A comparison study of polyominoes explorations in a physical and virtual manipulative environment

This study develops virtual manipulative, polyominoes kits for junior high school students to explore polyominoes. The current work conducts a non‐equivalent group pretest–post‐test quasi‐experimental design to compare the performance difference between using physical manipulatives and virtual manipulatives in finding the number of polyominoes. Sixty eighth‐grade students from two different classes in a junior high school in Taipei County of Taiwan participated in this study. The current research randomly selected one class as the experiment group and the other as the control group. Students in the experiment group used virtual manipulatives to explore polyominoes and those in the control group used physical manipulatives. The results revealed that learning in the experiment group is as effective as that in the control group. This study identifies two obvious strategies (add one and reduce) among students in both groups. New ideas, including using new symbols to record the results and considering the influence of symmetry and rotation on the figures, occurred in the virtual manipulative group. Students in the virtual environment paid much more attention to exploring the polyomino problem.     

Reconstructing experiences with iScale

We present iScale, a survey tool for the retrospective elicitation of longitudinal user experience data. iScale aims to minimize retrospection bias and employs graphing to impose a process during the reconstruction of one's experiences. Two versions, the constructive and the value-account iScale, were motivated by two distinct theories on how people reconstruct emotional experiences from memory. These two versions were tested in two separate studies. Study 1 aimed at providing qualitative insight into the use of iScale and compared its performance to that of free-hand graphing. Study 2 compared the two versions of iScale to free recall, a control condition that does not impose structure on the reconstruction process. Overall, iScale resulted in an increase in the amount, the richness, and the test–retest consistency of recalled information as compared to free recall. These results provide support for the viability of retrospective techniques as a cost-effective alternative to longitudinal studies.     

Two infinite families of polyominoes that tile the plane by translation in two distinct ways

It has been proved that, among the polyominoes that tile the plane by translation, the so-called squares tile the plane in at most two distinct ways. In this paper, we focus on double squares, that is, the polyominoes that tile the plane in exactly two distinct ways. Our approach is based on solving equations on words, which allows us to exhibit properties about their shape. Moreover, we describe two infinite families of double squares. The first one is directly linked to Christoffel words and may be interpreted as segments of thick straight lines. The second one stems from the Fibonacci sequence and reveals some fractal features.     

Reconstructing regular meshes from points

We propose an algorithm for reconstructing regular meshes from unorganized point clouds. At first, a nearly isometric point parameterization is computed using only the location of the points. A mesh, composed of nearly equilateral triangles, is later created using a regular sampling pattern. This approach produces meshes with high visual quality and suitable for use with applications such as finite element analysis, which tend to impose strong constraints on the regularity of the input mesh. Geometric properties, such as local connectivity and surface features, are identified directly from the points and are stored independent of the resulting mesh. This decoupling preserves most details and allows more flexibility for meshing. The resulting parameterization supports several direct applications, such as texturing and bump mapping. In addition, novel boundary identification and cut parameterization algorithms are proposed to overcome the difficulties caused by cuts, non-closed surfaces and possible self-overlapping parameter patches. We demonstrate the effectiveness of our approach by reconstructing regular meshes from real datasets, such as a human colon obtained from CT scan and objects digitized using laser scanners.     

Reconstructing high-order surfaces for meshing

We consider the problem of reconstructing a high-order surface from a given surface mesh. This problem is important for many meshing operations, such as generating high-order finite elements, mesh refinement, mesh smoothing, and mesh adaptation. We introduce two methods called Weighted Averaging of Local Fittings and Continuous Moving Frames. These methods are both based on weighted least squares polynomial fittings and guarantee C ⁰ continuity. Unlike existing methods for reconstructing surfaces, our methods are applicable to surface meshes composed of triangles and/or quadrilaterals, can achieve third and even higher order accuracy, and have integrated treatments for sharp features. We present the theoretical framework of our methods, their accuracy, continuity, experimental comparisons against other methods, and applications in a number of meshing operations.     

Reconstructing history with computer graphics

Some applications of computer graphics to archeology are described. One project involved making a solid model of part of the Roman temple excavated at Bath, England, and its surroundings, comprising the Temple of Sulis Minerva, its precinct with surrounding colonnade, the Facade of the Four Seasons, and the barrel-roofed bathhouse that formerly enclosed what is now called the King's Bath. This model was constructed using a newly developed ray caster called DORA (divided object-space ray-casting algorithm). A second model was done of the Roman Fortress Baths in Caerleon, Wales. A quantity of archaeological graphics, both reconstructions and displays of data such as resistivity results, were also produced     

Reconstructing polygons from scanner data

A range-finding scanner can collect information about the shape of an (unknown) polygonal room in which it is placed. Suppose that a set of scanners returns not only a set of points, but also additional information, such as the normal to the plane when a scan beam detects a wall. We consider the problem of reconstructing the floor plan of a room from different types of scan data. In particular, we present algorithmic and hardness results for reconstructing two-dimensional polygons from point-wall pairs, point-normal pairs, and visibility polygons. The polygons may have restrictions on topology (e.g., to be simply connected) or geometry (e.g., to be orthogonal). We show that this reconstruction problem is NP-hard under most models, but that some restrictive assumptions do allow polynomial-time reconstruction algorithms.     

Reconstructing Curves without Delaunay Computation

A new non-Delaunay-based approach is presented to reconstruct a curve, lying in 2- or 3-space, from a sampling of points. The underlying theory is based on bounding curvature to determine monotone pieces of the curve. Theoretical guarantees are established. The implemented algorithm, based heuristically on the theory, proceeds by iteratively partitioning the sample points using an octree data structure. The strengths of the approach are (a) simple implementation, (b) efficiency-experimental performance compares favorably with Delaunay-based algorithms, (c) robustness-curves with multiple components and sharp corners are reconstructed satisfactorily, and (d) potential extension to surface reconstruction.     

