Wei Sun

The Mechanism Analysis of NaCl Solution Ice Formation Suppressed by Electric Field

The cells and tissues usually may be subjected to cryo-injure, but caused to die during freezing process for cryo-preservation. Among them, the most direct reason is extra-cellular and intra-cellular ice formation. How to control, reduce, or eliminate the ice formation has been an important research topic in fundamental cryobiology. The objective of this study was to test a hypothesis that the alternated electric field could significantly influence the solution of 0.9% NaCl freezing property at a relative slow cooling rate. The test sample consisted of 0.9% NaCl solution and it was frozen in 0.26 K/min cooling rate, simultaneously was exposed to alternating electric fields ranging from 50 Hz to 5M Hz. A system was built and utilized to measure the temperature of the test sample continually. It was founded that alternated electric fields strongly influenced the freezing property of the solution, included the undercooling point temperature of the solution and the latent heat produced by phrase transition during freezing process. The results were analyzed by using dielectric theory and ions moving phenomena, it indicated that the icons moving under alternated electric field is main factor influencing the property of 0.9% NaCl solution during freezing process

Effect of Alternated Electric Field on the Ice Formation During Freezing Process of 0.9%K2MnO4 Water

The effect of alternated electric field on the ice formation of 0.9%K2MnO4 water during freezing process is investigated. The pattern of ice crystal and frozen time are observed by a simple microscope system. The relationship between the ice formation and the frequency of applied electric field in the range from 1 kHz to 200 kHz is investigated. It is found that the influence of electric field is strongly dependent on the frequency of eclectic field. With the increase of the frequency, domain size of ice crystal and the frozen time decrease and reach the minimum at the frequency of 50 kHz. A candidate mechanism concerned with dielectric polarization and relaxation loss properties during the freezing process is assumed

10/350-

This paper presents a novel crowbar system of 10/350-μs pulse current. The crowbar pulse current system includes a crowbar pulse current waveform forming circuit, a controlling unit, and a measuring unit. The crowbar pulse current circuit consists of a main air triggered switch, a triggered vacuum switch (TVS) which is used as the crowbar switch, and two trigger signal generators. A kind of TVS is designed and fabricated. Its triggering characteristics are tested, and experimental results show that, compared with other reported similar switches, the TVS has excellent characteristics such as wide operating voltage scope from 1.3 to 120 kV, short discharging delay time with maximum delay time at 400 ns, and its jitter at ±10 ns. Based on the TVS, the crowbar 10/350-μs pulse current circuit and its controlling circuit are designed. With a 36-μF storage capacitor C and a 6-μH waveform forming inductance L, a 10/350-μs pulse current waveform with a maximum of 150 kA can be generated.

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High-power and high-current test technology has many requirements for a discharging switch, such as high hold-off voltage, wide operating voltage scope, short discharging delay time and jitter, strong charge transfer ability, and long lifetime. A high-voltage and high-current triggered vacuum switch (TVS) with a surface flashover trigger device has been designed, and the trigger device is made from a material whose relative dielectric constant εr is around 2500. The experimental circuits are set up, and the experiments are performed. The experimental results showed that the TVS can be used at a maximum voltage of up to 120 kV, the minimum operation voltage is 1.3 kV, the maximum discharging delay time is less than 400 ns, and the minimum discharging delay time and jitter reach to 100 and 10 ns, respectively. The maximum current switched is about 180 kA, and the maximum transfer charge per shot is larger than 2.5 C. The switch can satisfy the main demands of crowbar circuit applications and can be used on high-voltage and high-current application situations.

Crowbar Pulse Current System

An auto impulse current measuring system for surge protective device (SPD) with power source was studied, the system was composed of impulse current generator, programmable logical controller (PLC), couple and decouple network (CDN), power tracking circuit and intelligent digital peak measuring instrument. It can carry common and different mode tests for SPD, the maximum impulse current amplitude is up to 200 kA, the accuracy of measuring impulse peak is less than plusmn1%, and the accuracy of phase tracking power frequency is less than plusmn3deg

A High-Voltage and High-Current Triggered Vacuum Switch

The effects of pulsed current electromagnetic fields (PCEMF) on human peripheral lymphocytes sister chromatid exchanges (SCE), and micronuclei (MN) frequencies were investigated. PCEMF were produced by 8/20 μs pulsed current generation with two model types, a long straight wire and a solenoid. Human peripheral lymphocyte samples were exposed to PCEMF (a pulse per min, and continuing for 1 h). SCE and MN assays were used to evaluate the genotoxic effects. The results indicated that SCE and MN incidences correlated positively with B m and dB/dt. For the long straight wire model, as B m reached 8.48 × 10−2 T and dB/dt = 1.06 × 104 T s−1, the effect was significant. As B m reached 1.70 × 10−1 T and dB/dt = 2.13 × 104 T s−1, the effect was marked. For the solenoid model, the conditions of significant effect were B m = 0.264 T and dB/dt = 3.30 × 103 T s−1 and B m = 1.32 T and dB/dt = 1.650 × 104 T s−1. Data indicated that dB/dt was an important factor in increasing the frequencies of MN and SCE in human peripheral lymphocytes.