Documents disponibles écrits par cet auteur

Cycle performances of the mixture HFC-161 + HFC-134a as the substitution of HFC-134a in automotive air conditioning systems / Xiao Hong Han in International journal of refrigeration, Vol. 36 N° 3 (Mai 2013) 

Public ISBD [article]  in International journal of refrigeration > Vol. 36 N° 3 (Mai 2013) . - pp. 913–920 Titre : Cycle performances of the mixture HFC-161 + HFC-134a as the substitution of HFC-134a in automotive air conditioning systems Titre original : Performances des cycles utilisant le mélange HFC-161 + HFC-134a pour remplacer le HFC-134a dans les systèmes de conditionnement d'air automobiles Type de document : texte imprimé Auteurs : Xiao Hong Han, Auteur ; Li Peng, Auteur ; Ying Jie Xu, Auteur Année de publication : 2013 Article en page(s) : pp. 913–920 Note générale : Refrigeration Langues : Anglais (eng) Mots-clés : Air  conditioning  automotive;  HFC-161  +  HFC-134a;  HFC-134a;  Experiment;  Cycle  performance Résumé : In this paper, the mixture of HFC-161/HFC-134a (0.6/0.4 in mass fraction), named ‘M5’, is proposed as a substitution of HFC-134a used in automotive air conditioning systems. The theoretical and experimental cycle performances for M5 and HFC-134a were conducted at the condensation temperature from 50 °C–65 °C, evaporation temperature from −5 °C–10 °C. Theoretical results show that COP of M5 is very close to that of HFC-134a, the specific refrigeration capacity and volumetric refrigeration capacity of M5 are much higher than those of HFC-134a. Experimental results show that COP of M5 is a bit higher than that of HFC-134a, the refrigeration capacity and compressor power of M5 are about 32% and 30% higher than those of HFC-134a, respectively, the compressor discharge temperature and pressure ratio of M5 are about 15% higher and 10.9% lower than those of HFC-134a, respectively. Considering the good performance and compatibility with the existing system, M5 is a potential alternative refrigerant for HFC-134a. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700712002873 [article] Cycle performances of the mixture HFC-161 + HFC-134a as the substitution of HFC-134a in automotive air conditioning systems = Performances des cycles utilisant le mélange HFC-161 + HFC-134a pour remplacer le HFC-134a dans les systèmes de conditionnement d'air automobiles [texte imprimé] / Xiao Hong Han, Auteur ; Li Peng, Auteur ; Ying Jie Xu, Auteur . - 2013 . - pp. 913–920. Refrigeration Langues : Anglais (eng) in International journal of refrigeration > Vol. 36 N° 3 (Mai 2013) . - pp. 913–920 Mots-clés : Air  conditioning  automotive;  HFC-161  +  HFC-134a;  HFC-134a;  Experiment;  Cycle  performance Résumé : In this paper, the mixture of HFC-161/HFC-134a (0.6/0.4 in mass fraction), named ‘M5’, is proposed as a substitution of HFC-134a used in automotive air conditioning systems. The theoretical and experimental cycle performances for M5 and HFC-134a were conducted at the condensation temperature from 50 °C–65 °C, evaporation temperature from −5 °C–10 °C. Theoretical results show that COP of M5 is very close to that of HFC-134a, the specific refrigeration capacity and volumetric refrigeration capacity of M5 are much higher than those of HFC-134a. Experimental results show that COP of M5 is a bit higher than that of HFC-134a, the refrigeration capacity and compressor power of M5 are about 32% and 30% higher than those of HFC-134a, respectively, the compressor discharge temperature and pressure ratio of M5 are about 15% higher and 10.9% lower than those of HFC-134a, respectively. Considering the good performance and compatibility with the existing system, M5 is a potential alternative refrigerant for HFC-134a. En ligne : http://www.sciencedirect.com/science/article/pii/S0140700712002873

