The Qiangtang Basin of the Tibetan Plateau,located in the eastern Tethys tectonic domain,is the largest new marine petroliferous region for exploration in China.The scientific drilling project consisting primarily of ...The Qiangtang Basin of the Tibetan Plateau,located in the eastern Tethys tectonic domain,is the largest new marine petroliferous region for exploration in China.The scientific drilling project consisting primarily of well QK-1 and its supporting shallow boreholes for geological surveys(also referred to as the Project)completed in recent years contributes to a series of new discoveries and insights into the oil and gas preservation conditions and source rock evaluation of the Qiangtang Basin.These findings differ from previous views that the Qiangtang Basin has poor oil and gas preservation conditions and lacks high-quality source rocks.As revealed by well QK-1 and its supporting shallow boreholes in the Project,the Qiangtang Basin hosts two sets of high-quality regional seals,namely an anhydrite layer in the Quemo Co Formation and the gypsum-bearing mudstones in the Xiali Formation.Moreover,the Qiangtang Basin has favorable oil and gas preservation conditions,as verified by the comprehensive study of the sealing capacity of seals,basin structure,tectonic uplift,magmatic activity,and groundwater motion.Furthermore,the shallow boreholes have also revealed that the Qiangtang Basin has high-quality hydrocarbon source rocks in the Upper Triassic Bagong Formation,which are thick and widely distributed according to the geological and geophysical data.In addition,the petroleum geological conditions,such as the type,abundance,and thermal evolution of organic matter,indicate that the Qiangtang Basin has great hydrocarbon-generating potential.展开更多
A grain boundary diffusion(GBD)process with Pr_(80-x)Al_(x)Cu_(20)(x=0,10,15,20)low melting point alloys was applied to commercial 42M sintered Nd–Fe–B magnets.The best coercivity enhancement of a diffused magnet wa...A grain boundary diffusion(GBD)process with Pr_(80-x)Al_(x)Cu_(20)(x=0,10,15,20)low melting point alloys was applied to commercial 42M sintered Nd–Fe–B magnets.The best coercivity enhancement of a diffused magnet was for the Pr_(65)Al_(15)Cu_(20)GBD magnet,from 16.38 kOe to 22.38 kOe.Microstructural investigations indicated that increase in the Al content in the diffusion source can form a continuous grain boundary(GB)phase,optimizing the microstructure to enhance the coercivity.The coercivity enhancement is mainly due to the formation of a continuous GB phase to separate the main phase grains.Exchange decoupling between the adjacent main phase grains is enhanced after the GBD process.Meanwhile,the introduction of Al can effectively promote the infiltration of Pr into the magnet,which increases the diffusion rate of rare-earth elements within a certain range.This work provides a feasible method to enhance coercivity and reduce the use of rare-earth resources by partial replacement of rare-earth elements with non-rare-earth elements in the diffusion source.展开更多
Deep and ultra-deep reservoirs have gradually become the primary focus of hydrocarbon exploration as a result of a series of significant discoveries in deep hydrocarbon exploration worldwide.These reservoirs present u...Deep and ultra-deep reservoirs have gradually become the primary focus of hydrocarbon exploration as a result of a series of significant discoveries in deep hydrocarbon exploration worldwide.These reservoirs present unique challenges due to their deep burial depth(4500-8882 m),low matrix permeability,complex crustal stress conditions,high temperature and pressure(HTHP,150-200℃,105-155 MPa),coupled with high salinity of formation water.Consequently,the costs associated with their exploitation and development are exceptionally high.In deep and ultra-deep reservoirs,hydraulic fracturing is commonly used to achieve high and stable production.During hydraulic fracturing,a substantial volume of fluid is injected into the reservoir.However,statistical analysis reveals that the flowback rate is typically less than 30%,leaving the majority of the fluid trapped within the reservoir.Therefore,hydraulic fracturing in deep reservoirs not only enhances the reservoir permeability by creating artificial fractures but also damages reservoirs due to the fracturing fluids involved.The challenging“three-high”environment of a deep reservoir,characterized by high temperature,high pressure,and high salinity,exacerbates conventional forms of damage,including water sensitivity,retention of fracturing fluids,rock creep,and proppant breakage.In addition,specific damage mechanisms come into play,such as fracturing fluid decomposition at elevated temperatures and proppant diagenetic reactions at HTHP conditions.Presently,the foremost concern in deep oil and gas development lies in effectively assessing the damage inflicted on these reservoirs by hydraulic fracturing,comprehending the underlying mechanisms,and selecting appropriate solutions.It's noteworthy that the majority of existing studies on reservoir damage primarily focus on conventional reservoirs,with limited attention given to deep reservoirs and a lack of systematic summaries.In light of this,our approach entails initially summarizing the current knowledge pertaining to the types of fracturing fluids employed in deep and ultra-deep reservoirs.Subsequently,we delve into a systematic examination of the damage processes and mechanisms caused by fracturing fluids within the context of hydraulic fracturing in deep reservoirs,taking into account the unique reservoir characteristics of high temperature,high pressure,and high in-situ stress.In addition,we provide an overview of research progress related to high-temperature deep reservoir fracturing fluid and the damage of aqueous fracturing fluids to rock matrix,both artificial and natural fractures,and sand-packed fractures.We conclude by offering a summary of current research advancements and future directions,which hold significant potential for facilitating the efficient development of deep oil and gas reservoirs while effectively mitigating reservoir damage.展开更多
