This article aims to study the geomorpometric features of alluvial fans since they act as a small-scale geomorphic unit response to tectonics and climate changes around the Chaka-Qinghai Lake area in the northeastern ...This article aims to study the geomorpometric features of alluvial fans since they act as a small-scale geomorphic unit response to tectonics and climate changes around the Chaka-Qinghai Lake area in the northeastern Tibetan Plateau. We quantitatively extracted geomorphic parameters, such as the surface area and slope of alluvial fans adjacent to the Qinghai Nan Shan and Ela Shan. Alluvial fans in the Chaka Lake partition area, south of the Qinghai Nan Shan, are featured by a small area and short length, but the largest slope. Geomorphic parameters of the alluvial fans in Ela Shan area are in- termediate in size, and the alluvial fans in the Qinghai Lake partition area north of Qinghai Nan Shan have the gentlest slope. Together with the regional faulting activity analysis, we suggest that the alluvial fans with the high slopes in the south of Qinghai Nan Shan are mainly controlled by the reverse faulting along the Qinghai Nan Shan faults, and the strike-slip movement of the Eia Shan fault zone plays a weak role. In contrast, due to the lack of active faults, the alluvial fans near the Qinghai Lake area north of the Qinghai Nan Shan only respond to regional erosion, transportation, and deposition proc- esses, thereby forming relatively gentle geomorphic units.展开更多
“Chiral-induced spin selectivity(CISS)”and its device applications are predominantly at the experimental stage,with mechanisms not fully understood.There is a need for new chiral materials with simple structures and...“Chiral-induced spin selectivity(CISS)”and its device applications are predominantly at the experimental stage,with mechanisms not fully understood.There is a need for new chiral materials with simple structures and high room-temperature electron spin polarization rates,crucial for theoretical studies and low-power spin optoelectronic devices.This study examines the CISS effect in carbon nanotubes,graphene chiral rolls,and graphene chiral stacks.While all three exhibit chirality,only the one-side follow curved surface of the graphene rolls demonstrates the CISS effect.Using true and false chirality analysis from Professor Barron,we found that only the charge motion(current)on the chiral surface is true chiral,leading to spin polarization.Thus,the CISS phenomenon occurs when charge motion on the chiral surface is chiral.Both chiral surface structures and chiral charge motion are necessary for electron spin polarization.Further theoretical validation of these conditions will enhance CISS theory.展开更多
Crankshaft is regarded as an important component of engines, and it is an important application of remanufacturing because of its high added value. However, the fatigue failure research of remanufactured crankshaft is...Crankshaft is regarded as an important component of engines, and it is an important application of remanufacturing because of its high added value. However, the fatigue failure research of remanufactured crankshaft is still in its primary stage. Thus, monitoring and investigating the fatigue failure of the remanufacturing crankshaft is crucial. In this paper, acoustic emission （AE） technology and machine vision are used to monitor the four-point bending fatigue of 42CrMo, which is the material of crankshaft. The specimens are divided into two categories, namely, pre-existing crack and non-pre- existing crack, which simulate the crankshaft and crank- shaft blank, respectively. The analysis methods of para- meter-based AE techniques, wavelet transform （WT） and SEM analysis are combined to identify the stage of fatigue failure. The stage of fatigue failure is the basis of using AE technology in the field of remanufacturing crankshafts. The experiment results show that the fatigue crack propagation style is a transgranular fracture and the fracture is a brittle fracture. The difference mainly depends on the form of crack initiation. Various AE signals are detected by parameter analysis method. Wavelet threshold denoising and WT are combined to extract the spectral features of AE signals at different fatigue failure stages.展开更多
