Jinhui Peng

Metamaterial electromagnetic concentrators with arbitrary geometries

The electromagnetic concentrators play an important role in the harnessing of light in solar cells or similar devices, where high field intensities are required. The material parameters for two-dimensional (2D) metamaterial-assisted electromagnetic concentrators with arbitrary geometries are derived based on transformation-optical approach. Enhancements in field intensities of the 2D concentrator have been shown by full-wave simulation. All theoretical and numerical results validate the material parameters for the 2D concentrator with irregular cross section we developed.

An external cloak with arbitrary cross section based on complementary medium and coordinate transformation

Electromagnetic cloak is a device which makes an object invisible for electromagnetic irradiation in a certain frequency range. Material parameters for the complementary medium-assisted external cylindrical cloak with arbitrary cross section are derived based on combining the concepts of complementary media and transformation optics. It can make the object with arbitrary shape outside the cloaking domain invisible, as long as an antiobject is embedded in the complementary media layer. Moreover, we find that the shape, size and the position of the antiobject is dependent on the contour of the cloak and the coordinate transformation. The external cloaking effect has been verified by full-wave simulation.

Microwave sensor for measuring the properties of a liquid drop

A novel microwave sensor for measuring the properties of a liquid drop has been invented, its analytical theory established and a working prototype has been constructed and tested. It was also found that the theory based on the microwave sensor is in good agreement with the experimental results. Excellent linearity is achieved by optimizing the design, with an accuracy of distilled water drop volume measurement of approximately 0.5 µl, and this microwave sensor has been used to measure surface tension, species concentration and the microwave absorption properties of a liquid drop simultaneously, which are the key parameters in the fields of physical chemistry and microwave chemistry.

SIMULATION AND ANALYSIS OF ASYMMETRIC METAMATERIAL RESONATOR-ASSISTED MICROWAVE SENSOR

Based on the field enhancement principle of trapped modes, two new asymmetric metamaterial resonators are presented. Transmission response (S21) of the rectangular wave-guide filled with an asymmetric metamaterial resonator is simulated. Results show that the asymmetric resonator possesses high Q-factor and improved sensitivity. The microwave sensor based on the asymmetric resonator can be flexibly tailored to design requirement by varying the asymmetry parameter or the topological structure of the resonator. The asymmetric metamaterial resonator-assisted microwave sensor will have potential applications in biosensor and chemosensor fields for sensing minute amounts of dielectric sample substance.

A new equation for the description of dielectric losses under microwave irradiation

A new equation was developed to describe quantitatively the dielectric loss of materials that is a key parameter in the fields of microwave chemistry and microwave processing of materials under microwave irradiation. This equation can be applied to explain the complicated thermal runaway phenomenon that has relations with dielectric relaxation and to simulate the dielectric loss under microwave irradiation. It was also found that the simulation results based on this equation are in good agreement with the Volge–Fulcher law. The new equation has potential application in the study of microwave interaction with solid materials, especially in materials processing which involves microwave chemistry, synthesis, sintering, melting, joining, surface-modifications, quality improvements, etc and it is hoped that the dynamic process of material under microwave irradiation could be explained.

Electromagnetic concentrators with arbitrary geometries based on Laplace’s equation

Concentrators with arbitrary geometries are designed based on the numerical solution of Laplaces equation, with which the material parameters can be independently obtained without any knowledge of the corresponding coordinate transformation. Results show that the concentrator designed using the numerical method has the same scattering and concentrating properties as that designed using the analytical method, except for a slight difference in the stretching region, which, however does not influence the design of the concentrator. The method developed in this paper is general and flexible for designing arbitrary concentrators. The validity of such a method and the concentrating effects are confirmed by full-wave simulations.

AN EXTERNAL CLOAK WITH ARBITRARY CROSS SECTION BASED ON COMPLEMENTARY MEDIUM

Electromagnetic cloak is a device which makes an object invisible for electromagnetic irradiation in a certain frequency range. Material parameters for the complementary medium-assisted external cylindrical cloak with arbitrary cross section are derived based on combining the concepts of complementary media and transformation optics. It can make the object with arbitrary shape outside the cloaking domain invisible, as long as an antiobject is embedded in the complementary layer. The external cloaking efiect has been verifled by full-wave simulation. Moreover, the efiect of metamaterial losses is studied, and small losses less than or equal to 0.01 do not disturb the cloaking efiect.

MODELING THE DIELECTRIC RESPONSE IN HETEROGENEOUS MATERIALS USING 3D RC NETWORKS

A model of 3D RC networks was developed to describe the dielectric response of heterogeneous materials and was compared with the results of the 2D RC network model. We show that the universal dielectric response (UDR) of heterogeneous materials is a common feature of both 2D and 3D very large networks with randomly positioned resistors and capacitors, and that the percolation threshold of the 2D and 3D bond network are close to 0.5 and 0.25, respectively. In addition, it was found that the percolation threshold of the 3D network is in good agreement with the result of the coherent potential (CP) formula.

Microwave absorbing properties and electric field distribution of conductor-dielectric compound

Complex permittivity of the conductor-dielectric compound was calculated based on the effective medium theory. Four main results are as follows: microwave absorbing peak shows a blue shift with the increase of conductivity of the inclusion; Increasing the permittivity of the dielectric embedding matrix, significant amplification of the effective permittivity is observed; For fixed surface fraction, effective complex permittivity is independent with the granularity of the inclusion; local electric field enhancement effect is the main reason that powder metal can be heated by microwave.

Full connectivity and probabilistic coverage in random deployed 3D WSNs

Connectivity and coverage problem is an important and fundamental issue in sensor networks, which reflects how well a sensor network is communication-connected and monitored by sensors. While connectivity and coverage problem in two dimensional wireless sensor networks (WSNs) have been well studied, three dimensional WSNs have gained relatively less attention in present literatures. This paper discusses the connectivity and coverage problem in random deployed three dimensional WSNs. We propose an experimental analysis of the fundamental relationship between connectivity probability, the number of nodes and the nodes transmitting ranges. Based on probability model, we calculate a feasible range of the number of nodes for an effective sensing coverage in a three dimensional sensing field. Thus, a practical guidance for random deployment in three dimensional WSNs from connectivity and coverage perspective is given.