This paper is concerned with the Cauchy problem for a 3D fluid-particle interaction model in the so-called flowing regime inℝ3.Under the smallness assumption on both the external potential and the initial perturbation...This paper is concerned with the Cauchy problem for a 3D fluid-particle interaction model in the so-called flowing regime inℝ3.Under the smallness assumption on both the external potential and the initial perturbation of the stationary solution in some Sobolev spaces,the existence and uniqueness of global smooth solutions in H3 of the system are established by using the careful energy method.展开更多
In this article, the names of 3 varieties of Monarda didyma L., which are considered to be introduced species, some indicators of the water regime in the climatic conditions of Uzbekistan: the amount of water in the l...In this article, the names of 3 varieties of Monarda didyma L., which are considered to be introduced species, some indicators of the water regime in the climatic conditions of Uzbekistan: the amount of water in the leaves, water deficit, water storage capacity were studied in spring and summer, and seasonal changes were determined. According to these indicators of the water regime, the studied varieties belong to the labile water regime, high green mass (centner), seed yield (how many grams), resistance to diseases and pests have been determined, which shows that it is promising for introduction in the conditions of our republic. Therefore, it is recommended to breed these varieties in the foothills and hilly regions of Uzbekistan, where the amount of precipitation is more than 400 - 500 mm.展开更多
This study investigates the influence of different curing regimes on the microstructure and macro properties of ultra-high performance fiber reinforced cementitious composite (UHPFRCC), and aims to discover whether ...This study investigates the influence of different curing regimes on the microstructure and macro properties of ultra-high performance fiber reinforced cementitious composite (UHPFRCC), and aims to discover whether it is possible to produce qualified UHPFRCC using different curing regimes. A control mix of UHPFRCC is prepared. The mechanical performance and the short-term durability of the UHPFRCC matrix under three curing regimes are studied. In addition, the microstructures of the UHPFRCC matrix with different curing conditions are analyzed by combining scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP). The results explore how different UHPFRCC curing regimes affect its microstructure and how the microstructure affects its macro behavior. Heat and steam curing for 3 d is succeeded to produce the UHPFRCC with nearly the same mechanical properties and durability as those of the 90 d standard curing. However, the heat cured UHPFRCC does not show great resistance to chloride-ion penetration.展开更多
A synthesis is given in this paper on late Mesozoic deformation pattern in the zones around the Ordos Basin based on lithostratigraphic and structural analyses. A relative chronology of the late Mesozoic tectonic stre...A synthesis is given in this paper on late Mesozoic deformation pattern in the zones around the Ordos Basin based on lithostratigraphic and structural analyses. A relative chronology of the late Mesozoic tectonic stress evolution was established from the field analyses of fault kinematics and constrained by stratigraphic contact relationships. The results show alternation of tectonic compressional and extensional regimes. The Ordos Basin and its surroundings were in weak N-S to NNE-SSW extension during the Early to Middle Jurassic, which reactivated E-W-trending basement fractures. The tectonic regime changed to a multi-directional compressional one during the Late Jurassic, which resulted in crustal shortening deformation along the marginal zones of the Ordos Basin. Then it changed to an extensional one during the Early Cretaceous, which rifted the western, northwestern and southeastern margins of the Ordos Basin. A NW-SE compression occurred during the Late Cretaceous and caused the termination of sedimentation and uplift of the Ordos Basin. This phased evolution of the late Mesozoic tectonic stress regimes and associated deformation pattern around the Ordos Basin best records the changes in regional geodynamic settings in East Asia, from the Early to Middle Jurassic post-orogenic extension following the Triassic collision between the North and South China Blocks, to the Late Jurassic multi-directional compressions produced by synchronous convergence of the three plates (the Siberian Plate to the north, Paleo-Pacific Plate to the east and Lhasa Block to the west) towards the East Asian continent. Early Cretaceous extension might be the response to collapse and lithospheric thinning of the North China Craton.展开更多
The Miami Isopycnal Coordinate Ocean Model (MICOM) is adopted to simulate the intevdecadal variability in the Pacific Ocean with most emphasis on regime shifts in the North Pacific. The computational domain covers 60&...The Miami Isopycnal Coordinate Ocean Model (MICOM) is adopted to simulate the intevdecadal variability in the Pacific Ocean with most emphasis on regime shifts in the North Pacific. The computational domain covers 60°N to 40°S with an enclosed boundary condition for momentum flux, whereas there are thermohalirie fluxes across the southern end as a restoring term. In addition, sea surface salinity of the model relaxes to the climatological season cycle, which results in climatological fresh water fluxes. Surface forcing functions from January 1945 through December 1998 are derived from the Comprehensive Ocean and Atmospheric Data Set (COADS). Such a numerical experiment reproduces the observed evolution of the interdecadal variability in the heat content over the upper 400-m layer by a two-year lag. Subduction that occurs at the ventilated thermocline in the central North Pacific is also been simulated and the subducted signals propagate from 35°N to 25°N, taking about 8 to 10 years, in agreement with the expendable Bathy Thermograph observation over recent decades. Interdecadal signals take a southwest-ward and downward path rather than westward propagation, meaning they are less associated with the baroclinic planetary waves. During travel, the signals appear to conserve potential vorticity. Therefore, the ventilated thermocline and related subduction are probably the fundamental physics for interdecadal variability in the mid-latitude subtropics of the North Pacific.展开更多
The cumulative effect of cascade hydropower stations on river ecological environment has been widely concerned because of the significant streamflow hydrology change induced by dam constructions. The characteristics o...The cumulative effect of cascade hydropower stations on river ecological environment has been widely concerned because of the significant streamflow hydrology change induced by dam constructions. The characteristics of the change in the lower reaches of the Jinsha River, China are analyzed based on long-term(1952–2015) hydrological and sedimentological data. The averaging coefficient, reservoir regulation coefficient(RRC), incoming sediment coefficient(ISC), and sediment transport modulus(STM), which reflect the variation of streamflow and sediment regimes, are defined and calculated. The results show that the construction and regulation of reservoirs reduces flow in flood season, increases flow in dry season, significantly altering the monthly discharge regimes. These alterations also led directly to changes in the timing of extreme flows at Pingshan Station. The monthly flow records at the basin outlet are reconstructed using stepwise regression, to reduce reservoir impacts. Comparisons of observed and reconstructed monthly flows demonstrate that the previous studies overestimated the cumulative effects of cascade reservoirs on flow processes. Furthermore, this study clearly illustrates that the reduction in sediment trapping and sediment transportation capacity together lead to the sharp reduction in annual sediment yield at the Pingshan Station. The earlier constructed reservoirs have more obvious effects on the ISC and STM than the more recent reservoirs and the effect of sediment trapping is related to reservoir location, on the main stream versus tributaries.展开更多
