Rigid body dynamicsIn the physical science of dynamics, rigid-body dynamics studies the movement of systems of interconnected bodies under the action of external forces. The assumption that the bodies are rigid (i.e. they do not deform under the action of applied forces) simplifies analysis, by reducing the parameters that describe the configuration of the system to the translation and rotation of reference frames attached to each body. This excludes bodies that display fluid, highly elastic, and plastic behavior.
Speeds and feedsThe phrase speeds and feeds or feeds and speeds refers to two separate velocities in machine tool practice, cutting speed and feed rate. They are often considered as a pair because of their combined effect on the cutting process. Each, however, can also be considered and analyzed in its own right. Cutting speed (also called surface speed or simply speed) is the speed difference (relative velocity) between the cutting tool and the surface of the workpiece it is operating on.
Line shaftA line shaft is a power-driven rotating shaft for power transmission that was used extensively from the Industrial Revolution until the early 20th century. Prior to the widespread use of electric motors small enough to be connected directly to each piece of machinery, line shafting was used to distribute power from a large central power source to machinery throughout a workshop or an industrial complex. The central power source could be a water wheel, turbine, windmill, animal power or a steam engine.
LaserWriterThe LaserWriter is a laser printer with built-in PostScript interpreter sold by Apple, Inc. from 1985 to 1988. It was one of the first laser printers available to the mass market. In combination with WYSIWYG publishing software like PageMaker, that operated on top of the graphical user interface of Macintosh computers, the LaserWriter was a key component at the beginning of the desktop publishing revolution. Laser printing Laser printing traces its history to efforts by Gary Starkweather at Xerox in 1969, which resulted in a commercial system called the Xerox 9700.
Constant-velocity jointA constant-velocity joint (also called a CV joint) is a mechanical coupling which allows the shafts to rotate freely (without an appreciable increase in friction or backlash) as the angle between the two shafts moves within a certain range. A common use of CV joints is in front-wheel drive vehicles, where they are used to transfer the engine's power to the wheels, even as the angle of the driveshaft varies due to the operation of the suspension.
Axes conventionsIn ballistics and flight dynamics, axes conventions are standardized ways of establishing the location and orientation of coordinate axes for use as a frame of reference. Mobile objects are normally tracked from an external frame considered fixed. Other frames can be defined on those mobile objects to deal with relative positions for other objects. Finally, attitudes or orientations can be described by a relationship between the external frame and the one defined over the mobile object.
ProcurementProcurement is the method of discovering and agreeing to terms and purchasing goods, services, or other works from an external source, often with the use of a tendering or competitive bidding process. The term may also refer to a contractual obligation to "procure", i.e. to "ensure" that something is done. When a government agency buys goods or services through this practice, it is referred to as government procurement or public procurement.
Line printerA line printer prints one entire line of text before advancing to another line. Most early line printers were impact printers. Line printers are mostly associated with unit record equipment and the early days of digital computing, but the technology is still in use. Print speeds of 600 lines per minute (approximately 10 pages per minute) were achieved in the 1950s, later increasing to as much as 1200 lpm. Line printers print a complete line at a time and have speeds in the range of 150 to 2500 lines per minute.
Shock (mechanics)A mechanical or physical shock is a sudden acceleration caused, for example, by impact, drop, kick, earthquake, or explosion. Shock is a transient physical excitation. Shock describes matter subject to extreme rates of force with respect to time. Shock is a vector that has units of an acceleration (rate of change of velocity). The unit g (or g) represents multiples of the acceleration of gravity and is conventionally used. A shock pulse can be characterised by its peak acceleration, the duration, and the shape of the shock pulse (half sine, triangular, trapezoidal, etc.
Government procurementGovernment procurement or public procurement is the procurement of goods, services and works on behalf of a public authority, such as a government agency. Amounting to 12 percent of global GDP in 2018, government procurement accounts for a substantial part of the global economy. To prevent fraud, waste, corruption, or local protectionism, the laws of most countries regulate government procurement to some extent. Laws usually require the procuring authority to issue public tenders if the value of the procurement exceeds a certain threshold.
