Waveguide characterization of chiral material: theory

A new procedure to extract all three constitutive parameters of chiral material from waveguide measurements is presented. Two chiral slabs of different length must be measured. Their scattering parameters are inverted in a largely analytical way, complemented by a simple and fast convergent numerical algorithm. Tests with synthetic scattering data show the method to be very accurate and stable     

Effective electromagnetic and chiral parameters of chiral composite material

The effective parameters of chiral composite are studied using a simple model, that is, randomly oriented non-interacting wire helices embedded in a nonchiral host medium. It is found that both the effective permittivity ? and permeability μ are independent on the handedness of the chiral objects while the effective chirality admittance ξ is dependent. It is also found that when the ratio of the radius of the chiral helix to its pitch is about 0.23, maximum chirality admittance is achieved. The effective parameters of equichiral sample are also discussed.     

An approximate model for artificial chiral material

This paper presents an approximate, but simple, theoretical model for computing the constitutive parameters of artificial chiral materials made by embedding small conducting helices in a lossy isotropic achiral host material. The model explicitly includes helix resonance and the first-order effects of reradiation from the helix, near-field losses, and mutual coupling. Computations made using the model are compared with published data and qualitative agreement is obtained     

Quantitative study of effective parameters of chiral composite material

The effective parameters of chiral composite are studied quantitatively using a model, say, chiral spheres immersed in a nonchiral host medium. The effects of the volume fraction of the chiral phase, f, the parameters of the host medium, ε and μ, on the effective properties of the composite are calculated. As an example, the microwave reflection properties of a chiral composite coating is compared with that of its host medium coating.     

含手性氯酸钠晶粒凝胶材料的制备及偏振特性研究

本文采用标准水溶液法生长出各向同性的手性氯酸钠 (NaClO3 )微小晶粒 ,以溶胶 -凝胶法获得含手性氯酸钠晶粒的透明凝胶材料 ,同时对其偏振特性进行了测试 ,并观察到了这种材料的旋光特性。     

Backward-wave-oscillator spectrometry in standards and material characterization

Tunable backward-wave oscillators (BWO) equipped with computer aided control and data processing means are applied for liquid (e.g. mineral oil) and solid (Si, GaAs, YBaCuO) sample spectrometry in the frequency range above 200 GHz.     

Dynamic characterization of Built-In Current Sensors based on PN junctions: Analysis and experiments

The goal of this work is to analyze the performance of PN junction-based Built-in Current Sensors (BICS) for I _DDQ testing. Two types of BIC Sensors are analyzed: one based on a simple PN junction as the sensing element (DBICS), and the other based on a lateral BJT (PBICS). The sensitivity, speed and performance of the BICS are studied by showing their dependence on circuit parameters. Design constraints of such sensors in order to achieve performance criteria on CUT and BICS are analyzed. The dynamic analysis of the BICS is compared with experimental results when the PN junction BICS are used on a CMOS circuit.     

A mechatronics educational laboratory – Programmable logic controllers and material handling experiments

The integration of robotics, conveyors, sensors, and programmable logic controllers into manufacturing and material handling processes requires engineers with technical skills and expertise in these systems. The coordination of assembly operations and supervisory control demands familiarity with mechanical and electrical design, instrumentation, actuators, and computer programming for successful system development. This paper presents an educational mechatronics laboratory that encourages multi-disciplinary hands-on engineering discovery within team settings. Three focused progressive experiments are reviewed that allow students to program and operate a programmable logic controller, a traditional conveyor system, and a distributed servo-motor based conveyor. The students also program and implement two robotic arms for material handling applications. The equipment, learning objectives, and experimental methodology for each laboratory are discussed to offer insight. A collaborative design project case study is presented in which student teams create a smart material handling system. Overall, engineering graduates have generally been required to learn material handling and other multi-disciplinary concepts in the field, and therefore, a well-rounded engineering curriculum should incorporate mechatronics in both the classroom and laboratory.     

