Flutter and forced response, as two main branches of aeroelasticity, can lead to high-cycle fatigue failure of turbomachinery blades. Efficiently and accurately assessing aeroelastic performance of turbomachinery blad...Flutter and forced response, as two main branches of aeroelasticity, can lead to high-cycle fatigue failure of turbomachinery blades. Efficiently and accurately assessing aeroelastic performance of turbomachinery blades is essential in the routine design. In this work, the Time Collocation Method (TCM) which uses the cubic B-spline to approximate flow variables is first thoroughly studied and then combined with the moving grid technique to analyze aeroelastic flow fields. To showcase its advantage over the Harmonic Balance (HB) method which uses a truncated Fourier series to approximately represent flow variables, a matrix analysis of the one-dimensional advection equation is first performed. The results of stability analysis are verified by two test cases: the Durham linear oscillating turbine cascade and a two-blade-row transonic compressor. The vibration of the blade of the first case is driven by a motor while the excitation force of the second case comes from blade row interaction. The results show that the time collocation method has a faster convergence rate and is more stable than the harmonic balance method, especially for cases with a large maximum grid reduced frequency. More importantly, the time collocation method is capable of accurately predicting aeroelastic performance of turbomachinery blades.展开更多
Unveiling the underlying physical mechanisms governing the fracture of brittle rocks is imperative for preventing rockbursts.The novelty of this study lies in the analysis of the dynamic response process of rock three...Unveiling the underlying physical mechanisms governing the fracture of brittle rocks is imperative for preventing rockbursts.The novelty of this study lies in the analysis of the dynamic response process of rock three-dimensional(3D)deformation under true triaxial stress,and the surge behavior of timedependent multifractal spectrum has been successfully used to warn of progressive failure inside the rock.Firstly,this study analyzed the dynamic adjustment trajectory of rock deformation,specifically lateral strain,within the framework of the Poisson effect.This analysis highlighted the intricate dependence of rock mechanical properties on the intermediate principal stress.Secondly,by defining the crack interval function(ICF),this study compared the disparities between the two crack growth stages(strengthening stage and weakening stage)under varying stress levels.It was found that the fracture activity of granite system has significant multifractal characteristics.Notably,the multifractal spectrum emerges as a valuable tool for characterizing the distinct fracture properties of rocks,encompassing both the crack scale and the associated energy.Finally,a quantitative criterion grounded in the multifractal parameters of the acoustic emission(AE)time series was formulated,and it indicates that the abrupt changes observed in the time-dependent fractal spectra can serve as precursor indicators for the progressive development of rockbursts.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
An evaluation approach for the response time probability distribution of workflows based on the fluid stochastic Petri net formalism is presented. Firstly, some problems about stochastic workflow net modeling are disc...An evaluation approach for the response time probability distribution of workflows based on the fluid stochastic Petri net formalism is presented. Firstly, some problems about stochastic workflow net modeling are discussed. Then how to convert a stochastic workflow net model into a fluid stochastic Petri net model is described. The response time distribution can be obtained directly upon the transient state solution of the fluid stochastic Petri net model. In the proposed approach, there are not any restrictions on the structure of workflow models, and the processing times of workflow tasks can be modeled by using arbitrary probability distributions. Large workflow models can be efficiently tackled by recursively using a net reduction technique.展开更多
A time domain finite element method （FEM） for the analysis of transient elastic response of a very large floating structure （VLFS） subjected to arbitrary time-dependent external loads is presented. This method is ...A time domain finite element method （FEM） for the analysis of transient elastic response of a very large floating structure （VLFS） subjected to arbitrary time-dependent external loads is presented. This method is developed directly in time domain and the hydrodynamic problem is formulated based on linear, inviscid and slightly compressible fluid theory and the structural response is analyzed on the thin plate assumption. The time domain finite element procedure herein is validated by comparing numerical results with available experimental data. Finally, the transient elastic response of a pontoon-type VLFS under the landing of an airplane is computed by the proposed time domain FEM. The time histories of the applied force and the position and velocity of an airplane during landing are modeled with data from a Boeing 747-400 jumbo jet.展开更多
While emergency medical service (EMS) response time (ERT) is a major factor associated with the survival of patients with cardiovascular disease (CVD), relatively few studies have explored the factors associated with ...While emergency medical service (EMS) response time (ERT) is a major factor associated with the survival of patients with cardiovascular disease (CVD), relatively few studies have explored the factors associated with ERT. This study aimed to assess the current status of ERT and to identify the factors affecting ERT in patients with CVD in China. Between January 1, 2011 and December 31, 2015, EMS responses to CVD incidents in Guangzhou, China, were examined. The primary outcome was ERT, defined as the time from receipt of an emergency call to the arrival of paramedics on the scene. Factors associated with ERT were evaluated by multivariable logistic regression. A total of 44 383 CVD incidents were analysed. The median ERT was 12.58 min (interquartile range=9.98-15.67). Among the risk factors, distance (OR=13.73, 95% CI=11.76- 16.04), level of hospital (OR=1.57, 95% CI=1.40-1.75), and site of the incident (OR=1.53, 95% CI=1.38-1.69) were the top three significant factors affecting the ERT. Our results suggest that greater attention should be given to factors affecting the ERT. It is essential to make continuous efforts to promote the development of effective interventions to reduce the response time.展开更多
