Potential Difference Distribution Research Articles

Path-related unexpected injection charges in BaTiO3 ferroelectric thin films studied by Kelvin force microscopy

The collective effect of injection charges constructed in a dot array using scanning probe microscopy (SPM) in BaTiO3 ferroelectric thin films was investigated with Kelvin force microscopy (KFM). Unexpected charges were observed in the SPM tip paths where poling bias was zero. The analysis of the array with different poling biases shows that the collective effect of the injection charges in the dot array induced a potential difference between film and tip, which in turn injected unexpected charges. The calculated potential difference distribution along the tip’s paths correlates well with KFM images of the unexpected charges.

Solid-liquid coexistence of polydisperse fluids via simulation

We describe a simulation method for the accurate study of the equilibrium freezing properties of polydisperse fluids under the experimentally relevant condition of fixed polydispersity. The approach is based on the phase switch Monte Carlo method of Wilding and Bruce [Phys. Rev. Lett. 85, 5138 (2000)]. This we have generalized to deal with particle size polydispersity by incorporating updates which alter the diameter sigma of a particle, under the control of a distribution of chemical potential differences mu(sigma). Within the resulting isobaric semi-grand-canonical ensemble, we detail how to adapt mu(sigma) and the applied pressure such as to study coexistence, while ensuring that the ensemble averaged density distribution rho(sigma) matches a fixed functional form. Results are presented for the effects of small degrees of polydispersity on the solid-liquid transition of soft spheres.

Three-Dimensional Identification of Semi-Elliptical Crack on the Back Surface by Means of Direct-Current Electrical Potential Difference Method With Multiple-Probe Sensor (PVP2006-ICPVT-11-93359)

AbstractCracks are popular defects initiated in structural components and their accurate evaluation is very important to assure the reliability of various plants. The direct-current electrical potential difference method is known as one of the most effective methods for the evaluation of the cracks. In this paper, a method of three-dimensional identification of a semi-elliptical crack existing on the back surface of a conductive plate by the direct-current electrical potential difference method with a multiple-probe sensor is proposed. The geometrical condition of the crack was specified by six parameters, the surface and inward angles of the crack plane, θsur and θin, the length and depth of the crack, c and a, and the two-dimensional location of the crack center, (yc,zc), on the back surface. The identification was carried out based on the distribution of electrical potential difference on the surface of the plate measured with a sensor composed of grid-arranged multiple probes called the “multiple-probe sensor.” As an approximate cracked body and a quick analysis method were used, a number of repeated electrical potential field analyses necessary for the identification of the crack became possible within a practical time. The validity of the method was numerically confirmed by carrying out the identification based on the result of the finite element analysis. The proposed method could be extended to the online monitoring of a semi-elliptical crack initiated on the inner surface of tubular components by means of the multiple-probe sensor placed on the outer surface.

Three-Dimensional Identification of Semi-Elliptical Surface Crack by Means of Direct-Current Electrical Potential Difference Method With Multiple-Probe Sensor

A method of three-dimensional identification of a semi-elliptical surface crack by direct-current electrical potential difference method with a multiple-probe sensor was proposed and its validity was numerically examined. The condition of the surface crack embedded in a conductive plate was specified by the two-dimensional location of the crack center, length, and depth of the crack, and the surface and inward angles of the crack plane. Identification was carried out based on the distribution of the electrical potential difference around the crack measured on the surface of the plate with the “multiple-probe sensor” which is composed of many probes aligned in two orthogonal directions. The location and surface angle were evaluated using the point symmetry of the potential difference distribution. The inward angle was determined by the magnitude of symmetry of potential difference distribution with reference to the evaluated crack line. Finally, length and depth of the crack were determined using the exact solution of potential difference for an inclined inner elliptical crack which yields similar potential difference to that of the inclined semi-elliptical surface crack. The validity of the method was numerically confirmed by carrying out the evaluation based on the result obtained by finite element analysis.

