Stochastic diferential equations with the time average have received increasing attentions in recent years since they can ofer better explanations for some fnancial models.Since the time average is involved in this cl...Stochastic diferential equations with the time average have received increasing attentions in recent years since they can ofer better explanations for some fnancial models.Since the time average is involved in this class of stochastic diferential equations,in this paper,the linear growth condition and the Lipschitz condition are diferent from the classical conditions.Under the special linear growth condition and the special Lipschitz condition,this paper establishes the existence and uniqueness of the solution.By using the Lyapunov function,this paper also establishes the existence and uniqueness under the local Lipschitz condition and gives the p-th moment estimate.Finally,a scalar example is given to illustrate the applications of our results.展开更多
This paper presents the complete mathematical model and predicts the performance of switched reluctance generator with time average and small signal models. The complete mathematical model is developed in three stages...This paper presents the complete mathematical model and predicts the performance of switched reluctance generator with time average and small signal models. The complete mathematical model is developed in three stages. First, a switching model is developed based on quasi-linear inductance profile. Next, based on the switching behaviour, a time average model is obtained to measure the difference between the excitation and generation time in each switching cycle. Finally, to track control voltage and current wave shapes, a small signal model is designed. The effectiveness of the complete multilevel model combining electrical machine, power converter, load and control with programming language is demonstrated through simulations. A PI controller is used for controlling the voltage of the generator. The results presented show that the controller exhibits accurate tracking control of load voltage under different operating conditions. This demonstrates that the proposed model is able to perform an accurate control of the generated output voltage even in transient situations. The simulation is performed to choose the control parameters and study the performance of switched reluctance generator prior to its actual implementation. Initial experimental results are presented using NI-Data acquisition card to control the output power according to load requirements.展开更多
In the simulation output analysis,there are some measures that should be calculated by time average concept such as the mean queue length.Especially,the confidence interval of those measures might be required for stat...In the simulation output analysis,there are some measures that should be calculated by time average concept such as the mean queue length.Especially,the confidence interval of those measures might be required for statistical analysis.In this situation,the traditional method that utilizes the central limit theorem(CLT)is inapplicable if the output data set has autocorrelation structure.The bootstrap is one of the most suitable methods which can reflect the autocorrelated phenomena in statistical analysis.Therefore,the confidence interval for a time averaged measure having autocorrelation structure can also be calculated by the bootstrap methods.This study introduces the method that constructs these confidence intervals applying the bootstraps.The bootstraps proposed are the threshold bootstrap(TB),the moving block bootstrap(MBB)and stationary bootstrap(SB).Finally,some numerical examples will be provided for verification.展开更多
In this paper, the problems of stability for a class of switched positive descriptor systems(SPDSs)with average dwell time(ADT) switching are investigated. First, based on the equivalent switched system and the proper...In this paper, the problems of stability for a class of switched positive descriptor systems(SPDSs)with average dwell time(ADT) switching are investigated. First, based on the equivalent switched system and the properties of the projector matrix, sufficient stabilities are given for the underlying systems in both continuoustime and discrete-time contexts. Then, a sufficient stability condition for the SPDS with both stable and unstable subsystems is obtained. The stability results for the SPDSs are represented in terms of a set of linear programmings(LPs) by the multiple linear co-positive Lyapunov function(MLCLF) approach. Finally, three numerical examples are given to illustrate the effectiveness of the obtained theoretical results.展开更多
This paper investigates the correlation between stochastic resonance （SR） and the average phase-synchronization time which is between the input signal and the output signal in a bistable system driven by colour-corr...This paper investigates the correlation between stochastic resonance （SR） and the average phase-synchronization time which is between the input signal and the output signal in a bistable system driven by colour-correlated noises. The results show that the output signal-to-noise ratio can reach a maximum with the increase of the average phase- synchronization time, which may be helpful for understanding the principle of SR from the point of synchronization; however, SR and the maximum of the average phase-synchronization time appear at different optimal noise level, moreover, the effects on them of additive and multiplicative noise are different.展开更多
Understanding the occurrence and characteristics of dry and wet events is crucial for effective disaster prevention,resource management,and risk reduction in vulnerable regions.This study analyzed the spatiotemporal p...Understanding the occurrence and characteristics of dry and wet events is crucial for effective disaster prevention,resource management,and risk reduction in vulnerable regions.This study analyzed the spatiotemporal patterns of dry-wet events and their transition characteristics in Uttar Pradesh,India.The standardized precipitation evapotranspiration index(SPEI)at a monthly timescale was utilized to identify hotspot regions vulnerable to concurrent and frequent dry and wet events and their transitions.The severity,duration,and intensity of dry and wet events were characterized with the run theory over SPEI time series data from 18 synoptic stations in Uttar Pradesh over 48 years(1971-2018),sourced from the Indian Institute of Tropical Meteorology and the India Meteorological Department.Multiple assessment methods were utilized to examine the interaction of these extreme events,considering characteristics such as wet-dry ratio,average transition time,and rapid transition times from wet to dry events and from dry to wet events.Average wet durations ranged from 1.27 to 1.58 months,and average dry durations ranged from 1.29 to 1.82 months.Rapid transition times from dry to wet events ranged from 2.5 to 4.1 months,and those for wet-to-dry events ranged from 2.1 to 5.3 months.The eastern region experienced a significantly high number of dry events,while the western and Bundelkhand regions experienced more intense dry events.In contrast,the eastern region had intense wet events.This research on the occurrence of dry-wet events and their transitions can provide valuable insights for government decision-making and disaster prevention and reduction efforts.展开更多
