SCIENCE & TECHNOLOGY

Quake and bomb-proof construction
Jagvir Goyal

The news that Mukesh Ambani is aspiring to build a bomb-proof and earthquake proof bungalow in Mumbai has aroused public curiosity if construction of such a building is possible. The buildings constructed in India and the world are always termed as “Earthquake resistant” and never as “Earthquake proof”.

The science of festivals
Rajesh Kochhar

We have got so used to celebrating first January as the New Year day that we forget that there are other calendars also. Similarly we often get so absorbed in gazetted holidays and religious celebrations that we forget that many festivals have manifest scientific basis.

Prof Yash Pal

Prof Yash Pal

THIS UNIVERSE 
PROF YASH PAL
When we throw a jug of  water on the floor the  water flows, but not a small 
drop of water, which forms a dome-like structure on the ground. 
Why the difference?


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Quake and bomb-proof construction
Jagvir Goyal

The news that Mukesh Ambani is aspiring to build a bomb-proof and earthquake proof bungalow in Mumbai has aroused public curiosity if construction of such a building is possible. The buildings constructed in India and the world are always termed as “Earthquake resistant” and never as “Earthquake proof”.

However Ambani wants his house to be earthquake proof. He has hired James Young, an architect in Singapore, to do the job for him. His multi-storeyed dream house is also supposed to have a helipad on its roof.

After World War II, the desire to have a bomb proof house has raised its head many times. Prohibitive cost of construction has been a major hurdle in its fulfilment.

Increased terrorism around the world has also been necessitating the existence of an affordable and manageable bombproof building system for the protection of military structures, strategically sensitive areas such a power plants and skyscraping commercial centres.

When Ambani is planning to spend a whooping Rs. 120 crore on his dream house, it can certainly become a reality.

Simplest idea during World War II times to save oneself from the attack of a bomb was to build a room in the basement with extraordinarily thick concrete walls.

Therefore, building 700 mm thick RCC walls around a house, avoiding use of bricks which act as deadly missiles during bomb attacks and designing a building to withstand six times the normal wind load can look to be a solution for possible protection from a bomb but not practicable at all. An alternative has to be there.

Tricorn Technology Ltd., London, a company that has initiated and participated in the development of blast proof and bombproof technology for security purposes has developed a polymer compound that can help in construction of bombproof houses.

The compound is a combination of gypsum and some polymers. Patented as PMG, it can certainly help in bombproof construction and in protection of personnel and buildings against bombs, blast and projectile damage.

Gypsum has been used in the construction industry for hundreds of years. It has good fire resistance and sound absorption properties besides being low cost and easy to repair. Its weakness is its susceptibility to water penetration and poor weather resistance.

Tricorn has developed some plastic polymers to greatly increase gypsum’s resistance to water and weather without losing its inherent qualities. By combination of gypsum with these plastic polymers, PMG has been developed by this company.

Polymer Modified Gypsum (PMG) has been found to be having excellent water resistant capabilities. It has also been found having natural and chemically gentle nature which enables its use as a matrix around various types of aggregates, additives and reinforcement.

The polymers used for PMG have a high degree of cross-polymer linking that in addition to providing excellent defensive capabilities also give three dimensional stability and strength to the structure.

Due to theses unique and flexible properties of PMG, it may act for state-of-the-art bombproof technology for the protection of personnel and property from terrorist bomb attacks. Not only that, it can be very easily used to bombproof any existing structures or buildings as its flexibility enables us to mould it to any shape.

Further, it has been found to be providing great resistance to nuclear, biological and chemical attacks also. PMG gains importance as there is no other material available at present that may act as a bombproof material.

Another helping material developed by the same company for defence purposes is Armorcrete. It is a low cost composite material particularly designed to withstand armour piercing bullets.

Both PMG and Armorcrete can be used in defence applications and in bombproof building construction.

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The science of festivals
Rajesh Kochhar

We have got so used to celebrating first January as the New Year day that we forget that there are other calendars also. Similarly we often get so absorbed in gazetted holidays and religious celebrations that we forget that many festivals have manifest scientific basis.

All Hindu festivals are based on what is commonly known as the Vikrami calendar. It is a twin-track calendar. It keeps track of the sun’s ingress into the 12 zodiacal signs (the samkrantis) as also of the lunar phases. The month in this calendar is actually made by the moon; it extends from one new (or full) moon to the next. Just as a Gregorian year can have 365 or 366 days, a Vikrami year consists of either 12 or 13 lunations.

The benchmark for the Vikrami calendar is the spring equinox (which falls on about 23 March). Because of the accumulated error, the Vikrami calendar nominally considers the Baisakhi day to be the spring equinox. The New Year must begin with the new moon preceding this date.

For carrying out calculations, a lunation is divided into 30 unequal parts called tithis. A tithi can begin any time in a day. The celebration/observance is then transferred to a civil day, beginning with sunrise. It is this transfer that sometimes causes confusion as regards the actual day of a festival. Similarly, if a month is repeated, there are rules laid down on when to observe/celebrate. (Different panchangs can have different rules.)

While the Gregorian new year is ushered in with a hangover, the Vikrami new year is greeted with piety. The first nine tithis constitute the navaratris, the last one being celebrated as Ramanavami. Six months later comes another navaratri observance, including Durgashtami. The tenth tithi is celebrated as Vijayadashami, which being outside the navaratri permits relaxed celebration. The following new moon is Deepavali. The poornima after this is celebrated as Guru Nanak Jayanti.

Shivaratri is essentially a commemoration of amavasya; it is observed just a tithi before amavasya (the thin moon, waiting to disappear is invariably associated with Shiva). The last shivaratri of the year is called Mahashivaratri. The last full moon of the year is Holi.

In other words, about 15 days after Mahashivaratri comes Holi. A fortnight later comes the spring navaratri. Easter is an older equinoctial observance incorporated into the Christian calendar. Easter Sunday is the Sunday following the full moon following the spring equinox.

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THIS UNIVERSE 
PROF YASH PAL
When we throw a jug of water on the floor the water flows, but not a small 
drop of water, which formsa dome-like structureon the ground. 
Why the difference?

Molecules of water attract each other. That is the reason it stays a cohesive liquid with a well-defined surface. For a molecule inside the liquid there is no net force on a molecule because it is attracted in all directions. On the other hand for molecules on the surface there is a net force pulling them inside. This force produces something like an elastic membrane.

This membrane likes to be as small as possible. If the amount of water is small its gravitational force downward is also small.

In such a situation the elastic force can overwhelm the gravitational force and the membrane can wrap around the molecules of water.

You get a drop! Such drops can move over a slightly oily surface without the water
spreading out.

If on the other hand the amount of water is large enough its weight does not allow the membrane to wrap round it and the water spills out.

Thus it is a game of balancing two different forces. One is the weight of the water: that is the gravitational force.

The other is the adhesive force between the molecules that can produce surface tension, essentially a film that would like to become as small as possible.

For small masses, the surface force wins out and we get spherical drops. For large masses the surface force becomes unimportant.

This is the reason that raindrops are nearly spherical; the dewdrops on leaves and grass are also round.

And drops of water spilling out of water poured out of a jug form mound-like structures instead of spreading out like the mass of water.

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