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191.
北极快速变化的生态环境响应 总被引:1,自引:0,他引:1
北冰洋由于其特殊的地理位置,成为全球变化响应最为敏感的地区。本文聚焦北极海冰变化幅度最大的西北冰洋,从营养盐、叶绿素、浮游植物群落和沉积碳埋藏等变化来讨论海洋生态环境对北极快速变化的响应。尽管太平洋北向流和北极周边河流输入加强可以增加西北冰洋上层营养盐储库,但由于夏季硅藻旺发向沉积物迁出大量生源元素,使得上层营养盐相对亏损,部分海域存在显著的氮限制和硅限制。随海冰减退,尽管夏末海盆区浮游植物呈现小型化趋势,但西北冰洋总体上浮游植物现存量和初级生产力呈现增高的趋势;伴随叶绿素极大层下移、北扩,以硅藻为代表的生物泵过程得以更高效的运转。在沉积物埋藏的有机碳中,除原先北冰洋生态系统占据重要比份的冰藻外,硅藻等藻类的有机碳埋藏也逐渐增加。西北冰洋海洋初级生产力的增加不仅促进了生物泵的运转和碳的埋藏,而且给海洋生态系统提供了更多的食物来源。北极海域目前已成为全球碳源汇格局变化最大、海洋生态系统改变最显著的地区之一。 相似文献
192.
深海岩芯取样钻机是开展海洋科学研究、深海资源探测和海底地质取样所必备的关键性装备,随着深海运载器的大规模应用,利用运载器优势发展深海运载器小型岩芯取样探测技术得到了国内外学者的关注,并形成了研究热点方向。在深海运载器作业工具应用认识基础上,首次聚焦运载器岩芯取样钻机研究,对国内外运载器岩芯取样钻机的发展现状、技术特点进行了全面综述。同时,基于"蛟龙"号岩芯钻机研制及应用经验,讨论了发展运载器岩芯取样钻机的关键技术。最后总结了后续发展方向,以期为我国深海运载器岩芯钻机的研发和应用提供技术参考。 相似文献
193.
194.
Zhi-Jia Tian Xiao-Wei Liu Hai-Bo Yuan Bing-Qiu Chen Mao-Sheng Xiang Yang Huang Chun Wang Hua-Wei Zhang Jin-Cheng Guo Juan-Juan Ren Zhi-Ying Huo Yong Yang Meng Zhang Shao-Lan Bi Wu-Ming Yang Kang Liu Xian-Fei Zhang Tan-Da Li Ya-Qian Wu Jing-Hua Zhang 《天文和天体物理学研究(英文版)》2018,(5)
Stellar systems composed of single, double, triple or higher-order systems are rightfully regarded as the fundamental building blocks of the Milky Way. Binary stars play an important role in formation and evolution of the Galaxy. Through comparing the radial velocity variations from multiepoch observations, we analyze the binary fraction of dwarf stars observed with LAMOST. Effects of different model assumptions, such as orbital period distributions on the estimate of binary fractions,are investigated. The results based on log-normal distribution of orbital periods reproduce the previous complete analyses better than the power-law distribution. We find that the binary fraction increases with Teff and decreases with [Fe/H]. We first investigate the relation between α-elements and binary fraction in such a large sample as provided by LAMOST. The old stars with high [α/Fe] dominate with a higher binary fraction than young stars with low [α/Fe]. At the same mass, earlier forming stars possess a higher binary fraction than newly forming ones, which may be related with evolution of the Galaxy. 相似文献
195.
Multi-conjugate adaptive optics(MCAO),consisting of several deformable mirrors(DMs),can significantly increase the adaptive optics(AO)correction field of view.Current MCAO can be realized by either star-oriented or layer-oriented approaches.For solar AO,ground-layer adaptive optics(GLAO)can be viewed as an extreme case of layer-oriented MCAO in which the DM is conjugated to the ground,while solar tomography adaptive optics(TAO)that we proposed recently can be viewed as star-oriented MCAO with only one DM.Solar GLAO and TAO use the same hardware as conventional solar AO,and therefore it will be important to see which method can deliver better performance.In this article,we compare the performance of solar GLAO and TAO by using end-to-end numerical simulation software.Numerical simulations of TAO and GLAO with different numbers of guide stars are conducted.Our results show that TAO and GLAO produce the same performance if the DM is conjugated to the ground,but TAO can only generate better performance when the DM is conjugated to the best height.This result has important application in existing one-DM solar AO systems. 相似文献
196.
