Multiscale modelling and simulation of single crystal superalloy turbine blade casting during directional solidification process

As the key parts of an aero-engine,single crystal(SX)superalloy turbine blades have been the focus of much attention.However,casting defects often occur during the manufacturing process of the SX turbine blades.Modeling and simulation technology can help to optimize the manufacturing process of SX blades.Multiscale coupled models were proposed and used to simulate the physical phenomena occurring during the directional solidification(DS)process.Coupled with heat transfer(macroscale)and grain growth(meso-scale),3D dendritic grain growth was calculated to show the competitive grain growth at micro-scale.SX grain selection behavior was studied by the simulation and experiments.The results show that the geometrical structure and technical parameters had strong influences on the grain selection effectiveness.Based on the coupled models,heat transfer,grain growth and microstructure evolution of a complex hollow SX blade were simulated.Both the simulated and experimental results show that the stray grain occurred at the platform of the SX blade when a constant withdrawal rate was used in manufacturing process.In order to avoid the formation of the stray crystal,the multi-scale coupled models and the withdrawal rate optimized technique were applied to the same SX turbine blade.The modeling results indicated that the optimized variable withdrawal rate can achieve SX blade castings with no stray grains,which was also proved by the experiments.

Complex adaptive system theory,agent-based modeling,and simulation in dominant technology formation

Dominant technology formation is the key for the hightech industry to“cross the chasm”and gain an established foothold in the market(and hence disrupt the regime).Therefore,a stimulus-response model is proposed to investigate the dominant technology by exploring its formation process and mechanism.Specifically,based on complex adaptive system theory and the basic stimulus-response model,we use a combination of agent-based modeling and system dynamics modeling to capture the interactions between dominant technology and the socio-technical landscape.The results indicate the following:(i)The dynamic interaction is“stimulus-reaction-selection”,which promotes the dominant technology’s formation.(ii)The dominant technology’s formation can be described as a dynamic process in which the adaptation intensity of technology standards increases continuously until it becomes the leading technology under the dual action of internal and external mechanisms.(iii)The dominant technology’s formation in the high-tech industry is influenced by learning ability,the number of adopting users and adaptability.Therein,a“critical scale”of learning ability exists to promote the formation of leading technology:a large number of adopting users can promote the dominant technology’s formation by influencing the adaptive response of technology standards to the socio-technical landscape and the choice of technology standards by the socio-technical landscape.There is a minimum threshold and a maximum threshold for the role of adaptability in the dominant technology’s formation.(iv)The socio-technical landscape can promote the leading technology’s shaping in the high-tech industry,and different elements have different effects.This study promotes research on the formation mechanism of dominant technology in the high-tech industry,presents new perspectives and methods for researchers,and provides essential enlightenment for managers to formulate technology strategies.

Droplet morphology analysis of drop-on-demand inkjet printing

As an accurate 2D/3D fabrication tool,inkjet printing technology has great potential in preparation of micro electronic devices.The morphology of droplets produced by the inkjet printer has a great impact on the accuracy of deposition.In this study,the drop-on-demand(DoD)inkjet simulation model was established,and the accuracy of the simulation model was verified by corresponding experiments.The simulation result shows that the velocity of the droplet front and tail,as well as the time to disconnect from the nozzle is mainly affected by density(ρ),viscosity(μ)and surface tension(σ)of droplets.When the liquid filament is about to disconnect from the nozzle,the filament length and filament front velocity are found to have a linear correlation withσ/ρμand ln(ρ/(μσ1/2)).

Modeling and simulation for individualized therapy of amisulpride in Chinese patients with schizophrenia:focus on inter interindi⁃vidual variability,therapeutic reference range and laboratory alert level

