摘要：
The enhancement of surface functional groups of biochar is essential to improving the biochar contaminant adsorption. Current pyrolysis methods that are accompanied by activation are energy consuming and costly. Herein, a novel wet-pyrolysis system that was carried out in open air, with simultaneous conversion and modification to produce an effective biochar adsorbent, is described. Within this system, the surface of the biochar was oxidized partially to produce sufficient functional groups at the surface, whereas carbonization of thebiomass (miscanthus sacchariflora) occurs under an acidic catalyst. The characteristic results confirmed the attachment of abundant surface functional groups, including hydroxyl and carboxyl groups, which increased in content with the ongoing reaction time. Neutralization with sodium carbonate removed the hydrogen bonds and enhanced the adsorption properties. The biochar that was obtained by using this technique exhibited an excellent cadmium adsorption capacity of 197 mg.g(-1) and a high removal efficiency of 99%. Analysis of the Cd-loaded biochar indicated that adsorption occurred via ion exchange, and formed cadmium complexes. It could be concluded that this novel wet-pyrolysis system is a promising approach to produce biochar efficiently and cost-effectively for heavy-metal remediation. (C) 2019 Elsevier Ltd. All rights reserved.
摘要：
<p style='text-indent:20px;'>In this paper, we investigate the dynamics of the following family of rational maps</p><p style='text-indent:20px;'><disp-formula> <label/> <tex-math id="FE1"> \begin{document}$ \begin{equation*} f_{\lambda}(z) = \frac{z^{2n} - \lambda^{3n+1}}{z^n(z^{2n} - \lambda^{n - 1})} \end{equation*} $\end{document} </tex-math> </disp-formula></p><p style='text-indent:20px;'>with one parameter <inline-formula><tex-math id="M1">\begin{document}$ \lambda \in \mathbb{C}^* - \{\lambda: \lambda^{2n + 2} = 1\} $\end{document}</tex-math></inline-formula>, where <inline-formula><tex-math id="M2">\begin{document}$ n\geq 2 $\end{document}</tex-math></inline-formula>. This family of rational maps is viewed as a singular perturbation of the bi-critical map <inline-formula><tex-math id="M3">\begin{document}$ P_{-n}(z) = z^{-n} $\end{document}</tex-math></inline-formula> if <inline-formula><tex-math id="M4">\begin{document}$ \lambda \neq 0 $\end{document}</tex-math></inline-formula> is small. It is proved that the Julia set <inline-formula><tex-math id="M5">\begin{document}$ J(f_\lambda) $\end{document}</tex-math></inline-formula> is either a quasicircle, a Cantor set of circles, a Sierpiński carpet or a degenerate Sierpiński carpet provided the free critical orbits of <inline-formula><tex-math id="M6">\begin{document}$ f_\lambda $\end{document}</tex-math></inline-formula> are attracted by the super-attracting cycle <inline-formula><tex-math id="M7">\begin{document}$ 0\leftrightarrow\infty $\end{document}</tex-math></inline-formula>. Furthermore, we prove that there exists suitable <inline-formula><tex-math id="M8">\begin{document}$ \lambda $\end{document}</tex-math></inline-formula> such that <inline-formula><tex-math id="M9">\begin{document}$ J(f_\lambda) $\end{document}</tex-math></inline-formula> is a Cantor set of circles but the dynamics of <inline-formula><tex-math id="M10">\begin{document}$ f_{\lambda} $\end{document}</tex-math></inline-formula> on <inline-formula><tex-math id="M11">\begin{document}$ J(f_{\lambda}) $\end{document}</tex-math></inline-formula> is not topologically conjugate to that of any known rational maps with only one or two free critical orbits (including McMullen maps and the generalized McMullen maps). The connectivity of <inline-formula><tex-math id="M12">\begin{document}$ J(f_{\lambda}) $\end{document}</tex-math></inline-formula> is also proved if the free critical orbits are not attracted by the cycle <inline-formula><tex-math id="M13">\begin{document}$ 0\leftrightarrow\infty $\end{document}</tex-math></inline-formula>. Finally we give an estimate of the Hausdorff dimension of the Julia set of <inline-formula><tex-math id="M14">\begin{document}$ f_\lambda $\end{document}</tex-math></inline-formula> in some special cases.</p>
关键词：
*Composite farming paddy ecosystem;*Equilibrium;*Hopf bifurcation;*Maximum yield of rice;*Stability
摘要：
As one of the Globally Important Agricultural Heritage Systems (GIAHS), rice field composite farming is an ecological measure in rice production, which can reduce the amount of chemical fertilizers, pesticides and herbicides. This research studies the interaction among rice, weed, inorganic fertilizer and herbivore in a composite farming paddy ecosystem. We develop a differential equation model to analyze the relations and interactions among those components. Results show the existence of an equilibrium for paddy and weed extinction, one or two equilibria for rice extinction, an equilibrium for weed extinction, and an equilibrium for rice and weed coexistence. Based on the obtained stability conditions of these equilibria, measures are proposed to avoid the existence or the stability of equilibria for rice extinction. Other measures are proposed to lead to a stable equilibrium for weed extinction, which is the most desirable result in rice production. Conditions for maximizing the yield of rice are also obtained by taking the relative mortality of rice as variable. In addition, we discover the existence of Hopf bifurcation phenomenon in the system, and develop the critical value of Hopf bifurcation by taking the artificial fertilizer rate as the bifurcation parameter. Our findings provide effective guidance and insights for rice production in a composite farming paddy ecosystem.
