What is Hi: Definition and 291 Discussions

The University of Iceland (Icelandic: Háskóli Íslands [ˈhauːˌskouːlɪ ˈistlan(t)s]) is a public research university in Reykjavík, Iceland and the country's oldest and largest institution of higher education. Founded in 1911, it has grown steadily from a small civil servants' school to a modern comprehensive university, providing instruction for about 14,000 students in twenty-five faculties. Teaching and research is conducted in social sciences, humanities, law, medicine, natural sciences, engineering and teacher education. It has a campus concentrated around Suðurgata street in central Reykjavík, with additional facilities located in nearby areas as well as in the countryside.

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  1. J

    Hi all,Let λ>0 and define an equivalence relation on

    Hi all, Let λ>0 and define an equivalence relation on ℝn-{0} by (x~y) \Leftrightarrow (there is an s\inZ such that λsx=y) I would like to know what the quotient space ℝn-{0}/~ looks like. I know that it is a set of equivalence classes. To understand it better I wanted to see how it...
  2. Z

    Hi all. Need Advice. Thank you

    Hi all. Need Advice. Thank you :) Hi all. Sorry if this kind of question has been posted but I try googling my question, so here is where I end up. Most of the threads that I read didn't actually specifically answer my question. Anyway, my question is, "How do I study and become a...
  3. T

    Hi FriendsI am a young Bangladeshi and a freelancer. I want to

    Hi Friends I am a young Bangladeshi and a freelancer. I want to gather and share knowledge here.
  4. R

    Hi guys, Need some help on something I didn't know I didn't

    Hi guys, Need some help on something I didn't know I didn't know. How do you factorize this? -λ3+7λ+6=0 I assumed this? -λ(λ2-7) + 6 = 0 λ = 6 λ = ±√7 But that's wrong as the answers in the book are -2, -1, and 3. Can someone give me a little guidance on this, I have only...
  5. P

    Hi allWhy does a molten metal solidify with decrease in

    Hi all Why does a molten metal solidify with decrease in temperature. or in other words why is a closed packed structure more stable than an amorphous liquid melt. I have read that the free energy below melting point is lesser for solid state than that of for liquid state at the same...
  6. N

    Hi In the Diffraction Handbook

    Hi In the Diffraction Handbook http://gratings.newport.com/library/handbook/chapter6.asp#6.2.4 it says: A grating used in the Littrow or autocollimating configuration diffracts light of wavelength λ back along the incident light direction (Figure 6-4). In a Littrow monochromator, the...
  7. P

    Solve for Image Height: Find Hi with f, M, s & s

    Homework Statement With a lens with f = 25 cm, we want to project an image that is 5 times bigger than object, so M = 5 - Find the image distance s' - Find the image height Hi Homework Equations 1/f = 1/s + 1/s' M = s'/s = Hi/Ho With: f = focus distance of lens M =...
  8. K

    Hi i with this perfect number program Please help

    Perfect Number Program Java Methods A perfect number is a positive integer equal to the sum of all its divisors (including 1 but excluding the number itself). For example: 28 = 1 + 2 + 4 + 7 + 14 According to Euclid, any solution to (2n-1) that results in a prime number will indicate that...
  9. P

    Hi Our teacher told us the following:F = m * v² / r = m * 4 pi² /

    hi Our teacher told us the following: F = m * v² / r = m * 4 pi² / T² * r = m * 4 pi² / k * 1 / r² = c * m / r² F = y * mM / r2 Why is there the k and 1 / r² and later the c?
  10. A

    Hi guys, i was studying on transformers losses, i in some

    hi guys, i was studying on transformers losses, i need help in some problems. why open-circuit test show only excitation losses and not i2R losses.. thanks...
  11. S

    Hi guys. Imagine how dumb I feel for never having heard of this

    Hi guys. Imagine how dumb I feel for never having heard of this equation before today. I have a serious exam coming up and the only thing I know is that this will definitely be coming up. I know it's applications, but I have no clue how to apply it proper. There are no calculators allowed...
  12. J

