Human population density

For humans, population density is the number of people per unit of area (which may include or exclude cultivated or potentially productive area). Commonly this may be calculated for a county, city, country, another territory, or the entire world.

The world population is 6.6 billion, and Earth's area is 510 million square kilometers (200 million square miles). Therefore the world-wide human population density is 6.6 billion / 510 million = 13 per km² (33 per sq mi), or 43 per km² (112 per sq mi) if only the Earth's land area of 150 million km² (58 million sq mi) is taken into account. This density rises when the population grows. It also includes all continental and island land area, including Antarctica. Considering that over half of the earth's land mass consists of areas inhospitable to human inhabitation, such as deserts and high mountains, and that population tends to cluster around seaports and fresh water sources, this number by itself does not give the most accurate measurement of human population density.

Several of the most densely-populated territories in the world are city-states, microstates, micronations, or dependencies. These territories share a relatively small area and a high urbanization level, with an economically specialized city population drawing also on rural resources outside the area, illustrating the difference between high population density and overpopulation.

Cities with high population densities are, by some, considered to be overpopulated, though the extent to which this is the case depends on factors like quality of housing and infrastructure or access to resources. Most of the most densely-populated cities are in southern and eastern Asia, though Cairo and Lagos in Africa also fall into this category.

City population is however, heavily dependent on the definition of "urban area" used: densities are typically higher for the central municipality itself, than when more recently-developed and administratively unincorporated suburban communities are included, as in the concepts of agglomeration or metropolitan area, the latter including sometimes neighbouring cities.

DoDAF

The Department of Defense Architecture Framework (DoDAF) defines a standard way to organize an enterprise architecture (EA) or systems architecture into complementary and consistent views. All major U.S. Government Department of Defense (DoD) weapons and information technology system procurements are required to develop and document an EA using the views prescribed in the DoDAF. While it is clearly aimed at military systems, DoDAF has broad applicability across the private, public and voluntary sectors around the world, and represents only one of a large number of systems architecture frameworks.It is especially suited to large systems with complex integration and interoperability challenges, and is apparently unique in its use of "operational views" detailing the external customer's operating domain in which the developing system will operate

Twentieth-century iconography

In the early-twentieth century Germany, Aby Warburg (1866–1929) and his followers Fritz Saxl (1890–1948) and Erwin Panofsky (1862–1968) elaborated the practice of identification and classification of motifs in images to using iconography as a means to understanding meaning. Panofsky codified an influential approach to iconography in his 1939 Studies in Iconology, where he defined it as "the branch of the history of art which concerns itself with the subject matter or meaning of works of art, as opposed to form,"[3] although the distinction he and other scholars drew between particular definitions of "iconography" (put simply, the identification of visual content) and "iconology" (the analysis of the meaning of that content), has not been generally accepted, though it is still used by some writers.

In the United States, where Panofsky immigrated in 1931, students such as Frederick Hartt, and Meyer Schapiro continued under his influence in the discipline. In an influential article of 1942, Introduction to an "Iconography of Mediaeval Architecture", Richard Krautheimer, a specialist on early medieval churches and another German emigré, extended iconographical analysis to architectural forms.

The period from 1940 can be seen as one where iconography was especially prominent in art history. Whereas most icongraphical scholarship remains highly dense and specialized, some analyses began to attract a much wider audience, for example Panofsky's theory (now generally out of favour with specialists) that the writing on the rear wall in the Arnolfini Portrait by Jan van Eyck turned the painting into the record of a marriage contract. Holbein's The Ambassadors has been the subject of books for a general market with new theories as to its iconography, and the best-sellers of Dan Brown include theories, disowned by most art historians, on the iconography of works by Leonardo da Vinci.

Technological advances allowed the building-up of huge collections of photographs, with an iconographic arrangement or index, which include those of the Warburg Institute and the Index of Christian Art at Princeton (which has made a specialism of iconography since its early days in America). These are now being digitised and made available online, usually on a restricted basis.

