A Jeffcott rotor-magnetic bearing with time delays is investigated in this paper. Firstly, it is found that the characteristic equation of the system satisfies the conditions of the singularity. Secondly, the center m...A Jeffcott rotor-magnetic bearing with time delays is investigated in this paper. Firstly, it is found that the characteristic equation of the system satisfies the conditions of the singularity. Secondly, the center manifold reduction and normal form are employed to study the bifurcation from simple zero and zero-purely imaginary singularities. The results of this paper will help to understand the influence of the time delays in feedback loop on the dynamics of rotor-magnetic bearing system.展开更多
Research on the use of EHR is contradictory since it presents contradicting results regarding the time spent documenting. There is research that supports the use of electronic records as a tool to speed documentation;...Research on the use of EHR is contradictory since it presents contradicting results regarding the time spent documenting. There is research that supports the use of electronic records as a tool to speed documentation;and research that found that it is time consuming. The purpose of this quantitative retrospective before-after project was to measure the impact of using the laboratory value flowsheet within the EHR on documentation time. The research question was: “Does the use of a laboratory value flowsheet in the EHR impact documentation time by primary care providers (PCPs)?” The theoretical framework utilized in this project was the Donabedian Model. The population in this research was the two PCPs in a small primary care clinic in the northwest of Puerto Rico. The sample was composed of all the encounters during the months of October 2019 and December 2019. The data was obtained through data mining and analyzed using SPSS 27. The evaluative outcome of this project is that there is a decrease in documentation time after implementation of the use of the laboratory value flowsheet in the EHR. However, patients per day increase therefore having an impact on the number of patients seen per day/week/month. The implications for clinical practice include the use of templates to improve workflow and documentation as well as decreasing documentation time while also increasing the number of patients seen per day. .展开更多
Due to the non-stationary characteristics of vibration signals acquired from rolling element bearing fault, thc time-frequency analysis is often applied to describe the local information of these unstable signals smar...Due to the non-stationary characteristics of vibration signals acquired from rolling element bearing fault, thc time-frequency analysis is often applied to describe the local information of these unstable signals smartly. However, it is difficult to classitythe high dimensional feature matrix directly because of too large dimensions for many classifiers. This paper combines the concepts of time-frequency distribution（TFD） with non-negative matrix factorization（NMF）, and proposes a novel TFD matrix factorization method to enhance representation and identification of bearing fault. Throughout this method, the TFD of a vibration signal is firstly accomplished to describe the localized faults with short-time Fourier transform（STFT）. Then, the supervised NMF mapping is adopted to extract the fault features from TFD. Meanwhile, the fault samples can be clustered and recognized automatically by using the clustering property of NMF. The proposed method takes advantages of the NMF in the parts-based representation and the adaptive clustering. The localized fault features of interest can be extracted as well. To evaluate the performance of the proposed method, the 9 kinds of the bearing fault on a test bench is performed. The proposed method can effectively identify the fault severity and different fault types. Moreover, in comparison with the artificial neural network（ANN）, NMF yields 99.3% mean accuracy which is much superior to ANN. This research presents a simple and practical resolution for the fault diagnosis problem of rolling element bearing in high dimensional feature space.展开更多
The rolling bearing friction torque which is characterized by its uncertainty and nonlinearity affects heavily the dynamic performance of a system such as missiles, spacecrafts and radars, etc. It is difficult to use ...The rolling bearing friction torque which is characterized by its uncertainty and nonlinearity affects heavily the dynamic performance of a system such as missiles, spacecrafts and radars, etc. It is difficult to use the classical statistical theory to evaluate the dynamic evaluation of the rolling bearing friction torque for the lack of prior information about both probability distribution and trends. For this reason, based on the information poor system theory and combined with the correlation dimension in chaos theory, the concepts about the mean of the dynamic fluctuant range （MDFR） and the grey relation are proposed to resolve the problem about evaluating the nonlinear characteristic and the dynamic uncertainty of the rolling bearing friction torque. Friction torque experiments are done for three types of the rolling bearings marked with HKTA, HKTB and HKTC separately; meantime, the correlation dimension and MDFR are calculated to describe the nonlinear characteristic and the dynamic uncertainty of the friction torque, respectively. And the experiments reveal that there is a certain grey relation between the nonlinear characteristic and the dynamic uncertainty of the rolling bearing friction torque, viz. MDFR will become the nonlinear increasing trend with the correlation dimension increasing. Under the condition of fewer characteristic data and the lack of prior information about both probability distribution and trends, the unitive evaluation for the nonlinear characteristic and the dynamic uncertainty of the rolling bearing friction torque is realized with the grey confidence level of 87.7%-96.3%.展开更多
