Electric Current Intensity Research Articles

Effect of the Electromagnetic Vibration Intensity on Microstructural Refinement of Al-7%Si Alloy

The static magnetic field and the alternating electric field were simultaneously imposed on the melt of Al-7%Si hypo-eutectic alloy, and primary α-dendrite particles were refined by electromagnetic vibrations imposed during solidification. The refinement mechanism of primary α-dendrite particles was quantitatively investigated in terms of vibration intensity. When the vibration intensity was increased, coarse equiaxed dendrite particles decreased, and primary α-dendrites approached a globular shape that size was about 25 μm in diameter. By contrast, dendrite arm spacing (DAS) remained intrinsically unchanged even if vibration intensity was changed with electric current intensity. Refinement of primary α-dendrite particles was likely to be caused by collapse of dendrite arms due to the micro-explosion and stirring of the melt.

Magnetic fields in the human hippocampal area evoked by a somatosensory oddball task.

We recorded neuromagnetic fields evoked by a somatosensory oddball task requiring subjects to discriminate target stimuli from nontarget stimuli, which are different in stimulation intensity, with a mental count of the target stimuli. A whole head type 80-channel magnetoencephalography (MEG) system with a 50-mm baseline gradiometer array was used. Targets and nontargets were somatosensory stimuli with an electrical current intensity of twice and three times the sensory threshold, respectively. The source current locations of the evoked magnetic fields in three dimensions and the equivalent current dipole (ECD) moments were calculated by using a single dipole model, assuming the brain as a sphere. In 28 of 63 recording sessions for 7 subjects, the loci of neuronal activities were observed in the left and/or right hippocampal areas. The latency of left hippocampal activity (293 +/- 49 ms) was significantly shorter than that of the right (333 +/- 45 ms) (P = 0.027, non-paired t-test). In view of previous studies that have shown the time window of sensory integration as approximately 200-300 ms, sensory information may be transferred to hippocampal areas following sensory integration.

Influence of the electrical sliding speed on friction and wear processes in an electrical contact copper–stainless steel

Among the various parameters that influence the friction and wear behaviour of a copper–stainless steel couple crossed by an electrical current and in a dry contact is the sliding speed. The tests were carried out under ambient environment and the sliding speed was in the range of 0.2–8 ms −1. The electrical current intensity was varied from 0 to 40 A and held constant during each experiment. The normal load was maintained constant corresponding to an average Hertzian stress of 10 7 Pa. It appears that the friction coefficient and the wear rate increase at first with the speed, reach their maximums, then slowly decrease and tend to constant values. Over the entire range of sliding speeds two types of wear are observed. These latters are essentially mild wear as long as hard debris do not appear at the interface and severe wear when debris consisting of oxides or oxide metal mixture become big enough, they are removed from the surface and have abrasive effect. The results are discussed in terms of observations of wear debris size and composition, wear track study, metallographic study of worn surfaces and friction and electrical contact resistance records.

Abnormal transient phenomena in the continuous casting process: Part 1

This paper is the first of a series of two describing online monitoring of the continuous casting machine and the abnormal transient phenomena observed. The present paper, Part 1, pays attention to assessment of the friction between the billet and mould based upon the cam rod force and the electric current intensity of the mould oscillation motor. Information relating to casting parameters before 58 breakouts has been obtained with a monitoring computing program. Almost 40% of the breakouts could have been forecast through assessment of the billet-mould friction force before the breakouts. Transient phenomena in the withdrawal machine have been detected. The jerking of the strand is related to high billet-mould friction; however, other parameters such as the billet cutoff unit and roller bed design also have some effects on this transient phenomenon. Some mechanisms influencing the jerking of the strand are proposed.

A new type magnetofluidic actuator

A new type magnetofluidic actuator, based on the magnetic fluid free surface profile around a linear vertical electric current is presented in the paper. It consists of a nonmagnetic box with a horizontal separating wall with orifices, containing a magnetic fluid in the lower part, water in the higher part and an optical device in the lower part opposite to the commanding electric current wire. When the box is placed near a vertical electric wire, the magnetic fluid's free surface reaches its equilibrium profile in a time interval depending on orifice dimensions and allows the optical device to give a command signal. Advantages such as simplicity of design and construction, high reliability determined by inexistence of moving mechanical parts and large range of working electric current intensities are put into evidence.

Computer aided design of a high electric current magnetofluidic sensor

A new type of high electric current sensor based on the correlation between the electric current intensity and the shape of the free surface of a magnetic fluid around a vertical linear conducting wire is presented. The basic hydrostatic and magnetostatic equations describing the sensor behavior are deduced and solved in real cases in order to allow the design of a new type of sensor, taking into account the electric current intensity range, magnetic fluid characteristics and sensor physical dimensions. Important advantages of the new sensor, such as the zero resistance, the absence of moving mechanical parts, no limitation of the electric current intensity range, the use for ac and dc measurements without modifications and without direct intervention on the electric circuit, are put into evidence.

