Influence of the coorbital resonance on the rotation of the Trojan satellites of Saturn

The Cassini spacecraft collects high resolution images of the saturnian satellites and reveals the surface of these new worlds. The shape and rotation of the satellites can be determined from the Cassini Imaging Science Subsystem data, employing limb coordinates and stereogrammetric control points. This is the case for Epimetheus (Tiscareno et al. 2009) that opens elaboration of new rotational models (Tiscareno et al. 2009; Noyelles 2010; Robutel et al. 2011). Especially, Epimetheus is characterized by its horseshoe shape orbit and the presence of the swap is essential to introduce explicitly into rotational models. During its journey in the saturnian system, Cassini spacecraft accumulates the observational data of the other satellites and it will be possible to determine the rotational parameters of several of them. To prepare these future observations, we built rotational models of the coorbital (also called Trojan) satellites Telesto, Calypso, Helene, and Polydeuces, in addition to Janus and Epimetheus. Indeed, Telesto and Calypso orbit around the L_4 and L_5 Lagrange points of Saturn-Tethys while Helene and Polydeuces are coorbital of Dione. The goal of this study is to understand how the departure from the Keplerian motion induced by the perturbations of the coorbital body, influences the rotation of these satellites. To this aim, we introduce explicitly the perturbation in the rotational equations by using the formalism developed by Erdi (1977) to represent the coorbital motions, and so we describe the rotational motion of the coorbitals, Janus and Epimetheus included, in compact form

Effect of Grain Refinement on Microstructure and Wear Behavior of Cast Al-7Si Alloys

The present work deals with the study of wear of Al-7Si alloys without and with the addition of grain refinerssuch as, Al-5Ti-1.25C, Al-5Ti-0.8C and Al-5Ti-1B individually. Grain refiner additions have shown grainrefinement in the cast Al-7Si alloys. Microstructures showed morphological changes in a- Al phases fromdendrite to equiexed. These changes in structure showed improvement in wear resistance of Al-7Si alloys.Forthis, pin-on-disc test has been performed on Al-7Si alloy samples with varying addition level of grain refiners.The worn-out surfaces of the samples were characterized by SEM studies in order to understand the wearmechanism of Al-7Si alloys against steel disc. Worn-out surfaces of Al-7Si alloys pins exhibited different surfacemorphologies. Although it has been found that wear mechanism was same for both without and with grainrefined Al-7Si alloys. However untreated samples exhibits higher wear loss than that of grain refined samples. Itwas noticed that with addition of grain refiner, the samples gave smaller debris particles.This showed less wear loss during such conditions

A PERFORMANCE MODELING AND DECISION SUPPORT SYSTEM FOR A FEED WATER UNIT OF A THERMAL POWER PLANT

<p>ENGLISH ABSTRACT: The present paper discusses the performance modeling and decision support system for a feed water unit of a thermal power plant using the concept of performance analysis and modeling. A feed water unit ensures a proper supply of water for the sound functioning of a thermal power plant. The decision support system for a feed water unit has been developed with the help of performance modeling using a probabilistic approach. After drawing a transition diagram, differential equations are generated. After that, steady state probabilities are determined. Some decision matrices are also developed, which provide various performance levels for different combinations of failure and repair rates of all subsystems. Based upon various availability values obtained in decision matrices and plots of failure rates / repair rates of various subsystems, the performance of each subsystem is analyzed, and maintenance decisions are made for all subsystems.</p><p>AFRIKAANSE OPSOMMING: Vertoningsanalise en –modellering word gedoen vir die toevoerwatersisteem van ‘n termiese kragstasie. Toevoerwater is ‘n belangrike factor vir die doeltreffende bedryf van ‘n kragstasie. Die vertoningsanalise en –model is probalisties van aard. ‘n Toestandoorgangsdiagram en bypassende differensiaalvergelykings word gebruik, gevolg deur bepaling van die bestandige sisteemtoestand. Bykomende aandag word gegee aan relevante subsisteme. Die vertoning van subsisteme word gebasseer op verskeie beskikbaarheidswaardes om sodoende instandhouding to optimiseer.</p&gt

Large Thermoelectric Power Factor in TiS2 Crystal with Nearly Stoichiometric Composition

