Minimum Color Research Articles

Fast printing of thin, large area, ITO free electrochromics on flexible barrier foil

Processing of large area, indium tin oxide (ITO) free electrochromic (EC) devices has been carried out using roll-to-roll (R2R) processing. By use of very fine high-conductive silver grids with a hexagonal structure, it is possible to achieve good transparency of the electrode covered substrates and when used in EC devices switching times are similar to corresponding ITO devices. This is obtained without the uneven switching of larger areas, which is generally observed when using ITO because of its high-sheet resistance. The silver electrode structures for 18 × 18 cm2 devices can be processed at high speed (10 m/min) on PET by flexographic printing and the EC polymer ECP-Magenta as well as a minimal color changing polymer MCCP by slot-die coating, showing the potential for fast fabrication of large volumes of low-priced flexible EC devices by use of R2R processing techniques. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013

Development of the LED measurement system of chromaticity coordinates correction

In this paper, we propose a procedure to adjust the chromaticity coordinates by using a few samples of the color measurement coordinate to do the error correction and choose the correction method of minimum color error difference average to be the procedure of measuring instruments, and to construct an efficient and predictable calibration procedure. This research adopts some engineering statistics methods, such as median and average methods, and corrects the experiments to obtain the chromaticity coordinates. The four calibration methods that we designed lower the average value of the color errors as 0.034. Moreover, the minimum average value of errors in the X-axis could be revised to 6.3% while the minimum average value of errors in the Y-axis 8.8%. The accuracy of best calibrated chromaticity coordinates could achieve to the percentage 71.1%.

EFFECTS OF PROCESSING METHOD AND STORAGE TEMPERATURE ON CLEAR POMEGRANATE JUICE TURBIDITY AND COLOR

ABSTRACT Clear pomegranate juice possesses a very attractive color and low turbidity that are affected by processing methods and storage temperatures. In this study, different extraction (pressing with fruit husk and pressing only with fruit arils), clarification (hot and cold) and filtration (via kieselguhr or active charcoal) techniques were compared to determine their effect on color and turbidity. All samples were stored at two different temperatures for 6 months. Cold clarification and low storage temperature (5C) produced pomegranate juice with minimum color loss (total color difference, ΔE = 1.45) and low turbidity (0.91 NTU) even after 6 months of storage. PRACTICAL APPLICATIONS Pomegranate juice is a favorite beverage with a high total phenolic content related to the management of many metabolic disorders. However, excessive concentrations of these valuable compounds cause visual problems in the juice that reduce its appeal to consumers. The procedures for producing clear pomegranate juice are very important. This study focused on the ability of different extraction, clarification and filtration techniques to produce clear juice and the effect of storage temperatures on the development of turbidity and color in the extracted juice. Although mainly hot clarification procedures are preferred in the commercial fruit juice industry, we found that cold clarification is minimized turbidity and color. Also, using active charcoal filtration and storage of the product at lower temperature and can help to maintain initial juice characteristics during the shelf life.

Development of polarization dental imaging modality and evaluation of its clinical feasibility

ObjectivesIn the evaluation of tooth color, the specular reflection caused by roughness or saliva on the tooth surface may cause artefacts in image analysis. In this study, a polarization dental imaging modality (PDIM) was developed to obtain cross-polarized images and, therefore, to address the problem of specular reflection. Its clinical validity was evaluated by performing 3 studies of shade tab selection for implant, plaque distribution detection, and evaluation of tooth whitening. MethodsIn vivo human tooth and shade guide color images were obtained, and the minimum color difference between them was calculated for the best color matching shade tab selection. A dental plaque disclosing agent was used to differentiate plaque regions on teeth, and plaque distribution was detected by applying the K-means algorithm. In vivo human teeth were treated with a commercial tooth whitening gel, and tooth whitening was quantitatively evaluated using the PDIM images. ResultsThe PDIM produced repeatable glare-free tooth color images by effectively removing the specular reflection from the tooth surface. The cross-polarized tooth images were successfully utilized for shade guide selection, plaque detection, and tooth whitening by minimizing artefacts in the quantitative image analysis. The PDIM could simultaneously provide both qualitative and quantitative assessment of the tooth condition in clinical diagnosis. ConclusionsThe clinical feasibility of the PDIM was successfully verified in 3 clinical studies by showing its clinical efficacy as a new imaging modality.

