The protective structures required for performing critical operations are vulnerable to the blast and shock loads of advanced weapons. A blast valve is an important component of such structures for ventilation during normal conditions and for protection from blast/ shock during explosion. In this paper, various aspects of blast valve design and related studies are briefly reviewed. The concept and effects of blast wave, blast impact, numerical modelling and deformation of circular plate (one of the critical components of blast valve) have been discussed. The merits and demerits of sensing mechanisms viz. remote and direct sensing are discussed. The leakage of blast pressure during finite closing period of the valve (one of the critical problems) and the shock tube as a major experimental facility for testing of blast valves are briefly discussed.Keywords: Blast valve, wave, leakage, closure mechanism, shock tube Figure 1. Schematic of blast closure valve.
Katishool, low back ache (lumbago) is the most common problem in middle and old age people hampering the normal activity. There are several reasons associated with the pain such as – neurological, metabolic, degenerative, traumatic, bad posture, restless lifestyle, etc. Gridhasi is one of the Nanatmaja Vata Vyadhi, characterised by Katishool where the site of pain starts from the Sphika (back region) and then radiates to Kati, Pristha, Uru, Janu, Jangha, Pada in order. The signs and symptoms mentioned in ayurvedic texts resembles the medical condition named sciatica. Sciatica describes leg pain that is localised in the distribu-tion of one or more lumbosacral nerve roots, typically L4-S2, with or without neurological deficit. This causes abnormality in the gait of the patient. Gridhasi being a dominant lifestyle disorder needs a proper management and Siravedhan is one of the propitious managements of Gridhasi described in Ayurveda classics. Acharya Sushruta explained the importance of Siravedhan by accepting it as Ardha Chikitsa (half of the therapeutic measure) in Shalya tantra like Basti in Kayachikitsa. Acharya Sushruta also mentioned that the diseases which are not relieved so quickly by Snehana, Lepanadi measure, in this Siravedhan do wonders by acting as an emergency management to achieve good results.
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