The field measurements of decay rates and time lags of heat conduction in a building construction taken in Nanjing during the summer of 2001 are presented.The decay rates and time lags are calculated according to the ...The field measurements of decay rates and time lags of heat conduction in a building construction taken in Nanjing during the summer of 2001 are presented.The decay rates and time lags are calculated according to the frequency responses of the heat absorbed by the room＇s internal surfaces,inside surface temperature,indoor air temperature and outdoor synthetic temperature.The measured results match very well with the theoretical results of the zeroth and the first order values of the decay rates and time lags of heat conduction in the building construction,but the difference between the measured values and the theoretical values for the second order is too great to be accepted.It is therefore difficult to accurately test the second order value.However,it is still advisable to complete the analysis using the zeroth-and the first-orders values of the decay rates and time lags of heat conduction in building construction under field conditions,because in these cases the decay rates of heat conduction reach twenty which meets the requirements of engineering plans.展开更多
Recently, canopy transpiration （Ec） has been often estimated by xylem sap-flow measurements. However, there is a significant time lag between sap flow measured at the base of the stem and canopy transpiration due to...Recently, canopy transpiration （Ec） has been often estimated by xylem sap-flow measurements. However, there is a significant time lag between sap flow measured at the base of the stem and canopy transpiration due to the capacitive exchange between the transpiration stream and stem water storage. Significant errors will be introduced in canopy conductance （gc） and canopy transpiration estimation if the time lag is neglected. In this study, a cross-correlation analysis was used to quantify the time lag, and the sap flowbased transpiration was measured to pararneterize Jarvistype models of gc and thus to simulate Ec of Populus cathayana using the Penman-Monteith equation. The results indicate that solar radiation （Rs） and vapor pressure deficit （VPD） are not fully coincident with sap flow and have an obvious lag effect; the sap flow lags behind Rs and precedes VPD, and there is a 1-h time shift between Eo and sap flow in the 30-min interval data set. A parameterized Jarvis-type gc model is suitable to predict P. cathayana transpiration and explains more than 80% of the variation observed in go, and the relative error was less than 25%, which shows a preferable simulation effect. The root mean square error （RMSEs） between the predicted and measured Ec were 1.91×10^-3 （with the time lag） and 3.12×10^-3cm h^-1 （without the time lag）. More importantly, Ec simulation precision that incorporates time lag is improved by 6% compared to the results without the time lag, with the mean relative error （MRE） of only 8.32% and the mean absolute error （MAE） of 1.48 × 10^-3 cm h^-1.展开更多
Flow shop scheduling problem with time lags is a practical scheduling problem and attracts many studies. Permutation problem（PFSP with time lags） is concentrated but non-permutation problem（non-PFSP with time lags...Flow shop scheduling problem with time lags is a practical scheduling problem and attracts many studies. Permutation problem（PFSP with time lags） is concentrated but non-permutation problem（non-PFSP with time lags） seems to be neglected. With the aim to minimize the makespan and satisfy time lag constraints, efficient algo- rithms corresponding to PFSP and non-PFSP problems are proposed, which consist of iterated greedy algorithm for permutation（IGTLP） and iterated greedy algorithm for non-permutation （IGTLNP）. The proposed algorithms are verified using well-known simple and complex instances of permutation and non-permutation problems with various time lag ranges. The permutation results indicate that the proposed IGTLP can reach near optimal solution within nearly 11% computational time of traditional GA approach. The non-permutation results indicate that the proposed IG can reach nearly same solution within less than 1% com- putational time compared with traditional GA approach. The proposed research combines PFSP and non-PFSP together with minimal and maximal time lag consideration, which provides an interesting viewpoint for industrial implementation.展开更多
Various optimal boundary control problems for linear infinite order distributed hyperbolic systems involving constant time lags are considered. Constraints on controls are imposed. Necessary and sufficient optimality ...Various optimal boundary control problems for linear infinite order distributed hyperbolic systems involving constant time lags are considered. Constraints on controls are imposed. Necessary and sufficient optimality conditions for the Neumann problem with the quadratic performance functional are derived.展开更多
Recently, lots of smoothing techniques have been presented for maneuvering target tracking. Interacting multiple model-probabilistic data association （IMM-PDA） fixed-lag smoothing algorithm provides an efficient sol...Recently, lots of smoothing techniques have been presented for maneuvering target tracking. Interacting multiple model-probabilistic data association （IMM-PDA） fixed-lag smoothing algorithm provides an efficient solution to track a maneuvering target in a cluttered environment. Whereas, the smoothing lag of each model in a model set is a fixed constant in traditional algorithms. A new approach is developed in this paper. Although this method is still based on IMM-PDA approach to a state augmented system, it adopts different smoothing lag according to diverse degrees of complexity of each model. As a result, the application is more flexible and the computational load is reduced greatly. Some simulations were conducted to track a highly maneuvering target in a cluttered environment using two sensors. The results illustrate the superiority of the proposed algorithm over comparative schemes, both in accuracy of track estimation and the computational load.展开更多
