停车设施选址的双层规划模型

为了解决城市停车难问题,针对目前日益紧张的土地资源和快速增长的交通流量,考虑停车设施对路网上交通流的影响,提出一种在土地利用规划基础上的,对路网影响最小,停车场使用者步行时间最省的停车设施选址的双层规划模型,借助现有的交通规划软件(Emme)进行求解,并应用于上海市江湾-五角场副中心地区停车设施规划研究中.     

基于最小生成树的二维图像深度分配

随着三维视频资源需求的增长,二维转三维(2D-3D)转换技术成为三维(3D)图像处理技术研究的焦点.由于2D视频中没有包含深度信息,2D-3D转换技术的关键在于2D视频中深度信息的提取.提出一种基于最小生成树的二维图像深度分配方法.利用最小生成树的方法对图像进行分割,然后先验理论对分割区域进行深度分配以产生合适的深度图像.最小生成树的方法不需要设置较多参数,对于不同场景的图像有较强的自适应性,而且最小生成树算法具有算法简单,运行速度快的优势.     

Cabri 3D软件在一堂立体几何课中的尝试与应用

<正>Cabri 3D软件是法国国家科研中心(CNRS)和法国格勒诺布尔的约瑟夫一福希尔大学研制的三维几何模型软件,研究项目起始于1985年.Cabri 3D的手册中写道:"通过使用Cabri 3D,您能更快掌握几何构造、观察和操控各种三维空间图形,如直线,平面,圆锥,球体,棱锥.您也可以创建从简单到复杂的各种动态几何结构,您还可以进行空间测量,甚至根据作图时的数据重现您构造图形过程,拥有Cabri 3D,您就拥有了助人学习解答几何与数学问题的非凡工具."这一软件特别适合于高中立体几何的教学,比起利用模型或手绘几何体的方式进行教学,     

多无人机对组网雷达的协同干扰问题研究

在现代战场中,航迹欺骗干扰技术是针对组网雷达提出的协同干扰技术,旨在利用多架无人机在同一时刻对组网雷达中的部分雷达实施相互关联的虚假目标欺骗干扰.充分考虑了实际情况下无人机飞行模态、飞行速度、飞行高度的约束限制,对雷达的位置分布以及虚假航迹线进行可视化,并将三维空间模型投影到二维平面后进行建模分析.主要针对一个虚拟的无人机航迹欺骗干扰问题,建立时空模型,通过构建可达交互矩阵和雷达扫描算法,结合0-1整数规划,得到无人机协同飞行的最优策略.     

基于模糊——随机规划的WEEE回收物流网络优化研究

针对废旧电子电气设备(WEEE)绿色回收问题,根据实际需求刻画其回收物流网络结构;在模型构建中.考虑参数为随机和模糊共存的情况,提出应用随机机会约束规划和模糊机会约束规划相结合的方法来建模;设模型参数是相互独立的,合理利用转换定理将不确定规划转变为常规数学规划,并借助LINGO软件求解最优方案.     

面向韧性提升的相互依赖关键基础设施网络灾后修复模型研究

科学合理制定相互依赖关键基础设施网络(Interdependent Critical Infrastructure Network, ICINs)遭灾后毁坏组件的修复计划是其安全管理的至关重要内容。本文首先明确了ICINs的韧性测度,分析了其灾后修复策略;然后基于网路流理论,以最大化ICINs的韧性为目标,构建了在有限灾后修复资源约束下,ICINs的灾后修复任务选择与调度的混合整数规划模型,并设计了遗传算法进行求解;最后通过不同规模的用例实验对模型和遗传算法进行了测试。研究表明:(1)该模型具有解决相关问题的可行性与有效性;(2)设计的遗传算法能获得质量较高的满意解,且对于大规模问题,遗传算法的求解时间与求解结果优于Cplex软件;(3)将网络之间的功能与空间相互依赖同时纳入模型中,能使ICINs的韧性达到更高。研究可为ICINs的灾后修复决策提供辅助。     

微电网环境下基于RFID信息的光伏建筑蓄电池充放电优化及其调度

能源危机的加剧促使人们不断的开发新能源,同时对于现有能源的使用也趋于高效化.民用和商业建筑物对于电能的消耗超过了70%,为了提高建筑物的能源利用效率,文章提出了一种基于校园微电网环境的蓄电池优化调度模型.由于基于RFID技术的校园ID卡的广泛使用,并提出利用ID卡的信息来构建校园内人的行为模型,同时利用光伏电池板的物理模型来刻画光伏建筑发电系统的输出,并采用场景树的方法对所建立的随机规划模型进行求解.最后,通过一个案例比较了场景树方法和一个启发式调度策略,为采用基于事件的方法求解此类网络化离散事件系统进行了初步探索.     

虚拟前交叉韧带重建手术中的触觉计算技术

虚拟手术训练仿真系统在医学教育训练中有着重要意义.膝关节损伤是运动伤的常见病,前交叉韧带(anterior cruciate ligament,ACL)重建手术是膝关节镜手术难度较大的术式之一.重点介绍软件实现虚拟ACL重建手术中的关键触觉技术,提出了钻孔模型表面模拟和钻孔骨道内壁模拟两个算法,实验效果表明了算法的有效性.     

