A Call-Admission Control (CAC) Algorithm for Providing Guaranteed QoS in Cellular Networks

Future broadband wireless access systems are expected to integrate various classes of mobile terminals (MTs), each class with a different type of quality of service (QoS) requirement. When the load on a wireless network is high, the guarantee of QoS for each class of MTs is a challenging task. This study considers two classes of MTs—profiled MTs and nonprofiled or regular MTs. It is assumed that profiled users require a guaranteed QoS. The measure of QoS is the probability of forced termination of a call that was allowed to access the network. Two previous handoff prioritization schemes—(i) prerequest scheme and (ii) guard channel scheme—decrease handoff failure (and hence forced termination). In this work, we compare and contrast both the schemes through extensive simulation and we find that neither guard channel nor channel prerequest scheme can guarantee a desired level of QoS for the profiled MTs. We then propose a novel call-admission control (CAC) algorithm that can maintain any desired level of QoS, while the successful call completion rate is very high. In the proposed algorithm, the new call arrival rate is estimated continuously, and when the estimated arrival rate is higher than a predetermined level, some new calls are blocked irrespective of the availability of channels. The objective of this new call preblocking is to maintain a cell's observed new call arrival rate at no more than the predetermined rate. We show that the proposed method can guarantee any desired level of QoS for profiled users.     

双极RF功率管的深阱结终端

给出了双极 RF功率管新的深阱结终端结构 .模拟分析表明 ,具有优化宽度、优化深度且填充绝缘介质的深阱结终端结构能使雪崩击穿电压提高到理想值的 95 %以上 .实验结果表明 ,深阱结终端结构器件 DCT2 6 0的BVCBO为理想值的 94 % ,比传统终端结构器件高 14 % ;与传统结构相比 ,在不减小散热面积的情况下 ,该结构还减小集电结面积和漏电流 ,器件的截止频率提高 33% ,功率增益提高 1d B     

高温超导电缆的研发现状和发展趋势

与常规电缆相比,高温超导电缆具有体积小、重量轻、容量大、电流密度高、损耗低、环境友好等优势,为未来电网提供了一种新的电力传输方式。随着高温超导线材取得的重要研究进展,国际上相继开展了高温超导电缆的研发,已有多条超导电缆工程成功地进行了挂网示范运行。本文介绍高温超导电缆的研发进展情况,并简单对高温超导电缆的发展趋势和关键技术做出展望。     

一种新型检测电梯超载用模拟加载装置的设计

阐述了常用的电梯超载保护装置的型式和目前的检测方法。针对配备机房称重式加载保护装置的电梯难以利用普通模拟加载装置进行检测的问题,设计了一套新型电梯模拟加载装置,并介绍了其相应的测试方法。该加载装置具有操作方便、简单易携．精度高．重复性好．容错率高等优点。     

Short and long crack data for fatigue of 2024‐T3 Al sheets: binariness of scale segmentation in space and time

Pedagogically speaking, crack initiation–growth–termination (IGT) belongs to the process of fracture, the modelling of which entails multiscaling in space and time. This applies to loadings that are increased monotonically or repeated cyclically. Short and long crack data are required to describe IGT for scale ranges from nano to macro, segmented by the SI system of measurement. Unless the data at the nano scale can be connected with the macro, IGT remains disintegrated. The diversity of non‐homogeneity of the physical properties at the different scale ranges results in non‐equilibrium. These effects dubbed as non‐equilibrium and non‐homogeneous are hidden in the test specimens and must be realized. They can be locked into the reference state of measurement at the mi‐ma scale range by application of the transitional functions and transferred to the nano‐micro and macro‐large scale ranges. The aim of this work is to convert the ordinary crack length data to those referred to as short cracks that are not directly measurable. All test data are material, loading and geometry (MLG) specific. The results obtained for the 2024‐T3 aluminium sheets hold only for the MLG tested. The differences are more pronounced for the short cracks. These effects can be revealed by comparing the incremental crack driving force (CDF) for the ma‐mi range the ma‐large range and the na‐mi range The CDF is equivalent to the incremental volume energy density factor (VEDF). The incremental mi‐ma CDF is found to be 10–10⁵ kg mm^?1 for cracks 3–55 mm long travelling at an average velocity of 10^?5 mm s^?1. The crack velocity rises to 10^?3 mm s^?1 when the incremental CDF is increased to 10⁵–10⁶ kg mm^?1, while the crack lengths are 49–260 mm. The crack velocity for the na‐mi range of 0.040–0.043 mm slowed down to 10^?8 mm s^?1, and the incremental CDF reduces further to 10^?8–10^?2 kg mm^?1. Note that changed several orders of magnitude while the crack advanced from 0.040 to 0.044 mm. Such behaviour is indicative of the highly unstable nature of nanocracks. All results are based on using the transitionalized crack length (TCL). The TCL fatigue crack growth increment Δa is postulated to depend on the incremental CDF ΔS or ΔVEDF. The form invariance of , and is invoked by scale segmentation to reveal the multiscale nature of IGT that is inherent to fatigue crack growth. While the choice of directionality from micro to macro is not the same as that from macro to micro, this difference will not be addressed in this work.     

