Numerical Analysis and Scientific Computing Commons^™

Grpstring: An R Package For Analysis Of Groups Of Strings, Hui Tang, Elizabeth L. Day, Molly B. Atkinson, Norbert J. Pienta

The R Journal

The R package GrpString was developed as a comprehensive toolkit for quantitatively analyzing and comparing groups of strings. It offers functions for researchers and data analysts to prepare strings from event sequences, extract common patterns from strings, and compare patterns be tween string vectors. The package also finds transition matrices and complexity of strings, determines clusters in a string vector, and examines the statistical difference between two groups of strings.

Lba: An R Package For Latent Budget Analysis, Enio G. Jelihovschi, Ivan Bezerra Allaman

The R Journal

The latent budget model is a mixture model for compositional data sets in which the entries, a contingency table, may be either realizations from a product multinomial distribution or distribution free. Based on this model, the latent budget analysis considers the interactions of two variables; the explanatory (row) and the response (column) variables. The package lba uses expectation-maximization and active constraints method (ACM) to carry out, respectively, the maximum likelihood and the least squares estimation of the model parameters. It contains three main functions, lba which performs the analysis, goodnessfit for model selection and goodness of fit and the plotting …

Tackling Uncertainties Of Species Distribution Model Projections With Package Mopa, M. Iturbide, J. Bedia, J.M. Gutiérrez

The R Journal

Species Distribution Models (SDMs) constitute an important tool to assist decision-making in environmental conservation and planning in the context of climate change. Nevertheless, SDM projections are affected by a wide range of uncertainty factors (related to training data, climate projections and SDM techniques), which limit their potential value and credibility. The new package mopa provides tools for designing comprehensive multi-factor SDM ensemble experiments, combining multiple sources of uncertainty (e.g. baseline climate, pseudo-absence realizations, SDM techniques, future projections) and allowing to assess their contribution to the overall spread of the ensemble projection. In addition, mopa is seamlessly integrated with the climate4R …

Panjen: An R Package For Ranking Transformations In A Linear Regression, Cathrine Ulla Jensen, Toke Emil Panduro

The R Journal

PanJen is an R-package for ranking transformations in linear regressions. It provides users with the ability to explore the relationship between a dependent variable and its independent variables. The package offers an easy and data-driven way to choose a functional form in multiple linear regression models by comparing a range of parametric transformations. The parametric functional forms are benchmarked against each other and a non-parametric transformation. The package allows users to generate plots that show the relation between a covariate and the dependent variable. Furthermore, PanJen will enable users to specify specific functional transformations, driven by a priori and theory-based …

Mmpf: Monte-Carlo Methods For Prediction Functions, Zachary M. Jones

The R Journal

Machine learning methods can often learn high-dimensional functions which generalize well but are not human interpretable. The mmpf package marginalizes prediction functions using Monte-Carlo methods, allowing users to investigate the behavior of these learned functions, as on a lower dimensional subset of input features: partial dependence and variations thereof. This makes machine learning methods more useful in situations where accurate prediction is not the only goal, such as in the social sciences where linear models are commonly used because of their interpretability.

Many methods for estimating prediction functions produce estimated functions which are not directly human-interpretable because of their complexity: …

Infotrad: An R Package For Estimating The Probability Of Informed Trading, Duygu Çelik, Murat Tiniç

The R Journal

The purpose of this paper is to introduce the R package InfoTrad for estimating the probability of informed trading (PIN) initially proposed by Easley et al. (1996). PIN is a popular information asymmetry measure that proxies the proportion of informed traders in the market. This study provides a short survey on alternative estimation techniques for the PIN. There are many problems documented in the existing literature in estimating PIN. InfoTrad package aims to address two problems. First, the sequential trading structure proposed by Easley et al. (1996) and later extended by Easley et al. (2002) is prone to sample selection …

Modeling Recombination In Solar Cells, Paul Chery

Macalester Journal of Physics and Astronomy

Solar cells are a competitive alternative to nonrenewable energy sources such as fossil fuels. However, the efficiency of these devices is limited by photogenerated carrier recombination. We use a finite difference numerical model to study recombination phenomena in the absorber layer of solar cells including alternate recombination models and the effects of spatial distribution of recombination centers. We compare the effect of using the constant lifetime approximation for recombination to the full Shockley-Read-Hall expression in Silicon solar cells and find that the constant lifetime approximation holds for high defect densities but not for high photon flux densities. Finally, we simulate …

