Wind power prediction holds significant value for the stability of the electrical grid when wind power is connected to the grid. Using neural networks for wind power prediction may have some ...limitations, such as slow speed and low accuracy. This paper proposes to enhance the power prediction accuracy and speed by optimizing the neural network through health assessment wind turbines. Firstly, based on wind turbine actual operating data, a health assessment is conducted to obtain a health matrix of wind turbine. Then, by calculating the weights of the matrix, the power prediction strategy of the network is optimized. Following that, matrix approximation hyperparameters are utilized to expedite the optimization process. Finally, some tests are conducted on neural network power prediction, act as optimized back propagation (BP) neural network and whale swarm algorithm–support vector regression (WSA-SVR) neural networks are employed for wind power prediction. Results show noticeable optimization: after optimizing the BP network, power prediction accuracy increased by about 40%, and prediction speed rose by about 20%; after optimizing the WSA-SVR network, power prediction accuracy improved by 10%, and prediction speed surged by about 45%. Further analysis shows that this method can improve the accuracy and speed of most neural network wind power prediction algorithms.
Underground coal gasification (UCG) is an important part of the low-carbon green coal mining technology system. With the implementation of the carbon peaking and carbon neutralization and the ...maturity of UCG, UCG will inevitably perform large-scale and industrialized production, which will certainly cause some issues such as serious waste of UCG sites caused by large-scale surface residual subsidence and poor foundation of fractured rocks. The key to the reuse of the surface site after UCG is to ensure that the surface residual subsidence does not exceed the design index of the building (structure). However, there is still a lack of methods for predicting residual subsidence on the surface of UCG. Under such background, combined with the characteristics of the UCG process, this paper analyzed the mechanism of the surface residual subsidence after UCG, and concluded that the root resource of the surface residual subsidence after UCG was the stripping and yielding of the hyperbolic coal pillars. Next, a calculation model of the maximum stripping width and yielding zone width of the “hyperbolic” coal pillar for UCG was established by the theoretical analysis method, and a method for predicting the surface residual subsidence with the consideration of coal pillar stripping and yielding was proposed and applied to Ulanqab UCG test site. The research findings have important theoretical and practical significance for the UCG site stability evaluation and land resource reuse.
Resource-based cities often face land scarcity during their developmental and expansionary phases. However, repurposing the goaf sites of suburban coal mines has been recognized as an effective ...strategy for alleviating this issue, particularly pertinent for suburban coal mines using strip mining techniques to protect ground-level structures. Old strip mining goaf is easily influenced by disturbance and leads to secondary surface deformation, which will threaten the construction above old strip mining goaf. Therefore, it is essential to provide a basis and reference for decision-makers regarding surface residual subsidence for strip mining. In the paper, based on the morphology and structure of the old strip mining goaf before the surface residual subsidence, the reason and mechanism of the residual subsidence of old strip mining goaf are studied. The results show that the main reasons for the “activation” of old strip mining goaf are the re-compaction of the under-compacted part of the fractured rock mass in the caving zone, the stripping and yielding of coal pillar under the action of groundwater erosion, weathering, and the collapse of residual voids. Based on the above analysis, a prediction model of the surface residual subsidence of the old strip mining goaf is proposed, which takes into account the compaction of the under-compacted area, the collapse of the residual voids, and the stripping and yielding of the coal pillar. The proposed method is implemented to evaluate the stability of a city viaduct goaf. Our research outcomes bear valuable theoretical and practical implications for site stability assessments of old strip mining goafs and the sustainable repurposing of land resources in suburban resource-based cities.
A novel maximum power point tracking method based on sliding mode control and average state model of PV generation systems is developed. This method consists of two parts: term of constant control ...and term of index control. It is different from the conventional sliding mode control which uses a constant speed control law. The developed method uses a controllable sliding mode switching function which can automatically adjust the approaching speed, so as to enable the photovoltaic system to achieve fast dynamic response and stable output power. System simulations using MATLAB are performed. Compared with conventional methods, simulation results show that maximum power point tracking times for the novel method both in start-up phase and in cases of environmental changes can be shorten by more than 50%. A experimental platform of 150W PV system has been established to conduct tests. Experimental results show that the maximum power point tracking times both in start-up phase and in load stepping phase including the illumination change phase, can be significantly decreased. These results indicate that the developed method owns better dynamic response than constant speed control law. It can be used in photovoltaic generation system.
