Search

Iron-based superconductors have been considered to be very promising in high-field applications for which multifilamentary wire and tape conductors with high mechanical strength are essential. In this work, 7-,19-, and 114-filament Sr0.6K0.4Fe2As2 (Sr-122) superconducting wires and tapes with silver as matrix and iron as outer reinforcing sheath were produced by the ex situ powderin- tube method. The mass densities of Sr-122 phase in 7- and 19-filament conductors were investigated by microhardness characterization, which revealed a positive correlation between hardness and transport critical current density (Jc) in round wires and flat tapes with various thicknesses. For Sr-122/Ag/Fe 114-filament conductors, in which an average cross-sectional filament size smaller than 50 lm was achieved by drawing into round wires of 2.0mm in diameter, the transport Jc can be significantly enhanced by flat rolling, as for the 7- and 19-filament conductors. The highest transport Jc for Sr-122 filaments in the 7-, 19-, and 114-filament Sr-122/Ag/Fe tapes reached 1.4×104, 8.4×103, and 6.3×103A cm-2 (4.2 K, 10T), respectively, showing a Jc degradation with the increase of filament number. This Jc degradation can be ascribed to the sausage effect for SR-122 filaments in longitudinal direction and the grain refinement in these very fine filaments. [ABSTRACT FROM AUTHOR]

An enhanced electrochemical method for accurately measuring cathodic protection (CP) currents through protective coatings has been developed as a means of quantifying the permeability and ‘cathodic shielding’ characteristics of nominally intact coating films. This method takes advantage of the fact that cathodic currents could significantly affect the alkalinity of areas under disbonded coatings to self-validate the correctness of current density measurements. In addition, the method provides a high level of accuracy and control over the environment. The method was evaluated using a series of ideally CP-shielding and non-CP-shielding materials, as well as, commercial pipeline coatings. A robust correlation of the measured current with generation of hydroxyl ions and the local alkalinity was established in all cases. For some commercial field joint epoxy pipeline coatings, results suggest that low CP levels could allow sufficient ionic current through a coating to promote a high-alkalinity local environment. However, this may not be the case for fusion-bonded epoxy coatings, which shielded CP and maintained a near-neutral pH under the coating. [ABSTRACT FROM AUTHOR]

The Mo-doped BiFe1−xMoxO3, where x =  0 and 0.6, samples were synthesised by the solid-state reaction method. Admirable ferroelectric and piezoelectric properties are expected on substituting solid solutions of bulk BFO with other oxide perovskite compounds. It offers an alternative and is an environment-friendly candidate for lead-free ferroelectric and piezoelectric devices. The prepared samples were investigated by XRD, Fourier transform infrared spectroscopy (FTIR), current density (JE) measurement, PE loop tracer and field emission scanning electron microscopy to examine their crystal structure, bonding nature, current density, ferroelectric hysteresis loop and surface morphology. The Mo-doped BFO shows a change in structure, increased grain size, reduction in current density and enhancement in the PE loop on doping Mo at the Fe site. [ABSTRACT FROM AUTHOR]

This paper presents a laboratory study aiming to evaluate the performance of electromagnetic (EM) density gauges as a non-destructive tool for hot mix asphalt (HMA) density measurement. In total, 36 HMA testing slabs with different compositions were prepared in laboratory. EM density gauge data were collected from these slabs using two common types of gauges, i.e., PQI 301 and PaveTracker 2701B, and compared with their bulk densities measured by the standard saturated surface dry (SSD) method. It was found that measurement direction, asphalt binder content, mixture air void content, and thickness of the testing slabs do not affect the accuracy of the EM density gauges. However, EM density gauge measurements are affected by the presence of moisture, gradation of asphalt mixture and gauge calibration method. It was also concluded that the accuracy of PaveTracker with mix calibration is comparable to that of the conventional standard method. [ABSTRACT FROM AUTHOR]

The current density–electric field (J-\xi ) characteristics of four insulators of dramatically different electrical qualities are assessed in terms of their operative electronic conduction mechanisms. Conduction in the two high-quality insulators is dominated by Ohmic conduction and Fowler–Nordheim tunneling, whereas conduction in the two low-quality insulators involves Ohmic conduction and space-charge limited current (SCLC). Ohmic conduction and SCLC are somewhat puzzling mechanisms for contributing to insulator leakage current since they require the existence of an Ohmic contact at the cathode. Our conventional understanding of an Ohmic contact makes it difficult to ascertain how an Ohmic contact could be formed to a wide bandgap insulator. This Ohmic contact dilemma is resolved by formulating an equivalent circuit appropriate for assessing the J-\xi characteristics of an insulator and then recognizing that an insulator Ohmic contact is obtained when the injection-limited current density from the cathode electrode is greater than that of the operative bulk-limited current density, i.e., Ohmic or SCLC for the four insulators under consideration. [ABSTRACT FROM PUBLISHER]

