Identification of coating defects in cathodically protected underground pipelines

Coating defects may occur, for many different reasons, at some points on the surface of a cathodically protected structure. These defects behave anodically and may cause strong localized corrosion. It is possible to identify the position of coating defects by using measured values of the electrochemical potential at some points in the electrolyte or on its surface. To achieve this, an inverse BEM‐based genetic algorithm is developed to identify the position of defects in cathodically protected underground pipelines. The formulation is validated through its application to practical problems involving strongly non‐linear polarization curves, infinite electrolytes, unknown number of defects and measurement noise. Copyright © 2003 John Wiley & Sons, Ltd.     

Applying spatial hydraulic principles to quantify stream habitat

Flow complexity plays an important role in stream ecology. Yet, a paucity of research exists with regard to quantifying flow complexity and relating it to the habitats that aquatic organisms utilize. Here we provide a generalized example of how two‐dimensional (2‐D) numerical hydraulic models and spatial hydraulic metrics can be used to simulate and quantify biologically important flow patterns within streams. A detailed topographic survey, incorporating meso‐scale topographic features (e.g. exposed boulders and bedrock outcrops) is performed for a small urbanized stream. The 2‐D hydraulic model RMA2 is then used to model the flow conditions within the stream reach. Model results demonstrate that the meso‐scale topographic features create highly complex flow patterns of potential biological importance. Recently developed spatial hydraulic metrics, based on hydraulic engineering principles (vorticity, circulation and kinetic energy gradients), are then used to quantify the various types of flow complexity found within the stream reach. In particular, spatial hydraulic metrics are used to quantify the stream reach's overall flow complexity and the flow complexity surrounding three chub mounds. A method for uniquely characterizing circulation zones is then developed and applied to five circulation zones within the study reach. The principles used in performing this study's topographic survey, spatial explicit hydraulic modelling and spatial hydraulic analyses, form a general framework for quantifying flow complexity in any stream. The ways in which using hydraulic models and spatial hydraulic metrics can help establish better habitat suitability criteria and design best management practices for use in stream and catchment area restoration projects is discussed. Copyright © 2005 John Wiley & Sons, Ltd.     

Statistical Uncertainty and the Estimation of Log Law Parameters

It is experimentally demonstrated that fitting the log law to the mean velocity profile in turbulent open-channel flow to determine the friction velocity, roughness length, and zero-plane displacement, can lead to relatively high standard errors in these parameters. It is also demonstrated that this approach, where the log law alone is used to estimate these parameters, may yield values of these parameters that are significantly different from those obtained when the friction velocity is determined independently of the log law. Although the statistical estimation of the three log law parameters from mean velocity data alone is frequently necessary, this procedure can lead to inaccurate and imprecise estimates of these quantities.     

Partially Adaptive Econometric Methods For Regression and Classification

Assumptions about the distributions of domain variables are important for much of statistical learning, including both regression and classification problems. However, it is important that the assumed models are consistent with the stylized facts. For example selecting a normal distribution permits modeling two data characteristics—the mean and the variance, but it is not appropriate for data which are skewed or have thick tails. The adaptive methods developed here offer the flexibility found in many machine learning models, but lend themselves to statistical interpretation, as well. This paper contributes to the development of partially adaptive estimation methods that derive their adaptability from membership in families of distributions, which are distinguished by modifications of simple parameters. In particular, we have extended the methods to include recently proposed distributions, including example applications and computational details.     

Cultural Differences in Collaborative Authoring of Wikipedia

This article explores the relationship between national culture and computer‐mediated communication (CMC) in Wikipedia. The articles on the topic game from the French, German, Japanese, and Dutch Wikipedia websites were studied using content analysis methods. Correlations were investigated between patterns of contributions and the four dimensions of cultural influences proposed by Hofstede (Power Distance, Collectivism versus Individualism, Femininity versus Masculinity, and Uncertainty Avoidance). The analysis revealed cultural differences in the style of contributions across the cultures investigated, some of which are correlated with the dimensions identified by Hofstede. These findings suggest that cultural differences that are observed in the physical world also exist in the virtual world.     

