Credit default prediction for the energy industry is essential to promoting the healthy development of the energy industry in China. While previous studies have constructed various credit default prediction models with brilliant performance, the class-imbalance problem in the credit default dataset cannot be ignored, where the numbers of credit default cases are usually much smaller than the number of non-default ones. To address the class-imbalance problem, we proposed a novel CT-XGBoost model, which adds to XGBoost with two algorithm-level methods for class imbalance, including the cost-sensitive strategy and threshold method. Based on the credit default dataset consisting of energy corporates in western China, which suffers from the class-imbalance problem, the CT-XGBoost model achieves better performance than the conventional models. The results indicate that the proposed model can efficiently alleviate the inherent class-imbalance problem in the credit default dataset. Moreover, w... [more]

In recent years, connected automated vehicles (CAVs) have attracted much attention, and the coordination strategy of CAVs in isolated intersections has been widely discussed. However, these algorithms for isolated intersections cannot be directly applied in a multi-intersection road network (MiRN). The coordination strategy in the MiRN requires further investigation. This paper proposes a two-tier strategy for CAV coordination in the MiRN. First, we analyze the coordination problem in isolated intersections and formulate it as a mixed-integer programming problem. Then, for the MiRN, we propose a consensus prediction method to estimate the travel time for CAVs with different paths. Finally, a novel coordination approach is given, showing how to determine the optimal path for CAVs. The experimental results demonstrate the efficiency of the proposed strategy under various traffic flow rates. Compared with the fixed signal time assignment method and the actuated signal time assignment meth... [more]

It is critical to address energy issues as we move through the first half of the twenty-first century, as societies become firmly aware of the consequences of resource scarcity and the disastrous consequences of climate change from human activity (especially heavy industry) [...]

Aiming to solve the problems of poor CO2 displacement efficiency and serious gas-channeling and low well-opening rates in ultra-low permeability reservoirs, we carry out CO2 displacement experiments under different permeability reservoirs by using different development methods, water drive to gas drive procedures, and different fracture positions to clarify the effects of physical formation properties, injection methods, and fracture parameters on CO2 displacement efficiency in C8 ultra-low permeability reservoirs. The experimental results show that the recovery degree of CO2 miscible drive increases with an increase in permeability. When the gas−oil ratio is greater than 2000 m3/m3, serious gas channeling can be observed in both the miscible drive and immiscible drive. In addition, when the water drive is altered to be a gas drive, the water cut of 0.45 mD and 0.98 mD cores decreased, and the recovery degree increased by 13.4% and 16.57%, respectively. A long fracture length will dete... [more]

Charging and discharging current behavior under high DC electric field in polypropylene (PP) film is closely related to the charge transport and accumulation process, which has an important effect on the electrical insulating properties of PP. In this paper, the dependence of the charging and discharging current of polypropylene films on time and electric field has been comprehensively studied. The results showed that the transient and steady current values of the charging and discharging process increase with the increase of electric field. Dependence of the charging current on the electric field conformed well to the space charge limited current (SCLC) theory with a transition electric field of 270 kV/mm, at which the charge transport changed from ohmic conduction to SCLC conduction. The carrier mobility derived from the discharging current became significantly smaller with increase of the charging electric field. The charge accumulation after discharging was derived from the integra... [more]

This paper highlights field studies to determine the nature of variations in the load on the sucker-rod string during short-term gas extraction from the wellbore annulus. The results of step-by-step gas extraction from the annular spaces of the wells of fields developed by PJSC TATNEFT are provided. In the course of investigations, we have obtained both the trends of maximum and minimum loads on the polished rod during annular gas extraction, and the dependence of maximum load increment on the rod string with respect to pump size and pressure variation in the annular space. The analysis of the research data resulted in the elaboration of guidelines for short-term extraction of annular gas from wells operated by the PCP units.

