Verification and validation(V&V)is a helpful tool for evaluating simulation errors,but its application in unsteady cavitating flow remains a challenging issue due to the difficulty in meeting the requirement of an...Verification and validation(V&V)is a helpful tool for evaluating simulation errors,but its application in unsteady cavitating flow remains a challenging issue due to the difficulty in meeting the requirement of an asymptotic range.Hence,a new V&V approach for large eddy simulation(LES)is proposed.This approach offers a viable solution for the error estimation of simulation data that are unable to satisfy the asymptotic range.The simulation errors of cavitating flow around a projectile near the free surface are assessed using the new V&V method.The evident error values are primarily dispersed around the cavity region and free surface.The increasingly intense cavitating flow increases the error magnitudes.In addition,the modeling error magnitudes of the Dynamic Smagorinsky-Lilly model are substantially smaller than that of the Smagorinsky-Lilly model.The present V&V method can capture the decrease in the modeling errors due to model enhancements,further exhibiting its applicability in cavitating flow simulations.Moreover,the monitoring points where the simulation data are beyond the asymptotic range are primarily dispersed near the cavity region,and the number of such points grows as the cavitating flow intensifies.The simulation outcomes also suggest that the re-entrant jet and shedding cavity collapse are the chief sources of vorticity motions,which remarkably affect the simulation accuracy.The results of this study provide a valuable reference for V&V research.展开更多
systematic verification and validation(V&V)of our previously proposed momentum source wave generation method is performed.Some settings of previous numerical wave tanks(NWTs)of regular and irregular waves have bee...systematic verification and validation(V&V)of our previously proposed momentum source wave generation method is performed.Some settings of previous numerical wave tanks(NWTs)of regular and irregular waves have been optimized.The H2-5 V&V method involving five mesh sizes with mesh refinement ratio being 1.225 is used to verify the NWT of regular waves,in which the wave height and mass conservation are mainly considered based on a Lv3(H s=0.75 m)and a Lv6(H s=5 m)regular wave.Additionally,eight different sea states are chosen to validate the wave height,mass conservation and wave frequency of regular waves.Regarding the NWT of irregular waves,five different sea states with significant wave heights ranging from 0.09 m to 12.5 m are selected to validate the statistical characteristics of irregular waves,including the profile of the wave spectrum,peak frequency and significant wave height.Results show that the verification errors for Lv3 and Lv6 regular wave on the most refined grid are−0.018 and−0.35 for wave height,respectively,and−0.14 and for−0.17 mass conservation,respectively.The uncertainty estimation analysis shows that the numerical error could be partially balanced out by the modelling error to achieve a smaller validation error by adjusting the mesh size elaborately.And the validation errors of the wave height,mass conservation and dominant frequency of regular waves under different sea states are no more than 7%,8% and 2%,respectively.For a Lv3(H_(s)=0.75 m)and a Lv6(H_(s)=5 m)regular wave,simulations are validated on the wave height in wave development section for safety factors FS≈1 and FS≈0.5-1,respectively.Regarding irregular waves,the validation errors of the significant wave height and peak frequency are both lower than 2%.展开更多
Nuclear industries have faced the unfavorable circumstance such as components obsolescence and aging of instrumentation and control system, therefore, nuclear society is striving to resolve this issue fundamentally. V...Nuclear industries have faced the unfavorable circumstance such as components obsolescence and aging of instrumentation and control system, therefore, nuclear society is striving to resolve this issue fundamentally. Various studies have been conducted to address components obsolescence of instrumentation and control system. Intuitively FPGA （field programmable gate arrays） technology is replacing the high level of micro-processor type equipped with various software and hardware which causes acceleration of the aging and obsolescence in I ＆ C （instrumentation and control） system in nuclear power plants. FPGAs are highlighted as an alternative means for obsolete control systems. When engineers design the control system of NPPs （nuclear power plants） with FPGAs, it is important to meet the system development life cycles and conduct the verification and validation activities regarding to FPGA-based applications for use in NPPs. Because the verification and validation process is more important than the design process, engineer should consider the characteristics of FPGA, HDL （hardware description language） programming, faults mode, and optimization technique. And also these characteristics should be reflected in verification and validation activities. As a minimum requirement, system designers require that HDL-programmed applications should be developed in accordance with system development life cycle and HPD design process. In the verification and validation processes, a review, test, and analysis activities should be properly conducted.展开更多
Multi-agent technology has been used in many complex distributed and concurrent systems. A railway system is such a safety critical system and careful inves- tigation of the functional components is very important. St...Multi-agent technology has been used in many complex distributed and concurrent systems. A railway system is such a safety critical system and careful inves- tigation of the functional components is very important. Study of the various functional components in communi- cation-based train control （CBTC） system necessitates a good structural design followed by its validation and ver- ification through a formal modelling technique. The work presented here is the follow up of our multi-agent-based CBTC system for Indian railway designed using the methodology for engineering system of software agents. Behavioural analysis of the designed system involves several operating scenarios that arise during train run, and helps in understanding the reaction of the system to such situations. This validation and verification are very important as it allows the system designer to critically evaluate the desired function of the system and to correct the design errors, if any, before its actual implementation. Modelling, validation and verification of the structural design through Coloured petri net （CPN） are central to this paper. Analysis of simulation results validates the efficacy of the design.展开更多
