HydroponicsHydroponics is a type of horticulture and a subset of hydroculture which involves growing plants, usually crops or medicinal plants, without soil, by using water-based mineral nutrient solutions. Terrestrial or aquatic plants may grow with their roots exposed to the nutritious liquid or the roots may be mechanically supported by an inert medium such as perlite, gravel, or other substrates. Despite inert media, roots can cause changes of the rhizosphere pH and root exudates can affect rhizosphere biology and physiological balance of the nutrient solution by secondary metabolites.
Astrophysical jetAn astrophysical jet is an astronomical phenomenon where outflows of ionised matter are emitted as extended beams along the axis of rotation. When this greatly accelerated matter in the beam approaches the speed of light, astrophysical jets become relativistic jets as they show effects from special relativity. The formation and powering of astrophysical jets are highly complex phenomena that are associated with many types of high-energy astronomical sources.
Milgram experimentThe Milgram experiment(s) on obedience to authority figures were a series of social psychology experiments conducted by Yale University psychologist Stanley Milgram. They measured the willingness of study participants, 40 men in the age range of 20 to 50 from a diverse range of occupations with varying levels of education, to obey an authority figure who instructed them to perform acts conflicting with their personal conscience. Participants were led to believe that they were assisting an unrelated experiment, in which they had to administer electric shocks to a "learner".
Potential flowIn fluid dynamics, potential flow (or ideal flow) describes the velocity field as the gradient of a scalar function: the velocity potential. As a result, a potential flow is characterized by an irrotational velocity field, which is a valid approximation for several applications. The irrotationality of a potential flow is due to the curl of the gradient of a scalar always being equal to zero. In the case of an incompressible flow the velocity potential satisfies Laplace's equation, and potential theory is applicable.
FluidicsFluidics, or fluidic logic, is the use of a fluid to perform analog or digital operations similar to those performed with electronics. The physical basis of fluidics is pneumatics and hydraulics, based on the theoretical foundation of fluid dynamics. The term fluidics is normally used when devices have no moving parts, so ordinary hydraulic components such as hydraulic cylinders and spool valves are not considered or referred to as fluidic devices. A jet of fluid can be deflected by a weaker jet striking it at the side.
Air purifierAn air purifier or air cleaner is a device which removes contaminants from the air in a room to improve indoor air quality. These devices are commonly marketed as being beneficial to allergy sufferers and asthmatics, and at reducing or eliminating second-hand tobacco smoke. The commercially graded air purifiers are manufactured as either small stand-alone units or larger units that can be affixed to an air handler unit (AHU) or to an HVAC unit found in the medical, industrial, and commercial industries.
Wind speedIn meteorology, wind speed, or wind flow speed, is a fundamental atmospheric quantity caused by air moving from high to low pressure, usually due to changes in temperature. Wind speed is now commonly measured with an anemometer. Wind speed affects weather forecasting, aviation and maritime operations, construction projects, growth and metabolism rate of many plant species, and has countless other implications. Wind direction is usually almost parallel to isobars (and not perpendicular, as one might expect), due to Earth's rotation.
CompostCompost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical, and biological properties. It is commonly prepared by decomposing plant and food waste, recycling organic materials, and manure. The resulting mixture is rich in plant nutrients and beneficial organisms, such as bacteria, protozoa, nematodes, and fungi. Compost improves soil fertility in gardens, landscaping, horticulture, urban agriculture, and organic farming, reducing dependency on commercial chemical fertilizers.
History of printingThe history of printing starts as early as 3000 BC, when the proto-Elamite and Sumerian civilizations used cylinder seals to certify documents written in clay tablets. Other early forms include block seals, hammered coinage, pottery imprints, and cloth printing. Initially a method of printing patterns on cloth such as silk, woodblock printing for texts on paper originated in China by the 7th century during the Tang dynasty, leading to the spread of book production and woodblock printing in other parts of Asia such as Korea and Japan.
Heat transferHeat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy (heat) between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, thermal convection, thermal radiation, and transfer of energy by phase changes. Engineers also consider the transfer of mass of differing chemical species (mass transfer in the form of advection), either cold or hot, to achieve heat transfer.
AeroponicsAeroponics is the process of cultivating plants in an air or mist environment, eliminating the need for soil or an aggregate medium. The term "aeroponic" originates from the Greek words aer ("air") and ponos ("work"). It falls under the category of hydroponics, as water is employed in aeroponics to deliver nutrients to the plants. The fundamental principle of aeroponic growing entails suspending plants in a closed or semi-closed environment while spraying their dangling roots and lower stems with a nutrient-rich water solution in an atomized or sprayed form.
Printing pressA printing press is a mechanical device for applying pressure to an inked surface resting upon a print medium (such as paper or cloth), thereby transferring the ink. It marked a dramatic improvement on earlier printing methods in which the cloth, paper, or other medium was brushed or rubbed repeatedly to achieve the transfer of ink and accelerated the process. Typically used for texts, the invention and global spread of the printing press was one of the most influential events in the second millennium.
