The surface properties and photocatalytic activities of ZnO ultrafine particles

We prepared ZnO ultrafine particles (UFPs) by thermal decomposition of the precursor zinc carbonate hydroxide. The surface properties of the as-prepared particles were studied using TEM, XRD, BET, SPS, EPR, IR, and XPS. The surface contains active species such as oxygen deficiencies and hydroxyl that improve photocatalytic activities. The concentrations of active species decreased as the calcination temperature increased along with the surface areas and photovoltage. The ZnO UFP have a significant EPR signal resulting from O²⁻ deficiencies on the surface, which can capture and trap electrons. During photocatalytic degradation of phenol, the photocatalytic activities of the particles decreased as their size increased, which means that these activities depend mainly on surface properties.     

LiCl-Urea两元体系离子液体的研究

自从1914年第一种离子液体[EtNH3]NO3问世以来,室温离子液体的研究与应用取得了飞速的发展,离子液体以其诸多的优良性能,在催化、有机反应、萃取、以及气相色谱、电化学中得到了广泛地应用。近几年来,多元离子液体体系的研究受到关注。本文报导了由LiCl简单盐和Urea形成的二元体系离子液体,最低共熔点为55℃(LiCl的熔点是608℃,尿素本身的熔点是132℃)。     

Preparation of CdSe/ZnSe Core-shell Nanocrystal in One-step Reaction

IntroductionSemiconductor nanocrystals show strong size-de-pendent properties when their size is similar to or smal-ler than the excition Bohr radius of the bulk materialsand quantum confinement occurs for the space-con-fined motion of the electrons and holes in the nano-re-gion of materials[1—5].Because of the excellent opticaland electronic properties,semiconductor nanocrystalsare currently being investigated as emitting materials forthin-film light-emitting devices(LED)[6,7],low-thresh-ol…     

低杂波控制电流分布与改善约束研究

在HT-7超导托卡马克装置上利用低杂波电流驱动有效地控制了等离子体电流分布,并使等离子体约束性能改善。数值模拟与硬X射线测量结果均表明,低杂波的发射功率谱、纵场和等离子体密度对改变等离子体电流分布有明显的影响。在优化低杂波电流驱动实验参数的条件下,等离子体密度、温度分布发生了理想的变化。在电子和离子温度分布上出现了内部输运垒,同时等离子体的能量约束时间和粒子约束时间均有提高。     

FCC催化剂氢气还原活化脱镍研究

我国的FCC催化剂在使用中镍污染较为严重, 镍不仅会破坏催化剂的结构, 而且还会影响反应产物的分布, 增加企业的生产成本. 本研究提出了氢气还原活化＋稀硝酸洗涤的脱镍新方法, 具有良好的效果. 镍在FCC催化剂上以NiAl₂O₄和Ni₂SiO₄的形式存在, 这些物种在700 ℃以下就可以被氢气还原, 并且随着温度的升高, 不仅催化剂表面的镍能够被还原, 而且催化剂体相中的镍也可以迁移到表面从而被还原, 但这种迁移受到平衡的限制. 还原后生成的金属镍可以溶于稀硝酸, 因而可以洗涤除去. 在适宜的条件下, 经过一次还原＋酸洗处理, 脱镍率可达到50%以上; 经过两次处理, 脱镍率可达75%以上. 脱镍后催化剂的微反活性可以得到大幅度提高.     

有根森林优先约束的单机随机排序问题

讨论单机随机排序问题,目标函数为确定工件的排列顺序使工件的加权完工时间和的数学期望最小.设工件间的优先约束为有根森林,机器发生随机故障.对此情况,给出了多项式时间的最优算法.     

具有不耐烦顾客和多重工作休假的排队库存系统

研究具有不耐烦顾客和多重工作休假的M/M/1/N排队库存系统模型,分别考虑了系统中库存为零时服务员休假和系统中顾客数为零时服务员休假两种休假方式,基于(s,S)库存策略,运用矩阵迭代方法得到了系统稳态概率分布,并给出系统相关性能指标,进而建立系统平均库存费用函数.通过数值算例对比分析了两种休假方式下的系统主要参数变化对系统重要性能指标的影响,并在最优费用的层面对两个模型的优劣进行了对比分析.     

The Effect of Doping with the Polymer Metallic Complex Poly Zinc Acrylate on Superconducting Bulk MgB<Subscript>2</Subscript>

In this work, the effect of doping with 5% to 20% poly zinc acrylate (PZA) complexes on MgB₂ phase formation was studied. The changes of the lattice parameter and the amount of substituted carbon in the microstructure as well as the critical temperature and the critical current density (J _c) of bulk MgB₂ have been studied systematically. Both differential thermal analysis–thermogravimetric (DTA–TG) analysis and infrared (IR) spectrometry results show that the PZA was decomposed between 400°C and 600°C, and the main decomposition products were carbonized polymers and ZnO. The lattice parameter a in all PZA-doped MgB₂ samples was decreased by different degrees, which indicates gradual substitution of carbon on the boron sites in the MgB₂ crystal structure. Compared with the undoped sample, the J _c values of all the doped samples were enhanced by about an order of magnitude under high magnetic fields. The J _c value of the MgB₂ sample with 20% PZA doping sintered at 800°C for 1 h reached 8 kA/cm² at 5 K and 8 T. Transmission electron microscopy (TEM) images revealed a considerable amount of second-phase particles of ~5 nm size, and a high density of dislocations was observed in the MgB₂ grains.     

住宅小区的智能化设计探究

现代住宅在面向大型化、高层化发展的过程中,向着智能化方向发展。我国的智能化建筑起步晚,和发达国家还有很大差距,其小区的智能化设计研究任重而道远。本文通过简要介绍了智能化住宅小区目前的发展现所存在的问题,并提出了住宅小区智能化设计措施,为我国住宅小区的智能化设计研究提供了一定的借鉴作用。     

VxWorks下基于ML507嵌入式系统的中断处理

随着Xilinx公司Virtex5系列FPGA内嵌了Powerpc处理器,嵌入式操作系统VxWorks的加入使构建更为复杂的嵌入式平台成为可能。VxWorks提供的中断处理机制延迟小,符合实时性要求。文中分析了基于Powerpc440处理器的中断处理机制,并详细阐述了中断处理的编程过程。