SERS谱峰强度随电位的变化

ＳＥＲＳ谱峰强度随电位的变化顾仁敖，吴芸，乔专虹（苏州大学化学系２１５００６）田中群，李五湖（厦门大学化学系３６１００５）ＴｈｅＤｅｐｅｎｄｅｎｃｅｏｆＴｈｅＳＥＲＳＩｎｔｅｎｓｉｔｉｅｓｏｎＴｈｅｐｏｔｅｎｔｉａｌ￥ＧｕＲｅｎａｏ；ＷｕＹｕｎａｎｄ...     

SERS谱峰强度比与电位的关系

ＳＥＲＳ谱峰强度比与电位的关系顾仁敖，吴芸，乔专虹，姚建林（苏州大学化学系２１５００６）田中群，李五湖（厦门大学化学系３６１００５）ＴｈｅＤｅｐｅｎｄｅｎｃｅｏｆＴｈｅＳＥＲＳＩｎｔｅｎｓｉｔｉｅｓＲａｔｅｏｎＴｈｅＰｏｔｅｎｔｉａｌ￥ＧｕＲｅｎａｏ...     

The NUCLEON experiment: The current status

The main purpose of the NUCLEON experiment is direct measurements of the energy spectra of cosmic rays in the range 10¹¹–10¹⁵ eV with the use of the lightweight facility during a prolonged orbital flight. The energy is determined using a technique based on the measurement of the spatial density of secondary particles produced in the initial event of inelastic interaction. The schematic diagram of the NUCLEON facility, the current status of the project, the results of testing the prototype, and plans are presented.     

跑道型结构光子晶体波导定向耦合器

鉴于波导定向耦合器在集成光路以及光电集成方面的广泛应用,提出了一种基于光子晶体波导间高效耦合的光子晶体定向耦合器。通过主波导和耦合波导间的耦合,可以实现对波长为1 490 nm和1 550 nm电磁波的高效分光。在将器件长度控制在30 μm左右的同时,其总效率高达93.05%。另外,发现主波导和耦合波导间介质柱结构参数对电磁波的耦合周期有着极大的影响。并通过将介质柱沿z方向拉伸0.1a(a为晶格周期),设计了工作波长为1 530 nm和1 540 nm的光子晶体定向耦合器,器件长度仅为60 μm。通过拉伸介质柱的纵向长度,可以大幅减小耦合周期,这对缩小器件体积以及实现更为密集的波分复用有着重要的意义。     

电极形状与紫外探测器灵敏度关系的研究

在传统工艺的基础上,改变电极的形状可以提高氮化镓(GaN)基材料光导型紫外探测器的灵敏度.经过计算可知,虽然三棱形电极可以使探测器有效受光率提高100％,但工艺复杂,难以实现;而半圆柱形电极虽然使氮化镓薄膜有效受光率仅提高20％左右,但工艺简单,便于加工.     

数字天顶摄影仪的图像处理

垂线偏差的测量过去一直受天文坐标测量困难的影响而效率低下.为了快速、精确地测得垂线偏差,提出了利用大面阵CCD构成数字天顶摄影仪,对拍摄的恒星影像进行搜索、细分定位处理,计算出测站点的天文坐标的基本原理;再根据GPS测得的大地坐标,解出垂线偏差.并且结合本系统自身的条件,提出了快速在大面阵CCD图象中搜索多个恒星目标的新方法.通过软件模拟,结果表明了该方案的可行性.     

实现水窗波段X射线激光的途径

研究了类氢、类氦、类锂和类钠离子等四种实现复合机制Ｘ射线激光的方案，对可能实现水窗波段Ｘ射线激光的几种方案比较，分析了其各种的优缺点，并讨论了可能的具体实验方法。     

把科学精神与人文精神结合起来——科学与人文漫话之八

在揭示了科学精神与人文精神的本质意义的基础上,论证了科学精神与人文精神结合的必然性及有效性.     

