基于时频分析的高频地波雷达目标检测算法

为提高海事监测中高频地波雷达(High Frequency Surface Wave Radar,HFS-WR)对运动目标的检测准确率,提出了一种基于频谱细化和小波尺度谱重排时频分析的运动目标检测算法.对HFSWR的接收信号进行频率细化处理以提高后续时频分析的频率分辨率;然后,进行基于Morlet小波的时频分析以提取目标的时频分布特征,为提高时频分布的集中性和抑制交叉项干扰,对小波尺度谱进行重排;根据得到的时频分布特征实现可疑目标区的精确检测.实验结果表明:该算法能有效检测多普勒频率相差很小的运动目标以及海杂波附近的运动目标,可用于对常规目标检测算法无法判定的可疑目标区域进行精细、准确的目标检测与分析.     

Quantitative Time-Resolved Fluorescence Spectrum of the Cortical Sarcoma and the Adjacent Normal Tissue

The difference in time-resolved fluorescence spectrum between the cortical sarcoma and the adjacent normal tissue was studied in both experimental and theoretical ways. The Clinical data were obtained in vivo using a time-resolved fluorescence spectrometer employing a single fiber-optic probe for excitation and detection. Tissue was modeled as s-180 sarcoma tumor surrounded with normal muscle and was mediated by the Palladium-porphyrin photosensitizer (Pd-TCPP). The emitted fluorescence was considered as arising from the tumor tissue or the normal muscle, due to the presence of the photosensitizer. A computational code which could simulating time-resolved fluorescence emission was presented and applied to comparing fluorescence decay of photosensitizer in different stages of tumor growth. In this code the different stages of the tumor was modeled through changing the time τ, the delay of the fluorescence photon emission and z _max, the thickness of the tumor. It was found in the in vivo experiment that the fluorescence from tumor tissue decayed more quickly than from the adjacent normal muscle. For the ten rats in the first experiment day, the mean decay constant of tumor T _s and normal tissue T _n were 554 and 526 μs, respectively. And T _s increased with the tumor growth, from 554 μs in the first day to 634 μs in the eighth day while T _s kept steady. It was believed that the more adequate oxygen supplied by the normal tissue can more effectively quench the fluorescence and in the normal tissue the photosensitizer lifetime is smaller. As a result the simulated time-resolved fluorescence spectrum of normal tissue showed more quickly decay. And the thickness of the tumor can also delay the fluorescence decay. Both the experimental and simulated results indicated that the germination of the tumor would increase the decay constant of the time-resolved fluorescence spectrum. So decay constant of the tumor tissue spectrum should be larger than that of adjacent normal tissue for the reason of hypoxia and overgrouth. This fact could be of use in the tumor diagnoses.     

An approach to the measurement of shunt resistance of individual subcells in thin‐film tandem devices

In this paper, the selective illumination approach is adopted to separately extract the shunt resistance of the individual subcells belonging to a tandem cell. The method relies on simple theoretical considerations and is based on the measurement of the current–voltage characteristic of the tandem cell by alternately keeping one of the subcells under dark conditions. Numerical simulations are employed to support the reliability of the technique, which is experimentally tested on micromorph devices deposited onto glass covered by a V‐shaped transparent conducting oxide and subject to different thermal treatments. Copyright © 2013 John Wiley & Sons, Ltd.     

