Heterogeneously catalyzed hydrolytic dehydrogenation of ammonia borane is a remarkable structure sensitive reaction. In this work, a strategy by using polyoxometalates(POMs) as the ligands is proposed to engineer the ...Heterogeneously catalyzed hydrolytic dehydrogenation of ammonia borane is a remarkable structure sensitive reaction. In this work, a strategy by using polyoxometalates(POMs) as the ligands is proposed to engineer the surface and electronic properties of Pt/CNT catalysts toward the enhanced hydrogen generation rate and durability. Three kinds of POMs, i.e., silicotungstic acid(STA), phosphotungstic acid(PTA)and molybdophosphoric acid(PMA), are comparatively studied, among which the STA shows positive effects on the catalytic activity and durability. A catalyst structure-performance relationship is established by a combination of kinetic and isotopic analyses with multiple characterization techniques, such as HAADF-STEM, EDS, Raman spectroscopy and XPS. It is shown that the STA compared to the other two POMs can increase the Pt binding energy and thus promote the reaction. The insights demonstrated here could open a new avenue for boosting the reaction by employing the POMs as the ligands to engineer the catalyst electronic properties.展开更多
Double fortified salt containing both potassium iodate and ferrous fumarate microcapsules was produced at an Indian commercial facility. The packaged product became discolored, turning yellow, to a degree that would i...Double fortified salt containing both potassium iodate and ferrous fumarate microcapsules was produced at an Indian commercial facility. The packaged product became discolored, turning yellow, to a degree that would impact consumer acceptance. Therefore, there was a need for an investigation into the cause and possible remedy for this discoloration. The components of the fortified salt product, storage conditions, and processing characteristics were taken into consideration. Canadian and Indian salt samples were prepared unfortified as well as with iodine and/or iron microcapsules;stored at 25°C and 45°C in glass, polyethylene, or commercial polymer film. Some samples were heat treated prior to storage. Salt samples containing iodine that were heated before storage in packaging material turned yellow in color. From this study, it was found that due to heat and the presence of a sacrificial antioxidant component in the packaging film, potassium iodate was reduced to elemental iodine (I<sub>2</sub>) turning packaged salt samples to a yellow/orange color. Hence it is recommended that in the manufacture of foods containing potassium iodate, the packaging material selected should be free from readily accessible antioxidants.展开更多
A three-dimensional direct numerical simulation is carried out to predict the surface oscillation and flow structure of isothermal liquid bridges of 5 cSt silicone oil held vertically between solid disks. By subjectin...A three-dimensional direct numerical simulation is carried out to predict the surface oscillation and flow structure of isothermal liquid bridges of 5 cSt silicone oil held vertically between solid disks. By subjecting liquid bridges to various horizontal vibrations, the surface resonance frequencies are clearly determined numerically and compared well with the existing analytical model predictions. The investigation on the flow structure inside the liquid bridge reveals, for the first time, the flow structure and the existence of transw',rsal vortices inside the liquid bridge when a horizontal vibration is applied.展开更多
Froth flotation is an essential processing technique for upgrading low-grade ores.Flotation separation would not be efficient without chemical surfactants(collectors,depressants,frothers,etc.).Depressants play a criti...Froth flotation is an essential processing technique for upgrading low-grade ores.Flotation separation would not be efficient without chemical surfactants(collectors,depressants,frothers,etc.).Depressants play a critical role in the selective separation of minerals in that they deactivate unfavorable mineral surfaces and hinder them from floating into the flotation concentration zone.Pyrite is the most common and challenging sulfide gangue,and its conventional depressants could be highly harmful to nature and humans.Therefore,using available,affordable,eco-friendly polymers to assist or replace hazardous reagents is mandatory for a green transition.Polysaccharide-based(starch,dextrin,carboxymethyl cellulose,guar gum,etc.)polymers are one of the most used biodegradable depressant groups for pyrite depression.Despite the satisfactory flotation results obtained using these eco-friendly depressants,several gaps still need to be addressed,specifically in investigating surface interactions,adsorption mechanisms,and parameters affecting their depression performance.As a unique approach,this review comprehensively discussed previously conducted studies on pyrite depression with polysaccharide-based reagents.Additionally,practical suggestions have been provided for future assessments and developments of polysaccharide-based depressants,which pave the way to green flotation.This robust review also explored the depression efficiency and various adsorption aspects of naturally derived depressants on the pyrite surface to create a possible universal trend for each biodegradable depressant derivative.展开更多
