biology, geology, the atmospheric and 
earth sciences, and math and engineering concepts.  
In addition to the availability at the Teacher 
Resource Centers, NASA Select transmits on SatCom F2R, 
Transponder 13, C Band, 72 Degrees West Longitude, 
Frequency 3954.5 MHz, Vertical Polarization and Audio on 6.8 
MHz.  

To find out more and about tape availability, call the NASA 
Teacher Resource Center nearest you. 
In Virginia, call (804)727-0900, extension 757.
-- 
From Loretta A. Cardinale, Ph.D.
Virginia Space Grant Consortium
Newsgroups: sci.aeronautics
From: brndlfly@athena.mit.edu (Matthew T Velazquez)
Subject: Re: Boomerangs
Organization: Massachusetts Institute of Technology
Distribution: usa
Date: Tue, 17 Nov 1992 17:08:57 GMT

vkochend@nyx.cs.du.edu (vance kochenderfer) writes:

> Of course, the boomerang will not develop any lift from the frictionless
> air and will simply travel in a straight line as it falls to the ground.

This is just intuition speaking.

The gross aerodynamic properties of a boomerang are such that it will return 
to the point from which it was launched with (about) the same speed with which
it was thrown.  Tossing one off a moving train is exactly the same as ground
launching it with a howitzer.  That means that some guy back in the dining car
is going to be pelted by a boomerang.

Friction has very little to do with lift.  The only purpose friction serves is
to make an engineer ruin a perfectly good airplane by putting an engine on it.
:o)#

			-T
				T Velazquez
				MIT Aero/Astro
				brndlfly@athena.mit.edu
"Crayolas are one of the few things the human race has in common."
				-Robert Fulghum

Newsgroups: sci.aeronautics
From: wd@cs.tu-berlin.de (Wolfgang Diestelkamp)
Subject: Re: Boomerangs
Organization: Technical University of Berlin, Germany
Distribution: usa
Date: Wed, 18 Nov 1992 11:22:04 GMT

In article <1992Nov17.170857.15462@athena.mit.edu> brndlfly@athena.mit.edu (Matthew T Velazquez) writes:

[ ... ]
> 
> Friction has very little to do with lift.  The only purpose friction serves is
> to make an engineer ruin a perfectly good airplane by putting an engine on it.
> :o)#

Well, yes, exept that it is proportional to the lift generated :-)
(simplifying a little by assuming a constant angle-of-attack and
airfoil).
Of course this does not imply that friction actually *generates*
lift.
Why not restart the "why does a wing fly" thread :-?
-- 
Wolfgang Diestelkamp
wd@cs.tu-berlin.de
wolfgang@first.gmd.de

Newsgroups: sci.aeronautics
From: crouse@eng.umd.edu (Gil Crouse)
Subject: Re: Boomerangs (was: Re: UL used for sitcom plot)
Date: Wed, 18 Nov 92 13:58:00 GMT
Organization: University of Maryland
Summary: no viscosity = no lift

In article <27605@oasys.dt.navy.mil> kphillip@oasys.dt.navy.mil (Kenneth Phillips) writes:
>In sci.aeronautics, mechalas@gn.ecn.purdue.edu (John P. Mechalas) writes:
>>Lift is caused by circulation of the fluid about the body.  In an inviscid
>>fluid, there is no circulation, and hence no lift.  Of course, there's no
>>drag either.  :)
>
>
>If you get no lift in inviscid flow, we had better rewrite all the texts
>on aerofoil theory..

At the risk of restarting the "why do wings produce lift" thread, no
viscosity = no lift.  While it appears that inviscid flow techniques
can be used to predict the lift on a wing, this is not really true.
There is a hidden assumption in airfoil theory, and that is the Kutta
condition.  In order to predict lift using an inviscid flow model, the
Kutta condition on the trailing edge of the airfoil must be enforced.
The Kutta condition is that the flow leaves the trailing edge
smoothly.  This is a viscous assumption, and in a truly inviscid flow,
there is no reason to make this assumption.

Several followups to this thread have brought up the concept of skin
friction.  Note that I'm not talking about friction here.
Viscosity != friction.  Friction on the surface of the airfoil doesn't
contribute to the lift.  It is the viscosity of the fluid that
prevents the flow from rounding the sharp trailing edge of the
airfoil.  Since the flow can't round the trailing edge (Kutta
condition), circulation is setup around the airfoil and lift is
produced.

