How does a Hard Disk work...?

HDDs record data by magnetizing a ferromagnetic material directionally, to represent either a 0 or a 1 binary digit. They read the data back by detecting the magnetization of the material. A typical HDD design consists of a spindle which holds one or more flat circular disks called platters, onto which the data is recorded. The platters are made from a non-magnetic material, usually glass or aluminum, and are coated with a thin layer of magnetic material. Older disks used iron(III) oxide as the magnetic material, but current disks use a cobalt-based alloy.
The platters are spun at very high speeds. Information is written to a platter as it rotates past mechanisms called read-and-write heads that operate very close over the magnetic surface. The read-and-write head is used to detect and modify the magnetization of the material immediately under it. There is one head for each magnetic platter surface on the spindle, mounted on a common arm. An actuator arm (or access arm) moves the heads on an arc (roughly radially) across the platters as they spin, allowing each head to access almost the entire surface of the platter as it spins. The arm is moved using a voice coil actuator or (in older designs) a stepper motor.
The magnetic surface of each platter is divided into many small sub-micrometre-sized magnetic regions, each of which is used to encode a single binary unit of information. In today's HDDs each of these magnetic regions is composed of a few hundred magnetic grains. Each magnetic region forms a magnetic dipole which generates a highly localized magnetic field nearby. The write head magnetizes a magnetic region by generating a strong local magnetic field nearby. Early HDDs used an electromagnet both to generate this field and to read the data by using electromagnetic induction. Later versions of inductive heads included metal in Gap (MIG) heads and thin film heads. In today's heads, the read and write elements are separate but in close proximity on the head portion of an actuator arm. The read element is typically magneto-resistive while the write element is typically thin-film inductive.
In modern drives, the small size of the magnetic regions creates the danger that their magnetic state be lost because of thermal effects. To counter this, the platters are coated with two parallel magnetic layers, separated by a 3-atom-thick layer of the non-magnetic element ruthenium, and the two layers are magnetized in opposite orientation, thus reinforcing each other. Another technology used to overcome thermal effects to allow greater recording densities is perpendicular recording, which has been used in some hard drives as of 2006.
Hard disk drives are sealed to prevent dust and other sources of contamination from interfering with the operation of the hard disks heads. The hard drives are not air tight, but rather utilize an extremely fine air filter, to allow for air inside the hard drive enclosure. The spinning of the disks causes the air to circulate forcing any particulates to become trapped on the filter. The same air currents also act as a gas bearing which enables the heads to float on a cushion of air above the surfaces of the disks.

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Flash Memory Card FAQs

1.

What is a Memory Card? How do memory cards work?

A memory card is a form of solid state storage device, with no moving parts; it functions electronically instead of mechanically. A memory card is a non-volatile computer memory data storage device used with electronic devices where data can be electrically erased and reprogrammed. They are small, do not require power and are ideal for portable devices. A few examples of electronics that use memory cards include; digital cameras, laptop computers, mobile telephones, music players, televisions, video game consoles, and other electronics. Due to its high ability to store data without power, small form factor, re-recordability, and rugged environmental specifications, memory cards are extremely useful.

2.

What is the difference between various memory card formats?

There are many different flash memory cards on the market. A few examples of Memory Cards include; SD cards, miniSD cards, microSD cards, SDHC cards, Compact Flash cards, memory sticks, Memory Stick Pro, Memory Stick Pro Duo, multimedia cards, smartmedia cards and XD cards. With such a long list of different flash memory card formats to choose from, it may be confusing to find the right memory card. Before you go out to purchase a memory card, confirm the format(s) supported by your digital devices prior to purchase. For example, your digital camera may only take an XD card (make sure by referring to the manufacturer of the digital device), do not go out and purchase an SD card. The Memory Stick, Memory Stick Pro and Memory Stick Duo are memory cards that work with only a few host devices, primarily with Sony brands.

3.	I just purchased a memory card. Why doesn’t my memory card work?
	It is advised that you format the new memory card in the electronic device before use. Refer to the instruction manual of the electronic device to learn how to format your memory card.

4.

How do I use my memory card? What are handling instructions to use the memory card?

It is advised for use of all memory cards to not remove them from devices while data is being processed. In other words, power off the host device prior to removing the memory card. Since flash memory is sensitive to power loss, it is recommended that you remove the memory card in devices that are low on batteries. Data on the memory card cards may be corrupted by sudden power loss. To reduce chances of electrostatic discharge (ESD) avoid touching the metal connectors of memory cards, especially those of the Secure Digital cards, Smart Media cards and XD cards.

