Before you can tie your shoelaces for one of the worlds most remote races,you must first navigate through wild seas,endure(忍受)freezing temperatures and go on a journey that tests more than just your physical enduran...Before you can tie your shoelaces for one of the worlds most remote races,you must first navigate through wild seas,endure(忍受)freezing temperatures and go on a journey that tests more than just your physical endurance.This is no ordinary race;it requires thorough preparation and a strong will.展开更多
This study proposes a method for calculating the probability distribution of structural responses at different intensities using the endurance time(ET)method.The results can be used to calculate the fragility curve of...This study proposes a method for calculating the probability distribution of structural responses at different intensities using the endurance time(ET)method.The results can be used to calculate the fragility curve of structural collapse.The ET method involves dynamic analysis of a structure under an intensifying record over time.While conventional ET methods can determine the median of the structural response,they lack the ability to calculate its dispersion.To address this limitation,the present study utilizes ET analysis and single-degree-of-freedom(SDOF)systems to develop a method that considers the record-to-record variability for calculating the probability distribution of structural response.The accuracy of this method is evaluated by comparing it with the incremental dynamic analysis(IDA)method using special moment frames.The results demonstrate that the proposed method achieves a reasonably accurate estimation of dispersion while significantly reducing the computational burden(by approximately 95%)compared to the IDA method.展开更多
In this study,application of the spectral representation method for generation of endurance time excitation functions is introduced.Using this method,the intensifying acceleration time series is generated so that its ...In this study,application of the spectral representation method for generation of endurance time excitation functions is introduced.Using this method,the intensifying acceleration time series is generated so that its acceleration response spectrum in any desired time duration is compatible with a time-scaled predefined acceleration response spectrum.For this purpose,simulated stationary acceleration time series is multiplied by the time dependent linear modulation function,then using a simple iterative scheme,it is forced to match a target acceleration response spectrum.It is shown that the generated samples have excellent conformity in low frequency,which is useful for nonlinear endurance time analysis.In the second part of this study,it is shown that this procedure can be extended to generate a set of spatially correlated endurance time excitation functions.This makes it possible to assess the performance of long structures under multi-support seismic excitation using endurance time analysis.展开更多
Background: The physiological and biochemical demands of intense exercise elicit both muscle-based and systemic responses. The main adaptations to endurance exercise include the correction of electrolyte imbalance, a ...Background: The physiological and biochemical demands of intense exercise elicit both muscle-based and systemic responses. The main adaptations to endurance exercise include the correction of electrolyte imbalance, a decrease in glycogen storage and the increase of oxidative stress, intestinal permeability, muscle damage, and systemic inflammatory response. Adaptations to exercise might be influenced by the gut microbiota, which plays an important role in the production, storage, and expenditure of energy obtained from the diet as well as in inflammation,redox reactions, and hydration status.Methods: A systematic and comprehensive search of electronic databases, including MEDLINE, Scopus, Clinical Trials.gov, Science Direct,Springer Link, and EMBASE was done. The search process was completed using the keywords: "endurance", "exercise", "immune response","microbiota", "nutrition", and "probiotics".Results: Reviewed literature supports the hypothesis that intestinal microbiota might be able to provide a measureable, effective marker of an athlete's immune function and that microbial composition analysis might also be sensitive enough to detect exercise-induced stress and metabolic disorders. The review also supports the hypothesis that modifying the microbiota through the use of probiotics could be an important therapeutic tool to improve athletes' overall general health, performance, and energy availability while controlling inflammation and redox levels.Conclusion: The present review provides a comprehensive overview of how gut microbiota may have a key role in controlling the oxidative stress and inflammatory responses as well as improving metabolism and energy expenditure during intense exercise.展开更多
Purpose:To determine the intra-tester reliability of clinical measurements that assess five components related to core stability:strength. endurance,flexibility,motor control,and function. Methods:Participants were 15...Purpose:To determine the intra-tester reliability of clinical measurements that assess five components related to core stability:strength. endurance,flexibility,motor control,and function. Methods:Participants were 15 college-aged males who had not suffered any orthopedic injury in the past year.Core strength measurements included eight isometric tests and a sit-up test.The four core endurance tests were the trunk flexor test,trunk extensor test,and bilateral side bridge tests.Flexibility tests included the sit-and-reach test and active range of the trunk and hip joint motions.Proprioception via passive reposition tests of the hips and a single limb balance test on an unsteady platform were used to evaluate core motor control.Functional measurements consisted of a squat test and a single leg hop test for time and distance.Measurements were performed during two data collection sessions with a week’s rest between the sessions.Intra-class correlation coefficients were calculated to establish reliability. Results:The overall intra-rater reliability for all core stability related measurements ranged from low(ICC = 0.35,left hip reposition) to very high(ICC = 0.98,sit-and-reach).As a group,the core endurance tests were observed to be the most reliable. Conclusion:There are highly reliable tests in each of the five groups.Overall,core endurance tests are the most reliable measurements,followed by the flexibility,strength,neuromuscular control,and functional tests,respectively.展开更多
