Development of an electrically controlled terahertz-wave modulator

An electrically-driven terahertz (THz)-wave modulator was numerically designed and experimentally fabricated to realize amplitude modulation of incident THz waves. The THz wave modulator is composed of an array of high electron mobility transistors (HEMTs), an array of split-ring resonators (SRRs), and metal electrodes. Driven by the time-varying gate voltage, the width and thickness of the conducting channel in the HEMT is changed, resulting in the variation in the density of the two-dimensional electron gas (2DEG). With variation of the 2DEG density, the SRR exhibits different transmittance for THz waves. Our measurement results show that ~28% modulation depth under an applied gate voltage varying from ?3 V to 0 V can be obtained.     

The light-emitting device consisting of organic white-light components

A material compound, 9,9-bis{4′-[2″-(carbazolyl)-vinyl]-phenyl}fluorene (F-CZV), was specially synthesized and used to fabricate the efficient white organic light-emitting devices (WOLEDs). The absorption peaks appear at 340 nm and 346 nm in dilute dichloromethane solution and film, respectively. The photoluminescence peaks appear at 350 nm and 400 nm in the solution and film, respectively. Photoluminescent quantum yield in solution is ca 0.82 by using quinine sulfate as the standard. In an optimized electroluminescent device structure of ITO/NPB (40 nm)/F-CZV (30 nm)/BPhen (40 nm)/Mg:Ag, the saturated white-light emission was observed at Commission International De L’Eclairage (CIE) coordinates of (0.30, 0.33) at 10 V. The El spectrum of the device is close to independent of the applied driving voltage. It’s maximum brightness and current efficiency is 700 cd/m² and 0.41 cd/A, respectively.     

微波元器件自动测试系统

为了提高微波元器件的测试效率,保证测试的一致性,研发了微波元器件入检自动测试系统,使用计算机在外部执行测试程序来控制矢量网络分析仪,从而实现自动化测试.该自动测试系统中矢量网络分析仪采用的是美国Agilent公司生产的8722ES,通过该仪器上的GPIB接口,使用熟悉的SCPI命令创建程序,利用Visual Basic 6.0程序语言进行软件编译.实践证明,该测试系统运行程序可靠,可显著提高器件检测的效率和准确性.     

新型微波介质陶瓷材料与元件的研制

报告本课题组承担的863计划项目“新型微波介质陶瓷材料与元件的研制”，在实验工作中不仅采用传统的固相反应法而且利用共沉淀和水热合成等溶液反应技术，还采用凝胶浇注成型复杂形状的微波陶瓷元件，并利用流延成型技术制备大尺寸微波集成陶瓷基板等；研制成功具有高电容率和品质因子并接近于零的谐振频率温度系数的系列化微波介质陶瓷；开发成功多种微波介质元器件，包括：介质谐振器、介质滤波器、GPS片式天线、微波电容器、通信电缆滤波接头和微波集成基板等。     

The roles of B-site ions in lead strontium zirconate titanate thin films for electrically tunable device applications

B-site modification lead strontium zirconate titanate Pb_0.4Sr_0.6Zr_xTi_1 − xO₃ (PSZT, x = 0-0.7) thin films were prepared on Pt/TiO₂/SiO₂/Si substrates by a sol-gel method. The XRD results indicate that paraelectric PSZT thin films at room temperature are obtained as x approaches 0.2. The temperature-dependent dielectric and hysteresis loop measurements reveal that the thin films have diffuse phase transition characteristics and relaxor-like behavior with nano-polar regions in the paraelectric films at room temperature. The Curie temperature of the PSZT thin films varies with the Zr contents, exhibiting a complex trend. This can be attributed to two competitive factors: higher mobility of Ti⁴⁺ than Zr⁴⁺ and smaller open space left for the displacement of Ti ions with the increase of Zr content. The further increase of the Zr contents leads to the simultaneous decrease of dielectric constant, dielectric loss and tunability. PSZT (x = 0.4) thin film shows the largest figure of merit of 24.3 with a moderate tunability of 55.8% and a dielectric loss of 0.023. This suggests that B-site ions have different roles in modifying the electrically tunable performance of PSZT thin films for tunable microwave device applications.     

