A dual-mode multiuser detector for DS-CDMA systems

We introduce a dual-mode multiuser detector that dynamically switches its detection mode between matched-filter and decorrelator operations based on the channel characteristics. This detector significantly reduces the overall computational requirement while maintaining similar performance as that of the decorrelator. The switching mechanism of our dual-mode detector is designed by exploiting the performance-complexity tradeoff between the decorrelator and the matched-filter. Extensions of this idea to other types of multiuser detectors are also proposed     

同位素中子源活化瞬发分析装置

一、基本原理自六十年代中期以来,中子活化瞬发γ射线元素分析技术(PNAA)得到人们广泛重视。与通常的中子活化分析(NAA)技术相比,它分析的是样品中的主要成分,若用同位素中子源,还可进行实时在线连续测定及现场分析。PNAA技术是用热中子与待测元素发生中子俘获反应,处于激发态的产物核在瞬间     

基于DELPHI的镍氢电池管理系统软件设计

通过对镍氢电池性能的研究，给出了一个应用ISA总线技术构建的、基于DELPHI编程平台的镍氢电池管理系统的设计方案，重点介绍了该系统的软件技术和实现方法。     

Ring‐opening polymerization of D,L‐lactide by rare earth 2,6‐dimethylaryloxide

Ring‐opening polymerization of D,L ‐lactide (LA) has been successfully carried out by using rare earth 2,6‐dimethylaryloxide (Ln(ODMP)₃) as single component catalyst or initiator for the first time. The effects of different rare earth elements, solvents, monomers and catalyst concentration as well as polymerization temperature and time on the polymerization were investigated. The results show that La(ODMP)₃ exhibits higher activity to prepare poly(D,L ‐lactide) (PLA) with a viscosity molecular weight of 4.5 × 10⁴ g mol^?1 and the conversion of 97 % at 100 °C in 45 min. The catalytic activity of Ln(ODMP)₃ has following sequence: La > Nd > Sm > Gd > Er > Y. A kinetic study has indicated that the polymerization is first order with respect to both monomer and catalyst concentration. The apparent activation energy of the polymerization of LA with La(ODMP)₃ is 69.6 kJ mol^?1. The analyses of polymer ends indicate that the LA polymerization proceeds according to ‘coordination–insertion’ mechanism with selective cleavage of the acyl–oxygen bond of the monomer. Copyright © 2004 Society of Chemical Industry     

Effect of surfactants and liquid hydrocarbons on gas hydrate formation rate and storage capacity

Hydrate formation rate plays an important role in making hydrates for the storage and transport of natural gas. Micellar surfactant solutions were found to increase gas hydrate formation rate and storage capacity. With the presence of surfactant, hydrate could form quickly in a quiescent system and the energy costs of hydrate formation reduced. Surfactants (an anionic surfactant, a non‐ionic surfactant and their mixtures) and liquid hydrocarbons (cyclopentane and methylcyclohexane) were used to improve hydrate formation. The experiments of hydrate formation were carried out in the pressure range 3.69–6.82 MPa and the temperature range 274.05–277.55 K. The experimental pressures were kept constant during hydrate formation in each experimental run. The effect of anionic surfactant (sodium dodecyl sulphate (SDS)) on natural gas storage in hydrates is more pronounced compared to a non‐ionic surfactant (dodecyl polysaccharide glycoside (DPG)). The induction time of hydrate formation was reduced with the presence of cyclopentane (CP). Cyclopentane and methylcyclohexane (MCH) could increase hydrate formation rate, but reduced hydrate storage capacity The higher methylcyclohexane concentration, the lower the hydrate storage capacity. Copyright © 2003 John Wiley & Sons, Ltd.     

Optimal transfer trees and distinguishing trees for testing observable nondeterministic finite-state machines

The fault-state detection approach for blackbox testing consists of two phases. The first is to bring the system under test (SUT) from its initial state to a targeted state t and the second is to check various specified properties of the SUT at t. This paper investigates the first phase for testing systems specified as observable nondeterministic finite-state machines with probabilistic and weighted transitions. This phase involves two steps. The first step transfers the SUT to some state t' and the second step identifies whether t' is indeed the targeted state t or not. State transfer is achieved by moving the SUT along one of the paths of a transfer tree (TT) and state identification is realized by using diagnosis trees (DT). A theoretical foundation for the existence and characterization of TT and DT with minimum weighted height or minimum average weight is presented. Algorithms for their computation are proposed.     

β″－Al_2O_3陶瓷的强化和韧化

研究了稳定ＺｒＯ＿２和部份稳定ＺｒＯ＿２对β″－Ａｌ＿２Ｏ＿３陶瓷的强化和韧化作用，观察了不同种类、不同含量的ＺｒＯ＿２对β″－Ａｌ＿２Ｏ＿３陶瓷的显微结构、力学性能和电导率的影响，探讨了β″－Ａｌ＿２Ｏ＿３的韧化机理。     

电子表格EXCEL5.0在选煤线性规划问题中的应用

采用电子表格软件ＥＸＣＥＬ５．０可以方便地解决许多选煤生产中的线性规划问题。本文通过选煤过程线性规划实例介绍ＥＸＣＥＬ５．０在此领域的应用方法。     

Oxygen absorption kinetics in YBa2Cu3Ox

The oxygen absorption process in highly aligned YBa₂Cu₃O_x samples in air and in pure oxygen was studied at several constant temperatures. The process can be expressed in two steps, a chemical reaction controlled step and a diffusion controlled step. The kinetic equations are as follows respectively:

(1 − a_t) ln(1 − a_t) + a_t = k_Dt

The activation energy was calculated using an Arrhenius equation. The technical conditions of heat treatment for oxygen absorption of highly aligned YBa₂Cu₃O_x crystals are discussed.     

Traction-based Completed Adjoint Double Layer Boundary Element Method in elasticity

This paper is concerned with a traction-based Completed Adjoint Double Layer Boundary Element Method to solve for the surface traction of a system of rigid particles embedded in an elastic matrix. The main feature of the method is a single layer representation of the displacement field, which leads to a system of second-kind integral equations for the traction field, the extreme eigenvalue of which could be deflated, allowing iterative solution strategies to be effectively applied. The method is therefore most suitable for large-scale simulations of particulate solids. The method is benchmarked against some known analytic solutions, including the difficult stress singularity problems at sharp edges. The effectiveness of the method in dealing with a large number of inclusions is also demonstrated with an elongational deformation problem involving up to 25 inclusions.Research supported by the Australian Research Council (to NP-T and X-JF) and the National Natural Science Foundation of China (X-JF).