Debris flows are among the most common geological disasters in China,and have been particularly frequent in Sichuan Province since the Wenchuan earthquake on 12 May 2008.The construction of debris flow drainage channe...Debris flows are among the most common geological disasters in China,and have been particularly frequent in Sichuan Province since the Wenchuan earthquake on 12 May 2008.The construction of debris flow drainage channels is a countermeasure used to distribute debris flow fans,and these channels play a critical role in the mitigation and prevention of damage resulting from debris flows.Under field conditions,the useful life of drainage channels can be greatly shortened as a result of strong abrasions to the drainage structure caused by the debris flow.Field investigations have shown that the types of damage to drainage channels include(a) erosion caused by hyper-concentrated silt flow,(b) impact fractures and foundation scour at the groundsills of the drainage channel,(c) destruction of the drainage channel outlet,and(d) destruction of the drainage channel caused by debris flow abrasion.In addition,based on the destruction of the drainage channel during the debris flow drainage process,a new type of drainage channel with energy dissipation components was proposed and applied in a steep,narrow gully for debris flow mitigation.Moreover,design and engineering repair recommendations for drainage channels are provided as a reference for repairing the damage to the channel.The results can provide an important reference for the effective repair and optimal design of drainage channels.展开更多
Mountain forests are more prone to environmental predispositions(EPs)than submountain ones.While remote sensing of mountain forests enables instantaneous damage mapping,the investigation of the causes requires field d...Mountain forests are more prone to environmental predispositions(EPs)than submountain ones.While remote sensing of mountain forests enables instantaneous damage mapping,the investigation of the causes requires field data.However,a local field or regionally modeled environmental characteristics influence remote data evaluation differently.This study focused on the evaluation of EPs effects damaging mountain forests between various spatial resolutions during environmental change.The evaluation was divided into managed and natural forests in the Hruby Jeseník Mts.(Czech Republic;240-1491 m a.s.l.;50.082°N,17.231°E).Damage was assessed through the discrimination analysis of the normalised difference vegetation index(NDVI)by MODIS VI during alternating drought and flood periods 2003-2014.The local environmental influence was assessed using the discrimination function(DF)separability of forest damage in the training sets.The regional influence was assessed through map algebra estimated via the DF and a forest decline spatial model based on EPs from differences between risk growth conditions and biomass fuzzy sets.Management,EPs and soil influenced forest NDVI at different levels.The management afflicted the NDVI more than the EPs.The EPs afflicted the NDVI more than the soil groups.Strong winters and droughts had a greater influence on the NDVI than the flood events,with the winter of 2005/2006 inverting the DF direction,and the 2003 drought increasing differences in managed forest biomass and decreasing differences in natural forest biomasses.More than 50% of declining managed forests in the training sets occurred on Leptosols,Podzols and Histosols.On a regional scale,the soil influence was eliminated by multiple predispositions.The EPs influenced 96% of natural forest and 65% of managed forest,though managed forest damage was more evident.The mountain forest NDVI decline was dependent on both management and risk predispositions.展开更多
Objective: to explore the types and causes of knee joint injuries of officers and soldiers in a armed police department, and to provide effective reference data for avoiding more knee joint injuries of officers and so...Objective: to explore the types and causes of knee joint injuries of officers and soldiers in a armed police department, and to provide effective reference data for avoiding more knee joint injuries of officers and soldiers in the future. Methods: patients with knee injury in an armed Police department from July 2019 to July 2021 were selected, and the types and causes of knee injury in these 200 patients were analyzed according to the "Diagnostic Classification Criteria for Military Training Injuries of the People's Liberation Army". Results: (1) Among the 200 patients, 121 patients had single knee injury and 79 patients had double knee injury. (2) Among the 200 patients, medial ligament injury was the least, followed by anterior cruciate ligament injury, and meniscus injury was the most common injury type. (3) Analysis of injury causes included cross-country 5km, 400M barrier running, variable speed running, and others. Cross-country and 400M barrier running were significantly higher than variable speed running and other training items, and the difference was statistically significant (P<0.05). (4) Among the 200 patients, there were recruits, soldiers of one year, two years and more than two years. The incidence of knee joint injury in recruits was significantly higher than that in soldiers of one year, two years and more than two years, with statistical significance (P<0.05). Conclusion: knee joint injury is the most common in the training of armed police officers and soldiers. In order to improve the combat effectiveness of troops, it is necessary to prevent knee joint injury of officers and soldiers.展开更多
