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A new method to measure complexity in binary or weighted networks and applications to functional connectivity in the human brain

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BMC BIOINFORMATICS 2016年第1期17卷 1-18页

作者： Hahn, Klaus Massopust, Peter R. Prigarin, Sergei HMGU German Res Ctr Environm Hlth Inst Computat Biol Ingolstadter Landstr 1 D-85764 Neuherberg Germany Tech Univ Munich Ctr Math Res Unit M6 D-85747 Garching Germany Novosibirsk State Univ Inst Computat Math & Math Geophys Siberian Branch Russian Acad Sci Novosibirsk 630090 Russia

Background: Networks or graphs play an important role in the biological sciences. Protein interaction networks and metabolic networks support the understanding of basic cellular mechanisms. In the human brain, networks of functional or structural connectivity model the information-flow between cortex regions. In this context, measures of network properties are needed. We propose a new measure, Ndim, estimating the complexity of arbitrary networks. This measure is based on a fractal dimension, which is similar to recently introduced box-covering dimensions. However, box-covering dimensions are only applicable to fractal networks. The construction of these network-dimensions relies on concepts proposed to measure fractality or complexity of irregular sets in R-n. Results: The network measure Ndim grows with the proliferation of increasing network connectivity and is essentially determined by the cardinality of a maximum k-clique, where k is the characteristic path length of the network. Numerical applications to lattice-graphs and to fractal and non-fractal graph models, together with formal proofs show, that Ndim estimates a dimension of complexity for arbitrary graphs. Box-covering dimensions for fractal graphs rely on a linear log-log plot of minimum numbers of covering subgraph boxes versus the box sizes. We demonstrate the affinity between Ndim and the fractal box-covering dimensions but also that Ndim extends the concept of a fractal dimension to networks with non-linear log-log plots. Comparisons of Ndim with topological measures of complexity ( cost and efficiency) show that Ndim has larger informative power. Three different methods to apply Ndim to weighted networks are finally presented and exemplified by comparisons of functional brain connectivity of healthy and depressed subjects. Conclusion: We introduce a new measure of complexity for networks. We show that Ndim has the properties of a dimension and overcomes several limitations of presently used topolo

关键词： Network analysis Complexity measure computational algorithm Fractal dimension Human brain application Functional connectivity

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Energy balance analysis of wind-based pumped hydro storage systems in remote island electrical networks

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APPLIED ENERGY 2010年第8期87卷 2427-2437页

作者： Kaldellis, J. K. Kapsali, M. Kavadias, K. A. TEI Piraeus Lab Soft Energy Applicat & Environm Protect Athens 12201 Greece

The introduction of pumped hydro storage (PHS) systems in isolated electrical grids, such as those found in island regions, appears to be a promising solution that is able to face both the high electricity production cost and the continuously increasing power demand encountered in these areas In this context, the current work presents a methodology for the sizing of PHS systems that exploit the excess wind energy amounts produced by local wind farms, otherwise rejected due to imposed electrical grid limitations. The methodology is accordingly applied to the Greek island of Lesbos Initially, a calculation of the wind power penetration ability to the local grid is carried out and the corresponding curtailments of existing and future wind farms are determined. An integrated computational algorithm is then presented which simulates the operation of the system during an entire year and gives in detail the hourly operational status as well as the various energy losses of the system main components. Based on the application results obtained, the ability of the wind energy to remarkably contribute to the electrification of the remote islands becomes evident. (C) 2010 Elsevier Ltd. All rights reserved.

关键词： Wind power penetration Wind power curtailments computational algorithm Electricity generation cost Renewable energy storage

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A model for the statistical design of multivariate control charts with multiple control regions

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APPLIED MATHEMATICS AND COMPUTATION 2000年第1期109卷 73-91页

作者： Jolayemi, JK Univ Zululand Dept Math Sci ZA-3886 Kwa Dlangezwa South Africa

This paper develops a statistical model for the design of multivariate control charts with multiple control regions (MCCMCR). The model produces the sample size and values of the control limits needed for the operations of MCCMCR. It allows the consumers and the producers to specify desired values for the risks and power functions that have the greatest effects on the efficiency of the chart. Numerical examples are given to illustrate the model and to study the properties of MCCMCR. (C) 2000 Elsevier Science Inc. All rights reserved.

关键词： multivariate control charts sample size control-limit constants assignable causes computational algorithm

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Should You Trust Your Money to a Robot?

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BIG DATA 2015年第2期3卷 55-58页

作者： Dhar, Vasant NYU Stern Sch Business New York NY 10011 USA

Financial markets emanate massive amounts of data from which machines can, in principle, learn to invest with minimal initial guidance from humans. I contrast human and machine strengths and weaknesses in making investment decisions. The analysis reveals areas in the investment landscape where machines are already very active and those where machines are likely to make significant inroads in the next few years.

关键词： Artificial intelligence Big data computational algorithm Robotics

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Reconstructing gene regulatory networks in single-cell transcriptomic data analysis

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Zoological Research 2020年第6期41卷 599-604页

作者： Hao Dai Qi-Qi Jin Lin Li Luo-Nan Chen Key Laboratory of Systems Biology Shanghai Institute of Biochemistry and Cell BiologyCenter for Excellence in Molecular Cell ScienceChinese Academy of SciencesShanghai 200031China Institute of Brain-Intelligence Technology Zhangjiang LaboratoryShanghai 201210China University of Chinese Academy of Sciences Beijing 100049China School of Life Science and Technology ShanghaiTech UniversityShanghai 201210China Key Laboratory of Systems Biology Hangzhou Institute for Advanced StudyUniversity of Chinese Academy of SciencesChinese Academy of SciencesHangzhouZhejiang 310024China Center for Excellence in Animal Evolution and Genetics Chinese Academy of SciencesKunmingYunnan 650223China

Gene regulatory networks play pivotal roles in our understanding of biological processes/mechanisms at the molecular *** studies have developed sample-specific or cell-type-specific gene regulatory networks from single-cell transcriptomic data based on a large amount of cell ***,we review the state-of-the-art computational algorithms and describe various applications of gene regulatory networks in biological studies.

