基于分段函数的结构动应力谱分布估计方法

以某型动车组制动吊座的疲劳关键点为例,采集并处理其动应力数据,得到其实测动应力谱;针对等组距直方图不能满足动应力谱分布估计的问题,提出非等距分组的方法。分别使用工程领域常用的截尾正态分布函数、对数正态分布函数和威布尔分布函数以及色谱领域常用的Giddings分布函数进行实测动应力谱的分布拟合,结果表明：单一使用某一分布函数得到的分布拟合结果不能通过卡方检验,且截尾正态分布函数的拟合精度最低;Giddings分布函数对前6组数据拟合得较好,威布尔分布函数对中间组（7～12组）数据拟合得较好,对数正态分布函数对尾部（13～17组）数据拟合得较好。因此根据不同分布函数在不同谱级段体现出的拟合优势,构建分段函数分布模型,并顺利通过了卡方检验。基于分段函数分布模型得到的结构动应力谱的Miner线性累积损伤与实测谱损伤的总体走势一致,且其每级损伤均大于实测谱损伤,从而得到对结构疲劳寿命做出偏安全的预估。

一种新的高速列车动应力谱分布估计方法

为克服参数估计方法对动应力谱分布估计的局限,引入一种非参数估计方法--核密度估计法。为验证算法的有效性,选取标准正态分布函数进行验证,结果表明所得概率密度曲线与真实概率密度曲线吻合很好,同时也证明了数据组距的大小对核密度估计结果没有影响。将高速列车关键部位动应力实测数据进行数据处理,将得到的实测应力谱利用核密度法进行估计并推断,结果显示核密度估计的谱损伤曲线与实测谱损伤曲线的总体走势一致且前者的每级损伤值均略大于后者,这表明利用核密度估计方法对动应力谱的拟合估计有一定误差且略偏保守,然而这种保守的估计方法对于保证结构在运用时的安全却是十分有益的。

重型燃气轮机叶片离心载荷下应力特性的研究

针对重型燃气轮机叶片疲劳寿命研究的需要,通过设计和搭建的全尺寸叶片疲劳试验装置,模拟离心载荷工况下的低周疲劳试验,开展离心载荷下叶片应力分布和疲劳寿命预测的研究。该全尺寸叶片疲劳试验装置能够模拟低周疲劳中的等效离心载荷工况,为叶片试验提供必要的条件和手段。同时,对叶片进行网格划分和有限元仿真计算后,得到叶片Von mises应力分布结果,发现叶身应力最大处位于中部偏下边缘薄壁侧。然后将有限元仿真及应力试验相结合,提出叶片疲劳试验的离心载荷等效方法。在此基础上完成叶片的动应力试验,获得应力时间历程数据,并且给出离心载荷应力谱。结果表明,叶身中部边缘的应力水平最高,动应力谱幅值与频数概率的分布服从6阶麦克劳林拟合函数,用等效离心载荷疲劳寿命进行叶片寿命预测的结果是偏安全的,该结论可作为优化设计和试验研究的参考依据。

Degradation of microcystin-RR in water by chlorine dioxide

Due to the potent hepatotoxicity and tumor-promoting activity of microcystins, a successful removal of these toxins during drinking water treatment processes is of increasing concem. The oxidation kinetics of MC-RR by chlorine dioxide （ClO2） was studied with HPLC and characterization of the reaction products was performed with UV-spectrometry, TOC and LC-MS. Our experimental results show that the oxidation process is a second order overall and a first order with respect to ClO2 and MC-RR. The activation energy of MC-RR degradation by ClO2 is 53.07 kJ/mol. The rate constant k of the action can be increased by increasing temperature and decreasing pH value and ranged from 6.11 × 10^2 L/（mol.min） to 5.29× 10^2 L/（mol-min） at pH from 3.44 to 10.41 at 10℃. Reaction products were determined to be organic and volatile, because they could be almost removed from aqueous solution by heating for 15 min at 60 ~C. In addition, the main oxidation products have m/z values of 1072 and are identified as dihydroxy isomers of MC-RR.

