Lumped-Element Dynamic Electro-Thermal model of a superconducting magnet

Modeling accurately electro-thermal transients occurring in a superconducting magnet is challenging. The behavior of the magnet is the result of complex phenomena occurring in distinct physical domains (electrical, magnetic and thermal) at very different spatial and time scales. Combined multi-domain effects significantly affect the dynamic behavior of the system and are to be taken into account in a coherent and consistent model.A new methodology for developing a Lumped-Element Dynamic Electro-Thermal (LEDET) model of a superconducting magnet is presented. This model includes non-linear dynamic effects such as the dependence of the magnet’s differential self-inductance on the presence of inter-filament and inter-strand coupling currents in the conductor. These effects are usually not taken into account because superconducting magnets are primarily operated in stationary conditions. However, they often have significant impact on magnet performance, particularly when the magnet is subject to high ramp rates.Following the LEDET method, the complex interdependence between the electro-magnetic and thermal domains can be modeled with three sub-networks of lumped-elements, reproducing the electrical transient in the main magnet circuit, the thermal transient in the coil cross-section, and the electro-magnetic transient of the inter-filament and inter-strand coupling currents in the superconductor. The same simulation environment can simultaneously model macroscopic electrical transients and phenomena at the level of superconducting strands.The model developed is a very useful tool for reproducing and predicting the performance of conventional quench protection systems based on energy extraction and quench heaters, and of the innovative CLIQ protection system as well.     

工质为R134a绝热型毛细管数值模拟

根据均相流等多项假设,运用两相流动基本方程建立了绝热毛细管分布参数的稳态数学模型。模型中分别利用了常用的2种计算沿程摩阻系数方法（Churchill关联式、Jung等人推荐工质为R22的摩阻系数关联式）,模拟结果表明用这2种方法来模拟均能获得较高精度,但工质为R134a时优先考虑前者,因此在模拟毛细管时不同工质有不同的最佳摩阻系数关联式。     

Development of a variable quench pressure relief valve for superconducting magnet system

A new variable quench pressure relief valve (VQRV) for a superconducting magnet system has been developed at the High Energy Accelerator Research Organization (KEK). The VQRV is designed that the setting of the blowout pressure can be freely controlled and be maintenance-free for long-term operation.A prototype VQRV was tested under a high radiation environment up to 2.5 MGy. The heat load of 1.5 W at 4.2 K and a seat leakage rate of 4.5 × 10⁻⁷ kg/s at 4.2 K of the VQRV were confirmed. It has enough performances for the cryogenic system operation in the Japan Proton Accelerator Research Complex (J-PARC) neutrino beam line.The design and test results of the VQRV are described in this technical note.     

Optimizing workholding efficiency through fixture function simulation

In the past two decades, simulating workpiece–fixture interactions has remarkably drawn the attention of academia. However, many aspects of the workpiece–fixture system, specifically workpiece–fixture contact condition, still enjoy research effort. For the efficient use of Automated Fixture Design (AFD) systems, verification of their outputs is required. This paper presents a workholding simulation approach that considers assessment of AFD system outputs regarding different workholding parameters. The effect of friction forces on workholding and part rigid body stability is considered. Besides, determining deformation and stress in the workpiece, locators and clamps are modelled and their elastic deformation and stress distribution are computed. A procedure based on the application of contact elements in finite-element method is developed to quantify the status of contact between the workholding elements and the workpiece. Clamping tightness is modelled and its effect on the workpiece–fixture system performance is quantified. The central component of the verification tool is the use of nonlinear finite-element analysis to model the frictional interactions in workpiece–fixture system.     

High strain rate torsional testing of a high manganese steel: Design and simulation

In this study, some less-discussed aspects of designing a high strain rate torsional testing machine adapted from the Kolsky bar setup are surveyed with an emphasis on the clamping system design. Dynamic torsional experiments with true strain rates in the range of ∼500–1700 /s are conducted on specimens of a high-Mn TRIP/TWIP steel. Deformation characteristics of torsional specimens with different geometries are studied through coupled field thermo-mechanical finite element analyses using ANSYS commercial software package. The effect of specimen geometry on the stress and strain distributions and accuracy of the experimental results is also studied. Using the FEM analysis, deformation temperature rise is attained over the specimen gauge zone and its influence on the stacking fault energy and mechanical behavior of the steel is investigated.     

