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991.
We study nonlinear optical behaviors in pulse propagation through a medium consisting of four-level cascade-type cold atoms, where a radio-frequency (RF) field couples upper two-folded levels and double-dark resonances (DDRs) can arise. By numerically solving the coupled Bloch-Maxwell equations for atom and field simultaneously in space and time, we demonstrate dynamic control of light propagation and optical switching in such a four-level atomic medium. The proposed scheme may have potential applications in the design of optical switching and optical storage devices. 相似文献
992.
Tzu-Pin Chen Chi-Jhung Lee Li-Yang Chen Tsung-Han Tsai Yi-Jhung Liu Chien-Chang Huang Tai-You Chen Shiou-Ying Cheng Wen-Chau Liu 《Superlattices and Microstructures》2009
The interesting InGaP/GaAs heterojunction bipolar transistors (HBTs) with different surface passivations on the base surface are fabricated and studied. Experimentally, the HBT device with sulfur treatment passivation displays the lowest offset voltage. However, the device with a 0.02 μm-thick emitter ledge structure reveals better transistor behaviors such as higher current gain and lower base surface recombination current. In addition, it also exhibits improved thermal stability. For the reliability test, the device with a 0.02 μm-thick emitter ledge structure shows the best performance. Therefore, from experimental results, the HBT device performance could be improved by appropriate base surface treatments, e.g., sulfur passivation and emitter ledge structure. 相似文献
993.
Multiple laser beams demonstrate many advantages as energy sources in diamond synthesis. In a reported amazingly-fast multiple
laser coating technique, CO2 gas is claimed as the sole precursor or secondary precursor for forming a diamond or diamond-like carbon, which remains poorly
understood. The absorption coefficient changes under the irradiation of multiple lasers are one of the keys to resolve the
mysteries of multiple laser beam coating processes. This study investigates the optical absorption in CO2 gas at the CO2 laser wavelength. The resonance absorption process is modeled as an inverse process of the lasing transitions of CO2 lasers. The well-established CO2 vibrational-rotational energy structures are used as the basis for the calculations with the Boltzmann distribution for equilibrium
states and the three-temperature model for non-equilibrium states. Based on the population distribution, our predictions of
the CO2 absorption coefficient changes as a function of temperature are in agreement with the published data. 相似文献
994.
S.-H. Yen M.-C. Tsai M.-L. Tsai Y.-J. Shen T.-C. Hsu Y.-K. Kuo 《Applied Physics A: Materials Science & Processing》2009,97(3):705-708
The Auger recombination is recently proposed as one of the possible origins for the deteriorated internal quantum efficiency
of InGaN light-emitting diodes. The Auger recombination behavior is quite different under widely varied Auger coefficients.
The effect of Auger coefficient on the efficiency and output power is investigated numerically. The simulation results indicate
that the Auger recombination with large Auger coefficient greatly decreases the efficiency in the whole current range under
study. It is found that the electron current leakage and nonuniform hole distribution are the possible mechanisms responsible
for the efficiency droop at high injection current. 相似文献
995.
The solutions of navigation observation equations for CAPS 总被引:2,自引:2,他引:0
Chinese scientists invent the navigation and positioning system based on commercial communications satellites and develop
them successfully into China Area Positioning System (CAPS). In principle, this system is different from the GPS broadcasting
satellite navigation class, where the propagation epoch of original navigation signals for pseudo-range measurement is from
a ground master control station rather than from satellite transponders. This paper addresses the establishment of the three
observation equation models for the navigation and positioning system based on communications satellites, and expresses them
identically to operator equations and optimized models. Furthermore, both algorithms of the linear solution for the observable
characteristic equation and the least-squares solution for the condition number more than 4 are discussed, with several methods
for the exact solution, such as improving the behavior of coefficient matrices, right estimation for the weighted right hand
side and selection of iteration forms of solutions, and the influence of the condition number on improving navigation and
positioning accuracy is also analyzed carefully. Hopefully, all the works would be contributive to further development of
the navigation and positioning system based on communications satellites, and be potentially valuable to other satellite navigation
and positioning systems.
Supported by the National Basic Research and Development Program of China (Grant No. 2007CB815500) 相似文献
996.
We present two deterministic secure quantum communication schemes over a collective-noise. One is used to complete the secure
quantum communication against a collective-rotation noise and the other is used against a collective-dephasing noise. The
two parties of quantum communication can exploit the correlation of their subsystems to check eavesdropping efficiently. Although
the sender should prepare a sequence of three-photon entangled states for accomplishing secure communication against a collective
noise, the two parties need only single-photon measurements, rather than Bell-state measurements, which will make our schemes
convenient in practical application. 相似文献
997.
Light emitting diode (LED) has more advantages compared with a traditional incandescent light bulb and a fluorescent lamp,
such as small size, low quantity of heat, long life, low power consumption, fast response, plain packaging and ease of develop
ment of a frivolous short product. A methodology is proposed to improve the uniformity of the LED illumination system. As
a light source in a backlight unit (BLU), the requirement for optical characteristics of a LED is different from highly directional
conventional ones. New diffused-type LEDs need to be developed to fulfill the requirement of the BLU industry. A non-spherical
lens is designed to optimize uniformity, and a great improvement in uniformity from 28.4 to 64% is demonstrated. In the future,
it may used in an LED display to improve the unevenness of illumination. 相似文献
998.
An overview of the special issue of the Journal of Nanoparticle Research on Occupational and Environmental Health of nanotechnology
is presented. Papers published in this special issue show considerable progress in understanding nanoparticle toxicity, monitoring,
generation, dustiness, filtration, and applications of nanoparticles. More research is needed to ensure safe handling of nanomaterials
as nanotechnology continues to develop at an incredible pace.
相似文献
Chuen-Jinn TsaiEmail: |
999.
基于经典电动力学导出的表征简单离子磁化率的磁性点价gi所构建的分子磁性连接性指数?mF及45种碱金属化合物的摩尔磁化率χm的实测数据集,利用粒子群寻优的支持向量回归(SVR)方法,建立了基于0F和1F的碱金属化合物χm的预测模型,并与基于多元线性回归(MLR)模型的计算结果进行了比较.结果显示,基于9次交叉验证的SVR模型预测的平均绝对误差、平均相对误差绝对值以及均方根误差均比MLR模型小,表明SVR模型的回归预测能力优于MLR.研究表明,磁性连接性指数mF是一种合适的分子描述符,SVR是一种预测碱金属化合物χm的有效方法.
关键词:
碱金属化合物
摩尔磁化率
支持向量回归
预测 相似文献
1000.
采用嵌入原子势,使用分子动力学方法对金属Al不同低指数晶面的表面熔化现象分别进行了模拟.分析了熔化过程中样品结构组态的变化.模拟结果表明对于不同的自由表面,表面熔化呈现出明显的各向异性行为.Al(110)面在低于熔点的温度之下发生预熔化;(111)与(001)面都出现过热现象.与(111)面不同,(001)面发生过热现象时表面原子层为类液层,而(111)面仍然保持很好的晶格结构,即预熔化的Al(001)面在高于熔点的温度下,仍可以在很长的时间内处于相对稳定的亚稳态.由模拟得到Al的热力学熔点为950 K左右,与实验值基本符合.
关键词:
分子动力学
表面熔化
过热 相似文献