The pore size distribution is often an important parameter for transport processes in porous media.Cryoporometry experiments can provide such data in the meso and macropore size up to 1 mm providing the sample tempera...The pore size distribution is often an important parameter for transport processes in porous media.Cryoporometry experiments can provide such data in the meso and macropore size up to 1 mm providing the sample temperature is finely controlled.We use a Peltier based system inserted directly into the NMR probe to control the temperature within 0.05℃and impose temperature ramps down to 0.002℃/min,necessary to characterize the largest pore sizes.The pore size information in the macropore range cannot be obtained from gas adsorption techniques while mercury injection is questionable for the material considered here.For porous materials made of paramagnetic minerals such as lithium-iron phosphate(LiFePO_(4),LFP)or nickel-manganese-cobalt oxides(NMC)and saturated with octamethylcyclotetrasiloxane(OMCTS),the T_(2)relaxation times are very short such as protons from the liquid and frozen phases cannot be separated.Hence the usual cryoporometry experiment cannot be performed.Instead,we propose to use the T_(1)contrast to separate these phases.The method is studied in detail along with some temperature effects linked with the T_(1)variation of the bulk frozen OMCTS.We show an example on two cathode materials part of industrial battery product.展开更多
Colloidal transport and deposition in porous media are complex processes that result from the interaction between hydrodynamics(velocity,pore geometry,etc.)and Derjaguin-Landau-Verwey-Overbeek(DLVO)forces(particle-par...Colloidal transport and deposition in porous media are complex processes that result from the interaction between hydrodynamics(velocity,pore geometry,etc.)and Derjaguin-Landau-Verwey-Overbeek(DLVO)forces(particle-particle and particle-surface).They have important implications for engineering applications involving the reinjection of a fluidinto a medium,such as geothermal energy.The investigation of permeability stability is critical to ensure the sustainability of activities.This work aims to study the clogging mechanisms in a rock-like porous medium using a microfluidicdevice.The pore-throat network distributions reveal that the micromodel geometry mimics real rock samples.The transport of a monodispersed suspension is studied at different concentrations.Image analysis,velocity fieldmodeling,and pressure drop measurement are used to assess preferential clogging sites and porous medium permeability reduction,respectively.Experiments have shown that retention sites are located around preferential flow paths with relatively high flow velocities.When clogged,the pore thresholds are the deposition zones that lead to a reduction in permeability.However,pore bodies may also constitute deposition zones.Interestingly,as the concentration of the suspension increases,the kinetics of the permeability reduction are delayed,and the clogging mechanisms,as well as the type of deposit,evolve.Finally,at very high concentrations,the effects of hydrodynamic stripping are more important.These observations emphasize the role of the porous medium geometry in colloidal transport and deposition and thus permeability reduction.展开更多
Characterization and optimization of physical and chemical properties of drilling fluids are critical for the efficiency and success of drilling operations.In particular,maintaining the optimal levels of solids conten...Characterization and optimization of physical and chemical properties of drilling fluids are critical for the efficiency and success of drilling operations.In particular,maintaining the optimal levels of solids content is essential for achieving the most effective fluid performance.Proper management of solids content also reduces the risk of tool failures.Traditional solids content analysis methods,such as retort analysis,require substantial human intervention and time,which can lead to inaccuracies,time-management issues,and increased operational risks.In contrast to human-intensive methods,machine learning may offer a viable alternative for solids content estimation due to its pattern-recognition capability.In this study,a large set of laboratory reports of drilling-fluid analyses from 130 oil wells around the world were compiled to construct a comprehensive data set.The relationships among various rheological parameters were analyzed using statistical methods and machine learning algorithms.Several machine learning algorithms of diverse classes,namely linear(linear regression,ridge regression,and ElasticNet regression),kernel-based(support vector machine)and ensemble tree-based(gradient boosting,XGBoost,and random forests)algorithms,were trained and tuned to estimate solids content from other readily available drilling fluid properties.Input variables were kept consistent across