After landing in the Utopia Planitia,Tianwen-1 formed the deepest landing crater on Mars,approximately 40 cm deep,exposing precious information about the mechanical properties of Martian soil.We established numerical ...After landing in the Utopia Planitia,Tianwen-1 formed the deepest landing crater on Mars,approximately 40 cm deep,exposing precious information about the mechanical properties of Martian soil.We established numerical models for the plume-surface interaction(PSI)and the crater formation based on Computational Fluid Dynamics(CFD)methods and the erosion model modified from Roberts’Theory.Comparative studies of cases were conducted with different nozzle heights and soil mechanical properties.The increase in cohesion and internal friction angle leads to a decrease in erosion rate and maximum crater depth,with the cohesion having a greater impact.The influence of the nozzle height is not clear,as it interacts with the position of the Shock Diamond to jointly control the erosion process.Furthermore,we categorized the evolution of landing craters into the dispersive and the concentrated erosion modes based on the morphological characteristics.Finally,we estimated the upper limits of the Martian soil’s mechanical properties near Tianwen-1 landing site,with the cohesion ranging from 2612 to 2042 Pa and internal friction angle from 25°to 41°.展开更多
Convolutional neural networks(CNNs) exhibit excellent performance in the areas of image recognition and object detection, which can enhance the intelligence level of spacecraft. However, in aerospace, energetic partic...Convolutional neural networks(CNNs) exhibit excellent performance in the areas of image recognition and object detection, which can enhance the intelligence level of spacecraft. However, in aerospace, energetic particles, such as heavy ions, protons, and alpha particles, can induce single event effects(SEEs) that lead CNNs to malfunction and can significantly impact the reliability of a CNN system. In this paper, the MNIST CNN system was constructed based on a 28 nm systemon-chip(SoC), and then an alpha particle irradiation experiment and fault injection were applied to evaluate the SEE of the CNN system. Various types of soft errors in the CNN system have been detected, and the SEE cross sections have been calculated. Furthermore, the mechanisms behind some soft errors have been explained. This research will provide technical support for the design of radiation-resistant artificial intelligence chips.展开更多
The neutron-induced total cross sections of natural lead have been measured in a wide energy range(0.3 eV-20 MeV)on the back-streaming white neutron beamline(Back-n)at the China Spallation Neutron Source.Neutron energ...The neutron-induced total cross sections of natural lead have been measured in a wide energy range(0.3 eV-20 MeV)on the back-streaming white neutron beamline(Back-n)at the China Spallation Neutron Source.Neutron energy was determined by the neutron total cross-section spectrometer using the time-of-flight technique.A fast multi-cell fission chamber was used as the neutron detector,and a 10-mm-thick high-purity natural lead sample was employed for the neutron transmission measurements.The on-beam background was determined using Co,In,Ag,and Cd filters.The excitation function of ^(nat)Pb(n,tot)reaction below 20 MeV was calculated using the TALYS-1.96 nuclear-reaction modeling program.The present results were compared with previous results,the evaluated data available in the five major evaluated nuclear data libraries(i.e.,ENDF/B-VIII.0,JEFF-3.3,JENDL-5,CENDL-3.2,and BROND-3.1),and the theoretical calculation curve.Good agreement was found between the new results and those of previous experiments and with the theoretical curves in the corresponding region.This measurement obtained the neutron total cross section of natural lead with good accuracy over a wide energy range and added experimental data in the resonance energy range.This provides more reliable experimental data for nuclear engineering design and nuclear data evaluation of lead.展开更多
The grain boundary phase affects the magnetic properties and corrosion resistance of sintered NdFeB magnets.In this work,a small amount of In was added to NdFeB magnets by induction melting to systematically investiga...The grain boundary phase affects the magnetic properties and corrosion resistance of sintered NdFeB magnets.In this work,a small amount of In was added to NdFeB magnets by induction melting to systematically investigate its effect on the evolution of the microstructure,magnetic properties and corrosion resistance of NdFeB magnets.Microstructural analysis illustrated that minor In addition generated more grain boundary phases and an abundant amorphous phase at the triple-junction grain boundary.While the addition of In failed to enhance the magnetic isolation effect between adjacent matrix grains,its incorporation fortuitously elevated the electrochemical potential of the In-containing magnets.Besides,during corrosion,an In-rich precipitate phase formed,hindering the ingress of the corrosive medium into the magnet.Consequently,this significantly bolstered the corrosion resistance of the sintered NdFeB magnets.The phase formation,magnetic properties and corrosion resistance of In-doped NdFeB magnets are detailed in this work,which provides new prospects for the preparation of high-performance sintered NdFeB magnets.展开更多
AIM:To evaluate the application of an intelligent diagnostic model for pterygium.METHODS:For intelligent diagnosis of pterygium,the attention mechanisms—SENet,ECANet,CBAM,and Self-Attention—were fused with the light...AIM:To evaluate the application of an intelligent diagnostic model for pterygium.METHODS:For intelligent diagnosis of pterygium,the attention mechanisms—SENet,ECANet,CBAM,and Self-Attention—were fused with the lightweight MobileNetV2 model structure to construct a tri-classification model.The study used 1220 images of three types of anterior ocular segments of the pterygium provided by the Eye Hospital of Nanjing Medical University.Conventional classification models—VGG16,ResNet50,MobileNetV2,and EfficientNetB7—were trained on the same dataset for comparison.To evaluate model performance in terms of accuracy,Kappa value,test time,sensitivity,specificity,the area under curve(AUC),and visual heat map,470 test images of the anterior segment of the pterygium were used.RESULTS:The accuracy of the MobileNetV2+Self-Attention model with 281 MB in model size was 92.77%,and the Kappa value of the model was 88.92%.The testing time using the model was 9ms/image in the server and 138ms/image in the local computer.The sensitivity,specificity,and AUC for the diagnosis of pterygium using normal anterior segment images were 99.47%,100%,and 100%,respectively;using anterior segment images in the observation period were 88.30%,95.32%,and 96.70%,respectively;and using the anterior segment images in the surgery period were 88.18%,94.44%,and 97.30%,respectively.CONCLUSION:The developed model is lightweight and can be used not only for detection but also for assessing the severity of pterygium.展开更多
