Color Regions Research Articles

Photoluminescence features of trivalent holmium doped Ca2La8(SiO4)6O2 phosphors

Abstract This study examines the optical properties of Ca2La8−x (SiO4)6O2:xHo3+ phosphors derived using the sol–gel method. X-ray diffraction data and Rietveld analysis confirmed that the phosphors formed in hexagonal phase with an average estimated crystalline size of 27 nm. The prominent excitation peak observed at wavelength 463 nm corresponding to excitation energy 2.68 eV was due to the 5I8 → 5G6 + 5F1 transition. The photoluminescence emission spectra revealed that the synthesized phosphors emitted in the green color region with the 5S2 + 5F4 → 5I8 transition, releasing 2.27 eV energy. The emission and excitation analyses revealed the presence of concentration quenching as the Ho3+ concentration exceeded 0.03 mol in the Ca2La8−x (SiO4)6O2:xHo3+ series. Further, photometry analysis demonstrated a color purity exceeding 94 %, which supports the candidacy of these phosphors for solid-state lighting applications.

Positional Isomeric Cyano-Substituted Bis(2-phenylpyridine)(acetylacetonate)iridium Complexes for Efficient Organic Light-Emitting Diodes with Extended Color Range.

Bis(2-phenylpyridine)(acetylacetonate)iridium, Ir(ppy)2(acac), is a benchmark green emitter for phosphorescent organic light-emitting diodes (PhOLEDs). In this work, we reported three positional isomeric cyano-substituted Ir(ppy)2(acac) complexes, i.e., Ir(3-CN), Ir(4-CN), and Ir(10-CN), with the emission in the yellow to red region (544-625 nm). Through theoretical investigation and single-crystal analysis, it was found that the introduction of cyano substitution at various positions of the ppy ligand allows for tuning the electron distribution and coordination bond length of Ir complexes. Therefore, the charge transfer property of Ir complexes is enhanced such that the energy gap of the cyano-substituted Ir(ppy)2(acac) complexes was reduced. In addition, Ir(3-CN), Ir(4-CN), and Ir(10-CN) exhibited high PLQYs of 83, 54, and 75%, respectively, with the phosphorescence lifetime in the range of 0.79-2.08 μs. Notably, the device utilizing Ir(3-CN) as the emitter exhibited a maximum external quantum efficiency (EQE) of 25.4%, current efficiency of 56.9 cd A-1, power efficiency of 68.7 lm W-1, and brightness of 61,340 cd m-2 at 8 V. The EQE of this device remained 24.3 and 19.9% at luminances of 1,000 and 10,000 cd m-2, corresponding to the efficiency roll-off of 4.3 and 21.7%, respectively. Comparing to the Ir complexes using the ligand with an extended conjugated structure, our results demonstrated a simple molecular design strategy for phosphorescence emitters with reduced molecular weight for efficient PhOLEDs in the yellow to red color region.

A New Automatic Watercolour Painting Algorithm Based on Dual Stream Image Segmentation Model with Colour Space Estimation

Image processing plays a crucial role in automatic watercolor painting by manipulating the digital image to achieve the desired watercolor effect. segmentation in automatic watercolor painting algorithms is essential for region-based processing, color mixing and blending, capturing brushwork and texture, and providing artistic control over the final result. It allows for more realistic and expressive watercolor-like paintings by processing different image regions individually and applying appropriate effects to each segment. Hence, this paper proposed an effective Dual Stream Exception Maximization (DSEM) for automatic image segmentation. DSEM combines both color and texture information to segment an image into meaningful regions. This approach begins by converting the image from the RGB color space to a perceptually-based color space, such as CIELAB, to account for variations in lighting conditions and human perception of color. With the color space conversion, DSEM extracts relevant features from the image. Color features are computed based on the values of the color channels in the chosen color space, capturing the nuances of color distribution within the image. Simultaneously, texture features are derived by computing statistical measures such as local variance or co-occurrence matrices, capturing the textural characteristics of the image. Finally, the model is applied over the deep learning model for the classification of the color space in the painting. Simulation analysis is performed compared with conventional segmentation techniques such a CNN and RNN. The comparative analysis states that the proposed DSEM exhibits superior performance compared to conventional techniques in terms of color space estimation, texture analysis and region merging. The performance of classification with DSEM is ~12% higher than the conventional techniques.

