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
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
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
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
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
In this paper, a continuous sliding mode controller with disturbance observer is proposed for the tracking control of hypersonic vehicles to suppress the chattering. The finite time disturbance observer is involved to...In this paper, a continuous sliding mode controller with disturbance observer is proposed for the tracking control of hypersonic vehicles to suppress the chattering. The finite time disturbance observer is involved to make that the continuous sliding mode controller has the property of disturbance rejection.Due to continuous terms replacing the discontinuous term of traditional sliding mode control, switching modes of velocity and altitude firstly arrive at small regions with respect to disturbance observation errors. Switching modes keep zero and velocity and altitude asymptotically converge to their reference commands after disturbance observation errors disappear. Simulation results have proved the proposed method can guarantee the tracking of velocity and altitude with continuous sliding mode control laws,and also has the fast convergence rate and robustness.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
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
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
Background:Early detection and management of gastric adenoma are important for preventing gastric cancer.The present study aimed to evaluate the predictors of missed gastric adenoma on screening endoscopy in Korea and...Background:Early detection and management of gastric adenoma are important for preventing gastric cancer.The present study aimed to evaluate the predictors of missed gastric adenoma on screening endoscopy in Korea and identify the risk factors associated with interval precancerous gastric lesions.Methods:All cases of gastric adenomas diagnosed via screening endoscopy between 2007 and 2019 were reviewed.Among them,those who had undergone endoscopy within 3 years were included in the present study.Missed gastric adenoma was defined as gastric adenoma diagnosed within 3 years after negative screening endoscopy.Results:In total,295 cases of gastric adenoma were identified.Of these,95(32.2%)were missed gastric adenoma cases(mean age,60.6 years;average interval between final and index endoscopies,12.6months);the remaining 200(67.8%)were newly detected adenoma cases.Univariate analysis revealed thatmale sex,endoscopist experience,observation time,and presence of gastric intestinalmetaplasia(pathologically proven)were associated with missed gastric adenoma.Multivariate analysis revealed that gastric intestinal metaplasia(odds ratio[OR],2.736;95%confidence interval[CI],1.320–5.667;P=0.007)and shorter observation time of the index screening endoscopy(B,0.011;OR,0.990;95%CI,0.986–0.993;P<0.001)were independent risk factors for missed gastric adenoma.The optimal cut-off for the observation time for detecting gastric adenoma was 3.53minutes(area under curve,0.738;95%CI,0.677–0.799;P<0.001).Conclusions:Gastric intestinal metaplasia is an indication of missed gastric adenoma.Therefore,careful inspection of gastric mucosa with gastric intestinal metaplasia and proper observation time can lower the possibility of missing the gastric adenoma during screening.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
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
The Tangjiashan landslide dam failed on June 10, 2008, which was the largest one formed during the Wenchuan earthquake in China. No human lives were lost in this dam failure. This paper presents a description of the d...The Tangjiashan landslide dam failed on June 10, 2008, which was the largest one formed during the Wenchuan earthquake in China. No human lives were lost in this dam failure. This paper presents a description of the dam, including the dam geometry, the hydrograph and the reservoir capacity, the diversion channel and the drainage from the lake. Several empirical models are applied to predict the breach parameters, the peak outflows and the reservoir volumes during this breach event. The main objective of the study is to compare various prediction models and to make recommendation of the best model for the prediction of the breach width, the failure time, and the peak outflow. The breach widths predicted by the Froehlich methods with considerations of the reservoir storages and the effect of failure mode are considered to be more reasonable. All prediction methods discussed in this paper are found to underestimate the breach formation time due to the complex material and the large thickness of the dam. The results from the soil conservation services(SCS) method compare well with the observed peak outflow. The Marone method in combination with the coefficient expressions proposed by Macchione gives excellent results in the simulation of the reservoir volume-level curve.展开更多
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.
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 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.
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supported by National Natural Science Foundation of China(61125306,61273092,61301035,61304018,and 61411130160)National HighTechnology Research and Development Program of China(2014AA051901)+4 种基金Tianjin Science and Technology Supporting Program(14JCQNJC05400)Research Innovation Program of Tianjin University(2013XQ0101)Hubei Science and Technology Supporting Program(XYJ2014000314)Science Foundation of China Supported by Science and Technology on Aircraft Control Laboratory(20125848004)China Post-doctoral Science Foundation(2014M561559)
文摘In this paper, a continuous sliding mode controller with disturbance observer is proposed for the tracking control of hypersonic vehicles to suppress the chattering. The finite time disturbance observer is involved to make that the continuous sliding mode controller has the property of disturbance rejection.Due to continuous terms replacing the discontinuous term of traditional sliding mode control, switching modes of velocity and altitude firstly arrive at small regions with respect to disturbance observation errors. Switching modes keep zero and velocity and altitude asymptotically converge to their reference commands after disturbance observation errors disappear. Simulation results have proved the proposed method can guarantee the tracking of velocity and altitude with continuous sliding mode control laws,and also has the fast convergence rate and robustness.
