波在PTL介质中传播的旅行时反演

本文对Byun(1990)的横向各向同性介质的旅行时反演方法作了两点改进:其一是根据优化后的V_r值计算一个初始的F值,然后再根据这个初始值进行最小均方误差分析;其二是对初始值进行优化分析时,提出用测量值(或由式(4)和式(10)计算的理论值)作为实际值进行拟合,而Byun的方法是用式(11)的计算来得到一个实际值。理论模型证明:本文所述方法有一个比较宽的适应性,而Byun方法只在弱各向异性时才可以得到较精确的结果。     

传播介质特性对爆破震动信号分析中小波包时频特征的影响

传播介质是指爆破震动赖以向外传播的地层介质 ,其基本特征是影响爆破震动时频分布的主要因素之一。当传播介质中有爆破震动通过时 ,其动态响应将会因其原地结构的不同而在响应持续时间、频谱、响应的衰减等特征方面均有较大差异。本文利用岩体 (岩土混合体 )基本质量指标BQ值以及完整性系数Kv 来量化传播介质特性。通过对不同岩层地质条件下产生的爆破震动进行小波包分析 ,探讨了传播介质特性量化参数与爆破震动时频分布之间的关系。研究中发现 ,传播介质特性对单段波形小波包细节信号的主振频带分布、峰值质点振速及衰减阻尼比等时频特征参数均有较大影响 ,其中主振频带分布范围随着传播介质的完整性系数Kv 值减小而增大 ,优势频率值随完整性系数Kv 值减小而增加 ,而峰值质点振速及衰减阻尼比与完整性系数Kv 值之间的规律性不强     

声波在多层介质中传播的四端参数模型应用分析研究

声波在两种介质的交界面透射和反射时 ,借鉴机械四端参数法 ,利用声学边界条件 ,引入了四端参数矩阵 ,建立四端参数模型。通过对四端参数矩阵的分析 ,探讨了在简谐平面波垂直入射的条件下 ,声波在多层介质中的传播特性 ,并推导出声透射系数和声反射系数的一般计算公式。     

推进波作用下的底泥起动

在介绍推进波作用下底泥起动特点的基础上，将上层水体作为粘性流体，底泥作为粘弹性体，推导了推进波作用下泥床面剪应力的表达式，并根据试验结果，给出了推进波作用下底泥起动时的床面剪应力与底泥流变参数的关系。     

Kerr型介质界面上弱非线性TM表面波的传播特性

本文研究Ｋｅｒｒ型介质界面上弱非线性ＴＭ表面波的性质。数值计算表明了沿线性与非线性介质界面传播的ＴＭ表面波的自散焦特性。     

中波同步广播的回顾及同步技术的探讨

本文回顾了实施中波同步广播的经历，分析了目前运行中的同步网所存在的问题。笔者根据１０余年参与同步广播运行管理，科研的体会，论述了实施良好同步广播的措施。就同步广播的发展：标频传送，同步激励的性及同步网的管理三个关键方面的，提出了探讨性的建议和意见。     

石英砂均质滤料截污规律的分析研究

应用分层取样法测试了滤以的截污量。通过滤柱实验，2能够更好地分析研究石英砂均质滤料层截留浊质物的变化规律。     

大中型风力发电机组可靠性研究

研究了大中型风力发电机组的可靠性，讨论了可靠性指标的分配，可靠性设计的四个重要方面、可靠性试验计算机模拟。     

Stability analysis of an adaptive packet access scheme for mobile communication systems with high propagation delays

In this paper, we investigate a packet access scheme that is able to support mixed traffics in the presence of high propagation delays. Referring to a Time‐Code Division Multiple Access air interface, we propose a Medium Access Control (MAC) protocol based on a random access scheme. A successful attempt grants the use of a slot‐code resource. This protocol is named Adaptive Time Code‐Packet Reservation Multiple Access (ATC‐PRMA), since the access parameters are changed, depending on the traffic load conditions, so as to fulfil Quality of Service requirements. Numerical examples are carried out for the Low Earth Orbit (LEO)‐Mobile Satellite System (MSS) scenario, but all these considerations could be applied to High‐Altitude Platform Stations (HAPSs) as well. In both cases, high propagation delays prevent an immediate feedback to users. An analytical approach is proposed to study the stability of our MAC scheme. Accordingly, we define a criterion for optimizing system performance. The predicted ATC‐PRMA behaviour is supported by simulation results. Finally, we show the performance improvement of ATC‐PRMA with respect to a MAC protocol not employing adaptive parameters. Copyright © 2003 John Wiley & Sons, Ltd.     

Enantioselective extraction of mandelic acid enantiomers based on chiral ligand exchange

Based on the chiral ligand exchange, the distribution behavior of mandelic acid enantiomers, and the partition of Cu^2 at different pH values were studied in a water/alcohol two-phase system containing Cu^2 and N-ndodecyl-L-proline(A). The influences of the solvent sort, the pH value, the concentrations of Cu^2 and chiral ligand on the partition coefficient(K) and separation factor(α) were discussed. The experimental results show that the A formed has more stable ternary complex with D-mandelic acid enantiomer than with L-mandelic acid enantiomer. There is an important influence of the pH value on K and a. When the pH values are less than 3.5, the formation of binary complexes is thermodynamically unfavourable. K and a become maximum when pH values are above 3.5 and the molar ratio of the chiral ligand to Cu^2 is 2:1.