01-04-2020-Орловская И.В., Самсонова Л.С. Учебник английского языка для технических университетов и вузов (6-е издание, 2006)(1) (1171846), страница 58
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With four or more satellites inview, the receiver can determine the user's 3D position (latitude,longitude and altitude). Once the user's position has been determined, the GPS unit can calculate other information, such asspeed, bearing (пеленг), track, trip distance, distance to destination, sunrise and sunset time and more.Today's GPS receivers are extremely accurate within an average of three to five meters thanks to their parallel multi-channeldesign.The 24 satellites that make up the GPS space segment are orbiting the earth about 12,000 miles above us.
They are constantlymoving, making two complete orbits in less than 24 hours. Thesesatellites are travelling at speeds of roughly 7,000 miles an hour.GPS satellites are powered by solar energy. They have backupbatteries onboard to keep them running in the event of a solareclipse (затмение), when there's no solar power. Small rocketboosters on each satellite keep them flying in the correct path.Here are some other interesting facts about the GPS satellites:1.
The first GPS satellite was launched in 1978.2. A full constellation (созвездие) of 24 satellites was achievedin 1994.3. Each satellite is built to last about 10 years. Replacements areconstantly being built and launched into orbit.4. A GPS satellite weighs approximately 2,000 pounds and isabout 17 feet across with the solar panels extended.5. Transmitter power is only 50 watts or less.GPS satellites transmit two low power radio signals. The signalstravel by line of sight, meaning they will pass through clouds, glassand plastic but will not go through most solid objects such as buildings and mountains.A GPS signal contains three different bits of information — apseudorandom code, ephemeris data and almanac data.Some factors that can degrade the GPS signal and thus affectaccuracy include the following:1.
The satellite signal slows as it passes through the atmosphere.2702. The GPS signal is reflected off objects such as tall buildingsor large rock surfaces before it reaches the receiver. This increasesthe travel time of the signal, thereby causing errors.3. A receiver's built-in clock is not as accurate as the atomicclocks onboard the GPS satellites. Therefore, it may have veryslight timing errors.4. The more satellites a GPS receiver can «see,» the better theaccuracy.
Buildings, terrain, electronic interference, or sometimeseven dense foliage (листва) can block signal reception, causing position errors or possibly no position reading at all. GPS units typically will not work indoors, underwater or underground.To be read after Lesson 9Getting into Deep WaterThe dark depths of the Gulf of Mexico, once frequented by onlythe sea creatures, are now alive with human activity.
Miniaturesubmarines and robot-like vehicles move around the ocean bottomwhile divers make their way around incredible underwater structures — taller than New York City skyscrapers, but almost totallybeneath the surface of the waves. Modem-day explorers are usingtechnology worth of Jules Verne and Jacques Cousteau to find freshsupplies of oil and natural gas.Until recently, drilling in the Gulf was concentrated close toshore in water as deep as 9 m.
But now the scientists are looking tohundreds of meters deep and 160 km and more from land.The deep water research began in 1984. Since then many American companies have built the world's deepest production platforms of more than 100 storeys high. Finding gas and oil deposits atlarge depth is not an easy technological task.Voyage to the Bottom of the SeaThere is an American project of one-person submarine, whichwill «fly» to the bottom on inverted wings rather than simply sinking under its own weight as the bathyscaphes did.
This design ismore like an aeroplane than a balloon. It could one day make exploring the ocean depth as easy as flying a plane is today.The most difficult problem is to find a material that is also lightenough to allow the craft to float back to the surface if there is aloss of power or some other emergency. Alumina, a hard ceramic,was chosen for the vessel.271The pilot's capsule is about a meter in diameter, 5 centimetersthick and about 2 meters long.
It is capped at one end with a ceramic hemisphere and at the other with a glass viewing dome. Therest of the craft, including the wings on either side and the casingat the rear for the motors, are made of a lightweight compositematerial.In addition to the pilot, the pressure vessel houses the controlsand instrument panel, the life-support system and a 24-volt powersupply. The pilot effectively operates the craft by radio control.The batteries feed a pair of electric motors that can drive thecraft at up to 14 knots (25 kilometers per hour).
The craft coulddive vertically but this would be uncomfortable for the pilot wholies face downwards in the cylindrical chamber. So it descends atan angle of up to 45\ «Deep Flight» is designed to be as streamlined as possible. This means making the submarine's cross sectionas small as possible and providing as little equipment as possible onthe hull.At a cruising speed of 10 knots «Deep Flight» will descend at arate of 200 meters per minute and reach 11,000 meters in about anhour in the Mariana Trench (Марианская впадина), the deepestsite on Earth. The weight of the craft is 2.5 tonnes, which is aboutthe same as a large car. This will allow it to be launched from anyvessel.To be read after Lesson 10Laser TechnologyIn the last decade there was outstanding progress in the development of laser technology and its application in science, industryand commerce.
