Marine structures are frequently subjected to repeated impact loadings,resulting in failure of the structures,even causing serious accidents.The analytical expressions of dimensionless permanent deflection and impact ...Marine structures are frequently subjected to repeated impact loadings,resulting in failure of the structures,even causing serious accidents.The analytical expressions of dimensionless permanent deflection and impact force of a metal beam based on maximal normal yield surface are derived by membrane factor method(MFM),then the results are compared with repeated impact tests.It can be found that the solutions based on MFM are between the upper and lower bounds,and very close to the results of the repeated impact tests,indicating the theoretical model proposed can predict the plastic responses of the metal beam accurately.What’s more,the influences of impact location and boundary condition on the dynamic responses of the beam subjected to repeated impacts are determined.Results show that,as the distance of impact location from the middle span of the beam increases,the permanent deflection decreases,while the impact force increases.Meanwhile,the influences of impact location enhance as the impact number increases.When the permanent deflection is smaller than the thickness,the effect of boundary condition on the plastic responses is significant.However,when the deflection is larger than the thickness,the beam will be like a string and only axial force works,resulting in little influence of boundary condition on the plastic responses of the beam.展开更多
本试验旨在测定2-3周龄天府肉鸭的净能（NE）需要量。选取7日龄天府肉鸭300只,其中50只随机分为自由采食组和15%、25%、35%、45%限饲组,进行代谢试验,测定不同饲喂水平下饲粮的表观代谢能（AME）。另外250只用于饲养试验和比较屠宰试验...本试验旨在测定2-3周龄天府肉鸭的净能（NE）需要量。选取7日龄天府肉鸭300只,其中50只随机分为自由采食组和15%、25%、35%、45%限饲组,进行代谢试验,测定不同饲喂水平下饲粮的表观代谢能（AME）。另外250只用于饲养试验和比较屠宰试验。试验开始前选取10只用于初始体成分的测定,其余240只随机分为5个组（同代谢试验）。14日龄时,从自由采食组选10只屠宰,测定试验中期试验鸭体成分;21日龄时,从每个组选10只屠宰,测定试验末期试验鸭体成分。根据自由采食组和限饲组饲粮的AME和试验鸭的生长性能、体成分,获得试验鸭在不同饲喂水平的产热量（HP）和代谢能摄入量（MEI）,建立MEI和log10HP间的回归方程,外推到MEI为0时的HP即为维持净能需要量（NEm）;根据自由采食组试验鸭在3个阶段的机体总能量（BE）和体重（BW）,建立二者间的回归方程,方程的斜率为生长净能需要量（NEg）。结果如下：不同饲喂水平间,天府肉鸭的饲粮AME、平均日采食量（ADFI）、平均日增重（ADG）、料重比（F/G）、体脂肪、体蛋白、体能量、以脂肪形式沉积的能量（REf）、以蛋白质形式沉积的能量（REp）、MEI、沉积能（RE）和HP均存在显著差异（P〈0.05）。限饲组肉鸭的饲粮AM E、F/G、体蛋白和体水分显著高于自由采食组（P〈0.05）,ADFI、ADG、体脂肪、体能量、REf、REp、MEI、RE和HP却显著低于自由采食组（P〈0.05）。2-3周龄天府肉鸭MEI和log10HP间的回归方程为：log10HP=2.76＋0.000 1×MEI,BW与BE的回归方程为：BE=-768.87＋10.71×BW。由此可见,2-3周龄天府肉鸭的NEm为577.03 k J/（kg BW0.75·d）,NEg为10.71 k J/g,2-3周龄天府肉鸭NE需要量的析因模型为：NE=577.03BW0.75＋10.71△W。展开更多
Using foxtail millet (Setaria italica (L.) Beauv.) male-sterile line 1066A as female parent and Yugu 1 primary trisomic series (1 - 7) and tetrasomics 8, 9 as male parents, chromosome location of gene for male-sterili...Using foxtail millet (Setaria italica (L.) Beauv.) male-sterile line 1066A as female parent and Yugu 1 primary trisomic series (1 - 7) and tetrasomics 8, 9 as male parents, chromosome location of gene for male-sterility and yellow seedling in line 1066A was studied by primary trisomic analysis. The plants of F-1 generation of trisomics 2 - 9 were obtained by crossing with a great many plants of 1066A. F-1 generation of trisomics was similar to their male parent in morphologic characters, the color of their seedling was green, and pollen was partially fertile. The segregation ratio of fertility to sterility is 3:1 in F-2 generation of trisomics 2, 3, 4, 5, 7, 8 and 9; and 14:1 only in F-2 generation of trisomic 6 (chi(0.05)(2) = 0.012). The segregation ratio of green seedling to yellow seedling is 12:1 only in F-2 generation of trisomic 7 (chi(0.05)(2) = 0.31), but in other cases, this ratio is 3:1. The results indicated that the male-sterility gene was located on chromosome 6, and the gene for yellow seedling was monogenic recessive and located on chromosome 7. The rate of trisomics transmission by pollen was tested, trisomics 8 and 9 were the highest in rates of trisomics transmission and followed by trisomics 6 and 4.展开更多
