Local scour around pipelines crossing rivers or in marine environments is a significant concern.It can lead to failure of the pipelines resulting in environmental side effects and economic losses.This study developed ...Local scour around pipelines crossing rivers or in marine environments is a significant concern.It can lead to failure of the pipelines resulting in environmental side effects and economic losses.This study developed an experimental method to reduce local scour around pipelines with a steady flow of clear water by installing cylindrical and cubical sacrificial piles.Three sizes of sacrificial piles were examined in a linear arrangement.Sacrificial piles were installed on the upstream side of the pipeline at three distances.Maximum scour depth reduction rates below the pipeline were computed.The results showed that sacrificial piles could protect a pipeline from local scour.A portion of scoured sediment around the sacrificial piles was deposited beneath the pipeline.This sediment accumulation reduced the scour depth beneath the pipeline.Analysis of the experimental results demonstrated that the size of piles(d),the spacing between piles,and the distance between the pipe and piles(Xp)were the variables that reduced the maximum scour beneath the pipeline with a diameter of D.For the piles with d=0.40D and 0.64D,X_(p)=4OD was the optimal distance to install a group of piles,and cubical piles could mitigate scour more effectively than cylindrical piles under similar conditions.For the piles with d=D,the greatest reduction in scour depth was achieved at X_(p)=50D with any desired spacings between piles,and cylindrical piles in this dimension could protect the pipeline against scour more effectively than cubical piles.展开更多
In this study, the effects of hot water temperature on clarity, total soluble solids, polyphenol oxidase （PPO） and color of banana juice during hot water ex-traction were discussed based on the theory in which heat ...In this study, the effects of hot water temperature on clarity, total soluble solids, polyphenol oxidase （PPO） and color of banana juice during hot water ex-traction were discussed based on the theory in which heat treatment might induce the pectin and protein in banana pulp to form insoluble products. The results showed the hot water temperature had a significant effect on the formation of insol-uble polymers in banana pulp from pectin and protein. In 75 ℃ water, the pectin and protein in banana pulp were most inclined to form insoluble products. Under this condition, the clarity of banana juice was also highest. The light transmittance at 660 nm was close to 90%. In the banana juice, extracted by 75 ℃ water, the pectin and protein contents were lowest, and they were lower than 7.3 mg/100 ml and 12.9 mg/100 ml respectively. The 75 ℃ water could not inactivate completely the pectin in banana pulp due to its high heat resistance, Therefore, 0.05% L-cys-teine or ascorbic acid needed to be added into banana pulp to inhibit the browning of juice induced by residual PPO.展开更多
The effects of oblique submerged scouring jets on sand beds with various particle sizes have been studied experimentally.In particular,a total of 25 experiments have been carried out to explore the influences of the j...The effects of oblique submerged scouring jets on sand beds with various particle sizes have been studied experimentally.In particular,a total of 25 experiments have been carried out to explore the influences of the jet angle and application time on the considered submerged sand beds.Test results conducted with a specially-designed device have shown that the scouring efficiency attains a maximum when the inclination angle is in the range between 15°and 20°and then it decreases when the inclination angle becomes higher.展开更多
Forest clear cutting alters the hydrological processes such as interception, evapotranspiration and infiltration of the forested watershed and consequently increases the amount of water and sediment leaving the waters...Forest clear cutting alters the hydrological processes such as interception, evapotranspiration and infiltration of the forested watershed and consequently increases the amount of water and sediment leaving the watershed. This study was conducted in the Upper Pearl River Watershed (UPRW) located in east-central Mississippito evaluate and compare the potential impacts of forest clear cutting on water and sediment yields using the Soil and Water Assessment Tool (SWAT) model. For this purpose, five hypothetical scenarios representing clear cutting at 10%, 20%, 30%, 55% and 75% of the total forest area of the watershed were generated. The SWAT model was first calibrated (1981-1995) and validated (1996-2008) for monthly stream flow, and later verified (February 2010 to December 2010) for monthly sediment load. Results show that the SWAT model was able to simulate stream flow and sediment load satisfactorily during the calibration/validation and verification periods, respectively. The potential changes caused in yields as a result of the changes in clearcut area were computed by comparing predicted yields from each clear cutting scenario and a base condition. Results from five scenarios demonstrate substantial increase in yields with an increase in the percentage of forest area clearcut. When compared with the base scenario, potential changes in water and sediment yields occur between 17% to 96% and 33% to 250%, respectively, with an increase in clearcut area from 10% to 75%. Results also indicate that, for all scenarios, percentage wise change is larger for sediment yield. Although predicted water and sediment yields generated from each scenario are subject to further verification with observed data, this study provides useful information about the potential amount of water and sediment yields that may be produced under each scenario, and that the potential changes that may happen on yields if similar magnitude of clear cutting occurs in the UPRW or in similar watershed.展开更多