Traffic-related pollutants adversely affect air quality, especially in regions near major roadways. The vehicleinduced turbulence(VIT) is a significant factor that controls the initial dilution, dispersion, and ultima...Traffic-related pollutants adversely affect air quality, especially in regions near major roadways. The vehicleinduced turbulence(VIT) is a significant factor that controls the initial dilution, dispersion, and ultimately the chemical and physical fate of pollutants by altering the conditions in the microenvironment. This study used a computational fluid dynamics(CFD) software FLUENT to model the vehicle-induced turbulence(VIT) generated on roadways, with a focus on impact of vehicle-vehicle interactions, traffic density and vehicle composition on turbulent kinetic energy(TKE). We show, for the first time, that the overall TKE from multiple vehicles traveling in series can be estimated by superimposing the TKE of each vehicle, without considering the distance between them while the distance is greater than one vehicle length. This finding is particularly significant since it enables a new approach to VIT simulations where the overall TKE is calculated as a function of number of vehicles. We found that the interactions between vehicles traveling next to each other in adjacent lanes are insignificant,regardless the directions of the traffic flow. Consequently, simulations of different traffic scenarios can be substantially simplified by treating two-way traffic as one-way traffic, with less than 5% difference in the overall volume-averaged TKE. We also developed equations that allow the estimation of the overall volume-averaged TKE as a function of the number and the type of vehicles.展开更多
Searching for alternative energy sources continues to grow in recent times due to the fear of energy insecurity in the near future and environmental and sociopolitical issues associated with the use of fossil fuel. Am...Searching for alternative energy sources continues to grow in recent times due to the fear of energy insecurity in the near future and environmental and sociopolitical issues associated with the use of fossil fuel. Among the renewable energy sources, biomass is the only source that has carbon in its building blocks which can be processed to liquid fuel. In this study, pyrolysis of oil palm residues (trunk, frond and empty fruit bunch) was carried out in a fixed bed tubular reactor under nitrogen atmosphere at 30 mL/min, 30?C/min heating rate and 600?C reaction temperature. Pyrolysis products (bio-oil, bio-char and non-condensable gas) were characterized. Water content, acidity (pH), higher heating value (HHV) and oxygen content of the bio-oil varied between 39.28 - 43 wt%, 2.92 - 3.20, 19.29 - 21.92 MJ/kg and 58.47 - 59.85 wt% respectively. Low pH, highwater and oxygen contents in the oil make it unsuitable for being used as fuel and therefore require upgrading. Scanning electron microscopy and ultimate analysis of the bio-char suggests that it is a porous material and consists mainly carbon between 82.22 - 84.96 wt% and has HHV in the range of 25.98 - 27.65 MJ/kg. This may be used as solid biofuel, adsorbent and source of carbon. High percentage of hydrogen (H2) and carbon monoxide (CO) were observed in the non-condensable gas which may be processed to transportation fuel via Fisher-Tropsch process. Oil palm residues represent good source of renewable energy when all the pyrolysis products are efficiently utilized.展开更多
Atmospheric carbon dioxide concentration [CO2],incoming solar radiation and sea ice coverage are among the most important factors that control the global climate.By applying the simple cell-to-cell mapping technique t...Atmospheric carbon dioxide concentration [CO2],incoming solar radiation and sea ice coverage are among the most important factors that control the global climate.By applying the simple cell-to-cell mapping technique to a simplified atmosphere-ocean-sea ice feedback climate model,effects of these factors on the stability of the climatic system are studied.The current climatic system is found to be stable but highly nonlinear.The resiliency of stability increases with [CO2] to a summit when [CO2] reaches 290 μL/L which is comparable to the pre-industrial level,suggesting carbon dioxide is essential to the stability of the global climate.With [CO2] rising further,the global climate stability decreases,the mean ocean temperature goes up and the sea ice coverage shrinks in the polar region.When the incoming solar radiation is intensified,the ice coverage gradually diminishes,but the mean ocean temperature remains relatively constant.Overall,our analysis suggests that at the current levels of three external factors the stability of global climate is highly resilient.However,there exists a possibility of extreme states of climate,such as a snow-ball earth and an ice-free earth.展开更多
The main purpose of this study was to optimize microwave assisted alkaline extraction of the hemicellulose, xylan, from birch wood. The simultaneous effects of process variables such as time (10 - 30 minutes), concent...The main purpose of this study was to optimize microwave assisted alkaline extraction of the hemicellulose, xylan, from birch wood. The simultaneous effects of process variables such as time (10 - 30 minutes), concentration of sodium hydroxide solution (4 - 8 wt%), solid to liquid ratio (1:8 to 1:20, g:mL), and sample size (5 - 10 g) on the temperature of the wood slurry, wood dissolution, and yield of extraction were evaluated. A central composite design (CCD) and response surface methodology (RSM) were used for the optimization of the extraction process. Based on the CCD, quadratic models were developed to correlate the extraction process variables with the responses such as temperature of wood slurry, wood dissolution, and yield of xylan and the models were analyzed using appropriate statistical methods (ANOVA). Statistical analysis showed that all the models developed were found to be adequate for the prediction of the respective responses. Optimization of the process was performed using a numerical optimization available in the software to maximize the yield of xylan and the optimum process variables for the maximum yield of xylan was found to be: 10 g of wood fibres, 8 wt% of NaOH solution, 1:10 solid to liquid ratio (g:mL) and 25 minutes of irradiation time. About 72.5% of the xylan present in the birch wood was extracted using the optimized extraction parameters.展开更多
