Maximum Electric Potential Research Articles

Numerical analysis of arc characteristics in two-electrode GTAW

A two-dimensional numerical model is developed to describe the arc characteristics in two-electrode gas tungsten arc welding. The influence of different welding current, shielding gas, and shielding gas flow rate is investigated. The arc characteristics are analyzed by studying the distributions of physical quantities including arc temperature, electric potential, and total heat flux on the workpiece. The simulated results reveal that a higher arc temperature value is obtained in helium arc than in argon arc. For obtaining high arc temperature, there is an optimum range for shielding gas flow rate and too high or too low is not appropriate. In addition, the increase of welding current results in the increase of the maximum arc temperature, electric potential, and total heat flux. To validate the accuracy of simulated results, welding experiments are performed and the arc temperature is calculated by the spectral signal of arc plasma. The simulated results are compared with the experimental ones and there is a good agreement.

AC frequency-based electrical stimulation of hydrogel microactuators employing Parylene-N coated electrodes

This article demonstrates the first AC-frequency based electrical actuation of hydrogels employing coplanar microelectrodes coated with Parylene-N. For the first time hydrogel microactuators were operated at applied voltages up to 40Vpk-pk without any electrolyte electrolysis or external pumping equipment. An RC circuit model was developed to determine the characteristic frequency required to overcome electrostatic shielding, as the hydrogels were actuated in the polarizable potassium hydroxide (KOH). The characteristic actuation frequency was found to be between 10kHz and 1GHz, with the minimum frequency at an electrolyte concentration of 1mM and Parylene-N thickness of 100nm. This circuit model was also extended to calculate the total capacitance of the hydrogel-based system. To validate the circuit model, the total capacitance of the system was experimentally measured using capacitance and admittance spectroscopy, for Parylene-N thicknesses from 2145±55nm to 565±7nm and from 1mM to 10mM KOH. Good agreement was found at higher frequencies, while at lower frequencies the system demonstrated frequency and concentration dependent behavior. The spectroscopy results were used to calculate the apparent power of the system based off the maximum electric potential of 40Vpk-pk applied during actuation, with an absolute minimum and maximum of ~2×10−4VA and ~2×10−2VA, respectively. To determine actuation dynamics systems were fabricated with Parylene-N thicknesses from 907±28nm to 348±13nm and equilibrated with 1mM or 5mM KOH, providing a system above and a system below the predicted characteristic frequency, respectively. The 1mM KOH system displayed true strains from 18% to 30% with response times from 14.7s to 4.7s, with optimum response at applied electric fields of 16kV/m or 40Vpk-pk with an 80% duty cycle. The 5mM KOH system had a maximum true strain of ~7% and response time of 14.9s. The trend observed while increasing frequency was also observed when a 1mM KOH sample was subjected to increasing applied electric potential, which showed a 674% increase in true strain and a 703% decrease in response time, from 15Vpk-pk to 40Vpk-pk. All systems actuated displayed deformation at all frequencies tested; thus even a minimal frequency can disturb electrostatic shielding, but above the characteristic frequency deformation and response times were optimum. This work overcomes the previous operational challenges associated with electrical hydrogel actuation, and investigates the electrical and actuation characteristics of the hydrogel-based system. Moreover, as hydrogels operated at lower frequencies still displayed actuation, hydrogel actuation could occur at low power zones enabling its integration within ultra-low power portable systems.

Dust accumulation effect on efficiency of Si photovoltaic modules

We experimentally studied the electrical efficiency effects of naturally forming atmospheric dust deposits on commercial photovoltaic panels. The variable considered for measurements was the electric potential for three commercial silicon modules: monocrystalline, polycrystalline, and amorphous. A mathematical model was developed to determine maximum potential as a function of temperature and of total incident radiation. The study presents two essential parts: the naturally deposited dust particles and the variation in maximum electric potential between clean and dirty modules. The results indicate that the maximum reduction in potential is around of 6% for monocrystalline and polycrystalline modules and of 12% for the amorphous silicon.

Steady viscoelastic fluid flow between parallel plates under electro-osmotic forces: Phan-Thien–Tanner model

The electro-osmotic flow of a viscoelastic fluid between parallel plates is investigated analytically. The rheology of the fluid is described by the Phan-Thien–Tanner model. This model uses the Gordon–Schowalter convected derivative, which leads to a non-zero second normal stress difference in pure shear flow. A nonlinear Poisson–Boltzmann equation governing the electrical double-layer field and a body force generated by the applied electrical potential field are included in the analysis. Results are presented for the velocity and stress component profiles in the microchannel for different parametric values that characterize this flow. Equations for the critical shear rates and maximum electrical potential that can be applied to maintain a steady fully developed flow are derived and discussed.