On RF material characterization in the stripline cavity

We examine the accuracy of the air-filled stripline cavity in measuring the dielectric and magnetic properties of bulk materials in the frequency range of 150-2000 MHz. Measured data on complex permittivity and permeability for several different-sized specimens of dielectric and magnetic materials were compared with reference values obtained using other techniques of known uncertainties. Major differences were noted for both complex permittivity and permeability data, and we largely attribute these to less-than-optimal perturbation of the internal cavity fields by the material specimens under test. The technique is particularly unsuited to measuring the dielectric loss of the higher-permittivity low-loss materials due to energy scatter by the specimen under test. In order to improve measurement accuracy, we suggest guidelines on the range of specimen electric and magnetic volume needed for optimal cavity perturbation     

Electromagnetic characterization of ceramic material produced with natural zeolite

The aim of this study is to investigate the electromagnetic characterization of ceramic panel produced with natural zeolite via considering the frequency-dependent transmission (T), reflection (R) and absorption (A) coefficients. For this purpose, first of all, frequency-dependent complex dielectric values(dielectric permittivity and tangent loss) of material are measured via LCR meter and complex dielectric values used in three dimensional(3D) electromagnetic simulation tool. Then, Debye parameters such as static permittivity(ε_s), optic permittivity(ε_∞) and relaxation time(τ) are derived by using genetic algorithms. Finally, to validate the simulation results, T, R and A coefficients obtained from simulations are compared with frequency-dependent T, R and A values calculated by using the transmission-line equation.     

InSb晶片材料性能表征与机理分析

对2 in InSb(111)晶片材料位错密度、X光形貌、X射线双晶衍射半峰宽和电学参数进行了整片均匀性测试表征.结果表明材料整体性能极佳,并结合InSb晶体生长原理对晶片材料位错密度、掺杂浓度区域性分布进行了深层机理分析.     

X-ray diffraction characterization of LPE HgCdTe heterojunction photodiode material

High-resolution x-ray diffraction has been used to measure the composition difference between P and N layers in HgCdTe heterojunction photodiode material grown by liquid phase epitaxy. The composition (band gap) difference is a critical parameter in long wavelength photodiodes because it affects dark current and the formation of photocurrent collection barriers. We find that symmetric 333 reflections cannot resolve the small composition differences of interest. However, by making use of the asymmetric 246 reflection, small composition differences (0.03) can be resolved. There is good agreement between rocking curves and secondary ion mass spectroscopy composition depth profiles, both in the value of the composition difference and in the extent of compositional grading in the top layer. High-resolution x-ray diffraction shows promise as a nondestructive, relatively rapid technique for screening as-grown heterojunction material for carrier collection barriers.     

纳米银线/还原石墨烯复合材料的制备与表征

用改进的Hummer法制备了氧化石墨烯(GD),并制备 了表面用聚乙烯吡咯烷酮修饰的纳米银线(AgNWs), 通过原位还原法将二者复合成一种新型的水溶性AgNWs/还原石墨烯(RGD)材料,克服了石 墨烯材料不易分散 的缺点。用X射线衍射(XRD)、紫外-可见分光(UV-vis)光度计、扫描电子显 微镜(SEM)和傅里 叶变换红外(FT-IR)光谱分析仪对样品结构和形貌进行了表征。结果表明,制备的AgNWs/RG D材料具有与前驱 体不同的物理参数,有望在非线性光学、光电传感器和生物抑菌等方面有良 好的表现。     

用于光传输实验研究的湍流箱的设计和特性分析

大气中折射率起伏主要由温度的随机变化引起,因此可通过调节气流的温度和速度来人工地产生湍流并控制其强度,基于此原理设计并研制了一种用于光传输实验研究的大气湍流箱.通过同时测量传榆光波的到达角起伏和闪烁,得到了箱内光传输路径上大气折射率结构常数C2n和湍流内尺度l0.实验结果显示,C2n和l0分别受箱内温度和风速的影响.C2n在温度45℃、风速0.48 m/s时达到1.58×10-11 m-2/3,lo在温度25℃、风速1.04 m/s情况下为2.33 mm.对对数光强时间功率谱的分析表明,此湍流箱所产生的湍流适合用于光波大气传榆湍流效应的实验研究.     

