Monday, April 25, 2011

Polar Satellite Launch Vehicle (PSLV)

Polar Satellite Launch Vehicle

The Polar Satellite Launch Vehicle (PSLV), is an expendable launch system developed and operated by the Indian Space Research Organisation (ISRO). It was developed to allow India to launch its Indian Remote Sensing (IRS) satellites into sun synchronous orbits, a service that was, until the advent of the PSLV, commercially viable only from Russia. PSLV can also launch small size satellites into geostationary transfer orbit (GTO). The PSLV has launched 41 satellites (19 Indian and 22 from other countries) into a variety of orbits to date.

PSLV costs 17 million USD flyaway cost for each launch.

The PSLV has four stages using solid and liquid propulsion systems alternately. The first stage is one of the largest solid-fuel rocket boosters in the world and carries 138 tonnes of Hydroxyl-terminated polybutadiene (HTPB) bound propellant with a diameter of 2.8 m.

The second stage employs the Vikas engine and carries 41.5 tonnes of liquid propellant – Unsymmetrical Di-Methyl Hydrazine (UDMH) as fuel and Nitrogen tetroxide (N2O4) as oxidizer.

The third stage uses 7 tonnes of HTPB-based solid propellant and produces a maximum thrust of 324 kN.

The fourth and the terminal stage of PSLV has a twin engine configuration using liquid propellant. With a propellant loading of 2 tonnes (Mono-Methyl Hydrazine as fuel + Mixed Oxides of Nitrogen as oxidiser), each of these engines generates a maximum thrust of 7.4 kN.

The mission lifted the veil of despondency that had fallen over the Indian Space Research Organisation (ISRO) after the failure of the GSLV-D3 with an indigenous cryogenic stage in April last year and of the GSLV-F06 with a Russian cryogenic engine in December.

Mission Director P. Kunhikrishnan praised “the excellent performance” of the rocket's four stages and their sub-systems.

The ResourceSat-2 is intended to continue the remote sensing data services and to provide data with enhanced multispectral and spatial coverage. ResourceSat-2 also carries an additional payload known as AIS (Automatic Identification System) from COMDEV, Canada as an experimental payload for ship surveillance.

The C16 launch also included the first Singapore-built satellite, the X-Sat which is a mini-satellite project undertaken as a collaboration among the Nanyang Technological University and different organisations within Singapore.

The third satellite was a joint Indo-Russian stellar and atmospheric satellite mission named YouthSat, developed with the participation of university students

Friday, February 25, 2011

Paramilitary Forces in India

TODO

New Countries of the world

In February 2011, the official results of a referendum in South Sudan indicated that South Sudan would likely become the world's newest country. However, the declaration of independence is not expected for South Sudan until July 9, 2011. At that point, this page will be updated.

Since 1990, 33 new countries have been created. The dissolution of the USSR and Yugoslavia in the early 1990s caused the creation of most of the newly independent states.

You probably know about many of these changes but a few of these new countries seemed to slip by almost unnoticed. This comprehensive listing will update you about the countries which have formed since 1990.

Union of Soviet Socialist Republics

Fifteen new countries became independent with the dissolution of the USSR in 1991. Most of these countries declared independence a few months preceding the fall of the Soviet Union in late 1991.

Former Yugoslavia

Yugoslavia dissolved in the early 1990s into five independent countries.

Bosnia and Herzegovina, February 29, 1992
Croatia, June 25, 1991
Macedonia (officially The Former Yugoslav Republic of Macedonia) declared independence on September 8, 1991 but wasn't recognized by the United Nations until 1993 and the United States and Russia in February of 1994
Serbia and Montenegro, (also known as the Federal Republic of Yugoslavia), April 17, 1992 (see below for separate Serbia and Montenegro entries)
Slovenia, June 25, 1991

Other New Countries

Thirteen other countries became independent through a variety of causes.

