Decomposition of 1,1‐dimethyl‐1‐silacyclobutane on a tungsten filament—evidence of both ring C?C and ring Si?C bond cleavages

The decomposition of 1,1‐dimethyl‐1‐silacyclobutane (DMSCB) on a heated tungsten filament has been studied using vacuum ultraviolet laser single photon ionization time‐of‐flight mass spectrometry. It is found that the decomposition of DMSCB on the W filament to form ethene and 1,1‐dimethylsilene is a catalytic process. In addition, two other decomposition channels exist to produce methyl radicals via the Si? CH₃ bond cleavage and to form propene (or cyclopropane)/dimethylsilylene. It has been demonstrated that both the formation of ethene and that of propene are stepwise processes initiated by the cleavage of a ring C? C bond and a ring Si? C bond, respectively, to form diradical intermediates, followed by the breaking of the remaining central bonds in the diradicals. The formation of ethene via an initial cleavage of a ring C? C bond is dominant over that of propene via an initial cleavage of a ring Si? C bond. When the collision‐free condition is voided, secondary reactions in the gas‐phase produce various methyl‐substituted 1,3‐disilacyclobutane molecules. The dominant of all is found to be 1,1,3,3‐tetramethyl‐1,3‐disilacyclobutane originated from the dimerization of 1,1‐dimethylsilene. Copyright © 2010 John Wiley & Sons, Ltd.     

Observation of the crystallization and supersaturation of mixed component NaNO3-Na2SO4 droplets by FTIR-ATR and Raman spectroscopy

We present here a study of the phase behavior of mixed component NaNO(3)-Na(2)SO(4) (SNS) droplets with NaNO(3) to Na(2)SO(4) molar ratios of 1:1, 3:1, and 10:1, comparing observations with thermodynamic predictions. Measurements are made by Fourier transform infrared attenuated total reflection and micro-Raman spectroscopy for SNS droplets deposited on ZnSe and quartz substrates, respectively. The conventional deliquescence/efflorescence hysteresis in phase behavior is observed. On drying, heterogeneous crystallization leads to phase behavior that is consistent with bulk solution thermodynamics, with the formation of the mixed salt NaNO(3)·Na(2)SO(4)·H(2)O, Na(2)SO(4) (s), and NaNO(3) (s) all observed to form at relative humidities that coincide with predictions by the aerosol inorganics model. However, conditioning of the droplet at high relative humidity prior to drying is observed to lead to quantitative differences between the fractions of different salts formed. When substrate effects do not influence the crystallization process, supersaturated solutions are formed, and this leads to the observation of contact ion pairs. Such measurements of the phase behavior of mixed component droplets are important for testing the reliability of thermodynamic models.     

Prediction of the thermodynamic properties of 1-alkyl-3-methylimidazolium lactate ionic liquids [C n mim][Lact] (n = 2, 3, 4, 5, and 6) by parachor

An ionic liquid (IL) based on lactate, 1-butyl-3-methylimidazolium lactate ([C₄mim][Lact]), has been prepared and characterized by ¹H nuclear magnetic resonance (NMR) spectroscopy and differential scanning calorimetry (DSC). Since the IL can form strong hydrogen bonds with water, trace water is a problematic impurity in the IL. Using the standard addition method (SAM), the density, refractive index and surface tension of [C₄mim][Lact] were measured in the temperature range (308.15 to 343.15 ± 0.05) K. On the basis of the experimental data, the parachor and molar volume for [C₄mim][Lact], and the molecular volume V _m, surface tension γ, molar enthalpy of vaporization Δ_l ^g H _m ⁰, refractive index n _D, and the thermal expansion coefficients α, for the homologues [C _n mim][Lact] (n = 2, 3, 4, 5, and 6) were estimated using semi-empirical methods. The estimated values are in good agreement with the experimental data.     