11Cr-0.4Mo-2W-CuVNb steel （ASME Gr.122） is used for boiler components in ultra- supercritical （USC） thermal power plants. The creep strength of high-Cr steel welds decreases due to the formation of Type IV creep d...11Cr-0.4Mo-2W-CuVNb steel （ASME Gr.122） is used for boiler components in ultra- supercritical （USC） thermal power plants. The creep strength of high-Cr steel welds decreases due to the formation of Type IV creep damage in the heat-affected zone （HAZ） during long-term use at high temperatures. In the present study, the processes and mechanisms of Type Ⅳ creep damage were elucidated by investigating the long-term creep strength, microstructure and damage behavior of Gr.122 steel welds. Creep tests using thick welded joints were interrupted at several time steps, and the initiation, evolution and distribution of creep damage were measured. It was found that the formation and growth of creep damage was suppressed during the steady- state stage; creep voids formed at 0.5 of life, and coalesced to form a crack after 0.9 of life. Type IV creep damage was mostly observed in the area about 30% below the surface of the plate. Differences in creep damage behavior between Gr.122 and Gr.91 steel welds were examined. Experimental creep damage distribution was compared with computed versions using the finite element method and damage mechanics.展开更多
Carbon fiber reinforced polymer(CFRP)has many remarkable merits.It is lightweight and has great rigidity and high intensity. High-durability cable produced from CFRP as reinforcement material is widely used in bridge ...Carbon fiber reinforced polymer(CFRP)has many remarkable merits.It is lightweight and has great rigidity and high intensity. High-durability cable produced from CFRP as reinforcement material is widely used in bridge construction projects.However, there is a dearth of studies regarding damage types and mechanism under fatigue load of CFRP bridge cables.In this paper,we adopt acoustic emission(AE)technology to monitor fatigue damage and failure of the CFRP bridge cables,specifically by monitoring the bridge cable’s fatigue test process and using wavelet transformation to analyze data.Results show that damage on the CFRP cable is divided into three stages.Based on wavelet singularity theory,in each stage of AE,the burst signal is obtained and its time-frequency distribution is achieved through wavelet analysis.According to the analysis results,failure modes in each phase and type of acoustic emission source are easy to determine.The characteristics of waveform,types of damages, and frequency distribution of CFRP bridge cable in different damage phases are collected.Research shows that the method used to determine the types of fatigue damage on the CFRP cable is feasible according to the range of distribution characteristic parameters for acoustic emission signal and type of waveform.展开更多
The Early Cretaceous terrestrial revolution involved global shifts from gymnosperm-to angiosperm-dominated floras.However,responses of insect herbivores to these changes remain unexamined.We evaluated 2176 highly samp...The Early Cretaceous terrestrial revolution involved global shifts from gymnosperm-to angiosperm-dominated floras.However,responses of insect herbivores to these changes remain unexamined.We evaluated 2176 highly sampled plant specimens representing 62 species/morphotypes from the 126 Ma Dawangzhangzi plant assemblage of Northeastern China.Our study consisted of horsetails,ferns,ginkgoaleans,czekanowskialeans,conifers,and an angiosperm.Their herbivory was evaluated by the functional feeding groups of hole feeding,margin feeding,and surface feeding(ectophytic feeders);piercer and suckers,and ovipositing insects(ectoendophytic feeders);mining,galling,and borings(endophytic feeders);and pathogens,collectively constituting 65 damage types(DTs).The plant assemblage was assessed for herbivory richness by DT richness,component community structure,and DT specialization on plant hosts;for herbivory intensity,it was evaluated for DT frequency,herbivorized surface area,and feeding event occurrences.Using feeding event occurrences,the data supported seven species/morphotypes as most intensely herbivorized:Liaoningocladus boii(76.6%),Czekanowskia sp.1(8.4%),Czekanowskia rigida(4.10%),Lindleycladus lanceolatus(3.5%),Ginkgoites sp.2(2.0%),Podozamites sp.1(1.1%),and Solenites sp.1(0.9%).The most herbivorized taxa were pinaleans(conifers),then czekanowskialeans,and lastly ginkgoaleans;the monodominant component community was the conifer Liaoningocladus boii.DT host specialization levels were low.The plant assemblage had an overall low 0.86%of foliage removed by herbivores,explained by physical and chemical antiherbivore defenses,and parasitoid attack.Although Paleozoic,gymnosperm-dominated assemblages had greater herbivory,component community structure of the three most herbivorized taxa are more similar to modern bracken fern and willow than modern gymnosperm taxa.展开更多