You Are What You Eat: Within-Subject Increases in Fruit and Vegetable Consumption Confer Beneficial Skin-Color Changes

BackgroundFruit and vegetable consumption and ingestion of carotenoids have been found to be associated with human skin-color (yellowness) in a recent cross-sectional study. This carotenoid-based coloration contributes beneficially to the appearance of health in humans and is held to be a sexually selected cue of condition in other species.Methodology and Principal FindingsHere we investigate the effects of fruit and vegetable consumption on skin-color longitudinally to determine the magnitude and duration of diet change required to change skin-color perceptibly. Diet and skin-color were recorded at baseline and after three and six weeks, in a group of 35 individuals who were without makeup, self-tanning agents and/or recent intensive UV exposure. Six-week changes in fruit and vegetable consumption were significantly correlated with changes in skin redness and yellowness over this period, and diet-linked skin reflectance changes were significantly associated with the spectral absorption of carotenoids and not melanin. We also used psychophysical methods to investigate the minimum color change required to confer perceptibly healthier and more attractive skin-coloration. Modest dietary changes are required to enhance apparent health (2.91 portions per day) and attractiveness (3.30 portions).ConclusionsIncreased fruit and vegetable consumption confers measurable and perceptibly beneficial effects on Caucasian skin appearance within six weeks. This effect could potentially be used as a motivational tool in dietary intervention.

Large Rainbow Matchings in Edge-Coloured Graphs

Arainbow subgraphof an edge-coloured graph is a subgraph whose edges have distinct colours. Thecolour degreeof a vertexvis the number of different colours on edges incident withv. Wang and Li conjectured that fork≥ 4, every edge-coloured graph with minimum colour degreekcontains a rainbow matching of size at least ⌈k/2⌉. A properly edge-colouredK4has no such matching, which motivates the restrictionk≥ 4, but Li and Xu proved the conjecture for all other properly coloured complete graphs. LeSaulnier, Stocker, Wenger and West showed that a rainbow matching of size ⌊k/2⌋ is guaranteed to exist, and they proved several sufficient conditions for a matching of size ⌈k/2⌉. We prove the conjecture in full.

A minimally coloured dioxypyrrole polymer as a counter electrode material in polymeric electrochromic window devices

As the colour palette of solution processable electrochromic conjugated polymers has extended from hues of purple and blue to vibrant colours such as yellow, orange, red, green, and cyan, the need for a counter electrode material that provides charge balance in electrochromic devices, but lends minimal colour, has become increasingly necessary. Nowhere is this more true than in absorptive/transmissive window-type devices where a high level of transparency and near colourlessness is needed in the device bleached state. This argument can also be extended to absorptive/reflective display-type devices where an “on” (coloured) and “off” (bleached or white) state is desired. Here, we report the development of a highly electroactive, low colouration efficiency propylenedioxypyrrole-based polymer that exhibits a low redox potential and minimal colour saturation in both fully neutralised and fully oxidised states. Thin films of the polymer, spray-cast onto transparent electrodes exhibited relatively low composite colouration efficiencies at 555 nm of 35 cm2C−1, contrasted with the the high colouration efficiency ECP-Magenta that exhibits 633 cm2C−1. We further demonstrate the utilisation of this polymer as an effective charge balancing counter electrode material in an absorptive/transmissive window-type device wherein the vibrantly coloured state and highly transmissive, near colourless bleached state of ECP-Magenta is maintained giving an overall device contrast of 61% at 540 nm.

