This study identified castor oil and phosphate ester as effective retarders through setting time,tensile,and flexural tests,and determined their optimal dosages.The mechanism by which phosphate ester affects the setti...This study identified castor oil and phosphate ester as effective retarders through setting time,tensile,and flexural tests,and determined their optimal dosages.The mechanism by which phosphate ester affects the setting time of polyurethane was further investigated using molecular dynamics simulations.Fourier transform infrared spectroscopy was also employed to systematically study the physical and chemical interactions between phosphate esters and polyurethane materials.The results demonstrate that a 1%concentration of phosphate ester provides the most effective retarding effect with minimal impact on the strength of polyurethane.When phosphate ester is added to the B component of the two-component polyurethane system,its interaction energy with component A decreases,as do the diffusion coefficient and aggregation degree of component B on the surface of component A.This reduction in interaction slows the setting time.Additionally,the addition of phosphate ester to polyurethane leads to the disappearance or weakening of functional groups,indicating competitive interactions within the phosphate ester components that inhibit the reaction rate.展开更多
The bio-clogging using bacteria can be an eco-friendly and sustainable alternative to conventional grouting methods for seepage control.However,it remains unclear to date how the dilute concentration of bacterium and ...The bio-clogging using bacteria can be an eco-friendly and sustainable alternative to conventional grouting methods for seepage control.However,it remains unclear to date how the dilute concentration of bacterium and medium during field installation can affect the setting time of bacterium and its correlation with permeability reduction.In this study,the setting time of bacterium and its effectiveness in permeability reduction were addressed through experimental and theoretical investigations.A series of sand column was cultivated using different concentrations of Leuconostoc mesenteroides and culture medium.The distribution and composition of the bacterial product(i.e.dextran)were observed by refractometer,scanning electron microscope(SEM),and energy dispersive X-ray spectroscopy(EDS).Soil permeability was recorded using a constant head test.The results revealed that bacterium was effective to produce dextran at the setting time of about 5 d after installation.This dextran can reduce the permeability of bio-mediated soil by two orders of magnitude,even without culture medium supply.In general,the dextran production decreased proportionally with increase of bacterium and medium concentration.However,at 50%bacterium and medium concentration by weight,it still has a significant influence on permeability reduction with similar setting time,compared to 100%concentration.展开更多
In order to veritably measure the first peak of hydration heat evolution that has been illustrated important in indicating cement behavior in early hydration, an improved way of water addition into cement in isotherma...In order to veritably measure the first peak of hydration heat evolution that has been illustrated important in indicating cement behavior in early hydration, an improved way of water addition into cement in isothermally calorimetric experiment is put forward. The experimental results indicated that: the magnitude of first peak of heat evolution varies from sample to sample, correlation between heat evolution during first peak of heat evolution and initial (as well as final) setting time is unsatisfactory when samples are not classified; while groups of sample classified based on strength grade represent satisfactory correlations, which indicating the existence of close relation between hydration heat evolution in much earlier hydration age and setting property of cement in rather later age. Importance of first peak in hydration heat evolution for understanding cement setting property and reasons for sample classification are also discussed in this paper.展开更多
This paper discusses the problem of finite-time stability with respect to a closed, but not necessarily compact, invariant set for a class of nonlinear systems with discontinuous right-hand sides in the sense of the F...This paper discusses the problem of finite-time stability with respect to a closed, but not necessarily compact, invariant set for a class of nonlinear systems with discontinuous right-hand sides in the sense of the Filippov solutions. When the Lyapunov function is Lipschitz continuous and regular, the Lyapunov theorem on finite-time stability with respect to a closed invariant set is presented.展开更多
Plant aggregate-based building materials are a viable solution for reducing greenhouse gas emissions and providing good thermal and acoustic performances.In this study,the investigated lightweight mortars require a hy...Plant aggregate-based building materials are a viable solution for reducing greenhouse gas emissions and providing good thermal and acoustic performances.In this study,the investigated lightweight mortars require a hydraulic reaction.Laboratory and on-site empirical observations about plant aggregate-based materials indicate a delay in setting time and a decrease in the mechanical performances of concretes based on plant aggregates.The natural origin of plant-aggregates causes a lot of variability in their properties.Related studies have shown that the incompatibility between plant aggregates and cement is mainly caused by the dissolved and decomposed components of plant aggregates in alkaline environments.Currently,no research on the specific impact of each component on the setting time of lime-based binder exists.In this work,the impact of some soluble compounds(e.g.,sucrose,glucose,fructose,pectin)on the setting reaction of the lime matrix was studied using Vicat test,thermogravimetric analysis(TGA)and FT-IR spectroscopy.Experimental results showed that carbohydrates such as glucose and sucrose not only affect the setting time but also have a long-term impact on the carbonation of lime.The measure of the setting time by Vicat test appears as a possible indicator to predict the compatibility between the matrix and plant aggregates.展开更多
