The effect zones of layer face for RCC （rolled control concrete） dam have gradual change characteristics. Based on the analysis thought of complex material, a model was built to analyze above principle of RCC dam by...The effect zones of layer face for RCC （rolled control concrete） dam have gradual change characteristics. Based on the analysis thought of complex material, a model was built to analyze above principle of RCC dam by use of series-wound and shunt-wound connection. Some methods were proposed to determine the instantaneous Young＇s modulus, delayed Young＇s modulus and viscosity coefficient of effect zones of layer face. Above models and methods were used to mine the principle of gradual change of key calculation parameters which can response the characteristics of effect zones. The principle of gradual change was described. A model was established to analyze the threedimensional viscoelastic problem of RCC dam. Above programs were developed. The examples show that the proposed models and methods to determine the key calculation parameters of effect zones can reflect the status of RCC dam accurately.展开更多
AIM:To investigate the impact of preoperative anterior corneal topographic parameters on the morphology of the postoperative effective optical zone(EOZ)in patients undergoing keratorefractive lenticule extraction(KLEx...AIM:To investigate the impact of preoperative anterior corneal topographic parameters on the morphology of the postoperative effective optical zone(EOZ)in patients undergoing keratorefractive lenticule extraction(KLEx)and wavefront-guided LASIK(WG-LASIK).METHODS:This retrospective study included 310 eyes from patients who underwent either KLEx(via small incision lenticule extraction,171 eyes)or WG-LASIK(139 eyes).Patients were stratified into subgroups based on the median values of spherical equivalent(SE)and anterior corneal topographic parameters.Postoperative EOZ parameters were measured 1mo after surgery and compared across subgroups.Correlation analysis and multivariable linear regression analysis were performed to explore the associations between preoperative anterior corneal topographic parameters and EOZ parameters.RESULTS:A total of 310 eyes were included(KLEx:171 eyes from 88 patients;WG-LASIK:139 eyes from 82 patients).The mean age was 30.65±5.67y in the KLEx cohort and 29.06±5.94y in the WG-LASIK cohort.In the KLEx cohort,SE,preoperative mean keratometry(Km),steep keratometry(K2),and anterior corneal astigmatism(K2-K1)were positively correlated with the postoperative optical zone reduction ratio(RR=EOZ/planned optical zone×100%;all P<0.01).Multivariable regression identified SE[β=0.027,95%confidence interval(CI):0.022-0.032,P<0.001],Km(β=0.009,95%CI:0.002-0.016,P=0.014),and anterior corneal astigmatism(β=0.031,95%CI:0.013-0.049,P<0.001)as significant predictors of RR(R²=0.456,P<0.001).In the WG-LASIK cohort,SE was positively correlated with RR(P<0.01);K2 and anterior corneal astigmatism were positively correlated with both RR(P<0.05)and EOZ eccentricity(P<0.01).Multivariable regression showed SE(β=0.015,95%CI:0.007-0.023,P<0.001)and anterior corneal astigmatism(β=0.029,95%CI:0.012-0.047,P=0.001)were significant predictors of RR(R²=0.121,P<0.001).CONCLUSION:Preoperative anterior corneal topographic parameters,particularly anterior corneal astigmatism,significantly affect postoperative EOZ morphology in both KLEx and WG-LASIK.Additionally,Km is a predictor of EOZ reduction specifically in KLEx.展开更多
This study aims to investigate the correlation between the permeation effect and microfabric of the slip zone soils with Huangtupo landslide in the Three Gorges Reservoir as the study case. Based on the permeability t...This study aims to investigate the correlation between the permeation effect and microfabric of the slip zone soils with Huangtupo landslide in the Three Gorges Reservoir as the study case. Based on the permeability test and scanning electron microscope(SEM) images analysis, the fractal theory and probability entropy are used to quantify the characteristics of the remodeling specimens. First, the relationships between initial moisture content(IMC) and microstructure of the soil(percentage of particle area(PPA), pore roundness(Rp)) before and after permeability test are summarized. Then, the fractal dimension of the soil(pore distribution(Dpd), pore size(Dps)) are analyzed under the permeation effect. Based on the probability entropy, the entropy of pore(Ep) is used to characterize the porosity orientation, and the rose diagrams are used to show the particle orientation under the permeation effect. Finally, the relationship between the microstructure of the soil and its mechanical property is discussed. Results show that under the permeation effect, the microstructure of the soil has undergone tremendous changes. A flat long pore channel is formed. The order of the pore arrangement is enhanced, and soil particles switch the long axis to parallel infiltration direction to reach a new steady state. It can be inferred that the strength of soil would be weakened if the fractal dimension of soil pore decreases under any external environment.展开更多
