Most propellers on merchant vessels are constructed of______．A.manganese bronzeB.cast ironC.mild steelD.improved plow steel
Most propellers on merchant vessels are constructed of______．
A.manganese bronze
B.cast iron
C.mild steel
D.improved plow steel
相关考题：
The SOLAS Convention in its successive forms is generally regarded as the most important of all international treaties concerning the ______of merchant ships.A.pollutionB.economizationC.safetyD.efficiency
The most common type of davit found on merchant vessels today is the ______．A.RadialB.Sheath-screwC.GravityD.Quadrantal
Which statement about tunnel bow thrusters fitted to large vessels is TRUE ________．A.They are effective on most vessels at speeds up to 10 knotsB.Because of their location，most modern installations have as much power as a tugC.They are fully effective at all draftsD.When going astern at slow speed，they provide effective steering control
Aboard damaged vessels, the MOST important consideration is preserving ______.A.bilge pumping capacityB.reserve buoyancyC.level attitudeD.Instability
Kort nozzles are installed around the propellers of some vessels to ______.A.increase the thrust of the propellerB.protect the propeller from striking sawyersC.protect the propeller from striking barges towed on the hipD.protect the propeller from touching bottom in low water
共用题干第三篇Iron DeficienciesExperts have observed for years that endurance athletes,particularly females,frequently have iron deficiencies.Now a new study by a team of Purdue University researchers suggests that even moderate exercise may lead to reduced iron in the blood of women."We found that women who were normally inactive and then started a program of moderate exercise showed evidence of iron loss,"says Roseanne M.Lyle,associate professor at Purdue.Her study of 62 formerly inactive women who began exercising three times a week for six months was published in the journal Medicine & Science in Sports & Exercise."Women who consumed additional meat or took iron supplements were able to bounce back,"she notes."But the new exercisers who followed their normal diet showed a significant decrease in iron levels."Iron deficiency is very common among women in general,affecting one in four female teenagers and one in five women aged 18 to 45,respectively.But the ratio is even greater among active women,affecting up to 80 percent of female endurance athletes.This means,Lyle says,that"too many women ignore the amount of iron they take in."Women of childbearing age are at greatest risk,since their monthly bleeding is a major source of iron loss.Plus,many health-conscious women increase their risk by rejecting red meat,which contains the most easily absorbed form of iron.And because women often restrict their diet in an effort to control weight,they may not consume enough iron-rich food,and are liable to experience a deficiency."The average woman takes in only two thirds of the recommended daily allowance of iron," notes another expert."For a woman who already has a poor iron status,any additional iron loss from exercise may be enough to tip her over the edge into a more serious deficiency,"notes the expert. Exercise can result in iron loss through a variety of mechanisms.Some iron is lost in sweat,and,for unknown reasons,intense endurance exercise is sometimes associated with bleeding of the digestive system.The best sources of iron,and the only sources of the form of iron most readily absorbed by the body,are meat,chicken,and fish.Good sources of other forms of iron include dates,beans,and some leafy green vegetables.Who will have a significant decrease in iron levels?A:All the women.B:All the inactive women.C:Women who start to do moderate exercise and follow their normal diet.D:Women who start to do moderate exercise and consume additional meat or take iron supplements.
共用题干第三篇Iron DeficienciesExperts have observed for years that endurance athletes,particularly females,frequently have iron deficiencies.Now a new study by a team of Purdue University researchers suggests that even moderate exercise may lead to reduced iron in the blood of women."We found that women who were normally inactive and then started a program of moderate exercise showed evidence of iron loss,"says Roseanne M.Lyle,associate professor at Purdue.Her study of 62 formerly inactive women who began exercising three times a week for six months was published in the journal Medicine & Science in Sports & Exercise."Women who consumed additional meat or took iron supplements were able to bounce back,"she notes."But the new exercisers who followed their normal diet showed a significant decrease in iron levels."Iron deficiency is very common among women in general,affecting one in four female teenagers and one in five women aged 18 to 45,respectively.But the ratio is even greater among active women,affecting up to 80 percent of female endurance athletes.This means,Lyle says,that"too many women ignore the amount of iron they take in."Women of childbearing age are at greatest risk,since their monthly bleeding is a major source of iron loss.Plus,many health-conscious women increase their risk by rejecting red meat,which contains the most easily absorbed form of iron.And because women often restrict their diet in an effort to control weight,they may not consume enough iron-rich food,and are liable to experience a deficiency."The average woman takes in only two thirds of the recommended daily allowance of iron," notes another expert."For a woman who already has a poor iron status,any additional iron loss from exercise may be enough to tip her over the edge into a more serious deficiency,"notes the expert. Exercise can result in iron loss through a variety of mechanisms.Some iron is lost in sweat,and,for unknown reasons,intense endurance exercise is sometimes associated with bleeding of the digestive system.The best sources of iron,and the only sources of the form of iron most readily absorbed by the body,are meat,chicken,and fish.Good sources of other forms of iron include dates,beans,and some leafy green vegetables.Who will show evidence of iron loss?A:Inactive women.B:Active women.C:Women who do a program of moderate exercises regularly.D:Women who are inactive and start to do moderate exercises.