Objective:To investigate the changes and clinical significance of inflammation, antioxidation, insulin resistance and bone metabolism in patients with chronic periodontitis.Methods: 50 patients with chronic periodonti...Objective:To investigate the changes and clinical significance of inflammation, antioxidation, insulin resistance and bone metabolism in patients with chronic periodontitis.Methods: 50 patients with chronic periodontitis treated in our hospital from January 2017 to March 2018 were selected as the observation group and 50 cases of periodontal health were selected as control group. The expression levels of related indicators of inflammation [including macrophage migration inhibitory factor (MIF), monocyte chemoattractant protein-1 (MCP-1), granulocyte-macrophage colony-stimulating factor (GM-CSF)], antioxidant [including nitric oxide (NO) and nitric oxide synthase (NOS)], insulin resistance [including adiponectin, leptin (LEP)] and bone metabolism [including visfatin and calcitonin gene-related peptide (CGRP)] in the two groups were observed and compared.Results: Except for the levels of adiponectin [(3.03±0.40) ng/L] and CGRP [(32.40±12.61) μg/L] in the observation group [(5.33±0.63) ng/L and (49.84±13.36) μg/L, respectively] were significantly lower than those in the control group (P<0.05). The levels of MIF [(14.15±4.40) ng/mL], MCP-1 [(0.93±0.13) μg/L], GM-CSF [(1.71±0.51) μg/L], NO [(84.67±26.02) μmol/L], NOS [(49.71±9.52) μ/mL], LEP [(0.88±0.27) μg/L] and visfatin [(80.34±33.57) μg/L] were significantly higher than those in the control group ((11.27±1.95) ng/mL, (0.51±0.07) μg/L, (0.45±0.17) μg/L, (54.80±9.33) μmol/L, (30.29±4.63) μ/mL, (0.47±0.11) μg/L and (34.61±14.02) μg/L, respectively)All above differences were significant (P<0.05).Conclusions: Patients with chronic periodontitis are prone to inflammatory reaction. And the degree of inflammation is deeper. It is easy to stimulate antioxidant effect and resist periodontal infection. It may also aggravate insulin resistance to increase blood sugar or affect bone metabolism and osteoporosis.展开更多
To reduce the experimental uncertainty in the 235 U resonance energy region and improve the detection efficiency for neutron total cross section measurements compared with those obtained with the neutron total cross s...To reduce the experimental uncertainty in the 235 U resonance energy region and improve the detection efficiency for neutron total cross section measurements compared with those obtained with the neutron total cross section spectrometer(NTOX), a dedicated lithium-containing scintillation detector has been developed on the Back-n beam line at the China Spallation Neutron Source. The Fast Scintillator-based Neutron Total Cross Section(FAST) spectrometer has been designed based on a Cs2Li La Br6(CLLB) scintillator considering the γ-ray flash and neutron environment on the Back-n beam line. The response of the CLLB scintillator to neutrons and γ-rays was evaluated with different 6Li/7 Li abundance ratios using Geant4. The neutron-γdiscrimination performance of the CLLB has been simulated considering different scintillation parameters, physical designs,and light readout modes. A cubic 6Li-enriched( > 90%) CLLB scintillator, which has a thickness of 4-9 mm and side length of no less than 50 mm to cover the Φ 50 mm neutron beam at the spectrometer position, has been proposed coupling to a side readout SiPM array to construct the FAST spectrometer. The developed simulation techniques for neutron-γ discrimination performance could provide technical support for other neutron-induced reaction measurements on the Back-n beam line.展开更多
Pterygium is a prevalent ocular disease that can cause discomfort and vision impairment.Early and accurate diagnosis is essential for effective management.Recently,artificial intelligence(AI)has shown promising potent...Pterygium is a prevalent ocular disease that can cause discomfort and vision impairment.Early and accurate diagnosis is essential for effective management.Recently,artificial intelligence(AI)has shown promising potential in assisting clinicians with pterygium diagnosis.This paper provides an overview of AI-assisted pterygium diagnosis,including the AI techniques used such as machine learning,deep learning,and computer vision.Furthermore,recent studies that have evaluated the diagnostic performance of AI-based systems for pterygium detection,classification and segmentation were summarized.The advantages and limitations of AI-assisted pterygium diagnosis and discuss potential future developments in this field were also analyzed.The review aims to provide insights into the current state-of-the-art of AI and its potential applications in pterygium diagnosis,which may facilitate the development of more efficient and accurate diagnostic tools for this common ocular disease.展开更多
AIM:To conduct a classification study of high myopic maculopathy(HMM)using limited datasets,including tessellated fundus,diffuse chorioretinal atrophy,patchy chorioretinal atrophy,and macular atrophy,and minimize anno...AIM:To conduct a classification study of high myopic maculopathy(HMM)using limited datasets,including tessellated fundus,diffuse chorioretinal atrophy,patchy chorioretinal atrophy,and macular atrophy,and minimize annotation costs,and to optimize the ALFA-Mix active learning algorithm and apply it to HMM classification.METHODS:The optimized ALFA-Mix algorithm(ALFAMix+)was compared with five algorithms,including ALFA-Mix.Four models,including Res Net18,were established.Each algorithm was combined with four models for experiments on the HMM dataset.Each experiment consisted of 20 active learning rounds,with 100 images selected per round.The algorithm was evaluated by comparing the number of rounds in which ALFA-Mix+outperformed other algorithms.Finally,this study employed six models,including Efficient Former,to classify HMM.The best-performing model among these models was selected as the baseline model and combined with the ALFA-Mix+algorithm to achieve satisfactor y classification results with a small dataset.RESULTS:ALFA-Mix+outperforms other algorithms with an average superiority of 16.6,14.75,16.8,and 16.7 rounds in terms of accuracy,sensitivity,specificity,and Kappa value,respectively.This study conducted experiments on classifying HMM using several advanced deep learning models with a complete training set of 4252 images.The Efficient Former achieved the best results with an accuracy,sensitivity,specificity,and Kappa value of 0.8821,0.8334,0.9693,and 0.8339,respectively.Therefore,by combining ALFA-Mix+with Efficient Former,this study achieved results with an accuracy,sensitivity,specificity,and Kappa value of 0.8964,0.8643,0.9721,and 0.8537,respectively.CONCLUSION:The ALFA-Mix+algorithm reduces the required samples without compromising accuracy.Compared to other algorithms,ALFA-Mix+outperforms in more rounds of experiments.It effectively selects valuable samples compared to other algorithms.In HMM classification,combining ALFA-Mix+with Efficient Former enhances model performance,further demonstrating the effectiveness of ALFA-Mix+.展开更多
