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.

Origin of ice age theory

The plan that, in the past, glaciers had been far more extensive was folk knowledge in some alpine regions of Europe (Imbrie and Imbrie, p25, quote a woodcutter telling de Charpentier of the former extent of the Swiss Grimsel glacier). No single person imaginary the idea. Between 1825 and 1833, Jean de Charpentier assembled proof in support of this idea. In 1836 Charpentier influenced Louis Agassiz of the theory, and Agassiz published it in his book Étude sur les glaciers of 1840.

At this early stage of knowledge, what were being studied were the glacial periods within the past few hundred thousand years, during the present ice age. The far previous ice ages' very existence was unsuspected.

Astronomy of Natural Science

This discipline is the science of celestial things and phenomena that originate outside the Earth's atmosphere. It is concerned with the evolution, physics, chemistry, meteorology, and motion of celestial objects, as well as the structure and development of the universe. Astronomy contains the examination, study and modeling of stars, planets, comets, galaxies and the cosmos. Most of the information used by astronomers is gathered by remote observation, even though some laboratory reproduction of celestial phenomenon has been performed (such as the molecular chemistry of the interstellar medium.)

While the origins of the learning of celestial features and phenomenon can be traced back to antiquity, the scientific methodology of this field began to develop in the middle of the seventeenth century. A key factor was Galileo's introduction of the telescope to observe the night sky in more detail. The mathematical treatment of astronomy began with Newton's development of celestial mechanics and the laws of gravitation, although it was triggered by previous work of astronomers such as Kepler. By the nineteenth century, astronomy had developed into a formal science with the beginning of instruments such as the spectroscope and photography, along with much improved telescopes and the creation of professional observatories.

Book Paper

A book paper (or publishing paper) is a paper which is designed exclusively for the publication of printed books. Traditionally, book papers are off white or low white papers (easier to read), are dense to minimise the show through of text from one side of the page to the other and are (generally) made to tighter caliper or thickness specifications, particularly for case bound books. Typically, books papers are light weight papers 60–90g/m² and often particular by their caliper/substance ratios (volume basis). For example, a bulky 80g/m² paper may possibly have a caliper of 120 microns (0.12mm) which would be Volume 15 (120×10/80) where as a low bulk 80g/m² may have a caliper of 88 microns, giving a volume 11. This volume basis then allows the calculation of a books PPI (printed pages per inch) which is an essential factor for the design of book jackets and the binding of the finished book.

Generally, higher bulk papers are more obscure and rougher than lower bulk papers, although lower bulk papers, with their smoother outside, will be capable of reproducing finer printed images.

Line Printers

Line printers, as the name implies, print an whole line of text at a time. Three principal designs are existed. In drum printers, a drum carries the whole character set of the printer repeated in each column that is to be printed. In chain printers (also called as train printers), the character set is arranged multiple times around a chain that travels horizontally past the print line. In either case, to print a line, specifically timed hammers strike against the back of the paper at the exact moment that the correct character to be printed is passing in front of the paper. The paper presses forward touching a ribbon which then presses against the character form and the impression of the character form is printed onto the paper.

Comb printers characterize the third major design. These printers were a hybrid of dot matrix printing and line printing. In these printers, a comb of hammers printed a part of a row of pixels at one time (for example, every eighth pixel). By shifting the comb back and forth slightly, the complete pixel row could be printed (continuing the example, in just eight cycles). The paper then highly developed and the next pixel row was printed. Because far less motion was involved than in a conservative dot matrix printer, these printers were very fast compared to dot matrix printers and were competitive in speed with formed-character line printers while also being able to print dot-matrix graphics.

Line printers were the fastest of all impact printers and were used for largeness printing in large computer centres. They were almost never used with personal computers and have now been replaced by high-speed laser printers.

The heritage of line printers lives on in many computer operating systems, which use the abbreviations "lp", "lpr", or "LPT" to refer to printers.

Modern Print Technology

Toner-Based Printers

Toner-based printers work using the Xerographic standard that is at work in most photocopiers: by adhering toner to a light-sensitive print drum, then using static electricity to transfer the toner to the printing medium to which it is fused with heat and pressure.

The most regular type of toner-based printer is the laser printer, which uses precision lasers to cause adherence. Laser printers are known for high quality prints, good print speed, and a low (Black and White) cost-per-copy; they are the most general printer for many general-purpose office applications. They are far less frequently used as consumer printers due to a high initial cost.

Laser printers are existing in both color and monochrome varieties.

Another toner based printer is the LED printer which uses an array of LEDs as an alternative of a laser to cause toner adhesion to the print drum.

Recent research has also indicated that Laser printers produce potentially dangerous ultrafine particles, possibly causing health problems associated with respiration. The degree of particle emissions varies with age, model and design of each printer but is commonly proportional to the amount of toner required. Furthermore, a well ventilated workspace would allow such ultrafine particles to disperse thus reducing the health side effects.

System-of-Systems Engineering (SoSE)

System-of-Systems Engineering (SoSE) is a set of developing processes and methods for manipulative and implementing solutions to System-of-Systems problems. SoSE is moderately new term being used in Department of Defense applications, but is increasingly being applied to non-military/security related problems (e.g., transportation, healthcare, Internet, search and rescue, space exploration). SoSE is more than systems engineering of multifaceted systems because design for System-of-Systems problems is performed under some level of uncertainty in the requirements and the constituent systems, and it involves considerations in multiple levels and domains (as per Ref. 2 and 3). Whereas SE focuses on building the system right, SoSE focuses on choosing the right system(s) to gratify the requirements.