2024/2025年前冬,即2024年12月1日—2025年1月15日,北半球季风区发生了1979年以来极为严重的干旱事件,其中中国东部地区尤为显著。此次事件对中国东部地区的经济发展和生态系统都造成了严重的影响。本文基于ERA5再分析资料,深入探究了...2024/2025年前冬,即2024年12月1日—2025年1月15日,北半球季风区发生了1979年以来极为严重的干旱事件,其中中国东部地区尤为显著。此次事件对中国东部地区的经济发展和生态系统都造成了严重的影响。本文基于ERA5再分析资料,深入探究了此次中国东部极端干旱事件的成因及潜在物理机制。研究结果表明,造成此次极端干旱事件的直接原因是中国东部水汽异常辐散。从环流角度来看,北太平洋的异常气旋以及青藏高原南侧的异常反气旋导致中国东部主要受干冷的偏北风影响,进而引起中国东部和南方地区水汽辐散异常和降水偏少,诱发并维持了此次极端干旱事件。进一步研究表明,大气内部模态环北半球遥相关型可能是北太平洋气旋异常形成的主要原因,青藏高原前期秋季积雪异常偏少是青藏高原上空的深厚暖高压形成的原因,二者导致中国东部地区持续受异常偏北气流控制,进而引发局地降水减少。而2024/2025年前冬弱La Ni a型海温异常则通过调控Walker环流,引起南海上空异常气旋的形成,进一步抑制了中国东部地区的降水。在全球变暖背景下,更剧烈的水汽辐合、辐散可能会引发更严重的季风区极端降水或干旱事件,这为复杂气候背景下区域性干旱事件的预测提供了一定的理论依据。展开更多
To solve the problem of only surface carbonation and realize high-efficiency carbonation of recycled coarse aggregate,the method of carbonated recycled coarse aggregate with nano materials pre-soaking was first put fo...To solve the problem of only surface carbonation and realize high-efficiency carbonation of recycled coarse aggregate,the method of carbonated recycled coarse aggregate with nano materials pre-soaking was first put forward.The carbonation effect of modified recycled coarse aggregate with three different carbonation methods was evaluated,and water absorption,apparent density and crush index of modified recycled coarse aggregate were measured.Combined with XRD,SEM,and MIP microscopic analysis,the high-efficiency carbonation strengthening mechanism of modified recycled coarse aggregate was revealed.The experimental results show that,compared with the non-carbonated recycled coarse aggregate,the physical and microscopic properties of carbonated recycled coarse aggregate are improved.The method of carbonation with nano-SiO_(2) pre-soaking can realize the high-efficiency carbonation of recycled coarse aggregate,for modified recycled coarse aggregate with the method,water absorption is reduced by 23.03%,porosity is reduced by 44.06%,and the average pore diameter is 21.82 nm.The high-efficiency carbonation strengthening mechanism show that the pre-socked nano-SiO_(2) is bound to the hydration product Ca(OH)_(2) of the old mortar with nano-scale C-S-H,which can improve the CO_(2) absorption rate,accelerate the carbonation reaction,generate more stable CaCO_(3) and nano-scale silica gel,and bond to the dense three-dimensional network structure to realize the bidirectional enhancement of nano-materials and pressurized carbonation.It is concluded that the method of carbonation with nano-SiO_(2) pre-soaking is a novel high-efficiency carbonation modification of recycled coarse aggregate.展开更多
Carbonated recycled powder as cementitious auxiliary material can reduce carbon emissions and realize high-quality recycling of recycled concrete.In this paper,microscopic property of recycled powder with three carbon...Carbonated recycled powder as cementitious auxiliary material can reduce carbon emissions and realize high-quality recycling of recycled concrete.In this paper,microscopic property of recycled powder with three carbonation methods was tested through XRD and SEM,the mechanical property and microstructure of recycled powder mortar with three replacement rates were studied by ISO method and SEM,and the strengthening mechanism was analyzed.The results showed that the mechanical property of recycled powder mortar decreased with the increasing of replacement rate.It is suggested that the replacement rate of recycled powder should not exceed 20%.The strength index and activity index of carbonated recycled powder mortar were improved,in which the flexural strength was increased by 27.85%and compressive strength was increased by 20%at the maximum.Recycled powder can be quickly and completely carbonated,and the improvement effect of CH pre-soaking carbonation was the best.The activity index of carbonated recycled powder can meet the requirements of Grade II technical standard for recycled powder.Microscopic results revealed the activation mechanism of carbonated recycled powder such as surplus calcium source effect,alkaline polycondensation effect and carbonation enhancement effect.展开更多
文摘2024/2025年前冬,即2024年12月1日—2025年1月15日,北半球季风区发生了1979年以来极为严重的干旱事件,其中中国东部地区尤为显著。此次事件对中国东部地区的经济发展和生态系统都造成了严重的影响。本文基于ERA5再分析资料,深入探究了此次中国东部极端干旱事件的成因及潜在物理机制。研究结果表明,造成此次极端干旱事件的直接原因是中国东部水汽异常辐散。从环流角度来看,北太平洋的异常气旋以及青藏高原南侧的异常反气旋导致中国东部主要受干冷的偏北风影响,进而引起中国东部和南方地区水汽辐散异常和降水偏少,诱发并维持了此次极端干旱事件。进一步研究表明,大气内部模态环北半球遥相关型可能是北太平洋气旋异常形成的主要原因,青藏高原前期秋季积雪异常偏少是青藏高原上空的深厚暖高压形成的原因,二者导致中国东部地区持续受异常偏北气流控制,进而引发局地降水减少。而2024/2025年前冬弱La Ni a型海温异常则通过调控Walker环流,引起南海上空异常气旋的形成,进一步抑制了中国东部地区的降水。在全球变暖背景下,更剧烈的水汽辐合、辐散可能会引发更严重的季风区极端降水或干旱事件,这为复杂气候背景下区域性干旱事件的预测提供了一定的理论依据。
