5,312 research outputs found

    Experimental and Numerical Investigations of Thermal Ignition of a Phase Changing Energetic Material

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    Fortuitous exposure to high temperatures initiates reaction in energetic materials and possibilities of such event are of great concern in terms of the safe and controlled usage of explosive devices. Experimental and numerical investigations on time to explosion and location of ignition of a phase changing polymer bonded explosive material (80 per cent RDX and 20 per cent binder), contained in a metallic confinement subjected to controlled temperature build-up on its surface, are presented. An experimental setup was developed in which the polymer bonded explosive material filled in a cylindrical confinement was provided with a precise control of surface heating rate. Temperature at various radial locations was monitored till ignition. A computational model for solving two dimensional unsteady heat transfer with phase change and heat generation due to multi-step chemical reaction was developed. This model was implemented using a custom field function in the framework of a finite volume method based standard commercial solver. Numerical study could simulate the transient heat conduction, the melting pattern of the explosive within the charge and also the thermal runaway. Computed values of temperature evolution at various radial locations and the time to ignition were closely agreeing with those measured in experiment. Results are helpful both in predicting the possibility of thermal ignition during accidents as well as for the design of safety systems

    Effective Utilization of quarry waste and industrial waste as partial replacement of fine aggregates in concrete to resist acid attack

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    The aim of this study is to observe the concrete resistance towards acid attack. This is studied on M40 grade concrete, inwhich 5% by weight of binder is replaced with metakaolin and fine aggregate is replaced partially with the range of 5 to20% by marble sludge powder and green sand simultaneously. Four different mixes other than control mix is taken for thisstudy. The 100mm cubes are casted, cured and average compressive strength is compared with conventional concreteand those cured under two different acids. The two different acids taken for this study are Hydrochloric Acid and SulphuricAcid. The average percentage loss of weight and average compressive strength of cubes before and after two differentacids for all the mixes are investigated. From the experimental results, it is inferred that the control mix when cured underboth 1% concentrated HCl and H2SO4 solutions showed a high loss in weight comparing with modified concrete. Theincrease in marble powder and green sand upto 10% by weight of fine aggregate gives high reduction in loss of weight.The mix with 10% marble powder and green sand offered comparatively better solutions insisting the concrete modifiedwith the same can be recommended for making good and acid resisting concrete

    Magnetism of Ta Dichalcogenide Monolayers Tuned by Strain and Hydrogenation

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    The effects of strain and hydrogenation on the electronic and magnetic properties of monolayers of Ta based dichalcogenides (TaX2; X = S, Se, Te) are investigated using density-functional theo-ry. We predict a complex scenario of strain-dependent magnetic phase transitions involving par-amagnetic, ferromagnetic, and modulated antiferromagnetic states. Covering one of the two chalcogenide surfaces with hydrogen switches the antiferromagnetic/nonmagnetic TaX2 mono-layers to a semiconductor. Our research opens new pathways towards the manipulation of mag-netic properties for future optoelectronics and spintronics applications.Comment: 13 pages, 5 figure

    UNDERSTANDING OF NIRUHABASTI: COMPILATION FROM SUSHRUTA SAMHITA

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    Basti is a special treatment of Ayurveda, among Panchakarma therapies. According to Bruhatrayee, Basti therapy is the best when we treat Vata related disorder. Basti has both preventive and curative perspectives. Basti describes as Ardha Chikitsa, because being the best in maintaining quality and quantity of life. Basti when used properly promotes physical development, complexion, strength, immunity and life span. Bruhatrayee described various types of Basti. Among various types of Basti, Niruha Basti is important type described by all Acharya. There are various opinions about Niruha Basti, its types, method of preparation, indications, contraindications, complications and uses. The present article is an attempt to compile information about Niruha Basti according to Sushruta
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