As important methods to guide the field soil compaction,the standard and modified Proctor tests for laboratory compaction have remained unchanged for decades,which should be improved to better understand the compactio...As important methods to guide the field soil compaction,the standard and modified Proctor tests for laboratory compaction have remained unchanged for decades,which should be improved to better understand the compaction process and the properties of soils.In this study,an accelerometer was installed on a Marshall impact compactor to capture the dynamic response of three types of soils during compaction.The experimental test results indicated that the acceleration curve for each blow gradually evolved to a stable pattern following the progress of compaction,and the impact and gyratory locking points were linearly related with coefficient of determination R2equal to 0.59.The impact compaction curve could be further constructed by filtering the structural resonance,which can be used to quantify the compactability of soil materials.Although each type of soil had a unique set of compaction curves,the slope and value of compaction curve altered accordingly as the moisture content changed for the same soil.In addition,the average acceleration value at the final compaction stage could serve as the target value of soil stiffness.展开更多
The transient impulse features caused by rolling bearing faults are often present in the resonance frequency band which is closely related to the dynamic characteristics of the machine structure.Informative frequency ...The transient impulse features caused by rolling bearing faults are often present in the resonance frequency band which is closely related to the dynamic characteristics of the machine structure.Informative frequency band identification is a crucial prerequisite for envelope analysis and thereby accurate fault diagnosis of rolling bearings.In this paper,based on the ratio of quasi-arithmetic means and Gini index,improved Gini indices(IGIs)are proposed to quantify the transient impulse features of a signal,and their effectiveness and advantages in sparse quantification are confirmed by simulation analysis and comparisons with traditional sparsity measures.Furthermore,an IGI-based envelope analysis method named IGIgram is developed for fault diagnosis of rolling bearings.In the new method,an IGI-based indicator is constructed to evaluate the impulsiveness and cyclostationarity of the narrow-band filtered signal simultaneously,and then a frequency band with abundant fault information is adaptively determined for extracting bearing fault features.The performance of the IGIgram method is verified on the simulation signal and railway bearing experimental signals and compared with typical sparsity measures-based envelope analysis methods and log-cycligram.The results demonstrate that the proposed IGIs are efficient in quantifying bearing fault-induced transient features and the IGIgram method with appropriate power exponent can effectively achieve the diagnostics of different axle-box bearing faults.展开更多
Intelligent compaction （IC） is a relatively new technology for asphalt paving industry. The present study evaluated the effectiveness and potential issues of the IC technology for flexible pavement resurfacing const...Intelligent compaction （IC） is a relatively new technology for asphalt paving industry. The present study evaluated the effectiveness and potential issues of the IC technology for flexible pavement resurfacing construction using two field projects. In the first project, a geostatistical semivariogram model was established and the parameters derived from it were compared with univariate statistical parameters for the Compaction Meter Value （CMV） data. Further analyses illustrated the effect of temperature on the CMV value and compaction uniformity. In the second project, a multivariate analysis was performed between in situ tests and IC data. The possibility of combining various IC data to predict the asphalt layer density and improve the current quality control and assurance system was discussed.展开更多
文摘As important methods to guide the field soil compaction,the standard and modified Proctor tests for laboratory compaction have remained unchanged for decades,which should be improved to better understand the compaction process and the properties of soils.In this study,an accelerometer was installed on a Marshall impact compactor to capture the dynamic response of three types of soils during compaction.The experimental test results indicated that the acceleration curve for each blow gradually evolved to a stable pattern following the progress of compaction,and the impact and gyratory locking points were linearly related with coefficient of determination R2equal to 0.59.The impact compaction curve could be further constructed by filtering the structural resonance,which can be used to quantify the compactability of soil materials.Although each type of soil had a unique set of compaction curves,the slope and value of compaction curve altered accordingly as the moisture content changed for the same soil.In addition,the average acceleration value at the final compaction stage could serve as the target value of soil stiffness.
基金supported by the National Key Research and Development Program of China (Grant No.2019YFB1405401)the National Natural Science Foundation of China (Grant No.P110520G02004)the China Scholarship Council (Grant No.202107000033),which are highly appreciated by the authors。
文摘The transient impulse features caused by rolling bearing faults are often present in the resonance frequency band which is closely related to the dynamic characteristics of the machine structure.Informative frequency band identification is a crucial prerequisite for envelope analysis and thereby accurate fault diagnosis of rolling bearings.In this paper,based on the ratio of quasi-arithmetic means and Gini index,improved Gini indices(IGIs)are proposed to quantify the transient impulse features of a signal,and their effectiveness and advantages in sparse quantification are confirmed by simulation analysis and comparisons with traditional sparsity measures.Furthermore,an IGI-based envelope analysis method named IGIgram is developed for fault diagnosis of rolling bearings.In the new method,an IGI-based indicator is constructed to evaluate the impulsiveness and cyclostationarity of the narrow-band filtered signal simultaneously,and then a frequency band with abundant fault information is adaptively determined for extracting bearing fault features.The performance of the IGIgram method is verified on the simulation signal and railway bearing experimental signals and compared with typical sparsity measures-based envelope analysis methods and log-cycligram.The results demonstrate that the proposed IGIs are efficient in quantifying bearing fault-induced transient features and the IGIgram method with appropriate power exponent can effectively achieve the diagnostics of different axle-box bearing faults.
文摘Intelligent compaction （IC） is a relatively new technology for asphalt paving industry. The present study evaluated the effectiveness and potential issues of the IC technology for flexible pavement resurfacing construction using two field projects. In the first project, a geostatistical semivariogram model was established and the parameters derived from it were compared with univariate statistical parameters for the Compaction Meter Value （CMV） data. Further analyses illustrated the effect of temperature on the CMV value and compaction uniformity. In the second project, a multivariate analysis was performed between in situ tests and IC data. The possibility of combining various IC data to predict the asphalt layer density and improve the current quality control and assurance system was discussed.
