南海北部海域沉积物中生物钡、碳氮同位素的组成特征及其与表层水体初级生产之间的关系     

倪建宇  赵军  江巧文  姚旭莹 《海洋学报》2019,41(2):41-51

通过对采集自南海北部的D06和S0612两个短柱状沉积物样品中的不同赋存形态钡、有机碳和生物硅的含量以及有机质碳氮同位素组成的分析,结果表明沉积物中的钡主要以碎屑钡和自生的生物钡形式存在。沉积物中生物钡的含量在10.3~385.2 μg/g之间,平均值为177.0 μg/g,据此计算的新生产力在12.3~146.7 mg/（d·m2）（以碳计）之间,平均为78.9 mg/（d·m2）;D06站计算的结果和附近站位的实测值相当。沉积物中有机碳的含量在0.64%~1.34%之间,平均值为0.89%,C/N比值为4.96~5.93,平均值为5.54。有机碳的δ13C值在-22.98‰~-20.73‰之间,平均值为-21.46‰,依据端元组份同位素组成计算的陆源有机质比率显示,D06站位的有机质主要来自海洋生物,而S0612站位则受陆源有机质的影响较大。沉积物中有机质的δ15N值在3.96‰~6.29‰之间,平均值为5.26‰,反映的是该海区氮源的同位素组成,而不受硝酸盐利用率的影响。  相似文献   

中国本土主题公园旅游体验质量评价及空间分异特征研究     

肖妮  黄悦  刘继生 《地理科学》2019,39(6):978-986

以旅游网评为大数据样本,构建评价体系,测度中国本土69家主题公园的旅游体验质量,揭示其空间分异特征。结果表明：① 旅游网评为全维度评价提供了数据支撑,语义分析可量化旅游主体、客体和情景体验质量;② 旅游体验质量呈现“两头小、中间大”等级结构特征,旅游主体和客体两维度得分级差分布显著,旅游情景维度波动性最大;③ 不同类型的主题公园的相对优势和相对劣势明显不同;④ 不同等级的主题公园旅游体验质量分化不明显;⑤ 主题公园及其旅游体验质量的空间分布在市域尺度上出现空间错位,空间集聚效益显著。  相似文献   

Possible records of space weathering on Vesta: Case study in a brecciated eucrite Northwest Africa 1109     

Shu‐Zhou Wang  Ai‐Cheng Zhang  Run‐Lian Pang  Yang Li  Jia‐Ni Chen 《Meteoritics & planetary science》2019,54(4):836-849

Records of space weathering are important for understanding the formation and evolution of surface regolith on airless celestial bodies. Current understanding of space weathering processes on asteroids including asteroid‐4 Vesta, the source of the howardite–eucrite–diogenite (HED) meteorites, lags behind what is known for the Moon. In this study, we studied agglutinates, a vesicular glass‐coating lithic clast, and a fine‐grained sulfide replacement texture in the polymict breccia Northwest Africa (NWA) 1109 with electron microscopy. In agglutinates, nanophase grains of FeNi and FeS were observed, whereas npFe⁰ was absent. We suggested that the agglutinates in NWA 1109 formed from fine‐grained surface materials of Vesta during meteorite/micrometeorite bombardment. The fine‐grained sulfide replacement texture (troilite + hedenbergite + silica) should be a result of reaction between S‐rich vapors and pyroxferroite. The unique Fe/Mn values of relict pyroxferroite indicate a different source from normal HED pyroxenes, arguing that the reaction took place on or near the surface of Vesta. The fine‐grained sulfide replacement texture could be a product of nontypical space weathering on airless celestial bodies. We should pay attention to this texture in future returned samples by asteroid exploration missions.  相似文献   

