期刊文献+
共找到956篇文章
< 1 2 48 >
每页显示 20 50 100
Assessment of China’s forest fi re occurrence with deep learning, geographic information and multisource data
1
作者 Yakui Shao Zhichao Wang +4 位作者 Zhongke Feng Linhao Sun Xuanhan Yang Jun Zheng Tiantian Ma 《Journal of Forestry Research》 SCIE CAS CSCD 2023年第4期963-976,共14页
Considerable economic losses and ecological damage can be caused by forest fi res,and compared to suppression,prevention is a much smarter strategy.Accordingly,this study focuses on developing a novel framework to ass... Considerable economic losses and ecological damage can be caused by forest fi res,and compared to suppression,prevention is a much smarter strategy.Accordingly,this study focuses on developing a novel framework to assess forest fi re risks and policy decisions on forest fi re management in China.This framework integrated deep learning algorithms,geographic information,and multisource data.Compared to conventional approaches,our framework featured timesaving,easy implementation,and importantly,the use of deep learning that vividly integrates various factors from the environment and human activities.Information on 96,594 forest fi re points from 2001 to 2019 was collected on Moderate Resolution Imaging Spectroradiometer(MODIS)fi re hotspots from 2001 to 2019 from NASA’s Fire Information Resource Management System.The information was classifi ed into factors such as topography,climate,vegetation,and society.The prediction of forest fi re risk was generated using a fully connected network model,and spatial autocorrelation used to analyze the spatial aggregation correlation of active fi re hotspots in the whole area of China.The results show that high accuracy prediction of fi re risks was achieved(accuracy 87.4%,positive predictive value 87.1%,sensitivity 88.9%,area under curve(AUC)94.1%).Based on this,it was found that Chinese forest fi re risk shows signifi cant autocorrelation and agglomeration both in seasons and regions.For example,forest fi re risk usually raises dramatically in spring and winter,and decreases in autumn and summer.Compared to the national average,Yunnan Province,Guangdong Province,and the Greater Hinggan Mountains region of Heilongjiang Province have higher fi re risks.In contrast,a large region in central China has been recognized as having a long-term,low risk of forest fi res.All forest risks in each region were recorded into the database and could contribute to the forest fi re prevention.The successful assessment of forest fi re risks in this study provides a comprehensive knowledge of fi re risks in China over the last 20 years.Deep learning showed its advantage in integrating multiple factors in predicting forest fi re risks.This technical framework is expected to be a feasible evaluation tool for the occurrence of forest fi res in China. 展开更多
关键词 Forest fi res Deep learning Spatial autocorrelation Risk zoning Management strategies
下载PDF
Identifying anthropogenic and natural causes of wildfires by maximum entropy method-based ignition susceptibility distribution models 被引量:1
2
作者 Fatih Sari 《Journal of Forestry Research》 SCIE CAS CSCD 2023年第2期355-371,共17页
Turkey has a high potential for wildfires along its Mediterranean coast because of its dense forest cover and mild climate.An average of 250 wildfires occurs every year with more than 10,000 hectares destroyed due to ... Turkey has a high potential for wildfires along its Mediterranean coast because of its dense forest cover and mild climate.An average of 250 wildfires occurs every year with more than 10,000 hectares destroyed due to natural and human-related causes.The study area is sensitive to fires caused by lightning,stubble burning,discarded cigarette butts,electric arcing from power lines,deliberate fire setting,and traffic accidents.However,52%of causes could not be identified due to intense wildfires occurring at the same time and insufficient equipment and personnel.Since wildfires destroy forest cover,ecosystems,biodiversity,and habitats,they should be spatially evaluated by separating them according to their causes,considering environmental,climatic,topographic and forest structure variables that trigger wildfires.In this study,wildfires caused by lightning,the burning of agriculture stubble,discarded cigarette butts and power lines were investigated in the provinces of Aydin,Mugla and Antalya,where 22%of Turkey’s wildfires occurred.The MaxEnt method was used to determine the spatial distribution of wildfires to identify risk zones for each cause.Wildfires were used as the species distribution and the probability of their occurrence estimated.Additionally,since the causes of many wildfires are unknown,determining the causes is important for fire prediction and prevention.The highest wildfire occurrence risks were 9.7%for stubble burning,30.2%for lightning,4.5%for power lines and 16.9%by discarded cigarette butts.In total,1,266 of the 1,714 unknown wildfire causes were identified by the analysis of the cause-based risk zones and these were updated by including cause-as signed unknown wildfire locations for verification.As a result,the Area under the ROC Curve(AUC)values were increased for susceptibility maps. 展开更多
