Short Definition and 523 Threads

Hey guys having a bit of problem with my year 1 essay. Would really appreciate any help :) What are the main sources of gamma ray bursts both short and long duration? I know some are from supernovae but where do others come from?

This is a little bit of a weird one. The question asks me to prove that [\hat{L}^2,\hat{L}_z ] is equal to zero. I know what to do with it and how commutators work, and I know that L2 = Lx2 + Ly2 + Lz2 (where the 2 means squared) and I have expressions for Lx2, Ly2 and Lz2, but I was just...

I am looking for a way to calculate the power spectrum of short signals of variable duration (between 200 and 500 ms). Standard methods seem wildly inaccurate. Are there any tricks for short segments? Thanks anyone for a response.

The figure below shows a worker poling a boat-a very efficient mode of transportation-across a shallow lake. He pushes parallel to the length of the light pole, exerting on the bottom of the lake a force of 225 N. Assume the pole lies in the vertical plane containing the boat's keel. At one...

What kind of short term and long term effects does DMT have on the brain?

Hi I was Just hoping to ask a short question about improper integrals ... when there are two limits in the integral: the 1st limit is divergent but the second limit is indeterminate... can it be automatically divergent? or do you need to evaluate first the second limit using LHR? so that...

Homework Statement Two particles move along an x axis. Position of particle 1 is x = 6t^2 + 3t + 2. The acceleration of particle 2 is given by a = -8t and at t=0, its velocity is 20 m/s. When the velocities of the particles match, what is their velocity? Homework Equations The...

Is there a limit to the possible amplification of Short Wave radio transmission and/or reception? A friend of mine wants to build a massive amplifier / transmitter. If a limit does exist what is the physical law used to explain it?

What does it mean when an integral sign has a short horizontal line drawn on it?

In battery, after finishing of its construction and positive & negative electrode creation, why we will need an external electrical lead (for example copper wires) for transmission of energy between two poles? Why no short circuit occurs between positive and negative electrodes through...

Let A and B be real invertible n x n matrices so that B = (AT)-1. Show that Bm = (I - B1A1T)(AmT)+, where B1 = [b1, ..., bm], Bm = [bm+1, ..., bn], A1 = [a1, ..., am], Am = [am+1, ..., an]. Any pointers on how one would go about proving the above? I'm fresh out of ideas. I'm not...

hello to all at PF! As I understand that this is an international forum, I would like to post my group's survey here to gain an international perspective! It's about the self-service concept. Thanks for all your efforts! Have a nice day!

I saw farmhouse magazine on chuck phallahnuik's (no clue how his name is spelled; dude who wrote fight club) website and figured I'd submit a story. They accepted it which is pretty cool :smile: My story's "white clouds," is very short, I hope you like it if you read it but if you don't that's...

This isn't really homework, but close enough. I suppose this is quite simple, but my head's all tangled up for today. Anyways, Given the real symmetric matrix LTL = UDUT, find L. I suppose L = +- D1/2UT, and it's clear this choice of L satisfies the given equation. But can it be proven that...

I don't know where else to ask something like this, but a friend of mine had her period and lasted a day and a half.. and is worried that she could be pregnant... but that's not possible if her eggs dropped because she started her period right?

Hello All, I'm designing a driver board to control some MOSFETs. I have some mic4427 MOSFET drivers to drive the gates into avalanche mode but the function generators I am using to trigger the chips only put out 50% duty cycle square waves. I'm working in a wide frequency range from 1 kHz to...

Hi all! This is a neat forum; wish I'd found it sooner... I'm writing a short scifi story, and am having trouble understanding time dilation, which happens to be an integral part of the story. Anyway, here's my question: Its common scifi staple where starfarers travel at close to the speed...

Can some1 tell me r there any short term courses available on aerodynamics or can anybody refer me a good book...

Can someone give me a short description about dihedrals? for example what would be the elements of D10? or D4?

Homework Statement This is starting to get a bit trick because of mixed information. Anyways, does anyone know the effects of osteoporosis in terms of short term versus long term? Homework Equations N/A The Attempt at a Solution Spine fractures caused by osteoporosis are likely...

Idea for a short story. Say you had a colony ship that had its atmo contained by acceleration alone. It had an atmo that was comparable in depth to a planet. (Don't worry about it escaping, just help me with the radiation aspect.) Think of Niven's Ringworld. How much radiation would...

Homework Statement "find a point P on the parabola x^2-4y = 0 for which is minimum the distance PO/PF, where O is the origin and F the focus of the parabola" the solution is P(0;0), coincides with the origin, this is also clear graphically. The Attempt at a Solution Please follow...

Okay, I am really curious as to how you solve this question, I can't seem to figure it out. I am sure most of you will think it's a piece of cake, but I'm not a physics person at all :p If the suitcase was lifted 0.75 meters, how much force was required? (Hint: Use the equation for "work")...

