Computational Experimental Methods Research Articles

A deterministic sequential maximin Latin hypercube design method using successive local enumeration for metamodel-based optimization

Space-filling and projective properties of design of computer experiments methods are desired features for metamodelling. To enable the production of high-quality sequential samples, this article presents a novel deterministic sequential maximin Latin hypercube design (LHD) method using successive local enumeration, notated as sequential-successive local enumeration (S-SLE). First, a mesh-mapping algorithm is proposed to map the positions of existing points into the new hyper-chessboard to ensure the projective property. According to the maximin distance criterion, new sequential samples are generated through successive local enumeration iterations to improve the space-filling uniformity. Through a number of comparative studies, several appealing merits of S-SLE are demonstrated: (1) S-SLE outperforms several existing LHD methods in terms of sequential sampling quality; (2) it is flexible and robust enough to produce high-quality multiple-stage sequential samples; and (3) the proposed method can improve the overall performance of sequential metamodel-based optimization algorithms. Thus, S-SLE is a promising sequential LHD method for metamodel-based optimization.

Multilayer, Implicit, Parallel Algorithm for the Equation of Heat Conduction in a Parallelepiped

With the use of the method of computational experiment, a problem of heat distribution in a parallelepiped is investigated. It is shown that a three-dimensional problem can be solved on a PC.

Spectroscopic Properties of Naphthalene on the Surface of Ice Grains Revisited: A Combined Experimental-Computational Approach.

An experimental-computational method is used to investigate the spectroscopic behavior of naphthalene on the surface of ice grains. UV-vis diffuse reflectance and fluorescence spectroscopies of naphthalene combined with DFT and ADC(2) calculations provide evidence for the occurrence of excited-state associates. The measured and calculated bathochromic shifts of the S0 → S1 electronic transitions related to naphthalene dimers or naphthalene-ice interactions do not exceed 3 nm. The bands observed in the emission spectrum of frozen naphthalene solutions are assigned to excited dimers of different mutual orientations, naphthalene phosphorescence, and fluorescence of anthracene present as a trace impurity and populated by the energy transfer from excited naphthalene. Photochemical reactivity in/on ice and snow is dependent on the absorption properties and speciation of the compounds present in these media. Hence, within this study, we exploit frozen solutions of naphthalene to demonstrate both the absence of considerable bathochromic shift and a strong tendency to aggregate.

Investigation on partition of plastic work converted to heat during plastic deformation for reactor steels based on inverse experimental-computational method

Abstract This paper aims at studying the ratio of plastic work converted to heat, β (Taylor and Quinney, 1934) in pressure vessel steels used in VVER-440 energetic reactors by an inverse-experimental and computational analysis. The experiments were performed with different strain rates on a thermal-mechanical testing machine from DSI (model GLEEBLE-3800). Because of the magnitude of strain rate during the experiments it cannot be modelled as an adiabatic process, also the heat transfer during the tests has to be taken into account. Analytical model was carried out to account for the conduction, convection and radiation heat losses that occur during the tests. A thermodynamically based thermo-elasto-plastic model is used to describe both the stress–strain behavior and temperature evolution in these steels under monotonic uniaxial loading. The governing equation system of thermo-elasto-plasticity was implemented in MATLAB software. It is found that β is always smaller for compression than that of tension. The results for 15Ch2MFA (bainitic structure with fine grains) show a rather strong dependence on strain rate, whereas 08Ch18N10T (austenitic structure with coarse grains) is practically independent. The results obtained by the investigation correspond to the literature.

Thermal radiation of heterogeneous combustion products in the model rocket engine plume

The work presents a method of complex investigation of thermal radiation emitted by heterogeneous combustion products in the model rocket engine plume. Realization of the method has allowed us to obtain full information on the results in all stages of calculations. Dependence of the optical properties (complex refractive index), the radiation characteristics (coefficients and cross sections) and emission characteristics (flux densities, emissivity factors) of the main determining factors and parameters was analyzed. It was found by the method of computational experiment that the presence of the gaseous phase in the combustion products causes a strongly marked selectivity of emission, due to which the use of gray approximation in the calculation of thermal radiation is unnecessary. The influence of the optical properties, mass fraction, the function of particle size distribution, and the temperature of combustion products on thermal radiation in the model rocket engine plume was investigated. The role of "spotlight" effect–increasing the amount of energy of emission exhaust combustion products due to scattering by condensate particles radiation from the combustion chamber–was established quantitatively.

