基于模糊识别方法的脉象信号分类识别

为了能够对脉象信号客观化、定量化的识别研究,采用模糊理论方法对脉象信号进行分类识别,将脉象信号的指感描述和判定规则进行客观描述和定量化,确定脉象指感因素的模糊输入变量;根据脉象信号的提取特征和脉象分类确定输出模糊变量;根据脉象定义确定模糊推理规则,从而完成可信度表示的脉象分类。得出采用模糊识别方法可以有效完成脉象信号分类识别的结论。     

模糊数学综合评判法在织物热湿舒适性评价中的应用

用模糊数学理论建立织物的热湿舒适性评价数学模型,对确定数学模型、计算权重、建立模糊关系矩阵和综合评价合成运算方法等进行了详述。通过模糊变换B=A.R,综合所得模糊信息,对织物的热湿舒适性进行了综合评价。     

遗传算法与模糊控制的融合研究

遗传算法是将问题的求解用染色体的形式表示,在其复制、交叉、变异的进化过程中收敛为一个最适应环境的染色体,即为问题的解。用遗传算法对模糊控制中的录属度函数进行编码,确定适应函数,作遗传运算与微量调整,可实现对录属度函数及控制规则的优化,改善模糊控制器的性能。     

冷藏陈列柜多机并联压缩机组节能的实验研究

阐述了冷藏陈列柜多机并联压缩机组的节能机理，通过与单机机组的试验比较与分析，充分说明了并联压缩机组的节能效果和优势。     

冷藏陈列柜空气预冷器设计

冷藏陈列柜中蒸发器结霜会使蒸发器换热性能恶化,空气阻力增加,进而使整个制冷系统性能下降.采用蒸发器分级,增加过热器作为空气预冷器等措施对原有的冷藏陈列柜进行了改造.实验结果表明,系统改进后,风幕的封闭能力大大提高,延长了融霜周期,从而降低了陈列柜的能耗.     

基于CWW评价包装造型感性方法研究

为准确反映消费者感性认知的不确定性,以犹豫模糊语言术语集描述消费者主观判断,分析其运算规则,构建语言计算(computing with words,CWW)犹豫模糊模型。实例分析表明,以犹豫模糊术语集描述消费者感性偏好并利用语言计算实现信息集结,有助于准确反映消费者主观认知,减少消费者对包装造型感性判断的不确定性。     

一类时变关联大系统的分散模糊变结构控制

提出了一种适用于一类时变关联大系统的分散模糊变结构控制方法,考虑到对于复杂系统,系统不确定性变化和关联变化的界很难预先确定下来,在分散变结构控制律中引入模糊规则来确定变结构切换控制的大小,由于模糊规则的引入,明显减弱了一般分散变结构控制系统的抖颤问题,同时在设计控制器时不需要确切知道系统不确定变化的具体情况,简化了控制器设计,仿真结果表明该控制方法是有效的。     

敞开式食品冷藏陈列柜研究进展

冷藏陈列柜作为食品冷链的末端设备,对保证食品品质和安全起到了重要作用。文章分别从冷藏陈列柜风幕性能、环境温湿度、柜体结构优化、蒸发器的结霜融霜、系统节能和相变蓄冷材料的应用等方面阐述了国内外的研究进展,主要分析了影响食品冷藏陈列柜柜内速度场和温度场分布的相关因素及改进方法,并从节约能源的角度论述了当前食品冷藏陈列柜的研究热点及今后发展方向,指出了冷藏陈列柜研究中存在的一些问题,为今后进一步研究提供参考依据。     

中密度纤维板热压时间模糊控制研究

针对中密度纤维板热压过程中可能因热压时间不合理导致纤维板出现水渍和鼓泡等质量缺陷,提出了一种热压时间模糊控制器。应用模糊控制的基本思想建立热压时间模糊控制器,结合Mamdani推理算法构建热压时间模糊控制查询表,用查表的方法代替模糊规则推理运算,实现热压过程的优化控制。仿真结果表明,优化后的控制系统超调量少,稳定性高,具有良好的控制精度。     

综合评判在教学质量评估中的应用

采用模糊数学理论对数学课教学质量评判进行数学建模 ,得到了三级模糊综合评判模型M( ., ) ,经确定评判因素集 ,确定权重、评语集和等级评语向量 ,确定隶属度向量和评价矩阵以及合成等步骤得到的简化模型 M( ., )能使运算简化 .结果表明 ,该模型用于教学质量评估 ,客观公正 ,可信度高 .     

