For k-valued(control)networks,two types of(control)invariant subspaces are proposed,namely,the state-invariant and dual-invariant subspaces,which are subspaces of the state space and dual space,respectively.Algorithms...For k-valued(control)networks,two types of(control)invariant subspaces are proposed,namely,the state-invariant and dual-invariant subspaces,which are subspaces of the state space and dual space,respectively.Algorithms are presented to check whether a dual subspace is dual-(control)invariant,and to construct state feedback controls.The bearing space of k-valued(control)networks is introduced.Using the structure of the bearing space,the universal invariant subspace is presented,which is independent of the dynamics of particular networks.Finally,the relation between the stateinvariant subspaces and the dual-invariant subspaces of a network is investigated.A duality property shows that if a dual subspace is invariant,then its perpendicular state subspace is also invariant,and vice versa.展开更多
This paper proposed a new empirical K-value equation is developed to calculate dew pressure for gas condensate reservoirs.This equation is applicable in the wide ranges of composition,temperature,and pressure by consi...This paper proposed a new empirical K-value equation is developed to calculate dew pressure for gas condensate reservoirs.This equation is applicable in the wide ranges of composition,temperature,and pressure by considering the effect of composition via two equations for normal boiling point and critical temperature of the mixture.The range of dew pressure,temperature,heptane plus mole fraction,methane mole fraction,N2 mole fraction,CO2 mole fraction,and H2S mole fraction are fallen into 2666.7e9655 Psia,40e350.87F,0.0021e0.213,0.3344e0.9668,0e0.4322,0e0.0864,and 0e0.942 respectively.As an important point,the proposed equation has any adjustable parameters,in addition,this equation indicates that in order to predict of dew pressure of gas condensate reservoirs,trial and error was not needed and therefore,computational speed increases beyond the accuracy.Moreover,the accuracy is validated by comparing against the experimental data of 81 gas condensate reservoirs samples from published literature and the results of Wilson,Whitson,and Ghafoori equations.Compared to the experimental data,the absolute average deviations of dew pressure calculations for the proposed equation,Wilson,Whitson,and Ghafoori were 7.6%,97.6%,99.4%,and 94.9%respectively.展开更多
The spray-deposition was used to produce billets of Mg-4Al-1.5Zn-3Ca-1Nd(A alloy)and Mg-13Al-3Zn-3Ca-1Nd(B alloy),and evolution of deformation substructure and Mg_(x)Zn_(y)Ca_(z)metastable phase in fine-grained(3μm)M...The spray-deposition was used to produce billets of Mg-4Al-1.5Zn-3Ca-1Nd(A alloy)and Mg-13Al-3Zn-3Ca-1Nd(B alloy),and evolution of deformation substructure and Mg_(x)Zn_(y)Ca_(z)metastable phase in fine-grained(3μm)Mg alloys was investigated by scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD),and electron backscattered diffraction(EBSD).It was found that different dislocation configurations were formed in A and B alloys.Redundant free dislocations(RFDs)and dislocation tangles were the ways to form deformation substructure in A alloy,no RFDs except dislocation tangles were found in B alloy.The interaction between nano-scale second phase particles(nano-scale C15 andβ-Mg_(17)(Al,Zn)_(12)phase)and different dislocation configurations had a significant effect on the deformation substructures formation.The mass transfer of Mg_(x)Zn_(y)Ca_(z)metastable phases and the stacking order of stacking faults were conducive to the Mg-Nd-Zn typed long period stacking ordered(LPSO)phases formation.Nano-scale C15 phases,Mg-Nd-Zn typed LPSO phases,c/a ratio,β-Mg_(17)(Al,Zn)_(12)phases were the key factors influencing the formation of textures.Different textures and grain boundary features(GB features)had a significant effect on k-value.The non-basal textures were the main factor affecting k-value in A alloy,while the high-angle grain boundary(HAGB)was the main factor affecting k-value in B alloy.展开更多
This study investigates the influence of using ground palm oil fuel ash(G-POFA) from 10%-30% as cement replacement(by weight) on the cement mortar's pH under various curing conditions. These findings were suppleme...This study investigates the influence of using ground palm oil fuel ash(G-POFA) from 10%-30% as cement replacement(by weight) on the cement mortar's pH under various curing conditions. These findings were supplemented by thermal gravimetric analysis(TGA). Moreover, the resistance of G-POFA blended cement mortars to water absorption and sorptivity was determined. Further, the k-value test was carried out to explain the pozzolanic and filler behavior of G-POFA and to support the results obtained from TGA. It was found that there was no significant impact of several curing conditions on the pH of mortars. The mortar with 10% G-POFA in replacement of cement(G-POFA-10) exhibited the best resistance against water absorption and sorptivity.展开更多
