Fluid seepage into rock pores not only generates poroelastic stress but also exerts seepage force on the rock skeleton. However, since the mechanism of the effect of seepage force on the stress field ...around the wellbore is not clear, conventional methods calculate the stress field only taking into account the poroelastic stress without the coupled effects of seepage force and rock deformation. Based on the theory of porous medium, this paper presents an analytical solution of the circumferential stress field formed by the seepage force around the wellbore and introduces the solution into traditional calculation models to overcome these issues. The numerical study by MATLAB
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was used to simulate the stress field around the wellbore. Numerical simulation results show that the seepage force generates a circumferential tensile action and reduces in-situ circumferential compressive stress around the wellbore. Under the effect of seepage force, the effective circumferential stress around the wellbore becomes smaller. When considering seepage force, effective circumferential stress along the θ = 0 direction at the wellbore wall is reduced by about 32% compared with traditional numerical results. In addition, the circumferential stress field formed by the seepage force increases the possibility of rock failure at the well wall. The analytical results indicate that the seepage force should be considered in the stress field calculation around the wellbore, especially in reservoirs with low permeability.
The interaction between hydraulic fractures and natural fractures have significant influence on the geometry of hydraulic fracture network in fractured reservoirs. In previous mathematical model, the ...interaction relationship of non-intersecting fractures in propagation process were often been ignored, which resulted the inaccuracy of simulation results. Based on boundary element method and rock failure criterion, we established mathematical model to study the fracture interaction mechanisms and fracture network morphology under induced stress. Simulation results show that hydraulic fracture with incipient propagation superiority are more likely to have a rapid propagation and inhibit the continuous initiation of surrounding micro fractures. Under proper conditions, single natural fracture can deflect the propagation direction of hydraulic fracture by at least 22°. Firstly proposed that shielding and transmission efforts of induced stress by natural fracture are the fundamental reason that affect the complexity of fracture network, which can reduce the normal stress around natural fracture by 50% in this paper. When the inclination Angle of natural fractures is between 45 and 70°, it is more favorable to form complex fracture network. This study is of great significance for the control of fracture network morphology and the further improvement of fracturing effect.
•Established a propagation model considering the interference between non-contact fractures.•The asymmetrical distribution of stress is likely to cause the coalescence of fracture.•The tip of hydraulic fracture will gradually deflect as it approaches natural fracture.•Natural fracture have both shielding and transferring effects on induced stress.•Simulated the plane fracture network morphology influenced by different parameters.
Vivianite widely existed in digested sludge and activated sludge as a potential phosphate resource recovered from wastewater treatment plants (WWTPs). As an important product of extracellular ...electron transfer (EET) and biological iron reduction, the production of vivianite can be enhanced by conductive materials. Carbon nanotubes (CNTs) with excellent electrical conductivity have been reported to promote electron transfer, which was applied in wastewater treatment to accelerate the degradation of the contaminants. However, the impact of CNTs on vivianite formation was barely reported. In this study, the iron reduction, vivianite recovery, and the biotoxicity of CNTs were investigated in order to determine the influence of CNTs towards the vivianite production. The enhancement of vivianite production after CNTs adding reached up to 17 % by promoting the electron transfer between dissimilative iron-reducing bacteria (DIRB) and Fe(III). However, at the initial stage (0–24 h), Fe(III) reduction efficiency decreased by 81 % after inoculating with sewage sludge, which was attributed to CNTs destroying of the cell membrane (as indicated by SEM, CLSM and AFM analysis). The biotoxicity of CNTs stimulated DIRB to secret extracellular polymeric substances (EPS) and form bio-flocs to resist the physical puncture. After 48 h, the proportion of living DIRB in 1000 mg/L CNTs batch increased to 98 %, which was 79 % higher than 12 h. As a result, the vivianite recovery of raw sewage with 1000 mg/L CNTs increased to 44 ± 1 %, which was 33 % higher than that in the CNT-0.
