Hue uniformity and the CIELAB space and color difference formula

The hue uniformity of the CIELAB system is investigated using a hue circle of Munsell colors at value 6 and chroma 14 and experimentally determined hue coefficient data. CIELAB hue differences for equal Munsell hue increments are found to vary up to nearly a factor 4, and hue coefficients differ from the experimentally determined ones by up to 40% at certain wavelengths. Dominant wavelengths assigned by the CIELAB system to individual Munsell hues are found to vary up to 35 nm from those of the Munsell Renotations. Four other color space systems are compared with widely differing but comparable results. The CIE 2° color-matching functions are adapted to result in a set of opponent-color functions accurately representing the Munsell Hue and Chroma data. A call is made for the experimental determination of the “standard hue observer” as a step toward an improved color space/color-difference formula. © 1998 John Wiley & Sons, Inc. Col Res Appl, 23, 314–322, 1998     

Color names,stimulus color,and their subjective links

The aim of the research reported by this study was on the one hand to identify what colors were associated with particular words in relation to a specific language (Italian), by portraying them in color stimuli on the screen of a monitor; and on the other hand to verify whether some words of that language denoted colors that were either particularly well defined or confused with others. In an experiment using special software, the subjects were asked to produce colors directly, instead of choosing among a number of colors presented on the screen. The results showed that (i) it is possible to identify the color‐stimuli to which the terms of a language refer; that (ii) the “best” colors Giallo (Yellow), Rosso (Red), Blu (Blue), and Verde (Green) which the subjects were requested to produce were very similar to the corresponding unique hues; that (iii) among the mixed hues there were perceptually intermediate colors, that is, ones exactly midway between two consecutive unique colors: Arancione (Orange) and Viola (bluish Purple); that (iv) Turquoise and Lime were clearly positioned in the mental space of color of the participants; and that (v) for Italian speakers some hues coincide: Azzurro (Azure) and Celeste (Cerulean); Arancione (Orange), RossoGiallo (RedYellow) and Carota (Carrot); Lime and GialloVerde (YellowGreen), so that their color terms can be considered synonyms. Our most interesting finding, however, is that for Italian speakers these four mixed colors with their specific names (Lime, Turchese (Turquoise), Viola (bluish Purple) and Arancione (Orange) fall perceptually in the middle of each of the four quadrants formed in the hue circle by the four unique hues. The resulting circle is therefore characterized by eight colors of which four are unique and four are intermediate mixed. It would be advisable to repeat the study cross‐culturally to test for possible similarities and differences in color meanings with speakers of different languages. © 2016 Wiley Periodicals, Inc. Col Res Appl, 42, 89–101, 2017     

The influence of color on impulsiveness and arousal: Part 1 – Hue

Impulsiveness and arousal are two similar yet distinct emotional and behavioral states that have been shown to be influenced by color in many fields, such as clothing and environment design. This series of studies investigates the fundamental theory of how color impacts on people's impulsiveness and arousal states. To achieve this goal, psychophysical methods were used to examine the impact of color environment on impulsiveness and arousal. Two main factors were used to quantify them: response time and error rate in problem solving. The psychophysical experiment was designed to examine whether, in a particular color environment, the response time and error rate were different. Participants sat in front of a large TV screen showing different colored backgrounds against which a range of psychometric tests were completed. The color backgrounds varied in hue. During the experiment, participants were required to give their responses to each of the psychometric tests as quickly and accurately as possible. The results showed that different colors can significantly influence response time and error rate, which suggests that color has a distinct influence on impulsiveness and arousal. Gender difference has also been investigated. This article mainly discusses hue influence on impulsiveness and arousal. The influence of chroma along with hue will be explored in the next article.     

Determination of constant Hue Loci for a CRT gamut and their predictions using color appearance spaces

A colorimetrically characterized computer-controlled CRT display was used to determine 24 loci of constant perceived hue for pseudo-object related stimuli, sampling the display's interior color gamut at constant lightness and the edge of its gamut at variable lightness. Nine observers performed three replications generating matching data at 132 positions. the constant hue loci were used to evaluate the correlation between perceived hue and hue angle of CIELAB, CIELUV, Hunt, and Nayatani color appearance spaces. the CIELAB, CIELUV, and Hunt spaces exhibited large errors in the region of the blue CRT primary, while the Nayatani and CIELUV spaces produced large errors in the region of the red primary for constant lightness stimuli. Along the edge of the CRT's color gamut (variable lightness stimuli), all the spaces had a similar trend, large errors in the cyan region. the differences in performance between the four spaces were not statistically significant for the constant lightness stimuli. For the variable lightness stimuli, CIELAB and CIELUV had statistically superior performance in comparison with the Nayatani space and equal performance in comparison with the Hunt space. It was concluded that for imaging applications, a new color appearance space needs to be developed that will produce small hue error artifacts when used for gamut mapping along loci of constant hue angle. © 1995 John Wiley & Sons, Inc.     