The generalized constitutive model relating the resilient modulus (MR) of flexible pavement layer materials to stress state, adopted by the Mechanistic-Empirical Pavement Design Guide (MEPDG), contains a set of consta...The generalized constitutive model relating the resilient modulus (MR) of flexible pavement layer materials to stress state, adopted by the Mechanistic-Empirical Pavement Design Guide (MEPDG), contains a set of constants known as k-values (k1, k2, and k3) which are associated with the physical state of the layer materials. In Ghana, natural gravels constitute the predominant and sometimes the sole layer materials for most flexible pavements yet representative k-values of gravel materials, have not been determined to permit full application and implementation of the mechanistic-empirical design concept to pavements involving such materials. In this study, k-values characterising typical natural quartzitic gravels used for road construction in the country were derived by regression techniques from MR values determined using laboratory repeated load triaxial test. Using multiple linear regression technique, correlation relationships were then developed between the k-values and the physical properties of the gravels, namely, percentages of materials passing the 9.5 mm (P9.5) and 2.0 mm (P2.0) sieves, liquid limit (LL), maximum dry density (ρdmax), and optimum moisture content (wopt). The regression analysis returned k1 values which ranged between 441 and 958 with a mean of 516;k2 which varied between 0.0636 and 0.2168 with a mean value of 0.1216;and, k3 values which ranged between 0.1257 and 3.1590 with a mean value of 1.723. Contrary to what is mostly reported in literature, the analysis returned positive k3 values for all but one gravel material, suggesting stress hardening under octahedral shear stress for those materials. While an expanded sample base is required to fully characterize the whole gamut of natural gravels used in pavement construction in the country, this study on limited quartzitic gravel samples has given a good indication of strong linear correlations between the k-values and the index properties of the gravels, to permit estimates of the constants for such gravels be made where capability and opportunity for conducting resilient modulus tests do not exist.However, further work is recommended to fully characterise the exact nature of k3 values for quartzitic gravels in the country.展开更多
Soil erodibility(K-factor)is an essential factor in soil erosion prediction and conservation practises.The major obstacles to any accurate,large-scale soil erodibility estimation are the lack of necessary data on soil...Soil erodibility(K-factor)is an essential factor in soil erosion prediction and conservation practises.The major obstacles to any accurate,large-scale soil erodibility estimation are the lack of necessary data on soil characteristics and the misuse of variable K factor calculators.In this study,we assessed the per-formance of available erodibility estimators Universal Soil Loss Equation(USLE),Revised Universal Soil Loss Equation(RUSLE),Erosion Productivity Impact Calculator(EPIC)and the Geometric Mean Diameter based(Dg)model for different geographic regions based on the Chinese soil erodibility database(CSED).Results showed that previous estimators overestimated almost all K-values.Furthermore,only the USLE and Dg approaches could be directly and reliably applicable to black and loess soil regions.Based on the nonlinear best ftting techniques,we improved soil erodibility prediction by combining Dg and soil or ganic matter(SOM).The NSE,R^(2)and RE values were 0.94,0.67 and 9.5%after calibrating the results independently:similar model performance was showed for the validation process.The results obtained via the proposed approach were more accurate that the former K-value predictions.Moreover,those improvements allowed us to effectively establish a regional soil erodibility map(1:250,000 scale)of water erosion areas in China.The mean K-value of Chinese water erosion regions was 0.0321(t ha h).(ha MJ mm)^(-1)with a standard deviation of 0.0107(t ha h).(ha MJ mm)^(-1);K-values present a decreasing trend from North to South in water erosion areas in China.The yield soil erodibility dataset also sa-tisfactorily corresponded to former K-values from diferent scales(local,regional,and national).展开更多
Freeze-thaw damage is one of the main threats to the long time performance of the concrete pavement in the cold regions. This project aims to evaluate the influence of the freeze-thaw damages on pavement distresses un...Freeze-thaw damage is one of the main threats to the long time performance of the concrete pavement in the cold regions. This project aims to evaluate the influence of the freeze-thaw damages on pavement distresses under different climate conditions. Based on the Long-Term Pavement Performance （LTPP） data base, the freeze-thaw damage generated by four different kinds of climate conditions are considered in this project： wet-freeze, wet-non freeze, dry- freeze and dry-non freeze. The amount of the transverse crack and the joint spalling, along with the International Roughness Index （IR/） are compared among the test sections located in these four different climate conditions. The back calculation with the Falling Weight Deflectometer （FWD） test results based on the ERES and the Estimation of Concrete Pavement Parameters （ECOPP） methods are conducted to obtain concrete slab elastic modulus and the subgrade k-value. These two parameters both decrease with service time under freeze condition. Finally, MEPDG simulation is conducted to simulate the IR/development with service year. These results showed the reasonable freeze-thaw damage development with pavement service life and under different climate conditions.展开更多
基金supported partly by the National Natural Science Foundation of China under Grant Nos.62073315 and 62350037。
文摘For k-valued(control)networks,two types of(control)invariant subspaces are proposed,namely,the state-invariant and dual-invariant subspaces,which are subspaces of the state space and dual space,respectively.Algorithms are presented to check whether a dual subspace is dual-(control)invariant,and to construct state feedback controls.The bearing space of k-valued(control)networks is introduced.Using the structure of the bearing space,the universal invariant subspace is presented,which is independent of the dynamics of particular networks.Finally,the relation between the stateinvariant subspaces and the dual-invariant subspaces of a network is investigated.A duality property shows that if a dual subspace is invariant,then its perpendicular state subspace is also invariant,and vice versa.
