Search

To explore the reaction mechanism of sludge, slag, lime, and fly ash in high temperature environments, the unconfined compressive strength (UCS) test was hereby implemented to study the effect on curing age, curing temperature, slag content and fly ash content about the strength of sludge. Scanning electron microscopy (SEM) was used to observe the microscopic composition of the substance, and X-ray diffraction (XRD) was used to analyze the mineral composition at the micro level to further disclose its reinforcement mechanism. The experimental results demonstrate the difference in the strength measured by different dosage of curing agent, and results indicate that the strength of high temperature curing sample was obviously higher than that of low temperature curing sample. When the curing temperature rises, the pozzolanic reaction and hydration reaction between materials are accelerated, and a certain amount of gel products are produced, playing a precipitation and bonding role between particles. The 28 days and 90 days strengths of the sludge samples with 20% fly ash and 80% slag dosing at 40°C were 1139 KPa and 1194 KPa, which were 1.4 and 1.1 times of that of pure cement solidified sludge. At 60°C, the strength of 14 days, 28 days and 90 days were 802 KPa, 1298 KPa and 1363 KPa, which were 1.1, 1.5 and 1.3 times of that of pure cement solidified sludge. Under the influence of an alkaline environment, the silicon-aluminum grid structure was interconnected into a denser network structure, and the compressive strength of lime-activated fly ash-slag was thus continuously enhanced. Affected by the high temperature, lime-activated fly ash-slag solidified sludge could significantly improve the middle and late strength of the sample. The research showed that the new solidification material can replace partly the concrete curing agent, thereby alleviating the carbon emission and environmental pollution problems arising from cement solidified sludge. [ABSTRACT FROM AUTHOR]

Subsurface fluid injection and extraction can reactivate faults and induce earthquakes. In current research, faults are typically described as symmetrical structures and the presence of asymmetric structures is often overlooked. The reality is that numerous asymmetric faults exist within the Earth's crust. The architectural and permeability characteristics of fault zones differ significantly between symmetrical and asymmetrical faults. These differences may have a great influence on fault stability during fluid injection or extraction. In this study, the impact of fault zone structures on fluid-induced slips and seismic activity were investigated through numerical analysis. The findings indicated that symmetrical faults were more likely to induce larger slips and earthquakes during various subsurface fluid operations. For asymmetric faults, larger induced slips occurred when fluid was operated in a hanging wall reservoir than in a footwall reservoir. In symmetrical faults, the opposite was true. When evaluating the stability of a fault in subsurface fluid engineering, the fault structure and fluid pattern and their combined effects must be considered comprehensively. [ABSTRACT FROM AUTHOR]

Cement solidification was a widely used method to broaden the resource utilization of dredged sludge. However, the organic matter in sludge limit the application of cement solidification. The fulic acid (FA) was used to simulate the natural organic matter in sludge. With the increase in FA content, the sludge gradually changed from low-liquid-limit clay to high-liquid-limit clay. The unconfined compression test showed that the strength of cement-solidified dredged sludge (CDS) decreased with FA content. The influence mechanism of the FA on cement solidification was revealed by a water content test, a hydration heat test, scanning electron microscopy, and thermogravimetric analysis. FA hindered the conversion of pore water to combined water and reduced the hydration heat inside CDS. The FA in sludge weakened the internal bond within CDS by hindering the development of C-S-H gel from spheroidal to flake. At the same time, the final amount of hydrates such as C-S-H, C-A-H and AFt also decreased in the CDS containing FA. The weakening mechanism of FA on the strength of CDS can be attributed to three aspects: (1) FA adsorbed on the surface of cement minerals and hindered the contact between cement minerals and pore water; (2) acidic FA reduced the pH of the pore liquid in CDS; (3) the carboxyl and hydroxyl functional groups of FA adsorbed calcium ions in pore liquid through ion coordination. [ABSTRACT FROM AUTHOR]

