Dear Editor,This letter presents an improved repetitive controller(IRC) that uses a complex-coefficient filter to enhance the tracking performance of a system for periodic signals. Compared with the low-pass filter us...Dear Editor,This letter presents an improved repetitive controller(IRC) that uses a complex-coefficient filter to enhance the tracking performance of a system for periodic signals. Compared with the low-pass filter used in the conventional repetitive controller(CRC), the complex-coefficient filter causes less change in the phase and amplitude of a signal at the frequencies of the periodic signal, especially at the fundamental frequency, when the two filters have the same cutofffrequency.展开更多
In the steel slag-based mine backfill cementitious material systems,the hydration reaction mechanisms and synergistic effects of steel slag(SS),granulated blast furnace slag(GBFS),and desulfurization gypsum(DG)are cru...In the steel slag-based mine backfill cementitious material systems,the hydration reaction mechanisms and synergistic effects of steel slag(SS),granulated blast furnace slag(GBFS),and desulfurization gypsum(DG)are crucial for performance optimization and regulation.However,existing studies have yet to fully reveal the underlying synergistic mechanisms,which limits the application and promotion of high SS content in mine backfill and low-carbon building materials.This study systematically explores the synergistic effects between various solid wastes and their regulation of the hydration process in the SS-based cementitious system through multi-scale characterization techniques.The results show that GBFS,by releasing active Si^(4+)and Al^(3+),triggers a synergistic activation effect with Ca^(2+)provided by SS,promoting the formation of C-S-H gel and ettringite,significantly optimizing the hardened paste microstructure.When the GBFS content reaches 30%,the C-S-H content increases by 40.8%,the pore size distribution improves,the proportion of large pores decreases by 68.7%,and the 90-day compressive strength increases to 5 times that of the baseline group.The sulfate activation effect of DG accelerates the hydration of silicate minerals,but excessive incorporation(>16%)can lead to microcracks caused by the expansion of AFt crystals,resulting in a strength reduction.Under the synergistic effect of 8%DG and 30%GBFS,the hydration reaction is most intense,with the peak heat release rate reaching 0.92 mW/g and the cumulative heat release amount being 240 J/g.By constructing a“SS-GBFS-DG-cement”quaternary synergistic system(mass ratio range:SS:GBFS:cement:DG=(50–62):(20–40):10:(8–12)),the matching of active components in high-content SS systems was optimized,significantly improving microstructural defects and meeting engineering application requirements.This study provides a theoretical basis for the component design and performance regulation of high-content SS-based cementitious materials.展开更多
0 INTRODUCTION In recent years,modern railways have been actively under construction in the complex mountainous area of Southwest China.However,rockfall poses a significant threat to both construction and operation ph...0 INTRODUCTION In recent years,modern railways have been actively under construction in the complex mountainous area of Southwest China.However,rockfall poses a significant threat to both construction and operation phases of railway projects(Yan et al.,2023;Chen et al.,2022;Fanos and Pradhan,2018).展开更多
Rivers and groundwater are the main water sources for cities.The mutual transformation between river water and groundwater makes it difficult to accurately evaluate and rationally utilize water resources.Scientificall...Rivers and groundwater are the main water sources for cities.The mutual transformation between river water and groundwater makes it difficult to accurately evaluate and rationally utilize water resources.Scientifically quantifying the interaction of surface water and groundwater remains challenging.Taking Chan River Basin as an example,this study aimed to determine the interconversion processes of groundwater and surface water by hydrogeochemical genesis mechanism analysis,isotope tracing,and end-member mixing analysis(EMMA).28 surface water samples and 23 groundwater samples were collected and analyzed during December 2023 and January 2024.Results showed thewater bodies in the study area were dominated by the HCO_(3)-Ca,HCO_(3)-Ca·Mg·Na,and HCO_(3)·SO_(4)-Ca·Na types,with hydrogeochemical processes controlled by the weathering and dissolution of both carbonate and silicate rock minerals.The river water in the upper reaches of the study area is mainly recharged by groundwater,with the average recharge ratio of 54.10%.Similarly,river water is still recharged by groundwater in the middle reaches,the average recharge ratio changes to 28.61%.In the downstream area,where Xi’an City located,due to the heavy exploitation of groundwater,the river water recharges to groundwater with an average recharge ratio of 85.23%,although in the immediate middle reaches,groundwater still replenishes surface waterwith a recharge rate of 75.00%.The results laid the bases for the reasonable utilization of water resources in the Chan River Basin and also served as a reference in other regions of the world.展开更多
0 INTRODUCTION The Qinling Mountains(QM),located at the geographical center of China,serve as a crucial dividing line between the northern and southern and play a vital role as an ecological security barrier,significa...0 INTRODUCTION The Qinling Mountains(QM),located at the geographical center of China,serve as a crucial dividing line between the northern and southern and play a vital role as an ecological security barrier,significantly influencing the country's geological,geographical,and ecological landscape(Jia et al.,2023;Peng et al.,2023).The QM stretch from the White Stone Mountain in the northern part of Lintan County,Gansu Province,to the Funiu Mountains in Henan Province in the east.展开更多
