Comparison of different uncertainty techniques in urban stormwater quantity and quality modelling

Urban drainage models are important tools used by both practitioners and scientists in the field of stormwater management. These models are often conceptual and usually require calibration using local datasets. The quantification of the uncertainty associated with the models is a must, although it is rarely practiced. The International Working Group on Data and Models, which works under the IWA/IAHR Joint Committee on Urban Drainage, has been working on the development of a framework for defining and assessing uncertainties in the field of urban drainage modelling. A part of that work is the assessment and comparison of different techniques generally used in the uncertainty assessment of the parameters of water models. This paper compares a number of these techniques: the Generalized Likelihood Uncertainty Estimation (GLUE), the Shuffled Complex Evolution Metropolis algorithm (SCEM-UA), an approach based on a multi-objective auto-calibration (a multialgorithm, genetically adaptive multi-objective method, AMALGAM) and a Bayesian approach based on a simplified Markov Chain Monte Carlo method (implemented in the software MICA). To allow a meaningful comparison among the different uncertainty techniques, common criteria have been set for the likelihood formulation, defining the number of simulations, and the measure of uncertainty bounds. Moreover, all the uncertainty techniques were implemented for the same case study, in which the same stormwater quantity and quality model was used alongside the same dataset. The comparison results for a well-posed rainfall/runoff model showed that the four methods provide similar probability distributions of model parameters, and model prediction intervals. For ill-posed water quality model the differences between the results were much wider; and the paper provides the specific advantages and disadvantages of each method. In relation to computational efficiency (i.e. number of iterations required to generate the probability distribution of parameters), it was found that SCEM-UA and AMALGAM produce results quicker than GLUE in terms of required number of simulations. However, GLUE requires the lowest modelling skills and is easy to implement. All non-Bayesian methods have problems with the way they accept behavioural parameter sets, e.g. GLUE, SCEM-UA and AMALGAM have subjective acceptance thresholds, while MICA has usually problem with its hypothesis on normality of residuals. It is concluded that modellers should select the method which is most suitable for the system they are modelling (e.g. complexity of the model’s structure including the number of parameters), their skill/knowledge level, the available information, and the purpose of their study.     

Evolution of the fractal dimension for simultaneous coagulation and sintering

Simulation results on the evolution of aggregate structure in aerosol processes with coagulation and sintering as the dominant mechanisms are presented. A model for simulation of the three-dimensional morphology of nano-structured aggregates formed by concurrent coagulation and sintering is applied. The model is based on a stochastic diffusion controlled cluster-cluster aggregation algorithm and sintering is modeled as a successive overlapping of spherical primary particles, which are allowed to grow in order to maintain mass conservation. This leads to computer simulated structured aggregates which are then subject to evaluation. Two different methods to determine the fractal dimension are presented which give comparable results. It is shown that even very small particles show the same fractal behavior. Furthermore, equilibrium structures assuming a constant ratio of the characteristic collision time to the characteristic fusion time are considered as well as the kinetics of structural changes due to a change in the ambient conditions.     

Rapid production of micropatterned surfaces using a fluid dynamical instability

The continuous, high speed patterning of polyethylene films with a micron‐structured silicone coating was investigated in a roll coating process that did not depend on the use of prestructured tools. Thermally curable polydimethylsiloxane (PDMS) resin was rheologically modified by the addition of highly agglomerated, aerosol‐derived silica and resulted in a Herschel–Bulkley fluid. Application of the modified siloxane in a roll coating process resulted in a fluid dynamical instability at high capillary numbers promoting the spontaneous formation of randomly branched surface structures. The shear‐thinning properties of the nanoparticle‐doped PDMS resin were adjusted as to preserve the wet, structured coating during the following thermal curing step. The highly regular pattern was characterized in terms of averaged branch width and could be controlled from micro‐ to millimeter size by adjusting coating roll velocity and roll gap distance. The adhesive properties of the structured coating were compared to unstructured conventional silicone coatings by measuring the release force of pressure‐sensitive adhesives. For rubber‐based tape, the release force of patterned PDMS was reduced by a factor of up to eight if compared to smooth reference silicone. These ultra‐low adhesive coatings may find applications in packaging, food processing, and for covering sanitary surfaces, offering a cost‐effective alternative to conventional surface structuring methods. POLYM. ENG. SCI., 46:1541–1547, 2006. © 2006 Society of Plastics Engineers     

