Simultaneous estimation of Poisson means

In the simultaneous estimation of means from independent Poisson distributions, an estimator is developed which incorporates a prior mean and variance for each Poisson mean estimated. This estimator possesses substantially smaller risk than the usual estimator in a region of the parameter space and seems superior to other estimators proposed to estimate p Poisson means. It is indicated through two asymptotic results that, unlike the conjugate Bayes estimator, the risk of the estimator does not greatly exceed the risk of the usual estimator outside of the region of risk improvement.     

Simulation of near-infrared photodiode detectors based on β-FeSi_2/4H-SiC heterojunctions

In this paper,we propose a near-infrared p-type β-FeSi2/n-type 4H-SiC heterojunction photodetector with semiconducting silicide(β-FeSi2) as the active region for the first time.The optoelectronic characteristics of the photodetector are simulated using a commercial simulator at room temperature.The results show that the photodetector has a good rectifying character and a good response to near-infrared light.Interface states should be minimized to obtain a lower reverse leakage current.The response spectrum of the β-FeSi2/4H-SiC detector,which consists of a p-type β-FeSi2 absorption layer with a doping concentration of 1×1015cm-3 and a thickness of 2.5 μm,has a peak of 755 mA/W at 1.42 μm.The illumination of the SiC side obtains a higher responsivity than that of the β-FeSi2 side.The results illustrate that the β-FeSi2/4H-SiC heterojunction can be used as a near-infrared photodetector compatible with near-infrared optically-activated SiC-based power switching devices.     

PVK空穴传输层对Ndq3近红外发光二极管性能的影响

以PEDOT∶PSS作为空穴注入层,聚合物PVK作为空穴传输层,制备了结构为ITO/PEDOT∶PSS/PVK/8-羟基喹啉钕(Ndq3)/Al的近红外OLED,研究了PVK与PEDOT∶PSS功能层对器件I-V特性和EL光谱的影响。结果显示,在EL光谱中的905,1 064,1 340 nm处均观察到了荧光发射,分别对应于Nd3+的4F3/2→4I9/2、4F3/2→4I11/2和4F3/2→4I13/2能级跃迁。与参考器件对比分析认为,PEDOT∶PSS高的导电性降低了器件的串联电阻,增大了器件的工作电流;PVK与PEDOT∶PSS共同降低了空穴的注入势垒,实现了Ndq3发光层区域的载流子的注入平衡并改善了器件的发射强度。此外,PVK有效降低了ITO电极表面粗糙度,也是器件性能提高的原因之一。     

182Os 核yrast带相继SU(3)–U(5)–SU(3)结构相变势能曲面的一种可能理解

基于联合实施微观相互作用玻色子模型的最大F旋方案 (sdIBM-F_max)与γ射线能量-自旋曲线 (γ-ray energy over spin curves, E-GOS)方案, 成功描述了¹⁸²Os核yrast带相继的SU(3)–U(5)–SU(3)结构相变, 由于缺少直观解释而显得抽象. 本文借助微观sdIBM-F_max的微观参数与Bohr哈密顿量的势能曲面方程之间存在的泛函关系, 几何地给出了对这种相继相变途径的另外一种可能理解; 并阐述了在完全变形核的高角动量态中, 由于量子效应在高激发态与低激发态之间生成高简并的临界区, 提供了γ振动能量会变得低于转动能量的一个可能途径, 从而实现了SU(3)–U(5)的相变. 关键词： yrast带结构演化 势能曲面 相变临界区 182Os核')" href="#">¹⁸²Os核     

Systematic Study on the Superdeformed Bands of Double Odd Nuclei in A～130 Region

Properties of the superdeformed bands of odd-odd nuclei in A～130 mass region are investigated systematically within the supersymmetry scheme including many-body interactions and a perturbation possessing the SO(5) (or SU(5)) symmetry on the rotational symmetry. The obtained γ-ray energies, the dynamical moments of inertia, and energy differences △Eγ - △Eγ^ref agree wlth experimental data. It shows that this approach is quite powerful in describing odd-odd nuclei in 130 mass region.     

