Mobile telephony
by Swarn Bajaj
Q. How does a mobile phone work?

European Mars Express
by Radhakrishna Rao
THE 14 nation European Space Agency, has taken a bold initiative to pioneer a more flexible way of building space science missions by making use of making use of “off the shelf” or readily available technological elements. To this end, it has awarded a £ 60-million Euro contract to Matra Marconi Space, which will design and build the Mars Express spacecraft in time for launch in June, 2003. As envisaged now, Mars Express will allow European space scientists to investigate whether there is, or ever was, life on the red planet.

Science Quiz
by J. P. Garg

Proper utilisation of flyash
by Amar Chandel & G.S. Dhillon

IN India nearly 850 lakh tonnes of flyash and furnace bottom ash (FBA) is produced annually by 82 thermal plants burning bituminous coal and its safe disposal poses problems for the power plant operators. The Government of India in 1994 launched a Technology Mission directed towards promoting safe disposal of coal combustion products (CCPs) i.e. flyash and FBA, so that ecosystem is not polluted. By 1998, the efforts resulted in utilisation of flyash amounting to 5 per cent at the national level.

NTPC (National) Thermal Power Corporation, which is major player in thermal power generation, has taken several steps to promote flyash utilisation. These are: i) setting up of pilot plant for production of flyash, lime bricks, ii) plant for production of alum from flyash, and iii) utilisation of flyash for production of PPC (Pozzolana Portland Cement).

For utilisation of ash for purposes referred above, the flyash should be available in dry form and should conform to the requirements of the I.S. 3812 i.e. the amount of unburnt carbon should be less than 5% and the lime reactivity should be within the range of 30 to 40 kg/cm2. For this purpose the flyash collected from second or third field of ESPs (Electro-Static Precipators) is stored in dry state till utilisation.

In Punjab nearly 34 lakh tonnes of flyash (plus FBA) is being produced annually by its three thermal plants of capacity of 2120 MW, located at Ropar, Bathinda and Lehra Mohabbat. At present the operating agency PSEB (Punjab State Electricity Board) is affecting the disposal of flyash and FBA by making slurry with 10 parts water to one part ash, in ash disposal ponds. At Ropar 1975 acres of land has been acquired for ash disposal ponds and at Bathinda the ash pond spread over 840 acres of land. But at Lehra Mohabbat, the Board is finding it difficult to acquire beyond 160 acres of land, which is likely to get filled with the next few years. There is also difficulty in finding sufficient water for affecting disposal of ash in a slurry form. So the authorities are switching over to the paste mode of ash disposal.

Directed towards utilisation of flyash, the PSEB has entered into an agreement with cement companies (ACC and Ambujas) for setting up Clinker grinding units in close proximity of the thermal plants, and resulting product PPC with flyash admixture will be produced. The present day utilisation at Ropar is around four lakh tonnes annually, whereas at Bathinda it is much lower at around 17330 tonnes.

Compared to the above scenario, let us look at the European scenario as to what extent and in what mode, the flyash ad FBA is being utilised.

DENMARK has achieved 100% utilisation of coal ashes generated by its thermal plant burning bituminous coal. The flyash is being used in production of cement, concrete, building material, roads etc. Whatever amount cannot be utilised is exported to the neighbouring European countries.

The flyash, in regard to its physical and chemical properties, has to conform to the requirements of European Standard EN 450 if it is to be used for production of cement or concrete. In case of flyash to be used in production of building materials and road work, there are no special requirements to be met by the flyash, but the owner of the building has to be informed as to what material (flyash) has been used. When flyash or FBA is used for filling the low lying areas and the load bearing areas, a cover of sand or gravel, at least 20 cm thick, need be provided to guard against possible radioactive radiations from the coal ashes used in the fill.

Denmark does not permit the use of flyash as fertiliser due to danger of possible transfer of heavy metals from flyash to the crops grown. In the flyash at least 25 heavy metals have been detected.

HOLLAND also claims hundred per cent utilisation of coal combustion products (CCPs). About 58 % of flyash is utilised as raw material for production of clinker, which is ground to produce cement. In the above process the flyash substitutes part of clay, in the clay-lime mix used for making cement clinker. About 10% of flyash is used as “filler” in the concrete and another 10% as the asphalt filler, 18% of flyash is used for production light weight artificial gravel. The balance 4% is utilised in various other uses.

The cement industry of Holland is manufacturing Class A Portland flyash Cement, which though having similar properties as the normal Class A Portland Cement, but claims to ensure greater durability of concrete structures built with the former cement. The presence of small quantity of unburnt carbon particles in flyash is not considered harmful as the particles are not reactive in nature, so do not affect the properties of hardened concrete. For flyash considered suitable for use in concrete applications is the K—Index which is the extent of flyash which can be regarded as cement in the design of the concrete mixes.

