变加速动力学系统的广义高斯最小拘束原理

变加速运动在日常生活和工程问题中普遍存在.变加速动力学又称牛顿猝变动力学,因其在混沌理论和非线性动力学中的应用而获得广泛关注.高斯原理是一个具有极值性质的微分变分原理.因此,研究变加速动力学系统的广义高斯原理在理论和应用两方面都有重要意义.文章提出并研究变加速动力学系统的广义高斯原理.首先,引入急动度空间的广义高斯变分概念,将质点的达朗贝尔原理对时间求导数后与广义高斯变分点乘,并利用高斯意义下的理想约束条件,建立了变加速动力学系统的广义高斯原理.在此基础上,通过构造广义拘束函数建立并证明变加速动力学系统的广义高斯最小拘束原理,并给出原理的阿佩尔形式、拉格朗日形式和尼尔森形式.其次,研究原理对变质量力学的推广.从密歇尔斯基方程出发,将它对时间求导并与广义高斯变分点乘,建立了具有理想约束的变质量变加速动力学系统的广义高斯原理.通过构造变质量系统的广义拘束函数,建立并证明变质量力学系统变加速运动的广义高斯最小拘束原理.文中以开普勒-牛顿空间问题为例,利用所得的广义高斯最小拘束原理方法进行计算,验证了方法的有效性.     

Effect of measurement on the geometric phase during evolution of a quantum system

The effect of measurement on the development of the geometric phase is discussed during the evolution of a quantum system, for the model of measurement considered. It is shown that the development of the geometric phase is inhibited in the limit of high frequency of measurement, thereby erasing the memory of the quantum system.     

A Weak Convergence Theorem for A Finite Family of Asymptotically Nonexpansive Mappings

The purpose of this paper is to prove a new weak convergence theorem for a finite family of asymptotically nonexpansive mappings in uniformly convex Banach space.     

Effects of exogenic chloride on oxidative degradation of chlorinated azo dye by UV-activated peroxodisulfate

Recently, the degradation of organic compounds in saline dye wastewater by sulfate radicals (SO₄⁻)-based advanced oxidation processes (AOPs) have attracted much attention. However, previous studies on these systems have selected non-chlorinated dyes as model compounds, and little is known about the transformation of chlorinated dyes in such systems. In this study, acid yellow 17 (AY-17) was selected as a model of chlorinated contaminants, and the degradation kinetics and evolution of oxidation byproducts were investigated in the UV/PDS system. AY-17 can be efficiently degraded (over 98% decolorization) under 90 min irradiation at pH 2.0–3.0, and the reaction follows pseudo-first order kinetics. Cl^‒ accelerated the degradation of AY-17, but simultaneously led to an undesirable increase of absorbable organic halogen (AOX). Several chlorinated byproducts were identified by liquid chromatography-mass spectrometry (LC–MS/MS) in the UV/PDS system. It indicates that endogenic chlorine and exogenic Cl^– reacted with SO₄⁻ to form chloride radicals, which are involved in the dechlorination and rechlorination of AY-17 and intermediates. The possible degradation mechanisms of AY-17 photooxidative degradation are proposed. This work provides valuable information for further studies on the role of exogenic chloride in the degradation of chlorinated azo dyes and the kinetic parameters in the PDS-based oxidation process.     

橡胶基多效协同自修复防水复合材料的研究

制备了环氧树脂改性高吸水纤维,随后将改性纤维与天然橡胶通过混、流延、压延、硫化等工艺制备了环境友好型三层复合自修复防水材料,通过SEM、FT-IR、TY-8000万能材料试验机、BTS-001电动不透水仪等考察了自修复防水材料的微观结构、机械性能、抗氧化性能、自修复性能及防渗透性能等。结果表明,高吸水纤维有助于提高其拉伸强度,最大拉伸强度为1.83MPa,断裂伸长率达到700%以上。防水材料完全切断,自修复24h后,其切口部分无可见痕迹,裂口完全愈合,且24h内无水滴渗漏。自修复48h后拉伸强度可达原始材料的2.36倍,断裂伸长率达到80%左右。     

X-Ray Structure of 8-Quinolinolato Lanthanide Complex: (8-Quinolinolato)bis(2,6-di-tert-butyl-4-methylphenoxo)samarium

