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743 items in total found

Journal Articles | 2017

Child labour and human capital in developing countries - a multi-period stochastic model

Indrajit Thakurta and Errol D'Souza

Economic Modelling

This study investigates the co-determination of child labour and human capital acquisition through a life cycle model. It explores three categories of households with zero, ten and fifteen years' education of household heads who also have differential access to financial markets. Results show that financially excluded, uneducated households prefer assets with negative returns over human capital investments in their offspring, and hence fall into an intergenerational poverty trap. Their educational investments begin only after an income threshold is reached and the same may be funded through transfers or withdrawal of educational subsidies from college educated households without lowering their human capital investments. Educational subsidies and higher access to educational inputs work best for middle educated households who have higher demand for education. For policy analysis, this study quantifies the contributions of income support, financial inclusion, lower uncertainty and subsidised education in reducing the supply of child labour.

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Journal Articles | 2017

A stochastic model for the throughput analysis of passing dual yard cranes

Suruchika Saini, Debjit Roy, and Rene De Koster

Computers & Operations Research

New container terminal technologies such as passing dual yard cranes per stack promise increase in stacking throughput capacity. However, dual yard cranes can interfere, which reduces the cranes’ throughput capacity. Using crane operational protocols, we develop a stochastic model for two passing dual yard cranes and obtain closed-form expressions for the crane throughput capacity with interference delays. We then develop an approximate model to estimate the expected throughput times for both balanced and unbalanced stack configuration. A detailed discrete-event simulation is built to validate the analytical model. We show that interference effects between the cranes can reduce the crane throughput capacity by an average of 35% and interference delays increase with an increase in the number of bays in the stack. We use the model to develop operational insights.

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Journal Articles | 2017

Determinants of safe and productive truck driving: empirical evidence from long-haul cargo transport.

Jelle de Vries, Rene De Koster, Serge Rijsdijk, and Debjit Roy

Transportation Research Part E-Logistics and Transportation Review,

Using GPS data of 370 long-haul trips in India, survey data of 49 truck drivers, and ERP data, this study examines the role of driver personality characteristics in predicting risky and productive driving. The results show that more conscientious drivers display more risky driving behavior. More extravert drivers are less productive, whereas driver safety consciousness positively relates to productivity. These results can serve as a starting point for further studies into how long-haul transport companies may use individual truck driver characteristics in their training and selection procedures to meet operational safety and productivity objectives.

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Journal Articles | 2017

Optimal stack layout in a sea container terminal with automated lifting vehicles

Akash Gupta, Debjit Roy, Rene de Koster, and Sampanna Parhi

International Journal of Production Research

Container terminal performance is largely determined by its design decisions, which include the number and type of quay cranes, stack cranes, transport vehicles, vehicle travel path and stack layout. We investigate the orientation of the stack layout (parallel or perpendicular to the quayside) on the throughput time performance of the terminals. Previous studies in this area typically use deterministic optimisation, and a few studies use probabilistic travel times and simulation to analyse the effect of stack layout on terminal throughput times. In this research, we capture the stochasticity with an integrated queuing network modelling approach to analyse the performance of container terminals with parallel stack layout using automated lifting vehicles. Using this analytical model, we investigate 1008 parallel stack layout configurations on throughput times and determine the optimal stack layout configuration. We find that, assuming an identical width of the internal transport area, container terminals with parallel stack layout perform better (from 4–12% in terms of container throughput times) than terminals with a perpendicular stack layout.

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Journal Articles | 2017

A Multi-tier linking approach to analyze performance of autonomous vehicle-based storage and retrieval systems

Debjit Roy, Ananth Krishnamurthy, Sunderesh S. Heragu, and Charles Malmborg

Computers & Operations Research

To improve operational flexibility, throughput capacity, and responsiveness in order fulfillment operations, several distribution centers are implementing autonomous vehicle-based storage and retrieval system (AVS/RS) in their high-density storage areas. In such systems, vehicles are self-powered to travel in horizontal directions (x- and y- axes), and use lifts or conveyors for vertical motion (z-axis). In this research, we propose a multi-tier queuing modeling framework for the performance analysis of such vehicle-based warehouse systems. We develop an embedded Markov chain based analysis approach to estimate the first and second moment of inter-departure times from the load-dependent station within a semi-open queuing network. The linking solution approach uses traffic process approximations to analyze the performance of sub-models corresponding to individual tiers (semi-open queues) and the vertical transfer units (open queues). These sub-models are linked to form an integrated queuing network model, which is solved using an iterative algorithm. Performance estimates such as expected transaction cycle times and resource (vehicle and vertical transfer unit) utilization are determined using this algorithm, and can be used to evaluate a variety of design configurations during the conceptualization phase.

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Journal Articles | 2017

Integrated fleet mix and routing decision for hazmat transportation: A developing country perspective.

