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201.
Kecun Zhang Jianjun Qu Qinghe Niu Zhefan Jing Zhishan An 《Environmental Earth Sciences》2013,70(7):3107-3113
Based on the detailed wind data, this paper aims to investigate wind regime, drift potential and the movement of mega-dunes at the Crescent Moon Spring, an important scenic spot in western China and to clarify the dominant factors that control sand transport in this region. The results of this paper revealed that the dominant wind directions at the spring were NW and SW. The spring region belonged to a low-energy wind environment. The wind regime and sand drift potential were hugely influenced by local topography, and the regional atmospheric circulation intensified the complexity of their variations. Besides, the movement of the southern and northern mega-dune towards the spring greatly endangered the preservation of this scenic spot. These results provide insights into the characteristics of wind-blown sand at the Crescent Moon Spring that will guide efforts to control sand damages. 相似文献
202.
对天山北麓黄土分布特点与形成年代的研究,以及以此为载体应用各代用指标的古气候重建已经取得了不少进展。在前人工作的基础上,选取黄土—古土壤序列分明,底部S3古土壤发育的鹿角湾剖面为主要研究对象,结合天山北麓的其他多个典型黄土剖面,运用色度、粒度、常量地球化学元素含量和环境磁学参数等指标,探讨大约30万年以来的古气候演变。鹿角湾黄土实验结果显示,各古气候代用指标随剖面深度变化与黄土—古土壤更替大概一致,剖面上部(L2及其以上)与下部区别明显。粒度分布揭示黄土物源输入主要受控于两股不同风系,随黄土古土壤的更替两者的主次地位发生变化。环境磁学实验结果显示,剖面下部磁性弱,频率磁化率低,但古土壤层稳定单畴含量较高,反映湿润成壤环境下超顺磁亚铁磁性矿物溶解或转化为弱磁性矿物;剖面上部比剖面下部的磁性要强,磁性矿物粒度更粗;S0为磁性成壤增强模式,与其他黄土古土壤层不同。再结合其他典型剖面的记录,可以推断研究区30万年以来有干旱化的趋势,但S2发育阶段总体上可能比S3发育阶段略为湿润,这一阶段之后气候明显变干,S1发育阶段明显比S2与S3发育阶段干旱,干旱化趋势一直保持至全新世开始之前。 相似文献
203.
The theoretical design of the polarimeter used for the Fibre Arrayed Solar Optical Telescope (FASOT) is described. It has the following characteris- tics: (1) It is provided with the function of optical polarization switching, which makes the high-effciency polarimetry possible; (2) In the waveband of 750 nm, the polarimetric effciency is higher than 50% for the every Stokes parameter, and higher than 86.6% for the total polarization, thus an observer can make the simultaneous polarization measurements on multiple magnetosensitive lines in such a broad range of wavelength; (3) According to the selected photospheric and chromospheric lines, the measurement can be focused on either linear polarization or circular polarization; (4) The polarimeter has a loose tolerance on the manufacturing technology of polarimetric elements and installation errors. All this makes this polarimeter become a high-performance polarimetric device. 相似文献
204.
Household consumption represents an important proportion of all energy consumption,and it is an important source of CO2 emission. But household consumption and carbon emissions are often overlooked in climate change policies and measures. Through literature review, the research status of household consumption and carbon emissions were reviewed. On this basis, the main aspects and directions of the research are summarized and the main research of household carbon emissions should focus on three aspects in the future: ①The impact of income, consumption levels and other factors on household carbon emission; ②The relationship between direct and indirect carbon emissions of household carbon emission; ③The structure and source of household carbon emission. In future research, there are four issues which need in-depth study: ①Index and models study of household carbon emissions;②Impact of demographic change on household carbon emissions; ③The path of how to achieve sustainable and green urban lifestyle;④The relevant policy research of household carbon emissions. 相似文献
205.
根据对1980年汛期在黄河18个水文站采集样品的分析结果,本文讨论了黄河悬浮物的粒度、矿物和化学组成从上游到下游的地理分异。 相似文献
206.
ChangLiang Yin TanDong Yao LiDe Tian DongNian Liu WuSheng Yu DongMei Qu 《中国科学D辑(英文版)》2008,51(7):966-975
Oxygen stable isotope of atmospheric water vapor is widely used to study the modern process of climate. Atmospheric water
vapor samples were collected at Dlingha, northeast of Tibetan Plateau during the period from July 2005 to February 2006. The
variation of δ
18O and the relationships between δ
18O and both the temperature and specific humidity are analyzed in this paper. Results show that the seasonal variation of δ
18O of atmospheric water vapor at Delingha is remarkable with higher δ
18O in summer and lower δ
18O in winter. The temporal variation of vapor δ
18O shows obvious fluctuations, with magnitude of over 37‰ The daily variation of the δ
18O is highly correlated with air temperature. The relationship between δ
18O and atmospheric water vapor content is complex. Study shows that δ
18O of atmospheric water vapor is positively correlated with specific humidity in winter in seasonal scale and inversely correlated
with specific humidity in summer rainy period. The δ
18O values of atmospheric water vapor are lower than those of precipitation at Delingha, and the average difference is 10.7‰
Variations of δ
18O of atmospheric water vapor is also found to be affected by precipitation events, The model results show that the precipitation
effect could have caused the vapor δ
18O in the raining season to lower by 7% in average in July and August.