文摘This paper proposed a new empirical K-value equation is developed to calculate dew pressure for gas condensate reservoirs.This equation is applicable in the wide ranges of composition,temperature,and pressure by considering the effect of composition via two equations for normal boiling point and critical temperature of the mixture.The range of dew pressure,temperature,heptane plus mole fraction,methane mole fraction,N2 mole fraction,CO2 mole fraction,and H2S mole fraction are fallen into 2666.7e9655 Psia,40e350.87F,0.0021e0.213,0.3344e0.9668,0e0.4322,0e0.0864,and 0e0.942 respectively.As an important point,the proposed equation has any adjustable parameters,in addition,this equation indicates that in order to predict of dew pressure of gas condensate reservoirs,trial and error was not needed and therefore,computational speed increases beyond the accuracy.Moreover,the accuracy is validated by comparing against the experimental data of 81 gas condensate reservoirs samples from published literature and the results of Wilson,Whitson,and Ghafoori equations.Compared to the experimental data,the absolute average deviations of dew pressure calculations for the proposed equation,Wilson,Whitson,and Ghafoori were 7.6%,97.6%,99.4%,and 94.9%respectively.
基金financial support by the National Natural Science Foundation of China(No.51364032)the Inner Mongolia Natural Science Foundation(No.2022MS05028)。
文摘The spray-deposition was used to produce billets of Mg-4Al-1.5Zn-3Ca-1Nd(A alloy)and Mg-13Al-3Zn-3Ca-1Nd(B alloy),and evolution of deformation substructure and Mg_(x)Zn_(y)Ca_(z)metastable phase in fine-grained(3μm)Mg alloys was investigated by scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD),and electron backscattered diffraction(EBSD).It was found that different dislocation configurations were formed in A and B alloys.Redundant free dislocations(RFDs)and dislocation tangles were the ways to form deformation substructure in A alloy,no RFDs except dislocation tangles were found in B alloy.The interaction between nano-scale second phase particles(nano-scale C15 andβ-Mg_(17)(Al,Zn)_(12)phase)and different dislocation configurations had a significant effect on the deformation substructures formation.The mass transfer of Mg_(x)Zn_(y)Ca_(z)metastable phases and the stacking order of stacking faults were conducive to the Mg-Nd-Zn typed long period stacking ordered(LPSO)phases formation.Nano-scale C15 phases,Mg-Nd-Zn typed LPSO phases,c/a ratio,β-Mg_(17)(Al,Zn)_(12)phases were the key factors influencing the formation of textures.Different textures and grain boundary features(GB features)had a significant effect on k-value.The non-basal textures were the main factor affecting k-value in A alloy,while the high-angle grain boundary(HAGB)was the main factor affecting k-value in B alloy.
文摘This study investigates the influence of using ground palm oil fuel ash(G-POFA) from 10%-30% as cement replacement(by weight) on the cement mortar's pH under various curing conditions. These findings were supplemented by thermal gravimetric analysis(TGA). Moreover, the resistance of G-POFA blended cement mortars to water absorption and sorptivity was determined. Further, the k-value test was carried out to explain the pozzolanic and filler behavior of G-POFA and to support the results obtained from TGA. It was found that there was no significant impact of several curing conditions on the pH of mortars. The mortar with 10% G-POFA in replacement of cement(G-POFA-10) exhibited the best resistance against water absorption and sorptivity.
