离子注入诱导量子阱界面混合效应的光致荧光谱研究

采用多元芯片方法获得了一系列不同离子注入剂量的GaAsAlGaAs非对称耦合量子阱单元,通过光致荧光谱测量,研究了单纯的离子注入导致的界面混合效应.荧光光谱行为与有效质量理论计算研究表明,Al原子在异质结界面的扩散在离子注入过程中已基本完成,而热退火作用主要是去除无辐射复合中心. 关键词： 量子阱 离子注入 光致荧光谱 界面混合     

1,2,4,6—四苯基—2—羟基—8—氮杂双环[3、2、1]辛烷的核磁共振研究

用多种核磁共振实验方法并结合其它结构信息,确定1,2,4,6-四苯基-2-羟基8-氮杂双环[3、2、1]辛烷的化学结构,并指定该化合物的核磁共振归属。     

Assessment of dispersion corrections in DFT calculations on large biological systems

The performance of empirical dispersion corrections in DFT calculations has been assessed for several large, genuine biological systems that include MbAB, H64L(AB), and V68N(AB) (AB?=?CO, O₂), where Mb stands for a wild-type myoglobin, H64L is the (histidine64?→?leucine) mutated myoglobin, and V68N is the (valine68?→?asparagine) mutated myoglobin. The effects of the local protein environment are accounted for by including the five nearest surrounding residues in the calculated systems and they are examined by comparing the binding energies of AB to the myoglobin and to the porphyrin (Por) without residues. Three versions of Grimme's dispersion correction methods, labeled as DFT-D1, DFT-D2, and DFT-D3, were all tested. In the first version (-D1), the dispersion correction (E_disp) is calculated only for noncovalent interactions between molecular fragments and E_disp within a covalent molecule is not calculated. For the DFT functionals, for which the calculated Por–AB binding energies are already too large, only further overestimation occurs when a dispersion correction is made. The geometry optimizations show that the DFT-D2 and DFT-D3 approaches give too short distances between the residues and the heme moiety in the myoglobins and their calculated relative binding energies ΔE_bind(myoglobin-AB/Por–AB) are in poor agreement with experiment in most cases. DFT-D1 performs very well, ensuring structural and energetic features in close agreement with experiment.     

Magnetic transition and large reversible magnetocaloric effect in EuCu1.75P2 compound

The magnetocaloric effect(MCE) in EuCu1.75P2 compound is studied by the magnetization and heat capacity measurements.Magnetization and modified Arrott plots indicate that the compound undergoes a second-order phase transition at TC ～ 51 K.A large reversible MCE is observed around TC.The values of maximum magnetic entropy change(-△SxMma) reach 5.6 J·kg-1·K-1 and 13.3 J·kg-1·K-1 for the field change of 2 T and 7 T,respectively,with no obvious hysteresis loss in the vicinity of Curie temperature.The corresponding maximum adiabatic temperature changes(△Tadmax) are evaluated to be 2.1 K and 5.0 K.The magnetic transition and the origin of large MCE in EuCu1.75P2 are also discussed.     

高质量等曲率物参光像面数字全息显微系统

对等曲率物参光像面数字全息显微成像系统进行研究,分析了光路配置方法,推导了系统的点扩散函数,并由此指出了决定系统成像分辨率的因素及系统的成像特点,最后讨论了再现像光场一次位相畸变校正的方法.结果表明,等曲率物参光像面数字全息具有最大的信息容量;该系统的成像分辨率取决于显微物镜的数值孔径和CCD的像元大小,与CCD的光敏面尺寸无关;物体各点中通过显微物镜的所有频率成分均能被系统完全记录与再现,样品被照亮区域的大小对记录条件和再现像质没有影响;等曲率物参光像面数字全息系统是一种优化的全息记录与再现系统,利用该系统可以实现高质量成像.实验结果验证了理论分析的正确性.     

潘宁源放电的全三维电磁粒子模拟/蒙特卡罗碰撞数值算法研究

深入研究潘宁放电的物理机制, 研制了全三维高品质算法粒子模拟软件(PIC), 设计并添加了相应物理情景的蒙特卡罗碰撞模块(MCC), 并对电子、氢分子离子(H₂⁺)、氢正离子(H⁺)、氢三正离子(H₃⁺)同时进行了跟踪, 成功研制了全三维电磁PIC/MCC数值算法. 结合国内研究较热的潘宁放电模型, 对该算法进行模拟验证. 模拟结果显示: 采用有效的滤波算法能抑制电磁数值噪声, 电子能量呈麦克斯韦分布, 由于电子的径向漂移和加速导致离子源顶端H₂⁺产量较大. 关键词： 潘宁离子源 高品质算法 粒子模拟/蒙特卡罗     

DESIGNING A DIFFRACTIVE OPTICAL ELEMENT FOR CONTROLLING THE BEAM PROFILE IN A THREE-DIMENSIONAL SPACE USING THE SIMULATED ANNEALING ALGORITHM

We have designed a spatially quantized diffractive optical element (DOE) for controlling the beam profile in a three-dimensional space with the help of the simulated annealing (SA) algorithm. In this paper, we investigate the annealing schedule and the neighbourhood which are the deterministic parameters of the process that warrant the quality of the SA algorithm. The algorithm is employed to solve the discrete stochastic optimization problem of the design of a DOE. The objective function which constrains the optimization is also studied. The computed results demonstrate that the procedure of the algorithm converges stably to an optimal solution close to the global optimum with an acceptable computing time. The results meet the design requirement well and are applicable.     

Resolution and sensitivity enhancements in strong grating based fiber Fabry–Perot interferometric sensor system utilizing multiple reflection beams

We investigate an asymmetric intensive fiber Bragg grating (FBG) defined Fabry–Perot (F–P) sensor system decoded by a multiple-path-matched Michelson interferometer. The interrogation of higher order reflection beams cannot only solve the problem of the degraded resolution induced by the spectral mismatch of the FBGs, but also amplify the effect of the fiber strain on the phase of the light. We demonstrate multiple reflection beams in the F–P cavity based on the concept of the FBG effective length for constructing respective interrogation interferometers, and present a cost function with optimized system parameters to improve noise properties. The performances of interrogating the second, third and fourth order reflection beams are compared in a strain sensing experiment arrangement. Under the condition of the same optical path length mismatch, the interrogation of the fourth order reflection beam can achieve 9.8 dB sensitivity enhancement and 3 dB resolution promotion compared with the result using the second order reflection beam.     

颜色视觉匹配中显示器颜色色差阈值的评价

为了对阴极射线管(Cathode ray tube,CRT)显示器颜色恰可辨别的小色差阈值进行评价,在中性灰背景下,用编制的颜色匹配程序,在CRT显示器上随机产生颜色,分别调节程序中R、G、B通道的值,使匹配色与随机色达到视觉上的一致,进行颜色视觉匹配实验,测量CRT显示器上随机色和匹配色的L*a*b*值.用不同的色差公式对实验数据分别从明度、色调、饱和度进行比较分析,色差公式评价小色差的性能是CIEDE2000优于CMC(2∶1)和CIEL*a*b*.在a*b*图上绘制实验颜色恰可辨别图.不同色差公式计算的CRT显示器恰可辨别小色差阈值不同.