Solvent-enhanced Depolymerization of Lignin under Microwave Irradiation

Lignin is considered an ideal natural material for the production of sustainable monophenols. In this study, a microwave-assisted depolymerization (MAD) strategy was developed. The introduction of solvent vapors in the dynamic vapor flow reaction system was performed to enhance the lignin conversion efficiency. The results showed that no liquid products were generated from the MAD of lignin without solvent vapors. With the introduction of solvents (CH₃OH, HCHO, HCOOH, and CH₂Cl₂), liquid products appeared (especially with CH₂Cl₂, which had the highest yield of 41.9 wt%). Results from gas chromatography/mass spectrometry of liquid products showed that seven kinds of compounds, including guaiacols, phenols, syringols, methoxyphenyls, heterocycles, esters, and aromatics were identified. CH₂Cl₂ can significantly enhance the production of monophenols (guaiacols, phenols, and syringols). The introduction of these solvent vapors can also facilitate the generation of porous char with high Brunauer-Emmett-Teller specific surface areas. Some carbon nanospheres deposited on the surface of the char were obtained with the assistance of CH₂Cl₂. This study provides a facile method for the utilization of lignin in the field of bio-based fine chemicals.     

移动群智感知系统边云协同工人招募算法

针对移动群智感知系统中基于云平台的工人招募算法无法满足大规模网络实时任务需求的问题,提出边云协同工人招募算法,旨在减少数据传输时延,降低智能设备的能耗。在云服务层完成任务的接收、划分、发布和结果收集;在边缘层获取工人的实时信息,构建招募工人模型;在感知层完成任务传播和数据采集。实验结果表明,考虑到传感器类型、工人报价、最大分配任务数等多种因素的影响,所提算法既满足了任务成本和时间的约束,又在空间覆盖率和运行时间方面获得了较好的性能。     

TC4钛合金激光焊接接头组织及耐蚀性研究

采用光纤激光器对4 mm TC4板材进行对接试验,研究了焊接接头各个区域的组织特点、硬度变化及耐蚀性差异,探究显微组织对硬度及耐蚀性的影响。研究表明,焊接接头焊缝截面形貌为T形,存在少量气孔。焊缝存在粗大的原β柱状晶,晶内组织为细小的马氏体α′相;熔合线附近观察到贯穿热影响区和焊缝的原β柱状晶;热影响区组织为等轴晶,晶内组织为马氏体α′相、少量原始α相和原始β相。焊接接头的显微硬度从母材到焊缝呈现逐渐增加的趋势,至焊缝中心达到最高,约为母材的1.78倍。焊缝显微硬度也存在差异,从焊缝顶端至焊缝底端呈现不断下降的趋势。电化学测试结果表明,焊缝的Rct值分别是母材和热影响区的4.32倍和2.58倍,且具有最高的自腐蚀电位和最小的电流密度,表征为最优耐蚀性。     

基于双重保护拓扑的变压器直流偏磁抑制措施

超／特高压直流输电系统调试或故障时的单极-大地运行方式,均可导致直流偏磁现象,半岛地质环境下此效应尤为突出。结合山东半岛电网的具体线路架构和数据,对基于变压器中性点串电容的直流偏磁抑制方案进行了优化分析,提出采用并联避雷器和火花间隙的双重保护拓扑,并给出了直流偏磁抑制装置中的中性点电容器、旁路开关、电子开关、限流电抗器等的选择,以及避雷器与火花间隙的选择与配合。仿真结果表明,在系统发生故障时,所提出的双重保护拓扑可有效保护中性点直流偏磁抑制装置的安全。     

A highly sensitive non-enzymatic glucose sensor based on CuNi nanoalloys through one-step electrodeposition strategy

Journal of Applied Electrochemistry - In this contribution, a uniformly distributed CuNi active nanoalloys was obtained on the electrode substrate by one-step facile electrodeposition method, and a...     