It is possible to determine the pitting corrosion resistance of a stainless steel in a given solution of a chemical process by electrochemical techniques. However, it is known that the result is influenced by the test parameters. The aim of this study was to determine the influence of the main test parameters, scan rate, imax; agitation/flow rate, and surface pretreatment on the electrochemical response of 316Ti/1.4571 stainless steel in an acidic (250 ppm Cl−, pH: 4, T: 30 °C) and an alkaline (4% Cl−, pH: 9, T: 80 °C) solution. The results were compared with classical immersion test results. The main result was that the agitation/flow rate had the greatest impact, with stagnant conditions giving very conservative results, followed by imax, which had an influence on the repassivation potential. [ABSTRACT FROM AUTHOR]

We calculate vector-vector correlation functions at two loops using partially quenched chiral perturbation theory including finite volume effects and twisted boundary conditions. We present expressions for the flavor neutral cases and the flavor charged case with equal masses. Using these expressions we give an estimate for the ratio of disconnected to connected contributions for the strange part of the electromagnetic current. We give numerical examples for the effects of partial quenching, finite volume and twisting and suggest the use of different twists to check the size of finite volume effects. The main use of this work is expected to be for lattice QCD calculations of the hadronic vacuum polarization contribution to the muon anomalous magnetic moment. [ABSTRACT FROM AUTHOR]

In this work, analytical models of subthreshold characteristics for an ultrathin dual-metal quadruple gate MOSFET have been developed by considering the quantum confinement effects. The 2D Schrödinger’s equation has been solved analytically to obtain the threshold voltage and subthreshold current of ultrathin dual-metal quadruple gate MOSFET with minimum cross-section of 3 nm × 3 nm . The inversion charge density at the threshold condition is obtained by considering minimum sub-band energy levels with a square potential well approximation for a two dimensional (width and height) carrier confinement. The subthreshold characteristics have been analyzed by varying different device parameters like channel cross-section, gate length ratio, gate metal work functions and gate oxide thickness. Further, the effect of 2D charge carrier confinement on drain induced barrier lowering (DIBL) has also been discussed using the threshold voltage model. The proposed models are validated against the numerical simulation results obtained from 3D ATLAS device simulator. [ABSTRACT FROM AUTHOR]

In this work, an ultra-thin insulating layer, poly(methylmethacrylate) (PMMA), is incorporated between the emissive layer (EML) and hole transporting layer (HTL) within the inverted polymer light-emitting diodes (PLEDs). Such a structure helps to reduce the hole injection and balance the electrons and holes in the EML. PLEDs with optimal PMMA thickness of around 5.6 nm is observed to obtain a maximum current efficiency of 14.33 cd A −1 , which corresponds to 7.07% improvement compared to that of the device without PMMA layer (13.5 cd A −1 ). The device with best performance exhibits a superior low driving voltage of 2.5 V at 1 cd m −2 and shows a lower efficiency roll-off current efficiency which sustains 85% of the maximum value when the current density reaches 140 mA cm −2 . [ABSTRACT FROM AUTHOR]

The electrochemical behavior of phosphate species on Ag(111) and Ag(100) single crystal surfaces was studied by experimental techniques and theoretical calculations. Characteristic cathodic/anodic potential peaks (V p ) appear in the current density-potential curves ( j – V ) for H 2 PO 4 − , H 3 PO 4 , and in the case of PO 4 3 − for concentrations lower than 0.1 M, where the interaction is stronger for the Ag(100) electrode. This demonstrate that the adsorption is sensitive to the surface structure. The adsorption energy (E ads ) of the different species on both surfaces was studied by means of DFT-vdW calculations. All phosphate species have tri-dentate binding. The |E ads | increased for the H 3 PO 4 ; H 2 PO 4 − ; HPO 4 2 − and PO 4 3 − sequence, and the tetrahedral structures are compressed. Although the same trend was observed on both crystalline surfaces, the films have the symmetry of the substrate, C 3 v and C 4 v . The influence of hydroxide co-adsorption was studied for different [HPO 4 2 − ]/[PO 4 3 − ] ratios in solution. The strength of adsorption obtained from experimental and theoretical calculations show an excellent qualitative correlation. [ABSTRACT FROM AUTHOR]

Purpose The purpose of this paper is to design a current transformer model based on the principle of B-dot. It can reflect the change of transmission line current and meet the requirement of automation and intelligence for current measurement in power system.Design/methodology/approach In this paper, a new type of current transformer is designed on the principle of B-dot, which has the structure of the inverse series of planar air core coils and the form of printed circuit board (PCB). With this structure, the current transformers can induce magnetic field quite well. The finite element simulation for the current transformer with n layers structure is conducted in the Maxwell, which help to optimize the design of the current transformer.Findings By setting up the experimental platform, the experiment of the current transformer is carried out. The results of the test show that the measurement accuracy can satisfy the requirement of measurement. Besides, the new current transformer has good transient characteristics and can meet the needs of the development of smart grid.Originality value The new type of current transformer is based on the principle of B-dot, which is designed with a new type of non-contact PCB hollow coil current transformer. It has no iron core, no ferromagnetic effect and the phenomenon of ferromagnetic resonance. It has great progress in its insulation performance, volume and bandwidth response. In addition, the planar hollow coil of the inverse series structure can make the structure more accurate. [ABSTRACT FROM AUTHOR]