关键词 Wildfi re susceptibility MAXENT Geographical information systems Forest fi res
下载PDF
Geospatial characteristics of fire occurrences in southern hemispheric Africa and Madagascar during 2001-2020
3
作者 Chuyan Wan Shouraseni Sen Roy 《Journal of Forestry Research》 SCIE CAS CSCD 2023年第2期553-563,共11页
For this study of long-term spatial patterns and trends of active fires in southern hemispheric Africa and on Madagascar from 2001 to 2020,active fire data from the MODIS FIRMS global fire data products were analyzed.... For this study of long-term spatial patterns and trends of active fires in southern hemispheric Africa and on Madagascar from 2001 to 2020,active fire data from the MODIS FIRMS global fire data products were analyzed.The annual center of fire concentration tended to migrate toward the preserved rainforests and nature conservation areas in the Congo Basin and the mountain forests on the northeastern coast of Madagascar.Fire frequency varied seasonally at both study areas.We used geo statistical analysis techniques,such as measures of dispersion and emerging hot spot analysis,to reveal long-term trends in spatial patterns of fire events.In southern hemispheric Africa,the observed active fires tended to drift northward toward the Zambia-DRC border in the Congo basin.This northward migration progressed toward humid rainforests,which were better suited to sustaining repeated fire events.On Madagascar,the observed active fires tended to migrate toward the east coast in protected mountain forests.The spatial patterns of long-term trends showed a concentration of fires in the tropical regions of southern hemispheric Africa.Moreover,smaller clusters of new hot spots were located over eastern South Africa,overlapping with undifferentiated woodlands.On Madagascar,both hot and cold spots were identified and were separated by the highland region in the center of the island.Most of the eastern island was characterized by cold spots that received less precipitation than did the rest of the island.The presence of increasing hots spots in the densely vegetated areas highlights the urgent need for fire prevention and management in this region. 展开更多
关键词 Emerging hot spots analysis fiRMS Forest fi res Madagascar MODIS Southern hemispheric Africa Wildfi res
下载PDF
Mutual promotion of mitochondrial fi ssion and oxidative stress contributes to mitochondrial-DNAmediated infl ammation and epithelial-mesenchymal transition in paraquat-induced pulmonary fibrosis 被引量:1
4
作者 Jie Zhang Wen-jing Li +8 位作者 Shi-qiang Chen Ze Chen Chen Zhang Ran Ying Hong-bing Liu Long-wang Chen Ya-hui Tang Zhong-qiu Lu Guang-ju Zhao 《World Journal of Emergency Medicine》 SCIE CAS CSCD 2023年第3期209-216,共8页
BACKGROUND:Pulmonary fibrosis(PF)is one of the main causes of death in patients with paraquat(PQ)poisoning.This study aimed to evaluate the relationship between mitochondrial fi ssion and oxidative stress in PQ-induce... BACKGROUND:Pulmonary fibrosis(PF)is one of the main causes of death in patients with paraquat(PQ)poisoning.This study aimed to evaluate the relationship between mitochondrial fi ssion and oxidative stress in PQ-induced epithelial-mesenchymal transition(EMT)and PF.METHODS:C57BL/6 mice and MLE-12 cells were exposed to PQ to construct a PF model in vivo and in vitro.Histological changes in the lungs were examined by hematoxylin and eosin(H&E)staining.Mitochondrial morphology was detected by MitoTracker®Deep Red FM or transmission electron microscopy(TEM).Western blotting and immunofluorescence were used to determine the expression of protein.The migration ability of the cells was detected by the cell scratch test.Mitochondrial DNA(mtDNA)levels were assessed by real-time polymerase chain reaction(PCR).Enzyme-linked immunosorbent assay(ELISA)was applied to detect cytokine levels.Superoxide dismutase(SOD)activity and the levels of glutathione(GSH)and malondialdehyde(MDA)were detected by chemichromatometry.RESULTS:PQ exposure caused EMT and PF in vivo and in vitro.PQ destroyed mitochondrial structure and enhanced the expression of dynamin-related protein 1(Drp1),which were accompanied by oxidative stress.Inhibiting mitochondrial fission using mitochondrial division inhibitor-1(Mdivi-1),a selective inhibitor of Drp1,attenuated PQ-induced EMT and oxidative damage.Treatment with N-acetyl-L-cysteine(NAC),an antioxidant,reduced Drp1 expression,attenuated mitochondrial structure damage and inhibited PQ-induced EMT and PF.Both Mdivi-1 and NAC treatment markedly suppressed mtDNA release,the expression of Toll-like receptor 9(TLR9)and phosphorylation(P)-NF-κB p65 as well as cytokines(interleukin 6[IL-6],interleukin-1β[IL-1β],and tumor necrosis factor-α[TNF-α])production.CONCLUSION:Mutual promotion of mitochondrial fission and oxidative stress contributes to EMT in PQ-induced PF,which is associated with the mtDNA/TLR9/NF-κB pathway. 展开更多
