检索结果-南通市图书馆

Simulation procedure of unconfined seepage with an inner seepage face in a heterogeneous field

在线全文

学校读者我要写书评

暂无评论

Science china(Physics,Mechanics & Astronomy) 2013年第6期56卷 1139-1147页

作者： wu MengXi YANG LianZhi YU ting Institute of Mechanics Chinese Academy of Sciences Hydrochina Chengdu Engineering Corporation

An inner seepage face phenomenon is given and a numerical simulation procedure has been *** may appear at the interface of two materials when an unconfined seepage flows from a porous media to a coarser porous media with a higher *** and divergent problems may arise both in a saturated-only and in a variably saturated analysis while an inner seepage face is not simulated with a special *** position of the seepage face is determined during the nonlinear iteration process and the flux of the inner seepage face nodes is transferred to the downstream side *** and efficiency of the procedure are illustrated by the simulation of two dimensional steady state seepage examples of heterogeneous zoned dams which is usually used to validate *** analysis of a three-dimensional earth core rockfill dam is also presented *** procedure can also be applied to general transient seepage problems.

关键词： unconfined seepage inner seepage face finite element method free surface

Brain region-specific roles of brain-derived neurotrophic factor in social stress-induced depressive-like behavior

在线全文

学校读者我要写书评

暂无评论

Neural Regeneration Research 2025年第1期20卷 159-173页

作者： Man Han Deyang Zeng Wei Tan Xingxing Chen Shuyuan Bai Qiong wu Yushan Chen Zhen Wei Yufei Mei Yan Zeng Brain Science and Advanced Technology Institute Wuhan University of Science and TechnologyWuhanHubei ProvinceChina Geriatric Hospital Affiliated to wuhan University of Science and Technology WuhanHubei ProvinceChina School of Public Health Wuhan University of Science and TechnologyWuhanHubei ProvinceChina

Brain-derived neurotrophic factor is a key factor in stress adaptation and avoidance of a social stress behavioral *** studies have shown that brain-derived neurotrophic factor expression in stressed mice is brain region–specific,particularly involving the corticolimbic system,including the ventral tegmental area,nucleus accumbens,prefrontal cortex,amygdala,and *** how brain-derived neurotrophic factor participates in stress processing in different brain regions will deepen our understanding of social stress *** this review,we discuss the expression and regulation of brain-derived neurotrophic factor in stress-sensitive brain regions closely related to the pathophysiology of *** focused on associated molecular pathways and neural circuits,with special attention to the brain-derived neurotrophic factor–tropomyosin receptor kinase B signaling pathway and the ventral tegmental area–nucleus accumbens dopamine *** determined that stress-induced alterations in brain-derived neurotrophic factor levels are likely related to the nature,severity,and duration of stress,especially in the above-mentioned brain regions of the corticolimbic ***,BDNF might be a biological indicator regulating stress-related processes in various brain regions.

关键词： amygdala chronic mild stress chronic social defeat stress corticolimbic system depression hippocampus medial prefrontal cortex nucleus accumbens social stress models ventral tegmental area

Hybrid electromagnetic-triboelectric nanogenerator for harvesting vibration energy

在线全文

学校读者我要写书评

暂无评论

Nano Research 2015年第10期8卷 3272-3280页

作者： ting Quan Yingchun wu Ya Yang BeijingInstituteofNanoenergyandNanosystems ChineseAcademyofSciencesBeijing100083China

We report a hybrid nanogenerator that includes a triboelectric nanogenerator （TENG） and an electromagnetic generator （EMG） for scavenging mechanical energy. This nanogenerator operates in a hybrid mode using both the triboelectric and electromagnetic induction effects. Under a vibration frequency of 14 Hz, the fabricated TENG can deliver an open-circuit voltage of about 84 V, a short-circuit current of 43 μA, and a maximum power of 1.2 mW （the corresponding power per unit mass and volume are 1.82 mW/g and 3.4 W/m^3, respectively） under a loading resistance of 2 MΩ, whereas the fabricated EMG can produce an opencircuit voltage of about 9.9 V, a short-circuit current of 7 mA, and a maximum power of 17.4 mW （the corresponding power per unit mass and volume are 0.53 mW/g and 3.7 W/m^3, respectively） under a loading resistance of 2 kΩ. Impedance matching between the TENG and EMG can be achieved using a transformer to decrease the impedance of the TENG. Moreover, the energy produced by the hybrid nanogenerator can be stored in a home-made Li-ion battery. This research represents important progress toward practical applications of vibration energy generation for realizing self-charging power cells.

