BACKGROUND Colonic diverticular bleeding(CDB)is a leading cause of gastrointestinal blee-ding-related hospitalizations in Japan and is increasingly recognized as a signifi-cant burden in the United States.Identifying ...BACKGROUND Colonic diverticular bleeding(CDB)is a leading cause of gastrointestinal blee-ding-related hospitalizations in Japan and is increasingly recognized as a signifi-cant burden in the United States.Identifying the stigmata of a recent hemorrhage(SRH)during colonoscopy enables targeted hemostasis and reduces rebleeding.However,no benchmark exists for an appropriate observation duration,resulting in operator-dependent variation.Short observation periods may lead to missed SRH,whereas unnecessarily prolonged procedures,particularly in older patients,can increase patient burden and limit endoscopy unit availability.METHODS We retrospectively analyzed patients with acute hematochezia who underwent an initial colonoscopy between January 2017 and December 2024 at a Japanese tertiary hospital.The Observation time was measured from scope insertion to SRH detection(excluding therapeutic time)or withdrawal.The primary outcome,the“5%plateau time”,was defined as the point when the proportion of patients newly identified with SRH in each 5-minute interval consistently dropped below 5%.Computed tomography(CT)-based stratified analyses were performed by endoscopists who conducted≥10%of procedures.RESULTS Of the 1039 patients who underwent colonoscopy,845(mean age 77±11 years;64.5%male)were included.Nine board-certified endoscopists performed the procedures.SRH was detected in 286 patients(33.8%),with a median detection time of 19 minutes(interquartile range,12-28 minutes).The overall 5%plateau time was 40 minutes and varied according to the CT findings:40,35,and 30 minutes for no extravasation,right-sided extravasation,and left-sided extravasation,respectively.This time point corresponded to when 80%-90%of SRH cases were detected.De-spite variations in SRH detection rates and observation durations among endoscopists,the 5%plateau time was consistently approximately 40 minutes.CONCLUSION Although it varied according to the CT findings,the overall 5%plateau time was 40 minutes.This offers a practical benchmark for the minimum observation time without SRH detection.展开更多
Inconsistency is a fundamental problem in simultaneous localization and mapping(SLAM).Previous works from predecessors have studied the inconsistent problem of extended Kalman filter(EKF)SLAM algorithm focusing on the...Inconsistency is a fundamental problem in simultaneous localization and mapping(SLAM).Previous works from predecessors have studied the inconsistent problem of extended Kalman filter(EKF)SLAM algorithm focusing on the linearization errors.In this paper,we studied the inconsistency issue of EKF SLAM in theory based on measurement noise and observation time.In a simplified situation,we deduced some useful theorems of estimated covariance matrix.Then,we made use of them to investigate the inconsistency issue.We showed that the measurement noise and the observation times can drive the EKF SLAM out of consistency.Moreover,we demonstrated the explicit effects of measurement noise and observation times on inconsistency of the EKF SLAM.Our simulation experiments verified the results.展开更多
In many longitudinal studies, observation times as well as censoring times may be correlated with longitudinal responses. This paper considers a multiplicative random effects model for the longitudinal response where ...In many longitudinal studies, observation times as well as censoring times may be correlated with longitudinal responses. This paper considers a multiplicative random effects model for the longitudinal response where these correlations may exist and a joint modeling approach is proposed via a shared latent variable. For inference about regression parameters, estimating equation approaches are developed and asymptotic properties of the proposed estimators are established. The finite sample behavior of the methods is examined through simulation studies and an application to a data set from a bladder cancer study is provided for illustration.展开更多
The wavenumber spectral components WN4 at the mesosphere and low thermosphere(MLT)altitudes(70–10 km)and in the latitude range between±45°are obtained from temperature data(T)observed by the Sounding of the...The wavenumber spectral components WN4 at the mesosphere and low thermosphere(MLT)altitudes(70–10 km)and in the latitude range between±45°are obtained from temperature data(T)observed by the Sounding of the Atmosphere using Broadband Emission Radiometry(SABER)instruments on board the National Aeronautics and Space Administration(NASA)’s Thermosphere–Ionosphere–Mesosphere Energetics and Dynamics(TIMED)spacecraft during the 11-year solar period from 2002 to 2012.We analyze in detail these spectral components WNk and obtain the main properties of their vertical profiles and global structures.We report that all of the wavenumber spectral components WNk occur mainly around 100 km altitude,and that the most prominent component is the wavenumber spectral component WN4 structure.Comparing these long duration temperature data with results of previous investigations,we have found that the yearly variation of spectral component WN4 is similar to that of the eastward propagating non-migrating diurnal tide with zonal wavenumber 3(DE3)at the low latitudes,and to that of the semi-diurnal tide with zonal wavenumber 2(SE2)at the mid-latitudes:the amplitudes of the A4 are larger during boreal summer and autumn at the low-latitudes;at the mid-latitudes the amplitudes have a weak peak in March.In addition,the amplitudes of component WN4 undergo a remarkable short period variation:significant day-to-day variation of the spectral amplitudes A4 occurs primarily in July and September at the low-latitudes.In summary,we conclude that the non-migrating tides DE3 and SE2 are likely to be the origins,at the low-latitudes and the mid-latitudes in the MLT region,respectively,of the observed wavenumber spectral component WN4.展开更多
