用光学分数Fourier变换的方法测定自仿射分形的Hurst指数

采用光学分数Fourier变换的方法从实验上测定了规则自仿射分形图形的Hurst指数, 并将此方法推广到无规自仿射分形图形, 测定了几种无规自仿射分形图形的Hurst指数. 实验结果证实了光学分数Fourier变换方法分析自仿射分形图形的可行性.     

光纤Bragg光栅横向负载敏感特性的实验研究

对光纤Bragg光栅的横向负载敏感特性进行了实验研究 .利用光纤中的应力双折射效应 ,使光纤光栅横向受压 ,产生谐振波长分裂 .通过实验研究得到了良好的谐振波长分裂与横向负载的关系曲线 ;在此基础上 ,进行了波长寻址的多点横向负载分布测量的初步探索 ,完成了两光栅同时传感的实验研究 .     

利用信号与系统概念分析线天线的互阻抗

基于信号与系统理论 ,并利用数字信号处理技术 ,提出了一种分析线天线互阻抗的新方法 .在这种方法中 ,借用信号与系统的概念 ,将天线阵中天线单元的电流视为激励信号 ,将天线阵的空间结构视为系统函数 (或传递函数 ) ,而将单元天线间的互阻抗 (或其它电磁特性 )视为整个系统的响应 .通过这种等效 ,可将天线阵中天线单元间相互耦合看作信号与系统中的系统响应 ,进而可利用数字信号处理方法进行分析 .最后给出了利用该方法计算对称振子天线互阻抗的实例 ,计算结果证明了该方法的有效性 .     

无线局域网中AP和WB系统的设计

本论文主要研究了802.11b的无线局域网的接入点(AP)和网桥(WB)的设计方案,并实现了协议规定的主要业务.     

现代交流调速技术的发展与现状

脉宽调制变频技术应用于交流调速后,现代交流调速技术的发展和实用化走上了新的道路.本文综述了交流调速技术的发展和调速系统的基本类型,展望了它未来的发展方向.     

Inducing dopaminergic differentiation of expanded rat mesencephalic neural stem cells by ascorbic acid in vitro

Ascorbic acid (AA) induced differentiation of neural stem cells (NSCs) into dopaminergic (DAergic) neurons is reported.NSCs derived from rat mesencephalon were maintained and expanded in a defined medium containing mitogens of basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF).Compared with the control, ascorbic acid treatment led to more DAergic neuronal differentiation as indicated by the expression of tyrosine hydroxylase (TH) and dopamine transporter (DAT), which are specific markers of dopamine neurons.AA induction also enhanced expression of Nurr1 and Shh.PD98059, an inhibitor of mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) pathway, could block AA-induced Nurr1, TH and DAT mRNA expression.The results might suggest a new strategy to provide enough dopaminergic cells for the therapy of Parkinson's disease (PD), and Nurr1 and ERK signaling pathway might participate in the AA-induced DAergic differentiation.     

Biochemical characterization of the protein encoded by rice osRACD gene

A recombinant plasmid pET-racd was first constructed by cloning osRACD,the development-regulating gene that controls photoperiod fertility transformation in the photoperiod sensitive genic male sterile rice Nongken 58S,into a prokaryote expression vector pET28a(+).It was then transformed into E.Coli BL-21.Cutting with thrombin of the fusion protein extracted from transformants and PAGE separation yielded pure osRACD protein,which was further concentrated using ultrafiltration and renatured using glutathione oxidation/reduction refolding system for later functional study.As demonstrated by in vitro functional assay,the osRACD protein expressed in E.Coli B-21 shows remarkable activity in binding GTP specifically and hydrolyzing it.     

Poly(dimethylsiloxane) based microchip for DNA electrophoresis

A novel poly(dimethylsiloxane)(PDMS) -based microchip for DNA separation through electrophoresis has been developed using a micro-electro-mechanical-system(MEMS) technology. Unlike previous hybrid PDMS microchip, one PDMS film is first created on glass support by pressing method in our microchip. Thus, increased band-broadening phenomena, arising from the material nonuniformity at the walls of microchannel, can be avoided in electrophoresis process. A low-viscosity hydroxypropylmethylcellulose-100 (HPMC-100) is used as the separation medium for fluorescent intercalator-labeled double-stranded DNA (dsDNA) fragments. Mannitol is introduced to PDMS-based microchip as a separation medium additive to enhance separation efficiency. At applied electric field strength of 150 V/cm, excellent separations of the PCR marker could be achieved with an effective separation distance of 25mm .     

Relationship between the exposure dose of high intensity focused ultrasound and the heated necrosis element

Heated necrosis element of tissues is the basis for treating tumor by high intensity focused ultrasound (HIFU), so study on the relationship between the HIFU exposure dose and the heated necrosis element of tissues is of great significance for both HIFU clinical applications and basic research. Using Pennes and Rayleigh formulae the relationship between the exposure dose of an annular focused transducer and the heated necrosis element (I.e. Biological focused region) in a bovine liver in vitro at a depth of 2 cm is simulated in an exposure dose range with radiation sound intensity of 7000～25400 W/cm2 and exposure time of 0～20 s. The theoretical results appear to be in quite good agreement with the experimental ones. It is shown that on the basis of existing theories the heated necrosis element produced by HIFU exposure can be predicted. The deviation of the theory from the experiments under higher exposure dose has also been discussed.     

补零对有限长序列频谱及DFT的影响

补零是DFT中经常采用的方法，本文具体分析了零的不同位置对序列频谱及DFT产生不同的影响，及补零后DFT的计算公式，同时不仅从理论上证明而且利用MATLAB更加直观地说明补零只能使片列的频谱变得细致，但不能提高序列的频率分辨率，只有采集更多的有效数据，才能得到序列的高分辨率频谱。