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743 items in total found

Journal Articles | 2019

New valid inequalities for the optimal communication spanning tree problem

Yogesh Kumar Agarwal and Prahalad Venkateshan

Informs Journal On Computing

The problem of designing a spanning tree on an underlying graph to minimize the flow costs of a given set of traffic demands is considered. Several new classes of valid inequalities are developed for the problem. Tests on 10-node problem instances show that the addition of these inequalities results in integer solutions for a significant majority of the instances without requiring any branching. In the remaining cases, root gaps of less than 1% from the optimal solutions are realized. For 30-node problem instances, the inequalities substantially reduce the number of nodes explored in the branch-and-bound tree, resulting in significantly reduced computational times. Optimal solutions are reported for problems with 30 nodes, 60 edges, fully dense traffic matrices, and Euclidean distance-based flow costs. Problems with such flow costs are well-known to be a very difficult class of problems to solve. Using the inequalities substantially improves the performance of a variable-fixing heuristic. Some polyhedral issues relating to the strength of these inequalities are also discussed.

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Journal Articles | 2019

A new model for the asymmetric vehicle routing problem with simultaneous pickup and deliveries

Yogesh Kumar Agarwal and Prahalad Venkateshan

Operations Research Letters

The asymmetric vehicle routing problem with simultaneous pickup and deliveries is considered. This paper develops four new classes of valid inequalities for the problem. We generalize the idea of a no-good cut. Together, these help us solve 45-node randomly generated problem instances more efficiently. We report results on a set of benchmark instances in literature. In this set, we are able to show an order of magnitude improvement in computational times over currently published results in literature.

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Journal Articles | 2019

A cutting plane approach for the multi-machine precedence-constrained scheduling problem

Prahalad Venkateshan, Joseph Szmerekovsky, and George Vairaktarakis

Annals of Operations Research

A cutting-plane approach is developed for the problem of optimally scheduling jobs with arbitrary precedence constraints on unrelated parallel machines to minimize weighted completion time. While the single machine version of this problem has attracted much research efforts, enabling solving problems with up to 100 jobs, not much has been done on the multiple machines case. A novel mixed-integer programming model is presented for the problem with multiple machines. For this model, many classes of valid inequalities that cut off fractional linear programming solutions are developed. This leads to an increase of the linear programming lower bound from 89.3 to 94.6% of the corresponding optimal solution, and a substantial reduction in the computational time of an optimal branch-and-bound algorithm for this problem. This enables us to report optimal solutions for problem instances with up to 25 jobs and 5 machines, which is more than twice the size of problems for which optimal solutions have been reported in the literature thus far. For a special case of the problem—that of minimizing makespan—application of our model helps solve 18 of 27 previously unsolved problem instances to optimality.

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Journal Articles | 2019

Adoption and the impact of system of rice intensification on rice yields and household income: an analysis for India

Poornima Varma

Applied Economics

This paper examines the determinants and impacts of the adoption of five mutually exclusive practices System of Rice Intensification (SRI) on yields and household incomes using a multinomial endogenous treatment effects model. Farm household survey data is collected from selected districts of three States of India. Results suggest that the decision to adopt SRI is a function of experience in terms of age, farm assets, irrigation facility and information about SRI. The analysis showed that small and marginal farmers are more likely to adopt SRI as compared to large farmers. The National Food Security Mission (NFSM) came out to be significant and positive only in the case of few practices in some States. The welfare outcome results showed that the adoption increased the yield and income of three out of four practices-plant plus water, plant plus soil and plant plus water plus soil management. Briefly, the results show that the adoption of SRI especially full adoption of SRI has greater impact on the yield and income.

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Journal Articles | 2019

Casting the net: India's public distribution system after the Food Security Act

Jean Dreze, Prankur Gupta, Reetika Khera, and Isabel Pimenta

Economic & Political Weekly

A broad-brush assessment of the public distribution system is presented in six of India’s poorest states—Bihar, Chhattisgarh, Jharkhand, Madhya Pradesh, Odisha, and West Bengal—soon after the National Food Security Act, 2013 came into force. Important gains have been made, including broader coverage, lower targeting errors, accelerated PDS reforms, and a greater political commitment to food security. In four of the six reference states, the PDS seems to be doing reasonably well, but Bihar and Jharkhand still have a long way to go. Even in the leading states, much remains to be done to achieve the purpose of the NFSA: ending food insecurity.

