Applied Mechanics and Materials Vols. 347-350

Abstract: In considering of the triangle cantilever beam can improve the problem of stress concentration in rectangular cantilever beam, the piezoelectric power generating mathematical model of triangle cantilever piezoelectric vibrator is build base on piezoelectric equation and material mechanics. The effect of structure size on the electricity generating capacity is simulated with numerical The result shows that the applied electric field have less effect on the output voltage, and the substrate thickness and length of cantilever beam have bigger influence on the output voltage.

Abstract: An accurate method for extracting the elements of InP HBT small-signal model parameters is proposed in this paper. The method can accurately resolve the most important internal parameters from the measured S-parameters, and is not sensitive to the values of parasitic parameters. The initial values of the parasitic are extracted by using a set of test structure, and the intrinsic elements determined by using the analytical method are described as functions of the parasitic elements. The extraction procedure uses a set of closed-form expressions derived without any approximation. An experimental validation is carried out on three HBT devices and satisfactory results are obtained up to 20 GHz.

Abstract: AUTOSAR will make the software better portable and expansible, will shorten the development cycle and reduce the cost of development. Because of AUTOSARs module idea, this paper designs the communication stack basing on Controller Area Network (CAN), and describes the critical realization of CAN driver, CAN interface, CAN transport layer, communication and diagnostic management. So it can meet the requirement of automotives control network.

Abstract: Wherever possible, we have adopted the newest modern technology. The Au-Si binary alloy sintered chips are silicon or silicon carbide power devices. The sintered temperature is 380 to 390 °C. Using micro-infrared thermal image instrument, compares the microwave transient infrared thermal image test results of sample devices which chips welded process under two different process condition. Measured results show that the thermal resistance after chip welded process optimized is twenty percent smaller than before. It describes the importance of controlling the chip welded process parameters during assembly.

Abstract: This paper describes the design and implementation of Web based secure embedded system, including tiny secure Web server, embedded system-based CGI library, and utilities for security, such as CAPTCHA program and mail sending program. The entire system is designed in C by the author of this paper on Linux platform with GNU tool chain. A Web based secure embedded application demo system is also designed to show the architecture and running effect. On the premise of implementing essential functions, the scale of the system is designed as small as possible therefore it is suitable not only for embedded Linux development on Web based applications but also for embedded system course teaching in colleges and universities. By some further extensions, it can also be used on development of general Web based MIS.

Abstract: Simulation, Fabrication and characteristics of high voltage, normally-off JFETs in 4H-SiC are presented. The devices were built on ND= 1.01015 cm-3 doped 50μm thick n-type epilayer grown on a n+ 4H-SiC. Parameters of edge termination have been optimized by simulations. Its blocking voltage exceeds 4500V at gate bias VG = -6V and forward drain current is in excess of 3A at gate bias VG = 3V and drain bias VD = 5V corresponding a current density of 80A/cm2.

Abstract: In this paper, we will focus on channel estimation (CE) in orthogonal frequency-division multiplexing (OFDM) systems. The time-varying (TV) channelsare modeled by a basis expansion model (BEM). Due to the time-variation, the channel matrix in the frequency domain is no longer diagonal, but approximately banded.We use a pilot-aided algorithm for estimation of rapidly varying wireless channels in OFDM systems. Theperforms is goodwhen the channels vary on the scale of a single OFDM symbol duration, which occurs in mobile communication scenarios such as WiMAX, WAVE, and DVB-T.We recover Fourier coefficients of the channel taps by the pilot information.We then estimate the BEM coefficients of the channel taps from their respective Fourier coefficients using a recently developed inverse reconstruction method.We compare some BEM models in inverse methodsto find out the best ones in certain conditions.

Abstract: This paper proposes a novel method for realizing arbitrary fractional divider based on FPGA. Analyzing the limitations of the existing frequency-divided methods, a new model which consists of two-level dividers is put forward. An arbitrary frequency-divided clock output can be obtained by this method approaching 50% of duty cycle. When the division factor is greater than 128, the duty cycle can be very close to 50% of the clock output. This method is proved to be feasible on the FPGA chip of ALTERA.

Abstract: This paper describes the technical details of design and implementation of embedded system-based CAPTCHA (verification code) in C, including a brief analysis of techniques for implementing CAPTCHA, and a simple and practical CAPTCHA system designed by the author of this paper, which can be used not only in embedded systems but also ordinary Web based MIS or control systems, without the support of any dedicated graphics library. An example is provided to show the practical usage and effect of this CAPTCHA system on an embedded application demo system.

Abstract: Silicon carbide (SiC) static induction transistors (SITs) were fabricated using home-grown epi structures. The gate is a recessed gate - bottom contact (RG - B). The mesa space designed is 2.5 μm and the gate channel is 1.0 μm. The developed devices adopted a p-type Al ion implanted gate and power performance was improved by decreased leakage current and enhanced break-down voltage. The lift-off with assistant dielectric, dense gate recess etching, high temperature anneals and PECVD passivation process technologies are adopted. One cell has 200 source fingers and each source finger width is 50 μm. 0.5 mm SiC SIT yield a current density of 110 mA/mm at a drain voltage of 50 V. A maximum current density of 160 mA/mm was achieved with Vd = 80V, and the maximum transconductance is 40mS/mm. The device blocking voltage with a gate bias of-12 V was 400 V. Packaged 2 × 2-cm devices were evaluated using amplifier circuits designed for class AB operations. A total power output in excess of 70 W was obtained with a power density of 17.5 W/cm and gain of 5.5 dB at L band 1 GHz under pulse 100μs and cycle ratio 1% RF operation and 80V drain to source voltage.