Determining the shapes of yield curves for unsaturated soils by modified state surface approach / Xiong Zhang in Journal of geotechnical and geoenvironmental engineering, Vol. 136 N° 1 (Janvier 2010) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 1 (Janvier 2010) . - pp. 239-247 Titre : Determining the shapes of yield curves for unsaturated soils by modified state surface approach Type de document : texte imprimé Auteurs : Xiong Zhang, Auteur ; Juanyu Liu, Auteur ; Li Peng, Auteur Article en page(s) : pp. 239-247 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Unsaturated  soils  Elastoplastic  Constitutive  modeling  Loading/collapse  Yield  curve  State  boundary  surface Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Attention is increasingly paid to the elastoplastic behavior of unsaturated soils. In the development of an elastoplastic framework for unsaturated soils, it is necessary to determine the initial shape of the yield curve and its evolution with yielding. Accordingly, correct determination of shapes of yield curves is of significant importance. Existing methods rely on use of a series of specimens with “identical” stress history to determine the initial shape of yield curve. Preparation of such specimens requires thoughtful preparation, careful instrumentation, and lengthy equilibrium time, which makes identical specimens very difficult to obtain. As a result, the yield curve obtained through the existing methods could be misleading. Hence, this paper presents a simple method to correctly and rapidly determine the shapes of the yield curves and their evolution during yielding even if the soil specimens do no have identical stress histories. In this new method, a modified state surface approach, recently proposed to model the elastoplastic behavior of unsaturated soils under isotropic conditions, was applied. It overcomes the limitations in the existing methods, and allows correct and rapid determination of the elastic and plastic hardening surfaces, and then shapes of yield curves without additional laboratory work. An example was used to demonstrate the application of the proposed method. The comparison between the proposed method and other methods was discussed from which the capability and effectiveness of the proposed method were evaluated. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JGGEFK&ONLINE=YES&s [...] [article] Determining the shapes of yield curves for unsaturated soils by modified state surface approach [texte imprimé] / Xiong Zhang, Auteur ; Juanyu Liu, Auteur ; Li Peng, Auteur . - pp. 239-247. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 1 (Janvier 2010) . - pp. 239-247 Mots-clés : Unsaturated  soils  Elastoplastic  Constitutive  modeling  Loading/collapse  Yield  curve  State  boundary  surface Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Attention is increasingly paid to the elastoplastic behavior of unsaturated soils. In the development of an elastoplastic framework for unsaturated soils, it is necessary to determine the initial shape of the yield curve and its evolution with yielding. Accordingly, correct determination of shapes of yield curves is of significant importance. Existing methods rely on use of a series of specimens with “identical” stress history to determine the initial shape of yield curve. Preparation of such specimens requires thoughtful preparation, careful instrumentation, and lengthy equilibrium time, which makes identical specimens very difficult to obtain. As a result, the yield curve obtained through the existing methods could be misleading. Hence, this paper presents a simple method to correctly and rapidly determine the shapes of the yield curves and their evolution during yielding even if the soil specimens do no have identical stress histories. In this new method, a modified state surface approach, recently proposed to model the elastoplastic behavior of unsaturated soils under isotropic conditions, was applied. It overcomes the limitations in the existing methods, and allows correct and rapid determination of the elastic and plastic hardening surfaces, and then shapes of yield curves without additional laboratory work. An example was used to demonstrate the application of the proposed method. The comparison between the proposed method and other methods was discussed from which the capability and effectiveness of the proposed method were evaluated. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JGGEFK&ONLINE=YES&s [...]

