Use of generalized refined composite multiscale fractional dispersion entropy to diagnose the faults of rolling bearing

Nonlinear Dynamics - A typical symptom of vibration signals collected from rolling bearings with local faults is the existence of periodic transients, which makes the intrinsic structure of...     

微波瑞利散射法测定空气电火花激波等离子体射流的时变电子密度

大气压空气电火花激波等离子体射流的电子密度在亚微秒时间尺度上瞬变,其电子密度的测定很难.基于微波瑞利散射原理,本文测量了空气电火花冲击波流注放电等离子体射流的时变电子密度.实验结果表明:测量系统的标定参数A为1.04 × 105 V·Ω·m–2;空气流注放电等离子体射流的电子密度与等离子体射流的半径和长度有关,结合高速放电影像展示的等离子体射流的等效半径和等效长度,测定的电子密度在1020 m–3的量级,且随时间先快速增长至峰值再成指数衰减.此外,本文还探讨了等离子体射流的不同等效尺度对测定结果的影响;分析结果表明,采用时变等效半径和时变等效长度的计算结果最有效,且第1个快速波峰是由光电离的电离波导致的.     

An effective multi-channel fault diagnosis approach for rotating machinery based on multivariate generalized refined composite multi-scale sample entropy

Nonlinear Dynamics - Fault diagnosis of critical rotating machinery components is necessary to ensure safe operation. However, the commonly used rotating machinery fault diagnosis methods are...     

硼、氮共掺杂多孔碳的制备及其超电容性能

分别以含氮菲咯啉、四硼酸钾和醋酸锌为碳源、活化剂和模板,制备了B、N共掺杂多孔碳(BN-PC),并探究模板质量对BN-PC结构和储电性能的影响。当醋酸锌质量为5 g时,所得BN-PC₅中B、N杂原子含量分别为20.21%、18.29%。电化学测试结果表明,以6 mol·L^-1KOH为电解液,BN-PC₅电极展现出高的比电容(在0.05 A·g^-1电流密度下为255 F·g^-1)、优异的倍率性能(在20 A·g^-1电流密度下为188 F·g^-1)和卓越的循环稳定性(在5 A·g^-1的电流密度下循环10 000次比电容保持率为97%)。以3mol·L^-1ZnSO₄为电解液,在平均功率密度为56 W·kg^-1时,BN-PC₅电容器的能量密度可达27 Wh·kg^-1。     

Degradable nanocatalyst enables antitumor/antibacterial therapy and promotion of wound healing for diabetes via self-enhanced cascading reaction

Diabetic patients often have problems such as residual tumor and wound infection after tumor resection, causing severe clinical problems. It is urgent to develop effective therapies to reach oncotherapy/anti-infection/promotion of wound healing combined treatment. Herein, we propose CS/MnO₂-GOx (CMGOx) nanocatalysts for the specific catalytic generation of ^•OH to inhibit tumors and bacteria in a hyperglycemic environment. The good biocompatible chitosan (CS), as a carrier for the catalyst, exhibits excellent antibacterial effect as well as promotes wound healing. Glucose oxidase (GOx) is loaded on the surface of CS nanoparticles to generate H₂O₂ and gluconic acid by consuming glucose (starvation therapy, ST) and O₂. The MnO₂ depletes glutathione (GSH) to produce Mn²⁺, amplifying oxidative stress and further promoting the activity of Mn²⁺-mediated Fenton-like reaction to produce ^•OH (chemodynamic therapy, CDT) in weak acidic environment. Moreover, the produced gluconic acid lowers the pH of the environment, enhancing chemodynamic therapy (ECDT). The tumor cells and bacteria are efficiently eliminated by the synergistic effect of ST and ECDT. The MnO₂ nanoparticles at neutral environment decomposes H₂O₂ into O₂, which cooperate with CS to promote healing. The self-enhanced cascade reaction of CMGOx in situ exhibits excellent effects of antitumor/antibacterial therapy and promotion of wound healing, offering a promising integrated treatment for diabetic patients after tumor surgical resection.     

