Predicting the spectral reflectance factor of translucent paints using Kubelka‐Munk turbid media theory: Review and evaluation

The use of Kubelka‐Munk (K‐M) turbid media theory in predicting the spectral reflectance factor of an opaque specimen from the specimen's constituent optical constants is well established in practice and well described in the literature. For translucent samples, there is a paucity of published results and the approaches are disparate. Accordingly, a review of K‐M theory and its application for predicting the spectral reflectance factor of translucent samples is presented and tested. Four methods for determining the absorption and scattering coefficients with respect to a certain film thickness are described: the black‐white method, the infinite method, the masstone‐tint method, and the two‐region method. The black‐white and infinite methods use the general form of the K‐M equation. The masstone‐tint method can be used for both the general form and the opaque simplification. The two‐region method, combining opaque and translucent approaches, was enhanced in this research and included an opacity calculation to automatically differentiate opaque and translucent spectral regions and a smoothing technique to combine both spectral regions. The two‐region method was tested using a set of acrylic‐emulsion artist paints and glazes spanning a range of opacities from opaque to nearly transparent. The results were reasonable and provided statistically significant improvement compared with the opaque simplification, commonly used in art conservation science and industrial color matching. © 2009 Wiley Periodicals, Inc. Col Res Appl, 34, 417–431, 2009     

Linear modeling of modern artist paints using a modification of the opaque form of Kubelka‐Munk turbid media theory

A new model of turbid medium theory is proposed that combines the best parts of the opaque forms of Kubelka‐Munk single and two constant models. This model introduces an impurity index, a spectrally nonselective scattering coefficient for each chromatic component. The new model is shown to have a convex, linear dependence on colorant concentration so that it can be used for colorant identification in high‐resolution images of works of art while offering an extension to the single constant model that can predict the absorption and scattering of paints, both in mixture and pure (masstone) forms. The model was tested and validated using 28 matte acrylic dispersion paints, of the type used in modern painting. These paints had a wide range of absorption and scattering characteristics. © 2016 Wiley Periodicals, Inc. Col Res Appl, 42, 308–315, 2017     

New deviate observer (JF‐DO) obtained from experimental color‐matching functions for small fields of real observers

The CIE established the Standard Deviate Observer (SDO) CIE 1989 for fields of 10°, enabling the evaluation of discrepancies caused by the variability among these observers. This observer could also be applied to smaller fields, depending on the physiological causes of this variability in color‐matching functions (cmf's) among observers. Here, we have obtained a new Deviate Observer (which we call JF‐DO) established from the cmf's for small fields (2°) corresponding to two groups of real observers: JAM, MM and CF; AY, JR, MR, JL, JA and FA. Both groups of cmf's were measured experimentally in our laboratories using one for each of the different experimental methods and devices. All the new cmf's of the 9 real observers were referred to a new, unique system of unreal primaries, which we call X′Y′Z′ (derived in a way similar to that of the CIE 1931 XYZ system of unreal primaries). To establish a new JF‐DO for small fields, we followed a procedure similar to the one used by the CIE to establish the CIE 1989 SDO. A comparative study was also made between the cmf's of the CIE 1989 SDO (established for fields of 10°), the SDO from Stiles‐Burch (which we call Poza‐SDO, developed for small fields), and our JF‐DO. For this comparison, the cmf's of all these deviate observers were referred to the new system of unreal primaries X′Y′Z′. © 2003 Wiley Periodicals, Inc. Col Res Appl, 28, 209–215, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.10146     

Automatic detection of layout of color yarns of yarn‐dyed fabric. Part 1: Single‐system‐mélange color fabrics

To recognize the layout of color yarns of single‐system‐mélange color fabric automatically, a novel FCM‐based stepwise classification method is proposed in this article. This method consists of three main steps: (1) warp yarn segmentation, (2) weft color recognition, and (3) the layout of color warps recognition. In the first step, the yarn segmentation method based on mathematical statistics of subimages is adopted to localize warp yarns preliminarily; and then the segmentation results of warp yarn are corrected by misrecognized‐boundary remove and missing‐boundary interpolation. In the second step, the weft color is extracted based on RGB color histograms of whole fabric image. In the third step, the pixels in each warp yarn are classified into two clusters by fuzzy C‐means clustering (FCM) algorithm in CIELAB color model separately, and the preliminary recognized layout of color warps is obtained. All warp colors are clustered by FCM algorithm in CIELAB color model again and the precise layout of color warps is output. The experimental and theoretical analysis proved that the proposed method can recognize the layout of color yarns of single‐system‐ mélange color fabrics with satisfactory accuracy and good robustness. © 2015 Wiley Periodicals, Inc. Col Res Appl, 40, 626–636, 2015     

