Urmila Pyakurel

Urmila Pyakurel
Tribhuvan University · Central Department of Mathematics

PhD in Mathematics, Humboldt Post doc from Germany

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67
Publications
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667
Citations

Publications

Publications (67)
Article
Full-text available
A maximum dynamic multicommodity flow problem concerns with the transportation of several different commodities through the specific source-sink path of an underlying capacity network with the objective of maximizing the sum of commodity flows within a given time horizon. Motivated by the uneven road condition of transportation network topology, we...
Article
Full-text available
Multi-commodity flow problems concerned with the transshipment of more than one commodity from respective sources to the corresponding sinks without violating the capacity constraints on the arcs. If the objective of the problem is to send the maximum amount of flow within a given time horizon, then it becomes the maximum flow problem. In multi-com...
Article
Full-text available
Contraflow is one of the best and widely accepted techniques in evacuation planning problems, where the reversal of arcs is made to increase the amount and decrease the time of flow transmission. At the time of evacuation, if the flow value leaving the source node exceeds the bottleneck capacity of the network, then the storage of excess flow at co...
Article
Full-text available
e multicommodity flow problem deals with the transshipment of more than one commodity from respective sources to corresponding sinks without violating the capacity constraints. Due to the capacity constraints, flows out from the sources may not reach their sinks, and so, the storage of excess flows at intermediate nodes plays an important role in t...
Article
Full-text available
The aim of the maximum network flow problem is to push as much flow as possible between two special vertices, the source and the sink satisfying the capacity constraints. For the solution of the maximum flow problem, there exists a number of algorithms. The existing algorithms can be divided into two families. First, augmenting path algorithms that...
Article
Full-text available
The contraflow technique has been extensively used to evacuate people in disasters situation. By flipping the orientation of necessary road segments, the flow value increases, and the evacuation time decreases significantly. Contraflow problems with asymmetric capacity and symmetric transit time on arcs have polynomial-time solutions. But in uneven...
Article
Full-text available
In a transportation network such as an evacuation planning, if we transmit the people or goods from the dangerous zones to the safety places, there are chances of loss due to death, leakage or damage. To address this issue, the generalized network flow model incorporates a gain factor on each arc, which makes it different from the classical network...
Article
Full-text available
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 i...
Chapter
The evacuation planning problem models the process of shifting residents from emergency areas (sources) to safe places (sinks) as quickly and efficiently as possible. Most of the flow over time models used in the evacuation planning are based on the flow conservation constraints, i.e., the inflow should be equal to the outflow on each node except a...
Article
Full-text available
Multi-commodity flow problem appears when several distinct commodities are shipped from supply nodes to the demand nodes through a network without violating the capacity constraints. The quickest multi-commodity flow problem deals with the minimization of time satisfying given demand. Ingeneral, the quickest multi-commodity flow problems are comput...
Conference Paper
Full-text available
Prioritization is the process of deciding the relative importance or urgency of things or objects. It helps to focus on the objectives and goals in an efficient way. Prioritized flow problems are applicable for large scale disaster management problems. In this work, we introduce the priority based multi-commodity flow problem and develop a mathemat...
Article
Full-text available
Various network flow models, such as a flow maximization, a time minimization, a cost minimization, or a combination of them, have already been investigated. In most of the cases, they are considered subject to the flow conservation constraints. Here, we investigate the network flow models with intermediate storage, i.e., the inflow may be greater...
Article
Full-text available
The multicommodity flow problem arises when several different commodities are transshipped from specific supply nodes to the corresponding demand nodes through the arcs of an underlying capacity network. The maximum flow over time problem concerns to maximize the sum of commodity flows in a given time horizon. It becomes the earliest arrival flow p...
Article
Full-text available
Routing of more than one different commodity from specific origin nodes to the corresponding destination nodes through the arcs of an underlying network respecting the capacity constraints is one of the main problems in operational research. Among them, the quickest multi-commodity flow problem concerns with minimization of time taken to complete t...
Article
Full-text available
The model of lane reversals in the network flow theory is broadly accepted worldwide to increase the flow value by increasing the outbound arc capacity from the sources towards the sinks with lane reversals capability. There are different approaches, e.g., simulation, heuristic and analytical that are dealing this issue extensively. Specially, this...
Article
Dynamic network flow problems have wide applications in evacuation planning. From a given subset of arcs in a directed network, choosing the suitable arcs for facility location with a given objective is very important in the optimization of flow in emergency cases. Because of the decrease in capacity of an arc by placing a facility in it, there may...
Article
Full-text available
Traffic route guidance, destination optimization, and optimal route choice are some of the approaches to accelerate the evacuation planning process. Their effectiveness depends upon the evacuee arrival patterns at the pickup locations and their appropriate assignment to transit-vehicles in the network. Here, the integrated evacuation network topolo...
Article
Full-text available
In this paper, we investigate the minimum cost flow problem in two terminal series parallel network. We present modified minimum cost flow algorithm that computes the maximum dynamic and the earliest arrival flows in strongly polynomial time and also preserves all unused arc capacities. We also present strongly polynomial time minimum cost partial...
Article
Full-text available
