HDTenEightyP/NetNews huggingface dataset:
From: crcc6@Rosie.UH.EDU (Message from the Starship Enterprise)
Subject: A quantum mechanics question
Reply-To: crcc6@Rosie.UH.EDU
Organization: University of Houston
Date: Thu, 16 Apr 1992 23:27:48 GMT

            +        +
            +        +
   V(x)=OO  + V(x)=0 +  V(x)=OO (infinite potential to the right
            +        +           and left on the well)
            ++++++++++

           x=0      x=a

 Suppose you have a particle (1-D) in an infinite square well ....
assume also that the state of the system is the ground state of the
box, so |Psi> = sqrt (1/a) sin kx. If BOTH walls disolve at t=0,
the probability distributions of energy and momentum can be calculated
from Q(E)=|<En|Psi>|^2 and taking advantage from the fact that the
Hamiltonian and Momentum operators conmute for this particular new
state. All is joy and happines :-)

                
Now, consider the particle in the box problem again. Now at time t=0 
only the left side of the wall vanishes. The energy distribution can
be calculated using the formula above. How do you calculate the momentum
distribution????? - [H,P] =! 0 anymore .... -this is an old homework
problem I never solved ... thanks in advance



            +        
            +        
   V(x)=OO  + V(x)=0             
            +                             
            ++++++++++++++++++++++++++++++++++++

           x=0









  ***************************************************************************
  $^$ "I perceive the Universe as  ^^^^^^   Jose Luis Paredes             $^$
  $^$  a single equation .... and  ^^^^^^   Physicist by choice !!        $^$
  $^$  it's so simple!"            ^^^^^^   University of Houston         $^$
  $^$  Lt. Barkley -Star Trek TNG  ^^^^^^   Jose@crcc.uh.edu              $^$
  ***************************************************************************
From: pauls@trsvax.tandy.com
Date: 06 Apr 92 12:31 CDT
Newsgroups: sci.physics
Subject: SSC magnets - how?
Message-ID: <8400007@trsvax>
Nf-ID: #N:trsvax:8400007:000:305
Nf-From: trsvax.tandy.com!pauls    Apr  6 12:31:00 1992


AnotherSSC question:

1) How many magnets are used?

2) In relative terms, how do they compare to other magnets in use today?

3) What is MBTF of a magnet today (FermiLab)?

4) How many 'up days' (up hours??) does the average collider have today?

5) If a SSC magnet goes fubar, is the whole thing down?
From: palmer@sfu.ca (Leigh Palmer)
Subject: Re: Electrical Conductivity an Intensive Variable?
Organization: Simon Fraser University
Date: Tue, 14 Apr 1992 17:11:37 GMT

In article <92104.123138CCB104@psuvm.psu.edu> CCB104@psuvm.psu.edu asks:
>Is electrical conductivity considered to be an intensive variable? Please
>explain briefly why or why not if you decide to say yes or no! Thanks!
>Carey

I will assume this question was asked in the context of classical
thermodynamics.
In such a context "intensive" quantities pertain to the substance, but not to
the
extent, or size, of the system. Electrical conductivity is certainly in that
category *classically*, but in reality conductivity is dependent upon nonlocal
influences, and for systems with sufficiently small dimensions electrical
conduc-
tivity could certainly fail to satisfy the condition that it does not depend
upon
the size of the system.

This in no way relegates conductivity to the "extensive" category in such
cases.

Leigh Palmer
Newsgroups: sci.physics
From: dow@nova2.stanford.edu (Keith Dow)
Subject: Re: Yes, Virginia, there's no superluminal communication
Organization: Stanford University
Date: Tue, 14 Apr 1992 14:01:19 GMT

>But there's no "classical" experiment that led to the copenhagen instant
>observer-makes-collapse rule, is there?  Or is this also part of
>the Stern-Gerlach-type experiment?

There are modern experiments which support it though.
Organization: Penn State University
Date: Friday, 10 Apr 1992 09:05:28 EDT
From: <MRG3@psuvm.psu.edu>
Newsgroups: sci.physics
Subject: Re: What is not being conserved?


 tolman%asylum.utah.edu@cs.utah.edu (Kenneth Tolman) writes
.   In QM there is a probability that a photon will end up "hitting" a
.certain spot.  If there is only one photon, and it has a nondetermined
.end point, then some quantity is not being conserved.  Consider if I threw
.a ball, and then it appeared randomly.  How can there be equal and opposite
.reaction unless it is going to a specific place?
.
.   Obviously I have something wrong.  Does a photon have absolutely zero
.momentum?  I thought that the idea behind solar sailing was to take
.advantage of incredibly small momentums.
.
.  The other possibility is that it retroactively changes the transmitter.
.This seems pretty dubious.


