概念格的外延覆盖约简

概念格是数据分析与知识发现的一种有效的形式化工具.知识发现的一个重要课题是知识约简,因此,寻求简单有效的属性约简方法是很有必要的.近年来,概念格属性约简方法的研究得到了很多学者的关注,提出了多种形式的概念格属性约简方法.本文利用形式背景的外延基本元,提出了概念格的外延覆盖约简的概念.讨论了这种约简与已有的几种约简之间的关系.证明了外延覆盖约简等价于粒约简,且概念格属性协调集一定是外延覆盖协调集.给出了外延覆盖协调集的判定定理,借鉴粗糙集属性约简的思想,得到了利用辨识矩阵计算全部外延覆盖约简的Boole方法.     

MMAS与粗糙集在齿轮箱故障诊断中的应用

粗糙集理论是一种新的处理含糊和不确定性知识的数学工具,属性约简是粗集理论研究的重要内容,属性约简算法有很多种,而计算一个最佳约简是NP难问题。为了能够有效地获取信息系统的约简,提出了一种新的约简算法。该算法选择最大-最小蚂蚁系统(MMAS),以Fisher准则作为启发式信息来提高搜索效率,将蚁群优化算法引入属性约简中,利用粗糙集理论对故障诊断决策表进行约简,形成清晰、简明的故障诊断规则,为下一步的故障诊断打下了坚实的基础。     

一种基于FPGA的改进粗糙集属性约简方法

粗糙集理论是一种新型的数学工具,主要用于分析处理模糊和不确定知识。属性约简是其中的一个重要环节。本文结合遗传算法,提出了一种基于FPGA改进的粗糙集属性约简方法,在原研究的基础上,先利用属性重要度求解决策表的核属性,再运用于属性约简,从而减少遗传操作的迭代次数,加快属性约简速度。     

模糊决策属性约简及其在工位评估中的应用

受粗糙集理论中知识约简的启发,在模糊多属性决策理论中提出属性约简的概念,构建属性约简方法,寻求属性集合中所有最简单的保序属性约简子集以及属性约简核.用属性约简子集代替原有的属性集合,通常可以显著简化模糊多属性决策问题.还将此属性约简方法应用到生产线工位绩效评估中,表明此属性约简算法的实用性.     

诱导覆盖粗糙集的概念及性质

覆盖近似空间是对Pawlak的近似空间的一种扩展,李扉在《基于信息熵的覆盖信息系统的属性约简》中提到诱导覆盖的概念,现结合覆盖粗糙集模型的理论,讨论其性质。     

具有Fuzzy决策的信息系统的知识约简

知识约简是粗糙集理论的核心问题之一。讨论了具有Fuzzy决策的信息系统的知识约简问题。给出了知识约简的几种定义、相应的知识约简的判定定理和可辨识属性矩阵，从而为具有Fuzzy决策的信息系统的知识约简的计算提供了具体方法。     

多决策覆盖信息系统的约简

覆盖决策信息系统是研究热点之一,其中对于决策为覆盖的覆盖决策信息系统研究较少.本文利用特征函数将覆盖决策信息系统中以覆盖刻画的决策转化为由0和1组成的形式背景,进而给出了多决策覆盖信息系统的定义.在多决策覆盖信息系统中,通过构造相应的辨识矩阵,讨论了两类覆盖的约简,并研究了这两类约简对应的覆盖协调集与覆盖决策信息系统中...     

一种基于属性划分的序信息系统并行约简算法

在粗糙集理论中,序信息系统的属性约简是一个重要的问题.目前已取得一些初步的研究成果,但仍缺乏有效的计算方法,主要表现为求解约简耗时过长.本文采用"分而治之"的策略,利用递减划分对属性进行分组,从而将原系统分解为规模相近的若干子系统,并在互不影响的情况下同步计算各子系统的核与约简,然后将子系统的核与约简合并得到原系统的核与约简.算例分析验证了本文提出的属性约简方法的可行性和有效性.     