An Agent-based Simulation System for Evolution of Interplay between E-Commerce Vendor and Consumers

We use computational experiment method integrated multi-agent, advanced GA (Genetic Algorithm), and complex network to study the interactive evolution of e-commerce vendors and consumers. Key algorithms such as generating algorithm for consumer network, and advanced GA based on CA (Cellular Automata) for service vendor decisions, etc, are designed for the evolution behaviors of both e-commerce vendors and customers. We program the computational experiment system with NetLogo, and a simulation experiment is given. The experiment system can provide technique support to e-commerce firms in decision making with regards to service providing, consumer behavior management, etc.

Creating a web-oriented expert system for solving problems of optimization

Research goals: to create a web-oriented expert system on methods of optimization based on the principles of cloud technologies. Research objectives are designing and develop an expert system on based productive model of knowledge about the subject area. The object of research is a web-oriented expert system and the subjects of research are objectives and methods of optimization. In the research used the methods of mathematical modeling and computer experiment. The result of research is the knowledge base based on productive model of knowledge about the objectives and methods of optimization and developed on the it basis of web-oriented expert system for solving optimization problems. The expert system is created to guide the learning process in the preparation of mathematicians and applied mathematicians, professionals of IT and Economic Cybernetics. The main conclusions and recommendations. Web-oriented expert system created for use in the educational process at university training in mathematics, applied mathematics, information technology and economic cybernetics. In the future development of software modules for solving some classes of optimization problems directly on the site of an expert system that will enable use it to solve real problems of small and medium businesses.

Study of the Pressure Drop and Thermal Performance of an Air-Air Heat Exchanger for Aero-engine Application

In this paper, a comparison of the pressure drop and thermal performance between an improved air-air heat exchanger and a former one designed for aero-engines applications is performed. In order to model the flow field through the heat exchanger, both computational fluid dynamics (CFD) and experiment method were used. For this purpose, a model of the heat exchanger has been constructed and mounted in the test section of a wind tunnel to investigate the pressure drop and heat transfer performance of different heat exchangers by changing the tube geometry. And the exact tube bundle arrangement of the heat exchanger was simulated in CFD. The results are compared with experimental data for the same inlet conditions and were found to be in agreement. The results showed that the pressure drop of the improved heat exchanger reduced by over 10% and heat transfer increased by almost 25%. Thus, both the CFD and the experiment method could be used for the detailed investigation of the flow field and heat transfer performance of the heat exchanger so that useful conclusions of heat exchangers designed for aero-engines could be derived.

Firm Environmental Innovation Behavior Under Heterogeneous Demand: An Adaptive, Agent-Based Modeling Approach

Because of the complexity and diversity of human behavior, social systems are unpredictable and difficult to quantify. With the development of computer technology, scholars have begun to construct artificial systems to simulate real social systems in order to explore the trajectory of social phenomena. In this paper, we combined complex system modeling theory with a computational experimental method to construct an adaptive, multi-agent-based system. For this purpose, we constructed heterogeneous firm and consumer agents. Each agent has its own properties, behavioral rules, and interaction rules, which can be adjusted according to its experiences. Our model is based on an abstraction of the real world. We first applied the model to simulate consumers' product selection process and firms' product innovation deci- sion-making process. Then, we analyzed the internal mechanisms affecting consumers' green demand and firms' envi- ronmental behavior. The experimental results revealed that consumer preferences for products with high environmental performance encourage firms to pursue environmental innovation. When green demand among consumers is sufficiently high, firms can obtain high economic profits when they engage in environmental innovation, whereas when green demand among consumers is low, the government should intervene with mechanisms such as subsidies or incentives to encourage firms to engage in environmental innovation. However, as a rapid increase in green demand would quickly lead to a market monopoly, firms should respond to changes in the market in a timely manner to avoid being eliminated from the market.

Application of Computational-Experimental Methods for Designing Optimized Semitrailer Axle Supports

Computational and experimental methods were applied to the design and optimization of a semitrailer axle support subjected to fatigue loads. Numerical results based on the finite element method (FEM) were correlated with extensometric tests to assess the accuracy of the computational method. This paper is focused on the “minimum radius manoeuvre.” This situation represents the highly critical load case occurring in a semitrailer operation where the tractor vehicle pulls the semitrailer's kingpin at approximately 90° with respect to its longitudinal axis, and high stress and strain phenomena take place in the axle supports’ structure. Loads and boundary conditions that correspond to this load case were first adjusted by means of experimental tests and could be later applied to each semitrailer axle support in the numerical model. In this analysis, the stress-strain elastic-plastic curves of the base material, the welding, and the HAZ have been incorporated to the numerical models. Fatigue S- N curves combined with the maximum Von Mises equivalent stresses obtained in the computational analysis provided a maximum number of cycles that the semitrailer axle support could reach in case of the minimum radius manoeuvre being applied to the vehicle in a repeated manner. The initial design could then be optimized to improve its fatigue life.

