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# Posts

### November 27, 2014

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In my algorithms class today, I covered minimum spanning trees, one property of which is that they (or rather maximum spanning trees) can be used to find the bottleneck in communications bandwidth between any two vertices in a network. Suppose the network edges are labeled by bandwidth, and we compute the maximum spanning tree using these labels. Then between any two vertices the path in this tree has the maximum bandwidth possible, among all paths in the network that connect the same two […]
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Yves Wiaux, who soon will have many more firends, just sent me the following  Hi Igor Jason McEwen and myself have just been awarded £2M from UK research councils for research on compressive imaging in astronomy and medicine, along with Mike Davies and other colleagues.Press releases about the funded initiative may be found on Edinburgh Heriot-Watt University website at http://www.hw.ac.uk/news-events/news/pioneering-work-helps-join-dots-across-known-19548.htm ,and on […]
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If you watch this and you could swear you remember Johnny and Mr. Carlson discussing Pink Floyd, you're not imagining things. Hulu uses the DVD edit which cuts out almost all of the copyrighted music. . As for my favorite line, it comes from the Buffy episode "Pangs" and it requires a bit of a set up (which is a pain because it makes it next to impossible to work into a conversation).Buffy's luckless friend Xander had accidentally violated a native American grave yard and, in addition to […]
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Alleged intellectual Christina Hoff Summers (I know, I know, it’s bad form to give away the punchline of a joke so early) recently had this to say: Dear liberals, When you side with today’s 3rd wave intersectional feminism, you are siding with the intellectual equivalent of creationism. As a liberal feminist whose day job actually […]

### November 26, 2014

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These last few weeks the news has been full of lots of seemingly conflicting messages about renewables, so I figured it was worth talking about things a little bit in a post. First, the good news.  The old conventional wisdom that solar can never match prices with conventional generation is just plain false at this […]
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Introduction I just read an interesting article about an arctic environmental problem being presented by a Soviet-era nuclear submarine that had been scuttled back in 1982 (Figure 1). Apparently, scientists are now concerned that the submarine’s reactor could leak dangerous … Continue reading →
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In a previous post I showed how to write and solve a unit loss function G(k). Here I show how to use it. Here I solve some (s,Q) inventory models. These models have a variable Q: order quantity. It is sometimes argued to use the EOQ order quantity for this. In the model I try to see how much difference it makes when we use this EOQ or just solve for Q in the (s,Q) models directly. The results are: ----    155 PARAMETER results  […]
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Whether introduced as children in elementary school, as adults in the workplace, or somewhere in between, the concept of magic squares has fascinated people for centuries; The Wikipedia article has discoveries of magic squares dating back to 650 B.C. in China. Magic Squares of size n (for n >= 3) are n by n grids […]
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Jennifer Wilson wrote a post about productive struggle that you can find here. I did my usual trick of sending myself the link. I have a filter on my school email that automatically labels emails from me and files them away under "Twitter" so that I never actually see these emails. Thankfully I keep vague recollections of what I have tagged and earlier this week I knew to search my "Twitter" label for something interesting relating to sine law.I stole this from Jennifer's post, having first […]
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Noted psychology researchers and methods skeptics Leif Nelson and Uri Simonsohn write: A recent Psych Science (.pdf) paper found that sports teams can perform worse when they have too much talent. For example, in Study 3 they found that NBA teams with a higher percentage of talented players win more games, but that teams with […] The post Leif and Uri need to hang out with a better class of statisticians appeared first on Statistical Modeling, Causal Inference, and Social Science.
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Given some recent discussions, I perhaps ought to go back and clarify my position on Google's driverless cars. The Google part is important. Lots of companies, particularly big auto makers like GM and Nissan, are seriously pursuing this research. However, when you read a news account about autonomous vehicles, most of the time it's a story about Google which is troublesome for at least two reasons: first because there are some big concerns that are particularly applicable to Google's approach; […]
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This is the second in my series of posts pointing out resources on my site. This week’s topic is Emacs. Emacs kill (cut) commands Emacs point (cursor) movement Getting started with Emacs on Windows Notes on Unicode in Emacs See also the Twitter account UnixToolTip and blog posts tagged Emacs. Last week: Miscellaneous math notes […]
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In a 1964 paper titled “On the Einstein Podolsky Rosen paradox” John Bell showed the incompatibility of a certain class of hidden variable theories and Quantum Mechanics using Bell’s famous inequalities. Alain Aspect in turn used Bell’s inequalities to put … Continue reading →
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In the Matrix Factorization Jungle Page, there is a section for subspace clsutering that reads like:Subspace Clustering: A = AX  with unknown X, solve for sparse/other conditions on X  In recent times, when looking for subspace clustering algorithms, the conditions on X were focused on X having a zero main diagonal and sparse entries otherwise but in the following paper, the authors seek a low rank version of X instead and call that matrix/operator a linear […]
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A few years ago, I developed this checkers variant based on non-transitive relationships to help my students get some experience working with the concept. I'll talk more about the game and its development later, but in the meantime, here's a link to the webstore at Amazon.For another example of non-transitive play, check this out. If nothing else, it will give you something to talk about if you ever meet Warren Buffet.
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This is an excellent time to go back and reread "Against Law, For Order" by Mike Konczal. Since this essay appeared in April of 2012, we've seen the acquittal of George Zimmerman, the grand jury ruling on Darren Wilson and any number of additional incidents that support Konczal's troubling but convincing argument.
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“[I]t hardly ever happened that Gerard Debreu posed a question—and if he did, not without already knowing the answer…. Debreu … [wanted to] earn recognition without exposing himself as a person.” - Til Dueppe, Gerard Debreu’s Secrecy: His Life in Order and Silence

