arc, arch
An arc is the discharge that occurs when a gas is ionized. A high voltage is pulsed across the lamp to "ignite" or "strike" the arc, after which the discharge can be maintained at a lower voltage. Natural lightning is now considered an electric spark, not an arc. An arc lamp or arc light is a lamp that produces light by an electric arc (also called a voltaic arc). In the late 1800s, electric arc lighting was in wide use for public lighting.
Electric arc between strands of wire; The 15 kW xenon [氙] short-arc lamp used in the IMAX projection system.
Arc welding is a welding process that is used to join metal to metal by using electricity to create enough heat to melt metal, and the melted metals when cool result in a binding of the metals. It is a type of welding that uses a welding power supply to create an electric arc between a metal stick ("electrode") and the base material to melt the metals at the point of contact. Arc welders can use either direct (DC) or alternating (AC) current, and consumable or non-consumable electrodes. One of the most common types of arc welding is shielded metal arc welding (SMAW), which is also known as manual metal arc welding (MMAW) or stick welding.
A reflex arc is a neural pathway that controls a reflex. In vertebrates, most sensory neurons do not pass directly into the brain, but synapse in the spinal cord. 反射弧是控制反射的神经通路。在脊椎动物中，大多数感觉神经元不直接进入大脑，而是在脊髓中形成突触。
An arch is a vertical curved structure that spans an elevated space and may or may not support the weight above it, or in case of a horizontal arch like an arch dam, the hydrostatic pressure against it.
白鹤滩大坝; Semi-circular arches using brick and/or stone block construction at the Great Wall, China
In ancient China, most architecture was wooden, including the few known arch bridges from literature and one artistic depiction in stone-carved relief. Therefore, the only surviving examples of architecture from the Han Dynasty (202 BC - 220 AD) are rammed earth defensive walls and towers, ceramic roof tiles from no longer existent wooden buildings, stone gate towers, and underground brick tombs that, although featuring vaults, domes, and archways, were built with the support of the earth and were not free-standing.
China's oldest surviving stone arch bridge is the Anji Bridge, built between 595 and 605 during the Sui Dynasty; it is the oldest open-spandrel segmental arch bridge in stone. 赵州桥是一座位于河北省石家庄市赵县城南上的石拱桥，因赵县古称赵州而得名。赵州桥始建于隋代，由匠师李春设计建造，后由宋哲宗赐名安济桥，并以之为正名。赵州桥是世界上现存年代久远、跨度最大、保存最完整的单孔坦弧敞肩石拱桥。
A spandrel is a roughly triangular space, usually found in pairs, between the top of an arch and a rectangular frame; between the tops of two adjacent arches or one of the four spaces between a circle within a square.
Arch- combines with nouns referring to people to form new nouns that refer to people who are extreme examples of something. For example, archbishop, arch-enemy, and arch-rival.
六级/考研单词: arc, discharge, volt, pulse, ignite, lightning, spark, strand, melt, bind, alternate, shield, manual, cord, vertical, curve, span, elevate, horizon, dam, construct, depict, thereby, dynasty, tile, subway, dome, triangle, adjacent, noun