A nanostructured gold-silver soaked in polyethylene glycol 400 (Au-Ag@PEG) is designed using gold(I) chloride and silver nitrate (AgNO3) as precursors and, polyethylene glycol 400 (PEG) as capping agent. The result of...A nanostructured gold-silver soaked in polyethylene glycol 400 (Au-Ag@PEG) is designed using gold(I) chloride and silver nitrate (AgNO3) as precursors and, polyethylene glycol 400 (PEG) as capping agent. The result of the structure characterization using Selected Area Electron Diffraction (SAED) has showed that the synthesized nanomaterial has a good crystallinity while Transmission Electron Microscopy (TEM), energy dispersive X-ray spectrometry (EDX) and Dynamic Light Scattering (DLS) measurements suggest mixed Au-Ag nanoparticles with an average diameter size of around 7 nm and 30 nm for Au and Ag respectively.展开更多
The aim of this study was to evaluate the effect of chewing simulation on wear of artificial enamel abraded against zirconia-based crowns. Fifteen crown preparations were scanned for the manufacturing of crowns using ...The aim of this study was to evaluate the effect of chewing simulation on wear of artificial enamel abraded against zirconia-based crowns. Fifteen crown preparations were scanned for the manufacturing of crowns using computer-aided-design/computer-aided-machining technique (CAD/CAM), according to the following (n = 5): Polished (PM) and glazed (GM) monolithic zirconia (1.5 mm uniform thickness), and Bilayer (BL - 0.8 mm zirconia coping, 0.7 mm porcelain veneer) crowns. The samples were cemented and chewing simulation (2.5 million cycles/0-80N/artificial saliva/37°C) was performed with steatite indenters (6 mm diameter) as antagonists. Assuming the uniformity of the unaged samples, antagonists were scanned using a surface profilometer and the material loss volume was calculated. Roughness of the crowns’ occlusal surface was also analyzed using the profilometer. Scanning electron microscopy was used to characterize the abraded surface. One-way ANOVA and Tukey test (p = 0.05) were employed for analysis of wear results. A significant difference was observed among the groups (p 3 ± 0.015) than those abraded against monolithic zirconia, polished (PM - 0.167 mm3 ± 0.02) and glazed (0.101 mm3 ± 0.03), which were similar to each other. Veneering porcelain results in more pronounced wear of the artificial enamel than monolithic zirconia. However, mastication against monolithic Y-TZP also imposes wear to the opposing teeth.展开更多
The dry deposition process refers to the flux loss of an atmospheric pollutant due to uptake of the pollutant by the earth’s surfaces.Dry deposition flux of a chemical species is typically calculated as the product o...The dry deposition process refers to the flux loss of an atmospheric pollutant due to uptake of the pollutant by the earth’s surfaces.Dry deposition flux of a chemical species is typically calculated as the product of its surface-layer concentration and its dry deposition velocity(V_(d)).Field measurement based V_(d) data are very scarce or do not exist for many chemical species considered in chemistry transport models.In the present study,gaseous and particulate dry deposition schemes were applied to generate a database of hourly V_(d) for 45 gaseous species and three particle size ranges for two years(2016–2017)at a 15 kmby 15 km horizontal resolution across North America.Hourly V_(d) of the 45 gaseous species ranged from<0.001 to 4.6 cm/sec across the whole domain,with chemical species-dependentmedian(mean)values being in the range of 0.018–1.37 cm/sec(0.05–1.43 cm/sec).The spatial distributions of the two-year average V_(d) showed values higher than 1–3 cm/sec for those soluble and reactive species over certain land types.Soluble species have the highest V_(d) over water surfaces,while insoluble but reactive species have the highest V_(d) over forests.Hourly V_(d) of PM_(2.5) across the whole domain ranged from 0.039 to 0.75 cm/sec with median(mean)value of 0.18(0.20)cm s^(−1),while the mean V_(d) for PM_(2.5)–10 is twice that of PM_(2.5).Uncertainties in the modeled V_(d) are typically on the order of a factor of 2.0 or larger,which needs to be considered when applying the dataset in other studies.展开更多
Generating hydrogen gas from biomass is one approach to lowering dependencies on fossil fuels for energy and chemical feedstock, as well as reducing greenhouse gas emissions. Using both equilibrium simulations and bat...Generating hydrogen gas from biomass is one approach to lowering dependencies on fossil fuels for energy and chemical feedstock, as well as reducing greenhouse gas emissions. Using both equilibrium simulations and batch experiments with NaOH as a model alkaline, this study established the technical feasibility of converting various biomasses (e.g., glucose, cellulose, xylan and lignin) into H2-rich gas via catalyst-free, alkali-thermal gasification at moderate temperatures (as low as 300℃). This process could produce more H2 with less carbon-containing gases in the product than other comparable methods. It was shown that alkali-thermal gasification follows CxHyO2 + 2xNaOH + (x-z)H20 = (2x+y/2-z)H2 +xNa2CO3, with carbonate being the solid product which is different from the one suggested in the literature. Moreover, the concept of hydrogen genera- tion potential (H2-GP)-the maximum amount of H2 that a biomass can yield, was introduced. For a given biomass CxHyO2, the H2-GP would be (2x + y/2-z) moles of H2. It was demonstrated experimentally that the H2-GP was achievable by adjusting the amounts of H20 and NaOH, temperature and pressure. Keywords hydrogen generation potential, biomass, lignocellulose, alkali-thermal gasification, sodium hydroxide展开更多
