级联三能级系统中极化拍频的不对称特性

在泵浦光为窄带或宽带的情形下,我们对级联三能级系统中极化拍频的不对称特性进行了研究,发现这种不对称特性是由于光学元件色散所导致的零延时的漂移引起的.     

填充右左手材料矩形屏蔽微带线色散特性的比较研究

运用矢量有限元法对填充右左手材料的矩形屏蔽微带线的色散特性进行比较研究,包括矩形单信号对称屏蔽微带线,矩形单信号不对称屏蔽微带线,矩形双信号对称屏蔽微带线,矩形双信号位置不对称屏蔽微带线,矩形双信号宽度不对称屏蔽微带线以及矩形双信号厚度不对称屏蔽微带线六种情况.讨论这些屏蔽微带线的主模色散特性随填充材料的变化,色散特性的研究有助于矩形屏蔽微带线和左手材料在新型微波器件中的应用.     

四维杂化弦

利用十维N-S玻色弦和四维费米弦杂化,我们给出了四维杂化弦.其内部规范对称群为[SU(2)]⁶.它的基态包含有四维时空的超引力多重态及四维超杨-Mills规范多重态.四维杂化弦具有超对称、无快子态及洛仑兹不变等特性.     

非对称全同质点共线系统的振动

研究了直线型三个、四个全同质点体系在不对称的边界条件下的内部运动，发现一些新的振动模式。     

关于RLC电路谐振特性曲线的对称性问题

通过引入不对称因子δ从理论上讨论了ＲＬＣ谐振回路的谐振曲线相对于谐振频率的牟称性问题，计算表明，在低Ｑ值下谐振曲线是不对称的，为使整条曲线具的近似的对称特性，要求回路的Ｑ〉１００。     

单周期激光脉冲序列作用下H原子光电离率的不对称性

采用非微扰散射理论，分别研究了线偏振的单周期激光脉冲序列以及圆偏振的单周期激光脉冲序列作用下，H原子的光电离特性。对相反方向上的光电子的不对称性进行了研究，结果表明其不对称程度与载波－包络（CE）相位、激光强度及光电子的动能有关。线偏振时，最大电离率随CE相位变化，且不对称程度随CE相位的变化呈正弦曲线特性；圆偏振时，最大电离率是常数，不随CE相位变化，但不对称程度随CE相位的变化仍呈正弦曲线特性。     

基于元胞自动机模型的道路突发瓶颈现象研究

针对特殊交通事件诱发的道路突发瓶颈现象,结合驾驶员在瓶颈现象发生前后的行为变化,提出了一个考虑驾驶员在瓶颈处驾驶特性的元胞自动机模型,并利用该模型分析了瓶颈现象对驾驶特性的影响.结果发现,该模型可以刻画不对称换道和瓶颈处抢道行为所产生的一些复杂的交通现象.研究表明,在瓶颈处实行不对称交替通行可以提高系统流量.     

两种新型对称卟啉的合成及紫外可见光谱特性研究

本文采用一种新型的合成方法合成了两种新型对称卟啉meso-四（对苯甲酰胺基苯基）卟啉和meso－四（邻苯甲酰胺基苯基）卟啉,用元素分析,红外光谱,核磁共振谱对两种卟啉进行了表征,并对其紫外可见光谱特性进行了研究。     

水中倒影的计算机仿真实验研究

本文讨论了用matlab对水中倒影所做的计算机仿真实验,解释了不对称微幅波浪中的倒影的一个特性。     

基于对称变换的人脸图像眼睛定位方法

利用图像灰度分布的特性,从计算对称值的角度出发,利用梯度对称变换,实现了一种自动定位人脸图像中眼睛的算法。经计算机模拟实验表明,它对一定程度的背景干扰以及光照的变化不敏感,对正面人脸且在眼睛张开的情况下,对称变换的定位准确率可以达到95%以上。     

RLC暂态电路的理论分析和数值模拟

利用Maple符号计算软件做RLC电路方程的拉普拉斯变换,得到电路的精确解,绘制解的图像,并且理论分析了这些解的特点,得到了一些有助于教学应用的结论.     

Modifying a graphene layer by a thymine or a uracil nucleobase: DFT studies

The hybridizations of a graphene layer by a thymine and a uracil nucleobase have been investigated by performing density functional theory (DFT) calculations. The isolated and hybrid structures have been firstly stabilized to reach the minimum energy and the electronic properties have been subsequently evaluated for the optimized structures. The structural and atomic scale parameters indicated that the tip of graphene is important in determining the properties of new hybrids. Moreover, different effects of thymine and uracil nucleobases have been identified in the hybrid structures. Quadrupole coupling constants have been evaluated to characterize the atomic scale properties, in which the most notable effects of hybridizations have been observed for the atoms close to the linking regions whereas negligible effects have been seen for other atoms.     

