酚类抗氧化剂的主要转化产物 ——醌的研究进展

酚类抗氧化剂在抗氧化过程中的主要转化产物为醌类物质，为了更深入地了解这些醌类物质的特点，从化学结构、检测方法、抗氧化作用等方面总结常用抗氧化剂生育酚、鼠尾草酚、迷迭香酚、茶多酚、特丁基对苯二酚（TBHQ）的主要转化产物生育醌、鼠尾草醌、迷迭香醌、表儿茶素类醌及叔丁基对苯醌（TBBQ）的研究进展，另外，对一些醌类的细胞毒性进行了归纳。上述几种酚类抗氧化剂的转化产物醌类物质，多采用高效液相色谱法检测，它们中大部分具有抗氧化活性，有些则在一定条件下具有促氧化效果。目前，关于醌类细胞毒性的研究主要集中在TBBQ和生育醌。今后应加强醌类物质抗氧化作用、细胞毒性以及定量分析方法等方面的研究，以期为科学认识抗氧化剂和开发新型抗氧化剂奠定基础。The main transformation products of phenolic antioxidants in the antioxidant process are quinones. In order to gain a deeper understanding of the properties of these quinones, the progress of research on the main transformation products (tocoquinone, sage quinone, rosemary quinone, epigallocatechin quinone and tert-butyl benzoquinone (TBBQ)) of the commonly used antioxidants (tocopherol, carnosol, rosemanol, tea polyphenols and tert-butyl hydroquinone (TBHQ) ) was reviewed in terms of their chemical structures, detection methods, antioxidant activities, and the cytotoxicity of some of them. Quinones, the transformation products of the above phenolic antioxidants, are mostly detected by high performance liquid chromatography (HPLC) and most of them have antioxidant activity, while some have pro-oxidant effects under certain conditions. Currently, studies of quinone cytotoxicity mainly focus on TBBQ and tocoquinone. In the future, research on the antioxidant effects, cytotoxicity and quantitative analysis methods of quinones should be intensified to lay the foundations for the scientific understanding of antioxidants and the development of new antioxidants

Premixed flame ignition: Theoretical development

Premixed flame ignition is a fundamental issue in combustion. A basic understanding of this phenomenon is crucial for fire safety control and for the development of advanced combustion engines. Significant efforts have been devoted to understanding the mechanisms of ignition and determining critical ignition conditions, such as critical flame radius, minimum ignition energy, and minimum ignition power, which have remained challenging research topics for centuries. This review provides an in-depth investigation of the forced-ignition of laminar premixed flames in a quiescent flammable mixture, with emphasis on theoretical developments, particularly those based on activation energy analysis. First, the fundamental concepts are overviewed, including spark ignition, characteristic time scales, and critical ignition conditions. Then, the chronological development of premixed flame ignition theories is discussed, including homogeneous explosion, thermal ignition theory, flame ball theory, quasi-steady ignition theory, and, more importantly, transient ignition theory. Premixed flame ignition consists of three stages: flame kernel formation, flame kernel expansion, and transition to a selfsustaining flame. These stages are profoundly affected by the coupling of positive stretch with preferential diffusion, characterized by the Lewis number. Specifically, positive stretch makes the expanding ignition kernel weaker at larger Lewis numbers, consequently increasing the critical ignition radius and MIE. The premixed flame ignition process is dominated by flame propagation dynamics. Both quasi-steady and transient ignition theories demonstrate that the critical flame radius for premixed ignition differs from either flame thickness (by thermal ignition theory) or flame ball radius (by flame ball theory). Particularly, the transient ignition theory appropriately acknowledges the "memory effect" of external heating, offering the most accurate description of the evolution of the ignition kernel and the most sensible evaluation of minimum ignition energy. In addition, the effects of transport and chain-branching reactions of radicals, finite droplet vaporization, and repetitive heating pulses on premixed flame ignition are discussed. Finally, a summary of major advances is provided, along with comments on the applications of premixed flame ignition theory in ignition enhancement. Suggested directions for future research are presented

Theoretical analysis on the forced ignition of a quiescent mixture by heat and radical sources