关键词： hybrid nanogenerator triboelectric electromagnetic Li-ion battery vibration energy

Aircraft safety analysis based on differential manifold theory and bifurcation method

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Frontiers of Information Technology & Electronic Engineering 2019年第2期20卷 292-299页

作者： chi ZHOU Ying-hui LI wu-ji ZHENG Peng-wei wu School of Aeronautics and Astronautics Engineering Air Force Engineering University

Loss of control(LOC) is considered one of the leading causes of fatal aircraft accidents worldwide. Reducing LOC is critical to improve flight safety. Although it is still vaguely defined, LOC is generally associated with a flight state that is outside the safety envelope, with nonlinear influences of aircraft dynamics and incorrect handling by the flight crew. We have studied how nonlinear factors and pilot operations contribute to LOC. In this study, the stall point and bifurcation point are confirmed using the bifurcation analysis, and the results show that the aircraft will stall when excessive elevator movement is commanded. Moreover, even though there may be an equilibrium state in one of the elevator deflections, the flight state may still be outside the flight safety envelope. When the flight state is near the edge of the flight safety envelope, the strategy to regulate the elevator deflection is super-sensitive, and a slight change in the elevator deflection may contribute to a flight state outside the safety envelope. To solve this issue, the differential manifold theory is introduced to determine the safety envelope. Examples are provided using NASA's generic transport model.

关键词： Loss of control Safety envelope Aircraft dynamic Bifurcation analysis Differential manifold theory

Differences in Meteorological Conditions between Days with Persistent and Non-Persistent Pollution in Beijing, china

在线全文

学校读者我要写书评

暂无评论

Journal of Meteorological Research 2018年第1期32卷 81-98页

作者： ting YOU Renguang wu Gang HUANG Center for Monsoon System Research Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 College of Atmospheric Sciences Chengdu University of Information Technology Chengdu 610225 State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 Laboratory for Regional Oceanography and Numerical Modeling Qingdao National Laboratory for Marine Science and Technology Qingdao 266237 Joint Center for Global Change Studies Beijing 100875 University of chinese Academy of Sciences Beijing 100049

We compared the regional synoptic patterns and local meteorological conditions during persistent and non-persistent pollution events in Beijing using US NCEP–Department of Energy reanalysis outputs and observations from meteorological stations. The analysis focused on the impacts of high-frequency（period 〈 90 days） variations in meteorological conditions on persistent pollution events（those lasting for at least 3 days）. Persistent pollution events tended to occur in association with slow-moving weather systems producing stagnant weather conditions, whereas rapidly moving weather systems caused a dramatic change in the local weather conditions so that the pollution event was short-lived. Although Beijing was under the influence of anomalous southerly winds in all four seasons during pollution events, notable differences were identified in the regional patterns of sea-level pressure and local anomalies in relative humidity among persistent pollution events in different seasons. A region of lower pressure was present to the north of Beijing in spring, fall, and winter, whereas regions of lower and higher pressures were observed northwest and southeast of Beijing, respectively, in summer. The relative humidity near Beijing was higher in fall and winter, but lower in spring and summer. These differences may explain the seasonal dependence of the relationship between air pollution and the local meteorological variables. Our analysis showed that the temperature inversion in the lower troposphere played an important part in the occurrence of air pollution under stagnant weather *** results from this study are based on a limited number of events and thus require validation using more data.

关键词： persistent and non-persistent pollution events regional synoptic patterns local meteorological conditions temperature inversion stability index Beijing

Adsorption of lead on multi-walled carbon nanotubes with different outer diameters and oxygen contents: Kinetics, isotherms and thermodynamics

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2013年第1期25卷 195-203页

作者： Fei Yu Yanqing wu Jie Ma chi Zhang School of Environmental Science and Engineering Shanghai Jiao Tong University State Key Laboratory of Pollution Control and Resource Reuse School of Environmental Science and EngineeringTongji University

The effects of different outer diameters and surface oxygen contents on the adsorption of heavy metals onto six types of multi-walled carbon nanotubes （MWCNTs） were investigated in an aqueous solution and lead was chosen as a model metal ion. The results indicated that the percentage removal and adsorption capacity of lead remarkably increased with decreasing outer diameter due to larger specific surface area （SSA）. The SSA-normalized maximum adsorption capacity （qJSSA） and SSA-normalized adsorption coefficient （KdSSA） were strongly positively correlated with surface oxygen content, implying that lead adsorption onto MWCNTs significantly increases with the rise of oxygen content and decreases with decreasing SSA. The calculated thermodynamic parameters indicated that adsorption of lead on MWCNTs was endothermic and spontaneous. When the oxygen content of MWCNTs increased from 2.0% to 5.9%, the standard free energy （AGt） became more negative, which implied that the oxygenated functional groups increased the adsorption affinity of MWCNTs for lead. Through calculation of enthalpy （△H0）, AGO and free energy of adsorption （Ea）, lead adsorption onto MWCNTs was recognized as a chemisorption process. The chemical interaction between lead and the phenolic groups of MWCNTs could be one of the main adsorption mechanisms due to highly positive correlations between the phenolic groups and Kd/SSA or qm/SSA.