This study reports on the propagation of elastic waves in 1D and 2D mass spring structures.An analytical and computation model is presented for the 1D and 2D mass spring systems with different examples.An enhancement ...This study reports on the propagation of elastic waves in 1D and 2D mass spring structures.An analytical and computation model is presented for the 1D and 2D mass spring systems with different examples.An enhancement in the band gap values was obtained by modeling the structures to obtain low frequency band gaps at small dimensions.Additionally,the evolution of the band gap as a function of mass value is discussed.Special attention is devoted to the local resonance property in frequency ranges within the gaps in the band structure for the corresponding infinite periodic lattice in the 1D and 2D mass spring system.A linear defect formed of a row of specific masses produces an elastic waveguide that transmits at the narrow pass band frequency.The frequency of the waveguides can be selected by adjusting the mass and stiffness coefficients of the materials constituting the waveguide.Moreover,we pay more attention to analyze the wave multiplexer and DE-multiplexer in the 2D mass spring system.We show that two of these tunable waveguides with alternating materials can be employed to filter and separate specific frequencies from a broad band input signal.The presented simulation data is validated through comparison with the published research,and can be extended in the development of resonators and MEMS verification.展开更多
The aim of the present work is to introduce a pattern-based method for assisting the user during the temporal Requirement Specification （RS） phase. Indeed, since the user usually has to handle abstract notation as w...The aim of the present work is to introduce a pattern-based method for assisting the user during the temporal Requirement Specification （RS） phase. Indeed, since the user usually has to handle abstract notation as well as mathematical-based languages within this phase, RS is becoming more and more tedious and error-prone especially when dealing with complex systems. The authors＇ method begins by defining a new typology while taking into account all the common temporal requirements one may meet when specifying a system. Then, a literal word-based formal grammar able to express all the types of the identified requirements has been developed. Actually, the goal is to assist the user during the requirement identification with some means that are simple, intuitive, albeit rigorous. Finally, a generic set of observation patterns relative to the new time constraint taxonomy is defined. In practice, to check a given temporal constraint, its relative observation pattern is instantiated to obtain an observer that will stand for a watchdog for the associated requirement on the system.展开更多
This study evaluates the development of a testing process for the automotive software domain, highlighting challenges stemming from the absence of adequate processes. The research demonstrates the application of Desig...This study evaluates the development of a testing process for the automotive software domain, highlighting challenges stemming from the absence of adequate processes. The research demonstrates the application of Design Science Research methodology in developing, an automotive software testing process—ProTSA, using six functional testing modules. Additionally, the study evaluates the benefits of implementing ProTSA in a specific Original Equipment Manufacturer (OEM) using an experimental single-case approach with industry professionals’ participation through a survey. The study concludes that combining testing techniques with effective communication and alignment is crucial for enhancing software quality. Furthermore, survey data indicates that implementing ProTSA leads to productivity gains by initiating tests early, resulting in time savings in the testing program and increased productivity for the testing team. Future work will explore implementing ProTSA in cybersecurity, over-the-air software updates, and autonomous vehicle testing processes. .展开更多
In dynamic problems the electric and magnetic fields are inseparable. At the same time, a multitude of electrostatic and magnetostatic effects permit mutually independent description. This separation appears to be pos...In dynamic problems the electric and magnetic fields are inseparable. At the same time, a multitude of electrostatic and magnetostatic effects permit mutually independent description. This separation appears to be possible and thermodynamically consistent when the bulk energy density depends only on the polarization density or, alternatively, on the magnetization density. However, when the bulk energy density depends simultaneously on the both densities, then, the electrostatic and magnetostatic effects should be studied together. There appear interesting cross-effects;among those are the change of the internal electrostatic field inside a specimen under the influence of the external magnetic fields, and vice versa. Below, in the framework of thermodynamic approach the boundary value problem for magnetoelectric plate is formulated and analyzed. The exact solution is established for the isotropic pyroelectric plate.展开更多
The article describes the digital instrumentation and control system for unit 5 ＆ 6 of YangJiang NPP, involving the overall I ＆ C （instrumentation and control） structure, the basic requirements and independent ver...The article describes the digital instrumentation and control system for unit 5 ＆ 6 of YangJiang NPP, involving the overall I ＆ C （instrumentation and control） structure, the basic requirements and independent verification and validation. Advanced I ＆ C systems for YangJiang NPPs have to meet increasing demands for safety and availability. Additionally, the specific requirements coming from the nuclear qualification have to be fulfilled.展开更多
A general framework（methodology and procedures） for verification and validation（V＆V） of large eddy simulations in computational fluid dynamics（CFD） is derived based on two hypotheses. The framework allows for q...A general framework（methodology and procedures） for verification and validation（V＆V） of large eddy simulations in computational fluid dynamics（CFD） is derived based on two hypotheses. The framework allows for quantitative estimations of numerical error, modeling error, their coupling, and the associated uncertainties. To meet different needs of users based on their affordable computational cost, various large eddy simulation（LES） V＆V methods are proposed. These methods range from the most sophisticated seven equation estimator to the simplest one-grid estimator, which will be calibrated using factors of safety to achieve the objective reliability and confidence level. Evaluation, calibration and validation of various LES V＆V methods in this study will be performed using rigorous statistical analysis based on an extensive database. Identification of the error sources and magnitudes has the potential to improve existing or derive new LES models. Based on extensive parametric studies in the database, it is expected that guidelines for performing large eddy simulations that meet pre-specified quality and credibility criteria can be obtained. Extension of this framework to bubbly flow is also discussed.展开更多
