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Steady state equilibrium of ships maneuvering under combined action of wind and wave
No full textManeuverability is important in ship design stage not only for ship performance but also for safety reason regarding the collision and stability especially in quartering following waves. The International Maritime Organization (IMO) therefore developed maneuvering criteria and collision regulation to ensure the ship safety against collision. This paper discusses maneuvering performance of ship under combined action of wind and wave. The steady state equations of ship maneuvering were numerically solved using the Newton-Rhapson method in order to obtain the drift angle, the rudder angle and the ship forward speed. Results of numerical simulations show that the combined action of wind and wave has significant effect on the drift angle and the rudder angle in the range of wind and wave direction between 20.0 degrees and 120.0 degrees. The ship forward speed significantly changes due to alteration of wind velocity in the wind and wave direction smaller than 40.0 degrees or in the wind and wave direction larger than 140.0 degrees. The wave height has significant effect on the ship forward speed in the wind and wave direction between 20.0 degrees and 80.0 degrees
Karakteristik Geometri dan Pengaruhnya Terhadap Stabilitas Kapal Ferry Ro-Ro Indonesia
No full textStabilitas merupakan salah satu parameter keselamatan kapal dalam pelayaran sebagaimana dipersyaratakan oleh Organisasi Maritim Internasional (IMO) serta Biro Klasifikasi Indonesia (BKI).Untuk mengetahui karakteristik stabilitas selama proses desain, penting untuk mengetahui hubungan antara geometri dengan karakteristik stabilitas kapal. Paper ini membahas tentang hubungan antara karakteristik geometri dan karakteristik stabilitas serta pengaruhnya terhadap desain kapal ferry ro-ro Indonesia. Lengan stabilitas kapal untuk beberapa variasi rasio lebar dan sarat, rasio lambung timbul dan lebar serta titik berat dihitung dan dievaluasi dengan menggunakan kriteria stabilitas IMO. Berdasarkan hasil evaluasi stabilitas, diperoleh nilai minimum rasio lebar dan sarat serta rasio lambung timbul dan lebar kapal yang memenuhi kriteria stabilitas IMO. Stabilitas kapal cenderung menjadi semakin baik jika rasio lebar dan sarat semakin besar. Kapal dengan sarat yang lebih besar memiliki stabilitas yang lebih baik untuk rasio lebar dan sarat yang sama. Stabilitas kapal juga menjadi semakin baik ketika rasio lambung timbul dan lebar semakin besar. Pengaruh rasio lambung timbul dan lebar kapal terhadap stabilitas tidak signifikan ketika rasio tersebut kurang dari 0.06. Perbedaan karakteristik stabilitas secara signifikan dipengaruhi oleh rasio lambung timbul dan lebar kapal ketika rasio tersebut lebih besar dari 0.10. Perbedaan karakteristik tersebut dapat disebabkan oleh karakteristik bentul lambung kapal
Yaw Motion Stability of an Indonesian Ro-Ro Ferry in Adverse Weather Conditions
Get PDFThe yaw motion stability and
course-keeping ability of ships are important factors with regard to collision
danger, particularly for ships operating in narrow channels, crowded routes, or
port areas. Yaw motion may become unstable due to external forces, such as
wind. To investigate yaw stability and course-keeping ability, this study
developed a nonlinear dynamic system of a three-degree-of-freedom mathematical
model to determine steady state equilibrium. Yaw motion behavior was then
analyzed using the eigenvalue characteristic of the obtained equilibrium
points. The numerical results for an Indonesian ro-ro ferry showed that the
rudder angle required to maintain the ship’s course tended to increase as wind
velocity increased. In beam wind, the necessary rudder angle was larger than
the maximum possible rudder angle when the wind velocity was 24 m/s or more.
The ship could be controlled by the rudder during operation, but its yaw motion
tended to be unstable in following wind. The stable oscillation of yaw motion
occurs when the wind velocity is higher than 11 m/s, and the range of heading
and rudder angles increases as wind velocity increases
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
Prediction of Ship Turning Maneuvers in Constant Wind and Regular Waves
Get PDFA ship usually performs maneuvers under the influence of external forces and moments, such as wind, waves, and current. Therefore, it is important to understand the maneuvering behavior of ships under the action of external forces. This paper discusses the turning maneuvers of an Indonesian roro ferry under the combined influence of constant wind and regular waves using the mathematical modelling group (MMG). The ship’s position relative to the wave trough is added to the original MMG model to estimate the exciting forces and moment induced by the waves. The results of a numerical simulation show that the effect of wave height on turning ability is more significant for a small wavelength; this effect decreases as the wavelength increases. The effect of wavelength on the sway force and yaw moment is more significant compared with its effect on the surge force. The ship’s initial position relative to the wave trough does not have a significant effect on the turning characteristic and it can be neglected for the present study’s subject ship. Overall, the results of the present work compare well with published data
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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