An accelerated decay test and a natural decay test were conducted synchronically to explore the strength degradation of decaying wood members under long-term exposure to natural environment.A natural decay test was ca...An accelerated decay test and a natural decay test were conducted synchronically to explore the strength degradation of decaying wood members under long-term exposure to natural environment.A natural decay test was carried out to measure the bending strength,compressive strength parallel to grain and modulus of elasticity of the wood members,with 6 groups of specimens decayed in natural environment for 3 to 18 months respectively.To compare with corresponding decay test,in which 6 other groups of specimens were measured under accelerated conditions.The experimental data collected were evaluated by Pearson productmoment for the correlation.The results indicate that the mechanical properties of the accelerated decay were highly correlated with those in natural environment,both of which decreased in the same trend.Under the given test conditions,the mean value of the accelerated decay test data were curve-fitted to achieve the time-dependent degradation model of the bending strength,the compressive strength parallel to grain,as well as the modulus of elasticity.Due to the high correlation,the acceleration shift factors(ASF)of the two tests were derived,where the bending strength of 2.934,the compressive strength parallel to grain of 2.519 and the elastic modulus of 2.346 were employed to formulate the strength degradation models in the long-term natural environment.The results verify that the exponential functionσ=σ0e^(-βt)enables to exactly capture the degradation of the mechanical properties of wood members decayed in natural environment.展开更多
Based on GC-MS data of saturate and aromatic hydrocarbon fractions in crude oils from Well TD 2 and the Yingmaili and Tazhong area in the Tarim Basin, the end-member oil derived from Cambrian-Lower Ordovician source r...Based on GC-MS data of saturate and aromatic hydrocarbon fractions in crude oils from Well TD 2 and the Yingmaili and Tazhong area in the Tarim Basin, the end-member oil derived from Cambrian-Lower Ordovician source rocks was determined. The analytical results show that the crude oil from Well TD2 is rich in 3-6 ring polycyclic aromatic hydrocarbons without alkyl group, suggesting that this oil was altered by an abnormally thermal event. It contains a complete series of normal alkanes and 25-norhopanes,展开更多
The science that underpins our knowledge and understanding of Isotope-Based Hydrograph separation (IHS) has gained grounds, over the last few decades, in the identification of streamflow sources. However, challenges s...The science that underpins our knowledge and understanding of Isotope-Based Hydrograph separation (IHS) has gained grounds, over the last few decades, in the identification of streamflow sources. However, challenges still exist in identifying appropriate tracers and the right combination of end-members for the IHS process. In a two-component IHS analysis, the application of the dual isotopes tracers, δ18O and (or) δ2H, is regarded as the simplest method. We undertook an IHS study within a nested system of eight Prairie watersheds located in South central Manitoba, Canada. The work evaluated about 17,000 results emanating from the application of a combination of two potential tracers (δ18O and δ2H) and eight each of potential “old” and “new” water end-members in a two-component IHS process. The outcome showed occurrences of many mathematically possible but hydrologically unacceptable IHS results. The observation was particularly predominant within relatively larger perennial sub-catchments of the watershed. It is also shown that inter-site sub-catchment isotopic end-member transferability is possible within watersheds of similar physio-hydrographic characteristics. We suggest that a careful evaluation of the physio-hydrographic characteristics of catchments be considered in IHS studies in addition to the recommended guidelines in the selection of tracers and end-members.展开更多
