Using ahp and topsis to evaluate welding processes for manufacturing plain carbon stainless steel storage tank

Purpose: In the plain carbon stainless steel storage tank manufacturing industry, there are many types of welding processes used. When selecting the most appropriate welding process is usually done intuitively by the manufacturer depending on its own pre-experiences or common applications in similar companies. However, this approach has a shortsighted view since it generally ignores many conflicting criteria effecting the suitable welding process selection. To overcome this problem, this study aims to evaluate important criteria and alternative welding processes by using some of multi-criteria decision-making approaches to come up with better manufacturing decisions. Design/methodology/approach: This study uses a combined methodology of Analytical Hierarchy Process (AHP) and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). Since both of these techniques require experts’ contributions, a group meeting is held with the experts from academia and industry. Findings: The study identified the important criteria for welding selection process in storage tank manufacturing. With the help of experts in the domain, both weights of decision criteria and ranking of alternative welding processes were determined. Research limitations/implications: Since the techniques used in the study depend on expert’s contribution, the expert knowledge on the welding process is critical. When the expert changes the resulting decision may also change. Therefore, the selection of the expert(s) must be done carefully. Practical implications: The findings of the study are valid for the specific case of the storage tank manufacturing. The study helps manufacturers to understand the framework of welding process selection and make them aware of various techniques (e.g., AHP and TOPSIS). The approach may also be welcomed by other welding applications. Originality/value: The main contribution of the study is mostly on the practical side. To the authors’ best knowledge, this paper is one of few studies investigating the selection of welding process for a plain carbon stainless steel storage tank manufacturing. It may help to increase the attention of researchers on multi-criteria decision-making applications in the welding field. © International OCSCO World Press. All rights reserved. 201

Geochemical, Isotopic and Single Crystal 40Ar/39Ar Age Constraints on the Evolution of the Cerro Galan Ignimbrites

The giant ignimbrites that erupted from the Cerro Galan caldera complex in the southern Puna of the high Andean plateau are considered to be linked to crustal and mantle melting as a consequence of delamination of gravitationally unstable thickened crust and mantle lithosphere over a steepening subduction zone. Major and trace element analyses of Cerro Galan ignimbrites (68-71% SiO2) that include 65 new analyses can be interpreted by evolution at three crustal levels. AFC modeling and new fractionation corrected d18O values from quartz (+7.63-8.85%o) are consistent with the ignimbrite magmas being near 50:50 mixtures of enriched mantle (87Sr/86Sr ~ 0.7055) and crustal melts (87Sr/86Sr near 0.715-0.735). Processes at lower crustal levels are predicated on steep heavy REE patterns (Sm/Yb = 4-7), high Sr contents (>250 ppm) and very low Nb/Ta (9-5) ratios, which are attributed to amphibolite partial melts mixing with fractionating mantle basalts to produces hybrid melt that rise leaving a gravitationally unstable garnet-bearing residue. Processes at mid crustal levels create large negative Eu anomalies (Eu/Eu* = 0.45-0.70) and variable trace element enrichment in a crystallizing mush zone with a temperature near 800-850ºC The mush zone was repeatedly recharged from depth and partially evacuated into upper crustal magma chambers at times of regional contraction. Crystallinity differences in the ignimbrites are attributed to biotite, zoned plagioclase and other antecrysts entering higher level chambers where variable amounts of near-eutectic crystallization occurs at temperature as low as 680ºC just preceding eruption. 40Ar/39Ar single crystal sanidine weighted mean plateau and isochron ages combined with trace element patterns show that the Galan ignimbrite erupted in more than one batch including a ~ 2.13 Ma intracaldera flow and outflows to the west and north at near 2.09 and 2.06 Ma. Episodic delamination of gravitationally unstable lower crust and mantle lithosphere and injection of basaltic magmas whose changing chemistry reflects their evolution over a steepening subduction zone could trigger the eruptions of the Cerro Galan ignimbrites.Fil: Kay, Suzanne Mahlburg. Cornell University; Estados UnidosFil: Coira, Beatriz Lidia Luisa. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Wörner, Gerhard. Universität Göttingen; AlemaniaFil: Kay, Robert W.. Cornell University; Estados UnidosFil: Singer, Bradley S.. University of Wisconsin; Estados Unido

