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Sensei

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Everything posted by Sensei

  1. Somebody ideate a number. Other players have to find out what is this number. Player post his number and original author can answer only "higher", "lower" or "equal" - game is done and we know winner. To not cheat original author has to make photo of his number with monitor in background open with SFN thread visible so we can verify date. If allowed number is between 0...1000 number should be found after just 9-10 answers, if you know proper algorithm how to play it
  2. It's not the speed like you think.. If you receive or send one huge packet of data, most of cpu time is spend not in Python, but in operating system. In Counter-Strike: Source each player is receiving maybe something like 5-6 kb of data per second. So when 40 players play a game, server has to send 200-240 kb of data per second (and receive 40 kb from players). I think so it's compressed data, not raw. So server has to compress it and decompress (perhaps even 8000 times per second). Because there is really a lot to send *) But it's not 200 kb of data in one packet! It's more likely 2000-4000 packets with 50-100 bytes each. With steady delays between them, like 10-20 miliseconds. It's not one thread receiving data, but more likely 40 threads, each one waiting for data from just single player. If it would be one thread, processing data of one player would influence receiving data from other players when client would send them in wrong moment while server is busy processing other player data. We don't know details chosen by game developer to discuss it with detail. For example who calculates collisions: server or client? If client does it, then if some of them won't receive packet (lost packet) he will be alife, while other player will see him dead (?!) so it's strong argument for calculating this stuff on server side, and just broadcast info about death to clients (dead body remain in place, so it's broadcast even when it's not longer playing). The more will be done on client side of game, the more likely somebody will make cheat utilizing it. If client has to calculate final position of player after movement, cheat can change position of player twice as fast as usual f.e. or walking through walls (no collision checking), or flying (no gravity calculations). *) for instance some player is throwing away weapon, it's flying in air, all other 40 players can see this weapon in air flying, and they can catch it while it's in air.. Otherwise it'll land on the ground, or reflect from walls or other people, and stay there for future.. Player can buy as much weapons as he/she wants (up to default money 16 k$) and throw it away. So if every player will do it, for all 16k$, with 1k$ price of each weapon, we will end up with something like 640 weapon items laying on the ground in whole playfield.. And there are other items like grenades that can be laying on the ground as well.
  3. Yes. Half-life of unstable particle is time. And the main parameter to calculate quantity of particles that decayed is also time. More info and equation about radioactive decay you will find in this thread http://www.scienceforums.net/topic/83245-a-question-on-radioactive-decay/?p=806204 You can load it to OpenOffice SpreadSheet and play with parameters to see effects. Cloud chamber is using vapor of Isopropyl alcohol + air. In Bubble Chamber there is used liquid Hydrogen IIRC. Vacuum wouldn't work. Highly energetic particles need medium which will take their energy and slow them down. If we will put medium such as aluminum plate between unstable isotope, we will see that our shield disallowed or reduced quantity of traces behind it. That depends. You have to check what isotope they used for particular experiment and calculate decay energy. You can learn how to calculate decay energy in this thread http://www.scienceforums.net/topic/83451-radioactive-decay-and-information-split-from-what-is-real-in-physics/?p=808149 In decay which emits neutrino (f.e. beta decay-, beta decay+), kinetic energy of beta particle is not constant. If beta particle takes decay energy with itself, neutrino takes less, and vice versa. It's mentioned in Beta Decay article, so simply read it http://en.wikipedia.org/wiki/Beta_decay Atom of one isotope changes to atom of other isotope. Very easy to see it (cloud chamber that costs $20), and relatively easy to check (produce pure isotope then leave it for a while (or couple years), and then separate isotopes in it to see changes). Electron can annihilate with positron producing two or more gamma photons..
  4. And we can see traces leaved by them in Cloud Chamber. Long thin traces are from beta particles (electron or positron). Short thick traces are from alpha particles. The more kinetic energy has particle, the longer trace.
  5. No. Just electron. Aluminum atom has 49218 times more mass than electron. Copper atom has 117667 times more mass than electron. Gold atom has 359109 times more mass than electron. When electron flows through conductor it sometimes hits atom, losing a bit of its kinetic energy, and heating atom, which is receiving electron's kinetic energy. The less this happens (lower resistance), the better conductor. If we have atom which lacks electron (ion+), and atom which has more electrons (ion-), the one that has more can give electron to the one which lack it. In batteries that have 1400 mAh on negative electrode we have 5000 Coulombs = 5000*6.24*10^18 = 3.12*10^22 electrons, and on positive electrode there are positive ions in the same quantity, which lacks electrons. After closing circuit electrons flow from negative electrode to positive electrode. Positive ions are attracting electrons. Each electron will have kinetic energy that corresponds to voltage difference. f.e. if voltage is 1 V, single electron will have 1 eV kinetic energy (electron volt unit). if voltage is 3.5 V, electron will have 3.5 eV kinetic energy. E=h*c/wavelength so wavelength = h*c/E = 4.135667*10^-15 * 299792458 / 3.5 = 354 nm UV LED have voltage drop 3.2-3.5 V (a bit is probably lost). So they emit photons with energies 3.2-3.5 eV, which correspond to wavelengths 387 nm .. 354 nm. Photon in ultraviolet spectrum. Where did you get such conclusions? I said "If you have single electron, charge Q will be -1.602*10^-19 C. If you have single proton, charge Q will be +1.602*10^-19 C." One has positive, other negative.
