本文通过现场调查和实验分析,介绍了新疆阿尔泰山区泥炭地分布、类型及泥炭性状特征,对比山区内不同泥炭地的泥炭累积过程差异及主要影响因素。结果表明,新疆阿尔泰山泥炭地主要分布在海拔1700~2500 m的山间洼地,以草本和草本-泥炭藓沼...本文通过现场调查和实验分析,介绍了新疆阿尔泰山区泥炭地分布、类型及泥炭性状特征,对比山区内不同泥炭地的泥炭累积过程差异及主要影响因素。结果表明,新疆阿尔泰山泥炭地主要分布在海拔1700~2500 m的山间洼地,以草本和草本-泥炭藓沼泽为主。受地形和局地气候影响,泥炭地呈现出西北多且泥炭层厚、东南少而泥炭层浅的分布特征,东南部泥炭含水率和有机质含量远低于西北部。山区泥炭主要形成于早全新世时期,不同泥炭地的形成时间、泥炭累积速率和碳、氮含量变化存在差异。季节性冻土区铁力沙汗泥炭发育于约10000 cal a B.P.,而多年冻土区哈拉萨孜泥炭形成的起始时间约为14000 cal a B.P.。铁力沙汗泥炭累积速率表现为在泥炭起始发育时期较高,中全新世时期降低,晚全新世时期又上升的变化趋势,而哈拉萨孜呈现整体持续下降的变化趋势。铁力沙汗泥炭在中全新世时期的碳、氮含量明显高于其他时期,而哈拉萨孜泥炭碳、氮含量变化趋势整体较为平缓,仅在晚全新世时期变化显著。研究发现,除区域气候变化外,地质构造、水文条件以及植被变化过程等局地环境因素,也是影响山区泥炭累积和发育过程的主要因素。因此,在选用泥炭样本重建区域古气候时,要加强局地环境变化对区域气候重建过程的影响研究。展开更多
The increasing demand for sustainable and environmentally friendly materials has driven research towards the development of green composites.In this work,the flax/polylactic acid(PLA)braided yarns were fabricated by b...The increasing demand for sustainable and environmentally friendly materials has driven research towards the development of green composites.In this work,the flax/polylactic acid(PLA)braided yarns were fabricated by braiding PLA filaments with 4 to 24 spindles on flax yarns.After curing at different temperatures(180℃and 190℃),the core/sheath structural flax/PLA composite yarns were manufactured.According to the results of the tensile test,the flax/PLA composite yarn with 4-spindle PLA yarns as a sheath layer and at a curing temperature of 180℃reached the maximum elastic modulus of about(5.79±0.65)GPa and the maximum tensile strength of about(162.17±18.18)MPa.This flax/PLA composite yarn with good mechanical properties would be suitable for green composites in the automobile manufacturing industry and building materials.展开更多
貂熊（Gulo gulo）属食肉目,鼬科,貂熊属。此种有两个亚种,分别为古北亚种（G.g.gulo）和新北亚种（G.g.luscus）。新北亚种分布在北美北部地区;古北亚种分布在欧亚大陆,我国分布为此亚种（朴仁珠和张明海,2000）。貂熊主要栖息在高山...貂熊（Gulo gulo）属食肉目,鼬科,貂熊属。此种有两个亚种,分别为古北亚种（G.g.gulo）和新北亚种（G.g.luscus）。新北亚种分布在北美北部地区;古北亚种分布在欧亚大陆,我国分布为此亚种（朴仁珠和张明海,2000）。貂熊主要栖息在高山、苔原、泰加林、北方森林区域、沼泽等环境（Mitchell-Jones et al.,1999）。展开更多
Carbon nanotube(CNT)yarns with adjustable diameters were manufactured by twisting CNT films with varied twists.Different from traditional CNT fibers,CNT yarns exhibited a larger diameter(423μm)and a higher tensile fo...Carbon nanotube(CNT)yarns with adjustable diameters were manufactured by twisting CNT films with varied twists.Different from traditional CNT fibers,CNT yarns exhibited a larger diameter(423μm)and a higher tensile force(1988 cN).The results showed that CNT yarns with the twist angle of 35°exhibited the highest conductivity(886 S/cm)and the highest tensile strain(35%).展开更多
为探究"三高一扰动"特殊环境下切顶卸压无煤柱自成巷顶板砂岩切缝的动态力学性能,利用自主设计的岩土体动态冲击力学试验系统,对粉砂岩进行不同热–水–力耦合条件下的冲击压缩试验,研究动态应力–应变特征、动变形模量与加...为探究"三高一扰动"特殊环境下切顶卸压无煤柱自成巷顶板砂岩切缝的动态力学性能,利用自主设计的岩土体动态冲击力学试验系统,对粉砂岩进行不同热–水–力耦合条件下的冲击压缩试验,研究动态应力–应变特征、动变形模量与加载率关系、以及加载率、轴压、围压、渗透水压、温度、吸收能与峰值应力和峰值应变的动态力学性能,利用扫描电镜(Scanning Electron Microscopy,SEM)研究粉砂岩试样断口面微观结构。研究结果表明:(1)在不同的动荷载作用下,粉砂岩试样的峰值应力和峰值应变均随轴压、围压、渗透水压、温度的升高而不断增大,脆性逐渐减弱而延性逐渐增强,变形破坏总体分为压密、弹性变形、塑性变形和破坏4个阶段;(2)动变形模量随着加载率的增大呈现出先增大后减小的发展趋势,动变形模量136GPa左右为一个临界阈值;(3)轴压、围压、水和温度对砂岩在热–水–力耦合特定环境下的动态冲击力学性能具有一定的增强效应;(4)随着峰值应变的增加,粉砂岩试样的吸收能呈线性增加趋势,其破碎变形与吸收能呈正相关。展开更多