BACKGROUND: To invent a novel cardiopulmonary resuscitation(CPR) time point recorder to synchronously and automatically record the time and to identify its effectiveness in humans.METHODS: A CPR time point recorder wa...BACKGROUND: To invent a novel cardiopulmonary resuscitation(CPR) time point recorder to synchronously and automatically record the time and to identify its effectiveness in humans.METHODS: A CPR time point recorder was invented after the doctors were familiar with the traditional Utstein recovery registration mode and mastered the registration time points required. The progress of CPR was simulated. The standard and correct times were recorded, and the doctors performing the recovery collected the data about the times using our CPR time point recorder or the memory registration mode.RESULTS: The deviation times were 21.4±24.7 seconds for the memory group and 3.57±4.58 seconds for CPR time point recorder group. The deviation of times increased signifi cantly depending on the increase of the operation items in the memory group. A similar phenomenon was found in the timer group but with a smaller difference(P<0.01).CONCLUSION: A CPR time point recorder could reduce the deviation of operate-time, especially after a long-time operation, and for procedures with more operating items, compared with the memory mode. It was a more advantageous and accurate method for the Utstein registration.展开更多
The central and northwestern Tibetan Plateau region,also called＂Qiangtang Plateau＂（30°27＇25＂-35°39＇13＂N,83o41＇14＂-95°10＇46＂E）,is the highest and largest arcticalpine area of the Earth coveri...The central and northwestern Tibetan Plateau region,also called＂Qiangtang Plateau＂（30°27＇25＂-35°39＇13＂N,83o41＇14＂-95°10＇46＂E）,is the highest and largest arcticalpine area of the Earth covering approximately 600,000km^2 with altitude ranging from 4600 to 5100 m a.s.l.（Song et al.,2012,Fig.1）.展开更多
Gas bearings,which have the advantages of low frictional resistance and power loss,high rotational speed and high temperature operation,and long life,are more suitable than are traditional liquid lubricated bearings b...Gas bearings,which have the advantages of low frictional resistance and power loss,high rotational speed and high temperature operation,and long life,are more suitable than are traditional liquid lubricated bearings because of their high precision,high rotational speed,and special condition support.However,the problem of starting a closed-cycle compression system with gas bearings still needs to be solved for practical application.Thus,a new start-up method for a closed-cycle compression system with aerostatic gas bearings is proposed in this paper.Further,this paper presents a numerical simulation and experimental investigation of the method’s feasibility and characteristics during the start-up process when the gas tank’s initial pressure is fixed.The results show that the gas tank volume is approximately directly proportional to the start-up time allowable,and a gas tank volume sufficiently small,which not only ensures the feasibility of start-up,but also affects other components only slightly,can be obtained.A perfect combination of radial and axial loads also can be achieved to make the start-up time allowable as long as possible.R134a is a better choice for the working medium than is air,as the start-up time allowable is longer,which leads to a smaller gas tank.This research proposes a new start-up method for a closed-cycle compression system with aerostatic gas bearings which has sufficient load capacity to support system during the start-up method.展开更多
Carbon fiber reinforced polymer composites (CFRP) have been applied to aerospace and automobile structures. For many CFRP structures, mechanical metallic fasteners are usually adopted. For the fasteners used in intern...Carbon fiber reinforced polymer composites (CFRP) have been applied to aerospace and automobile structures. For many CFRP structures, mechanical metallic fasteners are usually adopted. For the fasteners used in internal structures such as a wing box, the damage to the CFRP structures around fastener holes is visually quite difficult to find. A simple method to find the damage around fastener holes is required. In this study a self-sensing time domain reflectometry (TDR) method is newly applied to detect bearing failure around the fastener holes of CFRP structures. A microstrip-line method is generally used to create a transmission line. When the transmission line is mounted near the metallic fasteners, they may affect the impedance of the transmission line. In this study, the effect of distance between the fasteners and the transmission line was numerically investigated using a finite difference time domain analysis method. After finding the appropriate distance, experiments were performed to detect the bearing failure around a fastener hole. The experiments showed the performance of the self-sensing TDR for detecting bearing failure.展开更多
