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Search Results: 1 - 10 of 1172 matches for " Annealing "
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Limited Resequencing for Mixed Models with Multiple Objectives  [PDF]
Patrick R. McMullen
American Journal of Operations Research (AJOR) , 2011, DOI: 10.4236/ajor.2011.14025
Abstract: This research presents a problem relevant to production scheduling for mixed models – production schedules that contain several unique items, but each unique item may have multiple units that require processing. The presented research details a variant of this problem where, over multiple processes, resequencing is permitted to a small degree so as to exploit efficiencies with the intent of optimizing the objectives of required set-ups and parts usage rate via an efficient frontier. The problem is combinatorial in nature. Enumeration is used on a variety of test problems from the literature, and a search heuristic is used to compare optimal solutions with heuristic based solutions. Experimentation shows that the heuristic solutions approach optimality, but with opportunities for improvement.
Influence of Hot Band Annealing and Cold Rolling on Texture and Ridging of 430 Stainless Steel Containing Aluminum  [PDF]
Sudipta Patra, Lokesh Kumar Singhal
Materials Sciences and Applications (MSA) , 2013, DOI: 10.4236/msa.2013.41009
Abstract:

An approach to optimize the processing parameters to get superior ridging resistance and mechanical properties in commercial production of 430 ferritic stainless steel has been studied. Attention was also paid to improve productivity and energy saving without hampering the surface and mechanical property aspects of the material. Hot rolled coils annealed by slow cooling under insulated cover exhibit better ridging resistance than bell annealing treatment with a minor decrease in ductility. Soaking temperature prior to hot rolling has a significant effect on ridging resistance.

Y3Fe5O12 Prepared by Mechanosynthesis from Different Iron Sources  [PDF]
Claudia A. Cortés-Escobedo, Ana M. Bolarín-Miró, Félix Sánchez-De Jesús, Raúl Valenzuela, Elizabeth P. Juárez-Camacho, Iván L. Samperio-Gómez, Souad Ammar
Advances in Materials Physics and Chemistry (AMPC) , 2013, DOI: 10.4236/ampc.2013.31A006
Abstract:

Yttrium iron garnet, Y3Fe5O12 (YIG) powders were synthesized by mechanochemical processing (MCP) from different iron sources (FeO, Fe2O3 and Fe3O4) mixed with Y2O3, followed by a heat treatment. The aim of this work is to demonstrate that MCP followed by annealing at very low temperatures (as compared with the classic solid state reaction) can induce the formation of nanostructured YIG. The effect of iron source on final structure was also studied. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the synthesized powders. The precursors mixed in a stoichiometric ratio to obtain YIG were milled at room temperature in a shaker mixer mill with a ball:powder weight ratio of 10:1. A partial synthesis of YIG was achieved after 9 h of milling time by using the three sources of iron; however, a significant fraction of the product was the perovskite YFeO3. The largest yield of YIG was obtained by using FeO. In all cases a single garnet phase could only be completely obtained after an annealing process at 900?C, around 400?C lower than the typical temperatures to prepare the material by solid state reaction. An analysis of the microstrain and lattice parameters associated with peak displacements is discussed.

