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Posts

April 25, 2015

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2:36 AM | spring-of-mathematics:discretetopology: A cabled knot K is...
spring-of-mathematics:discretetopology: A cabled knot K is a knot obtained by taking a torus knot T(p,q) inside a solid torus, then tying that solid torus into the shape of another knot P, called the companion knot. This gives a natural splitting of the cabled knot’s complement M_K into two pieces: the complement of the companion knot M_P, and the interior of that solid torus without the knot C(p,q), called the cable space.An important notion in knot theory is the existence of […]
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2:06 AM | This is where I got my numbers on radiation shielding for Mars One
CEO Bas Lansdorp writing for Space.com:The Mars One habitat will be covered by a necessary layer of soil that provides shielding even against galactic cosmic rays. Sixteen feet (5 meters) of Martian soil provides the same protection as the Earth's atmosphere — equivalent to 1,000 grams per square cm(227.6 ounces per square inch) of shielding. The Mars One habitat can support a soil layer 36 feet (11 m) thick. If the settlers spend, on average, two hours per day outside the habitat, their […]
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12:39 AM | did-you-kno: No One Can Solve This Impossible Math Problem For 14-Year-OldsThis might melt your...
did-you-kno: No One Can Solve This Impossible Math Problem For 14-Year-OldsThis might melt your brain. If you struggled with this, you’re like me. If not, please explain (like I’m 5).Continue Reading. I love this! Took me longer than it should have, but I finally got it :D
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12:16 AM | Code for Teachers: What do you want to learn to build?
A conversation with Dan Anderson(@dandersod) this morning has pushed me to revisit a coding for teachers concept that I've nudged forward before, but haven't made happen to my liking yet. There's an amazing variety of coding materials and tutorials out … Continue reading →
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12:14 AM | Three versions of the same problem
My younger son and I have been studying angles for the last week. I decided to run through a few clock problems for a review. The secret about this exercise is that all three problems are pretty much the same problem in a slightly different form. Question 1: How many degrees does the hour hand…
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12:06 AM | Streaming H
Items  I_i s (+ve integers,  I_i \in [1,U]) arrive one after another, and for any n, after having seen n items, you have to return an approximation to H_n which is the H-index of the first n items. I_1,...,I_n  (The H-index of a set of number is largest k such that there are at least k items each >= k). A student in Rutgers posed this problem.This problem has a simple worstcase solution: sing log_{1+\eps} U space, get  (1+\eps) one-sided error approximation by maintaining […]
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12:00 AM | Peirce’s 1880 “Algebra Of Logic” Chapter 3 • Comment 7.4
Dyadic relations enjoy yet another form of graph-theoretic representation as labeled bipartite graphs or labeled bigraphs.  I’ll just call them bigraphs here, letting the labels be understood in this logical context. The figure below shows the bigraphs of the 16 … Continue reading →