The inconsistency and disharmony in China’s environmental legal system are seriously undermining the authority and effectiveness of environmental laws, making it hard to achieve the national environmental legislative...The inconsistency and disharmony in China’s environmental legal system are seriously undermining the authority and effectiveness of environmental laws, making it hard to achieve the national environmental legislative goals. It is found in this study that at least 18 administrative regulations and rules conflict with the five recently-revised environmental laws. The legislative vacancy rate of province-level environmental laws reaches 27.8%, and that of city-level environmental laws in the major cities reaches 59.7%. Besides, 66% of the local including both province-level and city-level environmental laws have the problem of legislative lags, with an average lag of 2547.8 days. In addition, there are many legal conflicts between national environmental laws and local environmental laws. In order to help China to build a harmonious and unified environmental legal system, some suggestions are proposed in this study, including comprehensively examining the lower-level environmental laws, strengthening the leading role of local people’s congresses in environmental legislation, improving the construction of filing and review mechanism, and optimizing the mechanisms for information disclosure and public participation.展开更多
BASED on the Nussbaum’s results, we studied in ref. [2] the conditions for the existence of oscillatory periodic solutions to the differential-delay equations (DDEs)
Calculating the time lags over different timescales using the cross-correlation technique may lead to a biased estimate of small timescales.Given a timescale for lightcurve binning,we propose to subtract the local ave...Calculating the time lags over different timescales using the cross-correlation technique may lead to a biased estimate of small timescales.Given a timescale for lightcurve binning,we propose to subtract the local average instead of the global average during the cross-correlation,in order to filter variations on timescales larger than the bin size.The new method allows us to make an unbiased estimate of the time lags using RXTE/PCA data on timescales as small as-5 ms,where the Fourier technique becomes invalid.We calculate the time lag spectra of Cygnus X-1 at different spectral states with the new method,and find that the source appears to have similar X-ray lags on small timescales independent of its spectral states.展开更多
The Qinba Mountains are climatically and ecologically recognized as the north-south transitional zone of China.Analysis of its phenology is critical for comprehending the response of vegetation to climatic change.We r...The Qinba Mountains are climatically and ecologically recognized as the north-south transitional zone of China.Analysis of its phenology is critical for comprehending the response of vegetation to climatic change.We retrieved the start of spring phenology(SOS)of eight forest communities from the MODIS products and adopted it as an indicator for spring phenology.Trend analysis,partial correlation analysis,and GeoDetector were employed to reveal the spatio-temporal patterns and climatic drivers of SOS.The results indicated that the SOS presented an advance trend from 2001 to 2020,with a mean rate of−0.473 d yr^(−1).The SOS of most forests correlated negatively with air temperature(TEMP)and positively with precipitation(PRE),suggesting that rising TEMP and increasing PRE in spring would forward and delay SOS,respectively.The dominant factors influencing the sensitivity of SOS to climatic variables were altitude,forest type,and latitude,while the effects of slope and aspect were relatively minor.The response of SOS to climatic factors varied significantly in space and among forest communities,partly due to the influence of altitude,slope,and aspect.展开更多
Understanding the evolution and lag effects of droughts is critical to effective drought warning and water resources management.However,due to limited hydrological data,few studies have examined hydrological droughts ...Understanding the evolution and lag effects of droughts is critical to effective drought warning and water resources management.However,due to limited hydrological data,few studies have examined hydrological droughts and their lag time from meteorological droughts at a daily scale.In this study,precipitation data were collected to calculate the standardized precipitation index(SPI),and runoff data simulated by the variable infiltration capacity(VIC)model were utilized to compute the standardized runoff index(SRI).The three-threshold run theory was used to identify drought characteristics in China.These drought characteristics were utilized to investigate spatiotemporal variations,seasonal trends,and temporal changes in areas affected by meteorological and hydrological droughts.Additionally,the interconnections and lag effects between meteorological and hydrological droughts were explored.The results indicated that(1)drought occurred during approximately 28%of the past 34 years in China;(2)drought conditions tended to worsen in autumn and weaken in winter;(3)drought-affected areas shifted from northwest to northeast and finally to southern China;and(4)the correlation between meteorological and hydrological droughts was lower in the northwest and higher in the southeast,with all correlation coefficients exceeding 0.7.The lag times between meteorological and hydrological droughts were longest(5 d)in the Yangtze River,Yellow River,and Hai River basins,and shortest(0 d)in the Tarim River Basin.This study provides a scientific basis for effective early warning of droughts.展开更多
Purpose:The study examines the synergy and hysteresis in the evolution of funding and its supported literature,depicts their temporal correlation mechanism,which aids in improving trend predictions.Design/methodology/...Purpose:The study examines the synergy and hysteresis in the evolution of funding and its supported literature,depicts their temporal correlation mechanism,which aids in improving trend predictions.Design/methodology/approach:The study uses the LDA model to identify topics in funding texts and supported papers.A cosine similarity algorithm was employed to estimate the nexus between topics and construct the topic evolution time series.Similarly,the hysteresis effect in topic evolution is analyzed based on topic popularity and content,leading to insights into their temporal correlation mechanism.Findings:The study finds that fund and sponsored paper topics exhibit strong collaboration with a noticeable lag in evolution.The fund topics significantly influence sponsored paper topics after a two-year lag.Moreover,the lag effect is inversely proportional to the topic’s similarity.Research limitations:We use the LDA model to determine the hysteresis effect in topic evolution despite its limitations in handling long-tail words and domain-specific vocabulary.Furthermore,the timing of the emergence of the focal topic in funds is undermined,affecting the findings.Practical implications:These findings enhance the accuracy and scientific validity of trend prediction.Estimating and identifying patterns can help technology managers anticipate future research hotspots,supporting informed decision-making and technology management.Originality/value:This study introduces a research framework to quantitatively and visually analyze the hysteresis effect,revealing the correlation and evolutionary patterns between fund research topics and their funded papers.展开更多
