To gain understanding of the applicability of carbon fiber reinforced polymer (CFRP) cable in cable-supported bridges, based on the Runyang Bridge and Jinsha Bridge, a suspension bridge using CFRP cables and a cable-s...To gain understanding of the applicability of carbon fiber reinforced polymer (CFRP) cable in cable-supported bridges, based on the Runyang Bridge and Jinsha Bridge, a suspension bridge using CFRP cables and a cable-stayed bridge using CFRP stay cables are designed, in which the cable’s cross-sectional area is determined by the principle of equivalent axial stiffness. Numerical investigations on the aerodynamic stability of the two bridges are conducted by 3D nonlinear aerodynamic stability analysis. The results showed that as CFRP cables are used in cable-supported bridges, for suspension bridge, its aerodynamic stability is superior to that of the case using steel cables due to the great increase of the torsional frequency; for cable-stayed bridge, its aerodynamic stability is basically the same as that of the case using steel stay cables. Therefore as far as the wind stability is considered, the use of CFRP cables in cable-supported bridges is feasible, and the cable’s cross-sectional area should be deter-mined by the principle of equivalent axial stiffness.展开更多
In this work, nonlinear multimode aerodynamic analysis of the Jingsha Bridge under erection over the Yangtze River is conducted, and the evolutions of structural dynamic characteristics and the aerodynamic stability w...In this work, nonlinear multimode aerodynamic analysis of the Jingsha Bridge under erection over the Yangtze River is conducted, and the evolutions of structural dynamic characteristics and the aerodynamic stability with erection are numerically generated. Instead of the simplified method, nonlinear multimode aerodynamic analysis is suggested to predict the aerodynamic stability of cable-stayed bridges under erection. The analysis showed that the aerodynamic stability maximizes at the relatively early stages, and decreases as the erection proceeds. The removal of the temporary piers in side spans and linking of the main girder to the anchor piers have important influence on the dynamic characteristics and aerodynamic stability of cable-stayed bridges under erection.展开更多
A local improvement procedure based on tabu search(TS) was incorporated into a basic genetic algorithm(GA) and a global optimal algorithm,i.e.,hybrid genetic algorithm(HGA) approach was used to search the circular and...A local improvement procedure based on tabu search(TS) was incorporated into a basic genetic algorithm(GA) and a global optimal algorithm,i.e.,hybrid genetic algorithm(HGA) approach was used to search the circular and noncircular slip surfaces associated with their minimum safety factors.The slope safety factors of circular and noncircular critical slip surfaces were calculated by the simplified Bishop method and an improved Morgenstern-Price method which can be conveniently programmed,respectively.Comparisons with other methods were made which indicate the high efficiency and accuracy of the HGA approach.The HGA approach was used to calculate one case example and the results demonstrated its applicability to practical engineering.展开更多
Background The left atrial size has been considered as a useful marker of adverse cardiovascular outcomes. However, it is not well known whether left atrial area index (LAAI) has predictive value for prognosis in pa...Background The left atrial size has been considered as a useful marker of adverse cardiovascular outcomes. However, it is not well known whether left atrial area index (LAAI) has predictive value for prognosis in patients with unstable angina pectoris (UAP). This study was aimed to assess the association between LAAI and outcomes in UAP patients. Methods We enrolled a total of 391 in-hospital patients diag- nosed as UAP. Clinical and echocardiographic data at baseline were collected. The patients were followed for the development of ad- verse cardiovascular (CV) events, including hospital readmission for angina pectoris, acute myocardial infarction (AMI), congestive heart failure (CHF), stroke and all-cause mortality. Results During a mean follow-up time of 26.3±8.6 months, 98 adverse CV events occurred (84 hospital readmission for angina pectoris, four AMI, four CHF, one stroke and five all-cause mortality). In a multivariate Cox model, LAAI [OR: 1.140, 95% CI: 1.01±1.279, P = 0.026], diastolic blood pressure (OR: 0.976, 95% CI: 0.956-0.996, P = 0.020) and pulse pressure (OR 1.020, 95% CI: 1.007-1.034, P = 0.004) were independent predictors for adverse CV events in UAP patients. Conclusions LAAI is a predictor of adverse CV events independent of clinical and other echocardiographic parameters in UAP patients.展开更多