The electro-thermal actuators(ETA)are smart devices that can convert electric energy into mechanical energy under electro-heating stimulation,showing great potential in the fields of soft robotics,artificial muscle an...The electro-thermal actuators(ETA)are smart devices that can convert electric energy into mechanical energy under electro-heating stimulation,showing great potential in the fields of soft robotics,artificial muscle and aerospace component.In this study,to build a low-voltage activating,fast responding ETA,a robust and flexible carbon nanotube film(CNTF)with excellent electrical and thermal conductivity was adopted as the conductive material.Then,an asymmetric bilayer structured ETA was manufactured by coating a thin layer of polydimethylsiloxane(PDMS)with high coefficient of thermal expansion(9.3×10^(-4)℃^(−1)),low young’s modulus(2.07 MPa)on a thin CNTF(~11μm).The as-produced CNTF/PDMS composite ETA exhibited a large deformation(bending angle~324°)and high electro heating performance(351℃)at a low driving voltage of 8 V within~12 s.The actuated movement and the generated heat could be controlled by adjusting the driving voltages and showed almost the same values in 20 cycles.Furthermore,the influences of the PDMS thickness and driving voltage on CNTF/PDMS composite ETA performance were systematically investigated.The CNTF/PDMS soft robotic hand which can lift 5.1 times and crab 1.3 times of its weight demonstrated its potential capability.展开更多
文摘本文通过现场调查和实验分析,介绍了新疆阿尔泰山区泥炭地分布、类型及泥炭性状特征,对比山区内不同泥炭地的泥炭累积过程差异及主要影响因素。结果表明,新疆阿尔泰山泥炭地主要分布在海拔1700~2500 m的山间洼地,以草本和草本-泥炭藓沼泽为主。受地形和局地气候影响,泥炭地呈现出西北多且泥炭层厚、东南少而泥炭层浅的分布特征,东南部泥炭含水率和有机质含量远低于西北部。山区泥炭主要形成于早全新世时期,不同泥炭地的形成时间、泥炭累积速率和碳、氮含量变化存在差异。季节性冻土区铁力沙汗泥炭发育于约10000 cal a B.P.,而多年冻土区哈拉萨孜泥炭形成的起始时间约为14000 cal a B.P.。铁力沙汗泥炭累积速率表现为在泥炭起始发育时期较高,中全新世时期降低,晚全新世时期又上升的变化趋势,而哈拉萨孜呈现整体持续下降的变化趋势。铁力沙汗泥炭在中全新世时期的碳、氮含量明显高于其他时期,而哈拉萨孜泥炭碳、氮含量变化趋势整体较为平缓,仅在晚全新世时期变化显著。研究发现,除区域气候变化外,地质构造、水文条件以及植被变化过程等局地环境因素,也是影响山区泥炭累积和发育过程的主要因素。因此,在选用泥炭样本重建区域古气候时,要加强局地环境变化对区域气候重建过程的影响研究。
基金National Natural Science Foundation of China(No.52273054)Shanghai Natural Science Foundation,China(No.20ZR1402200)。
文摘The increasing demand for sustainable and environmentally friendly materials has driven research towards the development of green composites.In this work,the flax/polylactic acid(PLA)braided yarns were fabricated by braiding PLA filaments with 4 to 24 spindles on flax yarns.After curing at different temperatures(180℃and 190℃),the core/sheath structural flax/PLA composite yarns were manufactured.According to the results of the tensile test,the flax/PLA composite yarn with 4-spindle PLA yarns as a sheath layer and at a curing temperature of 180℃reached the maximum elastic modulus of about(5.79±0.65)GPa and the maximum tensile strength of about(162.17±18.18)MPa.This flax/PLA composite yarn with good mechanical properties would be suitable for green composites in the automobile manufacturing industry and building materials.
