Potential Difference Method Research Articles

Beryllium overlayers on Mo(1 1 2) and Mo(0 1 1) surfaces

Low-energy electron diffraction, Auger electron spectroscopy and contact potential difference methods have been used to study formation of Be overlayers on the Mo(1 1 2) and (0 1 1) surfaces in the temperature range from T=78K up to the beginning of Be desorption. At a coverage θ=1, where θ is defined as the ratio between concentrations of adatoms and surface substrate atoms, overlayers were found to be pseudomorphic on both the substrates. Various types of close-packed Be structures were observed at θ>1. Annealing of the Mo samples covered with Be caused not only overlayer ordering, but also a partial solution of Be in the near-surface layer of Mo and creation of a surface alloy. It is inferred that the work function changes, positive on Mo(1 1 2) up to 0.4eV and negative on Mo(0 1 1) down to −0.6eV, are caused mainly by changes in surface roughness while the contribution of polarization of the BeMo adsorption bond seems to be only minor.

Electron work function of intermetallic compounds in the cerium-cobalt system

The concentration dependences of the electron work function for lithium samples in the cobaltrich region of the state diagram of the Ce-Co binary mixture is studied by the contact potential difference method at 20°C. It is shown that the electron work function isotherm has the shape of a broken line with kinks corresponding to intermetallic compounds formed in the cerium-cobalt binary system.

Experimental Study of Three-Dimensional Identification of Semi-Elliptical Crack on the Back Surface by Means of Direct-Current Electrical Potential Difference Method of Multiple-Point Measurement Type

A method for identification of a semi-elliptical crack on the back surface of metal plate by means of direct-current electrical potential difference method (DC-PDM) of multiple-point measurement type was proposed by the authors previously. Geometry of the crack was given by the two-dimensional location of the crack center, the surface and inward angles of the crack, and the length and depth of the crack. In this paper, experiments on the crack identification were carried out using six metal plates with different geometries of semi-elliptical cracks made on the back surface by electric discharge machining. Geometrical parameters of the crack were evaluated by the proposed method. The result of identification was successful and it was clarified that the semi-elliptical crack on the back surface can be identified nondestructively by dc-PDM of multiple-point measurement type.

1205 直流電位差法の分岐き裂への適用に関する検討(OS12.破壊力学とき裂の解析・き裂進展シミュレーション(2),OS・一般セッション講演)

1205 直流電位差法の分岐き裂への適用に関する検討(OS12.破壊力学とき裂の解析・き裂進展シミュレーション(2),OS・一般セッション講演)

Thermodynamics of resolvation of Mg2+, Ca2+, Cd2+, and Cu2+ ions in aqueous-ethanol mixtures on the basis of volta potential difference method

The volta potential difference method at 298.15 K was used to determine the real primary medium effect for magnesium, calcium, cadmium, and copper ions, and also the real Gibbs transfer energy of these ions from water into a mixed water ethanol (EtOH) solution. The surface potential value at the nonaqueous solution/gas phase interface \( \Delta \chi _{H_2 O}^{EtOH} \) was obtained. With account for this value, chemical thermodynamic characteristics of the studied ions in the water-ethanol solvent were calculated and the effect of composition and nature of the mixed solvent on the values obtained was analyzed. The dependence of variation in the thermodynamic characteristics of cation resolvation was established on their crystallographic radius that corresponds to the following sequence: Ca2+ < Cd2+ < Cu2+ < Mg2+.

Work function dynamics in activated thermionic cathode

Work function distributions along the length and over the hot edge of a cylindrical activated thermionic cathode and the temporal variation of these distributions during 20-h operation of arc discharge at various currents have been determined using the contact potential difference (CPD) method. Results obtained by CPD for the cathode spot agree with the data provided by the thermoelectron method. It is confirmed that metal atoms and ions in the cathode region of discharge exhibit the phenomenon of recycling.

A three-point electrical potential difference method for in situ monitoring of propagating mixed-mode cracks at high temperature

In this paper an electrical potential difference method for the real-time assessment of both the length and the direction of Mode II cracks is presented. Three measuring electrodes are placed in selected positions over the gauge area of a specially designed shear specimen and their readings are associated with the actual position of the crack tip using Finite Element Analysis (FEA). This information can be processed in real-time to provide continuous monitoring of the crack as it propagates either in pure Mode II (in-plane shear) or mixed Mode I (tension) and Mode II if the inclination of the crack exceeds 20°. In fatigue testing it is possible to produce d α / dN - Δ K II (in pure-shear) and d α / dN - Δ K I (in mixed-mode) plots on-line as the test is in execution. The method has been calibrated with optical measurements using a long-distance observation microscope on the nickel-based superalloy CMSX4 at high temperature. The main finding was that the central two sensing electrodes were sensitive to the length of the crack and insensitive to the crack angle, whereas the readings from the third electrode were sensitive to the crack angle and thus the exact position of the crack tip could be traced in real-time. Special techniques were implemented to rule-out thermoelectric effects and thermal stresses on the specimen.