AIM:To analyze the characteristics and correlation of phacoemulsification parameters and anterior segment parameters in cataract patients with different blood glucose levels.METHODS:A total of 45 type 2 diabetic catar...AIM:To analyze the characteristics and correlation of phacoemulsification parameters and anterior segment parameters in cataract patients with different blood glucose levels.METHODS:A total of 45 type 2 diabetic cataract patients(45 eyes)treated in our hospital from March 2023 to April 2024 were stratified into two groups based on glycosylated hemoglobin(HbA1c)levels:group A:HbA1c<7%(n=18)and group B:7%≤HbA1c<8.5%(n=27);a total of 94 age-matched age-related cataract patients(94 eyes)were enrolled as the control group(group C).All underwent phacoemulsification with intraocular lens implantation.Anterior segment parameters,including corneal,lens and anterior chamber measurements,were recorded.Correlations between phacoemulsification parameters and anterior segment parameters were analyzed,and differences among groups were compared.RESULTS:In groups A and B,effective phacoemulsification time(EPT)negatively correlated with corneal endothelial cell density(CECD)(r=-0.315,P=0.035).Average phacoemulsification time(APT)positively correlated with the anterior corneal surface radius of curvature(Rm;r=0.402,P=0.006)and negatively correlated with the flat axis meridian curvature(K 1),steep axis meridian curvature(K 2),mean curvature(Km)of the anterior corneal surface,and lens density at 6 mm zones(PDZ3;all P<0.05).Average phacoemulsification energy(AVE)positively correlated with mean lens density(LD-mean),lens density at 2 mm zones(PDZ1),lens density at 4 mm zones(PDZ2),and PDZ3(all P<0.05),and negatively with pupil diameter(r=-0.385,P=0.009).In the group C,EPT showed a positive correlation with Pentacam nucleus staging(PNS)density grade,PDZ1,PDZ2,and PDZ3(all P<0.05).A positive correlation was observed between AVE and PNS classification(r=0.246,P=0.018).Conversely,AVE exhibited a negative correlation with CECD(r=-0.245,P=0.018).EPT in groups A and B was higher than that in the group C(P<0.05).Both EPT and APT in the group B were higher than those in the group A(P<0.05).In diabetic cataract patients,CECD,corneal density(CD),and posterior corneal surface height positively correlated with diabetes duration(P<0.05).Posterior corneal surface K 1 and Rm positively correlated with 7%≤HbA1c<8.5%(P<0.05).Total corneal astigmatism negatively correlated with HbA1c,2-hour post-breakfast blood glucose(2hPBG),and fasting insulin(FINS;P<0.05).CD and lens thickness(LT)positively correlated with FINS(P<0.05).CONCLUSION:Phacoemulsification parameters and blood glucose-related indices exhibited varying degrees of correlation with anterior segment parameters in cataract patients with different blood glucose levels.EPT in diabetic cataract patients was higher than that in age-related cataract patients,while EPT and APT in diabetic cataract patients with poor glycemic control were higher than those with good glycemic control.展开更多
This research focuses on detecting faults in flight vehicles with unstable subsystems operating asynchronously.By accounting for asynchronous switching,a switched model is established,and filters for fault detection(F...This research focuses on detecting faults in flight vehicles with unstable subsystems operating asynchronously.By accounting for asynchronous switching,a switched model is established,and filters for fault detection(FD)in unstable subsystems are developed.The FD challenge is then transformed into an H∞filtering issue.Utilizing the multiple discontinuous Lyapunov function(MDLF)approach and the mode-dependent average dwell time(MDADT)method,sufficient conditions are derived to ensure stability during both fast and slow switching.Furthermore,the existence and solutions for FD filters are provided through linear matrix inequalities(LMIs).The simulation outcomes demonstrated the excellent performance of the developed method in studied cases.展开更多
Travel time through a ring road with a total length of 80 km has been predicted by a viscoelastic traffic model(VEM), which is developed in analogous to the non-Newtonian fluid flow. The VEM expresses a traffic pressu...Travel time through a ring road with a total length of 80 km has been predicted by a viscoelastic traffic model(VEM), which is developed in analogous to the non-Newtonian fluid flow. The VEM expresses a traffic pressure for the unfree flow case by space headway, ensuring that the pressure can be determined by the assumption that the relevant second critical sound speed is exactly equal to the disturbance propagation speed determined by the free flow speed and the braking distance measured by the average vehicular length. The VEM assumes that the sound speed for the free flow case depends on the traffic density in some specific aspects, which ensures that it is exactly identical to the free flow speed on an empty road. To make a comparison, the open Navier-Stokes type model developed by Zhang(ZHANG, H. M. Driver memory, traffic viscosity and a viscous vehicular traffic flow model. Transp. Res. Part B, 37, 27–41(2003)) is adopted to predict the travel time through the ring road for providing the counterpart results.When the traffic free flow speed is 80 km/h, the braking distance is supposed to be 45 m,with the jam density uniquely determined by the average length of vehicles l ≈ 5.8 m. To avoid possible singular points in travel time prediction, a distinguishing period for time averaging is pre-assigned to be 7.5 minutes. It is found that the travel time increases monotonically with the initial traffic density on the ring road. Without ramp effects, for the ring road with the initial density less than the second critical density, the travel time can be simply predicted by using the equilibrium speed. However, this simpler approach is unavailable for scenarios over the second critical.展开更多
