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FUCKING SUPER DIODES WHAT THE FUCK
Anonymous
2017-06-26 09:53:35
Post No. 8997638
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What the fuck is wrong with this circuit? It seems sound in theory, but when I breadboard it up, I get all sorts of crazy numbers.
Here's the idea: The op-amp is wired up as a precision rectifier a.k.a a "super diode" with an unequal value for the input and feedback resistors such that when the signal is rectified, it is also amplified. When the switch is closed (on), a small signal of ~150mV AC goes in, and a half-wave rectified and filtered DC output of about 2.8V should be the result (when the voltage divider pot on the output is set to 5k ohms). When the switch is open (off), the circuit gets no signal, so there is nothing for the op-amp to pass and rectify, and so there should be no output at all. Normally, with no signal, the voltage at TP1, TP2, TP3, and the output should all be 0V.
When I actually breadboard this thing up and power it, TP1 and TP3 read ~4.5VDC, TP2 reads as ~5.4VDC, and on the output I get ~1.5VDC /with no AC signal on the input/. When I add the signal in, I get no change.
The op-amp I'm using is one half of a TL082 dual op-amp. I've tried each side of two different TL082 chips, and used both a bench power supply and a 9V battery. I've checked and rechecked the connections, even to the point of 2 complete scrap-and-rewires.
What is wrong with this circuit?
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Oh dear.
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>>8997638
The upper diode should be connected to TP2 and not TP3 (see https://en.wikipedia.org/wiki/Precision_rectifier )
+ should be ground but you're setting it to 4.5V thus offseting everything.
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>>8997641
OP here. I tried connecting the upper diode to TP2 but got the same result. I'm setting a virtual ground to the non-inverting input such that the circuit can presumably run off of a single +9VDC rail. Perhaps this circuit can only work in a dual rail configuration?
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So lads, just got my final year results. I'm going to graduate with a 1st in mathematics despite going to literally 2% of my lectures, handing in only half my assignments, and learning all the material by reading the textbook in the one or two days before the exam.
Have I finally proved I'm not a brainlet?
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>>9003451
Hmm... Ok?
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>>9003451
No. Sounds like you went to a shitty university with piss poor standards. A give away for that is having assignments in your final year.
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Geometric approach for Linear Algebra
Anonymous
2017-06-26 04:48:29
Post No. 8998066
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Hi /sci/,
Based on the following argument that describes the importance of understanding the geometry of linear algebra:
https://www.youtube.com/watch?v=kjBOesZCoqc&list=PLZHQObOWTQDPD3MizzM2xVFitgF8hE_ab&index=1
I was recommended the following book which focuses on the geometric intuition of linear algebra.
http://www.springer.com/gp/book/9780387940991
I just finished calculus and am a complete beginner when it comes to linear algebra. I would love to hear /sci/'s perspective on the video and the textbook (which is on gen.lib)
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>when the graduate student in charge of the class decides to teach linear algebra as set theory
Holy fuck what a nightmare.
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>>8998241
lol turbo autism
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>>8998241
That sounds like fun. What is the rigorous set representation of a matrix?
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>The universe is in it's infancy with less than .1% of it's total life span having occurred
>There is no evidence that there is any other intelligent life in the universe and the Femi paradox seems to show that we are the only ones in our galactic cluster and possibly even observable universe
Why is it so hard to believe that we are the first intelligent life? At first I thought it was unlikely but after thinking about it's by far the most likely explanation. How does it feel to know that humans are going to become "The old ones" that you always see in sci fi? How come science fiction doesn't seem to want to deal with this?
328 Posts / 47 Images
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The Native Americans had no evidence for quite a long time that there was any other intelligent life on Earth, some things just take time.
Absence of evidence is not evidence of absence
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>>8992584
They didn't have science or ever tried looking for other civilizations
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>>8992620
>They didn't have science or ever tried looking for other civilizations
and Earthlings don't have whatever it takes to find life outside of our planet, what's your point?
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Found this gem on Instagram just now.
If this doesn't prove pop-sci is a meme once and for all, I do not know what will
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>>8990477
Its worded horribly, but in essence it is true.
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>>8990557
lol what?! not a single word is true.
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>>8990562
Explain why, and show your working.
