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131.
A new percolation problem is posed where the sites on a lattice are randomly occupied but where only those occupied sites with at least a given numberm of occupied neighbors are included in the clusters. This problem, which has applications in magnetic and other systems, is solved exactly on a Bethe lattice. The classical percolation critical exponents=gg=1 are found. The percolation thresholds vary between the ordinary percolation thresholdp
c
(m=1)=l/(z – 1) andp
c(m=z) =[l/(z – 1)]1/(z–1). The cluster size distribution asymptotically decays exponentially withn, for largen, p p
c
.Supported in part by National Science Foundation grant DMR78-10813. 相似文献
132.
CHEN Wen-Tong GUO Guo-Cong ZENG Xi-Rui LI Xin-Fa FANG Xiao-Niu KUANG Han-Mao LIU Dong-Sheng LIU Li-Min 《结构化学》2007,26(10)
The title compound (4,4'-H2bipy)[CdBr4]·H2O 1 has been synthesized via hydrothermal reaction and characterized by X-ray diffraction. The crystal belongs to monoelinic,space group P21/c with a=8.260(3), b=23.926(7), c=9.774(2) (A), β=106.777(9)°,C10H12Br4CdN2O, Mr=608.26, V=1849.4(9)(A)3, Z=4, Dc=2.185 g/cm3, S=1.005, μ(MoKα)=9.814 mm-1, F(000)=1128, R=0.0646 and wR=0.0989. The crystal structure analysis of 1reveals that the title compound features an isolated structure, based on discrete 4,4'-H2bipy moieties and lattice water molecules which are linked by hydrogen bonds together with tetrahedral cadmium atoms terminally coordinated by four bromine atoms. 相似文献
133.
134.
Capillary gc is now rapidly expanding. Naturally, initiation is most often attempted on the basis of the experience acquired with packed columns. However, such an extrapolation is successful only if a number of essential peculiarities of capillary gc are considered. Based on practical examples this paper discusses six essential details: 1) design and maintenance of the gas flow paths, 2) the greatly increased importance of sampling technique, which should not be confined just to stream splitting, 3) the problems in quantitative analysis arising from small sample size, 4) specific sources of trouble related to small amounts of liquid phase, 5) specific arguments for the choice of the carrier gas, clearly pointing to hydrogen as the ideal carrier and, 6) the different way to approach column production. Figures for all selected examples are given. 相似文献
135.
For lattices with two kinds of points (black and white), distributed according to a translation-invariant joint probability distribution, we study statistical properties of the sequence of consecutive colors encountered by a random walker moving through the lattice. The probability distribution for the single steps of the walk is considered to be independent of the colors of the points. Several exact results are presented which are valid in any number of dimensions and for arbitrary probability distributions for the coloring of the points and the steps of the walk. They are used to derive a few general properties of random walks on lattices containing traps.Presented at the Symposium on Random Walks, Gaithersburg, MD, June 1982. 相似文献
136.
The ionic transport process in polymer electrolytes (such as polyethylene oxide) wassimulated numerically on a two dimensional square lattice where charge carriers areaccommodated by the lattice sites connected randomly with available bonds to represent theamorphous chain configuration. Following the dynamic bond percolation theory(DBPT),the chainmotion contribution to the ionic conduction was incorporated via periodical renewal of the randombond configuration. To check and extend the prediction made by DBPT employing global abruptbond renewal,spatial correlation of the bond reassignment was introduced to the system by: 1)regional bond renewal and 2) organized bond motion. It is found that the difference between thediffusivities simulated involving regional bond renewal and those of DBPT becomes negligiblewhen the bond renewal rate approaches the carrier hopping rate. 相似文献
137.
Uekawa N Kajiwara J Kakegawa K Sasaki Y 《Journal of colloid and interface science》2002,250(2):285-290
An ethanol solution of Ti-peroxy compounds was prepared from the ethanol solution of titanium isopropoxide (Ti(O-iPr)4) and H2O2. Heating of the ethanol solution of the Ti-peroxy compounds at 348 K formed a Ti-peroxy gel, and heat treatment of the gel at 348 K for more than 6 h formed gels that consisted of anatase nanoparticles. The diameter of the anatase nanoparticles increased from 9 to 15 nm as the heating time increased from 6 to 48 h. According to the results of the N2 adsorption measurement, the anatase nanoparticles had micropores, and the specific surface area (SBET) was in the range of 254 to 438 m2/g. The particle size, lattice strain, specific surface area, and photocatalytic activity of the anatase nanoparticles can be regulated by the heating time of the Ti-peroxy gel at 348 K. 相似文献
138.
Sumio Kato Masataka Ogasawara Mikio Sugai Shinichi Nakata 《Catalysis Surveys from Asia》2004,8(1):27-34
Studies on the role of oxygen vacancy in structural change of nonstoichiometric perovskites and a property of oxygen-deficient perovskite-related K2NiF4 compounds are reviewed.The structural changes on which the authors focused are cation ordering and lattice distortion. The relationship between the distortion and oxygen vacancy was investigated by comparing the structures of Sr2(Sr1-xMx)TaO6-d (M = Ca2+ and Nd3+) solid solutions. It was found that distortion of a perovskite-type lattice decreased with an increasing amount of oxygen vacancies. In order to investigate the relationship between the cation ordering on octahedral sites and oxygen vacancy, structures of stoichiometric Sr2-xLaxCo1-yTa1+yO6 and oxygen-deficient Sr2-xLaxMg1-yTa1+yO6-d solid solutions were compared. The authors' work reveals that the cation ordering affects the amount of oxygen vacancies in addition to cation charge and size. 相似文献
139.
Ogata Atsushi Mizuno Koichi Kushiyama Satoshi Yamamoto Toshiaki 《Plasma Chemistry and Plasma Processing》1998,18(3):363-373
The behavior of lattice oxygen species of the ferroelectric material during methane oxidation was investigated using a nonthermal plasma reactor packed with BaTiO
3
pellets. Lattice oxygen species in BaTiO
3
play an important role in the formation of N
2
O and the oxidation of CH
4
. The oxidation products such as CO and CO
2
were formed from independent reaction pathways. Lattice oxygen species were able to preferentially oxidize the carbon species deposited on the pellet surface into CO. Also, N
2
O and NO
x
were independently formed in the N
2–O
2
reaction, suggesting that different oxygen species give N
2
O and NO
x. N
2
O was produced by the oxidation of molecular nitrogen with lattice oxygen species. 相似文献
140.
The heteronuclear cross-relaxation rates in polymers were determined by selective and conventional ~(13)C spin-lattice relaxation experiments, the proton-carbon distances were calculated by the theoretical formula, and two-dimensional NOE spectra of the polymers were also measured. The results showed that (1) the measured proton-carbon distances coincide with the distances from molecular models, (2) there is the observable dipolar cross-relaxation effect between the quaternary carbons and their neighboring protons, and (3) the optimum mixing times depend on the relaxation properties of the proton and carbon. 相似文献