Characteristics of island growth of Hg1−xCdx Te on (100) CdTe substrates by chemical vapor transport

The characteristics of island growth of Hg_1−xCd_xTe (MCT) by chemical vapor transport on (100) CdTe substrates have been studied, for the first time, by optical microscopy, by infrared transmission spectroscopy, and by chemical etching. Nonuniformities of the growth thickness, of the growth rate, and of the composition of islands are observed. Based on the experimental results, the origin and the inhibition of island growth of MCT on (100) CdTe substrates are discussed.     

A study of risk-based non-destructive in-service inspection

Based on the concept of probabilistic fracture mechanics, non-destructive inspection policies are studied in this paper. Special attention is paid to the reduction of structural failure probability through the employment of in-service inspection (ISI). Analytical formulation is derived and numerical examples are presented. In addition to the conclusions drawn from numerical experience, the present study indicates how appropriate ISI schedule can be planned by considering the risk of structural failure in situ.     

MoS2纳米材料在食品检测中的研究进展

二硫化钼(MoS_2)纳米材料典型的"三层夹心"片层结构,使其具有特殊的物理、化学、光学、电学特性,也为其在食品检测中的应用奠定了基础。本文首先简单介绍了二硫化钼的不同制备方法,包括机械剥离法、液相剥离法等,化学气相沉积法和水热法,并对制备方法的优缺点和应用领域进行比较,然后综述了基于MoS_2纳米材料的检测方法在食品检测领域的研究现状,主要包括比色法、荧光法、电化学传感器、光纤传感器和基于场效应晶体管的传感器等新型检测方法,简单述评MoS_2的性能在检测中的应用,以及检测方法的特点、原理和应用,最后对展望了基于MoS_2的检测技术在食品检测中的发展前景,以及可能面临的挑战。     

Transient behavior of Hg1−xCdxTe film growth on (111)B CdTe substrates by chemical vapor transport

As part of a systematic investigation of the effects of substrate surfaces on epitaxial growth, the transient behavior of Hg_1−xCd_xTe film growth on (111)B CdTe by chemical vapor transport (CVT) has been studied as a function of growth time under vertical stabilizing (hot end on top) and vertical destabilizing (hot end at bottom) ampoule orientations. The experim ental results show the morphological transition of the Hg_1−xCd_xTe deposition on (111)B CdTe at 545°C from three-dimensional islands to layers within about 0.5 and 0.75 h for the growth under vertical stabilizing and destabilizing conditions, respectively. The combined effects of small convective flow disturbances on the growth morphology and defect formation are measurable. The overall trends of the time dependent growth rates and compositions of the Hg_1−xCd_xTe epitaxial layers under stabilizing and destabilizing conditions are similar. The system atically higher growth rates of the Hg_1−xCd_xTe films by about 10% under vertical destabilizing conditions could be influenced by a small convective contribution to the mass transport. The combined results show that improved Hg_1−xCd_xTe epitaxial layers of low twin density on (111)B CdTe substrates can be obtained by CVT under vertical stabilizing conditions.     

基于联邦强化学习的分布式模型剪枝

联邦学习系统中, 在资源受限的边缘端进行本地模型训练存在一定的挑战. 计算、存储、能耗等方面的限制时刻影响着模型规模及效果. 传统的联邦剪枝方法在联邦训练过程中对模型进行剪裁, 但仍存在无法根据模型所处环境自适应修剪以及移除一些重要参数导致模型性能下降的情况. 本文提出基于联邦强化学习的分布式模型剪枝方法以解决此问题. 首先, 将模型剪枝过程抽象化, 建立马尔可夫决策过程, 使用DQN算法构建通用强化剪枝模型, 动态调整剪枝率, 提高模型的泛化性能. 其次设计针对稀疏模型的聚合方法, 辅助强化泛化剪枝方法, 更好地优化模型结构, 降低模型的复杂度. 最后, 在多个公开数据集上将本方法与不同基线方法进行比较. 实验结果表明, 本文所提出的方法在保持模型效果的同时减少模型复杂度.     

Histamine content and histamine-forming bacteria in dried milkfish (Chanos chanos) products

Thirty-two dried milkfish products sold in five retail markets in southern Taiwan were purchased and tested to determine the occurrence of histamine and histamine-forming bacteria. Except for histamine and cadaverine, the average content of various biogenic amines in tested samples was less than 8.5 mg/100 g. Most of the tested dried milkfish products (78.1%) had histamine levels greater than the FDA guideline of 5 mg/100 g for scombroid fish and/or product, while fourteen of them (43.7%) contained > 50 mg/100 g hazard action level. Thirty histamine-producing bacterial strains, capable of producing 5.4 ppm to 562 ppm of histamine in trypticase soy broth supplemented with 1.0% L-histidine (TSBH), were identified as Enterobacter aerogenes (seven strains), Citrobacter sp. (one strain), Staphylococcusxylosus (ten strains), S. sciuri (one strain), Bacillus thuringiensis (two strains), Citrobacter freundii (five strains), Klebsiella pneumoniae (one strain) and E. cloacae (three strains), by 16S rDNA sequencing with PCR amplification.