scholarly journals Abstract Earliest Arrival Transshipment with Network Reconfiguration

2018 ◽  
Vol 35 (1-2) ◽  
pp. 1-9
Author(s):  
Ram Chandra Dhungana ◽  
Tanka Nath Dhamala
Keyword(s):  
Network Flow ◽  
Flow Model ◽  
Dynamic Network ◽  
Flow Paths ◽  
Optimal Flow ◽  
Switching Property ◽  
Efficient Approximation Algorithm ◽  
Np Complete ◽  
Efficient Approximation ◽  
Time Point

The abstract flow model is the generalization of network flow model which deals with the flow paths (routes) satisfying the switching property. Contraflow model increases the flow value by reversing the required arc directions from the sources to the sinks. In this paper, we integrate the concepts of abstract flow and contraflow to introduce abstract earliest arrival transshipment contraflow model in multi-terminal abstract network. The abstract contraflow on multi-terminal dynamic network is NP-Complete. We present an efficient approximation algorithm to solve the problem. This approach satisfies the demand of sinks by sending optimal flow at every possible time point and seeks to eliminate the crossing conflicts.

scholarly journals Abstract Contraflow Models and Solution Procedures for Evacuation Planning

2018 ◽  
Vol 10 (4) ◽  
pp. 89
Author(s):  
Ram Chandra Dhungana ◽  
Urmila Pyakurel ◽  
Tanka Nath Dhamala
Keyword(s):  
Efficient Solution ◽  
Flow Model ◽  
Efficient Algorithms ◽  
Evacuation Planning ◽  
Flow Paths ◽  
Evacuation Time ◽  
Solution Approach ◽  
Switching Property ◽  
Risk Areas

The abstract flow model deals with the flow  paths (routes) that satisfy the switching property. Contraflow is a widely accepted solution approach that increases the flow and decreases the evacuation time making the traffic smooth during evacuation by reversing the required road directions from the risk areas to the safe places. In this paper, we integrate the concepts of abstract flow and contraflow, give mathematical formulations of these models and present efficient algorithms for solving the abstract contraflow problems. The efficient solution procedures are presented for  maximum dynamic, lexicographically maximum and earliest arrival abstract contraflow  problems. This approach maximizes the flow value in given time and seeks to eliminate the crossing conflicts.

scholarly journals Abstract Contraflow Models and Solution Procedures for Evacuation Planning

2018 ◽  
Vol 10 (4) ◽  
pp. 88 ◽  
Author(s):  
Ram Chandra Dhungana ◽  
Urmila Pyakurel ◽  
Tanka Nath Dhamala
Keyword(s):  
Efficient Solution ◽  
Flow Model ◽  
Efficient Algorithms ◽  
Evacuation Planning ◽  
Flow Paths ◽  
Evacuation Time ◽  
Solution Approach ◽  
Switching Property ◽  
Risk Areas

The abstract flow model deals with the flow  paths (routes) that satisfy the switching property. Contraflow is a widely accepted solution approach that increases the flow and decreases the evacuation time making the traffic smooth during evacuation by reversing the required road directions from the risk areas to the safe places. In this paper, we integrate the concepts of abstract flow and contraflow, give mathematical formulations of these models and present efficient algorithms for solving the abstract contraflow problems. The efficient solution procedures are presented for  maximum dynamic, lexicographically maximum and earliest arrival abstract contraflow  problems. This approach maximizes the flow value in given time and seeks to eliminate the crossing conflicts.

scholarly journals A survey on network contraflow evacuation planningproblems

2015 ◽  
Vol 3 ◽  
pp. 44-53
Author(s):  
Phanindra Prasad Bhandari ◽  
Shree Ram Khadka
Keyword(s):  
Network Flow ◽  
Dynamic Network ◽  
Route Planning ◽  
Evacuation Planning ◽  
Solution Strategies ◽  
General Network ◽  
Evacuation Route Planning ◽  
Network Flow Optimization ◽  
Evacuation Route ◽  
Potential Remedy

Evacuation planning is becoming crucial due to an increasing number of natural and human-created disasters over last few decades. One of the efficient ways to model the evacuation situation is a network flow optimization model. This model captures most of the necessities of the evacuation planning. Moreover, dynamic network contraflow modeling is considered a potential remedy to decrease the congestion due to its direction reversal property and it addresses the challenges of evacuation route planning. However, there do not exist satisfactory analytical results to this model for general network. In this paper, it is tried to provide an annotated overview on dynamic network contraflow problems related to evacuation planning and to incorporate models and solution strategies to them developed in this field to date.

scholarly journals Optimum Flows in Directed Bipartite Dynamic Network. The Static Approach

2020 ◽  
Vol 14 ◽  
Keyword(s):  
Combinatorial Optimization ◽  
Network Flow ◽  
Dynamic Network ◽  
Time Varying ◽  
Flow Models ◽  
Dynamic Network Flow ◽  
Static Approach ◽  
Network Flow Models ◽  
Discrete Values ◽  
Time Expanded Network

The theory of flows is one of the most important parts of Combinatorial Optimization and it has various applications. In this paper we study optimum (maximum or minimum) flows in directed bipartite dynamic network and is an extension of article [9]. In practical situations, it is easy to see many time-varying optimum problems. In these instances, to account properly for the evolution of the underlying system overtime, we need to use dynamic network flow models. When the time is considered as a variable discrete values, these problems can be solved by constructing an equivalent, static time expanded network. This is a static approach.

Operation of a CCHP System Using an Optimal Energy Dispatch Algorithm

2008 ◽  
Author(s):  
Heejin Cho ◽  
Sandra D. Eksioglu ◽  
Rogelio Luck ◽  
Louay M. Chamra
Keyword(s):  
Energy Efficiency ◽  
Energy Cost ◽  
Network Flow ◽  
Flow Model ◽  
Energy Requirement ◽  
Optimal Operation ◽  
Operational Conditions ◽  
Optimal Energy ◽  
Network Flow Model ◽  
The Cost

The Combined Cooling, Heating, and Power (CCHP) systems have been widely recognized as a key alternative for thermal and electric energy generation because of the outstanding energy efficiency, reduced environmental emissions, and relative independence from centralized power grids. Nevertheless, the total energy cost of CCHP systems can be highly dependent on the operation of individual components and load balancing. The latter refers to the process of fulfilling the thermal and electrical demand by partitioning or “balancing” the energy requirement between the available sources of energy supply. The energy cost can be optimized through an energy dispatch algorithm which provides operational/control signals for the optimal operation of the equipment. The algorithm provides optimal solutions on decisions regarding generating power locally or buying power from the grid. This paper presents an initial study on developing an optimal energy dispatch algorithm that minimizes the cost of energy (i.e., cost of electricity from the grid and cost of natural gas into the engine and boiler) based on energy efficiency constrains for each component. A deterministic network flow model of a typical CCHP system is developed as part of the algorithm. The advantage of using a network flow model is that the power flows and efficiency constraints throughout the CCHP components can be readily visualized to facilitate the interpretation of the results. A linear programming formulation of the network flow model is presented. In the algorithm, the inputs include the cost of the electricity and fuel and the constraints include the cooling, heating, and electric load demands and the efficiencies of the CCHP components. This algorithm has been used in simulations of several case studies on the operation of an existing micro-CHP system. Several scenarios with different operational conditions are presented in the paper to demonstrate the economical advantages resulting from optimal operation.

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