During the microstructural analysis of weakly cemented sandstone,the granule components and ductile structural parts of the sandstone are typically generalized.Considering the contact between granules in the microstru...During the microstructural analysis of weakly cemented sandstone,the granule components and ductile structural parts of the sandstone are typically generalized.Considering the contact between granules in the microstructure of weakly cemented sandstone,three basic units can be determined:regular tetrahedra,regular hexahedra,and regular octahedra.Renormalization group models with granule-and pore-centered weakly cemented sandstone were established,and,according to the renormalization group transformation rule,the critical stress threshold of damage was calculated.The results show that the renormalization model using regular octahedra as the basic units has the highest critical stress threshold.The threshold obtained by iterative calculations of the granule-centered model is smaller than that obtained by the pore-centered model.The granule-centered calculation provides the lower limit(18.12%),and the pore-centered model provides the upper limit(36.36%).Within this range,the weakly cemented sandstone is in a phase-like critical state.That is,the state of granule aggregation transforms from continuous to discrete.In the relative stress range of 18.12%-36.36%,the weakly cemented sandstone exhibits an increased proportion of high-frequency signals(by 83.3%)and a decreased proportion of low-frequency signals(by 23.6%).The renormalization calculation results for weakly cemented sandstone explain the high-low frequency conversion of acoustic emission signals during loading.The research reported in this paper has important significance for elucidating the damage mechanism of weakly cemented sandstone.展开更多
Centrifugal pumps are widely used in engineering for a variety of applications.A known drawback of these devices is the high-level noise generated during operations,which can affect their stability and adversely influ...Centrifugal pumps are widely used in engineering for a variety of applications.A known drawback of these devices is the high-level noise generated during operations,which can affect their stability and adversely influence the entire working environment.By combining the Powell vortex sound theory,numerical simulations and experimental measurements,this research explores the trends of variation and the corresponding underlying mechanisms for the flow-induced noise at various locations and under different operating conditions.It is shown that the total sound source intensity(TSSI)and total sound pressure level(TSPL)in the impeller,in the region between the inlet to the outlet and along the circumferential extension of the volute,are much higher than those at pump inlet and outlet.Additionally,under various rotational speeds with the design flow rate(Condition 1),the TSSI and TSPL at pump inlet and outlet are higher than those obtained with the opening of the valve kept unchanged(Condition 2);vice versa when these two parameters are evaluated at various locations in the impeller and the volute under the Condition 2,they exceed the equivalent values obtained for the other Condition 1.展开更多
[Objectives]The quality of Scylla paramammosain produced in Fujian,Sanmen and Shanghai were analyzed and evaluated.[Methods]Adult Scylla paramammosain from Fujian,Sanmen and Shanghai were separated for their muscles a...[Objectives]The quality of Scylla paramammosain produced in Fujian,Sanmen and Shanghai were analyzed and evaluated.[Methods]Adult Scylla paramammosain from Fujian,Sanmen and Shanghai were separated for their muscles and gonads,which were analyzed for nutritional components.[Results]The muscle moisture content of S.paramammosain from Sanmen was significantly higher than those in S.paramammosain from Fujian and Shanghai.The muscle protein contents of S.paramammosain from the three regions ranked as Shanghai>Fujian>Sanmen(P<0.05).The muscles of S.paramammosain from Shanghai had the highest crude fat and crude ash contents.The moisture contents of the gonads of the S.paramammosain from the three regions had no significant differences.The protein contents of the gonads of S.paramammosain from the three regions ranked as Shanghai>Sanmen>Fujian(P<0.05).The S.paramammosain from Sanmen had the highest crude fat and crude ash contents in gonads.The contents of 17 amino acids detected in the muscles and gonads of S.paramammosain from the three different regions were different.The total amounts of total amino acids(TAA),essential amino acids(EAA)and flavor amino acids(FAA)in the muscles of S.paramammosain from Sanmen were significantly lower than those produced in Fujian and Shanghai(P<0.05),but the proportions of essential amino acids(EAA)and flavor amino acids were not significantly different.The proportion of EAA and FAA in the gonads of S.paramammosain produced in the three areas were significantly different(P<0.05).There were also differences in the fatty acid composition of the muscles and gonads of S.paramammosain from the three different regions.The proportion of EPA in the muscles of S.paramammosain from Fujian was higher than those of other two groups,but the differences were not significant;the proportion of DHA was significantly higher than those of other two groups,and the differences were significant(P<0.05);and the proportions of n3 PUFA in muscles of S.paramammosain produced in Fujian and Sanmen were significantly higher than that of S.paramammosain produced in Shanghai(P<0.05).The proportions of EPA,DHA and n6 PUFA in the gonads of S.paramammosain produced in Sanmen were significantly higher than those produced in Fujian and Shanghai(P<0.05),while the n3 PUFA was the highest in S.paramammosain produced in Fujian.The proportions of n6/n3 PUFA in S.paramammosain produced in the three different regions were significantly different(P<0.05).In summary,it could be seen that the nutritional composition of S.paramammosain produced in different regions has its own characteristics.[Conclusions]This study provides basic data for the establishment of quality evaluation standards for S.paramammosain,and provides a new perspective for the evaluation of breeding models.展开更多