RADS — a computer package for refrigeration analysis, design and simulation

A commercially available computer package for refrigeration analysis, design and simulation is described. Its main applications are heat load determination, multi-stage compression plant layout design, and simulation of the interactions between refrigerant plant, applications and control systems.     

一种新型永磁球形步进电动机的研究

针对国际上新提出的一种永磁球形结构步进电动机进行了研究。首先运用积分方程法和三维有限元法进行了磁场计算,在此基础上应用麦氏张量法和虚位移法对其转矩特性进行求解,获得了电机的矩角特性,并通过不同的方法对比验证了计算结果的正确性。同时提出一种基于加权无向图的运动控制算法,通过对路径进行搜索,实现了对电机通电状态的有效控制,达到了沿着期望运动轨迹运动的目的。在对电机及其滑轨支架位置检测系统进行运动学分析的基础上,对电机实际步进运动过程和编码器输出进行了仿真研究,结果显示出了位置检测系统和控制算法的有效性。     

Application of defect simulation as a tool for more efficient failure analysis

In modern VLSI processes, increasing process complexity has resulted in an exponential rise in the costs of thorough failure analysis. In this paper, we present a defect simulation-based failure analysis methodology, which can be used to significantly reduce both costs and turn-around time for failure analyses. The methodology is based on the ability to generate a defect dictionary, which can relate defect characteristics to some easily measurable symptoms of defect occurrence.     

Hybrid simulation modelling as a supporting tool for sustainable product service systems: a critical analysis

Manufacturing companies are increasingly shifting their value proposition from a product-centric perspective to Product-Service-System (PSS). This evolution allows companies to improve the customisation of their offer and to contribute to reduce material flows and consumption, thus enhancing sustainability. However, when companies introduce PSS offers, they have to face higher complexity and dynamism, as customer behaviours, process requirements and sustainability assessment must be considered during the design and the development of the new solutions. In this paper, after the identification of the main PSS dynamic features, the authors argue that business process simulation (BPS) could represent an effective tool to cope with the dynamics and the complexity entailed in a sustainable PSS. This paper analyses and compares existing BPS approaches identifying the hybrid simulation (HS) modelling as a promising approach. In fact, according to the critical PSS features, HS allows grasping PSS features and integrating customer, company and environmental sustainability perspectives into the model, thus, supporting effective PSS design and assessment. These findings have been validated in a test case where a hybrid model (integrating Discrete Event Simulation with Agent-Based Modelling) has been compared against a pure DES model. The results highlight the advantages of the hybrid modelling approach with respect to DES in supporting the engineering of a sustainable, customer-oriented PSS provision process.     

An object-oriented framework for versatile discrete objects simulation using design patterns

This paper proposes a framework for versatile discrete objects simulation. The framework, named VEDO, is developed using object-oriented technology with design patterns. VEDO is capable of handling simultaneously discrete objects of various shapes and various mechanisms of interactions between discrete objects. It also has great flexibility in facilitating additions of new discrete object shapes and solution algorithms for discrete object interactions. Based on the proposed framework, a discrete objects simulation system, named Knight&Anne, has been implemented in C++ in this study. In addition, some application examples are given to demonstrate the capability and flexibility of the framework.The support from the National Science Council of Republic of China under Grant No. NSC91-2211-E-002-097 and NSC91-2211-E-399-001 is greatly appreciated. In addition, the authors would like to thank Prof. Chuin-Shan Chen of National Taiwan University for his review and suggestions on the design and implementation of the proposed framework as well as Mr. Li-Shin Lin and Mr. Jenn-Feng Li for their help on example studies.     

Hardware-in-the-loop simulation for a production system

This paper proposes a hardware-in-the-loop simulation (HILS) approach for the design and verification of a production system. The design of a production system involves two major activities: mechanical design (device specification and layouts) and electrical design (device behaviour and system control). Conventionally, the mechanical and electrical design activities have been performed sequentially, wasting time. We propose a concurrent procedure of mechanical and electrical design based on the HILS methodology to cope with this problem. The proposed HILS approach provides two major benefits: (1) the verified control program can be directly used for the real plant with minor adaptations; and (2) the verified 3D layout model can be used to generate the detailed drawings for the implementation of the plant. We can minimise the stabilisation time of a production system, since most mechanical and electrical errors can be found and fixed using HILS.     

