Applications of GSTARS Computer Models for Solving River and Reservoir Sedimentation Problems

GSTARS (Generalized Sediment Transport model for Alluvial River Simulation) is a series of computer models developed by the U.S. Bureau of Reclamation while the author was employed by that agency. The stream tube concept is used in all GSTARS models which allow us to solve one-dimensional equations for each stream tube independently and obtain semi-two-dimensional variation of the hydraulic conditions along and across stream tubes for rivers and reservoirs. Sedi-ment transport, scour, and deposition processes are simulated along each stream tube independently to give us a semi-three-dimensional variation of the bed geometry. Most sediment transport computer models assume that channel width is given and cannot change during the simulation process. GSTARS models apply the theory of minimum stream power to the determination of optimum channel width and channel geometry. The concepts of channel side stability, and active, inactive, and armoring layers are used in all GSTARS models for realistic long-term simulation and prediction of the scour and deposition processes in rivers and reservoirs.GSTARS models have been applied in many countries for solving a wide range of river and reservoir sedimentation problems. Case studies will be used to illustrate the applications of GSTARS computer models.

Computer Model of Phase Transformation From Hot-Deformed Austenite in Niobium Microalloyed Steels

Based on thermodynamics and kinetics, a new mathematical model was developed to calculate the CCT diagrams and the transformation kinetics in low carbon niobium steels, in which the effect of deformation on the degree of supercooling was taken into account. The undercooling caused by deformation is the major reason for the increase of the starting transition temperature during continuous cooling. The critical cooling rate of bainite formation is within 2--5 ℃s for the studied niobium steels and deformation is suitable for the occurrence of pearlite. The ferrite volume fraction increases with the increase of the austenite boundary area, and decreases with the increase of the cooling rate. The calculated CCT diagrams and the volume fraction of each phase are in good agreement with the measurements.

FINITE ELEMENT COMPUTER MODEL OF MICROWAVE HEATED CERAMICS

At present,the concerned papers appeared in special magazines about discussing or introducing finite element method for calculating temperature distribution in ceramic body during microwave sintering, are not a good many, but it seems that finite element method is more convenient than finite difference method in dealing with special or complex geometry of ceramic body. In this paper, we describe a 3D finite element model simulating the heating pattern of ceramic microwave sintering in TE(10N) single-mode rectangular cavity in which the microwave energy deposition pattern in the samples can be expressed as an analysis function of space, and present a series of transient temperature distributions and heating rates of ceramic cylinders and cuboids tender variable thermal conductivities, dieletric loss factors,power consumer-levels, etc. These digital solutions may provide a better understanding of eliminating thermal runaway and improving temperature homogeneity.

非参数CD-CAT题库Q矩阵优化设计

开展非参数CD-CAT题库Q矩阵的优化设计,并将它用于指导题库题目编制或选择,且它无需模型参数估计,这对于促进非参数CD-CAT进入课堂评价至关重要.受p-优化的启发,该文提出比例法生成优化Q矩阵,同时将已有的参数化模型题库设计方法推广到非参数化题库Q矩阵的优化设计.模拟研究结果显示:比例法和推广的融合法都有较好表现,而且当题库量较少时比例法更有优势.

CD-CAT中基于SCAD惩罚和EM视角的在线标定方法开发——G-DINA模型

G-DINA(the generalizeddeterministic input,noisy and gate)模型限制条件少,应用范围广,满足大量心理与教育评估测验数据的要求。研究提出一种适用于G-DINA等模型的同时标定新题Q矩阵与项目参数的认知诊断计算机化自适应测验(CD-CAT)在线标定新方法SCADOCM,以期促进CD-CAT在实践中的推广与应用。本研究分别基于模拟题库以及真实题库进行研究,结果表明:相比传统的SIE方法,SCADOCM在各实验条件下均具有较为理想的标定精度与标定效率,应用前景较好;SIE方法不适用于饱和的G-DINA等模型,其各实验条件下的Q矩阵标定精度均较低。

Multi-scale modeling in microstructure evolution of materials

Intelligent design and control of the microstructure to tailor properties of materials is the dream that materials scientists have been worked hard for many years. Formation of research area of computational materials science paves the way to realize the dream. Simulation of microstructure evolution is a chief branch of the computational materials science and has caused great attention from materials researchers. Multi-scale modeling gets popular just within 5-6 years recently due to huge research works to try to shorten the distance between simulation and application. People have to command one or more classical simulation methods in order to do the multi-scale modeling so chief simulation methods will be discussed first and then more reviews in detail are given to the phase field simulation. The main part of the paper is carried out to introduce two key approaches to do the multi-scale modeling job. It is suggested that extension of the multiscale modeling is necessary to study the technologies to link microstructure simulation, processing simulation and property simulation each other as well as to build bridges between different simulation methods and between analytical models and numerical models.