This article aims to address the global exponential synchronization problem for fractional-order complex dynamical networks(FCDNs)with derivative couplings and impulse effects via designing an appropriate feedback con...This article aims to address the global exponential synchronization problem for fractional-order complex dynamical networks(FCDNs)with derivative couplings and impulse effects via designing an appropriate feedback control based on discrete time state observations.In contrast to the existing works on integer-order derivative couplings,fractional derivative couplings are introduced into FCDNs.First,a useful lemma with respect to the relationship between the discrete time observations term and a continuous term is developed.Second,by utilizing an inequality technique and auxiliary functions,the rigorous global exponential synchronization analysis is given and synchronization criterions are achieved in terms of linear matrix inequalities(LMIs).Finally,two examples are provided to illustrate the correctness of the obtained results.展开更多
In this study,we use observations from the Sounding of the Atmosphere using Broadband Emission Radiometry(SABER)instrument onboard the Thermosphere–Ionosphere–Mesosphere Energetics and Dynamics(TIMED)satellite to de...In this study,we use observations from the Sounding of the Atmosphere using Broadband Emission Radiometry(SABER)instrument onboard the Thermosphere–Ionosphere–Mesosphere Energetics and Dynamics(TIMED)satellite to develop and apply a new local-time binning method to investigate the long-term evolution of mesospheric water vapor at high latitudes.The proposed method accounts for the gradual local-time drift of the SABER orbit by aligning seasonal observation windows and selecting samples observed at similar local times.This approach minimizes tidal aliasing and ensures more consistent sampling,yielding more reliable estimates of long-term water vapor trends at high latitudes.The results show that drying signals primarily appear in the polar regions.However,in the southern hemisphere,a drying trend is observed only in autumn,whereas winter and summer mainly show moistening trends.In contrast,the northern hemisphere exhibits drying signals in the polar regions during all seasons,showing a clear seasonal asymmetry.Additionally,the water vapor trend in the northern hemisphere is particularly pronounced in February(late winter),with moistening reaching up to+2.0 ppmv.The winter in the southern hemisphere(July–August)also shows moistening,but the trend is still weaker than in the northern hemisphere.These differences highlight the strong moistening trend in the northern hemisphere during winter and underscore the significant asymmetry in seasonal water vapor changes between the two hemispheres.These findings emphasize the limitations of water vapor trend estimates across different seasons and latitudes.Moreover,they provide new insights into the spatiotemporal variability associated with tidal structures,underscoring the importance of optimizing local-time sampling strategies for reliable long-term trend detection.展开更多
The cooperative output tracking problem of multi-agent systems in finite time is considered.In order to enable the agents to quickly track and converge to external system within a finite time,a novel distributed outpu...The cooperative output tracking problem of multi-agent systems in finite time is considered.In order to enable the agents to quickly track and converge to external system within a finite time,a novel distributed output feedback control strategy based on the finite-time state observer is designed.This distributed finite-time observer can not only solve cooperative output tracking problems when the agents can not get external system signal,but also make the systems have a faster convergence and a good robustness.The stability of the system in finite time is proved based on Lyapunov function.Numerical simulations results have been provided to demonstrate the effectiveness of the proposed protocol.展开更多
The target motion analysis（TMA） for a moving scanning emitter with known fixed scan rate by a single observer using the time of interception（TOI） measurements only is investigated in this paper.By transforming the...The target motion analysis（TMA） for a moving scanning emitter with known fixed scan rate by a single observer using the time of interception（TOI） measurements only is investigated in this paper.By transforming the TOI of multiple scan cycles into the direction difference of arrival（DDOA） model,the observability analysis for the TMA problem is performed.Some necessary conditions for uniquely identifying the scanning emitter trajectory are obtained.This paper also proposes a weighted instrumental variable（WIV） estimator for the scanning emitter TMA,which does not require any initial solution guess and is closed-form and computationally attractive.More importantly,simulations show that the proposed algorithm can provide estimation mean square error close to the Cramer-Rao lower bound（CRLB） at moderate noise levels with significantly lower estimation bias than the conventional pseudo-linear least square（PLS） estimator.展开更多
With deep mining of coal mines, prospecting multilayer water-filled goaf has become a new content that results from geophysical exploration in coalfields. The central loop transient electromagnetic （TEM） method is f...With deep mining of coal mines, prospecting multilayer water-filled goaf has become a new content that results from geophysical exploration in coalfields. The central loop transient electromagnetic （TEM） method is favorable for prospecting conductive layers because of the coupling relationship between its field structure and formation. However, the shielding effect of conductive overburden would not only require a longer observation time when prospecting the same depth but also weaken the anomalous response of underlying layers. Through direct time domain numerical simulation and horizontal layered earth forward modeling, this paper estimates the length of observation time required to prospect the target, and the distinguishable criterion of multilayer water-filled goal is presented with observation error according to the effect of noise on observation data. The observed emf curves from Dazigou Coal Mine, Shanxi Province can distinguish multilayer water-filled goaf. In quantitative inversion interpretation of observed curves, using electric logging data as initial parameters restrains the equivalence caused by coal formation thin layers. The deduced three-layer and two-layer water-filled goals are confirmed by the drilling hole. The result suggests that when observation time is long enough and with the anomalous situation of underlying layers being greater than the observation error, the use of the central loop TEM method to orosoect a multilaver water-filled goaf is feasible.展开更多
