A comprehensive understanding of the dynamic frictional characteristics in rock joints under high normal load and strong confinement is essential for ensuring the safety of deep engineering construction and mitigating...A comprehensive understanding of the dynamic frictional characteristics in rock joints under high normal load and strong confinement is essential for ensuring the safety of deep engineering construction and mitigating geological disasters.This study conducted shear experiments on rough rock joints under displacement-controlled dynamic normal loads,investigating the shear behaviors of joints across varying initial normal loads,normal loading frequencies,and normal loading amplitudes.Experimental results showed that the peak/valley shear force values increased with initial normal loads and normal loading frequencies but showed an initial increase followed by a decrease with normal loading amplitudes.Dynamic normal loading can either increase or decrease shear strength,while this study demonstrates that higher frequencies lead to enhanced friction.Increased initial normal loading and normal loading frequency result in a gradual decrease in joint roughness coefficient(JRC)values of joint surfaces after shearing.Positive correlations existed between frictional energy dissipation and peak shear forces,while post-shear joint surface roughness exhibited a negative correlation with peak shear forces through linear regression analysis.This study contributes to a better understanding of the sliding responses and shear mechanical characteristics of rock joints under dynamic disturbances.展开更多
Polymorphism in egg coloration is prominent in the Common Cuckoo (Cuculus canorus) and a common host, the Ashy-throated Parrotbill (Paradoxornis alphonsianus). Egg polymorphism has probably evolved as a consequence of...Polymorphism in egg coloration is prominent in the Common Cuckoo (Cuculus canorus) and a common host, the Ashy-throated Parrotbill (Paradoxornis alphonsianus). Egg polymorphism has probably evolved as a consequence of frequency-dependent selection in both host and parasite, and has, according to human vision, resulted in discrete immaculate white, pale blue and blue egg phenotypes within a single population. However, egg mimicry assessment is not always straightforward, and previous studies have shown that human based comparisons applied to the coloration of bird eggs may be inadequate. Here, we objectively quantify egg color of both parasite and host by spectrophotometry and assess egg mimicry of the Common Cuckoo to the eggs of its Ashy-throated Parrotbill host. Our results revealed that egg reflectance spectra agree well with the assessment based on human vision that cuckoo eggs mimic those of the parrotbill host, in both visible (VIS) and ultraviolet (UV) ranges. However, the white cuckoo egg shows slightly poorer mimicry than the blue cuckoo egg in corresponding host clutches. We suggest that the white parrotbill egg morph (and subsequently the whitish cuckoo egg color) may have evolved after the evolution of the blue egg morph due to strong selection from parasites in the cuckoo-parrotbill system.展开更多
[Objective] The aim was to explore response characters of NDVI of different types of vegetation to climate change. [Method] Based on NDVI data acquired by SPOT/VGT and meteorological data of five meteorological statio...[Objective] The aim was to explore response characters of NDVI of different types of vegetation to climate change. [Method] Based on NDVI data acquired by SPOT/VGT and meteorological data of five meteorological stations during 19982011, the change trend of NDVI and the relevant correlation with meteorological factors were analyzed in the research area. [Result] NDVI of different types of vegetation in Zhalong wetland kept increasing, especially after 2004. Of the vegetations, NDVI was of significant positive correlation with average temperature, average minimum temperature, average maximum temperature, rainfall and average relative humidity in a ten-day period （P 0.01）. In addition, NDVI responses are of different characters to meteorological factors. The responses of NDVI of vegetations were of lag phase to meteorological factors in Zhalong wetland. Specifically, the lag phase of ten-day average temperature and ten-day average minimum temperature was 10-20 d; the lag phase of ten-day average maximum temperature was 20 -30 d; the lag phase of ten-day rainfall was 20 d; the lag phase of ten-day averager relative humidity was 0-10 d. [Conclusion] The research provides references for further exploration of vegetations’ responses to climate change and formulation of vegetation protection and utilization under background of climate change.展开更多
An experimental study has been carried out investigatesystematically the effects of acoustic cavi- tation parameters andfluid subcooling on boiling of acetone around a horizontal circulartube. The experimental results...An experimental study has been carried out investigatesystematically the effects of acoustic cavi- tation parameters andfluid subcooling on boiling of acetone around a horizontal circulartube. The experimental results show that acoustic cavitation enhancedremarkably the boiling heat transfer and decreased the incipientboiling superheat and that cavitation bubbles effect on boiling heattransfer reduced with cavitation distance. For boiling curves in aform of h-q', elevated cavitation distance shift nucleate boilingcurves to the right of the cor- responding ordinary pool boilingcurve. The associated mechanism of heat transfer enhancement isanalyzed with the consideration of cavitation bubble influence onvapor embryo.展开更多
To study the relationship between under-urbanization and international trade, we set up a model of the transfer of surplus rural labor in an open economy using 1995-2010 data from 40 countries and regions where indust...To study the relationship between under-urbanization and international trade, we set up a model of the transfer of surplus rural labor in an open economy using 1995-2010 data from 40 countries and regions where industrialization was incomplete. Our findings indicate that if, in an open economy, there is a substantial labor surplus and in which domestic goods and services can be sold to foreign markets, there will be a significantly positive correlation between the net export ratio and the degree to which urbanization lags behind industrialization; countries or regions with higher marketization level, lower urban unemployment rate and poorer public health facilities are more likely to be under- urbanized; and an inverted U-shaped relationship exists between under-urbanization and percapita GDR展开更多
基金Projects(52174092,51904290)supported by the National Natural Science Foundation,ChinaProject(BK20220157)supported by the Natural Science Foundation of Jiangsu Province,China+1 种基金Project(232102321009)supported by Henan Province Science and Technology Key Project,ChinaProject(2022YCPY0202)supported by Fundamental Research Funds for the Central Universities,China。
文摘A comprehensive understanding of the dynamic frictional characteristics in rock joints under high normal load and strong confinement is essential for ensuring the safety of deep engineering construction and mitigating geological disasters.This study conducted shear experiments on rough rock joints under displacement-controlled dynamic normal loads,investigating the shear behaviors of joints across varying initial normal loads,normal loading frequencies,and normal loading amplitudes.Experimental results showed that the peak/valley shear force values increased with initial normal loads and normal loading frequencies but showed an initial increase followed by a decrease with normal loading amplitudes.Dynamic normal loading can either increase or decrease shear strength,while this study demonstrates that higher frequencies lead to enhanced friction.Increased initial normal loading and normal loading frequency result in a gradual decrease in joint roughness coefficient(JRC)values of joint surfaces after shearing.Positive correlations existed between frictional energy dissipation and peak shear forces,while post-shear joint surface roughness exhibited a negative correlation with peak shear forces through linear regression analysis.This study contributes to a better understanding of the sliding responses and shear mechanical characteristics of rock joints under dynamic disturbances.
