GSM数字移动通信系统的越区切换

切换技术是GSM数字移动通信系统保证移动中用户通信质量的一个重要手段。本文简要说明切换及其起因、启动标准和类型 ,并阐述基站决定切换启动的三个不同阶段的算法和要求 ,最后重点介绍网络系统中各种不同范围切换控制的信令关系及其实现过程。     

Identification of material and geometrical parameters for microstructures by dynamic finite element model updating

This paper describes a procedure to identify material and geometrical parameters for microstructures using the concept of finite element model updating. This scheme utilizes measured and finite element analysis (FEA) natural frequencies that are paired together according to their mode shapes, and it incorporates an optimization sequence that formulates the frequency differences as an error vector to be minimized. To demonstrate the effectiveness of the proposed procedure, two examples are shown in this paper. One example involves a microcantilever fabricated from a single-crystalline silicon wafer, and the updating process is applied on the cantilever to identify its Young’s modulus. The identified Young’s modulus (along <100> direction) of 130.29 GPa is very comparable to those in the literature. The other example concerns a commercial, V-shaped silicon nitride probe used in an atomic force microscope. The natural frequencies and mode shapes of the probe are measured, the FEA performed, and the probe thickness and the Young’s modulus of the silicon nitride substrate determined. The identified thickness is also verified by SEM images of the probe. Both examples show that the updating procedure converged in just a few iterations.     

Nano Temperature Sensor Using Selective Lateral Growth of Carbon Nanotube Between Electrodes

This paper presents lateral growth of carbon nanotube (CNT) between two electrodes and its use as nano temperature sensor. Fabrication of electrodes is made by MEMS techniques. The CNT is grown selectively by microwave plasma chemical vapor deposition between two electrodes. After wire bonding, the grown CNT is tested and calibrated. The growth conditions of CNT, such as the flow rate of CH₄ or N₂ gas, are varied to obtain a high-quality CNT sensor. SEM is used to observe the shape and structure of CNT, while Raman spectrum analysis is used to indicate the degree of graphitization or amorphous structure in the CNT. The I-V curve of CNT is measured at different temperature, and a linear relationship between the electric resistance of CNT and the temperature is obtained. This result indicates that CNT can be used as a temperature sensor     

Optimal short‐term scheduling of shunt compensators via a decomposition algorithm

Abstract

The short term (one day) scheduling of VAr controllers involves the setting of shunt compensators, EHV taps and generator voltages. A decomposition approach is presented to solve the problem of optimal short‐term scheduling of shunt compensators in this paper. The entire problem is decomposed into two levels: the master and the slave levels. The master level deals with minimization of the depreciation cost of compensators in order to reduce the control actions for compensators while satisfying operating constraints. The slave level treats minimization of capitalized MW losses while satisfying system security constraints by adjusting generator voltages and taps. These two levels interact through linear constraints in the iteration process. The IEEE 30‐bus and a practical 265‐bus systems, namely Taiwan Power System, are used to serve as samples to show the applicability of the presented approach.     

Selection of an optimal set of cutting-tool sizes for 21/2D pocket machining

The availability of high speed automatic tool change mechanisms in modem CNC machining centers is making it practical to consider the use of multiple cutting-tool (specifically, flat end-mill) sizes to reduce the total time for machining a 21/2D) pocket. However, current CAD/CAM systems do not support pocket machining using multiple cutting-tool sizes. In this paper, we describe a two-phase methodology for selecting an optimal set of cutting-tool sizes to machine a 21/2D pocket. In the first phase, we employ a new concept called the Voronoi mountain in order to calculate the material volume that can be removed by a specific cutting-tool size, the material volume that will subsequently remain to be machined, and the cutter-paths (and corresponding processing times) for each cutting-tool. In the second phase, we apply a dynamic programming approach for optimal selection of cutting-tool sizes on the basis of the processing time. Our computational experiments indicate that substantial savings in processing time can be achieved by using multiple cutting-tool sizes to machine 21/2D pockets.     