A Terahertz Spectral Database Based on Browser/Server TechniqueSCIEI北大核心CSCD

With the solution of key scientific and technical problems and development of instrumentation, the application of terahertz technology in various fields has been paid more and more attention. Owing to the unique characteristic advantages, terahertz technology has been showing a broad future in the fields of fast, non-damaging detections, as well as many other fields. Terahertz technology combined with other complementary methods can be used to cope with many difficult practical problems which could not be solved before. One of the critical points for further development of practical terahertz detection methods depends on a good and reliable terahertz spectral database. We developed a BS (browser/server) -based terahertz spectral database recently. We designed the main structure and main functions to fulfill practical requirements. The terahertz spectral database now includes more than 240 items, and the spectral information was collected based on three sources: (1) collection and citation from some other abroad terahertz spectral databases; (2) collected from published literatures; and (3) spectral data measured in our laboratory. The present paper introduced the basic structure and fundament functions of the terahertz spectral database developed in our laboratory. One of the key functions of this THz database is calculation of optical parameters. Some optical parameters including absorption coefficient, refractive index, etc. can be calculated based on the input THz time domain spectra. The other main functions and searching methods of the browser/server-based terahertz spectral database have been discussed. The database search system can provide users convenient functions including user registration, inquiry, displaying spectral figures and molecular structures, spectral matching, etc. The THz database system provides an on-line searching function for registered users. Registered users can compare the input THz spectrum with the spectra of database, according to the obtained correlation coefficient one can perform the searching task very fast and conveniently. Our terahertz spectral database can be accessed at http://www.teralibrary.com. The proposed terahertz spectral database is based on spectral information so far, and will be improved in the future. We hope this terahertz spectral database can provide users powerful, convenient, and high efficient functions, and could promote the broader applications of terahertz technology.     

片段化森林中檵木幼苗种内叶经济性状变异及其驱动因子

在异质性生境中,种内功能性状变异有助于植物对环境的适应,进而影响种群更新、群落构建和生态系统过程。探讨了种内叶经济性状的变异及受生境异质性的塑造情况。以千岛湖片段化生境中的常见种檵木（Loropetalum chinense）的幼苗为研究对象,测定了200株檵木幼苗个体水平的7个叶经济性状（比叶面积SLA、叶全碳量C、叶全氮量N等）及其对应的生境因子（郁闭度、土壤全碳量、土壤全氮量等）,采用相关性检验、主成分分析和线性混合效应模型等方法探讨片段化森林中檵木幼苗的种内叶经济性状变异及生境异质性对该变异的驱动作用。结果显示：（1） 在7个叶经济性状所构成的21对相关性分析中,有12对显著相关。经主成分分析降维后,主成分1（PC1）占性状总变异的43.02%,主要与比叶面积、叶绿素浓度、叶全氮量呈正相关,与叶干物质质量分数和叶碳氮比呈负相关,体现了檵木的种内叶经济谱,可反映叶片的最大光合效率。（2）片段化对生境条件和叶经济性状均有影响。岛屿森林群落的郁闭度显著低于大陆。相对于大陆,岛屿中的檵木幼苗趋向于更小的PC1值（缓慢投资-收益策略）;大岛边缘较大岛内部偏向于更小的PC1值。（3）生境因子中,郁闭度对PC1具有显著正效应。研究表明,片段化生境中的檵木在幼苗阶段存在叶经济谱,生境片段化可通过影响生境条件进而改变檵木幼苗的叶经济性状。随着生境片段化程度的加剧,檵木幼苗的叶经济性状逐渐向缓慢投资-收益策略靠拢。     

基于夹层氮化硅波导的可见-中红外超连续谱特性研究

提出一种低厚度氮化硅-蓝宝石-氮化硅夹层波导结构。利用其色散波辐射现象和中红外相位匹配条件,结合波导脉冲传输模型,讨论了夹层波导不同物理尺寸对相位匹配点和光谱展宽的影响,数值模拟获得了0.5~4 μm的超连续谱展宽,并且在-40 dB水平下具有更远中红外色散波产生。通过该模型,详细解释了非线性波导脉冲传输的潜在机制。理论模型分析表明,通过优化氮化硅及蓝宝石夹层的物理尺寸,进而改变相位匹配条件,可以在较宽的波长范围内控制色散波的位置。     

