Ultrahigh Strength Steel: Development of Mechanical Properties Through Controlled Cooling

Structural steels with very high strength are referred as ultrahigh strength steels. The designation of ultrahigh strength is arbitrary, because there is no universally accepted strength level for this class of steels. As structural steels with greater and greater strength were developed, the strength range has been gradually modified. Commercial structural steel possessing a minimum yield strength of 1380 MPa (200 ksi) are accepted as ultrahigh strength steel (Philip, 1990). It has many applications such as in pipelines, cars, pressure vessels, ships, offshore platforms, aircraft undercarriages, defence sector and rocket motor casings. The class ultrahigh strength structural steels are quite broad and include several distinctly different families of steels such as (a) medium carbon low alloy steels, (b) medium alloy air hardening steel, (c) high alloy hardenable steels, and (d) 18Ni maraging steel. In the recent past, developmental efforts have been aimed mostly at increasing the ductility and toughness by improving the melting and the processing techniques. Steels with fewer and smaller non-metallic inclusions are produced by use of selected advanced processing techniques such as vacuum deoxidation, vacuum degassing, vacuum induction melting, vacuum arc remelting (VAR) and electroslag remelting (ESR). These techniques yield (a) less variation of properties from heat to heat, (b) greater ductility and toughness especially in the transverse direction, and (c) greater reliability in service (Philip, 1978). The strength can be further increased by thermomechanical treatment with controlled cooling

Hydrodynamics of chiral squirmers

Many microorganisms take a chiral path while swimming in an ambient fluid. In this paper we study the combined behavior of two chiral swimmers using the well-known squirmer model taking into account chiral asymmetries. In contrast to the simple squirmer model, which has an axisymmetric distribution of slip velocity, the chiral squirmer has additional asymmetries in the surface slip, which contribute to both translations and rotations of the motion. As a result, swimming trajectories can become helical and chiral asymmetries arise in the flow patterns. We study the swimming trajectories of a pair of chiral squirmers that interact hydrodynamically. This interaction can lead to attraction and repulsion, and in some cases even to bounded states where the swimmers continue to periodically orbit around a common average trajectory. Such bound states are a signature of the chiral nature of the swimmers. Our study could be relevant to the collective movements of ciliated microorganisms

Effect of Foundation-Reservoir Interaction on Seismic Behaviour of Gravity Dams

This paper discusses the combined effect of foundation-reservoir interaction on the seismic response of concrete gravity dam by considering a case study: Bichom Concrete Gravity Dam located in Arunachal Pradesh, India. The dam comprises of overflow and non-overflow monoliths and seismic analysis was carried out for both monoliths separately for Design Basis Earthquake excitation (DBE) assuming linear behaviour. The significance of foundation flexibility on the seismic response of dam was investigated by comparing the response of dam with rigid and flexible foundations. The hydrodynamic effect of impounded water is modeled as an added mass by Chopra’s Method. Effect of foundation-reservoir interaction on the response of both monoliths, such as time period, crest displacement, base reactions and stress distributions are discussed in this paper. It is predicted from the analysis that the dam with rigid foundation is relatively safe except some minor cracks at the heel of non-overflow monolith, but the dam with flexible foundation suffers moderate damage when the reservoir is empty and full

Correspondence between Electro-Magnetic Field and other Dark Energies in Non-linear Electrodynamics

In this work, we have considered the flat FRW model of the universe filled with electro-magnetic field. First, the Maxwell's electro-magnetic field in linear form has been discussed and after that the modified Lagrangian in non-linear form for accelerated universe has been considered. The corresponding energy density and pressure for non-linear electro-magnetic field have been calculated. We have found the condition such that the electro-magnetic field generates dark energy. The correspondence between the electro-magnetic field and the other dark energy candidates namely tachyonic field, DBI-essence, Chaplygin gas, hessence dark energy, k-essenece and dilaton dark energy have been investigated. We have also reconstructed the potential functions and the scalar fields in this scenario.Comment: 11 pages, 7 figure

Development of a method to identify change in the pattern of extreme streamflow events in future climate: Application on the Bhadra reservoir inflow in India

Study region: Bhadra basin (1968 km2), located in peninsular India, is considered for demonstration. Study focus: A general framework to assess the impact of climate change on the pattern of daily extreme streamflow events is proposed. Whereas, the impact is confirmed in the recent literature for most of the hydrologic variables at monthly/seasonal time scale, assessment and quantification at finer time scale, e.g. daily, is challenging. Complexity increases for the derived hydrologic variables, such as soil moisture and streamflow as compared to primary hydrologic variables, such as precipitation. The proposed general framework is demonstrated with the daily inflow to the Bhadra reservoir. Different statistical limits of extremes are defined and change in daily extreme pattern (number and magnitude) in the future (2006–2035) is assessed with respect to the baseline period (1971–2000). New hydrological insights for the region: Demonstration of the proposed methodology with the inflow to Bhadra reservoir reveals that the daily extreme events are expected to increase in number with the increase in the threshold of the extreme. For a particular threshold, the average magnitude of the extreme events in the future is found to be higher as compared to the baseline period. However, for monthly totals the case is not the same − it remains almost similar. The methodology, being general in nature, can be applied to other locations in order to assess the future change in streamflow and other derived variables

ROMP-derived Oligomeric Phosphates for Application in Facile Benzylation

The development of new ROMP-based oligomeric benzyl phosphates (OBPn) is reported for use as soluble, stable benzylating reagents. These oligomeric reagents are readily synthesized from commercially available materials and conveniently polymerized and purified in a one-pot process, affording bench stable, pure white, free-flowing solids on multi-gram scale. Utilization in benzylation reactions with a variety of nucleophiles is reported

Anthesis Dynamics, Pollen Availability and Enhancement of Seed to Ovule Ratio in \u3cem\u3eChrysopogon fulvus\u3c/em\u3e

Under the present scenario of severe green fodder shortage (64%) in India, grassland offers an opportunity to enhance fodder availability. To revitalize the existing denuded grasslands, seed is the best propagating material. Availability of quality seed in forage grasses is less than 20% of actual requirement/ demand. Hence, there is a need to enhance the production and productivity of grass seeds. Even the available grass seeds have very low germination percentage, which is mainly due to the absence of a caryopsis inside the fluffy seed material. Chrysopogon fulvus, commonly known as Guria grass or red false beard grass, is a tufted perennial tropical grassland species, with good palatability and green fodder potential of \u3e20 t/ha. With its ability to grow under annual rainfall of 300-1200 mm it is well suited for the rainfed situation of Indian grasslands. As per Indian minimum seed certification standards (IMSCS), the germination percentage of C. fulvus is only 15%. The low germination coincides with the low seed setting (14-18%) as recorded in bulk harvested sample by Bahukhandi et al. (2011). Enhancement of seed to ovule ratio not only increases germination percent but enhances productivity per se. With this background, the present study was undertaken to understand the reproductive morphology, pollen availability and effect of exogenous application of chemicals for enhancement of seed to ovule ratio in C. fulvus