To analyze the influence of the transit accessibility of stops on the travel mode choices of suburban residents,the number of the lines passing by the stops within an accessible range of the resident origin and destin...To analyze the influence of the transit accessibility of stops on the travel mode choices of suburban residents,the number of the lines passing by the stops within an accessible range of the resident origin and destination(OD)points and the average waiting time are used as the indexes of the transit accessibility of stops.Due to the correlation between travel time and accessible range,the transit accessibility of stops is contrasted as piecewise variables constrained by travel time.Taking the Jimei District of Xiamen,China,as an example,a binary logistic regression model of the suburban travel mode choice is constructed.The results show that it is necessary to construct transit accessibility of stops as piecewise variables.With a higher transit accessibility of stops,more residents will choose public transport.The choice of the travel mode is correlated with family attributes and personal characteristics.Morning and evening peak hours and travel distance have little effect on the choice of travel mode.Compared with the travel in urban areas,residents often chose public transport for travel within the suburbs.This research provides a basis for encouraging public transportation priority policies and decision making for transport planners in the suburbs.展开更多
The paper discussed about the staged construction analysis of two-span precast-girder bridge considering time dependent effects, namely creep and aging of concrete. Results obtained showed that it is very important to...The paper discussed about the staged construction analysis of two-span precast-girder bridge considering time dependent effects, namely creep and aging of concrete. Results obtained showed that it is very important to consider construction stage in the analysis of bridge because of stress resultants which are important in design process and very different from those obtained without the consideration of construction stage. This fact is especially important for bridges, because construction period continues along time and loads may change during the construction period and after.展开更多
This paper deals with the backscatter coefficients known as sigma0 at Ku band and C band based on the GDR-M (Merged Geophysical Data Record) of TOPEX/Poseidon (T/P) through Jan.1993 to Dec.2004 over land surface of Ch...This paper deals with the backscatter coefficients known as sigma0 at Ku band and C band based on the GDR-M (Merged Geophysical Data Record) of TOPEX/Poseidon (T/P) through Jan.1993 to Dec.2004 over land surface of China.After smoothing and interpolating the backscatter coefficients for both bands, we achieve the 5′×5′ grid data and the time series of backscatter coefficients in 12 years.The spatial distribution of sigma0 over typical areas (wetland, desert, mountainous area, agriculture base, etc.) of Chinese territory is analyzed and discussed.The fast Fourier transformation (FFT) is used to detect the cycles of seasonal variations of sigma0 time series and gives that the annual period is the major cycle.Meanwhile a semiannual period is also found in some places.We use the least squares method on both periods and find that the amplitude of annual period is obviously greater than that of semi-annual period.The relationship among the anomalousness of time series, variations of environment and climate change, and the serious natural calamity (flood, drought) is also discussed.Data of topography slope extracted from SRTM are used to do correlation analysis with the backscatter coefficients in parts of China to quantify the impact of slope on backscatter coefficients in Ku and C bands, and the results show that they all have a negative correlation but the magnitudes are different in different places with different coverages.Such as the area of Liaoning and Jilin has the maximum correlation -0.56, the Taklimakan Desert has the minimum correlation -0.11, and the other places commonly have correlations in (-0.3, -0.5).展开更多
Based on the collation and statistical analysis of flood and drought information in Baoji area from 1368 to 1911, and in the context of climate change, we investigated the spatio-temporal evolution characteristics of ...Based on the collation and statistical analysis of flood and drought information in Baoji area from 1368 to 1911, and in the context of climate change, we investigated the spatio-temporal evolution characteristics of drought and flood disaster chains in this area during the Ming and Qing dynasties using the methods of moving average, cumulative anomaly and wavelet analysis. The results are as follows:(1) We found a total of 297 drought and flood events from 1368 to 1911 in Baoji. Among these events, droughts and floods occurred separately 191 and 106 times, which accounted for 64.31% and 35.69% of the total events, respectively.(2) We observed distinct characteristics of flood and drought events in Baoji in different phases. The climate was relatively dry from 1368 to 1644. A fluctuant climate phase with both floods and droughts occurred from 1645 to 1804. The climate was relatively wet from 1805 to 1911. Moreover, we observed a pattern of alternating dry and wet periods from 1368 to 1911. In addition, 3 oscillation periods of drought and flood events occurred around 70 a, 110 a and 170 a, which corresponded to sunspot cycles.(3) We also observed an obvious spatial difference in drought and flood events in Baoji. The northern and eastern parts of Weihe River basin were regions with both frequent droughts and floods.(4) The sequential appearance of drought and flood disaster chains in Baoji from 1368 to 1911 was in response to global climate change. Since the 1760s, global climatic deterioration has frequently led to extreme drought and flood events.展开更多
基金The National Natural Science Foundation of China(No.52078224)Promotion Program for Young and Middle-Aged Teachers in Science and Technology Research at Huaqiao University(No.600005-Z17X0170).
