1,721,055 research outputs found
Using network science to disentangle supply networks: a case study in aerospace industry
No full textSupply chains in the aerospace sector are becoming more complex than ever
before, frequently causing delays on the production process. Complexity gave
rise to the term “supply networks”, changing the way we view supply chains
from a structural point of view. Structural properties are important to investigate
as they help define robustness and efficiency of systems. Although complexity
in structure is suspected by previous researchers who studied these networks,
empirical data to characterise what complexity means, and how it effects
properties of networks has been largely absent from literature. If empirical data
is available, network science can be used to understand structural properties of
such complex supply networks. Network science is a suitable Mathematical tool
for analysing the complex relationships and collaborations in the network and
summarizing the properties of network from a fundamental, structural
perspective. In this report, the author will apply network science to analyse the
structure of the Airbus supply network. Due to the lack of aerospace supply
chain data, firstly an empirical database is built. Analysis then focuses on the
real structure of Airbus supply network and identification of key firms or
communities under two scenarios: a non-weighted network in which the value of
link is either 1 or 0, and a weighted network in which the value of link presents
the strength of relationships among firms. While the weighted network indicates
more informed features of the supply network structure by considering the
weight of relationships, the non-weighted network can help us understand
fundamental patterns that determine the structure of the connections in the
network. The analysis indicates the Airbus supply network carries a power law
distribution, which means most resources are dominated by few firms, and the
network is robust to random firm failure but vulnerable to hub failure. The
network contains communities with strong relationships between them.These
communities do not only belong to the same industry and same region but have
emerged as the result of an interaction between the two effects. Some key firms
in the network own significant power of control the supply chain and fiancial
resources, occupying key positions that bridge communities in the network.The
study presents key structural features of a large scale network using empirical
data and act as a case example for using network science based analysis in
supply chains
Analysis of the evolution of aerospace manufacturing ecosystems
Get PDFThe aerospace manufacturing industry is predicted to continue growing.
Understanding its evolution is thus essential to prepare optimal conditions to
nurture its growth. This research aims to help the growth of emerging aerospace
ecosystems by identifying evolution patterns and categorising key enablers that
have encouraged the growth of developed ones. The term aerospace ecosystem
is used to embrace all the business activities and infrastructure that are related
to the entire aerospace’s supply chain in a specific country.
Inspired by studies that have successfully combined economics and network
science, in this research, bipartite country-product networks are developed based
on trade data over 25 years. The United Kingdom (UK), the United States of
America, France, Germany, Canada and Brazil’s are first analysed as evidence
suggests that their aerospace ecosystems are within the most developed in the
world. Then, China and Mexico’s networks are analysed and compared with
developed ones, as these countries have evidenced emergent aerospace
ecosystems. Results reveal that developed ecosystems tend to become more
analogous, as countries lean towards having a revealed comparative advantage
(RCA) in the same group of products. Further analysis shows that manufactured
products have a stronger correlation to an aerospace ecosystem than primary
products; and in particular, the automotive sector shows the highest correlation
with positive aerospace sector evolution.
Key enablers related to the growth of the UK and Mexico’s aerospace
ecosystems are identified and categorised using interpretive structural modelling
(ISM) and cross-impact matrix multiplication applied to classification (MICMAC)
methodologies. Results evidence relevant differences in the categorisation of key
enablers among a developed and emergent aerospace ecosystems. On the other
hand, it was identified that geopolitical factors and the automotive ecosystem are
underpinning enablers for both aerospace ecosystem’s evolution.
The final aim is that results of this research could be implemented on emerging
aerospace ecosystems by emulating the patterns and key enablers that have
characterised the evolution of developed aerospace ecosystems.PhD in Manufacturin
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Resilence of complex supply networks
Get PDFDuring recent decades supply chains have grown, and became increasingly interconnected due to globalisation and outsourcing. Empirical and theoretical studies now characterise supply chains as complex networks rather than the hierarchical, linear chain structures often theorised in classical literature. Increased topological complexity resulted in an increased exposure to risk, however existing supply chain risk
management methodologies are designed based on the linear structure assumption rather than interdependent network structures. There is a growing need to better understand the complexities of supply networks, and how to identify, measure and mitigate risks more efficiently.
The aim of this thesis is to identify how supply network topology influences resilience. More specifically, how applying well-established supply chain risk management strategies can decrease disruption impact in different supply network topologies. The influence of supply network topology on resilience is captured using a dynamic agent-based model based on empirical and theoretical supply network structures,
without a single entity controlling the whole system where each supplier is an independent decision-maker. These suppliers are then disrupted using various disruption scenarios. Suppliers in the network then apply inventory mitigation and contingent rerouting to decrease impact of disruptions on the rest of the network. To the best of author’s knowledge, this is the first time the impact of random disruptions and its reduction through risk management strategies in different supply network topologies have been assessed in a fully dynamic, interconnected environment.
The main lessons from this work are as follows: It has been observed that the supply network topology plays a crucial role in reducing impact of disruptions. Some supply network topologies are more resilient to random disruptions as they better fulfil customer demand under perturbations. Under random disruptions, inventory mitigation is a well-performing shock absorption mechanism. Contingent rerouting,
on the other hand, is a strategy that needs specific conditions to work well. Firstly, the strategy must be applied by companies in supply topologies where the majority of supply chain members have alternative suppliers. Secondly, contingent rerouting is only efficient in cases when the reaction time to supplier’s disruption is shorter than the duration of the disruption.
It has also been observed that the topological position of the individual company who applies specific risk management strategy heavily impacts costs and fill-rates of the overall system. This property is moderated by other variables such as disruption duration, disruption frequency and the chosen risk management strategy. An additional, important lesson here is that, choosing the supplier that suffered the most
from disruptions or have specific topological position in a network to apply a risk management strategy might not always decrease the costs incurred by the whole system. In contrast, it might increase it if not applied appropriately.
This thesis underpins the significance of topology in supply network resilience. The results from this work are foundational to the claim that it is possible to design an extended supply network that will be able reduce the impact of certain disruption types. However, the design must consider topological properties as well as moderating variables.PhD in Manufacturin
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