765 research outputs found
Hydrodynamic effects on fast monohulls or catamarans travelling through the critical speed in shallow water.
No full textThe speed of linear waves in shallow water approaches a constant value as the wavelength becomes large relative to the water depth. For ships travelling in shallow water, this speed is known as the `critical speed' and acts as a barrier, similar to the speed of sound for aeroplanes. The possibility of travelling at transcritical and supercritical speeds is discussed for existing monohull and catamaran ships. We explore the predicted linearised flow around a ship as it approaches the critical speed, and the singularities that result. Experimental results show the actual flow patterns that occur at ship speeds close to the critical speed, for monohulls or catamarans, in open water or confined channels.
References Ang, W. T. 1993 Nonlinear sinkage and trim for a slender ship in shallow water of finite width. Internal report, University of Adelaide. Chen, X. N. 1999 Hydrodynamics of wave-making in shallow water. Ph.D. thesis, University of Stuttgart. Chen, X. N., Sharma, S. D. and Stuntz, N. 2003 Wave reduction by S-Catamaran at supercritical speeds. Journal of Ship Research 47, No. 1, pp. 1--10. Constantine, T. 1960 On the movement of ships in restricted waterways. Journal of Fluid Mechanics 9, pp. 247--256. doi:10.1017/S0022112060001080 Dand, I. W., Dinham-Peren, T. A. and King, L. 1999 Hydrodynamic aspects of a fast catamaran operating in shallow water. Proceedings, Hydrodynamics of High Speed Craft, London, November 1999. Gourlay, T. P. 2000 Mathematical and Computational Techniques for Predicting the Squat of Ships. Ph.D. thesis, University of Adelaide. Gourlay, T. P. 2001 The supercritical bore produced by a high-speed ship in a channel. Journal of Fluid Mechanics 434, pp. 399--409. doi:10.1017/S002211200100372X Gourlay, T. P. and Tuck, E. O. 2001 The maximum sinkage of a ship. Journal of Ship Research 45, No. 1, pp. 50--58. Gourlay, T. P., Duffy, J. T. and Forbes, A. 2005 The bore produced between the hulls of a high-speed catamaran in shallow water. International Journal of Maritime Engineering 147, Part A3, pp. 1--8. Gourlay, T. P. 2006 A simple method for predicting the maximum squat of a high-speed displacement ship. Marine Technology 43, No. 3, pp. 146--151. Gourlay, T. P. 2008 Sinkage and trim of a fast displacement catamaran in shallow water. Journal of Ship Research 52, No. 3, pp. 175--183. Graff, W., Kracht, A. and Weinblum, G. 1964 Some extensions of D. W. Taylor's standard series. Trans. SNAME 72, 374--401. Huang, D. B., Sibul, O. J., Webster, W. C., Wehausen, J. V., Wu, D. M. and Wu, T. Y. 1982 Ships moving in the transcritical speed range. Proceedings, Conference on Behaviour of Ships in Restricted Waters, Varna, Vol. II, pp. 1--10. Insel, M. 1990 An investigation into the resistance components of high speed catamarans. Ph.D. thesis, Department of Ship Science, University of Southampton. Lea, G. K. and Feldman, J. P. 1972 Transcritical flow past slender ships. Proceedings, 9th Symposium on Naval Hydrodynamics, ONR, Washington D.C., p1527. Mei, C. C. 1976 Flow around a thin body moving in shallow water. Journal of Fluid Mechanics 77, pp. 737--751. doi:10.1017/S0022112076002863 Michell, J. H. 1898 The wave resistance of a ship. Philosophical Magazine 45, pp. 106--123. Mueller-Graf, B. 1995 General resistance aspects of advanced fast marine vehicles. Proceedings, Design of Advanced Fast Marine Vehicles, September, Glasgow. Newman, J. N. 1977 Marine Hydrodynamics, MIT Press. Stoker, J. J. 1957 Water Waves. Interscience. Tuck, E. O. Shallow water flows past slender bodies. Journal of Fluid Mechanics 26, pp. 81--95. doi:10.1017/S0022112066001101 Tuck, E. O. 1974 One-dimensional flows as slender-body problems, with applications to ships moving in channels. Proceedings, Workshop on Slender Body Theory, Ann Arbor. University of Michigan Report NAME 164, pp. 27--35
Evaluating Citebase, an open access Web-based citation-ranked search and impact discovery service
No full textCitebase is a new citation-ranked search and impact discovery service that measures citations of scholarly research papers which are openly accessible on the Web, i.e. papers that are assessable continuously online. Other services, such as ResearchIndex, have emerged in recent years to offer citation indexing of Web research papers. In the first detailed user evaluation of an open access Web citation indexing service, Citebase has been evaluated by nearly 200 users from different backgrounds. The paper details the procedures used in the evaluation, and analyses the results of this study, which took place between June and October 2002. It was found that within the scope of its primary components, the search interface and services available from its rich bibliographic records, Citebase can be used simply and reliably for the purpose intended, and that it compares favourably with other bibliographic services. It is shown tasks can be accomplished efficiently with Citebase regardless of the background of the user. More data need to be collected and the process refined before it is as reliable for measuring citation impact of indexed papers. Better explanations and guidance are required for first-time users. Coverage is seen as a limiting factor, even though Citebase indexes over 200,000 papers from arXiv. Non-physicists were frustrated at the lack of papers from other sciences. The principle of citation searching of open access archives has thus been demonstrated and need not be restricted to current users. Since the evaluation, Citebase has become a featured service of the ArXiv physics eprint archives
