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| SCIENCE TRIBUNE | Thursday, February 3, 2000, Chandigarh, India |
Need
for better solar cookers |
| Microwave cooking by Anupama Sandal & Manoranjan Kalia MICROWAVE heating in food processing has been around for over 40 years and predominant developments have been in the form of ovens for cooking and reheating foods in homes and catering establishments. Microwave oven cooking has recently gained popularity in the affluent societies of the big cities and metros of the country. |
Need for better solar cookers IN order to promote the greater use of renewable sources of energy so as to have a cleaner environment, the Ministry of Non-Conventional Energy Sources (MNES) has been supporting the development and sale of domestic solar cookers. Till 1997, about 4.3 lakh solar cookers had been sold by the ministry. Now the task has been passed on to the IREDA (Indian Renewable Energy Development Agency) to build up a mass movement. For that purpose a proper marketing mechanism is being created. Soft loans are being made available to the bulk users, intermediaries and manufacturers of the approved version of the solar cooker. PEDA (Punjab Energy Development Agency) has been deputed to do the needful in Punjab. The sponsored or the approved model is the box type solar cooker (Fig 1) which is supplied at a subsidised price of Rs 935 by PEDA. It is rectangular in shape with the top surface area of 0.6m2. Its two boxes (inner and outer) are made of 16 swg mild steel sheet and has overall weight of 25 kg. The depth of the inner box, which constitutes a critical parameter, is fixed at 15 cm and the inner surface of the inner box is painted black. The gap in between the two boxes is filled with an insulating material. In spite of the efforts made, so far the sponsored model has not caught public fancy. In this write-up an effort has been made to find out reasons why the solar cooker even at reduced (subsidised) price is not selling like “hot cakes”? Limitations of the sponsored model comprise the long drill to be followed by the user and salient features of the drill are listed next:- Keep the cooker in open space, free from shadows. The cooker should be so adjusted that the reflected rays of sun fall on the transparent glass lid and in that position tighten the position fixing hinges of the mirror. During the period of cooking adjustments have to be made three or four times to get optimum results. The cooker should be kept in sun for at least three quarter of an hour, before loading with cooking pots. The level of water along with other ingredients, should not be higher than half-way level of the cooking pot. The cooking pots should always be kept covered while cooking. The cooker should not be opened in operation or earlier than two hours, otherwise the food being cooked will remain uncooked due to the sudden loss of heat. So the spices should either be added before start of cooking or after completion of the cooking operation. While opening the glass lid, after food has been cooked, care need to be taken as the moment the lid is opened, the burst of steam escapes, which can cause injury to body or face of person opening the cooker. So the double lid should be carefully opened and the cooker should be allowed to cool off for 10 to 15 minutes before removal of the cooking pots. It is essential to use gloves of cotton cloth or napkin while removing the pots. Once the cooking operation is over, one has to clean the surfaces of the lid (inner and the top surface) with soft cloth. The cooker should be then put in a shaded and well protected place. While shifting or moving the cooker, the cooking pots should be taken out. Cooking generally takes 2 to 3 hours depending upon the intensity of the available sunshine radiations, type of food being cooked and the number of pots placed in the cooker. Summing up it may be said that the sponsored cooker-box type, intended to be promoted as an ideal domestic cooker, can serve the function to some extent if a rigid drill is followed and that too in summer season with long sunshine hours. It is not popular because it cannot be used to make chapatis and fry or grill (tandoori) food items, all of which are essential for the types of food consumed in Punjab. In contrast in concentrator type cookers, the cooking mode is similar to the day-to-day cooking as the heat is applied from below and this type of cookers can grill or bake. The sun rays are collected from a reasonably large surface area and focused to a point where the cooking pot is placed. Figure 2 shows some of the common or popular models. Kulkarni model marketed by Joyti Industries of Baroda has a parabolic concentrator 2m2. It incorporates a windshield and a cradle. It can be used for frying chapatis can also be made. At Mount Abu (Rajasthan) a large, shallow type parabolic concentrator is being used for cooking food for about 1200 inmates of the Institute or supply steam at 16 bar. The surface area of the parabolic concentrator is about 180m2. Boeing Co (USA) developed a parabolic concentrator cooker having an output of 450 watts (nearly) 1.5 times the conventional spun aluminium concentrator). Its reflecting surface of polished aluminium sheet is protected by vacuum deposited silicon-oxide coating. The concentrator is a honeycombed structure which is reinforced with fibreglass epoxy sandwich. Collapsible parabolic concentrators are more convenient than the conventional parabolic concentrators, which are bulky and difficult to transport. A Swedish model called umberayoler comprises a unit which opens out as an umbrella and its reflector is made from aluminium polyester sheet stuck to its concave side. It is popular for grilling dishes and fits in a specially designed suitcase and constitutes an ideal outfit for campers. Its cooking vessel is placed on a fixed platform and the umbrella is adjusted to focus sun rays on the pot. It has been found to give good results even on a windy day. A Russian model of folding variety of concentrator forms an essential equipment of its army units. Its rotating screws adjust the reflecting mirror and the cooking pot is kept in an insulated receiver. An Asymetrical Parabolic