单选题The main office building was constructed on the most ______ piece of land in town.AdesirableBdesireCdesiredDdesirably
单选题（）are increasingly used as main engine on merchant vessels, because they have a high Hp/Weight ratio.ASlow speed diesel enginesBMedium-speed diesel enginesCSteam enginesDGasoline engines
单选题Fire extinguishers on inspected vessels are numbered by size I through V，with I being（）.Aused for electrical fires onlyBthe smallestCthe most accessibleDthe most effective
单选题（） can be found on most medium to large merchant vessels even if the main engine is either a steam turbine or 2-stroke crosshead engine.AThe medium speed 4-stroke trunk piston engineBThe low speed 2-stroke crosshead engineCThe medium speed 2-stroke crosshead engineDThe low speed 4-stroke trunk piston engine
单选题Most very large ocean going vessels，such as bulk carriers and large tankers，tend to squat（）.Aby the bowBby the sternCat the end nearest the bottomDevenly fore and aft
单选题Fire detecting systems on merchant vessels may be arranged to sense （）.AsmokeBrate of temperature riseCionized particlesDall of the above
单选题Cast irons weakness in tension and under shock loading limits its use to low pressure steam, air, oil and low speed water fittingsThe above sentence, most probably means （）.Acast iron has weaknessBcast iron can stand up shock loadingCcast iron fittings are only suitable in low pressure situationDeast iron fittings are not suitable in low pressure situation
单选题To prevent damage by and to storage batteries aboardsmall passenger vessels they should be located（）.Ain trays constructed of material that is resistant to the electrolyteBso as to prevent movement when the vessel pitches and rollsCin a well ventilated areaDAll of the above
单选题The reason why more and more of the large merchant vessels are being powered by medium-speed diesel engines is （）.Athey operate between 150 and 450 rpmBthey are connected to the propeller by gearingCtheir smaller size and weightDthey can be connected directly to the propeller without gearing
单选题Several merchant ships are arriving at the scene of a distress incident. One of the them must assume the duties of the Coordinator Surface Search (CSS). Which of the following statements is TRUE?（）.ACSS duties are always assumed by passenger vessels，dry cargo vessels，or tankers in that order of precedenceBThe CSS must be established by mutual agreement between the ships concernedCA tanker should never be assigned CSS duties unless only tankers are presentDThe first vessel to arrive at the distress incident is designated as the CSS
单选题For vessels with （）, the meaning of the order would include the combination of pitch and revolutions as indicated in ships orders.Afixed pitch propellersBuncontrollable pitch propellerCconstant pitch propellersDvariable pitch propellers
单选题Kort nozzles are installed around the propellers of some vessels to（）.AIncrease the thrust of the propellerBProtect the propeller from striking sawyersCPrevent the propeller from striking barges towed on the shipDPrevent the propeller from touching bottom in low water
单选题On tank vessels equipped with power operated cargo tank valves, the type of power operator most commonly used is （）.AhydraulicBelectricCsteamDdiesel
单选题Most conducting materials such as copper, aluminum, iron, nickel, and tungsten （）.Aincrease in resistance with increased temperatureBincrease in resistance with decreased temperatureCdecrease in resistance with increased temperatureDincrease in conductance with increased temperature
单选题Cast iron pistons used in large propulsion diesel engines are constructed with （）Anot taper what so everBthe skirt being tapered and smaller than the crownCthe skirt being tapered and larger than the crownDthe crown being tapered and smaller than the skirt
单选题Several merchant ships are arriving at the scene of a distress incident. One of the them must assume the duties of the Coordinator Surface Search (CSS). Which of the following statements is TRUE? （）ACSS duties are always assumed by passenger vessels，dry cargo vessels，or tankers in that order of precedenceBThe CSS must be established by mutual agreement between the ships concernedCA tank vessel should never be assigned CSS duties unless only tank vessels are presentDThe first vessel to arrive at the distress incident is designated as the CSS
单选题Most propellers on merchant vessels are constructed of（）.Amanaganese bronzeBcast ironCmild steelDimproved plow steel
单选题Aboard damaged vessels，the MOST important consideration is preserving（）.Abilge pumping capacityBreserve buoyancyClevel attitudeDinstability
单选题After the Civil War the American clipper ships were gradually _____ by even larger and faster iron vessels.AchangedBtakenCreplacedDexchanged
单选题In most cases，when a large merchant vessel enters shallow water at high speed the（）.Amaneuverability will increaseBspeed will increaseCbow will squat farther than the sternDvessel will rise slightly，on a level plane