Semiparametric Analysis of Longitudinal Data with Informative Observation Times

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.

Wavenumber-4 spectral component extracted from TIMED/SABER observations

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.

IMPULSIVE EXPONENTIAL SYNCHRONIZATION OF FRACTIONAL-ORDER COMPLEX DYNAMICAL NETWORKS WITH DERIVATIVE COUPLINGS VIA FEEDBACK CONTROL BASED ON DISCRETE TIME STATE OBSERVATIONS

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.

Time Series Correlated Error's Simulation Scheme with the Application to Simulate the Ephemerides Error of CHAMP

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.

Cooperative output tracking of multi-agent systems under finite time

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.

A new strategy for ionospheric remote sensing using the 130.4/135.6 nm airglow intensity ratios

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.

Feasibility of central loop TEM method for prospecting multilayer water-fi lled goaf

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.

Analyzing Longitudinal Data with Informative Observation and Terminal Event Times

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.

Time-varying latent model for longitudinal data with informative observation and terminal event times

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.

晶体三维实时观察装置的研究

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.

Output Feedback Stabilization of an Unstable Wave Equation with Observations Subject to Time Delay

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.

Robust Nonsingular Fixed Time Terminal Sliding Mode Control for Atmospheric Pollution Detection Lidar Scanning Mechanism

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.

Thoroughly Testing Einstein’s Special Relativity Theory, and More

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.

Observability Inequality for the Kirchhoff-Rayleigh Plate Like Equation in a Short Time

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.

Moving scanning emitter tracking by a single observer using time of interception:Observability analysis and algorithm

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.

Clinical features of gastric adenoma detected within 3 years after negative screening endoscopy in Korea

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.

脉冲星计时阵列观测的随机背景信号对标量诱导引力波的限制

最近,NANOGrav、PPTA、EPTA和CPTA合作组各自独立报告了关于随机引力波背景的观测证据.尽管根据观测推断的引力波背景(幅度、频谱)与超大质量双黑洞并合的预言相一致,但这一观测也为搜寻宇宙早期的新物理现象提供了新的窗口.本文探讨了用早期宇宙中的标量诱导引力波来解释这一信号的可能性.作者采用参数化的拐折幂律谱作为随机引力波背景能谱的普适性描述,利用NANOGrav、PPTA和EPTA的新数据和贝叶斯推断的方法进行研究.本研究结果可以约束诱导引力波能谱的相关参数,并进一步对可能在早期宇宙中产生原初黑洞的各种暴胀模型给出限制,这些模型有望在未来的空间引力波观测实验中得到检验.

纳赫兹引力波对单态暗物质模型中电弱相变的影响

受脉冲星定时阵列合作组最近观测到的纳赫兹级随机引力波证据的启发,本文在标准模型的单态扩展中探讨了利用极端过冷的电弱相变解释这些观测结果的可能性,并考虑了相变对于暗物质的影响.研究结果表明,通过精细调节模型参数,相应的渗透温度可以连续降低到1 GeV甚至更低.在如此低的渗透温度下,单态暗物质可能在电弱相变之前就脱离热平衡,从而从热辐射中冻结出来.因此,相变期间产生的熵可以显著影响暗物质的残留密度.这减轻了单态扩展模型中同时解释重子生成和满足暗物质直接探测限制的压力,暗示着所考虑的新物理模型可能存在更广阔的参数空间,并可在未来的实验中得到验证.

Absorbing boundary condition as limiting case of imaginary potentials

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.

Precipitation behavior of titanium nitride on a primary inclusion particle during solidification of bearing steel

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.