The biodiversity quality of ground-layer invertebrates within the cropped area of a plantation of the biomass crop willow short-rotation coppice (SRC) grown within a floodplain was compared to the biodiversity quality...The biodiversity quality of ground-layer invertebrates within the cropped area of a plantation of the biomass crop willow short-rotation coppice (SRC) grown within a floodplain was compared to the biodiversity quality of the neighbouring plots of floodplain grassland and a mixed deciduous woodland plantation. Pitfall traps were used to collect ground beetles (Carabidae) and arachnids (Araneae and Opiliones) in the plots over a period of two years. A range of biodiversity indices was used to assess the biodiversity quality of each of the three plots, and the willow SRC was compared to each of the controls using Mann-Whitney tests. The willow SRC transitioned from almost bare ground to young woodland during the two years of the study, which affected comparisons with alternative land uses as the habitat during the second year was very different from the habitat at the start of the study. Compared to plantation woodland, in the first year, the effect was mostly positive, but this declined in the second year. Compared to grassland there was a largely negative effect in both years. However, when in combination with other habitats, willow SRC cultivation on floodplain land may have an overall positive effect on invertebrate biodiversity quality.展开更多
The composite board industry in Iran is obliged to use residues from forest operation as well as wood industry for competing with paper industry because of shortage of wood. In the present study we investigated the re...The composite board industry in Iran is obliged to use residues from forest operation as well as wood industry for competing with paper industry because of shortage of wood. In the present study we investigated the residues from poplar plantation used for particleboard production. Three kinds of wood materials, poplar branches, small di- ameter poplar wood (3-8 cm) and beech wood, were used in the experiment of particleboard production. The results demonstrated that the characteristic of particleboard made from poplar branches and small diameter wood is comparable to that made from mature beech wood. To avoid too much residual acid in the final board, the properties of boards produced with 1.5% hardener at 175℃ press temperature are acceptable, although the properties of particleboard produced with 2% hardener were higher than were higher than that of the board produced with lower hardener (1% or 1.5%).. The MOR, MOE and IB of particleboard made from branches were measured as 14.57, 2015, and 1.32 MPa, respectively, while The MOR, MOE and IB of particleboard produced from small diameter poplar wood were 19.90, 2199, and 1.86 MPa, respectively. The thickness swelling of boards made from branches after 2 and 24 h im- mersion in water was 20.14% and 31.26%. The utilization of branches and very small diameter wood of poplar is recommended for the survival and developments of particleboard industry in Iran.展开更多
To meet the need for effective management of poplar(Populus spp.)plantations in Sweden regarding different assortments,two equations were developed to estimate commercial stem volume for either any given top diameter ...To meet the need for effective management of poplar(Populus spp.)plantations in Sweden regarding different assortments,two equations were developed to estimate commercial stem volume for either any given top diameter or any stem fraction length.Data for fitting the equations came from 112 trees in 42 stands on farmland.Mean stand age,density and diameter at breast height(DBH)was 15.5 years,980 stems/ha,and 24.2 cm,respectively.Independent variables are for Eq.(1):DBH,total stem height(H)and given stem length fraction(h).For Eq.(2);DBH,H and given top diameter(d).Eq.(2)based on top diameter performed better than Eq.(1)based on stem length fraction with R2 of 0.994 and 0.991 respectively,and with Absolute Bias(AB)of 0.041 and 0.047(m3)respectively.The presented equations can be used to optimise the efficiency and profitability of poplar plantations when harvesting trees with larger diameters,for additional timber assortments other than bioenergy.展开更多
In the present paper, a nonlinear multi 'actuator disk' model is proposed to analyze the dynamicbehavior of flow instabilities, including rotating stall and surge, in high speed multistage axial compressors. T...In the present paper, a nonlinear multi 'actuator disk' model is proposed to analyze the dynamicbehavior of flow instabilities, including rotating stall and surge, in high speed multistage axial compressors. The model describes the duct flow fields using two dimensional, compressible and unsteadyEuler equations, and accounts for the influences of downstream plenum and throttle in the system aswell. It replaces each blade row of multistage compressors with a disk. For numerical calculations,the time marching procedure, using MacCormack two steps scheme, is used. The main purpose of thispaper is to predict the mechanism of two dimensional short wavelength rotating stall inception and theinteraction between blade rows in high speed multistage compressors. It has been demonstrated thatthe model has the ability to predict those phenomena, and the results show that some system parameters have a strong effect on the stall features as well. Results for a five stage high speed compressorare analyzed in detail, and comparison with the experimental data demonstrates that the model andcalculating results are reliable.展开更多
