text:
# Input 0 is incompatible with layer conv1d_40: expected ndim=3, found ndim=2 [closed]

i am working on computer vision using deep learning. my training data contains (x,128) shape. i am passing the same to conv1d layer but facing issues

below is my model

input_dim = (128,)
classifier = Sequential()

#convolutional layer 1
classifier.add(Convolution1D(32, kernel_size=3,input_shape = input_dim, activation = 'relu'))

#convolutional layer 2

#flatten

• Look at this answer, this is probably the same issue here: stackoverflow.com/a/49841111/9858126 – Sean Mirchi Jul 15 '19 at 8:21
• @SeanMirchi i tried it. but still facing the same issue – Ashu Jul 15 '19 at 9:48

Conv1D requires (batch-size, steps, dim) inputs. Your input sounds like (batch-size, steps). I'm guessing you have 128 steps of some univariate series. If so your input_dim is (128, 1). Your input may need to be reshaped to add an extra dimension at the end to conform.

your shape should be (img_w, img_h, num_colour_channels)

• This is a 1D convolution. You are answering as if the input is a 2D image and performing a 2D convolution, which would require 4-dimensional tensors, not 3. – Sean Owen Nov 21 at 20:35


text:
# Common Divisor Divides Integer Combination

## Corollary to Common Divisor in Integral Domain Divides Linear Combination

Let $c$ be a common divisor of two integers $a$ and $b$.

That is:

$a, b, c \in \Z: c \divides a \land c \divides b$

Then $c$ divides any integer combination of $a$ and $b$:

$\forall p, q \in \Z: c \divides \paren {p a + q b}$

### Corollary

$c \divides \paren {a + b}$

### General Result

Let $c$ be a common divisor of a set of integers $A := \set {a_1, a_2, \dotsc, a_n}$.

That is:

$\forall x \in A: c \divides x$

Then $c$ divides any integer combination of elements of $A$:

$\forall x_1, x_2, \dotsc, x_n \in \Z: c \divides \paren {a_1 x_2 + a_2 x_2 + \dotsb + a_n x_n}$

## Proof 1

We have that the Integers form Integral Domain.

The result then follows from Common Divisor in Integral Domain Divides Linear Combination.

$\blacksquare$

## Proof 2

 $\ds c$ $\divides$ $\ds a$ $\ds \leadsto \ \$ $\ds \exists x \in \Z: \,$ $\ds a$ $=$ $\ds x c$ Definition of Divisor of Integer $\ds c$ $\divides$ $\ds b$ $\ds \leadsto \ \$ $\ds \exists y \in \Z: \,$ $\ds b$ $=$ $\ds y c$ Definition of Divisor of Integer $\ds \leadsto \ \$ $\ds \forall p, q \in \Z: \,$ $\ds p a + q b$ $=$ $\ds p x c + q y c$ Substitution for $a$ and $b$ $\ds$ $=$ $\ds \paren {p x + q y} c$ Integer Multiplication Distributes over Addition $\ds \leadsto \ \$ $\ds \exists z \in \Z: \,$ $\ds p a + q b$ $=$ $\ds z c$ where $z = p x + q y$ $\ds \leadsto \ \$ $\ds c$ $\divides$ $\ds \paren {p a + q b}$ Definition of Divisor of Integer

$\blacksquare$

format: plain


text:
0
Research Papers: Natural and Mixed Convection

# Numerical Investigation of the Linear Stability of a Free Convection Boundary Layer Flow Using a Thermal Disturbance With a Slowly Increasing Frequency

[+] Author and Article Information
Manosh C. Paul

Department of Mechanical Engineering, University of Glasgow, Glasgow G12 8QQ, UKm.paul@mech.gla.ac.uk

D. Andrew S. Rees

Department of Mechanical Engineering, University of Bath, Bath BA2 7AY, UK

J. Heat Transfer 130(12), 122501 (Sep 18, 2008) (8 pages) doi:10.1115/1.2976554 History: Received September 19, 2007; Revised May 22, 2008; Published September 18, 2008

## Abstract

Numerical simulations are performed to investigate the linear stability of a two-dimensional incompressible free convection flow induced by a vertical semi-infinite heated flat plate. A small-amplitude local temperature disturbance with a slowly increasing frequency is introduced on the surface near to the leading edge in order to generate disturbance waves within the boundary layer. The aim is to compare the response of the thermal boundary layer with that obtained by selecting discrete disturbance frequencies. In the present study, air is considered to be the working fluid for which the value of the Prandtl number is taken to be $Pr=0.7$. The computational results show that the disturbance decays initially until it reaches a critical distance, which depends on the current frequency of the disturbance. Thereafter the disturbance grows, but the growth rate also depends on the effective frequency of the disturbance. Comparisons with previous work using constant disturbance frequencies are given, and it is shown that the sine-sweep technique is an effective method for analyzing the instability of convectively unstable boundary layers.

<>

## Figures

Figure 1

Contours of θ̂ recorded at various values of the temporal frequency, λ, for c=5×10−5. Here ten contour levels are plotted based on the global extrema within each frame (see the text of the paper). The dashed contour lines represent negative values of θ̂ while the solid lines represent positive θ̂.

Figure 2

Time variation of the surface rate of heat transfer recorded at (a) x∗=16 and (b) x∗=207 where c=5×10−5

Figure 3

Envelope of the maximum heat transfer response, Q, against time for various locations along the heated surface where c=5×10−5

Figure 4

Envelope of the maximum heat transfer response, Q, against distance for various disturbance frequencies, where c=5×10−5

Figure 5

Comparison of Q for the three different values of c and the discrete frequency (5). The dashed lines are for c=10−4, the dashed-dotted lines are for c=5×10−5, the solid lines are for c=2.5×10−5, and the circles are for the discrete frequency results.

Figure 6

The envelope of the curves presented in Figs.  45. For legends, see Fig. 5. The solid line with square symbols denotes the results for c=2.5×10−5 obtained by the finer grid, 960×96.

Figure 7

(a) The values of λ, which correspond to Qmax(x∗) shown in Fig. 6. These curves show which frequency corresponds to the most amplified disturbance at each value of x∗. (b) Neutral curves. The solid line with square symbols denotes the results for c=2.5×10−5 obtained by the finer grid, 960×96.

## Discussions

Some tools below are only available to our subscribers or users with an online account.

### Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related Proceedings Articles
Related eBook Content
Topic Collections


text:
My Math Forum Confused

 January 10th, 2012, 02:12 PM #11 Math Team     Joined: Jul 2011 From: North America, 42nd parallel Posts: 3,372 Thanks: 234 Re: Confused CRGreathouse wrote 'It's pretty rare that you can find useful, college-level resources at a public library or bookstore. Popular materials and high-school math (through calc) are common, but when was the last time you saw Galois theory at B&N?' http://search.barnesandnoble.com/Field- ... 0387947532 If there is a book in print, barnes and noble will get it to you in 24 hours, free shipping if the book costs 25 dollars or more. I used to hang out at 2 barnes and noble in nyc both had thousands of books about math and science, schaums outlines on hundreda of math and physics topics. Haven't been there since 2008 cause i moved. The barnes and noble at lincoln square was AWESOME! 4 massive floors with the entire 4th floor being a cafe. I would buy a coffe for $1.10 and get a 50c refill spending hours reading any book i wanted. Sometimes i would buy a latte for$5 no one ever complained. If the cafe was full, i would lay down on the carpet in a corner and use my schoolbag as a pillow,reading books i picked from their shelves. in 4 years not once did anyone complain, many others did the same as me. I learned more math at barnes and noble than any classroom, that's why i am sad and angry when i heard it is closing. http://newyork.untappedcities.com/2011/ ... nes-noble/ I bought many books from them, one book i bought twice, 'An imaginary tale' by Paul J. Nahin. The first time i bought it for me because it is a treasure of information regarding sqrt(-1), the second time as a gift for a friend. It was out of stock the second time so i paid for it and they shipped it free, got it the next morning. I also found books there about Quaternions, number theory, calculus, linalg, diffeq, you name it. Many books published by Springer Verlag...very good publishers of various mathematical content, including cutting edge research, Heck, i even learned some quantum mechanics at b&n. I remember picking up this book by John Archibald Wheeler about gravitation...1000 pages long and at least 10 difficult equations on every page HAHAHA-HAAAAHA Yeah i have to agree with CRGreathouse...mathematics of any consequence is very difficult indeed. read about Richard P. Feynman's work at the cafe...on and on... that place was a treasure repository of human intellectual achievement. Sad it is no more...
January 10th, 2012, 03:23 PM   #12
Math Team

Joined: Jul 2011
From: North America, 42nd parallel

Posts: 3,372
Thanks: 234

Re: Confused

Quote:
Originally Posted by Ballser
Thank you for all the replies!

