高可靠软件研究:向信息技术的未来投资

National Natural Science Foundation of China; Public Administration and Civil Service Bureau of Macau SAR; Companhia de Telecomunicacoes de Macau S.A.R.L.; Macau SAR Government Tourist Office

a higher-order duration calculus and its completeness

National Natural Science Foundation of China; Public Administration and Civil Service Bureau of Macau SAR; Companhia de Telecomunicacoes de Macau S.A.R.L.; Macau SAR Government Tourist Office

Tunable optical properties of nano-Au on vanadium dioxide

The optical properties of Au nanoparticles deposited on thermochromic thin films of VO2 are investigated using spectroscopy. A localized modification on the transmittance spectrum of VO2 film is formed due to the presence of Au nanoparticles which exhibit localized surface plasmon resonance (LSPR) in the visible-near IR region. The position of the modification wavelength region shows a strong dependence on the Au mass thickness and shifts toward the red as it increases. On the other hand, it was found that the LSPR of Au nanoparticles can be thermally tunable because of the thermochromism of the supporting material of VO2. The LSPR wavelength, lambda(SPR), shifts to the blue with increasing temperature, and shifts back to the red as temperature decreases. A fine tuning is achieved when the temperature is increased in a stepwise manner.

Nano-Ag on vanadium dioxide. I. Localized spectrum tailoring

We report on the utilization of localized surface plasmon resonance (LSPR) of Ag nanoparticles to tailor the optical properties Of VO2 thin film. Interaction of nano-Ag with incident light yields a salient absorption band in the visible-near IR region and modifies the spectrum Of VO2 locally. The wavelength of modification occurs in a limited spectral region rather than affects the full spectrum. The wavelength of modification shows a strong dependence on the metal nanoparticle size and shifts toward the red as the particle size or the mass thickness of nano-Ag increases. Also, we found that the wavelength can be shifted into the IR further by introducing a thin layer of TiO2 onto the nano-Ag. Interestingly, with the help of LSPR effects the VO2 film exhibits an anomalous thermochromic behavior in the modification wavelength region, which may be useful in optical switching applications.

Electron injection assisted phase transition in a nano-Au-VO2 junction

The semiconductor-metal transition of vanadium dioxide (VO2) thin films epitaxially grown on C-plane sapphire is studied by depositing Au nanoparticles onto the thermochromic films forming a metal-semiconductor contact, namely, a nano-Au-VO2 junction. It reveals that Au nanoparticles have a marked effect on the reduction in the phase transition temperature of VO2. A process of electron injection in which electrons flow from Au to VO2 due to the lower work function of the metal is believed to be the mechanism. The result may support the Mott-Hubbard phase transition model for VO2.

The exciton-longitudinal-optical-phonon coupling in InGaN/GaN single quantum wells with various cap layer thicknesses

This paper studies the exciton-longitudinal-optical-phonon coupling in InGaN/GaN single quantum wells with various cap layer thicknesses by low temperature photoluminescence (PL) measurements With increasing cap layer thickness, the PL peak energy shifts to lower energy and the coupling strength between the exciton and longitudinal-optical (LO) phonon, described by Huang-Rhys factor, increases remarkably due to an enhancement of the internal electric field With increasing excitation intensity, the zero-phonon peak shows a blueshift and the Huang-Rhys factor decreases These results reveal that there is a large built-in electric field in the well layer and the exciton-LO phonon coupling is strongly affected by the thickness of the cap layer

The growth and characterization of GaN grown on a gamma-Al2O3/(001) Si substrate by metalorganic vapor phase epitaxy

Wurtzite single crystal GaN films have been grown onto a gamma-Al2O3/Si(001) substrate in a horizontal-type low pressure MOVPE system. A thin gamma-Al2O3 layer is an intermediate layer for the growth of single crystal GaN on Si although it is only an oriented polycrystal film as shown by reflection high electron diffraction. Moreover, the oxide is not yet converted to a fully single crystal film, even at the stage of high temperature for the GaN layer as studied by transmission electron microscopy. Double crystal x-ray linewidth of (0002) peak of the 1.3 mu m sample is 54 arcmin and the films have heavy mosaic structures. A near band edge peaking at 3.4 eV at room temperature is observed by photoluminescence spectroscopy. Raman scattering does not detect any cubic phase coexistence.