Experimental investigation is performed to investigate the cooling characteristics in the front zone of effusion configuration. Effects of blowing ratio,multi-hole arrangement mode,hole-to-hole pitch and jet orientati...Experimental investigation is performed to investigate the cooling characteristics in the front zone of effusion configuration. Effects of blowing ratio,multi-hole arrangement mode,hole-to-hole pitch and jet orientation angle on the adiabatic film cooling effectiveness are concentrated on. The results show that the film layer displays an obvious"developing"feature in the front zone of effusion cooling scheme,for either the staggered or inline multi-hole arrangement. The varying gradient of the laterally-averaged adiabatic cooling effectiveness along the streamwise direction is greater for the staggered arrangement than that for the inline arrangement. The holes array arranged in staggered mode with small hole-tohole pitches is in favor of obtaining developed film coverage layer rapidly.展开更多
In this study, precision agriculture management zones were delineated using yield data over four years from the combine harvester equipped with yield monitor and DGPS receiver. Relative yields measured during each yea...In this study, precision agriculture management zones were delineated using yield data over four years from the combine harvester equipped with yield monitor and DGPS receiver. Relative yields measured during each year were interpolated to 4 m2 grid size using ordinary kriging. The resultant interpolated yield maps were averaged across years to create a map of the mean relative yield, which was then used for cluster analysis. The mean yield map of post-classification was processed by applying majority filtering with window sizes that were equivalent to the grid sizes of 12, 20, 28, 36, 44, 52 and 60 m. The scale effect of management zones was evaluated using relative variance reduction, test of significant differences of the means of yield zones, spatial fragmentation, and spatial agreement. The results showed that the post-classification majority filtering （PCMF） eliminated lots of isolated cells or patches caused by random variation while preserving yield means, high variance reduction, general yield patterns, and high spatial agreement. The zoned result can be used as yield goal map for preplant or in-season fertilizer recommendation in precision agriculture.展开更多
A multi-level evaluation index system is established with farmland protection as the target layer,farmland quantity,farmland quality andfarmland sustainable development as the criterion layer.And the index layer inclu...A multi-level evaluation index system is established with farmland protection as the target layer,farmland quantity,farmland quality andfarmland sustainable development as the criterion layer.And the index layer includes the quantity change of farmland,per capita farmland area,multiple cropping index,total grain yield,unit grain yield,per capita grain security coefficient,and unit machinery dynamical input.Both expert eval-uation method and factor analysis method are used to determine the weight of index.According to the data in farmland area,grain yield and eco-nomic development in Urumqi-Changji Economic Zone in the years 1996-2007,a comprehensive evaluation model of intensive farmland use inUrumqi-Changji Economic Zone is established after data standardization.The overall implementation effect of farmland protection policy is ana-lyzed by integrating the farmland quantity,farmland quality and sustainable development.Result shows that implementation effect of farmland pro-tection shows an upward trend in general in Urumqi-Changji Economic Zone in the years 1996-2007,with a fluctuation in the years 2000-2003and a stable rising phase from 2004 till now.The maximum value is 0.779 in the year 2007;the minimum value is 0.242 in the year 1996;and themean value in the years 1996-2007 is 0.454.Farmland protection at first strictly controls the farmland quantity,then pays attention to farmlandquality,and finally focuses on the sustainable use of farmland.展开更多
Mechanism interaction between cracks with different orientation angles is analyzed based on the principle of superposition and a flattening method. It is found that the maximum interaction effect does not occur when t...Mechanism interaction between cracks with different orientation angles is analyzed based on the principle of superposition and a flattening method. It is found that the maximum interaction effect does not occur when the microcrack is along the direction parallel or perpendicular to the principal tensile stress, which is different from the conclusion drawn by Ortiz （1987）. The mechanism of microcrack generation and the effect of the microcrack zone on the main crack tip are studied. It is concluded that the microcrack zone has effect on the main crack tip, which increases with the increase of microcrack density and length.展开更多
In this paper, a strong 1TCZ process and an 1TCZ - absent process during FGGE in 1979 were selected for comparison to explore how they were subject to the influence of the evolution of the upper easterly jets.
