Modelling the combined effects of salt,sorbic acid and nisin on the probability of growth of Clostridium sporogenes in a controlled environment (nutrient broth)

The safe preservation of new generation foods (high moisture, low salt, high pH and shelf stable under ambient conditions) is microbiologically challenging. The growth of Clostridium botulinum in low acid foods is a hazard for consumers. In this study the combined effect of salt (sodium chloride) (0–4% w/v), potassium sorbate (0–4% w/v) and nisin (0–300 ppm) at two different pHs (5.5 and 7) on the probability of growth of Clostridium sporogenes spores, as a non-toxigenic surrogate of C. botulinum, was evaluated in nutrient broth. Nutrient broth was used as it can easily and accurately be adjusted and controlled in terms of composition, and allows more rapid growth than is observed in food. The aims of this study were to develop probability of growth models in which the logit is expressed as a function of the concentrations of the selected preservatives. The developed models fit the data adequately. The c-values models were close to 1, indicating good predictive power. This indicates the performance of models would be satisfactory. The results of this study indicated that salt, potassium sorbate and nisin had significant inhibitory effects on the growth of C. sporogenes in high moisture (>95%) and high pH conditions (pH > 4.5). Combinations of the selected preservatives were more effective than any of them individually. The inhibitory effects of all three preservatives in the current study were pH dependent. Less stringent combinations of preservative concentrations were required experimentally to stop growth at pH 5.5 compared with pH 7.     

Novel dynamic semiempirical proton exchange membrane fuel cell model incorporating component voltages

This paper introduces a novel dynamic semiempirical model for the proton exchange membrane fuel cell (PEMFC). The proposed model not only considers the stack output voltage but also provides valid waveforms of component voltages, such as the no‐load, activation, ohmic, and concentration voltages of the PEMFC stack system. Experiments under no‐load, ramping load, and dynamic load conditions are performed to obtain various voltage components. According to experimental results, model parameters are optimised using the lightning search algorithm by providing valid theoretical ranges of parameters to the lightning search algorithm code. In addition, the correlation between the vapour and water pressures of the PEMFC is obtained to model the component voltages. Finally, all component voltages and the stack output voltage are validated by using the experimental/theoretical waveforms mentioned in previous research. The proposed model is also compared with a recently developed semiempirical model of PEMFC through particle swarm optimisation. The proposed dynamic model may be used in future in‐depth studies on PEMFC behaviour and in dynamic applications for health monitoring and fault diagnosis.     

石材干挂的设计与施工

主要阐述石材干挂设计要点．并针对石材干挂施工法在抗震设防区装饰工程应用中如何确保在重力荷载、风荷载和地震荷载和温度作用下建筑物的使用安全。     

非坚持型CSMA与坚持型CSMA退避算法的性能分析与比较

从非坚持型CSMA与坚持型CSMA协议的工作原理出发，分析非坚持型CSMA与坚持型CS-MA协议吞吐量的计算方法，然后模拟协议仿真，比较了两种协议的性能。     

盲道建设与使用状况的研究与思考

盲道作为无障碍设施建设中重要的组成部分，体现了社会进步和文明的提升．笔者针对长春市盲道建设与使用现状，从剖析盲道建设的内涵、发展历程出发，提出关于盲道建设中的规划与设计方面的建议，以期切实推动长春市无障碍设施建设．     

120W适配器的研发

本文介绍了100W以上功率适配器电源PFC及PWM两部分的设计理念以及降低空载功耗的方法。     

无盘Win98与Win2003终端的完美组合

无盘Windows98不能运行Office2003等最新的软件,本文介绍增设Windows2003终端服务器,使工作站以终端的方式运行最新版的软件。     

一种实用的成绩加密法

基于无纸化考虑系统对数据安全的要求，介绍了一种实用的成绩加密方法并对该方法的实现关键细节作了阐述。     

在Visual C++中利用COM实现对Word的调用

介绍了基于Wicrosoft公司提出的COM技术，在VisualC^ 中实现Windows环境计算机无纸化考试系统中对排版软件Word进行自动有效评分的方法。     

35kV真空断路器开断空载变压器时过电压的研究

切除空载变压器是真空断路器操作过电压问题最严重的情况，文中在真空断路器开断交流电流真空间隙介质恢复的物理过程的基础上，建立了灭弧室介质强度恢复的数学模型，采用Saber软件的MAST语言编程，对真空断路器开断空载变压器的一个完整过程进行了仿真计算。根据计算结果。分析了暂态过程，过电压的特点 及变压器，真空断路器参数对过电压的影响，并与平均恢复速度计算结果进行了比较，表明本文建立的灭弧室计算模型更接近于实测恢复特性。