Mechanical characteristics of oil palm fiber reinforced thermoplastics as filament for fused deposition modeling (FDM)

Fibers are increasingly in demand for a wide range of polymer composite materials. This study's purpose was the development of oil palm fiber (OPF) mixed with the thermoplastic material acrylonitrile butadiene styrene (ABS) as a composite filament for fused deposition modeling (FDM). The mechanical properties of this composite filament were then analyzed. OPF is a fiber extracted from empty fruit bunches, which has proved to be an excellent raw material for biocomposites. The cellulose content of OPF is 43%-65%, and the lignin content is 13%-25%. The composite filament consists of OPF (5%, mass fraction) in the ABS matrix. The fabrication procedure included alkalinizing, drying, and crushing the OPF to develop the composite. The OPF/ABS materials were prepared and completely blended to acquire a mix of 250 g of the material for the composition. Next, the FLD25 filament extrusion machine was used to form the OPF/ABS composite into a wire. This composite filament then was used in an FDM-based 3D printer to print the specimens. Finally, the printed specimens were tested for mechanical properties such as tensile and flexural strength. The results show that the presence of OPF had increased the tensile strength and modulus elasticity by approximately 1.9% and 1.05%, respectively. However, the flexural strength of the OPF/ABS composite had decreased by 90.6% compared with the virgin ABS. Lastly, the most significant outcome of the OPF/ABS composite was its suitability for printing using the FDM method.The full text can be downloaded at https://link.springer.com/content/pdf/10.1007%2Fs40436-019-00287-w.pdf     

An Optimized Neural Network with Bat Algorithm for DNA Sequence Classification

Recently, many researchers have used nature inspired metaheuristic algorithms due to their ability to perform optimally on complex problems. To solve problems in a simple way, in the recent era bat algorithm has become famous due to its high tendency towards convergence to the global optimum most of the time. But, still the standard bat with random walk has a problem of getting stuck in local minima. In order to solve this problem, this research proposed bat algorithm with levy flight random walk. Then, the proposed Bat with Levy flight algorithm is further hybridized with three different variants of ANN. The proposed BatLFBP is applied to the problem of insulin DNA sequence classification of healthy homosapien. For classification performance, the proposed models such as Bat levy flight Artificial Neural Network (BatLFANN) and Bat levy Flight Back Propagation (BatLFBP) are compared with the other state-of-the-art algorithms like Bat Artificial Neural Network (BatANN), Bat back propagation (BatBP), Bat Gaussian distribution Artificial Neural Network (BatGDANN). And Bat Gaussian distribution back propagation (BatGDBP), in-terms of means squared error (MSE) and accuracy. From the perspective of simulations results, it is show that the proposed BatLFANN achieved 99.88153% accuracy with MSE of 0.001185, and BatLFBP achieved 99.834185 accuracy with MSE of 0.001658 on WL5. While on WL10 the proposed BatLFANN achieved 99.89899% accuracy with MSE of 0.00101, and BatLFBP achieved 99.84473% accuracy with MSE of 0.004553. Similarly, on WL15 the proposed BatLFANN achieved 99.82853% accuracy with MSE of 0.001715, and BatLFBP achieved 99.3262% accuracy with MSE of 0.006738 which achieve better accuracy as compared to the other hybrid models.

     

A study of spin rectification effect enhancement of microwave field by a PIFA

The progress of spin rectification effect, which has the potential in powering the nanoscopic devices wirelessly, has been impeded by its low conversion efficiency. To solve this problem, a 5.8 GHz planar inverted F‐shaped antenna, which is designed to harvest radiated microwave power as well as foster a field enhanced area surrounding a permalloy (Py, Ni₈₀Fe₂₀) monolayer, is presented. The electric and magnetic field are enhanced by ~17.5‐fold and ~ 45‐fold, respectively. With the proposed antenna, a photovoltage of 0.85 μV can be detected in the monolayer 1.5 m away from the transmitting antenna, with input power of 30 dBm. This work provides an effective method to enhance the spin rectification effect signal in the far field region and paves the way for spintronic devices to be potentially utilized in practical wireless applications, such as quantum information, photovoltaics, and nanogenerator.     

Metal hydrides for lithium-ion batteries

Classical electrodes for Li-ion technology operate via an insertion/de-insertion process. Recently, conversion electrodes have shown the capability of greater capacity, but have so far suffered from a marked hysteresis in voltage between charge and discharge, leading to poor energy efficiency and voltages. Here, we present the electrochemical reactivity of MgH(2) with Li that constitutes the first use of a metal-hydride electrode for Li-ion batteries. The MgH(2) electrode shows a large, reversible capacity of 1,480 mAh g(-1) at an average voltage of 0.5 V versus Li(+)/Li(o) which is suitable for the negative electrode. In addition, it shows the lowest polarization for conversion electrodes. The electrochemical reaction results in formation of a composite containing Mg embedded in a LiH matrix, which on charging converts back to MgH(2). Furthermore, the reaction is not specific to MgH(2), as other metal or intermetallic hydrides show similar reactivity towards Li. Equally promising, the reaction produces nanosized Mg and MgH(2), which show enhanced hydrogen sorption/desorption kinetics. We hope that such findings can pave the way for designing nanoscale active metal elements with applications in hydrogen storage and lithium-ion batteries.     