Changes in the Indonesian Throughflow (ITF) and the South China Sea throughflow-measured by the Luzon Strait Transport (LST)-associated with the 1976/77 regime shift are analyzed using the Island Rule theory and t...Changes in the Indonesian Throughflow (ITF) and the South China Sea throughflow-measured by the Luzon Strait Transport (LST)-associated with the 1976/77 regime shift are analyzed using the Island Rule theory and the Simple Ocean Data Assimilation dataset. Results show that LST increased but ITF transport decreased after 1975. Such changes were induced by variations in wind stress associated with the regime shift. The strengthening of the easterly wind anomaly east of the Luzon Strait played an important role in the increase of LST after 1975, while the westerly wind anomaly in the equatorial Pacific contributed significantly to the decrease in ITF transport after 1975; accounting for 53% of the change. After 1975, the Kuroshio Current strengthened and the Mindanao Current weakened in response to a decrease in the total transport of the North Equatorial Current. Both the North Equatorial Countercurrent and the South Equatorial Current weakened after 1975, and an anomalous cyclonic circulation in the western equatorial Pacific prevented the tropical Pacific water from entering the Indian Ocean directly.展开更多
By extracting and comparing long-term trend components of coral gray value, sea surface temperature, cloudiness, and net heat flux for the period of 1946-1992, the relationships among them are addressed. There exists ...By extracting and comparing long-term trend components of coral gray value, sea surface temperature, cloudiness, and net heat flux for the period of 1946-1992, the relationships among them are addressed. There exists a prominent regime shift in the cloudiness associated with the corresponding variabilities of sea surface temperature and net heat flux occurred in the mid-1960s, which can be successfully recorded by coral gray value, a climatic proxy. Long-term cloudiness variations in the South China Sea are completely opposite to the equatorial western Pacific in the past five decades, whereas they share a similar trend to that over Asian monsoon prevailing waters. The fact that the coral gray value is highly correlated to cloudiness provides a unique perspective on utilizing this coral to study cloudiness variations in the pre-instrumental period.展开更多
Yardangs are typical aeolian erosion landforms,which are attracting more and more attention of geomorphologists and geologists for their various morphology and enigmatic formation mechanisms.In order to clarify the ae...Yardangs are typical aeolian erosion landforms,which are attracting more and more attention of geomorphologists and geologists for their various morphology and enigmatic formation mechanisms.In order to clarify the aeolian environments that influence the development of long-ridge yardangs in the northwestern Qaidam Basin of China,the present research investigated the winds by installing wind observation tower in the field.We found that the sand-driving winds mainly blow from the north-northwest,northwest and north,and occur the most frequent in summer,because the high temperature increases atmospheric instability and leads to downward momentum transfer and active local convection during these months.The annual drift potential and the ratio of resultant drift potential indicate that the study area pertains to a high-energy wind environment and a narrow unimodal wind regime.The wind energy decreases from northwest to southeast in the Qaidam Basin,with the northerly winds in the northwestern basin changing to more westerly in the southeastern basin.The strong and unidirectional wind regime for the long-ridge yardangs in the northwestern Qaidam Basin results from the combined effects of topographic obstacles such as the Altun Mountains and of the interaction between the air stream and the yardang bodies.Present study suggests that yardang evolution needs such strong and unidirectional winds in high-or intermediate-energy wind environments.This differs from sandy deserts or sandy lands,which usually develop at low-or intermediate-energy wind environments.Present study clarifies the wind regime corresponding to the long-ridge yardangs'development,and lays firm foundation to put forward the formation mechanisms for yardangs in the Qaidam Basin.展开更多
Peak discharge plays an important role in triggering channelized debris flows.The rainfall regimes and rainfall characteristics have been demonstrated to have important influences on peak discharge.In order to explore...Peak discharge plays an important role in triggering channelized debris flows.The rainfall regimes and rainfall characteristics have been demonstrated to have important influences on peak discharge.In order to explore the relationship between rainfall regimes and peak discharge,a measuring system was placed at the outlet of a small,debris flow-prone catchment.The facility consisted of an approximately rectangular stilling basin,ending with a sharp-crested weir.Six runoff events were recorded which provided a unique opportunity for characterizing the hydrological response of the debris flow-prone catchment.Then,a rainfall–runoff model was tested against the flow discharge measurements to have a deep understanding of hydrological response.Based on the calibrated rainfall-runoff model,twelve different artificially set rainfall patterns were regarded as the input parameters to investigate the effect of rainfall regimes on peak discharge.The results show that the rainfall patterns have a significant effect on peak discharge.The rainfall regimes which have higher peak rainfall intensity and peak rainfall point occur at the later part of rainfall process are easy to generate larger peak discharge in the condition of the same cumulative rainfall and duration.Then,in order to explore the relationship between rainfall characteristics and peak discharge under different cumulative precipitation and different duration,167 measured rainfall events were also collected.On the basis of rainfall depth,rainfall duration,and maximum hourly intensity,all the rainfall events were classified into four categories by using K-mean clustering.Rainfall regime 1 was composed of rainfall events with a moderate mean P(precipitation),a moderate D(duration),and a moderate I60(maximum hourly intensity).Rainfall regime 2 was the group of rainfall events with a high mean P,long D.Rainfall regime 3,however,had a low P and a long D.The characteristic of Rainfall regime 4 was high I60 and short duration with large P.The results show that the rainfall regime 2 and 4 are easier to generate peak discharge as the rainfall intensity plays an important role in generating peak discharge.The results in this study have implications for improving peak discharge prediction accuracy in debris flow gully.展开更多
