A novel method was proposed to design the structure of a bone tissue engineering scafold based on triply periodic minimal surface.In this method,reverse engineering software was used to reconstruct the surface from po...A novel method was proposed to design the structure of a bone tissue engineering scafold based on triply periodic minimal surface.In this method,reverse engineering software was used to reconstruct the surface from point cloud data.This method overcomes the limitations of commercially available software packages that prevent them from generating models with complex surfaces used for bone tissue engineering scafolds.Additionally,the fluid feld of the scafolds was simulated through a numerical method based on fnite volume and the cell proliferation performance was evaluated via an in vitro experiment.The cell proliferation and the mass flow evaluated in a bioreactor further verifed the flow feld simulated using computational fluid dynamics.The result of this study illustrates that the pressure value drops rapidly from 0.103 Pa to 0.011 Pa in the y-axis direction and the mass flow is unevenly distributed in the outlets.The mass flow in the side outlets is observed to be approximately 24.3 times higher thanthe bottom.Importantly,although the mean value of wall shear stress is signifcantly more than 0.05 Pa,there is stil a large area with a suitable shear stress below 0.05 Pa where most cells can proliferate well.The result shows that th inlet velocity 0.0075 m/s is suitable for cell proliferation in the scafold.This study provides an insight into the design analysis,and in vitro experiment of a bone tissue engineering scafold.展开更多
To seek effective ways of lowering development cost and tapping inter-well remaining reserves, sidetracking horizontal wells from old wells in Su10 and Su53 Block were conducted. The engineering and geological problem...To seek effective ways of lowering development cost and tapping inter-well remaining reserves, sidetracking horizontal wells from old wells in Su10 and Su53 Block were conducted. The engineering and geological problems such as leakage, collapse and sticking in slim-hole sidetracking, and difficult evaluation of remaining gas were gradually overcome, and a set of drilling and completion technology, well deployment optimization technology and geo-steering technology suitable for sidetracking horizontal wells in tight sandstone gas reservoirs have been worked out. By making full use of the old well, sidetracking horizontal wells can greatly reduce development costs, enhance the producing degree of inter-well remaining reserves, and get production 3-5 times of that of adjacent vertical wells.Its production effect is influenced by encountered sandstone length, the position of the horizontal segment in the reservoir, produced effective reservoir thickness, gas saturation, controlled reserves and fracturing effect, etc. Up to now, in Block Su10 and Su53, 12 sidetracking horizontal wells have been drilled, which have an average drilling cycle of 49 days, average horizontal section length of 689 m,average effective drilling ratio of 61.5%, average well-head pressure of 16.2 MPa, and daily output of 4.7×10~4 m^3 at the initial stage after production. By the end of 2017, the average yield increment was more than 1 000×10~4 m^3 with good effect. With the increase of low yield old wells, wells in the enrichment regions tend to be saturated and the rest gas-bearing areas are lower in grade, therefore, sidetracking horizontal well can be used for optimization of well pattern, well deployment mode and exploitation of remaining oil areas.展开更多
群落共存种对限制性资源的竞争响应是群落组建、维持与演替的重要影响因素。以黄土丘陵区摞荒群落共存种为研究对象,研究不同水分条件下的竞争响应差异,以期揭示生境变化时群落演替的植物竞争机理。试验设土壤水分与混植密度两个处理,...群落共存种对限制性资源的竞争响应是群落组建、维持与演替的重要影响因素。以黄土丘陵区摞荒群落共存种为研究对象,研究不同水分条件下的竞争响应差异,以期揭示生境变化时群落演替的植物竞争机理。试验设土壤水分与混植密度两个处理,其中混植密度采用CDS(Community density series)法,含3个密度水平(衡水试验为3、12、21株/m^2,变水试验为5、20、35株/m^2);土壤水分设衡水(高(75%FC)、中(60%FC)、低(45%FC) 3个水平)与变水(由高水(75%FC)经50 d持续干旱至低水(45%FC))两种处理。根据共存种株高的阶段性生长与其在群落中的相对生物量等生长表现,在CDS法基础上扩展并测算了生长变化量、相对生物量和相对生长率等指标。据此,研究竞争效应和水分胁迫效应的相对影响,共存种相对竞争能力和竞争等级对土壤水分变化的响应,及高水期因竞争引起的个体大小不对称性与低水期死亡率的关系。结果表明:1)不同水分多种混植共存条件下,竞争效应对多数共存种在群落中的生长表现较水分胁迫效应影响更大;以相对生物量为指标的竞争的群落效应(4.30±0.49)较水分胁迫的群落效应(-23.56±20.38)大,且二者累加效应(4.76±0.4)大于二者单项效应之和(-19.26±20.48),即竞争+水分胁迫对多种共存群落具有协同效应。2)当水分条件发生变化时,群落共存种的竞争等级并不完全相同(P>0.05),相应的会发生变化,且水分差别越大,共存种竞争等级的差别也越大;高水条件下群落共存种竞争所引起的群落效应最大(4.84±0.23),部分支持最大生长率理论,即限制性资源水平越高,群落共存种竞争越激烈。3)变水试验中,10种群落共存种在高水期因竞争引起的个体大小差异与低水期的死亡率呈正相关关系(P=0.015,r^2=0.801),根据资源动态两阶段假说,说明试验条件下群落共存种竞争是群落组建的重要因素。展开更多
基金Supported by National Natural Science Foundation of China(Grant Nos.51675312,51375273)
文摘A novel method was proposed to design the structure of a bone tissue engineering scafold based on triply periodic minimal surface.In this method,reverse engineering software was used to reconstruct the surface from point cloud data.This method overcomes the limitations of commercially available software packages that prevent them from generating models with complex surfaces used for bone tissue engineering scafolds.Additionally,the fluid feld of the scafolds was simulated through a numerical method based on fnite volume and the cell proliferation performance was evaluated via an in vitro experiment.The cell proliferation and the mass flow evaluated in a bioreactor further verifed the flow feld simulated using computational fluid dynamics.The result of this study illustrates that the pressure value drops rapidly from 0.103 Pa to 0.011 Pa in the y-axis direction and the mass flow is unevenly distributed in the outlets.The mass flow in the side outlets is observed to be approximately 24.3 times higher thanthe bottom.Importantly,although the mean value of wall shear stress is signifcantly more than 0.05 Pa,there is stil a large area with a suitable shear stress below 0.05 Pa where most cells can proliferate well.The result shows that th inlet velocity 0.0075 m/s is suitable for cell proliferation in the scafold.This study provides an insight into the design analysis,and in vitro experiment of a bone tissue engineering scafold.