You all made good points. I was thinking if there was any alternative way of studying math and later on getting some kind of income from it. But of course you must have degree anyways. I think I just have to move my ass to the department of mathematics and move forward there. Its the only way.

Quote:
 I'd hate to see you just trudge through all your math courses like this and have to do all the fun stuff outside of class. Have you spoken to anyone? Are you allowed to study independently? Are the classes outside the math department different? I mean, do you have math classes that are in another department that are taught differently? (That's the only interpretation I can make of your comment.) If so, can you take them within the math department?
I hardly go to the classes at all. I study to the tests from home. IF I study..The things they teach are not hard, but its just very hard for me to prepare for tests. I get bored and frustrated and cant go on. Its hard for me to just memorize and read certain things for tests..I think that's what the problem is fundamentally. I feel I'm very much different learner than what people usually are. Anyways I have to find out a way to move my ass forward when I get to the department of mathematics. I hope it will work.
At the moment I'm actually studying math in a university that is 100% for master of science so I would need to change university as well, in order to get to the math department.

I like to use my imagination a lot, trying to find out new things of things I have just learned, and then going even further from there, it could be thought as a bit crazy.
My dream is that I could study and investigate math by myself as a hermit and be able to feed myself same time, hehe. If I were rich I wouldn't have any problem. I would continue as I have to this day, but since I'm not rich the future doesn't look so bright. Of course money solves problems of almost all people hehe.

I hope I made myself a bit more clear, but please feel free to make sharp and even offensive questions and comments. I don't mind you being offensive at all. It could be helpful. I don't feel I have opened or revealed everything necessary regarding this issue to you. I hope to get some clarity on my mind from this thread.
Have you ever considered becomming an actuary? As far as i know, all you need to do is pass their exams which are given several times each year. Anyone can take the math exams... you don't need to be in school, just pay the exam fee. The exams are tough, i saw some sample questions, but a self learner like you could make it happen if you have what it takes. You will be free of university curriculum, just pass the exams and you become a member, they make very good money and there is always a need for financial analysts, more so in the next 20 years because of the financial crisis the planet is going through

You can take the exams as many times as you want AFAIK and most of them (All of them?) are multiple choice.

http://www.beanactuary.org/exams/

http://www.beanactuary.org/exams/rules/?fa=exam-fees

http://www.soa.org/education/exam%2Dreq/

I would pursue it myself if my brain wasn't already fried.

January 11th, 2012, 03:14 PM   #13
Senior Member

Joined: Apr 2011
From: USA

Posts: 782
Thanks: 1

Re: Confused

Sorry to answer more than one thing at the same time, but otherwise I'd be answering about 5-6 different postings. (At least I left the names on the quotes. )

Quote:
 Originally Posted by agentredlum The best way to learn is to be shown examples. Show me how to do the problem...then change the numbers and see if i can get the result. That would be teaching.
That sounds to me like teaching someone how to be an ape. Which I don't consider to be "teaching" at all. In fact, this is the very thing I find to be the problem: show how to run through the problem, imitate me, if you can do that, you know how to do the problem. Not! It means they can imitate a structure. Not sure where the idea came from that professors (and tutors) won't show examples, when in my experience, running through examples is all I ever see them do, without ever explaining what they mean, or what is underlying it. I realize different schools are different, but I work online and see students from schools all across the country and this same thing seems to be going on everywhere.

Granted, this might be a process that has to happen somewhere along the way. In pieces, within a context of explaining. One thing that can be done is having the student explain it back to you in their own words, not just do it. It also depends on what it is and the level it's at. Higher math becomes more abstract.

This is exactly what was always expected of me: learn this process. As a general rule, everyone around me would know "how" to do something far before I would. Because they repeated the process and could "ape it." While I was trying to understand it. The difference was that once I finally got around to understanding it, I actually understood it, and they didn't. So I could then do the problems that were different than the example by applying it, and applying it to future things we learned.

Quote:
 Originally Posted by agentredlum Have you ever considered becomming an actuary?
I'd be careful with all this. First, I'm not convinced that all you have to do is pass exams without any college on your record. Second, sometimes passing these types of exams is not about having knowledge about a subject, i.e. like learning about calculus or finance on your own. It's about learning the very specific things they want you to know. A lot of the work can also be tedious. I'd say look into the field carefully, and look into the requirements carefully. It also requires some business background. (No clue what type of math OP is interested in - this is a lot statistics and finance related.)

Quote:
Originally Posted by CRGreathouse
Quote:
 Originally Posted by agentredlum This has been my experience: professors don't know how to teach learners and mathematicians don't know how to write books for non-experts. Solutions are closely gaurded, and many times on an exam the student is asked unfair questions only experts understand.
I think that too many people go to college; it would be better if a number of those who have trouble would just drop out. Math is hard.

It's true that many math books are written poorly -- it's actually very hard to make them accessible. But the point stands regardless.
Totally agree with this. The school where I work always seems to bend over backwards to make sure people can pass classes they should have never been in. They try to dummy down math classes cause people can't pass them. Well, maybe they weren't meant to pass them. In some cases, I can see the point. Like they require every student take some math course, even if you're a theatre major. So I can see trying to find a way to make sure they can get through these lower-level classes or they'd have a lot of people never getting a degree in anything at all. They do have classes that aren't a prerequisite for anything, but they take the classes that are prerequisites for other courses and dummy those down too. I mean, huh? If someone has a major requiring more math, they have to be able to do math to at least some extent. I'm working with mostly business majors, and they are going to have to do a certain amount of math -- if they're terrible at it, change majors. (It's not like they're taking the same courses a math major would, but still....)

And some people simply don't belong in college, either due to the inability to learn anything at all, or because they're far too lazy to actually work for it. Getting a college degree wasn't meant to be a piece of cake, though I think an average person, with work, can manage to get one.

(But yes, a lot of math books stink. That's why the instructor has that much more requirement to be good. I really love the ones who do nothing but read the book - what a waste of a salary. I also have to agree that test questions are sometimes unfair, and I don't believe in dummying down tests. But some are unfair.)

January 11th, 2012, 03:50 PM   #14
Senior Member

Joined: Apr 2011
From: USA

Posts: 782
Thanks: 1

Re: Confused

I'm supposed to be getting ready to go somewhere. I hate when I do this. :P

Quote:
 Originally Posted by Ballser I hardly go to the classes at all. I study to the tests from home. IF I study..The things they teach are not hard, but its just very hard for me to prepare for tests. I get bored and frustrated and cant go on. Its hard for me to just memorize and read certain things for tests..I think that's what the problem is fundamentally. I feel I'm very much different learner than what people usually are. Anyways I have to find out a way to move my ass forward when I get to the department of mathematics. I hope it will work.
I think right now that may be what it comes down to: just dealing with it for the moment. It sounds like me with my third quarter of econ. The first two were more interesting and I had a better instructor, and then that third quarter came and I swear I couldn't read that book for more than 10 minutes before I'd be up pacing around the house cause I just couldn't tolerate it.

You also may not be that much of a different kind of learner - perhaps you just recognize it. If people are taught a certain way, that's all they know. If they were taught a different way, they might realize it works better.