Momentum is conserved, but quantum mechanically (that does not mean "only on
average")
If you threw the ball classically in a random direction, there will be a
reaction on you, random in direction, but precisely correlated with the
actual direction of the of the ball.  You can in fact determine (in principle)
the direction of the ball by measuring the reaction. The randomness can only
be a matter of ignorance of the well defined values for the components of
momentum.

If, on the other hand, you threw the ball  quantum mechanically, and the
randomness was a result of a quantum mechanical superposition, things
change bit.  It may be that no amount of idealization (for the particular
quantum interaction which caused you to throw the ball) can tell you which
direction the ball went, even in principle.  However, conservation laws
dictate that the correlations observed classically will still be found.
That is to say, if we observe (measure) the direction of the ball, we know
the direction of the reaction on you, even before measurement (100%
correlation).  If you measure the reaction, then you know the direction of the
photon, er ball.  You will never be able to make a _pair_ of measurements
which indicate that momentum was not conserved.

An idle comment: It is in the nature of the choices of what measurements
to make which give rise to such issues as the EPR "paradox" and Bells's
theorem.


regards
-Mike Gallis
From: jfw@ksr.com (John F. Woods)
Newsgroups: sci.physics
Subject: Re: Voltage drop in Silicon diode
Date: 10 Apr 92 10:45:47 EDT

raju@bass.bu.edu (rajminder Singh) writes:
>Hi there! I am  taking a course in Solid State Physics but I still 
>haven't been able to answer the basic question of why the voltage drop
>in a Silicon p-n junction is around 0.7 Volts ?

Having dropped that course pretty quickly, I might not be the best person to
answer the question (:-), but the ARRL Handbook provides a clear enough
explanation for me to summarize.  That voltage potential represents the
difference in the energies of the conduction bands of P material and N
material in the assembled diode, and will (I think) be equal to the difference
between the Fermi levels of the two materials when isolated (the energy level
at which half the electrons are in higher states and half are in lower states).
When the two materials are "joined", there is an initial flow of current which
shifts the energy levels in the two materials until the Fermi levels are equal,
which mean the conduction and valence bands in the two materials will shift
by corresponding amounts.  You've probably got a text that will explain it
more clearly than that (no, actually, if your texts are anything like mine,
the explanation will be less clear but far more detailed :-).

>Does this vary significantly
>with the doping level ?

Yes.

>What about the effect of temperature, current and
>the energy band gap (E) of the material used in the junction ?

Temperature and voltage I can answer pretty easily; the Handbook gives the
formula as V(t) = (t / 11 600) * ln(1 + If/(1E-13 * exp((t-300)*ln(2) / 4.5))).
Note that it depends on current as well, but not very much.

To calculate the voltage from the bands will require rereading a text I have
at home that I had trouble getting through the first time, so I won't :-).
However, in practical terms, germanium diodes have a gap of about .3 volts,
ordinary silicon diodes about .7, and LEDs of varying construction range from
1.5V (red, GaAs?) to 5V (blue, SiC).

Interesting tidbit:  common LEDs make moderately good voltage references in
the 1.5 to 3V range, depending on color.

Hope this helps, and I wish you better luck than I had.
From: wa2ise@cbnewsb.cb.att.com (robert.f.casey)
Newsgroups: sci.space
Subject: Re: Human UV vision
Date: 8 Apr 92 03:46:02 GMT
Organization: AT&T