A 3×3 factorial feeding trial was conducted to evaluate the production response of juvenile northern snakehead fish(Channa argus). Nine diets containing 3 protein levels(45%, 48% and 51%) and 3 lipid levels(9%,12...A 3×3 factorial feeding trial was conducted to evaluate the production response of juvenile northern snakehead fish(Channa argus). Nine diets containing 3 protein levels(45%, 48% and 51%) and 3 lipid levels(9%,12% and 15%) were formulated and fed to triplicate groups of juvenile northern snakehead(15.78 ± 0.09 g/fish) for 8 weeks. The formulated diets were named as P45 L9, P45 L12, P45 L15, P48 L9,P48 L12, P48 L15, P51 L9, P51 L12 and P51 L15(P-Protein, L-Lipid), respectively. Fish fed diets with the lowest protein and lipid combination(P45 L9) had the lowest growth performance. Weight gains(WG) of fish fed the 4 diets P48 L12, P48 L15, P51 L9, and P51 L12 were not significantly different(P> 0.05), but significantly higher(P < 0.05) than those of fish fed the other diets. Fish fed diets P48 L12 and P48 L15 had significantly lower(P < 0.05) feed conversion ratios(FCR) than the rest of the treatments. Protein retentions(PR) among fish fed the diets P45 L12, P45 L15, P48 L12, P48 L15, P51 L9, and P51 L12 were similar and significantly higher(P < 0.05) than those of fish fed the remaining diets. Protein sparing effect was observed in the treatments when fish was fed diets containing 45% or 48% dietary protein levels with dietary lipid increased from 9% to12%. Fish fed diets with 9% lipid tended to have lower viscerosomatic index(VSI), hepatosomatic index(HSI),and whole-body lipid. Increasing dietary protein level significantly increased(P < 0.05) liver moisture and lipid while dietary lipid level increased liver lipid. Intestinal lipase activity increased significantly(P < 0.05)with increasing dietary lipid and protein levels while intestinal a-amylase and protease activities were not significantly influenced(P > 0.05) by dietary treatments. Based on these results, the diet containing 48%protein with either 12% or 15% lipid is the optimal for supporting growth and feed utilization of juvenile northern snakehead under the current testing conditions.展开更多
基金the National Natural Science Foundation of China(Grant No.51534002)the Special Funds for Technological Innovation and Entrepreneurship of China Coal Science and Engineering Group Co.Ltd.(2018-TDMS011)。
文摘During the microstructural analysis of weakly cemented sandstone,the granule components and ductile structural parts of the sandstone are typically generalized.Considering the contact between granules in the microstructure of weakly cemented sandstone,three basic units can be determined:regular tetrahedra,regular hexahedra,and regular octahedra.Renormalization group models with granule-and pore-centered weakly cemented sandstone were established,and,according to the renormalization group transformation rule,the critical stress threshold of damage was calculated.The results show that the renormalization model using regular octahedra as the basic units has the highest critical stress threshold.The threshold obtained by iterative calculations of the granule-centered model is smaller than that obtained by the pore-centered model.The granule-centered calculation provides the lower limit(18.12%),and the pore-centered model provides the upper limit(36.36%).Within this range,the weakly cemented sandstone is in a phase-like critical state.That is,the state of granule aggregation transforms from continuous to discrete.In the relative stress range of 18.12%-36.36%,the weakly cemented sandstone exhibits an increased proportion of high-frequency signals(by 83.3%)and a decreased proportion of low-frequency signals(by 23.6%).The renormalization calculation results for weakly cemented sandstone explain the high-low frequency conversion of acoustic emission signals during loading.The research reported in this paper has important significance for elucidating the damage mechanism of weakly cemented sandstone.
基金the Key Research and Development Project of Shandong Province(2019GSF109084)Qilu University of Technology(Shandong Academy of Sciences)Young Doctors Cooperative Fund(2019BSHZ022).
文摘Centrifugal pumps are widely used in engineering for a variety of applications.A known drawback of these devices is the high-level noise generated during operations,which can affect their stability and adversely influence the entire working environment.By combining the Powell vortex sound theory,numerical simulations and experimental measurements,this research explores the trends of variation and the corresponding underlying mechanisms for the flow-induced noise at various locations and under different operating conditions.It is shown that the total sound source intensity(TSSI)and total sound pressure level(TSPL)in the impeller,in the region between the inlet to the outlet and along the circumferential extension of the volute,are much higher than those at pump inlet and outlet.Additionally,under various rotational speeds with the design flow rate(Condition 1),the TSSI and TSPL at pump inlet and outlet are higher than those obtained with the opening of the valve kept unchanged(Condition 2);vice versa when these two parameters are evaluated at various locations in the impeller and the volute under the Condition 2,they exceed the equivalent values obtained for the other Condition 1.
