介绍一种二元阈值方法在股票指数上的应用

二元极值的阈值方法的一个发展是用来考虑两个变量的联合分布。这个方法是建立在二元极值的点过程表示法的基础上。本文用参数 (Logistic模型 )和非参数模型对 1992 1999年的上海、深圳日收盘指数对数收益进行分析并给出分析结果。     

含有五边形—七边形缺陷的单壁纳米碳管的输运性质研究

运用第一性原理的密度泛函理论结合非平衡格林函数研究了含有五边形—七边形拓扑缺陷的纳米碳管异质结的输运性质.结果发现：拓扑缺陷对碳管的输运性质有很大影响；另外，不同类型的碳管形成的异质结的输运性质也有明显的差异. 关键词： 纳米碳管 输运性质 异质结 透射系数     

The Compactness of Commutators on the Heisenberg Group

We consider the commutators of the HSrmander multiplier with CMO-functions on the Heisenberg group. The result of compactness on L^P spaces is proved.     

红外动态图像生成技术概念研究

红外动态图像生成技术的基本概念包括基本术语及其定义。为了描述红外动态图像生成技术的特性,通常采用如光源类型、光谱波段、阵列规模、空间分辨率、填充因子、时间常数、帧频、闪烁、温度范围、串扰、均匀性、发射率、辐射对比度、动态范围、温度分辨率、调制传递函数、几何畸变及最大温度和最大辐射强度等概念。介绍了描述红外动态图像生成系统性能的基本概念的定义。转换器的指标定义对于转换器的设计和性能指标的测试都有重要的意义。     

用干涉方法测量薄膜应力

基于基片弯曲法和牛顿环的基本原理,使用He-Ne激光器、扩束镜、凸透镜和带分光镜的移测显微镜,搭建了薄膜应力测量装置.采用直流溅射法制备了厚度为30~144 nm的银薄膜,衬底采用厚度为0.15 mm、直径为18 mm的圆形玻璃片.实验发现,薄膜厚度对银薄膜的内应力有显著的影响,在薄膜厚度很小时,随着薄膜厚度的增加,应力迅速增大,达到最大值后,随着厚度的继续增加,薄膜应力下降较快并趋于稳定值.     

Monitoring the Aggregation of Dansyl Chloride in Acetone through Fluorescence Measurements

The aggregation of dansyl chloride (DNS-Cl) in acetone has been studied in detail by steady-state fluorescence techniques.It has been demonstrated that DNS-Cl is stable in acetone during purification and aggregation study processes.The aggregates are not solvolyzed in acetone,and do not take part n any chemical reactions either.It has been found that DNS-Cl tends to aggregate even when its concentration is much lower than its solubility in acetone.The aggregation is reversible,and both the aggregation and the deaggregation are very slow processes.Introduction of SDS has a positive effect upon the formation and stabilization of the aggregates.     

非齐次微分方程两点边值问题正解的存在性及多重性

本文考虑一类非齐次微分方程的两点边值问题,得到了一些有关其正解存在性与多重性的精确条件．     

高强混凝土弯压极限应变试验研究与计算

由于混凝土材料理化特性的差异,高强混凝土的弯压极限应变明显地小于普通混凝土,依据试验结果分析了高强混凝土的弯压极限应变变化规律,并给出了它的计算公式.     

Controllable Magnetic Focusing of Cold Atoms on a Chip

We propose a new lens scheme to focus cold atoms by using a controllable inhomogeneous magnetic field from a square current-carrying wire fabricated on a chip. The spatial distributions of the magnetic field are calculated, and the results show that the generated magnetic field is a two-dimensional （2D） quadrupole one and can be used to focus cold atoms or a cold atomic beam. The dynamic processes of cold atoms passing through our square wire layout and its focusing properties are studied by using Monte Carlo simulations. Our study shows that the atomic clouds can be focused effectively by our magnetic lens scheme, and the focal length of the atomic lens and its radius of focused spot can be continuously changed by adjusting the current in the wires.     

Photodecomposition of several compounds commonly used as sunscreen agents

The photolysis reactions of three compounds commonly used as a sunscreen agents, Parsol 1789 (1-[4-(1,1-dimethylethyl)phenyl]-3-(4-methoxyphenyl)-1,3- propanedione), Oxybenzone ((2-hydroxy-4-methoxyphenyl)phenyl-methanone) and Padimate O (2-ethylhexyl-4-(dimethylamino)benzoate), were investigated to provide a chemical background to aid in the understanding of the photosensitization of the sunscreen agents. Photolysis was carried out in cyclohexane for 70–140 h using a mercury vapor lamp (450W) without excluding oxygen.

Irradation of Parsol 1789 in cyclohexane yielded tert-butylbenzene, p-tert-butylbenzoic acid and p-methoxybenzoic acid; products obtained from the combination of the sunscreen with the solvent included the cyclohexyl esters of p-methoxybenzoic acid, p-tert-butylbenzoic acid and methanoic acid; products obtained from the solvent included cyclohexanol, cyclohexanone and dicyclohexyl ether.

Irradiation of Oxybenzone in the cyclohexane for 100 h produced no detectable products by either gas or liquid chromatographic analysis. Oxybenzone was recovered unchanged and no products were observed from the photoinitiated reaction of oxygen with the solvent.

Irradiation of Padimate O in cyclohexane yielded the ethylhexyl esters of p-aminobenzoic acid, p-monomethylaminobenzoic acid and p-dimethylamino (o/m)-methylbenzoic acid, as well as products from the photoinitiated reaction of oxygen with the solvent.