关键词 PARAQUAT Mitochondrial fi ssion Oxidative stress Epithelial-mesenchymal transition Mitochondrial DNA
下载PDF
基于Wi-Fi Direct的文件信息系统的设计与实现
5
作者 王大鹏 《无线互联科技》 2013年第11期9-9,共1页
Wi-Fi Direct技术是近年新兴的近距离无线通信技术,该技术无需Wi-Fi热点即可实现设备之间的互联互通,在近距离无线通信技术中具有显著的优势和广阔的应用前景。本文设计并实现了基于Wi-Fi Direct技术的文件共享系统应用,具有传输速率高... Wi-Fi Direct技术是近年新兴的近距离无线通信技术,该技术无需Wi-Fi热点即可实现设备之间的互联互通,在近距离无线通信技术中具有显著的优势和广阔的应用前景。本文设计并实现了基于Wi-Fi Direct技术的文件共享系统应用,具有传输速率高、覆盖距离大、便捷易用、功能设计完善以及拓展性强等特点,具有很强的应用价值。 展开更多
关键词 wi—fi DIreCT ANDROID 信息共享
下载PDF
Smoldering charcoal detection in forest soil by multiple CO sensors
6
作者 Chunmei Yang Yuning Hou +2 位作者 Tongbin Liu Yaqiang Ma Jiuqing Liu 《Journal of Forestry Research》 SCIE CAS CSCD 2023年第6期1791-1802,共12页
Cleaning up residual fires is an important part of forest fire management to avoid the loss of forest resources caused by the recurrence of a residual fire.Existing residual fire detection equipment is mainly infrared... Cleaning up residual fires is an important part of forest fire management to avoid the loss of forest resources caused by the recurrence of a residual fire.Existing residual fire detection equipment is mainly infrared temperature detection and smoke identification.Due to the isolation of ground,temperature and smoke characteristics of medium and large smoldering charcoal in some forest soils are not obvious,making it difficult to identify by detection equipment.CO gas is an important detection index for indoor smoldering fire detection,and an important identification feature of hidden smoldering ground fires.However,there is no research on locating smoldering fires through CO detection.We studied the diffusion law of CO gas directly above covered smoldering charcoal as a criterion to design a detection device equipped with multiple CO sensors.According to the motion decomposition search algorithm,the detection device realizes the function of automatically searching for smoldering charcoal.Experimental data shows that the average CO concentration over the covered smoldering charcoal decreases exponentially with increasing height.The size of the search step is related to the reliability of the search algorithm.The detection success corresponding to the small step length is high but the search time is lengthy which can lead to search failure.The introduction of step and rotation factors in search algorithm improves the search efficiency.This study reveals that the average ground CO concentration directly above smoldering charcoal in forests changes with height.Based on this law,a CO gas sensor detection device for hidden smoldering fires has been designed,which enriches the technique of residual fire detection. 展开更多
关键词 Forest fi res Smoldering fire detection Wood carbon smoldering CO sensor
下载PDF
Hypoxia,angiogenesis and liver fibrogenesis in the progression of chronic liver diseases 被引量:23
7
作者 Claudia Paternostro Ezio David +1 位作者 Erica Novo Maurizio Parola 《World Journal of Gastroenterology》 SCIE CAS CSCD 2010年第3期281-288,共8页
Angiogenesis is a dynamic,hypoxia-stimulated and growth factor-dependent process,and is currently referred to as the formation of new vessels from preexisting blood vessels.Experimental and clinical studies have unequ... Angiogenesis is a dynamic,hypoxia-stimulated and growth factor-dependent process,and is currently referred to as the formation of new vessels from preexisting blood vessels.Experimental and clinical studies have unequivocally reported that hepatic angiogenesis,irrespective of aetiology,occurs in conditions of chronic liver diseases(CLDs) characterized by perpetuation of cell injury and death,inflammatory response and progressive fibrogenesis.Angiogenesis and related changes in liver vascular architecture,that in turn concur to increase vascular resistance and portal hypertension and to decrease parenchymal perfusion,have been proposed to favour fibrogenic progression of the disease towards the end-point of cirrhosis.Moreover,hepatic angiogenesis has also been proposed to modulate the genesis