This research focuses on identifying the damping ratio of bridges using nonstationary ambient vibration data. The damping ratios of bridges in service have generally been identified using operational modal analysis (...This research focuses on identifying the damping ratio of bridges using nonstationary ambient vibration data. The damping ratios of bridges in service have generally been identified using operational modal analysis (OMA) based on a stationary white noise assumption for input signals. However, most bridges are generally subjected to nonstationary excitations while in service, and this violation of the basic assumption can lead to uncertainties in damping identification. To deal with nonstationarity, an amplitude-modulating function was calculated from measured responses to eliminate global trends caused by nonstationary input. A natural excitation technique (NExT)-eigensystem realization algorithm (ERA) was applied to estimate the damping ratio for a stationarized process. To improve the accuracy of OMA-based damping estimates, a comparative analysis was performed between an extracted stationary process and nonstationary data to assess the effect of eliminating nonstationarity. The mean value and standard deviation of the damping ratio for the first vertical mode decreased after signal stationarization.展开更多
Aiming at prestressed anchor cable frame in the presence of reinforcement landslide problem, through the selection of test points, the paper study and tested soil pressure, frame internal force and prestress losses un...Aiming at prestressed anchor cable frame in the presence of reinforcement landslide problem, through the selection of test points, the paper study and tested soil pressure, frame internal force and prestress losses under prestressed anchor cable frame beam, reveal the law of internal force distribution, and provides a theory basis for the rational design of prestressed anchor cable in landslide.展开更多
In recent years, sinmlated annealing algo-rithms have been extensively developed and uti-lized to solve nmlti-objective optimization problems. In order to obtain better optimization perfonmnce, this paper proposes a N...In recent years, sinmlated annealing algo-rithms have been extensively developed and uti-lized to solve nmlti-objective optimization problems. In order to obtain better optimization perfonmnce, this paper proposes a Novel Adaptive Simulated Annealing (NASA) algorithm for constrained multi-objective optimization based on Archived Multi-objective Simulated Annealing (AMOSA). For han-dling multi-objective, NASA makes improverrents in three aspects: sub-iteration search, sub-archive and adaptive search, which effectively strengthen the stability and efficiency of the algorithnm For handling constraints, NASA introduces corresponding solution acceptance criterion. Furtherrrore, NASA has also been applied to optimize TD-LTE network perform-ance by adjusting antenna paranleters; it can achieve better extension and convergence than AMOSA, NS-GAII and MOPSO. Analytical studies and simulations indicate that the proposed NASA algorithm can play an important role in improving multi-objective optimi-zation performance.展开更多
On the basis of the theoretical analysis of a single-machine infinite-bus (SMIB), using the modified linearized Phil- lips-Heffron model installed with unified power flow controller (UPFC), the potential of the UP...On the basis of the theoretical analysis of a single-machine infinite-bus (SMIB), using the modified linearized Phil- lips-Heffron model installed with unified power flow controller (UPFC), the potential of the UPFC supplementary controller to enhance the dynamic stability of a power system is evaluated by measuring the electromechanical controllability through singular value decomposition (SVD) analysis. This controller is tuned to simultaneously shift the undamped electromeehanical modes to a prescribed zone in the s-plane. The problem of robust UPFC based damping controller is formulated as an optimization problem according to the eigenvalue-based multi-objective function comprising the damping factor, and the damping ratio of the undamped electromechanical modes to be solved using gravitational search algorithm (GSA) that has a strong ability to find the most optimistic results. The different loading conditions are simulated on a SMIB system and the rotor speed deviation, internal voltage deviation, DC voltage deviation and electrical power deviation responses are studied with the effect of this flexible AC transmission systems (FACTS) controller. The results reveal that the tuned GSA based UPFC controller using the proposed multi-objective function has an excellent capability in damping power system with low frequency oscillations and greatly enhances the dynamic stability of the power systems.展开更多
