RE211晶须实验研究的现状及意义

 作为RE123（REBa2Cu3O7-δ）包晶分解的产物,RE211（RE2BaCuO5）在构成RE123块材、薄膜及涂层导体中扮演着一个重要的角色。在RE123块材中,RE211粒子与RE123晶粒的晶界缺陷能够产生强磁通钉扎,有利于提高临界电流密度（Jc）。探明RE211包裹物形成的原因,对于获得高品质RE123膜十分重要;对于涂层导体,在交替生长Y211与Y123多层膜的过程中引入第二相的纳米尺度的Y211粒子,可以大大提高高磁场下的Jc值。由于RE211对RE123的形成及其超导性能有很大的影响,研究RE211的生长并且生长出大线度RE211晶须,就有很重要的意义。本文简要总结了RE211晶须实验研究的成果和现状,对RE211晶须实验和理论研究的意义以及应用前景进行了讨论;报道了笔者所在小组采用熔体法在单晶炉中生长大尺寸（最长15.5mm）Sm211晶须的方法和条件     

铅基多孔材料的反重力渗流铸造工艺与平均孔径测试

针对铅基多孔材料反重力渗流铸造新工艺,研究填料粒子预热温度、熔体温度、充型压力和填料粒子粒径等工艺参数对渗流成型过程的影响规律,获得孔径可控、结构均匀的铅基多孔阳极的制备技术.同时,针对所制备多孔材料孔径大且孔形不规则问题,提出一种适用于大孔径及孔形不规则的多孔材料平均孔径测试方法.研究结果表明:采用反重力渗流铸造法制备铅基多孔材料的关键是合理选择铸造温度、充型压力和粒子预热温度这3个工艺参数,粒径对制备工艺的影响较小;当铅液的铸造温度为430～490℃,填料粒子的预热温度为240～280℃,充型压力为0.06～0.08 MPa时制备的多孔样品渗流长度长,且孔洞均匀、缺陷少,效果最好.该方法可用于大孔径孔形不规则的多孔材料平均孔径的测量.     

（RE）BaCuO／Ag Composites： The Role of Silver in Bulk Materials and Joints

We have investigated the phase equilibria in (RE)BaCuO/Ag systems, the influence of Ag on the processing of (RE)BaCuO/Ag composites and the resulting properties. YBaCuO/Ag composites have been grown by the modified melt crystallization process with YBa2Cu3O7, Y2O3, Pt and Ag2O in the precursor. The improved strength of the YBaCuO/Ag composites compared with the conventional YBaCuO bulk material permitted us to magnetize these materials to achieve trapped fields up to 16 T (at 24 K) in the gap of a mini-magnet. The investigation of the microstructure revealed a remarkable increase of the spacing between micro-cracks especially of those perpendicular to a/b-planes when 12wt% Ag was added. In the case of SmBaCuO/Ag composites, Ag has a strong influence on processing and causes interactions between RE123 seeds and the sample. We show the growth of single-grain SmBaCuO/Ag composites in air and discuss the influence of post-annealing on increasing Tc and Jc. Furthermore, YBaCuO/Ag composites have been shown to be appropriate materials used as a solder to join large single grains to large arrays or to “repair” grain boundaries in arrays grown by a multiseeding technique.     

动目标图像实时输入与处理微机视觉系统

本文介绍了一种基于微机的动目标图像实时输入与处理视觉系统。采用局部总线设计技术,集输入与处理为一体,使设计达到了单板化,将其直接插入IBM-PC及其兼容机槽内即可构成系统。并采用流水线、并行作业和时间重叠等方法,可将动目标实时从复杂背景中分割出来。通过场控制器,本系统可一边输入,一边运算,进行实时图像加减、特征提取、边缘检测和二值化运算等;多种运算方式使本系统在尽可能大的空间范围内跟踪动目标。本文提出了“扩展虚存”思想;设计了高速DMA控制器;应用了硬件开窗技术。系统经过运行实验,可满足一般性动目标的分割与跟踪。     

Nanoengineering of Flux Pinning Sites in High-Tc Superconductors

Volume pinning forces were determined for a variety of bulk high-Tc superconductors of the 123-type from magnetization measurements. By means of scaling of the pinning forces, the acting pinning mechanisms in various temperature ranges were identified. The Nd-based superconductors and some YBCO crystals exhibited a dominating pinning of the δTc-type (i.e. , small, superconducting pinning sites). In contrast to this, the addition of insulating 211 particles provided pinning of the δ/-type; providing effective pinning in the entire temperature range acting as a "background" pinning mechanism for the peak effect. Due to the small coherence lengths of the high-Tc compounds, effective pinning sites are defects or particles of nanometer size relative to ζ3. Integral magnetic measurements of the magnetization as a function of temperature in large applied magnetic fields (up to 7 T) revealed that practically all high-Tc compounds were spatially inhomogeneous, which could be caused by oxygen deficiency (YBCO)     