The challenges in evacuation planning have been vital because of rapid disasters and limited road capacity. Contraflow strategy is very effective and widely accepted approach for the optimal use of available road network in evacuation management that increases the outward road capacities from the disastrous areas towards the safe destinations. Mode...
Article
Full-text available
Contraflow technique has gained a considerable focus in evacuation planning research over the past several years. In this work, we design efficient algorithms to solve the maximum, lex-maximum, earliest arrival, and quickest dynamic flow problems having constant attributes and their generalizations with partial contraflow reconfiguration in the con...
Article
Full-text available
Despite of implicit flow conservation on every arc of traditional network flow model, the generalized network flow model assumes the proportional and symmetric loss factor on each arc. This paper considers two terminal lossy networks specifying the portion of flow entering an arc at its tail node that reaches to its head node. We studied the genera...
Article
Full-text available
People have unpleasant experience of driving through congested road network of urban areas, where transit time is not constant but flow-dependent. Network flow over time with flow-dependent transit times is more realistic than flow over time with fixed transit time on arcs which is an active area of research from last two decades. In traffic assign...
Article
Mathematical modeling of evacuation planning problems focus on sending evacuees from danger areas (sources) to safe places (sinks). Contraflow strategy, i.e. reversing the direction of usual traffic flow towards the sinks, is an effective strategy in such cases, to increase the outbound capacity of the road segments so that there is an increase in...
Article
Full-text available
Network flow over time is an important area for the researcher relating to the traffic assignment problem. Transmission times of the vehicles directly depend on the number of vehicles entering the road. Flow over time with fixed transit times can be solved by using classical (static) flow algorithms in a corresponding time expanded network which is...
Chapter
In the context of growing number of natural or man-made disasters, operations research methodologies are imperative for optimal and equitable use of resources available for saving life and relief supports. On the PPRR risk management model, preparedness or planning is most important in unavoidable disasters, as most of the damages are due to lack o...
Article
Full-text available
In the last decades, research on emergency traffic management has received high attention from the operations research community and many pioneer researchers have established it as one of the most fertile research areas. We consider the computationally hard flows over time problems from wider perspective including flow/time dependent attributes (dy...
Conference Paper
Full-text available
Contraflow evacuation planning is the process of shifting maximum number of evacuees from the dangerous areas to the safer places with arc reversals capability as quickly and efficiently as possible. We introduce the partial contraflow approach with the inflow dependent and load dependent transit times. In both cases, we present efficient algorithm...
Conference Paper
Full-text available
Contraflow evacuation planning increases the outward road capacities from the disastrous areas with lane reversals towards safer places. It is highly applicable for shifting maximum number of evacuees from disastrous areas to the safer places as quickly and efficiently as possible. We introduce the partial contraflow approach to solve the dynamic f...
Conference Paper
Full-text available
The traditional network flow models that implicitly assume the flow conservation on every arcs have not been addressing the practical applications of physical transformation. Departed flow may not reach the destination due to leaks, evaporation, breeding, theft rates and so on. For this we consider the positive multipliers on the arcs that specify...
Conference Paper
Full-text available
Because of rapidly increasing number of natural and human-created disasters worldwide, researchers in the field of emergency management are highly motivated towards emergency planning and the field is being quite emerging. The operations research modeling has been the most effective approach in addressing these issues, at least partially. Although...
Conference Paper
Full-text available
When facilities are to be placed on the arcs of an evacuation network, it is imperative to find the appropriate arcs to place the facilities to minimize the effect of the reduction in arc capacities in the efficiency of evacuation. In this work, we introduce quickest FlowLoc problem to identify the optimal arcs to place emergency facilities so that...
Conference Paper
Full-text available
Dissimilar to conventional static flow problem, this research studies network flows in relation to time. Any one caught up in a traffic jam would know that the existing premise of flow overtime with constant transit times on the arcs cannot access the real life road traffic. Challenges with flows overtime and constant transit times can be rephrased...
Conference Paper
Full-text available
Network flow over time is an important area for the researcher relating to the traffic assignment problem. Transmission time of the vehicles directly depends on the number of vehicles entering the road. Flow over time with fixed transit times can be solved by using classical (static) flow algorithms in a corresponding time expanded network which is...
Article
Full-text available
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 c...
Article
Impacts of the threats mainly caused by increasing number of natural and men-created disasters all over the world have been extremely costly. Many nations are much affected by such, including Nepal suffered by frequent devastating earthquake kills and damages. The OR models and solution techniques, for saving and serving the life and property, have...
Article
Full-text available
Because of increasing number of natural and human created disasters worldwide, a research on challenging issues of emergency management are being quite emerging for the betterment of today's complex real-life. The diversified operational research models and their solutions techniques together with their simulation schemes are yet not evident in rea...
Article
The optimization models and algorithms with their implementations on flow over time problems have been emerging field of research because of largely increasing human-created and natural disasters worldwide. For an optimal use of transportation network to shift affected people and normalize the disastrous situation as quickly and efficiently as poss...
Poster
Full-text available