of portal-systemic shunts and increase splanchnic blood flow,thus potentially affecting complications of cirrhosis.Hepatic angiogenesis is also crucial for the growth and progression of hepatocellular carcinoma.Recent literature has identified a number of cellular and molecular mechanisms governing the cross-talk between angiogenesis and fibrogenesis,with a specifi c emphasis on the crucial role of hypoxic conditions and hepatic stellate cells,particularly when activated to the myofibroblast-like pro-fibrogenic.Experimental anti-angiogenic therapy has been proven to be effective in limiting the progression of CLDs in animal models.From a clinical point of view,anti-angiogenic therapy is currently emerging as a new pharmacologic intervention in patients with advanced fibrosis and cirrhosis. 展开更多
关键词 Chronic liver diseases Hepatic myofi broblasts HYPOXIA Liver angiogenesis Liver fi brogenesis
下载PDF
Numerical simulations of shake-table experiment for dynamic soil-pile-structure interaction in liquefi able soils 被引量:15
8
作者 Tang Liang Baydaa Hussain Maula +1 位作者 Ling Xianzhang Su Lei 《Earthquake Engineering and Engineering Vibration》 SCIE EI CSCD 2014年第1期171-180,共10页
A shake-table experiment on pile foundations in liquefi able soils composed of liquefi able sand and overlying soft clay is studied. A three-dimensional(3D) effective stress fi nite element(FE) analysis is employed to... A shake-table experiment on pile foundations in liquefi able soils composed of liquefi able sand and overlying soft clay is studied. A three-dimensional(3D) effective stress fi nite element(FE) analysis is employed to simulate the experiment. A recently developed multi-surface elasto-plastic constitutive model and a fully coupled dynamic inelastic FE formulation(u-p) are used to model the liquefaction behavior of the sand. The soil domains are discretized using a solid-fl uid fully coupled(u-p) 20-8 noded brick element. The pile is simulated using beam-column elements. Upon careful calibration, very good agreement is obtained between the computed and the measured dynamic behavior of the ground and the pile. A parametric analysis is also conducted on the model to investigate the effect of pile-pinning, pile diameter, pile stiffness, ground inclination angle, superstructure mass and pile head restraints on the ground improvement. It is found that the pile foundation has a noticeable pinning effect that reduces the lateral soil displacement. It is observed that a larger pile diameter and fi xed pile head restraints contribute to decreasing the lateral pile deformation; however, a higher ground inclination angle tends to increase the lateral pile head displacements and pile stiffness, and superstructure mass seems to effectively infl uence the lateral pile displacements. 展开更多
关键词 LIQUEFACTION pile pinning soil improvement pile deformation EARTHQUAKE nonlinear fi nite element method shake-table experiment
下载PDF
3D magnetotelluric inversions with unstructured finite-element and limited-memory quasi-Newton methods 被引量:8
9
作者 Cao Xiao-Yue Yin Chang-Chun +3 位作者 Zhang Bo Huang Xin Liu Yun-He Cai Jing 《Applied Geophysics》 SCIE CSCD 2018年第3期556-565,共10页
Traditional 3D Magnetotelluric(MT) forward modeling and inversions are mostly based on structured meshes that have limited accuracy when modeling undulating surfaces and arbitrary structures. By contrast, unstructured... Traditional 3D Magnetotelluric(MT) forward modeling and inversions are mostly based on structured meshes that have limited accuracy when modeling undulating surfaces and arbitrary structures. By contrast, unstructured-grid-based methods can model complex underground structures with high accuracy and overcome the defects of traditional methods, such as the high computational cost for improving model accuracy and the difficulty of inverting with topography. In this paper, we used the limited-memory quasi-Newton(L-BFGS) method with an unstructured finite-element grid to perform 3D MT inversions. This method avoids explicitly calculating Hessian matrices, which greatly reduces the memory requirements. After the first iteration, the approximate inverse Hessian matrix well approximates the true one, and the Newton step(set to 1) can meet the sufficient descent condition. Only one calculation of the objective function and its gradient are needed for each iteration, which greatly improves its computational efficiency. This approach is well-suited for large-scale 3D MT inversions. We have tested our algorithm on data with and without topography, and the results matched the real models well. We can recommend performing inversions based on an unstructured finite-element method and the L-BFGS method for situations with topography and complex underground structures. 展开更多
