The influence of space irradiated PIN photodetector on BER in satellite laser communication system

By analyzing the radiation dose on PIN photodetectors in space radiation environment, the variation of photocurrent and dark current after radiation is obtained. On the basis, the bit error rate of satellite laser communication based on space radiation dose of PIN photodetectors is established. According to simulation, when radiation dose is about 1.6 × 10³ Gy and 7 × 10⁴ Gy, bit error rate reaches 10⁻⁶ induced by 50 MeV and 10 MeV protons separately; and when radiation dose is within the range of 5 × 10 Gy–6 × 10⁵ Gy, electrons and gamma-ray irradiation also cause increase in bit error rate to 10⁻⁶. The principle of damage dose on bit error rate is investigated, and the influence of decision threshold on bit error rate is further discussed. The result shows that when radiation dose is 1 MGy, if decision threshold is increased from 4.3 × 10⁻⁷ A to 5.5 × 10⁻⁷ A, bit error rate will decrease about 4 orders of magnitude. Hence, a proper decision threshold can improve system bit error rate efficiently.     

定量型多指标决策的层次分析法探讨

本文采用等级标度与层次分析综合的方法对定量型多指标决策问题进行了讨论，它既是层次分析法在定量型多指标决策中的合理推广，同时也为定量型多指标决策问题提供了一种行之有效的方法．     

Multicriteria analysis in decision making under information uncertainty

This paper presents results of research related to multicriteria decision making under information uncertainty. The Bellman–Zadeh approach to decision making in a fuzzy environment is utilized for analyzing multicriteria optimization models (X,M models) under deterministic information. Its application conforms to the principle of guaranteed result and provides constructive lines in obtaining harmonious solutions on the basis of analyzing associated maxmin problems. This circumstance permits one to generalize the classic approach to considering the uncertainty of quantitative information (based on constructing and analyzing payoff matrices reflecting effects which can be obtained for different combinations of solution alternatives and the so-called states of nature) in monocriteria decision making to multicriteria problems. Considering that the uncertainty of information can produce considerable decision uncertainty regions, the resolving capacity of this generalization does not always permit one to obtain unique solutions. Taking this into account, a proposed general scheme of multicriteria decision making under information uncertainty also includes the construction and analysis of the so-called X,R models (which contain fuzzy preference relations as criteria of optimality) as a means for the subsequent contraction of the decision uncertainty regions. The paper results are of a universal character and are illustrated by a simple example.     

Using a partially observable Markov chain model to assess colonoscopy screening strategies – A cohort study

Colorectal cancer (CRC) is notoriously hard to combat for its high incidence and mortality rates. However, with improved screening technology and better understanding of disease pathways, CRC is more likely to be detected at early stage and thus more likely to be cured. Among the available screening methods, colonoscopy is most commonly used in the U.S. because of its capability of visualizing the entire colon and removing the polyps it detected. The current national guideline for colonoscopy screening recommends an observation-based screening strategy. Nevertheless, there is scant research studying the cost-effectiveness of the recommended observation-based strategy and its variants. In this paper, we describe a partially observable Markov chain (POMC) model which allows us to assess the cost-effectiveness of both fixed-interval and observation-based colonoscopy screening strategies. In our model, we consider detailed adenomatous polyp states and estimate state transition probabilities based on longitudinal clinical data from a specific population cohort. We conduct a comprehensive numerical study which investigates several key factors in screening strategy design, including screening frequency, initial screening age, screening end age, and screening compliance rate. We also conduct sensitivity analyses on the cost and quality of life parameters. Our numerical result demonstrates the usability of our model in assessing colonoscopy screening strategies with consideration of partial observation of true health states. This research facilitates future design of better colonoscopy screening strategies.     

Subwavelength structures for high power laser antireflection application on fused silica by one-step reactive ion etching

In this paper we report a simple method to fabricate a novel subwavelength structure surface on fused silica substrate using one-step reactive ion etching with two-dimensional polystyrene colloidal crystals as masks. The etching process and the morphologies of the obtained structure are controlled. We show that the period of the obtained fused silica pillar-like arrays were determined by the initial polystyrene nanoparticle size. The height of pillar arrays can be adjusted by controlling the etching duration, which is proved to be of importance in tailoring the antireflection properties of subwavelength structures surface. The novel subwavelength structures surface exhibit excellent broadband antireflection properties, but the size of the pillar affects the antireflective properties in short wavelength region. We anticipate this method would offer a convenient and scalable way for inexpensive and high-efficiency high power laser field designs.     

酸蚀与紫外激光预处理结合提高熔石英损伤阈值

采用HF酸刻蚀和紫外激光预处理相结合的方式提升熔石英元件的负载能力,用质量分数为1%的HF缓冲溶液对熔石英刻蚀1~100 min,综合透过率、粗糙度和损伤阈值测试结果,发现刻蚀时间为10 min的熔石英抗损伤能力最佳。采用355 nm紫外激光对HF酸刻蚀10 min的熔石英进行预处理,结果表明：紫外预处理能量密度在熔石英零损伤阈值的60%以下时,激光损伤阈值单调递增;能量到达80%时,阈值反而低于原始样片的损伤阈值。适当地控制酸蚀时间和紫外激光预处理参数能有效提高熔石英的抗损伤能力。     

Global Priority Estimation in Multiperson Decision Making

The analytic hierarchy process generalized to synthesizing local preferences across a complex hierarchy structure into global priorities in multiperson decision making is considered in various approaches. They include classic eigenvector synthesis and multiplicative method, and several other suggested techniques, such as three-dimensional eigenvectors, and simultaneous linear and nonlinear estimations by whole hierarchy structure in synthetic optimizing procedures. A numerical example from marketing research with many criteria, subcriteria, alternatives, and respondents is presented. The quality of approximation compared by different approaches shows that the best results are produced by the nonlinear synthetic priority techniques. The techniques described have been successfully used in dozens of real-world projects and are very helpful for practical managerial decision making in complex hierarchies. Dr. Stan Lipovetsky is Senior Research Director, GfK Custom Research North America, Marketing Science, Research Center for Excellence. The author thanks Professor T. Rapcsak and two reviewers for insightful suggestions that improved the paper.     

量子阱单激子光增益实现超低阈值连续波激光

胶质纳米晶光增益材料对于开发新一代的高效激光器前景巨大.采用外延生长法制备原子尺寸厚度的Ⅱ型CdSe/CdTe复合纳米片,研究该异质结构的光学性质及其对应的电荷动力学过程,以此探讨其光增益性能及激光应用潜能.光谱结果表明,Ⅱ型纳米片有效的电子与空穴分离结构使其表现出较大的斯托克斯位移（△_S=100 meV）和较强的激子-激子库伦排斥力（△_XX=50 meV）.△_S和△_XX的协同效应使"激子-双激子"吸收能相比单激子发射能提高了约150 meV,打破了一般纳米晶结构中两者的简并关系,这将有效抑制光吸收损失并促进单激子光增益.单激子光增益机制下该纳米片较长的单激子寿命（τ_x=394 ns）使连续激光泵浦的理论功率阈值低至12 W/cm²,这为开发实用性更强的、超低阈值的连续波激光器提供可能.