The plume-surface interaction(PSI)is a common phenomenon that describes the environment surrounding the landers resulting from the impingement of hot rocket exhaust on the regolith of planetary bodies.The PSI will cau...The plume-surface interaction(PSI)is a common phenomenon that describes the environment surrounding the landers resulting from the impingement of hot rocket exhaust on the regolith of planetary bodies.The PSI will cause obscuration,erosion of the planetary surface,and high-speed spreading of dust or high-energy ejecta streams,which will induce risks to a safe landing and cause damage to payloads on the landers or to nearby assets.Safe landings and the subsequent scientific goals of deep-space exploration in China call for a comprehensive understanding of the PSI process,including the plume flow mechanics,erosion mechanism,and ejecta dynamics.In addition,the landing crater caused by the plume provides a unique and insightful perspective on the understanding of PSI.In particular,the PSI can be used directly to constrain the composition,structure,and mechanical properties of the surface and subsurface soil.In this study,we conducted a systematic review of the phenomenology and terrestrial tests of PSI:we analyzed the critical factors in the PSI process and compared the differences in PSI phenomena between lunar and Martian conditions;we also reviewed the main erosion mechanisms and the evolution and development of terrestrial tests on PSI.We discuss the problems with PSI,challenges of terrestrial tests,and prospects of PSI,and we show the preliminary results obtained from the landing crater caused by the PSI of Tianwen-1.From analysis of the camera images and digital elevation model reconstructions,we concluded that the landing of Tianwen-1 caused the deepest crater(depth>40 cm)on a planetary surface reported to date and revealed stratigraphic layers in the subsurface of Martian soil.We further constrained the lower bounds of the mechanical properties of Martian soil by a slope stability analysis of the Tianwen-1 landing crater.The PSI may offer promising opportunities to obtain greater insights into planetary science,including the subsurface structure,mineral composition,and properties of soil.展开更多
MicroRNA390(miR390)is involved in plant growth and development by down-regulating the expression of the downstream genes trans-acting short interfering RNA3(TAS3)and AUXIN RESPONSE FACTORs(ARFs).There is a scarcity of...MicroRNA390(miR390)is involved in plant growth and development by down-regulating the expression of the downstream genes trans-acting short interfering RNA3(TAS3)and AUXIN RESPONSE FACTORs(ARFs).There is a scarcity of research on the involvement of the miR390-TAS3-ARFs pathway in the stem development of Populus.Here,differentially expressedmiRNAs during poplar stem development were screened by small RNA sequencing analysis,and a novel function of miR390b in stem development was revealed.Overexpression of miR390b(OE-miR390b)resulted in a large increase in the number of xylem fiber cells and a slight decrease in the cell length at the longitudinal axis.Overall increases in stem elongation and plant height were observed in the OE-miR390b plants.According to transcriptome sequencing results and transient co-expression analysis,TAS3.1 and TAS3.2 were identified as the target genes of miR390 in poplar and were negatively regulated by miR390 in the apex.The transcription levels of ARF3.2 and ARF4 were significantly repressed in OE-miR390b plants and strongly negatively correlatedwith the number of xylem fiber cells along the longitudinal axis.These findings indicate that the conserved miR390-TAS3-ARFs pathway in poplar is involved in stem elongation and plant height growth.展开更多
基金funded by projects of the National Natural Science Foundation of China(91955204,42241202)the Second Tibetan Plateau Scientific Expedition and Research(2019QZKK080301)a project entitled Tectonics,Sedimentation,Evolution,and Basic Petroleum Geology of the Qiangtang Basin(2021DJ0801)of the Forward-looking Basic Subjects of PetroChina’s 14th Five-Year Plan.
文摘The Qiangtang Basin of the Tibetan Plateau,located in the eastern Tethys tectonic domain,is the largest new marine petroliferous region for exploration in China.The scientific drilling project consisting primarily of well QK-1 and its supporting shallow boreholes for geological surveys(also referred to as the Project)completed in recent years contributes to a series of new discoveries and insights into the oil and gas preservation conditions and source rock evaluation of the Qiangtang Basin.These findings differ from previous views that the Qiangtang Basin has poor oil and gas preservation conditions and lacks high-quality source rocks.As revealed by well QK-1 and its supporting shallow boreholes in the Project,the Qiangtang Basin hosts two sets of high-quality regional seals,namely an anhydrite layer in the Quemo Co Formation and the gypsum-bearing mudstones in the Xiali Formation.Moreover,the Qiangtang Basin has favorable oil and gas preservation conditions,as verified by the comprehensive study of the sealing capacity of seals,basin structure,tectonic uplift,magmatic activity,and groundwater motion.Furthermore,the shallow boreholes have also revealed that the Qiangtang Basin has high-quality hydrocarbon source rocks in the Upper Triassic Bagong Formation,which are thick and widely distributed according to the geological and geophysical data.In addition,the petroleum geological conditions,such as the type,abundance,and thermal evolution of organic matter,indicate that the Qiangtang Basin has great hydrocarbon-generating potential.
