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Air conditioners and refrigerators work the same way. Instead of cooling just the small, insulated space inside of a refrigerator, an air conditioner cools a room, a whole house, or an entire business.
Air conditioners use chemicals that easily convert from a gas to a liquid and back again. This chemical is used to transfer heat from the air inside of a home to the outside air.
The machine has three main parts. They are a compressor, a condenser and an evaporator. The compressor and condenser are usually located on the outside air portion of the air conditioner. The evaporator is located on the inside the house, sometimes as part of a furnace. That's the part that heats your house.
The working fluid arrives at the compressor as a cool, low-pressure gas. The compressor squeezes the fluid. This packs the molecule of the fluid closer together. The closer the molecules are together, the higher its energy and its temperature.
The working fluid leaves the compressor as a hot, high pressure gas and flows into the condenser. If you looked at the air conditioner part outside a house, look for the part that has metal fins all around. The fins act just like a radiator in a car and helps the heat go away, or dissipate, more quickly.
When the working fluid leaves the condenser, its temperature is much cooler and it has changed from a gas to a liquid under high pressure. The liquid goes into the evaporator through a very tiny, narrow hole. On the other side, the liquid's pressure drops. When it does it begins to evaporate into a gas.
As the liquid changes to gas and evaporates, it extracts heat from the air around it. The heat in the air is needed to separate the molecules of the fluid from a liquid to a gas. The evaporator also has metal fins to help in exchange the thermal energy with the surrounding air.
By the time the working fluid leaves the evaporator, it is a cool, low pressure gas. It then returns to the compressor to begin its trip all over again. Connected to the evaporator is a fan that circulates the air inside the house to blow across the evaporator fins. Hot air is lighter than cold air, so the hot air in the room rises to the top of a room.
There is a vent there where air is sucked into the air conditioner and goes down ducts. The hot air is used to cool the gas in the evaporator. As the heat is removed from the air, the air is cooled. It is then blown into the house through other ducts usually at the floor level.
This continues over and over and over until the room reaches the temperature you want the room cooled to. The thermostat senses that the temperature has reached the right setting and turns off the air conditioner. As the room warms up, the thermostat turns the air conditioner back on until the room reaches the temperature.

Biometric Applications

Biometric techniques are providing a highly-secured identification and personal verification solutions thereby providing a robust solution to many challenging problems in security. The collection of Biometric characteristics is done using a device called a sensor used to acquire the data needed for verification or identification and to convert the data to a digital code. Among various devices, digital cameras can be used for face recognition, ear recognition etc or a telephone for voice recognition etc. A biometric system operates in verification mode or identification mode. In verification mode the system validation of a person identity is performed by comparing the captured biometric data with the biometric template stored in the database and is mainly used for positive recognition.
Applications:

Health Care:
The applications in this sector includes the use of biometrics to identify or verify the identity of individuals interacting with a health-care entity or acting in the capacity of health-care employee or professional. The main aim of biometrics is to prevent fraud, protect the patient information and control the sell of pharmaceutical products. Some typical application are:

* PC/Network Access - the biometrics are used to control a secure access of the employees to the hospital network, primarily, in order to protect the patient information.
* Access to personal information - Using biometrics, the medical patient information maybe stored on smart card or secure networks, this will enable the access of the patients to their personal information.

* Patient identification - In case of emergency, when a patient does not have identification document and is unable no communicate, biometric identification may be a good alternative to identify.


Travel and Immigration:
The application in this sector includes the use of biometrics to identify or verify the identity of individual interacting during the course of travel, with a travel or immigration entity or acting in the capacity of travel or immigration employee. Typical application are:

* Air travel - In many airport are already used a biometric system in order to reduce the inspection processing time for authorized travelers.
* Border crossing - The use of biometrics to control the travelers crossing the national or state border is increasing, specially in regions with high volume of travelers or illegal immigrants.

* Passports - Some country already issues passports with biometric information on a barcode or smart chips. The use of biometrics prevent the emission of multiple passports for the same person and also facilitates the identification at the airports and border controls.

Bluetooth

What is Bluetooth?

Bluetooth is a wireless technology that allows computers, phones and other devices to talk to each other over short distances (up to 100 meters). Bluetooth uses radio waves (in the 2.4 Gigahertz range), and is designed to be a secure and inexpensive way of connecting and exchanging information between devices without wires.

You'll find Bluetooth in many of the newer mobile phones, handheld computers, laptops, printers, handheld organizers, as well as in all sorts of products.

Best of all, you do not have to pay a penny for the service! It's not an extra cell phone or cable bill that you have to add to your budget. Simply by the technology and you're done! All you need to do is connect it with what you are using.

Here is one problem that’s the battery use which occurs mostly on your cell phone but also occurs in other technology such as music players. You're using up more battery power when you leave your Bluetooth enabled on your phone all day. To disregard all this, the best thing that you can possibly do is disable it once you are completed with the transfer. It only takes a few seconds to enable and disable so it wouldn't hurt to disable it once you are done using it.

Portable entertainment devices such as MP3 or DVD players which allow people to listen to music or watch films are now commonplace. What do you think are the main advantages and disadvantages of this development?

Nowadays, electronic products such as MP3 or DVD players become to be part of human's life. People uses these techniques everywhere as its compact and easy to carry because they are smaller than a CD player so it fits in you pocket. For example we can carry our MP3 players during jogging or travelling. Besides that, it has lots of applications such as calendar, clock, or even games, also you can watch any videos. On the other hand, these portable devices have some disadvantages, as the screens are very small, and the sound quality won't be that much clear. As well as it can cause hear damages because of using headphones. However, MP3 or DVD players play a great role in humans life, as they are movable techniques and easy to use.

Mobile Phone

A mobile phone allows calls into the public switched telephone system over a radio link. Early mobile phones were usually bulky and permanently installed in vehicles; they provided limited service because only a few frequencies were available for a geographic area. Modern cellular "cell" phones or hand phones make use of the cellular network concept, where frequencies are re-used repeatedly within a city area, allowing many more users to share access to the radio bandwidth.

A mobile phone can make and receive telephone calls to and from the public telephone network which includes other mobiles and fixed-line phones across the world. It does this by connecting to a cellular network provided by a mobile network operator.
In addition to telephony, modern mobile phones also support a wide variety of other services such as text messaging, MMS, email, Internet access, short-range wireless communications (infrared, Bluetooth), business applications, gaming and photography. Mobile phones that offer these more general computing capabilities are referred to as smartphones.