Concentrator with a point focus has been used for solar
cookers and it has the merit that cooking vessel is
located inside a glass chamber at the focal point. This
provides for convenient cooking and the assembly can be
easily rotated during the cooking operations to keep
track of the sun. The cooker has a small size convenient
for campers. |
Internet is 30 years old IF you are spending a few days or a few months outside India, you need not lose touch with your dear and near ones. You can read all the newspapers in English as well as in regional languages. And one must thank the internet for this revolution. Thirty years ago, on October 29, the inaugural message was sent over the first keyboard of what was to become the Internet. It was just the simple word “login”. There were only two computers on what was then known as the Arpanet, the percursor to the Internet built by the American Defence Department’s Advanced Research Project Agency (ARPA). And so the revolution quietly began. A strange mixture of American Army’s money, development in computer science and engineering expertise slowly brought on the Internet, as we know today. A month later a third computer node was installed at the University of California at Santa Barbara (UCSB). The reach extended outside California to the University of Utah very soon. No celebrations were held to commemorate the joining of the two coasts with a link to Cambridge, Mass., where a small consulting company called Bolt Beranek & Newman had won the contract to build and run the Arpa-net. What emerged could be barely recognizable today. There were no @ signs, no dot coms, no World Wide Web, nothing called E-mail. The main purpose was to let university-based researchers for the Defence Department agency share computer resources. Many system engineers were reluctant. Computer power was scarce then. The personal computer had not appeared on the scene. Why should they share it with strangers? But from very early on, a handful of visionaries realised the power that would come from putting a computer on everybody’s desk, then gradually weaving them into one great matrix. In an age when computers were still identified in the public mind with punch cards and spinning reels of tape, some of the early pioneers of the information age showed stunning foresight. As long ago as 1945, Dr Vannevar Bush, the engineer, educator and government research adviser, came up with the basic idea of the personal computer, a device he called the memex — a mechanical extension of human memory that was as big as a desk and stored all your documents, including encyclopedias and reference libraries. The memex would work something like an associate memory. A user researching the history of the bow and arrow might start by calling up an encyclopedia article. When he found another relevant passage in a book, he would link the documents with a few keystrokes, encoding them with crude hyperlinks, and even add his own annotations. Thus any user could build up information through the maze of materials available to him. A decade and a half later, Dr J.C.R. Licklider, one of the most visionary computer scientists of his day, took another leap with his predictions of a “Galactic Network” linking everyone to a universe of information. He and one of his colleagues imagined nothing less than “a vast network of networks, ever-changing in both content and configuration”. There would be no need for letters, telegrams, telephone calls or even business trips. People would simply link their computers. Dictionaries, encyclopedias, investment advice, tax counselling, advanced scientific modelling programmes — all would be available within the net. Two years after the first transmission, the number of host computers grew to 23. The @ symbol was invented in 1972, and a year later 75 per cent of the Arpanet traffic was E-mail. It was starting to look like the Net. Before long, other organisations, like the National Science Foundation of the US, wanted their own networks. By the late 1970s, ARPA authorities were putting the finishing touches on the common language called TCP/IP that would weave the patches of individual users into the electronic blanket, which came to be called the Internet. By the year 1984, the
net had grown to include 1,000 host computers. And in
1991 came the World Wide Web followed by mosaic, the
graphical interface, or browser that inspired Netscape
and Explorer. The number of Internet hosts quickly
exceeded a million, and this year that number has
multiplied 50 times. (ANF) |