The International Technology Roadmap for Semiconductors challenges the device research community to reduce the transistor footprint containing all components to 40 nanometers within the next decade. We report on a p-channel transistor scaled to such an extremely small dimension. Built on one semiconducting carbon nanotube, it occupies less than half the space of leading silicon technologies, while delivering a significantly higher pitch-normalized current density—above 0.9 milliampere per micrometer at a low supply voltage of 0.5 volts with a subthreshold swing of 85millivolts per decade. Furthermore,we show transistors with the same small footprint built on actual high-density arrays of such nanotubes that deliver higher current than that of the best-competing silicon devices under the same overdrive,without any normalization. We achieve this using low-resistance end-bonded contacts, a high-purity semiconducting carbon nanotube source, and self-assembly to pack nanotubes into full surface-coverage aligned arrays. [ABSTRACT FROM AUTHOR]

The effect of fluid flow on discharge characteristics in a dielectric liquid was determined. Tests were performed for flow in a 100 micron high, 5 mm wide, 50 mm long microchannel at Reynolds numbers up to 13 and applied DC potentials up to 1.5 kV through 100 micro planar electrode pairs along the floor of the channel. The current within the conduction regime increased as the flow rate increased for the case where the flow was in the same direction as the applied electric field. In the injection regime, there was an optimum flow rate for maximum current. [ABSTRACT FROM AUTHOR]

Introducing periodic Ag gratings in the rear side of thin-film silicon excites localized surface plasmon (LSP) and Fabry-Perot (FP) effect. These two effects as well as an intrinsic one pass through absorption overlay together and all contribute to the light absorption in silicon. On the basis of electromagnetic field's linear superposition, the absorptivity caused by LSP effect is separated from the overall absorptivity of a 500-nm-thick silicon and quantized by short current density. Finite difference time domain (FDTD) calculations were performed to obtain the absorptivity of silicon with different Ag grating parameters. The contribution of LSP effect to the light absorption is evaluated by photocurrent ratio and investigated under different Ag grating parameters. It is found that, as LSP effect is excited most intensively, the light absorption of silicon will also be enhanced extremely. By careful design, the overall short current density of silicon is optimized up to 25.4 mA/cm, where the contribution of LSP effect accounts for 38.6 %. Comparing to 14.5 mA/cm for a reference silicon stack, it increases up to almost 75 %. These results may give design suggestions in implementation of plasmonic solar cell as high efficiency devices. [ABSTRACT FROM AUTHOR]

The structure of AlN/GaN heterostructures with an ultrathin AlN barrier is calculated for normally-off transistors. The molecular-beam epitaxy technology of in situ passivated SiN/AlN/GaN heterostructures with a two-dimensional electron gas is developed. Normally-off transistors with a maximum current density of ~1 A/mm, a saturation voltage of 1 V, a transconductance of 350 mS/mm, and a breakdown voltage of more than 60 V are demonstrated. Gate lag and drain lag effects are almost lacking in these transistors. [ABSTRACT FROM AUTHOR]

Electrochemical impedance spectroscopy (EIS), linear polarization (LP), Tafel and cyclic voltammetry (CV) were performed to investigate the exchange current density (i 0 ) of U/U 3+ reaction in LiCl-KCl eutectic salt under different UCl 3 concentrations (0.5 wt%–4 wt%) and temperature conditions (723 K–798 K). The EIS spectra were measured by applying minimum overpotential from equilibrium potential and fitted to the proposed equivalent circuit. From the EIS experiments, the calculated values of i 0 were varied from 0.0054 A cm −2 to 0.102 A cm −2 . For the LP and Tafel methods, i 0 values were determined from the linear fitting at small and large overpotential ranges of the current-potential curves. The measurement for i 0 via CV was done analogously to the LP method. All i 0 values have the linear trend with the change of concentration and temperature; however, these values measured by LP, Tafel, and CV methods are greatly influenced by the change in electrode surface area. Overall, i 0 agreed within 33% relative error range with the EIS method being the most consistent and accurate in comparison to reported literature values. Dimensionless analysis was done on the EIS data sets providing insightful correlations for prediction of i 0 under various experimental conditions. [ABSTRACT FROM AUTHOR]