Theoretical basis of a simulation package for the integrated optimisation of profile and trajectory of satellite launch vehicles

Introducing the concepts of set-theoretic sequencing logic, hierarchic optimisation and sensitivity-directed iterative simulation, this paper provides a theoretical basis for the development of a simulation package for the three-dimensional atmospheric controlled flight of satellite launch vehicles subject to specified control constraints. The approach described here enables the optimisation of the profile of the vehicle to be carried out together with its trajectory, given the orbital objectives. The simulation package, SIMSPACE II, developed on this basis, is shown to have features superior to the MATS program and related packages.     

多风机组合式空调机组CFD仿真分析

对四风机机组进行CFD仿真分析,结果表明,垂直气流横断面上的速度分布与风机的气流分布有一定的关联,若风机对称分布,气流相应也会对称分布;距离风机越远的横断面,其速度分布越均匀;表冷器盘管具有导流作用,且其空气侧压降越大,出风面速度越均匀。在过气流方向的截面上,风机内的速度最大;风机出口处,由于气流截面突变,气流速度变化率最大,会产生剧烈的紊流。     

A simulation based approach for supply network control

We focus on the problem of strategic network design in the context of multi-site enterprises. We develop a simulation model for various supply network designs evaluation. The suggested model is generic in the sense that only input data modifications are needed to adapt the model to a given supply network structure, while the model's procedural logic stays unchanged. The model reproduces the dynamics of the totality of the supply chain activities. It takes into account control policies related to the inventory management and to the scheduling of production activities. It also carries out local optimisations by dynamically allocating the customers’ demands to the appropriate distribution site and the replenishment orders expressed by the distribution and production sites of the enterprise so as to minimise a global cost function. Simulation execution permits to compute various performance measures. These indicators inform the decision-maker about the profit of the enterprise and about its customer's service level. In this paper, we propose to detail the simulation model. Then, for a fictitious problem of supply network design based on two real life applications, we highlight the influence of the control policies on the performance of the studied enterprise.     

基于通用信号处理平台的数字声呐仿真研究

传统的声呐设计,采用专用硬件配以专用软件实现实时信号处理,开发周期长,可靠性可维修性较低。利用通用信号处理平台实现数字声呐设计是今后的一种发展方向。分析了数字声呐设计的基本原则,研究了一种利用通用信号处理平台实现传统数字声呐的仿真设计方法。分析了通用信号处理平台的总体设计、硬软件组成及功能特点,利用该平台,按照50%冗余设计,完成了48路圆柱型基阵主动声呐的实时仿真设计。通过该仿真设计实例,说明数字声呐可以方便地采用通用信号处理平台来实现。     

Probabilistic physics-of-failure models for component reliabilities using Monte Carlo simulation and Weibull analysis: a parametric study

In reliability engineering, component failures are generally classified in one of three ways: (1) early life failures; (2) failures having random onset times; and (3) late life or ‘wear out’ failures. When the time-distribution of failures of a population of components is analysed in terms of a Weibull distribution, these failure types may be associated with shape parameters β having values <1, 1, and >1 respectively. Early life failures are frequently attributed to poor design (e.g. poor materials selection) or problems associated with manufacturing or assembly processes.

We describe a methodology for the implementation of physics-of-failure models of component lifetimes in the presence of parameter and model uncertainties. This treats uncertain parameters as random variables described by some appropriate statistical distribution, which may be sampled using Monte Carlo methods. The number of simulations required depends upon the desired accuracy of the predicted lifetime. Provided that the number of sampled variables is relatively small, an accuracy of 1–2% can be obtained using typically 1000 simulations.

The resulting collection of times-to-failure are then sorted into ascending order and fitted to a Weibull distribution to obtain a shape factor β and a characteristic life-time η.