Relational Discrimination Learning Using Multiple Stimulus Pairs with Different Colors and Color Regions in Pigeons

Relational Discrimination Learning Using Multiple Stimulus Pairs with Different Colors and Color Regions in Pigeons

Fluorescence Study of Pr3+ Doped CdS Nanoparticles and its Applications in Sensors and Detectors.

Fluorescence spectra of Pr3+ doped CdS nanoparticles, synthesized by chemical precipitation method, have been recorded at room temperature. The synthesized particles are nearly spherical shaped and the grain size is decreased with the increase in Pr3+ concentration. The chemical identity of the nanoparticles was confirmed by EDAX spectrum, the absorption peaks was confirmed by FTIR spectrum and then the recorded values were compared with the CIE diagram. The oscillator strengths of the 4f ↔ 4I transitions are parameterized in terms of three phenomenological Judd-Ofelt intensity parameters Ωλ (λ = 2, 4 and 6). Using the fluorescence data and these Ωλ parameters, theoretical and experimental study of various radiative properties viz., spontaneous emission probability (A), radiative life time , fluorescence branching ratio and stimulated emission cross-section were evaluated. The values of these parameters indicate that 3P0→ 3H4 transition can be considered to be good laser transition in the visible colour region. Also, excitation with 493 nm, leads to similar blue regions. The synthesized Pr3+ doped CdS nanomaterials could be useful for sensing and detecting devices, particularly for temperature sensing measurement and bio-sensing detection.

One-shot colored reflectance direction field imaging system for optical inspection.

Detecting microscale defects on the surface of an object is often difficult with conventional cameras. Microscale defects are known to greatly affect the bidirectional reflectance distribution function (BRDF) of light rays reflected from the surface. Therefore, an imaging system for capturing the reflectance direction field by color mapping using a multicolor filter placed in front of an imaging lens is proposed, which can have a simple structure. From the color variations of light rays passing through several different color regions of the multicolor filter, this imaging system can detect the extent of broadening of the BRDF. The effectiveness of the imaging system for optical inspection is experimentally validated by testing it on a plastic surface that has a shallow scratch with a depth of a few micrometers.

Catalog of Planetary Nebulae Detected by GALEX and Corollary Optical Surveys

Planetary nebulae (PNs) consist of an ionized envelope surrounding a hot central star (CSPN) that emits mostly at ultraviolet (UV) wavelengths. UV observations, therefore, provide important information on both the CSPN and the nebula. We have matched the PNs in the Hong Kong/Australian Astronomical Observatory/Strasbourg Hα catalog with the Galaxy Evolution Explorer (GALEX) UV sky surveys, the Sloan Digital Sky Survey (SDSS) data release 16, and the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) PS1 second release. A total of 671 PNs were observed by GALEX with the far-UV (FUV; 1344 Å–1786 Å) and/or the near-UV (NUV; 1771 Å–2831 Å) detectors on (GUVPNcat); 83 were observed by SDSS (PNcatxSDSSDR16) and 1819 by Pan-STARRS (PNcatxPS1MDS). We merged a distilled version of these matched catalogs into GUVPNcatxSDSSDR16xPS1MDS, which contains a total of 375 PNs with both UV and optical photometry over a total spectral coverage of ∼1540 Å–9610 Å. We analyzed separately 170 PNs resolved in GALEX images and determined their UV radius by applying a flux profile analysis. The CSPN flux could be extracted separately from the PN emission for 8 and 50 objects with SDSS and Pan-STARRS counterparts, respectively. The multiband photometry was used to distinguish between compact and extended PNs and CSPNs (binary CSPNs) by color–color diagram analysis. We found that compact PN candidates could be identified by using the r − i < − 0.4 and −1 < FUV−NUV < 1 colors, whereas binary CSPN candidates in given T eff ranges (all with color r−i > −0.4) can be identified in the color region (FUV−NUV) ≤ 6(r−i)+1.3, −0.8 < FUV−NUV < 0.4, and r−i < 0.75.

