非自治动力系统中周期跟踪和极限跟踪的研究

根据自治动力系统中周期跟踪性和极限跟踪性的定义,将其引入到非自治动力系统。研究了非自治动力系统中周期跟踪性和极限跟踪性的动力学性质,得到：(1)若F={fi}i=0∞拓扑共轭于G={gi}i=0∞,则F具有周期跟踪性当且仅当G具有周期跟踪性;(2)若F={fi}i=0∞拓扑共轭于G={gi}i=0∞,则F具有极限跟踪性当且仅当G具有极限跟踪性;(3)若乘积系统(X×Y,F×G)具有周期跟踪性,则(X,F)和(Y,G)具有周期跟踪性。 以上结论对非自治动力系统中跟踪性的发展有一定的促进作用。     

多源异构土地基础数据一体化管理检索方法研究

为了从多源异构的复杂土地基础数据中快速准确地提取用户所需信息,提出了基于元数据的一体化管理检索方法.在元数据信息提取、元数据加权索引、实体同义词扩展检索3个环节中,结合土地领域专业知识和用户实际需求,设计和开发了共享元数据表结构、加权元数据中字段相对重要性和信息熵因子,构建地名实体和专题数据层实体同义词库,并集成到包括中文分词、实体识别、同义词扩展、索引检索和相似度计算的一体化管理检索框架中,解决了多源异构土地基础数据统一管理和精确检索的问题.实践表明,该方法较传统的通用信息检索方法具有更好的适用性和更高的准确率.     

单螺杆发动机在不同进气压力下的实验研究

为了改善原有气动发动机的缺陷,提出了一种新型的气动发动机—单螺杆膨胀机,其具有容积效率高、结构控制简单、噪声低、寿命长等特点。为了测试单螺杆膨胀机的各项性能,建立了单螺杆膨胀机压缩空气动力系统,对膨胀机在不同进气压力下进行了实验研究.实验结果表明:随着进气压力升高膨胀机输出功率及总效率升高,而气耗率下降,即膨胀机在高进气压力下具有较好的动力性能、经济性能和较高的总效率。     

清代绿色蟠龙邮票印刷材料无损分析

利用超景深三维视频显微镜, 激光显微共聚焦拉曼光谱仪和扫描电镜-能谱仪对一张清代绿色蟠龙邮票样品的纸张, 油墨等印刷材料进行无损分析。结果表明,该样票采用手工雕刻凹版印刷,所用承印物为长纤维机制纸,未经过涂布, 无水印, 背胶;纸张填料中含有Al, Si等元素,推断纸张填料可能是高岭土(Al₂O₃·2SiO₂·2H₂O)之类的物质。绿色油墨包含了蓝色普鲁士蓝(Prussian Blue,Fe₄[Fe(CN)₆]₃·14-16H₂O)和黄色铬酸铅[Lead(Ⅱ) chromate,PbCrO₄]颜料,根据印刷色彩学色料减色和色光加色理论分析,邮票样品呈现的绿色是由蓝色颜料普鲁士蓝和黄色颜料铬酸铅混合呈色的结果;油墨填料中含有Na, Mg, S, Cl, K, Ca, V, Zn, Ba等元素,推断油墨填料为MgCO₃, CaCO₃, BaSO₄等物质。上述三项技术联用,在邮票等纸质品的无损分析中具有广阔的应用前景。     

Near-Field Fluorescence and Topography Characterization of a Single Nanometre Fluorophore by Apertureless Tip-Enhanced Scanning Near-Field Microscopy

Tip-enhanced near-field fluorescence and topography characterization of a single nanometre fluorophore is conducted by using an apertureless scanning near-field microscopy system. A fluorophore with size 80hm is mapped with a spatial resolution of 10hm. The corresponding near-field fluorescence data shows significant signal enhancement due to the apertureless tip-enhanced effect. With the nanometre spatial resolution capability and nanometre local tip-enhanced effect, the apertureless tip-enhanced scanning near-field microscopy may be further used to characterize a single molecule by realizing the local near-field spectrum assignment corresponding to topography at nanometre scale.     

A Method for Quantitative Analysis of Chemical Mixtures with THz Time Domain Spectroscopy

A method for analysing chemical mixtures quantitatively with terahertz time domain spectroscopy is proposed. The experimental results demonstrate the feasibility of this technique. Transmission coefficient of THz wave at the sample surface is taken into account to improve the analytic precision, lsomer mixtures are chosen as the experimental samples. Compared to similar techniques, the analytic precision could be improved evidently in this method.     

非视线紫外通信大气传输特性的蒙特卡罗模拟

基于蒙特卡罗方法建立了紫外光非视线传输多次散射模型,利用单次散射近似法和实验方法验证了模型的有效性,并利用该模型完成了非视线紫外光通信大气传输特性的模拟.模拟时光波长取紫外光通信的最佳工作波段(250 nm附近),分析了不同传输距离下能见度、风、雨、雾等参量对系统能量透射比的影响.结果指出,系统能量透射比随传输距离增大而剧烈减小,在天气较差传输条件下能量衰减得更快;风力大小的变化对通信系统影响不大.较近距离通信传输时(一两百米),通信系统受天气条件的影响较小.     

核动力航空推进探析

文献调研国外核动力航空推进相关技术研究,美国GE与PW公司通过ANP计划已试验验证了核动力航空推进的可行性;分析认为核动力航空推进当前最佳用途是长航时无人机与巡航导弹动力,关键技术是核屏蔽的轻量化设计、热交换效率与速率、热力系统设计与新型结构问题;核动力航空推进若采用蒸汽介质的二回路闭式循环驱动螺旋桨,蒸汽透平及动力系统设计没有技术障碍,闭式循环蒸汽流量关键取决于蒸汽透平汽耗率与热交换循环时间。     

New Soliton-like Solutions and Multi-soliton Structures for Broer-Kaup System with Variable Coefficients

By using the further extended tanh method [Phys. Lett. A 307 （2003） 269; Chaos, Solitons ＆ Fractals 17 （2003） 669] to the Broer-Kaup system with variable coefficients, abundant new soliton-like solutions and multl-solitonlike solutions are derived. Based on the derived multi-soliton-like solutions which contain arbitrary functions, some interesting multi-soliton structures are revealed.     

Analysis of Nanostructural Waveguides Using Fourth-Order Accurate Finite Difference Methods with Nonuniform Scheme

We successfully apply fourth-order accurate finite difference methods with nonuniform scheme to analysis the symmetric slot waveguides. The results of numerical simulations show that the present nonuniform formula offers the results more accurate than the previously presented second order schemes.