I don't understand something on this problem: Q: A uniform plane wave with \vec E = \hat x E_x propagates in a lossless simple medium ( \epsilon_r = 4 \,\,\,\, \mu_r = 1 \,\,\,\, \sigma = 0 ) in the +z-direction. Assume that E_x is sinusoidal with a frequency of 100 (MHz) and has a...

I'm confused based on what I've been reading. Does short-range order for a crystal change when it is melted, or is onyl long range order affected by the state of matter an melting has little to no affect on the short range order of the crystal. Is that right or does the shrot range order change...

hey can you find the phase/gain margin of unstable system. I am asked for the phase margin of this system, but the nyquist plot reveals that -1 is encicled verfiying that the system is unstable,.. how can you get a phase margin of an unstable system?

So I had an argument with a friend, more like a discussion where we disagreed. It led to some interesting questions, or at least they are to me. I made a simple electromagnet using a battery, a nail, and an insulated copper wire wrapped around the nail many times with the ends of the...

http://www.shodor.org/~jingersoll/weave4/tutorial/tutorial.html

Hey guys, Since i all know i am going to be a "star actor" (please no laughing now). I give you this link of a movie in which i played. It is made by students from Sint Lukas in Bruxelles. Ok, the movie is very short and it is in Dutch but i think that the plot should be clear if you...

integral identity if we have \int dt f(t) = \int dt g(t) where both integrals are indefinite integrals, can we immediately conclude that f(t) = g(t) ? I know this doesn't work with definite integrals.

If I set up an interference experiment and make one path much longer than the other would I still see an interference pattern? If so why? It would seem to me that having one path very long would give which-way information because you could easily time the photons to see which path it went...

how is (tan X)(cos X) = (sin X) false? tan is sin/cos so when you multiply by cos, you get sin...yet the answer i was given was false? how so?

I am a HongKonger. My chemistry teacher comes from Canada and he wears short sleeves shirt every day, even when the temperarure is 10 degree Celcius. May I know is it true that Canadians still wears short sleeves shirt at 10 degree Celcius? I feel freezing. They are very strong...

express (2^1/2-1)^10 in the form k^1/2-(k-1)^1/2 where k is a positive integer.{the square roots need not be irrational}we can do this by binomial theorem but it is very tedious.is there a short & appropriate method to solve this problem?

what is short circuit and wat happens to different circuits when it occurs.wat operates it .

Could someone explain in a short and simple way the basic operation principle of a TEM?

Can somebody answer my question in a unique word? Are stars considered black bodies?

According to the equations, the tension of a string depends only on the the force acting (pulling) on it, and not on the length of the string. So why can someone with a bow and arrow with a long string (long bow) exert more force on an arrow than a bow with a short string (short bow)? Does it...

The statement, "when a resistor fails, it will normally open." is true. But I don't understand: when a resistor fails, doesn't that mean that the resistor doesn't work? so doesn't that mean that resistance=0=short circuit?

What exactly is an echelon matrix? I searched the web and did find some useful results but I'm still a little confused. :confused: Thanks in advance for any help. :smile:

Hello folks. The hinge for a story I am writing is based on a theory that I can't back. It's not entirely original, but bear with me. With this machine, you could recreate any combination of energy that has ever existed - and therefore any object/being. The only thing I have going...

What does an " ')' expected " error signify? How did I not use parentheses correctly? The error is in this line: System.out.println(num1 + " " + num2 + " " + num 3 + " " + num4 + " " + num5) ; What possible mistake can there be in parentheses?

I'm not very knowledged in genetics, although I'm interested in the subject, and was hoping someone could give me some insight into any possible reasons for why I'm short. I'm a caucasian male and I'm only around 5'7". I know I take after my father who is also around my height, but I don't...

Guys can post on the poll. It is separated so we know what guys and girls think. I'm a guy and I think we should have short hair. I have long hair myself, which goes past my eyebrows. I personally want it to reach the bottom of my eyes. I really like short hair, but long hair feels good...

*I don't know who's familiar with the AP system, but does anybody know any good review books for the AP Physics C test? (NOT the "B" Test) *I've found books that prepare for BOTH tests, but there is a large difference between AP Physics B & C, and I'm hoping for a book that discusses just...

What's the difference between a short circuit and a parallel circuit? In a short circuit, my teacher told me that no current will passs through the more resistive path. I doubt it. If this is wrong, then I could distinguish the difference and similarities between them. If not, I really need...

could anyone please give me a short summary of econometrics and what it uses to "predict" future economic states? thanks

I am designing a 500mA source circuit using a npn and pnp transistors. How can I protect the pnp if the output is shorted to gnd. Both transistors are in common collector configuration.

This may be an odd post, but I'm writing a short film in which a college student is having some trouble with a general physics course. Having never taken physics myself, I'm looking for sample dialogue to use in a particular scene. What I need help with is the professor's dialogue in this...

Here is a paper on the arxiv, preprint of an encyclopedia entry, which might be useful to many to introduce the ideas and techniques used in perturbative quantization of different fields. If you are content to accept for the moment brief definitions instead of leisurely motivations of the...