Quote:
 I like to use my imagination a lot, trying to find out new things of things I have just learned, and then going even further from there, it could be thought as a bit crazy.
I don't think it's crazy. I just don't know that it fits into the structure of your average class. Upper level classes seem to be more encouraging about going outside of things a bit or getting into research and whatnot. Lower level classes seem a lot more structured. I once had an argument with my stats teacher over a lab. To this day I contend that I'm right, as I was trying to apply it realistically to this business model. She told me I was being "too creative." (???) It wasn't creative - it was just realistic. So I screwed it all up cause I couldn't stay within the confines of what was a terrible lab.

Quote:
 My dream is that I could study and investigate math by myself as a hermit and be able to feed myself same time, hehe. If I were rich I wouldn't have any problem. I would continue as I have to this day, but since I'm not rich the future doesn't look so bright. Of course money solves problems of almost all people hehe.
Well, I'm a bit of a hermit (that's why my friends are online - sheesh), and I feel for you here. I have lots of things I'd rather be doing if I were rich and didn't have to work. Work can be very structured as well. I have a feeling this problem of yours is going to extend to work as well, and not just school. People sometimes don't understand when I say I can't stand jobs where I have to do everything someone else's way - it's too structured. I need to to just know what you need, and then let me do it my way to get to the goal.

Quote:
 What is generally taught: "This is A, that is B. You do **** and you get E." Students learning: "This is A, that is B. I do **** and I get E. Now I know this thing." I don't say that's bad. Particularly if you just need math as a tool for applications of it.
You are absolutely right!! I run across a lot of people like this. If they can follow the process and get to the answer, then they "know how to do it." And they don't care about understanding anything else about it, cause they just want through the class. Of course, this is usually when the class isn't their major area. I don't in any way consider they "know this thing." They know how to follow a process. And then as soon as the next problem turns the tables on them, like wants them to work into it backwards or something, they have no clue. And in the next chapter when they have to utilize the thing for something else, they have to learn it from scratch again as though they never saw it before.

Quote:
 Now the reason why I say that I feel myself being a very different learner is because I study and learn by exploring and using imagination. If someone says me "This is that and that is this. Remember it in the exam." I will not be using my imagination or exploring anything and I will be extremely bored compared to the other way I study, learn and investigate math.
Very true - again sometimes you just have to do what you have to do to get through something. College is going to have a certain amount of structure. You need to find things that you can do outside of that to keep your interest. You may have to spend time figuring out what exactly interests you and see if you can follow that path.

I believe I saw where you said you're a first-year student? So you're going to be in all the basic junk. And I don't think you're all that "different." If you are at basic levels, you're with a lot of people who may be heading off very different directions than you, and maybe they don't care about this particular stuff. It's a bit like me with my accounting major: all business majors (and some non-business majors) have to take the first-year accounting. For a marketing major, they may hate the stuff. Worse, computer networking majors have to take it. That's a real hoot - they don't care about accounting. (Even grad students who didn't have it as an undergrad have to go back to this basic class.) But then you get to the upper level classes, where everyone is specifically an accounting major, it's a totally different story. Now they're interested. Now they want to understand. Now we have the teachers who specialize in this area and are also interested in it, and interested in the students. Yes, I still had to take stuff totally not my thing (auditing ), but upper level stuff was definitely more interesting, and I was among students who were more interested in it. Hopefully this will happen to you when you get further along. (This is of course assuming I understood you correctly.)

Remember that you're in an area that your average person hates. Most people hate math and find it difficult. You are obviously going to get a different attitude when you come to a forum that's a bunch of math geeks. (And occasionally an accounting geek. ) So you may find some solace here.

 January 11th, 2012, 08:39 PM #15 Math Team     Joined: Jul 2011 From: North America, 42nd parallel Posts: 3,372 Thanks: 234 Re: Confused I would like to pose a question and my opinion for the answer as food for thought. Question: Why do students struggle in college level courses even though they meet the prerequisites for the course? The answer (in my opinion) It has nothing to do with the intelligence of the student, it has everything to do with the desire of the college to maximize profits by making students take the same course more than once. Most professors explain a few key points, then strap a jet engine on a concept and vrooom! the student is left to figure out the consequences of theorems and when to apply them. Most professors apply a 'sink or swim' philosophy but they don't jump in to help you if you sink. In your opinion, CRGreathouse and Erimass, there are too many idiots masquerading as students in colleges, maybe so, perhaps universities shouldn't advertise that higher learning is for everyone that can pass the entrance exams? As far as the ape comment is concerned, in my opinion, most people have to learn that way before they can learn how to think like a mathematician. You know what i really hate? professors who won't tell you what is on the exam, who won't administer a pretest so you can know exactly what is expected of you. These are the same professors who treat the course as some sort of contest between them and the student's...you have to outsmart them before they give you a decent grade. Think of all the students who take the same course again and again. Paying good money what do they get in return? whipped air and mental masturbation. It's called 'THE COTTAGE INDUSTRY' Nice scam they have going on. By the time one has figured out college is not for them, one has spent several thousand dollars.
January 11th, 2012, 08:48 PM   #16
Global Moderator

Joined: Nov 2006
From: UTC -5

Posts: 16,046
Thanks: 938

Math Focus: Number theory, computational mathematics, combinatorics, FOM, symbolic logic, TCS, algorithms
Re: Confused

Quote:
 Originally Posted by agentredlum It has nothing to do with the intelligence of the student, it has everything to do with the desire of the college to maximize profits by making students take the same course more than once.
That's not it.

Do you know why? Because the professors who set the standards are not the ones who benefit (financially) from having students retake classes.

But further, students who fail classes are much more likely to drop out of that college entirely (for another, a community college, or no college at all). The university almost certainly makes more money on students who pass than those who fail for that reason. So no, I don't think that's it at all.

Quote:
 Originally Posted by agentredlum Most professors apply a 'sink or swim' philosophy but they don't jump in to help you if you sink.
I agree. That's really not the professor's job, though.

Quote:
 Originally Posted by agentredlum You know what i really hate? professors who won't tell you what is on the exam, who won't administer a pretest so you can know exactly what is expected of you. These are the same professors who treat the course as some sort of contest between them and the student's...you have to outsmart them before they give you a decent grade.
You expect professors to tell you what will be on the exam?!? What is this, middle school?

January 11th, 2012, 09:35 PM   #17
Math Team

Joined: Jul 2011
From: North America, 42nd parallel

Posts: 3,372
Thanks: 234

Re: Confused

Quote:
Originally Posted by CRGreathouse
Quote:
 Originally Posted by agentredlum It has nothing to do with the intelligence of the student, it has everything to do with the desire of the college to maximize profits by making students take the same course more than once.
That's not it.

Do you know why? Because the professors who set the standards are not the ones who benefit (financially) from having students retake classes.

But further, students who fail classes are much more likely to drop out of that college entirely (for another, a community college, or no college at all). The university almost certainly makes more money on students who pass than those who fail for that reason. So no, I don't think that's it at all.

Quote:
 Originally Posted by agentredlum Most professors apply a 'sink or swim' philosophy but they don't jump in to help you if you sink.
I agree. That's really not the professor's job, though.

Quote:
 Originally Posted by agentredlum You know what i really hate? professors who won't tell you what is on the exam, who won't administer a pretest so you can know exactly what is expected of you. These are the same professors who treat the course as some sort of contest between them and the student's...you have to outsmart them before they give you a decent grade.
You expect professors to tell you what will be on the exam?!? What is this, middle school?
The professors are puppets who preserve the status quo, otherwise they get fired long before they get tenure, or are in a position to set standards. it is a mistake to think management doesn't pull their strings. It is a fact that colleges make more money on lower level math courses than all the other math courses combined. It is a fact that many students repeat these same courses fattening up the college. There is an endless supply of 'customers' waiting to take these courses, it doesn't matter if they drop out, many more suckers are available, it's called 'THE COTTAGE INDUSTRY'

What is the professors job? To challenge your ability by obscuring the details and make you feel stupid when you don't understand?

So... you don't want the students to know what is on the exam? Only an expert can pass your course...how will you turn your students into experts in 3 MONTHS? All you are doing is identifying geniuses, you are not teaching, which is the job of a professor.

