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The purpose of this paper is to address the novel issues of executing graph optimization tasks on distributed simple growing biological systems.
Abstract
Purpose
The purpose of this paper is to address the novel issues of executing graph optimization tasks on distributed simple growing biological systems.
Design/methodology/approach
The author utilizes biological and physical processes to implement non‐classical, and in principle more powerful, computing devices. The author experimentally verifies his previously discovered techniques on approximating spanning trees during single cell ontogeny. Plasmodium, a vegetative stage of slime mold Physarum polycephalum, is used as experimental computing substrate to approximate spanning trees. Points of given data set are represented by positions of nutrient sources, then a plasmodium is placed on one of the data points. Plasmodium develops and span all sources of nutrients, connecting them by protoplasmic strands. The protoplasmic strands represent edges of the computed spanning tree.
Findings
Offers experimental implementation of plasmodium devices for approximation of spanning tree.
Practical implications
The techniques, discussed in the paper, can be used in design and development of soft bodied robotic devices, including gel‐based robots, reconfigurable massively robots, and hybrid wet‐hardware robots.
Originality/value
Discusses original ideas on growing spanning trees, and provide innovative experimental implementation.
Details
Keywords
Shashank Gupta and Piyush Gupta
Material handling (MH) is an important facility in any manufacturing system. It facilitates the transport of in-process material from one workstation (WS) to another. MH devices…
Abstract
Purpose
Material handling (MH) is an important facility in any manufacturing system. It facilitates the transport of in-process material from one workstation (WS) to another. MH devices do imply incurring capital costs and, therefore, minimizing their deployment without compromising on smooth material flow will ensure savings in addition to the optimal use of productive shop floor space and, avoid space cluttering. The purpose of this paper is to evaluate the minimal network that connects all the WSs, therefore ensuring economic and safe manufacturing operations.
Design/methodology/approach
Graph theoretical approach and Prim’s algorithm for minimal spanning tree is used to evaluate the minimal span of the MH devices. The algorithm is initialized by translating the graph of WSs into a distance matrix to evaluate the minimal MH network.
Findings
The minimal length of the MH devices is evaluated for a typical case study.
Research limitations/implications
The step-by step methodology explained in the manuscript acts as a good guide for practicing operational managers. The shortcoming of the methodology is that, it presumes the use of modular MH devices that will need to be reconfigured based on dynamic changes to the manufacturing system.
Practical implications
The methodology is explained in detail to enable the practicing managers to use it for designing their MH networks in any manufacturing system.
Originality/value
There is no evidence to indicate the use of minimal spanning tree algorithm for design of MH networks in a manufacturing system. This paper attempts to fill this gap.
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Keywords
Changqing Luo, Mengzhen Li and Zisheng Ouyang
– The purpose of this paper is to study the correlation structure of the credit spreads.
Abstract
Purpose
The purpose of this paper is to study the correlation structure of the credit spreads.
Design/methodology/approach
The minimal spanning tree is used to find the risk center node and the basic correlation structure of the credit spreads. The dynamic copula and pair copula models are applied to capture the dynamic and non-linear correlation structure.
Findings
The authors take the enterprise bond with trading data from January 2013 to December 2013 as the research sample. The empirical study of minimum spanning tree shows that the credit risk of corporate bonds forms a network structure with a center node. Meanwhile, the correlation between credit spreads shows dynamic characteristics. Under the framework of dynamic copula, the lower tail dependence is less than the upper tail dependence, thus, in economic boom period, the dynamic correlation is more significant than in recession period. The authors also find that the centrality of credit risk network is not significant according to the pair copula and Granger causality test. The empirical study shows that the goodness-of-fit of D vine is superior to Canonical vine, and the Granger causality test additionally proves that the center node has influence on few other nodes in the risk network, thus the center node captured by the minimum spanning tree is a weak center node, and this characteristic of credit risk network indicates that the risk network of credit spreads is generated mostly by the external shocks rather than the internal risk contagion.
Originality/value
This paper provides new ideas for investors and researchers to analyze the credit risk correlation or contagion.
Details
Keywords
Andrew Adamatzky and Pedro P.B. de Oliveira
This paper seeks to develop experimental laboratory biological techniques for approximation of existing road networks, optimizing transport links, and designing alternative…
Abstract
Purpose
This paper seeks to develop experimental laboratory biological techniques for approximation of existing road networks, optimizing transport links, and designing alternative optimal solutions to current transport problems. It studies how slime mould of Physarum polycephalum approximate highway networks of Brazil.