文摘The biodiversity quality of ground-layer invertebrates within the cropped area of a plantation of the biomass crop willow short-rotation coppice (SRC) grown within a floodplain was compared to the biodiversity quality of the neighbouring plots of floodplain grassland and a mixed deciduous woodland plantation. Pitfall traps were used to collect ground beetles (Carabidae) and arachnids (Araneae and Opiliones) in the plots over a period of two years. A range of biodiversity indices was used to assess the biodiversity quality of each of the three plots, and the willow SRC was compared to each of the controls using Mann-Whitney tests. The willow SRC transitioned from almost bare ground to young woodland during the two years of the study, which affected comparisons with alternative land uses as the habitat during the second year was very different from the habitat at the start of the study. Compared to plantation woodland, in the first year, the effect was mostly positive, but this declined in the second year. Compared to grassland there was a largely negative effect in both years. However, when in combination with other habitats, willow SRC cultivation on floodplain land may have an overall positive effect on invertebrate biodiversity quality.
文摘The composite board industry in Iran is obliged to use residues from forest operation as well as wood industry for competing with paper industry because of shortage of wood. In the present study we investigated the residues from poplar plantation used for particleboard production. Three kinds of wood materials, poplar branches, small di- ameter poplar wood (3-8 cm) and beech wood, were used in the experiment of particleboard production. The results demonstrated that the characteristic of particleboard made from poplar branches and small diameter wood is comparable to that made from mature beech wood. To avoid too much residual acid in the final board, the properties of boards produced with 1.5% hardener at 175℃ press temperature are acceptable, although the properties of particleboard produced with 2% hardener were higher than were higher than that of the board produced with lower hardener (1% or 1.5%).. The MOR, MOE and IB of particleboard made from branches were measured as 14.57, 2015, and 1.32 MPa, respectively, while The MOR, MOE and IB of particleboard produced from small diameter poplar wood were 19.90, 2199, and 1.86 MPa, respectively. The thickness swelling of boards made from branches after 2 and 24 h im- mersion in water was 20.14% and 31.26%. The utilization of branches and very small diameter wood of poplar is recommended for the survival and developments of particleboard industry in Iran.
文摘To meet the need for effective management of poplar(Populus spp.)plantations in Sweden regarding different assortments,two equations were developed to estimate commercial stem volume for either any given top diameter or any stem fraction length.Data for fitting the equations came from 112 trees in 42 stands on farmland.Mean stand age,density and diameter at breast height(DBH)was 15.5 years,980 stems/ha,and 24.2 cm,respectively.Independent variables are for Eq.(1):DBH,total stem height(H)and given stem length fraction(h).For Eq.(2);DBH,H and given top diameter(d).Eq.(2)based on top diameter performed better than Eq.(1)based on stem length fraction with R2 of 0.994 and 0.991 respectively,and with Absolute Bias(AB)of 0.041 and 0.047(m3)respectively.The presented equations can be used to optimise the efficiency and profitability of poplar plantations when harvesting trees with larger diameters,for additional timber assortments other than bioenergy.
文摘In the present paper, a nonlinear multi 'actuator disk' model is proposed to analyze the dynamicbehavior of flow instabilities, including rotating stall and surge, in high speed multistage axial compressors. The model describes the duct flow fields using two dimensional, compressible and unsteadyEuler equations, and accounts for the influences of downstream plenum and throttle in the system aswell. It replaces each blade row of multistage compressors with a disk. For numerical calculations,the time marching procedure, using MacCormack two steps scheme, is used. The main purpose of thispaper is to predict the mechanism of two dimensional short wavelength rotating stall inception and theinteraction between blade rows in high speed multistage compressors. It has been demonstrated thatthe model has the ability to predict those phenomena, and the results show that some system parameters have a strong effect on the stall features as well. Results for a five stage high speed compressorare analyzed in detail, and comparison with the experimental data demonstrates that the model andcalculating results are reliable.