Minimum Electric Field Strength Research Articles

Optimization design of insulation structure of multiwinding high-frequency transformer based on response surface method

PurposeThe purpose of this paper is to study the insulation structure optimization method of multiwinding high-frequency transformer (HFT).Design/methodology/approachThis paper takes 100 kW, 10 kHz multiwinding HFT as the research object. First, the distribution of electric field strength within the core window of multiwinding HFT with different winding configurations is simulated by the electrostatic field finite element method. The symmetrical hybrid winding structure with minimum electric field strength is selected as the insulation design. To reduce the electric field strength at the end region of the winding, the electrostatic ring and angle ring are designed based on the response surface method.FindingsThe optimal results show that the maximum electric field strength can be reduced by 15.4%, and the low voltage stress can be achieved.Originality/valueThe above research provides guidance and basis for the optimal design of insulation structure of multiwinding HFT.

Impact of molecular architectures on mesogen reorientation relaxation and post-relaxation stress of liquid crystal elastomers under electric fields

Applying electric fields to liquid crystal elastomers (LCEs) has attracted attention as a fast and energy-efficient actuation method for soft robotics. It is helpful to predict the minimum electric field strength that can drive the mesogen reorientation and the time required for the reorientation of LCEs with specific molecular architecture to optimize LCE electrical actuation. In this study, molecular dynamics (MD) simulations of main- and side-chain LCE systems under an applied electric field were performed, and the relaxations of stress and orientational order were observed. The minimum electric field strength that can drive the reorientation for each LCE molecular system was estimated. The time required for reorientation follows a power law of the electric field strength, and the reorientation time for side-chain LCEs is much shorter than that for main-chain LCEs. The behavior of the relaxation value of stress with respect to the electric field strength differed markedly between the main- and side-chain LCEs. These results suggest that designing LCEs at the molecular architecture level and using different LCE molecules in different actuation sites are essential to more precise soft robotics.

Highly Sensitive Measurement of a Megahertz rf Electric Field with a Rydberg-Atom Sensor

Rydberg atoms have great potential in electric field measurement and have an advantage with a large frequency bandwidth from the kHz to the THz scale. However, the sensitivity for measuring a weak MHz electric field signal is limited by the spectroscopic resolution, because the weak electric field induces only a small perturbation of the population and energy level shift of the Rydberg atoms. Here, we report highly sensitive measurement of a weak MHz electric field using electromagnetically induced transparency with Rydberg atoms in a thermal atomic system. Using the heterodyne method on a 30-MHz electric field, we successfully measure the minimum electric field strength to be \textcolor{black}{37.3 $\mathrm{\mu V/cm}$} with a sensitivity up to $-65$ dBm/Hz and a linear dynamic range over 65 dB. Additionally, we measure an amplitude-modulated signal and demodulate the signal with a fidelity over 98\%. This work extends the sensitivity of atomic sensors for measuring MHz electric fields, which advances atomic electric field-sensing technology.

Novel platinum bipolar electrode for irreversible electroporation in prostate cancer: preclinical study in the beagle prostate

The exposure of the prostate to high electric field strength during irreversible electroporation (IRE) has been extensively investigated. Multiple monopolar electrodes, however, have risks of organ piercing and bleeding when placing electrodes. A novel bipolar electrode made of pure platinum and stainless steel was developed for prostate cancer ablation. Voltages of 500 and 700 V were applied to the beagle prostate with this electrode to evaluate ablated tissues and their characteristics. IRE procedures were technically successful in all dogs without procedure-related complications. The current that flowed through the anode and cathode while applying 500 and 700 V were 1.75 ± 0.25 A and 2.22 ± 0.35 A, respectively. TUNEL assays showed that the estimated ablated areas when applying 500 and 700 V were 0.78 cm2 and 1.21 cm2, respectively. The minimum electric field strength threshold required for induction of IRE was 800 V/cm. The platinum electrode was resistant to corrosion. The IRE procedure for beagle prostates using a single bipolar electrode was technically feasible and safe. The novel bipolar electrode has great potential for treating human prostate cancer with fewer IRE-related complications.

