目的:用计算机模型工具来研究经颅直流电刺激(transcranial direct current stimulation,tDCS)临床治疗问题,将真实体积逼近模拟经颅电刺激法(realistic volumetric⁃approach to simulate transcranial electric stimulation,ROAST)以观...目的:用计算机模型工具来研究经颅直流电刺激(transcranial direct current stimulation,tDCS)临床治疗问题,将真实体积逼近模拟经颅电刺激法(realistic volumetric⁃approach to simulate transcranial electric stimulation,ROAST)以观察tDCS临床治疗过程中的电极位置误差,并从电极位置误差定量分析tDCS临床疗效性问题。方法:以F3、F4位置治疗抑郁为例,仿真计算颅内靶区所激励电场剂量,对比tDCS治疗电极位置误差对颅内治疗靶区电场剂量产生的影响,并给出施加2 mA和4 mA电流时电场剂量变化曲线。结果:仿真显示32种物理位置误差,矩形电极,圆形电极分别造成电场剂量变化是-10.3%~72.4%,-12.9%~11.3%,既有减少也有增加;此结果正是由于大脑皮质具有非均匀性。当电场剂量减少时,颅内靶区会出现小于有效电场剂量的情况,因此有可能出现tDCS临床治疗疗效不好。仿真还发现当tDCS施加4 mA时,颅内靶区均会大于有效电场剂量,且32种误差位置在颅内靶区电场剂量变化规律和施加2 mA时基本一致,电场剂量变化程度与施加电流大小基本无关。结论:ROAST可为临床一线医生寻找tDCS治疗的个体剂量和优化方案。展开更多
The dependence of elastic moduli of shales on the mineralogy and microstructure of shales is important for the prediction of sweet spots and shale gas production. Based on 3D digital images of the microstructure of Lo...The dependence of elastic moduli of shales on the mineralogy and microstructure of shales is important for the prediction of sweet spots and shale gas production. Based on 3D digital images of the microstructure of Longmaxi black shale samples using X-ray CT, we built detailed 3D digital images of cores with porosity properties and mineral contents. Next, we used finite-element （FE） methods to derive the elastic properties of the samples. The FE method can accurately model the shale mineralogy. Particular attention is paid to the derived elastic properties and their dependence on porosity and kerogen. The elastic moduli generally decrease with increasing porosity and kerogen, and there is a critical porosity （0.75） and kerogen content （ca. ≤3%） over which the elastic moduli decrease rapidly and slowly, respectively. The derived elastic moduli of gas- and oil-saturated digital cores differ little probably because of the low porosity （4.5%） of the Longmaxi black shale. Clearly, the numerical experiments demonstrated the feasibility of combining microstructure images of shale samples with elastic moduli calculations to predict shale properties.展开更多
In order to predict the long-term rutting of asphalt pavement, the effective temperature for pavement rutting is calculated using the numerical simulation method. The transient temperature field of asphalt pavement wa...In order to predict the long-term rutting of asphalt pavement, the effective temperature for pavement rutting is calculated using the numerical simulation method. The transient temperature field of asphalt pavement was simulated based on actual meteorological data of Nanjing. 24-hour rutting development under a transient temperature field was calculated in each month. The rutting depth accumulated under the static temperature field was also estimated and the relationship between constant temperature parameters was analyzed. Then the effective temperature for pavement rutting was determined based on the rutting equivalence principle. The results show that the monthly effective temperature is above 40 t in July and August, while in June and September it ranges from 30 to 40 Rutting development can be ignored when the monthly effective temperature is less than 30 t. The yearly effective temperature for rutting in Nanjing is around 38. 5 t. The long-term rutting prediction model based on the effective temperature can reflect the influences of meteorological factors and traffic time distribution.展开更多
文摘目的:用计算机模型工具来研究经颅直流电刺激(transcranial direct current stimulation,tDCS)临床治疗问题,将真实体积逼近模拟经颅电刺激法(realistic volumetric⁃approach to simulate transcranial electric stimulation,ROAST)以观察tDCS临床治疗过程中的电极位置误差,并从电极位置误差定量分析tDCS临床疗效性问题。方法:以F3、F4位置治疗抑郁为例,仿真计算颅内靶区所激励电场剂量,对比tDCS治疗电极位置误差对颅内治疗靶区电场剂量产生的影响,并给出施加2 mA和4 mA电流时电场剂量变化曲线。结果:仿真显示32种物理位置误差,矩形电极,圆形电极分别造成电场剂量变化是-10.3%~72.4%,-12.9%~11.3%,既有减少也有增加;此结果正是由于大脑皮质具有非均匀性。当电场剂量减少时,颅内靶区会出现小于有效电场剂量的情况,因此有可能出现tDCS临床治疗疗效不好。仿真还发现当tDCS施加4 mA时,颅内靶区均会大于有效电场剂量,且32种误差位置在颅内靶区电场剂量变化规律和施加2 mA时基本一致,电场剂量变化程度与施加电流大小基本无关。结论:ROAST可为临床一线医生寻找tDCS治疗的个体剂量和优化方案。
基金supported by the Chinese Academy of Sciences Strategic Leading Science and Technology projects(Grant No.XDB10010400)the China Postdoctoral Science Foundation(Grant No.2015M570142)
文摘The dependence of elastic moduli of shales on the mineralogy and microstructure of shales is important for the prediction of sweet spots and shale gas production. Based on 3D digital images of the microstructure of Longmaxi black shale samples using X-ray CT, we built detailed 3D digital images of cores with porosity properties and mineral contents. Next, we used finite-element （FE） methods to derive the elastic properties of the samples. The FE method can accurately model the shale mineralogy. Particular attention is paid to the derived elastic properties and their dependence on porosity and kerogen. The elastic moduli generally decrease with increasing porosity and kerogen, and there is a critical porosity （0.75） and kerogen content （ca. ≤3%） over which the elastic moduli decrease rapidly and slowly, respectively. The derived elastic moduli of gas- and oil-saturated digital cores differ little probably because of the low porosity （4.5%） of the Longmaxi black shale. Clearly, the numerical experiments demonstrated the feasibility of combining microstructure images of shale samples with elastic moduli calculations to predict shale properties.
基金The National Natural Science Foundation of China(No.51378121)the Fok Ying Tung Education Foundation(No.141076)the Scientific Innovation Research of College Graduates in Jiangsu Province(No.KYLX_0164)
文摘In order to predict the long-term rutting of asphalt pavement, the effective temperature for pavement rutting is calculated using the numerical simulation method. The transient temperature field of asphalt pavement was simulated based on actual meteorological data of Nanjing. 24-hour rutting development under a transient temperature field was calculated in each month. The rutting depth accumulated under the static temperature field was also estimated and the relationship between constant temperature parameters was analyzed. Then the effective temperature for pavement rutting was determined based on the rutting equivalence principle. The results show that the monthly effective temperature is above 40 t in July and August, while in June and September it ranges from 30 to 40 Rutting development can be ignored when the monthly effective temperature is less than 30 t. The yearly effective temperature for rutting in Nanjing is around 38. 5 t. The long-term rutting prediction model based on the effective temperature can reflect the influences of meteorological factors and traffic time distribution.