基金supported by the National Natural Science Foundation of China (Nos. 31071938 and 31272328 to WL, 31101646 and 31260514 to CY)Program for New Century Excellent Talents in University (NCET-10-0111 to WL)Key Project of Chinese Ministry of Education (No. 212136 to CY)
文摘Polymorphism in egg coloration is prominent in the Common Cuckoo (Cuculus canorus) and a common host, the Ashy-throated Parrotbill (Paradoxornis alphonsianus). Egg polymorphism has probably evolved as a consequence of frequency-dependent selection in both host and parasite, and has, according to human vision, resulted in discrete immaculate white, pale blue and blue egg phenotypes within a single population. However, egg mimicry assessment is not always straightforward, and previous studies have shown that human based comparisons applied to the coloration of bird eggs may be inadequate. Here, we objectively quantify egg color of both parasite and host by spectrophotometry and assess egg mimicry of the Common Cuckoo to the eggs of its Ashy-throated Parrotbill host. Our results revealed that egg reflectance spectra agree well with the assessment based on human vision that cuckoo eggs mimic those of the parrotbill host, in both visible (VIS) and ultraviolet (UV) ranges. However, the white cuckoo egg shows slightly poorer mimicry than the blue cuckoo egg in corresponding host clutches. We suggest that the white parrotbill egg morph (and subsequently the whitish cuckoo egg color) may have evolved after the evolution of the blue egg morph due to strong selection from parasites in the cuckoo-parrotbill system.
基金Supported by the Special Fund for Meteorological-Scientific Research in the Public Interest (GYHY201306036)Heilongjiang Science Technology Department Key Program (GZ09C102)~~
文摘[Objective] The aim was to explore response characters of NDVI of different types of vegetation to climate change. [Method] Based on NDVI data acquired by SPOT/VGT and meteorological data of five meteorological stations during 19982011, the change trend of NDVI and the relevant correlation with meteorological factors were analyzed in the research area. [Result] NDVI of different types of vegetation in Zhalong wetland kept increasing, especially after 2004. Of the vegetations, NDVI was of significant positive correlation with average temperature, average minimum temperature, average maximum temperature, rainfall and average relative humidity in a ten-day period （P 0.01）. In addition, NDVI responses are of different characters to meteorological factors. The responses of NDVI of vegetations were of lag phase to meteorological factors in Zhalong wetland. Specifically, the lag phase of ten-day average temperature and ten-day average minimum temperature was 10-20 d; the lag phase of ten-day average maximum temperature was 20 -30 d; the lag phase of ten-day rainfall was 20 d; the lag phase of ten-day averager relative humidity was 0-10 d. [Conclusion] The research provides references for further exploration of vegetations’ responses to climate change and formulation of vegetation protection and utilization under background of climate change.
基金Supported bv the National Key Basic Research Science Foundation of China (G2000026305).
文摘An experimental study has been carried out investigatesystematically the effects of acoustic cavi- tation parameters andfluid subcooling on boiling of acetone around a horizontal circulartube. The experimental results show that acoustic cavitation enhancedremarkably the boiling heat transfer and decreased the incipientboiling superheat and that cavitation bubbles effect on boiling heattransfer reduced with cavitation distance. For boiling curves in aform of h-q', elevated cavitation distance shift nucleate boilingcurves to the right of the cor- responding ordinary pool boilingcurve. The associated mechanism of heat transfer enhancement isanalyzed with the consideration of cavitation bubble influence onvapor embryo.
基金a research product of the CASS Innovation Project "Urbanization,Structural Effects and China's Economic Growth Model"
文摘To study the relationship between under-urbanization and international trade, we set up a model of the transfer of surplus rural labor in an open economy using 1995-2010 data from 40 countries and regions where industrialization was incomplete. Our findings indicate that if, in an open economy, there is a substantial labor surplus and in which domestic goods and services can be sold to foreign markets, there will be a significantly positive correlation between the net export ratio and the degree to which urbanization lags behind industrialization; countries or regions with higher marketization level, lower urban unemployment rate and poorer public health facilities are more likely to be under- urbanized; and an inverted U-shaped relationship exists between under-urbanization and percapita GDR
