Via fence

A via fence, also called a picket fence, is a structure used in planar electronic circuit technologies to improve isolation between components which would otherwise be coupled by electromagnetic fields. It consists of a row of via holes which, if spaced close enough together, form a barrier to electromagnetic wave propagation.

Modern electronics have components and sub-units at high densities to achieve small size. Typically, many functions are integrated on to the same board or die. If not properly shielded from each other, many problems can result including poor frequency response, noise performance, and distortion.

Via fences are used to shield microstrip and stripline transmission lines, guard edges of printed circuit boards, shield functional circuit units from each other, and to form the walls of waveguides integrated into a planar format. Via fences are cheap and easy to implement, but use up board space and are not as effective as solid metal walls.

Purpose

Planar technologies are used at microwave frequencies and make use of printed circuit tracks as transmission lines. As well as interconnections, these lines can be used to form components of functional units such as filters and couplers. Planar lines readily couple to each other when in close proximity, an effect called parasitic coupling. The coupling is due to fringing fields spreading from the edges of the line and intersecting adjacent lines or components. This is a desirable feature within the unit where it is made use of as part of the design. It is not desirable, however, that the fields couple to adjacent units. Modern electronic devices are usually required to be small. That, and the drive to keep down costs, leads to a high degree of integration and circuit units in less than desirable proximity. Via fences are one method that can be used to reduce parasitic coupling between such units.

VIA

Via or VIA may refer to one of the following:

Science and technology

Transportation

Other

STAR (interbank network)

STAR is an interbank network and EFTPOS network in the United States. It is the largest American interbank network, with 2 millionATMs, 134 million cardholders and over 5,700 participating financial institutions. The STAR Network began in 1984 and was acquired by First Data Corporation in 2003. The network is owned and operated by STAR Networks, a subsidiary company of First Data.

Mergers

The network has existed since the 1980s, and has since included several other networks, mostly in the 2000s:

See also

References

External links

Geomantic figures

The 16 geomantic figures are the primary symbols used in divinatory geomancy. Each geomantic figure represents a certain state of the world or the mind, and can be interpreted in various ways based upon the query put forth and the method used to generate the figures. When geomancy was introduced to Europe in the Middle Ages, the figures acquired astrological meanings and new forms of interpretation. The figures bear superficial resemblance to the ba gua, the eight trigrams used in the I Ching, a Chinese classic text.

Properties of the figures

Each of the figures is composed of four lines, each line containing either one or two points. Each line represents one of the four classical elements: from top to bottom, the lines represent fire, air, water, and earth. When a line has a single point, the element is said to be active; otherwise, with two points, the element is passive. Because there are four lines, and since each line can be either active or passive, there are 2⁴, or 16, different figures. The different combinations of elements yields different representations or manifestations of the figure's energy.

Fence

A fence is a structure that encloses an area, typically outdoors, and is usually constructed from posts that are connected by boards, wire, rails or netting. A fence differs from a wall in not having a solid foundation along its whole length.

Alternatives to fencing include a ditch (sometimes filled with water, forming a moat).

Types

By function

Horse jumping obstacles

Various obstacles are found in competitive sports involving horse jumping. These include show jumping, hunter, and the cross-country phase of the equestrian discipline of eventing. The size and type of obstacles vary depending on the course and the level of the horse and rider, but all horses must successfully negotiate these obstacles in order to complete a competition. Fences used in hunter and eventing are generally made to look relatively rustic and natural.

In jumping competition, they are often brightly colored and creatively designed. In hunter and jumper competition, obstacles are constructed to fall down if struck by the horse. In eventing, they are built to be solid, though for safety, certain elements may be designed to break away if hit.

Arrowhead

Also called chevrons, these fences are shaped like triangles, with the point facing towards the ground. They are generally very narrow, usually only a few feet wide. Arrowhead fences require the rider to keep their horse straight between their hands and legs, as it is easy for a run-out to occur due to the narrowness of the fence. These fences are often used in combination with other obstacles to increase their difficulty, such as right after a bank or as the second obstacle in a bending line. This tests the rider's ability to regain control of his/her horse following an obstacle.

Fence (finance)

Fence (also known as a Dutch Rudder) is an investment strategy that uses options to limit the range of possible returns on a financial instrument.

A fence consists of the following elements:

The expiration dates of all the options are usually the same. The call strike is normally chosen in such a way that the sum total of the three option premiums are equal to zero.

This investment strategy will ensure that the value of the investment at expiry will be between the strike price on the short call and the strike price on the long put. Thus possible gains and losses (the value of the financial instrument minus the cost of acquiring it) are confined to a specified range.