Dynamic disturbances certainly reduce shear strength of rock joints,yet the mechanism needs deeper explanation.We investigate the shear behavior of a rough basalt joint by conducting laboratory shear experiments.Const...Dynamic disturbances certainly reduce shear strength of rock joints,yet the mechanism needs deeper explanation.We investigate the shear behavior of a rough basalt joint by conducting laboratory shear experiments.Constant and superimposed oscillating normal loads are applied at the upper block.Meanwhile,the bottom block moves at a constant shear rate.We investigate the shear behavior by:1)altering the normal load oscillation frequency with a same shear rate,2)altering the shear rate with a same normal load oscillation frequency,and 3)altering the normal load oscillation frequency and shear rate simultaneously with a constant ratio.The results show that the oscillating normal load reduces the coefficient of friction(COF).The reduce degree of COF increases with higher shear rate,decreases when increasing normal load oscillation frequency,and keeps constant if the special ratio,v/f(shear rate divided by normal oscillation frequency),is constant.Moreover,we identify a time lag between peak normal load and peak shear load.And the lagging proportion increases with higher shear rate,and decreases with larger static COF.Our results imply that a lower creep rate with a higher normal load oscillation frequency easily destabilizes the creeping fault zones.展开更多
This paper propose a comprehensive data-driven prediction framework based on machine learning methods to investigate the lag synchronization phenomenon in coupled chaotic systems,particularly in cases where accurate m...This paper propose a comprehensive data-driven prediction framework based on machine learning methods to investigate the lag synchronization phenomenon in coupled chaotic systems,particularly in cases where accurate mathematical models are challenging to establish or where system equations remain unknown.The Long Short-Term Memory(LSTM)neural network is trained using time series acquired from the desynchronization system states,subsequently predicting the lag synchronization transition.In the experiments,we focus on the Lorenz system with time-varying delayed coupling,studying the effects of coupling coefficients and time delays on lag synchronization,respectively.The results indicate that with appropriate training,the machine learning model can adeptly predict the lag synchronization occurrence and transition.This study not only enhances our comprehension of complex network synchronization behaviors but also underscores the potential and practical applications of machine learning in exploring nonlinear dynamic systems.展开更多
The Madden-Julian Oscillation(MJO)is a key atmospheric component connecting global weather and climate.It func-tions as a primary source for subseasonal forecasts.Previous studies have highlighted the vital impact of ...The Madden-Julian Oscillation(MJO)is a key atmospheric component connecting global weather and climate.It func-tions as a primary source for subseasonal forecasts.Previous studies have highlighted the vital impact of oceanic processes on MJO propagation.However,few existing MJO prediction approaches adequately consider these factors.This study determines the critical region for the oceanic processes affecting MJO propagation by utilizing 22-year Climate Forecast System Reanalysis data.By intro-ducing surface and subsurface oceanic temperature within this critical region into a lagged multiple linear regression model,the MJO forecasting skill is considerably optimized.This optimization leads to a 12 h enhancement in the forecasting skill of the first principal component and efficiently decreases prediction errors for the total predictions.Further analysis suggests that,during the years in which MJO events propagate across the Maritime Continent over a more southerly path,the optimized statistical forecasting model obtains better improvements in MJO prediction.展开更多
Climate change may have detrimental effects on different sectoral growth in global economy and according to the Intergovernmental Panel on Climate Change,the impacts of climate change will be more vigorous in the comi...Climate change may have detrimental effects on different sectoral growth in global economy and according to the Intergovernmental Panel on Climate Change,the impacts of climate change will be more vigorous in the coming years.The climatic and non-climatic driving forces behind the economic sectoral performances involve short-and long-run interconnections among variables.This study attempts to investigate the effect of climatic factors(temperature and precipitation)along with non-climatic factors,including foreign direct investment(FDI),human capital index(HCI),natural capital(NC),and information and communication technology(ICT)on three major sectors of the economy(agricultural sector,industrial sector,and service sector)through non-linear model framework by employing cross-sectionally augmented autoregressive distributed lag(CS-ARDL)estimation technique.It considers a panel of 56 selected countries from different income groups,including high-income countries,upper-middle-income countries,lower-middle-income countries,and low-income countries,covering the period 1985-2022.The confirmation of slope heterogeneity,cross-sectional dependence,stationarity,and cointegration among variables lends support to the robustness of results.The augmented mean group(AMG)robustness test was applied to check robustness and the results were found mostly consistent with estimation method.The results revealed that upper-middle-income countries are more vulnerable to extreme temperatures compared to high-income countries.The results also confirmed an inverted U-shaped relationship between each sector’s output and precipitation in upper-middle-income countries.In contrast,for upper-middle-income,lower-middle-income,and low-income countries,this relation exists in industrial sector only in long run.This indicates that precipitation is initially beneficial for production activities.However,beyond a certain threshold of precipitation,this trend reverses,i.e.,the output of the economic sectors tends to decline.Furthermore,there is no supporting evidence that confirms a short-run non-linear relation between precipitation and agricultural yields.In upper-middle-income countries,the results confirmed that FDI is a driving factor behind both agricultural sector and service sector in long run while short-run results indicated a negative association but insignificant.This study also showed that in long run,an increase in HCI contributes to improving the output of the three sectors for high-income countries.The empirical findings provide valuable insights for policy-makers and governments to formulate coherent adaptation and mitigation strategies,thereby accelerating the transition of sectoral productivity from low to high levels in the sample countries.展开更多