The quality as well as reliability of electrical energy transmitted to consumers is one of the main parameters of successful operation of the power system. The searching of optimal coefficient's combination of PSS (...The quality as well as reliability of electrical energy transmitted to consumers is one of the main parameters of successful operation of the power system. The searching of optimal coefficient's combination of PSS (power system stabilizer) is the main goal of this article. The possibility of application of the new combined approach for the optimal excitation's settings search is presented. MC (Monte Carlo) method, in order to search and select the optimal combination of excitation system, was applied. The proposed method has been researched with a mathematical model of the power system. This model has been built using Matlab/Simulink software. Paper shows advantages and disadvantages of the proposed methods.展开更多
Transition metal nitrides have been suggested to have both high hardness and good thermal stability with large potential application value, but so far stable superhard transition metal nitrides have not been synthesiz...Transition metal nitrides have been suggested to have both high hardness and good thermal stability with large potential application value, but so far stable superhard transition metal nitrides have not been synthesized. Here, with our newly developed machine-learning accelerated crystal structure searching method, we designed a superhard tungsten nitride, h-WN6, which can be synthesized at pressure around 65 GPa and quenchable to ambient pressure. This h-WN6 is constructed with single-bonded armchair-like N6 rings and presents ionic-like features, which can be formulated as W^2.4+N^2.4-. It has a band gap of 1.6 eV at 0GPa and exhibits an abnormal gap broadening behavior under pressure. Excitingly, this h-WN6 is found to be the hardest among transition metal nitrides known so far (Vickers hardness around 57 GPa) and also has a very high melting temperature (around 1,900 K). Additionally, the good gravimet- ric (3.1 kJ/g/and volumetric (28.0 kJ/cm3) energy densities make this nitrogen-rich compound a potential high-energy-density material, These predictions support the designing rules and may stimulate future experiments to synthesize superhard and high-energy-density material.展开更多
Behavioral "traditions", i.e. behavioral patterns that are acquired with the aid of social learning and that are relatively stable in a group, have been observed in several species. Recently, however, it has been qu...Behavioral "traditions", i.e. behavioral patterns that are acquired with the aid of social learning and that are relatively stable in a group, have been observed in several species. Recently, however, it has been questioned whether non-human social learning is faithful enough to stabilize those patterns. The observed stability could be interpreted as a result of various constraints that limit the number of possible alternative behaviors, rather than of the fidelity of transmission mechanisms. Those constraints can be roughly described as "internal", such as mechanical (bodily) properties or cognitive limitations and predispositions, and "ex- ternal", such as ecological availability or pressures. Here we present an evolutionary individual-based model that explores the re- lationships between the evolution of faithful social learning and behavioral constraints, represented both by the size of the beha- vioral repertoire and by the "shape" of the search space of a given task. We show that the evolution of high-fidelity transmission mechanisms, when associated with costs (e.g. cognitive, biomechanical, energetic, etc.), is only likely if the potential behavioral repertoire of a species is large and if the search space does not provide information that can be exploited by individual learning. Moreover we show how stable behavioral patterns ("traditions") can be achieved at the population level as an outcome of both high-fidelity and low-fidelity transmission mechanisms, given that the latter are coupled with a small behavioral repertoire or with a search space that provide substantial feedback. Finally, by introducing the possibility of environmental change, we show that intermediate rates of change favor the evolution of faithful social learning展开更多
