Particle Shapes in the Drinking Water Filtration Process     

Michał Zielina 《洁净——土壤、空气、水》2011,39(11):941-946

Depth filtration is still one of the most important water treatment processes. It remains difficult to model mathematically because of the complexity of the process and the impact of numerous suspension parameters. The shape of the grains and suspension particles or flocs are among these parameters. The results of theoretical calculations suggest their visible impact on filtration. The shape of the media grain is relatively easy to measure. The shapes of the flocs or suspension particles, which are commonly not perfectly spherical, are much more difficult to predict. However, a few apparatuses developed lasting recent years make this possible. The FPIA 3000, manufactured by Malvern Instruments, uses flow particle image analysis method to measure 26 shape parameters of the suspension particles. Experimental measurement of suspension particle shape after flocculation and after depth filtration has allowed us to answer the question regarding the possible application of this measuring technique in water filtration technology. The experiments have also provided us with detailed information about the shape of flocs and suspension particles in filtered water. High number of particles characterized by circularity lower than 0.8 was detected in flocculated water inflowing to the filter. The particles remained in the outflow was characterized by visibly higher circularity than the particles inflowing to the filter. The results revealed much better removal of the particles characterized by lower circularity during filtration, whereas relation between convexity of the particles and their removal efficiency was not so evident.  相似文献   

台风“巨爵”近海急剧加强的特征及成因分析     

邓文剑  ;吴振鹏  ;吴乃庚  ;林良勋 《广东气象》2014,(3):9-14

源自东风波动的0915号台风"巨爵"在自东向西靠近广东沿海时出现了近海急剧加强的异常现象。利用热带气旋定位资料、NCEP全球同化分析资料、卫星云图以及海上平台自动站探测资料等对"巨爵"近海加强特征和成因进行了诊断分析。结果表明:"巨爵"形成源自于西太副高南侧的东风波动,副高演变及引起的"北高南低"和"东高西低"的形势与"巨爵"环流增强发展密切相关;弱的垂直风切变、高空明显的辐散出流以及台风中心正涡度增大并向对流层中上层拓展有利于"巨爵"强度增强;低层弱冷空气南下,一方面从增加气压梯度和温度梯度来加强台风环流和暖心结构,另一方面通过触发外围对流云团发展并往台风中心输送进而对"巨爵"近海加强产生重要的触发作用;孟加拉湾西南季风气流、105°~110°E附近越赤道气流和西太副高西侧东南气流3支气流汇合为"巨爵"近海加强提供了充沛水汽条件。  相似文献   

国家1：50000地形数据库重点要素动态更新     

刘建军  赵仁亮  张元杰  李雪梅  刘建炜 《测绘软科学研究》2014,(1):37-40

国家1：50 000地形数据库是国家基础地理信息数据库的主要内容之一,是用途最广、使用频率最多的基础测绘成果,保持其现势性是我国基础测绘工作的重要使命。2012年国家测绘地理信息局组织实施了对该数据库的快速动态更新,实现了每年更新一次,每年发布新版。本文主要总结介绍了全国1：50 000地形数据库动态更新项目取得的主要创新和数据成果。  相似文献   

Evaluation of data fusion and image segmentation in earth observation based rapid mapping workflows     

《ISPRS Journal of Photogrammetry and Remote Sensing》2014

This paper is an exploratory study, which aimed to discover the synergies of data fusion and image segmentation in the context of EO-based rapid mapping workflows. Our approach pillared on the geographic object-based image analysis (GEOBIA) focusing on multiscale, internally-displaced persons’ (IDP) camp information extraction from very high spatial resolution (VHSR) images. We applied twelve pansharpening algorithms to two subsets of a GeoEye-1 image scene that was taken over a former war-induced ephemeral settlement in Sri Lanka. A multidimensional assessment was employed to benchmark pansharpening algorithms with respect to their spectral and spatial fidelity. The multiresolution segmentation (MRS) algorithm of the eCognition Developer software served as the key algorithm in the segmentation process. The first study site was used for comparing segmentation results produced from the twelve fused products at a series of scale, shape, and compactness settings of the MRS algorithm. The segmentation quality and optimum parameter settings of the MRS algorithm were estimated by using empirical discrepancy measures. Non-parametric statistical tests were used to compare the quality of image object candidates, which were derived from the twelve pansharpened products. A wall-to-wall classification was performed based on a support vector machine (SVM) classifier to classify image objects candidates of the fused images. The second site simulated a more realistic crisis information extraction scenario where the domain expertise is crucial in segmentation and classification. We compared segmentation and classification results of the original images (non-fused) and twelve fused images to understand the efficacy of data fusion. We have shown that the GEOBIA has the ability to create meaningful image objects during the segmentation process by compensating the fused image’s spectral distortions with the high-frequency information content that has been injected during fusion. Our findings further questioned the necessity of the data fusion step in rapid mapping context. Bypassing time-intensive data fusion helps to actuate EO-based rapid mapping workflows. We, however, emphasize the fact that data fusion is not limited to VHSR image data but expands over many different combinations of multi-date, multi-sensor EO-data. Thus, further research is needed to understand the synergies of data fusion and image segmentation with respect to multi-date, multi-sensor fusion scenarios and extrapolate our findings to other remote sensing application domains beyond EO-based crisis information retrieval.  相似文献   

Fallow,labour and livelihood in shifting cultivation: implications for deforestation in northern Lao PDR     

Charlotte Seidenberg  Ole Mertz  Morten Bilde Kias 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(2):71-80

