Efficiency analysis of numerical integrations for finite element substructure in real-time hybrid simulation

Finite element（FE） is a powerful tool and has been applied by investigators to real-time hybrid simulations（RTHSs）. This study focuses on the computational efficiency, including the computational time and accuracy, of numerical integrations in solving FE numerical substructure in RTHSs. First, sparse matrix storage schemes are adopted to decrease the computational time of FE numerical substructure. In this way, the task execution time（TET） decreases such that the scale of the numerical substructure model increases. Subsequently, several commonly used explicit numerical integration algorithms, including the central difference method（CDM）, the Newmark explicit method, the Chang method and the Gui-λ method, are comprehensively compared to evaluate their computational time in solving FE numerical substructure. CDM is better than the other explicit integration algorithms when the damping matrix is diagonal, while the Gui-λ（λ = 4） method is advantageous when the damping matrix is non-diagonal. Finally, the effect of time delay on the computational accuracy of RTHSs is investigated by simulating structure-foundation systems. Simulation results show that the influences of time delay on the displacement response become obvious with the mass ratio increasing, and delay compensation methods may reduce the relative error of the displacement peak value to less than 5% even under the large time-step and large time delay.

Quick System-Level DDR3 Signal Integrity Simulation Research

Double data rate synchronous dynamic random access memory （DDR3） has become one of the most mainstream applications in current server and computer systems. In order to quickly set up a system-level signal integrity （SI） simulation flow for the DDR3 interface, two system-level SI simulation methodologies, which are board-level S-parameter extraction in the frequency-domain and system-level simulation assumptions in the time domain, are introduced in this paper. By comparing the flow of Speed2000 and PowerSI/Hspice, PowerSI is chosen for the printed circuit board （PCB） board-level S-parameter extraction, while Tektronix oscilloscope （TDS7404） is used for the DDR3 waveform measurement. The lab measurement shows good agreement between simulation and measurement. The study shows that the combination of PowerSI and Hspice is recommended for quick system-level DDR3 SI simulation.

Calibration of a rule-based intelligent network simulation model

This paper is focused on calibration of an intelligent network simulation model （INS1M） with reallife transportation network to analyse the INSIM＇s feasibility in simulating commuters＇ travel choice behaviour under the influence of real-time integrated multimodal traveller information （IMTI）. A transportation network model for the central and western areas of Singapore was simulated in PARAMICS and integrated with INSIM expert system by means of an application programming interface to form the INSIM. Upon calibration, INSIM was able to realistically present complicated scenarios in which real-time IMTI was provided to commuters and the network performance measures being recorded.

Nano-Electronic Simulation Software (NESS): A Novel Open-Source TCAD Simulation Environment

This paper presents the latest status of the open source advanced TCAD simulator called Nano-Electronic Simulation Software(NESS)which is currently under development at the Device Modeling Group of the University of Glasgow.NESS is designed with the main aim to provide an open,flexible,and easy to use simulation environment where users are able not only to perform numerical simulations but also to develop and implement new simulation methods and models.Currently,NESS is organized into two main components:the structure generator and a collection of different numerical solvers;which are linked to supporting components such as an effective mass extractor and materials database.This paper gives a brief overview of each of the components by describing their main capabilities,structure,and theory behind each one of them.Moreover,to illustrate the capabilities of each component,here we have given examples considering various device structures,architectures,materials,etc.at multiple simulation conditions.We expect that NESS will prove to be a great tool for both conventional as well as exploratory device research programs and projects.

Simulation Operating System and Integrated Simulation Software

In this paper, a new concept of simulation operating system (SIMOS) is described. A detailed definition of SIMOS is given, and two integrated simulation software (IPSOS and IMSS) are introduced based on SIMOS.

基于多系统集成仿真方法的燃气轮机动态特性仿真研究

In order to simulate the actual operation process of gas turbine more accurately,this paper uses multi system integration simulation technology to study the dynamic characteristics of gas turbine.Firstly,considering the factors such as variable stator vanes,air extraction,cooling mixing and multiple inertias,a refined model of gas turbine is established.Then,AMESim is used to establish the model of the VSV actuator of the gas turbine,and Flowmaster is used to establish the model of the secondary air system of the gas turbine.Finally,the multi-system integration simulation model of gas turbine is established by using interface technology to study the dynamic characteristics of gas turbine under load mutation.The simulation results show that the established multisystem simulation model of gas turbine can effectively simulate the dynamic operation process of gas turbine under the condition of load mutation,which is of great significance to the simulation research of gas turbine.