The study aims to investigate county-level variations of the COVID-19 disease and vaccination rate. The COVID-19 data was acquired from usafact.org, and the vaccination records were acquired from the Ohio vaccination ...The study aims to investigate county-level variations of the COVID-19 disease and vaccination rate. The COVID-19 data was acquired from usafact.org, and the vaccination records were acquired from the Ohio vaccination tracker dashboard. GIS-based exploratory analysis was conducted to select four variables (poverty, black race, population density, and vaccination) to explain COVID-19 occurrence during the study period. Consequently, spatial statistical techniques such as Moran’s I, Hot Spot Analysis, Spatial Lag Model (SLM), and Spatial Error Model (SEM) were used to explain the COVID-19 occurrence and vaccination rate across the 88 counties in Ohio. The result of the Local Moran’s I analysis reveals that the epicenters of COVID-19 and vaccination followed the same patterns. Indeed, counties like Summit, Franklin, Fairfield, Hamilton, and Medina were categorized as epicenters for both COVID-19 occurrence and vaccination rate. The SEM seems to be the best model for both COVID-19 and vaccination rates, with R2 values of 0.68 and 0.70, respectively. The GWR analysis proves to be better than Ordinary Least Squares (OLS), and the distribution of R2 in the GWR is uneven throughout the study area for both COVID-19 cases and vaccinations. Some counties have a high R2 of up to 0.70 for both COVID-19 cases and vaccinations. The outcomes of the regression analyses show that the SEM models can explain 68% - 70% of COVID-19 cases and vaccination across the entire counties within the study period. COVID-19 cases and vaccination rates exhibited significant positive associations with black race and poverty throughout the study area.展开更多
In 2019,China had over 13.14 million dementia cases,with incidence rates of(56.47–207.08)/100,000[1].Early cognitive impairment—a key dementia symptom—reduces quality of life,increases care dependence,and lowers su...In 2019,China had over 13.14 million dementia cases,with incidence rates of(56.47–207.08)/100,000[1].Early cognitive impairment—a key dementia symptom—reduces quality of life,increases care dependence,and lowers survival in older adults[2].A decline in physical function can also be observed in older adults with increasing age.Grip strength has been shown to be a marker of overall physiological function in older adults.展开更多
This paper develops a multi-year lag Input-Holding-Output （I-H-O） Model on education with exclusion of the idle capital to address the reasonable education structure in support of a sustainable development strategy ...This paper develops a multi-year lag Input-Holding-Output （I-H-O） Model on education with exclusion of the idle capital to address the reasonable education structure in support of a sustainable development strategy in China. First, the model considers the multiyear lag of human capital because the lag time of human capital is even longer and more important than that of fixed capital. Second, it considers the idle capital resulting from the output decline in education, for example, student decrease in primary school. The new generalized Leonitief dynamic inverse is deduced to obtain a positive solution on education when output declines as well as expands. After compiling the 2000 I-H-O table on education, the authors adopt modifications-by-step method to treat nonlinear coefficients, and calculate education scale, the requirement of human 2020. It is found that structural imbalance of human development. capital, and education expenditure from 2005 to capital is a serious problem for Chinese economic展开更多
The general mutual information （GMI） and general conditional mutual information （GCMI） are considered to measure lag dependences in nonlinear time series. Both of the measures have the property of invariance with ...The general mutual information （GMI） and general conditional mutual information （GCMI） are considered to measure lag dependences in nonlinear time series. Both of the measures have the property of invariance with transform. The statistics based on GMI and GCMI are estimated using the correlation integral. Under the hypothesis of independent series, the estimators have Gaussian asymptotic distributions. Simulations applied to generated nonlinear series demonstrate that the methods appear to find frequently the correct lags.展开更多
基金The Advance Research Projects of Southeast Universityfor the National Natural Science Foundation of China(No.XJ0701262)the National Key Technologies R&D Program of China during the 11th Five-Year Plan Period(No.2008BAJ12B04,2008BAJ12B05,2006BAJ03A04)
文摘The field measurements of decay rates and time lags of heat conduction in a building construction taken in Nanjing during the summer of 2001 are presented.The decay rates and time lags are calculated according to the frequency responses of the heat absorbed by the room＇s internal surfaces,inside surface temperature,indoor air temperature and outdoor synthetic temperature.The measured results match very well with the theoretical results of the zeroth and the first order values of the decay rates and time lags of heat conduction in the building construction,but the difference between the measured values and the theoretical values for the second order is too great to be accepted.It is therefore difficult to accurately test the second order value.However,it is still advisable to complete the analysis using the zeroth-and the first-orders values of the decay rates and time lags of heat conduction in building construction under field conditions,because in these cases the decay rates of heat conduction reach twenty which meets the requirements of engineering plans.
