Epitaxy of SiGe HBT Structure by High Vacuum/Rapid Thermal Processing/Chemical Vapor Deposition

The strained SiGe material has been grown by using the newly developed High Vacuum/Rapid Thermal Processing/Chemical Vapor Deposition (HV/RTP/CVD) system.Device quality material is grown by handling process after careful design. The Ge fraction varies up to 0 25, and the n and p type doping is well controlled,which are both adapted to the fabrication of Heterojunction Bipolar Transistors (HBT). The SiGe HBT structure, namely n Si/i p + i SiGe/n Si structure, has been investigated, with which, the HBTs are fabricated and show good performance. The new system has been proved potential and practicable.

笑笑“糖”

儿子：“妈妈，这次我考试得了第5名，快给我煮个鸡蛋。” 妈妈：“好孩子，进步真快。妈妈今天给你煮两个鸡蛋。”

Operation reliability for on-ramp junction of urban freeway

A disorder situation of traffic operation always appears in on-ramp junction area of urban freeway,because the operation action for vehicles presents the weaving condition,especially for different vehicle types.Based on the analysis on the cellular automata theory,and combining with on-site survey data,several key parameters were defined,namely,cellular length,cellular speed,cellular acceleration,updating time interval.In addition,cellular acceleration rule,cellular deceleration rule,random rule,lane-changing rule and other micro-simulation rules were set,and cellular automaton micro-simulation model was set up.Further-more,a micro-simulation module was developed for traffic operation actions of on-ramp junction with Matlab toolbox.Finally,a simulation experiment for traffic operation reliability was done with this micro-simulation module,and the situation of change for on-ramp junction area was obtained under the conditions of different mainline design speed,acceleration lane length,vehicle generation probability and lane-changing probability.The results show that operation reliability for on-ramp junction is determined by the parameters of the probability of vehicle generation and the length of acceleration lane,especially for on-ramp.

The Performance Analysis of the Wavelet-OFDM New Scheme in AWGN Channel

Orthogonal frequency division multiplexing （OFDM） is a special form of multi-carrier transmission that uses the policy of divide and rule. In this scheme, a large number of orthogonal, overlapping, narrow band sub-channels （subcarriers） are transmitted in parallel and divide the available transmission bandwidth. This techniqueis originally based on the Fast Fourier Transform of the information data. In order to improve the performance of the OFDM and overcome some limitations, an alternative OFDM approach based on the Wavelet Transform is proposed. In this paper, we study the performance of such systems in additive white Gaussian channel （AWGN）. MATLAB simulations are realized and performance comparisons are presented.

百强榜人物——我的书法情结

时间过得真快,一转眼,我在书法这条路上已走了将近二十个春秋。回首自己在黑白世界里经历的沟沟坎坎,大有剪不断、理还乱,别有一番滋味在心头的感觉。我是在农村长大的。小时候家里很贫穷。我喜欢绘画完全是受哥哥的影响。

Precise simulation of surface acoustic wave devices using frequency-dependent coupling-of-modes parameters

Herein we extract all the frequency-dependent coupling-of-modes （COM） parameters, which will be used to the rapid simulation and optimal design of surface acoustic wave （SAW） devices. FEM/BEM is used to calculate the exact field distributions of forward and backward surface acoustic waves within a finite-length periodic grating at every frequency. The middle compo- nent of the grating, regarded as a periodic structure, is selected to be investigated which can satisfy the presupposition of the COM model. From these field distributions, the values of P-matrix elements of one cell are calculated. The COM parameters taken as functions of frequency are accurately obtained. Specifically, the frequency-dependent relationships of reflection coefficient and propagation velocity are obtained independently. Using the resultant COM parameters, a one-port resonator on the substrate of 128°YX-LiNbO3 is simulated and the admittance curve shows good agreement with the simulating results using FEM/BEM. These results verify the validity and accuracy of this method.

A Numerical Modeling of the Vortex-induced Vibration of Cascade in Turbomachinery using Immersed Boundary Method

Based on the immersed boundary method,a fast simulation for solving unsteady,incompressible,viscous flow associated with the oscillating cascade is established on a quasi-three-dimensional coordinate system.The numerical method is applied to the simulation of the flow passing an oscillating circular cylinder which is forced to move in X direction under prescribed motions in water at rest at low Keulegan-Carpenter numbers.Then vor-tex-induced vibration of a cylinder with two degrees of freedom which oscillates in in-line direction and transverse direction is simulated using this method.The results are in good agreement with the previous research.Then the method is extended to the oscillating cascade simulation of making various comparisons.It is found that the IBPA(inter blade phase angle) will change as the time goes on,because of the non-uniformity of the flow in the circumferential direction,until the oscillating cascade goes to a stable situation.The reduced velocity and the number of blades are chosen to investigate the effects of them on IBPA.The results indicate that both the reduced velocity and the number of blades are the main factors which influence IBPA.It is worth noting that the coupling process is not necessary to generate any body-fitting grids,which makes it much faster in computational process for such a complicated fluid-structure interaction problem.

Mn-doped SiGe thin films grown by UHV/CVD with room-temperature ferromagnetism and high hole mobility

In this work,silicon-germanium(SiGe)thin films are epitaxially grown on Ge substrates by ultra-high vacuum chemical vapor deposition and then doped with Mn element by ion-implantation and subsequent rapid thermal annealing(RTA).The characterizations show that the epitaxial SiGe thin films are single-crystalline with uniform tensile strain and then become polycrystalline after the ion implantation and following RTA.The magnetization measurements indicate that the annealed thin films exhibit Mn concentration-dependent ferromagnetism up to 309 K and the X-ray magnetic circular dichroism characterizations reveal the spin and orbital magnetic moments from the substitutional Mn element.To minimize the influence of anomalous Hall effect,magneto-transport measurements at a high magnetic field up to 31 T at 300 K are performed to obtain the hole mobility,which reaches a record-high value of~1230 cm^(2)V^(-1)s^(-1),owing to the crystalline quality and tensile strain-induced energy band modulation of the samples.The first demonstration of Mn-doped SiGe thin films with roomtemperature ferromagnetism and high carrier mobility may pave the way for practical semiconductor spintronic applications.

Diagnosis Petri Net Model for Power System

This paper puts forward a new fault diagnosis model based on Petri net.In this new fault diagnosis method,an associated tree is f irst defi ned to describe the logic according to the protections and circuit breakers.After that a Petri net diagnosis model comes into being and the precise diagnosis of power grid elements can be realized at the same time.The simulation results given in this paper illustrate that this fault diagnosis method can make a rapid diagnosis in complex fault situation and give accurate results to power grid fault diagnosis.