In article <1992Apr6.174236.23885@aio.jsc.nasa.gov> hack@arabia.uucp (Edmund Hack) writes:
>
>Use of local anesthesia is standard procedure these days for cataract surgery.
>However, the patient is usually given sedation ahead of time, so they are kind
>of dopey and placid.  The eye is then anesthetized and the surgery done.  The
>most common sedative is Versed, a Valium derivative that is very fast acting,
>has a very short half-life and produces amnesia in 90%+ of patients given it.
>My wife is an anesthesiologist and said Versed is one of the big breakthrus
>in the last 10 years in anesthesia - it sedates the patient, but blocks short
>term memory, so they forget things a few seconds after they happen.
>
I've had one cataract and two retina detachment repair jobs done in the past
few years, each under local.  And they gave me some "I don't care what you
do to me" sedation industrial strength drug of some sort.  And yes, I can see
more blue and violet with the eye with the plastic lens in it, and the focus
range isn't too bad considering it's not adjustable.  How's this for wierd
medicine:  the retina detachments were repaired by the surgeon applying a
controlled amount of liquid nitrogen on the outer surface of the eyeball
next to the detached retina site, and then he puts a silicon rubber strap
around the eyeball (about half way between the front and back, you can't
see it, it's buried in the head).  Don't ask me how he installed the band,
I can't imagine that he could pull the eye out of the head some, as the 
eye pointing muscles and optic nerve can't have much slack in the head.
Yea, the sedation zeroed my memory of this.  The liquid nitrogen is suppose
to cause scar tissue to form, grabbing and locking the retina down.  It
seems the retina isn't normally all that well attached to anything, it
just being swandwiched between the eyeball and vitrious jelly stuff inside.
Doctors generally don't want to mess with eyes unless they have to, because
if they screw up, you go blind, which is obviously a serious disaster.  
But a retina detaching will make you blind, so they have to get to work on
it quickly (If you see a blackout of a patch of side vision, have an eye
surgeon inspect it immediately.  Also fake flashes of white light can
mean trouble).  
Ah.. to bring some sci.space content to this, what if an astronaut gets
a serious problem like retina detachnents en route to Mars?  
Newsgroups: sci.space,sci.astro
From: stgprao@xing.unocal.com (Richard Ottolini)
Subject: Re: Isaac Asimov, Science fact and fiction writer
Originator: stgprao@xing
Organization: Unocal Corporation, Anaheim, California
Date: Wed, 8 Apr 1992 15:10:08 GMT

Today's LA Times ran an article citing many Caltech and JPL scientists who
were inspired to become scientists by Issac's fiction and non-fiction.
Newsgroups: sci.space
From: ewright@convex.com (Edward V. Wright)
Subject: Re: SDI update
Organization: Engineering, CONVEX Computer Corp., Richardson, Tx., USA
Date: Wed, 8 Apr 1992 23:33:24 GMT
X-Disclaimer: This message was written by a user at CONVEX Computer
              Corp. The opinions expressed are those of the user and
              not necessarily those of CONVEX.

>>>... What steps are being taken now to ensure this system
>>>doesn't accidently shoot down a shuttle?

>>About the same ones taken to make sure that Patriot doesn't accidentally
>>shoot down an airliner.

>Which isn't really correct.  You see, when you have an independent
>space-based system comprised of several thousand autonomous pieces all
>whizzing around 100+ miles up, it's rather difficult to pull the plug
>on them.  You rely on controls, certainly.  But these controls are NOT
>(no way, no how, can't be) as good as the very simple control of
>having the device under your physical control.

You are making a bad assumption here: that the normal state of affairs
will be that interceptors have permission to fire automatically and will 
do so unless someone on the ground overrides.  In reality, they will
probably be controlled in much the same way as nuclear weapons are today:
that is to say, the weapons are normally disabled and must receive an
explicit "go code" before they can launch.   

>Unfortunately, if one of these things decides that the shuttle
>is an Enemy Attacker, nobody can do much to stop it from going off and
>killing the thing - it's not like you can walk up and pull out the
>plug.

No, somebody has to broadcast the code to plug it in.  

>Our Patriot might mark the target and
>say to its operator:  "I am going to engage this target in 10 seconds
>and there is nothing you can do to stop me".  But there *is*.  The
>operator can, if necessary, drop a grenade on top of it.  It's messy,
>but it works.  

This is just plain silly.  Electronic authorization codes have prevented
the accidental launch of an ICBM for more than 30 years.  No one has ever
had to drop a grenade to prevent one from being launched, and dropping a
hand grenade on an ICBM silo designed to survive a near miss by a thermo-
nuclear warhead wouldn't do anything but qualify you for a psychiatric
discharge, anyway. 

>The moral is that strategic weapons should *always* be kept under
>physical control.  Proposals to do otherwise are just dangerous.

The moral is that it's pretty easy to package political propaganda
up as safety concerns.  The fact that we've never had an accidental 
ICBM launch after more than 30 years shows the safeguards are adequate.
If they're adequate to prevent an accidental launch of a nuclear warhead
that could kill millions, they're adequate to prevent the launch of an
interceptor that could destroy a single Shuttle.  Gosh-wow statements
meant to frighten and pander -- "whizzing around 100+miles up" -- not 
withstanding.
  