基金Supported by the Project of Great Wall Drilling Company in CNPC(2015A25-2(2012))
文摘To seek effective ways of lowering development cost and tapping inter-well remaining reserves, sidetracking horizontal wells from old wells in Su10 and Su53 Block were conducted. The engineering and geological problems such as leakage, collapse and sticking in slim-hole sidetracking, and difficult evaluation of remaining gas were gradually overcome, and a set of drilling and completion technology, well deployment optimization technology and geo-steering technology suitable for sidetracking horizontal wells in tight sandstone gas reservoirs have been worked out. By making full use of the old well, sidetracking horizontal wells can greatly reduce development costs, enhance the producing degree of inter-well remaining reserves, and get production 3-5 times of that of adjacent vertical wells.Its production effect is influenced by encountered sandstone length, the position of the horizontal segment in the reservoir, produced effective reservoir thickness, gas saturation, controlled reserves and fracturing effect, etc. Up to now, in Block Su10 and Su53, 12 sidetracking horizontal wells have been drilled, which have an average drilling cycle of 49 days, average horizontal section length of 689 m,average effective drilling ratio of 61.5%, average well-head pressure of 16.2 MPa, and daily output of 4.7×10~4 m^3 at the initial stage after production. By the end of 2017, the average yield increment was more than 1 000×10~4 m^3 with good effect. With the increase of low yield old wells, wells in the enrichment regions tend to be saturated and the rest gas-bearing areas are lower in grade, therefore, sidetracking horizontal well can be used for optimization of well pattern, well deployment mode and exploitation of remaining oil areas.
文摘群落共存种对限制性资源的竞争响应是群落组建、维持与演替的重要影响因素。以黄土丘陵区摞荒群落共存种为研究对象,研究不同水分条件下的竞争响应差异,以期揭示生境变化时群落演替的植物竞争机理。试验设土壤水分与混植密度两个处理,其中混植密度采用CDS(Community density series)法,含3个密度水平(衡水试验为3、12、21株/m^2,变水试验为5、20、35株/m^2);土壤水分设衡水(高(75%FC)、中(60%FC)、低(45%FC) 3个水平)与变水(由高水(75%FC)经50 d持续干旱至低水(45%FC))两种处理。根据共存种株高的阶段性生长与其在群落中的相对生物量等生长表现,在CDS法基础上扩展并测算了生长变化量、相对生物量和相对生长率等指标。据此,研究竞争效应和水分胁迫效应的相对影响,共存种相对竞争能力和竞争等级对土壤水分变化的响应,及高水期因竞争引起的个体大小不对称性与低水期死亡率的关系。结果表明:1)不同水分多种混植共存条件下,竞争效应对多数共存种在群落中的生长表现较水分胁迫效应影响更大;以相对生物量为指标的竞争的群落效应(4.30±0.49)较水分胁迫的群落效应(-23.56±20.38)大,且二者累加效应(4.76±0.4)大于二者单项效应之和(-19.26±20.48),即竞争+水分胁迫对多种共存群落具有协同效应。2)当水分条件发生变化时,群落共存种的竞争等级并不完全相同(P>0.05),相应的会发生变化,且水分差别越大,共存种竞争等级的差别也越大;高水条件下群落共存种竞争所引起的群落效应最大(4.84±0.23),部分支持最大生长率理论,即限制性资源水平越高,群落共存种竞争越激烈。3)变水试验中,10种群落共存种在高水期因竞争引起的个体大小差异与低水期的死亡率呈正相关关系(P=0.015,r^2=0.801),根据资源动态两阶段假说,说明试验条件下群落共存种竞争是群落组建的重要因素。