A study on thermomechanical deformation of elastic beam with embedded shape memory alloy wires

The bending deformation of an elastic beam with eccentrically embedded shape memory alloy (SMA) wires under the activation of electrical current has been investigated. A procedure, which accounts for the effect of transient heat transfer and gives rise to the beam bending responding to prescribed input electrical current profile is used for analysis. It is found that influences of ambient temperature, electric current intensity and prestrain of SMA on the bending deformation of beam are significant.

The electrochemical production of highly effective polyaluminum chloride

This paper presents a new electrolytic method for the synthesis of PAC (polyaluminum chloride). The ECR (electrochemical reactor) used aluminum sheets as anode and AlCl 3 aqueous solution as electrolyte. This method adopted low voltage and high electric current intensity during electrolysis. Some factors of the electrochemistry and the chemistry of the aqueous solution, affecting the formation of the most effective species of PAC, were also studied. The liquid product of PAC, in which the most effective species, Alb (The polymeric Al component estimated by the ferron method), was above 70% by weight of the total aluminum with a basicity, B (OH/Al molar ratios)=2.4, was successfully generated. The results measured by the ferron method and 27Al NMR method showed that the Alb or Al 13 content of the E-PAC (PAC prepared by electrolysis) were obviously higher than that of the general PAC and other coagulants.

Influence of isoflurane anesthesia on motor evoked potentials elicited by transcortical, brainstem, and spinal root stimulation

Electrical stimulation over the motor cortexl base ofthe skulll and cervical spine motor roots was performed in 9 male rats (41 0 ± 86 g) before and after induction with isoflurane at 7 MAC concentration. The mean latency and amplitude of descending spinal evoked potential (OSEP) from spinal cord and motor evoked potentials (MEPs) from forearm muscles obtained after motor cortexl brainsteml and cervical root stimulations were calculated and compared. The electrical current intensity to elicit the MEPs after corticall brainsteml and spinal roots stimulation were 23.4 ± 7.61 7.0 ± 3.71 and 7.4 ± 0.8 mAl respectively. The brainstem stimulation activated descending motor pathways with a latency midway between that produced by electrical stimulation over the motor cOrtexI and by electrical stimulation over the cervical enlargements. The latency difference between cortical (8.8 ± 3.2 msec) and brainstem (5.7 ± 7.2 msec) stimulation was 3.7 ± 2.3 msec in all forearm extensor muscles. The latency difference between cervical (3.6 ± 0.9 msec) and brainstem stimulation (5.7 ± 7.2 msec) was 2.3 ± 7.7 msec for the same musclesl suggesting the brainstem stimulation activates the descending motor neurons at the level of cervicalmedullary junction. The amplitudes were 789 ± 7471 672 ± 3541 and 765 ± 389 µV for corticall brainsteml and cervical root stimulations. The inhalation anesthesia isoflurane at 7MAC (7.2%) completely abolished the cortical and brainstem MEPs within minutesl while the MEPs elicited by direct stimulation of the cervical spinal roots remained unchanged. Our results indicate synaptic-dependent MEPs elicited at motor cortex or brainstem levels are highly sensitive to isoflurane anesthesia. [Neural Res 1998; 20: 555-558]

Electrolytic denitrification: Long term performance and effect of current intensity

The long-term performance of the biofilm-electrode reactor is demonstrated for denitrification. The total nitrate and nitrite concentration, oxidation-reduction potential (ORP), total organic carbon (TOC), color, and viable cell count in the effluent, were monitored to evaluate the performance of the reactor. Initially, the applied electric current intensity was varied from 0 to 100 mA. A nitrate removal efficiency exceeding 98% was achieved at a current of 20 mA when phosphate was used as a buffer. Current intensities between 20 to 25 mA resulted in the lowest effluent concentrations of nitrate, whereas, lower current intensities affected proportionately less nitrate reduction. For higher current intensities, hydrogen inhibition and charge induced repulsion caused decreased reduction efficiencies. ORP was governed by both the concentrations of hydrogen and effluent nitrate. A total nitrate removal efficiency of 85% was achieved at a current level of 25 mA in the absence of any nutrient. No appreciable change occurred in viable cell count in the effluent with time.

