Study of the shade tabs of the toothguide 3D master through cluster analysis

To find out whether the 26 shade tabs of the Toothguide 3D Master can be grouped according to the five groups of lightness proposed by the manufacturer (Vita‐Zahnfabrik) the three color coordinates L*, C*, and h were studied. Upper central incisor color was measured through the Easyshade Compact spectrophotometer using 1361 participants aged between 16 and 89. The color of the middle third was registered in the Toothguide 3D Master nomenclature and in the CIELCh‐system. Principal Component Analysis and Cluster analysis, were applied for data processing. The statistical analysis reveals the existence of five cluster groups. Cluster 1 comprises samples 1M1 ‐ 2L1.5 ‐ 2M1 ‐ 2R1.5 ‐ 3L1.5 ‐ 3M1. Cluster 2 comprises 1M2 ‐ 2L2.5 ‐ 2M2 ‐ 2M3 ‐ 2R2.5 ?3M2 ‐ 3L2.5. Cluster 3 comprises 3R1.5 ‐ 4L1.5 ‐ 4L2.5 ‐ 4M1 ‐ 4M2 ‐ 4R1.5 ‐ 5M1. Cluster 4 comprises 3M3 ‐ 3R2.5 ‐ 4M3 ‐ 4R2.5. And, finally, Cluster 5 comprises: 5M2 ‐ 5M3. The 26 shade tabs in the Toothguide 3D Master can be grouped into five clusters following coordinates L*, C*, and h resulting from the dental spectrophotometer Vita Easyshade compact. The shade tabs that compose each cluster do not belong to the same lightness group. © 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 194–200, 2015     

Color of natural tooth crown in Japanese people

The aim of this study was to investigate the color of the natural maxillary incisor tooth from Japanese people of all age groups. These results were compared with the Trubyte Bioblend shade guide. The subjects of this study were in the age range of 13–84, 42 male and 45 female making 87 people in total. Areas with 1.0‐mm diameter at five sites were measured along the tooth axis for L*,a*,b*, according to CIELAB color spaces using a Spectroradiometric Color Computer. At the incisal site, two significant positive correlations were found between age and a* (r = 0.376, p < 0.001), and b* (r = 0.483, p < 0.001). At the center site, a significant negative correlation (r = −0.418, p < 0.001) was found between age and L*, but positive correlation (r = 0.497, p < 0.001) was found between age and b*. At the cervical site, a significant negative correlation (r = −0.326, p < 0.01) was found between age and L*, but positive correlation (r = 0.702, p < 0.001) was found between age and b*. Near the root, particularly, the values of a* were greater than those suggested by the Trubyte Bioblend shade guide. In conclusion, as the Trubyte Bioblend shade guide does not match the natural tooth color in red‐green chromaticity near the root, it is significant for us in dentistry to develop new shade guides that match the Japanese people based on the data collected. © 2000 John Wiley & Sons, Inc. Col Res Appl, 25, 43–48, 2000     

Color stability of denture shade tabs is affected by exposure to daylight and decontamination protocols

The purpose of this study was to investigate the effect of light exposure and decontamination protocols on the color stability of denture shade guide tabs. Fifty tabs for shades 62, 66, and 69 (Biotone IPN, Dentsply Sirona) were submitted to baseline L*a*b* measurements (EasyShade, Vita), separated into 5 experimental groups (n = 10), and subjected to one of the following conditions: G1–distilled water (DW‐H₂O)–control; G2 ?70% alcohol; G3–sodium hypochlorite 1% (NaClO); G4–no light exposure; G5–natural light exposure for 6 months. The experimental conditions were designed to simulate 6 months of clinical use. After the test period, final color measurements were recorded. The mean tristimulus coordinate difference (ΔL*,Δa*,Δb*) and total color difference values () were analyzed using 2‐way ANOVA and the Tukey test, α = .05. G2 (alcohol) produced less (P < .05) color change in shade 69 than G3 (NaClO). G5 (light exposure) affected the color stability for all shades, producing a statistical difference (P < .05) from G4 (no light exposure). It was concluded that natural light changes the color stability of the shade guides and that decontamination with 70% alcohol had the least impact on the color stability of the shade guide tabs.     

