1,720,968 research outputs found
Effects of cracked semi-infinite ice sheets on the wave excited motion of a body floating on water
No full textThis study investigates the hydrodynamics of a floating body near cracked semi-infinite ice sheets under wave action, addressing two configurations: an ice channel (Model 1) and a single cracked ice sheet adjacent to open water (Model 2). By combining eigenfunction expansions with Green's identity under linear wave theory and Kirchhoff-Love plate assumptions, we solve the coupled wave-ice-body interaction problem through multi-subdomain matching. The results reveal that crack locations and ice thickness critically govern resonance phenomena. Key findings include: (1) Crack-induced wave reflections generate distinct oscillation patterns-U-shaped in Model 1 and Z-shaped in Model 2-with peak forces amplified at critical wavenumbers; (2) Increased crack distance enhances oscillation amplitudes, and cracks in the ice sheet prevents the amplitude of the wave-induced excitation forces from increasing with the wave number. Notably, cracks elevate heave motions by 30-50% compared to intact ice, crucial for polar vessel design. This work establishes predictive relationships between ice defects, hydrodynamic coefficients, and body responses, providing actionable insights for optimizing Arctic engineering structures in fractured ice environments
Hydrodynamic interactions between waves and cylinder arrays of relative motions composed of truncated floating cylinders with five degrees of freedom
No full textThe hydrodynamic interactions between waves and a truncated floating circular cylinder array were examined in this work. Each cylinder of the array is allowed to oscillate with five degrees of freedom (DOFs), and there can be relative motions among different cylinders. The hydrodynamic responses of such arrays in the presence of ambient incident waves were studied using a semi-analytical technique, in which, the unknown coefficients of radiation-diffraction velocity potentials caused by array motions were expressed by the linear combination of each cylinder's to-be-calculated oscillation amplitudes in each direction. Then, for each cylinder in the array, the amplitude of each degree of freedom was computed. Variations in the oscillation amplitudes of the cylinders in the array with wavenumbers for various incidence angles and column spacing, and amplitude distributions of free surface elevation for various wavenumbers were given. Additionally, extensions to the situation of multidirectional irregular waves were presented. Last but not least, we examined the effects of other DOFs (nonheave) on hydrodynamic responses and wave energy extraction performances (capture width w and interaction factor q) by comparing the results obtained by the 5-DOF and the 1-DOF (heave) models. In terms of response amplitude and wave energy extraction performance, the 5-DOF model's results were significantly different from those of the 1DOF model. Therefore, it is suggested to use the 5-DOF model to analyze such cylindrical arrays.</p
Approximate calculation method of hydrodynamic solution of an array with a large number of truncated cylinders
No full textBased on linear wave theory, the hydrodynamic problem of the array of truncated cylinders with relative motion is studied, and the calculation formulas of hydrodynamic force/moment, added mass, and added damping coefficients are given. Firstly, the effect of the evanescent mode on the hydrodynamic coefficients are studied by the truncated two-cylinders as an example. And based on this, an approximation formula for the heave added mass of the truncated two-cylinders is given. After that, a fast formula for calculating the added mass coefficient of an oscillating cylinder of the rectangularly arranged array with a large number of cylinders caused by evanescent mode is presented. Finally, the approximate calculation method of the hydrodynamic coefficients for a large number of rectangular arrays with a given amplitude are summarized. The method is able to efficiently solve the hydrodynamic coefficients of the array with a large number of cylinders, providing an idea to evaluate the performance of such models in engineering.</p
A Novel Type of Wave Energy Converter with Five Degrees of Freedom and Preliminary Investigations on Power-Generating Capacity
No full textIn order to further improve the power-generating capacity of the wave energy converter (WEC) of oscillating buoy type, this paper puts forward a novel type where the WEC can move and extract power in five degrees of freedom. We make a detailed hydrodynamic analysis of such WECs. Each buoy is modeled as a floating truncated cylinder with five degrees of freedom: surge, sway, heave, roll, and pitch, and there are relative motions among buoys in the array. Linear power take-off (PTO) characteristics are considered for simplicity. Under the linear wave theory, a semi-analytical method based on the eigenfunction expansion and Graf's addition theorem for Bessel functions is proposed to analyze the hydrodynamic interactions among the WEC array under the action of incident waves, and the amplitude response and power extraction of the WEC array are then solved. After verifying the accuracy of hydrodynamic analysis and calculation, we make preliminary case studies, successively investigating the power-generating capacity of a single WEC, an array of two WECs, and an array of five WEC; then, we compare their results with the conventional heaving WECs. The results show that the WEC with five degrees of freedom can significantly improve the power extraction performance.</p
Hydrodynamic interactions among wave energy converter array and a hierarchical genetic algorithm for layout optimization
No full textThis paper focuses on the layout optimization and hydrodynamic investigation of wave energy converter (WEC) array. For hydrodynamic analysis, each buoy is modeled as a truncated floating cylinder that can move with five degrees of freedom. The hydrodynamic response of such an array is analyzed by a semi-analytical method. Then, the power extraction by the array is used as the objective function for layout optimization. To improve efficiency, especially for an array with a large number of WECs, a novel hierarchical optimization method based on matrix coded genetic algorithm is proposed. Within this method, a large-scale array is firstly divided into several levels of small-scale arrays which are easy to handle, then, the genetic algorithm developed in this paper is used to optimize the small array of each level. An example of two-level optimization is given in this paper and compared with the result by conventional optimization routine. Finally, we investigate the influence of introducing other degrees of freedom, besides the heave mode, on the performance of arrays. Results show that as the constraints get weaker in non-heave directions, the effect of other degrees of freedom on the WEC array interaction factor becomes more and more obvious.</p
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
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