Color Difference Values Research Articles

Effect of Titanium-Base Abutment Height on Optical Properties of Monolithic Anterior Zirconia Crowns.

The effects of different heights of ti-base abutments on the color of anterior screw-retained zirconia restorations fabricated using computer-aided design and computer-aided manufacturing (CAD-CAM) technologies may affect the optical clinical outcome. The purpose of this study was to measure and compare the color parameters of zirconia crowns in different shades on ti-base abutments. Identical specimens (N = 160) were milled to restore the screw-retained central maxillary incisor crown, using 5% mol yttria zirconia (5Y-TZP). The specimens were designed using computer design software to match 3.5 mm and 5.5-mm ti-base abutments and milled using one CAD-CAM technology. Specimens were divided into four main groups depending on zirconia shade (A1/0, A2/3, A3.5/4 and B2/3) and then assigned to two subgroups according to ti-base height. Color measurements in the CIELab coordinates were made using a spectrophotometer under room-light conditions. Color difference (ΔE*) values were calculated using the CIE76 and CIEDE2000 formula. Within the group of A0/1 and A2/3, for 5.5 mm abutment height, a significant difference was found between the means of colors ∆E00 and ∆Eab (<i>p</i> &amp;lt; 0.01). Using a 5.5 mm-height ti-base abutment may produce a clinically unacceptable outcome (ΔEab &amp;gt; 2) in A1/0 and A2/3 color groups.

An Adaptive Joint Bilateral Interpolation-Based Color Blending Method for Stitched UAV Images

Given a source UAV (unmanned aerial vehicle) image Is and a target UAV image It, it is a challenging problem to correct the color of all target pixels so that the subjective and objective quality effects between Is and It can be as consistent as possible. Recently, by referring to all stitching color difference values on the stitching line, a global bilateral joint interpolation-based (GBJI-based) color correction method was proposed. However, because all stitching color difference values may contain aligned and misaligned stitching pixels, the GBJI-based method suffers from a perceptual artifact near the misaligned stitching pixels. To remedy this perceptual artifact, in this paper, we propose an adaptive joint bilateral interpolation-based (AJBI-based) color blending method such that each target pixel only adaptively refers to an adequate interval of stitching color difference values locally. Based on several testing stitched UAV images under different brightness and misalignment situations, comprehensive experimental results demonstrate that in terms of PSNR (peak signal-to-noise ratio), SSIM (structural similarity index), and FSIM (feature similarity index), our method achieves higher objective quality effects and also achieves better perceptual effects, particularly near the misaligned stitching pixels, when compared with the GBJI-based method and the other state-of-the-art methods.

Effect of heat and pulsed electric field treatment on the physicochemical and nutritional properties of carrots.

Carrots are widely used in home cooking and vegetable processing industries because of their high nutritional value. However, different processing methods may produce a negative impact on carrot texture and nutrition quality. Therefore, the development of better processing methods to preserve the texture and nutrition quality of carrots will be beneficial to the carrot industry. The effects of heat and pulsed electric field (PEF) treatments with different heat temperatures (T) and holding time (th ) on comprehensive changes in thermal efficiency profiles, and physicochemical (color, hardness, cell structural damage) and nutritional (releasable β-carotene contents) properties of carrots were studied. In addition, electrical conductivity (σ) and soluble matter contents (°Brix) were determined for the heat-treated extracts. The value of total color difference (∆E) and cell structural damage index (Z) of carrots, σ and °Brix of extracts all increased with increasing T and th under different heat experimental conditions, whereas the value of cutting force (F) presented an opposite tendency and content of releasable β-carotene decreased after th > 2min at T=100 °C. The results show that PEF heating is beneficial in preventing changes in physicochemical and nutritional properties of carrots compared to traditional heat treatment. PEF has potential as a heating technology in the food industry. © 2022 Society of Chemical Industry.

