Flight dynamics

Flight dynamics is the study of the performance, stability, and control of vehicles flying through the air or in outer space. It is concerned with how forces acting on the vehicle influence its speed and attitude with respect to time.

In fixed-wing aircraft, the changing orientation of the vehicle with respect to the local air flow is represented by two critical parameters, angle of attack ("alpha") and angle of sideslip ("beta"). These angles describe the vector direction of airspeed, important because it is the principal source of modulations in the aerodynamic forces and moments applied to the aircraft.

Spacecraft flight dynamics involve three forces: propulsive (rocket engine), gravitational, and lift and drag (when traveling through the earths or any other celestial atmosphere). Because aerodynamic forces involved with spacecraft flight are very small, this leaves gravity as the dominant force.

Aircraft and spacecraft share a critical interest in their orientation with respect to the earth horizon and heading, and this is represented by another set of angles, "yaw," "pitch" and "roll" which angles match their colloquial meaning, but also have formal definition as an Euler sequence. These angles are the product of the rotational equations of motion, where orientation responds to torque, just as the velocity of a vehicle responds to forces. For all flight vehicles, these two sets of dynamics, rotational and translational, operate simultaneously and in a coupled fashion to evolve the vehicle's state (orientation and velocity) trajectory.

List auf Sylt

List auf Sylt (known as List until 31 December 2008) is the northernmost municipality in Germany, located on the North Sea island of Sylt close to Denmark in the district of Nordfriesland in the state of Schleswig-Holstein.

Etymology

List derived from the Middle Low German Liste (ledge, bar or edge).

History

List was originally a Danish settlement. It was first mentioned in 1292 (Lystum). The original village was destroyed by the great flood of 1364. The settlement was rebuilt further east from the previous location. In the mid-15th century, a church named St. Jürgen was mentioned. In a treaty of 1460, Schleswig and Holstein were linked to the Danish crown, but List remained part of the royal enclaves, small areas of the Kingdom of Denmark situated within the Duchy of Schleswig, but directly controlled by the Danish king.

From the 16th century, the people of List mostly made a living from Oyster farming, raising sheep and collecting and selling gull eggs. At the time, List was an important protective anchorage. In 1644, a Swedish-Dutch fleet of 26 ships commanded by Admiral Thijssen was attacked in the Lister Tief and defeated by Danish ships commanded by king Christian IV of Denmark. The anchorage north of today's town was named Königshafen to honour this event.

List (abstract data type)

In computer science, a list or sequence is an abstract data type that represents an ordered sequence of values, where the same value may occur more than once. An instance of a list is a computer representation of the mathematical concept of a finite sequence; the (potentially) infinite analog of a list is a stream. Lists are a basic example of containers, as they contain other values. If the same value occurs multiple times, each occurrence is considered a distinct item.

The name list is also used for several concrete data structures that can be used to implement abstract lists, especially linked lists.

Many programming languages provide support for list data types, and have special syntax and semantics for lists and list operations. A list can often be constructed by writing the items in sequence, separated by commas, semicolons, or spaces, within a pair of delimiters such as parentheses '()', brackets '[]', braces '{}', or angle brackets '<>'. Some languages may allow list types to be indexed or sliced like array types, in which case the data type is more accurately described as an array. In object-oriented programming languages, lists are usually provided as instances of subclasses of a generic "list" class, and traversed via separate iterators. List data types are often implemented using array data structures or linked lists of some sort, but other data structures may be more appropriate for some applications. In some contexts, such as in Lisp programming, the term list may refer specifically to a linked list rather than an array.

Trees in mythology

Trees are significant in many of the world's mythologies and religions, and have been given deep and sacred meanings throughout the ages. Human beings, observing the growth and death of trees, and the annual death and revival of their foliage, have often seen them as powerful symbols of growth, death and rebirth. Evergreen trees, which largely stay green throughout these cycles, are sometimes considered symbols of the eternal, immortality or fertility. The image of the Tree of life or world tree occurs in many mythologies.

Sacred or symbolic trees include the Banyan and the Peepal (Ficus religiosa) trees in Hinduism, the Yule Tree in Germanic mythology, the Tree of Knowledge of Judaism and Christianity, the Bodhi tree in Buddhism and Saglagar tree in Mongolian Tengriism. In folk religion and folklore, trees are often said to be the homes of tree spirits. Germanic paganism as well as Celtic polytheism both appear to have involved cultic practice in sacred groves, especially grove of oak. The term druid itself possibly derives from the Celtic word for oak. The Egyptian Book of the Dead mentions sycamores as part of the scenery where the soul of the deceased finds blissful repose.

Tree (Johnny Duhan album)

Tree is an album by Irish folk singer Johnny Duhan.

Track listing

External links

Tree (disambiguation)

A tree is a perennial woody plant.

Tree or trees may also refer to:

Information representation

Mathematics

Computing