How do Laser Printers Work?

 

Laser printers have become ubiquitous in the office and copying environment. The first laser printer was developed in 1971 by Xerox, and in 1977 it was brought to the commercial market. The rapid, crisp printing soon made laser printers a popular choice for many consumers, although the internal workings of the printer remained mysterious to many. Because of the name, some consumers think that laser printers use a laser actively on the paper in some way. In fact, laser printers actually harness static electricity to print, although lasers do play a role in the printing process.

Laser printers begin a print job by receiving data from a computer and routing it through a central controller, a small computer inside the printer which manages the printer. Many laser printers have a controller which is capable of handling several jobs at once, enqueuing them, and then printing them. This ability to handle multiple sets of data makes laser printers quite popular. After the controller has determined what is going to be printed, the process begins.

Inside a laser printer there is a drum which holds an electric charge. Next to the drum is a transfer corona roller, which can negatively or positively charge the drum as needed, as well as a toner unit. In most laser printers, the drum starts out positively charged, although this process can also work in reverse. The controller manipulates a small laser to “write” on the drum with a negative charge, creating an electrostatic image.

Then, the drum is rolled through the toner, which is positively charged so that it will cling to the areas of negative charge on the printer drum. The printer feeds a piece of paper, which is given an even stronger negative charge by the transfer corona wire before being rolled past the drum. The electrostatic image on the drum will transfer to the paper, which is then discharged to prevent it from clinging to the drum. Then it is fed through a fuser which heats the toner and causes it to bind with the fibres in the paper.

Meanwhile, the drum passes a discharge lamp, which will expose the entire surface of the drum and erase the electrostatic image. The transfer corona wire applies another positive charge, and the printer is ready for the next page or job.

Colour laser printers work by performing multiple passes. Most printers have blue, red, and yellow ink, in addition to black, which can be combined to form any colour. Some printers progressively lay the ink onto the drum so that the image will print with one pass of the paper, while others recirculate the paper multiple times to apply progressive layers of colour. Large colour printers sometimes have separate drum and toner assemblies for each colour, with the paper passing each drum separately.

The History of Dell

 

Dell, Inc, which was ranked the 25th largest company on the Fortune 500 list by Forbes magazine, began its cosmic rise in 1984 when Michael Dell used a mere $1000 dollars to found PC’s Limited. Working in a college dorm room at the University of Texas, Michael Dell had a goal to produce IBM compatible computers from stock components to suit individual customer needs.

The company vision was to produce computers that could easily be fitted with individual components to build a computer system to accommodate individual requirements. The goal was to give the customer exactly what they needed or wanted. The computers were built from stock parts as they were ordered. In 1985, the founder dropped out of school, got a family loan for $300,000 dollars and began to give his full attention to the new company.

Later the same year the company introduced its first company designed computer, the Turbo PC.  The computer boasted an Intel 8088 processor that ran at an impressive speed of 8MHz. And it sold in the United States for $795 dollars. The computer systems, which were advertised in computer magazines nationally, were purchased through direct sales. Given a list of options, the customers choose the components they wanted and the computers were built as they were ordered. By ordering the components wholesale, the company was able to provide great pricing, which proved to be much lower than their competitors’. The company’s business formula proved to be a great success and the first year of trading they grossed more than $73 million dollars.

Ireland welcomed the new company in 1987, and became the first of many international operations. 1988 ushered in the new company name, Dell Computer Corporation and this company with humble beginnings grew from a $30 million dollar company to a company worth $90 million dollars. Although the company attempted to market their computers via warehouse club stores and superstores, the public, now used to having the ability to choose and build as they wanted, did not respond as hoped and the company returned to direct sales.

Dell’s 10th anniversary was celebrated in 1994 with the release of a brand new logo. And 1996 found the company selling the popular computer systems direct to the customer on Dell’s own internet website. When the company acquired Compaq in 1999 they became known as the top seller of personal computer systems in the United States.

2002 became the year of company expansion as Dell began to also provide such products as televisions, digital audio players and computer printers. The following year, 2003 the company became known as Dell Inc. in an effort to acknowledge the company’s expansion into other products. The year 2004 saw a new manufacturing assembly plant near Winston- Salem, North Carolina and Michael Dell while deciding to appoint Kevin Rollins as new CEO, decided to retain the position of Chairman of the Board. In 2007 CEO Kevin Rollins resigned and Michael Dell resumed his position as CEO. Dell is also one of the largest suppliers of dedicated servers to web hosting companies.

While true that Dell Inc. has experienced some trouble spots in the past few years, the company continues to be one of the largest computer manufacturers due mainly to the long record of customer satisfaction. While others have adopted the model of direct sales, Dell Inc. continues to be the most successful and the most popular.

How do Inkjet Printers Work?