Occurrence of mafic dykes in Himalaya has been intriguing and debated since long because of its difficulty to ascent and emplacement through a thickened crust.Mafic dykes in Kumaun Lesser Himalaya(KLH)of central Indian
In this paper, we introduce the concept of (4/3)? bandwidth interval based forecasting. The historical enrollments of the university of Alabama are used to illustrate the proposed method. In this paper we use the new ...In this paper, we introduce the concept of (4/3)? bandwidth interval based forecasting. The historical enrollments of the university of Alabama are used to illustrate the proposed method. In this paper we use the new simplified technique to find the fuzzy logical relations.展开更多
The conventional time function of electromechanical relays is hard to coordinate with other relays. In order to promote the application of inverse-time overcurrent relays, a new time function for microprocessor-type r...The conventional time function of electromechanical relays is hard to coordinate with other relays. In order to promote the application of inverse-time overcurrent relays, a new time function for microprocessor-type relay is proposed. The setting of the trip time for this relay is performed by determining the shortest trip time and the longest trip time, respectively. The results of analysis show that with the new time function, the inverse-time overcurrent relay is easy to coordinate with other relays and has a comparatively shorter trip time, and that the fault happens in the protective zone.展开更多
According to the characteristics of granular soil,the technological requirements of the special-purpose cement for stabilizing granular soil are put forward to meet the demands of implementation of highway base engine...According to the characteristics of granular soil,the technological requirements of the special-purpose cement for stabilizing granular soil are put forward to meet the demands of implementation of highway base engineering.A kind of slow-setting and slight-expansive cement is developed by the cross experiment method in slag-clinker-gypsum-alkaline system,the final setting time of the cement can be prolonged to 8h,and it has properties of low dry shrinkage,high flexural strength and good crack resistance.The strength of granular soil stabilized by the cement is increased by 20% compared with that stabilized by Chinese 425-Grade slag cement.展开更多
The applicability of ultrasonic pulse velocity （UPV） method to in-situ monitor setting and hardening process of foamed concrete （FC） was systematically investigated. The UPVs of various FC pastes were automaticall...The applicability of ultrasonic pulse velocity （UPV） method to in-situ monitor setting and hardening process of foamed concrete （FC） was systematically investigated. The UPVs of various FC pastes were automatically and continuously measured by a specially designed ultrasonic monitoring apparatus （UMA）. Ultrasonic tests were performed on FC mixtures with different density （300, 500, 800 and 1 000 kg/m3）, and different fly ash contents （0%, 20%, 40% and 60%）. The influence of curing temperatures （20, 40, 60 and 80~C） was also studied. The experimental results show that three characteristic stages can be clearly identified during the setting process of an arbitrary FC paste： dormant stage, acceleration stage, and deceleration stage. Wet density, fly ash content, and curing temperature have great impact on setting behavior. A stepwise increase of the wet density results in shorter dormant stage and larger final UPV. Hydration reaction rate is obviously promoted with an increase in curing temperature. However, the addition fly ash retards the microstn,lcture formation. To aid in comparing with the ultrasonic results, the consistence spread test and Vicat needle test （VNT） were also conducted. A correlation between ultrasonic and VNT results was also established to evaluate the initial and final setting time of the FC mixtures. Finally, certain ranges of UPV with reasonable widths were suggested for the initial and final setting time, respectively.展开更多
The approach proposed in the study is based on the revision of the concept of time as a point on the real axis. It uses the concept of fuzzy time as the set of real numbers with a finite, but not equal to one, functio...The approach proposed in the study is based on the revision of the concept of time as a point on the real axis. It uses the concept of fuzzy time as the set of real numbers with a finite, but not equal to one, function of membership to the time set, i.e. the fuzzy time concept. It is postulated that in fuzzy time t the system dynamics follows from the standard variational principle of the least action and is ordinary Hamilton-Jacobi mechanics. This validates the passage to the limit from fuzzy mechanics to ordinary variational conservative mechanics. The Liouville equation is solved by the method of successive approximations in the time domain of a much larger characteristic scale of fuzziness, using interaction as a small parameter. A standard diagram technique is used. It can be shown that the defuzzification of the Liouville equation inevitably reduces the reversible part in the description to the irreversible evolutionary equation. The latter leads to the second law of thermodynamics. Generalization to the quantum case is possible, i.e. the so-called fuzzy Pauli equation can be drawn.展开更多
