International Journal of Modeling, Simulation, and Scientific Computing

Modeling and simulation (M&S) play a critical role in both engineering and basic research processes. Computer-based models have existed since the 1950s, and those early models have given way to the more complex computational and physics-based simulations used today. As such, a great deal of research has been done to establish what level of trust should be given to simulation outputs and how to verify and validate the models used in these simulations. This paper presents an overview of the theoretical work done to date defining formal definitions for, and methods of, verification and validation (V&V) of computer models. Simulation models are broken down into three broad categories: analytical and simulation models, computational and physics-based models, and simulations of autonomous systems, and the unique theories and methods developed to address V&V of these models are presented. This paper also presents the current problems in the theoretical field of V&V for models as simulations move from single system models and simulations to more complex simulation tools. In particular, this paper highlights the lack of agreed-upon methods for V&V of simulations of autonomous systems, such as an autonomous unmanned vehicles, and proposes some next steps needed to address this problem.

Complex product system contains a number of different subsystems. The characteristics of multi-discipline and strong coupling exhibit due to the interconnection of subsystems. To achieve system-level optimization, integrated design on each subsystem is required. The traditional designing method using single simulation software is difficult to reflect the dynamic coupling among multiple subsystems. Therefore, the establishment of integrated design platform which is capable of multi-disciplinary and multi-domain simulation is necessary. This paper summarized the present design methods for multi-disciplinary integrated simulation platforms and the key technologies. Moreover, a case study with results was also provided to show the advantage of integrated multi-domain simulation. It will provide an important integrated authentication platform for the multi-disciplinary optimum design of complex product system.

Complex System Modeling, Simulation and Optimization Language (CoSMSOL) is problem-oriented and designed to run on multi-core computers. This paper provides the system environment of CoSMSOL and proposes the modeling methods of complex system, language text specification, function library, algorithm library, parallel simulation algorithms and intelligent optimization algorithms which support continuous system, discrete system and agent systems. Also, we developed a simulation language compiler of CoSMSOL, which is employed in two case studies generating a multi-entity war gaming system and an aerodynamic spacecraft model. The two cases illustrate main functions and implementation processes of CoSMSOL. The results validate that CoSMSOL is useful to model agent-based system and aerospace system.

Based on Mecanum wheels and “$Y$”-shaped planetary wheels, we combine these two kinds of wheels’ respective motion principle with their advantages to design a new type of four-wheeled robot: install the Mecanum wheels at the end of “$Y$”-shaped planetary wheel group. The wheel designed based on Mecanum wheels and “$Y$”-shaped planetary wheel can adapt to the complex terrain such as stairs, steps, and at the same time it can achieve the rotation of the whole body in a limited space. This paper studies the adaptability of the four-wheeled robot to the stairs, analyzing and calculating the parameters of the four-wheeled robot and the stairs.

Evacuation modeling is a promising measure to support decision making in scenarios such as flooding, explosion, terrorist attack and other emergency incidents. Given the special attention to the terrorist attack, we build up an agent-based evacuation model in a railway station square under sarin terrorist attack to analyze such incident. Sarin dispersion process is described by Gaussian puff model. Due to sarin’s special properties of being colorless and odorless, we focus more on the modeling of agents’ perceiving and reasoning process and use a Belief, Desire, Intention (BDI) architecture to solve the problem. Another contribution of our work is that we put forward a path planning algorithm which not only take distance but also comfort and threat factors into consideration. A series of simulation experiments demonstrate the ability of the proposed model and examine some crucial factors in sarin terrorist attack evacuation. Though far from perfect, the proposed model could serve to support decision making.

The traditional Dead Reckoning algorithm predicts the future motion state based on a determined polynomial predictor, and the forecasting performance would vary with different types of motion entities. This paper proposes an enhanced dead reckoning algorithm based on hybrid extrapolation models, which can be used to reduce the communication in a distributed interactive simulation. The proposed algorithm perform extrapolation using a number of candidate predictors. Its idea is based on the assumption that a complex trajectory can be decomposed into several simple trajectories. The experimental evaluations show that the enhanced Dead Reckoning algorithm provides better performance in correction data reduction and accurate estimation.