Xref: sparky sci.space:7580 news.answers:1083
From: ewright@convex.com (Edward V. Wright)
Subject: Re: Human UV vision
Organization: Engineering, CONVEX Computer Corp., Richardson, Tx., USA
Date: Wed, 8 Apr 1992 21:30:12 GMT
X-Disclaimer: This message was written by a user at CONVEX Computer
              Corp. The opinions expressed are those of the user and
              not necessarily those of CONVEX.

In <YdrC22m00WBKI6t78H@andrew.cmu.edu> Kevin William Ryan <kr0u+@andrew.cmu.edu> writes:

>>Thanks for your reply. Now I wonder what the "color" of UV is! (My guess 
would be blue.)

Color perception is a matter of learning and culture, so unless you
had UV perception since childhood and grew up in a culture that
distunuished it as a color, I doubt you could tell the difference
between violet and ultraviolet. 

>>In recent years, they've been replacing the lens with a plastic lens 
>>implanted in the eye.... It's logical to assume that UV filtration would
>> be built into the replacement lens.

The early plastic lenses didn't.  This may have changed now that we've
learned more about the dangers of UV radiation and (I would presume)
developed better UV-protective coatings.

>    Saw a PBS show the other day on cataract removal in India, where
>cataracts are apparently a major problem. Traveling field hospitals
>remove the cataracts at the rate of one every seven minutes per table,
>100-250 in a day, under _local_ {AAAHHH!!} anesthetic, 

Most eye surgery, even in the US, is done under local anesthetic.  The
dangers involved in general anesthesia are greater than most people
realize and far outweigh the phsychological discomfort of having someone
take a knife to your eyes while you are awake.
From: cchung@sneezy.phy.duke.edu (Charles Chung)
Newsgroups: sci.space
Subject: Re: Solar Power Satellites... what do *you* know?
Date: 8 Apr 92 01:29:20 GMT

I'm glad that I've started a new thread, but could any of you guys  
give me any good references on SPS?  I still need to deliver that  
paper...

Thanks,

-Chuck
Newsgroups: sci.space
From: holder@cse.uta.edu (Larry Holder)
Subject: Structural Databases
Organization: Computer Science & Engineering, Univ. of Texas at Arlington
Date: Wed, 15 Apr 1992 22:08:50 GMT

We are looking for databases to be used for testing an intelligent
structural data analysis tool.  I have read the FAQ on data sources
for sci.space, but none of the sources describe relationships among
the entities represented.  The database should be structural or a
flat representation of a structural environment (e.g., coordinates of
3d entities).  The database will be converted to a graph
representation for input to the system.  Any pointers to such
databases would be appreciated.

Thank you.

-- 
Larry Holder (holder@cse.uta.edu)

University of Texas at Arlington, Department of Computer Science Engineering
Box 19015, Arlington, TX 76019-0015, Phone: 817-273-2596, FAX: 817-273-2548
Newsgroups: sci.space
From: henry@zoo.toronto.edu (Henry Spencer)
Subject: Re: DCz
Date: Wed, 8 Apr 1992 05:33:59 GMT
Organization: U of Toronto Zoology

In article <7hpjav+@lynx.unm.edu> carls@triton.unm.edu (Mr.HolierThanThou) writes:
>       Let's saywe use RP1 (not the best fuel maybe but a good one)
>and the vehicle will be unmanned for simplicity. Let's call the
>payload 10,000 kg. For engines let's use two types, a small 
>ramjet to get to 31 km and a rocket engine that propels the craft
>to mach 1, shuts off, and starts again at 31 km to propel the craft
>into orbit (note the engine should be optimised for vacuum
>proformance).
>       You can use any technology and hardware that is available
>now ...

That lets out your ramjets completely.  Ramjets capable of going beyond
perhaps Mach 6 have never been flown (barring possible secret programs).
What you are asking for is NASP, not Delta Clipper.

I don't understand this fascination people have with air-breathing engines.
Look, guys, ROCKETS ARE BETTER if you want a fast-moving low-risk program.
They are perfectly adequate for the job, they require far fewer design
compromises, and we understand them a lot better.

For nearly 35 years, we have had an operational LOX/RP1 launcher that
can carry about 1500kg -- or a one-man capsule -- to orbit using 1.5
stages and no airbreathing engines.  That extra 0.5 stage, and the fact
that it's an expendable, are annoying... but this thing was built with
1950s technology.  (It's the Atlas, by the way; John Glenn rode one.)

We really don't need ramjets to get a single-stage launcher into orbit.
And we don't want them either:  they are a liability, not an asset.