all models for interpretation and comparison purposes.In the final stage,different evaluation metrics were employed to evaluate and compare the performance of different classes of machine learning models.Among all algorithms tested,random forests algorithm was found to be the best predictive model resulting in consistently high accuracy.Further optimization of the random forests model resulted in a mean absolute percentage error(MAPE)of 3.9%and 9.6%and R^(2) of 0.99 and 0.93 for the training and testing sets,respectively.Analysis of residuals,their histograms and Q-Q normality plots showed Gaussian distributions with residuals that are scattered around a mean of zero within error ranges of±1%and±4%,for training and testing,respectively.The selected model was further validated by applying the rheological measurements from mud samples taken from an offshore well from the Gulf of Mexico.The model was able to estimate total solids content in those four mud samples with an average absolute error of 1.08% of total solids content.The model was then used to develop a web-based graphical-user-interface(GUI)application,which can be practically used at the rig site by engineers to optimize drilling fluid programs.The proposed model can complement automation workflows that are designed to measure fundamental rheological properties in real time during drilling operations.While a standard retort test can take approximately 2 h at the rig site,such kind of real-time estimations can help the rig personnel to timely optimize drilling fluids,with a potential of saving 2920 man-hours in a given year for a single drilling rig.展开更多
Cu/ZrO2/SiO2 are efficient catalysts for the selective hydrogenation of CO2 to CH3OH. In order to understand the role of ZrO2 in these mixed-oxides based catalysts, in situ X-ray absorption spectroscopy has been carri...Cu/ZrO2/SiO2 are efficient catalysts for the selective hydrogenation of CO2 to CH3OH. In order to understand the role of ZrO2 in these mixed-oxides based catalysts, in situ X-ray absorption spectroscopy has been carried out on the Cu and Zr K-edge. Under reaction conditions, Cu remains metallic, while Zr is present in three types of coordination environment associated with 1) bulk ZrO2, 2) coordinatively saturated and 3) unsaturated Zr(Ⅳ) surface sites. The amount of coordinatively unsaturated Zr surface sites can be quantified by linear combination fit of reference X-Ray absorption near edge structure (XANES) spectra and its amount correlates with CH3OH formation rates, thus indicating the importance of Zr(Ⅳ) Lewis acid surface sites in driving the selectivity toward CH3OH. This finding is consistent with the proposed mechanism, where CO2 is hydrogenated at the interface between the Cu nanoparticles that split H2 and Zr(Ⅳ) surface sites that stabilizes reaction intermediates.展开更多
A high-order leap-frog based non-dissipative discontinuous Galerkin time- domain method for solving Maxwell＇s equations is introduced and analyzed. The pro- posed method combines a centered approximation for the eval...A high-order leap-frog based non-dissipative discontinuous Galerkin time- domain method for solving Maxwell＇s equations is introduced and analyzed. The pro- posed method combines a centered approximation for the evaluation of fluxes at the in- terface between neighboring elements, with a Nth-order leap-frog time scheme. More- over, the interpolation degree is defined at the element level and the mesh is refined locally in a non-conforming way resulting in arbitrary level hanging nodes. The method is proved to be stable under some CFL-like condition on the time step. The convergence of the semi-discrete approximation to Maxwelrs equations is established rigorously and bounds on the global divergence error are provided. Numerical experiments with high- order elements show the potential of the method.展开更多
Enzymatic hydrolysis of lignocellulose is often considered to be the major economic bottleneck of the production process of bioethanol from lignocellulose. It is generally admitted that the most efficient organism for...Enzymatic hydrolysis of lignocellulose is often considered to be the major economic bottleneck of the production process of bioethanol from lignocellulose. It is generally admitted that the most efficient organism for the production ofcellulolytic enzymes is the fungus Trichoderma reesei, mostly due to its high secretion capacity. Unfortunately, this fungus secretes very low concentrations of β-glucosidase, thereby often requiring β-glucosidase supplementation for complete cellulose hydrolysis. It is especially important to have sufficient quantities of β-glucosidase in order to prevent inhibition of cellobiohydrolases by cellobiose. In order to optimize the produced cocktail, a more efficient β-glucosidase was cloned into T. reesei CL847 strain. The new strain, called CL847 TR3002, secretes the evolved β-glucosidase and was tested for cellulase production in laboratory-scale reactors. Its growth kinetics and cellulase production were characterized using fed-batch and chemostat modes under various culture conditions. The cellulase activities of the evolved strain were compared with activities of the parent strain. In addition, hydrolysis of a steam exploded wheat straw was performed at three different enzyme-loading levels （5 mg/g, 10 mg/g and 20 mg/g of dry matter） and a new kinetic model was developed.展开更多
