氧化铅纳米棒的非晶-单晶转变

一维纳米材料由于其相对于块体材料的独特物理化学性能已成为国际上的研究热点。近年来,随着电子显微技术的发展,对一维纳米材料形成机理的探索也在不断拓展。氧化铅作为一种重要的电极材料,在工业上有着广泛的应用;有报道说氧化铅材料的尺寸和形貌对其电学性能有着重要影响,故一维形貌的纳米氧化铅材料为开发新型的电极材料提供了机遇 。     

MIMO-OFDM技术与IEEE 802.11n标准

MIMO-OFDM把OFDM技术和MIMO技术的优势结合起来，在不需要增加传输功率和扩大带宽的前提下能够增加数据的传输速率，正在成为无线通信的一个研究热点。简单介绍了MIMO—OFDM技术的原理以及实现MIMO—OFDM的关键技术，同时讨论了其在下一代高速无线局域网标准802．11n中的应用。     

政务信息资源目录体系技术概述

政务信息资源目录体系是政务信息资源开发和利用的基础设施，主要介绍了包括政务信息资源目录体系的基本概念、主要作用．关键标准。支撑技术及应用模式。     

电子束直写技术制作GHz频带声表面波器件

电子束具有刻写微细图形尺寸的能力，容易实现亚微米宽格栅的声表面波器件制造，因此可达到器件的高频化和在设计上更具灵活性。该文介绍了器件图形的数据处理策略，基片的制备和工艺过程。描述了在电子束曝光过程中采取的一些独特方法，生产了性能良好的吉赫兹频带滤波器、谐振器和延迟线等声表面波器件。     

一种MTD的优化设计及实际应用

根据某型雷达的具体情况，MTD的滤波器组采用了切比雪夫加权设计方法，对相关的信号处理方法如恒虚警检测等关键问题作了讨论。测试结果表明，该MTD系统对地杂波的抑制比大于55dB，对动杂波的抑制比大于45dB，能够达到较好的动目标检测效果。     

星载寄生式SAR系统干涉性能与空间分辨能力分析

以星载寄生式SAR系统成像信号模型为基础,详细分析了这一新系统的干涉性能和空间分辨能力,给出了 各自的限制条件。分析了两者限制的本质一致性,并统一以基线形式表示出来,同时提出了距离向有效基线和方位向有效 基线的新概念。最后以Cartwheel编队构形进行了实例分析,特别指出了基线耦合、多基线对性能的影响。     

In Situ Preparation and Thermoelectric Properties of B4C1−x –TiB2 Composites

B₄C_1?x –TiB₂ composites were prepared by in situ reactive spark plasma sintering of B₄C with addition of nano-TiO₂ powder. The effect of TiO₂ addition on the sinterability of boron carbide was studied. The composition and the microstructure of the dense composites are characterized by means of x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive x-ray spectroscopy (EDX). The studies show that the composites contain boron carbide and TiB₂ phases with a homogeneous structure. In addition, the correlation between the composition and the thermoelectric properties was investigated. The electrical conductivity of the composite increased with increasing addition of TiO₂, and the Seebeck coefficient decreased with TiO₂ addition. The percolation threshold ø _c for TiB₂ in the B₄C_1?x –TiB₂ system was found to be in the range of 0.139 to 0.189. The thermal conductivity was reduced in the whole measuring temperature range from 50°C to 800°C below ø _c. Accordingly, a significant enhancement in the dimensionless figure of merit ZT of the composites was achieved compared with that of boron carbide without TiO₂ addition, with ZT achieving its maximum value at 10 wt.% TiO₂.     

SOA工作条件对全光异或输出性能的影响研究

理论分析了SOA动态模型和SOA-MZI全光异或原理,采用光通信系统设计软件OptiSystem搭建了基于SOA-MZI的全光异或实验模型,仿真研究了注入SOA的数据信号光功率、连续探测光功率、偏置电流等工作条件对异或输出消光比、Q值以及误码性能的影响,取得了一组最佳工作条件,即数据信号光功率为3dBm,连续探测光功率为0dBm,偏置电流为600mA,此时可以得到最佳的异或输出性能:消光比约11.5dB,Q值约22,误码率约10-108量级。研究方法和相关结论可以推广到基于SOA的其他全光信号处理应用中,为未来全光网络的全面建设做准备。     

软抛光垫条件下非晶态Ge2Sb2Te5的化学机械抛光

Chemical mechanical planarization（CMP） of amorphous Ge₂Sb₂Te₅（a-GST） is investigated using two typical soft pads（politex REG and AT） in acidic slurry.After CMP,it is found that the removal rate（RR） of a-GST increases with an increase of runs number for both pads.However,it achieves the higher RR and better surface quality of a-GST for an AT pad.The in-situ sheet resistance（R_s） measure shows the higher R_s of a-GST polishing can be gained after CMP using both pads and the high R_s is beneficial to lower the reset current for the PCM cells. In order to find the root cause of the different RR of a-GST polishing with different pads,the surface morphology and characteristics of both new and used pads are analyzed,it shows that the AT pad has smaller porosity size and more pore counts than that of the REG pad,and thus the AT pad can transport more fresh slurry to the reaction interface between the pad and a-GST,which results in the high RR of a-GST due to enhanced chemical reaction.     

SAFE: A Source Deduplication Framework for Efficient Cloud Backup Services

Due to the relatively low bandwidth of WAN that supports cloud backup services and the increasing amount of backed-up data stored at service providers, the deduplication scheme used in the cloud backup environment must remove the redundant data for backup operations to reduce backup times and storage costs and for restore operations to reduce restore times. In this paper, we propose SAFE, a source deduplication framework for efficient cloud backup and restore operations. SAFE consists of three salient features, (1) Hybrid Deduplication, combining the global file-level and local chunk-level deduplication to achieve an optimal tradeoff between the deduplication efficiency and overhead to achieve a short backup time; (2) Semantic-aware Elimination, exploiting file semantics to narrow the search space for the redundant data in hybrid deduplication process to reduce the deduplication overhead; and (3) Unmodified Data Removal, removing the files and data chunks that are kept intact from data transmission for some restore operations. Through extensive experiments driven by real-world datasets, the SAFE framework is shown to maintain a much higher deduplication efficiency/overhead ratio than existing solutions, shortening the backup time by an average of 38.7 %, and reduce the restore time by a ratio of up to 9.7 : 1.