1,720,975 research outputs found
Numerical modelling of parametric resonance of a heaving point absorber wave energy converter
No full textTHESIS 1058
On-site energy generation for a decarbonized Irish manufacturing industry
No full textThe objective of the thesis is to explore whether it is technically, economically and en-vironmentally feasible for an Irish manufacturing facility to become an energy prosumer, byproducing energy on-site, and decrease the environmental impact of its electric and thermalenergy demand as the energy sector is progressively decarbonized. A new model has been de-veloped and implemented in Matlab in this thesis. It allows to simulate the techno-economicand environmental feasibility of on-site energy generation for a manufacturing facility throughan integrated Variable Renewable Energy (VRE) system and a Combined Heat and Power(CHP) system. The model is built as a robust and flexible tool that can be used for any fa-cility worldwide by updating inputs such as geographical location, solar and wind availabilityand hourly energy demand. The implemented model allows also to evaluate the feasibility ofon-site energy generation in possible future scenarios by conducting a sensitivity analysis ofparameters that may change in the future, such as discount rate, commodities price and gridcarbon intensity.An existing Irish manufacturing facility has been used as a real case study to providerealistic data as input to the analysis, capturing real requirements and constraints that char-acterize this type of end-user. The first option investigated to decarbonize the electric loadof the facility is an on-site VRE system composed of solar PV and wind turbines. The mod-elled VRE system results technically viable but not economically feasible in isolation: its PayBack Time is too high (PBT >25 years) to be attractive for a manufacturing facility andit would remain unattractive even with substantial subsidies and a reduction in the capitalcost of VRE technologies. The second option investigated, both to economically support theon-site VRE system and to decarbonize the thermal energy load of the facility, is to add anon-site CHP system. The integrated system results to be both technically and economicallyfeasible with aPBTclose to 6 years. However, the environmental benefits of reducing carbonemissions by producing energy for self consumption on-site are limited in time: if the projectwas to be commissioned in 2020, the cumulative emissions savings would become negativein 2040 as the electric grid is progressively decarbonized, creating a potential misalignmentbetween decarbonizing policies and the manufacturing facility’s economic strategy. Anotherissue arises with the installation of the on-site system: the almost constant electric load ofthe manufacturing facility becomes more variable and difficult to predict due to the intermit-tency of renewable sources. Despite its inherent operating flexibility, the CHP system doesnot significantly reduce the occurrence of high fluctuations in the residual electric load thatthe grid has to cover.It is concluded that a techno-economic opportunity does exist for on-site energy cogener-ation in the Irish manufacturing industry, however the environmental benefits are limited intime. The effects on the electric grid of a switch from a predictable and constant load to amore variable one should be considered as the penetration of distributed generation increase
Low order resonance of an elastic fluid-conveying tube
No full textThe two-dimensional motion of a slender elastic
fluid-carrying tube is considered. The tube is clamped
at the upper end, at its lower end a point mass is fixed,
and at some intermediate position two springs support the
tube in transversal direction. Adopting model equations
for the tube-liquid system from previous works, the loss
of stability of the trivial position of the tube is investigated.
While a linear stability analysis indicates several
possibilities of stability losses, special attention is paid
to the Hopf-Hopf (coupled Flutter) instability where the
occurence of a (1 : 3) internal resonance is detected for
distinct parameter values. In a non-linear analysis the
post-bifurcation behaviour is investigated for the case of
the (1 : 3) resonance. For limiting cases, the dynamics
of the tube is shown to be described by Duffing´s
and by Mathieu´s equation, respectively, associated with
(quasi)periodic motions of the tube
A new technique for vortex methods in computational fluid dynamics
No full textTHESIS 6795The random vortex method is a Lagrangian technique which involves solving the stream function-vorticity formulation of the Navier-Stokes equations. Discrete vortex particles, which are created at the surface to satisfy zero slip, are convected in the inviscid flow, while diffusion is modelled as a random walk. The interaction of the discrete vortices can be computed more efficiently by use of a cloud-in-cell technique. Here the vorticity of the particles is spread onto a fixed Eulerian mesh, providing a source term for the Poisson equation which can be easily solved to provide the stream function (and hence velocity) field on the mesh. The cloud-in-cell technique has traditionally been used with regular polar or Cartesian grids in two dimensions, thus requiring conformal transformation and/or multi-grid methods for application to complex geometries. A new method, referred to herein as the cloud-in-element method, is presented which allows a single unstructured mesh to be used for multiple bodies and arbitrary geometries in two dimensions. The technique requires a computationally
efficient location of point vortices in an unstructured mesh, which has been made possible by use of reference matrices. A finite element method is used to solve the
velocity field on the unstructured mesh. The method is shown to be computationally efficient, with a process time
which varies linearly with the number of point vortices used in the simulation. A preliminary study of accuracy and mesh dependency has shown the method to be stable, with increasing accuracy for finer discretisations in space and time. The algorithm is described, and results for the standard case of impulsively started flow over a circular cylinder are presented for a range of Reynolds numbers
from 40 to 9500. Good quantitative agreement for Strouhal number and total drag has been achieved. Qualitative agreement of the instantaneous streamline pattern
and flow structure was also observed. Vorticity plots are presented for flow over two cylinders, showing the application of the method to multiple bodies
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
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