The aim of this paper is first to establish a general prediction framework for turning(period)term structures in COVID-19 epidemic related to the implementation of emergency risk management in the practice,which allow...The aim of this paper is first to establish a general prediction framework for turning(period)term structures in COVID-19 epidemic related to the implementation of emergency risk management in the practice,which allows us to conduct the reliable estimation for the peak period based on the new concept of“Turning Period”(instead of the traditional one with the focus on“Turning Point”)for infectious disease spreading such as the COVID-19 epidemic appeared early in year 2020.By a fact that emergency risk management is necessarily to implement emergency plans quickly,the identification of the Turning Period is a key element to emergency planning as it needs to provide a time line for effective actions and solutions to combat a pandemic by reducing as much unexpected risk as soon as possible.As applications,the paper also discusses how this“Turning Term(Period)Structure”is used to predict the peak phase for COVID-19 epidemic in Wuhan from January/2020 to early March/2020.Our study shows that the predication framework established in this paper is capable to provide the trajectory of COVID-19 cases dynamics for a few weeks starting from Feb.10/2020 to early March/2020,from which we successfully predicted that the turning period of COVID-19 epidemic in Wuhan would arrive within one week after Feb.14/2020,as verified by the true observation in the practice.The method established in this paper for the prediction of“Turning Term(Period)Structures”by applying COVID-19 epidemic in China happened early 2020 seems timely and accurate,providing adequate time for the government,hospitals,essential industry sectors and services to meet peak demands and to prepare aftermath planning,and associated criteria for the Turning Term Structure of COVID-19 epidemic is expected to be a useful and powerful tool to implement the so-called“dynamic zero-COVID-19 policy”ongoing basis in the practice.展开更多
Using the Normalized Difference Vegetation Index （NDVI） as an indicator of vegetation growth, we explored the characteristics and differences in the response to drought of five vegetation biomes in Northeast China, ...Using the Normalized Difference Vegetation Index （NDVI） as an indicator of vegetation growth, we explored the characteristics and differences in the response to drought of five vegetation biomes in Northeast China, including typical steppe, desert steppe, meadow steppe, deciduous coniferous forest and deciduous broad-leaved forest during the period 1982 2009. The results indicate that growing season precipitation may be the primary vegetation growth-limiting factor in grasslands. More than 70% of the temporal variations in NDVI can be explained by the amount of precipitation during the growing season in typical and desert steppes. During the same period, the mean temperature in the growing season could explain nearly 43% of the variations in the mean growing season NDVI and is therefore a dominant growth-limiting factor for forest ecosystems. Therefore, the NDVI trends differ largely due to differences in the vegetation growth-limiting factors of the different vegetation biomes. The NDVI responses to droughts vary in magnitude and direction and depend on the drought-affected areas of the five vegetation types. Specifically, the changes in NDVI are consistent with the variations in precipitation for grassland ecosystems. A lack of precipitation resulted in decreases in NDVI, thereby reducing vegetation growth in these regions. Conversely, increasing precipitation decreased the NDVI of forest ecosystems. The results also suggest that grasslands under arid and semi-arid environments may be more sensitive to drought than forests under humid environments. Among grassland ecosystems, desert steppe was most sensitive to drought, followed by typical steppe; meadow steppe was the least sensitive.展开更多
A previous paper showed that the real numbers between 0 and 1 could be represented by an infinite tree structure, called the ‘infinity tree’, which contains only a countably infinite number of nodes and arcs. This p...A previous paper showed that the real numbers between 0 and 1 could be represented by an infinite tree structure, called the ‘infinity tree’, which contains only a countably infinite number of nodes and arcs. This paper discusses how a finite-state Turing machine could, in a countably infinite number of state transitions, write all the infinite paths in the infinity tree to a countably infinite tape. Hence it is argued that the real numbers in the interval [0, 1] are countably infinite in a non-Cantorian theory of infinity based on Turing machines using countably infinite space and time. In this theory, Cantor’s Continuum Hypothesis can also be proved. And in this theory, it follows that the power set of the natural numbers P(ℕ) is countably infinite, which contradicts the claim of Cantor’s Theorem for the natural numbers. However, this paper does not claim there is an error in Cantor’s arguments that [0, 1] is uncountably infinite. Rather, this paper considers the situation as a paradox, resulting from different choices about how to represent and count the continuum of real numbers.展开更多