Electrothermal (ET) plasma discharges have application to mass acceleration technologies relevant to military ballistics and magnetic confinement fusion reactor operation. ET plasma discharges are initiated in capillary geometries by passing large currents (order of tens of kiloamperes) along the capillary axis. A partially ionized plasma then forms and radiates heat to the capillary walls inducing ablation. Ablated particles enter the capillary plasma source and cause a pressure surge that can propel pellets to velocities exceeding 2 km/s. These devices present several advantages over other mass accelerator technologies due to their simple design and ability to achieve high projectile launch frequencies. In order to investigate the operation of ET plasma discharges in more detail than previously possible, a 2-D, multifluid model has been developed to simulate the plasma-fluid dynamics that develop in these devices during operation. In this paper, the 2-D simulation model is used to investigate the effect of source geometry and current density on discharge characteristics. Peak pressure and electric field magnitudes for pulsed discharge operation are shown to scale well with theoretical and empirical scaling laws for steady-state discharge operation. The pulse shape of the source internal pressure is shown to change significantly with increasing source radius. The behavior of other plasma parameters is investigated. In addition, observations of the departure from the ablation-controlled arc regime are presented. This analysis suggests that, for the current pulse length investigated, source radii higher than 4 mm require significantly more current density in order to produce sufficient ablation to stabilize the plasma discharge. [ABSTRACT FROM AUTHOR]

A two-dimensional axisymmetrical computing model is formulated with using of which the mathematical modeling of the normal glow discharge in molecular hydrogen is fulfilled in an axial magnetic field with the induction B = 0.1 T in the pressure range p = 1.25−5 Torr and the current-source electromotive force E = 1−3 kV. [ABSTRACT FROM AUTHOR]

Fuel cell sensors with polymer electrolyte membrane for ethanol gas concentration measurement in human exhaled breath were studied for the purpose of reduction of platinum (Pt) catalyst loading in both sensor electrodes and decreasing the sensor production cost. The sensors with Nafion electrolyte and different catalyst loading electrodes including 10, 20, 30, and 40% Pt/C with 0.1, 0.2, 0.25, and 0.3 mg/cm 2 Pt loadings, respectively, were fabricated and tested in this study. The results confirm that the sensor catalyst loading can be reduced by approximately 130 times compared to the catalyst loading in commercial sensors without notably changes on the sensor performance. In addition, fabrication of sensors with very low Pt loading on the cathode side is possible and can be economically favorable for manufacturing ethanol gas sensors. It also has been shown that the peak current density measurement method, which expedites the sensor recovering time, can be used for low catalyst loading sensors due to the observation of very good linearity behavior of the sensor with changing the ethanol gas concentration. [ABSTRACT FROM AUTHOR]

Magnetically induced current densities and integrated ring-current strength susceptibilities have been calculated at the density functional theory (DFT) level for a test set consisting of 17 ring-shaped molecules using the gauge-including magnetically induced current (GIMIC) method. Reliable values for the ring-current strengths have been obtained by performing numerical integration of the current-density susceptibility passing a cut plane perpendicularly to the molecular ring. The current densities and ring current strengths were calculated at the DFT level using the B3LYP functional and def2-TZVP basis sets. Current densities and ring-current strengths have also been calculated at the Hartree-Fock self-consistent field (HF-SCF) level using Dunning's aug-cc-pVTZ basis sets, which allow a direct comparison with ring-current strengths that have previously been estimated using ring-current models based on magnetic shielding calculations. Current density calculations at both levels of theory show that the magnetic shielding based ring-current models are not a very accurate means to estimate the magnetically induced ring current strengths, whereas they provide qualitatively the correct aromaticity trends for the studied molecules. [ABSTRACT FROM AUTHOR]

The results on the effects of different anode potentials on current densities, coulombic efficiencies and microbial communities are contradictory and have not been studied with xylose, an important constituent of lignocellulosic materials. In this study, the effects of different anode potentials (+0.2, 0 and −0.2 V vs. Ag/AgCl) on current generation, xylose degradation and microbial communities were examined with an exoelectrogenic enrichment culture originating from anaerobic sludge. Anode potential of +0.2 V (vs. Ag/AgCl) resulted in the highest current density and coulombic efficiency of 1.5 ± 0.2 A/m 2 and 62 ± 11%, respectively, and there was no accumulation of soluble metabolites. With anode potentials of 0 and −0.2 V the current densities remained low and acetate, butyrate and propionate were detected in the end of batch runs. Different anode potentials resulted in substantial differences in the anodic bacterial species. At more positive anode potentials, Ochrobactrum intermedium reported to be capable of direct electron transfer dominated. At more negative anode potentials, a known mediator-producer, Alcaligenes faecalis , and Desulfitobacterium hafnience , that has been reported to use mediated electron transfer, were detected. This study shows that the anode potential has a substantial effect on microbial communities and on xylose metabolism. [ABSTRACT FROM AUTHOR]

