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871.
872.
Water molecules and terephthalic acid, respectively, exist as a self-assembled monolayer of cyclic (H2O)6 clusters and (TA)infinity chiral chains between the zincophosphate sheets (in blue wires); the irremovable template H3tren3+ ions (in purple wires) are dynamic and could translate back and forth on the sheets during the conversion of the supramolecule contained in one another. 相似文献
873.
We study the class of rectilinear polygons, calledX – Y polygons, with horizontal and vertical edges, which are frequently used as building blocks for very large-scale integrated (VLSI) circuit layout and wiring. In the paper we introduce the notion of convexity within the class ofX – Y polygons and present efficient algorithms for computing theX – Y convex hulls of anX – Y polygon and of a set ofX – Y polygons under various conditions. Unlike convex hulls in the Euclidean plane, theX – Y convex hull of a set ofX – Y polygons may not exist. The condition under which theX – Y convex hull exists is given and an algorithm for testing if the given set ofX – Y polygons satisfies the condition is also presented. 相似文献
874.
By the reaction of sodium N,N′-ethylenedisalicylamidatocuprate ( I ) pentahydrate, Na2[Cu(samen)]·5H2O, with a manganese ( I ) salt and 2,2′-dipyridyl (bpy) or 1,10-phenanthroline (phen), the binuclear metal complexes [Cu(samen) Mn(L)2] (L ? bpy, phen) have been synthesized. Based on IR, elemental analyses and electronic spectra, the complexes are proposed to consist of a four-coordinated Cu( I ) in a distorted planar environment and Mn( I ) in a distorted octahedron. The complexes have been characterized with variable-temperature magnetic susceptibility (4.2—300 K) and the susceptibility data were least-squares fit to susceptibility equation derived from the spin Hamiltonian including single-ion zero-field interaction for Mn2+ ion, H?—2JS1·S2—DS, where D is the axial zero-field splitting parameter for the Mn(II) ion. The exchange integral, J, was found to be —34.6 and —28.8 cm?1 for [Cu(samen)Mn(bpy)2] and [Cu(samen)Mn(phen)2] respectively. The weak antiferromagnetic spin-exchange interaction can be interpreted by considering σ-π exchange pathway. 相似文献
875.
Electronic structures for armchair-edge graphene nanoribbons under a small uniaxial strain 总被引:2,自引:0,他引:2
W. H. Liao B. H. Zhou H. Y. Wang G. H. Zhou 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,76(3):463-467
We theoretically investigate the electronic structures for
armchair-edge graphene nanoribbons (AGNRs) under a small in-plane
uniaxial strain along armchair (longitudinal) and zigzag
(transversal) direction, respectively. We demonstrate that, by both
the tight-binding calculation and first-principles study, the
applying of a small asymmetrical strain results in variation of
energy subband spacing, which opens a band gap for metallic AGNRs
and modifies the band gaps for semiconducting AGNRs near the Fermi
level. It is believed that these results are of importance in the
band gap engineering and electromechanical applications of
graphene-nanoribbon-based devices. 相似文献
876.
X. H. Deng T. B. Wang J. T. Liu J. H. Huang T. B. Yu Q. H. Liao N. H. Liu 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,78(1):7-12
We proposed a type of heterostructure by combining two
photonic crystals (PCs) consisting of alternating negative-index materials
and positive-index materials layers. It is demonstrated by transfer matrix
method that the proposed structure has a polarization-independent
omnidirectional band gap (OBG), which is independent of the incident angle
for both TE and TM polarizations. Compared to a single PC, the frequency
range of the OBG in a heterostructure can be notably enlarged. Such a
structure has potential applications in improving planar microcavities,
optical fibers, and Fabry-Pérot resonators, etc. 相似文献
877.
Shan-tao Liao 《Frontiers of Mathematics in China》2006,1(1):1-52
Let M
n
be an n-dimensional compact C
∞-differentiable manifold, n ≥ 2, and let S be a C
1-differential system on M
n
. The system induces a one-parameter C
1 transformation group φ
t
(−∞ < t < ∞) over M
n
and, thus, naturally induces a one-parameter transformation group of the tangent bundle of M
n
. The aim of this paper, in essence, is to study certain ergodic properties of this latter transformation group.
Among various results established in the paper, we mention here only the following, which might describe quite well the nature
of our study.