Growth and characterization of GaN on LiGaO2 and LiAlO2

The nearly lattice-matched LiGaO2 and LiAlO2 substrates have been used for the growth of GaN by LP-MOVPE. GaN epilayers have been grown on the two substrates at very low input partial pressure of hydrogen and relatively low growth temperature. The difference in the growth rate, crystal and optical qualities of hexagonal GaN epilayers grown on LiAlO2 and LiGaO2 substrate with two polar domains are investigated. LiAlO2 and LiGaO2 single crystal with a single domain structure and an adequate surface plane are promising substrates for the growth of high quality of hexagonal GaN thin films.

Yellow luminescence mechanism and persistent photoconductivity in n-GaN single crystal films grown on alpha-Al2O3(0001) substrates by LP-MOCVD

Unintentionally doped and Si-doped single crystal n-GaN films have been grown on alpha-Al2O3 (0001) substrates by LP-MOCVD. Room temperature photoluminescence measurement showed that besides the bandedges, the spectrum of an undoped sample was a broad deep-level emission band peaking from 2.19 to 2.30eV, whereas the spectrum for a Si-doped sample was composed of a dominant peak of 2.19eV and a shoulder of 2.32eV. At different temperatures, photoconductance buildup and its decay were also observed for both samples.. The likely origins of persistent photoconductivity and yellow luminescence, which might be associated with deep defects inclusive of either Ga vacancy(V-Ga)/Ga vacancy complex induced by impurities or N antisite (N-Ga), will be proposed.

森林管理对动物生境影响的模拟研究——以小兴安岭友好林业局为例

理解森林管理对野生动物生境的累积效应，需要对不同森林管理预案作出预测、分析和评价。本文，以小兴安岭友好林业局为研究区，利用空间直观景观模型LANDIS模拟其在6种森林管理预案—无采伐、皆伐、择伐I（禁伐区不采伐，限伐区和商品林区每10年采伐面积分别为5%和10%）、择伐II（限伐区和商品林区10%和15%）、造林I（采伐同择伐I，伐后人工更新）和造林II（采伐同择伐II，伐后人工更新）下200年内的森林景观变化。在查阅文献、野外考察和咨询相关专家的基础上，以GIS为平台，构建有着不同生境需求的3种动物：松鼠（Sciurus vulgaris）、马鹿（Cervus elaphus）和花尾榛鸡（Bonasa bonasia）在景观尺度上的生境适宜度指数（Habitat suitability index, HSI）模型，利用Arc的宏语言AML（Arc Macro Language）将LANDIS的输出结果与3种动物的HSI模型相结合，借助生境单元和类水平（Class level）上的景观指数（结合度指数等）评价动物生境，以反映不同森林管理预案对动物生境的影响。研究结果表明： 1）对于LANDIS的模拟结果而言，不同森林管理预案往往导致不同的森林演替动态：无采伐和2造林方案下，森林逐渐向成、过熟林演替，且造林方案显著增加了营林树种的分布面积；择伐I和择伐II下，由于成、过熟林被采伐，森林向后期演替的速度较为缓慢，而皆伐下，中、幼龄林的比重较大。定性而言，对于偏好早期演替的动物而言，皆伐下的生境适宜性较高；对于偏好中、后期演替森林的动物而言，2种择伐方案下生境适宜性较高；对于偏好后期演替的动物而言，无采伐和2造林方案下生境适宜性较高。 2）对于松鼠，无采伐和2造林预案下的生境单元和适宜生境（HSI≥0.5）结合度指数较高，适宜生境的平均斑块面积较大，表明这3种预案下的生境适宜性较高，而2择伐预案由于移去了大量成、过熟林，导致松鼠生境适宜性的下降，对于皆伐，尽管采伐量比2择伐预案的小，由于其不利于针叶林的天然更新，对松鼠的生境破坏更为严重。 3）对于马鹿，皆伐和2造林预案下的生境单元和结合度指数较高，而无采伐下的生境单元和结合度指数整体上又小于2择伐预案下的，这表明，适当的干扰反而利于提高马鹿的生境适宜性，因为，若没有这些采伐、造林等干扰活动，森林的郁闭度会随着树冠的封闭而逐渐加大，下层的许多不耐荫的树种就会消失或减少，降低马鹿的食物来源。 4）对于花尾榛鸡，若不考虑营林活动对其干扰，2造林预案下的生境单元和结合度指数较高，其次为无采伐预案，而皆伐和2择伐方案下较低，这表明，单纯的采伐的将减小花尾榛鸡的生境适宜性。 生态系统是一复杂的系统，因此，不可能存在适于所有动物的森林管理预案，对于管理预案的选择取决于管理者多方面（经济、生态和社会）的权衡。本文是将LANDIS与HSI相结合模拟评估森林管理预案对动物生境影响的一次尝试，研究结果表明了这一方法的实用性。尽管这一方法存在一定的局限性，但利用这一方法，能够可视化和量化结果，并比较不同森林管理预案，从生物多样性保护出发，为森林管理提供决策支持。最后，需要声明的是，本研究侧重方法的探讨，作为实际应用，还需要大量的野外工作来验证HSI模型。