It is well known that sufficiently strong electrostatic fields are able to change the morphology of Large Area Field Emitters (LAFEs). This phenomenon affects the electrostatic interactions between adjacent sites on a LAFE during field emission and may lead to several consequences, such as: the emitter's degradation, diffusion of absorbed particles on the emitter's surface, deflection due to electrostatic forces, and mechanical stress. These consequences are undesirable for technological applications, since they may significantly affect the macroscopic current density on the LAFE. Despite the technological importance, these processes are not completely understood yet. Moreover, the electrostatic effects due to the proximity between emitters on a LAFE may compete with the morphological ones. The balance between these effects may lead to a non trivial behavior in the apex-Field Enhancement Factor (FEF). The present work intends to study the interplay between proximity and morphological effects by studying a model amenable for an analytical treatment. In order to do that, a conducting system under an external electrostatic field, with a profile limited by two mirror-reflected triangular protrusions on an infinite line, is considered. The FEF near the apex of each emitter is obtained as a function of their shape and the distance between them via a Schwarz-Christoffel transformation. Our results suggest that a tradeoff between morphological and proximity effects on a LAFE may provide an explanation for the observed reduction of the local FEF and its variation at small distances between the emitter sites. [ABSTRACT FROM AUTHOR]

This article presents a preliminary study of the measurement of local current density in all-vanadium redox flow batteries. Two batteries are designed and manufactured in this study, and the experimental results are compared. In the first cell, the current collector is divided into 25 segments, and the flow field plate is not segmented, whereas in the other cell, the flow field plate is segmented. The effects of the electrolyte flow rate on the battery efficiencies and the local current density variation are investigated. The experimental results show that the current density near the outlet significantly decreases when the discharge capacity approaches zero. In addition, the battery has a larger discharge depth at a higher electrolyte flow rate. [ABSTRACT FROM AUTHOR]

Spectrally resolved and kinetic response of electroluminescence was monitored from resistively heated carbon nanotube (CNT) macroassemblies. Sensitive detection system and custom-made setup for high-speed optoelectronic measurements were employed to investigate unsorted and single chirality-enriched CNTs. By increasing the content of (7,6) or (6,5) CNTs in a sample, the E11 emission peak in the infrared region became more narrow (~150 nm), hence approaching that of commercial emitters for this spectral range. Moreover, electroluminescence initiation in CNTs occurred very rapidly and reached its full intensity within tens of milliseconds. Interestingly, observed delay between bias voltage application and electroluminescence proved triplet-triplet annihilation in the macroscopic assembly of CNTs. [ABSTRACT FROM AUTHOR]

We have demonstrated a two-section dual-wavelength diode laser incorporating distributed Bragg reflectors, with a peak-wavelength separation of 62.5 nm at 300 K. Each lasing wavelength has a different temperature dependence, providing a difference-tuning of 0.11 nm/K. We discuss the mechanisms governing the light output of the two competing modes and explain how the short wavelength can be relatively insensitive to output changes at the longer wavelength. Starting from an initial condition when the output at both wavelengths are equal, a 500% increase in the long wavelength output causes the short wavelength output to fall by only 6%. [ABSTRACT FROM AUTHOR]

The test facility ELISE, equipped with a large RF-driven ion source (1 × 0.9 m2) of half the size of the ion source for the ITER neutral beam injection (NBI) system, has been constructed over the last three years at the Max-Planck-Institut für Plasmaphysik (IPP), Garching, and is now operational. The first measurements of the dependence of the co-extracted electron currents on various operational parameters have been performed. ELISE has the unique feature that the electron currents can be measured individually on both extraction grid segments, leading to vertical spatial resolution. Although performed in volume operation, where the negative hydrogen ions are created in the plasma volume solely, the results are very encouraging for operation with caesium, this being necessary in order to achieve the relevant negative ion currents for the ITER NBI injectors. The amount of co-extracted electrons could be suppressed sufficiently with moderate magnetic filter fields and by plasma grid bias. Furthermore, the electron extraction is more or less decoupled from the main plasma, as the observed vertical asymmetry of electron extraction is not correlated at all with the plasma asymmetry, which is anyway rather small. Both effects are superior to the experience from the small IPP prototype source; the reason for these encouraging results is most probably the larger size of the source as well as the new geometry of the source having unbiased areas in its centre. The reasons, however, for the observed asymmetry of the extracted electron currents and their dependencies on various operational parameters are not well understood. [ABSTRACT FROM AUTHOR]

The influence of ion current density on the thickness of coatings deposited in a vacuum arc setup has been investigated to optimize the coating porosity. A planar probe was used to measure the ion current density distribution across plasma flux. A current density from 20 to 50 A/m^2 was obtained, depending on the probe position relative to the substrate center. TiN coatings were deposited onto the cutting inserts placed at different locations on the substrate, and SEM was used to characterize the surfaces of the coatings. It was found that low-density coatings were formed at the decreased ion current density. A quantitative dependence of the coating thickness on the ion current density in the range of 20–50 A/m^2 were obtained for the films deposited at substrate bias of 200 V and nitrogen pressure 0.1 Pa, and the coating porosity was calculated. The coated cutting inserts were tested by lathe machining of the martensitic stainless steel AISI 431. The results may be useful for controlling ion flux distribution over large industrial-scale substrates. [ABSTRACT FROM PUBLISHER]

