GROWTH DYNAMICS OF INDIGENOUS MICROBIAL POPULATIONS ON VEGETABLES AFTER DECONTAMINATION AND DURING REFRIGERATED STORAGE

To ensure microbiological stability and safety in minimally processed (MP) salad vegetables, it is essential to consider the microbiology of this produce during cultivation and harvesting, and the potential changes to this microbiology through preparation, distribution and storage. This study takes two salad vegetables (lettuce and white cabbage) and, having enumerated a range of different physiological groups of microorganisms present on unwashed produce, determines the impact on each microbial group of applying a decontamination step in the preparation protocol. The disinfectant used was sodium dichloroisocyanurate. Decontamination reduced the total microbial load significantly on both vegetables. The levels of different microbial groups enumerated differed significantly between vegetables. All the microbial populations were reduced, but the biocidal effect of chlorine treatment varied with vegetable type. Reduction of the levels of lactic acid bacteria and aerobic psychrotrophs on cabbage was only achieved with inclusion of the decontamination step, and this effect, in general, did not last more than 3 days. Decontamination significantly reduced the levels of coliforms, and although the levels increased during refrigerated storage, they did not exceed initial levels found on unwashed produce. In addition, the levels found on treated cabbage remained lower than produce washed with water only.     

极化电流行波方向继电器在带并联电抗器输电线上的特性

由于传统的光纤电流差动保护无法直接应用于带并联电抗器的输电线路,均需要进行补偿。基于极化电流行波方向继电器应用于带并联电抗器的线路,文中深入分析了并联电抗器上的行波过程、传输频域分析以及对基于小波变换的极化电流行波方向继电器的影响。结果表明,带并联电抗器的线路不会影响暂态行波波头的方向,同时也不会影响工频行波波头的提取。因此,基于极化电流行波方向继电器的保护能够直接适用于带有并联电抗器的线路。电磁暂态程序(EMTP)的仿真和实际装置的测试结果均表明了该保护在带并联电抗器线路上的优良特性。     

用有限元法分析水树尺寸对电场分布的影响

鉴于水树是交联聚乙烯(XLPE)绝缘电缆的主要劣化现象之一,而正确的评价电场分布对理解水树的生长机理及水树引起的介质击穿非常重要,利用有限元方法研究了水树枝初步生长阶段其几何参数(宽度和长度)对水树内部电场的影响。有限元分析结果显示:在相同宽度和相同介电常数的条件下,发散型水树越长,水树尖端的电场增强越明显;而在相同水树长度的条件下,水树枝宽度对水树尖端最大电场强度的影响很小;水树枝长度对电场分布的影响随内部介电常数的大小而变化,水树内部介电常数越大,水树长度对电场分布的影响越小。     

On the storage and regeneration of optimum routes

The implementation of many real-time automated routing procedures is dependent on a method of rapidly obtaining optimum routes in a very short amount of time for networks having large numbers of vortices. A method for the rapid regeneration of optimum routes is formulated in this paper. The method initially requires the solution of a sot of simultaneous inequalities. The solution of the resulting simultaneous inequalities provides points in a real space of n dimensions that are used with a metric to facilitate the decision process in obtaining any optimum route.

The problem is initially formulated to take advantage of a particular metric for solution as a problem of linear simultaneous inequalities and iterating solutions of linear simultaneous equations. The application of sparse matrix techniques to facilitate large scale problems is given along with an example using three metrics.     

Microorganisms Isolated from Surimi Processing Operations

Heterotrophic bacteria isolated from two shore-based surimi processing plants in Alaska were identified to the genus level. In one plant, the major bacterial constituents were Flavobacterium and Pseudomonas, followed by Moraxella, Aeromonas, Lactobacillus, Serratia, and Acinetobacter. In the other plant, major bacterial groups were Flavobacterium and Arthrobacter/Corynebacterium, followed by Pseudomonas and Acinetobacter. Pseudomonas, Aeromonas, and Serratia were capable of rapid growth as low as 8°C, with respective generation times 3.0, 3.1, and 3.6 hours. Freezing and thawing of surimi reduced microbial counts to 45–67% of the pre-frozen load; however, the composition of the microbial flora was maintained. The plant environment was a potential source of microbial contamination.     

数字化集成保护控制系统的实现方案

变电站数字化、智能化为站域信息共享提供了技术保障,因此开发了一种新型数字化集成保护控制(DIPC)系统。系统主要由设备层智能终端(IT)、合并单元(MU)和系统层多功能保护控制器(MPCU)三大核心部分构成,分别给出了它们的硬件架构和软件设计方案。该系统基于IEC61850标准,采用两级相量计算和保护起动判据,提高了保护的快速性和可靠性。测试结果表明,该系统可对故障作出快速、可靠的反应,其集成通信和运算能力满足保护跳闸的要求。     

Microorganisms on Commercially Processed Alaskan Finfish

Whole and processed Alaskan fish were examined for aerobic plate counts, total coliforms, and Escherichia coli. Washing whole salmon and halibut reduced skin microbial counts from 10³/cm² to 10²/cm². Whole and dressed fish had coliform counts less than 13/cm² and E. coli counts less than 0.3/cm². Alaska pollock and Pacific cod fillets had microbial counts between 10³/g and 10⁶/g, coliform counts less than 70/g, and E. coli counts less than 4/g. Whole fish contained microbial flora predominated by Moraxella species whereas dressed fish and fillets had microbial flora consisting of Arthrobacter/Corynebacterium, Flavobacterium, and Pseudomonas species. Microorganisms on conveyor belts and other contact surfaces may have contributed contaminants to fillets.     

碱添加量对金属离子的分布和pH变化的影响

提出了一种计算公式,定量地计算了既有氢氧化物沉淀又有氢氧配离子形成的化学反应体系中的金属离子的分布,考察了影响沉淀和配离子形成的各种因素.基于提出的公式,计算了锌、镉、铜、镍、铁(Ⅲ)、铁(Ⅱ)、铝、钙、镁的沉淀率,理论计算与实验结果一致.