云环境下P2P流媒体传输关键技术

随着流媒体应用需求的日益增加,不断改进和完善现有流媒体系统性能势在必行,将云计算引入流媒体系统成为未来流媒体系统的一大趋势．本文简单分析了云计算、CDN（ContentDeliveryNetwork）St]P2P（PeertoPeer）网络的优缺点和研究现状．主要讨论并分析了云环境下的P2P流媒体传输系统所面临的带宽问题、流媒体数据处理、服务质量问题和系统中的关键技术——虚拟化技术、存储管理技术、调度技术和复制技术．此外,从搭建云计算实验环境角度。本文列举了目前比较流行的5种仿真实验手段．     

古方“四物汤”治疗银屑病计算机网络药理学研究

采用化学空间、分子对接、网络技术等计算机药理学方法,研究古方"四物汤"治疗银屑病的药理学作用机制。结果表明:(1)四物汤中分子在化学空间上具有类药性质;(2)运用分子对接方法将四物汤中295个化合物与银屑病51个公认的靶标相互联系,分析四物汤治疗银屑病的可能作用机理及活性分子、有效成分群,揭示了四物汤多靶点、多药物、多途径的分子作用机制;(3)通过复杂网络分析探索四物汤治疗银屑病的配伍规律。结论:四物汤具有较好口服吸收性质:通过分子-靶标,靶标-靶标和分子-分子的网络分析推测四物汤主要是通过金属蛋白酶、表皮生长因子受体、一氧化氮合酶等抗银屑病表皮增殖、血管生成及异常的免疫调节机制:当归在四物汤治疗银屑病中发挥重要的作用。     

一种以人为中心的智能化城市交通综合监控方法

随着我国城市化的进程、汽车行业的蓬勃发展和人民生活水平的日益提高,行驶在城市道路上的车辆越来越多,造成了一系列的问题,如何更加高效地监控城市交通,近年来已经成为了研究重点。研究表明,交通监控员通过远程调阅路面监控录像的模式,实施有效监控的推荐显示屏幕个数只有4个,因此,传统的交通监控模式将导致很高的交通事件漏报率和误报率。针对这些问题,提出了一个以人为中心的智能化城市交通监控方法,主要特点包括:1．采用眼球追踪技术,对交通监控员的眼球活动状态进行跟踪和分析,根据已建立的事件模型和判定模型进行快速屏幕切换操作;2．通过结合RFID技术,对道路上车辆的RFID标签进行追踪和统计分析,根据模型进行交通事件快速预警和关联分析。该方法的使用比较简单,能有效提升交通监控员的交通事件发现率。     

Nanoparticle-based lift-off technique for ultra-thin nanoporous film preparation

Ultra-thin membrane with nanoscale through hole has great potential in biomedical applications, where precise controllability of porosity, pore size and film thickness is urgently required. The present work proposed a cost-effective way to prepare the ultra-thin nanoporous film with a promising controllability. Monodispersed nanoparticle, rather than photoresist, is used as the sacrificial material for this new lift-off process. By releasing the particles, holes can be achieved with predeter-mined characters. A 110 nm-thick nanoporous aluminum film with well-controlled pore＇s diameter was successfully fabricated to validate the technique. The technique has wider process window and better applicability than other nanofabrication methods.     

Optimal design and motion control of biomimetic robotic fish

This paper is concerned with the design, optimization, and motion control of a radiocontrolled, multi-link, free-swimming biomimetic robotic fish based on an optimized kinematic and dynamic model of fish swimming. The performance of the robotic fish is determined by both the fish＇s morphological characteristics and kinematic parameters. By applying ichthyologic theories of propulsion, a design framework that takes into consideration both mechatronic constraints in physical realization and feasibility of control methods is presented, under which a multiple linked robotic fish that integrates both the carangiform and anguilliform swimming modes can be easily developed. Taking account of both theoretic hydrodynamic issues and practical problems in engineering realization, the optimal link-lengthratios are numerically calculated by an improved constrained cyclic variable method, which are successfully applied to a series of real robotic fishes. The rhythmic movements of swimming are driven by a central pattern generator （CPG） based on nonlinear oscillations, and up-and-down motion by regulating the rotating angle of pectoral fins. The experimental results verify that the presented scheme and method are effective in design and implementation.     

A new similarity computing method based on concept similarity in Chinese text processing

The paper proposes a new text similarity computing method based on concept similarity in Chinese text processing. The new method converts text to words vector space model at first, and then splits words into a set of concepts. Through computing the inner products between concepts, it obtains the similarity between words. The new method computes the similarity of text based on the similarity of words at last. The contributions of the paper include： 1） propose a new computing formula between words; 2） propose a new text similarity computing method based on words similarity; 3） successfully use the method in the application of similarity computing of WEB news; and 4） prove the validity of the method through extensive experiments.     

