This study investigates the impacts of mixing time,execution procedure,cement dosage(α),and total water-to-cement ratio(W_(Total)/C)on the mixing energy(E)of deep soil mixing(DSM)columns and how E influences the stre...This study investigates the impacts of mixing time,execution procedure,cement dosage(α),and total water-to-cement ratio(W_(Total)/C)on the mixing energy(E)of deep soil mixing(DSM)columns and how E influences the strength of treated sand.Columns with a diameter of 7.5 cm were constructed using three mixing times(130,190,and 250 s),two execution procedures(normal and zigzag),threeαvalues(300,400,and 500 kg/m^(3)),and three W_(Total)/C ratios(2.5,3.0,and 3.5).For comparison,equivalent laboratory samples were also examined.Results revealed that increasing the mixing time andα,adopting the zigzag execution procedure,and reducing the W_(Total)/C ratio increase E.Outcomes indicated that an increase in E from 0.49-0.70 kJ to 0.70-0.90 kJ,0.90-1.10 kJ,and 1.10-1.40 kJ improves the unconfined compressive strength(UCS)of columns on average by 66%,124%,and 179%,respectively,and the secant modulus by 61%,110%,and 152%.Average strain at maximum stress also rises from 0.68%to 0.75%,0.81%,and 0.84%,respectively.The study identified a threshold in the direct relationship between E and the strength ratio(λ),beyond whichλdid not increase significantly with further increases in E.Additionally,at low and high E levels,DSM samples mainly failed by crushing and cracking modes,respectively.In DSM columns withα=500 kg/m^(3)and W_(Total)/C=2.5,increasing average E from 0.77 kJ to 0.95 kJ,1.08 kJ,and 1.28 kJ resulted in a reduction of coefficients of variation of UCS from 30.4%to 27.8%,24.5%,and 21.1%,respectively.展开更多
Reachability testing is an important approach to testing concurrent programs. It generates and exercises syn- chronization sequences automatically and on-the-fly without saving any test history. Existing reach, abilit...Reachability testing is an important approach to testing concurrent programs. It generates and exercises syn- chronization sequences automatically and on-the-fly without saving any test history. Existing reach, ability testing can be classified into exhaustive and t-way testing. Exhaustive testing is impractical in many cases whilie t-way testing may decrease the capability of fault detection in some cases. In this paper, we present a variable strengda reachability testing strategy, which adopts the dynamic framework of reachability testing and uses a variable strength combinatorial strategy. Different parameter groups are provided with different covering strength. Variable strength testing covers no t-way combinations but the necessary combinations of parameters having mutual interactions in a concurrent program. It is more reasonable than t-way testing because uniform interactions between parameters do not often exist in concurrent systems. We propose a merging algorithm that implements the variable strength combinatorial testing strategy and conduct our experiment on several concurrent programs. The experimental results indicate that our variable strength reachability testing reaches a good tradeoff between the effectiveness and efficiency. It can keep the same capability of fault detection as exhaustive reachability testing while substantially reducing the number of synchronization sequences and decreasing the execution time in most cases.展开更多
Covering arrays(CA)of strength t,mixed level or fixed level,have been applied to software testing to aim for a minimum coverage of all t-way interactions among components.The size of CA increases with the increase of ...Covering arrays(CA)of strength t,mixed level or fixed level,have been applied to software testing to aim for a minimum coverage of all t-way interactions among components.The size of CA increases with the increase of strength interaction t,which increase the cost of software testing.However,it is quite often that some certain components have strong interactions,while others may have fewer or none.Hence,a better way to test software system is to identify the subsets of components which are involved in stronger interactions and apply high strength interaction testing only on these subsets.For this,in 2003,the notion of variable strength covering arrays was proposed by Cohen et al.to satisfy the need to vary the size of t in an individual test suite.In this paper,an effective deterministic construction of variable strength covering arrays is presented.Based on the construction,some series of variable strength covering arrays are then obtained,which are all optimal in the sense of their sizes.In the procedure,two classes of new difference matrices of strength 3 are also mentioned.展开更多
