Investigation of radiative interactions in supersonic internal flows

Analyses and numerical procedures are presented to study the radiative interactions of absorbing emitting species in chemically reacting supersonic flow in various ducts. The 2-D time dependent Navier-Stokes equations in conjunction with radiative flux equation are used to study supersonic flows undergoing finite rate chemical reaction in a hydrogen air system. The specific problem considered is the flow of premixed radiating gas between parallel plates. Specific attention was directed toward studying the radiative contribution of H2O, OH, and NO under realistic physical and flow conditions. Results are presented for the radiative flux obtained for different gases and for various combination of these gases. The problem of chemically reacting and radiating flows was solved for the flow of premixed hydrogen-air through a 10 deg compression ramp. Results demonstrate that the radiative interaction increases with an increase in pressure, temperature, amount of participating species, plate spacing, and Mach number. Most of the energy, however, is transferred by convection in the flow direction. In general the results indicate that radiation can have a significant effect on the entire flow field

AMMONIA GAS(NH3) SENSING OF SnO2-CuO MIXED OXIDE THICK FILM AT OPERATING TEMPERATURE

Objective To develop ammonia gas sensor by SnO2-CuO Mixed oxide thick film which is highly sensitive at particular optimum temperature.Materials and Methods:The SnO2 and CuO powder mixed with different ratio and heated at 8000C and then this powder is used to prepared thickfilms by a screen – printing technique on glass substrate.Results:The NH3 gas sensing properties, preferably the rate of response of CuO-SnO2 sensors are influenced by the CuO doping and operatingtemperature. XRD analysis showed that crystallite size is small (97.3nm) for 50SnO2-50CuO composition. Thermal analysis (TG/DTA) is the calculateof change in weight and energy in the form of heat as the material is being cooled or heated at a constant rate. The resistance change per ppm is foundto be 82 MΩ for SA5 sample.Conclusion : 50SnO2-50CuO composition sample is optimize for better sensing material as regards to other

Reverse supply chains: A source of opportunities and challenges

Reverse supply chains: A source of opportunities and challenges

A Goal Programming Approach to the Remanufacturing Supply Chain Model

Copyright 2001 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.The current trend of depletion of natural resources due to an ever-increasing number of consumer goods manufactured has led to an increase in the quantity of used and outdated products discarded. From an environmental point of view, it is not only desirable to disassemble, reuse, remanufacture and/or recycle the discarded products, in many cases it can also be economically justified. This situation being the motive, in recent years there have been several studies reported on disassembly, remanufacturing and/or recycling environments. Since “environmentally conscious manufacturing" is a relatively new concept that brings new costs and profits into consideration, its analysis cannot be provided by readily available techniques. This paper presents a quantitative methodology to determine the allowable tolerance limits of planned/unplanned inventory in a remanufacturing supply chain environment based on the decision-maker’s unique preferences. To this end, an integer goal-programming model that provides a unique solution for the allowable inventory level is presented. The objective of the supply-chain model is to determine the number of a variety of components to be kept in the inventory while economically fulfilling the demand of a multitude of components, and yet have an environmentally benign policy of minimizing waste generation.A numerical example is presented to illustrate the methodology.http://dx.doi.org/10.1117/12.41726

A Genetic Algorithm for Disassembly Process Planning

Copyright 2001 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.When a product reaches it’s end-of-life, there are several options available for processing it including reuse, remanufacturing, recycling, and disposing (the least desirable option). In almost all cases, a certain level of disassembly may be necessary. Thus, finding an optimal (or near optimal) disassembly sequence is crucial to increasing the efficiency of the process. Disassembly operations are labor intensive, can be costly, have unique characteristics and cannot be considered as reverse of assembly operations. Since the complexity of determining the best disassembly sequence increases with the increase in the number of parts of the product, it is extremely crucial that an efficient methodology for disassembly process planning be developed. In this paper, we present a genetic algorithm for disassembly process planning. A case example is considered to demonstrate the functionality of the algorithm.http://dx.doi.org/10.1117/12.45526

Karbon emisyon politikalarının tersine tedarik zincir ağı tasarımı üzerindeki etkileri

Reverse Supply Chain is described as an initiative that plays an important role in the global supply chain for those who seek environmentally responsible solutions for their end-of-life products. The relative economic and environmental benefits of reverse supply chain are influenced by costs and emissions during collection, transportation, recovery facilities, disassembly, recycling, remanufacturing, and disposal of unrecoverable components. The design of reverse supply chain network takes into account social, economic and environmental objectives. This paper addresses the design of reverse supply chain under the three common regulatory policies, strict carbon caps, carbon tax, and carbon cap-and-trade.Küresel tedarik zincirinde önemli bir rol oynayan tersine tedarik zinciri, ömrünü tamamlamış ürünler için çevreye karşı sorumlu çözümler arayanların bir girişimi olarak tanımlanmaktadır. Tersine tedarik zincirinin nispi ekonomik ve çevresel faydaları, toplama, nakliye, geri kazanım tesisleri, demontaj, geri dönüşüm, yeniden imalat ve geri dönüşü olmayan bileşenlerin imha edilmesi sırasında oluşan maliyetler ve emisyonlardan etkilenmektedir. Tersine tedarik zinciri ağ tasarımı sosyal, ekonomik ve çevresel hedefleri dikkate almaktadır. Bu makale, sıkı karbon kapsülleri, karbon vergisi, karbon emisyon üst sınırı ve ticareti olmak üzere üç ortak düzenleyici politikada ters tedarik zincirinin tasarımını ele almaktadır

Casting of thrown away tool steel bits in the centrifugal casting route

Cutting tools get worn out due to wear and are ground in order to use them again. This wear may be due to abrasive wear, diffusion wear, fatigue wear, adhesive wear. Wear of tool steels leads to shortening of the length, so small that the tool bits are no more usable. These waste and thrown away tool bits were collected which may include steel waste, pig iron, molybdenum iron, chromium iron, vanadium iron, tungsten iron and other waste material. This mixture was melted in induction furnace at temperature about 1600 o C to 1700 o C. After that the casting of the melt was done through the centrifugal route at speeds of 200 rpm and 250 rpm. The cast obtained is in the shape of tool steel cylinder. Then the samples were prepared for the hardness test, machinability test and SEM analysis. The hardness was measured across the radius of the cast cylinder by using Rockwell hardness test machine in C-scale. The machinability test specimens were taken from the outer zone of the cast cylinder and the test was carried out in Lathe by keeping the variables such as rotation speed (420 rpm), feed rate (0.15 KM), rack angle (10 0 ) material to be machined (mild steel) and time of machining (5 minutes 40 seconds) constant. The machinability of the centrifugally cast samples were compared with the as-cast samples. SEM micrographs were taken for the outer region of the cast cylinder and a comparative study was made with the as-cast samples. We found that there is an increase in hardness values with the distance from the centre to the outer periphery of the cast samples also the hardness values are higher for speed 250 rpm than 200 rpm. The Machinability of the centrifugally cast samples was better than generally used tool steels