The present paper investigates the turbulent cavitating flow around the Clark-Y hydrofoil with special emphasis on the influence of cavitation models by verification and validation(V&V)method.RANS solver coupled w...The present paper investigates the turbulent cavitating flow around the Clark-Y hydrofoil with special emphasis on the influence of cavitation models by verification and validation(V&V)method.RANS solver coupled with the three major cavitation models(i.e.,Zwart-Gerber-Belamri,Schnerr and Sauer and full cavitation model,which are abbreviated to ZGB model,SS model and FC model respectively)is employed in this paper.The results indicate that the three cavitation models can properly reproduce the cavitation evolutions.ZGB model and SS model give better prediction in the overall cavitation patterns.FC model exhibits an obvious under-estimation for the sheet cavity,and the predicted volume fraction is closely related to the turbulent flow.The verification and validation procedure is involved to quantitatively assess the accuracy of these three cavitation models.It is indicated that the V&V procedure is suitable for the unsteady cavitating flow.The errors estimate is robust and conservative within the cavitation region,while gets closer to zero in the no-cavitation region.In addition,ZGB model exhibits the highest overall accuracy among the three models,which further verifies its wide applicability.展开更多
In this paper, we investigate the verification and validation（V＆V） procedures for the URANS simulations of the turbulent cavitating flow around a Clark-Y hydrofoil. The main focus is on the feasibility of various R...In this paper, we investigate the verification and validation（V＆V） procedures for the URANS simulations of the turbulent cavitating flow around a Clark-Y hydrofoil. The main focus is on the feasibility of various Richardson extrapolation-based uncertainty estimators in the cavitating flow simulation. The unsteady cavitating flow is simulated by a density corrected model（DCM） coupled with the Zwart cavitation model. The estimated uncertainty is used to evaluate the applicability of various uncertainty estimation methods for the cavitating flow simulation. It is shown that the preferred uncertainty estimators include the modified Factor of Safety（FS1）, the Factor of Safety（FS） and the Grid Convergence Index（GCI）. The distribution of the area without achieving the validation at the U v level shows a strong relationship with the cavitation. Further analysis indicates that the predicted velocity distributions, the transient cavitation patterns and the effects of the vortex stretching are highly influenced by the mesh resolution.展开更多
In the present paper, the Vortex Identified Zwart-Gerber-Belamri（VIZGB） cavitation model coupled with the SST-CC turbulence model is used to investigate the unsteady tip-leakage cavitating flow induced by a NACA0009...In the present paper, the Vortex Identified Zwart-Gerber-Belamri（VIZGB） cavitation model coupled with the SST-CC turbulence model is used to investigate the unsteady tip-leakage cavitating flow induced by a NACA0009 hydrofoil. A qualitative comparison between the numerical and experimental results is made. In order to quantitatively evaluate the reliability of the numerical data, the verification and validation（V＆V） procedures are used in the present paper. Errors of numerical results are estimated with seven error estimators based on the Richardson extrapolation method. It is shown that though a strict validation cannot be achieved, a reasonable prediction of the gross characteristics of the tip-leakage cavitating flow can be obtained. Based on the numerical results, the influence of the cavitation on the tip-leakage vortex（TLV） is discussed, which indicates that the cavitation accelerates the fusion of the TLV and the tip-separation vortex（TSV）. Moreover, the trajectory of the TLV, when the cavitation occurs, is close to the side wall.展开更多
When building dependable systems by integrating untrusted software components that were not originally designed to interact with each other, it is likely the occurrence of architectural mismatches related to assumptio...When building dependable systems by integrating untrusted software components that were not originally designed to interact with each other, it is likely the occurrence of architectural mismatches related to assumptions in their failure behaviour. These mismatches, if not prevented during system design, have to be tolerated during runtime. This paper presents an architectural abstraction based on exception handling for structuring fault-tolerant software systems. This abstraction comprises several components and connectors that promote an existing untrusted software element into an idealised fault-tolerant architectural element. Moreover, it is considered in the context of a rigorous software development approach based on formal methods for representing the structure and behaviour of the software architecture. The proposed approach relies on a formal specification and verification for analysing exception propagation, and verifying important dependability properties, such as deadlock freedom, and scenarios of architectural reconfiguration. The formal models are automatically generated using model transformation from UML diagrams： component diagram representing the system structure, and sequence diagrams representing the system behaviour. Finally, the formal models are also used for generating unit and integration test cases that are used for assessing the correctness of the source code. The feasibility of the proposed architectural approach was evaluated on an embedded critical case study.展开更多
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 comput...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 simula-tions 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 mod-els 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 cate-gories: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 prob-lems 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 high-lights 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.展开更多
