Based upon empirical mode decomposition (EMD) method and Hilbert spectrum, a method for fault diagnosis of roller bearing is proposed. The orthogonal wavelet bases are used to translate vibration signals of a roller b...Based upon empirical mode decomposition (EMD) method and Hilbert spectrum, a method for fault diagnosis of roller bearing is proposed. The orthogonal wavelet bases are used to translate vibration signals of a roller bearing into time-scale representation, then, an envelope signal can be obtained by envelope spectrum analysis of wavelet coefficients of high scales. By applying EMD method and Hilbert transform to the envelope signal, we can get the local Hilbert marginal spectrum from which the faults in a roller bearing can be diagnosed and fault patterns can be identified. Practical vibration signals measured from roller bearings with out-race faults or inner-race faults are analyzed by the proposed method. The results show that the proposed method is superior to the traditional envelope spectrum method in extracting the fault characteristics of roller bearings.展开更多
Purpose:This study intends to examine the factors influencing user adoption of location based service(LBS).Design/methodology/approach:This paper develops the research model for user adoption of LBS with the technolog...Purpose:This study intends to examine the factors influencing user adoption of location based service(LBS).Design/methodology/approach:This paper develops the research model for user adoption of LBS with the technology acceptance model(TAM) as the theoretical foundation.Using a questionnaire and sampling method,empirical data was collected from 386 participants.Structured equation modeling was used to test the validity of the proposed model.Findings:The results show that I) perceived ease of use.perceived usefulness and perceived playfulness were direct determinants of behavioral intention,and perceived ease of use has the greatest impact of the three;2) emergency,ubiquity,technology maturity and social trust all have positive and significant impacts on perceived ease of use;3) emergency and social trust significantly influence perceived usefulness positively:4) individualization and social impact significantly affect perceived playfulness positively.Research limitations:Subjects were from China’s mainland,which limits the generalizability of the research findings.The interaction effects of age,gender and user experience were not included.Practical implications:This study offers LBS operators,marketers and application developers insights into the way to attract more users by increasing perceived usefulness,ease of use and playfulness of LBS.Originality/value:Location based service is still a relatively new concept and there were few theoretical and empirical studies that examine user adoption of the serv ice.This study contributes to existing LBS adoption studies by modifying and extending TAM and meanwhile the empirical study will help the research community gain a deeper understanding of the factors affecting user adoption of LBS.展开更多
In this paper, we discuss a special class of sets of bivariate empirical points, namely, numerical cartesian sets. We find that the stable quotient bases for numerical cartesian sets are unique if they exist. Furtherm...In this paper, we discuss a special class of sets of bivariate empirical points, namely, numerical cartesian sets. We find that the stable quotient bases for numerical cartesian sets are unique if they exist. Furthermore, the corresponding border bases are the unique stable border bases for the vanishing ideals of numerical cartesian sets.展开更多
For social workers who are interested in research associated with validating methodology for the amelioration of human problems,or the mastery of intervention models,used in direct practice;definitive consensus,on gui...For social workers who are interested in research associated with validating methodology for the amelioration of human problems,or the mastery of intervention models,used in direct practice;definitive consensus,on guidelines,remains elusive.Much has been written in recent years about the necessity of the profession to be guided by either empirical research,which has validated specific interventions,or by the theory,heuristic rules,and the decision‐making schema of experienced practitioners.The debate is not simply limited to clinical practice issues,or factions defending or refuting,a particular theoretical stance.On one hand,social research has in recent years,invalidated some long held practice models,and has modified our understanding of core social problems.Yet,social research is an often difficult and arduous pursuit,which may require some time to make thorough evaluation,as compared to the immediacy of emerging social concerns.This transmission of scholarly research findings takes time and considerable effort to disseminate and gain understanding and acceptance within the practice community even when well received.On the other hand,practitioners serve as the wellspring of observations,which are often translated into models or theory,and frequently become the subject matter of empirical research.However,few in the practice community are encouraged or committed,to systematically review research findings so as to modify practice approaches,which have not been well validated by recent research findings.展开更多
To prevent early bridge failures, effective Structural Health Monitoring (SHM) is vital. Vibration-based damage assessment is a powerful tool in this regard, as it relies on changes in a structure’s dynamic character...To prevent early bridge failures, effective Structural Health Monitoring (SHM) is vital. Vibration-based damage assessment is a powerful tool in this regard, as it relies on changes in a structure’s dynamic characteristics as it degrades. By measuring the vibration response of a bridge due to passing vehicles, this approach can identify potential structural damage. This dissertation introduces a novel technique grounded in Vehicle-Bridge Interaction (VBI) to evaluate bridge health. It aims to detect damage by analyzing the response of passing vehicles, taking into account VBI. The theoretical foundation of this method begins with representing the bridge’s superstructure using a Finite Element Model and employing a half-car dynamic model to simulate the vehicle with suspension. Two sets of motion equations, one for the bridge and one for the vehicle are generated using the Finite Element Method, mode superposition, and D’Alembert’s principle. The combined dynamics are solved using the Newmark-beta method, accounting for road surface roughness. A new approach for damage identification based on the response of passing vehicles is proposed. The response is theoretically composed of vehicle frequency, bridge natural frequency, and a pseudo-frequency component related to vehicle speed. The Empirical Mode Decomposition (EMD) method is applied to decompose the signal into its constituent parts, and damage detection relies on the Intrinsic Mode Functions (IMFs) corresponding to the vehicle speed component. This technique effectively identifies various damage scenarios considered in the study.展开更多
基金This project is supported by National Natural Science Foundation of China (No.50205050).
