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“… Here we discuss some literature on stellar bow shocks and show observations of some of them, enhanced by image processing techniques, in particular by the recently proposed AstroFracTool software.”
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“Guessing the identity of anonymous referees just seems like an activity with very little upside. If you guess wrong (which you are likely to do despite your convictions to the contrary), you may wrongly believe that someone is “against you.” You will never know whether you have guessed right and even if you have, how useful is that information really? Obviously, people will continue to do it anyway. All I can say is that you should leave open the possibility that you are wrong even if your identification of the referee seems obvious given your working assumptions about how referees write their reports.”
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“[Open Questions] Most of the encoding schemes considered in this paper use randomness and therefore are not given explicitly. As a result, the encoding and decoding schemes are not efficient. Finding explicit and efficient encoding and decoding schemes for the scenarios described in the paper remains open.”
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“We formulate a mathematical model for daily activities of a cow (eating, lying down, and standing) in terms of a piecewise affine dynamical system. We analyze the properties of this bovine dynamical system representing the single animal and develop an exact integrative form as a discrete-time mapping. We then couple multiple cow “oscillators” together to study synchrony and cooperation in cattle herds. We comment on the relevant biology and discuss extensions of our model. With this abstract approach, we not only investigate equations with interesting dynamics but also develop interesting biological predictions. In particular, our model illustrates that it is possible for cows to synchronize \emph{less} when the coupling is increased.”
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“This work deals with a classic problem: “Given a set of coins among which there is a counterfeit coin of a different weight, find this counterfeit coin using ordinary balance scales, with the minimum number of weighings possible, and indicate whether it weighs less or more than the rest”. The method proposed here not only calculates the minimum number of weighings necessary, but also indicates how to perform these weighings, it is easily mechanizeable and valid for any number of coins. Instructions are also given as to how to generalize the procedure to include cases where there is more than one counterfeit coin.”
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“The results of this study hold implications not only for the development of artificial photosynthesis systems as a renewable non-polluting source of electrical energy, but also for the future development of quantum-based technologies in areas such as computing – a quantum computer could perform certain operations thousands of times faster than any conventional computer.”
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“Might there be more to last week’s crash than a “fat fingered” trade, or someone mistakenly entering a “billion” instead of a “million?” An online stock trader has a video showing an unusual spike in trading volume, followed by a very quick sell-off, by funds at large investment firms BlackRock and Vanguard and some other funds 30 to 15 minutes before the big crash. Prescience? Watch the video, check the logs, and decide for yourself.”
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“…For example, when estimating a contour integral of an analytic function, we might transform the contour to a circle and use equally spaced points on the circle.
However, when simulating Canberra’s future climate and water supply, it would not be a good idea to assume that exceptionally dry years were equally spaced!…”
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“The beauty contest game concept originated with John Maynard Keynes [5] and has been studied in [3,7] and many other articles and experiments as a simple model of cognition and behavior. In a beauty contest game, all players guess a number within a given interval, with the goal of guessing p times the average of all other guesses, where p is a number in the interval (0, 1). For instance, for p = 1⁄2 and an interval of [0, 100], a player attempts to guess what will be half of the average of all guesses (including the player’s guess).…”
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“… The results imply that several families of constraint satisfaction problems exhibit a complexity dichotomy: the problems are in P or NP-hard, depending on the choice of the allowed relations. As concrete examples, we investigate fundamental algebraic constraint satisfaction problems. The first class consists of all first-order expansions of (Q;+). The second class is the affine variant of the first class. In both cases, we obtain full dichotomies by utilising our general methods.”
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“… The results obtained are in good agreement with numerical simulations and reproduce random networks behavior in the appropriate limits. Finally, it is demonstrated that our model predicts higher epidemic thresholds for clustered structures than for random topologies.”
Monthly Archives: May 2010
links for 2010-05-09
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“… The present work introduces new heuristic segmentation algorithms for the following optimization problem: Find a segmentation of an approximated matrix using only allowed fields and minimize the approximation error. Finally, the decomposition algorithms were implemented into an optimization programme in order to examine the assumptions of the algorithms for a clinical example. As a result, identical dose distributions with much fewer segments and a significantly smaller number of monitor units could be achieved using dosimetric constraints. Consequently, the dose delivery is more efficient and less time consuming.”