January 11th, 2012, 11:33 PM   #18
Senior Member

Joined: Apr 2011
From: USA

Posts: 782
Thanks: 1

Re: Confused

Boy, you have a worse opinion of education than I do, and mine's pretty bad. What I'm reading from you is that you're going to already hate a school whether you know anything about it or not. I'm not saying you're not entitled to your opinion - you are. But I have to wonder how much of this is emotion rather than opinion.

Quote:
 Originally Posted by agentredlum Question: Why do students struggle in college level courses even though they meet the prerequisites for the course? The answer (in my opinion) It has nothing to do with the intelligence of the student, it has everything to do with the desire of the college to maximize profits by making students take the same course more than once.
I strongly disagree with this as well. I disagree for two reasons, one of which is what CRG said. I have to wonder how you seem to know the inner workings of a school and things that really should be private. Are you on the inside track to have knowledge of these things, or is this just an opinion?

I went back to school after many years. I was still good at basic math and remembered really, really basic algebra. I faked my way through the pass-out-of-basic-algebra test and got into this business algebra class. I was way ahead of the people who had just come out of the prerequisite. I mean, huh? (I've always picked up on math fairly easily, but I hadn't had any of this junk for like 15 years.) If they're using a class for a prerequisite, they need a C. Most people getting a C don't really know the material all that great. (Or they know it really well and the instructor's a jerk, or they have bad test anxiety, or something else unusual.) So who is thinking they actually have the needed material to move on to the next class? If they just wanted them to pay for it again, why pass them on?

We also have some lousy part-time instructors. They know the material really well themselves -- after all, they have a degree in it, presumably meaning they were better than average at the subject. And then seem to think the class should be that way. This is why I think the upper level classes are better - now you have majors only in them. In lower level, you have people who are average. If the instructor doesn't get that, the class is gone. (We at least have a good tutorial program that gets a lot of business. These bad instructors keep me in business. But that's also why I consider that I "teach" rather than "tutor.")

Quote:
 Most professors apply a 'sink or swim' philosophy but they don't jump in to help you if you sink.
Yeah, I'll agree with that, although in many cases they don't have time to deal with individual people. But some try harder than others.

Quote:
 In your opinion, CRGreathouse and Erimass, there are too many idiots masquerading as students in colleges, maybe so, perhaps universities shouldn't advertise that higher learning is for everyone that can pass the entrance exams?
I don't know that they do advertise that. I was looking to go back to school and nearly everywhere I went, while advertising the bright wonderful future you're going to have with one of their degrees, also tended to note that it was going to take some work. One school seemed to take pride in how hard it was going to be. (Maybe they like students who like a real challenge.)

Quote:
 As far as the ape comment is concerned, in my opinion, most people have to learn that way before they can learn how to think like a mathematician.
I'm not a mathematician so I don't now how they think. I would hope that someone who is set to be a mathematician would have an innate ability to think about math without just being an ape. Yes, someone has to be shown a certain amount of stuff. But what I'm calling being an ape may be different than what you'd call it, who knows.

Quote:
 You know what i really hate? professors who won't tell you what is on the exam, who won't administer a pretest so you can know exactly what is expected of you. These are the same professors who treat the course as some sort of contest between them and the student's...you have to outsmart them before they give you a decent grade.
I have two opinions on this. The fact that they won't tell you what's on the exam in and of itself I have no issues with at all. If I were a professor, I wouldn't likely give you a pretest either, nor would I tell you what's on the test. And I'm certainly not trying to have a contest with you. I would state from the start of the class that I will go over all topics that are going to be on the test, plain and simple. Yes, I very likely might hand out some practice problems so people can see what my problems might be like versus the book, but I wouldn't hand out some pretest so you can see exactly what I'm putting on the exam. If you came to class, you'd know what topics I just taught.

Having said that, I've seen some instructors with some pretty crapola tests. Like stuff that's nothing like what was done in class. Or stuff that's really not important. And personally, I don't think they're trying to get anyone to outsmart them. I just think they're stupid and occasionally smarta**es. (It's usually those part-timers with the worst tests.)

Quote:
 Think of all the students who take the same course again and again. Paying good money what do they get in return? whipped air and mental masturbation. It's called 'THE COTTAGE INDUSTRY' Nice scam they have going on. By the time one has figured out college is not for them, one has spent several thousand dollars.
I don't think college is a scam. I do believe there are some schools better than other schools. I think some are very hard. I think some baby people. I will make some generalizations about the general education system, which has a lot of reasons behind it, but "scam" isn't one of them. But you might want to also keep in mind that any private school is a business. (I just bet you have a few theories about businesses in general though.)

There are good teachers and bad, good schools and bad. And yes, I do believe there are school systems and colleges which are probably up to no good. (In fact, I know there are.) But as a general rule I would not say colleges are just scamming people.

If I had to summarize what I think the problem is, I simply think the concept of "teaching" has gotten lost and has been replaced by "show a process and memorize." This not only hurts in terms of the subject matter of whatever class it is, but also hurts in terms of having no expectations that a student actually learn to think on their own, or for that matter, be responsible for themselves. I'm seeing a lot of problems with people just not being capable of having an independent thought and want their hands held. (That's a parenting problem as well.)

 January 12th, 2012, 06:33 AM #19 Math Team     Joined: Jul 2011 From: North America, 42nd parallel Posts: 3,372 Thanks: 234 Re: Confused Well, I'm not an expert, as i mentioned in a previous post, my brain is fried, but i can still analyse facts and form my own opinions. Fact: Private institutions charge way too much and don't provide a quality education worth the money they charge. They also make a lot of money from donations but it is not enough for the greedy arrogant bastards. With the amount of money they make from private donations alone,private colleges could be free of charge, they are not. It seems they are more interested in figuring out what the students are willing to pay for their education, not interested in how to make education better. Courses are constantly tweaked so that the pass rate falls somewhere between 50%-70% Fact: Public colleges make a lot more money from students than most people know. In addition to tuition (let's say $5000 per year) public colleges receive state and federal aid for every full time student enrolled. Roughly around$15000 so the total amount of money a public college makes off of a full time student (or full time equivalent FTE) is roughly 20000 per year. These numbers are rough estimates and funding changes from state to state. Also it is difficult to find info on this. I spoke with vice chancellor of CUNY when i was senator of math club. He explained funding issues to club officers on campus. His intention was to explain the tuition hikes cause he believed THE MONEY WASN'T ENOUGH! LOL I formed my own opinion. Had he known i was going to disagree with him he probably would not have informed us. The main idea is that public colleges do not maintain their existance from tuition. I would be surprised if tuition constitutes more than 20% of the total monetary intake. They squeeze the state and federal goverment as much as they can, then they squeeze the students. These are not the actions of a noble institution, but corrupt business practices. That's why i say colleges are run like a business, maximize profits-minimize cost. A student attending public college thinks he/she is paying tuition, not really, the student is paying a lot more than that and the quality of the instruction sucks, even more so when you figure out how much it's really costing you. Similarly at private institutions who make money from donations, you think you are paying $40000 per year but the college is making$200000 a year off of you, just by you being there. The quality of education also sucks there as well. Anyway, the numbers are rough guestimates but the points should be clear. Point: People are being robbed under the disguise of 'higher learning' Point: Learning institutions have strayed from the main focus of 'Academy' as envisioned by ancient philosophers and ressurected by renaissance philosophers.
 January 12th, 2012, 06:49 AM #20 Math Team     Joined: Jul 2011 From: North America, 42nd parallel Posts: 3,372 Thanks: 234 Re: Confused What i find very amusing is how they advertise 'small class sizes and 80% of professors employed here are Phd' but when you take the class it's usually an auditorium with hundreds of students and some graduate student teaching, you can't even get the Phd on the phone!. LOL Yeah, the upper level courses may have small class size but thats because most of the students are too busy being recycled in the lower level courses. Recycled and fleeced HAHAHAHAHA! Many of these Phd's don't speak the language and are not even on campus, probably engaged in '''research''' in another part of the world. Yet, the colleges use the fact of this so called 'employment' to boost their credibility and draw suckers like moths to a flame. HAHAHA-HAAAA!