The rail transit in sulfate-rich areas faces the combined effects of stray current and salt corrosion;however,the sulfate ion transport and concrete degradation mechanisms under such conditions are still unclear.To ad...The rail transit in sulfate-rich areas faces the combined effects of stray current and salt corrosion;however,the sulfate ion transport and concrete degradation mechanisms under such conditions are still unclear.To address this issue,novel sulfate transport and mesoscale splitting tests were designed,with a focus on considering the differences between the interfacial transition zone(ITZ)and cement matrix.Under the influence of stray current,the ITZ played a pivotal role in regulating the transport and mechanical failure processes of sulfate attack,while the tortuous and blocking effects of aggregates almost disappeared.This phenomenon was termed the“stray current-induced ITZ effect.”The experimental data revealed that the difference in sulfate ion transport attributed to the ITZ ranged from 1.90 to 2.31 times,while the difference in splitting strength ranged from 1.56 to 1.64 times.Through the real-time synchronization of splitting experiments and microsecond-responsive particle image velocimetry(PIV)technology,the mechanical properties were exposed to the consequences of the stray currentinduced ITZ effect.The number of splitting cracks in the concrete increased,rather than along the central axis,which was significantly different from the conditions without stray current and the ideal Brazilian disk test.Furthermore,a sulfate ion mass transfer model that incorporates reactivity and electrodiffusion was meticulously constructed.The embedded finite element calculation exhibited excellent agreement with the experimental results,indicating its reliability and accuracy.Additionally,the stress field was determined utilizing analytical methods,and the mechanism underlying crack propagation was successfully obtained.Compared to the cement matrix,a stray current led to more sulfates,more microstructure degradation,and greater increases in thickness and porosity in the ITZ,which was considered to be the essence of the stray current-induced ITZ effect.展开更多
The effective segregation coefficient K-e of oxygen in terbium metal was deduced from a comparison of the theoretical curves with the concentration distributions found experimentally after a floating zone refining tre...The effective segregation coefficient K-e of oxygen in terbium metal was deduced from a comparison of the theoretical curves with the concentration distributions found experimentally after a floating zone refining treatment. Thp result shows that K-e is equal to 1.2 which is an important parameter for floating zone refining terbium.展开更多
This paper, by applying the theories of landscape ecology, illustrates the role and mechanism of windbreak system in the establishment and maintenance of oasis ecosystem on the basis of systematic analysis of characte...This paper, by applying the theories of landscape ecology, illustrates the role and mechanism of windbreak system in the establishment and maintenance of oasis ecosystem on the basis of systematic analysis of characteristics and ecological crises of China's desert, and especially of desert zone in western China. Furthermore, direct economic benefits are summarized.展开更多
The G. Abu Garadi area is covered mainly by metasediments, alkali feldspar granites and stream sediments. The alkali feldspar granite is traversed by a major strike-slip fault trending in an N-S direction as well as t...The G. Abu Garadi area is covered mainly by metasediments, alkali feldspar granites and stream sediments. The alkali feldspar granite is traversed by a major strike-slip fault trending in an N-S direction as well as two subordinate sets of faults trending NW to WNW for the first one and NE for the second one. These faults represent the shear zones affected by magmatic (syngenetic) as well as hydrothermal (epigenetic) activities causing alteration of the granitic rocks. The most common alteration features are albitization, greisenization and koalinitization. The mass balance calculations of the studied altered samples show enrichments in Zr, Y, Ni, U, Th and Ga and depletions in Zn, Sr, Nb, Ba, Pb, Cu and V. Only the greisenized samples exhibit a significant enrichment in Nb, ∑REE budget and pronounced lanthanide tetrad effect (M-type), especially TE1,4, while weakly expressed tetrad effects are for the other albitized and koalinitized samples. Mineralogically, the common accessory minerals in the altered samples include samarskite-(Y), betafite, uranothorite, zircon, fluorite and cassiterite. The greisenized granites contain high eU and eTh than the other altered types, where they are characterized by an assemblage of the radioactive minerals; samarskite-(Y), betafite, uranothorite in addition to zircon. The inter-element relationships between U and Th and also their ratios illustrate that the radioelement distribution in these granites is mainly governed by magmatic processes, in addition to post-magmatic ones. The distribution of chemical elements and the fractionation of some isovalents within the shear zone are largely controlled by the newly formed mineral phases. With respect to uranium mobilization, uranium migrated from the host alkali feldspar granites of G. Abu Garadi, while the shear zones acted as traps for the migrated uranium. Moreover, U migrated in the shear zone during greisenization and albitization, and migrated out during koalinitization.展开更多
