Recent content by quantumlight

  1. Q

    Area of a Square: Derivation & Integration

    I tried that but was having trouble getting rid of the square root of two term. Do you think that's just an error in the textbook? I tried to think of du as \stackrel{1}{2}sqrt{(dt)^{2}}, but that only makes it 1/2 rather than root 2. The reason I used the parallelogram was that it got...
  2. Q

    Area of a Square: Derivation & Integration

    So I was reviewing my random process notes. In it there is an integral that they have that I can't seem to get the right derivation of when they try to simply the math for ergodic mean. Basically, you have the following: A square from (-T,T) on both the x-axis and y-axis. What they want to...
  3. Q

    Why is oversampling by 4^n times necessary for increasing ADC resolution?

    I found online that if you want to increase the resolution of ADCs by n-bit, you need to oversample by 4^n times. My question is, why is it not that if you want to increase by 1-bit, you need 2 times the samples and 2-bit, you need 4 and 3 - bit you need 6?
  4. Q

    FDM vs OFDM: Why Can OFDM Overlap Without ICI?

    Thanks. I get it from that perspective but how does it work when you demodulate with cos(2πfct) where fc matches the carrier. when you take the combined signal and integrate from 0 to T, you theoretically could obtain the original signal with just that carrier back perfectly because integral...
  5. Q

    FDM vs OFDM: Why Can OFDM Overlap Without ICI?

    I was working on my thesis when this question popped into my head, why can't there be overlap in FDM wihout ICI but you are allowed to overlap in OFDM without ICI? Also why is the maximum overlap of subchannels 50% in OFDM before ICI occurs? From math point of view as long as the carriers are...
  6. Q

    Transmission Lines: Frequency Limitations & Attenuation

    I am writing my senior thesis on communication networks and this question sort of popped into my head: What determines what frequencies you can use in a landline connection? (e.g. say I have a wire connecting point A to B to send a bunch of signals, what prevents me from using the entire...
  7. Q

    Resonant modes of simply supported square plate

    I did this in ANSYS, but I am wondering what is the analytical solution to this. Does anyone know?
  8. Q

    Batteries in parallel with a diode

    I was wondering what the effects are if any if I connect a 17V DC source in parallel with a 9 V battery but the 9 V battery has a diode that prevents current from flowing into it. Thanks
  9. Q

    What Does It Mean When Col A Is a Subspace of the Null Space of A?

    I am just wondering what is meant when someone says the Col A is a subspace of null Space of A. What can you infer from that? Also what is a null space of A(transpose)A How do they relate to A? Are there theorems about this that I can look up?
  10. Q

    How Quickly Can a Train Accelerate on a Curve Without Exceeding Comfort Limits?

    Homework Statement Bob and Villie are able to tolerate acceleration of 0.2g, the driver wants to accelerate from 250km/h to 300 km/h on a curved piece of track, the radius of curvature is 5km, what is the minimum time the driver can use to change speed? Homework Equations...
  11. Q

    Why is current considered a scalar in physics textbooks?

    current has a direction and magnitude, intuitively it should be a vector but my physics textbook describes it as a scalar. Why is that?
  12. Q

    Why does the equilibrium constant vary only with temperature?

    why does the equilibrium constant vary only with temperature? and why is pure substances like solids and liquids not count toward the equilibirum equation? why do you have to have a reference pressure of 1 atm? (i know this is to take away the units but does this hav a logical function...
  13. Q

    Chem/phys question not sure what this is

    oops yeah its 2+ uhmmm its dynamic
  14. Q

    Chem/phys question not sure what this is

    ok this is in my Nuclear chemistry section (go figure) a small amount of Pb-212, in the form of 3+ ion, is injected into a saturated solution of PbCl2 that is in contact with the solid salt. A short time later some of the Pb-212 is found in solid PbCl2 in the saturated solution. What does...
  15. Q

    Giant list of science fair project ideas

    for me i did one on weather control...using water absorbent crystals in diapers to destroy clouds :smile: ... ended up in failure because i wasnt able to create a controlled cloud but a year later i found out that the cloudy formation when dry ice sublimes is actually cloud (i know amazing eh?)...
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