Toward Developing a Syllabus-Oriented Computer-Based Question-Banks Software to Support Partially Computerized Exams

Aims: This study aims at designing and implementing syllabus-oriented question-bank system that is capable of producing paper-based exams with multiple forms along with answer keys. The developed software tool is named Χ(Chi)-Pro Milestone and supports four types of questions, namely: Multiple-choice, True/False, Short-Answer and Free-Response Essay questions. The study is motivated by the fact that student number in schools and universities is continuously growing at high, non-linear, and uncontrolled rates. This growth, however, is not accompanied by an equivalent growth of educational resources (mainly: instructors, classrooms, and labs). A direct result of this situation is having relatively large number of students in each classroom. It is observed that providing and using online-examining systems could be intractable and expensive. As an alternative, paper-based exams can be used. One main issue is that manually produced paper-based exams are of low quality because of some human factors such as instability and relatively narrow range of topics [1]. Further, it is observed that instructors usually need to spend a lot of time and energy in composing paper-based exams with multiple forms. Therefore, the use of computers for automatic production of paper-based exams from question banks is becoming more and more important. Methodology: The design and evaluation of X-Pro Milestone are done by considering a basic set of design principles that are based on a list of identified Functional and Non-Functional Requirements. Deriving those requirements is made possible by developing X-Pro Milestone using the Iterative and Incremental model from software engineering domain. Results: We demonstrate that X-Pro Milestone has a number of excellent characteristics compared to the exam-preparation and question banks tools available in market. Some of these characteristics are: ease of use and operation, user-friendly interface and good usability, high security and protection of the question bank-items, high stability, and reliability. Further, X-Pro Milestone makes initiating, maintaining and archiving Question-Banks and produced exams possible. Putting X-Pro Milestone into real use has showed that X-Pro Milestone is easy to be learned and effectively used. We demonstrate that X-Pro Milestone is a cost-effective alternative to online examining systems with more and richer features and with low infrastructure requirements.

乳腺癌患者新发心血管疾病预测模型的建立与验证:基于内蒙古区域医疗数据

目的:开发和验证乳腺癌患者新发心血管疾病(cardiovascular disease,CVD)的3年预测模型。方法:基于内蒙古区域医疗数据,纳入接受抗肿瘤治疗的18岁以上乳腺癌女性患者。多因素Fine&Gray模型纳入预测因子后,使用Lasso回归筛选变量,在训练集上拟合Cox比例风险、Logistic回归、Fine&Gray、随机森林和XGBoost模型,在测试集上分别用受试者工作特征(receiver operating characteristics,ROC)曲线下面积(area under the curve,AUC)和校准曲线评价模型区分度和校准度。结果:共纳入19325例接受抗肿瘤治疗的乳腺癌患者,平均年龄(52.76±10.44)岁,中位随访时间1.18年[四分位距(interquartile range,IQR):2.71]。7856例患者(40.65%)在乳腺癌诊断3年内发生CVD。Lasso回归筛选的预测因子为乳腺癌诊断年龄、居住地国内生产总值(gross domestic product,GDP)、肿瘤分期、高血压、缺血性心脏病及脑血管疾病既往史、手术类型、化疗类型、放疗类型。不考虑生存时间时,XGBoost模型的AUC显著高于随机森林模型[0.660(95%CI:0.644~0.675)vs.0.608(95%CI:0.591~0.624),P<0.001]和Logistic回归[0.609(95%CI:0.593~0.625),P<0.001],Logistic回归和XGBoost模型的校准度更好。考虑生存时间时,Cox比例风险模型和Fine&Gray模型的AUC差异无统计学意义[0.600(95%CI:0.584~0.616)vs.0.615(95%CI:0.599~0.631),P=0.188],但Fine&Gray模型的校准度更好。结论:基于区域医疗数据建立乳腺癌新发CVD的预测模型具有可行性。不考虑生存时间时,Logistic回归和XGBoost模型的预测性能更好;考虑生存时间时,Fine&Gray模型的预测性能更好。

针织立体构型产品的全成形工艺设计

为探讨针织立体构型产品在全成形电脑横机上的成形编织方式以实现一次成形编织,研究了针织立体构型产品的成形工艺和计算方法,根据外观轮廓的不同,将其进行分类,并在产品立体构型转化为二维纸样的基础上,对筒状结构、立方体结构和球状结构进行工艺建模,解析其成形工艺和算法。结果表明:在三维结构到二维纸样再到全成形纸样的转换过程中,利用三角换算法可形成筒状构型的直线轮廓,利用平行四边形转换法可实现立方体构型的三维结构,利用逆拟合法可形成球状构型的弧形轮廓。通过弧形灯罩的实例验证,最终能得到符合要求的全成形产品。

基于快速原型的个体匹配骨骼造型方法

为了改进个体匹配骨骼的设计与制造的速度和精度 ,缩短病人的等待时间和提高骨骼外形的匹配程度 .采取不经过曲面重构而直接利用快速原型完成人工骨骼模型的造型方法 ,即直接将患者骨骼的断层图像数据转化为快速原型分层制造的轮廓数据格式 ,并快速制造骨骼的实体原型 ,而对其形状的修改和编辑是在实物原型上进行的 .研究结果表明 ,这种方法具有速度快、精度高的特点 ,能很好地满足个体匹配骨骼对设计制造的速度和精度的要求 .