Transmission electron microscopy and surface- and bulk-sensitive spectroscopic methods were used to study the morphology and the electronic structure of a hybrid organic-inorganic system composed of gold nanoparticles...Transmission electron microscopy and surface- and bulk-sensitive spectroscopic methods were used to study the morphology and the electronic structure of a hybrid organic-inorganic system composed of gold nanoparticles （NP＇s） which were distributed in an organic matrix. Au atoms deposited onto a copper phthalocyanine （CuPc） surface diffuse into the organic matrix and self-assemble in well defined NP＇s with metallic properties. No formation of a continuous metallic Au film on top of the CuPc film is observed up to nominal coverages as large as 130 A.展开更多
Mango is a widely cultivated and consumed fruit in Brazil and one of the most important alternatives to take advantage of the production excess is dehydration. Therefore, this work aims at establishing better operatio...Mango is a widely cultivated and consumed fruit in Brazil and one of the most important alternatives to take advantage of the production excess is dehydration. Therefore, this work aims at establishing better operational conditions for ＂spray-drying＂ processes, in order to obtain the powder of mango pulp by means of a rotational central compounded planning, and also at carrying out the physicochemical characterization of both the integral mango pulp and the powder obtained from the operational conditions mentioned above. Both integral mango pulp and powder were analyzed as for the following physicochemical characteristics： humidity, pH, titratable acidity, soluble solids （~Brix）, vitamin C and color--through parameters L＊, a＊, b＊ and h0, Chrome （C＊） and color difference （AEL＊a＊b＊）. The experimental planning used presented significant differences at 5% of probability, showing that the model was adjusted to the data in accordance to F test, thus being possible to determine the best process conditions. In addition, the average results of the physicochemical parameters pointed out that the pulp used was in accordance with the patterns established by the quality and identity patterns for mango pulp. Moreover, it showed that the powder obtained had good physicochemical quality.展开更多
The enzymatic hydrolysis of cellulose is still considered as a main limiting step of the biological production of biofuels from ligno-cellulosic biomass. Glycoside hydrolases from Trichoderma reesei are currently used...The enzymatic hydrolysis of cellulose is still considered as a main limiting step of the biological production of biofuels from ligno-cellulosic biomass. Glycoside hydrolases from Trichoderma reesei are currently used to produce fermentable glucose units from degradation of cellulose packed in a complex assembly of cellulose microfibrils. The present work describes the structural evolution of two prototypical samples of cellulose (a micro-crystalline cellulose and a bleached sulfite pulp) over 5 length scale orders of magnitude. The results were obtained through wide angle, small angle and ultra-small angles synchrotron X-ray scattering, completed by Small Angle Neutron Scattering and particle size analyzers. These structural evolutions were followed as a function of enzymatic conversion. The results show that whereas there is no change at the nanometer scale, drastic changes occur at micron. The observed decrease of the size of the cellulose particles is accompanied by a smoothing of the crystalline surfaces that can be explained by a two-step mechanism of the enzymatic hydrolysis.展开更多
This paper presents an overview of the state of the art about the late effects of ionizing radiation on skeletal muscle, helping new research and showing unexplored areas. For this, it was evaluated the interest repor...This paper presents an overview of the state of the art about the late effects of ionizing radiation on skeletal muscle, helping new research and showing unexplored areas. For this, it was evaluated the interest reported by the scientific literature regarding the late effects in skeletal muscle resulting from exposure to ionizing radiation. Original and experimental papers mainly containing the key expressions “ionizing radiation” and “effects on skeletal muscle” were searched in computerized databases, and published in any language. Only 33 papers matched the search criteria. Analyzing the investigated radioinduced biological effects in those contributions, four topics were identified as being of major interest: 1) alterations in cellular metabolism and protein degradation;2) repercussions on satellite cells;3) formation of fibrosis and muscle atrophy;4) tissue regeneration. It was verified that no study evaluated possible late effects related to either morphology or properties of skeletal muscles after an exposure to ionizing radiation. Several aspects do not make possible a successful replication;all experiments of eligible group of articles are discussed, such as, lack of raw data, use of no sound methodology and inappropriate statistical technique. Briefly, the subject of this review is an open field of research.展开更多
