词边界信息在句中的分布

用经过删除的语音歧义句作材料，研究了词边界信息在句中的分布。结果说明，在歧义句中歧义音节是最重要的切分线索；向歧义音节的前后过渡也对词切分有贡献；歧义音节和过渡以外的部分在一定条件下对切分有帮助。</p

High-index-faceted platinum nanoparticles: insights into structural and thermal stabilities and shape evolution from atomistic simulations

National Natural Science Foundation of China [51271156, 11204252]; Natural Science Foundation of Fujian Province of China [2013J06002]; Specialized Research Fund for the Doctoral Program of Higher Education of China [20130121110012]High-index-faceted Pt nanoparticles exhibit exceptional electrocatalytic activity owing to the high density of low coordinated sites on their surface, and thus have attracted extensive studies over the past few years. In this study, we have employed atomistic simulations to systematically investigate the structural and thermal stabilities and shape evolution of Pt nanoparticles with different high-index facets, that is, tetrahexahedra enclosed by {hk0} facets, trapezohedra by {hkk} ones, and trisoctahedra by {hhk} ones. The results show that {221} faceted trisoctahedral nanoparticles display the best structural and thermal stabilities while {410} faceted tetrahexahedral ones display the worst. The shape stability of these nanoparticles generally decreases in the order from trapezohedron to tetrahexahedron to trisoctahedron. For the same type of polyhedron, the structural, thermal and shape stabilities of the nanoparticles all decrease according to the order of {2kl}, {3kl} and {4kl} facets. Further analyses have discovered that a large proportion of high-coordinated surface atoms are beneficial for enhancing both the thermal and shape stabilities. This work provides an in-depth understanding of surface structures and thermodynamic evolution of high-index-faceted metallic nanoparticles

Tetrahexahedral Pt-Pd alloy nanocatalysts with high-index facets: An atomistic perspective on thermodynamic and shape stabilities

Metallic nanoparticles with high-index facets exhibit exceptional electrocatalytic activity owing to the high density of low coordination sites at the surface, thus they have attracted intense interest over the past few years. Alloying could further improve their catalytic activity by the synergy effects of high-index facets and electronic structures of components. Using atomistic simulations, we have investigated thermodynamic and shape stabilities of tetrahexahedral Pt-Pd alloy nanoparticles respectively bound by {210} and {310} facets. Energy minimization through Monte Carlo simulations has indicated that the outermost layer is predominated by Pd atoms while Pt atoms preferentially occupy the sub-outermost layer of nanoparticles. Molecular dynamics simulations of the heating process have shown that the {210} faceted nanoparticles possess better thermodynamic and shape stabilities than the {310} faceted ones. The coordination numbers of surface atoms were used to explore the potential origin of the different stabilities. Furthermore, a high Pt ratio will help enhance their stabilities. For both faceted nanoparticles, the melting has homogeneously developed from the surface into the core, and the tetrahexahedra have finally evolved into sphere-like shape prior to the overall melting. These results are helpful for understanding the composition and thermodynamic properties of high-index faceted nanoparticles, and are also of practical importance to the development of alloy nanocatalysts. ? 2014 The Royal Society of Chemistry

Single-crystalline and multiple-twinned gold nanoparticles: an atomistic perspective on structural and thermal stabilities

National Natural Science Foundation of China [51271156, 11204252]; Natural Science Foundation of Fujian Province of China [2013J06002]; Fundamental Research Funds for the Central Universities of China [2012121010]Morphologies of gold nanoparticles play an important role in determining their chemical and physical (catalytic, electronic, optical, etc.) properties. Therefore, a fundamental understanding of the morphological stability is of crucial importance to their applications. In this article, we employed atomistic simulations to systematically investigate the structural and thermal stabilities of gold particles with eight representative nanoshapes, including single-crystalline and multiple-twinned structures. Our investigation has revealed that the truncated octahedron and the octahedron possessed the best structural stability, while the tetrahedron and the icosahedron did the worst. Further analyses have discovered different thermal stabilities and diverse melting behaviors in these particles. Especially, an inhomogeneous melting of the icosahedron was disclosed, and the relevant mechanism was elucidated. This study provides significant insight not only into the experimental preparation of gold nanoparticles but also into the design of gold nanostructures with both high catalytic activity and excellent stability

