United States Navy
The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. It is the largest and most capable navy in the world and it has been estimated that in terms of tonnage of its active battle fleet alone, it is larger than the next 13 navies combined, which includes 11 U. S. allies or partner nations. With the highest combined battle fleet tonnage and the world's largest aircraft carrier fleet, with eleven in service, two new carriers under construction. With 319,421 personnel on active duty and 99,616 in the Ready Reserve, the Navy is the third largest of the service branches, it has 282 deployable combat vessels and more than 3,700 operational aircraft as of March 2018, making it the second-largest air force in the world, after the United States Air Force. The U. S. Navy traces its origins to the Continental Navy, established during the American Revolutionary War and was disbanded as a separate entity shortly thereafter.
The U. S. Navy played a major role in the American Civil War by blockading the Confederacy and seizing control of its rivers, it played the central role in the World War II defeat of Imperial Japan. The US Navy emerged from World War II as the most powerful navy in the world; the 21st century U. S. Navy maintains a sizable global presence, deploying in strength in such areas as the Western Pacific, the Mediterranean, the Indian Ocean, it is a blue-water navy with the ability to project force onto the littoral regions of the world, engage in forward deployments during peacetime and respond to regional crises, making it a frequent actor in U. S. foreign and military policy. The Navy is administratively managed by the Department of the Navy, headed by the civilian Secretary of the Navy; the Department of the Navy is itself a division of the Department of Defense, headed by the Secretary of Defense. The Chief of Naval Operations is the most senior naval officer serving in the Department of the Navy.
The mission of the Navy is to maintain and equip combat-ready Naval forces capable of winning wars, deterring aggression and maintaining freedom of the seas. The U. S. Navy is a seaborne branch of the military of the United States; the Navy's three primary areas of responsibility: The preparation of naval forces necessary for the effective prosecution of war. The maintenance of naval aviation, including land-based naval aviation, air transport essential for naval operations, all air weapons and air techniques involved in the operations and activities of the Navy; the development of aircraft, tactics, technique and equipment of naval combat and service elements. U. S. Navy training manuals state that the mission of the U. S. Armed Forces is "to be prepared to conduct prompt and sustained combat operations in support of the national interest." As part of that establishment, the U. S. Navy's functions comprise sea control, power projection and nuclear deterrence, in addition to "sealift" duties, it follows as certain as that night succeeds the day, that without a decisive naval force we can do nothing definitive, with it, everything honorable and glorious.
Naval power... is the natural defense of the United States The Navy was rooted in the colonial seafaring tradition, which produced a large community of sailors and shipbuilders. In the early stages of the American Revolutionary War, Massachusetts had its own Massachusetts Naval Militia; the rationale for establishing a national navy was debated in the Second Continental Congress. Supporters argued that a navy would protect shipping, defend the coast, make it easier to seek out support from foreign countries. Detractors countered that challenging the British Royal Navy the world's preeminent naval power, was a foolish undertaking. Commander in Chief George Washington resolved the debate when he commissioned the ocean-going schooner USS Hannah to interdict British merchant ships and reported the captures to the Congress. On 13 October 1775, the Continental Congress authorized the purchase of two vessels to be armed for a cruise against British merchant ships. S. Navy; the Continental Navy achieved mixed results.
In August 1785, after the Revolutionary War had drawn to a close, Congress had sold Alliance, the last ship remaining in the Continental Navy due to a lack of funds to maintain the ship or support a navy. In 1972, the Chief of Naval Operations, Admiral Elmo Zumwalt, authorized the Navy to celebrate its birthday on 13 October to honor the establishment of the Continental Navy in 1775; the United States was without a navy for nearly a decade, a state of affairs that exposed U. S. maritime merchant ships to a series of attacks by the Barbary pirates. The sole armed maritime presence between 1790 and the launching of the U. S. Navy's first warships in 1797 was the U. S. Revenue-Marine, the primary predecessor of the U. S. Coast Guard. Although the USRCS conducted operations against the pirates, their depredations far outstripped its abilities and Congress passed the Naval Act of 1794 that established a permanent standing navy on 27 March 1794; the Naval Act ordered the construction and manning of six frigates and, by October 1797, the first three were brought into service: USS United States, USS Constellation, USS Constitution.
