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787 results on '"Huang, Kama"'

153. Highly Efficient Microwave Power System of Magnetrons Utilizing Frequency-Searching Injection-Locking Technique With No Phase Shifter

Author

Lai, Chao, primary, Zhao, Chaoxia, additional, Li, Kang, additional, Cai, Danli, additional, Zhang, Yi, additional, Yang, Yang, additional, Zhu, Huacheng, additional, Agrawal, Dinesh K., additional, Slawecki, Tania, additional, Wu, Li, additional, Zhou, Yanping, additional, Chen, Qian, additional, Zhou, Lin, additional, and Huang, Kama, additional

Published
2020
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154. The empirical formula for calculating the complex effective permittivity of an aqueous electrolyte solution at microwave frequency

Author

Yang, Xiaoqing and Huang, Kama

Subjects
Remote sensing, Microwave measurements, Electronic measurements, Earth sciences research, Business, Earth sciences, Electronics and electrical industries
Abstract

So far, some models have been established to calculate the complex effective permittivity of an aqueous electrolyte solution. Almost all of the models based on the fitting parameters in Debye's equation were used to calculate the complex effective permittivity of a few aqueous electrolyte solutions, such as saline water and seawater. In this paper, we propose a new empirical formula to calculate the complex effective permittivity of a mixed aqueous electrolyte solution based on the measurement of complex impact factors for fundamental ions. The calculated complex effective permittivities of six mixed aqueous electrolyte solutions were compared with the measured results at 915 and 2450 MHz. The complex permittivity of saline water obtained by this model was compared with the published data as well. Good agreement can be observed. Index Terms--Aqueous electrolyte solution, complex effective permittivity, empirical formula, microwave frequency.

Published
2005

156. Measurement/computation of effective permittivity of dilute solution in saponification reaction

Author

Huang, Kama, Cao, Xuejun, Liu, Changjun, and Xu, Xiao-Bang

Subjects
Microwaves -- Usage, Chemistry -- Research, Chemistry -- Equipment and supplies, Business, Computers, Electronics, Electronics and electrical industries
Abstract

For better application of microwaves in chemistry, the interaction between the microwave and chemical reaction needs to be further studied. Since the reactants form a complicated mixture, which changes with time, an effective permittivity can be used to describe the molecular polarization of the mixture in the reaction. The effective permittivity is expected to change with the frequency of the microwave, temperature, and reaction time. However, in many cases, change of the effective permittivity in saponification reaction is too small to be detected using traditional methods. In this paper, we present a hybrid experimental/computational method for determining the effective permittivity in saponification reaction. First, we use a resonant coaxial sensor to measure the reflection coefficients. To predict its performance, the electromagnetic-field distribution near the sensor and the reflection coefficient are calculated employing the frequency-dependent finite-difference time-domain method. Second, we develop a genetic-algorithm-based inverse-calculation technique and employ it to determine the complex permittivity of pure water from the measured reflection coefficient and compare the results with that obtained from Debye's equation. Finally, the hybrid experimental/computational method is employed to determine the effective permittivity of a dilute solution in a typical saponification reaction. Results are presented and discussed. Index Terms--Effective permittivity, inverse calculation, measurement, saponification reaction.

Published
2003

158. Substrate integrated waveguide omnidirectional filtering antenna with a controllable radiation null for 5.8 GHz WiFi application.

Author

Yu, Sha, Cheng, Fei, Gu, Chao, Zhang, Bing, and Huang, Kama

Subjects
COPLANAR waveguides, OMNIDIRECTIONAL antennas, SUBSTRATE integrated waveguides, WAVEGUIDE filters, CAVITY resonators, RADIATION, MONOPOLE antennas
Abstract

A filtering antenna composed of a monopole and two stacked circular substrates integrated waveguide (SIW) cavity for 5.8 GHz WiFi application is proposed in this letter. Cross‐coupling between the feeding probe and the second SIW cavity resonator is utilized to generate a radiation null at the frequency above the working band. By properly designing the location of the feeding probe and the size of the coupling slot between the two SIW resonators, the frequency of the radiation null can be adjusted. Experimental results of the fabricated filtering antenna show good agreement with the simulated performance. The measured filtering antenna response has a return loss greater than 10 dB with a fractional bandwidth of 16.4% centered at 5.48 GHz while there is a radiation null at 6.85 GHz. Omnidirectional patterns are achieved in horizontal plane with a maximum gain of 1.1 dBi. The proposed filtering antenna has the merits of compact size and good stopband radiation suppression. [ABSTRACT FROM AUTHOR]

Published
2022
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159. Structural Engineering in Graphite‐Based Metal‐Ion Batteries.

Author

Luo, Pan, Zheng, Cheng, He, Jiawei, Tu, Xin, Sun, Wenping, Pan, Hongge, Zhou, Yanping, Rui, Xianhong, Zhang, Bing, and Huang, Kama

Subjects
STRUCTURAL engineers, GRAPHITE, STRUCTURAL engineering, GRAPHITE intercalation compounds, LITHIUM-ion batteries, POTASSIUM ions, SODIUM ions
Abstract

Graphite‐derived carbon materials have been widely used in metal‐ion batteries due to their good mechanical and electrical properties, cost effectiveness, light weight, and environmental friendliness. Though natural graphite has been commercially used in lithium‐ion batteries, the small interlayer spacing hinders its application in other metal‐ion batteries. As such, numerous works have been done to enhance the metal‐ion storage capability of graphite and its derivatives. In this review, structural engineering on graphite including expanded graphite, graphite intercalation compounds and porous graphite, and the corresponding electrolyte engineering for lithium‐ion batteries, sodium ion batteries, potassium ion batteries, and dual ion batteries are summarized, aiming to make a comparison between various strategies and give a suggestion on future work in this area. [ABSTRACT FROM AUTHOR]

Published
2022
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186. A simple method for calculating electric and magnetic fields in GTEM cell

Author

Huang, Kama and Liu, Yongqin

Subjects
Electromagnetic fields -- Measurement, Electromagnetic measurements -- Research, Business, Computers, Electronics, Electronics and electrical industries
Abstract

A method based on coordinate transformation is presented to calculate the electric and magnetic field distributions in gigahertz TEM cells (GTEM cells). Here quasi-static approximations are employed, therefore the results are valid once operational frequencies well below the cutoff frequency of the cell. The method is illustrated by calculating the fields in a typical test structure. The results indicated here are useful in radiated emission and susceptibility studies.

Published
1994

187. Abnormal characteristics of binary molecular clusters in DMSO–ethanol mixtures under external electric fields

Author

Zhiyan Wu and Huang, Kama

Subjects
Physics::Medical Physics
Abstract

For the nonlinearly phenomena on the dielectric properties of dimethyl sulfoxide (DMSO)–ethanol mixtures under a low intensity microwave field, we propose a conjecture that there exist some abnormal molecular clusters. To interpret the mechanism of abnormal phenomena and confirm our conjecture about the existence of abnormal molecular clusters, an in-depth investigation about the structure evolutions of (DMSO)m(C2H5OH)n (m = 0–4; n = 0–4; m + n ≤ 4) molecular clusters induced by external electric fields has been given by using density functional theory. The results show that there exist some binary molecular clusters with large cluster radii in mixtures, and some of them are unstable under exposure of electric fields. It implies that the existence of certain abnormal molecular clusters in DMSO-ethanol mixtures results in their abnormality of dielectric properties.

Published
2018
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