Response characteristics and optimization of electroporation: simulation based on finite element method

ABSTRACT Electroporation has been widely used in biology, medicine, and the food industry as a means to transport various molecules through the cell membrane. The phenomenon of electroporation is the result of cell membrane damage caused by the application of an electric field. In order to understand more precisely how cells function, we established a dielectric model of a spherical cell and analyzed its characteristics by the finite element method. The effects of altering different electrical parameters were determined. The results showed that the electric field strength was positively related to the transmembrane voltage (TMV) and pore density. There was a minimum electric field strength necessary to induce a critical TMV for the formation of pores. Pulse width also had to be long enough to charge the cell membrane, compared with the normal membrane charging time constant of about 1 μs. When the pulse width was shorter than the charging time constant, it was necessary to increase pulse frequency to create a high enough TMV. The rise-time of the electric pulse also affected electroporation: a fast rise-time pulse not only allowed penetration of the plasma membrane but also the organelle membrane. With slow rise-time pulse, the organelle was shielded from electroporation. This study defines the response characteristics of electrical parameters on the electric load cell and establishes the specificity of parameters for different purposes.

Estimation of sheath electric field in inductively coupled hydrogen plasma on the basis of Doppler-broadened absorption spectrum of hydrogen Balmer-α line

We examined the applicability of the Doppler-broadened absorption spectrum of the hydrogen Balmer-α line to the estimation of the sheath electric field in plasma. The Stark splitting of the fine-structure components was calculated by solving the time-independent Schrödinger equation at various electric field strengths, and the theoretical absorption spectrum was obtained by the superposition of the fine-structure components with the same Doppler broadening widths. The spectrum of the Balmer-α line of atomic hydrogen, which was measured by standard diode laser absorption spectroscopy, was fitted with the theoretical spectrum. We succeeded in determining the translational temperature of atomic hydrogen, which was obtained from the Doppler broadening width, and the electric field strength by the spectral fitting. We have evaluated that the minimum electric field strength that can be detected by the present method is approximately 350 V cm−1 when the translational temperature of atomic hydrogen is 400–500 K.

Path planning of UHV live working hanging basket method based on grid-ant colony algorithm

The live working paths for equipotential operators in the hanging basket method is determined by minimum safety values of various clearances stipulated in regulations. However, the optimization of the safety path planning by the complex gaps is scarce. In this paper, an optimization method for path planning is proposed based on ant colony algorithm. Grid model is established to partition the operation area into different calculation districts, in which key parameters are grid data and obstacle grids. Grid data are the maximum value of the electric field strength on the body surface, calculated by the finite element model. And obstacle grids are grids that dissatisfy the requirements of complex gaps and their data are larger than the air breakdown field strength. Then ant colony algorithm is employed to search for the best operation path with the minimum working distance and the minimum electric field strength value. After that, an application case is illustrated to demonstrate the optimizing processes. At last, the shock U50 test and power frequency corona discharge test are implemented to verify the safety of the optimized path. Therefore, the path obtained by the proposed method scientifically and effectively shortens the distance of the hanging basket method.

The charge alteration of asphaltenes during electro-deposition

Electro-deposition (E-D) has been proposed as a promising method for dealing with the asphaltenes deposition issue. An observed alteration of the native, positive asphaltene charge during the process has attracted wide attention since it influences the feasibility and efficiency of this method. To investigate this phenomenon, E-D of various asphaltenes with resins was studied. The results demonstrate that the charge alteration of asphaltenes is the result of net adsorption of negative charges within the fluid onto the asphaltenes under high electric field strength. The minimum electric field strength required to trigger the charge alteration of asphaltenes from coal tar and bitumen were 12000 V/cm and 4500 V/cm, respectively, exhibiting a strong influence of chemical composition of asphaltenes on the charge alteration. Moreover, the adsorption of resins on asphaltenes resulted in the repression of charge alteration behavior that varied with different resins. The resins from bitumen had the highest repression on asphaltenes from bitumen, as 2 g/L-resin can increase the minimum electric field strength required for charge alteration to 12000 V/cm. The results of the work provide an essential guide for the further development of an E-D procedure that could be used for efficient asphaltenes removal.

