Optimization of the Acoustic Pressure Distribution in a Resonant Photoacoustic Cell

The size of a cylindrical photoacoustic cell with suitable size was selected so that the resonant frequency of the first radial mode was equal to that of a longitudinal higher mode. By maintaining two thin coaxial tubes at each end, a enhanced photoacoustic cell was constructed with two tubes of 1/2 and 1/4 of the wavelength. In this enhanced photoacoustie cell, both the first radial resonance and the higher longitudinal resonance were excited adequately. Coupling of two acoustic modes makes the acoustic energy concentrating in the middle of the cell. The surface loss was decreased, the acoustic quality factor and pressure amplitude increased obviously as compared with conventional cylindrical cell.     

Discrete Green's Function for Lattice Random Walk

A lattice random walk model based on particles scattering on discrete lattice of homogenous space is introduced. The discrete Green's function (DFG) for two-dimensional and three-dimensional lattice random walk of photon is found and proved by mathematical induction. The convolution theorem of photon lattice random walk is presented. They can be used with the method of images to calculate the photon density distribution in semi-infinite and finite slab homogenous turbid media such as tissue.     

7-(苯并噻唑-2-偶氮)-8-羟基喹啉-5-磺酸与镉显色反应的研究和应用

在 p H4 .8的邻苯二甲酸氢钾 - Na OH介质中 ,非离子表面活性剂 Tween- 80存在下 ,7- (苯并噻唑 - 2 -偶氮 ) - 8-羟基喹啉 - 5 -磺酸 (BTAQS)与镉形成 2∶ 1的紫红色配合物 ,其最大吸收波长 λmax=5 6 0 nm,表观摩尔吸光系数为 8.71× 10 4L· mol-1·cm-1,镉含量在 0— 6 μg/ 10 m L范围内服从比耳定律。用于矿样中镉的测定 ,相对误差小于 3% ,相对标准偏差小于 2 .5 % (n=5 )。     

激光点火系统温度效应及其控制技术的研究

激光点火系统应用于武器系统必须符合高低温性能的要求。研究了激光点火系统的高低温特性,得到了激光二极管阈值电流和输出光功率随温度变化的规律。基于对规律的分析,研制了带温控技术的激光点火系统。该系统以单片机为控制部件,以TEC为温控部件,以负温度系数热敏电阻为测温元件。     

Vacuum-free fabrication of high-performance semitransparent perovskite solar cells via e-glue assisted lamination process

From a base material of conductive polymer(poly-(3,4-ethylenedioxythiophene):poly(styrenesulfonate),PEDOT:PSS),a flexible and high-conductivity(as low as 45Ω/sq)transparent electrode was fabricated on polydimethylsiloxane elastomer by an acid treatment and transfer process.Combined with the D-sorbitol-doped PEDOT:PSS electric glue,we successfully demonstrated a vacuum-free and ambient lamination fabrication process for semi-transparent perovskite solar cells using triple cation Cs_(0.05)(MA_(0.17)FA_(0.83))_(0.95)Pb(I_(0.83)Br_(0.17))_3perovskite.By this manufacturing-friendly lamination process,we fabricated semitransparent perovskite solar cell devices with power conversion efficiencies up to 16.4%and variable transparencies.     

A large deviation for occupation time of critical branching α-stable process

In this paper we establish a large deviation principle for the occupation times of critical branching α-stable processes for large dimensions d > 2α, by investigating two related nonlinear differential equations. Our result is an extension of Cox and Griffeath’s (in 1985) for branching Brownian motion for d > 4.     

Γ分布密度函数的性质

分析了Γ分布密度函数的性质,指出了该密度函数与相应参数之间的关系.主要研究第二个参数对密度的影响,证明了β增大时Γ(α,β)分布密度极大值也增大,还指出了β变化时Γ(α,β)分布密度与另一特定密度曲线交点的变化规律.     

Pump spectral linewidth influence on stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS) and self‐termination behavior of SRS in liquids

The threshold, temporal behavior, and conversion efficiency of stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SBS) in three liquids (benzene, hexane, and dimethyl sulfoxide) and two crystals (calcite and barium nitrate) have been investigated under three largely different spectral linewidth conditions. Pumped with 532‐nm and nanosecond duration laser pulses of ≤ 0.01 cm^?1 linewidth, only SBS can be generated in all tested liquids with a high nonlinear reflectivity. However when the pump spectral linewidth is ～0.07 cm^?1 or ～0.8 cm^?1, both SBS and SRS can be observed in benzene while only SRS can be generated in dimethyl sulfoxide; in all these cases SRS is the dominant contribution to the stimulated scattering but the efficiency values are drastically decreased due to the self‐termination behavior of SRS in liquids, which arises from the thermal self‐defocusing of both pump beam and SRS beam owing to Stokes‐shift related opto‐heating effect. In contrast, for SRS process in the two crystals, the thermal self‐defocusing influence is negligible benefitting from their much greater thermal conductivity, and a higher conversion efficiency of SRS generation can be retained under all three pump conditions.