Evacuation Planning problem is the process of shifting maximum number of evacuees from the disastrous areas to the safer places as quickly and efficiently as possible. By reconfiguration of given transformation network, different mathematical models are developed to deal the problem with optimal use of available resources. We focus on Partial lane...
Article
Full-text available
The research in evacuation planning has been very much motivated due to the rapidly increased number of disasters world wide. It supports to remove the evacuees from dangerous areas to safe areas. Contraflow reconfiguration during evacuation make traffic smooth by reversing the required road directions from dangerous areas to safe areas that improv...
Article
Full-text available
Contraflow reconfiguration allows the arc reversals that increases the outbound road capacities. During emergency, the maximum number of evacuees should be moved from the disastrous areas to the safe destinations. Contraflow technique is one of the widely accepted mathematical models for the efficient solution of evacuation planning problem. In lit...
Article
Full-text available
A productive research in the emerging field of disaster management plays a quite important role in relaxing this disastrous advanced society. The planning problem of saving affected areas and normalizing the situation after any kind of disasters is very challenging. For the optimal use of available road network, the contraflow technique increases t...
Article
Full-text available
The research in evacuation planning has been very much motivated due to the rapidly increased number of disasters world-wide. It is the process of shifting maximum number of evacuees from the disastrous areas to the safe destinations as quickly and efficiently as possible. The contraflow model allows the arc reversals that increase the outbound roa...
Conference Paper
Full-text available
Increasing disasters worldwide have drawn the attention of researchers to the emerging field of disaster management. We consider the key models on transportation and planning networks for maximizing the flow and minimizing the cost within the limited time horizon in emergencies. Although there are varieties of models and solution techniques in evac...
Article
Contraflow technique is the widely accepted model on network optimization. It allows arc reversal that increases the arc capacities. The earliest arrival transshipment contraflow is an important model that transship the given flow value by sending the maximum amount at each time point from the beginning within given time period by reversing the dir...
Conference Paper
Contraflow reconfiguration allows the arc reversal that increases the outbound road capacities. During emergency, the maximum number of evacuees should be moved from the disastrous areas to safe destinations. Contraflow technique is one of the widely accepted mathematical models for the efficient solution of evacuation planning problem. From the an...
Article
Full-text available
Transportation network models within the framework of operations research have been established as one of the emerging field of research frontiers in today's very disastrous life and dense traffic system. The discrete as well as continuous flow over time models have been widely considered by social, engineering and applied scientists with wide vari...
Thesis
Full-text available
The research in evacuation planning has been very much motivated due to the rapidly increased number of disasters world-wide. It is the process of shifting maximum number of evacuees from the disastrous areas to the safe destinations as quickly and efficiently as possible. Various mathematical models for flow maximization and time minimization have...
Poster
Full-text available
A solution to the evacuation planning problem shifts the maximum number of evacuees from the disastrous areas (sources) to the safe destinations (sinks) as quickly and efficiently as possible. Contraflow strategy is one of the widely accepted mathematical model for the solution that increases the outbound road capacities by reversing the direction...
Article
Full-text available
Due to the increasing number of natural or man-made disasters, the application of operations research methods in evacuation planning has seen a rising interest in the research community. From the beginning, evacuation planning has been highly focused on car-based evacuation. Recently, also the evacuation of transit depended evacuees with the help o...
Article
Full-text available
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 s...
Article
Full-text available
After different disasters the evacuation planning support to remove the residence from accidental areas to safe destinations. Contraflow solutions minimize the congestion and make the traffic smooth during evacuation by reversing the required road directions from risk areas to safe places. Mathematical models and solution approaches appear for the...
Article
Full-text available
Efficient evacuation transportation is important for the evacuation planning since one needs to evacuate as many evacuees as possible within the limited time. Contraflow problem, which increases the outbound capacity of the transportation network by reversing the direction, has been important for efficient evacuation. Various aspects of the contraf...
Technical Report
Full-text available
Due to the increasing number of natural or man-made disasters, the application of operations research methods in evacuation planning has seen a rising interest in the research community. From the beginning, evacuation planning has been highly focused on car-based evacuation. Recently, also the evacuation of transit depended evacuees with the help o...
Article
Full-text available
The transportation network problem was modeled as a non-linear problem in the continuous time that makes complication during evacuation planning. Ib solve the evacuation problem approximately as quickly as possible we adopt the model of simple graph in discrete time setting. The earliest arrival flow (EAF) and the contraflow problems that have been...
Article
Full-text available
Generalized maximum dynamic flow, earliest arrival flow and contraflow problems have been extensively discussed as core problems in the research of evacuation planning. In this work, we formulate and justify the solution procedure of two problems. First, we present the generalized maximum dynamic contraflow problem where a maximum amount of evacuee...
Article
Full-text available
Both the earliest arrival flow and the contraflow problems have been highly focused in the research of evacuation planning. We formulated the earliest arrival contraflow problem, where as many evacuees as possible should be sent from dangerous places to safe destinations in every time period by reversing the direction of roads at time zero. A stron...
Presentation
Full-text available
This presentation discusses the possibility of intermediate storage to reduce the evacuation time.