Color Formulation of Cotton Fabrics Using Multi-Objective Ant Colony Optimization

ABSTRACT The formulation of colors is one of the most important aspects of colorimetry. For dyeing and finishing industries, mastering this step is a major problem to be solved. In this paper, a multi-objective ant colony optimization algorithm is developed to optimize the reproduction of the desired shades. The multi-objective function of the proposed algorithm minimizes simultaneously the CMC color differences and the metamerism index between the standard and the reproduced colors. Two ranges of dyes were used to dye cotton fabrics. The elaborated multi-objective algorithm showed good results with small values of color differences and metamerism index. All CMC color differences values were less or at the limit of the acceptability threshold of 1, and about 75% of samples exhibited minimum metamerism and are considered as a good match.

Novel Yellow Azo Pyridone Derivatives with Different Halide Atoms for Image-Sensor Color Filters.

Novel yellow azo pyridone dye derivatives were synthesized for use in image-sensor color filters. The synthesized compounds have a basic chemical structure composed of azo, hydroxy, amide, and nitrile groups as well as different halide groups. New materials were evaluated on the basis of their optical, thermal, and surface properties under conditions mimicking those of a commercial device fabrication process. A comparison of their related performance revealed that, among the four prepared compounds, 5-((4,6-dichlorocyclohexa-2,4-dien-1-yl)diazenyl)-6-hydroxy-1,4-dimethyl-2-oxo-1,2-dihydropyridine-3-carbonitrile (Cl-PAMOPC) exhibited the best performance as an image-sensor color filter material, including a solubility greater than 0.1 wt% in propylene glycol monomethyl ether acetate solvent, a high decomposition temperature of 263 °C, and stable color difference values of 4.93 and 3.88 after a thermal treatment and a solvent-resistance test, respectively. The results suggest that Cl-PAMOPC can be used as a green dye additive in an image-sensor colorant.

Transcriptomic Analysis of the Differences in Leaf Color Formation during Stage Transitions in Populus × euramericana ‘Zhonghuahongye’

To explore the mechanism underlying the leaf color variation of Populus × euramericana ‘Zhonghuahongye’ (‘Zhonghong’ poplar) leaves at different maturation stages, we used ‘Zhonghong’ poplar leaves and analyzed the L* (lightness), a* (redness), and b* (yellowness) color difference values and the pigment contents in the three maturation stages. The Illumina HiSeqTM 2000 high−throughput sequencing platform was used for transcriptome sequencing analysis, and leaf color changes during stage transitions were preliminarily explored. Overall, with the increase in L* and b* during leaf development, the a*, C* (colour saturation), and chromatic values decreased, the total anthocyanin content decreased, and the chlorophyll and carotenoid content increased. A total of 11,868 differentially expressed genes were identified by transcriptome sequencing. Comparing the expression differences of structural genes involved in anthocyanin synthesis in the leaves at different stages, we identified 5612 genes in the R1 vs. R2 comparison, 10,083 in the R1 vs. R3 comparison, and 6068 in the R2 vs. R3 comparison (R1, R2, R3 refer to samples obtained on 1 April, 6 April, and 11 April, respectively). Key genes such as DFR (Dihydroflavanol 4−reductase), ANS (anthocyanidin synthase), FLS(flavonol synthase) , CHS(chalcone synthase), BZ1(Bronze 1), bHLH35, and bHLH63 were identified. These structural genes and those that encode transcription factors may be related to the regulation of anthocyanin synthesis. Here, the key genes related to leaf color change in ‘Zhonghong’ poplar were discovered, providing an important genetic basis for the subsequent genetic improvement of ‘Zhonghong’ poplar.