The distributed and customized 3D printing can be realized by 3D printing services in a cloud manufacturing environment. As a growing number of 3D printers are becoming accessible on various 3D printing service platforms, there raises the concern over the validation of virtual product designs and their manufacturing procedures for novices as well as users with 3D printing experience before physical products are produced through the cloud platform. This paper presents a 3D model to help users validate their designs and requirements not only in the traditional digital 3D model properties like shape and size, but also in physical material properties and manufacturing properties when producing physical products like surface roughness, print accuracy and part cost. These properties are closely related to the process of 3D printing and materials. In order to establish the 3D model, the paper analyzes the model of the 3D printing process selection in the cloud platform. Triangular intuitionistic fuzzy numbers are applied to generate a set of 3D printers with the same process and material. Based on the 3D printing process selection model, users can establish the 3D model and validate their designs and requirements on physical material properties and manufacturing properties before printing physical products.

Modeling how military commanders carry out operations is considered complicated, requiring the capability of not only planning for multiple subordinates but also responding to unexpected events during execution. This paper presents an Hierarchical Task Network (HTN) embedded planning and execution control architecture for small unit commander agents. To be adaptive to dynamic world state changes, the architecture employs a partial planning mechanism and generates actions only applicable to current situations. It is also able to coordinate subordinates’ actions and handle execution failures at runtime. We demonstrate the architecture’s use with an infantry company scenario, where the commander orders three platoons assaulting a defined hill. Our approach shows the effectiveness to control multiple entities in dynamic environments, making the architecture well-suited to represent small unit commanders’ behavior.

Excessive predation pressure from the waterfowl Phalacrocorax carbo (Great Cormorant) on Plecoglossus altivelis (Ayu) has recently been a severe problem of river environment in Japan. Local fishery cooperatives are currently suffering from economic difficulties due to decrease of the fish catch of P. altivelis. Local fishery cooperatives and municipalities have been enthusiastically trying to develop countermeasures that can effectively reduce the predation pressure; however, their effectiveness and efficiency have not been systematically quantified well. This aim can be achieved with the help of an appropriate mathematical model. In this paper, based on a pure death process, a practical stochastic control model for population dynamics of released P. altivelis in river environment under predation pressure from P. carbo, harvesting by human, and environmental fluctuations is proposed. Finding an optimal management strategy ultimately reduces to solving a 2D Hamilton–Jacobi–Bellman equation, which is performed with a finite element scheme. Its application to a Japanese river environment successfully computes the optimal management strategy that is consistent with the reality. Numerical sensitivity analysis of the presented mathematical model is also performed for comprehension of dependence of the optimal strategy on the model parameters.

Assembly simulations such as assembly process simulation and assembly tolerance simulation have become an effective means to evaluate and analyze product assembly design and assembly process planning. Being core aspect of simulation implementation, building an assembly simulation model is rather time-consuming because of its high complexity. Furthermore, modeling has a significant influence on the popularization and application of simulation technology. In this paper, data needed by assembly process and tolerance simulation are addressed to propose a data-driven approach for assembly simulation modeling. The application process and the architecture of modeling framework for assembly simulation are presented as well. An assembly sequence simulation example is given to illustrate the application of the framework. The framework provides a new idea for the realization of automatic modeling for assembly simulation.

Desktop Virtualization is an essential problem in cloud manufacturing to make full use of shared resources so as to meet the practical application requirements. In this paper, an efficient virtualization solution for desktop transferring is presented for sharing resources. Our strategy is not limited to transfer desktops between virtual machines (VMs), transmission between virtual and physical machines is also achieved. A three-layer systemic structure based on web environment is proposed in the study. We employ the application program library Libvirt and kernel-based virtual machine (KVM) technique to manage VMs with dynamic customization scheme, which gains better virtualization performance. Moreover, we present two different schemes for desktop graphics transferring. One is based on the transport protocol virtual network computing (VNC), and the other adopts the simple protocol for independent computing environment (SPICE), which both achieve more satisfactory results. The validity of our scheme is demonstrated on some experimental results and systemic qualitative evaluation is also provided.

