高速传输系统CAD/CAM齿形误差最优化算法

本文提出了一种CAD/CAM齿形误差的最优化算法。本算法收敛速度快、拟合误差小,能够按照预定设计要求对齿形精度加以控制,实现最优化自动搜索,同时给出数值计算结果。     

高功率离子束在漂移管中的中性化传输

 介绍了“闪光二号”加速器产生的高功率离子束在漂移管中的传输实验。对比了采用中性化措施前后的传输情况，分析了中性化措施对离子束束斑半径、束流均匀性的影响。根据实测的二极管电压模拟得到了传输一定距离后的束流波形，与实测结果符合较好。采取适当的中性化措施后，高功率离子束可以有效传输80 cm以上，束流发散得到抑制，束流均匀性得到改善。     

光子晶体Vlasov天线辐射特性研究

 通过在Vlasov天线口径上加装金属面,再在金属面上环绕天线口径排布金属圆柱构成光子晶体,设计出一种新型的光子晶体Vlasov天线。数值仿真及实验结果均表明,光子晶体的带隙特性改善了天线的辐射特性,使得E面上的最大增益在工作频段内平均提高了2.43 dB。     

ICP-AES测定高纯碲中11种杂质元素

电感耦合等离子体原子发射光谱法 (ICP- AES)同时测定高纯碲中 11种杂质元素。用离峰扣背景法消除背景干扰 ,检出限能满足高纯碲中杂质元素的测定要求 ,加标回收率在 94 .0 %— 10 8%之间。     

高功率LED热特性测试方法研究与应用

叙述了利用动态电学测试方法测量高功率LED热阻和结温的原理、试验装置、测量步骤和影响测试结果的因素.研究结果表明,该方法具有测试结构简单、稳定性高等特点,可作为高功率LED热阻和结温的一种测试方法.     

High pressure X-ray diffraction study of CdAl2Se4 and Raman study of AAl2Se4 (A=Hg, Zn) and CdAl2X4 (X=Se, S)

We report the results of an X-ray diffraction study of CdAl₂Se₄ and of Raman studies of HgAl₂Se₄ and ZnAl₂Se₄ at room temperature, and of CdAl₂S₄ and CdAl₂Se₄ at 80 K at high pressure. The ambient pressure phase of CdAl₂Se₄ is stable up to a pressure of 9.1 GPa above which a phase transition to a disordered rock salt phase is observed. A fit of the volume pressure data to a Birch-Murnaghan type equation of state yields a bulk modulus of 52.1 GPa. The relative volume change at the phase transition at ∼9 GPa is about 10%. The analysis of the Raman data of HgAl₂Se₄ and ZnAl₂Se₄ reveals a general trend observed for different defect chalcopyrite materials. The line widths of the Raman peaks change at intermediate pressures between 4 and 6 GPa as an indication of the pressure induced two stage order-disorder transition observed in these materials. In addition, we include results of a low temperature Raman study of CdAl₂S₄ and CdAl₂Se₄, which shows a very weak temperature dependence of the Raman-active phonon modes.     

An investigation of the structure and bond rotational potential of some fluorinated ethanes by NMR spectroscopy of solutions in nematic liquid crystalline solvents

NMR spectra of 1,2-dibromo-1,1-difluoroethane and 1-bromo-2-iodo-tetrafluoroethane dissolved in nematic liquid crystalline solvents have been analysed to yield the magnitudes and signs of the scalar couplings, J(ij), and total anisotropic couplings, T(ij), between all the (1)H, (19)F, and (13)C nuclei, except for those between two (13)C nuclei. The values obtained for T(ij) in principle contain a contribution from J(ij)(aniso), the component along the static applied magnetic field of the anisotropic part of the electron-mediated spin-spin coupling. Neglecting this contribution allows partially averaged dipolar couplings, D(ij), to be extracted from the T(ij), and these were used to determine the structure, orientational order, and the conformational distribution generated by rotation about the C-C bond. The values obtained are compared with the results of calculations by ab initio and density functional methods. The differences found are no greater than those obtained for similar compounds which do not contain fluorine, so that there is no definitive evidence for significant contributions from J(CF)(aniso) or J(FF)(aniso) in the two compounds studied.     

Anomalous behavior of conductivity of the confined Q1D electron system over liquid helium

Conductivity of electrons in a quasi-one-dimensional (Q1D) system over liquid helium in narrow channels with the parabolic profile of the potential well has been investigated at temperature T, from 0.4 to 1.8 K, for different driving electric fields and radius of channel curvature. The interval of linear electron densities varied from 2.18×10³ up to 1.7×10⁶ cm⁻¹.

The inverse mobility (1/μ_eff) in the electron-ripplon scattering region at the high linear densities of charges in the channel increases with temperature decreasing. This anomalous behavior of the electron transport in the low-temperature region has been explained by either the electron ordering or the polaronic effects in confined conducting channels. The nonlinear behavior of the electron velocity as a function of a driving electric field is supposed to be due to Breg–Cherenkov radiation of the ripplons. The radiation occurred if the velocity of electrons in the channel approaches to the critical value.     

A phenomenological theory of the isotropic to chiral smectic-C phase transition

In this paper we discuss the direct isotropic to chiral smectic-C phase transition on the basis of a phenomenological theory. The model free energy is written in terms of the coupled order parameters including the spontaneous polarization. We present a detailed analysis of the different phases that can occur and analyze the question under which conditions a direct isotropic to chiral smectic-C phase transition is possible when compared to other phase transitions. On the basis of this model the isotropic-smectic-C^* transition is always of first order. The theoretical predictions are compared with the available experimental results.-1     

Fiber Optic Excitation of Silicon Microspheres in Amorphous and Crystalline Fluids

ABSTRACT

This study investigates the optical resonance spectra of free-standing monolithic single crystal silicon microspheres immersed in various amorphous fluids, such as air, water, ethylene glycol, and 4-Cyano-4’-pentylbiphenyl nematic liquid crystal. For the various amorphous fluids, morphology-dependent resonances with quality factors on the order of 10⁵ are observed at 1428 nm. The mode spacing is always on the order of 0.23 nm. The immersion in various amorphous fluids affects the spectral response of the silicon microsphere and heralds this technique for use in novel optofluidics applications. Even though the nematic liquid crystal is a highly birefringent, scattering, and high-index optical medium, morphology-dependent resonances with quality factors on the order of 10⁵ are observed at 1300 nm in the elastic scattering spectra of the silicon microsphere, realizing a liquid-crystal-on-silicon geometry. The relative refractive index and the size parameter of the silicon microsphere are the parameters that affect the resonance structure. The more 4-Cyano-4’-pentylbiphenyl interacting with the silicon microsphere, the lower the quality factor of the resonances is. The more 4-Cyano-4’-pentylbiphenyl is interacting with the silicon microsphere, the lower the mode spacing Δλ of the resonances is. The silicon microspheres wetted with nematic liquid crystal can be used for optically addressed liquid-crystal-on-silicon displays, light valve applications, or reconfigurable optical networks.