基于CFD技术的高效节能冷柜研发

针对目前冷柜的研究开发主要靠经验和简单的计算,存在产品的开发周期长,费用高的缺点,提出了基于CFD技术的冷柜研发,介绍了CFD技术、封闭式冷冻陈列柜的结构及其热负荷组成。建立三维非稳态模型,编译用户自定义函数即UDF(User-Defined Function)程序,利用有限容积法优化冷柜内温度场/流场。应用结果表明基于CFD技术的冷柜研发不仅具有效率高、能耗低等特点,而且可以掌握柜内温度分布规律、改善了柜内部气流组织状况,提高了温度分布的均匀性,提高食物保鲜效果。     

柜外环境对立式冷藏陈列柜食品温度影响的研究

本文研究了环境温度、湿度及灯光照度相互之间对立式敞开式冷藏陈列柜食品温度的影响,以期为降低食品冷藏温度和提高冷藏食品的品质提供依据.实验发现立式敞开式冷藏陈列柜柜外环境温度、湿度以及灯光辐射对柜内食品温度的影响很大.随着柜外环境温度、湿度的升高,柜内食品的温度逐渐升高;随着柜外灯光照射强度的增加,柜内食品温度也逐渐升高,且当灯光强度达到一定程度时,增加少量的灯光都会对食品温度产生较大的影响,即降低环境温湿度及灯光照度有利于降低柜内食品温度,能较好保持好冷藏食品的品质,并且在较低湿度下运行,可以节省陈列柜能耗.     

Heat transfer modelling in a refrigerated display cabinet: The influence of operating conditions

The product temperature in refrigerated display cabinets is very variable and directly influences the safety and quality of food products. This variability is due to the type of display cabinet (vertical, horizontal), the position of the product inside the cabinet, fluctuations in the ambient temperature in supermarkets (day/night, opening hours, seasons, air conditioning, etc.) and the surrounding conditions of the display cabinet (in front of another refrigerated display cabinet or in front of grocery products, etc.).This study proposes a heat transfer model to predict the load temperature in an open vertical display cabinet. Heat transfer by conduction, convection and radiation was taken into account in the model. Four load positions were considered: top/front, top/rear, bottom/front and bottom/rear where the product temperatures are significantly different. The model was validated by comparing predicted values with experimental ones. Then it was used to predict the influence of various parameters such as the ambient temperature in the supermarket, the radiation temperature of the surrounding walls and the internal/external infiltration rates. Through integration of quality and microbiological predictive models, this approach can be used as a numerical tool for quality and sanitary evaluation of products displayed in display cabinets. The developed model will be further used in the modelling of the cold chain, which comprises several types of refrigeration equipment.     

涂布机干燥箱温度模糊自适应PID控制

涂布机干燥箱温度系统具有非线性、强耦合、时变的特性,用普通PID控制器,温度偏差范围大。模糊自适应PID控制器可以适时调整K p、K i、K d的参数值。仿真及实用结果表明:模糊自适应PID控制器比常规PID控制器在干燥箱温度控制中具有更好的效果。     

Dynamic solid-state microwave defrosting strategy with shifting frequency and adaptive power improves thawing performance

Nonuniform microwave heating causes localized over-heating in frozen food products, lowering the quality of the thawed products. The solid-state microwave system has the potential to enhance heating performance as it provides flexible control over microwave parameters, e.g., frequency and power. The real-time collected microwave power reflection enables dynamic parameter control. This study developed two dynamic solid-state defrosting strategies: 1) selective frequency shifting strategy that only selectively shifted frequencies with high efficiency, 2) adaptive power control strategy that adapted power input with simultaneously orderly shifted frequencies. Results showed that the adaptive power control strategy had a better defrosting performance on frozen mashed potato and pork chop samples. Besides, with the adaptive power control strategy, the rotation of the turntable did not pose a significant improvement on the standard deviation of the temperature distribution in the defrosted products when compared to the stationary heating, which might be due to the minimized movement of samples at the center of the. The absolute changes in temperature profiles contributed by the rotation were considerable, indicating the importance of turntable.Industrial relevanceThis study developed novel microwave control strategies for defrosting processes, taking the advantage of the flexible control over the microwave parameters provided by the solid-state technique. With the proposed strategy, the microwave defrosting performance can be significantly improved in comparison with the magnetron-based microwave oven performance. The implemented dynamic strategy is promising to be embedded in the algorithm for use by the future smart microwave ovens.     

