|
vacuums 音标拼音: [v'ækjumz] Vacuum \ Vac" u* um\ ( v[ a^] k"[- u]*[ u^] m), n.; pl. E. { Vacuums} ( v[ a^] k"[- u]*[ u^] mz), L. { Vacua} ( v[ a^] k"[- u]*[. a]). [ L., fr. vacuus empty. See { Vacuous}.] 1. ( Physics) A space entirely devoid of matter ( called also, by way of distinction, absolute vacuum); hence, in a more general sense, a space, as the interior of a closed vessel, which has been exhausted to a high or the highest degree by an air pump or other artificial means; as, water boils at a reduced temperature in a vacuum. [ 1913 Webster] [ 1913 Webster] 2. The condition of rarefaction, or reduction of pressure below that of the atmosphere, in a vessel, as the condenser of a steam engine, which is nearly exhausted of air or steam, etc.; as, a vacuum of 26 inches of mercury, or 13 pounds per square inch. [ 1913 Webster] { Vacuum brake}, a kind of continuous brake operated by exhausting the air from some appliance under each car, and so causing the pressure of the atmosphere to apply the brakes. { Vacuum pan} ( Technol.), a kind of large closed metallic retort used in sugar making for boiling down sirup. It is so connected with an exhausting apparatus that a partial vacuum is formed within. This allows the evaporation and concentration to take place at a lower atmospheric pressure and hence also at a lower temperature, which largely obviates the danger of burning the sugar, and shortens the process. { Vacuum pump}. Same as { Pulsometer}, 1. { Vacuum tube} ( Phys.), ( a) a glass tube provided with platinum electrodes and exhausted, for the passage of the electrical discharge; a Geissler tube. ( a) any tube used in electronic devices, containing a vacuum and used to control the flow of electrons in a circuit, as a vacuum diode, triode, tetrode, or pentode. { Vacuum valve}, a safety valve opening inward to admit air to a vessel in which the pressure is less than that of the atmosphere, in order to prevent collapse. { Torricellian vacuum}. See under { Torricellian}. [ 1913 Webster]
|
安装中文字典英文字典查询工具!
中文字典英文字典工具:
英文字典中文字典相关资料:
|