Experimental Investigation of Macrosegregation During Vertical Solidification of Lead–Tin Alloys

Thermosolutal convection during solidification of alloys is one of the major causes of macrosegregation. An experimental investigation was carried out on lead–tin alloys to study the evolution of macrosegregation during vertical solidification in laboratory. The emphasis was on accurate measurements of temperatures during solidification as well as segregation measurements and microstructural examination of solidified samples. The nominal compositions of ingots were Pb–35% Sn, Pb–19 wt% Sn and Sn–15 wt% Pb. Experiments were carried out at two superheats and different cooling rates. With decreasing cooling rate, increase in axial macrosegregation was observed in lead rich alloys. No macrosegregation was observed in tin rich alloys. Convection of interdendritic liquid was found to be responsible for macrosegregation. Also, from experimental data, heat flux to cooling water, local solidification times in the melt as well as dendritic arm spacings were determined.     

Genetic adaptive search model of hot metal desulphurization

Genetic adaptive search (GAS) techniques, based on the mechanics of natural genetics, are used in this paper to find an optimal model of desulphurization process of iron-melt by powder injection. Industrial data on 400 t torpedo are used to evaluate contributions of transitory and permanent contact reactions to the overall desulphurization process during calcium carbide powder injection. The results obtained with GAS agree more closely with the plant data than the theoretical model. GAS solutions are also found to be better than regression models. These results suggest immediate application of GAS in similar metallurgical problems.     

Process Control and Optimization of the AOD Process Using Genetic Algorithm

The AOD process of making stainless steel is very popular because of its fast rate of decarburization and excellent control of composition and temperature. Both static and dynamic models are available for process control. The objective of the present study is to demonstrate the applicability of GA in adapting a process control model to a particular plant environment and subsequently optimize the blowing scheme to reduce overall costs. Deviation of the predicted results of the process control model, from the actual plant data, is first minimized by adjusting the chemical reaction rate parameters and heat balance equation. It is found that the adaptation of the process control model to an actual situation is feasible only below 0.8% carbon. After adapting the model, optimization is done through GA wherein the objective function contains the cost of refractory, process time, chromium loss etc. It is thus possible to devise a blowing scheme to arrive at the desired end point composition and temperature at the lowest cost.     

Thermal application of composites of iron and magnesium in thermosyphon solar water heating system

A novel and low-cost mixture of iron and magnesium have been synthesized and used as selective coatings for flat plate absorber in solar water heating system. The commercial black paint is fabricated with the mixture of composition Fe₃(PO₄)₂·0.1Mg₂P₂O₇·1.9 MgSO₄(FPM3A). The composition of the coating mixture has been characterized by various analytical techniques. Thermal studies of these mixtures were accomplished using differential scanning calorimetry and thermo-gravimetric analysis. From the thermal analysis, it has been observed that the mixtures can be used as thermal heat storage materials. The FPM3A-modified black paint has been tested in a thermosyphon solar water heater prototype. The average water temperature and efficiency of the flat plate absorber with FPM3A-modified black paint have increased by an average of 7.5° and around 12%, respectively, in comparison with that with commercial unprocessed black paint.     

Pythagorean fuzzy TOPSIS for multicriteria group decision-making with unknown weight information through entropy measure

In this study, a new technique for order preference by similarity to ideal solution (TOPSIS)-based methodology is proposed to solve multicriteria group decision-making problems within Pythagorean fuzzy environment, where the information about weights of both the decision makers (DMs) and criteria are completely unknown. Initially, generalized distance measure for Pythagorean fuzzy sets (PFSs) is defined and used to initiate a new Pythagorean fuzzy entropy measure for computing weights of the criteria. In the decision-making process, at first, weights of DMs are computed using TOPSIS through the geometric distance model. Then, weights of the criteria are determined using the entropy weight model through the newly defined entropy measure for PFSs. Based on the evaluated criteria weights, TOPSIS is further applied to obtain the score value of alternatives corresponding to each decision matrix. Finally, the score values of the alternatives are aggregated with the calculated DMs’ weights to obtain the final ranking of the alternatives to avoid the loss of information, unlike other existing methods. Several numerical examples are considered, solved, and compared with the existing methods.     

A distribution free newsvendor model with consignment policy and retailer’s royalty reduction

Reducing the system cost and achieving significant profit are the key factors for every successful business sector. A consignment contract under distribution-free approach may be a fruitful combination to achieve a profitable business. This model deals with a single-period newsvendor problem with a consignment policy. The consignment policy is an agreement between any two parties, named as the consignor and the consignee. Under Stackelberg approach, firms act as leader and follower. Both parties carry some parts of the holding cost instead of one. A new policy for paying the fixed fee to the consignee is introduced. This paper considers no specific probability distribution for customer’s demand except a known mean and standard deviation. An efficient approach is proposed to reduce the retailer’s cost and building a sustainable consignment contract. The solution of this model is obtained using distribution free approach. A comparison between the traditional supply chain policy and the consignment policy is established. The price-sensitivity on demand is analysed. Some numerical examples and graphical representations are given for both traditional and consignment policy. Result proves that consignment policy is dominating over the traditional policy and a significant reduction of retailer’s royalty is found.     

India’s national food security programme: a strategic insight

Indian National Food Security Programme, with a goal to provide highly subsidized food grains to more than 800 million people in every nook and corner of the vast country, faces strategic challenges related to production, procurement, storage, transportation, distribution, finance, and organization. While the production issues are related to low yield, small farm size, and lack of financial support, the procurement process is skewed and lacks integration with the markets. The storage facilities are inadequate and are non-optimally located. Transportation facilities lack coordination leading to multiple loading and unloading of the food grains. Leakage and improper distribution of food grains are also big challenges. Very high subsidy, inefficient processes, and a large work force have brought to the fore the question of financial viability of the programme. There are also organizational issues related to payment disparity and resistance to labor reforms. The paper has also given a framework for efficient implementation of the programme using cloud system with effective procurement and stock management policy measures.     

Polyphenol oxidase-based luminescent enzyme hydrogel: an efficient redox active immobilized scaffold

A novel, functionally potent polyphenol oxidase (10000 U)-mediated urchin-shaped composite-based luminescent enzyme hydrogel network as immobilized scaffold for oxido-reductase efficiency on phenolic substrates including phenol, resorcinol, catechol and quinol was synthesized and characterized through fluorescence spectroscopy along with scanning electron microscopy and transmission electron microscopy.     

A Study on the Effects of Damage Models and Wavelet Bases for Damage Identification and Calibration in Beams

Abstract:   Damage detection and calibration in beams by wavelet analysis involve some key factors such as the damage model, the choice of the wavelet function, the effects of windowing, and the effects of masking due to the presence of noise during measurement. A numerical study has been performed in this article addressing these issues for single and multispan beams with an open crack. The first natural modeshapes of single and multispan beams with an open crack have been simulated considering damage models of different levels of complexity and analyzed for different crack depth ratios and crack positions. Gaussian white noise has been synthetically introduced to the simulated modeshape and the effects of varying signal-to-noise ratio have been studied. A wavelet-based damage identification technique has been found to be simple, efficient, and independent of damage models and wavelet basis functions, once certain conditions regarding the modeshape and the wavelet bases are satisfied. The wavelet-based damage calibration is found to be dependent on a number of factors including damage models and the basis function used in the analysis. A curvature-based calibration is more sensitive than a modeshape-based calibration of the extent of damage.