A smart reheating and defrosting microwave oven based on infrared temperature sensor and humidity sensor

Microwave oven is widely used around the world since the functions of reheating and defrosting are convenient and efficient. However, these functions in traditional microwave oven are not intelligent for the control effects deeply rely on the users' experience. Besides, heating without food is very dangerous since there is no no-load detection. Therefore, in this paper, infrared array sensor and humidity sensor are combined together to achieve a smart microwave oven. Besides, no-load detection method, detection method for humidity sensor, pre-processing method for infrared sensor, location identification method for the food, and intelligent control methods for defrosting and reheating are proposed in detail. Experimental results demonstrate that the eigenvalues of load tests are all smaller than 1.5, while they are all larger than 1.5 in the no-load tests. The detection accuracy is 100% in the 200 test cases. In addition, the final temperatures of the meats (i.e. pork, fish, drumstick and chicken) after intelligent defrosting control are all between −2 °C and 25 °C, and the mean temperature ranges from 1 °C to 2.5 °C, which meets the expected target. Besides, the maximum control error of “Heating Target” is 3.5 °C, and the maximum difference between the mean temperature of multiple measurements and the corresponding target is 1.56 °C. The control error and control deviation of the temperature range for “Milk” are both less than 1 °C. As for “Reheating” control, the maximum control error and control deviation of the temperature range for the food with less moisture content are 0.18 °C and 2.5 °C, while they are 2.7 °C and 3.2 °C for the food with more moisture content. Moreover, the food quality after reheating or defrosting with the proposed smart microwave oven is better than that with the traditional microwave oven. In general, the proposed no-load detection method, and the intelligent control methods for defrosting and reheating are effective.     

Evaluation of the effect of defrosting practices of ground beef on the heat tolerance of Listeria monocytogenes and Salmonella Enteritidis

The effect of common defrosting practices of ground beef, including (i) defrosting in the refrigerator (5 °C for 15 h), (ii) defrosting at room temperature (25 °C for 12 h) and (iii) defrosting in the microwave, on the heat tolerance of artificially inoculated Listeria monocytogenes and Salmonella Enteritidis, was studied. The thermal inactivation of S. Enteritidis was not, overall, affected by defrosting practices. In contrast, defrosting at room temperature resulted, overall, in an increased heat tolerance of L. monocytogenes compared to the rest tested defrosting practices. Inactivation kinetics of the two pathogens for the different defrosting practices were determined by fitting the data to the Weibull model. The δ parameter of the Weibull model (heat challenge time (min) required for the first 1-log reduction) for S. Enteritidis and for defrosting at 25 °C, microwave defrosting, defrosting at 5 °C and for the control (fresh ground beef inoculated with the pathogens just before the heat challenge trials) was 1.13, 1.62, 1.60 and 0.96, respectively, while the corresponding values for L. monocytogenes were 20.13, 10.82, 9.95 and 9.47, respectively. The findings of this study should be useful in risk assessments and in developing food handling guidelines for the consumers.     

基于模糊分数阶PID的食品包装机张力控制系统设计

针对食品包装机袋膜张力较难控制问题,设计了一种模糊分数阶PID袋膜张力控制系统。利用专家知识和成熟经验,结合分数阶控制,制定分数阶PID 5个参数的控制规则,实现分数阶PID参数在线实时整定,提升了袋膜张力控制精度和稳定性。以PLC和触摸屏为核心,以TIA Protal为开发平台,完成控制系统硬件设计、网络组态、程序设计,实现控制系统升级。仿真结果表明:模糊分数阶PID控制器具有响应速度快、模型失配鲁棒性好、抗干扰能力强的优势。该控制系统能够满足包装机袋膜张力控制精度和稳定性需求。     

Grey prediction fuzzy control for pH processes in the food industry

Proper regulation of pH value is an important issue in the food industry for quality production. A food pH process usually has non-linear dynamics with system uncertainty. This study treats the pH regulation process of a reactor tank as a grey box with partially known system information. The behaviour of the process is predicted one-step ahead with a first-order grey model. A fuzzy controller takes the prediction together with the current system response to regulate the discharge of base (NaOH) or acid (HCl) solution into the reactor tank to arrive at a desired pH value. The integrated grey prediction fuzzy control (GPFC) strategy is simple in control-law derivation and system implementation and is efficient in computation. The developed GPFC was validated with perform base/acid titration and continuous acidification/deacidification control. The controlled system response error was trivial in the titration and was less than 1% in the continuous control under proper agitation of the reactants. The system was used to control Acetobacter xylinum fermentation for cellulose production. The GPFC scheme exerted smooth control action, achieved a trivial steady-state error in pH control, and yielded more cellulose and acetic acid products but consumed much less material than PID or manual control.