文摘To analyze the influence of the transit accessibility of stops on the travel mode choices of suburban residents,the number of the lines passing by the stops within an accessible range of the resident origin and destination(OD)points and the average waiting time are used as the indexes of the transit accessibility of stops.Due to the correlation between travel time and accessible range,the transit accessibility of stops is contrasted as piecewise variables constrained by travel time.Taking the Jimei District of Xiamen,China,as an example,a binary logistic regression model of the suburban travel mode choice is constructed.The results show that it is necessary to construct transit accessibility of stops as piecewise variables.With a higher transit accessibility of stops,more residents will choose public transport.The choice of the travel mode is correlated with family attributes and personal characteristics.Morning and evening peak hours and travel distance have little effect on the choice of travel mode.Compared with the travel in urban areas,residents often chose public transport for travel within the suburbs.This research provides a basis for encouraging public transportation priority policies and decision making for transport planners in the suburbs.
文摘The paper discussed about the staged construction analysis of two-span precast-girder bridge considering time dependent effects, namely creep and aging of concrete. Results obtained showed that it is very important to consider construction stage in the analysis of bridge because of stress resultants which are important in design process and very different from those obtained without the consideration of construction stage. This fact is especially important for bridges, because construction period continues along time and loads may change during the construction period and after.
基金supported by National Natural Science Founda-tion of China(Grant Nos.40974004 and 40774009)International Sci&Tech Cooperation Program of China(Grant No.2009DFB00130)+1 种基金Key Laboratory of Mapping from Space of NASMG,China(Grant No.K201103)the R&I Team Supporting Program and Graduate Sci.&Tech Innovation Fund of SDUST,China(Grant No.YCB110010)
文摘This paper deals with the backscatter coefficients known as sigma0 at Ku band and C band based on the GDR-M (Merged Geophysical Data Record) of TOPEX/Poseidon (T/P) through Jan.1993 to Dec.2004 over land surface of China.After smoothing and interpolating the backscatter coefficients for both bands, we achieve the 5′×5′ grid data and the time series of backscatter coefficients in 12 years.The spatial distribution of sigma0 over typical areas (wetland, desert, mountainous area, agriculture base, etc.) of Chinese territory is analyzed and discussed.The fast Fourier transformation (FFT) is used to detect the cycles of seasonal variations of sigma0 time series and gives that the annual period is the major cycle.Meanwhile a semiannual period is also found in some places.We use the least squares method on both periods and find that the amplitude of annual period is obviously greater than that of semi-annual period.The relationship among the anomalousness of time series, variations of environment and climate change, and the serious natural calamity (flood, drought) is also discussed.Data of topography slope extracted from SRTM are used to do correlation analysis with the backscatter coefficients in parts of China to quantify the impact of slope on backscatter coefficients in Ku and C bands, and the results show that they all have a negative correlation but the magnitudes are different in different places with different coverages.Such as the area of Liaoning and Jilin has the maximum correlation -0.56, the Taklimakan Desert has the minimum correlation -0.11, and the other places commonly have correlations in (-0.3, -0.5).
基金National Natural Science Foundation of China,No.41601016Philosophy and Social Science Research Fund in Shaanxi,No.2017E003Fundamental Research Funds for Key Subject Physical Geography of Baoji University of Arts and Sciences
文摘Based on the collation and statistical analysis of flood and drought information in Baoji area from 1368 to 1911, and in the context of climate change, we investigated the spatio-temporal evolution characteristics of drought and flood disaster chains in this area during the Ming and Qing dynasties using the methods of moving average, cumulative anomaly and wavelet analysis. The results are as follows:(1) We found a total of 297 drought and flood events from 1368 to 1911 in Baoji. Among these events, droughts and floods occurred separately 191 and 106 times, which accounted for 64.31% and 35.69% of the total events, respectively.(2) We observed distinct characteristics of flood and drought events in Baoji in different phases. The climate was relatively dry from 1368 to 1644. A fluctuant climate phase with both floods and droughts occurred from 1645 to 1804. The climate was relatively wet from 1805 to 1911. Moreover, we observed a pattern of alternating dry and wet periods from 1368 to 1911. In addition, 3 oscillation periods of drought and flood events occurred around 70 a, 110 a and 170 a, which corresponded to sunspot cycles.(3) We also observed an obvious spatial difference in drought and flood events in Baoji. The northern and eastern parts of Weihe River basin were regions with both frequent droughts and floods.(4) The sequential appearance of drought and flood disaster chains in Baoji from 1368 to 1911 was in response to global climate change. Since the 1760s, global climatic deterioration has frequently led to extreme drought and flood events.