Combination Forecasting Of Stock Index Time Series Based On Cooperative Game Theory, Luo Wei

Journal of System Simulation

Abstract: In view of the characteristics of nonlinear, large amplitude, frequent fluctuations in China's stock market, a prediction method of intelligent composite stock index time series based on the cooperative game is presented. The prediction model of stock index time series is established by using neural network method based on the correlations among the various economic indicators, and the development trend and laws of stock index time series are established by using the improved ARIMA method. The two methods are combined by importing cooperative game method. Simulation results show that the prediction accuracy of the presented method is controlled …

Real-Time Simulator For Spatial Information Networks Based On Analog If Signal Processing, Zeguo Yang, Ma Shang, Diaopeng Huang, Jianhao Hu, Lixiang Liu

Journal of System Simulation

Abstract: To solve the problem of real-time simulation of spatial information network with high dynamic network topology, a real-time simulator based on the IF signal processing is proposed. Compared with traditional channel simulator, it supports both the channel transmission characteristics like channel fading, Doppler shift, noise, and path delay, and the real-time simulation of dynamic network topology changes. The simulator supports 8~128 70 MHz IF (0~20 MHz signal bandwidth) emulated nodes with flexible link type configuration. The maximal fading depth is 100 dB, the maximal Doppler shift is 2 MHz, and the maximal path delay can reach up …

A Lightweight Modeling And Simulation Technical Framework For Complex Systems, Ji Hang, Junhua Zhou, Guoqiang Shi, Tingyu Lin, Junjie Xue

Journal of System Simulation

Abstract: Aiming at the modeling and simulation verification of complex systems, the paper established a lightweight simulation technical framework and a system building method. The simulation technical framework is built based on distributed network communication middleware and has graphic user interface, simulation management and run control modules, it packages effective and lightweight network middleware, object management, event management and time management and it is capable of interoperability and its members have abilities of reusable and combinable. The results show that the framework can supports flexible construction and effective simulation on complex systems.

Temperature Characteristics Of Contact Wire Under Different Driving Intervals, Hongwei Wang, Zhang Kai, Zhiyong Wang, Fengyi Guo, Liu Shuai, Zhang Qiong

Journal of System Simulation

Abstract: To reduce the wear of pantograph and catenary system while decreasing the headway, the temperature field of the contact wire is studied. A simulation model is established by using the COMSOL Multiphysics software. The effectiveness of the model is verified with temperature experiments. Temperature field of the contact wire of freight locomotive and passenger locomotive in different intervals is studied by simulation. The smaller the headway of trains, the higher the temperature value, and the shorter the balance process. Under the constraint of temperature field, the headway of freight locomotive couldn't be less than 180s under long term operation. …

Analysis And Simulation Of Temperature Control For Battery Pole Piece Electromagnetic Heating Roller, Jing Ran, Feng Hua, Yonggeng Wang, Haiping Song, Yanjun Xiao

Journal of System Simulation

Abstract: With the application of electromagnetic heating roller on battery pole piece rolling,the processing technology, quality and efficiency of the battery pole piece are improved. The special heating technology of electromagnetic heating roller which involves multi-physics coupling in the process of conversion makes it difficult to control the heating process and determine the control index. By studying the electromagnetic heating theory, the mathematical model of electromagnetic heating roller is established and the simulation and analysis of the electromagnetic heating roller using MATLAB software and the finite difference method are carried out. The distribution, change rule and influence factors of the …

Modeling & Simulation Technology In Manufacturing, Zhang Lin, Longfei Zhou

Journal of System Simulation

Abstract: With the continuous deepening of the application of information technology in the manufacturing field, the informatization of manufacturing systems is developing from unit digital manufacturing to integration networked manufacturing, and then to the comprehensive digital, networked and intelligent manufacturing. As a comprehensive information technology integrating computer, model theory, and scientific computing, modeling & simulation technology plays an irreplaceable role during the development of manufacturing informatization and is widely applied in all phases of the whole product lifecycle, such as design, manufacturing, testing, maintenance, purchase, sales and other phase. This paper reviews and summarizes the research and application of modeling …

Research On Maturity Evaluation Technology Of Complex Digital Industrial System, Geng Chao, Shiyou Qu, Tingyu Lin, Guoqiang Shi, Yingying Xiao, Wang Mei, Qiudan Ma, Ji Hang

