检索结果-南通市图书馆

Effects of vegetation near-soil-surface factors on runoff and sediment reduction in typical grasslands on the Loess Plateau,China

在线全文

学校读者我要写书评

暂无评论

Journal of Arid Land 2022年第3期14卷 325-340页

作者： LI Panpan WANG Bing YANG Yanfen liU Guobin State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau Institute of Soil and Water ConservationNorthwest A&F UniversityYangling 712100China State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau Institute of Soil and Water ConservationChinese Academy of Sciences and Ministry of Water ResourcesYangling 712100China

Vegetation near-soil-surface factors can protect topsoil from erosion,however,their contributions to the reduction of soil erosion,especially under natural rainfall events,have not been systematically recognized.This study was performed to quantify the effects of near-soil-surface factors on runoff and sediment under natural rainfall events on grasslands dominated by Bothriochloa ischaemum(linn.)Keng(BI grassland)and Artemisia gmelinii Thunb.(AG grassland)in two typical watersheds on the Loess Plateau,China in 2018.By successive removal of the plant canopy,litter,biological soil crusts(BSCs)and plant roots,we established five treatments including plant roots,plant roots+BSCs,plant roots+BSCs+litter,intact grassland and bare land in each grassland type.In total,twenty runoff plots(5 m×3 m)with similar slopes and aspects were constructed in the two types of grasslands.Results showed that plant canopy,litter and roots reduced runoff,while BSCs,which swelled in the presence of water,increased runoff.In contrast,all of these factors reduced sediment yield.In addition,the reductions in runoff and sediment yield increased with I30(maximum 30-min rainfall intensity)for each vegetation near-soil-surface factor except for BSCs.Among these factors,plant canopy had the largest contribution to runoff reduction,accounting for 48.8% and 39.9% in the BI and AG grasslands,respectively.The contributions of these vegetation near-soil-surface factors to sediment yield reduction were similar(21.3%-29.9%)in the two types of grasslands except for BSCs in the AG grassland(10.3%).The total reduction in runoff in the BI grassland(70.8%)was greater than that in the AG grassland(53.1%),while the reduction in sediment yield was almost the same in both grasslands(97.4%and 96.7%).In conclusion,according to the effects of different vegetation near-soil-surface factors on runoff and sediment production,our results may provide more complete insight and scientific basis into the effects of various vegetation related factors in controlling soil ero

关键词： vegetation near-soil-surface factor grassland arid and semi-arid soil erosion Loess Plateau

Regulating bulkhead pressure of EPB shield machines through DEM modeling and data mining

在线全文

学校读者我要写书评

暂无评论

Underground Space 2023年第1期8卷 15-29页

作者： panpan Cheng Fang liu Youjun Xu Yuanhai li State Key Laboratory of Disaster Reduction in Civil Engineering Shanghai 200092China Key Laboratory of Geotechnical and Underground Engineering of the Ministry of Education Tongji UniversityShanghai 200092China School of Civil Engineering Inner Mongolia University of Science and TechnologyBaotou 014010China State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and TechnologyXuzhouJiangsu 221116China

Proper regulation of the earth pressure on the bulkhead of earth-pressure balanced(EPB)shield tunneling machines is significant to ensure safe construction.This study proposes a procedure for regulating the bulkhead pressure by combining numerical simulations and data mining,and applies the procedure to a metro line constructed in sandy pebble stratum using EPB shield.Firstly,the relationship between the bulkhead pressure and the pressure on the tunnel face is carefully obtained from discrete element modeling,and the required supporting earth pressure is derived by considering the arching effect.Secondly,aided with the machine learning method,a model is constructed for predicting the average bulkhead pressure per ring according to the operational parameters(i.e.,the average driving speed and the rotation speed of the screw conveyor).Given the target value of the bulkhead pressure,the optimal values of the operational parameters are obtained from the model.In addition,an autoregressive moving average stochastic process model is developed to monitor the real-time fluctuation of the bulkhead pressure and guide the actions taken in time to avoid dramatic fluctuations.The results indicate that the pressure difference between the tunnel face and the bulkhead is considerable,and the consideration of the arching effect can avoid overestimating the bulkhead pressure.A combination of the machine learning model and the stochastic process model provides a plausible performance in regulating the bulkhead pressure around the target value without dramatic fluctuation.

