Visual determination of hue suprathreshold color-difference tolerances

This research extends the previous RIT-DuPont research on suprathreshold color-difference tolerances in which CIELAB was sampled in a balanced factorial design to quantify global lack of visual uniformity. The current experiments sampled hue, specifically. Three complete hue circles at two lightnesses (L* = 40 and 60) and two chroma levels ( = 20 and 40) plus three of the five CIE recommended colors (red, green, blue) were scaled, visually, for hue discrimination, resulting in 39 color centers. Forty-five observers participated in a forced-choice perceptibility experiment, where the total color difference of 393 sample pairs were compared with a near-neutral anchor-pair stimulus of 1.03 A supplemental experiment was performed by 30 additional observers in order to validate four of the 39 color centers. A total of 34,626 visual observations were made under the recently established CIE recommended reference conditions defined for the CIE94 color-difference equation. The statistical method logit analysis with three-dimensional normit function was used to determine the hue discrimination for each color center. A three-dimensional analysis was required due to precision limitations of a digital printer used to produce the majority of colored samples. There was unwanted variance in lightness and chroma in addition to the required variance in hue. This statistical technique enabled estimates of only hue discrimination. The three-dimensional analysis was validated in the supplemental experiment, where automotive coatings produced with a minimum of unwanted variance yielded the same visual tolerances when analyzed using one-dimensional probit analysis. The results indicated that the hue discrimination suprathresholds of the pooled observers varied with CIELAB hue angle position. The suprathreshold also increased with the chroma position of a given color center, consistent with previous visual results. The results were compared with current color-difference formulas: CMC, BFD, and CIE94. All three formulas had statistically equivalent performance when used to predict the visual data. Given the lack of a hue-angle dependent function embedded in CIE94, it is clear from these results that neither CMC nor BFD adequately predict the visual data. Thus, these and other hue-suprathreshold data can be used to develop a new color-difference formula with superior performance to current equations. © 1998 John Wiley & Sons, Inc. Col Res Appl, 23, 302–313, 1998     

Visual determination of hue suprathreshold color‐difference tolerances using CRT‐generated stimuli

Suprathreshold hue color‐difference tolerances were measured at four color centers using CRT‐generated stimuli. The tolerances, defined using CIELAB, were measured using two different methods of presentation. In the Absolute Experiment, the stimuli were presented at luminance levels that matched those of the previous object‐color experiments, so that the CRT stimuli were nearly metameric to the originals. In the Relative Experiment, the white point of the monitor was defined as L* = 100 at a corresponding chromaticity to the object‐color viewing environment, but at a lower luminance level. The results from these two experiments followed the same general trends; however, they were significantly different from each other for three of the four color centers. The same trends were seen in the object‐color results, although neither CRT experimental condition produced tolerances that were conclusively more similar to the object‐color results than the other. The feasibility of the use of the CRT has been demonstrated. It is likely that parametric effects of stimulus presentation are the cause of the differences in results among the different experiments, as opposed to differences in the mode of appearance. These parametric effects can be studied more quickly and economically using a computer‐controlled CRT display. © 1999 John Wiley & Sons, Inc. Col Res Appl, 24, 164–176, 1999     

Lightness dependencies and the effect of texture on suprathreshold lightness tolerances

A psychophysical experiment was performed to determine the effects of lightness dependency on suprathreshold lightness tolerances. Using a pass/fail method of constant stimuli, lightness tolerance thresholds were measured using achromatic stimuli centered at CIELAB L* = 10, 20, 40, 60, 80, and 90 using 44 observers. In addition to measuring tolerance thresholds for uniform samples, lightness tolerances were measured using stimuli with a simulated texture of thread wound on a card. A texture intermediate between the wound thread and the uniform stimuli was also used. A computer‐controlled CRT was used to perform the experiments. Lightness tolerances were found to increase with increasing lightness of the test stimuli. For the uniform stimuli this effect was only evident at the higher lightnesses. For the textured stimuli, this trend was more evident throughout the whole lightness range. Texture had an effect of increasing the tolerance thresholds by a factor of almost 2 as compared to the uniform stimuli. The intermediate texture had tolerance thresholds that were between those of the uniform and full‐textured stimuli. Transforming the results into a plot of threshold vs. intensity produced results that were more uniform across the three conditions. This may indicate that CIELAB is not the best space in which to model these effects. © 2000 John Wiley & Sons, Inc. Col Res Appl, 25, 241–249, 2000     