Optimization of Raw Sugar Beet Juice Purification Process Conditions Using Bentonite by Response Surface Methodology

In this study, response surface methodology was used to determine the optimum raw sugar beet juice purification process conditions using bentonite to produce inverted liquid sugar. For this purpose, impact of factors on the purification process such as bentonite concentration (1-5 gr/li), pH (3.5-6) and temperature (35-95 ˚C) was investigated. For each response, a second-order polynomial model was developed using multiple linear regression analysis. Correlation coefficients of fitted regression models of color, turbidity, ash, adjusted purity and invert sugar for juice purification process were determined as 0.95, 0.89, 0.90, 0.91 and 0.96 respectively. Results showed that while increasing the bentonite concentration increased the turbidity content but the adjusted purity decreased, and had no significant effect on other parameters. At lower pH levels, separation of color and turbidity causes by bentonite, but was in creased it decreased separation of ash and also increased invert sugar levels. With increasing temperature from 35˚C, to 95˚C, Separation of color and turbidity causes and invert sugar and adjusted purity content as well as increased, while this variable has no significant effect on syrup ash content. The optimum conditions of raw sugar beet juice purification process using bentonite was determined to obtain minimum color, turbidity and ash with maximum invert sugar and adjusted purity which were verified experimentals were found to be bentonite concentration of 1.70 gr/li, pH of 4.47 and temperature of 75˚C. At this optimum point, color, turbidity, ash, adjusted purity and invert sugar content were found to be 1664 ICU420, 6.3 NTU, 0.55 %, 93.9 % and 1.60 %, respectively.

New techniques for approximating optimal substructure problems in power-law graphs

The remarkable discovery of many large-scale real networks is the power-law distribution in degree sequence: the number of vertices with degree i is proportional to i−β for some constant β>1. A lot of researchers believe that it may be easier to solve some optimization problems in power-law graphs. Unfortunately, many problems have been proved NP-hard even in power-law graphs. Intuitively, a theoretical question is raised: are these problems on power-law graphs still as hard as on general graphs?In this paper, we show that many optimal substructure problems, such as Minimum Dominating Set, Minimum Vertex Cover and Maximum Independent Set, are easier to solve in power-law graphs by illustrating better inapproximability factors. An optimization problem has the property of optimal substructure if its optimal solution on some given graph is essentially the union of the optimal sub-solutions on all maximal connected components. In particular, we prove the above problems and a more general problem (ρ-Minimum Dominating Set) remain APX-hard and their constant inapproximability factors on general power-law graphs by using the cycle-based embedding technique to embed any d-bounded graphs into a power-law graph. In addition, in simple power-law graphs, we further prove the corresponding inapproximability factors of these problems based on the graphic embedding technique as well as that of Maximum Clique and Minimum Coloring using the embedding technique in [1]. As a result of these inapproximability factors, the belief that there exists some (1+o(1))-approximation algorithm for these problems on power-law graphs is proven to be not always true. At last, we do in-depth investigations in the relationship between the exponential factor β and constant greedy approximation algorithms.

Configuration and minimal coloring of disbalanced graphs

Configuration and minimal coloring of disbalanced graphs

Stationary and Adaptive Color-Shift Reduction Methods Based on the Bilevel Driving Technique for Phosphor-Converted White LEDs

The bilevel driving technique has realized a 2-D control of the luminosity and emitted color of white LEDs with duty cycle and forward current levels. Unfortunately, various combinations of these dimming control parameters can lead to significant changes in junction temperature, which further modify the luminosity and emitted color of LEDs. In this paper, the theoretical aspects of these complex interactions and the impact of bilevel drive on the color-shift properties of white LEDs are discussed in detail by using a mathematical color-shift model. Two color-shift reduction methods are proposed based on the insights obtained from this model. This study shows that a heat sink's thermal resistance that minimizes the overall color shift over dimming can be uniquely determined from the knowledge of some measurable LED parameters, and gives rise to a global minimum color shift. If such a thermal resistance cannot be realized due to practical limitations, the second method that utilizes an adaptive change of forward current levels over dimming can be adopted. Based on their nature, these methods are classified as stationary and adaptive methods, respectively. Their validity is supported by experimental measurements on a commercial white LED.