Computer simulation experiment is very important in the phase of project design, the availability of simulated result highly depends on the scheme of error simulation. Time series observations are normally correlated....Computer simulation experiment is very important in the phase of project design, the availability of simulated result highly depends on the scheme of error simulation. Time series observations are normally correlated. This paper first discusses the formula of correlated error propagation, then derives the formula of simulating time series correlated errors. This formula is then used to simulate correlated ephemerides errors of CHAMP, then the ephemerides are used to recover the gravity vector at satellite altitude with finite differential formula. The formulae derived in this paper are verified with the difference between the recovered gravity vectors and the `true values’ which are directly computed with the same gravity model as that generating the ephemerides.展开更多
Longitudinal data often arise when subjects are followed over a period of time, and in many situations, there may exist informative observation times and a dependent terminal event such as death that stops the follow-...Longitudinal data often arise when subjects are followed over a period of time, and in many situations, there may exist informative observation times and a dependent terminal event such as death that stops the follow-up. In this article, we propose joint modeling and analysis of longitudinal data with possibly informative observation times and a dependent terminal event in which a common subject-specific latent variable is used to characterize the correlations. A borrow-strength estimation procedure is developed for parameter estimation, and both large-sample and finite^sample properties of the proposed estimators are established. In addition, some goodness-of-fit methods for assessing the adequacy of the model are provided. An application to a bladder cancer study is illustrated.展开更多
Longitudinal data often occur in follow-up studies, and in many situations, there may exist informative observation times and a dependent terminal event such as death that stops the follow-up. We propose a semiparamet...Longitudinal data often occur in follow-up studies, and in many situations, there may exist informative observation times and a dependent terminal event such as death that stops the follow-up. We propose a semiparametric mixed effect model with time-varying latent effects in the analysis of longitudinal data with informative observation times and a dependent terminal event. Estimating equation approaches are developed for parameter estimation, and asymptotic properties of the resulting estimators are established. The finite sample behavior of the proposed estimators is evaluated through simulation studies, and an application to a bladder cancer study is provided.展开更多
Crystal growth is a complex process,and until now there isn’t a satisfied real t ime observation method.Under the space high temperature in situ observation inst rument(SHITISOI),we develop a three dimensioned real t...Crystal growth is a complex process,and until now there isn’t a satisfied real t ime observation method.Under the space high temperature in situ observation inst rument(SHITISOI),we develop a three dimensioned real time observation device for the crystal.By it,we can acquire image of crystal in three dimension,moreover,i t would provide technique for remote science control in the future space experimen t.We develop the device not only apply to real time observation also adapt to r e mote science research.We use annular quartz glass so as to in situ observe the c hange of interface.And two heater were put its upon and down,thus they form two different temperature zones.We apply to Bridgeman method crystal growth by using special lift to move the quartz crucible.Presently we have developed a pass mus t er furnace, and can get the NaNO 3 crystal.We could observe the fluid flow stat ue and the interface move by tracer particle.We get the effect of unsteady conve ction,which is important both in land and space crystal growth.展开更多
Titanium nitride precipitation on a primary inclusion particle during solidification of bearing steel has been tracked by varying temperature in a confocal scanning violet laser microscope.Upon precipitation,an obviou...Titanium nitride precipitation on a primary inclusion particle during solidification of bearing steel has been tracked by varying temperature in a confocal scanning violet laser microscope.Upon precipitation,an obvious growth of titanium nitride on a primary inclusion particle was observed due to the rapid solute diffusion in liquid steel.The onset of titanium nitride precipitation did not change with primary inclusion particle size,but the time of growth was greater for a smaller primary inclusion particle.Meanwhile,the particle size displayed little influence on the total precipitated amount of titanium nitride on it under the same conditions.At the later period of solidification,almost no change occurred in inclusion size,but the inclusion shape varied from circle to almost square in two-dimension,or cubic in three-dimension,to attain the equilibrium with steel.展开更多