The swiss light source: The SLS team

The British Association (BA) Festival of Science is a special opportunity for any member of the public interested in science to meet together with scientists and discuss as well as review science and its achievements. One such opportunity arose when the turn of the northwest of England came to host the Annual BA Festival of Science at the University of Liverpool in September 2008. A session of synchrotron radiation science reviewing the contributions of the SRS as well as a look to the future was held. A review of accelerator science was given by Mike Poole, Director of ASTeC at STFC. John Helliwell, Professor of Structural Chemistry at Manchester University, reviewed biology and medicine; Bob Cernik, Professor of Materials Science at Manchester University, reviewed materials science; and Tracy Turner, of the Photon Science Department of STFC, reviewed future light sources.     

The tessiturogram

Tessitura is the term used to describe the portion of the vocal or instrumental compass employed most commonly in a specific composition. Tessitura differs from range in that it does not take into account isolated notes of extraordinarily high or low pitch. The tessiturogram provides graphic analysis of the frequency of note occurrence within each composition or piece. Use of the tessiturogram by singers, teachers, musical directors, and phoniatricians aids in objective determination of appropriate repertoire.     

The K-Quotient

The Rayleigh Quotient and a recently proposed Timoshenko Quotient [1] are upper bounds to the fundamental eigenvalue of a discrete dynamic system. The closeness of these upper bounds to the fundamental eigenvalue depends on the closeness of the trial vectors to the eigenmode used in the calculation. In the present paper, a new quotient is presented. This quotient does not require the closeness of the trial vector to the eigenmode and its accuracy is improvable by raising the numerical value of the parameter p.     

The $-game

We propose a payoff function extending Minority Games (MG) that captures the competition between agents to make money. In contrast with previous MG, the best strategies are not always targeting the minority but are shifting opportunistically between the minority and the majority. The emergent properties of the price dynamics and of the wealth of agents are strikingly different from those found in MG. As the memory of agents is increased, we find a phase transition between a self-sustained speculative phase in which a “stubborn majority” of agents effectively collaborate to arbitrage a market-maker for their mutual benefit and a phase where the market-maker always arbitrages the agents. A subset of agents exhibit a sustained non-equilibrium risk-return profile. Received 5 June 2002 / Received in final form 21 November 2002 Published online 27 January 2003 RID="a" ID="a"e-mail: sornette@unice.fr RID="b" ID="b"CNRS UMR7536 RID="c" ID="c"CNRS UMR6622     

The a-theorem

The c-theorem is a profound result applying to statistical mechanical theories or quantum field theories in two dimensions. Such theories may be described by a set of parameters which vary as we increase or decrease the scale on which we observe the system, until we reach a fixed point or critical point where the couplings have fixed values. The c-theorem defines a quantity (the c-function) which always increases (or is constant) with increasing scale and thereby gives a valuable insight into the ‘flows’ of the couplings between fixed points. The a-theorem is a proposed generalisation of the c-theorem to higher dimensions, especially four. In this article, we describe the c-theorem, starting in the simpler statistical mechanical context and then showing how in quantum field theory the theorem is most easily formulated in a curved spacetime. We then sketch how these concepts are applied in the more technically complex scenario of four dimensions.     

The LE-statistic

We introduce a quantity called LE-statistic. It is an easily computable functional of ordinal data with versatile applications. We demonstrate its usefulness as a statistic in a nonparametric independence test of paired samples, and as a complexity measure of a scalar time series. For chaotic orbits of one-dimensional dynamical systems it is related to the Lyapunov characteristic exponent.     

The Turbutron

The physics of the turbutron is reviewed. This newly proposed high-power millimeter-wave source consists of an intensely oscillating relativistic turbulent electron plasma created in and beyond the gap of a diode configuration. The diode consists of an explosive cathode emitter and an extended anode structure connected to the inner and outer conductors, respectively, of a high-voltage pulse line under conditions of space-charge saturation. The gap spacing determines the dominant mode of the turbulent longitudinal waves which are directly converted into free transverse waves polarized parallel to the electron beam. The applied voltage waveform, cathode diameter, total scalar potential, nonlinear bunching mechanisms, and virtual-cathode dynamics determine the complex spectral characteristics. For a turbutron with a megavolt pulse across a 3-mm gap and without a resonator, calculations predict the immediate feasibility of gigawatt power levels at 35 GHz.