Anand Kumar, Debjit Roy Vedat Verter, and Dheeraj Sharma

European Journal of Operational Research

In developing countries, truck purchase cost is the dominant criteria for fleet acquisition-related decisions. However, we contend that other cost factors such as loss due to the number of en route truck stoppages based on a truck type and recovery cost associated with a route choice decision, should also be considered for deciding the fleet mix and minimizing the overall costs for long-haul shipments. The resulting non-linear model, with integer variables for the number and type of trucks, and the route choices, is solved via genetic algorithm. Using real data from a bulk liquid hazmat transporter, the trade-offs between the cost of travel, loss due to number of truck stoppages, and the long-term recovery cost associated with the risk of exposure due to a hazmat carrier accident are discussed. The numerical experiments show that when factors related to public safety and truck stoppages are taken into account for transportation, the lowest total cost and optimal route choice do not align with the cheapest truck type option; rather, the optimal solution corresponds to another truck type and route with total costs significantly less than the total costs associated with the cheapest truck type. Our model challenges the current truck purchasing strategy adopted in developing countries using the cheapest truck criteria.

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Journal Articles | 2017

Tests of independence for $2 \times 2$ contingency table with random margins

Yuan Yu, Dhiman Bhadra, and Balgobin Nandram

International Journal of Statistics and Probability

Fisher's exact test is commonly used for testing the hypothesis of independence between the row and column variables in a $r \times c$ contingency table. It is a ``small-sample'' test since it is used when the sample size is not large enough for the Pearsonian chi-square test to be valid. Fisher's exact test conditions on both margins of a $2 \times 2$ table leading to a hypergeometric distribution of the cell counts under independence. Moreover, it is conservative in the sense that its actual significance level falls short of the nominal level. In this paper, we modify Fisher's exact test by lifting the restriction of fixed margins and allow the margins to be random. In doing so, we propose two new tests - a likelihood ratio test in a frequentist framework and a Bayes factor test in a Bayesian framework, both of which are based on a new multinomial distributional framework. We apply the three tests on data from the Worcester Heart Attack study and compare their power functions in assessing gender difference in the therapeutic management of patients with acute myocardial infarction (AMI).

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Journal Articles | 2017

Emergence of distributed coordination in Kolkata Paise Restaurant problem with finite information

Diptesh Ghosh and Anindya S. Chakrabarti

Physica: Statistical Mechanics and its Applications

In this paper, we study a large-scale distributed coordination problem and propose efficient adaptive strategies to solve the problem. The basic problem is to allocate finite number of resources to individual agents in the absence of a central planner such that there is as little congestion as possible and the fraction of unutilized resources is reduced as far as possible. In the absence of a central planner and global information, agents can employ adaptive strategies that uses only a finite knowledge about the competitors. In this paper, we show that a combination of finite information sets and reinforcement learning can increase the utilization fraction of resources substantially.

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Journal Articles | 2017

Global risk and demand for gold by central banks

Balagopal Gopalakrishnan and Sanket Mohapatra

Applied Economics Letters

This paper examines the influence of global risk on the holding of gold by central banks based on annual data for 100 countries during 1990-2015. We use a dynamic panel generalized method of moments (GMM) model to estimate this effect, controlling for a variety of domestic factors. Consistent with portfolio diversification and perception of gold as a safe asset, we find that the gold holdings of central banks increase in response to higher global risk. This effect is larger for high-income countries than for developing countries. Moreover, greater capital account openness is associated with a stronger response of central banks' gold holding to global risk, while a higher ratio of overall reserves to imports is associated with a weaker response. We also find evidence that the sensitivity depends on whether the currency regime followed is fixed or floating, with higher responsiveness in the case of fixed rate regimes. The baseline results are robust to alternate estimation methods, exclusion of crisis years, active and passive management of gold reserves and additional controls. These findings suggest that central banks adjust their gold holdings in response to changes in global risk conditions, with the magnitude of response depending on reserve management capacity and country-specific vulnerabilities.

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Journal Articles | 2017

Ownership structure and internationalization of Indian firms

Chitra Singla, Rejie George, and Rajaram Veliyath

Journal of Business Research

This paper examines the relationship between ownership structure and the firm internationalization, in a longitudinal sample of Indian firms. Drawing from principal-principal (PP) agency theory and the resource-based view (RBV) of the firm, we argue that divergent motivations among the firm's owners affect the firm's inclination to pursue internationalization, while resource heterogeneity among the firm's owners affects the firm's capability to pursue internationalization. Since both motivation and capability are required for a firm to pursue any strategic initiative, we argue that differences in ownership, which influences both the motivation and the capability of firms, impact firm's internationalization strategies in different ways. In addition, through examining two modes of internationalization, i.e., outward foreign direct investment (FDI) and exports from a prominent emerging economy, we uncover an interesting dichotomy. While family and other domestic owners favor exports (and not FDI), foreign owners favor both exports and FDI. Further, we find that family owners have a dominant influence on internationalization and their preferences appear to supersede those of the other owners.

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