3G今年要发牌 手机电视跟上来

“发展3G的条件已经具备,运营企业要做好充分准备”,在2月28日召开的中国电信业发展与政策通报会上,信息产业部副部长娄勤俭明确要求电信运营商要看清市场趋势,做好业务开发、市场培育等方面的工作。在此之前,信息产业部也提出要推动电信运营商向信息服务业转型,内涵就是从传统的语音服务向数据多媒体及综合信息服务拓展。在这样的背景下,发展3G无疑是未来电信转型的重点,而手机电视业务,则可能是3G的重中之重。     

H.264在IPTV系统中的应用

H.264的核心竞争力I P T V系统中所采用的编码协议有多种。在国内,目前主要有MPEG-4、H.264、AVS等。其中,H.264是电信运营商非常看好的一种协议,有望被广泛应用于视频节目的传送过程中。H.264是ITU-T的VCEG(视频编码专家组)和ISO/IEC的MPEG(活动图像编码专家组)的联合视频组(JVT:JointVideoTeam)开发的数字视频编码标准,它既是ITU-T的H.264,又是ISO/IEC的MPEG-4的第十部分。H.264最具价值之处无疑是更高效率的数据压缩比。压缩技术的基本原理就是将视频文件中的非重要信息过滤,使数据能更快地在网络中传输。在同等图…     

Effect of low temperature aging on microstructure and mechanical properties of super-high strength aluminum alloy

The effects of heat treatment on the microstructure and mechanical properties of two alloys, namely Al- 12.2%Zn-2.48%Cu-2.0%Mg-0.15%Zr-0. 166%Ag（alloy 1）, and Al-9.99%Zn-1.72%Cu-2.5%Mg-0.13%Zr（alloy 2） were investigated. The results show that low temperature aging after promotive solution treatment can increase elongation without the loss of strength for the studied alloys. The optimum aging treatment （T6） for alloy 1 and alloy 2 is 100 ℃/80 h and 100 ℃/48 h, respectively. Compared with other heat treatment alloys, alloy 1 and alloy 2 show super-high tensile strength up to 753 MPa and 788 MPa, remaining 9.3% and 9.7% elongation under T6 condition, respectively. During aging, trace addition of Ag enhances the formations of GP zone and metastable phase, and stabilizes GP zone and metastable phase to a higher temperature. Trace addition of Ag prolongs the aging time of reaching the peak strength and delays over-aging condition of the alloy. However, trace addition of Ag promotes the formation of coarse constituent in the alloy and consumes hardening alloying elements of Zn and Mg. Moreover, the addition of the transition element Zr in 7000 series super-high alloy forms incoherent Al3 Zr dispersoid which can serve as nucleation sites for nonuniform precipitation of η phase during aging process. The higher the aging temperature, the greater the tendency for nonuniform precipitation of η phase.     

Optimization of extraction and determination of emodin from Polygonum cuspidatum Sieb. et Zucc. products by HPLC-DAD

A uniform experimental design procedure was used to investigate the effects of some operating parameters on the extraction of emodin from Polygonum cuspidatum Sieb. et Zucc. products. Variables tested were volume ratio of material to solvent, size of material, extraction time and temperature and composition of extraction solvent （mixtures of acetone-water）. Each variable was tested at seven levels; 7 experiments were performed in random order. Analyses of the extracts were performed by high-performance liquid chromatography with diode array detection（HPLC-DAD）. Analytical responses were processed by using a forward regression analysis, in order to find polynomial function describing the relationship between variables and responses. For all the analytes the experimental conditions for providing the highest extraction yield inside the experimental domain considered were found. Finally, a simple, rapid and accurate analytical method was developed for the determination of emodin by high performance liquid chromatography. The separation is achieved within 25 rain on an ODS column using methanol and water as gradient mobiles. Emodin can be quantified by using external standard method detecting at 436 nm. Good linearity is obtained with correlation coefficient exceeding 0.9986 and the detection limit and the quantification limit are 1.53 and 3.23 mg/L respectively. This method shows good reproducibility for the quantification of the emodin with intra-day and inter-day relative standard deviation less than 2.3% and 5.6% respectively. Under optimized extraction conditions, the recovery of the standard is 96.5%. The validated method is successfully applied to quantify the emodin in seven Polygonum cuspidatum sieb. Et zucc. products, which provided an idea for the pre-treatment of determination of active compounds in traditional Chinese medicines.     

基于UML／Power Designer的信息系统分析方法

本文主要针对基于UML／Power Designer的信息系统分析方法进行研究：在基于面向对象UML的平台上，以CRM客户关系管理信息系统为研究对象，对其需求模型。总体设计模型和详细设计模型进行了分析设计，并采用了基于UML建模语言的CASE工具Power Designer进行进一步的辅助分析和设计，得到了CRM的相关实现模型。本文的研究对管理信息系统的分析方法提供了一种实用的技术途径。     

戴尔推出最高性能PowerEdge服务器

戴尔近日宣布面向国内市场推出采用英特尔最高性能至强5100系列（即Woodcrest）处理器的第九代PowerEdge服务器——再度体现戴尔致力降低数据中心复杂度的承诺。[编者按]     

基于WEB的教材管理系统的设计与实现

文章通过对教材管理过程的分析,提出了基于WEB的网上教材管理系统的设计思想,阐述了该系统的功能和相关的技术。     

U型管地热换热器中介质轴向温度的数学模型

基于能量平衡原理,经过分析与推导,得出了流体在U型埋管换热器流动过程中无量纲温度沿无量纲深度变化的关系式.根据埋管换热器的入口温度,能更为精确地求出流体的出口温度,为进一步分析影响地热换热器性能的因素提供了条件.     

Q235钢筋母材冷作硬化试验研究

建筑工程上采用冷轧加肋的方法使Q235钢筋母材强度得到提高，以达到预制构件的应用要求，生产的预制构件等级愈高，其中的冷轧带肋钢筋的强度也就要求愈高，通常需要更换钢筋母材及相应,为此，利用前期扭转冷作硬化的研究成果，对工程中普遍使用的Q235钢筋母材加肋冷作硬化问题进行了试验研究，得出了在不改变Q235钢筋母材情况下，只要在工序中充分考虑到预扭转冷作硬化的影响，就可以使冷轧带肋钢筋达到更高的等级，工程意义显著。     

科研项目管理信息处理技术的研究

利用常用办公软件Office 2000的家族组员Access 2000建立科研项目信息数据库,发挥软件Office 2000本身的强大功能,使管理系统具有通用性好、功能强大、易于操作等特点,能进行快速查询、报表、网上交流等,从而实现对科研项目全过程的信息化管理.