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Search Results: 1 - 10 of 479745 matches for " S. L. Pityana "
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Laser Surface Alloying of 316L Stainless Steel with Ru and Ni Mixtures
M. B. Lekala,J. W. van der Merwe,S. L. Pityana
International Journal of Corrosion , 2012, DOI: 10.1155/2012/162425
Abstract: The surfaces of AISI 316L stainless steel were laser alloyed with ruthenium powder and a mixture of ruthenium and nickel powders using a cw Nd:YAG laser set at fixed operating parameters. The microstructure, elemental composition, and corrosion characteristics of the alloyed zone were analyzed using optical and scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and corrosion potential measurements. The depth of alloyed zone was measured using the AxioVision program and found to be approximately 1.8?mm for all the alloyed specimens. Hardness profile measurements through the surface-substrate interface showed a significant increase from 160?HV for the substrate to a maximum of 247?HV for the alloyed layer. The sample laser alloyed with 80?wt% Ni-20?wt% presented the most noble corrosion potential of ?V and the lowest corrosion current density . 1. Introduction Minor additions of ruthenium to the bulk volume of steels resulted in a significant improvement of corrosion resistance in many reducing environments [1]. Ruthenium modified alloys possesses properties which render them candidate alloys to replacing the expensive nickel-based alloys which are currently used in more aggressive corrosion environments [2]. However, owing to the high-cost associated with ruthenium, bulk alloying is currently not a feasible means, although opportunities to explore the method exist. For instance, Streicher [3] observed a synergistic benefit when ruthenium and nickel were added together to steels. This observation offers an opportunity to reduce the amount of ruthenium per bulk volume added in the alloying process, yet presents significant improved corrosion resistance. Thus, minor additions of ruthenium together with nickel present an economically sound approach of modifying corrosion properties of alloys. Furthermore, since corrosion is a surface phenomenon, an equally cost-effective approach is to add these only on the surface, where protection is most required. Laser surface modification techniques have been extensively studied for selective improvement of surfaces for wear, hardness, and corrosion [4–7]. The laser surface alloying technique is particularly applicable in cases where a change in the chemical composition and microstructure of the surface is required. The laser surface alloying technique enables external alloying elements to be added into the bulk material via a laser generated melt pool. Generally, the external alloy material is either preplaced on the desired surface of the substrate or fed into the melt pool. The alloy
Numerical Study to Represent Non-Isothermal Melt-Crystallization Kinetics at Laser-Powder Cladding  [PDF]
V. G. Niziev, F. Kh. Mirzade, V. Ya. Panchenko, M. D. Khomenko, R. V. Grishaev, S. Pityana, C. V. Rooyen
Modeling and Numerical Simulation of Material Science (MNSMS) , 2013, DOI: 10.4236/mnsms.2013.32008
Abstract: The study of laser-powder cladding process subject to heat transfer, melting and crystallization kinetics has been carried out numerically and experimentally. The Kolmogorov-Avrami equation was applied to describe the kinetics of the phase transitions. Characteristic behavior of temperature and conversion fields has been analyzed. Melt pool dimensions, clad height dependences on mass feed rate, laser power and scanning velocity have been investigated. It has been demonstrated that the melt zone has the boundary distinct from the melting isotherm due to the fact that melting occurs with superheating and crystallization takes place at undercooling. The calculated melt pool depth and clad height are in a good agreement with the experimental results.