Time domain averaging(TDA) is essentially a comb filter,it cannot extract the specified harmonics which may be caused by some faults,such as gear eccentric.Meanwhile,TDA always suffers from period cutting error(PCE) t...Time domain averaging(TDA) is essentially a comb filter,it cannot extract the specified harmonics which may be caused by some faults,such as gear eccentric.Meanwhile,TDA always suffers from period cutting error(PCE) to different extent.Several improved TDA methods have been proposed,however they cannot completely eliminate the waveform reconstruction error caused by PCE.In order to overcome the shortcomings of conventional methods,a flexible time domain averaging(FTDA) technique is established,which adapts to the analyzed signal through adjusting each harmonic of the comb filter.In this technique,the explicit form of FTDA is first constructed by frequency domain sampling.Subsequently,chirp Z-transform(CZT) is employed in the algorithm of FTDA,which can improve the calculating efficiency significantly.Since the signal is reconstructed in the continuous time domain,there is no PCE in the FTDA.To validate the effectiveness of FTDA in the signal de-noising,interpolation and harmonic reconstruction,a simulated multi-components periodic signal that corrupted by noise is processed by FTDA.The simulation results show that the FTDA is capable of recovering the periodic components from the background noise effectively.Moreover,it can improve the signal-to-noise ratio by 7.9 dB compared with conventional ones.Experiments are also carried out on gearbox test rigs with chipped tooth and eccentricity gear,respectively.It is shown that the FTDA can identify the direction and severity of the eccentricity gear,and further enhances the amplitudes of impulses by 35%.The proposed technique not only solves the problem of PCE,but also provides a useful tool for the fault symptom extraction of rotating machinery.展开更多
A new class of hybrid impulsive and switching models are introduced and their robust exponential stability and control synthesis are addressed. The proposed switched system is composed of stable subsystems and unstabl...A new class of hybrid impulsive and switching models are introduced and their robust exponential stability and control synthesis are addressed. The proposed switched system is composed of stable subsystems and unstable subsystems, which not only involves state delay and norm-bounded time-varying parameter uncertainties, but also contains the impulsive switching effects between the subsystems. Based on the extension of the system dimension and the concept of average dwell time, a kind of practically useful switching rule is presented which guarantees the desired robust exponential stability. A switched state feedback controller is also given.展开更多
The problem of the robust fault detection filter design for time-varying delays switched systems is considered in the framework of mixed H-/H∞. Firstly, the weighted H∞ performance index is utilized as the robustnes...The problem of the robust fault detection filter design for time-varying delays switched systems is considered in the framework of mixed H-/H∞. Firstly, the weighted H∞ performance index is utilized as the robustness performance, and the H- index is used as the sensitivity performance for obtaining the robust fault detection filter. Then a novel multiple Lyapunov-Krasovskii function is proposed for deriving sufficient existence conditions of the robust fault detection filter based on the average dwell time technique. By introducing slack matrix variable, the coupling between the Lyapunov matrix and system matrix is removed, and the conservatism of results is reduced. Based on the robust fault detection filter, residual is generated and evaluated for detecting faults. In addition, the results of this paper are dependent on time delays,and represented in the form of linear matrix inequalities. Finally,the simulation example verifies the effectiveness of the proposed method.展开更多
Periodic components are of great significance for fault diagnosis and health monitoring of rotating machinery.Time synchronous averaging is an effective and convenient technique for extracting those components.However...Periodic components are of great significance for fault diagnosis and health monitoring of rotating machinery.Time synchronous averaging is an effective and convenient technique for extracting those components.However,the performance of time synchronous averaging is seriously limited when the separate segments are poorly synchronized.This paper proposes a new averaging method capable of extracting periodic components without external reference and an accurate period to solve this problem.With this approach,phase detection and compensation eliminate all segments'phase differences,which enables the segments to be well synchronized.The effectiveness of the proposed method is validated by numerical and experimental signals.展开更多
Minimizing time cost in time-shared operating systems is considered basic and essential task,and it is the most significant goal for the researchers who interested in CPU scheduling algorithms.Waiting time,turnaround ...Minimizing time cost in time-shared operating systems is considered basic and essential task,and it is the most significant goal for the researchers who interested in CPU scheduling algorithms.Waiting time,turnaround time,and number of context switches are themost time cost criteria used to compare between CPU scheduling algorithms.CPU scheduling algorithms are divided into non-preemptive and preemptive.RoundRobin(RR)algorithm is the most famous as it is the basis for all the algorithms used in time-sharing.In this paper,the authors proposed a novel CPU scheduling algorithm based on RR.The proposed algorithm is called Adjustable Time Slice(ATS).It reduces the time cost by taking the advantage of the low overhead of RR algorithm.In addition,ATS favors short processes allowing them to run longer time than given to long processes.The specific characteristics of each process are;its CPU execution time,weight,time slice,and number of context switches.ATS clusters the processes in groups depending on these characteristics.The traditionalRRassigns fixed time slice for each process.On the other hand,dynamic variants of RR assign time slice for each process differs from other processes.The essential difference between ATS and the other methods is that it gives a set of processes a specific time based on their similarities within the same cluster.The authors compared between ATS with five popular scheduling algorithms on nine datasets of processes.The datasets used in the comparison vary in their features.The evaluation was measured in term of time cost and the experiments showed that the proposed algorithm reduces the time cost.展开更多
We study the open quantum random walk (OQRW) with time-dependence on the one-dimensional lattice space and obtain the associated limit distribution. As an application we study the return probability of the OQRW. We al...We study the open quantum random walk (OQRW) with time-dependence on the one-dimensional lattice space and obtain the associated limit distribution. As an application we study the return probability of the OQRW. We also ask, "What is the average time for the return probability of the OQRW?"展开更多