Τhe effect of wood‐fiber type on the thermomechanical performance of a biodegradable polymer matrix

The effect of type and content of wood fibers on the thermal, mechanical and rheological behavior of the commercial biodegradable polyester product, Ecovio® (BASF) is analytically studied. Ecovio® is basically a blend of poly(butylene adipate‐terephthalate) copolyester (Ecoflex®, BASF) and polylactide. Three different types of wood fibers, based either on raw cellulose (Arbocel) or selected conifers (Lignocel), with varying fiber size at various weight fractions were used for this purpose. The role of these fibers on the thermomechanical performance of Ecovio® was investigated in terms of several experimental techniques including scanning electron microscopy, differential scanning calorimetry, dynamic mechanical analysis, creep, tensile testing, and water uptake at room temperature. At the low wood fiber content (20 wt %), Lignocel composite's properties are predominant compared with the Arbocel composites. It has been found, that at this wood content, an efficient compatibility between matrix and fibers is achieved, leading to superior reinforcement. This trend is completely reversed at higher filler loading, probably due to the poor interfacial adhesion between the matrix and Lignocel occurring at 30 wt %. This behavior was supported by all the experimental methods employed. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42185.     

Benzotriazinyl‐mediated controlled radical polymerization of styrene

The stable free radical polymerization (SFRP) process based on (1,3‐diphenyl‐1,4‐dihydro‐1,2,4‐benzotriazin‐4‐yl), the so‐called ‘Blatter radical’, and several C‐7 substituted derivatives is introduced for the first time for the polymerization of styrene. Polystyrenes characterized by polydispersity indices in the 1.05 ? 1.27 range were obtained in the presence of the Blatter radical and its derivatives containing CF₃, Ph, Fur‐2‐yl and 4‐PhC₆H₄ substituents, while polymerization proceeded either in a non‐controlled manner or in very low polymerization yields in the presence of derivatives containing halogen (Cl, Br, I) substituents. This preliminary investigation, demonstrating the potential use of the Blatter radical and its derivatives in mediated SFRP, creates new opportunities to design and develop radicals to optimize performance in such polymerization processes. © 2013 Society of Chemical Industry     

Electrochromic devices operating with electrolytes based on boronate ester compounds and various alkali metal salts

Various polymer electrolytes based on boronate esters and different lithium and sodium salts have been evaluated in electrochromic (EC) devices based on WO₃ films. The results showed that the ionic conductivity of the electrolytes was not the most important parameter for the colouration performance of these devices. The use of solid electrolytes containing LiClO₄ resulted in a higher colouration performance than the corresponding liquid electrolytes, even though the latter exhibited a significantly higher conductivity. The results also showed that the transfer process at the interface between the WO₃ layer and the electrolyte played a major role for the colouration process. The presence of Lewis acidic boronate ester groups in the electrolytes significantly improved the performance of the EC devices. The incorporation of boron in the composition of the electrolytes allowed the use of solid electrolytes instead of liquid ones, thus avoiding leakage problems. Furthermore, the highest colouration performance was found in EC devices operating with inexpensive salts. Because of their poor stability, the electrolytes based on LiCl and LiBr were not suitable, while those incorporating LiClO₄ salt exhibited excellent overall characteristics.     

A triangular element based on Reissner-Mindlin plate theory

A new triangular plate bending element based on the Reissner-Mindlin theory is developed through a mixed formulation emanating from the Hu-Washizu variational principle. A main feature of the formulation is the use of a linear transverse shear interpolation scheme with discrete constraint conditions on the edges. The element is shown to avoid shear locking, converge to the Kirchhoff plate theory as the plate thickness approaches zero, and generally exhibit excellent behaviour on a series of standard problems and tests.