OBJECTIVE To explain the high inter-individual variability and the frequency of exceeding the therapeutic reference range and the laboratory alert level of amisulpride,a popula⁃tion pharmacokinetic model in Chinese patients with schizophrenia was built based on therapeu⁃tic drug monitoring data to guide individualized therapy.METHODS Plasma concentration data(330 measurements from 121 patients)were ana⁃lyzed using a nonlinear mixed-effects model⁃ing approach with first-order conditional estima⁃tion with interaction(FOCE I).The concentra⁃tions of amisulpride were detected by HPLC-MS/MS.Age,weight,sex,combination medication history and renal function status were evaluated as main covariates.The model was internally val⁃idated using goodness-of-fit,bootstrap and nor⁃malized prediction distribution error.Recom⁃mended dosage regimens for patients with key covariates were estimated on the basis of Monte Carlo simulations and the established model.RESULTS A one-compartment model with first-order absorption and elimination was found to adequately characterize amisulpride concentra⁃tion in Chinese patients with schizophrenia.The population estimates of the apparent volume of distribution(V/F)and apparent clearance(CL/F)were 12.7 L and 1.12 L·h-1,respectively.Age sig⁃nificantly affected the clearance of amisulpride and the final model was as follow:CL/F=1.04×(AGE/32)-0.624(L·h-1).To avoid exceeding the lab⁃oratory alert level(640μg·L-1),the model-based simulation results showed that the recommended dose of amisulpride was no more than 600 mg per day for patients aged 60 years,800 mg per day for those aged 40 years and 1200 mg per day for those aged 20 years,respectively.CON⁃CLUSION Dosage optimization of amisulpride can be carried out according to age to reduce the risk of adverse reactions.The model can be used as a suitable tool for designing individual⁃ized therapy for Chinese patients with schizo⁃phrenia.

A Numerical Convex Lens for the State-Discretized Modeling and Simulation of Megawatt Power Electronics Systems as Generalized Hybrid Systems

Modeling and simulation have emerged as an indispensable approach to create numerical experiment platforms and study engineering systems.However,the increasingly complicated systems that engineers face today dramatically challenge state-of-the-art modeling and simulation approaches.Such complicated systems,which are composed of not only continuous states but also discrete events,and which contain complex dynamics across multiple timescales,are defined as generalized hybrid systems(GHSs)in this paper.As a representative GHS,megawatt power electronics(MPE)systems have been largely integrated into the modern power grid,but MPE simulation remains a bottleneck due to its unacceptable time cost and poor convergence.To address this challenge,this paper proposes the numerical convex lens approach to achieve state-discretized modeling and simulation of GHSs.This approach transforms conventional time-discretized passive simulations designed for pure-continuous systems into state-discretized selective simulations designed for GHSs.When this approach was applied to a largescale MPE-based renewable energy system,a 1000-fold increase in simulation speed was achieved,in comparison with existing software.Furthermore,the proposed approach uniquely enables the switching transient simulation of a largescale megawatt system with high accuracy,compared with experimental results,and with no convergence concerns.The numerical convex lens approach leads to the highly efficient simulation of intricate GHSs across multiple timescales,and thus significantly extends engineers’capability to study systems with numerical experiments.

Dynamics modeling and simulation of mechanism with joint clearance

The existence of clearance in the joints of mechanisms system is inevitable.The movements of the real mechanism are deflection from the ideal mechanism due to the clearances and the motion accuracy is decreased.The effects of the hinge clearance on the crank and rocker mechanism system are studied.The system dynamics equation with clearance is presented.The contact dynamics model is established using the nonlinear equivalent spring-damp model and the friction effect is considered by using Coulomb friction model.Then the models are incorporated into ADAMS,and based on the model,large numbers numeric simulations are made.The regularity of contact forces in clearance are studied in detail.And the effects of clearance size,clearance friction on the mechanism dynamics characteristic are analyzed.The simulation results can predict the effects of clearance on the mechanism dynamics characteristic preferably.

THE EXTRACTION EQUILIBRIUM MODEL AND SIMULATION OF COUNTERCURRENT SOLVENT EXTRACTION OF Gd-Tb-Dy-HCl-HEH(EHP)-KEROSENE SYSTEM

The extraction equilibrium mathematic models for gadolinium,terbium and dysprosium in HCl-1.5 mol/L HEH(EHP)system covering a relatively wide range of lanthanide concentration and acidity,have been developed.There are four independent variables and nine parameters.The average relative error is 4.56%.A computer program for the simulation of the counter current solvent extraetion process has also been written.Thus,the Gd,Tb and Dy concentrations in both aqueous and organic phase in eaeh stage as well as the aqueous acidity may be calculated.Product purities,distribution ratio and extraction factors may also be obtained thereby.The simulation results so obtained may serve as the referenee data for designing solvent ex- traction processes including those processes providing apart from the conventional outgoing organic stream, outgoing raffinate and an extra outgoing third exit stream either organic or aqueous.