Multi-proxies of lacustrine sediments, such as total carbon (TC), total organic carbon (TOC), total inorganic carbon (TIC), total nitrogen (TN), total sulfur (TS), hydrogen index (HI), oxygen index (OI) and stable car...Multi-proxies of lacustrine sediments, such as total carbon (TC), total organic carbon (TOC), total inorganic carbon (TIC), total nitrogen (TN), total sulfur (TS), hydrogen index (HI), oxygen index (OI) and stable carbon isotopic composition of organic matter (δ^(13)C_(org)), were analyzed using a 7.3 m core from Zige Tangco. The source of the organic matter in the sediment was mainly from autochthonous phyto-plankton, therefore the significances of proxies can be interpreted as that high TOC, TOC/TS, HI and δ^(13)C_(org) values, low TC, TIC values corresponded to warm and wet climatic condition, and vice versa. The process of climatic development in the Zige Tangco region was hence recovered. During the early and Mid-Holocene, the climate was warm and wet and intensive cold events occurred during the periods of 8600 to 8400 cal a BP and 7400 to 7000 cal a BP. In the second half of Holocene, the climate became cold and dry gradually. The palaeoclimatic process during Holocene in Zige Tangco region matched well with that in Co Ngoin region which is ca 40 km to the south-east. Therefore this palaeoclimatic process represents the Holocene climatic feature in the Central Tibetan Plateau which has the same pattern in the Northern Tibetan Plateau, but the time and duration of some climatic events might be different. We can conclude that in Holocene solar insolation controlled the climatic pattern on the central Tibetan Plateau.展开更多
Tin monosulfide(Sn S), which is composed of earth-abundant elements, holds promise as useful high-performance solar absorber and thermoelectric material. In addition to the ground-state Pnma phase, a series of metasta...Tin monosulfide(Sn S), which is composed of earth-abundant elements, holds promise as useful high-performance solar absorber and thermoelectric material. In addition to the ground-state Pnma phase, a series of metastable phases in different crystalline structures have been reported experimentally or theoretically, yet the phase stability diagrams remain elusive. In this article, we provide a comprehensive materials design study of new phases of Sn S using first-principles global optimization structure search calculations. We find that the two-dimensional layered phases are generally more energetically favored than the three-dimensional connected phases. In addition, we discover several new phases with comparable energetics. Four lower-energy phases show clear phonon stabilities evidenced by an absence of imaginary modes. The electronic band structures, carrier transport properties, and absorption spectra of the newly discovered phases are investigated and discussed toward potential applications for solar cells and thermoelectric devices.展开更多
基金Project (No. 502118) supported by the Natural Science Foundation of Zhejiang Province, China
文摘To gain understanding of the applicability of carbon fiber reinforced polymer (CFRP) cable in cable-supported bridges, based on the Runyang Bridge and Jinsha Bridge, a suspension bridge using CFRP cables and a cable-stayed bridge using CFRP stay cables are designed, in which the cable’s cross-sectional area is determined by the principle of equivalent axial stiffness. Numerical investigations on the aerodynamic stability of the two bridges are conducted by 3D nonlinear aerodynamic stability analysis. The results showed that as CFRP cables are used in cable-supported bridges, for suspension bridge, its aerodynamic stability is superior to that of the case using steel cables due to the great increase of the torsional frequency; for cable-stayed bridge, its aerodynamic stability is basically the same as that of the case using steel stay cables. Therefore as far as the wind stability is considered, the use of CFRP cables in cable-supported bridges is feasible, and the cable’s cross-sectional area should be deter-mined by the principle of equivalent axial stiffness.
基金Project supported by China Postdoctoral Science Foundation (No.2002031245) and the Natural Science Foundation of Zhejiang Prov-ince (No. 502118) China
文摘In this work, nonlinear multimode aerodynamic analysis of the Jingsha Bridge under erection over the Yangtze River is conducted, and the evolutions of structural dynamic characteristics and the aerodynamic stability with erection are numerically generated. Instead of the simplified method, nonlinear multimode aerodynamic analysis is suggested to predict the aerodynamic stability of cable-stayed bridges under erection. The analysis showed that the aerodynamic stability maximizes at the relatively early stages, and decreases as the erection proceeds. The removal of the temporary piers in side spans and linking of the main girder to the anchor piers have important influence on the dynamic characteristics and aerodynamic stability of cable-stayed bridges under erection.