Why is it important to verify/validate model transformations？ The motivation is to improve the quality of the trans- formations, and therefore the quality of the generated software artifacts. Verified/validated model...Why is it important to verify/validate model transformations？ The motivation is to improve the quality of the trans- formations, and therefore the quality of the generated software artifacts. Verified/validated model transformations make it possible to ensure certain properties of the generated software artifacts. In this way, verification/validation methods can guarantee different requirements stated by the actual domain against the generated/modified/optimized software products. For example, a verified/ validated model transformation can ensure the preservation of certain properties during the model-to-model transformation. This paper emphasizes the necessity of methods that make model transformation verified/validated, discusses the different scenarios of model transformation verification and validation, and introduces the principles of a novel test-driven method for verifying/ validating model transformations. We provide a solution that makes it possible to automatically generate test input models for model transformations. Furthermore, we collect and discuss the actual open issues in the field of verification/validation of model transformations.展开更多
The large eddy simulation(LES)is used to resolve the flow structure in the cavitating turbulent flow around the Clark-Y hydrofoil coupled with a homogeneous cavitation model.A new method is proposed in this paper to c...The large eddy simulation(LES)is used to resolve the flow structure in the cavitating turbulent flow around the Clark-Y hydrofoil coupled with a homogeneous cavitation model.A new method is proposed in this paper to calculate the LES error of the time-averaged streamwise velocity for the LES verification and validation(V&V).From the instantaneous cavity patterns,it is demonstrated that the predicted results agree fairly well with the experimental data.With this new proposed method,the LES errors can be easily and effectively calculated with a limited mesh number,and the method might be used in the other applications of the LES V&V.Results of the LES errors obtained by the new method show that the relatively steady flow can be simulated with small errors,while the complex flow structures at the cavity shedding region might lead to an increase of errors in the LES modeling.In addition,the distributions of the resolved Reynolds stresses are used to estimate the influences of the cavitation on the turbulent fluctuations.Results indicate that the turbulent fluctuations for the cavitating flow are much larger in magnitude as compared to the cases without cavitation.展开更多
In this paper,we propose an approach to formally verify and rigorously validate a simulation system against the specification of the real system.We implement the approach in a verification and validation calculator to...In this paper,we propose an approach to formally verify and rigorously validate a simulation system against the specification of the real system.We implement the approach in a verification and validation calculator tool that takes as input a set of statements that capture the requirements,internal conditions of the system and expected outputs of the real system and produces as output whether the simulation satisfies the requirements,faithfully represents the internal conditions of the system and produces the expected outputs.We provide a use case to show how subject matter experts can apply the tool.展开更多
In this letter, the attached turbulent cavitating flow around the Clark-Y hydrofoil is investigated by the numerical simulation with special emphasis on error analysis of large eddy simulation（LES） for the unsteady ...In this letter, the attached turbulent cavitating flow around the Clark-Y hydrofoil is investigated by the numerical simulation with special emphasis on error analysis of large eddy simulation（LES） for the unsteady cavitation simulation. The numerical results indicate that the present simulation can capture the periodic cavity shedding behavior and show a fairly good agreement with the available experimental data. Further analysis demonstrates that the cavitation has a great influence on LES numerical error and modeling error. The modeling error and numerical error are almost on the same order of magnitude, while the modeling error often shows a little bit larger magnitude than numerical error. The numerical error and modeling error sometimes can partially offset each other if they have the opposite sign. Besides, our results show that cavitation can extend the magnitudes and oscillation levels of numerical error and modeling error.展开更多
The methodological quality of subject-specific finite element analysis papers depends on the rigor of the study design and detailed description of key elements,while assessment instruments are often confined to clinic...The methodological quality of subject-specific finite element analysis papers depends on the rigor of the study design and detailed description of key elements,while assessment instruments are often confined to clinical trials or quasi-experiments.This study aims to present an instrument for methodological quality assessment of singlesubject finite element analysis used in computational orthopaedics(MQSSFE).Based upon existing instruments and relevant review papers,a pilot version was developed consisting of 37 items with 6 domains,including study design and presentation of findings,subject recruitment,model reconstruction and configuration,boundary and loading conditions(simulation),model verification and validation,and model assumption and validity.We interviewed four experts in the field to assess the face validity and refined the instrument.The instrument was tested for interrater reliability among two assessors on nine finite element study papers.Also,the criterion validity was evaluated by comparing the similarity of the MQSSFE and the modified Down and Black instrument.The intraclass correlation coefficient was 0.965,while the MQSSFE was significantly moderately correlated with the modified Down and Black instruments(r=0.61).We believed that MQSSFE was adequately appropriate,reliable,and valid for assessing the methodological quality for finite element studies used in computational orthopaedics.The instrument could facilitate quality assessment in the systematic reviews of finite element models and checklists for fidelity.展开更多
基金Supported by the National Key R&D Program of China(2022YFB3303501)the National Natural Science Foundation of China(Project Nos.52176041 and 12102308)the Fundamental Research Funds for the Central Universities(Project Nos.2042023kf0208 and 2042023kf0159).