The HyFrance Group was originally formed in France to support the European project HyWays, by providing （former projects HyFrancel and HyFrance2） the French data and possible hydrogen pathways according to national ...The HyFrance Group was originally formed in France to support the European project HyWays, by providing （former projects HyFrancel and HyFrance2） the French data and possible hydrogen pathways according to national specificities. HyFrance3 is a new project that focuses on the economic competitiveness of different steps of the hydrogen chain, from the production to end usage, at the time horizon of 2030 in France. The project is coordinated by CEA with the other partners being： ADEME （co-funding）, AFH2, CNRS, IFP, Air Liquide, EdF, GdF Suez, TOTAL, ALPHEA. The project is divided into 4 sub-projects, that address present and future French hydrogen industrial markets for chemical ＆ refinery uses, the analysis of the interplay between wind energy production and storage of hydrogen for different automotive requirements （refuelling stations, BtL plants, H2/NG mix）, massive hydrogen storage to balance various offer and demand characteristics, and the supply network （pipeline option competitiveness vs. trucked in supply） to distribute hydrogen in a French region for automotive applications. Technical and economical issues, as well as GHG emissions, are addressed.展开更多
As intrinsically carbon-free molecules,ammonia and hydrogen are considered as fuels for internal combustion engines,mainly for long-distance or off-road applications.These alternative fuels have different combustion c...As intrinsically carbon-free molecules,ammonia and hydrogen are considered as fuels for internal combustion engines,mainly for long-distance or off-road applications.These alternative fuels have different combustion characteristics,reactivity,and exhaust gas compositions compared to conventional fuels,raising questions about the suitability of lubricants in engines operating with them.The impact of ammonia,hydrogen,and their blends on lubricants in internal combustion engines is a relatively new topic,with few reference studies available.However,degradation processes of lubricants have been studied in the context of hydrocarbon fuels,and in compressors using ammonia as a refrigerant,for example.This work presents a review of the literature on engine oil degradation phenomena in relation to ammonia and hydrogen combustion characteristics.In particular,it highlights the current state of knowledge regarding compatibility with unburnt gases,elevated nitrogen oxide levels,and water.Additionally,it summarizes the latest insights into the contribution of lubricants to pollutant emissions.展开更多
The molecular simulations of the well-known high explosive β-HMX (cyclotetramethylene tetranitramine) anditsfluorine containing polymer-bonded explosives(PBXs) were carried out with the combination method of quantum ...The molecular simulations of the well-known high explosive β-HMX (cyclotetramethylene tetranitramine) anditsfluorine containing polymer-bonded explosives(PBXs) were carried out with the combination method of quantum mechanics, molecular mechanics and molecular dynamics. The atomic cluster model, containing the β-HMX molecule and the polymer molecule whose chain dimension was about the same as β-HMX’s, was fully optimized by AM1 and PM3 semi-empirical molecular orbital and molecular mechanical methods using COMPASS and PCFF force field. Then the calculated binding energy is found to be linearly correlated to each other. Molecular dynamics simulations using COM- PASS force field were performed for β-HMX crystal and the PBXs involving β-HMX and a series of fluorine containing polymers. Their elastic coefficients, moduli and Poisson’s ratios were calculated. It is found that the mechanical prop- erties of β-HMX can be effectively improved by blending with fluorine containing polymers in small amounts.展开更多