基金Project(50878082)supported by the National Natural Science Foundation of ChinaProject(2012C21058)supported by the Public Welfare Technology Application Research of Zhejiang Province,China
文摘A local improvement procedure based on tabu search(TS) was incorporated into a basic genetic algorithm(GA) and a global optimal algorithm,i.e.,hybrid genetic algorithm(HGA) approach was used to search the circular and noncircular slip surfaces associated with their minimum safety factors.The slope safety factors of circular and noncircular critical slip surfaces were calculated by the simplified Bishop method and an improved Morgenstern-Price method which can be conveniently programmed,respectively.Comparisons with other methods were made which indicate the high efficiency and accuracy of the HGA approach.The HGA approach was used to calculate one case example and the results demonstrated its applicability to practical engineering.
文摘Background The left atrial size has been considered as a useful marker of adverse cardiovascular outcomes. However, it is not well known whether left atrial area index (LAAI) has predictive value for prognosis in patients with unstable angina pectoris (UAP). This study was aimed to assess the association between LAAI and outcomes in UAP patients. Methods We enrolled a total of 391 in-hospital patients diag- nosed as UAP. Clinical and echocardiographic data at baseline were collected. The patients were followed for the development of ad- verse cardiovascular (CV) events, including hospital readmission for angina pectoris, acute myocardial infarction (AMI), congestive heart failure (CHF), stroke and all-cause mortality. Results During a mean follow-up time of 26.3±8.6 months, 98 adverse CV events occurred (84 hospital readmission for angina pectoris, four AMI, four CHF, one stroke and five all-cause mortality). In a multivariate Cox model, LAAI [OR: 1.140, 95% CI: 1.01±1.279, P = 0.026], diastolic blood pressure (OR: 0.976, 95% CI: 0.956-0.996, P = 0.020) and pulse pressure (OR 1.020, 95% CI: 1.007-1.034, P = 0.004) were independent predictors for adverse CV events in UAP patients. Conclusions LAAI is a predictor of adverse CV events independent of clinical and other echocardiographic parameters in UAP patients.
基金supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIP) (2017R1A2B4008973)supported by grants (17SCIPB119960-02) from the Ministry of Land+2 种基金 Infrastructure and Transport of the Korean Governmentpartially supported by the BK21 PLUS research program of the National Research Foundation of Koreathe New Technology Research Center for Bridges through the Institute of Engineering Research at Seoul National University
文摘This research focuses on identifying the damping ratio of bridges using nonstationary ambient vibration data. The damping ratios of bridges in service have generally been identified using operational modal analysis (OMA) based on a stationary white noise assumption for input signals. However, most bridges are generally subjected to nonstationary excitations while in service, and this violation of the basic assumption can lead to uncertainties in damping identification. To deal with nonstationarity, an amplitude-modulating function was calculated from measured responses to eliminate global trends caused by nonstationary input. A natural excitation technique (NExT)-eigensystem realization algorithm (ERA) was applied to estimate the damping ratio for a stationarized process. To improve the accuracy of OMA-based damping estimates, a comparative analysis was performed between an extracted stationary process and nonstationary data to assess the effect of eliminating nonstationarity. The mean value and standard deviation of the damping ratio for the first vertical mode decreased after signal stationarization.
文摘Aiming at prestressed anchor cable frame in the presence of reinforcement landslide problem, through the selection of test points, the paper study and tested soil pressure, frame internal force and prestress losses under prestressed anchor cable frame beam, reveal the law of internal force distribution, and provides a theory basis for the rational design of prestressed anchor cable in landslide.
