In order to improve the rutting resistance of asphalt mixtures in the middle course to reduce the rutting of asphalt pavement, the influence of different types of gradation with their own optimal asphaltaggregate rati...In order to improve the rutting resistance of asphalt mixtures in the middle course to reduce the rutting of asphalt pavement, the influence of different types of gradation with their own optimal asphaltaggregate ratios is analyzed. Some investigations are made out on the mixture in the middle course through the modified wheel tracking test in air bath and the Hamburg wheel tracking test （HWTT） in water bath, and the results of which are compared with the corresponding research in Germany. Results show that the Sup20 and the modified AC-20I have better performance than that of AC-20I under the same test conditions. In addition, the high-quality bitumen and hard aggregate can improve the rutting performance of the mixture in water-submerged conditions. The selection of modified asphalt, hard aggregate and a reasonable gradation are essential to the improvement of the rutting resistance of the mixtures used in the middle course.展开更多
In order to investigate the high-temperature performances of the asphalt pavement hot-applied sealant, as well as to reduce failures of the sealant pullout, the softening point test and the flow test（two existing met...In order to investigate the high-temperature performances of the asphalt pavement hot-applied sealant, as well as to reduce failures of the sealant pullout, the softening point test and the flow test（two existing methods for evaluating high-temperature performances） were conducted. It was found that both tests could not accurately reflect the adhesion performances of the sealant at high temperatures. For this purpose, the adhesion test for PSAT（pressure sensitive adhesive tape） has been taken as a reference to develop a device that is suitable for evaluating the adhesion performances, by modifying relevant test parameters according to the road conditions at high temperatures. Thirteen common sealants were tested in the modified adhesion test, softening point test and f low test. The experimental results show that no significant correlation（p〉0.05） exists between the adhesion value, softening point, adhesion value and flow value; while a significant correlation（p〈0.05） exists between the softening point and flow value. The modified adhesion test is efficient in distinguishing the hightemperature adhesion performances of different sealants, and can be used as a standard method for evaluating such performances.展开更多
From the mathematical principles, the generalized potential theory can be employed to create constitutive model of geomaterial directly. The similar Cam-clay model, which is created based on the generalized potential ...From the mathematical principles, the generalized potential theory can be employed to create constitutive model of geomaterial directly. The similar Cam-clay model, which is created based on the generalized potential theory, has less assumptions,clearer mathematical basis, and better computational accuracy. Theoretically, it is more scientific than the traditional Cam-clay models. The particle flow code PFC3 D was used to make numerical tests to verify the rationality and practicality of the similar Cam-clay model. The verification process was as follows: 1) creating the soil sample for numerical test in PFC3 D, and then simulating the conventional triaxial compression test, isotropic compression test, and isotropic unloading test by PFC3D; 2)determining the parameters of the similar Cam-clay model from the results of above tests; 3) predicting the sample's behavior in triaxial tests under different stress paths by the similar Cam-clay model, and comparing the predicting results with predictions by the Cam-clay model and the modified Cam-clay model. The analysis results show that the similar Cam-clay model has relatively high prediction accuracy, as well as good practical value.展开更多
Crack initiation and propagation have been investigated under tensile and shear loading in ceramically and carbon bonded refractories.A wedge splitting test procedure and a modified shear test have been applied.Test r...Crack initiation and propagation have been investigated under tensile and shear loading in ceramically and carbon bonded refractories.A wedge splitting test procedure and a modified shear test have been applied.Test results have been used for material characterization especially with respect to brittleness.Furthermore a microscopic fractographic test procedure was developed and applied on fractured test specimens.In order to explain brittleness dependence on structure properties correlation of fractographic and fracture mechanical results has been evaluated.Frequently brittleness reduction is achieved by a lower amount of transgranular crack propagation associated with a strength decrease while maintaining specific fracture energy unchanged.Deviations from pure linear fracture mechanics increase with decreasing brittleness and contribute to specific fracture energy.Shear specimens may show two generations of cracks,a first one initiated by tensile loads （stable propagation） and a second one by shear loads （unstable propagation）.展开更多
This paper investigates the asymptotic properties of the modified likelihood ratio statistic for testing homogeneity in bivariate normal mixture models with an unknown structural parameter. It is shown that the modifi...This paper investigates the asymptotic properties of the modified likelihood ratio statistic for testing homogeneity in bivariate normal mixture models with an unknown structural parameter. It is shown that the modified likelihood ratio statistic has χ22 null limiting distribution.展开更多