March 21, 1990 - Namibia became independent of South Africa.
May 22, 1990 - North and South Yemen merged to form a unified Yemen.
October 3, 1990 - East Germany and West Germany merged to form a unified Germany after the fall of the Iron Curtain.
September 17, 1991 - The Marshall Islands was part of the Trust Territory of Pacific Islands (administered by the United States) and gained independence as a former colony.
September 17, 1991 - Micronesia, previously known as the Caroline Islands, became independent from the United States.
January 1, 1993 - The Czech Republic and Slovakia became independent nations when Czechoslovakia dissolved.
May 25, 1993 - Eritrea was a part of Ethiopia but seceded and gained independence.
October 1, 1994 - Palau was part of the Trust Territory of Pacific Islands (administered by the United States) and gained independence as a former colony.
May 20, 2002 - East Timor (Timor-Leste) declared independence from Portugal in 1975 but did not became independent from Indonesia until 2002.
June 3, 2006 - Montenegro was part of Serbia and Montenegro (also known as Yugoslavia) but gained independence after a referendum.
June 5, 2006 - Serbia became its own entity after Montenegro split.
Febraury 17, 2008 - Kosovo unilaterally declared independence from Serbia.

Electromagnetic Spectrum: Cell Phone

Electromagnetic (EM) radiation is a stream of photons, traveling in waves. The photon is the base particle for all forms of EM radiation.

But what's a photon?

It's a bundle of energy -- of light -- always in motion. In fact, the amount of energy a photon carries makes it sometimes behave like a wave and sometimes like a particle. Scientists call thiswave-particle duality.

Low-energy photons (such as radio) behave like waves, while high-energy photons (such as X-rays) behave more like particles.

EM radiation can travel through empty space. This differentiates it from other types of waves, such as sound, which need a medium to move through. All forms of EM radiation reside on theelectromagnetic spectrum, which ranks radiation from lowest energy/longest wavelength to highest energy/shortest wavelength. The higher the energy, the stronger, and therefore more dangerous, the radiation. The only difference between a radio wave and a gamma ray is the energy level of the photons

How Cell Phone works:

One of the most interesting things about a cell phone is that it is actually a radio -- an extremely sophisticated radio, but a radio nonetheless.

Cell-phone Codes

Cell Phone Codes

Electronic Serial Number (ESN) - a unique 32-bit number programmed into the phone when it is manufactured

Mobile Identification Number (MIN) - a 10-digit number derived from your phone's number

System Identification Code (SID) - a unique 5-digit number that is assigned to each carrier by the FCC

While the ESN is considered a permanent part of the phone, both the MIN and SID codes are programmed into the phone when you purchase a service plan and have the phone activated.

All cell phones have special codes associated with them. These codes are used to identify the phone, the phone's owner and the service provider.

Let's say you have a cell phone, you turn it on and someone tries to call you. Here is what happens to the call:

When you first power up the phone, it listens for an SID (see sidebar) on the control channel. The control channel is a special frequency that the phone and base station use to talk to one another about things like call set-up and channel changing. If the phone cannot find any control channels to listen to, it knows it is out of range and displays a "no service" message.
When it receives the SID, the phone compares it to the SID programmed into the phone. If the SIDs match, the phone knows that the cell it is communicating with is part of its home system.
Along with the SID, the phone also transmits a registration request, and the MTSO keeps track of your phone's location in a database -- this way, the MTSO knows which cell you are in when it wants to ring your phone.
The MTSO gets the call, and it tries to find you. It looks in its database to see which cell you are in.
The MTSO picks a frequency pair that your phone will use in that cell to take the call.
The MTSO communicates with your phone over the control channel to tell it which frequencies to use, and once your phone and the tower switch on those frequencies, the call is connected. Now, you are talking by two-way radio to a friend.
As you move toward the edge of your cell, your cell's base station notes that your signal strength is diminishing. Meanwhile, the base station in the cell you are moving toward (which is listening and measuring signal strength on all frequencies, not just its own one-seventh) sees your phone's signal strength increasing. The two base stations coordinate with each other through the MTSO, and at some point, your phone gets a signal on a control channel telling it to change frequencies. This hand off switches your phone to the new cell.