Revolution in fibre optics OPTICAL fibres, which are widely used in telecommunication, are ready to enter your homes as passage for room light. As is well known the working of optical fibres depends upon the phenomenon called total internal reflection. In it the inner thin glass wire of thickness of 5x1014 nm is coated by some reflecting medium of lesser refractive index. This coating acts as a rarer medium. The filament burning bulbs, an invention of Thomas Alva Edison, were replaced by fluorescent tubes long ago keeping conservation of energy in mind. The fluorescent tubes are to be replaced by compact fluorescent lamps (CFL) which not only give 6-7 times more light per watt than a bulb but also have a much longer life span (of almost 10 years). The negative aspect of CFL is that these are very costly though there is no doubt that this device will prove to be revolutionary in lighting our rooms. Two questions arose, though separately, in the minds of lamp manufacturers and scientists working in the field of fibre optics. 1. Whether optical fibres can be used as ducts for passage of light from a single source to different rooms? 2. Whether the velocity of light can be controlled to a large extent? The answer of first question is in the form of fibre optics lighting system which has three parts — the generator, the end (or side) light and a terminator. This system has special filters to eliminate IR or UV radiations. The generator has a lamp (halogen, high pressure discharge lamp or other focus lamps). The light from octopus like structure (as devised by Philips co) is focused into fibre cables which appear as tentacles of this octopus. The (optical fibre) cables have diameters of 1-5mm with their ends polished such that they distribute light at some definite angle. Since it will be optical fibres from a single source of light to every room of house, we will not need electrical wiring at all. There will be no heat as there is no electricity hence this system will not only be shock-free but also environment/user friendly. Optical fibre tentacles reaching room will emit small portion of light through its walls to produce uniform brightness like a neon bulb. The speed of light in a
medium depends upon the refractive index. The glass has
an average value of 1.5 for this index. thus in an
optical fibre light speed cannot be controlled. YN
Taranenko and LG Kazovsky, scientists in Stanford
university, California, are trying to control the speed
of light in optical fibres. Their work is after a
recently observed mechanism — Stimulated Brillouin
Scattering (SBS). In this case two copropagating waves, a
light wave and a flexural acoustic wave are injected into
the fibre. These two waves interact in the medium of
optical fibre. A new wave is generated having frequency
equal to frequency difference of the injected waves. This
three wave envelop is called “soliton”. The
soliton may be assumed as a controlled photon (remember
wave — particle duality). It has been observed that
though refractive index of fibre medium was 1.5, density
2.3 g/cm3, acoustic velocity 5.76 x 103m/s and acoustic
wave frequency 16.6 MHz, the speed of light (i.e.
solitons) could be controlled upto 3x104 m/s. In this
case injected light power was 200 MW and pulse duration
varied between several microseconds to several
milliseconds. The controlled speed depends highly on life
time of three wave envelop soliton (TWES) which is
approximately equal to attenuation time of the acoustic
wave (3.5 ms in present case. |
Microwave cooking MICROWAVE heating in food processing has been around for over 40 years and predominant developments have been in the form of ovens for cooking and reheating foods in homes and catering establishments. Microwave oven cooking has recently gained popularity in the affluent societies of the big cities and metros of the country. Those are considered to be one of the most energy efficient type of ovens and most rapid method for reheating food items. These are space saving, clean, eco-friendly and pollution free. Meat and meat products are cooked in different ways and the eating quality, nutrient and biological value, palatability and acceptability of the various preparations vary to a great extent. In one of the study at Agricultural University, Palampur, HP, the microwave cooked chevon (goat meat) had more of water soluble vitamins, crude protein content and less of crude fat and cholesterol contents compared to other conventional methods. It had better taste although colour was not good. From the table given below it is clear that the microwave oven cooking is 10 times cheaper than pressure cooking, almost 30 times cheaper than deep fat frying on flame and 20 times cheaper than roasting. Economic evaluation of cooking methods of chevon
The
authors are food and nutrition experts at HPKV, Palampur. |
New products & discoveries A virtual market place PricewaterhouseCooprs, a leading professional services organisation, has launched e.conomy (www.pwc.economy.com), a powerful web-based business to business marketplace designed to deliver significant price discounts and help member companies realise the promise of e-commerce. E.conomy focuses on members’ everyday needs, offering reduced prices on the indirect goods and services essential to all businesses. E.conomy will be able to meet substantially all of a company’s purchasing requirements like a single primary marketplace. Hitachi business applications Citrix Systems Inc. has entered into a global agreement with Hitachi Ltd enabling a broad base of users to gain ubiquitous access to the latest full-function business application on Hitachi wireless handheld devices. The inclusion of Citrix Independent Computing Architecture technology in Hitachi’s Handheld PC