  6. 2.1 A * 3600s = 7560 C. 7560 C / 2.1 C/s = 3600 s = 1 hour to charge to full with 2.1 A current. Is it plausible estimated time (assuming you don't play game at the same time ) ? Amper hour unit Ah is simply 3600 Coulombs. 1 Coulomb is 6.24*10^18 electrons. That's no surprise. After all it's more electrons per second. 1 A is 6.24*10^18 electrons, 2.1 A is 1.31*10^19 electrons per second. Apparently these games are using more energy than charger is able to provide. I guess so, heavy 3d. Do you have app showing cpu/gpu percentage usage with history.. ? Perhaps some application running all the time in background that's eating energy? Also loading a lot data to memory might have such effect. Typical computer random access memory must be refreshed periodically by current to sustain content. I had one Nokia 10 years ago that ate power like crazy when it was full of data. After deleting everything it could work several times longer. Current ebook technology is using screens that use power only while changing display. Games changes display even 30 FPS. Not sure whether such screens are used by some mobile phone. Might be highly model dependent.
  7. Q in Coulombs [C] is charge. It's kinda like quantity of particles. 1 C = 6.24*10^18 electrons. If you have single electron, charge Q will be -1.602*10^-19 C. If you have single proton, charge Q will be +1.602*10^-19 C. Electrons and electrons repel. Protons and protons repel. Electrons and protons attract. So, if you have Q1=-1 C and Q2=-1 C, after multiplication negative by negative, we will receive positive value. F=k*-1 C * -1 C / r^2 = k*1*1/r^2 If Q1=+1 C and Q2=+1 C F=k*1*1/r^2 effect will be the same. You can see how it works using electroscope. http://en.wikipedia.org/wiki/Electroscope "leafs" are free to move. The higher quantity of electrons will gather on them, the further leafs will be from each other.
  8. Imagine you have discharged cell phone battery to null. How long it takes you to charge it to 100% full again? If your cell phone battery has 1000 mAh, and loading current would be 2.1 A, it would charge to full in just 500 seconds = 8 min 20 sec (let's assume no loses). With 0.2 A, it would be 80 mins+. Mine cell phone battery has 3.7 V and 3.7 Wh on its back. Which is 1000 mAh. How could you do it? Typical voltage meter has as largest resistance as possible, usually a few mega ohms AFAIK. And ampere meter has the smallest resistance as possible. http://www.allaboutcircuits.com/vol_1/chpt_8/5.html
  9. Sensei

    divide the circle

    You can upload PNG,JPG,GIF here. Just click More Reply Options.
  10. I plugged DC motor (from old cassette Walkman or so) to 5.5 V 4 AA batteries that I had at hand. Without anything Ampere meter is showing 2.4 A. With DC motor Ampere meter is showing 0.210 A, voltage drop on DC motor is 1.5 V (4 V remaining). With DC motor and 210 ohm resistor, 0 A, and motor doesn't want to run. With DC motor and 4.3 ohm resistor, 0.19 A, voltage drop 1.5 V. Motor runs but slightly slower than without resistor.
  11. Sensei

    logarithm

    log10 ( 10 ) = 1, because 10^1=10 log10 ( 100 ) = 2, because 10^2=100 log10 ( 1000 ) = 3, because 10^3=1000 etc. log2 ( 2 ) = 1, because 2^1=2 log2 ( 16 ) = 4, because 2^4=16 log2 ( 256 ) = 8, because 2^8=256 etc. Common bases: ln(x) = loge(x), base is e log(x) = log10(x), base is 10 In your example, if base is 5, then log5(125)=3
  12. Problem will be when the all people of the world will use more energy than Sun produces per day (and reaches our planet surface). And no more fossil or nuclear fuels will be available. But if all fossil fuels will be burned, air will have a lot of CO2 , which can be taken back by algae, or other vegetables. I have suspicion that you have no idea what is electromagnetic radiation.. This sounds like saying "Nicholas Kang invented sun, stars and light"..