As you travel, the signal is passed from cell to cell.

Let's say you're on the phone and you move from one cell to another -- but the cell you move into is covered by another service provider, not yours. Instead of dropping the call, it'll actually be handed off to the other service provider.

If the SID on the control channel does not match the SID programmed into your phone, then the phone knows it is roaming. The MTSO of the cell that you are roaming in contacts the MTSO of your home system, which then checks its database to confirm that the SID of the phone you are using is valid. Your home system verifies your phone to the local MTSO, which then tracks your phone as you move through its cells. And the amazing thing is that all of this happens within seconds.

The less amazing thing is that you may be charged insane rates for your roaming call. On most phones, the word "roam" will come up on your phone's screen when you leave your provider's coverage area and enter another's. If not, you'd better study your coverage maps carefully -- more than one person has been unpleasantly surprised by the cost of roaming. Check your service contract carefully to find out how much you're paying when you roam.

Note that if you want to roam internationally, you'll need a phone that will work both at home and abroad. Different countries use different cellular access technologies. More on those technologies later. First, let's get some background on analog cell-phone technology so we can understand how the industry has developed.

Along Comes Digital

Digital cell phones are the second generation (2G) of cellular technology. They use the same radio technology as analog phones, but they use it in a different way. Analog systems do not fully utilize the signal between the phone and the cellular network -- analog signals cannot be compressed and manipulated as easily as a true digital signal. This is the reason why many cable companies are switching to digital -- so they can fit more channels within a given bandwidth. It is amazing how much more efficient digital systems can be.

Digital phones convert your voice into binary information (1s and 0s) and then compress it (see How Analog-Digital Recording Works for details on the conversion process). This compression allows between three and 10 digital cell-phone calls to occupy the space of a single analog call.

Many digital cellular systems rely on frequency-shift keying (FSK) to send data back and forth over AMPS. FSK uses two frequencies, one for 1s and the other for 0s, alternating rapidly between the two to send digital information between the cell tower and the phone. Clever modulation and encoding schemes are required to convert the analog information to digital, compress it and convert it back again while maintaining an acceptable level of voice quality. All of this means that digital cell phones have to contain a lot of processing power.

Let's take a good look inside a digital cell phone.

Inside a Digital Cell Phone

On a "complexity per cubic inch" scale, cell phones are some of the most intricate devices people use on a daily basis. Modern digital cell phones can process millions of calculations per second in order to compress and decompress the voice stream.

The parts of a cell phone

If you take a basic digital cell phone apart, you find that it contains just a few individual parts:

An amazing circuit board containing the brains of the phone
An antenna
A liquid crystal display (LCD)
A keyboard (not unlike the one you find in a TV remote control)
A microphone
A speaker
A battery

The circuit board is the heart of the system. Here is one from a typical Nokia digital phone:

The front of the circuit board

The back of the circuit board

In the photos above, you see several computer chips. Let's talk about what some of the individual chips do. The analog-to-digital and digital-to-analog conversion chips translate the outgoing audio signal from analog to digital and the incoming signal from digital back to analog. You can learn more about A-to-D and D-to-A conversion and its importance to digital audio in How Compact Discs Work. The digital signal processor (DSP) is a highly customized processor designed to perform signal-manipulation calculations at high speed.

The microprocessor handles all of the housekeeping chores for the keyboard and display, deals with command and control signaling with the base station and also coordinates the rest of the functions on the board.

The microprocessor

The ROM and Flash memory chips provide storage for the phone's operating system and customizable features, such as the phone directory. The radio frequency (RF) and power section handles power management and recharging, and also deals with the hundreds of FM channels. Finally, the RF amplifiers handle signals traveling to and from the antenna.