Concrete setting and hardening processes are the most critical phases during construction works, influencing properties of a concrete structure. The initial set is important as it provides an estimate when concrete ha...Concrete setting and hardening processes are the most critical phases during construction works, influencing properties of a concrete structure. The initial set is important as it provides an estimate when concrete has reached a point that it can no longer he vibrated without damaging concrete. The point at which final set occurs is important since it provides an estimate when the development of concrete strength and stiffness starts. In this study, experimental work is performed under laboratory conditions to indentify the setting time of cement paste using ultrasonic waves. Correlation between the ultrasonic wave parameters （speed, amplitude and energy） passing through the fresh cement paste and setting time determined using the Vicat test method is analyzed. A method of acoustic emission is also used and acoustic signals recorded in cement paste during hydration are presented.展开更多
To enhance the accuracy of intuitionistic fuzzy time series forecasting model, this paper analyses the influence of universe of discourse partition and compares with relevant literature. Traditional models usually par...To enhance the accuracy of intuitionistic fuzzy time series forecasting model, this paper analyses the influence of universe of discourse partition and compares with relevant literature. Traditional models usually partition the global universe of discourse, which is not appropriate for all objectives. For example, the universe of the secular trend model is continuously variational. In addition, most forecasting methods rely on prior information, i.e., fuzzy relationship groups (FRG). Numerous relationship groups lead to the explosive growth of relationship library in a linear model and increase the computational complexity. To overcome problems above and ascertain an appropriate order, an intuitionistic fuzzy time series forecasting model based on order decision and adaptive partition algorithm is proposed. By forecasting the vector operator matrix, the proposed model can adjust partitions and intervals adaptively. The proposed model is tested on student enrollments of Alabama dataset, typical seasonal dataset Taiwan Stock Exchange Capitalization Weighted Stock Index (TAIEX) and a secular trend dataset of total retail sales for social consumer goods in China. Experimental results illustrate the validity and applicability of the proposed method for different patterns of dataset.展开更多
基金Funded by the National Natural Science Foundation of China(No.52370128)the Fundamental Research Funds for the Central Universities(No.2572022AW54)。
文摘This study identified castor oil and phosphate ester as effective retarders through setting time,tensile,and flexural tests,and determined their optimal dosages.The mechanism by which phosphate ester affects the setting time of polyurethane was further investigated using molecular dynamics simulations.Fourier transform infrared spectroscopy was also employed to systematically study the physical and chemical interactions between phosphate esters and polyurethane materials.The results demonstrate that a 1%concentration of phosphate ester provides the most effective retarding effect with minimal impact on the strength of polyurethane.When phosphate ester is added to the B component of the two-component polyurethane system,its interaction energy with component A decreases,as do the diffusion coefficient and aggregation degree of component B on the surface of component A.This reduction in interaction slows the setting time.Additionally,the addition of phosphate ester to polyurethane leads to the disappearance or weakening of functional groups,indicating competitive interactions within the phosphate ester components that inhibit the reaction rate.
基金This work is supported by King Mongkut’s Institute of Technology Ladkrabang(Grant No.2563-02-01-014).
文摘The bio-clogging using bacteria can be an eco-friendly and sustainable alternative to conventional grouting methods for seepage control.However,it remains unclear to date how the dilute concentration of bacterium and medium during field installation can affect the setting time of bacterium and its correlation with permeability reduction.In this study,the setting time of bacterium and its effectiveness in permeability reduction were addressed through experimental and theoretical investigations.A series of sand column was cultivated using different concentrations of Leuconostoc mesenteroides and culture medium.The distribution and composition of the bacterial product(i.e.dextran)were observed by refractometer,scanning electron microscope(SEM),and energy dispersive X-ray spectroscopy(EDS).Soil permeability was recorded using a constant head test.The results revealed that bacterium was effective to produce dextran at the setting time of about 5 d after installation.This dextran can reduce the permeability of bio-mediated soil by two orders of magnitude,even without culture medium supply.In general,the dextran production decreased proportionally with increase of bacterium and medium concentration.However,at 50%bacterium and medium concentration by weight,it still has a significant influence on permeability reduction with similar setting time,compared to 100%concentration.