Simultaneous optimization and solution of systems described by differential/algebraic equations

Engineering approaches to the solution of constrained variational problems often involve converting the problem into a nonlinear programming (NLP) problem and solving it using current NLP methods. These methods usually use a sequential optimization and solution strategy. We propose a method, using piecewise constant functions for the independent variables, that combines the technologies of quasi-Newton optimization algorithms and global spline collocation to simultaneously optimize and integrate systems described by differential/algebraic equations. A computer implementable algorithm is discussed and three test problems are solved. The algorithm allows the solution of a more general class of optimization problems than previous methods employing this strategy.     

Dynamic simulation of chemical processes described by distributed and lumped parameter models

Currently available dynamic simulation routines are limited to processes in which the units can be described by lumped parameter models. In this paper, a general procedure is presented which permits the units to be described by both distributed and lumped parameter models. The partial differential equations resulting from a distributed parameter model are transformed into a set of ordinary differential equations by discretizing the spatial variable. The coupling of this set of discretized equations to the sets from other units is accomplished through the boundary conditions which represent the inlet and outlet of the unit. The resulting large set of time-dependent ordinary differential equations is solved simultaneously using a Gear-type integrator. The method is demonstrated by considering the start-up of a process composed of a tubular reactor, a gas absorption column and a completely mixed tank.     

Investigating seasonal color change in the environment by color analysis and information visualization

Color, as one of the most important dimensions of vision, plays a key role in place identity and people's experience in the environment. This study aims to investigate people's visual experience of seasonal color change in the environment, and proposes an approach for analyzing and communicating environmental colors by combining color analysis and information visualization. Employing crowdsourced Flickr photos, the approach is tested in four gardens: the Humble Administrator's Garden, Ryoanji, the Garden of Versailles, and Central Park in New York. The results show direct comparisons of seasonal color change patterns in different environments, and reflect characteristics of the environments as well as people's experience of color during the four seasons. The primary contribution of this study is to provide a way of communicating colors in landscape design and color research.     

直接染料色相特性在染料系偏光膜的应用初探

直接紫01、直接蓝02、直接黄03标准溶液色相系数分别为-0.8498、-3.117、-2.4441,不同染料标准溶液具有不同的色相特性。将直接染料色相特性应用于进料色相检验、染色液色相检测、染色液组成比例测定等,从源头确保染料色相稳定,监控了染色液的色相变化,对于保证染料系偏光膜产品的品质稳定具有重要的意义。     

Surface color and color constancy

Color constancy is often treated as the tendency of surfaces to stay the same perceived color under changing illumination or context (removing/adding/replacing surrounding objects). But these types of color constancies are not basic ones and there is another kind of color constancy that is fundamental for the explanation of all color constancy phenomena. We experience it when looking at a curved uniformly colored surface or when changing the shape of the surface. A new concept of surface color is developed and the variety of all perceived colors is suggested to be described as a nine-dimensional set of 3 X 3 matrices corresponding to different surface colors. Examples of color matrices calculated for some colored surfaces being viewed by the standard viewer are presented and arguments supporting the concept are discussed. It is shown that the set of color matrices represents all perceived colors quite adequately.     

Extension of dominant wavelength scale to the full hue cycle and evidence of fundamental color symmetry

Dominant wavelength is a psychophysical scale presently limited to the spectrum. It is extended into the nonspectrals to designate the hue cycle in a continuous wavelength-based scale. To omit the fading spectrum ends, the extended scale is based on the limited spectrum of optimum color stimuli (442–613 nm). The hue cycle interval is found by many methods in agreement, e.g., from the spacing of the ideal primaries (additive and subtractive). These were recently defined as the complementary maxima and minima of several visual functions (e.g., saturation/W, spectral sensitivity, λ discrimination, complementary efficiency). Five of these six primaries are spectral, uniformly spaced at (40 ± 4) nm intervals. Interpolating the sixth (531 c magenta) as similarly spaced between adjacent primaries (blue 447 nm and red 607 nm) gives it the dual designation 407/647 as both ends of the cycle, an interval equivalent to 240 nm. Nonspectral hues are numbered serially with wavelength by interpolating green–purple complementary pairs as sinusoidallike spectral pairs. Applying the extended scale to a color circle, the six primaries reveal a sextuple symmetry of (60 ± 2)°. Only these three pairs are both complements and opposites. In a graph (hue cycles as x and y axes) of x + y color-mixture, loci of constant λ center symmetrically on the RGB primaries near 607, 531, 447 nm. © 1993 John Wiley & Sons, Inc.     

Application of dynamic programming to high-dimensional systems described by difference equations

The application of dynamic programming using an interative procedure, which employs domain contraction and accessible grid points for the state vector, is investigated for solving optimal control problems where the system is described by a set of difference equations. A model of a gas absorber with six state variables and two control variables is used to examine the feasibility of the proposed algorithm and to analyze the effects of the grid size and of the domain contraction factor. This algorithm yields rapid convergence to the optimum even when a relatively coarse grid with as few as 11 grid points is used.     