This paper investigates the problem of event-triggered finite-time <i>H</i><sub>∞</sub> control for a class of switched stochastic systems. The main objective of this study is to design an eve...This paper investigates the problem of event-triggered finite-time <i>H</i><sub>∞</sub> control for a class of switched stochastic systems. The main objective of this study is to design an event-triggered state feedback <i>H</i><sub>∞</sub> controller such that the resulting closed-loop system is finite-time bounded and satisfies a prescribed <i>H</i><sub>∞</sub> level in some given finite-time interval. Based on stochastic differential equations theory and average dwell time approach, sufficient conditions are derived to ensure the finite-time stochastic stability with the prescribed <i>H</i><sub>∞</sub> performance for the relevant closed-loop system by employing the linear matrix inequality technique. Finally, the desired state feedback <i>H</i><sub>∞</sub> controller gain matrices can be expressed in an explicit form.展开更多
Queue is an act of joining a line to be served and it is part of our everyday human involvement. The objectives of the study focused on using a mathematical model to determine the waiting time of two selected banks as...Queue is an act of joining a line to be served and it is part of our everyday human involvement. The objectives of the study focused on using a mathematical model to determine the waiting time of two selected banks as well as compare the average waiting time between the banks. The study uncovered the extent of usage of queuing models in achieving customer satisfaction as well as permitting to make better decisions relating to potential waiting times for customers. The study adopted a case study and observational research with the source of data being primary. Purposive sampling technique was used to select the two banks under study with the target population comprising of all the customers who intended to transact businesses with the banks within the period of 11 am to 12 pm. The sample sizes for the first, second and third day of the first bank are twenty-eight (28), seventeen (17) and twenty (20) respectively with three servers on each day whereas that for the first, second and third day of the second bank is twenty (20), nine (9) and seventeen (17) with two servers on each day. A multiple server (M/M/s) Model was adopted, and Tora Software was the statistical tool used for the analysis. Findings of the study revealed that the second bank had a higher utilization factor than the first bank. Also, the number of customers in the banking hall of the second bank was higher than that of the first bank during the entire period of observation. Finally, it takes customers of the first bank lesser minutes to complete their transaction than the second bank. In conclusion, the three days observations revealed different banking situations faced by customers in both banks which had effect on waiting time of customer service. The waiting time of customer service has effect on the number of customers in the queue and system, the probability associated with the emptiness of the system and the utilization factor. Based on the results, the study recommended, <i><span>inter</span></i> <i><span>alia</span></i><span>, </span><span>that the management of the second bank should adopt a three-server (M/M/3)</span><span> model.展开更多
The exponential stability is investigated for a class of continuous time linear systems with a finite state Markov chain form process and the impulsive jump at switching moments. The conditions, based on the average d...The exponential stability is investigated for a class of continuous time linear systems with a finite state Markov chain form process and the impulsive jump at switching moments. The conditions, based on the average dwell time and the ratio of expectation of the total time running on all unstable subsystems to the expectation of the total time running on all stable subsystems,assure the exponential stability with a desired stability degree of the system irrespective of the impact of impulsive jump. The uniformly bounded result is realized for the case in which switched system is subjected to the impulsive effect of the excitation signal at some switching moments.展开更多
To improve spectrum utilization and minimize interference to Primary User (PU), an adaptive spectrum decision method is proposed for Secondary User (SU), while taking traffic load balancing and spectrum heterogeneity ...To improve spectrum utilization and minimize interference to Primary User (PU), an adaptive spectrum decision method is proposed for Secondary User (SU), while taking traffic load balancing and spectrum heterogeneity into consideration. Long-term statistics and current sensing results are integrated into the proposed decision method of spectrum access. Two decision methods, namely probability based and sensing based, are presented, compared and followed by performance analysis in terms of delay. For probability based spectrum decision, Short-Time-Job-First (STJF) priority queuing discipline is employed to minimize average residual time and theoretical conclusion is derived in a novel way. For sensing based decision we treat the interrupted service of SU as newly incoming and re-decision process is initialized to find available spectrum in a First-Available-First-Access (FAFA) fashion. Effect of sensing error in PHY layer is also analyzed in terms of extended average residual time. Simulation results show that, for relatively low arriving rate of SU traffic, the proposed spectrum decision method yields at least a delay reduction of 39.5% compared with non-adaptive method. The proposed spectrum decision can significantly improve delay performance even facing sensing errors, which cause performance degeneration to both PU and SU.展开更多
基金supported by National Science Foundation of China(Grant No.11001091)Program for New Century Excellent Talents in University
文摘Stochastic diferential equations with the time average have received increasing attentions in recent years since they can ofer better explanations for some fnancial models.Since the time average is involved in this class of stochastic diferential equations,in this paper,the linear growth condition and the Lipschitz condition are diferent from the classical conditions.Under the special linear growth condition and the special Lipschitz condition,this paper establishes the existence and uniqueness of the solution.By using the Lyapunov function,this paper also establishes the existence and uniqueness under the local Lipschitz condition and gives the p-th moment estimate.Finally,a scalar example is given to illustrate the applications of our results.