关键词 Magnetotelluric(MT) 3D inversion UNSTRUCTUreD fi nite-element METHOD QUASI-NEWTON METHOD L-BFGS
下载PDF
Three-dimensional inversion of controlled-source audio-frequency magnetotelluric data based on unstructured fi nite-element method 被引量:6
10
作者 Chen Xiang-Zhong Liu Yun-He +4 位作者 Yin Chang-Chun Qiu Chang-Kai Zhang Jie Ren Xiu-Yan Zhang Bo 《Applied Geophysics》 SCIE CSCD 2020年第3期349-360,共12页
We propose a new 3D inversion scheme to invert the near-and transition-zone data of CSAMT with topography accurately.In this new method,the earth was discretized into unstructured tetrahedra to fit the ragged topograp... We propose a new 3D inversion scheme to invert the near-and transition-zone data of CSAMT with topography accurately.In this new method,the earth was discretized into unstructured tetrahedra to fit the ragged topography and the vector fi nite-element method was adopted to obtain precise responses and good sensitivity.To simulate the attitude and shape of the transmitter,we divided a long-grounded transmitter into dipoles and integrated these dipoles to obtain good responses in the near-and transition-fi eld zones.Next,we designed an L2 norm-based objective functional and applied a standard quasi-Newton method as the optimization method to solve the inverse problem and guarantee steady convergence.We tested our 3D inversion method first on synthetic data and then on a field dataset acquired from select sites near Changbai Mountain,China.In both tests,the new inversion algorithm achieved excellent fitting between the predicted and observed data,even in near-and transition-fi eld zones,and the inversion results agreed well with the true model.These fi ndings reveal that the proposed algorithm is eff ective for 3D inversion of CSAMT data. 展开更多
关键词 CSAMT 3D inversion TOPOGRAPHY unstructured grids fi nite-element
下载PDF
基于Wi-FiDirect的WLAN与TD-LTE共存研究 被引量:1
11
作者 傅金希 张玲 张欣 《移动通信》 2014年第3期48-51,共4页
Wi-Fi Direct在实际应用中有着广泛的发展前景。采用确定性分析以及蒙特卡洛静态仿真方法,通过系统级仿真,研究了室内场景下基于Wi-Fi Direct的WLAN系统对于TD-LTE系统的影响。
关键词 Wi—fi DIreCT TD—LTE 干扰共存 系统级仿真
下载PDF
Effect of solidification parameters on the microstructures of a single crystal Ni-based superalloy AM3 被引量:4
12
作者 Yu Zhuhuan Liu Lin +3 位作者 Zhao Xinbao Zhang Weiguo Zhang Jun Fu Hengzhi 《China Foundry》 SCIE CAS 2010年第3期217-223,共7页
A single crystal Ni-based superalloy AM3 was processed at withdraw rates of 3.5, 10, 50, 100, 200, and 500 μm·s-1, respectively.The as-cast microstructures and solidification segregation ratio were characterized... A single crystal Ni-based superalloy AM3 was processed at withdraw rates of 3.5, 10, 50, 100, 200, and 500 μm·s-1, respectively.The as-cast microstructures and solidification segregation ratio were characterized with various withdraw rates.The shape and size of carbide microstructures were determined.As expected, the primary and secondary dendrite arm spacings (PDAS and SDAS) decrease with the increase of withdraw rate.The highest volume fraction of eutectic γ/γ' is observed at the 100 μm·s-1 withdraw rate.The volume fraction of eutectic γ/γ' does not appear to be a strong function of the withdraw rate.With increasing withdraw rate, interface morphologies change in the sequence of planar, cellular, and dendrite.There is a general refinement of the microstructure as the withdraw rate increases.EPMA analysis showed that withdraw rate does not have obvious influence on the segregation of elements. 展开更多
关键词 Ni-based superalloy single crystal withdraw rate solidi fi cation PDAS SDAS
下载PDF
Experimental study on the seismic behavior of high strength concrete fi lled double-tube columns 被引量:13
13
作者 Qian Jiaru Li Ningbo +1 位作者 Ji Xiaodong Zhao Zuozhou 《Earthquake Engineering and Engineering Vibration》 SCIE EI CSCD 2014年第1期47-57,共11页
To study the seismic behavior of high strength concrete fi lled double-tube(CFDT) columns,each consisting of an external square steel tube and an internal circular steel tube,quasi-static tests on eight CFDT column sp... To study the seismic behavior of high strength concrete fi lled double-tube(CFDT) columns,each consisting of an external square steel tube and an internal circular steel tube,quasi-static tests on eight CFDT column specimens were conducted.The test variables included the width-to-thickness ratio(β1) and the area ratio(β2) of the square steel tube,the wall thickness of the circular steel tube,and the axial force(or the axial force ratio) applied to the CFDT columns.The test results indicate that for CFDT columns with a square steel tube with β1 of 50.1 and 24.5,local buckling of the specimen was found at a drift ratio of 1/150 and 1/50,respectively.The lateral force-displacement hysteretic loops of all specimens were plump and stable.Reducing the width-to-thickness ratio of the square steel tube,increasing its area ratio,or increasing the wall thickness of the internal circular steel tube,led to an increased fl exural strength and deformation capacity of the specimens.Increasing the design value of the axial force ratio from 0.8 to 1.0 may increase the fl exural strength of the specimens,while it may also decrease the ultimate deformation capacity of the specimen with β1 of 50.1. 展开更多