>       For a back of the envelope start, you can say that the
>rocket engine has a Isp vac. of 330sec and a mass of 1 kg per
>1 kNewton of thrust (about), and the fuel will be .5$ per kg
>(this includes your LOX and you got ripped off at that).

Fuel costs for almost any conceivable launcher are trivial.  The real
question, for either expendable or reusable, is how many man-years of
effort have to go into getting the thing ready for launch.  Existing
launchers are expensive because of all the guys with clipboards, not
because of the fuel or the metal.
-- 
GCC 2.0 is to C as SVR4 is to Unix.     | Henry Spencer @ U of Toronto Zoology
                             -Dick Dunn |  henry@zoo.toronto.edu  utzoo!henry
From: jim@netlink.cts.com (Jim Bowery)
Newsgroups: sci.space
Subject: Re: U.S. commerce, government buy Russian engine
Date: 7 Apr 92 19:19:14 GMT
Article-I.D.: netlink.RukViB1w164w
Organization: NetLink Online Communications, San Diego CA

Nick Szabo writes:
>More information on the Russian Hall effect electric rocket engines has 
been
>released.  Fifty (50) of these  "stationary plasma thrusters" have flown 
>in space on operational Soviet spacecraft for stationkeeping.  They operate 

>by ionizing xenon gas and accelerating that plasma with a magnetic field.  
>The following are on sale for c. $50-100K per unit:
>
>SPT-70
>specific impulse: 1,600 s.
>thrust: 0.009 lbs.
>power: 660 watts
>weight: 3.3 lbs.
>design life: 3,500 hrs.
>
>SPT-100
>specific impulse: 1,600 s.
>thrust: 0.018 lbs.
>power: 1,350 watts
>weight: ??
>lifetime: 4,000 hrs.
>
 
They are selling their reliability -- and cheap too, although
price isn't all that important in these systems.
 
The Hughes system has around 2500s and similar power efficiency.
At these higher isps the economic differences aren't all that
great.  The Soviets are going to sell these things for awhile
but they aren't going to be a big money maker.
 
The big gains come in apogee circularization, which requires the
higher thrust engines.  I don't think the CISers have that much
of a lead over Hughes in that regime.

--                    
INTERNET:  jim@netlink.cts.com (Jim Bowery)
UUCP:   ...!nosc!ryptyde!netlink!jim
NetLink Online Communications * Public Access in San Diego, CA (619) 435-6181
From: jesus@sys6626.bison.mb.ca (norman paterson)
Newsgroups: sci.space
Subject: New "rockoon" concept
Date: Wed, 15 Apr 92 21:54:17 CST
Organization: system 6626 BBS, Winnipeg MB

This is to announce my project which has been in the works for the last 
two years.  It inolves the construction of a dual airship platform from 
which a sounding rocket will be launched.  Combining the technology of 
old, re. Zepplin type technology, with modern materials, powerplants, and 
computers,  I am building this to demonstrate the feasibility of 
launching satellite launch vehicles from very large airship platforms.
Norman Paterson   CANADA

;--- (norman paterson) a user of sys6626, running waffle 1.64
;E-mail: jesus@sys6626.bison.mb.ca
;system 6626: 63 point west drive, winnipeg manitoba canada R3T 5G8
Newsgroups: sci.space
From: prb@access.digex.com (Pat)
Subject: Re: U.S. black programs
Organization: Express Access, Greenbelt, Maryland USA
Date: Wed, 8 Apr 1992 23:51:44 GMT

In article <1992Apr3.195904.5197@cfa203.harvard.edu> willner@cfa.harvard.edu (Steve Willner) writes:
>
>> In <1992Apr1.222545.14128@cfa203.harvard.edu>, I wrote:
>> >  Classification slows any research effort by some large factor.  
>
>
>In article <ewright.702249837@convex.convex.com>, ewright@convex.com
>(Edward V. Wright) writes: 
>> This is a powerful argument, of course.  The problem is, I'm not sure
>> it's true.  
>[Compares quick A-11 development to current lengthy development times.]
>
>Reread my original statement, noting the difference between "research
>effort" and the task of developing a product when all the information
>needed to do so is already known.

Of course teh A-12 which was black threw away a few billion
dollars and never produced.  The A-11/SR-71 like the U-2
were successes because of the people involved not the classification.

at teh same time as the SR-71,  China lake was developing the sidewinder
missile.  the did it in 19 months for 10,000 bucks developing the single]
most effective air to air IR guided missile.    

Appollo was developed white world and was a tremendous R&D effort.