文摘This paper presents the complete mathematical model and predicts the performance of switched reluctance generator with time average and small signal models. The complete mathematical model is developed in three stages. First, a switching model is developed based on quasi-linear inductance profile. Next, based on the switching behaviour, a time average model is obtained to measure the difference between the excitation and generation time in each switching cycle. Finally, to track control voltage and current wave shapes, a small signal model is designed. The effectiveness of the complete multilevel model combining electrical machine, power converter, load and control with programming language is demonstrated through simulations. A PI controller is used for controlling the voltage of the generator. The results presented show that the controller exhibits accurate tracking control of load voltage under different operating conditions. This demonstrates that the proposed model is able to perform an accurate control of the generated output voltage even in transient situations. The simulation is performed to choose the control parameters and study the performance of switched reluctance generator prior to its actual implementation. Initial experimental results are presented using NI-Data acquisition card to control the output power according to load requirements.
文摘In the simulation output analysis,there are some measures that should be calculated by time average concept such as the mean queue length.Especially,the confidence interval of those measures might be required for statistical analysis.In this situation,the traditional method that utilizes the central limit theorem(CLT)is inapplicable if the output data set has autocorrelation structure.The bootstrap is one of the most suitable methods which can reflect the autocorrelated phenomena in statistical analysis.Therefore,the confidence interval for a time averaged measure having autocorrelation structure can also be calculated by the bootstrap methods.This study introduces the method that constructs these confidence intervals applying the bootstraps.The bootstraps proposed are the threshold bootstrap(TB),the moving block bootstrap(MBB)and stationary bootstrap(SB).Finally,some numerical examples will be provided for verification.
基金the National Natural Science Foundation of China(Nos.61374070 and 61374154)the Fundamental Research Funds for the Central Universities of China(Nos.DUT14QY14 and DUT14QY31)
文摘In this paper, the problems of stability for a class of switched positive descriptor systems(SPDSs)with average dwell time(ADT) switching are investigated. First, based on the equivalent switched system and the properties of the projector matrix, sufficient stabilities are given for the underlying systems in both continuoustime and discrete-time contexts. Then, a sufficient stability condition for the SPDS with both stable and unstable subsystems is obtained. The stability results for the SPDSs are represented in terms of a set of linear programmings(LPs) by the multiple linear co-positive Lyapunov function(MLCLF) approach. Finally, three numerical examples are given to illustrate the effectiveness of the obtained theoretical results.
文摘This paper investigates the correlation between stochastic resonance （SR） and the average phase-synchronization time which is between the input signal and the output signal in a bistable system driven by colour-correlated noises. The results show that the output signal-to-noise ratio can reach a maximum with the increase of the average phase- synchronization time, which may be helpful for understanding the principle of SR from the point of synchronization; however, SR and the maximum of the average phase-synchronization time appear at different optimal noise level, moreover, the effects on them of additive and multiplicative noise are different.
文摘Understanding the occurrence and characteristics of dry and wet events is crucial for effective disaster prevention,resource management,and risk reduction in vulnerable regions.This study analyzed the spatiotemporal patterns of dry-wet events and their transition characteristics in Uttar Pradesh,India.The standardized precipitation evapotranspiration index(SPEI)at a monthly timescale was utilized to identify hotspot regions vulnerable to concurrent and frequent dry and wet events and their transitions.The severity,duration,and intensity of dry and wet events were characterized with the run theory over SPEI time series data from 18 synoptic stations in Uttar Pradesh over 48 years(1971-2018),sourced from the Indian Institute of Tropical Meteorology and the India Meteorological Department.Multiple assessment methods were utilized to examine the interaction of these extreme events,considering characteristics such as wet-dry ratio,average transition time,and rapid transition times from wet to dry events and from dry to wet events.Average wet durations ranged from 1.27 to 1.58 months,and average dry durations ranged from 1.29 to 1.82 months.Rapid transition times from dry to wet events ranged from 2.5 to 4.1 months,and those for wet-to-dry events ranged from 2.1 to 5.3 months.The eastern region experienced a significantly high number of dry events,while the western and Bundelkhand regions experienced more intense dry events.In contrast,the eastern region had intense wet events.This research on the occurrence of dry-wet events and their transitions can provide valuable insights for government decision-making and disaster prevention and reduction efforts.