A new type of localized oscillatory pattern is presented in a two-layer coupled reaction-diffusion system under conditions in which no Hopf instability can be discerned in either layer.The transitions from stationary ...A new type of localized oscillatory pattern is presented in a two-layer coupled reaction-diffusion system under conditions in which no Hopf instability can be discerned in either layer.The transitions from stationary patterns to asynchronous and synchronous oscillatory patterns are obtained.A novel method based on decomposing coupled systems into two associated subsystems has been proposed to elucidate the mechanism of formation of oscillating patterns.Linear stability analysis of the associated subsystems reveals that the Turing pattern in one layer induces the other layer locally,undergoes a supercritical Hopf bifurcation and gives rise to localized oscillations.It is found that the sizes and positions of oscillations are determined by the spatial distribution of the Turing patterns.When the size is large,localized traveling waves such as spirals and targets emerge.These results may be useful for deeper understanding of pattern formation in complex systems,particularly multilayered systems.展开更多
Achieving industrial-level electrochemical CO_(2)reduction to formate remains a significant challenge due to limitations in catalyst selectivity and interfacial proton management at high current densities.In a recent ...Achieving industrial-level electrochemical CO_(2)reduction to formate remains a significant challenge due to limitations in catalyst selectivity and interfacial proton management at high current densities.In a recent study,Prof.Guo and colleagues report the development of Turingstructured electrocatalysts,which incorporate reaction-diffusion-inspired topologies to engineer mesoscale surface patterns.This design enables precise modulation of the interfacial microenvironment,enhancing CO_(2)activation and suppressing competing hydrogen evolution.The resulting catalysts achieve efficient and stable CO_(2)-to-formate conversion under industrially relevant conditions,offering a promising strategy for scalable carbon-neutral chemical production.展开更多
基金supported by the Fund of the Insti-tute of Geology,CEA(No.IGCEA1115)the National Natural Science Foundation of China(Nos.41203012,41272196)
文摘This article aims to study the geomorpometric features of alluvial fans since they act as a small-scale geomorphic unit response to tectonics and climate changes around the Chaka-Qinghai Lake area in the northeastern Tibetan Plateau. We quantitatively extracted geomorphic parameters, such as the surface area and slope of alluvial fans adjacent to the Qinghai Nan Shan and Ela Shan. Alluvial fans in the Chaka Lake partition area, south of the Qinghai Nan Shan, are featured by a small area and short length, but the largest slope. Geomorphic parameters of the alluvial fans in Ela Shan area are in- termediate in size, and the alluvial fans in the Qinghai Lake partition area north of Qinghai Nan Shan have the gentlest slope. Together with the regional faulting activity analysis, we suggest that the alluvial fans with the high slopes in the south of Qinghai Nan Shan are mainly controlled by the reverse faulting along the Qinghai Nan Shan faults, and the strike-slip movement of the Eia Shan fault zone plays a weak role. In contrast, due to the lack of active faults, the alluvial fans near the Qinghai Lake area north of the Qinghai Nan Shan only respond to regional erosion, transportation, and deposition proc- esses, thereby forming relatively gentle geomorphic units.
基金support of this research,we gratefully acknowledge the National Natural Science Foundation of China(No.22375141).
文摘“Chiral-induced spin selectivity(CISS)”and its device applications are predominantly at the experimental stage,with mechanisms not fully understood.There is a need for new chiral materials with simple structures and high room-temperature electron spin polarization rates,crucial for theoretical studies and low-power spin optoelectronic devices.This study examines the CISS effect in carbon nanotubes,graphene chiral rolls,and graphene chiral stacks.While all three exhibit chirality,only the one-side follow curved surface of the graphene rolls demonstrates the CISS effect.Using true and false chirality analysis from Professor Barron,we found that only the charge motion(current)on the chiral surface is true chiral,leading to spin polarization.Thus,the CISS phenomenon occurs when charge motion on the chiral surface is chiral.Both chiral surface structures and chiral charge motion are necessary for electron spin polarization.Further theoretical validation of these conditions will enhance CISS theory.