关键词： EPB shield machine Bulkhead pressure Discrete element method Support vector regression Autoregressive moving average model

Human β-defensin 2 enhances IL-1β production and pyroptosis through P2X7-mediated NLRP3 expression in macrophages

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

BIOCELL 2022年第5期46卷 1197-1207页

作者： panpan WANG GANG li li GAO CHUANJIANG ZHAO Department of Periodontology Guanghua School and Hospital of StomatologySun Yat-sen UniversityGuangzhouChina Guangdong Provincial Key Laboratory of Stomatology Guanghua School and Hospital of StomatologySun Yat-sen UniversityGuangzhouChina Department of Oral Implantology Delun DentalGuangzhouChina

Periodontal disease is the leading cause of tooth loss,which is also a high-risk factor for other diseases including oral cancer and cardiovascular disease.Periodontitis is one of the most common type of periodontal diseases.Interleukin-1β(IL-1β)plays a key role in the pathogenesis of periodontitis.However,the mechanism how IL-1βis produced during periodontitis is still unclear.In the present study,we found that humanβ-defensin 2(hBD2)enhances IL-1βproduction through an LPS-primed human acute monocytic leukemia(THP-1)macrophage model.Inhibition of P2X purinoceptor 7(P2X7)reduced hBD2-enhanced IL-1βproduction.Incubation of LPS-primed THP-1 macrophages with potassium chloride also suppressed hBD2-enhanced IL-1βproduction.Silence of inflammasome adaptor Nod-like receptor family pyrin domain containing 3(NLRP3)led to reduced hBD2-enhanced IL-1βproduction.likewise,inhibition of caspase-1 also resulted in the decrease of IL-1β.Moreover,an ethidium bromide uptake test indicated that hBD2-activated caspase-1 mediated pyroptotic pore formation.Subsequent lactate dehydrogenase detection and flow cytometric analysis indicated that hBD2 also induced pyroptosis.In brief,these findings illustrated not only the mechanism of hBD2 in enhancing the inflammatory response,but also provided novel therapeutic targets for periodontitis.

关键词： Periodontitis Humanβ-defensin 2 IL-1β Signal transduction Pyroptosis

Shear behaviour of a rock bridge sandwiched between incipient joints under the influence of hydraulic pressures

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

International Journal of Mining Science and Technology 2023年第2期33卷 233-242页

作者： Shicheng Wang Xuxu Yang lichao li panpan Sun Lei Yang Fuwei li Shandong Key Laboratory of Civil Engineering Disaster Prevention and Mitigation Shandong University of Science and TechnologyQingdao 266590China School of Civil Engineering and Architecture Shandong University of Science and TechnologyQingdao 266590China

The rock bridges sandwiched in incipiently jointed rock mass were considered as barriers that block the fluid seepage,and provide certain shear strength reservation.For better revealing the influence of hydraulic pressure on the failure behaviour of rock bridges,direct shear tests were carried out through a newly proposed method on rock samples that contain two parallel incipient joints.By developing the gypsum-silicone pad coupling samples,a conventional triaxial test system was qualified to implement direct shear tests with satisfied sealing capability.The results showed that the rock bridges could be failed through the tensile failure,shear failure and mixed failure mechanism.The hydraulic pressure would facilitate the tensile failure mechanism and induce rougher fracture surfaces;while the normal stress would facilitate the shear failure mechanism and induce less rough fracture.The hydraulic pressure reduced the global shear strength of the rock block through reducing the efficient normal stress applied on the rock bridge area,which was highly dependent on the joint persistence,k.Moreover,because of the iterating occurrence of the hydraulic pressure lag with the fracture propagation,the rock bridge failure stage in the shear stress-shear displacement curves displayed a fluctuation trend.

关键词： Direct shear tests Hydraulic pressure Rock bridge Failure mechanism Hydraulic pressure lag Rock joints

Soil type and wetting intensity control the enhancement extent of N_(2)O efflux in soil with drought and rewetting cycles

在线全文

学校读者我要写书评

暂无评论

International Soil and Water Conservation Research 2024年第1期12卷 137-144页

作者： panpan Jiao Lei Yang Zhongwu li Peng Zheng Xiaodong Nie School of Geographical Sciences Hunan Normal UniversityChangsha 410081China State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau The Research Center of Soil and Water Conservation and Ecological EnvironmentChinese Academy of Sciences and Ministry of EducationYangling 712100China Institute of Soil and Water Conservation Chinese Academy of Sciences and Ministry of Water ResourcesYangling 712100China University of Chinese Academy of Sciences Beijing 100049China Key Laboratory of Soil Environment and Pollution Remediation Institute of Soil ScienceChinese Academy of SciencesNanjing 210008China