长白山林区露水河林业局森林资源变化研究

长白山林区是我国国有重点林区，丰富的森林资源是大自然赐以我们的巨大宝库，如何正确处理保护与利用的关系是一项值得长期、全方位研究的重大课题。本文以长白山林区露水河林业局为研究区，从森林资源空间分布格局及变化、森林资源统计变化特征、森林景观格局及其变化三个角度研究了该局森林资源在十五年间的变化情况，并对未来森林资源保护与利用提出了建设性意见。具体研究如下：1．森林资源空间分布格局及变化研究。基于森林生态学理论，以RS及GIS作为技术支持，通过图像单元统计及图像叠加分析、过去森林资源利用状况评价、两个时段主要河流沿岸缓冲区分析、未来利用森林资源的空间选择、目前森林资源质量分析，重点研究了十五年来该局森林资源空间变化特征。结果表明，研究区森林资源由于人类强烈的经营活动，各类地物发生显著变化。2．基于森林资源二类调查数据，研究了各类森林资源面积、林分蓄积构成变化。结果表明，从林木总面积、蓄积指标上看现存森林资源结构较为合理，但以具体树种的面积、蓄积指标来分析，现存森林资源构成存在一些问题，蓄积总量构成占主导地位的五、六种树种中，成熟林、过熟林占相当大比例，后续储备蓄积结构失衡。3．基于景观生态学数量方法研究了森林景观格局及其变化。结果表明，当地人类活动的频繁程度正在加强，并对森林景观格局产生重大影响，主要林分类型在各类地物中保持相对稳定。