文摘AIM:To analyze the characteristics and correlation of phacoemulsification parameters and anterior segment parameters in cataract patients with different blood glucose levels.METHODS:A total of 45 type 2 diabetic cataract patients(45 eyes)treated in our hospital from March 2023 to April 2024 were stratified into two groups based on glycosylated hemoglobin(HbA1c)levels:group A:HbA1c<7%(n=18)and group B:7%≤HbA1c<8.5%(n=27);a total of 94 age-matched age-related cataract patients(94 eyes)were enrolled as the control group(group C).All underwent phacoemulsification with intraocular lens implantation.Anterior segment parameters,including corneal,lens and anterior chamber measurements,were recorded.Correlations between phacoemulsification parameters and anterior segment parameters were analyzed,and differences among groups were compared.RESULTS:In groups A and B,effective phacoemulsification time(EPT)negatively correlated with corneal endothelial cell density(CECD)(r=-0.315,P=0.035).Average phacoemulsification time(APT)positively correlated with the anterior corneal surface radius of curvature(Rm;r=0.402,P=0.006)and negatively correlated with the flat axis meridian curvature(K 1),steep axis meridian curvature(K 2),mean curvature(Km)of the anterior corneal surface,and lens density at 6 mm zones(PDZ3;all P<0.05).Average phacoemulsification energy(AVE)positively correlated with mean lens density(LD-mean),lens density at 2 mm zones(PDZ1),lens density at 4 mm zones(PDZ2),and PDZ3(all P<0.05),and negatively with pupil diameter(r=-0.385,P=0.009).In the group C,EPT showed a positive correlation with Pentacam nucleus staging(PNS)density grade,PDZ1,PDZ2,and PDZ3(all P<0.05).A positive correlation was observed between AVE and PNS classification(r=0.246,P=0.018).Conversely,AVE exhibited a negative correlation with CECD(r=-0.245,P=0.018).EPT in groups A and B was higher than that in the group C(P<0.05).Both EPT and APT in the group B were higher than those in the group A(P<0.05).In diabetic cataract patients,CECD,corneal density(CD),and posterior corneal surface height positively correlated with diabetes duration(P<0.05).Posterior corneal surface K 1 and Rm positively correlated with 7%≤HbA1c<8.5%(P<0.05).Total corneal astigmatism negatively correlated with HbA1c,2-hour post-breakfast blood glucose(2hPBG),and fasting insulin(FINS;P<0.05).CD and lens thickness(LT)positively correlated with FINS(P<0.05).CONCLUSION:Phacoemulsification parameters and blood glucose-related indices exhibited varying degrees of correlation with anterior segment parameters in cataract patients with different blood glucose levels.EPT in diabetic cataract patients was higher than that in age-related cataract patients,while EPT and APT in diabetic cataract patients with poor glycemic control were higher than those with good glycemic control.
基金the National Natural Science Foundation of China(Grant Nos.62303380,62176214,62101590,62003268)the Aeronautical Science Foundation of China(Grant No.201907053001).
文摘This research focuses on detecting faults in flight vehicles with unstable subsystems operating asynchronously.By accounting for asynchronous switching,a switched model is established,and filters for fault detection(FD)in unstable subsystems are developed.The FD challenge is then transformed into an H∞filtering issue.Utilizing the multiple discontinuous Lyapunov function(MDLF)approach and the mode-dependent average dwell time(MDADT)method,sufficient conditions are derived to ensure stability during both fast and slow switching.Furthermore,the existence and solutions for FD filters are provided through linear matrix inequalities(LMIs).The simulation outcomes demonstrated the excellent performance of the developed method in studied cases.
基金Project supported by the Russian Foundation for Basic Research(No.18-07-00518)the National Natural Science Foundation of China(No.10972212)
文摘Travel time through a ring road with a total length of 80 km has been predicted by a viscoelastic traffic model(VEM), which is developed in analogous to the non-Newtonian fluid flow. The VEM expresses a traffic pressure for the unfree flow case by space headway, ensuring that the pressure can be determined by the assumption that the relevant second critical sound speed is exactly equal to the disturbance propagation speed determined by the free flow speed and the braking distance measured by the average vehicular length. The VEM assumes that the sound speed for the free flow case depends on the traffic density in some specific aspects, which ensures that it is exactly identical to the free flow speed on an empty road. To make a comparison, the open Navier-Stokes type model developed by Zhang(ZHANG, H. M. Driver memory, traffic viscosity and a viscous vehicular traffic flow model. Transp. Res. Part B, 37, 27–41(2003)) is adopted to predict the travel time through the ring road for providing the counterpart results.When the traffic free flow speed is 80 km/h, the braking distance is supposed to be 45 m,with the jam density uniquely determined by the average length of vehicles l ≈ 5.8 m. To avoid possible singular points in travel time prediction, a distinguishing period for time averaging is pre-assigned to be 7.5 minutes. It is found that the travel time increases monotonically with the initial traffic density on the ring road. Without ramp effects, for the ring road with the initial density less than the second critical density, the travel time can be simply predicted by using the equilibrium speed. However, this simpler approach is unavailable for scenarios over the second critical.
