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1h
comment ImageSize as absolute (metric) value
@Kuba I agree that this doesn't seem right. Sometimes an assumption of 72 dpi is hard-coded and ImageSize uses that assumption; other times there is the ImageResolution option as well. It seems that ImageSize is always supposed to be printer's points, though, even if the front end doesn't know how many pixels that corresponds to. RasterSize is explicitly pixels.
1h
comment Error propagation code
You may be interested in this: with expr = ComplexExpand[Abs[a + I b]], PropagateCovariance[expr, {a, b}] // Simplify is (2 a b cov[a, b] + a^2 var[a] + b^2 var[b])/(a^2 + b^2). This is the (first-order approximation of the) variance in f as a function of the variances in a and b.
1h
comment ImageSize as absolute (metric) value
@Kuba I don't know whether the default may change in future, but it does know what the actual screen resolution is even though it doesn't use it. See "ScreenInformation" /. SystemInformation["Devices"] vs. Options[$FrontEndSession, FontProperties]
1h
comment ImageSize as absolute (metric) value
@Kuba what does pp == px mean?
1h
comment Why does Mathematica report that $\int_1^\infty\frac{\sin(\sqrt{x})}{\sqrt{x}}dx$ = $2\cos(1)$?
Verison 5.2 gives Integrate::idiv (divergent integral) message.
21h
comment Data logger component identification
@DavidRoberts these colors mean 15K (they are read starting from the legs). Here is one like it (Spehro's link shows the wrong picture for the described product), but as he says, the nominal value doesn't define everything you need to know about it. You can try to replace it, but it may not be exact.
1d
comment Closed form expression for a resistor ladder network
I had wanted to write it like this, but the comment box was resisting at first: $$\frac{ \left(-2+\sqrt{3}\right)^n \left(-1+\sqrt{3}\right) + \left(-2-\sqrt{3}\right)^n \left(1+\sqrt{3}\right)} {\left(-2-\sqrt{3}\right)^n - \left(-2+\sqrt{3}\right)^n}$$ I think this way it has a pleasing symmetry to it.
1d
comment Closed form expression for a resistor ladder network
A really great answer. It can be written a bit more simply: $$\frac{2 \sqrt{3} \left(2+\sqrt{3}\right)^n}{\left(2+\sqrt{3}\right)^n-\left(2-\sqrt{3}\right)^n}-\sqrt{3}+1$$ (But I cheated and used Mathematica.)
1d
comment What's the difference between a thermal imaging sensor and an infrared CCD?
Who says that FLIR implies HgCdTe only? As I understand it, FLIR just means any infrared image sensor (not even necessarily a staring-mode focal plane array) that is not "sideways-looking" as with a pushbroom imager. Moreover, since most people are not concerned with aircraft or any other situation where pushbroom imaging would be a viable approach, I think the term is of dubious value and vague meaning when used more generally.
2d
comment Micron-Scale Linear Actuation
@FreddyTuxworth Newport are somewhat known for their high prices. They sell mainly into the scientific market for people who want a reliable pre-engineered solution and are not very sensitive to cost. Other companies such as Parker Motion will have cheaper offerings. What you basically need is an anti-backlash lead screw, stepper motor, and linear and/or rotary encoder. It will not be cheap for good quality components, but they are available for significantly less than one can expect to pay at Newport. You might be looking at $500 rather than $5000.
Feb
8
comment converting differential signal to single ended
I am not quite sure why you need a differential signal of such large amplitude. However, you can use a differential output opamp or comparator to achieve this.
Feb
8
comment Which Is The World's First Electronics Devise Which Are PatentT?
Please, do your own research. I am not going to find a list of the 10 earliest devices for your entertainment. You are wrong about the diode; it was patented after the coherer.
Feb
8
comment Which Is The World's First Electronics Devise Which Are PatentT?
Electric relays were invented much earlier, but it isn't clear to me whether one ought to consider them electronic or electrical.
Feb
8
comment Which Is The World's First Electronics Devise Which Are PatentT?
I would hazard a guess that the first patented electronic device was a coherer. It was invented a few years before this patent was filed. There are earlier patents for e.g. batteries and light bulbs, but these are electrical rather than truly electronic devices.
Feb
8
comment High voltage power supply and shunt regulator design
I just want to point out that most tube amplifiers do not use high-quality power supplies. The typical approach is just rectified a.c. with a bit of smoothing; normally no regulation is used. "Tube sound" comes in part from an unregulated and relatively high-impedance power supply that sags under load. So it may not be beneficial for your application to pay too much attention to this part of the design, if that application is audio.
Feb
8
comment Low-noise amplification of microphone signals, tubes or chips?
@nocomprende that is not the right way to think of it. Tubes are hot and have a high impedance, but electrons in them move in vacuum under the influence of a static electric field, without being randomly scattered by thermal fluctuations as in a bulk conductor. Thus tubes do not suffer from Johnson noise except to the extent of their small internal resistance. They are still subject to amplifying thermal noise from the external circuit, of course, and still exhibit shot noise due to the discreteness of electrons.
Feb
8
comment how does a Kelvin probe works?
Please note that Kelvin sensing (the 4-wire connection method) is a very different thing to a Kelvin probe device. The latter is used to perform a measurement of an absolute electric potential, unlike a voltmeter, which measures a potential difference. You should certainly not confuse these two unrelated concepts.
Feb
8
comment VIsible Light COmmunication using Arduino for masters thesis
I would say it depends significantly on your master's programme. Some will require novel research and a significant new contribution to the literature. Others only require the student to demonstrate a solid understanding of the field. I presume yours is of the latter type if you have only 6 months for it and this project is only part of the requirements. In that case, I don't see why you couldn't do this project if you want to. But you will make it easier for yourself and be more likely to produce something of enduring value if you choose a topic in which your supervisor has some experience.
Feb
8
comment Low-noise amplification of microphone signals, tubes or chips?
Here is a nice article that expands on some of the ideas you put forward in this answer. One point it makes that seems to be worth repeating here is that one must be careful about the input capacitance of JFETs; generally speaking there is a trade-off between noise density and capacitance for the reasons you outline here. Some more detailed information and microphone preamp designs are in this application note for the Linear Systems LSK489 low-noise JFET.
Feb
7
comment What would you ask Mathematica to do on a big system?
Well, yes and no. Undoubtedly MPI libraries do take advantage of libraries like hwloc and limic2 to accomplish what one cannot easily do otherwise. But good performance is possible even without them, and process management is an MPI-2/3 addition, while many programs still only require MPI-1 functionality. The fundamental difference between MPI and MathLink, as I see it, is that MPI libraries do their utmost to minimize latency, contention, and per-communicator resource consumption. By the way, I believe that on Windows memory-mapped I/O is done through the pagefile, not separate files.
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