Chemical solidification based on cement is one of the most widely used methods to treat marine dredged silt (DS) with very poor engineering properties. This study investigated the strength and microstructure of cement-solidified salt-rich dredged silt (CSDS) modified by nanoparticles. The unconfined compressive strength (UCS) test showed that the UCS of CSDS containing 9% NaCl was obviously lower than that without NaCl. Furthermore, the detrimental effect of chloride salt on the UCS increased with its content significantly. The nano-SiO2 (NS) used as cement additives can significantly improve the UCS of CSDS and adding 8% NS can reduce cement usage by at least 40%. Compared with NS, the nano-MgO (NM) mainly improved the early UCS of CSDS within 7 days. The needle-like Friedel's salt (the reaction product of chloridion with cement) and lamellar brucite (expansive mineral) were clearly detected by the X-ray diffraction test. The calcium silicate hydrate and magnesium silicate hydrate mainly contributed to construct the skeleton, which was confirmed by the scanning electron microscopy images. The NS and NM with high reactivity can be used as effective cement additives to overcome the negative effect of chloride salt, so as to increase the strength of CSDS. [ABSTRACT FROM AUTHOR]

Objective: Decompression surgery in patients with spinal cord injury (SCI) has a neuroprotective effect by alleviating secondary injury and improving neurological outcomes. N-Acetylcysteine (NAC), a drug approved by the United States Food and Drug Administration, has been shown to play neuroprotective roles via attenuation of apoptosis and inflammation. The purpose of the present study was to investigate the effects of early or late decompression surgery in combination with NAC administration on acute SCI, as well as investigate the underlying mechanisms of its actions. Methods: In this study, an acute SCI model was established in rats. The rats were treated with decompression surgery 24/48 h post-SCI in combination with or without NAC. Results: The results showed that decompression surgery in combination with NAC lead to a better outcome than decompression alone, as demonstrated by the higher Basso, Beattie, and Bresnahan scores. Histopathological examination demonstrated that early decompression surgery in combination with NAC exerted the best therapeutic effect on spinal cord recovery, which was further confirmed by the extent of inflammation and apoptosis. Additionally, we found that NAC might compensate for a lack of late surgery. Conclusions: Collectively, early decompression surgery and NAC could be a promising combination for the treatment of acute SCI, and its therapeutic effects may be associated with the regulation of inflammation and apoptosis. [ABSTRACT FROM AUTHOR]

The unconfined compressive strength (UCS) of sludge with different consistency limits solidified by cement was investigated. The results showed that under the condition of constant initial water content, a higher liquid index of soil resulted in higher UCS. A novel strength-evaluation model based on the ratio of the liquid index to the cement content was developed, and the prediction deviation of the model was within 30%. The influence mechanism of the consistency limit of sludge on the cement solidification was revealed by scanning electron microscopy, mercury intrusion porosimetry, X-ray diffractometer and thermogravimetric analysis. For the cement-solidified dredged sludge (CDS) with a lower liquid index, a large amount of hydrate was interlaced with each other and wrapped soil particles, promoting the formation of a dense structure. For the CDS with a higher liquid index, hydrates such as C-S-H and ettringite challenged each other to play the role of "cementing particles" and "filling pores", resulting in the formation of the porous structure. The mineralogical analyses confirmed that more C-S-H gels and ettringites were generated in the CDS with a lower liquid index, but less calcite was formed due to its denser structure. In engineering applications, reducing the liquid index by adjusting the consistency limit can improve the strength performance of CDS. [ABSTRACT FROM AUTHOR]

