SCIENCE & TECHNOLOGY
 



 

Fire safety of multiplexes
Jagvir Goyal
M
ULTIPLEX era is on. Every big city is planning to have multiplexes. Gurgaon and Delhi have many; Faridabad and Chandigarh have one each. Panchkula has auctioned multiplex sites and many others are in planning stage. Soon a city without a multiplex will be reckoned as a backward one.

Prof Yash PalUnderstanding the universe
with Prof Yash Pal
When light enters from one medium to another its speed changes. Between its wavelength and frequency, which one changes?
Light, like other forms of electromagnetic radiation, is an oscillating electromagnetic disturbance that propagates in a direction normal to the direction of oscillation.

New products & discoveries

  • Sound with space and motion

  • Food for thought

  • Birds use herbs

  • “Visionary” computers

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Fire safety of multiplexes
Jagvir Goyal

MULTIPLEX era is on. Every big city is planning to have multiplexes. Gurgaon and Delhi have many; Faridabad and Chandigarh have one each. Panchkula has auctioned multiplex sites and many others are in planning stage. Soon a city without a multiplex will be reckoned as a backward one.

As the number of multiplexes rises now and multiplies later, the shock unleashed by the news of a fire in a multiplex may severally shake the confidence of visiting public and hold them, back thereby defeating the very purpose behind existence of multiplexes. It is therefore extremely important that full fire safety measures are taken while building multiplexes and no relaxation on any account is allowed in doing so.

Devastating fires in Gopala Towers, Sidhartha Continental, Vigyan Bhawan, Krishi Bhawan and Uphaar Cinema in Delhi are a few incidents still fresh in the minds of people. Each of these mishaps sent a grim reminder to the builders of the country to adopt minimum required standards of fire fighting and evacuation facilities in public places. But again, the elementary precautions and safety measures against fire have not been adhered to while raising big or highrise buildings.

Mere provision of fire extinguishers, fire alarms or keeping contact with fire stations is not enough to kill a fire breakout and avoid loss of human life and property in a multiplex. Micro-planning needs to be done and stringent provisions made to prevent occurrence of a fire.

Most of the fires that occur in multi-storey buildings are due to electrical shortcircuits. Same rule is applicable to multiplexes also. To avoid a short circuit in a multiplex and Prevention of fire, following steps need to be taken at the time of its construction :

1. Separate shafts should be provided to carry electric cables. These shouldn’t be common with water supply or telephone lines. All shafts should be provided with fire resistant seals having a fire resistance of minimum two hours. All electrical ducts should be closed type so that fire may not travel from one floor to another.

2. Every Distribution Board should be provided with auto-trip MCBs which may trip on large current variations and Earth Leakage Circuit Breakers (ELCBs ) which may cut off power supply on any leakages.

3. All materials used in electrification and lighting of multiplexes should be ISI marked and fire resistant. Specially the wires must be fire resistant and should emit little smoke on burning.

4. Separate conduits should be provided for different circuits and no two phases should be passing in same conduits.

5. High capacity equipment like transformers, projectors, DG sets, microprocessors and amplifiers should have separate copper earthing arrangements.

6. Special clause should exist in the rent/lease document to make retailers to stick to above provisions in their part of electrical wiring.

In order to minimise chances of spread of fire, following points should be kept in mind during the construction of multiplexes:

1. Minimum use of wood should be made. Wherever used, wood should be painted with fire resistant paints. Sometimes some paper or fabric covering is provided over the walls of cinema halls in a multiplex. These should also be treated with fire retarding chemicals. The kitchens should not be wooden but should use stainless steel shelves and cabinets. Kitchen walls should have ceramic tiles instead of wooden panels often provided these days.

2. All retailers should also be bound to use minimum of wood and treat it, wherever used, with fire retardant paints. This clause should exist in the standard agreement document.

3. As far as possible, kitchens should be planned as isolated from the main restaurants.

4. Building basements are always more susceptible to fire. All basements should have sprinklers installed in them. It is preferable if the basements of multiplexes accommodate the water storage tanks to meet its requirements for AC plant, domestic purposes and for fire-fighting. If the number of water tanks is more than one as is usually done to keep domestic water separate, provision should be made to inter-connect the tanks with fire water tank to transfer water to it in case of fire. All basements must have adequate ventilation and exhaust machinery.

