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Parasitic effects significantly interfere with systematic model‐parameter extraction, making linear fitting of spiral inductors challenging when the number of turns exceeds 6, as seen in existing works. Based on the single‐π model, we propose a parameter‐extraction technique using an additional three ladder R–L ladder network in series to more accurately predict skin and proximity effects. Compared to the latest enhanced π‐circuit model, our proposed model with parameter‐extraction technique in multi‐laps inductors accurately predicts the characteristics of series inductance (Leff) and quality factor (Q) across the self‐resonant frequency, especially at the peak. This model could be used directly for the model of the on‐chip inductor in both academic and industrial fields. [ABSTRACT FROM AUTHOR]

Poor sealing of gas extraction boreholes is one key to restrict gas extraction efficiency. In this paper, a novel borehole sealed quality detection device for the gas extraction of a coal mine is developed based on the theory of air leakage. By comparing the amount of gas extracted at different test points, it is possible to determine whether there is air leakage around the borehole, and the specific leakage position and leakage amount. Moreover, this device has the advantages of simple operation and a short test period. Based on the above analysis, a corresponding air leakage disposal method was proposed to handle the leaky boreholes. Field tests showed that the air–gas mixture flow in the test borehole was reduced by a factor of approximately 1.55 and the concentration of pure seam gas was increased approximately six times after the disposal of the air leaks. The combination of the leakage disposal method and the leakage detection device can accurately seal the borehole at the position of the leak, thus effectively ensuring the effectiveness of gas extraction from the borehole. The findings have important implications for improving the efficiency of gas extraction in coal mining operations. [ABSTRACT FROM AUTHOR]

A proper understanding of the effect of methane diffusion on coal reservoir permeability rebound and recovery is essential, as coal reservoir permeability is the key parameter influencing the efficiency of coalbed methane migration and computational research on it is lacking. In this paper, the multifield coupling model for methane migration was established. Then, two parameters, the influence coefficient of diffusion on permeability rebound (DPRB) and the influence coefficient of diffusion on permeability recovery (DPRC), were proposed to quantify the effect of methane diffusion on rebound and recovery of coal reservoir permeability. Subsequently, we used COMSOL software to study the variation rules of the coal reservoir permeability rebound time, permeability recovery time, and permeability rebound value, DPRB, and DPRC for different geologic parameters. The results shown that the permeability rebound time and recovery time are proportional to the coal seam initial pressure, but inversely proportional to the initial permeability and initial diffusion coefficient. The rebound value decreases with increasing coal seam initial pressure and initial permeability, but ascends with rising initial diffusion coefficient. DPRB declines with increasing coal seam initial pressure, initial permeability, and initial diffusion coefficient, but they are all greater than 0.7, indicating that methane diffusion has a significant effect on permeability rebound. The DPRC values for different coal seam initial pressures, initial permeabilities, and initial diffusion coefficients are above 0.98, which implies that methane diffusion dominates the permeability recovery process. Finally, a conceptual model was presented to research the mechanism of diffusion influence on rebound and recovery of coal reservoir permeability, and the implications for enhanced drainage of deep coalbed methane were discussed. Therefore, the results of this paper can provide a theoretical foundation for deep coalbed methane-enhanced extraction. [ABSTRACT FROM AUTHOR]

Enhanced coalbed methane recovery with CO2 coal seam storage (CO2-ECBM) technology is an important way to achieve China's strategic goals of carbon peak and carbon neutrality. Presently, to date there has been rarely research conducted on the effect of coal sample scale on pore structure under supercritical CO2 (ScCO2) fluids. In this study, a high-pressure geological environment simulation system was adopted to analyze coal samples of different scales for ScCO2 saturation. Subsequently, low-pressure nitrogen gas adsorption (LP-N2GA), mercury intrusion porosimetry (MIP), and low-field nuclear magnetic resonance (LF-NMR) were used to analyze the pore structure and fractal dimension changes in saturated coal samples at different scales. The experimental results show that the mesopore ratios of cylindrical and granular coal decrease by an average of 1.68% and 2.30%, respectively, after the saturation of ScCO2. The proportion of macropores in cylindrical coal increased by an average of 5.50% after ScCO2 saturation, while the proportion of macropores in granular coal changed by 176.86% compared to cylindrical coal. The fractal dimension of the ScCO2 saturated coal samples obtained with LP-N2GA, MIP, and LF-NMR all show a decreasing trend, again confirming the modification of the coal pore surface by ScCO2. Finally, a conceptual model is presented to analyze the mechanism of the effect of coal sample scale on the pore structure under ScCO2. The difference in the transport paths of ScCO2 molecules at different coal scales is the main reason for the difference in the evolution of the pore structure. In addition, the impact of the amount of adsorption obtained in the laboratory using coal samples of different scales on the assessment of the CO2 storage capacity was discussed. Therefore, the results of this study are expected to provide a reference for the CO2 storage capacity assessment of the CO2-ECBM project. [ABSTRACT FROM AUTHOR]

