Study of a microwave assisted vacuum drying process applied to the granulated pharmaceutical drug hydrochlorthiazide.

Drying processes have evolved considerably over the years, aiming at the best conditions to shorten the processing time, but maintaining the highest final product quality. The application of vacuums to the microwave drying process might be interesting, especially for thermally sensitive products because the reduced boiling point of the solvent allows a lower temperature processing. The objective of the present work is to study and evaluate the process of drying a granulated product that is the basis of the drug hydrochlorthiazide, with an initial moisture content of 21% in dry basis. This study monitored the drying kinetics, product temperature and power absorbed by the sample using a bench scale vacuum microwave dryer. The equipment consisted of a cylindrical pressure vessel crossed by a wave guide, setting up a system whereby the vacuum pressure, the sample weight and the incident, reflected and residual microwave powers could be measured and evaluated, throughout the entire process. The experimental runs were established with an approximate incident microwave power at 20 W for absolute pressure levels of 50 and 75 mbar, working with samples of about 1.4 g. It was observed that the vacuum microwave process kinetics at both pressure levels showed little difference. The processes were carried out almost entirely in a regime of water evaporation, the product's temperature remaining below the solvent boiling temperature. The drying times were similar for both processes, whereas the absorbed power was slightly higher at the pressure of 75 mbar.     

扫描离子电导显微镜及其在医学研究中的初步应用

扫描离子电导显微镜(scanning ion conductance microscopy,SICM)是一种非接触式的扫描探针显微技术(scanning probe microscopy,SPM),可以实现生物样品在近生理条件下的成像.随着技术发展,目前广泛应用于生物医学领域的SICM主要包括两种:跳跃式离子电导显微技术(hopping probe ion conductance microscopy,HPICM)和外加压力模式的SICM.前者可以应用于软的、黏的、对外力或其它机械信号敏感的样品的高分辨成像;后者可以通过探针微管对样品局部施加外力刺激或化学、电学、光学或生物分子等信号,实现对样品动力学性质或相关生理过程局部的原位研究.此外,SICM技术具有良好的开放性,能够越来越多地与其它技术手段联用,极大地丰富了其在生物医学领域的应用,可用于疾病发病机理、药物作用以及临床诊断等的研究.但是,目前SICM时间分辨率较低,这制约了它在生物体系动力学行为方面的研究.     

Microwave radiometric technique to retrieve vapor, liquid and ice.II. Joint studies of radiometer and radar in winter clouds

For pt.I see ibid., vol.35, no.2, p.224-36 (1997). A neural network-based retrieval technique is developed to infer vapor, liquid, and ice columns using two- and three-channel microwave radiometers. Neural network-based inverse scattering methods are capable of merging various data streams in order to retrieve microphysical properties of clouds and precipitation. The method is calibrated using National Oceanic and Atmospheric Administration (NOAA) results in a cloud-free condition. The performance of two- and three-channel neural network-based techniques is verified by independent NOAA estimates. The estimates of vapor and liquid agree with NOAA values. In the presence of ice, the liquid estimates deviated from NOAA's estimates. One of the major contributions of the three-channel radiometer is the estimation of ice in a winter cloud. The three-channel radiometer not only improves estimates of vapor and liquid, but also retrieves the ice column. Passive remote sensing can be ameliorated with the help of active remote sensing methods. The three-channel radiometer is used for estimating columnar contents of vapor, liquid, and ice in a cloud. It is shown that vertical profiles of median size diameter, number concentration, liquid water content, and ice water content can be inferred by combining radar reflectivity and radiometer observations. The combined remote sensor method is applied to Winter Icing and Storms Project (WISP) data to obtain detailed microphysical properties of clouds and precipitation. The authors also derived Z- Ice Water Content (IWC) and Z- Liquid Water Content (LWC) relationships and they are consistent with the earlier results     

微波功率管测量的微波辐射分析与防护

该文介绍了微波辐射防护的理论知识和安全标准,以及微波功率管测量系统的配置和测量流程。对测量系统的微波电磁辐射进行了分析,列举了在微波功率管测试工作中采取的一些防护措施和测评结果,阐述了使用程控化测量系统对微波辐射防护的益处。     

Numerical simulation of an industrial microwave assisted filter dryer: criticality assessment and optimization.

Industrial-scale filter dryers, equipped with one or more microwave input ports, have been modelled with the aim of detecting existing criticalities, proposing possible solutions and optimizing the overall system efficiency and treatment homogeneity. Three different loading conditions have been simulated, namely the empty applicator, the applicator partially loaded by both a high-loss and low loss load whose dielectric properties correspond to the one measured on real products. Modeling results allowed for the implementation of improvements to the original design such as the insertion of a wave guide transition and a properly designed pressure window, modification of the microwave inlet's position and orientation, alteration of the nozzles' geometry and distribution, and changing of the cleaning metallic torus dimensions and position. Experimental testing on representative loads, as well as in production sites, allowed for the confirmation of the validity of the implemented improvements, thus showing how numerical simulation can assist the designer in removing critical features and improving equipment performances when moving from conventional heating to hybrid microwave-assisted processing.     