A methodology for kinetic modeling of conversion processes is presented.The proposed approach allows to overcome the lack of molecular detail of the petroleum fractions and to simulate the reactions of the process by ...A methodology for kinetic modeling of conversion processes is presented.The proposed approach allows to overcome the lack of molecular detail of the petroleum fractions and to simulate the reactions of the process by means of a two-step procedure.In the first step,a synthetic mixture of molecules representing the feedstock is generated via a molecular reconstruction method,termed SR-REM molecular reconstruction.In the second step,a kinetic Monte Carlo method,termed stochastic simulation algorithm(SSA),is used to simulate the effect of the conversion reactions on the mixture of molecules.The resulting methodology is applied to the Athabasca vacuum residue hydrocracking.An adequate molecular representation of the vacuum residue is obtained using the SR-REM algorithm.The reaction simulations present a good agreement with the laboratory data for Athabasca vacuum residue conversion.In addition,the proposed methodology provides the molecular detail of the vacuum residue conversion throughout the reactions simulations.展开更多
The study presented hereby investigates experimentally and with CFD simulations the gas distribution effect on the hydrodynamic of a Geldart Group A turbulent fluidized bed. Experiments were carried out on a cold flow...The study presented hereby investigates experimentally and with CFD simulations the gas distribution effect on the hydrodynamic of a Geldart Group A turbulent fluidized bed. Experiments were carried out on a cold flow fluidized bed column with an even and uneven gas distribution. Local solid volume fraction profiles were measured using optical probes at different bed heights and along two radial directions. Optical probe measurements allow catching a clear hydrodynamic difference between both even and uneven gas distributions. These results were then used to assess CFD simulations with the code Barracuda^(TM) (MP-PIC approach). It is noteworthy that the choice of drag correlation and boundary conditions strongly influences the agreement between the experimental and CFD results. Once the correct parameters are chosen, CFD simulations captured the effect of gas distribution changes.展开更多
文摘The pore size distribution is often an important parameter for transport processes in porous media.Cryoporometry experiments can provide such data in the meso and macropore size up to 1 mm providing the sample temperature is finely controlled.We use a Peltier based system inserted directly into the NMR probe to control the temperature within 0.05℃and impose temperature ramps down to 0.002℃/min,necessary to characterize the largest pore sizes.The pore size information in the macropore range cannot be obtained from gas adsorption techniques while mercury injection is questionable for the material considered here.For porous materials made of paramagnetic minerals such as lithium-iron phosphate(LiFePO_(4),LFP)or nickel-manganese-cobalt oxides(NMC)and saturated with octamethylcyclotetrasiloxane(OMCTS),the T_(2)relaxation times are very short such as protons from the liquid and frozen phases cannot be separated.Hence the usual cryoporometry experiment cannot be performed.Instead,we propose to use the T_(1)contrast to separate these phases.The method is studied in detail along with some temperature effects linked with the T_(1)variation of the bulk frozen OMCTS.We show an example on two cathode materials part of industrial battery product.
文摘Colloidal transport and deposition in porous media are complex processes that result from the interaction between hydrodynamics(velocity,pore geometry,etc.)and Derjaguin-Landau-Verwey-Overbeek(DLVO)forces(particle-particle and particle-surface).They have important implications for engineering applications involving the reinjection of a fluidinto a medium,such as geothermal energy.The investigation of permeability stability is critical to ensure the sustainability of activities.This work aims to study the clogging mechanisms in a rock-like porous medium using a microfluidicdevice.The pore-throat network distributions reveal that the micromodel geometry mimics real rock samples.The transport of a monodispersed suspension is studied at different concentrations.Image analysis,velocity fieldmodeling,and pressure drop measurement are used to assess preferential clogging sites and porous medium permeability reduction,respectively.Experiments have shown that retention sites are located around preferential flow paths with relatively high flow velocities.When clogged,the pore thresholds are the deposition zones that lead to a reduction in permeability.However,pore bodies may also constitute deposition zones.Interestingly,as the concentration of the suspension increases,the kinetics of the permeability reduction are delayed,and the clogging mechanisms,as well as the type of deposit,evolve.Finally,at very high concentrations,the effects of hydrodynamic stripping are more important.These observations emphasize the role of the porous medium geometry in colloidal transport and deposition and thus permeability reduction.
