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Recent advances in catalytic combustion of AP-based composite solid propellants

Defence Technology（防务技术） 2021年第3期17卷 1013-1031页

作者： Narendra Yadav Prem Kumar Srivastava mohan varma Department of Space Engineering&Rocketry India Department of Chemistry Birla Institute of TechnologyMesraRanchiIndia

Composite solid propellants(CSPs) have widely been used as main energy source for propelling the rockets in both space and military applications. Internal ballistic parameters of rockets like characteristic exhaust velocity, specific impulse, thrust, burning rate etc., are measured to assess and control the performance of rocket motors. The burn rate of solid propellants has been considered as most vital parameter for design of solid rocket motors to meet specific mission requirements. The burning rate of solid propellants can be tailored by using different constituents, extent of oxidizer loading and its particle size and more commonly by incorporating suitable combustion catalysts. Various metal oxides(MOs),complexes, metal powders and metal alloys have shown positive catalytic behaviour during the combustion of CSPs. These are usually solid-state catalysts that play multiple roles in combustion of CSPs such as reduction in activation energy, enhancement of rate of reaction, modification of sequences in reaction-phase, influence on condensed-phase combustion and participation in combustion process in gas-phase reactions. The application of nanoscale catalysts in CSPs has increased considerably in recent past due to their superior catalytic properties as compared to their bulk-sized counterparts. A large surface-to-volume ratio and quantum size effect of nanocatalysts are considered to be plausible reasons for improving the combustion characteristics of propellants. Several efforts have been made to produce nanoscale combustion catalysts for advanced propellant formulations to improve their energetics. The work done so far is largely scattered. In this review, an effort has been made to introduce various combustion catalysts having at least a metallic entity. Recent developments of nanoscale combustion catalysts with their specific merits are discussed. The combustion chemistry of a typical CSP is briefly discussed for providing a better understanding on role of co

关键词： Composite solid propellants Burn rate modifier Metallic nano-catalysts Catalytic combustion Thermal decomposition

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Analysis of Trends of Sleep-Related Breathing Disorders in Patients with Systemic Essential Hypertension

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International Journal of Clinical Medicine 2015年第8期6卷 561-569页

作者： Santosh Kumar Sinha Anand Kumar Avinash Jain Ramesh Thakur Chandra mohan varma Vinay Krishna Avdhesh Kumar Nirlep Gajiwala Ashok Thakkar L.P.S. Institute of Cardiology G.S.V.M. Medical College Kanpur India M.L. Chest Hospital G.S.V.M. Medical College Kanpur India Sahajanand Medical Technologies Pvt. Ltd. Surat India

Background: Studies have revealed a strong link between sleep-related breathing disorders and essential hypertension. However, the trends of sleep-disordered breathing in hypertensive patients have not been analyzed frequently. Methods: In this prospective, single-center and observational study, random patients with systemic essential hypertension, who were visiting GSVM Medical College, Kanpur, India between December 2012 and July 2014, were selected. After obtaining informed consent, patients were analyzed for symptoms of sleep-disordered breathing and Epworth Sleepiness Scale. Subsequently, all patients underwent overnight polysomnography to estimate the events of apnea and hypopnea. Observed data were compared between stage I and stage II hypertensive patients. Results: A total of 51 patients (age: 45.7 ± 13.43 years), comprising 36 stage I hypertensives and 15 stage II hypertensives, were enrolled in the study. About 47% of these patients displayed no symptoms of sleep-disordered breathing. Compared to stage I hypertensives, higher percentage of stage II hypertensives reported excessive day time sleepiness. Sleep latency time and sleep architecture were comparable between stage I and stage II hypertensives. Stage II hypertensives displayed shorter total sleep time and higher snore time than stage I hyper-tensives. Apnea Hypopnea Index (AHI) values increased with the severity of hypertension. Nocturnal oxygen desaturation was present in 25.0% and 53.3% of stage I and II hypertensives respectively. Mean lowest oxygen saturation was lower and the mean C-reactive protein levels were higher in stage II hypertensives as compared to stage I hypertensives. The mean C-reactive protein levels increased with increasing AHI scores, while the mean lowest oxygen saturation decreased with increasing AHI scores. Conclusion: Almost half of the hypertensives patients reported no symptoms of sleep-disordered breathing. Sleep-disordered breathing was more common and was more sever

关键词： Apnea Hypertension Polysomnography Sleep Disorders

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Recent advances in catalytic combustion of AP-based composite solid propellants

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Defence technology 2021年第3期

作者： Narendra Yadav Prem Kumar Srivastava mohan varma

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Change Detection of Desert Sand Dunes: A Remote Sensing Approach

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Advances in Remote Sensing 2014年第1期3卷 10-22页

作者： Surender varma Vatsal Shah Biplab Banerjee Krishna mohan Buddhiraju Center of Studies in Resources Engineering IIT Bombay Mumbai India ElectricalEnginering IIT Bombay Mumbai India

Deserts are one of the major landforms on the Earth. While deserts occupy about one-fifth of Earth’s land surface, they have been studied to a much lesser extent. All over the world, desert landforms are expanding ever rapidly and more and more human settlements are finding place in desert regions for habitation. Thus, quantifying and monitoring dunes becomes more relevant from a managerial perspective. Analyzing desert areas using satellite imagery is a challenging task due to weak textural differences and nearly homogeneous spectral responses in most parts of the terrain. In this paper, a post-clustering methodology for change detection of desert sand dunes is proposed. Features based on Radon spectrum are used to cluster dunes of various orientations. These clustered boundaries are used to detect if there are any changes occurring in the dune regions. In the experiments, remote sensing data covering various dune regions of the world are observed for possible changes in dune orientations. In all the cases, it is seen that there are no major changes in desert dune orientations since three decades.

关键词： Change Detection Desert Land Forms Monitoring Sand Dunes

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Listening to his inner voice? An unusual urethral foreign body: A review of literature and few learning points

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Asian Journal of Urology 2018年第2期5卷 131-132页

作者： Abheesh varma Hegde A.Nagaraja Rao A.mohan Suryakanth Choubey Revanna Siddappa Kanagali Gotam Pipara Department of Urology St.Johns Medical College HospitalBangaloreIndia

Dear Editor,Urethral foreign body insertions are rare *** objects are known to be *** have a low incidence,with males 1.7 times more likely to commit the act than ***,haematuria,strangury,urinary frequency and urinary retention are common presenting *** such patients do not provide the history of self insertion due to embarrassment and can hence present *** cases can lead on to sepsis and death[1e4].Multiple objects have been implicated in foreign body insertion into the ***,insertion of ear phones is a *** report one such unusual case here.

关键词： urinary insertion unusual

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