The Kutta condition and the concept of circulation may not "explain"
lift, but they provide the foundation of the analytical models of
flow about airfoils.

Gil Crouse
crouse@eng.umd.edu
Newsgroups: sci.aeronautics
From: brunet@aix1.uottawa.ca (Sophie Brunet, CCS Health Sciences 7876637)
Subject: refuellers
Originator: brunet@aix1.uottawa.ca
Organization: University of Ottawa Computer Centre
Date: Fri, 20 Nov 92 15:20:06 GMT


I have a friend in the aircraft industry who wants to purchase one or more
refuellers.  If anyone has any information about used refuellers for sale,
please send me email directly to brunet@aix1.uottawa.ca or  at
sophie@labsun1.med.uottawa.ca .  Any information would be appreciated very
much.


Thank you,

Sophie Brunet
University of Ottawa
From: skjohn01@nx26.mik.uky.edu (stephen k johnson)
Newsgroups: sci.aeronautics
Subject: AERO-CAR??
Date: 18 Nov 92 23:49:46 GMT
Article-I.D.: ms.1992Nov18.234947.11909
Organization: University Of Kentucky, Dept. of Math Sciences

I was just wondering if anyone on here had ever heard of the Aero-Car.
I think it was manafactured in the 50's.Only a few were made.I think about  
100.If you have E-Mail me.PLEASE!!



						Kelly


---------------------
Stephen Kelly Johnson
SKJOHN01@MIK.UKY.EDU
---------------------
From: afallen@lims02.lerc.nasa.gov (E. Allen Arrington)
Subject: wind tunnel dew point
News-Software: VAX/VMS VNEWS 1.41    
Organization: 1st Kentucky Cavalry Co. C
Date: 18 Nov 1992 09:35 EST  

Okay, all you wind tunnel folks out there, here's a topic for you:

Currently at NASA Lewis, we are upgrading our 8x6 Supersonic wind tunnel
(propulsion type continuous flow atmospheric tunnel, Mach range of 0.36 to  
2.0).  The upgrades being made are basically flow quality related (new 
improved screens and honeycomb, better tunnel contours, that sort of thing)
Included in this are improvements to tunnel instrumentation, including 
measurement of dew point.  A great deal of study was done in our 10x10 SWT; 
the results of this work showed that a Stephens Analytical Hygrometer 
DEWLUXE 20 was the best choice.  I would like some info from the wind 
tunnel people out there about how y'all measure dew point, what accuracy is 
needed, over what Mach number range it is critcal, etc., etc.  

Thanks in advance.

E. Allen Arrington  
        Trooper, 1st Kentucky Cavalry, Co. C 
(and operations engineer, Sverdrup Technology, NASA Lewis Research Center)                 
Newsgroups: sci.aeronautics
From: vkochend@nyx.cs.du.edu (vance kochenderfer)
Subject: Re: AERO-CAR??
X-Disclaimer: Nyx is a public access Unix system run by the University
	of Denver for the Denver community.  The University has neither
	control over nor responsibility for the opinions of users.
Organization: Nyx, Public Access Unix at U. of Denver Math/CS dept.
Date: Thu, 19 Nov 92 22:57:35 GMT

     As a related item, you may want to look up the Piasecki airjeep.
There was another hovering car someone built for the army, but I can't
for the life of me remember what it's called.

Vance Kochenderfer
Virginia Tech             |   "You want to get ahold of Mrs. Potter? I don't
vkochend@nyx.cs.du.edu    |    know, she's awfully ticklish.." -Groucho Marx
Newsgroups: sci.aeronautics
From: sawdey@matterhorn.ee.umn.edu (Aaron Sawdey)
Subject: Re: AERO-CAR??
Organization: University of Minnesota, Minneapolis, EE dept.
Date: Sun, 22 Nov 1992 22:55:19 GMT

In <69993@cup.portal.com> mmm@cup.portal.com (Mark Robert Thorson) writes:

>There was an article in _Smithsonian_ magazine on this, about five years ago.
>The one which was most successful was produced in small numbers back in
>the 1950's.  I believe it was a pusher design, and that it used some sort
>of unorthodox system to transfer power to the propellor.  This was its
>main weakness, because it made the plane a maintenance hog.

>One of these planes was used for short time by a Seattle radio station
>to report on traffic conditions.  One of the people who flew in it
>said it was fun to honk the horn at seagulls.

