In this work rice oil was tested when it is dripped onto a high temperature surface. The tests conducted determined the lowest temperature at which rice oil ignited and the highest temperature at ...which rice oil did not ignite in three tests conducted at the same temperature. The results of this study show that the values of the evaluated temperatures are of major importance regarding the use of rice oil as an eco-friendly lubricant. Thus, the highest temperature at which rice oil did not ignites is 465 °C, while the lowest temperature at which rice oil ignited is 470 °C. Moreover, at the end of the 8 tests performed, part of the oils collected in the tray of the installations used in the present study were subjected to spectrophotometric tests. Based on the obtained data, the transmittance spectra were plotted and the trichromatic components and coordinates were calculated, as well as the colour differences of the tested oils.
•A specific training for a panel to evaluate orange juice colour is proposed.•Commercial orange juices were evaluated instrumentally and visually.•Instrumental colour measurements and visual ...evaluation were correlated.•The colour attribute intensity correlated significantly with chroma and lightness.•Difference colour threshold was 1.5 and 2.8 units for trained and untrained panel.
This study was aimed at training a panel of assessors to evaluate specifically orange juice colour, and to establish the colour difference threshold in orange juice for a trained and untrained panel. Panellists were first preselected using Farnsworth–Munsell 100-Hue Test and then trained with a specific method for orange juice colour. This training allowed assessors to evaluate visually orange juice samples in hue and intensity. The final selection of assessors was a panel of 8 trained observers with reproducibility and repeatability, and a significant discrimination among the samples (p<0.05).
On the other hand, commercial orange juices were evaluated both instrumentally by image analysis and visually by the trained panel, and the untrained panel. Instrumental colour measurements and visual evaluation were correlated. Values around 1.5 and 2.8 CIELAB units could be consider the threshold for colour differences between two orange juices for the trained and untrained panel, respectively.
Background
Accurate skin colour measurements are important for numerous medical applications including the diagnosis and treatment of cutaneous disorders and the provision of maxillofacial soft ...tissue prostheses.
Methods
In this study, we obtained accurate skin colour measurements from four different ethnic groups (Caucasian, Chinese, Kurdish, Thai) and at four different body locations (Forehead, cheek, inner arm, back of hand) with a view of establishing a new skin colour database for medical and cosmetic applications. Skin colours are measured using a spectrophotometer and converted to a device‐independent standard colour appearance space (CIELAB) where skin colour is expressed as values along the three dimensions: Lightness L*, Redness a* and Yellowness b*. Skin colour differences and variation are then evaluated as a function of ethnicity and body location.
Results
We report three main results: (1) When plotted in a standard colour appearance space (CIELAB), skin colour distributions for the four ethnic groups overlap significantly, although there are systematic mean differences. Between ethnicities, the most significant skin colour differences occur along the yellowness dimension, with Thai skin exhibiting the highest yellowness (b*) value and Caucasian skin the lowest value. Facial redness (a*) is invariant across the four ethnic groups. (2) Between different body locations, there are significant variations in redness (a*), with the forehead showing the highest redness value and the inner arm the lowest. (3) The colour gamut is smallest in the Chinese sample and largest in the Caucasian sample, with the Chinese gamut lying entirely the Caucasian gamut. Similarly, the largest variability in skin tones is found in the Caucasian group, and the smallest in the Chinese group.
Conclusion
Broadly speaking, skin colour variation can be explained by two main factors: individual differences in lightness and yellowness are mostly due to ethnicity, whereas differences in redness are primarily due to different body locations. Variations in lightness are more idiosyncratic probably reflecting the large influence of environmental factors such as exposure to sun.
This study proposes an algorithm for classifying colour differences in dyed fabrics using random vector functional link (RVFL) optimised using an improved hunger games search (HGS) algorithm to ...replace the inefficient traditional classification methods. First, to prevent the HGS algorithm from easily arriving at the local optimal solution, we used the grey wolf optimiser (GWO) to generate the solution set of the HGS algorithm. Subsequently, to reduce the impact of the randomness of the input weight and hidden layer offset on the classification accuracy of RVFL, we used the improved HGS to optimise these two parameters of RVFL. Finally, the RVFL optimised using the improved HGS algorithm is used for classifying the colour differences of dyed fabrics. The performance of the proposed classification algorithm is compared with HGS algorithms improved using the whale optimiser, sine cosine algorithm, and Harris hawks optimiser. The results revealed that the proposed algorithm possesses several advantages, including the maximum, minimum, and average classification errors; good stability; and fast convergence.
Relating instrumental measurements to visually perceived colour-differences, under specific illuminating and viewing conditions, is one of the challenges of advanced colorimetry. Experimental data ...are used to devise new colour-difference formulas as well as to assess the performance of other colour-difference formulas. In this paper, we analyse the consistency of experimental data employed at the development of the last CIE recommended colour-difference formula, CIEDE2000. Because of the subjective and imprecise nature of these data, we adopt a fuzzy approach, so that finally, for each experimental datum, we establish the fuzzy degree to which it can be considered consistent with the remaining data. The results of our analyses show that only a few data are associated with a rather low degree of consistency. These data in many cases correspond to colour pairs with a very small colour-difference for which visual assessments seem to be overestimated.