Kinetics of CO2/coal gasification in molten blast furnace slag / Li Peng in Industrial & engineering chemistry research, Vol. 51 N° 49 (Décembre 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 49 (Décembre 2012) . - pp 15872–15883 Titre : Kinetics of CO2/coal gasification in molten blast furnace slag Type de document : texte imprimé Auteurs : Li Peng, Auteur ; Qingbo Yu, Auteur ; Qin Qin, Auteur Année de publication : 2013 Article en page(s) : pp 15872–15883 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Gasification  Kinetics Résumé : The coal/CO2 gasification reactions in molten BF (blast furnace) slag were studied kinetically by temperature-programmed thermogravimetry using a thermal analyzer. The effect of heating rates and molten BF slag on coal gasification were studied, and the activation energies, frequency factors, and most possibility mechanism functions were calculated. The results show that the order of reactivity sequence at these temperatures was DT (Datong) coal > FX (Fuxin) coal > coke. With the increase in heating rate, the carbon conversion, and the peak value of reaction rate increased at the same reaction time, the carbon conversion curve shifts to a higher temperature and the reaction rate curve shifts rightward systematically, both of the time required for the carbon conversion to reach nearly unity and the time necessary for reaction rate to reach its maximum decreased. The carbon conversion and reaction rates were sensitive to BF slag; at the same time, the carbon conversion and reaction rates of coal gasification with slag are higher than those without slag. The time required for the carbon conversion to reach nearly unity and the time required for the reaction rate to reach maximum with slag are both shorter than that without slag. In the presence of BF slag, the carbon conversion curve shifts to lower temperature, the peak value of reaction rate is higher than that without slag, and the reaction rate curve also shifts to lower temperature. The molten BF slag acts as a good catalyst to coal gasification. Without molten BF slag, the mechanism functions of coke and FX coal are a C1 model (phase boundary reaction (n = 2) model), while the mechanism function of DT coal is a C2 model (phase boundary reaction (n = 3/2) model). However, with molten BF slag, the mechanism function of coke is a D5 model (3-D diffusion (anti-Jander) model), the mechanism function of DT coal is a D4 model (3-D diffusion model), and the mechanism function of FX coal is a C2 model (phase boundary reaction (n = 3/2) model). The activation energies and frequency factors decrease as heating rates increase. The kinetic compensation effect of coal/CO2 gasification in molten BF slag exists. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie301678s [article] Kinetics of CO2/coal gasification in molten blast furnace slag [texte imprimé] / Li Peng, Auteur ; Qingbo Yu, Auteur ; Qin Qin, Auteur . - 2013 . - pp 15872–15883. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 49 (Décembre 2012) . - pp 15872–15883 Mots-clés : Gasification  Kinetics Résumé : The coal/CO2 gasification reactions in molten BF (blast furnace) slag were studied kinetically by temperature-programmed thermogravimetry using a thermal analyzer. The effect of heating rates and molten BF slag on coal gasification were studied, and the activation energies, frequency factors, and most possibility mechanism functions were calculated. The results show that the order of reactivity sequence at these temperatures was DT (Datong) coal > FX (Fuxin) coal > coke. With the increase in heating rate, the carbon conversion, and the peak value of reaction rate increased at the same reaction time, the carbon conversion curve shifts to a higher temperature and the reaction rate curve shifts rightward systematically, both of the time required for the carbon conversion to reach nearly unity and the time necessary for reaction rate to reach its maximum decreased. The carbon conversion and reaction rates were sensitive to BF slag; at the same time, the carbon conversion and reaction rates of coal gasification with slag are higher than those without slag. The time required for the carbon conversion to reach nearly unity and the time required for the reaction rate to reach maximum with slag are both shorter than that without slag. In the presence of BF slag, the carbon conversion curve shifts to lower temperature, the peak value of reaction rate is higher than that without slag, and the reaction rate curve also shifts to lower temperature. The molten BF slag acts as a good catalyst to coal gasification. Without molten BF slag, the mechanism functions of coke and FX coal are a C1 model (phase boundary reaction (n = 2) model), while the mechanism function of DT coal is a C2 model (phase boundary reaction (n = 3/2) model). However, with molten BF slag, the mechanism function of coke is a D5 model (3-D diffusion (anti-Jander) model), the mechanism function of DT coal is a D4 model (3-D diffusion model), and the mechanism function of FX coal is a C2 model (phase boundary reaction (n = 3/2) model). The activation energies and frequency factors decrease as heating rates increase. The kinetic compensation effect of coal/CO2 gasification in molten BF slag exists. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie301678s