文摘貂熊（Gulo gulo）属食肉目,鼬科,貂熊属。此种有两个亚种,分别为古北亚种（G.g.gulo）和新北亚种（G.g.luscus）。新北亚种分布在北美北部地区;古北亚种分布在欧亚大陆,我国分布为此亚种（朴仁珠和张明海,2000）。貂熊主要栖息在高山、苔原、泰加林、北方森林区域、沼泽等环境（Mitchell-Jones et al.,1999）。
文摘Carbon nanotube(CNT)yarns with adjustable diameters were manufactured by twisting CNT films with varied twists.Different from traditional CNT fibers,CNT yarns exhibited a larger diameter(423μm)and a higher tensile force(1988 cN).The results showed that CNT yarns with the twist angle of 35°exhibited the highest conductivity(886 S/cm)and the highest tensile strain(35%).
文摘为探究"三高一扰动"特殊环境下切顶卸压无煤柱自成巷顶板砂岩切缝的动态力学性能,利用自主设计的岩土体动态冲击力学试验系统,对粉砂岩进行不同热–水–力耦合条件下的冲击压缩试验,研究动态应力–应变特征、动变形模量与加载率关系、以及加载率、轴压、围压、渗透水压、温度、吸收能与峰值应力和峰值应变的动态力学性能,利用扫描电镜(Scanning Electron Microscopy,SEM)研究粉砂岩试样断口面微观结构。研究结果表明:(1)在不同的动荷载作用下,粉砂岩试样的峰值应力和峰值应变均随轴压、围压、渗透水压、温度的升高而不断增大,脆性逐渐减弱而延性逐渐增强,变形破坏总体分为压密、弹性变形、塑性变形和破坏4个阶段;(2)动变形模量随着加载率的增大呈现出先增大后减小的发展趋势,动变形模量136GPa左右为一个临界阈值;(3)轴压、围压、水和温度对砂岩在热–水–力耦合特定环境下的动态冲击力学性能具有一定的增强效应;(4)随着峰值应变的增加,粉砂岩试样的吸收能呈线性增加趋势,其破碎变形与吸收能呈正相关。
基金supported by This work was financially supported by the State Key Laboratory for Modification of Chemical Fibers and Polymer Materials as well as the Fundamental Research Fund of Shanghai Natural Science Foundation(Grant No.17ZR1400800).
文摘The electro-thermal actuators(ETA)are smart devices that can convert electric energy into mechanical energy under electro-heating stimulation,showing great potential in the fields of soft robotics,artificial muscle and aerospace component.In this study,to build a low-voltage activating,fast responding ETA,a robust and flexible carbon nanotube film(CNTF)with excellent electrical and thermal conductivity was adopted as the conductive material.Then,an asymmetric bilayer structured ETA was manufactured by coating a thin layer of polydimethylsiloxane(PDMS)with high coefficient of thermal expansion(9.3×10^(-4)℃^(−1)),low young’s modulus(2.07 MPa)on a thin CNTF(~11μm).The as-produced CNTF/PDMS composite ETA exhibited a large deformation(bending angle~324°)and high electro heating performance(351℃)at a low driving voltage of 8 V within~12 s.The actuated movement and the generated heat could be controlled by adjusting the driving voltages and showed almost the same values in 20 cycles.Furthermore,the influences of the PDMS thickness and driving voltage on CNTF/PDMS composite ETA performance were systematically investigated.The CNTF/PDMS soft robotic hand which can lift 5.1 times and crab 1.3 times of its weight demonstrated its potential capability.