The display and keypad contacts

The display has grown considerably in size as the number of features in cell phones have increased. Most current phones offer built-in phone directories, calculators and games. And many of the phones incorporate some type of PDA or Web browser.

The SIM card on the circuit board

The SIM card removed

Some phones store certain information, such as the SID and MIN codes, in internal Flash memory, while others use external cards that are similar to SmartMedia cards.

The cell-phone speaker, microphone and battery backup

Cell phones have such tiny speakers and microphones that it is incredible how well most of them reproduce sound. As you can see in the picture above, the speaker is about the size of a dime and the microphone is no larger than the watch battery beside it. Speaking of the watch battery, this is used by the cell phone's internal clock chip.

What is amazing is that all of that functionality -- which only 30 years ago would have filled an entire floor of an office building -- now fits into a package that sits comfortably in the palm of your hand!

In the next section, we'll get into the cell-phone networking methods.

Cell Phone Network Technologies: 2G

There are three common technologies used by 2G cell-phone networks for transmitting information (we'll discuss 3G technologies in the 3G section):

Frequency division multiple access (FDMA)
Time division multiple access (TDMA)
Code division multiple access (CDMA)

Although these technologies sound very intimidating, you can get a good sense of how they work just by breaking down the title of each one.

The first word tells you what the access method is. The second word, division, lets you know that it splits calls based on that access method.

FDMA puts each call on a separate frequency.
TDMA assigns each call a certain portion of time on a designated frequency.
CDMA gives a unique code to each call and spreads it over the available frequencies.

The last part of each name is multiple access. This simply means that more than one user can utilize each cell.

FDMA
FDMA separates the spectrum into distinct voice channels by splitting it into uniform chunks of bandwidth. To better understand FDMA, think of radio stations: Each station sends its signal at a different frequency within the available band. FDMA is used mainly for analog transmission. While it is certainly capable of carrying digital information, FDMA is not considered to be an efficient method for digital transmission.

In FDMA, each phone uses a different frequency.

TDMA
TDMA is the access method used by the Electronics Industry Alliance and the Telecommunications Industry Association for Interim Standard 54 (IS-54) and Interim Standard 136 (IS-136). Using TDMA, a narrow band that is 30 kHz wide and 6.7 milliseconds long is split time-wise into three time slots.

Narrow band means "channels" in the traditional sense. Each conversation gets the radio for one-third of the time. This is possible because voice data that has been converted to digital information is compressed so that it takes up significantly less transmission space. Therefore, TDMA has three times the capacity of an analog system using the same number of channels. TDMA systems operate in either the 800-MHz (IS-54) or 1900-MHz (IS-136) frequency bands.

TDMA splits a frequency into time slots.

Unlocking Your GSM Phone

Any GSM phone can work with any SIM card, but some service providers "lock" the phone so that it will only work with their service. If your phone is locked, you can't use it with any other service provider, whether locally or overseas. You can unlock the phone using a special code -- but it's unlikely your service provider will give it to you. There are Web sites that will give you the unlock code, some for a small fee, some for free.

GSM
TDMA is also used as the access technology for Global System for Mobile communications (GSM). However, GSM implements TDMA in a somewhat different and incompatible way from IS-136. Think of GSM and IS-136 as two different operating systems that work on the same processor, like Windows and Linux both working on an Intel Pentium III. GSM systems use encryption to make phone calls more secure. GSM operates in the 900-MHz and 1800-MHz bands in Europe and Asia and in the 850-MHz and 1900-MHz (sometimes referred to as 1.9-GHz) band in the United States. It is used in digital cellular and PCS-based systems. GSM is also the basis for Integrated Digital Enhanced Network (IDEN), a popular system introduced by Motorola and used by Nextel.

GSM is the international standard in Europe, Australia and much of Asia and Africa. In covered areas, cell-phone users can buy one phone that will work anywhere where the standard is supported. To connect to the specific service providers in these different countries, GSM users simply switch subscriber identification module (SIM) cards. SIM cards are small removable disks that slip in and out of GSM cell phones. They store all the connection data and identification numbers you need to access a particular wireless service provider.