 

Although inkjet printers were first mass-produced in the 1980s, it was only in the 1990s that prices dropped low enough for that technology to be brought into the mass consumer market. Canon claims to have invented what it calls ‘bubble jet’ technology in 1977, when a researcher accidentally touched an ink-filled syringe with a hot soldering iron and the heat forced a drop of ink out of the needle. And so began the development of a new printing method.

Inkjet printers have made rapid technological advances in recent years. First, the three-color printer succeeded in making colour inkjet printing an affordable option; but as the superior four-color models became cheaper to produce and sell, it wound up being the standard and users’ choice.

Inkjet printing has two chief benefits over laser printers: lower printer cost and colour-printing capabilities. But while inkjet printers are priced much less than laser printers, they are actually more expensive to use and maintain. Cartridges need to be changed more frequently and the special coated paper required to produce high-quality output is very expensive. At a cost per page level, inkjet printing costs about 10 times more than laser printing.

Operation

Inkjet printing, like laser printing, is a non-impact process. Ink is emitted from nozzles while they pass over media. The operation of an inkjet printer is easy to visualize: liquid ink in various colours being squirted onto paper and other media, like plastic film and canvas, to build an image. A print head scans the page in horizontal strips, using the printer’s motor assembly to move it from left to right and back again, while the paper is rolled up in vertical steps, again by the printer. A strip (or row) of the image is printed, then the paper moves on, ready for the next strip. To speed things up, the print head doesn’t print just a single row of pixels in each pass, but a vertical row of pixels at a time.

For most inkjet printers, the print head takes about half a second to print the strip across a page. On a typical 8 1/2″-wide page, the print head operating at 300 dpi deposits at least 2,475 dots across the page. This translates into an average response time of about 1/5000th of a second. Quite a technological feat! In the future, however, advances will allow for larger print heads with more nozzles firing at faster frequencies, delivering native resolutions of up to 1200dpi and print speeds approaching those of current colour laser printers (3 to 4 pages per minute in colour, 12 to 14ppm in monochrome). In other words, declining costs for improving technology.

There are several types of inkjet printing. The most common is “drop on demand” (DOD), which means squirting small droplets of ink onto paper through tiny nozzles; like turning a water hose on and off 5,000 times a second. The amount of ink propelled onto the page is determined by the print driver software that dictates which nozzles shoot droplets, and when.

The nozzles used in inkjet printers are hairbreadth fine and on early models they became easily clogged. On modern inkjet printers this is rarely a problem, but changing cartridges can still be messy on some machines. Another problem with inkjet technology is a tendency for the ink to smudge immediately after printing, but this, too, has improved drastically during the past few years with the development of new ink compositions.

Climate Change

 

December 2010 the British weather delivered an early and spectacular cold blast to mark the start of the climate-change talks in Cancún, Mexico. Snow fell heavily in much of the country, and lightly over all of it; temperatures dropped to below -10°C. The chill might not presage another enduringly severe winter like that of 2009-10, but it has already brought a familiar crop of stories about traffic turmoil and closed schools. It might also add to Britain’s scepticism about climate change (already more widespread than in many other European countries).

It shouldn’t. While the beginning of 2010 is remembered by northern Europeans, Russians and inhabitants of America’s southern states as very cold, it was warm elsewhere, peculiarly so in Canada and Greenland. The average global temperature from January to March was the fourth highest on record. This is one of the reasons why 2010 as a whole seems likely to rank first or second in the list of average annual temperatures (depending on which bunch of climate scientists is doing the ranking).

Europe’s cold winters and the warmth of the planet as a whole might even be linked. There is some evidence that the summer heat stored in the newly ice-free seas north of Siberia may induce shifts in the atmosphere’s circulation, when the heat is given up to the air in subsequent autumns and winters. Those shifts might in turn encourage seasonal patterns in which the Arctic is warm and the continents below it cold, as in early 2010. Since the sea-ice area looks likely to go on shrinking, such a link, if indeed it exists, would probably mean more cold winters in Britain and much of Europe.

Other research suggests that warming may actually have alleviated recent freezes. A team of French climate scientists analysed last winter’s European weather day by day. For each day’s arrangements of high pressure, low pressure, wind speed and the like, they looked for similar days at similar times of year in records stretching back to 1948. In general, cold winter days in 2010 turned out to be less cold than equivalent days in earlier years had been.

Overall, judging by pressures and winds, 2009-10 should have been as cold as 1963, the coldest winter in the records analysed, with temperatures on average 4°C lower than normal. Instead it was the 13th coldest winter with an average temperature just 1.3°C below normal. Britons put out by the current bout of cold weather will get little satisfaction from the thought that it could have been worse. But it used to be.

So what is in store for the 2011 winter season, will we experience another cold snap that throws the country into disarray or will it be mild winter?

Photovoltaic – The Application of The Future

 

You’ve probably seen calculators with solar cells — devices that never need batteries and in some cases, don’t even have an off button. As long as there’s enough light, they seem to work forever. You may also have seen larger solar panels, perhaps on emergency road signs, call boxes, buoys and even in parking lots to power the lights.