优势变精度粗糙集构建采矿方案评价体系的研究

影响采矿方案的因素错综复杂,为了建立科学合理的采矿方案评价体系,首先将影响因素进行分级,利用模糊数学确定各级影响因素的权重.由于噪声数据的存在,采用优势变精度粗糙集构建采矿方案评价体系,可以辨识规则间的不相容性,对条件属性进行约简,并生成最少偏好规则集,分类质量为100%.然后利用灰色关联度理论对约简后的属性进行优势分析,得到各属性对于方案的重要程度,完善采矿方案评价体系.研究结果表明：优势变精度粗糙集相对于经典粗糙集更具规则性,构建采矿方案评价体系是科学有效的.     

基于属性分辨力的决策表属性约简

决策表的属性约简,又称知识约简,是粗糙集理论最核心内容之一,最优属性约简是NP难问题。根据粗糙集理论,本文定义了特征集以及属性分辨力概念,提出了基于特征集和属性分辨的启发式搜索算法,在一定程度上提高了搜索效率。     

Enhancement of microcrystalline n-i-p solar cell performance via use of pre-covering layers and H2 treatment

We study the effects of a-Si:H and μc-Si:H covering layers and an H₂ treatment on the characteristics of μc-Si:H thin film solar cells deposited in open single chamber very high frequency plasma enhanced chemical vapor deposition systems. Secondary ion mass spectrometry is used to evaluate the phosphor concentration in the μc-Si:H material. Compared to use of an a-Si:H covering layer, use of a μc-Si:H covering layer reduces dopant contamination by a relative 50%, and improves efficiency by a relative 6%, and use of an H₂ treatment reduces dopant contamination by a relative 64%, and improves efficiency by a relative 17%.     

城市复杂环境场平爆破降尘降噪试验研究

复杂环境城镇爆破工程逐渐增多,城市环境建设特别是在创建卫生文明城市中对降噪和防尘的要求也随之提高,基于常用降噪降尘措施,通过现场试验:爆前洒水、覆盖彩条布、单发雷管覆盖介质,探讨切实可行的降尘、降噪、减震方法,得出爆区覆盖彩条布降尘效果最佳,平均降尘率达41.2％以上;地表雷管覆盖介质为水、沙、碎石时降噪效果最佳,平均...     

Effect of Relative Reduction on Property of Steel-Mushy Cu-Graphite Composite

The rolling treatment of steel-mushy QTi3.5-3.5 graphite composite was conducted under different relative reduction at room temperature. The effect of room-temperature rolling on interfacial mechanical property of steel-mushy QTi3.5-3.5 graphite composite was studied and the relationship between interfacial shear strength and relative reduction was established. The results show that, for steel-mushy QTi3.5-3.5 graphite composite, which consists of 1.2 mm-thick 08AI steel plate and 2.8 mm-thick QTi3.5-3.5 graphite layer, there is a nonlinear relationship between interfacial shear strength and relative reduction in graphite layer. When relative reduction is smaller than 1.1%, interfacial shear strength increases with increasing the relative reduction. When relative reduction is larger than 1.1%, interfacial shear strength decreases with increasing the relative reduction. When relative reduction is 1.1%, the largest interfacial shear strength of 145.2 MPa can be obtained.     

Influence of Rolling Treatment on Interfacial Shear Strength of Steel-mushy Al-7graphite Bonding Plate

At room temperature, the rolling treatment of steel-mushy Al-7graphite bonding plate was carried out under different relative reduction. The influence of rolling on interfacial mechanical property of this bonding plate was studied. The results show that, for steel-mushy Al-7graphite bonding plate which is made up of 1.2 mm in thickness 08AI steel plate and 2.0 mm in thickness Al-7graphite layer, there is a nonlinear relationship between interfacial shear strength of bonding plate and relative reduction of rolling. When relative reduction of rolling is smaller than 2.59%, with the increasing of relative reduction, interfacial shear strength of bonding plate increases gradually. When relative reduction of rolling is bigger than 2.59%, with the increasing of relative reduction, interfacial shear strength of bonding plate decreases continuously. When relative reduction of rolling is 2.59%, the largest interfacial shear strength 77.0 MPa can be obtained.     

