Pulsed Electric Energy Research Articles

Effect of pulsed electric field treatment on enzyme kinetics and thermostability of endogenous ascorbic acid oxidase in carrots (Daucus carota cv. Nantes)

The objective of this research was to study the enzyme kinetics and thermostability of endogenous ascorbic acid oxidase (AAO) in carrot purée (Daucus carota cv. Nantes) after being treated with pulsed electric field (PEF) processing. Various PEF treatments using electric field strength between 0.2 and 1.2kV/cm and pulsed electrical energy between 1 and 520kJ/kg were conducted. The enzyme kinetics and the kinetics of AAO thermal inactivation (55–70°C) were described using Michaelis–Menten model and first order reaction model, respectively. Overall, the estimated Vmax and KM values were situated in the same order of magnitude as the untreated carrot purée after being exposed to pulsed electrical energy between 1 and 400kJ/kg, but slightly changed at pulsed electrical energy above 500kJ/kg. However, AAO presented different thermostability depending on the electric field strength applied. After PEF treatment at the electric field strength between 0.2 and 0.5kV/cm, AAO became thermolabile (i.e. increase in inactivation rate (k value) at reference temperature) but the temperature dependence of k value (Ea value) for AAO inactivation in carrot purée decreased, indicating that the changes in k values were less temperature dependent. It is obvious that PEF treatment affects the temperature stability of endogenous AAO. The changes in enzyme kinetics and thermostability of AAO in carrot purée could be related to the resulting carrot purée composition, alteration in intracellular environment and the effective concentration of AAO released after being subjected to PEF treatment.

Analysis of magnetic Rayleigh–Taylor instability in a direct energy conversion system which converts inertial fusion plasma kinetic energy into pulsed electrical energy

A direct energy conversion scheme to convert plasma kinetic energy into pulsed electrical energy, based on magnetic flux compression (MFC) by an inertial fusion plasma sphere, has been examined earlier. The plasma sphere, expanding across a magnetic field, is subject to the Magnetic Rayleigh–Taylor (MRT) instability. Therefore, 2D MHD simulations have been performed to analyze the MRT instability and its implications for the proposed MFC system. The simulation takes into account the effects of MFC and geometric divergence due to spherical plasma expansion. Single-mode sinusoidal perturbation evolution exhibits linear exponential growth followed by a non-linear phase towards stagnation time. We also note that near the time of stagnation, the growth in amplitude of the modes, although exponential in nature, is much lower than the growth predicted by linear theory. Furthermore, the instability amplitudes are not large enough for αin⩽0.1λin to severely disturb the smooth MFC during the first expansion phase. However, the growth of modes with αin⩾λin causes plasma jetting, especially for longer λ modes, and can lead to significant reduction in MFC efficiency.

150 kJ Compact Capacitive Pulsed Power System for an Electrothermal Chemical Gun

A 150 kJ compact capacitive pulsed power system (CCPPS) capable of delivering electrical energy into an electrothermal chemical (ETC) gun on a vehicle has been studied. The CCPPS provides pulsed electrical energy into a capillary plasma injector which generates plasma of tens of thousands <TEX>$^{\circ}K$</TEX> in temperature and has a nonlinear resistance depending on the current. The design requirements of the CCPPS are as follows: the maximum power of 250 MW, the pulse width of about 0.6 ms, the volume of no more than 0.5 cubic meter, the efficiency of energy transfer over 80 % and the repetition rate of 4~5 times per minute. The constructed CCPPS is composed of four 37.5 kJ capacitor bank modules in parallel to make a trapezoid pulse shape and to satisfy the design requirements. Each module is designed to achieve high reliability, safety, efficiency and energy density to endure severe operating conditions. The results of the performance test on the CCPPS using a 120 mm ETC gun are described.

An Eulerian MHD model for the analysis of magnetic flux compression by expanding diamagnetic fusion plasma sphere

The process of magnetic flux compression (MFC) inside a solenoid by expanding diamagnetic plasma sphere produced by an inertial fusion micro-explosions and its application as a direct energy conversion scheme to convert a part of plasma kinetic energy into pulsed electrical energy has been recently reported [1]. For a detailed analysis of this concept, an Eulerian multi-material MHD model is developed using magnetic vector potential formulation for electro-magnetic field calculations and classical volume-of-fluid method for material interface tracking. The diffusion term in the magnetic induction equation is solved implicitly while the advection terms are computed using a second-order MUSCL scheme. An iteration procedure using ADI scheme is used for the free space field calculation. In this paper, we describe the details of the new MHD model, its validation against the semi-analytical solutions (for magnetic Reynolds number ≫1) of magnetic convective-diffusion equations and application to explore the concept of MFC by expanding plasma sphere. The simulation results show that the algorithm is capable of handling complex plasma dynamics inside the MFC system. Also, the results indicate the development and the evolution of MRT like instability near the stagnation point. The magnetic field diffusion into the plasma during the expansion phase is found to be negligible.