A Novel PWM Technique in Digital Control / Li Peng in IEEE transactions on industrial electronics, Vol. 54 N°1 (Fevrier 2007) 

Public ISBD [article]  in IEEE transactions on industrial electronics > Vol. 54 N°1 (Fevrier 2007) . - 338-346 p. Titre : A Novel PWM Technique in Digital Control Titre original : Une Technique du Roman PWM dans la Commande Numérique Type de document : texte imprimé Auteurs : Li Peng, Auteur ; Yong Kang, Auteur ; Xuejun Pei ; Chen, Jian, Auteur Article en page(s) : 338-346 p. Note générale : Génie Electrique Langues : Anglais (eng) Mots-clés : Digital  control  High  frequency  Pulse  width  modulation  (PWM)  technique  Resolution.Fréquence  de  commande  numérique  Technique  de  modulation  de  largeur  d'impulsion  Résolution. Index. décimale : 621.38 Dispositifs électroniques. Tubes à électrons. Photocellules. Accélérateurs de particules. Tubes à rayons X Résumé : One problem with microprocessor-based high-frequency pulsewidth-modulation (PWM) converters is the modulating resolution limitation caused by limited-time resolution of hardware timers. In this paper, a novel PWM technique, the double PWM (DPWM), is proposed. DPWM combines the advantages of low-frequency modulation and high-frequency switching in power conversion and resolves the contradiction between high frequency and accuracy in a digital control scheme. DPWM effectively increases the resolution in digital control, while the harmonics introduced by this method is found to be negligible. Theoretical analysis, characteristics, and design considerations are given, and they are verified by experiments on a 5.5-kW 20-kHz insulated-gate-bipolar-transistor boost-buck converter. Un problème avec les convertisseurs à haute fréquence sur microprocesseur de la modulation de largeur d'impulsion (PWM) est la limitation de modulation de résolution provoquée par résolution limitée de temps des temporisateurs de matériel. En cet article, on propose une technique du roman PWM, le double PWM (DPWM). DPWM combine les avantages de la modulation de basse fréquence et de la commutation à haute fréquence dans la conversion de puissance et résout la contradiction entre la fréquence et l'exactitude dans un arrangement de commande numérique. DPWM augmente efficacement la résolution dans la commande numérique, alors que les harmoniques présentés par cette méthode s'avère négligeables. L'analyse, les caractéristiques, et des considérations de conception sont données, et eux théoriques sont vérifiés par des expériences sur un convertisseur bipolaire de mâle de poussée de transistor de la porte 5.5-kW isolé par 20-kHz. DEWEY : 621 ISSN : 0278-0046 RAMEAU : Modulation En ligne : pe105@mail.hust.edu.cn [article] A Novel PWM Technique in Digital Control = Une Technique du Roman PWM dans la Commande Numérique [texte imprimé] / Li Peng, Auteur ; Yong Kang, Auteur ; Xuejun Pei ; Chen, Jian, Auteur . - 338-346 p. Génie Electrique Langues : Anglais (eng) in IEEE transactions on industrial electronics > Vol. 54 N°1 (Fevrier 2007) . - 338-346 p. Mots-clés : Digital  control  High  frequency  Pulse  width  modulation  (PWM)  technique  Resolution.Fréquence  de  commande  numérique  Technique  de  modulation  de  largeur  d'impulsion  Résolution. Index. décimale : 621.38 Dispositifs électroniques. Tubes à électrons. Photocellules. Accélérateurs de particules. Tubes à rayons X Résumé : One problem with microprocessor-based high-frequency pulsewidth-modulation (PWM) converters is the modulating resolution limitation caused by limited-time resolution of hardware timers. In this paper, a novel PWM technique, the double PWM (DPWM), is proposed. DPWM combines the advantages of low-frequency modulation and high-frequency switching in power conversion and resolves the contradiction between high frequency and accuracy in a digital control scheme. DPWM effectively increases the resolution in digital control, while the harmonics introduced by this method is found to be negligible. Theoretical analysis, characteristics, and design considerations are given, and they are verified by experiments on a 5.5-kW 20-kHz insulated-gate-bipolar-transistor boost-buck converter. Un problème avec les convertisseurs à haute fréquence sur microprocesseur de la modulation de largeur d'impulsion (PWM) est la limitation de modulation de résolution provoquée par résolution limitée de temps des temporisateurs de matériel. En cet article, on propose une technique du roman PWM, le double PWM (DPWM). DPWM combine les avantages de la modulation de basse fréquence et de la commutation à haute fréquence dans la conversion de puissance et résout la contradiction entre la fréquence et l'exactitude dans un arrangement de commande numérique. DPWM augmente efficacement la résolution dans la commande numérique, alors que les harmoniques présentés par cette méthode s'avère négligeables. L'analyse, les caractéristiques, et des considérations de conception sont données, et eux théoriques sont vérifiés par des expériences sur un convertisseur bipolaire de mâle de poussée de transistor de la porte 5.5-kW isolé par 20-kHz. DEWEY : 621 ISSN : 0278-0046 RAMEAU : Modulation En ligne : pe105@mail.hust.edu.cn

