基于双F-P标准具的波长锁定

提出了一种基于双法布里-珀罗(F-P)标准具的波长锁定方法,利用Littman结构的外腔型可调谐激光器、标准具、波长计等搭建了一套波长锁定实验系统,将激光器调至波长范围内任意波长,分别在关闭和开启波长锁定的两种情况下记录波长变化,实验结果表明,该波长锁定方法能显著提高Littman结构可调谐激光器的波长稳定性。     

微波真空干燥技术

<正> 微波属于电磁波,具有干涉,衍射、透射、反射等一系列的电磁波波动特性。微波能量藉电磁波来传输,对于处在微波场中的物质,微波会产生反射、吸收和穿透现象。由磁控管射出的微波,经激励腔和波导进入装载着被加热物的微波谐振腔,在谐振腔内来回振荡,从而加热物料。 微波与传统加热工艺的不同之处,在于依靠高频电磁振荡来引发分子运动,使物料整体加热。由于外部水分的蒸发,或与外部介质的热交换,外部温度比内部低,从而形成一个由内向外的温度梯度,水分在物料中总是倾向于从高温处向低温处运动。水分的蒸发是一个从内向外迁移的过程,因此物料内部     

基于电场分布的单波导矩形微波喷动床结构设计

针对矩形微波喷动床,基于喷动腔内电场强度及电场分布均匀性进行结构分析与优化。采用的评价指标为反映电场分布均匀性的变异系数COV、平均电场强度E_(mean)和反映电场局部集聚参数E_(max)/E_(mean)。利用多物理场耦合软件COMSOL Multiphysics对喷动腔内电场强度进行数值模拟,通过单因素和正交试验法分别分析喷动床结构参数a(喷动床宽)、H(波导位置)和L(喷动床高)对评价指标的影响。结果发现,a对COV和E_(max)/E_(mean)的影响最显著,H对E_(mean)的影响最显著;a与L的交互作用对COV,E_(mean)和E_(max)/E_(mean)的影响均显著。单波导矩形微波喷动床的优化结构为:a=427mm,H=200mm,L=1 000mm。     

食物位置对热风微波耦合加热效果的影响

给出了微波与热风耦合同步加热物料的数学物理模型,以微波与热风耦合加热土豆为例,建立了完整的三维仿真模型,采用数值模拟法,分别得到了位于耦合加热腔内7个不同位置上土豆最终温度场的分布参数,并以实验加以验证,对数值模拟所得的仿真结果进行了分析与评定。结果表明,不同位置对热风微波耦合加热物料的效果影响极大,这主要体现在影响微波电磁场能量转化为热能功率的大小,以及密度分布及被加热食品温度场分布的不均匀性,故在采用热风微波加热食品时,应当要重视物料位置对耦合加热效果的影响。     

微波加热鸡肉和土豆的传热仿真分析研究

为了更好地了解与研究家用微波炉微波加热过程中即食食品的传热特性,本文建立了电磁与传热耦合的仿真模型,研究鸡肉和土豆的空间温度和瞬态温度变化规律,并通过实验研究在-5~95℃范围内,鸡肉在频率为2450 MHz时的介电特性和热物理特性。基于温度对鸡肉介电和热物理特性的分析,将温度可分成两个范围:-5~0℃和0~95℃,各温度范围内的鸡肉特性变化趋势不同。仿真模型包括加热腔、波导以及可旋转的转盘和物料。通过比较不同转速对仿真结果的影响,综合考虑仿真所用时间以及物料的均匀性,选用7.5 r/min作为转盘转速。当微波功率为700 W时,组合样品的仿真结果显示,经过90 s的微波加热,空间温度场分布和瞬态温度曲线与实验结果保持一致,微波仿真组合样品的模型是可行的,研究结果为优化微波加热冷藏快餐的均匀性研究提供一定依据。     

“微波炉”是不是“安全炉”

微波炉是利用微波加热的设备,由于其方便、快捷、保鲜和卫生等优点,并具有烹饪、加热、解冻等功能,已经走进了千家万户,且深受使用者青睐。微波是一种波长短、频率高的电磁波,具有一定的能量。微波炉在工作时,由微波源磁控管发出微波,通过波导传入加热腔内,反复穿透被加热的食物,使其极性分子随着微波周期以每秒几十亿次的惊人速度来回摆动、摩擦,从而产生高热,在很短时间内即可完成加热过程。     

