Kolkata Puja guide

 
Origin of Durga - The Mythology
Durga, a beautiful warrior seated upon a tiger. Devi is the great goddess of the Hindus,the consort of Shiva and she is worshiped in various forms corresponding to her two aspects: benevolence and fierceness. She is Uma, "light"; Gauri, "yellow or brilliant"; Parvati, "the mountaineer"; and Jagatmata, "the-mother-of-the-world" in her milder guise. The terrible emanations are Durga "the inaccessible"; Kali, "the black"; Chandi, "the fierce"; and Bhairavi, "the terrible."
Descent of the Goddess
Durga, a beautiful warrior seated upon a tiger, was the first appearance of the great goddess. The circumstance of her miraculous arrival was the tyranny of the monster-demon Mahishasur, who through terrific austerities had acquired invincible strength. The gods were afraid of this water-buffalo bull because neither Vishnu nor Shiva could prevail against him. It seemed that the joint energy of Shakti was only capable of vanquishing Mahisha, and so it was the eighteen-armed Durga who went out to do battle.
Battlefield
She went to battle on her ferocious mount lion, armed with the weapons given to her by the other Gods. Durga is one of the angry and aggressive aspects of the goddess Shakti, whose role in Hindu mythology was to fight and conquer demons and also personify the Sakti or female aspect of any male deity. In the battle, she fought and killed the evil Mahishasura and restored heaven to the Gods. Since then the goddess is invoked for protection from the powers of evil. Durga Puja is observed in her honor, to celebrate her victory over evil.
Revered Mother
She has been worshiped from about 400 AD, but probably earlier, to the present. Her literary references are chiefly the Ramayana and Mahabharata, epic and Puranic texts, and she is mentioned by name in Vedic literature. In general, Durga is regarded in northern India as the gentle bride epitomizing family unity while in southern India she is revered more in her warrior aspect.
 