应用于3.3kV IGBT的线性渐变掺杂结终端扩展的设计与优化

本文将线性渐变掺杂结终端扩展（LG-JTE）技术用于3.3kV IGBT并进行了试验验证。和采用多次光刻和离子注入传统结终端扩展技术不同,LG-JTE只用一张注入窗口宽度随与主结的距离线性变化的掩膜版。结合仿真设计了采用LG-JTE的IGBT,并在国内工艺平台上成功流片,其测试耐压达到3.7kV,接近理想的平行平面情形的耐压。     

基于相邻宏块率失真代价的JMVC快速算法

为了降低JMVC(Joint Multiview Video Coding联合多视点视频编码)编码复杂度,提出一种根据前一编码宏块参考方向和率失真代价,提前终止JMVC模式选择的算法。该算法首先获取前一宏块的率失真代价和参考方向,随后根据前一宏块参考方向为当前宏块的搜索设定一个率失真代价门限,最后利用此门限实现提前终止。实验结果显示,相比于JMVC原始算法,本文算法的编码质量没有下降,而编码时间节省了34.86%~54.23%。算法可以在保证编码质量的前提下,有效地较低编码复杂度。     

采用浮空场限制环的耐压10kV碳化硅二极管的开发

The design, fabrication, and electrical characteristics of the 4H-SiC JBS diode with a breakdown voltage higher than 10 kV are presented. 60 floating guard rings have been used in the fabrication. Numerical simulations have been performed to select the doping level and thickness of the drift layer and the effectiveness of the edge termination technique. The n-type epilayer is 100 μm in thickness with a doping of 6 × 10^14 cm^-3. The on-state voltage was 2.7 V at JF = 13 A/cm^2.     

A study of ceramic addition in end termination of multilayer ceramics capacitors with cofiring process

The silver paste with ceramics addition as end termination was performed on multilayer ceramic capacitors (MLCC) based on ZnO–B₂O₃ + Zn_0.95Mg_0.05TiO₃ + 0.25TiO₂ ceramic (ZnBO-ZMT′) with Ag95–Pd05 internal electrodes. A green sheet was prepared by tape casting using the ZnBO-ZMT′ powders. Ag95–Pd05 was attached on the green sheet as an internal electrode. After lamination, the green chips were pre-sintered at 800 °C for 1 h, then samples were dipped the external electrodes and were cofired together at 900 °C for 2 h. There is no extra curing process, so the production cost may be cut down and thermal shock of the MLCCs may be reduced. To improve the mismatch between end termination and dielectric body during sintering, the silver paste with different amounts of ceramics, e.g., 20, 30 and 40 wt.%, was added in this study. The mechanical and electrical properties of the MLCCs were investigated subsequently. The results showed that end termination with 40 wt.% ceramic addition has good performances on mechanical properties of MLCC, but equivalent series resistance (ESR) is a little bit higher compared to end termination with 20 and 30 wt.% ceramic addition.