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Journal Articles | 2019

Contestations around water allocation during a climate crisis in India: The case of 'IPL vs. drought'

Arpit Shah and Navdeep Mathur

Global Environmental Change

In this paper, we analyze a major controversy regarding the allocation of water for Indian Premier League (IPL) cricket matches during a period of extreme drought in the state of Maharashtra in India. We use a discursive approach to public policy to understand water policy production and to analyze the competing narratives on water advanced by opposing discourse coalitions during the ‘IPL vs. drought’ controversy. We find that the neoliberal view of ‘water as an economic good’ is dominant and institutionalized in the water allocation priorities determined by the Maharashtra State government. This is resisted by civil society actors like Loksatta and by the Indian judiciary, who view ‘water as a Human Right.’ Our reading of the ‘IPL vs. drought’ public interest litigation (PIL) shows that Loksatta’s decision to target water allocation for the IPL through the Courts leverages the popularity of the IPL in the Indian media, as well as the uneven unfolding of neoliberalism across institutions of the state in India. At the same time, Loksatta’s PIL focuses solely on the IPL and does not pay attention to the water allocation to larger users like industry and sugarcane cultivation that best represent the institutionalization of the neoliberal view of water in Maharashtra. We argue that the focus on the IPL makes it the site of contesting water policy on ideological grounds. We conclude by examining the challenge provided by Loksatta’s PIL to the dominant neoliberal view of water in Maharashtra.

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Journal Articles | 2019

Antecedents to innovation in emerging markets: Evidence from India

Mohammad Fuad and Arun Kumar Jain

International Journal of Innovation Management

Firms utilise both internal and external knowledge reservoirs in order to innovate. This study explores the drivers of innovation specifically, role of business groups, alliances, degree of internationalisation and financial slack on innovation. Hypotheses are tested using patent data on a sample of Indian firms. Group affiliation, financial slack and degree of internationalisation are found to positively impact innovation output. This study contributes towards the nascent literature on innovation in the Indian context.

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Journal Articles | 2019

Confidence soft sets and applications in supplier selection

Manish Aggarwal

Computers & Industrial Engineering

The evaluation of the alternatives against multiple criteria is of the utmost importance in a multi-criteria decision making (MCDM) problem. It is often the case that the experts have a varying degree of confidence in their evaluations. That is, an evaluation has an associated degree of credibility. To take into account this crucial piece of information in determining the best choice, we present a new data structure. More specifically, we present a confidence-based soft set. We also extend the same to the fuzzy and intuitionistic fuzzy domains. The proposed concepts are elucidated through a number of illustrative examples. We establish their usefulness in a real case-study.

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Journal Articles | 2019

A new family of fuzzy discrete choice models

Manish Aggarwal

IEEE Transactions on Fuzzy Systems

Often in real-world decision making, it is difficult to crisply evaluate the utility values as required in the case of conventional choice models. Besides, a decision maker (DM) has his/her own relative importance for each of the attributes. The attributes may also be interacting positively (synergy) or negatively, the degree of which is specific to the DM. A new family of discrete choice models is introduced with a motivation that takes into account the human factors in real-world multiattribute decision making. More specifically, the proposed choice models are based on fuzzy subjective utilities that are easier to elicit. The proposed models are further extended to take into account the unique attitudinal character of the DM, the relative weight vector, and the degree of interaction among the different attributes. A real case study illustrates the usefulness of the study.

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Journal Articles | 2019

Modelling human decision behaviour with preference learning

Manish Aggarwal and Ali Fallah Tehrani

INFORMS Journal on Computing

In the real world, an attribute value is perceived differently by different individuals. Emphasizing on this aspect, we extend the discrete choice models with perceived values that are subjective and specific to a decision-maker (DM). The proposed choice models are augmented with the parameters of an entropy function, besides the utility coefficients, to model a DM's complex choice behavior. A variety of higher order choice models are also proposed. The proposed models are further extended with a DM's reference-value for each attribute. A real and illustrative application is included.

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