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81.
Anodic formation of titania nanowires has been interpreted using a bamboo-splitting model; however, a number of phenomena are difficult to explain with this model. Herein, transition from nanotubes to nanowires is investigated by varying the anodizing conditions. The results indicate that the transition requires a large number of hydrogen ions to reduce the passivated area of tube walls, and therefore can be observed only in an intermediate chemical dissolution environment. Accordingly, a model in terms of stretching and splitting is proposed to interpret the transition process. The model provides a basis to suppress the nanowires with surface treatments before anodization and to clear the nanowires with an ultrasonication process after anodization. The nanotube-nanowire transition also arises when the tubes are directly used in dye-sensitized solar cells. Treatment with titanium tetrachloride solution for about 10 h is found to be effective in suppressing the nanowires, and thus improving the photovoltaic properties of the solar cells. 相似文献
82.
Synergy effects are the motives to enter into strategic alliances; however due to lack of adequate preparation or planning, these alliances often fail. It is of no doubt that a successful strategic alliance depends on choosing the correct alliance partners and appropriate resource allocation. In this paper, the fuzzy multi-objective dummy programming model is proposed to overcome the above-mentioned problems. Two types of strategic alliances, joint ventures and mergers and acquisitions (M&A), are demonstrated to choose the best alliance partners and allocate the optimal alliance resources in a numerical example. Based on the results, our method can provide the optimal alliance cluster and satisfaction in strategic alliances. 相似文献
83.
The voltage power spectrum of NbSe3 has been studied in the upper charge-density wave (CDW) state where only one CDW exists. In the non-Ohmic regime sharp spikes appear in the spectrum. The frequency of these spikes increases monotonically with current as in the lower CDW state. We study the “fine structure” of the spectrum and find evidence for “frequency pulling” between the modes. A linear coupled-mode treatment is used to model this effect. There is also evidence of heterodyning of an intrinsic (current independent) 2MHz mode. We briefly discuss these phenomena in terms of Fröhlich sliding conductivity. Difficulties with the simple two-fluid model as well as models based on solid state turbulence are pointed out. 相似文献
84.
Viscosities of solutions of polystyrene in toluene were measured for concentrations up to 400 kg m?3 at 298 K. Polymers of molecular weights ranging from 8.7 × 103 to 2.4 × 106 were used. It is observed that viscosity of the polymer solution increases with increasing concentration and molecular weight; the rate of increase is greater at higher values of the two parameters. A master curve for the system is constructed by using the experimental data for viscosity, concentration and molecular weight of the polymer. Regions of various polymer interactions in solution are identified. 相似文献
85.
86.
Ong Chong Pin 《Advances in Mathematics》1975,15(3):269-311
Classical or Newtonian Mechanics is put in the setting of Riemannian Geometry as a simple mechanical system (M, K, V), where M is a manifold which represents a configuration space, K and V are the kinetic and potential energies respectively of the system. To study the geometry of a simple mechanical system, we study the curvatures of the mechanical manifold (Mh, gh) relative to a total energy value h, where Mh is an admissible configuration space and gh the Jacobi metric relative to the energy value h. We call these curvatures h-mechanical curvatures of the simple mechanical system.Results are obtained on the signs of h-mechanical curvature for a general simple mechanical system in a neighborhood of the boundary ?Mh = {xεM: V(x) = h} and in a neighborhood of a critical point of the potential function V. Also we construct functions defined globally on Mh, called curvature functions which characterize the sign of the h-mechanical curvature. Applications are made to the Kepler problem and the three-body problem. 相似文献
87.
We present here a different and modified configuration in order to obtain the curvature fringes by incorporating phase shifting and image processing techniques. Optical fibers are used for obtaining shear fringes in which we have used Wollaston prism as the shear element. 相似文献
88.
89.
Nonstationary phase processes are defined and a surrogate distribution approximation (SDA) method for analyzing transient and nonstationary queueing systems with nonstationary phase arrival processes is presented. Regardless of system capacityc, the SDA method requires the numerical solution of only 6K differential equations, whereK is the number of phases in the arrival process, compared to theK(c+1) Kolmogorov forward equations required for the classical method of solution. Time-dependent approximations of mean and variance of the number of entities in the system and the number of busy servers are obtained. Empirical test results over a wide range of systems indicate the SDA is quite accurate.This research was partially funded by National Science Foundation grant ECS-8404409. 相似文献
90.
The thermal conductivity, κ, of NbSe3 has been measured by novel self-heating techniques that allowed the electric field dependence of κ to also be measured. Measurements were made from 35 K to room temperature. Above the charge density wave transitions, the phonon thermal conductivity is 4–7 times the electron thermal conductivity, and it rises smoothly below the transitions, indicating that phonon-phonon scattering predominates. Phonon mean free parths have been estimated at 187 A° at 60 K and 60 A° at 150 K. No clear anomalies were observed at the phase transitions, giving upper limits to changes in the phonon mean free path. No field dependence of κ was observed. 相似文献