Conversion of plasma energy into electrical pulse by magnetic flux compression

A conceptual study of magnetic flux compression inside a cylindrical coil by an expanding inertial fusion plasma sphere across the magnetic field produced by the coil itself have been performed numerically using a two-dimensional magnetohydrodynamic (MHD) simulations. The concept may find application in inertial fusion energy (IFE) system as a direct energy conversion scheme to convert a part of fusion plasma kinetic energy into pulsed electrical energy. Important theoretical and technical issues that has to be addressed are discussed. Preliminary theoretical analysis are given for the analysis of MHD interchange instabilities of expanding plasma across magnetic field. Overall efficiency of the system is determined numerically for a typical set of initial plasma and system parameters. Ultrahigh coil inter-turn voltages are predicted. Therefore, the application of magnetic self-insulation to avoid coil inter-turn break-down is considered. Also, we have analysed the system performance with different load conditions.

Influence of pulsed electric field energy on the damage degree in alfalfa tissue

The objectives of this study were to investigate the influence of pulsed electric field (PEF) parameters on the damage degree of alfalfa mash, and to determine the relationship between the maximum damage degree and the energy used. Alfalfa mash was treated with PEF at various electric field strengths of 1.25, 1.90, and 2.50 kV/cm. The capacitance of the discharge capacitor was varied from 0.5 to 1.5 μF in steps of 0.5 μF. The pulse number was increased gradually to the point where the impedance became constant. There was no significant increase in the rate of damage beyond 0.5 kJ applied energy. The rate of change of the damage degree at 0.5 kJ was highest when the capacitance was 1.5 μF for all the voltages. Increase in the electric field strength led to decrease in energy needed to obtain the maximum damage degree. To achieve an efficient result for alfalfa juice extraction, the capacitance of the discharge capacitor should preferably be 1 μF or more. In order to minimize energy consumption for a given damage degree in alfalfa, it is desirable to have the highest energy per pulse and fewer number of pulses.

Simulation of the temperature increase in pulsed electric field (PEF) continuous flow treatment chambers

The application of intense pulsed electric fields (PEF) in foods is intended to be a non-thermal method to inactivate microorganisms. However, it is well known that an increase in temperature is present in this process due to ohmic heating, where the pulsed electric field energy input is transformed into heat. The aim of this study was to investigate the computer modeled temperature increase in the outflow for different flow-through PEF treatment chamber designs. Given equal experimental conditions, the temperature increase is indicative of the PEF dose, and a more uniform temperature profile is thus indicative of a more homogeneous PEF treatment. The radial distribution of the temperature increase was simulated in computer models of four different chambers. The temperature increase was found to be more homogeneous in the treatment chambers making use of a decrease in the insulator diameter, i.e. a design letting the insulators and electrodes intersect at angles close to 90°. The maximum temperature increase was found close to the wall, where the flow velocity is low. Cooling of the electrodes and electric insulators is recommended to avoid too high a temperature increase. The minimum temperature increase found was 29% of the calculated average in the worst case studied here. The minimum PEF dose to which the food was subjected would thus is less than the intended dose, since the food clearly was not subjected to the intended electric field strength during the intended exposure time. This is an important result in terms of food safety in the sense that a minimum PEF treatment should be guaranteed. The microbiological inactivation was experimentally evaluated using two of the treatment chamber designs. The result is consistent with the simulations and shows a small increase in inactivation and less needed energy input giving less average temperature increase for the chamber implementing a contraction of the diameter of the insulating spacer.

Kinetics of electroporation-assisted chlorination of Giardia muris

Electroporation is a process whereby the treatment of cells with short pulses of electrical energy enhances the permeability of the cells towards external solutes. In this study we report on the kinetics with which this permeability enhancement can assist with the inactivation of Giardia muris cysts by free chlorine. Cysts in buffer and in partially treated surface water were treated with combinations of electroporation and disinfection. Different electroporation and disinfection conditions were used. From these data, we were able to develop a modified Hom model to describe the data. Under the conditions investigated, electroporation was able to reduce the chemical doses required for cyst inactivation, although it had little or no intrinsic inactivation activity.

Magnetic advanced hybrid (MAH) gun

The feasibility of the MAH gun is analytically demonstrated for velocities in the 4 to 8 km/s range. The gun design represents a modification of conventional gun. No power source, power conditioning devices, or opening switch are required, which makes the MAH gun superior to other electromagnetic guns. Chemical energy is used to accelerate the projectile to high velocity through magnetic collision. In addition, fast firing is possible since no pulsed electric energy is required. High-temperature superconductors will have significant impact on the gun design, especially if no cooling is required. >

