WorldWideScience

Sample records for random search theory

  1. Theory of Randomized Search Heuristics in Combinatorial Optimization

    DEFF Research Database (Denmark)

    The rigorous mathematical analysis of randomized search heuristics(RSHs) with respect to their expected runtime is a growing research area where many results have been obtained in recent years. This class of heuristics includes well-known approaches such as Randomized Local Search (RLS), the Metr......The rigorous mathematical analysis of randomized search heuristics(RSHs) with respect to their expected runtime is a growing research area where many results have been obtained in recent years. This class of heuristics includes well-known approaches such as Randomized Local Search (RLS...... analysis of randomized algorithms to RSHs. Mostly, the expected runtime of RSHs on selected problems is analzyed. Thereby, we understand why and when RSHs are efficient optimizers and, conversely, when they cannot be efficient. The tutorial will give an overview on the analysis of RSHs for solving...

  2. Random searching

    International Nuclear Information System (INIS)

    Shlesinger, Michael F

    2009-01-01

    There are a wide variety of searching problems from molecules seeking receptor sites to predators seeking prey. The optimal search strategy can depend on constraints on time, energy, supplies or other variables. We discuss a number of cases and especially remark on the usefulness of Levy walk search patterns when the targets of the search are scarce.

  3. Optimal search behavior and classic foraging theory

    International Nuclear Information System (INIS)

    Bartumeus, F; Catalan, J

    2009-01-01

    Random walk methods and diffusion theory pervaded ecological sciences as methods to analyze and describe animal movement. Consequently, statistical physics was mostly seen as a toolbox rather than as a conceptual framework that could contribute to theory on evolutionary biology and ecology. However, the existence of mechanistic relationships and feedbacks between behavioral processes and statistical patterns of movement suggests that, beyond movement quantification, statistical physics may prove to be an adequate framework to understand animal behavior across scales from an ecological and evolutionary perspective. Recently developed random search theory has served to critically re-evaluate classic ecological questions on animal foraging. For instance, during the last few years, there has been a growing debate on whether search behavior can include traits that improve success by optimizing random (stochastic) searches. Here, we stress the need to bring together the general encounter problem within foraging theory, as a mean for making progress in the biological understanding of random searching. By sketching the assumptions of optimal foraging theory (OFT) and by summarizing recent results on random search strategies, we pinpoint ways to extend classic OFT, and integrate the study of search strategies and its main results into the more general theory of optimal foraging.

  4. Levy flights and random searches

    Energy Technology Data Exchange (ETDEWEB)

    Raposo, E P [Laboratorio de Fisica Teorica e Computacional, Departamento de Fisica, Universidade Federal de Pernambuco, Recife-PE, 50670-901 (Brazil); Buldyrev, S V [Department of Physics, Yeshiva University, New York, 10033 (United States); Da Luz, M G E [Departamento de Fisica, Universidade Federal do Parana, Curitiba-PR, 81531-990 (Brazil); Viswanathan, G M [Instituto de Fisica, Universidade Federal de Alagoas, Maceio-AL, 57072-970 (Brazil); Stanley, H E [Center for Polymer Studies and Department of Physics, Boston University, Boston, MA 02215 (United States)

    2009-10-30

    In this work we discuss some recent contributions to the random search problem. Our analysis includes superdiffusive Levy processes and correlated random walks in several regimes of target site density, mobility and revisitability. We present results in the context of mean-field-like and closed-form average calculations, as well as numerical simulations. We then consider random searches performed in regular lattices and lattices with defects, and we discuss a necessary criterion for distinguishing true superdiffusion from correlated random walk processes. We invoke energy considerations in relation to critical survival states on the edge of extinction, and we analyze the emergence of Levy behavior in deterministic search walks. Finally, we comment on the random search problem in the context of biological foraging.

  5. Theory of random sets

    CERN Document Server

    Molchanov, Ilya

    2017-01-01

    This monograph, now in a thoroughly revised second edition, offers the latest research on random sets. It has been extended to include substantial developments achieved since 2005, some of them motivated by applications of random sets to econometrics and finance. The present volume builds on the foundations laid by Matheron and others, including the vast advances in stochastic geometry, probability theory, set-valued analysis, and statistical inference. It shows the various interdisciplinary relationships of random set theory within other parts of mathematics, and at the same time fixes terminology and notation that often vary in the literature, establishing it as a natural part of modern probability theory and providing a platform for future development. It is completely self-contained, systematic and exhaustive, with the full proofs that are necessary to gain insight. Aimed at research level, Theory of Random Sets will be an invaluable reference for probabilists; mathematicians working in convex and integ...

  6. Cover times of random searches

    Science.gov (United States)

    Chupeau, Marie; Bénichou, Olivier; Voituriez, Raphaël

    2015-10-01

    How long must one undertake a random search to visit all sites of a given domain? This time, known as the cover time, is a key observable to quantify the efficiency of exhaustive searches, which require a complete exploration of an area and not only the discovery of a single target. Examples range from immune-system cells chasing pathogens to animals harvesting resources, from robotic exploration for cleaning or demining to the task of improving search algorithms. Despite its broad relevance, the cover time has remained elusive and so far explicit results have been scarce and mostly limited to regular random walks. Here we determine the full distribution of the cover time for a broad range of random search processes, including Lévy strategies, intermittent strategies, persistent random walks and random walks on complex networks, and reveal its universal features. We show that for all these examples the mean cover time can be minimized, and that the corresponding optimal strategies also minimize the mean search time for a single target, unambiguously pointing towards their robustness.

  7. Random matrix theory

    CERN Document Server

    Deift, Percy

    2009-01-01

    This book features a unified derivation of the mathematical theory of the three classical types of invariant random matrix ensembles-orthogonal, unitary, and symplectic. The authors follow the approach of Tracy and Widom, but the exposition here contains a substantial amount of additional material, in particular, facts from functional analysis and the theory of Pfaffians. The main result in the book is a proof of universality for orthogonal and symplectic ensembles corresponding to generalized Gaussian type weights following the authors' prior work. New, quantitative error estimates are derive

  8. Random vibrations theory and practice

    CERN Document Server

    Wirsching, Paul H; Ortiz, Keith

    1995-01-01

    Random Vibrations: Theory and Practice covers the theory and analysis of mechanical and structural systems undergoing random oscillations due to any number of phenomena— from engine noise, turbulent flow, and acoustic noise to wind, ocean waves, earthquakes, and rough pavement. For systems operating in such environments, a random vibration analysis is essential to the safety and reliability of the system. By far the most comprehensive text available on random vibrations, Random Vibrations: Theory and Practice is designed for readers who are new to the subject as well as those who are familiar with the fundamentals and wish to study a particular topic or use the text as an authoritative reference. It is divided into three major sections: fundamental background, random vibration development and applications to design, and random signal analysis. Introductory chapters cover topics in probability, statistics, and random processes that prepare the reader for the development of the theory of random vibrations a...

  9. Survey of random surface theory

    International Nuclear Information System (INIS)

    Froehlich, J.

    1985-01-01

    The author describes some recent results in random surface theory. Attention is focused on those developments which are relevant for a quantum theory of strings. Some general remarks on the status of mathematical quantum field theory are included at the beginning. (orig.)

  10. PREFACE: The random search problem: trends and perspectives The random search problem: trends and perspectives

    Science.gov (United States)

    da Luz, Marcos G. E.; Grosberg, Alexander; Raposo, Ernesto P.; Viswanathan, Gandhi M.

    2009-10-01

    reactive component, e.g., eating, mating, etc. From the comments above, it is clear that the subject can be treated from the perspective of different fields and subfields of physics and mathematics: statistical mechanics, stochastic processes, Lévy walks and flights, complex systems, fractal geometry, and non-linear phenomena. Some important questions in random searches, especially in the case of discrete landscapes, are also associated with graph theory, random lattices, and complex networks. The aim of this special issue is to bring together, in a single publication, all or most of the relevant theoretical concepts-ideas together with discussions of recent findings that are important for understanding the main elements of random searches. In addition, we will address the types of problems which are characteristic of random searching. Thus, we sincerely hope that this collection of works will provide a good overview for anyone interested in this field. Finally, we should thank the editors and staff of Journal of Physics A: Mathematical and Theoretical for opining that random searches are an interesting topic of research deserving a topical publication. Furthermore, we are very grateful to Rebecca Gillan for helping us at all stages of the preparation and organization of this special issue. Finally, we would like to thank the contributing authors who share with the guest editors the enthusiasm and interest for this fascinating field of research.

  11. Search along persistent random walks

    International Nuclear Information System (INIS)

    Friedrich, Benjamin M

    2008-01-01

    Optimal search strategies and their implementations in biological systems are a subject of active research. Here we study a search problem which is motivated by the hunt of sperm cells for the egg. We ask for the probability for an active swimmer to find a target under the condition that the swimmer starts at a certain distance from the target. We find that success probability is maximal for a certain level of fluctuations characterized by the persistence length of the swimming path of the swimmer. We derive a scaling law for the optimal persistence length as a function of the initial target distance and search time by mapping the search on a polymer physics problem

  12. Staggered chiral random matrix theory

    International Nuclear Information System (INIS)

    Osborn, James C.

    2011-01-01

    We present a random matrix theory for the staggered lattice QCD Dirac operator. The staggered random matrix theory is equivalent to the zero-momentum limit of the staggered chiral Lagrangian and includes all taste breaking terms at their leading order. This is an extension of previous work which only included some of the taste breaking terms. We will also present some results for the taste breaking contributions to the partition function and the Dirac eigenvalues.

  13. Heuristic Search Theory and Applications

    CERN Document Server

    Edelkamp, Stefan

    2011-01-01

    Search has been vital to artificial intelligence from the very beginning as a core technique in problem solving. The authors present a thorough overview of heuristic search with a balance of discussion between theoretical analysis and efficient implementation and application to real-world problems. Current developments in search such as pattern databases and search with efficient use of external memory and parallel processing units on main boards and graphics cards are detailed. Heuristic search as a problem solving tool is demonstrated in applications for puzzle solving, game playing, constra

  14. Random measures, theory and applications

    CERN Document Server

    Kallenberg, Olav

    2017-01-01

    Offering the first comprehensive treatment of the theory of random measures, this book has a very broad scope, ranging from basic properties of Poisson and related processes to the modern theories of convergence, stationarity, Palm measures, conditioning, and compensation. The three large final chapters focus on applications within the areas of stochastic geometry, excursion theory, and branching processes. Although this theory plays a fundamental role in most areas of modern probability, much of it, including the most basic material, has previously been available only in scores of journal articles. The book is primarily directed towards researchers and advanced graduate students in stochastic processes and related areas.

  15. Efficient search by optimized intermittent random walks

    International Nuclear Information System (INIS)

    Oshanin, Gleb; Lindenberg, Katja; Wio, Horacio S; Burlatsky, Sergei

    2009-01-01

    We study the kinetics for the search of an immobile target by randomly moving searchers that detect it only upon encounter. The searchers perform intermittent random walks on a one-dimensional lattice. Each searcher can step on a nearest neighbor site with probability α or go off lattice with probability 1 - α to move in a random direction until it lands back on the lattice at a fixed distance L away from the departure point. Considering α and L as optimization parameters, we seek to enhance the chances of successful detection by minimizing the probability P N that the target remains undetected up to the maximal search time N. We show that even in this simple model, a number of very efficient search strategies can lead to a decrease of P N by orders of magnitude upon appropriate choices of α and L. We demonstrate that, in general, such optimal intermittent strategies are much more efficient than Brownian searches and are as efficient as search algorithms based on random walks with heavy-tailed Cauchy jump-length distributions. In addition, such intermittent strategies appear to be more advantageous than Levy-based ones in that they lead to more thorough exploration of visited regions in space and thus lend themselves to parallelization of the search processes.

  16. Quantum random-walk search algorithm

    International Nuclear Information System (INIS)

    Shenvi, Neil; Whaley, K. Birgitta; Kempe, Julia

    2003-01-01

    Quantum random walks on graphs have been shown to display many interesting properties, including exponentially fast hitting times when compared with their classical counterparts. However, it is still unclear how to use these novel properties to gain an algorithmic speedup over classical algorithms. In this paper, we present a quantum search algorithm based on the quantum random-walk architecture that provides such a speedup. It will be shown that this algorithm performs an oracle search on a database of N items with O(√(N)) calls to the oracle, yielding a speedup similar to other quantum search algorithms. It appears that the quantum random-walk formulation has considerable flexibility, presenting interesting opportunities for development of other, possibly novel quantum algorithms

  17. Analytical Methods in Search Theory

    Science.gov (United States)

    1979-11-01

    X, t ) ,I pick g(x,t;E), *(x,tjc) and find the b necessary to satisfy the search equation. SOLUTION: This is an audience participation problem. It...Cnstotiaticon G11trant,’ ’I pp 2110 Path lestegsls,’ to pp., Jun IBM Iltetteol Pepsi pp., Ott 1313 (Tt o besubmitoet lot pubtinatteon l t Messino, Daidit

  18. Random search for a dark resonance

    DEFF Research Database (Denmark)

    Kiilerich, Alexander Holm; Mølmer, Klaus

    A pair of resonant laser fields can drive a three-level system into a dark state where it ceases to absorb and emit radiation due to destructive interference. We propose a scheme to search for this resonance by randomly changing the frequency of one of the fields each time a fluorescence photon...

  19. Random Matrix Theory and Econophysics

    Science.gov (United States)

    Rosenow, Bernd

    2000-03-01

    Random Matrix Theory (RMT) [1] is used in many branches of physics as a ``zero information hypothesis''. It describes generic behavior of different classes of systems, while deviations from its universal predictions allow to identify system specific properties. We use methods of RMT to analyze the cross-correlation matrix C of stock price changes [2] of the largest 1000 US companies. In addition to its scientific interest, the study of correlations between the returns of different stocks is also of practical relevance in quantifying the risk of a given stock portfolio. We find [3,4] that the statistics of most of the eigenvalues of the spectrum of C agree with the predictions of RMT, while there are deviations for some of the largest eigenvalues. We interpret these deviations as a system specific property, e.g. containing genuine information about correlations in the stock market. We demonstrate that C shares universal properties with the Gaussian orthogonal ensemble of random matrices. Furthermore, we analyze the eigenvectors of C through their inverse participation ratio and find eigenvectors with large ratios at both edges of the eigenvalue spectrum - a situation reminiscent of localization theory results. This work was done in collaboration with V. Plerou, P. Gopikrishnan, T. Guhr, L.A.N. Amaral, and H.E Stanley and is related to recent work of Laloux et al.. 1. T. Guhr, A. Müller Groeling, and H.A. Weidenmüller, ``Random Matrix Theories in Quantum Physics: Common Concepts'', Phys. Rep. 299, 190 (1998). 2. See, e.g. R.N. Mantegna and H.E. Stanley, Econophysics: Correlations and Complexity in Finance (Cambridge University Press, Cambridge, England, 1999). 3. V. Plerou, P. Gopikrishnan, B. Rosenow, L.A.N. Amaral, and H.E. Stanley, ``Universal and Nonuniversal Properties of Cross Correlations in Financial Time Series'', Phys. Rev. Lett. 83, 1471 (1999). 4. V. Plerou, P. Gopikrishnan, T. Guhr, B. Rosenow, L.A.N. Amaral, and H.E. Stanley, ``Random Matrix Theory

  20. Randomized Search Strategies With Imperfect Sensors

    National Research Council Canada - National Science Library

    Gage, Douglas W

    1993-01-01

    .... An important class of coverage applications are those that involve a search, in which a number of searching elements move about within a prescribed search area in order to find one or more target...

  1. Supersymmetry in random matrix theory

    International Nuclear Information System (INIS)

    Kieburg, Mario

    2010-01-01

    I study the applications of supersymmetry in random matrix theory. I generalize the supersymmetry method and develop three new approaches to calculate eigenvalue correlation functions. These correlation functions are averages over ratios of characteristic polynomials. In the first part of this thesis, I derive a relation between integrals over anti-commuting variables (Grassmann variables) and differential operators with respect to commuting variables. With this relation I rederive Cauchy- like integral theorems. As a new application I trace the supermatrix Bessel function back to a product of two ordinary matrix Bessel functions. In the second part, I apply the generalized Hubbard-Stratonovich transformation to arbitrary rotation invariant ensembles of real symmetric and Hermitian self-dual matrices. This extends the approach for unitarily rotation invariant matrix ensembles. For the k-point correlation functions I derive supersymmetric integral expressions in a unifying way. I prove the equivalence between the generalized Hubbard-Stratonovich transformation and the superbosonization formula. Moreover, I develop an alternative mapping from ordinary space to superspace. After comparing the results of this approach with the other two supersymmetry methods, I obtain explicit functional expressions for the probability densities in superspace. If the probability density of the matrix ensemble factorizes, then the generating functions exhibit determinantal and Pfaffian structures. For some matrix ensembles this was already shown with help of other approaches. I show that these structures appear by a purely algebraic manipulation. In this new approach I use structures naturally appearing in superspace. I derive determinantal and Pfaffian structures for three types of integrals without actually mapping onto superspace. These three types of integrals are quite general and, thus, they are applicable to a broad class of matrix ensembles. (orig.)

  2. Supersymmetry in random matrix theory

    Energy Technology Data Exchange (ETDEWEB)

    Kieburg, Mario

    2010-05-04

    I study the applications of supersymmetry in random matrix theory. I generalize the supersymmetry method and develop three new approaches to calculate eigenvalue correlation functions. These correlation functions are averages over ratios of characteristic polynomials. In the first part of this thesis, I derive a relation between integrals over anti-commuting variables (Grassmann variables) and differential operators with respect to commuting variables. With this relation I rederive Cauchy- like integral theorems. As a new application I trace the supermatrix Bessel function back to a product of two ordinary matrix Bessel functions. In the second part, I apply the generalized Hubbard-Stratonovich transformation to arbitrary rotation invariant ensembles of real symmetric and Hermitian self-dual matrices. This extends the approach for unitarily rotation invariant matrix ensembles. For the k-point correlation functions I derive supersymmetric integral expressions in a unifying way. I prove the equivalence between the generalized Hubbard-Stratonovich transformation and the superbosonization formula. Moreover, I develop an alternative mapping from ordinary space to superspace. After comparing the results of this approach with the other two supersymmetry methods, I obtain explicit functional expressions for the probability densities in superspace. If the probability density of the matrix ensemble factorizes, then the generating functions exhibit determinantal and Pfaffian structures. For some matrix ensembles this was already shown with help of other approaches. I show that these structures appear by a purely algebraic manipulation. In this new approach I use structures naturally appearing in superspace. I derive determinantal and Pfaffian structures for three types of integrals without actually mapping onto superspace. These three types of integrals are quite general and, thus, they are applicable to a broad class of matrix ensembles. (orig.)

  3. Harmony Search Method: Theory and Applications

    Directory of Open Access Journals (Sweden)

    X. Z. Gao

    2015-01-01

    Full Text Available The Harmony Search (HS method is an emerging metaheuristic optimization algorithm, which has been employed to cope with numerous challenging tasks during the past decade. In this paper, the essential theory and applications of the HS algorithm are first described and reviewed. Several typical variants of the original HS are next briefly explained. As an example of case study, a modified HS method inspired by the idea of Pareto-dominance-based ranking is also presented. It is further applied to handle a practical wind generator optimal design problem.

  4. Ordered random variables theory and applications

    CERN Document Server

    Shahbaz, Muhammad Qaiser; Hanif Shahbaz, Saman; Al-Zahrani, Bander M

    2016-01-01

    Ordered Random Variables have attracted several authors. The basic building block of Ordered Random Variables is Order Statistics which has several applications in extreme value theory and ordered estimation. The general model for ordered random variables, known as Generalized Order Statistics has been introduced relatively recently by Kamps (1995).

  5. Dirac operator, chirality and random matrix theory

    International Nuclear Information System (INIS)

    Pullirsch, R.

    2001-05-01

    Quantum Chromodynamics (QCD) is considered to be the correct theory which describes quarks and gluons and, thus, all strong interaction phenomena from the fundamental forces of nature. However, important properties of QCD such as the physical mechanism of color confinement and the spontaneous breaking of chiral symmetry are still not completely understood and under extensive discussion. Analytical calculations are limited, because in the low-energy regime where quarks are confined, application of perturbation theory is restricted due to the large gluon coupling. A powerful tool to investigate numerically and analytically the non-perturbative region is provided by the lattice formulation of QCD. From Monte Carlo simulations of lattice QCD we know that chiral symmetry is restored above a critical temperature. As the chiral condensate is connected to the spectral density of the Dirac operator via the Banks-Casher relation, the QCD Dirac spectrum is an interesting object for detailed studies. In search for an analytical expression of the infrared limit of the Dirac spectrum it has been realized that chiral random-matrix theory (chRMT) is a suitable tool to compare with the distribution and the correlations of the small Dirac eigenvalues. Further, it has been shown that the correlations of eigenvalues on the scale of mean level spacings are universal for complex physical systems and are given by random-matrix theory (Rm). This has been formulated as the Baghouse-Giannoni-Schmit conjecture which states that spectral correlations of a classically chaotic system are given by RMT on the quantum level. The aim of this work is to analyze the relationship between chiral phase transitions and chaos to order transitions in quantum field theories. We study the eigenvalues of the Dirac operator for Quantum Electrodynamics (QED) with compact gauge group U(1) on the lattice. This theory shows chiral symmetry breaking and confinement in the strong coupling region. Although being

  6. The Theory of Random Laser Systems

    International Nuclear Information System (INIS)

    Xunya Jiang

    2002-01-01

    Studies of random laser systems are a new direction with promising potential applications and theoretical interest. The research is based on the theories of localization and laser physics. So far, the research shows that there are random lasing modes inside the systems which is quite different from the common laser systems. From the properties of the random lasing modes, they can understand the phenomena observed in the experiments, such as multi-peak and anisotropic spectrum, lasing mode number saturation, mode competition and dynamic processes, etc. To summarize, this dissertation has contributed the following in the study of random laser systems: (1) by comparing the Lamb theory with the Letokhov theory, the general formulas of the threshold length or gain of random laser systems were obtained; (2) they pointed out the vital weakness of previous time-independent methods in random laser research; (3) a new model which includes the FDTD method and the semi-classical laser theory. The solutions of this model provided an explanation of the experimental results of multi-peak and anisotropic emission spectra, predicted the saturation of lasing modes number and the length of localized lasing modes; (4) theoretical (Lamb theory) and numerical (FDTD and transfer-matrix calculation) studies of the origin of localized lasing modes in the random laser systems; and (5) proposal of using random lasing modes as a new path to study wave localization in random systems and prediction of the lasing threshold discontinuity at mobility edge

  7. Supersymmetry - When Theory Inspires Experimental Searches

    CERN Document Server

    AUTHOR|(CDS)2070740

    2014-01-01

    We review, in the first part of this work, many pioneering works on supersymmetry and organize these results to show how supersymmetric quantum field theories arise from spin-statistics, N{\\oe}ther and a series of no-go theorems. We then introduce the so-called superspace formalism dedicated to the natural construction of supersymmetric Lagrangians and detail the most popular mechanisms leading to soft supersymmetry breaking. As an application, we describe the building of the Minimal Supersymmetric Standard Model and investigate current experimental limits on the parameter space of its most constrained versions. To this aim, we use various flavor, electroweak precision, cosmology and collider data. We then perform several phenomenological excursions beyond this minimal setup and probe effects due to non-minimal flavor violation in the squark sector, revisiting various constraints arising from indirect searches for superpartners. Next, we use several interfaced high-energy physics tools, including the FeynRule...

  8. Random geometry and Yang-Mills theory

    International Nuclear Information System (INIS)

    Froehlich, J.

    1981-01-01

    The author states various problems and discusses a very few preliminary rigorous results in a branch of mathematics and mathematical physics which one might call random (or stochastic) geometry. Furthermore, he points out why random geometry is important in the quantization of Yang-Mills theory. (Auth.)

  9. Randomized Item Response Theory Models

    NARCIS (Netherlands)

    Fox, Gerardus J.A.

    2005-01-01

    The randomized response (RR) technique is often used to obtain answers on sensitive questions. A new method is developed to measure latent variables using the RR technique because direct questioning leads to biased results. Within the RR technique is the probability of the true response modeled by

  10. Greedy Local Search and Vertex Cover in Sparse Random Graphs

    DEFF Research Database (Denmark)

    Witt, Carsten

    2009-01-01

    . This work starts with a rigorous explanation for this claim based on the refined analysis of the Karp-Sipser algorithm by Aronson et al. Subsequently, theoretical supplements are given to experimental studies of search heuristics on random graphs. For c 1, a greedy and randomized local-search heuristic...... finds an optimal cover in polynomial time with a probability arbitrarily close to 1. This behavior relies on the absence of a giant component. As an additional insight into the randomized search, it is shown that the heuristic fails badly also on graphs consisting of a single tree component of maximum......Recently, various randomized search heuristics have been studied for the solution of the minimum vertex cover problem, in particular for sparse random instances according to the G(n, c/n) model, where c > 0 is a constant. Methods from statistical physics suggest that the problem is easy if c

  11. Simulation of random walks in field theory

    International Nuclear Information System (INIS)

    Rensburg, E.J.J. van

    1988-01-01

    The numerical simulation of random walks is considered using the Monte Carlo method previously proposed. The algorithm is tested and then generalised to generate Edwards random walks. The renormalised masses of the Edwards model are calculated and the results are compared with those obtained from a simple perturbation theory calculation for small values of the bare coupling constant. The efficiency of this algorithm is discussed and compared with an alternative approach. (author)

  12. Scattering quantum random-walk search with errors

    International Nuclear Information System (INIS)

    Gabris, A.; Kiss, T.; Jex, I.

    2007-01-01

    We analyze the realization of a quantum-walk search algorithm in a passive, linear optical network. The specific model enables us to consider the effect of realistic sources of noise and losses on the search efficiency. Photon loss uniform in all directions is shown to lead to the rescaling of search time. Deviation from directional uniformity leads to the enhancement of the search efficiency compared to uniform loss with the same average. In certain cases even increasing loss in some of the directions can improve search efficiency. We show that while we approach the classical limit of the general search algorithm by introducing random phase fluctuations, its utility for searching is lost. Using numerical methods, we found that for static phase errors the averaged search efficiency displays a damped oscillatory behavior that asymptotically tends to a nonzero value

  13. Dynamic random walks theory and applications

    CERN Document Server

    Guillotin-Plantard, Nadine

    2006-01-01

    The aim of this book is to report on the progress realized in probability theory in the field of dynamic random walks and to present applications in computer science, mathematical physics and finance. Each chapter contains didactical material as well as more advanced technical sections. Few appendices will help refreshing memories (if necessary!).· New probabilistic model, new results in probability theory· Original applications in computer science· Applications in mathematical physics· Applications in finance

  14. Search for Directed Networks by Different Random Walk Strategies

    Science.gov (United States)

    Zhu, Zi-Qi; Jin, Xiao-Ling; Huang, Zhi-Long

    2012-03-01

    A comparative study is carried out on the efficiency of five different random walk strategies searching on directed networks constructed based on several typical complex networks. Due to the difference in search efficiency of the strategies rooted in network clustering, the clustering coefficient in a random walker's eye on directed networks is defined and computed to be half of the corresponding undirected networks. The search processes are performed on the directed networks based on Erdös—Rényi model, Watts—Strogatz model, Barabási—Albert model and clustered scale-free network model. It is found that self-avoiding random walk strategy is the best search strategy for such directed networks. Compared to unrestricted random walk strategy, path-iteration-avoiding random walks can also make the search process much more efficient. However, no-triangle-loop and no-quadrangle-loop random walks do not improve the search efficiency as expected, which is different from those on undirected networks since the clustering coefficient of directed networks are smaller than that of undirected networks.

  15. Social patterns revealed through random matrix theory

    Science.gov (United States)

    Sarkar, Camellia; Jalan, Sarika

    2014-11-01

    Despite the tremendous advancements in the field of network theory, very few studies have taken weights in the interactions into consideration that emerge naturally in all real-world systems. Using random matrix analysis of a weighted social network, we demonstrate the profound impact of weights in interactions on emerging structural properties. The analysis reveals that randomness existing in particular time frame affects the decisions of individuals rendering them more freedom of choice in situations of financial security. While the structural organization of networks remains the same throughout all datasets, random matrix theory provides insight into the interaction pattern of individuals of the society in situations of crisis. It has also been contemplated that individual accountability in terms of weighted interactions remains as a key to success unless segregation of tasks comes into play.

  16. Introduction to random matrices theory and practice

    CERN Document Server

    Livan, Giacomo; Vivo, Pierpaolo

    2018-01-01

    Modern developments of Random Matrix Theory as well as pedagogical approaches to the standard core of the discipline are surprisingly hard to find in a well-organized, readable and user-friendly fashion. This slim and agile book, written in a pedagogical and hands-on style, without sacrificing formal rigor fills this gap. It brings Ph.D. students in Physics, as well as more senior practitioners, through the standard tools and results on random matrices, with an eye on most recent developments that are not usually covered in introductory texts. The focus is mainly on random matrices with real spectrum. The main guiding threads throughout the book are the Gaussian Ensembles. In particular, Wigner’s semicircle law is derived multiple times to illustrate several techniques  (e.g., Coulomb gas approach, replica theory). Most chapters are accompanied by Matlab codes (stored in an online repository) to guide readers through the numerical check of most analytical results.

  17. Decoherence in optimized quantum random-walk search algorithm

    International Nuclear Information System (INIS)

    Zhang Yu-Chao; Bao Wan-Su; Wang Xiang; Fu Xiang-Qun

    2015-01-01

    This paper investigates the effects of decoherence generated by broken-link-type noise in the hypercube on an optimized quantum random-walk search algorithm. When the hypercube occurs with random broken links, the optimized quantum random-walk search algorithm with decoherence is depicted through defining the shift operator which includes the possibility of broken links. For a given database size, we obtain the maximum success rate of the algorithm and the required number of iterations through numerical simulations and analysis when the algorithm is in the presence of decoherence. Then the computational complexity of the algorithm with decoherence is obtained. The results show that the ultimate effect of broken-link-type decoherence on the optimized quantum random-walk search algorithm is negative. (paper)

  18. Effects of a random noisy oracle on search algorithm complexity

    International Nuclear Information System (INIS)

    Shenvi, Neil; Brown, Kenneth R.; Whaley, K. Birgitta

    2003-01-01

    Grover's algorithm provides a quadratic speed-up over classical algorithms for unstructured database or library searches. This paper examines the robustness of Grover's search algorithm to a random phase error in the oracle and analyzes the complexity of the search process as a function of the scaling of the oracle error with database or library size. Both the discrete- and continuous-time implementations of the search algorithm are investigated. It is shown that unless the oracle phase error scales as O(N -1/4 ), neither the discrete- nor the continuous-time implementation of Grover's algorithm is scalably robust to this error in the absence of error correction

  19. NATO Advanced Research Institute on Search Theory and Applications

    CERN Document Server

    Stone, Lawrence

    1980-01-01

    The NATO Advanced Research Institute on Search Theory and Appli­ cations was held at the Hotel Algarve in Praia Da Rocha, Portugal, from March 26 through March 30, 1979, and was sponsored by the NATO Special Programme Panel on Systems Science. There were forty-one participants representing a wide range of backgrounds and interests. The purpose of the institute was to bring together people working in search theory and applications with potential users of search techniques to stimulate the increased application of recent­ ly developed search technology to civilian problems such as search and rescue, mineral exploration, surveillance, and fishing. Con­ versely, it was felt that by exposing search analysts to potential applications and new problems, they would be stimulated to develop new techniques for these applications and problems. The exchange of ideas and problems necessary to accomplish these goals was provided in the meeting workshops. There were three workshops, Search and Rescue, Exploration, and Sur...

  20. Random matrix theories and chaotic dynamics

    International Nuclear Information System (INIS)

    Bohigas, O.

    1991-01-01

    A review of some of the main ideas, assumptions and results of the Wigner-Dyson type random matrix theories (RMT) which are relevant in the general context of 'Chaos and Quantum Physics' is presented. RMT are providing interesting and unexpected clues to connect classical dynamics with quantum phenomena. It is this aspect which will be emphasised and, concerning the main body of RMT, the author will restrict himself to a minimum. However, emphasis will be put on some generalizations of the 'canonical' random matrix ensembles that increase their flexibility, rendering the incorporation of relevant physical constraints possible. (R.P.) 112 refs., 35 figs., 5 tabs

  1. Key Elasticities in Job Search Theory : International Evidence

    OpenAIRE

    Addison, John T.; Centeno, Mário; Portugal, Pedro

    2004-01-01

    This paper exploits the informational value of search theory, after Lancaster and Chesher (1983), in conjunction with survey data on the unemployed to calculate key reservation wage and duration elasticities for most EU-15 nations.

  2. Search theory a game theoretic perspective

    CERN Document Server

    2014-01-01

    The first book focusing on search and rendezvous that will appeal to the computer science, mathematics and biology communities as well as non-experts Most chapters include case studies or surveys Includes a chapter on mobility in governed social networks

  3. Random matrix theory with an external source

    CERN Document Server

    Brézin, Edouard

    2016-01-01

    This is a first book to show that the theory of the Gaussian random matrix is essential to understand the universal correlations with random fluctuations and to demonstrate that it is useful to evaluate topological universal quantities. We consider Gaussian random matrix models in the presence of a deterministic matrix source. In such models the correlation functions are known exactly for an arbitrary source and for any size of the matrices. The freedom given by the external source allows for various tunings to different classes of universality. The main interest is to use this freedom to compute various topological invariants for surfaces such as the intersection numbers for curves drawn on a surface of given genus with marked points, Euler characteristics, and the Gromov–Witten invariants. A remarkable duality for the average of characteristic polynomials is essential for obtaining such topological invariants. The analysis is extended to nonorientable surfaces and to surfaces with boundaries.

  4. Randomized central limit theorems: A unified theory.

    Science.gov (United States)

    Eliazar, Iddo; Klafter, Joseph

    2010-08-01

    The central limit theorems (CLTs) characterize the macroscopic statistical behavior of large ensembles of independent and identically distributed random variables. The CLTs assert that the universal probability laws governing ensembles' aggregate statistics are either Gaussian or Lévy, and that the universal probability laws governing ensembles' extreme statistics are Fréchet, Weibull, or Gumbel. The scaling schemes underlying the CLTs are deterministic-scaling all ensemble components by a common deterministic scale. However, there are "random environment" settings in which the underlying scaling schemes are stochastic-scaling the ensemble components by different random scales. Examples of such settings include Holtsmark's law for gravitational fields and the Stretched Exponential law for relaxation times. In this paper we establish a unified theory of randomized central limit theorems (RCLTs)-in which the deterministic CLT scaling schemes are replaced with stochastic scaling schemes-and present "randomized counterparts" to the classic CLTs. The RCLT scaling schemes are shown to be governed by Poisson processes with power-law statistics, and the RCLTs are shown to universally yield the Lévy, Fréchet, and Weibull probability laws.

  5. The search for higher symmetry in string theory

    Energy Technology Data Exchange (ETDEWEB)

    Witten, E [Institute for Advanced Study, Princeton, NJ (USA)

    1989-11-17

    Some remarks are made about the nature and role of the search for higher symmetry in string theory. These symmetries are most likely to be uncovered in a mysterious 'unbroken phase', for which (2+1)-dimensional gravity provides an interesting and soluble model. New insights about conformal field theory, in which one gets 'out of flatland' to see a wider symmetry from a higher-dimensional vantage point, may offer clues to the unbroken phase of string theory. (author).

  6. Concentrated Hitting Times of Randomized Search Heuristics with Variable Drift

    DEFF Research Database (Denmark)

    Lehre, Per Kristian; Witt, Carsten

    2014-01-01

    Drift analysis is one of the state-of-the-art techniques for the runtime analysis of randomized search heuristics (RSHs) such as evolutionary algorithms (EAs), simulated annealing etc. The vast majority of existing drift theorems yield bounds on the expected value of the hitting time for a target...

  7. Optimal random search for a single hidden target.

    Science.gov (United States)

    Snider, Joseph

    2011-01-01

    A single target is hidden at a location chosen from a predetermined probability distribution. Then, a searcher must find a second probability distribution from which random search points are sampled such that the target is found in the minimum number of trials. Here it will be shown that if the searcher must get very close to the target to find it, then the best search distribution is proportional to the square root of the target distribution regardless of dimension. For a Gaussian target distribution, the optimum search distribution is approximately a Gaussian with a standard deviation that varies inversely with how close the searcher must be to the target to find it. For a network where the searcher randomly samples nodes and looks for the fixed target along edges, the optimum is either to sample a node with probability proportional to the square root of the out-degree plus 1 or not to do so at all.

  8. Asymptotic theory of weakly dependent random processes

    CERN Document Server

    Rio, Emmanuel

    2017-01-01

    Presenting tools to aid understanding of asymptotic theory and weakly dependent processes, this book is devoted to inequalities and limit theorems for sequences of random variables that are strongly mixing in the sense of Rosenblatt, or absolutely regular. The first chapter introduces covariance inequalities under strong mixing or absolute regularity. These covariance inequalities are applied in Chapters 2, 3 and 4 to moment inequalities, rates of convergence in the strong law, and central limit theorems. Chapter 5 concerns coupling. In Chapter 6 new deviation inequalities and new moment inequalities for partial sums via the coupling lemmas of Chapter 5 are derived and applied to the bounded law of the iterated logarithm. Chapters 7 and 8 deal with the theory of empirical processes under weak dependence. Lastly, Chapter 9 describes links between ergodicity, return times and rates of mixing in the case of irreducible Markov chains. Each chapter ends with a set of exercises. The book is an updated and extended ...

  9. Pseudo-Hermitian random matrix theory

    International Nuclear Information System (INIS)

    Srivastava, S.C.L.; Jain, S.R.

    2013-01-01

    Complex extension of quantum mechanics and the discovery of pseudo-unitarily invariant random matrix theory has set the stage for a number of applications of these concepts in physics. We briefly review the basic ideas and present applications to problems in statistical mechanics where new results have become possible. We have found it important to mention the precise directions where advances could be made if further results become available. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. Theory of Random Anisotropic Magnetic Alloys

    DEFF Research Database (Denmark)

    Lindgård, Per-Anker

    1976-01-01

    A mean-field-crystal-field theory is developed for random, multicomponent, anisotropic magnetic alloys. It is specially applicable to rare-earth alloys. A discussion is given of multicritical points and phase transitions between various states characterized by order parameters with different...... spatial directions or different ordering wave vectors. Theoretical predictions based on known parameters for the phase diagrams and magnetic moments for the binary rare-earth alloys of Tb, Dy, Ho, and Er, Tb-Tm, Nd-Pr, and pure double-hcp Nd agree qualitatively with the experimental observations...... fluctuation corrections in the mean-field results is also discussed....

  11. ARSTEC, Nonlinear Optimization Program Using Random Search Method

    International Nuclear Information System (INIS)

    Rasmuson, D. M.; Marshall, N. H.

    1979-01-01

    1 - Description of problem or function: The ARSTEC program was written to solve nonlinear, mixed integer, optimization problems. An example of such a problem in the nuclear industry is the allocation of redundant parts in the design of a nuclear power plant to minimize plant unavailability. 2 - Method of solution: The technique used in ARSTEC is the adaptive random search method. The search is started from an arbitrary point in the search region and every time a point that improves the objective function is found, the search region is centered at that new point. 3 - Restrictions on the complexity of the problem: Presently, the maximum number of independent variables allowed is 10. This can be changed by increasing the dimension of the arrays

  12. Optimizing Event Selection with the Random Grid Search

    Energy Technology Data Exchange (ETDEWEB)

    Bhat, Pushpalatha C. [Fermilab; Prosper, Harrison B. [Florida State U.; Sekmen, Sezen [Kyungpook Natl. U.; Stewart, Chip [Broad Inst., Cambridge

    2017-06-29

    The random grid search (RGS) is a simple, but efficient, stochastic algorithm to find optimal cuts that was developed in the context of the search for the top quark at Fermilab in the mid-1990s. The algorithm, and associated code, have been enhanced recently with the introduction of two new cut types, one of which has been successfully used in searches for supersymmetry at the Large Hadron Collider. The RGS optimization algorithm is described along with the recent developments, which are illustrated with two examples from particle physics. One explores the optimization of the selection of vector boson fusion events in the four-lepton decay mode of the Higgs boson and the other optimizes SUSY searches using boosted objects and the razor variables.

  13. Cooperative mobile agents search using beehive partitioned structure and Tabu Random search algorithm

    Science.gov (United States)

    Ramazani, Saba; Jackson, Delvin L.; Selmic, Rastko R.

    2013-05-01

    In search and surveillance operations, deploying a team of mobile agents provides a robust solution that has multiple advantages over using a single agent in efficiency and minimizing exploration time. This paper addresses the challenge of identifying a target in a given environment when using a team of mobile agents by proposing a novel method of mapping and movement of agent teams in a cooperative manner. The approach consists of two parts. First, the region is partitioned into a hexagonal beehive structure in order to provide equidistant movements in every direction and to allow for more natural and flexible environment mapping. Additionally, in search environments that are partitioned into hexagons, mobile agents have an efficient travel path while performing searches due to this partitioning approach. Second, we use a team of mobile agents that move in a cooperative manner and utilize the Tabu Random algorithm to search for the target. Due to the ever-increasing use of robotics and Unmanned Aerial Vehicle (UAV) platforms, the field of cooperative multi-agent search has developed many applications recently that would benefit from the use of the approach presented in this work, including: search and rescue operations, surveillance, data collection, and border patrol. In this paper, the increased efficiency of the Tabu Random Search algorithm method in combination with hexagonal partitioning is simulated, analyzed, and advantages of this approach are presented and discussed.

  14. Optimal Quantum Spatial Search on Random Temporal Networks.

    Science.gov (United States)

    Chakraborty, Shantanav; Novo, Leonardo; Di Giorgio, Serena; Omar, Yasser

    2017-12-01

    To investigate the performance of quantum information tasks on networks whose topology changes in time, we study the spatial search algorithm by continuous time quantum walk to find a marked node on a random temporal network. We consider a network of n nodes constituted by a time-ordered sequence of Erdös-Rényi random graphs G(n,p), where p is the probability that any two given nodes are connected: After every time interval τ, a new graph G(n,p) replaces the previous one. We prove analytically that, for any given p, there is always a range of values of τ for which the running time of the algorithm is optimal, i.e., O(sqrt[n]), even when search on the individual static graphs constituting the temporal network is suboptimal. On the other hand, there are regimes of τ where the algorithm is suboptimal even when each of the underlying static graphs are sufficiently connected to perform optimal search on them. From this first study of quantum spatial search on a time-dependent network, it emerges that the nontrivial interplay between temporality and connectivity is key to the algorithmic performance. Moreover, our work can be extended to establish high-fidelity qubit transfer between any two nodes of the network. Overall, our findings show that one can exploit temporality to achieve optimal quantum information tasks on dynamical random networks.

  15. Optimal Quantum Spatial Search on Random Temporal Networks

    Science.gov (United States)

    Chakraborty, Shantanav; Novo, Leonardo; Di Giorgio, Serena; Omar, Yasser

    2017-12-01

    To investigate the performance of quantum information tasks on networks whose topology changes in time, we study the spatial search algorithm by continuous time quantum walk to find a marked node on a random temporal network. We consider a network of n nodes constituted by a time-ordered sequence of Erdös-Rényi random graphs G (n ,p ), where p is the probability that any two given nodes are connected: After every time interval τ , a new graph G (n ,p ) replaces the previous one. We prove analytically that, for any given p , there is always a range of values of τ for which the running time of the algorithm is optimal, i.e., O (√{n }), even when search on the individual static graphs constituting the temporal network is suboptimal. On the other hand, there are regimes of τ where the algorithm is suboptimal even when each of the underlying static graphs are sufficiently connected to perform optimal search on them. From this first study of quantum spatial search on a time-dependent network, it emerges that the nontrivial interplay between temporality and connectivity is key to the algorithmic performance. Moreover, our work can be extended to establish high-fidelity qubit transfer between any two nodes of the network. Overall, our findings show that one can exploit temporality to achieve optimal quantum information tasks on dynamical random networks.

  16. Expedite random structure searching using objects from Wyckoff positions

    Science.gov (United States)

    Wang, Shu-Wei; Hsing, Cheng-Rong; Wei, Ching-Ming

    2018-02-01

    Random structure searching has been proved to be a powerful approach to search and find the global minimum and the metastable structures. A true random sampling is in principle needed yet it would be highly time-consuming and/or practically impossible to find the global minimum for the complicated systems in their high-dimensional configuration space. Thus the implementations of reasonable constraints, such as adopting system symmetries to reduce the independent dimension in structural space and/or imposing chemical information to reach and relax into low-energy regions, are the most essential issues in the approach. In this paper, we propose the concept of "object" which is either an atom or composed of a set of atoms (such as molecules or carbonates) carrying a symmetry defined by one of the Wyckoff positions of space group and through this process it allows the searching of global minimum for a complicated system to be confined in a greatly reduced structural space and becomes accessible in practice. We examined several representative materials, including Cd3As2 crystal, solid methanol, high-pressure carbonates (FeCO3), and Si(111)-7 × 7 reconstructed surface, to demonstrate the power and the advantages of using "object" concept in random structure searching.

  17. Track theory and nuclear photographic emulsions for Dark Matter searches

    International Nuclear Information System (INIS)

    Ditlov, V.A.

    2013-01-01

    This work is devoted to the analysis of possibilities of nuclear emulsions for Dark Matter search, particles of which can produce slow recoil-nuclei. Tracks of such recoil-nuclei in developed nuclear emulsion consist from several emulsion grains. The analysis was carried out with Monte-Carlo calculations made on the basis of the Track Theory and the various factors influencing Dark Matter particles registration efficiency were investigated. Problems, which should be solved for optimal utilization of nuclear emulsions in Dark Matter search, were formulated. B ody - Highlights: ► Specific features of Dark Matter Search in nuclear photographic emulsions. ► Track theory for WIMP search in nuclear emulsions. ► Primary efficiency for single WIMP registration. ► Properties of primary WIMP registration efficiency. ► Primary registration efficiency of WIMP flow

  18. The use of random walk in field theory

    International Nuclear Information System (INIS)

    Brydges, D.

    1984-01-01

    Ferromagnetic spin systems and gauge theories where the gauge group is topologically a sphere, e.g. Z 2 , U(1) and SU(2) are related to the theory of random walk and random surfaces respectively. I survey some applications of this theme to the phi 4 field theories. (orig.)

  19. Discussion: The Forward Search: Theory and Data Analysis

    DEFF Research Database (Denmark)

    Johansen, Søren; Nielsen, Bent

    2010-01-01

    The Forward Search Algorithm is a statistical algorithm for obtaining robust estimators of regression coefficients in the presence of outliers. The algorithm selects a succession of subsets of observations from which the parameters are estimated. The present note shows how the theory of empirical...

  20. Intermittent random walks: transport regimes and implications on search strategies

    International Nuclear Information System (INIS)

    Gomez Portillo, Ignacio; Campos, Daniel; Méndez, Vicenç

    2011-01-01

    We construct a transport model for particles that alternate rests of random duration and flights with random velocities. The model provides a balance equation for the mesoscopic particle density obtained from the continuous-time random walk framework. By assuming power laws for the distributions of waiting times and flight durations (for any velocity distribution with finite moments) we have found that the model can yield all the transport regimes ranging from subdiffusion to ballistic depending on the values of the characteristic exponents of the distributions. In addition, if the exponents satisfy a simple relationship it is shown how the competition between the tails of the distributions gives rise to a diffusive transport. Finally, we explore how the details of this intermittent transport process affect the success probability in an optimal search problem where an individual searcher looks for a target distributed (heterogeneously) in space. All the results are conveniently checked with numerical simulations

  1. Search for a perfect generator of random numbers

    International Nuclear Information System (INIS)

    Musyck, E.

    1977-01-01

    Theoretical tests have been carried out by COVEYOU and MAC PHERSON to verify the applications of the LEHMER algorithm. In a similar way, a theoretical method is proposed to evaluate in a rigorous way the random character of numbers generated by a shift register. This theory introduces the concept of ''degree of randomness'' of the elements, taken in a definite order, of a shift register. It permits making the judicious choice of the elements of the shift register which will produce the bits of the random numbers. On the other hand, a calculation method is developed in order to verify the primitive character of any shift register of high complexity. A new test, called ''slice test'', of empirical and theoretical use is also described; it constitutes a significant contribution to the understanding of certain properties of pseudo-random sequences. As a practical example, a random number generator structure formed with 32 bits, built out of a shift register with 61 elements and 60 modulo-2 adder circuits was made. The author is convinced that this generator can be considered to be practically perfect for all empirical applications of random numbers, particularly for the solution of Monte-Carlo problems. (author)

  2. Optimization by GRASP greedy randomized adaptive search procedures

    CERN Document Server

    Resende, Mauricio G C

    2016-01-01

    This is the first book to cover GRASP (Greedy Randomized Adaptive Search Procedures), a metaheuristic that has enjoyed wide success in practice with a broad range of applications to real-world combinatorial optimization problems. The state-of-the-art coverage and carefully crafted pedagogical style lends this book highly accessible as an introductory text not only to GRASP, but also to combinatorial optimization, greedy algorithms, local search, and path-relinking, as well as to heuristics and metaheuristics, in general. The focus is on algorithmic and computational aspects of applied optimization with GRASP with emphasis given to the end-user, providing sufficient information on the broad spectrum of advances in applied optimization with GRASP. For the more advanced reader, chapters on hybridization with path-relinking and parallel and continuous GRASP present these topics in a clear and concise fashion. Additionally, the book offers a very complete annotated bibliography of GRASP and combinatorial optimizat...

  3. Literature in Focus: "Axions: Theory, Cosmology, and Experimental Searches"

    CERN Document Server

    2009-01-01

    Axions are peculiar hypothetical particles that could both solve the CP problem of quantum chromodynamics and at the same time account for the dark matter of the universe. Based on a series of lectures by world experts in this field held at CERN, this volume provides a pedagogical introduction to the theory, cosmology and astrophysics of these fascinating particles and gives an up-to-date account of the status and prospect of ongoing and planned experimental searches. Learners and practitioners of astroparticle physics will find in this book both a concise introduction and a current reference work to a showcase topic that connects the "inner space" of the elementary particle world with the "outer space" of the universe at large. The book will be presented by Markus Kuster. "Axions: Theory, Cosmology, and Experimental Searches", edited by M. Kuster (Technische Universität Darmstadt), G. Raffelt (Max-Planck-Institu...

  4. Syndemics: A theory in search of data or data in search of a theory?

    Science.gov (United States)

    Tsai, Alexander C

    2018-06-01

    The concept of a syndemic was proposed more than two decades ago to explain how large-scale social forces might give rise to co-occurring epidemics that synergistically interact to undermine health in vulnerable populations. This conceptual instrument has the potential to help policymakers and program implementers in their endeavors to improve population health. Accordingly, it has become an increasingly popular heuristic for advocacy, most notably in the field of HIV treatment and prevention. However, most empirical studies purporting to validate the theory of syndemics actually do no such thing. Tomori et al. (2018) provide a novel case study from India illustrating how the dominant empirical approach fails to promote deeper understanding about how hazardous alcohol use, illicit drug use, depression, childhood sexual abuse, and intimate partner violence interact to worsen HIV risk among men who have sex with men. In this commentary, I relate the theory of syndemics to other established social science and public health theories of disease distribution, identify possible sources of conceptual and empirical confusion, and provide concrete suggestions for how to validate the theory using a mixed-methods approach. The hope is that more evidence can be mobilized -- whether informed by the theory of syndemics or not -- to improve health and psychosocial wellbeing among vulnerable populations worldwide. Copyright © 2018 Elsevier Ltd. All rights reserved.

  5. Stochastic optimal foraging: tuning intensive and extensive dynamics in random searches.

    Directory of Open Access Journals (Sweden)

    Frederic Bartumeus

    Full Text Available Recent theoretical developments had laid down the proper mathematical means to understand how the structural complexity of search patterns may improve foraging efficiency. Under information-deprived scenarios and specific landscape configurations, Lévy walks and flights are known to lead to high search efficiencies. Based on a one-dimensional comparative analysis we show a mechanism by which, at random, a searcher can optimize the encounter with close and distant targets. The mechanism consists of combining an optimal diffusivity (optimally enhanced diffusion with a minimal diffusion constant. In such a way the search dynamics adequately balances the tension between finding close and distant targets, while, at the same time, shifts the optimal balance towards relatively larger close-to-distant target encounter ratios. We find that introducing a multiscale set of reorientations ensures both a thorough local space exploration without oversampling and a fast spreading dynamics at the large scale. Lévy reorientation patterns account for these properties but other reorientation strategies providing similar statistical signatures can mimic or achieve comparable efficiencies. Hence, the present work unveils general mechanisms underlying efficient random search, beyond the Lévy model. Our results suggest that animals could tune key statistical movement properties (e.g. enhanced diffusivity, minimal diffusion constant to cope with the very general problem of balancing out intensive and extensive random searching. We believe that theoretical developments to mechanistically understand stochastic search strategies, such as the one here proposed, are crucial to develop an empirically verifiable and comprehensive animal foraging theory.

  6. Ising model of a randomly triangulated random surface as a definition of fermionic string theory

    International Nuclear Information System (INIS)

    Bershadsky, M.A.; Migdal, A.A.

    1986-01-01

    Fermionic degrees of freedom are added to randomly triangulated planar random surfaces. It is shown that the Ising model on a fixed graph is equivalent to a certain Majorana fermion theory on the dual graph. (orig.)

  7. Statistical Theory of the Vector Random Decrement Technique

    DEFF Research Database (Denmark)

    Asmussen, J. C.; Brincker, Rune; Ibrahim, S. R.

    1999-01-01

    decays. Due to the speed and/or accuracy of the Vector Random Decrement technique, it was introduced as an attractive alternative to the Random Decrement technique. In this paper, the theory of the Vector Random Decrement technique is extended by applying a statistical description of the stochastic...

  8. Random walks, critical phenomena, and triviality in quantum field theory

    International Nuclear Information System (INIS)

    Fernandez, R.; Froehlich, J.; Sokal, A.D.

    1992-01-01

    The subject of this book is equilibrium statistical mechanics - in particular the theory of critical phenomena - and quantum field theory. A general review of the theory of critical phenomena in spin systems, field theories, and random-walk and random-surface models is presented. Among the more technical topics treated in this book, the central theme is the use of random-walk representations as a tool to derive correlation inequalities. The consequences of these inequalities for critical-exponent theory and the triviality question in quantum field theory are expounded in detail. The book contains some previously unpublished results. It addresses both the researcher and the graduate student in modern statistical mechanics and quantum field theory. (orig.)

  9. Pseudo random signal processing theory and application

    CERN Document Server

    Zepernick, Hans-Jurgen

    2013-01-01

    In recent years, pseudo random signal processing has proven to be a critical enabler of modern communication, information, security and measurement systems. The signal's pseudo random, noise-like properties make it vitally important as a tool for protecting against interference, alleviating multipath propagation and allowing the potential of sharing bandwidth with other users. Taking a practical approach to the topic, this text provides a comprehensive and systematic guide to understanding and using pseudo random signals. Covering theoretical principles, design methodologies and applications

  10. Some open problems in random matrix theory and the theory of integrable systems

    OpenAIRE

    Deift, Percy

    2007-01-01

    We describe a list of open problems in random matrix theory and integrable systems which was presented at the conference ``Integrable Systems, Random Matrices, and Applications'' at the Courant Institute in May 2006.

  11. Probability, random variables, and random processes theory and signal processing applications

    CERN Document Server

    Shynk, John J

    2012-01-01

    Probability, Random Variables, and Random Processes is a comprehensive textbook on probability theory for engineers that provides a more rigorous mathematical framework than is usually encountered in undergraduate courses. It is intended for first-year graduate students who have some familiarity with probability and random variables, though not necessarily of random processes and systems that operate on random signals. It is also appropriate for advanced undergraduate students who have a strong mathematical background. The book has the following features: Several app

  12. Palm theory for random time changes

    Directory of Open Access Journals (Sweden)

    Masakiyo Miyazawa

    2001-01-01

    Full Text Available Palm distributions are basic tools when studying stationarity in the context of point processes, queueing systems, fluid queues or random measures. The framework varies with the random phenomenon of interest, but usually a one-dimensional group of measure-preserving shifts is the starting point. In the present paper, by alternatively using a framework involving random time changes (RTCs and a two-dimensional family of shifts, we are able to characterize all of the above systems in a single framework. Moreover, this leads to what we call the detailed Palm distribution (DPD which is stationary with respect to a certain group of shifts. The DPD has a very natural interpretation as the distribution seen at a randomly chosen position on the extended graph of the RTC, and satisfies a general duality criterion: the DPD of the DPD gives the underlying probability P in return.

  13. Statistical theory of correlations in random packings of hard particles.

    Science.gov (United States)

    Jin, Yuliang; Puckett, James G; Makse, Hernán A

    2014-05-01

    A random packing of hard particles represents a fundamental model for granular matter. Despite its importance, analytical modeling of random packings remains difficult due to the existence of strong correlations which preclude the development of a simple theory. Here, we take inspiration from liquid theories for the n-particle angular correlation function to develop a formalism of random packings of hard particles from the bottom up. A progressive expansion into a shell of particles converges in the large layer limit under a Kirkwood-like approximation of higher-order correlations. We apply the formalism to hard disks and predict the density of two-dimensional random close packing (RCP), ϕ(rcp) = 0.85 ± 0.01, and random loose packing (RLP), ϕ(rlp) = 0.67 ± 0.01. Our theory also predicts a phase diagram and angular correlation functions that are in good agreement with experimental and numerical data.

  14. Application of Regulatory Focus Theory to Search Advertising

    Science.gov (United States)

    Mowle, Elyse N.; Georgia, Emily J.; Doss, Brian D.; Updegraff, John A.