文摘Based upon empirical mode decomposition (EMD) method and Hilbert spectrum, a method for fault diagnosis of roller bearing is proposed. The orthogonal wavelet bases are used to translate vibration signals of a roller bearing into time-scale representation, then, an envelope signal can be obtained by envelope spectrum analysis of wavelet coefficients of high scales. By applying EMD method and Hilbert transform to the envelope signal, we can get the local Hilbert marginal spectrum from which the faults in a roller bearing can be diagnosed and fault patterns can be identified. Practical vibration signals measured from roller bearings with out-race faults or inner-race faults are analyzed by the proposed method. The results show that the proposed method is superior to the traditional envelope spectrum method in extracting the fault characteristics of roller bearings.
基金supported by the National Natural Science Foundation of China(Grant No.:71273197)
文摘Purpose:This study intends to examine the factors influencing user adoption of location based service(LBS).Design/methodology/approach:This paper develops the research model for user adoption of LBS with the technology acceptance model(TAM) as the theoretical foundation.Using a questionnaire and sampling method,empirical data was collected from 386 participants.Structured equation modeling was used to test the validity of the proposed model.Findings:The results show that I) perceived ease of use.perceived usefulness and perceived playfulness were direct determinants of behavioral intention,and perceived ease of use has the greatest impact of the three;2) emergency,ubiquity,technology maturity and social trust all have positive and significant impacts on perceived ease of use;3) emergency and social trust significantly influence perceived usefulness positively:4) individualization and social impact significantly affect perceived playfulness positively.Research limitations:Subjects were from China’s mainland,which limits the generalizability of the research findings.The interaction effects of age,gender and user experience were not included.Practical implications:This study offers LBS operators,marketers and application developers insights into the way to attract more users by increasing perceived usefulness,ease of use and playfulness of LBS.Originality/value:Location based service is still a relatively new concept and there were few theoretical and empirical studies that examine user adoption of the serv ice.This study contributes to existing LBS adoption studies by modifying and extending TAM and meanwhile the empirical study will help the research community gain a deeper understanding of the factors affecting user adoption of LBS.
基金Partially supported by the National Grand Fundamental Research 973 Program (2004CB318000) of China
文摘In this paper, we discuss a special class of sets of bivariate empirical points, namely, numerical cartesian sets. We find that the stable quotient bases for numerical cartesian sets are unique if they exist. Furthermore, the corresponding border bases are the unique stable border bases for the vanishing ideals of numerical cartesian sets.
文摘For social workers who are interested in research associated with validating methodology for the amelioration of human problems,or the mastery of intervention models,used in direct practice;definitive consensus,on guidelines,remains elusive.Much has been written in recent years about the necessity of the profession to be guided by either empirical research,which has validated specific interventions,or by the theory,heuristic rules,and the decision‐making schema of experienced practitioners.The debate is not simply limited to clinical practice issues,or factions defending or refuting,a particular theoretical stance.On one hand,social research has in recent years,invalidated some long held practice models,and has modified our understanding of core social problems.Yet,social research is an often difficult and arduous pursuit,which may require some time to make thorough evaluation,as compared to the immediacy of emerging social concerns.This transmission of scholarly research findings takes time and considerable effort to disseminate and gain understanding and acceptance within the practice community even when well received.On the other hand,practitioners serve as the wellspring of observations,which are often translated into models or theory,and frequently become the subject matter of empirical research.However,few in the practice community are encouraged or committed,to systematically review research findings so as to modify practice approaches,which have not been well validated by recent research findings.
文摘To prevent early bridge failures, effective Structural Health Monitoring (SHM) is vital. Vibration-based damage assessment is a powerful tool in this regard, as it relies on changes in a structure’s dynamic characteristics as it degrades. By measuring the vibration response of a bridge due to passing vehicles, this approach can identify potential structural damage. This dissertation introduces a novel technique grounded in Vehicle-Bridge Interaction (VBI) to evaluate bridge health. It aims to detect damage by analyzing the response of passing vehicles, taking into account VBI. The theoretical foundation of this method begins with representing the bridge’s superstructure using a Finite Element Model and employing a half-car dynamic model to simulate the vehicle with suspension. Two sets of motion equations, one for the bridge and one for the vehicle are generated using the Finite Element Method, mode superposition, and D’Alembert’s principle. The combined dynamics are solved using the Newmark-beta method, accounting for road surface roughness. A new approach for damage identification based on the response of passing vehicles is proposed. The response is theoretically composed of vehicle frequency, bridge natural frequency, and a pseudo-frequency component related to vehicle speed. The Empirical Mode Decomposition (EMD) method is applied to decompose the signal into its constituent parts, and damage detection relies on the Intrinsic Mode Functions (IMFs) corresponding to the vehicle speed component. This technique effectively identifies various damage scenarios considered in the study.