 Tags confused

,

### confused by higher level mathematics -"common core"

Click on a term to search for related topics.
 Thread Tools Display Modes Linear Mode

 Similar Threads Thread Thread Starter Forum Replies Last Post charlieboon Calculus 5 February 23rd, 2013 11:01 AM ccfoose Algebra 3 April 16th, 2012 10:55 PM Siedas Algebra 9 March 10th, 2012 02:29 PM momoftwo New Users 4 August 19th, 2009 07:15 PM charlieboon Algebra 0 December 31st, 1969 04:00 PM

 Contact - Home - Forums - Cryptocurrency Forum - Top


text:
学术活动
 您现在的位置：首页 > 学术活动 > 专题学术报告/Seminar
 专题学术报告/Seminar
 •  Holographic description of entanglement entropy and conformal block in $AdS_3/CFT_2$ [2017-04-26] •  Higgs-top coupling at LHC and Higgs factories [2017-04-21] •  Study of Low-Lying Baryons with Hamiltonian Effective Field Theory [2017-04-13] •  Chiral matter: hydrodynamics and holography [2017-04-12] •  Story of my 35-year research regarding organic films: Development of Maxell-displace cu... [2017-04-08] •  Holographic entanglement negativity [2017-04-05] •  Duality between 2+1d conformal field theories: theory and numerics [2017-03-31] •  Validity of EFT for physics beyond the SM [2017-03-28] •  Combing the Horizon Fluff: Logarithmic corrections to black hole entropy from horizon f... [2017-03-28] •  Correspondence between genus expansion and \alpha' expansion in string theory [2017-03-28] •  高精度测量Th-229核光钟跃迁计划 [2017-03-28] •  CDCC calculations of total, complete and incomplete fusion for reactions of 6Li with 14... [2017-03-27] •  CFT correlation functions from S-matrix singularities [2017-03-23] •  On the SM EFT and its deformations [2017-03-16] •  Photons from the Early Stages of Relativistic Heavy Ion Collisions [2017-03-08] •  Machine Learning for Many-Body Physics [2017-03-07] •  Extraction of mean-field potential in self-consistent calculations [2017-03-03] •  Unexpected asymmetry of the charge asymmetry in the fission at high excitation energies [2017-03-03] •  NMR simulation of topological phases [2017-03-01] •  The Macdonald Refined topological vertex [2017-02-23]
 共50页  首页上一页12345下一页下5页尾页
 IE6.0浏览器，1024X768分辨率 版权所有 © 中国科学院理论物理研究所 地址：北京市海淀区中关村东路55号　邮政编码：100190【京ICP备05002865号】 京公网安备1101080094号


text:
40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
 Mariner elog, Page 3 of 3 Not logged in
ID Date Author Type Category Subject
9   Wed Mar 24 17:42:50 2021 PacoGeneralDesign specsSilicon TM dichroic coatings for phase I

Yeah, the magnitudes are the inverse weighted scalar costs (so they lie on the appropriate relative scale) and indeed larger enclosed areas point to better optima. I would be careful though, because the lines connecting the scalar costs depend on the order of the vector elements (for the plot)... so I guess if I take the cost vector and shuffle the order I would get a different irregular polygon, but maybe the area is preserved regardless of the order in which the scalars are displayed...

 Quote: Cool starfish 🌟 . What is the interpretation of the area enclosed by the vertices? Is that the (reciprocal) cost? So the better solution maximizes the area enclosed?

Attached is a cartoon partial view into the heat load experienced by the Mariner assembly.

The omnigraffle file with more explicit arrow labelling in the 'layers' tab is available here. The dashed red lines along to top represent vacuum chamber radiation incident on all sides of the OS/IS, not just from the top. Off picture to the right is the BS, left is the beam tube/ETM chamber -- hence the lower absored laser power (solid line) absorbtion (PR power + no HR coating absorption).

Parameters:

• Emissivities are listed outside the cartoon.
• Shields consist of polished aluminum outer surfaces and high emissivity inner surfaces.
• 1 W input power, 50 W power recycling, 30 kW cavity power
• All shields held at 77K
• 20 ppm/cm bulk silicon absoprtion, 5 ppm coating absorption

Assumptions

• Steady state condition, where the shields are able to be cooled/held to 77K
• Holes punched into the inner shield for stops, magnets, etc are assumed to shine RT light onto 123K TM
• This is very conservative, MOS will stablize at some temp and the OS should block ~all vacuum chamber radiation not funneled through inner shield snout

Missing or wrong

• [M] Contribution of MOS conduction and emission on the outer shield heat budget
• [M] Inner shield
• [W] OS inner surface currently modelled as one surface seeing incident RT light, need to accomodate the view factor of each of the 5 high e sides to the open maw of the OS
• [M] Conduction through shield masses, how efficient is it to link them with straps
• [M] no AR coating absorption
• [M/W] Cold finger cooling power from room temp shield to 77K cryocooler ('wrong' label because 61W is only the heat load once shields are cooled):
• Worst case to reach: 1.5m connection between tank flange and shield (from flange at bottom of the tank)
• Phosphorous deoxidized copper:  5 cm diameter
• ETP copper:  3.5 cm diameter
• Best case: 0.5m connection, from flange at level of OS
• Phos deox Cu: 3 cm diameter
• ETP Cu: 2 cm diameter
• $q_{\text{conductive}} = \frac{A}{L} \left[\int_{4\, \text{K}}^{T_2} \lambda(T) dT - \int_{4\, \text{K}}^{T_1} \lambda(T)dT \right]$
73   Thu Aug 4 13:44:56 2022 Jennifer HritzGeneralOptical ContactingSuccess with slowly heating

Yesterday, I did two rounds of slowly heating 4 samples to the maximum hot plate temperature. This was to formally test if my success with a single sample earlier in the week was a fluke. Note that the hot plate takes about 10-15 minutes to reach a stable temperature when it is turned up one notch.

First round:
I bonded 4 samples by putting methanol in the gap between the glass slides and letting it dry to create a gap.
Starting at room temperature, I heated the slides on each setting for roughly 15 minutes, then let them cool down naturally over the course of an hour. 3 broke broke at medium heat, and 1 survived the whole process. I belive these broke because the bonds were weaker and I heated them slightly too quickly. In previous tests, I would manually switch the hot plate on and off, but I wanted to see if the hot plate could heat up slow enough on its own.

Second round:
I bonded 4 samples by scrubbing the slides with methanol, using a compressed air duster to blow off the fibers, rubbing them together with the pressure of my fingers, and repeating this whole procedure until they stuck (it took 2-4 repeats).
Starting at room temperature, I heated the slides on each setting for exactly 20 minutes, then let them cool down naturally over the course of an hour. All of them survived to the maximum temperature (the pictures show them at the start and end of the heating, note the temperature). I credit this to the stronger bonding proceedure and the extra 5 minutes for them to adjust to the temperature. I did not turn the hot plate on or off at any point, I just let it heat up at its own rate.

I cannot tell if the bonds are stronger. The size and shape of the Newtons rings did not change.

Attachment 1: PXL_20220803_232203193.jpg
Attachment 2: PXL_20220804_002433906.jpg
34   Fri Oct 1 12:01:24 2021 PacoGeneralDesign specsTM Barrel coating emissivity

[Paco, Nina, Aidan]

We ran our stack emissivity calculation on different AR stacks to try and make a decision for the TM barrel coatings. This code has yet to be validated by cross checking against tmm as suggested by Chris. The proposed layer structures by Aidan and Nina are:

1. *| Air || SiO2 x 800 nm || Ta2O5 x 5 um || Silicon |*
2. *| Air || Ta2O5 x 10 um || Sio2 x 20 nm || Silicon |*
3. *| Air || SiO2 x 100 nm || TiO2 x 1 um || Silicon |*

Attachments # 1-3 show the emissivity curves for these simple dielectric stacks. Attachment #4 shows the extinction coefficient data used for the three different materials. The next step is to validate these results with tmm, but so far it looks like TiO2 might be a good absorbing film option.