Investigation of the radial compression of carbon nanotubes with a scanning probe microscope

Efforts have been made to characterize the mechanical properties of carbon nanotubes. Previous work has concentrated on the tubes' longitudinal properties, and studies of their radial properties have lagged behind. We have used a scanning probe microscope with an indentation/scratch function to investigate the radial compression of multiwalled carbon nanotubes under an asymmetric stress. In particular, we have determined the radial compressive elastic modulus at different compression levels and have estimated the compressive strength to be well beyond 5.3 GPa.     

插入生长AlGaAs薄膜对InAs量子点探测器性能的影响

利用分子束外延生长获得的两个InAs量子点样品制备了n型的量子点红外探测器.对于其中一个器件,在InAs量子点有源区的底部和顶部分别插入生长了AlGaAs势垒层.利用透射电阻显微技术研究了两个样品的结构特性;利用光致发光光谱和光电流谱研究了两个器件的光电性质.实验结果表明,AlGaAs层的插入对器件的探测性质有显著的影响.利用有三维效质量近似模型的计算结果,指认了带内光电流谱中峰结构的起源. 关键词： InAs 量子点 AlGaAs薄膜 光致发光光谱 有效质量近似模型     

插入生长AlGaAs薄膜对InAs量子点探测器性能的影响

利用分子束外延生长获得的两个InAs量子点样品制备了n型的量子点红外探测器.对于其中一个器件，在InAs量子点有源区的底部和顶部分别插入生长了AlGaAs势垒层.利用透射电阻显微技术研究了两个样品的结构特性；利用光致发光光谱和光电流谱研究了两个器件的光电性质.实验结果表明，AlGaAs层的插入对器件的探测性质有显著的影响.利用有三维效质量近似模型的计算结果，指认了带内光电流谱中峰结构的起源.     

On wave propagation in a random micropolar thermoelastic medium,second moments,and associated Green’s tensor

The couple stress theory developed by Eringen comprises granular materials as also composite fibrous materials. As such, micropolar materials present an inclusive model of composite materials. This article endeavors to study aspects of wave propagation in a random weakly thermal micropolar elastic medium. The smooth perturbation technique has been employed. The classical thermoelasticity has been used. Six different types of waves have been observed to propagate in the random interacting medium. Dispersion equations have been derived. The effects due to random variations of micropolar elastic and thermal parameters have been observed. Change of phase speed occurs on account of randomness. Attenuation coefficients for high-frequency waves have been computed. Second moment properties have been discussed with application to wave propagation in the random micropolar elastic medium. 36 + 1 components of the associated Green’s tensor have been computed. Integrals involving correlation functions have been transformed to radial forms. A special type of correlation function has been used to approximately measure effects of random variations of parameters.     

Quantum glassiness in strongly correlated clean systems: an example of topological overprotection

This Letter presents solvable examples of quantum many-body Hamiltonians of systems that are unable to reach their ground states as the environment temperature is lowered to absolute zero. These examples, three-dimensional generalizations of quantum Hamiltonians proposed for topological quantum computing, (1) have no quenched disorder, (2) have solely local interactions, (3) have an exactly solvable spectrum, (4) have topologically ordered ground states, and (5) have slow dynamical relaxation rates akin to those of strong structural glasses.     

Electromagnetic cavity to explore disordered systems

In the course of characterizing an electromagnetic cavity we have come to understand details of transmission and reflection traces, some of which may be useful as tools to investigate local modes in random media. We have demonstrated quantitative agreement of frequency shift observations with theory, have demonstrated that the spatial distribution of electric and magnetic fields can be measured using insulating and conducting spheres, and have used perturbation due to wires and disks to demonstrate the local direction of electric and magnetic fields. We have observed that not only frequency shifts but also spatial shifts of modes can be used to observe the intensity of interaction of modes with extended objects in the cavity.     

分形用于材料断裂韧性研究的不定性问题

 本文基于物理、断裂力学与分形三者必须自洽的原则，提出了消除码尺的量纲与量值选择的不确定性的几何与物理准则，克服了分形用于断裂韧性研究中的不确定性困难。本文的某些观点用于分形在其它学科中的应用，也颇有益处。     

Characteristic of microstructured optical fibers: an analytical approach

We have recently developed a simple analytical model to study propagation characteristics of microstructured optical fibers (MOFs). We have used this model to study splice losses between two MOFs and also between an MOF and a conventional fiber. We have also presented here the results on evolution of fundamental mode from near-field to far-field, the effective mode area and the beam divergence using this model. Comparisons with available experimental and modeling results have also been included.