Laser cutting, welding and machining are beginning to be big business. The market for laser systems representsaround 2.5 % of the world machine tool market.Which country is the biggest producer and consumer of lasers?Why, Japan, naturally: Japan produced 46 % of world's lasers in1989, while figures for Europe and the USA are 32 % and 22 %. Japan is building 1,200 to 2,000 CO2 lasers per year of which some95 % are over 500 W power and 80 % of them are used for cuttingoperations.Europe is the second largest user and the third largest producer.In 1990 Europe's market for lasers was $128 million, of whichGermany consumed about $51 million, and Italy — $12 million.272The Germany met 90 % of its demands through domestic producers. Growth rate of the European market is estimated at 10 to 15 %per year.In the future the main trend influencing the industry will be laser source prices.
The prices are dropping. There appear lasers ofmodular construction. The complexity of laser machines is rising.Multi-axes systems are in more use now. Recently a 7-axis CNC laser machining center has been introduced. In addition to X,Y andZ axes, there are two rotary axes, A and C, and two more linearaxes, и and V, to give a trepanning (прорезать большие отверстия) motion to the laser.Optical Disks and DrivesOptical disks can store information at much higher densitiesthan magnetic disks. Thus, they are ideal for multimedia applications where images, animation and sound occupy a lot of diskspace. Besides, they are not affected by magnetic fields.
This meansthat they are secure and stable, e.g. they can be transported throughaiфort metal detectors without damaging the data. However, optical drives are slower than hard disks. While there are hard driveswith an average access time of 8 milliseconds (ms), most CD-ROMdrives have an access time of 150 to 20 ms.There are various types of optical drives, which have become areality. CD-ROM systems use optical technology. The data is retrieved using a laser beam.
To read CD-ROM disks, you need anoptical drive (a CD-ROM player). A typical CD-ROM disk canhold 650 MB (megabytes) of sound, text, photographs, music, multimedia materials and applications. In addition, most CD-ROMdrives can be used to play audio CDs. Do you remember that CDstands for compact disk?Yet CD-ROM technology has one disadvantage. The data on aCD-OM cannot be changed or «written» to, i.e. it is impossible toadd your own material to what is on the disk. It is like a music CD.It is not designed for you to write on, it is designed to hold a lot ofinformation that the user doesn't need to change.Magneto-optical (MO) drives use both a laser and an electromagnet to record information.
Consequently, MO disks arerewritable, that is they can be written to, erased, and than writtenagain. They are available in two formats. Their capacity may bemore than 2 GB (gigabyte) or 230 to 640 MB. Such combined devices are good for back up purposes and storage of large amounts ofinformation such as a dictionary or encyclopaedia.273То be read after Lesson 11Space CoolingA new method of cooling that can generate cryogenic temperatures of 200 °C below zero without the use of electricity and withalmost no moving parts has been tested at the Jet Propulsion Laboratory in Pasadena, California.
The refrigerator used for the purpose was recently tested to — 253 °C, only 20 degrees aboveabsolute zero, the lowest possible temperature.In space such cooling system could increase the life of futurespace station refuelling ports by cooling the large liquid-hydrogenfuel tanks which are likely to be in service.In future earth applications it could be used for cooling hydrogen-powered cars and planes, as well as for cooling superconducting motors and computers.According to the JPL (Jet Propulsion Laboratory) experts thekey lies in the use of hydrides, materials that interact with hydrogen. These materials absorb tremendous amounts of hydrogen gasat room temperature.
The engineers of the JPL have taken advantage of this property to build a series of devices that act as compressors and provide a continuous cooling stream of liquid hydrogen.The system saves weight in space since it can use direct solarheat instead of electricity from heavier, inefficient electric systems.Because it has so few moving parts and uses the same supply of gasin a closed cycle, it could operate for many decades. Because of itslong potential lifetime, the system could be used to cool infraredsensors during missions to the other planets, which may take 10years or more to complete.The Propulsion Challenge^Magsails are a form of solar sails that use a completely differenttype of physical interaction with the Sun.
Magsail is a simple loop(петля, контур) of high-temperature superconducting wire carrying a persistent^ current. The charged particles in the solar wind aredeflected^ by the magnetic field, producing thrust. Although thethrust density in the solar ion wind flux is 5,000 times less than thethrust density in the solar photonflux^,the mass of a solar sail goesdirectly with the area, whereas the mass of the magsail rises withthe perimeter of the enclosed area.The effective cross-sectional area of the magnetic field aroundthe magsail is about a hundred times the physical area of the loop.As a result, preliminary calculations show the thrust-to-weight ra274tio of a magsail can be an order of magnitude (порядок величины)better than a solar sail.
Recent thermal balance calculations indicate that a properly Sun-shielded^ cable can be passively maintained at a temperature of 65 К in space, well below the superconducting transition point for many of the new high temperature superconductors.Notes to the Text1. problem, difficulty, invitation to see which is better2. continuing3. cause to turn away from4. flow5. protectedComputer GraphicsComputer graphics are known to be pictures and drawings produced by computers. A graphics program interprets the input provided by the user and transports it into images that can be displayedon the screen, printed on paper or transferred to microfilm. In theprocess the computer uses hundreds of mathematical formulas toconvert the bits of data into precise shapes and colours. Graphicscan be developed for a variety of uses including illustrations, architectural designs and detailed engineering drawings.Mechanical engineering uses sophisticated programs for applications in computer-aided design (CAD) and computer-aidedmanufacturing (CAM).
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