A preliminary comparison of CIE color differences to textile color acceptability using average observers

Ninety‐six nylon pairs were prepared, including red, yellow, green, and blue standards, each at two lightness levels with CIE94 ΔE units ranging from 0.15 to 4.01. Visual assessments of acceptability were carried out by 21 females. Logistic regression compared visual results to four color‐difference equations, CIELAB, CMC, CIE94, and CIEDE2000. It was found that CMC most closely represented judgments of average observers. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 288–294, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20124     

Hybrid biogeography based optimization for constrained optimal spot color matching

Biogeography‐based optimization (BBO) is a new evolutionary algorithm which mimics the immigration and emigration of species among islands. Used widely in packaging and printing to obtain a colorful appearance, the spot color matching (SCM) is formulated as a complex multi‐dimensional optimization problem. In this article, BBO is combined with the harmony search (HS) and opposition‐based learning (OBL) approaches to construct an effective hybrid algorithm for solving the SCM problem. HS is used to enhance the local searching ability of BBO, and OBL is employed to increase the diversity of initial population; consequently, the exploration and exploitation abilities of the hybrid algorithm are enhanced and well balanced. Experiment results are presented to show the effectiveness of the proposed scheme. © 2013 Wiley Periodicals, Inc. Col Res Appl, 39, 607–615, 2014     

浅析乘用车颜色匹配控制方法

介绍了色彩空间和基本原理,分析了影响整车外观色差的主要因素,包括油漆材料、喷涂工艺、喷涂环境、喷涂设备,提出了控制汽车外观色差的方法。     

Image quality evaluation for high dynamic range and wide color gamut applications using visual spatial processing of color differences

High dynamic range (HDR) and wide color gamut imagery has an established video ecosystem, spanning image capture to encoding and display. This drives the need for evaluating how image quality is affected by the multitudes of ecosystem parameters. The simplest quality metrics evaluate color differences on a pixel‐by‐pixel basis. In this article, we evaluate a series of these color difference metrics on four HDR and three standard dynamic range publicly available distortion databases consisting of natural images and subjective scores. We compare the performance of the well‐established CIE L*a*b* metrics (ΔE₀₀ , ΔE₉₄ ) alongside two HDR‐specific metrics (ΔE_Z [J_za_zb_z], ΔE_ITP [IC_TC_P]) and a spatial CIE L*a*b* extension (). We also present a novel spatial extension to ΔE_ITP derived by optimizing the opponent color contrast sensitivity functions. We observe that this advanced metric, , outperforms the other color difference metrics, and we quantify the improved performance with the steps of metric advancement.     

The new deviate visual functions improving the instrumental estimation on the visual color difference for the metamers with about 1° field size

Although the CIE1931 and 1964 color matching functions have been used in color specification for decades, many researchers, from Allen in 1970 to Hu and Houser in 2006, have found that there still exists a great visual mismatch on the discrimination of color difference as in terms of the CIE color matching functions. Hence, some significant error would be made on color specification due to employing the CIE1931 and 1964 color matching functions. Therefore, six color difference formulae developed from different experimental methods are used to derive various deviate visual functions (DVFs) respectively, and to investigate the effect of these DVFs on the performance of the color difference formulae tested in estimating visual color difference. The results indicate that the performance of the color difference formulae in estimating color difference is significantly improved by the deviate visual functions derived in this study. The CIE94 color difference formula has the best performance in predicting the total visual color difference (ΔV_T) using the DVFs and DVFIIs having the mean values 29 and 27 in PF/4 unit, respectively, while the CMC(l:c) the worst the ones 37 and 38. © 2009 Wiley Periodicals, Inc. Col Res Appl, 34, 115–127, 2009     

Multiobjective optimization for designing and operating more sustainable water management systems for a city in Mexico

This article proposes a multiobjective optimization model for the design of a macroscopic water system of a Mexican city that solves simultaneously the planning and scheduling of water storage and distribution tasks. The model, which considers rainwater harvesting and reclaimed water reusing as alternative water sources, maximizes the revenues from water sales and minimizes simultaneously the water consumption and land use. A case study based on the city of Morelia in Mexico was solved. It was found that the use of alternative water sources (such as harvested rainwater) along with an appropriate planning and scheduling of storage and distribution tasks have the potential to reduce the pressure over natural reservoirs significantly. Our approach considers simultaneously economic and environmental concerns, thereby contributing to the implementation of more sustainable alternatives in urban water distribution. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2428–2446, 2015     

A Benders decomposition framework for the optimization of disjunctive superstructures with ordered discrete decisions

This study introduces the logic-based discrete-Benders decomposition (LD-BD) for Generalized Disjunctive Programming (GDP) superstructure problems with ordered Boolean variables. The key idea is to obtain Benders cuts that use neighborhood information of a reformulated version of Boolean variables. These Benders cuts are iteratively refined, which guarantees convergence to a local optimum. A mathematical case study, the optimization of a network with Continuous Stirred-Tank Reactors (CSTRs) in series, and a large-scale problem involving the design of a distillation column are considered to demonstrate the features of LD-BD. The results from these case studies have shown that the LD-BD method exhibited good performance by finding attractive locally optimal solutions relative to existing logic-based solvers for GDP problems. Based on these tests, the LD-BD method is a promising strategy to solve optimal synthesis problems with ordered discrete decisions emerging in chemical engineering applications.     

