EXTENSION OF THE RELATIONAL DATABASE AND ITS ALGEBRA WITH ROUGH SET TECHNIQUES

This paper describes a database model based on the original rough sets theory. Its rough relations permit the representation of a rough set of tuples not definable in terms of the elementary classes, except through use of lower and upper approximations. The rough relational database model also incorporates indiscernibility in the representation and in all the operators of the rough relational algebra. This indiscernibility is based strictly on equivalence classes which must be defined for every attribute domain. There are several obvious applications for which the rough relational database model can more accurately model an enterprise than does the standard relational model. These include systems involving ambiguous, imprecise, or uncertain data. Retrieval over mismatched domains caused by the merging of one or more applications can be facilitated by the use of indiscernibility, and naive system users can achieve greater recall with the rough relational database. In addition, applications inherently “rough” could be more easily implemented and maintained in the rough relational database.     

二进制分辨矩阵在连续属性约简中的研究

针对二进制分辨矩阵无法处理连续型数据,提出一种基于邻域的改进二进制分辨矩阵及其属性约简方法。实验结果表明,与先数据离散化,后属性约简的方法相比,利用文中方法提取出的特征属性的分类能力更高。     

基于类间分散度和类内集中度的文本特征选择。

特征选择是文本分类的关键步骤之一,所选特征子集的优劣直接影响文本分类的结果。论文首先定义了两种特征分类能力：一种是特征对类间文档的分散程度,该分散度越大越好;另一种是特征对类内文档的聚集程度,该集中度越大越好。然后把这两种特征影响度有机地结合起来设计了一个新的特征选择方法,该方法能够对所选特征进行综合考虑,从而使获得的特征集具有较好的代表性。仿真实验表明所提特征选择方法在一定程度上能够提高文本分类性能。     

关于新建炉EDTA低浓度清洗的探讨

阐述了EDTA清洗锅炉的基本原理,低浓度清洗新建炉的工艺、方法及控制要点,EDTA低浓度清洗与协调EDTA清洗的经济性比较,为新建炉EDTA低浓度清洗探索了方向。     

水电水利工程压力钢管灌浆孔应力集中敏感性因素研究

水电水利工程压力钢管开孔灌浆后,需对灌浆孔严密封堵,处理不好会对工程安全运行留下隐患。在总结国内外灌浆孔常用封堵方案基础上,以某水电站地下埋管为例,建立平面有限元模型,分析其灌浆开孔后管壁应力集中现象,研究了补强板厚度及堵头坡口深度对压力钢管灌浆孔应力集中的敏感性。结果表明,应力集中程度随补强板厚度及堵头坡口深度增加递减,堵头坡口深度对其影响更加敏感。对于地下埋管管壁上开灌浆孔的非高强钢,建议灌浆后孔口进行封堵,补强板厚度宜与钢管壁厚相同,并适当增加坡口深度。当钢管壁厚较大时,堵头坡口深度宜不小于钢管壁厚的1/4~1/3。     

MICP技术改性膨胀土试验研究

为了探究膨胀土新型改良技术,引进微生物诱导碳酸钙沉淀(MICP)新型环保的土体加固技术,利用巴氏芽孢八叠球菌开展MICP压力灌浆改性膨胀土室内试验,研究了胶结液浓度对膨胀土力学性能、微观结构及水理特性的影响,揭示了MICP技术改性膨胀土的作用机理,评价了MICP压力灌浆改性膨胀土试验的效果。试验结果表明:灌浆处理后试样的无侧限抗压强度最大增加了379.4%,土体刚度也有所提高;试样的膨胀性、渗透性均有明显改善,膨胀力最高可减少25.3 kPa,渗透系数最大减少3个数量级;试验改性效果随着胶结液浓度的增大而提高,但当胶结液浓度增大到一定程度后,改性效果不再显著。研究成果验证了MICP技术用于改性膨胀土的有效性和可行性。     