In this paper, the time reversal processes of impulse response of crust are simulated by means of a dynamical finite element method (DFEM). The results indicate that a small undulating load during a long period may ca...In this paper, the time reversal processes of impulse response of crust are simulated by means of a dynamical finite element method (DFEM). The results indicate that a small undulating load during a long period may cause a focused brevity impact in a chaos-response system. The physical principle for this phenomenon is that the wave interferes or multiples superposition. Based on this knowledge, a new view toward the mechanism for preparing and triggering an earthquake is proposed. Finally, an interpretation of crust response to the sea tides is given.展开更多
With the increase in the power receiving proportion and an insufficient peak regulation capacity of the local units, the receiving-end power grid struggles to achieve peak regulation in valley time. To solve this prob...With the increase in the power receiving proportion and an insufficient peak regulation capacity of the local units, the receiving-end power grid struggles to achieve peak regulation in valley time. To solve this problem while considering the potential of the large-scale charge load of electric vehicles(EVs), an aggregator-based demand response(DR) mechanism for EVs that are participating in the peak regulation in valley time is proposed in this study. In this aggregator-based DR mechanism, the profits for the power grid’s operation and the participation willingness of the EV owners are considered. Based on the characteristics of the EV charging process and the day-ahead unit generation scheduling, a rolling unit commitment model with the DR is established to maximize the social welfare. In addition, to improve the efficiency of the optimization problem solving process and to achieve communication between the independent system operator(ISO) and the aggregators, the clustering algorithm is utilized to extract typical EV charging patterns. Finally, the feasibility and benefits of the aggregator-based DR mechanism for saving the costs and reducing the peak-valley difference of the receiving-end power grid are verified through case studies.展开更多
Magneto-rhelological（MR） dampers are devices that employ rheological fluids to modify their mechanical properties. Their mechanical simplicity, high dynamic range, lower power requirements, large force capacity, rob...Magneto-rhelological（MR） dampers are devices that employ rheological fluids to modify their mechanical properties. Their mechanical simplicity, high dynamic range, lower power requirements, large force capacity, robustness and safe maimer of operation in cases of failure have made them attractive devices for semi-active real-time control in civil, aerospace and automotive applications. Time response characteristic is one of the most important technical performances of MR dampers, and response time directly affects the control frequency, application range and the actual effect of MR dampers. In this study, one kind of finite difference solution for predicting the response time ofmagneto-rheological dampers from ＂off-state＂ to ＂on-state＂ is put forward. A laminar flow model is used to describe the flow in the MR valve, and a bi-viscous fluid flow model is utilized to describe the relationship of shear stress and shear rate of MR fluid. An explicit difference format is used to diseretize the Novior-Stoks equation, and stability condition of this algorithm is built by Von-Neumann stability criterion. The pressure gradient along the flow duct is solved by a dichotomy algorithm with iteration, and the changing curve of the damping force versus time of MR damper is obtained as well. According to the abovementioned numerical algorithm, the damping forces versus time curves from ＂off-state＂ to ＂on-state＂ of a cylindrical piston type MR damper are computed. Moreover, the MR damper is installed in a material test system（MTS）, the magnetic field in the wire circles of the MR damper is ＂triggered＂ when the MR damper is imposed to do a constant speed motion, and the damping force curves are recorded. The comparison between numerical results and experimental results indicates that this finite difference algorithm can be used to estimate the response time delay of MR dampers.展开更多
In injuries reducing ambulance response time (time from injury to hospital arrival) is an important factor for saving people’s lives. Helicopter emergency medical services can reduce out-of-hospital transport times b...In injuries reducing ambulance response time (time from injury to hospital arrival) is an important factor for saving people’s lives. Helicopter emergency medical services can reduce out-of-hospital transport times because of their high speed and their ability to travel in straight paths?unlike ground ambulance which are restricted to road network paths, as well as the ability toaccess rural or remote area injuries that are difficult to reach by ground ambulance. GIS technology aids air ambulance movement planning to reduce out-of-hospital response time based on mathematical and geographic models to support decision making which is necessary from out-of-hospital care providers. The goal of this study is to use GIS to develop an efficient DSS to outline where air ambulance can reduce response times, by using spatial analysis tools to create Euclidean distance and direction zones around receiving hospitals. The study concludes that GIS technology can be used to develop an efficient DSS to outline where air ambulance can reduce response times, by creating surfaces of Euclidean allocation, direction, and distance that can be used to improve initial response times for the civil defense air rescue and air ambulance services.展开更多
