1,720,993 research outputs found
Aeronautical life-cycle mission modelling framework for conceptual design
No full textThis thesis introduces a novel framework for life cycle mission modelling during conceptual aeronautical design. The framework supports object-oriented mission definition using Geographical Information System technology. Design concepts are defined generically, enabling simulation of most aeronautical vessels and many non-aeronautical vehicles. Moreover, the framework enables modelling of entire vessel fleets, business competitors and dynamic operational changes throughout a vessel life cycle. Vessels consist of components deteriorating over time. Vessels carry payload that operates within the vessel environment.An agent-based simulation model implements most framework features. It is the first use of an agent-based simulation utilising a Geographical Information System during conceptual aeronautical design. Two case studies for unmanned aircraft design apply the simulation. The first case study explores how the simulation supports conceptual design phase decisions. It simulates four different unmanned aircraft concepts in a search-and-rescue scenario including lifeboats. The goal is to learn which design best improves life cycle search performance. It is shown how operational and geographical impacts influence design decision making by generating novel performance information. The second case study studies the simulation optimisation capability: an existing aircraft design is modified manually based on simulation outputs. First, increasing the fuel tank capacity has a negative effect on life cycle performance due to mission constraints. Therefore, mission definition becomes an optimisation parameter. Changing mission flight speeds during specific segments leads to an overall improved design
A generic operational simulation for early design civil unmanned aerial vehicles
No full textContemporary aerospace programmes often suffer from large cost overruns, delivery delays and inferior product quality. This is caused in part by poor predictive quality of the early design phase processes with regards to the operational environment of a product. This paper develops the idea of a generic operational simulation that can help designers to rigorously analyse and test their early product concepts. The simulation focusses on civil Unmanned Air Vehicle products and missions to keep the scope of work tractable. The research agenda is introduced along with ideas, initial results and future work. Designers specify details about their product, its environment and anticipated operational procedures. The simulation returns information that can help to estimate the value of the product using the value-driven design approach. Information will include recurring and non-recurring mission cost items. The research aim is to show that an operational simulation can improve early design concepts, thereby reducing delays and cost overruns. Moreover, a trade-off between mission fidelity and model generality is sought along with a generic ontology of civil Unmanned Air Vehicle missions and guidelines about capturing operational informatio
Evaluating design decisions in real-time using operations modelling
No full textContemporary design processes of large aerospace products are rigidly focused on customer specifications in order to meet their expectations. Life cycle costs, design space exploration and value engineering are neglected, often leading to substantial cost overruns and delivery delays. Moreover, customer specifications are not scrutinized and design decisions are made ignoring potential operational knowledge. Value-driven design suggests a new approach using flexible customer specifications in order to find optimal designs by exploring the solution space. One aspect of this optimization is the simulation of the anticipated operational life of a product in order to gain operational knowledge and analyse customer specifications. This paper suggests that an operational simulation can be used actively or reactively by designers during the design process to improve a product. It is investigated how an operational simulation can act as a design decision support tool and how it can react to customer specifications. Answers are presented by means of a simulation model recreating the operational life of a Search-and-Rescue Unmanned Air Vehicle developed in parallel at the University of Southampton. The simulation's ability for acting as a decision support tool is explored by conducting a fuel tank size optimization. Reactive capabilities are explored by calculating the surplus value of using UAVs. This exemplifies the derivation of product specifications as the simulation reveals the value and hence usefulness of given customer specifications. It is shown that operational simulations benefit designers and overall product value by analysing product specifications and guiding designers to more informed design decision
Complex agent interactions in operational simulations for aerospace design
No full textProduct complexity in the aerospace industry has grown fast while design procedures and techniques did not keep pace. Product life cycle implications are largely neglected during the early design phase. Also, aerospace designers fail to optimize products for the intended operational environment. This study shows how a design, simulated within its anticipated operational environment, can inform about critical design parameters, thereby creating a more targeted design improving the chance of commercial success. An agent-based operational simulation for civil Unmanned Aerial Vehicles conducting maritime Search-and-Rescue missions is used to design and optimize aircrafts. Agent interactions with their environment over the product life-cycle are shown to lead to unexpected model outputs. Unique insights into the optimal design are gained by analysis of the operational performance of the aircraft within its simulated environmen
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
A generic unifying ontology for civil unmanned aerial vehicle missions
Full text linkThe aerospace industry struggles to account appropriately for the operational environment of a product during the early design phase. This can lead to suboptimal designs that can compromise the commercial success of a product. An agent-based operational simulation is shown to reduce the knowledge gap and increase understanding of aerospace products interacting with their operational environments early on. The simulation aims to be a generic tool to model any mission scenario for Unmanned Aerial Vehicles. This paper suggests a unifying ontology aiming to find a small set of parameters that map to almost any conceivable mission. This is achieved by combining Geographical Information Systems (GIS) maps with an agent-based framework. Database structure and integration into the operational simulation is demonstrated by introducing a generic mission case study
Variations on the Author
Full text link“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
Full text linkWe 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
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