    Hi guys I hope with your help I will be successful

    Hi guys. I'd like to make an introduction somewhere but there doesn't seem to be a forum for that here. Basically I am an older student who, despite having low grades all throughout school, always loved science. I decided to go back to adult school to upgrade my marks and then go to university...
  13. B

    Hi This is the definition of simultaneity I was taught: Two

    Hi! This is the definition of simultaneity I was taught: Two events that are simultaneous in one frame of reference need not be simultaneous in a frame moving relative to the first frame. I'm wondering if this concept only applies to relativistic phenomenon, and if not, would you happen...
  14. L

    Hi all,I am reading a paper related to astrophysics and I am stuck

    Hi all, I am reading a paper related to astrophysics and I am stuck in a step in a calculation. It is about orbiting gas in a spiral galaxy and it calculates the errors in the fitted rotation velocity if one of the viewing angles is incorrectly estimated. My problem is that I don't understand...
  15. G

    Hi why do many dyes who have a conjugated system of delocalized

    hi why do many dyes who have a conjugated system of delocalized electrons absorb, not a particular wavelenght, but often a whole range of wavelenghts? so if there is a dye, that absorbs let me say all wavelenghts between 640-680nm. how is this possible? for me, this would mean, that...
  16. F

    Hi PF,I have been working quite heavy shifts of late being a truck

    Hi PF, I have been working quite heavy shifts of late being a truck driver but enjoy a few cans of beer when I can and wanted to know if there is anything I can put together at home that will give me a simple indication of my alcohol reading i.e green or red light. How would I go about...
  17. G

    Hi nice to be in a Universe I understand

    I am a nerd, youngish, not old, studying teh Physics. My name is Vulcan. Says it all. Posted a little to see if this forum was for me; seems so so far. :smile:
  18. B

    Hi Folks,I am currently reading Brian Greene's 'The Fabric of the

    Hi Folks, I am currently reading Brian Greene's 'The Fabric of the Cosmos' which is excellent. I am trying to get my head around the Delayed Choice Quantum Eraser in this book. Is there a website link I could follow up that explains it well? I have already looked at...
  19. M

    Hi guys ,I have to give a presentation on UAV's ,i have some

    Hi guys ,I have to give a presentation on UAV's ,i have some experience with RC planes but that's about it .Now there's few things about UAV's in particular that I'm unaware of ,if you could help me it'd be of great help . GROUND DATA TERMINAL AIRBORNE DATA TERMINAL AIRBORNE DATA RELAY...
  20. P

    Hi, How do I find the height of the triangle , the triangle is set

    Hi, How do I find the height of the triangle , the triangle is set at 30 degrees and the length is 5 meters any help would be appreciated.
  21. J

    How Do New Members Best Engage in Online Forums?

    Hi All, I am John from CA. I am new here and here i love to meet new members. In this forum i want to share some useful things and also want to lean from forum members.
  22. Moonbear

    What Happens When Physics Meets Microwaves in a Summer Honors Program?

    Hi everyone! I was thinking of you all today and thought I'd drop in and say hi and let you know I'm still alive and well. I thought of you all because I'm working a faculty for a summer program with our state's honors students, and one of the RAs, who is a physics major, did a demo for the...
  23. M

    Hi, Can anybody explain in a few words what the

    Hi, Can anybody explain in a few words what the "spin glass" is ? Can a material that exhibits a magnetic hysteresis (ferromagnetism) at both 5 K and 300 K be in a way a "spin-glass" also ? As recently, we have measured a material that despite the fact it is exhibiting a magnetic loop at any...
  24. M

    Hi I have a question about POVMsim confused as to how they

    Hi I have a question about POVMs im confused as to how they correspond to actual measurements we do in a lab, and how non-orthogonal measurements fit into this context. For example we have some POVM with elements E_i. I read in Nielsen and Chuang that we do a measurement and get outcome m...
  25. M

