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      Volume 44, Issue 10

      October 2019

    • Recovery of basic valuable metals and alloys from E-waste using microwave heating followed by leaching and cementation process


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      The whole world understands about the crisis of harmful electronic waste as it is increasing the usage and its disposal. The Government of India asked researchers to come out with innovative alternative solutions, apart from existing conventional methods for safe reuse, recycling and proper disposal particularly for electronic solid waste system. The solution is found which consists of microwave heat treatment followed by acid leaching. The e-waste was first crushed and then the sample was melted in microwave heat treatment to recover the valuable metal in the form of metallic mixture. This mixture was further subjected to acid leachingprocess in the presence of hydrogen peroxide to form leached liquor. The analysis with X-ray diffraction, image mapping and energy-dispersive X-ray spectroscopy shows that the leached liquor sample mainly contain iron, aluminum and copper, mostly in the form of alloys. The results with field-emission scanning electron microscope analysis, also shows that approximately ninety percent leaching efficiency is observed for nickel, cobalt and copper with hydrochloric acid as solvent, whereas iron and aluminum produced less than forty percent.Further, these results are also compared with the existing methods based on the response surface method through thermal plasma process.

    • Investigations for machinability of primary recycled thermoplastics with secondary recycled rapid tooling


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      This paper highlights the machinability of primary recycled thermoplastics as workpiece (WP) material with secondary recycled (reinforced) thermoplastic composites as rapid tooling (RT). Both WP and RT have been 3D printed on commercial fused deposition modelling. For investigating machinability of primaryrecycled thermoplastics, un-reinforced WP of low-density polyethylene (LDPE) and high-density polyethylene (HDPE) has been selected. The RT materials were secondary reinforced (recycled) LDPE with double particle size Al₂O₃ particles and HDPE with triple particle size Al₂O₃. The machinability has been calculated in terms of weight loss of WP, while machining on a vertical milling set-up. This study also reports the surface hardness, porosity, surface roughness (Ra) and photomicrographic observations of WP and RT under controlled machining conditions. Further thermal analysis suggests that primary recycled thermoplastic can be successfully machined with secondary recycled RT, resulting in improved thermal stability and surface properties.

    • Multi-objective optimization of process parameter in EDM using low-frequency vibration of workpiece assigned for SKD61


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      Integrated vibration in electrical discharge machining (EDM) plays a key role in achieving high efficiency. High levels of variables can be employed in this approach due to integration. However, simultaneous optimization of the EDM parameters to achieve multi-objectives is still very complex and challenging. Studies on integrated vibration are still in a preliminary stage. This report addresses multi-objective optimization in EDM for SKD61 die steel using low-frequency vibration. MOORA (Multi-objective optimization based on ratio analysis) was chosen to resolve this multi-objective optimization problem. The material removal rate (MRR), tool wear rate (TWR) and surface roughness (SR) were selected as performance measures in the EDM process. An analytical hierarchical process (AHP) was used to determine the weight value of the quality indicators. The results indicate that low-frequency vibrations significantly improve machining efficiency. When the frequency of the vibrations increased, MRR increased significantly such that MRRMAX = 64.48%. TWR and SR are smaller and their increase are given as TWRMAX = 20.3% and SRMAX = 18.47%. MOORA has been identified as a suitable alternative to multi-objective optimization in an EDM process using low-frequency vibrations for an assigned workpiece. The optimum parameters required to achieve the multi-objective were Ton = = 25 μs,I = 8 A, Tof = 5.5 μs and F = 512 Hz, at the resultant quality criteria of MRR = 9.564 mm³/min, TWR = 1.944 mm³/min and SR = 3.24 μm with a maximum error of 8.24%.

