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| SCIENCE TRIBUNE | Thursday, January 24, 2002, Chandigarh, India |
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Viewing
the invisible and knowing the unknown NEW PRODUCTS &
DISCOVERIES
Magnetic field
reversed itself |
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Viewing
the invisible and knowing the unknown THE term “image” may be defined as the “manifestation of reality in a virtual way”. Every action of living beings is controlled to a great extent by their reaction to the image of the site of action or we may say that the interpretation of the sight seen acts as the stimuli behind every action. Of late, images have achieved a great practical importance in almost every field of modern life like space research, military surveillance, law enforcement, medical diagnosis, navigation, remote sensing, industrial process control and measurement, intelligent robot etc. Nowadays images do not mean to be taken in visible wavelengths only. A lot of other bands are being employed to get decisive images that are required to face the challenges in these various fields.
For electromagnetic waves, the distance travelled before getting attenuated off, directly varies with their wavelengths. Again, we know that wavelength is just the inverse of frequency. The energy of a wave again varies with the frequency. But the fact is that the wave with highest frequency or energy has the highest penetrability in solid media, on the contrary it gets attenuated much faster due to absorptive losses while travelling through space, than its least frequency counterpart. Let us take an instance. The dawn and dusk sky appears reddish because while the sun drops below the horizon, the colours viz. violet, indigo, blue, green etc fail to reach our eye while red reaches easily by virtue of its longest wavelength in the visible spectrum. Thus we may infer that the longer the wavelength the greater is the range of the wave (without much absorptive losses). Now it is well established that there are other wavelengths too beyond the visible range, i.e. before violet we have ultraviolet and beyond red we have infrared bands. Further, there are waves with much longer wavelengths as microwave,
millimetre wave etc. whereas, with much higher frequency as X-ray, gamma-ray etc., with various ranges of application. So, when visible light rays fail to penetrate the muscles of human body, X-rays do that comfortably to provide us the image of the skeleton, because they possess a much higher energy and thereby greater penetrability than their visible counterparts. Of these different waves, Gamma rays possess the highest frequency, while radio waves possess the longest wavelength. Consequently, ultraviolet and gamma rays fail to reach the earth surface to a considerable extent, thereby sparing our skins from getting exposed to unwanted radiations. Thus today we are able to reveal the truth underneath almost everything by the application of suitable wavelength. Actually, an object can be detected by a certain wavelength only when the size of the object is comparable to the probing wavelength. This is the reason behind the invisibility of electrons under visible lights. Of late a wide variety of images are taken under infrared, X-ray, millimetre wave or microwave as per the specific requirement. In astrophysics and space research we often encounter situations where its virtually impossible to take the image at most of the available wavelengths. Radio waves, by virtue of their longest wavelength, are the most suitable for this purpose. Again, night-vision is a must in modern warfare. Aiming targets during night or even under dense fog or smoke is a great challenge. This problem is solved by the successful application of Infrared cameras. The visual image is clearly showing a truck, some smoke and a mountain in the background whereas in the thermal infrared image both the targets (the truck and a helicopter) are clearly (but partly) visible. The infrared image also allows one to see through the smoke. But, simply we can’t choose a longer wavelength for any type of long-range operation because resolution varies inversely with wavelength. “Resolution” is defined as the ability to distinguish between two adjacent points. So, we have to make a compromise between these two factors, i.e. we have to choose the wavelength so that it can serve for longer travelling range with lesser absorptive losses but with an appreciable resolution as well. We can now acquire images of different targets under varying environmental conditions by employing the suitable wavelength and its sensor, chosen after assessing the different parameters viz. range of application, surrounding environment, depth of point of vision, alignment of target etc. But only acquisition of images is not sufficient for drawing any inference from them. An example will clear my intention here. The first space vehicle sent with the objective of imaging the solar system and its accessories had cost some billions of dollars. At the first attempt then, some 14 images were collected and dispatched to Earth. The huge price value of each single image acquired can easily be estimated. But unfortunately, those images can’t be interpreted at all due to very poor resolution, noise and other technical factors. This is where actually the need of image processing was felt first. Several image sensors are being employed these days for different operating conditions, viz. high resolution CCD cameras (Visible range), Forward Looking Infra-Red (FLIR) cameras, Millimetre Wave (MMW) radar, Low-Light Television cameras etc. Further, there are basically two type of imaging, active and passive. These basic techniques can be understood by stating that, in active systems the sensor generates a wave towards the target and thereby the reflected wave is received. In passive systems, the sensor itself does not initiate any wave, but only the emitted waves from the target are detected. There are well-defined advantages and limitations of these two techniques as well. Digital image processing is the technique of enhancing the quality of the obtained images through some suitable algorithms comprised of steps like noise reduction, edge enhancement, filtering etc. The processed image is now much simpler to interpret. The search for the ideal wavelength for a specific purpose and the appropriate image processing steps is still on to provide a better manifestation of reality in exactly a virtual way!! |
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NEW PRODUCTS & DISCOVERIES IT may not be ready for George Bush’s “first war of the 21st century.” But it may well be ready if there’s a second. In perhaps the most audacious upgrade of high-speed weaponry since the introduction of the Gatling Gun, Australian inventor Mike O’Dwyer has developed a machine gun that can fire bullets at a rate of 1 million rounds per minute. Firepower like this is causing the U.S. and Australian militaries to sit up and take notice. Both are funding deeper research into O’Dwyer’s ideas, which he cooked up in his garage during more than a decade as an Australian retail store executive. Osama bin Laden, however, needn’t worry. The research is long-term and isn’t expected to yield any new lethal weapons anytime soon. Even so, the implications of the new technology’s ability to change warfare are immense. And somewhat amazingly, the theory is pretty simple. Rather than use mechanical firing pins to shoot bullets one by one, O’Dwyer’s gun holds multiple bullets in the barrel — one behind the other. Electronic charges set off in different parts of the barrel, just fractions of a second apart, fire the bullets in blindingly fast succession using traditional gunpowder. The result is akin to a laser beam of lead and it offers several advantages over a regular machine gun.