GERMANY has more than 30 years of experience in utilisation of flyash. About 76% of the flyash is used for production of cement or concrete and the rest is used in road construction or filling low lying areas. FBA is used mainly for production of building materials. The marketing of flyash, including creation of its storage at the thermal plants, forms an important industrial activity in Germany. Majority of flyash is produced during winter when thermal plants have very high plant load factor. But the building activity during that period is sluggish. So storage of flyash is needed and there exists storage capacity of 40,000 m3 for flyash to store it in a dry state fit for use.

Strict control over quality of flyash is maintained in Germany on the material to be utilised. The agency responsible for quality control not only keeps watch over the coal used, but also its milling and burning process, so that the flyash is of consistently good quality. Continuous and daily testing of the flyash produced at the thermal plants is done and it covers the determination of chemical and physical characteristics. The most important aspect of quality control of flyash is that it is conducted by a third party, which carries approval of the building industry or the other consumers of the flyash.

Disposal of flyash is permitted in special cases when the material is not found conforming to the required specification. For getting a licence to run a thermal plant in Germany, the operator has to prove that he has “capability and capacity” for utilisation of CCPs that will be produced by the thermal plant. He has to give guarantee for full utilisation in the near future at least.

Germany has not acquired capability for making flyash bricks, as in that country both sand and clay are available in abundance and at a reasonable price.

FBA has found a recent application in green roofs i.e. the rooftop gardens which are extremely popular in Germany. FBA goes to make plant sub-stratum and it improves its water holding capacity. FBA is used to produce the lightweight artificial aggregate for use in concrete blocks and thermal insulating masonry mortars which are supplied in ready mixed state at the building site. Non-aerated concrete blocks are also produced using FBA. The most common use of FBA is in the road construction as bedding material for concrete pavements, load bearing layers for parking lots and in embankments.

UK produces about 62 lakh tonnes of flyash by burning locally produced and imported coal in its thermal plants. Prior to privatisation, the thermal plants were operated as base load stations, but now they work in two shifts as peak load station. This results in production of flyash greatly varying in quality and quantity. Due to this reason the utilisation of flyash in the UK has not crossed the 90% mark.

The various utilisation modes are similar to one adopted in the other European countries discussed above. R&D activity in the UK is directed towards establishing new and improved uses of flyash and FBA. The demand for FBA in the UK has reached a level that demand is far more than production. So old deposits of FBA in lagoons or ash ponds are being dug up and the material utilised. The ASH RESOURCES LTD. located at Eggborough near the thermal plant is engaged in producing lightweight aggregate from flyash and FBA which is used for production of building materials utilising modern technology.

In order to transform flyash and FBA from waste material needing disposal to a resource which can be used beneficially, considerable efforts are needed by the thermal plant operators and manufacturers of flyash admixtured products (PPC and flyash bricks). These efforts should go beyond holding of workshops attended by a selected few. Confidence in the products produced can come if the State Electricity Boards themselves start using these products and also set up demonstration plants.

Mobile telephony
by Swarn Bajaj

Q. How does a mobile phone work?

A. A mobile phone basically consists of a handset along with a SIM card (Subscriber Identity Module.). The SIM provides the handset with an identity. Without this, the handset is not operational. A SIM works like a memory chip in a computer. This SIM identifies the subscriber to the network.

Q. Do all handsets from overseas work in India?

A. Handset compatible with the GSM-900 or GSM-1800 technology, or alternatively, dualband handsets work in India. It is possible to verify this at the time of purchase or from the literature that accompanies the handset.

Q. Isn’t it dangerous to talk over a mobile phone and drive?

A. it is not advisable to drive and talk over the mobile at the same time. There are different ways to get around this. The best practice is to pull over during a call and only continue driving after having completed the call. Another alternative that many users are not aware of is that they can purchase a hands-free kit which gets attached to the handset. This kit works like a pair of headphones with a mike, and thereby allows the driver to keep both hands on the wheel during a call. Another option that drivers have is to divert their calls to their voice mail during their drive, and retrieve the calls after they have reached their destination.

Q. I feel that mobiles are more of a status symbol, Why do I really need to own one?

A. Mobile telephony has a number of uses and offers so much more than simply being able to talk over a phone. Be it for a child trying to reach his parents on their mobile, or for a young woman driving down a lonely road who uses it as a safety device to get assistance, the mobile phone has fast become a very valuable tool to stay connected world-wide. besides the obvious use of a mobile phone in emergencies when there is no other access to a landline phone, the cell phone is valued as business efficiency tool, for keeping in touch, to access on-line information and even as a source of entertainment. Most cellular operators offer services such as Voice Mail, Call Wait/Hold, Call Divert, and so on to increase efficiency and productivity while allowing one to be on the move. Mobile telephones have very rapidly become an essential feature of today’s world.

