共查询到20条相似文献,搜索用时 156 毫秒
1.
Minghui Song Kazutaka Mitsuishi Kazuo Furuya 《Physica E: Low-dimensional Systems and Nanostructures》2005,29(3-4):575
Nanometer-sized W-dendrites are fabricated on Al2O3 substrates with an electron-beam-induced deposition process. Dependence of growth of nanodendrite on surface topography is investigated with transmission electron microscopy. It is confirmed that the nanodendrite grows on convex surfaces but not around a hole on a substrate. These are attributed to different distribution of charges on surfaces with different topographies during electron beam irradiation when charges are produced on the surface due to emission of second electrons. The charges accumulate on convex surface and do not distribute around a hole. Therefore, the nanodendrite grows on the former and not on the latter. 相似文献
2.
Shi-xuan Du Ye-liang Wang Qi Liu Hai-gang Zhang Hai-ming Guo Hong-jun Gao 《Frontiers of Physics in China》2010,5(4):380-386
The motion of single molecules on surfaces plays an important role in nanoscale engineering and bottom-up construction of
complex devices at single molecular scale. In this article, we review the recent progress on single molecular rotors self-assembled
on Au(111) surfaces. We focus on the motion of single phthalocyanine molecules on the reconstructed Au(111) surface based
on the most recent results obtained by scanning tunneling microscopy (STM). An ordered array of single molecular rotors with
large scale is self-assembled on Au(111) surface. Combined with first principle calculations, the mechanism of the surface-supported
molecular rotor is investigated. Based on these results, phthalocyanine molecules on Au (111) are a promising candidate system
for the development of adaptive molecular device structures. 相似文献
3.
肖香珍 《原子与分子物理学报》2017,34(4):617-623
采用密度泛函理论,在slab模型下,研究了NH_x(x=1~3)在Ir(100)、Ir(111)和Ir(110)表面上的最稳定吸附位置、几何构型以及逐步脱氢分解过程,计算了相应的吸附能和活化能.计算结果表明,在Ir(100)、Ir(111)面上,NH_3是以C_3轴垂直吸附在顶位,在Ir(110)上,NH_3是以N-Ir键与表面成68.6°吸附在顶位,且吸附能依赖于表面的结构而不同,相比而言,NH_3更容易吸附在开放表面Ir(100)、Ir(110)面上,说明NH_3在这些表面的吸附具有结构敏感性.NH_(x(x=1~3))的分解,在Ir(100),NH_3的吸附与分解存在竞争,在Ir(110)面NH_3最容易分解,在Ir(111)面NH_3是分子性吸附,不能分解.NH_2、NH在三个表面均能够分解,在Ir(110)面活化能均较高. 相似文献
4.
《Journal of Nonlinear Mathematical Physics》2013,20(2):236-246
In this article, we focus on left-invariant pseudo-Einstein metrics on Lie groups. To begin with, we give some examples of pseudo-Einstein metrics on Lie groups. Also we calculate the Levi-civita connection, and then Ricci tensor associated with left-invariant pseudo-Riemannian metrics on the unimodular Lie groups of dimension three. Furthermore, we show that the left-invariant pseudo-Einstein metric on SL(2) is unique up to a constant. At last, we study the left-invariant pseudo-Riemannian metrics on compact Lie groups and classify the pseudo-Einstein metrics on the low-dimensional compact Lie groups. 相似文献
5.
