The electrochemical oscillations that occur during the etching of InP and the three-dimensional (3D) porous structure of the resulting material were studied by performing electrochemical etching in a 3.5 mol L−1 NaCl solution at different temperatures and current densities. The characteristics of the oscillations were modified by adjusting the electrochemical parameters. The relationship between the oscillations and the porous structure of the etched InP was investigated. In the experiments, porous InP with a gradient-index (GI) structure was formed at relatively low temperatures (10–22 °C) and current densities (100–300 mA cm−2). Furthermore, two types of incomplete pores observed in the bottom layer of the porous structure of InP were found to correspond to incomplete oscillations (one-quarter and one-half of an oscillation, respectively), which provided useful insight into how pore growth proceeds in the etched InP. Based on the results obtained in this work, the growth mechanism of porous InP is discussed in this article.

The point defects and photoluminescence (PL) spectra of gallium nitride (GaN) epilayers with Mg, Zn, and unintentional doping were investigated in this study. The concentration of point defects (Ga vacancy and its related complexes) in the Zn-doped GaN is consistent with that in the Mg-doped GaN, but lower than that in undoped GaN. It is suggested that Zn (Mg) atoms occupy Ga sites and suppress the formation of Ga vacancies. Comparing the blue luminescence (BL) band intensity of GaN:Zn with that of GaN:Mg, a factor of 10 strong PL intensity demonstrates that a moderate incorporation of Zn to GaN is likely to improve the structural quality of GaN. Detailed studies on 2.93 eV BL band for GaN:Zn reveal that the Zn related BL band behaves as a donor-acceptor pairs character. For the acceptor level, isolated Zn(Ga)with the activation energy of 0.386 eV above the valence band is obtained from temperature-dependent PL measurements, whereas the deep donor defect responsible for the 2.93 eV band is deduced to be 164 meV below the conduction band. An O-N-H complex model is suggested to explain the deep donor origin.

In this paper, a novel scheduler is designed for multiple traffic classes with reduced feedback. The novel scheduler consists of two stages, i.e., at the first scheduling stage, the inter-traffic scheduler dynamically allocates the clustered bandwidth resources to each traffic class by a periodic and triggered way; at the second scheduling stage, and the intra-traffic scheduler schedules different users’ packets within each traffic class simultaneously. In order to reduce the feedback, each user only reports the CQI of n subchannels that have the best normalized SNR. The proposed algorithm not only enhances the system throughput but also reduces the feedback load under the condition that the QoS requirements of RT traffic are satisfied. Simulations validate the effectiveness and good performance of the proposed scheme.

采用热化学气相沉积的方法在选择性液相外延方法制备的GaAs微尖上生长碳纳米管.利用扫描电子显微镜以及拉曼光谱对生长的碳纳米管进行表征.结果表明:GaAs微尖在高温下重新结晶成条状梯形GaAs阵列,生长的碳纳米管连接在相邻的GaAs阵列之间,形态规整,具有较好的石墨微晶结构.在此基础上,提出在微尖上生长纳米管的模型,为实现微纳器件互联提供了一种新方法.

We present the transition state of porous InP from three to two dimensions, which is explored during electrochemical etching at constant current density in NaCl solutions on n-InP(100) wafers. The `node' of the three dimensional structure revealed by scanning electron microscopy are consistent with the oscillatory periods, and that the smooth curve is corresponding to the uniformly vertical pores along with the <;001> direction. In addition, the onset and end of the oscillations shift ahead of times with increasing current densities. Furthermore, the transition of porous InP was discussed based on the surface curvature, the diffusion-control, and the reactive heat.

提高学生的实践能力和创新能力,不仅是经济社会发展对人才素质的要求,也是学生自身发展和增强就业竞争力的现实需要。我国已经成为一个制造业的大国,如何从中国制造升级到中国创造,加强创新能力的培养就成为我国高等教育的重要环节之一。北京城市学院电子信息工程专业在培养应用型本科人才的实践能力、创新能力方面做了一些探索,本文从创新能力培养理念、提供创新实践平台等多方面阐述了如何培养学生的实践创新能力,在此基础上构建完善的培养体系,为创新能力的培养提供保障。

This paper first introduces the performance analysis of two classical channel quality indicator (CQI) feedback schemes which are best-n feedback and the threshold based feedback and derives the mathematical expressions of average capacity which is described by Theorem 1 and 2. Then, a reduced feedback scheme is designed for multiple traffics and multi-channel. The novel scheme combines the best-n feedback and the threshold based feedback together to reduce the feedback overhead. The proposed scheme can not only guarantee the quality of service (QoS) requirement of real time (RT) traffic but also reduce feedback overhead at the cost of a marginal increased downlink overhead. Simulation results demonstrated the good performance of the proposed feedback scheme.

In this paper, a novel semi-static inter-cell interference coordination scheme based on spectrum pool is proposed for cellular OFDMA systems. In the proposed scheme, the spectrum is divided into three partitions, called major subbands group, minor subbands group and spectrum pool group. The major subbands and the spectrum pool are used by all users in a cell and the minor subbands only can be used by cell center users. The proposed scheme consists of two stages, i.e. at the frequency planning stage, the eNB allocates the major subbands and the spectrum pool to cell edge users and the minor subbands to the cell center users according to variation of the cell edge traffic load; at the intra-cell scheduling stage, the cell edge users are scheduled based on the major subbands and the spectrum pool first, and then the cell center users are scheduled on the remaining resources. The proposed scheme not only enhances the cell edge throughput but also reduces the inter-cell signaling overhead and complexity. Simulation results and performance analysis validate the effectiveness and good performance of the proposed scheme.

The crossing porous structure of InP has been obtained by electrochemical etching in NaF solutions. The behavior of the periodic oscillation occurs at different potential ranges for the different concentrations of solutions, and it will disappear with the concentration of the solution decreased. The scanning electron microscope (SEM) image shows that the pores have two directions on the surface and are perpendicular to each other. The two directions are assigned to [011] and [01¯1], respectively. The SEM image of the cross-section also shows that the two directions are assigned to [111]B and [11¯1¯]B. Both are due to the selective etching of F− ions. The crossing porous structure of InP is a very promising feature for the three-dimensional structure of III–V compound semiconductors for photonic band gap materials.

介绍了利用物理气相沉积的技术制备有机物并五苯场效应晶体管(OTFT)的方法.通过扫描电镜(SEM)和X射线衍射谱(XRD)对并五苯薄膜的分析,发现并五苯薄膜具有良好的表面形貌和晶体特性.其载流子迁移率达0.3cm2/Vs,并五苯晶体管具有低电压特性.