云迹风反演中高密度示踪云选取技术的研究     

杨文凯  白洁  严卫  刘健文 《气象》2007,33(4):35-39

云迹风反演中的一项很重要的工作是选取随风移动、变化缓慢的云，即示踪云。文中设计了一种示踪云选取算法，以改善云迹风的质量和密度分布。该算法的特色是反演风的位置并不固定在反演网格的中心位置，而是通过梯度分析的方法使反演风的位置得到优化，再经过积雨云检测和灰度分布均匀程度检验，剔除不适合用来反演的目标物。对用该方法选取的示踪云进行云迹风反演，然后对反演出的云迹风进行环流分析，并与探空风进行比较。结果表明，反演出的云迹风质量好，密度很高，清晰地反映出天气系统的风场结构。  相似文献   

Segregation and Residential Mobility of Vietnamese Immigrants in Brisbane,Australia     

Sonya M. Glavac  Brigitte Waldorf 《The Professional geographer》1998,50(3):344-357

The study focuses on residential mobility propensities of Vietnamese immigrants in the city of Brisbane, Australia, as a principal force contributing to the persistence or change of ethnic residential segregation over time. Using 1990 survey data, discrete-time logit models are estimated to assess the effects of locational, contextual, and personal characteristics on the likelihood of changing residence within the city. The results indicate that locational variables operate in such a way that the most dominant Vietnamese neighborhood in Brisbane increases its prominence even further, while secondary Vietnamese clusters are likely to weaken. The results also indicate that initial settlement conditions are important for the first move only, whereas personal attributes contribute to variations in mobility propensities primarily in the second move. This implies that the composition of the immigrant population potentially influences the speed at which changes in ethnic residential patterns will occur in urban areas.  相似文献   

A comparison of estimated and calculated effective porosity   总被引：1，自引：1，他引：0  

Daniel B. Stephens  Kuo-Chin Hsu  Mark A. Prieksat  Mark D. Ankeny  Neil Blandford  Tracy L. Roth  James A. Kelsey  Julia R. Whitworth 《Hydrogeology Journal》1998,6(1):156-165

 Effective porosity in solute-transport analyses is usually estimated rather than calculated from tracer tests in the field or laboratory. Calculated values of effective porosity in the laboratory on three different textured samples were compared to estimates derived from particle-size distributions and soil–water characteristic curves. The agreement was poor and it seems that no clear relationships exist between effective porosity calculated from laboratory tracer tests and effective porosity estimated from particle-size distributions and soil–water characteristic curves. A field tracer test in a sand-and-gravel aquifer produced a calculated effective porosity of approximately 0.17. By comparison, estimates of effective porosity from textural data, moisture retention, and published values were approximately 50–90% greater than the field calibrated value. Thus, estimation of effective porosity for chemical transport is highly dependent on the chosen transport model and is best obtained by laboratory or field tracer tests. Received, March 1997 · Revised, August 1997 · Accepted, August 1997  相似文献   

Biostratigraphy and depositional facies of the Cretaceous-Tertiary boundary strata in Amakusa-Shimojima,Kyushu, Western Japan     

M. Tashiro  A. Taira  T. Matsumoto 《Cretaceous Research》1980,1(1):13-26

The Upper Himenoura Subgroup exposed in the island of Amakusa-Shimojima, Kyushu, Japan shows an example of the terminal Cretaceous stratigraphic record in the circum Pacific region. This sequence is a part of the Upper Cretaceous intra-arc basins of southwest Japan. Four cycles of upward coarse-graded facies are recognized. Each cycle consists of a basinal mud facies in the lower part and a tide-dominated shallow marine to brackish coarse clastic facies in the upper part. Biostratigraphic correlation chiefly based on ammonites, inocerami and trigoniids indicates that this sequence is Campanian to Maastrichtian in age. The occurrence of the above three fossils decreases upward and is terminated at the top of the sequence, being replaced by a molluscan assemblage similar to the Danian. This suggests that the sedimentation may have continued to the very end of the Cretaceous period and possibly to the beginning of the Tertiary.  相似文献   

