与特殊性质&对偶的空间及相关结论

X是拓扑空间,令&={A:A是X的具有性质&的子集},如果对于X的任意邻域指派φ,都存在A∈&,使得X=U{φ(χ):χ∈A},则称X是与性质&对偶的空间.对于给定的特殊性质&,主要讨论了与性质&对偶的空间的一些基本性质,并给出了X是与性质&对偶空间的充分必要条件.这些结论可应用于多种空间类,作为其中的一推论,得到每个正则弱(8)-加细(离散对偶)-散布空间是离散对偶空间.另外,还讨论了aD-空间的相关结论.

Abstract：

Let X be a space,and &={A:A is a subset of X,and has property &}.A space X is dual the property & if for any neighborhood assignment φ for X,there is a subset A(X,A∈& such that X=U{φ (χ):χ∈ A}.In this note,we mainly discuss properties of spaces which are dually special &,and also give a necessary and sufficient condition for spaces which are dually special & These conclusions can be heId for many spaces.As a corollary,we have that if X is a regular weak (8)-refinable(dually discrete)-scattered space,then X is dually discrete.We also get some conclusions conserning aD-spaces.     

Influence of surface finish and annealing treatment on oxidation behavior of Ti-48Al-8Cr-2Ag alloy

The effect of surface finish and annealing treatment on the oxidation behavior of Ti-48Al-8Cr-2Ag (molar fraction, %) alloy was investigated at 900 and 1 000 °C, respectively in air. Thermal gravimetric analysis (TGA) was conducted for the characterization of oxidation kinetics. The microstructures of oxide scales were studied by scanning electron microscopy (SEM) and transmission election microscopy (TEM) techniques. Unfavorable effect of the annealing treatment on the oxidation behavior of the coating was also investigated. The results indicate that the oxidation behavior of the alloy is influenced by surface finish and annealing treatment. The oxidation rate of ground sample is lower than that of the polished alloy at 1 000 °C in air. The former forms a scale of merely Al₂O₃, and the latter forms a scale of the mixture of Al₂O₃ and TiO₂. Annealing can improve the formation of TiO₂. Foundation item: Project(2007430028) supported by the Science and Technique Foundation of Henan Educational Committee, China     

砖墙-钢筋砼剪力墙组合结构的抗震性能分析

砖墙-钢筋混凝土剪力墙组合结构是从砌体结构的基础上发展起来的一种新结构体系,该种结构在砼墙配置合理的情况下具有良好的抗震性能,在设防烈度为8度地区建造这种结构的房屋是可行的.     

Hydroformylation of functional alkenes with heterodonor phosphine rhodium catalysts: substrate or ligand directed regioselectivity?

The catalytic activity and selectivity of heterodonor phosphine rhodium catalysts prepared in situ were tested in the hydroformylation of functional alkenes (ethyl acrylate, methyl methacrylate, styrene, 4-vinyl-1-cyclohexene, dicyclopentadiene and cis-1,2,3,6-tetrahydrophthalic anhydride). Systematic variation of the heterodonor atom in the ortho position of the ligand showed that the heterodonor atom has a significant influence on the activities and selectivities of the reaction. However, the activity seems to depend mainly on the modifying ligand, and the regioselectivity mainly on the substrate (i.e., the structure and functionality of the alkene). Nevertheless, regioselective control is only obtained through synergy between the substrate and the catalyst. Clear regiocontrol was observed in the hydroformylation of ,-unsaturated esters and styrene with an in situ formed o-(thiomethylphenyl)diphenylphosphine rhodium catalyst.     

Synergistic Sex Pheromone Components of White-Spotted Tussock Moth, Orgyia thyellina

In 1996, the exotic white-spotted tussock moth (WSTM), Orgyia thyellina (Lepidoptera: Lymantriidae), was discovered in Auckland, New Zealand. Because establishment of WSTM would threaten New Zealand's orchard industry and international trade, eradication of WSTM with microbial insecticide was initiated. To monitor and complement eradication of WSTM by capture of male moths in pheromone-baited traps, pheromone components of female WSTM needed to be identified. Coupled gas chromatographic–electroantennographic detection analysis of pheromone gland extract revealed several compounds that elicited responses from male moth antennae. Mass spectra of the two most EAD-active compounds suggested, and comparative GC-MS of authentic standards confirmed, that they were (Z)-6-heneicosen-11-one (Z6–11-one) and (Z)-6-heneicosen-9-one, the latter termed here thyellinone. In field experiments in Japan, Z6–11-one plus thyellinone at a 100:5 ratio attracted WSTM males, whereas either ketone alone failed to attract a single male moth. Addition of further candidate pheromone components did not enhance attractiveness of the binary blend. Through the 1997–1998 summer, 45,000 commercial trap lures baited with 2000 g of Z6–11-one and 100 g of thyellinone were deployed in Auckland towards eradication of the residual WSTM population.Dedicated to my dear mother in honor of her 75th birthday     