文摘The generalized constitutive model relating the resilient modulus (MR) of flexible pavement layer materials to stress state, adopted by the Mechanistic-Empirical Pavement Design Guide (MEPDG), contains a set of constants known as k-values (k1, k2, and k3) which are associated with the physical state of the layer materials. In Ghana, natural gravels constitute the predominant and sometimes the sole layer materials for most flexible pavements yet representative k-values of gravel materials, have not been determined to permit full application and implementation of the mechanistic-empirical design concept to pavements involving such materials. In this study, k-values characterising typical natural quartzitic gravels used for road construction in the country were derived by regression techniques from MR values determined using laboratory repeated load triaxial test. Using multiple linear regression technique, correlation relationships were then developed between the k-values and the physical properties of the gravels, namely, percentages of materials passing the 9.5 mm (P9.5) and 2.0 mm (P2.0) sieves, liquid limit (LL), maximum dry density (ρdmax), and optimum moisture content (wopt). The regression analysis returned k1 values which ranged between 441 and 958 with a mean of 516;k2 which varied between 0.0636 and 0.2168 with a mean value of 0.1216;and, k3 values which ranged between 0.1257 and 3.1590 with a mean value of 1.723. Contrary to what is mostly reported in literature, the analysis returned positive k3 values for all but one gravel material, suggesting stress hardening under octahedral shear stress for those materials. While an expanded sample base is required to fully characterize the whole gamut of natural gravels used in pavement construction in the country, this study on limited quartzitic gravel samples has given a good indication of strong linear correlations between the k-values and the index properties of the gravels, to permit estimates of the constants for such gravels be made where capability and opportunity for conducting resilient modulus tests do not exist.However, further work is recommended to fully characterise the exact nature of k3 values for quartzitic gravels in the country.
基金This study was supported by the National Natural Science Foundation of China(Grant no.41401299)the National Basic Research Program of China(Grant no.2007CB407201)the USDA-ARS Grazinglands Research Laboratory.The authors would like to thank Dr.Römkens M.J.M.,Dr.Xiangming Xiao,the editors and anonymous reviewers for their helpful comments and suggestions.
文摘Soil erodibility(K-factor)is an essential factor in soil erosion prediction and conservation practises.The major obstacles to any accurate,large-scale soil erodibility estimation are the lack of necessary data on soil characteristics and the misuse of variable K factor calculators.In this study,we assessed the per-formance of available erodibility estimators Universal Soil Loss Equation(USLE),Revised Universal Soil Loss Equation(RUSLE),Erosion Productivity Impact Calculator(EPIC)and the Geometric Mean Diameter based(Dg)model for different geographic regions based on the Chinese soil erodibility database(CSED).Results showed that previous estimators overestimated almost all K-values.Furthermore,only the USLE and Dg approaches could be directly and reliably applicable to black and loess soil regions.Based on the nonlinear best ftting techniques,we improved soil erodibility prediction by combining Dg and soil or ganic matter(SOM).The NSE,R^(2)and RE values were 0.94,0.67 and 9.5%after calibrating the results independently:similar model performance was showed for the validation process.The results obtained via the proposed approach were more accurate that the former K-value predictions.Moreover,those improvements allowed us to effectively establish a regional soil erodibility map(1:250,000 scale)of water erosion areas in China.The mean K-value of Chinese water erosion regions was 0.0321(t ha h).(ha MJ mm)^(-1)with a standard deviation of 0.0107(t ha h).(ha MJ mm)^(-1);K-values present a decreasing trend from North to South in water erosion areas in China.The yield soil erodibility dataset also sa-tisfactorily corresponded to former K-values from diferent scales(local,regional,and national).
文摘Freeze-thaw damage is one of the main threats to the long time performance of the concrete pavement in the cold regions. This project aims to evaluate the influence of the freeze-thaw damages on pavement distresses under different climate conditions. Based on the Long-Term Pavement Performance （LTPP） data base, the freeze-thaw damage generated by four different kinds of climate conditions are considered in this project： wet-freeze, wet-non freeze, dry- freeze and dry-non freeze. The amount of the transverse crack and the joint spalling, along with the International Roughness Index （IR/） are compared among the test sections located in these four different climate conditions. The back calculation with the Falling Weight Deflectometer （FWD） test results based on the ERES and the Estimation of Concrete Pavement Parameters （ECOPP） methods are conducted to obtain concrete slab elastic modulus and the subgrade k-value. These two parameters both decrease with service time under freeze condition. Finally, MEPDG simulation is conducted to simulate the IR/development with service year. These results showed the reasonable freeze-thaw damage development with pavement service life and under different climate conditions.