Mobile robot path planning is an important research branch in the field of mobile robots. The main disadvantage of the traditional artificial potential field (APF) method is prone to local minima problems. Improved artificial potential field (IAPF) method is presented in this paper to solve the problem in the traditional APF method for robot path planning in different conditions. We introduce the distance between the robot and the target point to the function of the original repulsive force field and change the original direction of the repulsive force to avoid the trap problem caused by the local minimum point. The IAPF method is suitable for mobile robot path planning in the complicated environment. Simulation and experiment results at the robot platform illustrated the superiority of the modified IAPF method.

Calculation of assembly clearance is the basis of analysis on assembly problems, and the real assembly surface is the nonideal surface. In this paper, the concept of assembly clearance on nonideal surface is defined and the calculation algorithm of assembly clearance is designed. Based on the calculation, the concept of clearance surface is put forward to express the distribution of assembly clearance on nonideal surface as it can assist the analysis of assembly problems. Finally, the effectiveness of the algorithm is verified by the calculation of the assembly clearance between the surfaces of piston and cylinder.

Cloud manufacturing (CMfg), combining the idea and technologies of cloud computing and Internet of Things, is an emerging service-oriented manufacturing model. The supply–demand matching of manufacturing resources is one of the key technologies for implemention. However, resources in CMfg system are geographically distributed, functional of similar and dynamically changeable, and these features make it difficult to obtain higher accuracy for existing matching methods. In order to select the most satisfied resources in CMfg, a semantics-based supply–demand classification matching method (SDCM) is proposed. Firstly, the implementing framework of SDCM is constructed. Then, combined with the theories of ontology and dynamic description logic, a semantics-based SDCM algorithm is designed, which includes four implementation stages, respectively, basic information matching, IOPE parameters (Input, Outputs, Preconditions, Effects) matching, QoS (Quality of Service) matching and comprehensive matching. Finally, a case verifies the feasibility and effectiveness of the proposed method.

Discrete Level of Detail (LOD) strategy is an effective solution for balancing the inherent contradiction between quality and speed in computer graphics. However, application of this strategy requires both the appropriate selection approach and the visually comfortable transition procedure to reduce the popping effects introduced by switching between different levels. In this paper, a novel automatic LOD selection method based on viewpoint entropy was proposed. Firstly, the traditional calculation method of viewpoint entropy contained in a scene was improved for the preprocessing of LOD models. Then, the runtime rendering scheme combined with our selection method was designed for balance of frame rate during real-time rendering, and a novel smoothing LOD transition strategy based on Alternate Frame Rendered (ALR) was put forward for elimination of popping effects. Finally, an example of complex scene combined with our proposal was researched to verify its real-time performance and ability in holding continuity of rendered images. Experimental studies show the effectiveness for stabilizing frame rate and improvements in reducing loss of continuity.

In view of the merits and demerits of current oil spill visualization methods, the paper involves a study on a new type of visualization approach targeting oil spill at sea. To be specific, the visualization of sea oil spill is implemented with the adoption of texture projection method. The texture projection-induced jaggedly edge is displayed in the performance test results. Under the circumstance, Gauss smoothing filter is introduced to secure the smooth convergence of texture edge and thus bring forth satisfactory dynamic visualization effect. Already, this means has already been successfully applied to the Oil Spill Emergency 3D Drilling System, which evidenced the validity and reliability of the new method.

Rolling characteristics of the canard-controlled rocket with a free-spinning tail are researched based on 3-dimensional Navier–Stokes (N–S) equations. The slide mesh technology of computational fluid dynamics is used to numerically simulate the flow field when tails rotate relative to the rocket body and research the varying pattern of roll moment coefficients of the whole rocket, tail, and canard with Mach number. The comparison between the computation results and a part of experimental data shows that the simulation method is accurate. The convergence criterion during the numerical simulation is put forward; the induced rotation speed of the free-spinning tail and the roll moment coefficient of the rocket under this rotation in actual flight when the canard deflects by 10${}^{\circ }$ for roll control are obtained and the reason for the free-spinning tail being able to eliminate roll coupling is analyzed. The research provides a reference for the configuration design of canard-controlled rockets with a free-spinning tail and the numerical simulation of their aerodynamic characteristics.