The seismic design of gravity retaining walls is based mostly on the pseudo static method.The seismic earth pressure is assumed to be a constant without considering the wave traveling effect when the seismic wave prop...The seismic design of gravity retaining walls is based mostly on the pseudo static method.The seismic earth pressure is assumed to be a constant without considering the wave traveling effect when the seismic wave propagates through the slope.However,under continuous ground motion,the actual earth pressure on the retaining wall varies with time.The present seismic earth pressure calculation method yields results that differ significantly from the actual scenario.Considering this,a slip surface curve was assumed in this study.It is more suitable for engineering practice.In addition,a theoretical calculation model based on energy dissipation was established.The time history of seismic earth pressure response under continuous ground motion was calculated using the equilibrium equation between the external power and the internal energy dissipation power of the sliding soil wedge.It can more effectively reflect the stress scenario of a retaining wall under seismic conditions.To verify the applicability of the proposed approach,a large-scale shaking table test was conducted,and the time history of the seismic earth pressure response obtained from the experiment was compared with the calculation results.The results show that the proposed approach is applicable to the calculation of the time history of seismic earth pressure response of gravity retaining walls.This lays the foundation for the seismic design of retaining structures by using dynamic time history.展开更多
The Fork-Join program consisting of K parallel tasks is a useful model for a large number of computing applications. When the parallel processor has multi-channels, later tasks may finish execution earlier than their ...The Fork-Join program consisting of K parallel tasks is a useful model for a large number of computing applications. When the parallel processor has multi-channels, later tasks may finish execution earlier than their earlier tasks and may join with tasks from other programs. This phenomenon is called exchangeable join (EJ), which introduces correlation to the task’s service time. In this work, we investigate the response time of multiprocessor systems with EJ with a new approach. We analyze two aspects of this kind of systems: exchangeable join (EJ) and the capacity constraint (CC). We prove that the system response time can be effectively reduced by EJ, while the reduced amount is constrained by the capacity of the multiprocessor. An upper bound model is constructed based on this analysis and a quick estimation algorithm is proposed. The approximation formula is verified by extensive simulation results, which show that the relative error of approximation is less than 5%.展开更多
In this paper, Endurance Time Analysis （ETA） method which is a new time-history based dynamic pushover procedure is introduced and its application in linear analysis of concrete arch dams is investigated. In this me...In this paper, Endurance Time Analysis （ETA） method which is a new time-history based dynamic pushover procedure is introduced and its application in linear analysis of concrete arch dams is investigated. In this method the structure is subjected to gradually intensifying acceleration functions and its performance is evaluated based on the length of the time duration that can satisfy required performance criteria. For this purpose Dez arch dam is selected as case study, fluid-structure interaction is taken into account and F.E. model of the system is excited in three performance levels. ETA method gives an approximation of maximum response at the equivalent target time, resulted from analyzing the system based on natural records. Extracted results are displacement, velocity and acceleration of the crest at crown cantilever. Results show using of ETA method can reduce at least 50% in number of analyses and 70% in total time of analyses at the current case. Furthermore, it is found that although the results of the ETA are not exactly consistent with the results of time-history analyses using real ground motions, errors are reasonable and ETA can identify performance levels of the dam with acceptable accuracy.展开更多
The source region of the Yellow River(SRYR),with its semi-humid to semi-arid climate,is crucial for understanding water resource dynamics.Precipitation is key for replenishing surface water and balancing the ecosystem...The source region of the Yellow River(SRYR),with its semi-humid to semi-arid climate,is crucial for understanding water resource dynamics.Precipitation is key for replenishing surface water and balancing the ecosystem’s water cycle.However,the soil moisture response to precipitation across climate zones and soil layers remains poorly understood due to limited long-term data.This study examines the response of soil moisture to precipitation at multiple time scales in the SRYR,using data from Maqu,Mado,Ngoring Lake sites,and the Maqu monitoring network(MMN),along with CN05.1 precipitation and GLEAM v3.8a soil moisture data.Results show that the semi-humid area requires more precipitation to trigger soil moisture responses compared to the semi-arid area in the SRYR.Surface soil at Maqu,MMN,Ngoring Lake,and Mado sites require at least 8.6,8.4,5.2,and 2.84 mm of precipitation,respectively,for effective replenishment.Significant responses to precipitation events were observed in soil layers at 40 cm and above in the semi-humid area,while at 20 cm and above in the semi-arid area.Precipitation volume is the primary factor influencing soil moisture,affecting both the increment and time lag to maximum moisture.Precipitation intensity and pre-rain moisture have no direct effect.In the central SRYR,accumulated precipitation has a greater impact.Root-zone soil moisture has a weaker correlation with precipitation compared to surface soil moisture but persists longer,responding for up to 10 days,while surface soil moisture responds more immediately but only lasts about 5 days.展开更多