Unmanned Aerial Vehicle（UAV） is developing towards the direction of High Altitude Long Endurance（HALE）. This will have an important influence on the stability of its airborne electronic equipment using passive the...Unmanned Aerial Vehicle（UAV） is developing towards the direction of High Altitude Long Endurance（HALE）. This will have an important influence on the stability of its airborne electronic equipment using passive thermal management. In this paper, a multi-node transient thermal model for airborne electronic equipment is set up based on the thermal network method to predict their dynamic temperature responses under high altitude and long flight time conditions. Some relevant factors are considered into this temperature prediction model including flight environment,radiation, convection, heat conduction, etc. An experimental chamber simulating a high altitude flight environment was set up to survey the dynamic thermal responses of airborne electronic equipment in a UAV. According to the experimental measurement results, the multi-node transient thermal model is verified without consideration of the effects of flight speed. Then, a modified way about outside flight speed is added into the model to improve the temperature prediction performance. Finally, the corresponding simulation code is developed based on the proposed model. It can realize the dynamic temperature prediction of airborne electronic equipment under HALE conditions.展开更多
Evaluation of structural performance under seismic excitations from low intensity to high intensity is essential to verify the seismic resistant capacity of a structure, and usually carried out by the incremental dyna...Evaluation of structural performance under seismic excitations from low intensity to high intensity is essential to verify the seismic resistant capacity of a structure, and usually carried out by the incremental dynamic analysis (IDA) method or pushover method. The recently developed endurance time (ET) method is another method that uses dynamic pushover excitations, i.e., endurance time acceleration function, to obtain results similar to those obtained by IDA or pushover methods with low computational cost and acceptable accuracy. This study proposes an improvement on the ET method by considering more restrictions for both the elastic and inelastic response spectra in the generation procedure, and by specifying a target duration. Four reinforced concrete frame structures with 4, 8, 12, and 16 stories are adopted to verify the accuracy of the improved method. Comparison of the results obtained by the proposed method, the ET method and the IDA method shows that the improved method has a higher accuracy than the ET method. For evaluation of structural responses under specifi c ground motion intensity, which is typically required in seismic design codes, the results obtained by the proposed method are compared with fi ve commonly used ground motion selection methods, and shows the proposed method provides acceptable accuracy for engineering applications.展开更多
After intraperitoneal injection of 20 mg/kg lead acetate, rats received 8 weeks of treadmill exercise （15-22 m/min, 25-64 minutes） and/or treadmill exercise at 1.6 km/h until exhaustion. The markers related to neuro...After intraperitoneal injection of 20 mg/kg lead acetate, rats received 8 weeks of treadmill exercise （15-22 m/min, 25-64 minutes） and/or treadmill exercise at 1.6 km/h until exhaustion. The markers related to neurotoxicity were measured by enzyme-linked immunosorbent assay method. 8 weeks of treadmill exercise significantly increased brain-derived neurotrophic factor level in the hippocampus （P = 0.04） and plasma level of total antioxidant capacity of rats exposed to lead acetate （P 〈 0.001）, and significantly decreased plasma level of malondialdehyde （P 〈 0.001）. Acute exercise only decreased the hippocampal malondialdehyde level （P = 0.09） and increased brain-derived neurotrophic factor level in the hippocampus （P = 0.66）. Acute exercise also enhanced the total antioxidant capacity in rats exposed to lead acetate, insignificantly （P = 0.99）, These findings suggest that chronic treadmill exercise can significantly decrease neurotoxicity and alleviate oxidative stress in rats exposed to lead acetate. However, acute endurance exercise was not associated with these beneficial effects.展开更多
In endurance time(ET) method structures are subjected to a set of predesigned intensifying excitations. These excitations are produced in a way that their response spectrum, while complying with a specifi ed spectrum,...In endurance time(ET) method structures are subjected to a set of predesigned intensifying excitations. These excitations are produced in a way that their response spectrum, while complying with a specifi ed spectrum, intensifi es with time so they can be used approximately to simulate the average effects of several ground motions scaled to different intensities. In this paper applicability of the ET method for evaluating collapse potential of buildings is investigated. A set of four steel moment frames is used for collapse assessment. The process of using ET method in collapse evaluation is explained and the results are compared with incremental dynamic analysis(IDA) results. It is shown that although the computational effort using the ET method is much less than the IDA analysis, the results of both methods are consistent. Finally collapse fragility curves using ET and IDA methods are produced and it is shown that the probabilities of collapse in different hazard levels are also consistent.展开更多
Liquid storage tanks are essential structures that are often located in residential and industrial areas; thus an assessment of their seismic performance is an important engineering issue. In this paper, the seismic r...Liquid storage tanks are essential structures that are often located in residential and industrial areas; thus an assessment of their seismic performance is an important engineering issue. In this paper, the seismic response ofunanchored steel liquid storage tanks is investigated using the endurance time （ET） dynamic analysis procedure and compared to responses obtained for anchored tanks under actual ground motions and intensifying ET records. In most cases, the results from ground motions are properly obtained with negligible differences using ET records. It is observed that uplifting of the tank base, which is closely related to the tank aspect ratio, has the greatest significance in the responses of the tank and can be predicted with reasonable accuracy by using currently available ET records.展开更多
