所屬科目:研究所、轉學考(插大)◆機械製造
12. Chvorinov's rule states that total solidification time is proportional to which one of the following quantities: (A) (A/V), (B) (C)(D) V, (E) V/A; where A is surface area of casting, Hris heat of fusion, Tm is melting temperature, and V is volume of casting?
40. Which of the following situation may cause selfexcited vibration (chatter): (A)poor surface roughness(B)continuous chips produced(C)inhomogeneities in the workpiece material (D) poor accuracy of thework-piece (E)all of the above?
46. Which of the following item is NOT belong to semiconductor properties: (A) Resistance between and 108 Ω-cm, (B) higher operating temperature, (C) electrical properties can be altered when controlled amounts of impurity atoms added to their crystal structures, (D) has a smaller energy gap (E) none of the above ?