10.1007/s11451-008-1031-2

The processes accompanying the formation of ytterbium films on the Si(111) surface at room temperature are investigated by the contact potential difference method, Auger electron spectroscopy, low-energy electron diffraction, and thermal desorption spectroscopy. It is shown that the grown metal films are uniform in thickness and that Si atoms virtually do not dissolve in the films. The atoms of the silicon substrate can diffuse in limited amounts into the Yb metal film only when the surface is bombarded by high-energy primary electron beams employed in Auger electron spectroscopy. The results obtained permit the conclusion that the previously observed oscillations of the work function in Yb-Si(111) thin-film structures cannot originate from dissolution of silicon atoms in the ytterbium film.

214 直流電位差法を用いたはんだボール/銅接合界面き裂評価に及ぼす銅線はく離とボイドの影響に関する3次元有限要素解析(材料力学V)

214 直流電位差法を用いたはんだボール/銅接合界面き裂評価に及ぼす銅線はく離とボイドの影響に関する3次元有限要素解析(材料力学V)

FSMモニタリングにおけるき裂の進展評価指標について

In order to evaluate the crack propagation behavior in FSM-monitoring, which is one of the non destructive inspection methods based on the electric potential difference method, a series of experiments and analyses were carried out. It was confirmed that the change of crack propagation direction or the initiation and propagation of cracks could be monitored by the variation of FC value corresponding to the potential difference change. It was elucidated that the initial potential difference largely affected FC value. The results indicated that arrangement of pairs and current direction should be noted for removing the effect of initial potential difference in monitoring of crack initiation and propagation. When the effect cannot be removed, not only FC value but also the potential difference change should be used as the measure for crack propagation in FSM-monitoring.

Irreversible structure transitions in Gd monolayers on Mo(112)

Low-energy electron diffraction (LEED), Auger electron spectroscopy (AES) and contact potential difference (CPD) methods have been used to investigate the structure of Gd monolayers deposited on Mo(112) at T = 78 K and the changes upon annealing in a wide temperature range, up to the beginning of desorption. In the submonolayer coverage range (θ < 0.67), the film structures p(1.3×1) and p(2×1) already formed at T = 78 K, testifying that Gd adatoms possess some mobility at rather low temperatures. The p(1.3×1) structure was found to appear at 0.07 < θ < 0.25, but it irreversibly turned into the p(2×1) structure when the annealing temperature, Tan, exceeded 500 K. Above θ = 0.25, the p(2×1) structure emerged immediately at 78 K. Formation of step arrays was observed in the range of Tan = 500–1200 K and is attributed to surface alloying. The suggestion of surface alloying is corroborated by data on annealing induced variations of the work function and Auger peak of Gd. In the coverage range 0.5 < θ < 0.67, the phase p(2×1) was found to coexist with the phase c(1.5×2), which corresponds to a physical monolayer. No evidence of surface alloy in the complete monolayer was revealed. Distinction between ordering scenarios for the systems Gd/Mo(1 1 2) and Dy/Mo(112) is discussed.

Numerical Characterization of Dosimetry, Human Body Resistance and Heart Current Resulting from Power‐Frequency Touch Current for an Anatomically Realistic Human Model

AbstractCharacteristics of power‐frequency touch current inside an anatomically realistic human model of Japanese adult were numerically analyzed under various scenarios of current paths using a modified scalar potential finite difference (SPFD) method. Then, complex distributions of the current density in the model were visually illustrated. Results of the dosimetry of current density for excitable tissues indicates that the touch current within the reference level (0.5 mA) does not always satisfy the basic restriction of current density in the light of ICNIRP guideline for general public. Two sets of the internal body resistances Ri (i.e., 1130–1510Ω and 1460–1920Ω) are obtained, depending on the conductivity sets used. Although Ri considerably depends on the current scenario concerned, the highest values of Ri were obtained for the hand‐to‐hand scenario, regardless of the conductivity set. The inhomogeneous model always gives a higher value of Ri than does the homogeneous model that has a single conductivity equivalent to the weighted‐average conductivity of the inhomogeneous model. It is found that the conductivity of muscle has significant influence on Ri, and that the resistance around the wrist and ankle is one of the predominant parameters to decide Ri. It is clearly shown that the current scenarios affect the pattern of the heart current flow, especially the direction of it, to a large extent. It is found that a current of 34–40% of touch current flows into the heart, and then the heart‐current ratio is remarkably larger than old data. The heart‐current factors of around 0.85 obtained are almost independent of the current scenarios, unlike those indicated in IEC60479‐1, provided that the direction of heart current is ignored. © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley &amp; Sons, Inc.