Anonymous
/ccg/ - Climate Change General 2017-06-15 08:42:03 Post No.8976591
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/ccg/ - Climate Change General 2017-06-15 08:42:03 Post No.8976591
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/ccg/ - Climate Change General
Anonymous
2017-06-15 08:42:03
Post No. 8976591
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410ppm Edition
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Is it when we reach 600 ppm that shit starts to go down?
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>>8976598
I don't think there is such a thing as a sharp boundary of dangerous CO2 concentration
the last time CO2 had the present concentration in the atmosphere was in the middle Miocene, some 12 Million years ago. At that time, temperature were between 3° and 6°C warmer and sea level was between 25 and 40 meters higher than today. That doesn't mean we will get the same conditions (because solar insolation definitely also played a factor besides CO2) but climatologists say that we have already locked in a long-term rise of sea level of between 4 and 9 meters, even with a hypothetical stabilization of GHG concentration at the present level.
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>>8976612
Honestly, we're pretty fucked if that is accurate. A 30ft sea level increase is more than enough to destabilize the entirety of global infrastructure and displace hundreds of millions, not to mention the effect on the ocean as it overtakes all of that waste.
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Anyone here read Blanchard's stuff on hebephilia, specifically his arguments why it would be maladaptive?
Hebephilia is the preference for pubescent girls about 11-14. He argues this is a disorder and would have been maladaptive in prehistoric times.
What he doesn't realise is that it's common practice in primitive foraging societies for men to acquire pubescent girls as wives which means it must be adaptive otherwise it wouldn't have become common practice. Far from being maladaptive or a disorder, hebephilic preferences seem to be an adaptation for acquiring pubescent wives.
Blanchard has none of this, he thinks it's maladaptive and he's tried to back this up with reproductive statistics and stuff but his arguments don't work.
One argument involves the reproductive statistics from the Pume tribe gathered by Kramer. They show that girls who start reproducing before the age of 17 have fewer surviving offspring that those who start later and the younger the girl the fewer offspring.
He thinks this means that men who acquired say a 12yo wife would get fewer offspring from her than a man who acquires a 17yo wife but this doesn't follow for the simple reason that girls don't start reproducing at the age that men acquire them but rather a few years later. It's really stupid. He ignores the fact that most girls in the Pume tribe are married off before the age of 14 so we know the strategy works fine.
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>>9004100
go back to pol you pedo
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>>9004100
>it's common practice in primitive foraging societies for men to acquire pubescent girls as wives which means it must be adaptive otherwise it wouldn't have become common practice.
Cultural practice and societal norms aren't evolutionary traits.
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>>9004118
Universal cultural practice and societal norms almost certainly are, such as the practice of marrying pubescent girls.
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This guy is only 7-10 solar masses wtf
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>>9003536
is it made only of hydrogen or something?
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>>9003536
>what is density
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>>9003536
mass =/= volume fgt
Anonymous
/SCI! help me with this double integral! 2017-06-29 02:35:21 Post No.9003286
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/SCI! help me with this double integral! 2017-06-29 02:35:21 Post No.9003286
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/SCI! help me with this double integral!
Anonymous
2017-06-29 02:35:21
Post No. 9003286
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so the problem is
get the area of:
sqrt (x) + sqrt (y) = 2.
x = 0 , y = 0.
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https://www.symbolab.com/solver/double-integrals-calculator
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>>9003286
>The answer is trivial
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>>9003286
I get it to be 8/3.
What are you struggling with?
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Is there a reason why the more woman tend to be in a field the more bullshit it is?
If you want proof look at any field dominated by men like Math and Physics and compare that going down the line from Psychology to the social "sciences".
Are woman on average just not able to think empirically?
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yes, women are children with bigger bodies that we have decided to treat like adults
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>>9002501
*tips fedora*
I see we have another enlightened gentleman here
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>>9002469
This is one of the places were IQ helps infer some things. A majority of women place very average, while there are very few women in standard deviations far above and below the median.
Men are the opposite, meaning that in any given subject, especially those that have rigor and empirical methods, there will be more men at the peak of the subject, and conversely just as many men that can't even grasp fundamental concepts.