Unfortunately, the 850MHz/1900-MHz GSM phones used in the United States are not compatible with the international system. If you live in the United States and need to have cell-phone access when you're overseas, you can either buy a tri-band or quad-band GSM phone and use it both at home and when traveling or just buy a GSM 900MHz/1800MHz cell phone for traveling. You can get 900MHz/1800MHz GSM phones from Planet Omni, an online electronics firm based in California. They offer a wide selection of Nokia, Motorola and Ericsson GSM phones. They don't sell international SIM cards, however. You can pick up prepaid SIM cards for a wide range of countries at Telestial.com.

CDMA
CDMA takes an entirely different approach from TDMA. CDMA, after digitizing data, spreads it out over the entire available bandwidth. Multiple calls are overlaid on each other on the channel, with each assigned a unique sequence code. CDMA is a form of spread spectrum, which simply means that data is sent in small pieces over a number of the discrete frequencies available for use at any time in the specified range.

In CDMA, each phone's data has a unique code.

All of the users transmit in the same wide-band chunk of spectrum. Each user's signal is spread over the entire bandwidth by a unique spreading code. At the receiver, that same unique code is used to recover the signal. Because CDMA systems need to put an accurate time-stamp on each piece of a signal, it references the GPS system for this information. Between eight and 10 separate calls can be carried in the same channel space as one analog AMPS call. CDMA technology is the basis for Interim Standard 95 (IS-95) and operates in both the 800-MHz and 1900-MHz frequency bands.

Ideally, TDMA and CDMA are transparent to each other. In practice, high-power CDMA signals raise the noise floor for TDMA receivers, and high-power TDMA signals can cause overloading and jamming of CDMA receivers.

2G is a cell phone network protocol. Click here to learn about network protocols for Smartphones.

Now let's look at the distinction between multiple-band and multiple-mode technologies.

Radiation from Cell Phone:

When talking on a cell phone, a transmitter takes the sound of your voice and encodes it onto a continuous sine wave (see How Radio Works to learn more about how sound is transmitted). A sine wave is just a type of continuously varying wave that radiates out from the antenna and fluctuates evenly through space. Sine waves are measured in terms of frequency, which is the number of times a wave oscillates up and down per second. Once the encoded sound has been placed on the sine wave, the transmitter sends the signal to the antenna, which then sends the signal out.

Radiation in cell phones is generated in the transmitter and emitted through the antenna.

Cell phones have low-power transmitters in them. Most car phones have a transmitter power of 3 watts. A handheld cell phone operates on about 0.75 to 1 watt of power. The position of a transmitter inside a phone varies depending on the manufacturer, but it is usually in close proximity to the phone's antenna. The radio waves that send the encoded signal are made up of electromagnetic radiation propagated by the antenna. The function of an antenna in any radio transmitter is to launch the radio waves into space; in the case of cell phones, these waves are picked up by a receiver in the cell-phone tower.

Monday, February 21, 2011

Bahrain

Bahrain
Bahrain, officially Kingdom of Bahrain, is a small island country located near the western shores of the Persian Gulf and ruled by the Al Khalifa royal family. Bahrain is an archipelago of thirty-three islands, the largest is Bahrain Island.
Bahrain is known for its oil and pearls. The Qal’at al-Bahrain (The Ancient Harbour and Capital of Dilmun) has been declared a UNESCO World Heritage Site.
GOVERNMENT
Bahrain is an absolute monarchy headed by the King, Shaikh Hamad bin Isa Al Khalifa; the head of government is the Prime Minister, Shaikh Khalīfa bin Salman al Khalifa, who presides over a cabinet of twenty-five members, where 80% of its members are from the royal family. Bahrain has a bicameral legislature with a lower house, the Chamber of Deputies, elected by universal suffrage and an upper house, the Shura Council, appointed by the king. Both houses have forty members
Shia - Sunni Relations
Bahrain’s Shia majority has often received poor treatment in employment, housing, and infrastructure, while Sunnis have a preferential status. The government of Bahrain even imports Sunnis from Baluch tribal areas and Syria in an attempt to increase the Sunni percentage

