K.-M. Huang’s research while affiliated with Sichuan University and other places

In this paper, an efficient finite element method (FEM) in solving electromagnetic scattering from body coated by thin-layer materials based on nonlinear coordinate transformation is presented. To solve scattering thin-layer material problems accurately, the traditional FEM employs rigor meshes to discretize the thin-layer structure resulting in numerous meshes, unknowns and ill-conditioned matrices. It requires much expensive storage and computational time. The proposed approach employing nonlinear coordinate transformation maps the dense thin-layer geometry space into a sparse space. In this manner, the need of rigor local mesh refinement can be eliminated. Thus, it provides an efficient approach to compute scattering from body coated by thin-layer materials. Two examples validate the efficiency and accuracy of the proposed method.

Microwave heating has been widely used and the heating uniformity is related to the characteristics of electric field. In this paper, we investigate the stability of electric field in a multimode microwave cavity by analyzing the spectrum and the condition number of integral equation. Results show that the stability of the electric field is mainly dependent on microwave frequency, the permittivity of heating object and cavity geometrical parameters. Particularly, when the heating object has a low loss factor, the electric field is generally unstable. Namely, a tiny shift of the parameters mentioned above will result in dramatic changes of electric field distribution. Besides, the instability of the electric field increases with the lower loss, the higher microwave frequency or the larger permittivity of the heating object.

In this paper we present a fast time-domain algorithm to study the electromagnetic pulse heating on dispersive medium. Using the proposed fast algorithm, the long heating process can be compressed by accelerating thermal conduction and scaling the power dissipation density. Comparing with the previous computation of several pulse periods, the proposed algorithm can deal with the heating process up to billions of pulse periods. Besides, employing the proposed algorithm, we study a 2D water post heated by electromagnetic pulses. The results reveal that comparing with continuous microwave heating, pulse heating cannot improve temperature uniformity or enhance heating efficiency.

The aim of the present work is to obtain effective permittivity of the reaction mixture during esterification reactions that can be used in a dynamic simulation environment and analysis the dielectric properties during the reaction process. Microwave heating serves as an excellent tool for carrying out such reactions and the multiphysics simulations need effective permittivity as one of the most important inputs. In this work, we perform the esterification reaction between ethanol, acetic acid and butyric acid using a temperature cycle in order to measure the effective permittivity of the reaction mixture. The obtained result is fitted using a bivariate function of the concentration of one of the products of the reaction and temperature of the mixture. The computed results show good agreement with measured values with maximum errors for the synthesis reactions of ethyl butyrate and ethyl acetate being 4.94% and 3.68%, respectively.

In this paper, we evaluate specific absorption rates (SAR) in a human head exposed to radiation of a mobile phone at two frequencies of Global System for Mobile (GSM) Communications, when people do and don’t wear glasses. The simulation includes phone call and internet surfing states. Since the eyes are sensitive to electromagnetic radiation, we focus on the maximal SAR in eyes. Based on finite-difference time-domain (FDTD) calculation method, we find that wearing glasses obviously alters the distribution of SAR and may increase SAR. The maximal SAR in eyes with glasses is even eight times more than that without glasses. The maximal SAR is more sensitive to the frame of glasses than the spectacle lens. In all, wearing glasses may possibly induce higher risk of the health hazard to eyes exposed to the radiation of a mobile phone. The results could offer valuable results for designing glasses to reduce SAR in eyes.

Dielectric properties of alcohol-alcohol (methanol + n-propanol and methanol + ethanol) mixtures were measured at the selected microwave frequency (5.65 GHz) by a sensitive sensor method using a network analyzer. The effects of concentration in terms of molar fractions on dielectric properties were investigated.

When the dielectric properties of the sample are too poor to allow efficient heating by microwave radiation, the use of container that have large loss tangent values can significantly overcome these problems and enable adequate heating of the whole sample. In this paper, carbon tetrachloride at silicon carbide container with three different configurations were heated indirectly by microwave. The uniformities of temperature were analyzed using COMSOL Multiphysics under different configurations during microwave heating. It was concluded that the temperature uniformities were influenced by the parameters of different configurations, when the improvement in electric field uniformity is not obvious for one configuration, it can be significantly improved by changing to another specific configuration.

Stir, rotation and other methods have been widely used to improve the heating uniformity during microwave heating nowadays. In this paper, the heating uniformity of water with rotation or stir and their combination under microwaves were investigated through multiphysics calculation. It was found that among the three above cases, the temperature uniformity of water under microwave heating with the combination of stir and rotation is the best. The improvement of temperature uniformity of microwave heating water with rotating tray is poor while the speed is increasing; within a certain range, contrarily,increase of the stir speed can significantly improve the temperature uniformity of water. The hotspots cannot be completely dispelled by stir.