Optimization of slot-coating processes: minimizing the amplitude of film-thickness oscillation

Slot coating is one of the most common coating methods for high-precision coatings. The flow limits of steady-state operation have been extensively analyzed in the literature. However, even the best-designed slot-coating operations are subjected to small oscillations on process conditions, such as flow rate, vacuum pressure and gap fluctuations. These time-dependent events lead to thickness variations on the deposited liquid layer that may be unacceptable for product performance. Therefore, the design of slot-coating processes, e.g. the specification of process conditions and die geometry, has to take into account not only the behavior of steady-state flow but also how the flow responds to small periodic disturbances. The process parameters should be such that the film-thickness oscillation is minimized. In this study, coating-thickness variations related to an ongoing oscillation of the coating gap is studied for different process parameters and frequency of the perturbation by solving the transient Navier–Stokes equations with appropriate boundary conditions for free-surface flow. The amplitude of the deposited film-thickness oscillation is used as the objective function of a bound-constrained optimization algorithm. The results show that at a fixed web speed and wet thickness, the film-thickness amplitude may be reduced by a factor of 4 by adjusting other process parameters.     

Structure-Preserving Reshape for Textured Architectural Scenes

Modeling large architectural environments is a difficult task due to the intricate nature of these models and the complex dependencies between the structures represented. Moreover, textures are an essential part of architectural models. While the number of geometric primitives is usually relatively low (i.e., many walls are at surfaces), textures actually contain many detailed architectural elements.
We present an approach for modeling architectural scenes by reshaping and combining existing textured models, where the manipulation of the geometry and texture are tightly coupled. For geometry, preserving angles such as oor orientation or vertical walls is of key importance. We thus allow the user to interactively modify lengths of edges, while constraining angles. Our texture reshaping solution introduces a measure of directional autosimilarity to focus stretching in areas of stochastic content and to preserve details in such areas.
We show results on several challenging models, and show two applications: Building complex road structures from simple initial pieces and creating complex game-levels from an existing game based on pre-existing model pieces.     

Use of aggregates for road fills in the mangrove regions of Brazil

The paper describes an experiment performed on the use of natural aggregates, on a large scale, as a new alternative for highway fills in mangrove regions, where the subsoil is basically formed by soft and sensitive marine clays. The use of such aggregates has advantageously substituted the common processes used in those regions, that is the use of conventional compacted earth-fill on the ground surface or sand fills, performed in excavated trenches and then also used as subgrade reinforcement.     

Numerical evaluation of a granular column reinforced by geosynthetics using encasement and laminated disks

Structures built on soft strata may experience substantial settlement, large lateral deformation of the soft layer and global or local instability. Granular columns reinforced by geosynthetic materials reduce settlement and increase the bearing capacity of the composite ground. Reinforcement is more common in the form of geosynthetic encasement, but laminated disks can also be used. This paper compares these two forms of reinforcement by means of unit cell finite element analyses. Numerical results were initially validated using field and experimental data, and parametric studies were subsequently performed. The parametric studies varied the geosynthetic interval and the geosynthetic tensile stiffness of the laminated disks as well as the length of the reinforced column. The analyses showed that in both modes; encasement and laminated disks; the geosynthetic increases the vertical stress mobilized on the reinforced column and reduces settlement on soft soil. It was also observed that in order to achieve the same performance as with encased column, the optimum interval between laminated disks is dependent on the stiffness of the geosynthetics and the column reinforced length.     

Spatial heterogeneities,institutions, and income: Evidence for Brazil

Political institutions are an essential component to explain income variation. Brazilian municipalities are characterized by a great contrast in the colonization process and its impacts on the current income level and distribution, and other development aspects. This study analyzes the spatial heterogeneity of the relationship between institutional quality and the municipalities' economic development. We use a spatial moving window method applied to weighted regressions—Geographically Weighted Regression (GWR). We find evidence that good institutions increase income and other variables related to economic development. In addition, the institutional quality influence on economic development measures is distinct across the Brazilian regions.     