The thermomechanical modelling method is becoming an important tool nowadays for the refractory researchers, suppliers and end-users. On one hand, applications focus on the post-mortem thermomechanical analysis to int...The thermomechanical modelling method is becoming an important tool nowadays for the refractory researchers, suppliers and end-users. On one hand, applications focus on the post-mortem thermomechanical analysis to interpret the occurred fitiluw phenomena of refractories in service. On the other hand, a priori investigation is very helpful for the design of refractory lining con- cepts before putting them into effect; as a result it will minimize the probability of refractory lining premature .failure and save costs for the refractory suppliers as well as for the end-users. For both investigation routines, suitable material constitutive models and testing approa- ches are of relevance. Existing material constitutive mod- els often used for refractories are the fictitious crack model acting for tensile failure, the Mohr - Coulomb or Drucker- Prager model describing shear failure, and the Norton - Bailey model representing creep. To charac- terize tbe tensile and shear fitilure of refractories at room temperatare and elevated temperatures, a wedge splitting test and a modified shear test can be applied, respectively. The creep behavior and corresponding creep parameters of refractories can be determined with an appropriate creep testing device at elevated loads. The proper appli- cation of material constitutive models and testing approa-ches allows for improving the thermo-mechanical modelling and the optimizatian of the lining design.展开更多
Warm mix asphalt （WMA} is a new technology which asphalt mix is produced and placed at normal temperature. It has advantages including low cost, environmentally friendly, haul-convenience, and so on. WMA has been wid...Warm mix asphalt （WMA} is a new technology which asphalt mix is produced and placed at normal temperature. It has advantages including low cost, environmentally friendly, haul-convenience, and so on. WMA has been widely tested and applied in the USA in the last decade, but it has just started in China. Recently, a new WMA using a new plastic- macromolecule-normal temperature additive, which was called ＂SMC＂ by the production company, was introduced as asphalt modifier. Based on discussing the strength forming process of this new WMA with SMC, a series of laboratory tests, including Marshall stability test （MST）, boiling test （BT）, modified immersion Marshall test （MIMT）, freeze-thaw split- ring test （FTST）, rutting test （RT）, low-temperature bending test （LTBT）, and abrasion loss test （ALT）, were conducted in this study to assess the performance of this WMA and the capability of applying it on low volume roads in China. SMC modified asphalt mixed under normal temperature is used in testing samples. It was found that this WMA product exhibited merits on its strength, which was about 6.7 kN bigger than the requirement of 5.0 kN in the JTG F40-2004, on high-temperature stability, which is about 1100 times/ram greater than the requirement of 600-1000 times/mm in the ）TG F40-2004, and on its storage stability. Based on these indicators, it is recommended that this product could be used for low volume low class roads construction. However, due to the relatively lower water resistance and low-temperature cracking resistance, this product is suggested to be applied first in the areas with warm weather and little rainfall. In order to improve the perfor- mance of this WMA with SMC, further research on this SMC asphalt modifier should be continued.展开更多
There has been a rapid progress in designing valid and effective statisticalhypothesis tests for the order of a finite mixture model.In particular,EM-test forthe order of the mixture model has been developed and found...There has been a rapid progress in designing valid and effective statisticalhypothesis tests for the order of a finite mixture model.In particular,EM-test forthe order of the mixture model has been developed and found effective when thecomponent distribution contains a single parameter.EM-test is found to be particularlyeffective and elegant for the order of normal mixture in both mean and variance.Theidea behind EM-test has been found widely applicable.In this paper,we investigatethe use of EM-test for the order of a finite normal mixture in the mean parameterwith equal but unknown component variances.We show that for any positive integermo≥2,the limiting distribution of the EM-test for the order of mo against the higherorder alternative is x^(5)_(m0-1).A genetic example is used to illustrate the application ofthe EM-test.展开更多
Finite mixture models are widely used in scientific investigations.Due to their non-regularity,there are many technical challenges concerning inference problems on various aspects of the finitemixture models.After dec...Finite mixture models are widely used in scientific investigations.Due to their non-regularity,there are many technical challenges concerning inference problems on various aspects of the finitemixture models.After decades of effort by statisticians,substantial progresses are recorded recently in characterising large sample properties of some classical inference methods when applied to finitemixture models,providing effective numerical solutions formixture model-based data analysis,and the invention of novel inference approaches.This paper aims to provide a comprehensive summary on large sample properties of some classical statistical methods and recently developed modified likelihood ratio test and EM-test for the order of the finite mixture model.The presentation de-emphasises the rigour in order to gain some insights behind some complex technical issues.The paper wishes to recommend the EM-test as the most promising approach to data analysis problems from all models with mixture structures.展开更多
文摘In order to improve the rutting resistance of asphalt mixtures in the middle course to reduce the rutting of asphalt pavement, the influence of different types of gradation with their own optimal asphaltaggregate ratios is analyzed. Some investigations are made out on the mixture in the middle course through the modified wheel tracking test in air bath and the Hamburg wheel tracking test （HWTT） in water bath, and the results of which are compared with the corresponding research in Germany. Results show that the Sup20 and the modified AC-20I have better performance than that of AC-20I under the same test conditions. In addition, the high-quality bitumen and hard aggregate can improve the rutting performance of the mixture in water-submerged conditions. The selection of modified asphalt, hard aggregate and a reasonable gradation are essential to the improvement of the rutting resistance of the mixtures used in the middle course.