文摘Verification and validation(V&V)is a helpful tool for evaluating simulation errors,but its application in unsteady cavitating flow remains a challenging issue due to the difficulty in meeting the requirement of an asymptotic range.Hence,a new V&V approach for large eddy simulation(LES)is proposed.This approach offers a viable solution for the error estimation of simulation data that are unable to satisfy the asymptotic range.The simulation errors of cavitating flow around a projectile near the free surface are assessed using the new V&V method.The evident error values are primarily dispersed around the cavity region and free surface.The increasingly intense cavitating flow increases the error magnitudes.In addition,the modeling error magnitudes of the Dynamic Smagorinsky-Lilly model are substantially smaller than that of the Smagorinsky-Lilly model.The present V&V method can capture the decrease in the modeling errors due to model enhancements,further exhibiting its applicability in cavitating flow simulations.Moreover,the monitoring points where the simulation data are beyond the asymptotic range are primarily dispersed near the cavity region,and the number of such points grows as the cavitating flow intensifies.The simulation outcomes also suggest that the re-entrant jet and shedding cavity collapse are the chief sources of vorticity motions,which remarkably affect the simulation accuracy.The results of this study provide a valuable reference for V&V research.
基金supported by the National Key R&D Program of China(Grant No.2022YFB3303500).
文摘systematic verification and validation(V&V)of our previously proposed momentum source wave generation method is performed.Some settings of previous numerical wave tanks(NWTs)of regular and irregular waves have been optimized.The H2-5 V&V method involving five mesh sizes with mesh refinement ratio being 1.225 is used to verify the NWT of regular waves,in which the wave height and mass conservation are mainly considered based on a Lv3(H s=0.75 m)and a Lv6(H s=5 m)regular wave.Additionally,eight different sea states are chosen to validate the wave height,mass conservation and wave frequency of regular waves.Regarding the NWT of irregular waves,five different sea states with significant wave heights ranging from 0.09 m to 12.5 m are selected to validate the statistical characteristics of irregular waves,including the profile of the wave spectrum,peak frequency and significant wave height.Results show that the verification errors for Lv3 and Lv6 regular wave on the most refined grid are−0.018 and−0.35 for wave height,respectively,and−0.14 and for−0.17 mass conservation,respectively.The uncertainty estimation analysis shows that the numerical error could be partially balanced out by the modelling error to achieve a smaller validation error by adjusting the mesh size elaborately.And the validation errors of the wave height,mass conservation and dominant frequency of regular waves under different sea states are no more than 7%,8% and 2%,respectively.For a Lv3(H_(s)=0.75 m)and a Lv6(H_(s)=5 m)regular wave,simulations are validated on the wave height in wave development section for safety factors FS≈1 and FS≈0.5-1,respectively.Regarding irregular waves,the validation errors of the significant wave height and peak frequency are both lower than 2%.
文摘Nuclear industries have faced the unfavorable circumstance such as components obsolescence and aging of instrumentation and control system, therefore, nuclear society is striving to resolve this issue fundamentally. Various studies have been conducted to address components obsolescence of instrumentation and control system. Intuitively FPGA （field programmable gate arrays） technology is replacing the high level of micro-processor type equipped with various software and hardware which causes acceleration of the aging and obsolescence in I ＆ C （instrumentation and control） system in nuclear power plants. FPGAs are highlighted as an alternative means for obsolete control systems. When engineers design the control system of NPPs （nuclear power plants） with FPGAs, it is important to meet the system development life cycles and conduct the verification and validation activities regarding to FPGA-based applications for use in NPPs. Because the verification and validation process is more important than the design process, engineer should consider the characteristics of FPGA, HDL （hardware description language） programming, faults mode, and optimization technique. And also these characteristics should be reflected in verification and validation activities. As a minimum requirement, system designers require that HDL-programmed applications should be developed in accordance with system development life cycle and HPD design process. In the verification and validation processes, a review, test, and analysis activities should be properly conducted.
