共查询到20条相似文献,搜索用时 31 毫秒
1.
Bai-Lin Qin Qinghua Zhang Barbosa-Canovas G.V. Swanson B.G. Pedrow P.D. 《Dielectrics and Electrical Insulation, IEEE Transactions on》1994,1(6):1047-1057
Processing foods with HV pulsed electric fields (PEF) is a new technology to inactivate microorganisms and denature enzymes with only a small increase in temperature. Introduction of this new technology will replace or complement conventional thermal processing methods. It will also provide consumers with safe, nutritious foods with fresh quality. For a given peak value of field intensity and amount of electric energy input, PEF inactivation of microorganisms is closely related to the waveform of applied pulses. Inactivation of microorganisms was studied with different waveshapes including exponential decay, oscillatory decay, square waves, and bipolar pulses. Microbial inactivation was tested in a parallel-plate static treatment chamber. Treatment field intensity ranged from 12 to 40 kV/cm while pulse length ranged from 30 to 180 μs. From the microbial test results, bipolar square-wave pulses are the most efficient in terms of microbial inactivation for commercial PEF pasteurization 相似文献
2.
Sato M. Ishida N.M. Sugiarto A.T. Ohshima T. Taniguchi H. 《Industry Applications, IEEE Transactions on》2001,37(6):1646-1650
Recently, a sterilization method of microorganisms in liquid food using pulsed electric fields (PEFs) has been reported by some researchers. Considering the application to the food industry, the energy efficiency of the method becomes important. It is reported that microorganisms suspended in aqueous solution were killed linearly (logarithmic) by the PEF process using a parallel-plate electrode configuration. The PEF is generated by capacitor discharge through a switch (using stationary, rotary, vacuum tube, and semiconductor, etc.). The survivability ratio decreases with increasing operating temperature and increasing capacitance value of the capacitor. Although many kinds of microorganisms suspended in liquid foods were treated by the PEF system, the energy efficiency was still low in the case of high-conductivity liquid. The authors developed a new electrode system for concentrating the electric field in a liquid food medium. The new electrode configuration made it possible to raise the energy efficiency for the pulsed sterilization process compared to that for conventional parallel-plate or concentric-cylinder electrode systems 相似文献
3.
Recent advances in the field of high-voltage pulse power technology have provided scope for the development of nonthermal sterilization methods free from the disadvantages commonly encountered with existing physical, chemical, or radiation sterilization. The flexibility allowed in the application of electrical energy can make high-field sterilization economical, compact, energy efficient, and environmentally acceptable. The main thrust of present research in this field is the application of high-field electric pulse technology to kill microorganisms in a manner consistent with development of industrial scale nonthermal sterilization methods 相似文献
4.
El-Hag A. H. Dadarwal R. Gonzalez O. R. Jayaram S. H. Griffiths M. W. 《Industry Applications, IEEE Transactions on》2010,46(1):9-15
5.
6.
7.
8.
9.
10.
介绍了利用无线通信技术在遥测方面的突出优越性,将其与单片机技术相结合应用于中高压电力系统中对关键点进行在线测温,有效解决了高低压问信号传输的电位隔离问题,实现了对多个温度信号的高精度监测和传输。结果表明,该系统具有抗干扰、耐高压、工作稳定、容易扩展功能等优点,具有广阔的前景。 相似文献
11.
12.
介质阻挡放电对橙汁灭菌及其品质的影响 总被引:5,自引:3,他引:2
为了消除加热杀菌的不利影响,开发和研究冷灭菌技术日益受到人们的重视。为此,利用大气压空气中平行平板介质阻挡放电(DBD)产生的低温等离子体对橙汁灭菌效果及品质的影响进行了研究。选取了3种具有代表作用的微生物(革兰氏阳性的金黄色葡萄球菌、革兰氏阴性的大肠杆菌和典型真菌的代表白色念球菌)。研究了不同处理时间下低温等离子体对掺入橙汁中微生物的灭活效果。此外,还研究了低温等离子体对橙汁货架期的影响,并且利用一系列生物医学检测手段和仪器(2,4二硝基苯肼比色法、氢氧化钠滴定法、数字阿贝折射仪、pH计和分光光度计)对经低温等离子体处理前后的橙汁维生素C的质量浓度、总酸、糖度(°Brix)、pH值和浊度进行了测量,考察了pH值对微生物的灭活效果。实验结果表明:低温等离子体可以快速有效地杀灭掺入橙汁中的微生物(金黄色葡萄球菌、大肠杆菌和白色念球菌)并延长橙汁储存的货架期,而且等离子体对橙汁营养及理化性质的影响不大。pH值在等离子体菌类灭活中不起主要作用,分析后认为等离子体中的带电粒子和氧自由基(ROS)才可能是导致菌类灭活的主要因素。 相似文献
13.
14.
高温超导变压器高压绕组的绝缘设计和试验 总被引:1,自引:0,他引:1
为了研究630kVA/10.5kV三相高温超导变压器雷电冲击情况下的绝缘问题,设计研制了一台与630kVA超导变压器高压绕组1∶1的模型。导线采用与超导变压器所用高温超导Ag合金包套不锈钢加强Bi2223多芯带材同样尺寸的CuNi合金带材,导线以聚酰亚胺薄膜采用双半叠包工艺进行绝缘。高压绕组模型为多层圆筒式结构,层间置有层间绝缘和冷却通道。液氮温度77K下远高于国家规定的该电压等级标准(75kV)要求的155kV,雷电全波冲击试验、波过程的测量试验以及对波过程仿真计算的结果表明,测量结果和理论计算结果比较吻合,冲击电位分布接近线性,没有形成震荡,为630kVA/10.5kV高温超导变压器的成功研制提供了依据。 相似文献
15.
