Computer Modeling System Research Articles

Computer Simulation and Modelling System of Non-Stationary Heat Exchange Processes

This article suggests the solution to the up-to-date task of improving and increasing the energy efficiency of buildings and quality of functioning of systems, controlling boilers and heating devices, by using computer simulation and modelling of heat exchange processes of the building and operation of the heating systems. The authors present proven (checked) mathematical models, applicable for external protections, rooms, heaters, boilers, insulated and non-insulated piping. The authors offer an automated system of computer simulation and modelling, which not only allows us to solve mathematical models, but also to complement them with information from a real object and improve them by introducing corrective factors and coefficients.

A morphodynamic model for cohesive sediments transport

ABSTRACT The dynamics of cohesive sediments in natural water bodies is of great importance for coastal engineering. Quite often, it is necessary to assess sedimentological processes in regions where cohesive sediments are prevalent, such as in many harbors. Such assessments poses challenges, especially in quantitative evaluations, as the physics involved in the transport, sedimentation and erosion of cohesive sediments is rather complex. For that, by all means, it is important to have analysis tools capable of computing cohesive sediments dynamics. This paper presents the development of a vertically averaged eulerian transport model for suspended cohesive sediments. Such model is currently available on SisBaHiA®, which is a computational modeling system developed and maintained in COPPE/UFRJ. After describing the model implementation, we present a discussion on consistency and validation tests, for each implemented mechanism within the sedimentological process, with a focus in the erosion and sedimentation fluxes. In sequence, we compare model results with the theoretical results and, for some tests, with the results of the simulations performed with the Delft3D® and Telemac® modeling systems. These models are similar to the one presented in this paper, and are well accepted and widely used on professional projects and studies. The tests showed that the developed model results were consistent for all the evaluated mechanism, and hence it’s positively verified.

Quantifying Structural Effects of Amino Acid Ligands in Pd(II)-Catalyzed Enantioselective C–H Functionalization Reactions

Delineating complex ligand effects on enantioselectivity is a longstanding challenge in asymmetric catalysis. With α-amino acid ligands, the essential difficulty lies in accurately describing integrated perturbations induced by simultaneous variation about the α side chain and N protecting group of the ligand, which hampers an intuitive understanding of the structure–enantioselectivity relationships. To deconvolute such complexity in chiral amino acid enabled enantioselective C–H functionalization reactions, a computational organometallic model system was developed. Whereas a model based only on a conventional results in diminished predictive power, the ground state Pd(II)-based models display an excellent ability to describe the observed enantioselectivity. These structures were leveraged using a multivariate modeling approach to successfully describe Pd(II)-catalyzed C–H alkylation, alkenylation, and two C–H arylation reactions, wherein descriptors of torsion angle, percent buried volume, and NBO charge...

Application of information technologies when training in the master’s degree program

This article considers the use of computer technologies in teaching applied mathematics in Moscow Aviation Institute (for master’s degree program). We provide the list of disciplines, which reflect the specificity of training directions. The possibilities of forming extension packages for computer modeling systems are discussed. Much attention is paid to developing the skills of independent work in the learning process. Attention is drawn to the use of intelligent training simulators, web technologies and expert systems for distance learning.

OVERCOMING ENGINEERING CHALLENGES OF PROVIDING AN EFFECTIVE USER INTERFACE TO A LARGE SCALE DISTRIBUTED SYNTHETIC ENVIRONMENT ON THE US TERAGRID: A SYSTEMS ENGINEERING SUCCESS STORY

