已选分类
工学
单选题The method used during design and manufacturing to determine the impact of a product or system on the environment. A) Life cycle analysis B) Life cycle inventory C) Systemsapproach D) Characterization
单选题最难以形成非晶态结构的是______。
单选题在体心立方结构中，伯氏矢量为a[00]的位错______分解为。(A)不能(B)能(C)可能
单选题Protons and neutrons are known as______ A) Electrons B) Neutrinos C) Nucleons D) Quarks
单选题处于高弹态的线型非晶态高分子材料，其力学状态主要决定于______。
单选题In the design of machine parts and structural members, ______ must be taken into consideration to ensure that a machine part is safe for operation under normal operating conditions. A) allowablestress B) designstress C) factorofsafety D) safe stress
单选题
能进行攀移的位错可能是________。
A、弗兰克位错 B、肖克利位错 C、螺型全位错
单选题下面关于回复与再结晶机制的差别中，正确的为______。
单选题凝固时不能有效降低晶粒尺寸的是以下哪种方法?______。
单选题How many space lattices (Bravais lattices) can atoms form in seven crystal systems? A) 3 B) 4 C) 8 D) 14
单选题Which composite fabrication technique can only use chopped fibers in their end-use products? A．Spay up B．Filament winding C．Resin Transfer Molding D．Pultrusion, E. Hand Layup
单选题A和B组成的二元系中出现α和β两相平衡时，两组的成分(x)-自由能(G)的关系为______。
单选题在置换型固溶体中，原子扩散的方式一般为______。 (A) 原子互换机制 (B) 间隙机制 (C) 空位机制
单选题Vickers hardness numbers are a measure of the size of the penetration made by ______ with different loads. A) 10-mmsteelball B) tungsten carbide sphere C) diamond pyramid indentor D) diamond cone indentor
单选题多晶体塑性变形时，至少需要______独立的滑移系。
单选题从高分子(polymer)的重复结构单元(mer)的对称性可知，最易结晶(crystallization)的是______。
单选题在金属、陶瓷和高分子中最易结晶的是______。
单选题A key difference between a thermoplastic polymer and an elastomeric material like rubber is that ______. A．rubber has a relatively small number of covalent crosslinks and thermoplastic polymers have none B．thermoplastics dont melt when heated but rubbers do C．rubber can be subjected to extensive plastic deformation whereas typical thermoplastics have little plasticity D．all of the above
单选题The objective of vulcanizing rubber A．To improve processibility B．To increase hardness and chemical resistance C．To reduce materials cost D．To increase amorphousness
单选题硅酸盐熔体的粘度随碱金属氧化物含量的增加而迅速增大。