This paper reports the improvement of electrical,ferroelectric and endurance of Hf_(0.5)Zr_(0.5)O_(2)(HZO)thinfilm capacitors by implementing W electrode.The W/HZO/W capacitor shows excellent pristine 2 P_(r)values of...This paper reports the improvement of electrical,ferroelectric and endurance of Hf_(0.5)Zr_(0.5)O_(2)(HZO)thinfilm capacitors by implementing W electrode.The W/HZO/W capacitor shows excellent pristine 2 P_(r)values of 45.1 gC/cm^(2)at±6 V,which are much higher than those of TiN/HZO/W(34.4μC/cm^(2))and W/HZO/TiN(26.9μC/cm^(2))capacitors.Notably,the maximum initial 2 P_(r)value of W/HZO/W capacitor can reach as high as 57.9μC/cm^(2)at±7.5 V.These strong ferroelectric polarization effects are ascribed to the W electrode with a fairly low thermal expansion coefficient which provides a larger in-plane tensile strain compared with TiN electrode,allowing for enhancement of o-phase formation.Moreover,the W/HZO/W capacitor also exhibits higher endurance,smaller wake-up effect(10.1%)and superior fatigue properties up to 1.5×10^(10)cycles compared to the TiN/HZO/W and W/HZO/TiN capacitors.Such improvements of W/HZO/W capacitor are mainly due to the decreased leakage current by more than an order of magnitude compared to the W/HZO/TiN capacitor.These results demonstrate that capping electrode material plays an important role in the enhancement of o-phase formation,reduces oxygen vacancies,mitigates wake-up effect and improves reliability.展开更多
The present paper reports the unusual enhancement of endurance life of ball bearings subjected to carbonitriding treatment. The microstructure was characterized by scanning electron microscopy and correlated with hard...The present paper reports the unusual enhancement of endurance life of ball bearings subjected to carbonitriding treatment. The microstructure was characterized by scanning electron microscopy and correlated with hardness and X-ray diffraction analysis. Endurance tests at 90% reliability revealed that the carbonitrided bearings exhibit nearly ten times more life than the non-carbonitrided bearings. This is attributed to synergic combination of retained austenitic, fine martensitic microstructure and ultrafine carbide precipitates obtained by carbonitriding treatment.展开更多
Objective: This systematic review aimed to critically analyze the literature to determine how high-intensity intermittent training(HIIT) affects recreational endurance runners in the short-and long-term.Methods: Elect...Objective: This systematic review aimed to critically analyze the literature to determine how high-intensity intermittent training(HIIT) affects recreational endurance runners in the short-and long-term.Methods: Electronic databases were searched for literature dating from January 2000 to October 2015. The search was conducted using the key words "high-intensity intermittent training" or "high-intensity interval exercise" or "interval running" or "sprint interval training" and "endurance runners" or "long distance runners". A systematic approach was used to evaluate the 783 articles identified for initial review. Studies were included if they investigated HIIT in recreational endurance runners. The methodological quality of the studies was evaluated using the Physiotherapy Evidence Database(PEDro) scale(for intervention studies) and the modified Downs and Black Quality Index(for cross-sectional studies).Results: Twenty-three studies met the inclusionary criteria for review. The results are presented in 2 parts: cross-sectional(n = 15) and intervention studies(n = 8). In the 15 cross-sectional studies selected, endurance runners performed at least 1 HIIT protocol, and the acute impact on physiological, neuromuscular, metabolic and/or biomechanical variables was assessed. Intervention studies lasted a minimum of 4 weeks, with 10 weeks being the longest intervention period, and included 2 to 4 HIIT sessions per week. Most of these studies combined HIIT sessions with continuous run(CR) sessions; 2 studies' subjects performed HIIT exclusively.Conclusion: HIIT-based running plans(2 to 3 HIIT sessions per week, combining HIIT and CR runs) show athletic performance improvements in endurance runners by improving maximal oxygen uptake and running economy along with muscular and metabolic adaptations. To maximize the adaptations to training, both HIIT and CR must be part of training programs for endurance runners.展开更多
To overcome the problems encountered in predicting the endurance of electricpowered fixed-wing unmanned aerial vehicles(UAVs),which were stemmed from the dynamic changes in electric power system efficiency and battery...To overcome the problems encountered in predicting the endurance of electricpowered fixed-wing unmanned aerial vehicles(UAVs),which were stemmed from the dynamic changes in electric power system efficiency and battery discharge characteristics under different operating conditions,the required battery power model and battery discharge model were studied.The required battery power model was determined using an approximate model of electric power system efficiency based on wind tunnel testing and the self-adaptive penalty function.Furthermore,current correction and ambient temperature correction terms were proposed for the trained Kriging model representing the discharge characteristics under standard operation,and then the discharged capacity-terminal voltage model was established.Through numerical integration of this model with the required battery power model,the electric-powered fixed-wing UAV endurance prediction model was obtained.Laboratory tests indicated that the proposed endurance model could precisely calculate the battery discharge time and accurately describe the battery discharge process.The similarity of the theoretical and flight test results reflected the accuracy of the proposed endurance model as well as the importance of considering dynamic changes in power system efficiency in endurance calculations.The proposed endurance model meeting precision requirements can be used in practical engineering applications.展开更多
The endurance time (ET) method is a time history based dynamic analysis in which structures are subjected to gradually intensifying excitations and their performances are judged based on their responses at various exc...The endurance time (ET) method is a time history based dynamic analysis in which structures are subjected to gradually intensifying excitations and their performances are judged based on their responses at various excitation levels. Using this method, the computational effort required for estimating probable seismic demand parameters can be reduced by an order of magnitude. Calculation of the maximum displacement or target displacement is a basic requirement for estimating performance based on structural design. The purpose of this paper is to compare the results of the nonlinear ET method with the nonlinear static pushover (NSP) method of FEMA 356 by evaluating performances and target displacements of steel frames. This study will lead to a deeper insight into the capabilities and limitations of the ET method. The results are further compared with those of the standard nonlinear response history analysis. We conclude that results from the ET analysis are in proper agreement with those from standard procedures.展开更多