Conversion of chemical energy in an explosive by a magnetohydrodynamic method

In this paper, we examined different practical methods for realizing the MHD method for converting chemical energy of a condensed explosive into pulsed electrical energy. It was shown that explosive MHD generators, which are compact sources of powerful pulses of electrical energy, are characterized by their relative simplicity, autonomy, and maneuverability of firing and they are capable of operating in the frequency-periodic mode. The moderate, compared to MC generator, weight-size characteristics of the generator (∼1 J/g, ∼1 J/cm3) are the necessary tradeoff for the new operational quality, namely, the nondestructibility of the setup. At the present time, a considerable amount of experimental information has been accumulated on the study of processes that determine the efficiency of the generator. Based on this information, a number of projects have been proposed for explosive MHD generators in the megajoule range. Practical experience has been gained in creating frequency-periodic action generators as well as autonomous setups using superconducting magnetic systems. The increase in the operational efficiency of an explosive MHD generator is primarily related to increasing the magnetic Reynolds number of the flow, which can be attained, in particular, by using different schemes for accumulating the energy of the explosion. The use of a metallic liner, which expands under the pressure of the detonation products, in an explosive MHD generator is, in the practical sense, apparently hopeless. The general information available in the literature on the parameters and properties of explosive MHD generators give a basis for concluding that this generator is a promising source of powerful energy pulses. In a certain range of parameters, it can be an alternative to the use of storage batteries, inductive accumulator, and an explosive magnetic generator, and according to a number of indicators (nondestructibility, autonomy, frequency-periodic operational mode) has advantages over them.

Direct conversion of CO2 laser energy to high-voltage electrical energy using a laser-produced plasma

High-voltage high-current pulses of electrical energy (700 V, 14 A, 10 kW) are generated with efficiencies greater than 0.1% for a duration of 30 nsec when a 3–4-J CO2 TEA laser is focused on a copper cathode in a special vacuum cell designed to collect the ejected high-energy electrons. Potential applications as a high-voltage source and as a detector are discussed.

Percutaneous Electrical Stimulation for Clinical Tibial Fracture Repair

Observations on stress generated electrical currents in bone have stimulated interest in the possible osteogenetic effect of externally applied electrical energy to establish diaphyseal bone defects in animals and man. This report records the observed effects of pulsed electrical energy directed through a metal (Riordan pin) electrode placed in a large proximal tibial shaft dedect in a young man who sustained loss of bone from a gunshot wound. The fixation pin placed directly into the defect provided the cathode (-) electrode. The anode (+) electrode consisted of an aluminum foil band placed on the skin adjacent to the leg. The tibia had 282 consecutive days of electrical stimulation and provided X-ray and clinical evidence of enhanced osteogenetic activity. The degree of osteogenetic response attributable to the electrical stimulation is undetermined because other factors, including cast immobilization, time and minimal touchdown (25 pounds) weight-bearing in the cast during the period of observation, may also have had some influence on the healing response. Circumstantial clinical evidence indicates that the applied electrical energy was of primary importance in the healing process. This theoretically and technically acceptable source of osteogenetic activity merits continued, intensive investigation.

Pulsed electrical energy for soft-tissue injuries.

Pulsed electrical energy for soft-tissue injuries.

Non-Destructive Screening for Thermal Second Breakdown

The feasibility of developing nondestructive screening techniques to determine the second breakdown vulnerability of semiconductor devices at submicrosecond pulse conditions has been demonstrated. In addition, it has been shownl that second breakdown can be nondestructively initiated under certain current limiting conditions without causing degradation in device operating characteristics or device second breakdown vulnerability level to subsequent pulses of electrical energy. A low energy current impulse damage mechanism at second breakdown initiation has also been observed. The experimental investigations were performed using 1N4148 diodes fabricated with various junction areas and a fixed diffusion depth. The complete results of this work are documented in Reference 1.

Pulse Power Failure Modes in Semiconductors

Semiconductor devices operating under both biased and unbiased conditions are vulnerable to permanent damage from relatively moderate levels of pulsed electrical energy, particularly of submicrosecond pulse duration. An experimental study was performed to determine the permanent damage levels associated with a number of different devices and to identify the failure mechanisms associated with each. The device types investigated included general purpose and high speed computer diodes, a medium power diode, medium frequency and UHF transistor amplifiers, and a dielectrically isolated diode gate expander. The permanent damage levels associated with these devices were determined both for positive and negative polarity pulses at different conditions of quiescent bias and pulse width. The pulse duration times included the range of 30 to 300 nanoseconds, and in some instances, up to 1 microsecond. Failure models for both thermal second breakdown induced damage to the semiconductor junction and thermal damage to the device interconnecting leads and metallization patterns were also developed.

Electromagnetic Interference Control Considerations Solenoid Operated Control Devices

Relay and solenoid controlled devices have historically been a common source of electromagnetic interference. The pulsed electrical energy resulting from actuation and deactuation generates broad frequency spectrum interference. Establishment of meaningful component and subsystem specifications and application of proper design techniques can minimize the interference generated by such devices and subsystems and can also minimize their susceptibility to other interference sources. This paper reviews the approaches which will significantly minimize electromagnetic interference problems.