基金supported by National Natural Science Foundation of China(Grant Nos.5112502251005173)+1 种基金PhD Programs Foundation of Ministry of Education of China(Grant No.20110201110025)the Fundamental Research Funds for the Central Universities of China
文摘Time domain averaging(TDA) is essentially a comb filter,it cannot extract the specified harmonics which may be caused by some faults,such as gear eccentric.Meanwhile,TDA always suffers from period cutting error(PCE) to different extent.Several improved TDA methods have been proposed,however they cannot completely eliminate the waveform reconstruction error caused by PCE.In order to overcome the shortcomings of conventional methods,a flexible time domain averaging(FTDA) technique is established,which adapts to the analyzed signal through adjusting each harmonic of the comb filter.In this technique,the explicit form of FTDA is first constructed by frequency domain sampling.Subsequently,chirp Z-transform(CZT) is employed in the algorithm of FTDA,which can improve the calculating efficiency significantly.Since the signal is reconstructed in the continuous time domain,there is no PCE in the FTDA.To validate the effectiveness of FTDA in the signal de-noising,interpolation and harmonic reconstruction,a simulated multi-components periodic signal that corrupted by noise is processed by FTDA.The simulation results show that the FTDA is capable of recovering the periodic components from the background noise effectively.Moreover,it can improve the signal-to-noise ratio by 7.9 dB compared with conventional ones.Experiments are also carried out on gearbox test rigs with chipped tooth and eccentricity gear,respectively.It is shown that the FTDA can identify the direction and severity of the eccentricity gear,and further enhances the amplitudes of impulses by 35%.The proposed technique not only solves the problem of PCE,but also provides a useful tool for the fault symptom extraction of rotating machinery.
基金the National Natural Science Foundation of China(No.60674027)China Postdoctoral Science Foundation(No.20070410336)the Postdoctor Foundation of Jiangsu Province(No.0602042B).
文摘A new class of hybrid impulsive and switching models are introduced and their robust exponential stability and control synthesis are addressed. The proposed switched system is composed of stable subsystems and unstable subsystems, which not only involves state delay and norm-bounded time-varying parameter uncertainties, but also contains the impulsive switching effects between the subsystems. Based on the extension of the system dimension and the concept of average dwell time, a kind of practically useful switching rule is presented which guarantees the desired robust exponential stability. A switched state feedback controller is also given.
基金supported by the National Natural Science Foundation of China(6127316261403104)
文摘The problem of the robust fault detection filter design for time-varying delays switched systems is considered in the framework of mixed H-/H∞. Firstly, the weighted H∞ performance index is utilized as the robustness performance, and the H- index is used as the sensitivity performance for obtaining the robust fault detection filter. Then a novel multiple Lyapunov-Krasovskii function is proposed for deriving sufficient existence conditions of the robust fault detection filter based on the average dwell time technique. By introducing slack matrix variable, the coupling between the Lyapunov matrix and system matrix is removed, and the conservatism of results is reduced. Based on the robust fault detection filter, residual is generated and evaluated for detecting faults. In addition, the results of this paper are dependent on time delays,and represented in the form of linear matrix inequalities. Finally,the simulation example verifies the effectiveness of the proposed method.
基金Supported by National Postdoctoral Program for Innovative Talent of China (Grant No.BX20180031)。
文摘Periodic components are of great significance for fault diagnosis and health monitoring of rotating machinery.Time synchronous averaging is an effective and convenient technique for extracting those components.However,the performance of time synchronous averaging is seriously limited when the separate segments are poorly synchronized.This paper proposes a new averaging method capable of extracting periodic components without external reference and an accurate period to solve this problem.With this approach,phase detection and compensation eliminate all segments'phase differences,which enables the segments to be well synchronized.The effectiveness of the proposed method is validated by numerical and experimental signals.
基金The authors extend their appreciation to Deanship of Scientific Research at King Khalid University for funding this work through the Research Groups Project under Grant Number RGP.1/95/42.