[Objectives] To study the effects of maca extract on the exercise endurance and ultrastructure of mitochondria in spinal neurons.[Methods]First,50 Wistar rats were randomly divided into 5 groups. The control group: no...[Objectives] To study the effects of maca extract on the exercise endurance and ultrastructure of mitochondria in spinal neurons.[Methods]First,50 Wistar rats were randomly divided into 5 groups. The control group: no swimming,administered intragastrically the same volume of distilled water; simple swimming group: free swimming,administered intragastrically the same volume of distilled water; maca extract groups: free swimming,and treated with 4. 0,5. 3,and 8. 0 g/kg dose of maca extracts. Swimming rats swam freely in the circulating water flow of swimming pool and administered for 15 d. On the 16 th d,after the swimming endurance test,the rats were killed painlessly. The ultrastructure of the mitochondria in the spinal neurons was observed with a projection electron microscope,muscle glycogen,malondialdehyde( MDA),superoxide dismutase( SOD),glutathione peroxidase( GSH-Px) and free calcium in muscle were measured by radioimmunoassay.[Results] Compared with the simple swimming group,the swimming time before sinking and total swimming time extended 19. 83%,60. 28%,77. 55% and 55. 34%,73. 91% and 94. 47% respectively,and the differences were statistically significant( P < 0. 01). The sinking times decreased by 34. 35%,51. 18% and 57. 96% respectively,the differences were statistically significant( P < 0. 01). MDA and free calcium decreased by 20. 10%,31. 49% and 38. 72%,respectively with statistically significant differences( P < 0. 01) and 6. 42%,17. 58%and 26. 35% respectively. The levels of SOD,GSH-Px and muscle glycogen increased by 5. 12%,22. 74%,52. 53%,44. 22%,77. 79%and 98. 45% respectively,with statistically significant differences( P < 0. 01) and 35. 08%,47. 83% and 81. 88%,respectively,with statistically significant differences( P < 0. 01). The volume density( Vd),surface density( Sd) and number density( Nd) of mitochondria of spinal neurons decreased by 7. 79%,18. 18%,31. 17%,16. 95%,27. 34%,43. 31% and 13. 51%,23. 19% and 43. 15% respectively.[Conclusions]Maca extract can protect ultrastructure of the mitochondria in the spinal neurons,antioxidant activity,increase muscle glycogen,and improving the exercise capacity.展开更多
To avoid the numerical complexities of the battery discharge law of electric-powered rotorcrafts,this study uses the Kriging method to model the discharge characteristics of Li-Po batteries under standard conditions.A...To avoid the numerical complexities of the battery discharge law of electric-powered rotorcrafts,this study uses the Kriging method to model the discharge characteristics of Li-Po batteries under standard conditions.A linear current compensation term and an ambient temperature compensation term based on radial basis functions are then applied to the trained Kriging model,leading to the complete discharged capacity-terminal voltage model.Using an orthogonal experimental design and a sequential method,the coefficients of the current and ambient temperature compensation terms are determined through robust optimization.An endurance calculation model for electric-powered rotorcrafts is then established,based on the battery discharge model,through numerical integration.Laboratory tests show that the maximum relative error of the proposed discharged capacity-terminal voltage model at detection points is 0.0086,and that of the rotorcraft endurance calculation model is 0.0195,thus verifying their accuracy.A flight test further demonstrates the applicability of the proposed endurance model to general electric-powered rotorcrafts.展开更多
With the rapid development of machine learning,the demand for high-efficient computing becomes more and more urgent.To break the bottleneck of the traditional Von Neumann architecture,computing-in-memory(CIM)has attra...With the rapid development of machine learning,the demand for high-efficient computing becomes more and more urgent.To break the bottleneck of the traditional Von Neumann architecture,computing-in-memory(CIM)has attracted increasing attention in recent years.In this work,to provide a feasible CIM solution for the large-scale neural networks(NN)requiring continuous weight updating in online training,a flash-based computing-in-memory with high endurance(10^(9) cycles)and ultrafast programming speed is investigated.On the one hand,the proposed programming scheme of channel hot electron injection(CHEI)and hot hole injection(HHI)demonstrate high linearity,symmetric potentiation,and a depression process,which help to improve the training speed and accuracy.On the other hand,the low-damage programming scheme and memory window(MW)optimizations can suppress cell degradation effectively with improved computing accuracy.Even after 109 cycles,the leakage current(I_(off))of cells remains sub-10pA,ensuring the large-scale computing ability of memory.Further characterizations are done on read disturb to demonstrate its robust reliabilities.By processing CIFAR-10 tasks,it is evident that~90%accuracy can be achieved after 109 cycles in both ResNet50 and VGG16 NN.Our results suggest that flash-based CIM has great potential to overcome the limitations of traditional Von Neumann architectures and enable high-performance NN online training,which pave the way for further development of artificial intelligence(AI)accelerators.展开更多
Probabilistic Seismic Loss Estimation is a methodology used as a quantitative and explicit expression of the performance of buildings using terms that address the interests of both owners and insurance companies. Appl...Probabilistic Seismic Loss Estimation is a methodology used as a quantitative and explicit expression of the performance of buildings using terms that address the interests of both owners and insurance companies. Applying the ATC 58 approach for seismic loss assessment of buildings requires using Incremental Dynamic Analysis （IDA）, which needs hundreds of time-consuming analyses, which in turn hinders its wide application. The Endurance Time Method （ETM） is proposed herein as part of a demand propagation prediction procedure and is shown to be an economical alternative to IDA. Various scenarios were considered to achieve this purpose and their appropriateness has been evaluated using statistical methods. The most precise and efficient scenario was validated through comparison against IDA driven response predictions of 34 code conforming benchmark structures and was proven to be sufficiently precise while offering a great deal of efficiency. The loss values were estimated by replacing IDA with the proposed ETM-based procedure in the ATC 58 procedure and it was fotmd that these values suffer from varying inaccuracies, which were attributed to the discretized nature of damage and loss prediction functions provided by ATC 58.展开更多
文摘Before you can tie your shoelaces for one of the worlds most remote races,you must first navigate through wild seas,endure(忍受)freezing temperatures and go on a journey that tests more than just your physical endurance.This is no ordinary race;it requires thorough preparation and a strong will.