基金supported by the Qinghai province natural science foundation project(2015-ZJ-902)the Qinghai province science and technology plan program(2014-NK-A4-4)
文摘Recently, canopy transpiration （Ec） has been often estimated by xylem sap-flow measurements. However, there is a significant time lag between sap flow measured at the base of the stem and canopy transpiration due to the capacitive exchange between the transpiration stream and stem water storage. Significant errors will be introduced in canopy conductance （gc） and canopy transpiration estimation if the time lag is neglected. In this study, a cross-correlation analysis was used to quantify the time lag, and the sap flowbased transpiration was measured to pararneterize Jarvistype models of gc and thus to simulate Ec of Populus cathayana using the Penman-Monteith equation. The results indicate that solar radiation （Rs） and vapor pressure deficit （VPD） are not fully coincident with sap flow and have an obvious lag effect; the sap flow lags behind Rs and precedes VPD, and there is a 1-h time shift between Eo and sap flow in the 30-min interval data set. A parameterized Jarvis-type gc model is suitable to predict P. cathayana transpiration and explains more than 80% of the variation observed in go, and the relative error was less than 25%, which shows a preferable simulation effect. The root mean square error （RMSEs） between the predicted and measured Ec were 1.91×10^-3 （with the time lag） and 3.12×10^-3cm h^-1 （without the time lag）. More importantly, Ec simulation precision that incorporates time lag is improved by 6% compared to the results without the time lag, with the mean relative error （MRE） of only 8.32% and the mean absolute error （MAE） of 1.48 × 10^-3 cm h^-1.
基金Supported by National Natural Science Foundation of China(Grant No.71301008)Beijing Municipal Natural Science Foundation of China(Grant No.9144030)
文摘Flow shop scheduling problem with time lags is a practical scheduling problem and attracts many studies. Permutation problem（PFSP with time lags） is concentrated but non-permutation problem（non-PFSP with time lags） seems to be neglected. With the aim to minimize the makespan and satisfy time lag constraints, efficient algo- rithms corresponding to PFSP and non-PFSP problems are proposed, which consist of iterated greedy algorithm for permutation（IGTLP） and iterated greedy algorithm for non-permutation （IGTLNP）. The proposed algorithms are verified using well-known simple and complex instances of permutation and non-permutation problems with various time lag ranges. The permutation results indicate that the proposed IGTLP can reach near optimal solution within nearly 11% computational time of traditional GA approach. The non-permutation results indicate that the proposed IG can reach nearly same solution within less than 1% com- putational time compared with traditional GA approach. The proposed research combines PFSP and non-PFSP together with minimal and maximal time lag consideration, which provides an interesting viewpoint for industrial implementation.
文摘Various optimal boundary control problems for linear infinite order distributed hyperbolic systems involving constant time lags are considered. Constraints on controls are imposed. Necessary and sufficient optimality conditions for the Neumann problem with the quadratic performance functional are derived.
基金This work is supported by the Projects of the State Key Fundamental Research (No. 2001CB309403)
文摘Recently, lots of smoothing techniques have been presented for maneuvering target tracking. Interacting multiple model-probabilistic data association （IMM-PDA） fixed-lag smoothing algorithm provides an efficient solution to track a maneuvering target in a cluttered environment. Whereas, the smoothing lag of each model in a model set is a fixed constant in traditional algorithms. A new approach is developed in this paper. Although this method is still based on IMM-PDA approach to a state augmented system, it adopts different smoothing lag according to diverse degrees of complexity of each model. As a result, the application is more flexible and the computational load is reduced greatly. Some simulations were conducted to track a highly maneuvering target in a cluttered environment using two sensors. The results illustrate the superiority of the proposed algorithm over comparative schemes, both in accuracy of track estimation and the computational load.