A Flow Time Model for Melt‐Cast Insensitive Explosive Process

Diphasic flows of concentrated suspensions of melt‐cast insensitive explosives exhibit specific rheological properties. In order to limit the handling of pyrotechnical products presenting a risk with respect to the mechanical and thermal shocks, a lot of work has been undertaken for many years in the civil engineering sector. The objective of this study is to propose a predictive model of the flow time of a concentrated suspension through a nozzle located at the bottom of a tank. Similar to our industrial process, the suspension is made out of insensitive energetic materials and flows under gravity. Experimental results are compared to three models (Quemada, Krieger‐Dougherty, and Mooney) predicting the viscosity μ of a suspension as a function of the solid volume fraction ϕ, the maximum packing density ϕ_m and the viscosity μ₀ of the interstitial liquid. De Larrard's model is used to calculate ϕ_m. The value of viscosity measured for the pure liquid is close to the one predicted by the Bernoulli theorem, where liquids are considered as incompressible and inviscid. Finally, it was found that the Quemada's model gives a fair agreement between predictions and experiments.     

A three‐function numerical model for the prediction of vulcanization‐reversion of rubber during sulfur curing

The cross‐linking mechanisms of sulfur vulcanization are not analytically known and, therefore, reticulation kinetics has to be deduced macroscopically from standardized tests. One of the most popular laboratory test to characterize curing and reversion is the oscillating disk rheometer ODR, which gives a quantitative assessment of scorch, cure rate, and state of cure. In this article, a numerical two‐step approach, which is based on the utilization of experimental ODR data and aimed at predicting the degree of vulcanization of thick rubber items cured with accelerated sulfur, is presented. In step one, a composite numerical three‐function curve is used to fit experimental rheometer data, able to describe the increases of the viscosity at successive curing times and at different controlled temperatures, requiring only few points of the experimental cure curve to predict the global behavior. Both the case of indefinite increase of the torque and reversion can be reproduced with the model. In step two, considering the same rubber compound of step one, numerical cure curves at different temperatures are collected in a database and successively implemented in a Finite Element software, which is specifically developed to perform thermal analyzes on complex 2D/3D geometries. As an example, an extruded thick EPDM section is considered and meshed through eight‐noded isoparametric plane elements. Several FEM simulations are repeated by changing exposition time t_c and external curing temperature T_n, to evaluate for each (t_c,T_n) couple the corresponding mechanical properties of the item at the end of the thermal treatment. A recently presented bisectional approach, alternating tangent (AT), is used to drastically reduce the computational efforts required to converge to the optimal solution associated with the maximum value of an output property, tensile strength. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Fluid‐phase coexistence for the oxidation of CO2 expanded cyclohexane: Experiment,molecular simulation,and COSMO‐SAC

The gas solubility of pure oxygen and of pure carbon dioxide as well as of their gaseous mixture are measured in the ternary liquid mixture cyclohexane + cyclohexanone + cyclohexanol at 313.6 K with a high‐pressure view‐cell technique using the synthetic method. The new experimental data are used to assess the capability of molecular simulation and conductor‐like screening model (COSMO)‐SAC to predict multicomponent fluid‐phase coexistence behavior. These methods are also compared systematically on the basis of experimental binary fluid‐phase coexistence data. In that comparison also the Peng–Robinson (PR) equation of state is included as a reference. Molecular simulation and COSMO‐SAC yield good results and are found to be far superior to the PR equation of state both in predictive and in adjusted mode. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2236–2250, 2013     

A combined process of biocatalysis and cell activity regeneration for the asymmetric reduction of 3‐oxo ester with immobilized baker's yeast

BACKGROUND: A process combining biocatalytic reaction and cell activity regeneration was designed for the asymmetric reduction of 3‐oxo ester. By immobilizing resting baker's yeast (Saccharomyces cerevisiae) in calcium alginate beads, the high yield and long catalyst life were achieved in the aqueous phase in this process with methyl acetoacetate (MAA) as the model substrate. RESULTS: Two combined fixed‐bed reactors were able to work steadily for at least 16 days. The activity of immobilized baker's yeast could be retained by re‐culture with culture medium regularly. The re‐culture time for bead reactivation was optimized to be 30 h. High yield (about 80%) and high enantiomeric excess (>95%) were maintained after 12 batches of asymmetric reduction. The immobilized beads retained their original shapes even after a long reaction time in the fixed‐bed reactor, while the beads broke after reaction of five batches in a flask. CONCLUSION: The combined process of biocatalysis and cell activity regeneration was successfully achieved in the asymmetric reduction and decreased the breakage of beads as well as increased the efficiency of catalyst. Copyright © 2008 Society of Chemical Industry