Acceptance conditions in automated negotiation
No full textIn every negotiation with a deadline, one of the negotiating parties has to accept an offer to avoid a break off. A break off is usually an undesirable outcome for both parties, therefore it is important that a negotiator employs a proficient mechanism to decide under which conditions to accept. When designing such conditions one is faced with the acceptance dilemma: accepting the current offer may be suboptimal, as better offers may still be presented. On the other hand, accepting too late may prevent an agreement from being reached, resulting in a break off with no gain for either party. Motivated by the challenges of bilateral negotiations between automated agents and by the results and insights of the automated negotiating agents competition (ANAC), we classify and compare state-of-the-art generic acceptance conditions. We focus on decoupled acceptance conditions, i.e. conditions that do not depend on the bidding strategy that is used. We performed extensive experiments to compare the performance of acceptance conditions in combination with a broad range of bidding strategies and negotiation domains. Furthermore we propose new acceptance conditions and we demonstrate that they outperform the other conditions that we study. In particular, it is shown that they outperform the standard acceptance condition of comparing the current offer with the offer the agent is ready to send out. We also provide insight in to why some conditions work better than others and investigate correlations between the properties of the negotiation environment and the efficacy of acceptance conditions.MediamaticsElectrical Engineering, Mathematics and Computer Scienc
Mathematical and Computational Techniques for Predicting the Squat of Ships
No full textThis thesis deals with the squat of a moving ship; that is, the
downward displacement and angle of trim caused by its forward
motion. The thesis is divided into two parts, in which the ship is
considered to be moving in water of constant depth and non-constant depth
respectively. In both parts, results are given for ships in channels
and in open water.
Since squat is essentially a Bernoulli effect, viscosity is
neglected throughout most of the work, which results in a boundary value problem involving Laplace's equation. Only qualitative statements about the effect of
viscosity are made.
For a ship moving in water of constant depth, we first consider a
one-dimensional theory for narrow channels. This is
described for both linearized flow, where the disturbance due to the
ship is small, and
nonlinear flow, where the disturbance due to the ship is large. For
nonlinear flow we develop an iterative method for determining the
nonlinear sinkage and trim. Conditions for the existence of steady
flow are determined, which take into account the squat of the ship.
We then turn to the problem of ships moving in open water, where
one-dimensional theory is no longer applicable. A well-known
slender-body shallow-water theory is modified to remove the
singularity which occurs when the ship's speed is equal to the
shallow-water wave speed. This is done by including the effect of
dispersion, in a manner similar to the derivation of the
Korteweg-deVries equation. A finite-depth theory is also used to model
the flow near the critical speed.
For a ship moving in water of non-uniform depth, a linearized
one-dimensional theory is derived which is applicable to unsteady flow. This
is applied to simple bottom topographies, using analytic as well as numerical methods. A corresponding slender-body shallow-water
theory for variable depth is also developed, which is valid for ships
in channels or open water. Numerical results are
given for a step depth change, and an analytic solution to the problem
is discussed.Thesis (Ph.D.)--Applied Mathematics, 2000
Musikstädte as real and imaginary soundscapes: urban musical images as literary motifs in twentieth-century German modernism
No full textPhDThis study examines German literary images of musical life as part of the wider sound identity of the modern German city at the turn of the twentieth century. Focussing on a forty-year period from 1890 to 1930, synonymous with the emergence of the modern German metropolis as an aesthetic object, the project assesses, compares and contrasts how musical life in the Musikstädte was perceived and portrayed by writers in an increasingly noisy urban environment. How does urban musical life influence and condition city writings? What are the differences and similarities between the writings on various musical cities? Can an urban textual sound identity be derived from these differences and similarities? The approach employed to answer these questions is a new, cross-disciplinary one to urban sound in literature, moving beyond reading the key sounds of the urban soundscape using urban musicology, sensorial anthropology and cultural poetics towards a literary contextualisation of the urban aural experience.
