Estimating block selectivities for physical database design

Access path deployment is a critical issue in physical database design. Access paths typically include a clustered index as the primary access path and a set of secondary indexes as auxiliary access paths. To deploy the right access paths requires an effective algorithm and accurate estimation of the parameters used by the algorithm. One parameter central to any index-selection algorithm is the block selectivity of a query. Existing methods for estimating block selectivities are limited by restrictive assumptions. Furthermore, most existing methods produce estimates useful for aiding the selection of secondary indexes only. Little research has been done in the area of estimating block selectivities for supporting the selection of the clustered index. The paper presents a set of methods that do not depend on any specific assumption, produce accurate estimates, and can be used to aid in selecting the clustered index as well as secondary indexes     

基于感知器的快速彩色图像无损压缩算法

针对彩色图像像素和颜色分量之间存在的相关性，将神经网络中的感知器技术引入彩色图像的无损压缩算法中，提出了一种新的预测模型。应用感知器的自学习和自适应能力，对预测值进行自适应调整，使算法在运行过程中具有很小的预测残差并具有较小的动态范围。同时应用颜色空间变换来减小颜色分量间的相关性。相对于新的国际标准JPEG—LS，这种预测模型具有较低的计算复杂性。对比实验结果说明，这种算法的性能明显优于传统算法，在压缩比损失很小的前提下，其执行速度高于JPEG—LS。     

Structure evolution of conductive polymer composites revealed by solvent vapor induced time-dependent percolation

The authors of this paper synthesized a series of amphiphilic triblock copolymers of polystyrene-b-poly(ethylene glycol)-b-polystyrene (PS-PEG-PS) having different PEG/PS ratios with nearly identical molecular weights of the entire copolymers. The interfacial interactions in the composites consisting of carbon black and the copolymers can thus be tailored. When these conducting composites are exposed to certain solvent vapors, their electrical resistances greatly increase, showing the gas sensitivity. The present work indicated that this switching behavior is controlled by the structural relaxation of the composites because matrix swelling acts as the main mechanism. The response time has been correlated with absolute temperature by Arrhenius equation, and the estimated activation energy reflects mobility of the fillers involved in the solvent induced expansion of the surrounding polymer. Therefore, by using the gas sensibility of the conductive composites, the structure evolution of the composite materials in solid state and the effect of filler/matrix interfacial interaction on the relaxation property of the matrix polymer has been inspected. It was found that lower activation energy represents stronger interfacial interaction in case good solvent of the matrix was used for the test.     

Novel blood-compatible waterborne polyurethane using chitosan as an extender

A series of novel block polymers of polyurethane (PU) and chitosan have been prepared in two steps. The first step is the preparation of PU prepolymer, obtained from polytetramethylene oxide glycol (PTMO, M_n = 1000), isophrone diisocyanate (IPDI), and 2,2′-dimethylol propionic acid (DMPA), followed by ionizing PU prepolymer with triethylamine (TEA). The second step involves PU chain-extended by water-soluble chitosan of low molecular weight (M_n = 5000) by self-emulsion polymerization method. The sizes of the latex particles, morphology, and copolymer architecture have been characterized by dynamic light scattering (DLS), general tensile test, infrared spectroscopy (IR), surface contact angle measurement, and transmission electron microscopy (TEM). Furthermore, it shows that the addition of chitosan remarkably increases anticoagulative property of PU elastomers confirmed by the recalcification time. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

首届文博会向创意产业迈进

创意产业为期5天的首届“中国北京国际文化创意产业博览会”12月10日至14日在北京国际展览中心举行，首届北京文博会包括展览展示，论坛峰会，推介交易，创意活动，文艺演出等五大系列的第十场活动，境外共有5个国际性组织和40多个国家和地区的400多位嘉宾应邀参会参展，[第一段]     

c-BN color change with bonded water added into the h-BN–Mg system

Cubic boron nitride (c-BN) crystals were synthesized in conditions of high temperature and high pressure (HTHP) when different kinds of bonded water were respectively added into the system of h-BN–Mg. All bonded water used in this work could reduce the temperature of growing c-BN compared to that in the system of h-BN–Mg. The c-BN color could change from black to yellow when certain amounts of bonded water, such as NiSO₄·6H₂O and CuSO₄·5H₂O, Mg(OH)_2, were added. However, c-BN color remained black no matter how much bonded water, such as NiCl₂·6H₂O, CuCl₂·2H₂O, and SnCl₂·2H₂O, was added. The bonded water can be classified into Chlorine-containing bonded water (Cl-BW) and Chlorine-free bonded water (ClF-BW) according to their different characters and effects on the synthesized c-BN color.     

硬质合金与铁基复合材料热等静压扩散连接

以烧结结态硬质合金和粉末态铁基复合材料为连接对象，研究了两种材料的热等静压扩攻连接工艺，获得了直接连接接头和加镍作中间过渡层的间接连接接头，考察了接头的结合界面形貌，界面的元素扩散和界面结合强度。     

Long-term progression in chronic manganism: ten years of follow-up

We studied the long-term clinical course of five patients with chronic manganese intoxication. The mean scores of the King's College Hospital Rating Scale for Parkinson's disease increased from 15.0 +/- 4.2 in 1987 to 28.3 +/- 6.70 in 1991 and then to 38.1 +/- 12.9 in 1995. The deterioration was most prominent in gait, rigidity, speed of foot tapping, and writing. Tissue concentrations of manganese in blood, urine, scalp hair, and pubic hair returned to normal. Follow-up MRIs did not show paramagnetic high-signal intensity on T1-weighted images. The data indicate that clinical progression in patients with manganese parkinsonism continues even 10 years after cessation of exposure.