We demonstrate here that global-scale determination of a key ionospheric parameter,the peak height of the F_(2)region(h_(m)F_(2)),can be obtained by making a simple ratio measurement of the atomic oxygen 130.4 and 135...We demonstrate here that global-scale determination of a key ionospheric parameter,the peak height of the F_(2)region(h_(m)F_(2)),can be obtained by making a simple ratio measurement of the atomic oxygen 130.4 and 135.6 nm emissions in the far-ultraviolet nightglow with a nadir-viewing system such as a pair of photometers suitable for flight on a CubeSat.We further demonstrate that measurements from an altitude that is within the typical range of nighttime h_(m)F_(2)250−450 km can provide the ratios that are needed for retrieval of the h_(m)F_(2).Our study is conducted mostly through numerical simulations by using radiative transfer models of the two emissions coupled with empirical models of the atmosphere and ionosphere.Modeling results show that the relationship between the h_(m)F_(2)and the intensity ratio is sensitive to the altitude from which the emissions are observed,primarily because of the distinctly different degrees of resonant scattering of the two emissions in the atmosphere.A roughly quadratic relationship can be established for observations from an orbit of~400 km,which enables h_(m)F_(2)retrieval.Parametric analysis indicates that the relationship can be affected by the ambient atmospheric conditions through resonant scattering and O2 absorption.For typical nighttime conditions with h_(m)F_(2)250−450 km,retrieval of the h_(m)F_(2)from synthetic observations shows that the typical errors are only a few kilometers(up to~20 km),depending on the accuracy of the ambient conditions predicted by the empirical models.Our findings pave the way for use of the 130.4/135.6 nm intensity ratios for global-scale monitoring of the nighttime ionosphere at mid to low latitudes.展开更多
This paper focuses on boundary stabilization of a one-dimensional wave equation with an unstable boundary condition,in which observations are subject to arbitrary fixed time delay.The observability inequality indicate...This paper focuses on boundary stabilization of a one-dimensional wave equation with an unstable boundary condition,in which observations are subject to arbitrary fixed time delay.The observability inequality indicates that the open-loop system is observable,based on which the observer and predictor are designed:The state of system is estimated with available observation and then predicted without observation.After that equivalently the authors transform the original system to the well-posed and exponentially stable system by backstepping method.The equivalent system together with the design of observer and predictor give the estimated output feedback.It is shown that the closed-loop system is exponentially stable.Numerical simulations are presented to illustrate the effect of the stabilizing controller.展开更多
Imaginary potentials such as V(x)=−iσ1Ω(x)(withσ>0 a constant,Ωa subset of 3-space,and 1Ωits characteristic function)have been used in quantum mechanics as models of a detector.They represent the effect of a‘...Imaginary potentials such as V(x)=−iσ1Ω(x)(withσ>0 a constant,Ωa subset of 3-space,and 1Ωits characteristic function)have been used in quantum mechanics as models of a detector.They represent the effect of a‘soft’detector that takes a while to notice a particle in the detector volumeΩ.In order to model a‘hard’detector(i.e.one that registers a particle as soon as it entersΩ),one may think of taking the limitσ→∞of increasing detector strengthσ.However,as pointed out by Allcock,in this limit the particle never entersΩ;its wave function gets reflected at the boundary∂ΩofΩin the same way as by a Dirichlet boundary condition on∂Ω.This phenomenon,a cousin of the‘quantum Zeno effect,’might suggest that a hard detector is mathematically impossible.Nevertheless,a mathematical description of a hard detector has recently been put forward in the form of the‘absorbing boundary rule’involving an absorbing boundary condition on the detecting surface∂Ω.We show here that in a suitable(non-obvious)limit,the imaginary potential V yields a non-trivial distribution of detection time and place in agreement with the absorbing boundary rule.That is,a hard detector can be obtained as a limit,but it is a different limit than Allcock considered.展开更多
Einstein’s Special Relativity (ESR) has enjoyed spectacular success as a mathematical construct and in terms of the experiments to which it has been subjected. Possible vulnerabilities of ESR will be explored that br...Einstein’s Special Relativity (ESR) has enjoyed spectacular success as a mathematical construct and in terms of the experiments to which it has been subjected. Possible vulnerabilities of ESR will be explored that break the symmetry of reciprocal observations of length, time, and mass. It is shown how Newton could also have derived length contraction . Einstein’s General Relativity (EGR) will also be discussed occasionally such as a changed perspective on gravitational waves due to a small change in ESR. Some additional questions addressed are: Did Einstein totally eliminate the Ether? Is the physical interpretation of ESR completely correct? Why should there be a maximum speed limit, and should it always be the same? The mass-energy equation is revisited to show that in 1717 Newton could have derived the modern , and not known that it violates the foundation of his mechanics. Tributes are paid to Einstein and others.展开更多
A robust nonsingular fixed time terminal sliding mode control scheme with a time delay disturbance observer is proposed for atmospheric pollution detection lidar scanning mechanism(APDL-SM)system.Distinguished from th...A robust nonsingular fixed time terminal sliding mode control scheme with a time delay disturbance observer is proposed for atmospheric pollution detection lidar scanning mechanism(APDL-SM)system.Distinguished from the conventional terminal sliding mode control methods,the authors design a novel fixed-time terminal sliding surface,the convergence time of sliding mode phase of which has a constant upper bound that is designable by adjusting only one parameter.Moreover,in order to overcome the problem of unknown upper bound of lumped uncertainty including model uncertainty,friction effect and external disturbances from the port environment,the authors propose a time delay disturbance observer to provide an estimation for the system lumped uncertainty.By using the Lyapunov synthesis,the explicit analysis of the convergence time upper bound are performed.Finally,simulation studies are conducted on the APDL-SM system to show the fast convergence rate and strong robustness of the proposed control scheme.展开更多