Interpretation of AC surface current density by deconvolution of potential differences in solution

In localized electrochemical impedance techniques, the measurable AC potential difference in solution is related to the AC surface current distribution simply by using Ohm’s law. However, this relationship is not true for the cases in which current distribution is non-uniform. In order to correctly obtain the surface current density, deconvolutions of the solution potential difference using the base line stripping procedure and the Fast Fourier Transform method have been simulated and discussed. A more accurate spatial estimate of the surface current density distribution can be obtained by deconvoluting the measured potential difference distribution in the solution than by simply using Ohm’s law. The accuracy of the deconvolution using the base line stripping procedure is greatly dependent on the errors of measurement, and experimental data with a very low noise level are therefore required. Deconvolution by a Fast Fourier Transform is also very sensitive to noise and discontinuity in the potential difference distribution, but the sensitivity can be dramatically reduced to an acceptable level by using a low pass filter.

Exact piezoelastic solution of simply-supported orthotropic circular cylindrical panel in cylindrical bending

This work presents an exact piezoelastic solution of an infinitely long, simply-supported, orthotropic, piezoelectric, radially polarised, circular cylindrical shell panel in cylindrical bending under pressure and electrostatic excitation. The general solution of the governing differential equations is obtained by separation of variables. The displacements and electric potential are expanded in appropriate trigonometric Fourier series in the circumferential coordinate to satisfy the boundary conditions at the simply-supported longitudinal edges. The governing equations reduce to Euler Cauchy type of ordinary differential equations. Their general solution involves six constants for each Fourier component. These are solved from the algebraic equations obtained by satisfying the boundary conditions at the lateral surfaces. The solution of the inverse problem of inferring the applied pressure field from the given measured distribution of electrical potential difference between the lateral surfaces of the shell has also been presented. Numerical results are presented for typical pressure and electrostatic loadings for various values of radius to thickness ratio.

直流ポテンシャル法による表面き裂形状検出システム

Surface crack configuration can be detected by DC potential drop method. The simplified inverse method for determining the surface crack shape has been developed based on the FEM analysis for various deep surface cracks with different aspect ratios. The method has been applied to fatigue surface cracks introduced at the inside surface of stainless steel pipes. The cracks shape could be estimated with an accuracy of ±0.3mm in depth. In order to verify the method, a pipe internal scanner was devised for the measurement of potential difference distribution in 12 inch pipe. The scanner can pass through not only an elbow but also a vertical pipe. The crack position and the detailed crack configuration can be analyzed automatically from the measured potential difference distribution.

Exact piezothermoelastic axisymmetric solution of a finite transversely isotropic cylindrical shell

This work presents an exact piezothermoelastic solution of a finite transversely isotropic piezoelectric cylindrical shell under axisymmetric thermal, pressure and electrostatic excitation. The general solution of the governing equations is obtained in terms of potential functions which satisfy the boundary conditions at the ends. The axisymmetric loadings are expanded as a Fourier series in the axial coordinate. The coefficients in the infinite set of potential functions are obtained by solving sets of six algebraic equations resulting from the satisfaction of boundary conditions at the inner and outer surfaces of the shell for each Fourier component. The inverse problem of inferring the applied temperature and pressure fields from the given measured distribution of electrical potential difference between the inner and outer surfaces of the shell has also been solved. Numerical results are presented for typical pressure, thermal and electrostatic loadings.

Exact piezothermoelastic solution of simply-supported orthotropic circular cylindrical panel in cylindrical bending

This work presents an exact piezothermoelastic solution of infinitely long, simply supported, cylindrically orthotropic, piezoelectric, radially polarised, circular cylindrical shell panel in cylindrical bending under thermal and electrostatic excitation. The general solution of the governing differential equations is obtained by separation of variables. The displacements, electric potential and temperature are expanded in appropriate Fourier series in the circumferential coordinate to satisfy the boundary conditions at the simply-supported longitudinal edges. The governing equations reduce to Euler-Cauchy type of ordinary differential equations. Their general solution involves six constants for each Fourier component. These are solved from the algebraic equations obtained by satisfying the boundary conditions at the lateral surfaces. The solution of the inverse problem of inferring the applied temperature field from the given measured distribution of electrical potential difference between the lateral surfaces of the shell has also been presented. Numerical results are presented for typical thermal and electrostatic loadings for various values of radius to thickness ratio.

