When using HBase to store tiles of remote sensing images, the spatial position of a tile is often used as the first part of the tile's rowkey so that tiles with high spatial correlations are stored close together to improve query efficiency. We refer to this storage method as the Geo-First model. However, Geo-First models have two problems: the load between nodes is unbalanced, and the accumulation of time-series remote sensing images has a negative impact on storage and query efficiency. Considering these two problems, we proposed a method for storing remote sensing images based on Google S2 and HBase. In our method, two strategies are adopted to eliminate these problems: the balanced placement strategy (BPS) and the periodic storage strategy (PSS). We evaluated our method by focusing on the effectiveness of BPS and PSS. The results show that our method achieves higher tile storage and query efficiency than three Geo-First models based on latitude and longitude, Geohash code, and Google S2 code. BPS effectively balances the load between nodes, while PSS alleviates the negative impact of the accumulation of time-series remote sensing images. Both BPS and PSS greatly improve tile storage and query efficiency.INDEX TERMS HBase, remote sensing images, Google S2, load balancing, tile storage mode.

The study is conducted for the 3-D seepage field analysis and the seepage control measurements optimization of a hydropower project, which is located in Sichuan Province, China. The seepage control measurements are introduced in this paper. An equivalent method is adopted to simulate drainage holes and the approach of determining equivalent permeability coefficient is presented. The 3-D seepage field with seepage control system is analyzed comprehensively by the water head contours, uplift on the dam foundation, and so on. The necessities of setting the grouting curtain and the drainage holes are discussed respectively. Further the optimal design of the grouting curting and drainage holes of the dam foundation is studied. The results show that special attention should be paid to ensure the well-operation of the seepage control system and the optimization of decreasing the depth of the drainage curtains and grouting curtains properly can be considered.

An equivalent method that simulate drainage holes is adopted in the analysis of 3-D seepage field. The Initial Flow Method is applied in this paper to deal with the unconfined seepage problem. In this paper, the finite element model of a gravity dam project is established and the seepage field is analyzed.

According to the research of vertical migration and occurrence of Cd and As in acid paddy soil, the conclusions are as follows. The longitudinal migration of Cd in TZkb1, TZ1, TZ2, TZ3 and TZ5 found that Cd in the upper and lower layers of soil columns all lost to varying degrees with the increase of water injection contents (irrigation years). With the longitudinal leaching of irrigation water, when the adsorption capacity of the soil was greater than the water injection and rinsing capacity, the trend of accumulation (TZ4-TZ6) further appeared. The vertical migration results of As in TZkb1, TZ1, TZ2, TZ3 and TZ5 found that As mainly accumulated in the upper layer of soil columns. Without considering other output ways, it can be seen that the binding ability of As to acid paddy soil was stronger than Cd, and its cumulative efficiency in 20 years was higher than Cd. However Cd cumulative efficiency of TZ3 and TZ5 in acid paddy soil may be greater than As with time. In general, As was less affected by irrigation water on vertical leaching of soil columns compared with Cd.