Using a combination of stable isotope(15N) and radionuclide(226Ra) analyses, we examine possible controls on the interactions between melting ice and the uptake of nitrogen in the Prydz Bay during the 2006 austral sum...Using a combination of stable isotope(15N) and radionuclide(226Ra) analyses, we examine possible controls on the interactions between melting ice and the uptake of nitrogen in the Prydz Bay during the 2006 austral summer.We find that specific rates of uptake for nitrate and ammonium correlate positively to their concentrations, thus suggesting a substrate effect. In the study area, we observe that regions along open, oceanic water have high fratios(nitrate uptake/nitrate+ammonium uptake), while areas near the Amery Ice Shelf have significantly low fratios. Further analysis reveals a negative correlation between the f-ratio and the melt water fraction, thus implying that the melting of ice plays an essential role in regulating pelagic N dynamics in the Southern Ocean(SO). Stratification, produced by melting ice, should profoundly affect the efficiency of the SO’s biological pump and consequently affect the concentration of CO2 in the atmosphere. Results presented in this study add information to an already significant base of understanding of the controls on pelagic C and N dynamics in the SO. This provides unique insights for either interpreting past changes in geologic records or for predicting future climate change trends.展开更多
Since the mid-late Eocene, North China has been subjected to extensional stress, resulting in the formation and development of basins. The dynamic origin of this crustal extension has long been an issue of debate. Thi...Since the mid-late Eocene, North China has been subjected to extensional stress, resulting in the formation and development of basins. The dynamic origin of this crustal extension has long been an issue of debate. This paper presents the results of kinematic analyses of faults obtained from two seperated areas in North China. In the Weihe graben situated on the southernmost margin of the Ordos block, analyses of fault kinematics were coupled with an analysis of the basin's subsidence history. Three successive extensional tectonic phases accompaning the basin's formation and development have been distinguished. The Palaeogene extension was oriented in a WNW-ESE direction; the Neogene extension in a NE-SW direction and the Pliocene-Quaternary extension in a NW-SE direction. Such changes have also been recorded by fault kinematics along the southern Tanlu fault zone. This has been demonstrated by three successive sets of fault striations indicating normal dip slip resulting from NW-SE extension, then left-lateral slip with a normal component resulting from NE-SW extension, and right-lateral slip with a minor normal component, respectively. The kinematic history of faults and their chronological evolution indicate changes in continental dynamics acting in North China over Cenozoic time.展开更多
Temperature and water flow through a culvert beneath the Alaska Highway near Beaver Creek,Yukon,were measured at hourly intervals between June and October 2013.These data were used to simulate the effect of the culver...Temperature and water flow through a culvert beneath the Alaska Highway near Beaver Creek,Yukon,were measured at hourly intervals between June and October 2013.These data were used to simulate the effect of the culvert on the thermal regime of the road embankment and subjacent permafrost.A 2-D thermal model of the embankment and permafrost was developed with TEMP/W and calibrated using field observations.Empirical relations were obtained between water temperatures at the entrance to the culvert,flow into the culvert,and water temperatures inside the structure.Water temperatures at the entrance and inside the culvert had a linear relation,while water temperatures inside the culvert and water flow were associated by a logarithmic relation.A multiple linear regression was used to summarize these relations.From this relationship,changes in the flow rate and water temperatures at the entrance of the culvert were simulated to obtain predicted water temperatures in the culvert.The temperatures in the culvert were used in the thermal model to determine their effects on the ground thermal regime near the culvert.Variation of ±10% in water flow rate had no impact on the thermal regime underneath the culvert.Variation of water temperature at the entrance of the culvert had a noticeable influence on the thermal regime.A final simulation was conducted without insulation beneath the culvert.The thaw depth was 30 cm with insulation,and 120 cm without insulation,illustrating the importance of insulation to the ground thermal regime.展开更多
The pre-sliding regime is typically neglected in the dynamic modelling of mechanical systems. However, the change in contact state caused by static friction may decrease positional accuracy and control precision. To i...The pre-sliding regime is typically neglected in the dynamic modelling of mechanical systems. However, the change in contact state caused by static friction may decrease positional accuracy and control precision. To investigate the relationship between contact status and contact force in pre-sliding friction, an optical experimental method is presented in this paper.With this method, the real contact state at the interface of a transparent material can be observed based on the total reflection principle of light by using an image processing technique. A novel setup, which includes a pair of rectangular trapezoidal blocks, is proposed to solve the challenging issue of accurately applying different tangential and normal forces to the contact interface. The improved Otsu's method is used for measurement. Through an experimental study performed on polymethyl methacrylate(PMMA), the quantity of contact asperities is proven to be the dominant factor that affects the real contact area. The relationship between the real contact area and the contact force in the pre-sliding regime is studied, and the distribution of static friction at the contact interface is qualitatively discussed. New phenomena in which the real contact area expands along with increasing static friction are identified. The aforementioned relationship is approximately linear at the contact interface under a constant normal pressure, and the distribution of friction stress decreases from the leading edge to the trailing edge.展开更多
In this paper, ocean-atmosphere coupled regimes are identified on the basis of SVD analysis, cluster analysis and composite analysis. The coupled regimes in cold seasons are identified as the clusters of the ocean-atm...In this paper, ocean-atmosphere coupled regimes are identified on the basis of SVD analysis, cluster analysis and composite analysis. The coupled regimes in cold seasons are identified as the clusters of the ocean-atmosphere coupled states in a low dimensional phase space spanned by the first four SVD modes. Three coupled regimes are found. The first two coupled regimes reflect the ENSO episodes and the accompanying PNA patterns. The third regime, i.e., EAWM regime, is characterized by the strong EAWM activity and the specific SST anomaly. The composite analysis gives further evidences to the identification of EAWM regime and also demonstrates the dynamical process of its formation. The anomaly pattern of the tropical Pacific SSTA in the strong EAWM year differs significantly from that of the La Nina year.展开更多