    Hi everybody,this is my first post. So sorry for the possible

    Hi everybody, this is my first post. So sorry for the possible trivial question. Can someone explain me what is Y-bjorken? And what is the difference with X-bjorken? Thanks
  26. T

    Hi, I have attached a Di-electric study graph of Copper. a) How

    Hi, I have attached a Di-electric study graph of Copper. a) How can I do the di-electric measurement from this graph? b) How can I measure the loss of di-electric? c) How can I measure the di-electric constant? d) The graph gives the result which is linear. Is it essential that the...
  27. C

    Hi folks Im new to this forum and have a question that I hope someone

    Hi folks! I am new to this forum and have a question that I hope someone can answer. I have 4 circular holes, 3", 4", 5" and 6". I am covering the holes with 14 gauge sheetmetal. The sheetmetal is circular also and overlaps the holes 1" all the way around. My question is, how many pounds would...
  28. K

    Hi all,First up, I should make the point that I am not a

    Hi all, First up, I should make the point that I am not a physicist. I studied physics at school, but can't say I was ever any good. As such, this question may have a very obvious answer that I have missed. That said, it has been puzzling me for a while so I thought I would ask a forum of...
  29. H

    Navigating Neighborly Etiquette: Saying Hi or Not?

    I think I need some guidance with being polite. If my neighbors are outside talking and they get quiet as I come out of my car, does that mean I am supposed to say hi? Sometimes people get angry at me for not saying hello, and then sometimes they get angry when I say hello, so I don't know...
  30. M

    MATLAB Hi everyone. im a beginner to matlab, i want to calculate the fourier

    hi everyone. I am a beginner to matlab, i want to calculate the Fourier series Coefficients of a discrete periodic signal with period N=100 and plot it. the signal is real and even
  31. P

    Hi Guys,When the eye sees an object, there has to be light

    Hi Guys, When the eye sees an object, there has to be light reflecting from or emitting from the object itself. How does this happen with a hologram? Does the interference pattern actually scatter the light so we can see it?
  32. PainterGuy

    Hi, :smile:Please take a see on this Google

    Hi, :smile: Please take a see on this Google Doc: https://docs.google.com/viewer?a=v&pid=explorer&chrome=true&srcid=0B_XrsbDdR9NEZTY5MWU3NjUtMzk5NS00MDRiLWFjMjgtNTVjY2IwNGUxNWZk&hl=en&authkey=CPWM-YUI Can you help me with the highlighted part please? I don't understand it. Perhaps you can...
  33. B

    Could a High Temperature Absolute Encoder Fill a Niche Market?

    Hi, as part of a project I needed a slim (<10mm) small diameter (<30mm) through hole absolute encoder that works at 100 degC. I wanted this to be able to determine a motorized valve position, so it needed to slip onto the gearbox output shaft between the motor and the valve. Anyway, I...
  34. J

    Hi, the wikipedia article on fermium states that it is the last

    Hi, the wikipedia article on fermium states that it is the last element that can be synthesized by neutron bombardment but decides not to explain why. Can anybody give a layman's explanation? Thanks.
  35. A

    Hi guys,does anyone knows what is the physical interpretation of

    hi guys,does anyone knows what is the physical interpretation of second(third, fourth,...) derivative?
  36. X

    Solving Momentum Homework Questions: Q1 & Q2

    Homework Statement Two Questions: 1) A 9.0-kg ball is traveling to the right at 8.0 m/s until it impacts a 3.0-kg stationary ball. After the collision, the 9.0-kg ball is traveling at 5.61 m/s at an angle of 7.8º above the horizontal. Calculate the velocity of the 3.0-kg ball after the...
  37. X

    Hi, Momentum (Classical Physics) Help

    Homework Statement Using the graph below, what is the magnitude of the impulse provided to a 48 g tennis ball that is swerved due south? Also, What is the velocity of the ball when the racquet and ball separate? Homework Equations p=mv (I think). Fnet x delta Time = P (maybe)?The Attempt...
  38. P

