163 research outputs found
Krein Space-Based H
This paper investigates the finite-time H∞ fault estimation problem for linear time-delay systems, where the delay appears in both state and measurement equations. Firstly, the design of finite horizon H∞ fault estimation is converted into a minimum problem of certain quadratic form. Then we introduce a stochastic system in Krein space, and a sufficient and necessary condition for the minimum is derived by applying innovation analysis approach and projection theory. Finally, a solution to the H∞ fault estimation is obtained by recursively computing a partial difference Riccati equation, which has the same dimension as the original system. Compared with the conventional augmented approach, the solving of a high dimension Riccati equation is avoided
The Effect of 4D Effective Cosmological Constant On The Stability of Randall-Sundrum Scenario
We study the Randall-Sundrum model with a small 4D effective cosmological
constant on the brane, and drive a corrected radion potential following the
Goldberger-Wise mechanism. We then discuss the effect of the 4D effective
cosmological constant on the stability of the brane-system, and find that to
quintessence determined by updated observation, the proper distance between the
two branes required to solve the hierarchy problem can exist. However, during
inflation, whether we can get an reasonable hierarchy scale is still uncertain.Comment: 6 pages, 2 figures, to be published in Mod. Phys. Lett.
Chemotherapy and prognosis in advanced thymic carcinoma patients
OBJECTIVE: The role of chemotherapy in treating advanced thymic carcinoma is unclear. The purpose of the current study was to investigate the efficacy of chemotherapy and the prognostic factors for patients with advanced thymic carcinoma. METHODS: A retrospective review of the medical records of 86 patients treated with chemotherapy for advanced thymic carcinoma was conducted between 2000 and 2012 at our institution. The clinical characteristics, chemotherapy regimens and prognostic factors were analyzed. Survival curves were plotted using the Kaplan-Meier method and the Cox proportional hazard model was used for multivariate analysis. RESULTS: Of the 86 patients, 56 were male and 30 were female. The median survival time was 24.5 months. For the first-line chemotherapy treatment, the objective response rate was 47.7% and the disease control rate was 80.2%. The median progression-free survival for all patients was 6.5 months for first-line chemotherapy. No significant differences in progression-free survival were observed among the different chemotherapy regimens. Multivariate analyses revealed that the prognostic factors for overall survival included performance status (p=0.043), histology grade (p=0.048), and liver metastasis (p=0.047). CONCLUSION: Our results suggest that there is no difference in efficacy between multiagent and doublet regimens. The prognosis of patients with advanced thymic carcinoma can be predicted based on histological grade, liver metastasis and performance status
Two-Field Quintom Models in the w-w' Plane
The w-w' plane, defined by the equation of state parameter for the dark
energy and its derivative with respect to the logarithm of the scale factor, is
useful to the study of classifying the dynamical dark energy models. In this
note, we examine the evolving behavior of the two-field quintom models with w
crossing the w=-1 barrier in the w-w' plane. We find that these models can be
divided into two categories, type A quintom in which w changes from >-1 to <-1
and type B quintom in which w changes from -1 as the universe expands.Comment: 5 pages, 2 figures, RevTeX, Accepted for publication as a Brief
Report in Physical Review
Global Practical Tracking by Output Feedback for Nonlinear Systems with Unknown Growth Rate and Time Delay
This paper is the further investigation of work of Yan and Liu, 2011, and considers the global practical tracking problem by output feedback for a class of uncertain nonlinear systems with not only unmeasured states dependent growth but also time-varying time delay. Compared with the closely related works, the remarkableness of the paper is that the time-varying time delay and unmeasurable states are permitted in the system nonlinear growth. Motivated by the related tracking results and flexibly using the ideas and techniques of universal control and dead zone, an adaptive output-feedback tracking controller is explicitly designed with the help of a new Lyapunov-Krasovskii functional, to make the tracking error prescribed arbitrarily small after a finite time while keeping all the closed-loop signals bounded. A numerical example demonstrates the effectiveness of the results
Two-field Models of Dark Energy with Equation of State Across -1
In this paper, we study the possibility of building two-field models of dark
energy with equation of state across -1. Specifically we will consider two
classes of models: one consists of two scalar fields (Quintessence+Phantom) and
another includes one scalar (Phantom) and one spinor field (Neutrino). Our
studies indicate to some extent that two-field models give rise to a simple
realization of the dynamical dark energy model with the equation of state
across .Comment: 5 pages, 4 figures Revtex
Brane Inflation from Rotation of D4 Brane
In this paper, a inflationary model from the rotation of D4-brane is
constructed. We show that for a very wide rage of parameter, this model
satisfies the observation and find that regarded as inflaton, the rotation of
branes may be more nature than the distance between branes. Our model offers a
new avenue for brane inflation.Comment: 6 pages, no figure
On Stability Of The Crystal Universe Models
We generalize the Goldberger-Wise mechanism and study the stability of the
Crystal Universe models. We show that the model can be stabilized, however for
configurations of Crystal Universe in the absence of fine-tuning, brane
crystals are not equidistant, i.e. a pair is far away from adjacent
pair, except for the fixed points of the orbifold, which differs from
the assumptions taken in the literature.Comment: 10 pages, 4 figure
Fully-Passive versus Semi-Passive IRS-Enabled Sensing: SNR and CRB Comparison
This paper investigates the sensing performance of two intelligent reflecting
surface (IRS)-enabled non-line-of-sight (NLoS) sensing systems with
fully-passive and semi-passive IRSs, respectively. In particular, we consider a
fundamental setup with one base station (BS), one uniform linear array (ULA)
IRS, and one point target in the NLoS region of the BS. Accordingly, we analyze
the sensing signal-to-noise ratio (SNR) performance for a target detection
scenario and the estimation Cram\'er-Rao bound (CRB) performance for a target's
direction-of-arrival (DoA) estimation scenario, in cases where the transmit
beamforming at the BS and the reflective beamforming at the IRS are jointly
optimized. First, for the target detection scenario, we characterize the
maximum sensing SNR when the BS-IRS channels are line-of-sight (LoS) and
Rayleigh fading, respectively. It is revealed that when the number of
reflecting elements equipped at the IRS becomes sufficiently large, the
maximum sensing SNR increases proportionally to for the semi-passive-IRS
sensing system, but proportionally to for the fully-passive-IRS
counterpart. Then, for the target's DoA estimation scenario, we analyze the
minimum CRB performance when the BS-IRS channel follows Rayleigh fading.
Specifically, when grows, the minimum CRB decreases inversely
proportionally to and for the semi-passive and fully-passive-IRS
sensing systems, respectively. Finally, numerical results are presented to
corroborate our analysis across various transmit and reflective beamforming
design schemes under general channel setups. It is shown that the
fully-passive-IRS sensing system outperforms the semi-passive counterpart when
exceeds a certain threshold. This advantage is attributed to the additional
reflective beamforming gain in the IRS-BS path, which efficiently compensates
for the path loss for a large .Comment: 13 pages,7 figure
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