Journal of System Simulation

Abstract: Under the background of a new round of the innovation of science and technology and the revolution of industry, the complex digital industrial system is constantly innovating and shaping. Firstly, the paper established maturity evaluation model of the complex digital industrial system based on system engineering. Then, the paper proposed multi - index maturity analysis method and multi - enterprise maturity synthesis method of the complex digital industrial system. Combined with the digital industrial system of aerospace complex product, an evaluation example is presented. The results show that the maturity evaluation method can be used to standardize and guide …

Identification Of Closed Loop Projection Subspace For Motor Based On Hankel Correlation Function, Minghong She

Journal of System Simulation

Abstract: To solve estimation deviation problem of model parameter in the closed-loop system identification, the subspace identification model and state space model based on the estimation of the correlation function are presented, and through the correlation function estimation and zero space followed by projection, the block Hankel matrix of identification framework was filled so as to obtain the scope of the extended observability matrix; on the basis of the same projection on the time offset set of related data, the RQ decomposition of the projection is calculated by numerical calculation, and the dynamic estimation of the system model is obtained. …

High Frequency Blend Clips Matching Based Fire Sound Synthesis, Yin Qiang, Shiguang Liu

Journal of System Simulation

Abstract: Aimed at the problem which generated by fire sound simulation in virtual reality field, a new fire sound synthesis method was proposed. Most of the sound synthesis methods currently separate the fire sound into low and high frequencies for synthesizing. The influence of low frequency fire sound models was considered and the low frequency signal was synthesized based on the physical visual fire model data. The high frequency sound signal was synthesized based on high frequency blend clips matching method. According to the characteristics of the fire's high frequency, the different frequency bands of high noise signal …

Clustering Method Based On Graph Data Model And Reliability Detection, Yanyun Cheng, Huisong Bian, Changsheng Bian

Journal of System Simulation

Abstract: For the data in feature space, traditional clustering algorithm can take clustering analysis directly. High-dimensional spatial data cannot achieve intuitive and effective graphical visualization of clustering results in 2D plane. Graph data can clearly reflect the similarity relationship between objects. According to the distance of the data objects, the feature space data are modeled as graph data by iteration. Cluster analysis based on modularity is carried out on the modeling graph data. The two-dimensional visualization of non-spherical-shape distribution data cluster and result is achieved. The concept of credibility of the clustering result is proposed, and a method is proposed, …

Aerodynamic Simulation Of Multi-Dof Flapping-Wing Air Vehicle Of Bird-Like Based On Xflow Software, Yonggang Yang, Hanping Su

Journal of System Simulation

Abstract: The aerodynamic characteristics analysis of flapping-wing is of great significance to the design, manufacturing and control of the aircraft. In this paper, a simple motion model of multiple-Degrees-of- Freedom (multi-DOF) of “swing-torsion-bending and folding” is established by analyzing the flight characteristics of bird-like flapping wing. The flapping-wing air vehicle of multi-DOF is numerically simulated in the case of unsteady flow at low Reynolds number by XFlow software. The effects of flapping wing shape, frequency and inflow on surrounding air are analyzed. The simulation results provide theory and technique supports for the flapping-wing air vehicle'research and development.

Simulation Analysis Of Magnetic Field Effect In Induction Heating Coil Of Porous Silicon Core Furnace, Jingang Li, Gaoyuan Liu

Journal of System Simulation

Abstract: A new technology of porous coil disposable drawing a plurality of single crystal silicon rod can solve the problem of low efficiency and high cost of zone melting method of single induction heating coil in drawing monocrystalline silicon. However,the missing of the theoretical research and mature technology leads to different sizes of monocrystalline silicon rods. According to electromagnetic theory,Some characterisitics of the porous coil are studied,including magnetic field model,operating principle,magnetic field distribution.To prove the mechanism of the technology, a mathematical model of the porous coil is constructed based on Matlab and Ansys software. The magnetic flux density distribution …

Synthesizing Rotational Human Motion With Physical Reality, Wei Yi, Shihong Xia

Journal of System Simulation

Abstract: Both keyframes and their timings play an important role in synthesizing physically realistic human motion. However, physically plausible timings are hard to set by manual. By combing keyframes and the physics-based optimization, a new method is proposed to solve physically plausible timings of given keyframes. Firstly, the keyframes and the initial value of the timings of keyframes are set through a graphical user interface. Secondly, the physically plausible timings of keyframes are obtained by optimizing a small-size nonlinear optimization model. Finally, the rotational human motion is synthesized by the keyframes and the computed timings of keyframes. Experiments are performed …