With the arrival of computing, the Iconclass system, a highly complex way of classifying the content of images, with 28,000 classification types, and 14,000 keywords, was developed in the Netherlands as a standard classification for recording collections, with the idea of assembling huge databases that will allow the retrieval of images featuring particular details, subjects or other common factors. For example, the Iconclass code "71H7131" is for the subject of "Bathsheba (alone) with David's letter", whereas "71" is the whole "Old Testament" and "71H" the "story of David". A number of collections of different types have been classified using Iconclass, notably many types of old master print, the collections of the Gemäldegalerie, Berlin and the German Marburger Index. These are available, usually on-line or on DVD. The system can also be used outside pure art history, for example on sites like Flickr.

Paleolithic

Paleolithic means "Old Stone Age." This was the earliest period of the Stone Age. The Lower Paleolithic predates Homo sapiens, beginning with Homo habilis and the earliest use of stone tools some 2.5 million years ago. Homo sapiens originated some 200,000 years ago, ushering in the Middle Paleolithic.

Sometime during the Middle Paleolithic, humans also developed language, music, early art, as well as systematic burial of the dead.

Humans spread from East Africa to the Near East some 80 millennia ago, and further to southern Asia and Australasia some 60 millennia ago, northwestwards into Europe and eastwards into Central Asia some 40 millennia ago, and further east to the Americas from ca. 15 millennia ago. The Upper Paleolithic is taken to begin some 40 millennia ago, with the appearance of "high" culture. Expansion to North America and Oceania took place at the climax of the most recent Ice Age, when today's temperate regions were extremely inhospitable. By the end of the Ice Age some 12,000 BP, humans had colonised nearly all the ice-free parts of the globe.

Throughout the Paleolithic, humans generally lived as nomadic hunter-gatherers. Hunter-gatherer societies have tended to be very small and egalitarian, though hunter-gatherer societies with abundant resources or advanced food-storage techniques have sometimes developed a sedentary lifestyle, complex social structures such as chiefdoms, and social stratification; and long-distance contacts may be possible, as in the case of Indigenous Australian "highways."

Wi-Fi Reach

Due to reach requirements for wireless LAN applications, power consumption is fairly high compared to some other low-bandwidth standards. Especially Zigbee and Bluetooth supporting wireless PAN applications refer to much lesser propagation range of <10m (ref. e.g. IEEE Std. 802.15.4 section 1.2 scope). Range is always making battery life a concern.

Wi-Fi networks have limited range. A typical Wi-Fi home router using 802.11b or 802.11g with a stock antenna might have a range of 32 m (120 ft) indoors and 95 m (300 ft) outdoors. Range also varies with frequency band. Wi-Fi in the 2.4 GHz frequency block has slightly better range than Wi-Fi in the 5 GHz frequency block. Outdoor range with improved (directional) antennas can be several kilometres or more with line-of-sight.

Wi-Fi performance decreases roughly quadratically as the range increases at constant radiation levels.

Buckler

A buckler (French bouclier 'shield', from old French bocle, boucle 'boss') is a small shield gripped in the fist -- it was generally used as a companion weapon in hand-to-hand combat during the Middle Ages, as its size made it poor protection against missile weapons (e.g., arrows) but useful in deflecting the blow of an opponent's sword or mace. There are two major forms of medievally documented bucklers. The first is a simple round shield with the fist positioned directly behind the boss with a variety of shapes of face and depths of rim. These could also have projections from the top and bottom as in Hans Talhoffer's Fechtbücher or serrated rings around the boss as in one example in the Wallace Collection. The second major form is a corrugated rectangle as suggested by Achille Marozzo in his Opera Nova.

Transcendental number

In mathematics, a transcendental number is a complex number that is not algebraic, that is, not a solution of a non-zero polynomial equation with rational coefficients. In other words, transcendental numbers are numbers that do not arise from Euclidean geometry or ordinary algebraic expressions.

The most prominent examples of transcendental numbers are π and e. Only a few classes of transcendental numbers are known, indicating that it can be extremely difficult to show that a given number is transcendental.

However, transcendental numbers are not rare: indeed, almost all real and complex numbers are transcendental, since the algebraic numbers are countable, but the sets of real and complex numbers are uncountable. All transcendental numbers are irrational, since all rational numbers are algebraic. (The converse is not true: not all irrational numbers are transcendental.)