Friction phenomena and phase transition in the underdamped two-dimensional Frenkel-Kontorova model

Locked-to-sliding phase transition has been studied in the driven two-dimensional Frenkel-Kontorova model with the square symmetric substrate potential. It is found that as the driving force increases, the system transfers from the locked state to the sliding state where the motion of particles is in the direction different from that of driving force. With the further increase in driving force, at some critical value, the particles start to move in the direction of driving force. These two critical forces, the static friction or depinning force, and the kinetic friction force for which particles move in the direction of driving force have been analyzed for different system parameters. Different scenarios of phase transitions have been examined and dynamical phases are classified. In the case of zero misfit angle, the analytical expressions for static and kinetic friction force have been obtained.

Enhance the optical absorptivity of nanocrystalline TiO2 film with high molar extinction coefficient ruthenium sensitizers for high performance dye-sensitized solar cells

We report two new heteroleptic polypyridyl ruthenium complexes, coded C101 and C102, with high molar extinction coefficients by extending the pi-conjugation of spectator ligands, with a motivation to enhance the optical absorptivity of mesoporous titania film and charge collection yield in a dye-sensitized solar cell. On the basis of this C101 sensitizer, several DSC benchmarks measured under the air mass 1.5 global sunlight have been reached.

Conjugation of Selenophene with Bipyridine for a High Molar Extinction Coefficient Sensitizer in Dye-Sensitized Solar Cells

A high molar extinction coefficient heteroleptic polypyridyl ruthenium sensitizer, featuring a conjugated electron-rich selenophene unit in its ancillary ligand, has been synthesized and demonstrated as an efficient sensitizer in dye-sensitized solar cells. A nanocrystalline titania film stained with this sensitizer shows improved optical absorptivity, which is highly desirable for dye-sensitized solar cells with a thin photoactive layer. With preliminary testing, this sensitizer has already achieved a high efficiency of 10.6% measured under the air mass 1.5 global conditions.

An Extremely High Molar Extinction Coefficient Ruthenium Sensitizer in Dye-Sensitized Solar Cells: The Effects of pi-Conjugation Extension

We report a heteroleptic ruthenium complex (007) featuring the electron-rich 5-octyl-2,2'-bis(3,4-ethylenedioxythiophene) moiety conjugated with 2,2-bipyridine and exhibiting 10.7% power conversion efficiency measured at the AM1.5G conditions, thanks to the enhanced light-harvesting that is closely related to photocurrent. This C107 sensitizer has an extremely high molar extinction coefficient,of 27.4 x 10(3) M-1 cm(-1) at 559 nm in comparison to its analogue C103 (20.5 x 10(3) M-1 cm(-1) at 550 nm) or Z907 (12.2 x 10(3) M(-1)cm(-1) at 521 nm) with the corresponding 5-hexyl-3,4-ethylenedioxythiopliene- or nonyl-substituted bipyridyl unit. The augmentation of molar extinction coefficients and the bathochromic shift of low-energy absorption peaks along with the pi-conjugation extension are detailed by TD-DFT calculations. The absorptivity of mesoporous titania films grafted with Z907, C103, or C107 sublinearly increases with the molar extinction coefficient of sensitizers, which is consistent with the finding derived from the surface coverage measurements that the packing density of those sensitizers decreases with the geometric enlargement of ancillary ligands.

Estimation thermal expansion coefficient from lattice energy for inorganic crystals

By using the study of the lattice energy and the structural parameters of binary inorganic crystals, a new parameter reflecting the thermal expansion property has been found, the relation between the linear expansion coefficient and new parameter has been established. A semiempirical method for evaluation of linear expansion coefficient from the lattice energy is presented, and developed to the complex crystals. The estimated values of the linear expansion coefficients of both simple and complex crystals are in good agreement with the experimental values.

Calculation of the thermal expansion coefficient for Bi2Sr2CaCu2O8

An estimation method of thermal expansion coefficient in term of lattice energy which was developed earlier for simple materials is extended to a complex material of Bi2Sr2CaCu2O8 (Bi-2212). The calculation of the chemical bond property and thermal expansion coefficient of Bi-2212 has been carried out and the theoretical values were in good agreement with the corresponding experimental results. The dependence of the thermal expansion coefficient on the different structures and on the flexible oxidation states of Bi and Cu are investigated. The results indicate that the thermal expansion coefficients of Bi-2212 are insensitive to the low lattice distortion of the average structure and the changes of formal valences of Bi and Cu ions.

A novel electrochemical method for simultaneously measuring diffusion coefficient and ion transference number

This paper introduces a new method to estimate the diffusion coefficient and transference number of a salt or an electroactive ion in a solution with little or no supporting electrolyte. The above two parameters can be obtained from a single potential step experiment without previous knowledge of either one. It would appear that the method could also be used in the study of ion transport in a high viscosity solvent or a solid electrolyte. (C) 1998 Elsevier Science S.A.

