Embryonic Development of the Avian Sternum and Its Morphological Adaptations for Optimizing Locomotion
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The sternum is part of the forelimb appendicular skeleton found in most terrestrial vertebrates and has become adapted across tetrapods for distinctive modes of locomotion. We review the regulatory mechanisms underlying sternum and forelimb development and discuss the possible gene expression modulation that could be responsible for the sternal adaptations and associated reduction in the forelimb programme found in flightless birds. In three phylogenetically divergent vertebrate lineages that all undertake powered flight, a ventral extension of the sternum, named the keel, has evolved independently, most strikingly in volant birds. In flightless birds, however, the sternal keel is absent, and the sternum is flattened. We review studies in a variety of species that have analysed adaptations in sterna morphology that are related to the animal’s mode of locomotion on land, in the sky and in water.Keywords:
Sternum
Keel
Forelimb
Appendicular skeleton
The comfort on the fishing ship is paid more and more attention. This paper studies the outer keel structure type of small ocean-going squid fishing ships. By using 3-D potential theory, the wave-induced motion’s response is calculated using the scatter diagram of working areas, finally the calculation values have been compared with the non-outer keel ones. It provided the resonable basis of design and application of the outer keel.
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The article discusses whether the model of loose granular medium is applicable to the analysis of physical processes in the ridge keel. It is argued that the model is not valid for dealing with a number of problems such as the evolution of the ridge keel. It is also suggested that the decrease in keel porosity in time is primarily caused by thermodynamic factors.
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Based on designing and constructing practices of fishing vessels,the structural features of the new knife-like keel were analyzed and compared with the traditional square keel,so as to postulate the opinions and suggestions for improving of the knife-like keel.
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A highly specialized analysis of functionality of a retractable keel lifting mechanism is presented in the paper.Because of its special design a retractable keel is vulnerable to rough sea conditions.To alleviate possible malfunctions or even damage to the keel, an analysis of lifting the keel during rough sea (WMO sea state 6) is performed.Reliable estimation of load acting on a keel is crucial for the subsequent functional or structural analysis of the keel.Aiming to obtain these loads, a sea wave analysis is performed first, where a wave train is determined by respecting statistical data regarding the required sea condition.Two wave cases are considered: head seas (waves coming from the front) and beam seas (lateral waves).A deterministic dynamic analysis on the wave-hull-keel system is then performed.The response of this system is obtained in the form of a time dependent acceleration of the centre of gravity of the vessel and in a time dependent lifting force, i.e., the force which is required for lifting the moveable part of the keel during rough sea.Finally, the required pulling force of the lifting mechanism is determined.
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In this paper the authors present a numerical and experimental analysis of the winged keel originally developed for the International twelve-metre class yacht Australia II that won the America's Cup in 1983. After briefly explaining why this keel was evolved in 1981, some basic considerations are presented relating keel performance to various design parameters. The results of numerical flow analyses and wind-tunnel measurements on a model of a winged keel are then presented and compared. The differences between the performance with and without winglets fitted to the keel are discussed. The fitting of winglets appreciably enhances the performance of a low-aspect-ratio lifting surface such as the keel of a twelve-metre yacht.
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The etiology of the keel chest deformity, still being a hypothetical explanation and a matter of investigation, is probably caused by secondary elongation of rib cartilages during growth spurts, which result in prominences of the rib themselves or are conjoined with a protrusion of the sternum (Figs. and 2a–c) to a variable extent and shape. Therefore, the surgical correction is aimed at shortening the affected cartilages with or without sternum osteotomies.
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본 연구에서는 서해안의 해양레저 대중화를 위해 누구나 세일링을 즐길 수 있고, 두 개의 킬로 선체를 지지하여 육상 및 갯벌에서도 선체가 기울지 않고 설 수 있는 트윈킬 요트를 개발하고자 한다. 기존 세일링 요트중 성능이 좋은 편인 블루워터21의 선형을 활용하고 트윈킬 요트의 경우 모노킬 요트보다는 저항성능이 불리할 것으로 예상되므로, 블루워터21의 모노킬 면적 및 무게중심 등을 고려한 트윈킬을 개발하여 모형시험을 수행하였다. 그 결과, 모노킬과 트윈킬의 저항성능에 대한 차이가 약 4 %정도로 예상보다 크지 않음을 확인하였다. The research developed twin keel yacht for everyone which is able to stand erectly on mud flat without list and intended to commercialize the development product for popularization of west coast's marine leisure industry. Yacht's linear was utilized by "Blue Water21" has superior performance among the existing sailing yachts and twin keel model has been tested by calculation of mono keel's extent and its center of gravity. The result was that only 4 % of difference have been identified between mono keel and twin keel's hydrodynamic resistance which was smaller difference than predicted.
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This paper presents a complete and consistent formulation to study the seismic response of a free-standing ship supported by an arrangement of n keel blocks which are all located in a dry dock. It is considered that the foundation of the system is subjected to both horizontal and vertical in plane excitation. The motion of the system is classified in eight different modes which are Rest (relative), Sliding of keel blocks, Rocking of keel blocks, Sliding of the ship, Sliding of both keel blocks and the ship, Sliding and rocking of keel blocks, Rocking of keel blocks with sliding of the ship, and finally Sliding and rocking of keel blocks accompanied with sliding of the ship. For each mode of motion the governing equations are derived, and transition conditions between different modes are also defined. This formulation is based on a number of fundamental assumptions which are 2D idealization for motion of the system, considering keel blocks as the rigid ones and the ship as a massive rigid block too, allowing the similar motion for all keel blocks, and supposing frictional nature for transmitted forces between contacted parts. Also, the rocking of the ship is not likely to take place, and the complete ship separation from keel blocks or separation of keel blocks from the base is considered as one of the failure mode in the system. The formulation presented in this paper can be used in its entirety or in part, and they are suitable for investigation of generalized response using suitable analytical, or conducting a time-history sensitivity analysis.
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The current study was designed with the aim to study the gross morphological features of the sternum in four dead birds of Common Moorhen. The sternum gives attachment to important flight muscles in birds. The dorsal view of sternal body of Common Moorhen was roughly pyramidal. The average length of sternal body was 4.2 centimetres. Sternal keel was highly developed. The average height of sternum was 1.1 centimetres, whereas the curvature length of keel was 4.7 centimetres.
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Model tests with five different keels in combination with one particular hull form have been carried out in the Delft Towing Tank. The variations include a plain deep keel, a keel-centre board, a plain restricted draft keel,a "Scheel" keel and a "winglet" keel. Based on the experimental results performance predictions are given for a 63 ft yacht for windspeeds up to 25 knots. The measured side force and resistance as a function of heeling angle, leeway angle and forward speed are used to analyse the relative merits of the considered keel-hull combinations.
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