Social status is seen as an important topic in management and organisational sciences. Despite the extensive research on the upper echelons of management, little is known about the influence of social status on R&D investment decisions. We examine the effects of pre-entrepreneurial social status on R&D investments based on imprinting theory, using 2000–2014 data for 20,177 Chinese private small- and medium-sized enterprises. The results reveal that entrepreneurs with an upper and lower social status show a stronger tendency to make R&D investments than middle-class counterparts. The findings are robust to various sensitivity tests. In addition, we explore the moderating influences of political capital and institutional environment, both of which enhance the positive relationship between social status and R&D investments. Our study finds that social status has a lasting and varying impact on decisions to engage in innovation behaviours. The findings contribute to research on Chinese firm innovation and offer key implications for social status and imprinting theorising. [ABSTRACT FROM AUTHOR]

Cement-stabilized dredged sediment (CDS) when used as a new road construction material cannot only solve the problem of abandoned sediment disposal, but also effectively save natural soil resources. This study aimed to evaluate the strength and permeability of CDS and establish corresponding prediction models from the perspective of a stabilization mechanism. The soil–water composition and pore size distribution were investigated by the nuclear magnetic resonance (NMR) technique. The results demonstrated that more liquid pore water inside the CDS specimen transformed into combined water with cement hydration. The amount of combined water, which essentially characterized the hydration process of cement, presented a linear relationship with log (t). The cementation and filling action of hydrates resulted in the transformation of large pores into smaller ones, hence the optimal pore size decreased with an increasing curing period and cement content. The stress–strain curves and hydraulic conductivity were determined based on unconfined compression and flexible wall penetration tests, respectively. The unconfined compressive strength increased exponentially with the amount of combined water, and the functional correlations of hydraulic conductivity and micropore parameters were established. The reliability of the NMR technique as a new method to study the microscopic evolution mechanism of the strength and permeability of CDS was further verified by scanning electron microscopy and mercury intrusion porosimetry tests. [ABSTRACT FROM AUTHOR]

This study examines the impact of economic downturns on leisure life, using the Chinese General Social Survey data from 2010 to 2015. The results show that economic downturns significantly decrease individuals' time allocated to leisure activities. Specifically, participation in educational activities increases during economic downturns, while participation in social interaction and entertainment does not change. We also find that economic downturns significantly reduce the average frequency of individuals' participation in active entertainment activities (e.g. reading, participating in cultural activities, listening to music at home, participating in physical exercise, watching live sports games, and doing handwork), but do not significantly affect the average frequency of individuals' participation in passive entertainment activities (e.g. watching TV or DVD at home, watching movies in a cinema, shopping, gathering with relatives, gathering with friends, and surfing the Internet). [ABSTRACT FROM AUTHOR]

Hot dry rock (HDR) geothermal energy has many advantages, such as being renewable, clean, widely distributed, and without time and weather limitations. Hydraulic fracturing is usually needed for the exploitation of HDR geothermal energy. It has many hidden faults in the reservoir/caprock sequences. Injecting fluid into underground formations during hydraulic fracturing often induces fault slip and leads to earthquakes. Therefore, to well understand the induced fault slip and earthquakes is important for the applications and development of HDR geothermal exploitation. In this study, we investigated the hazardous injection area of the induced earthquakes during hydraulic fracturing. The study was based on a hydraulic fracturing test in Qiabuqia geothermal field in China. According to the field, a fault-surrounding rock-fracturing region system was developed to study the influences of fluid injection on the stability of the specific fault. A total of 60 hydraulic fracturing regions and 180 numerical experiments were designed. The results revealed that the hazardous injection regions that threaten the fault's stability were near to the fault and concentrated on the following four areas: (a) above the top of the fault in underlying strata; (b) above the top of the hanging wall of the fault in underlying strata; (c) near to the fault planes in both footwall and hanging wall; (d) at the bottom of the footwall of the fault in underlying strata. The hazardous injection area can be controlled effectively by adjusting the injection pressure. [ABSTRACT FROM AUTHOR]