    2015-01-01

    Purpose The purpose of this paper is to test the utility of regulatory focus theory principles in a real-world setting; specifically, Internet hosted text advertisements. Effect of compatibility of the ad text with the regulatory focus of the consumer was examined. Design/methodology/approach Advertisements were created using Google AdWords. Data were collected for the number of views and clicks each ad received. Effect of regulatory fit was measured using logistic regression. Findings Logistic regression analyses demonstrated that there was a strong main effect for keyword, such that users were almost six times as likely to click on a promotion advertisement as a prevention advertisement, as well as a main effect for compatibility, such that users were twice as likely to click on an advertisement with content that was consistent with their keyword. Finally, there was a strong interaction of these two variables, such that the effect of consistent advertisements was stronger for promotion searches than for prevention searches. Research limitations/implications The effect of ad compatibility had medium to large effect sizes, suggesting that individuals’ state may have more influence on advertising response than do individuals’ traits (e.g. personality traits). Measurement of regulatory fit was limited by the constraints of Google AdWords. Practical implications The results of this study provide a possible framework for ad creation for Internet advertisers. Originality/value This paper is the first study to demonstrate the utility of regulatory focus theory in online advertising. PMID:26430293

  15. Application of Regulatory Focus Theory to Search Advertising.

    Science.gov (United States)

    Mowle, Elyse N; Georgia, Emily J; Doss, Brian D; Updegraff, John A

    The purpose of this paper is to test the utility of regulatory focus theory principles in a real-world setting; specifically, Internet hosted text advertisements. Effect of compatibility of the ad text with the regulatory focus of the consumer was examined. Advertisements were created using Google AdWords. Data were collected for the number of views and clicks each ad received. Effect of regulatory fit was measured using logistic regression. Logistic regression analyses demonstrated that there was a strong main effect for keyword, such that users were almost six times as likely to click on a promotion advertisement as a prevention advertisement, as well as a main effect for compatibility, such that users were twice as likely to click on an advertisement with content that was consistent with their keyword. Finally, there was a strong interaction of these two variables, such that the effect of consistent advertisements was stronger for promotion searches than for prevention searches. The effect of ad compatibility had medium to large effect sizes, suggesting that individuals' state may have more influence on advertising response than do individuals' traits (e.g. personality traits). Measurement of regulatory fit was limited by the constraints of Google AdWords. The results of this study provide a possible framework for ad creation for Internet advertisers. This paper is the first study to demonstrate the utility of regulatory focus theory in online advertising.

  16. Evaluating random search strategies in three mammals from distinct feeding guilds.

    Science.gov (United States)

    Auger-Méthé, Marie; Derocher, Andrew E; DeMars, Craig A; Plank, Michael J; Codling, Edward A; Lewis, Mark A

    2016-09-01

    Searching allows animals to find food, mates, shelter and other resources essential for survival and reproduction and is thus among the most important activities performed by animals. Theory predicts that animals will use random search strategies in highly variable and unpredictable environments. Two prominent models have been suggested for animals searching in sparse and heterogeneous environments: (i) the Lévy walk and (ii) the composite correlated random walk (CCRW) and its associated area-restricted search behaviour. Until recently, it was difficult to differentiate between the movement patterns of these two strategies. Using a new method that assesses whether movement patterns are consistent with these two strategies and two other common random search strategies, we investigated the movement behaviour of three species inhabiting sparse northern environments: woodland caribou (Rangifer tarandus caribou), barren-ground grizzly bear (Ursus arctos) and polar bear (Ursus maritimus). These three species vary widely in their diets and thus allow us to contrast the movement patterns of animals from different feeding guilds. Our results showed that although more traditional methods would have found evidence for the Lévy walk for some individuals, a comparison of the Lévy walk to CCRWs showed stronger support for the latter. While a CCRW was the best model for most individuals, there was a range of support for its absolute fit. A CCRW was sufficient to explain the movement of nearly half of herbivorous caribou and a quarter of omnivorous grizzly bears, but was insufficient to explain the movement of all carnivorous polar bears. Strong evidence for CCRW movement patterns suggests that many individuals may use a multiphasic movement strategy rather than one-behaviour strategies such as the Lévy walk. The fact that the best model was insufficient to describe the movement paths of many individuals suggests that some animals living in sparse environments may use

  17. Analysis of Search Engines and Meta Search Engines\\\\\\' Position by University of Isfahan Users Based on Rogers\\\\\\' Diffusion of Innovation Theory

    Directory of Open Access Journals (Sweden)

    Maryam Akbari

    2012-10-01

    Full Text Available The present study investigated the analysis of search engines and meta search engines adoption process by University of Isfahan users during 2009-2010 based on the Rogers' diffusion of innovation theory. The main aim of the research was to study the rate of adoption and recognizing the potentials and effective tools in search engines and meta search engines adoption among University of Isfahan users. The research method was descriptive survey study. The cases of the study were all of the post graduate students of the University of Isfahan. 351 students were selected as the sample and categorized by a stratified random sampling method. Questionnaire was used for collecting data. The collected data was analyzed using SPSS 16 in both descriptive and analytic statistic. For descriptive statistic frequency, percentage and mean were used, while for analytic statistic t-test and Kruskal-Wallis non parametric test (H-test were used. The finding of t-test and Kruscal-Wallis indicated that the mean of search engines and meta search engines adoption did not show statistical differences gender, level of education and the faculty. Special search engines adoption process was different in terms of gender but not in terms of the level of education and the faculty. Other results of the research indicated that among general search engines, Google had the most adoption rate. In addition, among the special search engines, Google Scholar and among the meta search engines Mamma had the most adopting rate. Findings also showed that friends played an important role on how students adopted general search engines while professors had important role on how students adopted special search engines and meta search engines. Moreover, results showed that the place where students got the most acquaintance with search engines and meta search engines was in the university. The finding showed that the curve of adoption rate was not normal and it was not also in S-shape. Morover

  18. Random matrix theory for heavy-tailed time series

    DEFF Research Database (Denmark)

    Heiny, Johannes

    2017-01-01

    This paper is a review of recent results for large random matrices with heavy-tailed entries. First, we outline the development of and some classical results in random matrix theory. We focus on large sample covariance matrices, their limiting spectral distributions, the asymptotic behavior...

  19. Random matrix theory for pseudo-Hermitian systems: Cyclic blocks

    Indian Academy of Sciences (India)

    We discuss the relevance of random matrix theory for pseudo-Hermitian systems, and, for Hamiltonians that break parity and time-reversal invariance . In an attempt to understand the random Ising model, we present the treatment of cyclic asymmetric matrices with blocks and show that the nearest-neighbour spacing ...

  20. Random matrix theory for pseudo-Hermitian systems: Cyclic blocks

    Indian Academy of Sciences (India)

    Abstract. We discuss the relevance of random matrix theory for pseudo-Hermitian sys- tems, and, for Hamiltonians that break parity P and time-reversal invariance T. In an attempt to understand the random Ising model, we present the treatment of cyclic asym- metric matrices with blocks and show that the nearest-neighbour ...

  1. Quasilinear theory without the random phase approximation

    International Nuclear Information System (INIS)

    Weibel, E.S.; Vaclavik, J.

    1980-08-01

    The system of quasilinear equations is derived without making use of the random phase approximation. The fluctuating quantities are described by the autocorrelation function of the electric field using the techniques of Fourier analysis. The resulting equations posses the necessary conservation properties, but comprise new terms which hitherto have been lost in the conventional derivations

  2. Guided basin-hopping search of small boron clusters with density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Ng, Wei Chun; Yoon, Tiem Leong [School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Lim, Thong Leng [Faculty of Engineering and Technology, Multimedia University, Melacca Campus, 75450 Melaka (Malaysia)

    2015-04-24

    The search for the ground state structures of Boron clusters has been a difficult computational task due to the unique metalloid nature of Boron atom. Previous research works had overcome the problem in the search of the Boron ground-state structures by adding symmetry constraints prior to the process of locating the local minima in the potential energy surface (PES) of the Boron clusters. In this work, we shown that, with the deployment of a novel computational approach that incorporates density functional theory (DFT) into a guided global optimization search algorithm based on basin-hopping, it is possible to directly locate the local minima of small Boron clusters in the PES at the DFT level. The ground-state structures search algorithm as proposed in this work is initiated randomly and needs not a priori symmetry constraint artificially imposed throughout the search process. Small sized Boron clusters so obtained compare well to the results obtained by similar calculations in the literature. The electronic properties of each structures obtained are calculated within the DFT framework.

  3. Guided basin-hopping search of small boron clusters with density functional theory

    International Nuclear Information System (INIS)

    Ng, Wei Chun; Yoon, Tiem Leong; Lim, Thong Leng

    2015-01-01

    The search for the ground state structures of Boron clusters has been a difficult computational task due to the unique metalloid nature of Boron atom. Previous research works had overcome the problem in the search of the Boron ground-state structures by adding symmetry constraints prior to the process of locating the local minima in the potential energy surface (PES) of the Boron clusters. In this work, we shown that, with the deployment of a novel computational approach that incorporates density functional theory (DFT) into a guided global optimization search algorithm based on basin-hopping, it is possible to directly locate the local minima of small Boron clusters in the PES at the DFT level. The ground-state structures search algorithm as proposed in this work is initiated randomly and needs not a priori symmetry constraint artificially imposed throughout the search process. Small sized Boron clusters so obtained compare well to the results obtained by similar calculations in the literature. The electronic properties of each structures obtained are calculated within the DFT framework

  4. Job Search and Social Cognitive Theory: The Role of Career-Relevant Activities

    Science.gov (United States)

    Zikic, Jelena; Saks, Alan M.

    2009-01-01

    Social cognitive theory was used to explain the relationships between career-relevant activities (environmental and self career exploration, career resources, and training), self-regulatory variables (job search self-efficacy and job search clarity), variables from the Theory of Planned Behavior (job search attitude, subjective norm, job search…

  5. Low-temperature random matrix theory at the soft edge

    International Nuclear Information System (INIS)

    Edelman, Alan; Persson, Per-Olof; Sutton, Brian D.

    2014-01-01

    “Low temperature” random matrix theory is the study of random eigenvalues as energy is removed. In standard notation, β is identified with inverse temperature, and low temperatures are achieved through the limit β → ∞. In this paper, we derive statistics for low-temperature random matrices at the “soft edge,” which describes the extreme eigenvalues for many random matrix distributions. Specifically, new asymptotics are found for the expected value and standard deviation of the general-β Tracy-Widom distribution. The new techniques utilize beta ensembles, stochastic differential operators, and Riccati diffusions. The asymptotics fit known high-temperature statistics curiously well and contribute to the larger program of general-β random matrix theory

  6. CALL FOR PAPERS: Special issue on the random search problem: trends and perspectives

    Science.gov (United States)

    da Luz, Marcos G. E.; Grosberg, Alexander Y.; Raposo, Ernesto P.; Viswanathan, Gandhi M.

    2008-11-01

    This is a call for contributions to a special issue of Journal of Physics A: Mathematical and Theoretical dedicated to the subject of the random search problem. The motivation behind this special issue is to summarize in a single comprehensive publication, the main aspects (past and present), latest developments, different viewpoints and the directions being followed in this multidisciplinary field. We hope that such a special issue could become a particularly valuable reference for the broad scientific community working with the general random search problem. The Editorial Board has invited Marcos G E da Luz, Alexander Y Grosberg, Ernesto P Raposo and Gandhi M Viswanathan to serve as Guest Editors for the special issue. The general question of how to optimize the search for specific target objects in either continuous or discrete environments when the information available is limited is of significant importance in a broad range of fields. Representative examples include ecology (animal foraging, dispersion of populations), geology (oil recovery from mature reservoirs), information theory (automated researchers of registers in high-capacity database), molecular biology (proteins searching for their sites, e.g., on DNA ), etc. One reason underlying the richness of the random search problem relates to the `ignorance' of the locations of the randomly located `targets'. A statistical approach to the search problem can deal adequately with incomplete information and so stochastic strategies become advantageous. The general problem of how to search efficiently for randomly located target sites can thus be quantitatively described using the concepts and methods of statistical physics and stochastic processes. Scope Thus far, to the best of our knowledge, no recent textbook or review article in a physics journal has appeared on this topic. This makes a special issue with review and research articles attractive to those interested in acquiring a general introduction to the

  7. The Theory of Planned Behaviour Applied to Search Engines as a Learning Tool

    Science.gov (United States)

    Liaw, Shu-Sheng

    2004-01-01

    Search engines have been developed for helping learners to seek online information. Based on theory of planned behaviour approach, this research intends to investigate the behaviour of using search engines as a learning tool. After factor analysis, the results suggest that perceived satisfaction of search engine, search engines as an information…

  8. Problems in probability theory, mathematical statistics and theory of random functions

    CERN Document Server

    Sveshnikov, A A

    1979-01-01

    Problem solving is the main thrust of this excellent, well-organized workbook. Suitable for students at all levels in probability theory and statistics, the book presents over 1,000 problems and their solutions, illustrating fundamental theory and representative applications in the following fields: Random Events; Distribution Laws; Correlation Theory; Random Variables; Entropy & Information; Markov Processes; Systems of Random Variables; Limit Theorems; Data Processing; and more.The coverage of topics is both broad and deep, ranging from the most elementary combinatorial problems through lim

  9. Expected Fitness Gains of Randomized Search Heuristics for the Traveling Salesperson Problem.

    Science.gov (United States)

    Nallaperuma, Samadhi; Neumann, Frank; Sudholt, Dirk

    2017-01-01

    Randomized search heuristics are frequently applied to NP-hard combinatorial optimization problems. The runtime analysis of randomized search heuristics has contributed tremendously to our theoretical understanding. Recently, randomized search heuristics have been examined regarding their achievable progress within a fixed-time budget. We follow this approach and present a fixed-budget analysis for an NP-hard combinatorial optimization problem. We consider the well-known Traveling Salesperson Problem (TSP) and analyze the fitness increase that randomized search heuristics are able to achieve within a given fixed-time budget. In particular, we analyze Manhattan and Euclidean TSP instances and Randomized Local Search (RLS), (1+1) EA and (1+[Formula: see text]) EA algorithms for the TSP in a smoothed complexity setting, and derive the lower bounds of the expected fitness gain for a specified number of generations.

  10. Raney Distributions and Random Matrix Theory

    Science.gov (United States)

    Forrester, Peter J.; Liu, Dang-Zheng

    2015-03-01

    Recent works have shown that the family of probability distributions with moments given by the Fuss-Catalan numbers permit a simple parameterized form for their density. We extend this result to the Raney distribution which by definition has its moments given by a generalization of the Fuss-Catalan numbers. Such computations begin with an algebraic equation satisfied by the Stieltjes transform, which we show can be derived from the linear differential equation satisfied by the characteristic polynomial of random matrix realizations of the Raney distribution. For the Fuss-Catalan distribution, an equilibrium problem characterizing the density is identified. The Stieltjes transform for the limiting spectral density of the singular values squared of the matrix product formed from inverse standard Gaussian matrices, and standard Gaussian matrices, is shown to satisfy a variant of the algebraic equation relating to the Raney distribution. Supported on , we show that it too permits a simple functional form upon the introduction of an appropriate choice of parameterization. As an application, the leading asymptotic form of the density as the endpoints of the support are approached is computed, and is shown to have some universal features.

  11. Chaotic motion and random matrix theories

    International Nuclear Information System (INIS)

    Bohigas, O.; Giannoni, M.J.

    1983-01-01

    The authors discussed how to characterize level fluctuations. In full generality, one needs the set of k-level cluster functions Y/sub k/. Some of the most relevant qualitative features of GOE fluctuations have been emphasized: level repulsion (small probability of occurrence of small spacings) and spectral rigidity (for instance, logarithmic increase with L of the variance of the number of levels to be found in an interval of length L). This is in contrast with what happens for a spectrum obtained by adding spacings coming from random independent trials distributed like e/sup - x/, viz.a Poisson spectrum. In this case there is by construction no level repulsion but level clustering (the variance of the number of levels increases linearly with L). The effect of level repulsion is that levels appear rather evenly distributed, and when spectral rigidity is present the spectrum looks incompressible. It is important to notice that the spacing distribution p(x) contains no information about spacing correlations, one of the main characteristics of GOE-fluctuation patterns. The role of exact symmetries is prominent and GOE-predictions apply to levels having the same set of exact quantum number (Jπ)

  12. Universality in chaos: Lyapunov spectrum and random matrix theory

    Science.gov (United States)

    Hanada, Masanori; Shimada, Hidehiko; Tezuka, Masaki

    2018-02-01

    We propose the existence of a new universality in classical chaotic systems when the number of degrees of freedom is large: the statistical property of the Lyapunov spectrum is described by random matrix theory. We demonstrate it by studying the finite-time Lyapunov exponents of the matrix model of a stringy black hole and the mass-deformed models. The massless limit, which has a dual string theory interpretation, is special in that the universal behavior can be seen already at t =0 , while in other cases it sets in at late time. The same pattern is demonstrated also in the product of random matrices.

  13. Universality in chaos: Lyapunov spectrum and random matrix theory.

    Science.gov (United States)

    Hanada, Masanori; Shimada, Hidehiko; Tezuka, Masaki

    2018-02-01

    We propose the existence of a new universality in classical chaotic systems when the number of degrees of freedom is large: the statistical property of the Lyapunov spectrum is described by random matrix theory. We demonstrate it by studying the finite-time Lyapunov exponents of the matrix model of a stringy black hole and the mass-deformed models. The massless limit, which has a dual string theory interpretation, is special in that the universal behavior can be seen already at t=0, while in other cases it sets in at late time. The same pattern is demonstrated also in the product of random matrices.

  14. Blind Measurement Selection: A Random Matrix Theory Approach

    KAUST Repository

    Elkhalil, Khalil

    2016-12-14

    This paper considers the problem of selecting a set of $k$ measurements from $n$ available sensor observations. The selected measurements should minimize a certain error function assessing the error in estimating a certain $m$ dimensional parameter vector. The exhaustive search inspecting each of the $n\\\\choose k$ possible choices would require a very high computational complexity and as such is not practical for large $n$ and $k$. Alternative methods with low complexity have recently been investigated but their main drawbacks are that 1) they require perfect knowledge of the measurement matrix and 2) they need to be applied at the pace of change of the measurement matrix. To overcome these issues, we consider the asymptotic regime in which $k$, $n$ and $m$ grow large at the same pace. Tools from random matrix theory are then used to approximate in closed-form the most important error measures that are commonly used. The asymptotic approximations are then leveraged to select properly $k$ measurements exhibiting low values for the asymptotic error measures. Two heuristic algorithms are proposed: the first one merely consists in applying the convex optimization artifice to the asymptotic error measure. The second algorithm is a low-complexity greedy algorithm that attempts to look for a sufficiently good solution for the original minimization problem. The greedy algorithm can be applied to both the exact and the asymptotic error measures and can be thus implemented in blind and channel-aware fashions. We present two potential applications where the proposed algorithms can be used, namely antenna selection for uplink transmissions in large scale multi-user systems and sensor selection for wireless sensor networks. Numerical results are also presented and sustain the efficiency of the proposed blind methods in reaching the performances of channel-aware algorithms.

  15. An infinite-dimensional weak KAM theory via random variables

    KAUST Repository

    Gomes, Diogo A.; Nurbekyan, Levon

    2016-01-01

    We develop several aspects of the infinite-dimensional Weak KAM theory using a random variables' approach. We prove that the infinite-dimensional cell problem admits a viscosity solution that is a fixed point of the Lax-Oleinik semigroup. Furthermore, we show the existence of invariant minimizing measures and calibrated curves defined on R.

  16. An infinite-dimensional weak KAM theory via random variables

    KAUST Repository

    Gomes, Diogo A.

    2016-08-31

    We develop several aspects of the infinite-dimensional Weak KAM theory using a random variables\\' approach. We prove that the infinite-dimensional cell problem admits a viscosity solution that is a fixed point of the Lax-Oleinik semigroup. Furthermore, we show the existence of invariant minimizing measures and calibrated curves defined on R.

  17. Generating functionals for quantum field theories with random potentials

    International Nuclear Information System (INIS)

    Jain, Mudit; Vanchurin, Vitaly

    2016-01-01

    We consider generating functionals for computing correlators in quantum field theories with random potentials. Examples of such theories include cosmological systems in context of the string theory landscape (e.g. cosmic inflation) or condensed matter systems with quenched disorder (e.g. spin glass). We use the so-called replica trick to define two different generating functionals for calculating correlators of the quantum fields averaged over a given distribution of random potentials. The first generating functional is appropriate for calculating averaged (in-out) amplitudes and involves a single replica of fields, but the replica limit is taken to an (unphysical) negative one number of fields outside of the path integral. When the number of replicas is doubled the generating functional can also be used for calculating averaged probabilities (squared amplitudes) using the in-in construction. The second generating functional involves an infinite number of replicas, but can be used for calculating both in-out and in-in correlators and the replica limits are taken to only a zero number of fields. We discuss the formalism in details for a single real scalar field, but the generalization to more fields or to different types of fields is straightforward. We work out three examples: one where the mass of scalar field is treated as a random variable and two where the functional form of interactions is random, one described by a Gaussian random field and the other by a Euclidean action in the field configuration space.

  18. Literature search strategies for conducting knowledge-building and theory-generating qualitative systematic reviews.

    Science.gov (United States)

    Finfgeld-Connett, Deborah; Johnson, E Diane

    2013-01-01

    To report literature search strategies for the purpose of conducting knowledge-building and theory-generating qualitative systematic reviews. Qualitative systematic reviews lie on a continuum from knowledge-building and theory-generating to aggregating and summarizing. Different types of literature searches are needed to optimally support these dissimilar reviews. Articles published between 1989-Autumn 2011. These documents were identified using a hermeneutic approach and multiple literature search strategies. Redundancy is not the sole measure of validity when conducting knowledge-building and theory-generating systematic reviews. When conducting these types of reviews, literature searches should be consistent with the goal of fully explicating concepts and the interrelationships among them. To accomplish this objective, a 'berry picking' approach is recommended along with strategies for overcoming barriers to finding qualitative research reports. To enhance integrity of knowledge-building and theory-generating systematic reviews, reviewers are urged to make literature search processes as transparent as possible, despite their complexity. This includes fully explaining and rationalizing what databases were used and how they were searched. It also means describing how literature tracking was conducted and grey literature was searched. In the end, the decision to cease searching also needs to be fully explained and rationalized. Predetermined linear search strategies are unlikely to generate search results that are adequate for purposes of conducting knowledge-building and theory-generating qualitative systematic reviews. Instead, it is recommended that iterative search strategies take shape as reviews evolve. © 2012 Blackwell Publishing Ltd.

  19. Random matrix theory in nuclear structure: past, present and future

    International Nuclear Information System (INIS)

    Kota, V.K.B.

    2012-01-01

    Random matrix theory (RMT) introduced by Wigner in 50's to describe statistical properties of slow-neutron resonances in heavy nuclei such as 232 Th, was developed further in the 60's by Dyson, Mehta, Porter and others and in the 70's by French, Pandey, Bohigas and others. Going beyond this, the demonstration that level fluctuations of quantum analogues of classically chaotic few-degrees-of-freedom systems follow random matrix theory (integrable systems follow Poisson as shown by Berry) in 1984 by Bohigas and others on one hand and the recognition from 1995 onwards that two-body random matrix ensembles derived from shell model have wide ranging applications on the other, defined new directions in RMT applications in nuclear physics. Growth points in RMT in nuclear physics are: (i) analysis of nuclear data looking for order-chaos transitions and symmetry (Time-reversal, Parity, Isospin) breaking; (ii) analysis of shell model driven embedded (or two-body) random matrix ensembles giving statistical properties generated by random interactions in the presence of a mean-field; (iii) statistical nuclear spectroscopy generated by embedded ensembles for level densities, occupancies, GT strengths, transition strength sums and so on; (iv) the new paradigm of regular structures generated by random interactions as brought out by studies using various nuclear models; (v) random matrix theory for nuclear reactions with particular reference to open quantum systems; (vi) RMT results from nuclear physics to atomic physics, mesoscopic physics and quantum information science. Topics (i)-(vi) emphasizing recent results are discussed. (author)

  20. Renewal theory for perturbed random walks and similar processes

    CERN Document Server

    Iksanov, Alexander

    2016-01-01

    This book offers a detailed review of perturbed random walks, perpetuities, and random processes with immigration. Being of major importance in modern probability theory, both theoretical and applied, these objects have been used to model various phenomena in the natural sciences as well as in insurance and finance. The book also presents the many significant results and efficient techniques and methods that have been worked out in the last decade. The first chapter is devoted to perturbed random walks and discusses their asymptotic behavior and various functionals pertaining to them, including supremum and first-passage time. The second chapter examines perpetuities, presenting results on continuity of their distributions and the existence of moments, as well as weak convergence of divergent perpetuities. Focusing on random processes with immigration, the third chapter investigates the existence of moments, describes long-time behavior and discusses limit theorems, both with and without scaling. Chapters fou...

  1. Ab initio random structure search for 13-atom clusters of fcc elements

    International Nuclear Information System (INIS)

    Chou, J P; Hsing, C R; Wei, C M; Cheng, C; Chang, C M

    2013-01-01

    The 13-atom metal clusters of fcc elements (Al, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au) were studied by density functional theory calculations. The global minima were searched for by the ab initio random structure searching method. In addition to some new lowest-energy structures for Pd 13 and Au 13 , we found that the effective coordination numbers of the lowest-energy clusters would increase with the ratio of the dimer-to-bulk bond length. This correlation, together with the electronic structures of the lowest-energy clusters, divides the 13-atom clusters of these fcc elements into two groups (except for Au 13 , which prefers a two-dimensional structure due to the relativistic effect). Compact-like clusters that are composed exclusively of triangular motifs are preferred for elements without d-electrons (Al) or with (nearly) filled d-band electrons (Ni, Pd, Cu, Ag). Non-compact clusters composed mainly of square motifs connected by some triangular motifs (Rh, Ir, Pt) are favored for elements with unfilled d-band electrons. (paper)

  2. Quantify uncertain emergency search techniques (QUEST) -- Theory and user's guide

    International Nuclear Information System (INIS)

    Johnson, M.M.; Goldsby, M.E.; Plantenga, T.D.; Porter, T.L.; West, T.H.; Wilcox, W.B.; Hensley, W.K.

    1998-01-01

    As recent world events show, criminal and terrorist access to nuclear materials is a growing national concern. The national laboratories are taking the lead in developing technologies to counter these potential threats to the national security. Sandia National laboratories, with support from Pacific Northwest National Laboratory and the Bechtel Nevada, Remote Sensing Laboratory, has developed QUEST (a model to Quantify Uncertain Emergency Search Techniques), to enhance the performance of organizations in the search for lost or stolen nuclear material. In addition, QUEST supports a wide range of other applications, such as environmental monitoring, nuclear facilities inspections, and searcher training. QUEST simulates the search for nuclear materials and calculates detector response for various source types and locations. The probability of detecting a radioactive source during a search is a function of many different variables, including source type, search location and structure geometry (including shielding), search dynamics (path and speed), and detector type and size. Through calculation of dynamic detector response, QUEST makes possible quantitative comparisons of various sensor technologies and search patterns. The QUEST model can be used as a tool to examine the impact of new detector technologies, explore alternative search concepts, and provide interactive search/inspector training

  3. An adaptive random search for short term generation scheduling with network constraints.

    Directory of Open Access Journals (Sweden)

    J A Marmolejo

    Full Text Available This paper presents an adaptive random search approach to address a short term generation scheduling with network constraints, which determines the startup and shutdown schedules of thermal units over a given planning horizon. In this model, we consider the transmission network through capacity limits and line losses. The mathematical model is stated in the form of a Mixed Integer Non Linear Problem with binary variables. The proposed heuristic is a population-based method that generates a set of new potential solutions via a random search strategy. The random search is based on the Markov Chain Monte Carlo method. The main key of the proposed method is that the noise level of the random search is adaptively controlled in order to exploring and exploiting the entire search space. In order to improve the solutions, we consider coupling a local search into random search process. Several test systems are presented to evaluate the performance of the proposed heuristic. We use a commercial optimizer to compare the quality of the solutions provided by the proposed method. The solution of the proposed algorithm showed a significant reduction in computational effort with respect to the full-scale outer approximation commercial solver. Numerical results show the potential and robustness of our approach.

  4. Theory of activated glassy dynamics in randomly pinned fluids

    Science.gov (United States)

    Phan, Anh D.; Schweizer, Kenneth S.

    2018-02-01

    We generalize the force-level, microscopic, Nonlinear Langevin Equation (NLE) theory and its elastically collective generalization [elastically collective nonlinear Langevin equation (ECNLE) theory] of activated dynamics in bulk spherical particle liquids to address the influence of random particle pinning on structural relaxation. The simplest neutral confinement model is analyzed for hard spheres where there is no change of the equilibrium pair structure upon particle pinning. As the pinned fraction grows, cage scale dynamical constraints are intensified in a manner that increases with density. This results in the mobile particles becoming more transiently localized, with increases of the jump distance, cage scale barrier, and NLE theory mean hopping time; subtle changes of the dynamic shear modulus are predicted. The results are contrasted with recent simulations. Similarities in relaxation behavior are identified in the dynamic precursor regime, including a roughly exponential, or weakly supra-exponential, growth of the alpha time with pinning fraction and a reduction of dynamic fragility. However, the increase of the alpha time with pinning predicted by the local NLE theory is too small and severely so at very high volume fractions. The strong deviations are argued to be due to the longer range collective elasticity aspect of the problem which is expected to be modified by random pinning in a complex manner. A qualitative physical scenario is offered for how the three distinct aspects that quantify the elastic barrier may change with pinning. ECNLE theory calculations of the alpha time are then presented based on the simplest effective-medium-like treatment for how random pinning modifies the elastic barrier. The results appear to be consistent with most, but not all, trends seen in recent simulations. Key open problems are discussed with regard to both theory and simulation.

  5. On the expected duration of a search for a fixed pattern in random data

    DEFF Research Database (Denmark)

    Nielsen, Peter Tolstrup

    1973-01-01

    An expression is obtained for the expected duration of a search to find a givenL-ary sequence in a semi-infinite stream of randomL-ary data. The search time is found to be an increasing function of the lengths of the "bifices" of the pattern, where the term bifix denotes a sequence which is both...

  6. Statistical mechanics and stability of random lattice field theory

    International Nuclear Information System (INIS)

    Baskaran, G.

    1984-01-01

    The averaging procedure in the random lattice field theory is studied by viewing it as a statistical mechanics of a system of classical particles. The corresponding thermodynamic phase is shown to determine the random lattice configuration which contributes dominantly to the generating function. The non-abelian gauge theory in four (space plus time) dimensions in the annealed and quenched averaging versions is shown to exist as an ideal classical gas, implying that macroscopically homogeneous configurations dominate the configurational averaging. For the free massless scalar field theory with O(n) global symmetry, in the annealed average, the pressure becomes negative for dimensions greater than two when n exceeds a critical number. This implies that macroscopically inhomogeneous collapsed configurations contribute dominantly. In the quenched averaging, the collapse of the massless scalar field theory is prevented and the system becomes an ideal gas which is at infinite temperature. Our results are obtained using exact scaling analysis. We also show approximately that SU(N) gauge theory collapses for dimensions greater than four in the annealed average. Within the same approximation, the collapse is prevented in the quenched average. We also obtain exact scaling differential equations satisfied by the generating function and physical quantities. (orig.)

  7. Phase stability of random brasses: pseudopotential theory revisited

    International Nuclear Information System (INIS)

    Rahman, S.M.M.

    1987-06-01

    We review the theoretical development concerning the phase stability of random brasses. The introductory discussion of the subject embraces the rules of metallurgy in general, but we emphasize on the roles of electron-per-atom ratio in the major bulk of our discussion. Starting from the so-called rigid-band model the discussion goes up to the recent higher-order pseudopotential theory. The theoretical refinements within the pseudopotential framework are discussed briefly. The stability criteria of the random phases are analysed both in the static lattice and dynamic lattice approximations. (author). 71 refs, figs and tabs

  8. Random discrete Morse theory and a new library of triangulations

    DEFF Research Database (Denmark)

    Benedetti, Bruno; Lutz, Frank Hagen

    2014-01-01

    We introduce random discrete Morse theory as a computational scheme to measure the complexity of a triangulation. The idea is to try to quantify the frequency of discrete Morse matchings with few critical cells. Our measure will depend on the topology of the space, but also on how nicely the space...... is triangulated. The scheme we propose looks for optimal discrete Morse functions with an elementary random heuristic. Despite its naiveté, this approach turns out to be very successful even in the case of huge inputs. In our view, the existing libraries of examples in computational topology are “too easy......” for testing algorithms based on discrete Morse theory. We propose a new library containing more complicated (and thus more meaningful) test examples....

  9. On the Runtime of Randomized Local Search and Simple Evolutionary Algorithms for Dynamic Makespan Scheduling

    DEFF Research Database (Denmark)

    Neumann, Frank; Witt, Carsten

    2015-01-01

    combinatorial optimization problem, namely makespan scheduling. We study the model of a strong adversary which is allowed to change one job at regular intervals. Furthermore, we investigate the setting of random changes. Our results show that randomized local search and a simple evolutionary algorithm are very...

  10. Theory Learning as Stochastic Search in the Language of Thought

    Science.gov (United States)

    Ullman, Tomer D.; Goodman, Noah D.; Tenenbaum, Joshua B.

    2012-01-01

    We present an algorithmic model for the development of children's intuitive theories within a hierarchical Bayesian framework, where theories are described as sets of logical laws generated by a probabilistic context-free grammar. We contrast our approach with connectionist and other emergentist approaches to modeling cognitive development. While…

  11. Cuckoo search and firefly algorithm theory and applications

    CERN Document Server

    2014-01-01

    Nature-inspired algorithms such as cuckoo search and firefly algorithm have become popular and widely used in recent years in many applications. These algorithms are flexible, efficient and easy to implement. New progress has been made in the last few years, and it is timely to summarize the latest developments of cuckoo search and firefly algorithm and their diverse applications. This book will review both theoretical studies and applications with detailed algorithm analysis, implementation and case studies so that readers can benefit most from this book.  Application topics are contributed by many leading experts in the field. Topics include cuckoo search, firefly algorithm, algorithm analysis, feature selection, image processing, travelling salesman problem, neural network, GPU optimization, scheduling, queuing, multi-objective manufacturing optimization, semantic web service, shape optimization, and others.   This book can serve as an ideal reference for both graduates and researchers in computer scienc...

  12. Emergence of an optimal search strategy from a simple random walk.

    Science.gov (United States)

    Sakiyama, Tomoko; Gunji, Yukio-Pegio

    2013-09-06

    In reports addressing animal foraging strategies, it has been stated that Lévy-like algorithms represent an optimal search strategy in an unknown environment, because of their super-diffusion properties and power-law-distributed step lengths. Here, starting with a simple random walk algorithm, which offers the agent a randomly determined direction at each time step with a fixed move length, we investigated how flexible exploration is achieved if an agent alters its randomly determined next step forward and the rule that controls its random movement based on its own directional moving experiences. We showed that our algorithm led to an effective food-searching performance compared with a simple random walk algorithm and exhibited super-diffusion properties, despite the uniform step lengths. Moreover, our algorithm exhibited a power-law distribution independent of uniform step lengths.

  13. Random matrix theory for transition strengths: Applications and open questions

    Science.gov (United States)

    Kota, V. K. B.

    2017-12-01

    Embedded random matrix ensembles are generic models for describing statistical properties of finite isolated interacting quantum many-particle systems. A finite quantum system, induced by a transition operator, makes transitions from its states to the states of the same system or to those of another system. Examples are electromagnetic transitions (then the initial and final systems are same), nuclear beta and double beta decay (then the initial and final systems are different) and so on. Using embedded ensembles (EE), there are efforts to derive a good statistical theory for transition strengths. With m fermions (or bosons) in N mean-field single particle levels and interacting via two-body forces, we have with GOE embedding, the so called EGOE(1+2). Now, the transition strength density (transition strength multiplied by the density of states at the initial and final energies) is a convolution of the density generated by the mean-field one-body part with a bivariate spreading function due to the two-body interaction. Using the embedding U(N) algebra, it is established, for a variety of transition operators, that the spreading function, for sufficiently strong interactions, is close to a bivariate Gaussian. Also, as the interaction strength increases, the spreading function exhibits a transition from bivariate Breit-Wigner to bivariate Gaussian form. In appropriate limits, this EE theory reduces to the polynomial theory of Draayer, French and Wong on one hand and to the theory due to Flambaum and Izrailev for one-body transition operators on the other. Using spin-cutoff factors for projecting angular momentum, the theory is applied to nuclear matrix elements for neutrinoless double beta decay (NDBD). In this paper we will describe: (i) various developments in the EE theory for transition strengths; (ii) results for nuclear matrix elements for 130Te and 136Xe NDBD; (iii) important open questions in the current form of the EE theory.

  14. A random-matrix theory of the number sense.

    Science.gov (United States)

    Hannagan, T; Nieder, A; Viswanathan, P; Dehaene, S

    2017-02-19

    Number sense, a spontaneous ability to process approximate numbers, has been documented in human adults, infants and newborns, and many other animals. Species as distant as monkeys and crows exhibit very similar neurons tuned to specific numerosities. How number sense can emerge in the absence of learning or fine tuning is currently unknown. We introduce a random-matrix theory of self-organized neural states where numbers are coded by vectors of activation across multiple units, and where the vector codes for successive integers are obtained through multiplication by a fixed but random matrix. This cortical implementation of the 'von Mises' algorithm explains many otherwise disconnected observations ranging from neural tuning curves in monkeys to looking times in neonates and cortical numerotopy in adults. The theory clarifies the origin of Weber-Fechner's Law and yields a novel and empirically validated prediction of multi-peak number neurons. Random matrices constitute a novel mechanism for the emergence of brain states coding for quantity.This article is part of a discussion meeting issue 'The origins of numerical abilities'. © 2017 The Author(s).

  15. Superstrings and the search for the theory of everything

    International Nuclear Information System (INIS)

    Peat, D.

    1988-01-01

    This book contains the following chapters: A Crisis in Physics; From Points to Strings; Nambu's String Theory; Grand Unification; Superstrings; Heterotic Strings: Two Dimensions in One; From Spinors to Twistors; Twistor Space; Twistor Gravity; and Into Deep Waters

  16. Parametric Level Statistics in Random Matrix Theory: Exact Solution

    International Nuclear Information System (INIS)

    Kanzieper, E.

    1999-01-01

    During recent several years, the theory of non-Gaussian random matrix ensembles has experienced a sound progress motivated by new ideas in quantum chromodynamics (QCD) and mesoscopic physics. Invariant non-Gaussian random matrix models appear to describe universal features of low-energy part of the spectrum of Dirac operator in QCD, and electron level statistics in normal conducting-superconducting hybrid structures. They also serve as a basis for constructing the toy models of universal spectral statistics expected at the edge of the metal-insulator transition. While conventional spectral statistics has received a detailed study in the context of RMT, quite a bit is known about parametric level statistics in non-Gaussian random matrix models. In this communication we report about exact solution to the problem of parametric level statistics in unitary invariant, U(N), non-Gaussian ensembles of N x N Hermitian random matrices with either soft or strong level confinement. The solution is formulated within the framework of the orthogonal polynomial technique and is shown to depend on both the unfolded two-point scalar kernel and the level confinement through a double integral transformation which, in turn, provides a constructive tool for description of parametric level correlations in non-Gaussian RMT. In the case of soft level confinement, the formalism developed is potentially applicable to a study of parametric level statistics in an important class of random matrix models with finite level compressibility expected to describe a disorder-induced metal-insulator transition. In random matrix ensembles with strong level confinement, the solution presented takes a particular simple form in the thermodynamic limit: In this case, a new intriguing connection relation between the parametric level statistics and the scalar two-point kernel of an unperturbed ensemble is demonstrated to emerge. Extension of the results obtained to higher-order parametric level statistics is

  17. Skew-orthogonal polynomials and random matrix theory

    CERN Document Server

    Ghosh, Saugata

    2009-01-01

    Orthogonal polynomials satisfy a three-term recursion relation irrespective of the weight function with respect to which they are defined. This gives a simple formula for the kernel function, known in the literature as the Christoffel-Darboux sum. The availability of asymptotic results of orthogonal polynomials and the simple structure of the Christoffel-Darboux sum make the study of unitary ensembles of random matrices relatively straightforward. In this book, the author develops the theory of skew-orthogonal polynomials and obtains recursion relations which, unlike orthogonal polynomials, depend on weight functions. After deriving reduced expressions, called the generalized Christoffel-Darboux formulas (GCD), he obtains universal correlation functions and non-universal level densities for a wide class of random matrix ensembles using the GCD. The author also shows that once questions about higher order effects are considered (questions that are relevant in different branches of physics and mathematics) the ...

  18. Exact Markov chains versus diffusion theory for haploid random mating.

    Science.gov (United States)

    Tyvand, Peder A; Thorvaldsen, Steinar

    2010-05-01

    Exact discrete Markov chains are applied to the Wright-Fisher model and the Moran model of haploid random mating. Selection and mutations are neglected. At each discrete value of time t there is a given number n of diploid monoecious organisms. The evolution of the population distribution is given in diffusion variables, to compare the two models of random mating with their common diffusion limit. Only the Moran model converges uniformly to the diffusion limit near the boundary. The Wright-Fisher model allows the population size to change with the generations. Diffusion theory tends to under-predict the loss of genetic information when a population enters a bottleneck. 2010 Elsevier Inc. All rights reserved.

  19. Cooperative random Levy flight searches and the flight patterns of honeybees

    International Nuclear Information System (INIS)

    Reynolds, A.M.

    2006-01-01

    The most efficient Levy flight (scale-free) searching strategy for N independent searchers to adopt when target sites are randomly and sparsely distributed is identified. For N=1, it is well known that the optimal searching strategy is attained when μ=2, where the exponent μ characterizes the Levy distribution, P(l)=l -μ , of flight-lengths. For N>1, the optimal searching strategy is attained as μ->1. It is suggested that the orientation flights of honeybees can be understood within the context of such an optimal cooperative random Levy flight searching strategy. Upon returning to their hive after surveying a landscape honeybees can exchange information about the locations of target sites through the waggle dance. In accordance with observations it is predicted that the waggle dance can be disrupted without noticeable influence on a hive's ability to maintain weight when forage is plentiful

  20. Random matrix theory and portfolio optimization in Moroccan stock exchange

    Science.gov (United States)

    El Alaoui, Marwane

    2015-09-01

    In this work, we use random matrix theory to analyze eigenvalues and see if there is a presence of pertinent information by using Marčenko-Pastur distribution. Thus, we study cross-correlation among stocks of Casablanca Stock Exchange. Moreover, we clean correlation matrix from noisy elements to see if the gap between predicted risk and realized risk would be reduced. We also analyze eigenvectors components distributions and their degree of deviations by computing the inverse participation ratio. This analysis is a way to understand the correlation structure among stocks of Casablanca Stock Exchange portfolio.

  1. Enumeration of RNA complexes via random matrix theory

    DEFF Research Database (Denmark)

    Andersen, Jørgen E; Chekhov, Leonid O.; Penner, Robert C

    2013-01-01

    molecules and hydrogen bonds in a given complex. The free energies of this matrix model are computed using the so-called topological recursion, which is a powerful new formalism arising from random matrix theory. These numbers of RNA complexes also have profound meaning in mathematics: they provide......In the present article, we review a derivation of the numbers of RNA complexes of an arbitrary topology. These numbers are encoded in the free energy of the Hermitian matrix model with potential V(x)=x(2)/2 - stx/(1 - tx), where s and t are respective generating parameters for the number of RNA...

  2. Saddle-points of a two dimensional random lattice theory

    International Nuclear Information System (INIS)

    Pertermann, D.

    1985-07-01

    A two dimensional random lattice theory with a free massless scalar field is considered. We analyse the field theoretic generating functional for any given choice of positions of the lattice sites. Asking for saddle-points of this generating functional with respect to the positions we find the hexagonal lattice and a triangulated version of the hypercubic lattice as candidates. The investigation of the neighbourhood of a single lattice site yields triangulated rectangles and regular polygons extremizing the above generating functional on the local level. (author)

  3. Application of random matrix theory to biological networks

    Energy Technology Data Exchange (ETDEWEB)

    Luo Feng [Department of Computer Science, Clemson University, 100 McAdams Hall, Clemson, SC 29634 (United States); Department of Pathology, U.T. Southwestern Medical Center, 5323 Harry Hines Blvd. Dallas, TX 75390-9072 (United States); Zhong Jianxin [Department of Physics, Xiangtan University, Hunan 411105 (China) and Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)]. E-mail: zhongjn@ornl.gov; Yang Yunfeng [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Scheuermann, Richard H. [Department of Pathology, U.T. Southwestern Medical Center, 5323 Harry Hines Blvd. Dallas, TX 75390-9072 (United States); Zhou Jizhong [Department of Botany and Microbiology, University of Oklahoma, Norman, OK 73019 (United States) and Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)]. E-mail: zhouj@ornl.gov

    2006-09-25

    We show that spectral fluctuation of interaction matrices of a yeast protein-protein interaction network and a yeast metabolic network follows the description of the Gaussian orthogonal ensemble (GOE) of random matrix theory (RMT). Furthermore, we demonstrate that while the global biological networks evaluated belong to GOE, removal of interactions between constituents transitions the networks to systems of isolated modules described by the Poisson distribution. Our results indicate that although biological networks are very different from other complex systems at the molecular level, they display the same statistical properties at network scale. The transition point provides a new objective approach for the identification of functional modules.

  4. Communication: Random phase approximation renormalized many-body perturbation theory

    International Nuclear Information System (INIS)

    Bates, Jefferson E.; Furche, Filipp

    2013-01-01

    We derive a renormalized many-body perturbation theory (MBPT) starting from the random phase approximation (RPA). This RPA-renormalized perturbation theory extends the scope of single-reference MBPT methods to small-gap systems without significantly increasing the computational cost. The leading correction to RPA, termed the approximate exchange kernel (AXK), substantially improves upon RPA atomization energies and ionization potentials without affecting other properties such as barrier heights where RPA is already accurate. Thus, AXK is more balanced than second-order screened exchange [A. Grüneis et al., J. Chem. Phys. 131, 154115 (2009)], which tends to overcorrect RPA for systems with stronger static correlation. Similarly, AXK avoids the divergence of second-order Møller-Plesset (MP2) theory for small gap systems and delivers a much more consistent performance than MP2 across the periodic table at comparable cost. RPA+AXK thus is an accurate, non-empirical, and robust tool to assess and improve semi-local density functional theory for a wide range of systems previously inaccessible to first-principles electronic structure calculations

  5. Mathematical conversations multicolor problems, problems in the theory of numbers, and random walks

    CERN Document Server

    Dynkin, E B

    2006-01-01

    Comprises Multicolor Problems, dealing with map-coloring problems; Problems in the Theory of Numbers, an elementary introduction to algebraic number theory; Random Walks, addressing basic problems in probability theory. 1963 edition.

  6. Searching for axions and ALPs from string theory

    Energy Technology Data Exchange (ETDEWEB)

    Ringwald, Andreas

    2012-09-15

    We review searches for closed string axions and axion-like particles (ALPs) in IIB string flux compactifications. For natural values of the background fluxes and TeV scale gravitino mass, the moduli stabilisation mechanism of the LARGE Volume Scenario predicts the existence of a QCD axion candidate with intermediate scale decay constant, f{sub a} {proportional_to}10{sup 9/12} GeV, associated with the small cycles wrapped by the branes hosting the visible sector, plus a nearly massless and nearly decoupled ALP associated with the LARGE cycle. In setups where the visible sector branes are wrapping more than the minimum number of two intersecting cycles, there are more ALPs which have approximately the same decay constant and coupling to the photon as the QCD axion candidate, but which are exponentially lighter. There are exciting phenomenological opportunities to search for these axions and ALPs in the near future. For f{sub a} {proportional_to}10{sup 11/12} GeV, the QCD axion can be the dominant part of dark matter and be detected in haloscopes exploiting microwave cavities. For f{sub a} {proportional_to}10{sup 9/10} GeV, the additional ALPs could explain astrophysical anomalies and be searched for in the upcoming generation of helioscopes and light-shining-through-a-wall experiments.

  7. Experimental implementation of a quantum random-walk search algorithm using strongly dipolar coupled spins

    International Nuclear Information System (INIS)

    Lu Dawei; Peng Xinhua; Du Jiangfeng; Zhu Jing; Zou Ping; Yu Yihua; Zhang Shanmin; Chen Qun

    2010-01-01

    An important quantum search algorithm based on the quantum random walk performs an oracle search on a database of N items with O(√(phN)) calls, yielding a speedup similar to the Grover quantum search algorithm. The algorithm was implemented on a quantum information processor of three-qubit liquid-crystal nuclear magnetic resonance (NMR) in the case of finding 1 out of 4, and the diagonal elements' tomography of all the final density matrices was completed with comprehensible one-dimensional NMR spectra. The experimental results agree well with the theoretical predictions.

  8. In search for the unified theory of fundamental interactions

    International Nuclear Information System (INIS)

    Ansel'm, A.A.

    1980-01-01

    The problem of developing the unified theory of fundamental interactions is considered in a popular form. The fundamental interactions include interactions between really elementary particles (quarks and leptons) which are performed by strong, weak, electromagnetic and gravitational forces. The unified theory is based on the requirement of ''Local symmetry''. The problem on invariance of strong interaction theory to local isotopic transformation was proposed for the first time by Yang and Mills, who introduced fields, called compensating (they compensate additional members in the theory equations, appearing during local transformations) Quanta of these fields (calibrating bosons) are massless particles with a spin, equal to one. The bosons should have the mass different from zero in order to be the carriers of real strong and weak interactions. At present there exist two mechanisms, due to which the mentioned controdiction can be overcome. One of these mechanisms - spontaneous symmetry distortion, the other mechanism - ''non-escape'', or ''captivity'' of the particles. The main ideas of building the realistic model of strong interaction are briefly presented

  9. Gauge symmetry breaking in gauge theories -- in search of clarification

    NARCIS (Netherlands)

    Friederich, Simon

    2013-01-01

    The paper investigates the spontaneous breaking of gauge symmetries in gauge theories from a philosophical angle, taking into account the fact that the notion of a spontaneously broken local gauge symmetry, though widely employed in textbook expositions of the Higgs mechanism, is not supported by

  10. Online games: a novel approach to explore how partial information influences human random searches

    Science.gov (United States)

    Martínez-García, Ricardo; Calabrese, Justin M.; López, Cristóbal

    2017-01-01

    Many natural processes rely on optimizing the success ratio of a search process. We use an experimental setup consisting of a simple online game in which players have to find a target hidden on a board, to investigate how the rounds are influenced by the detection of cues. We focus on the search duration and the statistics of the trajectories traced on the board. The experimental data are explained by a family of random-walk-based models and probabilistic analytical approximations. If no initial information is given to the players, the search is optimized for cues that cover an intermediate spatial scale. In addition, initial information about the extension of the cues results, in general, in faster searches. Finally, strategies used by informed players turn into non-stationary processes in which the length of e ach displacement evolves to show a well-defined characteristic scale that is not found in non-informed searches.

  11. Quasi-steady-state analysis of two-dimensional random intermittent search processes

    KAUST Repository

    Bressloff, Paul C.

    2011-06-01

    We use perturbation methods to analyze a two-dimensional random intermittent search process, in which a searcher alternates between a diffusive search phase and a ballistic movement phase whose velocity direction is random. A hidden target is introduced within a rectangular domain with reflecting boundaries. If the searcher moves within range of the target and is in the search phase, it has a chance of detecting the target. A quasi-steady-state analysis is applied to the corresponding Chapman-Kolmogorov equation. This generates a reduced Fokker-Planck description of the search process involving a nonzero drift term and an anisotropic diffusion tensor. In the case of a uniform direction distribution, for which there is zero drift, and isotropic diffusion, we use the method of matched asymptotics to compute the mean first passage time (MFPT) to the target, under the assumption that the detection range of the target is much smaller than the size of the domain. We show that an optimal search strategy exists, consistent with previous studies of intermittent search in a radially symmetric domain that were based on a decoupling or moment closure approximation. We also show how the decoupling approximation can break down in the case of biased search processes. Finally, we analyze the MFPT in the case of anisotropic diffusion and find that anisotropy can be useful when the searcher starts from a fixed location. © 2011 American Physical Society.

  12. Quasi-steady-state analysis of two-dimensional random intermittent search processes

    KAUST Repository

    Bressloff, Paul C.; Newby, Jay M.

    2011-01-01

    We use perturbation methods to analyze a two-dimensional random intermittent search process, in which a searcher alternates between a diffusive search phase and a ballistic movement phase whose velocity direction is random. A hidden target is introduced within a rectangular domain with reflecting boundaries. If the searcher moves within range of the target and is in the search phase, it has a chance of detecting the target. A quasi-steady-state analysis is applied to the corresponding Chapman-Kolmogorov equation. This generates a reduced Fokker-Planck description of the search process involving a nonzero drift term and an anisotropic diffusion tensor. In the case of a uniform direction distribution, for which there is zero drift, and isotropic diffusion, we use the method of matched asymptotics to compute the mean first passage time (MFPT) to the target, under the assumption that the detection range of the target is much smaller than the size of the domain. We show that an optimal search strategy exists, consistent with previous studies of intermittent search in a radially symmetric domain that were based on a decoupling or moment closure approximation. We also show how the decoupling approximation can break down in the case of biased search processes. Finally, we analyze the MFPT in the case of anisotropic diffusion and find that anisotropy can be useful when the searcher starts from a fixed location. © 2011 American Physical Society.

  13. Large-deviation theory for diluted Wishart random matrices

    Science.gov (United States)

    Castillo, Isaac Pérez; Metz, Fernando L.

    2018-03-01

    Wishart random matrices with a sparse or diluted structure are ubiquitous in the processing of large datasets, with applications in physics, biology, and economy. In this work, we develop a theory for the eigenvalue fluctuations of diluted Wishart random matrices based on the replica approach of disordered systems. We derive an analytical expression for the cumulant generating function of the number of eigenvalues IN(x ) smaller than x ∈R+ , from which all cumulants of IN(x ) and the rate function Ψx(k ) controlling its large-deviation probability Prob[IN(x ) =k N ] ≍e-N Ψx(k ) follow. Explicit results for the mean value and the variance of IN(x ) , its rate function, and its third cumulant are discussed and thoroughly compared to numerical diagonalization, showing very good agreement. The present work establishes the theoretical framework put forward in a recent letter [Phys. Rev. Lett. 117, 104101 (2016), 10.1103/PhysRevLett.117.104101] as an exact and compelling approach to deal with eigenvalue fluctuations of sparse random matrices.

  14. Random walk theory and exchange rate dynamics in transition economies

    Directory of Open Access Journals (Sweden)

    Gradojević Nikola

    2010-01-01

    Full Text Available This paper investigates the validity of the random walk theory in the Euro-Serbian dinar exchange rate market. We apply Andrew Lo and Archie MacKinlay's (1988 conventional variance ratio test and Jonathan Wright's (2000 non-parametric ranks and signs based variance ratio tests to the daily Euro/Serbian dinar exchange rate returns using the data from January 2005 - December 2008. Both types of variance ratio tests overwhelmingly reject the random walk hypothesis over the data span. To assess the robustness of our findings, we examine the forecasting performance of a non-linear, nonparametric model in the spirit of Francis Diebold and James Nason (1990 and find that it is able to significantly improve upon the random walk model, thus confirming the existence of foreign exchange market imperfections in a small transition economy such as Serbia. In the last part of the paper, we conduct a comparative study on how our results relate to those of other transition economies in the region.

  15. Superforce the search for a grand unified theory of nature

    CERN Document Server

    Davies, Paul

    1985-01-01

    Many scientists believe we are on the verge of a "Theory of Everything" - a complete unification of all the fundamental forces and particles of nature. In this book, the physicist and author Paul Davies gives an account of the quest for a superforce that will explain how the physical universe is put together. The book describes the bewildering array of subatomic particles that have been discovered in recent years, and shows how their properties form abstract patterns and mathematical symmetries, hinting at deep linkages. It explains how the forces that act between these particles may require the existence of unseen extra dimensions of space, and why the latest bizarre theory suggests that the basic entities out of which all matter is built may not be particles at all, but strings. Aimed at the general reader, this account shows that a unified theory may be within our grasp, and that a single superforce may acmcount not only for the nature of matter, but even for the manner in which the universe came into exis...

  16. A method in search of a theory: peer education and health promotion.

    Science.gov (United States)

    Turner, G; Shepherd, J

    1999-04-01

    Peer education has grown in popularity and practice in recent years in the field of health promotion. However, advocates of peer education rarely make reference to theories in their rationale for particular projects. In this paper the authors review a selection of commonly cited theories, and examine to what extent they have value and relevance to peer education in health promotion. Beginning from an identification of 10 claims made for peer education, each theory is examined in terms of the scope of the theory and evidence to support it in practice. The authors conclude that, whilst most theories have something to offer towards an explanation of why peer education might be effective, most theories are limited in scope and there is little empirical evidence in health promotion practice to support them. Peer education would seem to be a method in search of a theory rather than the application of theory to practice.

  17. Optimizing Linear Functions with Randomized Search Heuristics - The Robustness of Mutation

    DEFF Research Database (Denmark)

    Witt, Carsten

    2012-01-01

    The analysis of randomized search heuristics on classes of functions is fundamental for the understanding of the underlying stochastic process and the development of suitable proof techniques. Recently, remarkable progress has been made in bounding the expected optimization time of the simple (1...

  18. Fitness levels with tail bounds for the analysis of randomized search heuristics

    DEFF Research Database (Denmark)

    Witt, Carsten

    2014-01-01

    The fitness-level method, also called the method of f-based partitions, is an intuitive and widely used technique for the running time analysis of randomized search heuristics. It was originally defined to prove upper and lower bounds on the expected running time. Recently, upper tail bounds were...

  19. Information theory, animal communication, and the search for extraterrestrial intelligence

    Science.gov (United States)

    Doyle, Laurance R.; McCowan, Brenda; Johnston, Simon; Hanser, Sean F.

    2011-02-01

    We present ongoing research in the application of information theory to animal communication systems with the goal of developing additional detectors and estimators for possible extraterrestrial intelligent signals. Regardless of the species, for intelligence (i.e., complex knowledge) to be transmitted certain rules of information theory must still be obeyed. We demonstrate some preliminary results of applying information theory to socially complex marine mammal species (bottlenose dolphins and humpback whales) as well as arboreal squirrel monkeys, because they almost exclusively rely on vocal signals for their communications, producing signals which can be readily characterized by signal analysis. Metrics such as Zipf's Law and higher-order information-entropic structure are emerging as indicators of the communicative complexity characteristic of an "intelligent message" content within these animals' signals, perhaps not surprising given these species' social complexity. In addition to human languages, for comparison we also apply these metrics to pulsar signals—perhaps (arguably) the most "organized" of stellar systems—as an example of astrophysical systems that would have to be distinguished from an extraterrestrial intelligence message by such information theoretic filters. We also look at a message transmitted from Earth (Arecibo Observatory) that contains a lot of meaning but little information in the mathematical sense we define it here. We conclude that the study of non-human communication systems on our own planet can make a valuable contribution to the detection of extraterrestrial intelligence by providing quantitative general measures of communicative complexity. Studying the complex communication systems of other intelligent species on our own planet may also be one of the best ways to deprovincialize our thinking about extraterrestrial communication systems in general.

