A near-optimal multiuser detector for DS-CDMA systems using semidefinite programming relaxation

A multiuser detector for direct-sequence code-division multiple-access systems based on semidefinite programming (SDP) is proposed. It is shown that maximum likelihood (ML) detection can be carried out by "relaxing" the associated integer programming problem to a dual SDP problem, which leads to a detector of polynomial complexity. Computer simulations that demonstrate that the proposed detector offers near-optimal performance with considerably reduced computational complexity compared with that of existing primal-SDP-relaxation based detectors are presented.     

A vectorial boundary element method analysis of integrated optical waveguides

In this paper, a new vectorial boundary element method is introduced and applied to the modal analysis of dielectric waveguides with piecewise homogeneous refractive indexes. The procedure, which is free of spurious modes, determines the full field distribution from the longitudinal fields at the refractive index boundaries. Singular kernels are evaluated through series solutions while the electric field discontinuity at corners is accommodated through either a grid refinement technique or a semianalytic approach. Our formalism generates propagation constants and modal field distributions for several representative refractive index profiles with far higher accuracy than standard finite-difference or finite-element procedures.     

高沸石配比陶瓷纤维复合纸制备中助留剂的选择

考察了沸石复合纸板制备中助留剂对无机物留着的影响。结果表明,PDADMAC或A-PAM单元体系、PVAm/A-PAM二元助留体系的作用效果差,PDADMAC/A-PAM二元助留体系的留着效果显著,PDADMAC的相对分子质量对留着效果的影响不大,PDADMAC与A-PAM的电荷量比是决定无机物留着的主要因素,本研究的条件下,最佳正负电荷量比为3.0～5.0。     

由信息时代作战特点探讨我军信息化建设途径

信息技术的发展及其在军事领域的应用,改变了未来战争的作战方式,使其在作战理念、作战手段、作战空间以及作战实施方面呈现出不同于传统作战方式的特点。本文对信息时代的作战特点进行了分析总结,并在此基础上对加强我军信息化建设途径进行了探讨。     

Dynamic responses and damages of water-filled pre-pressurized metal tube impacted by mass

An account is given of some principal observations made from a series of experiments in which three-span pipe beams were subjected to central impact by indenters with different nose shapes. These pipes were filled and pre-pressurized with water in order to identify the main effects produced by the fluid–structure interaction. In comparison, the impact experiments of the pipes with no water were also carried out. The perforation failure modes and corresponding critical impact energies were obtained in different test conditions. The experimental results indicated that the critical perforation energy and the deformation of the wall of the pipe were significantly influenced by the presence of the water and the pressure.     

一种有机化合物名称编码与亚结构检索方法

本文以 IUPAC 为基础,考虑有机化合物母体和取代基的关联,采用库中已有的化合物名称进行亚结构检索,这种检索方法,由于由化合物名称所劈裂的编码数量较少,所以索引文件小,检索速度较快。另外,这种方法是侧重在化学上有意义的母体和宫能团,它可以和碎片编码亚结构检索方法互相补充。     

热分析在PVA纤维预处理中的应用

用差热、热重法对原丝的热性能及由不同预处理方法所引起的PVA纤维的热行为变化进行了研究;并通过模拟脱水条件,用不同升温速率,求出了经不同预处理纤维的脱水反应活化能。结果表明,PVA原丝在230℃有一软化点,三种预处理都不同程度地影响了原丝的热效应变化;纤维在180～340℃主要为脱水反应;原丝及经脱水剂、O_3和O_3综合脱水剂处理的纤维,其脱水反应的表观活化能分别为:164.3kJ/mol,92.9kJ/mol,130.5kJ/mol和117.6kJ/mol。     

硬度匹配对40CrNiMo滚子接触疲劳性能的影响

通过对“软－软”、“中－软”、“中－中”、“中－硬”四组不同硬度匹配的滚子接触疲劳试验得出四条Ｐ－Ｎ曲线。并发现中硬度材料的接触疲劳寿命高于软材料，而当主试样为中硬时，与之相匹配的陪试件硬度越高，主试样的寿命越短，通过分析讨论解释了产生上述现象的原因及其失效机理。     

多量程数据采集记录装置的设计

通常的数据采集与记录装置不易实现多量程测量。通过对标度方程进行分析得知,要改变量程只须改变两个参数——标度因子和量程下限。我们设计了一个使用单片机的多量程数据采集和记录装置,能处理多达256种量程。本文叙述了算法分析、硬件和软件的设计以及该装置的性能指标。