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CO2 flooding is considered one of the most important methods for reducing CO2 emissions and increasing oil production from reservoirs. However, the challenges of low recovery rates and poor economic benefits in CO2 immiscible flooding significantly hinder its widespread application. To address these issues, this paper proposes the use of ultrasonic-assisted CO2 immiscible flooding to enhance oil recovery (EOR) and analyzes its underlying mechanisms. First, the distribution characteristics of residual oil in CO2 immiscible flooding were examined using high pressure mercury injection (HPMI), nuclear magnetic resonance (NMR), and microscopic visualization displacement (MVD) experiments. Next, the changes in oil recovery and residual oil distribution after applying ultrasonic-assisted CO2 immiscible flooding were analyzed. Finally, the mechanism of EOR through ultrasonic-assisted CO2 immiscible flooding was summarized based on the results of interfacial tension (IFT) tests. The findings indicate that the recovery rate of CO2 immiscible flooding without ultrasound is 53.33 %, with residual oil primarily distributed in the form of films and flakes within the pores. The ultrasonic assisted CO2 immiscible flooding with frequency of 28 KHz and power of 200 W was provided by ultrasonic horn, and the recovery rate increased by 62.84 % after 60 min. With ultrasonic assistance, the recovery rate increased to 62.84 %, and the maximum radius of residual oil droplets was reduced from 81.8 μm to 36.5 μm. Additionally, the amount of residual oil in the 0.1 μm to 1 μm range slightly decreased, suggesting that ultrasonic assistance mainly improves the recovery of flake residual oil, with a slight improvement in film residual oil recovery as well. Ultrasound can enlarge the pore and throat radius and reduce the interfacial tension in the CO2-oil system, allowing more flake residual oil to be displaced. Moreover, the high-frequency vibrations of the ultrasound can reduce the thickness of the oil film, enhancing the recovery of film residual oil. This study supports the further application of ultrasonic-assisted CO2 immiscible flooding in both scientific research and engineering practice.

IntroductionHorizontal ecological compensation (HEC) has the potential to incentivize inclusive green growth in cities.MethodsUsing the multi-stage difference-in-differences (DID) method, this study examines the impact of HEC policies as a quasi-natural experiment. Panel data are analyzed; the data pertain to 87 cities in the Yangtze River Basin, from 2007 to 2020.ResultsThe findings indicate that HEC policies significantly contribute to inclusive green growth, with consistent effects across different estimators. The moderating effect test reveals that urban industrial pollution levels and green innovation are key pathways through which HEC policies influence inclusive green growth. Further analysis shows that the positive impact of HEC is more pronounced in watersheds with high marketization and in downstream regions, suggesting that HEC may exacerbate regional disparities in inclusive green growth.DiscussionThis study offers insights for China and also for other developing countries seeking to promote urban inclusive green growth and achieve sustainable development goals.

Shenmu Gas Field in Ordos Basin shows the characteristics of low quality gas reservoir, and its deve-lopment effect is quite different from that of surrounding gas fields, which brings some problems to the exploration deployment and sustainable production of the gas field. In order to reveal the origin of low-quality gas reservoirs, the microscopic characteristics and formation mechanism of Taiyuan Formation reservoirs in Shenmu Gas Field were studied based on microscopic experiments at different scales. The results show that the reservoir of Taiyuan Formation in Shenmu Gas Field is characterized by "rich in quartz, poor in feldspar, and high content of rock detritus". The reservoir of Taiyuan Formation is a low porosity and ultra-low permeability tight sandstone reservoir with small pore-fine throat combination, poor pore throat connectivity, and weak reservoir permeability. The formation of low-quality reservoirs in Taiyuan Formation is affected by the matrix, the content of rock detritus in eruptive rocks and diagenesis. During the late Carboniferous to early Permian, the formation of the reservoir was significantly affected by the volcanic activity of the Inner Mongolia ancient uplift in the north of the Ordos Basin. The content of matrix and rock detritus of the eruptive rock in the sandstone was generally high. The rock detritus of the eruptive rock provided the main material basis for the development of secondary pores. While the matrix blocked the pores, it also produced a certain number of matrix dissolved pores, which had a dual impact on the reservoir. The dissolution during diagenesis is critical to the formation of Taiyuan Formation reservoir, and the increased porosity accounts for 64.3% of the current porosity. At the end of the Late Cretaceous, the late Yanshan movement led to the structural inversion of the Ordos Basin, the readjustment of gas and water, and the escape of natural gas along the fault in the eastern part of the basin. Finally, the low quality gas reservoir of Taiyuan Formation in Shenmu Gas Field is formed. The next exploration focus of Shenmu Gas Field should be based on the clear macro distribution law of diagenesis and favorable lithologic traps, and further search for the development area with high content of eruptive rock detritus and low content of matrix.