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“Unless we get better legislators, and a couple of hundred years of history says not to count on that, enhancing the automatic stabilizers may be our best bet going forward. There’s considerable empirical evidence showing that they work, including this new evidence that automatic stabilizers work “always and everywhere”…”
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“We report on experiments of many small motors — cell phone vibrators — glued to and interacting through a resonant plate. We find that individual motors interacting with the plate demonstrate hysteresis in their steady-state frequency due to interactions with plate resonances. For multiple motors running simultaneously, the degree of synchronization between motors increases when the motors’ frequencies are near a resonance of the plate, and the frequency at which the motors synchronize shows a history dependence.”
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“We describe von Neumann’s elegant idea for sampling from the exponential distribution, Forsythe’s generalization for sampling from a probability distribution whose density has the form exp(-G(x)), where G(x) is easy to compute (e.g. a polynomial), and my refinement of these ideas to give an efficient algorithm for generating pseudo-random numbers with a normal distribution. Later developments are also mentioned.”
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“It clearly looks as if the NASDAQ was trying to protect the interests of some institutions which lost large sums of money during Thursday’s collapse. These institutions likely did not have safeguards in place to deal with a lack of bidders. When their automated market orders hit the market in the absence of bidders, transactions were done at ridiculously low prices. But as NASDAQ has noted, there was no failure of their systems.”
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“So when France and Germany make sure that Greece can pay its debt, they are also rescuing, well, France and Germany. Also makes it clear exactly how contagion could work in practice.”
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“The aim of this chapter is twofold. In the first part we will provide a brief overview of the mathematical and statistical foundations of graphical models, along with their fundamental properties, estimation and basic inference procedures. In particular we will develop Markov networks (also known as Markov random fields) and Bayesian networks, which comprise most past and current literature on graphical models. In the second part we will review some applications of graphical models in systems biology.”
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“Project Euler is a series of challenging mathematical/computer programming problems that will require more than just mathematical insights to solve. Although mathematics will help you arrive at elegant and efficient methods, the use of a computer and programming skills will be required to solve most problems.
The motivation for starting Project Euler, and its continuation, is to provide a platform for the inquiring mind to delve into unfamiliar areas and learn new concepts in a fun and recreational context.”
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“It is a mantra of the deficit hawks that they are working to ensure their children and grandchildren will one day have the same opportunities that they have had. But right now, in real time, those same children and grandchildren are having those opportunities taken away. …”
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“Building a repository of proof-checked mathematical knowledge is without any doubt a lot of work, and besides the actual formalization process there also is the task of maintaining the repository. Thus it seems obvious to keep a repsoitory as small as possible, in particular each piece of mathematical knowledge should be formalized only once. In this paper, however, we claim that it might be reasonable or even necessary to duplicate knowledge in a mathematical repository. We analyze different situations and reasons for doing so and provide a number of examples supporting our thesis.”
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“In this work, decision tree learning algorithms and fuzzy inferencing systems are applied for galaxy morphology classification. In particular, the CART, the C4.5, the Random Forest and fuzzy logic algorithms are studied and reliable classifiers are developed to distinguish between spiral galaxies, elliptical galaxies or star/unknown galactic objects. Morphology information for the training and testing datasets is obtained from the Galaxy Zoo project while the corresponding photometric and spectra parameters are downloaded from the SDSS DR7 catalogue.”
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“The properties of polymer liquids on hard and soft substrates are investigated by molecular dynamics simulation of a coarse-grained bead-spring model and dynamic single-chain-in-mean-field (SCMF) simulations of a soft, coarse-grained polymer model. Hard, corrugated substrates are modelled by an FCC Lennard-Jones solid while polymer brushes are investigated as a prototypical example of a soft, deformable surface. From the molecular simulation we extract the coarse-grained parameters that characterise the equilibrium and flow properties of the liquid in contact with the substrate: the surface and interface tensions, and the parameters of the hydrodynamic boundary condition. The so-determined parameters enter a continuum description like the Stokes equation or the lubrication approximation.”