In this paper, for any given observation time and suitable moving observation domains, the author establishes a sharp observability inequality for the Kirchhoff-Rayleigh plate like equation with a suitable potential i...In this paper, for any given observation time and suitable moving observation domains, the author establishes a sharp observability inequality for the Kirchhoff-Rayleigh plate like equation with a suitable potential in any space dimension. The approach is based on a delicate energy estimate. Moreover, the observability constant is estimated by means of an explicit function of the norm of the coefficient involved in the equation.展开更多
文摘BACKGROUND Colonic diverticular bleeding(CDB)is a leading cause of gastrointestinal blee-ding-related hospitalizations in Japan and is increasingly recognized as a signifi-cant burden in the United States.Identifying the stigmata of a recent hemorrhage(SRH)during colonoscopy enables targeted hemostasis and reduces rebleeding.However,no benchmark exists for an appropriate observation duration,resulting in operator-dependent variation.Short observation periods may lead to missed SRH,whereas unnecessarily prolonged procedures,particularly in older patients,can increase patient burden and limit endoscopy unit availability.METHODS We retrospectively analyzed patients with acute hematochezia who underwent an initial colonoscopy between January 2017 and December 2024 at a Japanese tertiary hospital.The Observation time was measured from scope insertion to SRH detection(excluding therapeutic time)or withdrawal.The primary outcome,the“5%plateau time”,was defined as the point when the proportion of patients newly identified with SRH in each 5-minute interval consistently dropped below 5%.Computed tomography(CT)-based stratified analyses were performed by endoscopists who conducted≥10%of procedures.RESULTS Of the 1039 patients who underwent colonoscopy,845(mean age 77±11 years;64.5%male)were included.Nine board-certified endoscopists performed the procedures.SRH was detected in 286 patients(33.8%),with a median detection time of 19 minutes(interquartile range,12-28 minutes).The overall 5%plateau time was 40 minutes and varied according to the CT findings:40,35,and 30 minutes for no extravasation,right-sided extravasation,and left-sided extravasation,respectively.This time point corresponded to when 80%-90%of SRH cases were detected.De-spite variations in SRH detection rates and observation durations among endoscopists,the 5%plateau time was consistently approximately 40 minutes.CONCLUSION Although it varied according to the CT findings,the overall 5%plateau time was 40 minutes.This offers a practical benchmark for the minimum observation time without SRH detection.
文摘Inconsistency is a fundamental problem in simultaneous localization and mapping(SLAM).Previous works from predecessors have studied the inconsistent problem of extended Kalman filter(EKF)SLAM algorithm focusing on the linearization errors.In this paper,we studied the inconsistency issue of EKF SLAM in theory based on measurement noise and observation time.In a simplified situation,we deduced some useful theorems of estimated covariance matrix.Then,we made use of them to investigate the inconsistency issue.We showed that the measurement noise and the observation times can drive the EKF SLAM out of consistency.Moreover,we demonstrated the explicit effects of measurement noise and observation times on inconsistency of the EKF SLAM.Our simulation experiments verified the results.
基金supported by the National Natural Science Foundation of China Grants(No.10571169 and 10731010)the National Basic Research Program of China (973 Program) (No.2007CB814902)
文摘In many longitudinal studies, observation times as well as censoring times may be correlated with longitudinal responses. This paper considers a multiplicative random effects model for the longitudinal response where these correlations may exist and a joint modeling approach is proposed via a shared latent variable. For inference about regression parameters, estimating equation approaches are developed and asymptotic properties of the proposed estimators are established. The finite sample behavior of the methods is examined through simulation studies and an application to a data set from a bladder cancer study is provided for illustration.
基金The present work is supported by National Science Foundation of China(41604138,41427901,41621063,41474133,41674158,41874179,41322030).
文摘The wavenumber spectral components WN4 at the mesosphere and low thermosphere(MLT)altitudes(70–10 km)and in the latitude range between±45°are obtained from temperature data(T)observed by the Sounding of the Atmosphere using Broadband Emission Radiometry(SABER)instruments on board the National Aeronautics and Space Administration(NASA)’s Thermosphere–Ionosphere–Mesosphere Energetics and Dynamics(TIMED)spacecraft during the 11-year solar period from 2002 to 2012.We analyze in detail these spectral components WNk and obtain the main properties of their vertical profiles and global structures.We report that all of the wavenumber spectral components WNk occur mainly around 100 km altitude,and that the most prominent component is the wavenumber spectral component WN4 structure.Comparing these long duration temperature data with results of previous investigations,we have found that the yearly variation of spectral component WN4 is similar to that of the eastward propagating non-migrating diurnal tide with zonal wavenumber 3(DE3)at the low latitudes,and to that of the semi-diurnal tide with zonal wavenumber 2(SE2)at the mid-latitudes:the amplitudes of the A4 are larger during boreal summer and autumn at the low-latitudes;at the mid-latitudes the amplitudes have a weak peak in March.In addition,the amplitudes of component WN4 undergo a remarkable short period variation:significant day-to-day variation of the spectral amplitudes A4 occurs primarily in July and September at the low-latitudes.In summary,we conclude that the non-migrating tides DE3 and SE2 are likely to be the origins,at the low-latitudes and the mid-latitudes in the MLT region,respectively,of the observed wavenumber spectral component WN4.