The estimation of the quality factor Q plays a fundamental role in enhancing seismic resolution via absorption compensation in the near-surface layer.We present a new geometry that can be used to acquire field data by...The estimation of the quality factor Q plays a fundamental role in enhancing seismic resolution via absorption compensation in the near-surface layer.We present a new geometry that can be used to acquire field data by combining surface and cross-hole surveys to decrease the effect of geophone coupling on Q estimation.In this study,we drilled number of receiver holes around the source hole,each hole has different depth and each geophone is placed geophones into the bottom of each receiver hole to avoid the effect of geophone coupling with the borehole wall on Q estimation in conventional cross-hole seismic surveys.We also propose a novel tomographic inversion of the Q factor without the effect of the source signature,and examine its stability and reliability using synthetic data.We estimate the Q factors of the near-surface layer in two different frequency bands using field data acquired in the Dagang Oilfield.The results show that seismic absorption in the nearsurface layer is much greater than that in the subsurface strata.Thus,it is of critical practical importance to enhance the seismic solution by compensating for near-surface absorption.In addition,we derive different Q factors from two frequency bands,which can be treated,to some extent,as evidence of a frequency-dependent Q.展开更多
The engineering properties of metals and alloys are related to their structures. The change in mechanical properties of the metals and alloys can be achieved by the process of heat treatment. Induction hardening is on...The engineering properties of metals and alloys are related to their structures. The change in mechanical properties of the metals and alloys can be achieved by the process of heat treatment. Induction hardening is one such a process involves phase transformation by rapid heating and cooling of the outer surface. Induction hardening improves the outer surface hardness and wear resistant properties keeping the original toughness and ductility in the inner core. However past experiences shows that during heat treatment, parts have undergone dimensional changes due to thermal fluctuations and phase transformations. Dimensional changes can lead to excessive distortion in the component which always presented difficulties to the uses of many varieties of steels which can be hardened by induction hardening. The dimensional changes in components which have been induction hardened have for a long time proved costly and troublesome to manufacturers. These difficulties apply particularly in the automotive industry where the amount of distortion in rack and pinion assembly has been related to their noise level in operation and investigators have suggested a link between distortion and the initiation of fatigue failure. [1] Although the complete elimination of distortion would be an ideal aim, manufacturers are reconciled to the fact that a certain amount of distortion is an inherent part of the hardening process. However, if the amount of distortion is uniform and predictable, an allowance could be made in the initial machining operations. It was with these aims that investigations into the control of distortion in bright bar (EN 18D steel) used in rack application (Power steering assembly) have been carried out by parameter optimization展开更多
文摘Marine structures are frequently subjected to repeated impact loadings,resulting in failure of the structures,even causing serious accidents.The analytical expressions of dimensionless permanent deflection and impact force of a metal beam based on maximal normal yield surface are derived by membrane factor method(MFM),then the results are compared with repeated impact tests.It can be found that the solutions based on MFM are between the upper and lower bounds,and very close to the results of the repeated impact tests,indicating the theoretical model proposed can predict the plastic responses of the metal beam accurately.What’s more,the influences of impact location and boundary condition on the dynamic responses of the beam subjected to repeated impacts are determined.Results show that,as the distance of impact location from the middle span of the beam increases,the permanent deflection decreases,while the impact force increases.Meanwhile,the influences of impact location enhance as the impact number increases.When the permanent deflection is smaller than the thickness,the effect of boundary condition on the plastic responses is significant.However,when the deflection is larger than the thickness,the beam will be like a string and only axial force works,resulting in little influence of boundary condition on the plastic responses of the beam.