Conceptual Modeling and Simulation Application Analysis of In-service Assessment

Firstly,this paper expounds the conceptual connotation of inservice assessment in the new system,then applies modeling and Simulation in the field of in-service assessment,establishes the conceptual model of inservice assessment and its process,and finally analyzes the application of modeling and simulation in the specific links of in-service assessment.

Ferroelectricity of hafnium oxide-based materials:Current status and future prospects from physical mechanisms to device applications

The finding of the robust ferroelectricity in HfO_(2)-based thin films is fantastic from the view point of both the fundamentals and the applications.In this review article,the current research status of the future prospects for the ferroelectric HfO_(2)-based thin films and devices are presented from fundamentals to applications.The related issues are discussed,which include:1)The ferroelectric characteristics observed in HfO_(2)-based films and devices associated with the factors of dopant,strain,interface,thickness,defect,fabrication condition,and more;2)physical understanding on the observed ferroelectric behaviors by the density functional theory(DFT)-based theory calculations;3)the characterizations of microscopic and macroscopic features by transmission electron microscopes-based and electrical properties-based techniques;4)modeling and simulations,5)the performance optimizations,and 6)the applications of some ferroelectric-based devices such as ferroelectric random access memory,ferroelectric-based field effect transistors,and the ferroelectric tunnel junction for the novel information processing systems.

Numerical Modelling of the Powder Metallurgical Manufacturing Chain of High Strength Sintered Gears

This paper presents a digital model for the powder metallurgical(PM)production chain of high-performance sintered gears based on an integrated computational materials engineering(ICME)platform.Discrete and finite element methods(DEM and FEM)were combined to describe the macroscopic material response to the thermomechanical loads and process conditions during the entire production process.The microstructural evolution during the sintering process was predicted on the meso-scale using a Monte-Carlo Model.The effective elastic properties were determined by a homogenization method based on modelling a representative volume element(RVE).The results were subsequently used for the FE modelling of the heat treatment process.Through the development of multi-scale models,it was possible obtain characteristics of the microstructural features.The predicted hardness and residual stress distributions allowed the calculation of the tooth root load bearing capacity of the heat-treated sintered gears.

A molecular dynamics study of the structural change differences between Au_(225) and Au_(369) clusters on MgO surfaces at low temperature

The differences in structural change between Au225 and Au369 clusters with their （111） facets supported on MgO（100） surfaces at 5 K are studied by using molecular-dynamics simulations with the atomic interchange potentials of the Au/MgO interface. The parameters are obtained from the ab initio energies using the Chen-MSbius inversion method. Analyses of the pair distribution functions show that the two Au clusters use different deformation processes to adjust the distances between the interface atoms, owing to the misfit between the atom distances among the clusters and the substrates. The local structural changes are identified by atomic density profiles.

High adsorption and separation performance of CO_(2) over N2 in azo-based(N=N)pillar[6]arene supramolecular organic frameworks

Azo-based pillar[6]arene supramolecular organic frameworks are reported for CO_(2) and N_(2) adsorption and separation by density functional theory and grand canonical Monte–Carlo simulation.Azo-based pillar[6]arene provides suitable environment for CO_(2) adsorption and selectivity.The adsorption and selectivity results show that introducing azo groups can effectively improve CO_(2) adsorption and selectivity over N_(2),and both CO_(2) adsorption and CO_(2) selectivity over N_(2) follow the sequence pillar[6]arene N_(4)>pillar[6]arene N2>pillar[6]arene.Pillar[6]arene N_(4) exhibits CO_(2) adsorption capacity of1.36 mmol/g,and superior selectivity of CO_(2) over N_(2) of116.75 with equal molar fraction at 1 bar(1 bar=105 Pa)and 298 K.Interaction analysis confirms that both the Coulomb and van derWaals interactions between CO_(2) with pillar[6]arene frameworks are greater than that of N_(2).The stronger affinity of CO_(2) with pillar[6]arene N_(4) than other structures and the larger isosteric heat differences between CO_(2) and N2 rendered pillar[6]arene N4 to present the high CO_(2) adsorption capacity and high CO_(2) selectivity over N_(2).Our results highlight the potential of azo-functionalization as an excellent means to improve pillar[6]arene for CO_(2) capture and separation.