Q. People say owning a mobile is very expensive; that bills run up to Rs. 5,000-8,000 every month. Is this true?

A. No. Just like a landline phone, the bill depends upon the usage. However statistics clearly indicate that the average monthly bill ranges from Rs. 1200-1500. This figure is significantly lower than the general perception.

Q. I have heard that one can actually save with a mobile phone over DoT for long distance calling? How is this possible?

A. Long distance calls from mobile phones within Punjab are not charged at DoT’s STD rates. For example, a mobile call from Chandigarh to Amritsar during the day will cost Rs. 19.20 per minute as compared to Rs. 43.20 for the landline STD rate. This is because the caller pays only the airtime charge plus the cost of a local call since the call is routed through the cellular network and not the DoT network. Unlike the DoT network which charges calls based on distance, cellular operators in India have decided to offer this benefit to customers by not levying an additional charge for long-distance calls within their own network.

Q Why do cellular operators charge on incoming call?

A. The heavy investments the cell operators have had to make to set up the infrastructure allowing mobile telephony, coupled with costs of license fees, etc, have made it necessary to charge both incoming and outgoing calls. This is a common practice followed by many cellular operators across the globe.

Q. What is Roaming?

A. Roaming is a service that allows you to travel into other networks beyond the home network (Punjab in this case). Automatic Roaming has now made it possible to travel outside Punjab with just one number on which you can be contacted.

Q. What is Voice Mail?

A. A voice mail facility is like a personal answering machine that receives your messages when you are not available, when you are out of the coverage area, or when your phone is switched off. This service can be extremely helpful since it ensures that you are accessible at all times.

Q. What are the different handsets available in the market?

A. There is a wide variety of handset available in the market ranging in looks, the features they offer and their prices. The more popular ones are:

Nokia 5110 — This has a market price of Rs. 15,000/- It weighs 170 grams, its talk time (if you were to talk continuously the phone would last) is 5 hours, and its standby time (if the phone were kept on without talking) is 270 hours, with a charge time (the time it takes to recharge completely) of 1.5 hours.

Siemens S-6 — This has a market price of Rs. 9730/- It weighs 180 grams, a talk time of 4 hours, with a standby time of 60 hours. (This is available with Spice for Rs 6, 730.)

Q. Can I access the Internet using a mobile phone?

A. Yes, To access the Internet over the mobile network, you need to use a fax/data compatible handset, and should have access to the fax/data facility service from your service provider. In addition you need a PCMCIA (PC) card which will connect the laptop and the handset.

European Mars Express
by Radhakrishna Rao

THE 14 nation European Space Agency (ESA), has taken a bold initiative to pioneer a more flexible way of building space science missions by making use of making use of “off the shelf” or readily available technological elements. To this end, it has awarded a £ 60-million Euro contract to Matra Marconi Space (MMS), which will design and build the Mars Express spacecraft in time for launch in June, 2003. As envisaged now, Mars Express will allow European space scientists to investigate whether there is, or ever was, life on the red planet.

ESA took the decision, in principle, to send a mission to Mars shortly after the loss of the Russian spacecraft Mars 96 with several European experiments on board. The agency wanted to build on the Mars 96 payload experience to design a mission that would put Europe at the leading edge of Mars exploration. But ESA had to act quickly. Major space missions can take more than six years to go before the positioning of the planets in 2003 would offer the shorter travel time to Mars with the highest payload. Budgetary pressures were also forcing ESA to look for cheaper ways of building spacecraft. A Mars mission, therefore, seemed a good candidate to explore cheaper and faster working methods.

As it is, Mars Express is the first of a new type of “flexible” missions in ESA’s long-term scientific programme,which should be built and launched for about half the previous budget for similar missions. Costs are being saved by shortening the time form original concept to launch,re-using existing hardware, adopting new project management practices, and having access to reduced launcher costs.

Selection of the scientific payload by ESA,s scientific advisory bodies and mission definition by industry have been performed simultaneously, instead of sequentially as in previous missions. This has cut the time from concept to the awarding of today’s design and development contract from about five years to a little more than one year. The design and development phase will take under four years, compared with up to six previously.

