Preparation of AlN thin films for film bulk acoustic resonator application by radio frequency sputtering     

Kan Li  Hao Jin  De-miao Wang  Yi-fei Tang 《浙江大学学报(A卷英文版)》2009,10(3):464-470

Aluminum nitride （AlN） thin films with high c-axis orientation have been prepared on a glass substrate with an Al bottom electrode by radio frequency （RF） reactive magnetron sputtering. Based on the analysis of Berg＇s hysteresis model, the improved sputtering system is realized without a hysteresis effect. A new control method for rapidly depositing highly c-axis oriented AlN thin films is proposed. The N2 concentration could be controlled by observing the changes in cathode voltage, to realize the optimum processing condition where the target could be fixed stably in the transition region, and both stoichiometric film composition and a high deposition rate could be obtained. Under a 500 W RF power of a target with a 6 cm diameter, a substrate temperature of 450 ℃, a target-substrate distance of 60 mm and a N2 concentration of 25%, AlN thin film with preferential （002） orientation was deposited at 2.3 μm/h which is a much higher rate than previously achieved. Through X-ray diffraction （XRD） analysis, the full width at half maximum （FWHM） of AlN （002） was shown to be about 0.28°, which shows the good crystallinity and crystal orientation of AlN thin film. With other parameters held constant, any increase or decrease in N2 concentration results in an increase in the FWHM of AlN.  相似文献   

A simplified MMSE-based iterative receiver for MIMO systems     

Yuan Yang  Hai-lin Zhang 《浙江大学学报(A卷英文版)》2009,10(10):1389-1394

A simplified minimum mean square error （MMSE） detector is proposed for joint detection and decoding of multiple-input multiple-output （MIMO） systems. The matrix inversion lemma and the singular value decomposition （SVD） of the channel matrix are used to simplify the computation of the coefficient of the MMSE filter. Compared to the original MMSE detector, the proposed detector has a much lower computational complexity with only a marginal performance loss. The proposed detector can also be applied to MIMO systems with high order modulations.  相似文献   

Application of an immune algorithm to settlement prediction     

Jia Guo  Jun-jie Zheng  Yong Liu 《浙江大学学报(A卷英文版)》2009,10(1):93-100

The settlement curve of the foundation endured the ramp load is an S-type curve, which is usually simulated via Poisson curve. Aimed at the difficulty of preferences in Poisson curve, an immune algorithm （IA） is used. IA is able to obtain a multiple quasi-optimum solution while maintaining the population diversity. In this paper, IA is used in an attempt to obtain accurate settlement prediction. The predicted settlements obtained by IA are compared with those predicted by the least squares fitting method （LSM）, the Asaoka method and the genetic algorithm （GA）. The results show that IA is a useful technique for predicting the settlement of foundations with an acceptable degree of accuracy and has much better performance than GA and the Asaoka methods.  相似文献   

Adaptive fractional window increment of TCP in multihop ad hoc networks     

Liang-hui Ding  Wen-jun Zhang  Xin-bing Wang  Liang Qian  You-yun Xu 《浙江大学学报(A卷英文版)》2009,10(6):820-827

We propose an adaptive fractional window increasing algorithm （AFW） to improve the performance of the fractional window increment （FEW） in （Nahm et al., 2005）. AFW fully utilizes the bandwidth when the network is idle, and limits the operating window when the network is congested. We evaluate AFW and compare the total throughput of AFW with that of FeW in different scenarios over chain, grid, random topologies and with hybrid traffics. Extensive simulation through ns2 shows that AFW obtains 5% higher throughput than FeW, whose throughput is significantly higher than that of TCP-Newreno, with limited modi- fications.  相似文献   

A video structural similarity quality metric based on a joint spatial-temporal visual attention model     