Photoluminescence and thermoluminescence study of Ca1.02Sr1.98Al2O6: Dy phosphor synthesized by combustion method

In the present work, we have synthesized Ca1.02Sr1.98Al2O6 phosphors with different doping concentrations of Dy3+ (0.5 mol% to 4.0 mol%) by simple combustion method. The phase purity of the prepared phosphor has been confirmed by X-ray diffraction (XRD). Detailed investigations have been carried out to study the photoluminescence (PL) and thermoluminescence (TL) properties of the synthesized phosphors. Under 348 nm excitation, the PL emission spectrum shows two intense emission bands at blue and yellow color region due to the 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transition of Dy3+ ions. In addition, the TL properties of gamma-irradiated Dy3+ doped Ca1.02Sr1.98Al2O6 phosphors were investigated. According to the obtained PL and TL results, the synthesized phosphors have good prospects for future investigations on white LED and TLD applications.

Photoluminescence Studies of Europium Doped Di-Strontium Magnesium Silicate Phosphors

This article reports the study of photoluminescence spectra of Di Strontium Magnesium Silicate (Sr2MgSi2O7) doped with various concentration of Europium (Eu3+) prepared using solid-state reaction technique. The doping concentration (s) of Eu3+ were 0.2, 0.5, 1.0, 1.5, 2.0, 2.5 mol% respectively. Excitation spectrum monitored at 620 nm wavelength that exhibited two prominent peaks centered at 256 nm and 277 nm. Peak observed at 277 nm was more intense therefore the emission spectra were monitored at 277. Emission Spectra of all the samples revealed intense peaks centred at 607, 618 and 637 are attributed to 5D0 7F2 of Europium (III) ions accommodated at various lattice sites having different energies. Overall emission was found in the red colour region which was confirmed using a CIE chromaticity diagram with coordinate (0.4805, 0.3763). Critical distance for energy transfer in the concentration, beyond which concentration quenching occurred in PL spectra, was calculated. In this case, the critical distance was found to be 19.87 Å, therefore the mechanism involved in concentration quenching of Sr2MgSi2O7 doped with 2.0 mol % of Europium (III) must be only multipole-multipole exchange whereas the exchange interaction is ineffective.

Three-dimensional Virtual Models of the Kidney with Colored Perfusion Regions: A New Algorithm-based Tool for Optimizing the Clamping Strategy During Robot-assisted Partial Nephrectomy

BackgroundAn empirical selective clamping strategy based on the direction of the arterial branches can lead to failures during partial nephrectomy, even when assisted by three-dimensional virtual models (3DVMs). ObjectiveTo develop and test new 3DVMs that include kidney perfusion regions and evaluate their intraoperative accuracy in guiding selective clamping and their impact on postoperative renal function. Design, setting, and participantsFor patients with a kidney suitable for nephron-sparing surgery, 3DVMs were supplemented with a Voronoi diagram, a Euclidean distance–based mathematical tool, to calculate vascular-dominant regions the kidney. Surgical procedureRobot-assisted partial nephrectomy guided by perfusion-region (PR)-3DVMs. MeasurementsAll anatomic information given by the PR-3DVMs was collected. Selective or superselective clamping was planned and performed intraoperatively when feasible under 3DVM assistance. Changes in split renal function (SRF) and estimated renal plasmatic flow (ERPF) were evaluated for 51 patients who underwent baseline and 3-mo postoperative renal scintigraphy. Results and limitationsA total of 103 patients were prospectively enrolled. The median number of kidney and tumor perfusion regions were 8 (interquartile range [IQR] 7–10) and 3 (IQR 2–3), respectively. A clampless, selective clamping, and global clamping strategy was applied in eight (7.8%), 79 (76.6%), and 16 (15.5%) cases, respectively, with no differences between planning and surgery in terms of the number or order of arteries clamped or the perfusion regions that underwent ischemia. Among the 51 patients who underwent renal scintigraphy, the mean SRF decreased by 11.3%, 7.7%, and 1.7% after global, selective, and superselective clamping, respectively (p = 0.004). Similar results were obtained for ERPF (18.9%, 9.9%, and 6.0%; p = 0.02). The main limitation is the need for a bioengineer to manually refine the 3DVMs. ConclusionsUse of mathematical algorithms for 3DVMs allows precise estimation of kidney perfusion regions to maximize the efficacy of selective clamping and minimize renal function impairment. Patient summaryThree-dimensional models that include regions of blood flow to the kidney can be used to guide clamping of blood vessels when part of the kidney is being surgically removed. More limited clamping can reduce damage to the remaining portion of the kidney and result in better recovery of kidney function after surgery.