小液滴撞击壁面现象在喷雾冷却等领域都有广泛应用.为研究小液滴(微米)撞击热壁面(非沸腾区)传热过程,建立了二维液滴撞壁瞬态模型,并采用相场方法对小液滴换热过程中对流热通量和导热热通量的大小进行了对比.研究结果表明:液滴撞击壁面初期形成“冷斑”,有利于小液滴与壁面的传热;小液滴撞击壁面过程中热通量峰值存在于三相接触点附近,数量级在105—106 W/m2;小液滴撞击壁面过程中受壁面浸润性和液滴尺寸对传导热通量的影响较为显著,而速度和液滴尺寸对对流热通量的影响较为显著;大多数情况下,小液滴撞击壁面传导热通量数量级在103—105 W/m2,对流热通量数量级在104—106 W/m2,对流热通量大于传导热通量,在整个换热过程中占据主导地位. 相似文献
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We report results of calculations with a formalism that in principle applies quite generally for chemisorption on a real metallic substrate. Including the substrate structure within perturbation theory on a self-consistent jellium-plus-adatom calculation, we have computed the dependence of the binding energy of an adatom on the surface geometry. Specifically, in the case of hydrogen on Al, our model calculation predicts that the stable positions are bridge configurations on the (100) and (110) surfaces and atop positions on the (111) surface, and that they have almost the same heats of chemisorption (1.8–2.0 eV). For geometrical reasons the bridge configuration seems to be a reasonable result while the atop result for the (111) surface is more uncertain. Thus, chemisorption of H on Al should require predissociation of the H2 gas. In addition, the predicted values for hydrogen desorption imply that measurements on H on Al surfaces should be performed at low temperatures to avoid desorption. Results for H on a jellium of Na density indicates that hydrogen should be absorbed in rather than adsorbed on Na metal. 相似文献
8.
Jing-Jie Ma Li-Fang Wang Shu-Hong Ma Jie Yang 《The European Physical Journal B - Condensed Matter and Complex Systems》2018,91(8):185
The adsorption and dissociation of water monomer and dimer on stepped Co(0001) surface were studied by means of first-principles calculations. Present results indicate that the adsorption strength of water is greatly enhanced by the presence of step, while the activity of water monomer dissociation does not exhibit a noticeable improvement. Nevertheless, water dimer partial dissociation on stepped Co(0001) is more active than on flat Co(0001), and the promotion of oxygen atom on O–H bond cleavage of H2O is more prominent on stepped surface than on flat Co(0001). The findings reveal the importance of low coordinated surface atoms on metallic catalysts and the vital role of surface rippling on water dissociation. Together with previous reports, the activity of water dissociation on cobalt-based catalytic surfaces depends dominantly on O-containing species like oxygen atom, H2O or hydroxyl. 相似文献
9.
The decay of surface charges deposited on the dielectric material by the partial discharge (PD) activity has a great impact on the repetition of partial discharges. In this work, the effect of dielectric placed on the surface of ground electrode in a needle-plane configuration on the discharge activity was investigated, with the application of a periodic negative step voltage. The charge decay mechanisms on a corona charged dielectric surface were investigated based on a comparison between experiments and a FEM-based numerical model. The comparison indicates that the surface charges may decay due to different mechanisms depending on the applied stress. 相似文献
10.
E. Bauer 《Applied Physics A: Materials Science & Processing》1990,51(2):71-78
Phase transitions in two-dimensional metal layers on metal surfaces are discussed, with emphasis on systems with attractive lateral interactions on densely packed surfaces. The experimental tools which give information on these transitions are described briefly and the results obtained with them are illustrated by examples of various metals on W and Mo surfaces. 相似文献
11.
Jacques Bros Henri Epstein Michel Gaudin Ugo Moschella Vincent Pasquier 《Communications in Mathematical Physics》2010,295(1):261-288
We study a class of three-point functions on the de Sitter universe and on the asymptotic cone. A blending of geometrical
ideas and analytic methods is used to compute some remarkable integrals, on the basis of a generalized star-triangle identity
living on the cone and on the complex de Sitter manifold. We discuss an application of the general results to the study of
the stability of scalar particles on the de Sitter universe. 相似文献
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An extended Hückel (EH) study is performed on the clusters representing a formate adsorbed on Ru(001) and on
in order to investigate the effect of potassium on the selectivity of decomposition of formate on Ru(001). The adsorption geometry and the VSIP (valence state ionization potential) values of EH parameters are determined from ab initio calculations on small clusters. The EH calculation reproduces well the site preference of formate on each surface suggested from experiments. The C---H bond of formate, which is our focus in this study, is calculated to be almost the same on the two surfaces when the molecular plane of formate is perpendicular to the surface; but when the plane is tilted from the surface normal and thus the C---H bond approaches the surface, the C---H bond is weakened to a much higher extent on clean Ru(001) than on K-covered Ru(001). This is in good agreement with the experimental result that the presence of potassium changes the reaction pathway of the decomposition of formate on Ru(001) by suppressing C---H bond cleavage. 相似文献
14.