Different Forms of Durga
Nine different forms of Devi, worshiped over the nine days. As the ten-armed Goddess, Goddess Durga presents a radiantly beautiful form that is bewitching to behold. That special form is somehow simultaneously wrathful and benign and transmits profound spiritual teachings in an exacting manner. The nine-day period from the new moon day to the ninth day of Ashvina is considered the most auspicious time of the Hindu Calendar and is hence the most celebrated time of the year as Durga Puja. The nine different forms of Devi are worshiped over the nine days. These are the most popular forms under which she is worshiped:
Durga Shailputri (Daughter of Mountain)
She is a daughter of Himalaya and first among nine Durgas. In previous birth she was the daughter of Daksha. Her name was Sati - Bhavani. i.e. the wife of Lord Shiva. Once Daksha had organized a big Yagna and did not invite Shiva. But Sati being obstinate, reached there. Thereupon Daksha insulted Shiva. Sati could not tolerate the insult of husband and burnt herself in the fire of Yagna. In other birth she became the daughter of Himalaya in the name of Parvati - Hemvati and got married with Shiva. As per Upnishad she had torn and the egotism of Indra, etc. Devtas. Being ashamed they bowed and prayed that, "In fact, thou are Shakti, we all - Brahma, Vishnu and Shiv are capable by getting Shakti from you."
Brahmacharini
The second Durga Shakti is Brahamcharini. Brahma that is who observes penance(tapa) and good conduct. Here "Brahma" means "Tapa". The idol of this Goddess is very gorgeous. There is rosary in her right hand and Kamandal in left hand. She is full with merriment. One story is famous about her. In previous birth she was Parvati Hemavati the daughter of Himvan. Once when she was busy in games with her friends. Naradaji came to her and predicted seeing her Palm-lines that, "You will get married with a naked-terrible 'Bhole baba' who was with you in the form of Sati, the daughter of Daksh in previous birth. But now you have to perform penance for him." There upon Parvati told her mother Menaka that she would marry none except Shambhu, otherwise she would remain unmarried. Saying this she went to observe penance. That is why her name is famous as tapacharini - Brahmacharini. From that time her name Uma became familiar.
Chandraghanta
The name of third Shakti is Chandraghanta. There is a half-circular moon in her forehead. She is charmful and bright. She is Golden color. She has three eyes and ten hands holding with ten types of swords - etc. weapons and arrows etc. She is seated on Lion and ready for going in war to fight. She is unprecedented image of bravery. The frightful sound of her bell terrifies all the villains, demons and danavas.
KushmandaName of fourth Durga is Kushmanda. The Shakti creates egg, ie. Universe by mere laughing .She resides in solar systems. She shines brightly in all the ten directions like Sun. She has eight hands. Seven types of weapons are shining in her seven hands. Rosary is in her right hand. She seems brilliant riding on Lion. She likes the offerings of "Kumhde." Therefore her name "Kushmanda" has become famous.
Skanda Mata
Fifth name of Durga is "Skanda Mata". The daughter of Himalaya, after observing penance got married with Shiva. She had a son named "Skanda." Skanda is a leader of the army of Gods. Skanda Mata is a deity of fire. Skanda is seated in her lap. She has three eyes and four hands. She is white and seated on a lotus.
Katyayani
Sixth Durga is Katyayani. The son of "Kat" as "Katya". Rishi Katyayan born in this "Katya" lineage. Katyayan had observed penance with a desire to get paramba as his daughter. As a result she took birth as a daughter of Katyayan. Therefore her name is "Katyayani" . She has three eyes and eight hands. These are eight types of weapons missiles in her seven hands. Her vehicle is Lion.
Kalratri
Seventh Durga is Kalratri. She is black like night. Durga hairs are unlocked. She has put on necklaces shining like lightening. She has three eyes which are round like universe. Her eyes are bright. Thousands of flames of fire come out while respiring from nose. She rides on Shava (dead body). There is sharp sword in her right hand. Her lower hand is in blessing mood. The burning torch (mashal) is in her left hand and her lower left hand is in fearless style, by which she makes her devotees fearless. Being auspicious she is called "Shubhamkari."
Maha Gauri
The Eighth Durga is "Maha Gauri." She is as white as a conch, moon and Jasmine. She is of eight years old. Her clothes and ornaments are white and clean. She has three eyes. She rides on bull She has four hands. The above left hand is in "Fearless - Mudra" and lower left hand holds "Trishul." The above right hand has tambourine and lower right hand is in blessing style. She is calm and peaceful and exists in peaceful style. It is said that when the body of Gauri became dirty due to dust and earth while observing penance, Shiva makes it clean with the waters of Gangas. Then her body became bright like lightening. There fore, she is known as "Maha Gauri" .
Siddhidatri
Ninth Durga us Siddhidatri. There are eight Siddhis , they are- Anima, Mahima, Garima, Laghima, Prapti, Prakamya, Iishitva & Vashitva. Maha Shakti gives all these Siddhies. It is said in "Devipuran" that the Supreme God Shiv got all these Siddhies by worshipping Maha Shakti. With her gratitude the half body of Shiv has became of Goddess and there fore his name "Ardhanarishvar" has became famous. The Goddess drives on Lion. She has four hands and looks pleased. This form of Durga is worshiped by all Gods, Rishis-Munis, Siddhas, Yogis, Sadhakas and devotees for attaining the best religious asset.
 
Kolkata Durga puja Roadmap 2013
North and central kolkata puja guide map in BENGLA.
North and central kolkata puja guide map in ENGLISH.

South kolkata puja guide map in BANGLA.

South kolkata puja guide map in English

Thanks to. http://www.durga-puja.org/, http://www.durgaonline.com/maps

LIGHT-EMITTING DIODES (LED)

The increasing use of digital displays in calculators, watches, and all forms of instrumentation

has contributed to the current extensive interest in structures that will

emit light when properly biased. The two types in common use today to perform this

function are the light-emitting diode (LED) and the liquid-crystal display (LCD). Since

the LED falls within the family of p-n junction devices and will appear in some of the networks in the next few chapters, it will be introduced in this chapter. 

As the name implies, the light-emitting diode (LED) is a diode that will give off

visible light when it is energized. In any forward-biased p-n junction there is, within

the structure and primarily close to the junction, a recombination of holes and electrons.

This recombination requires that the energy possessed by the unbound free electron

be transferred to another state. In all semiconductor p-n junctions some of this

energy will be given off as heat and some in the form of photons. In silicon and germanium

the greater percentage is given up in the form of heat and the emitted light

is insignificant. In other materials, such as gallium arsenide phosphide (GaAsP) or

gallium phosphide (GaP), the number of photons of light energy emitted is sufficient

to create a very visible light source.

 The process of giving off light by applying an electrical source of energy is

called electroluminescence.

