Science of Armour Materials

This article discusses some basic principles that underlie design of effective armour materials against various modes of attack

Acoustic transducer apparatus with reduced thermal conduction

A horn is described for transmitting sound from a transducer to a heated chamber containing an object which is levitated by acoustic energy while it is heated to a molten state, which minimizes heat transfer to thereby minimize heating of the transducer, minimize temperature variation in the chamber, and minimize loss of heat from the chamber. The forward portion of the horn, which is the portion closest to the chamber, has holes that reduce its cross-sectional area to minimize the conduction of heat along the length of the horn, with the entire front portion of the horn being rigid and having an even front face to efficiently transfer high frequency acoustic energy to fluid in the chamber. In one arrangement, the horn has numerous rows of holes extending perpendicular to the length of horn, with alternate rows extending perpendicular to one another to form a sinuous path for the conduction of heat along the length of the horn

Generation of scalar-tensor gravity effects in equilibrium state boson stars

Boson stars in zero-, one-, and two-node equilibrium states are modeled numerically within the framework of Scalar-Tensor Gravity. The complex scalar field is taken to be both massive and self-interacting. Configurations are formed in the case of a linear gravitational scalar coupling (the Brans-Dicke case) and a quadratic coupling which has been used previously in a cosmological context. The coupling parameters and asymptotic value for the gravitational scalar field are chosen so that the known observational constraints on Scalar-Tensor Gravity are satisfied. It is found that the constraints are so restrictive that the field equations of General Relativity and Scalar-Tensor gravity yield virtually identical solutions. We then use catastrophe theory to determine the dynamically stable configurations. It is found that the maximum mass allowed for a stable state in Scalar-Tensor gravity in the present cosmological era is essentially unchanged from that of General Relativity. We also construct boson star configurations appropriate to earlier cosmological eras and find that the maximum mass for stable states is smaller than that predicted by General Relativity, and the more so for earlier eras. However, our results also show that if the cosmological era is early enough then only states with positive binding energy can be constructed.Comment: 20 pages, RevTeX, 11 figures, to appear in Class. Quantum Grav., comments added, refs update

Armour Protection and Affordable Protection for Futuristic Combat Vehicles

Protection creates a shift in the internal paradigm of the soldier and leads to multiplied psychological stamina for moving fearlessly in the battlefield which generates a major force-multiplier effect. Hence, the mechanized forces are still likely to be one of the dominant forces on the futuristic battlefield and would be the primary target of enemy forces capable of engaging from tank guns up to 4-5 km in a direct fire mode and up to 8-10 km in an indirect fire modes. Increased protection is possible only using advanced armour technology. Throughout the history of warfare, materials technologies have had a significant impact on land-combat force capabilities. Armour materials have progressed through improvements in metallic systems and development of advanced, lightweight (low areal density) composite materials. The advancements in ceramic systems have further improved the performance. Similarly, the advances in development of explosive reactive armour has generated efficient armour system against all contemporary high explosive antitank (HEAT) ammunition and missile threats for armoured vehicles. Yet, to achieve armour performance exceeding that of the current light combat vehicles and main battle tanks for new vehicular systems, weighing significantly less than the present combat vehicles, advances in new armour materials, systems, and survivability technologies are required. This paper describes various approaches and advancements in the metallic, ceramic, and composite armour materials and new dynamic armour systems that are essential to improve the survivability of armoured vehicles in the futurisitic multi-spectral battlefied scenarios.Defence Science Journal, 2011, 61(4), pp.394-402, DOI:http://dx.doi.org/10.14429/dsj.61.36

Lorentz Invariance and Origin of Symmetries

In this letter we reconsider the role of Lorentz invariance in the dynamical generation of the observed internal symmetries. We argue that, generally, Lorentz invariance can only be imposed in the sense that all Lorentz non-invariant effects caused by the spontaneous breakdown of Lorentz symmetry are physically unobservable. Remarkably, the application of this principle to the most general relativistically invariant Lagrangian, with arbitrary couplings for all the fields involved, leads by itself to the appearance of a symmetry and, what is more, to the massless vector fields gauging this symmetry in both Abelian and non-Abelian cases. In contrast, purely global symmetries are only generated as accidental consequences of the gauge symmetry.Comment: 10 page LaTeX fil

Normal and Oblique Impacts of Hard Projectile on Single and Layered Plates-An Experimental Study

The phenomenon of ordnance velocity impact of projectile on single and layered plates is of interest for many applications. In this paper. an experimental study of normal and oblique impacts or an ogive shaped, hard steel projectile on single and layered plates of mild steel and aluminium is presented. The projectiles were fired at an impact velocity of about 820 ms-1. The plate thickness was varied in the range 10 mm to 40 mm and the ratio of plate thickness to the diameter of the projectile varied in the range 1.5 to 13.0. Observations on target damage and measurements of incident and residual velocities for different angles of impact are presented. Plate thickness t*, for which the incident velocity is the ballistic limit, is determined. Computer simulations were carried out using a hydrodynamic code to simulate the normal impact of a projectile and compared these with the experimental results. Experiments were performed to evaluate the response of these plates of intermediate thickness when layered. and the results were compared to the results of single plate of same total thickness

Spatial Variation of Surface Water Quality of Vrishabhavathi Watershed Using GISÂ

Vrishabhavathi Watershed is a constituent of the Arkavathi River Basin, Bangalore Urban and Ramanagara District and covers an area of 381.465Km2, representing seasonally dry tropical climate. In Vrishabhavathi watershed Vrishabhavathi River is the main surface water source which is tributary of river Arkavathy, which joins the Cauvery River. It drains a major parts of Bangalore metropolis and is an outlet for domestic and industrial effluent of that area. Earlier this surface water is mainly used for agricultural purposes and drinking purposes. Since this watershed lies in Bangalore urban and Bangalore rural area, today this water is only used for agricultural purposes which are also not safe. In order to assess the surface water quality the present study has been undertaken to map the spatial variability of the surface water quality in the watershed using Geographical Information System. The water qualities of 24 stations were randomly selected in Vrishabhavathi watershed for the present study.GIS is an efficient tool for representation and analysis of spatial information related to water quality analysis. The spatial variation map for sensitive water quality parameters are generated and integrated using Arc GIS10.1. The final integrated map shows 3 priority classes such as Acceptable, Poor and Very poor water quality zones of the study area and provides a guideline for suitability of water for irrigation purpose

Differential Ballistic Response of Aramid-Glass Fibre Laminates to Soft and Hard Shots .

Ballistic perfonnance of all-glass, all-aramid and aramid-glass fibre-reinforced phenolic resincomposite laminates has been evaluated against 0.30 in. calibre soft ball and hard armour piercing (AP) bullets. It is observed that mass effective ness of glass fibre phenolic composites against impacts by APbullets can be improved by aramid fibre'reinforcement in the back of laminate. The perfonnance of a ramid phenolic composites against ball ammunition can be improved by hybridisation with glass fibre reinforcement at the front