Examples are given of the results obtained using three different models: (1) the Eyring–Peck (EP) model for corrosion of printed circuit boards; (2) a power-law corrosion growth (PCG) model which represents the progressive deterioration of oil and gas pipelines; and (3) a random shock-loading model of mechanical failure. It is shown that for any specific model the values of the Weibull shape parameters obtained may be strongly dependent on the degree of uncertainty of the underlying input parameters. Both the EP and PCG models can yield a wide range of values of β, from β>1, characteristic of wear-out behaviour, to β<1, characteristic of early-life failure, depending on the degree of dispersion of the uncertain parameters. If there is no uncertainty, a single, sharp value of the component lifetime is predicted, corresponding to the limit β=∞. In contrast, the shock-loading model is inherently random, and its predictions correspond closely to those of a constant hazard rate model, characterized by a value of β close to 1 for all finite degrees of parameter uncertainty.

The results are discussed in the context of traditional methods for reliability analysis and conventional views on the nature of early-life failures.     

Supply chain design and cost analysis through simulation

This paper is grounded on a discrete-event simulation model, reproducing a fast moving consumer goods (FMCG) supply chain, and aims at quantitatively assessing the effects of different supply configurations on the resulting total supply chain costs and bullwhip effect. Specifically, 30 supply chain configurations are examined, stemming from the combination of several supply chain design parameters, namely number of echelons (from 3 to 5), re-order and inventory management policies (EOQ vs. EOI), demand information sharing (absence vs. presence of information sharing mechanisms), demand value (absence vs. presence of demand ‘peak’), responsiveness of supply chain players. For each configuration, the total logistics costs and the resulting demand variance amplification are computed. A subsequent statistical analysis is performed on 20 representative supply chain configurations, with the aim to identify significant single and combined effects of the above parameters on the results observed. From effects analysis, bullwhip effect and costs outcomes, 11 key results are derived, which provide useful insights and suggestions to optimise supply chain design.     

Compact electro-thermal simulation of ESD-protection elements

Numerical simulations at the circuit level can improve the understanding of the behaviour of protection structures under system aspects. Full protection circuits with the influence of HBM ESD tester parasitics and additional parasitic elements in the circuitry have been investigated. Compact electro-thermal models for single protection elements (diodes and snapback nMOSFETs) have been developed. They help to explain differences between expected ESD-hardness and HBM-failure thresholds of protection structures.     

Non-Gaussian simulation of local material properties based on a moving-window technique

In this paper, a moving-window micromechanics technique, Monte Carlo simulation, and finite element analysis are used to assess the effects of microstructural randomness on the local stress response of composite materials. The randomly varying elastic properties are characterized in terms of a field of local effective elastic constitutive matrices using a moving-window technique based on a finite element model of a given digitized composite material microstructure. Once the fields are generated, estimates of the random properties are obtained for use as input to a simulation algorithm that was developed to retain spectral, correlation, and non-Gaussian probabilistic characteristics. Rapidly generated Monte Carlo simulations of the constitutive matrix fields are used in a finite element analysis to create a series of local stress fields associated with the random material sample under uniaxial tension. This series allows estimation of the statistical variability in the local stress response for the random composite. The identification of localized extreme stress deviations from those of the aggregate or effective properties approach highlight the importance of modeling the stochastic variability of the microstructure.     

Genetic algorithms and Monte Carlo simulation for optimal plant design

We present an approach to the optimal plant design (choice of system layout and components) under conflicting safety and economic constraints, based upon the coupling of a Monte Carlo evaluation of plant operation with a Genetic Algorithms-maximization procedure. The Monte Carlo simulation model provides a flexible tool, which enables one to describe relevant aspects of plant design and operation, such as standby modes and deteriorating repairs, not easily captured by analytical models. The effects of deteriorating repairs are described by means of a modified Brown–Proschan model of imperfect repair which accounts for the possibility of an increased proneness to failure of a component after a repair. The transitions of a component from standby to active, and vice versa, are simulated using a multiplicative correlation model. The genetic algorithms procedure is demanded to optimize a profit function which accounts for the plant safety and economic performance and which is evaluated, for each possible design, by the above Monte Carlo simulation.In order to avoid an overwhelming use of computer time, for each potential solution proposed by the genetic algorithm, we perform only few hundreds Monte Carlo histories and, then, exploit the fact that during the genetic algorithm population evolution, the fit chromosomes appear repeatedly many times, so that the results for the solutions of interest (i.e. the best ones) attain statistical significance.