Bi deficient, Mn doped 0.92(Na0.5Bi0.5)TiO3-0.08(K0.5Bi0.5)TiO3 single crystals were grown by carefully controlled top-seeded solution growth method. Local structures were investigated by transmission electron microscopy. The site occupation and valence state of manganese were characterized by electron paramagnetic resonance spectrum. The leakage current density in the as-grown single crystals is effectively depressed. The introduced defect complexes suppress the temperature induced phase transformation, increasing the depolarization temperature (165 °C) and thermal stability of ferroelectric properties. [ABSTRACT FROM AUTHOR]

We investigated the critical current density (Jc) of Ba0.5K0.5Fe2As2 single-crystalline microbridges with thicknesses ranging from 276 to 18 nm. The Jc of the microbridge with thickness down to 91 nm is 10.8 MA/cm2 at 35 K, and reaches 944.4 MA/cm2 by extrapolating Jc(T) to T = 0 K using a two-gap s-wave Ginzburg-Landau model, well in accordance with the depairing current limit. The temperature, magnetic field, and angular-dependence of Jc(T,H,θ) indicated weaker field dependence and weakly anisotropic factor of 1.15 (1 T) and 1.26 (5 T), which also yielded the validity of the anisotropic Ginzburg-Landau scaling. [ABSTRACT FROM AUTHOR]

The physical processes responsible for determining the current density at the cathode of a thermionic arc are considered. It is shown that depending on the arc current and gas pressure, the arc could operate in one of the two modes. In the case of relatively low arc current and/or relatively low gas pressure, the arc current density is determined by a limited ability of the near-cathode plasma to provide the necessary ion current density. In this case, current density is proportional to the pressure and independent of the arc current. The second mode is realized when the arc current and/or gas pressure are relatively high. In this mode, the current density is determined by variations in the voltage drop along the cathode surface. In the second mode, current density is independent of pressure and inversely proportional to the arc current in this mode. Another factor that should be taken into account when considering current distribution is non-local relationships between electron current, ion current and heat flux at the cathode. It is shown that local approximations fail at distances shorter than ▴r = 2(ation)1/2, where a is the plasma thermal diffusivity, and tion is the ionization time in the plasma. Non-locality is important when ▴r is comparable to the emitter dimension. Estimations for a high-current arc in 1 atm argon show that ▴r is in the range from 0.2 to 1 mm. Calculations showed that current and temperature distributions at the cathode obtained in the non-local approach could be quite different from those obtained in a local approximation. [ABSTRACT FROM AUTHOR]

We propose and demonstrate a simple and novel method to control the deflection in a suspended microstructure by using a dual current electroplating (DuCE) method. The key concept of this method is to divide the structure into two layers--a bottom layer and a top layer--and then apply respective current densities in electroplating to those two layers while all other conditions are kept the same. In addition to a flat structure, the direction of structure bending is freely controlled by virtue of the DuCE method. Cantilever Ni beams with a length of 400 μm, which were electroplated by the conventional single current electroplating method, bent downward with a deflection of 3.4 μm. On the contrary, by the DuCE method, cantilever beams with a length of 400 μm showed an almost flat structure as desired. (The current densities of the bottom layer, the top layer, and the ratio of the two current densities, are 0.15, 1.24 A dm-2, and 8.3, respectively.) Consequently, a nickel electroplated spiral structure with a length of 8600 μm was suspended flat with an end deflection of less than 0.7 μm (the ratio between the deflection and length is 0.007%). This work therefore represents the unprecedented ultra-long suspended microstructure with submicrometer deflection. [ABSTRACT FROM AUTHOR]

Proof-of-principle measurements of the electron densities, temperatures, and ionization states of spherically compressed multi-shocked CH (polystyrene) capsules have been achieved using spectrally resolved x-ray Thomson scattering. A total energy of 13.5 kJ incident on target is used to compress a 70 μm thick CH shell above solid-mass density using three coalescing shocks. Separately, a laser-produced zinc He-α x-ray source at 9 keV delayed 200 ps-800 ps after maximum compression is used to probe the plasma in the non-collective scattering regime. The data show that x-ray Thomson scattering enables a complete description of the time-dependent hydrodynamic evolution of shock-compressed CH capsules, with a maximum measured density of ρ > 6 g cm-3. In addition, the results demonstrate that accurate measurements of x-ray scattering from bound-free transitions in the CH plasma demonstrate strong evidence that continuum lowering is the primary ionization mechanism of carbon L-shell electrons. [ABSTRACT FROM AUTHOR]