含三氟乙酰苯基喹啉配体的铱配合物的合成及其电致发光性能

通过2-(4'-三氟乙酰苯基)-4-苯基喹啉(tfapqH)与三氯化铱反应生成了二氯桥中间体,然后用吡啶-2-甲酸(picH)解离得到双环金属铱配合物Ir(tfapq)₂pic。Ir(tfapq)₂pic在二氯甲烷中的发光波长为584 nm,量子产率约为0.846,磷光寿命为1.211 μs,比没有三氟乙酰修饰的铱配合物波长蓝移的10 nm,量子效率提高了约5%,磷光寿命降低了0.286 μs,辐射跃迁加快,半波宽度降低了约26%,色纯度提高。其HOMO能级为-5.405 eV,LUMO能级为-3.277 eV,能级相对于未修饰的配合物都有所降低,且HOMO降低更明显,总的效果是能级差增加。Ir(tfapq)₂pic 10%的热失重温度为301 ℃,比未修饰铱配合高近50 ℃。当Ir(tfapq)₂pic以2%质量浓度掺杂于PVK-PBD中做成电致发光器件时的效率最高,电致发光波长为594 nm。器件的启明电压为7.3 V,最大亮度为8 571 cd·m^-2,最大外量子效率为12.65%,对应的流明效率为22.14 cd·A^-1。色坐标是(0.58,0.40)。     

Characterization and reactivity of γ-Al_2O_3 supported Pd–Ni bimetallic nanocatalysts for selective hydrogenation of cyclopentadiene

Several g-Al2O3 supported Pd–Ni bimetallic nanocatalysts(Pd–Ni(x:y)/Al2O3; where x and y represent the mass ratio of Pd and Ni, respectively) were prepared by the impregnation method and used for selective hydrogenation of cyclopentadiene to cyclopentene. The Pd–Ni/Al2O3 samples were confirmed to generate Pd–Ni bimetallic nanoparticles by X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS) and transmission electron microscopy(TEM). The catalytic activity was assessed in view of the effects of different mass ratios of Pd and Ni, temperature, pressure, etc. Among all the samples, the Pd–Ni(1:1)/Al2O3(PN-1:1) catalyst showed extremely high catalytic ability. The conversion of cyclopentadiene and selectivity for cyclopentene can be simultaneously more than 90%.     

无溶剂高度分散Ni/MCM-41催化剂的制备及其萘加氢性能

分别用机械研磨无溶剂法、添加柠檬酸无溶剂法制备了Ni/MCM-41催化剂,对所制催化剂进行了分析表征,探究其萘加氢反应性能并与常规浸渍法进行了对比。与常规浸渍法相比,机械研磨无溶剂法所制催化剂的物理性质相近,金属镍分散度和萘加氢性能略有提高;添加柠檬酸无溶剂法则显著提升了催化剂的分散度和萘加氢性能,金属镍分散度由6.9%大幅提高至67.9%,萘加氢性能提高了近1倍。通过红外光谱、紫外光谱和热重分析,提出了添加柠檬酸对无溶剂法制备催化剂性能的促进作用机制。     

锂离子电池LiTi_(0.25)Fe_(0.75)SO_4F正极材料的电子结构

采用密度泛函理论平面波赝势的方法,计算了LiFeSO_4F和LiTi_(0.25)Fe_(0.75)SO_4F正极材料的电子结构。计算结果表明:当锂嵌入材料后,S、O和F的原子布居变化较小,电子主要填充在过渡金属的3d轨道,导致过渡金属被还原,成为电化学反应的活性中心。在嵌锂态中,锂和氧(氟)之间形成了离子键,而过渡金属(Ti和Fe)与氧(氟)之间则形成了共价键,S-O键的共价性最强。态密度的计算结果则表明:Ti和Fe均保持高自旋排列结构;LiFeSO_4F的两个自旋通道的带隙分别为2.88和2.29 e V,其导电性很差;Ti掺杂使体系的带隙消失,显著地提高了正极材料的导电性;LiTi_(0.25)Fe_(0.75)SO_4F系统中Ti-O和Ti-F键均比纯相中的Fe-O和Fe-F键的共价性更强,因此Ti掺杂材料具有更好的结构稳定性。