Due to his strong posture on having a strong standing Navy during this period, John Adams is "often called the father of the American Navy". In 1798–99 the Navy was involved in an undeclared Quasi-War with France. From 18
A pump is a device that moves fluids, or sometimes slurries, by mechanical action. Pumps can be classified into three major groups according to the method they use to move the fluid: direct lift and gravity pumps. Pumps operate by some mechanism, consume energy to perform mechanical work moving the fluid. Pumps operate via many energy sources, including manual operation, engines, or wind power, come in many sizes, from microscopic for use in medical applications to large industrial pumps. Mechanical pumps serve in a wide range of applications such as pumping water from wells, aquarium filtering, pond filtering and aeration, in the car industry for water-cooling and fuel injection, in the energy industry for pumping oil and natural gas or for operating cooling towers. In the medical industry, pumps are used for biochemical processes in developing and manufacturing medicine, as artificial replacements for body parts, in particular the artificial heart and penile prosthesis; when a casing contains only one revolving impeller, it is called a single-stage pump.
When a casing contains two or more revolving impellers, it is called a double- or multi-stage pump. In biology, many different types of chemical and biomechanical pumps have evolved. Mechanical pumps may be placed external to the fluid. Pumps can be classified by their method of displacement into positive displacement pumps, impulse pumps, velocity pumps, gravity pumps, steam pumps and valveless pumps. There are two basic types of pumps: centrifugal. Although axial-flow pumps are classified as a separate type, they have the same operating principles as centrifugal pumps. A positive displacement pump makes a fluid move by trapping a fixed amount and forcing that trapped volume into the discharge pipe; some positive displacement pumps use an expanding cavity on the suction side and a decreasing cavity on the discharge side. Liquid flows into the pump as the cavity on the suction side expands and the liquid flows out of the discharge as the cavity collapses; the volume is constant through each cycle of operation.
Positive displacement pumps, unlike centrifugal or roto-dynamic pumps, theoretically can produce the same flow at a given speed no matter what the discharge pressure. Thus, positive displacement pumps are constant flow machines. However, a slight increase in internal leakage as the pressure increases prevents a constant flow rate. A positive displacement pump must not operate against a closed valve on the discharge side of the pump, because it has no shutoff head like centrifugal pumps. A positive displacement pump operating against a closed discharge valve continues to produce flow and the pressure in the discharge line increases until the line bursts, the pump is damaged, or both. A relief or safety valve on the discharge side of the positive displacement pump is therefore necessary; the relief valve can be external. The pump manufacturer has the option to supply internal relief or safety valves; the internal valve is used only as a safety precaution. An external relief valve in the discharge line, with a return line back to the suction line or supply tank provides increased safety.
A positive displacement pump can be further classified according to the mechanism used to move the fluid: Rotary-type positive displacement: internal gear, shuttle block, flexible vane or sliding vane, circumferential piston, flexible impeller, helical twisted roots or liquid-ring pumps Reciprocating-type positive displacement: piston pumps, plunger pumps or diaphragm pumps Linear-type positive displacement: rope pumps and chain pumps These pumps move fluid using a rotating mechanism that creates a vacuum that captures and draws in the liquid. Advantages: Rotary pumps are efficient because they can handle viscous fluids with higher flow rates as viscosity increases. Drawbacks: The nature of the pump requires close clearances between the rotating pump and the outer edge, making it rotate at a slow, steady speed. If rotary pumps are operated at high speeds, the fluids cause erosion, which causes enlarged clearances that liquid can pass through, which reduces efficiency. Rotary positive displacement pumps fall into three main types: Gear pumps – a simple type of rotary pump where the liquid is pushed between two gears Screw pumps – the shape of the internals of this pump is two screws turning against each other to pump the liquid Rotary vane pumps – similar to scroll compressors, these have a cylindrical rotor encased in a shaped housing.