Digital printing techniques are increasingly present in the field of textile printing. Particularly prominent is the inkjet printing technique using water-based inks, UV LED inkjet printing also ...increasingly being in use. UV LED inkjet is primarily not intended for direct clothing printing; however, it can be used especially as a hybrid solution in the soft signage market. It is a great option for the printers that are not engaged only in textile printing, and want a more versatile print portfolio, extending it to non-clothing textile products, e.g. soft signage and non-wearable products. As these types of products often require colour reproduction of logos, accurate colour reproduction, good ink adhesion and sharpness are important just like in other printing technologies. In order to evaluate the impact of UV LED radiation amount on colour differences, ink bleeding and abrasion resistance, six different fabric samples (five woven and one nonwoven) were printed using a UV LED inkjet printer. Based on the results of colour difference, it was established that a reduction of UV radiation (by half the manufacturer’s recommended amount) had no effect on this parameter. However, perceptible colour differences were observed with the use of different M measurement conditions defined by the international standard ISO 13655-2017. Reducing the amount of UV radiation had no effect on the adhesion and durability of the printed ink. Small differences detected in these two parameters were mainly a consequence of the properties of textile materials and not of decreased UV radiation.
Abstract Objectives It is unknown if present-day pigments used for intrinsic colouration of maxillofacial prostheses are representative of human facial skin tones. This study's purpose was to measure ...L * a * b * values of pigmented elastomers coloured by eleven skin tone pigments and determine coverage error (CE) when the pigments were compared to human facial lip and nose colour data. Methods 11 skin tone pigments were combined at 0.1%, 1% and 10% by weight with A-2186 elastomer ( n = 3). L * a * b * values were measured with a spectrophotometer and group means were used to calculate Δ E * colour differences with each L * a * b * value obtained for human nose and lip. Pigmented elastomer CEs were calculated for nose and lip. Results were compared to CEs for proposed shade guide colours obtained from clustering analyses of facial skin colours. Results L * values of pigmented elastomers generally were higher than those measured for nose and lip, whereas a * values were lower. CEs for pigmented elastomers were higher than those obtained from the proposed shade guide obtained from clustered skin measurements. Conclusions Overall, the current commercial elastomers appeared to be too white and not red enough to adequately match the skin tones of the subject population. Adjustments must be made to the existing pigmenting system in order to adequately match the skin colours of the study population. Clinical significance The creation of a shade guide and a collection of intrinsic pigments representing the realm of human facial skin colours would greatly decrease the time a patient must sit while the clinician is obtaining an acceptable colour match for the silicone to be used for processing the final prosthesis, thereby increasing both patient satisfaction and clinician productivity.
Abstract
In practice it happens very frequently that yarn of certain fineness, which creates desired
colour effect on the woven fabrics surface, is not available. In consequence an available
yarn of ...different fineness has to be used instead, which can be observed on the woven
fabrics as a colour deviation compared with the desired effect. The aim of this research is
the possibility of colour values corrections of woven fabrics by changes of constructional
parameters. Simulations of woven fabrics are used for this purpose. In the case
described weft the yarn of higher fineness is substituted by the yarn of lower fineness and
equal colour values. Three possible ways of colour values correction by changes of
constructional parameters of the woven fabric are presented. In the first case, the colour
difference is corrected by increase of the weft threads density, the second way of
correction consists in the change of warp yarn fineness, and the third in decreasing of
warp threads density. The basic purpose of all the three types of correction is the equally
change of warp and weft contents in one colour rapport of the woven structure. In the
experimental part of our work, the colour values L*, a* and b*, and colour differences
DE*ab are investigated theoretically (using calculations on the basis of theoretical defined
fractions, and L*, a*, and b* values of yarns), as well as spectrophotometrically, on the
basis of printouts of simulations of woven fabrics prepared with the use of Arahne CAD
system. Two ways of determination of colour values of simulations and three types of
corrections are evaluated in the conclusions. It was find out that the correction with the
increase of weft thread density is the most successful, and the DE*ab values are minimal.
Extensive colour difference calculations (CIELAB and CMC models for CIE D
65/10°, Ill./Obs.) were applied to the colorimetric coordinates previously gathered on 224 pure or co-pigmented (by rutin) ...solutions of cyanin at pH between 2.5 and 5.5. CIELAB coordinates additionally recorded on acidic (0.1N HCl) methanolic and aqueous cyanin solutions (10
−5 M−2.5×10
−3 M) showed the considerable hue gamut covered by each series of solutions (1/6 and 1/8 of the colour circle). A markedly yellowing effect of water vs. methanol was observable and it represented the most influential parameter in the impressive CIELAB differences (Δ
E* up to 38 units) caused by the solvent. On aqueous cyanin solutions, successive one unit pH elevations resulted in huge colour gaps (up to Δ
E* > 60 units, at pH 3.5 vs. 2.5). The corresponding ‘loss of colour’ was mainly attributable to a decreasing chroma (Δ
C*) while the coupled hue differences (Δ
H*) corresponded to more or less deep blueing effects at pH elevations up to 4.5 and more unexpectedly to yellowing effects at pH increased to 5.5. Using CMC difference calculations, the colours of 0.1 N HCl aqueous solutions at low concentrations were best matched by those of cyanin solutions at pH 2.5 and about 2–2.5 fold higher concentrations; at high concentrations, their colours were preferentially simulated by solutions at each corresponding—or lower—cyanin concentration but co-pigmented by rutin (up to 4:1 ratio). Similar, but more complex features, emerged in the constitution of many best matched couples of colours from the database of model solutions at pHs 2.5–5.5. Close—or even identical—colour stimuli were also shown to be based on either closely matched or quite distinctly shaped spectral curves. The complete ‘colour by numbers’ approach presented in this series of papers may find applications in many fields in which anthocyanic pigments are employed, as natural food colorants for instance.
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