基于感性意象的白酒酒瓶造型多维度特征分析

目的 为了更深层地探寻消费者对白酒酒瓶造型设计的情感诉求,找到影响消费者感性意象的设计要素并构建情感意象与造型要素之间的联系.方法 提出一种从多维设计变量出发对白酒酒瓶造型进行感性工学研究的方法,从消费者的感性意象出发,运用人机界面元件(HIEs)解构方法对白酒酒瓶造型进行多维度设计特征分析,然后通过灰关联与因子分析筛选出最具有代表性的设计特征元素,并运用数量化Ⅰ类建立白酒酒瓶主设计特征元素与消费者感性意象之间的映射关系模型.结果 设计出新产品对构建的白酒酒瓶感性意象预测模型进行实例验证分析,模型预测值与实际评价值的T检验结果证明了该模型的有效性和可靠性.结论 实现了对白酒酒瓶造型的意象评价值预测,并了解到目标感性意象对应的设计特征要素.     

Fabrication,heat-treatment and formation mechanism of MgO fiber using propionic acid as ligand

Magnesium oxide (MgO) fibers were prepared by sol-gel method with magnesium propionate as precursor. Pure micrometer-sized MgO fibers were obtained after pretreated in two different atmospheres (water steam and air). The structure diagram of magnesium propionate precursor was achieved by analyses of the precursor fibers. The MgO fibers pretreated in different atmospheres were characterized by the use of XRD, FT-IR, TG-DSC and SEM analytical techniques, and the heat-conducting property of fibers was characterized by thermal conductivity test. The results show that Mg(OH)₂ crystalline phase appeared at the temperature range from 300 °C to 400 °C during the heat-treating process in water steam. They also show that the water steam is beneficial for the removal of organics, the crystallization of the fibers and the formation of dense, smooth and crack free fibers, but leads to the increase of the heat-conducting property of MgO fibers.     

A novel approach to prepare polyaniline/Polypyrrole@Cu-BTC/NH2-MIL-101(Fe) MOFs for electromagnetic wave absorption

In this study, the Cu-BTC and NH₂-MIL 101 (Fe)@polypyrrole and polyaniline core–shell particles were prepared by in situ polymerization of pyrrole and aniline monomers on the surface of Cu-BTC and NH₂-MIL 101 (Fe) for electromagnetic wave absorption applications. Firstly, the Cu-BTC (1,3,5 benzenetricarboxylic acid, BTC) and NH₂-chromium (III) terephthalate (MIL-101) were synthesized by solvothermal method. Secondly, the surface of Cu-BTC and NH₂-MIL 101 (Fe) mixtures were coated with polypyrrole (PPy) and polyaniline (PANI) by a polymerization of aniline (An) and pyrrole (Py) monomers and denoted as PP@Fe/Cu. For comparative studies, the aniline (An) and pyrrole (Py) monomers were polymerized in the same condition on the surface of NH₂-MIL-101 (Fe) powder without the presence of Cu-BTC and the final powder was denoted as PP@Fe. The morphologies, phase structures and magnetic properties of products were characterized by scanning electron microscope (SEM), X-ray diffractometer (XRD), and vibrating sample magnetometer (VSM) machines. The complex permeability and permittivity values of PP@Fe and PP@Cu/Fe were determined in the range of Ku band (12.4–18 GHz). The electromagnetic wave absorption performances were evaluated using obtained permittivity and permeability values. It was observed that PP@Fe and PP@Cu/Fe composites displayed excellent microwave absorption performances. The existence of Cu-BTC into NH₂-MIL 101 (Fe) further enhanced the minimum reflection loss from −60 dB to −80 dB.     

面向桥壳圆度圆柱度检测装置的并联PID伺服电动机控制器设计

针对重卡桥壳轴头圆度圆柱度在线测量对运动精度、平稳性以及鲁棒性等提出的伺服问题,在伺服运动系统机电耦合动力学建模研究的基础上,提出了基于位置、转速和电流三闭环调速的并联PID控制方法,并结合相位裕度和主导极点配置法整定控制器参数。基于自行搭建的桥壳在线检测实验装置对控制算法进行了实验验证,结果表明提出的控制方法可以根据工业现场对速度和位移跟踪性能要求调节权重,有效实现了伺服电动机匀速、平稳的高精度运动控制,并表现出良好的跟随性能和鲁棒性,极大地提高了桥壳检测装置的检测精度。