基于因子分析的区域经济不平衡发展研究

以构建的区域经济发展三维评价指标体系,作为GIS(地理信息系统)相应粒度多边形的主要属性,建立空间时态数据库.通过定义的相对发展度函数进行指标规范化后,经标准化并虚拟优、劣样品,利用因子分析将之变换为因子得分。在此基础,提出加权闵可夫斯基距离法三维评价模型,引入方差、聚集度等测度不平衡程度,通过序列快照模型等表达区域经济发展不平衡格局的动态,根据公因子方差、序相关分析等进行因素诊断与调控。方法应用于福建南平市区域经济不平衡发展研究中,实证表明方法方便、有效。     

基于房地产项目探析土地规划对环境退化的影响

针对土地利用规划对环境退化的影响,首先,构建PSR模型,从生态、经济和社会3个方面设置并构建因果指标体系群,来直观度量规划区内土地利用系统的协调关系,用于评价土地可利用程度;其次,构建ESM模型,将生态系统服务功能细分为10类,制定各项指标的评价方法和综合集成方法,选择影响评价的环境因子,采用市场价值、影子工程和成本替代等方法进行价值评估;再次,引入灰色生长曲线改进模型,使其更好地适应时间变化,来衡量土地项目造成的环境退化成本;最后,将评价模型应用于南昌房地产项目,根据收集的数据,分别计算在PSR模型中的土地利用协调度,直观判断该项目为初步协调,并定量计算在ESM模型中不同土地的生态系统服务价值.     

基于MVR-E技术的虚拟社区交流引擎的设计与实现

通过对多媒体及多用户虚拟现实技术结构的分析和研究,就如何在FlashCommunication Application Server环境下开发虚拟社区交流引擎,通过组件方式在互联网上建立虚拟现实站点,并就如何实现虚拟环境下何实现虚拟现实的三维显示、场景更替、对象行走以及各对象之间如何实现消息传递,给出了相应的解决方案.     

水合物沉积物的力学本构模型及参数离散元计算

为有效描述水合物沉积物在不同水合物饱和度与围压情况下的力学行为,该文基于广义Hooke(胡克)定律建立了水合物沉积物的应力 应变关系方程和弹性模量弱化方程;基于三轴压缩试验确定了水合物沉积物的软化系数和软化指数,基于颗粒流程序（PFC3D）开发了水合物沉积物初始弹性模量的离散元算法（DEM）.利用建立的应力 应变关系方程、弹性模量弱化方程和初始弹性模量DEM,数值模拟了水合物沉积物在6种不同水合物饱和度与围压情况下的力学行为.数值模拟结果与三轴压缩试验结果的对比表明,建立的应力 应变关系方程、弹性模量弱化方程和初始弹性模量DEM,能有效预测水合物沉积物的力学行为,可为水合物井筒设计与安全开采提供理论基础和计算方法.     

MODELING FIRM SPATIAL INTERDEPENDENCE USING NATIONAL DATA COVERAGES: A REGIONAL APPLICATION TO MANURE MANAGEMENT

Abstract A regional modeling framework using national data series is developed to estimate the net cost of land‐applying manure under possible policy provisions to limit water‐ and air‐quality emissions. The modeling framework, applied to the Chesapeake Bay watershed, integrates GIS‐based spatial data within an optimization model to capture spatial effects at a subwatershed scale.     

A reliable algorithm to solve 3D frictional multi-contact problems: Application to granular media

We present in this paper an improved non-smooth Discrete Element Method (DEM) in 3D based on the Non-Smooth Contact Dynamics (NSCD) method. We consider a three-dimensional collection of rigid particles (spheres) during the motion of which contacts can occur or break. The dry friction is modeled by Coulomb’s law which is typically non-associated. The non-associativity of the constitutive law poses numerical challenges. By adopting the use of the bi-potential concept in the framework of the NSCD DEM, a faster and more robust time stepping algorithm with only one predictor-corrector step where the contact and the friction are coupled can be devised. This contrasts with the classical method where contact and friction are treated separately leading to a time stepping algorithm that involves two predictor-corrector steps. The algorithm has been introduced in a 3D version of the NSCD DEM software MULTICOR. Numerical applications will show the robustness of the algorithm and the possibilities of the MULTICOR software for solving three-dimensional problems.     

Modeling and characterization of cyclic relaxation and ratcheting using the distributed-element model

Constitutive modeling of cyclic relaxation and ratcheting (cumulative inelastic deformation) is developed on the basis of the distributed-element model (DEM). Although the original DEM is capable of describing general, elastic–plastic behavior for cyclically stabilized materials, it has the inadequacy of not being able to account for the effect of cyclic relaxation and ratcheting. By introducing the nonlinear kinematic hardening rule proposed by Armstrong and Frederick into element behavior of the DEM, the model becomes effective in characterizing the behavior of cyclic relaxation and ratcheting. Validation of the modified DEM is conducted by simulating cyclic behavior of various metal materials, including CS 1018, heat-treated rail steel, and Grade 60 steel. The results show that the modified DEM demonstrates realistic behavior of materials in both uniaxial and biaxial cyclic relaxation and ratcheting. Furthermore, detailed investigation of element behavior in the model provides us with additional insight into complex behavior and characteristics of materials in cyclic relaxation and ratcheting.     

