Department of Mathematics
Permanent URI for this collectionhttp://localhost:4000/handle/123456789/1920
Browse
4 results
Search Results
Item A comparative study of ε-constraint, lp-metric, and weighted sum multi-objective optimization methods in a circular economy(Elsevier, 2024) Kulshrestha, Rakhee; Sangwan, Kuldip SinghApproximately 74.7 Mt (Million Metric Tonnes) of e-waste is expected to be produced in 2030, and laptop e-waste is one of the major constituents of this. The goal of this paper is to develop and optimize a mixed-integer linear programming (MILP) mathematical model for a laptop manufacturer in India, based on a framework that integrates secondary reuse concept associated with traditional circular economy waste avoidance strategies. The multi-objective solution techniques of ε-constraint, LP-metric, and weighted sum methods are used to optimize the circular economy model. The proposed model aids as a policy tool to decide the optimum number of inspection/collection centers, sales/distribution centers, disassembly centers, refurbishing centers, recycling centers, and their optimum locations and allocations. This study results suggest that reuse, secondary customer centers, refurbishing, and recycling of the laptops is not only economically beneficial to the organization but also environment friendly and helps to create more jobs in the rural economy.Item An integrated DEA-fuzzy AHP method for prioritization of renewable energy sources in India(Springer Nature, 2025-01) Agarwal, Shivi; Mathur, TrilokAs India’s population grows and urbanization accelerates, energy demand is increasing sharply while conventional sources fall behind. To tackle energy shortages and climate change, India must prioritize renewable energy sources (RES), which offer sustainable solutions. The country is rich in RES, which can enhance fuel mix for electricity generation. This study analyzes various RES in India-solar, geothermal, hydro, biomass, wave, onshore, and offshore wind energy -using an integrated data envelopment analysis (DEA) and fuzzy analytic hierarchy process (Fuzzy AHP) methodology. Four main parameters-technical, economic, environmental, and socio-political -are identified and supported by 19 criteria, with environmental parameters including both desirable and undesirable criteria. In first phase, undesirable criteria are transformed into desirable criteria using Modified Ratio model. DEA is then applied to calculate initial efficiency score of RES under each parameter category. Fuzzy AHP determines weights for each parameter. The weights and initial efficiency scores are then combined to calculate overall efficiency score and ranking of RES. Sensitivity analysis shows that results obtained from proposed methodology are significant, and robust. Offshore wind ranks highest in efficiency, followed by hydro and onshore wind, while geothermal scores lowest. This methodology could benefit developing nations and guide policymakers in adopting RES.Item A Multi-objective Mathematical Model for Socially Responsible Supply Chain Inventory Planning(Springer, 2022-11) Kulshrestha, RakheeThe supply chain inventory planning is well studied and analyzed in the literature considering various costs and other factors. However, social factor is largely overlooked although, it is important like cost factors which generally come from sourcing, production, storage and distribution. In the current work, a mathematical model for supply chain inventory was developed with four objectives (i.e., cost, local development, steadiness in employment and investment in green technology). The first objective is related to the total cost, which includes mostly inventory, manufacturing, and re-manufacturing related costs. The other two objectives are related to social aspects which focus on improvement in local development and steadiness in employment. The fourth objective is related to environmental aspect which focuses on the right time to invest in environmentally friendly machinery and technologies. The proposed model has the capability to obtain the optimal number of products to be manufactured and re-manufactured, number of inventories, number of employees to recruit and lay-off within a certain region in each quarter of the year, and decision on time to invest in green technology or pay govt. penalty, considering the upcoming demand in each quarter. The weighted sum method is applied to solve the multi-objective optimization problem.Item Optimization of Specific Energy, Scrap, and Surface Roughness in 3D Printing Using Integrated ANN-GA Approach(Elsevier, 2023) Kulshrestha, Rakhee; Sangwan, Kuldip Singh3D printing technology is fast emerging as a solution to convert cyber models to physical models quickly for visualization and feedback in Industry 4.0 environment. Energy efficiency, surface roughness, and material wastage are important performance responses and the effects of 3D printing parameters on these conflicting responses need to be studies to further improve the technology. Multiobjective optimization is a tool to obtain the right balance among conflicting performance responses. This paper aims to find the optimal values of infill, layer height, printing speed, extruder temperature, and scale to optimize specific energy, scrap, and surface roughness, simultaneously. Experiments were performed based on a Taguchi L-27 orthogonal array using PLA filament. A predictive model has been developed using artificial neural network (ANN) integrated with a genetic algorithm (GA) for obtaining Pareto solutions. Technique for order preference by similarity to ideal solution (TOPSIS) is used to obtain the most preferred solution from the Pareto solutions and analytical hierarchal process (AHP) is used to determine weights of the three objectives. The proposed methodology is expected to help the practitioners to rank and customise the decisions proactively in conflicting scenarios before the product is 3D printed, thereby improving sustainability and/or meeting product quality requirements