Seismic earthquakes are a real danger for the construction evolution of high rise buildings.The rate of earthquakes around the world is noteworthy in a wide range of construction areas.In this study,we present the dyn...Seismic earthquakes are a real danger for the construction evolution of high rise buildings.The rate of earthquakes around the world is noteworthy in a wide range of construction areas.In this study,we present the dynamic behavior of a high-rise RC building with dynamic isolators(lead-rubber-bearing),in comparison with a traditional shear wall system of the same building.Seismic isolation has been introduced in building construction to increase the structural stability and to protect the non-structural components against the damaging effects of an earthquake.In order to clarify the influence of incorporating lead rubber bearing isolators in the seismic response and in reducing seismic damages;a comparative study is performed between a fixed base system(shear wall system)and an isolated base system(Lead Rubber Bearing)on an irregular high rise reinforced concrete(RC)building located in Beirut consisting of 48 storeys almost asymmetric orthogonally.For this purpose,a non-linear analysis of a real earthquake acceleration record(EI Centro seismic signal)is conducted,so that the mode shapes,the damping ratio and the natural frequencies of the two models are obtained using ETABS software.The results prove a substantial elongation of the building period,as well as a reduction in the building displacement,the roof acceleration,the inter-storey drift ratio and the base shear force of isolated building relative to fixed-base building.This study proves that this technology is applicable to high rise buildings with acceptable results.展开更多
A series of experiments are conducted to confirm whether the vectors calculated for an early section of a continuous non-invasive fetal electrocardiogram （fECG） recording can be directly applied to subsequent sectio...A series of experiments are conducted to confirm whether the vectors calculated for an early section of a continuous non-invasive fetal electrocardiogram （fECG） recording can be directly applied to subsequent sections in order to reduce the computation required for real-time monitoring. Our results suggest that it is generally feasible to apply the initial optimal maternal and fetal ECG combination vectors to extract the fECG and maternal ECG in subsequent recorded sections.展开更多
Time effect of wet drilling pile is investigated through the static load experiment on pile No. 22 of Guanhe Bridge. Post-grouting under pile tip is adopted in the project. To study the bearing performance of the pile...Time effect of wet drilling pile is investigated through the static load experiment on pile No. 22 of Guanhe Bridge. Post-grouting under pile tip is adopted in the project. To study the bearing performance of the pile, the self-balanced method is used and two load cells are assembled in the pile body. The experiments are carried out before and after post-grouting. The upper part of the pile is not influenced by post-grouting under the pile tip. Experimental results of the upper part of the pile show that the bearing capacity and the rigidity of wet drilling pile increase with time passing on. Analysis results show the time effect of wet drilling pile is influenced by many factors, such as alteration of stress field around pile, characteristics of soil around pile, variety of mud cake, and property of residue under pile tip.展开更多
Objective: Government targets to reduce waiting times are putting enormous pressures on outpatient services. The implementation of an electronic care records service (CRS) at our hospital in 2008 has led to widespread...Objective: Government targets to reduce waiting times are putting enormous pressures on outpatient services. The implementation of an electronic care records service (CRS) at our hospital in 2008 has led to widespread press coverage of ensuing chaos in clinical administration. We wanted to know how this new electronic system impacted on our working patterns in outpatient clinics and – more specifically – on the time actually spent with the patients. Material & methods: This study was performed 4 and 12 months after implementation of CRS to assess its impact on the time distribution in clinic. Senior doctors were monitored with a stop clock during consultations. Timings for pre- and post-consultation administration, and the actual consultation with the patient were recorded. A total of 170 consultations were evaluated in this way. Results: The key findings were that the total time needed to spend on a urological outpatient of 16 minutes remains unchanged from the pre-CRS era, but a majority (57%) of this time is spent in administration on the computer without the patient involved. Conclusion: No more than 15 patients should be seen in a 4 hour outpatient clinic per doctor. This recommendation drawn up by BAUS before CRS remains still valid. Patient administration related to the consultation that has previously been done by administrative aides is now to be done by the doctors on the computer in the same consultation session. Intended to streamline patient pathways, this does reduce the quality interaction-time between doctor and patients significantly.展开更多
基金Supported by the Heilongjiang Province Department of Education Science and Technology Project (11544048)
文摘A Jeffcott rotor-magnetic bearing with time delays is investigated in this paper. Firstly, it is found that the characteristic equation of the system satisfies the conditions of the singularity. Secondly, the center manifold reduction and normal form are employed to study the bifurcation from simple zero and zero-purely imaginary singularities. The results of this paper will help to understand the influence of the time delays in feedback loop on the dynamics of rotor-magnetic bearing system.
