离子型共聚单体参与下的全氟丙烯酸酯无皂乳液共聚

离子型共聚单体参与下的全氟丙烯酸酯无皂乳液共聚;全氟烷基丙烯酸酯;无皂乳液;离子型共聚单体     

A 1.107 μm Yb3+-doped Phosphate Fiber Laser Pumped by a Ti:sapphire

Lasers and amplifiers in a single fiber have been developed rapidly, especially for optical fiber communication and various sensors, in the recent years. However, remarkable progress and achievement have been made mainly in silica fiber doped with rare earth elements. In this paper, we report the progress on the development of the Yb3+-doped phosphate fiber laser.     

Hydrophobic/hydrophilic solvation: inferences from Monte Carlo simulations and experiments

In this study Monte Carlo simulations are used to determine the solvation properties of model hydrophobic (xenon and hard sphere) and hydrophilic (dimethyl ether) solutes in SPC/E water. Various contributions to the experimental solvation entropy, including the solvent reorganization entropy, have been determined. The main conclusion drawn, which is in accord with solubility data, is that poor solubility correlates with poor solute-water interaction. At room temperature, energy dominates the aqueous solubility of both hydrophobic and hydrophilic solutes, rather than entropy. However, at higher temperatures the solubility can pass through a minimum, and then entropy becomes dominant. Another interesting finding is the presence of larger than expected cavities in water. Two different simulation results support this finding. This unexpected hollow structure in water explains why a hard sphere solute is more soluble in water than in a comparable hard sphere or Lennard-Jones solvent. Hydrogen bonding causes water to aggregate into clusters that produce a few large cavities rather than many smaller cavities. The propensity for clustering also explains why water gives the illusion of being a low density liquid. Sufficient theoretical apparatus is developed to connect theoretical solvation properties to those measured by simulation and experiment. Finally, based on gas solubility, an intuitive hydrophobic/hydrophilic scale is developed.     

Relation between the distribution of initiation sites of a discharge and the field nonuniformity at an electrode

The connection between the field nonuniformity at an electrode and the distribution of discharge initiation sites over its surface is described. The results of experiments on the breakdown of transformer oil in the cone-plane system of electrodes is analyzed within the framework of a multifractal model of the charge distribution [1]. The conclusion given in [1] that the regions with the maximum local field strength are not always the most probable sites for initiation of a discharge was experimentally confirmed. We observed the theoretically predicted transition of the discharge initiation sites at sharp points on the surface of a cone. For electrodes of stainless steel and transformer oil a value of the index relates the probability of initiation of a discharge to the local field strength was determined.Scientific — Research Institute of High Voltages at Tomsk Polytechnic Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 32–35, April, 1995.     

A molecular dynamics study of carbon dioxide in water: diffusion,structure and thermodynamics

Atomistic simulations are reported of a model of CO₂ in water. CO₂ is modelled by partial charges and Lennard-Jones interaction sites on each atom; the SPC/E model for water is used. Good agreement with experiment is found for the translational diffusion constants. The variation of the dynamics with the potential parameter was investigated. As expected, the orientational correlation times increase as the magnitude of the quadrupole moment is increased, but the translational diffusion constants are found to be surprisingly insensitive to the magnitude of the CO₂ quadrupole moment. The translational friction coefficient was resolved into electrostatic, Lennard-Jones and cross-terms; the Lennard-Jones contribution is found to be the largest. Varying the Lennard-Jones size parameter affects both translational and reorientational motion. In order to try to understand these results further, the variation of solvation free energy was investigated and the solvent structure around carbon dioxide was examined as the electrostatic and Lennard-Jones parameters were changed. The temperature dependence of the self-diffusion constant of pure SPC/E water was determined.     

Impulsive-discharge formation in water

This paper reports on research on an impulsive electrical discharge in deionized water (=2 × 10⁴ · m) in the voltage range 17–50 kV. The research showed that the discharge proceeds through the development of subsonic (U=17–22 kV) or supersonic (U=25–50 kV) streamers, depending on the electric-field strength at the surface of the tip. When voltage impulses having an amplitude of 20–25 kV are unleashed, the development of both types of streamers is observed in the discharge gap. The experiments carried out by the authors do not confirm the hydrodynamic origin of the disturbances at the initiating electrode that give rise to the discharge's development. The authors hypothesize that streamer development is due to the ionization of water molecules. The energy expenditures to ionize the molecules in the streamer channel are estimated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 88–92, January, 1989.