基金Project supported by the National Key Research and Development Program of China (Grant No.2021YFB3502802)Major Science and Technology Research and Development Project of Jiangxi Province,China (Grant No.20203ABC28W006)+2 种基金the Key Research and Development Program of Shandong Province,China (Grant No.2019JZZY010321)Major Project of“Science and Technology Innovation 2025”in Ningbo City (Grant No.2020Z046)the K.C.Wong Magna Fund in Ningbo University。
文摘A grain boundary diffusion(GBD)process with Pr_(80-x)Al_(x)Cu_(20)(x=0,10,15,20)low melting point alloys was applied to commercial 42M sintered Nd–Fe–B magnets.The best coercivity enhancement of a diffused magnet was for the Pr_(65)Al_(15)Cu_(20)GBD magnet,from 16.38 kOe to 22.38 kOe.Microstructural investigations indicated that increase in the Al content in the diffusion source can form a continuous grain boundary(GB)phase,optimizing the microstructure to enhance the coercivity.The coercivity enhancement is mainly due to the formation of a continuous GB phase to separate the main phase grains.Exchange decoupling between the adjacent main phase grains is enhanced after the GBD process.Meanwhile,the introduction of Al can effectively promote the infiltration of Pr into the magnet,which increases the diffusion rate of rare-earth elements within a certain range.This work provides a feasible method to enhance coercivity and reduce the use of rare-earth resources by partial replacement of rare-earth elements with non-rare-earth elements in the diffusion source.
基金Dao-Bing Wang was supported by the Beijing Natural Science Foundation Project(No.3222030)the National Natural Science Foundation of China(No.52274002)+1 种基金the PetroChina Science and Technology Innovation Foundation Project(No.2021DQ02-0201)Fu-Jian Zhou was supported by the National Natural Science Foundation of China(No.52174045).
文摘Deep and ultra-deep reservoirs have gradually become the primary focus of hydrocarbon exploration as a result of a series of significant discoveries in deep hydrocarbon exploration worldwide.These reservoirs present unique challenges due to their deep burial depth(4500-8882 m),low matrix permeability,complex crustal stress conditions,high temperature and pressure(HTHP,150-200℃,105-155 MPa),coupled with high salinity of formation water.Consequently,the costs associated with their exploitation and development are exceptionally high.In deep and ultra-deep reservoirs,hydraulic fracturing is commonly used to achieve high and stable production.During hydraulic fracturing,a substantial volume of fluid is injected into the reservoir.However,statistical analysis reveals that the flowback rate is typically less than 30%,leaving the majority of the fluid trapped within the reservoir.Therefore,hydraulic fracturing in deep reservoirs not only enhances the reservoir permeability by creating artificial fractures but also damages reservoirs due to the fracturing fluids involved.The challenging“three-high”environment of a deep reservoir,characterized by high temperature,high pressure,and high salinity,exacerbates conventional forms of damage,including water sensitivity,retention of fracturing fluids,rock creep,and proppant breakage.In addition,specific damage mechanisms come into play,such as fracturing fluid decomposition at elevated temperatures and proppant diagenetic reactions at HTHP conditions.Presently,the foremost concern in deep oil and gas development lies in effectively assessing the damage inflicted on these reservoirs by hydraulic fracturing,comprehending the underlying mechanisms,and selecting appropriate solutions.It's noteworthy that the majority of existing studies on reservoir damage primarily focus on conventional reservoirs,with limited attention given to deep reservoirs and a lack of systematic summaries.In light of this,our approach entails initially summarizing the current knowledge pertaining to the types of fracturing fluids employed in deep and ultra-deep reservoirs.Subsequently,we delve into a systematic examination of the damage processes and mechanisms caused by fracturing fluids within the context of hydraulic fracturing in deep reservoirs,taking into account the unique reservoir characteristics of high temperature,high pressure,and high in-situ stress.In addition,we provide an overview of research progress related to high-temperature deep reservoir fracturing fluid and the damage of aqueous fracturing fluids to rock matrix,both artificial and natural fractures,and sand-packed fractures.We conclude by offering a summary of current research advancements and future directions,which hold significant potential for facilitating the efficient development of deep oil and gas reservoirs while effectively mitigating reservoir damage.
基金supported by the Key Research Program of the Institute of Geology and Geophysics,CAS(Nos.IGGCAS-202102 and IGGCAS-201904)the National Natural Science Foundation of China(No.42230111)the CAS Key Technology Talent Program。
文摘After landing in the Utopia Planitia,Tianwen-1 formed the deepest landing crater on Mars,approximately 40 cm deep,exposing precious information about the mechanical properties of Martian soil.We established numerical models for the plume-surface interaction(PSI)and the crater formation based on Computational Fluid Dynamics(CFD)methods and the erosion model modified from Roberts’Theory.Comparative studies of cases were conducted with different nozzle heights and soil mechanical properties.The increase in cohesion and internal friction angle leads to a decrease in erosion rate and maximum crater depth,with the cohesion having a greater impact.The influence of the nozzle height is not clear,as it interacts with the position of the Shock Diamond to jointly control the erosion process.Furthermore,we categorized the evolution of landing craters into the dispersive and the concentrated erosion modes based on the morphological characteristics.Finally,we estimated the upper limits of the Martian soil’s mechanical properties near Tianwen-1 landing site,with the cohesion ranging from 2612 to 2042 Pa and internal friction angle from 25°to 41°.
