Variable Definition and 1000 Threads

A variable star is a star whose brightness as seen from Earth (its apparent magnitude) fluctuates.
This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are classified as either:

Intrinsic variables, whose luminosity actually changes; for example, because the star periodically swells and shrinks.
Extrinsic variables, whose apparent changes in brightness are due to changes in the amount of their light that can reach Earth; for example, because the star has an orbiting companion that sometimes eclipses it.Many, possibly most, stars have at least some variation in luminosity: the energy output of our Sun, for example, varies by about 0.1% over an 11-year solar cycle.

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  1. S

    Variable pulley distance - tensioner force help needed

    Greetings, lurked for a long time, but I need some help here so I joined up. Please have some patience with me if I miss any important information. I am working on a belted pulley drive system where the driveN pulley will move relative to the driveR while in the stopped state. An outside...
  2. J

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  3. S

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  4. S

    How Does Mass Leakage Affect the Velocity of a Cart?

    A cart has a load of 100 kg sand at start and it is pulled by a steady resultant force of 100N starting from rest. A hole in the cart causes steady leakage of 1kg/s. Find velocity v of the cart after 50s of motion.
  5. P

    Calculus of variations: multiple variables, functions of one variable

    Simply put, can you find the function which extremizes the integral J[f]=\iint L\left(x,y,f(x),f(y),f'(x),f'(y)\right) \,dx \,dy Where ##f## is the function to be extremized, and ##x## and ##y## are independent variables? A result seems possible by using the usual calculus of variation...
  6. M

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  7. M

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  8. M

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  9. M

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  10. C

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  11. M

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  12. S

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  13. Ravi Mohan

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  14. M

    350W PMA: Looking for a Variable Load Solution

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  15. U

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  16. R

    Variable capacitor q factor for fm radio jammer

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  17. T

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  18. K

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  19. D

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  20. A

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  21. I

    Partial derivatives, change of variable

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  22. N

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  23. L

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  24. S

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  25. D

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  26. D

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  27. H

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  28. D

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  29. A

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  30. A

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  31. C

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  32. ETBunce

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  33. C

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  34. Barioth

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  35. M

    How do you solve a non-linear ODE involving a variable mass dust particle?

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  36. mishima

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  37. C

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  38. I

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  39. Monsterboy

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  40. S

    Solving Three Variable Equations: Finding x, y, and z

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  41. R

    Can HMMs accommodate variable time delays in observations?

    Hello All, I'm building a HMM for some data where there are two different time delays. Specifically, I collect data in consecutive traces, such that the time delay between each data point within a trace is approximately fixed, and the time delay between each trace is approximately fixed, but...
  42. V

    MATLAB Minimizing a function in one variable in Matlab

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  43. H

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  44. D

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  45. D

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  46. S

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  47. R

    MHB Transform Random Var CDF to Standard Normal: F(x)=1-exp(-sqrt x)

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  48. B

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  49. H

    Isolating a variable gives me endless loop

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  50. M

    Can a Variable Inertia Flywheel Maintain Constant Speed?

    Hello, My question is: how much energy is needed for changing inertia of flywheel? example: on rotary shaft we have linear actuator which is moving some object (mass). by that movement, radius of flywheel is changing. ...if there is energy input to flywheel, mass is moving away form...
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