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“… Due to the tremendous growth of network-based services, intrusion detection has emerged as an important technique for network security. Recently data mining algorithms are applied on network-based traffic data and host-based program behaviors to detect intrusions or misuse patterns, but there exist some issues in current intrusion detection algorithms such as unbalanced detection rates, large numbers of false positives, and redundant attributes that will lead to the complexity of detection model and degradation of detection accuracy. The purpose of this study is to identify important input attributes for building an intrusion detection system (IDS) that is computationally efficient and effective.…”
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“We present an efficient solution to the following problem, of relevance in a numerical optimization scheme: calculation of integrals of the type \[\iint_{T \cap \{f\ge0\}} \phi_1\phi_2 \, dx\,dy\] for quadratic polynomials $f,\phi_1,\phi_2$ on a plane triangle $T$. The naive approach would involve consideration of the many possible shapes of $T\cap\{f\geq0\}$ (possibly after a convenient transformation) and parameterizing its border, in order to integrate the variables separately. Our solution involves partitioning the triangle into smaller triangles on which integration is much simpler.”
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“This paper presents an efficient human recognition system based on vein pattern from the palma dorsa. A new absorption based technique has been proposed to collect good quality images with the help of a low cost camera and light source. The system automatically detects the region of interest from the image and does the necessary preprocessing to extract features. A Euclidean Distance based matching technique has been used for making the decision. It has been tested on a data set of 1750 image samples collected from 341 individuals. The accuracy of the verification system is found to be 99.26% with false rejection rate (FRR) of 0.03%.”
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‘It turns out that people’s stated preferences have a weak relationship to who they actually like. Stated preferences, one study found, “seemed to vanish when it came time to choose a partner in physical space.”’
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“Every algorithm which can be executed on a computer can at least in principle be realized in hardware, i.e. by a discrete physical system. The problem is that up to now there is no programming language by which physical systems can constructively be described. Such tool, however, is essential for the compact description and automatic production of complex systems. This paper introduces a programming language, called Akton-Algebra, which provides the foundation for the complete description of discrete physical systems.…”
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“Performance tuning of Database Management Systems(DBMS) is both complex and challenging as it involves identifying and altering several key performance tuning parameters. The quality of tuning and the extent of performance enhancement achieved greatly depends on the skill and experience of the Database Administrator (DBA). As neural networks have the ability to adapt to dynamically changing inputs and also their ability to learn makes them ideal candidates for employing them for tuning purpose. In this paper, a novel tuning algorithm based on neural network estimated tuning parameters is presented. The key performance indicators are proactively monitored….The tuner alters these tuning parameters using the estimated values using a rate change computing algorithm. The preliminary results show that the proposed method is effective in improving the query response time for a variety of workload types.”
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“In this case, the computers kicked in their sell programs and there were no buy programs engaged — and so there was no market — and stocks wound up selling for a penny a share.
Now already known as the “flash crash,” this remarkable event will almost surely put a whole generation of young math whizzes out of business as Congress and the SEC crawl all over these operations and limit this kind of insane action.
I’m all for it because, and you can call me old fashioned, I don’t think the global equities markets should be an online gambling casino which is what they’ve become with the rise of the “quants” and their hyperactive supercomputers.”
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“… It avoids most of the shortcomings encountered with the now classic Black-Scholes-Merton framework. Several convincing computer simulations are presented. Some of them are dealing with abrupt changes, i.e., jumps.”
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“During the last decade, incremental sampling-based motion planning algorithms, such as the Rapidly-exploring Random Trees (RRTs) have been shown to work well in practice and to possess theoretical guarantees such as probabilistic completeness. However, no theoretical bounds on the quality of the solution obtained by these algorithms have been established so far. The first contribution of this paper is a negative result: it is proven that, under mild technical conditions, the cost of the best path in the RRT converges almost surely to a non-optimal value. Second, a new algorithm is considered, called the Rapidly-exploring Random Graph (RRG), and it is shown that the cost of the best path in the RRG converges to the optimum almost surely. Third, a tree version of RRG is introduced, called the RRT$^*$ algorithm, which preserves the asymptotic optimality of RRG while maintaining a tree structure like RRT.…”
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“Recent research on multiple kernel learning has lead to a number of approaches for combining kernels in regularized risk minimization. The proposed approaches include different formulations of objectives and varying regularization strategies. In this paper we present a unifying general optimization criterion for multiple kernel learning and show how existing formulations are subsumed as special cases. We also derive the criterion’s dual representation, which is suitable for general smooth optimization algorithms. Finally, we evaluate multiple kernel learning in this framework analytically using a Rademacher complexity bound on the generalization error and empirically in a set of experiments.”