全新世时期形成的连续性古洪积层是追溯古环境信息的可靠记录。重庆市丰都县玉溪遗址存在多期连续的文化层与洪积层,但已有研究并未系统分析该遗址区的古洪水发生机制及其气候背景,并且缺乏基于多期古洪积层的周期性研究。(1)本文基于...全新世时期形成的连续性古洪积层是追溯古环境信息的可靠记录。重庆市丰都县玉溪遗址存在多期连续的文化层与洪积层,但已有研究并未系统分析该遗址区的古洪水发生机制及其气候背景,并且缺乏基于多期古洪积层的周期性研究。(1)本文基于动物骨屑AMS ^(14)C年代数据,用Bacon程序拟合玉溪遗址剖面的沉积-年代关系,判定玉溪剖面古洪积层形成时段为约6.4 ka BP~7.3 ka BP。(2)古洪水沉积序列的粒度和端元分析结果显示,玉溪古洪积层由细粉砂-粉砂组成,表明古洪积层为溢岸憩流和滞水缓流堆积而成。(3)孢粉组合、磁化率、Rb/Sr和Si/Al比值等环境指标显示,玉溪剖面的古洪水沉积经历了早期湿热、中期温干、晚期暖湿三个阶段,其中古洪积层在温干阶段的沉积速率最大(30 cm·(100a)^(-1)),而且古洪水发生的频率亦高于湿热期。(4)古洪水沉积序列的小波功率谱分布特征表明,玉溪剖面的古洪水存在约30 a的短周期和约350 a的长周期;其长周期与区域性气候冷事件相关、短周期与ENSO事件导致的夏季风异常有关。本文提出的搬运洪积物的三种动力类型、干湿期古洪水的沉积速率差异以及古洪水泛滥的长短周期,对研究新石器早期重庆地区的人地关系和长江上游的洪水发生机制有参考意义。展开更多
青海湖湖东地区出露典型的风成沉积,对气候变化响应敏感,为古气候环境的重建提供了良好研究窗口。本文选取湖东地区厚度10 m的风成砂-砂质古土壤剖面为对象,运用端元分析模型对沉积物粒度数据进行分析,提取对气候变化反映敏感的粒级组分...青海湖湖东地区出露典型的风成沉积,对气候变化响应敏感,为古气候环境的重建提供了良好研究窗口。本文选取湖东地区厚度10 m的风成砂-砂质古土壤剖面为对象,运用端元分析模型对沉积物粒度数据进行分析,提取对气候变化反映敏感的粒级组分,进一步结合粒度组分、磁化率指标,阐释各端元指示的环境意义以及近32 ka BP以来青海湖湖东地区的环境演化过程。结果表明,大水塘剖面粒度组成以砂粒物质为主,粉砂次之,黏粒最少。剖面的沉积物粒度组分可分解为3个端元:EM1是受冬季风影响的敏感粒径,指示冬季风的强弱变化;EM2指示的是区域环境受风沙作用的强弱,与EM1指示相反,但共同反映冬季风的强弱;EM3指示受区域性低空风系的影响,以尘暴的形式搬运沉积。青海湖湖东地区的环境演化过程可划分为4个阶段:(1)末次冰期间冰阶阶段(32~23.2 ka BP),气候整体较湿润,风沙活动较弱;(2)末次冰期冰盛期阶段(23.2~15.8 ka BP),气候冷偏干,风沙活动增强;(3)末次冰期冰消期阶段(15.8~9.5 ka BP),气候仍以冷偏干为主,冷暖波动,但存在小幅度升温;(4)全新世阶段(9.5 ka BP以来),早期转暖、中期最暖、晚期转凉,气候波动显著。展开更多
杭嘉湖平原位于海陆交互的长江三角洲地区,极易受到海平面升降和极端气候事件的影响,对全球环境变化十分敏感。应用非参数化粒度端元分析模型提取杭嘉湖平原ZK3岩芯沉积物的端元组分,分析其物质来源;并结合植物藻类和磁化率指标全面揭...杭嘉湖平原位于海陆交互的长江三角洲地区,极易受到海平面升降和极端气候事件的影响,对全球环境变化十分敏感。应用非参数化粒度端元分析模型提取杭嘉湖平原ZK3岩芯沉积物的端元组分,分析其物质来源;并结合植物藻类和磁化率指标全面揭示各端元组分对区域全新世气候-海平面变化响应。结果表明:(1)EM1(16.4 μm)主要为洪泛沉积物,EM2(35.3 μm)主要为湖相沉积物,EM3(58.9 μm)则为海相沉积物;(2)杭嘉湖平原8000 a BP以来的气候-海平面变化大致可分为四个阶段:约8000—6200 a BP,受东亚夏季风影响,气候温暖湿润,海平面上升并趋于稳定,区域内同时受到海洋和陆源输入影响,发育海陆过渡相沉积;约6200—4800 a BP,气候趋于干凉化,陆地面积扩大,沉积环境转变为河流为主的洪泛沉积;至4800—3100 a BP,气候回暖,海平面略有回升,发育为湖相沉积;3100—140 a BP,气候趋冷干化,海平面下降,广泛发育为泛滥平原沉积环境。展开更多
To reveal the sediment transporting mechanism between the abandoned Huanghe River （Yellow River） Delta and radial sand ridges, “End Member” Model and grain size trend analysis have been employed to separate the “...To reveal the sediment transporting mechanism between the abandoned Huanghe River （Yellow River） Delta and radial sand ridges, “End Member” Model and grain size trend analysis have been employed to separate the “dynamic populations” in the surficial sediment particle spectra and to determine the possible sediment transporting pathway. The results reveal four “dynamic subpopulations”（EM1 to EM4） and two reverse sediment transporting directions： a northward transport tend from the radial sand ridges to mud patch, and a southward transport trend in deep water area outside the mud patch. Combined with the published hydrodynamic information, the transporting mechanism of dynamic populations has been discussed, and the main conclusion is that the transporting of finer subpopulations EM1 and EM2 is controlled by the “anticlockwise residual current circulation” forming during tidal cycle, which favor a northward transporting trend and the forming of mud patch on the north of radial sand ridges, while the transporting of coarser EM3 is mainly controlled by wind driven drift in winter, which favors a southward transporting direction.展开更多
基金supported by a grant from the National Natural Science Foundation of China(No.51208399)Natural Science Foundation of Hubei province of China(No.2018CFB645)Hubei Key Laboratory of Roadway Bridge and Structure Engineering(Wuhan University of Technology)(No.DQJJ201706).