Effects of different processing methods on the biochemical composition, color and non-volatile taste active compounds of whiteleg shrimp (Litopenaeus vannamei)

This study determined the biochemical composition, color change, and non-volatile taste-active composition in raw (FSM), boiled (BSM), hot air-dried (HSM), microwave-dried (MSM), and roasted (RSM) whiteleg shrimp meat. All the treatments significantly influenced the biochemical and taste profile of whiteleg shrimp. Processing primarily affected the color and was measured in terms of total color difference (ΔE) and hue angle (H°) values. The fatty acid profiles of FSM and BSM were similar and different from the remaining groups. Moreover, boiling has reduced the content of taste compounds except glucose significantly (P < 0.05) compared to other groups. For the taste evaluation, equivalent umami concentration (EUC) was determined for all the groups and is significantly different (P < 0.05) in the order of MSM>RSM>HSM>FSM>BSM. This study demonstrated that microwave drying showed a significant increase in the content of taste components and the umami flavor of whiteleg shrimp compared to other processing methods.

The Effect of Binder FS-462 and Sky Binder 235 on Color Fastness Resistance in 100% Polyester Printing with Pigment Dyes

The printing with pigment dyes on 100% polyester fabric is one of the materials that can be used to make clothes. Clothing products made with the printing technique must have a good color fastness. In printing with pigment dyes must be mixed with a binder. These binder have different solid content (% glucose). Therefore, the selection of the right binder is very important t produce quality fabrics with good color fastness. The purpose of this study was to determine the value of color fastness to washing and rubbing and the value of color differences in the printing process with pigment dyes on 100% polyester fabrics and to determine which binder had the best results. The method of this study used is an experiment with a lab scale. After experimenting with the printing process using the Binder FS-462 and Sky Binder 235, a test was conducted which stated that Binder FS-462 was the binder that had the best results. The test values ​​were obtained as follows, color fastness to washing on dark colors 4-5 for staining scale and 4 for grey scale, color fastnes to rubbing on dark colors 4 for dry and 2-3 for wet. The factory standard is for color fastness to washing 3 for staining scale and 4 for grey scale, color fastness to rubbing 3-4 for dry and 2-3 for wet, and color difference values ​​&gt;1.

Comparison between two ceramic veneer materials in their color and translucency before and after applying luting agent layer

Statement of problem: In making veneer restoration to restore the human teeth, it is essential to produce the color and the shape of the artificial restoration similar to the natural teeth and this is not easy produced. Therefore, the effect of cementation layer on optical characteristic of aesthetic restoration is one of the critical factors in controlling the aesthetic outcome of veneer restorations.&#x0D; The aim: The aim of this work is to evaluate the effect of luting cement on color and translucency of commercially available aesthetically ceramic veneer materials.&#x0D; Materials and methods: The materials used were Zirkon Zahn and IPS e.Max Empress. All the experimental samples of laminate veneers (LVs) were prepared using readymade veneer mould (3M ESPE) to standardize the thickness and the dimension of the tested samples. Single layer of the luting cement was applied on the fitting surface of the veneer samples. The samples prepared following the manufacturers’ instructions. Spectrophotometer was used to evaluate the color and translucency of tested samples.&#x0D; Results: The IPS e.max samples showed higher TP and Cab values compared with zirconia samples. However, color difference (∆E) values were higher for zirconia (3.28) compared with IPS e.max samples (2.92). Cement layer showed great effect on translucency and color parameter. Statistically, there was a high significant difference between tested samples (P&gt;0.000)&#x0D; Conclusion: The IPS e.max ceramic showed better color measurement than zirconia samples, however both materials found to be in the acceptable range of observation values. The luting cement had limiting the translucency and affects the aesthetic outcome.

Quality Improvement in Mackerel Fillets Caused by Brine Salting Combined with High-Pressure Processing.

