scholarly journals Almost Linear Time Algorithms for Some Problems on Dynamic Flow Networks

2021 ◽  
pp. 65-85
Author(s):  
Yuya Higashikawa ◽  
Naoki Katoh ◽  
Junichi Teruyama
Keyword(s):  
Linear Time ◽  
Evacuation Planning ◽  
Dynamic Flow ◽  
Flow Networks ◽  
Flow Network ◽  
Capacity Limits ◽  
Positive Edge ◽  
The Road ◽  
The People ◽  
Linear Time Algorithms

AbstractMotivated by evacuation planning, several problems regarding dynamic flow networks have been studied in recent years. A dynamic flow network consists of an undirected graph with positive edge lengths, positive edge capacities, and positive vertex weights. The road network in an area can be treated as a graph where the edge lengths are the distances along the roads and the vertex weights are the number of people at each site. An edge capacity limits the number of people that can enter the edge per unit time. In a dynamic flow network, when particular points on edges or vertices called sinks are given, all of the people are required to evacuate from the vertices to the sinks as quickly as possible. This chapter gives an overview of two of our recent results on the problem of locating multiple sinks in a dynamic flow path network such that the max/sum of evacuation times for all the people to sinks is minimized, and we focus on techniques that enable the problems to be solved in almost linear time.

scholarly journals Almost Linear Time Algorithms for Minsum k-Sink Problems on Dynamic Flow Path Networks

2021 ◽  
Author(s):  
Yuya Higashikawa ◽  
Naoki Katoh ◽  
Junichi Teruyama ◽  
Koji Watase
Keyword(s):  
Linear Time ◽  
Flow Path ◽  
Dynamic Flow ◽  
Linear Time Algorithms

scholarly journals Efficient Dynamic Flow Algorithms for Evacuation Planning Problems with Partial Lane Reversal

Mathematics ◽  
2019 ◽  
Vol 7 (10) ◽  
pp. 993 ◽  
Author(s):  
Urmila Pyakurel ◽  
Hari Nandan Nath ◽  
Stephan Dempe ◽  
Tanka Nath Dhamala
Keyword(s):  
Road Network ◽  
Polynomial Time Algorithm ◽  
Time Algorithm ◽  
Evacuation Planning ◽  
Dynamic Flow ◽  
The Road ◽  
Flow Problems ◽  
Dynamic Flows ◽  
The Difference ◽  
Planning Problems

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 context of evacuation planning. The partial static contraflow problems, that are foundations to the dynamic flows, are also studied. Moreover, the contraflow model with inflow-dependent transit time on arcs is introduced. A strongly polynomial time algorithm to compute approximate solution of the quickest partial contraflow problem on two terminal networks is presented, which is substantiated by numerical computations considering Kathmandu road network as an evacuation network. Our results show that the quickest time to evacuate a flow of value 100,000 units is reduced by more than 42% using the partial contraflow technique, and the difference is more with the increase in the flow value. Moreover, the technique keeps the record of the portions of the road network not used by the evacuees.

scholarly journals Maximum Entropy Analysis of Flow Networks: Theoretical Foundation and Applications

Entropy ◽  
2019 ◽  
Vol 21 (8) ◽  
pp. 776 ◽  
Author(s):  
Robert K. Niven ◽  
Markus Abel ◽  
Michael Schlegel ◽  
Steven H. Waldrip
Keyword(s):  
Maximum Entropy ◽  
Joint Probability ◽  
Financial Economic ◽  
Flow Networks ◽  
Flow Network ◽  
Physical Constraints ◽  
Generalized Maximum Entropy ◽  
Deterministic Solution ◽  
Network Properties ◽  
The Cost

The concept of a “flow network”—a set of nodes and links which carries one or more flows—unites many different disciplines, including pipe flow, fluid flow, electrical, chemical reaction, ecological, epidemiological, neurological, communications, transportation, financial, economic and human social networks. This Feature Paper presents a generalized maximum entropy framework to infer the state of a flow network, including its flow rates and other properties, in probabilistic form. In this method, the network uncertainty is represented by a joint probability function over its unknowns, subject to all that is known. This gives a relative entropy function which is maximized, subject to the constraints, to determine the most probable or most representative state of the network. The constraints can include “observable” constraints on various parameters, “physical” constraints such as conservation laws and frictional properties, and “graphical” constraints arising from uncertainty in the network structure itself. Since the method is probabilistic, it enables the prediction of network properties when there is insufficient information to obtain a deterministic solution. The derived framework can incorporate nonlinear constraints or nonlinear interdependencies between variables, at the cost of requiring numerical solution. The theoretical foundations of the method are first presented, followed by its application to a variety of flow networks.