基金supported by the Major National Science & Technology Specific Project of China under Grants No.2010ZX03002-007-02,No.2009ZX03002-002,No.2010ZX03002-002-03
文摘In recent years, sinmlated annealing algo-rithms have been extensively developed and uti-lized to solve nmlti-objective optimization problems. In order to obtain better optimization perfonmnce, this paper proposes a Novel Adaptive Simulated Annealing (NASA) algorithm for constrained multi-objective optimization based on Archived Multi-objective Simulated Annealing (AMOSA). For han-dling multi-objective, NASA makes improverrents in three aspects: sub-iteration search, sub-archive and adaptive search, which effectively strengthen the stability and efficiency of the algorithnm For handling constraints, NASA introduces corresponding solution acceptance criterion. Furtherrrore, NASA has also been applied to optimize TD-LTE network perform-ance by adjusting antenna paranleters; it can achieve better extension and convergence than AMOSA, NS-GAII and MOPSO. Analytical studies and simulations indicate that the proposed NASA algorithm can play an important role in improving multi-objective optimi-zation performance.
文摘On the basis of the theoretical analysis of a single-machine infinite-bus (SMIB), using the modified linearized Phil- lips-Heffron model installed with unified power flow controller (UPFC), the potential of the UPFC supplementary controller to enhance the dynamic stability of a power system is evaluated by measuring the electromechanical controllability through singular value decomposition (SVD) analysis. This controller is tuned to simultaneously shift the undamped electromeehanical modes to a prescribed zone in the s-plane. The problem of robust UPFC based damping controller is formulated as an optimization problem according to the eigenvalue-based multi-objective function comprising the damping factor, and the damping ratio of the undamped electromechanical modes to be solved using gravitational search algorithm (GSA) that has a strong ability to find the most optimistic results. The different loading conditions are simulated on a SMIB system and the rotor speed deviation, internal voltage deviation, DC voltage deviation and electrical power deviation responses are studied with the effect of this flexible AC transmission systems (FACTS) controller. The results reveal that the tuned GSA based UPFC controller using the proposed multi-objective function has an excellent capability in damping power system with low frequency oscillations and greatly enhances the dynamic stability of the power systems.
文摘The quality as well as reliability of electrical energy transmitted to consumers is one of the main parameters of successful operation of the power system. The searching of optimal coefficient's combination of PSS (power system stabilizer) is the main goal of this article. The possibility of application of the new combined approach for the optimal excitation's settings search is presented. MC (Monte Carlo) method, in order to search and select the optimal combination of excitation system, was applied. The proposed method has been researched with a mathematical model of the power system. This model has been built using Matlab/Simulink software. Paper shows advantages and disadvantages of the proposed methods.
基金financially supported by the Ministry of Science and Technology of the People’s Republic of China (2016YFA0300404 and 2015CB921202)the National Natural Science Foundation of China (51372112 and 11574133)+2 种基金the NSF of Jiangsu Province (BK20150012)the Fundamental Research Funds for the Central Universities,the Science Challenge Project (TZ2016001)Special Program for Applied Research on Super Computation of the NSFC-Guangdong Joint Fund (the second phase) under Grant No.U1501501
文摘Transition metal nitrides have been suggested to have both high hardness and good thermal stability with large potential application value, but so far stable superhard transition metal nitrides have not been synthesized. Here, with our newly developed machine-learning accelerated crystal structure searching method, we designed a superhard tungsten nitride, h-WN6, which can be synthesized at pressure around 65 GPa and quenchable to ambient pressure. This h-WN6 is constructed with single-bonded armchair-like N6 rings and presents ionic-like features, which can be formulated as W^2.4+N^2.4-. It has a band gap of 1.6 eV at 0GPa and exhibits an abnormal gap broadening behavior under pressure. Excitingly, this h-WN6 is found to be the hardest among transition metal nitrides known so far (Vickers hardness around 57 GPa) and also has a very high melting temperature (around 1,900 K). Additionally, the good gravimet- ric (3.1 kJ/g/and volumetric (28.0 kJ/cm3) energy densities make this nitrogen-rich compound a potential high-energy-density material, These predictions support the designing rules and may stimulate future experiments to synthesize superhard and high-energy-density material.