Simple SummaryHigh-pressure processing enhanced the pasteurization effect of mackerel fillets that had undergone brine salting and improved the effect of texture hardening and fish discolouration observed after the high-pressure treatment alone. Our findings provide seafood processors as an alternative option to improve the safety of salt-brined mackerel fillets.The purpose of the study is to investigate the effects of brine salting and high-pressure processing (HPP) on the microbial inactivation and quality parameters of mackerel fillets. Mackerel fillets were immersed in 3% and 9% sodium chloride brine for 90 min at refrigerator temperature, and then treated at 300, 400, 500, and 600 MPa pressure for 5 min. The microbial counts and physicochemical qualities of the fish were examined. In comparison with fish fillets treated with brine or high pressure alone, those treated with the combination of brine salting and HPP showed significantly reduced aerobic plate count (APC) and psychrotrophic bacteria count (PBC). The hardness and chewiness of salt-brined fillets were obviously lower than those of the unsalted fillets under the same pressure condition. Thus, brine salting imparted mackerel fillets a softer texture, which compensated for the HPP-induced increased hardness and chewiness of the fillets. The L* (lightness) and ΔE (colour difference) values of the fillets increased with increasing pressure, with or without brine salting. Conversely, a* (redness) values decreased with increasing pressure. The samples treated with 3% brine in combination with 300 or 400 MPa pressure had a* values similar to those of the samples processed under similar HPP conditions alone but showed lower ΔE values than the other groups. Therefore, as a very high pressure would adversely affect the texture and colour of the fish fillets, this study suggests that immersion in an appropriate brine concentration (3%) and treatment with HPP at 400 MPa for 5 min improved or maintained the colour and texture relatively well and produced a synergistic bactericidal effect.

Whitening Effect of Manalagi Apple (Malus sylvestris) Extract on Tea-Induced Tooth Discoloration

Introduction: Tooth discoloration is a change in color that occurs on the enamel and dentin surfaces of a tooth due to the habit of drinking tea. Some fruits are used as natural teeth whitening ingredients, such as Manalagi Apple (Malus sylvestris), which contains malic acid. Method: This study was an experimental study with a pre-and post-test control group design involving 27 samples divided into three groups, Control (K), P1, and P2. We immersed tooth samples from three groups in tea solution for two weeks. After that, the P1 group was immersed with 50% Manalagi Apple extract three times a day for one week and the P2 group three times a day for two weeks, while the Control group (K) did not get any treatment. We analyzed the tooth discoloration before and after immersing 50% of Manalagi Apple extracts utilizing a Colorimeter, with hunter L, a, and b color scales. The color difference value was obtained using the formula of ⧍E(Lab) = [(L)2+(a)2+(b)2]1/2]. Results: The ANOVA test results showed significant differences between the three sample groups (p = 0.00). Besides, the Post-hoc test revealed a significant difference between the K group and the P1 group with a p-value of 0.00 (p &lt;0.05). It also indicated a significant difference between the K group and the P2 group with a p-value of 0.00 (p &lt;0.05). Conclusions: Color changes occurred after immersing the teeth in Manalagi Apple extract for one and two weeks. Immersing the teeth for two weeks caused whiter teeth compared to immersing the teeth for one week.

Assessment of relative translucency and resultant color of contemporary resin-matrix ceramics indicated for laminate veneers and full crowns.

Evaluation of the optical properties of restorative materials is an important parameter for identifying clinical success. The aim of this study was to compare the translucency of contemporary resin-matrix ceramics (RMCs) and to evaluate the effect of cement shade on the final color of RMCs indicated for laminate veneers and full crowns. A hundred A2 shade RMC specimens were fabricated by using Mazic Duro (MD), CAMouflage NOW (CN), KZR-CAD HR2 (KZR), Grandio Block (GB), and Brilliant Crios (BC) at 0.7-mm and 1.5-mm thicknesses (n = 10). A2 shade composite resin was used for the foundation structure. Twenty resin-cement specimens were prepared from A2 and translucent shades at 0.1-mm thickness. Interchangeably, the foundation-cement-resin matrix ceramic assemblies were created with optical gel. The color coordinates were recorded using a spectrophotometer. After calculating translucency parameter (TP00) and color difference (ΔE00) values, data were analyzed statistically (P = 0.05). TP00 values were influenced by RMC type and thickness. TP00 values of RMCs can be listed in descending order as MD>GB = CN>BC=KZR. ΔE00 values were significantly influenced by all parameters and their interactions. MD exhibited higher ΔE00 values among tested RMCs. The effect of A2 cement was not perceived visually while TR cement demonstrated visually perceptible but clinically acceptable values for both laminate veneers and full crowns. As the material thickness decreased, the TP00 and ΔE00 values increased in all RMCs. Clinicians should carefully prefer cement shade and RMC material by contemplating their impact on the optical properties particularly when the restoration is thin.