Numerical simulation of time delay interferometry for TAIJI and new LISA     

Gang Wang  Wei-Tou Ni 《天文和天体物理学研究(英文版)》2019,(4):95-108

The success of LISA Pathfinder in demonstrating the LISA drag-free requirement paved the way for using space interferometers to detect low-frequency and middle-frequency gravitational waves(GWs). The TAIJI GW mission and the new LISA GW mission propose using an arm length of 3 Gm(1 Gm = 10~6 km) and an arm length of 2.5 Gm respectively. For a space laser-interferometric GW antenna,due to astrodynamical orbit variation, time delay interferometry(TDI) is needed to achieve nearly equivalent equal-arms for suppressing the laser frequency noise below the level of optical path noise, acceleration noise, etc in order to attain the requisite sensitivity. In this paper, we simulate TDI numerically for the TAIJI mission and the new LISA mission. To do this, we work out a set of 2200-day(6-year) optimized science orbits for each mission starting on 2028 March 22 using the CGC 2.7.1 ephemeris framework. Then we use the numerical method to calculate the residual optical path differences of the first-generation TDI configurations and the selected second-generation TDI configurations. The resulting optical path differences of the second-generation TDI configurations calculated for TAIJI, new LISA and eLISA are well below their respective requirements for laser frequency noise cancelation. However, for the first-generation TDI configurations, the original requirements need to be relaxed by 3 to 30 fold to be satisfied. For TAIJI and the new LISA, about one order of magnitude relaxation would be good and recommended; this could be borne on the laser stability requirement in view of recent progress in laser stability, or the GW detection sensitivities of the second-generation TDIs have to be used in the diagnosis of the observed data instead of the commonly used X, Y and Z TDIs.  相似文献   

结合面向对象和深度特征的高分影像树种分类     

滕文秀  王妮  施慧慧  许振宇 《测绘通报》2019,(4):38-42

针对传统手工提取特征方法需要专业领域知识,提取高质量特征困难的问题,将深度迁移学习技术引入到高分影像树种分类中,提出一种结合面向对象和深度特征的高分影像树种分类方法。为了获取树种的精确边界,该方法首先利用多尺度分割技术分割整幅遥感影像,并选择训练样本作为深度卷积神经网络的输入。为了避免样本数量少导致过拟合问题,采用迁移学习方法,使用ImageNet上训练的VGG16模型参数初始化深度卷积神经网络,并利用全局平局池化压缩参数,在网络最后添加1024个节点的全连接层和7个节点的Softmax分类器,利用反向传播和Adam优化算法训练网络。最后分类整幅遥感影像,生成树种专题地图。以安徽省滁州市的皇甫山国家森林公园为研究区,QuickBird高分影像作为数据源,采用本文方法进行树种分类。试验结果表明,本文方法树种分类总体精度和Kappa系数分别为78.98%和0.685 0,在保证树种精度的同时实现了端到端的树种分类。  相似文献   

多通道卫星云图云检测方法的研究   总被引：3，自引：1，他引：2  

马芳  张强  郭铌  张杰 《大气科学》2007,31(1):119-128

通过对2002年7、8、9三个月,范围为(8.65°N～59.65°N,73.22°E～134.42°E)的GMS-5卫星云图3000多次数字资料的取样,根据遥感原理和样本统计特征,探讨了常用的通道阈值法云检测方法,并尝试建立了红外分裂窗通道差值法和通道综合运算法的云检测方法。通过各种检测方法比较分析后发现:对通道阈值法,只要用红外一和可见光两个通道的阈值,就可得到较好的检测效果,但用这种方法阈值要随着太阳高度角和季节的变化发生相应的变化,虽阈值变化的幅度不大,却会对云检测工作带来很大的不便。此外,该方法云检测的结果存在地理位置的影响,即检测出的云量在中低纬度偏多而较高纬度偏少。作者建立的通道综合运算云检测方法,不仅改善了地理位置的变化对云检测带来的影响,而且通过红外分裂窗通道差值检测,可减弱太阳高度角的影响,减少了检测过程中阈值变化的繁琐,同时得到了更好的检测效果,检测结果与其可见光图像中的云区相比基本符合。  相似文献   

Chaos in a Bose-Einstein condensate     

王志霞  倪政国  从福仲  刘学深  陈蕾 《海洋学报(英文版)》2010,29(11)

