大口径反射镜高反射膜研究进展

大口径反射镜是大型反射式光学系统中关键的光学元件,在工作波段的反射率直接决定了光学系统的性能。随着地基、天基观测设备的发展,对大口径反射镜高反射膜提出了更宽的工作波段、更高的反射率、更好的环境适应性等要求。针对这些挑战,各种新的膜系结构、新的镀制方法、新的膜层材料纷纷出现,满足了大口径反射镜高反射膜的各种需求。本文对近些年国内外的大口径反射镜高反射膜研究进展予以综述,并预测大口径反射镜高反膜制备的技术趋势将由铝反射膜向银反射膜、由热蒸发向磁控溅射发展。     

电解水金属单原子催化剂的研究进展

氢能因其能量密度高、清洁无污染等特点,作为替代化石燃料的能源载体得到了广泛的研究.如何清洁高效地制备氢气受到了大量研究者的关注.当前,以化石能源的热反应所得副产氢气是主要来源.然而,采用该类方法不仅不能摆脱化石能源的使用以及温室气体的排放,还会造成生产氢气的纯度不高,碳氧化物杂质浓度过高的问题,严重影响氢气的后续使用.采用可再生能源(太阳能、风能等)所产富余电,进行电解水制氢,产生的氢气不含碳氧化合物杂质,纯度很高,可以真正实现碳的零排放,被认为是未来氢气来源的重要方式.目前,电解水制氢在制氢市场的所占份额较小,而造成这样局面的主要因素是该过程中的高能耗问题.为了降低能耗,开发高效催化剂加速两个电极上的电解反应的动力学尤为重要.近年,金属单原子催化剂(SACs)因其独特的结构,在很多研究中被用作电解水催化剂,进而开发出大量高性能的金属单原子电解水催化剂.本文综述了近年SACs在电解水催化方面的应用.首先,针对电解水反应本身,总结了阴阳极两侧的电极反应机制以及影响电极催化性能的关键吸附中间物种;然后,根据载体的不同,即合金、碳以及其它化合物将SACs分为三类,总结了相关电解水催化研究现状,并且针对不同类型SACs目前的发展情况,提出了它们各自存在的问题.其次,进一步总结了影响SACs电解水催化活性的因素,提出了四种决定SACs催化性能的影响因子,分别为金属原子的固有元素性质、配位环境、几何结构和负载量;同时讨论了这四类影响因素对SACs催化活性的影响机制,总结了调控各类影响因素的方法,为SACs的设计提出了一些建议.最后,展望了SACs在电解水催化中的应用,探讨了SACs在催化剂设计及催化机制研究方面的问题,提出了SACs在电解水催化中的未来发展方向.     

Functionalization of Graphene Oxide and its Biomedical Applications

Graphene oxide (GO) offers interesting physicochemical and biological properties for biomedicine due to its versatility, biocompatibility, small size, large surface area, and its ability to interact with biological cells and tissues. GO is a two-dimensional material of exceptional strength, unique optical, physical, mechanical, and electronic properties. Ease of functionalization and high antibacterial activity are two major properties identified with GO. Due to its excellent aqueous processability, amphiphilicity, surface functionalization capability, surface enhanced Raman scattering (SERS), and fluorescence quenching ability, GO chemically exfoliated from oxidized graphite is considered a promising material for biological applications. In addition, due to π-π* transitions, a low energy is required for electron movement, a property important in Biosensor and Bioimaging applications of GO. In this article, we present an overview of current advances in GO applications in biomedicine and discuss future perspectives. We conclude that GO is going to play a vital role in Biomedical applications in the near future.     

Wide-scope screening of polar contaminants of concern in water: A critical review of liquid chromatography-high resolution mass spectrometry-based strategies

The number of chemicals with potential to reach the environment is still largely unknown, which poses great challenges for both environmental scientists and analytical chemists. Liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS) is currently the instrumentation of choice for identification of wide-scope polar chemicals of concern (CECs) in water. This review critically evaluates all steps involved in screening for polar CECs in water, including sampling and extraction, analysis by LC-HRMS, data (pre-)treatment, evaluation and reporting. Passive samplers and direct injection, in combination with LC-HRMS, provide new opportunities compared with conventional grab water sampling, as do instrumental advances such as ion-mobility spectrometry coupled to HRMS (IM-HRMS). In this paper, we argue that target, suspect and non-target screening should not be viewed as three separate principles, but rather as conceptual approaches to general data treatment strategies that can be linked together. Due to the large amount of data generated, smart prioritisation strategies are needed, in particular for non-target screening, to reduce complexity and focus on data of high interest. We critically evaluate existing strategies and consider that each prioritisation step will result in data loss (as any other step in a screening study), requiring compromises depending on the research question to be tackled. Many different data treatment strategies have been developed in recent years, but structure elucidation remains a challenging and time-consuming task. We discuss current and potential future trends, e.g. effect-based methods that can be used as future prioritisation tools, technological advances like IM-HRMS and improved software solutions that can enable new data treatment strategies.     