  20. Searching for realism, structure and agency in Actor Network Theory.

    Science.gov (United States)

    Elder-Vass, Dave

    2008-09-01

    Superficially, Actor Network Theory (ANT) and critical realism (CR) are radically opposed research traditions. Written from a realist perspective, this paper asks whether there might be a basis for finding common ground between these two traditions. It looks in turn at the questions of realism, structure, and agency, analysing the differences between the two perspectives and seeking to identify what each might learn from the other. Overall, the paper argues that there is a great deal that realists can learn from actor network theory; yet ANT remains stunted by its lack of a depth ontology. It fails to recognize the significance of mechanisms, and of their dependence on emergence, and thus lacks both dimensions of the depth that is characteristic of critical realism's ontology. This prevents ANT from recognizing the role and powers of social structure; but on the other hand, realists would do well to heed ANT's call for us to trace the connections through which structures are constantly made and remade. A lack of ontological depth also underpins ANT's practice of treating human and non-human actors symmetrically, yet this remains a valuable provocation to sociologists who neglect non-human entities entirely.

  1. A solution to energy and environmental problems of electric power system using hybrid harmony search-random search optimization algorithm

    Directory of Open Access Journals (Sweden)

    Vikram Kumar Kamboj

    2016-04-01

    Full Text Available In recent years, global warming and carbon dioxide (CO2 emission reduction have become important issues in India, as CO2 emission levels are continuing to rise in accordance with the increased volume of Indian national energy consumption under the pressure of global warming, it is crucial for Indian government to impose the effective policy to promote CO2 emission reduction. Challenge of supplying the nation with high quality and reliable electrical energy at a reasonable cost, converted government policy into deregulation and restructuring environment. This research paper presents aims to presents an effective solution for energy and environmental problems of electric power using an efficient and powerful hybrid optimization algorithm: Hybrid Harmony search-random search algorithm. The proposed algorithm is tested for standard IEEE-14 bus, -30 bus and -56 bus system. The effectiveness of proposed hybrid algorithm is compared with others well known evolutionary, heuristics and meta-heuristics search algorithms. For multi-objective unit commitment, it is found that as there are conflicting relationship between cost and emission, if the performance in cost criterion is improved, performance in the emission is seen to deteriorate.

  2. Enumeration of RNA complexes via random matrix theory.

    Science.gov (United States)

    Andersen, Jørgen E; Chekhov, Leonid O; Penner, Robert C; Reidys, Christian M; Sułkowski, Piotr

    2013-04-01

    In the present article, we review a derivation of the numbers of RNA complexes of an arbitrary topology. These numbers are encoded in the free energy of the Hermitian matrix model with potential V(x)=x2/2-stx/(1-tx), where s and t are respective generating parameters for the number of RNA molecules and hydrogen bonds in a given complex. The free energies of this matrix model are computed using the so-called topological recursion, which is a powerful new formalism arising from random matrix theory. These numbers of RNA complexes also have profound meaning in mathematics: they provide the number of chord diagrams of fixed genus with specified numbers of backbones and chords as well as the number of cells in Riemann's moduli spaces for bordered surfaces of fixed topological type.

  3. Exploiting visual search theory to infer social interactions

    Science.gov (United States)

    Rota, Paolo; Dang-Nguyen, Duc-Tien; Conci, Nicola; Sebe, Nicu

    2013-03-01

    In this paper we propose a new method to infer human social interactions using typical techniques adopted in literature for visual search and information retrieval. The main piece of information we use to discriminate among different types of interactions is provided by proxemics cues acquired by a tracker, and used to distinguish between intentional and casual interactions. The proxemics information has been acquired through the analysis of two different metrics: on the one hand we observe the current distance between subjects, and on the other hand we measure the O-space synergy between subjects. The obtained values are taken at every time step over a temporal sliding window, and processed in the Discrete Fourier Transform (DFT) domain. The features are eventually merged into an unique array, and clustered using the K-means algorithm. The clusters are reorganized using a second larger temporal window into a Bag Of Words framework, so as to build the feature vector that will feed the SVM classifier.

  4. Intermittent random walks for an optimal search strategy: one-dimensional case

    International Nuclear Information System (INIS)

    Oshanin, G; Wio, H S; Lindenberg, K; Burlatsky, S F

    2007-01-01

    We study the search kinetics of an immobile target by a concentration of randomly moving searchers. The object of the study is to optimize the probability of detection within the constraints of our model. The target is hidden on a one-dimensional lattice in the sense that searchers have no a priori information about where it is, and may detect it only upon encounter. The searchers perform random walks in discrete time n = 0,1,2,...,N, where N is the maximal time the search process is allowed to run. With probability α the searchers step on a nearest-neighbour, and with probability (1-α) they leave the lattice and stay off until they land back on the lattice at a fixed distance L away from the departure point. The random walk is thus intermittent. We calculate the probability P N that the target remains undetected up to the maximal search time N, and seek to minimize this probability. We find that P N is a non-monotonic function of α, and show that there is an optimal choice α opt (N) of α well within the intermittent regime, 0 opt (N) N can be orders of magnitude smaller compared to the 'pure' random walk cases α = 0 and α = 1

  5. The application of foraging theory to the information searching behaviour of general practitioners.

    Science.gov (United States)

    Dwairy, Mai; Dowell, Anthony C; Stahl, Jean-Claude

    2011-08-23

    General Practitioners (GPs) employ strategies to identify and retrieve medical evidence for clinical decision making which take workload and time constraints into account. Optimal Foraging Theory (OFT) initially developed to study animal foraging for food is used to explore the information searching behaviour of General Practitioners. This study is the first to apply foraging theory within this context.Study objectives were: 1. To identify the sequence and steps deployed in identifiying and retrieving evidence for clinical decision making. 2. To utilise Optimal Foraging Theory to assess the effectiveness and efficiency of General Practitioner information searching. GPs from the Wellington region of New Zealand were asked to document in a pre-formatted logbook the steps and outcomes of an information search linked to their clinical decision making, and fill in a questionnaire about their personal, practice and information-searching backgrounds. A total of 115/155 eligible GPs returned a background questionnaire, and 71 completed their information search logbook. GPs spent an average of 17.7 minutes addressing their search for clinical information. Their preferred information sources were discussions with colleagues (38% of sources) and books (22%). These were the two most profitable information foraging sources (15.9 min and 9.5 min search time per answer, compared to 34.3 minutes in databases). GPs nearly always accessed another source when unsuccessful (95% after 1st source), and frequently when successful (43% after 2nd source). Use of multiple sources accounted for 41% of searches, and increased search success from 70% to 89%. By consulting in foraging terms the most 'profitable' sources of information (colleagues, books), rapidly switching sources when unsuccessful, and frequently double checking, GPs achieve an efficient trade-off between maximizing search success and information reliability, and minimizing searching time. As predicted by foraging theory, GPs

  6. The application of foraging theory to the information searching behaviour of general practitioners

    Directory of Open Access Journals (Sweden)

    Dowell Anthony C

    2011-08-01

    Full Text Available Abstract Background General Practitioners (GPs employ strategies to identify and retrieve medical evidence for clinical decision making which take workload and time constraints into account. Optimal Foraging Theory (OFT initially developed to study animal foraging for food is used to explore the information searching behaviour of General Practitioners. This study is the first to apply foraging theory within this context. Study objectives were: 1. To identify the sequence and steps deployed in identifiying and retrieving evidence for clinical decision making. 2. To utilise Optimal Foraging Theory to assess the effectiveness and efficiency of General Practitioner information searching. Methods GPs from the Wellington region of New Zealand were asked to document in a pre-formatted logbook the steps and outcomes of an information search linked to their clinical decision making, and fill in a questionnaire about their personal, practice and information-searching backgrounds. Results A total of 115/155 eligible GPs returned a background questionnaire, and 71 completed their information search logbook. GPs spent an average of 17.7 minutes addressing their search for clinical information. Their preferred information sources were discussions with colleagues (38% of sources and books (22%. These were the two most profitable information foraging sources (15.9 min and 9.5 min search time per answer, compared to 34.3 minutes in databases. GPs nearly always accessed another source when unsuccessful (95% after 1st source, and frequently when successful (43% after 2nd source. Use of multiple sources accounted for 41% of searches, and increased search success from 70% to 89%. Conclusions By consulting in foraging terms the most 'profitable' sources of information (colleagues, books, rapidly switching sources when unsuccessful, and frequently double checking, GPs achieve an efficient trade-off between maximizing search success and information reliability, and

  7. Searches for Randomized Controlled Trials of Drugs in MEDLINE and EMBASE Using Only Generic Drug Names Compared with Searches Applied in Current Practice in Systematic Reviews

    Science.gov (United States)

    Waffenschmidt, Siw; Guddat, Charlotte

    2015-01-01

    Background: It is unclear which terms should be included in bibliographic searches for randomized controlled trials (RCTs) of drugs, and identifying relevant drug terms can be extremely laborious. The aim of our analysis was to determine whether a bibliographic search using only the generic drug name produces sufficient results for the generation…

  8. Supplementary Appendix for: Constrained Perturbation Regularization Approach for Signal Estimation Using Random Matrix Theory

    KAUST Repository

    Suliman, Mohamed Abdalla Elhag; Ballal, Tarig; Kammoun, Abla; Alnaffouri, Tareq Y.

    2016-01-01

    In this supplementary appendix we provide proofs and additional simulation results that complement the paper (constrained perturbation regularization approach for signal estimation using random matrix theory).

  9. Searching for Survivors through Random Human-Body Movement Outdoors by Continuous-Wave Radar Array.

    Science.gov (United States)

    Li, Chuantao; Chen, Fuming; Qi, Fugui; Liu, Miao; Li, Zhao; Liang, Fulai; Jing, Xijing; Lu, Guohua; Wang, Jianqi

    2016-01-01

    It is a major challenge to search for survivors after chemical or nuclear leakage or explosions. At present, biological radar can be used to achieve this goal by detecting the survivor's respiration signal. However, owing to the random posture of an injured person at a rescue site, the radar wave may directly irradiate the person's head or feet, in which it is difficult to detect the respiration signal. This paper describes a multichannel-based antenna array technology, which forms an omnidirectional detection system via 24-GHz Doppler biological radar, to address the random positioning relative to the antenna of an object to be detected. Furthermore, since the survivors often have random body movement such as struggling and twitching, the slight movements of the body caused by breathing are obscured by these movements. Therefore, a method is proposed to identify random human-body movement by utilizing multichannel information to calculate the background variance of the environment in combination with a constant-false-alarm-rate detector. The conducted outdoor experiments indicate that the system can realize the omnidirectional detection of random human-body movement and distinguish body movement from environmental interference such as movement of leaves and grass. The methods proposed in this paper will be a promising way to search for survivors outdoors.

  10. Searching for Survivors through Random Human-Body Movement Outdoors by Continuous-Wave Radar Array

    Science.gov (United States)

    Liu, Miao; Li, Zhao; Liang, Fulai; Jing, Xijing; Lu, Guohua; Wang, Jianqi

    2016-01-01

    It is a major challenge to search for survivors after chemical or nuclear leakage or explosions. At present, biological radar can be used to achieve this goal by detecting the survivor’s respiration signal. However, owing to the random posture of an injured person at a rescue site, the radar wave may directly irradiate the person’s head or feet, in which it is difficult to detect the respiration signal. This paper describes a multichannel-based antenna array technology, which forms an omnidirectional detection system via 24-GHz Doppler biological radar, to address the random positioning relative to the antenna of an object to be detected. Furthermore, since the survivors often have random body movement such as struggling and twitching, the slight movements of the body caused by breathing are obscured by these movements. Therefore, a method is proposed to identify random human-body movement by utilizing multichannel information to calculate the background variance of the environment in combination with a constant-false-alarm-rate detector. The conducted outdoor experiments indicate that the system can realize the omnidirectional detection of random human-body movement and distinguish body movement from environmental interference such as movement of leaves and grass. The methods proposed in this paper will be a promising way to search for survivors outdoors. PMID:27073860

  11. Inference-Based Similarity Search in Randomized Montgomery Domains for Privacy-Preserving Biometric Identification.

    Science.gov (United States)

    Wang, Yi; Wan, Jianwu; Guo, Jun; Cheung, Yiu-Ming; C Yuen, Pong

    2017-07-14

    Similarity search is essential to many important applications and often involves searching at scale on high-dimensional data based on their similarity to a query. In biometric applications, recent vulnerability studies have shown that adversarial machine learning can compromise biometric recognition systems by exploiting the biometric similarity information. Existing methods for biometric privacy protection are in general based on pairwise matching of secured biometric templates and have inherent limitations in search efficiency and scalability. In this paper, we propose an inference-based framework for privacy-preserving similarity search in Hamming space. Our approach builds on an obfuscated distance measure that can conceal Hamming distance in a dynamic interval. Such a mechanism enables us to systematically design statistically reliable methods for retrieving most likely candidates without knowing the exact distance values. We further propose to apply Montgomery multiplication for generating search indexes that can withstand adversarial similarity analysis, and show that information leakage in randomized Montgomery domains can be made negligibly small. Our experiments on public biometric datasets demonstrate that the inference-based approach can achieve a search accuracy close to the best performance possible with secure computation methods, but the associated cost is reduced by orders of magnitude compared to cryptographic primitives.

  12. Effects of systematic phase errors on optimized quantum random-walk search algorithm

    International Nuclear Information System (INIS)

    Zhang Yu-Chao; Bao Wan-Su; Wang Xiang; Fu Xiang-Qun

    2015-01-01

    This study investigates the effects of systematic errors in phase inversions on the success rate and number of iterations in the optimized quantum random-walk search algorithm. Using the geometric description of this algorithm, a model of the algorithm with phase errors is established, and the relationship between the success rate of the algorithm, the database size, the number of iterations, and the phase error is determined. For a given database size, we obtain both the maximum success rate of the algorithm and the required number of iterations when phase errors are present in the algorithm. Analyses and numerical simulations show that the optimized quantum random-walk search algorithm is more robust against phase errors than Grover’s algorithm. (paper)

  13. Fetal MEG evoked response latency from beamformer with random field theory.

    Science.gov (United States)

    McCubbin, J; Vrba, J; Murphy, P; Temple, J; Eswaran, H; Lowery, C L; Preissl, H

    2010-01-01

    Analysis of fetal magnetoencephalographic brain recordings is restricted by low signal to noise ratio (SNR) and non-stationarity of the sources. Beamformer techniques have been applied to improve SNR of fetal evoked responses. However, until now the effect of non-stationarity was not taken into account in detail, because the detection of evoked responses is in most cases determined by averaging a large number of trials. We applied a windowing technique to improve the stationarity of the data by using short time segments recorded during a flash-evoked study. In addition, we implemented a random field theory approach for more stringent control of false-positives in the statistical parametric map of the search volume for the beamformer. The search volume was based on detailed individual fetal/maternal biometrics from ultrasound scans and fetal heart localization. Average power over a sliding window within the averaged evoked response against a randomized average background power was used as the test z-statistic. The significance threshold was set at 10% over all members of a contiguous cluster of voxels. There was at least one significant response for 62% of fetal and 95% of newborn recordings with gestational age (GA) between 28 and 45 weeks from 29 subjects. We found that the latency was either substantially unchanged or decreased with increasing GA for most subjects, with a nominal rate of about -11 ms/week. These findings support the anticipated neurophysiological development, provide validation for the beamformer model search as a methodology, and may lead to a clinical test for fetal cognitive development.

  14. The evolution of sex differences in mate searching when females benefit: new theory and a comparative test.

    Science.gov (United States)

    McCartney, J; Kokko, H; Heller, K-G; Gwynne, D T

    2012-03-22

    Sexual selection is thought to have led to searching as a profitable, but risky way of males obtaining mates. While there is great variation in which sex searches, previous theory has not considered search evolution when both males and females benefit from multiple mating. We present new theory and link it with data to bridge this gap. Two different search protocols exist between species in the bush-cricket genus Poecilimon (Orthoptera): females search for calling males, or males search for calling females. Poecilimon males also transfer a costly nuptial food gift to their mates during mating. We relate variations in searching protocols to variation in nuptial gift size among 32 Poecilimon taxa. As predicted, taxa where females search produce significantly larger nuptial gifts than those where males search. Our model and results show that search roles can reverse when multiple mating brings about sufficiently strong material benefits to females.

  15. Reflective Mindreading: Theory of Mind and the Search for Self in Antonio Machado's "Soledades"

    Science.gov (United States)

    Mills, Steven

    2011-01-01

    In Antonio Machado's collection "Soledades", the poet's search for identity guides an introspective quest where context, body, and mind form an intricate and inseparable connection. By extending cognitive capabilities to his natural environment, the poet, through embodied cognition and Theory of Mind, reads other people's and nature's minds to…

  16. Biclustering of gene expression data using reactive greedy randomized adaptive search procedure.

    Science.gov (United States)

    Dharan, Smitha; Nair, Achuthsankar S

    2009-01-30

    Biclustering algorithms belong to a distinct class of clustering algorithms that perform simultaneous clustering of both rows and columns of the gene expression matrix and can be a very useful analysis tool when some genes have multiple functions and experimental conditions are diverse. Cheng and Church have introduced a measure called mean squared residue score to evaluate the quality of a bicluster and has become one of the most popular measures to search for biclusters. In this paper, we review basic concepts of the metaheuristics Greedy Randomized Adaptive Search Procedure (GRASP)-construction and local search phases and propose a new method which is a variant of GRASP called Reactive Greedy Randomized Adaptive Search Procedure (Reactive GRASP) to detect significant biclusters from large microarray datasets. The method has two major steps. First, high quality bicluster seeds are generated by means of k-means clustering. In the second step, these seeds are grown using the Reactive GRASP, in which the basic parameter that defines the restrictiveness of the candidate list is self-adjusted, depending on the quality of the solutions found previously. We performed statistical and biological validations of the biclusters obtained and evaluated the method against the results of basic GRASP and as well as with the classic work of Cheng and Church. The experimental results indicate that the Reactive GRASP approach outperforms the basic GRASP algorithm and Cheng and Church approach. The Reactive GRASP approach for the detection of significant biclusters is robust and does not require calibration efforts.

  17. Motile male gametes of the araphid diatom Tabularia fasciculata search randomly for mates.

    Directory of Open Access Journals (Sweden)

    Robyn Edgar

    Full Text Available Sexuality in the marine araphid diatom Tabularia involves an unusual type of gamete, not only among diatoms but possibly in all of nature. The non-flagellated male gamete is free and vigorously motile, propelled by pseudopodia. However, the cues (if any in their search for compatible female gametes and the general search patterns to locate them are unknown. We tracked and compared male gamete movements in the presence and absence of receptive female gametes. Path linearity of male movement was not affected by presence of female gametes. Male gametes did not move towards female gametes regardless of their proximity to each other, suggesting that the detection range for a compatible mate is very small compared to known algal examples (mostly spermatozoids and that mate recognition requires (near contact with a female gamete. We therefore investigated how male gametes move to bring insight into their search strategy and found that it was consistent with the predictions of a random-walk model with changes in direction coming from an even distribution. We further investigated the type of random walk by determining the best-fit distribution on the tail of the move length distribution and found it to be consistent with a truncated power law distribution with an exponent of 2.34. Although consistent with a Lévy walk search pattern, the range of move lengths in the tail was too narrow for Lévy properties to emerge and so would be best described as Brownian motion. This is somewhat surprising because female gametes were often outnumbered by male gametes, thus contrary to the assumption that a Brownian search mode may be most optimal with an abundant target resource. This is also the first mathematically analysed search pattern of a non-flagellated protistan gamete, supporting the notion that principles of Brownian motion have wide application in biology.

  18. PARAMETRIC IDENTIFICATION OF STOCHASTIC SYSTEM BY NON-GRADIENT RANDOM SEARCHING

    Directory of Open Access Journals (Sweden)

    A. A. Lobaty

    2017-01-01

    Full Text Available At this moment we know a great variety of identification objects, tasks and methods and its significance is constantly increasing in various fields of science and technology.  The identification problem is dependent on a priori information about identification object, besides that  the existing approaches and methods of identification are determined by the form of mathematical models (deterministic, stochastic, frequency, temporal, spectral etc.. The paper considers a problem for determination of system parameters  (identification object which is assigned by the stochastic mathematical model including random functions of time. It has been shown  that while making optimization of the stochastic systems subject to random actions deterministic methods can be applied only for a limited approximate optimization of the system by taking into account average random effects and fixed structure of the system. The paper proposes an algorithm for identification of  parameters in a mathematical model of  the stochastic system by non-gradient random searching. A specific  feature  of the algorithm is its applicability  practically to mathematic models of any type because the applied algorithm does not depend on linearization and differentiability of functions included in the mathematical model of the system. The proposed algorithm  ensures searching of  an extremum for the specified quality criteria in terms of external uncertainties and limitations while using random searching of parameters for a mathematical model of the system. The paper presents results of the investigations on operational capability of the considered identification method  while using mathematical simulation of hypothetical control system with a priori unknown parameter values of the mathematical model. The presented results of the mathematical simulation obviously demonstrate the operational capability of the proposed identification method.

  19. Exploring multicollinearity using a random matrix theory approach.

    Science.gov (United States)

    Feher, Kristen; Whelan, James; Müller, Samuel

    2012-01-01

    Clustering of gene expression data is often done with the latent aim of dimension reduction, by finding groups of genes that have a common response to potentially unknown stimuli. However, what is poorly understood to date is the behaviour of a low dimensional signal embedded in high dimensions. This paper introduces a multicollinear model which is based on random matrix theory results, and shows potential for the characterisation of a gene cluster's correlation matrix. This model projects a one dimensional signal into many dimensions and is based on the spiked covariance model, but rather characterises the behaviour of the corresponding correlation matrix. The eigenspectrum of the correlation matrix is empirically examined by simulation, under the addition of noise to the original signal. The simulation results are then used to propose a dimension estimation procedure of clusters from data. Moreover, the simulation results warn against considering pairwise correlations in isolation, as the model provides a mechanism whereby a pair of genes with `low' correlation may simply be due to the interaction of high dimension and noise. Instead, collective information about all the variables is given by the eigenspectrum.

  20. Random matrix theory and fund of funds portfolio optimisation

    Science.gov (United States)

    Conlon, T.; Ruskin, H. J.; Crane, M.

    2007-08-01

    The proprietary nature of Hedge Fund investing means that it is common practise for managers to release minimal information about their returns. The construction of a fund of hedge funds portfolio requires a correlation matrix which often has to be estimated using a relatively small sample of monthly returns data which induces noise. In this paper, random matrix theory (RMT) is applied to a cross-correlation matrix C, constructed using hedge fund returns data. The analysis reveals a number of eigenvalues that deviate from the spectrum suggested by RMT. The components of the deviating eigenvectors are found to correspond to distinct groups of strategies that are applied by hedge fund managers. The inverse participation ratio is used to quantify the number of components that participate in each eigenvector. Finally, the correlation matrix is cleaned by separating the noisy part from the non-noisy part of C. This technique is found to greatly reduce the difference between the predicted and realised risk of a portfolio, leading to an improved risk profile for a fund of hedge funds.

  1. Rigorously testing multialternative decision field theory against random utility models.

    Science.gov (United States)

    Berkowitsch, Nicolas A J; Scheibehenne, Benjamin; Rieskamp, Jörg

    2014-06-01

    Cognitive models of decision making aim to explain the process underlying observed choices. Here, we test a sequential sampling model of decision making, multialternative decision field theory (MDFT; Roe, Busemeyer, & Townsend, 2001), on empirical grounds and compare it against 2 established random utility models of choice: the probit and the logit model. Using a within-subject experimental design, participants in 2 studies repeatedly choose among sets of options (consumer products) described on several attributes. The results of Study 1 showed that all models predicted participants' choices equally well. In Study 2, in which the choice sets were explicitly designed to distinguish the models, MDFT had an advantage in predicting the observed choices. Study 2 further revealed the occurrence of multiple context effects within single participants, indicating an interdependent evaluation of choice options and correlations between different context effects. In sum, the results indicate that sequential sampling models can provide relevant insights into the cognitive process underlying preferential choices and thus can lead to better choice predictions. PsycINFO Database Record (c) 2014 APA, all rights reserved.

  2. Random matrix theory filters and currency portfolio optimisation

    Science.gov (United States)

    Daly, J.; Crane, M.; Ruskin, H. J.

    2010-04-01

    Random matrix theory (RMT) filters have recently been shown to improve the optimisation of financial portfolios. This paper studies the effect of three RMT filters on realised portfolio risk, using bootstrap analysis and out-of-sample testing. We considered the case of a foreign exchange and commodity portfolio, weighted towards foreign exchange, and consisting of 39 assets. This was intended to test the limits of RMT filtering, which is more obviously applicable to portfolios with larger numbers of assets. We considered both equally and exponentially weighted covariance matrices, and observed that, despite the small number of assets involved, RMT filters reduced risk in a way that was consistent with a much larger S&P 500 portfolio. The exponential weightings indicated showed good consistency with the value suggested by Riskmetrics, in contrast to previous results involving stocks. This decay factor, along with the low number of past moves preferred in the filtered, equally weighted case, displayed a trend towards models which were reactive to recent market changes. On testing portfolios with fewer assets, RMT filtering provided less or no overall risk reduction. In particular, no long term out-of-sample risk reduction was observed for a portfolio consisting of 15 major currencies and commodities.

  3. Theory versus Practice in the Twentieth-Century Search for the Ideal Anaesthetic Gas.

    Science.gov (United States)

    Rae, Ian D

    2016-02-01

    At the beginning of the twentieth century, an anaesthetist could choose between nitrous oxide, chloroform, and ether (diethyl ether) for the induction of painrelieving unconsciousness. By the end of century, the choice was between a small number of fluorinated aliphatic ethers such as Enflurane, Desflurane, and Sevoflurane, and (in some jurisdictions) the rare gas, xenon. Between these endpoints researchers had identified a surprisingly broad range of hydrocarbons, noble gases, organohalogens, and aliphatic ethers that possessed anaesthetic properties. None was entirely satisfactory, but clinicians at various times and in various places employed substances in each of these categories. Behind the search for new anaesthetic gases was a theory of action (Meyer- Overton theory) that was known to be inadequate, but as no alternative was strong enough to displace it the search continued on purely empirical grounds, while lip-service was paid to the theory. By the time a theory couched in more modern terms was proposed, a suite of modern anaesthetic gases was in place, and there have been no attempts to use that theory to drive a new search.

  4. Electron traps in polar liquids. An application of the formalism of the random field theory

    International Nuclear Information System (INIS)

    Hilczer, M.; Bartczak, W.M.

    1992-01-01

    The potential energy surface in a disordered medium is described, using the concepts of the mathematical theory of random fields. The statistics of trapping sites (the regions of an excursion of the random field) is obtained for liquid methanol as a numerical example of the theory. (author). 15 refs, 4 figs

  5. Beyond effective field theory for dark matter searches at the LHC

    International Nuclear Information System (INIS)

    Buchmueller, O.; Dolan, Matthew J.; McCabe, Christopher

    2014-01-01

    We study the validity of effective field theory (EFT) interpretations of monojet searches for dark matter at the LHC for vector and axial-vector interactions. We show that the EFT approach is valid when the mediator has mass m med greater than 2.5 TeV. We find that the current limits on the contact interaction scale Λ in the EFT apply to theories that are perturbative for dark matter mass m DM <800 GeV. However, for all values of m DM in these theories, the mediator width is larger than the mass, so that a particle-like interpretation of the mediator is doubtful. Furthermore, consistency with the thermal relic density occurs only for 170≲m DM ≲510 GeV. For lighter mediator masses, the EFT limit either under-estimates the true limit (because the process is resonantly enhanced) or over-estimates it (because the missing energy distribution is too soft). We give some ‘rules of thumb’ that can be used to estimate the limit on Λ (to an accuracy of ∼50%) for any m DM and m med from knowledge of the EFT limit. We also compare the relative sensitivities of monojet and dark matter direct detection searches finding that both dominate in different regions of the m DM – m med plane. Comparing only the EFT limit with direct searches is misleading and can lead to incorrect conclusions about the relative sensitivity of the two search approaches

  6. Optimization of refueling-shuffling scheme in PWR core by random search strategy

    International Nuclear Information System (INIS)

    Wu Yuan

    1991-11-01

    A random method for simulating optimization of refueling management in a pressurized water reactor (PWR) core is described. The main purpose of the optimization was to select the 'best' refueling arrangement scheme which would produce maximum economic benefits under certain imposed conditions. To fulfill this goal, an effective optimization strategy, two-stage random search method was developed. First, the search was made in a manner similar to the stratified sampling technique. A local optimum can be reached by comparison of the successive results. Then the other random experiences would be carried on between different strata to try to find the global optimum. In general, it can be used as a practical tool for conventional fuel management scheme. However, it can also be used in studies on optimization of Low-Leakage fuel management. Some calculations were done for a typical PWR core on a CYBER-180/830 computer. The results show that the method proposed can obtain satisfactory approach at reasonable low computational cost

  7. Fluctuation theory for radiative transfer in random media

    International Nuclear Information System (INIS)

    Bal, Guillaume; Jing Wenjia

    2011-01-01

    We consider the effect of small scale random fluctuations of the constitutive coefficients on boundary measurements of solutions to radiative transfer equations. As the correlation length of the random oscillations tends to zero, the transport solution is well approximated by a deterministic, averaged, solution. In this paper, we analyze the random fluctuations to the averaged solution, which may be interpreted as a central limit correction to homogenization. With the inverse transport problem in mind, we characterize the random structure of the singular components of the transport measurement operator. In regimes of moderate scattering, such components provide stable reconstructions of the constitutive parameters in the transport equation. We show that the random fluctuations strongly depend on the decorrelation properties of the random medium.

  8. Evaluation of the efficiency of computer-aided spectra search systems based on information theory

    International Nuclear Information System (INIS)

    Schaarschmidt, K.

    1979-01-01

    Application of information theory allows objective evaluation of the efficiency of computer-aided spectra search systems. For this purpose, a significant number of search processes must be analyzed. The amount of information gained by computer application is considered as the difference between the entropy of the data bank and a conditional entropy depending on the proportion of unsuccessful search processes and ballast. The influence of the following factors can be estimated: volume, structure, and quality of the spectra collection stored, efficiency of the encoding instruction and the comparing algorithm, and subjective errors involved in the encoding of spectra. The relations derived are applied to two published storage and retrieval systems for infared spectra. (Auth.)

  9. Asymptotic Properties of Multistate Random Walks. I. Theory

    NARCIS (Netherlands)

    Roerdink, J.B.T.M.; Shuler, K.E.

    1985-01-01

    A calculation is presented of the long-time behavior of various random walk properties (moments, probability of return to the origin, expected number of distinct sites visited) for multistate random walks on periodic lattices. In particular, we consider inhomogeneous periodic lattices, consisting of

  10. Search of associative memory.

    NARCIS (Netherlands)

    Raaijmakers, J.G.W.; Shiffrin, R.M.

    1981-01-01

    Describes search of associative memory (SAM), a general theory of retrieval from long-term memory that combines features of associative network models and random search models. It posits cue-dependent probabilistic sampling and recovery from an associative network, but the network is specified as a

  11. Random electrodynamics: the theory of classical electrodynamics with classical electromagnetic zero-point radiation

    International Nuclear Information System (INIS)

    Boyer, T.H.

    1975-01-01

    The theory of classical electrodynamics with classical electromagnetic zero-point radiation is outlined here under the title random electrodynamics. The work represents a reanalysis of the bounds of validity of classical electron theory which should sharpen the understanding of the connections and distinctions between classical and quantum theories. The new theory of random electrodynamics is a classical electron theory involving Newton's equations for particle motion due to the Lorentz force, and Maxwell's equations for the electromagnetic fields with point particles as sources. However, the theory departs from the classical electron theory of Lorentz in that it adopts a new boundary condition on Maxwell's equations. It is assumed that the homogeneous boundary condition involves random classical electromagnetic radiation with a Lorentz-invariant spectrum, classical electromagnetic zero-point radiation. The implications of random electrodynamics for atomic structure, atomic spectra, and particle-interference effects are discussed on an order-of-magnitude or heuristic level. Some detailed mathematical connections and some merely heuristic connections are noted between random electrodynamics and quantum theory. (U.S.)

  12. A novel ternary content addressable memory design based on resistive random access memory with high intensity and low search energy

    Science.gov (United States)

    Han, Runze; Shen, Wensheng; Huang, Peng; Zhou, Zheng; Liu, Lifeng; Liu, Xiaoyan; Kang, Jinfeng

    2018-04-01

    A novel ternary content addressable memory (TCAM) design based on resistive random access memory (RRAM) is presented. Each TCAM cell consists of two parallel RRAM to both store and search for ternary data. The cell size of the proposed design is 8F2, enable a ∼60× cell area reduction compared with the conventional static random access memory (SRAM) based implementation. Simulation results also show that the search delay and energy consumption of the proposed design at the 64-bit word search are 2 ps and 0.18 fJ/bit/search respectively at 22 nm technology node, where significant improvements are achieved compared to previous works. The desired characteristics of RRAM for implementation of the high performance TCAM search chip are also discussed.

  13. Approximate design theory for a simple block design with random block effects

    OpenAIRE

    Christof, Karin

    1985-01-01

    Approximate design theory for a simple block design with random block effects / K. Christof ; F. Pukelsheim. - In: Linear statistical inference / ed. by T. Calinski ... - Berlin u. a. : Springer, 1985. - S. 20-28. - (Lecture notes in statistics ; 35)

  14. Constrained Perturbation Regularization Approach for Signal Estimation Using Random Matrix Theory

    KAUST Repository

    Suliman, Mohamed Abdalla Elhag; Ballal, Tarig; Kammoun, Abla; Al-Naffouri, Tareq Y.

    2016-01-01

    random matrix theory are applied to derive the near-optimum regularizer that minimizes the mean-squared error of the estimator. Simulation results demonstrate that the proposed approach outperforms a set of benchmark regularization methods for various

  15. Perturbation theory for the effective diffusion constant in a medium of random scatterers

    International Nuclear Information System (INIS)

    Dean, D S; Drummond, I T; Horgan, R R; Lefevre, A

    2004-01-01

    We develop perturbation theory and physically motivated resummations of the perturbation theory for the problem of a tracer particle diffusing in a random medium. The random medium contains point scatterers of density ρ uniformly distributed throughout the material. The tracer is a Langevin particle subjected to the quenched random force generated by the scatterers. Via our perturbative analysis, we determine when the random potential can be approximated by a Gaussian random potential. We also develop a self-similar renormalization group approach based on thinning out the scatterers; this scheme is similar to that used with success for diffusion in Gaussian random potentials and agrees with known exact results. To assess the accuracy of this approximation scheme, its predictions are confronted with results obtained by numerical simulation

  16. Numerical solution of field theories using random walks

    International Nuclear Information System (INIS)

    Barnes, T.; Daniell, G.J.

    1985-01-01

    We show how random walks in function space can be employed to evaluate field theoretic vacuum expectation values numerically. Specific applications which we study are the two-point function, mass gap, magnetization and classical solutions. This technique offers the promise of faster calculations using less computer memory than current methods. (orig.)

  17. Deus or Darwin: randomness and belief in theories about the origin of life

    NARCIS (Netherlands)

    Rutjens, B.T.; van der Pligt, J.; van Harreveld, F.

    2010-01-01

    A simple reminder of the fact that we do not always control life's outcomes reduced people's belief in Darwin's Theory of Evolution. This control-threat resulted in a relative preference for theories of life that thwart randomness, either by stressing the role of a controlling God (Intelligent

  18. A modern theory of random variation with applications in stochastic calculus, financial mathematics, and Feynman integration

    CERN Document Server

    Muldowney, Patrick

    2012-01-01

    A Modern Theory of Random Variation is a new and radical re-formulation of the mathematical underpinnings of subjects as diverse as investment, communication engineering, and quantum mechanics. Setting aside the classical theory of probability measure spaces, the book utilizes a mathematically rigorous version of the theory of random variation that bases itself exclusively on finitely additive probability distribution functions. In place of twentieth century Lebesgue integration and measure theory, the author uses the simpler concept of Riemann sums, and the non-absolute Riemann-type integration of Henstock. Readers are supplied with an accessible approach to standard elements of probability theory such as the central limmit theorem and Brownian motion as well as remarkable, new results on Feynman diagrams and stochastic integrals. Throughout the book, detailed numerical demonstrations accompany the discussions of abstract mathematical theory, from the simplest elements of the subject to the most complex. I...

  19. Long time tails in stationary random media. I. Theory

    NARCIS (Netherlands)

    Ernst, M.H.; Machta, J.; Dorfman, J.R.; Beijeren, H. van

    1984-01-01

    Diffusion of moving particles in stationary disordered media is studied using a phenomenological mode-coupling theory. The presence of disorder leads to a generalized diffusion equation, with memory kernels having power law long time tails. The velocity autocorrelation function is found to decay

  20. The neutral theory of biodiversity with random fission speciation

    NARCIS (Netherlands)

    Etienne, Rampal S.; Haegeman, Bart

    The neutral theory of biodiversity and biogeography emphasizes the importance of dispersal and speciation to macro-ecological diversity patterns. While the influence of dispersal has been studied quite extensively, the effect of speciation has not received much attention, even though it was already

  1. Computational prediction of muon stopping sites using ab initio random structure searching (AIRSS)

    Science.gov (United States)

    Liborio, Leandro; Sturniolo, Simone; Jochym, Dominik

    2018-04-01

    The stopping site of the muon in a muon-spin relaxation experiment is in general unknown. There are some techniques that can be used to guess the muon stopping site, but they often rely on approximations and are not generally applicable to all cases. In this work, we propose a purely theoretical method to predict muon stopping sites in crystalline materials from first principles. The method is based on a combination of ab initio calculations, random structure searching, and machine learning, and it has successfully predicted the MuT and MuBC stopping sites of muonium in Si, diamond, and Ge, as well as the muonium stopping site in LiF, without any recourse to experimental results. The method makes use of Soprano, a Python library developed to aid ab initio computational crystallography, that was publicly released and contains all the software tools necessary to reproduce our analysis.

  2. Solving the wind farm layout optimization problem using random search algorithm

    DEFF Research Database (Denmark)

    Feng, Ju; Shen, Wen Zhong

    2015-01-01

    , in which better results than the genetic algorithm (GA) and the old version of the RS algorithm are obtained. Second it is applied to the Horns Rev 1 WF, and the optimized layouts obtain a higher power production than its original layout, both for the real scenario and for two constructed scenarios......Wind farm (WF) layout optimization is to find the optimal positions of wind turbines (WTs) inside a WF, so as to maximize and/or minimize a single objective or multiple objectives, while satisfying certain constraints. In this work, a random search (RS) algorithm based on continuous formulation....... In this application, it is also found that in order to get consistent and reliable optimization results, up to 360 or more sectors for wind direction have to be used. Finally, considering the inevitable inter-annual variations in the wind conditions, the robustness of the optimized layouts against wind condition...

  3. A review of the theories of non-critical strings and random surfaces

    International Nuclear Information System (INIS)

    Ambjoern, J.

    1988-11-01

    I review the basic properties of the theory of random surfaces. It is shown that the theory gives a correct description of strings in dimensions d≤1 and of matter fields with central charge c≤1. In this region it coincides with the new results of Knizhnik, Polyakov and Zamolodchikov. Analytical and numerical results for the discretized model and for the standard continuum string model for d>1 indicate a trivial theory in this region. (orig.)

  4. Stochastic foundations in movement ecology anomalous diffusion, front propagation and random searches

    CERN Document Server

    Méndez, Vicenç; Bartumeus, Frederic

    2014-01-01

    This book presents the fundamental theory for non-standard diffusion problems in movement ecology. Lévy processes and anomalous diffusion have shown to be both powerful and useful tools for qualitatively and quantitatively describing a wide variety of spatial population ecological phenomena and dynamics, such as invasion fronts and search strategies. Adopting a self-contained, textbook-style approach, the authors provide the elements of statistical physics and stochastic processes on which the modeling of movement ecology is based and systematically introduce the physical characterization of ecological processes at the microscopic, mesoscopic and macroscopic levels. The explicit definition of these levels and their interrelations is particularly suitable to coping with the broad spectrum of space and time scales involved in bio-ecological problems.   Including numerous exercises (with solutions), this text is aimed at graduate students and newcomers in this field at the interface of theoretical ecology, mat...

  5. An application of random field theory to analysis of electron trapping sites in disordered media

    International Nuclear Information System (INIS)

    Hilczer, M.; Bartczak, W.M.

    1993-01-01

    The potential energy surface in a disordered medium is considered a random field and described using the concepts of the mathematical theory of random fields. The preexisting traps for excess electrons are identified with certain regions of excursion (extreme regions) of the potential field. The theory provides an analytical method of statistical analysis of these regions. Parameters of the cavity-averaged potential field, which are provided by computer simulation of a given medium, serve as input data for the analysis. The statistics of preexisting traps are obtained for liquid methanol as a numerical example of the random field method. 26 refs., 6 figs

  6. Pure random search for ambient sensor distribution optimisation in a smart home environment.

    Science.gov (United States)

    Poland, Michael P; Nugent, Chris D; Wang, Hui; Chen, Liming

    2011-01-01

    Smart homes are living spaces facilitated with technology to allow individuals to remain in their own homes for longer, rather than be institutionalised. Sensors are the fundamental physical layer with any smart home, as the data they generate is used to inform decision support systems, facilitating appropriate actuator actions. Positioning of sensors is therefore a fundamental characteristic of a smart home. Contemporary smart home sensor distribution is aligned to either a) a total coverage approach; b) a human assessment approach. These methods for sensor arrangement are not data driven strategies, are unempirical and frequently irrational. This Study hypothesised that sensor deployment directed by an optimisation method that utilises inhabitants' spatial frequency data as the search space, would produce more optimal sensor distributions vs. the current method of sensor deployment by engineers. Seven human engineers were tasked to create sensor distributions based on perceived utility for 9 deployment scenarios. A Pure Random Search (PRS) algorithm was then tasked to create matched sensor distributions. The PRS method produced superior distributions in 98.4% of test cases (n=64) against human engineer instructed deployments when the engineers had no access to the spatial frequency data, and in 92.0% of test cases (n=64) when engineers had full access to these data. These results thus confirmed the hypothesis.

  7. Random intermittent search and the tug-of-war model of motor-driven transport

    International Nuclear Information System (INIS)

    Newby, Jay; Bressloff, Paul C

    2010-01-01

    We formulate the 'tug-of-war' model of microtubule cargo transport by multiple molecular motors as an intermittent random search for a hidden target. A motor complex consisting of multiple molecular motors with opposing directional preference is modeled using a discrete Markov process. The motors randomly pull each other off of the microtubule so that the state of the motor complex is determined by the number of bound motors. The tug-of-war model prescribes the state transition rates and corresponding cargo velocities in terms of experimentally measured physical parameters. We add space to the resulting Chapman–Kolmogorov (CK) equation so that we can consider delivery of the cargo to a hidden target at an unknown location along the microtubule track. The target represents some subcellular compartment such as a synapse in a neuron's dendrites, and target delivery is modeled as a simple absorption process. Using a quasi-steady-state (QSS) reduction technique we calculate analytical approximations of the mean first passage time (MFPT) to find the target. We show that there exists an optimal adenosine triphosphate (ATP) concentration that minimizes the MFPT for two different cases: (i) the motor complex is composed of equal numbers of kinesin motors bound to two different microtubules (symmetric tug-of-war model) and (ii) the motor complex is composed of different numbers of kinesin and dynein motors bound to a single microtubule (asymmetric tug-of-war model)

  8. Random intermittent search and the tug-of-war model of motor-driven transport

    Science.gov (United States)

    Newby, Jay; Bressloff, Paul C.

    2010-04-01

    We formulate the 'tug-of-war' model of microtubule cargo transport by multiple molecular motors as an intermittent random search for a hidden target. A motor complex consisting of multiple molecular motors with opposing directional preference is modeled using a discrete Markov process. The motors randomly pull each other off of the microtubule so that the state of the motor complex is determined by the number of bound motors. The tug-of-war model prescribes the state transition rates and corresponding cargo velocities in terms of experimentally measured physical parameters. We add space to the resulting Chapman-Kolmogorov (CK) equation so that we can consider delivery of the cargo to a hidden target at an unknown location along the microtubule track. The target represents some subcellular compartment such as a synapse in a neuron's dendrites, and target delivery is modeled as a simple absorption process. Using a quasi-steady-state (QSS) reduction technique we calculate analytical approximations of the mean first passage time (MFPT) to find the target. We show that there exists an optimal adenosine triphosphate (ATP) concentration that minimizes the MFPT for two different cases: (i) the motor complex is composed of equal numbers of kinesin motors bound to two different microtubules (symmetric tug-of-war model) and (ii) the motor complex is composed of different numbers of kinesin and dynein motors bound to a single microtubule (asymmetric tug-of-war model).

  9. Random intermittent search and the tug-of-war model of motor-driven transport

    KAUST Repository

    Newby, Jay

    2010-04-16

    We formulate the \\'tug-of-war\\' model of microtubule cargo transport by multiple molecular motors as an intermittent random search for a hidden target. A motor complex consisting of multiple molecular motors with opposing directional preference is modeled using a discrete Markov process. The motors randomly pull each other off of the microtubule so that the state of the motor complex is determined by the number of bound motors. The tug-of-war model prescribes the state transition rates and corresponding cargo velocities in terms of experimentally measured physical parameters. We add space to the resulting Chapman-Kolmogorov (CK) equation so that we can consider delivery of the cargo to a hidden target at an unknown location along the microtubule track. The target represents some subcellular compartment such as a synapse in a neuron\\'s dendrites, and target delivery is modeled as a simple absorption process. Using a quasi-steady-state (QSS) reduction technique we calculate analytical approximations of the mean first passage time (MFPT) to find the target. We show that there exists an optimal adenosine triphosphate (ATP) concentration that minimizes the MFPT for two different cases: (i) the motor complex is composed of equal numbers of kinesin motors bound to two different microtubules (symmetric tug-of-war model) and (ii) the motor complex is composed of different numbers of kinesin and dynein motors bound to a single microtubule (asymmetric tug-of-war model). © 2010 IOP Publishing Ltd.

  10. Random intermittent search and the tug-of-war model of motor-driven transport

    KAUST Repository

    Newby, Jay; Bressloff, Paul C

    2010-01-01

    We formulate the 'tug-of-war' model of microtubule cargo transport by multiple molecular motors as an intermittent random search for a hidden target. A motor complex consisting of multiple molecular motors with opposing directional preference is modeled using a discrete Markov process. The motors randomly pull each other off of the microtubule so that the state of the motor complex is determined by the number of bound motors. The tug-of-war model prescribes the state transition rates and corresponding cargo velocities in terms of experimentally measured physical parameters. We add space to the resulting Chapman-Kolmogorov (CK) equation so that we can consider delivery of the cargo to a hidden target at an unknown location along the microtubule track. The target represents some subcellular compartment such as a synapse in a neuron's dendrites, and target delivery is modeled as a simple absorption process. Using a quasi-steady-state (QSS) reduction technique we calculate analytical approximations of the mean first passage time (MFPT) to find the target. We show that there exists an optimal adenosine triphosphate (ATP) concentration that minimizes the MFPT for two different cases: (i) the motor complex is composed of equal numbers of kinesin motors bound to two different microtubules (symmetric tug-of-war model) and (ii) the motor complex is composed of different numbers of kinesin and dynein motors bound to a single microtubule (asymmetric tug-of-war model). © 2010 IOP Publishing Ltd.

  11. Action-State Orientation and the Theory of Planned Behavior: A Study of Job Search in China

    Science.gov (United States)

    Song, Zhaoli; Wanberg, Connie; Niu, Xiongying; Xie, Yizhong

    2006-01-01

    Job search is an important element of people's careers and is especially critical for unemployed individuals. The current study surveyed a sample of 328 unemployed job seekers in China to test hypotheses related to the theory of planned behavior and action-state orientation theory. Results of the three-wave longitudinal study demonstrated that the…

  12. Non-equilibrium random matrix theory. Transition probabilities

    Energy Technology Data Exchange (ETDEWEB)

    Pedro, Francisco Gil [Univ. Autonoma de Madrid (Spain). Dept. de Fisica Teorica; Westphal, Alexander [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Gruppe Theorie

    2016-06-15

    In this letter we present an analytic method for calculating the transition probability between two random Gaussian matrices with given eigenvalue spectra in the context of Dyson Brownian motion. We show that in the Coulomb gas language, in large N limit, memory of the initial state is preserved in the form of a universal linear potential acting on the eigenvalues. We compute the likelihood of any given transition as a function of time, showing that as memory of the initial state is lost, transition probabilities converge to those of the static ensemble.

  13. Skew-orthogonal polynomials, differential systems and random matrix theory

    International Nuclear Information System (INIS)

    Ghosh, S.

    2007-01-01

    We study skew-orthogonal polynomials with respect to the weight function exp[-2V (x)], with V (x) = Σ K=1 2d (u K /K)x K , u 2d > 0, d > 0. A finite subsequence of such skew-orthogonal polynomials arising in the study of Orthogonal and Symplectic ensembles of random matrices, satisfy a system of differential-difference-deformation equation. The vectors formed by such subsequence has the rank equal to the degree of the potential in the quaternion sense. These solutions satisfy certain compatibility condition and hence admit a simultaneous fundamental system of solutions. (author)

  14. Non-equilibrium random matrix theory. Transition probabilities

    International Nuclear Information System (INIS)

    Pedro, Francisco Gil; Westphal, Alexander

    2016-06-01

    In this letter we present an analytic method for calculating the transition probability between two random Gaussian matrices with given eigenvalue spectra in the context of Dyson Brownian motion. We show that in the Coulomb gas language, in large N limit, memory of the initial state is preserved in the form of a universal linear potential acting on the eigenvalues. We compute the likelihood of any given transition as a function of time, showing that as memory of the initial state is lost, transition probabilities converge to those of the static ensemble.

  15. Extremes in random fields a theory and its applications

    CERN Document Server

    Yakir, Benjamin

    2013-01-01

    Presents a useful new technique for analyzing the extreme-value behaviour of random fields Modern science typically involves the analysis of increasingly complex data. The extreme values that emerge in the statistical analysis of complex data are often of particular interest. This book focuses on the analytical approximations of the statistical significance of extreme values. Several relatively complex applications of the technique to problems that emerge in practical situations are presented.  All the examples are difficult to analyze using classical methods, and as a result, the author pr

  16. Category Theory Approach to Solution Searching Based on Photoexcitation Transfer Dynamics

    Directory of Open Access Journals (Sweden)

    Makoto Naruse

    2017-07-01

    Full Text Available Solution searching that accompanies combinatorial explosion is one of the most important issues in the age of artificial intelligence. Natural intelligence, which exploits natural processes for intelligent functions, is expected to help resolve or alleviate the difficulties of conventional computing paradigms and technologies. In fact, we have shown that a single-celled organism such as an amoeba can solve constraint satisfaction problems and related optimization problems as well as demonstrate experimental systems based on non-organic systems such as optical energy transfer involving near-field interactions. However, the fundamental mechanisms and limitations behind solution searching based on natural processes have not yet been understood. Herein, we present a theoretical background of solution searching based on optical excitation transfer from a category-theoretic standpoint. One important indication inspired by the category theory is that the satisfaction of short exact sequences is critical for an adequate computational operation that determines the flow of time for the system and is termed as “short-exact-sequence-based time.” In addition, the octahedral and braid structures known in triangulated categories provide a clear understanding of the underlying mechanisms, including a quantitative indication of the difficulties of obtaining solutions based on homology dimension. This study contributes to providing a fundamental background of natural intelligence.

  17. Kinetic Theory of Electronic Transport in Random Magnetic Fields

    Science.gov (United States)

    Lucas, Andrew

    2018-03-01

    We present the theory of quasiparticle transport in perturbatively small inhomogeneous magnetic fields across the ballistic-to-hydrodynamic crossover. In the hydrodynamic limit, the resistivity ρ generically grows proportionally to the rate of momentum-conserving electron-electron collisions at large enough temperatures T . In particular, the resulting flow of electrons provides a simple scenario where viscous effects suppress conductance below the ballistic value. This new mechanism for ρ ∝T2 resistivity in a Fermi liquid may describe low T transport in single-band SrTiO3 .

  18. The use of grounded theory in studies of nurses and midwives' coping processes: a systematic literature search.

    Science.gov (United States)

    Cheer, Karen; MacLaren, David; Tsey, Komla

    2015-01-01

    Researchers are increasingly using grounded theory methodologies to study the professional experience of nurses and midwives. To review common grounded theory characteristics and research design quality as described in grounded theory studies of coping strategies used by nurses and midwives. A systematic database search for 2005-2015 identified and assessed grounded theory characteristics from 16 studies. Study quality was assessed using a modified Critical Appraisal Skills Programme tool. Grounded theory was considered a methodology or a set of methods, able to be used within different nursing and midwifery contexts. Specific research requirements determined the common grounded theory characteristics used in different studies. Most researchers did not clarify their epistemological and theoretical perspectives. To improve research design and trustworthiness of grounded theory studies in nursing and midwifery, researchers need to state their theoretical stance and clearly articulate their use of grounded theory methodology and characteristics in research reporting.

  19. Design, rationale, and baseline demographics of SEARCH I: a prospective cluster-randomized study

    Directory of Open Access Journals (Sweden)

    Albers F

    2012-07-01

    Full Text Available Frank Albers,1 Asif Shaikh,2 Ahmar Iqbal,31Medical Affairs Respiratory, 2Clinical Development and Medical Affairs, Field Based Medicine-Respiratory, Boehringer Ingelheim Pharmaceuticals, Inc, Ridgefield, CT, USA; 3Respiratory Medical Affairs, Pfizer Inc, New York, NY, USAAbstract: Questionnaires are available to identify patients at risk for several chronic diseases, including COPD, but are infrequently utilized in primary care. COPD is often underdiagnosed, while at the same time the US Preventive Services Task Force recommends against spirometric screening for COPD in asymptomatic adults. Use of a symptom-based questionnaire and subsequent handheld spirometric device depending on the answers to the questionnaire is a promising approach to identify patients at risk for COPD. Screening, Evaluating and Assessing Rate CHanges of diagnosing respiratory conditions in primary care 1 (SEARCH I was a prospective cluster-randomized study in 168 US primary care practices evaluating the effect of the COPD-Population Screener (COPD-PS™ questionnaire. The effect of this questionnaire alone or sequentially with the handheld copd-6TM device was evaluated on new diagnoses of COPD and on respiratory diagnostic practice patterns (including referrals for pulmonary function testing, referrals to pulmonologists, new diagnoses of COPD, and new respiratory medication prescriptions. Participating practices entered a total of 9704 consecutive consenting subjects aged ≥ 40 years attending primary care clinics. Study arm results were compared for new COPD diagnosis rates between usual care and (1 COPD-PS plus copd-6 and (2 COPD-PS alone. A cluster-randomization design allowed comparison of the intervention effects at the practice level instead of individuals being the subjects of the intervention. Regional principal investigators controlled the flow of study information to sub-investigators at participating practices to reduce observation bias (Hawthorne effect. The

  20. A simple heuristic for Internet-based evidence search in primary care: a randomized controlled trial

    Directory of Open Access Journals (Sweden)

    Eberbach A

    2016-08-01

    Full Text Available Andreas Eberbach,1 Annette Becker,1 Justine Rochon,2 Holger Finkemeler,1Achim Wagner,3 Norbert Donner-Banzhoff1 1Department of Family and Community Medicine, Philipp University of Marburg, Marburg, Germany; 2Institute of Medical Biometry and Informatics, University of Heidelberg, Heidelberg, Germany; 3Department of Sport Medicine, Justus-Liebig-University of Giessen, Giessen, Germany Background: General practitioners (GPs are confronted with a wide variety of clinical questions, many of which remain unanswered. Methods: In order to assist GPs in finding quick, evidence-based answers, we developed a learning program (LP with a short interactive workshop based on a simple ­three-step-heuristic to improve their search and appraisal competence (SAC. We evaluated the LP ­effectiveness with a randomized controlled trial (RCT. Participants (intervention group [IG] n=20; ­control group [CG] n=31 rated acceptance and satisfaction and also answered 39 ­knowledge ­questions to assess their SAC. We controlled for previous knowledge in content areas covered by the test. Results: Main outcome – SAC: within both groups, the pre–post test shows significant (P=0.00 improvements in correctness (IG 15% vs CG 11% and confidence (32% vs 26% to find evidence-based answers. However, the SAC difference was not significant in the RCT. Other measures: Most workshop participants rated “learning atmosphere” (90%, “skills acquired” (90%, and “relevancy to my practice” (86% as good or very good. The ­LP-recommendations were implemented by 67% of the IG, whereas 15% of the CG already conformed to LP recommendations spontaneously (odds ratio 9.6, P=0.00. After literature search, the IG showed a (not significantly higher satisfaction regarding “time spent” (IG 80% vs CG 65%, “quality of information” (65% vs 54%, and “amount of information” (53% vs 47%.Conclusion: Long-standing established GPs have a good SAC. Despite high acceptance, strong

  1. Decision making in family medicine: randomized trial of the effects of the InfoClinique and Trip database search engines.

    Science.gov (United States)

    Labrecque, Michel; Ratté, Stéphane; Frémont, Pierre; Cauchon, Michel; Ouellet, Jérôme; Hogg, William; McGowan, Jessie; Gagnon, Marie-Pierre; Njoya, Merlin; Légaré, France

    2013-10-01

    To compare the ability of users of 2 medical search engines, InfoClinique and the Trip database, to provide correct answers to clinical questions and to explore the perceived effects of the tools on the clinical decision-making process. Randomized trial. Three family medicine units of the family medicine program of the Faculty of Medicine at Laval University in Quebec city, Que. Fifteen second-year family medicine residents. Residents generated 30 structured questions about therapy or preventive treatment (2 questions per resident) based on clinical encounters. Using an Internet platform designed for the trial, each resident answered 20 of these questions (their own 2, plus 18 of the questions formulated by other residents, selected randomly) before and after searching for information with 1 of the 2 search engines. For each question, 5 residents were randomly assigned to begin their search with InfoClinique and 5 with the Trip database. The ability of residents to provide correct answers to clinical questions using the search engines, as determined by third-party evaluation. After answering each question, participants completed a questionnaire to assess their perception of the engine's effect on the decision-making process in clinical practice. Of 300 possible pairs of answers (1 answer before and 1 after the initial search), 254 (85%) were produced by 14 residents. Of these, 132 (52%) and 122 (48%) pairs of answers concerned questions that had been assigned an initial search with InfoClinique and the Trip database, respectively. Both engines produced an important and similar absolute increase in the proportion of correct answers after searching (26% to 62% for InfoClinique, for an increase of 36%; 24% to 63% for the Trip database, for an increase of 39%; P = .68). For all 30 clinical questions, at least 1 resident produced the correct answer after searching with either search engine. The mean (SD) time of the initial search for each question was 23.5 (7

  2. Replica field theory for a polymer in random media

    International Nuclear Information System (INIS)

    Goldschmidt, Yadin Y.

