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IIM Indore

Operation Management and Quantitative Techniques

We present a Lax-Friedrichs type scheme to compute the solutions of a class of non-local and non-linear systems of conservation laws in several space dimensions. The convergence of the approximate solutions is proved by providing suitable L 1 , L ∞ and BV uniform bounds. To illustrate the performances of the scheme, we consider an application to crowd dynamics. Numerical integrations show the formation of lanes in groups moving in opposite directions. This is joint work with R.M. Colombo (INDAM Unit, University of Brescia).

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Bulletin of the Brazilian Mathematical Society, New Series

Crowd dynamics through non-local conservation laws

We are grateful for the many insightful comments provided by the discussants. One team politely pointed out oversights in our literature review and the subsequent omission of a formidable comparator. Another made an important clarification about when a more aggressive variation (the so-called NoMax) would perform poorly. A third team offered enhancements to the framework, including a derivation of closed-form expressions and a more aggressive updating scheme; these enhancements were supported by an empirical study comparing new alternatives with old. The last team suggested hybridizing the statistical augmented Lagrangian (AL) method with modern stochastic search. Here we present our responses to these contributions and detail some improvements made to our own implementations in light of them. We conclude with some thoughts on statistical optimization using surrogate modeling and open-source software.

Technometrics

Rejoinder

Constrained blackbox optimization is a difficult problem, with most approaches coming from the mathematical programming literature. The statistical literature is sparse, especially in addressing problems with nontrivial constraints. This situation is unfortunate because statistical methods have many attractive properties: global scope, handling noisy objectives, sensitivity analysis, and so forth. To narrow that gap, we propose a combination of response surface modeling, expected improvement, and the augmented Lagrangian numerical optimization framework. This hybrid approach allows the statistical model to think globally and the augmented Lagrangian to act locally. We focus on problems where the constraints are the primary bottleneck, requiring expensive simulation to evaluate and substantial modeling effort to map out. In that context, our hybridization presents a simple yet effective solution that allows existing objective-oriented statistical approaches, like those based on Gaussian process surrogates and expected improvement heuristics, to be applied to the constrained setting with minor modification. This work is motivated by a challenging, real-data benchmark problem from hydrology where, even with a simple linear objective function, learning a nontrivial valid region complicates the search for a global minimum. Supplementary materials for this article are available online.

Modeling an augmented lagrangian for blackbox constrained optimization

Outbound logistics management practices, specific to India have drawn limited attention in the past. Recently though, this sector has garnered renewed attention of researchers and practitioners. Through an exploratory study, we attempt to understand and illustrate the outbound logistics management practices of automotive industry in India. Outbound logistics is divided into a set of interlinked functions based on a logistics framework and described accordingly. Based on findings from the exploratory study and extant literature in this field, a framework for the development of integrated logistics management practices in the aut omotive industry in India is derived and several research directions are proposed.

Decision

Outbound logistics management practices in the automotive industry: an emerging economy perspective

We propose and analyze finite volume Godunov type methods based on discontinuous flux for a  system of non-linear partial differential equations proposed by Hadeler and Kuttler to model the dynamics of growing sandpiles generated by a vertical source on a flat bounded rectangular table. The scheme is made well-balanced by modifying the flux function locally by including source term as a part of the convection term. Its extension to multi-dimensions is not straightforward for which an approach has been introduced here based on Transport Rays. This approach is compared with another approach for inclusion of source term which uses the idea of inverting the divergence operator relying on the Curl-free component of the Helmholtz decomposition of the source term. Numerical experiments are presented to illustrate the efficiency of the proposed scheme for both unsteady and steady state calculations and to make comparisons with the previously studied finite difference and semi-Lagrangian approaches by Falcone and Finzi Vita.

Journal of Computational Physics

Godunov-type numerical methods for a model of granular flow

The tourism industry was among the early adopters of information and communication technology (ICT), such as the Computer Reservation System of the early 1950s and the adoption of Global Distribution Systems in the late 1980s. However, after several decades of ICT adoption, the degree of adoption as well as use of ICT among enterprises related to travel and tourism (T&amp;T) has been quite uneven. The objective of this study is to provide a model that explains the ICT adoption process in the T&amp;T industry through a combination of Adoption Diffusion (AD) and Usage Diffusion (UD). The model incorporates the UD concepts of variety of use and rate of use with the perceived usefulness concept of AD. The UD model, unlike the AD model, focuses on the extent of use rather than on the act of adoption. The model consists of three main parts, namely, determinants, user patterns and outcomes. Based on these three dimensions, adopters are categorized into eight groups: Tech-Savvy, Obligatory, Early Adopter, Focused, Limited, Constrained, Follower and Laggards. The model was empirically tested and the results show that perceived usefulness is an important element in the adoption process. This model will be a ready reference for professionals, managers working in T&amp;T firms, policy makers and government bodies in strategy formulation. It will also help IT professionals and researchers who work in the T&amp;T domain.