The influences of model parameters on the characteristics of memristors

As the fourth passive circuit component, a memristor is a nonlinear resistor that can ＂remember＂ the amount of charge passing through it. The characteristic of ＂remembering＂ the charge and non-volatility makes memristors great potential candidates in many fields. Nowadays, only a few groups have the ability to fabricate memristors, and most researchers study them by theoretic analysis and simulation. In this paper, we first analyse the theoretical base and characteristics of memristors, then use a simulation program with integrated circuit emphasis as our tool to simulate the theoretical model of memristors and change the parameters in the model to see the influence of each parameter on the characteristics. Our work supplies researchers engaged in memristor-based circuits with advice on how to choose the proper parameters.

基于表面势的增强型p-GaN HEMT器件模型

为了满足功率电路及系统设计对p-GaN HEMT(High Electron Mobility Transistor)器件模型的需求,本文建立了一套基于表面势计算方法的增强型p-GaN HEMT器件SPICE(Simulation Program with Integrated Circuit Emphasis)模型.根据耗尽型GaN HEMT器件和增强型p-GaN HEMT器件结构的对比,推导出p-GaN栅结构电压解析公式.考虑到p-GaN栅掺杂效应和物理机理,推导出栅电容和栅电流解析公式.同时,与基于表面势的高电子迁移率晶体管高级SPICE模型内核相结合,建立完整的增强型p-GaN HEMT功率器件的SPICE模型.将所建立的SPICE模型与实测结果进行对比验证.结果表明,所建立的模型准确实现了包括转移特性、输出特性、栅电容以及栅电流在内的p-GaN HEMT器件的电学特性.模型仿真数据与实测数据拟合度误差均小于5%.本文所提出的增强型p-GaN HEMT器件模型在进行电路设计时具有重要的应用价值.

Modeling hydrogen exchange of proteins by a multiscale method

We proposed a practical way for mapping the results of coarse-grained molecular simulations to the observables in hydrogen change experiments.By combining an atomic-interaction based coarse-grained model with an all-atom structure reconstruction algorithm,we reproduced the experimental hydrogen exchange data with reasonable accuracy using molecular dynamics simulations.We also showed that the coarse-grained model can be further improved by imposing experimental restraints from hydrogen exchange data via an iterative optimization strategy.These results suggest that it is feasible to develop an integrative molecular simulation scheme by incorporating the hydrogen exchange data into the coarse-grained molecular dynamics simulations and therefore help to overcome the accuracy bottleneck of coarse-grained models.

Ontology-Based Semantic Multi-agent Framework for Micro-grids with Cyber Physical Concept

The distributed hierarchical control based on multi-agent system(MAS) is the main control method of micro-grids.By allowing more flexible interactions between computing components and their physical environments,cyber physical system(CPS) presents a new approach for the distributed hierarchical engineering system,with micro-grids included.The object of this paper is to integrate the CPS concept with MAS technology and propose a new control framework for micro-grids.With the analysis of the operating mode and control method of micro-grids,the cyber physical control concepts of ontologybased semantic agent are discussed.Then an MAS-based architecture of cyber physical micro-grid system and an intelligent electronic device(IED) function structure are proposed.Finally,in order to operate and test the cyber physical micro-grid concept,an integrated simulation model is presented.

Characteristics of titanium oxide memristor with coexistence of dopant drift and a tunnel barrier

The recent published experimental data of titanium oxide memristor devices which are tested under the same experi- mental conditions exhibit the strange instability and complexity of these devices. Such undesired characteristics preclude the understanding of the device conductive processes and the memristor-based practical applications. The possibility of the coexistence of dopant drift and tunnel barrier conduction in a memristor provides preliminary explanations for the undesired characteristics. However, current research lacks detailed discussion about the coexistence case. In this paper, dopant drift and tunnel barrier-based theories are first analyzed for studying the relations between parameters and physical variables which affect characteristics of mernristors, and then the influences of each parameter change on the conductive behaviors in the single and coexistence cases of the two mechanisms are simulated and discussed respectively. The simulation results provide further explanations of the complex device conduction. Theoretical methods of eliminating or reducing the coex- istence of the two mechanisms are proposed, in order to increase the stability of the device conduction. This work also provides the support for optimizing the fabrications of memristor devices with excellent performance.

Design of Multi-Valued Logic Circuit Using Carbon Nano Tube Field Transistors

The design of a three-input logic circuit using carbon nanotube field effect transistors(CNTFETs)is presented.Ternary logic must be an exact replacement for dual logic since it performs straightforwardly in digital devices,which is why this design is so popular,and it also reduces chip area,both of which are examples of circuit overheads.The proposed module we have investigated is a triple-logic-based one,based on advanced technology CNTFETs and an emphasis on minimizing delay times at various values,as well as comparisons of the design working with various load capacitances.Comparing the proposed design with the existing design,the delay times was reduced from 66.32 to 16.41 ps,i.e.,a 75.26%reduction.However,the power dissipation was not optimized,and increased by 1.44%compared to the existing adder.The number of transistors was also reduced,and the product of power and delay(P∗D)achieved a value of 0.0498053 fJ.An improvement at 1 V was also achieved.A load capacitance(fF)was measured at different values,and the average delay measured for different values of capacitance had a maximum of 83.60 ps and a minimum of 22.54 ps,with a range of 61.06 ps.The power dissipations ranged from a minimum of 3.38μW to a maximum of 6.49μW.Based on these results,the use of this CNTFET half-adder design in multiple Boolean circuits will be a useful addition to circuit design.