Deep-seated toppling in the upper reaches of the Lancang River,southwest China involves deformations exceeding 100 m in depth.The slope deformation is initiated by river downcutting and evolves distinctive characteris...Deep-seated toppling in the upper reaches of the Lancang River,southwest China involves deformations exceeding 100 m in depth.The slope deformation is initiated by river downcutting and evolves distinctive characteristics with a depth of river incision.In this study,we propose a system for evaluating the stability of deep-seated toppled slopes in different evolutionary stages.This system contains identification criteria for each evolutionary stage and provides the corresponding stability evaluation methods.Based on the mechanical and kinematic analysis of slope blocks,the specific stage of slope movement can be identified in the field through outcrop mapping,in situ tests,surface displacement monitoring,and adit and borehole explorations.The stability evaluation methods are established based on the limiting equilibrium theory and the strain compatibility between the undisturbed zone and the toppled zone.Finally,several sample slopes in different evolution stages have been investigated to verify the applicability and accuracy of the proposed stability evaluation system.The results indicate that intense tectonic activity and rapid river incision lead to a maximum principal stress ratio exceeding 10 near the slope surface,thus triggering widespread toppling deformations along the river valley.When considering the losses of joint cohesion during the further rotation process,the safety factor of the slope drops by 7%e28%.The self-stabilization of toppling deformation can be recognized by the layer symmetry configuration after the free rotation of the deflected layers.Intensely toppled rock blocks mainly suffer sliding failures beyond the layer symmetry condition.The factor of safety of the K73 rockslide decreased from 1.17 to 0.87 by considering the development of the potential sliding surface and the toesaturated zone.展开更多
It is generally accepted that the uniaxial compressive strength(UCS)and P-wave velocity of rocks tend to decrease simultaneously with increasing temperature.However,based on a great number of statistical data and syst...It is generally accepted that the uniaxial compressive strength(UCS)and P-wave velocity of rocks tend to decrease simultaneously with increasing temperature.However,based on a great number of statistical data and systematic analysis of the microstructure variation of rocks with temperature rising and corresponding propagation mechanism of elastic wave,the results show that(1)There are three different trends for the changes of UCS and P-wave velocity of sandstone when heated from room temperature(20C or 25C)to 800C:(i)Both the UCS and P-wave velocity decrease simultaneously;(ii)The UCS increases initially and then decreases,while the P-wave velocity decreases continuously;and(iii)The UCS increases initially and then fluctuates,while the P-wave velocity continuously decreases.(2)The UCS changes at room temperaturee400C,400Ce600C,and 600Ce800C are mainly attributed to the discrepancy of microstructure characteristics and quartz content,the transformation plasticity of clay minerals,and the balance between the thermal cementation and thermal damage,respectively.(3)The inconsistency in the trends of UCS and P-wave velocity changes is caused by the change of quartz content,phase transition of water and certain minerals.展开更多
In this paper, a new approach is presented for finite-time control problems for linear systems subject to time-varying parametric uncertainties and exogenous disturbance. The disturbance is assumed to be time varying ...In this paper, a new approach is presented for finite-time control problems for linear systems subject to time-varying parametric uncertainties and exogenous disturbance. The disturbance is assumed to be time varying and bounded. Sufficient conditions are obtained for the existence of a linear parameter-dependent state feedback gain, which can ensure that the closed-loop system is finite-time bounded （FTB）. The conditions can be reduced to feasibility problems involving LMIs. Numerical examples show the validity of the proposed methodology.展开更多
The sufficient bond between concrete and rock is an important prerequisite to ensure the effect of shotcrete support. However, in cold regions engineering protection system, the bond condition of rock and concrete sur...The sufficient bond between concrete and rock is an important prerequisite to ensure the effect of shotcrete support. However, in cold regions engineering protection system, the bond condition of rock and concrete surface is easily affected by freeze-thaw cycles, resulting in interface damage, debonding and even supporting failure. Understanding the micromechanisms of the damage and debonding of the rock-concrete interface is essential for improving the interface protection.Therefore, the micromorphology, micromechanical properties, and microdebonding evolution of the sandstone-concrete interface transition zone(ITZ) under varying freeze-thaw cycles(0, 5, 10, 15, 20) were studied using scanning electron microscope, stereoscopic microscope, and nano-indentation. Furthermore, the distribution range and evolution process of ITZ affected by freeze-thaw cycles were defined. Major findings of this study are as follows:(1) The microdamage evolution law of the ITZ under increasing freeze-thaw cycles is clarified, and the relationship between the number of cracks in the ITZ and freeze-thaw cycles is established;(2) As the number of freeze-thaw cycles increases, the ITZ's micromechanical strength decreases, and its development width tends to increase;(3) The damage and debonding evolution mechanisms of sandstone-concrete ITZ under freeze-thaw cycles is revealed, and its micromechanical evolution model induced by freeze-thaw cycles is proposed.展开更多
