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Wind power is a clean and renewable energy, yet it poses integration challenges to the grid due to its variable nature. Thus, Wind Power Forecasting (WPF) is crucial for its successful integration. However, existing WPF datasets often cover only a limited number of turbines and lack detailed information. To bridge this gap and advance WPF research, we introduce the Spatial Dynamic Wind Power Forecasting dataset (SDWPF). The SDWPF dataset not only provides information on power generation and wind speed but also details the spatial distribution of the wind turbines and dynamic contextual factors specific to each turbine. These factors include weather information and the internal status of each wind turbine, thereby enriching the dataset and improving its applicability for predictive analysis. Further leveraging the potential of SDWPF, we initiated the ACM KDD Cup 2022, a competition distinguished as the foremost annual event in data mining, renowned for presenting cutting-edge challenges and attracting top talent from academia and industry. Our event successfully draws registrations from over 2400 teams around the globe.

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In order to improve the consumption of renewable energies, certain amounts of circulating fluidized bed (CFB) boiler units should assume the task of deep peak regulation. However, the effect of CFB boiler load on pollutant emissions such as NOx still needs to be clarified. In this paper, the NOx emission characteristics of two industrial-scale CFB boilers within a wide load range (35%-100%) were further analyzed by using a comprehensive one-dimensional, two-phase CFB mathematical model. Simulation results reveal that, when the load ratio decreases, the NOx emission decreases first and then increases. The non-monotonic variation trend is also confirmed by the operational data collected from the SC-350 boiler. However, for different boilers, the load ratio corresponding to the turning point of NOx emission may be different, e.g., for the 135 MWe super high steam pressure boiler, it is about 40%, while for the 350 MWe supercritical boiler is 50%. On the one hand, the decrease in boiler load leads to a decline in the furnace temperature, which contributes to reducing NOx emission due to the decrease of volatile yields, the lower conversion rate of Vol-N to NOx, and the enhancement of the overall NO reduction on chars. On the other hand, at low loads, the excess air coefficient is generally set to high values, and air staging is weakened, resulting in adverse effects on the NOx emission control. In addition, when the CFB boiler operates at low loads, the solid circulation loop performance usually worsens, and the heat loss caused by incomplete combustion may increase. This study points out that high NOx emission is an unavoidable issue in the process of deep peak regulation for CFB boilers.

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Electrowetting (EW) is an effective method for droplet manipulation in microfluidics. In traditional EW, a conductive droplet is actuated, which spreads on a solid substrate. Recently, we considered an opposite phenomenon of droplet actuation in EW: inducing nonconductive droplet dewetting and detaching from the substrate. An oil/water system is used in which the oil droplet (nonconductive) is actuated on a flat substrate in surrounding water (conductive) by EW. In this work, alternating current (AC) electric fields are applied to EW, and the transient dynamics of droplet dewetting, oscillation, and detachment with the AC signals are investigated. The droplet is not in contact with electrodes, and it dances freely on the substrate. Experiments are performed in a wide range of voltages and AC frequencies. To demonstrate the droplet dynamics, we divide the full process of droplet manipulation into three distinguishable periods, that is, an initiating period, a steady oscillation period, and a detaching condition. Transient droplet dewetting is considered in the initiating period, and we obtain the distribution of the contact line friction factor. In steady oscillation, the oscillation resonance is verified from the oscillating amplitude of the contact line. Different periodical features are found for the droplet dancing at the resonance frequencies and departure from resonance. The droplet is detached at high voltages, and we provide a map for the detachable and nondetachable zones. The voltage is the dominant factor determining the droplet detachment; however, the AC frequency has notable influences on the critical voltage. The detachment is promoted when the AC frequency is within the region of the oscillation resonance (e.g., 20 < f < 75 Hz). In this region, the detaching process is not monotonic but instead, the droplet rebounds by several times before it is completely detached.

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The recent increase in municipal sludge worldwide has led to a great deal of interest in developing an efficient and environmentally friendly sludge treatment method. In the paper, the treatment of municipal sludge by hydrothermal oxidation (HTO) process with H2O2 as the oxidant was proposed. The impacts of HTO temperature and H2O2 mass fraction on the distribution of products, the moisture content, the migration behaviors of the heavy metals (HMs) of the resulted solid products, the concentration of volatile fatty acids (VFAs) and NH3-N contained in the resulted aqueous phase products and the pH value were investigated. The results indicated that the sludge reduction was achieved by HTO treatment, the increasing H2O2 mass fraction and HTO temperature can significantly improve the dewatering performance of the sludge. The potential toxicity fraction of Pb and Cd contained in the resulted solid residual increased with the increasing HTO severity and the potential toxicity fraction of solid residues was still lower than that of raw material. Acetic acid was the main VFAs produced from HTO treated sludge, and its concentration reached to the maximum value of 2923.41 mg/L at 230 °C under H2O2 mass fraction of 15%. The change in the pH of the resulted aqueous phase products was caused by the competition between the acidic (VFAs or CO2) or alkaline (NH3-N) substances derived from the sludge during HTO process. The HTO process was expected to be an efficient method for municipal sludge treatment due to its mild conditions and high heavy metal safety.