In this paper, the response time of all-optical AND logic gate using the triangular photonic crystal lattice is investigated. The proposed logic gate consists of a photonic crystal nano-resonator formed by changing th...In this paper, the response time of all-optical AND logic gate using the triangular photonic crystal lattice is investigated. The proposed logic gate consists of a photonic crystal nano-resonator formed by changing the size of the dielectric rods. The structure benefits the interference effect mechanism. The contrast ratio of the photonic crystal AND logic gate is obtained as 6 d B. In addition to simplicity, the designed nano-resonator increases the bit rate of logic gate. The delay time and footprint of logic gate are respectively 0.32 ps and 146 μm2. The proposed photonic crystal AND logic gate can operate at a bit rate of 3.12 Tbit/s。展开更多
The rotational seismic motions are estimated from one station records of the 1999 Jiji （Chi-Chi）, Taiwan, earthquake based on the theory of elastic plane wave propagation. The time-frequency response spectrum （TFRS...The rotational seismic motions are estimated from one station records of the 1999 Jiji （Chi-Chi）, Taiwan, earthquake based on the theory of elastic plane wave propagation. The time-frequency response spectrum （TFRS） of the rotational motions is calculated and its characteristics are analyzed, then the TFRS is applied to analyze the damage mechanism of one twelve-storey frame concrete structure. The results show that one of the ground motion components can not reflect the characteristics of the seismic motions completely; the characteristics of each component, especially rotational motions, need to be studied. The damage line of the structure and TFRS of ground motion are important for seismic design, only the TFRS of input seismic wave is suitable, the structure design is reliable.展开更多
A predator-prey model with prey dispersal and Holling type-Ⅱ functional response is investigated.In this model,the time delay due to the gestation of the predator and stagestructure for the predator are considered.By...A predator-prey model with prey dispersal and Holling type-Ⅱ functional response is investigated.In this model,the time delay due to the gestation of the predator and stagestructure for the predator are considered.By analyzing the corresponding characteristic equations,the local stability of each of the nonnegative equilibria is discussed.The existence of Hopf bifurcations at the positive equilibrium is established.By using Lyapunov functionals and LaSalle’s invariance principle,sufficient conditions are obtained for the global stability of the positive equilibrium,the nonnegative boundary equilibrium and the trivial equilibrium of the model,respectively.Numerical simulations are carried out to illustrate the main results.展开更多
In this paper the temperature dependence of responsivity and response time for 6H-SiC ultraviolet （UV） photodetector is simulated based on numerical model in the range from 300 K to 900 K. The simulation results sho...In this paper the temperature dependence of responsivity and response time for 6H-SiC ultraviolet （UV） photodetector is simulated based on numerical model in the range from 300 K to 900 K. The simulation results show that the responsivity and the response time of device are less sensitive to temperature and this kind of UV photodetector has excellent temperature stability. Also the effects of device structure and bias voltage on the responsivity and the response time are presented. The thicker the drift region is, the higher the responsivity and the longer the response time are. So the thickness of drift region has to be carefully designed to make trade-off between responsivity and response time.展开更多
Digital broadcasting system has become a high-light of research on computer application. To respond to the changes of the playbill in the broadcasting system in real time, the response time of the system must be studi...Digital broadcasting system has become a high-light of research on computer application. To respond to the changes of the playbill in the broadcasting system in real time, the response time of the system must be studied. There is scarcely the research on this area currently. The influence factors in the response time are analyzed; the model on the response time of the system service is built; how the influence factors affect the response time of the system service is validated; and four improvement measures are proposed to minimize the response time of system service.展开更多
The behavior of variable transparency glass is studied, and the response time analyzed and measured aimed at applications to welding goggles. Detection apparatus for goggle testing is involved in the design and develo...The behavior of variable transparency glass is studied, and the response time analyzed and measured aimed at applications to welding goggles. Detection apparatus for goggle testing is involved in the design and development. Charac-teristics of the apparatus are discussed based on experiments. The definition of nominal response time and effective response time are presented based on the analysis and calculation with experimental data.展开更多
基金supported by the Science Center for Gas Turbine Project,China(No.P2022-C-II-001-001)the National Science and Technology Major Project,Chinathe Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University,China(No.CX2022045).