A TiS$_{2}$ crystal with a layered structure was found to have a large thermoelectric power factor.The in-plane power factor $S^{2}/ \rho$ at 300 K is 37.1~$\mu$W/K$^{2}$cm with resistivity ($\rho$) of 1.7 m$\Omega$cm and thermopower ($S$) of -251~$\mu$V/K, and this value is comparable to that of the best thermoelectric material, Bi$_{2}$Te$_{3}$ alloy. The electrical resistivity shows both metallic and highly anisotropic behaviors, suggesting that the electronic structure of this TiS$_{2}$ crystal has a quasi-two-dimensional nature. The large thermoelectric response can be ascribed to the large density of state just above the Fermi energy and inter-valley scattering. In spite of the large power factor, the figure of merit, $ZT$ of TiS$_{2}$ is 0.16 at 300 K, because of relatively large thermal conductivity, 68~mW/Kcm. However, most of this value comes from reducible lattice contribution. Thus, $ZT$ can be improved by reducing lattice thermal conductivity, e.g., by introducing a rattling unit into the inter-layer sites.Comment: 11 pages, 4 figures, to be published in Physical Review

Zinc and Iron Nutrition to Increase the Productivity of Pearl Millet-Mustard Cropping System in Salt Affected Soils

The abiotic stresses, such as soil salinity and sodicity are largely responsible for the low productivity of crops mainly due to low availability of micro-nutrients especially as zinc (Zn) and iron (Fe). Therefore, judicious management of plant nutrients in these soils is as important as their reclamation. A field experiment was conducted for 4 consecutive years, consisting of 12 treatments laid out in randomized block design to evaluate the effect of rate and methods of zinc and iron as single or combined soil as well as foliar application in pearl millet-mustard cropping system grown on salt affected soils. Soil application of Zn and Fe were applied at the time of sowing with FYM or without FYM (addition of FYM done only in pearl millet) and foliar application of respective nutrients were also applied at 30 and 45 days after sowing of crops. The results of experiment showed that, application of FYM 10 t ha-1 along with 5 kg Zn+10 kg Fe significantly (p=0.05) improved the yield parameters of pearl millet and mustard followed by 5 kg ha-1 Zn and 10 kg ha-1 Fe as soil application. The results also indicated that combined soil application of 5 kg Zn+10 kg Fe +10 t FYM increased the pearl millet grain yield (36.6 q ha-1) and mustard seed yield (22.7 q ha-1) by 57.1% and 42.8% higher over control, however, yield improvement was 35.6 and 20.7 % due to application of 5 kg Zn+10 kg Fe without FYM, respectively, in pearl millet and mustard over control. Ferrous-iron content in both crops proved to be a better index of Fe nutrition status compared to total plant Fe and DTPA- extractable soil Fe under salt affected soils. Salt affected soils are having vast potential to produce a significant amount of food grain by applying optimum dose of Zn, Fe and FYM in pearl millet and mustard. Combined foliar application of Zn and Fe also increased the yields of pearl millet and mustard grown in saline soils. Ferrous iron (Fe2+) is better indicator for iron nutrition in crops

Seed degeneration in potato : the need for an integrated seed health strategy to mitigate the problem in developing countries

Seed potato degeneration, the reduction in yield or quality caused by an accumulation of pathogens and pests in planting material due to successive cycles of vegetative propagation, has been a long-standing production challenge for potato growers around the world. In developed countries this problem has been overcome by general access to and frequent use of seed, produced by specialized growers, that has been certified to have pathogen and pest incidence below established thresholds, often referred to as certified seed. The success of certified seed in developed countries has concentrated the research and development agenda on the establishment of similar systems in developing countries. Despite these efforts, certified seed has had little penetration into the informal seed systems currently in place in most developing countries. Small-scale farmers in these countries continue to plant seed tubers acquired through the informal seed system, i.e. produced on-farm or acquired from neighbours or local markets. Informal seed tubers frequently have poor health status, leading to significant reductions in yield and/or market value. This review emphasizes the need to refocus management efforts in developing countries on improving the health status of seed tubers in the informal system by integrating disease resistance and on-farm management tools with strategic seed replacement. This 'integrated seed health strategy' can also prolong the good health status of plants derived from certified seed, which would otherwise be diminished due to potential rapid infection from neighbouring fields. Knowledge gaps, development challenges and impacts of this integrated seed health strategy are discussed.PostprintPeer reviewe

Gravitational Charged Perfect Fluid Collapse in Friedmann Universe Models

This paper is devoted to study the gravitational charged perfect fluid collapse in the Friedmann universe models with cosmological constant. For this purpose, we assume that the electromagnetic field is so weak that it does not introduce any distortion into the geometry of the spacetime. The results obtained from the junction conditions between the Friedmann and the Reissner-Nordstr$\ddot{o}$m de-Sitter spacetimes are used to solve the field equations. Further, the singularity structure and mass effects of the collapsing system on time difference between the formation of apparent horizons and singularity have been studied. This analysis provides the validity of Cosmic Censorship Hypothesis. It is found that the electric field affects the area of apparent horizons and their time of formation.Comment: 17 pages, accepted for publication in Astrophys. Space Sc