Request Definition and 194 Threads

As part of a research project on Dam Safety I am making some calculations for wave runup an wind setup on a existing embankment dam. Looking for information, I found a citation of the US Army Corps of Engineers related to my research topic, but I have not been able to find this document on the...

Standard treatments (e.g., Rindler) of the foundations of Special Relativity invoke use of a "rigid rod" or "rigid scale" by an observer to construct his inertial frame -- by (somewhat fictionally) transporting the rod (and also cloning copies of a standard clock at every point in the frame)...

Greetings friends, I have a new idea for desalinating water but I am not good at physics. My idea may sound stupid and if so I am sorry for that in advance but please could you have a look. I am attaching the image to this post which will try to explain the simple idea to generate pressure for...

With the study of logic, lots of words get thrown around that I don't really understand their complete meaning. With a deductive argument the conclusion is true if the premises are true, and an argument is valid if all the inferences (and the conclusion) follow logically from the axioms. These...

Hi all, I would like to make a 555 timer circuit that when 12v is applied to the circuit an LED will light for 3 - 5 seconds and then go out. and remain out until the 12v is removed and reapplied. Any help greatly appreciated. Thanks

I'm looking for a pedagogic introduction to d-wave superconductivity on the level of field theory. Ideally, this would involve a derivation of d-wave superconductivity and the form of the gap parameter from some fundamental Hamiltonian (if such a derivation is even possible yet). Books and...

Would is be possible to change the default style for vectors from over-arrows (\vec{x}) to bold-face (\boldsymbol{x})? The latter is much easier on the eyes, looks less cluttered and is favoured by most publications (at least the ones I read). If it were a \LaTeX document, it would be very easy...

If you'd like for a guy to buy you flowers, you best have a vase on-hand! I bought a girl flowers yesterday, and we had to break the top off of a cheap vodka bottle and use it as a vase!

Greetings, I've been looking at Physics forums few months ago, but I never taught of making an account. So now I'am motivated and I have made one and this is my first post. I'am 17 years old, I'am a Java programmer. I have wide knowledge of many things in the computer world. I have a...

I'm looking for the title to a popular introductory book on graph theory. For the best possible recommendation, perhaps it would be wise for me to give you signals of my academic maturity. I completed undergraduate math major in May 2010. Since then I've been working, but I'm looking to get...

Where can one find a general and detailed exposition of Penrose diagrams? What I have seen so far, in the books, are relatively brief general comments and a couple of specific examples. Usually Minkowski and Schwarzschild metrics, sometimes one or two more.

I'm not looking forward to optics so I wanted to do some self-study, like learn the topic on my own and ask to write the final. It's basically a first year optics course, no calculus beyond high school is really required. My university uses the optics textbook "Introduction to Classical and...

Hey all, I am finishing the second year of the undergraduate physics program at my school. This involves taking a course which teaches us a lot of upper level (or so I am told) math in the span of one semester at a very fast pace. The class is very difficult, but it has sort of given me a...

I stumbled onto this forum looking for advice, and since it seems like the wonderful people here have provided excellent advice to others, I'm hoping they (you) could do the same for me? I'm in the gap between college freshman and sophomore. I spent my first year taking lit, art, and history...

I was trying to search for a similar topic, but as I haven't found one here it goes. Thought experiment: Periodically emitted chain of single photons of non-polarized light is split into two entangled pairs and they are traveling apart from each other. One going toward point A, the other toward...

Dear Colleagues, I need a reference (for the article "Steady-state physiology…" I have just written) that proves the pumping role of Na,K-ATPase. I have tried to locate any publication that demonstrates the pumping function of Na,K-ATPase, but have found nothing. Please help me with...

I'm thinking of uploading this piece to my portfolio, but I'm not sure if it's up to standards. As always, I'd like as many third part perspectives as I can get so I'm hoping the fine people here at PF with their impeccable tastes could perhaps lend me their ear. Listen to this on good speakers...

I'm working on a physics minor, which is 21 hours (13 advanced). Right now, I have 17 hours (9 advanced). I'll be taking Thermal Physics in the Spring which will bring my total to 20 hours (12 advanced). To achieve the minimum of 21 hours, I'd have to take another 3-hour class. There is a 1-hour...

Ok...so this isn't homework (well past that at 39!) but I'm trying to brush off the old cobwebs and solve a vehicle motion problem. Specically, I'm trying to find the Homework Statement Ok...so this isn't homework (well past that at 39!) but I'm trying to brush off the old cobwebs and...

Hi! I'm looking for an e-ink e-reader that is able to display mathematical/physical journal articles in pdf. Hence, I would to ask anyone with an e-reader to give their opinion on which ones to buy, and why. I think there are more people out there that wish to have a simple device that can...

I'd like a mathematical and/or scientific critique of the assertions made at the following website: EDIT: link to crackpot post deleted Note there are some comments on the side that are directed towards a mathematical critique of the poster's assertions. These critiques appear to be valid...

I Uwould be grateful if anybody can kindly help me with this particular doubt that cropped when I was working through Introduction to Quantum Mchanics by Griffiths ( Griffiths page 66 ) My question is how is the following obtained : aj = C / (J/2)! ( Please read j as subscript of...

I am familiar with the derivation of the probability density function of the sample mean but was looking for an equivalent derivation for the sample median. Does anyone know of a good, clear derivation of this PDF? Thanks, Natski

Homework Statement I need to write a program (or use one that's already written) to compute the elliptic integral of the 1st and 2nd kind - ie F and E respectively. Please note that this is NOT a homework assignment. Thus, I do not actually need to write the code, and will be happy to use...