    2000-01-01

    In this paper we revisit the problem of a (non-self-avoiding) polymer chain in a random medium which was previously investigated by Edwards and Muthukumar (EM) [J. Chem. Phys. 89, 2435 (1988)]. As noticed by Cates and Ball (CB) [J. Phys. (France) 49, 2009 (1988)] there is a discrepancy between the predictions of the replica calculation of EM and the expectation that in an infinite medium the quenched and annealed results should coincide (for a chain that is free to move) and a long polymer should always collapse. CB argued that only in a finite volume one might see a ''localization transition'' (or crossover) from a stretched to a collapsed chain in three spatial dimensions. Here we carry out the replica calculation in the presence of an additional confining harmonic potential that mimics the effect of a finite volume. Using a variational scheme with five variational parameters we derive analytically for d -1/(4-d) ∼(g ln V) -1/(4-d) , where R is the radius of gyration, g is the strength of the disorder, μ is the spring constant associated with the confining potential, and V is the associated effective volume of the system. Thus the EM result is recovered with their constant replaced by ln V as argued by CB. We see that in the strict infinite volume limit the polymer always collapses, but for finite volume a transition from a stretched to a collapsed form might be observed as a function of the strength of the disorder. For d V ' ∼exp(g 2/(2-d) L (4-d)/(2-d) ) the annealed results are recovered and R∼(Lg) 1/(d-2) , where L is the length of the polymer. Hence the polymer also collapses in the large L limit. The one-step replica symmetry breaking solution is crucial for obtaining the above results. (c) 2000 The American Physical Society

  3. A generalization of random matrix theory and its application to statistical physics.

    Science.gov (United States)

    Wang, Duan; Zhang, Xin; Horvatic, Davor; Podobnik, Boris; Eugene Stanley, H

    2017-02-01

    To study the statistical structure of crosscorrelations in empirical data, we generalize random matrix theory and propose a new method of cross-correlation analysis, known as autoregressive random matrix theory (ARRMT). ARRMT takes into account the influence of auto-correlations in the study of cross-correlations in multiple time series. We first analytically and numerically determine how auto-correlations affect the eigenvalue distribution of the correlation matrix. Then we introduce ARRMT with a detailed procedure of how to implement the method. Finally, we illustrate the method using two examples taken from inflation rates for air pressure data for 95 US cities.

  4. Random matrix theory and analysis of nucleus-nucleus collision at high energies

    International Nuclear Information System (INIS)

    Shahaliev, E.I.; Inst. of Radiation Problems, Baku; ); Kuznetsov, A.A.; Suleymanov, M.K.; ); Teryaev, O.V.; )

    2006-01-01

    A novel method for analysis of experimental data obtained at relativistic nucleus-nucleus collisions is proposed. The method, based on the ideas of Random Matrix Theory, is applied to detect systematic errors that occur at measurements of momentum distributions of emitted particles. The unfolded momentum distribution is well described by the Gaussian orthogonal ensemble of random matrices, when the uncertainty in the momentum distribution is maximal. The method is free from unwanted background contributions [ru

  5. VES/TEM 1D joint inversion by using Controlled Random Search (CRS) algorithm

    Science.gov (United States)

    Bortolozo, Cassiano Antonio; Porsani, Jorge Luís; Santos, Fernando Acácio Monteiro dos; Almeida, Emerson Rodrigo

    2015-01-01

    Electrical (DC) and Transient Electromagnetic (TEM) soundings are used in a great number of environmental, hydrological, and mining exploration studies. Usually, data interpretation is accomplished by individual 1D models resulting often in ambiguous models. This fact can be explained by the way as the two different methodologies sample the medium beneath surface. Vertical Electrical Sounding (VES) is good in marking resistive structures, while Transient Electromagnetic sounding (TEM) is very sensitive to conductive structures. Another difference is VES is better to detect shallow structures, while TEM soundings can reach deeper layers. A Matlab program for 1D joint inversion of VES and TEM soundings was developed aiming at exploring the best of both methods. The program uses CRS - Controlled Random Search - algorithm for both single and 1D joint inversions. Usually inversion programs use Marquadt type algorithms but for electrical and electromagnetic methods, these algorithms may find a local minimum or not converge. Initially, the algorithm was tested with synthetic data, and then it was used to invert experimental data from two places in Paraná sedimentary basin (Bebedouro and Pirassununga cities), both located in São Paulo State, Brazil. Geoelectric model obtained from VES and TEM data 1D joint inversion is similar to the real geological condition, and ambiguities were minimized. Results with synthetic and real data show that 1D VES/TEM joint inversion better recovers simulated models and shows a great potential in geological studies, especially in hydrogeological studies.

  6. Application of the random field theory in PET imaging - injection dose optimization

    Czech Academy of Sciences Publication Activity Database

    Dvořák, Jiří; Boldyš, Jiří; Skopalová, M.; Bělohlávek, O.

    2013-01-01

    Roč. 49, č. 2 (2013), s. 280-300 ISSN 0023-5954 R&D Projects: GA MŠk 1M0572 Institutional support: RVO:67985556 Keywords : random field theory * Euler characteristic * PET imaging * PET image quality Subject RIV: BD - Theory of Information Impact factor: 0.563, year: 2013 http://library.utia.cas.cz/separaty/2013/ZOI/boldys-0397176.pdf

  7. A note on the effective medium theory of random resistive-reactive medium

    International Nuclear Information System (INIS)

    Kumar, N.; Jayannavar, A.M.

    1981-06-01

    The effective medium theory for a system with randomly distributed point conductivity and polarizability is re-formulated, with attention to cross-terms involving the two disorder parameters. The treatment reveals a certain inconsistency of the conventional theory owing to the neglect of the Maxwell-Wagner effect. The results are significant for the critical resistivity and dielectric anomalies of a binary liquid mixture at the phase-separation point. (author)

  8. Applications of a general random-walk theory for confined diffusion.

    Science.gov (United States)

    Calvo-Muñoz, Elisa M; Selvan, Myvizhi Esai; Xiong, Ruichang; Ojha, Madhusudan; Keffer, David J; Nicholson, Donald M; Egami, Takeshi

    2011-01-01

    A general random walk theory for diffusion in the presence of nanoscale confinement is developed and applied. The random-walk theory contains two parameters describing confinement: a cage size and a cage-to-cage hopping probability. The theory captures the correct nonlinear dependence of the mean square displacement (MSD) on observation time for intermediate times. Because of its simplicity, the theory also requires modest computational requirements and is thus able to simulate systems with very low diffusivities for sufficiently long time to reach the infinite-time-limit regime where the Einstein relation can be used to extract the self-diffusivity. The theory is applied to three practical cases in which the degree of order in confinement varies. The three systems include diffusion of (i) polyatomic molecules in metal organic frameworks, (ii) water in proton exchange membranes, and (iii) liquid and glassy iron. For all three cases, the comparison between theory and the results of molecular dynamics (MD) simulations indicates that the theory can describe the observed diffusion behavior with a small fraction of the computational expense. The confined-random-walk theory fit to the MSDs of very short MD simulations is capable of accurately reproducing the MSDs of much longer MD simulations. Furthermore, the values of the parameter for cage size correspond to the physical dimensions of the systems and the cage-to-cage hopping probability corresponds to the activation barrier for diffusion, indicating that the two parameters in the theory are not simply fitted values but correspond to real properties of the physical system.

  9. Scale-free animal movement patterns: Levy walks outperform fractional Brownian motions and fractional Levy motions in random search scenarios

    International Nuclear Information System (INIS)

    Reynolds, A M

    2009-01-01

    The movement patterns of a diverse range of animals have scale-free characteristics. These characteristics provide necessary but not sufficient conditions for the presence of movement patterns that can be approximated by Levy walks. Nevertheless, it has been widely assumed that the occurrence of scale-free animal movements can indeed be attributed to the presence of Levy walks. This is, in part, because it is known that the super-diffusive properties of Levy walks can be advantageous in random search scenarios when searchers have little or no prior knowledge of target locations. However, fractional Brownian motions (fBms) and fractional Levy motions (fLms) are both scale-free and super-diffusive, and so it is possible that these motions rather than Levy walks underlie some or all occurrences of scale-free animal movement patterns. Here this possibility is examined in numerical simulations through a determination of the searching efficiencies of fBm and fLm searches. It is shown that these searches are less efficient than Levy walk searches. This finding does not rule out the possibility that some animals with scale-free movement patterns are executing fBm and fLm searches, but it does make Levy walk searches the more likely possibility.

  10. A portable high-quality random number generator for lattice field theory simulations

    International Nuclear Information System (INIS)

    Luescher, M.

    1993-09-01

    The theory underlying a proposed random number generator for numerical simulations in elementary particle physics and statistical mechanics is discussed. The generator is based on an algorithm introduced by Marsaglia and Zaman, with an important added feature leading to demonstrably good statistical properties. It can be implemented exactly on any computer complying with the IEEE-754 standard for single precision floating point arithmetic. (orig.)

  11. A note on the random walk theory of recoil movement in prolonged ion bombardment

    International Nuclear Information System (INIS)

    Koponen, Ismo

    1994-01-01

    A characteristic function is derived for the probability distribution of final positions of recoil atoms in prolonged ion bombardment of dense matter. The derivation is done within the framework of Poissonian random walk theory using a jump distribution, which is somewhat more general than those studied previously. ((orig.))

  12. Theory of Mind training in children with autism: a randomized controlled trial

    NARCIS (Netherlands)

    Begeer, S.M.; Gevers, C.; Clifford, P.; Verhoeve, M.; Kat, K.; Hoddenbach, E.; Boer, F.

    2011-01-01

    Many children with Autism Spectrum Disorders (ASD) participate in social skills or Theory of Mind (ToM) treatments. However, few studies have shown evidence for their effectiveness. The current study used a randomized controlled design to test the effectiveness of a 16-week ToM treatment in 8-13

  13. Theory of Mind Training in Children with Autism: A Randomized Controlled Trial

    Science.gov (United States)

    Begeer, Sander; Gevers, Carolien; Clifford, Pamela; Verhoeve, Manja; Kat, Kirstin; Hoddenbach, Elske; Boer, Frits

    2011-01-01

    Many children with Autism Spectrum Disorders (ASD) participate in social skills or Theory of Mind (ToM) treatments. However, few studies have shown evidence for their effectiveness. The current study used a randomized controlled design to test the effectiveness of a 16-week ToM treatment in 8-13 year old children with ASD and normal IQs (n = 40).…

  14. The string tension and the scaling behavior of SU(2) gauge theory on a random lattice

    International Nuclear Information System (INIS)

    Qui Zhaoming; Ren Haichang; Academia Sinica, Beijing; Wang Xiaoqun; Yang Zhixing; Zhao Enping

    1987-01-01

    The SU(2) gauge theory on an 8 4 random lattice has been studied by the Monte Carlo method. The string tensions have been evaluated. They display the expected scaling behavior for β = 1.2-1.3. The scale parameter Λ RAN has been determined approximately. (orig.)

  15. The theory of reflexivity: A non-stochastic randomness theory for business schools only?

    OpenAIRE

    Ehnts, Dirk; Carrión Álvarez, Miguel

    2013-01-01

    The Alchemy of Finance, a book written by George Soros (1987) on the workings of financial markets, 'has found a place in the reading lists of business schools as distinct from economics departments', according to the author (2003, 4). His theory of reflexivity, which is at the center of the book, states that interdependence exists between the cognitive and manipulative functions of market participants. While Soros claims that imperfect knowledge rules on financial markets, academic orthodoxy...

  16. Searching for answers to clinical questions using google versus evidence-based summary resources: a randomized controlled crossover study.

    Science.gov (United States)

    Kim, Sarang; Noveck, Helaine; Galt, James; Hogshire, Lauren; Willett, Laura; O'Rourke, Kerry

    2014-06-01

    To compare the speed and accuracy of answering clinical questions using Google versus summary resources. In 2011 and 2012, 48 internal medicine interns from two classes at Rutgers University Robert Wood Johnson Medical School, who had been trained to use three evidence-based summary resources, performed four-minute computer searches to answer 10 clinical questions. Half were randomized to initiate searches for answers to questions 1 to 5 using Google; the other half initiated searches using a summary resource. They then crossed over and used the other resource for questions 6 to 10. They documented the time spent searching and the resource where the answer was found. Time to correct response and percentage of correct responses were compared between groups using t test and general estimating equations. Of 480 questions administered, interns found answers for 393 (82%). Interns initiating searches in Google used a wider variety of resources than those starting with summary resources. No significant difference was found in mean time to correct response (138.5 seconds for Google versus 136.1 seconds for summary resource; P = .72). Mean correct response rate was 58.4% for Google versus 61.5% for summary resource (mean difference -3.1%; 95% CI -10.3% to 4.2%; P = .40). The authors found no significant differences in speed or accuracy between searches initiated using Google versus summary resources. Although summary resources are considered to provide the highest quality of evidence, improvements to allow for better speed and accuracy are needed.

  17. Discussion of The Forward Search: Theory and Data Analysis by Anthony C. Atkinson, Marco Riani, and Andrea Ceroli

    DEFF Research Database (Denmark)

    Johansen, Søren; Nielsen, Bent

    The Forward Search Algorithm is a statistical algorithm for obtaining robust estimators of regression coefficients in the presence of outliers. The algorithm selects a succession of subsets of observations from which the parameters are estimated. The present note shows how the theory of empirical...

  18. Discussion of 'The Forward Search: Theory and Data Analysis' by Anthony C. Atkinson, Marco Riani, and Andrea Ceroli

    DEFF Research Database (Denmark)

    Johansen, Søren; Nielsen, Bent

    The Forward Search Algorithm is a statistical algorithm for obtaining robust estimators of regression coefficients in the presence of outliers. The algorithm selects a succession of subsets of observations from which the parameters are estimated. The present note shows how the theory of empirical...

  19. Searches for T-odd interactions in nuclear processes: Review of the theory

    International Nuclear Information System (INIS)

    Herczeg, P.

    1995-01-01

    CP-violation has been seen so far only in the neutral kaon system. Its origin is still unknown. If the CPT theorem holds, as is the case in gauge theories, CP-violating interactions violate also time reversal (T) invariance. Regarding the CPT theorem there is some experimental evidence that the interaction responsible for the observed CP-violation violates T-invariance. The observed CP-violation may just be a manifestation of the weak interaction of the Standard Model (SM), or it is due to an interaction beyond the SM. In both cases some of the new interactions may give rise to observable CP-violation where the SM contribution is invisible. This underlines the importance of searching for CP-violating and T-violating effects in many processes. In this talk we shall review what has been learned about T-violating interactions that can be probed in nuclear processes from experiments outside of and within nuclear physics, and consider the role of nuclear physics experiments in obtaining further information on such interactions

  20. Efficient Algorithms for Searching the Minimum Information Partition in Integrated Information Theory

    Science.gov (United States)

    Kitazono, Jun; Kanai, Ryota; Oizumi, Masafumi

    2018-03-01

    The ability to integrate information in the brain is considered to be an essential property for cognition and consciousness. Integrated Information Theory (IIT) hypothesizes that the amount of integrated information ($\\Phi$) in the brain is related to the level of consciousness. IIT proposes that to quantify information integration in a system as a whole, integrated information should be measured across the partition of the system at which information loss caused by partitioning is minimized, called the Minimum Information Partition (MIP). The computational cost for exhaustively searching for the MIP grows exponentially with system size, making it difficult to apply IIT to real neural data. It has been previously shown that if a measure of $\\Phi$ satisfies a mathematical property, submodularity, the MIP can be found in a polynomial order by an optimization algorithm. However, although the first version of $\\Phi$ is submodular, the later versions are not. In this study, we empirically explore to what extent the algorithm can be applied to the non-submodular measures of $\\Phi$ by evaluating the accuracy of the algorithm in simulated data and real neural data. We find that the algorithm identifies the MIP in a nearly perfect manner even for the non-submodular measures. Our results show that the algorithm allows us to measure $\\Phi$ in large systems within a practical amount of time.

  1. Random Process Theory Approach to Geometric Heterogeneous Surfaces: Effective Fluid-Solid Interaction

    Science.gov (United States)

    Khlyupin, Aleksey; Aslyamov, Timur

    2017-06-01

    Realistic fluid-solid interaction potentials are essential in description of confined fluids especially in the case of geometric heterogeneous surfaces. Correlated random field is considered as a model of random surface with high geometric roughness. We provide the general theory of effective coarse-grained fluid-solid potential by proper averaging of the free energy of fluid molecules which interact with the solid media. This procedure is largely based on the theory of random processes. We apply first passage time probability problem and assume the local Markov properties of random surfaces. General expression of effective fluid-solid potential is obtained. In the case of small surface irregularities analytical approximation for effective potential is proposed. Both amorphous materials with large surface roughness and crystalline solids with several types of fcc lattices are considered. It is shown that the wider the lattice spacing in terms of molecular diameter of the fluid, the more obtained potentials differ from classical ones. A comparison with published Monte-Carlo simulations was discussed. The work provides a promising approach to explore how the random geometric heterogeneity affects on thermodynamic properties of the fluids.

  2. Recent progress in the theory of random surfaces and simplicial quantum gravity

    International Nuclear Information System (INIS)

    Ambjoern, J.

    1995-01-01

    Some of the recent developments in the theory of random surfaces and simplicial quantum gravity is reviewed. For 2d quantum gravity this includes the failure of Regge calculus, our improved understanding of the c>1 regime, some surprises for q-state Potts models with q>4, attempts to use renormalization group techniques, new critical behavior of random surface models with extrinsic curvature and improved algorithms. For simplicial quantum gravity in higher dimensions it includes a discussion of the exponential entropy bound needed for the models to be well defined, the question of ''computational ergodicity'' and the question of how to extract continuum behavior from the lattice simulations. ((orig.))

  3. Search for unity: notes for a history of quantum field theory

    International Nuclear Information System (INIS)

    Weinberg, S.

    1977-01-01

    The essential points of quantum field theory are recounted without using mathematics. The foundations of the theory, the initial states, the problem of infinities, the revival of the theory, and weak and strong interactions, are described. 72 references

  4. Raising Reliability of Web Search Tool Research through Replication and Chaos Theory

    OpenAIRE

    Nicholson, Scott

    1999-01-01

    Because the World Wide Web is a dynamic collection of information, the Web search tools (or "search engines") that index the Web are dynamic. Traditional information retrieval evaluation techniques may not provide reliable results when applied to the Web search tools. This study is the result of ten replications of the classic 1996 Ding and Marchionini Web search tool research. It explores the effects that replication can have on transforming unreliable results from one iteration into replica...

  5. Scaling Law for Photon Transmission through Optically Turbid Slabs Based on Random Walk Theory

    Directory of Open Access Journals (Sweden)

    Xuesong Li

    2012-03-01

    Full Text Available Past work has demonstrated the value of a random walk theory (RWT to solve multiple-scattering problems arising in numerous contexts. This paper’s goal is to investigate the application range of the RWT using Monte Carlo simulations and extending it to anisotropic media using scaling laws. Meanwhile, this paper also reiterates rules for converting RWT formulas to real physical dimensions, and corrects some errors which appear in an earlier publication. The RWT theory, validated by the Monte Carlo simulations and combined with the scaling law, is expected to be useful to study multiple scattering and to greatly reduce the computation cost.

  6. Summing Feynman graphs by Monte Carlo: Planar φ3-theory and dynamically triangulated random surfaces

    International Nuclear Information System (INIS)

    Boulatov, D.V.

    1988-01-01

    New combinatorial identities are suggested relating the ratio of (n-1)th and nth orders of (planar) perturbation expansion for any quantity to some average over the ensemble of all planar graphs of the nth order. These identities are used for Monte Carlo calculation of critical exponents γ str (string susceptibility) in planar φ 3 -theory and in the dynamically triangulated random surface (DTRS) model near the convergence circle for various dimensions. In the solvable case D=1 the exact critical properties of the theory are reproduced numerically. (orig.)

  7. Analysis of family-wise error rates in statistical parametric mapping using random field theory.

    Science.gov (United States)

    Flandin, Guillaume; Friston, Karl J

    2017-11-01

    This technical report revisits the analysis of family-wise error rates in statistical parametric mapping-using random field theory-reported in (Eklund et al. []: arXiv 1511.01863). Contrary to the understandable spin that these sorts of analyses attract, a review of their results suggests that they endorse the use of parametric assumptions-and random field theory-in the analysis of functional neuroimaging data. We briefly rehearse the advantages parametric analyses offer over nonparametric alternatives and then unpack the implications of (Eklund et al. []: arXiv 1511.01863) for parametric procedures. Hum Brain Mapp, 2017. © 2017 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc. © 2017 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.

  8. Random Matrix Theory of the Energy-Level Statistics of Disordered Systems at the Anderson Transition

    OpenAIRE

    Canali, C. M.

    1995-01-01

    We consider a family of random matrix ensembles (RME) invariant under similarity transformations and described by the probability density $P({\\bf H})= \\exp[-{\\rm Tr}V({\\bf H})]$. Dyson's mean field theory (MFT) of the corresponding plasma model of eigenvalues is generalized to the case of weak confining potential, $V(\\epsilon)\\sim {A\\over 2}\\ln ^2(\\epsilon)$. The eigenvalue statistics derived from MFT are shown to deviate substantially from the classical Wigner-Dyson statistics when $A

  9. Analysis of aeroplane boarding via spacetime geometry and random matrix theory

    International Nuclear Information System (INIS)

    Bachmat, E; Berend, D; Sapir, L; Skiena, S; Stolyarov, N

    2006-01-01

    We show that aeroplane boarding can be asymptotically modelled by two-dimensional Lorentzian geometry. Boarding time is given by the maximal proper time among curves in the model. Discrepancies between the model and simulation results are closely related to random matrix theory. The models can be used to explain why some commonly practiced airline boarding policies are ineffective and even detrimental. (letter to the editor)

  10. Large Neighborhood Search and Adaptive Randomized Decompositions for Flexible Jobshop Scheduling

    DEFF Research Database (Denmark)

    Pacino, Dario; Van Hentenryck, Pascal

    2011-01-01

    This paper considers a constraint-based scheduling approach to the flexible jobshop, a generalization of the traditional jobshop scheduling where activities have a choice of machines. It studies both large neighborhood (LNS) and adaptive randomized de- composition (ARD) schemes, using random...

  11. Constrained Perturbation Regularization Approach for Signal Estimation Using Random Matrix Theory

    KAUST Repository

    Suliman, Mohamed Abdalla Elhag

    2016-10-06

    In this work, we propose a new regularization approach for linear least-squares problems with random matrices. In the proposed constrained perturbation regularization approach, an artificial perturbation matrix with a bounded norm is forced into the system model matrix. This perturbation is introduced to improve the singular-value structure of the model matrix and, hence, the solution of the estimation problem. Relying on the randomness of the model matrix, a number of deterministic equivalents from random matrix theory are applied to derive the near-optimum regularizer that minimizes the mean-squared error of the estimator. Simulation results demonstrate that the proposed approach outperforms a set of benchmark regularization methods for various estimated signal characteristics. In addition, simulations show that our approach is robust in the presence of model uncertainty.

  12. High Dimensional Spectral Graph Theory and Non-backtracking Random Walks on Graphs

    Science.gov (United States)

    Kempton, Mark

    This thesis has two primary areas of focus. First we study connection graphs, which are weighted graphs in which each edge is associated with a d-dimensional rotation matrix for some fixed dimension d, in addition to a scalar weight. Second, we study non-backtracking random walks on graphs, which are random walks with the additional constraint that they cannot return to the immediately previous state at any given step. Our work in connection graphs is centered on the notion of consistency, that is, the product of rotations moving from one vertex to another is independent of the path taken, and a generalization called epsilon-consistency. We present higher dimensional versions of the combinatorial Laplacian matrix and normalized Laplacian matrix from spectral graph theory, and give results characterizing the consistency of a connection graph in terms of the spectra of these matrices. We generalize several tools from classical spectral graph theory, such as PageRank and effective resistance, to apply to connection graphs. We use these tools to give algorithms for sparsification, clustering, and noise reduction on connection graphs. In non-backtracking random walks, we address the question raised by Alon et. al. concerning how the mixing rate of a non-backtracking random walk to its stationary distribution compares to the mixing rate for an ordinary random walk. Alon et. al. address this question for regular graphs. We take a different approach, and use a generalization of Ihara's Theorem to give a new proof of Alon's result for regular graphs, and to extend the result to biregular graphs. Finally, we give a non-backtracking version of Polya's Random Walk Theorem for 2-dimensional grids.

  13. Maintenance overtime policies in reliability theory models with random working cycles

    CERN Document Server

    Nakagawa, Toshio

    2015-01-01

    This book introduces a new concept of replacement in maintenance and reliability theory. Replacement overtime, where replacement occurs at the first completion of a working cycle over a planned time, is a new research topic in maintenance theory and also serves to provide a fresh optimization technique in reliability engineering. In comparing replacement overtime with standard and random replacement techniques theoretically and numerically, 'Maintenance Overtime Policies in Reliability Theory' highlights the key benefits to be gained by adopting this new approach and shows how they can be applied to inspection policies, parallel systems and cumulative damage models. Utilizing the latest research in replacement overtime by internationally recognized experts, readers are introduced to new topics and methods, and learn how to practically apply this knowledge to actual reliability models. This book will serve as an essential guide to a new subject of study for graduate students and researchers and also provides a...

  14. Modifying attitude and intention toward regular physical activity using protection motivation theory: a randomized controlled trial.

    Science.gov (United States)

    Mirkarimi, Kamal; Eri, Maryam; Ghanbari, Mohammad R; Kabir, Mohammad J; Raeisi, Mojtaba; Ozouni-Davaji, Rahman B; Aryaie, Mohammad; Charkazi, Abdurrahman

    2017-10-30

    We were guided by the Protection Motivation Theory to test the motivational interviewing effects on attitude and intention of obese and overweight women to do regular physical activity. In a randomized controlled trial, we selected using convenience sampling 60 overweight and obese women attending health centres. The women were allocated to 2 groups of 30 receiving a standard weight-control programme or motivational interviewing. All constructs of the theory (perceived susceptibility, severity, self-efficacy and response efficacy) and all anthropometric characteristics (except body mass index) were significantly different between the groups at 3 study times. The strongest predictors of intention to do regular physical exercise were perceived response efficacy and attitude at 2- and 6-months follow-up. We showed that targeting motivational interviewing with an emphasis on Protection Motivation Theory constructs appeared to be beneficial for designing and developing appropriate intervention to improve physical activity status among women with overweight and obesity.

  15. Improvement of the Gravitational Search Algorithm by means of Low-Discrepancy Sobol Quasi Random-Number Sequence Based Initialization

    Directory of Open Access Journals (Sweden)

    ALTINOZ, O. T.

    2014-08-01

    Full Text Available Nature-inspired optimization algorithms can obtain the optima by updating the position of each member in the population. At the beginning of the algorithm, the particles of the population are spread into the search space. The initial distribution of particles corresponds to the beginning points of the search process. Hence, the aim is to alter the position for each particle beginning with this initial position until the optimum solution will be found with respect to the pre-determined conditions like maximum iteration, and specific error value for the fitness function. Therefore, initial positions of the population have a direct effect on both accuracy of the optima and the computational cost. If any member in the population is close enough to the optima, this eases the achievement of the exact solution. On the contrary, individuals grouped far away from the optima might yield pointless efforts. In this study, low-discrepancy quasi-random number sequence is preferred for the localization of the population at the initialization phase. By this way, the population is distributed into the search space in a more uniform manner at the initialization phase. The technique is applied to the Gravitational Search Algorithm and compared via the performance on benchmark function solutions.

  16. Subcritical Multiplicative Chaos for Regularized Counting Statistics from Random Matrix Theory

    Science.gov (United States)

    Lambert, Gaultier; Ostrovsky, Dmitry; Simm, Nick

    2018-05-01

    For an {N × N} Haar distributed random unitary matrix U N , we consider the random field defined by counting the number of eigenvalues of U N in a mesoscopic arc centered at the point u on the unit circle. We prove that after regularizing at a small scale {ɛN > 0}, the renormalized exponential of this field converges as N \\to ∞ to a Gaussian multiplicative chaos measure in the whole subcritical phase. We discuss implications of this result for obtaining a lower bound on the maximum of the field. We also show that the moments of the total mass converge to a Selberg-like integral and by taking a further limit as the size of the arc diverges, we establish part of the conjectures in Ostrovsky (Nonlinearity 29(2):426-464, 2016). By an analogous construction, we prove that the multiplicative chaos measure coming from the sine process has the same distribution, which strongly suggests that this limiting object should be universal. Our approach to the L 1-phase is based on a generalization of the construction in Berestycki (Electron Commun Probab 22(27):12, 2017) to random fields which are only asymptotically Gaussian. In particular, our method could have applications to other random fields coming from either random matrix theory or a different context.

  17. Certain theories of multiple scattering in random media of discrete scatterers

    International Nuclear Information System (INIS)

    Olsen, R.L.; Kharadly, M.M.Z.; Corr, D.G.

    1976-01-01

    New information is presented on the accuracy of the heuristic approximations in two important theories of multiple scattering in random media of discrete scatterers: Twersky's ''free-space'' and ''two-space scatterer'' formalisms. Two complementary approaches, based primarily on a one-dimensional model and the one-dimensional forms of the theories, are used. For scatterer distributions of low average density, the ''heuristic'' asymptotic forms for the coherent field and the incoherent intensity are compared with asymptotic forms derived from a systematic analysis of the multiple scattering processes. For distributions of higher density, both in the average number of scatterers per wavelength and in the degree of packing of finite-size scatterers, the analysis is carried out ''experimentally'' by means of a Monte Carlo computer simulation. Approximate series expressions based on the systematic approach are numerically evaluated along with the heuristic expressions. The comparison (for both forward- and back-scattered field moments) is made for the worst-case conditions of strong multiple scattering for which the theories have not previously been evaluated. Several significant conclusions are drawn which have certain practical implications: in application of the theories to describe some of the scattering phenomena which occur in the troposphere, and in the further evaluation of the theories using experiments on physical models

  18. Promoting fruit and vegetable consumption among students: a randomized controlled trial based on social cognitive theory.

    Science.gov (United States)

    Najimi, Arash; Ghaffari, Mohtasham

    2013-10-01

    To assess the effectiveness of an educational intervention based on social cognitive theory on increasing consumption of fruit and vegetable among Grade 4 students. The randomised study was conducted in Isfahan, Iran, during 2011 and comprised 138 students, who were randomly divided into intervention and control groups. Data was collected at the beginning and three months after the intervention. A self-administered questionnaire based on constructs of social cognitive theory and food consumption was used. Theory-based nutrition education was imparted on the intervention group. Data was analysed using SPSS 15 and appropriate statistical tests. The intervention group had 68 (49.27%) subjects, while there were 70 (50.72%) controls. After the intervention, mean scores of behavioural capability (p social support (p = 0.03), and observational learning (p = 0.002) had significantly improved in the intervention group. Nutritional behaviour also showed significant improvement on mean daily intake of fruits and vegetables in the intervention group (p social cognitive theory led to increase in the consumption of fruits and vegetables among students, which confirmed the efficiency of social cognitive theory for such interventions.

  19. Searching for Order Within Chaos: Complexity Theorys Implications to Intelligence Support During Joint Operational Planning

    Science.gov (United States)

    2017-06-09

    joint operational planning . 15. SUBJECT TERMS Complexity Theory , Complex Systems Theory , Complex Adaptive Systems, Dynamical Systems, Joint...complexity theory to analyze military problems and increase joint staff understanding of the operational environment during joint operational planning ?” the...13). Complex Systems Theory : “the study of the behavior of [complex adaptive] systems” (Ilachinski 2004, 4). For the purpose of this thesis there is

  20. Job search and the theory of planned behavior: Minority – majority group differences in The Netherlands

    NARCIS (Netherlands)

    E.A.J. van Hooft (Edwin); M.Ph. Born (Marise); T.W. Taris (Toon); H. van der Flier (Henk)

    2003-01-01

    textabstractThe labor market in many Western countries increasingly diversifies. However, little is known about job search behavior of 'non-traditional' applicants such as ethnic minorities. This study investigated minority – majority group differences in the predictors of job search behavior, using

  1. Research and development modelling in the frame of search - prognosis - risk theory

    International Nuclear Information System (INIS)

    Valeca, Serban Constantin

    2002-01-01

    The re-engineering of the power production processes is an approach targeting the future of the competitive power market, undertaken by the custom-tailored managers able to keep the pace of market. The new corporations must be controlled by a flexible management able to adapt the integrated processes to market's changes, to cope to the price and quality competition. Innovating the structures in the frame of a neural network approach may transform the risks in substantial savings of financial resources. Power production re-engineering concept implies three forces thrusting presently the companies toward renewal, namely, the clients, competition and changes. The clients became offensive the competition is more and more acute while the changes implies continuous advancements. The clients order specifically what they want and what they need while give up the producers' patterns. The competition inserts new products in the market, cheaper and of higher quality, thus eliminating the traditional producers. The fast changing of the technologies, products and service distributions or of the co-operation patterns with the client ensures a sustainable development of the corporations. An analysis of the present processes in business shows the following: - the recommended solutions of re-designing the processes should be adopted; - the highest rate of progress is ensured by a continuous innovating policy; - the high quality products and services should be introduced on market when the demand is maximum, while the prices should be shaped to protect optimally the corporation against economic financial risk. The monograph is a synthetical presentation of the economical-industrial re-engineering described in the frame of search-prognosis-risk model implying technological innovation, processes-products-services quality improvement as well as the human factor framed by training-ergonomic-results descriptors. The decision making issue closely related to information processing and cost

  2. GRASP (Greedy Randomized Adaptive Search Procedures) applied to optimization of petroleum products distribution in pipeline networks; GRASP (Greedy Randomized Adaptative Search Procedures) aplicado ao 'scheduling' de redes de distribuicao de petroleo e derivados

    Energy Technology Data Exchange (ETDEWEB)

    Conte, Viviane Cristhyne Bini; Arruda, Lucia Valeria Ramos de; Yamamoto, Lia [Universidade Tecnologica Federal do Parana (UTFPR), Curitiba, PR (Brazil)

    2008-07-01

    Planning and scheduling of the pipeline network operations aim the most efficient use of the resources resulting in a better performance of the network. A petroleum distribution pipeline network is composed by refineries, sources and/or storage parks, connected by a set of pipelines, which operate the transportation of petroleum and derivatives among adjacent areas. In real scenes, this problem is considered a combinatorial problem, which has difficult solution, which makes necessary methodologies of the resolution that present low computational time. This work aims to get solutions that attempt the demands and minimize the number of batch fragmentations on the sent operations of products for the pipelines in a simplified model of a real network, through by application of the local search metaheuristic GRASP. GRASP does not depend of solutions of previous iterations and works in a random way so it allows the search for the solution in an ampler and diversified search space. GRASP utilization does not demand complex calculation, even the construction stage that requires more computational effort, which provides relative rapidity in the attainment of good solutions. GRASP application on the scheduling of the operations of this network presented feasible solutions in a low computational time. (author)

  3. In Search of Meaning: Are School Rampage Shootings Random and Senseless Violence?

    Science.gov (United States)

    Madfis, Eric

    2017-01-02

    This article discusses Joel Best's ( 1999 ) notion of random violence and applies his concepts of pointlessness, patternlessness, and deterioration to the reality about multiple-victim school shootings gleaned from empirical research about the phenomenon. Best describes how violence is rarely random, as scholarship reveals myriad observable patterns, lots of discernable motives and causes, and often far too much fear-mongering over how bad society is getting and how violent we are becoming. In contrast, it is vital that the media, scholars, and the public better understand crime patterns, criminal motivations, and the causes of fluctuating crime rates. As an effort toward such progress, this article reviews the academic literature on school rampage shootings and explores the extent to which these attacks are and are not random acts of violence.

  4. QUEST: A model to quantify uncertain emergency search techniques, theory and application

    International Nuclear Information System (INIS)

    Johnson, M.M.; Goldsby, M.E.; Plantenga, T.D.; Wilcox, W.B.; Hensley, W.K.

    1996-01-01

    As recent world events show, criminal and terrorist access to nuclear materials is a growing national concern. The national laboratories are taking the lead in developing technologies to counter these potential threats to our national security. Sandia National Laboratories, with support from Pacific Northwest Laboratory and the Remote Sensing Laboratory, has developed QUEST (a model to Quantify Uncertain Emergency Search Techniques), to enhance the performance of organizations in the search for lost or stolen nuclear material. In addition, QUEST supports a wide range of other applications, such as environmental monitoring, nuclear facilities inspections, and searcher training. QUEST simulates the search for nuclear materials and calculates detector response fro various source types and locations. The probability of detecting a radioactive source during a search is a function of many different variables. Through calculation of dynamic detector response, QUEST makes possible quantitative comparisons of various sensor technologies and search patterns. The QUEST model can be used to examine the impact of new detector technologies, explore alternative search concepts, and provide interactive search/inspector training

  5. Search on a hypercubic lattice using a quantum random walk. II. d=2

    International Nuclear Information System (INIS)

    Patel, Apoorva; Raghunathan, K. S.; Rahaman, Md. Aminoor

    2010-01-01

    We investigate the spatial search problem on the two-dimensional square lattice, using the Dirac evolution operator discretized according to the staggered lattice fermion formalism. d=2 is the critical dimension for the spatial search problem, where infrared divergence of the evolution operator leads to logarithmic factors in the scaling behavior. As a result, the construction used in our accompanying article [A. Patel and M. A. Rahaman, Phys. Rev. A 82, 032330 (2010)] provides an O(√(N)lnN) algorithm, which is not optimal. The scaling behavior can be improved to O(√(NlnN)) by cleverly controlling the massless Dirac evolution operator by an ancilla qubit, as proposed by Tulsi [Phys. Rev. A 78, 012310 (2008)]. We reinterpret the ancilla control as introduction of an effective mass at the marked vertex, and optimize the proportionality constants of the scaling behavior of the algorithm by numerically tuning the parameters.

  6. Theory of the Flower Micelle Formation of Amphiphilic Random and Periodic Copolymers in Solution

    Directory of Open Access Journals (Sweden)

    Takahiro Sato

    2018-01-01

    Full Text Available The mixing Gibbs energy Δgm for the flower-micelle phase of amphiphilic random and periodic (including alternating copolymers was formulated on the basis of the lattice model. The formulated Δgm predicts (1 the inverse proportionality of the aggregation number to the degree of polymerization of the copolymer, (2 the increase of the critical micelle concentration with decreasing the hydrophobe content, and (3 the crossover from the micellization to the liquid–liquid phase separation as the hydrophobe content increases. The transition from the uni-core flower micelle to the multi-core flower necklace as the degree of polymerization increases was also implicitly indicated by the theory. These theoretical results were compared with experimental results for amphiphilic random and alternating copolymers reported so far.

  7. A multiple scattering theory for EM wave propagation in a dense random medium

    Science.gov (United States)

    Karam, M. A.; Fung, A. K.; Wong, K. W.

    1985-01-01

    For a dense medium of randomly distributed scatterers an integral formulation for the total coherent field has been developed. This formulation accounts for the multiple scattering of electromagnetic waves including both the twoand three-particle terms. It is shown that under the Markovian assumption the total coherent field and the effective field have the same effective wave number. As an illustration of this theory, the effective wave number and the extinction coefficient are derived in terms of the polarizability tensor and the pair distribution function for randomly distributed small spherical scatterers. It is found that the contribution of the three-particle term increases with the particle size, the volume fraction, the frequency and the permittivity of the particle. This increase is more significant with frequency and particle size than with other parameters.

  8. Theory-based self-management educational interventions on patients with type 2 diabetes: a systematic review and meta-analysis of randomized controlled trials.

    Science.gov (United States)

    Zhao, Fang-Fang; Suhonen, Riitta; Koskinen, Sanna; Leino-Kilpi, Helena

    2017-04-01

    To synthesize the effects of theory-based self-management educational interventions on patients with type 2 diabetes (T2DM) in randomized controlled trials. Type 2 diabetes is a common chronic disease causing complications that put a heavy burden on society and reduce the quality of life of patients. Good self-management of diabetes can prevent complications and improve the quality of life of T2DM patients. Systematic review with meta-analysis of randomized controlled trials following Cochrane methods. A literature search was carried out in the MEDLINE, EMBASE, CINAHL, PSYCINFO, and Web of Science databases (1980-April 2015). The risk of bias of these eligible studies was assessed independently by two authors using the Cochrane Collaboration's tool. The Publication bias of the main outcomes was examined. Statistical heterogeneity and random-effects model were used for meta-analysis. Twenty studies with 5802 participants met the inclusion criteria. The interventions in the studies were based on one or more theories which mostly belong to mid-range theories. The pooled main outcomes by random-effects model showed significant improvements in HbA1c, self-efficacy, and diabetes knowledge, but not in BMI. As for quality of life, no conclusions can be drawn as the pooled outcome became the opposite with reduced heterogeneity after one study was excluded. No significant publication bias was found in the main outcomes. To get theory-based interventions to produce more effects, the role of patients should be more involved and stronger and the education team should be trained beyond the primary preparation for the self-management education program. © 2016 John Wiley & Sons Ltd.

  9. Local random configuration-tree theory for string repetition and facilitated dynamics of glass

    Science.gov (United States)

    Lam, Chi-Hang

    2018-02-01

    We derive a microscopic theory of glassy dynamics based on the transport of voids by micro-string motions, each of which involves particles arranged in a line hopping simultaneously displacing one another. Disorder is modeled by a random energy landscape quenched in the configuration space of distinguishable particles, but transient in the physical space as expected for glassy fluids. We study the evolution of local regions with m coupled voids. At a low temperature, energetically accessible local particle configurations can be organized into a random tree with nodes and edges denoting configurations and micro-string propagations respectively. Such trees defined in the configuration space naturally describe systems defined in two- or three-dimensional physical space. A micro-string propagation initiated by a void can facilitate similar motions by other voids via perturbing the random energy landscape, realizing path interactions between voids or equivalently string interactions. We obtain explicit expressions of the particle diffusion coefficient and a particle return probability. Under our approximation, as temperature decreases, random trees of energetically accessible configurations exhibit a sequence of percolation transitions in the configuration space, with local regions containing fewer coupled voids entering the non-percolating immobile phase first. Dynamics is dominated by coupled voids of an optimal group size, which increases as temperature decreases. Comparison with a distinguishable-particle lattice model (DPLM) of glass shows very good quantitative agreements using only two adjustable parameters related to typical energy fluctuations and the interaction range of the micro-strings.

  10. Universality in random matrix theory and chiral symmetry breaking in QCD

    International Nuclear Information System (INIS)

    Akemann, G.

    2000-05-01

    In this work we review the topic of random matrix model universality with particular stress on its application to the study of chiral symmetry breaking in QCD. We highlight the role of microscopic and macroscopic matrix model correlation functions played in the description of the deep infrared eigenvalue spectrum of the Dirac operator. The universal microscopic correlation functions are presented for all three chiral symmetry breaking patterns, and the corresponding random matrix universality proofs are given for massless and massive fermions in a unified way. These analytic results have been widely confirmed from QCD lattice data and we present a comparison with the most recent analytic calculations describing data for dynamical SU(2) staggered fermions. The microscopic matrix model results are then re-expressed in terms of the finite-volume partition functions of Leutwyler and Smilga, where some of these expressions have been recently obtained using field theory only. The macroscopic random matrix universality is reviewed for the most simplest examples of bosonic and supersymmetric models. We also give an example for a non-universal deformation of a random matrix model - the restricted trace ensemble. (orig.)

  11. Combinatorial theory of the semiclassical evaluation of transport moments. I. Equivalence with the random matrix approach

    Energy Technology Data Exchange (ETDEWEB)

    Berkolaiko, G., E-mail: berko@math.tamu.edu [Department of Mathematics, Texas A and M University, College Station, Texas 77843-3368 (United States); Kuipers, J., E-mail: Jack.Kuipers@physik.uni-regensburg.de [Institut für Theoretische Physik, Universität Regensburg, D-93040 Regensburg (Germany)

    2013-11-15

    To study electronic transport through chaotic quantum dots, there are two main theoretical approaches. One involves substituting the quantum system with a random scattering matrix and performing appropriate ensemble averaging. The other treats the transport in the semiclassical approximation and studies correlations among sets of classical trajectories. There are established evaluation procedures within the semiclassical evaluation that, for several linear and nonlinear transport moments to which they were applied, have always resulted in the agreement with random matrix predictions. We prove that this agreement is universal: any semiclassical evaluation within the accepted procedures is equivalent to the evaluation within random matrix theory. The equivalence is shown by developing a combinatorial interpretation of the trajectory sets as ribbon graphs (maps) with certain properties and exhibiting systematic cancellations among their contributions. Remaining trajectory sets can be identified with primitive (palindromic) factorisations whose number gives the coefficients in the corresponding expansion of the moments of random matrices. The equivalence is proved for systems with and without time reversal symmetry.

  12. Searching for control: priming randomness increases the evaluation of ritual efficacy.

    Science.gov (United States)

    Legare, Cristine H; Souza, André L

    2014-01-01

    Reestablishing feelings of control after experiencing uncertainty has long been considered a fundamental motive for human behavior. We propose that rituals (i.e., socially stipulated, causally opaque practices) provide a means for coping with the aversive feelings associated with randomness due to the perception of a connection between ritual action and a desired outcome. Two experiments were conducted (one in Brazil [n = 40] and another in the United States [n = 94]) to evaluate how the perceived efficacy of rituals is affected by feelings of randomness. In a between-subjects design, the Scramble Sentence Task was used as a priming procedure in three conditions (i.e., randomness, negativity, and neutral) and participants were then asked to rate the efficacy of rituals used for problem-solving purposes. The results demonstrate that priming randomness increased participants' perception of ritual efficacy relative to negativity and neutral conditions. Implications for increasing our understanding of the relationship between perceived control and ritualistic behavior are discussed. Copyright © 2013 Cognitive Science Society, Inc.

  13. Fitness landscapes, heuristics and technological paradigms: a critique on random search models in evolutionary economics

    NARCIS (Netherlands)

    Frenken, K.

    2001-01-01

    The biological evolution of complex organisms, in which the functioning of genes is interdependent, has been analyzed as "hill-climbing" on NK fitness landscapes through random mutation and natural selection. In evolutionary economics, NK fitness landscapes have been used to simulate the evolution

  14. Modified polarized geometrical attenuation model for bidirectional reflection distribution function based on random surface microfacet theory.

    Science.gov (United States)

    Liu, Hong; Zhu, Jingping; Wang, Kai

    2015-08-24

    The geometrical attenuation model given by Blinn was widely used in the geometrical optics bidirectional reflectance distribution function (BRDF) models. Blinn's geometrical attenuation model based on symmetrical V-groove assumption and ray scalar theory causes obvious inaccuracies in BRDF curves and negatives the effects of polarization. Aiming at these questions, a modified polarized geometrical attenuation model based on random surface microfacet theory is presented by combining of masking and shadowing effects and polarized effect. The p-polarized, s-polarized and unpolarized geometrical attenuation functions are given in their separate expressions and are validated with experimental data of two samples. It shows that the modified polarized geometrical attenuation function reaches better physical rationality, improves the precision of BRDF model, and widens the applications for different polarization.

  15. Using random matrix theory to determine the number of endmembers in a hyperspectral image

    CSIR Research Space (South Africa)

    Cawse, K

    2010-06-01

    Full Text Available apply our method to synthetic images, including a standard test image developed by Chein-I Chang, with good results for Gaussian independent noise. Index Terms— Hyperspectral Unmixing, Random Ma- trix Theory, Linear Mixture Model, Virtual Dimension... function, and K is the number of endmembers. We assume Gaussian noise following the methods of [1] [5]. The first step in unmixing the image is to determine how many endmembers or constituents are contained in the scene. This is known as the Virtual...

  16. Random matrix theory and higher genus integrability: the quantum chiral Potts model

    International Nuclear Information System (INIS)

    Angles d'Auriac, J.Ch.; Maillard, J.M.; Viallet, C.M.

    2002-01-01

    We perform a random matrix theory (RMT) analysis of the quantum four-state chiral Potts chain for different sizes of the chain up to size L 8. Our analysis gives clear evidence of a Gaussian orthogonal ensemble (GOE) statistics, suggesting the existence of a generalized time-reversal invariance. Furthermore, a change from the (generic) GOE distribution to a Poisson distribution occurs when the integrability conditions are met. The chiral Potts model is known to correspond to a (star-triangle) integrability associated with curves of genus higher than zero or one. Therefore, the RMT analysis can also be seen as a detector of 'higher genus integrability'. (author)

  17. Theory of Mind Training in Children with Autism: A Randomized Controlled Trial

    OpenAIRE

    Begeer, Sander; Gevers, Carolien; Clifford, Pamela; Verhoeve, Manja; Kat, Kirstin; Hoddenbach, Elske; Boer, Frits

    2010-01-01

    Many children with Autism Spectrum Disorders (ASD) participate in social skills or Theory of Mind (ToM) treatments. However, few studies have shown evidence for their effectiveness. The current study used a randomized controlled design to test the effectiveness of a 16-week ToM treatment in 8-13 year old children with ASD and normal IQs (n = 40). The results showed that, compared to controls, the treated children with ASD improved in their conceptual ToM skills, but their elementary understan...

  18. The Hausdorff dimension of random walks and the correlation length critical exponent in Euclidean field theory

    International Nuclear Information System (INIS)

    Kiskis, J.; Narayanan, R.; Vranas, P.

    1993-01-01

    The authors study the random walk representation of the two-point function in statistical mechanics models near the critical point. Using standard scaling arguments, the authors show that the critical exponent v describing the vanishing of the physical mass at the critical point is equal to v θ /d w , where d w is the Hausdorff dimension of the walk, and v θ = var-phi, where var-phi is the crossover exponent known in the context of field theory. This implies that the Hausdorff dimension of the walk is var-phi/v for O(N) models. 3 refs

  19. Interfacial separation between elastic solids with randomly rough surfaces: comparison of experiment with theory

    Energy Technology Data Exchange (ETDEWEB)

    Lorenz, B; Persson, B N J [IFF, FZ-Juelich, D-52425 Juelich (Germany)

    2009-01-07

    We study the average separation between an elastic solid and a hard solid, with a nominally flat but randomly rough surface, as a function of the squeezing pressure. We present experimental results for a silicon rubber (PDMS) block with a flat surface squeezed against an asphalt road surface. The theory shows that an effective repulsive pressure acts between the surfaces of the form p{approx}exp(-u/u{sub 0}), where u is the average separation between the surfaces and u{sub 0} a constant of the order of the root-mean-square roughness, in good agreement with the experimental results.

  20. Statistical theory of dislocation configurations in a random array of point obstacles

    International Nuclear Information System (INIS)

    Labusch, R.

    1977-01-01

    The stable configurations of a dislocation in an infinite random array of point obstacles are analyzed using the mathematical methods of statistical mechanics. The theory provides exact distribution functions of the forces on pinning points and of the link lengths between points on the line. The expected number of stable configurations is a function of the applied stress. This number drops to zero at the critical stress. Due to a degeneracy problem in the line count, the value of the flow stress cannot be determined rigorously, but we can give a good approximation that is very close to the empirical value

  1. A cluster randomized theory-guided oral hygiene trial in adolescents-A latent growth model.

    Science.gov (United States)

    Aleksejūnienė, J; Brukienė, V

    2018-05-01

    (i) To test whether theory-guided interventions are more effective than conventional dental instruction (CDI) for changing oral hygiene in adolescents and (ii) to examine whether such interventions equally benefit both genders and different socio-economic (SES) groups. A total of 244 adolescents were recruited from three schools, and cluster randomization allocated adolescents to one of the three types of interventions: two were theory-based interventions (Precaution Adoption Process Model or Authoritative Parenting Model) and CDI served as an active control. Oral hygiene levels % (OH) were assessed at baseline, after 3 months and after 12 months. A complete data set was available for 166 adolescents (the total follow-up rate: 69%). There were no significant differences in baseline OH between those who participated throughout the study and those who dropped out. Bivariate and multivariate analyses showed that theory-guided interventions produced significant improvements in oral hygiene and that there were no significant gender or socio-economic differences. Theory-guided interventions produced more positive changes in OH than CDI, and these changes did not differ between gender and SES groups. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  2. Nothing Happens by Accident, or Does It? A Low Prior for Randomness Does Not Explain Belief in Conspiracy Theories.

    Science.gov (United States)

    Dieguez, Sebastian; Wagner-Egger, Pascal; Gauvrit, Nicolas

    2015-11-01

    Belief in conspiracy theories has often been associated with a biased perception of randomness, akin to a nothing-happens-by-accident heuristic. Indeed, a low prior for randomness (i.e., believing that randomness is a priori unlikely) could plausibly explain the tendency to believe that a planned deception lies behind many events, as well as the tendency to perceive meaningful information in scattered and irrelevant details; both of these tendencies are traits diagnostic of conspiracist ideation. In three studies, we investigated this hypothesis and failed to find the predicted association between low prior for randomness and conspiracist ideation, even when randomness was explicitly opposed to malevolent human intervention. Conspiracy believers' and nonbelievers' perceptions of randomness were not only indistinguishable from each other but also accurate compared with the normative view arising from the algorithmic information framework. Thus, the motto "nothing happens by accident," taken at face value, does not explain belief in conspiracy theories. © The Author(s) 2015.

  3. CAUSAL DYNAMICAL TRIANGULATIONS AND THE SEARCH FOR A THEORY OF QUANTUM GRAVITY

    DEFF Research Database (Denmark)

    Ambjørn, Jan; Görlich, Andrzej; Jurkiewicz, J.

    2013-01-01

    High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Lattice (hep-lat)......High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Lattice (hep-lat)...

  4. The Effects of Racial Conflict on Organizational Performance: A Search for Theory

    Science.gov (United States)

    Byrd, Marilyn Y.

    2007-01-01

    This article addresses the effect of racial conflict on organizational performance as an issue that needs theoretical support in the foundational theories of human resource development (HRD). While the field of HRD recognizes theories from multiple disciplines, the field lacks a theoretical framework to inform leadership in managing racial…

  5. Making Use of Theories about Literacy and Justice: Teachers Re-Searching Practice.

    Science.gov (United States)

    Comber, Barbara

    This paper explores the way teachers make use of and work on theory to disrupt and ultimately improve everyday educational practice. The paper argues that teachers working on and with theory can and do generate new forms of educative practices in the field of literacy education, which are based on explicit standpoints towards social justice in…

  6. Understanding unemployed people's job search behaviour, unemployment experience and well-being: a comparison of expectancy-value theory and self-determination theory.

    Science.gov (United States)

    Vansteenkiste, Maarten; Lens, Willy; De Witte, Hans; Feather, N T

    2005-06-01

    Previous unemployment research has directly tested hypotheses derived from expectancy-value theory (EVT; Feather, 1982, 1990), but no comparative analysis has been executed with another motivational framework. In one large study with 446 unemployed people, separate analyses provided good evidence for predictions derived from both EVT and self-determination theory (SDT; Deci & Ryan, 1985, 2000). Comparative analyses indicated that the type of people's job search motivation, as conceptualized through the notions of autonomous versus controlled motivation within SDT, is an important predictor of people's unemployment experience and wellbeing, beyond people's strength of motivation assessed within EVT through expectancies of finding a job and employment value. The importance of simultaneously testing two theoretical frameworks is discussed.

  7. Reliability Study of Energy Harvesting from Sea Waves by Piezoelectric Patches Consideraing Random JONSWAP Wave Theory

    Directory of Open Access Journals (Sweden)

    M. Ettefagh

    2018-03-01

    Full Text Available One of the new methods for powering low-power electronic devices employed in the sea, is using of mechanical energies of sea waves. In this method, piezoelectric material is employed to convert the mechanical energy of sea waves into electrical energy. The advantage of this method is based on not implementing the battery charging system. Although, many studies have been done about energy harvesting from sea waves, energy harvesting with considering random JONWSAP wave theory is not fully studied up to now. The random JONSWAP wave model is a more realistic approximation of sea waves in comparison of Airy wave model. Therefore, in this paper a vertical beam with the piezoelectric patches, which is fixed to the seabed, is considered as energy harvester system. The energy harvesting system is simulated by MATLAB software, and then the vibration response of the beam and consequently the generated power is obtained considering the JONWSAP wave theory. In addition, the reliability of the system and the effect of piezoelectric patches uncertainties on the generated power are studied by statistical method. Furthermore, the failure possibility of harvester based on violation criteria is investigated.  

  8. Multiobjective Optimization of Water Distribution Networks Using Fuzzy Theory and Harmony Search

    Directory of Open Access Journals (Sweden)

    Zong Woo Geem

    2015-07-01

    Full Text Available Thus far, various phenomenon-mimicking algorithms, such as genetic algorithm, simulated annealing, tabu search, shuffled frog-leaping, ant colony optimization, harmony search, cross entropy, scatter search, and honey-bee mating, have been proposed to optimally design the water distribution networks with respect to design cost. However, flow velocity constraint, which is critical for structural robustness against water hammer or flow circulation against substance sedimentation, was seldom considered in the optimization formulation because of computational complexity. Thus, this study proposes a novel fuzzy-based velocity reliability index, which is to be maximized while the design cost is simultaneously minimized. The velocity reliability index is included in the existing cost optimization formulation and this extended multiobjective formulation is applied to two bench-mark problems. Results show that the model successfully found a Pareto set of multiobjective design solutions in terms of cost minimization and reliability maximization.

  9. Cognitive factors predicting intentions to search for health information: an application of the theory of planned behaviour.

    Science.gov (United States)

    Austvoll-Dahlgren, Astrid; Falk, Ragnhild S; Helseth, Sølvi

    2012-12-01

    Peoples' ability to obtain health information is a precondition for their effective participation in decision making about health. However, there is limited evidence describing which cognitive factors can predict the intention of people to search for health information. To test the utility of a questionnaire in predicting intentions to search for health information, and to identify important predictors associated with this intention such that these could be targeted in an Intervention. A questionnaire was developed based on the Theory of Planned Behaviour and tested on both a mixed population sample (n=30) and a sample of parents (n = 45). The questionnaire was explored by testing for internal consistency, calculating inter-correlations between theoretically-related constructs, and by using multiple regression analysis. The reliability and validity of the questionnaire were found to be satisfactory and consistent across the two samples. The questionnaires' direct measures prediction of intention was high and accounted for 47% and 55% of the variance in behavioural intentions. Attitudes and perceived behavioural control were identified as important predictors to intention for search for health information. The questionnaire may be a useful tool for understanding and evaluating behavioural intentions and beliefs related to searches for health information. © 2012 The authors. Health Information and Libraries Journal © 2012 Health Libraries Group.