Visual evaluation at scale of threshold to suprathreshold color difference

Visual evaluation experiments of color discrimination threshold and suprathreshold color‐difference comparison were carried out using CRT colors based on the psychophysical methods of interleaved staircase and constant stimuli, respectively. A large set of experimental data was generated ranged from threshold to large suprathreshold color difference at the five CIE color centers. The visual data were analyzed in detail for every observer at each visual scale to show the effect of color‐difference magnitude on the observer precision. The chromaticity ellipses from this study were compared with four previous published data, of CRT colors by Cui and Luo, and of surface colors by RIT‐DuPont, Cheung and Rigg, and Guan and Luo, to report the reproducibility of this kind of experiment using CRT colors and the variations between CRT and surface data, respectively. The present threshold data were also compared against the different suprathreshold data to show the effect of color‐difference scales. The visual results were further used to test the three advance color‐difference formulae, CMC, CIE94, and CIEDE2000, together with the basic CIELAB equation. In their original forms or with optimized K_L values, the CIEDE2000 outperformed others, followed by CMC, and with the CIELAB and CIE94 the poorest for predicting the combined dataset of all color centers in the present study. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 198–208, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20106     

Performance testing of color-difference metrics using a color tolerance dataset

A color-difference dataset was developed for testing the performance of color metrics. The dataset comprises 45 color-difference vectors varying in five directions at nine color centers under conditions typical of commercial color decisions. Probit analysis was used to estimate the parameters of the population distribution of tolerances for each vector. In addition to estimating the median tolerance, the anlysis allows one to estimate the uncertainty of a tolerance and to test the adequacy of the underlying model tolerance distribution. The median tolerances were used to specify 45 color-difference pairs with equal visual color-difference magnitudes. The performance of eight color-difference metrics was compared using the normalized standard deviation of the color differences of the visually equal difference pairs as a measure of uniformity. A bootstrap statistical technique was used to quantify the variation in performance with varying samples of color centers and color-difference directions and to determine the significance of observed differences in uniformity performance. Some metrics based on weighted CIELAB dl*, dC*, dH* color-difference components had significantly superior performance compared to the CIE recommended color-difference metrics.     

重量分析法测定氰尿酸纯度

介绍了测定氰尿酸纯度的方法,即酸碱滴定法、电位滴定法和重量分析法。并通过对3种方法进行对比,重量分析法测定氰尿酸纯度要比酸碱滴定法、电位滴定法结果准确,且重现性好。     

Variability in estimation of suprathreshold small color differences

Intraobserver and interobserver variability in perceptual small color difference evaluation are known but are rarely analyzed phenomena. They raise the question if humans are equipped to make reliable and uniform estimates of this kind. Data from two recent well‐controlled studies show that intraobserver and, particularly, interobserver variability are surprisingly large. The use of a gray reference scale in place of a single gray reference pair has a small normative effect on the estimate. A large interobserver variability in the estimated magnitude of chromatic differences compared with achromatic reference pairs remains, with an average ratio between largest and smallest estimate of over 3:1 and ratios for individual observers and sample pairs ranging up to 28:1. No correlation was found between the reliability of judgment and the judged magnitude of difference: highly reliable observer groups are not more consistent. Relative reliability of estimate was found inversely related to magnitude of perceived difference. Consequences of these results for the development of improved color difference formulas are discussed. © 2009 Wiley Periodicals, Inc. Col Res Appl, 34, 367–374, 2009     

Influence of experimental parameters on the evaluation of color-difference ellipsoids

Using a set of red samples, we investigated the influence of the number of observers and samples on the accuracy of experimentally evaluated color-difference ellipsoids. The results show that an ellipsoid can be calculated with an accuracy corresponding to a mean error of calculated color differences below 10% if a set of about 50 samples is assessed 30 times by pair comparison, e.g., 15 observers twice each.     