Spatial and temporal variations of AOD over land at the global scale

Spatial and temporal variations of aerosol optical depth (AOD) over land at the global scale were investigated using the MODIS C005 data set from July 2002 to June 2007. Global average AOD, AOD_c (coarse mode AOD) and AOD_f (fine mode AOD) were mapped and analysed. It was found that AOD in Asia and Africa is nearly 2 times higher than that in South America, Europe and North America. A high level of η (fine model fraction (FMF) of AOD) was recorded where AOD is relatively low. Meanwhile, low η (0.05–0.3) was observed where AOD is extremely high. It suggests that coarse particles contribute much more than fine particles to global AOD over land. High AOD level in Nigeria and north India is dominated by coarse particles due to dust events. The average AOD in China (～0.7) is almost 50% higher than that in India (～0.55) and nearly 2–3 times higher than that in North America and Western Europe (0.2–0.3), due to spring dust in the west and intensive anthropogenic activities in the eastern part of China. Overall, the average AOD in the USA was limited in a relatively low level. At the same time, AOD in the western part of the USA (AOD_c?=?0.28 and AOD_f?=?0.06) is much higher than that in the east (AOD_c?=?0.06 and AOD_f?=?0.17). The annual cycle of global mean AOD showed a sinusoidal shape, where peaks occur during June–August and the lowest AODs appear in November–January. The peak month, peak value and possible sources for six major continents are Asia (April, AOD_peak?=?0.31, dust; June–July, AOD_peak?=?0.27, secondary aerosol), Africa (March, AOD_peak?=?0.28, dust; August, AOD_peak?=?0.28, wildfires), South America (September, AOD_peak?=?0.31, wildfires), North America (May–July, AOD_peak?=?0.18, dust and wildfires), Europe (March–April, AOD_peak?=?0.18, secondary aerosols), Oceania (December–January, AOD_peak?=?0.09, secondary aerosols). The inter-annual variation of AOD was insignificant at the global scale. However, the inter-annual variations at the regional scale were substantial. The abnormal peak of AOD during summer 2003 was probably due to dry and hot weather and intensive wildfires.     

An object-based analysis filtering algorithm for airborne laser scanning

Ground filtering is a key process to derive digital terrain models from airborne laser scanning data. Although many methods have been developed to tackle the filtering problem, it has not been fully solved so far. Current algorithms mainly focus on neighbourhood-based or directional filtering approaches. A new object-based analysis (OBA) method is proposed in this article. First, a grid index algorithm accelerates access to unorganized cloud points. Then, a segmentation algorithm is deployed based on the index, and objects are obtained. A filtering logic that utilizes the objects' characteristics is designed. Following this, the performance of the method is comprehensively tested using publicly available International Society for Photogrammetry and Remote Sensing (ISPRS) test data sets for nine urban and six rural regions, and the results are compared to those of eight other algorithms. The OBA method implemented in this article reveals good results without scene-wise optimization of the parameters, and it ranks third or fourth in most of the cases.     

Evaluation of MODIS derived perpendicular drought index for estimation of surface dryness over northwestern China

In this paper, drought status of northwestern China is evaluated using the Terra–Moderate Resolution Imaging Spectroradiometer (MODIS) data with a newly developed method called perpendicular drought index (PDI), which is defined as a line segment that is parallel with the soil line and perpendicular to the normal line of soil line intersecting the coordinate origin in the two‐dimensional scatter plot of red against near infrared (NIR) wavelength reflectance. To validate the PDI in macroscale applications, quantitative evaluation of drought conditions in Ningxia, Northwestern China is carried out by comparing the PDI with one of the well‐known drought indexes, namely, temperature‐vegetation index (TVX). Linear regression between ground‐measured soil moisture data and the PDI and the TVX was made. Results show that satellite based PDI and TVX has significant correlation with 0–20 cm averaged soil moisture obtained over the meteorological observing stations across the whole study area. The highest correlation of R ² = 0.48 for the PDI and R ² = 0.40 for the TVX is obtained when compared with average soil moisture from 0 to 20 cm soil depth. According to the drought critical values defined by soil hydrologic parameters including soil moisture, wilting coefficient and field moisture capacity, the PDI based drought guidelines are established, and then the drought status in the study area is evaluated using the PDI. It is evident from the results showing the spatial distribution of drought in northwestern China that the PDI is highly accordant with field drought status.     

仿真优化:理论与应用综述

对于现实中的复杂系统, 仿真优化是一种非常强大的分析和优化工具. 本文对仿真优化领域的相关理论与方法进行了介绍与回顾. 根据系统中决策变量的性质的不同(连续或者离散变量), 我们对仿真优化问题进行了分类. 而且我们对仿真优化领域中的重要技术进行了详细地讨论, 包括它们的原理、使用方法、优势和劣势以及应用等. 关于仿真优化领域未来的研究方向, 我们也进行了相关论述.