关键词：
Almost periodic solution;Exponential dichotomy;Multidirectional associative memory neural networks;Multistability
摘要：
In this paper, the multiplicity of almost periodic solutions is studied for a multidirectional associative memory (MAM) neural network with almost periodic coefficients and continuously distributed delays. Under some assumptions on activation functions, some invariant subsets of the MAM neural network are constructed. The existence of multiple almost periodic solutions are obtained by using the theory of exponential dichotomy and Schauder's fixed point theorem. Furthermore, a sufficient condition is derived for the local exponential stability of some almost periodic solutions and their exponential attracting domains are also given. An example is given to illustrate the effectiveness of the results. (C) 2015 Elsevier B.V. All rights reserved.
摘要：
A multidirectional associative memory (MAM) neural network with periodic coefficients and distributed delays is studied. By constructing a Poincaré mapping, some sufficient conditions are obtained ensuring existence, uniqueness and the global exponential stability of a periodic solution of MAM neural network. The result is new to MAM neural networks. An example is given to illustrate the effectiveness of the result.
关键词：
Semiconductor nanowire;Electrical failure;Schottky barrier;Bias polarity;In situ TEM
摘要：
The effect of bias polarity on the electrical breakdown behavior of the single ZnSe nanowire (NW) in the metal-semiconductor-metal (M-S-M) nanostructure under high current density and high bias conditions has been studied in the present paper. The experimental results show that the failure of the ZnSe NW in M-S-M nanostructure was sensitive to bias polarity since the NW commonly collapsed at the negatively biased Au metal electrode due to high Joule heat produced in NW at the reversely biased Schottky bather. Thus, the electrical breakdown behavior of the ZnSe NW was highly dominated by the cathode-controlled mode due to the high resistance of the depletion region of ZnSe NW at the reversely biased Schottky contact. (C) 2014 Chinese Materials Research Society. Production and hosting by Elsevier B.V. All rights reserved.
作者：
Wang, Yong;Tang, Jianfeng;Ouyang, Xicheng;Liu, Buqiong*;Lin, Rong Han
期刊：
Materials Research Bulletin,2013年48(6):2123-2127 ISSN：0025-5408
通讯作者：
Liu, Buqiong
作者机构：
[Ouyang, Xicheng; Tang, Jianfeng; Wang, Yong] Hunan Agr Univ, Dept Appl Phys, Changsha 410128, Hunan, Peoples R China.;[Liu, Buqiong] Hunan Agr Univ, Dept Grad Studies, Changsha 410128, Hunan, Peoples R China.;[Lin, Rong Han] Northwestern Univ, Dept Chem, Evanston, IL 60208 USA.
通讯机构：
[Liu, Buqiong] H;Hunan Agr Univ, Dept Grad Studies, Changsha 410128, Hunan, Peoples R China.
关键词：
A. Optical materials;D. Luminescence;D. Optical properties
摘要：
The AlN-doped BaMgAl10O17:Eu2+ phosphors were synthesized by conventional solid-state reaction. Powder X-ray diffraction (XRD), scanning electron microscope (SEM) and photoluminescence spectrum (PL) were used for characterization. The growth mechanism was carried out by computer simulation with CASTEP application, and revealed that an ideal hexagonal shape, particle size in 5 μm and 2.5–3 μm in thickness, could be obtained by AlN doping. Additionally, due to the low electronegativity of N3−, the AlN-doped sample showed 35% increase in PL intensity and improvement of thermal stability. These fine particle size and better photoluminescence properties are expected to be applicable to industrial production of BaMgAl10O17:Eu2+ phosphors.
关键词：
Titanium dioxide;mesoporous material;dye-sensitized solar cells
摘要：
Pure anatase TiO2 spheres with mesoporous structure were prepared by a simple urea assisted hydrothermal process at low temperature. X-ray Diffractometer, Scanning Electron Microscope, Transmission Electron Microscope, and N2 adsorption-desorption were used to characterize TiO2. The dye-sensitized solar cells results show that an overall light conversion efficiency of 6.96% which is 36.7% higher than that of the overall efficiency (5.09%) obtained from the P25 photoanode owing to the superior light scattering effect and the high level of dye loading capacity of microspheres.
摘要：
In this paper, three dimensional (3D) Cu2SnS3 architectures were successfully synthesized via a simple solvothermal route. The structure, morphology and optical properties of the as-prepared samples were characterized by using an X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV–vis diffuse reflectance spectra (UV–vis DRS). The SEM and TEM image indicated that the flower Cu2SnS3 architectures consist of large number of uniform nanosheets. The band gap is about 2.42 eV, which have been confirmed by UV–vis DRS. Photocatalytic activities by photodegradation reaction of methylene blue (MB) were investigated under visible-light irradiation. The results indicate the potential applications of the Cu2SnS3 architectures in visible-light-driven photocatalysts.