We perform a scanning tunneling microscopy and spectroscopy study on the electronic structures of √3×√3- silicene on Ag（111）. It is found that the coupling strength of √3×√3-silicene with the Ag-（111...We perform a scanning tunneling microscopy and spectroscopy study on the electronic structures of √3×√3- silicene on Ag（111）. It is found that the coupling strength of √3×√3-silicene with the Ag-（111） substrate is variable in different regions, giving rise to notable effects in experiments. This evidence of decoupling or variable interaction of silicene with the substrate is helpful to in-depth understanding of the structure and clectronic properties of silieene.展开更多
The fractured rock mass inherently exhibits uncertainty due to the presence of pre-existing discontinuities.In this study,a particle-based model incorporating the discrete fracture network(DFN)to elucidate the dynamic...The fractured rock mass inherently exhibits uncertainty due to the presence of pre-existing discontinuities.In this study,a particle-based model incorporating the discrete fracture network(DFN)to elucidate the dynamic tensile responses and asso-ciated uncertainty of rock mass.At first,the particle-based model was used synthesize the intact rock and split Hopkinson pressure bar(SHPB)system,while the fractures were represented using the smooth fracture model(SJM).Subsequently,the samples of the fractured rock mass with varying joint geometrical configurations were conducted the dynamic tensile test using the numerical SHPB system.The simulated results demonstrate a gradual decrease in dynamic tensile strength(TS)with increasing fracture intensity and fracture length,which can be effectively described by nonlinear exponential func-tions.Additionally,the fracture orientation significantly influences the dynamic TS,however,the anisotropic characteristics gradually diminish as the deviation angle approaches 90°.Furthermore,as fracture intensity and fracture length increase,the dynamic TS variability also rises steadily.However,no noticeable pattern is seen when considering cases with varying fracture orientations.When subjected to SHPB loading,the fractured rock mass primarily exhibits a combined tensile-shear failure mode,contrasting with the pure tensile failure mode exhibited by the intact rock.These findings contribute signifi-cantly to comprehending the dynamic tensile responses of the fractured rock mass and can further enhance the stability analysis of in-situ rock engineering.展开更多
Accurate estimation of Weibull parameters is an important issue for the characterization of the strength variability of brittle ceramics with Weibull statistics.In this paper,a simple method was established for the de...Accurate estimation of Weibull parameters is an important issue for the characterization of the strength variability of brittle ceramics with Weibull statistics.In this paper,a simple method was established for the determination of the Weibull parameters,Weibull modulus m and scale parameter σ0,based on Monte Carlo simulation.It was shown that an unbiased estimation for Weibull modulus can be yielded directly from the coefficient of variation of the considered strength sample.Furthermore,using the yielded Weibull estimator and the mean value of the strength in the considered sample,the scale parameter σ0 can also be estimated accurately.展开更多
文摘This study investigates the impacts of mixing time,execution procedure,cement dosage(α),and total water-to-cement ratio(W_(Total)/C)on the mixing energy(E)of deep soil mixing(DSM)columns and how E influences the strength of treated sand.Columns with a diameter of 7.5 cm were constructed using three mixing times(130,190,and 250 s),two execution procedures(normal and zigzag),threeαvalues(300,400,and 500 kg/m^(3)),and three W_(Total)/C ratios(2.5,3.0,and 3.5).For comparison,equivalent laboratory samples were also examined.Results revealed that increasing the mixing time andα,adopting the zigzag execution procedure,and reducing the W_(Total)/C ratio increase E.Outcomes indicated that an increase in E from 0.49-0.70 kJ to 0.70-0.90 kJ,0.90-1.10 kJ,and 1.10-1.40 kJ improves the unconfined compressive strength(UCS)of columns on average by 66%,124%,and 179%,respectively,and the secant modulus by 61%,110%,and 152%.Average strain at maximum stress also rises from 0.68%to 0.75%,0.81%,and 0.84%,respectively.The study identified a threshold in the direct relationship between E and the strength ratio(λ),beyond whichλdid not increase significantly with further increases in E.Additionally,at low and high E levels,DSM samples mainly failed by crushing and cracking modes,respectively.In DSM columns withα=500 kg/m^(3)and W_(Total)/C=2.5,increasing average E from 0.77 kJ to 0.95 kJ,1.08 kJ,and 1.28 kJ resulted in a reduction of coefficients of variation of UCS from 30.4%to 27.8%,24.5%,and 21.1%,respectively.