基金Supported by Key R&D Project in Zhejiang Province in 2018(2018C02019).
文摘[Objectives]The quality of Scylla paramammosain produced in Fujian,Sanmen and Shanghai were analyzed and evaluated.[Methods]Adult Scylla paramammosain from Fujian,Sanmen and Shanghai were separated for their muscles and gonads,which were analyzed for nutritional components.[Results]The muscle moisture content of S.paramammosain from Sanmen was significantly higher than those in S.paramammosain from Fujian and Shanghai.The muscle protein contents of S.paramammosain from the three regions ranked as Shanghai>Fujian>Sanmen(P<0.05).The muscles of S.paramammosain from Shanghai had the highest crude fat and crude ash contents.The moisture contents of the gonads of the S.paramammosain from the three regions had no significant differences.The protein contents of the gonads of S.paramammosain from the three regions ranked as Shanghai>Sanmen>Fujian(P<0.05).The S.paramammosain from Sanmen had the highest crude fat and crude ash contents in gonads.The contents of 17 amino acids detected in the muscles and gonads of S.paramammosain from the three different regions were different.The total amounts of total amino acids(TAA),essential amino acids(EAA)and flavor amino acids(FAA)in the muscles of S.paramammosain from Sanmen were significantly lower than those produced in Fujian and Shanghai(P<0.05),but the proportions of essential amino acids(EAA)and flavor amino acids were not significantly different.The proportion of EAA and FAA in the gonads of S.paramammosain produced in the three areas were significantly different(P<0.05).There were also differences in the fatty acid composition of the muscles and gonads of S.paramammosain from the three different regions.The proportion of EPA in the muscles of S.paramammosain from Fujian was higher than those of other two groups,but the differences were not significant;the proportion of DHA was significantly higher than those of other two groups,and the differences were significant(P<0.05);and the proportions of n3 PUFA in muscles of S.paramammosain produced in Fujian and Sanmen were significantly higher than that of S.paramammosain produced in Shanghai(P<0.05).The proportions of EPA,DHA and n6 PUFA in the gonads of S.paramammosain produced in Sanmen were significantly higher than those produced in Fujian and Shanghai(P<0.05),while the n3 PUFA was the highest in S.paramammosain produced in Fujian.The proportions of n6/n3 PUFA in S.paramammosain produced in the three different regions were significantly different(P<0.05).In summary,it could be seen that the nutritional composition of S.paramammosain produced in different regions has its own characteristics.[Conclusions]This study provides basic data for the establishment of quality evaluation standards for S.paramammosain,and provides a new perspective for the evaluation of breeding models.
基金supported by a grant(No.201524) from the Technical Support Group in Aquaculture of Zhejiang Ocean and Fisheries Bureau
文摘A 3×3 factorial feeding trial was conducted to evaluate the production response of juvenile northern snakehead fish(Channa argus). Nine diets containing 3 protein levels(45%, 48% and 51%) and 3 lipid levels(9%,12% and 15%) were formulated and fed to triplicate groups of juvenile northern snakehead(15.78 ± 0.09 g/fish) for 8 weeks. The formulated diets were named as P45 L9, P45 L12, P45 L15, P48 L9,P48 L12, P48 L15, P51 L9, P51 L12 and P51 L15(P-Protein, L-Lipid), respectively. Fish fed diets with the lowest protein and lipid combination(P45 L9) had the lowest growth performance. Weight gains(WG) of fish fed the 4 diets P48 L12, P48 L15, P51 L9, and P51 L12 were not significantly different(P> 0.05), but significantly higher(P < 0.05) than those of fish fed the other diets. Fish fed diets P48 L12 and P48 L15 had significantly lower(P < 0.05) feed conversion ratios(FCR) than the rest of the treatments. Protein retentions(PR) among fish fed the diets P45 L12, P45 L15, P48 L12, P48 L15, P51 L9, and P51 L12 were similar and significantly higher(P < 0.05) than those of fish fed the remaining diets. Protein sparing effect was observed in the treatments when fish was fed diets containing 45% or 48% dietary protein levels with dietary lipid increased from 9% to12%. Fish fed diets with 9% lipid tended to have lower viscerosomatic index(VSI), hepatosomatic index(HSI),and whole-body lipid. Increasing dietary protein level significantly increased(P < 0.05) liver moisture and lipid while dietary lipid level increased liver lipid. Intestinal lipase activity increased significantly(P < 0.05)with increasing dietary lipid and protein levels while intestinal a-amylase and protease activities were not significantly influenced(P > 0.05) by dietary treatments. Based on these results, the diet containing 48%protein with either 12% or 15% lipid is the optimal for supporting growth and feed utilization of juvenile northern snakehead under the current testing conditions.