文摘This study proposes a method for calculating the probability distribution of structural responses at different intensities using the endurance time(ET)method.The results can be used to calculate the fragility curve of structural collapse.The ET method involves dynamic analysis of a structure under an intensifying record over time.While conventional ET methods can determine the median of the structural response,they lack the ability to calculate its dispersion.To address this limitation,the present study utilizes ET analysis and single-degree-of-freedom(SDOF)systems to develop a method that considers the record-to-record variability for calculating the probability distribution of structural response.The accuracy of this method is evaluated by comparing it with the incremental dynamic analysis(IDA)method using special moment frames.The results demonstrate that the proposed method achieves a reasonably accurate estimation of dispersion while significantly reducing the computational burden(by approximately 95%)compared to the IDA method.
文摘In this study,application of the spectral representation method for generation of endurance time excitation functions is introduced.Using this method,the intensifying acceleration time series is generated so that its acceleration response spectrum in any desired time duration is compatible with a time-scaled predefined acceleration response spectrum.For this purpose,simulated stationary acceleration time series is multiplied by the time dependent linear modulation function,then using a simple iterative scheme,it is forced to match a target acceleration response spectrum.It is shown that the generated samples have excellent conformity in low frequency,which is useful for nonlinear endurance time analysis.In the second part of this study,it is shown that this procedure can be extended to generate a set of spatially correlated endurance time excitation functions.This makes it possible to assess the performance of long structures under multi-support seismic excitation using endurance time analysis.
文摘Background: The physiological and biochemical demands of intense exercise elicit both muscle-based and systemic responses. The main adaptations to endurance exercise include the correction of electrolyte imbalance, a decrease in glycogen storage and the increase of oxidative stress, intestinal permeability, muscle damage, and systemic inflammatory response. Adaptations to exercise might be influenced by the gut microbiota, which plays an important role in the production, storage, and expenditure of energy obtained from the diet as well as in inflammation,redox reactions, and hydration status.Methods: A systematic and comprehensive search of electronic databases, including MEDLINE, Scopus, Clinical Trials.gov, Science Direct,Springer Link, and EMBASE was done. The search process was completed using the keywords: "endurance", "exercise", "immune response","microbiota", "nutrition", and "probiotics".Results: Reviewed literature supports the hypothesis that intestinal microbiota might be able to provide a measureable, effective marker of an athlete's immune function and that microbial composition analysis might also be sensitive enough to detect exercise-induced stress and metabolic disorders. The review also supports the hypothesis that modifying the microbiota through the use of probiotics could be an important therapeutic tool to improve athletes' overall general health, performance, and energy availability while controlling inflammation and redox levels.Conclusion: The present review provides a comprehensive overview of how gut microbiota may have a key role in controlling the oxidative stress and inflammatory responses as well as improving metabolism and energy expenditure during intense exercise.
文摘Purpose:To determine the intra-tester reliability of clinical measurements that assess five components related to core stability:strength. endurance,flexibility,motor control,and function. Methods:Participants were 15 college-aged males who had not suffered any orthopedic injury in the past year.Core strength measurements included eight isometric tests and a sit-up test.The four core endurance tests were the trunk flexor test,trunk extensor test,and bilateral side bridge tests.Flexibility tests included the sit-and-reach test and active range of the trunk and hip joint motions.Proprioception via passive reposition tests of the hips and a single limb balance test on an unsteady platform were used to evaluate core motor control.Functional measurements consisted of a squat test and a single leg hop test for time and distance.Measurements were performed during two data collection sessions with a week’s rest between the sessions.Intra-class correlation coefficients were calculated to establish reliability. Results:The overall intra-rater reliability for all core stability related measurements ranged from low(ICC = 0.35,left hip reposition) to very high(ICC = 0.98,sit-and-reach).As a group,the core endurance tests were observed to be the most reliable. Conclusion:There are highly reliable tests in each of the five groups.Overall,core endurance tests are the most reliable measurements,followed by the flexibility,strength,neuromuscular control,and functional tests,respectively.
