be prepared from 由……制备
The formaldehyde can be prepared from methanol in the presence of a metal catalyst such as silver, copper and the like, and can also be separated from the oxidation products of hydrocarbons.
甲醛可由甲醇在银、铜等金属催化下脱氢或氧化制得，也可由烃类氧化产物分出。
A pitch mesophase can be prepared from petroleum pitch and coal tar pitch.
从石油沥青和煤沥青中制取沥青中间相物质。
The specimen shall be transverse, using dimensions less than standard if necessary, and shall be prepared from a wafer heat treated with the material to be delivered.
试样应当横向取，如果必要，尺寸可以低于标准要求。试样应当从与发运材料一同热处理的圆盘中取样。
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