Hot dry rock (HDR) geothermal energy has become promising resources for relieving the energy crisis and global warming. The exploitation of HDR geothermal energy usually needs an enhanced geothermal system (EGS) with artificial fracture networks by hydraulic fracturing. Fault reactivation and seismicity induced by hydraulic fracturing raise a great challenge. In this paper, we investigated the characteristics of fault slip and seismicity by numerical simulation. The study was based on a hydraulic fracturing project in the geothermal field of Yishu fault zone in China. It revealed that fluid injection during hydraulic fracturing can cause the faults that exist beyond the fluid-pressurized region to slip and can even induce large seismic event. It was easier to cause felt earthquakes when hydraulic fracturing was carried out in different layers simultaneously. We also examined the effects of the location, permeability, and area of the fracturing region on fault slip and magnitude of the resulting events. The results of the study can provide some useful references for establishing HDR EGS in Yishu fault zone. [ABSTRACT FROM AUTHOR]

Using a large sample of 10,668 small‐ and medium‐sized private Chinese enterprises over the 2006–2014 period, this study investigates the effect of the social class background of entrepreneurs on firm corporate environmental responsibility (CER) activities. The research question is developed using the concepts of imprinting theory. We measure the social class background of entrepreneurs as the level of occupational prestige held by the individual prior to starting a business. Results show that entrepreneurs drawn from the upper and lower social classes show a preference for the pursuit of environmental governance investment strategies. Moderating influences based on political capital and institutional environment are also explored. The theory and findings highlight that the social class background of entrepreneurs has a lasting and varying impact on the CER activities of a firm. The results are robust to a variety of sensitivity tests. The study extends our understanding of how and why enterprise CER behaviour varies, particularly in the context of Chinese private firms, and offers important implications for the task of sustainable development by enterprises. [ABSTRACT FROM AUTHOR]

At underground fluid injection sites with natural faults, understanding how to avoid the subsequent fault reactivation and induced seismicity plays a crucial role in the success of subsurface anthropogenic activities. In this work, with the objective of avoiding risky faults in site selection in the Shengli Oilfield, we investigated the faults that are usually encountered in the target demonstration zone; based on the geophysical observations of fault structures, we designed different fault tectonic scenarios to investigate the different penetration patterns of faults. We used the finite element-based numerical method to assess the influence of the effective lateral and vertical reservoir transmissivity in each fault penetration pattern. Our results indicate that when a permeable fault intersects into the target reservoir, it presents both barrier effect to reservoir transmissivity within the target reservoir and hydraulic connection between reservoirs. The effective lateral reservoir transmissivity is dominated by the barrier effect of the fault, and the effective vertical reservoir transmissivity is dominated by the hydraulic connection between reservoirs. Relatively impermeable faults with less contact with the target aquifer make higher effective lateral reservoir transmissivity and lower effective vertical reservoir transmissivity, which would mitigate the risk of caprock failure and the magnitude of the induced seismicity. [ABSTRACT FROM AUTHOR]

The abandonment process is a highly important part of project management for CO2 capture and storage (CCS) projects. For the first full procedure of a CO2 geological storage demonstration project in a deep saline aquifer in China, this paper describes the abandonment process of a CO2 operating well. The key idea that we advance is that wellbore integrity tests should be conducted before the abandonment, and consideration must be given to the CO2 corrosion resistance materials, the design method of sealing the plugs, monitoring tests (such as pressure tests), and the use of a long-term monitoring system (such as the original pressure test and a packer isolation test every year). According to Chinese regulations and related experience in the oil and gas industry, the factors chosen are the pressure factor, cap rock, potable water layer, unexploited resource layer, suspected leak path, perforated zone, productive hydrocarbon zone without perforation, and water-injection and waste-water treatment layers. We intuitively evaluate and quantify the plugged zones using the modified analytical hierarchy process (M-AHP) method to determine the positions of the plugs. Next, referring to the Chinese regulations on Well abandonment and inactive well practices, the last plug located in the Quaternary strata is compulsorily ensured, and the length of all plugs is also determined. Finally, the paper summarizes the methodology and presents suggestions for the abandonment process of the Shenhua CCS project. © 2017 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The symmetric autocorrelation function (SAF) has a huge computational complexity, which may limit the practical application of SAF‐based scaled inverse Fourier transform (SCIFT). Taking the relationship between SAF and summation into consideration, a frequency‐domain method is proposed for the fast implementation of the SCIFT, and the energy integration performance remains unchanged. Mathematic analysis and numerical simulations are provided to illustrate the efficiency of this method. [ABSTRACT FROM AUTHOR]

