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Electron band structure in germanium, my ass (2001)

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Re: Electron band structure in germanium, my ass (2001)

#371

Post by ryukoposting »

jerf wrote: post #27

One of my Core Memories when it comes to science, science education, and education in general was in my high school physics class, where we had to do an experiment to determine the gravitational acceleration of Earth. This was done via the following mechanism: Roll a ball off of a standard classroom table. Use a 1990s wristwatch's stopwatch mechanism to start the clock when the ball rolls of the table. Stop the stopw…

My teacher had a different solution to this exact problem. He ran the same test, but had us run it in the school's atrium, where we could drop objects a good 30 feet to the ground. It was a long enough drop that the stopwatches weren't as much of a hindrance. We destroyed a floor tile, but other than that, it went well to my recollection.

Re: Electron band structure in germanium, my ass (2001)

#372

Post by aleph_minus_one »

selimthegrim wrote: post #107
freedomben wrote: post #97

Earlier quoted context omitted.

That is enraging. I've seen similar things happen too and it blows my mind how ridiculous some of these teachers can be. I don't know if it's dehumanization of their students in their minds or an utter unwillingness to devote 30 seconds of directed attention to understanding the situation and making a reasonable judgment, but whatever the cause it is prolific. The only thing worse is when one of them will add somethi…

Just wait until that teacher is your graduate advisor.

That's why you should select your PhD advisor very carefully.

Re: Electron band structure in germanium, my ass (2001)

#373

Post by FrontierProject »

MattSayar wrote: post #289
concordDance wrote: post #281

Earlier quoted context omitted.

What's this a reference to? Not familiar with JIRA humiliation rituals.

Scrum/Kanban ceremonies with assigning points to tasks etc. GP is being melodramatic

I've been redditing for 15 years and until a week ago here on HN, I've never seen the previous commenter reffered to as GP. What is that an acronym for?

Re: Electron band structure in germanium, my ass (2001)

#374

Post by taneq »

don-code wrote: post #87
jerf wrote: post #27

One of my Core Memories when it comes to science, science education, and education in general was in my high school physics class, where we had to do an experiment to determine the gravitational acceleration of Earth. This was done via the following mechanism: Roll a ball off of a standard classroom table. Use a 1990s wristwatch's stopwatch mechanism to start the clock when the ball rolls of the table. Stop the stopw…

This is, more or less, exactly what happened when I took Electronics I in college. The course was structured in such a way that you could not move on to the next lab assignment until you completed the one before it. You could complete the lab assignments at your own pace. If you failed the lab, you failed the class, regardless of your grade. The second or third lab had us characterize the response of a transistor in…

That's awful, and unfortunately relatable. Most of my university courses were pretty good, but I had a computer graphics course where I got about 80% for my project, and about 30% for my final grade, which meant I apparently got 0% for my exam. I was a graphics nerd, I'd written a raytracer in C++, made a decent start on a game engine in Java (including software rasterizer with perspective-correct texturing, transparency, and model saving and loading with keyframe animated forward kinematics), along with numerous games and rendering programs. This graphics course was trivial stuff and barely got past explaining what a bitmap was and how to draw pictures using API calls. I couldn't have legitimately scored zero in the exam.

After weeks of trying to make an appointment with the lecturer to discuss it (and being told "you failed, get over it"). I got an email from the lecturer, admitting that they'd forgotten to add my exam score to my overall score. And from this point, it took months further to get my official grade corrected.

This same lecturer also once emailed out grades by opening their whole-course grading spreadsheet, deleting all the rows except for that student's grade, and then saving it as a new file.

With 'track changes' turned on.

Re: Electron band structure in germanium, my ass (2001)

#375

Post by immibis »

dragonwriter wrote: post #164
BeetleB wrote: post #85

Oh, BTW, the whole "Friction is directly proportional to the normal force": My Ass! I could never reproduce it well in the lab, because it's really not true. Take a heavy cube the shape of a book. Orient it so that the spine is on the floor. It's a lot more friction to move it in one direction than in the transverse direction. Yet the normal force is the same. Any kid knows this, and I feel dumb it never occurred to…

Friction is proportional to the normal force, more specifically, it is the normal force times the coefficient of friction. What you are describing (if the normal force is actually the same) is a contact situation where the coefficient of friction is different in different directions (anisotropic friction.)

When you define a new concept called "coefficient of friction" to be the friction force divided by the normal force, then yes, the friction force is the normal force times the coefficient of friction.

We can do this with any pair of values, such as current and voltage, but it's useful when the graph between current and voltage is close enough to linear, which means the corresponding coefficient is approximately constant. Well, is it? You have to show that with experiment. Once your data shows a line then you can calculate the slope of the line. If your data shows a parabola, you can calculate the quadratic equivalent of slope - don't calculate the actual slope and then declare that to be the result.