The work studied a non-catalytic upgrading of fast pyrolysis bio-oil by blending under supercritical conditions using methanol,ethanol and isopropanol as solvent and hydrogen donor.Characterisation of the bio-oil and ...The work studied a non-catalytic upgrading of fast pyrolysis bio-oil by blending under supercritical conditions using methanol,ethanol and isopropanol as solvent and hydrogen donor.Characterisation of the bio-oil and the upgraded bio-oils was carried out including moisture content,elemental content,pH,heating value,gas chromatography-mass spectrometry(GCMS),Fourier transform infrared radiation,13C nuclear magnetic resonance spectroscopy,and thermogravimetric analysis to evaluate the effects of blending and supercritical reactions.The GCMS analysis indicated that the supercritical methanol reaction removed the acids in the bio-oil consequently the pH increased from 2.39 in the crude bio-oil to 4.04 after the supercritical methanol reaction.The ester contents increased by 87.49% after the supercritical methanol reaction indicating ester formation could be the major deacidification mechanism for reducing the acidity of the bio-oil and improving its pH value.Simply blending crude bio-oil with isopropanol was effective in increasing the C and H content,reducing the O content and increasing the heating value to 27.55 from 17.51 MJ·kg^-1 in the crude bio-oil.After the supercritical isopropanol reaction,the heating value o f the liquid product slightly further increased to 28.85 MJ·kg^-1.展开更多
Biochar is traditionally used as solid fuel and for soil amendment where its electrical conductivity is largely irrelevant and unexplored.However,electrical conductivity is critical to biochar’s performance in new ap...Biochar is traditionally used as solid fuel and for soil amendment where its electrical conductivity is largely irrelevant and unexplored.However,electrical conductivity is critical to biochar’s performance in new applications such as supercapacitor energy storage and capacitive deionization of water.In this study,sugar maple and white pine were carbonized via a slow pyrolysis process at 600,800 and 1000°C and conductivities of monolithic biochar samples along the radial direction were measured using the 4-probe method.Biochars were characterized using an elemental analyzer,scanning electron microscopy,X-ray diffraction and Raman spectroscopy.The solid carbon in biochar samples was found to consist primarily of disordered carbon atoms with small graphitic nanocrystallites that grow with increasing temperature.The bulk conductivity of biochar was found to increase with pyrolysis temperature-1 to~1000 S/m for maple and 1 to~350 S/m for pine,which was accompanied by an increase in carbon content-91 to 97 wt%and 90 to 96 wt%for maple and pine,respectively.The skeletal conductivity of biochar samples carbonized at 1000°C is about 3300 S/m and 2300 S/m for maple and pine,respectively(assuming solid carbon is amorphous);both values are above that of amorphous carbon(1250-2000 S/m).This work demonstrated the importance of carbonization and graphitization to electrical conductivity and suggested electron hopping as a likely mechanism for electric conduction in biochar-an amorphous carbon matrix embedded with graphitic nanocrystallites.展开更多
Gold 3D cylindrical nanoelectrode ensembles (NEEs), 100 nm in diameter and 500 nm in length were prepared by electroless template synthesis in polycarbonate filter membranes, followed by selective controlled chemica...Gold 3D cylindrical nanoelectrode ensembles (NEEs), 100 nm in diameter and 500 nm in length were prepared by electroless template synthesis in polycarbonate filter membranes, followed by selective controlled chemical etching. The morphology of the nanowires and cylindrical NEEs was imaged by scanning electron microscopy. The protruding nanoelectrodes were in good parallel order. EDX study showed that the nanoelectrode elements consisted of pure gold. The electrochemical evaluation of the 3D electrodes was conducted using the well known [Fe(CN)6]^3-/[Fe(CN)6]^4- couple. Cyclic voltammgrams (CV) show a very low double layer charging current and a higher ratio of signal to background current than 2D disc NEEs. Electrochemical impedance spectroscopy (EIS) indicates that the 3D cylindrical NEEs effectively accelerate the charge transfer process, which is in consistent with the results of CV. The linear relationship with a slope of 0.5 between lg Ipc and lg v shows that linear diffusion is dominant on the 3D cylindrical NEEs at conventional scan rates.展开更多
Objectives:This study evaluates factors responsible for the floating of iron premix in double fortified salt(DFS),which initially affected the large-scale implementation of the salt fortification program in India,and ...Objectives:This study evaluates factors responsible for the floating of iron premix in double fortified salt(DFS),which initially affected the large-scale implementation of the salt fortification program in India,and provides solutions to the scale-up of the technology.Materials and Methods:To mitigate this time-sensitive scale-up challenge.First,the iron premix samples were obtained from the industrial scale-up pilot studies in India,evaluated for the impact of the amount of coating material(5 per cent,7.5 per cent,and 10 per cent(in weight)),type of formulation(soy stearin,SEPIFILM and hydroxypropyl methylcellulose),amount of titanium dioxide(25-35 per cent(in weight))used for color masking;Second,we studied the effect of change in the composition of the coating,from 10 per cent(in weight)soy stearin to a double coat with 5 per cent(in weight)hydroxypropyl methylcellulose and 5 per cent soy stearin or 10 per cent soy stearin and 1 per cent(in weight)lecithin mixture,on particle density,floating or sinking property of the iron premix,and on the stability of iodine in the DFS.Results:It was observed that the hydrophobic nature and the amount of soy stearin used for coating caused the floating issue.The double coating with 5 per cent hydroxypropyl methylcellulose and 5 per cent soy stearin was preferred because lecithin in soy stearin enhanced the moisture-aided adverse interaction between iron and iodine.Shelf-life storage studies proved over 80 per cent iodine retention after 12 months of storage in the DFS formulated with iron premix double-coated with hydroxypropyl methylcellulose and soy stearin.Conclusion:This proffered solution enabled the full implementation of the double fortification program in India.展开更多
