Novel halogenated cyclopentasilylene-2,4-dienes via DFT

In view of immense importance of silylenes and the fact that their properties undergo significant changes on substitution with halogens, here, we have used B3LYP/6-311++G** level of theory to access the effects of 1–4 halogens (X = F, Cl, Br, and I) on four unprecedented sets of cyclopentasilylene-2,4-dienes; with the following formulas: SiC₄H₃X ( 1 _X ), SiC₄H₂X₂ ( 2 _X ), SiC₄HX₃ ( 3 _X ), and SiC₄X₄ ( 4 _X ). In going down from F to I, the singlet (s)-triplet (t) energy gap (ΔE_s-t, a possible indication of stability), and band gap (ΔE_H-L) decrease while nucleophilicity (N), chemical potential (μ), and proton affinity (PA) increase. The overall order of N, μ, and PA for each X is 2 _X > 1 _X > 3 _X > 4 _X . Precedence of 2 _X over 1 _X is attributed to the symmetric cross conjugation in the former. The highest and lowest N are shown by 2 _I and 4 _F . The trend of divalent angle () for each X is 4 _X > 1 _X > 3 _X > 2 _X . The results show that in going from electron withdrawing groups (EWGs) to electron donating groups (EDGs), the ΔE_s-t and ΔE_H-L decrease while N, μ, and PA increase. Also, rather high N of our scrutinized silylenes may suggest new promising ligands in organometallic chemistry.     

Optical Properties of One-dimensional Three-component Photonic Band Gap Structure

1　IntroductionMaterialswithPhotonicBandGaps (PBG’s)havebeenwidelystudiedboththeoreticallyandex perimentallyinthepastfew years[1～ 4] .Theexis tenceofgaps,which prohibitthepropagationofelectromagnetic (EM )wavesinacertainrangeoffrequencies,canhavesignificantimpactsbothinsci enceandtechnology .Manypracticalapplicationsofthesestructureshavebeensuggestedanddemon strated ,suchasPhotonicCrystal (PC)microcavi ties[5] ,infraredPC[6] ,PClens[7] ,suppressingspontaneousemission ,manipulatinglight…     

A New Comb Circular Polarizer Suitable for Millimeter‐Band Application

This letter presents a new polarizer which has a simple comb structure inside a circular waveguide. The electrical performance of the proposed comb polarizer is optimized by a circular waveguide radius and by the physical parameters of the comb plates. This polarizer is suitable for providing good performance in millimeter‐band application because of its simple structure and low fabrication cost. In our experiments the dual‐band comb polarizer designed in band 1(K) and band 2(Ka) showed good electrical performance without any tuning elements.     

激光水下成像技术及其进展

介绍了近年发展起来的三种主要的激光水下成像方法，即常规水下激光成像、高分辨率水下激光三维成像和偏振激光成像，分析了它们各自的工作原理、特点以及各自的发展状况。     

反铁磁晶体的红外频率特性

研究了红外频段非线性s偏振表面波在反铁磁晶体和电介质交界面上的频率特性，求出了非线性色散方程，揭示了非线性s偏振表面波存在一个临界频率，低于这个频率，非线性s偏振表面波的频率范围，发现功率不再是决定导波频率范围的唯一因素，两种材料的介电常数比在这里起了至关重要的作用。     

Efficient Collocation Schemes for Singular Boundary Value Problems

We discuss an error estimation procedure for the global error of collocation schemes applied to solve singular boundary value problems with a singularity of the first kind. This a posteriori estimate of the global error was proposed by Stetter in 1978 and is based on the idea of Defect Correction, originally due to Zadunaisky. Here, we present a new, carefully designed modification of this error estimate which not only results in less computational work but also appears to perform satisfactorily for singular problems. We give a full analytical justification for the asymptotical correctness of the error estimate when it is applied to a general nonlinear regular problem. For the singular case, we are presently only able to provide computational evidence for the full convergence order, the related analysis is still work in progress. This global estimate is the basis for a grid selection routine in which the grid is modified with the aim to equidistribute the global error. This procedure yields meshes suitable for an efficient numerical solution. Most importantly, we observe that the grid is refined in a way reflecting only the behavior of the solution and remains unaffected by the unsmooth direction field close to the singular point.     

极化子导电到能带导电的转变

采用交流法测量大功率商用钛酸钡(BT)陶瓷加热器的电阻和加热功率随温度的变化关系.结果显示,BT陶瓷的电导特性在80℃附近出现了明显的转变,从低温时的极化子跳跃导电转变为高温时的能带导电,此时,电阻出现极小值,而加热功率出现极大值.     

IMPACCT: Methodology and Tools for Power-Aware Embedded Systems

Power-aware systems are those that must exploit a widerange of power/performance trade-offs in order to adapt to the power availabilityand application requirements. They require the integration of many novel powermanagement techniques, ranging from voltage scaling to subsystem shutdown.However, those techniques do not always compose synergistically with eachother; in fact, they can combine subtractively and often yield counterintuitive,and sometimes incorrect, results in the context of a complete system. Thiscan become a serious problem as more of these power aware systems are beingdeployed in mission critical applications.To address the problem of technique integration for power-aware embedded systems, we propose a new design tool framework called IMPACCT and the associated design methodology. The system modeling methodology includes application model for capturing timing/powerconstraints and mode dependencies at the system level. The tool performs power-awarescheduling and mode selection to ensure that all timing/power constraintsare satisfied and that all overhead is taken into account. IMPACCT then synthesizesthe implementation targeting a symmetric multiprocessor platform. Experimentalresults show that the increased dynamic range of power/performance settingsenabled a Mars rover to achieve significant acceleration while using lessenergy. More importantly, our tool correctly combines the state-of-the-arttechniques at the system level, thereby saving even experienced designersfrom many pitfalls of system-level power management.     

Conductive Mechanism of Organic Conductor

Organic conductor is a kind of organic compound which has special electronic and magnetic properties. The research of the organic compounds has received considerable attention because of their potential applications in many areas. The molecular conductive units are theoretically investigated as well as their energy gap and charge distribution. The relationship of conductivity and micro-mechanism is discussed.     

半导体芯片厂有害气体检测器使用经验之探讨

本文除概略介绍气体检测器的种类处，主要对气体检测器的原理和在实际使用中的局限性作一基本归纳叙述。限于篇幅，本文将论述的重点放在气体检测器的选用与设置规划上，提出个人的一点心得与看法，以作为未来设置气体检测器系统时之参考。