Synthesis and Functionalization of Fullerenes Encapsulating Atomic Phosphorus

Synthesis, purification, and electron spin properties of the endohedral fullerene P@C₆₀ are reported. Highly enriched material could be obtained for the first time, making this molecule accessible for further experiments. We report the first successful chemical modification of P@C₆₀ via cyclo-propanation to the C_2v symmetric monoadducts P@C₆₁(COOCH₃) and P@C₆₁(COOC₂H₅). X-band electron spin resonance data are presented and discussed. The phosphorus atom shows anisotropic hyperfine coupling in the modified fullerenes, in contrast to the unmodified case, and in contrast to similarly modified N@C₆₀.     

Elastic properties of adhesive polymers. II. Polymer films and bond lines by means of nanoindentation

Seven different polymers used frequently as adhesives and/or matrix polymers in wood, wood composites, and natural fiber‐reinforced composites were studied by uniaxial tensile tests and nanoindentation. It was shown that the elastic modulus, the hardness, the creep factor, and the elastic‐, plastic‐, and viscoelastic work of indentation of the seven different polymers is essentially the same regardless whether the polymers were tested in the form of pure films or in situ, i.e., in an adhesive bond line with spruce wood. An excellent correlation was found between the elastic modulus measured by tensile tests and the elastic modulus measured by nanoindentation. In spite of the good correlation, the elastic modulus measured by nanoindentation is significantly higher than the elastic modulus measured by tensile tests. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:1234–1239, 2006     

多轴加工提高生产效率

经济性和适用性是对加工大型零件加工中心的主要要求。Handtmann公司推出的双主轴高速加工机床,为生产力设定了新的标准。任何一家企业要想在市场上取得成功,就必须按用户要求不断改进其产品。Handtmann公司推出的UBZ龙门式加工中心不仅扩展了该公司的产品系列,而且在整个产品设计过程中与用户保持合作。同等占地面积,金属切除率提高一倍采用模块化设计,利用经过结构优化的不同模块可构成能满足用户要求的高效生产系统。由于机床占用空间已构成工厂规划的重要因素,在此情况下,必须寻求考虑到这个方面的解决办法,这就是转向双主轴的原因。…     

ZF公司面向中国的高性能变速器

文章介绍了ZF公司为轮式装载机特别研发的WG系列高性能变速器,其产品系列可覆盖9-30吨级的车辆.ZF高性能的动力换档变速器具有简单和坚固的零部件设计、采用精确调整轴承、整体式壳体结构和优越的电控系统等优点.     

Investigation on the effectiveness of the repair method 8.3 “Corrosion protection by increasing the electrical resistivity” in chloride-containing concrete Part 2: Chloride redistribution in concrete after application of a system sealing surface protective coating

This DFG-funded research project aimed to gain a better understanding of the mechanisms of the W-Cl repair principle within the framework of fundamental investigations, to contribute to the creation of the necessary basis for a broader application of the repair principle in practice. The focus was on the development of a model to describe the chloride redistribution after the application of a system sealing surface protective coating. On the basis of Fick's second law of diffusion, a mathematical model with a self-contained analytical solution was developed, with the help of which the chloride redistribution after application of a system sealing surface protective coating can be calculated under the idealized assumption of complete water saturation of the concrete. Furthermore, the influence of the dehydration of the concrete, expected as a result of the application of the repair principle W-Cl, on the chloride redistribution was investigated. On the basis of laboratory tests and numerical simulations, material-specific reduction functions were developed to quantify the relationship between the chloride diffusion coefficient and the ambient humidity.