Ultraviolet（UV） radiation has significant effects on ecosystems, environments, and human health, as well as atmospheric processes and climate change. Two ultraviolet radiation datasets are described in this paper. O...Ultraviolet（UV） radiation has significant effects on ecosystems, environments, and human health, as well as atmospheric processes and climate change. Two ultraviolet radiation datasets are described in this paper. One contains hourly observations of UV radiation measured at 40 Chinese Ecosystem Research Network stations from 2005 to 2015. CUV3 broadband radiometers were used to observe the UV radiation, with an accuracy of 5%, which meets the World Meteorology Organization＇s measurement standards. The extremum method was used to control the quality of the measured datasets. The other dataset contains daily cumulative UV radiation estimates that were calculated using an all-sky estimation model combined with a hybrid model. The reconstructed daily UV radiation data span from 1961 to 2014. The mean absolute bias error and root-mean-square error are smaller than 30% at most stations, and most of the mean bias error values are negative, which indicates underestimation of the UV radiation intensity. These datasets can improve our basic knowledge of the spatial and temporal variations in UV radiation. Additionally, these datasets can be used in studies of potential ozone formation and atmospheric oxidation, as well as simulations of ecological processes.展开更多
This paper presents an improved method for H-two control with regional stability constraints for the closedloop system. The controller is given by the convex combination of a set of fixed gains. Both continuous and di...This paper presents an improved method for H-two control with regional stability constraints for the closedloop system. The controller is given by the convex combination of a set of fixed gains. Both continuous and discrete-time systems in a known polytopic domain are investigated. New LMI-based sufficient conditions for the existence of parameterdependent Lyapunov functions are proposed. Numerical examples are given to show the proposed conditions provide useful and less conservative results for the problems of H-two control with regional stability constraints.展开更多
In this study, a novel procedure is presented for control and analysis of a group of autonomous agents with point mass dynamics achieving flocking motion by using a fuzzy-logic-based attractive/repulsive function. Two...In this study, a novel procedure is presented for control and analysis of a group of autonomous agents with point mass dynamics achieving flocking motion by using a fuzzy-logic-based attractive/repulsive function. Two cooperative control laws are proposed for a group of autonomous agents to achieve flocking formations related to two different centers (mass center and geometric center) of the flock. The first one is designed for flocking motion guided at mass center and the other for geometric center. A virtual agent is introduced to represent a group objective for tracking purposes. Smooth graph Laplacian is introduced to overcome the difficulties in theoretical analysis. A new fuzzy-logic-based attractive/repulsive function is proposed for separation and cohesion control among agents. The theoretical results are presented to indicate the stability (separation, collision avoidance and velocity matching) of the control systems. Finally, simulation example is demonstrated to validate the theoretical results.展开更多
Studying the roles of geological environment and human activities in shaping the ecological environment can reveal the coupled mutual feedback among the geological environment,the ecological environment,and human acti...Studying the roles of geological environment and human activities in shaping the ecological environment can reveal the coupled mutual feedback among the geological environment,the ecological environment,and human activities.Understanding these processes is important for ensuring effective natural resource planning,ecological environment protection,and sustainable economic and social development.In this study,the Qinling Mountains were used as an example,and suitable indicators were selected to establish a mutual feedback system incorporating the geological environment,the ecological environment,and human activities.Moreover,various mathematical methods,namely,coupling degree,coupling coordination degree,Geodetector,and correlation and partial correlation analysis,were employed to explore the spatiotemporal evolution,coupling coordination,and driving mechanism of the interactions among these systems.The study results revealed the following:(1)Spatial heterogeneity in the interactions among the geological environment,the ecological environment,and human activities in the Qinling Mountains is high;the carrying capacity of the geological environment constrains the ecological environment quality and the scope of human activities.Besides,human activities modify,damage,and restore the eco-geological environment.(2)From 2000 to 2020,human activities in the Qinling Mountains were characterized by rapid economic development and urbanization.The scope of human activities has continued to increase,and the ecological environment has generally improved.(3)The area with a high coupling degree between geological environment sensitivity and ecological environment quality is located in the central mountainous area,indicating that the geological environment greatly affects the ecological environment in the area.The coupling coordination degree between human activity intensity and ecological environment quality reflects the imbalance in the spatial distributions of urbanization development and human-land conflicts in the Qinling Mountains.(4)Temperature and human activities are the main factors influencing the ecological environment quality in the Qinling Mountains,with positive and negative effects,respectively.In contrast,precipitation is not the main factor limiting the ecological environment quality in the Qinling Mountains.This study quantitatively revealed,for the first time,the coupled mutual feedback and interactions among the geological environment,the ecological environment,and human activities.The proposed research method offers new ideas for eco-geological assessment research,and the research results provide theoretical support for ecological environment protection in the Qinling Mountains from eco-geo-environmental perspectives.展开更多
