Once operating trains are disabled on the railway lines,an efficient manner is to utilize the train for train rescue.Owning to the different train and coupler types,it is difficult to formulate uniform regulations for...Once operating trains are disabled on the railway lines,an efficient manner is to utilize the train for train rescue.Owning to the different train and coupler types,it is difficult to formulate uniform regulations for train to train rescue.In this paper,the longitudinal train dynamics of electric multiple units under rescue were analyzed by field and laboratory tests.The angling behavior of the brakinginduced coupler under compressed in-train forces was analyzed.A dynamic model for the train and draft gear system was developed considering accurate boundary limitations and braking characteristics.The safety indices and their limits for the coupled rescue train were defined.Thedynamic evaluations of different train to train rescue scenarios were analyzed.It is indicated that the coupler vertical rotation occurs during the emergency braking applied by the assisting train.The vertical force components of intrain forces lead to the carbody pitch behavior and even cause local destructions to the coupler system.The carbody pitch motion can arise the inference of in-train devices.Based on the safety evaluation of train and coupler system,the regulations for typical train to train rescue scenarios were formulated.展开更多
BACKGROUND: We compare educational environments(i.e. physical, emotional and intellectual experiences) of emergency medicine(EM) residents training in the United States of America(USA) and Saudi Arabia(SA).METHODS: A ...BACKGROUND: We compare educational environments(i.e. physical, emotional and intellectual experiences) of emergency medicine(EM) residents training in the United States of America(USA) and Saudi Arabia(SA).METHODS: A cross-sectional survey study was conducted using an adapted version of the validated Postgraduate Hospital Educational Environment Measure(PHEEM) survey instrument from April 2015 through June 2016 to compare educational environments in all emergency medicine residency programs in SA and three selected programs in the USA with a history of training Saudi physicians. Overall scores were compared across programs, and for subscales(autonomy, teaching, and social Support), using chi-squared, t-tests, and analysis of variance.RESULTS: A total of 219 surveys were returned for 260 residents across six programs(3 SA, 3 USA), with a response rate of 84%. Program-specific response rates varied from 79%–100%. All six residencies were qualitatively rated as "more positive than negative but room for improvement". Quantitative PHEEM scores for the USA programs were significantly higher: 118.7 compared to 109.9 for SA, P=0.001. In subscales, perceptions of social support were not different between the two countries(P=0.243); however, role autonomy(P<0.001) and teaching(P=0.005) were better in USA programs. There were no significant differences by post-graduate training year.CONCLUSION: EM residents in all three emergency medicine residency programs in SA and the three USA programs studied perceive their training as high quality in general, but with room for improvements. USA residency programs scored higher in overall quality. This was driven by more favorable perceptions of role autonomy and teaching. Understanding how residents perceive their programs may help drive targeted quality improvement efforts.展开更多
The wheel-rail adhesion control for regenerative braking systems of high speed electric multiple unit trains is crucial to maintaining the stability,improving the adhesion utilization,and achieving deep energy recover...The wheel-rail adhesion control for regenerative braking systems of high speed electric multiple unit trains is crucial to maintaining the stability,improving the adhesion utilization,and achieving deep energy recovery.There remain technical challenges mainly because of the nonlinear,uncertain,and varying features of wheel-rail contact conditions.This research analyzes the torque transmitting behavior during regenerative braking,and proposes a novel methodology to detect the wheel-rail adhesion stability.Then,applications to the wheel slip prevention during braking are investigated,and the optimal slip ratio control scheme is proposed,which is based on a novel optimal reference generation of the slip ratio and a robust sliding mode control.The proposed methodology achieves the optimal braking performancewithoutthewheel-railcontactinformation.Numerical simulation results for uncertain slippery rails verify the effectiveness of the proposed methodology.展开更多
AIM:To evaluate whether an endoscopy position detecting unit(UPD-3) can improve cecal intubation rates, cecal intubation times and visual analog scale(VAS) pain scores, regardless of the colonoscopist's level of e...AIM:To evaluate whether an endoscopy position detecting unit(UPD-3) can improve cecal intubation rates, cecal intubation times and visual analog scale(VAS) pain scores, regardless of the colonoscopist's level of experience.METHODS:A total of 260 patients(170 men and 90women)who underwent a colonoscopy were divided into the UPD-3-guided group or the conventional group(no UPD-3 guidance).Colonoscopies were performed by experts(experience of more than 1000colonoscopies)or trainees(experience of less than 100colonoscopies).Cecal intubation rates,cecal intubation times,insertion methods(straight insertion:shortening the colonic fold through the bending technique;roping insertion:right turn shortening technique)and patient discomfort were assessed.Patient discomfort during the endoscope insertion was scored by the VAS that was divided into 6 degrees of pain.RESULTS:The cecum intubation rates,cecal intubation times,number of cecal intubations that were performed in<15 min and insertion methods were not significantly different between the conventional group and the UPD-3-guided group.The number of patients who experienced pain during the insertion was markedly less in the UPD-3-guided group than in the conventional group.Univariate and multivariate analysis showed that the following factors were associated with lower VAS pain scores during endoscope insertion:insertion method(straight insertion)and UPD-3guidance in the trainee group.For the experts group,univariate analysis showed that only the insertion method(straight insertion)was associated with lower VAS pain scores.CONCLUSION:Although UPD-3 guidance did not shorten intubation times,it resulted in less patient painduring endoscope insertion compared with conventional endoscopy for the procedures performed by trainees.展开更多
基金supported by the National Natural Science Foundation of China [No.U1334206]the National Key R&D Program of China [No.2016YFB1200500]
文摘Once operating trains are disabled on the railway lines,an efficient manner is to utilize the train for train rescue.Owning to the different train and coupler types,it is difficult to formulate uniform regulations for train to train rescue.In this paper,the longitudinal train dynamics of electric multiple units under rescue were analyzed by field and laboratory tests.The angling behavior of the brakinginduced coupler under compressed in-train forces was analyzed.A dynamic model for the train and draft gear system was developed considering accurate boundary limitations and braking characteristics.The safety indices and their limits for the coupled rescue train were defined.Thedynamic evaluations of different train to train rescue scenarios were analyzed.It is indicated that the coupler vertical rotation occurs during the emergency braking applied by the assisting train.The vertical force components of intrain forces lead to the carbody pitch behavior and even cause local destructions to the coupler system.The carbody pitch motion can arise the inference of in-train devices.Based on the safety evaluation of train and coupler system,the regulations for typical train to train rescue scenarios were formulated.