文摘Behavioral "traditions", i.e. behavioral patterns that are acquired with the aid of social learning and that are relatively stable in a group, have been observed in several species. Recently, however, it has been questioned whether non-human social learning is faithful enough to stabilize those patterns. The observed stability could be interpreted as a result of various constraints that limit the number of possible alternative behaviors, rather than of the fidelity of transmission mechanisms. Those constraints can be roughly described as "internal", such as mechanical (bodily) properties or cognitive limitations and predispositions, and "ex- ternal", such as ecological availability or pressures. Here we present an evolutionary individual-based model that explores the re- lationships between the evolution of faithful social learning and behavioral constraints, represented both by the size of the beha- vioral repertoire and by the "shape" of the search space of a given task. We show that the evolution of high-fidelity transmission mechanisms, when associated with costs (e.g. cognitive, biomechanical, energetic, etc.), is only likely if the potential behavioral repertoire of a species is large and if the search space does not provide information that can be exploited by individual learning. Moreover we show how stable behavioral patterns ("traditions") can be achieved at the population level as an outcome of both high-fidelity and low-fidelity transmission mechanisms, given that the latter are coupled with a small behavioral repertoire or with a search space that provide substantial feedback. Finally, by introducing the possibility of environmental change, we show that intermediate rates of change favor the evolution of faithful social learning
基金National Natural Science Foundation of China (Grant Nos. 40471001 and 90411017)
文摘Multi-proxies of lacustrine sediments, such as total carbon (TC), total organic carbon (TOC), total inorganic carbon (TIC), total nitrogen (TN), total sulfur (TS), hydrogen index (HI), oxygen index (OI) and stable carbon isotopic composition of organic matter (δ^(13)C_(org)), were analyzed using a 7.3 m core from Zige Tangco. The source of the organic matter in the sediment was mainly from autochthonous phyto-plankton, therefore the significances of proxies can be interpreted as that high TOC, TOC/TS, HI and δ^(13)C_(org) values, low TC, TIC values corresponded to warm and wet climatic condition, and vice versa. The process of climatic development in the Zige Tangco region was hence recovered. During the early and Mid-Holocene, the climate was warm and wet and intensive cold events occurred during the periods of 8600 to 8400 cal a BP and 7400 to 7000 cal a BP. In the second half of Holocene, the climate became cold and dry gradually. The palaeoclimatic process during Holocene in Zige Tangco region matched well with that in Co Ngoin region which is ca 40 km to the south-east. Therefore this palaeoclimatic process represents the Holocene climatic feature in the Central Tibetan Plateau which has the same pattern in the Northern Tibetan Plateau, but the time and duration of some climatic events might be different. We can conclude that in Holocene solar insolation controlled the climatic pattern on the central Tibetan Plateau.
基金supported by the National Natural Science Foundation of China(Grant Nos.61722403,and 11674121)the Recruitment Program of Global Youth Experts in China+1 种基金Program for JLU Science and Technology Innovative Research Teamthe Special Fund for Talent Exploitation in Jilin Province of China
文摘Tin monosulfide(Sn S), which is composed of earth-abundant elements, holds promise as useful high-performance solar absorber and thermoelectric material. In addition to the ground-state Pnma phase, a series of metastable phases in different crystalline structures have been reported experimentally or theoretically, yet the phase stability diagrams remain elusive. In this article, we provide a comprehensive materials design study of new phases of Sn S using first-principles global optimization structure search calculations. We find that the two-dimensional layered phases are generally more energetically favored than the three-dimensional connected phases. In addition, we discover several new phases with comparable energetics. Four lower-energy phases show clear phonon stabilities evidenced by an absence of imaginary modes. The electronic band structures, carrier transport properties, and absorption spectra of the newly discovered phases are investigated and discussed toward potential applications for solar cells and thermoelectric devices.