Steam-assisted gravity drainage (SAGD) is a mature heavy oil thermal recovery technology but inherently limited to low recovery efficiency at mid-late stage due to the increasing heat loss in the steam chamber. Here, the dimethyl ether (DME)-assisted SAGD technology and its relevant transport and interfacial properties are specifically investigated through physical 2D heavy oil simulation. A total of four-set physical experiments, with different DME injection ratios, were conducted and compared with the traditional SAGD. The experimental results indicate DME is capable of reducing the heavy oil’s viscosity and interfacial tension at high temperatures. Three stages, rising, lateral expansion, and descending stages, are determined in the SAGD steam chamber’s development; the mid-late SAGD stage is defined when the steam chamber extends to the caprock boundary. With DME additions at the mid-late SAGD stage, higher oil recovery factor and sweep efficiency could be reached and the dew point temperature of steam chamber’s lead decreases by 0.7–1.8 °C. The optimum gas–water ratio is determined to be 3:1, with the fastest oil recovery growth and the highest final cumulative oil-vapor ratio of 0.163. This study provides reliable experimental bases and valuable analyses for the DME-SAGD technology and its application in heavy oil reservoirs.
Providing forecasts for ultra-long time series plays a vital role in various activities, such as investment decisions, industrial production arrangements, and farm management. This paper develops a novel distributed forecasting framework to tackle the challenges of forecasting ultra-long time series using the industry-standard MapReduce framework. The proposed model combination approach retains the local time dependency. It utilizes a straightforward splitting across samples to facilitate distributed forecasting by combining the local estimators of time series models delivered from worker nodes and minimizing a global loss function. Instead of unrealistically assuming the data generating process (DGP) of an ultra-long time series stays invariant, we only make assumptions on the DGP of subseries spanning shorter time periods. We investigate the performance of the proposed approach with AutoRegressive Integrated Moving Average (ARIMA) models using the real data application as well as numerical simulations. Our approach improves forecasting accuracy and computational efficiency in point forecasts and prediction intervals, especially for longer forecast horizons, compared to directly fitting the whole data with ARIMA models. Moreover, we explore some potential factors that may affect the forecasting performance of our approach.
Over the past 40 years, global tertiary expansion has been driven in part by the rise of the non-university sector. The growth of this sector, which includes vocational colleges, also contributes to increasingly diverse national higher education systems. Prior research has focused on inter-state variation in national systems, while very few studies have explored intra-state variation in the expansion of non-university sector. Building on the policy innovation and diffusion model, this study uses event history analysis to investigate key drivers behind Chinese prefecture cities' adoption of vocational colleges during the latest tertiary education expansion. The study employs a rich panel dataset from 273 Chinese cities between 2000 and 2014. Findings suggest that the socioeconomic and the politico-institutional contexts matter the most for cities' policy adoption, and the influence of policy diffusion is negative but not significant. Moreover, there is substantial heterogeneity across time and region. The characteristics of early adopters significantly differ from those of late adopters, and the diffusion paths vary within and across regions. This study illustrates that the emergence of sub-national government affiliated non-university institutions is driven by a complex combination of socioeconomic, politico-institutional, and policy forces. Results highlight the regional contextual factors that may override coercive pressure from national strategies to promote the non-university sector expansion and the structural diversity in the context of less developed economies.
Previous studies on the determinants of household tourism expenditure have assumed that households independently determine their tourism expenditure. However, the possible influence of neighbours on tourism expenditure has been overlooked. This study is the first to apply spatial lag analysis to investigate the neighbour effect in the determination of rural household tourism expenditure. The results indicate that there is a significant neighbour effect on the tourism expenditure of rural households. This neighbour effect varies by region and by household head attributes. This paper suggests that the neighbour effect does help to explain household tourism consumption in rural areas.