In order to solve the problem that the pore structure and the microscopic occurrence characteristics of fluid change with stress in real time during the depletion development of tight gas reservoirs, the pore structure, water production and irreducible water distribution characteristics of tight reservoirs in the eighth member of Permian Shihezi Formation, Shenmu Gas Field, Ordos Basin under different stress conditions were quantitatively characterized, and the influence of stress on gas-water relative permeability was analyzed by using nuclear magnetic resonance (NMR), high-pressure mercury injection (HPMI) and displacement experiments. The results show that when effective stress increases from 7 MPa to 17 MPa, reservoir porosity decreases from 8.39% to 7.65%, and the maximum pore radius decreases from 38.3 μm to 35.2 μm among which, the number of pore throats in the range of 0.3-18.9 μm decreases the most. The number of pores involved in seepage decreases due to the decrease of pore throat size, the bound water saturation increases from 51.3% to 59.7%, and the distribution range of the size of bound water increases from 0.012-17.4 μm to 0.012-20.1 μm. The changes of pore structure and bound water distribution characteristics further reduce the relative permeability of both gas and water phases, the relative permeability of gas phase decreases from 0.481 to 0.283, and that of isotonic point decreases from 0.157 to 0.09.

Study region: Yalong River Basin (YLRB), China. Study focus: The YLRB was selected to investigate the impacts of climatic and societal changes on water and energy security in the water-diverting area of China’s South-to-North water diversion project (SNWD-W). The future runoff and hydropower generation were projected using Watergap hydrological model (WGHM) under different Representative Concentration Pathway (RCP) scenarios and water withdrawals were predicted based on the shared socio-economic pathways (SSPs). New hydrological insights for the region: The results show that the future runoff and hydropower generation in the YLRB display significant increasing and decreasing trends under RCP8.5 and RCP2.6, respectively. The water stress index (WSI) is projected to increase by about 30%, but it is still lower than 0.2 even combined with the SNWD-W project. The future hydropower generation is projected to change by − 0.87–4.75% and 0.44–6.10% under RCP2.6 and RCP8.5 without water diversion, respectively. The slight increment caused by climate change cannot offset the substantial decrement caused by water diversion, especially in the maximum transfer amount scenario, which highlights the tradeoffs between the mitigation of water stress in the water-receiving area and the loss of hydropower generation in the water-diverting area. Our results provide a valuable reference for the water resources administration in the YLRB and the design of the water diversion scheme for the SNWD-W.

University mottos have been demonstrated to convey educational philosophies, but few studies have investigated the educational philosophies reflected by university mottos from countries along the “One Belt, One Road” (OBOR) route, with applying the analytical approaches like text mining and natural language processing (NLP). This present investigation constructed a database of university mottos from 1,535 universities in 61 countries along the OBOR route and applied NLP technology to explore the similarities and differences of educational philosophies among the universities along the OBOR route. Methods of NLP used in this article included text mining, cluster analysis, and Latent Dirichlet Allocation (LDA) topic model. The social network analysis (SNA) model was used to further analyze the interconnection and exchange of educational philosophies expressed through university mottos. Based on the five identified topic categories, we concluded that countries along the OBOR route have the same basic educational philosophy for higher education but have different emphases due to cultural differences, such as the different emphases on virtue education, collectivism, and individualism. Education for sustainability is another focus of higher education philosophy reflected by the topic categories of university mottos, which is consistent with the United Nations Sustainable Development Goals, for example, quality education. In addition to demonstrating the BRI impact on educational philosophies of countries along the OBOR route, this present investigation could also contribute to the growing body of knowledge about international cooperation and communication of higher education under the framework of BRI, for a globalized, shared and sustainable education in the post-COVID era.

