Coarse filters for shape matching

This article describes the coarse shape filters that support the 3D, Internet-based search engine ShapeSifter, which aims to locate parts already in production that have a shape similar to a desired new part. The search engine analyzes the target model's shape characteristics and performs a similarity match on the database's contents. Our main challenge is identifying shape metrics that produce effective characterizations of 3D models for similarity comparison. We focus on using three novel convex hull-based indices to carry out a preliminary coarse filtering of candidates prior to more detailed analysis. We also describe the crucial role played by two databases of benchmark objects. Unlike other shape-matching systems, we chose ShapeSifter's architecture (multistep query), 3D representation (triangulated mesh), and implementation (Java3D) to allow deployment online once it matures     

Promatech公司推出多用剑杆织机

意大利织机制造商Ｐｒｏｍａｔｅｃｈ公司以Ｓｏｍｅｔ品牌推出了一种新型剑杆织机。这种以“Ａｌｐｈａ”命名的织机于２００１年９月底首次在一个演示间里亮相，随后又成为新加坡ＩＴＭＡ　Ａｓｉａ展会上的一个亮点。Ｓｏｍｅｔ公司剑杆织机产品经理Ｐｉｅｒｍａｒｃｏ　Ａｒｎｏｌｄｉ先生说，这种新型织机操作简便，可靠性高和多用性强，能以非常高的织造速度织许多种织物。一、Ａｌｐｈａ剑杆织机的性能１．操作简便Ａｌｐｈａ的设计使操作工很容易接近机器和修复断头。例如：打纬点与胸梁之间的距离大幅度缩短，使操作工更容易用手来…     

Introduction of a nonlinearity measure for principal component models

Although principal component analysis (PCA) is an important tool in standard multivariate data analysis, little interest has been devoted to assessing whether the underlying relationship within a given variable set can be described by a linear PCA model or whether nonlinear PCA must be utilized. This paper addresses this deficiency by introducing a nonlinearity measure for principal component models. The measure is based on the following two principles: (i) the range of recorded process operation is divided into smaller regions; and (ii) accuracy bounds are determined for the sum of the discarded eigenvalues. If this sum is within the accuracy bounds for each region, the process is assumed to be linear and vice versa. This procedure is automated through the use of cross-validation. Finally, the paper shows the utility of the new nonlinearity measure using two simulation studies and with data from an industrial melter process.     

Case Study-Based Challenges of Quality Concrete Finishing for Architecturally Complex Structures

This paper focuses on the procedure utilized in the construction of tilt-up irregular concrete panels that are constructed on-site using concrete slabs and wooden formwork. The case study required high-quality concrete finishing. The erection and installation procedure called for a maximum panel-to-panel joint tolerance of 1.27?cm (0.5?in.), often 90° joints between panels. To meet precision requirements, the casting slabs were leveled and flattened with laser screed technology and smoothed with chemical solutions. To ensure that the final result met expectations, a mock-up model was built using different types of materials and to simulate site constraints. The architectural design is a composition of precast concrete panels like “Lego” pieces assembled similarly to a jigsaw puzzle. The unique construction process required a state-of-the-art analysis to produce the set quality. Quality conditions as set by the owner included creating a smooth concrete surface on all panels while avoiding damages and reducing equipment and material costs. The proposed methodology is described through its implementation on the case study, which is also described in this paper.     

Irrigation Modelling in the Context of Basin Water Resources

Management practices for irrigation schemes can often be improved by modelling the behaviour of a scheme and by evaluating its efficiency statistics. However, looking at an irrigation scheme without regard for other water uses within the river basin may not be effective. Efficiencies computed in this way are local and, since water may be used many times within the same basin, may not be realistic. Changes in water uses (e.g. irrigation, industrial, power production, urban water supply, navigation, environmental, recreational) will often have effects on other uses; and changes in irrigation schemes (management,structural, crop pattern) may affect other users within the basin. In addition, all water users will be affected by external changes such as changes in land cover or in climate. As demand for water increases, these links become more important until, at some stage, there is insufficient water for all users and hard choices must be made. Hydrological modelling is a tool that can be used to relate irrigation schemes to the other water uses within a river basin and can help in assessing real productivities and in evaluating alternative patterns of water usage. This paper discusses the techniques available to simulate irrigation schemes within overall basin water resources using, as an example, an intensively utilized basin in western Turkey.     

Using the MC68901 multifunction peripheral

First-generation microprocessor peripheral chips were each dedicated to specific functions (e.g. serial interface, parallel interface, timer). Some of today's peripherals are designed to carry out a wide range of functions. The 68901 multifunction peripheral (MFP), for example, combines the functions of a serial interface, a parallel interface, a timer and an interrupt generator. It is not possible to go into detail about the MFP here — its data manual is the size of a small book. Instead, this note illustrates the design of a complete single-board microcomputer built around the 68901 and the 68008 microprocessor.     

Transistor equivalent circuits

This paper surveys the history of the electric-circuit representation of the transistor over the past fifty years. During the first two decades after the transistor was announced in 1948, primary emphasis was on small-signal equivalent circuits, which could be used for linear-circuit analysis and design. In addition, parameters of many of these equivalent circuits for the bipolar junction transistor, which are described, were related to the physical construction of the device. Approximately two-thirds of the paper is devoted to this period, when the writer personally contributed to this effort. By the beginning of the third decade, transistor circuits had became more complex, and circuit analysis was carried out with the help of digital computers. Interest then shifted away from small-signal equivalent circuits to “models” for computer-aided circuit design (CACD). This transition, including the models used in the widely used CACD program SPICE, is described. MOS transistors are treated only briefly; by the time MOS transistors became commercially viable devices, emphasis then also had shifted to “models” for CACD. In conclusion, the writer notes that there is still hope for us aficionados of small-signal equivalent circuits; new types of transistors are still being characterized in this manner