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•CNTs enhance the bioreduction of Fe3+ and the efficiency of vivianite recovery.•CNTs cause the bacteria dead by the cell membrane collapse and fragments.•CNTs stimulate the dissimilatory iron reducing bacteria to secret polysaccharides.•CNTs enhance the electron transport between the bacteria and Fe(III).
Vivianite as a significant secondary mineral of dissimilatory iron reduction (DIR) exhibits marvelous potential to solve eutrophication as well as phosphorus shortage. Geobattery represents by ...natural organic matters (NOM) with rich functional groups influences bioreduction of natural iron mineral. Activated carbon (AC) which contains abundant functional groups is expected to serve as geobattery, but there remains insufficient understanding on its geobattery mechanism and how it benefits the vivianite formation. In this study, the charging and discharging cycle of “geobattery” AC enhanced extracellular electron transfer (EET) and vivianite recovery was demonstrated. Feeding with ferric citrate, AC addition increased vivianite formation efficiency by 141 %. The enhancement was attributed to the electron shuttle capacity of storage battery AC, which was contributed by the redox cycle between CO and O–H. Feeding with iron oxides, huge gap of redox potential between AC and Fe(III) minerals broke through the reduction energy barrier. Therefore the iron reduction efficiency of four Fe(III) minerals was accelerated to the same high level around 80 %, and the vivianite formation efficiency were increased by 104 %–256 % in pure culture batches. Except acting as storage battery, AC as a dry cell contributed 80 % to the whole enhancement towards iron reduction, in which O–H groups were the dominant driver. Due to the rechargeable nature and considerable electron exchange capacity, AC served as geobattery playing the role of both storage battery and dry cell on electron storaging and transferring to influence biogeochemical Fe cycle and vivianite recovery.
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•AC acted as geobattery playing the role of both storage battery and dry cell.•AC enhanced vivianite formation from Fe3+ by 141 % in sewage biomass batches.•·C=O and O–H equipped AC with electron shuttle capacity to serve as storage battery.•Redox potential gap between AC and Fe oxides broke the reduction energy barrier.•Chemical iron reduction by dry cell AC contributed 80 % to the enhancement.
While foreign pundits have alternatively blamed and praised the Chinese government's handling of the COVID-19 virus, little is known about how citizens within China understand this performance. This ...article considers how satisfied Chinese citizens are with their government's performance during the COVID-19 pandemic. It first considers the impact of authoritarian control, political culture, and/or actual government performance on citizen satisfaction. Then, it tests the consequences of satisfaction and specifically whether citizen satisfaction leads to greater trust. Analyzing data from the first post-COVID survey of its kind (n = 19,816) conducted from April 22 to 28 April 2020, the authors find that Chinese citizens have an overall high level of satisfaction, but that this satisfaction drops with each lower level of government. Further, authoritarian control, political culture, and awareness of government performance all contribute to citizen satisfaction and this in turn, has enhanced public support for the Chinese government.
Bipolar disorder and unipolar depressive disorder（UD） may be different in brain structure. In the present study,we performed voxel-based morphometry（VBM） to quantify the grey matter volumes in 23 ...patients with bipolar I depressive disorder（BP1） and 23 patients with UD,and 23 age-,gender-,and educationmatched healthy controls（HCs） using magnetic resonance imaging. We found that compared with the HC and UD groups,the BP1 group showed reduced grey matter volumes in the right inferior frontal gyrus and middle cingulate gyrus,while the UD group showed reduced volume in the right inferior frontal gyrus compared to HCs. In addition,correlation analyses revealed that the grey matter volumes of these regions were negatively correlated with the Hamilton depression rating scores. Taken together,the results of our study suggest that decreased grey matter volume of the right inferior frontal gyrus is a common abnormality in BP1 and UD,and decreasedgrey matter volume in the right middle cingulate gyrus may be specifi c to BP1.