凝胶注模成型钛-生物玻璃多孔生物复合材料研究

采用凝胶注模成型工艺制备了钛-生物玻璃复合材料坯体,研究了pH值、分散剂、固相含量(钛和生物玻璃在料浆中的质量分数)等因素对料浆和复合材料坯体性能的影响,对坯体的力学性能进行了测试,借助扫描电镜分析了坯体的微观组织.试验结果表明,料浆的pH值应控制在8.5～9.5的范围内;聚丙烯酸铵的浓度为2vol%时,料浆的流动性最好;采用搅拌法制备的复相料浆固相含量达到50%,复合材料坯体的抗弯强度达到40MPa;由于生物玻璃的加入,使得多孔生物材料表面的生物活性提高.     

自动识别并分割太赫兹图像中的可疑物

分析了太赫兹图像的特征,基于图像处理技术提出了一种新颖并且快速检测人体太赫兹图像的算法。使用改进的非局部均值滤波器来减少太赫兹图像中的噪声;应用主动形状模型(ASM)检测人体轮廓;采用基于TSED(total square euclidean distance)的k-means算法分割可疑物。实验结果表明,提出的算法能够很好地检测和分割太赫兹图像中的可疑物体。     

熔体静电纺丝技术研究进展

熔体静电纺丝技术作为一种不使用溶剂的超细纤维绿色制备工艺，在高性能无纺布、生物医药和高效过滤等方面有着广泛的应用。本文简单回顾了熔体静电纺丝研究历史，阐述了熔体静电纺丝工艺特点，综述了近年来熔体静电纺丝工艺、材料、装置及应用新进展，介绍了笔者团队熔体微分静电纺丝技术，并在最后提出几点对未来熔体静电纺丝研究重点的看法。通过本文，以期增进对超细纤维绿色制造新理论、新方法和新装备的认识。     

溶胶-凝胶技术制备纳米材料的研究进展

溶胶－凝胶技术是制备纳米材料的特殊工艺,工艺简单,易于操作。笔对溶胶－凝胶技术的基本过程、工艺特点进行了分析,从溶胶－凝胶技术在薄膜方面的应用、膜板合成纳米阵列,以及制备纳米复合材料等方面,对溶胶－凝胶技术制备纳米材料的研究状况进行了详尽阐述。     

MgB2超导材料的薄膜制备及其超导器件的实现

报道了采用电子束蒸发技术实现MgB₂薄膜制备的实验工作。通过蒸镀B膜和Mg/B多层膜两种前驱体,分别经高温区(～900℃)和中温区(～700℃)退火处理后成功获得了高质量的MgB₂薄膜样品。对样品的超导性能、晶体结构和表面形貌进行了详细的测量和表征,并对两类样品性质上所表现出的差异进行了分析。此外,还报道了在薄膜制备基础上利用微加工技术实现的超导微波谐振器的结果。     

铋系2223带材包套合金化对制备工艺的影响

对铋系2223高温超导带材的制备过程中所涉及的力学问题进行了理论分析和实验研究.结果表明,由于不同包套和超导芯间的变形阻力不同,导致带材制备过程中的变形均匀性有很大差别;通过对带材轧制过程中截面内的应力分析,解释了超导电流"肌肤效应"产生的原因;通过测量中间轧制过程中超导带材的电流密度,给出了不同包套带材单次轧制的最佳形变量.     

Perusing Piezoelectric Head Performance in a New 3-D Printing Design

Rapid prototyping (RP) is a computerized fabrication technology that additively builds highly complex three-dimensional physical objects layer by layer using data generated by computer, for example CAD or digital graphic. Three-dimensional printing (3DP) is one of such technologies that employ ink-jet printing technology for processing powder materials. During fabrication, a printer head is used to print a liquid on to thin layers of powder following the object’s profile as generated by the system computer. This work looks at redesigning 3DP machine, using piezoelectric demand-mode technology head in order to improve accuracy, surface finishing and color quality of constructed models. The layers created with aforesaid system are between 25 to 150 μm (steps of 25 μm).     