The soil behind a wall is in a stress state with self-weight stress and horizontal stress as the main stress for the Rankine retaining wall with horizontal fill. However, there is a certain wall-soil friction and bonding force in practice. The friction and bonding force may cause the principal stress deflection in the fill near the retaining wall, and the classical Rankine earth pressure theory is not applicable for this case. In the current study, the principal stress deflection of the fill near the retaining wall is processed both by the rotation and by the analysis of the stress from the Mohr circle in the fill behind the wall. The active and passive earth pressures of the retaining wall filled with the cohesive soil is derived, considering the wall-soil friction and bonding force. The influences of the fill friction angle and the wall-soil friction angle on the earth pressures are analyzed. The examples are further used to compare the results from this study with those with the improved Coulomb method. The results show that the Rankine earth pressure is a special case of the formula presented in this study. With the increase of the wall-soil friction angle and internal friction angle, the passive earth pressures gradually increase. The active earth pressures decrease with the increase of the internal friction angle, and the decreasing rate gradually decreases. When the internal friction angle is small, the active earth pressures decrease continuously with the increase of the wall-soil friction angle, and the decreasing speed gradually decreases. When the internal friction angle is large, the active earth pressures first decrease and then increase with the increase of the wall-soil friction angle. The effect of the fill friction angle is more obvious than that of the wall-soil friction angle. Compared with the results from other methods, the active earth pressures obtained with this method are larger, but the passive earth pressure is smaller, and their differences increase with the increase in the wall-soil friction, especially when the cohesion is considered. Because the deflection of the principal stress in the soil on the back of the wall is more consistent with the actual situations, the results from this study will be more suitable to compute the earth pressure in practice.

This paper presents a practical study on how to improve the ℋ∞ performance and meet the input–output constraints of the two-degrees-of-freedom (DOF) flexible-joint manipulator system (FJMS) with parameter uncertainties and external disturbances. For this reason, a robust constrained moving-horizon ℋ∞ controller is designed to improve the system ℋ∞ performance while still satisfying the input–output constraints of the uncertain system. First, the uncertain controlled system model of the two-DOF FJMS is established via the Lagrange equation method, Spong’s assumption, and the linear fractional transformation (LFT) technique. Then, the control requirements and input–output constraints of the uncertain system are transformed into the linear matrix inequality (LMI) via the theory of ℋ∞ control and the full-block multiplier technique. Next, the LMI optimization problem refreshed by the current state is addressed at each sample moment with the idea of the moving-horizon control of the model predictive control (MPC), and the calculated gain is implemented to the nonlinear closed-loop system under the state feedback structure. The validity and feasibility of the designed control scheme is finally verified via the results of simulation experiments.