关键词 high strength concrete fi lled double-tube(CFDT)column seismic behavior area ratio of the square steel tube width-to-thickness ratio of the square steel tube axial force ratio quasi-static test
下载PDF
Calibration of a hysteretic model for glass fiber reinforced gypsum wall panels 被引量:4
14
作者 Maganti Janardhana Robin Davis P +2 位作者 S.S.Ravichandran A.M.Prasad D.Menon 《Earthquake Engineering and Engineering Vibration》 SCIE EI CSCD 2014年第2期347-355,共9页
Glass fi ber reinforced gypsum(GFRG) wall panels are prefabricated panels with hollow cores, originally developed in Australia and subsequently adopted by India and China for use in buildings. This paper discusses ide... Glass fi ber reinforced gypsum(GFRG) wall panels are prefabricated panels with hollow cores, originally developed in Australia and subsequently adopted by India and China for use in buildings. This paper discusses identifi cation and calibration of a suitable hysteretic model for GFRG wall panels fi lled with reinforced concrete. As considerable pinching was observed in the experimental results, a suitable hysteretic model with pinched hysteretic rule is used to conduct a series of quasi-static as inelastic hysteretic response analyses of GFRG panels with two different widths. The calibration of the pinching model parameters was carried out to approximately match the simulated and experimental responses up to 80% of the peak load in the post peak region. Interestingly, the same values of various parameters(energy dissipation and pinching related parameters) were obtained for all fi ve test specimens. 展开更多
关键词 glass fi ber reinforced gypsum walls hysteretic model pinching model
下载PDF
Molecular Characterization of Hydrotreated Atmospheric Residue Derived from Arabian Heavy Crude by GC FI/FD TOF MS and APPI FT-ICR MS 被引量:4
15
作者 Diao Rui Wang Wei +3 位作者 Wang Naixin Liu Zelong Dai Lishun Tian Songbai 《China Petroleum Processing & Petrochemical Technology》 SCIE CAS 2012年第4期80-88,共9页
High resolution mass spectrometry in combination with distillation and SARA fractionation provides us an opportunity for in-depth understanding about the hydrotreating process at the molecular level. In this study, th... High resolution mass spectrometry in combination with distillation and SARA fractionation provides us an opportunity for in-depth understanding about the hydrotreating process at the molecular level. In this study, the atmospheric residue derived from Arabian heavy crude and its hydrotreated products were initially subjected to distillation and SARA fractionation. The saturates were characterized by GC FI/FD TOF MS. The aromatics and resins were characterized by APPI FT-ICR MS. Compositional changes of different compounds (paraffins, naphthenes, aromatic hydrocarbons, and heteroatomic compounds) contained in different distillates (vacuum gas oil, vacuum residue) were obtained. More detailed knowledge about the hydrotreating process was achieved. 展开更多
关键词 hydrotreating petroleum residue FT-ICR MS GC fi/FD TOF MS
下载PDF
Study on the crustal stress fi eld of the Tengchong volcanic area using composite focal mechanism method 被引量:3
16
作者 Sheng Shu-zhong Wan Yong-ge +4 位作者 Jiang Chang-sheng Wang Xiao-shan Liang Shan-shan Xiao Gen-ru Hu Xiao-hui 《Applied Geophysics》 SCIE CSCD 2021年第2期238-251,274,共15页
We calculated the crustal stress field using the composite focal mechanism method based on the P-wave initial motion polarity data of the Tengchong volcanic area from January 2011 to April 2019 obtained from the Bulle... We calculated the crustal stress field using the composite focal mechanism method based on the P-wave initial motion polarity data of the Tengchong volcanic area from January 2011 to April 2019 obtained from the Bulletin of Seismological Observations of Chinese stations.The magnitude range of earthquakes used in this study is 0–4,and their magnitudes are mainly approximately 1.0.To investigate the infl uence of the source location on the stress fi eld and obtain reliable stress fi elds of the study area,we applied the double-diff erence algorithm to relocate the seismic events,obtaining more accurate and reliable relative positions