基金Funded by Guangxi Science Foundation(No. 0639006)
文摘In order to veritably measure the first peak of hydration heat evolution that has been illustrated important in indicating cement behavior in early hydration, an improved way of water addition into cement in isothermally calorimetric experiment is put forward. The experimental results indicated that: the magnitude of first peak of heat evolution varies from sample to sample, correlation between heat evolution during first peak of heat evolution and initial (as well as final) setting time is unsatisfactory when samples are not classified; while groups of sample classified based on strength grade represent satisfactory correlations, which indicating the existence of close relation between hydration heat evolution in much earlier hydration age and setting property of cement in rather later age. Importance of first peak in hydration heat evolution for understanding cement setting property and reasons for sample classification are also discussed in this paper.
基金supported by the Mathematical Tianyuan Foundation (No. 10826078)the National Natural Science Foundation of China (No. 60874006)
文摘This paper discusses the problem of finite-time stability with respect to a closed, but not necessarily compact, invariant set for a class of nonlinear systems with discontinuous right-hand sides in the sense of the Filippov solutions. When the Lyapunov function is Lipschitz continuous and regular, the Lyapunov theorem on finite-time stability with respect to a closed invariant set is presented.
文摘Plant aggregate-based building materials are a viable solution for reducing greenhouse gas emissions and providing good thermal and acoustic performances.In this study,the investigated lightweight mortars require a hydraulic reaction.Laboratory and on-site empirical observations about plant aggregate-based materials indicate a delay in setting time and a decrease in the mechanical performances of concretes based on plant aggregates.The natural origin of plant-aggregates causes a lot of variability in their properties.Related studies have shown that the incompatibility between plant aggregates and cement is mainly caused by the dissolved and decomposed components of plant aggregates in alkaline environments.Currently,no research on the specific impact of each component on the setting time of lime-based binder exists.In this work,the impact of some soluble compounds(e.g.,sucrose,glucose,fructose,pectin)on the setting reaction of the lime matrix was studied using Vicat test,thermogravimetric analysis(TGA)and FT-IR spectroscopy.Experimental results showed that carbohydrates such as glucose and sucrose not only affect the setting time but also have a long-term impact on the carbonation of lime.The measure of the setting time by Vicat test appears as a possible indicator to predict the compatibility between the matrix and plant aggregates.
基金supported under a DST (ESS/16/290/2006) grant sanctioned to Santosh Kumar
文摘Occurrence of mafic dykes in Himalaya has been intriguing and debated since long because of its difficulty to ascent and emplacement through a thickened crust.Mafic dykes in Kumaun Lesser Himalaya(KLH)of central Indian
文摘In this paper, we introduce the concept of (4/3)? bandwidth interval based forecasting. The historical enrollments of the university of Alabama are used to illustrate the proposed method. In this paper we use the new simplified technique to find the fuzzy logical relations.
基金TheNationalNaturalScienceFoundationofChina (No .6 9774 0 2 4 )
文摘The conventional time function of electromechanical relays is hard to coordinate with other relays. In order to promote the application of inverse-time overcurrent relays, a new time function for microprocessor-type relay is proposed. The setting of the trip time for this relay is performed by determining the shortest trip time and the longest trip time, respectively. The results of analysis show that with the new time function, the inverse-time overcurrent relay is easy to coordinate with other relays and has a comparatively shorter trip time, and that the fault happens in the protective zone.
文摘According to the characteristics of granular soil,the technological requirements of the special-purpose cement for stabilizing granular soil are put forward to meet the demands of implementation of highway base engineering.A kind of slow-setting and slight-expansive cement is developed by the cross experiment method in slag-clinker-gypsum-alkaline system,the final setting time of the cement can be prolonged to 8h,and it has properties of low dry shrinkage,high flexural strength and good crack resistance.The strength of granular soil stabilized by the cement is increased by 20% compared with that stabilized by Chinese 425-Grade slag cement.