Comparisons of results of publication counting using different methods

Using a database for publications established at CEST and covering the period from 1981 to 2002 the differences in national scores obtained by different counting methods have been measured. The results are supported by analysing data from the literature. Special attention has been paid to the comparison between the EU and the USA. There are big differences between scores obtained by different methods. In one instance the reduction in scores going from whole to complete-normalized (fractional) counting is 72 per cent. In the literature there is often not enough information given about methods used, and no sign of a clear and consistent terminology and of agreement on properties of and results from different methods. As a matter of fact, whole counting is favourable to certain countries, especially countries with a high level of international cooperation. The problems are increasing with time because of the ever-increasing national and international cooperation in research and the increasing average number of authors per publication. The need for a common understanding and a joint effort to rectify the situation is stressed. The author sequence is alphabetic and does not reflect relative contributions to the work.     

A cycle-oriented incremental analysis of shakedown problems

An effective method for determination of a quasi-static shakedown loading and of a steady-state response is proposed. The classical optimization problem based on Melan's theorem is suitably reformulated to meet the requirements of incremental analysis. The main attention is focused on the reduction of a computational time required for a completion of a transient elastic–plastic phase of deformation. The method differs significantly from classical incremental analyses. Here, a load cycle is approximated by the finite number of loading systems covering the cycle. Each system is then combined with a separate domain of the structure in which the load system can be treated as a dominant one. In this manner, the structure consists of parts, each of them undergoing suitably chosen one-parameter loading only. Such a modification allows us to build a set of non-linear equations for all loading systems covering the whole load cycle. As a consequence the structure can be treated as the one in which the transient plastic phase of deformation is analysed load cycle by load cycle without making load increments inside the considered cycle. Due to this innovation a significant reduction of the computational time required for the solution of the steady-state response of the structure is obtained what is illustrated on 3-D frames. © 1997 John Wiley & Sons, Ltd.     

Sulfate reduction in deep-sea sediments

Sulfate reduction rates calculated from about 200 DSDP pore water sulfate profiles have been contoured and plotted on a map covering most areas of the world ocean. Rates show a remarkable spatial consistency, with high rates observed near the continental margins, becoming progressively lower toward the central ocean basins. Relatively elevated rates are also found in the eastern equatorial Pacific, a site of upwelling and correspondingly high rates of primary organic production. Overall, the distribution of sulfate reduction in pelagic sediments looks very similar to the distribution of primary organic carbon production. When rates are directly compared, however, the correlation between sulfate reduction and primary production is only moderately strong. Perhaps the most important influence on sulfate reduction is sediment deposition rate and the control this has over the fraction of the sedimentary organic carbon flux that becomes available for sulfate reduction. The slower the rate of sediment deposition the more time for oxic respiration and the less organic carbon that escapes to the zone of sulfate reduction. To predict most accurately sulfate reduction rates, however, the variables of primary production, water depth, and sediment deposition rate must all be integrated.     

Publication behaviour and international impact: Scandinavian clinical and social medicine, 1988–96

The paper presents the results of an empirical study of the Danish and Nordic Publication behaviour and international impact in Clinical and Social Medicine covering the period 1988–96. As indicators are applied the international visibility of Scandinavian research output, the publication activity per capita in SCI journals, the development over time of the national citation impact in an OECD and World context, and the ratio of cited papers relative to the World. Compared toMay's analysis (1997), covering 1981–94, the analysis shows that a certain reshuffle of national positions among the OECD countries in citation impact has occurred. UK and New Zealand as well as Denmark and Sweden have lost in ranking to Finland and Belgium, both countries coming up from behind. The most interesting results concern the opposite research policy strategies displayed by Finland and Denmark which result in similar impact patterns relative to the World impact. The implications are discussed.     

镁基复合材料的制备技术进展

镁基复合材料具有低的密度、优异的力学性能和物理性能,在汽车、航空航天等领域的应用需求日益增加,成为近年来新材料领域的研究热点。介绍了镁基复合材料基体的分类和不同的增强体类型,论述了镁基复合材料的制备方法及应用现状,并对镁基复合材料的发展进行了展望。     

Tribologisches Verhalten von harten und superharten Kohlenstoffschichten

Tribological behavior of superhard amorphous carbon films The tribological behaviour of amorphous carbon films is determined by monomolecular covering layers strongly attached to the surface. They cause the very low friction in normal humid air, their absence in dry air or vacuum leads to high friction. Any lubricants usually do not improve the tribological behaviour in comparison to air. However for non‐hydrogenated ta‐C films by attachment of specially adapted lubricants an additionally marked reduction of friction is possible.