文摘Reachability testing is an important approach to testing concurrent programs. It generates and exercises syn- chronization sequences automatically and on-the-fly without saving any test history. Existing reach, ability testing can be classified into exhaustive and t-way testing. Exhaustive testing is impractical in many cases whilie t-way testing may decrease the capability of fault detection in some cases. In this paper, we present a variable strengda reachability testing strategy, which adopts the dynamic framework of reachability testing and uses a variable strength combinatorial strategy. Different parameter groups are provided with different covering strength. Variable strength testing covers no t-way combinations but the necessary combinations of parameters having mutual interactions in a concurrent program. It is more reasonable than t-way testing because uniform interactions between parameters do not often exist in concurrent systems. We propose a merging algorithm that implements the variable strength combinatorial testing strategy and conduct our experiment on several concurrent programs. The experimental results indicate that our variable strength reachability testing reaches a good tradeoff between the effectiveness and efficiency. It can keep the same capability of fault detection as exhaustive reachability testing while substantially reducing the number of synchronization sequences and decreasing the execution time in most cases.
基金supported by the National Natural Science Foundation of China(Nos.11301342,61972241)the Natural Science Foundation of Shanghai(No.17ZR1419900)President Foundation of Shanghai Ocean University(NO.A2-2006-20-200212)。
文摘Covering arrays(CA)of strength t,mixed level or fixed level,have been applied to software testing to aim for a minimum coverage of all t-way interactions among components.The size of CA increases with the increase of strength interaction t,which increase the cost of software testing.However,it is quite often that some certain components have strong interactions,while others may have fewer or none.Hence,a better way to test software system is to identify the subsets of components which are involved in stronger interactions and apply high strength interaction testing only on these subsets.For this,in 2003,the notion of variable strength covering arrays was proposed by Cohen et al.to satisfy the need to vary the size of t in an individual test suite.In this paper,an effective deterministic construction of variable strength covering arrays is presented.Based on the construction,some series of variable strength covering arrays are then obtained,which are all optimal in the sense of their sizes.In the procedure,two classes of new difference matrices of strength 3 are also mentioned.
基金Supported by the National Basic Research Program of China under Grant Nos 2012CB921703 and 2013CB921702the National Natural Science Foundation of China under Grant Nos 11334011 and 91121003the Strategic Priority Research Program of the Chinese Academy of Sciences under Grant No XDB07000000
文摘We perform a scanning tunneling microscopy and spectroscopy study on the electronic structures of √3×√3- silicene on Ag（111）. It is found that the coupling strength of √3×√3-silicene with the Ag-（111） substrate is variable in different regions, giving rise to notable effects in experiments. This evidence of decoupling or variable interaction of silicene with the substrate is helpful to in-depth understanding of the structure and clectronic properties of silieene.
基金supported by the Program for Guangdong Introducing Innovative and Entrepreneurial Teams(2019ZT08G315)the National Natural Science Foundation of China(52304091,52004162 and 52274089)+1 种基金the Research Project of Education Department of Hunan Province(22B0427)the China postdoctoral science foundation(2023M741047).
文摘The fractured rock mass inherently exhibits uncertainty due to the presence of pre-existing discontinuities.In this study,a particle-based model incorporating the discrete fracture network(DFN)to elucidate the dynamic tensile responses and asso-ciated uncertainty of rock mass.At first,the particle-based model was used synthesize the intact rock and split Hopkinson pressure bar(SHPB)system,while the fractures were represented using the smooth fracture model(SJM).Subsequently,the samples of the fractured rock mass with varying joint geometrical configurations were conducted the dynamic tensile test using the numerical SHPB system.The simulated results demonstrate a gradual decrease in dynamic tensile strength(TS)with increasing fracture intensity and fracture length,which can be effectively described by nonlinear exponential func-tions.Additionally,the fracture orientation significantly influences the dynamic TS,however,the anisotropic characteristics gradually diminish as the deviation angle approaches 90°.Furthermore,as fracture intensity and fracture length increase,the dynamic TS variability also rises steadily.However,no noticeable pattern is seen when considering cases with varying fracture orientations.When subjected to SHPB loading,the fractured rock mass primarily exhibits a combined tensile-shear failure mode,contrasting with the pure tensile failure mode exhibited by the intact rock.These findings contribute signifi-cantly to comprehending the dynamic tensile responses of the fractured rock mass and can further enhance the stability analysis of in-situ rock engineering.
文摘Accurate estimation of Weibull parameters is an important issue for the characterization of the strength variability of brittle ceramics with Weibull statistics.In this paper,a simple method was established for the determination of the Weibull parameters,Weibull modulus m and scale parameter σ0,based on Monte Carlo simulation.It was shown that an unbiased estimation for Weibull modulus can be yielded directly from the coefficient of variation of the considered strength sample.Furthermore,using the yielded Weibull estimator and the mean value of the strength in the considered sample,the scale parameter σ0 can also be estimated accurately.