热风微波耦合干燥系统的设计与试验

介绍了热风微波耦合干燥系统的腔体结构、控制方法、工作原理,并完成了微波热风耦合干燥系统的设计与安装。以马铃薯为试验对象,研究了其在单一热风、微波干燥及热风微波耦合干燥状态下马铃薯丁的干燥特性,利用正交试验和方差分析,得到各因素对干燥综合效果影响主次顺序为:微波功率密度热风风速热风温度,影响马铃薯丁热风微波耦合干燥综合效果最优的组合为:热风温度50℃、微波功率密度6 W/g、热风风速1.6 m/s。试验结果验证了该系统的有效性和可行性,为马铃薯热风微波耦合干燥提供理论基础与数据依据。     

间歇微波—热风耦合干燥花生工艺优化及品质研究

为探究间歇微波—热风耦合干燥花生的最佳工艺参数,借助响应面优化分析方法,以花生干燥速率和干燥能效的综合评分为响应值,确定了花生间歇微波—热风耦合干燥的最佳工艺参数为:热风温度45 ℃,微波强度1.25 W/g,微波间歇比1.10。该条件下,花生间歇微波—热风耦合干燥速率为0.517 g/min,能效为0.433 MJ/g,干燥综合评分0.710,模型误差小于5%。基于此工艺参数探究该干燥方式对花生脂肪酶活动度、硬度、颜色和脂肪酸组成的影响。结果显示,间歇微波—热风耦合干燥是一种高效的干燥技术,能保证花生的品质。     

蒸发波导对海上微波通讯影响分析

随着技术的不断发展以及传输需求的不断改变,通讯频段逐步提高。在海上进行微波通讯时,不可避免地要受到传播媒质的影响,其中影响较大的就是蒸发波导。文章在介绍蒸发波导相关概念的基础上,利用电磁波传播模型分析了蒸发波导对微波通讯距离的影响。     

纤维表面具有纳米结构的超黑羊毛织物及制备方法

该发明涉及纺织品的功能性加工处理领域,尤其涉及表面具有纳米结构的超黑羊毛织物以及它的制备方法。将羊毛织物放入低温等离子体处理腔内。然后将处理腔内的压力抽至小于或等于10Pa,通入非聚合性气体调节处理腔内的压力为10—170Pa;然后放电进行低温等离子体处理,功率是10—300W,处理时间1～60min。在羊毛纤维表面形成纳米级凹凸结构并生成活性基团,然后进行常规染色。     

工业微波加热灭菌机械制造技术

本文对工业微波加热灭菌机械的加热、灭菌的机理和工业微波加热灭菌机械的发展前景，进行了简单的论述；并从制造工艺的角度，对其关键部件─—谐振腔、波导、微波漏能抑制系统、传送带托架的结构、材料、精度的关键及工艺要求进行了初步探讨，我们抛砖引玉力图引起同行们重视，不断提高微波加热灭菌机械的制造技术。     

新型微波真空干燥机设计

设计了一种集微波干燥与真空干燥于一体的新型装置,将波导和波源冷却装置融为一体,有效地解决了微波分布不均和微波源受热易损坏两大难题。物料室是微波室和真空室的交集,可以使物料既能受到微波辐射,又能处于真空环境中。分层设计的物料盘一方面可以方便拆卸,另一方面可以充分地利用物料室的空间。模块化的冷阱设计,使冷阱可以根据干燥的需求自由的装卸,可以有效地提高冷阱的利用效率。该微波真空干燥设备设计巧妙,安全可靠,可以满足高品质物料的干燥加工。     

Determination of added fat in meat paste using microwave and millimetre wave techniques

By evaluating the sensitivity of measurement parameters such as dielectric constant and microwave loss to fat content, several microwave and millimetre methods were compared to identify optimal frequency measurement bands. The results showed that the optimum frequency range lay between 8 and 20GHz where these parameters vary linearly, by up to a factor of 8, as fat is increased to 50% volume. A narrowband waveguide sensor cell was designed and constructed for this optimum range. The imaginary part (ε') of the complex permittivity demonstrated a better measurements resolution for determining fat content than the real part (ε'). The waveguide method has excellent repeatability as indicated by low relative standard deviation (RSD<4.88%). Temperature and sample density had minimal impact on the accuracy, repeatability and robustness of the final measurement system. A method of mixtures model for complex permittivity was shown to be a useful predictor of fat content.     

