Adaptive control of large space structures using recursive lattice filters

The use of recursive lattice filters for identification and adaptive control of large space structures is studied. Lattice filters were used to identify the structural dynamics model of the flexible structures. This identification model is then used for adaptive control. Before the identified model and control laws are integrated, the identified model is passed through a series of validation procedures and only when the model passes these validation procedures is control engaged. This type of validation scheme prevents instability when the overall loop is closed. Another important area of research, namely that of robust controller synthesis, was investigated using frequency domain multivariable controller synthesis methods. The method uses the Linear Quadratic Guassian/Loop Transfer Recovery (LQG/LTR) approach to ensure stability against unmodeled higher frequency modes and achieves the desired performance

Effect of Clamping Rigidity of the Armour on Ballistic Performance

Influence of the manner in which the armour plates are held during their ballistic testing on the armour performance, has been evaluated. One armour plate was clamped rigidly to the test stand while a second plate of identical composition, hardness, and dimensions was hung loosely from the target holder. Both these plates were impacted with the same type of projectiles and over the same impact velocity range. The nature of ballistic damage evaluated indicates that the manner in which the armour is held during ballistic testing has a negligible influence on its performance at least when the mass of the plate is substantially higher than that of the projectile

The dynamic indentation behavior of steel at large depths of penetration

The objective of the present study is to investigate the dynamic indentation behavior of steel plate material when impacted by ogive-shaped projectiles and in particular under indentation conditions involving large depths of penetration (i.e., depth of penetration greater than projectile radius). Toward the above purpose, dynamic indentation of steel plates of thickness 20, 40, and 80 mm have been carried out using projectiles of diameter 6.2 and 20 mm, and over a range of impact velocities so as to attain depths of penetration in the range 1.4 to 3.6 times the projectile radius. The results indicate that the dynamic hardness, the plastic zone size, specific energy consumed in plastic deformation within the plastic zone, and the average plastic strain within the plastic zone increases continuously with increasing values of depth of penetration normalized by projectile radius. Certain subtle differences regarding the nature of plastic deformation between indentation at large and shallow depths of penetration are presented. However, on a macroscopic scale, the indentation mechanisms and processes are broadly similar and show continuity in terms of behavior across the whole penetration depth range

Commercial prospects for nanomaterials in India

The area of nanoscience and technology is growing rapidly around the world and nanomaterials based products, especially in the consumer sector, are coming into market very rapidly. India is competing, with great difficulty, with other developed countries to make its position strong in this field. In other respect, several challenges have to be overcome in terms of production of nanomaterials at commercial scale, their processing, applications and commercialization. The present article describes the present state of nanomaterials based technology development, commercialization and future prospects for this technology in our country

Tribo-Corrosion 2006 - a passage to India to celebrate the 1st International Conference on Tribo-Corrosion

The 1st International Conference on Tribo-Corrosion was held in Hyderabad in India between 4 and 6 December 2006. The conference was hosted by the NFTDC (Non Ferrous Materials Technology Development Centre) in Hyderabad who organized a truly special programme events. A kaleidoscope of colour from the gardens surrounding the Institute, lit up specially for the event, greeted the visitors on their arrival for the opening ceremony and this was followed by an evening of dancing and song celebrating the cultures of Andhra Pradesh, of which Hyderabad is the capital. Such a full programme of events, including a visit to the famous Golkonda fort, together with the academic discussions, marked a memorable start to what is intended to become a regular event every 3 years on the Tribology and Corrosion Meetings series calendar

Accurate time-domain gravitational waveforms for extreme-mass-ratio binaries

The accuracy of time-domain solutions of the inhomogeneous Teukolsky equation is improved significantly. Comparing energy fluxes in gravitational waves with highly accurate frequency-domain results for circular equatorial orbits in Schwarzschild and Kerr, we find agreement to within 1% or better, which we believe can be even further improved. We apply our method to orbits for which frequency-domain calculations have a relative disadvantage, specifically high-eccentricity (elliptical and parabolic) "zoom-whirl" orbits, and find the energy fluxes, waveforms, and characteristic strain in gravitational waves.Comment: 6 pages, 9 figures, 2 tables; Changes: some errors corrected. Comparison with Frequency-domain now done in stronger fiel