一种基于SRT-8算法的SIMD浮点除法器的设计与实现

在科学计算、数字信号处理、通信和图像处理等应用中,除法运算是常用的基本操作之一。基于SRT 8除法算法,设计一个SIMD结构的IEEE 754标准浮点除法器,在同一硬件平台上能够实现双精度浮点除法和两个并行的单精度浮点除法。通过优化SRT 8迭代除法结构,提出商选择和余数加法的并行处理,并采用商数字存储技术降低迭代除法的计算延时,提高频率。同时,采用复用策略减少硬件资源开销,节省面积。实验表明,在40nm工艺下,本设计综合cell面积为18601.9681 μm2,运行频率可达2.5GHz,相对传统的SRT 8实现关键延迟减少了23.81%。     

新型8极9槽永磁同步电机静态场的分析

针对采用分布式绕组的缺点,提出一种采用集中式绕组的新型8极9槽永磁同步电机,并在此基础上改变磁钢的参数,对电机的结构进行优化。     

日晒牢度的色度学评价方法研究

传统的牢度测试方法一直是人工目测色差,受到环境、光源、工作人员的视力、辨色经验等因素的限制。随着电脑测色配色技术的迅速发展,研究证明使用仪器代替人眼来评价颜色之间的差异是完全可行的。在5级标准的牢度评价中,有关牢度等级和色度值变化规律已经逐步成熟,但8级评价体系的日晒牢度人工评定等级与色度值变化关系还未见报道。为客观评价日晒牢度,通过测定大量已人工评级的日晒试样的色度值,根据所得的色差值,建立了日晒牢度人工评级和计算机测色的色差值关系表。为了检验所建立的色差值与牢度级别的关系表,测定日晒牢度标准色样中各牢度级别对应的色差值,结果表明,在标准色样中,牢度级别对应的色差值基本符合所建立的关系表。这为日晒牢度的色差值评定提供了参考。     

钎焊温度对SiC/YG8接头微观组织的影响

在保温时间为5min、钎焊温度为940~990℃条件下,采用CuMnNi钎料钎焊SiC陶瓷与YG8硬质合金.利用金相显微镜、扫描电镜和能谱仪对接头的微观组织进行分析,研究钎焊温度对接头微观组织的影响.结果表明:在靠近SiC一侧生成一层带状反应层,主要由Cu基固溶体、硅化物、碳和碳化物组成;焊缝主要由基底Cu基固溶体以及Mn、Si、Co、Cu、Ni元素形成的化合物组成.随着钎焊温度的增加,焊缝的宽度减少,焊缝中心的Cu基固溶体基底减少,而化合物相增多.     

Ti4+ modified MgZrNb2O8 microwave dielectric ceramics with an ultra-high quality factor

Ti⁴⁺-modified MgZrNb₂O₈ (MgZr_1-xTi_xNb₂O₈, x = 0, 0.1, 0.2, 0.3, 0.4) ceramics were synthesized using the traditional solid-state reaction method. Pure MgZr_1–xTi_xNb₂O₈ was detected without any secondary phase via the X-ray diffraction patterns. According to the sintering behavior and the surface morphology results, the introduction of Ti⁴⁺ reduced the sintering temperature and promoted the grain growth. The correlations between the dielectric properties and the crystal structure were analyzed through the Rietveld refinement and Raman spectroscopy. The slight shifts of the Raman peaks, corresponding to different vibration modes, were induced by the substitution of Ti⁴⁺ for Zr⁴⁺ and related to the improved quality factor. In general, the sample of MgZr_0.9Ti_0.1Nb₂O₈ sintered at 1320°C for 4 h exhibited promising microwave dielectric properties with an ultra-high Q × f value of 130 123 GHz (at 7.308 GHz, 20°C), which is potential for 5G communication applications.