基金supported by the National Natural Science Foundation of China(21776077)the Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learning+3 种基金the Shanghai Rising-Star Program(17QA1401200)the Open Project of SKLOCE(SKL-Che-15C03)the Shanghai Natural Science Foundation(17ZR1407300 and 17ZR1407500)the State Key Laboratory of Organic-Inorganic Composites(oic201801007)。
文摘Heterogeneously catalyzed hydrolytic dehydrogenation of ammonia borane is a remarkable structure sensitive reaction. In this work, a strategy by using polyoxometalates(POMs) as the ligands is proposed to engineer the surface and electronic properties of Pt/CNT catalysts toward the enhanced hydrogen generation rate and durability. Three kinds of POMs, i.e., silicotungstic acid(STA), phosphotungstic acid(PTA)and molybdophosphoric acid(PMA), are comparatively studied, among which the STA shows positive effects on the catalytic activity and durability. A catalyst structure-performance relationship is established by a combination of kinetic and isotopic analyses with multiple characterization techniques, such as HAADF-STEM, EDS, Raman spectroscopy and XPS. It is shown that the STA compared to the other two POMs can increase the Pt binding energy and thus promote the reaction. The insights demonstrated here could open a new avenue for boosting the reaction by employing the POMs as the ligands to engineer the catalyst electronic properties.
文摘Double fortified salt containing both potassium iodate and ferrous fumarate microcapsules was produced at an Indian commercial facility. The packaged product became discolored, turning yellow, to a degree that would impact consumer acceptance. Therefore, there was a need for an investigation into the cause and possible remedy for this discoloration. The components of the fortified salt product, storage conditions, and processing characteristics were taken into consideration. Canadian and Indian salt samples were prepared unfortified as well as with iodine and/or iron microcapsules;stored at 25°C and 45°C in glass, polyethylene, or commercial polymer film. Some samples were heat treated prior to storage. Salt samples containing iodine that were heated before storage in packaging material turned yellow in color. From this study, it was found that due to heat and the presence of a sacrificial antioxidant component in the packaging film, potassium iodate was reduced to elemental iodine (I<sub>2</sub>) turning packaged salt samples to a yellow/orange color. Hence it is recommended that in the manufacture of foods containing potassium iodate, the packaging material selected should be free from readily accessible antioxidants.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11072057 and 51376040, the Foundation of Canadian Space Agency under Grant No 9F007-02-6019, and the Research Fund of Japan Aerospace Exploration Agency.
文摘A three-dimensional direct numerical simulation is carried out to predict the surface oscillation and flow structure of isothermal liquid bridges of 5 cSt silicone oil held vertically between solid disks. By subjecting liquid bridges to various horizontal vibrations, the surface resonance frequencies are clearly determined numerically and compared well with the existing analytical model predictions. The investigation on the flow structure inside the liquid bridge reveals, for the first time, the flow structure and the existence of transw',rsal vortices inside the liquid bridge when a horizontal vibration is applied.
基金a project financially supported by CAMM3,the Center of Advanced Mining and Metallurgy,a center of excellence at the Lule?University of Technology。
文摘Froth flotation is an essential processing technique for upgrading low-grade ores.Flotation separation would not be efficient without chemical surfactants(collectors,depressants,frothers,etc.).Depressants play a critical role in the selective separation of minerals in that they deactivate unfavorable mineral surfaces and hinder them from floating into the flotation concentration zone.Pyrite is the most common and challenging sulfide gangue,and its conventional depressants could be highly harmful to nature and humans.Therefore,using available,affordable,eco-friendly polymers to assist or replace hazardous reagents is mandatory for a green transition.Polysaccharide-based(starch,dextrin,carboxymethyl cellulose,guar gum,etc.)polymers are one of the most used biodegradable depressant groups for pyrite depression.Despite the satisfactory flotation results obtained using these eco-friendly depressants,several gaps still need to be addressed,specifically in investigating surface interactions,adsorption mechanisms,and parameters affecting their depression performance.As a unique approach,this review comprehensively discussed previously conducted studies on pyrite depression with polysaccharide-based reagents.Additionally,practical suggestions have been provided for future assessments and developments of polysaccharide-based depressants,which pave the way to green flotation.This robust review also explored the depression efficiency and various adsorption aspects of naturally derived depressants on the pyrite surface to create a possible universal trend for each biodegradable depressant derivative.