Heart current in an anatomically realistic human model due to contact with a low‐frequency energized source

AbstractDistributions of 60 Hz contact current around and inside the heart of the anatomically realistic human body are demonstrated under four scenarios: left hand to both feet, right hand to both feet, hand to hand, and foot to foot. The heart‐current ratios and the heart‐current factors are calculated. The new numerical method which is partly modified from the conventional scalar potential finite difference (SPFD) method is proposed. It is found that a part of ∼33–40% of the total contact current passes through the heart in three scenarios of one hand to either the other hand or feet, and these heart‐current ratios are much larger than the ones reported by Freiberger. Furthermore, the heart‐current factor is almost the same as the one in IEC 60479‐1 for the right‐hand‐to‐feet path, but is twice as much as the one in IEC 60479‐1 for the hand‐to‐hand path. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley &amp; Sons, Inc.

A Potential‐Based Inversion of Unconfined Steady‐State Hydraulic Tomography

The importance of estimating spatially variable aquifer parameters such as transmissivity is widely recognized for studies in resource evaluation and contaminant transport. A useful approach for mapping such parameters is inverse modeling of data from series of pumping tests, that is, via hydraulic tomography. This inversion of field hydraulic tomographic data requires development of numerical forward models that can accurately represent test conditions while maintaining computational efficiency. One issue this presents is specification of boundary and initial conditions, whose location, type, and value may be poorly constrained. To circumvent this issue when modeling unconfined steady-state pumping tests, we present a strategy that analyzes field data using a potential difference method and that uses dipole pumping tests as the aquifer stimulation. By using our potential difference approach, which is similar to modeling drawdown in confined settings, we remove the need for specifying poorly known boundary condition values and natural source/sink terms within the problem domain. Dipole pumping tests are complementary to this strategy in that they can be more realistically modeled than single-well tests due to their conservative nature, quick achievement of steady state, and the insensitivity of near-field response to far-field boundary conditions. After developing the mathematical theory, our approach is first validated through a synthetic example. We then apply our method to the inversion of data from a field campaign at the Boise Hydrogeophysical Research Site. Results from inversion of nine pumping tests show expected geologic features, and uncertainty bounds indicate that hydraulic conductivity is well constrained within the central site area.

1511 直流電位差法を用いたはんだボール/銅接合界面き裂評価における銅線位置とボイドの影響(OS15.電子デバイス・電子材料と計算力学(3),オーガナイズドセッション)

1511 直流電位差法を用いたはんだボール/銅接合界面き裂評価における銅線位置とボイドの影響(OS15.電子デバイス・電子材料と計算力学(3),オーガナイズドセッション)

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.

多端子型直流電位差法を用いた半楕円背面き裂の位置，寸法，形状と板厚の同時推定に関する電位場解析

多端子型直流電位差法を用いた半楕円背面き裂の位置，寸法，形状と板厚の同時推定に関する電位場解析

High stability and low driving voltage green organic light emitting diode with molybdenum oxide as buffer layer

Green organic light emitting diodes (OLEDs) with copper phthalocyanine (CuPc), 4,4′,4″-tris[3-methylphenyl(phenyl)amino]triphenymine (m-MTDATA) and molybdenum oxide (MoOx) as buffer layers have been investigated. The MoOx based device shows superior performance with low driving voltage, high power efficiency and much longer lifetime than those with other buffer layers. At the luminance of 100cd/m2, the driving voltage is 3.8V, which is 0.5V and 2.2V lower than that of the devices using CuPc (Cell-CuPc) and m-MTDATA (Cell-m-MTDATA) as buffer layer, respectively. Its power efficiency is 13.6Lm/W, which is 38% and 30% higher than that of Cell-CuPc and Cell-m-MTDATA, respectively. The projected half-life under the initial luminance of 100cd/m2 is 42,400h, which is more than 3.8 times longer than that of Cell-m-MTDATA and 24 times that of Cell-CuPc. The superior performance of Cell-MoOx is attributed to its high hole injection ability and the stable interface between MoOx and organic material. The work function of MoOx measured by contact potential difference method and the J–V curves of “hole-only” devices indicate that a small barrier between MoOx/N,N′-di(naphthalene-1-y1)-N,N′-dipheyl-benzidine (NPB) leads to a strong hole injection, resulting in the low driving voltage and the high stability.

Ｉｎ ｓｉｔｕ赤外分光測定法の実際 ２ 電位差測定法

Fundamental technical aspects for in situ infrared absorption spectroscopic measurements are described. Some of the potential difference methods used in electrochemical studies are reviewed.

Specific features of the formation of ytterbium films on the Si(111) surface at room temperature

The processes accompanying the formation of ytterbium films on the Si(111) surface at room temperature are investigated by the contact potential difference method, Auger electron spectroscopy, low-energy electron diffraction, and thermal desorption spectroscopy. It is shown that the grown metal films are uniform in thickness and that Si atoms virtually do not dissolve in the films. The atoms of the silicon substrate can diffuse in limited amounts into the Yb metal film only when the surface is bombarded by high-energy primary electron beams employed in Auger electron spectroscopy. The results obtained permit the conclusion that the previously observed oscillations of the work function in Yb-Si(111) thin-film structures cannot originate from dissolution of silicon atoms in the ytterbium film.