  13. What "current energy crisis"? Renewable energy sources are introduced to reduce CO2 production to atmosphere, not because there is not enough energy. Actually everybody wastes a lot of energy. On transmission to client. On transformation from high voltage to low voltage (and vice versa). See how hot are electronic devices. They should/could have ambient temperature. In true crisis, everybody will be paying attention to every kW of energy used, buying devices that use as less as possible energy. In true crisis, everybody will have their own solar panels. Couple floor building have a lot of space to cover it by solar panels from all sides, and produce much more energy than the all people who live inside are using. But it would be bankruptcy of power station business. Have you idea how to transfer energy from orbit to Earth surface to actually use it?
  14. When bike or car accelerates to certain speed, all its particles have uniform velocity. Once bike or car hits something and decelerates, driver or passengers maintain velocity that they had before accident, as they are not permanently attached to bike/car. As a result they fly in air (in motorbike case), or smashes on front seats or window (in car case). I have made simple animation for you to illustrate it. At the beginning all parts of stick have equal velocity. After hit, top part of stick is decelerated, but middle and bottom still have previous velocity. In extreme situation stick could even be partitioned. In simpler case, it's starting spinning. Actually it's very easy. Attach particle to different parts of object. Particle has position x,y,z velocity x,y,z acceleration ax,ay,az And during animation particle is moved to new location frame by frame (or for more precision sub-frames like f.e. 1/1000 of second). Collision routine is checking whether something exist or not in new location. Movement is accepted when there is nothing in new location. If no movement can be performed (collision), there is needed to calculate new velocity/acceleration. The more particles is calculated, the slower simulation, but the more realistic is effect. Every modern 3d game is using this technique. Rapid deceleration of body while head still maintain velocity (or vice versa) will cause break of neck. Two weeks ago I read in newspaper about women who literally lost head during such accident (ripped of from the rest of body).
  15. Surface of Earth is all day bombarded by protons from the Sun. So actually Sun is by itself sending its components all the time, without us having to fly for it. http://en.wikipedia.org/wiki/Solar_proton_event
  16. f.e. I have ideas for new experiments while reading about other people experiments. Little things that were not checked during the main experiment. If you're searching for something never seen before, unusual decay mode of some isotope should be relatively easy to find. I wrote Decay Energy calculating application. And it showed couple unusual decay modes possible. f.e. Hydrogen-5 should be able to decay to Helium-5 + e- + Ve + 21.5 MeV Default decay mode of H-5 -> H-3 + n0 + n0 + 1.8 MeV (double neutron emission). Checking this would require making Tritium, then bombarding Tritium by Tritium to produce Hydrogen-5 and protons, then checking whether we have He-4 inside after long time. Tritium is decaying to Helium-3. Hydrogen-5 is also decaying to Tritium and emitting two neutrons. If a bit of Hydrogen-5 would decay to Helium-5, it should decay quickly to Helium-4 and neutron (instead of He-3). If I were you I would start making experiments from building Cloud Chamber, the first particle detector of the world created by Wilson He got Noble price for it. http://en.wikipedia.org/wiki/Cloud_chamber There is no excuse to not have it. Costs approximately $20-$50 (much more for devices cooled by electricity (Peltier effect usually) ). You need to find good cheap supply of dry ice ($4 per kg here) Single time run of 40x25x25 cm (25 L) chamber requires >500 grams of dry ice. https://www.youtube.com/watch?v=VFVZU2YwwJ4 https://www.youtube.com/watch?v=Efgy1bV2aQo
  17. That depends on what kind of "network programming". From mine point of view of "network programming" it's using socket(), gethostbyname(), bind(), listen(), etc. etc. and making your own server of some protocol, or client to some protocol, or both. http://en.wikipedia.org/wiki/Berkeley_sockets Either Java and Python are not good for this task IMHO. They demand speed, especially server side. The best for making servers/clients is C/C++. Java is often used to make Internet games that doesn't demand speed (like chess, card games). Client side of network is run on user web browser, and connects to server (which actually doesn't have to be Java). Probably nobody would dare to write serious FPS for 40+ players in Java. FPS are the most demanding examples of client-server network applications. They require real-time transmission of data from client to server, and then server broadcasting all data to all players, and everything has to be done within miliseconds. While playing Counter-Strike: Source in same country you have pings like 20 ms-50 ms.