of seismic events with a clearer seismic belt.On the basis of relocation results,the study on the stress fi eld along the fault zone was conducted,and the infl uence of seismic event position on the stress fi eld was analyzed.Results show that,fi rst,the current stress regime in the shallow crust of the Tengchong volcanic area is strike-slip faulting,the orientation of the principal compressive stress axis is NE–SW,the orientation of the principal extension stress axis is SE–NW,the principal compressive and extension stress axes are nearly horizontal,and the dip angle of intermediate principal stress axis is relatively large.This reflects that the volcanic and seismic activities in the Tengchong volcanic area are mainly controlled by the collision and squeezing eff ect of the Indian–Eurasian plate.It also refl ects that the current tensile action caused by deep magma activity has little infl uence on the shallow crustal stress field.Second,the stress field along fault zones reveals that there exist local stress fi elds,such as the thrust stress regime at the strike-slip fault terminal area,which is consistent with the compressional area at the intersection of conjugate strike-slip faults indicated by previous study.Third,the stress fi eld results are consistent,regardless of using the original location in the bulletin or the relocated location,indicating that the infl uence of the event location error can be neglected when there are suffi cient data and refl ecting the stability of the composite focal mechanism method.The findings can serve as a reference for investigating geological structure movement,seismic activities,and volcanic activities in the Tengchong volcanic area. 展开更多
关键词 Tengchong volcanic area Composite focal mechanism Stress fi eld Double-diff erence location Conjugate Fault
下载PDF
Increased fibrosis progression rates in hepatitis C patients carrying the prothrombin G20210A mutation 被引量:2
17
作者 Nitsan Maharshak Philippe Halfon +7 位作者 Varda Deutsch Hava Peretz Shlomo Berliner Sigal Fishman Shira Zelber-Sagi Uri Rozovski Moshe Leshno Ran Oren 《World Journal of Gastroenterology》 SCIE CAS CSCD 2011年第45期5007-5013,共7页
AIM: To examine whether hepatitis C virus (HCV)-infected patients who carry hypercoagulable mutationssuffer from increased rates of liver fi brosis. METHODS: We analyzed DNA samples of 168 HCV patients for three commo... AIM: To examine whether hepatitis C virus (HCV)-infected patients who carry hypercoagulable mutationssuffer from increased rates of liver fi brosis. METHODS: We analyzed DNA samples of 168 HCV patients for three common hypercoagulable gene mutations: prothrombin 20210 (PT20210), factor V Leiden (FV Leiden) and methylene tetrahydrofolate reductase (MTHFR). The patients were consecutively recruited as part of the prospective "Fibroscore Study" in France. The effect of the various mutations on the rate of fi-brosis was analyzed statistically and was correlated with epidemiological, clinical and biochemical data such as grade and stage of liver biopsies, patients' risk factors for liver cirrhosis, and timing of infection. RESULTS: Fifty two of the patients were categorized as "fast fi brosers" and 116 as "slow fi brosers"; 13% of the "fast fi brosers" carried the PT20210 mutation as compared with 5.5% of the "slow fi brosers", with an odds ratio of 4.76 (P = 0.033; 95% CI: 1.13-19.99) for "fast" liver fibrosis. Carriage of MTHFR or FV Leiden mutations was not associated with enhanced liver fi brosis. CONCLUSION: Carriage of the PT20210 mutation is related to an increased rate of liver fi brosis in HCV patients. 展开更多
关键词 Hepatitis C virus Liver fi brosis Hyperco-agulation Prothrombin 20210
下载PDF
An Empirical Study of the Allocation Efficiency of Rural Financial Resources in Hubei Province from the Perspective of Agricultural Loans 被引量:3
18
作者 Xiaofang ZOU Xueqin JIANG 《Asian Agricultural Research》 2014年第8期38-41,共4页
The incompatibility of China's economy and finance has to some extent inhibited the development of rural economy. Taking Hubei Province for example,we measure the allocation efficiency of rural financial resources... The incompatibility of China's economy and finance has to some extent inhibited the development of rural economy. Taking Hubei Province for example,we measure the allocation efficiency of rural financial resources from the perspective of agricultural input and output,and use the modern rural financial development theory to set forth some policy recommendations on how to build a new rural financial resource allocation system. Studies have shown that the allocation efficiency of rural financial resources is low in China,and improving the allocation efficiency of rural financial resources is the key to perfecting rural financial environment while increasing financial support for agriculture. 展开更多