基金Project supported by the National Natural Science Foundation of China(Grant No.12305303)the Natural Science Foundation of Hunan Province of China(Grant Nos.2023JJ40520,2021JJ40444,and 2019JJ30019)+3 种基金the Research Foundation of Education Bureau of Hunan Province of China(Grant No.20A430)the Science and Technology Innovation Program of Hunan Province(Grant No.2020RC3054)the Natural Science Basic Research Plan in the Shaanxi Province of China(Grant No.2023-JC-QN-0015)the Doctoral Research Fund of University of South China。
文摘Convolutional neural networks(CNNs) exhibit excellent performance in the areas of image recognition and object detection, which can enhance the intelligence level of spacecraft. However, in aerospace, energetic particles, such as heavy ions, protons, and alpha particles, can induce single event effects(SEEs) that lead CNNs to malfunction and can significantly impact the reliability of a CNN system. In this paper, the MNIST CNN system was constructed based on a 28 nm systemon-chip(SoC), and then an alpha particle irradiation experiment and fault injection were applied to evaluate the SEE of the CNN system. Various types of soft errors in the CNN system have been detected, and the SEE cross sections have been calculated. Furthermore, the mechanisms behind some soft errors have been explained. This research will provide technical support for the design of radiation-resistant artificial intelligence chips.
基金This work is supported by the National Natural Science Foundation of China(No.12375296)the Key Laboratory of Nuclear Data Foundation(No.JCKY2022201C153)+2 种基金the Natural Science Foundation of Hunan Province of China(Nos.2021JJ40444,2020RC3054)the Youth Innovation Promotion Association CAS(No.2023014)the National Key Research and Development Plan(No.2022YFA1603303).
文摘The neutron-induced total cross sections of natural lead have been measured in a wide energy range(0.3 eV-20 MeV)on the back-streaming white neutron beamline(Back-n)at the China Spallation Neutron Source.Neutron energy was determined by the neutron total cross-section spectrometer using the time-of-flight technique.A fast multi-cell fission chamber was used as the neutron detector,and a 10-mm-thick high-purity natural lead sample was employed for the neutron transmission measurements.The on-beam background was determined using Co,In,Ag,and Cd filters.The excitation function of ^(nat)Pb(n,tot)reaction below 20 MeV was calculated using the TALYS-1.96 nuclear-reaction modeling program.The present results were compared with previous results,the evaluated data available in the five major evaluated nuclear data libraries(i.e.,ENDF/B-VIII.0,JEFF-3.3,JENDL-5,CENDL-3.2,and BROND-3.1),and the theoretical calculation curve.Good agreement was found between the new results and those of previous experiments and with the theoretical curves in the corresponding region.This measurement obtained the neutron total cross section of natural lead with good accuracy over a wide energy range and added experimental data in the resonance energy range.This provides more reliable experimental data for nuclear engineering design and nuclear data evaluation of lead.
基金funded by Ningbo Key R&D Plan and“Unveiling and Leading”(Grant No.2023Z093)Ningbo Science and Technology Innovation 2025 Major Special Project(Grant No.2022Z106)Hezhou City Central Leading Local Science and Technology Development Special Fund Project(Grant No.HK ZY2022002).
文摘The grain boundary phase affects the magnetic properties and corrosion resistance of sintered NdFeB magnets.In this work,a small amount of In was added to NdFeB magnets by induction melting to systematically investigate its effect on the evolution of the microstructure,magnetic properties and corrosion resistance of NdFeB magnets.Microstructural analysis illustrated that minor In addition generated more grain boundary phases and an abundant amorphous phase at the triple-junction grain boundary.While the addition of In failed to enhance the magnetic isolation effect between adjacent matrix grains,its incorporation fortuitously elevated the electrochemical potential of the In-containing magnets.Besides,during corrosion,an In-rich precipitate phase formed,hindering the ingress of the corrosive medium into the magnet.Consequently,this significantly bolstered the corrosion resistance of the sintered NdFeB magnets.The phase formation,magnetic properties and corrosion resistance of In-doped NdFeB magnets are detailed in this work,which provides new prospects for the preparation of high-performance sintered NdFeB magnets.
基金Supported by the National Natural Science Foundation of China(No.61906066)Scientific Research Fund of Zhejiang Provincial Education Department(No.Y202147191)+2 种基金Huzhou University Graduate Research Innovation Project(No.2020KYCX21)Sanming Project of Medicine in Shenzhen(SZSM202311012)Shenzhen Science and Technology Program(No.JCYJ20220530153604010).
文摘AIM:To evaluate the application of an intelligent diagnostic model for pterygium.METHODS:For intelligent diagnosis of pterygium,the attention mechanisms—SENet,ECANet,CBAM,and Self-Attention—were fused with the lightweight MobileNetV2 model structure to construct a tri-classification model.The study used 1220 images of three types of anterior ocular segments of the pterygium provided by the Eye Hospital of Nanjing Medical University.Conventional classification models—VGG16,ResNet50,MobileNetV2,and EfficientNetB7—were trained on the same dataset for comparison.To evaluate model performance in terms of accuracy,Kappa value,test time,sensitivity,specificity,the area under curve(AUC),and visual heat map,470 test images of the anterior segment of the pterygium were used.RESULTS:The accuracy of the MobileNetV2+Self-Attention model with 281 MB in model size was 92.77%,and the Kappa value of the model was 88.92%.The testing time using the model was 9ms/image in the server and 138ms/image in the local computer.The sensitivity,specificity,and AUC for the diagnosis of pterygium using normal anterior segment images were 99.47%,100%,and 100%,respectively;using anterior segment images in the observation period were 88.30%,95.32%,and 96.70%,respectively;and using the anterior segment images in the surgery period were 88.18%,94.44%,and 97.30%,respectively.CONCLUSION:The developed model is lightweight and can be used not only for detection but also for assessing the severity of pterygium.