文摘Flutter and forced response, as two main branches of aeroelasticity, can lead to high-cycle fatigue failure of turbomachinery blades. Efficiently and accurately assessing aeroelastic performance of turbomachinery blades is essential in the routine design. In this work, the Time Collocation Method (TCM) which uses the cubic B-spline to approximate flow variables is first thoroughly studied and then combined with the moving grid technique to analyze aeroelastic flow fields. To showcase its advantage over the Harmonic Balance (HB) method which uses a truncated Fourier series to approximately represent flow variables, a matrix analysis of the one-dimensional advection equation is first performed. The results of stability analysis are verified by two test cases: the Durham linear oscillating turbine cascade and a two-blade-row transonic compressor. The vibration of the blade of the first case is driven by a motor while the excitation force of the second case comes from blade row interaction. The results show that the time collocation method has a faster convergence rate and is more stable than the harmonic balance method, especially for cases with a large maximum grid reduced frequency. More importantly, the time collocation method is capable of accurately predicting aeroelastic performance of turbomachinery blades.
基金funding support from the National Natural Science Foundation of China(Grant No.U2034207)the Natural Science Foundation of Hebei Province(Grant No.E2021210099).
文摘Unveiling the underlying physical mechanisms governing the fracture of brittle rocks is imperative for preventing rockbursts.The novelty of this study lies in the analysis of the dynamic response process of rock three-dimensional(3D)deformation under true triaxial stress,and the surge behavior of timedependent multifractal spectrum has been successfully used to warn of progressive failure inside the rock.Firstly,this study analyzed the dynamic adjustment trajectory of rock deformation,specifically lateral strain,within the framework of the Poisson effect.This analysis highlighted the intricate dependence of rock mechanical properties on the intermediate principal stress.Secondly,by defining the crack interval function(ICF),this study compared the disparities between the two crack growth stages(strengthening stage and weakening stage)under varying stress levels.It was found that the fracture activity of granite system has significant multifractal characteristics.Notably,the multifractal spectrum emerges as a valuable tool for characterizing the distinct fracture properties of rocks,encompassing both the crack scale and the associated energy.Finally,a quantitative criterion grounded in the multifractal parameters of the acoustic emission(AE)time series was formulated,and it indicates that the abrupt changes observed in the time-dependent fractal spectra can serve as precursor indicators for the progressive development of rockbursts.
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.
基金The National Natural Science Foundation of China(No.60175027).
文摘An evaluation approach for the response time probability distribution of workflows based on the fluid stochastic Petri net formalism is presented. Firstly, some problems about stochastic workflow net modeling are discussed. Then how to convert a stochastic workflow net model into a fluid stochastic Petri net model is described. The response time distribution can be obtained directly upon the transient state solution of the fluid stochastic Petri net model. In the proposed approach, there are not any restrictions on the structure of workflow models, and the processing times of workflow tasks can be modeled by using arbitrary probability distributions. Large workflow models can be efficiently tackled by recursively using a net reduction technique.
文摘A time domain finite element method （FEM） for the analysis of transient elastic response of a very large floating structure （VLFS） subjected to arbitrary time-dependent external loads is presented. This method is developed directly in time domain and the hydrodynamic problem is formulated based on linear, inviscid and slightly compressible fluid theory and the structural response is analyzed on the thin plate assumption. The time domain finite element procedure herein is validated by comparing numerical results with available experimental data. Finally, the transient elastic response of a pontoon-type VLFS under the landing of an airplane is computed by the proposed time domain FEM. The time histories of the applied force and the position and velocity of an airplane during landing are modeled with data from a Boeing 747-400 jumbo jet.