Self-similar propagation region in passive optical fibers based on low-order approximation

For the first time, we numerically demonstrate that similaritons in passive fibers can only propagate with parabolic profile without oscillations in a limited self-similar propagation region when low-order approximation is applied. Dispersion-decreasing fiber (DDF) and nonlinearity increasing fiber (NIF) are used here to generate self-similar pulse in different passive ways. Moreover, we put forward several self-similar features to judge effective similariton propagation and determine self-similar region by numerical simulations and waveform observation. Finally we compare in DDF and NIF the dependence of these regions on incident pulse and fiber parameters in order to obtain parabolic similariton more effectively and steadily. These results extend the low-order propagation properties in passive fibers and are beneficial for the generation of high-quality similariton pulse by parameter selection in experimental studies and practical applications.     

Optical microstrip patch antennas design and analysis

This paper has presented transparent conductor oxide materials (TCOMs) based microstrip patch antennas with glass substrate and copper ground plane, which have been deeply analyzed in the visible spectrum region in comparison with the practical patch antenna model of indium tin oxide patch with glass substrate and different TCOMs based ground plane. As well as the study have investigated the effect of transparent oxide materials on patch antenna design instead of perfect conductor materials such as copper that has low cost and weight. The tradeoff between optical transparency and electrical conductivity will be evaluated for a range of visible regions. Microstrip transmission line feed method is used to predict the skin effects on a patch antenna and their impact on antenna efficiency, resonance frequency and optical transmission are also described. This study have discussed assessment of these tradeoffs and effect of TCOMs parameters on antenna design.     

Image segmentation using adaptive loopy belief propagation

Loopy belief propagation (LBP) algorithm over pairwise-connected Markov random fields (MRFs) has become widely used for low-level vision problems. However, Pairwise MRF is often insufficient to capture the statistics of natural images well, and LBP is still extremely slow for application on an MRF with large discrete label space. To solve these problems, the present study proposes a new segmentation algorithm based on adaptive LBP. The proposed algorithm utilizes local region information to construct a local region model, as well as a local interaction region MRF model for image segmentation. The adaptive LBP algorithm maximizes the global probability of the proposed MRF model, which employs two very important strategies, namely, “message self-convergence” and “adaptive label pruning”. Message self-convergence can improve the reliability of a pixel in choosing a label in local region, and label pruning can dismiss impossible labels for every pixel. Thus, the most reliable information messages transfer through the LBP algorithm. The experimental results show that the proposed algorithm not only obtains more accurate segmentation results but also greater speed.     

频域近红外光谱法研究生物组织内部光子传输特性

基于光子在生物组织中的辐射传输理论以及Feng模型,应用频域近红外光谱法研究生物组织中异质体位置的变化,对出射光的光强和相位变化的影响及规律。设计了一仿真实验,用牛奶代替强散射性质的生物组织,并在牛奶中放置一个高度可控的具有一定吸收系数和散射系数的小球。移动小球在牛奶中的高度,检测出射光的交流幅度AC、直流光强DC和相位延迟Phase的值,绘制小球位于不同深度时AC,DC和Phase的曲线,并探讨其变化规律。结果表明,随着小球在牛奶中深度的变化,光强AC,DC和相位Phase呈现一定的相关性;随着光源和检测器之间距离的增加,检测到的光强和相位曲线的波谷点均向右偏移;当小球偏离光源和检测器越远,对检测到的光强和相位的影响越小。验证了光子在生物组织中的传输规律,为用频域近红外光谱法进行组织光学参数的检测及组织中异质体位置的定位奠定了基础。     

高非线性光子晶体光纤深紫外超连续谱的研究

光子晶体光纤作为光学非线性良好介质,对超连续谱产生具有重要作用。深紫外超连续谱光源在许多应用中有急切的需求,然而由于实验条件和光纤参数等方面的影响,利用高非线性光子晶体光纤产生深紫外(<280 nm)超连续谱的报道较少。通过理论和实验研究了高非线性光子晶体光纤在深紫外区的频率变换,并分析其产生的物理机理。使用钛宝石飞秒激光器将实验室自制的光子晶体光纤在反常色散区泵浦,研究了不同泵浦功率和泵浦波长对深紫外区超连续谱的影响,结果表明：泵浦波长固定为860 nm时,深紫外频率光谱展宽范围随泵浦功率的增加而逐渐展宽;泵浦功率固定为0.4 W时,泵浦波长的增加不仅展宽超连续谱范围而且极大的提高了深紫外区光谱的转换效率。当泵浦波长为870 nm,泵浦功率为0.4 W,实验所用光子晶体光纤长度为1.45 m,零色散波长为825 nm时,光子与色散波的交叉相位调制使深紫外基模超连续谱扩展到最短波长212 nm。