A coastal historical evolution of the Yangtze River Delta was discussed in this paper on the basis of the historical data of the coastal zone and an estimation was made for the future change of the coast The emphasi...A coastal historical evolution of the Yangtze River Delta was discussed in this paper on the basis of the historical data of the coastal zone and an estimation was made for the future change of the coast The emphasis was put on the future climate change that will have influence on the sea wall, coastal navigation and freshwater resources in the Delta It was also pointed out that the global warming and precipitation increase in the Yangtze River Valley may exert more impact on the zone In addition, some measures describing how to adapt to the climate change and reduce its impact were put forward展开更多
Ecosystem services have become one of the core elements of ecosystem management and evaluation. As a key area of ecosystem services and for maintaining national ecological security, ecosystem changes and implementatio...Ecosystem services have become one of the core elements of ecosystem management and evaluation. As a key area of ecosystem services and for maintaining national ecological security, ecosystem changes and implementation effect evaluation are important in national key ecological function zones, for promoting the main function zone strategy and for improving the construction of an ecological civilization. This article studies the ecological zone of a tropical rainforest region in the central mountain area of Hainan Island, China. Multi-source satellite data and ground observation statistics are analyzed with geo-statistics method and ecological assessment model. The core analysis of this paper includes ecosystem patterns, quality and services. By means of spatial and temporal scale expansion and multidimensional space-time correlation analysis, the trends and stability characteristics of ecosystem changes are analyzed, and implementation effect evaluation is discussed. The analysis shows a variety of results. The proportion of forest area inside the ecological zone was significantly higher than the average level in Hainan Island. During 1990–2013, settlement gradually increased inside the ecological zone. After implementation of the zone in 2010, human activity intensity increased, with the main land use being urban construction and land reclamation. Water conservation in the ecological function zone was higher than that outside the zone. In general, it increased slightly, but had obvious fluctuations. Soil conservation inside the zone was also better than that outside. However, it demonstrated dramatic fluctuations and relatively poor stability during 1990–2013. The human disturbance index inside the zone was significantly lower than that outside, and had a lower biodiversity threat level. Especially in 2010–2013, the increased range of the human disturbance index inside the zone was significantly less than that outside.展开更多
The electrochemical behaviour, including free corrosion potential, free corrosion current density and polarization curve, of various thermal history zones on the weldment was measured in this paper. The weldment consi...The electrochemical behaviour, including free corrosion potential, free corrosion current density and polarization curve, of various thermal history zones on the weldment was measured in this paper. The weldment consisted of matrix, tempering zone. incomplete normalized zone, normalized zone, overtemperature zone, fusion line zone and weld metal zone. The electrochemical behaviour of the ferrite, pearlite and mixed structure in various zones have successfully measured. The results showed that there was a difference of free corrosion potential which is smaller than ca. 200mV between various zones and about 20-150mV potential difference between ferrite and pearlite in every zone. The free cormsion potential of fusion line zone was the most negative between various zones. The free corrosion potential of pearlite was some dozens mV more negative than ferrite. The corrosion course of various zones and of different phase structures on the weldment and their effect on corrosion attack of weldment were discussed.展开更多