Sliding frictional contact analysis of functionally graded piezoelectric layered half-plane

This paper investigates the sliding frictional contact problem of a layered half-plane made of functionally graded piezoelectric materials (FGPMs) in the plane strain state. It is assumed that the punch is a perfect electrical insulator with zero electric charge distribution, and the friction within the contact region is of Coulomb type. The electro-elastic properties of the FGPM layer vary exponentially along the thickness direction. The fundamental solutions for the applied concentrated linear forces perpendicular and parallel to the FGPM layer surface are obtained. Using the superposition theorem, the problem is reduced to a Cauchy singular integral equation which is then numerically solved to determine the contact tractions, contact region, maximum indentation depth, electrical potential and electromechanical fields. Numerical results show that both the material property gradient and the friction coefficient have significant influence on the contact performance of the FGPM layered half-plane.

Formation of maximum electric potential at the geomagnetic equator by the disturbance dynamo

The effect of a disturbance dynamo during geomagnetic activity on the equatorial ionospheric electric fields is investigated, using model results from the NACR/TIEGCM (National Center for Atmospheric Research Thermosphere Ionosphere Electrodynamics General Circulation Model). Model runs are made for different time‐lengths of geomagnetic activity, for different seasons, and for different solar activities to investigate how and where the maximum electric potential forms. Model results show that the maximum electric potential is located at around 300 km altitude and at local time after the pre‐reversal enhancement at equinox for high solar activity. For the case at solstice, without pre‐reversal enhancement, the location moves to around 110 km altitude and to the local time close to midnight. Giving various parameters in the model runs to simulate different background conditions, many important output quantities are used to study the distributions of perturbed electric potential at the geomagnetic equator. Model investigation indicates that normal quiet time electrodynamics, at different seasons with different solar activities, significantly affect the distribution of perturbed current density associated with geomagnetic activity. Furthermore, model results also reveal that significant perturbed zonal electric fields tend to build up six hours after the onset of geomagnetic activity, except at regions close to sunset and sunrise, and the perturbed vertical electric fields increase with the time length of geomagnetic activity.

Frictionless contact analysis of a functionally graded piezoelectric layered half-plane

This paper investigates the frictionless contact problem of a layered half-plane made offunctionally graded piezoelectric material (FGPM) in the plane strain state under theaction of a rigid punch whose shape may be flat, triangular or cylindrical. It is assumedthat the punch is a perfect electrical insulator with zero electric charge distribution. Theelectroelastic properties of the FGPM layer vary exponentially along the thicknessdirection. By using the Fourier integral transform technique, the problem is reduced to aCauchy singular integral equation which is then numerically solved to determine thecontact pressure, contact region, maximum indentation depth, normal stress,electrical potential and electric displacement fields. The stress intensity factor isalso given to quantitatively characterize the singularity behavior of the contactpressure at the ends of a flat and triangular punch. Numerical results show thatboth the material property gradient of the FGPM layer and the punch geometryhave a significant influence on the contact performance of the FGPM layeredhalf-plane.

Increasing the mass resolution in a TOF aerosol mass spectrometer using a nonlinear post focusing method

The mass resolution for the time of flight aerosol mass spectrometer for aerosol component analysis is dependent on the initial direction and energy of the ions. We have found that the shape of the optimum post focusing electric field is nonlinear. The maximum electric potential should be applied to the ions whose initial direction is 90°. To determine the post focusing effects, a laser ablation mass spectrometer was installed. By using this LA-MS, it was found that the average energy distribution of the laser ablated ions was 8 eV. To establish an optimum mass resolution, a time delay and a high voltage are needed. The study results showed that 1500 ns and 3.7 kV, respectively, were the optimum parameters for time delay and voltage for this system. Using these optimized parameters, good resolution between the isotope mass signals of copper was achieved.

High‐temperature oxidation of a metal particle: Nonisothermal model

AbstractA transient electric voltage of the order of 1 V may form during the combustion of a metal particle. The electrical field may form due to the different diffusion rate of the positive and negative charge carriers through a growing mixed‐ionic‐electronic conducting oxide shell. Unlike previous models, the effect of ambient gaseous oxygen transport to the particle surface is accounted for and steady‐state and charge neutrality in the oxide layer is not a priori assumed. Four key parameters affect the voltage‐temperature formation. The ratio between charge carries diffusion coefficients determines the surface electric potential amplitude, polarization and the time delay between the maximums of particle potential and temperature. The larger the difference between the diffusion coefficients, the greater is the voltage and the longer is the combustion time and the shorter is the time delay. The convection and radiation heat‐transfer coefficients exert a major impact on the time delay between the maximum of the surface electric potential and that of the temperature. The maximum electric potential and temperature are achieved almost at the same time when the transport coefficients are sufficiently large. This time difference decreases as either the heat‐transfer coefficients or the difference between the diffusion coefficients increase. Increasing the activation energy of the adsorption strongly decreased the oxidation, temperature and surface electric potential rate of rise during the early stage of the oxidation. Increasing the activation energy of the desorption increased the duration of the temperature and the potential drop in the later stage of the reaction. © 2005 American Institute of Chemical Engineers AIChE J, 2005

