Three-Dimensional Simulations of RESET Operation in Phase-Change Random Access Memory with Blade-Type Like Phase Change Layer by Finite Element Modeling

An optimized device structure for reducing the RESET current of phase-change random access memory （PCRAM） with blade-type like （BTL） phase change layer is proposed. The electrical thermal analysis of the BTL cell and the blade heater contactor structure by three-dimensional finite element modeling are compared with each other during RESET operation. The simulation results show that the programming region of the phase change layer in the BTL cell is much smaller, and thermal electrical distributions of the BTL cell are more concentrated on the TiN/GST interface. The results indicate that the BTL cell has the superiorities of increasing the heating efficiency, decreasing the power consumption and reducing the RESET current from 0.67mA to 0.32mA. Therefore, the BTL cell will be appropriate for high performance PCRAM device with lower power consumption and lower RESET current.

Simulation-Based Construction of Three-Dimensional Process Model for Punching Cartridge Cases

A method of constructing three-dimensional process model for the punching cartridge cases is presented based on DEFORM simulation analysis. Using DEFORM software,the finite element simulation models for the punching and forming process of cartridge cases are established,and the corresponding simulation result model of each intermediate procedure is obtained by continuously performing the forming process simulation. The simulation model cannot annotate size and process information due to poor interface between DEFORM software and CAD software. Thus,a 3D annotation module is developed with secondary development technology of UG NX software. Consequently,the final process model with dimension and process information is obtained. Then,with the current 3D process management system,the 3D punching and forming process design of cartridge cases can be completed further. An example is also provided to illustrate that the relative error between the simulation process model and the physical model is less than 2%,which proves the validity and reliability of the proposed method in this study.

Three-Dimensional Cerebral Aneurysm Models for Surgical Simulation and Education—Development of Aneurysm Models with Perforating Arteries and for Application of Fenestrated Clips

We modified a three-dimensional cerebral aneurysm model for surgical simulation and educational demonstration. Novel models are made showing perforating arteries arising around the aneurysm. Information about perforating arteries is difficult to obtain from individual radiological data sets. Perforators are therefore reproduced based on previous anatomical knowledge instead of personal data. Due to their fragility, perforating arteries are attached to the model using hard materials. At the same time, hollow models are useful for practicing clip application. We made a model for practicing the application of fenestrated clips for paraclinoid internal carotid aneurysms. Situating aneurysm models in the fissure of a brain model simulates the real surgical field and is helpful for educational demonstrations.

3D Modeling and Simulation of Fancy Fabrics in Weft Knitting

Weft knitted fancy fabrics are widely used in knitted garment design. Due to the complexity of the structures, their modeling and simulation needs to be solved in three-dimensional (3D) CAD developments. In this paper, 3D loop geometrical models of weft knitted fancy structures, including tuck stitch, jacquard stitch, transfer stitch and fleecy stitch, were developed based on an improved model of plain loop, and their central axes as some 3D space curves were achieved by using Non-Uniform Rational B-Splines (NURBS). The 3D visual simulation programme was written in C++ programming language using OpenGL, which was a function library of 3D graphics. Some examples of weft knitted fancy fabrics were generated and practical application of 3D simulation was discussed.

Application of Three-Dimensional Visual Simulation in Tidal Defense Engineering

Any tidal defense engineering involves the collection and analysis of massive information about engineering structures and their surrounding environment. Traditional method, which is carried out mainly by means of twodimensional drawings and textures, is not efficient and intuitive enough to analyze the whole project and reflect its spatial relationship. Three-dimensional visual simulation provides an advanced technical means of solving this problem. In this paper, triangular irregular network (TIN) model simplified by non-uniform rational B-splines (NURBS) technique was used to establish the digital terrain model (DTM) of a super large region. Simulation of dynamic water surface was realized by combining noise function with sine wave superposition method. Models of different objects were established with different modeling techniques according to their characteristics. Application of texture mapping technology remarkably improved the authenticity of the models. Taking the tidal defense engineering in the new coastal region of Tianjin as a case study, three-dimensional visual simulation and dynamic roaming of the study area were realized, providing visual analysis and visible demonstration method for the management and emergency decision-making associated with construction.

The numerical simulation for a 3D two-phase anisotropic medium based on BISQ model

Biot-flow and squirt-flow are the two most important fluid flow mechanisms in porous media containing fluids. Based on the BISQ （Biot-Squirt） model where the two mechanisms are treated simultaneously, the elastic wave-field simulation in the porous medium is limited to two-dimensions and two-components （2D2C） or two-dimensions and three-components （2D3C）. There is no previous report on wave simulation in three- dimensions and three-components. Only through three dimensional numerical simulations can we have an overall understanding of wave field coupling relations and the spatial distribution characteristics between the solid and fluid phases in the dual-phase anisotropic medium. In this paper, based on the BISQ equation, we present elastic wave propagation in a three dimensional dual-phase anisotropic medium simulated by the staggered-grid high-order finite-difference method. We analyze the resulting wave fields and show that the results are an improvement.

