Passive or unassisted ion permeation through lipid bilayers involves a type of rare events by which cells regulate their salt concentrations and pH. It is important to understand its mechanism in order to develop technologies of, for example, delivering or maintaining small drug-like molecules inside cells. In earlier simulations of passive ion permeations, the commonly used sampling methods usually define the positions of ions relative to the membrane as a measure of permeation, i.e., the collective variable, ignoring the active participations of other particles. Newly defined collective variables involving the movements of ions, lipids, and water molecules allow us to identify the transition paths on the free energy landscape using the 2D umbrella sampling techniques. In this work, this technique was used to study the permeation processes of some well-known ions, sodium, potassium, and chloride. It is found permeations of sodium and potassium are assisted by important lipid bilayer deformations and massive water solvation, while chloride may not. Chloride may have two different possible pathways, in which the energetic favorable one is similar to the solubility-diffusion model. The free energy barriers for the permeation of these ions are in semiquantitative agreement with experiments. Further analyses on the distributions of oxygens and interaction energies suggest the electrostatic interactions between ions and polar headgroups of lipids may greatly influence membrane deformation as well as the water wire and furthermore the free energy barriers of waterwire mediated pathways. For chloride, the nonwaterwire pathway may be energetically favorable.

This paper presents a new method for measuring AC field strength, with application of electrostriction effect of electrostrictive ceramics and technology of fiber Bragg grating. We use electrostriction effect to design the fiber-optic electric field sensor. This device turns the strain of electrostriction material influenced by electric field into the strain of fiber Bragg grating, then wavelength of feedback changes. We can get the strain of electrostriction material through the comparison between initial wavelength and wavelength of feedback, then measurement of electric field strength can be achieved by detecting the strain of electrostriction material. Experiments indicate that fiber-optic electric field sensor based on electrostriction effect is of effective value for measuring electric field strength, and the response of measuring system to AC electric field is linear. We apply an effective method for the research of measuring electric field strength.

Based on the UHVDC project from Hami to Zhengzhou, two typical faults for transient stress calculation of DC filter including ground fault on the DC line and incoming switching surge on the DC line are presented. The simulation steep-fronted models and factors including protective characteristics of arresters, parasitic inductances should be considered for these two faults are introduced. The protective level of arresters are obtained according to the calculated maximum according current of arresters, and the insulation levels of the filter equipment are defined according to the insulation margin. The research can provide technical supports for project construction.

Using Matlab/Simulink software established the simulation model of UHV transformer and UHV power grid.The characteristic of magnetizing inrush current for UHV transformer was obtained by simulation.The paper also analyzed the impact on differential protection from it. Closing resistor inside circuit breaker method was proposed to restrain magnetizing inrush current.The method cuts down the amplitude and accelerated the attenuation speed of it, so as to restrain it. The simulation analysis verified the effectiveness of the method.

Anisotropic etching process by potassium hydroxide (KOH) and isopropyl alcohol (IPA) mixed solution in the [100] orientation silicon wafer was studied experimentally. The effect parameters of KOH concentration, IPA concentration, reaction time and temperature for wafer surface morphology were analyzed by scanning electron microscope. The results show that: a uniform, high density and good pyramid shaped single crystalline silicon surface can be obtained at 3% KOH solution buffered with 8% IPA at 80°C for 30min. By comparing single crystalline silicon micro-surface with NaOH and IPA mixed solution system of industrial fabrication, the pyramid structure is more regular and uniform by using KOH and IPA mixed solution system, which is expected to obtain better optical properties.