Abstract With the outbreak of COVID-19 in Wuhan, aggressive countermeasures have been taken, including the implementation of the unprecedented lockdown of the city, which will necessarily cause huge economic losses for the city of Wuhan. In this paper, we attempt to uncover the interactions between epidemic prevention and control measures and economic-social development by estimating the health loss and meso-economic loss from a human-oriented perspective. We implemented a compartmental model for the transmission dynamics and health burden assessment to evaluate the health losses, then estimated the direct and indirect economic losses of industries using the Input-Output model. Based on these estimates, the first monthly health losses and meso-economic losses caused by the lockdown was assessed. The overall policy effect of the lockdown policy in Wuhan was also investigated. The health loss and meso-economic losses are used to evaluate the health burden and loss of residents’ mental health, the direct economic loss of several worst-hit industries, and the indirect economic loss of all industries, respectively. Our findings reveal that the health burden caused by this pandemic is estimated to be 4.4899 billion yuan (CNY), and the loss of residents’ mental health is evaluated to be 114.545 billion yuan, the direct economic losses in transport, logistics, and warehousing, postal service, food, and beverage service industries reach 21.6094 billion yuan, and the monthly indirect economic losses of all industries are 36.39661994 billion yuan caused by the lockdown. The total monthly economic losses during the lockdown reach 177.0413 billion yuan. However, the lockdown policy has been considered to reduce COVID-19 infections by >180 thousand, which saves about 20 thousand lives, as well as nearly 30 billion yuan on medical costs. Therefore, the lockdown policy in Wuhan has obvious long-term benefits on the society and the total economic losses will be at a controllable level if effective measures are taken to combat COVID-19.

Understanding and manipulating geological pore structures is of paramount importance for geo-energy productions and underground energy storages in porous media. Nevertheless, research emphases for long time have been focused on understanding the pore configurations, while few work conducted to modify and restructure the porous media. This study deploys ultrasonic treatments on typical geological in-situ core samples, with follow-up processes of high-pressure mercury injections and nitrogen adsorptions and interpretations from nuclear magnetic resonance and x-ray diffraction. The core permeability and porosity are found to increase by 8.3 mD, from 4.1 to 12.4 mD, and by 0.95%, from 14.03% to 14.98%, respectively. Meanwhile, the number and size of the micro- and mesopore are increased with progressing of ultrasonic treatment, while those of the macropore decrease, which finally increase the permeability and porosity. The increase of micro- and mesopore number, from x-ray diffraction results, is attributed to the migration and precipitation of clay minerals caused through ultrasonic wave. The relocation of clay minerals also helps to improve the pore-throat connectivity and modify the micro-scale heterogeneity. Basically, this study reveals the characterizations of geological pore reconfigurations post-ultrasonic treatments and interprets the associated mechanisms, which provides guidance to manipulate the geological pores and be of benefit for further porous media use in science and engineering.

When considering the friction and bonding force between the back of the retaining wall and the horizontal fill behind the wall, the principal stress of the soil element near the vertical back of the retaining wall is no longer vertical and horizontal but deflects to a certain extent. When the surface of the backfill becomes inclined, the principal stress of the soil behind the wall deflects in a more complicated way. In this paper, the cohesion of the soil element in the fill with an inclined surface is assumed, and the formulas for calculating the active and passive earth pressures of the retaining wall with inclined cohesive backfill are derived by rotating the principal stress of the soil element behind the wall. The proposed method is compared with the existing algorithm, and the influences of the inclination and the cohesion of the fill are analyzed. The results show that the proposed method is more universal. Both the active and passive earth pressures increase rapidly with the increase of the inclination of the fill. The active earth pressure and its horizontal component decrease with the increase of the cohesion of the fill, while the passive earth pressure and its horizontal component increase with the increase of the cohesion of the fill.

At present, the main development mode of “horizontal well + volume fracturing” is adopted in a tight glutenite reservoir. Due to the existence of conglomerate, the seepage characteristics are more complex, and the production capacity after volume fracturing is difficult to predict. In order to solve this problem, a dual media unstable seepage model was established for matrix seepage and discrete fracture network seepage when considering the trigger pressure gradient. By considering the Poisson's ratio of stress sensitivity in an innovative way, the coupling model of permeability and stress is improved, and the production prediction model of volume fracturing horizontal well in a tight glutenite reservoir based on the fluid-solid coupling effect is formed. The finite element method is used to numerically solve the model, and the fitting verification of the model is carried out; the impact of stress sensitivity, producing pressure difference, fracture length, number of fracture clusters and fracture flow capacity conductivity on productivity is analyzed, which has certain guiding significance for the efficient development of volume fracturing in a tight glutenite reservoir.