基金This research was supported by the National Natural Science Foundation of China （Grant Nos. 51535011 and 51275151）.
文摘Crankshaft is regarded as an important component of engines, and it is an important application of remanufacturing because of its high added value. However, the fatigue failure research of remanufactured crankshaft is still in its primary stage. Thus, monitoring and investigating the fatigue failure of the remanufacturing crankshaft is crucial. In this paper, acoustic emission （AE） technology and machine vision are used to monitor the four-point bending fatigue of 42CrMo, which is the material of crankshaft. The specimens are divided into two categories, namely, pre-existing crack and non-pre- existing crack, which simulate the crankshaft and crank- shaft blank, respectively. The analysis methods of para- meter-based AE techniques, wavelet transform （WT） and SEM analysis are combined to identify the stage of fatigue failure. The stage of fatigue failure is the basis of using AE technology in the field of remanufacturing crankshafts. The experiment results show that the fatigue crack propagation style is a transgranular fracture and the fracture is a brittle fracture. The difference mainly depends on the form of crack initiation. Various AE signals are detected by parameter analysis method. Wavelet threshold denoising and WT are combined to extract the spectral features of AE signals at different fatigue failure stages.
基金Supported by the National Natural Science Foundation of China(71971031,U1811462)
文摘The aim of this paper is first to establish a general prediction framework for turning(period)term structures in COVID-19 epidemic related to the implementation of emergency risk management in the practice,which allows us to conduct the reliable estimation for the peak period based on the new concept of“Turning Period”(instead of the traditional one with the focus on“Turning Point”)for infectious disease spreading such as the COVID-19 epidemic appeared early in year 2020.By a fact that emergency risk management is necessarily to implement emergency plans quickly,the identification of the Turning Period is a key element to emergency planning as it needs to provide a time line for effective actions and solutions to combat a pandemic by reducing as much unexpected risk as soon as possible.As applications,the paper also discusses how this“Turning Term(Period)Structure”is used to predict the peak phase for COVID-19 epidemic in Wuhan from January/2020 to early March/2020.Our study shows that the predication framework established in this paper is capable to provide the trajectory of COVID-19 cases dynamics for a few weeks starting from Feb.10/2020 to early March/2020,from which we successfully predicted that the turning period of COVID-19 epidemic in Wuhan would arrive within one week after Feb.14/2020,as verified by the true observation in the practice.The method established in this paper for the prediction of“Turning Term(Period)Structures”by applying COVID-19 epidemic in China happened early 2020 seems timely and accurate,providing adequate time for the government,hospitals,essential industry sectors and services to meet peak demands and to prepare aftermath planning,and associated criteria for the Turning Term Structure of COVID-19 epidemic is expected to be a useful and powerful tool to implement the so-called“dynamic zero-COVID-19 policy”ongoing basis in the practice.