ABSTRACTOver recent years’ large‐scale distributed synthetic environment enterprises have been evolving in a diverse range of scientific and engineering fields. These computer modelling and simulation systems are increasing in scale and dimension in order to allow scientists and engineers to explore the attributes and emergent properties of a given system design. Within the field of computational science, the grid facilitates very large‐scale collaborative simulation enterprises. The grid is similar to distributed interactive simulation/high level architecture (DIS/HLA) in that it supports interconnectivity but differs in the sense that it supports intercommunication of large super computing resources. An important factor in the rapid adoption of the grid has been its role in enabling access to significant supercomputing resources not usually available at a single institution. However, the major challenge for the grid has been the lack of an effective and ubiquitous interface to the huge computational resource (which can comprise over 6000 CPUs distributed across the globe) at any time and from any location. This paper describes a unique user interface built on systems engineering principles and practices to solve the problem of delivering real‐time interaction (from lightweight computing devices such as personal digital assistants, commonly known as tablet devices, to high end computing platforms) with simulations delivering high resolution 3D images. The application of our work has far reaching benefits for many sectors including: aerospace, medical informatics, engineering design, distributed simulation, and modelling.

An EcoCity model for regulating urban land cover structure and thermal environment: Taking Beijing as an example

Urban land-use/cover changes and their effects on the eco-environment have long been an active research topic in the urbanization field. However, the characteristics of urban inner spatial heterogeneity and its quantitative relationship with thermal environment are still poorly understood, resulting in ineffective application in urban ecological planning and management. Through the integration of “spatial structure theory” in urban geography and “surface energy balance” in urban climatology, we proposed a new concept of urban surface structure and thermal environment regulation to reveal the mechanism between urban spatial structure and surface thermal environment. We developed the EcoCity model for regulating urban land cover structure and thermal environment, and established the eco-regulation thresholds of urban surface thermal environments. Based on the comprehensive analysis of experimental observation, remotely sensed and meteorological data, we examined the spatial patterns of urban habitation, industrial, infrastructure service, and ecological spaces. We examined the impacts of internal land-cover components (e.g., urban impervious surfaces, greenness, and water) on surface radiation and heat flux. This research indicated that difference of thermal environments among urban functional areas is closely related to the proportions of the land-cover components. The highly dense impervious surface areas in commercial and residential zones significantly increased land surface temperature through increasing sensible heat flux, while greenness and water decrease land surface temperature through increasing latent heat flux. We also found that different functional zones due to various proportions of green spaces have various heat dissipation roles and ecological thresholds. Urban greening projects in highly dense impervious surfaces areas such as commercial, transportation, and residential zones are especially effective in promoting latent heat dissipation efficiency of vegetation, leading to strongly cooling effect of unit vegetation coverage. This research indicates that the EcoCity model provides the fundamentals to understand the coupled mechanism between urban land use structure and surface flux and the analysis of their spatiotemporal characteristics. This model provides a general computational model system for defining urban heat island mitigation, the greening ratio indexes, and their regulating thresholds for different functional zones.

Integration of scheduling and discrete event simulation systems to improve production flow planning

The increased availability of data and computer-aided technologies such as MRPI/II, ERP and MES system, allowing producers to be more adaptive to market dynamics and to improve production scheduling. Integration of production scheduling and computer modelling, simulation and visualization systems can be useful in the analysis of production system constraints related to the efficiency of manufacturing systems. A integration methodology based on semi-automatic model generation method for eliminating problems associated with complexity of the model and labour-intensive and time-consuming process of simulation model creation is proposed. Data mapping and data transformation techniques for the proposed method have been applied. This approach has been illustrated through examples of practical implementation of the proposed method using KbRS scheduling system and Enterprise Dynamics simulation system.

Application of Multidisciplinary Systems‐of‐Systems Optimization to an Aircraft Design Problem

ABSTRACTA generic mathematical formulation for Systems‐of‐Systems (SoS) optimization problems is presented. SoS optimization problems resemble the structure of a tree of Multidisciplinary Design Optimization (MDO) problems with additional unique features. The framework for solving such problems involves features from evolutionary computing, platform‐based design, and evolving design spaces. One important aspect of SoS Engineering, often overlooked, is the role it plays in improving the design of individual systems. In this vein, this work has sought to exemplify such a synergistic approach for aircraft design. A large‐scale SoS optimization problem for designing noise‐optimal aircraft and improved procedures for the approach phase is studied. Modules involving Computational Fluid Dynamics (CFD), noise modeling, multifidelity analysis, topology optimization, and autotuned control systems are used to obtain optimal solutions.

