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71.
Zhangping He Fei Zhang Yu Lei Zenan Lin Mengmeng Wang Gang Jin 《Polymer Engineering and Science》2020,60(9):2087-2096
Properties of an immiscible polymer blend have been proved to be closely related to dispersion uniformity of the minor phase. At present, dispersion uniformity is difficult to evaluate during the blending process, resulting in hysteretic feedback. Aiming at this problem, this work utilized near-infrared (NIR) spectroscopy to in-line characterize dispersion uniformity evolution during a twin-screw extrusion. A multichannel NIR measurement system was set up and applied to evaluate the blending process of polypropylene and polyolefin elastomer (POE). Based on the NIR spectra collected at different positions of the extruder, five prediction models of POE content were established using the light gradient boosting machine algorithm. Dispersion uniformity was characterized through the fluctuation of the predicted content. The evolution of dispersion under such processing parameters was consistent with scanning electron microscopy. 相似文献
72.
《International Journal of Hydrogen Energy》2020,45(53):28847-28859
Electrocatalyst support materials play significant role in the performance, durability and commercialization of fuel cells. This research work describes the preparation of metal oxide (nickel oxide (NiO), cobalt (Co) and copper (Cu) doped NiO) support materials on meshed titanium (Ti) substrate via a simple electro-deposition method for their application as novel support material for palladium (Pd) catalyst. Field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) techniques are employed to study morphology, composition and structure of fabricated electrodes, respectively. The electrocatalytic performance of fabricated electrodes toward ethanol oxidation reaction (EOR) in alkaline solution is examined by the cyclic voltammetry (CV), chronoamperometry (CA) techniques. Low peak potential (−0.2 V), increased peak current density (62.54 mA cm−2) and large electrochemical active surface area (16.02 m2 g−1) were remarkable properties of Pd/Cu–NiO/Ti electrode. The results of other electrochemical measurements, CO-striping voltammetry, long-term stability and electrochemical impedance spectroscopy (EIS) revealed that the Pd/Cu–NiO/Ti electrode has the privileged electrocatalytic performance for EOR relative to other prepared electrodes. Accordingly, the Pd/Cu–NiO/Ti can be considered as a hopeful electrode for ethanol electro-oxidation reaction in DEFCs. 相似文献
73.
《International Journal of Hydrogen Energy》2020,45(7):4490-4500
Al2O3 and MgAl2O4 supported 10% (w/w) Ni catalysts having a dispersion of 1.5 and 2.0% are active for DRM at 600 and 750 °C. High temperature reduction of both the calcined catalysts resulted in metallic Ni being formed, suggesting strong support metal interactions. The CH4 and CO2 conversion during DRM are relatively constant with time-on-stream, and are higher for Ni/MgAl2O4 than Ni/Al2O3. Carbon-whiskers are also detected on both catalysts. O2 co-feed of 2.6% (v/v) and increasing reaction temperature to 750 °C helped in decreasing the amount of carbon deposited, except for Ni/MgAl2O4 at 600 °C. Furthermore, higher conversions and H2/CO ratios are achieved. It appears that on spent Ni/MgAl2O4 a different type of carbon species was formed, and this carbon species was difficult to remove by oxygen at 600 °C. Thus, co-feeding O2, using an appropriate temperature, and choosing a suitable support can reduce the carbon present on the nickel catalysts during DRM. 相似文献
74.
研制了一种用于KDP晶体加工的平面飞切机床,该机床直线轴基于直线电动机驱动、液体静压导轨支承;刀具旋转轴采用高刚度气浮主轴+高刚度主轴旋转机构。基于高精度分辨率位置反馈+线性驱动器+PID控制算法,直线轴获得了1 mm/min速度下,0.018 mm/min的低速波动以及±0.01μm的位置精度;刀具微进给装置采用差动螺纹进给来实现,最终获得了进给分辨率1μm、锁紧后位置移动量小于1μm高精度进给。在优化工艺参数后,金刚石飞切机床加工100 mm×100 mm×10mm的KDP晶体后获得表面粗糙度Rq优于2 nm高精度指标;加工400 mm×400 mm×30 mm的铝镜后获得面形PV值优于3μm的高精度指标。 相似文献
75.
