Autonomous memristor chaotic systems of infinite chaotic attractors and circuitry realization

Nonlinear Dynamics - Memristor chaotic system has been attracted by many researchers because of the rich dynamical behaviors. However, some existed memristor chaotic systems have finite numbers of...     

Synthesis and characterization of nitrogen-doped carbon nanotubes by pyrolysis of melamine

Femtosecond laser material processing as micromachining and nanoparticles fabrication require a careful control of the fluences deposited on the samples. In many cases, best results are obtained by using fluences slightly above the Laser Ablation Threshold (LAT), therefore its accurate determination is an important requirement. LAT can be obtained by measuring the intensity of the acoustic signal generated during the ablation process as a function of the laser fluence. In this work femtosecond laser ablation thresholds of commercially polished stainless steel plates, white high impact polystyrene, frosted glass, antique rag papers and silicon oxynitride thin films were determined by using laser ablation induced photoacoustics (LAIP). Results were compared with similar data previously obtained by using a nanosecond Nd:YAG laser.     

Synthesis and characterization of nitrogen-rich carbon nitride nanobelts by pyrolysis of melamine

Nitrogen-rich g-C₃N₄ nanobelts were successfully synthesized via pyrolysis of melamine (C₃N₆H₆). The as-synthesized nanobelts are structurally uniform, and each belt is uniform in width and thickness along its length direction. The typical width is in the range of 600 nm and 1.5 μm, respectively. The typical length of belts is in the range of several hundreds of micrometers; some of them even have lengths on the order of millimeters. The structure and morphology were researched by XRD, SEM, TEM, CEA, XPS, FTIR, and TG measurements. The theoretical FTIR spectra are calculated to compare with experiment value. It is found that the NH₂ edges in the nanobelts are precisely for the reason of rich nitrogen. The photoluminescence (PL) spectrum was carried out. Two peaks at 443 and 500 nm were observed in the spectrum. In addition, a possible growth mechanism is also inferred by principle of VLS.     

Synergistic effect of efficient adsorption g-C3N4/ZnO composite for photocatalytic property

Novel g-C₃N₄/ZnO composite photocatalyst was synthesized from an oxygen-containing precursor by direct thermal decomposition urea in air without any other templates assistance. Different percentages of g-C₃N₄ were hybridized with ZnO via the monolayer-dispersed method. The prepared g-C₃N₄/ZnO composites were characterized by XRD, SEM, UV–vis diffuse reflectance spectra (DRS), FT-IR, TEM and XPS. The composites showed much higher efficiency for degradation of Rhodamine B (RhB) than ZnO under UV and visible light irradiation. Especially, the photocatalytic efficiency was the highest under UV light irradiation when the percentage of g-C₃N₄ was 6%. The improved photocatalytic activity may be due to synergistic effect of photon acquisition and direct contact between organic dyestuff and photocatalyst. Then, effective separation of photogenerated electron–hole pairs at the interface of g-C₃N₄ is an important factor for improvement of photocatalytic activity. This work indicates that g-C₃N₄ hybrid semiconductors photocatalyst is a promising material in pollutants degradation.     

Fe2O3/macroporous resin nanocomposites. High efficiency catalysts for hydroxylation of phenol with H2O2

Hydrated α-Fe₂O₃ nanoparticles were prepared inside resin pores byin situ forced hydrolysis of Fe³⁺ ions chemisorbed at the pore walls. They range from 20 to 50 ? in size and are spherical in shape. They were used in catalysis for hydroxylation of phenol with H₂O₂ and possessed very high hydroxylation activity.     

应变对Mo2C(001)表面电子结构及光学性质的影响

采用第一性原理方法研究应变对Mo₂C(001)表面电子结构及光学性质的影响。研究表明,在应变作用下Mo₂C(001)表面均为间接带隙半导体,带隙随着压应变和拉应变的增加而减小。当应变为-20%时,Mo₂C(001)表面由间接带隙半导体转变为金属性质。当应变为-20%、-15%、-10%、-5%、0%、5%、10%、15%、20%时,其带隙分别为0 eV、0.162 eV、0.376 eV、0.574 eV、0.696 eV、0.708 eV、0.604 eV、0.437 eV、0.309 eV。带隙变化的原因主要是Mo 4p、4d、5s态电子和C 3p态电子对应变敏感,在应变作用下受激发,活性增强导致价带顶在布里渊区G、A、L、M点之间变化,导带底在K、H点之间变化;当应变由-15%逐渐变化到20%时,吸收谱的第一峰逐渐减弱,并且第一峰对应的光电子能量减小,吸收带边向低能方向移动,表明光吸收随着压应变增大而增加,吸收带边随着拉应变增加向低能方向移动。其他光学性质表现出类似的变化规律,光学性质计算结果表明应变能够有效调节光吸收特性,增强光学利用率,研究结果为Mo₂C(001)作为新型光电子材料的应用提供理论支撑。     

矩阵方程ATXA=C的双对称最小二乘解的最佳逼近

1引言根据矩阵分解理论求解线性矩阵方程的问题已经有多位作者研究([2],[3],[5]-[11]),比如文[6],[7],[9]基于GSVD、CCD方法给出了几个矩阵方程的最小二乘解以及方程(组)相     

一类矩阵方程的公共解

By applying the GSVD of matrix pairs,we discuss common solutions of the matrix equations AXC = E, BXD = F, AXD = G, BXC = H, under consistent and nonconsistent case respectively. We also discuss common symmetric solutions of the matrix equations AXA^T = E, BXB^T = F, AXB^T = G, BXA^T = H under consistent and nonconsistent case respectively. The necessary and sufficient conditions for the existence and the expressions of solutions of these matrix equations are provided.