The thermodynamic stability of coupled heat and mass transfer described by linear wave equations

Applying Liapounov's direct method it was shown that the distributed steady states, approached by the solutions of the non-Fourier (wave) equations of energy and mass transfer, are always stable if the well-known classical thermodynamics criterion of stability-the negativity of thermostatic matrix C, is met. The assumptions associated with the simplest structure of the wave equations are revealed on the basis of the thermodynamic stability analysis.     

The perception of static colored noise: Detection and masking described by CIE94

We present psychophysical data on the perception of static colored noise. In our experiments, we use the CIE94 color difference formula to quantify the noise strength and for describing our threshold data. In Experiment 1 we measure the visual detection thresholds for fixed pattern noise on a uniform background color. The noise was present in one of three perceptual color dimensions lightness (L*), chroma (C*), or hue (h). Results show that the average detection threshold for noise in L* is independent of hue angle and significantly lower than that for noise in C* or h. Thresholds for noise in C* and h depend on hue angle in an opponent fashion. The measured detection thresholds, expressed in terms of the components ΔL*/k_LS_L, ΔC*/k_CS_C, and ΔH*/k_HS_H that build up the CIE94 color difference formula are used to tune CIE94 to our experimental conditions by adjusting the parametric scaling factors k_L, k_C, and k_H. In Experiment 2, we measure thresholds for recognizing the orientation (left, right, up, down) of a test symbol that was incremental in L*, C*, or h, masked by supra‐threshold background noise levels in L*, C*, or h. On the basis of the CIE94 color difference formula we hypothesized (a) a constant ratio between recognition threshold and noise level when the test symbol and background noise are in the same perceptual dimension, and (b) a constant recognition threshold when in different dimensions. The first hypothesis was confirmed for each color dimension, the second however, was only confirmed for background noise in L*. The L*, C*, h recognition thresholds increase with increasing background noise in C* or h. On the basis of some 16,200 visual observations we conclude that the three perceptual dimensions L*, C*, and h require different scaling factors (hue dependent for C* and h) in the CIE94 color difference formula, to predict detection threshold data for color noise. In addition these dimensions are not independent for symbol recognition in color noise. © 2008 Wiley Periodicals, Inc. Col Res Appl, 33, 178–191, 2008     

Convex relaxations for global optimization under uncertainty described by continuous random variables

This article considers nonconvex global optimization problems subject to uncertainties described by continuous random variables. Such problems arise in chemical process design, renewable energy systems, stochastic model predictive control, and many other applications. Here, we restrict our attention to problems with expected‐value objectives and no recourse decisions. In principle, such problems can be solved globally using spatial branch‐and‐bound. However, branch‐and‐bound requires the ability to bound the optimal objective value on subintervals of the search space, and existing techniques are not generally applicable because expected‐value objectives often cannot be written in closed‐form. To address this, this article presents a new method for computing convex and concave relaxations of nonconvex expected‐value functions, which can be used to obtain rigorous bounds for use in branch‐and‐bound. Furthermore, these relaxations obey a second‐order pointwise convergence property, which is sufficient for finite termination of branch‐and‐bound under standard assumptions. Empirical results are shown for three simple examples. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3023–3033, 2018     

Two-phase interactions through turbulent events as described by fluid–particle correlations

An experimental investigation of a vertical upward, two-phase pipe flow was undertaken to measure kinematic parameters of the fluid and solid phases. The kinematic parameters included Reynolds stress distributions based on quadrant analyses that provided insight in understanding the behavior of two-phase kinematic correlation profiles. The data collected was based on a two-color digital particle image velocimetry (DPIV) technique that simultaneously measured the velocity fields of the fluid and solid phases.From quadrant analysis results, differences in Reynolds stress quadrant profiles between the single- and two-phase conditions were observed near the wall in the range 0.8>r/R>0.55, corresponding to wall distances between 35 and 75 viscous lengths (y+). Correlation coefficients between the two phases were then calculated, using the fluctuating velocity components of each phase. The extent of the interaction between the two phases was tracked by the changing correlation values versus distance from the wall. The correlation of the fluid and solid phase velocities was highest in the core region of the pipe (y+∼120), where the effect of turbulent events is reduced; low correlation coefficient values were found at y+<75, where differences of magnitudes, inflection points, etc. of burst and sweep event quadrant analysis profiles were observed.The extent of the influence of wall dynamic turbulent events on the solid phase was observed both by the differences in the relative Reynolds stress quadrant profiles and, more readily, by the changing values of two-phase axial and radial correlation coefficients determined from the simultaneous fluid and solid fluctuating velocities measured by the two-color DPIV methodology. These changing values of the correlation coefficients across the tube reflect the different responses of low inertia (fluid tracers) and high inertia (solid phase glass spheres) particles to the turbulent events. Similar profiles of the axial and radial correlation coefficients were observed, indicating that for the geometry and flow conditions considered, one velocity component of each phase was sufficient to track the spatial extent of turbulent event effects and their interactions with the fluid and solid phases. It is found that the two-color DPIV methodology and two-phase correlation results can give critical insight into the performance of thermal-fluid processes, as burst and sweep events have a large impact on the kinematics and dynamics of particles in the two-phase flow.