Automated free fatty acid determination using flow injection analysis solvent extractions

A simplified, automated, colorimetric method is described for the determination of free fatty acids (FFA) in solution using solvent extraction flow injection analysis (SEFIA). A membrane separator utilizing a microporous Teflon membrane is used for a clean phase separation. A newly designed segmentor is used for segmenting the reagent and solvent streams. A linear relationship exists between normality and absorbance from 6×10⁻⁵ to greater than 3×10⁻² N for oleic acid and from 4.4×10⁻⁵ to 6×10⁻³ N for stearic acid. The correlation between concentration and absorbance in this method is better than in previously advanced copper soap colorimetric methods. The sample throughput is 130 injections/hr.     

统计技术在制定产品公差上的应用

产品公差是产品的质量特性之一,反映了产品的档次和信誉,是企业对用户的承诺,同时,对企业内部来讲,它直接影响企业的质量成本和经济效益.     

流动注射分析仪测定地表水中阴离子表面活性剂的研究

采用Quiekchem8500s2型连续流动注射分析仪对地表水中阴离子表面活性剂进行测定,标准曲线的相关系数为0．9995,方法检出限为0．004mg／L。对2种浓度的标准样品进行分析,测得值均在其保证值范围内。该方法简单、快速,对实际地表水样的测定结果与标准方法的相对误差在4．07％～10．64％,这表明流动注射法适用于地表水样品的快速测定。     

辣椒红色素提取工艺可视化分析

以干红辣椒为原料,用丙酮作为溶剂提取辣椒红色素,运用均匀设计法设计实验,采用可视分析方法分析实验数据,得到提取高品质的辣椒红色素的最佳工艺范围为:提取温度75~85℃,提取时间270~360 min,固液比为30~40 mL/g。     

Three-dimensional threshold of color-difference perceptibility in painted samples: Variability of observers in four CIE color regions

In four of the five CIE color regions, the correlation of perceptibility of color differences and colorimetric measures is studied for painted samples at threshold. Sample pairs resulting in three-dimensional color differences ranging from zero to just clearly perceptible were used. The variability of color-difference ellipsoids is shown for single observers and for observer groups. Randomisation of mean results by a Monte-Carlo method produces deviation ellipsoids that describe shells of uncertainty inherent in the data. Interobserver and inter-group variability turns out to be widely covered by random noise, but the variances leave some stability of ellipsoid shapes. Color-difference formulas should be able to predict color differences within the shells of uncertainty.     

Psychophysical verification of the accuracy of color and color-difference simulations of surface samples on a CRT display

We describe an experiment to visually quantify the accuracy of the simulation of the color and color-difference of surface samples on a CRT display unit. A gray-scale-anchored, magnitude-estimation experiment was performed to assess the absolute quality of the simulations and a forced-choice, paired-comparisons experiment was performed to assess the relative quality of the simulations. Results indicate that an average color difference for overall simulation accuracy can be under 3.0 CIELAB color-difference units for highcolor-temperature sources, and slightly worse for low-colortemperature sources. All simulations were well under the 6 to 12 unit differences reported for typical color reproduction. Possible reasons for the residual color differences between the current simulations and the theoretical limit are presented.     