A modified streamwise body force model of fan with distorted inflow for rapid propulsion-airframe integrated simulation

Streamwise Body Force Model(SBFM)could be used to simulate the force of blade on the airflow,resulting in rapid propulsion-airframe integrated simulation.However,when subjected to inlet distortion,the upstream flow field of fan stage is redistributed,which causes inaccurate prediction of fan stage performance.As inspired by the upstream influence of compressor,this paper aims to present a modification strategy for SBFM method to predict the compressor performance under circumferential inlet distortion without any knowledge of compressor geometry.Based on the linearized motion equation,the Upstream Influence Model(UIM)is introduced to predict the upstream flow field redistribution.Then the theoretical Mach number at Aerodynamic Interface Plane(AIP)position is calculated and selected to determine the corresponding body force coefficients based on the functional relationship between body force coefficients and Mach number,thus the upstream influence of compressor could be accurately quantified and the Modified Streamwise Body Force Model(MSBFM)could be established.Two studied cases are calculated with different methods and the upstream flow fields are analyzed.The prediction error of MSBFM method for compressor adiabatic efficiency is less than 3%,and the calculation efficiency is improved 20 times under the condition of ensuring computing accuracy.The MSBFM method has the potential for rapid propulsion-airframe integrated simulation.

Structural modeling of proteins by integrating small-angle x-ray scattering data

Elucidating the structure of large biomolecules such as multi-domain proteins or protein complexes is challenging due to their high flexibility in solution. Recently, an ＂integrative structural biology＂ approach has been proposed, which aims to determine the protein structure and characterize protein flexibility by combining complementary high- and lowresolution experimental data using computer simulations. Small-angle x-ray scattering（SAXS） is an efficient technique that can yield low-resolution structural information, including protein size and shape. Here, we review computational methods that integrate SAXS with other experimental datasets for structural modeling. Finally, we provide a case study of determination of the structure of a protein complex formed between the tandem SH3 domains in c-Cb1-associated protein and the proline-rich loop in human vinculin.

Streamwise-body-force-model for rapid simulation combining internal and external flow fields

A streamwise-body-force-model （SBFM） is developed and applied in the overall flow simulation for the distributed propulsion system, combining internal and external flow fields. In view of axial stage effects, fan or compressor effects could be simplified as body forces along the streamline. These body forces which are functions of local parameters could be added as source terms in Navier-Stokes equations to replace solid boundary conditions of blades and hubs. The val- idation of SBFM with uniform inlet and distortion inlet of compressors shows that pressure performance characteristics agree well with experimental data. A three-dimensional simulation of the integration configuration, via a blended wing body aircraft with a distributed propulsion system using the SBFM, has been completed. Lift coefficient and drag coefficient agree well with wind tunnel test results. Results show that to reach the goal of rapid integrated simulation combining internal and external flow fields, the computational fluid dynamics method based on SBFM is reasonable.

Electric Vehicle Charging Simulation Framework Considering Traffic,User,and Power Grid

The traffic and user have significant impacts on the electric vehicle(EV)charging load but are not considered in the existing research.We propose a novel integrated simulation framework considering the traffic,the user,and power grid as well as the EV traveling,parking and charging based on cellular automaton(CA).The traffic is modeled by the traffic module of the proposed framework based on CA,while the power grid and user are modeled in the EV charging module.The traffic flow,user’s charging preference,user’s charging satisfaction,and the total supply capability(TSC)in the surveyed region are considered in the proposed framework.Two cases are carried out to show the interactions between the user and power grid.It is shown that the proposed framework can accurately simulate the interactions among traffic situation,user's behavior and TSC,which are significantly lacking in the existing research.The proposed framework is scalable in considering additional interrelated elements.