Effects of Solution Atoms and Precipitates on Isochronal Annealing Behavior of Cold-Rolled Squeeze-Cast SiCw/Al Composites  [PDF]
Wenglong Zhang, Mingyuan Gu
Materials Sciences and Applications (MSA) , 2011, DOI: 10.4236/msa.2011.25062
Abstract: SiCw/Al and SiCw/6061Al composites, which contained 15 vol pct of whiskers, were fabricated through a squeeze cast route followed by cold rolling and isochronal annealing. Effects of whicker, solution atoms and precipitates on isochronal annealing behavior of cold rolled composites were investigated by comparing the isochronal annealing behavior between pure Al, SiCw/Al, solution-treated SiCw/6061Al and aged SiCw/6061Al. It was found that the recrystallization of SiCw/Al composite occurs earlier than that of pure Al, indicating SiCw has a role of particle stimulated nucleation. Solution atoms have no significant influence on the isochronal annealing behavior of SiCw/6061Al composite, while precipitates have such a strong retarding effect on the recrystallization of SiCw/6061Al composite that the isochronal annealing curve of aged SiCw/6061 composite loses the definable recrystallization step.
A Modified Particle Swarm Optimization Algorithm  [PDF]
Ai-Qin Mu, De-Xin Cao, Xiao-Hua Wang
Natural Science (NS) , 2009, DOI: 10.4236/ns.2009.12019
Abstract: Particle Swarm Optimization (PSO) is a new optimization algorithm, which is applied in many fields widely. But the original PSO is likely to cause the local optimization with premature convergence phenomenon. By using the idea of simulated annealing algo-rithm, we propose a modified algorithm which makes the most optimal particle of every time of iteration evolving continu-ously, and assign the worst particle with a new value to increase its disturbance. By the testing of three classic testing functions, we conclude the modified PSO algorithm has the better performance of convergence and global searching than the original PSO.
Nonequilibrium Diffusion of Boron in SiC at Low Temperatures  [PDF]
Iikham G. Atabaev, Tojiddin M. Saliev, Erkin N. Bakhranov, Dilmurad Saidov, Khimmatali Juraev, Chin C. Tin, Victor Adedeji, Bakhtiyar G. Atabaev, Nilufar G. Saidkhanova
Materials Sciences and Applications (MSA) , 2010, DOI: 10.4236/msa.2010.12010
Abstract: Nonequilibrium diffusion of Boron in 3C SiC was performed using a flow of carbon vacancies. The temperature of diffusion was 1150-1250℃ and concentration of Boron in doped area reached about 1019 to 1020 cm-3. It is shown that after thermal annealing in vacuum the characteristics of fabricated structures are close to those of the structures made by the conventional technology.
Influence of Defects on Low Temperature Diffusion of Boron in SiC  [PDF]
Ilkham G. Atabaev, Tojiddin M. Saliev, Dilmurad Saidov, Vadim A. Pak, Khimmatali Juraev, Chin-Che Tin, Bakhtiyar G. Atabaev, Vyacheslav N. Giryansky
Materials Sciences and Applications (MSA) , 2011, DOI: 10.4236/msa.2011.29163
Abstract: The low temperature diffusion of Boron in bulk SiC crystals is investigated and simplified model of such diffusion is presented. The method of UV stimulated etching by aqueous solution of KOH is proposed and some experimental data on influence of defects on quality of prepared p-n junctions are presented.
Optimization Model for Management of Water Quality in a Tidal River Using Upstream Releases  [PDF]
Moltot Zewdie Belayneh, Sreenivasa Murty Bhallamudi
Journal of Water Resource and Protection (JWARP) , 2012, DOI: 10.4236/jwarp.2012.43018
Abstract: This study deals with the management of water quality in a tidal river through optimal releases of water from an upstream environmental reservoir. A management model is proposed based on the simulation-optimization framework, in which a complete hydrodynamic model for transport of BOD and DO in a tidal river is linked to Simulated Annealing (SA) algorithm for optimization. The proposed management model is used to investigate the effect of tidal variation on the constant minimum in stream discharge that is required to maintain the water quality, for a given pollutant loading. It is demonstrated how the total upstream release volume can be minimized, while still maintaining the desired water quality, by resorting to an optimum temporal variation in releases from the upstream environmental reservoir. The performance of the methodology is evaluated for an illustrative river. The proposed model will be helpful in arriving at best water release policy for maintaining water quality in tidal rivers for given tidal variation and pollutant loading.
Laser Surface Annealing of Plasma Sprayed Coatings  [PDF]
Ahmed Ibrahim, Yue Hung
Journal of Surface Engineered Materials and Advanced Technology (JSEMAT) , 2012, DOI: 10.4236/jsemat.2012.223033
Abstract: Laser surface annealing provides a rapid and efficient means for surface alloying and modification of ceramic materials. In this study, Alumina-13% Titania coatings were sprayed with a water-stabilized plasma spray gun. The coated surface was treated by Excimer laser having a wavelength of 248 nm and pulse duration of 24 ns. The surface structure of the treated coating was examined by field emission scanning electron microscope and X-ray diffraction (XRD). A detailed analysis of the effects of various laser parameters including laser energy density (fluence), pulse repetition rate (PRR), and number of pulses on the morphology and the microstructure of the coatings are presented.
Isolated Cobalt Nanoparticles Prepared on HOPG in Ultrahigh Vacuum Using Thermal Annealing  [PDF]
Denis Lebedev, Niyaz Nurgazizov, Anton Chuklanov, Anastas Bukharaev
Advances in Nanoparticles (ANP) , 2013, DOI: 10.4236/anp.2013.23033
Abstract:

Cobalt nanoparticles on the surface of highly oriented pyrolytic graphite have been studied by atomic force microscopy. Thermal annealing in ultrahigh vacuum was used to change the size of cobalt nanoparticles and their surface distribution. The effect of two key parameters, annealing time and temperature, on the size and the surface distribution of nanoparticles has been studied. The dependence of the particle size on these parameters has been obtained. It has been shown that the main mechanism of the nanoparticle growth is Ostwald ripening.

 

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