W掺入对Ti0.8Zr0.2Ce0.2O2.4/Al2O3-TiO2-SiO2催化脱硝性能的优化

以Al₂O₃-TiO₂-SiO₂(ATS)为载体、Ti_0.8Zr_0.2Ce_0.2O_2.4(TZC)为催化活性组分, 采用挤出成型法制备系列整体式TZC/ATS及W掺入催化剂样品。研究了W掺入对催化剂TZC/ATS 的氨气选择性催化还原(NH₃-SCR)脱除NO活性及抗K₂O、CaO等毒性的影响, 比较了Ti_0.8Zr_0.2Ce_0.2W_0.08O_2.64/ATS(TZCW_0.4/ATS)催化剂与V₂O₅(WO₃)/TiO₂催化剂的抗K₂O、CaO等中毒性能, 并采用N₂-BET、XRD、SEM和NH₃-TPD等技术手段分别表征了催化剂的比表面积、固相结构、微观形貌及表面酸性。结果表明, 当活性组分中Ti/Zr/Ce/W元素摩尔比为4:1:1:0.4时, TZCW_0.4/ATS催化剂NH₃-SCR脱除NO的效率最高、稳定性最好。W掺入显著增强了催化剂的抗K₂O及CaO毒性能力, 且TZCW_0.4/ATS催化剂抗K₂O及CaO的中毒能力明显强于V₂O₅(WO₃)/TiO₂催化剂。分析表明, W掺入提高了TZCW_0.4/ATS催化剂的比表面积, 增加了催化剂的表面酸量, 从而优化了催化剂的脱硝性能。     

纳米MgO/SnO2复合粉体的制备及性能研究

采用共沉淀法制备了MgO/SnO2纳米复合粉体.用热重分析(TG)、X射线衍射仪(XRD)、透射电镜(TEM)和能谱(EDS)对样品的物相、形貌、粒径和组成进行了表征.并用DSC考察了纳米MgO/SnO2对RDX热分解的催化作用.结果表明 400℃煅烧样品的平均粒径约为3nm, MgO的掺杂可提高纳米SnO2粒子的热稳定性和对RDX热分解的催化作用, 它使RDX的分解峰温降低了8.5℃, 分解热增加了518J·g-1(约50%).     

化合物性能数据库及智能管理系统的设计与建立

以标准生成热数据为收集依据,建立了含有无机物、一般有机物、含氮有机物、金属有机物、高分子化合物等近5000种化合物的各种重要性能的Access数据库。并以Visual Basic 6.0为语言,编制了大型程序,能对数据库进行智能化管理,查询、检索极为便利,可按一定的格式打印。形成一本内容丰富、数据齐全的化合物性能数据手册。     

A Novel Random Backoff Algorithm to Enhance the Performance of IEEE 802.11 DCF

The Probability Distribution of Slot Selection (PDoSS) of IEEE 802.11 DCF is extremely uneven, which makes the packet collision probability very high. In this paper, we propose a novel RWBO+BEB backoff algorithm for 802.11 DCF to make the PDoSS even and thus decrease the packet collision probability. A Markov model is built for analyzing RWBO+BEB's PDoSS and saturation throughput. The model's correctness is validated by simulation. The performance of RWBO+BEB is also evaluated by simulation in terms of PDoSS, saturation throughput, packet collision probability and packet delay. The simulation results indicate that RWBO+BEB can decrease the packet collision probability to a large extent, utilize the channel more efficiently, and make the packet delay jitter much lower comparing to 802.11 DCF. Moreover, we analyze the relation of saturation throughput and packet collision probability to walking probability (p_d) and contention windows (w), respectively. The analysis indicates that RWBO+BEB has a remarkable feature: its saturation throughput keeps high, and packet collision probability keeps very low (which under 0.1) in a large range of p_d and w, this allows us to configure p_d and w more flexibly. Supported by the Program for New Century Excellent Talents in University (NCET 2005), the Research Project of Chongqing Municipal Education Commission of China (KJ050503), the Research Grants by the Science & Tech. Commission of Chongqing (8817) and the National Science Foundation of China (90304004). Li Yun was born in 1974. He is currently a Ph.D. candidate in University of Electronic Science and Technology of China. His research interests are in MAC protocol improvement and QoS in wireless ad hoc networks. Long Ke-Ping was born in 1968. He received his Ph.D. from University of Electronic Science and Technology of China in 1999. He is a professor Ph.D. supervisor in special research Centre for Optical Internet and Wireless Information Networks (COIWIN) at ChongQing University of Posts and Telecommunications. He was an IEEE member. He has over 120 research publications and 4 patents application. His research interests include: Optical Burst switching, modeling of optical networking, IP QoS mechanisms (Diffserv and Intserv, MPLS), WDM/SDH/ATM networks survivability, TCP/IP enhancements in wireless networks, and Mobile IP. Zhao Wei-liang was born in 1962 and received his Ph.D. degree from University of Electronic Science and Technology of China in 2001. He is a professor and a post-doctoral fellow in Beijing University of Posts & Telecommunications of China. His current interest lies in wireless communications.     

