Effects of Deposition Temperature on the Properties of Fluorinated Amorphous Carbon Films

Fluorinated amorphous carbon films (a-C:F) were prepared at different temperatures using a microwave electron cyclotron resonance chemical vapor deposition (ECR-CVD) reactor with CHF3 and C2H2 as source gases. Films were annealed at 500℃ in vacuum ambience inorder to investigate the relationship of their thermal stability, optical and electrical propertieswith deposition temperature. Results indicate that the films deposited at high temperature have a less CFx bonding and a more cross-linking structure thus a better thermal stability. They also have a lower bandgap, higher dielectric constant and higher leakage current.     

甘肃电网黑起动研究

电力系统全停后的黑起动方案研究,是保证电力系统安全运行的重要课题.围绕甘肃电网的网架结构特点,研究提出了甘肃电网的黑起动方案.通过计算分析,对甘肃电网黑起动过程中存在的问题提出了解决的对策.     

A novel integrated silicon capacitive microphone-floating electrode“electret” microphone (FEEM)

A novel principle “electret” microphone, i.e., floating electrode electret microphone, is proposed and implemented in this study. Single-chip fabrication and corrugation technique are used in the design and fabrication of the microphone. The floating electrode is encapsulated by highly insulated materials to ensure that there is no electric-leakage passage between the floating electrode and the electrodes of the microphone. Net-free electronic charges (not “bonded” charges as in traditional electret) in the floating electrode can excite the electric field, which is similar to that of the traditional electret. The floating electrode can be easily charged by use of the “hot” electron technique, available using the avalanche breakdown of the p⁺-n junction. Therefore, the electret microphone is rechargeable, which can greatly increase the lifetime of the device. The preamplifier has been on-chip integrated in a junction-field-effect transistor (JFET) source-follower type with resistors by use of ion implantation. Electret charges are banded in a deep potential trap, thus, this microphone can operate at a high temperature (as high as 300°C) and has high stability and reliability. Experiments show that the prototype has a 3-mV/Pa sensitivity and a larger than 21-kHz frequency bandwidth in a 1 mm ×1-mm diaphragm area. Microphone performance can be further improved by optimized process and design. The fabrication is completely integrated-circuit (IC) compatible, hence, the microphone shows promise in integrated acoustic systems     

Electrical Properties and Electroluminescence of 4H-SiC p-n Junction Diodes

Homoepitaxial growth of 4H-SiC on off-oriented Si-face(0001 ) substrates was performed by using the step-controlled epitaxy technique in a newly developed low-pressure hot-wall CVD (LP-HWCVD) system with a horizontal aircooled quartz tube at around 1500 ℃and 1.33 × 104 Pa by employing SiH4 C2H4 H2. In-situ doping during growth was carried out by adding NH3 gas into the precursor gases. It was shown that the maximum Hall mobility of the undoped 4H-SiC epilayers at room temperature is about 430 cm2 ·V -1 ·s -1 with a carrier concentration of ～ 1016 cm-3 and the highest carrier concentration of the N-doped 4H-SiC epilayer obtained at NH3 flow rate of 3 sccm is about 2.7 × 1021 cm-3 with a mobility of 0.75 cm2 ·V -1 ·S -1. SiC p-n junctions were obtained by epitaxially growing N-doped 4H-SiC epilayers on Aldoped 4H-SiC substrates. The C-V characteristics of the diodes were linear in the 1/C3-V coordinates indicating that the obtained p-n junctions were graded with a built-in voltage of 2.7 eV. The room temperature electroluminescence spectra of 4H-SiC p-n junctions are studied as a function of forward current. The D-A pair recombination due to nitrogen donors and the unintentional, deep boron center is dominant at low forward bias, while the D-A pair recombination due to nitrogen donors and aluminum acceptors are dominant at higher forward biases. The p-n junctions could operate at temperature of up to 400 ℃, which provides a potential for high-temperature applications.     

包钢连铸结晶器液位控制系统中控制器的设计应用

本文采用FUZZY－PID复合式自适应控制器来满足冶金连铸系统中对结晶器液位控制的要求，由于在长时间的连续铸钢过程中，塞棒头部受钢水的冲刷和腐蚀，使得塞棒头部为形较大，导致塞棒位置与钢水流量的特性关系发生较大变化，而这种变化无法用确定的数学关系式来描述，用常规PID控制器不能对此变化进行有效调节。本文采用模糊控制器对此变化作出反映，通过模糊控制运算结果来调节PID控制器的放大系数Kp始终在理想的范围内，从而使控制系统达到对结晶器液位控制的要求。     

交通事故后的交通运行风险状态等级预测方法

以事故数据为基础研究事后风险状态,建立了基于改进深度森林算法的交通运行风险状态等级预测模型.首先分析了事故特征重要度,建立了基于极端梯度提升算法的事故特征筛选机制,引入贝叶斯参数寻优和十折交叉验证法实现了深度森林模型的超参数优化;同时设计了循环多粒度扫描方法和加权级联森林结构,获取了交通运行风险状态等级与事故特征的映射...     

A distributed deadlock detection algorithm for mobile computing system

The mode of mobile computing originated from distributed computing and it has the un-idempotent operation property, therefore the deadlock detection algorithm designed for mobile computing systems will face challenges with regard to correctness and high efficiency. This paper attempts a fundamental study of deadlock detection for the AND model of mobile computing systems. First, the existing deadlock detection algorithms for distributed systems are classified into the resource node dependent （ RD ） and the resource node independent （RI） categories, and their corresponding weaknesses are discussed. Afterwards a new RI algorithm based on the AND model of mobile computing system is presented. The novelties of our algorithm are that： 1 ） the blocked nodes inform their predecessors and successors simultaneously; 2） the detection messages （agents） hold the predecessors information of their originator; 3 ） no agent is stored midway. Additionally, the quit-inform scheme is introduced to treat the excessive victim quitting problem raised by the overlapped cycles. By these methods the proposed algorithm can detect a cycle of size n within n - 2 steps and with （ n^2- n - 2 ）/2 agents. The performance of our algorithm is compared with the most competitive RD and RI algorithms for distributed systems on a mobile agent simulation platform. Experiment results point out that our algorithm outperforms the two algorithms under the vast majority of resource configurations and concurrent workloads. The correctness of the proposed algorithm is formally proven by the invariant verification technique.     

迟滞非线性系统的反演滑模控制器设计

为了消除迟滞对系统的不良影响,对一类Bouc-Wen模型表示的迟滞系统设计了反演滑模控制器。由于迟滞的非平滑、多映射等特性会引起系统振荡甚至造成系统不稳定,首先采用Bouc-Wen模型描述迟滞,分析了Bouc-Wen模型的特性并得到其上界值;然后引入滑模项以克服干扰,设计了反演滑模控制器,采用Lyapunov函数的设计过程以保证系统的稳定性;最后进行仿真实验,结果证明该控制方法有效。     

基于序列运算理论的孤立微电网经济运行模型

针对风力和光伏发电出力的随机性,提出一种基于机会约束规划的孤立微电网经济运行模型。鉴于部分机会约束难以转化成确定性约束,根据序列运算理论,利用可再生能源出力的概率分布生成概率性序列,使模型中的机会约束转化成确定性约束的等价类。因此模型具有混合整数规划的线性结构,可兼容如TOMLAB类的优化工具求解。仿真结果表明,与随机模拟求解相比,该方法具有计算速度快且结果稳定的优势。另外,为了考察概率性序列的合理性,还讨论了不同离散化步长对计算结果的影响,并进一步验证了所提出方法的有效性。