5.

Why are some of my files missing on my memory card? Why is some of my data corrupted on my memory card?

After uploading photos onto your computer, you may find that some of the photos are corrupted or missing. The memory card may be defective or a few of the sectors on the card may have been corrupted by sudden power loss. First try to format the card to solve data corruption issues; this could be done either on the devices (digital camera, mp3 player, pda) or on a computer. If this still does not solve the data corruption problem, you should run hard disk maintenance (such as Scandisk on PC's) on your digital media card. If problems still occur, contact the manufacturer of the memory card.

6.

My card is no longer recognized by my digital camera/memory card reader. Is something wrong with my memory card?

First, make sure that your card is inserted into the device properly; ensure that the pins of the card are facing the plastic in the card port. If the card is inserted properly and is still not recognized on the host devices, it is possible that the memory card has become defective over time. Attempt to format the memory card; this could be done either on the devices (digital camera, mp3 player, pda) or on a computer. If formatting the card is unsuccessful please contact the memory card manufacturer.

7.	Can I retrieve lost data from my memory card?
	You can use hard disk repair programs (Norton Disk Doctor, Scandisk and Disk First Aid) to recover data fragments from the corrupted memory card. Additionally, there are third party programs and data recovery services. Typically, data cannot be recovered if the memory card is not recognized on a device.

8.

Why does my memory card show less capacity than listed?

There are two main reasons why there is a discrepancy between listed capacity of the memory card and what shows up on your computer. The most likely reason that your 512MB memory card shows up with only 485MB worth of capacity is due to the small discrepancies in algorithms and file formats by various operating systems. Also a portion of memory space is reserved for system files and data sectors for better memory card performance. The second reason your card indicates less capacity on the device is due to capacity loss. When manufactured, some devices and card readers were not made to support higher capacity memory cards. An instance of this is 2 GB or higher capacity SD card that shows a memory capacity of 1 GB or less. It is always recommended that you research information on the device manufacturer to verify the correct supported format and capacity.

9.	How safe is the data stored on memory cards?
	Due to its small size, shockproof capability, sturdy shell and having no moving parts, memory cards have key advantages over other storage devices (CDs and DVDs). Memory cards are less prone to movement damage and are less fragile than CDs/DVDs.

10.

What should I consider before purchasing a new memory card?

Once you have done your research and know what type of flash card format to purchase there are two features you must consider: 1. Capacity and 2. Speed. Capacity of a flash memory card is the amount of data that that can be stored and are measured in MB (megabytes) or GB (gigabytes). The larger the capacity indicated on the card, the more room there is for data storage. To confirm the correct capacity sizes for the device, it is advised that you refer to the information provided by the manufacturer of the host device (digital camera, pda, mobile cellular phone). Speed of the flash memory card sometimes greatly affects a digital device's performance, especially if higher transfer speeds are needed for the digital device to perform a task. An example is using a low speed rating memory card for a digital camera that requires a higher speed rating. As a result of using a low speed memory card, data of the photo will written at a slower rate, thus increasing the amount of time needed to take photographs. Most flash memory cards use the X rating for speed. Please see more information on X speed rating below.

11.

What is the definition of X Speed Performance?

Flash cards with a higher X-speed rating are designed to perform faster. The X-speed rating can also be translated into another common measurement of performance - MegaBytes (MB) per second of write speed. To determine the actual MB per second, you must know the value of "X" and do the math using the multiplier number and the value of X as claimed by the product. For example: Value of X = 150 KiloBytes* per second, noted as 150 KB/sec 50X = 50(multiplier of 150KB/sec) =7,500 KB/sec = 7.5 MB/sec *1 KB = 1,000 Bytes; 1 MB = 1 million Bytes

12.

Is a Faster X Speed Rating always better?

When a Flash card is rated at 50X, does this mean that data will transfer at 7.5 MB/sec. in any digital camera or other host device? Not necessarily. A digital camera, cell phone, or other host device is itself limited by the speed of its interface to the Flash card. Often, the host device has a lower read and write speed than the Flash card, so the end result is that the Flash card cannot operate at its best performance level. A good example of this is that a digital camera may only support 10X write speeds, so using a 45X or faster Elite Pro card will not improve performance. Most cameras or other host devices do not have clearly documented Flash card interface read or write speeds, so it may be difficult to know your host device's exact capabilities. As a general rule of thumb, digital cameras with up to 5 megapixels will work just fine with standard-speed Flash cards (less than 45X). Newer professional cameras designed for continuous shooting with specifications of greater than 5 megapixels will benefit the most from Elite Pro/Ultimate cards rated at 45X or above. Using a high-quality Flash card reader to transfer data to a computer, a Flash card with a higher X-speed rating will generally transfer its data faster, thereby reducing the time to copy data from the Flash card to the computer's hard drive.

