The beach studied in this paper spans a length of 51 km and is one of several long sandy beaches in the southern Bohai Strait. Due to the obstruction of islands in the northeast and the influence of the underwater top...The beach studied in this paper spans a length of 51 km and is one of several long sandy beaches in the southern Bohai Strait. Due to the obstruction of islands in the northeast and the influence of the underwater topography, the wave environment in the offshore area is complex; beach types and sediment transport characteristics vary along different coasts. The coastlines extracted from six aerial photographs in different years were compared to demonstrate the evolving features. Seven typical beach profiles were selected to study the lateral beach variation characteristics. Continuous wind and wave observation data from Beihuangcheng ocean station during 2009 were employed for the hindcast of the local wave environment using a regional spectral wave model. Then the results of the wave hindcast were incorporated into the LITDRIFT model to compute the sediment transport rates and directions along the coasts and analyze the longshore sand movement. The results show that the coastline evolution of sand beaches in the southern Bohai Strait has spatial and temporal variations and the coast can be divided into four typical regions. Region(I), the north coast of Qimudao, is a slightly eroded and dissipative beach with a large sediment transport rate; Region(II), the southwest coast of Gangluan Port, is a slightly deposited and dissipative beach with moderate sediment transport rate; Region(III), in the central area, is a beach that is gradually transformed from a slightly eroded dissipative beach to a moderately or slightly strong eroded bar-trough beach from west to east with a relatively moderate sediment transport rate. Region(IV), on the east coast, is a strongly eroded and reflective beach with a weak sediment transport rate. The wave conditions exhibit an increasing trend from west to east in the offshore area. The distribution of the wave-induced current inside the wave breaking region and the littoral sediment transport in the nearshore region exhibit a gradual weakening tendency from west to east, which is opposite to the trend of the wave conditions outside the breaking region. The presence of submerged shoal(Dengzhou Shoal), deep trough(Dengzhou Channel), islands and irregular topography influnces the wave climate, beach types, wave-induced current features, littoral sediment transport trends and coastline evolution patterns in the southern Bohai Strait. Human activities, such as the sand exploitation of Dengzhou Shoal and other coastal engineering projects, also influence the beach morphology and coastline evolution.展开更多
Al-5Cu-4.5Mg-2.5Zn alloy was prepared and the alloy ingots were fabricated by squeeze casting in this work.Considering these negative effects of composition segregation and coarse second phases,some heat treatments we...Al-5Cu-4.5Mg-2.5Zn alloy was prepared and the alloy ingots were fabricated by squeeze casting in this work.Considering these negative effects of composition segregation and coarse second phases,some heat treatments were adopted in this research.Microstructures,element distribution,phase constitutions and mechanical properties of Al-5Cu-4.5Mg-2.5Zn alloy ingots before and after heat treatments were investigated.It was discovered that these heat treatments would influence and extremely optimize the microstructures and properties of Al-5Cu-4.5Mg-2.5Zn alloy.Except some residual S (Al_(2)CuMg) phase and a few of η phase,the precipitate free zone (PFZ) and the Guinier Preston zone (GPZ) formed in the alloy.It was also found that θ′′ (Al_(2)Cu) and η′′ (MgZn_(2)) phases formed and kept a consistent relationship with the aluminum matrix.As the result,these properties of ultimate tensile strength (UTS),percentage of elongation and Brinell hardness (HB) were greatly elevated.The UTS,percent of elongation and HB were 469 MPa,8.1% and 208 N/mm^(2),respectively.展开更多
Oil droplet size distribution （ODSD） plays a critical role in the rising velocity and transport of oil droplets in subsurface oil releases. In this paper, subsurface oil release experiments were conducted to study O...Oil droplet size distribution （ODSD） plays a critical role in the rising velocity and transport of oil droplets in subsurface oil releases. In this paper, subsurface oil release experiments were conducted to study ODSD under different experimental conditions in a laboratory water tank observed by two high-speed cameras in March and April 2017. The correlation formulas Oh=lO.2Re-~ and Oh=39.2Re-1 （Re represents Reynolds number and Oh represents Ohnesorge number） were established to distinguish the boundaries of the three instability regimes in dimensionless space based on the experimental results. The oil droplet sizes from the experimental data showed an excellent match to the Rosin-Rammler distribution function with determination coefficients ranging from 0.86 to 1.00 for Lvda 10-1 oil. This paper also explored the influence factors on and change rules ofoil droplet size. The volume median diameter d50 decreased steadily with increasing jet velocity, and a sharp decrease occurred in the laminar-breakup regime. At Weber numbers （We） 〈100, the orifice diameter and oil viscosity appeared to have a large influence on the mean droplet diameter. At 100〈We〈1 000, the oil viscosity appeared to have a larger influence on the relative mean droplet diameter.展开更多
ZrO_(2)-5CrMnMo composite samples were prepared by hot press sintering.When NiCoCrAlY powders were used as the bonding layer and the different mixtures of NiCoCrAlY alloy and 3YSZ (3mol% yttria stabilized zirconia) ce...ZrO_(2)-5CrMnMo composite samples were prepared by hot press sintering.When NiCoCrAlY powders were used as the bonding layer and the different mixtures of NiCoCrAlY alloy and 3YSZ (3mol% yttria stabilized zirconia) ceramic powders were used as the transition layers,the connection between zirconia ceramic and 5CrMnMo steel were strengthened.Three composite samples with different structures were fabricated by heat spraying and hot press sintering.Shear and thermal shock cycle tests were conducted to characterize connection strength and thermal shock resistance of these samples.The shear strength reached 95.69 MPa,and the heating shock cycles achieved to the maximum value of 27.7 times.Microstructures and connection interfaces were analyzed by scanning electron microscopy.The hardness and wearing resistance of 3YSZ coat and 5CrMnMo substrate were compared,and the heat insulation property of composite samples were also discussed.It is shown that these composite materials fabricated in this research are benefited to be used as squeeze casting dies.展开更多
