氦离子注入掺铈铌酸锶钡晶体平面光波导和它的光折变性质

室温下用2.8MeV氦离子注入在掺铈铌酸锶钡晶体上形成了平面光波导。用棱镜耦合法观察到了波导的暗模。计算的折射率分布表明在离子注入产生的损伤层中晶体的折射率减小，其中正常折射率减小约3．42％，反常折射率减小为2．55％。由PIPR方法拟合的波导中的折射率分布与TRIM’96给出的注入离子的密度分布基本一致。两波耦合实验表明离子注入可以延长折射率光栅的擦除时间。     

A complete miniaturized microstructured methanol fuel processor/fuel cell system for low power applications

A complete miniaturized methanol fuel processor/fuel cell system was developed and put into operation as compact hydrogen supplier for low power application. The whole system consisting of a micro-structured evaporator, a micro-structured reformer and two stages of preferential oxidation of CO (PROX) reactor, micro-structured catalytic burner, and fuel cell was operated to evaluate the performance of the whole production line from methanol to electricity. The performance of micro methanol steam reformer and PROX reactor was systematically investigated. The effect of reaction temperature, steam to carbon ratio, and contact time on the methanol steam reformer performance is presented in terms of catalytic activity, selectivity, and reformate yield. The performance of PROX reactor fed with the reformate produced by the reformer reactor was evaluated by the variation of reaction temperature and oxygen to CO ratio. The results demonstrate that micro-structured device may be an attractive power source candidate for low power application.     

3G背景下网络信息安全形势综述

文章总结了2009年信息安全领域发生的各种重要事件。3G背景下,网络信息传播对政治、经济、社会,以及用户的个人生活都产生了深远的影响,网络信息安全问题需要各方面及时认真对待和防范。     

基于小基高比的快速立体匹配方法

为了提高立体匹配效率和获得高精度的亚像素级视差,该文提出一种快速的小基高比立体匹配方法。该方法首先利用积分图像加速自适应窗口和规范互相关度量的计算,然后根据可靠性约束进一步拒绝错误匹配,再采用基于迭代二倍重采样的亚像素级匹配方法为可信点计算亚像素级视差,最后利用基于图分割的视差平面拟合方法获得稠密的亚像素级视差图。实验结果表明该方法不但可获得高精度的亚像素级视差而且还提高了算法的匹配效率,满足了小基高比立体重建的需求。     

大张坨储气库储层注采渗流特征研究

大张坨地下储气库是陕京输气管道的配套工程，保障天然气的调峰需要和供气安全，是由一个正在进行循环注气开发的凝析气藏改建而成的。为了保证地下储气库的长期使用寿命，需要研究在反复强注强采过程中气层的孔渗变化情况，为此开展了不同覆压条件下的孔隙度和渗透率反复测试实验和气水往复驱替实验。不同覆压孔渗测试实验结果证实,在储气库运行压力变化范围内孔隙度和渗透率变化幅度不大，而且这种变化基本上是可逆的。气水往复驱替实验结果证实，在气水两相反复驱替过程中气相有效渗透率呈下降的趋势，而且随着驱替次数的增加，两相共流区缩小，残余水下的气相渗透率和残余气下的水相渗透率都呈下降趋势。因此，只要将注采井选择在气藏构造的高部位，就能控制气水两相反复驱替造成的储层渗透率降低，这样不仅能够实现少井高产的目的，而且能够保证该储气库正常使用。这得到储气库运行实践的佐证。     

Balancing MXene Surface Termination and Interlayer Spacing Enables Superior Microwave Absorption

Surface chemistry and interlayer engineering determines the electrical properties of 2D MXene. However, it remains challenging to regulate the surface and interfacial chemistry of MXene simultaneously. Herein, simultaneous modulation of Ti₃C₂T_x MXene surface termination and layer spacing by alkali treatment are achieved. The electrical and electromagnetic properties of Ti₃C₂T_x are investigated in detail with respect to KOH and ammonia concentration dependence. A high concentration of KOH caused the Ti₃C₂T_x layer spacing to expand to 13.7 Å and the surface O/F ratio to increase to 33.84. Because of its weaker ionization effect, ammonia provides finer tuning compared to the drastic intercalation of KOH with a thorough sweeping of the F-containing groups. Ti₃C₂T_x is enriched with conductive -OH termination after ammonia treatment, which achieves an effective balance with the increased interlayer resistance. Therefore, NH₃H₂O-Ti₃C₂T_x achieves broad-band impedance matching and exhibits an efficient microwave loss of −49.1 dB at a low thickness of 1.7 mm, with an effective frequency bandwidth of 3.9 GHz. The results herein optimize the electrical properties of Ti₃C₂T_x using surface and interfacial chemistry to achieve broad microwave absorption, providing a framework for enhancing the electromagnetic wave loss of intrinsic MXene.     

喷淋水幕抑制化工聚集区火灾效果研究

为了揭示不同工况下喷淋水幕对化工聚集区火灾抑制效果影响规律,建立了FDS数值模型,通过改变单一变量分别模拟水幕开合状态、不同水幕排数、不同水幕喷头高度下火灾发展过程,分析不同工况条件下火源温度变化规律和烟气蔓延规律。结果表明：喷淋水幕开启后,位于储罐上方及水幕帘后的测点温度峰值同比下降19%及36%,可有效抑制高温烟气层蔓延;双排水幕帘相比单排水幕帘在抑制火源温度及烟气蔓延更具成效;初始喷头高度5.8 m时,相比其他高度在降低温度、加速烟气沉降方面更具优势。     

运动序列的短期统计特性

本文利用动态图象序列研究了运动序列的短期统计特性,对每个宏块经过压缩后所产生的比特数进行了分析,研究了量化比例因子和量化加权矩阵对短期统计特性的影响.统计结果表明,量化比例因子对每个宏块比特数的概率分布影响最为明显,量化加权矩阵对分布特性的轮廓影响很小,当量化比较精细时图象内容对分布特性的低比特部分影响比较明显,而粗量化时它的影响较弱.     

8Mbit／s数字电视系统的设计与实现

介绍了８Ｍｂｉｔ／ｓ数字电视系统的系统构成，给出了图象压缩编解码，声音压缩编解码和数据通信接口的实现方案，对系统中所采用的新缓存控制策略也作了分析。     

8Mbps数字电视编解码器系统

本文出了８Ｍｂｐｓ数字电视编解码器的硬件实现方案，包括视频、音频信道三个部分，同时给出了样机的测试结果，最后略地介绍了此编解码器的应用情况。