Design/methodology/approach
The 21 most populous urban areas in Brazil are considered and represented with source of nutrients placed in the positions of slime mould growing substrate corresponding to the areas. At the beginning of each experiment slime mould is inoculated in São Paulo area. Slime mould exhibits foraging behavior and spans sources of nutrients (which represent urban areas) with a network of protoplasmic tubes (which approximate vehicular transport networks). The structure of transport networks developed by slime mould are analyzed and compared with families of known proximity graphs. The paper also imitates slime‐mould response to simulated disaster.
Findings
It was found that the plasmodium of P. polycephalum develops a minimal approximation of a transport network spanning urban areas. Physarum‐developed network matches man‐made highway network very well. The high degree of similarity is preserved even when high‐demand constraints are placed on repeatability of links in the experiments. Physarum approximates almost all major transport links. In response to a sudden disaster, gradually spreading from its epicenter, the Physarum transport networks react by abandoning transport links affected by disaster zone, enhancement of those unaffected directly by the disaster, massive sprouting from the epicenter, and increase of scouting activity in the regions distant to the epicenter of the disaster.
Originality/value
Experimental methods and computer analysis techniques presented in the paper lay a foundation of novel biological laboratory approaches to imitation and prognostication of socio‐economical developments.
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Juan Gabriel Brida, Emiliano Alvarez, Gaston Cayssials and Matias Mednik
Our paper studies a central issue with a long history in economics: the relationship between population and economic growth. We analyze the joint dynamics of economic and…
Abstract
Purpose
Our paper studies a central issue with a long history in economics: the relationship between population and economic growth. We analyze the joint dynamics of economic and demographic growth in 111 countries during the period 1960–2019.
Design/methodology/approach
Using the concept of economic regime, the paper introduces the notion of distance between the dynamical paths of different countries. Then, a minimal spanning tree (MST) and a hierarchical tree (HT) are constructed to detect groups of countries sharing similar dynamic performance.
Findings
The methodology confirms the existence of three country clubs, each of which exhibits a different dynamic behavior pattern. The analysis also shows that the clusters clearly differ with respect to the evolution of other fundamental variables not previously considered [gross domestic product (GDP) per capita, human capital and life expectancy, among others].
Practical implications
Our results indirectly suggest the existence of dynamic interdependence in the trajectories of economic growth and population change between countries. It also provides evidence against single-model approaches to explain the interdependence between demographic change and economic growth.
Originality/value
We introduce a methodology that allows for a model-free topological and hierarchical description of the interplay between economic growth and population.
Details
Keywords
– This paper aims to present a framework enriching currency risk analyses based on information theory.
Abstract
Purpose
This paper aims to present a framework enriching currency risk analyses based on information theory.
Design/methodology/approach
Information-theoretic measures of predictability (entropy rate) and co-dependence (mutual information) are used to enhance existing methods of analysing and measuring currency risk.
Findings
The currency exchange rates have varying degrees of predictability, which should be accounted for in currency risk analyses. In case of baskets of currencies, a network approach rooted in portfolio theory may be useful.
Research limitations/implications
The currency exchange rate time series must be discretised for the information-theoretic analysis (although the results are robust). An agent-based simulation may be a necessary further study to show what the impact of accounting for predictability in managing currency risk is.
Practical implications
Practical analyses measuring currency risk should take predictability of currency rate changes into account wherever the currency exposure is actively managed.
Originality/value
The paper introduces predictability into measuring currency risk, which has previously been ignored, despite the nature of the risk being inherently tied to uncertainty of the currency rate changes. The paper also introduces a portfolio theory-based approach to quantifying currency risk, which accounts for non-linear co-dependence in the currency markets.
Details
Keywords
Matthias Wählisch and Thomas C. Schmidt
This paper aims to discuss problems, requirements and current trends for deploying group communication in real‐world scenarios from an integrated perspective.
Abstract
Purpose
This paper aims to discuss problems, requirements and current trends for deploying group communication in real‐world scenarios from an integrated perspective.