文摘Minimizing time cost in time-shared operating systems is considered basic and essential task,and it is the most significant goal for the researchers who interested in CPU scheduling algorithms.Waiting time,turnaround time,and number of context switches are themost time cost criteria used to compare between CPU scheduling algorithms.CPU scheduling algorithms are divided into non-preemptive and preemptive.RoundRobin(RR)algorithm is the most famous as it is the basis for all the algorithms used in time-sharing.In this paper,the authors proposed a novel CPU scheduling algorithm based on RR.The proposed algorithm is called Adjustable Time Slice(ATS).It reduces the time cost by taking the advantage of the low overhead of RR algorithm.In addition,ATS favors short processes allowing them to run longer time than given to long processes.The specific characteristics of each process are;its CPU execution time,weight,time slice,and number of context switches.ATS clusters the processes in groups depending on these characteristics.The traditionalRRassigns fixed time slice for each process.On the other hand,dynamic variants of RR assign time slice for each process differs from other processes.The essential difference between ATS and the other methods is that it gives a set of processes a specific time based on their similarities within the same cluster.The authors compared between ATS with five popular scheduling algorithms on nine datasets of processes.The datasets used in the comparison vary in their features.The evaluation was measured in term of time cost and the experiments showed that the proposed algorithm reduces the time cost.
文摘We study the open quantum random walk (OQRW) with time-dependence on the one-dimensional lattice space and obtain the associated limit distribution. As an application we study the return probability of the OQRW. We also ask, "What is the average time for the return probability of the OQRW?"
文摘This paper investigates the problem of event-triggered finite-time <i>H</i><sub>∞</sub> control for a class of switched stochastic systems. The main objective of this study is to design an event-triggered state feedback <i>H</i><sub>∞</sub> controller such that the resulting closed-loop system is finite-time bounded and satisfies a prescribed <i>H</i><sub>∞</sub> level in some given finite-time interval. Based on stochastic differential equations theory and average dwell time approach, sufficient conditions are derived to ensure the finite-time stochastic stability with the prescribed <i>H</i><sub>∞</sub> performance for the relevant closed-loop system by employing the linear matrix inequality technique. Finally, the desired state feedback <i>H</i><sub>∞</sub> controller gain matrices can be expressed in an explicit form.
文摘Queue is an act of joining a line to be served and it is part of our everyday human involvement. The objectives of the study focused on using a mathematical model to determine the waiting time of two selected banks as well as compare the average waiting time between the banks. The study uncovered the extent of usage of queuing models in achieving customer satisfaction as well as permitting to make better decisions relating to potential waiting times for customers. The study adopted a case study and observational research with the source of data being primary. Purposive sampling technique was used to select the two banks under study with the target population comprising of all the customers who intended to transact businesses with the banks within the period of 11 am to 12 pm. The sample sizes for the first, second and third day of the first bank are twenty-eight (28), seventeen (17) and twenty (20) respectively with three servers on each day whereas that for the first, second and third day of the second bank is twenty (20), nine (9) and seventeen (17) with two servers on each day. A multiple server (M/M/s) Model was adopted, and Tora Software was the statistical tool used for the analysis. Findings of the study revealed that the second bank had a higher utilization factor than the first bank. Also, the number of customers in the banking hall of the second bank was higher than that of the first bank during the entire period of observation. Finally, it takes customers of the first bank lesser minutes to complete their transaction than the second bank. In conclusion, the three days observations revealed different banking situations faced by customers in both banks which had effect on waiting time of customer service. The waiting time of customer service has effect on the number of customers in the queue and system, the probability associated with the emptiness of the system and the utilization factor. Based on the results, the study recommended, <i><span>inter</span></i> <i><span>alia</span></i><span>, </span><span>that the management of the second bank should adopt a three-server (M/M/3)</span><span> model.
基金the National Natural Science Foundation of China (60674027, 60574007)Doctoral Foundation of Education Ministry of China (20050446001).
文摘The exponential stability is investigated for a class of continuous time linear systems with a finite state Markov chain form process and the impulsive jump at switching moments. The conditions, based on the average dwell time and the ratio of expectation of the total time running on all unstable subsystems to the expectation of the total time running on all stable subsystems,assure the exponential stability with a desired stability degree of the system irrespective of the impact of impulsive jump. The uniformly bounded result is realized for the case in which switched system is subjected to the impulsive effect of the excitation signal at some switching moments.
基金supported partially by China's National 863 Program under Grant No.2009AA01Z207
文摘To improve spectrum utilization and minimize interference to Primary User (PU), an adaptive spectrum decision method is proposed for Secondary User (SU), while taking traffic load balancing and spectrum heterogeneity into consideration. Long-term statistics and current sensing results are integrated into the proposed decision method of spectrum access. Two decision methods, namely probability based and sensing based, are presented, compared and followed by performance analysis in terms of delay. For probability based spectrum decision, Short-Time-Job-First (STJF) priority queuing discipline is employed to minimize average residual time and theoretical conclusion is derived in a novel way. For sensing based decision we treat the interrupted service of SU as newly incoming and re-decision process is initialized to find available spectrum in a First-Available-First-Access (FAFA) fashion. Effect of sensing error in PHY layer is also analyzed in terms of extended average residual time. Simulation results show that, for relatively low arriving rate of SU traffic, the proposed spectrum decision method yields at least a delay reduction of 39.5% compared with non-adaptive method. The proposed spectrum decision can significantly improve delay performance even facing sensing errors, which cause performance degeneration to both PU and SU.