基金supported by Key Projectof Natural Science Foundation of China(61833005)the Natural Science Foundation of Hebei Province of China(A2018203288)。
文摘This article aims to address the global exponential synchronization problem for fractional-order complex dynamical networks(FCDNs)with derivative couplings and impulse effects via designing an appropriate feedback control based on discrete time state observations.In contrast to the existing works on integer-order derivative couplings,fractional derivative couplings are introduced into FCDNs.First,a useful lemma with respect to the relationship between the discrete time observations term and a continuous term is developed.Second,by utilizing an inequality technique and auxiliary functions,the rigorous global exponential synchronization analysis is given and synchronization criterions are achieved in terms of linear matrix inequalities(LMIs).Finally,two examples are provided to illustrate the correctness of the obtained results.
基金supported by the National Key R&D Program of China(Grant No.2022YFF0503703)the National Natural Science Foundation of China(Grant Nos.42130203,42275133,and 42241135).
文摘In this study,we use observations from the Sounding of the Atmosphere using Broadband Emission Radiometry(SABER)instrument onboard the Thermosphere–Ionosphere–Mesosphere Energetics and Dynamics(TIMED)satellite to develop and apply a new local-time binning method to investigate the long-term evolution of mesospheric water vapor at high latitudes.The proposed method accounts for the gradual local-time drift of the SABER orbit by aligning seasonal observation windows and selecting samples observed at similar local times.This approach minimizes tidal aliasing and ensures more consistent sampling,yielding more reliable estimates of long-term water vapor trends at high latitudes.The results show that drying signals primarily appear in the polar regions.However,in the southern hemisphere,a drying trend is observed only in autumn,whereas winter and summer mainly show moistening trends.In contrast,the northern hemisphere exhibits drying signals in the polar regions during all seasons,showing a clear seasonal asymmetry.Additionally,the water vapor trend in the northern hemisphere is particularly pronounced in February(late winter),with moistening reaching up to+2.0 ppmv.The winter in the southern hemisphere(July–August)also shows moistening,but the trend is still weaker than in the northern hemisphere.These differences highlight the strong moistening trend in the northern hemisphere during winter and underscore the significant asymmetry in seasonal water vapor changes between the two hemispheres.These findings emphasize the limitations of water vapor trend estimates across different seasons and latitudes.Moreover,they provide new insights into the spatiotemporal variability associated with tidal structures,underscoring the importance of optimizing local-time sampling strategies for reliable long-term trend detection.
基金National Natural Science Foundation of China(No.61663020)National Key R&D Program of China(No.2017YFB1201003-020)Natural Science Foundation of Gansu Province(No.17JR5RA096)
文摘The cooperative output tracking problem of multi-agent systems in finite time is considered.In order to enable the agents to quickly track and converge to external system within a finite time,a novel distributed output feedback control strategy based on the finite-time state observer is designed.This distributed finite-time observer can not only solve cooperative output tracking problems when the agents can not get external system signal,but also make the systems have a faster convergence and a good robustness.The stability of the system in finite time is proved based on Lyapunov function.Numerical simulations results have been provided to demonstrate the effectiveness of the proposed protocol.
基金co-supported by the Shanghai Aerospace Science and Technology Innovation Fund of China(No.SAST2015028)the Equipment Prophecy Fund of China(No.9140A21040115KG01001)
文摘The target motion analysis（TMA） for a moving scanning emitter with known fixed scan rate by a single observer using the time of interception（TOI） measurements only is investigated in this paper.By transforming the TOI of multiple scan cycles into the direction difference of arrival（DDOA） model,the observability analysis for the TMA problem is performed.Some necessary conditions for uniquely identifying the scanning emitter trajectory are obtained.This paper also proposes a weighted instrumental variable（WIV） estimator for the scanning emitter TMA,which does not require any initial solution guess and is closed-form and computationally attractive.More importantly,simulations show that the proposed algorithm can provide estimation mean square error close to the Cramer-Rao lower bound（CRLB） at moderate noise levels with significantly lower estimation bias than the conventional pseudo-linear least square（PLS） estimator.
基金supported by the National Science Foundation of China(No.41374129)Science and Technology Project of Shanxi Province(No.20100321066)Research and Development Project of National Major Scientifi c Research Equipment(No.ZDYZ2012-1-05-04)
文摘With deep mining of coal mines, prospecting multilayer water-filled goaf has become a new content that results from geophysical exploration in coalfields. The central loop transient electromagnetic （TEM） method is favorable for prospecting conductive layers because of the coupling relationship between its field structure and formation. However, the shielding effect of conductive overburden would not only require a longer observation time when prospecting the same depth but also weaken the anomalous response of underlying layers. Through direct time domain numerical simulation and horizontal layered earth forward modeling, this paper estimates the length of observation time required to prospect the target, and the distinguishable criterion of multilayer water-filled goal is presented with observation error according to the effect of noise on observation data. The observed emf curves from Dazigou Coal Mine, Shanxi Province can distinguish multilayer water-filled goaf. In quantitative inversion interpretation of observed curves, using electric logging data as initial parameters restrains the equivalence caused by coal formation thin layers. The deduced three-layer and two-layer water-filled goals are confirmed by the drilling hole. The result suggests that when observation time is long enough and with the anomalous situation of underlying layers being greater than the observation error, the use of the central loop TEM method to orosoect a multilaver water-filled goaf is feasible.