文摘Characterization and optimization of physical and chemical properties of drilling fluids are critical for the efficiency and success of drilling operations.In particular,maintaining the optimal levels of solids content is essential for achieving the most effective fluid performance.Proper management of solids content also reduces the risk of tool failures.Traditional solids content analysis methods,such as retort analysis,require substantial human intervention and time,which can lead to inaccuracies,time-management issues,and increased operational risks.In contrast to human-intensive methods,machine learning may offer a viable alternative for solids content estimation due to its pattern-recognition capability.In this study,a large set of laboratory reports of drilling-fluid analyses from 130 oil wells around the world were compiled to construct a comprehensive data set.The relationships among various rheological parameters were analyzed using statistical methods and machine learning algorithms.Several machine learning algorithms of diverse classes,namely linear(linear regression,ridge regression,and ElasticNet regression),kernel-based(support vector machine)and ensemble tree-based(gradient boosting,XGBoost,and random forests)algorithms,were trained and tuned to estimate solids content from other readily available drilling fluid properties.Input variables were kept consistent across all models for interpretation and comparison purposes.In the final stage,different evaluation metrics were employed to evaluate and compare the performance of different classes of machine learning models.Among all algorithms tested,random forests algorithm was found to be the best predictive model resulting in consistently high accuracy.Further optimization of the random forests model resulted in a mean absolute percentage error(MAPE)of 3.9%and 9.6%and R^(2) of 0.99 and 0.93 for the training and testing sets,respectively.Analysis of residuals,their histograms and Q-Q normality plots showed Gaussian distributions with residuals that are scattered around a mean of zero within error ranges of±1%and±4%,for training and testing,respectively.The selected model was further validated by applying the rheological measurements from mud samples taken from an offshore well from the Gulf of Mexico.The model was able to estimate total solids content in those four mud samples with an average absolute error of 1.08% of total solids content.The model was then used to develop a web-based graphical-user-interface(GUI)application,which can be practically used at the rig site by engineers to optimize drilling fluid programs.The proposed model can complement automation workflows that are designed to measure fundamental rheological properties in real time during drilling operations.While a standard retort test can take approximately 2 h at the rig site,such kind of real-time estimations can help the rig personnel to timely optimize drilling fluids,with a potential of saving 2920 man-hours in a given year for a single drilling rig.
基金E.L.,K.L.,P.W.,and S.T.are supported by the SCCER-Heat and Energy Storage program
文摘Cu/ZrO2/SiO2 are efficient catalysts for the selective hydrogenation of CO2 to CH3OH. In order to understand the role of ZrO2 in these mixed-oxides based catalysts, in situ X-ray absorption spectroscopy has been carried out on the Cu and Zr K-edge. Under reaction conditions, Cu remains metallic, while Zr is present in three types of coordination environment associated with 1) bulk ZrO2, 2) coordinatively saturated and 3) unsaturated Zr(Ⅳ) surface sites. The amount of coordinatively unsaturated Zr surface sites can be quantified by linear combination fit of reference X-Ray absorption near edge structure (XANES) spectra and its amount correlates with CH3OH formation rates, thus indicating the importance of Zr(Ⅳ) Lewis acid surface sites in driving the selectivity toward CH3OH. This finding is consistent with the proposed mechanism, where CO2 is hydrogenated at the interface between the Cu nanoparticles that split H2 and Zr(Ⅳ) surface sites that stabilizes reaction intermediates.
基金supported by a grant from the French National Ministry of Education and Research(MENSR,19755-2005)
文摘A high-order leap-frog based non-dissipative discontinuous Galerkin time- domain method for solving Maxwell＇s equations is introduced and analyzed. The pro- posed method combines a centered approximation for the evaluation of fluxes at the in- terface between neighboring elements, with a Nth-order leap-frog time scheme. More- over, the interpolation degree is defined at the element level and the mesh is refined locally in a non-conforming way resulting in arbitrary level hanging nodes. The method is proved to be stable under some CFL-like condition on the time step. The convergence of the semi-discrete approximation to Maxwelrs equations is established rigorously and bounds on the global divergence error are provided. Numerical experiments with high- order elements show the potential of the method.
文摘Enzymatic hydrolysis of lignocellulose is often considered to be the major economic bottleneck of the production process of bioethanol from lignocellulose. It is generally admitted that the most efficient organism for the production ofcellulolytic enzymes is the fungus Trichoderma reesei, mostly due to its high secretion capacity. Unfortunately, this fungus secretes very low concentrations of β-glucosidase, thereby often requiring β-glucosidase supplementation for complete cellulose hydrolysis. It is especially important to have sufficient quantities of β-glucosidase in order to prevent inhibition of cellobiohydrolases by cellobiose. In order to optimize the produced cocktail, a more efficient β-glucosidase was cloned into T. reesei CL847 strain. The new strain, called CL847 TR3002, secretes the evolved β-glucosidase and was tested for cellulase production in laboratory-scale reactors. Its growth kinetics and cellulase production were characterized using fed-batch and chemostat modes under various culture conditions. The cellulase activities of the evolved strain were compared with activities of the parent strain. In addition, hydrolysis of a steam exploded wheat straw was performed at three different enzyme-loading levels （5 mg/g, 10 mg/g and 20 mg/g of dry matter） and a new kinetic model was developed.