The Yellow River is the second largest river in China,and it is of paramount importance as it serves various hydro-ecological functions for its inhabitants and environment.It consumes 12%of the water in China,with ann...The Yellow River is the second largest river in China,and it is of paramount importance as it serves various hydro-ecological functions for its inhabitants and environment.It consumes 12%of the water in China,with annual runoff accounting for 2%of the whole country.For sustainable water resources management under climate change and land cover changes(mainly the vegetation change),it is essential to understand the terrestrial water storage change(WSC)and its major driving factors in the Yellow River Basin(YRB)[1].展开更多
Crop simulation models provide alternative, less time-consuming, and cost-effective means of deter- mining the sensitivity of crop yield to climate change. In this study, two dynamic mechanistic models, CERES （Crop E...Crop simulation models provide alternative, less time-consuming, and cost-effective means of deter- mining the sensitivity of crop yield to climate change. In this study, two dynamic mechanistic models, CERES （Crop Environment Resource Synthesis） and APSIM （Agricultural Production Systems Simulator）, were used to simulate the yield of wheat （Triticum aestivum L.） under well irrigated （CFG） and rain-fed （YY） conditions in relation to different climate variables in the North China Plain （NCP）. The study tested winter wheat yield sensitivity to different levels of temperature, radiation, precipitation, and atmospheric carbon dioxide （COa） concentration under CFG and YY conditions at Luancheng Agro-ecosystem Experimental Stations in the NCR The results from the CERES and APSIM wheat crop models were largely consistent and suggested that changes in climate variables influenced wheat grain yield in the NCR There was also significant variation in the sensitivity of winter wheat yield to climate variables under different water （CFG and YY） conditions. While a temperature increase of 2℃ was the threshold beyond which temperature negatively influenced wheat yield under CFG, a temperature rise exceeding 1℃ decreased winter wheat grain yield under YY. A decrease in solar radiation decreased wheat grain yield under both CFG and YY conditions. Although the sensitivity of winter wheat yield to precipitation was small under the CFG, yield decreased significantly with decreasing precipitation under the rain- fed YY treatment. The results also suggest that wheat yield under CFG linearly increased by ≈ 3.5% per 60 ppm （parts per million） increase in CO2 concentration from 380 to560ppm, and yield under YY increased linearly by ≈ 7.0% for the same increase in CO2 concentration.展开更多
The uplift of the Tibetan Plateau significantly altered the geomorphology and climate of the Euroasia by creating large mountains and rivers.Fishes are more likely to be affected relative to other organisms,as they ar...The uplift of the Tibetan Plateau significantly altered the geomorphology and climate of the Euroasia by creating large mountains and rivers.Fishes are more likely to be affected relative to other organisms,as they are largely restricted to river systems.Faced with the rapidly flowing water in the Tibetan Plateau,a group of catfish has evolved greatly enlarged pectoral fins with more numbers of fin-rays to form an adhesive apparatus.However,the genetic basis of these adaptations in Tibetan catfishes remains elusive.In this study,we performed comparative genomic analyses based on the chromosome-level genome of Glyptosternum maculatum in family Sisoridae and detected some proteins with conspicuously high evolutionary rates in particular in genes involved in skeleton development,energy metabolism,and hypoxia response.We found that the hoxd12a gene evolved faster and a loss-of-function assay of hoxd12a supports a potential role for this gene in shaping the enlarged fins of these Tibetan catfishes.Other genes with amino acid replacements and signatures of positive selection included proteins involved in low temperature(TRMU)and hypoxia(VHL)responses.Functional assays reveal that the G.maculatum TRMU allele generates more mitochondrial ATP than the ancestral allele found in low-altitude fishes.Functional assays of VHL alleles suggest that the G.maculatum allele has lower transactivation activity than the low-altitude forms.These findings provide a window into the genomic underpinnings of physiological adaptations that permit G.maculatum to survive in the harsh environment of the Tibetan Himalayas that mirror those that are convergently found in other vertebrates such as humans.展开更多
Snailfishes are an important component of the hadal fish fauna[1].Based on osteological and other morphological characters,Kido[2]recognized the Cyclopteridae as a sister group to the Liparidae and the superfamily Cot...Snailfishes are an important component of the hadal fish fauna[1].Based on osteological and other morphological characters,Kido[2]recognized the Cyclopteridae as a sister group to the Liparidae and the superfamily Cottoidea as a sister group to the two families.The close relationship between Liparidae and Cyclopteridae is展开更多
基金supported in part by the National Natural Science Foundation of China(61873348,6230 3266,62273200)JSPS(Japan Society for the Promotion of Science) KAKENHI(22H03998,23K25252)
文摘Dear Editor,This letter presents an improved repetitive controller(IRC) that uses a complex-coefficient filter to enhance the tracking performance of a system for periodic signals. Compared with the low-pass filter used in the conventional repetitive controller(CRC), the complex-coefficient filter causes less change in the phase and amplitude of a signal at the frequencies of the periodic signal, especially at the fundamental frequency, when the two filters have the same cutofffrequency.