As shown in Fig. 1 with its graphic symbol, the conducting surface connected

to the p-material is much smaller, to permit the emergence of the maximum number

of photons of light energy. Note in the figure that the recombination of the injected

carriers due to the forward-biased junction results in emitted light at the site of recombination.
There may, of course, be some absorption of the packages of photon energy
in the structure itself, but a very large percentage are able to leave, as shown in the figure.

Figure 1 (a) Process of

electroluminescence in the LED;

(b) graphic symbol.

The appearance and characteristics of a subminiature high-efficiency solid-state
lamp manufactured by Hewlett-Packard appears in Fig. 1.55. Note in Fig. 1.55b that
the peak forward current is 60 mA, with 20 mA the typical average forward current.
The test conditions listed in Fig. 1.55c, however, are for a forward current of 10 mA.
The level of VD under forward-bias conditions is listed as VF and extends from 2.2
to 3 V. In other words, one can expect a typical operating current of about 10 mA at
2.5 V for good light emission.

Two quantities yet undefined appear under the heading Electrical/Optical Characteristics
at TA  25°C. They are the axial luminous intensity (IV) and the luminous
efficacy (v). Light intensity is measured in candela. One candela emits a light flux
of 4 lumens and establishes an illumination of 1 footcandle on a 1-ft2 area 1 ft from
the light source. Even though this description may not provide a clear understanding
of the candela as a unit of measure, its level can certainly be compared between similar
devices. The term efficacy is, by definition, a measure of the ability of a device
to produce a desired effect. For the LED this is the ratio of the number of lumens
generated per applied watt of electrical energy. The relative efficiency is defined by the luminous intensity per unit current, as shown in Fig. 1.55g. The relative intensity
of each color versus wavelength appears in Fig. 1.55d.
Since the LED is a p-n junction device, it will have a forward-biased characteristic
(Fig. 1.55e) similar to the diode response curves. Note the almost linear increase in relative
luminous intensity with forward current (Fig. 1.55f). Figure 1.55h reveals that the
longer the pulse duration at a particular frequency, the lower the permitted peak current
(after you pass the break value of tp). Figure 1.55i simply reveals that the intensity is
greater at 0° (or head on) and the least at 90° (when you view the device from the side).

Figure 1.55 Hewlett-Packard subminiature high-efficiency red solid-state lamp: (a) appearance;

(b) absolute maximum ratings; (c) electrical/optical characteristics; (d) relative intensity versus wavelength;

(e) forward current versus forward voltage; (f) relative luminous intensity versus forward current;

(g) relative efficiency versus peak current; (h) maximum peak current versus pulse duration;

(i) relative luminous intensity versus angular displacement. (Courtesy Hewlett-Packard Corporation.)

Figure 1.55 Continued.

LED displays are available today in many different sizes and shapes. The lightemitting

region is available in lengths from 0.1 to 1 in. Numbers can be created by

segments such as shown in Fig. 1.56. By applying a forward bias to the proper p-type

material segment, any number from 0 to 9 can be displayed.

Figure 1.56 Litronix segment display.

There are also two-lead LED lamps that contain two LEDs, so that a reversal in

biasing will change the color from green to red, or vice versa. LEDs are presently

available in red, green, yellow, orange, and white, and white with blue soon to be

commercially available. In general, LEDs operate at voltage levels from 1.7 to 3.3 V,

which makes them completely compatible with solid-state circuits. They have a fast

response time (nanoseconds) and offer good contrast ratios for visibility. The power

requirement is typically from 10 to 150 mW with a lifetime of 100,000 hours. Their

semiconductor construction adds a significant ruggedness factor.

Field-Effect Transistors

         

 The field-effect transistor (FET) is a three-terminal device used for a variety of applications that match, to a large extent, those of the BJT transistor described in Chapters

3 and 4. Although there are important differences between the two types of devices,

there are also many similarities that will be pointed out in the sections to follow.

          

The primary difference between the two types of transistors is the fact that the

BJT transistor is a current-controlled device as depicted in Fig. 5.1a, while the JFET

transistor is a voltage-controlled device as shown in Fig. 5.1b. In other words, the current

IC in Fig. 5.1a is a direct function of the level of IB. For the FET the current I

will be a function of the voltage VGS applied to the input circuit as shown in Fig. 5.1b.

In each case the current of the output circuit is being controlled by a parameter of the

input circuit—in one case a current level and in the other an applied voltage.