基金financial support from Environment Canada and the Government of Ontario (72021622) for a scholarship to YK
文摘Traffic-related pollutants adversely affect air quality, especially in regions near major roadways. The vehicleinduced turbulence(VIT) is a significant factor that controls the initial dilution, dispersion, and ultimately the chemical and physical fate of pollutants by altering the conditions in the microenvironment. This study used a computational fluid dynamics(CFD) software FLUENT to model the vehicle-induced turbulence(VIT) generated on roadways, with a focus on impact of vehicle-vehicle interactions, traffic density and vehicle composition on turbulent kinetic energy(TKE). We show, for the first time, that the overall TKE from multiple vehicles traveling in series can be estimated by superimposing the TKE of each vehicle, without considering the distance between them while the distance is greater than one vehicle length. This finding is particularly significant since it enables a new approach to VIT simulations where the overall TKE is calculated as a function of number of vehicles. We found that the interactions between vehicles traveling next to each other in adjacent lanes are insignificant,regardless the directions of the traffic flow. Consequently, simulations of different traffic scenarios can be substantially simplified by treating two-way traffic as one-way traffic, with less than 5% difference in the overall volume-averaged TKE. We also developed equations that allow the estimation of the overall volume-averaged TKE as a function of the number and the type of vehicles.
文摘Searching for alternative energy sources continues to grow in recent times due to the fear of energy insecurity in the near future and environmental and sociopolitical issues associated with the use of fossil fuel. Among the renewable energy sources, biomass is the only source that has carbon in its building blocks which can be processed to liquid fuel. In this study, pyrolysis of oil palm residues (trunk, frond and empty fruit bunch) was carried out in a fixed bed tubular reactor under nitrogen atmosphere at 30 mL/min, 30?C/min heating rate and 600?C reaction temperature. Pyrolysis products (bio-oil, bio-char and non-condensable gas) were characterized. Water content, acidity (pH), higher heating value (HHV) and oxygen content of the bio-oil varied between 39.28 - 43 wt%, 2.92 - 3.20, 19.29 - 21.92 MJ/kg and 58.47 - 59.85 wt% respectively. Low pH, highwater and oxygen contents in the oil make it unsuitable for being used as fuel and therefore require upgrading. Scanning electron microscopy and ultimate analysis of the bio-char suggests that it is a porous material and consists mainly carbon between 82.22 - 84.96 wt% and has HHV in the range of 25.98 - 27.65 MJ/kg. This may be used as solid biofuel, adsorbent and source of carbon. High percentage of hydrogen (H2) and carbon monoxide (CO) were observed in the non-condensable gas which may be processed to transportation fuel via Fisher-Tropsch process. Oil palm residues represent good source of renewable energy when all the pyrolysis products are efficiently utilized.
基金Funded by the National Natural Science Foundation of China(No.20877105)
文摘Atmospheric carbon dioxide concentration [CO2],incoming solar radiation and sea ice coverage are among the most important factors that control the global climate.By applying the simple cell-to-cell mapping technique to a simplified atmosphere-ocean-sea ice feedback climate model,effects of these factors on the stability of the climatic system are studied.The current climatic system is found to be stable but highly nonlinear.The resiliency of stability increases with [CO2] to a summit when [CO2] reaches 290 μL/L which is comparable to the pre-industrial level,suggesting carbon dioxide is essential to the stability of the global climate.With [CO2] rising further,the global climate stability decreases,the mean ocean temperature goes up and the sea ice coverage shrinks in the polar region.When the incoming solar radiation is intensified,the ice coverage gradually diminishes,but the mean ocean temperature remains relatively constant.Overall,our analysis suggests that at the current levels of three external factors the stability of global climate is highly resilient.However,there exists a possibility of extreme states of climate,such as a snow-ball earth and an ice-free earth.
文摘The main purpose of this study was to optimize microwave assisted alkaline extraction of the hemicellulose, xylan, from birch wood. The simultaneous effects of process variables such as time (10 - 30 minutes), concentration of sodium hydroxide solution (4 - 8 wt%), solid to liquid ratio (1:8 to 1:20, g:mL), and sample size (5 - 10 g) on the temperature of the wood slurry, wood dissolution, and yield of extraction were evaluated. A central composite design (CCD) and response surface methodology (RSM) were used for the optimization of the extraction process. Based on the CCD, quadratic models were developed to correlate the extraction process variables with the responses such as temperature of wood slurry, wood dissolution, and yield of xylan and the models were analyzed using appropriate statistical methods (ANOVA). Statistical analysis showed that all the models developed were found to be adequate for the prediction of the respective responses. Optimization of the process was performed using a numerical optimization available in the software to maximize the yield of xylan and the optimum process variables for the maximum yield of xylan was found to be: 10 g of wood fibres, 8 wt% of NaOH solution, 1:10 solid to liquid ratio (g:mL) and 25 minutes of irradiation time. About 72.5% of the xylan present in the birch wood was extracted using the optimized extraction parameters.