文摘An accelerated decay test and a natural decay test were conducted synchronically to explore the strength degradation of decaying wood members under long-term exposure to natural environment.A natural decay test was carried out to measure the bending strength,compressive strength parallel to grain and modulus of elasticity of the wood members,with 6 groups of specimens decayed in natural environment for 3 to 18 months respectively.To compare with corresponding decay test,in which 6 other groups of specimens were measured under accelerated conditions.The experimental data collected were evaluated by Pearson productmoment for the correlation.The results indicate that the mechanical properties of the accelerated decay were highly correlated with those in natural environment,both of which decreased in the same trend.Under the given test conditions,the mean value of the accelerated decay test data were curve-fitted to achieve the time-dependent degradation model of the bending strength,the compressive strength parallel to grain,as well as the modulus of elasticity.Due to the high correlation,the acceleration shift factors(ASF)of the two tests were derived,where the bending strength of 2.934,the compressive strength parallel to grain of 2.519 and the elastic modulus of 2.346 were employed to formulate the strength degradation models in the long-term natural environment.The results verify that the exponential functionσ=σ0e^(-βt)enables to exactly capture the degradation of the mechanical properties of wood members decayed in natural environment.
基金Supported by the National Natural Science Foundation of China(41772119,41272169)
文摘Based on GC-MS data of saturate and aromatic hydrocarbon fractions in crude oils from Well TD 2 and the Yingmaili and Tazhong area in the Tarim Basin, the end-member oil derived from Cambrian-Lower Ordovician source rocks was determined. The analytical results show that the crude oil from Well TD2 is rich in 3-6 ring polycyclic aromatic hydrocarbons without alkyl group, suggesting that this oil was altered by an abnormally thermal event. It contains a complete series of normal alkanes and 25-norhopanes,
文摘The science that underpins our knowledge and understanding of Isotope-Based Hydrograph separation (IHS) has gained grounds, over the last few decades, in the identification of streamflow sources. However, challenges still exist in identifying appropriate tracers and the right combination of end-members for the IHS process. In a two-component IHS analysis, the application of the dual isotopes tracers, δ18O and (or) δ2H, is regarded as the simplest method. We undertook an IHS study within a nested system of eight Prairie watersheds located in South central Manitoba, Canada. The work evaluated about 17,000 results emanating from the application of a combination of two potential tracers (δ18O and δ2H) and eight each of potential “old” and “new” water end-members in a two-component IHS process. The outcome showed occurrences of many mathematically possible but hydrologically unacceptable IHS results. The observation was particularly predominant within relatively larger perennial sub-catchments of the watershed. It is also shown that inter-site sub-catchment isotopic end-member transferability is possible within watersheds of similar physio-hydrographic characteristics. We suggest that a careful evaluation of the physio-hydrographic characteristics of catchments be considered in IHS studies in addition to the recommended guidelines in the selection of tracers and end-members.
