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排序方式: 共有163条查询结果,搜索用时 31 毫秒
81.
82.
Nguyen CN Isaacson JI Shimmyo KB Chen A Stratt RM 《The Journal of chemical physics》2012,136(18):184504
It has been suggested that the most-efficient pathway taken by a slowly diffusing many-body system is its geodesic path through the parts of the potential energy landscape lying below a prescribed value of the potential energy. From this perspective, slow diffusion occurs just because these optimal paths become particularly long and convoluted. We test this idea here by applying it to diffusion in two kinds of well-studied low-dimensional percolation problems: the 2d overlapping Lorentz model, and square and simple-cubic bond-dilute lattices. Although the most efficient path should be at its most dominant with the high-dimensional landscapes associated with many-body problems, it is useful to examine simpler, low-dimensional, constant-potential-energy problems such as these ones, both because the simpler models lend themselves to more accurate geodesic-path-finding approaches, and because they offer a significant contrast to many of the models used in the traditional energy-landscape literature. Neither the continuum nor the lattice percolation examples are adequately described by our geodesic-path formalism in the weakly disordered (relatively-fast-diffusion) limit, but in both cases the formalism successfully predicts the existence of the percolation transition and (to a certain extent) the slow diffusion characteristic of near-percolation behavior. The numerical results for these models are not nearly accurate enough near their transitions to describe critical exponents, but the models do showcase the qualitative validity of the geodesic perspective in that they allow us to see explicitly how tortuous and sparse the optimal pathways become as the diffusion constants begin to vanish. 相似文献
83.
In-situ Investigation of BBr_3/benzene Solution by Fourier Transformation Infrared Spectroscopy 总被引:1,自引:0,他引:1
YU Li-li GAI Li-gang CUI De-liang WANG Qi-long . State Key Laboratory of Crystal Materials Sh ong University Jinan P. R. China . School of Chemical Engineering Sh ong Institute of Light Industry Jinan 《高等学校化学研究》2009,25(5):733-737
By means of the in-situ Fourier transformation infrared spectroscopy(FTIR), the properties of BBr3/benzene solution, which is usually used as the reactant and solution to synthesize BN by benzene-thermal method, have been investigated. The results show that there are some side reactions between BBr3 and benzene: (1) BBr3 as an electron-deficient molecule reacts with benzene at room temperature; (2) below 100 °C, substitution of Br atom for H atom of benzene(ring―H) dominates in BBr3/benzene solution; (3) cr... 相似文献
84.
Crystal Hoyt 《Israel Journal of Mathematics》2012,192(1):251-280
We classify good ?-gradings of basic Lie superalgebras over an algebraically closed field $\mathbb{F}$ of characteristic zero. Good ?-gradings are used in quantum Hamiltonian reduction for affine Lie superalgebras, where they play a role in the construction of super W-algebras. We also describe the centralizer of a nilpotent even element and of an $\mathfrak{s}\mathfrak{l}_2$ -triple in $\mathfrak{g}\mathfrak{l}\left( {\left. m \right|n} \right)$ and $\mathfrak{o}\mathfrak{s}\mathfrak{p}\left( {\left. m \right|2n} \right)$ . 相似文献
85.
86.
Dr. Ryan J. Rafferty Robert W. Hicklin Katherine A. Maloof Prof. Paul J. Hergenrother 《Angewandte Chemie (International ed. in English)》2014,53(1):220-224
Many compound screening collections are populated by members that possess a low degree of structural complexity. In an effort to generate compounds that are both complex and diverse, we have developed a strategy that uses natural products as a starting point for complex molecule synthesis. Herein we apply this complexity‐to‐diversity approach to abietic acid, an abundant natural product used commercially in paints, varnishes, and lacquers. From abietic acid we synthesize a collection of complex (as assessed by fraction of sp3‐hybridized carbons and number of stereogenic centers) and diverse (as assessed by Tanimoto analysis) small molecules. The 84 compounds constructed herein, and those created through similar efforts, should find utility in a variety of biological screens. 相似文献
87.
The capabilities of a compact and highly efficient NdAl 3 (BO 3) 4 (NAB) thin-disk laser are demonstrated.Under a pump power of 8.2 W,the NAB disk laser delivers an average output power of 4.6 W at 1 063 nm,with a slope efficiency of 64%.The difficulty and complexity of the thin-disk laser design are minimized by the high absorbance of the NAB crystal.To reduce the thermal effect,low repetition frequency pulsed 885 nm direct pumping is considered an efficient way to realize a compact and highly efficient NAB thin-disk laser. 相似文献
88.
David J. Wiedenfeld Vladimir N. Nesterov Mark A. Minton Crystal L. Montoya 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(7):o536-o538
The title compounds, 1‐chloro‐3,6‐dimethoxy‐2,5‐dimethylbenzene, (IIIa), and 1‐chloro‐3,6‐dimethoxy‐2,4‐dimethylbenzene, (IIIb), both C10H13ClO2, were obtained from 2,5‐ and 2,6‐dimethyl‐1,4‐benzoquinone, respectively, and are intermediates in the synthesis of ammonium quinone derivatives. The isomers have different substituents around the methoxy groups and crystallize in different space groups. In both molecules, the methoxy groups each have different orientations with respect to the benzene ring. In both cases, one methoxy group lies in the plane of the ring and can participate in conjugation with the aromatic system, while the second is almost perpendicular to the plane of the aromatic ring. The C—O—C bond angles around these substituents are also different: 117.5 (4) and 118.2 (3)° in (IIIa) and (IIIb), respectively, when the methoxy groups lie in the plane of the ring, and 114.7 (3) and 113.6 (3)° in (IIIa) and (IIIb), respectively, when they are out of the plane of the ring. 相似文献
89.
激光二极管抽运被动调Q周期极化铌酸锂腔内倍频激光特性的研究 总被引:1,自引:0,他引:1
提出了将饱和吸收Cr^4 :YAG晶体被动调Q开关同时作为布儒斯特片在三镜V型折叠谐振腔中起像散补偿作用的腔内倍频设计方案。在连续激光二极管端面抽运情况下,给出了V型谐振腔结构光束束腰半径和位置、像散补偿Cr^4 :YAG晶体的厚度和谐振腔折光角度的设计方法以及计算公式。采用周期极化铌酸锂晶体作为倍频元件,由于谐振腔内的基波和谐波具有相同的偏振办向,避免了腔内双折射引起的绿光噪声问题,得到了输出稳定的序列脉冲。在连续抽运功率为500 mW时,得到了平均功率12.7mW的脉冲绿光输出。 相似文献
90.