Influence of the addition of grinding dust to a magnesium phosphate cement matrix

Magnesium phosphate cement materials were prepared by reacting magnesium oxide with water-soluble phosphates such as mono-ammonium dihydrogen phosphate (ADP), which solidified at ambient temperature through the formation of hydrated phases in the material. Cylindrical specimens of magnesium phosphate cement were molded and varying amounts (0–40% weight) of grinding dust, waste generated in the clutch disc finishing process by grinding and polishing, were added to the ceramic matrices. The influence of the addition of grinding dust on the characteristics of the cement compositions was verified in terms of setting time, apparent porosity, density and leaching/solubilization tests. The setting time was analyzed according to NM 65 (the Vicat needle) and by indirect calorimetric measurements, the apparent porosity and density of the materials were analyzed by the water immersion method, based on the Archimedes principle. Using an Instron 5500R universal testing machine, various analyses were made to ascertain how the different waste contents in the compositions affected the mechanical strength (axial compression and tensile strength by diametral compression). The results obtained proved highly satisfactory for the application of this waste as an additive in magnesium phosphate mortars. The addition of grinding dust to the magnesium phosphate cement matrix did not affect the formation of new phases or the setting time to any appreciable extent, but an increase in grinding dust content led to an initial increase in strength up to a given limit (about 30% of waste).     

Effect of dentin pretreatment with potassium oxalate: A 6‐year follow‐up

Oxalate‐based products are effective against dentine sensitivity and have been studied as an option to improve long‐term adhesive bonding strength. Our aim was to evaluate the effect of potassium oxalate on the microtensile bond strength (µTBS) of the dentin/resin interface after 24 h, 1, and 6 years. Dentin on the occlusal surface of 16 human premolars was exposed and etched with 35% phosphoric acid. The teeth were divided into four groups. Two groups received 3% monohydrated potassium oxalate and the following adhesive systems and composites: Adper Scotchbond Multipurpose + FiltekZ350 (3M/ESPE) and Prime & Bond NT + Esthet‐X (Dentsply). Two control groups did not receive potassium oxalate. Teeth were cut into sticks and kept in distilled water at 37°C for 24 h, 1, and 6 years. The sticks underwent µTBS testing after storage. ANOVA, Tukey's post hoc test, and paired t test were used to compare storage times (α = 0.05). The fracture mode of the specimens was classified under a stereomicroscope (40×). Morphology of the hybrid layer and the fracture pattern were observed with scanning electronic microscopy (SEM). Mean µTBS was high at 24 h and decreased after 1 and 6 years. After 6 years, the mean µTBS values were similar with no statistically significant difference between the groups (p = .121). SEM images showed proper dentin hybridization. Dentin pretreatment with potassium oxalate did not affect hybrid layer formation, but bond strength decreased over time after 24 h. Therefore, the clinical use of potassium oxalate to increase dentin bond durability is not indicated.     

Sequential experimental design for model discrimination: Taking into account the posterior covariance matrix of differences between model predictions

Techniques for experimental design of experiments for model discrimination constitute important tools for scientists and engineers, as analyzed phenomena can very often be described fairly well by different mathematical models. As interpretation and use of available experimental data depend on the model structure, techniques for design of experiments for selection of the best model are of fundamental importance. Besides, experiments must often be designed for estimation of model parameters and reduction of variances of model predictions (or parameter estimates). These two classes of experimental design techniques generally lead to different experimental designs, although model discrimination and reduction of variances of parameter estimates are closely related to each other. In this work the posterior covariance matrix of difference between model predictions is taken into account during the design for model discrimination for the first time. The obtained results show that the model discrimination power becomes much higher when the posterior covariance matrix of difference between model predictions are considered during the experimental design, increasing the capability of model discrimination and simultaneously leading to improved parameter estimates.