Computational Construction as a Means to Coordinate Representations of Infinity

In this paper, we describe a design experiment aimed at helping students to explore and develop concepts of infinite processes and objects. Our approach is based on the design and development of a computational microworld, which afforded students the means to construct a range of representational models (symbolic, visual and numeric) of infinity-related objects (infinite sequences, in particular). We present episodes based on four students’ activities, seeking to illustrate how the available tools mediated students’ understandings of the infinite in rich ways, allowing them to discriminate subtle process-oriented features of infinite processes. We claim that the microworld supported students in the coordination of hitherto unconnected or conflicting intuitions concerning infinity, based on a constructive articulation of different representational forms we name as ‘representational moderation’.

Programming in Polygon R&D: Explorations with a Spatial Language II

This paper introduces the language associated with a polygon microworld called PolygonR&D, which has the mathematical crispness of Logo and has the discreteness and simplicity of a Turing machine. In this microworld, polygons serve two purposes: as agents (similar to the turtles in Logo), and as data (landmarks in the plane). Programming the spatial behaviour of polygon agents is achieved by a simple variable-free language. Although limited in the number of instructions, the language allows for complex outcomes such as creation of sophisticated tilings, algorithm visualization, simulations, and even numerical computation. The ease of constructing the variety of examples shown in this paper indicates the microworld’s potential in both secondary and post-secondary education. An erratum to this article can be found at     

变形网格及其在图像识别中的应用

网格特征是图像识别中一类重要特征,而变形模板对于复杂的图像识别问题如字符识别、数字识别、图标识别等表现出很好的性能,但变形模板很费时。该文针对网格特征提出了变形网格,并分析了变形模板与变形网格之间的近似等价性。所提方法对网格进行变形而不是对图像变形,因而速度比变形模板快得多,而且性能相差不大。把这种方法分别应用于图标识别和脱机手写汉字识别。图标识别实验中变形模板使识别率提高了7.5%,而变形网格使识别率提高了7.3%、手写汉字识别实验中变形模板使识别率提高了6.1%,而变形网格使识别率提高了5.8%。考虑到变形网格比变形模板快得多,所以这种方法是有优势的。     

Assessing Logo programming among Jordanian seventh grade students through turtle geometry

The present study is concerned with assessing Logo programming experiences among seventh grade students. A formal multiple-choice test and five performance tasks were used to collect data. The results provided that students’ performance was better than the expected score by the probabilistic laws, and a very low correlation between their Logo programming performance and school mathematics achievement was revealed. Most of the made misconceptions were due to geometrical aspects rather than Logo primitives, and were concentrated on the angle of rotation, the angle of complete rotation and the angle of regular polygon. In addition, students’ problem-solving ability was limited while conducting some Logo programming tasks, and acceptable in others. In regard to the results, it is recommended that teaching Logo programming should be used in different contexts that enhance students’ learning, and develop problem-solving processes.     

计算机在电视台标监测系统应用的研究

通过计算机对电视台标进行监测 ,实现了智能监测电视信号 ,大大提高了监测的准确性和可靠性 ,有效地预防非法信号的干扰 ,保证安全播出。     

基于H.264的台标字幕系统设计

提出了一种基于H.264标准的台标字幕系统的设计.该系统应用于数字电视网络前端视频图像上的台标字幕叠加,通过将H.264码流局部解码后进行空间域的字幕宏块叠加,然后再重新编码.在进行H.264局部解编码过程中采用了反向跟踪算法缩小解编码区域,从而在保持原视频图像质量的同时最大限度地降低系统处理的复杂度.     

基于离散余弦变换域处理的快速台标插入法

针对在MPEG-2视频中插入台标,提出了一种基于离散余弦变换域处理的快速台标插入法。与解码-相加-再编码的方法相比,该方法省去了离散余弦变换、反离散余弦变换和重新做运动估计等环节,大大节省了运算量,适合于硬件实时系统的实现。实验表明和解码-相加-再编码的方法相比,以图像质量的轻微下降,换取了较快的处理速度。     

C4D与AE制作简单的Logo演绎

本文介绍了C4D的建模以及菜单栏中的"复制"、"随机"的应用,AE与C4D结合制作简单的Logo演绎。     

Multi-object image retrieval based on shape and topology

We aim at developing a geometry-based retrieval system for multi-object images. We model both shape and topology of image objects including holes using a structured representation called curvature tree (CT); the hierarchy of the CT reflects the inclusion relationships between the objects and holes. To facilitate shape-based matching, triangle-area representation (TAR) of each object and hole is stored at the corresponding node in the CT. The similarity between two multi-object images is measured based on the maximum similarity subtree isomorphism (MSSI) between their CTs. For this purpose, we adapt a continuous optimization approach to solve the MSSI problem and a very effective dynamic programming algorithm to measure the similarity between the attributed nodes. Our matching scheme agrees with many recent findings in psychology about the human perception of multi-object images. Experiments on a database of 1500 logos and the MPEG-7 CE-1 database of 1400 shape images have shown the significance of the proposed method.