基于一般多面体模型的分割拼装成型

以STL模型为工艺规划的输入对象 ,设计了一种基于一般多面体模型的分割拼装数据处理算法 ;自动地实现了原型件的分割、定位结构设计等操作。工艺实验表明 ,文中设计的分割拼装成型方法通过对原始模型的分割、排样、并行制造后再拼装 ,可多方面提高快速成型设备的成型能力 ;可将制作大型件所需的成型时间缩短 50 %以上 ,同时可将成型精度提高 35%以上 ,且后处理更为方便。     

ETER超导磁体设计与制备中的若干关键力学问题

超导磁体是目前正在研制和建造中的大型新能源装置即国际热核聚变实验堆（ITER）的核心部件,主要用于约束等离子体在有限环状空间内的流动,其力学研究直接涉及磁体结构安全性以及等离子体的稳定运行时间．我国承担着ITER超导磁体制备的任务包并取得成效,但由于磁体设计和制造涉及材料科学、力学、电磁学等多学科的交叉,同时也涉及超导复合线缆绕制与测试分析等一系列关键性技术问题,目前这一领域的研究不管是国内还是国外尚远未满足越来越多的大型超导科学装置的需求．本文主要介绍了ITER超导磁体从CICC导体的复杂制备到运行过程中所涉及的力学、超导物理等相互耦合作用的基础理论与实验研究方面的国内外现状以及存在的主要问题,其中也简要介绍了兰州大学电磁固体力学研究组在超导电磁系统相关方面的部分研究进展与成果等．     

Ultrafast and direct imprint of nanostructures in silicon

The fabrication of micrometre- and nanometre-scale devices in silicon typically involves lithography and etching. These processes are costly and tend to be either limited in their resolution or slow in their throughput. Recent work has demonstrated the possibility of patterning substrates on the nanometre scale by 'imprinting' or directed self-assembly, although an etching step is still required to generate the final structures. We have devised and here demonstrate a rapid technique for patterning nanostructures in silicon that does not require etching. In our technique which -- we call 'laser-assisted direct imprint' (LADI) -- a single excimer laser pulse melts a thin surface layer of silicon, and a mould is embossed into the resulting liquid layer. A variety of structures with resolution better than 10 nm have been imprinted into silicon using LADI, and the embossing time is less than 250 ns. The high resolution and speed of LADI, which we attribute to molten silicon's low viscosity (one-third that of water), could open up a variety of applications and be extended to other materials and processing techniques.     

上海公园绿地景观水体透明度影响因子研究

于2010年,以上海市90个公园绿地共107个景观水体为研究对象,通过野外调查与室内分析,探寻水体透明度与光衰减系数的关系,并在此基础上分析影响水体透明度的主要因子.研究结果表明：（1）上海市公园绿地景观水体透明度普遍较低,平均透明度为（0.54±0.24） m,98.31%的水体透明度低于1 m;（2）透明度与光学衰减系数显著负相关,两者之间可建立数学关系式为Kd=0.017+〖SX(〗1.12〖〗ST〖SX)〗;（3）悬浮物是上海城市公园绿地水体透明度的主导影响因子,总磷和铵态氮通过控制浮游藻类的营养水平来影响水体透明度.研究结果为科学合理地评价景观水体水质尤其是水体透明度提供测度,并为水体环境的改善、水生植被的构建及水体的养护管理提供科学依据.     

MMC制备过程中预制件变形分析

从液态渗透理论分析了采用液态渗透法制备金属基复合材料（ＭＭＣ）过程中短纤维预制件的受力变化情况以及影响预制件变形的主要因素,并通过实验观察了氧化铝短纤维增强基复合材料制备过程中预制件的变形情况。     

Design and fabrication of superconducting HEB mixer

This paper describes the design and fabrication of superconducting hot electron bolometer （HEB） mixer based on ultra-thin superconducting NbN films. The high quality films were epitaxially grown on high resistance Si substrates. The device was fabricated by magnetron sputtering, electron beam lithography （EBL）, reactive ion etching （RIE）, lithography, and so on. The device＇s resistance-temperature （R-T） curves and current-voltage （I-V） curves were studied. The results of THz response of the device are presented. Y-factor technique was used to measure the device＇s noise temperature. When the device was irradiated with a laser radiation of 2.5 THz, the obtained lowest noise temperature of the device was 2213 K.     

顺序离子束溅射沉积制备GdAlO3单一晶相薄膜技术

顺序沉积薄膜制备技术包括前驱薄膜制备和后期薄膜热处理技术，特别适合复杂组分的薄膜制备．采用IM100离子束材料芯片沉积仪在MgO(100)基片上顺序沉积Gd2O3和Al单层薄膜，经后续低温扩散和高温晶化两步热处理得到GdAlO3单一晶相薄膜．以X射线衍射(XRD)、扫描电镜(SEM)等手段，分析所得GdAlO3薄膜的晶体结构和微观形貌，考察热处理过程对GdAlO3薄膜生长过程及微观结构的影响．实验结果表明顺序沉积薄膜制备技术具有化学计量比控制精确的优点，两步热处理可以得到结晶状况良好的单相结晶薄膜．