I'm setting up my first LIF experiment and I'm having some trouble. I'm measuring the nitrogen first positive system as has been done by numerous groups. The excitation beam is ~618 nm (v=0->4) and the detected fluorescence is around 676 nm (v=4->1). The plan is to use a barrier discharge (RF...

Hi, everyone: I need to give a small presentation in front of a group of non-mathematicians on connections, and covariant differentiation; I can handle the theory O.K-enough but I would like to have some solved problems/examples. Anyone know of a book or other sources with...

Please Can anyone help me with some information (Research, web sites,...ect) about DISPLAY DEVICES. Thank you in advance.

Request permission to discuss Schild’s paper. It is fundamental to the understanding of Quasars. Schild is a specialist in the area of quasar observation and theory. Quasars, Quasar evolution with redshift (change in the number of quasars, change in the quasar luminosity), Quasar's relationship...

Hi, I am a triple major (physics/astronomy/linguistics) at the end of my freshman year. I haven't really decided on a particular career path, but I have a very strong and genuine interest in these subjects. After reading some of the threads where other physics and astronomy majors posted their...

A Brief Conversation Overheard on a Side Street in Bedlam's Bazaar: Apprentice: My Puzzlemaster needs an anagram for the phrase "Iowa Hawkeyes". Wishmaster: What do you have to barter with for such a noble petition? Apprentice: For your wicked amusement...

Hello! Does anyone have a free ebook of Chemical Thermodynamic by Peter Rock A.?

Hi, I am a Kenyan scientist/academic and in dire need for equipment that is no longer in use in laboratories in the west. I have without success written to manyinstitutions in the UK requesting to acquire the equipment they no longer use eg old PCR machines, Centrifuges etc, but I have not...

Homework Statement Hello there, hope you are well. I am having trouble solving this problem involving Kirchoff's laws. I have attached a copy of the circuit and problem to this post in jpeg format. Thanks again in advance for any help. Mike Homework Equations The...

Hello, Anyone out there with the decade cmos 4017 model? Im using LT spice for some simulation but i can't find it in the standard library. Thanks in advance. Nash78

About the contractions... I'm not taking it lightly. Thanks to your recommendation, in the future, I will try to avoid them entirely, however, I believe that it's not worth the trouble of fixing on this paper. Thanks for the criticism, both of you. I really didn't noticed that I overused...

Homework Statement recently, i was on an assignment to develop a system or product based on 8085 to help handicap people.the assignment include software and hardware interfacing.any idea or suggestion please?i wonder what product can be create to help handicap people.need some direction to...

I have done a fair bit of research and reading on the subject I am asking about. There is not much - in fact virtually no - detailed information anywhere on the internet about this. If you have heard of Claude Shannon, Edward O Thorp, Norman Packard, Doyne Farmer and Thomas Bass, then you...

i am so confused.. does anybody know a good source to learn physics? every single source (book, website, etc.) says something different.. so.. can anybody please refer me to good reliable source? with no high math please.. here, for example one of the many things that confused me.. can i...

Earlier today, I just took the last examination paper for my examination in my third year in computer engineering. (One more year left to go.) Over the past year, now that I no longer have to do mathematics as a subject forced down my throat - it was a compulsory subject until the end of the...

I was only out for a semester, but I missed junior E&M and mechanics. My school offers these courses in a two semester sequence at the same time, so I've effectively been set back by a year. I realize it's not the end of the world, but I would very much like to find equivalent courses at schools...

I need to do research on Hydro Electrical power stations in South Africa. I am just confused whether I should just write about hydroelectric dams; or should I also include tidal power, wave power, and pumped-storage? Just the opinion that I need :) Thank you in advance!

Much of undergraduate economics is dedicated to the study of efficient markets. This is a useful simplification in many fields -- no one cares who they buy stock from, and gasoline, wheat, and other commodities are almost as undifferentiated. I've recently been considering markets that are...

Hello, I'm currenltly engaged in a debate - primarily with young-earth creationists (YECs) - about modern geocentrism. They are defending the position of Gerardus Bouw. I need some help from anyone out there who has expertise in orbits or in this debate in particular. Bouw's website is...

Homework Statement a 240nC point charge is placed at the center of an uncharged spherical consucting shell 20cm in radius. A) What is the surface charge density on the outer surface of the shell? B) What is the electric field strength at the shell's outer surface? Homework Equations A)...

I am a 25 year old high school teacher who wishes to further his understanding of physics to a point where some recent papers on theoretical physics can be read and understood. I graduated with a mathematics degree around 4 years ago and regards myself as fairly talented and able with...

Topological Strings = 3 Superstrings = 10 Bosonic strings 26 Tensionless strings = arbitrary Do you know of any others that could fit in other dimensions not listed above?

Hi, I have a project for heat transfer, I know what I want to do but I don't know how to do it on Matlab. My assignment is attachment 1 - project.pdf The first part I have done (attachment 2 - computer project.pdf) I know I should be using the Matrix Inversion Method, but as I need...

I know this may sound silly, but right now I'm a physics major just starting the calculus sequence and I just have a question or two about how everyone else studies math. Obviously, math is important for later on, so I want to learn it correctly and not just study enough to pass the tests...

I don't know if requesting things on here is taboo or crass, like I am treating it like craigslist or something. But this isn't a request for a trivial thing to me, so I don't think its crass. Anyway I was wondering if anyone on here is good at drawing and art on Photoshop, GIMP, etc and could...

Homework Statement Find the value of dy/dx at x=2 when x2+xy=5 The Attempt at a Solution To find y: 22+2y=5 y=1/2 To find dy/dx: 2x(dx/dx)+x(dy/dx)+y(dx/dx)=0 2x+x(dy/dx)+y=0 (dy/dx)=(-2x-y) / x Plug in y and x: dy/dx=-2(2)-(1/2) / 2 dy/dx=-9/4 when x=2