基金Funded by Joint Funds of the National Natural Science Foundation of China(No.U1904188)the Jiangxi Provincial Department of Education Science and Technology Project(Nos.GJJ171079,GJJ181023,and GJJ181022)。
文摘To solve the problem of only surface carbonation and realize high-efficiency carbonation of recycled coarse aggregate,the method of carbonated recycled coarse aggregate with nano materials pre-soaking was first put forward.The carbonation effect of modified recycled coarse aggregate with three different carbonation methods was evaluated,and water absorption,apparent density and crush index of modified recycled coarse aggregate were measured.Combined with XRD,SEM,and MIP microscopic analysis,the high-efficiency carbonation strengthening mechanism of modified recycled coarse aggregate was revealed.The experimental results show that,compared with the non-carbonated recycled coarse aggregate,the physical and microscopic properties of carbonated recycled coarse aggregate are improved.The method of carbonation with nano-SiO_(2) pre-soaking can realize the high-efficiency carbonation of recycled coarse aggregate,for modified recycled coarse aggregate with the method,water absorption is reduced by 23.03%,porosity is reduced by 44.06%,and the average pore diameter is 21.82 nm.The high-efficiency carbonation strengthening mechanism show that the pre-socked nano-SiO_(2) is bound to the hydration product Ca(OH)_(2) of the old mortar with nano-scale C-S-H,which can improve the CO_(2) absorption rate,accelerate the carbonation reaction,generate more stable CaCO_(3) and nano-scale silica gel,and bond to the dense three-dimensional network structure to realize the bidirectional enhancement of nano-materials and pressurized carbonation.It is concluded that the method of carbonation with nano-SiO_(2) pre-soaking is a novel high-efficiency carbonation modification of recycled coarse aggregate.
基金Funded by Joint Funds of the National Natural Science Foundation of China(No.U1904188)Jiangxi Provincial Department of Education Science and Technology Project(Nos.GJJ171079,GJJ181023 and GJJ181022)。
文摘Carbonated recycled powder as cementitious auxiliary material can reduce carbon emissions and realize high-quality recycling of recycled concrete.In this paper,microscopic property of recycled powder with three carbonation methods was tested through XRD and SEM,the mechanical property and microstructure of recycled powder mortar with three replacement rates were studied by ISO method and SEM,and the strengthening mechanism was analyzed.The results showed that the mechanical property of recycled powder mortar decreased with the increasing of replacement rate.It is suggested that the replacement rate of recycled powder should not exceed 20%.The strength index and activity index of carbonated recycled powder mortar were improved,in which the flexural strength was increased by 27.85%and compressive strength was increased by 20%at the maximum.Recycled powder can be quickly and completely carbonated,and the improvement effect of CH pre-soaking carbonation was the best.The activity index of carbonated recycled powder can meet the requirements of Grade II technical standard for recycled powder.Microscopic results revealed the activation mechanism of carbonated recycled powder such as surplus calcium source effect,alkaline polycondensation effect and carbonation enhancement effect.
文摘目的评估时空电阻抗断层成像(spatiotemporal electrical impedance tomography,ST-EIT)在言语发声任务下,能否有效捕捉并区分腭裂(cleft palate,CP)患者与正常对照(normal control,NC)的言语呼吸功能特征。方法本研究纳入75名受试者(CP组37例,NC组38例)。在标准化发声任务中,同步采集电阻抗断层成像(electrical impedance tomography,EIT)图像与口鼻气流信号,构建涵盖时间、气流与空间维度的三域特征,采用曼-惠特尼U检验(MannWhitney U test)比较组间差异。基于肺量计法(spirometry)、鼻音计(nasometry)及ST-EIT等多源数据,分别训练极端梯度提升(extreme gradient boosting,XGBoost)分类模型,采用5折交叉验证评估性能,并引入Shapley加性解释(Shapley additive explanations,SHAP)方法进行特征贡献分析。结果CP组呈现显著的呼吸表型差异。时间域中,吸/呼相位时长均显著缩短(P<0.001),吸/呼时间比显著升高;气流域中,呼气期平均气流与峰值气流显著增强,吸气期无明显差异;空间域中,感兴趣区(region of interest,ROI)1和4的潮气阻抗变化(tidal impedance variation,TIV)显著升高,ROI2显著降低,全局不均一性(global inhomogeneity,GI)较低,通气中心(center of ventilation,CoV)呈轻度升高。ST-EIT模型分类性能最佳,曲线下面积(area under the curve,AUC)达0.915,准确率优于单一肺功能检测或鼻音计检测。SHAP结果表明,时空特征对分类决策贡献最大。结论ST-EIT技术能有效揭示CP患者言语呼吸功能在时间-气流-空间三域的特异性改变,为床旁筛查、康复评估及随访监测提供了优于常规检测的客观量化依据。
