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Locally Varying Hubble Parameter in Terms of Reduced Friedmann Equation 被引量:1
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作者 Ayman Kassem 《International Journal of Astronomy and Astrophysics》 2021年第2期175-189,共15页
Assessment of the Hubble parameter as an indicator of the expansion rate of the universe holds a central position in the field of astronomy. From its initial estimate of about 500 km<span style="white-space:no... Assessment of the Hubble parameter as an indicator of the expansion rate of the universe holds a central position in the field of astronomy. From its initial estimate of about 500 km<span style="white-space:nowrap;">&sdot;</span>sec<sup>-1</sup><span style="white-space:nowrap;">&sdot;</span>parsc<sup>-1</sup>, this value had been steadily amended as the observational tools became more accurate and precise. Despite this, a gap remains between the value of observations relating to local and nonlocal estimations of the Hubble parameter that gave rise to what became known as the Hubble tension. This tension is addressed here while dealing with space fabric as a cosmological fluid that undergoes transition. 展开更多
关键词 Cosmic Fluid Transition locally Varying Hubble Parameter Energy Degrees of Freedom
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Comment on the paper “Hydromagnetic thin film flow of Casson fluid in non-Darcy porous medium with Joule dissipation and Navier's partial slip”
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作者 I.POP 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2018年第7期1057-1058,共2页
The present comment concerns some doubtful results included in the abovepaper.
关键词 local inertia parameter magnetic parameter Eckert number
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Stochastic maximum principle for systems driven by local martingales with spatial parameters
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作者 Jian Song Meng Wang 《Probability, Uncertainty and Quantitative Risk》 2021年第3期213-236,共24页
We consider the stochastic optimal control problem for the dynamical system of the stochastic differential equation driven by a local martingale with a spatial parameter.Assuming the convexity of the control domain,we... We consider the stochastic optimal control problem for the dynamical system of the stochastic differential equation driven by a local martingale with a spatial parameter.Assuming the convexity of the control domain,we obtain the stochastic maximum principle as the necessary condition for an optimal control,and we also prove its sufficiency under proper conditions.The stochastic linear quadratic problem in this setting is also discussed. 展开更多
关键词 Stochastic optimal control Stochastic maximum principle local martingale with a spatial parameter
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Adaptive bolus chasing computed tomography angiography by a local linear time and space parameter varying model:modeling,control,identification,and experimental results
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作者 Zhijun CAI Ge WANG Er-Wei BAI 《Frontiers of Electrical and Electronic Engineering in China》 CSCD 2010年第2期119-127,共9页
A high contrast to noise ratio(CNR)is always desirable for contrast-enhanced computed tomography angiography(CTA).To ensure a high CNR of the vascular images in CTA and potentially reduce the radiation exposure and co... A high contrast to noise ratio(CNR)is always desirable for contrast-enhanced computed tomography angiography(CTA).To ensure a high CNR of the vascular images in CTA and potentially reduce the radiation exposure and contrast usage,an adaptive bolus chasing method is proposed and evaluated compared to the existing constant-speed method.The proposed method is based on a local time and space parameter varying model of the contrast bolus.Optimal scan time for the next segment of the vasculature is estimated and predicted in real time and guides the computed tomography(CT)scanner table movement that guarantees that each segment of the vasculature is scanned with the maximum possible enhancement.Simulations and experimental results show that the proposed bolus chasing method outperforms the conventional constant-speed method substantially. 展开更多
关键词 adaptive control bolus chasing computed tomography angiography(CTA) local linear time and space parameter varying model
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Parameters identification of chaotic systems based on artificial bee colony algorithm combined with cuckoo search strategy 被引量:10
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作者 DING ZhengHao LU ZhongRong LIU JiKe 《Science China(Technological Sciences)》 SCIE EI CAS CSCD 2018年第3期417-426,共10页
Artificial bee colony(ABC) algorithm is motivated by the intelligent behavior of honey bees when seeking a high quality food source. It has a relatively simple structure but good global optimization ability. In order ... Artificial bee colony(ABC) algorithm is motivated by the intelligent behavior of honey bees when seeking a high quality food source. It has a relatively simple structure but good global optimization ability. In order to balance its global search and local search abilities further, some improvements for the standard ABC algorithm are made in this study. Firstly, the local search mechanism of cuckoo search optimization(CS) is introduced into the onlooker bee phase to enhance its dedicated search; secondly, the scout bee phase is also modified by the chaotic search mechanism. The improved ABC algorithm is used to identify the parameters of chaotic systems, the identified results from the present algorithm are compared with those from other algorithms. Numerical simulations, including Lorenz system and a hyper chaotic system, illustrate the present algorithm is a powerful tool for parameter estimation with high accuracy and low deviations. It is not sensitive to artificial measurement noise even using limited input data. 展开更多
关键词 chaotic systems parameter estimation swarm intelligence ABC CS local search
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