3299 Dynamic Afterload Cardiac Microtissue Model To Examine Molecular Pathways of Heart Failure

OBJECTIVES/SPECIFIC AIMS: This project aims to determine the key molecular pathways that link increased myocardial wall stress to cardiomyocyte hypertrophy and subsequent heart failure. We will use a cardiac microtissue (CMT) model with dynamically tunable cantilever stiffness to examine changes in CMT hypertrophy and electro-mechanical properties in response to increased afterload (cantilever stiffness). Subsequently, we will determine if inhibition of pro-hypertrophic or anti-hypertrophic pathways alter the hypertrophic response to increased afterload. Primary outcomes for this study are static/dynamic force, minimum electric field strength (VT), maximum capture rate (MCR), average cell area, and tissue cross-sectional thickness, and secondary outcomes are degree of myoblast activation and apoptosis. METHODS/STUDY POPULATION: CMT platforms will be fabricated using iron-doped polydimethylsiloxane (PDMS) to create magnetically tunable cantilevers. Cantilever stiffness will be increased with the application of an external magnetic field. Cantilever stiffness will be measured using a capacitance probe, where the force required to deflect both the cantilever and calibration probe is in accordance with Hooke’s Law. Human induced pluripotent stem cell cardiomyocyte (hiPSC-CMs) will be cultured and matured as 3D CMTs. In-vitro static/dynamic force generation will also be calculated by measuring the deflection of the cantilevers and applying Hooke’s law. CMTs will be paced using carbon electrodes to obtain VT and MCR. Structural data will be obtained using immunostaining and confocal microscopy. Finally, we will use pharmacologic inhibitors to inhibit molecular pathways that we identified in prior genetic screens such as ABCC8 (anti-hypertrophic mediator) and C1QTNF9 (pro-hypertrophic mediator). We will examine each of these pathways in low- and high-stiffness conditions. RESULTS/ANTICIPATED RESULTS: We believe increased afterload will cause significant hypertrophy, measured by increases in CMT cross-sectional thickness, cardiac myocyte area, myofibroblast activation, and myocyte apoptosis. In addition, we expect to see increases in static/dynamic force, increased voltage threshold, and decreased maximum capture rate. Preliminary results show a 64.3% increase in force generation when stiffness is increased by approximately 30%, and a 44.4% decrease in force generation when stiffness is decreased by approximately 30%. Finally, we expect that inhibiting a pro- or anti-hypertrophic molecular pathway will weaken or strengthen the hypertrophic response to increased afterload, respectively. DISCUSSION/SIGNIFICANCE OF IMPACT: To our knowledge, our lab is the first to create a dynamically tunable afterload system in the cantilever CMT model. This advance provides us with a robust platform to determine the molecular pathways that cause increased myocardial wall stress to result in cardiomyocyte hypertrophy and heart failure, which remain a critical knowledge gap in our understanding of cardiovascular disease. With more precise understanding of these pathways, we will equip ourselves with the knowledge to develop novel therapeutic agents to prevent the development or progression of heart failure.

Interfacial electrofluidics in confined systems.

Electrofluidics is a versatile principle that can be used for high speed actuation of liquid interfaces. In most of the applications, the fundamental mechanism of electro-capillary instability plays a crucial role, yet it’s potential richness in confined fluidic layers has not been well addressed. Electrofluidic displays which are comprised of thin pixelated colored films in a range of architectures are excellent systems for studying such phenomena. In this study we show theoretically and experimentally that confinement leads to the generation of a cascade of voltage dependent modes as a result of the electro-capillary instability. In the course of reconciling theory with our experimental data we have observed a number of previously unreported phenomena such as a significant induction time (several milliseconds) prior to film rupture as well as a rupture location not corresponding to the minimum electric field strength in the case of the standard convex water/oil interface used in working devices. These findings are broadly applicable to a wide range of switchable electrofluidic applications and devices having confined liquid films.