Performance study on a counter-rotating tidal current turbine by CFD and model experimentation

Among the various ocean energy resources in Korea, the tidal currents in the South western sea have a large potential for development tidal current power generation. The biggest advantage of tidal power is that it is not dependent on seasons or weather and is always constant. This makes power generation predictable and makes tidal power a more reliable energy source than other renewable energy sources. Marine current turbines convert the kinetic energy in tidal currents for power production. Single rotor turbines can obtain a theoretical maximum power coefficient of 59.3%, whereas dual rotor can obtain a maximum of 64%. Therefore by optimizing the counter rotating turbines, more power can be obtained than the single rotor turbines. In this study, we investigated the effect of varying the distance between the dual rotors on the performance and efficiency of a counter-rotating current turbine by using computational fluid dynamics (CFD) and experimental methods. It was found that the dual rotor produced more power than the single rotor. In addition, the blade gap distance affects the flow on the rear rotor blades as well as power output and performance of the turbine. The distance can be used a parameter for counter rotating turbine design. Finally, the numerical setup used for this study can be further used to evaluate the design of larger counter rotating blade designs.

De novo prediction of cis-regulatory elements and modules through integrative analysis of a large number of ChIP datasets.

BackgroundIn eukaryotes, transcriptional regulation is usually mediated by interactions of multiple transcription factors (TFs) with their respective specific cis-regulatory elements (CREs) in the so-called cis-regulatory modules (CRMs) in DNA. Although the knowledge of CREs and CRMs in a genome is crucial to elucidate gene regulatory networks and understand many important biological phenomena, little is known about the CREs and CRMs in most eukaryotic genomes due to the difficulty to characterize them by either computational or traditional experimental methods. However, the exponentially increasing number of TF binding location data produced by the recent wide adaptation of chromatin immunoprecipitation coupled with microarray hybridization (ChIP-chip) or high-throughput sequencing (ChIP-seq) technologies has provided an unprecedented opportunity to identify CRMs and CREs in genomes. Nonetheless, how to effectively mine these large volumes of ChIP data to identify CREs and CRMs at nucleotide resolution is a highly challenging task.ResultsWe have developed a novel graph-theoretic based algorithm DePCRM for genome-wide de novo predictions of CREs and CRMs using a large number of ChIP datasets. DePCRM predicts CREs and CRMs by identifying overrepresented combinatorial CRE motif patterns in multiple ChIP datasets in an effective way. When applied to 168 ChIP datasets of 56 TFs from D. melanogaster, DePCRM identified 184 and 746 overrepresented CRE motifs and their combinatorial patterns, respectively, and predicted a total of 115,932 CRMs in the genome. The predictions recover 77.9% of known CRMs in the datasets and 89.3% of known CRMs containing at least one predicted CRE. We found that the putative CRMs as well as CREs as a whole in a CRM are more conserved than randomly selected sequences.ConclusionOur results suggest that the CRMs predicted by DePCRM are highly likely to be functional. Our algorithm is the first of its kind for de novo genome-wide prediction of CREs and CRMs using larger number of transcription factor ChIP datasets. The algorithm and predictions will hopefully facilitate the elucidation of gene regulatory networks in eukaryotes. All the predicted CREs, CRMs, and their target genes are available at http://bioinfo.uncc.edu/mniu/pcrms/www/.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-1047) contains supplementary material, which is available to authorized users.