Attachment 1: stack_1.pdf
Attachment 2: stack_2.pdf
Attachment 3: stack_3.pdf
Attachment 4: interpolated_n_k.pdf
35   Fri Oct 1 13:24:40 2021 AidanGeneralDesign specsTM Barrel coating emissivity

I have to question whether this passes a sanity test. Surely in the case of Stack 2, the 10um thick Ta2O5 will absorb the majority of the incident radiation before it reaches the SiO2 layer beneath. It should at least be similar to just absorption in Ta2O5 with some Fresnel reflection from the AIr-Ta2O5 interface.

For example, at around 18um, K~2, so the amplitude attenuation factor in a 10um thick layer is 160,000x or a gain of 6E-6. So whatever is under the Ta2O5 layer should be irrelevant - there is negligible reflection.

 Quote: [Paco, Nina, Aidan] We ran our stack emissivity calculation on different AR stacks to try and make a decision for the TM barrel coatings. This code has yet to be validated by cross checking against tmm as suggested by Chris. The proposed layer structures by Aidan and Nina are: *| Air || SiO2 x 800 nm || Ta2O5 x 5 um || Silicon |* *| Air || Ta2O5 x 10 um || Sio2 x 20 nm || Silicon |* *| Air || SiO2 x 100 nm || TiO2 x 1 um || Silicon |* Attachments # 1-3 show the emissivity curves for these simple dielectric stacks. Attachment #4 shows the extinction coefficient data used for the three different materials. The next step is to validate these results with tmm, but so far it looks like TiO2 might be a good absorbing film option.

36   Fri Oct 1 14:11:23 2021 PacoGeneralDesign specsTM Barrel coating emissivity

Agree with this. Quickly running tmm on the same "stacks" gave the Attachment #1-3. (Ignore the vertical axis units... will post corrected plots) and extend the wavelength range to 100 um.

Attachment 1: stack_1.pdf
Attachment 2: stack_2.pdf
Attachment 3: stack_3.pdf
53   Thu Jun 16 14:04:30 2022 JuanGeneralSuspensionTable for Mariner Suspension Cryo

Today we looked at possible locations for where we will be setting up Mariner Suspension and Cryo chamber. The first option was the far left table in the CAML lab but it seems that there is going to be an issue with height clearance, so we have come up with another solution which takes a table from Koji's lab which is 3'x4' ft and moving it into CAML lab in the back right of the lab. To move the table we may need to call facilities to help us because we will most likely need to take the table apart to get it out of the lab. The aisle space in Koji's lab is about 43 inches, but the doorway, which is the tightest space, is 35 inches.

After we have set up the table in CAML we are planning on moving the Chamber in DOPO-lab to CAML. We plan to use skyhook with has a load limit of 500lbs/227kg this should be more than enough to move the chamber. We still need to get the wheeled base for skyhook we are in the works in doing so.

Also, We want to remove the previous setup from the chamber and leave it at DOPO-lab. Stephen is going to figure out how to keep it clean (sort of). Besides these transportation logistics, I am also working on the electronics as an immediate task and the electrical arrangement in the chamber.

to do list
- Check the table height
- Check the chamber height (base/cap)
- Check how much the chamber cap needs to be lifted (so that we can remove it)
- Is the weight capacity sufficient?

54   Thu Jun 16 19:43:36 2022 KojiGeneralSuspensionTable for Mariner Suspension Cryo

- B246/QIL Skyhook

• Find the base of Skyhook. It should be in the storage room (B246). Stephen contacted Chub for lab access. Done
• Assemble Skyhook with the base and check the stability/safety/capacity/height/etc

- DOPO

• Ask Paco to move the delicate instruments from the table. Done
• Bring Skyhook to DOPO. The chamber seems already vented.
• Find the way to place the cap on the floor safely and cleanly. => Stephen

• Open the cap and then remove the crackle interferometer. Wrap it with something and place it somewhere in the room. How? => Stephen

• Move the base to a dolly or something. Then put a cap on the base. => It'd be better to ask Caltech Transp for the chamber transportation.
• Do we have to temporarily remove the laser safety curtain?

- OMC Lab

• We probably need to separate the optical table and the base. Ask Caltech Transp to check how the work should be done.
• Do we have to temporarily move anything on the way?
• The table can be rolled out to the corridor and then rolled in to the CAML.

- CAML

• Remove the grey rack and push the desk to the East.
• Place the optical table.
• Place the rack close to the table.
55   Thu Jun 23 21:11:03 2022 KojiGeneralSuspensionTable for Mariner Suspension Cryo

Table moving effort in the OMC lab: See https://nodus.ligo.caltech.edu:8081/OMC_Lab/412

16   Tue Jun 22 22:28:09 2021 KojiGeneralDesign specsTest Mass wedge design

The ETM wedge of 0.5deg will allow us to separate the AR reflections. We will be OK with the ITM wedge of 0.5deg too. 0.36 deg for ITM is also OK, but not for the ETM.

- Attachment 1 shows the deflection of the 2128mn and 1418nm beams by the test mass wedge. Here, the wedge angle of 1deg was assumed as a reference. For the other wedge angle, simply multiply the new number (in deg) to the indicated values for the displacement and angle.

- Attachment 2 shows the simplified layout of the test masses for the calculation of the wedge angle. Here the ITM and ETM are supposed to be placed at the center of the in-vacuum tables. Considering the presence of the cryo baffles, we need to isolate the pick-off beam on the BS table. There we can place a black glass (or similar) beam dump to kill the AR reflection. For the ETM trans, the propagation length will be too short for in-vacuum dumping of the AR reflection. We will need to place a beam baffle on the transmon table.

- I've assumed the cavity parameter of L=38m and RoC(ETM)=57m (This yields the Rayleigh range zR=27m). The waist radii (i.e. beam radii at the ITM) for the 2128nm and 1418nm beams are 4.3mm and 3.5mm, while the beam radii at the ETM are 7.4mm and 6.0mm, respectively,

- Attachment 3: Our requirement is that the AR reflection of the ALS (1418nm) beam can be dumped without clipping the main beam.
If we assume the wedge angle of 0.5deg, the opening of the main and AR beams will be (2.462+4.462)*0.5 = 3.46 deg. Assuming the distance from the ETM to the in-air trans baffle is 45" (=1.14m), the separation of the beams will become 69mm. The attached figure shows how big the separation is compared with the beam sizes. I declare that the separation is quite comfortable. As the main and AR beams are distributed on both sides of the optic (i.e. left and right), I suppose that the beams are not clipped by the optical window of the chamber. But this should be checked.
Note that the 6w size for the 2128nm beam is 44mm. Therefore, the first lens for the beam shrinkage needs to be 3" in dia, and even 3" 45deg BS/mirrors are to be used after some amount of beam shrinkage.

- Attachment 4 (Lower): If we assume the same ITM wedge angle of 0.5deg as the ETM, both the POX/POY and the AR beams will have a separation of ~100mm. This is about the maximum acceptable separation to place the POX/POY optics without taking too much space on the BS chamber.

- Attachment 4 (Upper): Just as a trial, the minimum ITM wedge angle of 0.36deg was checked, this gives us the PO beam ~3" separated from the main beam. This is still comfortable to deal with these multiple beams from the ITM/

Attachment 1: wedge.pdf
Attachment 2: Layout.pdf
Attachment 3: ETM.pdf
Attachment 4: ITM.pdf
103   Mon Oct 17 23:17:25 2022 Jennifer HritzGeneralOptical ContactingTesting PWM code with actual samples

Now that I have (relatively) good PWM code, I wanted to do my first real test with actual samples. Since everything went smoothly, I will now work on building the original set up for the project, which included attaching thermocouples to two plates so we could precisely measure the heat between them.

As you can see in the pictures below, I am running an Arduino off of my laptop which controls an AC/DC control replay that turns the AC power to the hot plate on and off.