文摘The inconsistency and disharmony in China’s environmental legal system are seriously undermining the authority and effectiveness of environmental laws, making it hard to achieve the national environmental legislative goals. It is found in this study that at least 18 administrative regulations and rules conflict with the five recently-revised environmental laws. The legislative vacancy rate of province-level environmental laws reaches 27.8%, and that of city-level environmental laws in the major cities reaches 59.7%. Besides, 66% of the local including both province-level and city-level environmental laws have the problem of legislative lags, with an average lag of 2547.8 days. In addition, there are many legal conflicts between national environmental laws and local environmental laws. In order to help China to build a harmonious and unified environmental legal system, some suggestions are proposed in this study, including comprehensively examining the lower-level environmental laws, strengthening the leading role of local people’s congresses in environmental legislation, improving the construction of filing and review mechanism, and optimizing the mechanisms for information disclosure and public participation.
文摘BASED on the Nussbaum’s results, we studied in ref. [2] the conditions for the existence of oscillatory periodic solutions to the differential-delay equations (DDEs)
基金supported by the National Basic Research Program of China (Grant No. 2009CB824800)the National Natural Science Foundation of China (Grant No. 10533020)
文摘Calculating the time lags over different timescales using the cross-correlation technique may lead to a biased estimate of small timescales.Given a timescale for lightcurve binning,we propose to subtract the local average instead of the global average during the cross-correlation,in order to filter variations on timescales larger than the bin size.The new method allows us to make an unbiased estimate of the time lags using RXTE/PCA data on timescales as small as-5 ms,where the Fourier technique becomes invalid.We calculate the time lag spectra of Cygnus X-1 at different spectral states with the new method,and find that the source appears to have similar X-ray lags on small timescales independent of its spectral states.
基金National Key Research and Development Program of China,No.2023YFE0208100,No.2021YFC3000201Natural Science Foundation of Henan Province,No.232300420165。
文摘The Qinba Mountains are climatically and ecologically recognized as the north-south transitional zone of China.Analysis of its phenology is critical for comprehending the response of vegetation to climatic change.We retrieved the start of spring phenology(SOS)of eight forest communities from the MODIS products and adopted it as an indicator for spring phenology.Trend analysis,partial correlation analysis,and GeoDetector were employed to reveal the spatio-temporal patterns and climatic drivers of SOS.The results indicated that the SOS presented an advance trend from 2001 to 2020,with a mean rate of−0.473 d yr^(−1).The SOS of most forests correlated negatively with air temperature(TEMP)and positively with precipitation(PRE),suggesting that rising TEMP and increasing PRE in spring would forward and delay SOS,respectively.The dominant factors influencing the sensitivity of SOS to climatic variables were altitude,forest type,and latitude,while the effects of slope and aspect were relatively minor.The response of SOS to climatic factors varied significantly in space and among forest communities,partly due to the influence of altitude,slope,and aspect.
基金supported by the National Key Research and Development Program of China(Grant No.2023YFC3006505)the Fundamental Research Funds for the Central Universities of China(Grant No.B240203007)the National Key Laboratory of Water Disaster Prevention(Grant No.524015222)。
文摘Understanding the evolution and lag effects of droughts is critical to effective drought warning and water resources management.However,due to limited hydrological data,few studies have examined hydrological droughts and their lag time from meteorological droughts at a daily scale.In this study,precipitation data were collected to calculate the standardized precipitation index(SPI),and runoff data simulated by the variable infiltration capacity(VIC)model were utilized to compute the standardized runoff index(SRI).The three-threshold run theory was used to identify drought characteristics in China.These drought characteristics were utilized to investigate spatiotemporal variations,seasonal trends,and temporal changes in areas affected by meteorological and hydrological droughts.Additionally,the interconnections and lag effects between meteorological and hydrological droughts were explored.The results indicated that(1)drought occurred during approximately 28%of the past 34 years in China;(2)drought conditions tended to worsen in autumn and weaken in winter;(3)drought-affected areas shifted from northwest to northeast and finally to southern China;and(4)the correlation between meteorological and hydrological droughts was lower in the northwest and higher in the southeast,with all correlation coefficients exceeding 0.7.The lag times between meteorological and hydrological droughts were longest(5 d)in the Yangtze River,Yellow River,and Hai River basins,and shortest(0 d)in the Tarim River Basin.This study provides a scientific basis for effective early warning of droughts.
基金supported by National Natural Science Foundation of China(No.72104110 No.72274113)Basic Science(Natural Science)Research Projects in Higher Education Institutions in Jiangsu Province(No.22KJB630011)+2 种基金General Project of Philosophy and Social Sciences Research in Jiangsu Universities(No.2022SJYB0253)Taishan Scholar Foundation of Shandong province of China(tsqn202103069)Shandong Provincial Natural Science Foundation(No.ZR202111130115)。
文摘Purpose:The study examines the synergy and hysteresis in the evolution of funding and its supported literature,depicts their temporal correlation mechanism,which aids in improving trend predictions.Design/methodology/approach:The study uses the LDA model to identify topics in funding texts and supported papers.A cosine similarity algorithm was employed to estimate the nexus between topics and construct the topic evolution time series.Similarly,the hysteresis effect in topic evolution is analyzed based on topic popularity and content,leading to insights into their temporal correlation mechanism.Findings:The study finds that fund and sponsored paper topics exhibit strong collaboration with a noticeable lag in evolution.The fund topics significantly influence sponsored paper topics after a two-year lag.Moreover,the lag effect is inversely proportional to the topic’s similarity.Research limitations:We use the LDA model to determine the hysteresis effect in topic evolution despite its limitations in handling long-tail words and domain-specific vocabulary.Furthermore,the timing of the emergence of the focal topic in funds is undermined,affecting the findings.Practical implications:These findings enhance the accuracy and scientific validity of trend prediction.Estimating and identifying patterns can help technology managers anticipate future research hotspots,supporting informed decision-making and technology management.Originality/value:This study introduces a research framework to quantitatively and visually analyze the hysteresis effect,revealing the correlation and evolutionary patterns between fund research topics and their funded papers.