Dynamics of three-dimensional vesicles in dc electric fields.

A numerical and systematic parameter study of three-dimensional vesicle electrohydrodynamics is presented to investigate the effects of varying electric field strength and different fluid and membrane properties. The dynamics of vesicles in the presence of dc electric fields is considered, in both the presence and absence of linear shear flow. For suspended vesicles it is shown that the conductivity ratio and viscosity ratio between the interior and exterior fluids, as well as the vesicle membrane capacitance, substantially affect the minimum electric field strength required to induce a full prolate-oblate-prolate transition. In addition, there exists a critical electric field strength above which a vesicle will no longer tumble when exposed to linear shear flow.

Molecular Dynamics Simulations of Ice Nucleation by Electric Fields

Molecular dynamics simulations are used to investigate heterogeneous ice nucleation in model systems where an electric field acts on water molecules within 10-20 Å of a surface. Two different water models (the six-site and TIP4P/Ice models) are considered, and in both cases, it is shown that a surface field can serve as a very effective ice nucleation catalyst in supercooled water. Ice with a ferroelectric cubic structure nucleates near the surface, and dipole disordered cubic ice grows outward from the surface layer. We examine the influences of temperature and two important field parameters, the field strength and distance from the surface over which it acts, on the ice nucleation process. For the six-site model, the highest temperature where we observe field-induced ice nucleation is 280 K, and for TIP4P/Ice 270 K (note that the estimated normal freezing points of the six-site and TIP4P/Ice models are ∼289 and ∼270 K, respectively). The minimum electric field strength required to nucleate ice depends a little on how far the field extends from the surface. If it extends 20 Å, then a field strength of 1.5 × 10(9) V/m is effective for both models. If the field extent is 10 Å, then stronger fields are required (2.5 × 10(9) V/m for TIP4P/Ice and 3.5 × 10(9) V/m for the six-site model). Our results demonstrate that fields of realistic strength, that act only over a narrow surface region, can effectively nucleate ice at temperatures not far below the freezing point. This further supports the possibility that local electric fields can be a significant factor influencing heterogeneous ice nucleation in physical situations. We would expect this to be especially relevant for ice nuclei with very rough surfaces where one would expect local fields of varying strength and direction.

Critical Electric Field Strengths of Onion Tissues Treated by Pulsed Electric Fields

The impact of pulsed electric fields (PEF) on cellular integrity and texture of Ranchero and Sabroso onions (Allium cepa L.) was investigated. Electrical properties, ion leakage rate, texture, and amount of enzymatically formed pyruvate were measured before and after PEF treatment for a range of applied field strengths and number of pulses. Critical electric field strengths or thresholds (E(c)) necessary to initiate membrane rupture were different because dissimilar properties were measured. Measurement of electrical characteristics was the most sensitive method and was used to detect the early stage of plasma membrane breakdown, while pyruvate formation by the enzyme alliinase was used to identify tonoplast membrane breakdown. Our results for 100-μs pulses indicate that breakdown of the plasma membrane occurs above E(c)= 67 V/cm for 10 pulses, but breakdown of the tonoplast membrane is above either E(c)= 200 V/cm for 10 pulses or 133 V/cm for 100 pulses. This disparity in field strength suggests there may be 2 critical electrical field strengths: a lower field strength for plasma membrane breakdown and a higher field strength for tonoplast membrane breakdown. Both critical electric field strengths depended on the number of pulses applied. Application of a single pulse at an electric field up to 333 V/cm had no observable effect on any measured properties, while significant differences were observed for n≥10. The minimum electric field strength required to cause a measurable property change decreased with the number of pulses. The results also suggest that PEF treatment may be more efficient if a higher electric field strength is applied for a fewer pulses.