Computer simulation studies of solvent effect on electron transfer in acetonitrile solutions

The Molecular Dynamics method of computer simulation has been applied to evaluate the statistical distribution of the electrostatic potential difference eΔV between donor and acceptor sites immersed in acetonitrile solvent. By using this distribution the electron transfer rate constant for considered molecular systems has been calculated as a function of the free energy change of the reaction, ΔG. This dependence has been compared with the corresponding result calculated on the basis of the dielectric continuum model. It appears that a molecular model of solvent causes the shift of the inverted region for the charge separation reaction towards more negative values of ΔG. Consequently, the inverted region starts in the range of ΔG which is not accessible by experimental measurements. An estimation of the quantum correction to the potential difference distribution has been also performed. The correction calculated using the time correlation function of fluctuations in eΔV is found negligible.

マルチターミナルポテンシャル法による片側貫通き裂の検出に関する有限要素法による検討

The direct current potential drop method for on-line monitoring of side edge cracks was studied. In a plate with a single edge crack, the measured potential difference varies with crack position. Based on the distinctive distribution of potential difference, a multi-terminal DC potential technique was proposed for detecting crack length and position. In this technique, many potential difference measuring electrodes with the same spacing are fixed on the plate side. By comparing the many potential differences, the crack length and position can be calculated. The electrical field was analyzed by FEM, and the calibration curve and sensitivity were examined. The analyzed potential differences were classified based on the position. V1 is the potential difference between the electrode pair with a crack. V2 and V3 are the potential differences between electrode pairs without a crack, and are on either side of the V1 obtained electrode pair. V2 is closer to the crack than V3. V0 is the reference potential difference obtained by averaging the potential differences except V1, V2 and V3. The analysis shows that the potential difference ratio (V1+V2-V0)/V0 gives the accurate crack length, the difference of V2 and V3 gives the accurate crack position, and the sum of V2 and V3 gives the side on which the crack exists, that is, the surface or reverse-face.

A compact stripline transducer for measuring a pulsed electromagnetic field

A stripline transducer for measuring a pulsed electromagnetic field is proposed, the shape of which enables its electrical length to be increased considerably while keeping its actual dimensions small. An expression is obtained for the potential-difference distribution along the stripline transducer when it is excited by a pulsed electromagnetic field of step-shaped form. The theoretical results obtained are confirmed by experiment.

Application of electron-beam testing technique to potential profile measurements in thin film semiconductor devices

Abstract Electron-beam testing (EBT) technique was applied to measure the depth profile of the internal potential difference distribution and hence the internal electric field difference profile in a-Si:H solar cells whose conversion efficiency is essentially determined by the electric field profile in the intrinsic region. The a-Si:H solar cells were prepared for the EBT measurements by low-energy chemical plasma beam etching through a plasma-resistent mask (AZ PF 514) structured by electron-beam lithography. The measuring results show that the EBT technique is suitable beyond its traditional field of application to measure internal electric field difference profiles in semiconductor devices as e.g. solar cells. The measured potential and electric field difference distributions in reverse and forward biased a-Si:H solar cells are discussed in comparison with theoretical calculations in the literature.

Infinitely polydisperse fluids

A generalized semigrand formalism for polydisperse fluids is presented and is used to derive a thermodynamic consistency equation. In the infinitely polydisperse limit—corresponding to a flat distribution of chemical potential differences—a characteristic parameter is eliminated, and the description of the mixture is greatly simplified. In the case of infinitely polydisperse hard spheres, the absence of a characteristic diameter implies that all quantities must scale to the density, which provides the only length. This leads to an exact equation of state which, remarkably, is PV/NkBT=4/3 at all densities. The treatment is generalized, to show that there exists a whole family of stationary composition distributions which have invariant compressibility factors. Monte Carlo simulation is used to verify these results, and applications to other potentials are discussed. Infinitely polydisperse fluids provide a convenient starting point for new mixture theories.

A.D.C. electrical potential method for discrimination and sizing of an embedded crack and a surface crack on the back wall.