Tourism Recreation Research

A conceptual model for adoption of information communication technology in the travel and tourism industry

In an efficient stock market, the log-returns and their time-dependent variances are often jointly modelled by&nbsp; stochastic volatility models (SVMs). Many SVMs assume that errors in log-return and latent volatility process are uncorrelated, which is unrealistic. It turns out that if a non-zero correlation is included in the SVM (e.g., \cite{Shephard05}), then the expected log-return at time $t$ conditional on the past returns is non-zero, which is not a desirable feature of an efficient stock market. In this paper, we propose a mean-correction for such an SVM for discrete-time returns with non-zero correlation. We also find closed form analytical expressions for higher moments of log-return and its lead-lag correlations with the volatility process. We compare the performance of the proposed and classical SVMs on S\&amp;P 500 index returns obtained from NYSE.

International Journal of Statistics and Probability

Mean-correction and Higher Order Moments for a Stochastic Volatility Model with Correlated Errors

Women leadership has gathered momentum and is gaining acceptance. Women are equally competent in performing their roles and responsibilities as men. However, in the field of Supply Chain Management (SCM), the incidence of women leadership is relatively low. This conceptual paper attempts to address this inconsistency. The paper outlines the evolution of SCM and the challenges of Supply Chain (SC) leaders; particularly, how women as SC leaders can tackle challenges and enhance the overall performance of the Supply Chain. A conceptual model for women leadership in SCM has been proposed and the direction for future research has been laid out.

Organizational Behaviour and HRM

International Journal of Economic Research

Women leadership in supply chain management

The goal of this research is to study physicians' prescription decisions and patients' drug request behaviors jointly. We have developed a new zero-inflated multinomial (ZiMNL) choice model to study patient drug request data with excessive zero requests and a standard multinomial logit (MNL) model to capture physician prescriptions decisions. The two models are joined by a flexible nonparametric multivariate distribution for their random effects. We also adopt an analytically consistent expression for the interaction effect in our non-linear and joint modeling framework. We apply our model to a unique physician panel data set from the Erectile Dysfunction category. Our key empirical findings include the following: (1) the triggering of drug requests by DTCA is complicated with category level DTCA reducing patients' probability of making drug requests and drug specific DTCA driving drug requests for the advertised drug; (2) patient characteristics may play a role in the impact of DTCA on drug requests and the impact of patient requests on physicians' prescription decisions; (3) patient drug requests have a significant impact on physicians' prescription decisions and patients can be consistent with physicians in choosing a drug based on patient diagnosis level and some unobserved factors; (4) there are significant correlations among physician-level random effects that drive both patients' drug requests and physicians' prescription decisions, which validates the joint modeling approach.

WORKING PAPER

Ask your doctor if this product is right for you: a bayesian zero-in ated multinomial joint model for patient drug requests and physician prescriptions

An innovative business model for delivery of health services in low and middle income countries is based on cross-subsidizing across patients. Services are offered to poor patients for free, while other patients pay competitive market prices. Driven by their social mission, organizations often focus their marketing efforts only on poor patients via outreach and education. We analyze the outreach activities (camps) of Aravind Eye Hospital in India to learn whether these efforts produce additional spillover benefits of attracting paying patients to its hospitals. In particular, we estimate spatial and temporal (both short- and long-term) effects of camps on different types of paying patients. Based on nine years of historical data on the spatial origin of patient traffic and outreach camp locations, we find that camps have net positive effects on the number of paying patients. These effects are consistent with the camps acting as advertising for Aravind. We also find that the effects of camps are stronger for patients who pay a subsidized price than for those who pay full price, camps influence patients in a small geographic radius of six miles, and the effects persist for up to ten weeks after the camp. Camps also have long term positive effects beyond ten weeks on the number of new patients who pay full price. Further, effects become stronger with distance from the base hospital, a finding also consistent with camps acting as advertising. Our findings reinforce the viability of the cross-subsidization model since they identify a mechanism that creates synergy between the social mission and income generating sides of the organization.