As the rotor orbits, the vanes trap fluid between the rotor and the casing, drawing the fluid through the pump. Reciprocating pumps move the fluid using one or more oscillating pistons, plungers, or membranes, while valves restrict fluid motion to the desired direction. In order for suction to take place, the pump must first pull the plunger in an outward motion to decrease pressure in the chamber. Once the plunger pushes back, it will increase the pressure chamber and the inward pressure of the plunger will open the discharge valve and release the fluid into the delivery pipe at a high velocity. Pumps in this category range from simplex, with one cylinder, to in some cases quad cylinders, or more. Many reciprocating-type pumps are triplex cylinder, they can be either single-acting with suction during one direction of piston motion and discharge on the other, or double-acting with suction and discharge in both directions. The pumps can be powered manually, by air or steam
Buoyancy or upthrust, is an upward force exerted by a fluid that opposes the weight of an 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. 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, is equivalent to the weight of the fluid that would otherwise occupy the 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 non-inertial reference frame, which either has a gravitational field or is accelerating due to a force other than gravity defining a "downward" direction.
The center of buoyancy of an object is the centroid of the displaced volume of fluid. Archimedes' principle is named after Archimedes of Syracuse, who first discovered this law in 212 B. C. For objects and sunken, in gases as well as liquids, Archimedes' principle may be stated thus in terms of forces: Any object, wholly or immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object — with the clarifications that for a sunken object the volume of displaced fluid is the volume of the object, for a floating object on a liquid, the weight of the displaced liquid is the weight of the object. More tersely: buoyancy = weight of displaced fluid. Archimedes' principle does not consider the surface tension acting on the body, but this additional force modifies only the amount of fluid displaced and the spatial distribution of the displacement, so the principle that buoyancy = weight of displaced fluid remains valid; the weight of the displaced fluid is directly proportional to the volume of the displaced fluid.
In simple terms, the principle states that the buoyancy force on an object is equal to the weight of the fluid displaced by the object, or the density of the fluid multiplied by the submerged volume times the gravitational acceleration, g. Thus, among submerged objects with equal masses, objects with greater volume have greater buoyancy; this is known as upthrust. Suppose a rock's weight is measured as 10 newtons when suspended by a string in a vacuum with gravity acting upon it. Suppose that when the rock is lowered into water, it displaces water of weight 3 newtons; the force it exerts on the string from which it hangs would be 10 newtons minus the 3 newtons of buoyancy force: 10 − 3 = 7 newtons. Buoyancy reduces the apparent weight of objects that have sunk to the sea floor, it is easier to lift an object up through the water than it is to pull it out of the water. Assuming Archimedes' principle to be reformulated as follows, apparent immersed weight = weight − weight of displaced fluid inserted into the quotient of weights, expanded by the mutual volume density density of fluid = weight weight of displaced fluid, yields the formula below.
The density of the immersed object relative to the density of the fluid can be calculated without measuring any volumes.: density of object density of fluid = weight weight − apparent immersed weight Example: If you drop wood into water, buoyancy will keep it afloat. Example: A helium balloon in a moving car. During a period of increasing speed, the air mass inside the car moves in the direction opposite to the car's acceleration; the balloon is pulled this way. However, because the balloon is buoyant relative to the air, it ends up being pushed "out of the way", will drift in the same direction as the car's acceleration. If the car slows down, the same balloon will begin to drift backward. For the same reason, as the car goes round a curve, the balloon will drift towards the inside of the curve; the equation to calculate the pressure inside a fluid in equilibrium is: f + div σ = 0 where f is the force density exerted by some outer field on the fluid, σ is the Cauchy stress tensor. In this case the stress tensor is proportional to the identity tensor: σ i j = − p δ i j.