Drs. Ian Munro Ross (front) and 

G. C. Dacey

Just as there are npn and pnp bipolar transistors, there are n-channel and p-channel

field-effect transistors. However, it is important to keep in mind that the BJT transistor

is a bipolar device—the prefix bi- revealing that the conduction level is a function

of two charge carriers, electrons and holes. The FET is a unipolar device

depending solely on either electron (n-channel) or hole (p-channel) conduction.

The term field-effect in the chosen name deserves some explanation. We are all

familiar with the ability of a permanent magnet to draw metal filings to the magnet

without the need for actual contact. The magnetic field of the permanent magnet has

enveloped the filings and attracted them to the magnet through an effort on the part

of the magnetic flux lines to be as short as possible. For the FET an electric field is

established by the charges present that will control the conduction path of the output

circuit without the need for direct contact between the controlling and controlled

quantities.

There is a natural tendency when introducing a second device with a range of applications

similar to one already introduced to compare some of the general characteristics

of one versus the other. One of the most important characteristics of the FET

is its high input impedance. At a level of 1 to several hundred megohms it far exceeds

the typical input resistance levels of the BJT transistor configurations—a very important

characteristic in the design of linear ac amplifier systems. On the other hand,

the BJT transistor has a much higher sensitivity to changes in the applied signal. In

other words, the variation in output current is typically a great deal more for BJTs

than FETs for the same change in applied voltage. For this reason, typical ac voltage

gains for BJT amplifiers are a great deal more than for FETs. In general, FETs are

more temperature stable than BJTs, and FETs are usually smaller in construction than

BJTs, making them particularly useful in integrated-circuit (IC) chips. The construction

characteristics of some FETs, however, can make them more sensitive to handling

than BJTs.

Two types of FETs will be introduced in this chapter: the junction field-effect

transistor (JFET) and the metal-oxide-semiconductor field-effect transistor (MOSFET).

The MOSFET category is further broken down into depletion and enhancement

types, which are both described. The MOSFET transistor has become one of the most

important devices used in the design and construction of integrated circuits for digital

computers. Its thermal stability and other general characteristics make it extremely

popular in computer circuit design. However, as a discrete element in a typical

top-hat container, it must be handled with care (to be discussed in a later

section).

Once the FET construction and characteristics have been introduced, the biasing

arrangements will be covered in Chapter 6. The analysis performed in Chapter 4 using

BJT transistors will prove helpful in the derivation of the important equations and

understanding the results obtained for FET circuits.

First Trojan Asteroid Circling Sun In Earth’s Orbit Discovered

Pasadena – NASA’s Wide-field Infrared Survey Explorer (WISE) mission has discovered the first Trojan asteroid circling the sun in Earth’s orbit. Scientists long believed Earth would have Trojans, but they were difficult to detect.

According to a NASA news release, astronomers  have detected the first Trojan asteroid that is orbiting the sun in our planet’s orbit – Trojans are asteroids that share an orbit with a planet and are locked in by a stable gravitational balance between the sun and a planet.

Scientists have identified Trojans with Jupiter, Mars and Neptune and two of Saturn’s moons.

Before this discovery, it was acknowledged that Earth must have a Trojan asteroid, but there was a great difficulty proving it because they were hard to detect due to their small size and they appear near the sun.

“These asteroids dwell mostly in the daylight, making them very hard to see,” said study head, Martin Connors of Athabasca University. “But we finally found one, because the object has an unusual orbit that takes it farther away from the sun than what is typical for Trojans. WISE was a game-changer, giving us a point of view difficult to have at Earth’s surface.”

The study first began in January 2010 and ended in February of this year. Connors and his team scanned the entire sky using the WISE telescope and then utilized data from NEOWISE, which led to the observation of more than 155,000 asteroids between Mars and Jupiter and 500 near-Earth objects (NEOs).

The search concluded in two Trojan candidates, and ultimately 2010 TK7 was verified as an Earth Trojan, which is 1,000 feet (300 meters) in diameter.

“This observation illustrates why NASA’s NEO Observation program funded the mission enhancement to process data collected by WISE,” said NEOWISE program executive at NASA Headquarters in Washington, Lindley Johnson. “We believed there was great potential to find objects in near-Earth space that had not been seen before."

The discovery is published in the July 28 issue of the journal Nature.