Bias Arc Research Articles

Effect of Bias Arc on Microstructure and Corrosion Resistance of Q235/304 Dissimilar-Steel-Welded Joints.

To fully exploit the advantages of steel, the welding connection of dissimilar steels has been developed. In this work, the metallographic microstructures, elemental distributions, and electrochemical corrosion properties of the Q235 and 304 welds under different bias arcs were investigated. The arc bias caused the Q235-side heat-affected zone to widen, the microstructure consisted of ferrite and pearlite, and the ratio varied with decreasing distance from the fusion line. Elemental scans show that Cr and Ni concentration gradients exist near the fusion line. The 304-stainless-steel-side heat-affected zone was mainly composed of austenite grains, and the fusion zone was narrower but prone to cracking. Electrochemical tests revealed that 304 stainless steel had the best corrosion resistance, while Q235 had the worst corrosion resistance, and that the welded joints with an arc bias toward the 304 side had the best corrosion resistance. The samples' the passivation film which formed via electrochemical polarization had limited stability, but the over-passivation potential could be used as a reference for corrosion resistance. Overall, the arc bias and weld material properties significantly affected the microstructure and corrosion resistance of the joints.

High-precision VTEC derivation with GEONET

This paper proposes a new technique, namely Phase bias-based Small Grid Model (PSGM), to derive absolute ionospheric vertical total electron content (VTEC) with observations of Global Navigation Satellite System Earth Observation Network of Japan (GEONET). The proposed technique deals with the phase observations alone without handling the pseudoranges, which reduces the noise in VTEC estimation. A new parameter, the arc bias (Barc), is introduced to combine the phase ambiguities and differential phase biases. To solve Barc, equations are constructed under the assumption that the VTEC is identical in the same 0.1° × 0.1° grid. The performance of PSGM is evaluated with the observations in solar maximum year 2014. The root mean square error (RMSE) of PSGM is 0.40 TECU in average, the maximum RMSE is 0.73 TECU and the minimum RMSE is 0.26 TECU. The fitting accuracy of the VTEC results is improved compared with most of the existing methods.

Pure Al Coatings Prepared by Arc-Added Glow Plasma Depositing Technique and Subsequence Plasma Oxidation

Al coatings were prepared on 316L stainless steel substrate by arc-added glow plasma depositing technique and then plasma oxidized. The influences of bias voltage and arc source current on both the thickness and surface roughness of Al coatings were investigated respectively. Then, the microstructure and the composition of Al and Al2O3 coatings were characterized. Finally, the bonding force and the corrosion resistance of as-prepared alumina coatings were discussed. The results indicated that nanostructured pure Al coatings with surface roughness (Ra) of 267.93 nm were obtained when the bias of the substrate was-300V and the arc current was 70A. The Al2O3 coatings oxidized from nanoAl coatings were dense and uniform, with a bonding force of 37.4 N, an excellent corrosion potential of-0.202V and corrosion current of 0.197 μm·cm-2 in 3.5% NaCl solution.

Characterization of (Ti,Al)N Thin Film Coated by PVD Cathodic Arc Using TiAl Target

Sintered TiAl alloy with composition of 50 at.% Al and 50at.% Ti are used as target in the PVD cathodic arc system to produce (Ti,Al)N film. The coating conditions are operated using substrate bias voltage and arc current bias of 100V and 70 A, respectively. In addition, the coating time was set at 1.30 h with thru different values of nitrogen gas pressures: 1, 1.5and 2 Pa. After coating the film was characterized for thickness, surface roughness, adhesion, morphology, and phase structure. It was found that phase structures, film thicknesses and adhesion of the films deposited from different nitrogen pressures are not significantly different. However, the micrographs showed that the film prepared by using 1.5 Pa of reactive N2 gas is smoother with less droplets than those film prepared at the other two pressures.

A Reappraisal of Certain Aspects of Transistor Theory

ABSTRACT In the usual analyses of transistor action various assumptions are frequently made; for example, that space charge neutrality exists in the base region, that pn junctions are depleted of mobile carriers, that minority carrier densities next to reverse biased junctions arc near zero, etc. It is shown that none of these assumptions is strictly valid. A now examination of the problem, in which those assumptions are put in better perspective, leads to: (a) a complete, partially numerical, analysis of abrupt pn junctions in equilibrium showing the spatial distribution of holes, electrons and field; (6) a qualitative discussion of these distributions when current is flowing; (c) a revised expression for the small signal capacitance of abrupt pn junctions; (d) a now space-charge-neutral solution for the complex current gain of transistors (this is compared with Shockley's solution). Finally a preliminary numerical solution of the carrier and field distribution in a collector junction, under conditions o...