Here δij is the Kronecker delta. Using this the above equation becomes: f = ∇ p. Assuming the outer force field is conservative, it can be written as the negative gradient of some scalar valued function: f = − ∇
A berth is a bed or sleeping accommodation on vehicles. Space accommodations have contributed to certain common design elements of berths. While beds on large ships are little different from those on shore, the lack of space on smaller yachts means that bunks must be fit in wherever possible; some of these berths have specific names: V-berth Frequently yachts have a bed in the extreme forward end of the hull. Because of the shape of the hull this bed is triangular, though most have a triangular notch cut out of the middle of the aft end, splitting it into two separate beds and making it more of a V shape, hence the name; this notch can be filled in with a detachable board and cushion, creating something more like a double bed. The term "V-berth" is not used in the UK, instead the cabin as a whole is referred to. Settee berth The archetypal layout for a small yacht has seats running down both sides of the cabin, with a table in the middle. At night, these seats can be used as beds; because the ideal ergonomic distance between a seat-back and its front edge makes for a rather narrow bed, good settee berths will have a system for moving the back of the settee out of the way.
If they are to be used at sea, settee berths must have lee-cloths to prevent the user falling out of bed. Sometimes the settee forms part of a double bed for use in harbour using detachable pieces of the table and extra cushions; such beds are not referred to as settee berths. Pilot berth A narrow berth high up in the side of the cabin above and behind the back of the settee and right up under the deck. Sometimes the side of this bunk is "walled in" up to the sleeper's chest; the pilot berth is so called because they were so small and uncomfortable that nobody slept in them most of the time. Quarter berth A single bunk tucked under the cockpit. Found in smaller boats where there is not room for a cabin in this location. Lee cloths Are sheets of canvas or other fabric attached to the open side of the bunk and tucked under the mattress during the day or when sleeping in harbour; the lee cloth keeps the sleeping person in the bunk from falling out when the boat heels during sailing or rough weather.
Long-distance trains running at night have sleeping compartments with sleeping berths. In the case of compartments with two berths, one is on top of the other in a double-bunk arrangement; these beds are designed in conjunction with seats which occupy the same space, each can be folded away when the other is in use. Sleeper trains are common in Europe. There are nightly sleeper trains in most countries. Sleeper trains consist of single or double-berth compartments as well as couchettes which have 4 or 6 berths. Long-haul truckers sleep in berths known as sleeper cabs contained within their trucks; the sleeper-berth's size and location is regulated. Couchette car Pullman car
Sinking of the RMS Titanic
RMS Titanic sank in the early morning of 15 April 1912 in the North Atlantic Ocean, four days into the ship's maiden voyage from Southampton to New York City. The largest ocean liner in service at the time, Titanic had an estimated 2,224 people on board when she struck an iceberg at around 23:40 on Sunday, 14 April 1912, her sinking two hours and forty minutes at 02:20 on Monday, 15 April, resulted in the deaths of more than 1,500 people, making it one of history's deadliest marine disasters during peacetime. Titanic received six warnings of sea ice on 14 April but was travelling near her maximum speed when her lookouts sighted the iceberg. Unable to turn enough, the ship suffered a glancing blow that buckled her starboard side and opened six of her sixteen compartments to the sea. Titanic had been designed to stay afloat with four of her forward compartments flooded but no more, the crew soon realised that the ship would sink, they used distress flares and radio messages to attract help as the passengers were put into lifeboats.
In accordance with existing practice, Titanic's lifeboat system was designed to ferry passengers to nearby rescue vessels, not to hold everyone on board simultaneously. Compounding this, poor management of the evacuation meant many boats were launched before they were full; as a result, when Titanic sank, over a thousand passengers and crew were still on board. All those who jumped or fell into the water either drowned or died within minutes due to the effects of cold shock and incapacitation. RMS Carpathia arrived on the scene about an hour and a half after the sinking and rescued the last of the survivors by 09:15 on 15 April, some nine and a half hours after the collision; the disaster shocked the world and caused widespread outrage over the lack of lifeboats, lax regulations, the unequal treatment of the three passenger classes during the evacuation. Subsequent inquiries recommended sweeping changes to maritime regulations, leading to the establishment in 1914 of the International Convention for the Safety of Life at Sea.