关键词： Gene regulatory network Single-cell RNA sequencing computational algorithm Sample-specificnetwork Cell-type-specific network Cell-specific network

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A method for dynamic response analysis of time-variant discrete systems

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COMPUTERS & STRUCTURES 2000年第4期76卷 545-550页

作者： Kucharski, T Gdansk Tech Univ Dept Mech Engn PL-80952 Gdansk Poland

A method is proposed for analysing the transient response of structures when variation with respect to time of the stiffness and damping coefficients are taken into account. The state-variable technique is employed to formulate the dynamic equilibrium equation for the time-variant system. Excitation is represented as a series of impulses. It allows introduction of virtual initial conditions which are equivalent to the impulse excitations in the state space equations. The effective method for evaluation of a state transition matrix is used. Numerical tests of an illustrative example demonstrate the validity and effectiveness of the approach suggested in this paper. The method has great advantages when the behaviour of the semi-active system is calculated and the optimal control of the systems is simulated. (C) 2000 Elsevier Science Ltd. All rights reserved.

关键词： method for dynamic analysis computational algorithm computer simulation semi-active control system semi-active suspension

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A novel algorithm for computing autocorrelation of randomly sampled sequences

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CIRCUITS SYSTEMS AND SIGNAL PROCESSING 1999年第6期18卷 525-537页

作者： Lo, KC Hong Kong Polytech Univ Dept Elect & Informat Engn Kowloon Peoples R China

Random sampling is one of the methods used to achieve sub-Nyquist sampling. This paper proposes a novel algorithm to evaluate the circular autocorrelation of a randomly sampled sequence, from which its power density spectrum can be obtained. With uniform, sampling, the size of each lag (the step size) for computing an autocorrelation of a sequence is the same as the sampling period. When random sampling is adopted, the step size should be chosen such that the highest-frequency component of interest contained in a sequence can be accommodated. To find overlaps between a time sequence and its shifted version, an appropriate window is opened in one of the time sequences. To speed up the process, a marker is set to limit the range of searching for overlaps. The proposed method of estimating the power spectrum via autocorrelation is comparable in terms of accuracy and signal-to-noise ratio (SNR) to the conventional point rule. The techniques introduced can also apply to other operations for randomly sampled sequences.

关键词： random sampling digital signal processing spectral estimation computational algorithm

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An algorithm for mean residual life computation of (n - k + 1)-out-of-n systems: An application of exponentiated Weibull distribution

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APPLIED MATHEMATICS AND COMPUTATION 2011年第19期217卷 7806-7811页

作者： Gurler, Selma Capar, Sedat Dokuz Eylul Univ Fac Sci Dept Stat TR-35160 Buca Izmir Turkey

In this paper, we establish an algorithm for the computation of the mean residual life of a (n - k + 1)-out-of-n system in the case of independent but not necessarily identically distributed lifetimes of the components. An application for the exponentiated Weibull distribution is given to study the effect of various parameters on the mean residual life of the system. Also the relationship between the mean residual life for the system and that of its components is investigated. (C) 2011 Elsevier Inc. All rights reserved.

关键词： (n - k+1)-out-of-n systems Mean residual life function Permanents computational algorithm

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Solving posynomial geometric programming problems via generalized linear programming

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computational OPTIMIZATION AND APPLICATIONS 2002年第1期21卷 95-109页

作者： Rajgopal, J Bricker, DL Univ Pittsburgh Dept Ind Engn Pittsburgh PA 15261 USA Univ Iowa Dept Ind Engn & Management Iowa City IA 52242 USA

This paper revisits an efficient procedure for solving posynomial geometric programming (GP) problems, which was initially developed by Avriel et al. The procedure, which used the concept of condensation, was embedded within an algorithm for the more general (signomial) GP problem. It is shown here that a computationally equivalent dual-based algorithm may be independently derived based on some more recent work where the GP primal-dual pair was reformulated as a set of inexact linear programs. The constraint structure of the reformulation provides insight into why the algorithm is successful in avoiding all of the computational problems traditionally associated with dual-based algorithms. Test results indicate that the algorithm can be used to successfully solve large-scale geometric programming problems on a desktop computer.

关键词： geometric programming column generation linearization nonlinear optimization computational algorithm

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SOLUTION OF OPTIMAL LOAD FLOW PROBLEM BY MODIFIED RECURSIVE QUADRATIC-PROGRAMMING METHOD

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IEE PROCEEDINGS-C GENERATION TRANSMISSION AND DISTRIBUTION 1981年第5期128卷 288-294页

作者： LIPOWSKI, JS CHARALAMBOUS, C CONCORDIA UNIV DEPT ELECT ENGNMONTREAL H3G 1M8QUEBECCANADA

A computational algorithm is discussed, which is based on the modified recursive quadratic-programming method and is suitable for the solution of the optimal load flow problem. Efficiency of the algorithm is verified by solving several test problems including optimal load flow test problems associated with the 5-, 14-, 23-, and 57-bus power systems

关键词： load flow computational algorithm Optimisation techniques optimal load flow problem modified recursive quadratic programming method quadratic programming Network and transmission line calculations

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