Realization of Tapered Waveguide by Stretching the Rod Waveguide

By stretching the rod waveguide with different velocities in opposite directions, the tapered waveguide can be fabricated. In condition of taking no account of volume expansion caused by heating and under the assumptions of volume conservation,the rod waveguide can be stretched freely in the heated region without being stretched outside of the heated region. A model,which shows the relation of the transition shape and the two factors, that is the ratio of two velocity and the heated region length, is presented for the shape of the taper transition through mathematic deduction. Based on this model, a desired tapered waveguide can be fabricated. The tapered waveguide are widely used for fabricating tapered fiber couplers and sensors. In addition, the conclusion can be used for fabricating fused fiber coupler.     

Modulation spectroscopy as a tool for electronic material characterization

Modulation spectroscopy is an optical characterization tool that can be of great utility to the materials scientist. We present here numerous examples where a simple photo-reflectance and electroreflectance setup is used in our laboratory to determine such important material parameters as alloy composition and carrier concentration in a very short time. For determining alloy composition in semiconductors, contactless room temperature photoreflectance is nearly as sensitive as low temperature photoluminescence. Examples will be given on how to determine: the effects of surface preparation and implant damage; alloy composition and carrier homogeneity for large area wafers to better than 1%; the segregation coefficient of isoelectronic impurities in bulk semiconductors; the sub-band energies in quantum well structures; and the presence and homogeneity of built-in electric fields in MODFET structures. Particular emphasis will be placed on band edge and exciton effects on the photoreflectance and on the criteria used to distinguish between them. Materials studied included Si doped GaAs, Al_xGa_1-xAs for variousx grown by OMVPE and MBE, bulk InP doped with iso-electronic As and Sb, and MODFET structures.     

Analysis of Waveguide Post Configurations: Part 3 Influence of General Waveguide Terminations (Technical Notes)

Analysis of general post configurations in an infinitely long rectangular waveguide was presented earlier. This technical note considers the extension of that work to the case when the two waveguide ports are generally terminated.     

矩形波导到圆波导模式变换器的优化设计

在圆形槽波导微波毫米波器件中,常遇到矩形一圆形槽波导的模式变换问题,而矩形一圆波导模式变换是矩形一圆形槽波导模式变换的重要组成部分。本文应用有限元方法,首先由分析N端口波导结问题过渡到两端口的矩形一圆波导模式变换器,然后针对现有模式变换器的圆端口面的电场极化方向倾斜的问题利用加圆波导段的方法进行了优化,并设计了一个新的反射微小,结构紧凑和电场极化方向竖直的矩形一圆波导模式变换器．计算结果满足了设计要求。     

Process characterization and optimization based on censored datafrom highly fractionated experiments

Censored data resulting from life-test of durable products, coupled with complicated structures of screening experiments, makes process characterization very difficult. Existing methods can be inadequate for modeling such data because important effects and factor levels might be identified wrongly. This article presents an expectation-modeling-maximization (EMM) algorithm, where censored data are imputed as pseudo-complete samples and a forward regression is used to compare all main effects and 2-factor interactions for process characterization. Then, the best combination of controllable variables is determined in order to optimize predictions from the final model. A sensitivity study of the selected models, with changes of imputation and parameter estimation methods, shows the importance of using appropriate models and estimation methods in EMM. The author's analysis of the Specht (1985) heat-exchanger life-test data indicates that E, EG, EH in the wall data and A, K, D, DJ in the corner data are the dominating factors. However, in finding the best process recipe, one might use a model with a few additional terms, which leads to more accurate predictions for better process optimization