transmission line

In communications and electronic engineering, a transmission line is a specialized cable or other structure designed to conduct alternating current of radio frequency, that is, currents with a frequency high enough that their wave nature must be taken into account. Transmission lines are used for purposes such as connecting radio transmitters and receivers with their antennas (they are then called feed lines or feeders), distributing cable television signals, trunklines routing calls between telephone switching centres, computer network connections and high speed computer data buses.

This article covers two-conductor transmission line such as parallel line (ladder line), coaxial cable, stripline, and microstrip. Some sources also refer to waveguide, dielectric waveguide, and even optical fibre as transmission line, however these lines require different analytical techniques and so are not covered by this article; see Waveguide (electromagnetism).

The waterline

The waterline is the line where the hull of a ship meets the surface of the water. Specifically, it is also the name of a special marking, also known as an international load line, Plimsoll line and water line (positioned amidships), that indicates the draft of the ship and the legal limit to which a ship may be loaded for specific water types and temperatures in order to safely maintain buoyancy,[1] particularly with regard to the hazard of waves that may arise. Varying water temperatures will affect a ship’s draft; because warm water is less dense than cold water, providing less buoyancy. In the same way, fresh water is less dense than salinated or seawater with the same lessening effect upon buoyancy.

For vessels with displacement hulls, the hull speed is determined by, among other things, the waterline length.[citation needed] In a sailing boat, the waterline length can change significantly as the boat heels, and can dynamically affect the speed of the boat.

The waterline can also refer to any line on a ship’s hull that is parallel to the water’s surface when the ship is afloat in a normal position. Hence, all waterlines are one class of “ships lines” used to denote the shape of a hull in naval architecture plans.

In aircraft design, the term “waterline” refers to the vertical location of items on the aircraft. This is (normally) the “Z” axis of an XYZ coordinate system, the other two axes being the fuselage station (X) and buttock line (Y


Jump to navigation
Jump to search

サロメ(英・独:Salome, 仏:Saloméなど)は、ヘブライ語シャローム(Shalom, 「平和」)に起源する女性の名前。


The thermoelectric effect

is the direct conversion of temperature differences to electric voltage and vice versa via a thermocouple.[1] A thermoelectric device creates voltage when there is a different temperature on each side. Conversely, when a voltage is applied to it, heat is transferred from one side to the other, creating a temperature difference. At the atomic scale, an applied temperature gradient causes charge carriers in the material to diffuse from the hot side to the cold side.

This effect can be used to generate electricity, measure temperature or change the temperature of objects. Because the direction of heating and cooling is determined by the polarity of the applied voltage, thermoelectric devices can be used as temperature controllers.

The term “thermoelectric effect” encompasses three separately identified effects: the Seebeck effect, Peltier effect, and Thomson effect. The Seebeck and Peltier effects are different manifestations of the same physical process; textbooks may refer to this process as the Peltier–Seebeck effect (the separation derives from the independent discoveries by French physicist Jean Charles Athanase Peltier and Baltic German physicist Thomas Johann Seebeck). The Thomson effect is an extension of the Peltier–Seebeck model and is credited to Lord Kelvin.

Joule heating, the heat that is generated whenever a current is passed through a resistive material, is related, though it is not generally termed a thermoelectric effect. The Peltier–Seebeck and Thomson effects are thermodynamically reversible,[2] whereas Joule heating is not.

Line of greatest slope

Mountain biking
A mountain biker riding a trail which follows the line of greatest slope, or fall line.

In mountain biking the line of greatest slope defines the fall line, which is the path a trail will follow to descend a hill or mountain with the shortest path,[1] and will also cause the rider to gain the most velocity (assuming brakes are not used, and other factors such as rolling resistance are equal).
Mountain climbing
The line of greatest slope defines the path (red) a climber will take to gain the most elevation with the shortest possible path.

In mountain climbing, the line of greatest slope defines the fall line, which is the path a climber will take to gain the most elevation with the shortest possible path.
Map reading

The line of greatest slope has practical significance in map reading. On the terrain it is often far more discernible, even intuitively obvious, rather than accurately picking out the consistent height level on what is likely the undulating uneven ground along the ground represented on the contour line. But knowing that a greatest slope vector is orthogonal to the contour line, one can readily deduce the direction of the contour lines from the line of greatest slope. The extent and overall direction of the contour line to a map scale can only be found on the topographic map.

By noting the corresponding compass vector, walking along the contour one can line up a hand held compass aligning the expected direction, and eye-balling the line of contour’s estimated level, move up or down along the bearing faster— to closely locate a desired point (planned point) along the hillside.[clarification needed] Pragmatically, this can be ‘good enough’ for rough project landscaping, such as timber clear cutting the work site of a structure like a bridge abutment or connecting ramps. The approximation can then be refined by transit and other surveyor tools to construct on target.