When I was at Oshkosh '91 (I think -- could have been '90) somebody
did a 5-minute demo of an Aero-Car. The humorous point was when he put
on the turn-signal to signal his turn to final approach.
Newsgroups: sci.aeronautics.airliners
From: Mohamed Ishaq <mishaq@ccwf.cc.utexas.edu>
Subject: Info on the El-Al Plane crash
Reply-To: Mohamed Ishaq <mishaq@ccwf.cc.utexas.edu>
X-Original-Message-Id: <Pine.2.4.9211201205.A6611@louie.cc.utexas.edu>
Date: Fri, 20 Nov 1992 12:50:48 (CST)

I am looking for information on the El-Al 747-200 plane crash in the
Netherlands on Oct 4, 1992. I am planning on writing a report on the
application of non-destructive testing to engine mount fuse pins and am
analyzing the Boeing SB related to this crash and the China Airlines one
earlier this year.

I found your address on the user-net : sci.aeronautics.airliners. Once I
complete my report I will be more than happy to post it the network.

Thanks

Mohamed Ishaq - mishaq@ccwf.cc.utexas.edu
		P.O. Box 8171
		Austin, TX 78713-8171
		Tel: 512-472-9290

P.S. I kind of need this info ASAP		

Newsgroups: sci.aeronautics.airliners
From: bentson@CS.ColoState.EDU (Randolph Bentson)
Subject: Re: TV programme on 777
Organization: Colorado State University, Computer Science Department
X-Original-Message-ID: <Nov19.163031.47683@yuma.ACNS.ColoState.EDU>
Date: Thu, 19 Nov 1992 16:30:31 GMT

In article <airliners.1992.7@ohare.Chicago.COM> lomasm@t9.cs.man.ac.uk
(Martin Lomas) writes:
>...
>Fly by wire briefly explained.
>...
>Any other critics out there?
>
>
>Martin.
>

-NOT FROM THE SHOW-

Boeing is _very_ reluctant to use fly-by-wire.  Management
trusts computer solutions no more than members of this forum.  I
got the impression that this system has a pilot override as part
of it's basic design.  (A sort of "do what I say, not what you
think I want" mode.)

One interesting feature is the networking of non-flight related
computers.  Planes will have an internet that will also link
link to ground stations, satellites, and other planes.  They
will have the ability to do significant book-work while in the
air.  Flight crews will be able to order maintenance and
consumables, weather and traffic information can be exchanged,
etc.  It's likely there will be a network for passangers-- a big
step forward from airphone.

Boeing recently moved a great number of folks (on the order of
5000) that were scattered south of Seattle to a new facility in
Everett, Washington (about 50 miles north).  They did it on the
week-end so as not to disrupt anybody's work.  They figure this
will enhance communication among folks working.

-- 
    Randolph Bentson                 Colorado State University
    bentson@CS.ColoState.Edu         Computer Science Department
    303/491-5792                     Ft. Collins, CO 80523

Newsgroups: sci.aeronautics.airliners
From: Christopher Davis <ckd@eff.org>
Subject: Re: hydraulic problems with DC-10's??
X-Original-Message-Id: <199211200503.AA03970@loiosh.eff.org>
Date: Fri, 20 Nov 1992 00:03:12 -0500

Karl> == Karl Swartz <kls@ohare.Chicago.COM> 

 Karl> Probably the best general interest discussion of the DC-10 and
 Karl> all its problems is in The Sporty Game, by John Newhouse (Alfred
 Karl> A. Knopf, New York, 1982).  Chapter 5 in particular goes into
 Karl> great detail, though it of course predates the Sioux City crash.

Other good books on the subject include Moira Johnston's _The Last Nine
Minutes_ (which, being 1976, only discusses the Turkish Airlines
Ermenonville crash and the Windsor "incident" which foreshadowed it) and
John Nance's _Blind Trust_ (1986, also predating Sioux City).  (The
latter discusses many other air safety issues and incidents, including
the Air Florida crash in Washington, DC in 1982.)

_The Sporty Game_ tends to show its age in other areas as well; the dire
predictions of market failure for the 747, 757, and 767 have not quite
been borne out by intervening events :)


Newsgroups: sci.aeronautics.airliners
From: sdl@linus.mitre.org
Subject: hydraulic problems with DC-10's??
X-Original-Message-Id: <9211181502.AA03545@rigel.mitre.org>
Date: Wed, 18 Nov 92 10:02:08 -0500


Great new newsgroup!