Understanding hydrocarbon migration and accumulation mechanisms is one of the key scientif ic problems that should be solved for effective hydrocarbon exploration in the superimposed basins developed in northwest Chin...Understanding hydrocarbon migration and accumulation mechanisms is one of the key scientif ic problems that should be solved for effective hydrocarbon exploration in the superimposed basins developed in northwest China. The northwest striking No.1 slope break zone, which is a representative of superimposed basins in the Tarim Basin, can be divided into five parts due to the intersection of the northeast strike-slip faults. Controlled by the tectonic framework, the types and properties of reservoirs and the hydrocarbon compositions can also be divided into five parts from east to west. Anomalies of all the parameters were found on the fault intersection zone and weakened up-dip along the structural ridge away from it. Thus, it can be inferred that the intersection zone is the hydrocarbon charging position. This new conclusion differs greatly from the traditional viewpoint, which believes that the hydrocarbon migrates and accumulates along the whole plane of the No.1 slope break zone. The viewpoint is further supported by the evidence from the theory of main pathway systems, obvious improvement of the reservoir quality （2-3 orders of magnitude at the intersection zone） and the formation mechanisms of the fault intersection zone. Differential hydrocarbon migration and entrapment exists in and around the strike- slip faults. This is controlled by the internal structure of faults. It is concluded that the more complicated the fault structure is, the more significant the effects will be. If there is a deformation band, it will hinder the cross fault migration due to the common feature of two to four orders of magnitude reduction in permeability. Otherwise, hydrocarbons tend to accumulate in the up-dip structure under the control of buoyancy. Further research on the internal fault structure should be emphasized.展开更多
基金Project supported by the National Natural Science Foundation of China (Nos.50579010, 50539010)the National Basic Research Program of China (973 Program) (No.2002CB412707)the National Basic Research Program of Ministry of Water Resources, China (No.CT200612)
文摘The effect zones of layer face for RCC （rolled control concrete） dam have gradual change characteristics. Based on the analysis thought of complex material, a model was built to analyze above principle of RCC dam by use of series-wound and shunt-wound connection. Some methods were proposed to determine the instantaneous Young＇s modulus, delayed Young＇s modulus and viscosity coefficient of effect zones of layer face. Above models and methods were used to mine the principle of gradual change of key calculation parameters which can response the characteristics of effect zones. The principle of gradual change was described. A model was established to analyze the threedimensional viscoelastic problem of RCC dam. Above programs were developed. The examples show that the proposed models and methods to determine the key calculation parameters of effect zones can reflect the status of RCC dam accurately.
文摘AIM:To investigate the impact of preoperative anterior corneal topographic parameters on the morphology of the postoperative effective optical zone(EOZ)in patients undergoing keratorefractive lenticule extraction(KLEx)and wavefront-guided LASIK(WG-LASIK).METHODS:This retrospective study included 310 eyes from patients who underwent either KLEx(via small incision lenticule extraction,171 eyes)or WG-LASIK(139 eyes).Patients were stratified into subgroups based on the median values of spherical equivalent(SE)and anterior corneal topographic parameters.Postoperative EOZ parameters were measured 1mo after surgery and compared across subgroups.Correlation analysis and multivariable linear regression analysis were performed to explore the associations between preoperative anterior corneal topographic parameters and EOZ parameters.RESULTS:A total of 310 eyes were included(KLEx:171 eyes from 88 patients;WG-LASIK:139 eyes from 82 patients).The mean age was 30.65±5.67y in the KLEx cohort and 29.06±5.94y in the WG-LASIK cohort.In the KLEx cohort,SE,preoperative mean keratometry(Km),steep keratometry(K2),and anterior corneal astigmatism(K2-K1)were positively correlated with the postoperative optical zone reduction ratio(RR=EOZ/planned optical zone×100%;all P<0.01).Multivariable regression identified SE[β=0.027,95%confidence interval(CI):0.022-0.032,P<0.001],Km(β=0.009,95%CI:0.002-0.016,P=0.014),and anterior corneal astigmatism(β=0.031,95%CI:0.013-0.049,P<0.001)as significant predictors of RR(R²=0.456,P<0.001).In the WG-LASIK cohort,SE was positively correlated with RR(P<0.01);K2 and anterior corneal astigmatism were positively correlated with both RR(P<0.05)and EOZ eccentricity(P<0.01).Multivariable regression showed SE(β=0.015,95%CI:0.007-0.023,P<0.001)and anterior corneal astigmatism(β=0.029,95%CI:0.012-0.047,P=0.001)were significant predictors of RR(R²=0.121,P<0.001).CONCLUSION:Preoperative anterior corneal topographic parameters,particularly anterior corneal astigmatism,significantly affect postoperative EOZ morphology in both KLEx and WG-LASIK.Additionally,Km is a predictor of EOZ reduction specifically in KLEx.