Electron paramagnetic resonance (EPR) spectroscopy using sterically hindered amine is extensively applied to detect singlet oxygen (1O2) possibly generated in advanced oxidation processes. However, EPR-detectable 1O2 signals were observed in not only the 1O2-dominated hydrogen peroxide (H2O2)/hypochlorite (NaClO) reaction but surprisingly also the 1O2-absent Fe(II)/H2O2, UV/H2O2, and ferrate [Fe(VI)] process with even stronger intensities. By taking advantage of the characteristic reaction between 1O2 and 9,10-diphenyl-anthracene and near-infrared phosphorescent emission of 1O2, 1O2 was excluded in the Fe(II)/H2O2, UV/H2O2, and Fe(VI) process. The false detection of 1O2 was ascribed to the direct oxidation of hindered amine to piperidyl radical by reactive species [e.g., •OH and Fe(VI)/Fe(V)/Fe(IV)] via hydrogen transfer, followed by molecular oxygen addition (forming a piperidylperoxyl radical) and back reaction with piperidyl radical to generate a nitroxide radical, as evidenced by the successful identification of a piperidyl radical intermediate at 100 K and theoretical calculations. Moreover, compared to the highly oxidative species (e.g., •OH and high-valence Fe), the much lower reactivity of 1O2 and the profound nonradiative relaxation of 1O2 in H2O resulted it too selective and inefficient in organic contaminant destruction. This study demonstrated that EPR-based 1O2 detection could be remarkably misled by common oxidative species and thereby jeopardize the understandings on 1O2.
This research develops a spatial analytical framework to investigate the spatial distribution and dynamic evolution of academic patent commercialization. The results showed that the gravity center of academic patents commercialization in China shifted from southwest to northeast from 2010 to 2019, showing the characteristics of alternating spatial convergence and spatial divergence. Moreover, economic development will promote the centralization of the commercialization of academic patents, while local fiscal science and technology expenditure, development of local public libraries, regional urbanization and traffic decentralization will promote the decentralization of the commercialization of academic patents. Those findings affirm that spatial convergence or divergence of academic patent commercialization is the dynamic result of the contrast between the two forces of centralization and decentralization. This study provides an analytical framework for scholars to explore the dynamic spatial pattern evolution of academic patent commercialization.
Persistent, mobile, and toxic (PMT) substances are affecting the safety of drinking water and are threatening the environment and human health. Many PMT substances are used in industrial processing or consumer products, but their sources and emissions mostly remain unclear. This study presents a long-term source distribution and emission estimation of melamine, a high-production-volume PMT substance of emerging global concern. The results indicate that in China, approximately 1858.7 kilotonnes (kt) of melamine were released into the water (∼58.9%), air (∼27.0%), and soil systems (∼14.1%) between 1995 and 2020, mainly from its production and use in the decorative panels, textiles, and paper industries. The textile and paper industries have the highest emission-to-consumption ratios, with more than 90% emissions per unit consumption. Sewage treatment plants are the largest source of melamine in the environment for the time being, but in-use products and their wastes will serve as significant melamine sources in the future. The study prompts priority action to control the risk of PMT substances internationally.
The association between pandemic experience and immediate mental health risks, such as depression, is well-documented, yet the long-term effects remain unclear. This study examines the impact of early childhood exposure to the 2003 SARS pandemic on adulthood mental health after 17 years in China, using data from the 2020 China Family Panel Studies (CFPS). The analysis included 6289 participants, aged 3 to 30 years during the SARS outbreak, with an average age of 35.3 years at the time of survey. Adulthood mental health was assessed using Center for Epidemiologic Studies Depression Scale (CESD) and an indicator of clinical depression. The severity of local SARS outbreaks was assessed by cumulative cases per 10,000 population. Results show that each additional case per 10,000 population was linked to a 1.617-fold (95% confidence interval (CI): 1.425–1.836) increase in odds of depression after 17 years for younger children (aged 3–12 years in 2003) relative to older cohorts (aged 13-30). This risk was higher in children from rural areas (adjusted odds ratio (aOR) 3.64; 95% CI 2.92–4.55), with poor physical health (1.98; 1.59–2.48), and from low-income families (2.87; 2.03–4.05). The childhood pandemic experience elevated the probability of developing depression-prone personality traits, which contributes to the enduring impact of childhood pandemic experiences on adulthood mental health. These findings highlight the long-lasting psychological impact of early-childhood pandemic exposure, underscoring the need for targeted interventions to mitigate its effects on the younger generation and emphasizing the importance of monitoring long-term mental health and personality development in children post-pandemics, particularly in light of COVID-19.
