The size of pores or the grille spacing of water–sediment separation structures directly affects their regulation effect on the debris flow performance.A suitable pore size or grille spacing can effectively improve t...The size of pores or the grille spacing of water–sediment separation structures directly affects their regulation effect on the debris flow performance.A suitable pore size or grille spacing can effectively improve the water–sediment separation ability of the structure.The new funnel-type grating water–sediment separation structure(FGWSS)combines vertical and horizontal structures and provides a satisfactory water–sediment separation effect.However,the regulation effect of the grille spacing of the structure on the debris flow performance has not been studied.The regulation effect of the structure grille spacing on the debris flow performance is studied through a flume test,and the optimal structure grille spacing is obtained.An empirical equation of the relationship between the relative grille spacing of the structure and the sediment separation rate is established.Finally,the influence of the water–sediment separation structure on the regulation effect of debris flows is examined from two aspects:external factors(properties of debris flows)and internal factors(structural factors).The experimental results show that the gradation characteristics of solid particles in debris flows constitute a key factor affecting the regulation effect of the structure on the debris flow performance.The optimum grille spacing of the FGWSS matches the particle size corresponding to the material distribution curves d85~d90 of the debris flow.The total separation rate of debris flow particles is related to the grille spacing of the structure and the content of coarse and fine particles in the debris flow.展开更多
Computational Fluid Dynamics is used to assess the thermal(heat transfer)performances of an automobile engine considering different grille opening and closing degrees.For this purpose the entire vehicle is modelled an...Computational Fluid Dynamics is used to assess the thermal(heat transfer)performances of an automobile engine considering different grille opening and closing degrees.For this purpose the entire vehicle is modelled and three fundamental aspects are examined,namely,the open area of the air intake grille,the position of the upper and lower grilles and their shape.The results show that the opening area and position of the grille have some influence also on the aerodynamic characteristics of the automobile.With an increase in the opening angle of the grille,the CD(Drag Coefficient)value of the whole vehicle becomes higher.When the air intake grille of the car is fully open or closed,the CD value is 0.35434 or 0.31777,respectively,that is,the flow resistance in the engine compartment accounts for 10.32%of the CD value for the whole automobile.展开更多
In Ouagadougou, grilled meats in the form of pieces and brochettes are very popular and well-known to consumers. The aim of this study was to assess the microbial quality of mutton meat sold in Ouagadougou, Burkina Fa...In Ouagadougou, grilled meats in the form of pieces and brochettes are very popular and well-known to consumers. The aim of this study was to assess the microbial quality of mutton meat sold in Ouagadougou, Burkina Faso. A total of 120 samples were collected from 20 meat grillers 60 samples of fresh meat and 60 samples of grilled meat. The sampling was done between the month of August 2018 and the month of February 2019. The samples were analyzed according to standard methods. The test performed were counts of Aerobic Mesophilic Bacteria (AMB), yeasts and molds, enterobacteria, Campylobacter spp, Staphylococcus aureus, Bacillus cereus, Brucella spp, Pseudomonas aeruginosa, the search for salmonella, and the detection of antibiotics residues. Results showed a high count of AMB (8.77 and 6.78 log UFC/g);enterobacteria (6.58 and 3.05 log UFC/g), Staphylococcus aureus (6.45 and 4.35 log UFC/g), Bacillus cereus (6.98 and 4.52 log UFC/g), Campylobacter (6.03 and 3.86 log UFC/g), yeasts and molds (4.80 and 3.26 log UFC/g) and Pseudomonas aeruginosa (0.45 and 0.15 log UFC/g), respectively in fresh meat and grilled meat. Presumptive Salmonella was found in 95% of fresh meat samples and in 75% of grilled meat samples. In the tested samples, no Brucella spp were detected. However, residues of antibiotics were found in 5% of fresh meat samples and 5% of grilled meat samples. Means of moisture and pH were respectively 74.91% and 6.05% for fresh meat and 53.21% and 6.06% for grilled meat. The average microbial counts recorded in fresh and grilled meat are significantly high and indicate poor hygiene in the raw material and ready-to-eat meat. Good practices of hygiene and processing guides should be developed for the meat grilling value chain actors to reduce contamination risks.展开更多
Based onmultiphase flowtheory and capillary mechanics,the dimensionless bond number expression of the influence of string grille wire spacing on droplet spreading is derived.Taking a liquid film formed by spreading dr...Based onmultiphase flowtheory and capillary mechanics,the dimensionless bond number expression of the influence of string grille wire spacing on droplet spreading is derived.Taking a liquid film formed by spreading droplets based on Kelvin correlation,the Young-Laplace equation,and the Hagen-Poiseuille law,an equation for calculating the thickness and height of the liquid film is established with temperature,relative humidity and molar volume of liquid phase as independent variables.According to the theory of string grille filtration and dust removal,a dust removal efficiency calculation model covering the wet string grille wire group is constructed based on the liquid film thickness,height,wire diameter,water film area,and vortex shedding frequency.Finally,a theoretical analysis of the influence of water film area on the efficiency of wet string grille dust removal is carried out based on the spray pressure and the ratio of string grille wire distance to wire diameter.It is found that the effect of spray pressure on water film area and dust removal efficiency is more significant than the string grille wire distance diameter ratio.Moreover,the optimized combination of wet string grille wire distance diameter ratio 0.84,wind speed 3m/s and spray pressure 0.8 MPa is found,which could provide an important reference for engineering applications.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.42027806 and 42041006)。
文摘The size of pores or the grille spacing of water–sediment separation structures directly affects their regulation effect on the debris flow performance.A suitable pore size or grille spacing can effectively improve the water–sediment separation ability of the structure.The new funnel-type grating water–sediment separation structure(FGWSS)combines vertical and horizontal structures and provides a satisfactory water–sediment separation effect.However,the regulation effect of the grille spacing of the structure on the debris flow performance has not been studied.The regulation effect of the structure grille spacing on the debris flow performance is studied through a flume test,and the optimal structure grille spacing is obtained.An empirical equation of the relationship between the relative grille spacing of the structure and the sediment separation rate is established.Finally,the influence of the water–sediment separation structure on the regulation effect of debris flows is examined from two aspects:external factors(properties of debris flows)and internal factors(structural factors).The experimental results show that the gradation characteristics of solid particles in debris flows constitute a key factor affecting the regulation effect of the structure on the debris flow performance.The optimum grille spacing of the FGWSS matches the particle size corresponding to the material distribution curves d85~d90 of the debris flow.The total separation rate of debris flow particles is related to the grille spacing of the structure and the content of coarse and fine particles in the debris flow.