Computational and experimental study of the effect of inclination on hydrocyclone performance

In this paper, the effect of inclination on hydrocyclone performance is studied using both computational fluid dynamics (CFD) and experimental methods. Experiments with water medium and the corresponding water–air two-phase CFD simulations in a 75mm diameter cyclone are carried out at various inclined positions to the vertical plane. The two-phase CFD flow analysis shows that the water split to underflow decreases as the inclination increases, which is consistent with the experiments. The predicted flow velocity profiles were analyzed for different inclinations. An increase in the inclination results the air-core size reduction and reduced pressure drop profiles. Experimental classification also performed using the silica slurry. The experimental analysis shows the increased cut-size and the reduced water split with the inclination. Cross validation of inclined cyclone’s CFD data is attempted with Electrical Resistance Tomography (ERT) and High speed video imaging experiments. The inclination effect on hydrocyclone flow field is further analyzed in terms of turbulence parameters; turbulent intensities, and radial RMS velocities. Turbulent dispersion of the particles is calculated using the CFD data and plotted by using a dispersion index formulation. Fish hook phenomena and possible mechanism of particle classification under the influence of inclination is also explained. Experimentally measured cut size and water recovery to underflow for 10wt% silica slurry at various inclinations are compared with numerical predictions. Predicted efficiency curves are found in a close agreement with experiments for all the inclinations.

Alkaline Stability of Benzyl Trimethyl Ammonium Functionalized Polyaromatics: A Computational and Experimental Study

Alkaline stability of benzyl trimethylammonium (BTMA)-functionalized polyaromatic membranes was investigated by computational modeling and experimental methods. The barrier height of hydroxide initiated aryl-ether cleavage in the polymer backbone was computed to be 85.8 kJ/mol, a value lower than the nucleophilic substitution of the α-carbons on the benzylic position of BTMA cationic functional group, computed to be 90.8 kJ/mol. The barrier heights of aryl–aryl cleavage (polymer backbone) are 223.8–246.0 kJ/mol. The computational modeling study suggests that the facile aryl–ether cleavage is not only due to the electron deficiency of the aryl group but also due to the low bond dissociation energy arising from the ether substituent. Ex situ degradation studies using Fourier transform infrared (FTIR) and 1H nuclear magnetic resonance (NMR) spectroscopy indicated that 61% of the aryl–ether groups degraded after 2 h of treatment in 0.5 M NaOH at 80 °C. BTMA cationic groups degraded slowly over 48 h under the ...

Research approaches to mass casualty incidents response: development from routine perspectives to complexity science

Objective To review the research methods of mass casualty incident (MCI) systematically and introduce the concept and characteristics of complexity science and artificial system, computational experiments and parallel execution (ACP) method. Data sources We searched PubMed, Web of Knowledge, China Wanfang and China Biology Medicine (CBM) databases for relevant studies. Searches were performed without year or language restrictions and used the combinations of the following key words: “mass casualty incident”, “MCI”, “research method”, “complexity science”, “ACP”, “approach”, “science”, “model”, “system” and “response”. Study selection Articles were searched using the above keywords and only those involving the research methods of mass casualty incident (MCI) were enrolled. Results Research methods of MCI have increased markedly over the past few decades. For now, dominating research methods of MCI are theory-based approach, empirical approach, evidence-based science, mathematical modeling and computer simulation, simulation experiment, experimental methods, scenario approach and complexity science. Conclusions This article provides an overview of the development of research methodology for MCI. The progresses of routine research approaches and complexity science are briefly presented in this paper. Furthermore, the authors conclude that the reductionism underlying the exact science is not suitable for MCI complex systems. And the only feasible alternative is complexity science. Finally, this summary is followed by a review that ACP method combining artificial systems, computational experiments and parallel execution provides a new idea to address researches for complex MCI.

Reactivities of substituted α-phenyl-N-tert-butyl nitrones.

In this work, a series of α-phenyl-N-tert-butyl nitrones bearing one, two, or three substituents on the tert-butyl group was synthesized. Cyclic voltammetry (CV) was used to investigate their electrochemical properties and showed a more pronounced substituent effect for oxidation than for reduction. Rate constants of superoxide radical (O2•–) reactions with nitrones were determined using a UV–vis stopped-flow method, and phenyl radical (Ph•) trapping rate constants were measured by EPR spectroscopy. The effect of N-tert-butyl substitution on the charge density and electron density localization of the nitronyl carbon as well as on the free energies of nitrone reactivity with O2•– and HO2• were computationally rationalized at the PCM/B3LYP/6-31+G**//B3LYP/6-31G* level of theory. Theoretical and experimental data showed that the rates of the reaction correlate with the nitronyl carbon charge density, suggesting a nucleophilic nature of O2•– and Ph• addition to the nitronyl carbon atom. Finally, the substituent effect was investigated in cell cultures exposed to hydrogen peroxide and a correlation between the cell viability and the oxidation potential of the nitrones was observed. Through a combination of computational methodologies and experimental methods, new insights into the reactivity of free radicals with nitrone derivatives have been proposed.