基金supported by the National Key R&D Program of China (2017YFC1501301)the National Natural Science Foundation of China (No. 41572278 and No. 41772310)
文摘This study aims to investigate the correlation between the permeation effect and microfabric of the slip zone soils with Huangtupo landslide in the Three Gorges Reservoir as the study case. Based on the permeability test and scanning electron microscope(SEM) images analysis, the fractal theory and probability entropy are used to quantify the characteristics of the remodeling specimens. First, the relationships between initial moisture content(IMC) and microstructure of the soil(percentage of particle area(PPA), pore roundness(Rp)) before and after permeability test are summarized. Then, the fractal dimension of the soil(pore distribution(Dpd), pore size(Dps)) are analyzed under the permeation effect. Based on the probability entropy, the entropy of pore(Ep) is used to characterize the porosity orientation, and the rose diagrams are used to show the particle orientation under the permeation effect. Finally, the relationship between the microstructure of the soil and its mechanical property is discussed. Results show that under the permeation effect, the microstructure of the soil has undergone tremendous changes. A flat long pore channel is formed. The order of the pore arrangement is enhanced, and soil particles switch the long axis to parallel infiltration direction to reach a new steady state. It can be inferred that the strength of soil would be weakened if the fractal dimension of soil pore decreases under any external environment.
基金Supported by the National Natural Science Foundation of China(51276090)
文摘Experimental investigation is performed to investigate the cooling characteristics in the front zone of effusion configuration. Effects of blowing ratio,multi-hole arrangement mode,hole-to-hole pitch and jet orientation angle on the adiabatic film cooling effectiveness are concentrated on. The results show that the film layer displays an obvious"developing"feature in the front zone of effusion cooling scheme,for either the staggered or inline multi-hole arrangement. The varying gradient of the laterally-averaged adiabatic cooling effectiveness along the streamwise direction is greater for the staggered arrangement than that for the inline arrangement. The holes array arranged in staggered mode with small hole-tohole pitches is in favor of obtaining developed film coverage layer rapidly.
基金The study was funded by the National Natural Science Foundation of China （40471093, 40591118）Beijing Natural Science Foundation （4061002）.
文摘In this study, precision agriculture management zones were delineated using yield data over four years from the combine harvester equipped with yield monitor and DGPS receiver. Relative yields measured during each year were interpolated to 4 m2 grid size using ordinary kriging. The resultant interpolated yield maps were averaged across years to create a map of the mean relative yield, which was then used for cluster analysis. The mean yield map of post-classification was processed by applying majority filtering with window sizes that were equivalent to the grid sizes of 12, 20, 28, 36, 44, 52 and 60 m. The scale effect of management zones was evaluated using relative variance reduction, test of significant differences of the means of yield zones, spatial fragmentation, and spatial agreement. The results showed that the post-classification majority filtering （PCMF） eliminated lots of isolated cells or patches caused by random variation while preserving yield means, high variance reduction, general yield patterns, and high spatial agreement. The zoned result can be used as yield goal map for preplant or in-season fertilizer recommendation in precision agriculture.
基金Supported by the Xinjiang Social Science Fund Project (07JYB029)
文摘A multi-level evaluation index system is established with farmland protection as the target layer,farmland quantity,farmland quality andfarmland sustainable development as the criterion layer.And the index layer includes the quantity change of farmland,per capita farmland area,multiple cropping index,total grain yield,unit grain yield,per capita grain security coefficient,and unit machinery dynamical input.Both expert eval-uation method and factor analysis method are used to determine the weight of index.According to the data in farmland area,grain yield and eco-nomic development in Urumqi-Changji Economic Zone in the years 1996-2007,a comprehensive evaluation model of intensive farmland use inUrumqi-Changji Economic Zone is established after data standardization.The overall implementation effect of farmland protection policy is ana-lyzed by integrating the farmland quantity,farmland quality and sustainable development.Result shows that implementation effect of farmland pro-tection shows an upward trend in general in Urumqi-Changji Economic Zone in the years 1996-2007,with a fluctuation in the years 2000-2003and a stable rising phase from 2004 till now.The maximum value is 0.779 in the year 2007;the minimum value is 0.242 in the year 1996;and themean value in the years 1996-2007 is 0.454.Farmland protection at first strictly controls the farmland quantity,then pays attention to farmlandquality,and finally focuses on the sustainable use of farmland.
基金supported by the National Natural Science Foundation of China (Nos. 10972072, 50679022, and 10872052)National Basic Research Program of China (No. 2007CB714104)the state Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering at Hohai University (No. 2009585912)
文摘Mechanism interaction between cracks with different orientation angles is analyzed based on the principle of superposition and a flattening method. It is found that the maximum interaction effect does not occur when the microcrack is along the direction parallel or perpendicular to the principal tensile stress, which is different from the conclusion drawn by Ortiz （1987）. The mechanism of microcrack generation and the effect of the microcrack zone on the main crack tip are studied. It is concluded that the microcrack zone has effect on the main crack tip, which increases with the increase of microcrack density and length.
