Monday, September 29, 2008

Bluetooth 2.0

This version of the Bluetooth specification was released on November 10, 2004. It is backward-compatible with the previous version 1.1. The main difference is the introduction of an Enhanced Data Rate (EDR) for faster data transfer. The nominal rate of EDR is about 3 megabits per second, although the practical data transfer rate is 2.1 megabits per second.[8] The additional throughput is obtained by using a different radio technology for transmission of the data. Standard, or Basic Rate, transmission uses Gaussian Frequency Shift Keying (GFSK) modulation of the radio signal; EDR uses a combination of GFSK and Phase Shift Keying (PSK) modulation.

Tuesday, September 23, 2008


The British GEE system was developed during World War II. GEE used a series of transmitters sending out precisely timed signals, and the aircraft using GEE, RAF Bomber Command's heavy bombers, examined the time of arrival on an oscilloscope at the navigator's station. If the signal from two stations arrived at the same time, the aircraft must be an equal distance from both transmitters, allowing the navigator to determine a line of position on his chart of all the positions at that distance from both stations. By making similar measurements with other stations, additional lines of position can be produced, leading to a fix. GEE was accurate to about 165 yards (150 m) at short ranges, and up to a mile (1.6km) at longer ranges over Germany. Used after WWII as late as the 1960s in the RAF (approx freq was by then 68MHZ).

Tuesday, September 16, 2008


Hearing or audition is the sense of sound perception. Since sound is vibrations propagating through a medium such as air, the detection of these vibrations, that is the sense of the hearing, is a mechanical sense akin to a sense of touch, albeit a very specialized one. In humans, this perception is executed by tiny hair fibres in the inner ear which detect the motion of a membrane which vibrates in response to changes in the pressure exerted by atmospheric particles within a range of 20 to 22000 Hz, with substantial variation between individuals. Sound can also be detected as vibrations conducted through the body by tactition. Lower and higher frequencies than that can be heard are detected this way only. The inability to hear is called deafness.

Monday, September 08, 2008

Prehistoric life

Prehistoric life are the diverse organisms that have inhabited Earth from the origin of life about 3.8 billion years ago (b.y.a.) to the Historic period (about 3500 BC) when humans began to keep written records.

During the course of evolution, new forms of life developed and many other forms, such as the dinosaurs, became extinct. (See Timeline of evolution).

Prehistoric life evolved over this vast timespan from simple bacteria-like cells in the oceans to algae and protozoa, and ultimately to complex multicellular forms such as fungi, land plants, worms, molluscs, crustaceans, insects, and vertebrates.

In geologic terms, humans evolved very recently, only about 2.5 million years ago (mya). (See Geologic time scale, Human evolution).

Very few species of prehistoric life (such as the coelacanth) still exist today unchanged, tens of millions of years later, thereby making them living fossils. Yet other creatures, like sharks, have changed but a little over millions of years.

However, most life forms -- over 99 percent -- have become extinct, and so the only record of them ever existing that remains today are rock imprints, casts or other fossils.

Tuesday, September 02, 2008

Social anxiety disorder

Social anxiety disorder is also known as social phobia. Individuals with this disorder experience intense fear of being negatively evaluated by others or of being publicly embarrassed because of impulsive acts. Almost everyone experiences "stage fright" when speaking or performing in front of a group. Since occasionally there are artists or performers with social anxiety disorder who are able to perform publicly without significant anxiety, their love of performing and practicing their art may be diminishing their anxiety. Although some high-functioning phobics such as Glenn Gould are able to perform despite anxiety, most people with social phobias become so anxious that performance is out of the question. In fact, their fear of public scrutiny and potential humiliation becomes so pervasive that normal life can become impossible (den Boer 2000; Margolis & Swartz, 2001). Another social phobia is fear of intimacy, or "love-shyness", which most adversely affects certain men. Those afflicted find themselves unable to initiate intimate adult relationships (Gilmartin 1987).