Tuesday, February 27, 2007

2D computer graphics

The first advance in computer graphics was in the use of CRTs. There are two approaches to 2D computer graphics: vector and raster graphics. Vector graphics stores precise geometric data, topology and style such as: coordinate positions of points, the relations between points , and the color, thickness, and possible fill of the shapes. Most vector graphic systems can also use primitives of standard shapes such as circles, rectangles, etc.

Early vector-graphics displays were monochrome CRTs where the picture was drawn by the cathode ray being motivated about the screen along the required path.On a scanning display, a vector graphic image has to be transformed to a raster image to be viewed. Raster graphics is a uniform 2-dimensional grid of pixels. Each pixel has a specific value such as, for instance, brightness, color, transparency, or a combination of such values. A raster image has a finite resolution of a specific number of rows and columns. Standard computer displays shows a raster image of resolutions such as 1280 columnsx1024 rows of pixels. Today, one often combines raster and vector graphics in complex file formats.

Sunday, February 18, 2007


The term wildlife refers to living organisms that are not in any way artificial or domesticated and which survive in natural habitats. Wildlife can refer to flora but more usually refers to fauna. Wildlife is a very general term for life in ecosystems. Deserts, rainforests, plains, and other areas including the most built-up urban sites all have distinct forms of wildlife.

Humans have historically tended to split civilization from wildlife in a number of ways; besides the obvious difference in vocabulary, there are differing expectations in the legal, social, and moral sense. This has been a reason for debate during recorded history. Religions have often declared certain animals to be sacred, and in modern times concern for the environment has aggravated activists to protest the exploitation of wildlife for human benefit or entertainment. Literature has also made use of the traditional human separation from wildlife.

Tuesday, February 06, 2007


Sound is an interruption of mechanical energy that propagates through matter as a wave. Sound is characterized by the properties of sound waves which are frequency, wavelength, period, amplitude and velocity or speed. Noise and sound often mean the same thing; when they differ, a noise is a useless sound. In science and engineering, noise is an undesirable component that obscures a signal.

Humans perceive sound by the sense of hearing. By sound, we usually mean the vibrations that travel through air and can be heard by humans. However, scientists and engineers use a wider description of sound that includes low and high frequency vibrations in air that cannot be heard by humans, and vibrations that travel through all forms of matter, gases, liquids and solids. The matter that supports the sound is called the medium. Sound propagates as waves of irregular pressure, causing local regions of compression and rarefaction. Particles in the medium are displaced by the wave and oscillate. The scientific study of sound is called acoustics.

Friday, February 02, 2007

Heat wave

A heat wave is a prolonged period of extremely hot weather, which may be accompanied by high humidity. There is no universal definition of a heat wave the term is relative to the usual weather in the area. Temperatures that people from a hotter climate believe normal can be termed a heat wave in a cooler area if they are outside the normal climate pattern for that area.
The term is applied both to routine weather variation and to extraordinary spells of heat which may occur only once a century. Severe heat waves have caused catastrophic crop failures, thousands of deaths from hyperthermia, and widespread power outages due to increased use of air conditioning.

Heat waves often occur for the period of the Dog Days of summer; indeed the French term canicule, denoting the general phenomenon of a heat wave, derives from the Italian canicula applied to the star Sirius, also known as the "Dog Star." Some regions of the globe are more susceptible to heat waves than others, such as Mediterranean-type climates with a summer dry spell which becomes much hotter than usual during certain years