双曲冷却塔塔筒水平地震响应分析

为明确冷却塔在水平地震下的内力环向分布特征及内在原因,同时探究不同地震波时程与规范反应谱所得内力差异的原因,以某大型双曲冷却塔为例,在动力特性分析的基础上,通过反应谱方法和时程方法的水平地震响应计算及对比分析,对上述两个问题进行了研究。研究表明:由于仅侧弯振型对水平地震有贡献,而塔筒的侧弯振型和实际响应均表现为整体侧倾并伴随微弱的截面“流动”变形,这也使塔筒各内力的环向分布分别呈现正弦、余弦分布特征;其整体侧倾可类比于悬臂杆结构,塔筒子午向轴力FY、子午向弯矩MY、剪力FXY和扭矩MXY的环向分布可借助悬臂杆侧倾时截面正应力和剪应力分布来解释;而截面“流动”变形则决定了环向轴力FX和环向弯矩MX的环向分布;整体侧移显著而截面变形极小也使FY和FXY的幅值在塔筒中下部明显大于FX;由于冷却塔第1阶侧弯振型在水平地震响应中往往起绝对主导作用,因此可先对所选地震波计算得到其反应谱,对比第1阶侧弯振型周期对应的水平地震影响系数α值,即可初步推断不同时程及规范反应谱方法所得结果的大小关系。     

苗族服饰色彩体系构建研究

色彩是民族服饰的核心要素,也是民族文化元素的重要组成部分,构建一套兼具科学性与实用性的色彩体系极具挑战性。在传统色彩地理学方法基础上,通过提取主题色和改进的关联规则挖掘方法,获取色彩数据、寻找色彩规则,并对其进行自然色彩体系（NCS）编谱分析,构建了一套苗族服饰色彩体系（Miao’s costume color system,MCCS）。该体系有助于进一步挖掘苗族服饰的配色规律,实现对苗族服饰色彩的数字化保护,为民族服饰色彩传承机理的探索与研究提供新的思路。     

Cooperation of σ–π and σ*–π* Conjugation in the UV/Vis and Fluorescence Spectra of 9,10-Disilylanthracene

In 1996, we reported that silyl groups of 9,10-disilylanthracenes significantly affect the UV/Vis and fluorescence spectra. Although the results indicate that the silyl groups have strong electronic effects on anthracene, the details of the mechanisms responsible for this have not yet been clarified. This article describes the analysis of the UV/Vis and fluorescence spectra of 9,10-bis(diisopropylsilyl)anthracene by theoretical calculations. This study reveals that π conjugation of anthracene is extended by cooperation of σ–π and σ*–π* conjugation between the silyl groups and anthracene. This effect increases the transition moment of the π–π* transition of anthracene. As a result, the molecular extinction coefficient of the ¹L_a band and the fluorescence quantum yield are increased.     

硬脂酸镉和山嵛酸镉混合LB膜的微结构

X-ray diffraction (XRD) was used to investigate the microstructure and phase separation of mixed multilayers of cadmium stearate (SA) and behenate (BA) deposited onto hydrophilic glass by the Langmuir-Blodgett technique. No unitary fatty acid diffraction peaks in the XRD spectra of the mixed LB films, which reveals that domains in these samples are small and uniform. The interplanar spacing of the mixed LB films changes with the ratio of BA to SA in a step-shaped curve, which suggests that with the changing of the ratio between BA and SA, only three kinds of ordered structure form in the mixed system, and each microstructure, in particular, the short chains against long chains meshed microstructure can be maintained in a certain ratio range . In addition, for the meshed microstructure, the alkyl chains of both SA and BA stand straight or may have exactly the same small tilted angle from the substrate normal, as is indicated by the symmetric and asymmetric stretching vibration of methylene (CH2) peaks which are at 2847.80 and 2914.37 cm-1respectively in the Fourier transform infrared (FT-IR) transmission spectra. The mixed system always goes through a longitudinal regularity decreasing process when BA/SA is out of the intermediate ratio range (BA/SA: 1/5-1/1), which is illustrated by the relative XRD intensity changing with the ratio of BA/ SA in a \W" shape. These results for the mixed LB films of BA/SA provide meaningful data for choosing the mixture ratio when fabricating composite films with special structure.