Microwave Scattering Model for a Corn Canopy

In microwave remote sensing of agricultural canopy, the capability of a scattering model to accurately predict the scattering properties is of great importance. In the literature, a "discrete scatter" approach was usually deployed, where scattering behavior of the individual constituent of the canopy was determined, and was either summed up incoherently For a dielectric cylinder of finite length, the generalized Rayleigh-Gans approximation (GRGA) is usually applied in studying its scattering behavior. It approximates the induced current in a finite cylinder by assuming infinite length. Therefore, this method is valid for a needle shaped scatterer with radius much smaller than the wavelength. For corn canopy at C band, numerical comparison of the GRGA results of the bistatic scattering coefficients for the main stalk demonstrate appreciable discrepancy with that of method of moment (MoM) results. Moreover, GRGA fails to satisfy the reciprocity theore

Can Institutional Investor Clique Play a Governance Role? Based on the Perspective of Insider Reduction

This article takes China’s A-share non-financial industry listed companies from 2007 to 2015 as a sample, starting from the social network algorithm, to study whether the grouping behavior of institutional investors in the network can affect the degree of executive reduction in the future. The study found that there is a significant positive correlation between the shareholding ratio of institutional investors in group holdings and the degree of future reduction of executives. This article explores the interactive behavior of Chinese institutional investors in the network, and expands the research of institutional investors on corporate governance and executives’ future reduction behaviors

The Optimal Sine Pulse Frequency of Pulse Hydraulic Fracturing for Reservoir Stimulation

Pulse hydraulic fracturing (PHF) is a key technique for reservoir stimulation. PHF can well accelerate the rupture of rock. However, the supercharging mechanism of PHF is not fully understood. The main reason is that the pressure distribution and its variation, especially the peak pressure characteristics, are unclear inside the pipe and fissure. The present research focuses on the sine pulse applied at the inlet of a pipe or fracture to reveal the variation regularity of peak pressure with the pulse frequency, amplitude, pipe length, diameter and wave speed. First, the weakly compressible Navier–Stokes equations were developed to simulate the variation of fluid pressure. The computation codes were developed using the MacCormack method validated by the existing experimental data. Then, the sine pulse effect was studied inside the pipe and fissure. Last, a new frequency model was built to describe the relationship between the optimal pulse frequency, wave speed and pipe length. The results show that there is a family of frequencies at which the peak pressure of the endpoint can be significantly enhanced and that these frequencies are the optimal pulse frequency. It is found that the optimal pulse frequency depends on the pipe or fissure length and wave speed. At the optimal pulse frequency, the peak pressure at the endpoint can be increased by 100% or more, and the cavitation phenomenon occurs. However, the peak pressure decreases when with the decrease in the pipe diameter and fissure departure due to the friction drag effect of the wall. These new landmark findings are very important for the PHF technique. In addition, a new universal frequency model is built to predict the optimal sine pulse frequency. The present research shows the variation regularity of the fluid pressure inside the pipe and develops a sine frequency-controlled method, providing a potential guide for reservoir stimulation

The Optimal Sine Pulse Frequency of Pulse Hydraulic Fracturing for Reservoir Stimulation

Pulse hydraulic fracturing (PHF) is a key technique for reservoir stimulation. PHF can well accelerate the rupture of rock. However, the supercharging mechanism of PHF is not fully understood. The main reason is that the pressure distribution and its variation, especially the peak pressure characteristics, are unclear inside the pipe and fissure. The present research focuses on the sine pulse applied at the inlet of a pipe or fracture to reveal the variation regularity of peak pressure with the pulse frequency, amplitude, pipe length, diameter and wave speed. First, the weakly compressible Navier–Stokes equations were developed to simulate the variation of fluid pressure. The computation codes were developed using the MacCormack method validated by the existing experimental data. Then, the sine pulse effect was studied inside the pipe and fissure. Last, a new frequency model was built to describe the relationship between the optimal pulse frequency, wave speed and pipe length. The results show that there is a family of frequencies at which the peak pressure of the endpoint can be significantly enhanced and that these frequencies are the optimal pulse frequency. It is found that the optimal pulse frequency depends on the pipe or fissure length and wave speed. At the optimal pulse frequency, the peak pressure at the endpoint can be increased by 100% or more, and the cavitation phenomenon occurs. However, the peak pressure decreases when with the decrease in the pipe diameter and fissure departure due to the friction drag effect of the wall. These new landmark findings are very important for the PHF technique. In addition, a new universal frequency model is built to predict the optimal sine pulse frequency. The present research shows the variation regularity of the fluid pressure inside the pipe and develops a sine frequency-controlled method, providing a potential guide for reservoir stimulation

The Spatial Effect of Industrial Intelligence on High-Quality Green Development of Industry under Environmental Regulations and Low Carbon Intensity