Stable Thermally Activated Delayed Fluorescence‐Sensitized Red Fluorescent Devices through Physical Suppression of Dexter Energy Transfer

AbstractTo date, thermally activated delayed fluorescence‐sensitized fluorescent organic light‐emitting diodes (TSF‐OLEDs) have undergone substantial research to achieve high efficiency and good operational stability in wide color gamut regions. Usually, to achieve a highly efficient TSF device, the Förster resonance energy transfer rate (kFRET) should be enhanced, whereas the Dexter energy transfer rate (kDET) should be suppressed. Even though highly efficient devices are achieved in all RGB color regions by satisfying the BT2020 requirements, achieving long device lifetimes is still challenging. Herein, a highly stable red‐TSF device is reported by adopting a new Dexter energy transfer suppressive layer (DSL) adjacent to the main emissive layer. Here, the DSL can improve the distance between the excitons generated from the host‐TADF layer and the final dopant (FD) of the TSF device, which allows for suppressing the kDET. Furthermore, the detailed device mechanistic pathways are analyzed by varying the DSL doping concentration with different thicknesses in different positions. Among the fabricated devices, the DSL‐TSF device manifested a longer operational lifetime (LT95) over 370 h at 5000 cd m‐2 and reduced efficiency roll‐off compared with TSF devices. Such long lifetime and high stability in DSL‐TSF OLEDs are owing to the decreased kDET than TSF devices.

A study by portable X-ray fluorescence (pXRF) of the painting “Still Life with Vase, Plate and Flowers” (1886–1888)

Portable energy-dispersive X-ray fluorescence spectroscopy (pXRF) was employed in the characterization of the pigments present in the painting “Still Life with Vase, Plate and Flowers”, of unknown authorship, but previously attributed to Vincent van Gogh, belonging to the collection of the São Paulo Museum of Art (MASP). In situ pXRF measurements were carried out by means of a portable system in order to provide the museum with a scientific documentation about the materials in the painting. Spectra were taken at different color regions and different hues in the pictorial layer. Some of the materials identified in the painting were chalk and/or gypsum, lithopone, lead white, zinc white, bone black, barium yellow, chrome yellow, yellow ochre, chrome green, Prussian blue, cobalt blue, vermilion and red earth. Besides that, it was possible to suggest the use of a lake pigment. The pigments whose use is suggested by this work are in total agreement with those available to European artists in the end of the 19th century.

Preferred skin reproduction of different skin groups

To accurately reproduce preferred skin colour is an important goal in digital image colour reproduction. A psychophysical experiment was conducted to specify the preferred skin colour for different skin types. Ten original facial images were captured to cover different skin types, including Caucasian, Chinese, South Asian, African, different genders and different ages. For each original image, 49 rendered images, uniformly sampled within the skin colour ellipsoid in CIELAB colour space, were used to morph the skin colours. Thirty observers from each of three ethnic backgrounds, Caucasian, Chinese and South Asian, participated in the experiment to investigate ethnic differences. Ellipsoid models were developed to specify preferred skin colour regions and centres for each original image. These results can be used to improve skin colour reproduction of colour imaging products, for example on mobile phones, for different skin types.