基金sponsored by the Key Deployment Project of the Chinese Academy of Sciences (KZZD-EW-05-01)the Natural Science Foundation of China (Grant No. 41302283)+1 种基金the Young Scientists Research Fund of the Institute of Mountain Hazards and Environment, CAS (SDSQN-1305)the Young Science Foundation of Key Laboratory of Mountain Hazards and Earth Surface Processes, CAS
文摘Debris flows are among the most common geological disasters in China,and have been particularly frequent in Sichuan Province since the Wenchuan earthquake on 12 May 2008.The construction of debris flow drainage channels is a countermeasure used to distribute debris flow fans,and these channels play a critical role in the mitigation and prevention of damage resulting from debris flows.Under field conditions,the useful life of drainage channels can be greatly shortened as a result of strong abrasions to the drainage structure caused by the debris flow.Field investigations have shown that the types of damage to drainage channels include(a) erosion caused by hyper-concentrated silt flow,(b) impact fractures and foundation scour at the groundsills of the drainage channel,(c) destruction of the drainage channel outlet,and(d) destruction of the drainage channel caused by debris flow abrasion.In addition,based on the destruction of the drainage channel during the debris flow drainage process,a new type of drainage channel with energy dissipation components was proposed and applied in a steep,narrow gully for debris flow mitigation.Moreover,design and engineering repair recommendations for drainage channels are provided as a reference for repairing the damage to the channel.The results can provide an important reference for the effective repair and optimal design of drainage channels.
基金the support by the Project LM2018123 Cze COS of the Ministry of Education,Youth and Sports of the Czech Republic。
文摘Mountain forests are more prone to environmental predispositions(EPs)than submountain ones.While remote sensing of mountain forests enables instantaneous damage mapping,the investigation of the causes requires field data.However,a local field or regionally modeled environmental characteristics influence remote data evaluation differently.This study focused on the evaluation of EPs effects damaging mountain forests between various spatial resolutions during environmental change.The evaluation was divided into managed and natural forests in the Hruby Jeseník Mts.(Czech Republic;240-1491 m a.s.l.;50.082°N,17.231°E).Damage was assessed through the discrimination analysis of the normalised difference vegetation index(NDVI)by MODIS VI during alternating drought and flood periods 2003-2014.The local environmental influence was assessed using the discrimination function(DF)separability of forest damage in the training sets.The regional influence was assessed through map algebra estimated via the DF and a forest decline spatial model based on EPs from differences between risk growth conditions and biomass fuzzy sets.Management,EPs and soil influenced forest NDVI at different levels.The management afflicted the NDVI more than the EPs.The EPs afflicted the NDVI more than the soil groups.Strong winters and droughts had a greater influence on the NDVI than the flood events,with the winter of 2005/2006 inverting the DF direction,and the 2003 drought increasing differences in managed forest biomass and decreasing differences in natural forest biomasses.More than 50% of declining managed forests in the training sets occurred on Leptosols,Podzols and Histosols.On a regional scale,the soil influence was eliminated by multiple predispositions.The EPs influenced 96% of natural forest and 65% of managed forest,though managed forest damage was more evident.The mountain forest NDVI decline was dependent on both management and risk predispositions.
文摘Objective: to explore the types and causes of knee joint injuries of officers and soldiers in a armed police department, and to provide effective reference data for avoiding more knee joint injuries of officers and soldiers in the future. Methods: patients with knee injury in an armed Police department from July 2019 to July 2021 were selected, and the types and causes of knee injury in these 200 patients were analyzed according to the "Diagnostic Classification Criteria for Military Training Injuries of the People's Liberation Army". Results: (1) Among the 200 patients, 121 patients had single knee injury and 79 patients had double knee injury. (2) Among the 200 patients, medial ligament injury was the least, followed by anterior cruciate ligament injury, and meniscus injury was the most common injury type. (3) Analysis of injury causes included cross-country 5km, 400M barrier running, variable speed running, and others. Cross-country and 400M barrier running were significantly higher than variable speed running and other training items, and the difference was statistically significant (P<0.05). (4) Among the 200 patients, there were recruits, soldiers of one year, two years and more than two years. The incidence of knee joint injury in recruits was significantly higher than that in soldiers of one year, two years and more than two years, with statistical significance (P<0.05). Conclusion: knee joint injury is the most common in the training of armed police officers and soldiers. In order to improve the combat effectiveness of troops, it is necessary to prevent knee joint injury of officers and soldiers.
