基于XML/Web的嵌入式系统网络管理模型的研究

SNMP是目前广泛使用的一种网络管理协议,它具有简单、易于实现等优点,已成为网络管理领域中事实上的工业标准．然而随着网络的逐步发展,SNMP自身的缺陷不断显露出来,已不能对现代网络进行有效地管理．为弥补SNMP的缺陷,基于XML的新一代网络管理应运而生．根据网络管理的现状和XML的基本知识,分析了XML网络管理的发展前景,并进一步探讨设计了一种嵌入式系统的远程web管理模型,该模型使嵌入式系统管理员可以在任何时间和任何地点通过友好的、平台无关的GUI接口对嵌入式系统进行远程监控．最后对模型中主要组件的体系结构分别进行了设计．     

Sql Server数据库加密技术应用

随着信息系统越来越多的应用,数据的安全问题越来越受到重视。数据库安全性已经成为构造现代企业管理信息系统时必须考虑的问题,数据加密技术极大的解决了数据库中数据的安全问题,但实现方法各有侧重。本文主要讨论了数据加密算法以及密钥的管理,并以Sql Server 2005为例,实现一个简单的数据加密和解密。     

Room-temperature anomalous Hall effect and magnetroresistance in (Ga, Co)-codoped ZnO diluted magnetic semiconductor films

This paper reports that the(Ga,Co)-codoped ZnO thin films have been grown by inductively coupled plasma enhanced physical vapour deposition.Room-temperature ferromagnetism is observed for the as-grown thin films.The x-ray absorption fine structure characterization reveals that Co 2+ and Ga 3+ ions substitute for Zn 2+ ions in the ZnO lattice and exclude the possibility of extrinsic ferromagnetism origin.The ferromagnetic(Ga,Co)-codoped ZnO thin films exhibit carrier concentration dependent anomalous Hall effect and positive magnetoresistance at room temperature.The mechanism of anomalous Hall effect and magneto-transport in ferromagnetic ZnO-based diluted magnetic semiconductors is discussed.     

固相反应法制备Co掺杂ZnO的磁性和光学性能研究

研究了以固相反应法制备Co掺杂ZnO粉体的磁性和光学性能，测试结果表明对于均匀掺杂的Zn_0.95Co_0.05O粉体，Co²⁺随机取代Zn²⁺的位置进入ZnO晶格.Co²⁺之间的3d自旋电子耦合交换作用使得近邻的Co²⁺自旋反平行，Zn_0.95Co_0.05O粉体在3—300K表现为顺磁性，而非铁磁性. 关键词： ZnO 固相反应 稀磁半导体 顺磁性     

GIS数据格式无缝转换

地理信息系统（GIS：Geographic Information System）在国民经济中发挥着越来越重要的作用。基础地理信息数据库是地理信息系统的基础,但目前建设基础地理信息数据库的工作非常费时且繁琐,部分原因是因为在建库工作中需要进行大量格式转换。本文详细研究了AutoCAD格式和AreGIS的差异,然后提出一种数据格式的自动转换方法并加以实现。     

Fabrication of Ti ohmic contact to n-type 6H-SiC without high-temperature annealing

The effect of surface morphology of 6H-SiC substrate on the ohmic contact properties of Ti/6H-SiC structure is studied. The H-terminated surface on Si-face 6H-SiC is obtained by both dipping SiC into HF acid solution for 15 s and thermal heating SiC in hydrogen atmosphere at 1100 C for 10 min, while the H-terminated surface on C-face 6H-SiC could be obtained only by the latter method. Ti is deposited on Si-face and C-face SiC substrates with H-terminated surfaces and ohmic contact is obtained without high-temperature annealing.     

Magnetic properties of Mn-doped ZnO diluted magnetic semiconductors

A series of Mn-doped ZnO films have been prepared in different sputtering plasmas by using the inductively coupled plasma enhanced physical vapour deposition. The films show paramagnetic behaviour when they are deposited in an argon plasma. The Hall measurement indicates that ferromagnetism cannot be realized by increasing the electron concentration. However, the room-temperature ferromagnetism is obtained when the films are deposited in a mixed argon-nitrogen plasma. The first-principles calculations reveal that antiferromagnetic ordering is favoured in the case of the substitution of Mn^2＋ for Zn^2＋ without additional acceptor doping. The substitution of N for O （NO^-） is necessary to induce ferromagnetic couplings in the Zn-Mn-O system. The hybridization between N 2p and Mn 3d provides an empty orbit around the Fermi level. The hopping of Mn 3d electrons through the empty orbit can induce the ferromagnetic coupling. The ferromagnetism in the N-doped Zn-Mn-O system possibly originates from the charge transfer between Mn^2＋ and Mn^3＋ via NO^-, The key factor is the empty orbit provided by substituting N for O, rather than the conductivity type or the carrier concentration.     

歧口凹陷沙一段低熟烃源岩评价

利用烃源岩有机质丰度、生排烃特征、发育古环境、有机岩石学及原油特征等手段,探讨歧口凹陷沙一段低熟烃源岩生烃、排烃特征。研究结果表明,歧口凹陷沙一段低熟烃源岩有机质丰度高、类型好,具有集中排烃、高效排烃的特点。沙一下段烃源岩发育的环境主要为干旱气候下的咸水环境。藻类及显微组分中的矿物沥青基质是低熟烃源岩形成低熟油气的物质基础。歧口凹陷存在大量未熟-低熟的原油。     

杂质和缺陷对SiC单晶导热性能的影响

目前关于SiC单晶室温的导热性能,以及导热特性随温度的变化方面的研究报道还存在较大的差异,有关SiC单晶热导率的研究主要是沿c轴<0001>晶向或者垂直于c轴的某一晶向进行的,无法有效地解释热导率的各向异性.本文研究了4H-SiC和6H-SiC单晶<1100>,<1120>,<0001>三个不同晶向上热导率以及其随温度...     

V掺杂6H-SiC光导开关制备与性能研究

采用V掺杂半绝缘6H-SiC单晶衬底材料制备了平面电极型大功率SiC光导开关,用强度为150 J/mm2、波长为355 nm的脉冲激光对开关进行触发,在1~14 kV的外加电压范围内对光导开关的耐压特性、导通电阻等性能进行了研究。结果表明：随着开关外加电压的升高,开关的电流峰值呈现不断增大的趋势,当开关外加电压为14 kV时,电流峰值达185 A,对应的光导开关峰值功率为2.59 MW,开关的导通电阻约为22 。