超宽带匹配馈电结构的设计与实验

设计研制了一种低阻抗传输线向高阻抗超宽带天线馈电的馈电结构,理想情况下,该馈电方法可实现特性阻抗为50 的同轴传输线向特性阻抗为200 的超宽带天线匹配馈电。分别用TEM喇叭天线和抛物反射面天线进行了实验验证,结果表明,与同轴线直接馈电相比,采用该匹配馈电结构后,TEM喇叭天线的辐射场强提高了15%,反射面天线的辐射场强提高了27%。     

Identification of short‐chain poly‐3‐hydroxybutyrates in Saiga horn extracts using LC–MS/MS

Saiga horn extracts were analyzed with the goal of obtaining new information about compounds present in it. The purpose of this study is to find synthetic alternatives to Saiga horn extract, which is used in traditional Chinese medicine, by identifying potentially biologically active compounds in the extracts. Using high‐performance liquid chromatography coupled with high‐resolution mass spectrometry, we have been able to identify a series of short‐chain polyhydroxybutyrates in alcoholic extracts of Saiga horn. Optimized high‐performance liquid chromatography coupled with tandem mass spectrometry methods for analysis of short‐chain poly‐3‐hydroxybutyrates were developed and subsequently applied to investigate Saiga horn extract for the presence of these compounds, which might explain its biological actions, particularly for its antipyretic and procoagulant properties.     

Structural optimization of an acoustic horn

The objective of the present article is to find an optimal design of an acoustic horn in the case that the magnitude of the reflection wave integrated over the inflow boundary is to be minimized meanwhile the Helmholtz equation models the wave propagation. In contrast to the current approaches such as gradient-based optimization algorithms, we employ here a non-iterative method based on measure theory which dose not require any information of gradients and the differentiability of objective function in the optimization problem is not as a rule. Implementation of our fast convergence approach shows that the resulting horns, not only for single frequency optimization but also for a band of frequencies, are very efficient.     

Millimeter-Wave Profiled Corrugated Horns for the Quad Cosmic Background Polarization Experiment

In this paper we report on the design and validation process for the profiled corrugated horn antennas, which feed the bolometer array of a cosmology experiment known as QUaD located at the South Pole. This is a cosmic background radiation polarization project, which demands precise knowledge and control of the optical coupling to the signal in order to map the feeble E- and B-polarization mode structure. The system will operate in two millimeter wavelength bands at 100 and 150 GHz. The imaging horn array collects the incoming signal via on-axis front-end optics and a Cassegrain telescope, with a cold stop in front of the array to terminate side-lobe structure at an edge taper of –20dB. The corrugated horn design process was undertaken using in-house analytical software tools, based on modal scattering, specially developed for millimeter -wave profiled horn antennas. An important part of the instrument development was the validation of the horn design, in particular to verify low edge taper levels and the required well-defined band edges. Suitable feed horn designs were measured and were found to be in excellent agreement with theoretical predictions.     

Bayesian calibration in the estimation of the age of rhinoceros

In this paper the Bayesian approach for nonlinear multivariate calibration will be illustrated. This goal will be achieved by applying the Gibbs sampler to the rhinoceros data given by Clarke (1992, Biometrics, 48(4), 1081–1094). It will be shown that the point estimates obtained from the profile likelihoods and those calculated from the marginal posterior densities using improper priors will in most cases be similar.     

Neural Computation of Wide Aperture Dimension of Optimum Gain Pyramidal Horn

A new method based on the multilayered perceptron neural network architecture for computing the wide aperture dimension of the pyramidal horn is presented. The computed wide aperture dimension is used in successfully designing optimum gain pyramidal horn. The other design parameters of the horn are determined from the simple and explicit analytical formulas. These formulas do not need the application of the iterative methods, and are not restricted to the high gain horn designs. The gain of a designed pyramidal horn is determined with no path length error approximation. Better accuracy with respect to the previous design methods is obtained for various pyramidal horn design examples.     

