Observation on Defects in Poly-Si Films Prepared by RTCVD Under Nonideal Conditions

Polycrystalline silicon (poly-Si) thin films were deposited on quartz substrates by rapid thermal chemical vapor deposition (RTCVD) under nonideal conditions. Then, crystallographic defects in the poly-Si films were investigated by using transmission electron microscopy (TEM) and optical microscopy combined with defect etching. We found that as-deposited poly-Si films contain a lot of twin crystals, including first-order, second-order, third-order, and higher-order twinned crystals. Besides twinned crystals, stacking faults, dislocations, dislocation nets, dislocation loops, extended dislocations, and dislocation line arrays were also found. Finally, the origins of the defects were analyzed, being attributed to the peculiarities of the RTCVD-quartz growth system, stress caused by lattice and thermal mismatch, a huge temperature ramp, and nonideal deposition conditions. Although our experimental results cannot represent the crystallographic quality of poly-Si films prepared by RTCVD, they at least indicate what kinds and how many defects exist in poly-Si films when deposition conditions severely deviate from the optimum.     

机房环境综合监测系统的构建

本文介绍了如何利用RS-485总线技术和TCP/IP网络构建环境综合监测系统,实现对传感器、精密空调、UPS与高压配电柜等设备的连接和信息的实时采集工作,以及针对采集数据异常条件下的报警和解除的业务逻辑设计.     

Focus shift and phase correction in soft tissues during focused ultrasound surgery

During the treatment of soft tissue tumors using focused ultrasound surgery (FUS), the focus can shift away from the desired point due to tissue inhomogeneity. In this paper, a numerical method to calculate the focus shift in multiple-layered tissues and a faster phase-correction method to restore the focus were developed. Data from the simulations showed that the focus shifted about 2 mm along the transducer axis in multiple-layered soft tissues. After phase correction, the focus was restored at the desired point. The ex vivo experiments were conducted to verify the simulations, and the results agreed well with those of the simulations. An empirical formula was obtained to estimate the focus shift in a two-layered water-tissue model and was verified by numerical calculations. Moreover, the focus shift in multiple-layered tissues can be summed by the shifts in the component of each layer of tissues. The factors affecting the focus shift were studied. The focus shift varied linearly with the tissue acoustic speed and tissue thickness, whereas it slightly changed with transducer F number (radius of curvature/diameter). Overall, the findings of this study can help in the development of a better treatment plan for FUS in soft tissues.     

Performance analysis of two-way Amplify-and-Forward relaying system with multiple interferers at the relay

In this paper, we investigate the performance of the two-way Amplify-and-Forward (AF) relaying systems in an interference-limited Rayleigh fading environment. More specifically, assuming the presence of Rayleigh faded multiple interferers at the AF relay and noisy sources, an approximate closed-form expression for the Overall Outage Probability (OOP) and an integral expression for the average Symbol Error Probability (SEP) are derived. The analysis results are verified through comparison with the Monte Carlo simulation results.     

A First Principles Study of Ferroelectricity and Magnetism Coexisting in Fe-Doped K<Subscript>0.5</Subscript>Na<Subscript>0.5</Subscript>NbO<Subscript>3</Subscript>

First-principles calculations were performed to investigate the coexistence of ferroelectricity and magnetism in Fe-doped tetragonal K_0.5Na_0.5NbO₃ (KNN) with different Fe concentrations. It was found that all three systems can possess both magnetism and ferroelectricity, and the magnetism becomes stronger with an increase in the concentration of Fe. The magnetic properties are due to ferromagnetism of Fe, and the Fe-Nb and Fe-O bonds induce magnetic moments on Nb and O atoms. Ferroelectricity comes from the hybridization of Nb and O, as in the case of pure KNN. The predicted results provide insight into the origin of the induced magnetic moments and an approach for obtaining multiferroic materials.     

超高性能微波天线馈源系统的设计

本文介绍了用于微波接力天线馈源中的C波段超高性能馈源系统的设计方法,利用高频结构仿真软件对其进行了优化设计。对一些重要的和不易调整的尺寸用加偏差的方法来确定加工精度。计算结果与实测结果吻合的较好,在4．4～5GHz的频段中,整个馈源系统的驻波优于1．05,交叉极化鉴别率优于-40dB。     

帐篷定律与隧道无线数字通信信道建模

本文首先分析隧道环境下无线数字通信信道的研究现状，指出研究中应充分利用计算机仿真手段，给出隧道雹线电射线传输所遵循的帐篷定律，介绍各次射线传输距离的迭代算法，为隧道无线传输信道的计算机仿真提供了一种较为系统的方法。     

Synthesis of quasi-optimal digital phase-locking systems under the action of additive noises

Quasi-optimal synthesis of digital phase-locking systems (PLSs) is discussed to evaluate the information parameters of a frequency-modulated signal. An adaptive Kalman filter capable of functioning without a priori data on the statistical characteristics of input and test noises is employed. The model of the process under study is identified using the linear trend modified by the self-organization algorithm. Procedures and the results of numerical calculations are presented for the digital system of phase synchronization.     

An adaptive-focus statistical shape model for segmentation and shape modeling of 3-D brain structures

This paper presents a deformable model for automatically segmenting brain structures from volumetric magnetic resonance (MR) images and obtaining point correspondences, using geometric and statistical information in a hierarchical scheme. Geometric information is embedded into the model via a set of affine-invariant attribute vectors, each of which characterizes the geometric structure around a point of the model from a local to a global scale. The attribute vectors, in conjunction with the deformation mechanism of the model, warranty that the model not only deforms to nearby edges, as is customary in most deformable surface models, but also that it determines point correspondences based on geometric similarity at different scales. The proposed model is adaptive in that it initially focuses on the most reliable structures of interest, and gradually shifts focus to other structures as those become closer to their respective targets and, therefore, more reliable. The proposed techniques have been used to segment boundaries of the ventricles, the caudate nucleus, and the lenticular nucleus from volumetric MR images.     

一种基于交换机的彩铃业务实现方案

首先介绍了在GSM移动网络中实现彩铃业务的原理，然后提出一种基于交换机实现彩铃业务的技术方案，分析了此方案中媒体设备的物理结构和内部信令的交互过程，最后将该方案与基于智能网的方案进行了对比。