Optimal Convergence Rates of Classical Solutions for Vlasov-Poisson-Boltzmann System

The dynamics of charged dilute particles can be modeled by the two species Vlasov-Poisson-Boltzmann system when the particles interact through collisions in the self-induced electric field. By constructing the compensating function for multi-species particle system, the optimal time decay of global classical solutions to this system near a global Maxwellian is obtained through a refined energy method.     

Full scale model investigation on the acoustical protection of a balcony-like façade device (L)

The acoustical insertion losses produced by a balcony-like structure in front of a window are examined experimentally. The results suggest that the balcony ceiling is the most appropriate location for the installation of artificial sound absorption for the purpose of improving the broadband insertion loss, while the side walls are found to be the second best. Results also indicate that the acoustic modes of the balcony opening and the balcony cavity resonance in a direction normal to the window could have a great impact on the one-third octave band insertion losses. The maximum broadband road traffic noise insertion loss achieved is about 7 dB.     

Structural and optical properties of waveguides in YbVO4 crystals formed by 3.0 MeV Cu-ions implantation

We report on the structural and optical characterization of waveguides formed in YbVO₄ crystals by Cu²⁺-ion implantation with an energy of 3.0 MeV and doses of 3.0×10¹⁴-1.0×10¹⁵ ions/cm². The damage properties are determined by RBS/Channeling measurements with the help of simulation code RUMP. The m-line method is used to characterize the dark-mode spectroscopy in the planar waveguides. According to the reconstructed refractive index profile of the waveguide cross section, a numerical simulation is carried out to investigate the confinement of the light in the waveguides based on the beam propagation method.     

Controlling the XUV transparency of helium using two-pathway quantum interference

Atoms irradiated with combined femtosecond laser and extreme ultraviolet (XUV) fields ionize through multiphoton processes, even when the energy of the XUV photon is below the ionization potential. However, in the presence of two different XUV photons and an intense laser field, it is possible to induce full electromagnetic transparency. Taking helium as an example, the laser field modifies its electronic structure, while the presence of two different XUV photons and the laser field leads to two distinct ionization pathways that can interfere destructively. This work demonstrates a new approach for coherent control in a regime of highly excited states and strong optical fields.     

基于异面交会的空中运动目标定位算法及误差分析

介绍了空中运动目标定位测量的经纬定位仪单站定向和双站异面交会定位原理,并对影响定向和定位结果的各个因素进行了误差分析和仿真.结果表明,交会角在[40°,165°]时.测量精度有明显地改善,为组网测量布站提供了依据.黑火药爆炸试验测量结果验证了该方法的可行性和测量精度.     

Measurements of radiation vibrations of turbomachine blades using an optical-fiber displacement-sensing system

Turbomachine blades are critical equipment in the energy, chemical, aviation, and shipbuilding industries. Turbomachine-blade vibrations can cause high cycle fatigue, which reduces the blade lifetime. Their stable operation is a determining factor of safe and efficient production. In order to monitor and detect the turbomachine-blade vibrations and check whether whole or partial performance is normally operating, we design a reflective intensity-modulated optical-fiber sensing system for radial vibration detection of turbomachine blades and introduce the basic principles of the detection system in detail. We study some key technologies such as the control system of the laser-diode (LD) constant power and an optical-fiber coupling system with the optical-fiber-bundle structure. We analyze the sensor output characteristics and present some numerical simulations. In view of our experimental results, we show that the system elaborated can eliminate the effects caused by light-intensity fluctuations, optical-fiber flexural losses, and changes in the surface reflection coefficient, and can detect the radial vibrations of turbomachine blades in the presence of strong electromagnetic interference and under high temperatures.     

动态光谱的单拍提取

为了提高动态光谱(dynamic spectrum,DS)数据处理方法的效率与精度,采用单拍提取技术,即对所采集全部波长对应的光电容积脉搏波(photoelectric plethysmography,PPG)叠加平均所得到的全波段PPG,以单个脉搏为周期,提取其上升沿作为模板;用该模板校正各个波长PPG的上升沿,再以...