scholarly journals Application of Graph-Theory Based Algorithm for Identifying Convective Complex Systems over Greater Jakarta basins

2017 ◽  
Vol 58 ◽  
pp. 012002 ◽  
Author(s):  
D E Nuryanto ◽  
E Aldrian ◽  
H Pawitan ◽  
R Hidayat
Keyword(s):  
Graph Theory ◽  
Complex Systems

scholarly journals Determination of Kinetic Properties in Unimolecular Dissociation of Complex Systems from Graph-Theory Based Analysis of an Ensemble of Reactive Trajectories.

2021 ◽  
Author(s):  
Ariel F. Perez-Mellor ◽  
Riccardo Spezia
Keyword(s):  
Graph Theory ◽  
Complex Systems ◽  
Kinetic Properties ◽  
Unimolecular Dissociation ◽  
Theoretical Mass ◽  
Reactive Trajectories ◽  
Direct Counting ◽  
Dynamics Simulations ◽  
State Kinetic

<div>We describe and apply a general approach based on graph-theory to obtain kinetic and structural properties from direct dynamics simulations. In particular, we focus on the unimolecular fragmentation of complex systems in which, prior to dissociation, different events can take place, and notably isomerizations and formation of ion-molecule complex.</div><div>3-state and 4-state kinetic models are thus obtained and rate constants for global or specific pathways are obtained from direct counting and flux calculation, both being in agreement.<br />Finally, we show how a theoretical mass spectrum can also be obtained automatically.<br /></div>

scholarly journals Commentary: A network science summer course for high-school students

2020 ◽  
Vol 8 (4) ◽  
pp. 596-608
Author(s):  
Florian Klimm ◽  
Benjamin F. Maier
Keyword(s):  
High School ◽  
High School Students ◽  
Graph Theory ◽  
Complex Systems ◽  
Dynamic Systems ◽  
Network Science ◽  
School Students ◽  
Course Material ◽  
University Level

AbstractWe discuss a two-week summer course on “Network Science” and “Complex Systems” that we taught for 15 German high-school pupils of ages 16–18. In this course, we covered topics in graph theory, applied network science, programming, and dynamic systems alike. We find that “Network Science” is a well-suited course for introducing students to university-level mathematics. We reflect on difficulties regarding programming exercises and the discussion of more advanced topics in dynamic systems. We make the course material available and encourage fellow network scientists to organize similar outreach events.

scholarly journals Natural hazard risk of complex systems – the whole is more than the sum of its parts: I. A holistic modelling approach based on Graph Theory

2018 ◽  
Author(s):  
Marcello Arosio ◽  
Mario L. V. Martina ◽  
Rui Figueiredo
Keyword(s):  
Graph Theory ◽  
Complex Systems ◽  
Natural Hazards ◽  
Paradigm Shift ◽  
Holistic Approach ◽  
System Structure ◽  
Graph Metrics ◽  
Collective Risk ◽  
Cascade Effects ◽  
Reductionist Approach

Abstract. Assessing the risk of complex systems to natural hazards is an important and challenging problem. In today’s intricate socio-technological world, characterized by strong urbanization and technological trends, the connections, interdependencies and interactions between exposed elements are crucial. These complex relations call for a paradigm shift in collective risk assessments, from a reductionist approach to a holistic one. Most commonly, the risk of a system is estimated through a reductionist approach, based on the sum of the risk of its elements individually. In contrast, a holistic approach considers the whole system as a unique entity of interconnected elements, where those connections are taken into account in order to more thoroughly assess risk. To support this paradigm shift, this paper proposes a new holistic approach to assess the risk in complex systems based on Graph Theory. The paper is organized in two parts: part I describes the proposed approach, and part II presents an application to a pilot study in Mexico City. In part I, we demonstrate that by representing a complex system such as an urban settlement by means of a network (i.e. a graph), it is possible to take advantage of the techniques made available by the branch of mathematics called Graph Theory to analyse its properties. Moreover, it is possible to establish analogies between certain graph metrics (e.g. authority, degree, hub values) and risk variables (exposure, vulnerability and resilience). Leveraging these analogies, one can not only obtain a deeper knowledge of the system (structure, weaknesses, etc.), but also understand its risk mechanisms (how the impacts of a single or multiple natural hazards are propagated, where they are exacerbated), and therefore assess the disaster risk of the system as a whole, including second-order impacts and cascade effects.

scholarly journals Identifying Failure Scenarios in Complex Systems by Perturbing Markov Chain Models

