Analytical study of a flattened Gaussian beam through multi-apertured optical imaging systems of B = 0

By using the methods of the matrix decomposition and expansion of the hard-edged aperture function into a finite sum of complex Gaussian functions, the recurrence propagation expressions for a flattened Gaussian beam (FGB) through multi-apertured optical imaging systems of B = 0 are derived and illustrated with numerical examples. Comparisons with the straightforward numerical integration of the Collins formula and with the previous work are made. It is shown that the main advantages of our methods and results are the more accuracy and great reduction of computer time.     

Effects of air on the segregation of particles in a shaken granular bed

Effects of interstitial air on the motions of a large intruder in a shaken granular bed are studied experimentally as a function of ambient air pressure, particle size of the bed, and the density of the intruder. It is found that the intruder always rises from the granular bed in the absence of air. However, the intruder can acquire both positive and negative buoyancy in the presence of air. Negative buoyancy can be observed only when both the density of the intruder and the particle size of the bed are small enough. This negative buoyancy can be explained by the unusual air pressure distribution found in the bed.     

Fiber bragg gratings made with a phase mask and 800-nm femtosecond radiation

High-quality retroreflecting fiber Bragg gratings were written in standard Ge-doped telecom fiber (Corning SMF-28) after a few minutes exposure with pulsed 800-nm, 120-fs laser radiation by use of a deep-etch silica zero-order nulled phase mask optimized for 800 nm. Induced index modulations of 1.9 x 10(-3) were achieved with peak power intensities of 1.2 x 10(13) W/cm2 without any fiber sensitization. The fiber gratings are stable and did not erase after 2 weeks at 300 degrees C. The primary mechanism of induced index change results from a structural modification to the fiber core.     

On Two Parallel Matched Gratings Demodulation Method of Fiber Grating Strain Sensor

The method of demodulation with two parallel matched fiber Bragg gratings( FBGs)system is introduced to enlarge the range of strain that can be detected by the FBG sensor system.     

Study of the electric capacitance spectra on symmetric quantum-dot pattern

We have calculated the ground-state energy of the symmetric quantum-dot pattern by the ab initio calculation method, i.e. unrestricted Hartree-Fock-Roothaan (UHFR) method based on the Gaussian basis, and studied their electric capacitance spectra, assuming each quantum dot of quantum-dot pattern to be confined in a three-dimensional spherical potential well of finite depth. For the systems in question, our results show that our method and theoretical model not only give the electric capacitance peaks similar to s-shell and p-shell atom-like quantum dot, but also show some new fine-structure of electric capacitance in the symmetric quantum-dot pattern system. This method might be a feasible tool to study few-electron problems on the symmetric quantum-dot pattern system.     

Simultaneous Magneto-Optical Trapping of Fermionic ^40K and Bosonic ^87Rb Atoms

We report on simultaneous magneto-optical trapping of fermionic ^40K and bosonic 87Rb atoms. This trap is the first step towards quantum degenerate fermi gas ^40K. Laser lights for the two-species magneto-optical trap （MOT） are generated from diode lasers and tapered amplifier. The enriched ^40K dispenser is utilized in the experimental setup. We obtain up to 10^7 -10^8 ^40K and 10^8 -10^9 ^87Rb atoms respectively in the steady-state single-species MOT.     

近藤共振现象及其在低维电子系统中的实现

文章全面、系统地介绍了近藤效应、近藤问题、近藤共振现象的起源和研究历史的发展过程,提供了一个清晰而准确的近藤物理问题的图像.同时,文章还讨论了近年来近藤共振现象在各种低维电子关联系统中的实现.     

基于工业分析/元素分析和可见-近红外光谱预测农作物秸秆高位热值

越来越多的农作物秸秆用于生产生物质成型燃料(生物质颗粒),作为民用和工业锅炉的生物质燃料。高位热值是衡量生物质燃料燃烧性能的主要参数之一,反映了生物质可用能含量,但利用传统的氧弹分析法测试高位热值费时费力,急需一种快速准确的方法评估农作物秸秆的高位热值,以制备高质量的生物质颗粒燃料。基于工业分析/元素分析和可见-近红外光谱分析,对比分析了五种农作物秸秆(稻秸、麦秸、棉秆、油菜秆和玉米秆)的高位热值预测模型。首先,利用多元线性回归(MLR)、逐步回归(SWR)和反向传播人工神经网络(BPNN)模型,在基于五种农作物秸秆工业分析和元素分析基础上,提出了高位热值预测模型并进行验证。MLR模型具有较好的相关系数(R2),预测均方根误差(RMSEP)和预测标准差与参比标准差比值(RPD),分别为0.921 1,0.135 1和3.49。此外,利用可见-近红外光谱分析了农作物秸秆,发现对光谱数据作最小二乘法回归(PLR),可建立高位热值预测模型,预测R2和RMSEP分别为0.881 2和0.412 9。研究结果表明MLR模型和PLR模型分别适用于基于工业分析/元素分析和可见-近红外光谱建模,对农作物秸秆的高位热值快速检测设备研发能提供基础模型支持。     

数字电力系统（DPS）——新世纪电力系统科技发展方向

本文提出了数字电力系统（DPS）的概念,并对其主要功能、所需进行的基础研究工作以及如何实现等问题作了阐述。数字电力系统有助于实现电力系统的科学化管理和决策、系统状态实时评估与改善系统安全稳定性,制定和实行经济运行策略,对电力系统实施紧急控制和反事故控制等。本文还专门论述了建立数字电力系统所需的硬件支持问题。     

激光感生碰撞能量转移实验

首次观察到Eu(6s6p)^P9/2至Sr(5s10s)^1So、准稳态翼为紫翼的激光感生碰撞能量转移实验现象,其荧光波长为458.42nm,峰值转移激光波长为459.75nm,并对其激发函数谱随温度和随转移激光能量改变进行实验研究,测量了激光感生碰撞能量转移谱的截面,证实了激光感生碰撞能量转移谱为非对称谱。