表面吸附是石墨烯中质子(H~+)输运的基础步骤.本文基于第一性原理计算研究了B、N、S掺杂对石墨烯表面H~+吸附行为的影响.结果表明,B、N、S掺杂对石墨烯的晶体结构、内聚能及电子性质有重要影响,且影响程度与掺杂元素的性质密切相关,进而导致对石墨烯表面H~+吸附行为产生不同程度的影响.从吸附能的观点看,N、B、S掺杂对石墨烯表面H~+的吸附有利.研究结果对石墨烯在氢贮存、氢同位素分离、燃料电池等领域的应用具有重要的指导意义. 相似文献
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提出了一种适用于伪随机序列投影三维测量技术的子序列匹配快速算法.首先根据源序列的内容及子串长度构造由多层子表组成的表格;然后根据子序列的内容,从首字符开始从左到右,依次从首层表格开始向下查找;最后得到子序列在源序列中的位置.即根据首字符在首层表格中查到对应的第二层表格地址,再在第二层表格中根据第二个字符,查找第三层表格地址.以此类推,查出最后一层表格的地址.在最后一层表格中,根据末字符查找到该子序列在源序列中的位置.给出了理论分析并进行了实验验证,结果表明,在目前主流的计算机上,对于典型场景采用查表法的子序列匹配速度较常用算法快60倍以上. 相似文献
17.
设计了EAST 4.6GHz低杂波器件的一系列主动水冷冷却结构,阐述了直波导、波导弯头、天线单元的水冷结构设计,并使用有限元模拟软件ANSYS计算了这些部件的发热和对流冷却,计算并展示了部件上的温度分布二环结构变形。通过计算,优化直波导单面水冷结构为双面水冷。计算结果表明,立弯波导弯头的水冷结构明显好于侧弯弯头。原天线单元前端温度分布集中,热应力很大,不符合实验要求。优化后的天线单元前端的温升和热变形可以达到LHCD实验要求。 相似文献
18.
《Physics letters. [Part B]》1988,207(1):79-85
Recent observations of a deficit of cosmic ray muon-neutrino interactions in underground detectors suggest that the muon neutrinos may have oscillated to another state. We examine possible neutrino mass and mixing patterns, and their implications for vacuum and matter effects on solar neutrinos, on neutrinos passing through the earth, and on terrastrial neutrino beams. By invoking the see-saw mechanism of neutrino mass generation, we draw inferences on closure of the universe with neutrino masses, on the number of generations, on t-quark and fourth generation masses, and on the Peccei-Quinn symmetry breaking scale. Testable predictions are suggested. 相似文献
19.
The transformation properties of the projective canonical group are considered. It is shown that the group acts transitiv on functions defined on configuration space but not transitiv on those defined on the phase space. We prove moreover that this group is the largest finite-dimensional Lie group of point transformations determined on the configuration space. 相似文献
20.
用FTIR技术考察了甲醇在不同形态氧化锆上的吸附和活化转化行为.甲醇吸附在无定型和四方氧化锆上生成线式和桥式甲氧基物种,而在单斜氧化锆上还出现锥桥式甲氧基物种.在单斜和无定性氧化锆上的桥式羟基活泼而四方氧化锆上的线式羟基活泼.氧化锆表面吸附的甲氧基物种在晶格氧的作用下进一步转化,在单斜和无定性氧化锆上生成甲酸盐,并且可以进一步氧化为碳酸盐物种;而在四方氧化锆表面,甲氧基物种可以直接氧化为碳酸盐物种,这表明四方氧化锆的晶格氧比其他两种氧化锆上的更为活泼. 相似文献