Doping Copper Ions in a Metal-Organic Framework(UiO-66-NH2):Location Effect Examined by Ultrafast Spectroscopy

We constructed two types of copper-doped metal-organic framework(MOF),i.e.,Cu@UiO-66-NH2 and Cu-UiO-66-NH2.In the former,Cu2+ions are impregnated in the pore space of the amine-functionalized,Zr-based UiO-66-NH2;while in the latter,Cu^2+ions are incorporated to form a bimetal-center MOF,with Zr^4+being partially replaced by Cu2+in the Zr-O oxo-clusters.Ultrafast spectroscopy revealed that the photoinduced relaxation kinetics associated with the ligand-to-cluster charge-transfer state is promoted for both Cudoped MOFs relative to undoped one,but in a sequence of Cu-UiO-66-NH2>Cu@UiO-66-NH2>UiO-66-NH2.Such a sequence turned to be in line with the trend observed in the visible-light photocatalytic hydrogen evolution activity tests on the three MOFs.These findings highlighted the subtle effect of copper-doping location in this Zr-based MOF system,further suggesting that rational engineering of the specific metal-doping location in alike MOF systems to promote the photoinduced charge separation and hence suppress the detrimental charge recombination therein is beneficial for achieving improved performances in MOF-based photocatalysis.

Adsorption Reaction Dynamics of Systems Lysozyme and Nanodiamond/Nanosilica at pH=7-13

Adsorption reactions between surfaces of nanodiamond and nanosilica with diameter of 100 nm prepared as suspension solutions of 0.25μg/μL and lysozyme molecule with different concentrations of 7 mmol/L PPBS at pH=7, 9, 11, and 13 have been investigated by fluores- cence spectroscopy. Adsorption reaction constants and coverages of lysozyme with different concentrations of 0-1000 nmol/L under the influences of different pH values have been ob- tained. Helicities and conformations of the adsorbed lysozyme molecules, free spaces of every adsorbed lysozyme molecule on the surfaces of nanopartieles at different concentrations and pH values have been deduced and discussed. The highest adsorption capabilities for both sys- tems and conformational efficiency of the adsorbed lysozyme molecule at pH=13 have been obtained. Lysozyme molecules can be prepared, adsorbed and carried with optimal activity and helicity, with 2 and 10 mg/m2 on unit nanosurface, 130 and 150 mg/g with respect to the weight of nanoparticle, within the linear regions of the coverages at around 150-250 nmol/L and four pH values for nanodiamond and nanosilica, respectively. They can be prepared in the tightest packed form, with 20 and 55 mg/m2, 810-1680 and 580-1100 mg/g at threshold concentrations and four pH values for nanodiamond and nanosilica, respectively.

Kinetics of water–isocyanate reaction in N,N-dimethylformamide

The uncatalyzed reaction of p-tolyl isocyanate(p-TI)with water in N,N-dimethylformamide(DMF)was investigated by high performance liquid chromatography(HPLC).The reactions were carried out at different temperatures from 293 K to 323 K,using various molar ratios of water to p-TI.DMF,as a special amide,was proved to be an efficient catalyst for water–isocyanate reaction.Under the reaction conditions in this study,substituted urea was the only final product observed.An appreciable amount of intermediate p-toluidine was detected.Concentrations of the isocyanate group as well as the amine and urea were determined as a function of time.New kinetic equations were deduced for each of the substance on the basis of a multistep mechanism,instead of a simple second order reaction as usual.Kinetic constants were calculated using the software MATLAB.Furthermore,the effects of temperature and concentrations of reactants on the reaction rate and amine content were discussed.The activation energy of each step was also determined.

Reaction Kinetics of Trans-Sobrerol and 8-p-Menthen-1,2-diol with Hydroxyl Radical in Aqueous Solution： A Combined Experimental and Theoretical Study

Trans-sobrerol （Sob） and 8-p-menthen-1,2-diol （Limo-diol） are the primary products in the atmospheric oxidation of α-pinene and limonene, respectively. Because of their low volatility, they associate more likely to the liquid particles in the atmosphere, where they are subject to the aqueous phase oxidation by the atmospheric oxidants. In this work, through experimental and theoretical study, we first provide the rate constants of Sob and Limo-diol reacting with hydroxyl radical （.OH） in aqueous solution at room temperature of 3044-3 K and 1 atm pressure, which are （3.05±0.5）×10 9 and （4.57±0.2）×10 9 L/（mol.s）, respectively. Quantum chemistry calculations have also been employed to demonstrate the solvent effect on the rate constants in aqueous phase and the calculated results agree well with the measurements. Some reaction products have been identified based on liquid chromatography combined with mass spectroscopy and theoretical calculations.

