Transient loads analysis for space flight applications

A significant part of the flight readiness verification process involves transient analysis of the coupled Shuttle-payload system to determine the low frequency transient loads. This paper describes a methodology for transient loads analysis and its implementation for the Spacelab Life Sciences Mission. The analysis is carried out using two major software tools - NASTRAN and an external FORTRAN code called EZTRAN. This approach is adopted to overcome some of the limitations of NASTRAN's standard transient analysis capabilities. The method uses Data Recovery Matrices (DRM) to improve computational efficiency. The mode acceleration method is fully implemented in the DRM formulation to recover accurate displacements, stresses, and forces. The advantages of the method are demonstrated through a numerical example

Random vibration analysis of space flight hardware using NASTRAN

During liftoff and ascent flight phases, the Space Transportation System (STS) and payloads are exposed to the random acoustic environment produced by engine exhaust plumes and aerodynamic disturbances. The analysis of payloads for randomly fluctuating loads is usually carried out using the Miles' relationship. This approximation technique computes an equivalent load factor as a function of the natural frequency of the structure, the power spectral density of the excitation, and the magnification factor at resonance. Due to the assumptions inherent in Miles' equation, random load factors are often over-estimated by this approach. In such cases, the estimates can be refined using alternate techniques such as time domain simulations or frequency domain spectral analysis. Described here is the use of NASTRAN to compute more realistic random load factors through spectral analysis. The procedure is illustrated using Spacelab Life Sciences (SLS-1) payloads and certain unique features of this problem are described. The solutions are compared with Miles' results in order to establish trends at over or under prediction

Growth, mortality and stock assessment of two perches moontail bull's eye Priacanthus hamrur (PerciformeslPricanthidae) and thomycheek grouper Epinephelus diacanthus (Perciformes/Serranidae) from Bombay waters

Based on the data collected from 1989-n the growth, mortality and stock assessment of P. hamrur and E. diacanthus were calculated. The von Bertalanffy's growth functions worked out for P. hamrur were as follows Lro=360 mm, K=O.64 per year and that of E. diacanthus were Lro=494 mm and K=O.59 per year. Based on these calculations the growth of P. hamrur at the end of I-IV years works out to be as 171,260, 308 and 334 mm. The length attained by E. diacanthus at the end of I-IV years of its life works out to 223, 345, 414 and 451 mm respectively. The mortality coefficients - Z, M and F were worked out 2.24,1.13 and 1.11 for P. hamrur. The same for E. diacanthus was calculated as 1.74, 1.1 and 0.64 respectively. Stock assessment study shows that there is no decline in the catch at the present rate of explOitation. However, even if the efforts are trebled, the increase in the catch will not be proportionate and returns are not remunerative

Estimates of growth, mortality, recruitment pattern and MSY of important resources from the Maharashtra coast

Based on the data collected from the year 1987 - 1991 the growth, mortality and recruitment pattern of eighteen species of fish, two species of cephalopods and four species of penaeid prawns have been presented in the present communication_ The total mortality coefficient, (Z) varied from lowest of 1.20 for O.cuvieri to a highest of 10.78 for P.stylifera. The natural mortality coefficient, (M) varied from 0.52 for T. thalassinus to 3.44 for S.crassicornis. The average annual yield of eighteen species of fish, four species of prawns and two species of cephalopods are 65,083, 38,404 and 11,373 tons as against the MSYof 83,023, 72,460 and 10,475 tons respectively. The MSY estimated for the total fish stock is 1,77,753t where as the present yield is 1,14,859t. This indicates that higher yield can be obtained by increasing the effort

Fast Subpixel Full Search Motion Estimation

Motion estimation is one of the most important part in video coding, where only the difference between the current and reference frames will be coded by the encoder.There are many advancements happening in motion estimation techniques. The proposed algorithm provides high precision matching and even reduces the errors during compensation. The algorithm also reduces the computation time when compared to traditional Block matching techniques. It mainly aims at the motion estimation with subpixelaccuracy without interpolation, it is the combination of Block matching and the optical flow method.Fast computation may be evaluated by experimental results while even motion vectors are more accurate reducing the PSNR

Stability, Gain, and Robustness in Quantum Feedback Networks

This paper concerns the problem of stability for quantum feedback networks. We demonstrate in the context of quantum optics how stability of quantum feedback networks can be guaranteed using only simple gain inequalities for network components and algebraic relationships determined by the network. Quantum feedback networks are shown to be stable if the loop gain is less than one-this is an extension of the famous small gain theorem of classical control theory. We illustrate the simplicity and power of the small gain approach with applications to important problems of robust stability and robust stabilization.Comment: 16 page

Maximally robust controllers for multivariable systems

Published versio

Synchronization of Coupled Nonidentical Genetic Oscillators

The study on the collective dynamics of synchronization among genetic oscillators is essential for the understanding of the rhythmic phenomena of living organisms at both molecular and cellular levels. Genetic oscillators are biochemical networks, which can generally be modelled as nonlinear dynamic systems. We show in this paper that many genetic oscillators can be transformed into Lur'e form by exploiting the special structure of biological systems. By using control theory approach, we provide a theoretical method for analyzing the synchronization of coupled nonidentical genetic oscillators. Sufficient conditions for the synchronization as well as the estimation of the bound of the synchronization error are also obtained. To demonstrate the effectiveness of our theoretical results, a population of genetic oscillators based on the Goodwin model are adopted as numerical examples.Comment: 16 pages, 3 figure

Distribution of finfish resources along southeast coast of India in relation to certain environmental parameters

This paper embodies the distribution pattern of major finfish resources along the southeast coast of India as observed during the cruises operated by FORV Sagar Sampada. A total of 16 cruises (1985-90) operated along latitude 7° 15'- 15°00' N and longitude 75°50'- 82°3r E hauled a total catch 37.5 tonnes with a catch rate of 537 kg/hr. The catch was constituted mainly by threadfin breams (43%), perches (14%), barracudas (9.72%), carangids (8.56%) and elasmobranchs (4.81%). Seasonally higher catch rates were obtained during July- September period. Depth range of 60 - 80 m had denser population of finfish resources. Water temperature and salinity appeared to influence the distribution of major finfishes more than dissolved oxygen. Groups such as threadfin breams were found preferring cooler waters of Wadge Bank area, while barracudas appear to occupy warmer waters of Gulf of Mannar