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单选题
Aqueous Film Forming Foam (AFFF), commonly known as ‘light water’, is especially suitable for fighting （）
A
oil fires in the engine room bilges
B
class B fires in paint lockers
C
any class D fire
D
all of the above
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The BEST method of applying foam to a fire is to ______.A.spray directly on the base of the fireB.flow the foam down a nearby vertical surfaceC.sweep the fire with the foamD.spray directly on the surface of the fire
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When replacing a thermostatic expansion valve sensing bulb, it is necessary toA.apply a light film of oil to increase heat transferB.apply a light film of oil to prevent oxidationC.apply a heavy coating of grease to function as a heat sinkD.carefully coat the device with silicone sealant to reduce the effects of convective cooling
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Learn about Light1 .Ancient civilizations were amazed by the existence of light for thousands of years. The Greek philosophers believed that light was made up of countless,tiny particles that enter the human eye and create what we call vision. However,Empedocles and a Dutch scientist named Christian Huygens believed that light was like a wave. According to them,light spread out and travelled like a straight line. This theory was accepted during the 19th century.2 .In 1905,Albert Einstein published a research paper in which he explained what is re-ferred to as the photoelectric effect. This theory explains that particles make up light.The particles Einstein was referring to are weightless bundles（束）of electromagnetic（电磁）energy called photons（光子）.Today,scientists agree that light has a dual（二重）nature一it is part particle and part wave. It is a form of energy that allows us to see things around us.3 .Things that give off light are known as sources of light. During the day,the primary source of light is the sun. Other sources of light include stars,flames,flashlights,street lamps and glowing gases in glass tube.4 .When we draw the way light travels we always use straight lines. This is because nor-mally light rays travel in a straight line. However,there are some instances that can change the path and even the nature of light. They are reflection,absorption,interference（干扰）, etc.5 .Physicists have attempted to measure the speed of light since the early times. In 1849, Hippolyte Fizeau conducted an experiment by directing a beam of light to a mirror located kilometers away and placed a rotating cogwheel（旋转齿轮）between the beam and the mirror. From the rate of rotation of the wheel,number of wheel's teeth and distance of the mirror,he was able to calculate that the speed of light is 313 million meters per second. In a vacuum（真空）,however,the speed of light is 299,792,458 meters per second. This is about a million times faster than the speed of an airplane.Paragraph 5______A: How Is the Nature of Light Explained Today?B: What Are Sources of Light?C: How Did Physicists Measure the Speed of Light?D: How Does Light Travel?E: How Did People Think of Light Years Ago?F: What Causes a Shadow?
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共用题干
Better Solar Energy Systems:More Heat,More LightSolar photovoltaic（光电的）thermal energy systems , or PVTs , generate both heat and electricity , but _________ (51)now they haven't been very good at the heat-generating part compared to a stand-alone solar thermal collector. That ' s because they operate at low temperatures to cool crystalline silicon（晶体硅）solar cells, _______(52)lets the silicon generate more electricity but isn't a very efficient way to gather heat.That's a problem of economics.Good solar hot-water systems can harvest much more energy than asolar一electric system at a substantially lower _________(53).And it's also a space problem:photovoltaiccells can_________(54)up all the space on the roof,leaving little room for thermal applications.In a pair of studies,Joshua Pearce,an associate professor of materials science and engineering,has de- vised a_________(55)in the form of a