文摘While emergency medical service (EMS) response time (ERT) is a major factor associated with the survival of patients with cardiovascular disease (CVD), relatively few studies have explored the factors associated with ERT. This study aimed to assess the current status of ERT and to identify the factors affecting ERT in patients with CVD in China. Between January 1, 2011 and December 31, 2015, EMS responses to CVD incidents in Guangzhou, China, were examined. The primary outcome was ERT, defined as the time from receipt of an emergency call to the arrival of paramedics on the scene. Factors associated with ERT were evaluated by multivariable logistic regression. A total of 44 383 CVD incidents were analysed. The median ERT was 12.58 min (interquartile range=9.98-15.67). Among the risk factors, distance (OR=13.73, 95% CI=11.76- 16.04), level of hospital (OR=1.57, 95% CI=1.40-1.75), and site of the incident (OR=1.53, 95% CI=1.38-1.69) were the top three significant factors affecting the ERT. Our results suggest that greater attention should be given to factors affecting the ERT. It is essential to make continuous efforts to promote the development of effective interventions to reduce the response time.
基金State Natural Science Foundation (49834002) and the science foundation of HUST (J151005).
文摘In this paper, the time reversal processes of impulse response of crust are simulated by means of a dynamical finite element method (DFEM). The results indicate that a small undulating load during a long period may cause a focused brevity impact in a chaos-response system. The physical principle for this phenomenon is that the wave interferes or multiples superposition. Based on this knowledge, a new view toward the mechanism for preparing and triggering an earthquake is proposed. Finally, an interpretation of crust response to the sea tides is given.
基金supported by the Science and Technology Project from the State Grid Shanghai Municipal Electric Power Company of China (52094019006U)the Shanghai Rising-Star Program (18QB1400200)。
文摘With the increase in the power receiving proportion and an insufficient peak regulation capacity of the local units, the receiving-end power grid struggles to achieve peak regulation in valley time. To solve this problem while considering the potential of the large-scale charge load of electric vehicles(EVs), an aggregator-based demand response(DR) mechanism for EVs that are participating in the peak regulation in valley time is proposed in this study. In this aggregator-based DR mechanism, the profits for the power grid’s operation and the participation willingness of the EV owners are considered. Based on the characteristics of the EV charging process and the day-ahead unit generation scheduling, a rolling unit commitment model with the DR is established to maximize the social welfare. In addition, to improve the efficiency of the optimization problem solving process and to achieve communication between the independent system operator(ISO) and the aggregators, the clustering algorithm is utilized to extract typical EV charging patterns. Finally, the feasibility and benefits of the aggregator-based DR mechanism for saving the costs and reducing the peak-valley difference of the receiving-end power grid are verified through case studies.
基金supported by National Natural Science Foundation of China (Grant No. 50675106)
文摘Magneto-rhelological（MR） dampers are devices that employ rheological fluids to modify their mechanical properties. Their mechanical simplicity, high dynamic range, lower power requirements, large force capacity, robustness and safe maimer of operation in cases of failure have made them attractive devices for semi-active real-time control in civil, aerospace and automotive applications. Time response characteristic is one of the most important technical performances of MR dampers, and response time directly affects the control frequency, application range and the actual effect of MR dampers. In this study, one kind of finite difference solution for predicting the response time ofmagneto-rheological dampers from ＂off-state＂ to ＂on-state＂ is put forward. A laminar flow model is used to describe the flow in the MR valve, and a bi-viscous fluid flow model is utilized to describe the relationship of shear stress and shear rate of MR fluid. An explicit difference format is used to diseretize the Novior-Stoks equation, and stability condition of this algorithm is built by Von-Neumann stability criterion. The pressure gradient along the flow duct is solved by a dichotomy algorithm with iteration, and the changing curve of the damping force versus time of MR damper is obtained as well. According to the abovementioned numerical algorithm, the damping forces versus time curves from ＂off-state＂ to ＂on-state＂ of a cylindrical piston type MR damper are computed. Moreover, the MR damper is installed in a material test system（MTS）, the magnetic field in the wire circles of the MR damper is ＂triggered＂ when the MR damper is imposed to do a constant speed motion, and the damping force curves are recorded. The comparison between numerical results and experimental results indicates that this finite difference algorithm can be used to estimate the response time delay of MR dampers.
文摘In injuries reducing ambulance response time (time from injury to hospital arrival) is an important factor for saving people’s lives. Helicopter emergency medical services can reduce out-of-hospital transport times because of their high speed and their ability to travel in straight paths?unlike ground ambulance which are restricted to road network paths, as well as the ability toaccess rural or remote area injuries that are difficult to reach by ground ambulance. GIS technology aids air ambulance movement planning to reduce out-of-hospital response time based on mathematical and geographic models to support decision making which is necessary from out-of-hospital care providers. The goal of this study is to use GIS to develop an efficient DSS to outline where air ambulance can reduce response times, by using spatial analysis tools to create Euclidean distance and direction zones around receiving hospitals. The study concludes that GIS technology can be used to develop an efficient DSS to outline where air ambulance can reduce response times, by creating surfaces of Euclidean allocation, direction, and distance that can be used to improve initial response times for the civil defense air rescue and air ambulance services.
