Effects of functional groups on the graphene sheet for improving the thermomechanical properties of polyurethane nanocomposites

Dispersibility of graphene sheets in polymer matrices and interfacial interaction are challenging for producing graphene-based high performance polymer nanocomposites. In this study, three kinds nanofillers; pristine graphene nanoplatelets (GNPs), graphene oxide (GO), and functionalized graphene sheet (FGS) were used to prepare polyurethane (PU) composite by in-situ polymerization. To evaluate the efficacy of functional groups on the graphene sheets, PU reinforced with GNPs, GO, and FGS were compared through tensile testing and dynamic mechanical thermal analysis. The Young's moduli of 2 wt% GO and FGS based PU nanocomposites were found significantly higher than that of same amount of GNPs loading as an evidence of the effect of functional groups on graphene sheets for the mechanical reinforcement. The strong interaction of FGS with PU was responsible to exhibit notably high modulus (25.8 MPa) of 2 wt% FGS/PU composite than the same amount of GNPs and GO loading even at elevated temperature (100 °C).     

Stabilization of uncertain linear distributed delay systems with dissipativity constraints

This paper examines the problem of stabilizing linear distributed delay systems with nonlinear distributed delay kernels and dissipativity constraints. Specifically, the nonlinear distributed kernel includes functions such as polynomials, trigonometric and exponential functions. By constructing a Liapunov–Krasovskii functional related to the distributed kernels, sufficient conditions for the existence of a state feedback controller which stabilizes the uncertain distributed delay systems with dissipativity constraints are given in terms of linear matrix inequalities (LMIs). In contrast to existing methods, the proposed scenario is less conservative or requiring less number of decision variables based on the application of a new derived integral inequality. Finally, numerical examples are presented to demonstrate the validity and effectiveness of the proposed methodology.     

Robust assembly of urchin-like NiCo2O4/CNTs architecture as bifunctional electrocatalyst in Zn-Air batteries

Cost-effective bifunctional electrocatalysts with desirable oxygen catalytic activity to both of ORR and OER are essential to the large-scale commercial application of metal-air batteries. In this work, a robust hydrothermal assembly strategy is presented to fabricate the three-dimensional (3D) urchin-like hybrid material of acid-treated multiwall CNTs (MWCNTs) and needle-like NiCo₂O₄ as a cost-effective bifunctional oxygen electrocatalyst. Benefiting from the particular 3D urchin-like mesoporous structure providing rich transport channels for O₂ diffusion and electrolyte infiltration and abundant active sites for charge transfer reaction, and the synergistic effect of high electrocatalytically active NiCo₂O₄ and high conductive MWCNTs network, the optimized NCO@20%MWCNTs composite exhibits a superior OER and ORR catalytic activity. In its practical application, an ultrahigh initial round-trip efficiency of 79.4% and long-term cycle stability (950 cycles) at 10 mA cm⁻² are achieved in Zn-air battery. This simple strategy for construction of the cost-effective unique 3D porous urchin-like structure together with the improved electrochemical catalytic activity provides a great potential for material design in oxygen catalysis and metal-air batteries.     

A compact current-mode instrumentation amplifier for general-purpose sensor interfaces

The proposed amplifier architecture follows a consolidated topology based on second-generation current conveyors (CCIIs), optimized for fully-differential operation. The architecture uses gain-boosting to improve the offset and noise characteristics of a recently proposed design. Wide input and output ranges and high accuracy are obtained by designing the CCIIs according to an original two-stage architecture with local voltage feedback. Embedding of chopper switch matrices into the amplifier enables vector analysis of the input signal, expanding the application field. The main strengths of the proposed amplifier are compactness and versatility. Measurements performed on a prototype designed with a 0.18 μm CMOS process are described.     

A dual-band multiple-input multiple-output microstrip antenna with metamaterial structure for LTE and WLAN applications

A method to enhance the gain of microstrip dual-band multiple-input multiple-output (MIMO) antenna using partially reflective surface (PRS) layer is introduced and investigated in this paper. The proposed antenna consists of two FR4 substrates. The lower substrate has two radiating patches with parasitic elements that are supplied independently and create the MIMO property of the antenna. The upper substrate which is known as superstrate is arrays of PRS unit cells. The PRS layer printed on either side of a dielectric substrate and causes the antenna gain to increase in both frequency bands. The proposed antenna is appropriate for LTE (2.4–3.1 GHz) and WLAN (5.1–5.8 GHz) applications. The measured values of S₁₁ and S₂₂ parameters of the antenna are less than −10 dB and its FBR and gain are 12.5 dB and 5dBi, respectively. The average half power beam-width (HPBW) is roughly 108^○.     

金属卡宾催化剂在烯烃复分解反应中的研究进展

简要介绍了烯烃复分解反应及其反应机理,综述了金属卡宾催化剂在烯烃复分解反应中的研究进展,重点介绍了钨、钼、钌卡宾催化剂的发展和应用,并简述了其他体系金属卡宾催化剂的研究现状,最后指出了金属卡宾催化剂的发展方向。     

基于傅立叶分析的直齿圆柱齿轮参数测量

研究了采用数字图像处理技术对直齿圆柱齿轮几何尺寸进行非接触式测量。提出了基于傅立叶分析的直齿圆柱齿轮参数测量方法。实验证明：傅立叶分析对于直齿圆柱齿轮的快速、自动测量非常有效。     

Design and FPGA implementation of a new approximation for PAPR reduction

One of the main drawbacks of orthogonal frequency division multiplexing (OFDM) is its sensitivity to the peak-to-average power ratio (PAPR). To address this issue, a novel and efficient scheme based on multilayer perceptron (MLP) neural networks (NN) using radial basis function is proposed and implemented on FPGA. The proposed solution offers good performance as compared to previous algorithms in iterations, much lower complexity and low error rate. For a precise and less complex implementation of radial basis function, a novel approximation of the exponential function using Taylor series is proposed, implemented on FPGA and compared with Altera intellectual property core (IP core). It is shown that, the proposed approximation offers minimal resource consumption. In particular, we note a reduction of 9% and 6% in the use of lookup tables and DSP blocs.     

基于虚拟样机技术的坦克步兵战车实战演习仿真

BMP-2是前苏联时期制造的步兵战车，该战车虽制造年代久远，但对以后世界步兵战车的发展起到引导作用。其主要特点是坦克配备一门机关炮和拱肩反坦克导弹。为了实现该步兵车实战演习过程，在 ADAMS 中建立该步兵车的虚拟样机模型，对模型的各部件添加约束和驱动，并进行运动仿真，以显示该型步兵战车的强大作战力。     

溶胶-凝胶法合成磷酸铁锂正极材料

以FePO4·4H2O、LiOH·H2O、草酸为原料,以葡萄糖为碳源,采用溶胶-凝胶法合成磷酸铁锂正极材料。利用X射线衍射(XRD)、扫描电镜(SEM)等方法进行表征,并将材料组装成电池研究其电化学性能。结果表明:以葡萄糖为碳源,采用溶胶-凝胶法合成磷酸铁锂正极材料具有单一的橄榄石型晶体结构,充放电平台平稳。葡萄糖添加量为5.9%时,材料的充放电比容量和循环性能较高,室温下,0.1C和0.2C首次放电比容量达143.3mA·h/g和133.7mA·h/g,循环50次后仍保持在134.2mA·h/g和124.5mA·h/g。