谷氨酸发酵过程的一个预测模型

本文叙述了作者们利用上海天厨味精厂150M³发酵罐的批报数据,建立谷氨酸发酵过程的预测模型．在参数估计中,应用了带平方根滤波最小二乘法以及单纯形搜索法．仿真试验表明,本文提出的预测模型和工厂数据符合得很好．     

Sidewall defects of AlGaN/GaN HEMTs evaluated by low frequency noise analysis

The traditional dry etching isolation process in AlGaN/GaN HEMTs causes the gate metal to contact the mesa sidewalls region, forming a parasitic gate leakage path. In this paper, we suppress the gate leakage current from the mesa-sidewall to increase the gate-to-drain breakdown voltage and thereby reduce the interface trap density by using the ion implantation (I/I) isolation technology. According to the capacitance–voltage (C–V) measured curve, the hysteresis voltage was 9.3 mV and the interface state density was 5.26 × 10¹² cm⁻² for the I/I isolation sample. The 1/f noise phenomena and Schottky characteristics are particularly studied to indicate device linearity, which is sensitive to the semiconductor surface. The fluctuation that causes trapping/detrapping of free carriers near the gate interface can be reduced because side-wall plasma-induced damages were eliminated. The reduced DC and flicker noise variation of I/I isolation HEMTs is beneficial for high power transistor applications.     

Photovoltaic technology development: A perspective from patent growth analysis

To catch up with the need for utilizing sunlight as an alternative energy source, photovoltaic technology has developed considerably fast in the last thirty-plus years. This article examines this technology's development from the perspective of patent growth analysis. Patent data are analyzed to find the photovoltaic technology growth trajectory. Mainly affected by environmental factors such as the price of crude oil, we observe two long-term waves of development trajectories. The current wave is found to be in the later growth stage of its life-cycle. After examining the correlation between technology development and crude oil price, a significant correlation is found between crude oil price's growth rate and photovoltaic patents' growth rate. As far as the market is concerned, it lags 10 years behind photovoltaic technology development.With the assistance of keyword co-occurrence analysis, one can classify photovoltaic patents into five groups, with each carrying a characteristic of competing photovoltaic technologies: Emerging PV, CdTe, CIS/CIGS, Group III–V, and Silicon technologies. This research observes the patent growth trajectories for each technology. Among these competing technologies, Emerging PV, Group III–V, and Silicon are still growing strong, while CdTe and CIS/CIGS are in the mature stage. This result hints at a paradigm shift for photovoltaic technology development. Sustainability is added to the technical regime in addition to efficiency, cost, and reliability.A policy other than the existing mechanism such as a feed-in tariff is suggested to stabilize photovoltaic technology development through the means of removing oil price fluctuations. Finally, several strategic issues are discussed from the technology development community's point of view.     

Photovoltaic characteristics of silicon nanowire arrays synthesized by vapor-liquid-solid process

Silicon nanowire (SiNW) arrays were grown directly on a P type Si substrate, pre-deposited with gold catalyst, and then made into solar cell for photovoltaic characteristic measurement. Different growth conditions of SiNWs, including variation of the flow rate ratio of SiH₄ versus N₂, and the thickness of Au film, which can be sputtered into different size of nanoparticles, will be made in order to obtain an optimum photovoltaic conversion efficiency. The morphologies and crystalline structure of the nanowires are studied by SEM, TEM and XRD. The SiNW array surface is shown to have good antireflection property, and is expected to raise light absorption and short circuit current. The photovoltaic performance of the solar cells with SiNWs grown at different conditions is measured and discussed. More effort is still needed to raise the performance of SiNW solar cells.     

Selection of an optimal set of cutting-tools for a general triangular pocket

The size(s) of the cutting-tool (end-mill) chosen for machining a given pocket has a significant impact on the machining time. However, the selection of cutting-tool sizes is typically based on human judgment and estimates, and is therefore prone to be conservative and non-optimal. The focus of this paper is on the development of a procedure for selection of an optimal set of cutting-tools for staircase milling of general triangular pockets with round corners, such that the machining time is minimized. We first derive analytical models for determining the time for machining the pocket using a given cutting-tool. Subsequently, we employ a dynamicprogramming based approach that utilizes these analytical models to determine the best set of cutting-tools, from the available inventory of cutting-tools, to machine the pocket. The proposed approach can be extended for optimal selection of cutting-tools for rough-machining of 3-D sculptured cavities.