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921.
通过对青藏高原东北部黄河源开展广泛细致的野外考察,选择位于玛曲段黄河左岸第二级河流阶地(T2)之上,赋存典型风成黄土-古土壤序列的达尔琼东(DEQ-E)剖面进行系统采样。在室内对采集样品进行了磁化率、烧失量、吸湿水、粒度、土壤微形态、地球化学元素和光释光(OSL)测年等综合分析,结论表明:(1)黄河源玛曲段DEQ-E剖面地层序列由上至下依次为现代草甸土层(MS)-全新世中期古土壤层(S0)-全新世早期过渡性黄土层(Lt)-阶地漫滩相沉积层(T2-al);(2)黄河源玛曲段DEQ-E剖面风成黄土-古土壤序列风化成壤强度呈现出全新世中期古土壤层(S0)>全新世早期过渡性黄土层(Lt)>现代草甸土层(MS)的变化特征;(3)黄河源全新世的古气候演变可分为3个阶段:全新世早期(11000 a BP—9000 a BP),西风势力减弱,东亚夏季风逐步增强,气温趋于变暖,降水有所增加;全新世中期(9000 a BP—3100 a BP),东亚夏季风作用强盛,气候整体温暖湿润;全新世晚期(3100 a BP以来),东亚夏季风衰退,西风势力有所增强,导致气候转向干冷。该研究成果有助于理解青... 相似文献
922.
Bo FU Jingyi LI Thomas GASSER Philippe CIAIS Shilong PIAO Shu TAO Guofeng SHEN Yuqin LAI Luchao HAN Bengang LI 《大气科学进展》2022,39(8):1217-1228
Individual countries are requested to submit nationally determined contributions(NDCs) to alleviate global warming in the Paris Agreement. However, the global climate effects and regional contributions are not explicitly considered in the countries’ decision-making process. In this study, we evaluate the global temperature slowdown of the NDC scenario(?T =0.6°C) and attribute the global temperature slowdown to certain regions of the world with a compact earth system model.Considering reductions ... 相似文献
923.
Analysis on geo-effects of China’s overseas industrial parks: A case study of Cambodia Sihanoukville Special Economic Zone 总被引:1,自引:0,他引:1
China's overseas industrial parks contribute to political and economic cooperation,cultural exchange between home and host countries.Current studies mainly discuss the ef-fect of overseas industrial parks from the perspective of institutional and cultural difference,multi-scale coupling,as well as key partnerships,while little attention has been paid to the comprehensive analysis of overseas industrial parks.Based on a theoretical framework,this paper explores the overall effect of China's overseas industrial parks from the geo-effects perspective by using field interviews and a case study approach.The research shows that:(1)the geo-effects reveal the over effect of overseas industrial parks from the multiple and com-plementary dimensions of geopolitics,geo-economics,geo-society and geo-culture;(2)the Cambodia Sihanoukville Special Economic Zone,as a flagship BRI project,has produced the prominent and positive geo-effects;(3)the institutional-economic-cultural-environmental adaptability of overseas industrial parks is becoming important.Overseas industrial parks must be rooted in the politics,economy,society,and culture of host country;embedded in local social networks;balance the rights and interests of all stakeholders;and form the community of interests,community of destiny,and community of responsibility with political mutual trust,economic integration,cultural inclusiveness,and social harmony.The paper not only deepens the understanding about the overall effect of overseas industrial parks,but also provides decision support and theoretical reference for government policy makers and the overseas investment of enterprises. 相似文献
924.
This study conducted microtremor testing along six survey lines that cross three typical earth fissures in the Datong basin to determine the dynamic response characteristics of earth fissure sites with regard to the Fourier amplitude spectrum, response spectrum, and Arias intensity. The results show the following.(1) The predominant frequency of an earth fissure site is mainly affected by the thickness and the shear wave velocity of the soil layer and is minimally effected by the presence of an earth fissure.(2) Earth fissures have a pronounced amplification effect on dynamic response. Fourier amplitude, response acceleration, and Arias intensity are high near an earth fissure and decrease with an increase in distance from the earth fissure, tending toward stability at a distance of 20 m.(3) The area that is seriously affected by this amplification is within 6–8 m of an earth fissure, and the general affected area is farther out than this, to a distance of 25 m.(4) New construction should be avoided in an area affected by the amplification, and existing buildings in general and seriously affected areas need to be reinforced to increase their seismic fortification intensity. 相似文献
925.