文摘BACKGROUND: We compare educational environments(i.e. physical, emotional and intellectual experiences) of emergency medicine(EM) residents training in the United States of America(USA) and Saudi Arabia(SA).METHODS: A cross-sectional survey study was conducted using an adapted version of the validated Postgraduate Hospital Educational Environment Measure(PHEEM) survey instrument from April 2015 through June 2016 to compare educational environments in all emergency medicine residency programs in SA and three selected programs in the USA with a history of training Saudi physicians. Overall scores were compared across programs, and for subscales(autonomy, teaching, and social Support), using chi-squared, t-tests, and analysis of variance.RESULTS: A total of 219 surveys were returned for 260 residents across six programs(3 SA, 3 USA), with a response rate of 84%. Program-specific response rates varied from 79%–100%. All six residencies were qualitatively rated as "more positive than negative but room for improvement". Quantitative PHEEM scores for the USA programs were significantly higher: 118.7 compared to 109.9 for SA, P=0.001. In subscales, perceptions of social support were not different between the two countries(P=0.243); however, role autonomy(P<0.001) and teaching(P=0.005) were better in USA programs. There were no significant differences by post-graduate training year.CONCLUSION: EM residents in all three emergency medicine residency programs in SA and the three USA programs studied perceive their training as high quality in general, but with room for improvements. USA residency programs scored higher in overall quality. This was driven by more favorable perceptions of role autonomy and teaching. Understanding how residents perceive their programs may help drive targeted quality improvement efforts.
基金supported by the National Natural Science Foundation of China(Grant 51305437)Guangdong Innovative Research Team Program of China(Grant201001D0104648280)
文摘The wheel-rail adhesion control for regenerative braking systems of high speed electric multiple unit trains is crucial to maintaining the stability,improving the adhesion utilization,and achieving deep energy recovery.There remain technical challenges mainly because of the nonlinear,uncertain,and varying features of wheel-rail contact conditions.This research analyzes the torque transmitting behavior during regenerative braking,and proposes a novel methodology to detect the wheel-rail adhesion stability.Then,applications to the wheel slip prevention during braking are investigated,and the optimal slip ratio control scheme is proposed,which is based on a novel optimal reference generation of the slip ratio and a robust sliding mode control.The proposed methodology achieves the optimal braking performancewithoutthewheel-railcontactinformation.Numerical simulation results for uncertain slippery rails verify the effectiveness of the proposed methodology.
文摘AIM:To evaluate whether an endoscopy position detecting unit(UPD-3) can improve cecal intubation rates, cecal intubation times and visual analog scale(VAS) pain scores, regardless of the colonoscopist's level of experience.METHODS:A total of 260 patients(170 men and 90women)who underwent a colonoscopy were divided into the UPD-3-guided group or the conventional group(no UPD-3 guidance).Colonoscopies were performed by experts(experience of more than 1000colonoscopies)or trainees(experience of less than 100colonoscopies).Cecal intubation rates,cecal intubation times,insertion methods(straight insertion:shortening the colonic fold through the bending technique;roping insertion:right turn shortening technique)and patient discomfort were assessed.Patient discomfort during the endoscope insertion was scored by the VAS that was divided into 6 degrees of pain.RESULTS:The cecum intubation rates,cecal intubation times,number of cecal intubations that were performed in<15 min and insertion methods were not significantly different between the conventional group and the UPD-3-guided group.The number of patients who experienced pain during the insertion was markedly less in the UPD-3-guided group than in the conventional group.Univariate and multivariate analysis showed that the following factors were associated with lower VAS pain scores during endoscope insertion:insertion method(straight insertion)and UPD-3guidance in the trainee group.For the experts group,univariate analysis showed that only the insertion method(straight insertion)was associated with lower VAS pain scores.CONCLUSION:Although UPD-3 guidance did not shorten intubation times,it resulted in less patient painduring endoscope insertion compared with conventional endoscopy for the procedures performed by trainees.