Dynamic coupling correlation of gas film in dry gas seal with spiral groove

In working state, the dynamic performance of dry gas seal, generated by the rotating end face with spiral grooves, is determined by the open force of gas film and leakage flow rate. Generally, the open force and the leakage flow rate can be obtained by finite element method, computational fluid dynamics method and experimental measurement method. However, it will take much time to carry out the above measurements and calculations. In this paper, the approximate model of parallel grooves based on the narrow groove theory is used to establish the dynamic equations of the gas film for the purpose of obtaining the dynamic parameters of gas film. The nonlinear differential equations of gas film model are solved by Runge-Kutta method and shooting method. The numerical values of the pressure profiles, leakage flux and opening force on the seal surface are integrated, and then compared to experimental data for the reliability of the numerical simulation. The results show that the numerical simulation curves are in good agreement with experimental values. Furthermore, the opening force and the leakage flux are proved to be strongly correlated with the operating parameters. Then, the function-coupling method is introduced to analyze the numerical results to obtain the correlation formulae of the opening force and leakage flux respectively with the operating parameters, i.e., the inlet pressure and the rotating speed. This study intends to provide an effective way to predict the aerodynamic performance for designing and optimizing the groove styles in dry gas seal rapidly and accurately.

Linhas de montagem: revisão da literatura e oportunidades para pesquisas futuras

Este artigo tem por objetivo identificar as principais características de pesquisa no tema linhas de montagem, a fim de propor oportunidades para trabalhos futuros. Para tanto, foram revisadas 226 publicações relevantes sobre o tema nos últimos 50 anos (1960-2010) e analisados os principais assuntos, métodos e conteúdos dos trabalhos estudados. Como resultado, observa-se uma concentração de publicações em balanceamento e sequenciamento de linhas de montagem através de métodos de modelagem e experimentos computacionais, além de significativa quantidade de estudos de linhas de modelos mistos, justificada pela crescente demanda por variedade e customização dos produtos. Existe um desafio para a pesquisa de linhas de montagem que é traduzir para os modelos gerados a complexidade dos aspectos reais do funcionamento e configurações das linhas de montagem existentes. Diversos autores enfatizam dificuldades para obter modelos aplicáveis em diversos casos e situações específicas da realidade. Os autores apontam que existem decisões estratégicas importantes para as configurações das linhas que antecedem a utilização dos modelos disponíveis. Conclui-se que há oportunidades para trabalhos científicos relacionados às pesquisas práticas e aplicadas que envolvam casos e problemas reais, além de para uma abordagem mais ampla do tema, considerando os aspectos multidisciplinares das linhas de montagem e seu relacionamento com as estratégias de produção adotadas pelas empresas.

An agent-based distributed computational experiment framework for virtual supply chain network development

This paper focuses on research on virtual supply chain networks instead of real supply chain networks by making use of agent technology and computational experiment method. However, the recent research is inefficient in computational experiment modeling and lack of a related methodological framework. This paper proposes an agent-based distributed computational experiment framework with in-depth study of material flow, information flow and time flow modeling in supply chain networks. In this framework, a matrix-based formal representation method for material flow, a task-centered representation method for information flow and an agent-based time synchronization mechanism for time flow are proposed to aid building a high quality computational experiment model for a multi-layer supply chain network. In order to conduct the model, a computational experiment architecture for virtual supply chain networks is proposed. In this architecture, coordination mechanisms among agents based on material flow, information flow and time flow as well as consistency check methods for computational experiment models are discussed. Finally, an implementation architecture of the framework is given and a case of virtual supply chain network is developed to illustrate the application of the framework. The computational experiment results of the case show that the proposed framework, not only feasible but correct, has sound advantages in virtual supply chain network development, computational experiment modeling and implementation.

Компьютерное моделирование механизмов плавления наночастиц металлов различной формы

The report presents the basic models describing the melting temperature of nanomaterials based on different concepts of the structure of matter. It takes under consideration some drawbacks described models. Methods of computer experiment show the effect of the matrix and forms of nanoparticle on its melting point. Some mechanisms of melting metal nanoparticles of different shapes are described. Thermodynamic models give a qualitative description of the melting temperature of nanomate-rials, not taking into account any impact form nanoparticles, nor matrix in which the nanoparticle is, thus showing that the sample temperature will decrease with decreasing the size of nanoparticles. Statistical models take into account these effects and show that the melting temperature of the nanoparticles can either increase or decrease with decreasing the size of nanoparticles.