Manifold Based Local Classifiers: Linear and Nonlinear Approaches

In case of insufficient data samples in high-dimensional classification problems, sparse scatters of samples tend to have many ‘holes’—regions that have few or no nearby training samples from the class. When such regions lie close to inter-class boundaries, the nearest neighbors of a query may lie in the wrong class, thus leading to errors in the Nearest Neighbor classification rule. The K-local hyperplane distance nearest neighbor (HKNN) algorithm tackles this problem by approximating each class with a smooth nonlinear manifold, which is considered to be locally linear. The method takes advantage of the local linearity assumption by using the distances from a query sample to the affine hulls of query’s nearest neighbors for decision making. However, HKNN is limited to using the Euclidean distance metric, which is a significant limitation in practice. In this paper we reformulate HKNN in terms of subspaces, and propose a variant, the Local Discriminative Common Vector (LDCV) method, that is more suitable for classification tasks where the classes have similar intra-class variations. We then extend both methods to the nonlinear case by mapping the nearest neighbors into a higher-dimensional space where the linear manifolds are constructed. This procedure allows us to use a wide variety of distance functions in the process, while computing distances between the query sample and the nonlinear manifolds remains straightforward owing to the linear nature of the manifolds in the mapped space. We tested the proposed methods on several classification tasks, obtaining better results than both the Support Vector Machines (SVMs) and their local counterpart SVM-KNN on the USPS and Image segmentation databases, and outperforming the local SVM-KNN on the Caltech visual recognition database.     

Corrosion Monitoring Strategies—Choice Between Area and Point Measurements

There is increasing interest in the use of permanently installed monitoring systems to track the progress of corrosion. There is a choice between point thickness measurement systems, those that monitor the average thickness over a modest area, and large area monitoring systems that will detect relatively severe, localised corrosion. The relative merits of the different types of monitoring system are assessed for cases with different likely fractions of the total surface area affected by corrosion. If the wall loss is expected to be fairly uniform over the component surface then a small number of point sensors is the most attractive solution, whereas if the loss is likely to be highly localised at an unpredictable location and potentially severe, a large area monitoring system is most suitable. In the intermediate case of modest loss over a significant fraction of the surface, the choice is more complex. If the requirement is to detect relatively large wall loss that may be localised then the number of point sensors required increases substantially and the average thickness area monitoring systems appear to be more attractive. However, it is shown that corrosion distributions are frequently exponential, and this can lead to large maximum pit depths when the average wall loss is at the margin of detectability with current commercially available systems.     

Cyclotron resonance in HgTe/CdTe-based heterostructures in high magnetic fields

Cyclotron resonance study of HgTe/CdTe-based quantum wells with both inverted and normal band structures in quantizing magnetic fields was performed. In semimetallic HgTe quantum wells with inverted band structure, a hole cyclotron resonance line was observed for the first time. In the samples with normal band structure, interband transitions were observed with wide line width due to quantum well width fluctuations. In all samples, impurity-related magnetoabsorption lines were revealed. The obtained results were interpreted within the Kane 8·8 model, the valence band offset of CdTe and HgTe, and the Kane parameter E_P being adjusted.     

Space robotics supporting exploration missions: vision, force control and coordination strategy for crew assistants

Many research activities are being carried out about space exploration missions, in order to strongly improve man’s working conditions in planetary environments. Along this line, this work presents some results obtained within the development of an effective robotic crew assistant. This robot can execute a number of operations, both in a completely autonomous manner (i.e. without requiring human supervision) and in a strict cooperation with the astronauts; thus supporting and helping them in executing operations otherwise very difficult or unfeasible to be accomplished. The developed and then adopted functional and algorithmic control architecture for the considered robot assistant, also including vision and force feedback, is described with some details in the present paper.     

Hydrogen trapping: Synergetic effects of inorganic additives with cobalt sulfide absorbers and reactivity of cobalt polysulfide

The biphasic product CoS₂ + Co(OH)₂ obtained by oxidation of cobalt sulfide is known to trap hydrogen at room temperature and low pressure according to a balanced reduction equation. Adding various inorganic compounds to this original absorber induces their reduction by hydrogen in the same conditions at a significant rate: (i) excess cobalt hydroxide is reduced to metallic cobalt; (ii) nitrate ions are reduced to ammonia; (iii) sulfur and sodium thiosulfate are reduced to H₂S or NaHS and Na₂S, respectively. Without a hydrogen absorber these inorganic compounds are not reduced by H₂, suggesting synergetic effects involving H₂ and the hydrogen absorber. Amorphous cobalt polysulfide, CoS₅, is also reduced by hydrogen at room temperature and releases H₂S gas. In the presence of a base to neutralize H₂S gas, the reaction rate is initially slower than with the CoS₂ + Co(OH)₂ mixture due to the higher stability of polysulfide chains but the H₂ trapping yield is improved, making CoS₅ a good candidate for H₂ trapping.     

粉剂使用——制药设备新结构的解决办法

粉剂使用早已是化学产品与制药产品各种不同生产阶段的一部分.当然,以往在拟定新生产设备时,经常只是最后考虑粉剂使用,以人孔手工装载(图1)是一种喜欢的装料方法,所以,关于容器、可靠性和后勤等问题,都属于生产责任工作内.     

Matrix-fiber stress transfer in composite materials: Elasto-plastic model with an interphase layer

The matrix-fiber stress transfer in glass-epoxy composite materials was studied using analytical and experimental methods. The mathematical model that was developed calculates the stress fields in the fiber, interphase, and neighboring matrix near a fiber break. This scheme takes into account the elastic-plastic behavior of both the matrix and the interphase, and it includes the treatment of stress concentration near the discontinuities of the fibers. The radius of the fibers and the mechanical properties of the matrix were varied in order to validate the mathematical model. The computed values for the lengths of debonding, plastic deformation, and elastic deformation in the matrix near the fiber tip were confirmed by measurements taken under polarized light on loaded and unloaded single fiber samples.     

The effects of brominated flame retardants on the elements of fire hazard: a re‐examination of earlier results

Addition of halogen‐containing flame retardants to reduce ignitability and flame spread is presumed to increase both the quantity of smoke produced and the toxicity of the fire effluent. In the case of brominated flame retardants (BFRs), this does not appear to be the case. This work is a re‐examination of the results of an earlier series of experiments carried out at the U.S. National Bureau of Standard (now NIST), in which product pairs were studied, one product in each pair was treated with a BFR and one was not. Comparative hazard analysis, using information not available to the original investigators, shows that, for the products under study, all three aspects of hazard — heat, smoke obscuration and fire effluent toxicity — are either reduced or unaffected by the action of the brominated agents. In particular, hydrogen bromide, a component of the fire effluent when brominated agents are present, was shown to be unimportant in the toxic hazard of full‐scale fires involving BFR‐treated products. Copyright © 1999 John Wiley & Sons, Ltd.     

电子投影显示的新趋势

数字投影正以比任何其他大屏幕显示技术都快得多的速度在改进,有可能成为竞争中的优胜者,从面统治大屏幕HDTV消费类市场。但这还需要一段时间。