Circular surface electrode on a piezoelectric layer

This article considers a piezoelectric ceramic layer with a circular electrode attached to its surface. Exact solution is given for a piezoelectric medium whose thickness is considerably larger than the diameter of the electrode. Numerical solution for a piezoelectric layer of finite thickness is obtained. Field intensities near the edge of the electrode are established. Possible cracking initiation behavior is also discussed. Solutions are obtained for the maximum electric potential that the piezoelectric medium can be applied without catastrophic failure according to the criterion that the maximum stress intensity factor equals the fracture toughness of the ceramics.

Right atrial potential profiles during atrial fibrillation predict the success of atrial defibrillation

The right atrial electric potential was measured in 29 patients with chronic atrial fibrillation, and the clinical utility of these measurements in predicting the success of atrial defibrillation was investigated. The endocardial electric potential was recorded at 12 sites within the right atrium (high, middle, and low loci of anterior, posterior, lateral, and medial sites of the right atrium) with an electrode catheter. The duration and polar displacement of the atrial waves were measured at the one site that showed the maximum atrial electric potential among the 12 sites. The ratio of the maximum to the minimum atrial electric potential (atrial wave ratio) was calculated. Patients were classified into two groups according to the success (n = 6) or failure (n = 23) of atrial defibrillation. Electrophysiologic data were compared between the two groups, and correlations were evaluated between the data and the maximal left atrial diameter obtained from M-mode echocardiography. The two groups did not differ in the duration and polar displacement of the atrial waves. However, the atrial wave ratio was significantly lower in the success group than in the failure group, and the success rate of atrial defibrillation was also significantly greater in the patients with an atrial wave ratio of 10 or lower. This ratio showed a positive correlation with the maximal left atrial diameter; it became more difficult to achieve atrial defibrillation as the atrial wave ratio increased. Thus, the right atrial electric potential profile of patients with atrial fibrillation is a useful predictor of the success of atrial defibrillation.

Erythrocyte Hemolysis by Organic Tin and Lead Compounds

The effect of trialkyllead and trialkyltin on pig erythrocyte hemolysis has been studied and compared. The results of experiments showed that the hemolytic activity of organoleads increases with their hydrophobicity and follows the sequence: triethyllead chloride < tri-n-propyllead chloride < tributyllead chloride. And similarly in the case of organotins: triethyltin chloride < tri-n-propyltin chloride < tributyltin chloride. Comparison of the hemolytic activity of organoleads and organotins indicates that the lead compounds exhibit higher hemolytic activity. The methods of quantum chemistry allowed to determine the maximum electric potential of the ions R3Pb+ and R3Sn+, and suggest a relationship between the potential and toxicity.

IGF-II receptor number is increased in TE-85 osteosarcoma cells by combined magnetic fields.

Human osteosarcoma-derived osteoblast-like cells, TE-85, were used to assess the effect of a low frequency alternating magnetic field in combination with a controlled static magnetic field (combined magnetic fields, CMF) on insulin-like growth factor receptor regulation. In our culture system, application of a 15.3 Hz CMF induces a calculated maximum electrical potential in the culture media of 10(-5) V/m. Initial characterization of TE-85 cells demonstrated that (a) TE-85 cells contain both type I insulin-like growth factor (IGF-I) and IGF-II receptors and (b) dose dependence for IGF-stimulated cell proliferation were comparable to the affinities of the IGF's binding to membrane binding sites (i.e., receptors had dissociation constants in the low nanomolar concentration range). The studies with CMF exposure revealed that CMF treatment for 30 minutes increased the number of IGF-II receptors in a frequency-dependent manner without affecting the number of IGF-I receptors. The CMF-dependent increase in IGF-II receptor number was associated with a significant increase in the IGF-II dissociation constant. These results indicate that a membrane receptor levels can be altered by short-term exposure to low-energy, low-frequency electromagnetic fields and suggest a potential biochemical mechanism for electromagnetic effects on bone formation and remodeling.