    Hi i'm an applied maths student i'd like to study about catenary

    hi I'm an applied maths student i'd like to study about catenary.. where can i get details of catenary and its applications in detail?which book i can refer or is there any website i can go for?
  39. C

    Medical Can Masturbation Cause Undescended Testes?

    hi guys i am new here , help me in "undescended testes" hi guys , i hope all here are fine and well . I have "undescended testes" and i know it is caused due to my over masturbation when i wan young , now i left masturbation some what , but still my testicles or improper in position ...
  40. E

    Exploring the Bond Length of HI vs HCl

    Click http://www.xtremepapers.net/CIE/International%20A%20And%20AS%20Level/9701%20-%20Chemistry/9701_s02_qp_1.pdf" for question. Question 33. The atomic Radii of Iodine is much larger than Chlorine hence the bond length of HI should be smaller compared to HCl. Apparently, it is not so...
  41. F

    What are the latest theories on time and its relationship with the universe?

    Hi...I go by Fobio. Good to be here...and I thought I'd introduce myself. I'm a 30-something married banker who's into cars and amateur racing. In my high school years I did well in math and physics but did not pursue that in university. I've always had a interest in science to the point...
  42. E

    Help with Hi Power LED Resistors

    I have a project with two, separately wired high-power LEDs. LED #1 is a 1 watt LED rated at 3-4 Vdc at 350/700 mA LED #2 is a 3 watt LED rated at 2 Vdc at around 350/700 mA According to Resistor calculations, I get: LED #R1 = 4.7 Ohm, 2 Watt rating (for 700 mA) LED #R2 = 8.2 Ohm, 4...
  43. N

    Hi guysIn my statistics book there is an example. They say that we

    Hi guys In my statistics book there is an example. They say that we see 3 occurrences of type A, and theoretically expect 7. This is a difference of 4, since we know that the standard deviation is 1.65 (they calculate it), then the difference is 2.4 standard deviations. Looking at a table of...
  44. P

    Hi again. Checking one more to see if I get it.

    Homework Statement A train slowly climbs a 500 m mountain track which is at an angle of 10 degrees with respect to the horizontal. How much altitude does it gain? Homework Equations Looks a lot like the jogger one except you find change in y instead, right? Are we missing mass? Do I...
  45. T

    Hi, I have a problem. Its logarithms.

    325*(0.8)^t=5 Can anyone help me please?
  46. D

    How to Calculate the Percentage Composition of a Compound?

    A simple of an unknown with plants decomposition of the sample produces 0.09. 48 G of C , 0.1264 g of O and 0.0158 g of H . What is the % composition of the compound ?
  47. marcus

    Hi, from newcomer J. interested in string/M

    This greeting from a newcomer was posted out of place (in bibliography) so I copy here, to give J. his own thread. Please welcome. My comment: Jonny the core message here may actually belong in the "Academic guidance" forum up near the top of PF main menu. I will copy and highlight what I...
  48. C

    Say hi to you guys~ I'm from HK ^^

    Hello~ I'm a "little" girl studying in secondary 6 (7 after 1/9) in HK~ I love physics very much~ I want to major in electrical engineering or physics in university ^^ I find this forum is quite useful so I registered to be a member~ Hope you guys can understand my poor english~ ^^
  49. Z

    Where do I post this question? And, hi This is my first post

    Hi! I'm ZxWhatever (Short for Zxblqcktptydfkjsplkn, my username elsewhere). This is my first post here. I'm going into high school next year, and physics has always fascinated me, specifically quantum physics. You may think this is WAY to early to be thinking about a science fair, but I want...
  50. G

    How Can a Newbie Like Gwen Get Started in a Community?

    Hello Everybody, Gwen here...a newbie here. So glad to be part of this community.
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