基金Project(52474122)supported by the National Natural Science Foundation of ChinaProject(HSR202105)supported by the National Engineering Laboratory for High-speed Railway Construction,China+1 种基金Project(2025B1515020067)supported by the Natural Science Foundation of Guangdong Province of ChinaProject(2022A1515240009)supported by the Natural Science Foundation of Guangdong Province,China。
文摘Dynamic disturbances certainly reduce shear strength of rock joints,yet the mechanism needs deeper explanation.We investigate the shear behavior of a rough basalt joint by conducting laboratory shear experiments.Constant and superimposed oscillating normal loads are applied at the upper block.Meanwhile,the bottom block moves at a constant shear rate.We investigate the shear behavior by:1)altering the normal load oscillation frequency with a same shear rate,2)altering the shear rate with a same normal load oscillation frequency,and 3)altering the normal load oscillation frequency and shear rate simultaneously with a constant ratio.The results show that the oscillating normal load reduces the coefficient of friction(COF).The reduce degree of COF increases with higher shear rate,decreases when increasing normal load oscillation frequency,and keeps constant if the special ratio,v/f(shear rate divided by normal oscillation frequency),is constant.Moreover,we identify a time lag between peak normal load and peak shear load.And the lagging proportion increases with higher shear rate,and decreases with larger static COF.Our results imply that a lower creep rate with a higher normal load oscillation frequency easily destabilizes the creeping fault zones.
基金supported by the National Natural Science Foundation of China(No.52174184)。
文摘This paper propose a comprehensive data-driven prediction framework based on machine learning methods to investigate the lag synchronization phenomenon in coupled chaotic systems,particularly in cases where accurate mathematical models are challenging to establish or where system equations remain unknown.The Long Short-Term Memory(LSTM)neural network is trained using time series acquired from the desynchronization system states,subsequently predicting the lag synchronization transition.In the experiments,we focus on the Lorenz system with time-varying delayed coupling,studying the effects of coupling coefficients and time delays on lag synchronization,respectively.The results indicate that with appropriate training,the machine learning model can adeptly predict the lag synchronization occurrence and transition.This study not only enhances our comprehension of complex network synchronization behaviors but also underscores the potential and practical applications of machine learning in exploring nonlinear dynamic systems.
基金supported by the National Key Program for Developing Basic Science(Nos.2022YFF0801702 and 2022YFE0106600)the National Natural Science Foundation of China(Nos.42175060 and 42175021)the Jiangsu Province Science Foundation(No.BK20250200302).
文摘The Madden-Julian Oscillation(MJO)is a key atmospheric component connecting global weather and climate.It func-tions as a primary source for subseasonal forecasts.Previous studies have highlighted the vital impact of oceanic processes on MJO propagation.However,few existing MJO prediction approaches adequately consider these factors.This study determines the critical region for the oceanic processes affecting MJO propagation by utilizing 22-year Climate Forecast System Reanalysis data.By intro-ducing surface and subsurface oceanic temperature within this critical region into a lagged multiple linear regression model,the MJO forecasting skill is considerably optimized.This optimization leads to a 12 h enhancement in the forecasting skill of the first principal component and efficiently decreases prediction errors for the total predictions.Further analysis suggests that,during the years in which MJO events propagate across the Maritime Continent over a more southerly path,the optimized statistical forecasting model obtains better improvements in MJO prediction.
