211 research outputs found

    A Dual-Porosity-Stokes Model and Finite Element Method for Coupling Dual-Porosity Flow and Free Flow

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    In this paper, we propose and numerically solve a new model considering confined flow in dual-porosity media coupled with free flow in embedded macrofractures and conduits. Such situation arises, for example, for fluid flows in hydraulic fractured tight/shale oil/gas reservoirs. The flow in dual-porosity media, which consists of both matrix and microfractures, is described by a dual-porosity model. And the flow in the macrofractures and conduits is governed by the Stokes equation. Then the two models are coupled through four physically valid interface conditions on the interface between dual-porosity media and macrofractures/conduits, which play a key role in a physically faithful simulation with high accuracy. All the four interface conditions are constructed based on fundamental properties of the traditional dual-porosity model and the well-known Stokes-Darcy model. The weak formulation is derived for the proposed model, and the well-posedness of the model is analyzed. A finite element semidiscretization in space is presented based on the weak formulation, and four different schemes are then utilized for the full discretization. The convergence of the full discretization with the backward Euler scheme is analyzed. Four numerical experiments are presented to validate the proposed model and demonstrate the features of both the model and the numerical method, such as the optimal convergence rate of the numerical solution, the detail flow characteristics around macrofractures and conduits, and the applicability to the real world problems

    Study on Apparent Permeability Model for Gas Transport in Shale Inorganic Nanopores

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    Inorganic nanopores occurring in the shale matrix have strong hydrophilicity and irreducible water (IW) film can be formed on the inner surface of the pores making gas flow mechanisms in the pores more complex. In this paper, the existence of irreducible water (IW) in inorganic pores is considered, and, based on the Knudsen number (K (Formula presented.)) correction in shale pores, a shale gas apparent permeability model of inorganic nano-pores is established. The effect of the K (Formula presented.) correction on the apparent permeability, the ratio of flow with pore radius and the effect of IW on the apparent permeability are assessed. The main conclusions are as follows: (1) at low pressure (less than 10 MPa) and for medium pore size (pore radius range of 10 nm–60 nm), the effect of the K (Formula presented.) correction should be considered; (2) considering the effect of the K (Formula presented.) correction, bulk phase transport replaces surface diffusion more slowly; considering the existence of IW, bulk phase transport replaces surface diffusion more slowly; (3) with increase in pressure, the IW effect on gas apparent permeability decreases. Under low pressure, the IW, where pore size is small, promotes fluid flow, while the IW in the large pores hinders fluid flow. In conditions of ultra-high pressure, the IW promotes gas flow

    Molecular Packing Control Enables Excellent Performance and Mechanical Property of Blade-Cast All-Polymer Solar Cells

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    All-polymer solar cells (all-PSCs) are the most promising power generators for flexible and portable devices due to excellent morphology stability and outstanding mechanical property. Previous work indicates high crystallinity is beneficial to device performance but detrimental to mechanical property, therefore identifying the optimized ratio between crystalline and amorphous domains becomes important. In this work, we demonstrated highly efficient and mechanically robust all-PSCs by blade-coating technology in ambient environment based on PTzBI:N2200 system. By controlling the aggregation in solution state and ultrafast film formation process, a weakly ordered molecular packing morphology as well as small phase separation is obtained, which leads to not only the good photovoltaic performance (8.36%-one of the best blade-cast device in air) but also prominent mechanical characteristic. The controlled film shows a remarkable elongation with the crack onset strain of 15.6%, which is the highest result in organic solar cells without adding elastomers. These observations indicate the great promise of the developed all-PSCs for practical applications toward large-area processing technology

    Analysis and Research on the Characteristics of COVID-19 Epidemic in Urban Village and Its Prevention and Control Strategies in Primary Care Institutions

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    BackgroundFor a period of time, the outbreak of the COVID-19 outbreak in many urban villages in our country had caused concern. The dense and complex population structure of urban villages, with their inter-regional mobility, posed a challenge to the prevention and control of the epidemic.ObjectiveUrban village areasare more prone to regional outbreaks of infectious diseases because of their spatial environment, demographic characteristics, cross-regional mobility and the characteristics of residents' medical treatment behavior. The purpose of this study was tounderstand the characteristics of the COVID-19 epidemic situation in urban villages and the current situation and difficulties of primary care institutions in carrying out COVID-19 epidemic prevention and control measures, in order to provide references for primary care institutions to deal with normalized prevention and control, social dynamic clearing work and future infectious disease prevention and control.MethodsBy using public opinion analysis, literature retrieval, online interviews with epidemic prevention and control personnel and experts in urban village, the epidemic situation, prevention and control status of urban village were summarized, and the existing weak links and important loopholes were analyzed.ResultsBased on the relevant information, a total of six points of concern were extracted: (1) The number of mapping and screening objects was large, which was the focus and difficulty of epidemic prevention and control work in urban villages. (2) There was not strict closed-loop management lead to virus carriers who were not timely controlled, which caused a risk of spreading the epidemic. (3) The prevention and control of nosocomial infection in primary care institutions was not in place. (4) There were loopholes in the inspection of close contacts in the principle of territorial management; close contacts who did not live and work in the same administrative area but only screened in their living places, which may lead to the spread of the epidemic in workplaces where secondary close contacts may be at risk of infection were not screened in a timely manner. (5) Overload had become the norm, highlighting the large gap in primary health care manpower. (6) During the normalization of epidemic prevention and control, residents were paralyzed and careless, and the phenomenon of not wearing masks in public places and crowd gathering was common. Health education still needs to be strengthened and emphasized that residents were the first responsible for their own health.ConclusionPrimary care providers played an important role in the prevention and control of COVID-19 in urban village by undertaking community management, outpatient treatment, public health services, health education, vaccination, quarantine hotel stationing, joint prevention and control, etc. It was recommended that additional fever sentinel clinics be set up for early detection and isolation to avoid further spread of the epidemic, rental houses be requisitioned to meet the demand for isolated medical observation, primary care institutions be strengthened for hospitalization and prevention, green relief channels be opened to protect special groups from medical treatment, volunteers be organized to reinforce primary care institutions, and health education emphasized that residents were the first to be responsible for maintaining their own health and raised personal awareness of the risk of COVID-19 prevention and control