大气环境下的钢筋混凝土桥梁时变可靠度分析

为了探究钢筋混凝土桥梁抗力退化对桥梁可靠性能的影响,综合考虑一般大气环境下混凝土强度、钢筋强度、混凝土与钢筋黏结性能的降低,建立普通钢筋混凝土桥梁的抗力退化时变模型,分析规范车辆荷载作用的桥梁时变可靠度。研究结果表明,(1)一般大气环境下,桥梁抗力随着服役时间的增加而减小,其中钢筋强度退化对桥梁抗力的影响最大,其次是钢筋与混凝土黏结性能降低,而混凝土强度退化对桥梁抗力的影响相对较小; (2)桥梁可靠指标随着服役时间的增加而减小,密集行车占比越大,桥梁承载能力失效的概率就越大;非平稳车载作用下的桥梁可靠指标小于平稳车载,桥梁需要维修补强的时间比平稳车载提前; (3)多梁式简支梁桥在建造时应该提高边梁的安全储备,在管养时可以采取限载措施进行干预。     

Development of a multi‐scale ocean model by using particle Laplacian method for anisotropic mass transfer

The direct injection of CO₂ into the deep ocean is one of the feasible ways for the mitigation of the global warming, although there is a concern about its environmental impact near the injection point. To minimize its biological impact, it is necessary to make CO₂ disperse as quickly as possible, and it is said that injection with a pipe towed by a moving ship is effective for this purpose. Because the injection ship moves over a spatial scale of O(10²km), a mesoscale model is necessary to analyse the dispersion of CO₂. At the same time, since it is important to investigate high CO₂ concentration near the injection point, a small‐scale model is also required. Therefore, in this study, a numerical model was developed to analyse CO₂ dispersion in the deep ocean by using a fixed mesoscale and a moving small‐scale grid systems, the latter of which is nested and moves in the former along the trajectory of the moving ship. To overcome the artificial diffusion of mass concentration at the interface of the two different grid systems and to keep its spatial accuracy almost the same as that in the small‐scale, a particle Laplacian method was adopted and newly modified for anisotropic diffusion in the ocean. Copyright © 2010 John Wiley & Sons, Ltd.     

Ocean internal waves interpreted as oscillation travelling waves in consideration of ocean dissipation

Most studies of the synthetic aperture radar remote sensing of ocean internal waves are based on the solitary wave solutions of the Korteweg-de Vries （KdV） equation, and the dissipative term in the KdV equation is not taken into account. However, the dissipative term is very important, both in the synthetic aperture radar images and in ocean models. In this paper, the traveling-wave structure to characterize the ocean internal wave phenomenon is modeled, the results of numerical experiments are advanced, and a theoretical hypothesis of the traveling wave to retrieve the ocean internal wave parameters in the synthetic aperture radar images is introduced.     

Persistent Random Walks in Stationary Environment

We study the behavior of persistent random walks (RW) on the integers in a random environment. A complete characterization of the almost sure limit behavior of these processes, including the law of large numbers, is obtained. This is done in a general situation where the environmental sequence of random variables is stationary and ergodic. Szász and Tóth obtained a central limit theorem when the ratio /, of right- and left-transpassing probabilities satisfies /a<1 a.s. (for a given constant a). We consider the case where / has wider fluctuations; we shall observe that an unusual situation arises: the RW may converge a.s. to infinity even with zero drift. Then, we obtain nonclassical limiting distributions for the RW. Proofs are based on the introduction of suitable branching processes in order to count the steps performed by the RW.     

软件复用技术实现策略研究

首先分析和提出了一种基于ＯＷＥ（ＯｂｊｅｃｔＷｉｔｈ Ｅｖｅｎｔ）的软构件描述方法,然后深入探讨了如何利用面向对象方法实现软件复用的策略,最后着重分析了继承机制对软件复用的支持以及在分布处理环境中的改进方案．