ВИРТУАЛЬНОЕ МОДЕЛИРОВАНИЕ ЦЕНТРОБЕЖНОГО ЛИТЬЯ ВАЛКОВ

The work is devoted to the virtual simulation of a sheet roll working layer formation at a technological stage “casting-solidification”. To form a virtual model of a roller mould pouring and foundry solidification there was used a computer modeling system (CMS) which included initial and boundary conditions for a roller mould pouring process with highalloy cast iron in the field of centrifugal force action. The distribution of a metal working layer along an inner surface of a rotating mould at different technological parameters: mass of highalloy cast iron, its density, temperature and pouring velocity, temperature of metal and non-metal parts of a mould at the initial point of time, modes of rotation and conditions of mould cooling and others were investigated. It is established that under the influence of centrifugal forces a free surface of liquid melt obtains a parabolic form. The influence of basic technological parameters upon the vertex position of a paraboloid of revolution of highalloy liquid melt z0 is revealed. It is shown in the paper that it stipulates for the unevenness of a working layer value along a roller barrel. As a result of computations it is obtained that the value of a working layer at lower flanks of barrels is higher than that of upper sides. The average value of such an exceeding makes 0.012 m. As a result of a simulation analysis of a foundry formation process at different technological parameters it is determined that the distance increase between the vertex of a paraboloid of revolution and the metal area investigated raises the working layer evenness along a roller barrel 3.6 times. Hence, the increase of capacity for work of a rolling tool is expected. The results of investigations presented are basic for the works for the increase of centrifugal roller servicing characteristic increase.

First principles study of the thermodynamic and kinetic properties of U in an electrorefining system using molybdenum cathode and LiCl-KCl eutectic molten salt

Using first principles density functional theory (DFT) calculations we obtain thermodynamic and kinetic properties of U in an electrorefining process for spent nuclear fuels using a LiCl-KCl eutectic molten salt and Mo as a cathode. The thermodynamic stability of electrodeposited U from the molten salt onto the Mo(110) surface electrode is evaluated by activity coefficients as function of surface coverages of U and Cl. Additionally, ab-initio molecular dynamic simulations combined with the Stokes-Einstein-Sutherland relation enables us to calculate the viscosity of the LiCl-KCl eutectic molten salt. Our results well agree with previously reported experimental data endorsing the credibility. Based on our atomic-level mechanical understanding we propose that an accurate computational model system incorporating the electrochemical conditions of the electrorefining process essential for the purpose of establishing thermodynamic and kinetic database of U, otherwise critical deviations are inevitable. More interestingly, the effect of coadsorption of Cl with U on the Mo(110) surface plays a key role in stabilizing electrodeposited U on the cathode. Our approach can be useful for validating published experimental database and for identifying key factors guiding a rational design of highly efficient electrorefining system for spent nuclear fuels, and thus reducing high-level radioactive nuclear wastes.

Increasing the Efficiency of Liquid Phase Alkylation of Benzene with Propylene Using the Method of Mathematical Modeling

In this study the existing problems of liquid-phase alkylation of benzene with propylene problems are indicated. The paper describes the stages alkylation of benzene with propylene mathematical model development. The model allows to define the composition of the product stream under changing of plant process parameters: temperature, benzene/propylene molar ratio and feed space velocity. The error of the model does not exceed 7.5%. «Alkylation» computer modeling system is developed in Borland Delphi 7 and the optimization module of the process parameters is called «Optimization». In Aspen HYSYS the technological scheme of rectification products alkylation of benzene with propylene using aluminum chloride catalyst was developed. Integration of computer models allowed to determine the technological modes of production, providing isopropylbenzene outlet with higher quality.