基金the financial support of National Key R&D Program of China (No.2017YFB1201100)
文摘Unmanned Aerial Vehicle（UAV） is developing towards the direction of High Altitude Long Endurance（HALE）. This will have an important influence on the stability of its airborne electronic equipment using passive thermal management. In this paper, a multi-node transient thermal model for airborne electronic equipment is set up based on the thermal network method to predict their dynamic temperature responses under high altitude and long flight time conditions. Some relevant factors are considered into this temperature prediction model including flight environment,radiation, convection, heat conduction, etc. An experimental chamber simulating a high altitude flight environment was set up to survey the dynamic thermal responses of airborne electronic equipment in a UAV. According to the experimental measurement results, the multi-node transient thermal model is verified without consideration of the effects of flight speed. Then, a modified way about outside flight speed is added into the model to improve the temperature prediction performance. Finally, the corresponding simulation code is developed based on the proposed model. It can realize the dynamic temperature prediction of airborne electronic equipment under HALE conditions.
基金National Key R&D Program of China under Grant No.2016YFC0701500National Natural Science Foundation of China under Grant No.51578202
文摘Evaluation of structural performance under seismic excitations from low intensity to high intensity is essential to verify the seismic resistant capacity of a structure, and usually carried out by the incremental dynamic analysis (IDA) method or pushover method. The recently developed endurance time (ET) method is another method that uses dynamic pushover excitations, i.e., endurance time acceleration function, to obtain results similar to those obtained by IDA or pushover methods with low computational cost and acceptable accuracy. This study proposes an improvement on the ET method by considering more restrictions for both the elastic and inelastic response spectra in the generation procedure, and by specifying a target duration. Four reinforced concrete frame structures with 4, 8, 12, and 16 stories are adopted to verify the accuracy of the improved method. Comparison of the results obtained by the proposed method, the ET method and the IDA method shows that the improved method has a higher accuracy than the ET method. For evaluation of structural responses under specifi c ground motion intensity, which is typically required in seismic design codes, the results obtained by the proposed method are compared with fi ve commonly used ground motion selection methods, and shows the proposed method provides acceptable accuracy for engineering applications.
文摘After intraperitoneal injection of 20 mg/kg lead acetate, rats received 8 weeks of treadmill exercise （15-22 m/min, 25-64 minutes） and/or treadmill exercise at 1.6 km/h until exhaustion. The markers related to neurotoxicity were measured by enzyme-linked immunosorbent assay method. 8 weeks of treadmill exercise significantly increased brain-derived neurotrophic factor level in the hippocampus （P = 0.04） and plasma level of total antioxidant capacity of rats exposed to lead acetate （P 〈 0.001）, and significantly decreased plasma level of malondialdehyde （P 〈 0.001）. Acute exercise only decreased the hippocampal malondialdehyde level （P = 0.09） and increased brain-derived neurotrophic factor level in the hippocampus （P = 0.66）. Acute exercise also enhanced the total antioxidant capacity in rats exposed to lead acetate, insignificantly （P = 0.99）, These findings suggest that chronic treadmill exercise can significantly decrease neurotoxicity and alleviate oxidative stress in rats exposed to lead acetate. However, acute endurance exercise was not associated with these beneficial effects.
文摘In endurance time(ET) method structures are subjected to a set of predesigned intensifying excitations. These excitations are produced in a way that their response spectrum, while complying with a specifi ed spectrum, intensifi es with time so they can be used approximately to simulate the average effects of several ground motions scaled to different intensities. In this paper applicability of the ET method for evaluating collapse potential of buildings is investigated. A set of four steel moment frames is used for collapse assessment. The process of using ET method in collapse evaluation is explained and the results are compared with incremental dynamic analysis(IDA) results. It is shown that although the computational effort using the ET method is much less than the IDA analysis, the results of both methods are consistent. Finally collapse fragility curves using ET and IDA methods are produced and it is shown that the probabilities of collapse in different hazard levels are also consistent.
文摘Liquid storage tanks are essential structures that are often located in residential and industrial areas; thus an assessment of their seismic performance is an important engineering issue. In this paper, the seismic response ofunanchored steel liquid storage tanks is investigated using the endurance time （ET） dynamic analysis procedure and compared to responses obtained for anchored tanks under actual ground motions and intensifying ET records. In most cases, the results from ground motions are properly obtained with negligible differences using ET records. It is observed that uplifting of the tank base, which is closely related to the tank aspect ratio, has the greatest significance in the responses of the tank and can be predicted with reasonable accuracy by using currently available ET records.
基金financially supported by the National Natural Science Foundation of China(No.51872099)the Hong Kong Research Grant Council(No.15300619)+2 种基金the Science and Technology Program of Guangzhou(No.201905-0001)the Guangdong Science and Technology Project-International Cooperation(No.2021A0505030064)financial support by the Hong Kong Scholars Program(No.XJ2019006)。
文摘This paper reports the improvement of electrical,ferroelectric and endurance of Hf_(0.5)Zr_(0.5)O_(2)(HZO)thinfilm capacitors by implementing W electrode.The W/HZO/W capacitor shows excellent pristine 2 P_(r)values of 45.1 gC/cm^(2)at±6 V,which are much higher than those of TiN/HZO/W(34.4μC/cm^(2))and W/HZO/TiN(26.9μC/cm^(2))capacitors.Notably,the maximum initial 2 P_(r)value of W/HZO/W capacitor can reach as high as 57.9μC/cm^(2)at±7.5 V.These strong ferroelectric polarization effects are ascribed to the W electrode with a fairly low thermal expansion coefficient which provides a larger in-plane tensile strain compared with TiN electrode,allowing for enhancement of o-phase formation.Moreover,the W/HZO/W capacitor also exhibits higher endurance,smaller wake-up effect(10.1%)and superior fatigue properties up to 1.5×10^(10)cycles compared to the TiN/HZO/W and W/HZO/TiN capacitors.Such improvements of W/HZO/W capacitor are mainly due to the decreased leakage current by more than an order of magnitude compared to the W/HZO/TiN capacitor.These results demonstrate that capping electrode material plays an important role in the enhancement of o-phase formation,reduces oxygen vacancies,mitigates wake-up effect and improves reliability.