基金funded by the National Natural Science Foundation of China(No.52308316)Key Laboratory of Rock Mechanics and Geohazards of Zhejiang Province(No.ZJRMG-2022-01)+1 种基金Fudamental Research Funds for the CentralUniversities,CHD(No.300102265303)the Science and Technology Innovation Project of China Coal Technology&Engineering Group Shenyang Engineering Company(No.NKJ001-2025).
文摘In the steel slag-based mine backfill cementitious material systems,the hydration reaction mechanisms and synergistic effects of steel slag(SS),granulated blast furnace slag(GBFS),and desulfurization gypsum(DG)are crucial for performance optimization and regulation.However,existing studies have yet to fully reveal the underlying synergistic mechanisms,which limits the application and promotion of high SS content in mine backfill and low-carbon building materials.This study systematically explores the synergistic effects between various solid wastes and their regulation of the hydration process in the SS-based cementitious system through multi-scale characterization techniques.The results show that GBFS,by releasing active Si^(4+)and Al^(3+),triggers a synergistic activation effect with Ca^(2+)provided by SS,promoting the formation of C-S-H gel and ettringite,significantly optimizing the hardened paste microstructure.When the GBFS content reaches 30%,the C-S-H content increases by 40.8%,the pore size distribution improves,the proportion of large pores decreases by 68.7%,and the 90-day compressive strength increases to 5 times that of the baseline group.The sulfate activation effect of DG accelerates the hydration of silicate minerals,but excessive incorporation(>16%)can lead to microcracks caused by the expansion of AFt crystals,resulting in a strength reduction.Under the synergistic effect of 8%DG and 30%GBFS,the hydration reaction is most intense,with the peak heat release rate reaching 0.92 mW/g and the cumulative heat release amount being 240 J/g.By constructing a“SS-GBFS-DG-cement”quaternary synergistic system(mass ratio range:SS:GBFS:cement:DG=(50–62):(20–40):10:(8–12)),the matching of active components in high-content SS systems was optimized,significantly improving microstructural defects and meeting engineering application requirements.This study provides a theoretical basis for the component design and performance regulation of high-content SS-based cementitious materials.
基金supported by the Open Research Fund of Key Laboratory of Geological Hazards on Three Gorges Reservoir Area(China Three Gorges University),Ministry of Education(No.2022KDZ03)the Science and Technology Projects of Yunnan Provincial Science and Technology Department(No.202401AT070328)+1 种基金the Young talents project of“Xingdian Talent Support Program”in Yunnan Province(No.YNWR-QNBJ-2020-019)the Fund Project of China Academy of Railway Sciences Co.,Ltd.(No.2021YJ178)。
文摘0 INTRODUCTION In recent years,modern railways have been actively under construction in the complex mountainous area of Southwest China.However,rockfall poses a significant threat to both construction and operation phases of railway projects(Yan et al.,2023;Chen et al.,2022;Fanos and Pradhan,2018).
基金supported by the National Natural Science Foundation of China(Nos.42341102 and 42102288)the Forestry Science and Technology Innovation Project of Shaanxi Province(No.SXLK2023–02–1)+1 种基金the Fundamental Research Funds for the Central Universities,China(No.300102263401)the Fundamental Research Funds for the Central Universities,China(No.300102294905).
文摘Rivers and groundwater are the main water sources for cities.The mutual transformation between river water and groundwater makes it difficult to accurately evaluate and rationally utilize water resources.Scientifically quantifying the interaction of surface water and groundwater remains challenging.Taking Chan River Basin as an example,this study aimed to determine the interconversion processes of groundwater and surface water by hydrogeochemical genesis mechanism analysis,isotope tracing,and end-member mixing analysis(EMMA).28 surface water samples and 23 groundwater samples were collected and analyzed during December 2023 and January 2024.Results showed thewater bodies in the study area were dominated by the HCO_(3)-Ca,HCO_(3)-Ca·Mg·Na,and HCO_(3)·SO_(4)-Ca·Na types,with hydrogeochemical processes controlled by the weathering and dissolution of both carbonate and silicate rock minerals.The river water in the upper reaches of the study area is mainly recharged by groundwater,with the average recharge ratio of 54.10%.Similarly,river water is still recharged by groundwater in the middle reaches,the average recharge ratio changes to 28.61%.In the downstream area,where Xi’an City located,due to the heavy exploitation of groundwater,the river water recharges to groundwater with an average recharge ratio of 85.23%,although in the immediate middle reaches,groundwater still replenishes surface waterwith a recharge rate of 75.00%.The results laid the bases for the reasonable utilization of water resources in the Chan River Basin and also served as a reference in other regions of the world.
基金supported by two Special Programs of the National Natural Science Foundation of China(Nos.42341101,42442045)the National Key R&D Program of China(No.2024YFF1306502)the Basic Scientific Research Business Funds of Central Universities(No.300102263401)。
文摘0 INTRODUCTION The Qinling Mountains(QM),located at the geographical center of China,serve as a crucial dividing line between the northern and southern and play a vital role as an ecological security barrier,significantly influencing the country's geological,geographical,and ecological landscape(Jia et al.,2023;Peng et al.,2023).The QM stretch from the White Stone Mountain in the northern part of Lintan County,Gansu Province,to the Funiu Mountains in Henan Province in the east.