Using computational models to discover and understand mechanisms

Areas of biology such as cell and molecular biology have been dominated by research directed at constructing mechanistic explanations that identify parts and operations that when organized appropriately are responsible for the various phenomena they investigate. Increasingly the mechanisms hypothesized involve non-sequential organization of non-linear operations and so exceed the ability of researchers to mentally rehearse their behavior. Accordingly, scientists rely on tools of computational modeling and dynamical systems theory in advancing dynamic mechanistic explanations. Using circadian rhythm research as an exemplar, this paper explores the variety of roles computational modeling is playing. They serve not just to determine whether the mechanism will produce the desired behavior, but in the discovery process of hypothesizing mechanisms and in understanding why proposed mechanisms behave as they do.

Correction of gasoline blending recipes with the use of computer modelling system

The process of gasoline blending is a difficult multistage industrial technology. In this paper gasoline blending recipes for one of the largest refineries in Russian Federation were corrected by using of developed computer modelling system «Compounding». As the result of correction, production volume of high-octane and high-quality gasoline was increased on 47 wt. %.

Software tools for computing experiment aimed at multivariate analysis implementation

A concept for organization and planning of computational experiment aimed at implementation of multivariate analysis of complex multifactor models is proposed. It is based on the generation of calculations tree. The logical and structural schemes of the tree are given and software tools, as well, for the automation of work with it: calculation generation, carrying out calculations and analysis of the obtained results. Computer modeling systems and such special-purpose systems as RACS and PRADIS do not solve the problems connected with effective carrying out of computational experiment, consisting of its organization, planning, execution and analysis of the results. Calculation data storage for computational experiment organization is proposed in the form of input and output data tree. Each tree node has a reference to the calculation of model step performed earlier. The storage of calculations tree is realized in a specially organized directory structure. A software tool is proposed for creating and modifying design scheme that stores the structure of one branch of the calculation tree with the view of effective planning of multivariate calculations. A set of special-purpose software tools gives the possibility for the quick generation and modification of the tree, addition of calculations with step-by-step change in the model factors. To perform calculations, software environment in the form of a graphical user interface for creating and modifying calculation script has been developed. This environment makes it possible to traverse calculation tree in a certain order and to perform serial and parallel initiation of computational modules. To analyze the results, software tool has been developed, operating on the base of the tag tree. It is a special tree that stores input and output data of the calculations in the set of changes form of appropriate model factors. The tool enables to select the factors and responses of the model at various steps and to form easyto-read tables and graphs of functions for the selected parameters. The proposed solution has been tested in the process of verification for “Prognoz_R” software, greatly simplifying the preparation and carrying out of the design calculations for analysis of the developed computational model. Thus, the proposed software tools, due to the lack of universal ready-made solutions, can serve as an effective replacement for manual carrying out of computational experiments.

Validation metric of degradation model with dynamic performance

With more and more attention on degradation process, we need the degradation model to be accurate all over the time rather than only at some specific moments. However, the traditional validation metric only estimates difference of static features. A validation method proposed in this paper uses hypothesis testing to identify whether the distributions of experimental measurements and simulation results are consistent. Then, based on the deviation between sample means, a global validation metric which reflects the difference of degradation process between computational model and physical system all over the service time is derived from the statistics of deviation between sample means. Furthermore, curve fit method for discrete experimental measurements is introduced. The case of electro-hydraulic servo valve is studied, and the results show that the proposed validation metric is appropriate for the validation of degradation model with dynamic performance output.

In vivo kinematic evaluation of total hip arthroplasty during stair climbing.