Ballistic Wound Evaluation Based on Dye Diffusion Method

Ballistic gelatin is widely used as a kind of tissue simulants in wound ballistics. Evaluations of the wound tract of gelatin by projectiles are mainly based on fissures in the gelatin slices. For there are difficulties in building relationships between the areas and the fissures, a new method based on dye diffusion is proposed in this paper. Colored regions in the slices are obtained after penetration of a Chinese 7.62mm rifle bullet into the gelatin block. The colored regions can be divided into ‘X’, ‘I’ and branching ‘I’ shapes. In the second half of the penetration, there is a strong correlation between the areas of the regions and the energy dissipation of the bullet. However, the correlation is poor in the first half of the penetration. Branches of the colored regions mainly distributed at the heads and tails of the permanent cavities. The permanent cavities’ shapes have a great dependence on the nutation angles of the bullets. Orientation angles of the permanent cavities are determined by the precession angles of the bullets.

Invariant categorical color regions across illuminant change coincide with focal colors.

Are there regions in a color space where color categories are invariant across illuminant changes? If so, what characteristics make them more stable than other regions? To address these questions, we asked observers to give a color name to 424 colored surfaces, presented one at a time, under various chromatic illuminants. Results showed a high degree of categorical color constancy, especially under illuminants that occur in the natural environment. It was also shown that surfaces selected as a focal color (the best example of a color category) are more resistant to illuminant change than nonfocal color samples. We additionally ran an asymmetric color matching experiment to quantify the shift of color appearance induced by illuminant changes using surfaces that were all named gray, thereby disentangling the appearance-based color constancy from the categorical color constancy (which are often confounded). Results suggested that the appearance of color samples largely shifted owing to illuminant changes, even though all samples were named gray; showing that the constancy of a color category is substantially more robust than the constancy of color appearance.

A Novel Ensemble Based Reduced Overfitting Model with Convolutional Neural Network for Traffic Sign Recognition System

The ELVD (Ensemble-based Lenet VGGNet and DropoutNet) model is used in this paper to examine hypothetical principles and theoretical identification of a real-time image classification and object, tracking, and recognition device running on board a vehicle. Initially, we obtained the dataset from Kaggle. After loading the images, they were converted into 4D tensors and then into a grid. The model has to set the training to 70% training and 30% testing. The ELVD model uses 39,209 32 × 32-pixel color images for preparation, and 12,630 images specifically for research, in the GTSD (German Traffic Sign Detection) dataset. Each picture is a photograph of a traffic sign that corresponds to one of the 43 classes. The picture is a 32 × 32 × 3 sequence of pixel quality values in the RGB color region, defined as pixel values. The image’s class is hidden as a numerical value from 0 to 42. The image collection is somewhat unbalanced, and a few classes are represented significantly better than in the alternative model. The contrast and brightness of the images also differ significantly. The proposed model was created with CNN with Keras and applied with ensemble-based combined LeNet, VGGNet, and DropoutNet pooling layer for tuning the information. The proposed model compares the predicted class with the correct class for all input images and time calculation for predicting different road sign detection images. Underfitting is shown by a standard of low accuracy on the training and testing sets. For a small dataset, the trained model achieved a 98% accuracy level which implied that overfitting the model with the best results on classification accuracy, tested with 15 epochs, resulted in a loss of information of 0.059% and test accuracy of 98%, respectively. Next, the ELVD proposed models trained and validated with different class presents, dataset 2 achieved 93% training accuracy and testing accuracy predicted with 91%. Finally, the ELVD proposed model predicted the test results of unseen class information measured with the 60/km ph, which predicted 99% accuracy. The proposed model predicted noisy as well as unseen multiclass information with fast-moving vehicles. The usage of convolutional layer filter with ensemble-based VGGNet, DropouNet, and LeNet trained and predicted with a high classification accuracy of more than 99% combined ELVD model with fastest time calculation also the high accuracy prediction of selected image dataset labels that enables these models to be used in real-time applications. The ELVD model was also compared with other traditional models of VGGNet, LeNet, and DropoutNet; its detection time outperformed the other models, and it achieved a 98% detection label set of information. In the ELVD model, closure to various human abilities on a related responsibility differs from 97.3% to 99.5%; consequently, the ELVD model performs better than an average human.