Estimation of Dielectric Properties of Food Materials During Microwave Tempering and Heating

The present study concerns the estimation of the dielectric properties of both frozen and defrosted materials during a microwave tempering and heating process. A continuous wave at 2.45 GHz is fed into a rectangular waveguide and the sample, made of methylcellulose gel, fills the whole cross-section of the guide. Temperatures are detected within both frozen and defrosted samples during the heating treatment. The experimental temperatures are compared to the results obtained with a 2D finite element model, using the COMSOL® 4.2 software. The dielectric properties of the sample are estimated from the local temperature changes during the microwave tempering. For the defrosted zone, the estimation is compared to dielectric properties measurements with the open-ended coaxial probe. The results show good correspondence between experimental and simulated data. The uncertainties of the estimated permittivity and loss factors are also evaluated with a good accuracy for the frozen and defrosted phases. The estimation procedure is thus a promising tool in order to avoid complex experimental measurements of dielectric properties.     

Microwave freeze drying of sea cucumber (Stichopus japonicus)

Freeze drying (FD) yields the best quality of dried sea cucumber but at the cost of long drying time and also the overall cost. Air drying (AD) gives an unacceptably poor quality product. To achieve faster drying along with a high quality product a microwave freeze drying (MFD) technique was developed to dry sea cucumbers. The relationship between corona discharge and microwave power at various pressures and initial moisture content conditions was studied to avoid the possibility of corona discharge during MFD. According to the drying characteristics of MFD, a control strategy for the MFD process was also developed. MFD reduced the drying time by about half of conventional FD process and provided a similar good product quality.     

物理技术在涤纶染色中钉研究进展

文章运用物理新技术的方法解决了涤纶染色工艺中的问题。主要从生态角度介绍了一些物理染色技术——超声波、低温等离子体、超临界CO2流体、微波技术、微胶囊、紫外线辐射、电子预辐照等在涤纶染色中的作用机理与应用。物理技术可改善涤纶纤维或染色体系的染色性能,提高涤纶的加工质量;减少染整污水的排放,实现无水或非水染色,节约能源,有利于环保。     

High-efficiency continuous-flow microwave heating system based on metal-ring resonant structure

Continuous-flow microwave heating has been widely applied in liquid food processing, and the heating efficiency relies heavily on the dielectric property of loads with fixed dimensions in a certain cavity. Specifically, rectangular waveguides are widely applied, and straight pipes are usually inserted through the center of rectangular waveguides. However, maintaining high efficiency is always challenging since the dielectric property will vary with temperature. Therefore, a simple and cheap resonant structure is proposed in this paper to maintain high heating efficiency for loads with a large range of relative permittivity in both modeling and experiment. First, the straight pipe surrounded by metal rings in a rectangular waveguide with a short circuit terminal was introduced to concentrate the electric field in the pipe. Then, a multiphysics model was established to calculate the energy efficiency of various load permittivity. The position of the short circuit terminal and the dimensions of the metal ring were further optimized. Finally, energy efficiency experiments of different aqueous ethanol solutions and liquid foods and point temperature rise experiments of continuous-flow water were carried out, and the results showed that the proposed structure can be used to maintain high energy efficiency over large dielectric dynamic ranges compared with the conventional microwave heating system based on rectangular waveguides. Moreover, the effect of different parameters, the pipe permittivity, the pipe wall thickness and the metal ring gap, on the heating efficiency was discussed to show the robustness of the proposed structure.     

果蔬粉含水率在线检测系统设计

目的：为满足低含水率果蔬粉在线检测需求。方法：基于微波透射原理,设计了一套果蔬粉含水率在线检测系统。系统分为进料模块、检测模块、卸料模块和控制显示模块,并进行相应硬件和软件设计。以胡萝卜粉为试验物料,由第三方检测机构进行含水率微波透射和国标法检测比较,以评价装置检测性能。结果：该装置检测每份样品的含水率耗时约7.33 s,准确度为98.2%,重复性为0.15%。结论：基于系统设计的装置能够实现低含水率果蔬粉的在线、连续检测。     

Microwave radiation for control of Tribolium confusum in wheat and flour

The susceptibility of Tribolium confusum Jacquelin du Val to microwave energy was determined by irradiating vials of infested wheat or flour near the aperture of an optimum gain horn coupled through a waveguide to a magnetron operating at 8·5 GHz and 30 W average output at a pulse repetition frequency of 4000 Hz. Mortality was a function of exposure time and wheat moisture content. Adult mortality was higher in insulated samples of wheat than in non-insulated samples. Susceptivility of stages to radiation at 60°C was: eggs > pupae > adults > larvae. Survival of pupae near the surface of wheat indicated that heat was distributed non-uniformly. Mortality was higher in wheat than in white flour. Adults from 1·5 to 7 months old were equally susceptible to radiation.