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.
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.
文摘Background:Early detection and management of gastric adenoma are important for preventing gastric cancer.The present study aimed to evaluate the predictors of missed gastric adenoma on screening endoscopy in Korea and identify the risk factors associated with interval precancerous gastric lesions.Methods:All cases of gastric adenomas diagnosed via screening endoscopy between 2007 and 2019 were reviewed.Among them,those who had undergone endoscopy within 3 years were included in the present study.Missed gastric adenoma was defined as gastric adenoma diagnosed within 3 years after negative screening endoscopy.Results:In total,295 cases of gastric adenoma were identified.Of these,95(32.2%)were missed gastric adenoma cases(mean age,60.6 years;average interval between final and index endoscopies,12.6months);the remaining 200(67.8%)were newly detected adenoma cases.Univariate analysis revealed thatmale sex,endoscopist experience,observation time,and presence of gastric intestinalmetaplasia(pathologically proven)were associated with missed gastric adenoma.Multivariate analysis revealed that gastric intestinal metaplasia(odds ratio[OR],2.736;95%confidence interval[CI],1.320–5.667;P=0.007)and shorter observation time of the index screening endoscopy(B,0.011;OR,0.990;95%CI,0.986–0.993;P<0.001)were independent risk factors for missed gastric adenoma.The optimal cut-off for the observation time for detecting gastric adenoma was 3.53minutes(area under curve,0.738;95%CI,0.677–0.799;P<0.001).Conclusions:Gastric intestinal metaplasia is an indication of missed gastric adenoma.Therefore,careful inspection of gastric mucosa with gastric intestinal metaplasia and proper observation time can lower the possibility of missing the gastric adenoma during screening.
基金supported in part by the National Key R&D Program of China(2021YFC2203100)CAS Young Interdisciplinary Innovation Team(JCTD-2022–20)+8 种基金the National Natural Science Foundation of China(11875113,11961131007,12261131497,12003029,11833005,and 12192224)the 111 Project for“Observational and Theoretical Research on Dark Matter and Dark Energy”(B23042)Fundamental Research Funds for Central Universitiesthe Disposizione del Presidente INFN n.24433 in INFN Sezione di MilanoChina Postdoctoral Science Foundation(2023TQ0355)CSC Innovation Talent FundsUSTC Fellowship for International CooperationUSTC Research Funds of the Double First-Class InitiativeCAS project for young scientists in basic research(YSBR-006)。
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.
基金supported by the National Natural Science Foundation of China(12105248,11821505,12075300,and 12335005)the Peng-Huan-Wu Theoretical Physics Innovation Center(12047503)+1 种基金the Key R&D Program of the Ministry of Science and Technology(2017YFA0402204)the Key Research Program of the Chinese Academy of Sciences(XDPB15)。
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Project supported by the National Natural Science Foundation of China(Grant Nos.51209155,51109149)the Research Fund for the Doctoral Program of Higher Education of China(Grant No.20110181120093)
文摘The Tangjiashan landslide dam failed on June 10, 2008, which was the largest one formed during the Wenchuan earthquake in China. No human lives were lost in this dam failure. This paper presents a description of the dam, including the dam geometry, the hydrograph and the reservoir capacity, the diversion channel and the drainage from the lake. Several empirical models are applied to predict the breach parameters, the peak outflows and the reservoir volumes during this breach event. The main objective of the study is to compare various prediction models and to make recommendation of the best model for the prediction of the breach width, the failure time, and the peak outflow. The breach widths predicted by the Froehlich methods with considerations of the reservoir storages and the effect of failure mode are considered to be more reasonable. All prediction methods discussed in this paper are found to underestimate the breach formation time due to the complex material and the large thickness of the dam. The results from the soil conservation services(SCS) method compare well with the observed peak outflow. The Marone method in combination with the coefficient expressions proposed by Macchione gives excellent results in the simulation of the reservoir volume-level curve.