关键词 RURAL fiNANCIAL reSOURCES ALLOCATION efficiency fi
下载PDF
Neumann stochastic finite element method for calculating temperature field of frozen soil based on random field theory 被引量:3
19
作者 Tao Wang GuoQing Zhou 《Research in Cold and Arid Regions》 CSCD 2013年第4期488-497,共10页
To study the effect of uncertain factors on the temperature field of frozen soil, we propose a method to calculate the spatial average variance from just the point variance based on the local average theory of random ... To study the effect of uncertain factors on the temperature field of frozen soil, we propose a method to calculate the spatial average variance from just the point variance based on the local average theory of random fields. We model the heat transfer coefficient and specific heat capacity as spatially random fields instead of traditional random variables. An analysis for calculating the random temperature field of seasonal frozen soil is suggested by the Neumann stochastic finite element method, and here we provide the computational formulae of mathematical expectation, variance and variable coefficient. As shown in the calculation flow chart, the stochastic finite element calculation program for solving the random temperature field, as compiled by Matrix Laboratory (MATLAB) sottware, can directly output the statistical results of the temperature field of frozen soil. An example is presented to demonstrate the random effects from random field parameters, and the feasibility of the proposed approach is proven by compar- ing these results with the results derived when the random parameters are only modeled as random variables. The results show that the Neumann stochastic finite element method can efficiently solve the problem of random temperature fields of frozen soil based on random field theory, and it can reduce the variability of calculation results when the random parameters are modeled as spatial- ly random fields. 展开更多
关键词 fi'ozen soil Neumann expansion stochastic finite element method random temperature field
下载PDF
Experimental research on oil fi lm thickness and its microwave scattering during emulsifi cation 被引量:2
20
作者 Jie GUO Chenqi XU +3 位作者 Genwang LIU Xi ZHANG Junmin MENG Guangbo REN 《Journal of Oceanology and Limnology》 SCIE CAS CSCD 2022年第4期1361-1376,共16页
Synthetic Aperture Radar(SAR) plays a major role in identifying oil spills on the sea surface.However,obtaining information of oil spill thickness(volume) is still a challenge.Emulsification is an important process af... Synthetic Aperture Radar(SAR) plays a major role in identifying oil spills on the sea surface.However,obtaining information of oil spill thickness(volume) is still a challenge.Emulsification is an important process affecting the thickness and normalized radar cross section(NRCS) of oil film.Experiments of crude oil emulsification with C-band fully-polarized scatterometer were conducted combining airborne hyperspectral imaging spectrometer and 3 D laser scanner observation data,to provide experimental parameters and method to support accurate remote sensing monitoring on marine oil spill.It is further proved that through quantitative homogeneous emulsified oil spill experiments,to a certain extent,the NRCS of oil film increased during the emulsification process of crude oil.The backscattering mechanism of crude oil emulsification was explored using a semi-empirical model(SEM);the change of oil film NRCS was modulated by its dielectric constant and surface roughness,in which the dielectric constant showed a dominant effect.The relationship between thickness and NRCS of oil film was studied under two experimental conditions.The differences of NRCS between oil film and adjacent seawater(Δσ~0) and the damping ratio(DR) were found to have a linear relationship with oil thickness,which were best in the vertical polarization mode(VV) at 45° incident angle during the quantitative crude oil homogeneous emulsification process.In the natural emulsification process of continuous oil spill in which oil film was mixed with both crude oil and emulsified oil,an empirical equation of oil film thickness is preliminarily established.The Δσ~0,DR,and the empirical equation of oil film thickness were applied to the marine continuous oil spill incident on a 19-3 oil platform with spaceborne SAR image and successfully explained the distribution of the relative thickness of the oil film. 展开更多
关键词 crude oil emulsifi cation normalized radar cross section(NRCS) moisture content oil fi lm thickness damping ratio 1
下载PDF
上一页 1 2 48 下一页 到第
使用帮助 返回顶部