Using redundancy to strengthen the relaxation for the global optimization of MINLP problems

In this paper we present a strategy to improve the relaxation for the global optimization of non-convex MINLPs. The main idea consists in recognizing that each constraint or set of constraints has a meaning that comes from the physical interpretation of the problem. When these constraints are relaxed part of this meaning is lost. Adding redundant constraints that recover that physical meaning strengthens the relaxation. We propose a methodology to find such redundant constraints based on engineering knowledge and physical insight.     

A discrete particle swarm optimization approach for classification of Indian coal seams with respect to their spontaneous combustion susceptibility

Mine fires due to spontaneous combustion in coal mines is a global concern. This leads to serious environmental and safety hazards and considerable economic losses. Therefore it is essential to assess and classify the coal seams with respect to their proneness to spontaneous combustion to plan the production, storage and transportation capabilities in mines. This paper presents the formulation of clustering problem into a linear assignment model and the application of a discrete particle swarm optimization approach for the classification of coal seams based on their proneness to spontaneous combustion. In this research work, twenty nine coal samples of varying ranks belonging to both high and low susceptibilities to spontaneous combustion have been collected from all the major coalfields of India. Using moisture, volatile matter, and ash content and crossing point temperature of the coal samples as the parameters, the proposed algorithm has been applied to classify the coal seams into three different categories. This classification will be useful for the planners and field engineers for taking ameliorative measures in advance for preventing the occurrence of mine fires.     

基于离散粒子群的气液二相流型特征选择

针对气液二相流型识别中存在的大量无关或冗余的特征会降低分类器性能的缺陷,提出了离散粒子群算法(BPSO)和最小二乘支持向量机(LS-SVM)封装模式的流型特征选择方法.该方法分别采用小波包和经验模式分解方法(EMD)对原始压差波动信号进行分解,分别提取原始信号和各分解信号的时域量纲一指标组成融合特征.然后采用BPSO进...     

Using new packages for modelling, equation oriented simulation and optimization of a cogeneration plant

The development and testing of an equation-oriented (EO) mathematical model for the optimization of heat and power systems using a new state-of-the-art sequential quadratic programming (SQP) method called filterSQP has been reported in an earlier paper. The model has been extended to include combined cycle cogeneration plants (CCCPs), the economic optimization of which involves adding equipment investment, cost functions and operating cost models to the stream and unit operation models of the earlier paper. These systems are of substantial industrial interest and are substantially larger than those in Rodríguez-Toral et al., Computers and Chemical Engineering, August 2000. Their size and complexity required the use of a new flexible modelling system (FMS) recently created within our research group. FMS can be used to set up large systems of equations, create networks to be modelled and give starting guesses easily for problems of any size. Also, FMS is able to interact with solvers for EO simulation and optimization, which have been developed here and elsewhere. A number of EO simulation and optimization examples, from simple unit operations to a whole real cogeneration plant involving a commercial gas turbine with 1275 variables and equations, are used to demonstrate the applicability of the CCCP model and the modelling package.     

A generalized framework for solving dynamic optimization problems using the artificial chemical process paradigm: Applications to particulate processes and discrete dynamic systems

The solution of optimal control problems (OCPs) becomes a challenging task when the analyzed system includes non-convex, non-differentiable, or equation-free models in the set of constraints. To solve OCPs under such conditions, a new procedure, LARES-PR, is proposed. The procedure is based on integrating the LARES algorithm with a generalized representation of the control function. LARES is a global stochastic optimization algorithm based on the artificial chemical process paradigm. The generalized representation of the control function consists of variable-length segments, which permits the use of a combination of different types of finite elements (linear, quadratic, etc.) and/or specialized functions. The functional form and corresponding parameters are determined element-wise by solving a combinatorial optimization problem. The element size is also determined as part of the solution of the optimization problem, using a novel two-step encoding strategy. These building blocks result in an algorithm that is flexible and robust in solving optimal control problems. Furthermore, implementation is very simple.The algorithm's performance is studied with a challenging set of benchmark problems. Then LARES-PR is utilized to solve optimal control problems of systems described by population balance equations, including crystallization, nano-particle formation by nucleation/coalescence mechanism, and competitive reactions in a disperse system modeled by the Monte Carlo method. The algorithm is also applied to solving the DICE model of global warming, a complex discrete-time model.