The thermal regimes in sedimentary basins in the continental area of China are varied and reflect differences in geological settings. As a result of these variable thermal regimes, the history of hydrocarbon generatio...The thermal regimes in sedimentary basins in the continental area of China are varied and reflect differences in geological settings. As a result of these variable thermal regimes, the history of hydrocarbon generation in each basin is also different. An east-west profile of the thermal threshold across the continental basins of China, like the Liaohe Basin, the North China Basin, the Ordos Basin, the Qaidam Basin and the Tarim Basin, was constructed using large numbers of heat flow measurements, temperature data and rock thermophysical parameters. Isotherms, surface heat flow, mantle heat flow and Moho temperature beneath the basins are shown in the profile, which illustrates changes in some thermal characteristics between basins in east China and those in west China. Thermal evolution histories in basins were reconstructed using Easy%Ro method, apatite fission track annealing and other paleothermometers. Typical hydrocarbon generation histories of the primary source rocks were modeled by referring to the thermal evolution data. Thermal stages controlled source rocks maturation and oil and gas generation, and influenced the type of hydrocarbon (oil and gas) production in the basins.展开更多
Stress state of microalgal cells is caused under unfavorable conditions such as disordered light regime and depleted nitrogen. The stress state can impair photosynthetic efficiency, inhibit cell growth and result in t...Stress state of microalgal cells is caused under unfavorable conditions such as disordered light regime and depleted nitrogen. The stress state can impair photosynthetic efficiency, inhibit cell growth and result in the accumulation of triacylglycerol(TAG) from protective mechanisms. Continuous light or nitrogen starvation was applied on microalgae and performed effectively on inducing TAG production. To evaluate the light regime effect on inducing TAG production, the effect of different light regimes on nitrogen-starved Isochrysis zhangjiangensis was investigated in this work. The continuous light and nitrogen starvation elevated TAG content of biomass by 73% and 193%, respectively. Furthermore, the TAG accumulation of I. zhangjiangensis cell under nitrogen starvation decreased under aggravated stress from continuous illumination. Our results demonstrated that culturing the cells with 14 L: 10 D light regime under nitrogen starvation is the optimal mode to achieve maximal accumulation of TAG. A recovery in light regime was necessary for I. zhangjiangensis cultivation.展开更多
Although many studies relevant to snow cover and permafrost have focused on alpine, arctic, and subarctic areas, there is still a lack of understanding of the influences of seasonal snow cover on the thermal regime of...Although many studies relevant to snow cover and permafrost have focused on alpine, arctic, and subarctic areas, there is still a lack of understanding of the influences of seasonal snow cover on the thermal regime of the soils in permafrost regions in the mid-latitudes and boreal regions, such as that on the westem flank of the Da Xing'anling (Hinggan) Mountains, northeastern China. This paper gives a detailed analysis on meteorological data series from 2001 to 2010 provided by the Gen'he Weather Station, which is located in a talik of discontinuous permafrost zone and with sparse meadow on the observation field. It is inferred that snow cover is important for the ground thermal regime in the middle Da Xing'anling Mountains. Snow cover of 10-cm in thickness and five to six months in duration (generally November to next March) can reduce the heat loss from the ground to the atmosphere by 28%, and by 71% if the snow depth increases to 36 cm. Moreover, the occurrence of snow cover resulted in mean annual ground surface temperatures 4.7-8.2℃ higher than the mean annual air temperatures recorded at the Gen'he Weather Station, The beginning date for stable snow cover establishment (SE date) and the initial snow depth (SDi) also had a great influences on the ground freezing process. Heavy snowfall before ground surface freeze-up could postpone and retard the freezing process in Gen'he. As a result, the duration of ground freezing was shortened by at least 20 days and the maximum depth of frost penetration was as much as 90 cm shallower.展开更多
A Kerr-lens mode-locked Ti:sapphire laser operating in a non-soliton regime is demonstrated. Dispersive wave generation is observed as a result of third order dispersion in the vicinity of zero dispersion. The charac...A Kerr-lens mode-locked Ti:sapphire laser operating in a non-soliton regime is demonstrated. Dispersive wave generation is observed as a result of third order dispersion in the vicinity of zero dispersion. The characteristics of the Ti:sapphire l^ser operating in a positive dispersion regime are presented, where the oscillator directly generates pulses with duration continuously tunable from 0.37 ps to 2.11 ps, and 36 fs pulses are achieved atter extracavity compression. The oscillation is numerically simulated with an extended nonlinear Schr6dinger equation, and the simulation results are in good agreement with the experimental results.展开更多
This article focuses on two issues. The first concerns definitions of the Northern Sea Route (NSR) in old and new Russian legislation, and the second relates to Russian rules on icebreaker guiding. Based on a compre...This article focuses on two issues. The first concerns definitions of the Northern Sea Route (NSR) in old and new Russian legislation, and the second relates to Russian rules on icebreaker guiding. Based on a comprehensive comparative analysis of relevant Russian legal provisions enacted in 2013 and previous laws in this area, we offer the following conclusions. (1) Our legal analysis indicates that Russia's view of the NSR as a historical national transportation route has not changed. However, the new law redefines the scope and coverage of the NSR, which now comprises the internal waters, territorial sea, adjacent zone, and the exclusive economic zone of the Russian Federation. In fact, the new law resolves previous ambiguity regarding extension of the NSR boundary to the high seas. (2) Based on an analysis of the new rules on icebreaker guiding, the article concludes that NSR is transitioning from a mandatory icebreaker guiding regime into a permit regime. This is particularly evident in its provision of a concrete, practical, and predictable clause on permissible or impermissible conditions relating to independent navigation. According to the new rules, it is possible for foreign ships to undertake independent navigation in the NSR. The Russian NSR policy, therefore, appears to have changed significantly, and has future potential for opening the NSR up to the international community.展开更多
文摘This paper is concerned with the Cauchy problem for a 3D fluid-particle interaction model in the so-called flowing regime inℝ3.Under the smallness assumption on both the external potential and the initial perturbation of the stationary solution in some Sobolev spaces,the existence and uniqueness of global smooth solutions in H3 of the system are established by using the careful energy method.