有机磷灭蚊剂投放浓度和时间对水体总磷的影响

为分析新型低毒有机磷杀虫剂“1%双硫磷颗粒”投放对河道水质的影响,设置不同药剂投放浓度和不同反应时间的室内试验,以TP、NH₃-N及S^2-为目标因子,分析该药剂投放后水体污染物浓度。结果表明:不同试验组水样中S^2-质量浓度均小于0.02 mg/L,NH₃-N质量浓度处于0.029~0.036 mg/L之间,均达到地表水Ⅰ类标准;不同浓度药剂投放1 h后,水体TP质量浓度已达到稳定状态,且在60 h内均保持稳定,药剂投加量与水体TP质量浓度呈显著正相关(R²=0.85);不同处理组的药剂在水体中的TP释放量无明显差异,均在1.06~1.30 mg/g之间。“1%双硫磷颗粒”推荐适宜投放量不会使河道水质恶化到劣Ⅴ类,但增加药剂投放量会增加水体TP污染及富营养化风险。     

Photovoltaic effect and carrier transport mechanisms in Hg1-Mnxtdiodes

Hg_1-xMn_xTe semiconducting semimagnetic alloy has been examined in the context of its possible applications in infrared detectors. For analysis of detector properties the intrinsic carrier concentration has been calculated as a function of temperature and crystal composition. The starting material was In-doped Hg_1-xMn_xTe grown by the modified Bridgman method. The as-grown crystals with manganese content of 12-19% were p-type with carrier concentration and mobility of 100 cm²/ Vs at 77 K. An-type layer was formed on the surface by the annealing process in saturated Hg-vapour at 270-320° for 2 hrs. Capacitance-voltage curves have C^-3 dependence on applied voltage indicating that the junction is linearly graded. From standard electrical measurements and spectral characteristics the main detector parameters were determined and compared to those of Hg_1-xCd_xTe devices. The influence of material properties on detector parameters was analyzed. In order to estimate the carrier transport mechanisms, differential resistivities and current-voltage curves were measured over a wide range of temperaturesi.e. 25 to 300 K. From the temperature dependence of the R₀A product, it was established that at high temperatures (150-300 K) the carrier transport is dominated by a recombination-generation mechanism. In low temperature region the excess current at forward bias is probably attributed to carrier tunneling via energy states distributed randomly within the forbidden gap. At reverse bias the leakage surface or volume currents dominate in the carrier transport.     

二元稀土系AB5型贮氢电极合金的放电容量与晶胞体积和4f电子浓度的关系

制备了6个系列通式为AαA‘1-αB5的RE(NiCoMnTi)5贮氢电极合金(其中，AαA‘1-α为La，Ce，Pr，Nd4个元素中任意2个的组合)，测定了它们在100次循环中的最大放电容量Cmax及部分合金的晶胞体积Vcell．结果表明：Cmax主要由Vcell决定，Cmax先随Vcell的增大而增加，在Vcell≈85．66x10^-^3。nm^3时达到一极大值，然后又随Vcell的增大而减小；同时，Cmax还与4f电子浓度ne4f／naRE有关，A侧具有相同4f电子浓度的合金其Cmax随4f电子浓度的变化趋势相似．     

Continuous electromagnetic separation of inclusion from aluminum melt using alternating current

A novel scheme about the continuous electromagnetic purification of aluminum melt was put forward based on the utilization of a square separation pipe and a 50 Hz alternating current to produce electromagnetic force. It is experimentally found that with electrical current of 400 A/cm^2, it takes only 10 s to remove 95% inclusion from aluminum melt. Comprehensive numerical simulations were carried out to investigate the dynamics mechanisms behind the process. The results show that the removal of inclusion is attributed to the cooperative effects of electromagnetic buoyancy and the secondary flow induced by the rotational electromagnetic force, and the removal efficient increases with the size of inclusion and the electrical current imposed. Theoretical predictions on the distribution and removal efficiency of inclusion were supported by the experiments.