基金Founded by the key laboratory of high performance civil engineering materials(2010CEM002)the National Natural Science Foundation of China(51178106,51138002)+1 种基金the Program for New Century Excellent Talents in University(NCET-08-0116),973 Program(2009CB623200)the Program sponsored for scientific innovation research of college graduate in Jiangsu province(CXLX_0105)
文摘The applicability of ultrasonic pulse velocity （UPV） method to in-situ monitor setting and hardening process of foamed concrete （FC） was systematically investigated. The UPVs of various FC pastes were automatically and continuously measured by a specially designed ultrasonic monitoring apparatus （UMA）. Ultrasonic tests were performed on FC mixtures with different density （300, 500, 800 and 1 000 kg/m3）, and different fly ash contents （0%, 20%, 40% and 60%）. The influence of curing temperatures （20, 40, 60 and 80~C） was also studied. The experimental results show that three characteristic stages can be clearly identified during the setting process of an arbitrary FC paste： dormant stage, acceleration stage, and deceleration stage. Wet density, fly ash content, and curing temperature have great impact on setting behavior. A stepwise increase of the wet density results in shorter dormant stage and larger final UPV. Hydration reaction rate is obviously promoted with an increase in curing temperature. However, the addition fly ash retards the microstn,lcture formation. To aid in comparing with the ultrasonic results, the consistence spread test and Vicat needle test （VNT） were also conducted. A correlation between ultrasonic and VNT results was also established to evaluate the initial and final setting time of the FC mixtures. Finally, certain ranges of UPV with reasonable widths were suggested for the initial and final setting time, respectively.
文摘The approach proposed in the study is based on the revision of the concept of time as a point on the real axis. It uses the concept of fuzzy time as the set of real numbers with a finite, but not equal to one, function of membership to the time set, i.e. the fuzzy time concept. It is postulated that in fuzzy time t the system dynamics follows from the standard variational principle of the least action and is ordinary Hamilton-Jacobi mechanics. This validates the passage to the limit from fuzzy mechanics to ordinary variational conservative mechanics. The Liouville equation is solved by the method of successive approximations in the time domain of a much larger characteristic scale of fuzziness, using interaction as a small parameter. A standard diagram technique is used. It can be shown that the defuzzification of the Liouville equation inevitably reduces the reversible part in the description to the irreversible evolutionary equation. The latter leads to the second law of thermodynamics. Generalization to the quantum case is possible, i.e. the so-called fuzzy Pauli equation can be drawn.
文摘Concrete setting and hardening processes are the most critical phases during construction works, influencing properties of a concrete structure. The initial set is important as it provides an estimate when concrete has reached a point that it can no longer he vibrated without damaging concrete. The point at which final set occurs is important since it provides an estimate when the development of concrete strength and stiffness starts. In this study, experimental work is performed under laboratory conditions to indentify the setting time of cement paste using ultrasonic waves. Correlation between the ultrasonic wave parameters （speed, amplitude and energy） passing through the fresh cement paste and setting time determined using the Vicat test method is analyzed. A method of acoustic emission is also used and acoustic signals recorded in cement paste during hydration are presented.
基金supported by the National Natural Science Foundation of China(61309022)
文摘To enhance the accuracy of intuitionistic fuzzy time series forecasting model, this paper analyses the influence of universe of discourse partition and compares with relevant literature. Traditional models usually partition the global universe of discourse, which is not appropriate for all objectives. For example, the universe of the secular trend model is continuously variational. In addition, most forecasting methods rely on prior information, i.e., fuzzy relationship groups (FRG). Numerous relationship groups lead to the explosive growth of relationship library in a linear model and increase the computational complexity. To overcome problems above and ascertain an appropriate order, an intuitionistic fuzzy time series forecasting model based on order decision and adaptive partition algorithm is proposed. By forecasting the vector operator matrix, the proposed model can adjust partitions and intervals adaptively. The proposed model is tested on student enrollments of Alabama dataset, typical seasonal dataset Taiwan Stock Exchange Capitalization Weighted Stock Index (TAIEX) and a secular trend dataset of total retail sales for social consumer goods in China. Experimental results illustrate the validity and applicability of the proposed method for different patterns of dataset.