基于GIS的长白山森林资源动态与经营分析-以白河林业局为例

本文结合野外调查和森林经营资料，以GIS为核心技术，综合空间分析与多种统计方法，研究了采伐干扰下白河林业局森林资源的动态变化，并使用FoREsTA严森林资源经营管理决策支持系统进行模拟，对多种采伐方案进行了系统的研究。该研究对指导整个长白山区的采伐经营，保护森林资源，实现森林生态系统科学经营与景观管理具有重要的理论意义。主要结论如下：①采伐活动在一定时间内改变植物种群的生态位，伐后10年7个树种的生态位宽度升高并逐渐高出原始林的生态位宽度。其生态位重叠从采伐后至伐后5年降低，以后逐渐升高，20年时与原始林基本相同；伐后灌木种群的生态位宽度与生态位重叠都增大，伐后巧年逐渐降低，伐后20年与原始林基本相同。②采伐强度影响植物群落的多样性，10％采伐强度采伐干扰的乔木的多样性伐后先降低再逐渐增加，20％和30％采伐强度采伐干扰的乔木的多样性随时间变化没有明显的规律；10％与20％采伐强度的灌木的多样性伐后先升高再降低，30％采伐强度的灌木多样性伐后先减少再增加；在所有采伐干扰中，草本层的多样性自伐后5年起逐渐升高，伐后20年，多样性基本趋于稳定。与原始林的多样性相比，10％的采伐强度可以增加乔木、灌木和草本的多样性，20％采伐强度增加了灌木的多样性。③经过13年经营，白河林业局森林林龄、单位蓄积和郁闭度较高等级的森林面积减少，较低等级的森林面积增加。林分质量下降。④经过13年，林业用地景观更加破碎，复杂程度降低，人类的干扰程度增强；基于景观划分的经营类型出现较大差异。⑤利用FoREsTA严决策支持系统进行采伐决策时，应该根据资源分布选择不同的采伐方案。从景观经营的角度，森林景观空间结构方案以及森林景观空间结构方案与实际木材采伐方案相组合后的方案更具有参考价值。

Field emission from the structure of well-aligned TiO2/Ti nanotube arrays

Well-aligned TiO2/Ti nanotube arrays were synthesized by anodic oxidation of titanium foil in 0.5 wt.% HF in various anoclization voltages. The images of filed emission scanning electron microscopy indicate that the nanotubes structure parameters, such as diameter, wall thickness and density, can be controlled by adjusting the anoclization voltage. The peaks at 25.3 degrees and 48.0 degrees of X-ray diffraction pattern illuminate that the TiO2 nanotube arrays annealed at 500 degrees C are mainly in anatase phase. The filed emission (FE) properties of the samples were investigated. A turn-on electric field 7.8 V/mu m, a field enhancement factors approximately 870 and a highest FE current density 3.4 mA/cm(2) were obtained. The emission current (2.3 mA/cm(2) at 18.8 V/mu m) was quite stable within 480 min. The results show that the FE properties of TiO2/Ti have much relation to the structure parameters.

Synthesis and field emission of diamond-like carbon nanorods on TiO2/Ti nanotube arrays

Highly ordered TiO2/Ti nanotube arrays were fabricated by anodic oxidation method in 0.5 wt% HF. Using prepared TiO2/Ti nanotube arrays deposited Ni nanoparticles as substrate, high quality diamond-like carbon nanorods (DLCNRs) were synthesized by a conventional method of chemical vapor deposition at 750 degrees C in nitrogen atmosphere. DLCNRs were analyzed by filed emission scanning electron microscopy and Raman spectrometer. It is very interesting that DLCNRs possess pagoda shape with the length of 3-10 mu m. Raman spectra show two strong peaks about 1332 cm (1) and 1598 cm (1), indicating the formation of diamond-like carbon. The field emission measurements suggest that DLCNRs/TiO2/Ti has excellent field emission properties, a low turn-on field about 3.0 V/mu m, no evident decay at 3.4 mA/cm(2) in 480 min. (C) 2009 Elsevier B. V. All rights reserved.

EDTA溶液修复重金属污染土壤的效果及金属的形态变化特征

采用0.05mol.L-1的EDTA作为萃取剂,在一定的萃取条件下,对2种尾矿土壤中重金属进行土壤柱萃取实验,并采用优化的BCR(European Community Bureau of Reference)连续萃取方案对萃取前后的Pb、Zn、Cu和Cd进行形态分析.研究EDTA对4种金属的萃取效率及萃取前后的形态变化特征.结果表明,EDTA能有效的从土壤中萃取该4种金属,萃取效率依次为:Cd>Zn>Cu>Pb;金属的4种形态均能被EDTA萃取;在浅层土壤中,EDTA对酸可提态的金属的萃取效果尤为显著;在深层土壤中,酸可提取态、氧化物结合态、有机结合态和残余态4种形态的金属萃取效果,随着土壤柱深度的增加而降低.