Hybrid tilapia were reared at densities of 1, 5 or 10 fish per tank for four weeks. Mortality was 0 at 1 and 10 fish per tank, but was 25% at 5 fish per tank. Specific growth rate was highest at 1 fish per tank, and l...Hybrid tilapia were reared at densities of 1, 5 or 10 fish per tank for four weeks. Mortality was 0 at 1 and 10 fish per tank, but was 25% at 5 fish per tank. Specific growth rate was highest at 1 fish per tank, and lowest at 5 fish per tank. The lower growth rate at the intermediate stocking density was associated with reduced feed efficiency, but there was no reduction in feed intake or digestibility. The results suggested increased metabolic cost caused by aggressive behaviour at intermediate stocking density, which can be suppressed by a further increase in density.展开更多
Since forestation of pure forest of Pinus massoniana is liable to suffer from pest calamity, soilerosion, decrease of soil fertility, and difficulty in wood production in the hilly areas of southern China, weconducted...Since forestation of pure forest of Pinus massoniana is liable to suffer from pest calamity, soilerosion, decrease of soil fertility, and difficulty in wood production in the hilly areas of southern China, weconducted an investigation on the three types of forests in Gaoan County of Jiangxi Province, namely, thepure forest of Pinus massoniana, the pure forest of Schima superba, and the mixed forest consisting of thetwo species, setting up standard stand, measuring and studying the growing stock, biomass, leaf area, roots,soil, vegetation, pests, litters, soil erosion, microclimate, etc., with the following results. ① The averageheight, diameter at chest height, and volume of the mixed forest are higher than those of the pure forest ofPinus massoniana by 30.9%, 31.7% and 10.6%, respectively. ② The biomass of the mixed forest is 2.24times as much as that of the pure forest of Pinus massoniana. ③ The litters of the mixed forest is 3.37 timesand 1.96 times as much as the litters of the pure forest of Pinus massoniana and the pure forest of Schimasuperba respectively. ④ The occurrence of pest calamity per tree is lower and the conditions of soil erosionand microclimate are better than those of the pure forest of Pinus massoniana. ⑤ The mixed forest of the twospecies is an excellent mixed type of needle-leaf and deciduous forest worth being popularized in Chinassubtropical areas, especially in the low hilly areas. It is recommended in plantation that the mixed patterns bebetween trees, lines, small blocks, or scattered-dots, the ratio of mixture of Pinus massoniana and Schimasuperba be 5 to 1, or 3 to 1, and the initial space between trees be 1.2, 1.5, or 2.0 m while the initial densitybe 6 944 to 4 440 trees per square hectare.展开更多
Complex interactions of plates with ambient fluid are common in daily lives,e.g.flags flapping in wind,aerofoils oscillating in flow.Recently,the feasibility to harvest energy using the flutter motion has been demonst...Complex interactions of plates with ambient fluid are common in daily lives,e.g.flags flapping in wind,aerofoils oscillating in flow.Recently,the feasibility to harvest energy using the flutter motion has been demonstrated.The objectives of this study are to systematically explore the effects of the material damping on flag flutter,and then to study the energy interchange between the fluid and the flag.In this study,a two-dimensional model was developed.Three dimensionless parameters govern the system,i.e.the mass ratio between the structure and the fluid,the dimensionless fluid velocity and the dimensionless material damping.Results show that the critical velocity increases with the increase of the material damping.The oscillation frequency of the flag decreases with the increase of the material damping,and the time-averaged energy dissipation rate initially increases and then decreases.The increase of the material damping causes the transition of the system from a higher frequency oscillating state to a lower frequency oscillating state,and from a chaotic state to a periodic state.展开更多
文摘Hybrid tilapia were reared at densities of 1, 5 or 10 fish per tank for four weeks. Mortality was 0 at 1 and 10 fish per tank, but was 25% at 5 fish per tank. Specific growth rate was highest at 1 fish per tank, and lowest at 5 fish per tank. The lower growth rate at the intermediate stocking density was associated with reduced feed efficiency, but there was no reduction in feed intake or digestibility. The results suggested increased metabolic cost caused by aggressive behaviour at intermediate stocking density, which can be suppressed by a further increase in density.
文摘Since forestation of pure forest of Pinus massoniana is liable to suffer from pest calamity, soilerosion, decrease of soil fertility, and difficulty in wood production in the hilly areas of southern China, weconducted an investigation on the three types of forests in Gaoan County of Jiangxi Province, namely, thepure forest of Pinus massoniana, the pure forest of Schima superba, and the mixed forest consisting of thetwo species, setting up standard stand, measuring and studying the growing stock, biomass, leaf area, roots,soil, vegetation, pests, litters, soil erosion, microclimate, etc., with the following results. ① The averageheight, diameter at chest height, and volume of the mixed forest are higher than those of the pure forest ofPinus massoniana by 30.9%, 31.7% and 10.6%, respectively. ② The biomass of the mixed forest is 2.24times as much as that of the pure forest of Pinus massoniana. ③ The litters of the mixed forest is 3.37 timesand 1.96 times as much as the litters of the pure forest of Pinus massoniana and the pure forest of Schimasuperba respectively. ④ The occurrence of pest calamity per tree is lower and the conditions of soil erosionand microclimate are better than those of the pure forest of Pinus massoniana. ⑤ The mixed forest of the twospecies is an excellent mixed type of needle-leaf and deciduous forest worth being popularized in Chinassubtropical areas, especially in the low hilly areas. It is recommended in plantation that the mixed patterns bebetween trees, lines, small blocks, or scattered-dots, the ratio of mixture of Pinus massoniana and Schimasuperba be 5 to 1, or 3 to 1, and the initial space between trees be 1.2, 1.5, or 2.0 m while the initial densitybe 6 944 to 4 440 trees per square hectare.
基金supported by the National Natural Science Foundation of China(Grant Nos.10832010,11002138 and 11102027)the Innovation Project of CAS(Grant No.KJCX2-YW-L05)
文摘Complex interactions of plates with ambient fluid are common in daily lives,e.g.flags flapping in wind,aerofoils oscillating in flow.Recently,the feasibility to harvest energy using the flutter motion has been demonstrated.The objectives of this study are to systematically explore the effects of the material damping on flag flutter,and then to study the energy interchange between the fluid and the flag.In this study,a two-dimensional model was developed.Three dimensionless parameters govern the system,i.e.the mass ratio between the structure and the fluid,the dimensionless fluid velocity and the dimensionless material damping.Results show that the critical velocity increases with the increase of the material damping.The oscillation frequency of the flag decreases with the increase of the material damping,and the time-averaged energy dissipation rate initially increases and then decreases.The increase of the material damping causes the transition of the system from a higher frequency oscillating state to a lower frequency oscillating state,and from a chaotic state to a periodic state.