文摘Transmission electron microscopy and surface- and bulk-sensitive spectroscopic methods were used to study the morphology and the electronic structure of a hybrid organic-inorganic system composed of gold nanoparticles （NP＇s） which were distributed in an organic matrix. Au atoms deposited onto a copper phthalocyanine （CuPc） surface diffuse into the organic matrix and self-assemble in well defined NP＇s with metallic properties. No formation of a continuous metallic Au film on top of the CuPc film is observed up to nominal coverages as large as 130 A.
文摘Mango is a widely cultivated and consumed fruit in Brazil and one of the most important alternatives to take advantage of the production excess is dehydration. Therefore, this work aims at establishing better operational conditions for ＂spray-drying＂ processes, in order to obtain the powder of mango pulp by means of a rotational central compounded planning, and also at carrying out the physicochemical characterization of both the integral mango pulp and the powder obtained from the operational conditions mentioned above. Both integral mango pulp and powder were analyzed as for the following physicochemical characteristics： humidity, pH, titratable acidity, soluble solids （~Brix）, vitamin C and color--through parameters L＊, a＊, b＊ and h0, Chrome （C＊） and color difference （AEL＊a＊b＊）. The experimental planning used presented significant differences at 5% of probability, showing that the model was adjusted to the data in accordance to F test, thus being possible to determine the best process conditions. In addition, the average results of the physicochemical parameters pointed out that the pulp used was in accordance with the patterns established by the quality and identity patterns for mango pulp. Moreover, it showed that the powder obtained had good physicochemical quality.
基金financial support from ADEME for a doctoral fellowship to M.C.is gratefully acknowledged
文摘The enzymatic hydrolysis of cellulose is still considered as a main limiting step of the biological production of biofuels from ligno-cellulosic biomass. Glycoside hydrolases from Trichoderma reesei are currently used to produce fermentable glucose units from degradation of cellulose packed in a complex assembly of cellulose microfibrils. The present work describes the structural evolution of two prototypical samples of cellulose (a micro-crystalline cellulose and a bleached sulfite pulp) over 5 length scale orders of magnitude. The results were obtained through wide angle, small angle and ultra-small angles synchrotron X-ray scattering, completed by Small Angle Neutron Scattering and particle size analyzers. These structural evolutions were followed as a function of enzymatic conversion. The results show that whereas there is no change at the nanometer scale, drastic changes occur at micron. The observed decrease of the size of the cellulose particles is accompanied by a smoothing of the crystalline surfaces that can be explained by a two-step mechanism of the enzymatic hydrolysis.
文摘This paper presents an overview of the state of the art about the late effects of ionizing radiation on skeletal muscle, helping new research and showing unexplored areas. For this, it was evaluated the interest reported by the scientific literature regarding the late effects in skeletal muscle resulting from exposure to ionizing radiation. Original and experimental papers mainly containing the key expressions “ionizing radiation” and “effects on skeletal muscle” were searched in computerized databases, and published in any language. Only 33 papers matched the search criteria. Analyzing the investigated radioinduced biological effects in those contributions, four topics were identified as being of major interest: 1) alterations in cellular metabolism and protein degradation;2) repercussions on satellite cells;3) formation of fibrosis and muscle atrophy;4) tissue regeneration. It was verified that no study evaluated possible late effects related to either morphology or properties of skeletal muscles after an exposure to ionizing radiation. Several aspects do not make possible a successful replication;all experiments of eligible group of articles are discussed, such as, lack of raw data, use of no sound methodology and inappropriate statistical technique. Briefly, the subject of this review is an open field of research.
