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51.
激光光镊技术是一项在许多科学领域有广阔应用前景的技术。本文详细给出构建一台红外半导体激光光镊的设计思想及实例。由于采用了独特的对大功率多模红外激光选模整形和双透镜陷阱操纵技术等性能价格最优化选择 ,该系统易于构建 ,陷阱操作方便 ,其构建价格仅一般光镊的几十分之一 ,非常适合光镊技术的推广和一般实验室构建 相似文献
52.
Seong Hyuk Lee Junghee Lee Kwan-Gu Kang Joon Sik Lee 《Journal of Mechanical Science and Technology》2006,20(8):1292-1301
This article investigates numerically the carrier-phonon interactions in thin gallium arsenide (GaAs) film structures irradiated
by subpicosecond laser pulses to figure out the role of several recombination processes on the energy transport during laser
pulses and to examine the effects of laser fluences and pulses on non-equilibrium energy transfer characteristics in thin
film structures. The self-consistent hydrodynamic equations derived from the Boltzmann transport equations are established
for carriers and two different types of phonons, i.e., acoustic phonons and longitudinal optical (LO) phonons. From the results,
it is found that the two-peak structure of carrier temperatures depends mainly on the pulse durations, laser fluences, and
nonradiative recombination processes, two different phonons are in nonequilibrium state within such lagging times, and this
lagging effect can be neglected for longer pulses. Finally, at the initial stage of laser irradiation, SRH recombination rates
increases sufficiently because the abrupt increase in carrier number density no longer permits Auger recombination to be activated.
For thin GaAs film structures, it is thus seen that Auger recombination is negligible even at high temperature during laser
irradiation. 相似文献
53.
54.
非接触型光外差轮廓仪 总被引:1,自引:0,他引:1
本文介绍一种纳米级非接触型高精度光外差轮廓仪,它是基于普通光路的光外差干涉仪。工件表面被两束有微小频差的激光束所照射,其中一束经聚焦后用作测量光探针来扫描工件表面,另一束则用作参考光束。两束光经表面反射后产生干涉。测量信号和参考信号的相位差与表面的微不平值成正比。仪器的横向分辨率为2μm,高度分辨率为1 nm,它不需要对试样作大范围的调整,且可用试样自身作参考面。信号经光电转换后由微型计算机进行处理,它能快速完成测量、计算、显示及打印出各种参数和曲线。 相似文献
55.
智能同步光网络(ASON)与多业务传送平台(MSTP)固其先进的智能性、可靠性、灵活性而得以发展和运用。本文根据智能光网络与多业务传送平台枝术的发展情况,结合北京通信传送网络的实际情况,探讨北京通信传送网的建设思路. 相似文献
56.
Optical scattering in beef steak to predict tenderness using hyperspectral imaging in the VIS-NIR region 总被引:1,自引:0,他引:1
Kim Cluff Govindarajan Konda Naganathan Jeyamkondan Subbiah Renfu Lu Chris R. Calkins Ashok Samal 《Sensing and Instrumentation for Food Quality and Safety》2008,2(3):189-196
The objective of this research is to develop a non-destructive method for predicting cooked beef tenderness using optical
scattering of light on fresh beef muscle tissue. A hyperspectral imaging system (λ = 496–1,036 nm) that consists of a CCD
camera and an imaging spectrograph, was used to acquire beef steak images. The hyperspectral image consisted of 120 bands
with spectral intervals of 4.54 nm. Sixty-one fresh beef steaks, including 44 strip loin and 17 tenderloin cuts, were collected.
After imaging, the steaks were cooked and Warner-Bratzler shear (WBS) force values were collected as tenderness references.
The optical scattering profiles were derived from the hyperspectral images and fitted to the modified Lorentzian function.
Parameters, such as the peak height, full scattering width at half maximum (FWHM), and the slope around the FWHM were determined
at each wavelength. Stepwise regression was used to identify 7 key wavelengths and parameters. The parameters were then used
to predict the WBS scores. The model was able to predict WBS scores with an R = 0.67. Optical scattering implemented with hyperspectral imaging shows limited success for predicting current status of tenderness
in beef steak. 相似文献
57.
A. Bautista-Hernndez G. Loaiza-Gonzlez L. Meza-Montes U. Pal 《Solar Energy Materials & Solar Cells》2003,79(4):89
We have determined exciton energies for wurtzite CdS nanoparticles, both theoretically and experimentally. The empirical pseudopotential method has been used to calculate the bulk band structure. The discretization of reciprocal space was considered to get the energy gap and the corresponding exciton energy as a function of the nanoparticles size. The CdS nanoparticles were prepared by colloidal methods and the exciton energies were determined from optical absorption measurements. A good agreement between the calculated and the experimental exciton energies is obtained when an average over the experimental size distribution of the nanoparticles is included in the calculation. 相似文献
58.
A study of radiation effects on various types of glasses, dielectric optical coatings, cemented optics and fiber was undertaken with a view to select them for extreme radiation environments. Samples were exposed to different radiation doses in the Pakistan Research Reactor-I (PARR-I) for neutron and Cobalt 60 source for gamma irradiation. Transmissions were measured before and after irradiation. The dielectric coatings were subjected to additional tests (adhesion, abrasion and humidity, etc.) as per MIL-M-13508C and MIL-C-675C. All 15 glasses studied showed varying amounts of transmission loss as expected, with negligible degradation for three types. Recovery of transmissions with time/ageing was also studied, with more or less complete recovery with temperature annealing. A faster bleaching of darkened/brown glasses was achieved by using UV lamps or UV laser. The dielectric coatings (HR, AR) and one of the two commercial optical cements showed excellent resistance to neutrons and gamma radiations, and could be good candidates for the fabrication and utilization of optical components in extreme radiation environments. The data allowed several Chinese glasses to be studied for the first time. 相似文献
59.
The article analyzes the influence of the Internet Protocol (IP) access interface on the packet loss probability and delay
times in the optical packet switched network. The network and node model have been proposed, and the structure of the IP access
interface, including assembler and holder, have been included in the analysis. It has been shown that the increase of the
maximum optical packet sizes, as well as use of the holding feature as contention resolution mechanism, decrease the packet
loss probability, but introduce delays at the optical network access points. Modeling and analysis were based on the discrete
event simulation assuming self-similar traffic sources. IP packet lengths were modeled using empirical data.
This work has been conducted while the author was affiliated with the Telecommunication Laboratory, Swiss Federal Institute
of Technology (EPFL-STI-ITOP-TCOM), Lausanne, Switzerland 相似文献
60.