A discrete particle representation of hillslope hydrology: hypothesis testing in reproducing a tracer experiment at Gårdsjön,Sweden     

Jessica Davies  Keith Beven  Lars Nyberg  Allan Rodhe 《水文研究》2011,25(23):3602-3612

Despite the long history of the continuum equation approach in hydrology, it is not a necessary approach to the formulation of a physically based representation of hillslope hydrology. The Multiple Interacting Pathways (MIPs) model is a discrete realization that allows hillslope response and transport to be simultaneously explored in a way that reflects the potential occurrence of preferential flows and lengths of pathways. The MIPs model uses random particle tracking methods to represent the flow of water within the subsurface alongside velocity distributions that acknowledge preferential flows and transition probability matrices, which control flow pathways. An initial realization of this model is presented here in application to a tracer experiment carried out in Gårdsjön, Sweden. The model is used as an exploratory tool, testing several hypotheses in relation to this experiment. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

南京市降水化学特征及其来源研究   总被引：4，自引：0，他引：4       下载免费PDF全文

张泽锋  沈利娟  朱彬  岳江  王红磊  张秋晨 《大气科学学报》2015,38(4):473-482

为了解南京江北地区降水化学特征,分析了2011年3—6月共25个降水日的109个降水样品中的主要水溶性离子,并利用后向轨迹模式探讨了降水气团来源.结果表明:1)南京地区3—6月降水主要受南、北2种气团影响,北方气团降水的主要离子浓度高于南方气团降水.2)海盐示踪法和相关性分析显示,降水中NO₃^-和SO₄^2-主要来自燃煤、工业排放和汽车尾气;Ca²⁺主要来自地壳源;Cl^-主要来自海洋;海洋源和陆源对Mg²⁺和K⁺都有贡献,Mg²⁺的陆源贡献大于海洋源贡献,K⁺受海洋源的影响程度要低于Mg²⁺.3)南、北气团初期降水的各离子浓度高于总降水的各离子浓度,且初期降水的主要离子的富集系数高于总降水.这说明在降水初始阶段,雨水对南京大气中污染物(气态污染物和颗粒物)的云下冲刷去除作用较强,降水的离子浓度最高,局地源对降水离子的贡献较明显.  相似文献   

Quantitative assessment of dissolved radiotracers in the English Channel: Sources, average impact of la Hague reprocessing plant and conservative behaviour (1983, 1986, 1988, 1994)     

P. Bailly du Bois  P. Guguniat 《Continental Shelf Research》1999,19(15-16)

Knowledge of long-term movements of water-masses in the English Channel has been substantially improved using hydrodynamic modelling coupled with radio-tracers studies; nevertheless, the precision of results so obtained is still largely dependent on measurement precision. New tools are now available to make more accurate determinations of radio-tracer distribution: (1) Repositioning of station locations at the same tide reference-time, giving a homogeneous spatial data set, coupled with the possibility of interpolating and quantifying the amounts of dissolved radioactivity flowing through the English Channel; (2) the first measurements of tritium (³H) in seawater on a large scale in the English Channel demonstrate that this fully conservative radionuclide is a clearly identifiable marker of industrial releases; (3) recent campaigns carried out during the FLUXMANCHE II CCE (1994) programme show the general distribution of dissolved radionuclides ¹³⁷Cs, ¹³⁴Cs, ⁶⁰Co, ¹²⁵Sb, ¹⁰⁶Ru and ³H in the English Channel and the Irish Sea; and (4) the re-utilisation of data from previous campaigns (1983, 1986, 1988) provides indications, at any given location in the English Channel, about the average dilution and distribution of releases derived from the La Hague reprocessing plant. Excesses and losses of radionuclides are now quantified with respect to known source terms; estimates of losses are provided for non-conservative radionuclides, while an excess of ¹³⁷Cs was observed in the English Channel during the period 1983–1994. This excess, which has the same order of magnitude as the quantities released from La Hague plant in the English Channel, could be explained by about 1% of the Sellafield reprocessing plant releases entering the Channel. These results confirm and give a more detailed picture of the previously known distribution of water masses in the English Channel. They lead to clear information about transit times and dilution at this scale, and provide directly comparable data for the validation of hydrodynamic models.  相似文献   