文摘The present paper reports the unusual enhancement of endurance life of ball bearings subjected to carbonitriding treatment. The microstructure was characterized by scanning electron microscopy and correlated with hardness and X-ray diffraction analysis. Endurance tests at 90% reliability revealed that the carbonitrided bearings exhibit nearly ten times more life than the non-carbonitrided bearings. This is attributed to synergic combination of retained austenitic, fine martensitic microstructure and ultrafine carbide precipitates obtained by carbonitriding treatment.
基金the University of Jaén for its support to the present study
文摘Objective: This systematic review aimed to critically analyze the literature to determine how high-intensity intermittent training(HIIT) affects recreational endurance runners in the short-and long-term.Methods: Electronic databases were searched for literature dating from January 2000 to October 2015. The search was conducted using the key words "high-intensity intermittent training" or "high-intensity interval exercise" or "interval running" or "sprint interval training" and "endurance runners" or "long distance runners". A systematic approach was used to evaluate the 783 articles identified for initial review. Studies were included if they investigated HIIT in recreational endurance runners. The methodological quality of the studies was evaluated using the Physiotherapy Evidence Database(PEDro) scale(for intervention studies) and the modified Downs and Black Quality Index(for cross-sectional studies).Results: Twenty-three studies met the inclusionary criteria for review. The results are presented in 2 parts: cross-sectional(n = 15) and intervention studies(n = 8). In the 15 cross-sectional studies selected, endurance runners performed at least 1 HIIT protocol, and the acute impact on physiological, neuromuscular, metabolic and/or biomechanical variables was assessed. Intervention studies lasted a minimum of 4 weeks, with 10 weeks being the longest intervention period, and included 2 to 4 HIIT sessions per week. Most of these studies combined HIIT sessions with continuous run(CR) sessions; 2 studies' subjects performed HIIT exclusively.Conclusion: HIIT-based running plans(2 to 3 HIIT sessions per week, combining HIIT and CR runs) show athletic performance improvements in endurance runners by improving maximal oxygen uptake and running economy along with muscular and metabolic adaptations. To maximize the adaptations to training, both HIIT and CR must be part of training programs for endurance runners.
文摘To overcome the problems encountered in predicting the endurance of electricpowered fixed-wing unmanned aerial vehicles(UAVs),which were stemmed from the dynamic changes in electric power system efficiency and battery discharge characteristics under different operating conditions,the required battery power model and battery discharge model were studied.The required battery power model was determined using an approximate model of electric power system efficiency based on wind tunnel testing and the self-adaptive penalty function.Furthermore,current correction and ambient temperature correction terms were proposed for the trained Kriging model representing the discharge characteristics under standard operation,and then the discharged capacity-terminal voltage model was established.Through numerical integration of this model with the required battery power model,the electric-powered fixed-wing UAV endurance prediction model was obtained.Laboratory tests indicated that the proposed endurance model could precisely calculate the battery discharge time and accurately describe the battery discharge process.The similarity of the theoretical and flight test results reflected the accuracy of the proposed endurance model as well as the importance of considering dynamic changes in power system efficiency in endurance calculations.The proposed endurance model meeting precision requirements can be used in practical engineering applications.
文摘The endurance time (ET) method is a time history based dynamic analysis in which structures are subjected to gradually intensifying excitations and their performances are judged based on their responses at various excitation levels. Using this method, the computational effort required for estimating probable seismic demand parameters can be reduced by an order of magnitude. Calculation of the maximum displacement or target displacement is a basic requirement for estimating performance based on structural design. The purpose of this paper is to compare the results of the nonlinear ET method with the nonlinear static pushover (NSP) method of FEMA 356 by evaluating performances and target displacements of steel frames. This study will lead to a deeper insight into the capabilities and limitations of the ET method. The results are further compared with those of the standard nonlinear response history analysis. We conclude that results from the ET analysis are in proper agreement with those from standard procedures.