enables today’s mobile workforce to gain the same high quality of performance and access to robust business applications from remote locations can gain high-speed access to patient records hosted centrally on Citrix MetaFrame software. IDT launches 72-bit word widths Integrated Device Technology (IDT) has launced the new x72 SuperSync II FIFI (first-in/first-out) memories using 72-bit word widths which operates at 100 MHZ and are available in versions ranging from 32-K bit to 4-Mbit densities. Supporting the highest data transfer rates in the industry, the x72 FIFO are ideal for packet buffering and queuing in high-speed gigabit and terabit routers, as well as other applications using 64-bit microprocessors, DSPs or PCI interfaces. The x72 FIFOs are ideal for emerging high-speed terabit switches and routers used by Internet Service Providers (ISPs), Network Service Providers (NSPs) and carrier-class network operators for routing data, voice and video traffic over the service infrastructure. Network Associates ties up with NIIT Network Associates Inc. has tied up with NIIT for promoting NAI Security and Network Management product lines in the Indian sub-continent and in Asia. NIIT would promote the NAI Gauntlet Active Firewall’s, Cybercop Intrusion Protection and PGP Encryption/Authentication in the NAI Net Tools Secure Suite. Cisco’s Internet Home Platform Cisco Systems Inc. said it has developed an open Internet Home Platform for building high-speed, home networks that support New World services such as integrated data, voice and video. Cisco also announced alliance with GTE and Sun to offer consumers a complete package of products and services that transform any home into high-speed, “always on” Internet Home. In addition, Cisco announced an agreement with Whirlpool to help build Internet-ready home appliances and plans to work with home builders to construct future Internet homes. Cisco’s strategy is focused on delivering high-speed Internet access to the home market through cable, digital subscriber line (DSL) and wireless service providers, while enabling devices within the home to connect to each other and to the Internet. Cisco will incorporate its new open, standards-based Internet platform with the Cisco Internet Home Gateway product series, which will enable service providers to offer advanced home networking services to consumers. This new technology will help consumers use the power of the Internet in all aspects of their daily life — from high-speed Internet access to new Internet activities throughout the home such as downloading recipes on a built-in oven to securely monitor their home from work. HCL breaks Rs 40,000 price barrier HCL Infosystem Limited has announced the launch of Intel Pentium II microprocessor-based HCL BusyBee PC at Rs 39,990. Powered by the Intel Pentium II microprocessor, HCL BusyBee is equipped with 32 MB SDRAM, a 4.3 GB UDMA hard disk, integrated sound card, and a 4 MB AGP card. The unit comprises a 14-inch SVGA colour monitor, keyboard and mouse and comes pre-loaded with Windows 98. It is also supported by a one-year on-site warranty. According to the IMRB iTOPS 99, HCL leads the branded PC segment with 12.9 per cent market share, more than that of all three of its nearest competitors— Compaq with 5.6 per cent, IBM with 3.6 per cent and HP with 2.6 per cent — put together. Shopping channel India’s premier portal, rediff.com., has launched “marketplace”, its new virtual shopping channel. It offers the net shoppers a variety of merchandise, often at special prices. Award for Texas Instruments Texas Instruments’
newest customizable digital signal processor (DSP) core,
part of its C2700 series of DSP products, has won EDN
Asia’s competitive 1999 Component Design Award. |
Science
Quiz 1. What did James Watson, Francis Crick and Maurice Wilkins discover for which they were awarded the 1962 Nobel Prize for physiology or medicine? 2. The quality of music produced by a vocalist or from an instrument depends on the number and relative intensity of notes whose frequencies are integral multiples of that of the fundamental note. What are these multiple notes called? 3. Name the instrument which is used to measure the rate or rotation of a shaft and hence the speed of a vehicle. On what type of principle can it be made? 4. This liquid is biologically complete food but lacks mainly in iron and vitamin C. Can you name it? 5. Who invented the first practical and commercially successful mechanical typewriter having a complete keyboard layout? Who invented the electric typewriter? 6. What general name is given to inorganic non-metallic materials like pottery, bricks and porcelain which find wide use in computers, cutting tools, machinery parts etc because of their chemical inertness, hardness and immense strength? 7. This desert bird is the fastest-running flying bird. It runs more on the ground than it flies and can attain a speed of 24 km per hour. Name this bird that belongs to the cuckoo family. 8. This carbohydrate is found in some fruits, is useful in the formation of gels, and is essential for setting of jellies and jams. Can you name this polysachharide? 9. Some children suffer from a type of involuntary urinating condition called “enuresis”. What is this condition commonly known as? 10. CCMB, Hyderabad, is
a premier institute engaged in research in frontier areas
of modern biology, biochemistry and biotechnology. What
is the full name of this institute?
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