文摘In this article, the names of 3 varieties of Monarda didyma L., which are considered to be introduced species, some indicators of the water regime in the climatic conditions of Uzbekistan: the amount of water in the leaves, water deficit, water storage capacity were studied in spring and summer, and seasonal changes were determined. According to these indicators of the water regime, the studied varieties belong to the labile water regime, high green mass (centner), seed yield (how many grams), resistance to diseases and pests have been determined, which shows that it is promising for introduction in the conditions of our republic. Therefore, it is recommended to breed these varieties in the foothills and hilly regions of Uzbekistan, where the amount of precipitation is more than 400 - 500 mm.
基金The Scholarship Supported by the China Scholarship Councilthe Technical Research Program from NV Bekaert SA of Belgiumthe National Natural Science Foundation of China(No.50908047)
文摘This study investigates the influence of different curing regimes on the microstructure and macro properties of ultra-high performance fiber reinforced cementitious composite (UHPFRCC), and aims to discover whether it is possible to produce qualified UHPFRCC using different curing regimes. A control mix of UHPFRCC is prepared. The mechanical performance and the short-term durability of the UHPFRCC matrix under three curing regimes are studied. In addition, the microstructures of the UHPFRCC matrix with different curing conditions are analyzed by combining scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP). The results explore how different UHPFRCC curing regimes affect its microstructure and how the microstructure affects its macro behavior. Heat and steam curing for 3 d is succeeded to produce the UHPFRCC with nearly the same mechanical properties and durability as those of the 90 d standard curing. However, the heat cured UHPFRCC does not show great resistance to chloride-ion penetration.
基金funded by Sino-Probe 08-01the National Natural Science Foundation of China(grant No40572120)
文摘A synthesis is given in this paper on late Mesozoic deformation pattern in the zones around the Ordos Basin based on lithostratigraphic and structural analyses. A relative chronology of the late Mesozoic tectonic stress evolution was established from the field analyses of fault kinematics and constrained by stratigraphic contact relationships. The results show alternation of tectonic compressional and extensional regimes. The Ordos Basin and its surroundings were in weak N-S to NNE-SSW extension during the Early to Middle Jurassic, which reactivated E-W-trending basement fractures. The tectonic regime changed to a multi-directional compressional one during the Late Jurassic, which resulted in crustal shortening deformation along the marginal zones of the Ordos Basin. Then it changed to an extensional one during the Early Cretaceous, which rifted the western, northwestern and southeastern margins of the Ordos Basin. A NW-SE compression occurred during the Late Cretaceous and caused the termination of sedimentation and uplift of the Ordos Basin. This phased evolution of the late Mesozoic tectonic stress regimes and associated deformation pattern around the Ordos Basin best records the changes in regional geodynamic settings in East Asia, from the Early to Middle Jurassic post-orogenic extension following the Triassic collision between the North and South China Blocks, to the Late Jurassic multi-directional compressions produced by synchronous convergence of the three plates (the Siberian Plate to the north, Paleo-Pacific Plate to the east and Lhasa Block to the west) towards the East Asian continent. Early Cretaceous extension might be the response to collapse and lithospheric thinning of the North China Craton.
基金supported by the IARC-Frontier Research System for Global Changethe National Natural Science Foundation of China(40136010)the Chinese Academy of Sciences(KZCX2-205 and KZCX2-203).
文摘The Miami Isopycnal Coordinate Ocean Model (MICOM) is adopted to simulate the intevdecadal variability in the Pacific Ocean with most emphasis on regime shifts in the North Pacific. The computational domain covers 60°N to 40°S with an enclosed boundary condition for momentum flux, whereas there are thermohalirie fluxes across the southern end as a restoring term. In addition, sea surface salinity of the model relaxes to the climatological season cycle, which results in climatological fresh water fluxes. Surface forcing functions from January 1945 through December 1998 are derived from the Comprehensive Ocean and Atmospheric Data Set (COADS). Such a numerical experiment reproduces the observed evolution of the interdecadal variability in the heat content over the upper 400-m layer by a two-year lag. Subduction that occurs at the ventilated thermocline in the central North Pacific is also been simulated and the subducted signals propagate from 35°N to 25°N, taking about 8 to 10 years, in agreement with the expendable Bathy Thermograph observation over recent decades. Interdecadal signals take a southwest-ward and downward path rather than westward propagation, meaning they are less associated with the baroclinic planetary waves. During travel, the signals appear to conserve potential vorticity. Therefore, the ventilated thermocline and related subduction are probably the fundamental physics for interdecadal variability in the mid-latitude subtropics of the North Pacific.
基金financially supported by the National 973 Program of China (2015CB452701)the National Natural Science Foundation of China (Grant No. 51579161)
文摘The cumulative effect of cascade hydropower stations on river ecological environment has been widely concerned because of the significant streamflow hydrology change induced by dam constructions. The characteristics of the change in the lower reaches of the Jinsha River, China are analyzed based on long-term(1952–2015) hydrological and sedimentological data. The averaging coefficient, reservoir regulation coefficient(RRC), incoming sediment coefficient(ISC), and sediment transport modulus(STM), which reflect the variation of streamflow and sediment regimes, are defined and calculated. The results show that the construction and regulation of reservoirs reduces flow in flood season, increases flow in dry season, significantly altering the monthly discharge regimes. These alterations also led directly to changes in the timing of extreme flows at Pingshan Station. The monthly flow records at the basin outlet are reconstructed using stepwise regression, to reduce reservoir impacts. Comparisons of observed and reconstructed monthly flows demonstrate that the previous studies overestimated the cumulative effects of cascade reservoirs on flow processes. Furthermore, this study clearly illustrates that the reduction in sediment trapping and sediment transportation capacity together lead to the sharp reduction in annual sediment yield at the Pingshan Station. The earlier constructed reservoirs have more obvious effects on the ISC and STM than the more recent reservoirs and the effect of sediment trapping is related to reservoir location, on the main stream versus tributaries.