长汀县赢坪史前遗址发掘简报

2012年福建博物院对赢坪两处遗址进行了抢救性考古发掘,获得了一批包括石器、陶器、铜器、石范等内涵丰富的文化遗物,这批遗物可进一步了解闽西地区的史前文化发展序列及文化面貌,并且对于多地区文化间的交流研究也有一定的作用

research and protection of the digital evidence collecting system

随着计算机犯罪的不断增加,电子数据取证技术(digital forensic technology)越来越受到人们的重视.电子数据证据不同于传统的犯罪证据,它们更加容易消失和被破坏,为了获得完整可信的电子数据证据,提出应在敏感主机中预先安装设置电子数据证据收集系统(digital evidence collecting system,DECS),用来收集系统中的相关证据.由于DECS的某些模块往往存在于被攻击系统之中,提出使用安全隔离环境是保护电子数据证据收集机制有效的方法,并设计了一个安全保护机制--

杨树的氮营养在盐碱和镉胁迫下的作用

胡杨(Populus euphratica Oliv.)属于杨柳科(Salicaceae)25-35 种落叶开花植物中的一种，原产于北半球的大部分地区。胡杨、新疆杨(Populus bolleana Lauche.)和俄罗斯杨(Populus Russkii Jabl.)在新疆地区普遍存在，且在长期的极端条件和自然选择下，这些树种演化出了许多抗逆境胁迫的功能基因。对这些基因的研究具有重要的意义。这三种杨树对盐和镉胁迫的抗性表现出极大的不同。胡杨有较强的抗盐胁迫的能力，新疆杨次之，而俄罗斯杨则对盐较敏感。我们研究了胡杨和新疆杨幼叶和老叶对碱胁迫的响应，发现碱胁迫下，胡杨具有较强的抗性，主要是因为一方面它通过有效的机制，将 Na+离子区隔化至液泡中从而避免离子伤害；另一方面碱胁迫下它能更灵活的调整氮的吸收和代谢。新疆杨对碱胁迫的主要适应策略是通过积累大量有毒离子至老叶中从而避免对幼叶的伤害。氮营养影响了新疆杨幼叶和老叶对盐胁迫的响应机制。盐胁迫下，新疆杨老叶中积累更多的 Na+，以此来保护幼叶免受盐胁迫的伤害。外部环境缺氮时，幼叶表现的更敏感，此时出现如老叶在盐胁迫下的损伤性状。缺氮时，老叶对幼叶的保护策略失去效用。氮营养对俄罗斯杨的盐胁迫抗性也有较大的影响。盐胁迫使俄罗斯杨的根和叶均受到较大的损伤。但是经过低氮的适应后，再加入温和的盐分胁迫，一定程度上可以缓解盐胁迫造成的伤害。俄罗斯杨具有较强的抗镉胁迫性，外界不同浓度的 NO3- 影响俄罗斯杨对镉胁迫的抗性。在一定的范围之内，随着外部环境 NO3- 浓度的升高，俄罗斯杨的抗镉胁迫性逐渐增强。然而，低浓度的 NO3-和过高浓度的 NO3-都降低了俄罗斯杨对镉胁迫的抗性。NRT 家族基因的表达受到各种胁迫因子的影响。我们从胡杨的基因组中，克隆了 NRT1;5A，NRT1;5C，NRT1;8A，NRT1;8B，NRT1;9B，NRT1;7，NRT3;1A，NRT3;1B，和 NRT3;2A 这几个基因，通过组织培养技术将这几个基因转入了烟草中，并获得了转基因烟草的 T2 代种子。逆境胁迫处理下发现，烟草 PeNRT1;5A，NRT1;5C，NRT1;8A，NRT1;8B，NRT1;9B 的转基因植株对镉胁迫有很强的抗性。另外，NRT1;8B，NRT1;9B 和 NRT1;5C 的异源表达烟草植株对铜胁迫也表现出较显著的抗性

research on the methodology of development of dss based on object oriented model

通过对DSS中模型结构的研究,给出了基于面向对象模型库及其动态管理系统的DSS可重用体系结构,以及该体系结构的实现方法与工作流程.最后介绍了该项研究的应用情况

research on a definition method of digital forensic requirement

如何描述和规范计算机取证需求是计算机取证基本理论及基本方法研究中较为突出的一个问题.本文结合软件工程及安全工程的思想提出了场景需求定义法,它对计算机取证需求的制定给出了一套定义方法.基于以上定义方法,需求的制定可以面向所有计算机取证环境,即它不限定哪类取证环境应该提供哪些取证需求,而是在实际应用中根据实际需要来确定,这为描述不断变化的复杂现实应用环境中的安全需求提供了灵活性

trdm-temporal role-based delegation model

当前基于角色的系统的完全依赖于管理者的集中式管理方式,不能够满足分布环境下的系统管理的需求.基于角色的转授权模型(role-based delegation model, RDM)更适于分布式环境的授权管理,但当前的几种授权模型都不支持时限(temporary)和授权宽度.基于时限和授权宽度等方面,对RDM2000(role-based delegation model 2000)模型进行了扩充,提出了完备的具有时限的基于角色的转授权模型(temporal role-based delegation m