Documents disponibles écrits par cet auteur

Hydrolysis of microcrystalline cellulose in subcritical and supercritical water in a continuous flow reactor / Sandeep Kumar in Industrial & engineering chemistry research, Vol. 47 N° 23 (Décembre 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 N° 23 (Décembre 2008) . - p. 9321–9329 Titre : Hydrolysis of microcrystalline cellulose in subcritical and supercritical water in a continuous flow reactor Type de document : texte imprimé Auteurs : Sandeep Kumar, Auteur ; Gupta, Ram B., Auteur Année de publication : 2009 Article en page(s) : p. 9321–9329 Note générale : Chemistry engineering Langues : Anglais (eng) Mots-clés : Hydrolysis  Microcrystalline  cellulose  Supercritical  water  Flow  reactor Résumé : For cellulosic ethanol production, efficient hydrolysis of crystalline cellulose to easily fermentable sugars is important. The focus of this study is to maximize the yield of cellulose hydrolysis in subcritical and supercritical water at practically achievable reaction times. Microcrystalline cellulose is treated with subcritical and supercritical water in a temperature range of 302−405 °C, at a pressure of 27.6 MPa, and residence times of 2.5−8.1 s. Cellulose−water slurry of 2.7 wt % after mixing with preheated water is rapidly heated to the reaction temperature and then the reaction product is rapidly cooled in a continuous reactor. Cellulose partially dissolves in subcritical water at 302 °C and completely dissolves at 330 °C. About 65% of cellulose converts to the oligomers and monomers at 335 °C in 4.8 s and also at 354 °C in 3.5 s. Upon increase in the reaction time or temperature to supercritical region, oligomers and monomers partially degrade to glycoaldehyde dimer, d-fructose, 1,3-dihydroxyacetone dimer, anhydroglucose, 5-HMF, and furfural. The effect of temperature, pressure, and reaction time on formation of various products is studied. In addition, the effect of a base catalyst, K2CO3, is examined. The catalyst increases cellulose gasification in the temperature range studied (302−333 °C). En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801102j [article] Hydrolysis of microcrystalline cellulose in subcritical and supercritical water in a continuous flow reactor [texte imprimé] / Sandeep Kumar, Auteur ; Gupta, Ram B., Auteur . - 2009 . - p. 9321–9329. Chemistry engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 N° 23 (Décembre 2008) . - p. 9321–9329 Mots-clés : Hydrolysis  Microcrystalline  cellulose  Supercritical  water  Flow  reactor Résumé : For cellulosic ethanol production, efficient hydrolysis of crystalline cellulose to easily fermentable sugars is important. The focus of this study is to maximize the yield of cellulose hydrolysis in subcritical and supercritical water at practically achievable reaction times. Microcrystalline cellulose is treated with subcritical and supercritical water in a temperature range of 302−405 °C, at a pressure of 27.6 MPa, and residence times of 2.5−8.1 s. Cellulose−water slurry of 2.7 wt % after mixing with preheated water is rapidly heated to the reaction temperature and then the reaction product is rapidly cooled in a continuous reactor. Cellulose partially dissolves in subcritical water at 302 °C and completely dissolves at 330 °C. About 65% of cellulose converts to the oligomers and monomers at 335 °C in 4.8 s and also at 354 °C in 3.5 s. Upon increase in the reaction time or temperature to supercritical region, oligomers and monomers partially degrade to glycoaldehyde dimer, d-fructose, 1,3-dihydroxyacetone dimer, anhydroglucose, 5-HMF, and furfural. The effect of temperature, pressure, and reaction time on formation of various products is studied. In addition, the effect of a base catalyst, K2CO3, is examined. The catalyst increases cellulose gasification in the temperature range studied (302−333 °C). En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801102j

New pixel based approach for reverse play of MPEG video for streaming system / Sandeep Kumar in Signal processing. Image communication, Vol. 26 N° 8-9 (Octobre 2011) 