A Three-Dimensional Water Quality Model and Its Application to Jiaozhou Bay, China

A three-dimensional coupled physical and water quality model was developed and applied to the Jiaozhou Bay to study water quality involving nutrients, biochemical oxygen demand, dissolved oxygen, and phytoplankton that are closely related to eutrophication process. The physical model is a modified ECOM-si version with inclusion of flooding/draining processes over the intertidal zone. The water quality model is based on WASP5 which quantifies processes governing internal nutrients cycling, dissolved oxygen balance and phytoplankton growth. The model was used to simulate the spatial distribution and the temporal variation of water quality in the Jiaozhou Bay for the period of May 2005 to May 2006. In addition, the effect of reduction of riverine nutrients load was simulated and evaluated. The simulated results show that under the influence of nutrients discharged from river, the concentrations of nutrients and phytoplankton were higher in the northwest and northeast of the bay, and decreased from the inner bay to the outer. Affected by strong tidal mixing, the concentrations of all state variables were vertically homogeneous except in the deeper regions where a small gradient was found. Obvious seasonal variation of phytoplankton biomass was found, which exhibited two peaks in March and July, respectively. The variation of riverine waste loads had remarkable impact on nutrients concentration in coastal areas, but slightly altered the distribution in the center of the bay.

Three-dimensional tidal current numerical model of the Oujiang Estuary

The characteristics of three-dimensional （3-D） tidal current in the Oujiang Estuary are investigated according to in situ observations. The Oujiang Estuary has features of irregular coastline, complex topography, many islands, moveable boundary, and submerged dyke, therefore, σ 3-D numerical model oil an unstructured triangular grid has been degeloped. The σ coordinate transforination, the moveable boundary and submerged dyke treatment techniques were employed in the model so it is suitable for the tidal simulations in the Oujing Estuary with submerged dyke and moveable boundary problems. The model is evaluated with the in situ data, and the results show that the calculated water elevations at 19 stations and currents at 19 profiler stations are in good agreement with measured data both in magnitude and phase. This numerical model is applied to the 3-D tidal circulation simulations of experiments in stopping flow transport through the South Branch of the Oujiang Estuary, and the feasibility to cutoff the flow in the South Branch of the Oujiang Estuary is demonstrated by numerical simulation experiments. The developed numerical model simulated the 3-D tidal current circulations in complicated coastal and estuarine waters very well.

NUMERICAL SIMULATION OF SOUTH CHINA SEA MONSOON ONSET BASED ON GRAPES MODEL AND EXPERIMENTS ON INITIAL MODEL FIELDS

The Global and Regional Assimilation and Prediction System (GRAPES), a limited-area regional model, was used to simulate the onset of South China Sea summer monsoon. In view of the relatively insufficient information about the initial field in simulation predictions, the Advanced Microwave Sounding Unit-B (AMSU-B) data from a NOAA satellite were introduced to improve the initial values. By directly using the 3-dimensional variational data assimilation system of GRAPES, two schemes for assimilation tests were designed. In the design, Test 1 (T1) assimilates both sounding and AMSU-B data, and Test 2 (T2) assimilates only the conventional sounding data, before applying the model in simulation forecasts. Comparative experiments showed that the model was very sensitive to initial fields and successful in reproducing the monsoon onset, allocation of high- and low-level wind fields during the pentad of onset, and the northward advancement of the monsoon and monsoon rain bands. The scheme, however, simulated rainfall and the location of the subtropical high with deviations from observations. The simulated location of the subtropical high was more westward and northward and the simulated rainfall for the South China Sea was larger and covered a broader area.

The 3D simulation and optimized management model of groundwater systems based on eco-environmental water demand

Through the study of mutual process between groundwater systems and eco-environmental water demand, the eco-environmental water demand is brought into groundwater systems model as the important water consumption item and unification of groundwater抯 economic, environmental and ecological functions were taken into account. Based on eco-environmental water demand at Da抋n in Jilin province, a three-dimensional simulation and optimized management model of groundwater systems was established. All water balance components of groundwater systems in 1998 and 1999 were simulated with this model and the best optimal exploitation scheme of groundwater systems in 2000 was determined, so that groundwater resource was efficiently utilized and good economic, ecologic and social benefits were obtained.