文摘Objective:To investigate the changes and clinical significance of inflammation, antioxidation, insulin resistance and bone metabolism in patients with chronic periodontitis.Methods: 50 patients with chronic periodontitis treated in our hospital from January 2017 to March 2018 were selected as the observation group and 50 cases of periodontal health were selected as control group. The expression levels of related indicators of inflammation [including macrophage migration inhibitory factor (MIF), monocyte chemoattractant protein-1 (MCP-1), granulocyte-macrophage colony-stimulating factor (GM-CSF)], antioxidant [including nitric oxide (NO) and nitric oxide synthase (NOS)], insulin resistance [including adiponectin, leptin (LEP)] and bone metabolism [including visfatin and calcitonin gene-related peptide (CGRP)] in the two groups were observed and compared.Results: Except for the levels of adiponectin [(3.03±0.40) ng/L] and CGRP [(32.40±12.61) μg/L] in the observation group [(5.33±0.63) ng/L and (49.84±13.36) μg/L, respectively] were significantly lower than those in the control group (P<0.05). The levels of MIF [(14.15±4.40) ng/mL], MCP-1 [(0.93±0.13) μg/L], GM-CSF [(1.71±0.51) μg/L], NO [(84.67±26.02) μmol/L], NOS [(49.71±9.52) μ/mL], LEP [(0.88±0.27) μg/L] and visfatin [(80.34±33.57) μg/L] were significantly higher than those in the control group ((11.27±1.95) ng/mL, (0.51±0.07) μg/L, (0.45±0.17) μg/L, (54.80±9.33) μmol/L, (30.29±4.63) μ/mL, (0.47±0.11) μg/L and (34.61±14.02) μg/L, respectively)All above differences were significant (P<0.05).Conclusions: Patients with chronic periodontitis are prone to inflammatory reaction. And the degree of inflammation is deeper. It is easy to stimulate antioxidant effect and resist periodontal infection. It may also aggravate insulin resistance to increase blood sugar or affect bone metabolism and osteoporosis.
基金supported by the Key Laboratory of Nuclear Data Foundation(No.JCKY2022201C153)National Natural Science Foundation of China(No.11505216),Educational Commission of Hunan Province of China(No.19B488)Natural Science Foundation of Hunan Province of China(Nos.2021JJ40444 and 2020RC3054).
文摘To reduce the experimental uncertainty in the 235 U resonance energy region and improve the detection efficiency for neutron total cross section measurements compared with those obtained with the neutron total cross section spectrometer(NTOX), a dedicated lithium-containing scintillation detector has been developed on the Back-n beam line at the China Spallation Neutron Source. The Fast Scintillator-based Neutron Total Cross Section(FAST) spectrometer has been designed based on a Cs2Li La Br6(CLLB) scintillator considering the γ-ray flash and neutron environment on the Back-n beam line. The response of the CLLB scintillator to neutrons and γ-rays was evaluated with different 6Li/7 Li abundance ratios using Geant4. The neutron-γdiscrimination performance of the CLLB has been simulated considering different scintillation parameters, physical designs,and light readout modes. A cubic 6Li-enriched( > 90%) CLLB scintillator, which has a thickness of 4-9 mm and side length of no less than 50 mm to cover the Φ 50 mm neutron beam at the spectrometer position, has been proposed coupling to a side readout SiPM array to construct the FAST spectrometer. The developed simulation techniques for neutron-γ discrimination performance could provide technical support for other neutron-induced reaction measurements on the Back-n beam line.
基金Supported by National Natural Science Foundation of China(No.61906066)Scientific Research Fund of Zhejiang Provincial Education Department(No.Y202250196)+4 种基金Zhejiang Provincial Philosophy and Social Science Planning Project(No.21NDJC021Z)Natural Science Foundation of Ningbo City(No.202003N4072)Shenzhen Fund for Guangdong Provincial High-level Clinical Key Specialties(No.SZGSP014)Sanming Project of Medicine in Shenzhen(No.SZSM202011015)Shenzhen Fundamental Research Program(No.JCYJ20220818103207015).
文摘Pterygium is a prevalent ocular disease that can cause discomfort and vision impairment.Early and accurate diagnosis is essential for effective management.Recently,artificial intelligence(AI)has shown promising potential in assisting clinicians with pterygium diagnosis.This paper provides an overview of AI-assisted pterygium diagnosis,including the AI techniques used such as machine learning,deep learning,and computer vision.Furthermore,recent studies that have evaluated the diagnostic performance of AI-based systems for pterygium detection,classification and segmentation were summarized.The advantages and limitations of AI-assisted pterygium diagnosis and discuss potential future developments in this field were also analyzed.The review aims to provide insights into the current state-of-the-art of AI and its potential applications in pterygium diagnosis,which may facilitate the development of more efficient and accurate diagnostic tools for this common ocular disease.
