Biosynthesis and electrochemical characteristics of LiFePO4/C by microwave processing

The yeast cells are adopted as a template and cementation agent to prepare LiFePO₄/C with high surface area by co-precipitation and microwave processing. The electrochemical properties of the resultant products are investigated. The synthesized LiFePO₄/C is characterized by means of X-ray diffraction, transmission electron microscopy (TEM), Brunauer–Emmett–Teller method, and battery test instrument. The LiFePO₄/C particles with average size of 35-100 nm coated by porous carbon are observed by TEM. The LiFePO₄/C, with the specific surface area of 98.3 m²/g, exhibits initial discharge specific capacity of 147 mAh/g and good cycle ability. The yeast cells as a template are used to synthesize the precursor LiFePO₄/cells compounds. In microwave heating process, the use of yeast cells as reducing matter and cementation agent results in the enhancement of the electrochemical properties.     

水下气泡高速摄影光学系统设计

为了研究水下气泡的粒径、速度和浓度特性,提出基于高速电荷耦合器件(CCD)的气泡照明和三维摄影光学系统.采用532nm半导体激光器,基于伽利略结构用三个柱面镜设计了厚度1.5mm,宽度44mm的片光源。设计物像距530mm,放大率为0.4,1,2.5倍(×)的摄影光学系统,每组均由共用前组镜和会聚镜组成,中间以平行光中继。通过同步移动片光源和共用前组镜实现60mm×40mm视场内二维高速成像和纵向5mm扫描,具有结构简单、性能可靠的特点。对设计结果进行评价,0.4,1,2.5×成像光学系统在0.707ω,50lp/mm时调制传递函数值分别为0.58,0.55和0.38,能够分辨粒径范围为10～450μm的气泡。     

Transmission of a Gaussian beam after incidenting nonnormally on a Fabry–Perot etalon

The transmission of a Gaussian beam after incidenting nonnormally on a Fabry–Perot etalon has been investigated. After deriving the expression of the intensity of the transmitted beam, several key characteristics of the transmitted beam have been specified. The results show that the peak intensity of the transmitted beam decreases with the increase of the input angle, the position of the peak intensity of the transmitted beam is shifted, and the spot size of the transmitted beam is changed.     

Synthetic studies toward the construction of the cis-decalin portion of superstolides A and B. Application of a sequential double michael reaction and an anionic oxy-Cope rearrangement

A highly convergent strategy for the asymmetric synthesis of the cis-decalin portion of the antitumor macrolide superstolide A was developed. The key reactions in our approach involve a sequential double Michael reaction and an anionic oxy-Cope rearrangement.     

Influence of a Fabry–Perot etalon on a chirped optical pulse

Taking into consideration the fact that the output from a Fabry–Perot etalon is formed on the basis of the interference of the multi-reflected beams of the input pulse that enters the etalon, an analytical expression of the output pulse intensity has been derived for an input chirped Gaussian pulse passing through an etalon. Using the expression, the temporal width and the peak power of the output pulse is investigated. Results show that for a given etalon, the chirp factor and the width of the input pulse have intense effects on the width and the peak of the output pulse.     

有线电视系统中行波式半导体激光放大器功率特性研究

根据行波式半导体激光放大器的特点，可用输入功率的台劳级数表示放大器的输出功率，只求出级数各阶导数就可以方便地计算在多路有线电视系统中放大器引起的失真。文中出放大器的速率方程组的解，并在此基础上导出理想放大器的前三阶导数的解析表达式。     

Oscillation wavelength of fiber Bragg grating semiconductor lasers

Based on the physical fact that a laser containing a gain medium with homogenous line broadening oscillates at the wavelength which requires the smallest threshold gain due to the mode competition effect, after taking into account the wavelength-depended reflectivity distribution profile of a fiber Bragg grating, the oscillation wavelength λ_l of fiber Bragg grating semiconductor lasers has been investigated theoretically. The results show that the laser oscillation wavelength λ_B is not fixed at the Bragg reflection wavelength λ_l of fiber Bragg grating, and the offset between λ_B and λ_l depends on the reflectivity distribution profile of fiber Bragg grating and the gain profile of semiconductor gain medium.     

高斯光束斜入射非平行法布里-珀罗干涉仪后的透射光强分布

基于多光束干涉原理,推导出了高斯光束斜入射非平行法布里-珀罗干涉仪射后的透射光强表达式,在此基础上,着重研究了高斯光束入射角的大小以及法布里-珀罗干涉仪两反射端面的不平行度对透射光强分布的影响。研究结果表明：入射角的大小和干涉仪的不平行度对透射光的强度分布、峰值强度的大小和峰值强度的位置有很大的影响;在入射高斯光束具有较小的腰斑半径或法布里-珀罗干涉仪的两端面的反射率较大时,必须考虑高斯光束沿传输轴线的衍射效应;楔角为负的非平行法布里珀罗出射光斑的光强在“反跳”处急剧下降到零,可利用这一特点对距离进行精确测量。     

Numerical study of a harmonic mode-locked semiconductor optical amplifier fiber ring laser

An improved harmonic mode-locked Semiconductor optical amplifier (SOA) fiber ring lasers has been presented and numerically investigated based on the self-reproduction theory. The numerical result shows that a narrower optical pulse train with a more symmetrical-temporal shape can be obtained, when the modulation SOA is DC biased on high current, whereas the gain SOA is DC biased on the low current functions as a gain compensator in the experimental setup. Also, the system parameters effects on the characteristic of the harmonic mode-locked pulse have been investigated.