  10. Are We There Yet? The Search for a Theory of Everything

    CERN Document Server

    Emam, Moataz H

    2011-01-01

    We live in exciting times. The frontiers of physics have been pushed to unprecedented horizons. The Holy Grail of fundamental physics research today is to find and describe a theory that explains, at least in principle, all physical phenomena, which in turns explains chemistry, biology and other material sciences. This, however, is not without controversy. The current candidate for such a theory is known as string or superstring theory. It suffers from the problem of being a purely mathematical science with no experimental backing and belief in it has been criticized as bordering on "faith" as

  11. Random matrix theory for analyzing the brain functional network in attention deficit hyperactivity disorder

    Science.gov (United States)

    Wang, Rong; Wang, Li; Yang, Yong; Li, Jiajia; Wu, Ying; Lin, Pan

    2016-11-01

    Attention deficit hyperactivity disorder (ADHD) is the most common childhood neuropsychiatric disorder and affects approximately 6 -7 % of children worldwide. Here, we investigate the statistical properties of undirected and directed brain functional networks in ADHD patients based on random matrix theory (RMT), in which the undirected functional connectivity is constructed based on correlation coefficient and the directed functional connectivity is measured based on cross-correlation coefficient and mutual information. We first analyze the functional connectivity and the eigenvalues of the brain functional network. We find that ADHD patients have increased undirected functional connectivity, reflecting a higher degree of linear dependence between regions, and increased directed functional connectivity, indicating stronger causality and more transmission of information among brain regions. More importantly, we explore the randomness of the undirected and directed functional networks using RMT. We find that for ADHD patients, the undirected functional network is more orderly than that for normal subjects, which indicates an abnormal increase in undirected functional connectivity. In addition, we find that the directed functional networks are more random, which reveals greater disorder in causality and more chaotic information flow among brain regions in ADHD patients. Our results not only further confirm the efficacy of RMT in characterizing the intrinsic properties of brain functional networks but also provide insights into the possibilities RMT offers for improving clinical diagnoses and treatment evaluations for ADHD patients.

  12. About the origins of the general theory of relativity: Einstein's search for the truth

    OpenAIRE

    Trainer, M.

    2005-01-01

    On the 20th June 1933 Professor Einstein addressed a large and enthusiastic audience in the Victorian Gothic Bute Hall of the University of Glasgow. Einstein spoke 'About the Origins of the General Theory of Relativity'. In 1905 Einstein had changed the face of physics forever with the publication of his radical new ideas on special relativity. His general theory of relativity was introduced to the world in 1915. However in 1933, Einstein faced another challenge—survival in a world of change....

  13. In search of a principled theory of the 'value' of knowledge.

    Science.gov (United States)

    Castelfranchi, Cristiano

    2016-01-01

    A theory of the Value/Utility of information and knowledge (K) is not really there. This would require a theory of the centrality of Goals in minds, and of the role of K relative to Goals and their dynamics. K value is a notion relative to Goal value. Inf/K is precisely a resource, a means and the value of means depends on the value of their possible functions and uses. The claim of this paper is that Ks have a Value and Utility, they can be more or less 'precious'; they have a cost and imply some risks; they can be not only useful but negative and dangerous. We also examine the 'quality' of this resource: its reliability; and its crucial role in goal processing: activating goals, abandoning, choosing, planning, formulating intentions, decide to act. 'Relevance theory', Information theory, Epistemic Utility theory, etc. are not enough for providing a theory of the Value/Utility of K. And also truthfulness is not 'the' Value of K. Even true information can be noxious for the subject.

  14. In Search of a Theory: The Interpretative Challenge of Empirical Findings on Cultural Variance in Mindreading

    Directory of Open Access Journals (Sweden)

    Gut Arkadiusz

    2016-12-01

    Full Text Available In this paper, we present a battery of empirical findings on the relationship between cultural context and theory of mind that show great variance in the onset and character of mindreading in different cultures; discuss problems that those findings cause for the largely-nativistic outlook on mindreading dominating in the literature; and point to an alternative framework that appears to better accommodate the evident cross-cultural variance in mindreading. We first outline the theoretical frameworks that dominate in mindreading research, then present the relevant empirical findings, and finally we come back to the theoretical approaches in a discussion of their explanatory potential in the face of the data presented. The theoretical frameworks discussed are the two-systems approach; performance-based approach also known as modularity-nativist approach; and the social-communicative theory also known as the systems, relational-systems, dynamic systems and developmental systems theory. The former two, which both fall within the wider modular-computational paradigm, run into a challenge with the cross-cultural data presented, and the latter - the systemic framework - seems to offer an explanatorily potent alternative. The empirical data cited in this paper comes from research on cross-cultural differences in folk psychology and theory-of-mind development; the influence of parenting practices on the development of theory of mind; the development and character of theory of mind in deaf populations; and neuroimaging research of cultural differences in mindreading.

  15. A random-key encoded harmony search approach for energy-efficient production scheduling with shared resources

    Science.gov (United States)

    Garcia-Santiago, C. A.; Del Ser, J.; Upton, C.; Quilligan, F.; Gil-Lopez, S.; Salcedo-Sanz, S.

    2015-11-01

    When seeking near-optimal solutions for complex scheduling problems, meta-heuristics demonstrate good performance with affordable computational effort. This has resulted in a gravitation towards these approaches when researching industrial use-cases such as energy-efficient production planning. However, much of the previous research makes assumptions about softer constraints that affect planning strategies and about how human planners interact with the algorithm in a live production environment. This article describes a job-shop problem that focuses on minimizing energy consumption across a production facility of shared resources. The application scenario is based on real facilities made available by the Irish Center for Manufacturing Research. The formulated problem is tackled via harmony search heuristics with random keys encoding. Simulation results are compared to a genetic algorithm, a simulated annealing approach and a first-come-first-served scheduling. The superior performance obtained by the proposed scheduler paves the way towards its practical implementation over industrial production chains.

  16. Secession Of Crimea: Search Of The New Theory Of Law On Secession

    Directory of Open Access Journals (Sweden)

    Elena S. Aleksandrova

    2015-03-01

    Full Text Available In the present article author analyzes secession of the Autonomous Republic of Crimea in Ukraine in spring of 2014 through the light of existing international legal norms theories of the right to secession. Author discusses advantages and disadvantages of the theory of the initial right for the secession, including inscriptive and associative sub theory and human rights theory. The article focuses on the analysis of the Crimean secession complication by the existing normative theory, the subject - people are enough polyethnic, and self-determination is happening more on linguistic and cultural characteristics, as well as on the basis of historical memory. Author noted a gap in contemporary international law regarding the interpretation of the subject of the right to secession and bases for secession. In addition, the increase in the secessionist conflict in international relations is pushing to develop the Institute more detailed. The article stresses the need to develop a new normative theory of the right to secession, establishment of responsibilities of the parties in the implementation of secession. There is the hypothesis about the formation of a new historical stage of development of the right to self-determination in international law and, as a consequence, it becomes necessary to develop the regulatory limits and implementation in advance. In conclusion, author notes that the states themselves must feel the social processes and respect its citizens, to consider the unfortunate experience of other States in the suppression of social unrest. Latent and long-term secessions are still relevant and international law should promptly and effectively respond to their possible aggravation, offering a balanced approach and taking into account the previous one, albeit an ambiguous separation experience and recognition of secession.

  17. Search of unified theory of basic types of elementary particle interactions

    International Nuclear Information System (INIS)

    Anselm, A.

    1981-01-01

    Four types of forces are described (strong, weak, electromagnetic and gravitational) mediating the basic interactions of quarks and leptons, and attempts are reported of forming a unified theory of all basic interactions. The concepts are discussed, such as the theory symmetry (eg., invariance in relation to the Lorentz transformations) and isotopic symmetry (based on the interchangeability of particles in a given isotopic multiplet). Described are the gauge character of electromagnetic and gravitational interactions, the violation of the gauge symmetry and the mechanism of particle confinement. (H.S.)

  18. Theory of Mind training in children with autism: a randomized controlled trial.

    Science.gov (United States)

    Begeer, Sander; Gevers, Carolien; Clifford, Pamela; Verhoeve, Manja; Kat, Kirstin; Hoddenbach, Elske; Boer, Frits

    2011-08-01

    Many children with Autism Spectrum Disorders (ASD) participate in social skills or Theory of Mind (ToM) treatments. However, few studies have shown evidence for their effectiveness. The current study used a randomized controlled design to test the effectiveness of a 16-week ToM treatment in 8-13 year old children with ASD and normal IQs (n = 40). The results showed that, compared to controls, the treated children with ASD improved in their conceptual ToM skills, but their elementary understanding, self reported empathic skills or parent reported social behaviour did not improve. Despite the effects on conceptual understanding, the current study does not indicate strong evidence for the effectiveness of a ToM treatment on the daily life mindreading skills.

  19. The mean field theory in EM procedures for blind Markov random field image restoration.

    Science.gov (United States)

    Zhang, J

    1993-01-01

    A Markov random field (MRF) model-based EM (expectation-maximization) procedure for simultaneously estimating the degradation model and restoring the image is described. The MRF is a coupled one which provides continuity (inside regions of smooth gray tones) and discontinuity (at region boundaries) constraints for the restoration problem which is, in general, ill posed. The computational difficulty associated with the EM procedure for MRFs is resolved by using the mean field theory from statistical mechanics. An orthonormal blur decomposition is used to reduce the chances of undesirable locally optimal estimates. Experimental results on synthetic and real-world images show that this approach provides good blur estimates and restored images. The restored images are comparable to those obtained by a Wiener filter in mean-square error, but are most visually pleasing.

  20. Estimating filtration coefficients for straining from percolation and random walk theories

    DEFF Research Database (Denmark)

    Yuan, Hao; Shapiro, Alexander; You, Zhenjiang

    2012-01-01

    In this paper, laboratory challenge tests are carried out under unfavorable attachment conditions, so that size exclusion or straining is the only particle capture mechanism. The experimental results show that far above the percolation threshold the filtration coefficients are not proportional...... size exclusion theory or the model of parallel tubes with mixing chambers, where the filtration coefficients are proportional to the flux through smaller pores, and the predicted penetration depths are much lower. A special capture mechanism is proposed, which makes it possible to explain...... the experimentally observed power law dependencies of filtration coefficients and large penetration depths of particles. Such a capture mechanism is realized in a 2D pore network model with periodical boundaries with the random walk of particles on the percolation lattice. Geometries of infinite and finite clusters...

  1. A Novel Randomized Search Technique for Multiple Mobile Robot Paths Planning In Repetitive Dynamic Environment

    Directory of Open Access Journals (Sweden)

    Vahid Behravesh

    2012-08-01

    Full Text Available Presented article is studying the issue of path navigating for numerous robots. Our presented approach is based on both priority and the robust method for path finding in repetitive dynamic. Presented model can be generally implementable and useable: We do not assume any restriction regarding the quantity of levels of freedom for robots, and robots of diverse kinds can be applied at the same time. We proposed a random method and hill-climbing technique in the area based on precedence plans, which is used to determine a solution to a given trajectory planning problem and to make less the extent of total track. Our method plans trajectories for particular robots in the setting-time scope. Therefore, in order to specifying the interval of constant objects similar to other robots and the extent of the tracks which is traversed. For measuring the hazard for robots to conflict with each other it applied a method based on probability of the movements of robots. This algorithm applied to real robots with successful results. The proposed method performed and judged on both real robots and in simulation. We performed sequence of100tests with 8 robots for comparing with coordination method and current performances are effective. However, maximizing the performance is still possible. These performances estimations performed on Windows operating system and 3GHz Intel Pentium IV with and compiles with GCC 3.4. We used our PCGA robot for all experiments.  For a large environment of 19×15m2where we accomplished 40tests, our model is competent to plan high-quality paths in a severely short time (less than a second. Moreover, this article utilized lookup tables to keep expenses the formerly navigated robots made, increasing the number of robots don’t expand computation time.

  2. Topological characterization of antireflective and hydrophobic rough surfaces: are random process theory and fractal modeling applicable?

    Science.gov (United States)

    Borri, Claudia; Paggi, Marco

    2015-02-01

    The random process theory (RPT) has been widely applied to predict the joint probability distribution functions (PDFs) of asperity heights and curvatures of rough surfaces. A check of the predictions of RPT against the actual statistics of numerically generated random fractal surfaces and of real rough surfaces has been only partially undertaken. The present experimental and numerical study provides a deep critical comparison on this matter, providing some insight into the capabilities and limitations in applying RPT and fractal modeling to antireflective and hydrophobic rough surfaces, two important types of textured surfaces. A multi-resolution experimental campaign using a confocal profilometer with different lenses is carried out and a comprehensive software for the statistical description of rough surfaces is developed. It is found that the topology of the analyzed textured surfaces cannot be fully described according to RPT and fractal modeling. The following complexities emerge: (i) the presence of cut-offs or bi-fractality in the power-law power-spectral density (PSD) functions; (ii) a more pronounced shift of the PSD by changing resolution as compared to what was expected from fractal modeling; (iii) inaccuracy of the RPT in describing the joint PDFs of asperity heights and curvatures of textured surfaces; (iv) lack of resolution-invariance of joint PDFs of textured surfaces in case of special surface treatments, not accounted for by fractal modeling.

  3. CR-Calculus and adaptive array theory applied to MIMO random vibration control tests

    Science.gov (United States)

    Musella, U.; Manzato, S.; Peeters, B.; Guillaume, P.

    2016-09-01

    Performing Multiple-Input Multiple-Output (MIMO) tests to reproduce the vibration environment in a user-defined number of control points of a unit under test is necessary in applications where a realistic environment replication has to be achieved. MIMO tests require vibration control strategies to calculate the required drive signal vector that gives an acceptable replication of the target. This target is a (complex) vector with magnitude and phase information at the control points for MIMO Sine Control tests while in MIMO Random Control tests, in the most general case, the target is a complete spectral density matrix. The idea behind this work is to tailor a MIMO random vibration control approach that can be generalized to other MIMO tests, e.g. MIMO Sine and MIMO Time Waveform Replication. In this work the approach is to use gradient-based procedures over the complex space, applying the so called CR-Calculus and the adaptive array theory. With this approach it is possible to better control the process performances allowing the step-by-step Jacobian Matrix update. The theoretical bases behind the work are followed by an application of the developed method to a two-exciter two-axis system and by performance comparisons with standard methods.

  4. Mean-field Theory for Some Bus Transport Networks with Random Overlapping Clique Structure

    International Nuclear Information System (INIS)

    Yang Xuhua; Sun Bao; Wang Bo; Sun Youxian

    2010-01-01

    Transport networks, such as railway networks and airport networks, are a kind of random network with complex topology. Recently, more and more scholars paid attention to various kinds of transport networks and try to explore their inherent characteristics. Here we study the exponential properties of a recently introduced Bus Transport Networks (BTNs) evolution model with random overlapping clique structure, which gives a possible explanation for the observed exponential distribution of the connectivities of some BTNs of three major cities in China. Applying mean-field theory, we analyze the BTNs model and prove that this model has the character of exponential distribution of the connectivities, and develop a method to predict the growth dynamics of the individual vertices, and use this to calculate analytically the connectivity distribution and the exponents. By comparing mean-field based theoretic results with the statistical data of real BTNs, we observe that, as a whole, both of their data show similar character of exponential distribution of the connectivities, and their exponents have same order of magnitude, which show the availability of the analytical result of this paper. (general)

  5. The time-dependent relativistic mean-field theory and the random phase approximation

    International Nuclear Information System (INIS)

    Ring, P.; Ma, Zhong-yu; Van Giai, Nguyen; Vretenar, D.; Wandelt, A.; Cao, Li-gang

    2001-01-01

    The Relativistic Random Phase Approximation (RRPA) is derived from the Time-Dependent Relativistic Mean-Field (TD RMF) theory in the limit of small amplitude oscillations. In the no-sea approximation of the RMF theory, the RRPA configuration space includes not only the usual particle-hole ph-states, but also αh-configurations, i.e. pairs formed from occupied states in the Fermi sea and empty negative-energy states in the Dirac sea. The contribution of the negative-energy states to the RRPA matrices is examined in a schematic model, and the large effect of Dirac-sea states on isoscalar strength distributions is illustrated for the giant monopole resonance in 116 Sn. It is shown that, because the matrix elements of the time-like component of the vector-meson fields which couple the αh-configurations with the ph-configurations are strongly reduced with respect to the corresponding matrix elements of the isoscalar scalar meson field, the inclusion of states with unperturbed energies more than 1.2 GeV below the Fermi energy has a pronounced effect on giant resonances with excitation energies in the MeV region. The influence of nuclear magnetism, i.e. the effect of the spatial components of the vector fields is examined, and the difference between the nonrelativistic and relativistic RPA predictions for the nuclear matter compression modulus is explained

  6. Feministische Gesellschaftstheorie und die Suche nach der Anschlussfähigkeit Feminist Social Theory in Search of Connections

    Directory of Open Access Journals (Sweden)

    Silke Schneider

    2002-07-01

    Full Text Available Der Sammelband „Soziale Verortung der Geschlechter“ stellt einen Querschnitt aktueller feministischer Theoriediskussionen vor. Dass bei der Suche nach angemessenen gesellschaftsanalytischen Kategorien sowohl die Klassiker/-innen der Politischen Theorie und Gesellschaftstheorie wie auch ihre Epigonen mannigfache Kritik-, aber auch vielversprechende Anschlußpunkte zu bieten haben, vermögen alle Beiträge zu vermitteln. Somit bietet der Band mit seiner breit angelegten Konzeption, die wichtige und durchaus gegensätzliche Theorien verbindet, einen guten Überblick und regt gleichzeitig zur vertiefenden Lektüre an. Bemerkenswert ist, dass nahezu alle Beiträge für eine Verbindung von Empirie und Theorie plädieren und hierbei die Einbeziehung einer historischen Perspektive als grundlegend und unabdingbar für eine Analyse der Geschlechterverhältnisse als Teil gesellschaftlicher Entwicklung erachtet wird.The anthology “The Social Positionings of Gender” presents a cross section of current debates in feminist theory. The authors show how authors of classical political and social theory as well as their successors offer plenty of room for criticism, but also promising starting points in the search for appropriate socio-analytic categories. This anthology not only offers a good overview over current theory by connecting different (and at times contradicting schools of thought, but also inspires to engage in further reading on these issues. What is particularly remarkable about this work is that almost all of the contributions plead for a combination of empirical research and theoretical work, as they consider the inclusion of a historical perspective as fundamental and indispensable for an analysis of gender relations as part of societal developments.

  7. MMRW-BOOKS, Legacy books on slowing down, thermalization, particle transport theory, random processes in reactors

    International Nuclear Information System (INIS)

    Williams, M.M.R.

    2007-01-01

    Description: Prof. M.M..R Williams has now released three of his legacy books for free distribution: 1 - M.M.R. Williams: The Slowing Down and Thermalization of Neutrons, North-Holland Publishing Company - Amsterdam, 582 pages, 1966. Content: Part I - The Thermal Energy Region: 1. Introduction and Historical Review, 2. The Scattering Kernel, 3. Neutron Thermalization in an Infinite Homogeneous Medium, 4. Neutron Thermalization in Finite Media, 5. The Spatial Dependence of the Energy Spectrum, 6. Reactor Cell Calculations, 7. Synthetic Scattering Kernels. Part II - The Slowing Down Region: 8. Scattering Kernels in the Slowing Down Region, 9. Neutron Slowing Down in an Infinite Homogeneous Medium, 10.Neutron Slowing Down and Diffusion. 2 - M.M.R. Williams: Mathematical Methods in Particle Transport Theory, Butterworths, London, 430 pages, 1971. Content: 1 The General Problem of Particle Transport, 2 The Boltzmann Equation for Gas Atoms and Neutrons, 3 Boundary Conditions, 4 Scattering Kernels, 5 Some Basic Problems in Neutron Transport and Rarefied Gas Dynamics, 6 The Integral Form of the Transport Equation in Plane, Spherical and Cylindrical Geometries, 7 Exact Solutions of Model Problems, 8 Eigenvalue Problems in Transport Theory, 9 Collision Probability Methods, 10 Variational Methods, 11 Polynomial Approximations. 3 - M.M.R. Williams: Random Processes in Nuclear Reactors, Pergamon Press Oxford New York Toronto Sydney, 243 pages, 1974. Content: 1. Historical Survey and General Discussion, 2. Introductory Mathematical Treatment, 3. Applications of the General Theory, 4. Practical Applications of the Probability Distribution, 5. The Langevin Technique, 6. Point Model Power Reactor Noise, 7. The Spatial Variation of Reactor Noise, 8. Random Phenomena in Heterogeneous Reactor Systems, 9. Associated Fluctuation Problems, Appendix: Noise Equivalent Sources. Note to the user: Prof. M.M.R Williams owns the copyright of these books and he authorises the OECD/NEA Data Bank

  8. In search of the "lost capital". A theory for valuation, investment decisions, performance measurement

    OpenAIRE

    Magni, Carlo Alberto

    2007-01-01

    This paper presents a theoretical framework for valuation, investment decisions, and performance measurement based on a nonstandard theory of residual income. It is derived from the notion of "unrecovered" capital, which is here named "lost" capital because it represents the capital foregone by the investors. Its theoretical strength and meaningfulness is shown by deriving it from four main perspectives: financial, microeconomic, axiomatic, accounting. Implications for asset valuation, cap...

  9. Homeownership in Slovenia: Searching for an alternative theory on its excessive growth

    Directory of Open Access Journals (Sweden)

    Richard Sendi

    2017-06-01

    Full Text Available Recent studies generally show growing levels of homeownership across Europe. However, a comparison of statistical data shows a stark difference in the extent of homeownership between western Europe versus central and eastern Europe. Whereas the development and growth of homeownership in western Europe has been extensively discussed in the literature and various theories have been advanced, its strong dominance in central and eastern Europe has been barely examined. Due to the lack of thorough discourse on this topic, there thus continues to be a void in the literature, which is manifested in the absence of a sound explanation for the comparatively much higher expansion of homeownership in post-communist central and eastern Europe. This article contributes to filling this gap. The central argument is that theories that were developed to explain the growth of homeownership in western Europe (economies with a capitalist tradition might not necessarily apply to situations in central and eastern Europe (with previous communist centrally planned economies. Focusing on the case of Slovenia, the discussion is orientated towards developing an alternative theory that may be more relevant in explaining and understanding the growing preference for homeownership in the country.

  10. Filling of a Poisson trap by a population of random intermittent searchers

    KAUST Repository

    Bressloff, Paul C.; Newby, Jay M.

    2012-01-01

    We extend the continuum theory of random intermittent search processes to the case of N independent searchers looking to deliver cargo to a single hidden target located somewhere on a semi-infinite track. Each searcher randomly switches between a

  11. Spin-adapted open-shell random phase approximation and time-dependent density functional theory. I. Theory.

    Science.gov (United States)

    Li, Zhendong; Liu, Wenjian

    2010-08-14

    The spin-adaptation of single-reference quantum chemical methods for excited states of open-shell systems has been nontrivial. The primary reason is that the configuration space, generated by a truncated rank of excitations from only one component of a reference multiplet, is spin-incomplete. Those "missing" configurations are of higher ranks and can, in principle, be recaptured by a particular class of excitation operators. However, the resulting formalisms are then quite involved and there are situations [e.g., time-dependent density functional theory (TD-DFT) under the adiabatic approximation] that prevent one from doing so. To solve this issue, we propose here a tensor-coupling scheme that invokes all the components of a reference multiplet (i.e., a tensor reference) rather than increases the excitation ranks. A minimal spin-adapted n-tuply excited configuration space can readily be constructed by tensor products between the n-tuple tensor excitation operators and the chosen tensor reference. Further combined with the tensor equation-of-motion formalism, very compact expressions for excitation energies can be obtained. As a first application of this general idea, a spin-adapted open-shell random phase approximation is first developed. The so-called "translation rule" is then adopted to formulate a spin-adapted, restricted open-shell Kohn-Sham (ROKS)-based TD-DFT (ROKS-TD-DFT). Here, a particular symmetry structure has to be imposed on the exchange-correlation kernel. While the standard ROKS-TD-DFT can access only excited states due to singlet-coupled single excitations, i.e., only some of the singly excited states of the same spin (S(i)) as the reference, the new scheme can capture all the excited states of spin S(i)-1, S(i), or S(i)+1 due to both singlet- and triplet-coupled single excitations. The actual implementation and computation are very much like the (spin-contaminated) unrestricted Kohn-Sham-based TD-DFT. It is also shown that spin-contaminated spin

  12. Recent developments in the theory of protein folding: searching for the global energy minimum.

    Science.gov (United States)

    Scheraga, H A

    1996-04-16

    Statistical mechanical theories and computer simulation are being used to gain an understanding of the fundamental features of protein folding. A major obstacle in the computation of protein structures is the multiple-minima problem arising from the existence of many local minima in the multidimensional energy landscape of the protein. This problem has been surmounted for small open-chain and cyclic peptides, and for regular-repeating sequences of models of fibrous proteins. Progress is being made in resolving this problem for globular proteins.

  13. On Δβ and the search for asymptotic scaling in lattice gauge theory

    International Nuclear Information System (INIS)

    Petcher, D.

    1986-01-01

    An ansatz for the β-function of SU(3) lattice gauge theory in four dimensions whose parameters are determined by Monte Carlo data is used both to compare different sets of data for Δβ and to study systematic errors. The data for Δβ obtained from different values of the block spin renormalization group scaling factor are shown to be compatible within statistical errors. However the data is easily consistent with sizeable deviations (ca. 30% or more) from the two loop approximation to the renormalization group scaling formula for physical quantities in the region of coupling for which Δβ essentially takes on its asymptotic value. (orig.)

  14. The Big Bang and the Search for a Theory of Everything

    Science.gov (United States)

    Kogut, Alan

    2010-01-01

    How did the universe begin? Is the gravitational physics that governs the shape and evolution of the cosmos connected in a fundamental way to the sub-atomic physics of particle colliders? Light from the Big Bang still permeates the universe and carries within it faint clues to the physics at the start of space and time. I will describe how current and planned measurements of the cosmic microwave background will observe the Big Bang to provide new insight into a "Theory of Everything" uniting the physics of the very large with the physics of the very small.

  15. In search of a primitive ontology for relativistic quantum field theory

    Energy Technology Data Exchange (ETDEWEB)

    Lam, Vincent [University of Lausanne, CH-1015 Lausanne (Switzerland)

    2014-07-01

    There is a recently much discussed approach to the ontology of quantum mechanics according to which the theory is ultimately about entities in 3-dimensional space and their temporal evolution. Such an ontology postulating from the start matter localized in usual physical space or spacetime, by contrast to an abstract high-dimensional space such as the configuration space of wave function realism, is called primitive ontology in the recent literature on the topic and finds its roots in Bell's notion of local beables. The main motivation for a primitive ontology lies in its explanatory power: the primitive ontology allows for a direct account of the behaviour and properties of familiar macroscopic objects. In this context, it is natural to look for a primitive ontology for relativistic quantum field theory (RQFT). The aim of this talk is to critically discuss this interpretative move within RQFT, in particular with respect to the foundational issue of the existence of unitarily inequivalent representations. Indeed the proposed primitive ontologies for RQFT rely either on a Fock space representation or a wave functional representation, which are strictly speaking only unambiguously available for free systems in flat spacetime. As a consequence, it is argued that these primitive ontologies constitute only effective ontologies and are hardly satisfying as a fundamental ontology for RQFT.

  16. On Δβ and the search for asymptotic scaling in lattice gauge theory

    International Nuclear Information System (INIS)

    Petcher, D.

    1986-01-01

    An ansatz for the β-function of SU(3) lattice gauge theory in four dimensions whose parameters are determined by Monte Carlo data is used both to compare different sets of data for Δβ and to study systematic errors. The data for Δβ obtained from different values of the block-spin renormalization group scaling factor are shown to be compatible within statistical errors. However the data is easily consistent with sizeable deviations (ca. 30% or more) from the two-loop approximation to the renormalization group scaling formula for physical quantities in the region of coupling for which Δβ essentially takes on its asymptotic value. (orig.)

  17. Low Complexity Precoder and Receiver Design for Massive MIMO Systems: A Large System Analysis using Random Matrix Theory

    KAUST Repository

    Sifaou, Houssem

    2016-01-01

    transceivers. Using tools from random matrix theory, we determine deterministic approximations of the SINR and the transmit power in the asymptotic regime. Then, the optimal per-user weight coe cients that solve the max-min SINR problem are derived

  18. Analysis of sensitive questions across cultures : An application of multigroup item randomized response theory to sexual attitudes and behavior

    NARCIS (Netherlands)

    de Jong, M.G.; Pieters, R.; Stremersch, S.

    2012-01-01

    Answers to sensitive questions are prone to social desirability bias. If not properly addressed, the validity of the research can be suspect. This article presents multigroup item randomized response theory (MIRRT) to measure self-reported sensitive topics across cultures. The method was

  19. Randomized Approaches for Nearest Neighbor Search in Metric Space When Computing the Pairwise Distance Is Extremely Expensive

    Science.gov (United States)

    Wang, Lusheng; Yang, Yong; Lin, Guohui

    Finding the closest object for a query in a database is a classical problem in computer science. For some modern biological applications, computing the similarity between two objects might be very time consuming. For example, it takes a long time to compute the edit distance between two whole chromosomes and the alignment cost of two 3D protein structures. In this paper, we study the nearest neighbor search problem in metric space, where the pair-wise distance between two objects in the database is known and we want to minimize the number of distances computed on-line between the query and objects in the database in order to find the closest object. We have designed two randomized approaches for indexing metric space databases, where objects are purely described by their distances with each other. Analysis and experiments show that our approaches only need to compute O(logn) objects in order to find the closest object, where n is the total number of objects in the database.

  20. Generalized Information Theory Meets Human Cognition: Introducing a Unified Framework to Model Uncertainty and Information Search.

    Science.gov (United States)

    Crupi, Vincenzo; Nelson, Jonathan D; Meder, Björn; Cevolani, Gustavo; Tentori, Katya

    2018-06-17

    Searching for information is critical in many situations. In medicine, for instance, careful choice of a diagnostic test can help narrow down the range of plausible diseases that the patient might have. In a probabilistic framework, test selection is often modeled by assuming that people's goal is to reduce uncertainty about possible states of the world. In cognitive science, psychology, and medical decision making, Shannon entropy is the most prominent and most widely used model to formalize probabilistic uncertainty and the reduction thereof. However, a variety of alternative entropy metrics (Hartley, Quadratic, Tsallis, Rényi, and more) are popular in the social and the natural sciences, computer science, and philosophy of science. Particular entropy measures have been predominant in particular research areas, and it is often an open issue whether these divergences emerge from different theoretical and practical goals or are merely due to historical accident. Cutting across disciplinary boundaries, we show that several entropy and entropy reduction measures arise as special cases in a unified formalism, the Sharma-Mittal framework. Using mathematical results, computer simulations, and analyses of published behavioral data, we discuss four key questions: How do various entropy models relate to each other? What insights can be obtained by considering diverse entropy models within a unified framework? What is the psychological plausibility of different entropy models? What new questions and insights for research on human information acquisition follow? Our work provides several new pathways for theoretical and empirical research, reconciling apparently conflicting approaches and empirical findings within a comprehensive and unified information-theoretic formalism. Copyright © 2018 Cognitive Science Society, Inc.

  1. THEORY OF DISPERSED FIXED-DELAY INTERFEROMETRY FOR RADIAL VELOCITY EXOPLANET SEARCHES

    International Nuclear Information System (INIS)

    Van Eyken, Julian C.; Ge Jian; Mahadevan, Suvrath

    2010-01-01

    The dispersed fixed-delay interferometer (DFDI) represents a new instrument concept for high-precision radial velocity (RV) surveys for extrasolar planets. A combination of a Michelson interferometer and a medium-resolution spectrograph, it has the potential for performing multi-object surveys, where most previous RV techniques have been limited to observing only one target at a time. Because of the large sample of extrasolar planets needed to better understand planetary formation, evolution, and prevalence, this new technique represents a logical next step in instrumentation for RV extrasolar planet searches, and has been proven with the single-object Exoplanet Tracker (ET) at Kitt Peak National Observatory, and the multi-object W. M. Keck/MARVELS Exoplanet Tracker at Apache Point Observatory. The development of the ET instruments has necessitated fleshing out a detailed understanding of the physical principles of the DFDI technique. Here we summarize the fundamental theoretical material needed to understand the technique and provide an overview of the physics underlying the instrument's working. We also derive some useful analytical formulae that can be used to estimate the level of various sources of error generic to the technique, such as photon shot noise when using a fiducial reference spectrum, contamination by secondary spectra (e.g., crowded sources, spectroscopic binaries, or moonlight contamination), residual interferometer comb, and reference cross-talk error. Following this, we show that the use of a traditional gas absorption fiducial reference with a DFDI can incur significant systematic errors that must be taken into account at the precision levels required to detect extrasolar planets.

  2. Self-consistent Random Phase Approximation applied to a schematic model of the field theory

    International Nuclear Information System (INIS)

    Bertrand, Thierry

    1998-01-01

    The self-consistent Random Phase Approximation (SCRPA) is a method allowing in the mean-field theory inclusion of the correlations in the ground and excited states. It has the advantage of not violating the Pauli principle in contrast to RPA, that is based on the quasi-bosonic approximation; in addition, numerous applications in different domains of physics, show a possible variational character. However, the latter should be formally demonstrated. The first model studied with SCRPA is the anharmonic oscillator in the region where one of its symmetries is spontaneously broken. The ground state energy is reproduced by SCRPA more accurately than RPA, with no violation of the Ritz variational principle, what is not the case for the latter approximation. The success of SCRPA is the the same in case of ground state energy for a model mixing bosons and fermions. At the transition point the SCRPA is correcting RPA drastically, but far from this region the correction becomes negligible, both methods being of similar precision. In the deformed region in the case of RPA a spurious mode occurred due to the microscopical character of the model.. The SCRPA may also reproduce this mode very accurately and actually it coincides with an excitation in the exact spectrum

  3. Prognostic interaction patterns in diabetes mellitus II: A random-matrix-theory relation

    Science.gov (United States)

    Rai, Aparna; Pawar, Amit Kumar; Jalan, Sarika

    2015-08-01

    We analyze protein-protein interactions in diabetes mellitus II and its normal counterpart under the combined framework of random matrix theory and network biology. This disease is the fifth-leading cause of death in high-income countries and an epidemic in developing countries, affecting around 8 % of the total adult population in the world. Treatment at the advanced stage is difficult and challenging, making early detection a high priority in the cure of the disease. Our investigation reveals specific structural patterns important for the occurrence of the disease. In addition to the structural parameters, the spectral properties reveal the top contributing nodes from localized eigenvectors, which turn out to be significant for the occurrence of the disease. Our analysis is time-efficient and cost-effective, bringing a new horizon in the field of medicine by highlighting major pathways involved in the disease. The analysis provides a direction for the development of novel drugs and therapies in curing the disease by targeting specific interaction patterns instead of a single protein.

  4. Asymptotic Analysis of Large Cooperative Relay Networks Using Random Matrix Theory

    Directory of Open Access Journals (Sweden)

    H. Poor

    2008-04-01

    Full Text Available Cooperative transmission is an emerging communication technology that takes advantage of the broadcast nature of wireless channels. In cooperative transmission, the use of relays can create a virtual antenna array so that multiple-input/multiple-output (MIMO techniques can be employed. Most existing work in this area has focused on the situation in which there are a small number of sources and relays and a destination. In this paper, cooperative relay networks with large numbers of nodes are analyzed, and in particular the asymptotic performance improvement of cooperative transmission over direction transmission and relay transmission is analyzed using random matrix theory. The key idea is to investigate the eigenvalue distributions related to channel capacity and to analyze the moments of this distribution in large wireless networks. A performance upper bound is derived, the performance in the low signal-to-noise-ratio regime is analyzed, and two approximations are obtained for high and low relay-to-destination link qualities, respectively. Finally, simulations are provided to validate the accuracy of the analytical results. The analysis in this paper provides important tools for the understanding and the design of large cooperative wireless networks.

  5. Random matrix theory of the energy-level statistics of disordered systems at the Anderson transition

    Energy Technology Data Exchange (ETDEWEB)

    Canali, C M

    1995-09-01

    We consider a family of random matrix ensembles (RME) invariant under similarity transformations and described by the probability density P(H) exp[-TrV(H)]. Dyson`s mean field theory (MFT) of the corresponding plasma model of eigenvalues is generalized to the case of weak confining potential, V(is an element of) {approx} A/2 ln{sup 2}(is an element of). The eigenvalue statistics derived from MFT are shown to deviate substantially from the classical Wigner-Dyson statistics when A < 1. By performing systematic Monte Carlo simulations on the plasma model, we compute all the relevant statistical properties of the RME with weak confinement. For A{sub c} approx. 0.4 the distribution function of the level spacings (LSDF) coincides in a large energy window with the energy LSDF of the three dimensional Anderson model at the metal-insulator transition. For the same A = A{sub c}, the RME eigenvalue-number variance is linear and its slope is equal to 0.32 {+-} 0.02, which is consistent with the value found for the Anderson model at the critical point. (author). 51 refs, 10 figs.

  6. Random matrix theory of the energy-level statistics of disordered systems at the Anderson transition

    International Nuclear Information System (INIS)

    Canali, C.M.

    1995-09-01

    We consider a family of random matrix ensembles (RME) invariant under similarity transformations and described by the probability density P(H) exp[-TrV(H)]. Dyson's mean field theory (MFT) of the corresponding plasma model of eigenvalues is generalized to the case of weak confining potential, V(is an element of) ∼ A/2 ln 2 (is an element of). The eigenvalue statistics derived from MFT are shown to deviate substantially from the classical Wigner-Dyson statistics when A c approx. 0.4 the distribution function of the level spacings (LSDF) coincides in a large energy window with the energy LSDF of the three dimensional Anderson model at the metal-insulator transition. For the same A = A c , the RME eigenvalue-number variance is linear and its slope is equal to 0.32 ± 0.02, which is consistent with the value found for the Anderson model at the critical point. (author). 51 refs, 10 figs

  7. Random matrix theory of multi-antenna communications: the Ricean channel

    International Nuclear Information System (INIS)

    Moustakas, Aris L; Simon, Steven H

    2005-01-01

    The use of multi-antenna arrays in wireless communications through disordered media promises huge increases in the information transmission rate. It is therefore important to analyse the information capacity of such systems in realistic situations of microwave transmission, where the statistics of the transmission amplitudes (channel) may be coloured. Here, we present an approach that provides analytic expressions for the statistics, i.e. the moments of the distribution, of the mutual information for general Gaussian channel statistics. The mathematical method applies tools developed originally in the context of coherent wave propagation in disordered media, such as random matrix theory and replicas. Although it is valid formally for large antenna numbers, this approach produces extremely accurate results even for arrays with as few as two antennas. We also develop a method to analytically optimize over the input signal distribution, which enables us to calculate analytic capacities when the transmitter has knowledge of the statistics of the channel. The emphasis of this paper is on elucidating the novel mathematical methods used. We do this by analysing a specific case when the channel matrix is a complex Gaussian with arbitrary mean and unit covariance, which is usually called the Ricean channel

  8. Calibration of Discrete Random Walk (DRW) Model via G.I Taylor's Dispersion Theory

    Science.gov (United States)

    Javaherchi, Teymour; Aliseda, Alberto

    2012-11-01

    Prediction of particle dispersion in turbulent flows is still an important challenge with many applications to environmental, as well as industrial, fluid mechanics. Several models of dispersion have been developed to predict particle trajectories and their relative velocities, in combination with a RANS-based simulation of the background flow. The interaction of the particles with the velocity fluctuations at different turbulent scales represents a significant difficulty in generalizing the models to the wide range of flows where they are used. We focus our attention on the Discrete Random Walk (DRW) model applied to flow in a channel, particularly to the selection of eddies lifetimes as realizations of a Poisson distribution with a mean value proportional to κ / ɛ . We present a general method to determine the constant of this proportionality by matching the DRW model dispersion predictions for fluid element and particle dispersion to G.I Taylor's classical dispersion theory. This model parameter is critical to the magnitude of predicted dispersion. A case study of its influence on sedimentation of suspended particles in a tidal channel with an array of Marine Hydrokinetic (MHK) turbines highlights the dependency of results on this time scale parameter. Support from US DOE through the Northwest National Marine Renewable Energy Center, a UW-OSU partnership.

  9. Fatigue life estimation of MD36 and MD523 bogies based on damage accumulation and random fatigue theory

    International Nuclear Information System (INIS)

    Younesian, Davood; Solhmirzaei, Ali; Gachloo, Alireza

    2009-01-01

    Bogies are one of the multifunctional parts of trains which are extremely subjected to random loads. This type of oscillating and random excitation arises from irregularities of the track including rail surface vertical roughness, rail joints, variance in super-elevation, and also wheel imperfections like wheel flats and unbalancy. Since most of the prementioned sources have random nature, a random based theory should be applied for fatigue life estimation of the bogie frame. Two methods of fatigue life estimation are investigated in this paper. The first approach which is being implemented in time domain is based on the damage accumulation (DA) approach. Using Monte-Carlo simulation algorithm, the rail surface roughness is generated. Finite element (FE) model of the bogie is subjected to the generated random excitation in the first approach and the stress time histories are obtained, and consequently the fatigue life is estimated by using the rain-flow algorithm. In the second approach, the fatigue life is estimated in frequency domain. Power spectral density (PSD) of the stress is obtained by using the FE model of the bogie frame and the fatigue life is estimated using Rayleigh technique in random fatigue theory. A comprehensive parametric study is carried out and effects of different parameters like the train speeds and level of the rail surface vertical roughness on the estimated fatigue life are investigated

  10. A theory-based video messaging mobile phone intervention for smoking cessation: randomized controlled trial.

    Science.gov (United States)

    Whittaker, Robyn; Dorey, Enid; Bramley, Dale; Bullen, Chris; Denny, Simon; Elley, C Raina; Maddison, Ralph; McRobbie, Hayden; Parag, Varsha; Rodgers, Anthony; Salmon, Penny

    2011-01-21

    Advances in technology allowed the development of a novel smoking cessation program delivered by video messages sent to mobile phones. This social cognitive theory-based intervention (called "STUB IT") used observational learning via short video diary messages from role models going through the quitting process to teach behavioral change techniques. The objective of our study was to assess the effectiveness of a multimedia mobile phone intervention for smoking cessation. A randomized controlled trial was conducted with 6-month follow-up. Participants had to be 16 years of age or over, be current daily smokers, be ready to quit, and have a video message-capable phone. Recruitment targeted younger adults predominantly through radio and online advertising. Registration and data collection were completed online, prompted by text messages. The intervention group received an automated package of video and text messages over 6 months that was tailored to self-selected quit date, role model, and timing of messages. Extra messages were available on demand to beat cravings and address lapses. The control group also set a quit date and received a general health video message sent to their phone every 2 weeks. The target sample size was not achieved due to difficulty recruiting young adult quitters. Of the 226 randomized participants, 47% (107/226) were female and 24% (54/226) were Maori (indigenous population of New Zealand). Their mean age was 27 years (SD 8.7), and there was a high level of nicotine addiction. Continuous abstinence at 6 months was 26.4% (29/110) in the intervention group and 27.6% (32/116) in the control group (P = .8). Feedback from participants indicated that the support provided by the video role models was important and appreciated. This study was not able to demonstrate a statistically significant effect of the complex video messaging mobile phone intervention compared with simple general health video messages via mobile phone. However, there was

  11. Many-Body Quantum Chaos: Analytic Connection to Random Matrix Theory

    Science.gov (United States)

    Kos, Pavel; Ljubotina, Marko; Prosen, Tomaž

    2018-04-01

    A key goal of quantum chaos is to establish a relationship between widely observed universal spectral fluctuations of clean quantum systems and random matrix theory (RMT). Most prominent features of such RMT behavior with respect to a random spectrum, both encompassed in the spectral pair correlation function, are statistical suppression of small level spacings (correlation hole) and enhanced stiffness of the spectrum at large spectral ranges. For single-particle systems with fully chaotic classical counterparts, the problem has been partly solved by Berry [Proc. R. Soc. A 400, 229 (1985), 10.1098/rspa.1985.0078] within the so-called diagonal approximation of semiclassical periodic-orbit sums, while the derivation of the full RMT spectral form factor K (t ) (Fourier transform of the spectral pair correlation function) from semiclassics has been completed by Müller et al. [Phys. Rev. Lett. 93, 014103 (2004), 10.1103/PhysRevLett.93.014103]. In recent years, the questions of long-time dynamics at high energies, for which the full many-body energy spectrum becomes relevant, are coming to the forefront even for simple many-body quantum systems, such as locally interacting spin chains. Such systems display two universal types of behaviour which are termed the "many-body localized phase" and "ergodic phase." In the ergodic phase, the spectral fluctuations are excellently described by RMT, even for very simple interactions and in the absence of any external source of disorder. Here we provide a clear theoretical explanation for these observations. We compute K (t ) in the leading two orders in t and show its agreement with RMT for nonintegrable, time-reversal invariant many-body systems without classical counterparts, a generic example of which are Ising spin-1 /2 models in a periodically kicking transverse field. In particular, we relate K (t ) to partition functions of a class of twisted classical Ising models on a ring of size t ; hence, the leading-order RMT behavior

  12. Random matrix theory filters in portfolio optimisation: A stability and risk assessment

    Science.gov (United States)

    Daly, J.; Crane, M.; Ruskin, H. J.

    2008-07-01

    Random matrix theory (RMT) filters, applied to covariance matrices of financial returns, have recently been shown to offer improvements to the optimisation of stock portfolios. This paper studies the effect of three RMT filters on the realised portfolio risk, and on the stability of the filtered covariance matrix, using bootstrap analysis and out-of-sample testing. We propose an extension to an existing RMT filter, (based on Krzanowski stability), which is observed to reduce risk and increase stability, when compared to other RMT filters tested. We also study a scheme for filtering the covariance matrix directly, as opposed to the standard method of filtering correlation, where the latter is found to lower the realised risk, on average, by up to 6.7%. We consider both equally and exponentially weighted covariance matrices in our analysis, and observe that the overall best method out-of-sample was that of the exponentially weighted covariance, with our Krzanowski stability-based filter applied to the correlation matrix. We also find that the optimal out-of-sample decay factors, for both filtered and unfiltered forecasts, were higher than those suggested by Riskmetrics [J.P. Morgan, Reuters, Riskmetrics technical document, Technical Report, 1996. http://www.riskmetrics.com/techdoc.html], with those for the latter approaching a value of α=1. In conclusion, RMT filtering reduced the realised risk, on average, and in the majority of cases when tested out-of-sample, but increased the realised risk on a marked number of individual days-in some cases more than doubling it.

  13. A stochastic model for intermittent search strategies

    International Nuclear Information System (INIS)

    Benichou, O; Coppey, M; Moreau, M; Suet, P H; Voituriez, R

    2005-01-01

    It is often necessary, in scientific or everyday life problems, to find a randomly hidden target. What is then the optimal strategy to reach it as rapidly as possible? In this article, we develop a stochastic theory for intermittent search behaviours, which are often observed: the searcher alternates phases of intensive search and slow motion with fast displacements. The first results of this theory have already been announced recently. Here we provide a detailed presentation of the theory, as well as the full derivation of the results. Furthermore, we explicitly discuss the minimization of the time needed to find the target

  14. Confirmation bias in web-based search: a randomized online study on the effects of expert information and social tags on information search and evaluation.

    Science.gov (United States)

    Schweiger, Stefan; Oeberst, Aileen; Cress, Ulrike

    2014-03-26

    The public typically believes psychotherapy to be more effective than pharmacotherapy for depression treatments. This is not consistent with current scientific evidence, which shows that both types of treatment are about equally effective. The study investigates whether this bias towards psychotherapy guides online information search and whether the bias can be reduced by explicitly providing expert information (in a blog entry) and by providing tag clouds that implicitly reveal experts' evaluations. A total of 174 participants completed a fully automated Web-based study after we invited them via mailing lists. First, participants read two blog posts by experts that either challenged or supported the bias towards psychotherapy. Subsequently, participants searched for information about depression treatment in an online environment that provided more experts' blog posts about the effectiveness of treatments based on alleged research findings. These blogs were organized in a tag cloud; both psychotherapy tags and pharmacotherapy tags were popular. We measured tag and blog post selection, efficacy ratings of the presented treatments, and participants' treatment recommendation after information search. Participants demonstrated a clear bias towards psychotherapy (mean 4.53, SD 1.99) compared to pharmacotherapy (mean 2.73, SD 2.41; t173=7.67, Pinformation search and evaluation. This bias was significantly reduced, however, when participants were exposed to tag clouds with challenging popular tags. Participants facing popular tags challenging their bias (n=61) showed significantly less biased tag selection (F2,168=10.61, Pinformation as presented in blog posts, compared to supporting expert information (n=81), decreased the bias in information search with regard to blog post selection (F1,168=4.32, P=.04, partial eta squared=0.025). No significant effects were found for treatment recommendation (Ps>.33). We conclude that the psychotherapy bias is most effectively

  15. Obtaining Hartree-Fock and density functional theory doubly excited states with Car-Parrinello density matrix search

    Science.gov (United States)

    Liang, Wenkel; Isborn, Christine M.; Li, Xiaosong

    2009-11-01

    The calculation of doubly excited states is one of the major problems plaguing the modern day excited state workhorse methodology of linear response time dependent Hartree-Fock (TDHF) and density function theory (TDDFT). We have previously shown that the use of a resonantly tuned field within real-time TDHF and TDDFT is able to simultaneously excite both the α and β electrons to achieve the two-electron excited states of minimal basis H2 and HeH+ [C. M. Isborn and X. Li, J. Chem. Phys. 129, 204107 (2008)]. We now extend this method to many electron systems with the use of our Car-Parrinello density matrix search (CP-DMS) with a first-principles fictitious mass method for wave function optimization [X. Li, C. L. Moss, W. Liang, and Y. Feng, J. Chem. Phys. 130, 234115 (2009)]. Real-time TDHF/TDDFT is used during the application of the laser field perturbation, driving the electron density toward the doubly excited state. The CP-DMS method then converges the density to the nearest stationary state. We present these stationary state doubly excited state energies and properties at the HF and DFT levels for H2, HeH+, lithium hydride, ethylene, and butadiene.

  16. Studies of Ionic Photoionization Using Relativistic Random Phase Approximation and Relativistic Multichannel Quantum Defect Theory

    Science.gov (United States)

    Haque, Ghousia Nasreen

    The absorption of electromagnetic radiation by positive ions is one of the fundamental processes of nature which occurs in every intensely hot environment. Due to the difficulties in producing sufficient densities of ions in a laboratory, there are very few measurements of ionic photoabsorption parameters. On the theoretical side, some calculations have been made of a few major photoionization parameters, but generally speaking, most of the work done so far has employed rather simple single particle models and any theoretical work which has adequately taken into account intricate atomic many-body and relativistic effects is only scanty. In the present work, several complex aspects of atomic/ionic photoabsorption parameters have been studied. Non -resonant photoionization in neon and argon isonuclear as well as isoelectronic sequences has been studied using a very sophisticated technique, namely the relativistic random phase approximation (RRPA). This technique takes into account relativistic effects as well as an important class of major many-body effects on the same footing. The present calculations confirmed that gross features of photoionization parameters calculated using simpler models were not an artifact of the simple model. Also, the present RRPA calculations on K^+ ion and neutral Ar brought out the relative importance of various many-body effects such the inter-channel coupling. Inter-channel coupling between discrete bound state photoexcitation channels from an inner atomic/ionic level and photoionization continuum channels from an outer atomic/ionic level leads to the phenomena of autoionization resonances in the photoionization process. These resonances lead to very complex effects in the atomic/ionic photoabsorption spectra. These resonances have been calculated and studied in the present work in the neon and magnesium isoelectronic sequences using the relativistic multi-channel quantum defect theory (RMQDT) within the framework of the RRPA. The

  17. Effectiveness of a theory-based intervention to increase colorectal cancer screening among Iranian health club members: a randomized trial.

    Science.gov (United States)

    Salimzadeh, Hamideh; Eftekhar, Hassan; Majdzadeh, Reza; Montazeri, Ali; Delavari, Alireza

    2014-10-01

    Colorectal cancer is the third most commonly diagnosed cancer and the fourth leading cause of death in the world. There are few published studies that have used theory-based interventions designed to increase colorectal cancer screening in community lay health organizations. The present study was guided by the theoretical concepts of the preventive health model. Twelve health clubs of a municipal district in Tehran were randomized to two study groups with equal ratio. The control group received usual services throughout the study while the intervention group also received a theory-based educational program on colorectal cancer screening plus a reminder call. Screening behavior, the main outcome, was assessed 4 months after randomization. A total of 360 members aged 50 and older from 12 health clubs completed a baseline survey. Participants in the intervention group reported increased knowledge of colorectal cancer and screening tests at 4 months follow-up (p's theory-based intervention significantly improved self-efficacy, perceived susceptibility, efficacy of screening, social support, and intention to be screened for colorectal cancer, from baseline to 4 months follow-up (p's theory-based intervention was found to have a significant effect on colorectal cancer screening use as measured by self-report. The findings could have implications for colorectal cancer screening program development and implementation in primary health care settings and through other community organizations.

  18. SANS [small-angle neutron scattering] evaluation of the RPA [random phase approximation] theory for binary homopolymer mixtures

    International Nuclear Information System (INIS)

    Bates, F.S.; Koehler, W.C.; Wignall, G.D.; Fetters, L.J.

    1986-12-01

    A well characterized binary mixture of normal (protonated) and perdeuterated monodisperse 1,2 polybutenes has been studied by small-angle neutron scattering (SANS). For scattering wavevectors q greater than the inverse radius-of-gyration R/sub g/ -1 , the SANS intensity is quantitatively predicted by the random phase approximation (RPA) theory of deGennes over all measured values of the segment-segment interaction parameter Chi. In the region (Chi s-Chi)Chi s -1 > 0.5 the interaction parameter determined using the RPA theory for q > R/sub g/ -1 is greater than that calculated from the zero-angle intensity based on an Ornstein-Zernike plot, where Chi s represents the limit of single phase stability. These findings indicate a correlation between the critical fluctuation length ξ and R/sub g/ which is not accounted for by the RPA theory

  19. Learning cardiopulmonary resuscitation theory with face-to-face versus audiovisual instruction for secondary school students: a randomized controlled trial.

    Science.gov (United States)

    Cerezo Espinosa, Cristina; Nieto Caballero, Sergio; Juguera Rodríguez, Laura; Castejón-Mochón, José Francisco; Segura Melgarejo, Francisca; Sánchez Martínez, Carmen María; López López, Carmen Amalia; Pardo Ríos, Manuel

    2018-02-01

    To compare secondary students' learning of basic life support (BLS) theory and the use of an automatic external defibrillator (AED) through face-to-face classroom instruction versus educational video instruction. A total of 2225 secondary students from 15 schools were randomly assigned to one of the following 5 instructional groups: 1) face-to-face instruction with no audiovisual support, 2) face-to-face instruction with audiovisual support, 3) audiovisual instruction without face-to-face instruction, 4) audiovisual instruction with face-to-face instruction, and 5) a control group that received no instruction. The students took a test of BLS and AED theory before instruction, immediately after instruction, and 2 months later. The median (interquartile range) scores overall were 2.33 (2.17) at baseline, 5.33 (4.66) immediately after instruction (Paudiovisual instruction for learning BLS and AED theory were found in secondary school students either immediately after instruction or 2 months later.

  20. Evaluating the Use of Random Distribution Theory to Introduce Statistical Inference Concepts to Business Students

    Science.gov (United States)

    Larwin, Karen H.; Larwin, David A.

    2011-01-01

    Bootstrapping methods and random distribution methods are increasingly recommended as better approaches for teaching students about statistical inference in introductory-level statistics courses. The authors examined the effect of teaching undergraduate business statistics students using random distribution and bootstrapping simulations. It is the…

  1. Comparison of the efficacy of three PubMed search filters in finding randomized controlled trials to answer clinical questions.

    Science.gov (United States)

    Yousefi-Nooraie, Reza; Irani, Shirin; Mortaz-Hedjri, Soroush; Shakiba, Behnam

    2013-10-01

    The aim of this study was to compare the performance of three search methods in the retrieval of relevant clinical trials from PubMed to answer specific clinical questions. Included studies of a sample of 100 Cochrane reviews which recorded in PubMed were considered as the reference standard. The search queries were formulated based on the systematic review titles. Precision, recall and number of retrieved records for limiting the results to clinical trial publication type, and using sensitive and specific clinical queries filters were compared. The number of keywords, presence of specific names of intervention and syndrome in the search keywords were used in a model to predict the recalls and precisions. The Clinical queries-sensitive search strategy retrieved the largest number of records (33) and had the highest recall (41.6%) and lowest precision (4.8%). The presence of specific intervention name was the only significant predictor of all recalls and precisions (P = 0.016). The recall and precision of combination of simple clinical search queries and methodological search filters to find clinical trials in various subjects were considerably low. The limit field strategy yielded in higher precision and fewer retrieved records and approximately similar recall, compared with the clinical queries-sensitive strategy. Presence of specific intervention name in the search keywords increased both recall and precision. © 2010 John Wiley & Sons Ltd.

  2. Social Learning Theory Parenting Intervention Promotes Attachment-Based Caregiving in Young Children: Randomized Clinical Trial

    Science.gov (United States)

    O'Connor, Thomas G.; Matias, Carla; Futh, Annabel; Tantam, Grace; Scott, Stephen

    2013-01-01

    Parenting programs for school-aged children are typically based on behavioral principles as applied in social learning theory. It is not yet clear if the benefits of these interventions extend beyond aspects of the parent-child relationship quality conceptualized by social learning theory. The current study examined the extent to which a social…

  3. Quantum epistemology from subquantum ontology: Quantum mechanics from theory of classical random fields

    Science.gov (United States)

    Khrennikov, Andrei

    2017-02-01

    The scientific methodology based on two descriptive levels, ontic (reality as it is) and epistemic (observational), is briefly presented. Following Schrödinger, we point to the possible gap between these two descriptions. Our main aim is to show that, although ontic entities may be unaccessible for observations, they can be useful for clarification of the physical nature of operational epistemic entities. We illustrate this thesis by the concrete example: starting with the concrete ontic model preceding quantum mechanics (the latter is treated as an epistemic model), namely, prequantum classical statistical field theory (PCSFT), we propose the natural physical interpretation for the basic quantum mechanical entity-the quantum state ("wave function"). The correspondence PCSFT ↦ QM is not straightforward, it couples the covariance operators of classical (prequantum) random fields with the quantum density operators. We use this correspondence to clarify the physical meaning of the pure quantum state and the superposition principle-by using the formalism of classical field correlations. In classical mechanics the phase space description can be considered as the ontic description, here states are given by points λ =(x , p) of phase space. The dynamics of the ontic state is given by the system of Hamiltonian equations.We can also consider probability distributions on the phase space (or equivalently random variables valued in it). We call them probabilistic ontic states. Dynamics of probabilistic ontic states is given by the Liouville equation.In classical physics we can (at least in principle) measure both the coordinate and momentum and hence ontic states can be treated as epistemic states as well (or it is better to say that here epistemic states can be treated as ontic states). Probabilistic ontic states represent probabilities for outcomes of joint measurement of position and momentum.However, this was a very special, although very important, example of

  4. Distribution of Schmidt-like eigenvalues for Gaussian ensembles of the random matrix theory

    Science.gov (United States)

    Pato, Mauricio P.; Oshanin, Gleb

    2013-03-01

    We study the probability distribution function P(β)n(w) of the Schmidt-like random variable w = x21/(∑j = 1nx2j/n), where xj, (j = 1, 2, …, n), are unordered eigenvalues of a given n × n β-Gaussian random matrix, β being the Dyson symmetry index. This variable, by definition, can be considered as a measure of how any individual (randomly chosen) eigenvalue deviates from the arithmetic mean value of all eigenvalues of a given random matrix, and its distribution is calculated with respect to the ensemble of such β-Gaussian random matrices. We show that in the asymptotic limit n → ∞ and for arbitrary β the distribution P(β)n(w) converges to the Marčenko-Pastur form, i.e. is defined as P_{n}^{( \\beta )}(w) \\sim \\sqrt{(4 - w)/w} for w ∈ [0, 4] and equals zero outside of the support, despite the fact that formally w is defined on the interval [0, n]. Furthermore, for Gaussian unitary ensembles (β = 2) we present exact explicit expressions for P(β = 2)n(w) which are valid for arbitrary n and analyse their behaviour.