    The Orbitofrontal Cortex Gray Matter Is Associated With the Interaction Between Insomnia and Depression

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    Insomnia and depression are highly comorbid symptoms in both primary insomnia (PI) and major depressive disorder (MDD). In the current study, we aimed at exploring both the homogeneous and heterogeneous brain structure alteration in PI and MDD patients. Sixty-five MDD patients and 67 matched PI patients were recruited and underwent a structural MRI scan. The subjects were sub-divided into four groups, namely MDD patients with higher or lower insomnia, and PI patients with higher or lower severe depression. A general linear model was employed to explore the changes in cortical thickness and volume as a result of depression or insomnia, and their interaction. In addition, partial correlation analysis was conducted to detect the clinical significance of the altered brain structural regions. A main effect of depression on cortical thickness was seen in the superior parietal lobe, middle cingulate cortex, and parahippocampal gyrus, while a main effect of insomnia on cortical thickness was found in the posterior cingulate cortex. Importantly, the interaction between depression and insomnia was associated with decreased gray matter volume in the right orbitofrontal cortex, i.e., patients with co-occurring depression and insomnia showed smaller brain volume in the right orbitofrontal cortex when compared to patients with lower insomnia/depression. These findings highlighted the role of the orbitofrontal cortex in the neuropathology of the comorbidity of insomnia and depression. Our findings provide new insights into the understanding of the brain mechanism underlying comorbidity of insomnia and depression

    Tubeless video-assisted thoracic surgery for pulmonary ground-glass nodules: expert consensus and protocol (Guangzhou)

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    Neutrino Physics with JUNO

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    The Jiangmen Underground Neutrino Observatory (JUNO), a 20 kton multi-purposeunderground liquid scintillator detector, was proposed with the determinationof the neutrino mass hierarchy as a primary physics goal. It is also capable ofobserving neutrinos from terrestrial and extra-terrestrial sources, includingsupernova burst neutrinos, diffuse supernova neutrino background, geoneutrinos,atmospheric neutrinos, solar neutrinos, as well as exotic searches such asnucleon decays, dark matter, sterile neutrinos, etc. We present the physicsmotivations and the anticipated performance of the JUNO detector for variousproposed measurements. By detecting reactor antineutrinos from two power plantsat 53-km distance, JUNO will determine the neutrino mass hierarchy at a 3-4sigma significance with six years of running. The measurement of antineutrinospectrum will also lead to the precise determination of three out of the sixoscillation parameters to an accuracy of better than 1\%. Neutrino burst from atypical core-collapse supernova at 10 kpc would lead to ~5000inverse-beta-decay events and ~2000 all-flavor neutrino-proton elasticscattering events in JUNO. Detection of DSNB would provide valuable informationon the cosmic star-formation rate and the average core-collapsed neutrinoenergy spectrum. Geo-neutrinos can be detected in JUNO with a rate of ~400events per year, significantly improving the statistics of existing geoneutrinosamples. The JUNO detector is sensitive to several exotic searches, e.g. protondecay via the pK++νˉp\to K^++\bar\nu decay channel. The JUNO detector will providea unique facility to address many outstanding crucial questions in particle andastrophysics. It holds the great potential for further advancing our quest tounderstanding the fundamental properties of neutrinos, one of the buildingblocks of our Universe

    Potential of Core-Collapse Supernova Neutrino Detection at JUNO

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    JUNO is an underground neutrino observatory under construction in Jiangmen, China. It uses 20kton liquid scintillator as target, which enables it to detect supernova burst neutrinos of a large statistics for the next galactic core-collapse supernova (CCSN) and also pre-supernova neutrinos from the nearby CCSN progenitors. All flavors of supernova burst neutrinos can be detected by JUNO via several interaction channels, including inverse beta decay, elastic scattering on electron and proton, interactions on C12 nuclei, etc. This retains the possibility for JUNO to reconstruct the energy spectra of supernova burst neutrinos of all flavors. The real time monitoring systems based on FPGA and DAQ are under development in JUNO, which allow prompt alert and trigger-less data acquisition of CCSN events. The alert performances of both monitoring systems have been thoroughly studied using simulations. Moreover, once a CCSN is tagged, the system can give fast characterizations, such as directionality and light curve
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