The Dimensions of Reputation in Electronic Markets

We present a framework for identifying the different dimensions of online reputation and characterizing their influence on the pricing power of sellers. Our theory predicts that sellers with better recorded online reputation can successfully charge higher prices than competing sellers of identical products, and that their pricing power increases with their recorded level of experience. We develop and implement a new text mining technique that identities and quantitatively assesses dimensions of importance in reputation profiles, and use this technique to create a new data set containing detailed reputation profiles and prices for sellers in over 9,500 transactions for consumer software on Amazon.com's online secondary marketplace. The estimation of a set of econometric models on this data set validates the predictions of our theory, and further, ranks these dimensions of reputation based on their effect on measured seller value, identifying those that have the most significant impact on reputation. This paper is the first study that integrates econometric and text mining techniques toward a more complete analysis of the information captured by reputation systems, and it presents new evidence of the importance of their effective and judicious design.Information Systems Working Papers Serie

Shrimp farming by private enterprise- A case study

In view of the encouraging results shown by the research organisations of India and other countries in prawn culture on scientific methods, a commercial research and development project on prawn culture was established by the TATA Oil Mills Co. Ltd., at Pulicat. Experiments were conducted in aarthern ponds of size ranging from 0.4 to 1.25 ha- Stocking rates ranging from 6.5 to 15 prawns/mz were attempted and production to the tune of 0.5 to 1.0 tonne/ha/crop was achieved. Survival rate over 80% could be maintained in all the crops. An artificial feed formulated with shrimp meal, trash fish and vitamin mineral mix along with other usual ingredients, with a protein content of 40%, proved to be better than the other conventional feed. Effect of design of a pond, aging of pond, stocking density, stocking size and various hydrobioiogical parameters viz. salinity, dissolved oxygen and pH were also studied. The intensive stocking rate, the successful feed formula and the effective water managements adopted were the important reasons for the successful production of shrimps in this farm. The cost of production of 1 kg of shrimps considering the variable cost, varied from Ks 20.00 to 34.00 and thus a net revenue of Rg. 8000.00 to 20,000.00/ha/crop was achieved

Corrosion of Aircraft Aluminium Alloys in Acid Solutions & its Prevention by Inhibitors

THE corrosion of metals is a serious problem confronting the industrially advanced countries of the world. Modern developments and war-time experiences have made it possible to manufacture metals at lower costs than before. Secondly, new sources of minerals have been discovered, thereby enabling each nation to increase its capacity for the production of metals. Iron and steel, aluminium, copper and zinc are amongst the metals in common use. In practice all of them are liable to corrode in various environments : atmosphere, soil and liquid medium. The loss of metal due to corrosion necessitating repair or removal of metal parts is one of fundamental importance affecting the economy of a country. The cost of corrosion control is rather high, the estimated figures per annum for some of the countries being U.S.A.' close to 10 billion dollars, U.K.2 600 million pounds, Canada3 500 million dollars, Australia4 100 million pounds. and India5 154 crore rupees. It becomes incre-asingly important to preserve available metals in use since a time may come when some of them approach exhaus-tion. From the available figures it has been indicated that immediate attention should be given to the non- ferrous metals, and greater attention to ferrous res-ources. In the case of iron the losses due to corrosion are estimated to be about 7.6 per cent a year. Corrosion control methods, therefore, assume great importance6

The influence of heat treatment on the microstructural, mechanical and corrosion behaviour of cold sprayed SS 316L coatings

The present study evaluates the response of cold sprayed SS 316L coatings on mild steel substrate to aqueous corrosion in a 0.1 N HNO3 solution as determined using polarization tests. The corrosion behaviour of the SS 316L coating was studied not only in the as-coated condition, but also after heat treatment at 400, 800 and 1,100 °C. Heat treatment reduced the porosity, improved inter-splat bonding, increased the elastic modulus and more importantly increased the corrosion resistance of the cold sprayed SS 316L coating