Mars Express is making maximum use of pre-existing technology, which is either “off-the shelf” or has already been developed for other missions. This strategy, in fact, only works when a second mission, such as mars Express, can use in recurring manner, technology already applied in previous missions. In future, ESA plans to develop new technologies needed for innovative and ambitious missions also in separate, small technology missions called SMART. “European space industry is now sufficiently mature, thanks largely to previous experience with ESA missions, to take on these aspects of Mars Express as well as the associated risks” says Rudolf Schmidt, ESA Mars Express Project Manager.

Science Quiz
by J. P. Garg

1. “I can destroy the fleet (of Roman ships)”, said this Greek inventor. “By what means?”, asked the King of Syracuse. “By means of burning mirrors”, replied the scientist. The King consented and the scientist set the ships on fire. aName the great scientist. What type of mirrors did he use?

2. India will launch a big scientific programme in July this year to unravel the secrets of the monsoon. Called BOBMEX, this project will involve more than 10 Indian scientific and defence organisations. What is the complete name of this project?

3. A pendulum wall clock is likely to run slow in summer and fast in winter. To prevent this, a special alloy named invar is used for making clock pendula. What metals does this alloy contain? Which physical property makes it suitable for this purpose?

4. What is the process of protecting the human body against diseases called? By which means is this process brought about? Which type of substances are produced/injected in the body by this process?

5. We normally observe that it is easier to start a car on a warm day than on a chilly day. Which characteristic of the car battery causes this effect and how?

6. This woody shrub plant is the only plant in the world that produces “liquid wax”. The oil of its seeds has wide industrial uses and is similar to sperm whale oil in chemical composition. What is the most common name of this plant?

7. Name the chemical, released by certain nerve cells, on which learning and memory depend and that also serves as a transmitter in the nervous system.

8. Who discovered that the galaxies that are farther from the earth are moving away faster than those that are nearer? Which astronomical instrument has been named after this great astronomer?

9. Green vitriol is used an an insecticide, for dyeing purposes and in the preparation of blue black ink. What is the chemical name of green vitriol?

10. The abbreviations IGMDP and IRBM were in the news recently in connection with Indian scientific achievements. What are the full forms of IGMDP and IRBM?

ANSWERS

1. Archimedes; concave mirrors 2. Bay of Bengal and Monsoon Experiment 3. Iron and nickel; it has negligible coefficient of expansion 4. Immunisation; vaccines or serums; antibodies 5. Resistance of the battery (electrolyte) is less on a warm day (because of higher temperature), thus it supplies more current 6. Jojoba 7. Acetylcholine 8. American scientist Edwin Powell Hubble; Hubble Space Telescope, a large and sophisticated radio telescope put into space by the USA in 1990 9. Ferrous sulphate heptahydrate 10. Integrated Guided Missile Development Programme; Intermediate Range Ballistic Missile.

Computer carpentry
IMAGINE turning your child loose on your computer with a hammer, drill, sprayer, screw-driver and saw. Actually, it’s good idea — if you’ve got the Tonka Workshop CD-ROM Playset. The kit’s “tool set” installs on top of any standard-size keyboard. Using those tools and watching the action mirrored on screen, your child can build spaceships, houses, and bicycles. Price: $40. www.hasboro-interactive.com (Popular Science).

Scratch-resistant plastic lenses
German scientists have developed a new coating material which can do away with the need for high temperature curing of plastic lenses, thereby reducing the risk of being deformed while processing.

Lenses made of polymethyl methacrylate (PMMA) are as transparent as glass ones and virtually unbreakable.

In order to make such lenses scratch-free, they have to be coated with a hard surface layer. This is done by curing the material at about 80 degrees Celsius temperature. But the method is time-consuming and not well-accepted as at this temperature, the plastic softens and there is a chance of its being deformed.

Fraunhofer Institute for Silicate Research in Wurzburg has developed a coating material that cures without heat. The method can be integrated in the production of handheld magnifying glasses.

The lenses are coated with ORMOCER and cured by ultraviolet light. ORMOCER is a new class of materials that can combine vitereous and polymer components.

Light therapy for skin diseases
dietary supplements of selenium help make light therapy— a treatment protocol for a skin disease called psoriasis using light— safer, according to Scottish scientists who have undertaken a study to show the protective effects of selenium.

Psoriasis, a chronic, acute and inflammatory skin disease, is usually treated by a high intensity light source as the light stops the overgrowth of skin cells and damps down the inflammation in the skin. The treatment is combined with a chemical, psoralen, to increase the effectiveness of the therapy.

According to researchers from Edinburgh University, “just as someone who spends lots of time in the sun without adequate protection runs a higher risk of getting skin cancer, so these patients have a greater risk of developing skin cancer because they often require many courses of light therapy to keep psoriasis under control.