基金supported by the Chinese Academy of Sciences' Knowledge Innovation Program (Grant Nos.KZCX2-YW-214 and KZCX2-YW-BR-04)the National Natural Science Foundation of China (Grant Nos.40806005,40640420557 and 40625017)supported by a grant from the City University of Hong Kong (Project No. 7002329)
文摘Changes in the Indonesian Throughflow (ITF) and the South China Sea throughflow-measured by the Luzon Strait Transport (LST)-associated with the 1976/77 regime shift are analyzed using the Island Rule theory and the Simple Ocean Data Assimilation dataset. Results show that LST increased but ITF transport decreased after 1975. Such changes were induced by variations in wind stress associated with the regime shift. The strengthening of the easterly wind anomaly east of the Luzon Strait played an important role in the increase of LST after 1975, while the westerly wind anomaly in the equatorial Pacific contributed significantly to the decrease in ITF transport after 1975; accounting for 53% of the change. After 1975, the Kuroshio Current strengthened and the Mindanao Current weakened in response to a decrease in the total transport of the North Equatorial Current. Both the North Equatorial Countercurrent and the South Equatorial Current weakened after 1975, and an anomalous cyclonic circulation in the western equatorial Pacific prevented the tropical Pacific water from entering the Indian Ocean directly.
基金This research was supported by the National Natural Science Foundation of China under contract Nos 40136010 and 40305009the Guangdong Science Foundation under contract No.04001308.The authors thank the anonymous reviewers for their comments and suggestions.
文摘By extracting and comparing long-term trend components of coral gray value, sea surface temperature, cloudiness, and net heat flux for the period of 1946-1992, the relationships among them are addressed. There exists a prominent regime shift in the cloudiness associated with the corresponding variabilities of sea surface temperature and net heat flux occurred in the mid-1960s, which can be successfully recorded by coral gray value, a climatic proxy. Long-term cloudiness variations in the South China Sea are completely opposite to the equatorial western Pacific in the past five decades, whereas they share a similar trend to that over Asian monsoon prevailing waters. The fact that the coral gray value is highly correlated to cloudiness provides a unique perspective on utilizing this coral to study cloudiness variations in the pre-instrumental period.
基金supported by the National Natural Science Foundation of China (41601005)the Key Laboratory of Education Ministry on Environment and Resources in Tibetan Plateau (2018-QHS-K08)
文摘Yardangs are typical aeolian erosion landforms,which are attracting more and more attention of geomorphologists and geologists for their various morphology and enigmatic formation mechanisms.In order to clarify the aeolian environments that influence the development of long-ridge yardangs in the northwestern Qaidam Basin of China,the present research investigated the winds by installing wind observation tower in the field.We found that the sand-driving winds mainly blow from the north-northwest,northwest and north,and occur the most frequent in summer,because the high temperature increases atmospheric instability and leads to downward momentum transfer and active local convection during these months.The annual drift potential and the ratio of resultant drift potential indicate that the study area pertains to a high-energy wind environment and a narrow unimodal wind regime.The wind energy decreases from northwest to southeast in the Qaidam Basin,with the northerly winds in the northwestern basin changing to more westerly in the southeastern basin.The strong and unidirectional wind regime for the long-ridge yardangs in the northwestern Qaidam Basin results from the combined effects of topographic obstacles such as the Altun Mountains and of the interaction between the air stream and the yardang bodies.Present study suggests that yardang evolution needs such strong and unidirectional winds in high-or intermediate-energy wind environments.This differs from sandy deserts or sandy lands,which usually develop at low-or intermediate-energy wind environments.Present study clarifies the wind regime corresponding to the long-ridge yardangs'development,and lays firm foundation to put forward the formation mechanisms for yardangs in the Qaidam Basin.
基金financially supported by the National Natural Science Foundation of China (Grant No. 41772276)Key R&D project of Zhejiang Province (Grant No. 2017C03006)China Postdoctoral Science Foundation (Grant No. 2019M652083)
文摘Peak discharge plays an important role in triggering channelized debris flows.The rainfall regimes and rainfall characteristics have been demonstrated to have important influences on peak discharge.In order to explore the relationship between rainfall regimes and peak discharge,a measuring system was placed at the outlet of a small,debris flow-prone catchment.The facility consisted of an approximately rectangular stilling basin,ending with a sharp-crested weir.Six runoff events were recorded which provided a unique opportunity for characterizing the hydrological response of the debris flow-prone catchment.Then,a rainfall–runoff model was tested against the flow discharge measurements to have a deep understanding of hydrological response.Based on the calibrated rainfall-runoff model,twelve different artificially set rainfall patterns were regarded as the input parameters to investigate the effect of rainfall regimes on peak discharge.The results show that the rainfall patterns have a significant effect on peak discharge.The rainfall regimes which have higher peak rainfall intensity and peak rainfall point occur at the later part of rainfall process are easy to generate larger peak discharge in the condition of the same cumulative rainfall and duration.Then,in order to explore the relationship between rainfall characteristics and peak discharge under different cumulative precipitation and different duration,167 measured rainfall events were also collected.On the basis of rainfall depth,rainfall duration,and maximum hourly intensity,all the rainfall events were classified into four categories by using K-mean clustering.Rainfall regime 1 was composed of rainfall events with a moderate mean P(precipitation),a moderate D(duration),and a moderate I60(maximum hourly intensity).Rainfall regime 2 was the group of rainfall events with a high mean P,long D.Rainfall regime 3,however,had a low P and a long D.The characteristic of Rainfall regime 4 was high I60 and short duration with large P.The results show that the rainfall regime 2 and 4 are easier to generate peak discharge as the rainfall intensity plays an important role in generating peak discharge.The results in this study have implications for improving peak discharge prediction accuracy in debris flow gully.