基金Funded by the National Natural Science Foundation of China(Nos.51378242 and 51008146)the Transportation Industry Science and Technology Project of Beijing(No.kj2013-2-14)
文摘In order to investigate the high-temperature performances of the asphalt pavement hot-applied sealant, as well as to reduce failures of the sealant pullout, the softening point test and the flow test（two existing methods for evaluating high-temperature performances） were conducted. It was found that both tests could not accurately reflect the adhesion performances of the sealant at high temperatures. For this purpose, the adhesion test for PSAT（pressure sensitive adhesive tape） has been taken as a reference to develop a device that is suitable for evaluating the adhesion performances, by modifying relevant test parameters according to the road conditions at high temperatures. Thirteen common sealants were tested in the modified adhesion test, softening point test and f low test. The experimental results show that no significant correlation（p〉0.05） exists between the adhesion value, softening point, adhesion value and flow value; while a significant correlation（p〈0.05） exists between the softening point and flow value. The modified adhesion test is efficient in distinguishing the hightemperature adhesion performances of different sealants, and can be used as a standard method for evaluating such performances.
基金Projects(51378131,51378403)supported by the National Natural Science Foundation of ChinaProject(2012210020203)supported by the Fundamental Research Funds for the Central Universities,China
文摘From the mathematical principles, the generalized potential theory can be employed to create constitutive model of geomaterial directly. The similar Cam-clay model, which is created based on the generalized potential theory, has less assumptions,clearer mathematical basis, and better computational accuracy. Theoretically, it is more scientific than the traditional Cam-clay models. The particle flow code PFC3 D was used to make numerical tests to verify the rationality and practicality of the similar Cam-clay model. The verification process was as follows: 1) creating the soil sample for numerical test in PFC3 D, and then simulating the conventional triaxial compression test, isotropic compression test, and isotropic unloading test by PFC3D; 2)determining the parameters of the similar Cam-clay model from the results of above tests; 3) predicting the sample's behavior in triaxial tests under different stress paths by the similar Cam-clay model, and comparing the predicting results with predictions by the Cam-clay model and the modified Cam-clay model. The analysis results show that the similar Cam-clay model has relatively high prediction accuracy, as well as good practical value.
文摘Crack initiation and propagation have been investigated under tensile and shear loading in ceramically and carbon bonded refractories.A wedge splitting test procedure and a modified shear test have been applied.Test results have been used for material characterization especially with respect to brittleness.Furthermore a microscopic fractographic test procedure was developed and applied on fractured test specimens.In order to explain brittleness dependence on structure properties correlation of fractographic and fracture mechanical results has been evaluated.Frequently brittleness reduction is achieved by a lower amount of transgranular crack propagation associated with a strength decrease while maintaining specific fracture energy unchanged.Deviations from pure linear fracture mechanics increase with decreasing brittleness and contribute to specific fracture energy.Shear specimens may show two generations of cracks,a first one initiated by tensile loads （stable propagation） and a second one by shear loads （unstable propagation）.
基金the National Natural Science Foundation of China (Grant No. 10661003)the Natural Science Foundation of Guangxi (Grant No. 0728092) SRF for ROCS, SEM (Grant No. [2004]527)
文摘This paper investigates the asymptotic properties of the modified likelihood ratio statistic for testing homogeneity in bivariate normal mixture models with an unknown structural parameter. It is shown that the modified likelihood ratio statistic has χ22 null limiting distribution.