Uncertainty analysis for integrated water system simulations using GLUE with different acceptability thresholds

Integrated water quantity and quality simulations have become a popular tool in investigations on global water crisis.For integrated and complex models,conventional uncertainty estimations focus on the uncertainties of individual modules,e.g.,module parameters and structures,and do not consider the uncertainties propagated from interconnected modules.Therefore,this study investigated all the uncertainties of integrated water system simulations using the GLUE(i.e.,generalized likelihood uncertainty estimation)method,including uncertainties associated with individual modules,propagated uncertainties associated with interconnected modules,and their combinations.The changes in both acceptability thresholds of GLUE and the uncertainty estimation results were also investigated for different fixed percentages of total number of iterations(100000).Water quantity and quality variables(i.e.,runoff and ammonium nitrogen)were selected for the case study.The results showed that module uncertainty did not affect the runoff simulation performance,but remarkably weakened the water quality responses as the fixed percentage increased during calibration and validation periods.The propagated uncertainty from hydrological modules could not be ignored for water quality simulations,particularly during validation.The combination of module and propagated uncertainties further weakened the water quality simulation performance.The uncertainty intervals became wider owing to an increase in the fixed percentages and introduction of more uncertainty sources.Moreover,the acceptability threshold had a negative nonlinear relationship with the fixed percentage.The fixed percentages(20.0%-30.0%)were proposed as the acceptability thresholds owing to the satisfactory simulation performance and noticeably reduced uncertainty intervals they produced.This study provided methodological foundations for estimating multiple uncertainty sources of integrated water system models.

Aerodynamic configuration integration design of hypersonic cruise aircraft with inward-turning inlets

In this work, a novel airframe/propulsion integration design method of the wing-body configuration for hypersonic cruise aircraft is proposed, where the configuration is integrated with inward-turning inlets. With the help of this method, the major design concern of balancing the aerodynamic performance against the requirements for efficient propulsion can be well addressed. A novel geometric parametrically modelling method based on a combination of patched class and shape transition（CST） and COONs surface is proposed to represent the configuration, especially a complex configuration with an irregular inlet lip shape. The modelling method enlarges the design space of components on the premise of guaranteeing the configuration integrity via special constraints imposed on the interface across adjacent surfaces. A basic flow inside a cone shaped by a dual-inflection-point generatrix is optimized to generate the inward-turning inlet with improvements of both compression efficiency and flow uniformity. The performance improvement mechanism of this basic flow is the compression velocity variation induced by the variation of the generatrix slope along the flow path. At the design point, numerical simulation results show that the lift-to-drag ratio of the configuration is as high as 5.2 and the inlet works well with a high level of compression efficiency and flow uniformity. The design result also has a good performance on off-design conditions. The achievement of all the design targets turns out that the integration design method proposed in this paper is efficient and practical.

An integrated simulation method for PVSS parametric design using multi-objective optimization

An adequate strategy for achieving energy efficiency when designing a photovoltaic shading system(PVSS)shall find an equilibrium between sunlight heat gain and daylight trans-mittances through effective analysis tools in a building’s early design phases.However,traditional simulation methods are either time-consuming or lacking architectonical thinking.This paper proposes a new method for architects to integrate thermal and daylighting performance by using parametric script modelling and optimize their balance with multi-objective optimization(MOO)algorithm in PVSS design.A case study was conducted to demonstrate the workflow of proposed integrated simulation method in PVSS design,and further compared the results with that of three single-objective optimizations under the same design requirement.The findings show that the integrated framework is a feasible method for PVSS design and can be extended into the design of other advance shading system or building integrated photovoltaic.

Modeling net primary productivity of the terrestrial ecosystem in China from 1961 to 2005

Net primary productivity （NPP） is the structure and function of the ecosystem. NPP can most important index that represents the be simulated by dynamic global vegetation models （DGVM）, which are designed to represent vegetation dynamics relative to environ- mental change. This study simulated the NPP of China＇s ecosystems based on the DGVM Integrated Biosphere Simulator （IBIS） with data on climate, soil, and topography. The appli- cability of IBIS in the NPP simulation of China＇s terrestrial ecosystems was verified first. Comparison with other relevant studies indicates that the range and mean value of simula- tions are generally within the limits of observations; the overall pattern and total annual NPP are close to the simulations conducted with other models. The simulations are also close to the NPP estimations based on remote sensing. Validation proved that IBIS can be utilized in the large-scale simulation of NPP in China＇s natural ecosystem. We then simulated NPP with climate change data from 1961 to 2005, when warming was particularly striking. The following are the results of the simulation. （1） Total NPP varied from 3.61 GtC/yr to 4.24 GtC/yr in the past 45 years and exhibited minimal significant linear increase or decrease. （2） Regional differences in the increase or decrease in NPP were large but exhibited an insignificant overall linear trend. NPP declined in most parts of eastern and central China, especially in the Loess Plateau. （3） Similar to the fluctuation law of annual NPP, seasonal NPP also displayed an insignificant increase or decrease; the trend line was within the general level. （4） The re- gional differences in seasonal NPP changes were large. NPP declined in spring, summer, and autumn in the Loess Plateau but increased in most parts of the Tibetan Plateau.