The mechanisms leading to the deposition of colloidalparticlesin a copper–gold galvanic microreactor are investigated. Usingin situ current density measurements and particle velocimetry, weestablish correlations between the spatial arrangement and the geometryof the electrodes, current density distribution, and particle aggregationbehavior. Ionic transport phenomena are responsible for the occurrenceof strongly localized high current density at the edges and cornersof the copper electrodes at large electrode separation, leading toa preferential aggregation of colloidal particles at the electrodeedges. Preferential aggregation appears to be the result of a combinationof electrophoretic effects and changes in bulk electrolyte flow patterns.We demonstrate that electrolyte flow is most likely driven by electrochemicalpotential gradients of reaction products formed during the inhomogeneouscopper dissolution. [ABSTRACT FROM AUTHOR]

An algorithm of the indirect measurement of the parameters of three-element nonresonance two-terminal networks is proposed, based on an analysis of the transient which occurs in the two-terminal network when it is supplied with an harmonic voltage of fixed frequency. Theoretical formulas are obtained for calculating the parameters of the two-terminal networks. [ABSTRACT FROM AUTHOR]

The influence of green tape thickness on the Bi-2223 phase formation and texture evolution in Ag/Ni composite-sheathed tapes fabricated by the 'powder-in-tube' technique has been studied. Microstructural observations by SEM as well as critical current density ( J) measurements at 77 K, 0 T have been performed to analyze the performance of the tapes. The results show an important influence of the green tape thickness on the critical current depending on the content and texture of Bi-2223 phase. The J increases with decreasing thickness. Moreover, texture measured by omega scans shows that the texture of the Bi-2223 phase is significantly influenced by the thickness of the green tape after the first and final sintering processes. Alignment of Bi-2223 grains in the thin tapes is much better. Higher performance of Ag/Ni composite-sheathed Bi-2223 tapes can be obtained by controlling the thickness of the green tapes. [ABSTRACT FROM AUTHOR]

We have studied the one-step procedure for simultaneous synthesis and sintering of SiC-doped MgB by the spark plasma sintering technique. Two types of composition, one in which Mg is strongly deficient, with the atomic ratio $\mathrm{B/Mg} = 3.75$, and one in which Mg content is slightly higher than the stoichiometric value, specifically $\mathrm{B/Mg} = 1.87$, were investigated. The amount of SiC was 12 wt.% and 9 wt.%, respectively. For comparison we also studied the way the deficit of Mg can be compensated in a second process of sintering. The sample with Mg deficit shows that SiC is left almost unreacted but the results are spectacular: the highest critical temperature, 36.5 K, the highest upper critical field and the highest self-field critical current density 6.7×10 A/cm at 10 K. In the sample with overstoichiometric Mg, SiC is decomposed, carbon diffuses within MgB but the critical temperature is only of 35.8 K and the zero-field critical current density is one order of magnitude lower. The compensation of the deficit of Mg in the two-step procedure is not efficient. The critical temperature is even lower, 35.8 K, the upper critical field is also lower despite SiC decomposition and C diffusion within MgB and the critical current density is slightly above 10 A/cm. However, at low temperatures and fields of order 7 T the sample with overstoichiometric Mg and the sample prepared by the two-step procedure have higher critical current density. [ABSTRACT FROM AUTHOR]

This letter reports the fabrication and performance of back-illuminated separate absorption and multiplication AlGaN solar-blind avalanche photodiodes. Devices with a 60-μm-diameter active area and a double-mesa structure exhibit a low dark current density of 1.06 × 10-8 A/cm2 at the reverse bias of 20 V and a maximum multiplication gain up to 3000 at the reverse bias of 91 V. The temperature dependence of avalanche voltage shows a large positive temperature coefficient of 0.05 V/K, confirming that avalanche multiplication is the dominant gain mechanism in the photodiodes. [ABSTRACT FROM AUTHOR]

We report the results of magnetization measurements on the unconventional superconductor PrPt4Ge12 in its superconducting state. A distinct positive curvature is observed in the temperature dependence of the lower critical field H C1(T) and the upper critical field H C2(T) around 5.5 K. The zero field critical current density J C(T, H = 0) is found to vary nearly linearly with temperature. We argue that these observed features are due to the existence of two superconducting gaps in the material. The normalized superfluid density is estimated from the temperature dependence of H C1. Our detailed analysis of the normalized superfluid density using a two-gap model indicates the presence of line nodes in the larger gap. The H C2(T) line can be fitted with the Usadel equations, and the positive curvature in H C2(T) is shown to be consistent with the two-gap picture of superconductivity. [ABSTRACT FROM AUTHOR]

The n-ZnO/p-Si heterojunction was fabricated by depositing high quality single crystalline aluminium-doped n-type ZnO film on p-type Si using the laser molecular beam epitaxy technique. The heterojunction exhibited a good rectifying behavior. The electrical properties of the heterojunction were investigated by means of temperature dependence current density-voltage measurements. The mechanism of the current transport was proposed based on the band structure of the heterojunction. When the applied bias V is lower than 0.15 V, the current follows the Ohmic behavior. When 0:15 V < V < 0:6 V, the transport property is dominated by diffusion or recombination in the junction space charge region, while at higher voltages (V > 0:6 V), the space charge limited effect becomes the main transport mechanism. The current-voltage characteristic under illumination was also investigated. The photovoltage and the short circuit current density of the heterojunction aproached 270 mV and 2.10 mA/cm2, respectively. [ABSTRACT FROM AUTHOR]

