一类不确定分段线性系统的保性能控制

对于不确定分段线性系统稳定性分析以及控制器的优化设计问题,给出了一种基于分段二次李雅普诺夫函数的求解方法。运用这种方法,系统二次型保性能控制器设计将转化成求解一组线性矩阵不等式组的可解性问题,可以用软件较方便的求得结果。     

生物系统建模中参数估计的测量集选择——以信号转导通路模型研究为例(英文)

生物系统模型通常具有很高的维数,测量数据不完备、易受噪声污染,而且生物实验成本高,所以参数估计已经成为生物系统建模的挑战性问题之一.参数的精确估计取决于测量数据的数量和质量,因此,通过优化实验设计确定如何采集测量数据是非常重要的.针对动态系统的参数估计问题,尤其是生物反应系统,提出了一种确定富含信息的测量集选择方法,通过从设计的实验中获得测量数据,以最佳的统计质量估计系统的未知参数.该方法首先利用矩阵论的系统分析来确定估计参数所必需的测量状态的数目,再通过基于Fisher信息阵的优化实验设计决定每个测量状态的优先等级.最后,以信号转导通路模型为例,解释了该方法的优势和适用性.     

三环喹唑啉及其衍生物的电荷传输性质研究

使用电荷传输的半经典模型Marcus和密度泛函理论(DFT)方法,在B3LYP/631G**水平上对三环喹唑啉及其衍生物分子的电荷传输性质进行理论研究.结果显示,硫甲基取代分子的空穴传输和电子传输速率常数相当,速率常数为1.77×1012 s-1,预示可设计成空穴传输和电子传输材料.羟基取代、烷氧基取代、巯基取代分子的空穴传输载流子迁移率μ+与速率常数k+,比苯并菲(TOH)和六氮杂苯并菲(HATOH)液晶分子约大1个数量级,比其电子传输大近2个数量级,显示选择三环喹唑啉为刚性中心核合成盘状液晶半导体材料     

山区河流河床结构对推移质输沙率的影响

河床结构是山区河流河床在洪水过程中达到较强阻力及较高河床稳定性时床面大颗粒的组合,对山区河流的推移质输沙起重要影响．引入河床结构强度S对山区河流河床结构进行定量化研究,使用河床结构测量设备对河床强度进行测量,采用类似于坑测法的子母双槽进行推移质输沙率实测,对云南小江流域的15条主要支流河床结构及推移质输沙进行野外实测,发现推移质输沙强度至少受单宽水流能量与河床结构发育程度共同影响,在同等级水流能量条件下,河床结构的发育程度越高的河流（或河段）其推移质输沙强度越小,河床强度值越小的河流（或河段）推移质输沙强度越大．单宽水流能量小于50kg／（m·S）、河床结构强度大于0.35时,推移质输沙率接近零．     

一类高阶次随机非线性系统的状态反馈镇定

研究一类高阶随机非线性系统状态反馈镇定问题.结合反推技术和加权积分技术,通过适当地选取Lyapunov函数和设计参数,给出了一个自适应状态反馈控制器的设计过程.所设计的控制器保证了闭环系统是依概率全局稳定的.     

空调水系统变频运行对各子系统能效的影响分析

对福州市某办公建筑空调水系统变频改造的节能效果及其对空调各子系统能效的影响进行实测和分析.结果表明,变频改造节能效果明显,在空调日均负荷率约为50%的情况下,整个水输送系统节电率达48.8%,变频节能改造使整个空调系统的能耗下降18.2%,空调水系统能效得到显著提高,对冷水机组的运行能效比没有明显影响,但会使空调末端能效降低.     

