3G系统网络接入的安全构架

在介绍第三代移动通信系统网络接入的安全构架的基础上,分析了3G系统的优势,并讨论了3G系统中有待进一步研究的问题。     

用功率因数校正器(PFC)抑制电流谐波(3)

(接上一期) 4.3.2单片PFC PWM控制器 美国CMC半导体公司推出的单片PFC PWM控制器CM6800/1内含脉宽调制控制器,能促进小型低成本大容量电容在开关电源设计中的应用.同时该产品还可降低电力线路负载,减小场效应管的应力,从而设计出完全符合IEC-61000-3-2的开关电源产品.CM6800/1的主要特性如下:     

基于交织的零相关区序列偶集构造方法研究

移位序列的设计是交织法构造零相关区序列集的核心问题。该文根据相关函数分析了移位序列的约束条件,并据此条件提出一种基于交织构造零相关区序列集的方法。文中通过选择不同基序列和满足约束条件的移位序列,能够得到具有灵活零相关区长度的序列偶。该文将此序列偶和正交矩阵相结合,构造出具有一定序列长度和数目的零相关区序列偶集。该方法扩展了交织法的应用,可以构造具有一定容量和灵活零相关区的序列集。     

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.     

碰撞检测算法在三维游戏设计中的应用与研究

完美的3D游戏体验是游戏制作者与玩家所共同追求的,它不仅指的是游戏场景的华丽绚烂,游戏情节的跌宕起伏;还要看它虚拟现实的功能有多强。而这其中最需要解决的一个很重要的问题就是在游戏场景中虚拟物体之间相交碰撞的检测和处理,检测处理的精确性、实时性将直接决定一款游戏的在游戏情节的实现上是否合理以及虚拟现实的仿真程度如何。本文将重点阐述作者在三维游戏设计中关于碰撞检测技术应用研究的一些想法。     

烧结温度对漂珠/ZrO2多孔轻质材料性能的影响

以漂珠为成孔材料,以ZrO2为结合剂,采用凝胶注模的方法制备出多孔轻质材料。通过分析材料的微观形貌、物相组成、显气孔率、体积密度、抗弯强度等性能参数,研究了烧结温度1200℃~1500℃对材料性能的影响。结果得出,烧结温度达到1400℃时,漂珠外壳与氧化锆的界面结合不再明显,ZrO2颗粒由点接触扩展到面接触;烧结温度1400℃的试样中锆英石的峰最强,说明漂珠和氧化锆已烧结熔融;1400℃下制备试样的显气孔率最大(68%),体积收缩率(20.8%)最低,而抗弯强度可达7.5MPa;烧结温度控制在1400℃,可使材料处于烧结中期,保证材料的各项性能满足其应用需求。     

ATM视频传输中信元丢失的分析与对策

ＡＴＭ的出现使得我们能够实时地,高效地传输视频信号,但同时在传输过程中ＡＴＭ的信元丢失将是导致解压缩后的图像质量严重下降。文章首先基于ＭＰＥＧ－２标准,给出了一个基本的视频通信系统框架及各部分的码流格式,然后分析了系统中信元丢失的原因,特点和影响。文中给出了现有的各种减少信元丢失的方法及其如何隐藏信元丢失对图像质量造成的影响,分析其优质和适用场合,并讨论了以后的研究方向。     

透明液晶薄膜旋光色散特性研究

以透明塑料为基板,将液晶薄膜均匀涂于其上制成透明的具有旋光性的薄片,并用自行研制的旋光色散装置,对所制薄片的旋光色散特性进行了研究,测试结果显示其具有很大的旋光性.同时,用玻尔兹曼方程进行了理论拟合,发现拟合结果与实验结果有着极好的符合。     

A Hetero-Layered,Mechanically Reinforced,Ultra-Lightweight Composite Polymer Electrolyte for Wide-Temperature-Range,Solid-State Sodium Batteries

The practical use of polyethylene oxide polymer electrolyte in the solid-state sodium metallic batteries (SSMBs) suffers from the retard Na⁺ diffusion at the room temperature, mechanical fragility as well as the oxidation tendency at high voltages. Herein, a hetero-layered composite polymeric electrolyte (CPE) is proposed to enable the simultaneous interfacial stability with the high voltage cathodes (till 4.2 V) and Na metallic anode. Being incorporated within the polymer matrix, the sand-milled Na₃Zr₂Si₂PO₁₂ nanofillers and nanocellulose scaffold collectively endow the thin-layer (25 µm), ultralightweight (1.65 mg cm⁻²) CPE formation with an order of magnitude enhancement of the mechanical strength (13.84 MPa) and ionic conductivity (1.62 × 10⁻⁴ S cm⁻¹) as compared to the pristine polymer electrolyte, more importantly, the improved dimension stability up to 180 °C. Upon the integration of the hetero-layered CPE with the iron hexacyanoferrate FeHCF cathode (1 mAh cm⁻²) and the Na foil, the cell model can achieve the room-temperature cycling stability (93.73% capacity retention for 200 cycles) as well as the high temperature tolerance till 80 °C, which inspires a quantum leap toward the surface-wetting-agent-free, energy-dense, wide-temperature-range SSMB prototyping.     

Lithiation-Induced Defect Engineering to Promote Oxygen Evolution Reaction

Exploring efficient electrocatalysts for oxygen evolution reaction (OER) is an urgent need to advance the development of sustainable energy conversion. Though defect engineering is considered an effective strategy to regulate catalyst activity for enhanced OER performance, the controllable synthesis of defective oxides electrocatalysts remains challenging. Here, oxygen defects are introduced into NiCo₂O₄ nanorods by an electrochemical lithiation strategy. By tuning in situ lithiation potentials, the concentration of oxygen defects and the corresponding catalytic activity can be feasibly regulated. In addition, the relationship between the changes in the defect density and electronic structure and the lithiation cut-off voltages is revealed. The results show that NiCo₂O₄ nanorods undertook intercalation and two-step conversion reaction, in which the lithiation-induced conversion reaction gives rise to a CoO@NiO-based structure with higher defect density and lower oxidation states. As a result, the defective CoO@NiO-based catalyst exhibits exceptional OER activity with an overpotential of 270 mV at 10 mA cm⁻², which is about 74 mV below the pristine nanomaterials. This research proposes a novel strategy to explore high-performance catalysts with structural stability and defect control.