A Study on the Diagnosis Technology for Conservation Status of Painting Cultural Heritage Using Digital Image Analysis Program

In order to objectively and quantitatively diagnose the conservation status of painting cultural heritages, a digital image analysis program was used for the digital image of a Korean Buddhist painting. A technical method for diagnosing the conservation status by analyzing the color space of the Buddhist painting and calculating the shape information and damage area was suggested. To verify the applicability of the program, a standard color chart on various ground materials was produced. Color difference values of color information obtained using a color meter and a digital image analysis program were compared. Work efficiency, according to image resolution, was evaluated. It was possible to work efficiently with a size similar to that of an FHD image. Through the comparative evaluation of the individual deviation by the user, the accuracy and temporal advantages of the method using the digital image analysis program could be confirmed. As a result of comparing by color region extraction conditions, it was confirmed that the error range of the measured color information decreased as the 25 pixel diameter circle (average of circled regions of interest) size region and the number of measurements increased. Color space information was adjusted according to the characteristics of each damage type, and the shape of the damage was classified. In addition, the conservation status was evaluated by quantitatively calculating the area of damage with the Intensity Mean of the divided shape image.

Elimination of the color discrimination impairment along the blue-yellow axis in patients with hypothyroidism after treatment with levothyroxine as assessed by the Farnsworth-Munsell 100 hue test.

Our previous study has shown that individuals with untreated hypothyroidism display significantly higher partial error scores (P E S) along the blue-yellow axis compared to the red-green axis than normal individuals using the Farnsworth-Munsell 100 hue test [J. Opt. Soc. Am. A37, A18 (2020)JOAOD60740-323210.1364/JOSAA.382390]. We wished to determine how color discrimination may change when hypothyroidism has been treated to the point of euthyroidism. Color discrimination was reassessed for 17 female individuals who had undergone treatment for hypothyroidism, and the results were compared with 22 female individuals without thyroid dysfunction. No statistically significant difference was found in the total error score (T E S) for the first and second measurements for both groups (p>0.45). The P E S for the hypothyroid group improved significantly in the previously impaired color regions after the treatment. Color discrimination defects found in untreated hypothyroidism can be negated with treatment of the condition over an appropriate time period.

Retrieval-induced forgetting of spatial position depends on access to multiple shared features within categories

Retrieval-induced forgetting (RIF) is typically observed in verbal memory tasks, although a few studies have observed RIF in visual spatial tasks. This leaves an open question as to whether RIF depends on semantic identity to link across semantic properties of objects, or whether RIF depends on access to the perceptual features of objects. To explore RIF of spatial positions, we report three experiments utilizing a continuous measure of the accessibility and precision for objects that were distinguished by their shape, color, and spatial region. After a study phase, half of the objects in a single-color category were selectively practiced for their spatial position, by requiring the object to be placed in the exact spatial position seen previously. Finally, all objects were probed for their spatial position at test. No RIF occurred for objects that shared only one color feature but were located within the same spatial region (in Experiment 1) or when objects shared the same color, but were located within different spatial regions (in Experiment 3). However, RIF did occur when objects shared the same spatial region and the same color (Experiment 2). Overall, the interim recall of the spatial positions of cue-objects impairs access to the position of other cue-objects within the same color category, but only when these groups had sufficient overlapping and competing features. The finding that RIF only occurs to the accessibility of spatial positions, not the precision of visual spatial memory, was interpreted as consistent with inhibitory theories of forgetting.

Spatial frequency representation in V2 and V4 of macaque monkey.

Spatial frequency (SF) is an important attribute in the visual scene and is a defining feature of visual processing channels. However, there remain many unsolved questions about how extrastriate areas in primate visual cortex code this fundamental information. Here, using intrinsic signal optical imaging in visual areas of V2 and V4 of macaque monkeys, we quantify the relationship between SF maps and (1) visual topography and (2) color and orientation maps. We find that in orientation regions, low to high SF is mapped orthogonally to orientation; in color regions, which are reported to contain orthogonal axes of color and lightness, low SFs tend to be represented more frequently than high SFs. This supports a population-based SF fluctuation related to the 'color/orientation' organizations. We propose a generalized hypercolumn model across cortical areas, comprised of two orthogonal parameters with additional parameters.