At the time of her entry into service on 2 April 1912, Royal Mail Ship Titanic was the second of three Olympic-class ocean liner sister ships, was the largest ship in the world. She and her sister, RMS Olympic, were one and a half times the gross register tonnage of Cunard's RMS Lusitania and RMS Mauretania, the previous record holders, were nearly 100 feet longer. Titanic could carry 3,547 people in speed and comfort, was built on an unprecedented scale, her reciprocating engines were the largest, built, standing 40 feet high and with cylinders 9 feet in diameter requiring the burning of 600 long tons of coal per day. Her passenger accommodation the First Class section, was said to be "of unrivalled extent and magnificence", indicated by the fares that First Class accommodation commanded; the Parlour Suites with private promenade cost over US$4,350 for a one-way transatlantic passage. Third Class, though less luxurious than Second and First Classes, was unusually comfortable by contemporary standards and was supplied with plentiful quantities of good food, providing her passengers with better conditions than many of them had experienced at home.
Titanic's maiden voyage began shortly after noon on 10 April 1912 when she left Southampton on the first leg of her journey to New York. A few hours she called at Cherbourg in northern France, a journey of 80 nautical miles, where she took on passengers, her next port of call was Queenstown in Ireland. She left in the afternoon after taking on more stores. By the time she departed westwards across the Atlantic she was carrying 892 crew members and 1,320 passengers; this was only about half of her full passenger capacity of 2,435, as it was the low season and shipping from the UK had been disrupted by a coal miners' strike. Her passengers were a cross-section of Edwardian society, from millionaires such as John Jacob Astor and Benjamin Guggenheim, to poor emigrants from countries as disparate as Armenia, Italy, Sweden and Russia seeking a new life in America; the ship was commanded by 62-year-old Captain Edward John Smith, the most senior of the White Star Line's captains. He had four decades of seafaring experience and had served as captain of RMS Olympic, from which he was transferred to command Titanic.
The vast majority of the crew who served under him were not trained sailors, but were either engineers, firemen, or stokers, responsible for looking after the engines. The six watch officers and 39 able seamen constituted only around five percent of the crew, most of these had been taken on at Southampton so had not had time to familiarise themselves with the ship; the ice conditions were attributed to a mild winter that caused large numbers of icebergs to shift off the west coast of Greenland. A fire had begun in one of Titanic's coal bins 10 days prior to the ship's departure, continued to burn for several days into the voyage, but it was over on 14 April; the weather improved during the course of the day, from brisk winds and moderate seas in the morning to a crystal-clear calm by evening, as the ship's path took her beneath an arctic high pressure system. The waning crescent moon had set a few seconds after 15:00 on 14 Apri
In ships, frames are ribs that are transverse bolted or welded to the keel. Frames give the ship its shape and strength. In wooden shipbuilding, each frame is composed of several sections, so that the grain of the wood can follow the curve of the frame. Starting from the keel, these are the floor, the first futtock, the second futtock, the top timber, the rail stanchion. In steel shipbuilding, the entire frame can be formed in one piece by welding sections. Frame numbers are the numerical values given to the frames; the total number vary per the length of a ship. The frames support lengthwise members which run parallel from the bow to the stern; the clamp supports the transverse deck beams. Turpin, Edward A.. Merchant Marine Officers' Handbook. Centreville, MD: Cornell Maritime Press. ISBN 0-87033-056-X. Navy Ship Compartment Numbering
Science and technology of the Song dynasty
The Song dynasty provided some of the most significant technological advances in Chinese history, many of which came from talented statesmen drafted by the government through imperial examinations. The ingenuity of advanced mechanical engineering had a long tradition in China; the Song engineer Su Song admitted that he and his contemporaries were building upon the achievements of the ancients such as Zhang Heng, an astronomer and early master of mechanical gears. The application of movable type printing advanced the widespread use of woodblock printing to educate and amuse Confucian students and the masses; the application of new weapons employing the use of gunpowder enabled the Song to ward off its militant enemies—the Liao, Western Xia, Jin with weapons such as cannons—until its collapse to the Mongol forces of Kublai Khan in the late 13th century. Notable advances in civil engineering and metallurgy were made in Song China, as well as the introduction of the windmill to China during the thirteenth century.