TEM喇叭短脉冲响应特性与张角的依赖关系

基于传输线理论分析给出了TEM喇叭在高斯脉冲激励下的响应方程,并采用数值计算方法,从响应波形的下降沿拖尾振荡相对基线的浮动量和负峰下冲量的角度研究了在高斯脉冲及其微分形式脉冲激励下,TEM喇叭的响应特性与其张角的依赖关系.基于以单锥TEM室为核心的时域测试系统,实验研究了TEM喇叭的短电磁脉冲响应特性随张角的变化关系,...     

Characterization of cavitation under ultrasonic horn tip – Proposition of an acoustic cavitation parameter

Acoustic cavitation, generated by a piezo-driven transducer, is a commonly used technique in a variety of processes, from homogenization, emulsification, and intensification of chemical reactions to surface cleaning and wastewater treatment. An ultrasonic horn, the most commonly used acoustic cavitation device, creates unique cavitation conditions under the horn tip that depend on various parameters such as the tip diameter, the driving frequency of the horn, its amplitude, and fluid properties. Unlike for hydrodynamic cavitation, the scaling laws for acoustic cavitation are poorly understood. Empirical relationships between cavitation dynamics, ultrasonic horn operating conditions, and fluid properties were found through systematic characterization of cavitation under the tip. Experiments were conducted in distilled water with various sodium chloride salt concentrations under different horn amplitudes, tip geometries, and ambient pressures. Cavitation characteristics were monitored by high-speed (200,000 fps) imaging, and numerous relations were found between operating conditions and cavitation dynamics. The compared results are discussed along with a proposal of a novel acoustic cavitation parameter and its relationship to the size of the cavitation cloud under the horn tip. Similar to the classical hydrodynamic cavitation number, the authors propose for the first time an acoustic cavitation parameter based on experimental results.     

Characterization of keratin–collagen 3D scaffold for biomedical applications

Fabrication of keratin–collagen (KC) 3D scaffold with improved thermal denaturation rate is reported. In vitro application of (KC) scaffold stimulates basic extra cellular matrix constituents. KC Scaffold considerably reduced undesirable properties of both collagen and keratin while collagen incorporation reduces the fragility with increases of strength and flexibility in the scaffold. In addition to this, the scaffold showed homogenous well‐interconnected pores in the range of 10–100 µm when observed in scanning electron microscope. Usage of keratin in KC scaffold offers increased biodegradation rate and higher denaturation rate in addition to its rapid cell growth with normal morphology ultimately reaching cell population of 3.9–9.7 million per cm³ after 48 hr in KC scaffold. Circular dichroism (CD) and Fourier transform spectroscopy (FT‐IR) of KC showed presence of helical structure of collagen and ß‐turns of keratin confirming retention of native structures of both the proteins KC scaffold showed good swelling behavior and water uptake. Our study strongly supports the superidity of KC scaffold over the collagen or keratin when they are independently used for tissue engineering applications. Copyright © 2011 John Wiley & Sons, Ltd.     

Investigations of the barbell ultrasonic transducer operated in the full-wave vibrational mode

In this paper, the resonance frequency equation and expression of displacement amplitude magnifications of a full-wave barber ultrasonic horn are obtained. By discussing the relationships between the displacement amplitude magnifications and the geometrical dimensions, the optimized design of the horn for the largest magnification is proposed, which is helpful to improve the radiation power and the transfer efficiency of the acoustic energy of the ultrasonic oscillatory system. Based on the optimized design of the horn, we introduced a barbell ultrasonic transducer operated in the longitudinal full-wave vibrational model and obtained the resonance frequency equations. For comparison, the resonance frequencies of the full-wave barbell horn and the full-wave barbell transducer are also analyzed by finite element method (FEM). It is shown that the values obtained by theoretical analysis and FEM are in good agreement with experimental observations. We hope that the research of this paper is helpful for the use of the barbell horn and transducer in the applications such as ultrasonic liquid processing.