Perhaps now I can get a more definitive answer to the following:

Some of my pilot friends have accused the DC-10 as having a
particularly bad history of hydraulic problems (which have contributed
to a few crashes).  But do the statistics really support the notion
that the DC-10 really has a significantly worse safety record than
other wide-body jets, or is this just a myth?  Also, have all these
hydraulic problems been corrected, or does the DC-10 still suffer from
hydraulic problems even today?




Newsgroups: sci.aeronautics.airliners
From: Pete Mellor <pm@cs.city.ac.uk>
Subject: Re: TV programme on 777
X-Original-Message-Id: <3891.9211191222@csrsun8.cs.city.ac.uk>
Date: Thu, 19 Nov 92 12:22:53 GMT

Jonathan, 

> Would anyone who saw the whole programme like to provide a
> brief summary in this forum? 

(A slightly more temperate response to your question! :-) 

The programme concentrated mainly on the design of the airframe, and the use 
of CAD systems to do this. It described how the structural calculations and 
spatial arrangement of components could be handled using 3-D movable graphics. 
The design system was intended to be "paperless", with electronic transfer of 
designs between engineers' workstations, instead of blue-prints being dropped 
in in-trays. 

Examples of the sort of problems they were shown tackling were "What weight 
of metal can we drill out of this structure and still leave it strong enough 
to bear the stress?", and "When the kitchen door opens, does it hit the knees 
of the first-cklass passengers?". 

There was quite a bit of time devoted to the design of the doors, with a 
management requirement to have them all identical to cut production costs, 
and the design problems this entailed. The poor old designer took three months 
to solve this one first time round, under pressure from what the manager 
described as a "management ploy". ("Well, if *you* can't do it, which 
consultant do you suggest we bring in to solve it for you?") On the second 
version of the design, the problem of door uniformity was solved in a few 
weeks, and by the third iteration it was down to a few days. 

It definitely did have the feel of a "Boeing commercial" about it, with lots 
of "gee-whizz" shots of designers manipulating computer graphics, and 
anecdotes of the "Yes, of course we had problems, but just look how we learned 
to overcome them!" variety. (See the door problem above.) 

It was an interesting programme, but I was disappointed to find only one 
passing reference to the flight control systems, having originally watched 
it in the hope of learning about Boeing's approach to fly-by-computer. 

Pete
-------------------------------------------------------------------------------


Newsgroups: sci.aeronautics.airliners
From: sfg2483@uxa.cso.uiuc.edu (sfg2483 )
Subject: Manufacturer responsibility?
Organization: University of Illinois at Urbana
X-Original-Message-Id: <By1tLC.7Av@news.cso.uiuc.edu>
Date: Sat, 21 Nov 1992 04:24:47 GMT

Does anyone know if a manufacturer (e.g., Boeing) is responsible financially
for the results of an airplane crash if the crash is proven to be caused by
a faulty part it made? (E.g., a bad design of pins in the 747).

sfg2483@uxa.cso.uiuc.edu


Newsgroups: sci.aeronautics.airliners
From: Chijioke.Anyanwu@brunel.ac.uk (Chijioke D Anyanwu)
Subject: Re: TV programme on 777
Organization: Brunel University, West London, UK
X-Original-Message-Id: <2666.9211200818@gassendi.brunel.ac.uk>
X-Original-Message-ID: <By09px.21J@brunel.ac.uk>
Date: Fri, 20 Nov 1992 08:17:55 GMT

In article <airliners.1992.7@ohare.Chicago.COM>, lomasm@t9.cs.man.ac.uk (Martin Lomas) gives an excellent summary of last Sunday's Equinox on the 777 - I
definitely couldn't have done better.

He says
>Customers allowed into (some) of the Boeing meetings to discuss the
>777's design and to suggest mods. 'Open management' strategy.

Specifically Lord King: BA will be a launch customer as will Emirates which is
already advertising the fact.

One thing which he omitted and which I found quite interesting was
the amount of attention paid to the design of the toilet. Apparently,
banging toilet seats tend to cause some passengers some amount of distress
(thoughts of bombs going off?) and so a virtually noiseless toilet seat and
cover were designed.

Although as Martin pointed out FBW safety issues were not covered 
(something which I had rather expected in view of all the controversy
surrounding the A320), the programme really was a fascinating insight
into modern aircraft design and development.

Chijioke.