    • Pedospheric adsorption–desorption of anti-moulting agent Chlorfluazuron and transfer in agriculturally significant Arcadian soils


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      Agrochemical-based soil and water contamination has been posing serious threats to ecological balance. Current research investigates the sorption and mobility behaviour of a Benzylurea insecticide, Chlorfluazuron (CFZ), by a standard batch equilibrium method. After investigation of soils’ physical and chemical properties, sorption assays have been performed on five soils from agriculturally significant regions where CFZ can probably occur. CFZ expressed poor adsorption on the selected soils with linear adsorption coefficient, i.e.Kd(ads), ranging between 6.08 and 9.57 μg/mL and Freundlich adsorption coefficient Kf(ads) having a range of 4.18–9.01 μg/mL. Linear and Freundlich models displayed correlation coefficient R² value to be ≥0.84 and 0.83, respectively, reflecting the goodness of fit of the experimental data. Furthermore, the mobility of CFZ was assessed using the McCall classification based on Koc values. CFZ expressed high mobility in soils with less adsorption. The adsorptive and desorptive interactions were highly dependent upon soil physicochemical characteristics. Based on the current investigation, CFZ can be predicted to be a potential threat for soils with a low adsorptive affinity towards it. Future investigations in this regard can consider the use of sustainable materials and procedure for CFZ decontamination in vulnerable soils.

    • Experimental study on the pH for activating ground granulated blast-furnace slag activity at different temperatures


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      In order to explore the initial pH values of activator solution needed for early activation of slag at different temperatures, the effects of curing temperatures (5, 20 and 35°C) and pH (12.10, 12.55, 13.02 and 13.58) on the activation and hydration characteristics of ground granulated blast-furnace slag (GGBFS) wereinvestigated. Sodium hydroxide (NaOH) was used as the alkaline activator. The compressive strength and non evaporable water content of GGBFS paste cured for 1, 3, 7, 14 days were determined. The hydration characteristics of slag pastes at different temperatures and pH were analyzed by XRD and SEM. The results showed that the pH value required for slag activation decreased with increasing temperature. Based on the 3 days strength of slag paste, the pH values required for activation of slag activity at 5, 20 and 35°C were 13.58, 13.02and 12.10, respectively. With the high temperature and high pH of solution, a dense calcium-rich product formed on the surface of slag particles, which suppressed the further slag reaction. With the low temperature and highpH of solution, a layer of network product was found on the surface of the slag particles, and the later strength developed rapidly as the further hydration was not prevented. This study provides a reference for the application of alkali-activated slag.

    • Experimental study of the local scouring around sloped piers and its estimation using statistical tools


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      Local scouring around sloped bridge piers in steady currents was studied both experimentally and mathematically. The effects of different inclination angles, flow intensities, flow depths, and pier size on local scouring were investigated. The experimental results show that the scouring depth increases with an increase inthe values of discharge and pier width. The scouring depth for the sloped piers is smaller than the vertical piers one and the maximum scouring depth continuously decreases as the pier inclination angle increases. Prediction of the scouring depth around bridge piers using analytical models can be utilized in the feasibility studies of different models, and evaluations of the parametric analytical. Therefore, it was tried to model the scouring depth as a function of Froude number, flow intensity, and relative roughness parameters using non-dimensional analysis. The regression analysis based models were introduced to determine the scouring depth at upstream side of the pier using experimental tests data. Step-wise linear regression showed that the value of relative scouring depth has considerably good correlation only with two non-dimensionless parameters of inclination angle andnormalized approaching flow depth. In this regard, some linear and nonlinear regression tools were utilized to establish functional relationships between these variables. Statistical indices and residual analyses of the models revealed the suitability of the models. Comparison of the experimental and predicted value of relative scouring depth illustrates that the suggested models can reasonably predict this parameter.

    • MCAMC: minimizing the cost and makespan of cloud service using non-dominated sorting genetic algorithm-II


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      The number of cloud users and their aspiration for completion of tasks at less energy consumption and operating cost are rapidly increasing. Hence, the authors of this paper aim to minimize the makespan and operating cost by optimally scheduling the tasks and allocating the resources of cloud service. The optimum task scheduling and resource allocation are obtained for each objective function using the simple genetic algorithm. Further, the non-dominated solutions of the dual objectives are obtained using the non-dominated sorting geneticalgorithm-II, the most successful multi-objective optimization technique. A complex cloud service problem consisting of ten tasks, fifteen subtasks and fifteen heterogeneous resources is considered to investigate the proposed method. The numerical results obtained in the single objective and multi objective optimizationproblems show that the makespan and the operating cost are significantly reduced using the simple genetic algorithm and a wide range of non-dominated solutions are obtained in the multi-objective optimization problem, by which the cloud users shall be benefitted to choose the most appropriate solution based on the otherdesign constraints they have.