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How Does a Hovercraft Work?

Abstract
Have you ever ridden on a hovercraft? It is like gliding on a cushion of air! Make your own mini hovercraft in this experiment to test how hovercrafts work. Objective
In this experiment you will test if different volumes of air will cause a balloon powered hovercraft to travel for longer periods of time.
Introduction
A hovercraft is a vehicle that glides over a smooth surface by hovering upon an air cushion. Because of this, a hovercraft is also called an Air-Cushion Vehicle or ACV. The hovercraft creates vents of air, which are trapped beneath the vehicle by a curtain surrounding the base. These currents of air can create an air cushion on any smooth surface, land or water! Since a hovercraft can travel upon the surface of water, it is also called an amphibious vehicle. Here is a picture of a modern hovercraft and a diagram showing how the air vents create the air cushion (Wikipedia, 2007):
How does the air cushion beneath the hovercraft allow the vehicle to glide to freely? The key to the ease of movement is reducing friction. Vents of slowly moving, low-pressure air are ejected downwards against the surface close below it creating the air cushion. The air is trapped beneath the hovercraft by a flexible skirt, also called the curtain. The trapped air cushion greatly reduces the friction of the vehicle, allowing it to glide freely upon the smooth surface below.
In this experiment, you will build your own mini hovercraft using a CD, recycled bottle, and a balloon. You will use balloons of different sizes to test if more air will cause the hovercraft to travel for longer periods of time. A large balloon will provide a larger volume of air, and a small balloon will provide a smaller volume of air. Will a larger balloon make the hovercraft travel longer than a smaller balloon?

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When did facebook start??

Facebook is a social networking website, launched on February 4, 2004.

Facebook was founded by Mark Zuckerberg, a former Harvard student. Initially the membership of Facebook was restricted to students of Harvard College. It was subsequently expanded to MIT, Boston University, Boston College, Northeastern University and all Ivy League schools within two months. Many individual universities were added in rapid succession over the next year. Eventually, people with a university (e.g .edu, .ac.uk, etc.) email address from institutions across the globe were eligible to join. Networks were then initiated for high schools on February 27, 2006 and some large companies. Since September 11, 2006, anyone 13 or older may join.[2][3] Users can select to join one or more participating networks, such as a school, place of employment, geographic region, or social group.

The site has more than 64 million active users (including non-collegiate members) worldwide.[4] From September 2006 to September 2007 the site's traffic ranking increased from 60th to 7th, according to Alexa.[5] It is the most popular website for uploading photos, with 14 million uploaded daily.[4]

The name of the site refers to the paper facebooks depicting members of the campus community that some U.S. colleges and preparatory schools give to incoming students, faculty, and staff as a way to get to know other people on campus.

Facebook has met with a certain amount of criticism and controversy in its short lifespan, mainly because of privacy concerns, but also due to the politics of it's founders and some censorship issues.

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Venice Information and Venice Tourism

The city of Venice, Italy, is simply stunning and completely unique. Founded more than 1,500 years ago on 117 different islands, Venice is linked by a series of over 150 canals, 400 bridges and many ancient pavements. The historic city centre of Venice is divided into six quarters (sestieri) - Cannaregio, Castello, Dorsoduro, San Marco, San Polo and Santa Croce. All buildings in Venice are supported on slender oak and pine piles (posts) which are driven deep into the ground to create a solid foundation. As the soil is waterlogged, with no free oxygen, the piles remain strong and do not decay.

Venice is without doubt one of the most beautiful and popular cities in the world, and is always admired by the many tourists that visit throughout the year. There are several tourist information branches operated by the Azienda di Promozione Turistica, located on the Piazza San Marco, the Piazzale Roma, the Gran Viale Santa Maria Elisabetta, the Lungomare Adriatico, the Venice Pavilion and the Stazione di Santa Lucia. A further tourism outlet is conveniently situated in the arrivals hall at the Marco Polo Airport. If you have time for day trips, there are also many interesting towns to explore, such as Burano, Murano, Padua, Torcello, Verona and Vicenza.

Venice Life and Venice Travel Tips

Venice, Italy is one of the world's great cities and the locals are cheerful, friendly and generally very helpful. Good manners are welcome everywhere and expected by most people. Venice is undeniably a major-league cultural and historic city and worth a visit, whatever the time of year.