The multivariate range function of the high-speed maneuvering target induces modulations on both the envelop and phase, i.e., the range cell migration (RCM) and Doppler frequency migration (DFM) which degrade the long-time coherent integration used for detection and localization. To solve this problem, many long-time coherent integration methods have been proposed. Based on mechanisms of typical methods, this paper names two signal processing modes, i.e., processing unification (PU) mode and processing separation (PS) mode, and presents their general forms. Thereafter, based on the principle of the PS mode, a novel long-time coherent integration method, known as the generalized dechirp-keystone transform (GDKT), is proposed for radar high-speed maneuvering target detection and localization. The computational cost, energy integration, peak-to-sidelobe level (PSL), resolution, and anti-noise performance of the GDKT are analyzed and compared with those of the maximum likelihood estimation (MLE) method and keystone transform-dechirp (KTD) method. With mathematical analyses and numerical simulations, we validate two main superiorities of the GDKT, including (1) the statistically optimal anti-noise performance, and (2) the low computational cost. The real radar data is also used to validate the GDKT. It is worthwhile noting that, based on closed analytical formulae of the MLE method, KTD method, and GDKT, several doubts in radar high-speed maneuvering target detection and localization are mathematically interpreted, such as the blind speed sidelobe (BSSL) and the relationship between the PU and PS modes. [ABSTRACT FROM AUTHOR]

Background and Purpose: Predicting tumour response would be useful for selecting patients with locally advanced rectal cancer (LARC) for organ preservation strategies. We aimed to develop and validate a prediction model for T downstaging (ypT0-2) in LARC patients after neoadjuvant chemoradiotherapy and to identify those who may benefit from consolidation chemotherapy., Materials and Methods: cT3-4 LARC patients at three tertiary medical centers from January 2012 to January 2019 were retrospectively included, while a prospective cohort was recruited from June 2021 to March 2022. Eight filter (principal component analysis, least absolute shrinkage and selection operator, partial least-squares discriminant analysis, random forest)-classifier (support vector machine, logistic regression) models were established to select radiomic features. A nomogram combining radiomics and significant clinical features was developed and validated by calibration curve and decision curve analysis. Interaction test was conducted to investigate the consolidation chemotherapy benefits., Results: A total of 634 patients were included (426 in training cohort, 174 in testing cohort and 34 in prospective cohort). A radiomic prediction model using partial least-squares discriminant analysis and a support vector machine showed the best performance (AUC: 0.832 [training]; 0.763 [testing]). A nomogram combining radiomics and clinical features showed significantly better prognostic performance (AUC: 0.842 [training]; 0.809 [testing]) than the radiomic model. The model was also tested in the prospective cohort with AUC 0.727. High-probability group (score > 81.82) may have potential benefits from ≥ 4 cycles consolidation chemotherapy (OR: 4.173, 95 % CI: 0.953-18.276, p = 0.058, p interaction  = 0.021)., Conclusion: We identified and validated a model based on multicenter pre-treatment radiomics to predict ypT0-2 in cT3-4 LARC patients, which may facilitate individualised treatment decision-making for organ-preservation strategies and consolidation chemotherapy., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2022 The Authors.)

We have developed a simple and efficient approach for the synthesis of chemically converted graphene sheets via aryne cycloaddition under mild reaction conditions. The resulting highly functionalized and thermally stable aryne-modified graphene sheets can be well dispersed in various solvents.