Spectro 1-A Potential Spectrophotometer for Measuring Color and Myoglobin Forms in Beef.

The objective of this study was to compare the Color Muse Spectro 1 sensor to the HunterLab MiniScan XE Plus spectrophotometer for evaluating beef color. Color coordinates (lightness (L*), redness (a*), yellowness (b*), chroma (C*), and hue (h*)), myoglobin redox forms (metmyoglobin (MMb), deoxymyoglobin (DMb), and oxymyoglobin (OMb)), and metmyoglobin reducing ability (MRA) were measured on beef steaks over a 5-days storage period. The results indicated that L*, b*, C*, MMb%, OMb%, and MRA% values obtained with Spectro 1 were comparable to those of MiniScan. However, Spectro 1 values for a* were overestimated compared to MiniScan (p < 0.05), whereas those for h* and DMb% were underestimated (p < 0.05). Regardless, Spectro 1 had the capability to detect changes in color coordinates, myoglobin forms, and MRA throughout the storage period. Bland–Altman plots demonstrated that L*, b*, and C* are interchangeable between the two instruments, but it was not the case for a*, h*, myoglobin forms, and MRA. Color coordinates measured by Spectro 1 exhibited excellent stability over time, evidenced by the low total color difference (ΔE*ab) values. Collectively, these findings indicate that Spectro 1 is a potential alternative spectrophotometer for studying meat color and myoglobin redox forms.

Using Nix color sensor and Munsell soil color variables to classify contrasting soil types and predict soil organic carbon in Eastern India

Optimal soil management depends on rapid and frequent monitoring of key soil properties, which are conventionally measured in the laboratory using laborious wet-chemistry protocols. The Nix color sensor has recently exhibited promise for predicting several soil properties using soil color. This study evaluated the relationship between the Munsell Soil Color Chart (MSCC) color values of dry and ground surface soil samples to those reported by the Nix color sensor with (NixSTD) and without MSCC standardization (NixNON-STD) to classify 371 samples collected from three contrasting soil types, collected from three agro-climatic zones (coastal saline zone, red and laterite zone, and Gangetic alluvial zone) and to predict soil organic carbon (OC) using different multivariate data mining algorithms. Comparing the CIEL*a*b* color values reported by the MSCC and the NixSTD, an acceptable mean color difference (ΔE*ab) value of 5.20 was obtained, indicating the potential accuracy of the Nix sensor. Principal component analysis efficiently clustered the soil types using the RGB variables extracted from the MSCC color chips in tandem with the NixSTD/NixNON-STD data. Both classification tree and linear support vector machine algorithms perfectly classified all three contrasting soil types using NixNON-STD data alone. Besides, the combination of the MSCC and the NixNON-STD datasets produced the best OC prediction (R2 = 0.66) via random forest (RF) algorithm and indicated the potential of Nix in digital soil morphometrics. In most of the RF models, redness (a*), yellowness (b*), and yellow (Y) variables appeared influential, presumably because of their negative correlation with OC in red and laterite soils. More research is warranted to measure the impacts of variable soil moisture and other confounding soil morphological features on the soil classification and OC prediction performance to extend the approach for classifying soil types and predicting OC in-situ.