This study investigates the dark fermentation of fruit and vegetable waste under mesophilic conditions (30−34 °C), as a valorization route for H2 and volatile fatty acids production, simulating the open market waste composition over the year in two Mediterranean countries. Specifically, the study focuses on the effect of the (i) seasonal variability, (ii) initial pH, and (iii) substrate/inoculum ratio on the yields and composition of the main end products. Concerning the seasonal variation, the summer and spring mixtures led to +16.8 and +21.7% higher H2 production than the winter/autumn mixture, respectively. Further investigation on the least productive substrate (winter/autumn) led to 193.0 ± 7.4 NmL of H2 g VS−1 at a pH of 5.5 and a substrate/inoculum of 1. With the same substrate, at a pH of 7.5, the highest acetic acid yield of 7.0 mmol/g VS was observed, with acetic acid corresponding to 78.2% of the total acids. Whereas a substrate/inoculum of 3 resulted in the lowest H2 yield,... [more]

Household consumption has become an important field of carbon dioxide emissions. Urban−rural disparity in the household carbon emissions (HCEs) of residents and their influencing factors are relevant to HCE reduction. Taking Fujian as the study area, the LMDI and SDA models were used to analyze the effects of influencing factors for the direct household carbon emissions (DHCEs) and indirect carbon emissions (IHCEs) of urban and rural residents from 2006 to 2018. The HCEs continue to rise, approximately 65% from the IHCEs in 2017, and urban areas occupied 67% in 2018. The gap between urban and rural per capita HCEs is narrowing. In 2017, approximately 75% of urban per capita HCEs came from the IHCEs, while the per capita DHCEs’ occupation exceeded the IHCEs in rural areas. Per capita consumption expenditure has the largest positive effect on the DHCEs and IHCEs in urban and rural areas. With the urbanization process, the inhibition effect of rural DHCEs is larger than the positive effec... [more]

Thermal infrared imagery is very much gaining in importance in the diagnosis of energy losses in cultural heritage through non-destructive measurement methods. Hence, owing to the fact that it is a very innovative and, above all, safe solution, it is possible to determine the condition of the building, locate places exposed to thermal escape, and plan actions to improve the condition of the facility. The presented work is devoted to the technology of creating a dense point cloud and a 3D model, based on data obtained from UAV. It has been shown that it is possible to build a 3D point model based on thermograms with the specified accuracy by using thermal measurement marks and the dense matching method. The results achieved in this way were compared and, as the result of this work, the model obtained from color photos was integrated with the point cloud created on the basis of the thermal images. The discussed approach exploits measurement data obtained with three independent devices (t... [more]

The dynamic process of demographic aging is an important reason for the systematic increase in the share of people with reduced mobility in Polish society [...]

This paper aims at justifying the significance of investment in the improvement of labour productivity (LP) and importance of the latter on economic performance of companies manufacturing wind energy components (WEC) in Lithuania in terms of value added (VA) created, profitability and wage earned. The time period covered is 2000−2020. The following methods have been employed: analysis of legal acts, programmes, strategies, and business structure and finance indicators, interdependence (correlation and regression), trend, case analysis, logical economical reasoning and graphical representation. The research results of current status analysis showed that the business of WEC manufacturing is small in regard to their variety of products but increasing in terms of VA and employment in Lithuania. Investment has been found as a driver of improvement in LP. The calculated historical ratio of change in LP to investment showed that, on average, after 1000 EUR per employee has been invested in ta... [more]

For 15 years, the Gravity Recovery and Climate Experiment (GRACE) mission have monitored total water storage (TWS) changes. The GRACE mission ended in October 2017, and 11 months later, the GRACE Follow-On (GRACE-FO) mission was launched in May 2018. Bridging the gap between both missions is essential to obtain continuous mass changes. To fill the gap, we propose a new approach based on a remove−restore technique combined with an autoregressive (AR) prediction. We first make use of the Global Land Data Assimilation System (GLDAS) hydrological model to remove climatology from GRACE/GRACE-FO data. Since the GLDAS mis-models real TWS changes for many regions around the world, we further use least-squares estimation (LSE) to remove remaining residual trends and annual and semi-annual oscillations. The missing 11 months of TWS values are then predicted forward and backward with an AR model. For the forward approach, we use the GRACE TWS values before the gap; for the backward approach, we u... [more]