文摘Computational Fluid Dynamics is used to assess the thermal(heat transfer)performances of an automobile engine considering different grille opening and closing degrees.For this purpose the entire vehicle is modelled and three fundamental aspects are examined,namely,the open area of the air intake grille,the position of the upper and lower grilles and their shape.The results show that the opening area and position of the grille have some influence also on the aerodynamic characteristics of the automobile.With an increase in the opening angle of the grille,the CD(Drag Coefficient)value of the whole vehicle becomes higher.When the air intake grille of the car is fully open or closed,the CD value is 0.35434 or 0.31777,respectively,that is,the flow resistance in the engine compartment accounts for 10.32%of the CD value for the whole automobile.
文摘In Ouagadougou, grilled meats in the form of pieces and brochettes are very popular and well-known to consumers. The aim of this study was to assess the microbial quality of mutton meat sold in Ouagadougou, Burkina Faso. A total of 120 samples were collected from 20 meat grillers 60 samples of fresh meat and 60 samples of grilled meat. The sampling was done between the month of August 2018 and the month of February 2019. The samples were analyzed according to standard methods. The test performed were counts of Aerobic Mesophilic Bacteria (AMB), yeasts and molds, enterobacteria, Campylobacter spp, Staphylococcus aureus, Bacillus cereus, Brucella spp, Pseudomonas aeruginosa, the search for salmonella, and the detection of antibiotics residues. Results showed a high count of AMB (8.77 and 6.78 log UFC/g);enterobacteria (6.58 and 3.05 log UFC/g), Staphylococcus aureus (6.45 and 4.35 log UFC/g), Bacillus cereus (6.98 and 4.52 log UFC/g), Campylobacter (6.03 and 3.86 log UFC/g), yeasts and molds (4.80 and 3.26 log UFC/g) and Pseudomonas aeruginosa (0.45 and 0.15 log UFC/g), respectively in fresh meat and grilled meat. Presumptive Salmonella was found in 95% of fresh meat samples and in 75% of grilled meat samples. In the tested samples, no Brucella spp were detected. However, residues of antibiotics were found in 5% of fresh meat samples and 5% of grilled meat samples. Means of moisture and pH were respectively 74.91% and 6.05% for fresh meat and 53.21% and 6.06% for grilled meat. The average microbial counts recorded in fresh and grilled meat are significantly high and indicate poor hygiene in the raw material and ready-to-eat meat. Good practices of hygiene and processing guides should be developed for the meat grilling value chain actors to reduce contamination risks.
基金We thank Esther Posner,PhD,from Edanz Group China(www.liwenbianji.cn/ac)for English language editing on an earlier draft of this manuscript.This work was supported by the 2017 Hunan Provincial Graduate Research Innovation Project of China(No.CX2017B649)the National Natural Science Foundation of China(No.51774134)+2 种基金the Excellent Youth Project of Hunan Provincial Department of Education(No.19B223)the Hunan Provincial Natural Science Foundation of China(No.2019JJ60044)the Hunan Provincial Natural Science Foundation of China(No.2018JJ64028).
文摘Based onmultiphase flowtheory and capillary mechanics,the dimensionless bond number expression of the influence of string grille wire spacing on droplet spreading is derived.Taking a liquid film formed by spreading droplets based on Kelvin correlation,the Young-Laplace equation,and the Hagen-Poiseuille law,an equation for calculating the thickness and height of the liquid film is established with temperature,relative humidity and molar volume of liquid phase as independent variables.According to the theory of string grille filtration and dust removal,a dust removal efficiency calculation model covering the wet string grille wire group is constructed based on the liquid film thickness,height,wire diameter,water film area,and vortex shedding frequency.Finally,a theoretical analysis of the influence of water film area on the efficiency of wet string grille dust removal is carried out based on the spray pressure and the ratio of string grille wire distance to wire diameter.It is found that the effect of spray pressure on water film area and dust removal efficiency is more significant than the string grille wire distance diameter ratio.Moreover,the optimized combination of wet string grille wire distance diameter ratio 0.84,wind speed 3m/s and spray pressure 0.8 MPa is found,which could provide an important reference for engineering applications.