Hua Zhang  Xiang Tian  Yao-wu Chen 《浙江大学学报(A卷英文版)》2009,10(12):1696-1704

Objective video quality assessment plays a very important role in multimedia signal processing. Several extensions of the structural similarity （SSIM） index could not predict the quality of the video sequence effectively. In this paper we propose a structural similarity quality metric for videos based on a spatial-temporal visual attention model. This model acquires the motion attended region and the distortion attended region by computing the motion features and the distortion contrast. It mimics the visual attention shifting between the two attended regions and takes the burst of error into account by introducing the non-linear weighting fimctions to give a much higher weighting factor to the extremely damaged frames. The proposed metric based on the model renders the final object quality rating of the whole video sequence and is validated using the 50 Hz video sequences of Video Quality Experts Group Phase I test database.  相似文献   

Outlier detection by means of robust regression estimators for use in engineering science   总被引：1，自引：0，他引：1  

Serif Hekimoglu  R. Cuneyt Erenoglu  Jan Kalina 《浙江大学学报(A卷英文版)》2009,10(6):909-921

This study compares the ability of different robust regression estimators to detect and classify outliers. Well-known estimators with high breakdown points were compared using simulated data. Mean success rates （MSR） were computed and used as comparison criteria. The results showed that the least median of squares （LMS） and least trimmed squares （LTS） were the most successful methods for data that included leverage points, masking and swamping effects or critical and concentrated outliers. We recommend using LMS and LTS as diagnostic tools to classify outliers, because they remain robust even when applied to models that are heavily contaminated or that have a complicated structure of outliers.  相似文献   

Review: Research progress on Fabry-Perot resonator antenna     

Zhen-guo LIU  Zhi-chen GE  Xi-yuan CHEN 《浙江大学学报(A卷英文版)》2009,10(4)

The Fabry-Perot resonator (FPR) antenna has found wide applications in microwave and millimeter waves and recently attracted considerable interest, in this paper, a summary of planar and cylindrical structures, analytic models and research development is presented, and a comparison between these structures and analytic models is made, showing that such analytic models as the FP cavity mode, electromagnetic band gap (EBG) defect mode, transmission line mode, and leaky-wave mode are consistent when applied to analyze this type of resonator antenna. Some interesting topics under recent research, including dual or multi-band, improvement of gain bandwidth, low profile and beam control, are surveyed.  相似文献   

NURBS curve blending using extension     

Yong-jin Liu  Rong-qi Qiu  Xiao-hui Liang 《浙江大学学报(A卷英文版)》2009,10(4):570-576

Curve and surface blending is an important operation in CAD systems, in which a non-uniform rational B-spline （NURBS） has been used as the de facto standard. In local comer blending, two curves intersecting at that comer are first made disjoint, and then the third blending curve is added-in to smoothly join the two curves with G^1- or G^2-continuity. In this paper we present a study to solve the joint problem based on curve extension. The following nice properties of this extension algorithm are exploited in depth： （1） The parameterization of the original shapes does not change; （2） No additional fragments are created. Various examples are presented to demonstrate that our solution is simple and efficient.  相似文献   

从西方程序公正的演进逻辑看我国程序公正的制度建设   总被引：1，自引：0，他引：1  

何正平  胡燕 《四川师范大学学报(社会科学版)》2009,36(2):54-59

本文深入阐析了程序公正发展的源流及其深刻内涵,通过梳理程序公正的发展脉络,认为程序公正的发展演进有其内在逻辑规律,并追循其逻辑轨迹提出了程序公正的标准体系,进而为我国程序公正的制度建设提出切实可行的路径选择和制度措施.  相似文献   

和谐社会视角下教育公正发挥的作用及实现途径探析   总被引：1，自引：1，他引：0  

巩茹敏 《现代远距离教育》2009,(2):23-25

构建社会主义和谐社会,是我们党的奋斗目标,也是中国人民的美好追求。本文详细阐述了教育公正在构建和谐社会中发挥的重要作用,在此基础上,利用现代远程教育手段和技术,共享优质教育资源,提高受教育者素质,促进和实现教育公正。  相似文献