基金supported by the Strategic International Science and Technology Innovation Cooperation Project‘Research on On-line Monitoring and Evaluation Technology of Safety Status of Highspeed Railway Track-subgrade System’from the National Key R&D Program of China(Grant No.2018YFE0207100)the State Key Laboratory for Geomechanics and Deep Underground Engineering,China University of Mining&Technology/China University of Mining&Technology,Beijing(Grant No.SKLGDUEK1910)+1 种基金the Foundation of Engineering Research Center of Eco-environment in the Three Gorges Reservoir Region of China(Grant No.KF2018-01)the Youth Scientific and Technological Innovation Team of Southwest Petroleum University(Grant No.2018CXTD02)。
文摘The seismic design of gravity retaining walls is based mostly on the pseudo static method.The seismic earth pressure is assumed to be a constant without considering the wave traveling effect when the seismic wave propagates through the slope.However,under continuous ground motion,the actual earth pressure on the retaining wall varies with time.The present seismic earth pressure calculation method yields results that differ significantly from the actual scenario.Considering this,a slip surface curve was assumed in this study.It is more suitable for engineering practice.In addition,a theoretical calculation model based on energy dissipation was established.The time history of seismic earth pressure response under continuous ground motion was calculated using the equilibrium equation between the external power and the internal energy dissipation power of the sliding soil wedge.It can more effectively reflect the stress scenario of a retaining wall under seismic conditions.To verify the applicability of the proposed approach,a large-scale shaking table test was conducted,and the time history of the seismic earth pressure response obtained from the experiment was compared with the calculation results.The results show that the proposed approach is applicable to the calculation of the time history of seismic earth pressure response of gravity retaining walls.This lays the foundation for the seismic design of retaining structures by using dynamic time history.
基金Project supported by the National Natural Science Foundation of0 China (Nos. 60274011 and 60574067), and the Program for NewCentury Excellent Talents in University (No. NCET-04-0094), China
文摘The Fork-Join program consisting of K parallel tasks is a useful model for a large number of computing applications. When the parallel processor has multi-channels, later tasks may finish execution earlier than their earlier tasks and may join with tasks from other programs. This phenomenon is called exchangeable join (EJ), which introduces correlation to the task’s service time. In this work, we investigate the response time of multiprocessor systems with EJ with a new approach. We analyze two aspects of this kind of systems: exchangeable join (EJ) and the capacity constraint (CC). We prove that the system response time can be effectively reduced by EJ, while the reduced amount is constrained by the capacity of the multiprocessor. An upper bound model is constructed based on this analysis and a quick estimation algorithm is proposed. The approximation formula is verified by extensive simulation results, which show that the relative error of approximation is less than 5%.
文摘In this paper, Endurance Time Analysis （ETA） method which is a new time-history based dynamic pushover procedure is introduced and its application in linear analysis of concrete arch dams is investigated. In this method the structure is subjected to gradually intensifying acceleration functions and its performance is evaluated based on the length of the time duration that can satisfy required performance criteria. For this purpose Dez arch dam is selected as case study, fluid-structure interaction is taken into account and F.E. model of the system is excited in three performance levels. ETA method gives an approximation of maximum response at the equivalent target time, resulted from analyzing the system based on natural records. Extracted results are displacement, velocity and acceleration of the crest at crown cantilever. Results show using of ETA method can reduce at least 50% in number of analyses and 70% in total time of analyses at the current case. Furthermore, it is found that although the results of the ETA are not exactly consistent with the results of time-history analyses using real ground motions, errors are reasonable and ETA can identify performance levels of the dam with acceptable accuracy.
基金supported by the National Natural Science Foundation of China(Grant No.42325502,and 42275045)the West Light Foundation of the Chi-nese Academy of Sciences(Grant No.xbzg-zdsys-202215)+1 种基金the Sci-ence and Technology Research Plan of Gansu Province(Grant Nos.23JRRA654 and 20JR10RA070)iLEAPs(Integrated Land Ecosystem-Atmosphere Processes Study).