基金supported by the National Natural Science Foundation of China(Grant Nos.42307220 and 42090055)the Postdoctoral Research Project Funding of Shaanxi Province(Grant No.2023BSHEDZZ210).
文摘Deep-seated toppling in the upper reaches of the Lancang River,southwest China involves deformations exceeding 100 m in depth.The slope deformation is initiated by river downcutting and evolves distinctive characteristics with a depth of river incision.In this study,we propose a system for evaluating the stability of deep-seated toppled slopes in different evolutionary stages.This system contains identification criteria for each evolutionary stage and provides the corresponding stability evaluation methods.Based on the mechanical and kinematic analysis of slope blocks,the specific stage of slope movement can be identified in the field through outcrop mapping,in situ tests,surface displacement monitoring,and adit and borehole explorations.The stability evaluation methods are established based on the limiting equilibrium theory and the strain compatibility between the undisturbed zone and the toppled zone.Finally,several sample slopes in different evolution stages have been investigated to verify the applicability and accuracy of the proposed stability evaluation system.The results indicate that intense tectonic activity and rapid river incision lead to a maximum principal stress ratio exceeding 10 near the slope surface,thus triggering widespread toppling deformations along the river valley.When considering the losses of joint cohesion during the further rotation process,the safety factor of the slope drops by 7%e28%.The self-stabilization of toppling deformation can be recognized by the layer symmetry configuration after the free rotation of the deflected layers.Intensely toppled rock blocks mainly suffer sliding failures beyond the layer symmetry condition.The factor of safety of the K73 rockslide decreased from 1.17 to 0.87 by considering the development of the potential sliding surface and the toesaturated zone.
基金This work was supported by the National Natural Science Foundation of China(Grant No.41772333)the program of State Key Laboratory of Frozen Soil Engineering(Grant No.SKLFSE201713)the Shaanxi Province New-Star Talents Promotion Project of Science and Technology(Grant No.2019KJXX-049).
文摘It is generally accepted that the uniaxial compressive strength(UCS)and P-wave velocity of rocks tend to decrease simultaneously with increasing temperature.However,based on a great number of statistical data and systematic analysis of the microstructure variation of rocks with temperature rising and corresponding propagation mechanism of elastic wave,the results show that(1)There are three different trends for the changes of UCS and P-wave velocity of sandstone when heated from room temperature(20C or 25C)to 800C:(i)Both the UCS and P-wave velocity decrease simultaneously;(ii)The UCS increases initially and then decreases,while the P-wave velocity decreases continuously;and(iii)The UCS increases initially and then fluctuates,while the P-wave velocity continuously decreases.(2)The UCS changes at room temperaturee400C,400Ce600C,and 600Ce800C are mainly attributed to the discrepancy of microstructure characteristics and quartz content,the transformation plasticity of clay minerals,and the balance between the thermal cementation and thermal damage,respectively.(3)The inconsistency in the trends of UCS and P-wave velocity changes is caused by the change of quartz content,phase transition of water and certain minerals.
基金the Scientific Innovation Team Project of Hubei Provincial Department of Education (T200809)the Science Foundationof Education Commission of Hubei Province (No. D20081306)the Doctoral Pre-research Foundation of Three Gorges University
文摘In this paper, a new approach is presented for finite-time control problems for linear systems subject to time-varying parametric uncertainties and exogenous disturbance. The disturbance is assumed to be time varying and bounded. Sufficient conditions are obtained for the existence of a linear parameter-dependent state feedback gain, which can ensure that the closed-loop system is finite-time bounded （FTB）. The conditions can be reduced to feasibility problems involving LMIs. Numerical examples show the validity of the proposed methodology.
基金supported by the National Natural Science Foundation of China (Grant No.41772333)the National Natural Science Foundation of Shaanxi Province, China (Grant No.2018JQ5124)the New-Star Talents Promotion Project of Science and Technology of Shaanxi Province, China (Grant No.2019KJXX049)。
文摘The sufficient bond between concrete and rock is an important prerequisite to ensure the effect of shotcrete support. However, in cold regions engineering protection system, the bond condition of rock and concrete surface is easily affected by freeze-thaw cycles, resulting in interface damage, debonding and even supporting failure. Understanding the micromechanisms of the damage and debonding of the rock-concrete interface is essential for improving the interface protection.Therefore, the micromorphology, micromechanical properties, and microdebonding evolution of the sandstone-concrete interface transition zone(ITZ) under varying freeze-thaw cycles(0, 5, 10, 15, 20) were studied using scanning electron microscope, stereoscopic microscope, and nano-indentation. Furthermore, the distribution range and evolution process of ITZ affected by freeze-thaw cycles were defined. Major findings of this study are as follows:(1) The microdamage evolution law of the ITZ under increasing freeze-thaw cycles is clarified, and the relationship between the number of cracks in the ITZ and freeze-thaw cycles is established;(2) As the number of freeze-thaw cycles increases, the ITZ's micromechanical strength decreases, and its development width tends to increase;(3) The damage and debonding evolution mechanisms of sandstone-concrete ITZ under freeze-thaw cycles is revealed, and its micromechanical evolution model induced by freeze-thaw cycles is proposed.