5. A.C. ducts of every floor should be kept separate. Wherever AC system has to be kept centralised, air handling units should be kept separate for each floor. In centrally airconditioned multiplexes, the smoke may travel quickly through A.C. ducts and prove fatal. The smoke in a building spreads so quickly that it may engulf a multiplex within five minutes. This fact should be given due attention while planning airconditioning of a multiplex.

6. Smoke detectors provided in all areas of a multiplex should be optical or photo-electric or heat detector type which must work efficiently and detect smoke at the earliest. In theatres, projected beam smoke detectors equipped with receivers, transmitters and reflectors should be provided.

Fire fighting equipment: Despite taking all measures to prevent fires, a multiplex has to remain ever ready to fight a fire-breakout. For this certain equipment should be made readily available and kept in working condition. Some of these equipments are:

1. Fire alarm system: Addressable as well as manual.

2. Fire extinguishers: Portable, of water type, foam type, gas type and dry powder type.

3. Sprinkler system: Automatic with a minimum pressure of 5 kg/cm2. A sprinkler should itself burst at a preset temperature and start spraying water. Sprinklers should always be provided in all cinema halls and basements in addition to other places felt necessary.

4. Hydrant system: A multiplex should be equipped with wet risers able to deliver water at high pressure at the highest point. The system should be backed by DG sets to restore power supply to fire hydrants within 6 to 8 seconds of power failure. All hydrants should have independent hoses and spray nozzles with length of each hose sufficient to cover the beat circumference of a hydrant.

5. Building management system: To automatically trip all fans in case of fire to avoid spread of smoke.

6. Public address system: It must be computerised, should assess fire situation and address people in case of emergency.

7. Breathing apparatuses: To help people feeling suffocated and fire fighting staff.

8. Emergency lights: Battery operated emergency lights, able to run for 3 hours.

9. DG sets: To switch on ventilation fans as soon as the power supply fails.

Evacuation facilities: Despite all prevention and provisions, if the unfortunate thing happens, following evacuation facilities must exist in a multiplex to take people out :

1. Most important is to avoid a stampede. Generally, electric supply goes off and lifts become inoperative. People can escape only through staircases. All staircases should be minimum 8 feet wide while the main staircases connected to fire exits should be 10 to 12 feet wide.

2. Staircases for each floor level should be independent. Their location within the multiplex must be staggered.

3. Exercise should be made to check that a multiplex full of people can be evacuated within 4 to 5 minutes of a fire.

4. Staircases should be designed as enclosed type to keep them free of smoke.

Maintenance of fire-fighting provisions: Every multiplex must have trained manpower to fight fire in most efficient manner at any hour of day or night. Mock trials should be conducted on a regular basis, preferably every week, under the eye of an expert fire officer. All electric provisions should be checked regularly with a suspicious eye and kept in best conditions. Eliminating loose electric connections must be a special task during the checking process.

Smoking should be prohibited in a multiplex. If allowed, cinema halls should have smoking zones which must be kept under strict watch.
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Understanding the universe
with Prof Yash Pal

When light enters from one medium to another its speed changes. Between its wavelength and frequency, which one changes?

LIGHT, like other forms of electromagnetic radiation, is an oscillating electromagnetic disturbance that propagates in a direction normal to the direction of oscillation. Wavelength is the distance this disturbance travels during one oscillation.

Therefore it is given by velocity of propagation divided by the frequency of oscillation. In going from one medium to another it is the velocity of propagation that changes. This would affect the distance the disturbance travels in one cycle of oscillation, which is the wavelength. From this it would seem that frequency is the basic property and wavelength is a derivative quantity. Frequency is determined by the characteristics of the source.

What is the actual reason at the atomic level that decides the transparency and colour of a medium?

Glass is transparent for visible light. It is not so transparent in infrared, or other frequencies like x-rays, for example. Our atmosphere is conveniently transparent in the visible region of the spectrum, where sun gives out most of its radiation and where our eyes are most sensitive. But the very same atmosphere is opaque in most frequencies of far infrared, ultra violet, x-rays and gamma rays.

Therefore, as you suspect, the transparency, or otherwise, depends on the detailed structure of the material. Atomic, and molecular structure enters centrally in determining the scattering and absorption of radiation. Atoms and molecules have specific energy levels.