The planned viaduct in Jining, Shandong is a priority project in the city. However, the 63 working faces of a mine in Jining is only 3 m away from the planned viaduct, posing a serious threat to the ...safety of the viaduct’s construction. Consequently, it is essential to evaluate the stability of the planned viaduct’s goaf area under the influence of the 63 working faces. However, the 63 working faces are short faces, and there is a lack of corresponding prediction of surface residual subsidence. To address this issue, this paper employs theoretical analysis and numerical simulation to uncover the foundation deformation mechanism and characteristics of fractured rock and soil mass in the short goaf. Subsequently, a residual subsidence prediction method for the short goaf was proposed for the viaduct mined-out area. This new approach was implemented for the planned viaduct in Jining, and its effectiveness was validated through InSAR and leveling monitoring results. The research findings offer technical support for viaduct construction in areas affected by underground mining.
A protein molecule exists in either a compact folded state or a variable and open unfolded state. Since the unfolded state is favored by chain entropy, restricting its entropy is an attractive ...mechanism for shifting the equilibrium toward the folded state. A number of entropy-based strategies have been engineered or used by natural proteins to increase the folding stability: (a) shortening of loop lengths, (b) covalent linkage of dimeric proteins, (c) backbone cyclization, (d) catenation, (e) spatial confinement, and (f) macromolecular crowding. Theoretical analyses demonstrate the importance of accounting for consequences on the folded as well as the unfolded state and provide guidance for further exploitation of these stabilization strategies.
In this paper, the idea of Underground coal gasification coupled with supercritical carbon dioxide storage is proposed based on the problems of Underground coal gasification combustion area and ...carbon dioxide storage site, which provides a new technical approach for carbon peaking and carbon neutrality in the coal sector. At the same time, to solve the underground coal pillar design problem in the popularization and application of UCG-CCS, this paper adopts numerical simulation and theoretical analysis methods to reveal the deformation mechanism and bearing characteristics of “hyperbolic” type coal pillar in UCG-CCS. The results of this study are as follows: ① The injection of supercritical CO2 into the underground goaf can effectively reduce the load of the coal pillar bearing the overlying strata and improve the bearing capacity of the “hyperbolic” protective coal pillar. ② The size of the “hyperbolic” coal pillar in UCG-CCS slightly influences the coal pillar's stability under certain injection pressure. For safety in practical engineering, it is necessary to ensure that the CO2 injection pressure reaches its critical pressure of 7.38 MPa. ③ Based on numerical simulation results, when the width of the combustion cavity is 40 m, the width of the protective coal pillar is 56 m, the injection pressure of supercritical CO2 is 7.38 MPa, and the sealing depth ranges from 800 m to 1200 m, the protective coal pillars are in a stable state due to the pressure effect of supercritical CO2 on the coal pillar and the roof. The research results of this paper have important practical significance for promoting the site selection, product design, and application of UCG-CCS and provide a technical means for the coal industry to achieve carbon peak and carbon neutrality.
Today, reclamation and reuse of wastewater from textile, food and pharmaceutical industries are the big challenges for researchers to decrease the diseases and pollution in the world. Thus, this ...study was conducted for the design of V2O5@ZnO nanocomposite and its application as a photocatalyst for degradation of methyl orange under UV and visible irradiations. The V2O5@ZnO nanocomposite was synthesized with a homogeneous combination of hydrothermal synthesized ZnO nanorods and V2O5 nanoparticles. The morphological, structural, optical, electrochemical and photocatalytic degradation characterizations of prepared nanocomposite and its components were studied. Optical result showed the red shift in edge of absorption spectra of V2O5@ZnO nanocomposite toward the ZnO nanorods film which indicate the transferring enhancement of photo-generated carriers between two-components of nanocomposites. It can decrease the recombination rate of photo-excited charges due to interface effect through creation of the separation channel of electrons and holes. Electrochemical impedance spectroscopy analysis displayed lower charge transfer resistance and effective separation of photo-excited charges on V2O5@ZnO nanocomposite surface under visible light irradiation. Photocatalytic measurements showed 60% enhancement in the degradation efficiency for V2O5@ZnO nanocomposite under 3 hours irradiation of visible light toward the UV light. It can be attributed to the high effective surface area of homogeneously combining V2O5 nanoparticles and ZnO nanorods and narrowing the band gap of prepared nanocomposite toward the ZnO film. Furthermore, this finding showed the stable activity for degradation of methyl orange on the V2O5@ZnO nanocomposite film surface. These results indicate that the prepared V2O5@ZnO nanocomposite can be applied for high efficiency degradation of methyl orange under irradiation of visible light.
A chaotic model for generating multi-directional multi-scroll attractors via hyperbolic tangent function series is proposed in this paper. The dynamical mechanisms of this chaotic model are further ...investigated, including M-scroll, M×N-grid scroll, M×N×L-grid scroll chaotic attractors. Moreover, the dynamical behaviors of this system are theoretically analyzed and numerically simulated, such as equilibria and their stability, Lyapunov exponents and bifurcation diagrams. This system can be widely used in data encryption and secure communication.