Optical properties of (AlxGa1−x)0.52In0.48P at the crossover from a direct-gap to an indirect-gap semiconductor

The optical properties and the dynamics of excitons and the electron-hole plasma have been studied in disordered (AlxGa1−x)0.52In0.48P near to the direct-to-indirect band gap crossover. In particular we have investigated three epitaxial layers grown by solid-source molecular beam epitaxy with varying Al content x. Two of them have compositions in the immediate vicinity of the crossover point, the other is assigned to the indirect-gap regime. Both direct and indirect recombination processes contribute to the photon emission from the material. Since the relative importance of the different recombination processes depends strongly on temperature, excitation intensity, and excitation pulse duration, the processes can be identified by changing these parameters. As a result, we can determine the relative alignment of the conduction band minima and the distribution of the electrons among them. At high excitation levels the two crossover samples show stimulated emission at a photon energy of ∼2.29 eV, i.e., in the green spectral range. Using the variable stripe length method, we find an optical gain of up to ∼600 cm−1 at excitation levels of ∼350 kW/cm2.Stimulated emission involves direct recombination. This conclusion is reached from the experiments and from line-shape modeling, including a self-consistent treatment of populations and renormalization of the conduction band minima

Optical properties of (AlxGa1-x)(0.52)In0.48P at the crossover from a direct-gap to an indirect-gap semiconductor

The optical properties and the dynamics of excitons and the electron-hole plasma have been studied in disordered (AlxGa1−x)0.52In0.48P near to the direct-to-indirect band gap crossover. In particular we have investigated three epitaxial layers grown by solid-source molecular beam epitaxy with varying Al content x. Two of them have compositions in the immediate vicinity of the crossover point, the other is assigned to the indirect-gap regime. Both direct and indirect recombination processes contribute to the photon emission from the material. Since the relative importance of the different recombination processes depends strongly on temperature, excitation intensity, and excitation pulse duration, the processes can be identified by changing these parameters. As a result, we can determine the relative alignment of the conduction band minima and the distribution of the electrons among them. At high excitation levels the two crossover samples show stimulated emission at a photon energy of ∼2.29 eV, i.e., in the green spectral range. Using the variable stripe length method, we find an optical gain of up to ∼600 cm−1 at excitation levels of ∼350 kW/cm2.Stimulated emission involves direct recombination. This conclusion is reached from the experiments and from line-shape modeling, including a self-consistent treatment of populations and renormalization of the conduction band minima

Time Scales in Spectator Fragmentation

Proton-proton correlations and correlations of p-alpha, d-alpha, and t-alpha from spectator decays following Au + Au collisions at 1000 AMeV have been measured with an highly efficient detector hodoscope. The constructed correlation functions indicate a moderate expansion and low breakup densities similar to assumptions made in statistical multifragmentation models. In agreement with a volume breakup rather short time scales were deduced employing directional cuts in proton-proton correlations. PACS numbers: 25.70.Pq, 21.65.+f, 25.70.MnComment: 8 pages, with 5 included figures; To appear in the proceedings of the CRIS 2000 conference; Also available from http://www-kp3.gsi.de/www/kp3/aladin_publications.htm

Thermal and Chemical Freeze-out in Spectator Fragmentation

Isotope temperatures from double ratios of hydrogen, helium, lithium, beryllium, and carbon isotopic yields, and excited-state temperatures from yield ratios of particle-unstable resonances in 4He, 5Li, and 8Be, were determined for spectator fragmentation, following collisions of 197Au with targets ranging from C to Au at incident energies of 600 and 1000 MeV per nucleon. A deviation of the isotopic from the excited-state temperatures is observed which coincides with the transition from residue formation to multi-fragment production, suggesting a chemical freeze-out prior to thermal freeze-out in bulk disintegrations.Comment: 14 pages, 10 figures, submitted to Phys. Rev. C, small changes as suggested by the editors and referee