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“If a fund/institution/High Frequency Trader generates 100mm shares or contracts a day/week/month, market observers will tell you that’s a great thing because it creates a liquidity premium. In other words, because there is always someone on the other side of a trade, it is easier to match buyers and sellers and that ease creates smaller spreads and often lower pricing. On the surface that’s a great thing.
It is a great thing until the market becomes completely dependent on that liquidity. If every model expects X volume, what happens when that volume falls?”
links for 2010-05-08
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“One of the most effective techniques of experimental mathematics is to compute mathematical entities such as integrals, series or limits to high precision, then attempt to recognize the resulting numerical values. Recently these techniques have been applied with great success to problems in math– ematical physics. Notable among these applications are the identification of some key multi-dimensional integrals that arise in Ising theory, quantum field theory and in magnetic spin theory.”
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“…A version of the method independent of the contrast of the image is considered and is found to be useful for finding the most unusual part (and the most similar part) of the image conditioned on given image. The results can be used to scan large image databases, as for example medical databases.…”
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“…A version of the method independent of the contrast of the image is considered and is found to be useful for finding the most unusual part (and the most similar part) of the image conditioned on given image. The results can be used to scan large image databases, as for example medical databases.”
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“ECG Feature Extraction plays a significant role in diagnosing most of the cardiac diseases. One cardiac cycle in an ECG signal consists of the P-QRS-T waves. This feature extraction scheme determines the amplitudes and intervals in the ECG signal for subsequent analysis. The amplitudes and intervals value of P-QRS-T segment determines the functioning of heart of every human. Recently, numerous research and techniques have been developed for analyzing the ECG signal. The proposed schemes were mostly based on Fuzzy Logic Methods, Artificial Neural Networks (ANN), Genetic Algorithm (GA), Support Vector Machines (SVM), and other Signal Analysis techniques. All these techniques and algorithms have their advantages and limitations.…
links for 2010-05-01
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“The whole thing is a house of cards built on a toxic foundation. It’s a filthy coal-coated hand reaching from the 19th Century and holding us back by the ankle. It’s a body floating in New Orleans in 2005, a single-mother working three jobs in 2007, a foreclosed house in 2009, an oil-coated pelican in 2010.
We can do better. We have to do better.”
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“A “trading facility,” as defined under the U.S. Commodity Exchange Act, prohibits phone transactions, which is how swaps have been traded for three decades…Lincoln’s bill does create a framework for swaps to be traded competitively based on price, service and technology options, said Christopher Giancarlo, chairman of the Wholesale Markets Brokers’ Association Americas.”
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“Is it possible that if we keep our focus on longer term sustainability, we can still go just as fast in the short term? I believe that it is possible, and that we already have credible evidence that it is possible.
Most of us believe that over the longer term, speed is maximized by operating at a high, but not stupidly high, level of quality. The question is, what is “longer term”?”
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“One thing is for sure, Apple and Google haven’t left the carriers an exit, and that makes them dangerous. Also, I highly doubt Steve Jobs is going to leave the future of Apple up to the idiots at the telecom giants who have utterly failed to innovate. It will be an interesting soap opera for sure, stay tuned.”
links for 2010-04-30
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“A simple test is proposed for examining the correctness of a given completely specified response function against unspecified general alternatives in the context of univariate regression. The usual diagnostic tools based on residuals plots are useful but heuristic. We introduce a formal statistical test supplementing the graphical analysis. Technically, the test statistic is the maximum length of the sequences of ordered (with respect to the covariate) observations that are consecutively overestimated or underestimated by the candidate regression function. Note that the testing procedure can cope with heteroscedastic errors and no replicates. Recursive formulae allowing to calculate the exact distribution of the test statistic under the null hypothesis and under a class of alternative hypotheses are given.”