Sometimes you see people trying to measure the resistance of diodes, or worse, incorporating the resistance of diodes into calculations. What's the voltage across the diode? The current times the resistance, of course...

Re: Electron band structure in germanium, my ass (2001)

#376

Post by immibis »

russdill wrote: post #266
ptsneves wrote: post #103

Earlier quoted context omitted.

2000s? My university's wind tunnel instrumentation was mostly LabView.

It's been around a very long time and continues to be relevant. It's just a window in time where it was feasible to have a graphical application made on labview to be accessible to undergrads crossing over with such a thing being quite unstable.

I once wrote A* in LabVIEW for a robot.

It was a competition sponsored by National Instruments, so the code was supposed to be in LabVIEW. Another person wanted to write it as a C plugin, but I thought that was cheating.

There's A* built into LabVIEW, but it's for completely generic graphs so it takes a lot longer to run. The rewrite brought it from about 10 seconds to compute a path, down to about 0.5 seconds.

Re: Electron band structure in germanium, my ass (2001)

#377

Post by immibis »

dvh wrote: post #130

>Do you have any idea how hard it is to solder wires to germanium? I've just soldered SOT-723 onto SOT-23 adapter board, I can solder anything to anything

This is about the material, not the size. If the solder just doesn't stick, it doesn't matter how big it is.

Common solder is, of course, designed to stick really well to copper. Which it does. To solder more exotic things, you probably need a completely different alloy.

Re: Electron band structure in germanium, my ass (2001)

#378

Post by jodrellblank »

FrontierProject wrote: post #373
MattSayar wrote: post #289

Earlier quoted context omitted.

Scrum/Kanban ceremonies with assigning points to tasks etc. GP is being melodramatic

I've been redditing for 15 years and until a week ago here on HN, I've never seen the previous commenter reffered to as GP. What is that an acronym for?

GrandParent

Parent is the comment you're replying to, GrandParent is the comment above that, OP is the original poster.

Re: Electron band structure in germanium, my ass (2001)

#379

Post by jodrellblank »

kirubakaran wrote: post #213
realo wrote: post #151

Earlier quoted context omitted.

ALWAYS suspect some fuckup on the part of the knowledgeable people... especially them! Trust, but verify.

"Trust, but verify" is just a polite (ie corporate) way of saying "Don't trust until you verify", right?

I can only make sense of that saying in terms of how much trust to give, whether it's a high-trust or low-trust environment. Whether you assume good-will and basic competence or not.

e.g. you might assume that a sorting library from an internal developer at your company will put things in order but you might want to verify that it has reasonable worst-case performance for your use case. A no-trust situation might lead you to scrutinise everything about it - does it work at all, does it have horrendous performance in every case, is it a supply-chain attack with disguised errors leading to deliberate exploit holes.

In this case, "trust but verify" might mean assuming the Professor and TA are doing an experiment they have done before, which basically works, but might have made a mistake or missed something while setting it up, writing the slides, or explaining it to you. "Don't trust" might mean the TA got the experiment from ChatGPT, hates OP for being on a scholarship and is trying to sabotage their success, and the whole thing isn't an Electronics course it's really the Professor's practical joke/psychology experiment about stressing students.

Re: Electron band structure in germanium, my ass (2001)

#380

Post by jodrellblank »

somat wrote: post #324
don-code wrote: post #245

Earlier quoted context omitted.

I agree this seems overly principled to me. I recall a DSP class where there was an exam with a question like (not exactly this): > What does the following code print? > `printf("Hello, world!");` If you responded with: > Hello, world! ...which - of course - the whole class did, you got the question wrong. If you responded with: > "Hello, world!" ...which is actually not what that would print, you got the question ri…

Yeah that sucks, the hard life lesson where you have to swallow your pride and go "fine, I will put quotes on the infernal thing" But... it does not print a string, a string goes into it but what comes out of the function is not that programmatic feature we call a string in any way shape or form, what comes out depends on the output device specified, it may be ink on paper, lit phosphors, or a stream of bytes. none o…

"string" is a type that only makes sense inside the context of a specific programming language, because programming languages differ on what a string is and how it behaves (is it guaranteed to be valid UTF8, does it carry its own length around with it, is it runes/graphemes and can't be split on byte boundaries easily, is it mutable, etc).

Double quotes are a syntax sugar for string literals in source code, in a particular language, to avoid writing `string.from_byte_array([97, 98, 99])` or `new String({97, 98, 99});` or whatever. Strings are single quoted not double quoted in Dyalog APL, there's several different strings in SWI Prolog depending on using double quotes or backticks and how the flags are set.

stdout is an untyped byte stream which could go to a printer or Braille terminal or anything as you say, but could be terminal control codes, image data, or whatever. The OS doesn't tend to have a 'string type' ... but in PowerShell `write-output "a"` will write a .NET System.String to the output stream, but it won't use "printf()".

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