better PVT made with a different kind of silicon.Most solar panels are made with crystalline silicon,but you can also make solar cells out of amorphous（非晶形的）silicon , commonly known________( 56 ) thin-film silicon. They don ' t create as much elec-tricity,but they are lighter,flexible,and cheaper. And,because they________(57)much less silicon,they have a greener footprint._________(58),thin-film silicon solar cells are vulnerable to some bad一news physics in the form of the Staebler-Wronski effect."That means that their efficiency drops when you_________(59)them to light一pretty much the worst possible effect for a solar cell,"Pearce explains,which is one of the__________(60)thin-film solar panels make up only a small fraction of the market.However,Pearce and his team found a_______(61)to engineer around the Staebler-Wronski effect by incorporating thin-film silicon in a new________(62)of PVT. You don't have to cool down thin-film sili- con to make it work.In fact,Pearce's group discovered that by heating it to solar-thermal operating tempera- tures,near the boiling_________(63)of water,they could make thicker cells that largely_________(64) the Staebler-Wronski effect.When they applied the thin-film silicon directly to a solar thermal energy collector, they also found that by baking the cell once a day,they_________(65)the solar cell's electrical efficiency by over 10 percent._________(57)A:retrieveB:requireC:mergeD:exchange
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共用题干
Better Solar Energy Systems: More Heat, More LightSolar photovoltaic thermal energy systems,or PVTs,generate both heat and electricity,but until now they haven't been very good at the heat-generating part compared to a stand-alone solar thermal collector. That's because they operate at low temperatures to cool crystalline silicon solar cells,which lets the silicon generate more electricity but isn't a very efficient way to gather heat.That's a problem of economics. Good solar hot-water systems can harvest much more energy than a solar-electric system at a substantially lower cost. And it's also a space problem:photovol-taic cells can take up all the space on the roof,leaving little room for thermal applications.In a pair of studies,Joshua Pearce,an associate professor of materials science and engineer-ing,has devised a solution in the form of a better PVT made with a different kind of silicon.His research collaborators are Kunal Girotra from Thin Silicon in California and Michael Pathak and Stephen Harrison from Queen's University,Canada.Most solar panels are made with crystalline silicon,but you can also make solar cells out of amorphous silicon,commonly known as thin-film silicon.They don't create as much electricity, but they are lighter,flexible,and cheaper. And,because they require much less silicon,they have a greener footprint. Unfortunately,thin-film silicon solar cells are vulnerable to some bad-news physics in the form of the Staebler-Wronski effect."That means that their efficiency drops when you expose them to light-pretty much the worst possible effect for a solar cell,"Pearce explains,which is one of the reasons thin-film solar panels make up only a small fraction of the market.However,Pearce and his team found a way to engineer around the Staebler-Wronski effect by incorporating thin-film silicon in a new type of PVT. You don't have to cool down thin-film silicon to make it work.In fact,Pearce's group discovered that by heating it to solar-thermal operating temperatures,near the boiling point of water,they could make thicker cells that largely overcame the Staebler-Wronski effect. When they applied the thin-fulm silicon directly to a solar thermal en-ergy collector,they also found that by baking the cell once a day,they boosted the solar cell's e-lectrical efficiency by over 10 percent. Which of the following statrnents is true?A: Thin-film silicon's electrical efficiency improves when heated up.B: New techniques have been developed to produce thin-film silicon.C: Thin-film silicon works efficiently at low temperature.D: A new material enlarging the Staebler-WronsKi effect has been created.
