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“Brittle fracture”和“Ductile Fracture”的含义分别是（）
- A、脆性断裂和延性断裂；
- B、延性断裂和脆性断裂；
- C、脆性断裂和永久变形；
- D、塑性变形和永久变形
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更多 ““Brittle fracture”和“Ductile Fracture”的含义分别是（）A、脆性断裂和延性断裂；B、延性断裂和脆性断裂；C、脆性断裂和永久变形；D、塑性变形和永久变形” 相关考题
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New Understanding of Natural Silk's MysteriesNatural silk,as we all know,has a strength that man-made materials have long struggled to match.In a discovery that sounds more like an ancient Chinese proverb than a materials science breakthrough,MIT re- searchers have discovered that silk gets its strength from its weakness.Or,more specifically,its many weak- nesses. Silk gets its extraordinary durability and ductility（柔韧性）from an unusual arrangement of hydrogen bonds that are intrinsically very weak but that work together to create a strong,flexible structure.Most materials一especially the ones we engineer for strength一get their toughness from brittleness.As such,natural silks like those produced by spiders have long fascinated both biologists and engineers because of their light weight,ductility and high strength(pound for pound,silk is stronger than steel and far less brittle). But on its face,it doesn't seem that silks should be as strong as they are;molecularly,they are held together by hydrogen bonds , which are far weaker than the covalent（共价的）bonds found in other molecules.To get a better understanding of how silk manages to produce such strength through such weak bonds, the MIT team created a set of computer models that allowed them to observe the way silk behaves at the atomic level. They found that the arrangement of the tiny silk nanocrystals（纳米晶体）is such that the hydro- gen bonds are able to work cooperatively,reinforcing one another against external forces and failing slowlywhen they do fail,so as not to allow a sudden fracture to spread across a silk structure.The result is natural silks that can stretch and bend while retaining a high degree of strength.But while that's all well and good for spiders,bees and the like,this understanding of silk geometry could lead to new materials that are stronger and more ductile than those we can currently manufacture.Our best and strongest materials are generally expensive and difficult to produce(requiring high temperature treatments or energy-intensive processes).By looking to silk as a model,researchers could potentially devise new manufacturing methods that rely on inexpensive materials and weak bonds to create less rigid,more forgiving materials that are nonetheless stronger than anything currently on offer. And if you thought you were going to get out of this materials science story without hearing about carbon nanotubes（纳米碳管）, think again. The MIT team is already in the lab looking into ways of synthesizing silk-like structures out of materials that are stronger than natural silk-like carbon nanotubes. Super-silks are on the horizon.Biologists and engineers are interested in understanding natural silks because they are very light and brittle.A:RightB:WrongC:Not mentioned
考题
总体分布正态，总体方差已知，从总体中随即抽取容量为25的小样本。用样本平均数估计总体平均数的置信区间为（ ）
A.{img src="/main/97/u/2011040805490056962}frac{sigma}{sqrt{n-1}}" align='absmiddle'/}
B.{img src="/main/97/u/2011040805490056972}frac{sigma}{sqrt{n-1}}" align='absmiddle'/}
C.{img src="/main/97/u/2011040805490056982}frac{sigma}{sqrt{n}}" align='absmiddle'/}
D.{img src="/main/97/u/2011040805490056992}frac{sigma}{sqrt{n}}" align='absmiddle'/}
考题
总体分布正态，总体方差未知，从总体中随即抽取容量为25的小样本，此样本的标准差为S。用样本平均数估计总体平均数的置信区间为（ ）
A.{img src="/main/97/u/2011040805485456772^sigma overline{x}}" align='absmiddle'/}
B.{img src="/main/97/u/2011040805485456782^sigma overline{x}}" align='absmiddle'/}
C.{img src="/main/97/u/2011040805485456792}frac{S}{sqrt{n-1}}" align='absmiddle'/}
D.{img src="/main/97/u/2011040805485456802}frac{S}{sqrt{n-1}}" align='absmiddle'/}
考题
从“Ductile Fracture”的特征，以下哪一种说法是正确的（）A、断裂前无明显的塑性变形（永久变形），吸收的能量很少；B、明显的永久变形，并且经常有缩颈现象C、裂纹的扩展速度往往很快，几近音速。D、脆性断裂无明显的征兆可寻，断裂是突然发生的
考题
从“Brittle fracture”的特征，以下哪一种说法是错误的（）A、断裂前无明显的塑性变形（永久变形），吸收的能量很少；B、有一定的永久形变C、裂纹的扩展速度往往很快，几近音速。D、脆性断裂无明显的征兆可寻，断裂是突然发生的
考题
单选题Fracture damage to the end links of the anchor cable，or to the jews’ harp may be eliminated by（）.A
using a small diameter connecting shackleB
ensuring the swivel is well lubricated and free to turnC
installing the connecting shackle with the bow towards the anchorD
securing a piece of wood to the jews' harp
考题
单选题The symptoms of a fractured back are（）.A
leg cramps in the muscles in one or both legsB
pain and uncontrolled jerking of the legs and armsC
vomiting and involuntary urination or bowel movementD
pain at the site of the fracture and possible numbness or paralysis below the injury
考题
单选题With reference to a vessel’s structural integrity, the most significant characteristic of a cryogenic liquid is its （）.A
capability of causing brittle fracturesB
highly corrosive action on mild steelC
vapor cloud which reacts violently with saltwaterD
toxicity at atmospheric pressure
考题
单选题A compound fracture is a fracture in which（）.A
more than one bone is brokenB
the same bone is broken in more than one placeC
there is never any internal bleedingD
the bone may be visible
考题
单选题从“Ductile Fracture”的特征，以下哪一种说法是正确的（）A
断裂前无明显的塑性变形（永久变形），吸收的能量很少；B
明显的永久变形，并且经常有缩颈现象C
裂纹的扩展速度往往很快，几近音速。D
脆性断裂无明显的征兆可寻，断裂是突然发生的
考题
单选题“Brittle fracture”和“Ductile Fracture”的含义分别是（）A
脆性断裂和延性断裂；B
延性断裂和脆性断裂；C
脆性断裂和永久变形；D
塑性变形和永久变形
考题
单选题从“Brittle fracture”的特征，以下哪一种说法是错误的（）A
断裂前无明显的塑性变形（永久变形），吸收的能量很少；B
有一定的永久形变C
裂纹的扩展速度往往很快，几近音速。D
脆性断裂无明显的征兆可寻，断裂是突然发生的
考题
单选题患者男，38岁，因“骑自行车被小轿车撞伤，左胸着地”来诊。查体：意识清楚，R28次/min，HR92次/min，血压平稳，胸痛明显，左胸呼吸音减弱，肺浊音界上移。身体其余部分无损伤。该患者的可能诊断为（）.A
肋骨骨折（Rib FracturE.B
血胸（Hemothorax）C
气胸（Pneumothorax）D
肋骨骨折并血胸（Rib Fracture and Hemothorax）E
连枷胸（Flail chest）
考题
名词解释题骨折(fracture of bone)
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