Venice Life and Travel Tips: Language - Venice, Italy
Most Italian words are pronounced exactly as they are written, syllable by syllable, and there is often an emphasis on the last letter. A knowledge of Latin can be useful, both as the basis for Italian and also for reading the inscriptions on many monuments. 

Venice Property Market and Venice Real Estate Guide 

The Italian city of Venice is one of the most popular tourist destinations in the world, with stunning architecture, great museums and a sprawling network of picturesque canals. There is also some great shopping in 'the floating city', as well as a bustling commercial centre.

Buying property here can be a great investment, as large returns come to those who choose to rent property to holidaymakers. Long-stay rentals are available, however, and the city is home to six areas to choose from, all with varying advantages.

Venice Landmarks and Venice Monuments 

It is hardly surprising that Venice, one of Italy's most important cities, is crammed full of spectacular landmarks and monuments.

Famous throughout the world, many of these date back over 1,000 years and are in remarkable condition, thanks to faithful restoration and reconstruction work, and including Venice's world-famous Basilica San Marco and Rialto Bridge.

Here are some of the top Venice monuments and landmarks to visit.
  

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The Panama Canal

PANAMA CITY, Panama, August 4, 2011 - The Panama Canal Authority (ACP) and Port Everglades renewed their strategic alliance today with the signing of a Memorandum of Understanding (MOU).
First signed in August 2009, the MOU, which is renewable for five years, solidifies both entities' dedication to growth and best customer practices.
"Our partnership furthers our shared goal of promoting trade growth in Panama and Florida," said ACP Administrator/CEO Alberto Alemán Zubieta. "As we approach the completion of our expansion, we look forward to pursuing even more mutually beneficial activities with Port Everglades."
Areas of cooperation between the ACP and Port Everglades include joint advertising programs, data interchange and competitive market analyses of the shipping industry. This alliance will also continue to promote the "All-Water Route," the route from Asia to the U.S. East Coast via the Panama Canal.
Serving more than 150 ports and 70 countries, Port Everglades generates over $14 billion worth of business activity and approximately 140,000 jobs in Florida. More than 5.2 million tons of containerized cargo is transported through the Port. With the expansion of the Panama Canal slated for completion in 2014, it stands to benefit from anticipated growth.
"Just as the Panama Canal expansion is moving forward to meet the challenges of the future, so also is the Port Everglades Master/Vision Plan, providing us with a roadmap toward meeting those challenges. The strong working relationship between Port Everglades and the ACP will continue to provide mutual advantages in the years to come", said Port Everglades Port Director Phillip C. Allen.
Initially approved in 2007, the Master/Vision plan is a comprehensive, dynamic roadmap designed to guide the Port's growth through an estimated $2 billion in capital investments over a 20-year period. One major component is the deepening of the Port's channels from 42 feet to 50 feet.
Meanwhile, the Canal's expansion is well underway, following the recent commencement of the permanent concrete work for the new Atlantic side locks. The $5.25 billion project includes the construction of a new set of locks that will allow the transit of longer and wider ships.

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The Eiffel Tower

 

You couldn't possibly visit Paris without seeing the Eiffel Tower. Even if you do not want to visit this world famous structure, you will see its top from all over Paris. The tower rises 300 meters tall (984 ft); when it was completed at the end of the 19th century it was twice as high as the Washington Monument, at the time the tallest structure in the world.

1889 World Exhibition

The Eiffel Tower was built for the World Exhibition in 1889, held in celebration of the French Revolution in 1789.
The construction was only meant to last for the duration of the Exposition, but it still stands today, despite all protests from contemporary artists who feared the construction would be the advent of structures without 'individuality' and despite the many people who feared that this huge 'object' would not fit into the architecture of Paris.

Today, there is no such aversion anymore among the Parisians, and one could not imagine Paris without the Eiffel Tower, in fact it has become the symbol of the City of Light.

Gustave Eiffel

The man behind the Eiffel Tower was Gustave Eiffel, known from his revolutionary bridge building techniques, as employed in the great viaduct at Garabit in 1884. These techniques would form the basis for the construction of the Eiffel Tower. He was also known for the construction of the Statue of Liberty's iron framework.

The structure took more than two years to complete. Each one of the about 12,000 iron pieces were designed

separately to give them exactly the shape needed. All pieces were prefabricated and fit together using approx. 7 million nails.

The Tallest

Inaugurated March 31, 1889, the Eiffel Tower would be the tallest structure in the world until the completion of the Chrysler Building in 1930.

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