what are the characteristics of the same main group in the periodic table?
which of the following elements are alkali metals?
electrons in atoms would follow these principles.
which of the following bonds can be treated as weak bonds or secondary bonds?
atoms are made from a nucleus of protons and neutrons and a cloud of electrons.
the pauli exclusion principle is the quantum mechanical principle which states that two or more identical fermions (particles with half-integer spin) can occupy the same quantum state within a quantum system simultaneously.
when voltage is applied to an ionic material, entire ions must move to cause a current to flow, therefore, the electrical conductivity is very good.
what are molecular structure in polymer?
which bond can be existed in polymer?
the molecular weight of polymers is a fixed value.
a polymer chain is straight.
what is the coordination number for fcc structure?
how many atoms in hcp?
which of the following statement is correct?
the apf could not be same due to different crystal structure.
there are cations and anions in ceramics, therefore, the crystal could not be electrically neutral.
the chemical formula of a compound indicates the ratio of cations to anions, which must be stoichiometric.
in ionic crystals, many of the valence electrons are present in states where they are not localized close to the atoms but can move freely over the crystal, which is reflected in a high conductivity.
non-crystal cannot be called amorphous.
the cohesive forces in ionic crystals are electrostatic forces acting between the ions.
which of the following statement is incorrect?
which of the following statement about frankel's defect is incorrect？
空位平衡浓度与哪些因素有关？
which of the following statements about solid solutions are correct.
下列属于热缺陷的有
which of the following statements about dislocation are correct？
which of the following statement is correct？
所有晶体都包含缺陷。
defects do occur alone.
刃型位错的位错线不一定是直线。
在菲克第一定律中d 的含义是什么？
what are the factors that influence the diffusion?
扩散机理可分为哪些？
扩散系数与哪些因素有关？
the vacancy is in the same direction as the atom.
nonsteady-state diffusion means that the diffusion particle concentration distribution does not change with time.
扩散系数只取决于晶体结构。
solid-state diffusion is a means of mass transport within solid materials by stepwise atomic motion.
韧度是衡量材料韧性大小的力学性能指标，是指材料断裂前吸收( )的能力
对于脆性材料,其抗压强度一般比抗拉强度（ ）
金属疲劳的判断依据是( )。
常用的塑性判断依据是( )。
the internal force concentration caused by internal force is called stress.
the stress distribution on the notch section is uniform.