Climate change alters the intensity and frequency of drought and rewetting(D/W)events;however,the influence patterns of D/W on soil N_(2)O efflux in the water-limited area were not fully understood.Therefore,the impacts of D/W cycles varying in different extent of rewetting and frequency to N_(2)O efflux in two kinds of soil on the Loess Plateau were investigated.The incubation conditions consisted of 1)D/W treatments with four 7-day cycles from 10%water holding capacity(WHC)to 60%WHC or 90%WHC,2)constant moisture of 60%WHC and 90%WHC.The pulse of N_(2)O efflux rate under 10-60%WHC treatment was higher than that under 10-90%WHC treatment in calcic cambisols,while opposite trend was observed in earth-cumuli-orthic anthrosols.Meanwhile,the pulse of N_(2)O efflux rate decreased as cycle number increased for different wetting intensities and soil types.The direct N_(2)O efflux under 10-60%WHC and 10-90%WHC treatments were 5.49 and 1.89μg N_(2)O-N g^(-1)soil in calcic cambisols,with those being 1.92 and 10.85μg N_(2)O-N g^(-1)soil in earth-cumuli-orthic anthrosols,respectively.The N loss in earth-cumuli-orthic anthrosols was approximately 5.74 times greater than that in calcic cambisols under 10-90%WHC treatment,whereas the N loss under 10-60%WHC treatment was about 2.86 times greater in calcic cambisols than that in earth-cumuli-orthic anthrosols.This study suggested that extreme rainfall events can enhance the N_(2)O efflux and N loss in agricultural soils on the Loess Plateau in terms of soil type and wetting intensity,which should not be ignored in the N fertilizer management.

关键词： Drought/rewetting cycles N_(2)O efflux Wetting intensity Microbial biomass N Dissolved organic N Loess plateau

Role of nanoparticles in achieving macroscale superlubricity of graphene/nano-SiO_(2) particle composites

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Friction 2022年第9期10卷 1305-1316页

作者： panpan li li JI Hongxuan li Lei CHEN Xiaohong liU Huidi ZHOU Jianmin CHEN Key Laboratory of Science and Technology on Wear and Protection of Materials Lanzhou Institute of Chemical PhysicsChinese Academy of SciencesLanzhou 730000China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China

Recent studies have reported that adding nanoparticles to graphene enables macroscale superlubricity to be achieved.This study focuses on the role of nanoparticles in achieving superlubricity.First,because graphene nanoscrolls can be formed with nanoparticles as seeds under shear force,the applied load(or shear force)is adjusted to manipulate the formation of graphene nanoscrolls and to reveal the relationship between graphene-nanoscroll formation and superlubricating performance.Second,the load-carrying role of spherical nano-SiO_(2)particles during the friction process is verified by comparison with an elaborately designed fullerene that possesses a hollow-structured graphene nanoscroll.Results indicate that the incorporated nano-SiO_(2)particles have two roles in promoting the formation of graphene nanoscrolls and exhibiting load-carrying capacity to support macroscale forces for achieving macroscale superlubricity.Finally,macroscale superlubricity(friction coefficient:0.006–0.008)can be achieved under a properly tuned applied load(2.0 N)using a simple material system in which a graphene/nano-SiO_(2)particle composite coating slides against a steel counterpart ball without a decorated diamond-like carbon film.The approach described in this study could be of significance in engineering.

关键词： nano-SiO_(2)particles graphene macroscale superlubricity lubrication mechanism

Intermittent Geocast Routing in Urban Vehicular Delay Tolerant Networks

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Tsinghua Science and Technology 2016年第6期21卷 630-642页

作者： Zhiyuan li panpan Wu the School of Computer Science and Telecommunication Engineering Jiangsu University Zhenjiang 212013 China the Jiangsu High Technology Research Key Laboratory for Wireless Sensor Networks Nanjing 210003 China

Nowadays, both vehicular active safety service and user infotainment service have become two core applications for urban Vehicular Delay Tolerant Networks（u VDTNs）. Both core applications require a high data transmission capacity over u VDTNs. In addition, the connection between any two vehicles in u VDTNs is intermittent and opportunistic. Intermittent data dissemination over u VDTNs is a stringent and challenging issue. In this paper,we propose Intermittent Geocast Routing（IGR）. For the first step, IGR has to estimate the active connection time interval via the moving directions and velocities between any two vehicles. Second, the throughput function for u VDTNs is fitted by building a wavelet neural network traffic model. Third, the throughput function within the effective connection time interval is integrated to obtain the forwarding capability estimation of the node. Fourth, a high-efficiency geocast routing algorithm using the node forwarding capability for u VDTNs is designed. Finally, IGR is simulated on the opportunistic Network Environment simulator. Experimental results show that IGR can greatly improve the packet delivery ratio, transmission delay, delay jitter, and packet loss rate compared with the state of the art.