文摘A nanostructured gold-silver soaked in polyethylene glycol 400 (Au-Ag@PEG) is designed using gold(I) chloride and silver nitrate (AgNO3) as precursors and, polyethylene glycol 400 (PEG) as capping agent. The result of the structure characterization using Selected Area Electron Diffraction (SAED) has showed that the synthesized nanomaterial has a good crystallinity while Transmission Electron Microscopy (TEM), energy dispersive X-ray spectrometry (EDX) and Dynamic Light Scattering (DLS) measurements suggest mixed Au-Ag nanoparticles with an average diameter size of around 7 nm and 30 nm for Au and Ag respectively.
文摘The aim of this study was to evaluate the effect of chewing simulation on wear of artificial enamel abraded against zirconia-based crowns. Fifteen crown preparations were scanned for the manufacturing of crowns using computer-aided-design/computer-aided-machining technique (CAD/CAM), according to the following (n = 5): Polished (PM) and glazed (GM) monolithic zirconia (1.5 mm uniform thickness), and Bilayer (BL - 0.8 mm zirconia coping, 0.7 mm porcelain veneer) crowns. The samples were cemented and chewing simulation (2.5 million cycles/0-80N/artificial saliva/37°C) was performed with steatite indenters (6 mm diameter) as antagonists. Assuming the uniformity of the unaged samples, antagonists were scanned using a surface profilometer and the material loss volume was calculated. Roughness of the crowns’ occlusal surface was also analyzed using the profilometer. Scanning electron microscopy was used to characterize the abraded surface. One-way ANOVA and Tukey test (p = 0.05) were employed for analysis of wear results. A significant difference was observed among the groups (p 3 ± 0.015) than those abraded against monolithic zirconia, polished (PM - 0.167 mm3 ± 0.02) and glazed (0.101 mm3 ± 0.03), which were similar to each other. Veneering porcelain results in more pronounced wear of the artificial enamel than monolithic zirconia. However, mastication against monolithic Y-TZP also imposes wear to the opposing teeth.
文摘The dry deposition process refers to the flux loss of an atmospheric pollutant due to uptake of the pollutant by the earth’s surfaces.Dry deposition flux of a chemical species is typically calculated as the product of its surface-layer concentration and its dry deposition velocity(V_(d)).Field measurement based V_(d) data are very scarce or do not exist for many chemical species considered in chemistry transport models.In the present study,gaseous and particulate dry deposition schemes were applied to generate a database of hourly V_(d) for 45 gaseous species and three particle size ranges for two years(2016–2017)at a 15 kmby 15 km horizontal resolution across North America.Hourly V_(d) of the 45 gaseous species ranged from<0.001 to 4.6 cm/sec across the whole domain,with chemical species-dependentmedian(mean)values being in the range of 0.018–1.37 cm/sec(0.05–1.43 cm/sec).The spatial distributions of the two-year average V_(d) showed values higher than 1–3 cm/sec for those soluble and reactive species over certain land types.Soluble species have the highest V_(d) over water surfaces,while insoluble but reactive species have the highest V_(d) over forests.Hourly V_(d) of PM_(2.5) across the whole domain ranged from 0.039 to 0.75 cm/sec with median(mean)value of 0.18(0.20)cm s^(−1),while the mean V_(d) for PM_(2.5)–10 is twice that of PM_(2.5).Uncertainties in the modeled V_(d) are typically on the order of a factor of 2.0 or larger,which needs to be considered when applying the dataset in other studies.
文摘Generating hydrogen gas from biomass is one approach to lowering dependencies on fossil fuels for energy and chemical feedstock, as well as reducing greenhouse gas emissions. Using both equilibrium simulations and batch experiments with NaOH as a model alkaline, this study established the technical feasibility of converting various biomasses (e.g., glucose, cellulose, xylan and lignin) into H2-rich gas via catalyst-free, alkali-thermal gasification at moderate temperatures (as low as 300℃). This process could produce more H2 with less carbon-containing gases in the product than other comparable methods. It was shown that alkali-thermal gasification follows CxHyO2 + 2xNaOH + (x-z)H20 = (2x+y/2-z)H2 +xNa2CO3, with carbonate being the solid product which is different from the one suggested in the literature. Moreover, the concept of hydrogen genera- tion potential (H2-GP)-the maximum amount of H2 that a biomass can yield, was introduced. For a given biomass CxHyO2, the H2-GP would be (2x + y/2-z) moles of H2. It was demonstrated experimentally that the H2-GP was achievable by adjusting the amounts of H20 and NaOH, temperature and pressure. Keywords hydrogen generation potential, biomass, lignocellulose, alkali-thermal gasification, sodium hydroxide
文摘The work studied a non-catalytic upgrading of fast pyrolysis bio-oil by blending under supercritical conditions using methanol,ethanol and isopropanol as solvent and hydrogen donor.Characterisation of the bio-oil and the upgraded bio-oils was carried out including moisture content,elemental content,pH,heating value,gas chromatography-mass spectrometry(GCMS),Fourier transform infrared radiation,13C nuclear magnetic resonance spectroscopy,and thermogravimetric analysis to evaluate the effects of blending and supercritical reactions.The GCMS analysis indicated that the supercritical methanol reaction removed the acids in the bio-oil consequently the pH increased from 2.39 in the crude bio-oil to 4.04 after the supercritical methanol reaction.The ester contents increased by 87.49% after the supercritical methanol reaction indicating ester formation could be the major deacidification mechanism for reducing the acidity of the bio-oil and improving its pH value.Simply blending crude bio-oil with isopropanol was effective in increasing the C and H content,reducing the O content and increasing the heating value to 27.55 from 17.51 MJ·kg^-1 in the crude bio-oil.After the supercritical isopropanol reaction,the heating value o f the liquid product slightly further increased to 28.85 MJ·kg^-1.
