An adaptive cut‐cell method for environmental fluid mechanics

In this work we present a numerical method for solving the incompressible Navier–Stokes equations in an environmental fluid mechanics context. The method is designed for the study of environmental flows that are multiscale, incompressible, variable‐density, and within arbitrarily complex and possibly anisotropic domains. The method is new because in this context we couple the embedded‐boundary (or cut‐cell) method for complex geometry with block‐structured adaptive mesh refinement (AMR) while maintaining conservation and second‐order accuracy. The accurate simulation of variable‐density fluids necessitates special care in formulating projection methods. This variable‐density formulation is well known for incompressible flows in unit‐aspect ratio domains, without AMR, and without complex geometry, but here we carefully present a new method that addresses the intersection of these issues. The methodology is based on a second‐order‐accurate projection method with high‐order‐accurate Godunov finite‐differencing, including slope limiting and a stable differencing of the nonlinear convection terms. The finite‐volume AMR discretizations are based on two‐way flux matching at refinement boundaries to obtain a conservative method that is second‐order accurate in solution error. The control volumes are formed by the intersection of the irregular embedded boundary with Cartesian grid cells. Unlike typical discretization methods, these control volumes naturally fit within parallelizable, disjoint‐block data structures, and permit dynamic AMR coarsening and refinement as the simulation progresses. We present two‐ and three‐dimensional numerical examples to illustrate the accuracy of the method. Copyright © 2008 John Wiley & Sons, Ltd.     

Approaches to uncertainty evaluation based on proficiency testing schemes in chemical measurements

Since the advent of the Guide to the Expression of Uncertainty in Measurement (GUM) founding the principles of uncertainty evaluation, numerous projects have been carried out to develop alternative practical methods when it is impossible to model technical or economical aspects of the measurement process. These methods can use all the experimental data available to the laboratories, such as repeatability, reproducibility, quality-control charts, etc. The studies presented in this paper compare the results obtained by the modelling method from GUM with the uncertainties found by applying alternative methods. They show two examples, one in the field of environmental monitoring, the other in the biomedical field, based on the exploitation of PT schemes results. Presented at BERM-11, October 2007, Tsukuba, Japan.     

Studies of the naturally occurring biomethylation of selenium and the determination of the products

A systematic study of the biomethylation of selenium and the determination of the methylated species indicates preliminarily that selenium is susceptible to natural biomethylation under certain environmental conditions. Detectable levels of methylated selenium species, including dimethyl selenide [(CH₃)₂Se], dimethyl diselenide [(CH₃)₂Se₂] and dimethylselenone [(CH₃)₂SeO₂] have been detected by gas chromatography – graphite furnace atomic absorption spectrophotometry (GC – GF AA) from a variety of environmental samples. Findings of naturally methylated selenium species from both soil samples and related air samples suggest that there may exist a localized cycle of selenium between ground soil and the ambient air. Factors that influence the sensitivity and accuracy for the determination of alkyl selenide compounds by GC – GF AA have also been investigated. Flashlike injection mode and addition of about 10% of hydrogen gas to the argon carrier gas provide for highly sensitive detection. Reproducible determination can be obtained with a precision of about 6% and the detection limits are 0.3 ng Se m^?3.     

地铁车辆段咽喉区上盖建筑振动影响

城区地铁车辆段进行上盖物业开发可节约、集约利用地铁用地,缓解城市土地资源稀缺问题。地铁车辆段特别是其咽喉区振动是上盖物业开发的环境制约因素。为研究地铁车辆段咽喉区对上盖建筑的振动影响,建立轨道-地基土-上盖建筑三维有限元模型,采用等效荷载法,将实地采样的钢轨铅垂向振动加速度转化为列车钢轨铅垂向振动线荷载,作用于轨道上。在结合实测数据验证模型合理性的基础上,定量研究上盖平台厚度和离地高度、上盖建筑层数和结构等因素对室内环境振动(铅垂向Z振级VL_Zmax)的影响。结果表明,地铁车辆段咽喉区对高层建筑的振动影响整体大于多层建筑;由于振动波在屋顶自由端发生反射并与入射波叠加,导致不同楼层楼板中央VL_Zmax随楼层升高略有增加;框架结构建筑室内VL_Zmax大于剪力墙结构;增加上盖平台厚度可减小建筑室内VL_Zmax;上盖建筑室内VL_Zmax随上盖平台离地高度增加而增加(即随建筑楼层绝对离地高度增加而增大)。研究结果可为地铁车辆段上盖物业开发振动污染防治提供理论和工程技术依据。     

绿色环保化学机械抛光液的研究进展

原子级加工制造是实现半导体晶圆原子尺度超光滑表面的有效途径.作为大尺寸高精密功能材料的原子级表面制造的重要加工手段之一,化学机械抛光(chemical mechanical polishing,CMP)凭借化学腐蚀和机械磨削的耦合协同作用,成为实现先进材料或器件超光滑无损伤表面平坦化加工的关键技术,在航空、航天、微电子等众多领域得到了广泛应用.然而,为了实现原子层级超滑表面的制备,CMP工艺中常采用的化学腐蚀和机械磨削方法需要使用具有强烈腐蚀性和高毒性的危险化学品,对生态系统产生了不可逆转的危害.因此,本文以绿色环保高性能抛光液作为对象,对加工原子量级表面所采用的化学添加剂进行分类总结,详尽分析在CMP过程中化学添加剂对材料表面性质调制的作用机理,为在原子级尺度下改善表面性质提供可参考的依据.最后,提出了CMP抛光液在原子级加工研究中面临的挑战,并对未来抛光液发展方向作出了展望,这对原子尺度表面精度的进一步提升具有深远的现实意义.     