These advances, along with the introduction of paper-printed money, helped revolutionize and sustain the economy of the Song dynasty. Polymath geniuses – that is, people knowledgeable across an encyclopaedic range of topics – such as Shen Kuo and Su Song embodied the spirit of early empirical science and technology in the Song era. Shen is famous for discovering the concept of true north and magnetic declination towards the North Pole by calculating a more accurate measurement of the astronomical meridian, fixing the calculated position of the pole star that had shifted over the centuries; this allowed sailors to navigate the seas more with the magnetic needle compass first described by Shen. Shen was made famous for his written description of the inventor of movable type printing. Shen was interested in geology, as he formulated a theory of geomorphology and climate change over time after making observations of strange natural phenomena. Using contemporary knowledge of solar eclipses and lunar eclipses, he theorized that the sun and moon were spherical in shape, not flat, while expanding upon the reasoning of earlier Chinese astronomical theorists.
Along with his colleague Wei Pu in the Bureau of Astronomy, Shen used cosmological hypotheses when describing the variations of planetary motion, including retrogradation. One of Shen's greatest achievements, aided by Wei Pu, was correcting the lunar error by diligently recording and plotting the moon's orbital path three times a night over a period of five years. Shen had many political rivals at court who were determined to sabotage his work; the court accepted their corrections to lunar and solar error, but only adopted Shen and Wei's corrected plotting of the planetary orbital paths and various speeds. Su Song, one of Shen Kuo's political rivals at court, wrote a famous pharmaceutical treatise in 1070 known as the Bencao Tujing, which included related subjects on botany, zoology and mineralogy; this treatise included many medicinal applications, including the use of ephedrin as a pharmaceutical drug. He was the author of a large celestial atlas of five different star maps, his extensive written and illustrative work in cartography helped solve a heated border dispute between the Song dynasty and its Khitan neighbor of the Liao dynasty.
However, Su was most famous for his hydraulic-powered astronomical clock tower, crowned with a mechanically driven armillary sphere, erected in the capital city of Kaifeng in the year 1088. Su's clock tower employed the escapement mechanism two centuries before it was applied in clocks of Europe. Su's clock tower featured the earliest known endless power-transmitting chain drive in the world, as outlined in his horological treatise of 1092; the cases of these two men display the eagerness of the Song in drafting skilled officials who were knowledgeable in the various sciences which could benefit the administration, the military, the economy, the people. Intellectual men of letters like the versatile Shen Kuo dabbled in subjects as diverse as mathematics, geology, engineering, art criticism, military strategy, diplomacy, among others. On a court mission to inspect a frontier region, Shen Kuo once made a raised-relief map of wood and glue-soaked sawdust to show the mountains, roads and passes to other officials.
He once computed the total number of possible situations on a game board, another time the longest possible military campaign given the limits of human carriers who would bring their own food and food for other soldiers. Shen Kuo is noted for improving the designs of the inflow clepsydra clock for a more efficient higher-order interpolation, the armillary sphere, the gnomon, the astronomical sighting tube. Shen Kuo experimented with camera obscura, only a few decades after the first to do so, Ibn al-Haytham. There were many other important figures in the Song era besides Shen Kuo and Su Song, many of whom contributed to the technological innovations of the time period. Although the mechanically driven mile-marking device of the carriage-drawn odometer had been known in China since the ancient Han dynasty, the Song Shi provides a much greater description and more in-depth view of the device than earlier Chinese sources; the Song Shi states: The odometer. is painted red, with pictures of flowers and birds on the four sides, constructed in two storeys, handsomely adorned with carvings.
At the completion of every li, the wooden figure of a man in the lowe