Against the backdrop of global warming has become the main climate issue at present. Not only climate change itself, but some phenomena which occur together with it also has the worth of studying in ...order to deal with the current global warming problem that human beings are facing. To be specific, the Sea Level Rise caused by carbon dioxide emission. This paper will discuss the evidence from sea level which can prove how serious the impact of CO2 emission on climate change. According to the analysis, CO2 emission can enhance the tendency of the Sea Level Rise (SLR) and this trend will not stop at present even if the whole world stops to emit greenhouse gases including carbon dioxide, but will continue to affect people’s daily life in a long period of time. With this in mind, the public should be more alert for the reducing of emission of greenhouse gases and the adaption of Sea Level Rise.
Inferring causal relationships in observational time series data is an important task when interventions cannot be performed. Granger causality is a popular framework to infer potential causal ...mechanisms between different time series. The original definition of Granger causality is restricted to linear processes and leads to spurious conclusions in the presence of a latent confounder. To this end, we propose a deep learning model to detect non-linear Granger causality and directly account for latent confounders. Our approach consists of two components: 1. feed-forward neural networks to infer representations of the confounder from available proxy variables; 2. recurrent neural networks to construct forecasting models for the target time series with and without additional information. Conditioned on the proxy, if the target time series can be better predicted without extra information, our model concludes that the confounder alone Granger causes the target, and vice versa. To assess the proposed approach, we tested the model on both synthetic and real world time series with known causal relationships; results showed the superiority of our model relative to existing benchmarks.
•Granger causality tests in the presence of confounding can lead to biased results.•A neural network Granger causality test is proposed to model nonlinear dynamics.•Neural networks can infer representations of confounders from available proxies.
Incremental learning with concept drift has often been tackled by ensemble methods, where models built in the past can be retrained to attain new models for the current data. Two design questions ...need to be addressed in developing ensemble methods for incremental learning with concept drift, i.e., which historical (i.e., previously trained) models should be preserved and how to utilize them. A novel ensemble learning method, namely, Diversity and Transfer-based Ensemble Learning (DTEL), is proposed in this paper. Given newly arrived data, DTEL uses each preserved historical model as an initial model and further trains it with the new data via transfer learning. Furthermore, DTEL preserves a diverse set of historical models, rather than a set of historical models that are merely accurate in terms of classification accuracy. Empirical studies on 15 synthetic data streams and 5 real-world data streams (all with concept drifts) demonstrate that DTEL can handle concept drift more effectively than 4 other state-of-the-art methods.
Emerging non-volatile memory technologies are driving the next generation of storage systems and durable data structures. Among them, many hash table proposals employ NVM as the storage layer for ...both fast access and efficient persistence. Most of them are based on the assumption that NVM has cacheline access granularity, poor write endurance, DRAM-comparable read latency and relatively higher write latency. However, a commercial non-volatile memory product, namely Intel Optane DC Persistent Memory (Optane), has some interesting features that are different from previous assumptions, such as 256-byte OptaneLine access granularity, higher read latency than DRAM and DRAM-comparable write latency, limited read/write bandwidth, and hardware-layer wear-leveling. Confronted with the new challenges brought by Optane, we propose Rewo-Hash, a novel read-efficient and write-optimized persistent hash table. Our incremental contributions over our previous work are summarized as follows. First, provide a more detailed technical description for cached table-inclined read mechanism and log-free atomic write mechanism. Second, we devise a consistent shadowing synchronization scheme to mask the data synchronization overhead. Third, we propose a non-blocking lightweight resizing scheme and elaborate the crash recovery mechanism. Fourth, we conduct a comprehensive analysis of the implications of Intel ceasing the production of Optane, and provide a forward-looking perspective on the future of non-volatile memory. The experimental results show that compared with state-of-the-art NVM-Optimized hash tables, Rewo-Hash gains remarkable performance improvement.
•A cached table-inclined read mechanism speeds up search requests.•A log-free atomic write mechanism minimizes overhead for write requests.•An efficient shadowing synchronization mechanism enables fast data synchronization.•A non-blocking lightweight resizing scheme reduces table resizing overhead.•Rewo-Hash outperforms compared designs by 1.8x–15.1x for concurrent throughput.
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