Non-uniform electric field-induced yeast cell electrokinetic behavior

Common dielectrophoresis (c-DEP, i.e. neutral matter motion induced by non-uniform electric fields) has become a basic phenomenon of biochips intended for medical, biological and chemical assays, especially when they imply bioparticle handling. This paper deals with modelling and experimental verification of a castellated, c-DEP-based, microelectrode array intended to handle biological objects. The proposed microsystem was developed employing platinum electrodes patterned by lift-off, silicon micro machining and photoresin patterning techniques. Saccharomyces cerevisiae were used as test bioparticles for experimental verification. Yeast cells were repelled toward electrode bays and toward interelectrodic gaps tor frequencies around 20 MHz where there is minimum electric field strength, corresponding to a negative dielectrophoretic phenomenon. Yeast cell agglomerations were observed around electrode edges for frequencies of around 2 MHz where there is maximum electric field strength, thereby verifying the positive dielectrophoretic phenomenon. Bioparticles were separated from the electrode edges when the working frequency was reduced and they were dragged towards the electrode centre, remaining there while the frequency was low enough. Such atypical pattern may be explained due to the occurrence of positive dielectrophoresis overlap with electrohydrodynamic effects (i.e. the viscous drag force acting on the particles was greater than the dielectrophoretic force at frequencies where positive dielectrophoresis should occur). The experiments illustrated microsystem convenience in microhandling biological objects, the reby providing these microarrays’ possible use with other cells. Liquid motion resulting from electrohydrodynamic effects must also be taken into account when designing bioparticle micromanipulators, and could be used as a mechanism for cleaning electrode surfaces.

Field Trials for Terrestrial Digital Multimedia Broadcasting System

This paper presents the field trial results of the terrestrial digital multimedia broadcasting (T-DMB) service in Korea. The T-DMB system, based on the Eureka-147 digital audio broadcasting (DAB) system, provides streaming video, CD-quality audio and data services at speeds of up to 300 km/h using H.264 video codec along with additional channel coding and interleaving schemes. In order to provide seamless high-quality services on various radio channels, we measured the bit error rate (BER), electric field strength (EFS), and subjective video quality using specially-designed mobile test equipment. From the field tests we obtained the required effective EFS (EEFS) for error-free reception and also derived the minimum EFS from the link budget analysis. Furthermore, we present the optimal transmit and receive parameters for constructing the T-DMB networks and also developing T-DMB broadcasting equipment and mobile receivers

A new strategy for direct measurement of sinus atrial conduction time by sinus node threshold determination in a rat-isolated atrium

In this work we have searched for experimental evidence that would corroborate the idea that nodal threshold (NT) is the minimum electric field strength able to promote direct sinus node reset that, in turn, can be verified by a decrease in corrected sinus node recovery time (CSNRT). We have performed direct measurements of sinus node conduction time (SACT) and estimation of atrium sinus conduction time (ASCT). Stimulating pulses (pulse and train methods) generated a uniform electric field, with strength ranging from 1.5-fold to 5-fold the atrial threshold (AT), in the center of the perfusion chamber where isolated right atria were placed. The AT and NT were 67.4 and 192.7 mV cm−1, respectively. The CSNRT values, obtained with stimulation strength below or above NT, were, respectively (ms; mean ± standard error of mean) 38.1 ± 0.42 and 25.2 ± 0.30. In addition, we verified that NT corresponds to approximately 3-fold the AT; SACT was 1.34-fold ASCT and the overdrive suppression decreases with the increment of stimulation pulse strength. Therefore, by using a new and accurate approach for SNRT determination, we have provided additional experimental evidence for the development of alternative sinus node evaluation methods.