基金The work is a part of project named ＂＇Multi- Agent based Train Operation in Moving Block Setup＂ funded by Department of Information Technology （DIT）, Ministry of Commu- nications and Information Technology, Government of India, vide Grant Number 2（6）/2010-EC dated 21/03/2011.
文摘Multi-agent technology has been used in many complex distributed and concurrent systems. A railway system is such a safety critical system and careful inves- tigation of the functional components is very important. Study of the various functional components in communi- cation-based train control （CBTC） system necessitates a good structural design followed by its validation and ver- ification through a formal modelling technique. The work presented here is the follow up of our multi-agent-based CBTC system for Indian railway designed using the methodology for engineering system of software agents. Behavioural analysis of the designed system involves several operating scenarios that arise during train run, and helps in understanding the reaction of the system to such situations. This validation and verification are very important as it allows the system designer to critically evaluate the desired function of the system and to correct the design errors, if any, before its actual implementation. Modelling, validation and verification of the structural design through Coloured petri net （CPN） are central to this paper. Analysis of simulation results validates the efficacy of the design.
文摘This study reports on the propagation of elastic waves in 1D and 2D mass spring structures.An analytical and computation model is presented for the 1D and 2D mass spring systems with different examples.An enhancement in the band gap values was obtained by modeling the structures to obtain low frequency band gaps at small dimensions.Additionally,the evolution of the band gap as a function of mass value is discussed.Special attention is devoted to the local resonance property in frequency ranges within the gaps in the band structure for the corresponding infinite periodic lattice in the 1D and 2D mass spring system.A linear defect formed of a row of specific masses produces an elastic waveguide that transmits at the narrow pass band frequency.The frequency of the waveguides can be selected by adjusting the mass and stiffness coefficients of the materials constituting the waveguide.Moreover,we pay more attention to analyze the wave multiplexer and DE-multiplexer in the 2D mass spring system.We show that two of these tunable waveguides with alternating materials can be employed to filter and separate specific frequencies from a broad band input signal.The presented simulation data is validated through comparison with the published research,and can be extended in the development of resonators and MEMS verification.
文摘The aim of the present work is to introduce a pattern-based method for assisting the user during the temporal Requirement Specification （RS） phase. Indeed, since the user usually has to handle abstract notation as well as mathematical-based languages within this phase, RS is becoming more and more tedious and error-prone especially when dealing with complex systems. The authors＇ method begins by defining a new typology while taking into account all the common temporal requirements one may meet when specifying a system. Then, a literal word-based formal grammar able to express all the types of the identified requirements has been developed. Actually, the goal is to assist the user during the requirement identification with some means that are simple, intuitive, albeit rigorous. Finally, a generic set of observation patterns relative to the new time constraint taxonomy is defined. In practice, to check a given temporal constraint, its relative observation pattern is instantiated to obtain an observer that will stand for a watchdog for the associated requirement on the system.
文摘This study evaluates the development of a testing process for the automotive software domain, highlighting challenges stemming from the absence of adequate processes. The research demonstrates the application of Design Science Research methodology in developing, an automotive software testing process—ProTSA, using six functional testing modules. Additionally, the study evaluates the benefits of implementing ProTSA in a specific Original Equipment Manufacturer (OEM) using an experimental single-case approach with industry professionals’ participation through a survey. The study concludes that combining testing techniques with effective communication and alignment is crucial for enhancing software quality. Furthermore, survey data indicates that implementing ProTSA leads to productivity gains by initiating tests early, resulting in time savings in the testing program and increased productivity for the testing team. Future work will explore implementing ProTSA in cybersecurity, over-the-air software updates, and autonomous vehicle testing processes. .
文摘In dynamic problems the electric and magnetic fields are inseparable. At the same time, a multitude of electrostatic and magnetostatic effects permit mutually independent description. This separation appears to be possible and thermodynamically consistent when the bulk energy density depends only on the polarization density or, alternatively, on the magnetization density. However, when the bulk energy density depends simultaneously on the both densities, then, the electrostatic and magnetostatic effects should be studied together. There appear interesting cross-effects;among those are the change of the internal electrostatic field inside a specimen under the influence of the external magnetic fields, and vice versa. Below, in the framework of thermodynamic approach the boundary value problem for magnetoelectric plate is formulated and analyzed. The exact solution is established for the isotropic pyroelectric plate.
文摘The article describes the digital instrumentation and control system for unit 5 ＆ 6 of YangJiang NPP, involving the overall I ＆ C （instrumentation and control） structure, the basic requirements and independent verification and validation. Advanced I ＆ C systems for YangJiang NPPs have to meet increasing demands for safety and availability. Additionally, the specific requirements coming from the nuclear qualification have to be fulfilled.