Research in Moisture Transport through One and Two-layered Porous Composites

Research into the moisture transport processes in porous materials is primarily important for theoretical modelling and industrial applications in the design of energy saving buildings and living environments, etc. Based on experimental investigation, we propose new models which describe one-dimensional transport through one-layered uniform materials and dissimilar two-layered composites. Diffusivity as a function of moisture content is obtained through a Boltzman transformation, master curves, and combined numerical and regression techniques. Transport processes in one and two-layered composites are simulated on the basis of extended unsaturated Darcy’s Law using the finite element method (FEM). Simulation results show significantly different transport patterns of moisture profile when moisture migrates in different directions, and high agreement with experimental moisture profiles. Keywords Porous materials - moisture transport - two-layered composites - modelling and simulation Qingguo Wang graduated from Hebei Normal University, China, in 1985. He received the M.Sc. degree from Beijing Petroleum University in 1988 and the Ph.D. degree from the University of Luton, UK, in 2005. He is currently a Research Associate in the Department of Electrical Engineering and Electronics at the University of Liverpool, UK and an Associate Professor of Shijiazhuang Mechanical Engineering College, China. His research interests include measurement and control, mass and heat transportation, EMC, etc.Kemal Ahmet graduated in physics from the University of Leeds. Following the completion of his masters degree, he completed his Ph.D. at the University of London in the area of nuclear instrumentation in 1992. Until recently, he was a Principal Lecturer at the University of Luton, leading a research group in moisture instrumentation, measurement and monitoring. In 2004 he joined Medtronic, world leader in medical technology, and is currently working in the Neurologic Technologies division as a specialist in powered surgical instrumentation.Young Yue is a Principal Lecturer at the University of Luton, UK. He holds a B.Sc. in mechanical engineering from the Northeastern University, China, and a Ph.D. from Heriot-Watt University, UK. He is a chartered engineer and a member of the Institution of Mechanical Engineers, UK. Dr. Yue has been working in academia for 15 years following his 8 years of industrial experience. His main research interests are CAD/CAM, geometric modelling, virtual reality, and pattern recognition. He has over 70 publications in refereed books, journals and conferences.

Simulation research of energy management strategy for dual mode plug-in hybrid electrical vehicles

In this paper, a plug-in hybrid electrical vehicle(PHEV) is taken as the research object, and its dynamic performance and economic performance are taken as the research goals. Battery charge-sustaining(CS) period is divided into power mode and economy mode. Energy management strategy designing methods of power mode and economy mode are proposed. Maximum velocity, acceleration performance and fuel consumption are simulated during the CS period in the AVL CRUISE simulation environment. The simulation results indicate that the maximum velocity and acceleration time of the power mode are better than those in the economy mode. Fuel consumption of the economy mode is better than that in the power mode. Fuel consumption of PHEV during the CS period is further improved by using the methods proposed in this paper, and this is meaningful for research and development of PHEV.

INDUSTRIAL ENGINEERING AND VISUALISATION—A PRODUCT DEVELOPMENT PERSPECTIVE

Taking the actual project of teaching and researching process for example, the relationship between the industrial engineering and product development is discussed. And use the novel visualization technology to support the industrial engineering and product development. How to use the new computer modeling and simulating technologies to support the product development and industrial engineering, is introduced especially. The support includes both domestic products and industrial systems. The visualization and computer technologies take a very impo[tant role in some system or multi-direction modeling, those technologies mentioned above can help the industrial engineers study the effect of design on the whole life circle, including the producing steps. So the engineers can avoid making the wrong decision which may cause bad effects on the whole industrial engineering.

SVPWM Techniques and Applications in HTS PMSM Machines Control

This paper introduces the principle of space vector pulse width modulation （SVPWM）, and discusses a method for implementing the SVPWM based on MATLAB/SIMULINK, as well as modeling of AC servo system with permanent magnet synchronous motor （PMSM）. Simulation results show that the model is effective, and the method provides a frame of reference for software and hardware designs which can be applied in high temperature superconducting （HTS） flywheel energy storage system （FESS） and linear motor （LM）.

