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911.
Zhifu Xie 《Celestial Mechanics and Dynamical Astronomy》2010,107(3):353-376
In this paper, we consider the inverse problem of central configurations of n-body problem. For a given \({q=(q_1, q_2, \ldots, q_n)\in ({\bf R}^d)^n}\), let S(q) be the admissible set of masses denoted \({ S(q)=\{ m=(m_1,m_2, \ldots, m_n)| m_i \in {\bf R}^+, q}\) is a central configuration for m}. For a given \({m\in S(q)}\), let S m (q) be the permutational admissible set about m = (m 1, m 2, . . . , m n ) denotedThe main discovery in this paper is the existence of a singular curve \({\bar{\Gamma}_{31}}\) on which S m (q) is a nonempty set for some m in the collinear four-body problem. \({\bar{\Gamma}_{31}}\) is explicitly constructed by a polynomial in two variables. We proved:
相似文献
$S_m(q)=\{m^\prime | m^\prime\in S(q),m^\prime \not=m \, {\rm and} \, m^\prime\,{\rm is\, a\, permutation\, of }\, m \}.$
- (1)If \({m\in S(q)}\), then either # S m (q) = 0 or # S m (q) = 1.
- (2)#S m (q) = 1 only in the following cases:
- (i)If s = t, then S m (q) = {(m 4, m 3, m 2, m 1)}.
- (ii)If \({(s,t)\in \bar{\Gamma}_{31}\setminus \{(\bar{s},\bar{s})\}}\), then either S m (q) = {(m 2, m 4, m 1, m 3)} or S m (q) = {(m 3, m 1, m 4, m 2)}.
- (i)
912.
长江北支口门圆陀角附近潮滩沉积物粒度记录及其对环境变化的响应 总被引:7,自引:6,他引:1
江苏圆陀角位于长江口北支与江苏海岸交汇处,海岸沉积动力环境复杂,潮滩沉积物粒度变化记录了潮滩环境变化的信息.根据2007年4月采集的表层样和钻孔岩芯粒度分析,圆陀角附近Yyb断面表层沉积物粒度在互花米草滩前缘较粗,大堤前岸滩最粗,光滩和互花米草滩粒度较细.YY孔岩芯沉积物粒度组成以砂质粉砂为主,粒度变化自下向上呈先由粗变细再变粗的特点,表层样和钻孔岩芯粒度变化反映了潮滩沉积物对风暴潮、潮汐海洋动力、大米草和互花米草种植以及大规模围垦的综合响应.173Cs测年结果推算出YY孔岩芯1954年以来、1963年以来、1975年以来和1986年以来的平均沉积速率分别为2.38cm/a,2.23cm/a,2.44cm/a和1.24cm/a.岩芯沉积物的沉积速率总体随潮滩淤积增高而下降,1975~1986年间沉积速率的快速增加,主要与圆陀角附近互花米草的快速淤积有关. 相似文献
913.
914.
Geochemistry of soil gas in the seismic fault zone produced by the Wenchuan Ms 8.0 earthquake, southwestern China 总被引:2,自引:0,他引:2
Xiaocheng Zhou Jianguo Du Zhi Chen Jianwu Cheng Yi Tang Liming Yang Chao Xie Yueju Cui Lei Liu Li Yi Panxin Yang Ying Li 《Geochemical transactions》2010,11(1):1-10
The spatio-temporal variations of soil gas in the seismic fault zone produced by the 12 May 2008 Wenchuan Ms 8.0 earthquake were investigated based on the field measurements of soil gas concentrations after the main shock. Concentrations of He, H2, CO2, CH4, O2, N2, Rn, and Hg in soil gas were measured in the field at eight short profiles across the seismic rupture zone in June and December 2008 and July 2009. Soil-gas concentrations of more than 800 sampling sites were obtained. The data showed that the magnitudes of the He and H2 anomalies of three surveys declined significantly with decreasing strength of the aftershocks with time. The maximum concentrations of He and H2 (40 and 279.4 ppm, respectively) were found in three replicates at the south part of the rupture zone close to the epicenter. The spatio-temporal variations of CO2, Rn, and Hg concentrations differed obviously between the north and south parts of the fault zone. The maximum He and H2 concentrations in Jun 2008 occurred near the parts of the rupture zone where vertical displacements were larger. The anomalies of He, H2, CO2, Rn, and Hg concentrations could be related to the variation in the regional stress field and the aftershock activity. 相似文献
915.
Genming Luo Junhuang Huang Shucheng Xie Paul B. Wignall Xinyan Tang Xianyu Huang Hongfu Yin 《International Journal of Earth Sciences》2010,99(4):775-784
This paper investigates kerogen carbon isotopes, the difference between carbonate and kerogen carbon isotopes (Δ13Ccarb-kero = δ
13Ccarb − δ
13Ckero) and the difference between carbonate and n-C19 alkane compound-specific carbon isotopes (Δ13Ccarb-n-C19 = δ
13Ccarb − δ
13C
n-C19) during the Permian–Triassic transition at Meishan, South China. The results show that kerogen carbon isotopes underwent
both gradual and sharp shifts in beds 23–25 and 26–29, respectively. The differences between carbonate and organic carbon
isotopes, both the Δ13Ccarb-kero and Δ13Ccarb-n-C19, which are mainly affected by CO2-fixing enzyme and pCO2, oscillated frequently during the Permian–Triassic transition. Both the variations of Δ13Ccarb-n-C19 and Δ13Ccarb-kero coupled with the alternation between cyanobacteria and green sulfur bacteria indicated by biomarkers. The episodic low values
of Δ13Ccarb-n-C19 corresponded to episodic blooms of green sulfur bacteria, while the episodic high values of Δ13Ccarb-n-C19 corresponded to episodic blooms of cyanobacteria. The relationships between the variation of carbon isotopes and biota show
that the microbes which flourished after the extinction of macroorganism affected the carbon isotope fractionation greatly.