Visual Display Method of Enterprise Internal Control Information Based on Cluster Analysis Algorithm

In the face of today’s fast updating and wide variety of word segmentation, it is difficult to accurately identify the keyword segmentation in the enterprise’s internal control information. Therefore, a visual display method of enterprise internal control information based on cluster analysis algorithm is proposed. Fully considering the characteristics of enterprise internal control, on the basis of clarifying the visual display process of enterprise internal control information, the visual display coefficient of enterprise internal control information is optimized based on cluster analysis algorithm. By optimizing the visual display value, the visual display parameter fusion of enterprise internal control information is realized. The dimension of enterprise internal control information is reduced, and the mean value of color difference between pixels is used to ensure the separability of visual display images, so as to realize the visual display of enterprise internal control information. The experimental results show that the proposed method can accurately identify the enterprise internal control information, which shows that the practical application ability of this method has been improved.

A hydrogel-based chemosensor applied in conjunction with a Griess assay for real-time colorimetric detection of nitrite in the environment

Nitrite ions (NO2-) are Type A inorganic contaminants, and they exert significant effects and greatly threaten human health and the environment. In addition, excessive intake of this anion might cause harmful diseases. In this study, we have successfully developed a novel hydrogel-based chemosensor for sensing nitrite ions. We first synthesized a hydrogel, 2-naphthylacetic acid-L-phenylalanine-L-phenylalanine (Nap-FF), which was based on a naphthyl acetic moiety made by a liquid-phase synthetic strategy and then investigated its characteristics and the conditions required for hydrogelation. To detect nitrite ions affecting water quality, facile synthesis of the Nap-FF hydrogel and sulfanilamide were used. Then, based on the Griess mechanism for the reaction between NO2- and NapFF-sulfanilamide, a colorimetric Griess-based reaction was performed on the hydrogel. The results confirmed visually that our chemosensor showed extremely high sensitivity to nitrite, and a significant color change from transparent to yellow/orange was observed. Correspondingly, a linear relationship was observed between the NO2- concentration and the color difference value (ΔE*), the limit of detection (LOD) was 0.72 μM and the working concentration for NO2- ranged from 8.3 μM to 16.7 mM. Furthermore, interference testing of this sensor confirmed its high selectivity toward NO2- in the presence of environmentally relevant competing ions.

Structural, Thermal, and Optical Studies of Gamma Irradiated Polyvinyl Alcohol-, Lignosulfonate-, and Palladium Nanocomposite Film.

Nanocomposite (NC) films of polyvinyl alcohol (PVA), lignosulfonate (Lg), and nanosized palladium (Pd) were synthesized by ex-situ casting method. Samples from the synthesized PVA-Lg/Pd NC films were irradiated with 5–100 kGy γ doses. The effect of γ doses on the structural, thermal, and optical characteristics of the NC films were studied using different characterization techniques. The results indicated that the γ irradiation improves the decomposition temperature from 227 to 239 °C, signifying an increase in the thermal stability of the NC films. This was accompanied by a reduction of the melting temperature due to the increase of the amorphous phase. This can be attributed to the dominance of crosslinking. On the other hand, the refractive index increased from 2.21 to 2.32 while increasing the γ dose up to 100 kGy. This was associated with a reduction of the optical bandgap from 3.49 to 3.30 eV, which could be attributed to the increase in the amorphous phase as a result of crosslinking. This indicates an enhancement of the spreading of the NPs inside the blend matrix due to γ irradiation. This results in a more compacted construction of the PVA-Lg/Pd NC films. Furthermore, we used the Commission Internationale de E’Claire (CIE) method to estimate the change in color among the irradiated NC films and the pristine film. The PVA-Lg/Pd NC attained a significant color difference value greater than five, meaning permanent color changes.