scholarly journals A stochastic programming approach for Shelter location and evacuation planning

2018 ◽  
Vol 52 (3) ◽  
pp. 779-805 ◽  
Author(s):  
Vedat Bayram ◽  
Hande Yaman
Keyword(s):  
Stochastic Programming ◽  
Shortest Paths ◽  
Evacuation Planning ◽  
Programming Approach ◽  
Mean Values ◽  
The Road ◽  
Traffic Allocation ◽  
Evacuation Plan ◽  
Allocation Decisions

Shelter location and traffic allocation decisions are critical for an efficient evacuation plan. In this study, we propose a scenario-based two-stage stochastic evacuation planning model that optimally locates shelter sites and that assigns evacuees to nearest shelters and to shortest paths within a tolerance degree to minimize the expected total evacuation time. Our model considers the uncertainty in the evacuation demand and the disruption in the road network and shelter sites. We present a case study for a potential earthquake in Istanbul. We compare the performance of the stochastic programming solutions to solutions based on single scenarios and mean values.

scholarly journals Linear-Time Algorithms for Tree Root Problems

Algorithmica ◽  
2013 ◽  
Vol 71 (2) ◽  
pp. 471-495 ◽  
Author(s):  
Maw-Shang Chang ◽  
Ming-Tat Ko ◽  
Hsueh-I Lu
Keyword(s):  
Linear Time ◽  
Linear Time Algorithms

FAULT TOLERANT ROUTING IN HYPERCUBES AND STAR GRAPHS

1996 ◽  
Vol 06 (01) ◽  
pp. 127-136 ◽  
Author(s):  
QIAN-PING GU ◽  
SHIETUNG PENG
Keyword(s):  
Free Path ◽  
Fault Tolerant ◽  
Linear Time ◽  
Time Efficiency ◽  
Routing Problem ◽  
Star Graphs ◽  
Linear Time Algorithms ◽  
Better Than

In this paper, we give two linear time algorithms for node-to-node fault tolerant routing problem in n-dimensional hypercubes Hn and star graphs Gn. The first algorithm, given at most n−1 arbitrary fault nodes and two non-fault nodes s and t in Hn, finds a fault-free path s→t of length at most [Formula: see text] in O(n) time, where d(s, t) is the distance between s and t. Our second algorithm, given at most n−2 fault nodes and two non-fault nodes s and t in Gn, finds a fault-free path s→t of length at most d(Gn)+3 in O(n) time, where [Formula: see text] is the diameter of Gn. When the time efficiency of finding the routing path is more important than the length of the path, the algorithms in this paper are better than the previous ones.

scholarly journals China's Dilemmas on the Road to Reforms Under Xi Jinping

2015 ◽  
Vol 5 (1) ◽  
pp. 133-149
Author(s):  
Juhan Värk
Keyword(s):  
Central Committee ◽  
Shadow Banking ◽  
Xi Jinping ◽  
Strategic Partner ◽  
Military Reform ◽  
The Road ◽  
National Leader ◽  
The People ◽  
The World ◽  
On The Road

AbstractOn 15 November 2012, at the plenary session of the Central Committee of the Communist Party of China, Xi Jinping was elected the Party' general secretary, whereas he also became the chairman of the influential Central Military Commission. Too eager to wait to be inaugurated as President of the People' Republic of China in March 2013, the new national leader announced that in the following decade he is guided by the main objective of his predecessor Hu Jintao to double the prosperity of the people by the year 2020 and to keep the country' economy stable and growing fast. Unfortunately, it will be difficult for the new leader of China to implement his intentions, since, presumably, the country' new leadership will be from the older generation, hardliners, and, most importantly, politically conservative. But the difficulties lie in carrying out economic reforms because of rampant corruption and shadow banking in the central apparatus and in regions.According to the World Bank' analysis, China has become the world' largest economy. But the large expenditures to military reform and environmental protection are not sufficient for Xi Jinping to accomplish the goal to raise significantly the poor living standards of Chinese people. China has also faced difficulties in complying with the basic principles of its foreign policy, especially after the annexation of Crimea and its incorporation into the Russian Federation by China' strategic partner, Russia. In the past, China has carried out campaigns against “Americanization”, although with no tangible results. Thus, the leaders of today' China are faced with a number of dilemmas.

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