Bahrain

Talk with ULFA

Will Talks with Ulfa Go Anywhere?
VED MARWAH PROFESSOR, CENTRE FOR POLICY RESEARCH Yes, Because Ulfa is Under Pressure Two essential preconditions for the success of the talks are: one, the Ulfa has genuinely come to the conclusion that continuation of violence will no longer serve its purpose, and two, it as well as the government are serious about the talks and not entering into them for their short-term objectives. If the insurgents’ main aim is to buy time to arm and regroup and the state government is only interested in deluding the electorate on the eve of the state assembly elections, then the current talks would also end the same way as the previous ones. Last time too, driven out of the Bhutan forests, Ulfa cadres wanted a breathing space to recover and regroup. The much-publicised talks through some well-known and wellintentioned interlocutors came to nothing and we later saw a wave of fresh violence in Assam. This time, too, the timing of the talks and trumpeting them as a great achievement of the Gogoi government raise doubts about their sincerity. It would be a pity if the government were to squander this opportunity that has come primarily because of close cooperation of the Bangladesh government which hitherto was providing open sanctuary to Ulfa leaders there. The Ulfa leadership is under great stress and the ground situation in Assam has greatly improved. The outfit has lost much of its sheen and no longer enjoys much public support. It is finding it difficult to get fresh recruits. There is strong desire for peace and great public revulsion against extortion by Ulfa cadres in the state. But there also the negative side: there are reports of renewed Chinese interest in India’s northeast and its promised support to Ulfa. Pakistan’s ISI is also active in this region. The government should not read too much into the present lull. The situation could deteriorate in the foreseeable future. These talks are important and the government should not see them through the prism of partisan politics. A successful end to Ulfa and Naga insurgencies could play a major role in defeating the other hundred-odd insurgencies that are raging in the north-east.
HIREN GOHAIN CHIEF SPOKESMAN, SANMILITA JATIYA ABHIBARTAN (SJA) Only if Government Shows Wisdom One must realise that the failure or sabotaging of such talks at an opportune moment, with the public in Assam keen for a resolution of the conflict, especially in a strategically sensitive region, is bound to have costly consequences for the country. The climate is now favourable as never before. The General Council of Ulfa had decided overwhelmingly in favour of peace, and for the moment the few dissidents who did not attend have no power to weaken their resolve. The moot point is whether the government has the wisdom and political will to listen and make more than cosmetic changes in the status of Assam. The Ulfa leadership is now ready to give up the demand for sovereignty provided in return the people of Assam are empowered to shape their own future in accordance with their needs and aspirations. The Centre has earned in the last 60 years a lot more from the resources of Assam than it has cared to invest here, and the pattern of development too has not deviated much from that of colonial times. Pouring money in through thoughtless ‘packages’ only encourages plunder and loot by the privileged few. A thorough structural reform is the need of the hour. The people of Assam are raising that demand, and they must be heard. Some critics point to ethnic differences, but those are partly the result of skimpy handouts from the Centre that the Assamese elite were loath to share, and now that ethnic groups are awake and Ulfa leaders are sensitive to their rights, an equitable solution is possible. The SJA is preparing the framework, broadly covering different aspects and the Ulfa leadership is ready to listen to expert advice. In spite of provocations and temptations, the leadership has kept aloof from the ongoing electoral adjustments and manipulations and has not identified with any political group. P C Haldar, the interlocutor appointed by the government, has so far done everything in his power to remove bottlenecks on the road to a dialogue. Therefore, there isn’t any reason to be pessimistic about the talks. But the decision-makers must put the good of the country above narrow sectional interests and goals.