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| 1 | 内蒙古鄂尔多斯高原古冰缘遗迹科学考察研究进展显示文摘冰缘遗迹(特别是冷生楔形构造及融冻褶皱)是重建古气候及第四纪晚期多年冻土环境的重要证据。内蒙古鄂尔多斯高原是我国北方地区冰缘现象最为发育的地区之一。为准确了解鄂尔多斯高原冰缘遗迹类型及其分布特征、区域冻土演化历史等,中国科学院西北生态环境资源研究院和荷兰自由大学共同组成科研小组,于2018年5—6月组织了'鄂尔多斯高原冰缘遗迹科学考察'。考察区域涉及靖边—城川—乌审旗—鄂尔多斯东胜区一带约12000km2的范围。考察内容主要包括鄂尔多斯高原冰缘遗迹类型及特征、分布区域、各类型冰缘遗迹所指示的气候条件的初步推断等。结果表明:冻融褶皱和冷生楔体构造是鄂尔多斯高原主要存在的两大类冰缘遗迹。基于本次考察中关于冰缘遗迹的分布与特征等新发现,并综合前人研究成果,初步推断:在气温极低、多年冻土非常发育的时段,有利于形成各类冷生楔状构造,如冰楔假形和大型原生砂楔等;在气候转暖、多年冻土退化,但还没有全部融化完阶段,可能形成融冻褶皱;区域性大面积分布和成群出现的融冻褶皱一般反映较暖气候环境下,多年冻土层上部已退化到一定程度。基于光释光(OSL)年代测试结果,结合冰缘遗迹的特征及其所指示的古气候环境,初步重建了鄂尔多斯5万年以来的冻土环境变化序列。区内多年冻土在多年冻土最大期(LPM,25~19ka BP)时最发育,以大面积连续多年冻土为主;之后,随气温转暖,总趋势呈退化状态,多年冻土分布逐渐变为片状→岛状→零星斑状,直至现今全部融完变为深季节冻土区。 | 何瑞霞 金会军 蒋观利 张泽 陈雪梅 Raul David SERBAN Mihaela SERBAN Jef VANDENBERGHE Valentin V.SPEKTOR Hugh M.FRENCH | 2021 | 冰川冻土2021，43，1： | 2 |
| 2 | Observation of a highly conductive warm dense state of water with ultrafast pump–probe freeelectron-laser measurements显示文摘The electrical conductivity of water under extreme temperatures and densities plays a central role in modeling planetary magnetic fields.Experimental data are vital to test theories of high-energy-densitywater and assess the possible development and presence of extraterrestrial life.These states are also important in biology and chemistry studies when specimens in water are confined and excited using ultrafast optical or free-electron lasers(FELs).Here we utilize femtosecond optical lasers to measure the transient reflection and transmission of ultrathin water sheet samples uniformly heated by a 13.6 nm FEL approaching a highly conducting state at electron temperatures exceeding 20000 K.The experiment probes the trajectory ofwater through the high-energy-density phase space and provides insights into changes in the index of refraction,charge carrier densities,andACelectrical conductivity at optical frequencies.At excitation energy densities exceeding 10MJ/kg,the index of refraction falls to n0.7,and the thermally excited free-carrier density reaches ne531027 m−3,which is over an order of magnitude higher than that of the electron carriers produced by direct photoionization.Significant specular reflection is observed owing to critical electron density shielding of electromagnetic waves.Themeasured optical conductivity reaches 23104 S/m,a value that is one to two orders of magnitude lower than those of simplemetals in a liquid state.At electron temperatures below 15000 K,the experimental results agreewell with the theoretical calculations using density-functional theory/molecular-dynamics simulations.With increasing temperature,the electron density increases and the system approaches a Fermi distribution.In this regime,the conductivities agree better with predictions from the Ziman theory of liquid metals. | Z.Chen X.Na C.B.Curry S.Liang M.French A.Descamps D.P.DePonte J.D.Koralek J.B.Kim S.Lebovitz M.Nakatsutsumi B.K.Ofori-Okai R.Redmer C.Roedel M.Schörner S.Skruszewicz P.Sperling S.Toleikis M.Z.Mo S.H.Glenzer | 2021 | Matter and Radiation at Extremes2021，6，5： | 0 |
| 3 | 宽带卫星服务在亚洲的发展趋势显示文摘NSR(Northern Sky Research)公司为评估宽带卫星服务发展趋势,分别从企业IP VSAT宽带网络应用、单点接收用户(卫星宽带典型应用)和卫星IP中继应用这3部分进行了考察。这些应用都来自基于IP的典型用户,包括大型企业、政府和非政府组织、中小型企业、个人用户、SOHO一族和ISP服务商。以下市场趋势的调查研究来源于NSR公司的《全球卫星需求调查(第4版)》和《宽带卫星市场研究(第6版)》。 | Patrick M.French 宋青(翻译) | 2008 | 卫星与网络2008，，8： | 0 |
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