1D Electromagnetic Band Gap Analysis and Applications

In this chapter, a detailed study of the one-dimension electromagnetic band gap (1D-EBG) structures and their application in a directional antenna design are presented. To improve the ability and analyze and understand the behavior of 1D-EBG, three techniques of analysis are developed. The results show that the periodicity of the dielectric permittivity makes it possible to stop the waves propagation in certain frequency bands. A comparison between the different methods shows an excellent agreement. An evolution of the transmission coefficient of a structure consisting of six layers with a cavity of thickness equal a wavelength in the middle of the structure, shows that there is a peak of transmission which is formed at the center frequency of the band gap and reflects a resonance phenomenon. This phenomenon of frequency filtering is exploited for the design of a directive EBG antenna by introducing an excitation to the cavity center.

Effects of Reynolds Number on Vortex Structure Evolution in a Square Cavity with Two Opposite Moving Lids

The vortex structure of two-dimensional flow in a cavity is calculated using the differential quadrature method. The numerical simulation focuses on investigating the effects of Reynolds number on vortex structure evolution of the flow in a square cavity with two opposite and equal speed moving lids. The streamline patterns and bifurcation diagrams are determined. The numerical results show that the flow in the cavity takes on the streamline pattern of completely symmetric vortex structure when the Reynolds number approaches zero. With the Reynolds number increasing, the sizes and center positions of the sub-vortexes appear to be affected, whereas the saddle point is still located at the cavity center, resulting in a skewed flow pattern in the cavity. It is observed that one large vortex occupies the entire cavity and the shape of the large vortex becomes more circular after a critical value of the Reynolds number is exceeded. If the Reynolds number is increased further, two secondary eddies emerge simultaneously on the upper left corner and the lower right corner near the sidewalls. The center of the large vortex is invariably located at the cavity centre. For different Reynolds numbers, the streamline patterns are symmetric about the cavity center which is always a stagnation point.

Study the Coupling Characteristics of Line Defects and Point Defects in Photonic Crystals

In order to filter, we use the coupling methods of line defects and point defects in photonic crystals to verity through theories and experimentations, get micro-cavity center frequency and wavelength of the main waveguide frequency resonance, and the same frequency lights will enter micro-cavity. Results show waveguides and micro-cavity can support its modes within in their deficiencies, but defects still can transfer energies through the evanescent coupling, the evanescent coupling is the role of the photonic crystals to the integration of device.

Sensitivity and Response of a Triple-Axis Thermal MEMS-Based Acceleration Sensor

This paper investigates numerically the sensitivity and response of a novel tripleaxis thermal MEMSbased acceleration sensor. In this novel sensor, the heater forms an open ring on the top of a cavity, which improves the variation of temperature in the region just above the cavity center with vertical acceleration. By placing a temperature detector in this region, the sensitivity of vertical measurement is significantly improved and comparable with that of horizontal measurement whose detectors are outside the heater loop. Furthermore, the mutual effect is dramatically reduced. For instance, at the supplied power of 15mW to the heater, the sensitivity for the vertical measurement attains 0.062°C/g (g is gravity) while those for the horizontal measurements are 0.29°C/g, and cross sensitivities are less than 5%, for acceleration within 10g. The numerical analysis of response of the sensor shows that the sensor frequency bandwidth at 3 dB is about 70 Hz.

Study on Processing Parameters of Ceramic Injection Moulding

According to the heat transmission theory, in the aid of computer, the temperature distribution in the cylinder cavity was calculated. The temperature of the mould has much influence on the time for the injection material’s temperature of the cavity center to drop to the injection material softening temperature. The influence of the processing parameters on the density of the injection molding specimens was also investigated. It turns that the injection molding specimens’ density changes little with the increase of injection temperature and pressure, but changes a lot with the increase of holding pressure time.