Measuring the sensitivity of microwave components to bias variations

This paper presents a method to measure the sensitivity of microwave components to memory effects caused by the dc biasing circuit. This allows us to determine the required (impedance) properties of the dc biasing circuit to reduce slow dynamics under a certain level. The proposed measurement technique is based on the nonlinear vectorial network analyzer, which allows us to measure not only the absolute magnitude but also the absolute phase relations between the waves. Superimposing a multisine excitation signal on the dc bias allows us to measure the slow dynamics caused by the dc biasing circuit as a function of frequency and input power. Furthermore, it is verified whether or not the measured phenomena depend on the type of excitation signal.     

Release of components from a plastic container during microwave heating

A thermoformed, microwavable container made from a polypropylene/Saran®/polypropylene coextruded material was selected as the test container. Samples of the specimen were microwaved in sealed glass vials for periods ranging from 3 to 7 min. After heating, the head space of the vials was sampled and analysed. The microwaving process was carried out in an Amana Radarange® microwave oven on full power. Sample surface temperature as a function of microwaving time and the quantitative identification of volatile compounds released by the polymer during microwaving were determined. Five major components were detected and quantified in the head space of the vial using gas chromatography. The quantity of each component increased with increased microwaving time. Using mass spectrometry, the five components were identified; four were hydrocarbons and the fifth was butylated hydroxytoluene (BHT). Release of organic components during brief microwaving of polymers may be a near-the-surface phenomenon.     

Nonstationary crisis of nucleate boiling under the conditions of an electrically controlled heat load

Experimental data on the nonstationary heat exchange under a controlled heat load are presented. Investigations were carried out with cut plates specially formed to shape, on which the distribution of the heat-flow density is near-exponential (from the periphery to the center). Empirical dependences of the critical density of a heat flow and the heat-transfer coefficient on the rate of heating have been obtained. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 6, pp. 126–130, November–December, 2005.     

The electrical properties and quality factor of nickel electrodeposits

The quality factor Q, of the nickel electrodeposits prepared under different conditions (bath pH, current density, etc.), was measured by a Q-meter and the in-series method was utilized. The inductance (L) and ohmic resistance (R) were obtained through the resonance frequency (F) by use of appropriate equations. The measurements can be shown on C, L, R and Q against F plots. The above electrical properties of nickel electrodeposits are affected by the electrodeposition conditions and slightly by the deposits' thickness.     

快速检验技术在爆炸装置金属碎片中的应用

为了研究应用手持式X射线荧光光谱仪在爆炸案件现场快速检测自制爆炸装置相关金属碎片的可行性,探讨适用于自制爆炸装置关键组件中金属碎片的临场快速检验分析方法,利用手持式X射线荧光光谱仪对51个常见自制爆炸装置金属碎片样品进行检验,采用SPSS聚类分析Ward法和特征元素分析法对样品进行元素分析,实现对样品的区分,并且比较这两个分析方法在快速检验中的准确性和可行性。实验结果:手持式X射线荧光光谱仪携带方便、响应快速、数据准确;SPSS聚类分析Ward法可对所测数据快速分析,对现场金属碎片进行对比和区分。手持式X射线荧光光谱仪结合SPSS聚类分析Ward法可满足自制爆炸装置关键组件中金属碎片的临场快速检验需求。     

快速检验技术在爆炸装置金属碎片中的应用

为了研究应用手持式X射线荧光光谱仪在爆炸案件现场快速检测自制爆炸装置相关金属碎片的可行性,探讨适用于自制爆炸装置关键组件中金属碎片的临场快速检验分析方法,利用手持式X射线荧光光谱仪对51个常见自制爆炸装置金属碎片样品进行检验,采用SPSS聚类分析Ward法和特征元素分析法对样品进行元素分析,实现对样品的区分,并且比较这两个分析方法在快速检验中的准确性和可行性。实验结果:手持式X射线荧光光谱仪携带方便、响应快速、数据准确;SPSS聚类分析Ward法可对所测数据快速分析,对现场金属碎片进行对比和区分。手持式X射线荧光光谱仪结合SPSS聚类分析Ward法可满足自制爆炸装置关键组件中金属碎片的临场快速检验需求。     