Quantitative study of the formation of inorganic chemical species following corona discharge. II. Effect of SO 2 traces on the production of HNO 2 and HNO 3 in a humid atmosphere

The effect of sulfur dioxide traces on the formation of nitrous and nitric acid resulting from exposure to corona discharge in a composition-controlled, humid atmosphere was investigated. The production of NO 2 − and NO 3 − at the trace level was found to increase linearly with the corona discharge time, electric current intensity and quantity of electricity, but it was significantly lower in the presence of SO 2 traces. This decrease is attributed to the oxidation of SO 2 into sulfuric acid by OH radicals produced by corona discharge. The formation of S0 4 2− ions depends on the quantity of electricity and the amount of SO 2 introduced in the atmosphere, while the formation of HSO 3 − ions is a function of the electric wind and diffusion at air-water interface.

Diamagnetism in a plasma

This is an extension of a study of electric currents and force balance orthogonal to a unidirectional magnetic field of induction (B) in a collisionless plasma [K. D. Cole, Phys. Plasmas 3, 2717 (1996)]. All quantities are assumed to vary only in one direction orthogonal to B. Two new concepts are introduced, which are not in conventional plasma physics. First a magnetic polarization effect corresponding to electric polarization is found. This defines a contribution to the magnetic moment per unit volume of −ρmc2E2/B3. Second the conduction current is defined in terms of the curl of the magnetic field intensity H, in accordance with Maxwell. In this scheme, when there is no electric field, (1/4π)(∂H/∂z)B+(∂p⊥/∂z)=0, instead of the conventional equation with B/μ0 in place of H. In both schemes, j×B−∇p⊥=0. Though this makes no difference to the electric current intensity calculated in the two schemes, and no difference to the force balance equation, it makes a significant difference to the relationship between B and p⊥ in many plasma conditions of interest. When the electric field is nonzero, the situation is more complex. It is shown that the new diamagnetism of this paper and the dielectric current of the earlier one are consistent with special relativity. Some applications of the theory are discussed.

The average shape of the Magnetopause: A comparison of three‐dimensional global MHD and empirical models

We present a predictive model of the magnetopause, constructed using three‐dimensional global MHD simulations of the magnetosphere over a range in solar wind dynamic pressure and the north‐south component of the interplanetary magnetic field (IMF BZ). The magnetopause is identified in the simulations using electric current intensity, thermal pressure, and magnetic field line mapping. The magnetopause is fitted by least squares to an ellipse in each plane, and a fully three‐dimensional magnetopause surface is constructed by assuming an elliptical cross section at intermediate clock angles. There is considerable flaring of the magnetopause dependent on BZ in the noon‐midnight meridian plane due to reconnection but virtually no flaring in the equatorial plane. Despite this asymmetry, when averaged over clock angle, the model shows a general agreement with recent (axisymmetric) empirical magnetopause models and predicts observed magnetopause crossings with about the same accuracy as the empirical models. Unlike these empirical models, our model can directly investigate asymmetries between the meridian and equatorial planes. The subsolar distance, directly measured from the simulations, varies linearly with BZ for both northward and southward interplanetary magnetic field, as do distances to the magnetopause on the flanks. Magnetospheric plasma pressure causes these distances to scale with dynamic pressure by a power law whose exponent is a bit less than −1/6 on the dayside, but little deviation from this ideal Chapman‐Ferraro value is seen in the magnetotail. These uniform changes with Bz lead to approximate conservation of (1) magnetopause shape in the dayside equatorial plane, (2) projected area in the dayside meridian plane, and (3) magnetopause cross‐sectional area in the dawn‐dusk plane. The dawn‐dusk magnetopause cross section is nearly circular on average, but cross sections in the tail are elongated in the Z direction on average.

High electric field conduction mechanisms in electrode poling of electro-optic polymers

We investigated electrical conduction phenomena, which occurred during high electric field electrode poling of side chain χ(2) polymers. Electric current and second harmonic intensity were measured simultaneously in poling experiments performed on samples with and without an additional inorganic poly–methyl–siloxane layer. Current densities appeared to be limited by a Schottky-type potential barrier at the electrode/insulator interface. The field dependence of the current density was found to be Schottky charge emission for medium field strengths (EPOL≤100 V/μm) whereas it was dominated by Fowler–Nordheim tunneling at higher poling fields. In the presence of the siloxane layer, a significant suppression of tunneling current was observed. This leads to a reduced probability of singular dielectric breakdown events and shifts the limit of avalanche breakdown to higher internal effective poling field strengths.

Anionic gels as vehicles for electrically-modulated drug delivery. I. Solvent and drug transport phenomena.

