The glacial morphology of southern South American presents invaluable evidence to reconstruct former glacier behaviour and its relation to climate and environmental changes. However, there are still spatial and tempor...The glacial morphology of southern South American presents invaluable evidence to reconstruct former glacier behaviour and its relation to climate and environmental changes. However, there are still spatial and temporal gaps in the reconstruction of the Holocene Patagonian glacial landscape. Here we present the first geomorphological record for the Sierra Baguales Mountain Range(SBMR), forming the eastern foothills of the Southern Patagonian Andes 200 km from the Pacific coast. This area is topographically isolated from the Southern Patagonian Ice Field(SPIF), and is affected by the Westerly Winds. The study area shows evidence of ice sheet and alpine glaciations related to Andean uplift,which caused a marked climatic contrast between its western and eastern flanks since the Last Glacial Maximum(LGM). The regional rock mass strength and precipitation gradient acted as a controlling factor in the glacial cirque distribution and sizes, as well as in the development of glaciation types. We report new radiocarbon dates associated with warm/dry to cold/wet climatic changes during the middle Holocene, when former small alpine glaciers were located in the uppermost section of the SBMR basins, and eventually converged to form a small ice field or a composite valley glacier at lower elevations.This can be explained by an estimated regional temperature drop of 3.8°C±0.8°C, based on a 585±26m Equilibrium Line Altitude(ELA) descent, inferred by geomorphological evidence and the Accumulation Area Ratio(AAR), in addition to a free-air adiabatic lapse rate. Subsequently, the glaciers receded due to climatic factors including a rise in temperature, as well as non-climatic factors, mainly the glacier bedrock topography.展开更多
The effects of adding alloy element zinc on the static and dynamic mechanical properties of copper-zinc alloy were investigated. Tensile and low cycle fatigue behaviors of the C11000 copper and H63 copper-zinc alloy w...The effects of adding alloy element zinc on the static and dynamic mechanical properties of copper-zinc alloy were investigated. Tensile and low cycle fatigue behaviors of the C11000 copper and H63 copper-zinc alloy were obtained by using a miniature tester that combined the functions of in situ tensile and fatigue testing. A piezoelectric actuator was adopted as the actuator for the fatigue testing, and the feasibility of the fatigue actuator was verified by the transient harmonic response analysis based on static tensile preload and dynamic sinusoidal load. The experimental results show that the yield strength and tensile strength of the C11000 copper are improved after adding 37%(mass fraction) zinc, and H63 copper-zinc alloy presents more obvious cyclic hardening behavior and more consumed irreversible plastic work during each stress cycle compared with C11000 copper for the same strain controlled cycling. Additionally, based on the Manson-Coffin theory, the strain-life equations of the two materials were also obtained. C11000 copper and H63 copper-zinc alloy show transition life of 16832 and 1788 cycles, respectively.展开更多
文摘The glacial morphology of southern South American presents invaluable evidence to reconstruct former glacier behaviour and its relation to climate and environmental changes. However, there are still spatial and temporal gaps in the reconstruction of the Holocene Patagonian glacial landscape. Here we present the first geomorphological record for the Sierra Baguales Mountain Range(SBMR), forming the eastern foothills of the Southern Patagonian Andes 200 km from the Pacific coast. This area is topographically isolated from the Southern Patagonian Ice Field(SPIF), and is affected by the Westerly Winds. The study area shows evidence of ice sheet and alpine glaciations related to Andean uplift,which caused a marked climatic contrast between its western and eastern flanks since the Last Glacial Maximum(LGM). The regional rock mass strength and precipitation gradient acted as a controlling factor in the glacial cirque distribution and sizes, as well as in the development of glaciation types. We report new radiocarbon dates associated with warm/dry to cold/wet climatic changes during the middle Holocene, when former small alpine glaciers were located in the uppermost section of the SBMR basins, and eventually converged to form a small ice field or a composite valley glacier at lower elevations.This can be explained by an estimated regional temperature drop of 3.8°C±0.8°C, based on a 585±26m Equilibrium Line Altitude(ELA) descent, inferred by geomorphological evidence and the Accumulation Area Ratio(AAR), in addition to a free-air adiabatic lapse rate. Subsequently, the glaciers receded due to climatic factors including a rise in temperature, as well as non-climatic factors, mainly the glacier bedrock topography.
基金Projects(51275198,51422503)supported by the National Natural Science Foundation of ChinaProject(2012YQ030075)supported by Special Funds for Development of National Major Scientific Instruments and Equipments,China+1 种基金Project(NECT-12-0238)supported by Program for New Century Excellent Talents in University,ChinaProject(20150520108JH)supported by Young Scientist Fund of Jilin Province of China
文摘The effects of adding alloy element zinc on the static and dynamic mechanical properties of copper-zinc alloy were investigated. Tensile and low cycle fatigue behaviors of the C11000 copper and H63 copper-zinc alloy were obtained by using a miniature tester that combined the functions of in situ tensile and fatigue testing. A piezoelectric actuator was adopted as the actuator for the fatigue testing, and the feasibility of the fatigue actuator was verified by the transient harmonic response analysis based on static tensile preload and dynamic sinusoidal load. The experimental results show that the yield strength and tensile strength of the C11000 copper are improved after adding 37%(mass fraction) zinc, and H63 copper-zinc alloy presents more obvious cyclic hardening behavior and more consumed irreversible plastic work during each stress cycle compared with C11000 copper for the same strain controlled cycling. Additionally, based on the Manson-Coffin theory, the strain-life equations of the two materials were also obtained. C11000 copper and H63 copper-zinc alloy show transition life of 16832 and 1788 cycles, respectively.
