1,721,228 research outputs found
Minimising the sloshing impact in membrane LNG tank using a baffle
No full textLiquidised Natural Gas (LNG) is transported by LNG ships and it will slosh in partially filled tanks. This willcause damage to tank structures, e.g. cracks and fatigue, and affect ship’s stability. This paper presents numerical studies of LNG sloshing in partially filed membrane tank with a baffle on the bottom using Finite Volume Method to minimise impact pressure. The software Gambit and Fluent are used to generate the mesh and simulate the LNG sloshing motion. The LNG sloshing behaviour is analysed considering a two-dimensional membrane tank which moved in one direction only for each case studies. Two cases of the tank motions are considered, i.e., sway and roll. The LNG tank is excited by a regular sinusoidal wave and the excitation frequency is set as the natural frequency. Liquid filling levels considered are 25%, 50% and 75% of the tank depth,respectively. Moreover, the numerical results of the impact pressure are compared with the published experimental results and show good agreement. Furthermore, a vertical baffle is inserted on the bottom of the tank to control the maximum impact pressure and results are compared with non-baffle cases. The key findings are: the effect of liquid depth on the maximum impact pressure for rotational motion is more significant comparing with the horizontal motion and offer solutions for reducing impact pressure effectively. The maximum impact pressure for the tank with baffle is reduced nearly 50% comparing with the cases without baffle on the bottom of the tank
A power flow mode theory based on a system's damping distribution and power flow design approaches
Get PDFA power flow mode theory is developed to describe the natural power flow behaviour of a dynamic system based on its inherent damping distribution. The system's characteristic-damping matrix is constructed and it is shown that the eigenvalues and eigenvectors of this matrix identify natural power flow characteristics. These eigenvectors, or power flow mode vectors, are chosen as a set of base-vectors spanning the power flow space and completely describe the power flow in the system. The generalized coordinate of the velocity vector decomposed in this space defines the power flow response vector. A time-averaged power flow expression and theorems relating to its estimation are presented.Based on this theory, power flow design approaches are proposed to identify energy flow patterns satisfying vibration control requirements. The mode control factor defines the measure of the correlation between a power flow mode and a natural vibration mode of the system. Power flow design theorems are presented providing guidelines to construct damping distributions maximizing power dissipation or to suppress/retain a particular vibration mode and/or a motion.The developed damping-based power flow mode theory is compared with a mobility-based power flow model. It is shown that the proposed power flow model provides insight into the power flow dissipation mechanisms in dynamic systems.Examples are presented to demonstrate the applicability of the power flow mode theory and the power flow design approach. These examples demonstrate the generality of the theory, including non-symmetric damping matrices, and illustrate power flow design applications through modifications of the system's damping distribution using passive and/or active control components
Notes on the Metrocoris lituratus group (Heteroptera: Gerridae: Metrocoris) with descriptions of four new species in Sichuan Basin from China
No full textChen, Zhen Ye Ping-Ping, Bu, Wen-Jun (2016): Notes on the Metrocoris lituratus group (Heteroptera: Gerridae: Metrocoris) with descriptions of four new species in Sichuan Basin from China. Zootaxa 4117 (3): 359-374, DOI: 10.11646/zootaxa.4117.3.
Vibration energy flow analysis of the Van der Pol oscillator
No full textThis paper investigates the forced Van der Pol oscillator from a viewpoint of vibration flow and energy exchange. The method of averaging and the method of harmonic balance are used to derive analytical formulations of time-averaged power flow variables associated with steady-state periodic and quasi-periodic responses, respectively. Effects of bifurcations on time-averaged power flow are investigated both by analytical methods and numerical integrations. It is found that the time-averaged input power by the external harmonic force may become negative at some excitation frequencies. Correspondingly, the damping nonlinearity may lead to positive time-averaged dissipated power. The frequency band where there is negative time-averaged dissipated power is formulated through analytical approximations. It is also found that bifurcations of the forced oscillator from periodic to quasi-periodic responses may not lead to jump phenomenon in time-averaged input power. The work provides some new understanding of the power flow characteristics of the Van der Pol oscillator and demonstrates potential benefits of using such systems for vibration energy harvesting.</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
Peachbloom-glazed willow leaf-shaped vase (liu ye ping)
No full textThis is a small willow leaf-shaped vase (liu ye ping) with a flaring mouth, a waisted neck, slanting shoulders, a tapering body and a concave base. Once serving as an ornament in the Kangxi court, this type of vase is named after its slender profile, which resembles a willow leaf. The exterior of this small vase is thinly covered with a peachbloom (jiang dou hong) glaze down to the base. Peachbloom is a type of glaze developed in the Kangxi reign of the Qing dynasty as a result of attempts to imitate the red-glazed wares made in the Xuande reign of the Ming dynasty. The color is soft and elegant, like that of a peachbloom. Sometimes the color is variegated and there are green mottles in the glaze. The glaze on this vase seems to have faded and appears yellowish with a considerable number of green mottles. The outside of the base is unglazed, exposing the white body. The inside mouth is also glazed in peachbloom while the mouthrim is in a white glaze. The rest of the interior is unglazed.
The white glazed bottom of the concave base contains a reign mark da qing kang xi nian meaning Made during the Kangxi Reign of the Great Qing in two columns and in an underglaze blue.
According to a book titled gu wan zhi nan (Guide of Chinese Antiques) written in 1942 by Zhao Ruzhen, a prestigious modern connoisseur, antique peachbloom vessels are usually covered with a thick and lustrous layer of glaze; however, later copies are thinly and roughly glazed. Green mottles on the antique peachbloom vessels appear glossy, fine and smooth, but green mottles on later copies appear either too green or black. As to this small willow leaf-shaped vase, it is covered with a thin and rough layer of peachbloom glaze. The green mottles on it seem to be 'too green' and deliberately rendered. Therefore, it is evident that this piece is a later copy of the Kangxi products.Qing dynast
FIGURES 13–20 in Notes on the Metrocoris lituratus group (Heteroptera: Gerridae: Metrocoris) with descriptions of four new species in Sichuan Basin from China
No full textFIGURES 13–20. Habitus of Metrocoris spp. (apterous males). 13–16. M. sichuanensis Chen & Nieser, 1993 (13: Qingchen mountain; 14: Laojun mountain; 15: Xinmin village; 16: Hubaoxia Forest Park); 17. M. astictus sp. nov.; 18. M. falciformis sp. nov.; 19. M. guizhouensis sp. nov.; 20. M. zhengi sp. nov.. Scale 2.0 mm.Published as part of Chen, Zhen Ye Ping-Ping & Bu, Wen-Jun, 2016, Notes on the Metrocoris lituratus group (Heteroptera: Gerridae: Metrocoris) with descriptions of four new species in Sichuan Basin from China, pp. 359-374 in Zootaxa 4117 (3) on page 363, DOI: 10.11646/zootaxa.4117.3.4, http://zenodo.org/record/26971
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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