Supported by the National Natural Science Foundation of China (Grant Nos. 40671043, 40571039 and 40771048) and National Basic
Research Program of China (Grant No. 2005CB422002) 相似文献
207.
208.
扁平大跨度公路隧道松动荷载计算方法探讨 总被引:6,自引:0,他引:6
确定松动荷载的方法多为规范法和理论公式法,这些方法都建立在对以往隧道松动荷载统计和分析的基础上。双洞八车道扁平大跨度公路隧道是近几年发展起来的一种隧道形式。由于其跨度增加、扁平率降低,现有松动荷载的算方法是否适用于双洞八车道公路隧道,已成为隧道建设者面对的重要问题之一。以广州龙头山双洞八车道公路隧道为研究背景,概括和总结了各种松动荷载的计算方法;应用这些方法计算龙头山隧道的松动压力,分析和对比计算结果,并通过数值计算和实测围岩压力对各种方法的合理性进行了分析;根据各种方法的产生背景和内容,分析其各自的适用性;根据研究结果,对扁平大跨度公路隧道进行了适应性分析和讨论。 相似文献
209.
2008年3月21日新疆于田7.3级地震发震构造与震前地震活动特征研究 总被引:6,自引:0,他引:6
2008年3月21日新疆于田发生7.3级地震,打破了中国大陆6年多的7级地震平静,成为我国近期较为显著的一次地震事件.综合分析MS≥4.0余震分布、震区断裂性质以及等震线长轴方向等资料,认为郭扎错断裂是这次地震的发震构造;据Harvard震源机制解分析,这次地震是在近NS向力的作用下,郭扎错断裂发生略带走滑分量的拉张破裂所致.通过地震前震区附近地震活动特征分析发现,于田地震发生在1996年以来新疆南部及邻区7级地震有序分布的空段;震前震区附近有4级地震空区形成,空区持续91个月后发生了2006年9月12日皮山5.8级"信号震",其后1.5年发生于田7.3级地震. 相似文献
210.
Xuan Ding LianFeng Gao NianQiao Fang WenJun Qu Jian Liu JiangShan Li 《中国科学D辑(英文版)》2009,52(8):1091-1103
Base on the Os isotope stratigraphy together with the empirical growth rate models using Co concentrations, the growth ages
of the ferromanganese crusts MHD79 and MP3D10 distributed in the seamount of Pacific are confirmed. Through the contrast and
research on the previous achievements including ODP Leg 144 and the crusts CD29-2, N5E-06 and N1–15 of the seamount of the
Central Pacific, the uniform five growth and growth hiatus periods of them are found, and closely related to the Cenozoic
ocean evolvement process. In the Paleocene Carbon Isotope Maximum (PCIM), the rise of the global ocean productivity promoted
the growth of the seamount crust; the first growth hiatus (I) of the ferromanganese crust finished. In the Paleocene-Eocene
Thermal Maximum (PETM), though the vertical exchange of seawater was weakened, the strong terrestrial chemical weathering
led to the input of a great amount of the terrigenous nutrients, which made the bioproductivity rise, so there were no crust
hiatuses. During 52–50 Ma, the Early Eocene Optimum Climate (EECO), the two poles were warm, the latitudinal temperature gradient
was small, the wind-driven sea circulation and upwelling activity were weak, the terrestrial weathering was also weakened,
the open ocean bioproductivity decreased, and the ferromanganese crust had growth hiatus again (II). From early Middle Eocene-Late
Eocene, Oligocene, it was a long-term gradually cooling process, the strengthening of the sea circulation and upwelling led
to a rise of bioproductivity, and increase of the content of the hydrogenous element Fe, Mn and Co and the biogenous element
Cu, Zn, so that was the most favorable stage for the growth of ferromanganese crust (growth periods III and IV) in the studied
area. The hiatus III corresponded with the Eocene- Oligocene boundary, is inferred to relate with the global climate transformation,
celestial body impact event in the Eocene-Oligocene transition. From the early to the middle Miocene, a large-scale growth
hiatus (hiatus period IV) of the ferromanganese crust in the studied area is inferred to relate with temporary warm up climate
and ephemeral withdrawal of Antarctic bottom water in the early Miocene. After that, the Antarctic ice sheets extended, the
bottom water circumfluence strengthened, the ocean fertility increased, and the once interrupted crust continued to grow in
the late Miocene (growth period V).
Supported by China Ocean Mineral Resources Research and Development Association “10th Five Year” Topic (Grant No. DY105-01-04-14) 相似文献