Jayaram S.H. El-Hag A.H. Espino-Cortes F.P. Wong R.J. Leibovitch C. 《Industry Applications, IEEE Transactions on》2005,41(2):520-526
Many industrial applications like high-field food sterilization require short-duration fast-rise-time high-voltage pulses. Measurement of such narrow steep-front high-voltage pulses are always difficult, considering the potential levels and the time scales involved. In addition, by nature, liquid foods are highly conductive, hence, any small change in circuit inductance has substantial influence on the measured pulse. Further, the oscillations introduced by the circuit parameters influence the voltage magnitude and the effective treatment time. Hence, these points must be taken into account while computing the total treatment time and the energy actually spent, as these parameters influence the kinetics of food processing. In this paper, the effects of load impedance, the circuit inductance, and the location of the probe position that influence the shape of the measured pulse with liquid foods as load are discussed. It has also been shown that knowing the low-voltage conductivity of the food to be treated, and with a realistic estimation of circuit inductance, it is possible to predict the shape of the pulse under different test conditions using PSPICE circuit models. 相似文献
16.
用脉冲电场处理冷却水系统中的微生物是切实可行的。该法不同于向水中添加杀生剂的方法 ,其基本原理是用脉冲电场处理冷却水 ,使水中的微生物在流过冷却设备时暂时失去活动能力 ,不发生沉积。由实验可知 ,对单脉冲电场来说 ,微生物的抑制时间由脉冲持续时间和脉冲电场幅值或能量密度决定。用重复频率的脉冲处理冷却水中的微生物可在较小的电场强度下获得与较大电场强度单脉冲电场相同的效果。在使用时 ,对处理池中的电极施加脉冲电场 ,可通过改变电极间距改变施加的场强值。 相似文献
17.
Catalysts were used to enhance NOx removal reactions by the nonthermal plasma from room temperature to high temperature (500°C). The NOx removal rate was significantly affected by the type of the catalyst or the gas temperature. When the conventional three-way catalyst for automobiles was activated at 500°C, nonthermal plasma was not effective in removing NOx. When hydrocarbons (ethylene) were added to the synthetic flue gas, zeolite catalyst became very active at high temperature, The combination effect of nonthermal plasma and catalyst was confirmed below 200°C. More than 80% of NOx was removed from synthetic flue gas by the combination of zeolite catalyst and hydrocarbons without nonthermal plasma discharge at 500 °C. Nonthermal plasma treatment could be useful even at high temperatures, where catalytic reactions were dominant 相似文献
18.
Bruhn R.E. Pedrow P.D. Olsen R.G. Barbosa-Canovas G.V. Swanson B.G. 《Dielectrics and Electrical Insulation, IEEE Transactions on》1998,5(6):878-885
Nonthermal pasteurization of liquid foods by intense pulsed electric fields results in advantages over conventional heat pasteurization. Thermal damage to liquid foods can adversely affect the flavor and taste and result in loss of nutrients. Numerical modeling of heating parameters near the microbe during exposure to these intense electric fields is described. Boundary conditions at membrane interfaces included the continuity of temperature and continuity of heat flow. Temperature, heat flow vector, and heat source were included in the one-dimensional model. Two simulations are reported here. Simulation 1 consisted of a 0.5 μm wide microbe suspended in liquid with conductivity of 0.01 S/m and was treated with an applied electric field of 40 kV/cm for 375 ns. Simulation 2 contained a 1.0 μm wide microbe suspended in liquid with conductivity of 0.1 S/m and was treated with an applied electric field of 40 kV/cm for 1 μs. Comparison is made with a uniform conductivity model (ohmic), and it is shown that significant differences exist in the heating parameters between the two models. For the parameters used in these one-dimensional simulations, conditions for electroporation were found to exist without a significant temperature rise in the microbe 相似文献
19.
脉冲电场辅助提取花色苷及其影响 总被引:3,自引:1,他引:2
高压脉冲电场技术(pulsed electric field)是一种非热处理技术,它因能对生物细胞的细胞膜造成不可恢复的损伤而可应用于辅助提取细胞内物质。为此以红莓为实验材料,研究了PEF辅助提取法对红莓中花青素提取率的影响,并考察了在提取过程中PEF对花青素的降解作用。实验结果表明:PEF处理破坏了红莓果细胞的细胞膜,增大了细胞膜的通透性,从而增大了花色苷由细胞内向细胞外的传质过程,有效地提高了花色苷的提取率,并缩短了提取时间,提取率随着处理脉冲个数的增加而增大。在提取过程中,PEF对目标提取物Cy-3-gly具有显著的降解作用,且降解作用随着处理场强的增大及处理脉冲个数的增多而增大,PEF处理后的Cy-3-glu与对照样品具有相似的光谱特征,但在519nm处的吸收降低,333nm处的吸收稍有增大,这表明PEF处理使得Cy-3-glu生成了查尔酮类化合物。 相似文献
20.
为系统解决高电压复杂电磁场环境塔基设备供电问题,提出一种基于GaN(氮化镓,第三代半导体材料)器件的多米诺中继型无线供电系统及配置方法。首先基于电路互感耦合模型和有限元仿真对多米诺无线供电系统的频率特性和功效特性进行了分析,发现通过调节负载阻抗匹配和适当提高驱动频率,能够有效改善系统的传输功效特性和抗频率失调特性,并结合电场分布云图对系统的电磁兼容性进行验证。在此基础上搭建基于GaN器件的多米诺无线供电系统实验样机,测试结果表明该系统能够实现高电压等级远距离、高效率的无线供电,且具有较好的抗频率失调特性,为无线电能传输技术在高电压设备供电领域的应用提供了参考依据。 相似文献