2011 ◽  
Author(s):  
Christopher Dabrowski ◽  
Fern Hunt
Keyword(s):  
Graph Theory ◽  
Complex Systems ◽  
Real World ◽  
Nuclear Power ◽  
Power Plants ◽  
Search Space ◽  
Performance Degradation ◽  
Normal Operation ◽  
State Transitions ◽  
Distributed Computing Systems

In recent years, substantial research has been devoted to monitoring and predicting performance degradations in real-world complex systems within large entities such as nuclear power plants, electrical grids, and distributed computing systems. Special challenges are posed by the fact that such systems operate in uncertain environments, are highly dynamic, and exhibit emergent behaviors that can lead to catastrophic failure. Discrete Time Markov chains (DTMCs) provide important tools for analysis of such systems, because they represent dynamic behavior succinctly, provide a means to measure uncertainty, and can be used to make quantitative measurements of the potential for change to system performance. Moreover, DTMCs can be extended to be time-inhomogeneous, i.e. to represent behavior that varies over long durations. To date, DTMCs have been proposed for tasks such as fault detection and long-term condition equipment monitoring in real-world complex systems. However, the scope of these models has generally been restricted to describing states and state transitions that directly concern fault conditions or states of degradation. Less work has been done on using DTMCs to represent a more complete range of states a system may enter into during normal operation. Of special interest are sequences of states that involve failure scenarios, in which a system evolves from a normal operating state into undesirable state that leads to widespread performance degradation. Unfortunately, use of large DTMCs often involves large search spaces, a problem which in part motivates our work. This paper describes progress made on developing an approach for using larger, more detailed DTMC models of operational complex systems to uncover potential failure scenarios. The approach uses a combination of methods to perturb a DTMC, simulate alternative system evolutions, and identify scenarios in which a system proceeds from normal operation to failure. Key to the approach is the use of graph theory techniques to reduce the size of the search space involved in exploring alternative behaviors. We show how graph theory techniques can be used to identify critical state transitions which can be perturbed to simulate performance degradation. Using critical transitions, it is also possible to estimate the rate of performance degradation and to understand how this rate is likely to change in response to increased failure incidence. Examples are provided of the use of this approach on a DTMC of significant size to identify failure scenarios in a distributed resource allocation system.

scholarly journals Determination of Kinetic Properties in Unimolecular Dissociation of Complex Systems from Graph-Theory Based Analysis of an Ensemble of Reactive Trajectories.

2021 ◽  
Author(s):  
Ariel F. Perez-Mellor ◽  
Riccardo Spezia
Keyword(s):  
Graph Theory ◽  
Complex Systems ◽  
Kinetic Properties ◽  
Unimolecular Dissociation ◽  
Theoretical Mass ◽  
Reactive Trajectories ◽  
Direct Counting ◽  
Dynamics Simulations ◽  
State Kinetic

<div>We describe and apply a general approach based on graph-theory to obtain kinetic and structural properties from direct dynamics simulations. In particular, we focus on the unimolecular fragmentation of complex systems in which, prior to dissociation, different events can take place, and notably isomerizations and formation of ion-molecule complex.</div><div>3-state and 4-state kinetic models are thus obtained and rate constants for global or specific pathways are obtained from direct counting and flux calculation, both being in agreement.<br>Finally, we show how a theoretical mass spectrum can also be obtained automatically.<br></div>

scholarly journals Determination of Kinetic Properties in Unimolecular Dissociation of Complex Systems from Graph-Theory Based Analysis of an Ensemble of Reactive Trajectories.

2021 ◽  
Author(s):  
Ariel F. Perez-Mellor ◽  
Riccardo Spezia
Keyword(s):  
Graph Theory ◽  
Complex Systems ◽  
Kinetic Properties ◽  
Unimolecular Dissociation ◽  
Theoretical Mass ◽  
Reactive Trajectories ◽  
Direct Counting ◽  
Dynamics Simulations ◽  
State Kinetic

<div>We describe and apply a general approach based on graph-theory to obtain kinetic and structural properties from direct dynamics simulations. In particular, we focus on the unimolecular fragmentation of complex systems in which, prior to dissociation, different events can take place, and notably isomerizations and formation of ion-molecule complex.</div><div>3-state and 4-state kinetic models are thus obtained and rate constants for global or specific pathways are obtained from direct counting and flux calculation, both being in agreement.<br>Finally, we show how a theoretical mass spectrum can also be obtained automatically.<br></div>

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