Monotonic Stable Solutions for Minimum Coloring Games

For the class of minimum coloring games (introduced by Deng et al. (1999)) we investigate the existence of population monotonic allocation schemes (introduced by Sprumont (1990)). We show that a minimum coloring game on a graph G has a population monotonic allocation scheme if and only if G is (P4, 2K2)-free (or, equivalently, if its complement graph G is quasi-threshold). Moreover, we provide a procedure that for these graphs always selects an integer population monotonic allocation scheme.

Preliminary Assessment Concerning the Practical Implementation and Visual Perception of Color Rendering Modulation for Augmented Energy Savings

Digitally controlled lighting systems equipped with colored LEDs can produce a range of different qualities of light, adjustable to users' requirements. In this context, we explore a lighting control concept which involves strategic control of RYGB LEDs forming white light, employed to increase energy efficiency. There is a fundamental trade-off between color rendering (CR) and luminous efficacy. Specifically, we can reduce CR and increase efficacy when we redistribute spectral energy intensity in favor of wavelengths where the eye response is greatest, the yellow/green region of the spectrum. The notable point is that while changing CR, the light level and color temperature can stay constant, and hence the appearance of the modified white light remains unchanged. The strategy is to bring the lighting of unoccupied spaces to minimum color rendering to save energy without altering the appearance or light levels of the illumination, when the LED system dynamically shifts to 'energy saving mode' (low CR) from 'quality mode' (high CR) according to occupancy. This paper reports and discusses the results of an ongoing research project involving the exercise of LED color mixing re-working the spectrum of white light according to this fundamental energy vs. rendering trade-off. The research work encompasses two main domains: (a) a tunable LED light source with accompanying control equipment; and (b) human factors studies concerning how surfaces and spaces are perceived under a light source with changing spectral components. Results so far have supported the two fundamental hypotheses: (a) when fully developed, color rendering modulation could potentially enable significant power reductions; (b) the majority of subjects did not detect the color rendering changes.

Influence of sugar end syrup pH value on overall color rise in the sugar end and color of final molasses

Where chromatographic separation of sucrose from molasses produced is employed, the color of the molasses feed to the molasses separator operation has a relatively large effect on the color of the sucrose enriched extract produced from the separation process and, as a result, on the overall efficiency of sugar recovery from the molasses separation process. The subsequent sugar end processing efficiency of the separator sucrose enriched extract product to granulated sugar is quite dependent on the color loading of the extract being processed. This study evaluates the effect of manipulating and controlling the pH value of the A (high green) run-off syrup, B (intermediate) green run-off syrup and final molasses produced to achieve minimal color rise and a low final molasses color from the thick juice processed in the sugar end. The deliberate and precise control of green syrup pH value will produce molasses of the desired color relative to the quality of the beets being processed and the thick juice produced from such beet quality. It is further shown that the color of extract produced is highly dependent on the color of molasses feed to the molasses separation operation.

Minimum average colour space entropy – colour component transform based colour image compression

The standards given by joint photographic expert group (JPEG and JPEG2000) utilise the component colour space transform (CCT) and subband transform (SBT) for the purpose of image compression. The CCT reduces the redundancy between the RGB components and relates the different components of image at every pixel position. On the other side, SBT relates the different image pixels with its surroundings or vicinity within a component. The minimum average colour space entropy (MACSE) based CCT further reduces the inter colour component redundancy by exploiting the distribution of image pixels in spatial domain. This is a reversible process. The MACSE-CCT along with JPEG coding shows around 1.5 dB improvement in peak signal to noise ratio for very low bit-rates. The performance of this hybrid model is found better for very high spatial frequency images from the point of view of visual perception.