A local current sheet and a subsequent small interplanetary magnetic-flux rope were observed on 1 April 2003 by Wind and the Advanced Composition Explorer (ACE). A Petschek reconnection-like exhaust crossing of the local current sheet was identified using the Walén test. The Wind spacecraft re-entered the reconnection exhaust after the main exhaust encounter, and the reentry may be due to a spatial fold of the current-sheet surface itself. The absence of parallel strahls and the presence of antiparallel strahls on either side of the current sheet suggest that the magnetic-field lines before the exhaust and in the subsequent small flux rope are all open. The \(180^{\circ}\) pitch-angle strahls were clearly absent, and halo-suprathermal electron pitch-angle distributions were observed in the exhaust. This finding means that the open field lines of the magnetic-flux rope were reconnecting to the adjacent open field lines to produce U-shaped field lines disconnected from the Sun. These observations provide direct evidence that the magnetic fields of the interplanetary small magnetic-flux rope were disconnecting from the Sun through magnetic reconnection. This type of disconnected event potentially has important implications for the magnetic-flux budget of the heliosphere. 相似文献
926.
Xiao-Pan Li Yu-Hui Luo Hai-Yan Yang Cheng Yang Yan Cai Hai-Tao Yang Li Zhou Yu-Qiong Shan 《Astrophysics and Space Science》2018,363(8):169
We report a ~6.1 yr quasi-periodicity for the blazar S5 0716+714 using the radio light curves at 4.8, 8 and 14.5 GHz observed by the University of Michigan Radio Astronomical Observatory (UMRAO) from 1981 to 2012, by means of the Jurkevich, discrete correlation function (DCF) and power spectral analysis techniques. There are a general correlation among light curves at different frequencies and a time lag of \(170\pm 10\) days between 4.8 and 14.5 GHz light curves can be confirmed. We also estimate the orbit parameters assuming a binary black hole system, and the magnetic field strength under the jet comoving frame. 相似文献
927.
928.
This work studies a special type of cislunar periodic orbits in the circular restricted three-body problem called resonance transition periodic orbits, which switch between different resonances and revolve about the secondary with multiple loops during one period. In the practical computation, families of multiple periodic orbits are identified first, and then the invariant manifolds emanating from the unstable multiple periodic orbits are taken to generate resonant homoclinic connections, which are used to determine the initial guesses for computing the desired periodic orbits by means of multiple-shooting scheme. The obtained periodic orbits have potential applications for the missions requiring long-term continuous observation of the secondary and tour missions in a multi-body environment. 相似文献
929.
Linjie Chen Amin Aminaei Leonid I. Gurvits Marc Klein Wolt Hamid Reza Pourshaghaghi Yihua Yan Heino Falcke 《Experimental Astronomy》2018,45(2):231-253
In radio astronomy, the Ultra-Long Wavelengths (ULW) regime of longer than 10 m (frequencies below 30 MHz), remains the last virtually unexplored window of the celestial electromagnetic spectrum. The strength of the science case for extending radio astronomy into the ULW window is growing. However, the opaqueness of the Earth’s ionosphere makes ULW observations by ground-based facilities practically impossible. Furthermore, the ULW spectrum is full of anthropogenic radio frequency interference (RFI). The only radical solution for both problems is in placing an ULW astronomy facility in space. We present a concept of a key element of a space-borne ULW array facility, an antenna that addresses radio astronomical specifications. A tripole–type antenna and amplifier are analysed as a solution for ULW implementation. A receiver system with a low power dissipation is discussed as well. The active antenna is optimized to operate at the noise level defined by the celestial emission in the frequency band 1 ? 30 MHz. Field experiments with a prototype tripole antenna enabled estimates of the system noise temperature. They indicated that the proposed concept meets the requirements of a space-borne ULW array facility. 相似文献
930.
通过对2 131km高分辨率浅地层剖面资料分析和研究,揭示了威海市近海海域浅地层结构特征,分析了海洋灾害地质因素类型及分布特征,并绘制了主要灾害地质因素分布图。威海市近海海域65m以浅地层共分为5层,第一层为全新世泥质楔形体,地层厚度8~15m;第二层为末次盛冰期以来的海侵层,厚度一般小于3m;第三层为MIS2期的陆相沉积层,地层厚度3~8m;第四层为MIS3期的海相沉积层,厚度3~6m;第五层未完全揭示。近海海域灾害地质因素主要包括埋藏下切谷、浅部断层、浅层气、海底沙波沙脊、浅埋起伏基岩等5种类型;埋藏下切谷主要分布在南部海域U3地层单元中;浅部断层主要分布在南部海域水深大于20m的海底堆积平原;浅层气主要分布在北部海域,东部和南部海域面积较小;海底沙波沙脊主要分布在荣成成山头外海海域;浅埋起伏基岩主要分布在基岩海岸和岛屿较近的海域。 相似文献