文摘Ultraviolet（UV） radiation has significant effects on ecosystems, environments, and human health, as well as atmospheric processes and climate change. Two ultraviolet radiation datasets are described in this paper. One contains hourly observations of UV radiation measured at 40 Chinese Ecosystem Research Network stations from 2005 to 2015. CUV3 broadband radiometers were used to observe the UV radiation, with an accuracy of 5%, which meets the World Meteorology Organization＇s measurement standards. The extremum method was used to control the quality of the measured datasets. The other dataset contains daily cumulative UV radiation estimates that were calculated using an all-sky estimation model combined with a hybrid model. The reconstructed daily UV radiation data span from 1961 to 2014. The mean absolute bias error and root-mean-square error are smaller than 30% at most stations, and most of the mean bias error values are negative, which indicates underestimation of the UV radiation intensity. These datasets can improve our basic knowledge of the spatial and temporal variations in UV radiation. Additionally, these datasets can be used in studies of potential ozone formation and atmospheric oxidation, as well as simulations of ecological processes.
基金This work was supported by the Science Foundation of Education Commission of Hubei Province(No.D200613002)the Doctoral Pre-ResearchFoundation of Three Gorges University.
文摘This paper presents an improved method for H-two control with regional stability constraints for the closedloop system. The controller is given by the convex combination of a set of fixed gains. Both continuous and discrete-time systems in a known polytopic domain are investigated. New LMI-based sufficient conditions for the existence of parameterdependent Lyapunov functions are proposed. Numerical examples are given to show the proposed conditions provide useful and less conservative results for the problems of H-two control with regional stability constraints.
文摘In this study, a novel procedure is presented for control and analysis of a group of autonomous agents with point mass dynamics achieving flocking motion by using a fuzzy-logic-based attractive/repulsive function. Two cooperative control laws are proposed for a group of autonomous agents to achieve flocking formations related to two different centers (mass center and geometric center) of the flock. The first one is designed for flocking motion guided at mass center and the other for geometric center. A virtual agent is introduced to represent a group objective for tracking purposes. Smooth graph Laplacian is introduced to overcome the difficulties in theoretical analysis. A new fuzzy-logic-based attractive/repulsive function is proposed for separation and cohesion control among agents. The theoretical results are presented to indicate the stability (separation, collision avoidance and velocity matching) of the control systems. Finally, simulation example is demonstrated to validate the theoretical results.
基金supported by the National Natural Science Foundation of China Special Project“Evolution of the Qinling Ecological Geological Environment System and Disaster Risk Control”(Grant No.42341101)。
文摘Studying the roles of geological environment and human activities in shaping the ecological environment can reveal the coupled mutual feedback among the geological environment,the ecological environment,and human activities.Understanding these processes is important for ensuring effective natural resource planning,ecological environment protection,and sustainable economic and social development.In this study,the Qinling Mountains were used as an example,and suitable indicators were selected to establish a mutual feedback system incorporating the geological environment,the ecological environment,and human activities.Moreover,various mathematical methods,namely,coupling degree,coupling coordination degree,Geodetector,and correlation and partial correlation analysis,were employed to explore the spatiotemporal evolution,coupling coordination,and driving mechanism of the interactions among these systems.The study results revealed the following:(1)Spatial heterogeneity in the interactions among the geological environment,the ecological environment,and human activities in the Qinling Mountains is high;the carrying capacity of the geological environment constrains the ecological environment quality and the scope of human activities.Besides,human activities modify,damage,and restore the eco-geological environment.(2)From 2000 to 2020,human activities in the Qinling Mountains were characterized by rapid economic development and urbanization.The scope of human activities has continued to increase,and the ecological environment has generally improved.(3)The area with a high coupling degree between geological environment sensitivity and ecological environment quality is located in the central mountainous area,indicating that the geological environment greatly affects the ecological environment in the area.The coupling coordination degree between human activity intensity and ecological environment quality reflects the imbalance in the spatial distributions of urbanization development and human-land conflicts in the Qinling Mountains.(4)Temperature and human activities are the main factors influencing the ecological environment quality in the Qinling Mountains,with positive and negative effects,respectively.In contrast,precipitation is not the main factor limiting the ecological environment quality in the Qinling Mountains.This study quantitatively revealed,for the first time,the coupled mutual feedback and interactions among the geological environment,the ecological environment,and human activities.The proposed research method offers new ideas for eco-geological assessment research,and the research results provide theoretical support for ecological environment protection in the Qinling Mountains from eco-geo-environmental perspectives.
