向量优化问题的Benson真有效解的充分与必要条件

在广义凸条件下，研究了带控制参量的向量优化问题。给出了这个问题的向量Lagrangians函数的概念，获得了Benson真有效解的充分条件与必要条件。     

Presheaf models for CCS-like languages

The aim of this paper is to harness the mathematical machinery around presheaves for the purposes of process calculi. Joyal, Nielsen and Winskel proposed a general definition of bisimulation from open maps. Here we show that open-map bisimulations within a range of presheaf models are congruences for a general process language, in which CCS and related languages are easily encoded. The results are then transferred to traditional models for processes. By first establishing the congruence results for presheaf models, abstract, general proofs of congruence properties can be provided and the awkwardness caused through traditional models not always possessing the cartesian liftings, used in the breakdown of process operations, are side stepped. The abstract results are applied to show that hereditary history-preserving bisimulation is a congruence for CCS-like languages to which is added a refinement operator on event structures as proposed by van Glabbeek and Goltz.     

Negotiating the semantic gap: from feature maps to semantic landscapes

In this paper, we present the results of a project that seeks to transform low-level features to a higher level of meaning. This project concerns a technique, latent semantic indexing (LSI), in conjunction with normalization and term weighting, which have been used for full-text retrieval for many years. In this environment, LSI determines clusters of co-occurring keywords, sometimes, called concepts, so that a query which uses a particular keyword can then retrieve documents perhaps not containing this keyword, but containing other keywords from the same cluster. In this paper, we examine the use of this technique for content-based image retrieval, using two different approaches to image feature representation. We also study the integration of visual features and textual keywords and the results show that it can help improve the retrieval performance significantly.     

Generalization of the Lambertian model and implications for machine vision

Lambert's model for diffuse reflection is extensively used in computational vision. It is used explicitly by methods such as shape from shading and photometric stereo, and implicitly by methods such as binocular stereo and motion detection. For several real-world objects, the Lambertian model can prove to be a very inaccurate approximation to the diffuse component. While the brightness of a Lambertian surface is independent of viewing direction, the brightness of a rough diffuse surface increases as the viewer approaches the source direction. A comprehensive model is developed that predicts reflectance from rough diffuse surfaces. The model accounts for complex geometric and radiometric phenomena such as masking, shadowing, and interreflections between points on the surface. Experiments have been conducted on real samples, such as, plaster, clay, sand, and cloth. All these surfaces demonstrate significant deviation from Lambertian behavior. The reflectance measurements obtained are in strong agreement with the reflectance predicted by the proposed model. The paper is concluded with a discussion on the implications of these results for machine vision.     

Segregation phenomena in large-size cast multicrystalline Si ingots

In cast multicrystalline silicon ingots impurity concentrations vary along the ingot height due to segregation phenomena during the directional solidification. It is expected that these concentrations are the highest at the top of the ingot which solidifies last. The bottom of the ingot which solidifies first, and which is longer in contact with the crucible floor is contaminated by solid state diffusion. As a consequence, lifetime (τ_n) and diffusion length (L_n) of minority carriers are the highest in the central part of the ingot and decrease strongly in the top as well as at the bottom. However, the impurity concentration is so high at the extremities of the ingot that additional solid state segregation phenomena occur at extended defects, which extract impurities from the adjacent grains. That is revealed at grain boundaries (GBs) by τ_n and L_n scan maps and also by the variation of the mobility of the majority carriers which cross GBs.     

The reconstruction of past patterns of tilled fields from historical cadastral maps using GIS

Information derived from a historical infield cadastral map dated 1874 and its written protocol was combined with data on four landscape characteristics (distance to the hamlet, 1 slope, folded aspect and quaternary geology) in a GIS-based 3D model in an attempt to develop a methodology for reconstructing earlier tilled field patterns. The study area was the farm of Grinde in Western Norway. The areas that the farmers themselves considered to be best for growing crops in 1874 sloped gently, faced south-west, were close to the hamlet and were on glacio-fluvial deposits or a thick layer of moraine. More than 80% of the fields expected to be the oldest appeared to be correctly identified. This pilot study shows that it is possible to identify the probable location of the oldest tilled fields both on maps and in the terrain, using land consolidation documents or other data on crop sowing and yields from historical sources even where no land consolidation documents are available. The method may be helpful in determining areas that should be managed or protected in specific ways to maintain the value of the cultural landscape.     

对Ag/Cu薄膜退火应力的模拟

采用基片曲率法测量并研究了Ag／Cu薄膜的应力与温度的关系．初始应力为-250MPa压应力，退火后为370MPa拉应力．采用基于形变机制图的模型模拟了应力与温度关系的实验曲线，结果表明，温度和应力不同，在薄膜内起作用的主要形变机制也不同．可能的形变机制包括位错滑移、幂律蠕变以及扩散蠕变机制．薄膜比块体材料的应变速率低，在同样的应力下应变更加困难．在退火过程中，薄膜内先使应力松弛的是Ag，将Ag各蠕变机制中的激活能提高到块体材料的1.25～1.35倍，模拟曲线与实验曲线符合得很好。     

Clustering properties of hierarchical self-organizing maps

A multilayer hierarchical self-organizing map (HSOM) is discussed as an unsupervised clustering method. The HSOM is shown to form arbitrarily complex clusters, in analogy with multilayer feedforward networks. In addition, the HSOM provides a natural measure for the distance of a point from a cluster that weighs all the points belonging to the cluster appropriately. In experiments with both artificial and real data it is demonstrated that the multilayer SOM forms clusters that match better to the desired classes than do direct SOM's, classical k-means, or Isodata algorithms.     

Perceptual primitives from an extended 4D Hough transform

Directional features extracted from Gabor wavelets responses were used to train a structure of self-organising maps, thus classifying each pixel in the image within a neuron-map. Resulting directional primitives were grouped into perceptual primitives introducing an extended 4D Hough transform to group pixels with similar directional features. These can then be used as perceptual primitives to detect salient structures. The proposed method has independently fixed parameters that do not need to be tuned for different kind or quality of images. We present results in application to noisy FLIR images and show that line primitives for complex structures, such as bridges, or simple structures, such as runways, can be found by this approach. We compare and demonstrate the quality of our results with those obtained through a parameter-dependent traditional Canny edge detector and Hough line finding process.