  5. Distribution of Schmidt-like eigenvalues for Gaussian ensembles of the random matrix theory

    International Nuclear Information System (INIS)

    Pato, Mauricio P; Oshanin, Gleb

    2013-01-01

    We study the probability distribution function P (β) n (w) of the Schmidt-like random variable w = x 2 1 /(∑ j=1 n x 2 j /n), where x j , (j = 1, 2, …, n), are unordered eigenvalues of a given n × n β-Gaussian random matrix, β being the Dyson symmetry index. This variable, by definition, can be considered as a measure of how any individual (randomly chosen) eigenvalue deviates from the arithmetic mean value of all eigenvalues of a given random matrix, and its distribution is calculated with respect to the ensemble of such β-Gaussian random matrices. We show that in the asymptotic limit n → ∞ and for arbitrary β the distribution P (β) n (w) converges to the Marčenko–Pastur form, i.e. is defined as P n (β) (w)∼√((4 - w)/w) for w ∈ [0, 4] and equals zero outside of the support, despite the fact that formally w is defined on the interval [0, n]. Furthermore, for Gaussian unitary ensembles (β = 2) we present exact explicit expressions for P (β=2) n (w) which are valid for arbitrary n and analyse their behaviour. (paper)

  6. Realism, Instrumentalism, and Scientific Symbiosis: Psychological Theory as a search for truth and the discovery of solutions

    NARCIS (Netherlands)

    Cacioppo, J.T.; Semin, G.R.; Berntson, G.G.

    2004-01-01

    Scientific realism holds that scientific theories are approximations of universal truths about reality, whereas scientific instrumentalism posits that scientific theories are intellectual structures that provide adequate predictions of what is observed and useful frameworks for answering questions

  7. Contribution to the application of the random vibration theory to the seismic analysis of structures via state variables

    International Nuclear Information System (INIS)

    Maestrini, A.P.

    1979-04-01

    Several problems related to the application of the theory of random by means of state variables are studied. The well-known equations that define the propagation of the mean and the variance for linear and non-linear systems are first presented. The Monte Carlo method is next resorted to in order to determine the applicability of the hypothesis of a normally distributed output in case of linear systems subjected to non-Gaussian excitations. Finally, attention is focused on the properties of linear filters and modulation functions proposed to simulate seismic excitations as non stationary random processes. Acceleration spectra obtained by multiplying rms spectra by a constant factor are compared with design spectra suggested by several authors for various soil conditions. In every case, filter properties are given. (Author) [pt

  8. Random distance distribution for spherical objects: general theory and applications to physics

    International Nuclear Information System (INIS)

    Tu Shuju; Fischbach, Ephraim

    2002-01-01

    A formalism is presented for analytically obtaining the probability density function, P n (s), for the random distance s between two random points in an n-dimensional spherical object of radius R. Our formalism allows P n (s) to be calculated for a spherical n-ball having an arbitrary volume density, and reproduces the well-known results for the case of uniform density. The results find applications in geometric probability, computational science, molecular biological systems, statistical physics, astrophysics, condensed matter physics, nuclear physics and elementary particle physics. As one application of these results, we propose a new statistical method derived from our formalism to study random number generators used in Monte Carlo simulations. (author)

  9. The mesoscopic conductance of disordered rings, its random matrix theory and the generalized variable range hopping picture

    International Nuclear Information System (INIS)

    Stotland, Alexander; Peer, Tal; Cohen, Doron; Budoyo, Rangga; Kottos, Tsampikos

    2008-01-01

    The calculation of the conductance of disordered rings requires a theory that goes beyond the Kubo-Drude formulation. Assuming 'mesoscopic' circumstances the analysis of the electro-driven transitions shows similarities with a percolation problem in energy space. We argue that the texture and the sparsity of the perturbation matrix dictate the value of the conductance, and study its dependence on the disorder strength, ranging from the ballistic to the Anderson localization regime. An improved sparse random matrix model is introduced to capture the essential ingredients of the problem, and leads to a generalized variable range hopping picture. (fast track communication)

  10. The Relationship of Dynamical Heterogeneity to the Adam-Gibbs and Random First-Order Transition Theories of Glass Formation

    OpenAIRE

    Starr, Francis W.; Douglas, Jack F.; Sastry, Srikanth

    2013-01-01

    We carefully examine common measures of dynamical heterogeneity for a model polymer melt and test how these scales compare with those hypothesized by the Adam and Gibbs (AG) and random first-order transition (RFOT) theories of relaxation in glass-forming liquids. To this end, we first analyze clusters of highly mobile particles, the string-like collective motion of these mobile particles, and clusters of relative low mobility. We show that the time scale of the high-mobility clusters and stri...

  11. A theory of solving TAP equations for Ising models with general invariant random matrices

    DEFF Research Database (Denmark)

    Opper, Manfred; Çakmak, Burak; Winther, Ole

    2016-01-01

    We consider the problem of solving TAP mean field equations by iteration for Ising models with coupling matrices that are drawn at random from general invariant ensembles. We develop an analysis of iterative algorithms using a dynamical functional approach that in the thermodynamic limit yields...... the iteration dependent on a Gaussian distributed field only. The TAP magnetizations are stable fixed points if a de Almeida–Thouless stability criterion is fulfilled. We illustrate our method explicitly for coupling matrices drawn from the random orthogonal ensemble....

  12. Efficacy of theory-based HIV behavioral prevention among rural-to-urban migrants in China: a randomized controlled trial.

    Science.gov (United States)

    Li, Xiaoming; Lin, Danhua; Wang, Bo; Du, Hongfei; Tam, Cheuk Chi; Stanton, Bonita

    2014-08-01

    Our objective was to evaluate the efficacy of a cultural adaptation of a social cognitive theory-based HIV behavioral prevention program among young rural-to-urban migrants in China. The intervention design and assessment were guided by the Protection Motivation Theory (PMT). The intervention was evaluated through a randomized controlled trial with 6-month and 12-month follow-ups. The primary behavioral outcome was the use of condoms. Other outcome measures include HIV knowledge, condom use knowledge, HIV-related perceptions (PMT constructs), and intention to use condom. The mixed-effects regression models for condom use with regular partners indicated that overall frequency of condom use, condom use in last three sexual acts and proper condom use increased over time for the participants but the increases were significantly greater among the intervention group than the control group at 6-month and 12-month follow-ups. The mixed-effects models for HIV-related perceptions indicated that extrinsic rewards, intrinsic rewards, and response costs decreased while vulnerability, severity, response efficacy, and self-efficacy increased over time for the intervention group. The increases in HIV knowledge, condom use knowledge, and intention to use condom were also significantly greater among the intervention group than the control group. The data in the current study suggested efficacy of a social cognitive theory-based behavioral intervention in increasing condom use among young migrants in China. The intervention also increased protective perceptions and decreased risk perception posited by the theory (i.e., PMT).

  13. Fermi sea term in the relativistic linear muffin-tin-orbital transport theory for random alloys

    Czech Academy of Sciences Publication Activity Database

    Turek, Ilja; Kudrnovský, Josef; Drchal, Václav

    2014-01-01

    Roč. 89, č. 6 (2014), 064405 ISSN 1098-0121 R&D Projects: GA ČR(CZ) GAP204/11/1228 Institutional support: RVO:68081723 ; RVO:68378271 Keywords : electron transport * anomalous Hall effect * random alloys Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.736, year: 2014

  14. Random Schroedinger operators and the theory of disordered systems: some rigorous results

    International Nuclear Information System (INIS)

    Kunz, H.; Souillard, B.

    1981-01-01

    The authors report results on a class of finite difference Schroedinger operators with stochastic potentials. The Hamiltonian is then H(V)=-Δ+V; where Δ is the discretized Laplacian and the potential V acts as a multiplication operator. The potential V is random. (Auth.)

  15. Random matrix theory and acoustic resonances in plates with an approximate symmetry

    DEFF Research Database (Denmark)

    Andersen, Anders Peter; Ellegaard, C.; Jackson, A.D.

    2001-01-01

    We discuss a random matrix model of systems with an approximate symmetry and present the spectral fluctuation statistics and eigenvector characteristics for the model. An acoustic resonator like, e.g., an aluminum plate may have an approximate symmetry. We have measured the frequency spectrum and...

  16. Morphology on convolution lattices with applications to the slope transformand random set theory

    NARCIS (Netherlands)

    H.J.A.M. Heijmans (Henk); I.S. Molchanov (Ilya)

    1996-01-01

    textabstractThis paper develops an abstract theory for mathematical morphology on complete lattices. The approach is based upon the idea that objects are only known through information provided by a given collection of measurements (called evaluations in this paper). This abstract approach leads in

  17. submitter Searches at LEP

    CERN Document Server

    Kawagoe, Kiyotomo

    2001-01-01

    Searches for new particles and new physics were extensively performed at LEP. Although no evidence for new particle/physics was discovered, the null results set very stringent limits to theories beyond the standard model. In this paper, searches at LEP and anomalies observed in the searches are presented. Future prospect of searches at the new energy frontier machines is also discussed.

  18. Study of RNA structures with a connection to random matrix theory

    International Nuclear Information System (INIS)

    Bhadola, Pradeep; Deo, Nivedita

    2015-01-01

    This manuscript investigates the level of complexity and thermodynamic properties of the real RNA structures and compares the properties with the random RNA sequences. A discussion on the similarities of thermodynamical properties of the real structures with the non linear random matrix model of RNA folding is presented. The structural information contained in the PDB file is exploited to get the base pairing information. The complexity of an RNA structure is defined by a topological quantity called genus which is calculated from the base pairing information. Thermodynamic analysis of the real structures is done numerically. The real structures have a minimum free energy which is very small compared to the randomly generated sequences of the same length. This analysis suggests that there are specific patterns in the structures which are preserved during the evolution of the sequences and certain sequences are discarded by the evolutionary process. Further analyzing the sequences of a fixed length reveal that the RNA structures exist in ensembles i.e. although all the sequences in the ensemble have different series of nucleotides (sequence) they fold into structures that have the same pairs of hydrogen bonding as well as the same minimum free energy. The specific heat of the RNA molecule is numerically estimated at different lengths. The specific heat curve with temperature shows a bump and for some RNA, a double peak behavior is observed. The same behavior is seen in the study of the random matrix model with non linear interaction of RNA folding. The bump in the non linear matrix model can be controlled by the change in the interaction strength.

  19. Small random perturbations of infinite dimensional dynamical systems and nucleation theory

    International Nuclear Information System (INIS)

    Cassandro, M.; Olivieri, E.; Picco, P.

    1985-06-01

    We consider a stochastic differential equation with a standard space-time white noise and a double well non symmetric potential. The equation without the white noise term exhibits several equilibria two of which are stable. We study, in the double limit zero noise and thermodynamic limit the large fluctuations and compute the transition probability between the two stable equilibria (tunnelling). The unique stationary measure associated to the stochastic process described by our equation is strictly related to the Gibbs measure for a ferromagnetic spin system subject to a Kac interaction. Our double limit corresponds to the one considered by Lobowitz and Penrose in their rigorous version of the mean field theory of the first order phase transitions. The tunnelling between the two (non equivalent) equilibrium configurations is interpreted as the decay from the metastable to the stable state. Our results are in qualitative agreement with the usual nucleation theory

  20. Nursing Theory, Terminology, and Big Data: Data-Driven Discovery of Novel Patterns in Archival Randomized Clinical Trial Data.

    Science.gov (United States)

    Monsen, Karen A; Kelechi, Teresa J; McRae, Marion E; Mathiason, Michelle A; Martin, Karen S

    The growth and diversification of nursing theory, nursing terminology, and nursing data enable a convergence of theory- and data-driven discovery in the era of big data research. Existing datasets can be viewed through theoretical and terminology perspectives using visualization techniques in order to reveal new patterns and generate hypotheses. The Omaha System is a standardized terminology and metamodel that makes explicit the theoretical perspective of the nursing discipline and enables terminology-theory testing research. The purpose of this paper is to illustrate the approach by exploring a large research dataset consisting of 95 variables (demographics, temperature measures, anthropometrics, and standardized instruments measuring quality of life and self-efficacy) from a theory-based perspective using the Omaha System. Aims were to (a) examine the Omaha System dataset to understand the sample at baseline relative to Omaha System problem terms and outcome measures, (b) examine relationships within the normalized Omaha System dataset at baseline in predicting adherence, and (c) examine relationships within the normalized Omaha System dataset at baseline in predicting incident venous ulcer. Variables from a randomized clinical trial of a cryotherapy intervention for the prevention of venous ulcers were mapped onto Omaha System terms and measures to derive a theoretical framework for the terminology-theory testing study. The original dataset was recoded using the mapping to create an Omaha System dataset, which was then examined using visualization to generate hypotheses. The hypotheses were tested using standard inferential statistics. Logistic regression was used to predict adherence and incident venous ulcer. Findings revealed novel patterns in the psychosocial characteristics of the sample that were discovered to be drivers of both adherence (Mental health Behavior: OR = 1.28, 95% CI [1.02, 1.60]; AUC = .56) and incident venous ulcer (Mental health Behavior

  1. Theory of potentiostatic current transients for coupled catalytic reaction at random corrugated fractal electrode

    International Nuclear Information System (INIS)

    Jha, Shailendra K.; Kant, Rama

    2010-01-01

    We developed a mathematical model for the first order homogeneous catalytic chemical reaction coupled with an electron transfer (EC') on a rough working electrode. Results are obtained for the various roughness models of electrode corrugations, viz., (i) roughness as an exact periodic function, (ii) roughness as a random function with known statistical properties, and (iii) roughness as a random function with statistical self-affine fractality over a finite range of length scales. Method of Green's function is used in the formulation to obtain second-order perturbation (in roughness profile) expressions for the concentration, the local current density and the current transients. A general operator structure between these quantities and arbitrary roughness profile is emphasized. The statistically averaged (randomly rough) electrode response is obtained by an ensemble averaging over all possible surface configurations. An elegant mathematical formula between the average electrochemical current transient and surface structure factor or power-spectrum of roughness is obtained. This formula is used to obtain an explicit equation for the current on an approximately self-affine (or realistic) fractal electrode with a limited range of length scales of irregularities. This description of realistic fractal is obtained by cutoff power law power-spectrum of roughness. The realistic fractal power-spectrum consists of four physical characteristics, viz., the fractal dimension (D H ), lower (l) and upper (L) cutoff length scales of fractality and a proportionality factor (μ), which is related to the topothesy or strength of fractality. Numerical calculations are performed on final results to understand the effect of catalytic reaction and fractal morphological characteristics on potentiostatic current transients.

  2. Facilitating sunscreen use in women by a theory-based online intervention: a randomized controlled trial.

    Science.gov (United States)

    Craciun, Catrinel; Schüz, Natalie; Lippke, Sonia; Schwarzer, Ralf

    2012-03-01

    This study compares a motivational skin cancer prevention approach with a volitional planning and self-efficacy intervention to enhance regular sunscreen use. A randomized controlled trial (RCT) was conducted with 205 women (mean age 25 years) in three groups: motivational; volitional; and control. Sunscreen use, action planning, coping planning and coping self-efficacy were assessed at three points in time. The volitional intervention improved sunscreen use. Coping planning emerged as the only mediator between the intervention and sunscreen use at Time 3. Findings point to the role played by coping planning as an ingredient of sun protection interventions.

  3. Accounting for Sampling Error in Genetic Eigenvalues Using Random Matrix Theory.

    Science.gov (United States)

    Sztepanacz, Jacqueline L; Blows, Mark W

    2017-07-01

    The distribution of genetic variance in multivariate phenotypes is characterized by the empirical spectral distribution of the eigenvalues of the genetic covariance matrix. Empirical estimates of genetic eigenvalues from random effects linear models are known to be overdispersed by sampling error, where large eigenvalues are biased upward, and small eigenvalues are biased downward. The overdispersion of the leading eigenvalues of sample covariance matrices have been demonstrated to conform to the Tracy-Widom (TW) distribution. Here we show that genetic eigenvalues estimated using restricted maximum likelihood (REML) in a multivariate random effects model with an unconstrained genetic covariance structure will also conform to the TW distribution after empirical scaling and centering. However, where estimation procedures using either REML or MCMC impose boundary constraints, the resulting genetic eigenvalues tend not be TW distributed. We show how using confidence intervals from sampling distributions of genetic eigenvalues without reference to the TW distribution is insufficient protection against mistaking sampling error as genetic variance, particularly when eigenvalues are small. By scaling such sampling distributions to the appropriate TW distribution, the critical value of the TW statistic can be used to determine if the magnitude of a genetic eigenvalue exceeds the sampling error for each eigenvalue in the spectral distribution of a given genetic covariance matrix. Copyright © 2017 by the Genetics Society of America.

  4. Models of disordered media: some new results, including some new connections between composite-media, fluid-state, and random-flight theories

    International Nuclear Information System (INIS)

    Stell, G.

    1983-01-01

    Some new theoretical results on the microstructure of models of two-phase disordered media are given, as well as the new quantitative bounds on the thermal conductivity that follows for one such model (randomly centered spherical inclusions). A second set of results is then given for random flights, including random flights with hit expectancy prescribed in a unit hall around the flight origin. Finally, some interesting correspondences are demonstrated, via the Ornstein-Zernike equation, between random-flight results, liquid-state results and percolation-theory results. 27 references, 6 figures, 4 tables

  5. The relationship of dynamical heterogeneity to the Adam-Gibbs and random first-order transition theories of glass formation.

    Science.gov (United States)

    Starr, Francis W; Douglas, Jack F; Sastry, Srikanth

    2013-03-28

    We carefully examine common measures of dynamical heterogeneity for a model polymer melt and test how these scales compare with those hypothesized by the Adam and Gibbs (AG) and random first-order transition (RFOT) theories of relaxation in glass-forming liquids. To this end, we first analyze clusters of highly mobile particles, the string-like collective motion of these mobile particles, and clusters of relative low mobility. We show that the time scale of the high-mobility clusters and strings is associated with a diffusive time scale, while the low-mobility particles' time scale relates to a structural relaxation time. The difference of the characteristic times for the high- and low-mobility particles naturally explains the well-known decoupling of diffusion and structural relaxation time scales. Despite the inherent difference of dynamics between high- and low-mobility particles, we find a high degree of similarity in the geometrical structure of these particle clusters. In particular, we show that the fractal dimensions of these clusters are consistent with those of swollen branched polymers or branched polymers with screened excluded-volume interactions, corresponding to lattice animals and percolation clusters, respectively. In contrast, the fractal dimension of the strings crosses over from that of self-avoiding walks for small strings, to simple random walks for longer, more strongly interacting, strings, corresponding to flexible polymers with screened excluded-volume interactions. We examine the appropriateness of identifying the size scales of either mobile particle clusters or strings with the size of cooperatively rearranging regions (CRR) in the AG and RFOT theories. We find that the string size appears to be the most consistent measure of CRR for both the AG and RFOT models. Identifying strings or clusters with the "mosaic" length of the RFOT model relaxes the conventional assumption that the "entropic droplets" are compact. We also confirm the

  6. Unifying Pore Network Modeling, Continuous Time Random Walk Theory and Experiment - Accomplishments and Future Directions

    Science.gov (United States)

    Bijeljic, B.

    2008-05-01

    This talk will describe and highlight the advantages offered by a methodology that unifies pore network modeling, CTRW theory and experiment in description of solute dispersion in porous media. Solute transport in a porous medium is characterized by the interplay of advection and diffusion (described by Peclet number, Pe) that cause spreading of solute particles. This spreading is traditionally described by dispersion coefficients, D, defined by σ 2 = 2Dt, where σ 2 is the variance of the solute position and t is the time. Using a pore-scale network model based on particle tracking, the rich Peclet- number dependence of dispersion coefficient is predicted from first principles and is shown to compare well with experimental data for restricted diffusion, transition, power-law and mechanical dispersion regimes in the asymptotic limit. In the asymptotic limit D is constant and can be used in an averaged advection-dispersion equation. However, it is highly important to recognize that, until the velocity field is fully sampled, the particle transport is non-Gaussian and D possesses temporal or spatial variation. Furthermore, temporal probability density functions (PDF) of tracer particles are studied in pore networks and an excellent agreement for the spectrum of transition times for particles from pore to pore is obtained between network model results and CTRW theory. Based on the truncated power-law interpretation of PDF-s, the physical origin of the power-law scaling of dispersion coefficient vs. Peclet number has been explained for unconsolidated porous media, sands and a number of sandstones, arriving at the same conclusion from numerical network modelling, analytic CTRW theory and experiment. Future directions for further applications of the methodology presented are discussed in relation to the scale- dependent solute dispersion and reactive transport. Significance of pre-asymptotic dispersion in porous media is addressed from pore-scale upwards and the impact

  7. Measuring order in disordered systems and disorder in ordered systems: Random matrix theory for isotropic and nematic liquid crystals and its perspective on pseudo-nematic domains

    Science.gov (United States)

    Zhao, Yan; Stratt, Richard M.

    2018-05-01

    Surprisingly long-ranged intermolecular correlations begin to appear in isotropic (orientationally disordered) phases of liquid crystal forming molecules when the temperature or density starts to close in on the boundary with the nematic (ordered) phase. Indeed, the presence of slowly relaxing, strongly orientationally correlated, sets of molecules under putatively disordered conditions ("pseudo-nematic domains") has been apparent for some time from light-scattering and optical-Kerr experiments. Still, a fully microscopic characterization of these domains has been lacking. We illustrate in this paper how pseudo-nematic domains can be studied in even relatively small computer simulations by looking for order-parameter tensor fluctuations much larger than one would expect from random matrix theory. To develop this idea, we show that random matrix theory offers an exact description of how the probability distribution for liquid-crystal order parameter tensors converges to its macroscopic-system limit. We then illustrate how domain properties can be inferred from finite-size-induced deviations from these random matrix predictions. A straightforward generalization of time-independent random matrix theory also allows us to prove that the analogous random matrix predictions for the time dependence of the order-parameter tensor are similarly exact in the macroscopic limit, and that relaxation behavior of the domains can be seen in the breakdown of the finite-size scaling required by that random-matrix theory.

  8. Finite nucleus Dirac mean field theory and random phase approximation using finite B splines

    International Nuclear Information System (INIS)

    McNeil, J.A.; Furnstahl, R.J.; Rost, E.; Shepard, J.R.; Department of Physics, University of Maryland, College Park, Maryland 20742; Department of Physics, University of Colorado, Boulder, Colorado 80309)

    1989-01-01

    We calculate the finite nucleus Dirac mean field spectrum in a Galerkin approach using finite basis splines. We review the method and present results for the relativistic σ-ω model for the closed-shell nuclei 16 O and 40 Ca. We study the convergence of the method as a function of the size of the basis and the closure properties of the spectrum using an energy-weighted dipole sum rule. We apply the method to the Dirac random-phase-approximation response and present results for the isoscalar 1/sup -/ and 3/sup -/ longitudinal form factors of 16 O and 40 Ca. We also use a B-spline spectral representation of the positive-energy projector to evaluate partial energy-weighted sum rules and compare with nonrelativistic sum rule results

  9. Ordered Consumer Search

    OpenAIRE

    Armstrong, Mark

    2016-01-01

    The paper discusses situations in which consumers search through their options in a deliberate order, in contrast to more familiar models with random search. Topics include: network effects (consumers may be better off following the same search order as other consumers); the use of price and non-price advertising to direct search; the impact of consumers starting a new search with their previous supplier; the incentive sellers have to merge or co-locate with other sellers; and the incentive a...

  10. A search for light gluinos, and, Heavy quark effective field theory and B-physics with applications to the collider detector at Fermilab

    International Nuclear Information System (INIS)

    Cakir, M.B.

    1993-01-01

    In the first part of this dissertation a search for light gluinos in the 0(1 GeV) region - especially in radiative decays of vector quarkonia - is presented. It is shown that light gluinos have not been excluded by experiments to date. In fact some evidence contrary to that fact is presented. In the second part the recent Heavy Quark Effective Field Theory methods are used in calculating rare decays of vector and pseudoscalar mesons of b-quarks. Applications to the Collider Detector at Fermilab environment are discussed

  11. Simplification of Markov chains with infinite state space and the mathematical theory of random gene expression bursts

    Science.gov (United States)

    Jia, Chen

    2017-09-01

    Here we develop an effective approach to simplify two-time-scale Markov chains with infinite state spaces by removal of states with fast leaving rates, which improves the simplification method of finite Markov chains. We introduce the concept of fast transition paths and show that the effective transitions of the reduced chain can be represented as the superposition of the direct transitions and the indirect transitions via all the fast transition paths. Furthermore, we apply our simplification approach to the standard Markov model of single-cell stochastic gene expression and provide a mathematical theory of random gene expression bursts. We give the precise mathematical conditions for the bursting kinetics of both mRNAs and proteins. It turns out that random bursts exactly correspond to the fast transition paths of the Markov model. This helps us gain a better understanding of the physics behind the bursting kinetics as an emergent behavior from the fundamental multiscale biochemical reaction kinetics of stochastic gene expression.

  12. The efficacy of social cognitive theory-based self-care intervention for rational antibiotic use: a randomized trial.

    Science.gov (United States)

    Mohebbi, Bahram; Tol, Azar; Sadeghi, Roya; Yaseri, Mehdi; Akbari Somar, Negar; Doyore Agide, Feleke

    2018-05-19

    Misuse of antibiotics can be described as a failure to complete treatment, skipping of the doses and reuse of leftover medicines and overuse of antibiotics. Health education interventions are expected to enhance awareness and general belief on rational antibiotics use. Therefore, the study aimed to determine the efficacy of social cognitive theory (SCT)-based self-care intervention for rational antibiotic use. This randomized trial was conducted in a sample of 260 adults. The study participants were randomly assigned as the intervention (n=130) and a control (n=130) groups. The intervention group received self-care educational intervention of four sessions lasting 45-60 min augmented with the text messages and the control groups attended usual education program in health centers. The study participants were invited to complete questionnaires at the baseline and end of the intervention. The data were analyzed using SPSS version 23.0. Chi-square (X2), independent t-test and covariance analysis were used for data analysis. Prational antibiotic use showed a significant difference in intervention group before and after six months (P0.05). The study suggested that tailored appropriate educational programs based on SCT constructs can reflect a positive impact on appropriate antibiotics use. Therefore, a tailored health promotion intervention should be provided to enhance the awareness and general beliefs of the target groups.

  13. Random-matrix theory of amplifying and absorbing resonators with PT or PTT' symmetry

    International Nuclear Information System (INIS)

    Birchall, Christopher; Schomerus, Henning

    2012-01-01

    We formulate Gaussian and circular random-matrix models representing a coupled system consisting of an absorbing and an amplifying resonator, which are mutually related by a generalized time-reversal symmetry. Motivated by optical realizations of such systems we consider a PT or a PTT ' time-reversal symmetry, which impose different constraints on magneto-optical effects, and then focus on five common settings. For each of these, we determine the eigenvalue distribution in the complex plane in the short-wavelength limit, which reveals that the fraction of real eigenvalues among all eigenvalues in the spectrum vanishes if all classical scales are kept fixed. Numerically, we find that the transition from real to complex eigenvalues in the various ensembles display a different dependence on the coupling strength between the two resonators. These differences can be linked to the level spacing statistics in the Hermitian limit of the considered models. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Quantum physics with non-Hermitian operators’. (paper)

  14. Multicomponent mass transport model: theory and numerical implementation (discrete-parcel-random-walk version)

    International Nuclear Information System (INIS)

    Ahlstrom, S.W.; Foote, H.P.; Arnett, R.C.; Cole, C.R.; Serne, R.J.

    1977-05-01

    The Multicomponent Mass Transfer (MMT) Model is a generic computer code, currently in its third generation, that was developed to predict the movement of radiocontaminants in the saturated and unsaturated sediments of the Hanford Site. This model was designed to use the water movement patterns produced by the unsaturated and saturated flow models coupled with dispersion and soil-waste reaction submodels to predict contaminant transport. This report documents the theorical foundation and the numerical solution procedure of the current (third) generation of the MMT Model. The present model simulates mass transport processes using an analog referred to as the Discrete-Parcel-Random-Walk (DPRW) algorithm. The basic concepts of this solution technique are described and the advantages and disadvantages of the DPRW scheme are discussed in relation to more conventional numerical techniques such as the finite-difference and finite-element methods. Verification of the numerical algorithm is demonstrated by comparing model results with known closed-form solutions. A brief error and sensitivity analysis of the algorithm with respect to numerical parameters is also presented. A simulation of the tritium plume beneath the Hanford Site is included to illustrate the use of the model in a typical application. 32 figs

  15. Microcredit in theory and practice: using randomized credit scoring for impact evaluation.

    Science.gov (United States)

    Karlan, Dean; Zinman, Jonathan

    2011-06-10

    Microcredit institutions spend billions of dollars fighting poverty by making small loans primarily to female entrepreneurs. Proponents argue that microcredit mitigates market failures, spurs micro-enterprise growth, and boosts borrowers' well-being. We tested these hypotheses with the use of an innovative, replicable experimental design that randomly assigned individual liability microloans (of $225 on average) to 1601 individuals in the Philippines through credit scoring. After 11 to 22 months, we found evidence consistent with unmet demand at the current price (a roughly 60% annualized interest rate): Net borrowing increased in the treatment group relative to controls. However, the number of business activities and employees in the treatment group decreased relative to controls, and subjective well-being declined slightly. We also found little evidence that treatment effects were more pronounced for women. However, we did find that microloans increase ability to cope with risk, strengthen community ties, and increase access to informal credit. Thus, microcredit here may work, but through channels different from those often hypothesized by its proponents.

  16. Perturbation Theory for Scattering from Multilayers with Randomly Rough Fractal Interfaces: Remote Sensing Applications

    Directory of Open Access Journals (Sweden)

    Pasquale Imperatore

    2017-12-01

    Full Text Available A general, approximate perturbation method, able to provide closed-form expressions of scattering from a layered structure with an arbitrary number of rough interfaces, has been recently developed. Such a method provides a unique tool for the characterization of radar response patterns of natural rough multilayers. In order to show that, here, for the first time in a journal paper, we describe the application of the developed perturbation theory to fractal interfaces; we then employ the perturbative method solution to analyze the scattering from real-world layered structures of practical interest in remote sensing applications. We focus on the dependence of normalized radar cross section on geometrical and physical properties of the considered scenarios, and we choose two classes of natural stratifications: wet paleosoil covered by a low-loss dry sand layer and a sea-ice layer above water with dry snow cover. Results are in accordance with the experimental evidence available in the literature for the low-loss dry sand layer, and they may provide useful indications about the actual ability of remote sensing instruments to perform sub-surface sensing for different sensor and scene parameters.

  17. Perturbation Theory for Scattering from Multilayers with Randomly Rough Fractal Interfaces: Remote Sensing Applications.

    Science.gov (United States)

    Imperatore, Pasquale; Iodice, Antonio; Riccio, Daniele

    2017-12-27

    A general, approximate perturbation method, able to provide closed-form expressions of scattering from a layered structure with an arbitrary number of rough interfaces, has been recently developed. Such a method provides a unique tool for the characterization of radar response patterns of natural rough multilayers. In order to show that, here, for the first time in a journal paper, we describe the application of the developed perturbation theory to fractal interfaces; we then employ the perturbative method solution to analyze the scattering from real-world layered structures of practical interest in remote sensing applications. We focus on the dependence of normalized radar cross section on geometrical and physical properties of the considered scenarios, and we choose two classes of natural stratifications: wet paleosoil covered by a low-loss dry sand layer and a sea-ice layer above water with dry snow cover. Results are in accordance with the experimental evidence available in the literature for the low-loss dry sand layer, and they may provide useful indications about the actual ability of remote sensing instruments to perform sub-surface sensing for different sensor and scene parameters.

  18. Realism, instrumentalism, and scientific symbiosis: psychological theory as a search for truth and the discovery of solutions.

    Science.gov (United States)

    Cacioppo, John T; Semin, Gün R; Berntson, Gary G

    2004-01-01

    Scientific realism holds that scientific theories are approximations of universal truths about reality, whereas scientific instrumentalism posits that scientific theories are intellectual structures that provide adequate predictions of what is observed and useful frameworks for answering questions and solving problems in a given domain. These philosophical perspectives have different strengths and weaknesses and have been regarded as incommensurate: Scientific realism fosters theoretical rigor, verifiability, parsimony, and debate, whereas scientific instrumentalism fosters theoretical innovation, synthesis, generativeness, and scope. The authors review the evolution of scientific realism and instrumentalism in psychology and propose that the categorical distinction between the 2 is overstated as a prescription for scientific practice. The authors propose that the iterative deployment of these 2 perspectives, just as the iterative application of inductive and deductive reasoning in science, may promote more rigorous, integrative, cumulative, and useful scientific theories.

  19. Search for scalar-tensor gravity theories with a non-monotonic time evolution of the speed-up factor

    Energy Technology Data Exchange (ETDEWEB)

    Navarro, A [Dept Fisica, Universidad de Murcia, E30071-Murcia (Spain); Serna, A [Dept Fisica, Computacion y Comunicaciones, Universidad Miguel Hernandez, E03202-Elche (Spain); Alimi, J-M [Lab. de l' Univers et de ses Theories (LUTH, CNRS FRE2462), Observatoire de Paris-Meudon, F92195-Meudon (France)

    2002-08-21

    We present a method to detect, in the framework of scalar-tensor gravity theories, the existence of stationary points in the time evolution of the speed-up factor. An attractive aspect of this method is that, once the particular scalar-tensor theory has been specified, the stationary points are found through a simple algebraic equation which does not contain any integration. By applying this method to the three classes of scalar-tensor theories defined by Barrow and Parsons, we have found several new cosmological models with a non-monotonic evolution of the speed-up factor. The physical interest of these models is that, as previously shown by Serna and Alimi, they predict the observed primordial abundance of light elements for a very wide range of baryon density. These models are then consistent with recent CMB and Lyman-{alpha} estimates of the baryon content of the universe.

  20. Search for a Heavy Right-Handed W Boson and Heavy Right-Handed Neutrino of the Left-Right Symmetric Extension of the Standard Theory

    CERN Document Server

    AUTHOR|(INSPIRE)INSPIRE-00345539

    A search for a heavy right-handed $W_{R}$ boson, and heavy right-handed neutrinos $N_{\\ell}$ ($\\ell = e, \\mu$) performed by the CMS experiment is summarized here. Using the 2.6 fb$^{-1}$ of integrated luminosity recorded by the CMS experiment in 2015 at a center-of-mass energy of 13 TeV, this search seeks evidence of a $W_{R}$ boson and $N_{\\ell}$ neutrinos in events with two leptons and two jets. The data do not significantly exceed expected backgrounds, and are consistent with expected results of the Standard Theory given uncertainties. For Standard Theory extensions with strict left-right symmetry, and assuming only one $N_{\\ell}$ flavor contributes significantly to the $W_{R}$ decay width, mass limits are set in the two-dimensional $(M_{W_{R}}, M_{N_{\\ell}})$ plane at 95\\% confidence level. The limits extend to a $W_{R}$ mass of 3.3 TeV in the electron channel and 3.5 TeV in the muon channel, and span a wide range of $M_{N_{\\ell}}$ masses below $M_{W_{R}}$.

  1. Financial Strain and Regional Unemployment as Barriers to Job Search Self-Efficacy: A Test of Social Cognitive Career Theory

    Science.gov (United States)

    Dahling, Jason J.; Melloy, Robert; Thompson, Mindi N.

    2013-01-01

    Social cognitive career theory (SCCT) emphasizes the potential impact of contextual barriers on vocational self-efficacy, interests, and goals. However, most tests of SCCT to date have focused exclusively on person-level, perceptual barriers rather than objective, macroeconomic barriers that may influence large groups of people. In this study, we…

  2. Time-dependent observables in heavy ion collisions. Part II. In search of pressure isotropization in the φ 4 theory

    Science.gov (United States)

    Kovchegov, Yuri V.; Wu, Bin

    2018-03-01

    To understand the dynamics of thermalization in heavy ion collisions in the perturbative framework it is essential to first find corrections to the free-streaming classical gluon fields of the McLerran-Venugopalan model. The corrections that lead to deviations from free streaming (and that dominate at late proper time) would provide evidence for the onset of isotropization (and, possibly, thermalization) of the produced medium. To find such corrections we calculate the late-time two-point Green function and the energy-momentum tensor due to a single 2 → 2 scattering process involving two classical fields. To make the calculation tractable we employ the scalar φ 4 theory instead of QCD. We compare our exact diagrammatic results for these quantities to those in kinetic theory and find disagreement between the two. The disagreement is in the dependence on the proper time τ and, for the case of the two-point function, is also in the dependence on the space-time rapidity η: the exact diagrammatic calculation is, in fact, consistent with the free streaming scenario. Kinetic theory predicts a build-up of longitudinal pressure, which, however, is not observed in the exact calculation. We conclude that we find no evidence for the beginning of the transition from the free-streaming classical fields to the kinetic theory description of the produced matter after a single 2 → 2 rescattering.

  3. Correlations between Theories of Human Nature and Politics: A Search for a Relationship in the Work of Dewey and Rawls

    Science.gov (United States)

    1988-04-08

    to fathom assertion, but at lest two qualifications should be made. First, we must not confuse the idea with egoism . Even though the parties are...14Aristotle Nicomachean Ethics 5. 3. 1131a25. 15Rawls, Theory of Justice, p. 156. 16Actually, we might argue for a three part division in Rawls: noumenal...nature/nurture portion of the self. pij BIBLIOGRAPHY OF WORKS CITED Aristotle. Nicomachean Ethics . Dewey, John. Human Nature and Conduct: An

  4. Low Complexity Precoder and Receiver Design for Massive MIMO Systems: A Large System Analysis using Random Matrix Theory

    KAUST Repository

    Sifaou, Houssem

    2016-05-01

    Massive MIMO systems are shown to be a promising technology for next generations of wireless communication networks. The realization of the attractive merits promised by massive MIMO systems requires advanced linear precoding and receiving techniques in order to mitigate the interference in downlink and uplink transmissions. This work considers the precoder and receiver design in massive MIMO systems. We first consider the design of the linear precoder and receiver that maximize the minimum signal-to-interference-plus-noise ratio (SINR) subject to a given power constraint. The analysis is carried out under the asymptotic regime in which the number of the BS antennas and that of the users grow large with a bounded ratio. This allows us to leverage tools from random matrix theory in order to approximate the parameters of the optimal linear precoder and receiver by their deterministic approximations. Such a result is of valuable practical interest, as it provides a handier way to implement the optimal precoder and receiver. To reduce further the complexity, we propose to apply the truncated polynomial expansion (TPE) concept on a per-user basis to approximate the inverse of large matrices that appear on the expressions of the optimal linear transceivers. Using tools from random matrix theory, we determine deterministic approximations of the SINR and the transmit power in the asymptotic regime. Then, the optimal per-user weight coe cients that solve the max-min SINR problem are derived. The simulation results show that the proposed precoder and receiver provide very close to optimal performance while reducing signi cantly the computational complexity. As a second part of this work, the TPE technique in a per-user basis is applied to the optimal linear precoding that minimizes the transmit power while satisfying a set of target SINR constraints. Due to the emerging research eld of green cellular networks, such a problem is receiving increasing interest nowadays. Closed

  5. A mindful eating intervention: A theory-guided randomized anti-obesity feasibility study with adolescent Latino females.

    Science.gov (United States)

    Daly, Patricia; Pace, Thaddeus; Berg, Judith; Menon, Usha; Szalacha, Laura A

    2016-10-01

    While pediatric anti-obesity lifestyle interventions have received considerable attention, few show sustained impact on body mass index (BMI). Using the Information-Motivation-Behavioral Skills Theory as a framework, we examined the effects of a satiety-focused mindful eating intervention (MEI) on BMI, weight and mindful awareness. Utilizing a two-group, repeated measures design, 37 adolescent females with a BMI >90th percentile, recruited from a public high school in a Latino community in the Southwestern United States, were randomized 2:1, one third to the group receiving a 6-week MEI and two thirds to the comparison group (CG) receiving the usual care (nutrition and exercise information). During six weekly 90-min after school MEI group sessions, the behavioral skills of slow intentional eating were practiced with foci on satiety cues and triggers to overeat. Feasibility and acceptability were measured as participant retention (goal ≥55%) and evaluative comments from those in the MEI group, respectively. BMI and mindful awareness were measured on site at baseline, immediately post intervention, and at 4-week follow-up (week 10). Fifty-seven and 65% of those in the MEI and CG were retained throughout the study, respectively. MEI participants showed significantly lowered BMI compared with CG participants, whose weight increased (p90th percentile standard growth projections). Initial and sustained decline of BMI in the MEI group supports further study of this theory-guided approach, and the value of practicing satiety-focused mindful eating behavioral skills to facilitate health behavior change. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Moderating Effects of Parental Characteristics on the Effectiveness of a Theory of Mind Training for Children with Autism: A Randomized Controlled Trial

    Science.gov (United States)

    de Veld, Danielle M. J.; Howlin, Patricia; Hoddenbach, Elske; Mulder, Fleur; Wolf, Imke; Koot, Hans M.; Lindauer, Ramón; Begeer, Sander

    2017-01-01

    This RCT investigated whether the effect of a Theory of Mind (ToM) intervention for children with ASD was moderated by parental education level and employment, family structure, and parental ASD. Children with autism aged 8-13 years (n = 136) were randomized over a waitlist control or treatment condition. At posttest, children in the treatment…

  7. Moderating Effects of Parental Characteristics on the Effectiveness of a Theory of Mind Training for Children with Autism : A Randomized Controlled Trial

    NARCIS (Netherlands)

    de Veld, Danielle M J; Howlin, Patricia; Hoddenbach, Elske; Mulder, Fleur; Wolf, Imke; Koot, Hans M.; Lindauer, Ramón; Begeer, Sander

    2017-01-01

    This RCT investigated whether the effect of a Theory of Mind (ToM) intervention for children with ASD was moderated by parental education level and employment, family structure, and parental ASD. Children with autism aged 8–13 years (n = 136) were randomized over a waitlist control or treatment

  8. Moderating Effects of Parental Characteristics on the Effectiveness of a Theory of Mind Training for Children with Autism: A Randomized Controlled Trial

    NARCIS (Netherlands)

    de Veld, Danielle M. J.; Howlin, Patricia; Hoddenbach, Elske; Mulder, Fleur; Wolf, Imke; Koot, Hans M.; Lindauer, Ramón; Begeer, Sander

    2017-01-01

    This RCT investigated whether the effect of a Theory of Mind (ToM) intervention for children with ASD was moderated by parental education level and employment, family structure, and parental ASD. Children with autism aged 8-13 years (n = 136) were randomized over a waitlist control or treatment

  9. A randomized controlled trial of culturally adapted motivational interviewing for Hispanic heavy drinkers: Theory of Adaptation and Study Protocol

    Science.gov (United States)

    Lee, Christina S.; Colby, Suzanne M.; Magill, Molly; Almeida, Joanna; Tavares, Tonya; Rohsenow, Damaris J.

    2016-01-01

    Background The NIH Strategic Plan prioritizes health disparities research for socially disadvantaged Hispanics, to reduce the disproportionate burden of alcohol-related negative consequences compared to other racial/ethnic groups. Cultural adaptation of evidence-based treatments, such as motivational interviewing (MI), can improve access and response to alcohol treatment. However, the lack of rigorous clinical trials designed to test the efficacy and theoretical underpinnings of cultural adaptation has made proof of concept difficult. Objective The CAMI2 (Culturally Adapted Motivational Interviewing) study design and its theoretical model, is described to illustrate how MI adapted to social and cultural factors (CAMI) can be discriminated against non-adapted MI. Methods and Design CAMI2, a large, 12 month randomized prospective trial, examines the efficacy of CAMI and MI among heavy drinking Hispanics recruited from the community (n=257). Outcomes are reductions in heavy drinking days (Time Line Follow-Back) and negative consequences of drinking among Hispanics (Drinkers Inventory of Consequences). A second aim examines perceived acculturation stress as a moderator of treatment outcomes in the CAMI condition. Summary The CAMI2 study design protocol is presented and the theory of adaptation is presented. Findings from the trial described may yield important recommendations on the science of cultural adaptation and improve MI dissemination to Hispanics with alcohol risk. PMID:27565832

  10. Molecular Excitation Energies from Time-Dependent Density Functional Theory Employing Random-Phase Approximation Hessians with Exact Exchange.

    Science.gov (United States)

    Heßelmann, Andreas

    2015-04-14

    Molecular excitation energies have been calculated with time-dependent density-functional theory (TDDFT) using random-phase approximation Hessians augmented with exact exchange contributions in various orders. It has been observed that this approach yields fairly accurate local valence excitations if combined with accurate asymptotically corrected exchange-correlation potentials used in the ground-state Kohn-Sham calculations. The inclusion of long-range particle-particle with hole-hole interactions in the kernel leads to errors of 0.14 eV only for the lowest excitations of a selection of three alkene, three carbonyl, and five azabenzene molecules, thus surpassing the accuracy of a number of common TDDFT and even some wave function correlation methods. In the case of long-range charge-transfer excitations, the method typically underestimates accurate reference excitation energies by 8% on average, which is better than with standard hybrid-GGA functionals but worse compared to range-separated functional approximations.

  11. In search for the original image: Luciano Freire and the theory and practice of painting restoration in Portugal circa 1900

    Directory of Open Access Journals (Sweden)

    António João Cruz

    2007-01-01

    Full Text Available From the fragmentary statements found in several texts, especially from a report written in the 1930's that presents memoir notes, this paper intends to reconstitute, as much as possible, the restoration theory and practice of Luciano Freire (1864-1934. He treated many of the most important paintings belonging to Portuguese museums and, according to his words, those interventions were justified, above all, by the damages caused by past restorers, through repaints, which was frequent, or through cleaning, which originated the worst problems, and by the damages caused by the ambient conditions surrounding the paintings. In general, the interventions aimed at recovering the original image. Although Luciano Freire was, in theory, an adept of the complete cleaning of dirt and varnishes and complete removal of retouches and repaints, as it was done in National Gallery, London, in practice he admitted that when the retouches and repaints were well done and in good condition they were not to be removed. He considered that losses should be reintegrated and his thoughts were divided by the recovering the original image and the respect for the original work. He usually ended up considering that mimetic retouching could only be done when enough clues were present. Therefore, retouching had limits that, however, he recognizes, he crossed at times. Although did not use radiographs, he attributed great importance to treatment documentation through photography or other means.

  12. Applicability of special quasi-random structure models in thermodynamic calculations using semi-empirical Debye–Grüneisen theory

    International Nuclear Information System (INIS)

    Kim, Jiwoong

    2015-01-01

    In theoretical calculations, expressing the random distribution of atoms in a certain crystal structure is still challenging. The special quasi-random structure (SQS) model is effective for depicting such random distributions. The SQS model has not been applied to semi-empirical thermodynamic calculations; however, Debye–Grüneisen theory (DGT), a semi-empirical method, was used here for that purpose. The model reliability was obtained by comparing supercell models of various sizes. The results for chemical bonds, pair correlation, and elastic properties demonstrated the reliability of the SQS models. Thermodynamic calculations using density functional perturbation theory (DFPT) and DGT assessed the applicability of the SQS models. DGT and DFPT led to similar variations of the mixing and formation energies. This study provides guidelines for theoretical assessments to obtain the reliable SQS models and to calculate the thermodynamic properties of numerous materials with a random atomic distribution. - Highlights: • Various material properties are used to examine reliability of special quasi-random structures. • SQS models are applied to thermodynamic calculations by semi-empirical methods. • Basic calculation guidelines for materials with random atomic distribution are given.

  13. Motivation in pediatric motor rehabilitation: A systematic search of the literature using the self-determination theory as a conceptual framework.

    Science.gov (United States)

    Meyns, Pieter; Roman de Mettelinge, Tine; van der Spank, Judith; Coussens, Marieke; Van Waelvelde, Hilde

    2017-03-09

    Motivation is suggested as an important factor in pediatric motor rehabilitation. Therefore, we reviewed the existing evidence of (motivational) motor rehabilitation paradigms, and how motivation influences rehabilitation outcome using self-determination theory as conceptual framework. PubMed and Web-of-Science databases were systematically searched until June 2015. Data were independently extracted and critiqued for quality by three authors. Studies reporting motivational aspects were included. Most studies examined new technology (e.g., virtual reality [VR]). Out of 479 records, three RCT, six case-control, and six non-comparative studies were included with mixed quality. Motivation was rarely reported. Training individualization to the child's capabilities with more variety seemed promising to increase motivation. Motivation increased when the exercises seemed helpful for daily activities. Motivation in pediatric rehabilitation should be comprehensively assessed within a theoretical framework as there are indications that motivated children have better rehabilitation outcomes, depending on the aspect of motivation.

  14. Searching for Physics Beyond the Standard Model: Strongly-Coupled Field Theories at the Intensity and Energy Frontiers

    International Nuclear Information System (INIS)

    Brower, Richard C.

    2016-01-01

    This proposal is to develop the software and algorithmic infrastructure needed for the numerical study of quantum chromodynamics (QCD), and of theories that have been proposed to describe physics beyond the Standard Model (BSM) of high energy physics, on current and future computers. This infrastructure will enable users (1) to improve the accuracy of QCD calculations to the point where they no longer limit what can be learned from high-precision experiments that seek to test the Standard Model, and (2) to determine the predictions of BSM theories in order to understand which of them are consistent with the data that will soon be available from the LHC. Work will include the extension and optimizations of community codes for the next generation of leadership class computers, the IBM Blue Gene/Q and the Cray XE/XK, and for the dedicated hardware funded for our field by the Department of Energy. Members of our collaboration at Brookhaven National Laboratory and Columbia University worked on the design of the Blue Gene/Q, and have begun to develop software for it. Under this grant we will build upon their experience to produce high-efficiency production codes for this machine. Cray XE/XK computers with many thousands of GPU accelerators will soon be available, and the dedicated commodity clusters we obtain with DOE funding include growing numbers of GPUs. We will work with our partners in NVIDIA's Emerging Technology group to scale our existing software to thousands of GPUs, and to produce highly efficient production codes for these machines. Work under this grant will also include the development of new algorithms for the effective use of heterogeneous computers, and their integration into our codes. It will include improvements of Krylov solvers and the development of new multigrid methods in collaboration with members of the FASTMath SciDAC Institute, using their HYPRE framework, as well as work on improved symplectic integrators.

  15. Searching for Physics Beyond the Standard Model: Strongly-Coupled Field Theories at the Intensity and Energy Frontiers

    Energy Technology Data Exchange (ETDEWEB)

    Brower, Richard C. [Boston Univ., MA (United States). Physics and ECE Depts.

    2016-11-08

    This proposal is to develop the software and algorithmic infrastructure needed for the numerical study of quantum chromodynamics (QCD), and of theories that have been proposed to describe physics beyond the Standard Model (BSM) of high energy physics, on current and future computers. This infrastructure will enable users (1) to improve the accuracy of QCD calculations to the point where they no longer limit what can be learned from high-precision experiments that seek to test the Standard Model, and (2) to determine the predictions of BSM theories in order to understand which of them are consistent with the data that will soon be available from the LHC. Work will include the extension and optimizations of community codes for the next generation of leadership class computers, the IBM Blue Gene/Q and the Cray XE/XK, and for the dedicated hardware funded for our field by the Department of Energy. Members of our collaboration at Brookhaven National Laboratory and Columbia University worked on the design of the Blue Gene/Q, and have begun to develop software for it. Under this grant we will build upon their experience to produce high-efficiency production codes for this machine. Cray XE/XK computers with many thousands of GPU accelerators will soon be available, and the dedicated commodity clusters we obtain with DOE funding include growing numbers of GPUs. We will work with our partners in NVIDIA's Emerging Technology group to scale our existing software to thousands of GPUs, and to produce highly efficient production codes for these machines. Work under this grant will also include the development of new algorithms for the effective use of heterogeneous computers, and their integration into our codes. It will include improvements of Krylov solvers and the development of new multigrid methods in collaboration with members of the FASTMath SciDAC Institute, using their HYPRE framework, as well as work on improved symplectic integrators.

  16. Search for intermediate vector bosons

    International Nuclear Information System (INIS)

    Klajn, D.B.; Rubbia, K.; Meer, S.

    1983-01-01

    Problem of registration and search for intermediate vector bosons is discussed. According to weak-current theory there are three intermediate vector bosons with +1(W + )-1(W - ) and zero (Z 0 ) electric charges. It was suggested to conduct the investigation into particles in 1976 by cline, Rubbia and Makintair using proton-antiproton beams. Major difficulties of the experiment are related to the necessity of formation of sufficient amount of antiparticles and the method of antiproton beam ''cooling'' for the purpose of reduction of its random movements. The stochastic method was suggested by van der Meer in 1968 as one of possible cooling methods. Several large detectors were designed for searching intermediate vector bosons

  17. Effects and Moderators of a Short Theory of Mind Intervention for Children with Autism Spectrum Disorder: A Randomized Controlled Trial.

    Science.gov (United States)

    Begeer, Sander; Howlin, Patricia; Hoddenbach, Elske; Clauser, Cassandra; Lindauer, Ramon; Clifford, Pamela; Gevers, Carolien; Boer, Frits; Koot, Hans M

    2015-12-01

    Limited perspective taking or "Theory of Mind" (ToM) abilities are a core deficit of autism, and many interventions are aimed to improve ToM abilities. In this study, we investigated the effectiveness of a ToM treatment for children with autism spectrum disorders (ASD) and, for the first time, the moderating roles of social interaction style (SIS) and disruptive behavior (DB), to determine which children are most likely to respond to this intervention. The trial protocol is registered at www.trialregister.nl, trial number 2327 and published before the data collection was finished (www.trialsjournal.com). Children with autism aged 7-12 years (n = 97) were randomized over a waitlist control or a treatment condition. Outcome measures included ToM and emotion understanding, parent and teacher questionnaires on children's social skills, ToM-related social behavior, and autistic traits. Six-month follow-up parent reported data were collected for the treatment group. The treatment had a positive effect on ToM understanding, parent-reported ToM behavior, and autistic traits, but not on parent or teacher-reported social behavior. Passive SIS was associated with diminished treatment effects on autistic traits, but DB was unrelated to outcomes. The ToM intervention improved conceptual social understanding and ToM-related behavior of children with ASD. However, broader application of learned skills to other domains of functioning was limited. Individual differences with regard to treatment response are discussed. © 2015 International Society for Autism Research, Wiley Periodicals, Inc.

  18. Operator product expansion in Liouville field theory and Seiberg-type transitions in log-correlated random energy models

    Science.gov (United States)

    Cao, Xiangyu; Le Doussal, Pierre; Rosso, Alberto; Santachiara, Raoul

    2018-04-01

    We study transitions in log-correlated random energy models (logREMs) that are related to the violation of a Seiberg bound in Liouville field theory (LFT): the binding transition and the termination point transition (a.k.a., pre-freezing). By means of LFT-logREM mapping, replica symmetry breaking and traveling-wave equation techniques, we unify both transitions in a two-parameter diagram, which describes the free-energy large deviations of logREMs with a deterministic background log potential, or equivalently, the joint moments of the free energy and Gibbs measure in logREMs without background potential. Under the LFT-logREM mapping, the transitions correspond to the competition of discrete and continuous terms in a four-point correlation function. Our results provide a statistical interpretation of a peculiar nonlocality of the operator product expansion in LFT. The results are rederived by a traveling-wave equation calculation, which shows that the features of LFT responsible for the transitions are reproduced in a simple model of diffusion with absorption. We examine also the problem by a replica symmetry breaking analysis. It complements the previous methods and reveals a rich large deviation structure of the free energy of logREMs with a deterministic background log potential. Many results are verified in the integrable circular logREM, by a replica-Coulomb gas integral approach. The related problem of common length (overlap) distribution is also considered. We provide a traveling-wave equation derivation of the LFT predictions announced in a precedent work.

  19. Individual differences in the efficacy of a short theory of mind intervention for children with autism spectrum disorder: a randomized controlled trial.

    Science.gov (United States)

    Hoddenbach, Elske; Koot, Hans M; Clifford, Pamela; Gevers, Carolien; Clauser, Cassandra; Boer, Frits; Begeer, Sander

    2012-11-09

    Having a 'theory of mind', or having the ability to attribute mental states to oneself or others, is considered one of the most central domains of impairment among children with an autism spectrum disorder (ASD). Many interventions focus on improving theory of mind skills in children with ASD. Nonetheless, the empirical evidence for the effect of these interventions is limited. The main goal of this study is to examine the effectiveness of a short theory of mind intervention for children with ASD. A second objective is to determine which subgroups within the autism spectrum profit most from the intervention. This study is a randomized controlled trial. One hundred children with ASD, aged 7 to 12 years will be randomly assigned to an intervention or a waiting list control group. Outcome measures include the completion of theory of mind and emotion understanding tasks, and parent and teacher questionnaires on children's social skills. Follow-up data for the intervention group will be collected 6 months after the interventions. This study evaluates the efficacy of a theory of mind intervention for children with ASD. Hypotheses, strengths, and limitations of the study are discussed. Netherlands Trial Register NTR2327.

  20. Individual differences in the efficacy of a short theory of mind intervention for children with autism spectrum disorder: a randomized controlled trial

    Directory of Open Access Journals (Sweden)

    Hoddenbach Elske

    2012-11-01

    Full Text Available Abstract Background Having a ‘theory of mind’, or having the ability to attribute mental states to oneself or others, is considered one of the most central domains of impairment among children with an autism spectrum disorder (ASD. Many interventions focus on improving theory of mind skills in children with ASD. Nonetheless, the empirical evidence for the effect of these interventions is limited. The main goal of this study is to examine the effectiveness of a short theory of mind intervention for children with ASD. A second objective is to determine which subgroups within the autism spectrum profit most from the intervention. Methods This study is a randomized controlled trial. One hundred children with ASD, aged 7 to 12 years will be randomly assigned to an intervention or a waiting list control group. Outcome measures include the completion of theory of mind and emotion understanding tasks, and parent and teacher questionnaires on children’s social skills. Follow-up data for the intervention group will be collected 6 months after the interventions. Discussion This study evaluates the efficacy of a theory of mind intervention for children with ASD. Hypotheses, strengths, and limitations of the study are discussed. Trial registration Netherlands Trial Register NTR2327

  1. Lagrangian theory with zero component. Application to the study of the polymers in solution (chains with exclued volume) and of the properties of electrons in a random potential

    International Nuclear Information System (INIS)

    Des Cloizeaux, J.

