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Scuba Skills
Scuba skills are skills required to dive safely using self-contained underwater breathing apparatus (scuba set). Most of these skills are relevant to both open-circuit scuba and rebreather scuba, and many are also relevant to surface-supplied diving. Certain scuba skills, which are critical to divers' safety, may require more practice than is provided during standard recreational training. Some skills are generally accepted by recreational diver certification agencies as necessary for any scuba diver to be considered competent to dive without direct supervision. Others are more advanced, although some diver certification and accreditation organizations may consider some of these to also be essential for minimum acceptable entry-level competence. Divers are instructed and assessed on these skills during basic and advanced training and are expected to remain competent at their level of certification, either by practice or refresher courses. Many organizations recommend one of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diving Training -c
Diving most often refers to: * Diving (sport), the sport of jumping into deep water * Underwater diving, human activity underwater for recreational or occupational purposes Diving or Dive may also refer to: Sports * Dive (American football), a type of play in American football * Diving (association football), a simulation of being fouled * Diving (ice hockey), embellishing an infraction in an attempt to draw a penalty * Sport diving (sport), competitive scuba diving using recreational techniques in a swimming pool * Taking a dive, or match fixing, intentionally losing a match, especially in boxing Film and television Film * ''Dive'' (film), a 1929 German silent film * ''The Dive'' (1990 film), a Norwegian action thriller * ''Dive!'' (film), a 2010 documentary film by Jeremy Sefert * ''Dive'', a 2014 New Zealand short film written and directed by Matthew J. Saville * ''The Dive'' (2018 film), an Israeli film TV * ''Dive'' (TV series), a 2010 British drama * "The Dive" ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
US Navy 110827-N-ZZ999-243 Navy Diver 2nd Class Ryan Kithcens, Assigned To Mobile Diving And Salvage Unit (MDSU) 1, Dives Into San Diego Bay To Sea
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territories, nine Minor Outlying Islands, and 326 Indian reservations. The United States is also in free association with three Pacific Island sovereign states: the Federated States of Micronesia, the Marshall Islands, and the Republic of Palau. It is the world's third-largest country by both land and total area. It shares land borders with Canada to its north and with Mexico to its south and has maritime borders with the Bahamas, Cuba, Russia, and other nations. With a population of over 333 million, it is the most populous country in the Americas and the third most populous in the world. The national capital of the United States is Washington, D.C. and its most populous city and principal financial center is New York City. Paleo-Ameri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Torque
In physics and mechanics, torque is the rotational equivalent of linear force. It is also referred to as the moment of force (also abbreviated to moment). It represents the capability of a force to produce change in the rotational motion of the body. The concept originated with the studies by Archimedes of the usage of levers, which is reflected in his famous quote: "''Give me a lever and a place to stand and I will move the Earth''". Just as a linear force is a push or a pull, a torque can be thought of as a twist to an object around a specific axis. Torque is defined as the product of the magnitude of the perpendicular component of the force and the distance of the line of action of a force from the point around which it is being determined. The law of conservation of energy can also be used to understand torque. The symbol for torque is typically \boldsymbol\tau, the lowercase Greek letter ''tau''. When being referred to as moment of force, it is commonly denoted by . I ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Centroids
In mathematics and physics, the centroid, also known as geometric center or center of figure, of a plane figure or solid figure is the arithmetic mean position of all the points in the surface of the figure. The same definition extends to any object in ''n''-dimensional Euclidean space. In geometry, one often assumes uniform mass density, in which case the ''barycenter'' or ''center of mass'' coincides with the centroid. Informally, it can be understood as the point at which a cutout of the shape (with uniformly distributed mass) could be perfectly balanced on the tip of a pin. In physics, if variations in gravity are considered, then a ''center of gravity'' can be defined as the weighted mean of all points weighted by their specific weight. In geography, the centroid of a radial projection of a region of the Earth's surface to sea level is the region's geographical center. History The term "centroid" is of recent coinage (1814). It is used as a substitute for the older t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Centre Of Gravity
In physics, the center of mass of a distribution of mass in space (sometimes referred to as the balance point) is the unique point where the weighted relative position of the distributed mass sums to zero. This is the point to which a force may be applied to cause a linear acceleration without an angular acceleration. Calculations in mechanics are often simplified when formulated with respect to the center of mass. It is a hypothetical point where the entire mass of an object may be assumed to be concentrated to visualise its motion. In other words, the center of mass is the particle equivalent of a given object for application of Newton's laws of motion. In the case of a single rigid body, the center of mass is fixed in relation to the body, and if the body has uniform density, it will be located at the centroid. The center of mass may be located outside the physical body, as is sometimes the case for hollow or open-shaped objects, such as a horseshoe. In the case of a di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Centre Of Buoyancy