The purpose of this study was to elucidate the in vitro behavior of anionic gels as formulation matrices for electrically-modulated drug delivery. Agarose and combinations of agarose with other anionic polymers (carbomer 934P; xanthan gum) were selected and tested to evaluate their potential for drug delivery. Electrical current was applied by an automatic crossover power supply to minimize the current fluctuation. Hydrocortisone was selected as the model drug in order to minimize electrostatic interference with drug transport. Syneresis and drug migration were evaluated as a function of current application time and the intensity of electrical current. The data show that electrical current strength and gellant content can affect both the syneresis and drug migration. A linear correlation was found between hydrocortisone loss and mass loss via the exudate. Moreover, in agarose-carbomer 934P gel systems, cumulative gel mass loss is a linear function of time at low intensities of electrical current (e.g., 0.5 mA and 1 mA). However, hydrocortisone distribution, after electrical application, is relatively asymmetric in those agarose-carbomer 934P gels (and in agarose-xanthan gum gels) in contrast to gel matrices containing only agarose. In this study, the use of carbomer 934P in conjunction with agarose enables the formulator to achieve zero-order release with electrical application. Increased anisotropicity of a gel system due to the application of electrical current could alter the effectiveness of a drug delivery system.

Quantitative study of the formation of inorganic chemical species following corona discharge—I. Production of HNO 2 and HNO 3 in a composition-controlled, humid atmosphere

Nitrous and nitric acid formed after exposure to a corona discharge in a composition-controlled humid atmosphere were collected in an aqueous liquid phase at room temperature. It was found that the production of NO 2 − and NO 2 − ions at the trace level increased linearly with the corona discharge time, electric current intensity and quantity of electricity. The relative amount of nitrates formed was larger than that of nitrites.

Effects of disopyramide on the atrial fibrillation threshold in the human atrium

The effects of disopyramide on the atrial fibrillation threshold (AFT) in the human atrium were investigated. To evaluate atrial vulnerability, the following electrophysiologic parameters were measured before and after the administration of disopyramide (2 mg/kg) in 12 patients with paroxysmal atrial fibrillation: The right atrial effective refractory period (ERP) and percentage maximum atrial fragmentation (%MAF) were measured by atrial premature stimulation based on a cycle length of 500 ms. The inter-atrial conduction time (ACT) was measured by burst pacing (120/min) for 30 s. AFT was measured by applying a high-frequency (50 Hz) stimulation for 1 s given at the right atrial appendage. AFT was defined as the lowest intensity of electrical current that could induce atrial fibrillation lasting for more than 30 s. Disopyramide significantly reduced %MAF, and prolonged ERP and ACT. AFT was measured in all patients and the mean AFT was 3.1 ± 1.7 mA. After the administration of disopyramide, AFT significantly increased to 6.1 ± 3.6 mA. There was a positive correlation between ERP and AFT, and a negative correlation between %MAF and AFT. No correlation was detected between ACT and AFT. In conclusion, disopyramide increased AFT in the human atrium.

Build-up of thermoelectrets at phase transitions in fatty acids

Abstract The thermotropic mesomorphism of different fatty acids is illustrated by the thermodielectric effect and by micro structural observations. The fatty acids which are studied (arachidic, lauric and elaidic acids) have an initial space charge. The thermodielectric effect is due to charge separation and consists in the appearance of noticeable variations of electric current intensity as a function of the temperature at phase transitions.

Comparison of dayside current layers in Venus' Ionosphere and Earth's equatorial electrojet

The major physical aspects of the equatorial electrojet of Earth and the dayside ionospheric current layers of Venus are compared, viz., the electric current intensity and total current, roles of electric field, pressure and gravity, diffusion time scales, and the Bemouille effect. The largest potential differences, of the order of 10 volts, horizontally across the dayside ionosphere of Venus, have important implications for possible dynamo action in the Venus ionosphere and the application of an electric field from the lower atmosphere or from the solar wind. An upper limit to the horizontal scale of vertical magnetic fields in the Venus ionosphere is estimated thereby for the first time. New upper limits on the velocity in, and thickness of, a possible S layer at Venus (Cloutier et al., 1987) are presented. If an S layer exists, it is only for extreme conditions of the solar wind. A mechanism for formation of magnetic ropes in the Venus ionosphere is also proposed.

Some Optical Properties of the Elaidicum Acid in Mesophase

Abstract The liquid crystal (smectic C* type) properties of the elaidicum acid, from 28°C to 51°C have been studied and utilised in this paper. The electrical potential, the capacitance and the electric current intensity versus applied voltage on a membrane of liquid crystal were measured. The experimental results of these measurements and the microstructural aspects show that this acid has the dielectric properties of a liquid crystal and is ferroelectric. The dependence of the current on time, when an electric field is applied and removed, were investigated, too, the results confirming the previous conclusions. Taking into account these findings, different liquid crystal cells were realised and utilised for the “nonlinear lens” effect. This is the external self-focusing of laser light in the liquid crystal film. A He-Ne laser (Λ = 6328 A, P = 16-20 mW) was utilised for the experimental setup. The f NL change with the sample thickness and with the temperature was determined, the optical nonlinearity ϵ2 v...