基金The National Natural Science Foundation of China under contract No.41676174the Foundation for Innovative Research Groups of the National Natural Science Foundation of China under contract No.41721005the Science and Technology Basic Resources Investigation Program of China under contract No.2017FY201403
文摘Using a combination of stable isotope(15N) and radionuclide(226Ra) analyses, we examine possible controls on the interactions between melting ice and the uptake of nitrogen in the Prydz Bay during the 2006 austral summer.We find that specific rates of uptake for nitrate and ammonium correlate positively to their concentrations, thus suggesting a substrate effect. In the study area, we observe that regions along open, oceanic water have high fratios(nitrate uptake/nitrate+ammonium uptake), while areas near the Amery Ice Shelf have significantly low fratios. Further analysis reveals a negative correlation between the f-ratio and the melt water fraction, thus implying that the melting of ice plays an essential role in regulating pelagic N dynamics in the Southern Ocean(SO). Stratification, produced by melting ice, should profoundly affect the efficiency of the SO’s biological pump and consequently affect the concentration of CO2 in the atmosphere. Results presented in this study add information to an already significant base of understanding of the controls on pelagic C and N dynamics in the SO. This provides unique insights for either interpreting past changes in geologic records or for predicting future climate change trends.
基金supported by the programmes"Dynamique et Billan de la Terre","Imageric et Structure de la Terre"(Tectoscope)of In-stitut National des Sciences de l'Univers(INSU)and Centre National de la Recherche Scientifiquc(Paris,France).
文摘Since the mid-late Eocene, North China has been subjected to extensional stress, resulting in the formation and development of basins. The dynamic origin of this crustal extension has long been an issue of debate. This paper presents the results of kinematic analyses of faults obtained from two seperated areas in North China. In the Weihe graben situated on the southernmost margin of the Ordos block, analyses of fault kinematics were coupled with an analysis of the basin's subsidence history. Three successive extensional tectonic phases accompaning the basin's formation and development have been distinguished. The Palaeogene extension was oriented in a WNW-ESE direction; the Neogene extension in a NE-SW direction and the Pliocene-Quaternary extension in a NW-SE direction. Such changes have also been recorded by fault kinematics along the southern Tanlu fault zone. This has been demonstrated by three successive sets of fault striations indicating normal dip slip resulting from NW-SE extension, then left-lateral slip with a normal component resulting from NE-SW extension, and right-lateral slip with a minor normal component, respectively. The kinematic history of faults and their chronological evolution indicate changes in continental dynamics acting in North China over Cenozoic time.
基金Transport Canada for financial support and Yukon Highways and Public Works for their support,logistics and assistance during instrumentation at the new Beaver Creek Culvert and information regarding the rules for construction of culverts in Yukon
文摘Temperature and water flow through a culvert beneath the Alaska Highway near Beaver Creek,Yukon,were measured at hourly intervals between June and October 2013.These data were used to simulate the effect of the culvert on the thermal regime of the road embankment and subjacent permafrost.A 2-D thermal model of the embankment and permafrost was developed with TEMP/W and calibrated using field observations.Empirical relations were obtained between water temperatures at the entrance to the culvert,flow into the culvert,and water temperatures inside the structure.Water temperatures at the entrance and inside the culvert had a linear relation,while water temperatures inside the culvert and water flow were associated by a logarithmic relation.A multiple linear regression was used to summarize these relations.From this relationship,changes in the flow rate and water temperatures at the entrance of the culvert were simulated to obtain predicted water temperatures in the culvert.The temperatures in the culvert were used in the thermal model to determine their effects on the ground thermal regime near the culvert.Variation of ±10% in water flow rate had no impact on the thermal regime underneath the culvert.Variation of water temperature at the entrance of the culvert had a noticeable influence on the thermal regime.A final simulation was conducted without insulation beneath the culvert.The thaw depth was 30 cm with insulation,and 120 cm without insulation,illustrating the importance of insulation to the ground thermal regime.
基金Project supported by the National Natural Science Foundation of China(Grant No.11272171)the Natural Science Foundation of Beijing City,China(Contract No.3172017)the Education Ministry Doctoral Fund of China(Grant No.20120002110070)
文摘The pre-sliding regime is typically neglected in the dynamic modelling of mechanical systems. However, the change in contact state caused by static friction may decrease positional accuracy and control precision. To investigate the relationship between contact status and contact force in pre-sliding friction, an optical experimental method is presented in this paper.With this method, the real contact state at the interface of a transparent material can be observed based on the total reflection principle of light by using an image processing technique. A novel setup, which includes a pair of rectangular trapezoidal blocks, is proposed to solve the challenging issue of accurately applying different tangential and normal forces to the contact interface. The improved Otsu's method is used for measurement. Through an experimental study performed on polymethyl methacrylate(PMMA), the quantity of contact asperities is proven to be the dominant factor that affects the real contact area. The relationship between the real contact area and the contact force in the pre-sliding regime is studied, and the distribution of static friction at the contact interface is qualitatively discussed. New phenomena in which the real contact area expands along with increasing static friction are identified. The aforementioned relationship is approximately linear at the contact interface under a constant normal pressure, and the distribution of friction stress decreases from the leading edge to the trailing edge.
文摘In this paper, ocean-atmosphere coupled regimes are identified on the basis of SVD analysis, cluster analysis and composite analysis. The coupled regimes in cold seasons are identified as the clusters of the ocean-atmosphere coupled states in a low dimensional phase space spanned by the first four SVD modes. Three coupled regimes are found. The first two coupled regimes reflect the ENSO episodes and the accompanying PNA patterns. The third regime, i.e., EAWM regime, is characterized by the strong EAWM activity and the specific SST anomaly. The composite analysis gives further evidences to the identification of EAWM regime and also demonstrates the dynamical process of its formation. The anomaly pattern of the tropical Pacific SSTA in the strong EAWM year differs significantly from that of the La Nina year.