基金supported by the National Natural Science Foundation for the Youth(No.41106039)
文摘The beach studied in this paper spans a length of 51 km and is one of several long sandy beaches in the southern Bohai Strait. Due to the obstruction of islands in the northeast and the influence of the underwater topography, the wave environment in the offshore area is complex; beach types and sediment transport characteristics vary along different coasts. The coastlines extracted from six aerial photographs in different years were compared to demonstrate the evolving features. Seven typical beach profiles were selected to study the lateral beach variation characteristics. Continuous wind and wave observation data from Beihuangcheng ocean station during 2009 were employed for the hindcast of the local wave environment using a regional spectral wave model. Then the results of the wave hindcast were incorporated into the LITDRIFT model to compute the sediment transport rates and directions along the coasts and analyze the longshore sand movement. The results show that the coastline evolution of sand beaches in the southern Bohai Strait has spatial and temporal variations and the coast can be divided into four typical regions. Region(I), the north coast of Qimudao, is a slightly eroded and dissipative beach with a large sediment transport rate; Region(II), the southwest coast of Gangluan Port, is a slightly deposited and dissipative beach with moderate sediment transport rate; Region(III), in the central area, is a beach that is gradually transformed from a slightly eroded dissipative beach to a moderately or slightly strong eroded bar-trough beach from west to east with a relatively moderate sediment transport rate. Region(IV), on the east coast, is a strongly eroded and reflective beach with a weak sediment transport rate. The wave conditions exhibit an increasing trend from west to east in the offshore area. The distribution of the wave-induced current inside the wave breaking region and the littoral sediment transport in the nearshore region exhibit a gradual weakening tendency from west to east, which is opposite to the trend of the wave conditions outside the breaking region. The presence of submerged shoal(Dengzhou Shoal), deep trough(Dengzhou Channel), islands and irregular topography influnces the wave climate, beach types, wave-induced current features, littoral sediment transport trends and coastline evolution patterns in the southern Bohai Strait. Human activities, such as the sand exploitation of Dengzhou Shoal and other coastal engineering projects, also influence the beach morphology and coastline evolution.
基金Funded by the International Cooperation Project of the Ministry of Science and Technology of China (No. 2014DFR50320)the National Natural Science Foundation of China (No. 51174064)。
文摘Al-5Cu-4.5Mg-2.5Zn alloy was prepared and the alloy ingots were fabricated by squeeze casting in this work.Considering these negative effects of composition segregation and coarse second phases,some heat treatments were adopted in this research.Microstructures,element distribution,phase constitutions and mechanical properties of Al-5Cu-4.5Mg-2.5Zn alloy ingots before and after heat treatments were investigated.It was discovered that these heat treatments would influence and extremely optimize the microstructures and properties of Al-5Cu-4.5Mg-2.5Zn alloy.Except some residual S (Al_(2)CuMg) phase and a few of η phase,the precipitate free zone (PFZ) and the Guinier Preston zone (GPZ) formed in the alloy.It was also found that θ′′ (Al_(2)Cu) and η′′ (MgZn_(2)) phases formed and kept a consistent relationship with the aluminum matrix.As the result,these properties of ultimate tensile strength (UTS),percentage of elongation and Brinell hardness (HB) were greatly elevated.The UTS,percent of elongation and HB were 469 MPa,8.1% and 208 N/mm^(2),respectively.
基金The National Key Research and Development Program of China under contract No.2016YFC1402303
文摘Oil droplet size distribution （ODSD） plays a critical role in the rising velocity and transport of oil droplets in subsurface oil releases. In this paper, subsurface oil release experiments were conducted to study ODSD under different experimental conditions in a laboratory water tank observed by two high-speed cameras in March and April 2017. The correlation formulas Oh=lO.2Re-~ and Oh=39.2Re-1 （Re represents Reynolds number and Oh represents Ohnesorge number） were established to distinguish the boundaries of the three instability regimes in dimensionless space based on the experimental results. The oil droplet sizes from the experimental data showed an excellent match to the Rosin-Rammler distribution function with determination coefficients ranging from 0.86 to 1.00 for Lvda 10-1 oil. This paper also explored the influence factors on and change rules ofoil droplet size. The volume median diameter d50 decreased steadily with increasing jet velocity, and a sharp decrease occurred in the laminar-breakup regime. At Weber numbers （We） 〈100, the orifice diameter and oil viscosity appeared to have a large influence on the mean droplet diameter. At 100〈We〈1 000, the oil viscosity appeared to have a larger influence on the relative mean droplet diameter.
基金Funded by the National Natural Science Foundation of China(No.51174064)。
文摘ZrO_(2)-5CrMnMo composite samples were prepared by hot press sintering.When NiCoCrAlY powders were used as the bonding layer and the different mixtures of NiCoCrAlY alloy and 3YSZ (3mol% yttria stabilized zirconia) ceramic powders were used as the transition layers,the connection between zirconia ceramic and 5CrMnMo steel were strengthened.Three composite samples with different structures were fabricated by heat spraying and hot press sintering.Shear and thermal shock cycle tests were conducted to characterize connection strength and thermal shock resistance of these samples.The shear strength reached 95.69 MPa,and the heating shock cycles achieved to the maximum value of 27.7 times.Microstructures and connection interfaces were analyzed by scanning electron microscopy.The hardness and wearing resistance of 3YSZ coat and 5CrMnMo substrate were compared,and the heat insulation property of composite samples were also discussed.It is shown that these composite materials fabricated in this research are benefited to be used as squeeze casting dies.