基金supported financially by the National Basic Research Program of China under Grant No. 2010CB950504the General Program from the National Natural Science Foundation of China(No. 41175125)
文摘Using the Normalized Difference Vegetation Index （NDVI） as an indicator of vegetation growth, we explored the characteristics and differences in the response to drought of five vegetation biomes in Northeast China, including typical steppe, desert steppe, meadow steppe, deciduous coniferous forest and deciduous broad-leaved forest during the period 1982 2009. The results indicate that growing season precipitation may be the primary vegetation growth-limiting factor in grasslands. More than 70% of the temporal variations in NDVI can be explained by the amount of precipitation during the growing season in typical and desert steppes. During the same period, the mean temperature in the growing season could explain nearly 43% of the variations in the mean growing season NDVI and is therefore a dominant growth-limiting factor for forest ecosystems. Therefore, the NDVI trends differ largely due to differences in the vegetation growth-limiting factors of the different vegetation biomes. The NDVI responses to droughts vary in magnitude and direction and depend on the drought-affected areas of the five vegetation types. Specifically, the changes in NDVI are consistent with the variations in precipitation for grassland ecosystems. A lack of precipitation resulted in decreases in NDVI, thereby reducing vegetation growth in these regions. Conversely, increasing precipitation decreased the NDVI of forest ecosystems. The results also suggest that grasslands under arid and semi-arid environments may be more sensitive to drought than forests under humid environments. Among grassland ecosystems, desert steppe was most sensitive to drought, followed by typical steppe; meadow steppe was the least sensitive.
文摘A previous paper showed that the real numbers between 0 and 1 could be represented by an infinite tree structure, called the ‘infinity tree’, which contains only a countably infinite number of nodes and arcs. This paper discusses how a finite-state Turing machine could, in a countably infinite number of state transitions, write all the infinite paths in the infinity tree to a countably infinite tape. Hence it is argued that the real numbers in the interval [0, 1] are countably infinite in a non-Cantorian theory of infinity based on Turing machines using countably infinite space and time. In this theory, Cantor’s Continuum Hypothesis can also be proved. And in this theory, it follows that the power set of the natural numbers P(ℕ) is countably infinite, which contradicts the claim of Cantor’s Theorem for the natural numbers. However, this paper does not claim there is an error in Cantor’s arguments that [0, 1] is uncountably infinite. Rather, this paper considers the situation as a paradox, resulting from different choices about how to represent and count the continuum of real numbers.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12275065,12275064,12475203)the Natural Science Foundation of Hebei Province(Grant Nos.A2021201010 and A2024201020)+3 种基金Interdisciplinary Research Program of Natural Science of Hebei University(Grant No.DXK202108)Hebei Provincial Central Government Guiding Local Science and Technology Development Funds(Grant No.236Z1501G)Scientific Research and Innovation Team Foundation of Hebei University(Grant No.IT2023B03)the Excellent Youth Research Innovation Team of Hebei University(Grant No.QNTD202402)。
文摘A new type of localized oscillatory pattern is presented in a two-layer coupled reaction-diffusion system under conditions in which no Hopf instability can be discerned in either layer.The transitions from stationary patterns to asynchronous and synchronous oscillatory patterns are obtained.A novel method based on decomposing coupled systems into two associated subsystems has been proposed to elucidate the mechanism of formation of oscillating patterns.Linear stability analysis of the associated subsystems reveals that the Turing pattern in one layer induces the other layer locally,undergoes a supercritical Hopf bifurcation and gives rise to localized oscillations.It is found that the sizes and positions of oscillations are determined by the spatial distribution of the Turing patterns.When the size is large,localized traveling waves such as spirals and targets emerge.These results may be useful for deeper understanding of pattern formation in complex systems,particularly multilayered systems.
基金financially supported by the National Natural Science Foundation of China(No.22209024)Tongcheng R&D Foundation(No.CPCIF-RA-0102)the State Key Laboratory of Advanced Fiber Materials,Donghua University
文摘Achieving industrial-level electrochemical CO_(2)reduction to formate remains a significant challenge due to limitations in catalyst selectivity and interfacial proton management at high current densities.In a recent study,Prof.Guo and colleagues report the development of Turingstructured electrocatalysts,which incorporate reaction-diffusion-inspired topologies to engineer mesoscale surface patterns.This design enables precise modulation of the interfacial microenvironment,enhancing CO_(2)activation and suppressing competing hydrogen evolution.The resulting catalysts achieve efficient and stable CO_(2)-to-formate conversion under industrially relevant conditions,offering a promising strategy for scalable carbon-neutral chemical production.
