Application of the LQG/LTR technique to robust controller synthesis for a large flexible space antenna

The problem of synthesizing a robust controller is considered for a large, flexible space-based antenna by using the linear-quadratic-Gaussian (LQG)/loop transfer recovery (LTR) method. The study is based on a finite-element model of the 122-m hoop/column antenna, which consists of three rigid-body rotational modes and the first 10 elastic modes. A robust compensator design for achieving the required performance bandwidth in the presence of modeling uncertainties is obtained using the LQG/LTR method for loop-shaping in the frequency domain. Different sensor actuator locations are analyzed in terms of the pole/zero locations of the multivariable systems and possible best locations are indicated. The computations are performed by using the LQG design package ORACLS augmented with frequency domain singular value analysis software

Computation of Flow through an Annular Diffuser and Volute Exhaust

Turbulent flow in a diffuser with swirl occurs in many commonly used fluid mechanicaldevices,eg, diffusers located downstream of a gas turbine, and in certain types of combustionchambers. Diffusers are widely used for converting kinetic energy to pressure, and a reliableprediction method of such flows with the required flow conditions would lead to the design offluid machinery with improved efficiency. As a first step, turbulent swirling flow through a 12oincluded angle conical diffuser for a swirl parameter, m = 0.18 was numerically investigated usingvarious turbulence models like standard k- , RNG-based k- , shear-stress transport (SST) kandReynolds stress model (RSM). Though the comparison between the experimental and thepredicted mean velocity profile by RSM is superior to that by RNG kandSST models, the lattertwo models give closer comparison with the experimental pressure distribution. Subsequently,computation of flow inside a complex duct involving axisymmetric annular diffuser, transitionfrom rectangular to circular cross section, and exit pipe have been carried out using RNG kandSST k models.The comparison of computed and experimental results indicates that theSST k modelgives predictions with reasonable accuracy

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

Studies on species of Halimeda from Lakshadweep

Four Species of Halimeda viz. H. incrassata, H. opuntia. H simulans and H taenicola collected from Lakshadweep islands are described in detail

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 D'Yakonov fully explicit variant of the iterative decomposition method

AbstractIn this paper, a new iterative alternating decomposition (IADE) scheme of (4,2) order of accuracy is developed to solve the one-dimensional parabolic problem. It is based on the two-stage fractional splitting strategy suggested by D'Yakonov and found to be generally more accurate than the recently developed (2,2) accurate alternating group explicit (AGE) method of Peaceman-Rachford variant. As the method is fully explicit, its feature can be fully utilized for parallelization by means of a domain decomposition strategy

Implantless press fit graft fixation technique at Patella for MPFL reconstruction

Patellofemoral instability is one of the most prevalent knee disorders in adolescents. It is often multifactorial and complex. Often accompanied by insufficiency or tear of MPFL ligament. MPFL is primary soft tissue stabiliser of patella and acts as checkrein of lateral patella dislocation. There have been variations in surgical techniques including different choices of surgical techniques, graft material and fixation methods, despite these there is no conclusive evidence that a particular surgical option is superior to another. Recurrent Patella instability requires individualised surgical planning . In this article we present a surgical technique which is implantless socket type of press-fit fixation at patella

Experience paper on the operation of pilot project on oyster culture at Tuticorin

The technology of oyster culture was developed in India at the Central Marine Fisheries Research Institute. An experimental farm was established at Tuticorin bay in an area of 0.25 hectares. Different growout methods have been tried and it has been assessed that the shell string method could be practised with relatively low cost inputs with a production rate comparable to highly efficient systems such as rack and tray method or raft culture