基金Supported by Science and Technology Planning Project of Lanzhou City(2015-3-80)Science and Technology Innovation Team Project for Universities in Gansu Province(2016C-09)+3 种基金Talent Innovation and Entrepreneurship Project of Lanzhou City(2016-RC-85)Gansu Natural Science Foundation Project(17JR5RA158)Investigation Theory and Practice Research Center Project of Northwest Minority AreasGansu Province Evidence Science Characteristic Discipline Project
文摘[Objectives] To study the effects of maca extract on the exercise endurance and ultrastructure of mitochondria in spinal neurons.[Methods]First,50 Wistar rats were randomly divided into 5 groups. The control group: no swimming,administered intragastrically the same volume of distilled water; simple swimming group: free swimming,administered intragastrically the same volume of distilled water; maca extract groups: free swimming,and treated with 4. 0,5. 3,and 8. 0 g/kg dose of maca extracts. Swimming rats swam freely in the circulating water flow of swimming pool and administered for 15 d. On the 16 th d,after the swimming endurance test,the rats were killed painlessly. The ultrastructure of the mitochondria in the spinal neurons was observed with a projection electron microscope,muscle glycogen,malondialdehyde( MDA),superoxide dismutase( SOD),glutathione peroxidase( GSH-Px) and free calcium in muscle were measured by radioimmunoassay.[Results] Compared with the simple swimming group,the swimming time before sinking and total swimming time extended 19. 83%,60. 28%,77. 55% and 55. 34%,73. 91% and 94. 47% respectively,and the differences were statistically significant( P < 0. 01). The sinking times decreased by 34. 35%,51. 18% and 57. 96% respectively,the differences were statistically significant( P < 0. 01). MDA and free calcium decreased by 20. 10%,31. 49% and 38. 72%,respectively with statistically significant differences( P < 0. 01) and 6. 42%,17. 58%and 26. 35% respectively. The levels of SOD,GSH-Px and muscle glycogen increased by 5. 12%,22. 74%,52. 53%,44. 22%,77. 79%and 98. 45% respectively,with statistically significant differences( P < 0. 01) and 35. 08%,47. 83% and 81. 88%,respectively,with statistically significant differences( P < 0. 01). The volume density( Vd),surface density( Sd) and number density( Nd) of mitochondria of spinal neurons decreased by 7. 79%,18. 18%,31. 17%,16. 95%,27. 34%,43. 31% and 13. 51%,23. 19% and 43. 15% respectively.[Conclusions]Maca extract can protect ultrastructure of the mitochondria in the spinal neurons,antioxidant activity,increase muscle glycogen,and improving the exercise capacity.
文摘To avoid the numerical complexities of the battery discharge law of electric-powered rotorcrafts,this study uses the Kriging method to model the discharge characteristics of Li-Po batteries under standard conditions.A linear current compensation term and an ambient temperature compensation term based on radial basis functions are then applied to the trained Kriging model,leading to the complete discharged capacity-terminal voltage model.Using an orthogonal experimental design and a sequential method,the coefficients of the current and ambient temperature compensation terms are determined through robust optimization.An endurance calculation model for electric-powered rotorcrafts is then established,based on the battery discharge model,through numerical integration.Laboratory tests show that the maximum relative error of the proposed discharged capacity-terminal voltage model at detection points is 0.0086,and that of the rotorcraft endurance calculation model is 0.0195,thus verifying their accuracy.A flight test further demonstrates the applicability of the proposed endurance model to general electric-powered rotorcrafts.
基金This work was supported by the National Natural Science Foundation of China(Nos.62034006,92264201,and 91964105)the Natural Science Foundation of Shandong Province(Nos.ZR2020JQ28 and ZR2020KF016)the Program of Qilu Young Scholars of Shandong University.
文摘With the rapid development of machine learning,the demand for high-efficient computing becomes more and more urgent.To break the bottleneck of the traditional Von Neumann architecture,computing-in-memory(CIM)has attracted increasing attention in recent years.In this work,to provide a feasible CIM solution for the large-scale neural networks(NN)requiring continuous weight updating in online training,a flash-based computing-in-memory with high endurance(10^(9) cycles)and ultrafast programming speed is investigated.On the one hand,the proposed programming scheme of channel hot electron injection(CHEI)and hot hole injection(HHI)demonstrate high linearity,symmetric potentiation,and a depression process,which help to improve the training speed and accuracy.On the other hand,the low-damage programming scheme and memory window(MW)optimizations can suppress cell degradation effectively with improved computing accuracy.Even after 109 cycles,the leakage current(I_(off))of cells remains sub-10pA,ensuring the large-scale computing ability of memory.Further characterizations are done on read disturb to demonstrate its robust reliabilities.By processing CIFAR-10 tasks,it is evident that~90%accuracy can be achieved after 109 cycles in both ResNet50 and VGG16 NN.Our results suggest that flash-based CIM has great potential to overcome the limitations of traditional Von Neumann architectures and enable high-performance NN online training,which pave the way for further development of artificial intelligence(AI)accelerators.
文摘Probabilistic Seismic Loss Estimation is a methodology used as a quantitative and explicit expression of the performance of buildings using terms that address the interests of both owners and insurance companies. Applying the ATC 58 approach for seismic loss assessment of buildings requires using Incremental Dynamic Analysis （IDA）, which needs hundreds of time-consuming analyses, which in turn hinders its wide application. The Endurance Time Method （ETM） is proposed herein as part of a demand propagation prediction procedure and is shown to be an economical alternative to IDA. Various scenarios were considered to achieve this purpose and their appropriateness has been evaluated using statistical methods. The most precise and efficient scenario was validated through comparison against IDA driven response predictions of 34 code conforming benchmark structures and was proven to be sufficiently precise while offering a great deal of efficiency. The loss values were estimated by replacing IDA with the proposed ETM-based procedure in the ATC 58 procedure and it was fotmd that these values suffer from varying inaccuracies, which were attributed to the discretized nature of damage and loss prediction functions provided by ATC 58.