大陆深部地壳物质成分识别方法综述     

侯青叶  张本仁  赵志丹  路凤香  刘东盛  曹铁宁 《地质学报》2010,84(6):865-872

本文系统总结了大陆深部地壳物质成分识别研究方法和元素丰度合理性检验的方法,以期为大陆深部地壳物质成分探测提供技术方法体系。深部地壳物质成分识别的主要方法有:①因构造运动抬升出露到地表的中下地壳剖面;②地表出露的高级变质地体;③产于火山岩中的深部地壳捕掳体,如麻粒岩捕掳体;④地球物理测深资料与深部岩石物理性质的高温高压实验测定结果之间的拟合和⑤壳源岩浆岩源区地球化学示踪。元素丰度合理性检验的方法主要有地表热流和元素比值法。  相似文献   

时间矩在地下水相关参数确定中的应用     

李亮  陈余道  蒋亚萍 《地下水》2010,32(3):9-11

应用矩分析方法定量分析示踪剂数据需要一系列严格的步骤,包括数据标准化,浓度衰减的校正,去卷积,外推和积分。正确的分析,可以得出示踪剂扫描孔隙体积、流体几何和流体速度等场地的特殊信息,有助于了解库区边界的特征。通过实例分析,结果表明：采用时间矩方法确定地下水有关参数时,效果良好。  相似文献   

三种扇贝挥发性风味物质指纹图谱分析     

崔明仙  李妍  付睛睛  景福涛  陈希盼  张恩烁  李赞  徐晓辉  冯艳微  孙国华  李彬  王卫军  杨建敏 《海洋与湖沼》2022,53(3):743-758

为探究海湾扇贝(Argopecten irradians)、栉孔扇贝(Chlamys farreri)、虾夷扇贝(Patinopecten yessoensis)三种扇贝闭壳肌的挥发性风味物质差异,采用气相色谱-离子迁移谱(gas chromatography-ion mobility spectroscopy,GC-IMS)技术,对三种扇贝闭壳肌在新鲜(40℃)和加热(100℃)情况下进行挥发性成分分析。结果表明:在新鲜状态下,海湾扇贝(HWSB-F)、栉孔扇贝(ZKSB-F)、虾夷扇贝(XYSB-F)闭壳肌中,共定性出27种挥发性风味物质,其中醛类8种,醇类5种,酮类5种,酯类3种,以及醚类、苯类、酸类、烯类和噻唑等。在加热情况下,海湾扇贝(HWSB-C)、栉孔扇贝(ZKSB-C)、虾夷扇贝(XYSB-C)闭壳肌中共定性出52种挥发性风味物质,其中醛类20种,酯类5种,酮类7种,醇类8种,烯类4种,酸类2种,醚类2种,还包括吡嗪、胺类、苯类、含氧杂环等物质。对三种扇贝闭壳肌新鲜组和加热组指纹图谱进行分析,发现新鲜扇贝原有的挥发性风味物质加热后减少,且产生了新的其他种类的挥发性风味物质。扇贝闭壳肌加热组的挥发性风味物质种类较多,组成比较复杂,新鲜组的扇贝闭壳肌挥发性风味物质种类较少,组成简单。通过主成分分析,可在新鲜状态和加热状态下,有效区分三种扇贝闭壳肌组织。三种扇贝闭壳肌挥发性风味物质指纹图谱的建立,丰富了不同扇贝呈味物质的组成成分研究内容,证明GC-IMS技术可快速鉴别三种去壳扇贝闭壳肌的种类,为不同种扇贝闭壳肌以次充好提供检测依据。  相似文献