Gunpowder Gunpowder, also known as black powder, was the first chemical explosive and the only one known until the mid-19th century. It is a mixture of sulfur, charcoal, and potassium nitrate (saltpeter)—with the sulfur and charcoal acting as fuels, while the saltpeter works as an oxidizer.[2][3] Because of its burning properties and the amount of heat and gas volume that it generates, gunpowder has been widely used as a propellant in firearms and as a pyrotechnic composition in fireworks. Gunpowder was, according to prevailing academic consensus, invented in the 9th century in China,[4] and the earliest record of a written formula for gunpowder appears in the 11th century Song Dynasty text, Wujing Zongyao.[5] This discovery led to the invention of fireworks and the earliest gunpowder weapons in China. In the centuries following the Chinese discovery, gunpowder weapons began appearing in the Muslim world, Europe, and India. History[edit] Early Chinese rocket China[edit] Middle East[edit] C.
steeluniversity.org | steeluniversity.org | steeluniversity.org Home Page Crystallography A crystalline solid: atomic resolution image of strontium titanate. Brighter atoms are Sr and darker ones are Ti. Crystallography is the science that examines the arrangement of atoms in solids (see crystal structure). Before the development of X-ray diffraction crystallography (see below), the study of crystals was based on their geometry. Crystallographic methods now depend on the analysis of the diffraction patterns of a sample targeted by a beam of some type. These three types of radiation interact with the specimen in different ways. Theory[edit] Because of their highly ordered and repetitive structure, crystals give diffraction patterns of sharp Bragg reflection spots, and are ideal for analyzing the structure of solids. Notation[edit] Technique[edit] Once a crystal is obtained, data can be collected using a beam of radiation. Producing an image from a diffraction pattern requires sophisticated mathematics and often an iterative process of modelling and refinement. Biology[edit]
Standards What is a standard? A standard is a document that provides requirements, specifications, guidelines or characteristics that can be used consistently to ensure that materials, products, processes and services are fit for their purpose. We published over 21000 International Standards that can be purchased from the ISO store or from our members. What are the benefits of ISO International Standards? ISO International Standards ensure that products and services are safe, reliable and of good quality. Learn more about the benefits of ISO standards ISO standards in action We also have information about how ISO standards work in the real world. Learn more about ISO standards in action How to find a standard? ISO has over 21000 International Standards covering almost all aspects of technology and business.
Traditional Chinese medicine Traditional medicine in China Traditional Chinese medicine (TCM) is an alternative medical practice drawn from traditional medicine in China. It has been described as "fraught with pseudoscience", with the majority of its treatments having no logical mechanism of action.[1][2] Medicine in traditional China encompassed a range of sometimes competing health and healing practices, folk beliefs, literati theory and Confucian philosophy, herbal remedies, food, diet, exercise, medical specializations, and schools of thought.[3] In the early twentieth century, Chinese cultural and political modernizers worked to eliminate traditional practices as backward and unscientific. Traditional practitioners then selected elements of philosophy and practice and organized them into what they called "Chinese medicine" (Zhongyi). The demand for traditional medicines in China has been a major generator of illegal wildlife smuggling, linked to the killing and smuggling of endangered animals.[10] History[edit]
Forge A blacksmith's coal forge Wooden smithy in Opole, Upper Silesia, Poland Types of forges[edit] Coal/coke/charcoal forge[edit] Standard coal forge Over thousands of years of forging, these devices have evolved in one form or another as the essential features of this type of forge:[citation needed] Tuyere — a pipe through which air can be forced into the fireBellows or blower — a means for forcing air into the tuyereHearth — a place where the burning fuel can be contained over or against the tuyere opening. During operation, fuel is placed in or on the hearth and ignited. A typical Scottish smithy at Auchentiber, North Ayrshire, Scotland. A blacksmith balances the fuel and air in the fire to suit particular kinds of work. In a typical coal forge, a firepot will be centered in a flat hearth. If a larger fire is necessary, the smith increases the air flowing into the fire as well as feeding and deepening the coke heart. Gas forge[edit] A gas forge typically uses propane or natural gas as the fuel.
Sundial SSW facing, vertical declining sundial on Moot Hall, Aldeburgh, Suffolk, England. A combined analemmatic-equatorial sundial in Ann Morrison Park in Boise, Idaho, 43°36'45.5"N 116°13'27.6"W A sundial is a device that tells the time of day by the position of the Sun. In common designs such as the horizontal sundial, the sun casts a shadow from its style onto a surface marked with lines indicating the hours of the day. Introduction[edit] There are different types of sundials. The shadow-casting object, known as a gnomon, may be a long thin rod, or other object with a sharp tip or a straight edge. With sundials using light to indicate time, a line of light may be formed by allowing the sun's rays through a thin slit or focusing them through a cylindrical lens. Sundials differ in their portability and their need for orientation. Sundials indicate the local solar time, unless corrected for some other time. Apparent motion of the Sun[edit] Top view of an equatorial sundial. [citation needed]
Clock The clock is one of the oldest human inventions, meeting the need to consistently measure intervals of time shorter than the natural units: the day, the lunar month, and the year. Devices operating on several physical processes have been used over the millennia. A sundial shows the time by displaying the position of a shadow on a flat surface. There are a range of duration timers, a well-known example being the hourglass. The timekeeping element in every modern clock is a harmonic oscillator, a physical object (resonator) that vibrates or oscillates repetitively at a precisely constant frequency.[4] This object can be a pendulum, a tuning fork, a quartz crystal, or the vibration of electrons in atoms as they emit microwaves. The study of timekeeping is known as horology. History[edit] Time-measuring devices[edit] Sundials[edit] Simple horizontal sundial When the Sun is shining, its apparent position in the sky moves during a day, reflecting the rotation of the Earth. Water clocks[edit]
Ancient Egyptian technology Ancient Egyptian depiction of women engaged in mechanical rope making, the first graphic evidence of the craft, shown in the two lower rows of the illustration Technology in Dynastic Egypt[edit] Significant advances in ancient Egypt during the dynastic period include astronomy, mathematics, and medicine. Their geometry was a necessary outgrowth of surveying to preserve the layout and ownership of farmland, which was flooded annually by the Nile river. The 3,4,5 right triangle and other rules of thumb served to represent rectilinear structures, and the post and lintel architecture of Egypt. Egypt also was a center of alchemy research for much of the western world. Paper and writing[edit] A section of the Egyptian Book of the Dead, which is written and drawn on papyrus The word paper comes from the Greek term for the ancient Egyptian writing material called papyrus, which was formed from beaten strips of papyrus plants. Structures and construction[edit] Buildings[edit] Monuments[edit]
Calendar A calendar is a system of organizing days for social, religious, commercial or administrative purposes. This is done by giving names to periods of time, typically days, weeks, months, and years. A date is the designation of a single, specific day within such a system. Periods in a calendar (such as years and months) are usually, though not necessarily, synchronized with the cycle of the sun or the moon. A calendar is also a physical device (often paper). A calendar can also mean a list of planned events, such as a court calendar. The English word calendar is derived from the Latin word kalendae, which was the Latin name of the first day of every month.[1] Calendar systems[edit] A full calendar system has a different calendar date for every day. The simplest calendar system just counts time periods from a reference date. Other calendars have one (or multiple) larger units of time. Calendars that contain one level of cycles: Calendars with two levels of cycles: Solar calendars[edit] Uses[edit]