如何用英语介绍赵州桥

Zhaozhou Bridge
The Zhaozhou Bridge (traditional Chinese: 赵州桥; simplified Chinese: 赵州桥; pinyin: Zhàozhōu Qiáo) is the worlds oldest open-spandrel stone segmental arch bridge.[1] Credited to a craftsman named Li Chun, the bridge was constructed in the years 595-605 during the Sui Dynasty. Located in the southern part of Hebei Province, it is the oldest standing bridge in China, although the Chinese had built bridges over waterways since the ancient Zhou Dynasty.
Name and location
The Zhaozhou Bridge is also known as the Safe Crossing Bridge (traditional Chinese: 安济桥; simplified Chinese: 安济桥; pinyin: An Ji Qiáo, englished as the Anji Bridge) and the Great Stone Bridge (Chinese: 大石桥; pinyin: Dà Shí Qiáo). It crosses the Xiao River (traditional Chinese: ; simplified Chinese: 洨河; pinyin: Xiào Hé, Jiao He) in Zhao County, approximately 40 km southeast of the provincial capital Shijiazhuang. It is named for the nearby Zhao County (赵县), which was formerly known as Zhaozhou (赵州).
Construction
The Zhaozhou Bridge is about 50 m long with a central span of about 37 m. It stands 7.3 m tall and has a width of 9 m. The arch covers a circular segment less than a semicircle and has a rise-to-span ratio of approximately 1:5 (7.3 to 37 m). This is considerably smaller than the rise-to-span ratio of 1:2 of a semicircular arch bridge and subjects the abutments of the bridge to large forces.
The central arch is made of 28 thin, curved limestone slabs which are joined with iron dovetails. This allows the arch to adjust to shifts in its supports, and prevents the bridge from collapsing even when a segment of the arch breaks. The bridge has two small side arches on either side of the main arch. These side arches serve two important functions: First, they reduce the total weight of the bridge by about 15.3% or approximately 700 tons, which is vital because of the low rise-to-span ratio and the large forces on the abutments it creates. Second, when the bridge is submerged during a flood, they allow water to pass through, thereby reducing the forces on the structure of the bridge.
Li Chuns innovative spandrel-arch construction, while economising in materials, was also of considerable aesthetic merit. An inscription left on the bridge by Tang officials seventy years after its construction reads:
“ This stone bridge over the Jiao River is the result of the work of the Sui engineer Li Chun. Its construction is indeed unusual, and no-one knows on what principle he made it. But let us observe his marvellous use of stone-work. Its convexity is so smooth, and the wedge-shaped stones fit together so perfectly... How lofty is the flying-arch! How large is the opening, yet without piers!.. Precise indeed are the cross-bondings and joints between the stones, masonry blocks delicately interlocking like mill wheels, or like the walls of wells; a hundred forms (organised into) one. And besides the mortar in the crevices there are slender-waisted iron cramps to bind the stones together. The four small arches inserted, on either side two, break the anger of the roaring floods, and protect the bridge mightily. Such a master-work could never have been achieved if this man had not applied his genius to the building of a work which would last for centuries to come.[2] ”
Later history and reputation
In the next 1400 years, the bridge survived at least eight wars, ten major floods and numerous earthquakes, the nearest of which being the 7.2 degree Xingtai Earthquake in 1966. Yet, the support structure remains intact and the bridge is still in use. Only the ornamental railings have been replaced every few hundred years.
The intriguing design of the bridge has given rise to many legends. According to one legend, the bridge was built by a master architect named Lu Ban in a single night. In another story, the bridge was put to the test by two immortals who crossed it at the same time and Lu Ban saved it by wading into the water and supporting the structure.
Although Ming Dynasty authors compared the bridge to "a new moon rising above the clouds" and "a long rainbow hanging on a mountain waterfall"[2], it later fell into obscurity. When Professor Liang Sicheng (梁思成) of Tsing Hua University rediscovered the bridge on a field exploration of ancient architecture in Hebei province, made detailed measurements, and published a report and drawing ("An Chi Chiao the Great Stone Bridge Chao Hsien, Hobei, Sui Dynasty AD 569-617, Li Chun Master Builder"), it became world famous.
Zhaozhou Bridge was dedicated as an International Historic Civil Engineering Landmark by the American Society of Civil Engineers in 1991. The Chinese authorities nominated it for incription on the World Heritage List as having "a very important place in the world bridge building history".[2]
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You can tell your friend to google it online--Zhaozhou Bridge.

ZG螺纹、G螺纹、R螺纹分别有什么区别？

1、型号不同
G是指非螺纹密封的管螺纹，R是指用螺纹密封的管螺纹，ZG表示牙型角为55度的圆锥管螺纹。牙型角55度。
2、密封性不同
G螺纹内外螺纹均为圆柱形的管螺纹，配合后不具密封性；R螺纹旋紧后具有密封性。牙顶牙底均为圆弧形，锥螺纹的锥度为1：16；ZG表示牙型角为55度，锥度1：16，内.外螺纹牙型间无间隙。 
3、作用不同
G螺纹在管路中仅起联结作用，借助密封圈可用于静载下的低压管路。R螺纹有两种配合,一种配合为圆柱内螺纹/圆锥外螺纹，用于低压静载，如水、煤气管；另一种为圆锥内螺纹/圆锥外螺纹，用于高压和承受冲击的场合。ZG螺纹多用于高压.高温系统的管路联接中，内.外螺纹牙型间无间隙，不用填料而依靠牙型的变形来保证螺纹副的联接紧密性。

扩展资料：
一、螺纹检测系统：
1、硬件系统 螺纹参数自动检测系统基于PC架构，主要由照明系统、CCD相机和光路成像系统、、图像采集卡、图像处理系统、机械检测系统以及电控系统等组成。
测量时，经照明系统照明后，通过CCD相机和光路成像系统采集紧固件的螺纹图像，然后经过图像采集卡，将数字化图像传到计算机，计算机对该数字图像按相应算法处理后，计算出螺纹的牙型角、螺距和中径等参数，并与标准进行比较，计算出偏差。
2、软件系统 螺纹参数自动检测的软件系统主要包括系统控制模块 图像处理模块等。
系统控制模块：初始化；完成系统图像接口卡及标准参数的初始化配置。图像操作；采集并保存8位的灰色图像，捕获图像到内存。
图像处理模块：图像处理模块包括减少噪声、突出螺纹轮廓边缘信息的图像预处理算法，检测和提取轮廓边缘信息的边缘检测和提取算法，测量数字图像实际尺寸的系统标定算法，以及用于计算螺纹参数的算法等。
二、螺纹测量方法
1、螺纹夹角的测量
螺纹夹角也叫牙型角。螺纹夹角的测量可通过测量侧面角来实现，螺纹侧面角是螺纹侧面与螺纹轴线的垂直面之间的夹角。螺纹牙的近似轮廓在螺纹两侧直线段采样，对采样点进行直线最小二乘拟合。
2、螺距的测量
螺距是指螺纹上某一点至相邻螺纹牙上对应点之间的距离。测量时必须平行于螺纹轴线。
3、螺纹中径的测量
螺纹中径是中径线沿垂直于轴线距离，中径线是一个假想的线。
参考资料来源：百度百科-英制螺纹
参考资料来源：百度百科-圆锥螺纹