PREDICTION OF SOME PHYSICAL PROPERTIES OF OSMODEHYDRATED CARROT CUBES USING RESPONSE SURFACE METHODOLOGY

ABSTRACT In this study, response surface methodology was used to optimize the processing conditions and predict some physical properties of carrot cubes treated by osmotic dehydration. Temperature (30–50C), processing time (15–360 min), glucose syrup (30–50% w/w) and NaCl (5–15% w/w) concentrations were the factors investigated. Experiments were designed according to the central composite rotatable design. For each response, second-order polynomial models were developed using multiple linear regression analysis. With respect to texture firmness, density, rehydration capacity and color changes, both linear and quadratic effects were significant. Analysis of variance was performed to check the adequacy and accuracy of the fitted models. The optimal conditions for firmness, density and rehydration capacity and minimum color difference correspond to a temperature of 50C, 43.13% glucose syrup, 5% salt and a processing time of 221.82 min; these parameters yield firmness, density and rehydration capacity values of 38.06, 1.20 and 79.98%, respectively. PRACTICAL APPLICATIONS Response surface methodology is a statistical tool owning significant advantages in optimization and controlling of food process. Because the quality attributes are the most effective parameters influencing consumer choice, optimizing these parameters have a great practical and economical importance. Osmotic dehydration is a suitable way to produce the shelf-stable products or partially dehydrated foods ready to place in other complementary processes such as air-drying, freezing and others. The osmotically dehydrated carrots can be added directly into soups, stews or can be suited to a broad range of food formulations including instant soups, snack seasoning and so on.

Maximal independent sets in minimum colorings

Every graph G contains a minimum vertex-coloring with the property that at least one color class of the coloring is a maximal independent set (equivalently, a dominating set) in G . Among all such minimum vertex-colorings of the vertices of G , a coloring with the maximum number of color classes that are dominating sets in G is called a dominating- χ -coloring of G . The number of color classes that are dominating sets in a dominating- χ -coloring of G is defined to be the dominating- χ -color number of G . In this paper, we continue to investigate the dominating- χ -color number of a graph first defined and studied in [1].

Rainbow Matching in Edge-Colored Graphs

A rainbow subgraph of an edge-colored graph is a subgraph whose edges have distinct colors. The color degree of a vertex $v$ is the number of different colors on edges incident to $v$. Wang and Li conjectured that for $k\geq 4$, every edge-colored graph with minimum color degree at least $k$ contains a rainbow matching of size at least $\left\lceil k/2 \right\rceil$. We prove the slightly weaker statement that a rainbow matching of size at least $\left\lfloor k/2 \right\rfloor$ is guaranteed. We also give sufficient conditions for a rainbow matching of size at least $\left\lceil k/2 \right\rceil$ that fail to hold only for finitely many exceptions (for each odd $k$).

Optimization problems in multiple subtree graphs

We study various optimization problems in t-subtree graphs, the intersection graphs of t -subtrees, where a t -subtree is the union of t disjoint subtrees of some tree. This graph class generalizes both the class of chordal graphs and the class of t -interval graphs, a generalization of interval graphs that has recently been studied from a combinatorial optimization point of view. We present approximation algorithms for the Maximum Independent Set, Minimum Coloring, Minimum Vertex Cover, Minimum Dominating Set, and Maximum Clique problems.

Scheduling algorithms and routing structures for efficient convergecast in wireless sensor networks

Purpose – A primary task of wireless sensor networks is to measure environmental conditions. In most applications, a sink node is responsible for collecting data from the sensors through multihop communications. The communication pattern is called convergecast. However, radio congestion around the sink can easily become a bottleneck for the convergecast. The purpose of this paper is to consider both scheduling algorithms and routing structures to improve the throughput of convergecast.Design/methodology/approach – The paper addresses the issue from two perspectives. First by considering the transition scheduling that reduces radio interference to perform convergecast efficiently. Second, by studying the effects of routing structures on convergecast. A routing algorithm, called disjoint‐strip routing, is proposed as an alternative to existing shortest‐path routing.Findings – The paper shows that constructing a shortest‐length conflict‐free schedule is equivalent to finding a minimal vertex coloring. To sol...