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Paired Fins
Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only by muscles. Fish fins are distinctive anatomical features with varying structures among different clades: in ray-finned fish (Actinopterygii), fins are mainly composed of bony spines or rays covered by a thin stretch of scaleless skin; in lobe-finned fish (Sarcopterygii) such as coelacanths and lungfish, fins are short rays based around a muscular central bud supported by jointed bones; in cartilaginous fish (Chondrichthyes) and jawless fish (Agnatha), fins are fleshy " flippers" supported by a cartilaginous skeleton. Fins at different locations of the fish body serve different purposes, and are divided into two groups: the midsagittal ''unpaired fins'' and the more laterally located ''paired fins''. Unpaired fins are predominantly a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lampanyctodes Hectoris (fins)
Hector's lanternfish (''Lampanyctodes hectoris'') is a lanternfish in the family Myctophidae, the only species in the genus ''Lampanyctodes''. It is named after James Hector. It is a widespread marine fish, known from shallow tropical waters in the south-eastern Atlantic, from the western Pacific off Australia and New Zealand, and from the eastern Pacific off Chile. It is one of the few species of lanternfishes to inhabit shallow waters, and in those waters it is one of the most abundant species of fish, and central to the food chain of the upper continental slope. The abundance is due to its high fecundity — it spawns multiple times in the winter so that the fry can take advantage of the spring bloom of krill. It grows up to standard length (SL) and may reach the age of 3 years. It reaches sexual maturity at approximately SL and age of one year. Hector's lanternfish is fished commercially using Seine fishing, seine nets in the waters off South Africa, where catches have rea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coelacanth
Coelacanths ( ) are an ancient group of lobe-finned fish (Sarcopterygii) in the class Actinistia. As sarcopterygians, they are more closely related to lungfish and tetrapods (the terrestrial vertebrates including living amphibians, reptiles, birds and mammals) than to ray-finned fish. The name coelacanth originates from the Permian genus '' Coelacanthus'', which was the first scientifically named genus of coelacanths (in 1839), becoming the type genus of Coelacanthiformes as other species were discovered and named. Well-represented in freshwater and marine deposits from as early as the Devonian period (more than 410million years ago), they were thought to have become extinct in the Late Cretaceous, around 66million years ago. The first living species, ''Latimeria chalumnae'', the West Indian Ocean coelacanth, was described from specimens fished off the coast of South Africa from 1938 onward; they are now also known to inhabit the seas around the Comoro Islands off the eas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pitch (ship Motion)
Ship motions are the six degrees of freedom that a ship, boat, or other watercraft can experience. Reference axes The ''flight control surfaces#Vertical axis, vertical/Z axis'', or ''yaw axis'', is an imaginary line running vertically through the ship and through its centre of mass. A yaw motion is a side-to side movement of the bow and stern of the ship. The ''flight control surfaces#Transverse axis, transverse/Y axis'', ''lateral axis'', or ''pitch axis'' is an imaginary line running horizontally across the ship and through the centre of mass. A pitch motion is an up-or-down movement of the bow and stern of the ship. The ''flight control surfaces#Longitudinal axis, longitudinal/X axis'', or ''roll axis'', is an imaginary line running horizontally through the length of the ship, through its centre of mass, and parallel to the ''waterline''. A roll motion is a side-to-side or port-starboard tilting motion of the superstructure around this axis. Rotational There are t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Yaw (rotation)
A yaw rotation is a movement around the yaw axis of a rigid body that changes the direction it is pointing, to the left or right of its direction of motion. The yaw rate or yaw velocity of a car, aircraft, projectile or other rigid body is the angular velocity of this rotation, or rate of change of the heading angle when the aircraft is horizontal. It is commonly measured in degrees per second or radians per second. Another important concept is the yaw moment, or yawing moment, which is the component of a torque about the yaw axis. Measurement Yaw velocity can be measured by measuring the ground velocity at two geometrically separated points on the body, or by a gyroscope, or it can be synthesized from accelerometers and the like. It is the primary measure of how drivers sense a car's turning visually. It is important in electronic stabilized vehicles. The yaw rate is directly related to the lateral acceleration of the vehicle turning at constant speed around a constan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lift (force)
When a fluid flows around an object, the fluid exerts a force on the object. Lift is the Euclidean_vector#Decomposition_or_resolution, component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag (physics), drag force, which is the component of the force parallel to the flow direction. Lift conventionally acts in an upward direction in order to counter the force of gravity, but it is defined to act perpendicular to the flow and therefore can act in any direction. If the surrounding fluid is air, the force is called an aerodynamic force. In water or any other liquid, it is called a Fluid dynamics, hydrodynamic force. Dynamic lift is distinguished from other kinds of lift in fluids. Aerostatics, Aerostatic lift or buoyancy, in which an internal fluid is lighter than the surrounding fluid, does not require movement and is used by balloons, blimps, dirigibles, boats, and submarines. Planing (boat), Planing lift, in which only the lower po ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Directional Stability
Directional stability is the tendency of a vehicle or moving body to keep its orientation aligned with its direction of movement. When a car or an airplane gets turned a little relative to its direction of motion, it might correct itself, over-correct itself, or it might start to spin out of control. If it tends to correct itself, we say it's directionally stable, while if it tends to spin-out, we say it is directionally unstable. There are many factors that can effect dynamic stability including speed, weather and road conditions, vehicle shape and mass distribution, and tire properties. Vehicle oscillations associated with dynamic stability are frequently called "weather vaning". When the vehicle's orientation is perturbed from the direction of motion, a restoring moment may be produced which is in a direction ''opposite'' to the orientation disturbance. This can lead to oscillations in orientation around the center of mass similar to a weather vane rotating about its (verti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