Surface Photocatalysis-TPD Spectrometer for Photochemical Kinetics

A surface photocatalysis-TPD apparatus devoted to studying kinetics and mechanism of pho- tocatalytic processes with various signal crystal surfaces has been constructed. Extremely high vacuum （-0.2 nPa） in the ionization region is obtained by using multiple ultrahigh vacuum pumps. Compared with similar instruments built previously by others~ the H2, CH4 background in the ionization region can be reduced by about two orders of magnitude, and other residual gases in the ionization region can be reduced by about an order of magnitude. Therefore, the signal-to-noise ratio for the temperature programmed desorption （TPD） and time of flight （TOF） spectra is substantially enhanced, making experimental studies of pho- tocatalytic processes on surfaces much easier. In this work, we describe the new apparatus in detail and present some preliminary studies on the photo-induced oxygen vacancy defects on TiO2（110） at 266 nm by using the TPD and TOF methods. Preliminary results suggest that the apparatus is a powerful tool for studying kinetics and mechanism of photochemical processes.

The roles of heterogeneous chemical processes in the formation of an air pollution complex and gray haze

Urban and regional air pollutions are characterized by high concentrations of secondary pollutants such as photo-oxidants （mainly ozone） and fine particulate matter, which are formed through chemical reactions of the primary pollutants emitted from various sources. The accumulation of these pollutants under stagnant meteorological conditions results in the formation of gray haze, reducing visibility and causing major impacts on human health and climate. In an air pollution complex, the co- existence of high concentrations of primary and secondary gaseous and particulate pollutants provides a large amount of reac- tants for heterogeneous reactions on the surface of fine particles; these reactions change the oxidizing capacity of the atmos- phere, as well as chemical compositions along with the physicochemical and optical properties of particulate matter, thereby accelerating formation of the air pollution complex and gray haze. Using in situ technologies, such as diffuse reflectance infra- red Fourier-transform spectroscopy and single-particle Raman spectroscopy, we systematically investigated the reaction kinet- ics and mechanisms of gaseous pollutants （i.e., NO2, SO2, 03, and formaldehyde） on the surfaces of the major components of atmospheric particles such as CaCO3, kaolinite, montmorillonite, NaC1, sea salt, A1203, and Tit2. We found that the main re- action products were sulfate, nitrate, or formate, which can change the hygroscopicity and light extinction parameters of those particles significantly. By analyzing the reaction kinetics of these heterogeneous reactions, we identified synergetic mechanisms of the three ternary reaction systems, ,i.e., NOE-particles-H2O, SO2-particles-O3, and organics/SO2-particles-UV illumination. These synergetic mechanisms can provide experimental and theoretical bases for understanding the feedback mechanisms and nonlinear processes in the formation of an air pollution complex and gray haze.

In-depth study on aminolysis of poly(ε-caprolactone): Back to the fundamentals

The aminolysis can effectively introduce primary amine （- quent surface fiiofunctionalization reactions. However, less NH2） groups onto polyester materials, enabling a variety of subse- attention has been paid to the basic knowledge of aminolysis reac- tion in terms of reaction kinetics and its influences on materials properties. In this study, taking the widely used poly（e-caprolactone） （PCL） as a typical example, the influences of diamines and solvent property on the surface -NH2 density are firstly assessed by using X-ray photoelectron spectroscopy （XPS） and colorimetric analysis. Results show that smaller dia- mine molecules and nonpolar alcohols could accelerate the reaction. The reaction kinetics with 1,6-hexanediamine is further investigated as a function of temperature, reaction time, and diamine concentration. During the initial stage, the reaction shows a 1^st order kinetics with the diamine concentration and has an activation energy of 54.5 kJ/mol. Ionization state of the -NH2 groups on the PCL surface is determined, revealing that the pKa of -NH3^＋ （〈5） is much lower than that of the corresponding diamine molecules in solution. After aminolysis, surface hydrophilicity of PCL membrane is significantly enhanced, while surface elastic modulus and average molecular weight are decreased to some extent, and others such as weight, surface mor- phology and bulk mechanical strength are not apparently changed. The introduced -NH2 groups are found to be largely lost at 37 ℃, but can be mostly maintained at low temperature.