Cyclic inelastic behavior and analytical modelling of pile–leg interaction in jacket type offshore platforms

Structures in locations susceptible to severe seismic disturbances should be designed properly in order to resist lateral forces induced by earthquake motions. Steel offshore platforms are some of those structures which are built to withstand environmental and accidental loads during oil exploitation operation. Particular attention is being paid to earthquake loads in seismic active areas because it directly influences the capacity of the offshore installations.

In this paper, a small-scaled planar platform has been modelled analytically using nonlinear finite element program, based on an experimental test, conducted simultaneously in order to assess the local and global behavior of pile–leg interaction in Jacket Type Offshore Platforms (JTOPs). A combination of nonlinear beam column elements and fatigue affected elements are used to capture the inelastic cyclic behavior of planar frame as accurately as possible. Results of analytical tests are to be compared with experiments and it is concluded that an analytical approach can be best used for modelling JTOPs with reasonable accuracy regardless of the type and scale of the structure. Moreover, a special study on joints has been carried out and the best model has been selected to simulate brittle behavior of joints resulting from heat affected zone.     

On the formation of element carbon during decomposition of CaCO3 at High P-T parameters under reducing conditions

This work presents data on the experimental study of CaCO₃ stability (3.0–5.5 GPa; 1300–1400°C) under reducing conditions modeling the presence of metallic iron. It is established that CaCO₃ is stable at the above P-T parameters under reducing conditions (in the presence of metallic Ti). CaCO₃ decomposed only when it chemically interacted with iron, forming Ca-ferrites and releasing solid carbon in the form of graphite in the closed system (in sealed Pt-ampoules).     

Leachability of trace elements from two stabilized low lime Indian fly ashes

Fly ash is a waste by-product obtained from the burning of coal by thermal power plants for generating electricity. When bulk quantities are involved, in order to arrest the fugitive dust, it is stored wet rather than dry. Fly ash contains trace concentrations of heavy metals and other substances in sufficient quantities to be able to leach out over a period of time. In this study an attempt was made to study the leachabilities of a few selected trace metals: Cd, Cu, Cr, Mn, Pb and Zn from two different types of class F fly ashes. Emphasis is also laid on developing an alternative in order to arrest the relative leachabilities of heavy metals after amending them with suitable additives. A standard laboratory leaching test for combustion residues has been employed to study the leachabilities of these trace elements as a function of liquid to solid ratio and pH. The leachability tests were conducted on powdered fly ash samples before and after amending them suitably with the matrices lime and gypsum; they were compacted to their respective proctor densities and cured for periods of 28 and 180 days. A marked reduction in the relative leachabilities of the trace elements was observed to be present at the end of 28 days. These relative leachability values further reduced marginally when tests were performed at the end of 180 days.     

Phytodiversity and medicinal plant distribution in pasturelands of North Western Himalaya in relation to environmental gradients

This study aimed at elucidating phytodiversity of pasturelands of North-western Kashmir Himalayan biotic province in relation to various environmental gradients, with added focus on assessing distribution of important threatened medicinal plant taxa across surveyed pasturelands. A total of 16 sites that spanned across a broad altitudinal gradient(2502-4120 m) were selected. Phytosociological data like density, cover, frequency and abundance of vascular flora were collected and processed using gradient analysis. Soil moisture, nitrogen, organic carbon, acidity and electrical conductivity, altitude, degree of slope and human disturbance were recorded from each site. Analysis of species composition showed a total of 293 species of vascular plants, belonging to 192 genera and 64 families recorded from surveyed sites. Rank abundance exhibited that majority of species are locally rare and patchily distributed, with over 60% of species recording frequencies between 0%-20% and none showing frequencies more than 80%. Species richness showed significant variations and ranged from 20(Parihasmaidan) to 114(Nagbarren) for macro and 3.53±2.11(Thajwas) to 8.76± 1.01(Marsar) for micro-scale of measurement. The ShannonWiener(H') and Simpson's diversity(Ds) indices also varied greatly and were recorded highest(H'= 2.76 Ds= 0.36) for Marsar and lowest(0.87 0.62) for Parihasmaidan. The diversity attributes suggested that pasturelands with lower species richness and diversity on macro-scale were not always species poor and less diverse on micro-measurement scale. The life form groupings highlighted the hemicryptophytic character of vegetation and species with highest importance value index were Sibbaldia cuneata(5.71), Rumex nepalensis(2.89), Juniperus wallichiana(2.88), Cynodon dactylon(2.83), Poa annua(2.49) and Sambucus wightiana(2.41). The results of canonical correspondence analysis showed that effect of altitude and anthropogenic disturbance was overriding and among various environmental factors, species distribution was mainly correlated with altitude along first canonical axis, while to second axis anthropogenic disturbances were important. Using generalized additive model, these variables also appeared as significant predictors for distribution of various threatened taxa. The findings of this study may thus help in evolving an appropriate strategy and an ecological management tool for long term conservation and management of these mountain ecosystems.     

Studies of Plasma Dynamics in a Small Plasma Focus Operating in Hydrogen-Argon Mixtures

We report on experimental observations in PFP-I, a small 3.8 kJ plasma focus, which is operated in Hydrogen-Argon mixtures to investigate the effect of parameter modifications on the overall performance of the device. An extensive array of diagnostics is been used, which includes voltage and current probes in the external circuit, a novel small magnetic probes array located along the cathode rods, filtered PIN diodes located side and end on, and filtered multi-pinhole and slit-wire X-ray camera. Extended operating range from below 0.2 Torr upwards has been achieved. Hot spot formation has been investigated as a function of H₂-Ar mixing ratio. Hot spot sizes around 150 m in the soft X-ray region, have been inferred from the slit-wire measurements. Pin-hole time integrated X-ray pictures and time resolved PIN diode measurements have been used to determine characteristic hot-spot temperatures in the 350 to 450 eV range.     

Spectrophotometric investigation of five galaxies with A UV excess

The results of a spectroscopic investigation of galaxies Nos. 22, 35, 133, 317, and 321 from the lists of [M. A. Kazarian, Astrofizika,15, 5 (1979); M. A. Kazarian and é. S. Kazarian, Astrofizika,16, 17 (1980)] are given. The equivalent widths of lines, the relative intensities of emission lines, and their half-widths are determined. Translated from Astrofizika, Vol. 40, No. 4, pp. 619–626, October-December, 1997.     

Isotropic and anisotropic pointing models

This paper describes an alternative approach for generating pointing models for telescopes equipped with serial kinematics, esp. equatorial or alt-az mounts. Our model construction does not exploit any assumption for the underlying physical constraints of the mount, however, one can assign various effects to the respective components of the equations. In order to recover the pointing model parameters, classical linear least squares fitting procedures can be applied. This parameterization also lacks any kind of parametric singularity. We demonstrate the efficiency of this type of model on real measurements with meter-class telescopes where the results provide a root mean square accuracy of 1.5?2 arcseconds.