Since 2012, China has established a national voluntary greenhouse gas emission reduction trading mechanism, which realizes the filing of voluntary emission reduction projects such as carbon sinks and the issuance of certified voluntary emission reduction (CCER). Due to the challenges in the development, opera-tion, trading, and other stages of carbon sequestration projects, and the suspension of voluntary emission reduction-related applications by the competent authorities in 2017, the development of CCER carbon se-questration projects in China is relatively insufficient, and the number of registered projects accounts for only 2%. Therefore, this article, based on the CCER methodology development perspective of the Wind-Solar-Storage Integration Project, investigates and analyzes the structure of the project, the baseline methodology, and procedures for CCERs, economic evaluation, and additional challenges of the project, and verifies the feasibility of CCER development for the Wind-Solar-Storage Integration Project in the Ningxia region based on actual conditions. The article also proposes policy recommendations for the development of new energy carbon sequestration projects.

The coal power industry accounts for the largest proportion of carbon dioxide emissions, and is first included in the national carbon market, while the cost of carbon emissions has a certain impact on the coal power clearing price. Based on this, this paper constructs a bidding model of coal-fired power units considering the cost of carbon emissions; Taking Guangdong Province as an example, this paper simulates the change of the clearing price of the spot market of coal power units in the light, medium and heavy carbon market scenarios, and provides relevant suggestions for the construction of the electricity market and carbon market.

Traditional radome adversely influences the antenna performance besides protecting the antenna from the outside environment. In this work, one co‐design of a millimeter‐wave antenna and radome using parasitic patches is presented, featuring a low profile and high gain. First, the basic influence of radome on patch antenna is investigated on a transparent and low‐loss material cyclic olefin copolymer. Then, the electromagnetic interaction between the patches and the antenna is investigated in detail to reduce the adverse effect of field reflection and phase delay. One prototype of the co‐designed radome and antenna was fabricated for demonstration. The measured results show that the entire profile of the co‐designed radome and antenna is significantly reduced from traditional 0.5–0.2 λg and the gain is enhanced by 2.4 dB. [ABSTRACT FROM AUTHOR]

At present, researches on soft and hard coal mainly focus on influence of pore structure on its gas adsorption and desorption characteristics, but there are few researches on difference of gas desorption characteristics of soft and hard coal under condition of external moisture. In view of the above problem, the orthogonal experiments under different adsorption equilibrium pressure and external moisture content were carried out by using coal seam high-pressure water injection simulation experimental device, and the differences of gas desorption amount, gas desorption speed and diffusion coefficient of soft and hard coal under different external moisture were analyzed. The results show that with the increase of external moisture content, the gas desorption amount of soft and hard coal decreases, but the gas desorption amount of soft coal is always greater than that of hard coal; the external moisture can inhibit the gas desorption of soft and hard coal, but the inhibition effect of soft coal is stronger than that of hard coal; under different adsorption equilibrium pressure and external moisture content, the gas desorption speed of soft and hard coal is the highest at the initial moment, and it shows a decreasing trend with the extension of time and the increase of the external moisture content; under the same adsorption equilibrium pressure and similar external moisture content, the gas desorption speed of soft coal is always higher than that of hard coal and the diffusion coefficient of soft coal is higher than that of hard coal; the gas diffusion coefficient of soft and hard coal decreases with the increase of external moisture content under the same adsorption equilibrium pressure.