    1976-01-01

    The Lagrangian theory of a field with n components can be generalized for values of n which are not integers and in particular for n=0. This extension is made by introducing ordered Green's functions. It is shown how the zero components Lagrangian theory can be used to describe the behaviour of an isolated polymer or of a solution of polymers with large molecular masses. It is remarked that by analytic continuation with respect to the coupling constant, it should be possible to study the properties of electrons in a random potential and perhaps the nature of the mobility edges [fr

  2. Bayesian analysis of systems with random chemical composition: renormalization-group approach to Dirichlet distributions and the statistical theory of dilution.

    Science.gov (United States)

    Vlad, Marcel Ovidiu; Tsuchiya, Masa; Oefner, Peter; Ross, John

    2002-01-01

    We investigate the statistical properties of systems with random chemical composition and try to obtain a theoretical derivation of the self-similar Dirichlet distribution, which is used empirically in molecular biology, environmental chemistry, and geochemistry. We consider a system made up of many chemical species and assume that the statistical distribution of the abundance of each chemical species in the system is the result of a succession of a variable number of random dilution events, which can be described by using the renormalization-group theory. A Bayesian approach is used for evaluating the probability density of the chemical composition of the system in terms of the probability densities of the abundances of the different chemical species. We show that for large cascades of dilution events, the probability density of the composition vector of the system is given by a self-similar probability density of the Dirichlet type. We also give an alternative formal derivation for the Dirichlet law based on the maximum entropy approach, by assuming that the average values of the chemical potentials of different species, expressed in terms of molar fractions, are constant. Although the maximum entropy approach leads formally to the Dirichlet distribution, it does not clarify the physical origin of the Dirichlet statistics and has serious limitations. The random theory of dilution provides a physical picture for the emergence of Dirichlet statistics and makes it possible to investigate its validity range. We discuss the implications of our theory in molecular biology, geochemistry, and environmental science.

  3. The effect of implementing cognitive load theory-based design principles in virtual reality simulation training of surgical skills: a randomized controlled trial

    DEFF Research Database (Denmark)

    Andersen, Steven Arild Wuyts; Mikkelsen, Peter Trier; Konge, Lars

    2016-01-01

    training of mastoidectomy. Methods Eighteen novice medical students received 1 h of self-directed virtual reality simulation training of the mastoidectomy procedure randomized for standard instructions (control) or cognitive load theory-based instructions with a worked example followed by a problem......Background Cognitive overload can inhibit learning, and cognitive load theory-based instructional design principles can be used to optimize learning situations. This study aims to investigate the effect of implementing cognitive load theory-based design principles in virtual reality simulation....... Increased cognitive load when part tasks needed to be integrated in the post-training procedures could be a possible explanation for this. Other instructional designs and methods are needed to lower the cognitive load and improve the performance in virtual reality surgical simulation training of novices....

  4. Coherent light scattering of heterogeneous randomly rough films and effective medium in the theory of electromagnetic wave multiple scattering

    Energy Technology Data Exchange (ETDEWEB)

    Berginc, G [THALES, 2 avenue Gay-Lussac 78995 ELANCOURT (France)

    2013-11-30

    We have developed a general formalism based on Green's functions to calculate the coherent electromagnetic field scattered by a random medium with rough boundaries. The approximate expression derived makes it possible to determine the effective permittivity, which is generalised for a layer of an inhomogeneous random medium with different types of particles and bounded with randomly rough interfaces. This effective permittivity describes the coherent propagation of an electromagnetic wave in a random medium with randomly rough boundaries. We have obtained an expression, which contains the Maxwell – Garnett formula at the low-frequency limit, and the Keller formula; the latter has been proved to be in good agreement with experiments for particles whose dimensions are larger than a wavelength. (coherent light scattering)

  5. Search Help

    Science.gov (United States)

    Guidance and search help resource listing examples of common queries that can be used in the Google Search Appliance search request, including examples of special characters, or query term seperators that Google Search Appliance recognizes.

  6. Individual differences in the efficacy of a short Theory of Mind intervention for children with autism: A randomized controlled trial

    NARCIS (Netherlands)

    Hoddenbach, E.; Clifford, P.; Gevers, C.; Clauser, C.; Boer, F.; Koot, H.M.; Begeer, S.M.

    2012-01-01

    Background: Having a 'theory of mind', or having the ability to attribute mental states to oneself or others, is considered one of the most central domains of impairment among children with an autism spectrum disorder (ASD). Many interventions focus on improving theory of mind skills in children

  7. Random surfaces and strings

    International Nuclear Information System (INIS)

    Ambjoern, J.

    1987-08-01

    The theory of strings is the theory of random surfaces. I review the present attempts to regularize the world sheet of the string by triangulation. The corresponding statistical theory of triangulated random surfaces has a surprising rich structure, but the connection to conventional string theory seems non-trivial. (orig.)

  8. Search predicts and changes patience in intertemporal choice

    Science.gov (United States)

    Johnson, Eric J.

    2017-01-01

    Intertemporal choice impacts many important outcomes, such as decisions about health, education, wealth, and the environment. However, the psychological processes underlying decisions involving outcomes at different points in time remain unclear, limiting opportunities to intervene and improve people’s patience. This research examines information-search strategies used during intertemporal choice and their impact on decisions. In experiment 1, we demonstrate that search strategies vary substantially across individuals. We subsequently identify two distinct search strategies across individuals. Comparative searchers, who compare features across options, discount future options less and are more susceptible to acceleration versus delay framing than integrative searchers, who integrate the features of an option. Experiment 2 manipulates search using an unobtrusive method to establish a causal relationship between strategy and choice, randomly assigning participants to conditions promoting either comparative or integrative search. Again, comparative search promotes greater patience than integrative search. Additionally, when participants adopt a comparative search strategy, they also exhibit greater effects of acceleration versus delay framing. Although most participants reported that the manipulation did not change their behavior, promoting comparative search decreased discounting of future rewards substantially and speeded patient choices. These findings highlight the central role that heterogeneity in psychological processes plays in shaping intertemporal choice. Importantly, these results indicate that theories that ignore variability in search strategies may be inadvertently aggregating over different subpopulations that use very different processes. The findings also inform interventions in choice architecture to increase patience and improve consumer welfare. PMID:29078303

  9. Search predicts and changes patience in intertemporal choice.

    Science.gov (United States)

    Reeck, Crystal; Wall, Daniel; Johnson, Eric J

    2017-11-07

    Intertemporal choice impacts many important outcomes, such as decisions about health, education, wealth, and the environment. However, the psychological processes underlying decisions involving outcomes at different points in time remain unclear, limiting opportunities to intervene and improve people's patience. This research examines information-search strategies used during intertemporal choice and their impact on decisions. In experiment 1, we demonstrate that search strategies vary substantially across individuals. We subsequently identify two distinct search strategies across individuals. Comparative searchers, who compare features across options, discount future options less and are more susceptible to acceleration versus delay framing than integrative searchers, who integrate the features of an option. Experiment 2 manipulates search using an unobtrusive method to establish a causal relationship between strategy and choice, randomly assigning participants to conditions promoting either comparative or integrative search. Again, comparative search promotes greater patience than integrative search. Additionally, when participants adopt a comparative search strategy, they also exhibit greater effects of acceleration versus delay framing. Although most participants reported that the manipulation did not change their behavior, promoting comparative search decreased discounting of future rewards substantially and speeded patient choices. These findings highlight the central role that heterogeneity in psychological processes plays in shaping intertemporal choice. Importantly, these results indicate that theories that ignore variability in search strategies may be inadvertently aggregating over different subpopulations that use very different processes. The findings also inform interventions in choice architecture to increase patience and improve consumer welfare. Copyright © 2017 the Author(s). Published by PNAS.

  10. Decision-Making Theories and Models: A Discussion of Rational and Psychological Decision-Making Theories and Models: The Search for a Cultural-Ethical Decision-Making Model

    OpenAIRE

    Oliveira, Arnaldo

    2007-01-01

    This paper examines rational and psychological decision-making models. Descriptive and normative methodologies such as attribution theory, schema theory, prospect theory, ambiguity model, game theory, and expected utility theory are discussed. The definition of culture is reviewed, and the relationship between culture and decision making is also highlighted as many organizations use a cultural-ethical decision-making model.

  11. Use of Theory in Behavior Change Interventions.

    Science.gov (United States)

    Bluethmann, Shirley M; Bartholomew, L Kay; Murphy, Caitlin C; Vernon, Sally W

    2017-04-01

    Theory use may enhance effectiveness of behavioral interventions, yet critics question whether theory-based interventions have been sufficiently scrutinized. This study applied a framework to evaluate theory use in physical activity interventions for breast cancer survivors. The aims were to (1) evaluate theory application intensity and (2) assess the association between extensiveness of theory use and intervention effectiveness. Studies were previously identified through a systematic search, including only randomized controlled trials published from 2005 to 2013, that addressed physical activity behavior change and studied survivors who were theory items from Michie and Prestwich's coding framework were selected to calculate theory intensity scores. Studies were classified into three subgroups based on extensiveness of theory use (Level 1 = sparse; Level 2 = moderate; and Level 3 = extensive). Fourteen randomized controlled trials met search criteria. Most trials used the transtheoretical model ( n = 5) or social cognitive theory ( n = 3). For extensiveness of theory use, 5 studies were classified as Level 1, 4 as Level 2, and 5 as Level 3. Studies in the extensive group (Level 3) had the largest overall effect size ( g = 0.76). Effects were more modest in Level 1 and 2 groups with overall effect sizes of g = 0.28 and g = 0.36, respectively. Theory use is often viewed as essential to behavior change, but theory application varies widely. In this study, there was some evidence to suggest that extensiveness of theory use enhanced intervention effectiveness. However, there is more to learn about how theory can improve interventions for breast cancer survivors.

  12. Application of unfolding transformation in the random matrix theory to analyze in vivo neuronal spike firing during awake and anesthetized conditions

    Directory of Open Access Journals (Sweden)

    Risako Kato

    2018-03-01

    Full Text Available General anesthetics decrease the frequency and density of spike firing. This effect makes it difficult to detect spike regularity. To overcome this problem, we developed a method utilizing the unfolding transformation which analyzes the energy level statistics in the random matrix theory. We regarded the energy axis as time axis of neuron spike and analyzed the time series of cortical neural firing in vivo. Unfolding transformation detected regularities of neural firing while changes in firing densities were associated with pentobarbital. We found that unfolding transformation enables us to compare firing regularity between awake and anesthetic conditions on a universal scale. Keywords: Unfolding transformation, Spike-timing, Regularity

  13. Mixing a Grounded Theory Approach with a Randomized Controlled Trial Related to Intimate Partner Violence: What Challenges Arise for Mixed Methods Research?

    Science.gov (United States)

    Catallo, Cristina; Jack, Susan M.; Ciliska, Donna; MacMillan, Harriet L.

    2013-01-01

    Little is known about how to systematically integrate complex qualitative studies within the context of randomized controlled trials. A two-phase sequential explanatory mixed methods study was conducted in Canada to understand how women decide to disclose intimate partner violence in emergency department settings. Mixing a RCT (with a subanalysis of data) with a grounded theory approach required methodological modifications to maintain the overall rigour of this mixed methods study. Modifications were made to the following areas of the grounded theory approach to support the overall integrity of the mixed methods study design: recruitment of participants, maximum variation and negative case sampling, data collection, and analysis methods. Recommendations for future studies include: (1) planning at the outset to incorporate a qualitative approach with a RCT and to determine logical points during the RCT to integrate the qualitative component and (2) consideration for the time needed to carry out a RCT and a grounded theory approach, especially to support recruitment, data collection, and analysis. Data mixing strategies should be considered during early stages of the study, so that appropriate measures can be developed and used in the RCT to support initial coding structures and data analysis needs of the grounded theory phase. PMID:23577245

  14. Searching for What I Want

    DEFF Research Database (Denmark)

    Liu, Fei; Xiao, Bo Sophia; Lim, Eric

    2016-01-01

    Inefficiencies associated with online information search are amplifying in the current era of big data. Despite growing scholarly interest in studying Internet users’ information search behaviour, there is a paucity of theory-guided investigation in this regard. In this paper, we draw on the theory...

  15. Searching Algorithm Using Bayesian Updates

    Science.gov (United States)

    Caudle, Kyle

    2010-01-01

    In late October 1967, the USS Scorpion was lost at sea, somewhere between the Azores and Norfolk Virginia. Dr. Craven of the U.S. Navy's Special Projects Division is credited with using Bayesian Search Theory to locate the submarine. Bayesian Search Theory is a straightforward and interesting application of Bayes' theorem which involves searching…

  16. A Fast Reactive Power Optimization in Distribution Network Based on Large Random Matrix Theory and Data Analysis

    Directory of Open Access Journals (Sweden)

    Wanxing Sheng

    2016-05-01

    Full Text Available In this paper, a reactive power optimization method based on historical data is investigated to solve the dynamic reactive power optimization problem in distribution network. In order to reflect the variation of loads, network loads are represented in a form of random matrix. Load similarity (LS is defined to measure the degree of similarity between the loads in different days and the calculation method of the load similarity of load random matrix (LRM is presented. By calculating the load similarity between the forecasting random matrix and the random matrix of historical load, the historical reactive power optimization dispatching scheme that most matches the forecasting load can be found for reactive power control usage. The differences of daily load curves between working days and weekends in different seasons are considered in the proposed method. The proposed method is tested on a standard 14 nodes distribution network with three different types of load. The computational result demonstrates that the proposed method for reactive power optimization is fast, feasible and effective in distribution network.

  17. On Random Numbers and Design

    Science.gov (United States)

    Ben-Ari, Morechai

    2004-01-01

    The term "random" is frequently used in discussion of the theory of evolution, even though the mathematical concept of randomness is problematic and of little relevance in the theory. Therefore, since the core concept of the theory of evolution is the non-random process of natural selection, the term random should not be used in teaching the…

  18. Effects and Moderators of a Short Theory of Mind Intervention for Children with Autism Spectrum Disorder: A Randomized Controlled Trial

    NARCIS (Netherlands)

    Begeer, Sander; Howlin, Patricia; Hoddenbach, Elske; Clauser, Cassandra; Lindauer, Ramon; Clifford, Pamela; Gevers, Carolien; Boer, Frits; Koot, Hans M.

    2015-01-01

    Limited perspective taking or "Theory of Mind" (ToM) abilities are a core deficit of autism, and many interventions are aimed to improve ToM abilities. In this study, we investigated the effectiveness of a ToM treatment for children with autism spectrum disorders (ASD) and, for the first time, the

  19. Guided Search for Triple Conjunctions

    OpenAIRE

    Nordfang, Maria; Wolfe, Jeremy M

    2014-01-01

    A key tenet of Feature Integration Theory and related theories such as Guided Search (GS) is that the binding of basic features requires attention. This would seem to predict that conjunctions of features of objects that have not been attended should not influence search. However, Found (1998) reported that an irrelevant feature (size) improved the efficiency of search for a color × orientation conjunction if it was correlated with the other two features across the display compared to the cas...

  20. A theory for the origin of a self-replicating chemical system. I - Natural selection of the autogen from short, random oligomers

    Science.gov (United States)

    White, D. H.

    1980-01-01

    A general theory is presented for the origin of a self-replicating chemical system, termed an autogen, which is capable of both crude replication and translation (protein synthesis). The theory requires the availability of free energy and monomers to the system, a significant background low-yield synthesis of kinetically stable oligopeptides and oligonucleotides, the localization of the oligomers, crude oligonucleotide selectivity of amino acids during oligopeptide synthesis, crude oligonucleotide replication, and two short peptide families which catalyze replication and translation, to produce a localized group of at least one copy each of two protogenes and two protoenzymes. The model posits a process of random oligomerization, followed by the random nucleation of functional components and the rapid autocatalytic growth of the functioning autogen to macroscopic amounts, to account for the origin of the first self-replicating system. Such a process contains steps of such high probability and short time periods that it is suggested that the emergence of an autogen in a laboratory experiment of reasonable time scale may be possible.

  1. Contribution to the neutronic theory of random stacks (diffusion coefficient and first-flight collision probabilities) with a general theorem on collision probabilities

    International Nuclear Information System (INIS)

    Dixmier, Marc.

    1980-10-01

    A general expression of the diffusion coefficient (d.c.) of neutrons was given, with stress being put on symmetries. A system of first-flight collision probabilities for the case of a random stack of any number of types of one- and two-zoned spherical pebbles, with an albedo at the frontiers of the elements or (either) consideration of the interstital medium, was built; to that end, the bases of collision probability theory were reviewed, and a wide generalisation of the reciprocity theorem for those probabilities was demonstrated. The migration area of neutrons was expressed for any random stack of convex, 'simple' and 'regular-contact' elements, taking into account the correlations between free-paths; the average cosinus of re-emission of neutrons by an element, in the case of a homogeneous spherical pebble and the transport approximation, was expressed; the superiority of the so-found result over Behrens' theory, for the type of media under consideration, was established. The 'fine structure current term' of the d.c. was also expressed, and it was shown that its 'polarisation term' is negligible. Numerical applications showed that the global heterogeneity effect on the d.c. of pebble-bed reactors is comparable with that for Graphite-moderated, Carbon gas-cooled, natural Uranium reactors. The code CARACOLE, which integrates all the results here obtained, was introduced [fr

  2. Theory and implementation of a very high throughput true random number generator in field programmable gate array

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yonggang, E-mail: wangyg@ustc.edu.cn; Hui, Cong; Liu, Chong; Xu, Chao [Department of Modern Physics, University of Science and Technology of China, Hefei 230026 (China)

    2016-04-15

    The contribution of this paper is proposing a new entropy extraction mechanism based on sampling phase jitter in ring oscillators to make a high throughput true random number generator in a field programmable gate array (FPGA) practical. Starting from experimental observation and analysis of the entropy source in FPGA, a multi-phase sampling method is exploited to harvest the clock jitter with a maximum entropy and fast sampling speed. This parametrized design is implemented in a Xilinx Artix-7 FPGA, where the carry chains in the FPGA are explored to realize the precise phase shifting. The generator circuit is simple and resource-saving, so that multiple generation channels can run in parallel to scale the output throughput for specific applications. The prototype integrates 64 circuit units in the FPGA to provide a total output throughput of 7.68 Gbps, which meets the requirement of current high-speed quantum key distribution systems. The randomness evaluation, as well as its robustness to ambient temperature, confirms that the new method in a purely digital fashion can provide high-speed high-quality random bit sequences for a variety of embedded applications.

  3. Random tensors

    CERN Document Server

    Gurau, Razvan

    2017-01-01

    Written by the creator of the modern theory of random tensors, this book is the first self-contained introductory text to this rapidly developing theory. Starting from notions familiar to the average researcher or PhD student in mathematical or theoretical physics, the book presents in detail the theory and its applications to physics. The recent detections of the Higgs boson at the LHC and gravitational waves at LIGO mark new milestones in Physics confirming long standing predictions of Quantum Field Theory and General Relativity. These two experimental results only reinforce today the need to find an underlying common framework of the two: the elusive theory of Quantum Gravity. Over the past thirty years, several alternatives have been proposed as theories of Quantum Gravity, chief among them String Theory. While these theories are yet to be tested experimentally, key lessons have already been learned. Whatever the theory of Quantum Gravity may be, it must incorporate random geometry in one form or another....

  4. The effect of implementing cognitive load theory-based design principles in virtual reality simulation training of surgical skills: a randomized controlled trial.

    Science.gov (United States)

    Andersen, Steven Arild Wuyts; Mikkelsen, Peter Trier; Konge, Lars; Cayé-Thomasen, Per; Sørensen, Mads Sølvsten

    2016-01-01

    Cognitive overload can inhibit learning, and cognitive load theory-based instructional design principles can be used to optimize learning situations. This study aims to investigate the effect of implementing cognitive load theory-based design principles in virtual reality simulation training of mastoidectomy. Eighteen novice medical students received 1 h of self-directed virtual reality simulation training of the mastoidectomy procedure randomized for standard instructions (control) or cognitive load theory-based instructions with a worked example followed by a problem completion exercise (intervention). Participants then completed two post-training virtual procedures for assessment and comparison. Cognitive load during the post-training procedures was estimated by reaction time testing on an integrated secondary task. Final-product analysis by two blinded expert raters was used to assess the virtual mastoidectomy performances. Participants in the intervention group had a significantly increased cognitive load during the post-training procedures compared with the control group (52 vs. 41 %, p  = 0.02). This was also reflected in the final-product performance: the intervention group had a significantly lower final-product score than the control group (13.0 vs. 15.4, p  virtual reality surgical simulation training of novices.

  5. Local beam angle optimization with linear programming and gradient search

    International Nuclear Information System (INIS)

    Craft, David

    2007-01-01

    The optimization of beam angles in IMRT planning is still an open problem, with literature focusing on heuristic strategies and exhaustive searches on discrete angle grids. We show how a beam angle set can be locally refined in a continuous manner using gradient-based optimization in the beam angle space. The gradient is derived using linear programming duality theory. Applying this local search to 100 random initial angle sets of a phantom pancreatic case demonstrates the method, and highlights the many-local-minima aspect of the BAO problem. Due to this function structure, we recommend a search strategy of a thorough global search followed by local refinement at promising beam angle sets. Extensions to nonlinear IMRT formulations are discussed. (note)

  6. Search Patterns

    CERN Document Server

    Morville, Peter

    2010-01-01

    What people are saying about Search Patterns "Search Patterns is a delight to read -- very thoughtful and thought provoking. It's the most comprehensive survey of designing effective search experiences I've seen." --Irene Au, Director of User Experience, Google "I love this book! Thanks to Peter and Jeffery, I now know that search (yes, boring old yucky who cares search) is one of the coolest ways around of looking at the world." --Dan Roam, author, The Back of the Napkin (Portfolio Hardcover) "Search Patterns is a playful guide to the practical concerns of search interface design. It cont

  7. Random Fields

    Science.gov (United States)

    Vanmarcke, Erik

    1983-03-01

    Random variation over space and time is one of the few attributes that might safely be predicted as characterizing almost any given complex system. Random fields or "distributed disorder systems" confront astronomers, physicists, geologists, meteorologists, biologists, and other natural scientists. They appear in the artifacts developed by electrical, mechanical, civil, and other engineers. They even underlie the processes of social and economic change. The purpose of this book is to bring together existing and new methodologies of random field theory and indicate how they can be applied to these diverse areas where a "deterministic treatment is inefficient and conventional statistics insufficient." Many new results and methods are included. After outlining the extent and characteristics of the random field approach, the book reviews the classical theory of multidimensional random processes and introduces basic probability concepts and methods in the random field context. It next gives a concise amount of the second-order analysis of homogeneous random fields, in both the space-time domain and the wave number-frequency domain. This is followed by a chapter on spectral moments and related measures of disorder and on level excursions and extremes of Gaussian and related random fields. After developing a new framework of analysis based on local averages of one-, two-, and n-dimensional processes, the book concludes with a chapter discussing ramifications in the important areas of estimation, prediction, and control. The mathematical prerequisite has been held to basic college-level calculus.

  8. Beyond the search surface: visual search and attentional engagement.

    Science.gov (United States)

    Duncan, J; Humphreys, G

    1992-05-01

    Treisman (1991) described a series of visual search studies testing feature integration theory against an alternative (Duncan & Humphreys, 1989) in which feature and conjunction search are basically similar. Here the latter account is noted to have 2 distinct levels: (a) a summary of search findings in terms of stimulus similarities, and (b) a theory of how visual attention is brought to bear on relevant objects. Working at the 1st level, Treisman found that even when similarities were calibrated and controlled, conjunction search was much harder than feature search. The theory, however, can only really be tested at the 2nd level, because the 1st is an approximation. An account of the findings is developed at the 2nd level, based on the 2 processes of input-template matching and spreading suppression. New data show that, when both of these factors are controlled, feature and conjunction search are equally difficult. Possibilities for unification of the alternative views are considered.

  9. Random magnetism

    International Nuclear Information System (INIS)

    Tsallis, C.

    1980-03-01

    The 'ingredients' which control a phase transition in well defined system as well as in random ones (e.g. random magnetic systems) are listed and discussed within a somehow unifying perspective. Among these 'ingredients' we find the couplings and elements responsible for the cooperative phenomenon, the topological connectivity as well as possible topological incompatibilities, the influence of new degrees of freedom, the order parameter dimensionality, the ground state degeneracy and finally the 'quanticity' of the system. The general trends, though illustrated in magnetic systems, essentially hold for all phase transitions, and give a basis for connection of this area with Field theory, Theory of dynamical systems, etc. (Author) [pt

  10. Random magnetism

    International Nuclear Information System (INIS)

    Tsallis, C.

    1981-01-01

    The 'ingredients' which control a phase transition in well defined systems as well as in random ones (e.q. random magnetic systems) are listed and discussed within a somehow unifying perspective. Among these 'ingredients' the couplings and elements responsible for the cooperative phenomenon, the topological connectivity as well as possible topological incompatibilities, the influence of new degrees of freedom, the order parameter dimensionality, the ground state degeneracy and finally the 'quanticity' of the system are found. The general trends, though illustrated in magnetic systems, essentially hold for all phase transitions, and give a basis for connection of this area with Field theory, Theory of dynamical systems, etc. (Author) [pt

  11. The special theory of Brownian relativity: equivalence principle for dynamic and static random paths and uncertainty relation for diffusion.

    Science.gov (United States)

    Mezzasalma, Stefano A

    2007-03-15

    The theoretical basis of a recent theory of Brownian relativity for polymer solutions is deepened and reexamined. After the problem of relative diffusion in polymer solutions is addressed, its two postulates are formulated in all generality. The former builds a statistical equivalence between (uncorrelated) timelike and shapelike reference frames, that is, among dynamical trajectories of liquid molecules and static configurations of polymer chains. The latter defines the "diffusive horizon" as the invariant quantity to work with in the special version of the theory. Particularly, the concept of universality in polymer physics corresponds in Brownian relativity to that of covariance in the Einstein formulation. Here, a "universal" law consists of a privileged observation, performed from the laboratory rest frame and agreeing with any diffusive reference system. From the joint lack of covariance and simultaneity implied by the Brownian Lorentz-Poincaré transforms, a relative uncertainty arises, in a certain analogy with quantum mechanics. It is driven by the difference between local diffusion coefficients in the liquid solution. The same transformation class can be used to infer Fick's second law of diffusion, playing here the role of a gauge invariance preserving covariance of the spacetime increments. An overall, noteworthy conclusion emerging from this view concerns the statistics of (i) static macromolecular configurations and (ii) the motion of liquid molecules, which would be much more related than expected.

  12. Exercise motivation and adherence in cancer survivors after participation in a randomized controlled trial: an attribution theory perspective.

    Science.gov (United States)

    Courneya, Kerry S; Friedenreich, Christine M; Sela, Rami A; Quinney, H Arthur; Rhodes, Ryan E; Jones, Lee W

    2004-01-01

    The purpose of this study was to examine postprogram exercise motivation and adherence in cancer survivors who participated in the Group Psychotherapy and Home-Based Physical Exercise (GROUP-HOPE; Courneya, Friedenreich, Sela, Quinney, & Rhodes, 2002) trial. At the completion of the GROUP-HOPE trial, 46 of 51 (90%) participants in the exercise group completed measures of attribution theory constructs. A 5-week follow-up self-report of exercise was then completed by 30 (65%) participants. Correlational analyses indicated that program exercise, perceived success, expected success, and affective reactions were strong predictors of postprogram exercise. In multivariate stepwise regression analyses, program exercise and perceived success were the strongest predictors of postprogram exercise. Additionally, perceived success was more important than objective success in understanding the attribution process, and it interacted with personal control to influence expected success and negative affect. Finally, postprogram quality of life and changes in physical fitness were correlates of perceived success. We concluded that attribution theory may have utility for understanding postprogram exercise motivation and adherence in cancer survivors.

  13. Composite Differential Search Algorithm

    Directory of Open Access Journals (Sweden)

    Bo Liu

    2014-01-01

    Full Text Available Differential search algorithm (DS is a relatively new evolutionary algorithm inspired by the Brownian-like random-walk movement which is used by an organism to migrate. It has been verified to be more effective than ABC, JDE, JADE, SADE, EPSDE, GSA, PSO2011, and CMA-ES. In this paper, we propose four improved solution search algorithms, namely “DS/rand/1,” “DS/rand/2,” “DS/current to rand/1,” and “DS/current to rand/2” to search the new space and enhance the convergence rate for the global optimization problem. In order to verify the performance of different solution search methods, 23 benchmark functions are employed. Experimental results indicate that the proposed algorithm performs better than, or at least comparable to, the original algorithm when considering the quality of the solution obtained. However, these schemes cannot still achieve the best solution for all functions. In order to further enhance the convergence rate and the diversity of the algorithm, a composite differential search algorithm (CDS is proposed in this paper. This new algorithm combines three new proposed search schemes including “DS/rand/1,” “DS/rand/2,” and “DS/current to rand/1” with three control parameters using a random method to generate the offspring. Experiment results show that CDS has a faster convergence rate and better search ability based on the 23 benchmark functions.

  14. Optimal intermittent search strategies

    International Nuclear Information System (INIS)

    Rojo, F; Budde, C E; Wio, H S

    2009-01-01

    We study the search kinetics of a single fixed target by a set of searchers performing an intermittent random walk, jumping between different internal states. Exploiting concepts of multi-state and continuous-time random walks we have calculated the survival probability of a target up to time t, and have 'optimized' (minimized) it with regard to the transition probability among internal states. Our model shows that intermittent strategies always improve target detection, even for simple diffusion states of motion

  15. An inverse method for the identification of a distributed random excitation acting on a vibrating structure. Theory

    International Nuclear Information System (INIS)

    Granger, S.; Perotin, L.

    1997-01-01

    Maintaining the PWR components under reliable operating conditions requires a complex design to prevent various damaging processes, including fatigue and wear problems due to flow-induced vibration. In many practical situations, it is difficult, if not impossible, to perform direct measurements or calculations of the external forces acting on vibrating structures. Instead, vibrational responses can often be conveniently measured. This paper presents an inverse method for estimating a distributed random excitation from the measurement of the structural response at a number of discrete points. This paper is devoted to the presentation of the theoretical development. The force identification method is based on a modal model for the structure and a spatial orthonormal decomposition of the excitation field. The estimation of the Fourier coefficients of this orthonormal expansion is presented. As this problem turns out to be ill-posed, a regularization process is introduced. The minimization problem associated to this process is then formulated and its solutions is developed. (author)

  16. The mean distance to the nth neighbour in a uniform distribution of random points: an application of probability theory

    International Nuclear Information System (INIS)

    Bhattacharyya, Pratip; Chakrabarti, Bikas K

    2008-01-01

    We study different ways of determining the mean distance (r n ) between a reference point and its nth neighbour among random points distributed with uniform density in a D-dimensional Euclidean space. First, we present a heuristic method; though this method provides only a crude mathematical result, it shows a simple way of estimating (r n ). Next, we describe two alternative means of deriving the exact expression of (r n ): we review the method using absolute probability and develop an alternative method using conditional probability. Finally, we obtain an approximation to (r n ) from the mean volume between the reference point and its nth neighbour and compare it with the heuristic and exact results

  17. Magnetic monopole search experiments

    International Nuclear Information System (INIS)

    Stone, J.L.

    1986-01-01

    Experimental searches for the elusive magnetic monopole have extended over 50 years -- ever since Dirac showed that the existence of isolated magnetic charges could account for the observation of quantized electric charge. Early searches for Dirac's monopole were hampered since there was no indication of the expected monopole mass, velocity, or origin in the theory. Consequently, numerous experiments searched more or less blindly for relativistic low mass monopoles in the cosmic rays and in particle collisions at high energy accelerators. In this paper, the author reviews briefly the monopole properties which are relevant for their detection and summarize current experimental efforts using induction, ionization/excitation, and catalysis techniques

  18. Searching for Lorentz violation

    International Nuclear Information System (INIS)

    Allen, Roland E.; Yokoo, Seiichirou

    2004-01-01

    Astrophysical, terrestrial, and space-based searches for Lorentz violation are very briefly reviewed. Such searches are motivated by the fact that all superunified theories (and other theories that attempt to include quantum gravity) have some potential for observable violations of Lorentz invariance. Another motivation is the exquisite sensitivity of certain well-designed experiments and observations to particular forms of Lorentz violation. We also review some new predictions of a specific Lorentz-violating theory: If a fundamental energy m-bar c2 in this theory lies below the usual GZK cutoff E GZK , the cutoff is shifted to infinite energy; i.e., it no longer exists. On the other hand, if m-bar c2 lies above E GZK , there is a high-energy branch of the fermion dispersion relation which provides an alternative mechanism for super-GZK cosmic-ray protons

  19. Quantum fishes. The string theory and the search for the world formula; Quantenfische. Die Stringtheorie und die Suche nach der Weltformel

    Energy Technology Data Exchange (ETDEWEB)

    Luest, Dieter

    2014-11-01

    Can all physical phenomena from the smallest particles to the universe be uniquely described? The hottest candidate for such a world formula is the string theory. The renowned physicist Dieter Luest explains by means of a story of ''quantum fishes'', intelligent fishes in a pond, the foundations and essential principles of the string theory.

  20. A critical Analysis of Bidding Exemption and Unenforceability – In Search of a Theory that Allows the Application in Specific Cases

    Directory of Open Access Journals (Sweden)

    Felipe Cesar Lapa Boselli

    2016-10-01

    Full Text Available The paper aims to conduct a review of the legislation, doctrine and jurisprudence about the possibilities of public hiring without bidding, working on a theory for division of existing institutes and applying this theory in the central hypothesis of the article that it would be illegal to emergency hiring continuous service through the bidding process.

  1. Oxygen self-diffusion mechanisms in monoclinic Zr O2 revealed and quantified by density functional theory, random walk analysis, and kinetic Monte Carlo calculations

    Science.gov (United States)

    Yang, Jing; Youssef, Mostafa; Yildiz, Bilge

    2018-01-01

    In this work, we quantify oxygen self-diffusion in monoclinic-phase zirconium oxide as a function of temperature and oxygen partial pressure. A migration barrier of each type of oxygen defect was obtained by first-principles calculations. Random walk theory was used to quantify the diffusivities of oxygen interstitials by using the calculated migration barriers. Kinetic Monte Carlo simulations were used to calculate diffusivities of oxygen vacancies by distinguishing the threefold- and fourfold-coordinated lattice oxygen. By combining the equilibrium defect concentrations obtained in our previous work together with the herein calculated diffusivity of each defect species, we present the resulting oxygen self-diffusion coefficients and the corresponding atomistically resolved transport mechanisms. The predicted effective migration barriers and diffusion prefactors are in reasonable agreement with the experimentally reported values. This work provides insights into oxygen diffusion engineering in Zr O2 -related devices and parametrization for continuum transport modeling.

  2. Individual eigenvalue distributions of crossover chiral random matrices and low-energy constants of SU(2) × U(1) lattice gauge theory

    Science.gov (United States)

    Yamamoto, Takuya; Nishigaki, Shinsuke M.

    2018-02-01

    We compute individual distributions of low-lying eigenvalues of a chiral random matrix ensemble interpolating symplectic and unitary symmetry classes by the Nyström-type method of evaluating the Fredholm Pfaffian and resolvents of the quaternion kernel. The one-parameter family of these distributions is shown to fit excellently the Dirac spectra of SU(2) lattice gauge theory with a constant U(1) background or dynamically fluctuating U(1) gauge field, which weakly breaks the pseudoreality of the unperturbed SU(2) Dirac operator. The observed linear dependence of the crossover parameter with the strength of the U(1) perturbations leads to precise determination of the pseudo-scalar decay constant, as well as the chiral condensate in the effective chiral Lagrangian of the AI class.

  3. Comparison of two theory-based, fully automated telephone interventions designed to maintain dietary change in healthy adults: study protocol of a three-arm randomized controlled trial.

    Science.gov (United States)

    Wright, Julie A; Quintiliani, Lisa M; Turner-McGrievy, Gabrielle M; Migneault, Jeffrey P; Heeren, Timothy; Friedman, Robert H

    2014-11-10

    Health behavior change interventions have focused on obtaining short-term intervention effects; few studies have evaluated mid-term and long-term outcomes, and even fewer have evaluated interventions that are designed to maintain and enhance initial intervention effects. Moreover, behavior theory has not been developed for maintenance or applied to maintenance intervention design to the degree that it has for behavior change initiation. The objective of this paper is to describe a study that compared two theory-based interventions (social cognitive theory [SCT] vs goal systems theory [GST]) designed to maintain previously achieved improvements in fruit and vegetable (F&V) consumption. The interventions used tailored, interactive conversations delivered by a fully automated telephony system (Telephone-Linked Care [TLC]) over a 6-month period. TLC maintenance intervention based on SCT used a skills-based approach to build self-efficacy. It assessed confidence in and barriers to eating F&V, provided feedback on how to overcome barriers, plan ahead, and set goals. The TLC maintenance intervention based on GST used a cognitive-based approach. Conversations trained participants in goal management to help them integrate their newly acquired dietary behavior into their hierarchical system of goals. Content included goal facilitation, conflict, shielding, and redundancy, and reflection on personal goals and priorities. To evaluate and compare the two approaches, a sample of adults whose F&V consumption was below public health goal levels were recruited from a large urban area to participate in a fully automated telephony intervention (TLC-EAT) for 3-6 months. Participants who increase their daily intake of F&V by ≥1 serving/day will be eligible for the three-arm randomized controlled trial. A sample of 405 participants will be randomized to one of three arms: (1) an assessment-only control, (2) TLC-SCT, and (3) TLC-GST. The maintenance interventions are 6 months. All 405

  4. Quantumness, Randomness and Computability

    International Nuclear Information System (INIS)

    Solis, Aldo; Hirsch, Jorge G

    2015-01-01

    Randomness plays a central role in the quantum mechanical description of our interactions. We review the relationship between the violation of Bell inequalities, non signaling and randomness. We discuss the challenge in defining a random string, and show that algorithmic information theory provides a necessary condition for randomness using Borel normality. We close with a view on incomputablity and its implications in physics. (paper)

  5. Structural properties of small Lin (n = 5-8) atomic clusters via ab initio random structure searching: A look into the role of different implementations of long-range dispersion corrections

    Science.gov (United States)

    Putungan, Darwin Barayang; Lin, Shi-Hsin

    2018-01-01

    In this work, we looked into the lowest energy structures of small lithium clusters (Lin, n = 5, 6, 7, 8) utilizing conventional PBE exchange-correlation functional, PBE with D2 dispersion correction and PBE with Tkatchenko and Scheffler (TS) dispersion correction, and searched using ab initio random structure searching. Results show that in general, dispersion-corrected PBE obtained similar lowest minima structures as those obtained via conventional PBE regardless of the type of implementation, although both D2 and TS found several high-energy isomers that conventional PBE did not arrive at, with TS in general giving more structures per energy range that could be attributed to its environment-dependent implementation. Moreover, D2 and TS dispersion corrections found a lowest energy geometry for Li8 cluster that is in agreement with the structure obtained via the typical benchmarking method diffusion Monte Carlo in a recent work. It is thus suggested that for much larger lithium clusters, utilization of dispersion correction could be of help in searching for lowest energy minima that is in close agreement with that of diffusion Monte Carlo results, but computationally inexpensive.

  6. Inflationary string theory?

    Indian Academy of Sciences (India)

    strongly motivate a detailed search for inflation within string theory, although it has ... between string theory and observations provides a strong incentive for ..... sonably be expected to arise for any system having very many degrees of freedom.

  7. Moderator Roles of Optimism and Weight Control on the Impact of Playing Exergames on Happiness: The Perspective of Social Cognitive Theory Using A Randomized Controlled Trial.

    Science.gov (United States)

    Nguyen, Huynh Van; Huang, Han-Chung; Wong, May-Kuen; Yang, Ya-Hui; Huang, Tzu-Ling; Teng, Ching-I

    2018-04-30

    The literature on exergames has examined their impact on user-perceived psychological health (i.e., user-perceived happiness), but little is known about whether such an impact depends on user characteristics. Therefore, this study used the perspective of social cognitive theory (SCT) to identify potential moderators (i.e., whether the user is optimistic or attempting to control his or her weight) of the impact of playing exergames on user-perceived happiness. This large-scale randomized controlled trial recruited 337 college students (of whom 57.3% were female and all were aged 20-40 years) as participants. The participants were randomly assigned to the intervention group or the control group. Participants in the intervention group were asked to use an Xbox 360 to play 1 of 10 exergame programs for 30 minutes once a week for 2 weeks. Participants in the control group were not required to do so. Repeated-measures ANOVA was used for the analyses. The analytical results indicate that playing exergames helped to maintain happiness levels and prevented them from decreasing. The maintained happiness was more prominent among participants who were trying to control their weight, but did not differ between participants who were highly optimistic and those who were less optimistic. This study is the first using SCT to explain the contingent effect of playing exergames on user happiness. Exergames can maintain happiness among users, and such maintenance can be the strongest among users who are trying to control their weight.

  8. Random matrix theory analysis of cross-correlations in the US stock market: Evidence from Pearson’s correlation coefficient and detrended cross-correlation coefficient

    Science.gov (United States)

    Wang, Gang-Jin; Xie, Chi; Chen, Shou; Yang, Jiao-Jiao; Yang, Ming-Yan

    2013-09-01

    In this study, we first build two empirical cross-correlation matrices in the US stock market by two different methods, namely the Pearson’s correlation coefficient and the detrended cross-correlation coefficient (DCCA coefficient). Then, combining the two matrices with the method of random matrix theory (RMT), we mainly investigate the statistical properties of cross-correlations in the US stock market. We choose the daily closing prices of 462 constituent stocks of S&P 500 index as the research objects and select the sample data from January 3, 2005 to August 31, 2012. In the empirical analysis, we examine the statistical properties of cross-correlation coefficients, the distribution of eigenvalues, the distribution of eigenvector components, and the inverse participation ratio. From the two methods, we find some new results of the cross-correlations in the US stock market in our study, which are different from the conclusions reached by previous studies. The empirical cross-correlation matrices constructed by the DCCA coefficient show several interesting properties at different time scales in the US stock market, which are useful to the risk management and optimal portfolio selection, especially to the diversity of the asset portfolio. It will be an interesting and meaningful work to find the theoretical eigenvalue distribution of a completely random matrix R for the DCCA coefficient because it does not obey the Marčenko-Pastur distribution.

  9. Aerobic physical activity and resistance training: an application of the theory of planned behavior among adults with type 2 diabetes in a random, national sample of Canadians

    Directory of Open Access Journals (Sweden)

    Karunamuni Nandini

    2008-12-01

    Full Text Available Abstract Background Aerobic physical activity (PA and resistance training are paramount in the treatment and management of type 2 diabetes (T2D, but few studies have examined the determinants of both types of exercise in the same sample. Objective The primary purpose was to investigate the utility of the Theory of Planned Behavior (TPB in explaining aerobic PA and resistance training in a population sample of T2D adults. Methods A total of 244 individuals were recruited through a random national sample which was created by generating a random list of household phone numbers. The list was proportionate to the actual number of household telephone numbers for each Canadian province (with the exception of Quebec. These individuals completed self-report TPB constructs of attitude, subjective norm, perceived behavioral control and intention, and a 3-month follow-up that assessed aerobic PA and resistance training. Results TPB explained 10% and 8% of the variance respectively for aerobic PA and resistance training; and accounted for 39% and 45% of the variance respectively for aerobic PA and resistance training intentions. Conclusion These results may guide the development of appropriate PA interventions for aerobic PA and resistance training based on the TPB.

  10. Personalized Search

    CERN Document Server

    AUTHOR|(SzGeCERN)749939

    2015-01-01

    As the volume of electronically available information grows, relevant items become harder to find. This work presents an approach to personalizing search results in scientific publication databases. This work focuses on re-ranking search results from existing search engines like Solr or ElasticSearch. This work also includes the development of Obelix, a new recommendation system used to re-rank search results. The project was proposed and performed at CERN, using the scientific publications available on the CERN Document Server (CDS). This work experiments with re-ranking using offline and online evaluation of users and documents in CDS. The experiments conclude that the personalized search result outperform both latest first and word similarity in terms of click position in the search result for global search in CDS.

  11. Long term effects of self-determination theory and motivational interviewing in a web-based physical activity intervention: randomized controlled trial.

    Science.gov (United States)

    Friederichs, Stijn A H; Oenema, Anke; Bolman, Catherine; Lechner, Lilian

    2015-08-18

    Our main objective in the current study was to evaluate the long-term effectiveness (12 months from baseline) of I Move (a web-based computer tailored physical activity intervention, based on self-determination theory and motivational interviewing). To this end, we compared I Move to a web-based computer tailored physical activity intervention based on traditional health behavior theories (Active Plus), and to a no-intervention control group. As a secondary objective, the present study aimed to identify participant characteristics that moderate the long term effects of I Move and Active Plus. A randomized controlled trial was conducted, comparing three research conditions: 1) the I Move condition, participants in this condition received I Move; 2) the Active Plus condition, participants in this condition received Active Plus; 3) the control condition; participants in this condition received no intervention and were placed on a waiting list. Main outcome measures were weekly minutes of moderate to vigorous physical activity and weekly days with minimal 30 min of physical activity. All measurements were taken by web-based questionnaires via the study website. Intervention effects were analyzed using multilevel linear regression analyses. At 12 months from baseline, I Move was found to be effective in increasing weekly minutes of moderate to vigorous physical activity (ES = .13), while Active Plus was not. In contrast, Active Plus was found to be effective in increasing weekly days with ≥ 30 min PA at 12 months (ES = .11), while I Move was not. No moderators of the effects of I Move were found. The results suggest that web-based computer tailored physical activity interventions might best include elements based on both self-determination theory/motivational interviewing and traditional health behavioral theories. To be more precise, it is arguable that the focus of the theoretical foundations, used in new web-based PA interventions should depend on the

  12. Einstein's dice and Schrödinger's cat how two great minds battled quantum randomness to create a unified theory of physics

    CERN Document Server

    Halpern, Paul

    2015-01-01

    Albert Einstein and Erwin Schrödinger were friends and comrades-in-arms against what they considered the most preposterous aspects of quantum physics: its indeterminacy. Einstein famously quipped that God does not play dice with the universe, and Schrödinger is equally well known for his thought experiment about the cat in the box who ends up “spread out” in a probabilistic state, neither wholly alive nor wholly dead. Both of these famous images arose from these two men’s dissatisfaction with quantum weirdness and with their assertion that underneath it all, there must be some essentially deterministic world. Even though it was Einstein’s own theories that made quantum mechanics possible, both he and Schrödinger could not bear the idea that the universe was, at its most fundamental level, random. As the Second World War raged, both men struggled to produce a theory that would describe in full the universe’s ultimate design, first as collaborators, then as competitors. They both ultimately failed...

  13. Effects of Nursing Care Based on Watson's Theory of Human Caring on Anxiety, Distress, And Coping, When Infertility Treatment Fails: A Randomized Controlled Trial.

    Science.gov (United States)

    Durgun Ozan, Yeter; Okumuş, Hülya

    2017-06-01

    Introduction: The failure of infertility treatment leads to individual, familial, and social problems. The objective of this study was to evaluate the effectiveness of the nursing care program based on Watson's "Theory of Human Caring" on anxiety and distress caused by coping when the treatment fails. Methods: This study randomized controlled trial study was conducted from April to November 2012, with 86 Turkish women with infertility (intervention group: 45, control group: 41). Follow-up of 32 infertile women, who failed infertility treatment from intervention group, and 35 infertile women, who failed infertility treatment from control group, continued for another four weeks. Data were collected through Spiel Berger's State/Trait Anxiety Inventory, Distress Scale, and Ways of Coping Questionnaire. The analyses of data were conducted using SPSS ver 13. Results: The intervention and control groups significantly differed in terms of anxiety, distress, and coping levels. The intervention group's mean anxiety score decreased by thirteen points and distress by fourteen points (in a positive direction). The intervention group's mean positive coping style score increased. Whereas a negative increase was observed in the control group's values depending on the failure of the treatment. Conclusion: Watson's theory of human caring is recommended as a guide to nursing patients with infertility treatment to decrease levels of anxiety and distress, and to increase the positive coping style among infertile women.

  14. The effect of motivational interviewing-based intervention using self-determination theory on promotion of physical activity among women in reproductive age: A randomized clinical trial

    Science.gov (United States)

    Mahmoodabad, Seyed Saeed Mazloomy; Tonekaboni, Nooshin Rouhani; Farmanbar, Rabiollah; Fallahzadeh, Hossein; Kamalikhah, Tahereh

    2017-01-01

    Background Physical activity (PA) prevents chronic diseases. Self-determination theory (SDT) provides a useful framework to understand the nature of motivational interviewing (MI). Objective This study aimed to determine the effect of MI-based intervention using SDT on the promotion of PA among women in reproductive age. Methods Seventy women in reproductive age were selected by clustering sampling method for this randomized controlled trial. The questionnaire included the variables of physical fitness test, SDT, and global physical activity questionnaire (GPAQ). The validity of the questionnaires was approved using content validity ratio (CVR) and index (CVI). The reliability and internal consistency of the questionnaires and measures was approved using test-retest method and Cronbach’s alpha test, respectively. The intervention group (n=35) received four MI sessions through theory and one standard education session about PA. The control group (n=35) received a standard education session about PA. Results Four months after the intervention, an increase in the mean scores of total PA (pamotivation (p<0.01, ES= −0.56) over time, compared to the control group. Conclusion MI-based intervention using SDT was effective on the promotion of PA. Trial registration The Trial was registered at the Iranian Registry of Clinical Trial (http://www.irct.ir) with the Irct ID: IRCT2015101924592N1. PMID:28713522

  15. Random Decrement

    DEFF Research Database (Denmark)

    Asmussen, J.C.; Ibrahim, S.R.; Brincker, Rune

    Abstraet Thispaper demansirates how to use the Random Decrement (RD) technique for identification o flinear structures subjected to ambient excitation. The theory behind the technique will be presented and guidelines how to choose the different variables will be given. This is done by introducing...

  16. Random Decrement

    DEFF Research Database (Denmark)

    Asmussen, J. C.; Ibrahim, S. R.; Brincker, Rune

    This paper demonstrates how to use the Random Decrement (RD) technique for identification of linear structures subjected to ambient excitation. The theory behind the technique will be presented and guidelines how to choose the different variables will be given. This is done by introducing a new...

  17. Random Decrement

    DEFF Research Database (Denmark)

    Asmussen, J. C.; Ibrahim, R.; Brincker, Rune

    1998-01-01

    This paper demonstrates how to use the Random Decrement (RD) technique for identification of linear structures subjected to ambient excitation. The theory behind the technique will be presented and guidelines how to choose the different variables will be given. This is done by introducing a new...

  18. Application of the τ-function theory of Painleve equations to random matrices: PIV, PII and the GUE

    International Nuclear Information System (INIS)

    Forrester, P.J.; Witte, N.S.

    2000-01-01

    Tracy and Widom have evaluated the cumulative distribution of the largest eigenvalue for the finite and scaled infinite Gaussian unitary ensemble (GUE) in terms of a Painleve IV and Painleve II transcendent respectively. We generalise these results to the evaluation of E N (λ;a) :(Π n l=1 χ (l) (-∞,λ) (λ - λ l ) a ), where χ (l) (-∞) = 1 for λ l E (- ∞,λ] and χ (l) (-∞,λ) = 0 otherwise, and the average is with respect to the joint eigenvalue distribution of the GUE, as well as to the evaluation of F N (λ;a) :(Π N l=1 (λ - λ l ) a ). Of particular interest are E N (λ;2) and F N (λ;2)X and their scaled limits, which give the distribution of the largest eigenvalue and the density respectively. Our results are obtained by applying the Okamoto τ-function theory of Painleve IV and Painleve II equations, for which we give a self contained presentation based on the recent work of Noumi and Yamada. We point out that the same approach can be used to study the quantities E N (λ; a) and F N (λ; a) for the other classical matrix ensembles

  19. The Academy for Future Science Faculty: randomized controlled trial of theory-driven coaching to shape development and diversity of early-career scientists.

    Science.gov (United States)

    Thakore, Bhoomi K; Naffziger-Hirsch, Michelle E; Richardson, Jennifer L; Williams, Simon N; McGee, Richard

    2014-08-02

    Approaches to training biomedical scientists have created a talented research community. However, they have failed to create a professional workforce that includes many racial and ethnic minorities and women in proportion to their representation in the population or in PhD training. This is particularly true at the faculty level. Explanations for the absence of diversity in faculty ranks can be found in social science theories that reveal processes by which individuals develop identities, experiences, and skills required to be seen as legitimate within the profession. Using the social science theories of Communities of Practice, Social Cognitive Career Theory, identity formation, and cultural capital, we have developed and are testing a novel coaching-based model to address some of the limitations of previous diversity approaches. This coaching intervention (The Academy for Future Science Faculty) includes annual in-person meetings of students and trained faculty Career Coaches, along with ongoing virtual coaching, group meetings and communication. The model is being tested as a randomized controlled trial with two cohorts of biomedical PhD students from across the U.S., one recruited at the start of their PhDs and one nearing completion. Stratification into the experimental and control groups, and to coaching groups within the experimental arms, achieved equal numbers of students by race, ethnicity and gender to the extent possible. A fundamental design element of the Academy is to teach and make visible the social science principles which highly influence scientific advancement, as well as acknowledging the extra challenges faced by underrepresented groups working to be seen as legitimate within the scientific communities. The strategy being tested is based upon a novel application of the well-established principles of deploying highly skilled coaches, selected and trained for their ability to develop talents of others. This coaching model is intended to be a

  20. Effect of goal attainment theory based education program on cardiovascular risks, behavioral modification, and quality of life among patients with first episode of acute myocardial infarction: Randomized study.

    Science.gov (United States)

    Park, Moonkyoung; Song, Rhayun; Jeong, Jin-Ok

    2017-06-01

    Effect of goal-attainment-theory-based education program on cardiovascular risks, behavioral modification, and quality of life among patients with first episode of acute myocardial infarction: randomized study BACKGROUND: The behavioral modification strategies should be explored at the time of admission to lead the maximum effect of cardiovascular risk management. This randomized study aimed to elucidate the effects of a nurse-led theory-based education program in individuals with a first episode of acute myocardial infarction on cardiovascular risks, health behaviors, and quality of life over 6 months. The study involved a convenience sample of 64 patients with acute myocardial infarction who were randomly assigned to either the education group or the control group. The goal-attainment-based education program was designed to set the mutually agreed goals of risk management and the behavioral modification strategies for achieving those goals. Those in the control group received routine management only. The participants in both groups were contacted at 6-8 weeks and at 6 months after discharge to measure outcome variables. Repeated measure ANOVA was conducted using SPSSWIN (version 20.0) to determine the significance of differences in outcome variables over 6 months between the groups. Both groups showed significant positive changes in cardiovascular risks, health behaviors, and quality of life over 6 months. The 2-year risk of cardiovascular disease was significantly reduced in both study groups, but with no significant interaction effect (F=2.01, p=0.142). The performance and maintenance of health behaviors (F=3.75, p=0.029) and the mental component of quality of life (F=4.03, p=0.020) were significantly better in the education group than the control group. Applying a goal-oriented education program at an early stage of hospital management improved and maintained blood glucose, health behaviors, and mental component of the quality of life up to six months in

  1. A hybrid search algorithm for swarm robots searching in an unknown environment.

    Science.gov (United States)

    Li, Shoutao; Li, Lina; Lee, Gordon; Zhang, Hao

    2014-01-01

    This paper proposes a novel method to improve the efficiency of a swarm of robots searching in an unknown environment. The approach focuses on the process of feeding and individual coordination characteristics inspired by the foraging behavior in nature. A predatory strategy was used for searching; hence, this hybrid approach integrated a random search technique with a dynamic particle swarm optimization (DPSO) search algorithm. If a search robot could not find any target information, it used a random search algorithm for a global search. If the robot found any target information in a region, the DPSO search algorithm was used for a local search. This particle swarm optimization search algorithm is dynamic as all the parameters in the algorithm are refreshed synchronously through a communication mechanism until the robots find the target position, after which, the robots fall back to a random searching mode. Thus, in this searching strategy, the robots alternated between two searching algorithms until the whole area was covered. During the searching process, the robots used a local communication mechanism to share map information and DPSO parameters to reduce the communication burden and overcome hardware limitations. If the search area is very large, search efficiency may be greatly reduced if only one robot searches an entire region given the limited resources available and time constraints. In this research we divided the entire search area into several subregions, selected a target utility function to determine which subregion should be initially searched and thereby reduced the residence time of the target to improve search efficiency.

  2. Graph theory

    CERN Document Server

    Gould, Ronald

    2012-01-01

    This introduction to graph theory focuses on well-established topics, covering primary techniques and including both algorithmic and theoretical problems. The algorithms are presented with a minimum of advanced data structures and programming details. This thoroughly corrected 1988 edition provides insights to computer scientists as well as advanced undergraduates and graduate students of topology, algebra, and matrix theory. Fundamental concepts and notation and elementary properties and operations are the first subjects, followed by examinations of paths and searching, trees, and networks. S

  3. Varied Search Protocols Lead to Clinically Relevant Results. A review of: Patel, Manesh R., Connie M. Schardt, Linda L. Sanders, and Sheri A. Keitz. “Randomized Trial for Answers to Clinical Questions: Evaluating a Pre‐Appraised Versus a MEDLINE Search Protocol.” Journal of the Medical Library Association 94.4 (2006: 382‐6.

    Directory of Open Access Journals (Sweden)

    Marcy L. Brown

    2008-03-01

    Full Text Available Objective – To determine the success rate of electronic resources for answering clinical questions by comparing speed, validity, and applicability of two different protocols for searching the medical literature.Design – Randomized trial with results judged by blinded panel.Setting – Duke University Medical Center in Durham, North Carolina, United States ofAmerica.Subjects – Thirty‐two 2nd and 3rd year internal medicine residents on an eight week general medicine rotation at the Duke University Medical Center.Methods – Two search protocols were developed:Protocol A: Participants searched MEDLINE first, and then searched pre‐appraised resources if needed.Protocol B: Participants searched pre‐appraised resources first, which included UpToDate, ACP JournalClub, Cochrane Database of Systematic Reviews, and DARE. The residents then searched MEDLINE if an answer could not be found in the 66 initial group of pre‐appraised resources. Residents were randomised by computer-assisted block order into four blocks of eight residents each. Two blocks were assigned to Protocol A, and two to Protocol B. Each day, residents developed at least one clinical question related to caring for patients. The questions were transcribed onto pocket-sized cards, with the answer sought later using the assigned protocol. If answers weren’t found using either protocol, searches were permitted in other available resources. When an article that answered a question was found, the resident recorded basic information about the question and the answer as well as the time required to find the answer (less than five minutes; between five and ten minutes; or more than ten minutes. Residents were to select answers that were “methodologically sound and clinically important” (384. Ten faculty members formally trained in evidence‐based medicine (EBM reviewed a subset of therapy‐related questions and answers. The reviewers, who were blinded to the search protocols

  4. Random matrices and random difference equations

    International Nuclear Information System (INIS)

    Uppuluri, V.R.R.

