A Brief Survey of Just-In-Time Sequencing for Mixed-Model Systems *

Abstract The concept of penalizing jobs both for being tardy and for being early has proven one of most important and fertile research topics in Operations Research. In this survey, we consider just-in-time mixed-model, multi-level supply chains. Obtaining an optimal sequence in a multi-level chain is a challenging nonlinear integer programming problem. Problems for two or more levels are strongly NP-hard. The problem of minimizing deviations between actual and desired production for single-level can be solved efficiently. Also the multi-level problems with pegging assumption are solvable by reducing them to the single-level. Cyclic schedules are optimal for single-level problem. We present various ways of dealing with these problems such as the elegant concept of balanced words and different optimization techniques. We provide a short review of different mathematical models, discuss their complexity and compare them. The research results obtained in past several years are presented along with open problems and possible extensions

On Evacuation Planning Optimization Problems from Transit-based Perspective

Increasing number of complex traffic networks and disasters today has brought difficulty in managing the rush hours traffic as well as the large events in urban areas. The optimal use of the vehicles and their assignments to the appropriate shelters from the disastrous zones are highly complicated in emergency situations. The maximum efficiency and effectiveness of the evacuation planning can be achieved by the appropriate and significant assignment of the transit dependent vehicles during pre and post-disaster operations. This paper presents a comprehensive overview of the evacuation planning optimization techniques developed over the years, emphasizing the importance of their formulation and the solution strategies on disaster management from the transit-based perspective. Each technique is briefly described and presented lucidly with some of its known applications, significances, and solution strategies expecting that it should be able to guide much more interest into this important and growing area of research

Environmental Attitude of Young Nepalese and its Comparison with the Attitude of Environmentally Developed Costa Ricans

Cognition surveys on environmental attitudes were carried out in Costa Rica and Nepal for university students, and they were compared to each other from the viewpoint of cultural background. The surveys were made in classrooms using questionnaires consisted of about 60 questions. Summed results were shown for both nations on the view of values and knowledge regarding environmental problems, attitudes to the environmental deterioration, ethical responsibility to the problems, probable outcome of environmental condition in future, and so on. From the comparison between two nations, Nepalese were found to hold moderate attitudes to almost all environmental problems without expressing any clear opinions, whereas Costa Ricans have distinct and unified opinions common to all members indicating strong internalization of environmental thought

Continuous Time Dynamic Contraflow Models and Algorithms

The research on evacuation planning problem is promoted by the very challenging emergency issues due to large scale natural or man-created disasters. It is the process of shifting the maximum number of evacuees from the disastrous areas to the safe destinations as quickly and efficiently as possible. Contraflow is a widely accepted model for good solution of evacuation planning problem. It increases the outbound road capacity by reversing the direction of roads towards the safe destination. The continuous dynamic contraflow problem sends the maximum number of flow as a flow rate from the source to the sink in every moment of time unit. We propose the mathematical model for the continuous dynamic contraflow problem. We present efficient algorithms to solve the maximum continuous dynamic contraflow and quickest continuous contraflow problems on single source single sink arbitrary networks and continuous earliest arrival contraflow problem on single source single sink series-parallel networks with undefined supply and demand. We also introduce an approximation solution for continuous earliest arrival contraflow problem on two-terminal arbitrary networks

Network Reconfiguration with Orientation-Dependent Transit Times

Motivated by applications in evacuation planning, we consider a problem of optimizing flow with arc reversals in which the transit time depends on the orientation of the arc. In the considered problems, the transit time on an arc may change when it is reversed, contrary to the problems considered in the existing literature. Extending the existing idea of auxiliary network construction to allow asymmetric transit time on arcs, we present strongly polynomial time algorithms for solving single-source-single-sink maximum dynamic contraflow problem and quickest contraflow problem. The results are substantiated by a computational experiment in a Kathmandu road network. An algorithm to solve the corresponding earliest arrival contraflow problem with a pseudo-polynomial-time complexity is also presented. The partial contraflow approach for the corresponding problems has also been discussed

A Bicriteria Model for Saving a Path Minimizing the Time Horizon of a Dynamic Contraflow

The quickest contraflow in a single-source-single-sink network is a dynamic flow that minimizes the time horizon of a given flow value at the source to be sent to the sink allowing arc reversals. Because of the arc reversals, for a sufficiently large value of the flow, the residual capacity of all or most of the paths towards the source, from a given node, may be zero or reduced significantly. In some cases, e.g., for the movement of facilities to support an evacuation in an emergency, it is imperative to save a path from a given node towards the source. We formulate such a problem as a bicriteria optimization problem, in which one objective minimizes the length of the path to be saved from a specific node towards the source, and the other minimizes the quickest time of the flow from the source towards the sink, allowing arc reversals. We propose an algorithm based on the epsilon-constraint approach to find non-dominated solutions