一个紧凑的梯形领结无芯RFID标签的设计

提出了一种紧凑、低成本、可完全印制的缝隙加载领结型无芯射频识别标签的设计。标签由2个梯形金属贴片组成,2组谐振频率邻近的缝隙谐振器分别加载在2个贴片上。在不增加缝隙间相互耦合的前提下,标签在超宽带频段内容纳的数据位数提高了1倍,在35mm×33mm的合理尺寸内,12个缝隙谐振器对应12位数据。仿真给出了标签的雷达散射截面积曲线,实测是在双站天线配置下进行,在频域内测出了传输系数s21。实测和仿真结果一致,验证了本设计的合理性。该标签具有高数据位数和低成本,因其只需1个导电层,所以能被直接印刷在ID卡甚至纸张上。     

微波分离场加热焊锡膏的实验研究

微波加热作为一种快速、高效、清洁的加热方式,在材料处理领域得到了广泛应用。本文结合金属粉末的微波耗散机理,分析了焊锡膏在微波电场及磁场中的加热特性,通过实验研究了焊锡膏电路在微波电场、微波磁场中的加热效果。实验结果表明,微波电场和微波磁场均可快速加热焊锡膏,但高强度的微波电场容易激发等离子体,灼伤基板;而微波磁场则选择性地加热焊锡膏,实现快速加热融化焊点的同时保持基板在较低温度。通过对比微波磁场快速融化的焊点与传统方式加热融化焊点的微观结构,发现微波磁场快速加热融化的焊点具有极薄的金属间化合物厚度,有利于提高焊点强度。该研究为柔性等塑料基电路的焊接提供了一种良好的解决方案。     

A mathematical model for predicting spray atomization characteristics in an Eulerian–Eulerian framework

A new mathematical model is developed for calculating droplet break-up frequency based on both drag and turbulence induced fragmentation stresses. The droplet break-up model is introduced into a CFD methodology that is based on the Eulerian–Eulerian approach. The CFD solver couples the population balance equation along with the Navier–Stokes equations for predicting the droplets diameter. Finally, preliminary results using this CFD model are presented for the case of a coaxial airblast atomizer and a good agreement with the experimental data is achieved.     

Experimental study on an S-band near-field microwave magnetron power transmission system on hundred-watt level

A multi-magnetron microwave source, a metamaterial transmitting antenna, and a large power rectenna array are presented to build a near-field 2.45 GHz microwave power transmission system. The square 1 m² rectenna array consists of sixteen rectennas with 2048 Schottky diodes for large power microwave rectifying. It receives microwave power and converts them into DC power. The design, structure, and measured performance of a unit rectenna as well as the entail rectenna array are presented in detail. The multi-magnetron microwave power source switches between half and full output power levels, i.e. the half-wave and full-wave modes. The transmission antenna is formed by a double-layer metallic hole array, which is applied to combine the output power of each magnetron. The rectenna array DC output power reaches 67.3 W on a 1.2 Ω DC load at a distance of 5.5 m from the transmission antenna. DC output power is affected by the distance, DC load, and the mode of microwave power source. It shows that conventional low power Schottky diodes can be applied to a microwave power transmission system with simple magnetrons to realise large power microwave rectifying.     

微波辐射下CaSO4生成反应过程中的热点特性

在微波辐射化学反应过程中,常常会因为存在热点而导致爆炸或反应物烧毁等现象发生。本文以微波辐射下的硫酸钙生成反应为例,利用有限元方法求解Maxwell方程组、流体力学方程以及热传导方程,研究了微波辐射反应过程中热点的变化情况,并用实验验证了计算结果的正确性。研究结果表明：在加热过程中,随反应的进行,热点的位置是在不断变化的,且热点常出现在物质分相界面附近。     

High surface area niobium oxides as catalysts for improved hydrogen sorption properties of ball milled MgH2

We report, high surface area (up to 200 m²/g) nanocrystalline niobium oxide (so called p-Nb₂O₅) synthesized by ‘chimie douce’ route and its importance in enhancing the hydrogen sorption properties of MgH₂. p-Nb₂O₅ induces faster kinetics than commonly used commercial Nb₂O₅ (c-Nb₂O₅) when ball milled with MgH₂ (named (MgH₂)_catalyst) by reducing the time of desorption from 35 min in (MgH₂ )_c-Nb2O5 to 12 min in (MgH₂ )_p-Nb2O5 at 300 °C. The BET surface area of as-prepared Nb₂O₅ was tuned by heat treatment and its effect on sorption properties was studied. Among them, both p-Nb₂O₅ and Nb₂O₅:350 (p-Nb₂O₅ heated to 350 °C with a BET specific surface area of 46 m²/g) desorb 5 wt.% within 12 min, exhibiting the best catalytic activity. Furthermore, thanks to the addition of high surface area Nb₂O₅, the desorption temperature was successfully lowered down to 200 °C, with a significant amount of desorbed hydrogen (4.5 wt.%). In contrast, the composite (MgH₂ )_c-Nb2O5 shows no desorption at this “low” temperature.