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971.
The precise forecasting of water consumption is the basis in water resources planning and management. However, predicting water consumption fluctuations is complicated, given their non-stationary and non-linear characteristics. In this paper, a multiple random forests model, integrated wavelet transform and random forests regression (W-RFR), is proposed for the prediction of daily urban water consumption in southwest of China. Raw time series were first decomposed into low- and high-frequency parts with discrete wavelet transformation (DWT). The random forests regression (RFR) method was then used for prediction using each subseries. In the process, the input and output constructions of the RFR model were proposed for each subseries on the basis of the delay times and the embedding dimension of the attractor reconstruction computed by the C-C method, respectively. The forecasting values of each subseries were summarized as the final results. Four performance criteria, i.e., correlation coefficient (R), mean absolute percentage error (MAPE), normalized root mean square error (NRMSE) and threshold static (TS), were used to evaluate the forecasting capacity of the W-RFR. The results indicated that the W-RFR can capture the basic dynamics of the daily urban water consumption. The forecasted performance of the proposed approach was also compared with those of models, i.e., the RFR and forward feed neural network (FFNN) models. The results indicated that among the models, the precision of the predictions of the proposed model was greater, which is attributed to good feature extractions from the multi-scale perspective and favorable feature learning performance using the decision trees. 相似文献
972.
Abstract In terms of the condition of injection of water after polymer flooding of the Gudao oil field (Shengli, China), the following water quickly broke though the bank to the production wells, while most of residual oil remained in the formation. To solve the problem, two types of petroleum sulfonates made in China were selected to form an oil displacement agent (ODA) solution. The petroleum sulfonate available for crude oil from the Gudao oil field with the ultra-low interfacial tension can be found by drawing an oil/water interfacial tension contour diagram. The results show that the interfacial tension can be lower than 3.6 × 10?4 mN/m when the active agent is contained with 0.25% Kelamayi petroleum sulfonate (KPS) + 0.225% Anqing petroleum sulfonate (APS) and if the agent reduces water resistance by entering the tiny pore to improve sweep coefficient and oil displacement efficiency. The polymer has no influence on the balanced value of interfacial tension but delays the interfacial tension to reach the balance. Pouring 0.3 pore volume (PV) high-efficient ODA into reservoir can improve 17% oil recovery (OR). Synergistic effects of two types of petroleum sulfonate with low cost to enhance OR will have an excellent prospect for enhanced oil recovery (EOR). 相似文献
973.
Xiong Cao Yiping Shang Kejuan Meng Guodong Yue Liyuan Yang Yang Liu 《Journal of Energetic Materials》2013,31(3):356-364
ABSTRACTDesign and fabrication of micro- and nanostructures for energetic materials have attracted more attention recently to improve safety properties and enhance detonation performance. Exploring and developing dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (TKX-50) with unique microstructures, an emerging high-energy-density material with superior comprehensive properties, is of great significance for the potential applications. In this work, we reported that three-dimensional (3D) TKX-50 network-like nanostructures were designed and fabricated successfully via the liquid nitrogen-assisted spray freeze-drying method. Characterization results suggested 3D TKX-50 network-like nanostructures were constructed by self-assembly of small nanoparticles. Furthermore, a nucleation-and-growth self-assembly formation mechanism of the network-like nanostructures depended on the different concentrations of the aqueous solution of TKX-50 was proposed in detail based on the experimental results. More interestingly, thermal analysis results demonstrated these novel 3D TKX-50 network-like nanostructures are much easier to be activated and have a lower decomposition temperature than the raw material, due to decrease in particle sizes, and the impact sensitivity of 3D TKX-50 network-like nanostructures become more sensitive than that of raw TKX-50. Their friction sensitivity of as-prepared samples is similar to the raw materials. Therefore, this work could provide a new prospect for fabrication and application of TKX-50 nanostructures. 相似文献
974.
垂直轴对称横向各向同性(VTI)介质弹性波逆时偏移成像在每一步波场外推过程中都需要对纵、横波进行分离,以获得各自独立的qP波、qSV波成像剖面,因此纵、横波的分离效果决定了最终成像剖面的质量。本文针对纵横波波场分离过程中最为关键的分离算子进行了研究,分析了VTI介质中基于交错网格有限差分法波场外推过程中qP波、qSV波分离算法及波场分离算子的形态特征和影响因素。结果表明,VTI介质波场分离算子的中间部分取决于算子的阶数,两侧部分则体现了VTI介质的各向异性特征。 相似文献
975.
976.
977.
978.
979.
阐述了隔河岩水电厂发电机停机电制动的工作原理,分析了励磁系统改造后灭磁开关运行方式变化,引起电制动投运后退出运行时转子绕组过压的原因,提出了电制动控制优化改进方案,经过试验检验,证明此方案可行。 相似文献
980.