Microwave combustion synthesis of zinc substituted nanocrystalline spinel cobalt ferrite: Structural and magnetic studies

Zinc doped cobalt ferrite spinel nanoparticles were prepared by the microwave combustion method. All the samples were characterized by using X-ray diffraction technique (XRD), Scanning Electron Microscopy, energy dispersive X-ray analysis, UV–visible diffuse reflectance spectroscopy, Fourier transformed infrared (FT-IR) spectroscopy and vibrating sample magnetometry. The XRD patterns confirmed the formation of single phase CoFe₂O₄ inverse spinel structure without impurities. The lattice parameter increased from 8.380 to 8.396 Å with increasing Zn²⁺ fraction. The average crystallite sizes obtained by a Scherrer method varied between 46.22 nm and 30.79 nm. The estimated band gap energy values increases with an increasing zinc fraction (1.88–2.10 eV). The elemental composition of Zn, Co, and Fe was qualitatively obtained from energy dispersive X-ray (EDX) analysis.     

微波超视距通信信道特性分析与系统设计

针对微波中继通信单跳通信距离近、后勤保障困难、机动性差及难以适应复杂地形等缺点,通过分析微波超视距信道特性,提出微波超视距传输的设计思路。基于对微波超视距链路预计公式的推导,为系统设计提供基础和保障。通过对信道类型的分析,提出针对瑞利信道的抗衰落技术措施,进行仿真和分析。最后给出了一个工程实例,理论及实践的一致性结果,证明了其应用效果。     

微波近场成像检测乳腺癌及其微波热疗

介绍了微波热疗机理及人体乳房组织的电磁特性，指出微波近场成像检查乳腺癌的优势及其发展历程，并提出微波诊断和微波热疗在乳腺癌检测和治疗中应用的可能发展方向。     

微波功率晶体管的发展与分析

本文阐述了国内外硅双极微波功率晶体管和砷化镓微波功率场效应晶体管的发展历史和现状,并分析了微波功率晶体管的发展特点。介绍了HBT,HFET,MISFET,金刚石、SiC电子器件,真空微电子器件等用于或将用于微波、毫米波功率领域中的情况。提出了发展微波功率晶体管的几点想法。     

微波站的雷害及其防护

本文通过笔者对一些微波站遭受雷击的调查和整治、分析了雷害引入的途径，并提出了切实可行的防护措施。     

微波测量的发展动态和趋势

微波测量是微波领域的重要方面,它直接关系到设计的微波系统和微波器件性能的好坏.本文从测量仪器的发展动态和趋势出发,论述了微波测量发展的六个可能方面,供读者参考.     

A History of the Transactions on Microwave Theory and Techniques, Nov. 1980

From the Early days of our Society, through the many changes that have taken place in Administrative Committees, names and substance, there has been one "given." That was, and is, our TRANSACTIONS. From the first meeting of the Administrative Committee, May 1, 1952, through the name changes from Professional Group to Professional Technical Group to Group to Society/sup 1/, through twenty-seven Administrative Committees from Chairman Ben Warriner to Chairman Don Parker, from one issue per Administrative Committee term to one issue per month, this TRANSACTIONS, above all else, has been our pride and our mainstay.     

Microwave thermography: principles, methods and clinical applications.

We review the physical principles, method of operation, measurement limitations, and potential medical applications of microwave thermography. We present detailed results of a study of breast cancer detection at 1.3 and 3.3 GHz, including the dependence of detection rates on microwave frequency, time, tumor depth, and tumor size. At 1.3 GHz, microwave thermography detects breast cancer as well as infrared thermography (true-positive rate = 0.76 when true-negative rate = 0.63). When the two methods are combined, the true-positive rate increases by about 0.1 over that of either method alone.     

矿用VEG型固封式真空断路器的研究与应用

针对目前矿用高压真空配电装置普遍存在着分断时间较长的问题,研制开发了VEG型固封式真空断路器,并详细介绍其基本工作结构和工作原理,最后给出实际性能指标。数据表明该装置性能优良、保护齐全、使用方便,是理想的矿用真空断路器。     

矩磁微波石榴石材料的研制

本文叙述了添加Mn 的YIG、YGd、YGdAl、YGdCaVIn 系铁氧体材料的特性,Mn 对制备的材料矩形比有不同的影响,其中有些系列矩形比大于0.85,而矫顽力较小,温度稳定性好,用作S、C、X 波段锁式铁氧体移相器、开关是非常合适的,可以取代低磁矩的锂铁氧体材料,具有损耗小,耐功率的优点。     

微波能应用的回顾和展望

回顾二十年来微波能应用成功的实例，并展望多学科对微波功率应用迫切需求，有着丰富的内容。