三角网格上的代数曲面重建

提出一种用分片代数曲面构造三角曲面片的方法,利用具有公共边的2个三角形区域的4个顶点的函数值以及公共边2个端点的外法向量来构造一个二次曲面V(g)和一个截面V(h),其交V(g,h)即为2个三角曲面片的公共边界曲线.对每个已确定了边界条件的三角片内部进一步划分成3部分,每部分各自定义一个三次代数曲面.这3个三次代数曲面不仅在其交线处光滑拼接,而且分别沿三角形的边界与V(g)光滑拼接,从而构成一个具有GC1连续性的分片代数曲面.对于只属于一个三角片的边界留有一个自由度,可对曲面形状加以控制.     

用Web标准技术重构网站

随着网络技术的迅速发展,新Web标准的重要性越来越被人们所重视,本文对Web标准做了充分的阐述,并从技术方面说明了应用Web标准进行网站重构的具体方法。     

Reconstructing Open Surfaces from Image Data

In this paper a method for fitting open surfaces to data obtained from images is presented using a level set representation of the surface. This is done by tracking a curve, representing the boundary, on the implicitly defined surface. This curve is given as the intersection of the level set describing the surface and an auxiliary level set. These two level sets are propagated using the same motion vector field. Special care has to be taken in order for the surfaces not to intersect at other places than at the desired boundary. Methods for accomplishing this are presented and a fast scheme for finding initial values is proposed. This method gives a piecewise linear approximation of the initial surface boundary using a partition of the convex hull of the recovered 3D data. With the approach described in this paper, open surfaces can be fitted to e.g. point clouds obtained using structure from motion techniques. This paper solves an important practical problem since in many cases the surfaces in the scene are open or can only be viewed from certain directions. Experiments on several data sets support the method.     

Reconstructing civil society with intermedia communities

A healthy civil society is essential in order to deal with “wicked” societal problems. Merely involving institutional actors and mass media is not sufficient. Intermedia can play a crucial complementary role in strengthening civil society. However, the potential of these technologies needs to be carefully tailored to the requirements and constraints of the communities grown around them. The GRASS system for group report authoring is one carefully tailored socio-technical system aimed at unlocking this potential. Such systems may help to develop stakeholder communities that are more productive in societal conflict resolution.     

Reconstructing specimens using DIC microscope images

Differential interference contrast (DIC) microscopy is a powerful visualization tool used to study live biological cells. Its use, however, has been limited to qualitative observations. The inherent nonlinear relationship between the object properties and the image intensity makes quantitative analysis difficult. Toward quantitatively measuring optical properties of objects from DIC images, we develop a method to reconstruct the specimen's optical properties over a three-dimensional (3-D) volume. The method is a nonlinear optimization which uses hierarchical representations of the specimen and data. As a necessary tool, we have developed and validated a computational model for the DIC image formation process. We test our algorithm by reconstructing the optical properties of known specimens.     

三维模型对称平面重建的特征匹配方法

提出一种利用实物对称特征重建对称基准平面的方法：首先选择一组对称特征;然后将测量数据点投影在一过测量坐标原点的平面——定义为初始平面上,并用折线连接,旋转初始平面使两条折线重合,可以得到一个与对称平面平行的平面;接下来再移动这个平行平面,使对称特征到它的距离相等,这时的位置平面即为所求的对称平面。该方法已在逆向工程数据前处理系统中实现,并应用于摩托车外形塑件的逆向工程．     

Reconstructing convex sets from support line measurements

Algorithms are proposed for reconstructing convex sets given noisy support line measurements. It is observed that a set of measured support lines may not be consistent with any set in the plane. A theory of consistent support lines which serves as a basis for reconstruction algorithms that take the form of constrained optimization algorithms is developed. The formal statement of the problem and constraints reveals a rich geometry that makes it possible to include prior information about object position and boundary smoothness. The algorithms, which use explicit noise models and prior knowledge, are based on maximum-likelihood and maximum a posteriori estimation principles and are implemented using efficient linear and quadratic programming codes. Experimental results are presented. This research sets the stage for a more general approach to the incorporation of prior information concerning the estimation of object shape     

工业总线设备网络化改造的实现

利用低成本单片机与以太网控制芯片设计并实现了串口、现场总线转以太网TCP/IP模块,专门为单片机设计了由RTOS(嵌入式实时操作系统)与裁减后的TCP/IP协议栈构成的单片机嵌入式控制系统.完成了异种网络的融合.软件系统(包括TCP/IP协议栈)能够方便移植上各种8位、16位、32位处理器平台,实现各种嵌入式网络服务.成果对于工业设备的网络化实现提供了网关服务,满足对功能、成本、体积和功耗等要求.     

快速成型中STL数据模型的B-Rep实体精确重建

针对快速成型机广泛使用的STL数据模型,建立了STL文件拓扑重建的数据结构,给出了边界提取和面片分割的具体实施方法,实现了基于边界表示的实体建模．利用回转面的内在几何性质,提出了球面、柱面等规则曲面的识别方法,从而还原机械型面的原貌并实现规则型面的精确表示．对于自由曲面,采用调和映射参数化技术,实现了该类网格曲面的精确NURBS建模,给出了曲面片间保持G^1连续的优化拼接方法．实际的验证结果表明,重构的实体模型精度较高且便于系统间的数据交换,非常适于数控加工领域．