计算机模拟模型在黄土丘陵区土地可持续利用中的实证研究

针对黄土丘陵区的土地可持续利用问题 ,引入目前国际上较先进的水土流失与土地利用规划模型 APEX和 AV-SWAT,利用 GIS技术及陕北安塞县纸坊沟小流域定位站多年的连续观测资料 ,对模型在黄土丘陵区的适用性进行了初步验证。通过对该类型地区的水土流失量、作物产量、植被生物量等方面的测算 ,结果表明模型模拟计算的水土流失量与实际观测量的误差小于 10 % ,5年加权平均的作物模拟产量与实测值的差异不显著。从而为该类型区土地可持续利用方法论提供了新的计算工具 。

等级反应模型下计算机化自适应测验选题策略

计算机化自适应测验(CAT)中的选题策略,一直是国内外相关学者关注的问题。然而对多级评分的CAT的选题策略的研究却很少报导。本研究采用计算机模拟程序对等级反应模型(G raded Response Model)下CAT的四种选题策略进行研究。研究表明:等级难度值与当前能力估计值匹配选题策略的综合评价最高;在选题策略中增设“影子题库”可以明显提高项目调用的均匀性;并且不同的项目参数分布或不同的能力估计方法都对CAT评价指标有影响。

耳三维重建及虚拟内窥镜

目的 建立人体耳部可视化数字模型 ,探索虚拟耳内窥镜在内耳解剖研究中的作用。方法 应用首例中国数字化可视人体数据集 ,在SGI工作站上对耳部重要结构进行计算机三维重建及立体显示 ,并模仿耳内窥镜对中耳、内耳等结构进行观察。结果 成功获得耳部可视化模型 ,应用虚拟内窥镜可清楚显示中耳及内耳结构三维形态。结论 虚拟耳内窥镜观察有助于分析阐明耳内部结构的三维空间毗邻关系 ,可为耳部疾病的影像诊断及耳神经外科手术提供形态学资料。

XJ350修井机起升系统动力学仿真模型

深入了解修井机起升系统的动力学特性，以便缩短修井设备的研制周期，节约试验费用；运用机械系统动力学自动分析软件ＡＤＡＭＳ建立了ＸＪ３５０修井机起升系统的起升动力学仿真模型和下钻动力学仿真模型。在建立起升动力学仿真模型时，对杆柱采用了离散化的方式。上述模型稍做改动，就可以对不同井深时的起下钻做动力学分析。通过对仿真模型的运行。

RICAM1．3的结构与功能的改进及其应用

ＲＩＣＡＭ１．３（水稻生长日历模拟模型１．３）采用了发育进程、叶龄与叶面积模型的新例行程序、ＳＵＣＲＯＳ模型中干物质生产的例行子程序，以及在ＣＳＭＰ基础上改善的ＦＳＴ计算语言。因而，新版本ＲＩＣＡＭ将使农业技术管理和研究单位更便于应用。

抽油泵泵阀运动规律的计算机仿真

综合考虑了液体可压缩性、泵阀运动的魏氏效应对泵筒内液体连续流条件的影响,并考虑了泵阀运动的动力特性,建立了新的泵阀精确运动微分方程,该数学模型不存在奇点问题。本文应用数值积分法建立了泵阀运动规律的仿真模型,并编写了泵阀运动的计算机仿真程序。室内台架模拟试验结果表明,本文所建立的泵运动规律的数学模型是正确的。

基于关节坐标系的肌肉骨骼间附着点坐标转换方法

目的运动状态下对人体骨肌系统进行运动学及动力学分析时,应避免对人体造成伤害。本研究通过尸体切片、CT或者MRI图像重建等方法构建静态骨肌模型,并将其应用于活体进行分析。方法采用尸体切片数据重建下肢的三维骨肌模型,并对此骨肌模型及活体下肢建立统一规则的关节坐标系,详细描述人体骨肌系统模型和活体上相关肌肉骨骼间附着点空间坐标值转换。结果对研究对象膝关节屈曲运动中股二头肌短头力臂及长度进行计算和分析。结论该方法对提高人体运动学和动力学仿真及肌肉力预测具有重要意义。

单纱的计算机模拟

提出了用带有圆弧边的倾斜的矩形色块作为基本单元 ,并用其上随机产生的抛物线样条曲线作为毛羽的单纱的计算机模拟方法。用VC 实现过程中使用的主要成员函数。并给出实现纱线旋转功能的算法 。

道路交通事故再现模型研究

事故再现是道路交通事故责任鉴定或原因分析的重要方法 ,也是交通安全改善研究中的重要步骤 .文中介绍了事故再现的基本内容和事故再现模型的基础理论、方法 ,并在综述国内外近年来事故再现技术和模型研究现状的基础上 。

采水引起地面沉降的预计模型及电算化研究

论述了地下水开采引起地面沉降的力学机理,总结了地面沉降引起地质灾害的表现形式和地面沉降的研究现状;通过引入一个采水下沉系数 q,分析了地下水水势分布的几何特征,建立了地下水开采引起地面沉降的概率积分预计模型,利用 VB6.0 编制了预计计算程序。最后, 给出了一个单井计算和多井计算的实例,实现了预计模型的电算化。