Although these larger panels aren’t as common as solar-powered calculators, they’re out there and not that hard to spot if you know where to look. In fact, photovoltaics — which were once used almost exclusively in space, powering satellites’ electrical systems as far back as 1958 — are being used more and more in less exotic ways. The technology continues to pop up in new devices all the time, from sunglasses to electric vehicle charging stations.

The hope for a “solar revolution” has been floating around for decades — the idea that one day we’ll all use free electricity from the sun. This is a seductive promise, because on a bright, sunny day, the sun’s rays give off approximately 1,000 watts of energy per square meter of the planet’s surface. If we could collect all of that energy, we could easily power our homes and offices for free.

The solar cells that you see on calculators and satellites are also called photovoltaic (PV) cells, which as the name implies (photo meaning “light” and voltaic meaning “electricity”), convert sunlight directly into electricity. A module is a group of cells connected electrically and packaged into a frame (more commonly known as a solar panel), which can then be grouped into larger solar arrays, like the one operating at Nellis Air Force Base in Nevada.

Photovoltaic cells are made of special materials called semiconductors such as silicon, which is currently used most commonly. Basically, when light strikes the cell, a certain portion of it is absorbed within the semiconductor material. This means that the energy of the absorbed light is transferred to the semiconductor. The energy knocks electrons loose, allowing them to flow freely.

PV cells also all have one or more electric field that acts to force electrons freed by light absorption to flow in a certain direction. This flow of electrons is a current, and by placing metal contacts on the top and bottom of the PV cell, we can draw that current off for external use, say, to power a calculator. This current, together with the cell’s voltage (which is a result of its built-in electric field or fields), defines the power (or wattage) that the solar cell can produce.

Why is Halloween called Halloween?

 

Straddling the line between Autumn and Winter, plenty and paucity, life and death, Halloween is a time of celebration and superstition. It is thought to have originated with the ancient Celtic festival of Samhain, when people would light bonfires and wear costumes to ward off roaming ghosts. In the eighth century, Pope Gregory III designated November 1 as a time to honor all saints and martyrs; the holiday, All Saints’ Day, incorporated some of the traditions of Samhain. The evening before was known as All Hallows’ Eve and later Halloween. Over time, Halloween evolved into a secular, community-based event characterized by child-friendly activities such as trick-or-treating. In a number of countries around the world, as the days grow shorter and the nights get colder, people continue to usher in the winter season with gatherings, costumes and sweet treats.

Ancient Origins of Halloween
Halloween’s origins date back to the ancient Celtic festival of Samhain (pronounced sow-in). The Celts, who lived 2,000 years ago in the area that is now Ireland, the United Kingdom and northern France, celebrated their new year on November 1. This day marked the end of summer and the harvest and the beginning of the dark, cold winter, a time of year that was often associated with human death. Celts believed that on the night before the new year, the boundary between the worlds of the living and the dead became blurred. On the night of October 31 they celebrated Samhain, when it was believed that the ghosts of the dead returned to earth. In addition to causing trouble and damaging crops, Celts thought that the presence of the otherworldly spirits made it easier for the Druids, or Celtic priests, to make predictions about the future. For a people entirely dependent on the volatile natural world, these prophecies were an important source of comfort and direction during the long, dark winter.
To commemorate the event, Druids built huge sacred bonfires, where the people gathered to burn crops and animals as sacrifices to the Celtic deities. During the celebration, the Celts wore costumes, typically consisting of animal heads and skins, and attempted to tell each other’s fortunes. When the celebration was over, they re-lit their hearth fires, which they had extinguished earlier that evening, from the sacred bonfire to help protect them during the coming winter.

Today’s Halloween Traditions
The American Halloween tradition of “trick-or-treating” probably dates back to the early All Souls’ Day parades in England. During the festivities, poor citizens would beg for food and families would give them pastries called “soul cakes” in return for their promise to pray for the family’s dead relatives. The distribution of soul cakes was encouraged by the church as a way to replace the ancient practice of leaving food and wine for roaming spirits. The practice, which was referred to as “going a-souling” was eventually taken up by children who would visit the houses in their neighborhood and be given ale, food, and money.

The tradition of dressing in costume for Halloween has both European and Celtic roots. Hundreds of years ago, winter was an uncertain and frightening time. Food supplies often ran low and, for the many people afraid of the dark, the short days of winter were full of constant worry. On Halloween, when it was believed that ghosts came back to the earthly world, people thought that they would encounter ghosts if they left their homes. To avoid being recognized by these ghosts, people would wear masks when they left their homes after dark so that the ghosts would mistake them for fellow spirits. On Halloween, to keep ghosts away from their houses, people would place bowls of food outside their homes to appease the ghosts and prevent them from attempting to enter.