Public ISBD [article]  in Signal processing. Image communication > Vol. 26 N° 8-9 (Octobre 2011) . - pp. 482–492 Titre : New pixel based approach for reverse play of MPEG video for streaming system Type de document : texte imprimé Auteurs : Sandeep Kumar, Auteur ; Satish Chand, Auteur Année de publication : 2012 Article en page(s) : pp. 482–492 Note générale : Electronique Langues : Anglais (eng) Mots-clés : Backward  play  MPEG  video  Pixel  based  approach  Reverse  play  VCR  functionality Résumé : In macroblock based architecture of MPEG video streaming system with backward playback support, the macroblocks of the frames are divided into two categories: Backward Macroblock (BMB) and Forward/Backward Macroblock (FBMB). The BMB and FBMB are processed differently. This approach reduces the network bandwidth and buffer size requirements. In this paper, we propose a pixel based approach that accesses less data from the server and hence further saves the network bandwidth and buffer requirement. The I- or P-frame (say, frame n−1) is reverse-predicted from the currently decoded frame (i.e., frame n) that is stored in the frame buffer at the client system. Using the motion vector information of frame n, the positions of its various pixels are found in the frame n−1 and their exact values are found using the prediction errors of the frame n by just subtracting them from their values in the frame n. Thus, most of the pixels of frame n−1 are predicted from the frame n. Experimental results show that on an average 93.4% of pixels in the previous I- or P-frame can be reverse-predicted from the current P-frame. The rest 6.6% unpredicted pixels are accumulated in the form of blocks and those blocks are requested from the server. We also propose new Block Identification Algorithms to identify different blocks of unpredicted pixels in an image. They are Maximum Height Minimum Width (MHMW), First Come First Serve (FCFS), Maximum Area (MA), and Biggest Block (BB) algorithms. The server processes the MPEG video stream and returns the desired blocks. We also discuss a FindBlock algorithm for extracting a small block of any frame from the MPEG video stream. Thus, only the motion vectors, prediction errors of frame n, and the unpredicted pixels of the frame n−1 need to be transmitted to the client system. This makes considerable saving in system resources. ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science/article/pii/S0923596511000725 [article] New pixel based approach for reverse play of MPEG video for streaming system [texte imprimé] / Sandeep Kumar, Auteur ; Satish Chand, Auteur . - 2012 . - pp. 482–492. Electronique Langues : Anglais (eng) in Signal processing. Image communication > Vol. 26 N° 8-9 (Octobre 2011) . - pp. 482–492 Mots-clés : Backward  play  MPEG  video  Pixel  based  approach  Reverse  play  VCR  functionality Résumé : In macroblock based architecture of MPEG video streaming system with backward playback support, the macroblocks of the frames are divided into two categories: Backward Macroblock (BMB) and Forward/Backward Macroblock (FBMB). The BMB and FBMB are processed differently. This approach reduces the network bandwidth and buffer size requirements. In this paper, we propose a pixel based approach that accesses less data from the server and hence further saves the network bandwidth and buffer requirement. The I- or P-frame (say, frame n−1) is reverse-predicted from the currently decoded frame (i.e., frame n) that is stored in the frame buffer at the client system. Using the motion vector information of frame n, the positions of its various pixels are found in the frame n−1 and their exact values are found using the prediction errors of the frame n by just subtracting them from their values in the frame n. Thus, most of the pixels of frame n−1 are predicted from the frame n. Experimental results show that on an average 93.4% of pixels in the previous I- or P-frame can be reverse-predicted from the current P-frame. The rest 6.6% unpredicted pixels are accumulated in the form of blocks and those blocks are requested from the server. We also propose new Block Identification Algorithms to identify different blocks of unpredicted pixels in an image. They are Maximum Height Minimum Width (MHMW), First Come First Serve (FCFS), Maximum Area (MA), and Biggest Block (BB) algorithms. The server processes the MPEG video stream and returns the desired blocks. We also discuss a FindBlock algorithm for extracting a small block of any frame from the MPEG video stream. Thus, only the motion vectors, prediction errors of frame n, and the unpredicted pixels of the frame n−1 need to be transmitted to the client system. This makes considerable saving in system resources. ISSN : 0923-5965 En ligne : http://www.sciencedirect.com/science/article/pii/S0923596511000725