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77.
通过多碎细磨、原矿分级溢流优先浓缩脱水,进行了高浓度选铅银、选锌,锌尾矿再浓缩脱水选硫、选锰,同时匹配合理的选矿药剂,原矿浓缩水回用于磨矿分级和选铅,锌尾浓缩水回用于选锌,尾矿浓缩水回用于选硫、选锰,剩余各种废水经适度处理回用于选铅和磨矿分级等,使一段磨矿细度-74μm从70%提高到80%,铅、锌、硫入选初始浓度分别提高到50%、40%、50%,选矿废水全部分质回用。铅锌硫银回收率分别提高了1.5、2.83、13.57、1.01个百分点,硫精矿主品位从38.9%提高到46.5%,设备减少40%、能耗降低25%,节约了选矿药剂消耗和废水处理费用,实现了铅锌多金属矿产资源的高效回收和节能环保。 相似文献
78.
Vector vortex beams (VVBs) possess ubiquitous applications from particle trapping to quantum information. Recently, the bulky optical devices for generating VVBs have been miniaturized by using metasurfaces. Nevertheless, it is quite challenging for the metasurface-generated VVBs to possess arbitrary polarization and phase distributions. More critical is that the VVBs' annular intensity profiles demonstrated hitherto are dependent on topological charges and are hence not perfect, posing difficulties in spatially shared co-propagation of multiple vortex beams. Here, a single-layer metasurface to address all those aforementioned challenges in one go is proposed, which consists of two identical crystal-silicon nanoblocks with varying positions and rotation angles (i.e., four geometric parameters throughout). Those four geometric parameters are found to be adequate for independent and arbitrary control of the amplitude, phase, and polarization of light. Perfect VVBs with arbitrary polarization and phase distributions are successfully generated, and the constant intensity profiles independent of their topological charges and polarization orders are demonstrated. The proposed strategy casts a distinct perception that a minimalist design of just one single-layer metasurface can empower such robust and versatile control of VVBs. That provides promising opportunities for generating more complex vortex field for advanced applications in structural light, optical micromanipulation, and data communication. 相似文献
79.
Thermal comfort is an important factor for the design of buildings. Although it has been well recognized that many physiological parameters are linked to the state of thermal comfort or discomfort of humans, how to use physiological signal to judge the state of thermal comfort has not been well studied. In this paper, the feasibility of continuously determining feelings of personal thermal comfort was discussed by using electroencephalogram (EEG) signals in private space. In the study, 22 subjects were exposed to thermally comfortable and uncomfortably hot environments, and their EEG signals were recorded. Spectral power features of the EEG signals were extracted, and an ensemble learning method using linear discriminant analysis or support vector machine as a sub-classifier was used to build the discriminant model. The results show that an average discriminate accuracy of 87.9% can be obtained within a detection window of 60 seconds. This study indicates that it is feasible to distinguish whether a person feels comfortable or too hot in their private space by multi-channel EEG signals without interruption and suggests possibility for further applications in neuroergonomics. 相似文献
80.
当今的多相催化研究需要新的技术和方法从原子尺度上表征活性中心结构和反应中间体。本文作者课题组近期开发了理论模拟新技术来探索催化剂活性位点结构,即基于神经网络势函数的大规模原子模拟(LASP)软件中实现的全局神经网络势函数计算方法。本文介绍了该方法可以显著降低催化体系的计算代价,而维持与密度泛函理论同一级别的计算精度,从而解决多相催化中的许多复杂问题。本文对神经网络势函数方法的实现细节和目前已实现的应用场景进行了详细介绍。神经网络势函数可以用来预测材料晶体结构,理解高压氢化条件下TiO2表面的结构演化和确定三元氧化物ZnCrO晶相中合成气制甲醇活性位点。最后文章分析了神经网络势函数的局限性和今后可能的三个研究方向,即材料性质预测、多元素体系神经网络势函数构造和化学反应拟合。 相似文献