文摘Computer simulation experiment is very important in the phase of project design, the availability of simulated result highly depends on the scheme of error simulation. Time series observations are normally correlated. This paper first discusses the formula of correlated error propagation, then derives the formula of simulating time series correlated errors. This formula is then used to simulate correlated ephemerides errors of CHAMP, then the ephemerides are used to recover the gravity vector at satellite altitude with finite differential formula. The formulae derived in this paper are verified with the difference between the recovered gravity vectors and the `true values’ which are directly computed with the same gravity model as that generating the ephemerides.
基金Supported by the National Natural Science Foundation of China Grants(No.11231010 and 11171330)Key Laboratory of RCSDS,CAS(No.2008DP173182)
文摘Longitudinal data often arise when subjects are followed over a period of time, and in many situations, there may exist informative observation times and a dependent terminal event such as death that stops the follow-up. In this article, we propose joint modeling and analysis of longitudinal data with possibly informative observation times and a dependent terminal event in which a common subject-specific latent variable is used to characterize the correlations. A borrow-strength estimation procedure is developed for parameter estimation, and both large-sample and finite^sample properties of the proposed estimators are established. In addition, some goodness-of-fit methods for assessing the adequacy of the model are provided. An application to a bladder cancer study is illustrated.
基金supported by National Natural Science Foundation of China (Grant Nos. 11231010, 11171330 and 11201315)Key Laboratory of Random Complex Structures and Data Science, Chinese Academy of Sciences (Grant No. 2008DP173182)Beijing Center for Mathematics and Information Interdisciplinary Sciences
文摘Longitudinal data often occur in follow-up studies, and in many situations, there may exist informative observation times and a dependent terminal event such as death that stops the follow-up. We propose a semiparametric mixed effect model with time-varying latent effects in the analysis of longitudinal data with informative observation times and a dependent terminal event. Estimating equation approaches are developed for parameter estimation, and asymptotic properties of the resulting estimators are established. The finite sample behavior of the proposed estimators is evaluated through simulation studies, and an application to a bladder cancer study is provided.
文摘Crystal growth is a complex process,and until now there isn’t a satisfied real t ime observation method.Under the space high temperature in situ observation inst rument(SHITISOI),we develop a three dimensioned real time observation device for the crystal.By it,we can acquire image of crystal in three dimension,moreover,i t would provide technique for remote science control in the future space experimen t.We develop the device not only apply to real time observation also adapt to r e mote science research.We use annular quartz glass so as to in situ observe the c hange of interface.And two heater were put its upon and down,thus they form two different temperature zones.We apply to Bridgeman method crystal growth by using special lift to move the quartz crucible.Presently we have developed a pass mus t er furnace, and can get the NaNO 3 crystal.We could observe the fluid flow stat ue and the interface move by tracer particle.We get the effect of unsteady conve ction,which is important both in land and space crystal growth.
基金the financial support provided by the Key Technology Development of Bearing Steel for Major Equipment of China(No.2012AA03A503)
文摘Titanium nitride precipitation on a primary inclusion particle during solidification of bearing steel has been tracked by varying temperature in a confocal scanning violet laser microscope.Upon precipitation,an obvious growth of titanium nitride on a primary inclusion particle was observed due to the rapid solute diffusion in liquid steel.The onset of titanium nitride precipitation did not change with primary inclusion particle size,but the time of growth was greater for a smaller primary inclusion particle.Meanwhile,the particle size displayed little influence on the total precipitated amount of titanium nitride on it under the same conditions.At the later period of solidification,almost no change occurred in inclusion size,but the inclusion shape varied from circle to almost square in two-dimension,or cubic in three-dimension,to attain the equilibrium with steel.
基金the National Natural Science Foundation of China through Grant 8206100245the Chinese Meteorological Administration through Grant FY-APP-ZX-2022.0222.
文摘We demonstrate here that global-scale determination of a key ionospheric parameter,the peak height of the F_(2)region(h_(m)F_(2)),can be obtained by making a simple ratio measurement of the atomic oxygen 130.4 and 135.6 nm emissions in the far-ultraviolet nightglow with a nadir-viewing system such as a pair of photometers suitable for flight on a CubeSat.We further demonstrate that measurements from an altitude that is within the typical range of nighttime h_(m)F_(2)250−450 km can provide the ratios that are needed for retrieval of the h_(m)F_(2).Our study is conducted mostly through numerical simulations by using radiative transfer models of the two emissions coupled with empirical models of the atmosphere and ionosphere.Modeling results show that the relationship between the h_(m)F_(2)and the intensity ratio is sensitive to the altitude from which the emissions are observed,primarily because of the distinctly different degrees of resonant scattering of the two emissions in the atmosphere.A roughly quadratic relationship can be established for observations from an orbit of~400 km,which enables h_(m)F_(2)retrieval.Parametric analysis indicates that the relationship can be affected by the ambient atmospheric conditions through resonant scattering and O2 absorption.For typical nighttime conditions with h_(m)F_(2)250−450 km,retrieval of the h_(m)F_(2)from synthetic observations shows that the typical errors are only a few kilometers(up to~20 km),depending on the accuracy of the ambient conditions predicted by the empirical models.Our findings pave the way for use of the 130.4/135.6 nm intensity ratios for global-scale monitoring of the nighttime ionosphere at mid to low latitudes.