文摘In this paper, a strong 1TCZ process and an 1TCZ - absent process during FGGE in 1979 were selected for comparison to explore how they were subject to the influence of the evolution of the upper easterly jets.
基金supported by the State Major Program of National Natural Science Foundation of China(52090082)the National Key Research and Development Program of China(2022YFB2602200)the National Natural Science Foundation of China(52178423 and 52378398).
文摘The rail transit in sulfate-rich areas faces the combined effects of stray current and salt corrosion;however,the sulfate ion transport and concrete degradation mechanisms under such conditions are still unclear.To address this issue,novel sulfate transport and mesoscale splitting tests were designed,with a focus on considering the differences between the interfacial transition zone(ITZ)and cement matrix.Under the influence of stray current,the ITZ played a pivotal role in regulating the transport and mechanical failure processes of sulfate attack,while the tortuous and blocking effects of aggregates almost disappeared.This phenomenon was termed the“stray current-induced ITZ effect.”The experimental data revealed that the difference in sulfate ion transport attributed to the ITZ ranged from 1.90 to 2.31 times,while the difference in splitting strength ranged from 1.56 to 1.64 times.Through the real-time synchronization of splitting experiments and microsecond-responsive particle image velocimetry(PIV)technology,the mechanical properties were exposed to the consequences of the stray currentinduced ITZ effect.The number of splitting cracks in the concrete increased,rather than along the central axis,which was significantly different from the conditions without stray current and the ideal Brazilian disk test.Furthermore,a sulfate ion mass transfer model that incorporates reactivity and electrodiffusion was meticulously constructed.The embedded finite element calculation exhibited excellent agreement with the experimental results,indicating its reliability and accuracy.Additionally,the stress field was determined utilizing analytical methods,and the mechanism underlying crack propagation was successfully obtained.Compared to the cement matrix,a stray current led to more sulfates,more microstructure degradation,and greater increases in thickness and porosity in the ITZ,which was considered to be the essence of the stray current-induced ITZ effect.
文摘The effective segregation coefficient K-e of oxygen in terbium metal was deduced from a comparison of the theoretical curves with the concentration distributions found experimentally after a floating zone refining treatment. Thp result shows that K-e is equal to 1.2 which is an important parameter for floating zone refining terbium.
文摘This paper, by applying the theories of landscape ecology, illustrates the role and mechanism of windbreak system in the establishment and maintenance of oasis ecosystem on the basis of systematic analysis of characteristics and ecological crises of China's desert, and especially of desert zone in western China. Furthermore, direct economic benefits are summarized.
文摘The G. Abu Garadi area is covered mainly by metasediments, alkali feldspar granites and stream sediments. The alkali feldspar granite is traversed by a major strike-slip fault trending in an N-S direction as well as two subordinate sets of faults trending NW to WNW for the first one and NE for the second one. These faults represent the shear zones affected by magmatic (syngenetic) as well as hydrothermal (epigenetic) activities causing alteration of the granitic rocks. The most common alteration features are albitization, greisenization and koalinitization. The mass balance calculations of the studied altered samples show enrichments in Zr, Y, Ni, U, Th and Ga and depletions in Zn, Sr, Nb, Ba, Pb, Cu and V. Only the greisenized samples exhibit a significant enrichment in Nb, ∑REE budget and pronounced lanthanide tetrad effect (M-type), especially TE1,4, while weakly expressed tetrad effects are for the other albitized and koalinitized samples. Mineralogically, the common accessory minerals in the altered samples include samarskite-(Y), betafite, uranothorite, zircon, fluorite and cassiterite. The greisenized granites contain high eU and eTh than the other altered types, where they are characterized by an assemblage of the radioactive minerals; samarskite-(Y), betafite, uranothorite in addition to zircon. The inter-element relationships between U and Th and also their ratios illustrate that the radioelement distribution in these granites is mainly governed by magmatic processes, in addition to post-magmatic ones. The distribution of chemical elements and the fractionation of some isovalents within the shear zone are largely controlled by the newly formed mineral phases. With respect to uranium mobilization, uranium migrated from the host alkali feldspar granites of G. Abu Garadi, while the shear zones acted as traps for the migrated uranium. Moreover, U migrated in the shear zone during greisenization and albitization, and migrated out during koalinitization.
