In this paper, we obtain the lower and the upper bounds of the blowup time of the solutions to quasi-linear parabolic problems subject to Dirichlet(or Neumann) boundary condition. Our results are suitable for the problems with any smooth bounded domain ${\Omega \subset \mathbb{R}^n}$ and ${n \geq 3}$. In some special cases, we can even get the exact values of blowup time. 相似文献
The paper studies a generalized linear model(GLM)y_t = h(x_t~T β) + ε_t,t = l,2,...,n,where ε_1 = η_1,ε_1 =ρε_t +η_t,t = 2,3,...;n,h is a continuous differentiable function,η_t's are independent and identically distributed random errors with zero mean and finite variance σ~2.Firstly,the quasi-maximum likelihood(QML) estimators of β,p and σ~2 are given.Secondly,under mild conditions,the asymptotic properties(including the existence,weak consistency and asymptotic distribution) of the QML estimators are investigated.Lastly,the validity of method is illuminated by a simulation example. 相似文献
This paper is concerned with the constrained consensuses problem for a group of agents in disconnected topologies. By dividing the communication topology into a combination of directed trees, some necessary and sufficient conditions are derived for all the agents to asymptotically reach a single consensus and multiple consensuses, respectively. The obtained results indicate that arbitrary anticipant consensuses can be achieved, if additional constrained controllers are added to those agents with specific indexes. Some illustrative examples are provided to demonstrate the effectiveness of the proposed theoretical results. 相似文献
This paper is concerned with the better security of quantum image secret sharing (QISS) algorithm. The improved QISS (IQISS) scheme is implemented on both quantum gray image (FRQI) and quantum color image (MCQI). The new IQISS scheme comprises efficient sharing process and recovering process. The core idea of the sharing process is to combine encryption and measurement for two types of quantum secret images to acquire the quantum shadow images. In the recovering process, strip operation is firstly utilized on the shadow images. Afterwards, the decryption algorithm is used to recover the original quantum secret image. Experiments demonstrate that significant improvements in the security are in favor of the proposed approach.
At the generalized gradient approximation (GGA), the elastic constants of the orthorhombic phase of NH3BH3 were calculated with plane-wave pseudo-potential method. Our calculation showed that the orthorhombic phase NH3BH3 is a loose and brittle material, as well as hard to be deformed, also we calculated the elastic anisotropies and the Debye temperatures from the elastic constants. And from the band structure and density of state (DOS), we concluded that NH3BH3 is a wide-gap semiconductor and the band gap is almost 6.0 eV. The bonds between N atoms and H atoms show a strong covalent characteristic, B atoms and H atoms form ironic bonds, and so as to the B-N bonds. Electrons from the B atoms are absorbed by the H atoms around the B atoms, and the H atoms display electronegativity. 相似文献
In this study, selected Chinese, Japanese and US mathematics textbooks were examined in terms of their ways of conceptualizing and organizing content for the teaching and learning of fraction division. Three Chinese mathematics textbook series, three Japanese textbook series, and four US textbook series were selected and examined to locate the content instruction of fraction division. Textbook organization of fraction division and other content topics were described. Further analyses were then conducted to specify how the content topic of fraction division was conceptualized and introduced. Specific attention was also given to the textbooks’ uses of content constructs including examples, representations, and exercise problems in order to show their approaches for the teaching and learning of fraction division. The results provide a glimpse of the metaphors of mathematics teaching and learning that have been employed in Chinese, Japanese, and US textbooks. In particular, the results from the textbook analyses demonstrate how conceptual underpinnings were developed while targeting procedures and operations. Implications of the study are then discussed. 相似文献