The Application of Simulation Technique in Whole CIMS Life Cycle

The life cycle of CIMS (Computer Integrated Manufacturing System) includes four phases:requirement analyzing, designing, implementation and running. For reducing the risk of investment and achieving better economic results the simulation technique is needed in the above four phases of CIMS life cycle. Under the support of China 863/CIMS plan a series of simulation projects are established. Some of them are finished with succeed and have been used in application. In this paper four simulation projects are introduced.(1) The Integrated Manufacturing Simulation Software (IMSS). It is an integrated platform, based on the discrete event simulation principle. It can be used to analyze and design CIMS, especially FMS; and evaluate the daily production plan.(2) The Advanced Hierarchical Control System Emulator (AHCSE), a software system, based on the finite state machine principle. It can be used to analyze and design of CIMS hicrarchical control system, and check expanded system performance before expanding.(3) The Factory Scheduling Environment (FASE), a software system based on the discrete event simulation principle and artificial intelligence technology. It can be used for shop floor scheduling. (4) The Machining Process Simulator (MPS). It can simulate the machining process of machining center by computer. It can check the correctness of NC code (including interference and confliction) and replace the real machining center to support the simulation environment for shop floor scheduling and controlling. There are three companies and universities joining in these four projects, they are: Tsinghua University,Huazhong University of Technology, Beliing Institute of Computer Application and Simulation.

Modeling of Electromagnetic Wave Propagation and Its Applicationin Virtual Test

With the development of virtual test,the computation of the effect of different weather conditions on electromagnetic wave propagation is required in many simulation systems. Firstly,this paper presents a unique point of view for computing the electromagnetic wave attenuation ratio under different weather conditions by means of an independent electromagnetic wave propagation component that can be directly implemented in virtual test, and is easy to configure and easy to reuse. We present an analysis of the principles of electromagnetic wave propagation and the algorithms designed for realization of various propagation models within the electromagnetic wave propagation component. Secondly,this paper presents a use-case analysis and outlines the design of the component,verifies the developed models under various weather conditions,and obtains equivalent values as those obtained theoretically. Finally,we build a virtual test system,verify the system in different weather conditions,and again obtain equivalent values to those obtained theoretically. The algorithms in the electromagnetic wave propagation component are developed in the C language, which substantially improves the computational speed,and meets the real-time requirements of the virtual testing platform.

3D Model Simulating the Hydro-mechanical State of Unsaturated and Deformable Material during Hot air Drying

A three dimensional model to predict the hydro-mechanical state of unsaturated and deformable material during hot air drying has been proposed.The material viscoelastic behaviour was formulated using Bishop’s effective stress theory for partially saturated material using the liquid saturation as the Bishop parameter.The hydro-thermal and mechanical equations were coupled by the fluid pressure and the solid matter velocity.The model was applied to a deformable material(innovative clay-cellulose fibers composite)subjected to convective drying.A generalized Maxwell model with five elements,whose parameters were measured experimentally and correlated to water content was used to describe the material’s viscoelastic behavior.The hydro-thermal part of the proposed model was validated on the basis of a comparison of experimental and simulated drying rate curves.The Von Mises stress was simulated and compared to the experimental tensile strength in order to predict the time and the region of material failure.For a drying process at 95°C,the region of failure risk was identified.The failure may occur on the lateral surface of the slab in contact with air at a drying time of 2.5h.

Modeling and Control of a Biodiesel Transesterification Reactor

Dynamic Models for predicting the concentration profiles of the reactants and product in a Continuous Stirred Tank Reactor for the transesterification of used cooking oil (triglyceride) to biodiesel has been developed using the principle of conservation of mass. The developed system of differential equations were integrated numerically using fourth order Runge-Kutta algorithm embedded in ode 45 solver of 7.5 Mathlab program. The models were validated by solving the model equations with kinetic data and other relevant data from literatures. The results and trends were similar and in agreement with those from these literatures. Simulations of the reactor to (±) step changes in the inlet flowrates of the reactants (used cooking oil and methanol) showed great effect on biodiesel production, (instability—oscillations and reduction in output concentration of biodiesel). A feedback control strategy was developed with a Proportional-Integral (PI) Controller and a close loop model was developed for control studies. The closed loop response of the reactor output (biodiesel concentration) showed continuous oscillatory response with offset. Hence the controller parameters (proportional gain Kc and integral time ) were tuned using the “On-Line Trial and Error Method” implemented using MathLab Simulink to obtain optimum values that ensured quick stability of the closed-loop system, reduced or no oscillatory response and no offset. The optimum controller parameters were: proportional gain Kc =8.306 and integral time = 17.157 minutes.