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  1. Tunalover

    Conversion of kW to Btu

    I always remember that there is 3.413 Btu/hr per W. So there is 3413 Btu/hr per KW. ElectroMechanical Product Development (Electronics Packaging) UMD 1984 UCF 1993
  2. Tunalover

    Difference between datum of a Cylinder surface vs Cylinder Axis.

    Folks, Does anybody out there have an authoritative statement that defines the GD&T default conditions that create a simultaneous requirement (one functional group) from a set of features controlled with position and/or profile tolerances? ElectroMechanical Product Development (Electronics...
  3. Tunalover

    Environmental IR Radiation Entering Ground Equipment

    IRStuff I thought you were going to provide a source for your definition of "emittance". "Radiant emittance" is not "emittance". ElectroMechanical Product Development (Electronics Packaging) UMD 1984 UCF 1993
  4. Tunalover

    Drawings with GD&T callouts but no Basic Dimensions

    At one time there was a drawing note that read: DIMENSIONS LOCATING TRUE POSITION ARE BASIC. So, in other words, if a dimension leads to a feature with a geometric control then that dimension is basic. Any other dimension not enclosed in a rectangle is a bilateral tolerance with the positional...
  5. Tunalover

    reference text recommendations for Creo Parametric 4.0

    Folks, Any recommendations on a Creo Parametric 4.0 reference book? I'm not looking for a step-by-step study guide...I'm looking for something like "The Creo Parametric 4.0 Bible". TIA Bruce ElectroMechanical Product Development (Electronics Packaging) UMD 1984 UCF 1993
  6. Tunalover

    How to calculate a time duration in hours and minutes given initial and final times

    Folks: I have a need to calculate an event durations in XX.XX hours given a start time YY:YY gm and end time ZZ.ZZ gm. For example, YY:YY gm could be 7:13 am and ZZ.ZZ gm could be 3:23 pm. Can anyone clue me in on how to do this in Excel? TIA Bruce ElectroMechanical Product Development...
  7. Tunalover

    Environmental IR Radiation Entering Ground Equipment

    I didn't think so. ElectroMechanical Product Development (Electronics Packaging) UMD 1984 UCF 1993
  8. Tunalover

    Environmental IR Radiation Entering Ground Equipment

    IRStuff could you cite a source for that? ElectroMechanical Product Development (Electronics Packaging) UMD 1984 UCF 1993
  9. Tunalover

    Environmental IR Radiation Entering Ground Equipment

    IRStuff I beg to differ with you. NIST scientists see no difference between radiation properties called with "tance" or "ivity" as they use them interchangeably. But NIST's official position is the "ivity" is only for what they call "optically pure" surfaces. Of course, they didn't define...
  10. Tunalover

    Environmental IR Radiation Entering Ground Equipment

    Thanks for that! OK, I have Leinhard's book but for some reason, my page 533 is different than yours. I've included a screen capture showing the most relevant part. His book warns that the equation ε=α is only used in very specific circumstances and that ε λ (T,θ,Φ)=αλ (T,θ,Φ) is the more...
  11. Tunalover

    Environmental IR Radiation Entering Ground Equipment

    cswilson thank you for finding a big table of emittances for many materials. I have many in my files but could you provide a link to that one? I don't have so many for non-metals. I know of the ASTM methods for measuring the total hemispherical IR emittance of various surfaces. Most of your...
  12. Tunalover

    Environmental IR Radiation Entering Ground Equipment

    I have read that organic commercial finishes are decidedly "non-gray" and that many people fall into the trap of assuming they are gray. Are you saying that, although it's true that organic commercial finishes are generally non-gray, over the thermal IR spectrum (only) they are gray? Where can...
  13. Tunalover

    Environmental IR Radiation Entering Ground Equipment

    OK, The box sits high in the air at atmospheric pressure and everything in its surroundings is at temperature Ta. The surface (top) facing the sky sees sky radiation and the other five surfaces see radiation from the environment. My question is: how can I say that the total hemispherical IR...
  14. Tunalover

    Environmental IR Radiation Entering Ground Equipment

    IRStuff you have "IR" in your name but maybe not in your heat transfer. A piece of equipment will absorb heat from the UV, IR, and visible parts of the spectrum FROM THE SUN. And it will absorb IR heat from its surroundings. And the box will then reject the internal electronic power...
  15. Tunalover

    Working with EEs

    Guys, The science and engineering part of me tells me that an ME must be managed by another ME, at least in functional management. The reason I say this is purely in the interest of the company and their customers. Suppose a fresh-out ME created a new life-critical electronic product design...
  16. Tunalover

    Environmental IR Radiation Entering Ground Equipment

    Guys: For the IR heat absorbed from a terrestrial environment (but NOT including sunlight), how can I prove/show that the emittance and absorptance of a particular painted or unpainted metal surface are equal for that IR spectrum? I know it involves Kirchoff's Law but Kirchoff's Law is much...
  17. Tunalover

    Solution to the SDOF spring-mass-dashpot system subjected to a half-sine pulse

    thread384-436025 I found the closed-form solution thanks to Tom Irvine. Such a simple model does have practical value IMO in studying the vertical responses of shock-mounted equipment subjected to shock pulses like those in MIL-STD-810 simulating transit drop and other collisions. I worked on...
  18. Tunalover

    ORDINATE DIMENSIONING PER ANSI Y14.5 1998

    Guys, I've looked through the IPC drawing standards and IPC has fully adopted D&T per ASME Y14.5-2009. But I have yet to meet a PCB designer who cared one iota about using it. It's the old saw: it's not the design/drawing that makes parts fit, it's the "dead nuts" manufacturing methods...
  19. Tunalover

    Solving a non-linear equation a bunch of times

    Guys, Thanks for all the productive ideas! For lack of time and money, I ended up using MS Excel with its GoalSeeker solver. It took about four hours because it tool solving (using GoalSeeker) 212= 441 times. I changed the domains to go from 0 to 1 rather than 0.05 to 0.95. There was one...
  20. Tunalover

    Solving a non-linear equation a bunch of times

    Thanks guys. I don't think Smath is a good candidate to do this because, for one thing, I don't think it can do 3D graphs. Probably the best solution in the long run is to use MS Excel with VBA and Goal Seeker since Excel has good 3D graphing capability. Agent666 no I don't have the solution...

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