Ｉｎｔｒｏｄｕｃｔｉｏｎ8 Ｈｙｄｒｏｘｙｑｕｉｎｏｌｉｎｅｉｓａｃｌａｓｓｉｃａｌｃｈｅｌａｔｉｎｇａｇｅｎｔｆｏｒｔｒａｎｓｉｔｉｏｎｍｅｔａｌｓａｎｄｌａｎｔｈａｎｉｄｅｓ .Ｒｅｃｅｎｔｌｙｍｅｔａｌｃｏｍ ｐｌｅｘｅｓｉｎｃｏｒｐｏｒａｔｉｎｇ 8 ｑｕｉｎｏｌｉｎｏｌａｔｏｌｉｇａｎｄｓｈａｖｅｒｅｃｅｉｖｅｄｍｏｒｅａｎｄｍｏｒｅａｔｔｅｎｔｉｏｎ .Ｔｈｅｒｅｓｅａｒｃｈｉｎｔｅｒｅｓｔｐｒｏｂａｂｌｙａｒｉｓｅｓｆｒｏｍｔｗｏａｓｐｅｃｔｓ .Ｆｉｒｓｔ,8 ｑｕｉｎｏｌｉｎｏｌａｔｏｍｅｔ…     

Extremes for coherent risk measures

Various concepts appeared in the existing literature to evaluate the risk exposure of a financial or insurance firm/subsidiary/line of business due to the occurrence of some extreme scenarios. Many of those concepts, such as Marginal Expected Shortfall or Tail Conditional Expectation, are simply some conditional expectations that evaluate the risk in adverse scenarios and are useful for signaling to a decision-maker the poor performance of its risk portfolio or to identify which sub-portfolio is likely to exhibit a massive downside risk. We investigate the latter risk under the assumption that it is measured via a coherent risk measure, which obviously generalizes the idea of only taking the expectation of the downside risk. Multiple examples are given and our numerical illustrations show how the asymptotic approximations can be used in the capital allocation exercise. We have concluded that the expectation of the downside risk does not fairly take into account the individual risk contribution when allocating the VaR-based regulatory capital, and thus, more conservative risk measurements are recommended. Finally, we have found that more conservative risk measurements do not improve the fairness of the cost of capital allocation when the uncertainty with parameter estimation is present, even at a very high level.     

氢氧化铁溶胶制备条件对其电泳等性能的影响

In order to explore the optimum preparation conditions, effects of FeCl₃ dosage, hydrolysis temperature and dialysis time on the particle size, conductivity, pH and double layer potential (ζ) of Fe(OH)₃ sol were systematically studied. The ultraviolet-visible reflection spectrophotometry was used to track the particle size of Fe(OH)₃ sol. With the increase of FeCl₃ dosage, the particle size of the colloid increased, the reflectivity decreased and the reflection wavelength shifted to longer wavelength, which is in accordance with the quantum confinement effect theory. The excessive Cl^- would inhibit the conductivity, and the stability of Fe(OH)₃ sol with larger particle size would be worse. Because of the better synergistic effect of q/m and V/l under the action of electric field of 80 V with electrophoresis, the ζ of the Fe(OH)₃ sol prepared under the optimum conditions (c_FeCl3, 0.01 mol·L^-1; 100℃; dialysis time, 1 d) was 43.67 mV which was most close to the theoretical value of 44.00 mV.     

Evaluation of the porous structure development of chars from pyrolysis of rice straw: Effects of pyrolysis temperature and heating rate

The effects of pyrolysis temperature and heating rate on the porous structure characteristics of rice straw chars were investigated. The pyrolysis was done at atmospheric pressure and at temperatures ranging from 600 to 1000 °C under low heating rate (LHR) and high heating rates (HHR) conditions. The chars were characterized by ultimate analysis, field emission scanning electron microscope (FESEM), helium density measurement and N₂ physisorption method. The results showed that temperature had obvious influence on the char porous characteristics. The char yield decreased by approximately 16% with increasing temperature from 600 to 1000 °C. The carbon structure shrinkage and pore narrowing occurred above 600 °C. The shrinkage of carbon skeleton increased by more than 22% with temperatures rising from 600 to 1000 °C. At HHR condition, progressive increases in porosity development with increasing pyrolysis temperature occurred, whereas a maximum porosity development appeared at 900 °C. The total surface area (S_total) and micropore surface area (S_micro) reached maximum values of 30.94 and 21.81 m²/g at 900 °C and decreased slightly at higher temperatures. The influence of heating rate on S_total and S_micro was less significant than that of pyrolysis temperature. The pore surface fractal dimension and average pore diameter showed a good linear relationship.