文摘Local scour around pipelines crossing rivers or in marine environments is a significant concern.It can lead to failure of the pipelines resulting in environmental side effects and economic losses.This study developed an experimental method to reduce local scour around pipelines with a steady flow of clear water by installing cylindrical and cubical sacrificial piles.Three sizes of sacrificial piles were examined in a linear arrangement.Sacrificial piles were installed on the upstream side of the pipeline at three distances.Maximum scour depth reduction rates below the pipeline were computed.The results showed that sacrificial piles could protect a pipeline from local scour.A portion of scoured sediment around the sacrificial piles was deposited beneath the pipeline.This sediment accumulation reduced the scour depth beneath the pipeline.Analysis of the experimental results demonstrated that the size of piles(d),the spacing between piles,and the distance between the pipe and piles(Xp)were the variables that reduced the maximum scour beneath the pipeline with a diameter of D.For the piles with d=0.40D and 0.64D,X_(p)=4OD was the optimal distance to install a group of piles,and cubical piles could mitigate scour more effectively than cylindrical piles under similar conditions.For the piles with d=D,the greatest reduction in scour depth was achieved at X_(p)=50D with any desired spacings between piles,and cylindrical piles in this dimension could protect the pipeline against scour more effectively than cubical piles.
基金Supported by the Key Project of the National Twelfth-Five Year Research Program of China(2012BAD31B03)Guangdong Province Science and Technology Project(2011B010100041)~~
文摘In this study, the effects of hot water temperature on clarity, total soluble solids, polyphenol oxidase （PPO） and color of banana juice during hot water ex-traction were discussed based on the theory in which heat treatment might induce the pectin and protein in banana pulp to form insoluble products. The results showed the hot water temperature had a significant effect on the formation of insol-uble polymers in banana pulp from pectin and protein. In 75 ℃ water, the pectin and protein in banana pulp were most inclined to form insoluble products. Under this condition, the clarity of banana juice was also highest. The light transmittance at 660 nm was close to 90%. In the banana juice, extracted by 75 ℃ water, the pectin and protein contents were lowest, and they were lower than 7.3 mg/100 ml and 12.9 mg/100 ml respectively. The 75 ℃ water could not inactivate completely the pectin in banana pulp due to its high heat resistance, Therefore, 0.05% L-cys-teine or ascorbic acid needed to be added into banana pulp to inhibit the browning of juice induced by residual PPO.
基金The paper was supported by National Nature Fund of China(52071091)the Key Laboratory of Expressway Construction Machinery of Shanxi Province which is gained by Zhang(300102259512).
文摘The effects of oblique submerged scouring jets on sand beds with various particle sizes have been studied experimentally.In particular,a total of 25 experiments have been carried out to explore the influences of the jet angle and application time on the considered submerged sand beds.Test results conducted with a specially-designed device have shown that the scouring efficiency attains a maximum when the inclination angle is in the range between 15°and 20°and then it decreases when the inclination angle becomes higher.
文摘Forest clear cutting alters the hydrological processes such as interception, evapotranspiration and infiltration of the forested watershed and consequently increases the amount of water and sediment leaving the watershed. This study was conducted in the Upper Pearl River Watershed (UPRW) located in east-central Mississippito evaluate and compare the potential impacts of forest clear cutting on water and sediment yields using the Soil and Water Assessment Tool (SWAT) model. For this purpose, five hypothetical scenarios representing clear cutting at 10%, 20%, 30%, 55% and 75% of the total forest area of the watershed were generated. The SWAT model was first calibrated (1981-1995) and validated (1996-2008) for monthly stream flow, and later verified (February 2010 to December 2010) for monthly sediment load. Results show that the SWAT model was able to simulate stream flow and sediment load satisfactorily during the calibration/validation and verification periods, respectively. The potential changes caused in yields as a result of the changes in clearcut area were computed by comparing predicted yields from each clear cutting scenario and a base condition. Results from five scenarios demonstrate substantial increase in yields with an increase in the percentage of forest area clearcut. When compared with the base scenario, potential changes in water and sediment yields occur between 17% to 96% and 33% to 250%, respectively, with an increase in clearcut area from 10% to 75%. Results also indicate that, for all scenarios, percentage wise change is larger for sediment yield. Although predicted water and sediment yields generated from each scenario are subject to further verification with observed data, this study provides useful information about the potential amount of water and sediment yields that may be produced under each scenario, and that the potential changes that may happen on yields if similar magnitude of clear cutting occurs in the UPRW or in similar watershed.