Stair climbing is a physically demanding task and a painful limitation for patients suffering from severe hip osteoarthritis. Although total hip arthroplasty (THA) is the definitive treatment for end-stage osteoarthritis, it is not well understood whether THA restores hip kinematics during strenuous activities. The purpose of this study was to compare the 3D kinematics of THA and native hip during physically demanding tasks and correlate potential differences with THA components orientations/positions in patients with unilateral THA. In vivo hip kinematics were determined during step-up and leg stance activities using a validated combination of 3D CT-based computer modeling and dual fluoroscopic imaging system (DFIS). The THA side demonstrated an average 3.4° (±6.5°, range: -5.9° to 15.2°) greater internal rotation than the contralateral native hip, during the step-up activity but not during leg stance. The difference in internal rotation was highly correlated to the difference in femoral anteversion and anterior translation of hip joint center between implanted and native hip (R(2) = 0.71, p < 0.01). The results suggest the importance of accurate THA component placement in restoring normal hip kinematics during functional activities.

Electrogenic properties of the Na⁺/K⁺ ATPase control transitions between normal and pathological brain states.

Ionic concentrations fluctuate significantly during epileptic seizures. In this study, using a combination of in vitro electrophysiology, computer modeling, and dynamical systems analysis, we demonstrate that changes in the potassium and sodium intra- and extracellular ion concentrations ([K(+)] and [Na(+)], respectively) during seizure affect the neuron dynamics by modulating the outward Na(+)/K(+) pump current. First, we show that an increase of the outward Na(+)/K(+) pump current mediates termination of seizures when there is a progressive increase in the intracellular [Na(+)]. Second, we show that the Na(+)/K(+) pump current is crucial in maintaining the stability of the physiological network state; a reduction of this current leads to the onset of seizures via a positive-feedback loop. We then present a novel dynamical mechanism for bursting in neurons with a reduced Na(+)/K(+) pump. Overall, our study demonstrates the profound role of the current mediated by Na(+)/K(+) ATPase on the stability of neuronal dynamics that was previously unknown.

Application of Cumene Technology Mathematical Model

The work describes the existing problems of the technological systems for cumene synthesis catalyst AlCl3. The paper describes the stages of development of the mathematical model ofbenzene alkylation with propylene. The model allows the calculation of composition of the product stream when changing process parameters of the plant: temperature, molar ratio of benzene/propylene, feed space velocity. The error of the model does not exceed 7.5%. The computer modeling system «Alkylation» is developed in Borland Delphi 7, and the module optimization of the process parameters is called «Optimization». The calculations allowed reducing the catalyst consumption in the alkylation reactor (to 10-15%) and increasing the cumene concentration in the product mixture (to 25% wt.). The concentration of n-propylbenzene in the output stream is 0.05 wt%. The recommendations for optimization of the industrial alkylation unit are presented for implementation at OJSC «Omsky Kautchuk».

The Research of Kinematic Model in the Rehabilitative Training System

This paper provided a new method of controlling the rehabilitative training system for the patients with upper limb movement disorder. On the basis of the computer through the patient's healthy limb motion gesture motion parameters, analyzed the kinematic model of human upper limb joints, obtained the kinematic parameters of upper body. Study the establishment of different categories of patients with upper limb virtual computer model system for the detection of relevant parameters. And according to the requirements of upper limb rehabilitation training for patients with upper limb rehabilitative training system, researched the dynamics model of human upper limb, and indicated a method which may provide scientific and effective training methods to recover function rehabilitation for patients.

Validating the ACE Model for Evaluating Student Performance Using a Teaching-Learning Process Based on Computational Modeling Systems

The aim of this work is to adapt and test, in a Brazilian public school, the ACE model proposed by Borkulo for evaluating student performance as a teaching-learning process based on computational modeling systems. The ACE model is based on different types of reasoning involving three dimensions. In addition to adapting the model and introducing innovative methodological procedures and instruments for collecting and analyzing data, our main results showed that the ACE model is superior than written tests for discriminating students on the top and bottom of the scale of scientific reasoning abilities, while both instruments are equivalent for evaluating students in the middle of the scale.