基金supported by Pioneer Talents Program of Chinese Academy of Sciences and the National Natural Science Foundation of China(41971032)。
文摘The Yellow River is the second largest river in China,and it is of paramount importance as it serves various hydro-ecological functions for its inhabitants and environment.It consumes 12%of the water in China,with annual runoff accounting for 2%of the whole country.For sustainable water resources management under climate change and land cover changes(mainly the vegetation change),it is essential to understand the terrestrial water storage change(WSC)and its major driving factors in the Yellow River Basin(YRB)[1].
基金This study was supported by the National Natural Science Foundation of China （Grant No. 41401104）, Natural Science Foundation of Hebei Province, China （D2015302017）, China Postdoctoral Science Foundation funded project （2015M570167）, and also supported by the Planning Subject of the ＂Twelfth five-year-plan＂ in National Science and Technology for the Rural Development in China （2013BAD11B03-2）, and Science and Technology Planning Project of Hebei Academy of Science （15101）. We are grateful to the editors and anonymous reviewers for their insightful inputs at the review phase of this work.
文摘Crop simulation models provide alternative, less time-consuming, and cost-effective means of deter- mining the sensitivity of crop yield to climate change. In this study, two dynamic mechanistic models, CERES （Crop Environment Resource Synthesis） and APSIM （Agricultural Production Systems Simulator）, were used to simulate the yield of wheat （Triticum aestivum L.） under well irrigated （CFG） and rain-fed （YY） conditions in relation to different climate variables in the North China Plain （NCP）. The study tested winter wheat yield sensitivity to different levels of temperature, radiation, precipitation, and atmospheric carbon dioxide （COa） concentration under CFG and YY conditions at Luancheng Agro-ecosystem Experimental Stations in the NCR The results from the CERES and APSIM wheat crop models were largely consistent and suggested that changes in climate variables influenced wheat grain yield in the NCR There was also significant variation in the sensitivity of winter wheat yield to climate variables under different water （CFG and YY） conditions. While a temperature increase of 2℃ was the threshold beyond which temperature negatively influenced wheat yield under CFG, a temperature rise exceeding 1℃ decreased winter wheat grain yield under YY. A decrease in solar radiation decreased wheat grain yield under both CFG and YY conditions. Although the sensitivity of winter wheat yield to precipitation was small under the CFG, yield decreased significantly with decreasing precipitation under the rain- fed YY treatment. The results also suggest that wheat yield under CFG linearly increased by ≈ 3.5% per 60 ppm （parts per million） increase in CO2 concentration from 380 to560ppm, and yield under YY increased linearly by ≈ 7.0% for the same increase in CO2 concentration.
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences(XDB31000000)the National Natural Science Foundation of China(32170480,31972866,31702016,31601858,32022009)+5 种基金Chinese Academy of Sciences(Youth Innovation Promotion Association),Chinese Academy of Sciences(http://www.yicas.cn)the Pioneer Hundred Talents Program,and ZDBS-LYSM005)the Second Tibetan Plateau Scientific Expedition and Research Program(STEP,2019QZKK0501)State Key Laboratory of Genetic Resources and Evolution,Kunming Institute of Zoology,Chinese Academy of Sciences(GREKF21-04)the Young Top-notch Talent Cultivation Program of Hubei Provincesupported by the Wuhan Branch,Supercomputing Center,Chinese Academy of Sciences,China。
文摘The uplift of the Tibetan Plateau significantly altered the geomorphology and climate of the Euroasia by creating large mountains and rivers.Fishes are more likely to be affected relative to other organisms,as they are largely restricted to river systems.Faced with the rapidly flowing water in the Tibetan Plateau,a group of catfish has evolved greatly enlarged pectoral fins with more numbers of fin-rays to form an adhesive apparatus.However,the genetic basis of these adaptations in Tibetan catfishes remains elusive.In this study,we performed comparative genomic analyses based on the chromosome-level genome of Glyptosternum maculatum in family Sisoridae and detected some proteins with conspicuously high evolutionary rates in particular in genes involved in skeleton development,energy metabolism,and hypoxia response.We found that the hoxd12a gene evolved faster and a loss-of-function assay of hoxd12a supports a potential role for this gene in shaping the enlarged fins of these Tibetan catfishes.Other genes with amino acid replacements and signatures of positive selection included proteins involved in low temperature(TRMU)and hypoxia(VHL)responses.Functional assays reveal that the G.maculatum TRMU allele generates more mitochondrial ATP than the ancestral allele found in low-altitude fishes.Functional assays of VHL alleles suggest that the G.maculatum allele has lower transactivation activity than the low-altitude forms.These findings provide a window into the genomic underpinnings of physiological adaptations that permit G.maculatum to survive in the harsh environment of the Tibetan Himalayas that mirror those that are convergently found in other vertebrates such as humans.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB060101)
文摘Snailfishes are an important component of the hadal fish fauna[1].Based on osteological and other morphological characters,Kido[2]recognized the Cyclopteridae as a sister group to the Liparidae and the superfamily Cottoidea as a sister group to the two families.The close relationship between Liparidae and Cyclopteridae is