超临界流体干燥法制备纳米级TiO2的研究

本文以廉价无机盐为原料,采用溶胶-凝胶法（Sol－Gel）结合超临界流体干燥（SupercriticalFluidDrying简称SCFD）制备了纳米级TiO₂,并采用XRD、DTA－TG、TEM技术研究了Sol－Gel过程中溶液的pH值、浓度、陈化时间及SCFD技术等条件对TiO₂粒径大小的影响,实现了干燥晶化一步完成．用该方法制得的TiO₂超细粉体,粒径大都在3～6um之间,呈球形微粒,粉体晶型为锐钛矿型,并具有纯度高、热稳定性好、失重小和粒度分布均匀等特性．     

一种无线Ad Hoc网络的区分服务体系结构

提供服务质量保证是目前无线ad hoc网络的研究热点.本文对将区分服务应用于无线ad hoc网络进行了阐述,提出了一种应用于无线ad hoc网络的区分服务体系结构,最后进行了仿真验证.仿真结果证明,在无线ad hoc网络中区分服务可以在资源不够用的情况下,降低对低优先级的业务流的服务,保证对高优先级的业务流的服务,从而使得高优先级的业务流获得较大的吞吐量和较低的延迟.     

1021 t/h锅炉排烟温度偏高的原因分析及改进建议

本文提针对青山电厂１２号锅炉排烟温度偏高的问题,通过对现场运行情况和测试数据的分析以及各种理论计算结果的比较,初步找出了排烟温度偏高的原因,并提出了降低排烟温度的措施。     

一种超低相位噪声频率合成源方案设计

频率合成源是射频发生和频谱分析中最重要的组成之一,评价合成源性能指标的是输出信号的相位噪声、杂散、频率分辨率和频率切换时间.本文通过分析传统锁相环原理,提出一种通用的超低相位噪声合成源设计方案（带宽100MHz以内）.在锁相环基础上,通过引入直接数字合成（Direct digital synthesizer,DDS）混频鉴相技术,使得到的射频信号理论值达到0.1mHz的频率分辨率,同时将带内相位噪声指标优化17dB以上.新方案同时兼顾了杂散和频率切换时间指标,保障合成源的输出信号稳定可靠,使其在自动测试领域拥有广阔的应用前景.     

离线梗丝分离技术在PROTOS70中的应用

为解决PROTOS70卷接机组仅有一级、二级风选装置,存在梗丝分离不彻底的问题,参照PROTOS-M5卷接机组梗丝分离技术,在PROTOS70卷接机组加装离线梗丝分离装置中,增加了烟梗和烟丝垂直提升的距离,形成“之”字形风选通道,实现梗丝分离.使用离线梗丝分离后,减少了成品烟支丝中含梗缺陷频次,降低了梗中含丝率,单班可节约烟丝10～ 15 kg,该装置梗丝分离彻底,使用效果明显.