Visual gloss scaling and multidimensional scaling analysis of painted specimens

Painted panels were prepared in a wide range of gloss and in three achromatic colors (white, middle grey, and black) by varying the composition and heat treatment of an automotive acrylic-lacquer system. Magnitude scaling was used to estimate visual dissimilarities between the members of all possible pairs of specimens in series of 15–20 samples. The data were analyzed by multidimensional scaling using several commercially available computer programs. The experiments were carried out and the results are discussed for evaluation of several types of gloss: distinctness-of-image, specular, contrast, sheen, and reflection haze. The resulting interval scales were all unidimensional. The visual data were correlated with a variety of instrumental gloss measurements made on the same specimens by using commercially available glossmeters.     

Visual analysis of plastication of long‐glass fiber‐reinforced resins using a glass‐insert heating cylinder

The fiber‐reinforced plastication processes during the injection molding of reinforced resins with long fibers are difficult to observe through visualization cylinders because of possible obstacles, such as (1) opacification of melts, (2) abrasion on the inner surface of glass windows, and (3) breakage of glass windows under high pressures. In this study, we visualized the plastication process of long‐glass fiber‐reinforced resins containing 50 wt% fibers. In plastication experiments using three full‐flight screws with different compression ratios, we observed the instability of the melting process, the generation of solid beds and melt pools, and the breakup of melted segments. We demonstrated that the plastication process depends considerably on the compression ratio and clarified the characteristic molding phenomena related to fiber breakup. Based on our observations, we proposed a model that explains the different fiber breakage distributions at different compression ratios during the melting process of long‐glass fiber‐reinforced resins. POLYM. ENG. SCI., 59:1300–1309 2019. © 2019 Society of Plastics Engineers     

响应面分析法优化抑制褪色光度法测定自来水中氟

基于在pH=5.5的六次甲基四胺缓冲液介质中,氟离子对铬天青S与铝离子络合的阻抑作用,建立了测定微量氟的褪色光度法。利用响应面法优化测定条件,以反应时间、Al3+用量及铬天青S用量为影响因子,组合设计建立数学模型,以吸光度值作为响应值,进行响应面法分析。得到最佳测定条件:反应时间为66.17 s、Al3+用量为6.47 mL、铬天青S用量为5.19 mL,在此条件下,吸光度的实测值为0.687 7,相对误差为0.044%,RSD(n=3)=1.24%。     

大肠杆菌调控因子工程及其菌株耐受性研究进展

大肠杆菌具有金字塔式的基因表达等级调控网络,调控因子的自动调控、共调控和交叉调控,构成了复杂而又精细的转录调控网络。微生物通过扰动和优化这个高效的调控网络快速地响应环境变化,而适应新的耐受条件。微生物的耐受性是由多基因控制的复杂表型,通过大肠杆菌调控因子工程,可以大尺度重构调控网络,显著改进菌株耐受性,成为了近几年的研究热点。本文总结了大肠杆菌调控因子及其工程方法,综述了通过大肠杆菌调控因子工程重构代谢网络来提高菌株耐受性的最新研究进展,展望了通过大肠杆菌调控因子工程提高菌株鲁棒性的发展方向。     

单晶硅表面池沸腾可视化测量及数据分析

针对核态沸腾过程,利用高速摄像机和红外热成像设备对光滑、微坑、均匀微柱和槽型微柱四种不同单晶硅表面的沸腾现象进行了在线可视观测,获得了各表面气泡动力学演变过程及局部温度演变规律,揭露了基于动力学过程的沸腾强化机理。由沸腾曲线可知,光滑硅表面,沸腾起始过热度为6℃,而三种微结构表面,起沸过热度为3～4℃;同时,微坑、槽型微柱和均匀微柱表面核态沸腾的CHF较光滑表面分别提高了109%、129%和140%。动力学演变过程则证明了微坑的存在为核化沸腾提供了核化点,有效降低了核化能垒、缩短了壁面蓄能阶段的时长。微柱的存在大幅度增加了气泡核化密度,减小了脱离直径,缩短了脱离时间,促进了沸腾表面温度的均匀化。