SUMMARY In this paper, a new design for the flow channels is presented, and a parametric study of the proton exchange membrane (PEM) fuel cell is conducted in order to investigate the effect of the new flow channels, as well as different operating parameters, on the efficiency and energy output of the cell. Design parameters are selected based on studies presented in the literature to build a physical and practical model. With the new design of the flow channels, it is noticed that the cell efficiency increases from 33.8% to 47.7% if the temperature of the cell is increased. The power output of the cell increases from 2.6 to 282.5 W when the cell temperature and the current density are increased. Moreover, decrease in the efficiency of the cell ranges from 45.5% to 28.4% with the increase in the current density and membrane thickness. Based on the analytical model, design parameters were selected to manufacture a fuel cell that has a power output of 175 W and an efficiency of 35% running at 353 K and 3 bar, with an effective membrane area of 450 cm2. Experiments are conducted to investigate the effect of newly designed flow channels on pressure distribution. It is found that when hydrogen is supplied from both inlets, pressure across the channels become symmetric and, therefore increasing the power output. This study reveals that, with the proper choice of design parameters, a PEM fuel cell is an attractive economical, efficient, and environmental solution when compared with conventional systems of power generation such as gas turbines. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY Such factors as mole fractions of species, water generation, and conductivity influence the performance of proton exchange membrane fuel cells (PEMFCs). The geometrical shape of the fuel cells also should be considered a factor in predicting the performance because this affects the species' reaction speed and distribution. Specifically, the position between the channel and rib is an important factor influencing PEMFC performance because the current density distribution is affected by the channel and rib position. Three main variables that decide the current density distribution are selected in the paper: species concentration, overpotentials, and membrane conductivity. These variables should be considered simultaneously in deciding the current density distribution with the given PEMFC cell voltage. In addition, the inlet relative humidity is another factor affecting current density distribution and membrane conductivity. In this paper, two channel-to-rib models, namely, channel-to-channel and the channel-to-rib, are considered for comparing the PEMFC performance. Thorough performance comparisons between these two models are presented to explain which is better under certain parameters. A three-dimensional numerical PEMFC model is developed for obtaining the current density distribution. Water transfer mechanism because of electro osmotic drag and concentration diffusion also is presented to explain the PEMFC performance comparison between the two models. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Magnetically insulated transmission lines (MITLs) are key components in present high-power generators. In our experiments, the current density flows in the cathode of the MITL are so high that current loss cannot be neglected. At an input current of 0.7–1.4 MA, an experimental study on current loss is performed with austenitic and martensitic stainless steel. An empirical relation between loss current density and input current density was found. For current density around 1 MA/cm, the results show that the loss current density is nearly a power function of the input current density, and the power indices for austenitic and martensite stainless steel are about 4.3 and 3.3, respectively. [ABSTRACT FROM AUTHOR]

Novel pyreno-chalcone dendrimers 1, 2, and 3 were synthesized and their ability to act as an additive in the redox couple (I/I) of dye-sensitized nanocrystalline TiO solar cell has been tested. The redox couple doped with pyreno-chalcone dendrimer 3 gave a short circuit photocurrent density ( J) of 7.40 mA/cm, open circuit voltage ( V) of 820 mV, and a fill factor of 0.51, corresponding to an overall conversion efficiency (η) of 7.89% under 40 mW/cm irradiation. [ABSTRACT FROM AUTHOR]

We calculate the electromagnetic current with a more realistic approach in the RHIC and LHC energy regions in the article. We take the partons formation time as the initial time of the magnetic field response of QGP medium. The maximum electromagnetic current and the time-integrated current are two important characteristics of the chiral magnetic effect (CME), which can characterize the intensity and duration of fluctuations of CME. We consider the finite frequency response of CME to a time-varying magnetic field, find a significant impact from QGP medium feedback, and estimate the generated electromagnetic current as a function of time, beam energy and impact parameter. [ABSTRACT FROM AUTHOR]

A macroscopic model of the magnetoresistance effect in limited anisotropic semiconductors is built. This model allows us to solve the problem of measurement of physical magnetoresistance components of crystals and films. Based on a unified mathematical model the method is worked out enabling us to measure tensor components of the specific electrical resistance and the relative magnetoresistance of anisotropic semiconductors simultaneously. [ABSTRACT FROM AUTHOR]

Scanning tunnelling microscopy was used to study the morphological changes of the surface of a single-crystalline silver nanowire caused by a lateral electron current. At current densities of about 1.5 × 107 A cm−2, surface atoms are extracted from step edges, resulting in the motion of surface steps, islands and holes with a thickness or depth of one monolayer. Upon current reversal the direction of the material transport can be altered. The findings are interpreted in terms of the wind force. [ABSTRACT FROM AUTHOR]