Precession is a change in the orientation of the rotational axis of a rotating body. In an appropriate reference frame it can be defined as a change in the first Euler angle, whereas the third Euler angle defines the rotation itself. In other words, if the axis of rotation of a body is itself rotating about a second axis, that body is said to be precessing about the second axis. A motion in which the second Euler angle changes is called nutation. In physics, there are two types of precession: torque-free and torque-induced.
A gyroscope is a device used for measuring or maintaining orientation and angular velocity. It is a spinning wheel or disc in which the axis of rotation is free to assume any orientation by itself. When rotating, the orientation of this axis is unaffected by tilting or rotation of the mounting, according to the conservation of angular momentum.
A rudder is a primary control surface used to steer a ship, boat, submarine, hovercraft, airship, or other vehicle that moves through a fluid medium. On an airplane, the rudder is used primarily to counter adverse yaw and p-factor and is not the primary control used to turn the airplane. A rudder operates by redirecting the fluid past the hull or fuselage, thus imparting a turning or yawing motion to the craft. In basic form, a rudder is a flat plane or sheet of material attached with hinges to the craft's stern, tail, or afterend. Often rudders are shaped to minimize hydrodynamic or aerodynamic drag. On simple watercraft, a tiller—essentially, a stick or pole acting as a lever arm—may be attached to the top of the rudder to allow it to be turned by a helmsman. In larger vessels, cables, pushrods, or hydraulics may link rudders to steering wheels. In typical aircraft, the rudder is operated by pedals via mechanical linkages or hydraulics.
Gimbal lock is the loss of one degree of freedom in a multi-dimensional mechanism at certain alignments of the axes. In a three-dimensional three-gimbal mechanism, gimbal lock occurs when the axes of two of the gimbals are driven into a parallel configuration, "locking" the system into rotation in a degenerate two-dimensional space.
The Euler angles are three angles introduced by Leonhard Euler to describe the orientation of a rigid body with respect to a fixed coordinate system.
The chain pump is type of a water pump in which several circular discs are positioned on an endless chain. One part of the chain dips into the water, and the chain runs through a tube, slightly bigger than the diameter of the discs. As the chain is drawn up the tube, water becomes trapped between the discs and is lifted to and discharged at the top. Chain pumps were used for centuries in the ancient Middle East, Europe, and China.
Yi Xing, born Zhang Sui, was a Chinese astronomer, Buddhist monk, inventor, mathematician, mechanical engineer, and philosopher during the Tang dynasty. His astronomical celestial globe featured a liquid-driven escapement, the first in a long tradition of Chinese astronomical clockworks.
Science in the ancient world encompasses the earliest history of science from the protoscience of prehistory and ancient history to late antiquity. In ancient times, culture and knowledge were passed through oral tradition. The development of writing further enabled the preservation of knowledge and culture, allowing information to spread accurately.
Chain drive is a way of transmitting mechanical power from one place to another. It is often used to convey power to the wheels of a vehicle, particularly bicycles and motorcycles. It is also used in a wide variety of machines besides vehicles.
Su Song, courtesy name Zirong, was a Chinese polymathic scientist and statesman. Excelling in a variety of fields, he was accomplished in mathematics, astronomy, cartography, geography, horology, pharmacology, mineralogy, metallurgy, zoology, botany, mechanical engineering, hydraulic engineering, civil engineering, invention, art, poetry, philosophy, antiquities, and statesmanship during the Song dynasty (960–1279).
Song Yingxing was a Chinese scientist and encyclopedist who lived during the late Ming Dynasty (1368–1644). He was the author of Tiangong Kaiwu, an encyclopedia that covered a wide variety of technical subjects, including the use of gunpowder weapons. The British biochemist, sinologist, and historian Joseph Needham called Song Yingxing "The Diderot of China."
Ancient Chinese scientists and engineers made significant scientific innovations, findings and technological advances across various scientific disciplines including the natural sciences, engineering, medicine, military technology, mathematics, geology and astronomy.
Zhu Yu was a Chinese maritime historian during the Song dynasty. He retired in Huang Gang (黄岗) of the Hubei province, bought a country house and named it "Pingzhou". He called himself "Expert Vegetable Grower of Pingzhou (萍洲老圃)". Between 1111 and 1117 AD, Zhu Yu wrote the book Pingzhou Ketan, published in 1119 AD. It covered a wide variety of maritime subjects and issues in China at the time. His extensive knowledge of maritime engagements, technologies, and practices were because his father, Zhu Fu, was the Port Superintendent of Merchant Shipping for Guangzhou from 1094 until 1099 AD, whereupon he was elevated to the status of governor there and served in that office until 1102 AD.
Chinese exploration includes exploratory Chinese travels abroad, on land and by sea, from the travels of Han dynasty diplomat Zhang Qian into Central Asia during the 2nd century BC until the Ming dynasty treasure voyages of the 15th century that crossed the Indian Ocean and reached as far as East Africa.
Mechanical counters are counters built using mechanical components. They typically consist of a series of disks mounted on an axle, with the digits zero through nine marked on their edge. The right most disk moves one increment with each event. Each disk except the left-most has a protrusion that, after the completion of one revolution, moves the next disk to the left one increment. Such counters have been used as odometers for bicycles and cars and in tape recorders and fuel dispensers and to control manufacturing processes. One of the largest manufacturers was the Veeder-Root company, and their name was often used for this type of counter. Mechanical counters can be made into electromechanical counters, that count electrical impulses, by adding a small solenoid.
An inertial navigation system is a navigation device that uses motion sensors (accelerometers), rotation sensors (gyroscopes) and a computer to continuously calculate by dead reckoning the position, the orientation, and the velocity of a moving object without the need for external references. Often the inertial sensors are supplemented by a barometric altimeter and sometimes by magnetic sensors (magnetometers) and/or speed measuring devices. INSs are used on mobile robots and on vehicles such as ships, aircraft, submarines, guided missiles, and spacecraft. Older INS systems generally used an inertial platform as their mounting point to the vehicle and the terms are sometimes considered synonymous.
The Tang dynasty (618–907) of ancient China witnessed many advancements in Chinese science and technology, with various developments in woodblock printing, timekeeping, mechanical engineering, medicine, and structural engineering.
This is a timeline of the Song dynasty (960–1279). The Song dynasty was founded by Zhao Kuangyin, posthumously known as Emperor Taizu of Song, who ended the period of division known as the Five Dynasties and Ten Kingdoms period. The Song dynasty is commonly separated into two historical periods, the Northern Song (960–1127) and the Southern Song (1127–1279), divided by the loss of the north to the Jurchen Jin dynasty (1115–1234). In 1279, the Mongol Yuan dynasty conquered the Song.
This is a timeline of the Five Dynasties and Ten Kingdoms (907–979), which followed the collapse of the Tang dynasty in 907 AD. The Five Dynasties refer to the succession of dynasties which ruled northern China following the Tang collapse while the Ten Kingdoms, with the exception of Northern Han, ruled in southern China. This era of division ended in 979 AD with the rise of the Song dynasty under Emperor Taizu of Song, although the Song would never reconquer the northern territory lost to the Khitans, collectively known as the Sixteen Prefectures.
This is a timeline of the Yuan dynasty (1271–1368). The Yuan dynasty was founded by the Mongol warlord Kublai Khan in 1271 and conquered the Song dynasty in 1279. The Yuan dynasty lasted nearly a hundred years before a series of rebellions known as the Red Turban Rebellion resulted in its collapse in 1368 and the rise of the Ming dynasty.