文摘The HyFrance Group was originally formed in France to support the European project HyWays, by providing （former projects HyFrancel and HyFrance2） the French data and possible hydrogen pathways according to national specificities. HyFrance3 is a new project that focuses on the economic competitiveness of different steps of the hydrogen chain, from the production to end usage, at the time horizon of 2030 in France. The project is coordinated by CEA with the other partners being： ADEME （co-funding）, AFH2, CNRS, IFP, Air Liquide, EdF, GdF Suez, TOTAL, ALPHEA. The project is divided into 4 sub-projects, that address present and future French hydrogen industrial markets for chemical ＆ refinery uses, the analysis of the interplay between wind energy production and storage of hydrogen for different automotive requirements （refuelling stations, BtL plants, H2/NG mix）, massive hydrogen storage to balance various offer and demand characteristics, and the supply network （pipeline option competitiveness vs. trucked in supply） to distribute hydrogen in a French region for automotive applications. Technical and economical issues, as well as GHG emissions, are addressed.
文摘As intrinsically carbon-free molecules,ammonia and hydrogen are considered as fuels for internal combustion engines,mainly for long-distance or off-road applications.These alternative fuels have different combustion characteristics,reactivity,and exhaust gas compositions compared to conventional fuels,raising questions about the suitability of lubricants in engines operating with them.The impact of ammonia,hydrogen,and their blends on lubricants in internal combustion engines is a relatively new topic,with few reference studies available.However,degradation processes of lubricants have been studied in the context of hydrocarbon fuels,and in compressors using ammonia as a refrigerant,for example.This work presents a review of the literature on engine oil degradation phenomena in relation to ammonia and hydrogen combustion characteristics.In particular,it highlights the current state of knowledge regarding compatibility with unburnt gases,elevated nitrogen oxide levels,and water.Additionally,it summarizes the latest insights into the contribution of lubricants to pollutant emissions.
基金the National Natural Science Foundation of China(Grant Nos.10176012 and 20173028).
文摘The molecular simulations of the well-known high explosive β-HMX (cyclotetramethylene tetranitramine) anditsfluorine containing polymer-bonded explosives(PBXs) were carried out with the combination method of quantum mechanics, molecular mechanics and molecular dynamics. The atomic cluster model, containing the β-HMX molecule and the polymer molecule whose chain dimension was about the same as β-HMX’s, was fully optimized by AM1 and PM3 semi-empirical molecular orbital and molecular mechanical methods using COMPASS and PCFF force field. Then the calculated binding energy is found to be linearly correlated to each other. Molecular dynamics simulations using COM- PASS force field were performed for β-HMX crystal and the PBXs involving β-HMX and a series of fluorine containing polymers. Their elastic coefficients, moduli and Poisson’s ratios were calculated. It is found that the mechanical prop- erties of β-HMX can be effectively improved by blending with fluorine containing polymers in small amounts.
文摘A methodology for kinetic modeling of conversion processes is presented.The proposed approach allows to overcome the lack of molecular detail of the petroleum fractions and to simulate the reactions of the process by means of a two-step procedure.In the first step,a synthetic mixture of molecules representing the feedstock is generated via a molecular reconstruction method,termed SR-REM molecular reconstruction.In the second step,a kinetic Monte Carlo method,termed stochastic simulation algorithm(SSA),is used to simulate the effect of the conversion reactions on the mixture of molecules.The resulting methodology is applied to the Athabasca vacuum residue hydrocracking.An adequate molecular representation of the vacuum residue is obtained using the SR-REM algorithm.The reaction simulations present a good agreement with the laboratory data for Athabasca vacuum residue conversion.In addition,the proposed methodology provides the molecular detail of the vacuum residue conversion throughout the reactions simulations.
基金the Project“Programma di scambi internazionali con Universitàe Istituti di Ricerca Stranieri per la Mobilitàdi breve durata di Docenti,Studiosi e Ricercatori”promoted and funded by Universitàdegli Studi di Napoli Federico II.
文摘The study presented hereby investigates experimentally and with CFD simulations the gas distribution effect on the hydrodynamic of a Geldart Group A turbulent fluidized bed. Experiments were carried out on a cold flow fluidized bed column with an even and uneven gas distribution. Local solid volume fraction profiles were measured using optical probes at different bed heights and along two radial directions. Optical probe measurements allow catching a clear hydrodynamic difference between both even and uneven gas distributions. These results were then used to assess CFD simulations with the code Barracuda^(TM) (MP-PIC approach). It is noteworthy that the choice of drag correlation and boundary conditions strongly influences the agreement between the experimental and CFD results. Once the correct parameters are chosen, CFD simulations captured the effect of gas distribution changes.
