Bearings in a gas turbine engine are the key connecting components transmitting force and motion between rotors and thin-walled flexible casing.The bearing stiffness and damping of squeeze film damper(SFD)nearby beari...Bearings in a gas turbine engine are the key connecting components transmitting force and motion between rotors and thin-walled flexible casing.The bearing stiffness and damping of squeeze film damper(SFD)nearby bearings are easily affected by many factors,such as assembly process,load condition and temperature variation,resulting in uncertainties.The uncertainties may influence the response of the measuring point on the casing.Hence,it is difficult to carry out the fault diagnosis,whole machine balancing and other related works.In this paper,a double integral quantitative evaluation method is proposed to simultaneously analyze the influence of two uncertain dynamic coefficients on the response amplitude and phase of casing measuring points.Meanwhile,the coupling influence of stiffness and damping accompanied by dramatic changes with rotational speeds are essentially discussed.As an example,a typical engine bearing-casing system with complex dynamic characteristics is analyzed.The impact of uncertain dynamic coefficients on the unbalance response is quantitatively evaluated.展开更多
The technique of coupling two loudspeakers to obtain a signal proportional to the velocity of the cone is known. The sound at a distant point from a loudspeaker is related to the diaphragm displacement. Since the indu...The technique of coupling two loudspeakers to obtain a signal proportional to the velocity of the cone is known. The sound at a distant point from a loudspeaker is related to the diaphragm displacement. Since the induced e.m.f is proportional to the voice coil velocity,measurement of induced e.m.f enables us to obtain the displacement of the cone and hence we can plot the SPL curve for a loudspeaker. This method has some limitations in that it is particularly applicable only when one is interested in using the output of the second speaker used as a sensor in some further applications.展开更多
The Lewisian turning-point obviously increase the labor costs of Chinese manufacturing firms,it made the employee turnover to become the key problem that how to keep the enterprise human resource stability.Here,the co...The Lewisian turning-point obviously increase the labor costs of Chinese manufacturing firms,it made the employee turnover to become the key problem that how to keep the enterprise human resource stability.Here,the conceptual catastrophe model of employee turnover is built from the new perspective of empirical study and catastrophe theory.In particular,we developed a parameter estimation method of the Cusp catastrophe model based on qualitative simulation and fuzzy math,and then to demonstrate the rationality and robustness of this method by a practical case on a manufacturing enterprise.In the end,a series of virtual experiments are carried out for the employee turnover in the period of China’s economic transformation.The main results are that,how to measure the warning,critical and mutation area of employee turnover;the real relationship between the complex economic environment and the demission of employees;the control policy from the macroscopic governmental measures and microscopic enterprise ways.展开更多
基金co-supported by the Young Scientists Fund of the National Natural Science Foundation of China(No.51905025)the Joint Funds of the National Natural Science Foundation of China(No.U1708257)the Fundamental Research Funds for the Central Universities(No.JD1911)。
文摘Bearings in a gas turbine engine are the key connecting components transmitting force and motion between rotors and thin-walled flexible casing.The bearing stiffness and damping of squeeze film damper(SFD)nearby bearings are easily affected by many factors,such as assembly process,load condition and temperature variation,resulting in uncertainties.The uncertainties may influence the response of the measuring point on the casing.Hence,it is difficult to carry out the fault diagnosis,whole machine balancing and other related works.In this paper,a double integral quantitative evaluation method is proposed to simultaneously analyze the influence of two uncertain dynamic coefficients on the response amplitude and phase of casing measuring points.Meanwhile,the coupling influence of stiffness and damping accompanied by dramatic changes with rotational speeds are essentially discussed.As an example,a typical engine bearing-casing system with complex dynamic characteristics is analyzed.The impact of uncertain dynamic coefficients on the unbalance response is quantitatively evaluated.
文摘The technique of coupling two loudspeakers to obtain a signal proportional to the velocity of the cone is known. The sound at a distant point from a loudspeaker is related to the diaphragm displacement. Since the induced e.m.f is proportional to the voice coil velocity,measurement of induced e.m.f enables us to obtain the displacement of the cone and hence we can plot the SPL curve for a loudspeaker. This method has some limitations in that it is particularly applicable only when one is interested in using the output of the second speaker used as a sensor in some further applications.
基金supported by China National Nature Science Foundation(Grant No.71271093).
文摘The Lewisian turning-point obviously increase the labor costs of Chinese manufacturing firms,it made the employee turnover to become the key problem that how to keep the enterprise human resource stability.Here,the conceptual catastrophe model of employee turnover is built from the new perspective of empirical study and catastrophe theory.In particular,we developed a parameter estimation method of the Cusp catastrophe model based on qualitative simulation and fuzzy math,and then to demonstrate the rationality and robustness of this method by a practical case on a manufacturing enterprise.In the end,a series of virtual experiments are carried out for the employee turnover in the period of China’s economic transformation.The main results are that,how to measure the warning,critical and mutation area of employee turnover;the real relationship between the complex economic environment and the demission of employees;the control policy from the macroscopic governmental measures and microscopic enterprise ways.