Earth's mantle has a two-layered structure, with the upper and lower mantle domains separated by a seismic discontinuity at about 660 km (refs. 1,2 ). The extent of mass transfer between these mantle domains throughout Earth's history is, however, poorly understood. Continental crust extraction results in Ti-stable isotopic fractionation, producing isotopically light melting residues 3–7 . Mantle recycling of these components can impart Ti isotope variability that is trackable in deep time. We report ultrahigh-precision 49 Ti/ 47 Ti ratios for chondrites, ancient terrestrial mantle-derived lavas ranging from 3.8 to 2.0 billion years ago (Ga) and modern ocean island basalts (OIBs). Our new Ti bulk silicate Earth (BSE) estimate based on chondrites is 0.052 ± 0.006‰ heavier than the modern upper mantle sampled by normal mid-ocean ridge basalts (N-MORBs). The 49 Ti/ 47 Ti ratio of Earth's upper mantle was chondritic before 3.5 Ga and evolved to a N-MORB-like composition between approximately 3.5 and 2.7 Ga, establishing that more continental crust was extracted during this epoch. The +0.052 ± 0.006‰ offset between BSE and N-MORBs requires that <30% of Earth's mantle equilibrated with recycled crustal material, implying limited mass exchange between the upper and lower mantle and, therefore, preservation of a primordial lower-mantle reservoir for most of Earth's geologic history. Modern OIBs record variable 49 Ti/ 47 Ti ratios ranging from chondritic to N-MORBs compositions, indicating continuing disruption of Earth's primordial mantle. Thus, modern-style plate tectonics with high mass transfer between the upper and lower mantle only represents a recent feature of Earth's history.
The empirical research has not provided definitive answers to questions about how to assess and report academic adjustment and whether or not it influences psychological and sociocultural adjustments. This study is a longitudinal investigation into the relationship between academic and psychological adjustment of international students from South Asian countries in a cross-cultural learning context who partied in Teaching Chinese to Speakers of Other Languages (TCSOL) teacher education programs in Chinese universities. Using Zun's Self-Rating Depression Scale and the self-developed Scale of Academic Adaptation, the first test in December 2017 (T1) and the second in December 2019 (T2) were conducted to measure depression, learning motivation, learning behavior, learning efficacy, academic achievement, and satisfaction of South Asian students. The paper discovered significant positive correlations between five variables, indicating an interaction between the five aspects showing how involved and effective overseas students were in learning in China and a cross-lagged relationship between depression and academic adjustment. This longitudinal empirical study of international students in China aimed to help expand the application of cross-cultural adjustment theory in different educational backgrounds, and provide diverse samples and methods different from the traditional western perspective.
Antibiotics present in the natural environment would induce the generation of antibiotic-resistant bacteria (ARB), causing great environmental risks. The effects of antibiotic resistance genes (ARGs) and antibiotics on bacterial transport/deposition in porous media yet are unclear. By using E. coli without ARGs as antibiotic-susceptible bacteria (ASB) and their corresponding isogenic mutants with ARGs in plasmids as ARB, the effects of ARGs and antibiotics on bacterial transport in porous media were examined under different conditions (1–4 m/d flow rates and 5–100 mM NaCl solutions). The transport behaviors of ARB were comparable with those of ASB under antibiotic-free conditions, indicating that ARGs present within cells had negligible influence on bacterial transport in antibiotic-free solutions. Interestingly, antibiotics (5–1000 μg/L gentamicin) present in solutions increased the transport of both ARB and ASB with more significant enhancement for ASB. This changed bacterial transport induced by antibiotics held true in solution with humic acid, in river water and groundwater samples. Antibiotics enhanced the transport of ARB and ASB in porous media via different mechanisms (ARB: competition of deposition sites; ASB: enhanced motility and chemotaxis effects). Clearly, since ASB are likely to escape sites containing antibiotics, these locations are more likely to accumulate ARB and their environmental risks would increase.