文摘11Cr-0.4Mo-2W-CuVNb steel （ASME Gr.122） is used for boiler components in ultra- supercritical （USC） thermal power plants. The creep strength of high-Cr steel welds decreases due to the formation of Type IV creep damage in the heat-affected zone （HAZ） during long-term use at high temperatures. In the present study, the processes and mechanisms of Type Ⅳ creep damage were elucidated by investigating the long-term creep strength, microstructure and damage behavior of Gr.122 steel welds. Creep tests using thick welded joints were interrupted at several time steps, and the initiation, evolution and distribution of creep damage were measured. It was found that the formation and growth of creep damage was suppressed during the steady- state stage; creep voids formed at 0.5 of life, and coalesced to form a crack after 0.9 of life. Type IV creep damage was mostly observed in the area about 30% below the surface of the plate. Differences in creep damage behavior between Gr.122 and Gr.91 steel welds were examined. Experimental creep damage distribution was compared with computed versions using the finite element method and damage mechanics.
基金supported by the National Natural Science Foundation of China(Grant No.50808030)the Doctoral Fund of Ministry of Education of China(Grant No.200801411102)
文摘Carbon fiber reinforced polymer(CFRP)has many remarkable merits.It is lightweight and has great rigidity and high intensity. High-durability cable produced from CFRP as reinforcement material is widely used in bridge construction projects.However, there is a dearth of studies regarding damage types and mechanism under fatigue load of CFRP bridge cables.In this paper,we adopt acoustic emission(AE)technology to monitor fatigue damage and failure of the CFRP bridge cables,specifically by monitoring the bridge cable’s fatigue test process and using wavelet transformation to analyze data.Results show that damage on the CFRP cable is divided into three stages.Based on wavelet singularity theory,in each stage of AE,the burst signal is obtained and its time-frequency distribution is achieved through wavelet analysis.According to the analysis results,failure modes in each phase and type of acoustic emission source are easy to determine.The characteristics of waveform,types of damages, and frequency distribution of CFRP bridge cable in different damage phases are collected.Research shows that the method used to determine the types of fatigue damage on the CFRP cable is feasible according to the range of distribution characteristic parameters for acoustic emission signal and type of waveform.
基金supported by the National Natural Science Foundation of China(grants 41688103 and 32020103006).
文摘The Early Cretaceous terrestrial revolution involved global shifts from gymnosperm-to angiosperm-dominated floras.However,responses of insect herbivores to these changes remain unexamined.We evaluated 2176 highly sampled plant specimens representing 62 species/morphotypes from the 126 Ma Dawangzhangzi plant assemblage of Northeastern China.Our study consisted of horsetails,ferns,ginkgoaleans,czekanowskialeans,conifers,and an angiosperm.Their herbivory was evaluated by the functional feeding groups of hole feeding,margin feeding,and surface feeding(ectophytic feeders);piercer and suckers,and ovipositing insects(ectoendophytic feeders);mining,galling,and borings(endophytic feeders);and pathogens,collectively constituting 65 damage types(DTs).The plant assemblage was assessed for herbivory richness by DT richness,component community structure,and DT specialization on plant hosts;for herbivory intensity,it was evaluated for DT frequency,herbivorized surface area,and feeding event occurrences.Using feeding event occurrences,the data supported seven species/morphotypes as most intensely herbivorized:Liaoningocladus boii(76.6%),Czekanowskia sp.1(8.4%),Czekanowskia rigida(4.10%),Lindleycladus lanceolatus(3.5%),Ginkgoites sp.2(2.0%),Podozamites sp.1(1.1%),and Solenites sp.1(0.9%).The most herbivorized taxa were pinaleans(conifers),then czekanowskialeans,and lastly ginkgoaleans;the monodominant component community was the conifer Liaoningocladus boii.DT host specialization levels were low.The plant assemblage had an overall low 0.86%of foliage removed by herbivores,explained by physical and chemical antiherbivore defenses,and parasitoid attack.Although Paleozoic,gymnosperm-dominated assemblages had greater herbivory,component community structure of the three most herbivorized taxa are more similar to modern bracken fern and willow than modern gymnosperm taxa.
