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| 1 | Oceanic environmental changes of subarctic Bering Sea in recent 100 years: Evidence from molecular fossils显示文摘The core sample B2-9 from the seafloor of the subarctic Bering Sea was dated with 210 Pb to obtain a consecutive sequence of oceanic sedimentary environments at an interval of a decade during 1890—1999. A variety of molecular fossils were detected, including n-alkanes, isoprenoids, fatty acids, sterols, etc. By the characteristics of these fine molecules (C27, C28, and C29 sterols) and their molecular indices (Pr/Ph, ∑C+22/∑C?21, CPI and C18∶2/C18∶0) and in con- sideration of the variation of organic carbon content, the 100-year evolution history of subarctic sea paleoenvironment was reestablished. It is indicated that during the past 100 years in the Arctic, there were two events of strong climate warming (1920—1950 and 1980—1999), which resulted in an oxidated sediment environment owing to decreasing terrigenous organic matters and increasing marine-derived organic matters, and two events of transitory climate cooling (1910 and 1970—1980), which resulted in a slightly reduced sediment environment owing to increasing terrigenous organic matters and decreasing marine-derived organic matters. It is re- vealed that the processes of warming/cooling alternated climate are directly related to the Arctic and global climate variations. | LU Bing CHEN Ronghua ZHOU Huaiyang WANG Zipan CHEN Jianfang ZHU Chun | 2005 | Science China Earth Sciences2005,48,4: | 11 |
| 2 | Application of long-chain alkenones and U_(37)~k values for paleotemperature estimation in the Arctic Chukchi Sea-Bering Sea area显示文摘Long-chain alkenones were detected in samples of sea surface sediments from the Chukchi Sea and the Bering Sea areas, the Arctic Pole. The analysis result indicates that C37:3 methylketone is predominate in the long-chain alkenones from the Chukchi and Bering Sea sediments. The abundance of C37 to C39 unsaturated alkenones changes in an order of C37 > C38 > C39. Based on C37 /C38 ratio, the detected organism precursors of the long-chain alkenones are mainly coccolithophrid (Emiliania huxleyi). By the calibration relationship between U37k and U37k indices, the sea surface paleotemperature in these seas is estimated. The estimated values of U37k vary from 4.147℃ to 5.706℃ , with a mean value of 5.092℃. | Lu Bing, Chen Ronghua, Wang Zipan, Chen Jianfang, Liu Zhensheng 1. Key Laboratory of Submarine Geosciences, Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China | 2001 | Acta Oceanologica Sinica2001,20,3: | 4 |
| 3 | Alloying effects of the elements with a positive heat of mixing on the glass forming ability of Al-La-Ni amorphous alloys显示文摘The effects of Sn and Ga additions on the glass forming ability(GFA)of(Al86La5Ni9)100 xSnx(x=0,0.2,0.3,0.5,0.7,1 and 2at.%)and(Al86La5Ni9)100 xGax(x=0,0.2,0.5,1 and 1.5 at.%)alloys were systematically investigated.Unlike common microalloying methods,both Sn and Ga have a positive heat of mixing with the main component of Al.Our analysis confirmed that proper Sn addition can suppress the strong formation ofα-Al and enhance the GFA due to the positive heat of mixing between Sn and Al and the large difference in their atomic sizes.While the addition of Ga to the base alloy acted as the nucleation cites forα-Al and accelerated precipitation of theα-Al phase,thus deteriorating the GFA. | CHEN ZiPan GAO JingEn WU Yuan WANG Hui LIU XiongJun LU ZhaoPing | 2014 | Science China(Physics,Mechanics & Astronomy)2014,57,1: | 3 |
| 4 | Effects of trace elements on mechanical properties of the TiZrHfNb high-entropy alloy显示文摘Refractory high-entropy alloys have great potential to be utilized as high-temperature materials,and the repeatability and reproducibility of their mechanical properties are critical for practical applications.In this work,nevertheless,we found that the mechanical properties of the TiZrHfNb HEA greatly varied with the content of impurities in the samples even using high-purity raw materials.Specifically,the oxygen impurity is mainly responsible for the increment of the yield stress due to the strong interstitial hardening effect,whilst the ductility deterioration closely associates with the content of metalloid elements B,C,and Si.Our analysis reveals that the metalloid elements not only tend to segregate at grain boundaries but also enhance the aggregation of Zr and Ti.Such co-segregation induced the formation of strong(Zr,Ti)-metalloid bonds,resulting in grain boundary embrittlement and brittle fracture.Our current work demonstrates that the impurity contents in refractory HEAs need to be strictly controlled during production in order to improve their stability of mechanical performance. | Xiaoyuan Yuan Yuan Wu Meisa Zhou Xiongjun Liu Hui Wang Suihe Jiang Xiaobin Zhang Honghui Wu Xiaochun Liu Zipan Chen Xiangqi Xu Zhaoping Lu | 2023 | Journal of Materials Science & Technology2023,,21: | 0 |