Analysis of amplitudes of transmitted waves (TAVO) is an extension of the conventional AVO analysis using amplitudes of reflected waves. In this study, we introduce the common transmission point (CTP) gather, which is a new domain that is convenient for TAVO analysis. A CTP gather is formed by binning traces that have the same transmission point across a layer interface. We use the proposed domain to invert the ratios Δαα, Δρρ, Δββ, and βα in a model consisting of a gas channel nestled within an oil reservoir. The TAVO equations are fitted to amplitudes calculated by Zoeppritz equations within CTPs inside and outside the channel. Within each CTP gather, we use all traces with incidence angles less than 90% of the critical angle (if any) as TAVO approximations break down beyond this point. The proposed CTP TAVO analysis method estimated Δαα, Δρρ, Δββ, and βα in the gas channel within 1% of their corresponding true values.

In order to study the flame propagation characteristics of a ethylene/polyethylene hybrid explosion under pressure accumulation, a visual pressure-bearing gas/power hybrid-explosion experimental platform was built. The flame propagation characteristics of polyethylene and ethylene/polyethylene hybrid explosions in the closed vessel were analyzed. The results show that the flame brightness, flame front continuity and average flame propagation velocity of polyethylene dust explosion in the closed vessel increased first and then decreased when the polyethylene dust concentration increased. The curve of the flame propagation velocity with time had obvious pulsation characteristics. Adding 1% and 3% ethylene to different concentrations of polyethylene dust significantly improved its explosion flame brightness, flame front continuity and average flame propagation velocity. Moreover, it also improved the fluctuation amplitude of the explosion flame propagation velocity with time curve. The ex... [more]

World urbanization is an important process: it is predicted that by 2050 about 64% of the developing world and 86% of the developed world will be urbanized [...]

On the basis of theoretical considerations (mechanistic model), an equation was determined that allowed to calculate the free energy (Helmholtz) of a spherical droplet deposited on a flat surface in a system without external forces. Assuming isochoric and isothermal transformation of the system and a very fast conversion of mechanical energy into heat, the obtained equation allows to determine the trajectory of thermodynamic transformation consisting of the spreading of the droplet on the surface of the substrate. The similarities and differences in the behaviour of spherical droplets described by the mechanistic model and Young’s model, together with its improvements, were discussed. The trajectories of free energy changes during the spreading of droplets in a system in which the adhesive force acting perpendicular to the wetted surface was considered as well.

This article presents the electric field distribution E and dielectric losses ΔPdiel. in the insulation system of high-voltage cables. Such a system consists of inner and outer semiconductor screens and XLPE insulation. The aim of this study was to compare the values of E and ΔPdiel. between semiconductor screens and XLPE insulation. The objects of the research were high-voltage cables of 110 kV, 220 kV, 400 kV, and 500 kV. The geometrical dimensions of the cables, especially the radii of individual layers of insulation, as well as the electrical properties of the screens and XLPE, were taken from the literature. Semiconductor screens and XLPE insulation were treated as a system of three concentric cylinders. When determining the electric field distribution, both the electrical permittivity and electrical conductivity, which, in the case of semiconductor screens, play important roles, were taken into account. The obtained results prove that both the electric field distribution E and di... [more]

The Special Issue on “Green Energy Economies” was open for submission on 30 March 2021 and closed on 30 March 2022 [...]

Nuclear technology has multiple applications that are fundamental to our daily life [...]