A D. C. Electrical potential method has been developed to discriminate between an embedded crack and a surface crack on the back wall and then to evaluate their positions and sizes. The method consists of the following procedures : (1) Calculate two parameters, ΔΦmax and A, from a measured curve of potential difference distribution, whereΔΦmax is the maximum potential difference and A is an area characterizing the distribution. (2) Assuming a surface crack, calculate two values of its length fromΔΦmax and A. (3) If these two values are equal to each other, then the crack is discriminated as a surface crack. ( 4 ) In the case of an embedded crack, calculate the length from A and the depth fromΔΦmax. It has been found from experiments that the proposed method is useful for discriminating and sizing embedded cracks and surface cracks on back walls.

ポテンシャル法によるパイプ内面き裂形状の外面からの検出

The configuration of surface cracks has been detected by Direct Current Potential Drop Method (PDM). A simplified method for determining the reverse-face crack configuration was invented based on the FEM analysis of electrical fields near the surface cracks with different aspect ratios and depth. Here, the reverse-face crack is defined as the crack existing on the opposite side of the detecting surface of structural material, while the crack detected on the same side is defined as the surface crack. The newly developed method was applied to the detection of the fatigue cracks on the inside surface of 2 inch stainless steel pipes subjected to tensile cyclic stress. The potential difference distribution near the surface cracks was measured by using many potential difference measuring electrodes placed along the reverse-face cracks on the outside surface of the pipes with the same spacing as the wall thickness. The potential difference distribution obtained by the present simplified method showed that the reverse-face crack configuration could be determined with relatively good accuracy, if the crack depths were more than 30% of the wall thickness. Thus, the potential drop method is considered to be appropriate for an on-line monitoring system of the reverse-face cracks.

A NEW METHOD OF MEASURING THE WORK FUNCTION OF MATERIALS

This paper reports a new method of measuring the work function of meterials. The method is based on accurate measuring of energy distribution of secondary electrons and contact potential difference of meterials. We call it the method of secondary electron emission-contact potential difference (SEE-CPD method). The work function of pure metals of Ni, Al, Au and Mo were measured by this method. The results are well consistent with that obtained by using photo-electron and Kelvin's method. The fundamentals and applications of the SEE-CPD method are proved to be correct and reliable.

Study of P-R Segment Using Magnetocardiographic Measurement

Magnetocardiographic measurement and analysis of P-R segments were studied using a SQUID fluxmeter in a PTB high performance magnetically shielded room. It was found that auricle depolarization and repolarization processes could be clearly distinguished by the difference in polarity on the equivalent magnetic field distribution, and the equivalent potential difference distribution maps. This confirmed that performing analysis of PR segments makes a valuable contribution to research on cardiomagnetism.

TheApteronotus EOD field: Waveform and EOD field simulation

1. Electric organ discharges (EOD) were measured in a wave-type electric fish,Apteronotus, with an array of electrodes. 2. The EOD waveform observed in the transient area (area where the equipotential lines converged) was a triphasic one in comparison to a biphasic one in the rest of the area. Electronic circuit simulation suggested that the triphasic waveform resulted from incomplete electrocyte synchronization within the electric organ. 3. The EOD field was obtained by computer simulation using the finite-element-method. The simulated results were used for calculation of the transepidermal potential difference distribution. This distribution is discussed with respect to sensitivity differences of electroreceptors in various parts of the fish.

Radial electrogenic activity in the stem of Vigna sesquipedalis: involvement of spatially separate pumps

Abstract. The surface electric potential of Vigna sesquipedalis stem, relative to that of the root medium, was most negative in the elongating zone where the difference in pH between parenchyma (P) and xylem sap (X) was at a maximum. The surface electrical potential was found to be determined by the distribution of radial potential difference (Vsx comprised two components; Vsx=Vpx−Vps.There were two electromotive forces, generating Vps at the surface of the parenchyma symplast and Vpx between P and X; both were partially dependent on respiration. The depolarization of Vpx upon removal of O2 was maximal in the elongating zone, suggesting that the activity of an H+‐pump extruding protons from the parenchyma into the xylem in exchange for K+ was greatest in this zone.