Microform is a name given to special photographic films. Microforms contain reduced images of documents. Usually, documents stored on microform are reduced about 25 times. Microform is mainly used for archival purposes.
There are three common formats:
Properly stored (room temperature, 50% humidity), microform should be able to last up to 500 years.
Analog signal
An analog or analogue signal is any continuous signal.
The difference from a digital signal is that also very small fluctuations in the signal are meaningful. When one speaks of analog one often means an electrical context, however mechanical, pneumatic, hydraulic, and other systems may also convey analog signals.
An analog signal uses some property of the medium to convey the signal's information.
Any information may be conveyed by an analog signal, often such a signal is a measured change in physical phenomena, such as sound, light, temperature, position, or pressure.
For example, in sound recording, changes in air pressure (that is to say, sound) strike the diaphragm of a microphone which causes related changes in a voltage or the current in an electric circuit. The voltage or the current is said to be an "analog" of the sound.
See digital for a discussion of "digital vs. analog".
Microphone
A microphone, sometimes referred to as a mike or mic (both IPA pronunciation: ), converts sound into an electrical signal.
Microphones are used in many applications such as telephones, tape recorders, hearing aids, motion picture production, live and recorded audio engineering, in radio and television broadcasting and in computers for recording voice.
Sound passes through the air in waves, and as was said above, the microphone turns the sound wave into an electrical wave. Different kinds of microphones will turn the sound waves into electricity in different ways.
A pop filter (or pop shield) is often used in recording studios. It is an electronic filter that reduces or eliminates 'popping' sounds caused by fast moving air (such as air from the mouth).
The first microphones were invented as telephone transmitters. They included liquid and dynamic designs. Carbon transmitters were later used in this and other applications.
Digital signal
Digital signal can mean two different things:
Digital signals are digital representations of "discrete-time signals", which are often produced by changing an analog signal.
An analog signal is a datum that changes over time (for instance the temperature at a given place; the depth of a certain point in a pond; or the amplitude of the voltage at some node in a circuit). A discrete-time signal is a sampled version of an analog signal: the value of the datum is noted at fixed intervals (for example, every microsecond) rather than continuously.
In short, a digital signal is a quantized discrete-time signal; a discrete-time signal is a sampled analog signal.
In the digital revolution the usage of digital signals has increased significantly.
Many modern media devices, especially the ones that connect with computers use digital signals to represent signals that were traditionally represented as analog signals; cell phones, music and video players, personal video recorders, and digital cameras are examples.
In most applications, digital signals are represented as binary numbers, so their precision of quantization is measured in bits.
In computer architecture and other digital systems, a waveform that switches between two voltage levels representing the two states of a Boolean value (0 and 1) is referred to as a digital signal.
The clock signal is a special digital signal that is used to synchronize digital circuits.
The image shown can be considered the waveform of a clock signal.
Logic changes are triggered either by the rising edge or the falling edge.
Pneumatics
Pneumatics is the use of compressed air for mechanical motion. It has many uses.
Pneumatic transfer systems are employed in many industries to move powders and devices. Pneumatic devices are also used where electric motors cannot be used for safety reasons, such as deep in a mine where explosive dust or gases may be present.
electricity
Both pneumatics and hydraulics are applications of fluid power. Pneumatics uses air, which is compressible, while hydraulics uses relatively incompressible liquid media such as oil or water.
Duchy of Saxe-Gotha
Saxe-Gotha () was a state in today's Thuringia, Germany.
It was created in 1640 for Duke Ernest I and ended in 1680 when his lands were divided after his death in 1675. The area around Gotha passed to Ernest's eldest surviving son, Frederick of Saxe-Gotha-Altenburg, who also inherited Altenburg (which Ernest had inherited through his wife Elisabeth Sophie) and became Duke of Saxe-Gotha-Altenburg.
When the house of Saxe-Gotha and Altenburg became extinct in 1825, Saxe-Gotha-Altenburg was split. Saxe-Gotha passed to the Duke of Saxe-Coburg-Saalfeld who in turn gave Saalfeld to Saxe-Meiningen. The Duke of Saxe-Hildburghausen became Duke of Saxe-Altenburg, and gave Saxe-Hildburghausen to Saxe-Meiningen.
After the abolition of German monarchies at the end of the First World War it became a part of the newly created state of Thuringia in 1920.
Seafloor spreading
Seafloor spreading happens at the bottom of an ocean as tectonic plates move apart. The seafloor moves and carries continents with it. At ridges in the middle of oceans, new oceanic crust is created. The motivating force for seafloor spreading ridges is tectonic plate pull rather than magma pressure, although there is typically significant magma activity at spreading ridges.
At the Mid-Atlantic Ridge (and other places), material from the upper mantle rises through the faults between oceanic plates. It forms new crust as the plates move away from each other. The new crust then slowly moves away from the ridge. It is a place of earthquakes and volcanos. Seafloor spreading helps explain continental drift in plate tectonics. At oceanic trenches, seafloor crust slides down and under continental crust.
Earlier theories (e.g. by Alfred Wegener) of continental drift were that continents 'plowed' through the ocean. The modern idea is that the ocean floor itself moves and carries the continents with it as it expands from a mid-ocean ridge. Today, it is accepted. The phenomenon is caused by convection in the weak upper mantle, or asthenosphere.
Additionally spreading rates determine if the ridge is a fast, intermediate, or slow. As a general rule, fast ridges see spreading rate of more than 9 cm/year. Intermediate ridges have a spreading rate of 4-9 cm/year while slow spreading ridges have a rate less than 4 cm/year.
A mid-ocean ridge is an underwater mountain system. This consists of mountain chains, with a rift valley running along its spine, formed by plate tectonics. A mid-ocean ridge marks the boundary between two tectonic plates which are moving apart. A mid ocean ridge is made by a divergent boundary.
The mid-ocean ridges of the world are connected and form a single global mid-oceanic ridge system that is part of every ocean. The mid-oceanic ridge system is the longest mountain range in the world. The continuous mountain range is long. It is several times longer than the Andes, the longest continental mountain range. The total length of the oceanic ridge system is long.
Mid-ocean ridges are geologically active, with new magma constantly emerging onto the ocean floor and into the crust at and near rifts along the ridge axes. The crystallized magma forms new crust of basalt and gabbro.
The rocks making up the crust below the sea floor are youngest at the axis of the ridge and age with increasing distance from that axis. New magma of basalt composition emerges at and near the axis because of decompression melting in the underlying Earth's mantle.