考题
共用题干
Learn About Light1 Ancient civilizations were amazed by the existence of light for thousands of years?The Greek philoso- phrrs believed that light was made up of countless,tiny particles that enter the human eye and create what we call vision.However,Empedocles and a Dutch scientist named Christian Huygens believed that light wag like a wave.According to them,light spread out and travelled like a straight line.This theory was acceptedduring the 19th century.2 In 1905,Albert Einstein published a research paper in which he explained what is referred to as the photoelectric effect.This theory explains that particles make up light.The particles Einstein was referring to are weightless bundles（束）of electromagnetic（电磁）energy called photons（光子）.Today,scientists agree that light has a dual（二重）nature一it is part particle and part wave. It is a form of energy that allows us tosee things around us.3 Things that give off light are known as sources of light.During the day,the primary source of light is the sun.Other sources of light include stars,flames,flashllights,street lamps and glowing gases in glass tube.4 When we draw the way light travels we always use straight lines.This is because normally light rays travel in a straight line.However,there are some instances that can change the path and even the nature of light. They are reflection,absorption,interference（干扰）,etc.5 Physicists have attempted to measure the speed of light since the early times.In 1849,Hippolyte Fizeau conducted an experiment by directing a beam of light to a mirror located kilometers away and placed a rotating cogwheel（旋转齿轮）between the beam and the mirror. From the rate of rotation of the wheel, number of wheel'S teeth and distance of the mirror,he was able to calculate that the speed of light is 313 million meters per second.In a vacuum（真空）,however,the speed of light is 299,792,458 meters per second.This is about a million times faster than the speed of an airplane.Objects are visible to the human eye as light is_______. A:sources of lightB:the speed of light C:the path of lightD:a straight lineE:a beam of lightF:a form of energy
考题
A technician is troubleshooting a monitor displaying a blank screen and the power indicator light ison. Which of the following should the technician do next?（）A、Test the computer with a known-good monitor.B、Check if the monitor is still covered under the manufacturer’s warranty.C、Replace the monitor’s power cord with a known-good power cord.D、Swap out the computer’s video card.
考题
单选题A portable foam fire extinguisher is placed in operation by（）A
turning it upside downB
pressing the foam leverC
squeezing the grip handleD
opening the hose valve
考题
单选题Production of mechanical foam by a portable in-line foam proportioner（）.A
increases the size of foam bubbles formedB
increases the rate of foam productionC
improves the extinguishing properties of foamD
gives the nozzleman more freedom of movement，since it can be placed anywhere in the hose line
考题
单选题A change in engine speed is required before a governor is able to make a corrective movement of fuel rackThis aspect of governing is commonly expressed as a percent and is known as （）A
governor sensitivityB
governor promptnessC
speed droopD
isochronous governing
考题
单选题The type of fog that occurs on clear nights with very light breezes and forms when the earth cools rapidly by radiation is known as（）.A
Radiation fogB
Frontal fogC
Convection fogD
Advection fog
考题
单选题A camera takes light rays bounced off objects and _____ them on a sheet of a film.A
concentratesB
mixesC
combinesD
focuses
考题
单选题At 0530，your position is LAT 41°12.6’N，LONG 72°08.5’W. What is the color of New London Light?（）A
GreenB
WhiteC
RedD
Alternating white and green
考题
单选题Which of the following characteristic of lube oil helps to reduce the amount of deposits in the piston ring belt during the combustion process in a diesel engine?（）A
Low viscosity indexB
Low carbon forming tendenciesC
High film strengthD
High non-corrosive qualities
考题
单选题Which of the following statements regarding low expansion foam and its application is INCORRECT?（）.A
Foam should not be used on electrical firesB
One kilo of low expansion foam solution produces much more foamC
Foam is only efficient when it covers the top of burning combustiblesD
A stream of foam should be deflected off the deck in order to best agitate the fire
考题
单选题Enormously creative yet focused on his own commercial success, the film depicts Warhol as a complex and enigmatic figure.A
the film depicts Warhol asB
the film is a depiction of Warhol asC
Warhol in the film has been the depiction ofD
Warhol is depicted in the film asE
Warhol is depicted by the film for
考题
单选题The usual method of effectively applying foam on a fire is by （）.A
spraying directly on the base of the fireB
flowing the foam down a vertical surfaceC
sweeping the fire before you with the foamD
spraying directly on the surface of the fire
考题
单选题The BEST method of applying foam to a fire is to（）.A
spray directly on the base of the fireB
flow the foam down a nearby vertical surfaceC
sweep the fire with the foamD
spray directly on the surface of the fire
考题
单选题0ne of the limitations of foam as an extinguishing agent is that foam（）.A
cannot be made with salt waterB
is heavierthan oil and sinks below its surfaceC
is corrosive and to fire fightersD
conducts electricity
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