Attachment 1: first_real_PWM_test_samples_before_PXL_20221018_071840794.MP.jpg
Attachment 2: first_real_PWM_test_set_up_PXL_20221018_071943406.MP.jpg
Attachment 3: first_real_PWM_test_in_action_PXL_20221018_072832135.mp4
66   Thu Jul 14 14:55:01 2022 Jennifer HritzGeneralOptical ContactingTesting isopropanol and methanol

Note that I am just testing out different techniques, so I have not set up the thermocouples to precisely measure the temperatue.
On Tuesday, I developed a new method of putting water, isopropanol, or methanol on one slide then squishing the other slide on top of it to fill the gap with the afformentioned liquid. The slides are slippery at first, but as they dried, which took about 15 minutes, the bond forms. The bonds were strong enough that I could just barely push the slides appart by applying pressure to the side using my thumbs. I prepared 4 samples this way, 2 with iso and 2 with meth. I took one of each and heated them on Medium for 30 minutes under the brass hunk with the aluminum square on the bottom and copper foil on both sides of the samples. Earlier in the day, I tried heating them without the weight on top, but the heat just broke the bond. I took the remain two and set them aside as controls.
On Thursday, I returned to check the bonds. The heated samples had broken. I intented to check on Wednesday, but I was sick from food poisoning, so I do not know whether the bonds broke immediately after heating or due to sitting for an extra day. For the control samples, one also had a broken bond, but the other had become even stronger.
I noticed that, when the slides are successfully bonded, the shape and appearance of the Newton's rings change, which can be seen in the pictures. I speculate that the circles on the unbroken control are the bonded regions. Ideally, we want to see no Newton's rings.

Attachment 1: PXL_20220714_220953206.MP_2.jpg
Attachment 2: PXL_20220714_220940258.MP_2.jpg
Attachment 3: PXL_20220714_222105409.jpg
Attachment 4: PXL_20220713_003923957.jpg
105   Wed Oct 19 21:51:10 2022 Jennifer HritzGeneralOptical ContactingThe trials and tribulations of the thermocouples

I intended to test the new thermocouple set up today, but when I plugged them in, both did not read a temperature. It took me a long time to figure out what went wrong: when installing the K Type thermocouple connector, the wires of the thermocouple need to be pushed in as far in as possible, otherwise the circuit would not be completed. It took a lot of trial and error to figure this out. I first created a test "circuit" with wire and a resistor to make sure that the connector itself was not broken. Then I carefully observed how moving the wires in different places affected the reading.

Once I did carefully reassemble the thermocouples, they worked perfectly, as indicated by the non-zero current. I ran tests with my three thermocouples and two devices to see how precise the temperature reading is. The results are below and pictures of the readings can be found in the zip file. I cannot explain why one of the adhered thermocouples is hotter than the other.

 (°C) Fluke 17B+ Digital Multimeter Digital Thermometer 343 Thermocouples T1 T2 Adhered to Plate #1 23.1 27.4 26.1 Plate #2 26.6 28.8 28.5 Rod placed on Plate #1 21.7 24.5 24.0 Plate #2 21.3 24.1 24.0

Plate #1 and 2 refers to the two different aluminum plates. T1 and T2 refers to the two ports on the Digital Thermometer 343. It cannot read two thermocouples simultaneously (as far as I can tell); it's so one can be used as a baseline/reference value for the other.

Attachment 1: thermocouple_connector_test_ciruit_PXL_20221020_035719119.MP.jpg
Attachment 2: correct_assembly_PXL_20221020_042855181.MP.jpg
Attachment 3: resistance_through_broken_and_fixed_connector_PXL_20221020_035951538_20221020_041939698.MP.jpg
Attachment 4: broken_and_fixed_thermocouple_PXL_20221020_042242792_20221020_042201775.MP.jpg
Attachment 5: thermocouples_and_thermometers_room_temp.zip
20   Fri Aug 6 04:34:43 2021 KojiGeneralGeneralTheoretical Cooling Time Limit

I was thinking about how fast we can cool the test mass. No matter how we improve the emissivity of the test mass and the cryostat, there is a theoretical limitation. I wanted to calculate it as a reference to know how good the cooling is in an experiment.

We have a Si test mass of 300K in a blackbody cryostat with a 0K shield. How fast can we cool the test mass?

$m\,C_p(t)\,T'(t) = -\epsilon\,\sigma A\,[T(t)^4 - 0^4]$

$T(0) = T_0$

Then assume the specific heat is linear as

$C_p(t) = c_{p0} T(t)$

The actual Cp follows a nonlinear function (cf Debye model), but this is not a too bad assumption down to ~100K.

Then the differential equation can be analytically solved:

$T(t) = T_0 \left( 1 + t/t_0 \right )^{-1/2}$,

where the characteristic time of t0 is

$t_0 = \frac{m c_{p0}}{2\,\epsilon\,\sigma A\,T_0^2 }$.

Here T_0 is the initial temperature, cp0 is the slope of the specific heat (Cp(T_0) = c_p0 T_0). epsilon is the emissivity of the test mass, sigma is Stefan Boltzmann constant, A is the radiating surface area, and m is the mass of the test mass.

Up to the characteristic time, the cooling is slow. Then the temperature falls sqrt(t) after that.

As the surface-volume ratio m/A becomes bigger for a larger mass, in general, the cooling of the bigger mass requires more time.

For the QIL 4" mass, Mariner 150mm mass, and the Voyager 450mm mass, t0 is 3.8hr, 5.6hr, and 33.7hr respectively.

• If the emissivity is not 1, just the cooling time is expanded by that factor. (i.e. The emissivity of 0.5 takes x2 more time to cool)
• And if the shields are not cooled fast or have a finite temperature in the end, of course, the cooling will require more time.
• 1.25 t0 and 8 t0 tell us how long it takes to reach 200K and 100K.

This is the fundamental limit for radiation cooling. Thus, we have to use conductive cooling if we want to accelerate the cooling further more than this curve.

Attachment 1: cooling_curves.pdf
69   Fri Jul 22 13:47:47 2022 JuanGeneralGeneralUpdate

Just a general update of what I have been up to deriving Lagrange for double pendulum system and also been looking at code that koji gave to me I've add comment to some of the code also working on my report.

59   Thu Jul 7 10:23:04 2022 JuanGeneralGeneralUpdate

Almost done with coil driver boards

Attachment 1: IMG-5378.jpg
Attachment 2: IMG-5379.jpg
75   Mon Aug 15 16:37:51 2022 Juan GeneralGeneralUpdate on Sat Amp and OSEMs

Sat Amp

- Changes to sat amp 15.8 k ohm resistors instead of 16k The change has been made on Sat Amp - S1103733 & S1103732 ONLY Channel 4 and 2 have been changed on both boards.

OSEM

- I developed a test bed for our OSEM to measure force

I will attach images of the setup and some of the results from 3 different OSEMs.

Future Work

- For the current test bed, we are using a clear plastic bin although not ideal it manages to get the job done and works for now there could be a better solution for this,
- Next step for OSEM we want to use 40 m single pendulum to test OSEM and measure the transfer function.

Attachment 1: IMG-6458.jpg
Attachment 2: IMG-6355.jpg
Attachment 3: IMG-6459.jpg
Attachment 4: IMG-6460.jpg
Attachment 5: OSEMdata.png
106   Thu Oct 20 22:43:05 2022 Jennifer HritzGeneralOptical ContactingWired the thermocouples backwards

Since the two devices are giving different temperature readings, I would like to find out if this imprecision is linear (e.g. they are always 3°C off, so I just need to add/subtract 3°C after taking the measurements). If not, some sort of calibration is probably required. I decided to figure this out by running the heating tests I did before, but this time with the plates. This also serves as a test to see how the plates heat up.

Or rather, this is what I would have done, had I not realized that the thermometers were going down as the heat was increaing, meaning I had switched the polarity for both thermocouples. It turns out that this mix-up is a common mistake. I thought that I double checked that red was positive for thermocouples, but it is in fact not:
"red is the usual color for positive charges, whereas the red wire in thermocouple cables typically contains the negative signal. This coloration is ANSI standard for thermocouples, but it is not what most people expect."