Dependence of linear electro-optic coefficient on difference in the atomic sizes in zinc blende crystals

Covalent radii of the bonding elements have strong effects on the linear electro-optic coefficients of zinc blende crystals; these effects can be quantitatively determined by investigating the relation between the difference in the atomic sizes rho and the magnitude of the linear electro-optic tensor coefficient r(41). It is interesting to note that for the same cation Zn2+, Ga3+, or In3+ the magnitude of r(41) increases with increased covalent radius of the bonded anion r(beta). Especially with the increasing tendency of the parameter rho, the magnitude of r(41) of crystals that have a same cation will increase suddenly when the value of r(beta) becomes larger. (C) 1997 Academic Press.

Study on relationship between partition coefficient of compounds and topological indices

In this work, the A(m) indices and the molecular connectivity indices of fifty aromatic compounds have been calculated, and applied for studying on relationship between partition coefficient and structure of aromatic compounds. The results demonstrate that the property of compounds can be described better with revisionary A(m) indices.

Calculation of the nonlinear optical coefficient of the NdAl3(BO3)(4) crystal

For the first time, we present the calculation of the nonlinear optical coefficient of the NdAl3(BO3)(4) (NAB) crystal from a systematic and quantitative standpoint. Based on the dielectric theory of complex crystals and the Levine bond charge model, the method of calculation of the second-order nonlinear optical tensor coefficients of complex crystals has been given systematically. The chemical bond parameters and linear and nonlinear susceptibilities of the NAB crystal have been calculated in detail, and the calculated value of d(11)(NAB) is -5.81 x 10(-9) esu, which agrees with the measured value of 4.06 x 10(-9) esu.

STUDY ON MEASUREMENT OF DIFFUSION-COEFFICIENT OF LI ATOM IN LIQUID ALUMINUM

The tess potential-concentration curve was first applied to measure the concentration of an alloy. Attempt to use the V-c curve of Al-Li alloy in measuring the diffusion coeffictent of Li atom in liquid aluminium with anode chronopotentiometry at 720℃, was made and D_(Li/Al=4.94×10~(-5)cm~2·s~(-1) was obtained. The value is well consistent wish the theoretical value, D_(Li/Al)=4.85×10~(-5)cm~2·s~(-1) in terms of Stokes-Einstein equation.

Improvement of different source function expressions in SWAN model for the Bohai Sea

The simulating wave nearshore (SWAN) wave model has been widely used in coastal areas, lakes and estuaries. However, we found a poor agreement between modeling results and measurements in analyzing the chosen four typical cases when we used the default parameters of the source function formulas of the SWAN to make wave simulation for the Bohai Sea. Also, it was found that at the same wind process the simulated results of two wind generation expressions (Komen, Janssen) demonstrated a large difference. Further study showed that the proportionality coefficient alpha in linear growth term of wave growth source function plays an unperceived role in the process of wave development. Based on experiments and analysis, we thought that the coefficient alpha should change rather than be a constant. Therefore, the coefficient alpha changing with the variation of friction velocity U (*) was introduced into the linear growth term of wave growth source function. Four weather processes were adopted to validate the improvement in the linear growth term. The results from the improved coefficient alpha agree much better with the measurements than those from the default constant coefficient alpha. Furthermore, the large differences of results between Komen wind generation expression and Janssen wind generation expression were eliminated. We also experimented with the four weather processes to test the new white-capping mechanisms based on the cumulative steepness method. It was found that the parameters of the new white-capping mechanisms are not suitable for the Bohai Sea, but Alkyon's white-capping mechanisms can be applicable to the Bohai Sea after amendments, demonstrating that this improvement of parameter alpha can improve the simulated results of the Bohai Sea.

天津滨海新区软土不同含砂量的强度特征研究

Based on the features of soft soil in Tianjing Coastal New Developing Area, this kind of soil with different content of sand was researched systematically, according to the indoor experiment, about its characteristics of strength and deformation. The main results are summarized in the following: Firstly, on the basis of geological engineering investigation, the systemic experiments about the physical characteristics were conducted. The test soil samples were taken from the gray and gray-yellow silty soft soil which was formatted by near-shore marine sediment and marine-continental interactive sediment. The original condition of the sample soil was in saturation and the basic indexes are: liquid limit36.1%, plastic limit 18.8%, plasticity index. Then, the condensation characteristics of the soft soil were analyzed through high-pressure consolidation tests. The results show that，in various loading serials, the coefficient of compressibility under P=100kPa and 200kPa are all larger than 0.5MPa-1. So the sample soil is a kind of high-compressibility soil. Secondly, triaxial strength of undisturbed soil and remoulded soil was researched by using triaxial test. The types of stress-strain curve of both undisturbed and remoulded soil are the stress stabilization and softening type, which show the specific plastic character. Furthermore, the cohesion and friction angle of undisturbed soil changes, when the ambient pressure is different, instead of a stable value for all time; the cohesion and friction angle of remoulded soil changes with the compactness and sand-carrying capacity which is wholly higher than undisturbed soil. At last, the stress-strain results of both undisturbed and remoulded soil were normalized by using the ambient pressure as the normalization factor. The results show that, there are all some normalization characters in both undisturbed and remoulded soil, however, the feature of normalization of undisturbed soil is worse than the remoulded ones. The main reason is that the undisturbed samples are worse in equality and the unavoidable disturb through the process of sampling and experiments will also make them can not put up good normalization. Therefore, it is feasible to normalize the soil in Tianjing Coastal New Developing Area with the ambient pressure as normalization factor.