ROV仿真平台技术研究

遥控有缆机器人(ROV)在海洋资源开发、管道/线缆铺设中发挥着重要作用,但其海洋实验成本高昂,且要求操作员具有丰富的操作经验。为辅助培训ROV操作员并提高ROV实验效率,文章设计了一种硬件在环、具有三维可视化功能的仿真平台,其既可直接与现场应用的ROV控制系统连接进行软件测试与功能验证,又可以直接用于操作员培训。该平台通过ROV物理模型和ROV数学模型等模拟实物ROV,并在虚拟视景中构建ROV运动场景、在虚拟环境中模拟ROV作业。基于ROV数学模型,其计算ROV运动数据并将运动数据信息传递到ROV三维模型进行动态显示,同时将实时运动信息反馈给ROV控制系统。结合水池实验中ROV速度随推进器转速变化的实验数据,文章对比分析了实验数据与仿真平台计算数据。结果表明,该仿真平台能有效代替实物实验并辅助ROV操作员培训,可大大节省培训与实验成本,提升ROV操作员培训效率。

基于Modelica语言的ROV力学系统建模与仿真

本文针对因ROV在水下作业过程中的非线性及耦合运动特性而导致采用传统Simulink建模方法效率低下的问题,将Modelica语言应用于ROV力学系统建模过程中,提出了一种通用的、面向对象的水下航行器运动建模方法。简要介绍了Modelica语言的特性和优点,应用其面向对象的建模思想构建仿真框架,将ROV力学系统按受力性质进行分析、分类与模块功能划分,定义共用、可重用的底层运动学与力学连接器作为模块间交互接口,实现各模块由数学模型到仿真模型转化。在顶层模型中通过组件实例化整合各模块,应用组件连接机制,创建完整的ROV力学系统。选取工况对其运动特性进行仿真,分析仿真结果,以验证建模方法便捷性和正确性。

Three-dimensional finite element analysis on effects of tunnel construction on nearby pile foundation

A three-dimensional finite element simulation was carried out to investigate the effects of tunnel construction on nearby pile foundation.The displacement controlled model (DCM) was used to simulate the tunneling-induced volume loss effects.The numerical model was verified based on the results of a centrifuge test and a set of parametric studies was implemented based on this model.There is good agreement between the trend of the results of the centrifuge test and the present model.The results of parametric studies show that the tunnelling-induced pile internal force and deformation depend mainly on the pile?tunnel distance,the pile length to tunnel depth ratio and the volume loss.Two different zones are separated by a 45° line projected from the tunnel springline.Within the zone of influence,the pile is subjected to tensile force and large settlement;whereas outside the zone of influence,dragload and small settlement are induced.It is also established that the impact of tunnelling on a pile group is substantially smaller as compared with a single pile in the same location with the rear pile in a group,demonstrating a positive pile group effect.

Comprehensive evaluation of high-steep slope stability and optimal high-steep slope design by 3D physical modeling

High-steep slope stability and its optimal excavation design in Shuichang open pit iron mine were analyzed based on a large 3D physical simulation technique. An optimal excavation scheme with a relatively steeper slope angle was successfully implemented at the northwest wall between Nos. 4 and 5 exploration lines of Shuichang Iron Mine, taking into account the 3D scale effect. The phys-ico-mechanical properties of rock materials were obtained by laboratory tests conducted on sample cores from exploration drilling directly from the iron mine. A porous rock-like composite material was formed for the model, and the mechanical parameters of the material were assessed experimentally;specifically, the effect of water on the sample was quantitatively determined. We adopted an experimental setup using stiff modular applied static loading to carry out a visual excavation of the slope at a random depth. The setup was equipped with acous-tic emission （AE） sensors, and the experiments were monitored by crack optical acquirement, ground penetrating radar, and close-field pho-togrammetry to investigate the mechanisms of rock-mass destabilization in the high-steep slope. For the complex study area, the model re-sults indicated a clear correlation between the model＇s destabilization resulting from slope excavation and the collected monitoring informa-tion. During the model simulation, the overall angle of the slope increased by 1-6 degrees in different sections. Dramatically, the modeled excavation scheme saved over 80 million tons of rock from extraction, generating enormous economic and ecological benefits.

Research on an Integrated Modeling Method of Virtual Ship Assembly

A new method of virtual ship assembly modeling which integrates ship three-dimensional design and ship construction planning was described in this paper. A workflow model of simulation modeling based on the virtual ship assembly process was also established; furthermore, a method of information transformation between the ship three-dimensional design and ship construction plan was formulated. To meet the requirements of information sharing between different systems in the ship virtual assembly, a simulation database was created by using the software engineering design method and the relational data model. With the application of this database, the information of ship three-dimensional design, construction planning, and virtual assembly can be integrated into one system. Subsequently, this new method was applied as a tool to simulate the virtual assembly of a ship, and the results guarantee its rationality and reliability.