基金supported by the National Natural Science Foundation of China under Grant No.61203058the Training Program for Outstanding Young Teachers of North China University of Technology under Grant No.XN131+1 种基金the Construction Plan for Innovative Research Team of North China University of Technology under Grant No.XN129the Laboratory construction for Mathematics Network Teaching Platform of North China University of Technology under Grant No.XN041
文摘This paper focuses on boundary stabilization of a one-dimensional wave equation with an unstable boundary condition,in which observations are subject to arbitrary fixed time delay.The observability inequality indicates that the open-loop system is observable,based on which the observer and predictor are designed:The state of system is estimated with available observation and then predicted without observation.After that equivalently the authors transform the original system to the well-posed and exponentially stable system by backstepping method.The equivalent system together with the design of observer and predictor give the estimated output feedback.It is shown that the closed-loop system is exponentially stable.Numerical simulations are presented to illustrate the effect of the stabilizing controller.
文摘Imaginary potentials such as V(x)=−iσ1Ω(x)(withσ>0 a constant,Ωa subset of 3-space,and 1Ωits characteristic function)have been used in quantum mechanics as models of a detector.They represent the effect of a‘soft’detector that takes a while to notice a particle in the detector volumeΩ.In order to model a‘hard’detector(i.e.one that registers a particle as soon as it entersΩ),one may think of taking the limitσ→∞of increasing detector strengthσ.However,as pointed out by Allcock,in this limit the particle never entersΩ;its wave function gets reflected at the boundary∂ΩofΩin the same way as by a Dirichlet boundary condition on∂Ω.This phenomenon,a cousin of the‘quantum Zeno effect,’might suggest that a hard detector is mathematically impossible.Nevertheless,a mathematical description of a hard detector has recently been put forward in the form of the‘absorbing boundary rule’involving an absorbing boundary condition on the detecting surface∂Ω.We show here that in a suitable(non-obvious)limit,the imaginary potential V yields a non-trivial distribution of detection time and place in agreement with the absorbing boundary rule.That is,a hard detector can be obtained as a limit,but it is a different limit than Allcock considered.
文摘Einstein’s Special Relativity (ESR) has enjoyed spectacular success as a mathematical construct and in terms of the experiments to which it has been subjected. Possible vulnerabilities of ESR will be explored that break the symmetry of reciprocal observations of length, time, and mass. It is shown how Newton could also have derived length contraction . Einstein’s General Relativity (EGR) will also be discussed occasionally such as a changed perspective on gravitational waves due to a small change in ESR. Some additional questions addressed are: Did Einstein totally eliminate the Ether? Is the physical interpretation of ESR completely correct? Why should there be a maximum speed limit, and should it always be the same? The mass-energy equation is revisited to show that in 1717 Newton could have derived the modern , and not known that it violates the foundation of his mechanics. Tributes are paid to Einstein and others.
基金supported by the National Key Research and Development Project of China under Grant Nos.2018AAA0100800 and 2018YFE0106800the National Natural Science Foundation of China under Grant Nos.61903353,61725304,and 1761673361+2 种基金Major Science and Technology Project of Anhui Province under Grant No.912198698036SINOPEC Programmes for Science and Technology Development under Grant No.PE19008-8the Fundamental Research Funds for the Central Universities under Grant No.WK2100000013。
文摘A robust nonsingular fixed time terminal sliding mode control scheme with a time delay disturbance observer is proposed for atmospheric pollution detection lidar scanning mechanism(APDL-SM)system.Distinguished from the conventional terminal sliding mode control methods,the authors design a novel fixed-time terminal sliding surface,the convergence time of sliding mode phase of which has a constant upper bound that is designable by adjusting only one parameter.Moreover,in order to overcome the problem of unknown upper bound of lumped uncertainty including model uncertainty,friction effect and external disturbances from the port environment,the authors propose a time delay disturbance observer to provide an estimation for the system lumped uncertainty.By using the Lyapunov synthesis,the explicit analysis of the convergence time upper bound are performed.Finally,simulation studies are conducted on the APDL-SM system to show the fast convergence rate and strong robustness of the proposed control scheme.
基金supported by the National Natural Science Foundation of China(Nos.10831007,60821091,60974035)
文摘In this paper, for any given observation time and suitable moving observation domains, the author establishes a sharp observability inequality for the Kirchhoff-Rayleigh plate like equation with a suitable potential in any space dimension. The approach is based on a delicate energy estimate. Moreover, the observability constant is estimated by means of an explicit function of the norm of the coefficient involved in the equation.