(A) Let M be the set of regular points in M
n
of the differential system S. With respect to a given C
∞ Riemannian metric of M
n
, we consider the bundle
of all (n−2) spheres Q
x
n−2, x∈M, where Q
x
n−2 for each x consists of all unit tangent vectors of M
n
orthogonal to the trajectory through x. Then, the differential system S gives rise naturally to a one-parameter transformation group ψ
t
#
(−∞<t<∞) of
. For an l-frame α = (u
1, u
2,⋯, u
l
) of M
n
at a point x in M, 1 ≥ l ≥ n−1, each u
i
being in
, we shall denote the volume of the parallelotope in the tangent space of M
n
at x with edges u
1, u
2,⋯, u
l
by υ(α), and let
. This is a continuous real function of t. Let
α is said to be positively linearly independent of the mean if I
+
*(α) > 0. Similarly, α is said to be negatively linearly independent of the mean if I
−
*(α) > 0.
A point x of M is said to possess positive generic index κ = κ
+
*(x) if, at x, there is a κ-frame
,
, of M
n
having the property of being positively linearly independent in the mean, but at x, every l-frame
, of M
n
with l >
κ does not have the same property. Similarly, we define the negative generic index κ
−
*(x) of x. For a nonempty closed subset F of M
n
consisting of regular points of S, invariant under φ
t
(−∞ < t < ∞), let the (positive and negative) generic indices of F be defined by
Theorem
κ
+
*(F)=κ
−
*(F).
(B) We consider a nonempty compact metric space x and a one-parameter transformation group ϕ
t
(−∞ < t < ∞) over X. For a given positive integer l ≥ 2, we assume that, to each x∈X, there are associated l-positive real continuous functions
of −∞ < t < ∞. Assume further that these functions possess the following properties, namely, for each of k = 1, 2,⋯, l,
for each x∈X, each −∞ < s < ∞, and each −∞ < t < ∞.
Theorem
With X, etc., given above, let μ
be a normal measure of X that is ergodic and invariant under ϕ
t
(−∞
< t < ∞). Then, for a certain permutation k→p(k) of k= 1, 2,⋯, l, the set W of points x of X such that all the inequalities
(I
k
)
(II
k
)
(k=2, 3,⋯, l) hold is invariant under ϕ
t
(−∞
< t < ∞) and is μ-measurable with μ-measure1.
In practice, the functions h
xk
(t) will be taken as length functions of certain tangent vectors of M
n
. This theory, established such as in this paper, is expected to be used in the study of structurally stable differential
systems on M
n
.
Translated from Qualitative Theory of Differentiable Dynamical Systems, Beijing, China: Science Press, 1996, by Dr. SUN Wen-xiang, School of Mathematical Sciences, Peking University, Beijing 100871,
China. The Chinese version of this paper was published in Acta Scientiarum Naturalium Universitatis Pekinensis, 1963, 9: 241–265, 309–326 相似文献
(i*) | h k (x, t) = h xk (t) is a continuous function of the Cartesian product X×(−∞, ∞). |
(ii*) |
878.
The real-space densities of a polarized strongly interacting two-component Fermi gas of 6Li atoms reveal two low-temperature regimes, both with a fully paired core. At the lowest temperatures, the unpolarized core deforms with increasing polarization. Sharp boundaries between the core and the excess unpaired atoms are consistent with a phase separation driven by a first-order phase transition. In contrast, at higher temperatures the core does not deform but remains unpolarized up to a critical polarization. The boundaries are not sharp in this case, indicating a partially polarized shell between the core and the unpaired atoms. The temperature dependence is consistent with a tricritical point in the phase diagram. 相似文献
879.
The skeletal rearrangement of bicyclo[2.2.2]lactones, involving a mild and chemoselective palladium-catalysed translocation key-step, provides an efficient and diastereoselective access to synthetically useful bicyclo[3.3.0]lactones. 相似文献
880.
Weng CC Liao JD Wu YT Wang MC Klauser R Zharnikov M 《The journal of physical chemistry. B》2006,110(25):12523-12529
The modification of octadecanethiolate self-assembled monolayers on Au and Ag by nitrogen-oxygen downstream microwave plasma with variable oxygen content (up to 1%) has been studied by synchrotron-based high-resolution X-ray photoelectron spectroscopy. The primary processes were dehydrogenation, desorption of hydrocarbon and sulfur-containing species, and the oxidation of the alkyl matrix and headgroup-substrate interface. The exact character and the rates of the plasma-induced changes were found to be dependent on the substrate and plasma composition, with the processes in the aliphatic matrix and headgroup-substrate interface being mostly decoupled. In particular, the rates of all major plasma-induced processes were found to be directly proportional to the oxygen content in the plasma, which can be, thus, considered as a measure of the plasma reactivity. Along with the character of the observed changes, exhibiting a clear dominance of the oxidative processes, this suggests that the major effect of the oxygen-nitrogen downstream microwave plasma is provided by reactive oxygen-derived species in the downstream region, viz. long-living oxygen radicals and metastable species. 相似文献