Application-Specific Integrated Circuits - Addison Wesley Michael John Sebastian Smith
https://docs.google.com/file/d/0Bza2pMEd0piweldtWlNFSkYtTWc/edit
Showing posts with label question papers. Show all posts
Showing posts with label question papers. Show all posts
Thursday, 3 January 2013
ASIC EBOOK
Application-Specific Integrated Circuits - Addison Wesley Michael John Sebastian Smith
https://docs.google.com/file/d/0Bza2pMEd0piweldtWlNFSkYtTWc/edit
BPSK Subcarrier Intensity Modulated Free-Space Optical Communications in Atmospheric Turbulence Wasiu O. Popoola, Student Member, IEEE, and Zabih Ghassemlooy, Senior Member, IEEE
BPSK Subcarrier Intensity Modulated Free-Space
Optical Communications in Atmospheric Turbulence
Wasiu O. Popoola, Student Member, IEEE, and Zabih Ghassemlooy, Senior Member, IEEE
Abstract—Free-space optical communications (FSO) propagated
over a clear atmosphere suffers from irradiance fluctuation
caused by small but random atmospheric temperature fluctuations.
This results in decreased signal-to-noise ratio (SNR) and
consequently impaired performance. In this paper, the error
performance of the FSO using a subcarrier intensity modulation
(SIM) based on a binary phase shift keying (BPSK) scheme in
a clear but turbulent atmosphere is presented. To evaluate the
system error performance in turbulence regimes from weak to
strong, the probability density function (pdf) of the received
irradiance after traversing the atmosphere is modelled using the
gamma-gamma distribution while the negative exponential distribution
is used to model turbulence in the saturation region and
beyond. The effect of turbulence induced irradiance fluctuation
is mitigated using spatial diversity at the receiver. With reference
to the single photodetector case, up to 12 dB gain in the electrical
SNR is predicted with two direct detection PIN photodetectors in
strong atmospheric turbulence
for full paper mail me
Friday, 28 December 2012
Home-made Stethoscope
Home-made Stethoscope
Purpose
To demonstrate how sound waves can travel through enclosed spaces and become aplified by creating a home-made stethoscope.
Additional information
The stethoscope was invented in 1816 by French physician and inventor René-Théophile-Hyacinthe Laennec. The idea came to Laennec when he witnessed children playing with a long piece of wood that transmitted the sound of pins scratching the surface. After making the observation, the next day he rolled up a piece of paper into the shape of a funnel. He then used it to listen to the chests of his patients. Discovering the funnel amplified the sounds from his patients chests, Laennec (who had a background in carpentry) built a 25cm by 2.5cm hollowed wooden cylinder. This cylinder replaced the rolled up paper tube as a device to listen to his patients chest. He later modified this device with detachable parts. He notated the various sounds he heard with his primitive stethoscope and related them to anatomical findings at his patients autopsies. He published his findings in 1819 and the stethoscope, derived from the Greek word "stethos" (meaning chest), was born. As he neared death Laennec often referred to the stethoscope as "the cylinder" and bequeathed his own stethoscope to his nephew, accurately referring to it as the "the greatest legacy" of his life.
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Required materials
- 2 Funnels
- Old garden hose (it will need to be cut-up)
- Scissors
- Modeling clay
- Pen or pencil
- Journal
Estimated Experiment Time
About 15 minutes
Step-By-Step Procedure
- 1. Use your scissors to cut a piece of garden hose approximately 16 inches in length. Make sure to cut from the middle of the house as you'll need both ends to be even (don't use the end that connects to outdoor faucets).
- 2. Place one of the funnels onto the end of the garden hose. If it doesn't fit tightly, use some modeling clay to secure it.
- 3. Repeat step 2 with the other funnel on the other end of the garden hose.
- 4. Place one end of the funnel over your heart and the other end over your ear. What do you hear? Count your heartbeat rate for 30 seconds and note them in your journal.
- 5. Do some jumping jacks, run around, exert a lot of energy for about 1 minute.
- 6. Use your stethoscope again, with one end over your heart and one end to your ear. Now what do you hear? Again count your heart beat rate for 30 seconds and note them in your journal.
Note
If you're having trouble cutting the garden hose with a scissor, you may need to use a sharp knife or razor. As always, make sure you have the help of an adult when cutting objects!
Observation
Can you think of other materials you could use to create a home-made stethoscope? What other purposes, beyond listening to your heartbeat, can you find for the stethoscope?
Result
Stethoscopes can measure the rate of your heart and assist in determining how many times your heart beats per minute. The stethoscope works on the simple principle of acting as a sound amplifier that carries the sound along the hose to your ears.
Vibrating Coin
Vibrating Coin
Purpose
To demonstrate the expansion of air when heated.
Additional information
The temperature of a gas is directly proportional to the speed with which its molecules move. Increasing the temperature of a gas results in an increase of the average speed (and therefore the kinetic energy) of its molecules. This in turn causes the molecules to ‘spread out’ by virtue of a phenomenon known as thermal expansion.
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Required materials
- Coin
- Bottle
- Refrigerator
- Water
Estimated Experiment Time
Approximately 15 to 20 minutes
Step-By-Step Procedure
- 1. Place an empty bottle in a refrigerator to cool
- 2. Place the cooled bottle outside
- 3. Dip your finger in water and place a few drops around mouth of the bottle and the edge of the coin
- 4. Place a coin on the mouth of the bottle
- 5. Place both your hands around the bottle; hold firmly
- 6. Remove your hands after a while
Note
- Use a bottle with a mouth narrow enough to be closed completely with a coin.
- Applying water on the rim of the bottle mouth and the coin’s edge will help seal the bottle.
Observation
In approximately fifteen seconds from covering the bottle with your hands, the coin will start to vibrate up and down. When you do remove your hands after a short while, the coin continues to vibrate.
Result
As soon as the bottle is taken out of the refrigerator the temperature of the gas inside the bottle begins to rise; encasing the bottle with your hands increases the temperature further. When the bottle is heated, the air molecules inside it start moving faster and these molecules collide with the coin with more energy. This results in increased pressure which in turn is caused by the expanding air that escapes though the rim of the coin and makes it vibrate.
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