文摘A coastal historical evolution of the Yangtze River Delta was discussed in this paper on the basis of the historical data of the coastal zone and an estimation was made for the future change of the coast The emphasis was put on the future climate change that will have influence on the sea wall, coastal navigation and freshwater resources in the Delta It was also pointed out that the global warming and precipitation increase in the Yangtze River Valley may exert more impact on the zone In addition, some measures describing how to adapt to the climate change and reduce its impact were put forward
基金National Key R&D Program of China,No.2017YFC0506506,No.2016YFC0500206National Natural Science Foundation of China,No.41501484
文摘Ecosystem services have become one of the core elements of ecosystem management and evaluation. As a key area of ecosystem services and for maintaining national ecological security, ecosystem changes and implementation effect evaluation are important in national key ecological function zones, for promoting the main function zone strategy and for improving the construction of an ecological civilization. This article studies the ecological zone of a tropical rainforest region in the central mountain area of Hainan Island, China. Multi-source satellite data and ground observation statistics are analyzed with geo-statistics method and ecological assessment model. The core analysis of this paper includes ecosystem patterns, quality and services. By means of spatial and temporal scale expansion and multidimensional space-time correlation analysis, the trends and stability characteristics of ecosystem changes are analyzed, and implementation effect evaluation is discussed. The analysis shows a variety of results. The proportion of forest area inside the ecological zone was significantly higher than the average level in Hainan Island. During 1990–2013, settlement gradually increased inside the ecological zone. After implementation of the zone in 2010, human activity intensity increased, with the main land use being urban construction and land reclamation. Water conservation in the ecological function zone was higher than that outside the zone. In general, it increased slightly, but had obvious fluctuations. Soil conservation inside the zone was also better than that outside. However, it demonstrated dramatic fluctuations and relatively poor stability during 1990–2013. The human disturbance index inside the zone was significantly lower than that outside, and had a lower biodiversity threat level. Especially in 2010–2013, the increased range of the human disturbance index inside the zone was significantly less than that outside.
文摘The electrochemical behaviour, including free corrosion potential, free corrosion current density and polarization curve, of various thermal history zones on the weldment was measured in this paper. The weldment consisted of matrix, tempering zone. incomplete normalized zone, normalized zone, overtemperature zone, fusion line zone and weld metal zone. The electrochemical behaviour of the ferrite, pearlite and mixed structure in various zones have successfully measured. The results showed that there was a difference of free corrosion potential which is smaller than ca. 200mV between various zones and about 20-150mV potential difference between ferrite and pearlite in every zone. The free cormsion potential of fusion line zone was the most negative between various zones. The free corrosion potential of pearlite was some dozens mV more negative than ferrite. The corrosion course of various zones and of different phase structures on the weldment and their effect on corrosion attack of weldment were discussed.
基金supported by the National 973 Basic Research Program (Grant No.2006CB202308)the Major National Science & Technology Program (2008ZX05008-004-012)
文摘Understanding hydrocarbon migration and accumulation mechanisms is one of the key scientif ic problems that should be solved for effective hydrocarbon exploration in the superimposed basins developed in northwest China. The northwest striking No.1 slope break zone, which is a representative of superimposed basins in the Tarim Basin, can be divided into five parts due to the intersection of the northeast strike-slip faults. Controlled by the tectonic framework, the types and properties of reservoirs and the hydrocarbon compositions can also be divided into five parts from east to west. Anomalies of all the parameters were found on the fault intersection zone and weakened up-dip along the structural ridge away from it. Thus, it can be inferred that the intersection zone is the hydrocarbon charging position. This new conclusion differs greatly from the traditional viewpoint, which believes that the hydrocarbon migrates and accumulates along the whole plane of the No.1 slope break zone. The viewpoint is further supported by the evidence from the theory of main pathway systems, obvious improvement of the reservoir quality （2-3 orders of magnitude at the intersection zone） and the formation mechanisms of the fault intersection zone. Differential hydrocarbon migration and entrapment exists in and around the strike- slip faults. This is controlled by the internal structure of faults. It is concluded that the more complicated the fault structure is, the more significant the effects will be. If there is a deformation band, it will hinder the cross fault migration due to the common feature of two to four orders of magnitude reduction in permeability. Otherwise, hydrocarbons tend to accumulate in the up-dip structure under the control of buoyancy. Further research on the internal fault structure should be emphasized.