文摘A general framework（methodology and procedures） for verification and validation（V＆V） of large eddy simulations in computational fluid dynamics（CFD） is derived based on two hypotheses. The framework allows for quantitative estimations of numerical error, modeling error, their coupling, and the associated uncertainties. To meet different needs of users based on their affordable computational cost, various large eddy simulation（LES） V＆V methods are proposed. These methods range from the most sophisticated seven equation estimator to the simplest one-grid estimator, which will be calibrated using factors of safety to achieve the objective reliability and confidence level. Evaluation, calibration and validation of various LES V＆V methods in this study will be performed using rigorous statistical analysis based on an extensive database. Identification of the error sources and magnitudes has the potential to improve existing or derive new LES models. Based on extensive parametric studies in the database, it is expected that guidelines for performing large eddy simulations that meet pre-specified quality and credibility criteria can be obtained. Extension of this framework to bubbly flow is also discussed.
基金supported by the National Natural Science Foundation of China (Grant No. 52176041).
文摘The present paper investigates the turbulent cavitating flow around the Clark-Y hydrofoil with special emphasis on the influence of cavitation models by verification and validation(V&V)method.RANS solver coupled with the three major cavitation models(i.e.,Zwart-Gerber-Belamri,Schnerr and Sauer and full cavitation model,which are abbreviated to ZGB model,SS model and FC model respectively)is employed in this paper.The results indicate that the three cavitation models can properly reproduce the cavitation evolutions.ZGB model and SS model give better prediction in the overall cavitation patterns.FC model exhibits an obvious under-estimation for the sheet cavity,and the predicted volume fraction is closely related to the turbulent flow.The verification and validation procedure is involved to quantitatively assess the accuracy of these three cavitation models.It is indicated that the V&V procedure is suitable for the unsteady cavitating flow.The errors estimate is robust and conservative within the cavitation region,while gets closer to zero in the no-cavitation region.In addition,ZGB model exhibits the highest overall accuracy among the three models,which further verifies its wide applicability.
基金Project supported by the National Natural Science Foundation of China(Project Nos.51576143,11472197)
文摘In this paper, we investigate the verification and validation（V＆V） procedures for the URANS simulations of the turbulent cavitating flow around a Clark-Y hydrofoil. The main focus is on the feasibility of various Richardson extrapolation-based uncertainty estimators in the cavitating flow simulation. The unsteady cavitating flow is simulated by a density corrected model（DCM） coupled with the Zwart cavitation model. The estimated uncertainty is used to evaluate the applicability of various uncertainty estimation methods for the cavitating flow simulation. It is shown that the preferred uncertainty estimators include the modified Factor of Safety（FS1）, the Factor of Safety（FS） and the Grid Convergence Index（GCI）. The distribution of the area without achieving the validation at the U v level shows a strong relationship with the cavitation. Further analysis indicates that the predicted velocity distributions, the transient cavitation patterns and the effects of the vortex stretching are highly influenced by the mesh resolution.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51576143,11772239 and 91752105)the Science and Technology on Water Jet Propulsion Laboratory(Grant No.61422230101162223002)
文摘In the present paper, the Vortex Identified Zwart-Gerber-Belamri（VIZGB） cavitation model coupled with the SST-CC turbulence model is used to investigate the unsteady tip-leakage cavitating flow induced by a NACA0009 hydrofoil. A qualitative comparison between the numerical and experimental results is made. In order to quantitatively evaluate the reliability of the numerical data, the verification and validation（V＆V） procedures are used in the present paper. Errors of numerical results are estimated with seven error estimators based on the Richardson extrapolation method. It is shown that though a strict validation cannot be achieved, a reasonable prediction of the gross characteristics of the tip-leakage cavitating flow can be obtained. Based on the numerical results, the influence of the cavitation on the tip-leakage vortex（TLV） is discussed, which indicates that the cavitation accelerates the fusion of the TLV and the tip-separation vortex（TSV）. Moreover, the trajectory of the TLV, when the cavitation occurs, is close to the side wall.
基金supported by Fapesp/Brazil under Grant No. 06/02116-2 and CAPES/Brazil under Grant No. 0722-07-3Cecília Rubira is partially supported by CNPq/Brazil under Grant Nos. 301446/2006-7 and 484138/2006-5
文摘When building dependable systems by integrating untrusted software components that were not originally designed to interact with each other, it is likely the occurrence of architectural mismatches related to assumptions in their failure behaviour. These mismatches, if not prevented during system design, have to be tolerated during runtime. This paper presents an architectural abstraction based on exception handling for structuring fault-tolerant software systems. This abstraction comprises several components and connectors that promote an existing untrusted software element into an idealised fault-tolerant architectural element. Moreover, it is considered in the context of a rigorous software development approach based on formal methods for representing the structure and behaviour of the software architecture. The proposed approach relies on a formal specification and verification for analysing exception propagation, and verifying important dependability properties, such as deadlock freedom, and scenarios of architectural reconfiguration. The formal models are automatically generated using model transformation from UML diagrams： component diagram representing the system structure, and sequence diagrams representing the system behaviour. Finally, the formal models are also used for generating unit and integration test cases that are used for assessing the correctness of the source code. The feasibility of the proposed architectural approach was evaluated on an embedded critical case study.
