C离子注入Si中Si_(1-x)C_x合金的形成及其稳定性

利用离子注入和高温退火的方法在Si中生长了C含量为0.6%~1.0%的Si1?xCx合金, 研究了不同注入剂量下Si1?xCx合金的形成及其在退火过程中的稳定性. 如果注入剂量小于引起Si非晶化的剂量, 850℃退火后, 注入产生的损伤缺陷容易与C原子结合形成缺陷团簇, 难于形成Si1?xCx合金. 随着注入C离子剂量的增大, 注入产生的损伤增强, 容易形成Si1?xCx合金, 但注入的剂量增大到一定程度, Si1?xCx合金的应变将趋于饱和, 即只有部分C原子进入晶格位置形成合金相. Si1?xCx合金一旦形成, 在950℃仍比较稳定, 而温度高于1 000℃, 合金的应力将部分释放. 随着合金中C原子浓度的升高, 合金的稳定性变差.

A 3 Tesla Superconducting Magnet for Hall Sensor Calibration

A 3 T superconducting magnet with a 70 mm diameter warm bore and energy storage of 47 kJ has been successfully fabricated and tested, which can be used to calibrate Hall sensors in high magnetic field as well as conduct superconducting experiments. The magnet consists of three solenoid coils and an iron yoke. The homogeneity of the magnetic field in the region of interest (ROI) is +/- 6.0 x 10(-5). The coils of the magnet were fabricated with NbTi-Cu superconducting wire and the stray magnetic field is shielded by an iron yoke. The coils and yoke are fully immersed in a helium vessel. The optimized structural design, stress and quench simulation, fabrication and test results are presented in this paper.

新兴电子商务中的安全问题

全球经济发展已逐渐步入信息经济时代,电子商务已迅速发展成为推动社会经济发展的重要力量。我国电子商务的发展已初具规模,并呈现大规模、跨行业、跨组织的发展趋势。但其发展也正面

岷江上游典型时期景观格局变化及驱动力初步分析

岷江上游地区是我国一个重要的大尺度、复合型生态过渡带 ,也是一个生态系统脆弱区 ,研究其景观格局的变化 ,对于构筑我国的生态格局安全具有十分重要的意义 .本研究利用岷江上游地区 1986、1995、2 0 0 0年 3个时期的TM影像 ,分析了 3个时期的景观特征以及变化 .结果表明 ,岷江上游整体景观水平以草地景观为基质、森林景观以及其他景观类型作为斑块镶嵌其中 .森林景观面积经历了从 1986～1995年的上升 ,而后到 2 0 0 0年的下降过程 ;草地景观高盖度草面积不断减少 ;同时 ,森林景观和草地景观斑块总数一直增加 ,破碎化趋势明显 .岷江上游景观格局变化的驱动因子主要是日益增加的人口数量而导致的人为干扰 ,包括对土地利用方式与利用强度的改变、森林资源的掠夺性开采、草地资源的过度放牧以及气候、土壤等自然因素的变化 .

生态旅游农业及其在我国的发展

简介了生态旅游农业的内涵、特点及其国内外发展实例,阐述了生态旅游农业在我国发展的必要性、可能性及其有利条件,并提出生态旅游农业发展中应注意的几个问题。

无线多跳网中具有网络编码意识的机会路由协议

针对现有COPE协议消极编码的问题,提出一种具有网络编码意识的机会路由协议NCAOR。该协议兼取机会路由和网络编码的优势实现高效地报文投递。在每一跳转发时,节点均选取多个冗余邻居节点构成机会节点集协助数据发送。收到报文后,机会节点利用局部拓扑知识和侦听的邻居报文接收信息判断转发报文的网络编码机会,并通过综合路径距离和编码收益的效用函数评估报文转发效能,智能设置转发响应时间。仿真结果表明,该协议相对采用最短路径路由的COPE方案具有网络吞吐量大、能耗低和节点编码机会更多的优点。

Synthesis of carbon nanofibers for mediatorless sensitive detection of NADH

Highly sensitive amperometric detection of dihydronicotinamide adenine dinucleotide (NADH) by using novel synthesized carbon nanofibers (CNFs) without addition of any mediator has been proposed. The CNFs were prepared by combination of electrospinning technique with thermal treatment method and were applied without any oxidation pretreatment to construct the electrochemical sensor. In amperometric detection of NADH, a linear range up to 11.45 mu M with a low detection limit of 20 nM was obtained with the CNF-modified carbon paste electrode (CNF-CPE).

Magnetic Mesoporous Silica Spheres for Drug Targeting and Controlled Release

Magnetically functionalized mesoporous silica spheres with different size (average diameter, A.D.) from 150 nm to 2 mu m and pore size distribution were synthesized by generating magnetic FexOy nanoparticles onto the mesoporous silica hosts using the sol-gel method. The X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), N-2 adsorption/desorption results show that these composites conserved regular sphere morphology and ordered mesoporous structure after the formation of FexOy nanoparticles. XRD and X-ray photoelectron spectroscopy (XPS) analysis confirmed that the FexOy generated in these mesoporous silica hosts is mainly composed of gamma-Fe2O3. Magnetic measurements reveal that these composites with different gamma-Fe2O3 loading amounts possess super-paramagnetic properties at 300 K, and the saturation magnetization increases with increasing Fe ratio loaded.

Isothermal and nonisothermal crystallization kinetics of nylon-46

Isothermal and nonisothermal crystallization kinetics of nylon-46 were investigated with differential scanning calorimetry. The equilibrium melting enthalpy and the equilibrium melting temperature of nylon-46 were determined to be 155.58 J/g and 307.10 degreesC, respectively. The isothermal crystallization process was described by the Avrami equation. The lateral surface free energy and the end surface free energy of nylon-46 were calculated to be 8.28 and 138.54 erg/cm(2), respectively. The work of chain folding was determined to be 7.12 kcal/mol. The activation energies were determined to be 568.25 and 337.80 kJ/mol for isothermal and nonisothermal crystallization, respectively. A convenient method was applied to describe the nonisothermal crystallization kinetics of nylon-46 by a combination of the Avrami and Ozawa equations.

In situ analysis of electropolymerization of aniline by combined electrochemistry and surface plasmon resonance

The combination of electrochemistry with surface plasmon resonance (SPR) has been used to characterize the growth of polyaniline (PAn) on a gold electrode surface during potential cycling. Potential-modulated SPR characteristics of the PAn film were also revealed. The potential switch between the oxidized and reduced states of PAn can lead to a large change of SPR response due to the variation in the imaginary part of the dielectric constant of PAn film resulting from the transition of the film in conductivity. The redox transition of the PAn film during potential cycling is very profitable to the SPR measurements. Two modes of SPR measurement, SPR angular scan (R-theta) and the time evolution of the reflectivity change at a fixed angle (R-t), were displayed to study the growth process of the PAn film. The angle shift of the resonance minimum recorded at each cathodic limit of cyclic potential scanning allows for the unambiguous measurement of the film growth. During cyclic potential scanning, the R-t curve was repeatedly modulated with the direction of the potential ramp as a result of the redox switch of the PAn film, and the amplitude of potential-modulated reflectivity change was well correlated with the cyclic number. The time differential of the R-t curve permits continuous monitoring of the film growth process. These results illustrate that the combined technique is suitable for studying the electropolymerization process of a conducting polymer.