文摘Research on the use of EHR is contradictory since it presents contradicting results regarding the time spent documenting. There is research that supports the use of electronic records as a tool to speed documentation;and research that found that it is time consuming. The purpose of this quantitative retrospective before-after project was to measure the impact of using the laboratory value flowsheet within the EHR on documentation time. The research question was: “Does the use of a laboratory value flowsheet in the EHR impact documentation time by primary care providers (PCPs)?” The theoretical framework utilized in this project was the Donabedian Model. The population in this research was the two PCPs in a small primary care clinic in the northwest of Puerto Rico. The sample was composed of all the encounters during the months of October 2019 and December 2019. The data was obtained through data mining and analyzed using SPSS 27. The evaluative outcome of this project is that there is a decrease in documentation time after implementation of the use of the laboratory value flowsheet in the EHR. However, patients per day increase therefore having an impact on the number of patients seen per day/week/month. The implications for clinical practice include the use of templates to improve workflow and documentation as well as decreasing documentation time while also increasing the number of patients seen per day. .
基金Supported by Shaanxi Provincial Overall Innovation Project of Science and Technology,China(Grant No.2013KTCQ01-06)
文摘Due to the non-stationary characteristics of vibration signals acquired from rolling element bearing fault, thc time-frequency analysis is often applied to describe the local information of these unstable signals smartly. However, it is difficult to classitythe high dimensional feature matrix directly because of too large dimensions for many classifiers. This paper combines the concepts of time-frequency distribution（TFD） with non-negative matrix factorization（NMF）, and proposes a novel TFD matrix factorization method to enhance representation and identification of bearing fault. Throughout this method, the TFD of a vibration signal is firstly accomplished to describe the localized faults with short-time Fourier transform（STFT）. Then, the supervised NMF mapping is adopted to extract the fault features from TFD. Meanwhile, the fault samples can be clustered and recognized automatically by using the clustering property of NMF. The proposed method takes advantages of the NMF in the parts-based representation and the adaptive clustering. The localized fault features of interest can be extracted as well. To evaluate the performance of the proposed method, the 9 kinds of the bearing fault on a test bench is performed. The proposed method can effectively identify the fault severity and different fault types. Moreover, in comparison with the artificial neural network（ANN）, NMF yields 99.3% mean accuracy which is much superior to ANN. This research presents a simple and practical resolution for the fault diagnosis problem of rolling element bearing in high dimensional feature space.
