Enhanced light output in nitride-based light-emitting diodes by roughening the mesa sidewall

In this letter, we will report on a nitride-based light emitting diode with a mesa sidewall roughening process that increases light output power. The fabricated GaN-based light-emitting diode (LED) wafers were first treated through a photoelectrochemical (PEC) process. The Ga/sub 2/O/sub 3/ layers then formed around the GaN : Si n-type mesa sidewalls and the bottoms mesa etching regions. Selective wet oxidation occurred at the mesa sidewall between the p- and the n-type GaN interface. The light output power of the PEC treated LED was seen to increase by about 82% which was caused by a reduced index reflectance of GaN-Ga/sub 2/O/sub 3/-air layers, by a rough Ga/sub 2/O/sub 3/ surface, by a microroughening of the GaN sidewall surface, and by a selective oxidation step profile of the mesa sidewall that increases the light-extraction efficiency from the mesa sidewall direction. Consequently, this wet PEC treated process is suitable for high powered nitride-based LEDs lighting applications.     

A new distributed approximation algorithm for constructing minimum connected dominating set in wireless ad hoc networks

In recent years, constructing a virtual backbone by nodes in a connected dominating set (CDS) has been proposed to improve the performance of ad hoc wireless networks. In general, a dominating set satisfies that every vertex in the graph is either in the set or adjacent to a vertex in the set. A CDS is a dominating set that also induces a connected sub‐graph. However, finding the minimum connected dominating set (MCDS) is a well‐known NP‐hard problem in graph theory. Approximation algorithms for MCDS have been proposed in the literature. Most of these algorithms suffer from a poor approximation ratio, and from high time complexity and message complexity. In this paper, we present a new distributed approximation algorithm that constructs a MCDS for wireless ad hoc networks based on a maximal independent set (MIS). Our algorithm, which is fully localized, has a constant approximation ratio, and O(n) time and O(n) message complexity. In this algorithm, each node only requires the knowledge of its one‐hop neighbours and there is only one shortest path connecting two dominators that are at most three hops away. We not only give theoretical performance analysis for our algorithm, but also conduct extensive simulation to compare our algorithm with other algorithms in the literature. Simulation results and theoretical analysis show that our algorithm has better efficiency and performance than others. Copyright © 2005 John Wiley & Sons, Ltd.     

A new method for producing high melt strength polypropylene with reactive extrusion

A high‐melt‐strength polypropylene (HMSPP) was prepared using a twin‐screw reactive extruder from a commercial isotactic polypropylene through two stages, first, maleic anhydride is grafted to polypropylene to obtain a maleic anhydride‐grafted polypropylene (PP‐g‐MA), and then the grafted polymer is reacted with epoxy to extend the branched chain. Fourier transformed infrared spectroscopy indicated that maleic anhydride was grafted on polypropylene and reacted with epoxy. Melt flow rate and sag resistance test showed that the melt strength of the HMSPP improved considerably. Differential scanning calorimetry test showed that the long chain branches (LCBs) act as a nucleating agent in the crystallization of the HMSPP, which leads to a high crystallization temperature and crystallinity. Furthermore, the LCB efficiency of the HMSPP can also be calculated by analyzing its rheological property. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

赴日无线电监测技术考察报告

首先介绍了日本总务省关东综合通信局电波监理部的情况，然后对日本安立公司生产的RR510A型无线电监测接收机和技术参数以及MS8609A型数字移动无线发射机测试仪的功能进行了分析和介绍。     

On a three-dimensional axisymmetric boundary-value problem of nonlinear elastic deformation: Asymptotic solution and exponentially small error

In this paper, we study a three-dimensional axisymmetric boundary-value problem of a slender cylinder composed of a nonlinearly elastic material subjected to an axial force. Starting from the field equations, after a transformation and proper scalings, we identify a small variable and two small parameters, which characterize the present problem. Then, by an approach involving compound series-asymptotic expansions, a nonlinear ODE is derived, which governs the axial strain (the first-term in the series expansion). By imposing the zero radial displacement conditions at two ends, we manage to get the analytical solution of the axial strain, from which all other physical quantities can be deduced and thus the three-dimensional displacement field can be determined. Graphical results are presented, which show that there are two boundary layers near the two ends while the middle part is in a state of almost uniform extension. The asymptotic structure of the analytical solution is derived, which offers clear explanations to the structure of the deformed configuration and shows that the thickness of both boundary layers is of the order of the radius. We also point out the relevance of the present results to the St. Venant’s problem. In particular, we obtain the explicit uniformly-valid exponentially small error term, when the obtained deformed configuration is compared to the configuration of a uniform extension.     

The changes of lipid metabolism and hemorrheology in intrahepatic cholestasis during pregnancy

OBJECTIVE: To identify the influence of the increased level of serum cholyglycine (CG) on lipid metabolism and hemorrheology in patients with intrahepatic cholestasis during pregnancy (ICP). METHODS: The concentrations of serum CG, total cholesterol (CH), triglycerides (TG), high density lipoprotein-cholesterol (HDL-C), low density lipoprotein-cholesterol (LDL-C), high shear and low shear of blood specific viscosity (HS and LS), plasma specific viscosity (PV) and hematocrit (HCT) were measured in 68 cases of primiparas with single pregnancy and 30 healthy nonpregnant women respectively. The group of ICP was composed of 35 cases with CG > 6 mumol/L, the group of normal pregnancy, 33 cases with CG < 6 mumol/L. RESULTS: The means of CG and the lipidic parameters in the two pregnant groups were significantly higher than those in the non-pregnancy group (P < 0.02-0.001) except the means of HDL-C between the groups of ICP and non-pregnancy. The levels of LDL-C, LDL-C/HDL-C, LS, PV and HCT in the ICP were significantly higher than those in the normal pregnancy group (P < 0.02-0.001). CONCLUSIONS: There are significant changes of lipid metabolism and hemorrheology in patients with ICP. However, these changes could be corrected after pregnancy termination, when the level of serum CG returned to normal. The results suggest that the pathophysiologic changes of ICP are associated with increased level of serum CG.     

硬件握手双向选通型串行通信共享器的设计

本文介绍了ＩＢＭ－ＰＣ系列计算机通过ＲＳ－２３２Ｃ串行口与多个单片微机组成的分布式系统中一种可双向选通串行通信共享器的设计方法。给出通信共享器的设计电路；并对电路工作原理进行了详细剖析。     

噪声测量作为筛选光电耦合器件的一种方法

本文针对目前用于光电耦合器件筛选方法的不足，提出了用测量耦合器件噪声功率谱的方法来筛选掉噪声值大的器件，给出一批光电耦合器件的测量统计结果及在不同工作点时的噪声功率谱，并给出相应的筛选标准，实验结果表明，这种方法是有效、可行的。     

珠江口盆地开平凹陷油气聚集条件分析

珠江口盆地自新生代以来,曾先后受到不同方向张应力的作用,造成了不同时期构造体系的交叉叠合.中中新世以来构造运动强烈,并具有东强西弱的特点,对油气的运移与聚集产生了重要影响.开平凹陷的剧烈断裂和断陷活动始于始新世,并在同期沉积了巨厚的文昌组.晚渐新世以后,由于断裂活动非常微弱,在成熟的烃源岩与其上地层之间缺乏有效的油源断层,因而自生自储、近距离运移可能是开平凹陷油气聚集的基本特征.在凹陷内部,因重力滑动和欠压实泥岩共同作用所形成的KPll-1构造带可能是该区最具有油气远景的地区.