Energetic particle beams in the plasma sheet boundary layer following substorm expansion: Simultaneous near‐Earth and distant tail observations

We present simultaneous observations of energetic particles by ISEE 1 in the near‐earth geomagnetic tail and by ISEE 3 in the distant geomagnetic tail following the onset of a major substorm as indicated by ground magnetograms and synchronous orbit particle data. At substorm onset, both spacecraft are in the tail lobes. About 8 min after onset, ISEE 1 enters the plasma sheet; at the plasma sheet boundary, earthward directed ion beams are observed. At the same time (within the 128‐s time resolution) tailward directed ion and electron beams are observed at ISEE 3. These beams persist intermittently for 25 min. The observations are explained in terms of the substorm neutral line model, wherein the near‐earth and distant plasma sheet are disconnected after reconnection has proceeded to the last closed field line within the plasma sheet. Electron plasma and magnetic field data on ISEE 3 show that during the whole time period, ISEE 3 stays in the distant lobe and does not enter the plasma sheet. The plasmoid, expected to be released after reconnection has proceeded to the lobe field, is sensed by ISEE 3 as a traveling compression region. The velocity dispersion effects during the appearance and disappearance of the beams indicate that these beams are not due to temporal effects but due to crossing of layers with particles of different velocity emitted from a steady source. From the observation of gradient anisotropy effects in the high‐energy protons, the spacing of the layers of particles with different velocity can be derived. This allows determination of the maximum electric potential along the new neutral line. The corresponding electric field is considerably smaller than the energy of the highest energy particles observed. It is argued that the plasma sheet close to the substorm‐generated neutral line contains high fluxes of high‐energy particles that may be sufficient to produce the high‐energy boundary layer around plasmoids. Acceleration of the high energy particles may mainly occur during substorm recovery.

Research and development of geothermal resources in greece: present status and future prospects

Geothermal energy in Greece is attracting attention as a potentially important contributor to the national energy sources. The geological structure of this country is such that favourable conditions exist for geothermal resources. Hydrothermal systems have already been identified on the islands of Milos and Nisyros (Aegean Sea). Results of preliminary production tests in the five existing geothermal wells on Milos can guarantee the operation of geothermal electric condensing units to a total capacity of about 24 MW. The first exploratory wildcat well, drilled on Nisyros (caldera area) to a depth of 1816 m, confirmed the existence of a very high temperature deep reservoir. Integrated interpretation of prospectings carried out in the areas of second priority order (Lesbos, Loutraki-Sousaki, Platystomon, Aedipsos, Poros, etc.) is now under way, aimed at discovering other economically exploitable geothermal fields. The northern part of Greece, where the active tectonics of Macedonia (Strymon Valley and Langadas-Volvi zone) has favoured the existence of medium to low enthalpy geothermal systems, which can be exploited for direct heat applications. By the end of 1984 the first Greek geothermal power plant of 1.5 - 4 MW will be installed on Milos, and by the end of 1986 a 4 – 5 MW pilot plant could be installed on Nisyros, providing the second well proves productive. The maximum geothermal electric potential of Milos has been estimated at 100–200 MW. Therefore the electric energy produced could be transmitted economically from Milos to a significant number of islands in the Aegean Sea and to the mainland by means of a system of a.c. submarine cables by 1992. The availability of local geothermal sources on the islands of the Aegean Sea could thus represent appreciable savings in imported oil.

Spiky ion acoustic waves in collisionless auroral plasma

A theory of spiky electric fields in ‘inverted V’ precipitation regions is formulated and compared with recent spacecraft observations of solitary waves and double layers. The theory predicts that the electric fields propagate along the magnetic field as perturbed ion acoustic solitons that intensify by exchanging momentum with reflected particles. The solitons have minimum scale lengths of about 100 m and maximum electric potential and field amplitudes of 1–10 V and 1–10 mV/m. They propagate at the local ion acoustic speed (Cs ∼ 10–100 km/s), Doppler‐shifted by the drift speed of upward flowing cold ions. Both rarefactive and compressive solitons, with negative and positive electric potentials, respectively, are possible. Upward propagating compressive modes intensify when the upward flow of ionospheric ions exceeds roughly 10 Cs. The rarefactive mode intensifies when the upward field‐aligned current at 1 RE exceeds 0.1–1 μA/m² or when the upward cold ion drift is supersonic. The kinematic and dynamic properties of rarefactive solitons are consistent with the recent observations, although further analysis, both theoretical and experimental, are required for an unambiguous interpretation. The evolution of localized ion acoustic modes into small amplitude double layers is also discussed.