Thermal dehydration and vibrational spectra of hydrated sodium metaborates / Amy M. Beaird in Industrial & engineering chemistry research, Vol. 50 N° 13 (Juillet 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 13 (Juillet 2011) . - pp. 7746–7752 Titre : Thermal dehydration and vibrational spectra of hydrated sodium metaborates Type de document : texte imprimé Auteurs : Amy M. Beaird, Auteur ; Li Peng, Auteur ; Hilary S. Marsh, Auteur Année de publication : 2011 Article en page(s) : pp. 7746–7752 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Catalysis  Reaction  kinetics  Inorganic  reaction  mechanisms Résumé : Sodium metaborate hydrates are a class of compounds represented by the stoichiometry NaBO2·xH2O. Recently, sodium metaborate has received attention as the byproduct of sodium borohydride hydrolysis, a reaction that is under consideration for hydrogen storage applications. The aim of this work was to understand the disposition of water in the crystal structure of hydrated sodium metaborates and to characterize the thermal stability and dehydration of the various hydrated species to optimize hydrogen storage efficiency as well as recyclability of the borate. Observations from a suite of analytical techniques including thermal analyses (thermogravimetric analysis/differential scanning calorimetry), X-ray diffraction, and Raman spectroscopy were correlated to characterize the dehydration mechanism of commercially available sodium metaborates, with an emphasis on the dihydrate (x = 2). A transformation from tetrahedrally coordinated boron to trigonal boron occurs when NaB(OH)4 (x = 2) is heated between 25 and 400 °C. The first dehydration to Na3[B3O5(OH)2] (x = 1/3) releases 5 mol of water between 83 and 155 °C. The final mole of water is released between 249 and 280 °C, and Na3B3O6 (x = 0) is formed. Raman spectra are reported for x = 2 and 1/3 for the first time. First-principles density functional theory was used to compute Raman spectra of the x = 1/3 and 2 material in order to assign the modes. We found reasonably good agreement between the experimentally measured and calculated vibrational frequencies. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie102345j [article] Thermal dehydration and vibrational spectra of hydrated sodium metaborates [texte imprimé] / Amy M. Beaird, Auteur ; Li Peng, Auteur ; Hilary S. Marsh, Auteur . - 2011 . - pp. 7746–7752. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 13 (Juillet 2011) . - pp. 7746–7752 Mots-clés : Catalysis  Reaction  kinetics  Inorganic  reaction  mechanisms Résumé : Sodium metaborate hydrates are a class of compounds represented by the stoichiometry NaBO2·xH2O. Recently, sodium metaborate has received attention as the byproduct of sodium borohydride hydrolysis, a reaction that is under consideration for hydrogen storage applications. The aim of this work was to understand the disposition of water in the crystal structure of hydrated sodium metaborates and to characterize the thermal stability and dehydration of the various hydrated species to optimize hydrogen storage efficiency as well as recyclability of the borate. Observations from a suite of analytical techniques including thermal analyses (thermogravimetric analysis/differential scanning calorimetry), X-ray diffraction, and Raman spectroscopy were correlated to characterize the dehydration mechanism of commercially available sodium metaborates, with an emphasis on the dihydrate (x = 2). A transformation from tetrahedrally coordinated boron to trigonal boron occurs when NaB(OH)4 (x = 2) is heated between 25 and 400 °C. The first dehydration to Na3[B3O5(OH)2] (x = 1/3) releases 5 mol of water between 83 and 155 °C. The final mole of water is released between 249 and 280 °C, and Na3B3O6 (x = 0) is formed. Raman spectra are reported for x = 2 and 1/3 for the first time. First-principles density functional theory was used to compute Raman spectra of the x = 1/3 and 2 material in order to assign the modes. We found reasonably good agreement between the experimentally measured and calculated vibrational frequencies. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie102345j