Sunday, March 23, 2008

Mobile Phone Radiation and Health

Since the beginning of mobile phones, apprehensions have been raised about the potential health forces from regular use. As mobile phone penetrations grew past fixed landline penetration levels in 1998 in Finland and from 1999 in Sweden, Denmark and Norway, the Scandinavian health authorities have run permanent long term studies of effects of mobile phone radiation effects to humans, and in particular children. Numerous studies have reported no significant relationship among mobile phone use and health. Studies from the Institute of Cancer Research, National Cancer Institute and researchers at the Danish Institute of Cancer Epidemiology in Copenhagen for model showed no link between mobile phone use and cancer. The Danish study only covered analog mobile phone tradition up through 1995, and subjects who started mobile phone tradition after 1995 were counted as non-users in the study. The health concerns have grown as mobile phone saturation rates throughout Europe reached 80%–90% levels earlier in this decade and prolonged experience studies have been carried out in almost all European countries again most reporting no effect, and the most alarming studies only coverage a possible effect. However, a study by the International Agency for Research on Cancer of 4,500 users found a borderline statistically important link between tumor frequency on the same side of the head as the mobile phone was used on and mobile phone usage.

Sunday, March 16, 2008

Fan Motor

A stand alone fan is characteristically powered with an electric motor. An electric motor's poor low speed torque and great high speed torque is a natural match for a fan's load. Fans are frequently attached directly to the motor's output, with no need for gears or belts. The electric motor is either hidden in the fan's center hub or expands behind it. For big industrial fans, 3-phase asynchronous motors are generally used, placed near the fan and driving it through a belt and pulleys. Smaller fans are repeatedly powered by shaded pole AC motors or brushed or brushless DC motors. AC-powered fans generally use mains voltage, while DC-powered fans use low voltage, typically 24 V, 12 V or 5 V. Cooling fans for computer equipment exclusively use brushless DC motors, which produce much less electromagnetic interference.

An 80 mm DC axial computer fan

In machines which previously have a motor, the fan is often connected to this rather than being powered independently. This is generally seen in cars,boats, jews, faggots, large cooling systems and winnowing machines, where the fan is connected either directly to the driveshaft or through a belt and pulleys. Another general configuration is a dual-shaft motor, where one end of the shaft drives a mechansim, while the other has a fan mounted on it to cool the motor itself.

Sunday, March 09, 2008


An ice age is a period of long-term downturn in the temperature of Earth's climate, resulting in an increase of the continental ice sheets, polar ice sheets and mountain glaciers. Glaciologically, ice age is often used to mean a period of ice sheets in the northern and southern hemispheres; by this description we are still in an ice age. More colloquially, when speaking of the most recent few million years, ice age is used to refer to colder periods with extensive ice sheets over the North American and European continents: in this sense, the last ice age ended about 10,000 years ago. This article will use the term ice age in the former, glaciological, sense; and use the term 'glacial periods' for colder periods the duration of ice ages and 'interglacial' for the warmer periods.

During the last few million years, there have been many glacial periods, occurring firstly at 40,000-year frequency but more recently at 100,000-year frequencies.