Hydrological time series forecasting remains a difficult task due to its complicated nonlinear, non-stationary and multi-scale characteristics. To solve this difficulty and improve the prediction accuracy, a novel four-stage hybrid model is proposed for hydrological time series forecasting based on the principle of ‘denoising, decomposition and ensemble’. The proposed model has four stages, i.e., denoising, decomposition, components prediction and ensemble. In the denoising stage, the empirical mode decomposition (EMD) method is utilized to reduce the noises in the hydrological time series. Then, an improved method of EMD, the ensemble empirical mode decomposition (EEMD), is applied to decompose the denoised series into a number of intrinsic mode function (IMF) components and one residual component. Next, the radial basis function neural network (RBFNN) is adopted to predict the trend of all of the components obtained in the decomposition stage. In the final ensemble prediction stage, the forecasting results of all of the IMF and residual components obtained in the third stage are combined to generate the final prediction results, using a linear neural network (LNN) model. For illustration and verification, six hydrological cases with different characteristics are used to test the effectiveness of the proposed model. The proposed hybrid model performs better than conventional single models, the hybrid models without denoising or decomposition and the hybrid models based on other methods, such as the wavelet analysis (WA)-based hybrid models. In addition, the denoising and decomposition strategies decrease the complexity of the series and reduce the difficulties of the forecasting. With its effective denoising and accurate decomposition ability, high prediction precision and wide applicability, the new model is very promising for complex time series forecasting. This new forecast model is an extension of nonlinear prediction models.

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The development of advanced photoelectrode materials for water splitting is as important as recycling to solve environmental problems. In this Communication, we report a facile hydrothermal epitaxial growth of hematite films from ferrioxalate solution, where the pH, isoelectric point and crystal nature of the substrates play key roles in the film growth. In a photoelectrochemical cell, the hematite photoanodes showed high activity to oxidize water, oxalate or phenol molecules, resulting in hydrogen generation on the counter electrode. This work shines a new light in the direction of environmental waste recycling.There are two highly important unsolved issues for modern society to develop a sustainable energy infrastructure and to reduce humanity's footprint on the environment.[1] One is sustainable energy conversion from environmentally benign sources, such as the generation of biofuels from waste biomass, [2] and the generation of hydrogen from electrocatalytic, [3] photoelectrochemical (PEC) or photocatalytic water splitting.[4] The other issue is reducing the environmental burden, such as CO 2 gas emission and industrial waste solids or liquids.[5] The most promising strategy may be combing energy conversion/storage with waste remediation in an integrated device/process. For example, solar cells, photocatalytic cells or PEC cells [4b] can be applied to convert solar energy to electric energy or generate chemical energy from water. To significantly increase the solar conversion efficiency, narrower bandgap semiconductors made of earth-abundant materials, such as hematite (aFe 2 O 3 ), [6] BiVO 4 , WO 3 , doped TiO 2 , [7] Si and their nanostructures are in high demand. [4b, 8] A conformal semiconductor layer on a highly conductive substrate deposited by an epitaxial-like growth method is one of the most promising structures. [9] Compared with atomic layer deposition (ALD) for epitaxial growth, hydrothermal deposition [10] has many advantages, such as a low fabrication cost and easy scale-up. However, the achievement of high-quality epitaxial-like films is very challenging. Although there are several reviews on hydrothermal deposition, [11] the mechanistic study of solution epitaxial deposition for hematite films is still of great interest.Several hydrothermal methods have been employed to prepare iron oxide or ferric oxyhydroxide films. In the early 1990s, an a-Fe 2 O 3 film with (101) orientation on Si was deposited from iron nitrate and urea.[12] Recently, a similar hydrothermal deposition of hematite nanoflakes on fluorine-doped tin oxide (FTO) was reported by using of FeCl 3 and urea.[13] But most other reports for hematite films relied on akaganeite (bFeOOH) films as precursor, which converted to a-Fe 2 O 3 at a temperature over 290-310 8C.[14] For instance, Vayssieres et al. demonstrated hydrothermal growth of b-FeOOH nanorods arrays from a solution containing 0.15 m FeCl 3 and 1 m NaNO 3 at 100 8C.[15] Later, Ling et al. applied a similar method to prepare b-FeOOH nanowire arrays, wh...

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