Infrared (IR) heating is often used for the treatment of liquid and solid foods. IR treatment is known to enhance their shelf life by reducing moisture content and inactivating the microorganisms. Mung bean (a type of pulse from India) is a short season crop; suffers maximum storage loss when compared to other legume grains. The losses are due to moisture and temperature movements. Drying of grains is an important post-harvest operation. IR drying is advantageous over the conventional drying methods. In this paper, the drying of mung bean is considered. An experimental setup is developed to obtain the required moisture and temperature profiles. The equivalent model is simulated using COMSOL multiphysics software and the percentage error between the experimental and simulated models is calculated. Results of numerical implementation are presented and possible further extensions are identified.

High moisture content wheat kernels are subject to elevated respiration rates due to enzyme activity and mould growth that reduce the dry grain and may produce sufficient energy which may be harmful to wheat quality. Grain aeration provides a powerful nonchemical stored grain insect management. Currently, aeration is a suitable and economical device to overcome this problem. The moisture management is vital to prevent spoilage in stored grain. The objective of this study is to investigate the influence of using low relative humidity (RH) aeration on the wheat moisture content. The numerical investigation based on heat and mass balances is developed and used to simulate the evolution of grain temperature and moisture under various air RH in a wheat storage silo. Results show that the dehumidification of blown air had greater potential for decreasing RH of interstitial air and wheat moisture at $30^{\circ }$C temperature and RH of 40%, 50% and 60%.

Hydration represents the main unit operation in the industrial thermal process of dry dates. In this work, Tunisian Deglet Nour dates were hydrated experimentally at a laboratory scale by using saturated air as it is commonly undertaken in industry. This study focuses on the modeling of this unit operation in order to control the moisture uptake phenomenon during processing. A physic-based simplified numerical model describing moisture transfer during hydration was implemented in COMSOL${}^{\circledR }$Multiphysics software. The model considers the real geometry of dates instead of approaching the fruits by simplified shapes. Moisture diffusivities of two types of Deglet Nour dry dates characterized by different maturation stages were estimated. Results showed a good agreement between experimental and numerically computed values of average moisture content. Moisture profile in dates flesh was computed numerically using estimated moisture diffusivities. The numerical model proposed in this work could be therefore employed as a predictive tool to simulate and optimize the hydration operation of dates.

Laboratory experiments were conducted to determine the effect of foaming agent (egg white (EW)), foam stabilizer (carboxyl methyl cellulose (CMC)) and whipping time on drying rate and quality of tomato (Lycopersicon esculentus) paste dried under air oven, microwave oven and mechanical dryer. A 4³ factorial experiment in Randomized Complete Block Design (RCBD) was used to study the effect of four levels each of foaming agent (5%, 10%, 15% and 20%EW), foam stabilizer (0.15%, 0.30%, 0.45% and 0.60%CMC) and whipping time (3, 5, 7 and 9min) on the drying rate and the quality of foam-mat dried tomato powder in the three drying equipment. Each trial was performed in triplicates making a total number of 576 samples that were individually tested and measured. 25g sample of the paste was dried to a moisture content of 7.60% (wb) for 8h in mechanical dryer and oven dryer at temperatures of 55${}^{\circ }$C and 50${}^{\circ }$C, respectively, and 10min in microwave oven at 540W. Data obtained from the experiments were statistically analyzed using the analysis of variance (ANOVA) while the Duncan’s Multiple Range Test was used to compare the means. Results showed that the drying rate increased with increase in foaming agent, foam stabilizer and whipping with minimum values of 9.21g/h obtained in mechanical dryer, 9.31g/h in air oven and 8.05g/h in microwave oven. Increase in foaming agent, foam stabilizer and whipping time did not cause any adverse effect on vitamin C, ash, protein, fat, carbohydrate, crude fiber contents of the samples. Samples reached a stable moisture content of 7.60% (wb) in less than 8h in mechanical dryer and air and less than 10min in microwave oven. The results of the study showed that EW, CMC and whipping time influenced the drying rate and quality of foam-mat dried tomato powder.