基金Financial support by the Austrian Federal Government ( in particular from Bundesministerium für Verkehr,Innovation und Technologie and Bundesministerium für Wissenschaft, Forschung und Wirtschaft ) represented by sterreichische Forschungsf 9rderungs - gesellschaft mb H
文摘The thermomechanical modelling method is becoming an important tool nowadays for the refractory researchers, suppliers and end-users. On one hand, applications focus on the post-mortem thermomechanical analysis to interpret the occurred fitiluw phenomena of refractories in service. On the other hand, a priori investigation is very helpful for the design of refractory lining con- cepts before putting them into effect; as a result it will minimize the probability of refractory lining premature .failure and save costs for the refractory suppliers as well as for the end-users. For both investigation routines, suitable material constitutive models and testing approa- ches are of relevance. Existing material constitutive mod- els often used for refractories are the fictitious crack model acting for tensile failure, the Mohr - Coulomb or Drucker- Prager model describing shear failure, and the Norton - Bailey model representing creep. To charac- terize tbe tensile and shear fitilure of refractories at room temperatare and elevated temperatures, a wedge splitting test and a modified shear test can be applied, respectively. The creep behavior and corresponding creep parameters of refractories can be determined with an appropriate creep testing device at elevated loads. The proper appli- cation of material constitutive models and testing approa-ches allows for improving the thermo-mechanical modelling and the optimizatian of the lining design.
基金the financial support of National Natural Science Foundation of China(51378438)National 973 Program(2013CB036204)specific research funding from Ministry of Education(SWJTU12ZT05)
文摘Warm mix asphalt （WMA} is a new technology which asphalt mix is produced and placed at normal temperature. It has advantages including low cost, environmentally friendly, haul-convenience, and so on. WMA has been widely tested and applied in the USA in the last decade, but it has just started in China. Recently, a new WMA using a new plastic- macromolecule-normal temperature additive, which was called ＂SMC＂ by the production company, was introduced as asphalt modifier. Based on discussing the strength forming process of this new WMA with SMC, a series of laboratory tests, including Marshall stability test （MST）, boiling test （BT）, modified immersion Marshall test （MIMT）, freeze-thaw split- ring test （FTST）, rutting test （RT）, low-temperature bending test （LTBT）, and abrasion loss test （ALT）, were conducted in this study to assess the performance of this WMA and the capability of applying it on low volume roads in China. SMC modified asphalt mixed under normal temperature is used in testing samples. It was found that this WMA product exhibited merits on its strength, which was about 6.7 kN bigger than the requirement of 5.0 kN in the JTG F40-2004, on high-temperature stability, which is about 1100 times/ram greater than the requirement of 600-1000 times/mm in the ）TG F40-2004, and on its storage stability. Based on these indicators, it is recommended that this product could be used for low volume low class roads construction. However, due to the relatively lower water resistance and low-temperature cracking resistance, this product is suggested to be applied first in the areas with warm weather and little rainfall. In order to improve the perfor- mance of this WMA with SMC, further research on this SMC asphalt modifier should be continued.
文摘There has been a rapid progress in designing valid and effective statisticalhypothesis tests for the order of a finite mixture model.In particular,EM-test forthe order of the mixture model has been developed and found effective when thecomponent distribution contains a single parameter.EM-test is found to be particularlyeffective and elegant for the order of normal mixture in both mean and variance.Theidea behind EM-test has been found widely applicable.In this paper,we investigatethe use of EM-test for the order of a finite normal mixture in the mean parameterwith equal but unknown component variances.We show that for any positive integermo≥2,the limiting distribution of the EM-test for the order of mo against the higherorder alternative is x^(5)_(m0-1).A genetic example is used to illustrate the application ofthe EM-test.
基金The author likes to thank research fundings from the National Natural Science Foundation of China(Grant No 11690011)theNatural Science and Engineering Research Council(RGPIN-2014-03743).
文摘Finite mixture models are widely used in scientific investigations.Due to their non-regularity,there are many technical challenges concerning inference problems on various aspects of the finitemixture models.After decades of effort by statisticians,substantial progresses are recorded recently in characterising large sample properties of some classical inference methods when applied to finitemixture models,providing effective numerical solutions formixture model-based data analysis,and the invention of novel inference approaches.This paper aims to provide a comprehensive summary on large sample properties of some classical statistical methods and recently developed modified likelihood ratio test and EM-test for the order of the finite mixture model.The presentation de-emphasises the rigour in order to gain some insights behind some complex technical issues.The paper wishes to recommend the EM-test as the most promising approach to data analysis problems from all models with mixture structures.