The S.M.A.R.T. (small mass,affordable, rapid,transfer-less) digestion method for heavy metal determinations

The S.M.A.R.T. (small mass, affordable, rapid, transfer-less) digestion method was developed to determine heavy metal concentrations in small sample masses. The S.M.A.R.T. digestion method is a hot water bath digestion where sample digestion and dilution are performed in the original sample tube. This method is faster than the typical methods used and reduces potential sources of error. Masses as small as 0.01 g have been digested and analysed using this method. The preparation and digestion time is reduced from 10 h to less than 4 h. Acid volumes are reduced from millilitres to microlitres and the only disposable supplies needed are sample tubes and pipette tips. Method accuracy was determined by digesting seven replicates of two standard reference materials using the S.M.A.R.T. method and analysing samples by inductively coupled plasma mass spectrometry. The S.M.A.R.T. digestion method was found to provide excellent recoveries for Al (76 ± 2.7%), Mn (99 ± 11%), Co (92 ± 17%), Ni (93 ± 28%), Cu (109 ± 33%), Zn (97 ± 7.1%), As (108 ± 20%), Sr (90 ± 12%), Mo (84 ± 23%), Ag (91 ± 1.8%), Cd (95 ± 6.2%), Sn (139 ± 52%) and Pb (95 ± 22%). This study has successfully developed an efficient and reproducible digestion method for heavy metal determination in limited biomass samples.     

流动注射分析在环境水质重金属检测中的应用进展

重金属具有毒性大、不易被代谢、易被生物富集并有生物放大效应等特点,不但污染水环境,也严重威胁人类和水生生物的存在。近年来各类水环境中重金属污染日趋加剧,重金属的检测及处理方法有多种,而流动注射分析技术以其自动化程度高、分析速度快、精密度高、分析成本低等优点在水环境监测方面占有重要地位。介绍了流动注射在重金属检测方面的应用。     

水中镉含量的激光诱导击穿光谱高灵敏快速检测

 为了对水中的痕量镉进行高灵敏快速检测,实验采用一种未受污染的薄木片作为基底来吸收水样品,将其晾干后再用激光诱导击穿光谱（LIBS）技术对其进行分析,克服了用LIBS技术直接分析水样品时灵敏度低和稳定性差等问题。实验中选择214.44 nm的镉离子线作为分析线以提高光谱检测的灵敏度,建立了用于定量分析的校正曲线,镉的检出限达到55 μg/L,重复测量的信号相对标准偏差小于5%,单次测量的时间短于5 min。     

A life cycle framework for the investigation of environmentally benign nanoparticles and products

While significant advances in our understanding of the behavior of engineered nanoparticles in the environment continue, there remains a need to engage the nanoparticle research community directly in the development and evaluation of environmentally benign nanoparticles to ensure that nanomaterial‐based industries emerge as tools for sustainability rather than environmental liabilities. Current research efforts aimed at understanding the environmental implications of nanotechnology emphasize existing groups of nanoparticles and products already in commercial distribution. While this is clearly necessary, this approach fails to identify and address the many tradeoffs associated with product performance and environmental quality. We believe this to be a critical gap in the ongoing exploration of nanostructured materials and their properties and applications. We posit that a number of issues are not being holistically addressed, including resource availability and allocation, manufacturing energy requirements and embodied energy, material efficiency, environmental properties of nanomaterials and nanoproducts, and waste generation. An interdisciplinary approach to research, based on the life cycle paradigm and devoted to the identification, investigation, synthesis, testing, and analysis of groups of new, more environmentally conscious nanoparticles is needed. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Probing Ag nanoparticle surface oxidation in contact with (in)organics: an X‐ray scattering and fluorescence yield approach

Characterizing interfacial reactions is a crucial part of understanding the behavior of nanoparticles in nature and for unlocking their functional potential. Here, an advanced nanostructure characterization approach to study the corrosion processes of silver nanoparticles (Ag‐Nps), currently the most highly produced nanoparticle for nanotechnology, is presented. Corrosion of Ag‐Nps under aqueous conditions, in particular in the presence of organic matter and halide species common to many natural environments, is of particular importance because the release of toxic Ag⁺ from oxidation/dissolution of Ag‐Nps may strongly impact ecosystems. In this context, Ag‐Nps capped with polyvinolpyrrolidone (PVP) in contact with a simple proxy of organic matter in natural waters [polyacrylic acid (PAA) and Cl^? in solution] has been investigated. A combination of synchrotron‐based X‐ray standing‐wave fluorescence yield‐ and X‐ray diffraction‐based experiments on a sample consisting of an approximately single‐particle layer of Ag‐Nps deposited on a silicon substrate and coated by a thin film of PAA containing Cl revealed the formation of a stable AgCl corrosion product despite the presence of potential surface stabilizers (PVP and PAA). Diffusion and precipitation processes at the Ag‐Nps–PAA interface were characterized with a high spatial resolution using this new approach.