Fundamental Investigation for Firefly Phenomenon of Particle under DC Voltage in SF6 Gas

GIS is compacted by progress of arrester and reduction of impulse test voltage for specifications recently. Since field strength of inner surface for GIS tank is more strengthened than ever, it is more necessary that included particle in GIS is taken into consideration. When GCB and DS are opened, residual dc voltage occurs at conductor between GCB and DS. It is well known that movement of particle under ac voltage is different from that of dc voltage. Therefore it is very important that particle movement under dc voltage is taken into consideration, even if GIS is for ac.From the above, this paper deals with firefly phenomenon of particle under dc voltage in SF6 gas. It investigates that prevention of fire fly phenomenon by electric field strength of conductor. And the minimum electric field strength to continue firefly phenomenon of particle is made clear. Then the breakdown voltage with firefly particle is compared with that of particle; with a minute gap, fixed to conductor.

Theory of Electric Field Detachment of Charged Toner Particles in Electrophotography

In the electrophotographic process, electric fields are used to detach and move charged toner particles from one surface to another. In principle, electric field detachment occurs when the applied electrostatic force overcomes the toner adhesion force to a surface. For triboelectrically charged toner, many measurements have indicated that the electrostatic adhesion force is much greater than that calculated for a uniformly charged dielectric sphere, suggesting that the surface charge distribution on a toner particle is nonuniform. In the present work, the physics of the electrostatic force is described and a dumb-bell type charge distribution on triboelectrically charged toner particles is proposed as an approximation of nonuniformly charged particles. The electrostatic force on an isolated toner particle with a dumb-bell type charge distribution is computed by means of a recently developed computational method based on a Galerkin finite-element technique. The effect of the electrode spacing on the electric field detachment of charged toner particles is examined in particular. The results show that the magnitude of electrostatic force is rather insensitive to the electrode spacing when the particle is nonuniformly charged, unless the spacing is so small that the counter electrode is nearly touching the particle. The electrostatic force for detaching a charged particle is shown to become maximized when the particle charge and applied field strength satisfy a certain relationship. Formulas are also derived for the minimum electric field strength and the corresponding particle charge that are required for the maximized electrostatic detaching force to overcome the non-electrostatic components of adhesion. For triboelectrically charged toner particles, the components of the electrostatic force components are shown to be much greater than nonelectrostatic force components. If the particle charge is proportional to the particle surface area and the non-electrostatic force component is relatively insignificant, the detachment of toner particles in response to an applied electric field should be independent of the particle size.

A Study of the Factors Influencing Water Tree Growth

A wide range of experimental data from several sources, and covering most of the factors known to influence water tree growth, has been collated and assessed in terms of the independent growth parameters. Systematic trends have been identified wherever possible, allowing a critical evaluation of the postulated treeing mechanisms. On the basis of these data a general framework of tree growth has been deduced in terms of a composite process comprised of three phases: inception, rapid growth, and fluctuation-controlled growth. It is concluded that no postulated microscopic mechanism is adequate to describe the inception phase, although one or two may be applicable to the rapid growth phase after substantial modification. It is suggested that growth can best be regarded as a local fatigue mechanism requiring a minimum electric field strength to be operative. A microscopic picture of water tree growth is tentatively proposed embodying all the known properties of water trees. Suggestions are also made concerning the minimization of water treeing and the most important directions for future research.

Processes Involved in Reattainment of Steady‐State Conditions for the Anodizing of Aluminum Following Formation Voltage Changes

The dissolution processes involved in the formation of porous films in sulfuric acid have been studied by suddenly lowering the formation voltage and observing changes in the current flowing and the barrier layer capacitance as steady‐state conditions are re‐established. It was found that current changes always follow capacitance changes, and that the dissolution processes involved are (a) initially a short time region of chemical dissolution is found up to some point where the minimum electric field strength required for ionic migration is approached, and (b) a second stage dissolution assisted by the presence of this electric field. The change from one dissolution rate to the other is continuous as this minimum electric field is approached. On the basis of the Keller model, the required pore base orientation is proposed to occur during the second stage field‐assisted process.