基金supported by National Natural Science Foundation of China (Grant No. 50675011)Doctoral Scientific Research Enabling Foundation of Henan University of Science and Technology,China (Grant No. 09001318)
文摘The rolling bearing friction torque which is characterized by its uncertainty and nonlinearity affects heavily the dynamic performance of a system such as missiles, spacecrafts and radars, etc. It is difficult to use the classical statistical theory to evaluate the dynamic evaluation of the rolling bearing friction torque for the lack of prior information about both probability distribution and trends. For this reason, based on the information poor system theory and combined with the correlation dimension in chaos theory, the concepts about the mean of the dynamic fluctuant range （MDFR） and the grey relation are proposed to resolve the problem about evaluating the nonlinear characteristic and the dynamic uncertainty of the rolling bearing friction torque. Friction torque experiments are done for three types of the rolling bearings marked with HKTA, HKTB and HKTC separately; meantime, the correlation dimension and MDFR are calculated to describe the nonlinear characteristic and the dynamic uncertainty of the friction torque, respectively. And the experiments reveal that there is a certain grey relation between the nonlinear characteristic and the dynamic uncertainty of the rolling bearing friction torque, viz. MDFR will become the nonlinear increasing trend with the correlation dimension increasing. Under the condition of fewer characteristic data and the lack of prior information about both probability distribution and trends, the unitive evaluation for the nonlinear characteristic and the dynamic uncertainty of the rolling bearing friction torque is realized with the grey confidence level of 87.7%-96.3%.
基金supported by funding from the NSFC(81671882,81471832)the Natural Science Foundation of Guangdong Province of China(2016A030311039)the Science and Technology Foundation of Guangzhou City of China(201605110853481)
文摘BACKGROUND: To invent a novel cardiopulmonary resuscitation(CPR) time point recorder to synchronously and automatically record the time and to identify its effectiveness in humans.METHODS: A CPR time point recorder was invented after the doctors were familiar with the traditional Utstein recovery registration mode and mastered the registration time points required. The progress of CPR was simulated. The standard and correct times were recorded, and the doctors performing the recovery collected the data about the times using our CPR time point recorder or the memory registration mode.RESULTS: The deviation times were 21.4±24.7 seconds for the memory group and 3.57±4.58 seconds for CPR time point recorder group. The deviation of times increased signifi cantly depending on the increase of the operation items in the memory group. A similar phenomenon was found in the timer group but with a smaller difference(P<0.01).CONCLUSION: A CPR time point recorder could reduce the deviation of operate-time, especially after a long-time operation, and for procedures with more operating items, compared with the memory mode. It was a more advantageous and accurate method for the Utstein registration.
基金supported by NSFC(grant no.41173015)the China Scholarship Council(CSC)National Education Ministry Doctoral Foundation(grant no. 20100211110020).
文摘The central and northwestern Tibetan Plateau region,also called＂Qiangtang Plateau＂（30°27＇25＂-35°39＇13＂N,83o41＇14＂-95°10＇46＂E）,is the highest and largest arcticalpine area of the Earth covering approximately 600,000km^2 with altitude ranging from 4600 to 5100 m a.s.l.（Song et al.,2012,Fig.1）.
基金Supported by National Natural Science Foundation of China(Grant No.51706009).
文摘Gas bearings,which have the advantages of low frictional resistance and power loss,high rotational speed and high temperature operation,and long life,are more suitable than are traditional liquid lubricated bearings because of their high precision,high rotational speed,and special condition support.However,the problem of starting a closed-cycle compression system with gas bearings still needs to be solved for practical application.Thus,a new start-up method for a closed-cycle compression system with aerostatic gas bearings is proposed in this paper.Further,this paper presents a numerical simulation and experimental investigation of the method’s feasibility and characteristics during the start-up process when the gas tank’s initial pressure is fixed.The results show that the gas tank volume is approximately directly proportional to the start-up time allowable,and a gas tank volume sufficiently small,which not only ensures the feasibility of start-up,but also affects other components only slightly,can be obtained.A perfect combination of radial and axial loads also can be achieved to make the start-up time allowable as long as possible.R134a is a better choice for the working medium than is air,as the start-up time allowable is longer,which leads to a smaller gas tank.This research proposes a new start-up method for a closed-cycle compression system with aerostatic gas bearings which has sufficient load capacity to support system during the start-up method.