It is demonstrated that Smale-horseshoe chaos exists in the time evolution of the one-dimensional Bose--Einstein condensate driven by time-periodic harmonic or inverted-harmonic potential. A formally exact solution of the time-dependent Gross-Pitaevskii equation is constructed, which describes the matter shock waves with chaotic or periodic amplitudes and phases.  相似文献   

On predicting boat drift for search and rescue   总被引：1，自引：0，他引：1  

Zao Ni  Zhiping Qiu 《Ocean Engineering》2010,37(13):1169-1179

A theoretical model for predicting boat drift for search and rescue missions is presented in this work. The drift model is based on the law of physics which govern the motion of a floating body in a given wind and surface current field. In terms of the empirical aerodynamics force coefficients of the boat or any other drifting object, external wind field, and current field, the drift velocity of the boat being searched for can be obtained. The uncertainty of the characteristics of the boat’s drift is evaluated by interval analysis of the uncertainties of the characteristics of the drifting boat and external forcing fields. The search area expansion and the source of uncertainty are systematically evaluated. The current statistical model-based operational definitions of leeway drift, leeway rate, leeway angle, divergence angle, leeway divergence, downwind component of leeway, and crosswind component of leeway are clarified in light of the presented theoretical model. The divergence angle and leeway divergence are evaluated through the interval analysis of the uncertainty of the parameters involved.  相似文献   

长白山天池火山全新世3期浮岩长石斑晶中熔体包裹体高温热台实验研究   总被引：1，自引：0，他引：1  

李霓  Nicole Métrich  樊祺诚 《地震地质》2007,29(3):459-469

长白山天池火山在全新世曾多次喷发,以往研究结果基本上认定至少有3期喷发物:距今约5,000a前淡黄色碱流质浮岩、距今约1,000a前灰白色碱流质浮岩和碎屑流以及距今约300a的黑色粗面质浮岩和熔结凝灰岩。喷发物斑晶矿物中含有众多熔体包裹体,形貌特征各有不同。经Leitz1350高温热台对天池火山全新世3期喷发物长石中熔体包裹体的均一法测温实验,结果表明第1,3喷发期的岩浆温度相差不大,而千年大喷发期较为复杂,揭示当时有2个不同温度段的熔体存在,为大喷发可能由2种岩浆注入和混合而触发的论点提供了线索。实验还证实,个体小的熔体包裹体易于均一,而个体较大的、尤其是含有大量子晶的熔体包裹体则很难均一;均一温度与熔体包裹体大小、何时从较快升温速率变为较慢升温速率、是否为初次升温时测量得出有关。同一颗熔体包裹体多次数升温至均一,每次得到的均一温度不同,而且每升温一次得到的均一温度均比前一次高,证实了均一过程中的确有H扩散的现象  相似文献   

泥质变质岩系主要的矿物温度计与压力计   总被引：6，自引：0，他引：6  

吴春明  肖玲玲  倪善芹 《地学前缘》2007,14(1):144-150

简要介绍泥质变质岩中常用的温度计和压力计,对其可适用性、适用范围、质量优劣等进行了评述。经过对这些温度计和压力计的比较研究,我们发现石榴石-黑云母温度计、石榴石-白云母温度计、石榴石-蓝晶石(夕线石、红柱石)-斜长石-石英(GASP)压力计、石榴石-黑云母-斜长石-石英(GBPQ)压力计、石榴石-白云母-斜长石-石英(GMPQ)压力计、石榴石-黑云母-白云母-蓝晶石(夕线石、红柱石)-石英(GBMAQ)压力计、石榴石-金红石-钛铁矿-斜长石-石英(GRIPS)压力计的准确度较高,可以为地质工作者所采用。二云母温度计、白云母-斜长石温度计准确度还有待大幅度改进。石榴石-金红石-蓝晶石(夕线石、红柱石)-钛铁矿-石英(GRAIL)压力计、石榴石-堇青石温度计和石榴石-堇青石-蓝晶石(夕线石、红柱石)-石英(GCAQ)压力计等温压计的准确度及其可适用性,还有待于进一步研究。  相似文献