Questions

Questions (6)
Question
You may suggest some literature also. Thank you very much.
Question
I would like to know the current data of following region
1. Central Asia
2. Latin America and the Caribbean
3. Central and Eastern Europe
4. North America and Western
5. Sub-saharan Africa
6. East Asia and the Pacific
7. South and West Asia
Question
Can you suggest some recent, free and good simulation software used for emergency planning?
Question
Can you suggest best solver for the mixed-integer nonlinear programming?
Question
Please share the name  of new software if you are using.

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Projects

Projects (5)
Project
To solve the problem of society and industry by using graph theory.
Project
1. To find optimal transportation planning during evacuation process 2. To plan the optimal location of facilities for evacuation 3. To apply bi-level programming approach to model evacuation planning
Project
The aim is to complete the post-doc research as an Alexander von Humboldt Research Fellow at TU Bergakademie Freiberg, Germany from 2017 to 2019. The main goal of this research is to strengthen the mathematical models and methods for emergency planning. It is our believed that the the obtained knowledge and outcomes from this research would be very helpful to generate the efficient evacuation planning for the rescue process after the natural or man created disasters. It will also be applicable to control the traffic jam during rush hour traffic. As Nepal is a globally hot spot for natural disasters and the traffic mitigation is increasing in major cities, the results from this research will be very applicable in Nepal.