利用质疑改进教育信息技术标准化活动：更多关注其范围和原理

标准化对于开发“学习、教育和培训”（LET）中使用的“信息通信技术”（ICT）有重要意义,但ICT的利益相关者（stakeholders）却往往质疑标准化活动.本文提出,利用这种质疑形式来分析和改进当前的ICT标准化活动.讨论了由各方参与产生ICT标准过程的模型框架,其中一系列“为什么”的问题（Why questions）起着重要作用.讨论主要围绕两个方面：一是标准及相关事物在发展过程中的管理与核准;二是如何识别LET中的相关问题与可用来解决这些问题的创新技术.给出了两个事例： 一个是对“内容共享对象参考模型”（Sharable Content Object Reference Model, SCORM）的质疑,这能帮助理解该模型;特别是对其适用范围（scope）的质疑而使该模型更完善.另一个是对制定“新工作条款”（New Work Items）必要性的质疑,使人们认识到澄清标准中有关技术原理（rationale）的重要性.     

Review of wideband MIMO channel measurement and modeling for IMT-Advanced systems

In October 2005,the next generation mobile communication system was officially named as the International Mobile Telecommunications-Advanced(IMT-Advanced) by the ITU Radiocommunication Sector(ITU-R).Wideband multiple input and multiple output(MIMO) channel models in multiple propagation environments are fundamental for IMT-Advanced systems and such research has been initiated since 2003.The research challenges come from the fact that the wider bandwidth(20-100 MHz) and the advanced multiple antenna technology have been proposed for the IMT-Advanced system,thus leading to higher sampling rates and multiple spatial propagation channels.In this review,four aspects of wideband MIMO channel measurement and modeling are discussed:(1) radio channel measurement procedure and equipment;(2) large scale fading models;(3) small scale fading models;and(4) MIMO channel models.In particular,the large scale fading affected by the carrier frequency is investigated for urban macrocells and it shows that the higher carrier frequency results in greater loss for non-line-of-sight(NLoS) conditions in the cities of China,for which the frequency dependent factor is 32.1.Moreover,the dense and the obviously higher buildings also lead to a larger angle spread(AS) of both the angle of arrival and angle of departure in urban macrocell scenarios.The results indicate that there is the potential to explore the MIMO technique for an IMT-Advanced system with larger ASs,which would lead to the high system capacity.The progress on MIMO models is described and some methods for simplifying geometry-based stochastic channel models(GBSM) are proposed.Finally future research topics on channel measurement and modeling are identified.     

Photoresponse and carrier transport of protocrystalline silicon multilayer films

Alternating multilayer films of hydrogen diluted hydrogenated protocrystalline silicon (pc-Si:H) were prepared using a plasma-enhanced chemical vapor deposition technique.The microstructure of the deposited films and photoresponse characteristics of their Schottky diode structures were investigated by Raman scattering spectroscopy,Fourier transform infrared spectroscopy and photocurrent spectra.Microstructure and optical absorption analyses suggest that the prepared films were pc-Si:H multilayer films with a two-phase structure of silicon nanocrystals (NCs) and its amorphous counterpart and the band gap of the films showed a decreasing trend with increasing crystalline fraction.Photocurrent measurement revealed that silicon NCs facilitate the spatial separation of photo-generated carriers,effectively reduce the non-radiative recombination rate,and induce a photoresponse peak value shift towards the short-wavelength side with increasing crystallinity.However,the carrier traps near the surface defects of silicon NCs and their spatial carrier confinement result in a significant reduction of the diode photoresponse in the longwavelength region.An enhancement of the photoresponse from 350 to 1000 nm was observed when applying an increased bias voltage in the diode,showing a favorable carrier transport and an effective collection of photo-generated carriers was achieved.Both the spatial separation of the restricted electron-hole pairs in silicon NCs and the de-trapping of the carriers at their interface defects are responsible for the red-shift in photoresponse spectra and enhancement of external quantum efficiency.The results provide fundamental data for the carrier transport control of high-efficiency pc-Si:H solar cells.     

基于MATLAB的“信号与系统”实验教学改革

本文主要针对传统＂信号与系统＂硬件实验教学中存在的缺点,改革实验教学方法和教学手段,加强MATLAB软件仿真实验的项目。以周期性矩形波频谱分析的仿真实验项目为例,说明便捷、直观的仿真实验能够帮助学生理解抽象的概念、理论和分析方法,有效地提高了实验教学质量。