Measurement device for noise factor of microchannel plate

A new method for noise power factor determination of microchannel plates (MCPs) is described in this paper. The new measuring condition and specific measuring instrument are reported. The system consists of a vacuum chamber, an electron gun, a high-voltage supply, an imaging luminance meter, control units, a signal processing circuit, an A/D converter, a D/A converter, a communication unit, an industrial computer, and measurement software. This measuring method fills a void in measuring technology for the noise factor of MCPs, and it can make a scientific assessment of MCP noise characteristics and provide theoretical direction and technology support for the research and development of high-performance low light level (LLL) devices.     

Multi-step microwave reduction of graphite oxide and its use in the formation of electrically conductive graphene/epoxy composites

The multi-step MW reduction technique was developed in this study to obtain reduced graphene oxides; EG, RGO-1, and RGO-2 with MW irradiation time of 1, 2, and 3 min, respectively. Results of TGA, IR, and elemental analysis demonstrated that the degree of reduction of GO increased with increasing the MW irradiation time. Overall, 3 min of MW irradiation of GO in 3 steps was sufficient to obtain highly reduced GO (C/O ratio 10.38 by elemental analysis). The electrical percolation threshold of composites was observed as 1 wt% and 0.3 wt% for RGO-1 and RGO-2, respectively. Even at 0.5 wt% loading of RGO-2 in epoxy, the T_g value of the composite increased by 10 °C, indicating a strong interfacial interaction between graphene and epoxy resin.     

Electrodeposition growth of nanowire arrays with height gradient profiles for microwave device applications

A simple and nonexpensive adapted dip-coating technique is presented and used to fabricate arrays of magnetic nanowires with a linear varying height profile. This approach allows controlling the wire height from tenths of nanometers up to several micrometers. Furthermore, the main parameters of this height gradient can be controlled, such as the maximum wire height and the lateral span of the wire array, which can be predicted with excellent accuracy using a proposed analytical model. Moreover, we show that by sequential electrodeposition with dip-coating, arrays of these height varying wires can be grown. This technique represents a novel method to fill porous templates with controlled spatial growth, leading to the fabrication of novel structures and providing control over structural features on the nanoscale level. In particular, the use of these asymmetrically loaded magnetic nanowired substrates to obtain improved microwave nonreciprocal behavior is shown for a microwave phase shifter.     

Hollow hydroxyapatite microspheres as a device for controlled delivery of proteins

Hollow hydroxyapatite (HA) microspheres were prepared by reacting solid microspheres of Li₂O–CaO–B₂O₃ glass (106–150 μm) in K₂HPO₄ solution, and evaluated as a controlled delivery device for a model protein, bovine serum albumin (BSA). Reaction of the glass microspheres for 2 days in 0.02 M K₂HPO₄ solution (pH = 9) at 37°C resulted in the formation of biocompatible HA microspheres with a hollow core diameter equal to 0.6 the external diameter, high surface area (~100 m²/g), and a mesoporous shell wall (pore size ≈13 nm). After loading with a solution of BSA in phosphate-buffered saline (PBS) (5 mg BSA/ml), the release kinetics of BSA from the HA microspheres into a PBS medium were measured using a micro bicinchoninic acid (BCA) protein assay. Release of BSA initially increased linearly with time, but almost ceased after 24–48 h. Modification of the BSA release kinetics was achieved by modifying the microstructure of the as-prepared HA microspheres using a controlled heat treatment (1–24 h at 600–900°C). Sustained release of BSA was achieved over 7–14 days from HA microspheres heated for 5 h at 600°C. The amount of BSA released at a given time was dependent on the concentration of BSA initially loaded into the HA microspheres. These hollow HA microspheres could provide a novel inorganic device for controlled local delivery of proteins and drugs.