“海上丝绸之路”沿线重要港口竞争力评价 总被引:1,自引:0,他引:1
“海上丝绸之路”是促进亚欧和亚非互联互通的重要通道,对其沿线重要港口的竞争力研究,可以为海上丝绸之路的建设提供参考。本文综合考虑港口的自然条件、腹地环境、基础设施、服务水平、政府廉洁度,及其在航运网络中的地位差别等因素,运用熵权-层次分析法对沿线51个国家的99个重要港口的竞争力进行评价。结果表明,① 港口综合竞争力空间分布呈明显的区域化特征,且与国家经济发展水平显著相关,地中海地区港口竞争力普遍较强,亚洲次之,非洲最弱。② 港口的网络地位对竞争力的影响最大,竞争力强的港口多位于重要水域的战略通道,网络地位高,辐射范围广。③ 我国投资的部分沿线港口综合竞争力与成熟港口之间还存在一定差距,但是具备较大的竞争力提升空间。 相似文献
197.
The sky brightness is a critical parameter for estimating the coronal observation conditions for a solar observatory. As part of a site-survey project in Western China, we measured the sky brightness continuously at the Lijiang Observatory in Yunnan province in 2011. A sky brightness monitor (SBM) was adopted to measure the sky brightness in a region extending from 4.5 to 7.0 apparent solar radii based on the experience of the Daniel K. Inouye Solar Telescope (DKIST) site survey. Every month, the data were collected manually for at least one week. We collected statistics of the sky brightness at four bandpasses located at 450, 530, 890, and 940 nm. The results indicate that aerosol scattering is of great importance for the diurnal variation of the sky brightness. For most of the year, the sky brightness remains under 20 millionths per airmass before local Noon. On average, the sky brightness is less than 20 millionths, which accounts for 40.41% of the total observing time on a clear day. The best observation time is from 9:00 to 13:00 (Beijing time). The Lijiang Observatory is therefore suitable for coronagraphs investigating the structures and dynamics of the corona. 相似文献
198.
This paper investigates the influences of atom--field coupling and dipole--dipole coupling for atoms on the entanglement between two atoms by means of concurrence. The results show that the sudden death occurs when the atom--field coupling is strong enough, and the collapse and the revival appear when the dipole--dipole interaction is strong enough. 相似文献
199.
Photoluminescence (PL) spectra of Si nanocrystals (NCs) prepared by 130 keV Si ions implantation onto SiO2 matrix were investigated as a function of annealing temperature and implanted ion dose. PL spectra consist of two PL peaks, originated from smaller Si NCs due to quantum confinement effect (QCE) and the interface states located at the surface of larger Si NCs. The evolution of number of dangling bonds (DBs) on Si NCs was also investigated. For hydrogen-passivated samples, a monotonic increase in PL peak intensity with the dose of implanted Si ions up to 3× 1017 ions /cm2 is observed. The number of DBs on individual Si NC, the interaction between DBs at the surface of neighbouring Si NCs and their effects on the efficiency of PL are discussed. 相似文献
200.
Guoyan Ren Bafang Li Xue Zhao Yongliang Zhuang Mingyan Yan Hu Hou Xiukun Zhang Li Chen 《中国海洋大学学报(英文版)》2009,8(1):83-88
In order to select an optimum extraction method for the target glycoprotein (TGP) from jellyfish (Rhopilema esculentum) oral-arms, a high performance liquid chromatography (HPLC)-assay for the determination of the TGP was developed. Purified
target glycoprotein was taken as a standard glycoprotein. The results showed that the calibration curves for peak area plotted
against concentration for TGP were linear (r = 0.9984, y = 4.5895x+47.601) over concentrations ranging from 50 to 400 mgL-1. The mean extraction recovery was 97.84% (CV2.60%). The fractions
containing TGP were isolated from jellyfish (R. esculentum) oral-arms by four extraction methods: 1) water extraction (WE), 2) phosphate buffer solution (PBS) extraction (PE), 3) ultrasound-assisted
water extraction (UA-WE), 4) ultrasound-assisted PBS extraction (UA-PE). The lyophilized extract was dissolved in Milli-Q
water and analyzed directly on a short TSK-GEL G4000PWXL (7.8 mm×300 mm) column. Our results indicated that the UA-PE method
was the optimum extraction method selected by HPLC. 相似文献