Distribution of reinforcement particles in surface composite fabrication via friction stir processing: Suitable strategy

Fabrication of metal matrix surface composites (SCs) is an emerging trend of friction stir processing applications. Key factors affecting the properties of SCs are process parameters, tool geometry, tool dimensions and reinforcement strategies. In this research, effects of different reinforcement strategies and varying tool offset positions on dispersion of reinforcement particles in the base matrix are investigated. The experiments were performed in two phases using AA6063 as base metal at constant process parameters of 1120?rpm rotational speed, 40?mm/min traverse speed and 2.5° tilt angle. In the first phase, effect of six different reinforcement strategies on the reinforcement particles distribution and defect formation was studied. It was found that groove method with tool offset in retreating side (RS) exhibited better homogeneity in reinforcement distribution out of the six reinforcement strategies considered. In the second phase, effect of variation of tool offset in RS was investigated. Results from second phase of experimentation reflected that the best dispersion of reinforcement powder with larger stir zone area was found with 1.5?mm tool offset which is numerically half of the tool pin radius. The results were supported by macro and microstructural images obtained from the optical microscope and scanning electron microscope.     

Radial basis probabilistic neural network for differential protection of power transformer

Protection of medium- and large-power transformers has always remained an area of interest of relaying engineers. Conventionally, the protection is done making use of magnitude of various frequency components in differential current. A novel technique to distinguish between magnetising inrush and internal fault condition of a power transformer based on the difference in the current wave shape is developed. The proposed differential algorithm makes use of radial basis probabilistic neural network (RBPNN) instead of the conventional harmonic restraint- based differential relaying technique. A comparison of performance between RBPNN and heteroscedastic-type probabilistic neural network (PNN) is made. The optimal smoothing factor of heteroscedastic-type PNN is obtained by particle swarm optimisation technique. The results demonstrate the capability of RBPNN in terms of accuracy with respect to classification of differential current of the power transformer. For the verification of the developed algorithm, relaying signals for various operating conditions of the transformer, including internal faults and external faults, were obtained through PSCAD/EMTDC. The proposed algorithm has been implemented in MATLAB.     

Thermal energy reservoir capacities for solar absorption cooling systemsCapacité des accumulateurs d'énergie thermique pour les systèmes frigorifiques à absorption solaires

It is essential to incorporate both hot and cold energy storage for a solar absorption cooling system in order to maximize the saving of conventional electrical power. The paper correlates the thermal energy storage requirements with the daily cooling demand pattern of a building. The other parameters which affect the choice of the two storage volumes are the effective sunshine hours, the chiller cooling capacity, its daily operation period and the two storage temperature differentials. The results have been obtained in a generalized manner and applied to an actual building in Kuwait.     

Estimation of fuel and clad temperature of a research reactor during dry period of de-fuelling operation

Heat transfer and fluid flow studies related to spent fuel bundle of a research reactor in fuelling machine has been carried out. When the fuel is in reactor core, the heat generated in the fuel bundle is removed by heavy water under normal reactor operation. However, during the de-fuelling operation, the fuel bundle is exposed to air for some period called dry period. During this period, the decay heat from fuel bundle has to be removed by air flow. This flow of air is induced by natural convection only. In this period, the temperatures of fuel and clad rise. If clad temperature rises beyond a certain limit, structural failure may occur. This failure can result into release of fission products from fuel rod. Hence the temperature of clad has to be within specified limit under all conditions. The objective of this study is to estimate the clad temperature rise during the dry period.In the CFD simulation, the turbulent natural convection flow over fuel and radiation heat transfer are accounted. Standard k-? model for turbulence, Boussinesq approximation for computing the natural convection flow and IMMERSOL model for radiation are used.The steady state and transient CFD simulation of flow and heat is performed, using the CFD code PHOENICS. The steady state analysis provides the maximum temperature the clad will attain if fuel bundle is left exposed to air for sufficiently long time. For safe operation, the clad temperature should be limited to a specified value. From steady state CFD analysis, it is found that steady state clad temperature for various decay powers is higher than the limiting value. Hence transient analysis is also performed. In the transient analysis, the variation of clad temperature with time is predicted for various decay powers. Safe dry time, i.e. the time required for clad to reach the limiting value, is predicted for various decay powers. Determination of safe dry time helps in deciding the time available to the operator to drop the bundle in light water pool for storage. The analysis is found useful in optimizing the de-fuelling process.     

Extraction and Isolation of β‐Glucan from Grain Sources—A Review

A collective report on the extraction and isolation of β‐glucan from grain sources, namely, oat, barley, and wheat is presented. An analysis on the effect of medium, pH, and temperature on the purity and yield of the β‐glucan derived under acidic/alkaline/aqueous/enzymatic conditions is also made. Water extraction and alkali extraction processes are preferred as the yield and recovery of extracted β‐glucan were good. Cost‐effective development of the process for deriving high molecular weight β‐glucan is the current requirement for its wide applications in food and pharmaceutical industries.     

Microwave treatment of dehulled rapeseed to inactivate myrosinase and its effect on oil and meal quality

Rapeseed was dehulled using a Palyi pneumatic attrition system which produced 62–66% clean dehulled seed. Dehulled rapeseed was preconditioned to 7, 10 and 13% moisture levels, exposed to micro-wave irradiation for periods of up to 2.5 min and analyzed for residual thioglucoside glucohydrolase (myrosinase) activity. The 7% moisture samples heated slowly and required at least a 2.5 min treatment whereas 10 and 13% moisture samples heated more rapidly and required microwave exposures of 1.5 min or less for complete inactivation of the enzyme. The sulfur content of oils obtained from adequately microwave-treated samples (1.5 min for 10 and 13% and 2.5 min for 7% moisture samples) was equal to or lower than commercially processed crude rapeseed oils. The shorter microwave treatment of dehulled rapeseed produced considerably lighter oils and did not adversely affect the color of the meal. It also destroyed some of the rapeseed glucosinolates and improved the meal palatability. However, goitrogenic properties of microwave-treated rapeseed meal evaluated by mice feeding experiments did not appear different from untreated rapeseed meal.