Where women tend to fit in, is understanding some of these subjects in general, capable of studying and doing well, but not necessarily at laying the groundwork and breaking newer ground in the future.
This is not to say that there are not women that can not, just that there aren't nearly as many.
Just finished a MSc. Should I keep going for a PhD?
I like the idea of doing research but I've seen many people get burnt while doing a PhD.
How many of you are doctors? Maybe you doctors or people that have worked in a research a lab can give me some perspective.
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what's your field?
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>>9001948
Medical imaging and biosignals
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>>9001944
If you can manage your time, stick to plans and schedules, and are ready to travel a lot, then a PhD is not that terrible.
It also depends which kind of PI you have. Some group leaders are more laid back, others demand immediate results.
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Bluepill me on the Aurora, a legendary black project aircraft.
Apparently this F U C K I N G T R I A N G L E is capable of hypersonic flight. Stories about this thing are universally written and believed only by normies with no aerospace education. I know there are some aerospace fags on this board right now. Convince me that this thing doesn't exist for technical reasons.
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>>9001782
>go to /v/ to answer your aircraft related question
fucking love you /sci/
he's right btw. back to /pol/
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>>9001806
>tell me this engineering question
>reee go to /pol/
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Anything can be made into a plane, as long as you have enough control authority and fly by wire.
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What's all the stuff about another extinction level event happening with an asteroid attack.
Wouldn't Saturn and Jupiter save us?
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>>9001677
nah they hate earth.
compared to the rest of the planets earth is a whiny bitch
if an asteroid hits just make sure you jump right as it impacts so you cant start the human race over again for maybe like a month or two
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The next one (or ones) can come from any direction, at any time.
Chances are we won't know it until it hits us. Even if scientists did find it ahead of time, the general public would never be told.
Don't lose to much sleep over it though. Getting directly hit by an asteroid, would probably be the quickest and most painless way you could ever hope to die.
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>>9001759
If it's big enough for human extinction, I just hope it hits my fucking house first.
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Hi /sci/
I'm currently taking a differential equations course and we've had a few quizzes and exams where I'm solving a High Order Differential Equation (non-homogeneous) and I have to stop mid-problem because what I'm currently doing will not work. (I'm talking about, for example, if the equations is y''''+2y'''+2y''=3x^2, then I will get the complement solution, no biggie, but when I try to get the particular solution, I do (Ax^2 + Bx + C) , and after attempting to solve it, we know it won't work. So then I try (Ax^3 + Bx^2 + C), and after doing the work again, STILL IT DOESN'T WORK! Not until I do (Ax^4 + Bx^3 + Cx^2 + Dx + E) Does it work, BUT AFTER ALL THAT TIME I'VE LOST LIKE 7 MINUTES OR MORE AND MY EXAM/QUIZZES SCORES ARE AFFECTED.
Is there a way of knowing ahead of time to start with Ax^4.... rather than Ax^2 ?
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Your highest order differencial is 4 so chances are youll want something to plug into that part of the equ
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Have no clue what you're asking for. Can you provide a more clear example?
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>>9000374
Ifs its to the n order, then you take the n derivative.
If it has n constants then you take it to the n derivative, then solve
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When we dream, why does it authentically feel like we dream for hours and hours in this long pisode of a dream when in reality it only lasted for like 20 minutes or so?
Before getting woken up, I slept for like less than an hour, but in my mind, in my dream, it genuinely felt like it lasted for a day or so.
It's beyond my comprehension.
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>>8998311
because your perception of the passage of time is mediated by chemical systems that change when you sleep.
part of a field sobriety test is asking a person to count thirty seconds in their head, if they are intoxicated they might have trouble doing this accurately
I kind of think it's like when you are sleeping your brain is like a wheel spinning with zero friction, just perpetuating itself by itself at it's own rate, while when you are awake your brain is a wheel pulling you along a road.
Also haven't you noticed when you are having fun time goes by so much quicker?
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Another question would be, why do dreams feel 100% as authentic as our consciousness does in this base reality?
There's a part of me that thinks, if it doea feel one hundred percent real, then in a certain way maybe ithe is.
Maybe our minds function in two different ways: one in their dream world and one in the base reality world - but both are just as real as the other
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>>8998311
Bump