Attachment 1: wrong_correct_polarization_PXL_20221022_054250498_20221022_055117337.MP.jpg
58   Tue Jul 5 21:06:47 2022 JuanGeneralGeneralWork Update

Update of my current work I have finished one coil driver board and started on the last two that I need here is the progress and Ideally, I'll finish by tomorrow.

Attachment 1: IMG-5362.jpg
Attachment 2: IMG-5361.jpg
114   Thu Oct 27 22:12:21 2022 ranaGeneralOptical Contactingplotting and PID

The Arduino / AC PWM interface looks good. I recommend that you maintain the code in GitHub and post a link to the repo whenever you update the code. Use detailed commit messages so that it makes sense.

For the plotting, it would be good if you can use grid lines and markers for the data points. Then we can see the difference between the data and the fits, etc.

And to avoid the hysteresis, etc. you can record the temperature in your Arduino and use feedback to make the heater just go to whatever temperature you specify. So you would have a prescribed T(t) and the PID feedback loop would just make the heater take you there. Can your Arduino read the thermocouple?

60   Thu Jul 7 15:20:04 2022 ranaGeneralOptical Contactingsome useful links

For our optical contacting, Jennifer and I are starting out with glass (microscope slides), with the setup in the EE shop next to the drill press (photos from Jennifer to follow).

• https://www.laserfocusworld.com/optics/article/16546805/optical-fabrication-optical-contacting-grows-more-robust is a write up on contacting, and the link to Dan Shaddock's paper is also useful (need to sign up to get the acutal TSP writeup)
• Thesis on Silicon Bonding (https://escholarship.org/uc/item/5bm8g42k)
• https://youtu.be/qvBoGoh_-AE
ELOG V3.1.3-


text:
# Central limit theorem

#### bmccarty

##### New Member
It's been years since I've taken a statistics course. I recall taking several of them. But, apparently I took them to little good effect, since a friend recently posed a simple question that is really bugging me.

According to the central limit theorem (CLT), the standard deviation of sample means approaches sigma/sqrt(n), where sigma is the standard deviation of the population and n is the size of the samples.

I'd long since forgotten about the CLT and found myself running thought experiments. In my experiments, I used samples of size m, where m is the of the population. I think that's the source of my first mistake (since there's no notion of population size inherent in the CLT at all). In any case, that idea led me to think that the standard deviation of the population is the limit, as n -> m, of the standard deviation of the sample.

As a result, I was surprised to be reminded that the CLT tells us that the standard deviation of the sample mean actually gets smaller, and further from rather than closer to sigma, as n increases. It seemed reasonable that the standard deviation of the sample mean would better approximate the standard deviation of the population mean as the sample size increases.

I'm sure that statistics students must get caught in similar paradoxes from time to time. Is there a simple explanation for the flaw(s) in this apparently logical reasoning? I'm sure the source is an excess of calculus, which leads to seeing limits everywhere.


text:
Calculus: General Differentiation – #27836

Question: A bored student enters the number 0.5 in her calculator, and then repeatedly computes the square root of the number in the display. Taking a0 = 0.5 find a formula for the general term of the sequence {an} of the numbers that appear in the display, and find the limit of the sequence {an}


text:
## Physics: Principles with Applications (7th Edition)

As the string oscillates, it moves nearby air molecules, which vibrate at the same frequency. The speed of sound in air at the given temperature is 343 m/s. From the frequency of 330 Hz, we can find the wavelength of the sound wave in air. $\lambda = \frac{v}{f} = \frac{343 m/s}{330 Hz} = 1.04 m.$ The sound waves have a shorter wavelength in air than the waves have on the string.


text:
# Recent Blog Posts

I miss AIR's "Instancer" shaders in @pixarsrenderman. #vfx #cg

@mikeboers on . Visit on Twitter.

# Repairing Python Virtual Environments

## When upgrading Python breaks our environment, we can rebuild.

Python virtual environments are a fantastic method of insulating your projects from each other, allowing each project to have different versions of their requirements.

They work (at a very high level) by making a lightweight copy of the system Python, which symlinks back to the real thing whenever necessary. You can then install whatever you want in lib/pythonX.Y/site-packages (e.g. via pip), and you are good to go.

Depending on what provides your source Python, however, upgrading it can break things. For example, I use Homebrew, which (under the hood) stores everything it builds in versioned directories:

$readlink$(which python)
../Cellar/python/2.7.8_2/bin/python

Whenever there even a minor change to this Python, symlinks back to that versioned directory may not work anymore, which breaks my virtual environments:

$python dyld: Library not loaded: @executable_path/../.Python Referenced from: /Users/mikeboers/Documents/Flask-Images/venv/bin/python Reason: image not found Trace/BPT trap: 5  There is an easy fix: manually remove the links back to the old Python, and rebuild the virtual environment. Read more... (1 minute remaining to read.) Posted . Categories: . # The Evils of Gamifying Git ## Your green squares do you little good, and encourage bad behaviour. Nearly two years ago, GitHub introduced contribution calendars on everyone's profile, which roughly visualize how frequently one has been "contributing" for the past year. Through 2013, mine displayed some interesting patterns and features, many of which scream that they have a story: Having used GitHub as the primary code host for multiple full-time jobs, and a few growing open-source projects, I now believe that these calendars introduce, for me, two negative effects that vastly outweigh their benefits. Read more... (3 minutes remaining to read.) Posted . Categories: . Seems like LibreSSL is doing its job so far... https://www.openssl.org/news/secadv_20141015.txt #netsec @mikeboers on . Visit on Twitter. # Checking IMAP for a Pulse ## When you don't trust your mail client to tell you everything. I have been having trouble receiving email from Gmail via IMAP today. The Google Apps status dashboard does not reveal anything is wrong, so lets go spelunking! We use openssl to make the connection to transparently handle the TLS connection: $ openssl s_client -crlf -connect imap.gmail.com:993
* OK Gimap ready for requests from 172.218.163.116 zh1mb199258645pbc

We have a connection! The -crlf is critical for Gmail as the line endings are important to the "Gimap" server (and the protocol in general, but other servers I have tested are more accepting). If you weren't using encryption, you would nc imap.gmail.com 143 instead of using OpenSSL.

Lets poke the server a little.

Posted . Categories: .

# When Normals Aren't

## Classifying attributes as "normal" so Houdini will transform them.

I've been building a VFX pipeline for Shadows in the Grass that allows for artists to work in whatever applications they are the most skilled.

One little thing which has been a bit annoying is that somewhere between Blender and Houdini (of all pairings), geometry transferred via Collada does not have properly qualified normals. This results in some wacky behaviour when you start transforming your models:

Note that when spinning the above sphere, the normals are getting dragged along with the surface, but they remain pointing in the same direction in world space; they are not spinning with the surface. A very obvious effect of this is that the light appears to be spinning around the sphere, even though the light is stationary.

There is a simple enough fix, however.

Posted . Categories: .

CommonMark's olive branch FAQ changing from "Yes" to "We used to think so" was the saddest signal through the years. http://commonmark.org/

@mikeboers on . Visit on Twitter.

# Digital Ocean is Stingy on the Swap

## Sometimes a little swap space is all you need, but you have to put in a little effort for it.

I've been provisioning a pile of tiny VPSes (from Digital Ocean) for tiny web services for the last few weeks. While tuning one such site, I made an incorrect assumption that caused MySQL to fall over: Digital Ocean boxes default to having no swap space.

Assuming you want a little bit of leeway in your memory limits, it is easy to add some swap:

# Create a 1GB blank disk image.
dd if=/dev/zero of=/var/swap.img bs=1M count=1024

# Activate it as swap space.
mkswap /var/swap.img
swapon /var/swap.img

# Set it to activate at startup.
echo "/var/swap.img    none    swap    sw    0    0" >> /etc/fstab

Posted . Categories: .