### November 25, 2014

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I have used recently the tool sloccount on the source code of the latest stable version of Open Journal Systems (OJS 2.4.5). The result is given below. It suggests that the development from scratch of such a software is a non trivial expensive task: 18M USD. SLOC    Directory    SLOC-by-Language (Sorted) 193863  lib             php=115818,xml=77854,sh=160,perl=31 120061  plugins         […]
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References: Griffiths, David J. (2007), Introduction to Electrodynamics, 3rd Edition; Pearson Education – Problems 10.16. We can now work out the Liénard-Wiechert potentials for a point charge moving on a hyperbolic trajectory. We’re trying to find The motion is in one dimension, given by It’s worth noting here that for all times, and the velocity […]
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Richard Baraniuk, the founder and director of OpenStax College and Rice’s Victor E. Cameron Professor of Electrical and Computer Engineering, has been named recipient of the 2015 IEEE James H. Mulligan Jr. Education Medal. The medal, presented annually since 1956 … Continue reading →
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By Kimberly Kaufeld and Daniel Taylor-Rodriguez, both postdoctoral fellows at SAMSI this year. A few weeks ago, Daniel and I had the pleasure of presenting and attending the Field of Dreams conference in Phoenix, AZ. The conference is supported by … Continue reading →
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Having a convenient data structure like ILArray<T> brings many advantages when handling numerical data in your algorithms. On the convenience side, there are flexible options for creating subarrays, altering existing data (i.e. lengthening or shortening individual dimensions on the run), keeping dimensionality information together with the data, and last but not least: being able to […]
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References: Griffiths, David J. (2007), Introduction to Electrodynamics, 3rd Edition; Pearson Education – Problems 10.15. When we work out Liénard-Wiechert potentials for a moving point charge, we’ve been implicitly assuming that we can receive a signal from the charge from only one retarded time. That is, if the charge is moving on some trajectory , […]
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The NIPS 2014 proceedings are out, what paper did you fancy ?  Advances in Neural Information Processing Systems 27 (NIPS 2014)The papers below appear in Advances in Neural Information Processing Systems 27 edited by Z. Ghahramani and M. Welling and C. Cortes and N.D. Lawrence and K.Q. Weinberger.They are proceedings from the conference Neural Information Processing Systems 2014. Kernel Mean Estimation via Spectral Filtering Krikamol Muandet, Bharath Sriperumbudur, Bernhard […]
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This is the second of two articles about Bayesian analysis applied to World Cup soccer.  The previous article is here.Earlier this semester I posed this problem to my Bayesian statistics class at Olin College:In the final match of the 2014 FIFA World Cup, Germany defeated Argentina 1-0. How much evidence does this victory provide that Germany had the better team? What is the probability that Germany would win a rematch?Before you can answer a question like this, you have to […]
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References: Griffiths, David J. (2007), Introduction to Electrodynamics, 3rd Edition; Pearson Education – Problems 10.14. Griffiths shows in his example 10.3 that the Liénard-Wiechert potentials for a point charge moving at constant velocity that passes through the origin at time are These potentials can be expressed in a simpler form by defining the vector We […]
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As you might recall, the Elizabeth K. Dollard Professor says that to explain a concept to an unbeliever, explain it conditionally. For example, if you want to talk evolution with a religious fundamentalist, don’t try to convince him or her that evolution is true; instead preface each explanation with, “According to the theory of evolution […] The post I (almost and inadvertently) followed Dan Kahan’s principles in my class today, and that was a good thing (would’ve even […]
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What is "specifications grading", and could it precipitate a revolutionary change in how faculty assess student work in higher education? In this 4+1 interview, we chat with Linda Nilson, director of the Office of Teaching Effectiveness and Innovation at Clemson University, about her latest book _Specifications Grading: Restoring Rigor, Motivating Students, and Saving Faculty Time_ and the idea of specs grading.
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There's another flight going on between Viacom and a cable provider. Suddenlink, a major provider for much of the middle of the country, has recently dropped all of by a calms basic cable channels. This includes big names such as MTV, Nickelodeon, TVland, and Comedy Central. In Their place Suddenlink has scheduled some decidedly second-tier alternatives. Fans of Jon Stewart now have to make do with Jon Lovitz.The story hasn't gotten a lot of attention (as often happens when you're on Central […]
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I recently returned from Haiti, where I was a tourist traveling around the country for 6 days with my friends Jamie and Becky. As I spent time there, I felt increasingly aware of the difficult if not miserable spot that the country as a whole finds itself in, even though there are of course wonderful […]