Shifting cultivation is often blamed for deforestation in tropical upland areas. Based on a case study of three villages in northern Lao PDR, this paper combines household surveys with a remote sensing based analysis of forest cover, covering the period 1989–1999, in order to analyse changes in shifting cultivation practices and livelihood strategies and the impact of these on deforestation. Due to population pressure and relocation of villages, easily accessed land is increasingly scarce and fallow periods have been shortened during the 1990s. A net annual deforestation of about 1% was found in the area during the study period. This deforestation rate reflects shorter fallow periods in secondary forests rather than encroachment on mature forests, which are not used for cultivation by the farmers in the three villages. Farmers rate scarce labour as a major constraint on shifting cultivation; nonetheless, a tendency towards lower labour input with shorter fallow periods is observed, contradicting conventional intensification theory. Livelihoods are diversifying through the establishment of plantations, cultivation of wet rice and adoption of animal husbandry, but given the socio-economic conditions in the area, shifting cultivation is likely to remain the most suitable farming system in the near future.  相似文献   

Effects of land-use changes on structural characteristics of tropical high-altitude Andean headwater streams     

《Limnologica》2019

Streams are usually susceptible to land-use change, mainly in the tropics due to high dynamic climatic conditions. Native forests have been converted for agricultural purposes with significantly impacts in streams. Nowadays, forests plantations are taking place of some degraded land and its influence in headwater streams are not well understood in tropical high-altitude streams. Thus, this study aims to assess effects of land-use changes from pasture to Eucalyptus plantations in Colombian Andean catchments on stream water conditions and structural characteristics of stream channels. The study was conducted in three catchments, one catchment covered by pasture, one catchment that was converted from pasture to Eucalyptus plantations in 1995 and one pristine catchment with native forest cover. Physical, chemical and biological conditions of stream water were assessed by measurements of water temperature, concentration of dissolved oxygen and chlorophyll-a content of epiphytic communities. The structural characteristics of stream channels were evaluated using a visual-based habitat assessment protocol from the United States Environmental Protection Agency. Principal Component Analysis (PCA) showed native forest and Eucalyptus plantations catchments associated with stream conservation characteristics and pasture catchment with overall degraded conditions. However, the Permutational multivariate analysis of variance (PERMANOVA) showed significant differences between all streams indicating that, despite the overall positive conservation aspects of native and Eucalyptus catchments, their still different from each other. Pasture catchment showed the highest values for temperature and chlorophyll-a, and the lowest values for dissolved oxygen and final score for structural characteristics. Therefore, our results demonstrated that the land-use change from pasture to Eucalyptus plantation improved the stream water conditions and the structural characteristics of the studied headwater streams. Additionally, we propose the use of the rapid bioassessment protocol coupled some stream water characteristics as a rapid and useful tool for detecting effects of land-use changes on high-altitude Andean streams.  相似文献   

浅析野外金的快速分析方法   总被引：1，自引：0，他引：1  

高翠芬 《山东国土资源》2010,26(10)

该文选择野外快速测金的2种方法:氢醌容量法和目视比色法,从原理、试样分析、富集方法、吸附机理、解脱方式、试剂及分析手续几方面进行对比分析,着重对氢醌容量法作研究和完善工作。针对通过比对实验,确立分析测试条件,选择确定了快速、简便、经济的测试流程,并应用于样品测试,提高了检测速度。  相似文献   

广州市中山大道BRT主干道的联动分析     

李文翎  周俊滔  黄竞  吕拉昌 《热带地理》2010,30(2)

为探索BRT方案在高密度开发地区实施的可行性及其运行效益,采用实地调查与案例分析的方法,以广州中山大道BRT干道的设计为例,结合中山大道现有交通组织特点,指出BRT建设可能对其交叉路口交通组织、周边线路的联动和车辆过量占道等方面造成影响,认为实现"人地车"的协调才是城市交通规划的关键;提出促成交叉口BRT优先通行技术和ITS(智能交通系统)技术的应用、进一步优化运营模式、适当限制私人交通、合理规划公交地铁的驳接和大力发展快速公交并构建快速公交网络系统等措施。  相似文献   

准噶尔盆地南缘异常高压及其成因机制初探   总被引：12，自引：6，他引：6       下载免费PDF全文

李铁军 《地质科学》2004,39(2):234-244

实测地层压力、测井及泥浆比重等资料均显示准噶尔盆地南缘具有显著的异常高压现象,异常高压的分布主要受地层层位的控制,其中又以下第三系安集海河组的控制作用最为明显。异常高压的形成主要是快速沉积、厚层泥岩的封闭作用及构造应力等因素综合作用的结果,而粘土矿物转化、烃类生成作用的影响则相对较小。  相似文献   

天津市面向震害快速评估的房屋和人口空间化研究^*   总被引：1，自引：0，他引：1  

谷国梁  王晓蕾  李雅静  安立强  赵士达 《地震》2016,36(2):149-158

以天津市的大比例尺房屋空间数据和第六次人口普查数据为基础,利用GIS空间分析功能,模拟了天津市房屋和人口空间分布,产出1km格网的房屋数据和分时段人口公里格网数据。经检验,模拟的房屋和人口数据达到了较高精度,能够较准确地表达行政单元内部的房屋和人口空间分布。将模拟结果应用到设定地震震害评估中,与基于平均密度法的评估结果对比,表明基于公里格网评估的结果更为合理,减少了由于房屋和人口分布不均匀造成的误差,能够为地震应急工作提供可靠的数据支撑。  相似文献