Forced ignition of premixed flame plays a crucial role in fundamental combustion research. In this work, a theoretical investigation is conducted interpreting the flame kernel development subject to heat and radical ignition sources. Adopting simplified two-step reaction mechanism, the present theoretical model incorporates both chain-branching and recombination reaction paths and reveals their synergistic effect during the forced ignition process. The transient evolution of flame kernel driven by heat and radical addition can be obtained by solving an implicit ordinary differential equation, which is rigorously derived from first principles based on large activation energy asymptotics. The findings reveal that an increase in fuel Lewis number adversely affects the fuel supply rate at the flame front, while a decrease in the radical Lewis number inhibits radical accumulation, both of which exhibit negative impacts on ignition process. For ignition source with uniform rate profile, there exist a critical heating power, below which the flame kernel cannot reach the critical radius despite extended ignition duration. Exceeding this threshold, the minimum ignition energy varies non-monotonically with increasing heating power. Particularly, comparing with the purely thermal ignition source, the heat and radical ignition sources can effectively reduce the thermal load on ignition device, which can be attributed to the synergistic effects of heat and radicals in the ignition process. A comparative analysis on various rate profiles of ignition source, including uniform, trigonometric and Gaussian, indicates that the Gaussian profile has superior efficiency in facilitating flame kernel expansion and transition to self-sustained spherical flame. Specifically, ignition source with Gaussian profile shows the lowest minimum ignition energy, which is primarily due to its capability for concentrated and optimally timed energy deposition, especially for large fuel Lewis numbers. The present analysis provides insightful understandings of forced ignition for premixed flame and offers practical perspectives for real-world applications

Design of Supervisory Controller by Incorporating Dynamic Model into PCA

提出了一种新的监督控制器设计方法。利用降价的简化动态模型,通过在线仿真计算得到数据阵,然后把它们结合到PCA模型中,形成了组合动态模型与PCA模型的监督控制器设计。通过两个仿真实例表明,新方法改进了基本PCA监督控制器存在的问题,能适应不可建模扰动的影响

Modeling and Control of Sequencing Batch Reactors for Wastewater Treatment Processes

近年来采用序批式反应器工艺进行生化污水处理的研究日益受到关注 .在工艺流程设计、模型建立、操作优化、控制器设计等都取得大量的成果 .本文综述了这个领域一些最新的、与未来应用有关的研究进展

Modelling and Simulation of Integrated Urban Wastewater System

城市排污系统由排水管网、污水处理厂和受纳河流三部分组成。评价整个系统的性能以及建立实现可持续与有效管理的控制策略都需要将系统集成为一个整体模型。集成建模是一项复杂的任务,这不仅因为模型的庞大,还因为由于历史上各子系统的建模方法与建模目的不同所造成子系统模型在状态变量、过程等方面的不匹配.选择合适的基于ASM的各子系统模型,通过模型连接器实现不同子系统模型状态变量的相互转化,建立一个集成城市污水系统模型,可以实现集成城市污水系统的并行仿真

Software Development for Simulating Biological Wastewater Treatment Processes

基于国际水协会工作组发布的有关文件,构造了典型污水生化处理过程仿真的软件平台。所开发的软件不仅能够模拟脱碳、硝化脱氮、反硝化脱氮和脱氮除磷四种典型污水生化处理工艺过程的动态特性,也能够评价各种复杂先进控制策略的实施效果以及用于教育培训等。通过在不同气象输入条件下,仿真上述四种工艺配置以及在反硝化脱氮工艺控制评价上的应用等工作,表明了这个仿真系统的性能和有效性

波斑鸨在河北省的首次发现与饲养

波斑鸨（Otis undulata）与大鸨（O、tarda）、小鸨（O、tetrax）同属于鹤形目鸨科。据文献记载,仅分布于我国新疆西北部、苏联、亚洲西南部和北非等某些地区,冬时向南不超过阿拉伯半岛和印度西南部。河北省未见记载。 1985年4月,在河北省保定地区博野县一农户院捕到一只波斑鸨,送到保定市人民公园内喂养、展出。据查,此为国内动物园饲养展出波斑鸨的首例。波斑鸨外形似鸡,但具有长且为三个趾的足掌。体型较大鸨为小（全长645mm）。上体棕黄而杂以黑斑,头颈部淡棕色,喉白,前胸深灰色,下体自前胸以下纯白。嘴铅灰色,先端近黑色;脚、趾也为铅灰色、爪黑色。头顶和颈侧均具有

Review on research progress in process control

随着新材料、新工艺的不断涌现,对反馈控制系统性能的要求更加严格和精确,在过程控制领域出现了许多新的挑战性研究问题.首先综述了非线性分布参数过程(例如材料微结构、颗粒分布、流体流动)的控制、生物系统与生物医学过程的分析与控制、城市污水处理集成监控系统等的最新研究进展以及一些未来的研究方向.其次讨论了解决复杂控制问题所需的一些方法和集成工具,主要包括过程系统工程理论和方法、集成物理装置与通讯网络的控制系统组成等.最后指出了目前控制应用相对薄弱的领域是控制理论与工程界关注的重点