文摘本试验旨在测定2-3周龄天府肉鸭的净能（NE）需要量。选取7日龄天府肉鸭300只,其中50只随机分为自由采食组和15%、25%、35%、45%限饲组,进行代谢试验,测定不同饲喂水平下饲粮的表观代谢能（AME）。另外250只用于饲养试验和比较屠宰试验。试验开始前选取10只用于初始体成分的测定,其余240只随机分为5个组（同代谢试验）。14日龄时,从自由采食组选10只屠宰,测定试验中期试验鸭体成分;21日龄时,从每个组选10只屠宰,测定试验末期试验鸭体成分。根据自由采食组和限饲组饲粮的AME和试验鸭的生长性能、体成分,获得试验鸭在不同饲喂水平的产热量（HP）和代谢能摄入量（MEI）,建立MEI和log10HP间的回归方程,外推到MEI为0时的HP即为维持净能需要量（NEm）;根据自由采食组试验鸭在3个阶段的机体总能量（BE）和体重（BW）,建立二者间的回归方程,方程的斜率为生长净能需要量（NEg）。结果如下：不同饲喂水平间,天府肉鸭的饲粮AME、平均日采食量（ADFI）、平均日增重（ADG）、料重比（F/G）、体脂肪、体蛋白、体能量、以脂肪形式沉积的能量（REf）、以蛋白质形式沉积的能量（REp）、MEI、沉积能（RE）和HP均存在显著差异（P〈0.05）。限饲组肉鸭的饲粮AM E、F/G、体蛋白和体水分显著高于自由采食组（P〈0.05）,ADFI、ADG、体脂肪、体能量、REf、REp、MEI、RE和HP却显著低于自由采食组（P〈0.05）。2-3周龄天府肉鸭MEI和log10HP间的回归方程为：log10HP=2.76＋0.000 1×MEI,BW与BE的回归方程为：BE=-768.87＋10.71×BW。由此可见,2-3周龄天府肉鸭的NEm为577.03 k J/（kg BW0.75·d）,NEg为10.71 k J/g,2-3周龄天府肉鸭NE需要量的析因模型为：NE=577.03BW0.75＋10.71△W。
文摘Using foxtail millet (Setaria italica (L.) Beauv.) male-sterile line 1066A as female parent and Yugu 1 primary trisomic series (1 - 7) and tetrasomics 8, 9 as male parents, chromosome location of gene for male-sterility and yellow seedling in line 1066A was studied by primary trisomic analysis. The plants of F-1 generation of trisomics 2 - 9 were obtained by crossing with a great many plants of 1066A. F-1 generation of trisomics was similar to their male parent in morphologic characters, the color of their seedling was green, and pollen was partially fertile. The segregation ratio of fertility to sterility is 3:1 in F-2 generation of trisomics 2, 3, 4, 5, 7, 8 and 9; and 14:1 only in F-2 generation of trisomic 6 (chi(0.05)(2) = 0.012). The segregation ratio of green seedling to yellow seedling is 12:1 only in F-2 generation of trisomic 7 (chi(0.05)(2) = 0.31), but in other cases, this ratio is 3:1. The results indicated that the male-sterility gene was located on chromosome 6, and the gene for yellow seedling was monogenic recessive and located on chromosome 7. The rate of trisomics transmission by pollen was tested, trisomics 8 and 9 were the highest in rates of trisomics transmission and followed by trisomics 6 and 4.
基金supported by the National Natural Science Foundation of China(Grant No.41174117 and 41474109)the National Key Basic Research Development Program of China(Grant No.2013CB228606)
文摘The estimation of the quality factor Q plays a fundamental role in enhancing seismic resolution via absorption compensation in the near-surface layer.We present a new geometry that can be used to acquire field data by combining surface and cross-hole surveys to decrease the effect of geophone coupling on Q estimation.In this study,we drilled number of receiver holes around the source hole,each hole has different depth and each geophone is placed geophones into the bottom of each receiver hole to avoid the effect of geophone coupling with the borehole wall on Q estimation in conventional cross-hole seismic surveys.We also propose a novel tomographic inversion of the Q factor without the effect of the source signature,and examine its stability and reliability using synthetic data.We estimate the Q factors of the near-surface layer in two different frequency bands using field data acquired in the Dagang Oilfield.The results show that seismic absorption in the nearsurface layer is much greater than that in the subsurface strata.Thus,it is of critical practical importance to enhance the seismic solution by compensating for near-surface absorption.In addition,we derive different Q factors from two frequency bands,which can be treated,to some extent,as evidence of a frequency-dependent Q.
文摘The engineering properties of metals and alloys are related to their structures. The change in mechanical properties of the metals and alloys can be achieved by the process of heat treatment. Induction hardening is one such a process involves phase transformation by rapid heating and cooling of the outer surface. Induction hardening improves the outer surface hardness and wear resistant properties keeping the original toughness and ductility in the inner core. However past experiences shows that during heat treatment, parts have undergone dimensional changes due to thermal fluctuations and phase transformations. Dimensional changes can lead to excessive distortion in the component which always presented difficulties to the uses of many varieties of steels which can be hardened by induction hardening. The dimensional changes in components which have been induction hardened have for a long time proved costly and troublesome to manufacturers. These difficulties apply particularly in the automotive industry where the amount of distortion in rack and pinion assembly has been related to their noise level in operation and investigators have suggested a link between distortion and the initiation of fatigue failure. [1] Although the complete elimination of distortion would be an ideal aim, manufacturers are reconciled to the fact that a certain amount of distortion is an inherent part of the hardening process. However, if the amount of distortion is uniform and predictable, an allowance could be made in the initial machining operations. It was with these aims that investigations into the control of distortion in bright bar (EN 18D steel) used in rack application (Power steering assembly) have been carried out by parameter optimization