文摘Biochar is traditionally used as solid fuel and for soil amendment where its electrical conductivity is largely irrelevant and unexplored.However,electrical conductivity is critical to biochar’s performance in new applications such as supercapacitor energy storage and capacitive deionization of water.In this study,sugar maple and white pine were carbonized via a slow pyrolysis process at 600,800 and 1000°C and conductivities of monolithic biochar samples along the radial direction were measured using the 4-probe method.Biochars were characterized using an elemental analyzer,scanning electron microscopy,X-ray diffraction and Raman spectroscopy.The solid carbon in biochar samples was found to consist primarily of disordered carbon atoms with small graphitic nanocrystallites that grow with increasing temperature.The bulk conductivity of biochar was found to increase with pyrolysis temperature-1 to~1000 S/m for maple and 1 to~350 S/m for pine,which was accompanied by an increase in carbon content-91 to 97 wt%and 90 to 96 wt%for maple and pine,respectively.The skeletal conductivity of biochar samples carbonized at 1000°C is about 3300 S/m and 2300 S/m for maple and pine,respectively(assuming solid carbon is amorphous);both values are above that of amorphous carbon(1250-2000 S/m).This work demonstrated the importance of carbonization and graphitization to electrical conductivity and suggested electron hopping as a likely mechanism for electric conduction in biochar-an amorphous carbon matrix embedded with graphitic nanocrystallites.
文摘Gold 3D cylindrical nanoelectrode ensembles (NEEs), 100 nm in diameter and 500 nm in length were prepared by electroless template synthesis in polycarbonate filter membranes, followed by selective controlled chemical etching. The morphology of the nanowires and cylindrical NEEs was imaged by scanning electron microscopy. The protruding nanoelectrodes were in good parallel order. EDX study showed that the nanoelectrode elements consisted of pure gold. The electrochemical evaluation of the 3D electrodes was conducted using the well known [Fe(CN)6]^3-/[Fe(CN)6]^4- couple. Cyclic voltammgrams (CV) show a very low double layer charging current and a higher ratio of signal to background current than 2D disc NEEs. Electrochemical impedance spectroscopy (EIS) indicates that the 3D cylindrical NEEs effectively accelerate the charge transfer process, which is in consistent with the results of CV. The linear relationship with a slope of 0.5 between lg Ipc and lg v shows that linear diffusion is dominant on the 3D cylindrical NEEs at conventional scan rates.
基金funded by the Bill&Melinda Gates Foundation(OPP1151531)partially funded by the International Development Research Centre(IDRC),Canada(No.108123).
文摘Objectives:This study evaluates factors responsible for the floating of iron premix in double fortified salt(DFS),which initially affected the large-scale implementation of the salt fortification program in India,and provides solutions to the scale-up of the technology.Materials and Methods:To mitigate this time-sensitive scale-up challenge.First,the iron premix samples were obtained from the industrial scale-up pilot studies in India,evaluated for the impact of the amount of coating material(5 per cent,7.5 per cent,and 10 per cent(in weight)),type of formulation(soy stearin,SEPIFILM and hydroxypropyl methylcellulose),amount of titanium dioxide(25-35 per cent(in weight))used for color masking;Second,we studied the effect of change in the composition of the coating,from 10 per cent(in weight)soy stearin to a double coat with 5 per cent(in weight)hydroxypropyl methylcellulose and 5 per cent soy stearin or 10 per cent soy stearin and 1 per cent(in weight)lecithin mixture,on particle density,floating or sinking property of the iron premix,and on the stability of iodine in the DFS.Results:It was observed that the hydrophobic nature and the amount of soy stearin used for coating caused the floating issue.The double coating with 5 per cent hydroxypropyl methylcellulose and 5 per cent soy stearin was preferred because lecithin in soy stearin enhanced the moisture-aided adverse interaction between iron and iodine.Shelf-life storage studies proved over 80 per cent iodine retention after 12 months of storage in the DFS formulated with iron premix double-coated with hydroxypropyl methylcellulose and soy stearin.Conclusion:This proffered solution enabled the full implementation of the double fortification program in India.