The metacentric height (GM) is a measurement of the initial static stability of a floating body. It is calculated as the distance between the centre of gravity of a ship and its metacentre. A larger metacentric height implies greater initial stability against overturning. The metacentric height also influences the natural period of rolling of a hull, with very large metacentric heights being associated with shorter periods of roll which are uncomfortable for passengers. Hence, a sufficiently, but not excessively, high metacentric height is considered ideal for passenger ships. Metacentre When a ship heels (rolls sideways), the centre of buoyancy of the ship moves laterally. It might also move up or down with respect to the water line. The point at which a vertical line through the heeled centre of buoyancy crosses the line through the original, vertical centre of buoyancy is the metacentre. The metacentre remains directly above the centre of buoyancy by definition. In the diagram ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Buoyancy
Buoyancy (), or upthrust, is an upward force exerted by a fluid that opposes the weight of a partially or fully immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus the pressure at the bottom of a column of fluid is greater than at the top of the column. Similarly, the pressure at the bottom of an object submerged in a fluid is greater than at the top of the object. The pressure difference results in a net upward force on the object. The magnitude of the force is proportional to the pressure difference, and (as explained by Archimedes' principle) is equivalent to the weight of the fluid that would otherwise occupy the submerged volume of the object, i.e. the displaced fluid. For this reason, an object whose average density is greater than that of the fluid in which it is submerged tends to sink. If the object is less dense than the liquid, the force can keep the object afloat. This can occur only in a n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frau Beim Tauchen (2)
''Honorifics'' are words that connote esteem or respect when used in addressing or referring to a person. In the German language, honorifics distinguish people by age, sex, profession, academic achievement, and rank. In the past, a distinction was also made between married and unmarried women. Honorific pronouns Like many languages, German has pronouns for both familiar (used with family members, intimate friends, and children) and polite forms of address. The polite equivalent of "you" is "''Sie''." Grammatically speaking, this is the 3rd-person-plural form, and, as a subject of a sentence, it always takes the 3rd-person-plural forms of verbs and possessive adjective/ pronouns, even when talking to only one person. (Familiar pronouns have singular and plural forms.) Honorific pronouns are always capitalized except for the polite reflexive pronoun "''sich''." In letters, e-mails, and other texts in which the reader is directly addressed, familiar pronouns may be capitalized or not. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Underwater Photography
Underwater photography is the process of taking photographs while under water. It is usually done while scuba diving, but can be done while diving on surface supply, snorkeling, swimming, from a submersible or remotely operated underwater vehicle, or from automated cameras lowered from the surface. Underwater photography can also be categorised as an art form and a method for recording data. Successful underwater imaging is usually done with specialized equipment and techniques. However, it offers exciting and rare photographic opportunities. Animals such as fish and marine mammals are common subjects, but photographers also pursue shipwrecks, submerged cave systems, underwater "landscapes", invertebrates, seaweeds, geological features, and portraits of fellow divers. Equipment Some cameras are made for use underwater, including modern waterproof digital cameras. The first amphibious camera was the Calypso, reintroduced as the Nikonos in 1963. The Nikonos range was de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hypercapnia
Hypercapnia (from the Greek ''hyper'' = "above" or "too much" and ''kapnos'' = "smoke"), also known as hypercarbia and CO2 retention, is a condition of abnormally elevated carbon dioxide (CO2) levels in the blood. Carbon dioxide is a gaseous product of the body's metabolism and is normally expelled through the lungs. Carbon dioxide may accumulate in any condition that causes hypoventilation, a reduction of alveolar ventilation (the clearance of air from the small sacs of the lung where gas exchange takes place) as well as resulting from inhalation of CO2. Inability of the lungs to clear carbon dioxide, or inhalation of elevated levels of CO2, leads to respiratory acidosis. Eventually the body compensates for the raised acidity by retaining alkali in the kidneys, a process known as "metabolic compensation". Acute hypercapnia is called acute hypercapnic respiratory failure (AHRF) and is a medical emergency as it generally occurs in the context of acute illness. Chronic hypercap ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Respiratory Dead Space
Dead space is the volume of air that is inhaled that does not take part in the gas exchange, because it either remains in the conducting airways or reaches alveoli that are not perfused or poorly perfused. It means that not all the air in each breath is available for the exchange of oxygen and carbon dioxide. Mammals breathe in and out of their lungs, wasting that part of the inhalation which remains in the conducting airways where no gas exchange can occur. Components ''Total dead space'' (also known as physiological dead space) is the sum of the anatomical dead space and the alveolar dead space. Benefits do accrue to a seemingly wasteful design for ventilation that includes dead space. #Carbon dioxide is retained, making a bicarbonate-buffered blood and interstitium possible. #Inspired air is brought to body temperature, increasing the affinity of hemoglobin for oxygen, improving O2 uptake. #Particulate matter is trapped on the mucus that lines the conducting airways, allow ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