In order to thoroughly investigate how industrial intelligence influences green industrial development through direct, indirect, and spatial spillover effects in China and fill in the gaps left by earlier studies, the study combines industrial intelligence and green industrial development into a single analytical framework. The findings show that implementing industrial intelligence can proactively encourage high-quality green industrial development; additionally, a strong spatial correlation is shown between industrial intelligence and high-quality green industrial development. According to spatial spillover analysis, industrial intelligence fosters the development of green industries both inside and between regions. When regional heterogeneity is analyzed, it is revealed that the eastern part of China experiences industrial intelligence effects more strongly than the central region, while the western areas are unaffected. Environmental regulations are a crucial mediating mechanism for the operation of industrial intelligence; in particular, public-participation environmental regulation and market base environmental regulations strengthen the baseline relationship; however, industrial intelligence does not impact high-quality green industrial development through administrative environmental regulation. The partial mediating effect of carbon intensity was also observed. The findings could be used as a guide for decision-making by experts and policymakers in China and other developing nations to use industrial intelligence and support the green development of the sector during economic transformation

A Semianalytical Model for Simulating Fluid Flow in Tight Sandstone Reservoirs with a Bottom Aquifer

Water breaks through along fractures is a major concern in tight sandstone reservoirs with a bottom aquifer. Analytical models fail to handle the three-dimensional two-phase flow problem for partially penetrating inclined fractures, so time-consuming numerical simulation are often used for this problem. This paper presents an efficient semianalytical model for this problem considering three-dimensional fractures and two-phase flow. In the model, the hydraulic fracture is handled discretely with a numerical discrete method. The three-dimensional volumetric source function in real space and superposition principle are employed to solve the model analytically for fluid flow in the reservoir. The transient flow equations for flow in three-dimensional inclined fractures are solved by the finite difference method numerically, in which two-phase flow and stress-dependent properties are considered. The eventual solution of the model and transient responses are obtained by coupling the model for flow in the reservoir and discrete fracture dynamically. The validation of the semianalytical model is demonstrated in comparison to the solution of the commercial reservoir simulator Eclipse. Based on the proposed model, the effects of some critical parameters on the characteristics of water and oil flow performances are analyzed. The results show that the fracture conductivity, fracture permeability modulus, inclination angle of fractures, aquifer size, perforation location, and wellbore pressure drop significantly affect production rate and water breakthrough time. Lower fracture conductivity and larger inclination angle can delay the water breakthrough time and enhance the production rate, but the increment tends to decline gradually. Furthermore, water breakthrough will occur earlier if the wellbore pressure drop and aquifer size are larger. Besides, the stress sensitivity and perforation location can delay the water breakthrough time

Effect of proppant distribution in hydraulic fractures on coalbed methane extraction

Fracturing with proppants is often used to improve the permeability of coalbed methane (CBM) reservoir. The fracture is easy to close under the closure stress and the proppant distribution in fractures greatly influences the extraction efficiency of CBM. The past research mainly considered the impact of fracturing damage on the coalbed methane extraction but rarely investigated the influence of the proppant distribution forms on CBM extraction. Therefore, based on the theory of dual-porous media, this paper establishes a theoretical model of CBM extraction with different proppant distribution forms, which considers the proppant compaction, embedment, and fracture aperture change. The model is implemented numerically and is validated against field results of CBM production. The research results show that the extraction efficiency of CBM from high to low is the pulse proppant injection, continuous proppant injection, no proppant injection, no fracturing. The continuous proppant injection should ensure that the proppant placement rate is more than 60 %. The CBM extraction efficiency is the highest when the proppant column length is 0.2 m–0.3 m and the void area length is 0.5 m. The research results provide a theoretical basis for improving the extraction efficiency of coalbed methane using fracturing with sand injection

Online Estimation of Internal Short Circuit Resistance for Large-Format Lithium-Ion Batteries Combining a Reconstruction Method of Model-Predicted Voltage

The resistance of the internal short-circuit (ISC) has a potential evolution trend accompanied by an increasing safety risk. Thus, an accurate online resistance estimation for the ISC is crucial for evaluating its safety risk and taking staged handling measures. Since the ISC battery mainly presents abnormal stage of charge (SOC) depletion behaviors, the SOC estimation processes based on state observers and battery models will act an important basis of the ISC resistance estimation problem. However, as it will be exhibited in this paper, when directly using the measured voltage of the ISC battery as the output variable of the state observer, the battery model error will limit the SOC estimation accuracy and further lead to very inaccurate or even divergent ISC resistance estimation results for large-format batteries, which present quite slight SOC depletion behaviors at the ISC state. To this end, this paper proposes a novel SOC and ISC resistance co-estimation method which combines a reconstruction method of the model-predicted voltage of the ISC battery. Experimental validations are carried out with a 37 Ah battery, results show that the proposed method which uses the reconstructed model-predicted voltage (RMPV) as the output variable of the state observer only present maximum estimation errors of 39.96 Ω and 2.00 Ω for the ISC resistances of 100 Ω and 10 Ω, respectively