一种非视距环境下基于TOA三维定位的新方法研究

为消除非视距环境对TOA三维定位带来的误差,引入演化博弈模型,以各个测量基站作为博弈局中人,为非视距环境下的TOA三维定位问题建立了一般形式的复制动态模型.研究提出了基于演化博弈的TOA定位算法,通过迭代计算消除非视距误差,获得移动端的位置估计.进一步地,针对基站位置分布明显不均的情况,在演化博弈TOA定位算法的基础上,通过构造虚拟基站和虚拟测量值,提出了基于虚拟基站的三维定位算法.实验对比显示基于演化博弈的TOA定位算法略优于经典定位算法,在基站位置分布明显不均的情况下,基于虚拟基站的三维定位算法效果较明显.     

Theories of mathematics education: European perspectives, commentaries and viable research directions

We briefly comment on different perspectives on (1) the role of mathematics education theories, (2) the issue of plurality and healthy heterogeneity versus consolidation; (3) underlying inquiry systems or the implicit role of philosophy in theories of mathematics education. This paper also outlines developments within the European research scene on theory usage in mathematics education research, which complement the discussion at the 29th PME research forum in Melbourne.     

New eyes for building models from video

Models of real-world objects and actions for use in graphics, virtual and augmented reality and related fields can only be obtained through the use of visual data and particularly video. This paper examines the question of recovering shape models from video information. Given video of an object or a scene captured by a moving camera, a prerequisite for model building is to recover the three-dimensional (3D) motion of the camera which consists of a rotation and a translation at each instant. It is shown here that a spherical eye (an eye or system of eyes providing panoramic vision) is superior to a camera-type eye (an eye with restricted field of view such as a common video camera) as regards the competence of 3D motion estimation. This result is derived from a geometric/statistical analysis of all the possible computational models that can be used for estimating 3D motion from an image sequence. Regardless of the estimation procedure for a camera-type eye, the parameters of the 3D rigid motion (translation and rotation) contain errors satisfying specific geometric constraints. Thus, translation is always confused with rotation, resulting in inaccurate results. This confusion does not happen for the case of panoramic vision. Insights obtained from this study point to new ways of constructing powerful imaging devices that suit particular tasks in visualization and virtual reality better than conventional cameras, thus leading to a new camera technology. Such new eyes are constructed by putting together multiple existing video cameras in specific ways, thus obtaining eyes from eyes. For a new eye of this kind we describe an implementation for deriving models of scenes from video data, while avoiding the correspondence problem in the video sequence.     

Comparison of non-cohesive resolved and coarse grain DEM models for gas flow through particle beds

The Discrete Element Method (DEM) is a widely used approach for modelling granular systems. Currently, the number of particles which can be tractably modelled using DEM is several orders of magnitude lower than the number of particles present in common large-scale industrial systems. Practical approaches to modelling such industrial system therefore usually involve modelling over a limited domain, or with larger particle diameters and a corresponding assumption of scale invariance. These assumption are, however, problematic in systems where granular material interacts with gas flow, as the dynamics of the system depends heavily on the number of particles. This has led to a number of suggested modifications for coupled gas–grain DEM to effectively increase the number of particles being simulated. One such approach is for each simulated particle to represent a cluster of smaller particles and to re-formulate DEM based on these clusters. This, known as a representative or ‘coarse grain’ method, potentially allows the number of virtual DEM particles to be approximately the same as the real number of particles at relatively low computational cost. We summarise the current approaches to coarse grain models in the literature, with emphasis on discussion of limitations and assumptions inherent in such approaches. The effectiveness of the method is investigated for gas flow through particle beds using resolved and coarse grain models with the same effective particle numbers. The pressure drop, as well as the pre and post fluidisation characteristics in the beds are measured and compared, and the relative saving in computational cost is weighed against the effectiveness of the coarse grain approach. In general, the method is found perform reasonably well, with a considerable saving of computational time, but to deviate from empirical predictions at large coarse grain ratios.     

Path finding for human motion in virtual environments

This paper presents an efficient and robust technique for generating global motion paths for a human model in virtual environments. Initially, a scene is discretized using raster hardware to generate an environment map. An obstacle-free cell path sub-optimal according to Manhattan metric is generated between any two cells. Unlike 2D techniques present in literature, the proposed algorithm works for complex 3D environments suitable for video games and architectural walk-throughs. For obstacle avoidance, the algorithm considers both physical dimensions of the human and actions such as jumping, bending, etc. Path smoothening is carried out to keep the cell path as closely as possible to Euclidean straight-line paths.