  18. I am not sure why it's in politics.. The main problem is that doctors demand money for healing patients. They are thinking about it BEFORE they even get to medical university! They want to be "well paid" and quickly rich. Medic should not be just a job, to earn money, or (in current western standards) "a lot of money" (> $100k ?!? Insane!). It's kinda like wanting to be a priest because people will give money 'on a tray'... Nobody who wants/demands money should become medic or priest! Only people who truly wants to help other people should become medic. Without any money behind this. Who demands money for saving somebody life demands full condemnation! There is nearly not a week here without some scandal about "ambulance not send" to somebody who called for help, but because his/her injures/state was not health dangerous (by judge of call), and he/she died. All because of money. Ambulance management not let ambulance to go, to save money for possibly false alarm, that later it appeared to be true alarm.. All because of money! Ambulance stations should not be private businesses aimed at earning money.. ! Hospitals should not be private businesses aimed at earning money.. ! Outpatient clinics not be private businesses aimed at earning money.. ! If government has to pay every month pension/retirement we have obvious conflict of interest with government paid medics - if patient lives longer, government has to pay him/her more money, if he/she lives a lot longer, he/she will get more money than he/she paid in the past. So from government financial point of view, patient that pays for medical care whole life, and then after retirement dies as soon as possible is the best "client". All because of money! We have queues long for several years reservations to free doctor, that you would rather die than to live to see him.. At the end who has more than 50 usd (typical 1h price per visit) is going private (10% of minimum gov income per month for visit, so such doctor will earn 100% of minimum gov income in single 10h day! And up to 20-30 times more than regular people per month) Retired people (without money) (usually who need doctor the most) have to wait several years for visit at specialist. To get to specialist you need to get referral from general doctor. So actually you need to meet two doctors one and then another, even if you know what kind of disease you have. Even if you met 2nd doctor multiple times.
  19. In application I have functions: double get_isotope_mass( int protons, int neutrons ); // read isotope database and return mass in units double get_isotope_energy( int protons, int neutrons ); // call above, multiply by 931.494 MeV etc. return energy in [eV] double get_nucleus_energy( int protons, int neutrons ); // call above, and subtract electrons energy (protons * 0.5109989). return energy in [eV] All other code is only using get_nucleus_energy(). I wrote application, to not have to worry about calcs. Simply enter protons,neutrons quantity and app is displaying what are possible decay modes and Decay Energy. For instance decay of Plutonium-239 is prohibited in all modes but alpha decay, alpha decay energy 5.24454 MeV does match article http://en.wikipedia.org/wiki/Plutonium-239
  20. Not only. Proton emission also, double proton emission. It's easy to make mistake that will remain unnoticed if we will be doing such shortcuts. (in above example one electron and one proton will be free)
  21. I don't know about what book you're talking about. Certainly I didn't read it. I think so it's too late. If discussion will be progressing mods will split it to other thread. I see no problem. So, what is explanation of refractive index in your country.. ?
  22. Refractive Indexes are measured for specific wavelength/frequency of laser (or light in old times). Especially in gases it's even worser- there has to be taken into account also temperature and pressure. On wikipedia RI article there is also mentioned that RI changes with density of glass. For instance we have data RI=1.33 for f.e. 532 nm, RI=1.34 for f.e. 650 nm, RI=1.32 for f.e. 405 nm, then RI is obviously not constant. Different value of RI for different light wavelength/frequency. You said "Refraction is only a problem if the index isn't constant," And I am asking which material fulfills your RI constancy for lights with as largest range of frequencies as possible (preferably not just visible spectrum).. ?
  23. Which material has uniform refraction index in f.e. frequencies from 1 Hz to Compton Frequency?
  24. Do you know how to calculate Decay Energy of unstable radioactive isotope? First, find parent isotope mass. They're in f.e. wikipedia articles such as http://en.wikipedia.org/wiki/Isotopes_of_hydrogen (last portion of link is name of element). For instance Carbon-14 has 14.0032419894 u Then, you need to multiply it by 1u = 931.494 MeV to receive total energy of nucleus + electrons. Then you need to get rid of mass-energy of electrons. Multiplying 0.510999 MeV by quantity of protons/electrons. Subtract total energy of electrons from energy of isotope. Repeat it for daughter isotope. In Carbon-14 case it's Nitrogen-14. Subtract N-14 nucleus energy from C-14 nucleus energy. Subtract electron energy (it's emitted during decay together with antineutrino) Result will be Decay Energy of isotope (kinetic energy of particles + energy of neutrino in our case). Decay Energy must be positive value. If you will calculate Decay Energy from stable isotope such as Deuterium, Helium-3, Helium-4 for all possible decay modes you will see that D.E. would be negative value. Thus these particles are stable. For Carbon-14 it's 0.156 MeV. As you can see this value does match article: http://en.wikipedia.org/wiki/Carbon-14 Other examples: Fusion of proton-proton, decay of carbon-11 and decay of Mangan-54: I wrote computer application which has built-in database of isotopes and calculates possible decay modes and released energy.
  25. Deepak Kapur, do you saw Newton's cradle? http://en.wikipedia.org/wiki/Newton's_cradle It costs less than $10 in western countries, and allows visualizing conservation of momentum (while interaction) between objects with the same mass, or conservation of momentum between objects with different masses, etc. etc.
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