They determine which part of the spectrum would be absorbed and which would pass through unhindered. Indeed in most of experimental science, atomic physics, molecular physics, lot of chemistry and biology, astronomy and even nuclear physics we use different radiations to probe structures at the basic level. The experiments are interpreted with the help of known theory and depending on the results new theory often emerges.

In a physical balance with equal weights in the two pans the torques in two directions will be the same irrespective of the direction in which the horizontal bar of the balance is tilted. So why does this bar become horizontal?

I must say that this question had me flummoxed for a number of days till I talked to a physicist friend, Prof Shyam Tandon. When he pointed out the reason I felt quite foolish. Since I have understood the reason rather well, let me share it with you.

Contrary to what most of us assume the pivot of an ordinary balance is seldom at the centre of gravity of the balance that includes the rod, the pans and the weights. It is slightly displaced up or down with respect to that position. If now you calculate the moments in two directions when the two weights are the same you come out with the result that they are balanced when the rod is horizontal.

The departure of the centre of gravity from the position of the pivot needs to be extremely small and would be automatically realised in any balance we construct, without going to a lot of trouble to make sure that they do not coincide.

This is one of those cases where inaccuracy is beneficial! I must remark, however, that the sensitivity of the balance is influenced by the degree of departure from this coincidence.
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New products & discoveries

Sound with space and motion

A conversation snaps around you. A string trio plays in front of you as you turn your attention from cello to violin. A soprano walks across the stage, and you turn your head to follow her voice. Conventional sound recording cannot capture those experiences — but an invention by audio engineers at the University of California, is changing that.

Motion-tracked binaural sound (MTB) captures cues for direction, distance and movement and the subtleties of natural, ambient sound that other systems don’t. Developed by Ralph Algazi, Richard Duda and Dennis Thompson at the Interface Laboratory in the UC Davis Center for Image Processing and Integrated Computing (CIPIC), the patent-pending technique uses off-the-shelf equipment that won’t break the bank.

For the listener, it’s an eerie experience of listening to invisible people talking, playing music or singing around you while you can turn your attention from one to another.

“Conventional audio playback doesn’t reflect how you hear in real life,” Algazi said. “Your body, the shape of your head and the room acoustics all affect how you hear.”

Food for thought

Gayle C. Windham and her colleagues at the California Department of Health Services and at a La Jolla, Calif., consulting firm report that the age of menarche — when a girl first starts her monthly menstrual periods — is later among daughters of tea drinkers than among daughters of moms who typically choose coffee or another beverage. If confirmed, the findings may reflect “hormonal effects,” the researchers say.

There is considerable variability in when a child reaches developmental milestones, be they growth spurts or teenage mood swings and impulsivity. In girls, this is especially true for the timing of changes related to puberty. For instance, although breast development typically occurs between the ages of 9 and 11, it can happen as early as 6 — and in a few truly perplexing waves of early development, it has reached back to girls as young as 2. Similarly, menstrual periods typically begin around age 12, but they can start as early as 10 or as late as 15.

Birds use herbs

Researchers from Ohio Wesleyan University suggest that some birds may select nesting material with antimicrobial agents to protect their young from harmful bacteria. They present their findings at the 104th General Meeting of the American Society for Microbiology.

“If the fresh herbs and plant materials that parent birds bring into the nest have a sufficient concentration of antimicrobial compounds, they could protect the nestlings from harmful bacteria,” says researcher Jann Ichida.

To find out if plants brought into the nest might prevent disease, Ichida and colleagues tested twelve different volatile plant materials against feather-degrading bacteria. Results showed that several types of plant materials and extracts, including usnic acid, ascorbic acid, yarrow, and two oak species inhibited the growth of a number of harmful bacteria.

“Visionary” computers

They may never appreciate the poetry of a sprawling glove save, or the thrill of an overtime winner, but computers are a step closer to “seeing” the sport of ice hockey, thanks to research at the University of Calgary.

U of C computer scientist Dr Jeffrey Boyd and three of his students are using hockey to test and develop new applications in the fast-growing field of computer vision research. Compared to humans, computers are still extremely primitive when it comes to perceiving visual information that we take for granted: motion, texture, depth perception and colour, for example.

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