Functionally Graded Material: An Overview
Rasheedat M. Mahamood,Esther T. Akinlabi,Mukul Shukla,Sisa Pityana
Lecture Notes in Engineering and Computer Science , 2012,
Abstract:
Effect of Laser Power on Material Efficiency, Layer Height and Width of Laser Metal Deposited Ti6Al4V
Rasheedat M. Mahamood,Esther T. Akinlabi,Mukul Shukla,Sisa Pityana
Lecture Notes in Engineering and Computer Science , 2012,
Abstract:
Gas Flow Rate and Powder Flow Rate Effect on Properties of Laser Metal Deposited Ti6Al4V
Sisa Pityana,Rasheedat M. Mahamood,Esther T. Akinlabi,Mukul Shukla
Lecture Notes in Engineering and Computer Science , 2013,
Abstract:
Laser Metal Deposition of Ti6Al4V: A Study on the Effect of Laser Power on Microstructure and Microhardness
Rasheedat M. Mahamood,Esther T. Akinlabi,Mukul Shukla,Sisa Pityana
Lecture Notes in Engineering and Computer Science , 2013,
Abstract:
The Role of Transverse Speed on Deposition Height and Material Efficiency in Laser Deposited Titanium Alloy
Rasheedat M. Mahamood,Esther T. Akinlabi,Mukul Shukla,Sisa Pityana
Lecture Notes in Engineering and Computer Science , 2013,
Abstract:
Material Efficiency of Laser Metal Deposited Ti6Al4V: Effect of Laser Power
Rasheedat M. Mahamood,Esther T. Akinlabi,Mukul Shukla,Sisa Pityana
Engineering Letters , 2013,
Abstract:
Menopause, cessation of menses, vs. “menopause”, a primary brain disorder?  [PDF]
S. L. Jaffe
Advances in Bioscience and Biotechnology (ABB) , 2013, DOI: 10.4236/abb.2013.46A003
Abstract: The “menopause” (not menopause, the cessation of menses) mechanism responsible for its symptom complex (Menopausal Symptom Complex) (or, Climacteric Syndrome) including chronic fatigue, fibromyalgia, depression, tension headache, cervical vertigo, sleep disturbances, irritability, anxiety/panic attacks, cognitive changes (decreased concentration to obsessional/delusional thought), decreased libido, and vasomotor dysfunction remains elusive. And MSC, other than vasomotor dysfunction, is not significantly altered by treatment with sex hormones (estrogen/progesterone), which have major neoplastic and vascular side effects. Thus at present, there are minimal indications for treatment with these compounds. Confusion between menopause and “menopause” (MSC) as well as research money made available by pharma advocating ERT/HRT (estrogen replacement therapy/hormone replacement therapy) has produced both therapeutic and research inertia. Presently, there would appear to be mismanagement of a symptom complex which infers primary brainlimbic system dysfunction and for which there is no correlation with falling sex hormone levels. Pharmacological modification of the proposed aberrant limbic circuitry responsible for the MSC has been successfully accomplished using specific NT/MMs (neurotransmission/modulation modifiers) i.e. a combination of alpha-1 and norepinephrine reuptake blockers, and thus providing initial elucidation of this particular brain pathophysiology as well as an efficient treatment of a problem affecting up to 60% of women ages 35 to 55. Specific NT/MMs capable of affecting a number of neurotransmitter/receptor types within limbic circuitry appear to reverse the MSC which includes chronic fatigue and fibromyalgia, pointing to aberrant limbic circuitry as their etiology as well.
Higgs Bosons, Quark Masses and Two Components of Cabibbo Angle  [PDF]
L. S. Sitnikov
Journal of Modern Physics (JMP) , 2013, DOI: 10.4236/jmp.2013.412198
Abstract:

This paper discusses the discovery and study of the functional connection between the quark masses and their mixing parameters. That allowed calculating Cabibbo angle from the known values of the masses of two lower quarks. It has been established that mixing occurs not only among lower quarks, as it was known up to now, but the upper quarks, independently, do the same. A separate mixing angle is calculated for the latter. The existence of two Cabibbo angles, i.e. independent mixings of upper and lower quarks, is a strong argument in favor of models with not one, but with several Higgs bosons. Only taking into account such a link, it is possible to give the unified description of the dependence of the mass on the generation number for all charged fermions (except t-quark). It turns out that increments of values \"\" and N are linearly linked. (Here m and N—mass and generation number of fermion, A—common internal parameter of concerned fermions).

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