文摘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 simula-tions 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 mod-els 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 cate-gories: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 prob-lems 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 high-lights 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.
基金Project partially supported by the European Union and the European Social Fund(No.TAMOP-4.2.2.C-11/1/KONV-2012-0013)
文摘Why is it important to verify/validate model transformations？ The motivation is to improve the quality of the trans- formations, and therefore the quality of the generated software artifacts. Verified/validated model transformations make it possible to ensure certain properties of the generated software artifacts. In this way, verification/validation methods can guarantee different requirements stated by the actual domain against the generated/modified/optimized software products. For example, a verified/ validated model transformation can ensure the preservation of certain properties during the model-to-model transformation. This paper emphasizes the necessity of methods that make model transformation verified/validated, discusses the different scenarios of model transformation verification and validation, and introduces the principles of a novel test-driven method for verifying/ validating model transformations. We provide a solution that makes it possible to automatically generate test input models for model transformations. Furthermore, we collect and discuss the actual open issues in the field of verification/validation of model transformations.
基金supported by the National Natural Science Foundation of China(Grant Nos.51822903,11772239).
文摘The large eddy simulation(LES)is used to resolve the flow structure in the cavitating turbulent flow around the Clark-Y hydrofoil coupled with a homogeneous cavitation model.A new method is proposed in this paper to calculate the LES error of the time-averaged streamwise velocity for the LES verification and validation(V&V).From the instantaneous cavity patterns,it is demonstrated that the predicted results agree fairly well with the experimental data.With this new proposed method,the LES errors can be easily and effectively calculated with a limited mesh number,and the method might be used in the other applications of the LES V&V.Results of the LES errors obtained by the new method show that the relatively steady flow can be simulated with small errors,while the complex flow structures at the cavity shedding region might lead to an increase of errors in the LES modeling.In addition,the distributions of the resolved Reynolds stresses are used to estimate the influences of the cavitation on the turbulent fluctuations.Results indicate that the turbulent fluctuations for the cavitating flow are much larger in magnitude as compared to the cases without cavitation.
文摘In this paper,we propose an approach to formally verify and rigorously validate a simulation system against the specification of the real system.We implement the approach in a verification and validation calculator tool that takes as input a set of statements that capture the requirements,internal conditions of the system and expected outputs of the real system and produces as output whether the simulation satisfies the requirements,faithfully represents the internal conditions of the system and produces the expected outputs.We provide a use case to show how subject matter experts can apply the tool.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11772239,51576143 and 91752105)the Outstanding Youth Foundation of Natural Science Foundation of Hubei Province(Grant No.2017CFA048)
文摘In this letter, the attached turbulent cavitating flow around the Clark-Y hydrofoil is investigated by the numerical simulation with special emphasis on error analysis of large eddy simulation（LES） for the unsteady cavitation simulation. The numerical results indicate that the present simulation can capture the periodic cavity shedding behavior and show a fairly good agreement with the available experimental data. Further analysis demonstrates that the cavitation has a great influence on LES numerical error and modeling error. The modeling error and numerical error are almost on the same order of magnitude, while the modeling error often shows a little bit larger magnitude than numerical error. The numerical error and modeling error sometimes can partially offset each other if they have the opposite sign. Besides, our results show that cavitation can extend the magnitudes and oscillation levels of numerical error and modeling error.
基金This work was supported by the Key R&D Program granted by the Ministry of Science and Technology of China(reference number:2018YFB1107000)the National Natural Science Foundation of China(reference numbers:11732015,11972315)+1 种基金the Project of Academic Leader of Health System(reference number:PWRd2019-05)the Project of Novel Interdisciplinary of Health System(reference number:PWXx2020-08)in Pudong New Area,Shanghai,China.
文摘The methodological quality of subject-specific finite element analysis papers depends on the rigor of the study design and detailed description of key elements,while assessment instruments are often confined to clinical trials or quasi-experiments.This study aims to present an instrument for methodological quality assessment of singlesubject finite element analysis used in computational orthopaedics(MQSSFE).Based upon existing instruments and relevant review papers,a pilot version was developed consisting of 37 items with 6 domains,including study design and presentation of findings,subject recruitment,model reconstruction and configuration,boundary and loading conditions(simulation),model verification and validation,and model assumption and validity.We interviewed four experts in the field to assess the face validity and refined the instrument.The instrument was tested for interrater reliability among two assessors on nine finite element study papers.Also,the criterion validity was evaluated by comparing the similarity of the MQSSFE and the modified Down and Black instrument.The intraclass correlation coefficient was 0.965,while the MQSSFE was significantly moderately correlated with the modified Down and Black instruments(r=0.61).We believed that MQSSFE was adequately appropriate,reliable,and valid for assessing the methodological quality for finite element studies used in computational orthopaedics.The instrument could facilitate quality assessment in the systematic reviews of finite element models and checklists for fidelity.
