基于SIP的嵌入式网络可视电话的研究与实现

SIP(Session Initiation Protocol)是下一代网络(NGN)的核心控制协议之一。文章介绍了以SIP作为基础的嵌入式网络可视电话的结构设计,并提出了实验模型。

GSMBE外延生长GeSi/Sip-n异质结二极管

于2010-11-23批量导入

SIP在视频监控系统中的应用

SIP协议是由IETF提出的应用层信令协议，用来建立、修改和终止多方参与的多媒体会话进程，具有很好的可扩展性、灵活性、互操作性和可重用性。在视频监控系统中使用SIP协议实现呼叫处理过程，可以使视频监控系统具有更好的兼容性和扩展能力。本文以网络视频监控系统为背景，介绍了视频监控系统的功能划分和SIP协议的相关内容，提出了基于SIP协议的视频监控呼叫处理方案，设计了支持节点注册、呼叫处理、用户认证、状态查询等功能的呼叫处理子系统，并且在视频监控系统中实现。为了满足运营级视频监控系统对呼叫处理能力的高要求，设计并实现了基于分布式系统的高性能SIP服务器，在集群上完成对高性能SIP服务器的性能测试。本文工作的主要贡献是：在视频监控系统中设计并实现了基于SIP协议的呼叫处理子系统；在分布式系统上设计并实现了具有高呼叫处理能力的高性能SIP服务器。

Observation of photogalvanic current for interband absorption in InN films at room temperature

The linear and circular photogalvanic effects have been observed in undoped InN films for the interband transition by irradiation of 1060 nm laser at room temperature. The spin polarized photocurrent depends on the degree of polarization, and changes its sip when the radiation helicity changes from left-handed to right-handed. This result indicates the sizeable spin-orbit interaction in the InN epitaxial layer and provides an effective method to generate spin polarized photocurrent and to detect spin-splitting effect in semiconductors with promising applications on spintronics.

Surface Initiated Polymerization from Substrates of Low Initiator Density and Its Applications in Biosensors

Surface initiated polymerization (SIP) has become an attractive method for tailoring physical and chemical properties of surfaces for a broad range of applications. Most of those application relied on the merit of a high density coating. In this study we explored a long overlooked field of SIP. SIP from substrates of low initiator density. We combined ellipsometry with AFM to investigate the effect of initiatior density and polymerization time on the morphology of polymer coatings. In addition, we carefully adjusted the nanoscale separation of polymer chains to achieve a balance between nonfouling and immobilization capacities. We further tested the performance of those coating on various biosensors, such as quartz crystal microbalance, surface plasmon resonance, and protein microarrays. The optimized matrices enhanced the performance of those biosensors. This report shall encourage researches to explore new frontiers in SIP that go beyond polymer brushes.

Quartz crystal microbalance study of the kinetics of surface initiated polymerization

Surface initiated polymerization (SIP) is a valuable tool in synthesizing functional polymer brushes, yet the kinetic understanding of SIP lags behind the development of its application. We apply quartz crystal microbalance (QCM) to address two issues that are not fully addressed yet play a central role in the rational design of functional polymer brushes, namely quantitative determination of the kinetics and the initiator efficiency (IE) of SIP. SIP are monitored online using QCM. Two quantitative frequency-thickness (f-T) relations make the direct determination and comparison of the rate of polymerization possible even for different monomers. Based on the bi-termination model, the kinetics of SIP is simply described by two variables, which are related to two polymerization constants, namely a = 1/(k (p,s,app)-[M][R center dot](0)) and b = k (t,s,app)/(k (p,s,app)[M]). Factors that could alter the kinetics of SIP are studied, including (i) the molecular weight of monomers, (ii) the solvent used, (iii) the initial density of the initiator, (iv) the concentration of monomer, [M], and (v) the catalyst system (ratio among the ingredients, metal, ligands, and additives). The dynamic nature of IE is also described by these two variables, IE = a/(a + bt). Instead of the molecular weight and the polydispersity, we suggest that film thickness, the two kinetic parameters (a and b), and the initial density of the initiator and IE be the parameters that characterize ultra-thin polymer brushes. Besides the kinetics study of SIP, the reported method has many other applications, for example, in the fast screening of catalyst system for SIP and other polymerization systems.

Stable Isotope Probing:Linking Functional Activity to Specific Members of Microbial Communities

Linking organisms or groups of organisms to specific functions within natural environments is a fundamental challenge in microbial ecology. Advances in technology for manipulating and analyzing nucleic acids have made it possible to characterize the members of microbial communities without the intervention of laboratory culturing. Results from such studies have shown that the vast majority of soil organisms have never been cultured, highlighting the risks of culture-based approaches in community analysis. The development of culture-independent techniques for following the flow of substrates through microbial communities therefore represents an important advance. These techniques, collectively known as stable isotope probing (SIP), involve introducing a stable isotope-labeled substrate into a microbial community and following the fate of the substrate by extracting diagnostic molecular species such as fatty acids and nucleic acids from the community and determining which specific molecules have incorporated the isotope. The molecules in which the isotope label appears provide identifying information about the organism that incorporated the substrate. Stable isotope probing allows direct observations of substrate assimilation in minimally disturbed communities, and thus represents an exciting new tool for linking microbial identity and function. The use of lipids or nucleic acids as the diagnostic molecule brings different strengths and weaknesses to the experimental approach, and necessitates the use of significantly different instrumentation and analytical techniques. This short review provides an overview of the lipid and nucleic acid approaches, discusses their strengths and weaknesses, gives examples of applications in various settings, and looks at prospects for the future of SIP technology.