Combining the carbon isotope compositions and the pattern of size variation of the conodont Neogondolella, this paper supposes that anoxia of the photic zone at bed 24 was episodic and it would be caused by the degradation of terrigenous
organic matters by sulfate reducing bacteria in the upper water column. Considered together with results from previous research,
the high resolution variation of the biogeochemistry presents the sequence of the important geo-events during the Permian–Triassic
crisis. 相似文献
916.
Mingqun Huo Qian Sun Yuhua Bai Peng Xie Zhaorong Liu Jinlong Li Xuesong Wang Sihua Lu 《Journal of Atmospheric Chemistry》2010,67(1):29-43
Rainwater samples were collected at four sites, including Beijing and Mazhuang Town in the north of China, Shenzhen and Mangdang
Mountain in the south of China. Character of atmospheric particles and gases were also measured at Mazhuang Town and Mangdang
Mountain. Both of Beijing and Shenzhen are urban sites; Mazhuang Town and Mangdang Mountain are rural and remote sites respectively.
The atmospheric pollution at rural plain site in the north of China was more serious than that at remote mountain site in
the south of China. At Beijing, Mazhuang Town, Shenzhen and Mangdang Mountain the average pH values in rainwater were 6.02,
5.97, 4.72 and 4.81, respectively and the concentrations of total ions in rainwater were 1454, 1125, 187 and 191 μeq/l, respectively.
While the acidity of the rain was higher in the south than that in the north, the rainwater in the north of China was more
severely polluted than that in the south. The major acidic ion in the rainwater is SO42-, and NH4+ is the most important neutralizing ion in rainwater at the four sites, followed by Ca2+. The amounts of organic acid in precipitation were compared with other sites in the world. The ratios of organic acid to
total free acid in rainwater at Mangdang Mountain was 13.8% and the influence of organic acid on acidity of rainwater at mountain
site in the south of China is more important. The variation of atmospheric particles, gases and components in rainwater and
cloud-fog water during special rain and cloud-fog events was discussed. The importance of washout process varied with atmospheric
species. The impacts of rainfall, rain duration time and wind speed on wash-out process were estimated by regression analysis. 相似文献
917.
The governing equations for one‐dimensional consolidation of layered structured soils under time‐dependent loading are established. Using simplified k‐σ′ and mv‐σ′ models, n‐layered structured soils are transformed into (n + 1) or (n + 2)‐layered soils in which the thickness of upper and lower layers are gradually changing. The approximate solutions for the governing equations are then obtained under two types of boundary conditions, and the computer program is developed. Based on the solutions and computer program, the consolidation behavior of layered structured soils with soft interlayer is studied. It is shown that the permeability and compressibility of the soft interlayer have the greatest influences on the rate of settlement and rate of the dissipation of excess pore water pressure. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
918.
Fish sonars have long been used to survey and monitor migratory salmon in rivers and at sea. However, research has been lacking in the development of algorithms to extract fish tracks from data collected in a riverine or oceanic environment. Current fish trackers, based on a pulse-to-pulse tracking method, only work well under ideal conditions when targets are well separated and the signal-to-noise ratio is high. Fisheries biologists often have to identify fish traces visually from raw echograms. This approach is both labor-intensive and time-consuming, limiting the usefulness of hydroacoustic techniques for fisheries management. This paper presents a fish-tracking algorithm which sorts randomly distributed echoes into coherent fish traces. Fish counts obtained with the algorithm compare well with visual counts at two quite different sites in the Fraser River watershed. The key features of the algorithm are: (1) the linking mechanisms among sequential fish echoes are range-dependent; (2) the growth echo for a developing track depends not only on its space-time relation with the previous track echo (the pulse-to-pulse statistics) but also on its relation to the entire track being constructed; (3) there are a total of only five echo-association criteria in the algorithm; (4) the simplicity of the algorithm structure provides a convenient platform for implementing specific and sophisticated tracking criteria to meet specific needs; and (5) the user can fully control the performance of the algorithm by choosing values for the 11 well-defined tracking parameters 相似文献
919.
超压释放及其对油气运移和聚集的意义 总被引:22,自引:5,他引:22
从增压作用和减压作用相互关系的角度,探讨了超压释放的定义-超压趋向于静水压力降低的作用,根据超压释放的结果,超压释放可分为不完全释压和完全释压,依突破压力封闭的动力,超压释放可分为主动释压和被动释压。有两类不同的成因的超压释放通道,分别是自振通道和它拓普通,超压释放的主要机制有断裂活动,水力压裂,底辟作用,渗透性岩层输导作用,渗透作用,剥蚀作用和人为作用。超压释放提供了油气运移的现实动力,开拓了油气运移的通道,促进了生烃作用,有利于超压系统内的油气成藏,影响油气的分布。超压释放分析为探讨超压与油气的运聚提供了有效的方法。 相似文献
920.
Anthropogenic lead (Pb) has been found in Antarctic seawater, surface snow and ice-cores. Here, we analyzed a 3,000-year record of lead concentration in lake sediments affected by penguin droppings. We found that lead concentration in penguin droppings has significantly increased during the last 200 years, especially in the last 50 years, as compared to low and stable lead levels prior to the Industrial Revolution. This clearly indicates that global environmental pollution has influenced the Antarctic ecological system. Heavy metal (Pb) may find its way into the food web, bioaccumulate, and be passed along the chain to penguins. 相似文献