Earth abundant transition metal-based materials are widely served as peroxymonosulfate (PMS) activators for degradation of emerging contaminants. However, the agglomeration of catalyst particles and metal ion leaching hinder their practical applications for pollutant decomposition. In this study, a Co3O4-carbonized polyaniline composite (Co3O4/CPANI) was implemented for PMS activation. The Co3O4/CPANI + PMS system exhibited high catalytic performance toward tetracycline (TC) degradation (degradation efficiency of 92.11%, initial TC level of 20 mg/L). Moreover, the practical application potential of Co3O4/CPANI + PMS system was well verified with three antibiotics (i.e., TC, doxycycline (DOX), and ciprofloxacin (CIP)) at highest actual aquatic environmental levels (1.0 and 0.5 mg/L). In the established Co3O4/CPANI + PMS system, both radicals (•O2−, •OH and SO4•-) and non-radical (1O2) contributed to TC degradation, and 1O2 was the dominant reactive oxygen species (ROS). CO groups, oxygen vacancies (OVS), redox pairs of Co2+/Co3+ species, and graphitic N all served as active sites in the PMS activation process, especially, OVS were crucial for the generation of 1O2. This study provides an efficient method for the synthesis of metal-based nanocatalysts with low nanoparticle aggregation and metal leaching which could act as a sustainable PMS activator for the remediation of TC-polluted water environment.
Antibiotic resistance genes (ARGs) have become as emerging contaminant with great concerns worldwide due to their threats to human health. It is thus urgent to develop techniques to degrade ARGs in water. In this study, MoS2@Fe3O4 (MF) particles were fabricated and used to activate peroxymonosulfate (PMS) for the degradation of four types of free DNA bases (T, A, C, and G, major components of ARGs) and ARGs. We found that MF/PMS system could effectively degrade all four DNA bases (T within 10 min, A within 30 min, C within 5 min, and G within 5 min) in very short time. During the reaction process, MF could activate PMS to form the reactive radicals such as ·OH, SO4·−, O2·−, and 1O2, contributing to the degradation of DNA bases. Due to the low adsorption energy, high charge transfer, and great capability for PMS cleavage, MF exhibited excellent PMS adsorption and activation performances. MoS2 in MF could enhance the cycle of Fe(III)/Fe(II), improving the catalytic performance. Excellent catalytic performances of MF/PMS system were achieved in complex water matrix (including different solution pH, coexisting of anions and natural organic matter) as well as in real water samples (including tap water, river water, sea water, and sewage) especially under high salinity conditions due to the generation of Cl· radicals and HClO species. MF/PMS system could also efficiently degrade ARGs (chromosomal kanR and plasmid gmrA) and DNA extracted from antibiotic resistant bacteria (ARB) in super-short time. Moreover, complete disinfection of two types of model ARB (E. coli K-12 MG 1655 and E. coli S17–1) could also be achieved in MF/PMS system. The high degradation performances of MF/PMS system achieved in the reused experiments and the 14-day continuous flow reactor experiments indicated the stability of MF particles. Due to the magnetic property, it would be convenient to separate MF particles from water after use via using magnet, facilitating their reuse of MF and avoiding potential water contamination by catalysts. Overall, this study not only provided a deep insight on Fe/Mo-triggered PMS activation process, but also provided an effective and reliable approach for the treatment of DNA bases, ARGs, DNA, and ARB in water.