Electron beam-cured linseed oil - Diacrylate blends as a green alternative to overprint varnishes: Monitoring curing efficiency and surface coating properties

Electron beam (EB)-cured unsaturated vegetable oil and diacrylate was formulated as an alternative and green overprint varnish (OPV) for coatings in a finishing process. Linseed oil (LO) was applied with tripropylene glycol diacrylate (TPGDA) in different ratios to obtain EB-curable LO-based OPV (eLOPV). The eLOPV were irradiated by EB for curing using various absorbed doses of 10–100 kGy. Change of the functional groups, chemical structure and transition temperature of EB-cured eLOPV were characterized by FTIR, 13C-NMR and DSC. The curing efficacy was assessed by measuring conversion, gel fraction, swelling degree and by characterizing surface properties using solvent rub-test and cross-cut tape test methods. The EB-cured eLOPV exhibited great surface adhesion on substrates. The surface morphologies of the EB-cured eLOPV on papers and plywood sheets were observed by SEM. The results indicate that the eLOPV (LO-TPGDA blend 40: 60 w/w) was completely cured using EB at 30 kGy. Th optical properties were observed via yellowness and whiteness indexes according to ASTM E 313. Color difference and gloss value were measured using colorimeter and gloss meter, respectively. The eLOPV provide good surface qualities, i.e, good surface adhesion, low yellowness, homogeneous cured surface, high gloss value, and hydrophobic surface. Aiming at well-optimized formula and effective EB-curing process, the synthetic chemical can be reduced at least 50% w/w by using vegetable oil without photo-initiator. The utilization of LO and EB curing technology is a promising strategy for bio-/green-coatings approach.

EFFECT OF UV RADIATION ON CHANGE IN COLOR OF STEAMED BEECH WOOD

The wood of the beech (Fagus Sylvatica L.) was steamed with a saturated steam-air mixture at a temperature of t = 95°C, or saturated steam at t = 115°C and t = 135°C to obtain a pale pink, red-brown and rich brown-red color. Subsequently, samples of unsteamed and steamed beech wood were irradiated with a UV lamp in a Xenotest Q-SUN Xe-3-HS after drying in order to test the color stability of steamed beech wood. The color change of the wood surface was evaluated by means of measured values on the coordinates of the color space CIE L*a*b*. The results show that the surface of unsteamed beech wood as well as steamed beech wood with a steam-air mixture at a temperature of t = 95°C and saturated steam with a temperature of t = 125°C darkened and turned brown to a brown-yellow color due to UV radiation. The deep brown-red color of the surface of beech wood steamed with saturated steam with a temperature of t = 135°C brightened to a brown-yellow color similar to the color of unsteamed beech wood. The analysis of the changes in the color space CIE L* a* b* shows that the greater the darkening and browning of the beech wood by steaming, the smaller the changes in the values of ∆L*, ∆a* ∆b* of the steamed beech wood caused by UV radiation. The positive effect of steaming on UV resistance is evidenced by the decrease in the overall color difference ∆E*. While the value of the total color difference of unsteamed beech wood caused by UV radiation is ∆E* = 15.3, for beech wood steamed with a saturated steam-air mixture at t = 95°C it decreased to ∆E* = 9.5, which is a decrease of 37.9%, for steamed beech wood steamed with saturated steam with temperature t = 115°C is ∆E* = 6.2 which is a decrease of 59.4% and for steamed beech wood steamed with saturated steam with temperature t = 135°C is ∆E* = 4.5 which is a decrease of 70.5%.

Spectral reflectance estimation based on two-step k-nearest neighbors locally weighted linear regression

To improve the estimation accuracy of spectral reflectance from the given trichromatic value, a new two-step k-nearest neighbors locally weighted linear regression method is proposed. The algorithm has good local learning ability and can take into account the similarity of colorimetric and spectral reflectance space. The simulated and practical imaging experiments were carried out with Munsell matte and glossy dataset, respectively. Experimental results show that the mean root mean square error values of the spectral reflectance estimated by our model in simulated RGB, practical imaging Adobe RGB. and raw RGB data experiments are 0.00731, 0.01519, and 0.01453, respectively, and the mean color difference values under CIE standard illuminant D65 are 0.380, 1.311, and 1.180, respectively. In addition, we showed the calculation time cost of various models in the practical experiment. The calculation time of one sample for the proposed method is 0.094 s. The proposed method is better than several state-of-the-art methods in terms of comprehensive estimation performance and running efficiency.