Articles written in Sadhana

    • A mathematical model and solution methods for rail freight transportation planning in an Indian food grain supply chain


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      This paper addresses the rail transportation of food grains undertaken by Food Corporation of India (FCI) to meet the requirements of the food security programme called Public Distribution System (PDS). The research focuses on improving the allocation of railway rakes transporting food grains to a set of storage warehouses. A penalty factor based approach is adopted to represent the considerations in transportation planning and three penalty factors such as rake penalty factor, weekly penalty factor and capacity utilization penalty factor are introduced for the purpose. The single source - multiple destination problem is formulated and solved using exact method to minimize the sum of these three penalty factor values, termed total penalty. Further, a heuristic named optimum rake allocation algorithm is developed and tested using a set of 35 probleminstances. The proposed heuristic is found to be highly efficient in terms of solution quality and computation time. A case study of FCI Kerala Region is also carried out to validate the formulated model and the proposed heuristic. The work provides valuable insights into the practical issues encountered in rail freight transportationplanning and proposes an effective solution methodology to address them.

    • Dynamic tail re-assignment model for optimal line-of-flight breakages


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      The literature in aircraft routing focuses on cyclic rotation with the planned maintenance being assigned to the aircraft at the end of every rotation. The rotations are a set of flights provided with sufficient Maintenance Opportunity (MO) such that the planned maintenance could be carried out for the aircraft. In thisresearch, a novel mathematical model has been introduced to the operational aircraft route assignment which considers both planned and ad hoc maintenances of the aircraft. A line-of-flight is defined as the set of geographic and time feasible flights being assigned to the hypothetical aircraft without any actual operationalconstraints. The model is formulated for the scenario where commercial planning department independently makes the line-of-flights and the maintenances have to be incorporated in those line-of-flights with minimal perturbations. In addition to the exact solution, the problem has also been solved using two heuristic solutionapproaches for the tailored module which is called the Tail Re-assignment, a problem dealt with by many airlines. The Tail Re-assignment problem can be considered as an optimization as well as feasibility problem. The objective of this research is to provide a quick solution that is feasible and near-optimal which can help in the managerial decisions in the tactical horizon. The model is tested with eight schedules with flights varying from 45 to 314, and additionally with multiple maintenance hubs and planning horizon of 20 days. The solution has all the hard constraints satisfied with the total number of onward flight rule breakages difference being minimal. The computation result shows that heuristic solutions solve the schedule for a medium-sized airline in quick time with less than 2% deviation from the exact solution.

    • Workplace-based assessment and intervention design for waste sorting tasks in a developing country


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      Waste sorting is mainly done manually in developing countries and, the manual sorting of items may result in musculoskeletal disorders among the workers. The present work aims to assess sorting tasks in squatting posture performed by workers in a waste sorting facility in India’s southern part. The study also compares the current work environment with a sorting table proposed as an ergonomic intervention for waste sorting tasks. The study also validates the assessment methodology of employing 5th, 50th, and 95th percentile height subjects to simulate postures and interfacing with 5th, 50th, and 95th percentile digital human models. The critical postures of the workers involved in the sorting task at the sorting facility (pre-intervention and postintervention) were simulated with subjects of 5th (n=2), 50th (n=6), and 95th (n=2) percentile height. Theposture captured using Microsoft Kinect was interfaced to Siemens Jack software for posture analysis and biomechanical evaluation. The assessment revealed that the majority of the biomechanical risks resulted fromthe poorly designed workstation. The proposed intervention improved the posture of the workers and reduced biomechanical risks. Compared to the pre-intervention scenario, the proposed intervention reduced the compressiveforces at L4/L5 by 44%, shoulder flexion moment by 36%, and shoulder abduction moment by 31%. The proposed intervention suits industrial applications in developing countries where sorting/assembly tasks are involved. The assessment methodology of simulation of postures by the percentile height subjects, motion capture of postures using Microsoft Kinect, posture analysis and biomechanical evaluation in digital human modelling is cost-effective.

    • Impact of musculoskeletal disorders on various agricultural operations: a systematic review


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      Musculoskeletal disorders (MSDs) are common among agricultural workers, especially in developing countries like India, irrespective of crops and the various operations, which ergonomic interventions can minimize. Research on ergonomic interventions and post-intervention studies in agriculture is limited. Sixty-five papers were identified for the review. This systematic review identifies the effects of MSDs in various crops, which will provide a direction for future researchers and practitioners to contribute more to agricultural ergonomics.In addition, this study categorizes the research in terms of (i) the body parts affected due to MSDs, (ii) the continents where the study has been done, (iii) the farming operations which have been investigated, (iv) various MSDs evaluation methods used in agricultural fields. The review reveals that the prevalence of MSDs in various body parts are lower back (74%) followed by shoulder (63%), wrist/hand (62%), neck (57%), upper back (45%), knee/leg (38%), elbow (29%), angle/feet (26%) hip/thighs (22%), and fingers (8%). Further, most of the studies concentrate on harvesting operations (48%), and there exists immense scope for similar studies in preharvesting and post-harvesting operations. Ergonomic intervention and post-intervention studies among the agricultural workers are limited even in the developed countries. The review will help the researchers to identify the scope of ergonomic interventions among the various crops in different continents. In essence, this review pinpoints the various intervention gaps in different operations associated with farming in developing countries.

    • Does cognitive aspects of information and material presentation matter in worker allocation in an assembly line? A case study of a recycling unit in India


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      In most manufacturing units, the contribution of human labor remains a vital element that affects overall performance and output. The research explicated in this paper is conducted in a pen recycling unit in the southern part of India which is an initiative by a non-profit organization to reduce plastic waste and highlight the need for recycling. The objectives of the study are two-fold. Firstly, to investigate the influence of cognitive aspects namely information and material presentation on worker performance in an assembly line and secondlyto propose an economical worker allocation approach based on the findings of the first study considering the pen recycling unit. An experimental study was conducted with fifteen workers and was given eight different scenarioswith the combinations of presenting material and information with six pen varieties for assembly. The performance of workers is identified and appropriate allocations are made to suitable workstations. Further, a subjective measurement using NASA-TLX is also done to determine the mental workload of workers. The results indicate that individual worker performance varies significantly, much more than is assumed. This variation is due to the difference in cognitive capabilities among workers when they are introduced to differentproduct variants and work environments. It is expected that the proposed economical allocation method will be beneficial for similar micro, small and medium enterprises that contribute in achieving sustainability goals.

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