Optimal Control of Nonlinear Fractional-Order Systems with Multiple Time-Varying Delays

Journal of Optimization Theory and Applications - This paper considers an optimal control problem governed by nonlinear fractional-order systems with multiple time-varying delays and subject to...     

Bouncing universe models in an extended gravity theory

Some bouncing models are investigated in the framework of an extended theory of gravity. The extended gravity model is a simple extension of the General Relativity where an additional matter geometry coupling is introduced to account for the late time cosmic speed up phenomena. The dynamics of the models are discussed in the background of a flat FRW universe. Some viable models are reconstructed for specifically assumed bouncing scale factors. The behavior of the models are found to be decided mostly by the parameters of the respective models. The extended gravity based minimal matter-geometry coupling parameter has a role to remove the omega singularity occurring at the bouncing epoch. It is noted that the constructed models violate the energy conditions, however, in some cases this violation leads to the evolution of the models in phantom phase. The stability of the models are analyzed under linear homogeneous perturbations and it is found that, near the bounce, the models show instability but the perturbations decay out smoothly to provide stable models at late times.     

Mg,N掺杂β-Ga2O3光电性质的第一性原理计算

通过基于密度泛函理论的第一性原理计算,研究了Mg单掺杂、N单掺杂和不同浓度的Mg-N共掺杂β-Ga₂O₃的结构性质、电子性质和光学性质,以期获得性能比较优异的p型β-Ga₂O₃材料。建立了五种模型:Mg单掺杂、N单掺杂、1个Mg-N共掺杂、2个Mg-N共掺杂和3个Mg-N共掺杂β-Ga₂O₃。经过计算,3个Mg-N共掺杂β-Ga₂O₃体系的结构最稳定。此外,在5种模型中,3个Mg-N共掺杂β-Ga₂O₃体系的禁带宽度是最小的,并且N 2p和Mg 3s贡献的占据态抑制了氧空位的形成,从而增加了空穴浓度。因此,3个Mg-N共掺杂β-Ga₂O₃体系表现出优异的p型性质。3个Mg-N共掺杂体系的吸收峰出现明显红移,在太阳盲区的光吸收系数较大,这归因于导带Ga 4s、Ga 4p、Mg 3s向价带O 2p、N 2p的带间电子跃迁。本工作将为p型β-Ga₂O₃日盲光电材料的研究和应用提供理论指导。     

关于负超几何分布期望与方差算法的注记

研究了非还原取样模型中负超几何随机变量的联合分布,得到了若干有用的推论.据此给出了负超几何分布的期望和方差的一种分解算法.     

Mechanism of Insertion Reactions between Silylenoid H2SiLiF and GeH3R (R =F,OH, NH2): a Theoretical Study

Theoretical investigations on the insertion reaction mechanisms of three- membered-ring silylenoid H2 Si Li F with GeH 3R(R = F, OH, NH2) have been systematically carried out by combined density functional theory(DFT) and ab initio quantum chemical calculations. The geometries of all stationary points for these reactions were optimized using the B3 LYP method and then the QCISD method was used to calculate the single-point energies. The calculated results indicate that, there are one precursor complex(Q), one transition state(TS), and one intermediate(IM) which connect the reactants and the products along the potential energy surface. The insertion reactions of three-membered-ring silylenoid with Ge H3 R proceed in a concerted manner, forming H2RSi-Ge H3 and Li F. The calculated potential energy barriers of the three reactions are 29.17, 30.90, and 54.07 k J/mol, and the reaction energies for the three reactions are –127.05, –116.91, and –103.31 k J/mol, respectively. The insertion reactions in solvents are similar to those in vacuum. Under the same situation, the insertion reactions should occur easily in the following order: GeH 3-F GeH 3-OH GeH 3-NH2. The elucidations of the mechanism of these insertion reactions provided a new mode of silicon-germanium bond formation.     

Visible light-driven acridone catalysis for atom transfer radical polymerization

Acridone as a new kind of visible light photocatalyst has been developed to catalyze metal free atom transfer radical polymerization (ATRP). The photocatalyst possess low excited state potential as can undergo an oxidative quenching pathway to initiate ATRP of vinyl monomers. Kinetic study and light on/off reaction demonstrate the “living”/controlled nature of the polymerization by light. Block copolymers can be achieved by using PMMA as macroinitiator to reinitiate polymerization of other vinyl monomers, which shows highly preserved Br chain-end functionality in the synthesized polymers. Moreover, the polymerization can be conducted under air atmosphere as most photocatalysts need anaerobic condition, which may give inspiration of further application of this kind of photocatalyst.     

Single-shot morpho-functional and structural characterization of the left-ventricle in a mouse model of acute ischemia-reperfusion injury with an optimized 3D IntraGate cine FLASH sequence at 7T MR

Preclinical cardiac MR is challenging and time-consuming. A fast and comprehensive acquisition protocol and standardized image post-processing may improve preclinical research, reducing acquisition time, costs and variability of results. In the present study, we evaluated the feasibility of a contrast-enhanced 3D IntraGate steady-state cine sequence (ce-3D-IG-cine) with short acquisition time (11 min) for a single-shot combined characterization of left ventricle (LV) remodeling and infarct size (IS) in a mouse model of acute ischemia-reperfusion injury.Sixteen male C57BL/6N mice underwent 7T cardiac MR (Bruker, BioSpec 70/30) including optimized ce-3D-IG-cine (total scan time 11 min) at day 1, 5 and 28 after surgery. LV end-diastolic volume (EDV_MR) and ejection fraction (EF_MR) extracted from MR were compared to ones from short-axis (SA-EDV_echo, SA-EF_echo) and parasternal long-axis (LA-EDV_echo, LA-EF_echo) echocardiography. IS was manually and semiautomatically segmented from ce-3D-IG-cine using different standard deviation (SD +2, +3, +4, +5, +6 in respect to a reference tissue).Mice were sacrificed at day 28, immediately after imaging. IS at day 28 was compared to injury burden at histology.MR and echocardiographic morpho-functional parameters were compared, as IS from MR and histology. Bland-Altman plots were used to assess the agreement in ischemic burden segmentation.Volumetric and functional parameters measured on ce-3D-IG-cine correlated to the correspondent echocardiographic parameter (EDV_MR vs SA-EDV_echo: ρ = 0.813; EDV_MR vs LA-EDV_echo: ρ = 0.845; EF_MR vs SA-EF_echo ρ = 0.612; EF_MR vs LA-EF_echo ρ = 0.791; p < 0.001 in all cases).Manually segmented IS strongly correlated with the scar at histology (ρ = 0.904, p < 0.001). A threshold of +3SD showed the highest performance for semiautomatic assessment of IS compared to manual segmentation (ρ = 0.965, p < 0.001), with an overall reproducibility of 73%, and a peak reproducibility of 80% at day 1.The ce-3D-IG-cine sequence, manually or semiautomatically segmented using 3SD threshold, allows fast and comprehensive LV morpho-functional and structural characterization in myocardial ischemia-reperfusion injury model.