Simulation of water temperature distribution in Fenhe Reservoir

In order to evaluate the need of controlling the temperature of water discharged from the Fenhe Reservoir, the reservoir water temperature distribution was examined. A three-dimensional mathematical model was used to simulate the in-plane and vertical distribution of water temperature. The parameters of the model were calibrated with field data of the temperature distribution in the Fenhe Reservoir. The simulated temperature of discharged water is consistent with the measured data. The difference in temperature between the discharged water and the natural river channel is less than 3 ℃ under the current operating conditions. This will not significantly impact the environment of downstream areas.

Characterization and Three-dimensional Structural Modeling of Humic Acid via Molecular Mechanics and Molecular Dynamic Simulation

The humic acid（HA） sample obtained from the alluvial soil was characterized by elemental composition, pyrolysis gas chromatography-mass spectrometry（Py-GC-MS） and solid-state 13C nuclear magnetic resonance （13C NMR） spectroscopy. There is high fat content and a few nitrogen-containing functional groups in HA. Py-GC-MS demonstrates the characterization and structural identification of HA. One long list of identified pyrolysis products was proposed for the construction of conceptual model of HA. Solid-state 13C NMR data indicate there are higher values of alkyl-C, O-alkyl-C and aryl-C in HA. The elemental composition, structural carbon distribution and L3C NMR spectroscopy of simulated HA are consistent with those of experimental HA. HyperChem was used to simulate the three-dimensional molecular structure of the monomer, which was optimized by the molecular mechanics of the optimized potential for liquid simulations（OPLS） force field and molecular dynamics simulation to get the stable and balanced conformation. The deprotonation process study depicts that the degree of ionization of HA gets deeper, while the electronegativity of HA and the energy of van der Waals（vdW） increase. Moreover, the 3D structure of humic acid with -4 charges is the most stable. The deprotonation process is an endothermic process.

3-D NUMERICAL SIMULATION OF FRACTURE PROCESSES IN HETEROGENEOUS BRITTLE MATERIALS

By using the lattice model combined with finite element methods andstatistical techniques, a numerical approach is developed to establish mechanical models ofthree-dimensional heterogeneous brittle materials. A special numerical code is introduced, in whicha lattice model and statistical approaches are used to simulate the initial heterogeneity ofmaterial properties. The size of displacement-load step is adap-tively determined so that only fewelements would fail in each load step. When the tensile principal strain in an element exceeds theultimate strain of this element, the element is considered broken and its Young's modulus is set tobe very low. Some important behaviors of heterogeneous brittle materials are indicated using thiscode. Load-displacement curves and figures of three-dimensional fracture patterns are alsonumerically obtained, which are similar to those observed in laboratory tests.

ROV扭矩工具液压监测系统研究

ROV扭矩工具是海洋油气工程中水下生产系统常用的维修安装工具之一,其适应性与稳定性直接影响水下生产系统维修安装的效率与安全。目前国内对ROV扭矩工具的研究还处于认识和操作的基础阶段,核心技术还无法突破。结合API及ISO13628-8相关标准,设计了ROV扭矩工具的液压监控系统;然后建立液压马达回路数学模型,得到液压马达回路传递函数方框图;最后采用Matlab和AMESim两款软件对液压马达回路进行仿真和对比。采用AMESim软件对锁紧和换挡液压缸回路进行建模仿真,得到三个回路的输出曲线,通过分析,液压马达回路两个仿真结果具有较好一致性,数学模型准确无误,锁紧和换挡液压缸回路满足系统工作要求。仿真结果表明:设计的液压监控系统满足工程需要,可为ROV扭矩工具核心技术突破提供一定的技术参考。研究成果对我国ROV扭矩工具的国产化研究有一定的指导意义。

海洋渔业选择性捕捞ROV艏向控制方法研究

为减少海洋渔业资源过度开发,文中设计一种海洋渔业选择性捕捞ROV,用于捕捞过程中对幼鱼和稀有鱼种的保护。依据海洋渔业选择性捕捞作业要求,采用Solidworks软件完成ROV机械结构的设计。ROV运动系统具有非线性和强耦合性,遇到水流的作用会变得更加不稳定。为提高ROV在捕捞过程中艏向运动的稳定性能,设计一种模糊PID控制器对ROV进行艏向控制。根据ROV运动特点建立空间运动坐标系和ROV艏向运动数学模型表达式,在PID控制基础上引入模糊控制对PID的3个参数进行在线调整;在Matlab/Simulink环境下创建PID控制器与模糊PID控制器仿真模型,使用两种控制器对ROV进行30°和90°的艏向控制对比仿真。仿真结果表明,模糊PID控制较PID控制超调量分别减少4°、10°,系统达到稳定状态的时间也更短,是一种高性能与稳定的ROV艏向控制方式。