基金Supported by the National Natural Science Foundation of China(No.61906066)the Zhejiang Provincial Philosophy and Social Science Planning Project(No.21NDJC021Z)+4 种基金Shenzhen Fund for Guangdong Provincial High-level Clinical Key Specialties(No.SZGSP014)Sanming Project of Medicine in Shenzhen(No.SZSM202011015)Shenzhen Science and Technology Planning Project(No.KCXFZ20211020163813019)the Natural Science Foundation of Ningbo City(No.202003N4072)the Postgraduate Research and Innovation Project of Huzhou University(No.2023KYCX52)。
文摘AIM:To conduct a classification study of high myopic maculopathy(HMM)using limited datasets,including tessellated fundus,diffuse chorioretinal atrophy,patchy chorioretinal atrophy,and macular atrophy,and minimize annotation costs,and to optimize the ALFA-Mix active learning algorithm and apply it to HMM classification.METHODS:The optimized ALFA-Mix algorithm(ALFAMix+)was compared with five algorithms,including ALFA-Mix.Four models,including Res Net18,were established.Each algorithm was combined with four models for experiments on the HMM dataset.Each experiment consisted of 20 active learning rounds,with 100 images selected per round.The algorithm was evaluated by comparing the number of rounds in which ALFA-Mix+outperformed other algorithms.Finally,this study employed six models,including Efficient Former,to classify HMM.The best-performing model among these models was selected as the baseline model and combined with the ALFA-Mix+algorithm to achieve satisfactor y classification results with a small dataset.RESULTS:ALFA-Mix+outperforms other algorithms with an average superiority of 16.6,14.75,16.8,and 16.7 rounds in terms of accuracy,sensitivity,specificity,and Kappa value,respectively.This study conducted experiments on classifying HMM using several advanced deep learning models with a complete training set of 4252 images.The Efficient Former achieved the best results with an accuracy,sensitivity,specificity,and Kappa value of 0.8821,0.8334,0.9693,and 0.8339,respectively.Therefore,by combining ALFA-Mix+with Efficient Former,this study achieved results with an accuracy,sensitivity,specificity,and Kappa value of 0.8964,0.8643,0.9721,and 0.8537,respectively.CONCLUSION:The ALFA-Mix+algorithm reduces the required samples without compromising accuracy.Compared to other algorithms,ALFA-Mix+outperforms in more rounds of experiments.It effectively selects valuable samples compared to other algorithms.In HMM classification,combining ALFA-Mix+with Efficient Former enhances model performance,further demonstrating the effectiveness of ALFA-Mix+.
基金supported by the National Natural Science Foundation of China(Grant 42230111)the Key Research Program of the Institute of Geology and Geophysics,CAS(Mars Mission,Grant IGGCAS-202102)+1 种基金the Key Research Program of the Institute of Geology and Geophysics,CAS(Grant IGGCAS-201904)the CAS Key Technology Talent Program.
文摘The plume-surface interaction(PSI)is a common phenomenon that describes the environment surrounding the landers resulting from the impingement of hot rocket exhaust on the regolith of planetary bodies.The PSI will cause obscuration,erosion of the planetary surface,and high-speed spreading of dust or high-energy ejecta streams,which will induce risks to a safe landing and cause damage to payloads on the landers or to nearby assets.Safe landings and the subsequent scientific goals of deep-space exploration in China call for a comprehensive understanding of the PSI process,including the plume flow mechanics,erosion mechanism,and ejecta dynamics.In addition,the landing crater caused by the plume provides a unique and insightful perspective on the understanding of PSI.In particular,the PSI can be used directly to constrain the composition,structure,and mechanical properties of the surface and subsurface soil.In this study,we conducted a systematic review of the phenomenology and terrestrial tests of PSI:we analyzed the critical factors in the PSI process and compared the differences in PSI phenomena between lunar and Martian conditions;we also reviewed the main erosion mechanisms and the evolution and development of terrestrial tests on PSI.We discuss the problems with PSI,challenges of terrestrial tests,and prospects of PSI,and we show the preliminary results obtained from the landing crater caused by the PSI of Tianwen-1.From analysis of the camera images and digital elevation model reconstructions,we concluded that the landing of Tianwen-1 caused the deepest crater(depth>40 cm)on a planetary surface reported to date and revealed stratigraphic layers in the subsurface of Martian soil.We further constrained the lower bounds of the mechanical properties of Martian soil by a slope stability analysis of the Tianwen-1 landing crater.The PSI may offer promising opportunities to obtain greater insights into planetary science,including the subsurface structure,mineral composition,and properties of soil.
基金supported by the National Natural Science Foundation of China(32171821 and 31770639)Science and Technology Projects of Shennongjia Academy of Forestry,Hubei,China(Grant number:SAF202107)the Project 2662022YLYJ009 supported by the Fundamental Research Funds for the Central Universities.We are grateful to Professor Feng Li(Huazhong Agricultural University)for providing the vector pMS4v2,and Dr Kebing Du(Huazhong Agricultural University)for supplying the P.deltoides clones.
文摘MicroRNA390(miR390)is involved in plant growth and development by down-regulating the expression of the downstream genes trans-acting short interfering RNA3(TAS3)and AUXIN RESPONSE FACTORs(ARFs).There is a scarcity of research on the involvement of the miR390-TAS3-ARFs pathway in the stem development of Populus.Here,differentially expressedmiRNAs during poplar stem development were screened by small RNA sequencing analysis,and a novel function of miR390b in stem development was revealed.Overexpression of miR390b(OE-miR390b)resulted in a large increase in the number of xylem fiber cells and a slight decrease in the cell length at the longitudinal axis.Overall increases in stem elongation and plant height were observed in the OE-miR390b plants.According to transcriptome sequencing results and transient co-expression analysis,TAS3.1 and TAS3.2 were identified as the target genes of miR390 in poplar and were negatively regulated by miR390 in the apex.The transcription levels of ARF3.2 and ARF4 were significantly repressed in OE-miR390b plants and strongly negatively correlatedwith the number of xylem fiber cells along the longitudinal axis.These findings indicate that the conserved miR390-TAS3-ARFs pathway in poplar is involved in stem elongation and plant height growth.