    1975-01-01

    Mathematical models leading to products of random matrices and random difference equations are discussed. A one-compartment model with random behavior is introduced, and it is shown how the average concentration in the discrete time model converges to the exponential function. This is of relevance to understanding how radioactivity gets trapped in bone structure in blood--bone systems. The ideas are then generalized to two-compartment models and mammillary systems, where products of random matrices appear in a natural way. The appearance of products of random matrices in applications in demography and control theory is considered. Then random sequences motivated from the following problems are studied: constant pulsing and random decay models, random pulsing and constant decay models, and random pulsing and random decay models

  5. Unbiased structural search of small copper clusters within DFT

    International Nuclear Information System (INIS)

    Cogollo-Olivo, Beatriz H.; Seriani, Nicola; Montoya, Javier A.

    2015-01-01

    Highlights: • We have been able to identify novel metastable structures for small Cu clusters. • We have shown that a linear structure reported for Cu_3 is actually a local maximum. • Some of the structures reported in literature are actually unstable within DFT. • Some of the isomer structures found shows the limits of educated guesses. - Abstract: The atomic structure of small Cu clusters with 3–6 atoms has been investigated by density functional theory and random search algorithm. New metastable structures have been found that lie merely tens of meV/atom above the corresponding ground state, and could therefore be present at thermodynamic equilibrium at room temperature or slightly above. Moreover, we show that the previously proposed linear configuration for Cu_3 is in fact a local maximum of the energy. Finally, we argue that the random search algorithm also provides qualitative information about the attraction basin of each structure in the energy landscape.

  6. Searches for supersymmetry at CMS

    Energy Technology Data Exchange (ETDEWEB)

    Collaboration: F. Giordano on behalf of the CMS Collaboration

    2017-11-15

    Among the most promising prospects for a theory of physics beyond the standard model is supersymmetry. In this talk, the latest results from the CMS experiment at the LHC on searches for supersymmetry produced through strong production and electroweak production channels are presented using 20/fb of data from the 8 TeV LHC run, with particular focus on gluino and stop searches.

  7. Search Advertising

    OpenAIRE

    Cornière (de), Alexandre

    2016-01-01

    Search engines enable advertisers to target consumers based on the query they have entered. In a framework with horizontal product differentiation, imperfect product information and in which consumers incur search costs, I study a game in which advertisers have to choose a price and a set of relevant keywords. The targeting mechanism brings about three kinds of efficiency gains, namely lower search costs, better matching, and more intense product market price-competition. A monopolistic searc...

  8. Faceted Search

    CERN Document Server

    Tunkelang, Daniel

    2009-01-01

    We live in an information age that requires us, more than ever, to represent, access, and use information. Over the last several decades, we have developed a modern science and technology for information retrieval, relentlessly pursuing the vision of a "memex" that Vannevar Bush proposed in his seminal article, "As We May Think." Faceted search plays a key role in this program. Faceted search addresses weaknesses of conventional search approaches and has emerged as a foundation for interactive information retrieval. User studies demonstrate that faceted search provides more

  9. Social cognitive theory mediators of physical activity in a lifestyle program for cancer survivors and carers: findings from the ENRICH randomized controlled trial.

    Science.gov (United States)

    Stacey, F G; James, E L; Chapman, K; Lubans, D R

    2016-04-14

    Despite increasing numbers of cancer survivors and evidence that diet and physical activity improves the health of cancer survivors, most do not meet guidelines. Some social cognitive theory (SCT)-based interventions have increased physical activity behavior, however few have used objective physical activity measures. The Exercise and Nutrition Routine Improving Cancer Health (ENRICH) randomized controlled trial reported a significant intervention effect for the primary outcome of pedometer-assessed step counts at post-test (8-weeks) and follow-up (20-weeks). The aim of this study was to test whether the SCT constructs operationalized in the ENRICH intervention were mediators of physical activity behavior change. Randomized controlled trial with 174 cancer survivors and carers assessed at baseline, post-test (8-weeks), and follow-up (20-weeks). Participants were randomized to the ENRICH six session face-to-face healthy lifestyle program, or to a wait-list control. Hypothesized SCT mediators of physical activity behavior change (self-efficacy, behavioral goal, outcome expectations, impediments, and social expectations) were assessed using valid and reliable scales. Mediation was assessed using the Preacher and Hayes SPSS INDIRECT macro. At eight weeks, there was a significant intervention effect on behavioral goal (A = 9.12, p = 0.031) and outcome expectations (A = 0.25, p = 0.042). At 20 weeks, the intervention had a significant effect on self-efficacy (A = 0.31, p = 0.049) and behavioral goal (A = 13.15, p = 0.011). Only changes in social support were significantly associated with changes in step counts at eight weeks (B = 633.81, p = 0.023). Behavioral goal was the only SCT construct that had a significant mediating effect on step counts, and explained 22 % of the intervention effect at 20 weeks (AB = 397.9, 95 % CI 81.5-1025.5). SCT constructs had limited impact on objectively-assessed step counts in a multiple health

  10. Search algorithms as a framework for the optimization of drug combinations.

    Directory of Open Access Journals (Sweden)

    Diego Calzolari

    2008-12-01

    Full Text Available Combination therapies are often needed for effective clinical outcomes in the management of complex diseases, but presently they are generally based on empirical clinical experience. Here we suggest a novel application of search algorithms -- originally developed for digital communication -- modified to optimize combinations of therapeutic interventions. In biological experiments measuring the restoration of the decline with age in heart function and exercise capacity in Drosophila melanogaster, we found that search algorithms correctly identified optimal combinations of four drugs using only one-third of the tests performed in a fully factorial search. In experiments identifying combinations of three doses of up to six drugs for selective killing of human cancer cells, search algorithms resulted in a highly significant enrichment of selective combinations compared with random searches. In simulations using a network model of cell death, we found that the search algorithms identified the optimal combinations of 6-9 interventions in 80-90% of tests, compared with 15-30% for an equivalent random search. These findings suggest that modified search algorithms from information theory have the potential to enhance the discovery of novel therapeutic drug combinations. This report also helps to frame a biomedical problem that will benefit from an interdisciplinary effort and suggests a general strategy for its solution.

  11. Self-consistent Random Phase Approximation applied to a schematic model of the field theory; Approximation des phases aleatoires self-consistante appliquee a un modele schematique de la theorie des champs

    Energy Technology Data Exchange (ETDEWEB)

    Bertrand, Thierry [Inst. de Physique Nucleaire, Lyon-1 Univ., 69 - Villeurbanne (France)

    1998-12-11

    The self-consistent Random Phase Approximation (SCRPA) is a method allowing in the mean-field theory inclusion of the correlations in the ground and excited states. It has the advantage of not violating the Pauli principle in contrast to RPA, that is based on the quasi-bosonic approximation; in addition, numerous applications in different domains of physics, show a possible variational character. However, the latter should be formally demonstrated. The first model studied with SCRPA is the anharmonic oscillator in the region where one of its symmetries is spontaneously broken. The ground state energy is reproduced by SCRPA more accurately than RPA, with no violation of the Ritz variational principle, what is not the case for the latter approximation. The success of SCRPA is the the same in case of ground state energy for a model mixing bosons and fermions. At the transition point the SCRPA is correcting RPA drastically, but far from this region the correction becomes negligible, both methods being of similar precision. In the deformed region in the case of RPA a spurious mode occurred due to the microscopical character of the model.. The SCRPA may also reproduce this mode very accurately and actually it coincides with an excitation in the exact spectrum 40 refs., 33 figs., 14 tabs.

  12. Metaheuristics-Assisted Combinatorial Screening of Eu2+-Doped Ca-Sr-Ba-Li-Mg-Al-Si-Ge-N Compositional Space in Search of a Narrow-Band Green Emitting Phosphor and Density Functional Theory Calculations.

    Science.gov (United States)

    Lee, Jin-Woong; Singh, Satendra Pal; Kim, Minseuk; Hong, Sung Un; Park, Woon Bae; Sohn, Kee-Sun

    2017-08-21

    A metaheuristics-based design would be of great help in relieving the enormous experimental burdens faced during the combinatorial screening of a huge, multidimensional search space, while providing the same effect as total enumeration. In order to tackle the high-throughput powder processing complications and to secure practical phosphors, metaheuristics, an elitism-reinforced nondominated sorting genetic algorithm (NSGA-II), was employed in this study. The NSGA-II iteration targeted two objective functions. The first was to search for a higher emission efficacy. The second was to search for narrow-band green color emissions. The NSGA-II iteration finally converged on BaLi 2 Al 2 Si 2 N 6 :Eu 2+ phosphors in the Eu 2+ -doped Ca-Sr-Ba-Li-Mg-Al-Si-Ge-N compositional search space. The BaLi 2 Al 2 Si 2 N 6 :Eu 2+ phosphor, which was synthesized with no human intervention via the assistance of NSGA-II, was a clear single phase and gave an acceptable luminescence. The BaLi 2 Al 2 Si 2 N 6 :Eu 2+ phosphor as well as all other phosphors that appeared during the NSGA-II iterations were examined in detail by employing powder X-ray diffraction-based Rietveld refinement, X-ray absorption near edge structure, density functional theory calculation, and time-resolved photoluminescence. The thermodynamic stability and the band structure plausibility were confirmed, and more importantly a novel approach to the energy transfer analysis was also introduced for BaLi 2 Al 2 Si 2 N 6 :Eu 2+ phosphors.

  13. Gauge cooling for the singular-drift problem in the complex Langevin method — a test in Random Matrix Theory for finite density QCD

    Energy Technology Data Exchange (ETDEWEB)

    Nagata, Keitaro [KEK Theory Center, High Energy Accelerator Research Organization,1-1 Oho, Tsukuba 305-0801 (Japan); Nishimura, Jun [KEK Theory Center, High Energy Accelerator Research Organization,1-1 Oho, Tsukuba 305-0801 (Japan); Department of Particle and Nuclear Physics, School of High Energy Accelerator Science,Graduate University for Advanced Studies (SOKENDAI), 1-1 Oho, Tsukuba 305-0801 (Japan); Shimasaki, Shinji [KEK Theory Center, High Energy Accelerator Research Organization,1-1 Oho, Tsukuba 305-0801 (Japan); Research and Education Center for Natural Sciences, Keio University,Hiyoshi 4-1-1, Yokohama, Kanagawa 223-8521 (Japan)

    2016-07-14

    Recently, the complex Langevin method has been applied successfully to finite density QCD either in the deconfinement phase or in the heavy dense limit with the aid of a new technique called the gauge cooling. In the confinement phase with light quarks, however, convergence to wrong limits occurs due to the singularity in the drift term caused by small eigenvalues of the Dirac operator including the mass term. We propose that this singular-drift problem should also be overcome by the gauge cooling with different criteria for choosing the complexified gauge transformation. The idea is tested in chiral Random Matrix Theory for finite density QCD, where exact results are reproduced at zero temperature with light quarks. It is shown that the gauge cooling indeed changes drastically the eigenvalue distribution of the Dirac operator measured during the Langevin process. Despite its non-holomorphic nature, this eigenvalue distribution has a universal diverging behavior at the origin in the chiral limit due to a generalized Banks-Casher relation as we confirm explicitly.

  14. Effect of Motivational Interviewing on Physical Activity Intention among Obese and Overweight Women Using Protection Motivation Theory: A Randomized Clinical Trial

    Directory of Open Access Journals (Sweden)

    K. Mirkarimi

    2016-09-01

    Full Text Available Aims: As a growing problem, obesity is one of the most important worldwide health problems. One of the major factors leading to obesity is the sedentary lifestyle. The aim of this study was to investigate the effects of motivational interviewing on the physical activity intention in the obese or overweight women, using the protection motivation theory (PMT. Materials & Methods: In the clinical trial study, 60 obese or overweight women referred to the health centers of Gorgan were studied in 2015. The subjects, selected via non-probable and available sampling method, were randomly divided into two groups including control and motivational interviewing groups. Data was collected using a researcher-made questionnaire before the intervention and 2 and 6 months after in both groups. Data was analyzed by SPSS 18 software using independent T, Chi-square, repeated measures ANOVA, LSD, and one-variable and multivariable linear regression tests. Findings: The scores of all the constructs of PMT in motivational interviewing group significantly increased 2 and 6 months after he intervention (p0.05. The most powerful constructs predicting the intention towards the physical activities 2 months after the intervention were perceived-reply efficiency, self-efficiency, and perceived intensity, successively. In addition, such factors 6 months after the intervention were attitude and perceived intensity, successively. Conclusion: The motivational interviewing increases the scores of all the constructs of PMT, which leads to an increase in the physical activity intention in the obese or overweight women.

  15. The effects of a brief intervention to promote walking on Theory of Planned Behavior constructs: a cluster randomized controlled trial in general practice.

    Science.gov (United States)

    Williams, Stefanie L; Michie, Susan; Dale, Jeremy; Stallard, Nigel; French, David P

    2015-05-01

    Perceived behavioral control (PBC) is a consistent predictor of intentions to walk more. A previously successful intervention to promote walking by altering PBC has been adapted for delivery in general practice. This study aimed to evaluate the effect of this intervention on Theory of Planned Behavior (TPB) constructs in this context. Cluster randomized controlled trial, with n = 315 general practice patients. Practice nurses and Healthcare Assistants delivered a self-regulation intervention or information provision (control). Questionnaires assessed TPB variables at baseline, post-intervention, 6 weeks and 6 months. Walking was measured by pedometer. The control group reported significantly higher subjective norm at all follow-up time points. There were no significant differences between the two groups in PBC, intention, attitude or walking behavior. TPB variables significantly predicted intentions to walk more, but not objective walking behavior, after accounting for clustering. The lack of effect of the intervention was probably due to a failure to maintain intervention fidelity, and the unsuitability of the behavior change techniques included in the intervention for the population investigated. This previously successful intervention was not successful when delivered in this context, calling into question whether practice nurses are best placed to deliver such interventions. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  16. The impact of brief messages on HSV-2 screening uptake among female defendants in a court setting: a randomized controlled trial utilizing prospect theory.

    Science.gov (United States)

    Roth, Alexis M; Van Der Pol, Barbara; Fortenberry, J Dennis; Dodge, Brian; Reece, Michael; Certo, David; Zimet, Gregory D

    2015-01-01

    Epidemiologic data demonstrate that women involved with the criminal justice system in the United States are at high risk for sexually transmitted infections, including herpes simplex virus type 2 (HSV-2). Female defendants were recruited from a misdemeanor court to assess whether brief framed messages utilizing prospect theory could encourage testing for HSV-2. Participants were randomly assigned to a message condition (gain, loss, or control), completed an interviewer-administered survey assessing factors associated with antibody test uptake/refusal and were offered free point-of-care HSV-2 serologic testing. Although individuals in the loss-frame group accepted testing at the highest rate, an overall statistical difference in HSV-2 testing behavior by group (p ≤ .43) was not detected. The majority of the sample (74.6%) characterized receiving a serological test for HSV-2 as health affirming. However, this did not moderate the effect of the intervention nor was it significantly associated with test acceptance (p ≤ .82). Although the effects of message framing are subtle, the findings have important theoretical implications given the participants' characterization of HSV-2 screening as health affirming despite being a detection behavior. Implications of study results for health care providers interested in brief, low cost interventions are also explored.

  17. Increasing the quantity and quality of searching for current best evidence to answer clinical questions: protocol and intervention design of the MacPLUS FS Factorial Randomized Controlled Trials.

    Science.gov (United States)

    Agoritsas, Thomas; Iserman, Emma; Hobson, Nicholas; Cohen, Natasha; Cohen, Adam; Roshanov, Pavel S; Perez, Miguel; Cotoi, Chris; Parrish, Rick; Pullenayegum, Eleanor; Wilczynski, Nancy L; Iorio, Alfonso; Haynes, R Brian

    2014-09-20

    Finding current best evidence for clinical decisions remains challenging. With 3,000 new studies published every day, no single evidence-based resource provides all answers or is sufficiently updated. McMaster Premium LiteratUre Service--Federated Search (MacPLUS FS) addresses this issue by looking in multiple high quality resources simultaneously and displaying results in a one-page pyramid with the most clinically useful at the top. Yet, additional logistical and educational barriers need to be addressed to enhance point-of-care evidence retrieval. This trial seeks to test three innovative interventions, among clinicians registered to MacPLUS FS, to increase the quantity and quality of searching for current best evidence to answer clinical questions. In a user-centered approach, we designed three interventions embedded in MacPLUS FS: (A) a web-based Clinical Question Recorder; (B) an Evidence Retrieval Coach composed of eight short educational videos; (C) an Audit, Feedback and Gamification approach to evidence retrieval, based on the allocation of 'badges' and 'reputation scores.' We will conduct a randomized factorial controlled trial among all the 904 eligible medical doctors currently registered to MacPLUS FS at the hospitals affiliated with McMaster University, Canada. Postgraduate trainees (n=429) and clinical faculty/staff (n=475) will be randomized to each of the three following interventions in a factorial design (AxBxC). Utilization will be continuously recorded through clinicians’ accounts that track logins and usage, down to the level of individual keystrokes. The primary outcome is the rate of searches per month per user during the six months of follow-up. Secondary outcomes, measured through the validated Impact Assessment Method questionnaire, include: utility of answers found (meeting clinicians’ information needs), use (application in practice), and perceived usefulness on patient outcomes. Built on effective models for the point

  18. Advanced Search

    African Journals Online (AJOL)

    Search tips: Search terms are case-insensitive; Common words are ignored; By default only articles containing all terms in the query are returned (i.e., AND is implied); Combine multiple words with OR to find articles containing either term; e.g., education OR research; Use parentheses to create more complex queries; e.g., ...

  19. Optimal intermittent search strategies

    Energy Technology Data Exchange (ETDEWEB)

    Rojo, F; Budde, C E [FaMAF, Universidad Nacional de Cordoba, Ciudad Universitaria, X5000HUA Cordoba (Argentina); Wio, H S [Instituto de Fisica de Cantabria, Universidad de Cantabria and CSIC E-39005 Santander (Spain)

    2009-03-27

    We study the search kinetics of a single fixed target by a set of searchers performing an intermittent random walk, jumping between different internal states. Exploiting concepts of multi-state and continuous-time random walks we have calculated the survival probability of a target up to time t, and have 'optimized' (minimized) it with regard to the transition probability among internal states. Our model shows that intermittent strategies always improve target detection, even for simple diffusion states of motion.

  20. Random-walk enzymes

    Science.gov (United States)

    Mak, Chi H.; Pham, Phuong; Afif, Samir A.; Goodman, Myron F.

    2015-09-01

    Enzymes that rely on random walk to search for substrate targets in a heterogeneously dispersed medium can leave behind complex spatial profiles of their catalyzed conversions. The catalytic signatures of these random-walk enzymes are the result of two coupled stochastic processes: scanning and catalysis. Here we develop analytical models to understand the conversion profiles produced by these enzymes, comparing an intrusive model, in which scanning and catalysis are tightly coupled, against a loosely coupled passive model. Diagrammatic theory and path-integral solutions of these models revealed clearly distinct predictions. Comparison to experimental data from catalyzed deaminations deposited on single-stranded DNA by the enzyme activation-induced deoxycytidine deaminase (AID) demonstrates that catalysis and diffusion are strongly intertwined, where the chemical conversions give rise to new stochastic trajectories that were absent if the substrate DNA was homogeneous. The C →U deamination profiles in both analytical predictions and experiments exhibit a strong contextual dependence, where the conversion rate of each target site is strongly contingent on the identities of other surrounding targets, with the intrusive model showing an excellent fit to the data. These methods can be applied to deduce sequence-dependent catalytic signatures of other DNA modification enzymes, with potential applications to cancer, gene regulation, and epigenetics.

  1. Project TEAMS (Talking about Eating, Activity, and Mutual Support: a randomized controlled trial of a theory-based weight loss program for couples

    Directory of Open Access Journals (Sweden)

    Amy A. Gorin

    2017-09-01

    Full Text Available Abstract Background Obesity risk is shared between spouses, yet existing weight loss programs focus on individuals and not the marital dyad. Given the interdependence of weight in couples, weight management outcomes might be improved by targeting joint weight loss and the creation of an interpersonal milieu that supports long-term behavior change. According to Self-Determination Theory (SDT, greater autonomous self-regulation of behaviors, and subsequently better treatment outcomes, are observed in needs supportive environments in which personally meaningful choice is supported and criticism and control are minimized. Correlational analyses confirm these pathways in weight management, with needs support from one’s spouse or partner emerging as a distinct predictor of weight loss success. Research is now needed to establish causal links and to develop and test weight loss interventions designed to facilitate the needs supportive behavior of spouses. Methods Project TEAMS (Talking about Eating, Activity, and Mutual Support is a randomized controlled trial testing a couples-based intervention, grounded in SDT, designed to change the social context of weight loss by training spouses to provide needs support for each other’s eating and physical activity behavior. Sixty-four couples will be randomized to either 6 months of behavioral weight loss treatment informed by SDT (SDT-WL or to 6 months of standard behavioral weight loss treatment (BWL. Couples will attend weekly sessions for 6 months and will be assessed at 0, 3, 6, and 12 months. By bolstering needs support, SDT-WL is predicted to increase autonomous self-regulation and perceived competence and produce greater weight loss and maintenance than standard behavioral treatment. Exploratory analyses will examine the SDT process model prediction that the influence of needs support on treatment outcomes will be mediated by autonomous self-regulation and perceived competence. Discussion This

  2. Mobile Link - a theory-based messaging intervention for improving sexual and reproductive health of female entertainment workers in Cambodia: study protocol of a randomized controlled trial.

    Science.gov (United States)

    Brody, Carinne; Tuot, Sovannary; Chhoun, Pheak; Swendenman, Dallas; Kaplan, Kathryn C; Yi, Siyan

    2018-04-19

    In Cambodia, HIV prevalence is concentrated in key populations including among female entertainment workers (FEWs) who may engage in direct or indirect sex work. Reaching FEWs with sexual and reproductive health (SRH) services has been difficult because of their hidden and stigmatized nature. Mobile-phone-based interventions may be an effective way to reach this population and connect them with the existing services. This article describes study design and implementation of a randomized controlled trial (RCT) of a mobile health intervention (the Mobile Link) aiming to improve SRH and related outcomes among FEWs in Cambodia. A two-arm RCT will be used to determine the effectiveness of a mobile-phone-based text/voice messaging intervention. The intervention will be developed through a participatory process. Focus group discussions and in-depth interviews have been conducted to inform and tailor behavior change theory-based text and voice messages. During the implementation phase, 600 FEWs will be recruited and randomly assigned into one of the two arms: (1) a control group and (2) a mobile phone message group (either text messages [SMS] or voice messages [VM], a delivery method chosen by participants). Participants in the control group will also receive a weekly monitoring survey, which will provide real-time information to implementing partners to streamline outreach efforts and be able to quickly identify geographic trends. The primary outcome measures will include self-reported HIV and sexually transmitted infections (STI) testing and treatment, condom use, contraceptive use, and gender-based violence (GBV). If the Mobile Link trial is successful, participants will report an increase in condom use, linkages to screening and treatment for HIV and STI, and contraception use as well as a reduction in GBV. This trial is unique in a number of ways. First, the option of participation mode (SMS or VM) allows participants to choose the message medium that best links them

  3. Project TEAMS (Talking about Eating, Activity, and Mutual Support): a randomized controlled trial of a theory-based weight loss program for couples.

    Science.gov (United States)

    Gorin, Amy A; Powers, Theodore A; Gettens, Katelyn; Cornelius, Talea; Koestner, Richard; Mobley, Amy R; Pescatello, Linda; Medina, Tania Huedo

    2017-09-29

    Obesity risk is shared between spouses, yet existing weight loss programs focus on individuals and not the marital dyad. Given the interdependence of weight in couples, weight management outcomes might be improved by targeting joint weight loss and the creation of an interpersonal milieu that supports long-term behavior change. According to Self-Determination Theory (SDT), greater autonomous self-regulation of behaviors, and subsequently better treatment outcomes, are observed in needs supportive environments in which personally meaningful choice is supported and criticism and control are minimized. Correlational analyses confirm these pathways in weight management, with needs support from one's spouse or partner emerging as a distinct predictor of weight loss success. Research is now needed to establish causal links and to develop and test weight loss interventions designed to facilitate the needs supportive behavior of spouses. Project TEAMS (Talking about Eating, Activity, and Mutual Support) is a randomized controlled trial testing a couples-based intervention, grounded in SDT, designed to change the social context of weight loss by training spouses to provide needs support for each other's eating and physical activity behavior. Sixty-four couples will be randomized to either 6 months of behavioral weight loss treatment informed by SDT (SDT-WL) or to 6 months of standard behavioral weight loss treatment (BWL). Couples will attend weekly sessions for 6 months and will be assessed at 0, 3, 6, and 12 months. By bolstering needs support, SDT-WL is predicted to increase autonomous self-regulation and perceived competence and produce greater weight loss and maintenance than standard behavioral treatment. Exploratory analyses will examine the SDT process model prediction that the influence of needs support on treatment outcomes will be mediated by autonomous self-regulation and perceived competence. This study addresses the fundamental importance of interpersonal

  4. Statistic methods for searching inundated radioactive entities

    International Nuclear Information System (INIS)

    Dubasov, Yu.V.; Krivokhatskij, A.S.; Khramov, N.N.

    1993-01-01

    The problem of searching flooded radioactive object in a present area was considered. Various models of the searching route plotting are discussed. It is shown that spiral route by random points from the centre of the area examined is the most efficient one. The conclusion is made that, when searching flooded radioactive objects, it is advisable to use multidimensional statistical methods of classification

  5. Structures and Spectroscopic Properties of F-(H2O) n with n = 1-10 Clusters from a Global Search Based On Density Functional Theory.

    Science.gov (United States)

    Shi, Ruili; Wang, Pengju; Tang, Lingli; Huang, Xiaoming; Chen, Yonggang; Su, Yan; Zhao, Jijun

    2018-04-05

    Using a genetic algorithm incorporated in density functional theory, we explore the ground state structures of fluoride anion-water clusters F - (H 2 O) n with n = 1-10. The F - (H 2 O) n clusters prefer structures in which the F - anion remains at the surface of the structure and coordinates with four water molecules, as the F - (H 2 O) n clusters have strong F - -H 2 O interactions as well as strong hydrogen bonds between H 2 O molecules. The strong interaction between the F - anion and adjacent H 2 O molecule leads to a longer O-H distance in the adjacent molecule than in an individual water molecule. The simulated infrared (IR) spectra of the F - (H 2 O) 1-5 clusters obtained via second-order vibrational perturbation theory (VPT2) and including anharmonic effects reproduce the experimental results quite well. The strong interaction between the F - anion and water molecules results in a large redshift (600-2300 cm -1 ) of the adjacent O-H stretching mode. Natural bond orbital (NBO) analysis of the lowest-energy structures of the F - (H 2 O) 1-10 clusters illustrates that charge transfer from the lone pair electron orbital of F - to the antibonding orbital of the adjacent O-H is mainly responsible for the strong interaction between the F - anion and water molecules, which leads to distinctly different geometric and vibrational properties compared with neutral water clusters.

  6. An introduction to information theory

    CERN Document Server

    Reza, Fazlollah M

    1994-01-01

    Graduate-level study for engineering students presents elements of modern probability theory, information theory, coding theory, more. Emphasis on sample space, random variables, capacity, etc. Many reference tables and extensive bibliography. 1961 edition.

  7. Autonomous search

    CERN Document Server

    Hamadi, Youssef; Saubion, Frédéric

    2012-01-01

    Autonomous combinatorial search (AS) represents a new field in combinatorial problem solving. Its major standpoint and originality is that it considers that problem solvers must be capable of self-improvement operations. This is the first book dedicated to AS.

  8. Exotics searches in ATLAS

    CERN Document Server

    Wang, Renjie; The ATLAS collaboration

    2017-01-01

    Many theories beyond the Standard Model predict new physics accessible by the LHC. The ATLAS experiment all have rigorous search programs ongoing with the aim to find indications for new physics involving state of the art analysis techniques. This talk reports on new results obtained using the pp collision data sample collected in 2015 and 2016 at the LHC with a centre-of-mass energy of 13 TeV.

  9. Theory-based interventions combining mental simulation and planning techniques to improve physical activity: Null results from two randomized controlled trials

    Directory of Open Access Journals (Sweden)

    Carine Meslot

    2016-11-01

    Full Text Available Interventions to assist individuals in initiating and maintaining regular participation in physical activity are not always effective. Psychological and behavioural theories advocate the importance of both motivation and volition in interventions to change health behaviour. Interventions adopting self-regulation strategies that foster motivational and volitional components may, therefore, have utility in promoting regular physical activity participation. We tested the efficacy of an intervention adopting motivational (mental simulation and volitional (implementation intentions components to promote a regular physical activity in two studies. Study 1 adopted a cluster randomised design students in which participants (n=92 were allocated to one of three conditions: mental simulation plus implementation intention, implementation intention only, or control. Study 2 adopted a 2 (mental simulation vs. no mental simulation x 2 (implementation intention vs. no implementation intention randomised controlled design in which fitness centre attendees (n=184 were randomly allocated one of four conditions: mental simulation only, implementation intention only, combined, or control. Physical activity behaviour was measured by self-report (Study 1 or fitness centre attendance (Study 2 at 4- (Studies 1 and 2 and 19- (Study 2 only week follow-up periods. Findings revealed no statistically significant main or interactive effects of the mental simulation and implementation intention conditions on physical activity outcomes in either study. Despite adopting protocols consistent with previous research, utilizing objective behavioural measures, and having sufficient statistical power, results provide evidence that, in contrast to previous findings, the motivational and volitional components are not effective in changing physical activity behaviour. Future research should focus on the format of the intervention components, test the effects of each component alone and

  10. School-Based Nutrition Education Intervention Using Social Cognitive Theory for Overweight and Obese Iranian Adolescent Girls: A Cluster Randomized Controlled Trial.

    Science.gov (United States)

    Bagherniya, Mohammad; Sharma, Manoj; Mostafavi Darani, Firoozeh; Maracy, Mohammad Reza; Safarian, Mohammad; Allipour Birgani, Ramesh; Bitarafan, Vida; Keshavarz, Seyed Ali

    2017-10-01

    Background Nowadays childhood obesity has become one the most challenging issue which is considered as a principle public health problem all around the world. This study was conducted with the aim of evaluating the impact of a 7-month school-based nutrition education intervention using social cognitive theory (SCT) to prevent obesity among overweight and obese adolescent girls. Method In this cluster randomized community trial after choosing schools, a total of 172 overweight and obese girl students participated in the study (87 in the intervention and 85 in the control group). A 7-month intervention based on SCT for students, their parents, and teachers was conducted. At baseline and end of the study, body mass index (BMI), waist circumstances (WCs), dietary intake, and psychological questionnaires regarding the SCT constructs were obtained. Results After 7 months, the mean of BMI and WCs reduced in the intervention group from 29.47 (4.05) to 28.5 (4.35) and from 89.65 (8.15) to 86.54 (9.76), respectively, but in comparison to the control group, they were not statistically significant ( p values .127 and .504, respectively). In the intervention group, nutritional behaviors and most of the psychological variables (self-efficacy, social support, intention, and situation) were improved in favor of the study and they were significant in comparison to the control group ( p < .05). Conclusion Although school-based nutrition education intervention using SCT did not change significantly BMI and WCs among the targeted population in this study, dietary habits as well as psychological factors improved significantly in the intervention group. This trial was registered in Iranian Registry of Clinical Trials, www.irct.ir (IRCT2013103115211N1).

  11. Higgs and SUSY searches at future colliders

    Indian Academy of Sciences (India)

    ... searches at future colliders, particularly comparing and contrasting the capabilities of LHC and next linear collider (NLC), including the aspects of Higgs searches in supersymmetric theories. I will also discuss how the search and study of sparticles other than the Higgs can be used to give information about the parameters ...

  12. An Optimized Forecasting Approach Based on Grey Theory and Cuckoo Search Algorithm: A Case Study for Electricity Consumption in New South Wales

    Directory of Open Access Journals (Sweden)

    Ping Jiang

    2014-01-01

    Full Text Available With rapid economic growth, electricity demand is clearly increasing. It is difficult to store electricity for future use; thus, the electricity demand forecast, especially the electricity consumption forecast, is crucial for planning and operating a power system. Due to various unstable factors, it is challenging to forecast electricity consumption. Therefore, it is necessary to establish new models for accurate forecasts. This study proposes a hybrid model, which includes data selection, an abnormality analysis, a feasibility test, and an optimized grey model to forecast electricity consumption. First, the original electricity consumption data are selected to construct different schemes (Scheme 1: short-term selection and Scheme 2: long-term selection; next, the iterative algorithm (IA and cuckoo search algorithm (CS are employed to select the best parameter of GM(1,1. The forecasted day is then divided into several smooth parts because the grey model is highly accurate in the smooth rise and drop phases; thus, the best scheme for each part is determined using the grey correlation coefficient. Finally, the experimental results indicate that the GM(1,1 optimized using CS has the highest forecasting accuracy compared with the GM(1,1 and the GM(1,1 optimized using the IA and the autoregressive integrated moving average (ARIMA model.

  13. Optimal intermittent search strategies: smelling the prey

    International Nuclear Information System (INIS)

    Revelli, J A; Wio, H S; Rojo, F; Budde, C E

    2010-01-01

    We study the kinetics of the search of a single fixed target by a searcher/walker that performs an intermittent random walk, characterized by different states of motion. In addition, we assume that the walker has the ability to detect the scent left by the prey/target in its surroundings. Our results, in agreement with intuition, indicate that the prey's survival probability could be strongly reduced (increased) if the predator is attracted (or repelled) by the trace left by the prey. We have also found that, for a positive trace (the predator is guided towards the prey), increasing the inhomogeneity's size reduces the prey's survival probability, while the optimal value of α (the parameter that regulates intermittency) ceases to exist. The agreement between theory and numerical simulations is excellent.

  14. Optimal intermittent search strategies: smelling the prey

    Energy Technology Data Exchange (ETDEWEB)

    Revelli, J A; Wio, H S [Instituto de Fisica de Cantabria, Universidad de Cantabria and CSIC, E-39005 Santander (Spain); Rojo, F; Budde, C E [Fa.M.A.F., Universidad Nacional de Cordoba, Ciudad Universitaria, X5000HUA Cordoba (Argentina)

    2010-05-14

    We study the kinetics of the search of a single fixed target by a searcher/walker that performs an intermittent random walk, characterized by different states of motion. In addition, we assume that the walker has the ability to detect the scent left by the prey/target in its surroundings. Our results, in agreement with intuition, indicate that the prey's survival probability could be strongly reduced (increased) if the predator is attracted (or repelled) by the trace left by the prey. We have also found that, for a positive trace (the predator is guided towards the prey), increasing the inhomogeneity's size reduces the prey's survival probability, while the optimal value of {alpha} (the parameter that regulates intermittency) ceases to exist. The agreement between theory and numerical simulations is excellent.

  15. Search strategies

    Science.gov (United States)

    Oliver, B. M.

    Attention is given to the approaches which would provide the greatest chance of success in attempts related to the discovery of extraterrestrial advanced cultures in the Galaxy, taking into account the principle of least energy expenditure. The energetics of interstellar contact are explored, giving attention to the use of manned spacecraft, automatic probes, and beacons. The least expensive approach to a search for other civilizations involves a listening program which attempts to detect signals emitted by such civilizations. The optimum part of the spectrum for the considered search is found to be in the range from 1 to 2 GHz. Antenna and transmission formulas are discussed along with the employment of matched gates and filters, the probable characteristics of the signals to be detected, the filter-signal mismatch loss, surveys of the radio sky, the conduction of targeted searches.

  16. Search for negative U in the Ba1-xKxBi1-yPbyO3 system using constrained density-functional theory

    International Nuclear Information System (INIS)

    Vielsack, G.; Weber, W.

    1996-01-01

    Calculations using constrained density-functional theory have been carried out for the Ba 1-x K x Bi 1-y Pb y O 3 system, using a full-potential linearized-augmented-plane-wave method and employing fcc supercell geometries with two formula units. The results have been mapped onto Hubbard-type models in order to extract values of interaction parameters U at the Bi sites. Two different mapping procedures have been utilized. The first one is the standard method, based on the comparison of total-energy curvatures. The second method, proposed in the present work, relies on the analysis of single particle energies and yields much smaller numerical errors. For BaBiO 3 interaction parameters are obtained for the following models: (i) s and p orbitals at Bi and p orbitals at O sites. Here, U s =3.1±0.4 eV, U sp =1.4±0.2 eV, U p =2.2±0.4 eV are found, (ii) s(Bi) and p(O) orbitals, yielding U s =1.9±0.7 eV, and (iii) an effective one-band model, leading to U s =0.6±0.4 eV. Further studies have been performed for breathing distorted BaBiO 3 and for various Ba 1-x K x Bi 1-y Pb y O 3 alloys using virtual crystal approximations. The resulting U values are somewhat larger than for pure BaBiO 3 . Thus, in all cases, the values of Bi U parameters are found to be positive. There is no indication of a negative U of electronic origin. copyright 1996 The American Physical Society

  17. Leo Szilard Lectureship Award Talk - Universal Scaling Laws from Cells to Cities; A Physicist's Search for Quantitative, Unified Theories of Biological and Social Structure and Dynamics

    Science.gov (United States)

    West, Geoffrey

    2013-04-01

    Many of the most challenging, exciting and profound questions facing science and society, from the origins of life to global sustainability, fall under the banner of ``complex adaptive systems.'' This talk explores how scaling can be used to begin to develop physics-inspired quantitative, predictive, coarse-grained theories for understanding their structure, dynamics and organization based on underlying mathematisable principles. Remarkably, most physiological, organisational and life history phenomena in biology and socio-economic systems scale in a simple and ``universal'' fashion: metabolic rate scales approximately as the 3/4-power of mass over 27 orders of magnitude from complex molecules to the largest organisms. Time-scales (such as lifespans and growth-rates) and sizes (such as genome lengths and RNA densities) scale with exponents which are typically simple multiples of 1/4, suggesting that fundamental constraints underlie much of the generic structure and dynamics of living systems. These scaling laws follow from dynamical and geometrical properties of space-filling, fractal-like, hierarchical branching networks, presumed optimised by natural selection. This leads to a general framework that potentially captures essential features of diverse systems including vasculature, ontogenetic growth, cancer, aging and mortality, sleep, cell size, and DNA nucleotide substitution rates. Cities and companies also scale: wages, profits, patents, crime, disease, pollution, road lengths scale similarly across the globe, reflecting underlying universal social network dynamics which point to general principles of organization transcending their individuality. These have dramatic implications for global sustainability: innovation and wealth creation that fuel social systems, left unchecked, potentially sow the seeds for their inevitable collapse.

  18. En busca de una teoría útil de la innovación In search of a useful innovation theory

    Directory of Open Access Journals (Sweden)

    Winter Sidney

    2000-06-01

    Full Text Available Con este artículo clásico, los profesores Nelson Y Winter dieron inicio a la corriente evolutiva de estirpe schumpeteriana para el análisis de los procesos de innovación tecnológica. Su propuesta metodológica mostró la necesidad de abordar el cambio tecnológico con un enfoque menos formal -como el que aún predomina en la economía y de elaborar una teoría fundamentada empíricamente que explicara los procesos de innovación concretos y reales, como el que ilustra el ejemplo de la química de colorantes sintéticos. Este trabajo muestra que este enfoque permite integrar elementos de otras disciplinas, los cuales no se pueden reducir al postulado de la racionalidad optimizadora. Este texto es un documento fundamental en la historia del análisis del cambio técnico y la innovación tecnológica, y es un punto de referencia imprescindible para todo aquél que se interese en el tema.With this classic article, Professors Nelson and Winter launched the evolutionary approach, of Schumpeterian lineage, for the analysis of technological innovation processes. Their methodological proposal showed the need to tackle technological change with a less formal approach than that which is still dominant in economics, and to construct an empirically founded theory which would explain real, concrete innovation processes, such as the one they illustrate with the example of the chemistry of synthetic colorants. This paper showsthat this approach allows the integration of elements of other disciplines,which cannot be reduced to the postulate of optimizing rationality. This text is a fundamental document in the history of the analysis of technical change and technological innovation, andis an essential point of reference for all who are interested in thetopic.

  19. Intermittency and random matrices

    Science.gov (United States)

    Sokoloff, Dmitry; Illarionov, E. A.

    2015-08-01

    A spectacular phenomenon of intermittency, i.e. a progressive growth of higher statistical moments of a physical field excited by an instability in a random medium, attracted the attention of Zeldovich in the last years of his life. At that time, the mathematical aspects underlying the physical description of this phenomenon were still under development and relations between various findings in the field remained obscure. Contemporary results from the theory of the product of independent random matrices (the Furstenberg theory) allowed the elaboration of the phenomenon of intermittency in a systematic way. We consider applications of the Furstenberg theory to some problems in cosmology and dynamo theory.

  20. Finger Search in Grammar-Compressed Strings

    DEFF Research Database (Denmark)

    Bille, Philip; Christiansen, Anders Roy; Cording, Patrick Hagge

    2016-01-01

    random access, that is, given a position in the original uncompressed string report the character at that position. In this paper we study the random access problem with the finger search property, that is, the time for a random access query should depend on the distance between a specified index f...

  1. Exploration Opportunity Search of Near-earth Objects Based on Analytical Gradients

    Science.gov (United States)

    Ren, Yuan; Cui, Ping-Yuan; Luan, En-Jie

    2008-07-01

    The problem of search of opportunity for the exploration of near-earth minor objects is investigated. For rendezvous missions, the analytical gradients of the performance index with respect to the free parameters are derived using the variational calculus and the theory of state-transition matrix. After generating randomly some initial guesses in the search space, the performance index is optimized, guided by the analytical gradients, leading to the local minimum points representing the potential launch opportunities. This method not only keeps the global-search property of the traditional method, but also avoids the blindness in the latter, thereby increasing greatly the computing speed. Furthermore, with this method, the searching precision could be controlled effectively.

  2. Generalized Free-Surface Effect and Random Vibration Theory: a new tool for computing moment magnitudes of small earthquakes using borehole data

    Science.gov (United States)

    Malagnini, Luca; Dreger, Douglas S.

    2016-07-01

    Although optimal, computing the moment tensor solution is not always a viable option for the calculation of the size of an earthquake, especially for small events (say, below Mw 2.0). Here we show an alternative approach to the calculation of the moment-rate spectra of small earthquakes, and thus of their scalar moments, that uses a network-based calibration of crustal wave propagation. The method works best when applied to a relatively small crustal volume containing both the seismic sources and the recording sites. In this study we present the calibration of the crustal volume monitored by the High-Resolution Seismic Network (HRSN), along the San Andreas Fault (SAF) at Parkfield. After the quantification of the attenuation parameters within the crustal volume under investigation, we proceed to the spectral correction of the observed Fourier amplitude spectra for the 100 largest events in our data set. Multiple estimates of seismic moment for the all events (1811 events total) are obtained by calculating the ratio of rms-averaged spectral quantities based on the peak values of the ground velocity in the time domain, as they are observed in narrowband-filtered time-series. The mathematical operations allowing the described spectral ratios are obtained from Random Vibration Theory (RVT). Due to the optimal conditions of the HRSN, in terms of signal-to-noise ratios, our network-based calibration allows the accurate calculation of seismic moments down to Mw < 0. However, because the HRSN is equipped only with borehole instruments, we define a frequency-dependent Generalized Free-Surface Effect (GFSE), to be used instead of the usual free-surface constant F = 2. Our spectral corrections at Parkfield need a different GFSE for each side of the SAF, which can be quantified by means of the analysis of synthetic seismograms. The importance of the GFSE of borehole instruments increases for decreasing earthquake's size because for smaller earthquakes the bandwidth available

  3. Individual differences in the efficacy of a short theory of mind intervention for children with autism spectrum disorder: a randomized controlled trial

    OpenAIRE

    Hoddenbach Elske; Koot Hans M; Clifford Pamela; Gevers Carolien; Clauser Cassandra; Boer Frits; Begeer Sander

    2012-01-01

    Abstract Background Having a ‘theory of mind’, or having the ability to attribute mental states to oneself or others, is considered one of the most central domains of impairment among children with an autism spectrum disorder (ASD). Many interventions focus on improving theory of mind skills in children with ASD. Nonetheless, the empirical evidence for the effect of these interventions is limited. The main goal of this study is to examine the effectiveness of a short theory of mind interventi...

  4. Individual differences in the efficacy of a short theory of mind intervention for children with autism spectrum disorder: a randomized controlled trial

    NARCIS (Netherlands)

    Hoddenbach, Elske; Koot, Hans M.; Clifford, Pamela; Gevers, Carolien; Clauser, Cassandra; Boer, Frits; Begeer, Sander

    2012-01-01

    Background: Having a 'theory of mind', or having the ability to attribute mental states to oneself or others, is considered one of the most central domains of impairment among children with an autism spectrum disorder (ASD). Many interventions focus on improving theory of mind skills in children

  5. The effect of implementing cognitive load theory-based design principles in virtual reality simulation training of surgical skills: a randomized controlled trial

    DEFF Research Database (Denmark)

    Andersen, Steven Arild Wuyts; Mikkelsen, Peter Trier; Konge, Lars

    2016-01-01

    Cognitive overload can inhibit learning, and cognitive load theory-based instructional design principles can be used to optimize learning situations. This study aims to investigate the effect of implementing cognitive load theory-based design principles in virtual reality simulation training...

  6. Neural Network and Evidence Theory Based Improvements on Submarine Search Strategy of CGF%基于神经网络及证据理论的 CGF 搜潜策略改进

    Institute of Scientific and Technical Information of China (English)

    宦婧; 滕克难; 唐金国

    2013-01-01

    Since the Computer Generated Force ( CGF) can not take full advantage of battlefield information to optimize CGF submarine search strategy in the cooperative anti -submarine combat,the information fusion technology was introduced into the anti-submarine warfare simulation based on the effective interaction of the information between CGF .The basic confidence assignment of the evidence information was obtained using Back Propagation (BP) artificial neural network,and the information from antisubmarine CGF was synthesized by using the improved DS evidence theory .And thus the anti-submarine CGF mobile strategy was improved . Simulation results show that the introduction of artificial neural network and information fusion technology in antisubmarine CGF submarine search process can improve the anti -submarine efficiency .%针对目前多计算机生成兵力( Computer Generated Force ,CGF)协同反潜中无法充分利用战场信息实现CGF搜潜策略优化的问题,在CGF间可有效实现信息交互的前提下,将信息融合技术引入到反潜作战仿真中;利用BP (Back Propagation)人工神经网络获取证据信息的基本置信分配,通过改进的D-S(Dempster-Shafer)证据理论对反潜CGF获取的信息进行综合,以此改进反潜CGF的移动策略。仿真实验表明,在反潜CGF搜潜过程中引入人工神经网络和信息融合技术,可有效提高CGF搜潜的成功率。

  7. Initialization and Restart in Stochastic Local Search: Computing a Most Probable Explanation in Bayesian Networks

    Science.gov (United States)

    Mengshoel, Ole J.; Wilkins, David C.; Roth, Dan

    2010-01-01

    For hard computational problems, stochastic local search has proven to be a competitive approach to finding optimal or approximately optimal problem solutions. Two key research questions for stochastic local search algorithms are: Which algorithms are effective for initialization? When should the search process be restarted? In the present work we investigate these research questions in the context of approximate computation of most probable explanations (MPEs) in Bayesian networks (BNs). We introduce a novel approach, based on the Viterbi algorithm, to explanation initialization in BNs. While the Viterbi algorithm works on sequences and trees, our approach works on BNs with arbitrary topologies. We also give a novel formalization of stochastic local search, with focus on initialization and restart, using probability theory and mixture models. Experimentally, we apply our methods to the problem of MPE computation, using a stochastic local search algorithm known as Stochastic Greedy Search. By carefully optimizing both initialization and restart, we reduce the MPE search time for application BNs by several orders of magnitude compared to using uniform at random initialization without restart. On several BNs from applications, the performance of Stochastic Greedy Search is competitive with clique tree clustering, a state-of-the-art exact algorithm used for MPE computation in BNs.

  8. Internet Search Engines

    OpenAIRE

    Fatmaa El Zahraa Mohamed Abdou

    2004-01-01

    A general study about the internet search engines, the study deals main 7 points; the differance between search engines and search directories, components of search engines, the percentage of sites covered by search engines, cataloging of sites, the needed time for sites appearance in search engines, search capabilities, and types of search engines.

  9. Misuse of randomization

    DEFF Research Database (Denmark)

    Liu, Jianping; Kjaergard, Lise Lotte; Gluud, Christian

    2002-01-01

    The quality of randomization of Chinese randomized trials on herbal medicines for hepatitis B was assessed. Search strategy and inclusion criteria were based on the published protocol. One hundred and seventy-six randomized clinical trials (RCTs) involving 20,452 patients with chronic hepatitis B...... virus (HBV) infection were identified that tested Chinese medicinal herbs. They were published in 49 Chinese journals. Only 10% (18/176) of the studies reported the method by which they randomized patients. Only two reported allocation concealment and were considered as adequate. Twenty percent (30...

  10. Random a-adic groups and random net fractals

    Energy Technology Data Exchange (ETDEWEB)

    Li Yin [Department of Mathematics, Nanjing University, Nanjing 210093 (China)], E-mail: Lyjerry7788@hotmail.com; Su Weiyi [Department of Mathematics, Nanjing University, Nanjing 210093 (China)], E-mail: suqiu@nju.edu.cn

    2008-08-15

    Based on random a-adic groups, this paper investigates the relationship between the existence conditions of a positive flow in a random network and the estimation of the Hausdorff dimension of a proper random net fractal. Subsequently we describe some particular random fractals for which our results can be applied. Finally the Mauldin and Williams theorem is shown to be very important example for a random Cantor set with application in physics as shown in E-infinity theory.

  11. Clinician search behaviors may be influenced by search engine design.

    Science.gov (United States)

    Lau, Annie Y S; Coiera, Enrico; Zrimec, Tatjana; Compton, Paul

    2010-06-30

    Searching the Web for documents using information retrieval systems plays an important part in clinicians' practice of evidence-based medicine. While much research focuses on the design of methods to retrieve documents, there has been little examination of the way different search engine capabilities influence clinician search behaviors. Previous studies have shown that use of task-based search engines allows for faster searches with no loss of decision accuracy compared with resource-based engines. We hypothesized that changes in search behaviors may explain these differences. In all, 75 clinicians (44 doctors and 31 clinical nurse consultants) were randomized to use either a resource-based or a task-based version of a clinical information retrieval system to answer questions about 8 clinical scenarios in a controlled setting in a university computer laboratory. Clinicians using the resource-based system could select 1 of 6 resources, such as PubMed; clinicians using the task-based system could select 1 of 6 clinical tasks, such as diagnosis. Clinicians in both systems could reformulate search queries. System logs unobtrusively capturing clinicians' interactions with the systems were coded and analyzed for clinicians' search actions and query reformulation strategies. The most frequent search action of clinicians using the resource-based system was to explore a new resource with the same query, that is, these clinicians exhibited a "breadth-first" search behaviour. Of 1398 search actions, clinicians using the resource-based system conducted 401 (28.7%, 95% confidence interval [CI] 26.37-31.11) in this way. In contrast, the majority of clinicians using the task-based system exhibited a "depth-first" search behavior in which they reformulated query keywords while keeping to the same task profiles. Of 585 search actions conducted by clinicians using the task-based system, 379 (64.8%, 95% CI 60.83-68.55) were conducted in this way. This study provides evidence that

  12. Search for Odderon in theory and experiment

    CERN Document Server

    Fazal, E Aleem; Rashid, H; Saeed, M A; Tahir, S A; 10.1142/S0217751X0401969X

    2004-01-01

    The presence of Odderon at high energy has been in question for quite some time. We have confronted the Odderon description to the available data especially for pp and pp scattering including the most recent measurements by UA4/2, E710, CDF and E811 Collaborations. The Odderon in perturbative and nonperturbative QCD has also been discussed along with some phenomenological approaches. A comparison of the Odderon description with other models has also been made for p (p)p data including the measurements from cosmic ray, which corresponds to the LHC energy of 14 TeV. Our study especially focuses on the measurements at RHIC and LHC and the presence or otherwise of Odderon.

  13. Introduction to game theory

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The basic ideas of game theory were originated from the problems of maximum and minimum given by J.Yon Neumann in 1928. Later, wars accelerated the study of game theory, there are many developments that contributed to the advancement of game theory, many problems of optimum appeared in economic development process. Scientists applied mathematic methods to studying game theory to make the theory more profound and perfect. The axiomatic structure of game theory was nearly complete in 1944. The path of the development of game theory started from finite to infinite, from two players to many players, from expressing gains with quantity to showing the ending of game theory with abstract result, and from certainty problems to random problems. Thus development of game theory is closely related to the economic development. In recent years, the research on the non-differentiability of Shapley value posed by Belgian Mertens is one of the advanced studies in game theory.

  14. Quantum potential theory

    CERN Document Server

    Schürmann, Michael

    2008-01-01

    This volume contains the revised and completed notes of lectures given at the school "Quantum Potential Theory: Structure and Applications to Physics," held at the Alfried-Krupp-Wissenschaftskolleg in Greifswald from February 26 to March 10, 2007. Quantum potential theory studies noncommutative (or quantum) analogs of classical potential theory. These lectures provide an introduction to this theory, concentrating on probabilistic potential theory and it quantum analogs, i.e. quantum Markov processes and semigroups, quantum random walks, Dirichlet forms on C* and von Neumann algebras, and boundary theory. Applications to quantum physics, in particular the filtering problem in quantum optics, are also presented.

  15. Simulation of visual search in the natural 2-D situation

    OpenAIRE

    Blanka Borin

    2004-01-01

    The goal of this research was to imitate the process of visual search in a natural two-dimensional situation and also to investigate the influence of variable features on the speed of the visual search. The experiment was designed upon one of the most influential theories in the research field of the visual search phenomenon – The Feature Integration Theory (Treisman, 1982). Although the FIT theory claims, that in case of a larger number of synchronous targets the mechanism of attention...

  16. Job shop scheduling by local search

    NARCIS (Netherlands)

    Vaessens, R.J.M.; Aarts, E.H.L.; Lenstra, J.K.

    1994-01-01

    We survey solution methods for the job shop scheduling problem with an emphasis on local search. We discuss both cleterministic and randomized local search methods as well as the applied neighborhoods. We compare the computational performance of the various methods in terms of their effectiveness

  17. BSM searches (SUSY and Exotic) from ATLAS

    CERN Document Server

    ATLAS Collaboration; The ATLAS collaboration

    2015-01-01

    Searches for new physics beyond the Standard Model (SM) at the LHC are mainly driven by two approaches: a signature-based search where one looks for a deviation from the SM prediction in event yield or kinematic properties, and a more theory-oriented approach where the search is designed to look for specific signatures/topologies predicted by certain beyond standard model (BSM ) scenarios. Typical examples for the latter are searches for Supersymmetry and other BSM theories with extended symmetries. Supersymmetry predicts a new partner for every SM particle. An extension to the SM by introducing new gauge or global symmetries (including in Hidden Sector) usually leads to the presence of new heavy gauge bosons. Extensive searches for such particles have been performed in ATLAS at LHC in the context of Supersymmetry, Extended Gauge models, Technicolor, Little Higgs, Extra Dimensions, Left-Right symmetric models, and many other BSM scenarios. Highlights from these searches are presented.

  18. Signatures of active and passive optimized Lévy searching in jellyfish.

    Science.gov (United States)

    Reynolds, Andy M

    2014-10-06

    Some of the strongest empirical support for Lévy search theory has come from telemetry data for the dive patterns of marine predators (sharks, bony fishes, sea turtles and penguins). The dive patterns of the unusually large jellyfish Rhizostoma octopus do, however, sit outside of current Lévy search theory which predicts that a single search strategy is optimal. When searching the water column, the movement patterns of these jellyfish change over time. Movement bouts can be approximated by a variety of Lévy and Brownian (exponential) walks. The adaptive value of this variation is not known. On some occasions movement pattern data are consistent with the jellyfish prospecting away from a preferred depth, not finding an improvement in conditions elsewhere and so returning to their original depth. This 'bounce' behaviour also sits outside of current Lévy walk search theory. Here, it is shown that the jellyfish movement patterns are consistent with their using optimized 'fast simulated annealing'--a novel kind of Lévy walk search pattern--to locate the maximum prey concentration in the water column and/or to locate the strongest of many olfactory trails emanating from more distant prey. Fast simulated annealing is a powerful stochastic search algorithm for locating a global maximum that is hidden among many poorer local maxima in a large search space. This new finding shows that the notion of active optimized Lévy walk searching is not limited to the search for randomly and sparsely distributed resources, as previously thought, but can be extended to embrace other scenarios, including that of the jellyfish R. octopus. In the presence of convective currents, it could become energetically favourable to search the water column by riding the convective currents. Here, it is shown that these passive movements can be represented accurately by Lévy walks of the type occasionally seen in R. octopus. This result vividly illustrates that Lévy walks are not necessarily

  19. Firm Search for External Knowledge

    DEFF Research Database (Denmark)

    Sofka, Wolfgang; Grimpe, Christoph

    2012-01-01

    ignored the institutional context that provides or denies access to external knowledge at the country level. Combining institutional and knowledge search theory, we suggest that the market orientation of the institutional environment and the magnitude of institutional change influence when firms begin......The innovation performance of modern firms is increasingly determined by their ability to search and absorb external knowledge. However, after a certain threshold firms "oversearch" their environment and innovation performance declines. In this paper, we argue that prior literature has largely...... to experience the negative performance effects of oversearch. Based on a comprehensive sample of almost 8,000 firms from ten European countries, we find that institutions matter considerably for firms' search activity. Higher market orientation of institutions increases the effectiveness of firms' search...

  20. A comparison of random walks in dependent random environments

    NARCIS (Netherlands)

    Scheinhardt, Willem R.W.; Kroese, Dirk

    We provide exact computations for the drift of random walks in dependent random environments, including $k$-dependent and moving average environments. We show how the drift can be characterized and evaluated using Perron–Frobenius theory. Comparing random walks in various dependent environments, we