    • CFD simulation of local scouring around airfoil-shaped bridge piers with and without collar


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      In this paper, the effectiveness of airfoil-shaped pier with and without a collar on local scour depth reduction is numerically investigated utilizing FLOW-3D model. The results show that on a constant T* = VT/D (V: velocity, T: time, D: pier width), increasing the width of the ballet of pier would result on the reduction of maximum scour depth and it would mitigate the scouring depth behind the piers. Also, because of lack of uplift vortices in using airfoil-shaped pier, there would be no scouring behind the piers. Utilizing collar on the airfoil shaped pier would result in a reduction of maximum scouring depth in front of the pier as well and the upliftvortices behind the pier would reduce. Investigation of orientation discipline of the airfoil-shaped pier on flow route shows that the pier which is reversely placed in the flow direction (the keen part in front), will cause the horseshoe vortex to weaken and make the scouring to start from downstream. However, scouring caused by horseshoe vortex in front of the airfoil-shaped pier is strongly more than scouring caused by wake vortex in the rear of the pier.

    • Impact of microgrid operation on performance of radial distribution system


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      Voltage profile and real power loss are the criteria in determining performance of Radial Distribution System (RDS). Presence of Distributed Generators in RDS is assessed by ‘Penetration Ratio’. The use of PR fails in the analysis of the implications of the presence of a Microgrid on RDS as it is zero in islanded modeand sometimes in grid-connected mode. An attempt has been made to introduce a new term ‘Relief Factor’ to overcome this lacuna. This Factor is evaluated by developing an algorithm based on power flow analysis using Backward Forward Sweep method. The developed algorithm is tested on a 34 bus RDS by integration of a two shift industrial Microgrid. The power flow analysis is run for 24 snapshots of the day. Relief Factor is found to be suitable to analyze the impact of a Microgrid on the performance of RDS in both the modes of Microgrid operation viz. grid-connected mode and islanded mode.

    • The degradation behaviour of nickel-based superalloys in the medical waste incineration plant


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      The present work was aimed at analysing the oxidation behaviour of three nickel-based superalloys-Superni 718, Superni 75 and Superni 750, by conducting in-situ study in the secondary chamber of a medical waste incinerator at 800–850°C for 1000 h. It was observed that among the three superalloys, Superni 75 is best suited for such an environment. This was concluded by comparing the weight change after 100 h for total 1000 h, constituting 10 thermal cycles. The morphology of the oxide scale formed on the substrate was analysedusing FE-SEM. The elemental composition was obtained by EDS. The depth profiling of the scale was done using the XPS technique. The chemical composition was also examined by the XRD analysis. The superior oxidation property of Superni 75 is due to the higher Ni-Cr content. The oxidation resistance of the nickel-based superalloys in the aggressive environment of medical waste incinerator is attributed to the presence of chromia oxide-Cr₂O₃ and spinel NiCr₂O₄.

    • Sediment assessment for a watershed in arid region via neural networks


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      In the present study, the estimation of suspended sediment load is computed by four Artificial Neural Networks (ANNs) algorithms, Cascade Forward Back Propagation (CFBP), Feed Forward Back Propagation (FFBP), Radial Basis Function (RBF), and Recurrent Neural Network (RNN). Five cases of model inputare calibrated to establish the relationship among precipitation, discharge and suspended sediment load. While discharge and rainfall up to four previous days as employed for input, model gives pre-eminent performance. Sensitivity of all models is appraised concerning Nash-Sutcliffe coefficient (ENS) and coefficient of determination (R²) for predicting sediment load. Among all ANNs, MMF (Morgan-Morgan-Finney) model when trained with stream flow as the input in RNN, gives best result with coefficient of determination, R² as 0.9474, while the values for FFBP, CFBP and RBF are 0.9115, 0.8766 and 0.8511, respectively. Performance of all results show that an MMF model is superior to conventional SRC (Sediment Rating Curve) and MLR (Multiple Linear Regression) models in determining the complex relationship between discharge and suspended sediment load.

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