General expression for pdf of a sum of independent exponential random variables

In order to evaluate exactly the performance of some diversity schemes, the probability density function (pdf) of a sum of independent exponential random variables (r.v.'s) must be known. This paper proposes a simple method to find it by using characteristic function., The resultant pdf is successfully applied to formulate the closed-form BER expression of 2 Tx-J Rx transmit diversity as well as the outage probability of repetition coding.     

Finite-difference time-domain simulation of scattering from objectsin continuous random media

A three-dimensional (3D) finite-difference time-domain (FDTD) scheme is introduced to model the scattering from objects in continuous random media. FDTD techniques have been previously applied to scattering from random rough surfaces and randomly placed objects in a homogeneous background, but little has been done to simulate continuous random media with embedded objects where volumetric scattering effects are important. In this work, Monte Carlo analysis is used in conjunction with FDTD to study the scattering from perfectly electrically conducting (PEC) objects embedded in continuous random media. The random medium models under consideration are chosen to be inhomogeneous soils with a spatially fluctuating random permittivities and prescribed correlation functions. The ability of frequency averaging techniques to discriminate objects in this scenarion is also briefly investigated. The simulation scheme described in this work can be adapted and used to help in interpreting the scattered field data from targets in random environments such as geophysical media, biological media, or atmospheric turbulence     

桩帽处理对灌注桩高应变检测的影响

本文给出砼灌注桩高应变检测中桩帽的施工工艺 ,并讨论其对测试结果的影响。     

Effect of Synergistic Anticorrosion Treatments on Cycling Stability of Mg-Based Hydrogen Storage Electrode

In this paper, any two of the three anticorrosion agents, that is emulsifier (OP-10), soluble glass (Na2O·nSiO2) and glycerin (C3H8O3), were treated simultaneously on the surface of amorphous (a-) MgNi+5% Ml2Mg17 (Ml denotes the lanthanum-rich mish metal) electrode and the electrolyte. Effect of the synergistic anticorrosion treatment on charging/discharging cycle stability of the electrode was investigated. Contrasted with single treatment method, the cycling stability of the electrodes was further improved. The desirable synergistic anticorrosion method was that the electrode was treated by the soluble glass, and that OP-10 was added into the electrolyte. The cyclic voltammogram (CV) results of the electrode show clearly that the anticorrosion agent can change the electrochemical activity and mechanism of the electrode. The concentration of the anticorrosion agent in the electrolyte treated by the synergistic anticorrosion method was also investigated. The appropriate concentration of the anticorrosion agents in the electrolyte is 0.143%.     

高分子纳米LB膜的制备及其光刻性能研究

合成并表征了N-十六烷基丙烯酰胺（HDA）和对叔丁基苯酚甲基丙烯酸酯（BPhMA）的共聚物p（HDA-BPhMA）s。当HDA含量较高时，共聚物可在气，液界面上形成稳定，排列紧密的单分子薄膜，并可以Y型膜的方式沉积在各种固体基片上，形成多层均匀的Langrnuir-Blodgett（LB）膜。这种LB膜被成功地应用于光刻，获得了分辨率为0.5μm的LB膜图形。以该图形为抗蚀层，可将图形进一步转移至金属薄膜上，得到分辨率较高的金属图形，在图形转移的过程中，这种LB膜显示出较高的抗蚀性，有望作为纳米抗蚀薄膜材料在亚微米刻蚀领域得到应用。     

Effects of flux enhancing polymer on the characteristics of sludge in membrane bioreactor process.

A newly developed membrane performance enhancer (MPE) was used to prevent membrane fouling in a membrane bioreactor (MBR) process. It transpired that 1,000 mg/l of MPE reduced polysaccharide levels from 41 mg/I to 21 mg/I on average under the experimental condition. Repeated experiments also confirmed that 50-1,000 mg/l of MPE could reduce membrane fouling significantly and increase the intervals between membrane cleanings. Depending on MPE dosages and experimental conditions, trans-membrane pressure (TMP) increase was suppressed for 20-30 days, while baseline TMP surged within a few days. In addition, MPE allowed MBR operation even at 50,000 mg/l of total solid and reduced permeate COD. However, no evidence of toxicity for sludge was found from respiratory works.     

Tb3+,Mn2+作为激活剂的PDP绿色荧光粉的研究

分别介绍了以Mn^2＋和Tb^3＋作为激活中心的PDP用硅酸盐体系、铝酸盐体系、硼酸盐体系和磷酸盐等体系绿色荧光粉的研究现状。在以Mn^2＋作为发光中心的绿粉中，目前研究主要集中在通过调整Mn^2＋的离子浓度、添加其他杂质，探索使用新的基质材料，或是使用不同的合成技术等方法来改进其余辉时间过长、易时效劣化以及形貌上的不足。在以Tb^3＋作为激活中心的绿粉中，为了获取在真空紫外激发条件下高的发光效率，则主要围绕寻找在VUV区域内有强吸收的基质和能够有效进行能量传递的稀土敏化剂，以及利用量子剪裁效应来使得荧光粉发光量子效率大于1等方面进行。     

Ionothermal synthesis of a three-dimensional zinc phosphate with DFT topology using unstable deep-eutectic solvent as template-delivery agent

A three-dimensional zinc phosphate compound with DFT topology, designated as ZnPO₄-EU1, has been synthesized by an ionothermal approach from the system HF-ZnO–P₂O₅-choline chloride-imidazolidone. Ethylenediamine, derived from decomposition of the imidazolidone component of the deep-eutectic solvent (DES) itself, is delivered to the synthesis and serves as an appropriate template for ZnPO₄-EU1. Experiments in which the synthesis conditions were varied showed that ZnPO₄-EU1 may be prepared over a wide molar ratio of P/Zn = 0.55–13.0. Powder X-ray diffraction patterns have been obtained at intervals to track the crystallization process of this material. The experimental data show that Zn₃(PO₄)₂ · 4H₂O (a dense phase) was first isolated from the DES after reaction for 1 h. Subsequently, the pure phase of ZnPO₄-EU1 was obtained with increasing crystallization time from 12 h to 72 h. The experimental results show that the nucleation and crystallization take place with relatively low levels of solvent degradation, demonstrating that zinc phosphate with a three-dimensional framework can be synthesized by in situ generation of an appropriate template using an unstable DES at high temperatures (150–200 °C).     

BC480-22/42支架液压系统的大流量技术改造

分析了BC-480支架在综采工作面使用中液压系统配置低的原因,提出了系统的改造原则和方案,比较了改制前后支架的动作速度.     

Fracture toughness of thermoset composites reinforced by perfectly bonded impenetrable short fibers

The fracture toughness of brittle thermoset resins could be improved significantly by perfectly bonded tough, short fibers through both crack trapping and bridging effects. In this paper, the crack trapping effect was studied through the analysis of the change of strain energy associated with the crack propagation across a regular array of fibers, and the bridging effect was discussed based on the Andersson–Bergkvist model. The fracture resistance increases with the fiber volume fraction, and is independent of the elastic properties of the matrix, the crack length, and the cross-sectional diameter of the fibers.