关键词： adsorption lead multi-walled carbon nanotube diameter surface oxygen content

Detecting changes in long-period site responses after the M_w 7.6 chi-chi earthquake, Taiwan, using strong motion records

在线全文

学校读者我要写书评

暂无评论

Earthquake Engineering and Engineering Vibration 2015年第2期14卷 217-228页

作者： Teng-To Yu chi-Shin wu Youg-Sin Cheng Department of Resources Engineering Cheng Kung University (NCKU)

Temporal changes in site effects are obtained using the HVSR(horizontal-to-vertical spectral ratio) method and strong motion records after the M w 7.6 chi-chi earthquake, Taiwan. Seismic data recorded between 1995 and 2010 are used, comprising 3,708 data from 15 stations adjacent to the Chelungpu fault. Temporal fl uctuations are determined by analyzing the site effect variation using a time–frequency variation(TFV) diagram based on these seismic data. Stations adjacent to the fault show signifi cant disturbances in the resonance frequency at 16–26 Hz. Station TCU129 shows a 40% drop in fundamental frequency after the main shock, and a gradual return to the original state over nine years. For stations located farther from the fault zone, sudden changes in tectonic stress play a dominant role in temporal changes to the HVSR. An impact analysis of the directional factor confi rms our fi nding that the proximity of the fault to seismic stations has the most infl uence on data.

关键词： chi-chi earthquake horizontal-to-vertical spectral

Structural optimization strategy of pipe isolation tool by dynamic plugging process analysis

在线全文

学校读者我要写书评

暂无评论

Petroleum Science 2021年第6期18卷 1829-1839页

作者： ting-ting wu Hong Zhao Bo-Xuan Gao Fan-Bo Meng College of Mechanical and Transportation Engineering China University of PetroleumBeijing102249China

During the pipeline plugging process,both the pipeline and the pipe isolation tool(PIT)will be greatly damaged,due to the violent vibration of the flow *** this study,it was proposed for the first time to reduce the vibration of the flow field during the plugging process by optimizing the surface structure of the ***,the central composite design(CCD)was used to obtain the optimization schemes,and the drag coefficient and pressure coefficient were proposed to evaluate the degree of flow field ***,a series of computational fluid dynamics(CFD)simulations were performed to obtain the drag coefficient and pressure coefficient during dynamic *** the mathematical model of drag coefficient and pressure coefficient with the surface structure of the PIT were established ***,a modified particle swarm optimization(PSO)was applied to predict the optimal value of the surface structure of the ***,an experimental rig was built to verify the effectiveness of the *** results showed that the improved method could reduce the flow field vibration by 49.56%.This study provides a reference for the design of the PIT surface structure for flow field vibration technology.

关键词： Pipe isolation tool Dynamic analysis Drag coefficient Pressure coefficient Modified particle swarm optimization algorithm

Intelligent identification of landslides in loess areas based on the improved YOLO algorithm:a case study of loess landslides in Baoji City

在线全文

学校读者我要写书评

暂无评论

Journal of Mountain Science 2023年第11期20卷 3343-3359页

作者： LIU Qing wu ting-ting DENG Ya-hong LIU Zhi-heng School of Mechanical and Electrical Engineering Huainan Normal UniversityHuainan 232038China School of Geomatics Anhui University of Science and TechnologyHuainan 232001China School of Geology Engineering and Geomatics Chang’an UniversityXi’an 710064China School of Aerospace Science and Technology Xidian UniversityXi'an 710064China

Loess landslides are one of the geological hazards prevalent in mountainous areas of Loess Plateau,seriously threatening people's lives and property *** identification of landslides is a prerequisite for reducing the risk of landslide *** landslide interpretation methods often have the disadvantage of being laborious and difficult to use on a large scale compared with the recently developed deep learning-based landslide detection *** this study,we propose an improved deep learning model,landslide detectionyou only look once(LD-YOLO),based on the existing you only look once(YOLO)model for the intelligent identification of old and new landslides in loess ***,remote sensing images of landslides in Baoji City,Shaanxi Province,china are acquired from the Google Earth Engine *** landslide images of Baoji City(excluding Qianyang County)are used to establish a loess landslide dataset for training the *** landslide data of Qianyang County is used to verify the detection performance of the *** focal and efficient IoU(Focal-EIoU)loss function and efficient channel attention(ECA)mechanism are incorporated into the 7th version of YOLO(YOLOv7)model to construct the LD-YOLO model,which makes it more suitable for the landslide detection *** experiments yielded an improved LD-YOLO model with average precision of 92.05%,precision of 92.31%,recall of 90.28%,and F1-score of 91.28%for loess landslide *** landslides in Qianyang County were divided into two test sets,new landslides and old landslides,which were used to test the detection performance of LD-YOLO for both types of *** results show that LD-YOLO detects old landslides with a detection precision of 82.75%and a recall of 80%.When detecting new landslides,the detection precision is 94.29%and the recall is 91.67%.It indicates that our proposed LD-YOLO model has strong detection performance for both new and old landslides in loess areas

关键词： Loess landslide Deep learning Attention mechanism Data augmentation You only look once(YOLO)