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Manipulation of a conductive droplet by electrowetting has been a popular topic in microfluidics whereby wettability of the droplet on a solid surface is increased by applying a voltage between the conductive droplet and the insulated surface. However, the opposite phenomenon, e.g., decreasing the wettability of a nonconductive droplet and increasing its contact angle (CA) by the reversed electrowetting (REW) effect, has been scarcely reported. Such a process involves not only the transient dynamics of droplet dewetting but also a critical condition for droplet detachment from the adhesive surface. In this work, actuation of a nonconductive droplet in an aqueous surrounding fluid by REW is studied experimentally. Silicone oil is used for the actuated droplet, and filtered water is used as the surrounding fluid. The solid substrate is made of a glass substrate coated with an indium tin oxide (ITO) film and then deposited by a dielectric layer of Parylene C. Potential difference is applied between the substrate and the surrounding fluid, eliminating the disturbance from the top needle on the motion of the droplet. Three different regimes are identified in the full range of operation. An underactuated regime occurs at low applied voltages, in which the CA of the droplet shows a monotonic increase with the increase of voltage (V). The friction coefficient of the contact line decreases with V before the CA saturation (Vs) but shows little change when V > Vs. At high voltages, the contact line of the sessile droplet is contracted excessively by REW. The droplet shows oscillation, and it refers to the overactuated regime. A combined time scale is proposed, and it verifies that the viscous dissipation of the contact line and liquid inertia show comparable contributions in the droplet dynamics. At sufficiently high voltages, the droplet is rejected completely from the surface. A critical equation for the threshold voltage of droplet detachment is built, and its validity is confirmed by experimental results.

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Limestone particle size has a crucial influence on SO2 capture efficiency, however there are few studies on the sulfation reactivity, which covers a broad range of particle sizes at low SO2 concentrations. In this paper, a large-capacity thermogravimetric analyzer (LC-TGA) was developed to obtain the sulfur removal reaction rate under a wide range of particle sizes (3 µm-600 µm) and SO2 concentrations (250 ppm-2000 ppm), and then compared with the results of a traditional fixed bed reactor and a commercial TGA. The experimental results showed that the LC-TGA can well eliminate the external mass transfer and obtain a better measurement performance. Both the final conversion and the reaction rate reduced with the decreasing of SO2 concentration, but ultrafine limestone particles still showed the good sulfation reactivity even at 250 ppm SO2. An empirical sulfation model was established based on the experimental results, which can well predict the sulfation process of different limestone particle sizes at low SO2 concentrations. The model parameters have a strong negative correlation against the particle size, and the fit of the reaction order of SO2 was found to be about 0.6. The model form is very simple to incorporate it into available fluidized bed combustion models to predict SO2 emission.

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The typical properties and yield of the refined hydrothermolytic acid (RHTA) and refined hydrothermolytic oxidation acid (RHOA) respectively prepared from cotton stalk by the hydrothermolysis process with and without hydrogen peroxide at 180-280 °C were investigated. The pH of RHOA at 180-260 °C is lower than that of RHTA. The yield of RHOA prepared at 180-280 °C is higher than that of RHTA except 230 °C. Besides, the variation trend of RHOA yield at 180-260 °C is in accordance with that of RHTA yield at 200-280 °C. The composition of RHTA and RHOA were determined using gas chromatography and mass spectrometry. The acids content of RHOA at 200 °C reaches the maximum. The phenols of RHOA at 200-230 °C is significantly higher than that of RHTA. Under oxidation atmosphere, the formation of ketones is inhibited and the secondary reactions of furan derivatives is promoted. Overall, the oxidation processing can alleviate the severe hydrothermolysis conditions for preparing post-hydrothermolysis acid.

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In this paper, the thermal characteristics of sewage sludge and the transformation behavior of Pb and Cd during the thermal conversion process were addressed. The incineration process and pyrolysis process of the sewage sludge were investigated by thermogravimetric analysis. The results indicated that the thermal conversion process of the sewage sludge could be divided into three stages and the presence of oxygen could accelerate the decomposition of the sewage sludge. Furthermore, the effects of thermal conditions on the concentration ratio of Cd and Pb and their species partitioning in the residual char and ash were investigated. For the pyrolysis process, the maximum concentration ratio of Cd reached 41.64% at 500 °C and the lowest one 2.92% at 700 °C. Contrary, the concentration ratio of Pb remained above 93% as the temperature increased. Thus, the suitable temperature for the sewage sludge pyrolysis was below 500 °C. For the incineration process, the incineration temperature had great influence on the concentration ratio of Cd and Pb. When the incineration temperature increased from 700 °C to 900 °C, the concentration ratio of Cd decreased drastically from 99.32% to 10.96%. The maximum concentration ratio for Pb (95.31%) was reached at 800 °C. Besides, the lowest concentration ratio of Cd and Pb were obtained at a residence time of 30 min. The partitioning analyses of the Cd and Pb contained in the ash showed that the residence time had little effect on the partitioning of Cd and Pb, and the residual fractions of Cd and Pb were both above 90%. It was concluded that Cd and Pb were properly stabilized in the ash. Thus, Cd and Pb in the ash were difficult to be released into the environment and to cause secondary pollution.

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The yield and pH of the refined aqueous product (RAP) prepared by the hydrothermolysis of cotton stalk (CS) were investigated using response surface methodology with the variation of three parameters: CS/water ratio of 0.05-0.15w/w, temperature of 180-280 °C, and retention time of 0-30 min. At the best formulation (0.05w/w, 264.36 °C and 0 min), the yield and pH of RAP were 82.8% and 3.95, respectively. Additionally, the organic compounds contained in RAP prepared under the respective optimal formulation (pH: 0.05w/w, 251.43 °C and 0 min, yield: 0.05w/w, 280.00 °C and 0 min) were determined by gas chromatography and mass spectrometry. The results show that the kinds of compounds in RAP are identical or similar to those in the wood vinegar (WV), but their contents is slightly higher than that of the WV. In sum, it is feasible that RAP has the enormous potential to be utilized as WV probably because of its higher quality and value than WV.

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