文摘The source region of the Yellow River(SRYR),with its semi-humid to semi-arid climate,is crucial for understanding water resource dynamics.Precipitation is key for replenishing surface water and balancing the ecosystem’s water cycle.However,the soil moisture response to precipitation across climate zones and soil layers remains poorly understood due to limited long-term data.This study examines the response of soil moisture to precipitation at multiple time scales in the SRYR,using data from Maqu,Mado,Ngoring Lake sites,and the Maqu monitoring network(MMN),along with CN05.1 precipitation and GLEAM v3.8a soil moisture data.Results show that the semi-humid area requires more precipitation to trigger soil moisture responses compared to the semi-arid area in the SRYR.Surface soil at Maqu,MMN,Ngoring Lake,and Mado sites require at least 8.6,8.4,5.2,and 2.84 mm of precipitation,respectively,for effective replenishment.Significant responses to precipitation events were observed in soil layers at 40 cm and above in the semi-humid area,while at 20 cm and above in the semi-arid area.Precipitation volume is the primary factor influencing soil moisture,affecting both the increment and time lag to maximum moisture.Precipitation intensity and pre-rain moisture have no direct effect.In the central SRYR,accumulated precipitation has a greater impact.Root-zone soil moisture has a weaker correlation with precipitation compared to surface soil moisture but persists longer,responding for up to 10 days,while surface soil moisture responds more immediately but only lasts about 5 days.
文摘In this paper, the response time of all-optical AND logic gate using the triangular photonic crystal lattice is investigated. The proposed logic gate consists of a photonic crystal nano-resonator formed by changing the size of the dielectric rods. The structure benefits the interference effect mechanism. The contrast ratio of the photonic crystal AND logic gate is obtained as 6 d B. In addition to simplicity, the designed nano-resonator increases the bit rate of logic gate. The delay time and footprint of logic gate are respectively 0.32 ps and 146 μm2. The proposed photonic crystal AND logic gate can operate at a bit rate of 3.12 Tbit/s。
基金funded by the National Natural Science Foundation of China under grant No.50578125
文摘The rotational seismic motions are estimated from one station records of the 1999 Jiji （Chi-Chi）, Taiwan, earthquake based on the theory of elastic plane wave propagation. The time-frequency response spectrum （TFRS） of the rotational motions is calculated and its characteristics are analyzed, then the TFRS is applied to analyze the damage mechanism of one twelve-storey frame concrete structure. The results show that one of the ground motion components can not reflect the characteristics of the seismic motions completely; the characteristics of each component, especially rotational motions, need to be studied. The damage line of the structure and TFRS of ground motion are important for seismic design, only the TFRS of input seismic wave is suitable, the structure design is reliable.
基金Supported by the Social Science Foundation of Hebei Province(HB23TJO03)。
文摘A predator-prey model with prey dispersal and Holling type-Ⅱ functional response is investigated.In this model,the time delay due to the gestation of the predator and stagestructure for the predator are considered.By analyzing the corresponding characteristic equations,the local stability of each of the nonnegative equilibria is discussed.The existence of Hopf bifurcations at the positive equilibrium is established.By using Lyapunov functionals and LaSalle’s invariance principle,sufficient conditions are obtained for the global stability of the positive equilibrium,the nonnegative boundary equilibrium and the trivial equilibrium of the model,respectively.Numerical simulations are carried out to illustrate the main results.
文摘In this paper the temperature dependence of responsivity and response time for 6H-SiC ultraviolet （UV） photodetector is simulated based on numerical model in the range from 300 K to 900 K. The simulation results show that the responsivity and the response time of device are less sensitive to temperature and this kind of UV photodetector has excellent temperature stability. Also the effects of device structure and bias voltage on the responsivity and the response time are presented. The thicker the drift region is, the higher the responsivity and the longer the response time are. So the thickness of drift region has to be carefully designed to make trade-off between responsivity and response time.
文摘Digital broadcasting system has become a high-light of research on computer application. To respond to the changes of the playbill in the broadcasting system in real time, the response time of the system must be studied. There is scarcely the research on this area currently. The influence factors in the response time are analyzed; the model on the response time of the system service is built; how the influence factors affect the response time of the system service is validated; and four improvement measures are proposed to minimize the response time of system service.
基金the Science and Technology Commission of Shanghai Municipality (Grant No.052912015)
文摘The behavior of variable transparency glass is studied, and the response time analyzed and measured aimed at applications to welding goggles. Detection apparatus for goggle testing is involved in the design and development. Charac-teristics of the apparatus are discussed based on experiments. The definition of nominal response time and effective response time are presented based on the analysis and calculation with experimental data.
