Converging lens caus3es the rays of a parallel beam of light to come closer and pass through a point, i.e. the rays converge. It produces a real image at its principal focus. Such a lens is thicker at the center than the edge

聚光镜使一束平行光线愈聚愈拢而通过同一点,在其主焦点上产生实像,这种透镜的中心比边缘厚

属类：自然科学-物理-

Centrifugal force can cause a body spinning round a center to tend to fly off, while centripetal force can cause a body move toward the center or axis

离心力使绕一中心旋转之物体有飞离之势,而向心力则使物体向一中心或轴心运动

属类：自然科学-物理-

An incident ray of light is reflected when meeting the surface of a plane mirror

入射光线遇平面镜会产生反射

属类：自然科学-物理-

Diverging lens causes the rays of a parallel beam of light to spread out and appear to come form a point, i.e. the rays diverge. It produces a virtual image at its principal focus. Such a lens is thinner at the center than at the edge

散光镜使一束平行光线散开而形似出发于一点,在其主焦点上产生虚像,这种透镜的心比边缘薄

属类：自然科学-物理-

Making chip curl freely and reduce the load on tool has been shown a way of an idea application for a negative land

使切屑自由卷曲因而减少对刀具的载荷,已证明是理想应用倒棱的方法

属类：自然科学-物理-

Copper and aluminum are good conductors of heat and electricity

铜和铝是热和电的良导体

属类：自然科学-物理-

A change in the state or physical property of a material while remaining the same material is a physical change, e.g. ice melting to water

物理变化是指一种物质仅改变它的状态或物理性质,但仍然是同一种物质,例如冰溶化为水

属类：自然科学-物理-

Virtual image is an image from which rays of light appears to come. As no light rays actually pass through the image, it cannot be put on a screen

虚像似是发出光线的像,而实际上并无光线通过该像,因此该像不能呈现于屏上

属类：自然科学-物理-

Short cycle times are achieved by opening the mold before the molded part is completely set up

在模铸件安全硬化之前拆模,可缩短周期

属类：自然科学-物理-

An additional centrifugal clutch can often provide improved operation of the machine to be driven

增加一只离心式离合器,常常能够改善所驱动机器的运转

属类：自然科学-物理-

Such particles are far too tiny to be seen with the strongest microscope

这种粒子太小,即使用最高倍的显微镜也看不出来

属类：自然科学-物理-

Cryogenics : Study and use of low-temperature phenomena. The cryogenic temperature range is from-238°F (-150°C)to absolute zero.

低温技术:研究低温现象的产生和应用的技术。低温范围曾被定为从-150℃至绝对零度。

属类：自然科学-物理-

At low temperatures, matter has unusual properties. Substances that are naturally gases can be liquefied at low temperatures, and metals lose electrical resistance as they get colder

在低温条件下，物质会表现出非同寻常的特性,气态物质会在低温条件下液化,金属变得更冷后会失去电阻性。

属类：自然科学-物理-

Cryogenics dates from 1877, when oxygen was first cooled to the point at which it became a liquid-183°C); superconductivity was discovered in 1911.

低温学始于1877年，这一年首次将氧冷却到其液化点(-183℃)。1911年发现超导现象。

属类：自然科学-物理-

Applications of cryogenics include the storage and transport of liquefied gases, food preservation, cryosurgery, rocket fuels, and superconducting electromagnets

低温技术的应用包括液化天然气的储存和运输、食物保存、低温医学、火箭燃料和超导电磁体。

属类：自然科学-物理-

Damping: In physics, the restraint of vibratory motion, such as mechanical oscillations, noise, and alternating electric currents, by dissipating energy.

阻尼:物理学中，指因能量耗散使振荡、噪音、交流电之类的振动所受到的遏制。

属类：自然科学-物理-

Unless a child keeps pumping a swing, the back-and-forth motion decreases; damping by the air’s friction opposes the motion and removes energy from the system.

荡秋千的小孩除非不停地屈伸，否则秋千的运动就会因阻尼而停止;阻尼藉空气的摩擦会阻挠运动并移除系统的能量。

属类：自然科学-物理-

Viscous damping is caused by such energy losses as occur in liquid lubrication between moving parts or in a liquid forced through a small opening by a piston, as in automobile shock absorbers.

粘滞阻尼既可因各运动部件间存在液体润滑作用造成的能量损失而引起，也可因活塞迫使液体穿过小孔造成的能量损失而引起，像汽车避震器那样。

属类：自然科学-物理-

Hysteresis damping involves energy loss within the moving structure itself. Other types of damping include electrical resistance, radiation, and magnetic damping.

滞后阻尼是因运动结构内部本身的能量损失而引起的，有时也称结构阻尼。其它形式的阻尼包括电阻、辐射阻尼和磁阻尼。

属类：自然科学-物理-

Electric potential: Amount of work needed to move a unit electric charge from a reference point to a specific point against an electric field.

电动势:把单位电荷逆电场方向从一个参考点移到某给定点所作的功。

属类：自然科学-物理-