文摘Climate change may have detrimental effects on different sectoral growth in global economy and according to the Intergovernmental Panel on Climate Change,the impacts of climate change will be more vigorous in the coming years.The climatic and non-climatic driving forces behind the economic sectoral performances involve short-and long-run interconnections among variables.This study attempts to investigate the effect of climatic factors(temperature and precipitation)along with non-climatic factors,including foreign direct investment(FDI),human capital index(HCI),natural capital(NC),and information and communication technology(ICT)on three major sectors of the economy(agricultural sector,industrial sector,and service sector)through non-linear model framework by employing cross-sectionally augmented autoregressive distributed lag(CS-ARDL)estimation technique.It considers a panel of 56 selected countries from different income groups,including high-income countries,upper-middle-income countries,lower-middle-income countries,and low-income countries,covering the period 1985-2022.The confirmation of slope heterogeneity,cross-sectional dependence,stationarity,and cointegration among variables lends support to the robustness of results.The augmented mean group(AMG)robustness test was applied to check robustness and the results were found mostly consistent with estimation method.The results revealed that upper-middle-income countries are more vulnerable to extreme temperatures compared to high-income countries.The results also confirmed an inverted U-shaped relationship between each sector’s output and precipitation in upper-middle-income countries.In contrast,for upper-middle-income,lower-middle-income,and low-income countries,this relation exists in industrial sector only in long run.This indicates that precipitation is initially beneficial for production activities.However,beyond a certain threshold of precipitation,this trend reverses,i.e.,the output of the economic sectors tends to decline.Furthermore,there is no supporting evidence that confirms a short-run non-linear relation between precipitation and agricultural yields.In upper-middle-income countries,the results confirmed that FDI is a driving factor behind both agricultural sector and service sector in long run while short-run results indicated a negative association but insignificant.This study also showed that in long run,an increase in HCI contributes to improving the output of the three sectors for high-income countries.The empirical findings provide valuable insights for policy-makers and governments to formulate coherent adaptation and mitigation strategies,thereby accelerating the transition of sectoral productivity from low to high levels in the sample countries.
文摘The study aims to investigate county-level variations of the COVID-19 disease and vaccination rate. The COVID-19 data was acquired from usafact.org, and the vaccination records were acquired from the Ohio vaccination tracker dashboard. GIS-based exploratory analysis was conducted to select four variables (poverty, black race, population density, and vaccination) to explain COVID-19 occurrence during the study period. Consequently, spatial statistical techniques such as Moran’s I, Hot Spot Analysis, Spatial Lag Model (SLM), and Spatial Error Model (SEM) were used to explain the COVID-19 occurrence and vaccination rate across the 88 counties in Ohio. The result of the Local Moran’s I analysis reveals that the epicenters of COVID-19 and vaccination followed the same patterns. Indeed, counties like Summit, Franklin, Fairfield, Hamilton, and Medina were categorized as epicenters for both COVID-19 occurrence and vaccination rate. The SEM seems to be the best model for both COVID-19 and vaccination rates, with R2 values of 0.68 and 0.70, respectively. The GWR analysis proves to be better than Ordinary Least Squares (OLS), and the distribution of R2 in the GWR is uneven throughout the study area for both COVID-19 cases and vaccinations. Some counties have a high R2 of up to 0.70 for both COVID-19 cases and vaccinations. The outcomes of the regression analyses show that the SEM models can explain 68% - 70% of COVID-19 cases and vaccination across the entire counties within the study period. COVID-19 cases and vaccination rates exhibited significant positive associations with black race and poverty throughout the study area.
基金supported by the Shanghai New Three-year Action Plan for Public Health(Grant No.GWV-10.1-XK16)the US National Institute on Aging(RO1-AGO34479).
文摘In 2019,China had over 13.14 million dementia cases,with incidence rates of(56.47–207.08)/100,000[1].Early cognitive impairment—a key dementia symptom—reduces quality of life,increases care dependence,and lowers survival in older adults[2].A decline in physical function can also be observed in older adults with increasing age.Grip strength has been shown to be a marker of overall physiological function in older adults.
基金supporting by the Key Project of National Natural Science Foundation of China under Grant No. 60874119Innovation Funds of Chinese Academy of Sciences+6 种基金Research Fund for HurnanitiesSocial Sciences in colleges under Grant No. 06BJY102Key project in Jiangxi Soft Science Project under Grant No. [2006]188Jiangxi Research Fund for HumanitiesSocial Sciences in colleges under Grant No. 03J J01Henan Research Fund for HumanitiesSocial Sciences in colleges under Grant No. 2008-ZD-002
文摘This paper develops a multi-year lag Input-Holding-Output （I-H-O） Model on education with exclusion of the idle capital to address the reasonable education structure in support of a sustainable development strategy in China. First, the model considers the multiyear lag of human capital because the lag time of human capital is even longer and more important than that of fixed capital. Second, it considers the idle capital resulting from the output decline in education, for example, student decrease in primary school. The new generalized Leonitief dynamic inverse is deduced to obtain a positive solution on education when output declines as well as expands. After compiling the 2000 I-H-O table on education, the authors adopt modifications-by-step method to treat nonlinear coefficients, and calculate education scale, the requirement of human 2020. It is found that structural imbalance of human development. capital, and education expenditure from 2005 to capital is a serious problem for Chinese economic
基金Supported by the National Natural Science Foundation of China (Grant Nos.60375003 60972150)the Science and Technology Innovation Foundation of Northwestern Polytechnical University (Grant No.2007KJ01033)
文摘The general mutual information （GMI） and general conditional mutual information （GCMI） are considered to measure lag dependences in nonlinear time series. Both of the measures have the property of invariance with transform. The statistics based on GMI and GCMI are estimated using the correlation integral. Under the hypothesis of independent series, the estimators have Gaussian asymptotic distributions. Simulations applied to generated nonlinear series demonstrate that the methods appear to find frequently the correct lags.