Design/methodology/approach
The Hybrid Shared Tree is introduced – a new architecture and routing approach to combine network – and subnetwork‐layer multicast services in end‐system domains with transparent, structured overlays on the inter‐domain level.
Findings
The paper finds that The Hybrid Shared Tree solution is highly scalable and robust and offers provider‐oriented features to stimulate deployment.
Originality/value
A straightforward perspective is indicated in the paper for a mobility‐agnostic routing layer for future use.
Details
Keywords
Ornanong Puarattanaarunkorn, Kittawit Autchariyapanitkul and Teera Kiatmanaroch
Unlimited quantitative easing (QE) is one of the monetary policies used to stimulate the economy during the coronavirus disease 2019 (COVID-19) pandemic. This policy has affected…
Abstract
Purpose
Unlimited quantitative easing (QE) is one of the monetary policies used to stimulate the economy during the coronavirus disease 2019 (COVID-19) pandemic. This policy has affected the financial markets worldwide. This empirical research aims at studying the dependence among stock markets before and after unlimited QE announcements.
Design/methodology/approach
The copula-based GARCH (1,1) and minimum spanning tree models are used in this study to analyze 14 series of stock market data, on 6 ASEAN and 8 other countries outside the region. The data are divided into two periods to compare the differences in dependence.
Findings
The findings show changes in dependence among the volatility of daily returns in 14 stock markets during each period. After the unlimited QE announcement, the upper tail dependence became more apparent, while the role of the lower tail dependence was reduced. The minimum spanning tree can show the close relationships between stock markets, indicating changes in the connection network after the announcement.
Originality/value
This study allows the dependency to be compared between stock market volatility before and after the announcement of unlimited QE during the COVID-19 pandemic. Moreover, the study fills the literature gap by combining the copula-based GARCH and the minimum spanning tree models to analyze and reveal the systemic network of the relationships.
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Keywords
Aswini Kumar Mishra, Anand Theertha, Isha Mahesh Amoncar and Manogna R L
The authors examine network features such as connectivity, centrality, adjacency matrices, closeness and betweenness measures through a variety of indicators. The results of the…
Abstract
Purpose
The authors examine network features such as connectivity, centrality, adjacency matrices, closeness and betweenness measures through a variety of indicators. The results of the study indicate that over time there is a tendency for markets to integrate and segment due to various factors such as pandemics, financial crises, global trade relations and international investments.
Design/methodology/approach
This paper employs a visualized network technique to study the dynamics of integration and comovements in global equity markets of emerging economies. Daily closing prices of stock market indices of 24 countries from January 2013 to July 2020 are used to construct a minimum spanning tree network (MSTN) and graph network (GN).
Findings
The authors identify India and China as global power hubs and clusters among the emerging economies. India and Bangladesh serve as bridging countries connecting to various other clusters. Bosnia serves as a center in the European region owing to Bosnia's trade relations with neighboring countries. Although Brazil has witnessed the worst recession in the early years of the decade, Brazil has risen to be a central cluster among the Latin American countries. Finally, the authors find that African countries tend to form links with the rest of the world rather than with economies within the Africa continent.
Originality/value
This is the pioneering study that uses network models such as MSTN and GN supplemented with measures of centrality and connectivity to study financial market integration in emerging countries. Against this backdrop, this paper aims to work on a network visualization strategy to examine global stock market integration. The authors also try to use graphs and the spanning trees instead of the correlation models to understand the association between the markets, avoiding the downsides of the existing models. The authors' approach tries to visualize the network integration to examine the interconnectedness in the global stock market.
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This paper provides a foundation for a practical way of improving the effectiveness of an automatic retrieval system. Its main concern is with the weighting of index terms as a…
Abstract
This paper provides a foundation for a practical way of improving the effectiveness of an automatic retrieval system. Its main concern is with the weighting of index terms as a device for increasing retrieval effectiveness. Previously index terms have been assumed to be independent for the good reason that then a very simple weighting scheme can be used. In reality index terms are most unlikely to be independent. This paper explores one way of removing the independence assumption. Instead the extent of the dependence between index terms is measured and used to construct a non‐linear weighting function. In a practical situation the values of some of the parameters of such a function must be estimated from small samples of documents. So a number of estimation rules are discussed and one in particular is recommended. Finally the feasibility of the computations required for a non‐linear weighting scheme is examined.