一种多径环境下基于四阶累积量的阵列扩展测向方法

本文分析了基于四阶累积量的测向方法不能正确测量多径信号方向的原因，提出了一种多径环境下的基于四阶累积量的新型测向方法。该方法利用零点领处理方法抑制多径信号，然后采用四阶累积量进行阵列扩展测向。计算机模拟结果表明该方法在多径环境下具有良好的性能并且可能实现对足够多的信号进行测向。     

基于遗传算法的门限自回归模型在浅层地下水位预测中的应用

提出了建立门限自回归模型的一种简便通用的方法，用遗传算法可同时优化门限值和自回归系数．实例计算的结果说明了其可行性和有效性．该方法在各种工程时序预测中具有广泛的应用价值     

SQL语言中量词和空值的使用技术

在ＳＱＬ语言中可以引入全称量词符号ＦＯＲＡＬＬ，使ＳＱＬ语言使用更为自然，方便。本文讨论全称量词，存在量词和ＡＬＬ三种谓词之间的转换，联系和区别，以及空值存在时ＳＱＬ的使用技术。     

硼酸铝钕(NAB)晶体光学均匀性的测量

NAB晶体是一种综合性能较好的新型激光工作物质,有希望做成高效的小型固体激光器。本文介绍一种测量这种晶体光学均匀性的方法。 一般都采用在干涉仪上观测干涉图样来判定激光棒的光学均匀性。NAB晶体的吸收光谱曲线显示出其在可见光光谱区内有多个吸收峰。我们注意到:通常用做激光干涉仪光源的He-Ne激光器发射的632.8nm谱线正位于NAB晶体的一个吸收峰,并用输出约为45mW     

一种简便的评定引战配合效率方法

在导弹近炸引信起爆延时具有随机性基础上，本文建立了一种用延时及其数学特征表示的评定引战配合效率的简便方法，并对有关应用问题进行了讨论。     

The As-prepared surfaces of C-axis-oriented Nd1Ba2Cu3Oy thin films characterized using scanning probe microscopes

Recently, superconducting Nd₁Ba₂Cu₃O_y (Ndl23) thin films with high superconducting transition temperature (T _c) have been successfully fabricated at our institute employing the standard laser ablation method. In this paper, we report the results of surface characterization of the Nd123 thin films using an ultrahigh vacuum scanning tunneling microscope/spectroscopy (UHV-STM/STS) and an atomic force microscope (AFM) system operated in air. Clear spiral pattern is observed on the surfaces of Nd123 thin films by STM and AFM, suggesting that films are formed by two-dimensional island growth mode. Contour plots of the spirals show that the step heights of the spirals are not always the integer or half-integer number of thec-axis parameter of the structure. This implies that the surface natural termination layer of the films may not be unique. This result is supported byI-V STS measurements. The surface morphology of the Nd123 thin films is compared with that of thec-axis-oriented Y₁Ba₂Cu₃S_y thin films. Surface atomic images of the as-prepared Nd123 thin films are obtained employing both STM and AFM. STS measurements show that most of the surfaces are semiconductive. The results of STS measurements together with the fact that we are able to see the surface atomic images using scanning probe microscopes suggest that exposure to air does not cause serious degradation to the as-prepared surfaces of Nd123 thin films.     

OFA-II型定量荧光仪在油气勘探中的应用

定量荧光仪在现场应用中受到各种因素的影响:如岩屑样品浸泡时的干、湿;图谱是否出现了淬灭;环境温度的影响等等。文章通过具体事例给出解决这些问题的办法。     

非标准工况下空分设备增产氩的研究与实践

文章对非标准工况下的空分设备增产氩措施进行了研究。以宝钢6#60000m3/h空分设备为例,通过设计型算法和校核型算法,建立了空分设备精馏的数学模型,通过改变数学模型的参数,分析了在非标准工况下精馏塔内的组分浓度分布,并提出了优化后的操作方案和操作参数,实施后提高了空分设备的氩提取率,取得了显著的经济效益。     

Cyclotomic Linear Codes of Order $3$

In this correspondence, two classes of cyclotomic linear codes over GF(q) of order 3 are constructed and their weight distributions are determined. The two classes are two-weight codes and contain optimal codes. They are not equivalent to irreducible cyclic codes in general when q > 2.