Making Adhesives Safer Researchers have developed test procedures to investigate the quantity of hazardous isocyanate released by the various polyurethane glues, used widely in the chemical industry, that would help manufacturers to take account of these harmful emissions and take measures to reduce them at the earliest possible stage of product development. Although the isocyanate group is known to be extremely reactive, it is precisely this property that makes it so useful to the chemical industry. Much less toxic and volatile relatives of methyl isocyanate are widely used in the production of rapid-setting polyurethane foams and dual-component adhesives. But people who work with these substances, like garage mechanics, expose themselves to a distinct health risk, especially if they work in confined spaces. Scientists at the Fraunhofer Institute for Manufacturing Engineering and Applied Materials Research IFAM have constructed a special laboratory emission chamber, which allows them to measure the rates of emission at various temperatures, a report in Fraunhofer Gesellschaft said. “There is a wide spectrum of isocyanates used in PUR adhesives. The quantity of volatile substances given off into the surrounding atmosphere varies according to the boiling point or vapour pressure of the particular chemical, and according to the temperature at which it is processed and the method used to apply it,” Ronald Luschen of the IFAM Bonding Technology Centre said.
PTI |
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Magnetic field reversed itself RESEARCHERS
have developed an improved method of identifying magnetic signals in old geological strata and have used the new method to show that the Earth’s magnetic field really did reverse itself 10 million years ago. Particles of iron in sediments orient themselves in accordance with the local magnetic field of the earth. As the sediment consolidates and lithifies over the course of several decades, the particles of iron continue to lie in the direction of the original magnetic field. They thus preserve data on the state of the magnetic field when the sediment was being deposited. These data are used world-wide to date geological strata. The researchers developed a method which provides information on the carriers of the magnetic signal in sediments. Carriers include the iron oxides magnetic and hematite, a report in NWO Research Reports said. Studies of the earth’s past magnetic field are important for understanding of the “geodynamo”. Researchers use the term “geodynamo” to refer to the idea that the geomagnetic field is generated in the centre of the earth. The hypothesis is that the electricity that runs through the molten iron of the earth’s outer core causes the magnetic field. Using this method, the researchers were able to demonstrate that a short-lived change in the earth’s magnetic field really did take place about 10 million years ago. Hitherto, researchers had been unable to exclude the possibility that subsequent chemical or physical processes had altered the magnetic signal in the sediment. The earth’s magnetic field now points south, meaning that a compass needle points north. Some 800,000 years ago, a compass needle would have pointed south, having previously pointed north. Changes in the direction of the earth’s magnetic field are referred to as reversals. The Utrecht University researchers made another remarkable discovery using the new method. In an organically rich layer in the eastern Mediterranean, they found that bacteria had formed magnetic material. With the new method, they were able to distinguish between the bacterial material and the original magnetic signal.
PTI |
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Science & Technology crossword
Clues Across: 1. Equipment used for excavation in muddy areas. 5. An important hoisting equipment. 7. A premier concrete institute (abbr.) 8. A hydraulic water lifting machine. 9. Smoothened surface of a dockwall to avoid damage to vessels rubbing with it. 10. Must do this to give strength to concrete, plaster etc. 14. A term used for overhead tanks. 15. A code given to news-items received from Reuters/AFP/UPI. 17. A most effective heat treatment process to kill micro-organisms. 21. Abbr. For metric tone. 22. A type of barrier across a river. 23. Line at each end of a tennis court. Down: 2. An important parameter of coarse aggregate. 3. Provided in steel bridges. 4. Ingredients for water-proofing or for preventing leakage. 6. A big plant producing concrete. 11. Formed by logs fastened together to act as a substitute to boat. 12. Related to earth. 13. A mason’s tool. 16. A traffic-engineer cares for this. 18. One of India’s largest research, public relation and advertising agency. (abbr.) 19. A kind of wood. 20. A technique to develop work stations. Solution to last week’s crossword: |
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