含油轴承表面供油行为与自润滑机理分析

含油轴承是一类重要的减摩自润滑零件,轴承基体中油液的渗流特性对表面润滑性能有重要影响. 建立含油轴承孔隙渗流与表面油膜润滑的耦合力学模型,分析含油轴承系统中油液的渗流特性,探讨轴承表面油液的供油行为与自润滑机理. 结果表明:在含油轴承的收敛区内同时存在周向旋转流、径向伸缩流和法向渗析流,油液在各方向上的流动状况由该向流体压力梯度决定;受油膜压力影响,油液在接触区向多孔基体渗入,在接触区入口部位向多孔表面析出,由此构成了油液渗入和析出的闭环速度流线,增强摩擦界面间的泵吸效应. 油液在法向上的渗析速度随中心膜厚增加而减小,随转速升高而增大,渗析速度越大,对泵吸效应的增强作用越显著,接触区入口的油液也更易进入摩擦界面,保障含油轴承的良好自润滑效果. 研究结果对揭示含油轴承的供油自润滑机理具有重要意义.      

过饱和度理论及过饱和药物递送系统

在药物研发领域,如何有效提高难溶性药物的溶解与吸收是一个极具挑战的难题。目前,过饱和药物递送系统(Supersaturating drug delivery systems,SDDS)利用药物溶液处于过饱和态的优势,可同时提高难溶性药物的表观溶解度与渗透性。本文对过饱和度的理论及其在药物研发领域中的实际应用进行了系统的综述,介绍了过饱和度的产生与维持、及其与药物吸收的关系,归纳了常用的SDDS技术,并对无定形固体分散体、共晶、无定形/共无定形产生过饱和进行重点阐述。     

温度对气相传输法制备氧化锌晶体生长机制影响研究

为提高气相传输法制备微纳结构样品形貌的可控性,进行了生长温度调控下氧化锌晶体生长机制及其变化的实验研究.实验中的样品制备,以高纯度锌粉末为原料,在无模板、无催化条件下,通过加热蒸发-氧化冷却-生长晶体过程实现.其中,蒸发温度固定于750℃,反应区气体氛围保持稳定,生长区温度在450～ 600℃变化,制备出不同生长温度下样品.对所制备出诸样品,应用扫描电子显微镜、X-射线衍射仪和透射电子显微镜等方法,进行形貌与结构表征.基于表征结果,观察、分析、研究生长温度变化的影响,结合理论分析,得出了生长温度通过对生长过程中锌蒸汽过饱和度的影响,决定着不同生长机制,从而有着不同的形貌结构的样品.     

CO2水合物在砂中生成和分解的核磁共振弛豫响应

Quantification and characterization of hydrate formation and dissociation in sediments are highly important in the study of the physical properties of hydrate-bearing sediments. In this paper, the behavior of CO₂ hydrate formation and dissociation in sand is studied using the nuclear magnetic resonance (NMR) technique. The components of the pore space, including gas, liquid water, and hydrate, were quantified using a convenient method by which the hydration number was determined. No abrupt change in the relaxation behavior of the sample was found during hydrate formation and dissociation. In addition, the value of mean-log T2₂ appeared to be proportional to the liquid water content of the sample with or without the pore hydrate. A straightforward explanation is that the liquid water in the pore space remains in contact with grain surfaces, and relaxation occurs mainly at the grain surface. The results suggest that, rather than coating the grains, the hydrate is pore-filling or cementing.     

基于固相萃取－响应面优化的碳骨架在线催化/GC－MS/MS技术测定含油金属原料表面痕量氯污染物

采用碳骨架在线催化/气相色谱－串联质谱（Online catalytic/GC－MS/MS）技术建立了进口含油金属原料中多氯联苯（PCBs）、多氯萘（PCNs）、短链和中链氯化石蜡（SCCPs、MSCCPs）等含氯污染物的测定方法,考察了固相萃取（SPE）条件,研究了催化剂的制备、在线催化温度、氢气流速及氯化程度等对催化效率的影响,并运用三维响应面法优化催化条件。样品通过自制催化衬管在线脱氯加氢,目标物经催化后转化为碳骨架不变的正构烷烃和芳烃化合物,采用多反应监测模式进行检测。10种还原产物在0.02 ~ 1.00 μg/mL质量浓度范围内与其对应的峰面积呈线性关系,方法定量下限为0.26 ~ 5.33 μg/kg。样品的加标回收率为87.2% ~ 111%,相对标准偏差（RSD,n = 6）不大于7.1%。该方法催化快速、灵敏度高、准确性好,无需化学电离源或高分辨气相色谱－质谱仪即能达到较低的检出限,适用于含油金属原料中氯污染物的测定。     

Determination of 14 whitening active components in cosmetics by ultra-high performance liquid chromatography-triple quadrupole mass spectrometryEI北大核心CSCD

A method based on ultra high performance liquid chromatography-triple quadrupole mass spectrometry (UPLC-MS/ MS) was developed for the analysis of 14 whitening active components in oilycosmetics. The 14 whitening active components were extracted from cosmetics by supersonic extraction with 20 mmol / L potassium dihydrogen phosphate solution, purified by HLB solid phase extraction column and filtered with 0. 22 μm filter membrane. Shim-pack GIST C18 AQ chromatographic column was used for the separation of the whitening active components. Methanol-0. 1% formic acid solution(containing 5 mmol / L ammonium acetate)was employed as mobile phase for gradient elution, and the analytes were detected by electrospray ionization source with positive and negative ion alternate scanning mode and multiple reaction monitoring mode (MRM). The results showed that an effective separation was achieved within 10 min under the optimized conditions, 14 whitening active components exhibited good linear relationships in the respective linear range with the correlation coefficient more than 0. 999. The limits of detection were in the range of 0. 15-2. 5 mg / kg, and the limits of quantitation were in the range of 0. 5-7. 5 mg / kg. The recoveries were from 70% to 117%, and the relative standard deviations were between 0. 2% and 12% . © 2022, Youke Publishing Co.,Ltd. All rights reserved.     

第35届中国化学奥林匹克初赛试题第4题的巧解*

对2021年第35届中国化学奥林匹克竞赛初赛试题中第4题进行了详细地解析。运用自己建立的模型,加深了学生对干冰晶体结构的认识,算出了与其相关的晶胞参数和原子坐标等,解释了干冰晶体为什么不是面心立方而是简单立方点阵。基于物质组成与结构的隐性关系,借助不饱和度巧妙地推出了各分子式可能具有的结构。同时对试题中存在的问题发表了自己的看法,并提出了一些教学建议。     

A CLASS OF SIS EPIDEMIC MODEL WITH SATURATION INCIDENCE AND AGE OF INFECTION

Saturating contact rate of individual contacts is crucial in an epidemiology model.A mathematical SIR model with saturation incidence and age of infec- tion is formulated in this paper.In addition,we study the dynamical behavior of this model and define the basic reproductive number R_0.The authors also prove that the diseased-free equilibrium is globally asymptotically stable if R_0<1. The endemic equilibrium is locally asymptotically stable if K_1>αand R_0>1.