It is generally known that violent oil price volatility will cause market panic; however, the extent to which is worthy of empirical test. Firstly, this paper employs the TVP-VAR model to analyze the time-varying impacts of oil price volatility on the panic index using monthly data from January 1990 to November 2021. Then, after using the SVAR model to decompose the oil price volatility, this paper uses the PDL model to analyze the heterogeneous impacts of oil price volatility from different sources. Finally, based on the results of oil decomposition, this paper uses the TARCH model to analyze the asymmetric impacts of oil price volatility in different directions. The results show that: (1) oil price volatility can indeed cause market panic, and these impacts exhibit time-varying characteristics; (2) oil price volatility from different sources has different impacts on the panic index, and the order from high to low is oil-specific demand shocks, supply shocks, and aggregate demand shoc... [more]

Biogas resources in the Sanhu area of the Qaidam Basin have great potential, but there are few studies on biogas from shale, especially on the accumulation conditions of shale biogas. The study of biogas accumulation conditions of quaternary shale in the Sanhu area is of great significance to the theory of biogas accumulation and the guidance of exploration and development. This paper takes Quaternary shale in the Sanhu area as the research object. It is analyzed from multiple perspectives of shale hydrocarbon generation conditions, reservoir conditions, as well as hydrodynamic and structural conditions. Through the experiments of soluble organic carbon analysis and porosity and permeability analysis, the accumulation conditions of shale biogas reservoirs are clarified. The results show that the quaternary shale has a high soluble organic carbon content and high salinity formation water, which is conducive to late methane biochemical generation. Quaternary shale has the characteristics... [more]

The damage of a long tunnel is found in parts with an adverse geological structure zone under an earthquake. The phenomenon is normally the consequence of a non-uniform seismic load. Thus, to reveal the mechanism of the phenomenon, the dynamic response of the lining structure in a long tunnel passing through an adverse geological structure zone subjected to a non-uniform seismic load is mainly studied in this paper. Firstly, based on the random ground motion synthesis theory, the non-uniform ground motion acceleration−time history curves that reflect local site effects, such as traveling wave effects and attenuation effects, are generated. Secondly, the behavior of the tunnel with a different adverse geological structure zone (including different inclinations, thicknesses, and lithologies) under non-uniform seismic input is studied. Then, the impact of the different adverse geological structure zone on the internal force and safety factor of the tunnel lining is analyzed. Finally, the... [more]

The role of the road transportation of people and goods is increasing [...]

In this article, a new non-inverting buck-boost converter with superior characteristics in both bucking and boosting is presented. The proposed converter has some distinct features, such as high step-up/-down ability and low voltage/current stress on its switching devices. The voltage gain of the proposed converter is double the reported value for the traditional buck-boost converter. Although it has three switches, the three switches operate simultaneously, hence no dead-time is required. Two out of the three switches are under voltage stress equal to half of the output voltage. The overall efficiency of the system is promising because of the ability to select devices with low voltage drops. Converter analysis and steady-state performance in both continuous conduction mode (CCM) and discontinuous conduction mode (DCM) are presented in detail. A 1 kW hardware prototype of the converter was implemented in the laboratory; with a step-up ratio of 3.5 and 1 kW power, the measured efficienc... [more]

The shale oil horizontal wells in the Songliao Basin are affected by a lack of mature theories, technologies and experiences in the direction of wellbore stability. Wellbore collapse may occur, and in severe cases, the wellbore may be scrapped, resulting in huge economic losses. Therefore, aiming at addressing the above problems, rock mechanics experiments were carried out. Based on the theories of elasticity and rock mechanics, this paper considers not only the influence of the bedding plane, but also the influence of hydration on the strength weakening of the shale body and the bedding plane. The analysis shows that no matter under which in situ stress mechanism, the wellbore in the vertical well section is the most stable, and when the inclination angle is approximately 45°, the wellbore is most likely to be unstable. Changes in water content do not affect the most stable or unstable regions. Under the same conditions, the equivalent density of collapse pressure increases with the i... [more]