文摘The thermal regimes in sedimentary basins in the continental area of China are varied and reflect differences in geological settings. As a result of these variable thermal regimes, the history of hydrocarbon generation in each basin is also different. An east-west profile of the thermal threshold across the continental basins of China, like the Liaohe Basin, the North China Basin, the Ordos Basin, the Qaidam Basin and the Tarim Basin, was constructed using large numbers of heat flow measurements, temperature data and rock thermophysical parameters. Isotherms, surface heat flow, mantle heat flow and Moho temperature beneath the basins are shown in the profile, which illustrates changes in some thermal characteristics between basins in east China and those in west China. Thermal evolution histories in basins were reconstructed using Easy%Ro method, apatite fission track annealing and other paleothermometers. Typical hydrocarbon generation histories of the primary source rocks were modeled by referring to the thermal evolution data. Thermal stages controlled source rocks maturation and oil and gas generation, and influenced the type of hydrocarbon (oil and gas) production in the basins.
基金supported by the National High Technology Research and Development Program ‘863’ (No. 2012 AA052101)the Hundred Talent Program of the Chinese Academy of Sciences (No. A1097)
文摘Stress state of microalgal cells is caused under unfavorable conditions such as disordered light regime and depleted nitrogen. The stress state can impair photosynthetic efficiency, inhibit cell growth and result in the accumulation of triacylglycerol(TAG) from protective mechanisms. Continuous light or nitrogen starvation was applied on microalgae and performed effectively on inducing TAG production. To evaluate the light regime effect on inducing TAG production, the effect of different light regimes on nitrogen-starved Isochrysis zhangjiangensis was investigated in this work. The continuous light and nitrogen starvation elevated TAG content of biomass by 73% and 193%, respectively. Furthermore, the TAG accumulation of I. zhangjiangensis cell under nitrogen starvation decreased under aggravated stress from continuous illumination. Our results demonstrated that culturing the cells with 14 L: 10 D light regime under nitrogen starvation is the optimal mode to achieve maximal accumulation of TAG. A recovery in light regime was necessary for I. zhangjiangensis cultivation.
基金supported by the National Natural Science Foundation of China (Nos. 41201066, 41401028, and J0930003/J0109)the State Key Laboratory of Frozen Soils Engineering (No. SKLFSE-ZT-14)
文摘Although many studies relevant to snow cover and permafrost have focused on alpine, arctic, and subarctic areas, there is still a lack of understanding of the influences of seasonal snow cover on the thermal regime of the soils in permafrost regions in the mid-latitudes and boreal regions, such as that on the westem flank of the Da Xing'anling (Hinggan) Mountains, northeastern China. This paper gives a detailed analysis on meteorological data series from 2001 to 2010 provided by the Gen'he Weather Station, which is located in a talik of discontinuous permafrost zone and with sparse meadow on the observation field. It is inferred that snow cover is important for the ground thermal regime in the middle Da Xing'anling Mountains. Snow cover of 10-cm in thickness and five to six months in duration (generally November to next March) can reduce the heat loss from the ground to the atmosphere by 28%, and by 71% if the snow depth increases to 36 cm. Moreover, the occurrence of snow cover resulted in mean annual ground surface temperatures 4.7-8.2℃ higher than the mean annual air temperatures recorded at the Gen'he Weather Station, The beginning date for stable snow cover establishment (SE date) and the initial snow depth (SDi) also had a great influences on the ground freezing process. Heavy snowfall before ground surface freeze-up could postpone and retard the freezing process in Gen'he. As a result, the duration of ground freezing was shortened by at least 20 days and the maximum depth of frost penetration was as much as 90 cm shallower.
基金Project supported by the National Basic Research Program of China (Grant No. 2006CB806002)the National High Technology Research and Development Program of China (Grant No. 2007AA03Z447)+3 种基金National Natural Science Foundation of China (Grant Nos. 60678012 and 60838004)the Foundation for Key Program of Ministry of Education, China (Grant No. 108032)FANEDD(Grant No. 2007B34)NCET (Grant No. NCET-07-0597)
文摘A Kerr-lens mode-locked Ti:sapphire laser operating in a non-soliton regime is demonstrated. Dispersive wave generation is observed as a result of third order dispersion in the vicinity of zero dispersion. The characteristics of the Ti:sapphire l^ser operating in a positive dispersion regime are presented, where the oscillator directly generates pulses with duration continuously tunable from 0.37 ps to 2.11 ps, and 36 fs pulses are achieved atter extracavity compression. The oscillation is numerically simulated with an extended nonlinear Schr6dinger equation, and the simulation results are in good agreement with the experimental results.
基金Marine Science Research Project for Public Welfare "Assessment for Navigability of Arctic Sea Route and Research & Demonstration for Prediction System for Sea Route" (Grant no. 201205007-6)Research Project of Polar Right and Interest, the Department of International Cooperation of the State Oceanic Administration, China
文摘This article focuses on two issues. The first concerns definitions of the Northern Sea Route (NSR) in old and new Russian legislation, and the second relates to Russian rules on icebreaker guiding. Based on a comprehensive comparative analysis of relevant Russian legal provisions enacted in 2013 and previous laws in this area, we offer the following conclusions. (1) Our legal analysis indicates that Russia's view of the NSR as a historical national transportation route has not changed. However, the new law redefines the scope and coverage of the NSR, which now comprises the internal waters, territorial sea, adjacent zone, and the exclusive economic zone of the Russian Federation. In fact, the new law resolves previous ambiguity regarding extension of the NSR boundary to the high seas. (2) Based on an analysis of the new rules on icebreaker guiding, the article concludes that NSR is transitioning from a mandatory icebreaker guiding regime into a permit regime. This is particularly evident in its provision of a concrete, practical, and predictable clause on permissible or impermissible conditions relating to independent navigation. According to the new rules, it is possible for foreign ships to undertake independent navigation in the NSR. The Russian NSR policy, therefore, appears to have changed significantly, and has future potential for opening the NSR up to the international community.