文摘全新世时期形成的连续性古洪积层是追溯古环境信息的可靠记录。重庆市丰都县玉溪遗址存在多期连续的文化层与洪积层,但已有研究并未系统分析该遗址区的古洪水发生机制及其气候背景,并且缺乏基于多期古洪积层的周期性研究。(1)本文基于动物骨屑AMS ^(14)C年代数据,用Bacon程序拟合玉溪遗址剖面的沉积-年代关系,判定玉溪剖面古洪积层形成时段为约6.4 ka BP~7.3 ka BP。(2)古洪水沉积序列的粒度和端元分析结果显示,玉溪古洪积层由细粉砂-粉砂组成,表明古洪积层为溢岸憩流和滞水缓流堆积而成。(3)孢粉组合、磁化率、Rb/Sr和Si/Al比值等环境指标显示,玉溪剖面的古洪水沉积经历了早期湿热、中期温干、晚期暖湿三个阶段,其中古洪积层在温干阶段的沉积速率最大(30 cm·(100a)^(-1)),而且古洪水发生的频率亦高于湿热期。(4)古洪水沉积序列的小波功率谱分布特征表明,玉溪剖面的古洪水存在约30 a的短周期和约350 a的长周期;其长周期与区域性气候冷事件相关、短周期与ENSO事件导致的夏季风异常有关。本文提出的搬运洪积物的三种动力类型、干湿期古洪水的沉积速率差异以及古洪水泛滥的长短周期,对研究新石器早期重庆地区的人地关系和长江上游的洪水发生机制有参考意义。
文摘青海湖湖东地区出露典型的风成沉积,对气候变化响应敏感,为古气候环境的重建提供了良好研究窗口。本文选取湖东地区厚度10 m的风成砂-砂质古土壤剖面为对象,运用端元分析模型对沉积物粒度数据进行分析,提取对气候变化反映敏感的粒级组分,进一步结合粒度组分、磁化率指标,阐释各端元指示的环境意义以及近32 ka BP以来青海湖湖东地区的环境演化过程。结果表明,大水塘剖面粒度组成以砂粒物质为主,粉砂次之,黏粒最少。剖面的沉积物粒度组分可分解为3个端元:EM1是受冬季风影响的敏感粒径,指示冬季风的强弱变化;EM2指示的是区域环境受风沙作用的强弱,与EM1指示相反,但共同反映冬季风的强弱;EM3指示受区域性低空风系的影响,以尘暴的形式搬运沉积。青海湖湖东地区的环境演化过程可划分为4个阶段:(1)末次冰期间冰阶阶段(32~23.2 ka BP),气候整体较湿润,风沙活动较弱;(2)末次冰期冰盛期阶段(23.2~15.8 ka BP),气候冷偏干,风沙活动增强;(3)末次冰期冰消期阶段(15.8~9.5 ka BP),气候仍以冷偏干为主,冷暖波动,但存在小幅度升温;(4)全新世阶段(9.5 ka BP以来),早期转暖、中期最暖、晚期转凉,气候波动显著。
文摘杭嘉湖平原位于海陆交互的长江三角洲地区,极易受到海平面升降和极端气候事件的影响,对全球环境变化十分敏感。应用非参数化粒度端元分析模型提取杭嘉湖平原ZK3岩芯沉积物的端元组分,分析其物质来源;并结合植物藻类和磁化率指标全面揭示各端元组分对区域全新世气候-海平面变化响应。结果表明:(1)EM1(16.4 μm)主要为洪泛沉积物,EM2(35.3 μm)主要为湖相沉积物,EM3(58.9 μm)则为海相沉积物;(2)杭嘉湖平原8000 a BP以来的气候-海平面变化大致可分为四个阶段:约8000—6200 a BP,受东亚夏季风影响,气候温暖湿润,海平面上升并趋于稳定,区域内同时受到海洋和陆源输入影响,发育海陆过渡相沉积;约6200—4800 a BP,气候趋于干凉化,陆地面积扩大,沉积环境转变为河流为主的洪泛沉积;至4800—3100 a BP,气候回暖,海平面略有回升,发育为湖相沉积;3100—140 a BP,气候趋冷干化,海平面下降,广泛发育为泛滥平原沉积环境。
文摘To reveal the sediment transporting mechanism between the abandoned Huanghe River （Yellow River） Delta and radial sand ridges, “End Member” Model and grain size trend analysis have been employed to separate the “dynamic populations” in the surficial sediment particle spectra and to determine the possible sediment transporting pathway. The results reveal four “dynamic subpopulations”（EM1 to EM4） and two reverse sediment transporting directions： a northward transport tend from the radial sand ridges to mud patch, and a southward transport trend in deep water area outside the mud patch. Combined with the published hydrodynamic information, the transporting mechanism of dynamic populations has been discussed, and the main conclusion is that the transporting of finer subpopulations EM1 and EM2 is controlled by the “anticlockwise residual current circulation” forming during tidal cycle, which favor a northward transporting trend and the forming of mud patch on the north of radial sand ridges, while the transporting of coarser EM3 is mainly controlled by wind driven drift in winter, which favors a southward transporting direction.