文摘Carbon fiber reinforced polymer composites (CFRP) have been applied to aerospace and automobile structures. For many CFRP structures, mechanical metallic fasteners are usually adopted. For the fasteners used in internal structures such as a wing box, the damage to the CFRP structures around fastener holes is visually quite difficult to find. A simple method to find the damage around fastener holes is required. In this study a self-sensing time domain reflectometry (TDR) method is newly applied to detect bearing failure around the fastener holes of CFRP structures. A microstrip-line method is generally used to create a transmission line. When the transmission line is mounted near the metallic fasteners, they may affect the impedance of the transmission line. In this study, the effect of distance between the fasteners and the transmission line was numerically investigated using a finite difference time domain analysis method. After finding the appropriate distance, experiments were performed to detect the bearing failure around a fastener hole. The experiments showed the performance of the self-sensing TDR for detecting bearing failure.
文摘Seismic earthquakes are a real danger for the construction evolution of high rise buildings.The rate of earthquakes around the world is noteworthy in a wide range of construction areas.In this study,we present the dynamic behavior of a high-rise RC building with dynamic isolators(lead-rubber-bearing),in comparison with a traditional shear wall system of the same building.Seismic isolation has been introduced in building construction to increase the structural stability and to protect the non-structural components against the damaging effects of an earthquake.In order to clarify the influence of incorporating lead rubber bearing isolators in the seismic response and in reducing seismic damages;a comparative study is performed between a fixed base system(shear wall system)and an isolated base system(Lead Rubber Bearing)on an irregular high rise reinforced concrete(RC)building located in Beirut consisting of 48 storeys almost asymmetric orthogonally.For this purpose,a non-linear analysis of a real earthquake acceleration record(EI Centro seismic signal)is conducted,so that the mode shapes,the damping ratio and the natural frequencies of the two models are obtained using ETABS software.The results prove a substantial elongation of the building period,as well as a reduction in the building displacement,the roof acceleration,the inter-storey drift ratio and the base shear force of isolated building relative to fixed-base building.This study proves that this technology is applicable to high rise buildings with acceptable results.
基金supported by the National Natural Science Foundation of China(Grant No.61271079)
文摘A series of experiments are conducted to confirm whether the vectors calculated for an early section of a continuous non-invasive fetal electrocardiogram （fECG） recording can be directly applied to subsequent sections in order to reduce the computation required for real-time monitoring. Our results suggest that it is generally feasible to apply the initial optimal maternal and fetal ECG combination vectors to extract the fECG and maternal ECG in subsequent recorded sections.
文摘Time effect of wet drilling pile is investigated through the static load experiment on pile No. 22 of Guanhe Bridge. Post-grouting under pile tip is adopted in the project. To study the bearing performance of the pile, the self-balanced method is used and two load cells are assembled in the pile body. The experiments are carried out before and after post-grouting. The upper part of the pile is not influenced by post-grouting under the pile tip. Experimental results of the upper part of the pile show that the bearing capacity and the rigidity of wet drilling pile increase with time passing on. Analysis results show the time effect of wet drilling pile is influenced by many factors, such as alteration of stress field around pile, characteristics of soil around pile, variety of mud cake, and property of residue under pile tip.
文摘Objective: Government targets to reduce waiting times are putting enormous pressures on outpatient services. The implementation of an electronic care records service (CRS) at our hospital in 2008 has led to widespread press coverage of ensuing chaos in clinical administration. We wanted to know how this new electronic system impacted on our working patterns in outpatient clinics and – more specifically – on the time actually spent with the patients. Material & methods: This study was performed 4 and 12 months after implementation of CRS to assess its impact on the time distribution in clinic. Senior doctors were monitored with a stop clock during consultations. Timings for pre- and post-consultation administration, and the actual consultation with the patient were recorded. A total of 170 consultations were evaluated in this way. Results: The key findings were that the total time needed to spend on a urological outpatient of 16 minutes remains unchanged from the pre-CRS era, but a majority (57%) of this time is spent in administration on the computer without the patient involved. Conclusion: No more than 15 patients should be seen in a 4 hour outpatient clinic per doctor. This recommendation drawn up by BAUS before CRS remains still valid. Patient administration related to the consultation that has previously been done by administrative aides is now to be done by the doctors on the computer in the same consultation session. Intended to streamline patient pathways, this does reduce the quality interaction-time between doctor and patients significantly.