The literary motifs of the symphony, the gramophone and urban noise are put under the spotlight through the analysis of a wide range of modernist works by authors who have a special relationship with music. At the centre of this analysis are the Kaffeehausliteratur authors Hermann Bahr, Alfred Polgar and Peter Altenberg, the then Munich-based author Thomas Mann and the lesser known René Schickele. The analysis of these particular works is framed in the music-geographical context of the Musikstadt and literary underpinnings of this topos, ranging from Ingeborg Bachmann to Hans Mayer and, once again, Thomas Mann. In analysing these texts, the methodological approach devised by Strohm, who identifies the blending of a range of urban sounds as a definition of urban space and identity, is applied. His ideas combine historical literary
analysis, musical history and urban sociology. They are rarely used in the analysis of the auditory environment.Arts and Humanities Research Council
Westfield TrustWestfield Trust Studentship
Arts and Humanities Reseach Council (AHRC
The politics of journalistic creativity: expressiveness, authenticity and de-authorization
No full textThis article begins with the assertion that creativity in journalism has moved from being a matter of guile and ingenuity to being about expressiveness, and that this reflects a broader cultural shift from professional expertise to the authenticity of personal expression as dominant modes of valorization. It then seeks to unpack the normative baggage that underpins the case for creativity in the cultural industries. First, there is a prioritization of agency, which does not stand up against the phenomenological argument that we do not own our own practices. Second, creative expression is not necessarily more free, simply alternately structured. As with Judith Butler’s performativity model, contemporary discourses of creativity assume it to have a unique quality by which it eludes determination (relying on tropes of fluidity), whereas it can be countered that it is in spontaneous, intuitive practice that we are at our least agencical. Third, the article argues against the idea that by authorizing journalists (and audiences) to express themselves, creativity is democratizing, since the always-already nature of recognition means that subjects can only voice their position within an established terrain rather than engage active positioning
Prosperity without growth? : the transition to a sustainable economy
No full textThis report is summarised by the documents 'Prosperity without growth? : summary' and 'Ffyniant heb dwf? : crynodeb'Prosperity without Growth? analyses the complex relationships between growth, environmental crises and social recession.Publisher PD
Agricultural Trade Liberalization: Implications for Productive Factors in the U.S.
No full textThis report presents preliminary results of impacts on factors of production in the United States, following reductions in assistance to agriculture. Analysis was conducted by modifying the production structure of the U.S. country model in SWOPSIM to explicitly include inputs employed by agriculture. The results indicate that it is important to adequately model the production technology and include inputs, otherwise simulation results may not capture the impact of liberalization on input use and may not adequately represent changes in producer income.International Relations/Trade,
The Obstacles of Building a Successful NBA Franchise
No full textabstract: When I was unsure of what my thesis project would be, the professor of my thesis prep class, Jill Johnson, recommended that I choose a topic that I am passionate about. Immediately, my mind went to basketball and the NBA, the business and operations side of things to be specific. Initially, this research paper was going to look into market size and how those teams in a smaller market made their money and ran their teams. It was to focus on some of the more successful franchises that come from smaller markets, as well as those franchises that have been historically unsuccessful. However, the kind of data that I was looking for on market sizes was not very available. So I ended up focusing almost exclusively on the operations side of things. I wanted to see if there was one strategy for building a team that had proven to be more successful than others. I was not sure what sort of answers I would find, but I knew that there had to be some useful data that had yet to be discovered. I settled on researching the success of teams that build primarily using players they drafted versus teams that were built primarily through trades and free agent signings. I also wanted to illuminate the difficulties that front offices, particularly those in smaller markets, face when building a franchise. I chose to focus on things such as the luxury tax and betting on the wrong players. This paper went a lot of different directions before it became what it did. I want to thank all of those who helped me, particularly my director Tim McGuire, my second reader Peter Bhatia and Jill Johnson for helping me get started on the most intimidating, yet rewarding, project that I have ever been a part of
- …