April 24, 2015

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11:41 PM | MIQP bounds and performance
The performance of MIQP models is not always predictable. Here are the results for a small model we used to reproduce a performance issue with Cplex: Looks like Cplex is attempting a smart reformulation that fails terribly. An indication is the log line: Reduced MIQP objective Q matrix has 1 nonzeros. Also the negative best bound (compare this to the relaxed objective) is an indication. A small reformulation that simplifies the objective, leads to much better performance: […]
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11:41 PM | Network Models in Epidemiology - Considering Discrete and Continuous Dynamics
In the Fall, I developed a computational model for epidemiology. I modeled infection and recovery using a discrete dynamical system and considered a lattice network for the population. Since then, I have also considered infection for random network populations, and extracted some (hopefully) meaningful information. In December, I wrote that I would be producing a paper soon. Soon seemed to stretch on and on as I did not realize how big of a project this would turn into.Instead of attempting to […]
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11:15 PM | Ready to Learn
Cross posted from One Good Thing. https://onegoodthingteach.wordpress.com/2015/04/24/ready-to-learn/Since we had so many snow days, we lost two days of April break, today being one of them. When class started this morning my co-teacher and I had two students. It’s a contained class of seven, but still, two kids! Despite the lack of classmates, the pair dutifully estimated and shared their reasoning. My co-teacher volunteered to be the grapher in our model “describe the graph to someone […]
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11:00 PM | On This Day in Math - April 25
Pure mathematics is the world's best game. It is more absorbing than chess,more of a gamble than poker,and lasts longer than Monopoly. It's free. It can be played anywhere - Archimedes did it in a bathtub.~Richard J. Trudeau, Dots and LinesThe 115th day of the year; 115 is the 26th "Lucky" number. Lucky numbers are produced by a sieve method created by Stan Ulam around 1955. The term was introduced in 1955 in a paper by Gardiner, Lazarus, Metropolis and Ulam. They suggest also calling its […]
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10:15 PM | ontological argument
Filed under: Books, Kids, pictures Tagged: atheism, ontological argument, xkcd
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10:08 PM | Session Thoughts: Shadow Con, part 1
For those on the twitters and reading blogs, there was a nice build up in advertising to this event. I really didn’t know what to expect from Shadow Con until the day before when I got to ask some folks that were speaking at it during the math games night. The ‘TED-esque, but with a […]
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9:13 PM | Clog: “No, I just don’t get any of this, so I’ll just wait”
Seems like one of the side effects of my new emphasis on large scale problems is getting kids caught up when they come in late, weren’t paying attention, or otherwise find themselves lost.  I think tradition trains students to shut down when they are lost, as if the key to getting un-lost will be someone […]
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9:01 PM | Rosmarinus officinalis ‘Gallipoli’ (photo credit)Because the Great War was a mad, brutal, awful...
Rosmarinus officinalis ‘Gallipoli’ (photo credit)Because the Great War was a mad, brutal, awful struggle, distinguished more often than not by military and political incompetence; because the waste of human life was so terrible that some said victory was scarcely discernible from defeat; and because the war which was supposed to end all wars in fact sowed the seeds of a second, even more terrible, war –  we might think this Unknown Soldier died in vain.But, in honouring our war […]
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9:00 PM | Math Stars - for summer math and more
I have used Math Stars problem solving sets with my girls for several years, and they have always greatly enjoyed them. Math Stars include various puzzles and challenging math problems. They  come as PDF files (free and ready to download & use) in sets for grades 1-8. They're great to use for summer math  or for some fun problem solving at any time.I tend to use the problems from one grade level below the grade the student is in. One reason I like these so much is the variety of […]
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8:54 PM | SOTTO LA LENTE LOGICA DI GABRIELE LOLLI
Da sinistra: Gabriele Lolli e Yaroslav SergeyevForse non tutti conoscono Gabriele Lolli. Nato nel 1942 in un paesino in provincia di Alessandria, ha fatto una brillante carriera. Si è laureato in Matematica all'Università di Torino e si è specializzato in Logica Matematica presso la Yale University. Già Ordinario di Logica Matematica presso l'Università di Torino, successivamente diventa professore ordinario di Filosofia della Matematica in un'altra importante istituzione: la Scuola […]
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8:39 PM | EC & Sigmetrics accepted papers are out
I’m a little late in posting about this, but at this point the schedule for Sigmetrics is up, as is the list of accepted papers at EC.  So, it’s a good point to take a look at each to compare. First of all, congrats to all the folks in RSRG with paper(s)…we managed to get […]
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8:31 PM | Parrhesia (Part 5): Foucault, Heidegger and The Politics of Philosophical Contexts
I’d like to look here a little more at Foucault’s claim that Heideggerian ontology is internalist (see my discussion here), because I think it makes an important point about the political nature of context-setting. Although questions of context are of course very difficult, one can quite plausibly propose that Being...
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8:28 PM | When is Cheryl’s Birthday?
Birthdays are a fun tradition that you get to celebrate with your friends and family once a year…that is, if you tell them when your birthday is.  In a logic puzzle that has been making the rounds on the Internet, … Continue reading →
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8:14 PM | Impossible gear wheel
Impossible gear wheel   by Phil Taylor   http://im-possible.info/english/art/rendering/phil-taylor.html   Author - http://effectrode.deviantart.com/
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8:12 PM | Things Have Changed
I’ve been busy with other things, but after taking a look today at various new things related to quantum gravity, I was struck by how much things have changed sociologically in that subject over the last few years. Back in … Continue reading →
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7:52 PM | Under New Management
02:04 As I will be taking over Doug’s blog, I thought I’d tell you a bit about myself and what I hope to cover in future posts. Feel free to make requests for topics in the comments area at any time.   ... read more >>
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7:44 PM | Unizor - Geometry3D - Elements - Angles and Planes
The concept of an angle in general is related to a process of rotation. Thus, if two rays (half-lines) on a plane have a common beginning points, the angle between them can be viewed as an angle needed to rotate one ray around the common point (strictly speaking, counterclockwise is a positive direction and clockwise is negative) to coincide with another.Provided a unit of measurement of such a rotation (for instance, rotation around a full circle can be set as equal to 360 degree or 2π […]
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7:00 PM | CFP: Fifth Workshop on Social Computing and User-Generated Content
SCUGC 2015: The 5th Workshop on Social Computing and User-Generated Content https://sites.google.com/site/scugc2015/ June 16, 2015, Portland, Oregon. in conjunction with ACM Conference on Economics and Computation (ACM-EC 2015). SUBMISSIONS DUE: April 25, 2015 midnight EDT. The  workshop will bring together researchers and practitioners from a variety of relevant fields, including economics, computer science, and social […]
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6:34 PM | The Role of Reading in Math Class
My more recent endeavors have moved me away from exclusively math and allowed me to enter into the world of literacy, particularly elementary literacy. (Math teachers out there, if you haven’t gotten a chance to sit and participate in a conversation among elementary folks talking about kids learning to read, the essential components of curricula […]
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6:32 PM | Using Desmos on iPads… for the STAAR Test… Really!
Dear Desmos, (with the help of Casper Focus)… You made a liar out of me. Two short years later, @Desmos “made a liar out of me” Watch 24:40 @ HCMS on @livestream: http://t.co/94HuPTkf2A https://t.co/Tct5xhJE1H — Cathy Yenca  (@mathycathy) April … Continue reading →
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6:27 PM | Pi
via PrettyMaths
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6:14 PM | Train of Thought: C&Coincidence?
Spotting a C&C soda delivery truck--curious coincidence or semi-common occurrence?
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5:48 PM | Wandering Seminar (Wroclaw April 24, 2015)
I have given the first two lectures: lecture 1 (categories of dynamical systems, basics of entropy, exercises) lecture 2 (Lyapunov exponents, Oseledets theorem, applications)
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