关键词： urban vehicular delay tolerant networks geocast routing node forwarding capability connection time

Deep tectonics and seismogenic mechanisms of the seismic source zone of the Jishishan M_(s)6.2 earthquake on December 18,2023,at the northeast margin of the Tibetan Plateau

在线全文

学校读者我要写书评

暂无评论

Earth and Planetary Physics 2024年第3期8卷 514-521页

作者： Qiong Wang ShuYu li XinYi li Yue Wu panpan Zhao Yuan Gao Key Laboratory of Earthquake Prediction Institute of Earthquake ForecastingChina Earthquake AdministrationBeijing 100036China Institute of Geophysics China Earthquake AdministrationBeijing 100081China

On December 18,2023,an M_(s)6.2 earthquake occurred in Jishishan,Gansu Province,China.This earthquake happened in the eastern region of the Qilian Orogenic Belt,which is situated at the forefront of the NE margin of the Tibetan Plateau(i.e.,Qinghai-Tibet Plateau),encompassing a rhombic-shaped area that intersects the Qilian-Qaidam Basin,Alxa Block,Ordos Block,and South China Block.In this study,we analyzed the deep tectonic pattern of the Jishishan earthquake by incorporating data on the crustal thickness,velocity structure,global navigation satellite system(GNSS)strain field,and anisotropy.We discovered that the location of the earthquake was related to changes in the crustal structure.The results showed that the Jishishan M_(s)6.2 earthquake occurred in a unique position,with rapid changes in the crustal thickness,Vp/Vs,phase velocity,and S-wave velocity.The epicenter of the earthquake was situated at the transition zone between high and low velocities and was in proximity to a low-velocity region.Additionally,the source area is flanked by two high-velocity anomalies from the east and west.The principal compressive strain orientation near the Lajishan Fault is primarily in the NNE and NE directions,which align with the principal compressive stress direction in this region.In some areas of the Lajishan Fault,the principal compressive strain orientations show the NNW direction,consistent with the direction of the upper crustal fast-wave polarization from local earthquakes and the phase velocity azimuthal anisotropy.These features underscore the relationship between the occurrence of the Jishishan M_(s)6.2 earthquake and the deep inhomogeneous structure and deep tectonic characteristics.The NE margin of the Tibetan Plateau was thickened by crustal extension in the process of northeastward expansion,and the middle and lower crustal materials underwent structural deformation and may have been filled with salt-containing fluids during the extension process.The presence of this weak layer makes it easier for strong ea

关键词： Jishishan M_(s)6.2 earthquake crustal structure anisotropy stress and strain seismogenic mechanism northeast margin of the Tibetan Plateau

Stretchable iontronics with robust interface bonding between dielectric and ion-conducting elastomers

在线全文

学校读者我要写书评

暂无评论

Nano Research 2023年第9期16卷 11862-11870页

作者： Zhongpeng li panpan Zhang Yangshi Shao Zi-Hao Guo Xiong Pu School of Chemistry and Chemical Engineering Center on Nanoenergy ResearchSchool of Physical Science and TechnologyGuangxi UniversityNanning 530004China CAS Center for Excellence in Nanoscience Beijing Key Laboratory of Micro-Nano Energy and SensorBeijing Institute of Nanoenergy and NanosystemsChinese Academy of SciencesBeijing 101400China School of Nanoscience and Technology University of Chinese Academy of SciencesBeijing 100049China

Dry ion-conducting elastomers(ICEs)are emerging stretchable and ionic conductive materials that are demonstrated with excellent thermal stability and great promise in multifunctional iontronic devices.Nevertheless,the poor interface between the ICEs and the dielectric material is one of the issues hindering the application of the stretchable iontronic device.Herein,a polydimethylsiloxane(PDMS)based ion-conducting elastomer with dynamic crosslinking structures is reported,which achieves the stretchability of 475%and healing efficiency of 99%.More importantly,a robust interface bonding can be generated between the electrode and the dielectric material,which is beneficial to enhance the performance and lifespan of the flexible iontronic devices.Using this PDMS based ICE as the electrode and PDMS as the dielectric material,two stretchable iontronic devices(triboelectric nanogenerator and capacitive pressure sensor)are realized with overall self-healing and stretchable capabilities.These findings provide a promising strategy to achieve integrate stretchable iontronics or electronics with a robust interface between the electrode and dielectric materials.

关键词： ion-conducting elastomers robust interface iontronics triboelectric nanogenerator pressure sensor