高能Pb-Pb中心碰撞中产生的(A)和(A)强子的横质量分布和快度分布

用多源理想气体模型和三火球模型分析并计算了能量在40,80,158 AGeV下中心Pb-Pb碰撞中所产生的(A)和(A)强子的横质量分布和快度分布,发现模型计算的结果与NA49合作组的实验结果相一致.     

300～1100nm多波段成像光学系统设计及杂光分析

设计了一套300～1100nm多波段光学系统,该系统能对目标的近紫外、可见光和近红外3个波段同时成像,可满足目标多波段信息探测的要求。由于在光学系统中镜筒内壁反射和棱镜表面反射会产生杂光和鬼像,因此,利用Light—Tools软件对此系统的杂光和鬼像进行了模拟分析。模拟结果表明,视场之外11．7—18．3°和-11．7～-18．3°的入射光线被胶合棱镜上下表面反射后,会聚焦到3个探测器靶面范围内,形成鬼像;6．2°-9．8°和一6．2°--9．8°的入射光线被镜筒反射后会在3个探测器上形成杂光。利用设计的多波段光学系统进行了相关实验,结果证明了模拟分析的正确性,表明此分析能用于指导多波段光学系统的设计和研制。提出了减少杂光和鬼像的相应措施,实验结果验证了提出的措施能够减少杂光及消除鬼像,提高系统成像质量。     

高功率980nm垂直腔面发射激光器的亮度特性

在循环水冷却(工作环境温度控制在15℃)和连续注入电流条件下,从垂直腔面发射激光器(VCSEL)亮度基本定义出发,实验测量了不同注入电流时口径为400μm的高功率980nm InGaAs/GaAs应变量子阱垂直腔面发射激光器(VCSEL)的亮度特性。结果表明:在注入电流4 A时,随着注入电流的增加,亮度也跟着增加;当注入电流4A时,尽管输出功率在增加,但是器件的光束质量变差,M2因子升高,表明此时影响器件亮度的主导因素是M2因子,所以亮度减小;在注入电流为4A,输出功率为1.2W时,亮度达到最大值2.43kW/cm2.sr,此时的光束质量最好,M2因子为207。最后,分析了影响高功率VCSEL器件亮度特性的主要因素,提出了提高器件亮度特性的解决方法。     

光学特异材料的设计

In this contribution we review our latest achievements of combined experimental and theoretical studies to tailor the properties of optical metamaterials（MMs） at will. We give three examples of metamaterial designs that have been realized by means of electron-beam lithography and whose spectroscopic characteristics have been comprehensively investigated. In every case, our experiments are complemented by rigorous numer ical simulations. Particular emphasis is put on the significance of such tailored effective properties of optical MMs     

Numerical simulations of the impact of wavefront phase distortions of pump on the beam quality of OPA

<正>A numerical model of optical parametric amplification(OPA) is introduced to investigate the impact of wavefront phase distortion of pump on the beam quality of signal.Numerical results show that the unidentical walk-off directions of the pump and the idler waves are the main factors leading to the transfer of wavefront phase distortions of the pump to the signal,and by reducing the angle between the two directions,the beam quality factor(M~2) can be greatly decreased and hence the good beam quality of the signal can be maintained.     

MS-ADoG域结合ReNLU与VGG-16的矿井双波段图像融合算法

为满足矿井视频监控需求,针对现有图像融合算法获取的融合图像存在伪目标、模糊目标、晕光遮挡目标等问题,提出了一种基于多尺度和自适应高斯差分变换,结合修正非线性单元和VGG-16的矿井双波段图像融合算法.设计了基于多尺度和自适应高斯差分变换的源图像分解模型,将红外和可见光图像分解为基础图像和细节图像;构造了一种修正非线性单...     

具有连续参数齐次随机场的线性预测(Ⅲ)

提出和研究了一般的斜半平面及角状区域上的具有连续参数齐次随机场的线性预测问题,且推广了文[1]的结果.     

网络借贷收窄利率定价区间的影响研究——基于倾向性分数匹配法

随着网络借贷的发展,学术界对网络借贷的研究逐渐深入。利率定价机制是网络借贷机制设计的核心,体现了金融的本质——对风险的定价,并逐渐成为学术研究的话题。Wei和Lin^[1]曾记录和分析了美国网络借贷机制变更的过程。本文选用国内一家代表性的网络借贷平台数据,用倾向性分数匹配法对其利率定价机制变化前后的交易行为进行研究,发现当平台收窄了利率区间且降低了合格借款人的审核通过率,违约率反而更高。狭窄的利率区间降低了利率区分度,而利率区分度是投资人判断具体贷款所处风险水平的重要依据,实际上恶化了信息不对称,影响投资人投资行为,具体表现为满标时间延长、单笔贷款投标占比减少,并且投资人羊群行为加重。本文以期限利率周度标准差为利率区间的代理变量,解释了上述变化产生的原因。平台收窄利率区间,降低了贷款质量优劣的区分度,使得平台和投资人风险识别效率降低,未能达到平台运营优化的结果。本文丰富了网络借贷的学术研究,为网络借贷利率定价机制的发展提供参考。     

Thermodynamic Performance Characteristics of a Brownian Microscopic Heat Engine Driven by Discrete and Periodic Temperature Field

A Brownian microscopic heat engine with a particle hopping on a one-dimensional lattice driven by a discrete and periodic temperature field in a periodic sawtooth potential is investigated. In order to clarify the underlying physical pictures of the heat engine, the heat flow via the potential energy and the kinetic energy of the particles are considered simultaneously. Based on describing the jumps among the three states, the expressions of the efficiency and power output of the heat engine are derived analytically. The general performance characteristic curves are plotted by numerical calculation. It is found that the power output-efficiency curve is a loop-shaped one, which is similar to one for a real irreversible heat engine. The influence of the ratio of the temperature of the hot and cold reservoirs and the sawtooth potential on the maximum efficiency and power output is analyzed for some given parameters. When the heat flows via the kinetic energy is neglected, the power output-efficiency curve is an open-shaped one, which is similar to one for an endroeversible heat engine.     

Difference of Directions Between External Driving Force and Movement Direction of Center of Mass

Driven dynamics of a two-dimensional Frenkel-Kontorova model is studied in the paper. In our numerical simulations, it is found that the movement direction of the center of mass is not consistent with that of the external driving force except for some special symmetric directions at the lower driving force. Our results also indicate that the movement direction of the center of mass strongly depends on both the magnitude and the direction of the external driving force as well as the misfit angle between two layers.