CIE Whiteness Research Articles

New method of whiteness calibration of spectrophotometers

AbstractA method is described for determining and calibrating the CIE Whiteness Index (WI) of an OBA‐treated specimen without incorporating into the measurement system a mechanically adjustable UV filter. The method requires spectrophotometric measurement of the specimen under two lights: UV‐excluded to infer the reflectance r(λ) and UV to infer the fluorescence profile f(λ). Also required is a stored illuminant spectrum Iin(λ) that covers at least the whole visible wavelengths. Only one scalar value k is then needed to mathematically characterize the total spectral radiance factor (TSRF) of the same specimen under Iin(λ). Calibration uses a reference specimen with known WI, and adjusts k until the computed WI matches the reference WI value. If Iin(λ) is the illuminant chosen from ASTM E313 to define the WI, the k adjustment reduces to solving a single quadratic equation for k that involves the reference WI. In general, relative to directly measuring a specimen's TSRF, it is more instrument‐independent to use the current method to characterize TSRF. Therefore, if a fluorescent specimen is measured using UV and UV‐excluded illuminants, a complete, instrument‐stable characterization of the specimen's TSRF can be derived by adjusting k, which can be done through a closed‐form relation of k to the WI.

Non-conventional starch from cubio tuber (Tropaeolum tuberosum): Physicochemical, structural, morphological, thermal characterization and the evaluation of its potential as a packaging material

This work aimed to characterize the physicochemical, structural, morphological, and thermal properties of a non-conventional starch obtained from cubio (Tropaeolum tuberosum), as well as to evaluate the potential use of this native Andean tuber in the preparation of biodegradable packaging. The cubio starch (CUS) showed an intermediated apparent amylose content (31.2 %) accompanied by a high CIE whiteness index (90.8). About the morphology and particle size, the CUS exhibited irregular oval and round shapes and a smooth surface with a mean particle diameter of 14.04 ± 0.1 μm. Although it showed good stability regarding pasting properties, the final viscosity was low. Native CUS exhibits a typical B-type diffraction structure, with a relative crystallinity of 16 %. The resistant starch (RS) fraction of the CUS was 94 %, indicating a low susceptibility to enzymatic hydrolysis. The thermal analysis demonstrated that the CUS showed good thermal stability. Additionally, the films prepared using CUS as raw material showed continuous surfaces without porosities, good thermal stability, and high transparency. The results of this work demonstrate the industrial potential of the CUS as it presents characteristics comparable to commercial potato starch.

Whiteness Perception under LED Source with High Content of UV Radiation

Whiteness is an attribute of color perception with high brightness and low colorfulness. In this study, the correlation between instrumental measurement and visual assessment of whiteness of 40 optically brightened white samples was investigated under a LED light source of correlated color temperature (CCT) 5000K combined with Wood's UV-A lamp. Due to over exposure of UV radiation, tested samples were outside of CIE limit. In those cases, standard CIE whiteness formula show significant shift in whiteness interval scale. A high correlation was identified between visual assessment and modified Vik-Viková whiteness formula. The investigations have also shown that the existing CIBA plastic whiteness scale needs to be expanded.

Decolorization of dark-colored waste cotton fabric using redox decoloring agents.

A huge quantity of dark-colored waste cotton fabrics with a high content of dye powder is dumped in landfills and incinerated, which is a waste of resources and pollutes the land and atmosphere. Also, it is meaningful to effectively strip the color from these dark-colored waste cotton fabrics with minimal damage to the strength of the textiles. In this study, a dark-colored waste cotton fabric dyed with reactive dyes was subjected to chemical treatment with redox decoloring agents. The effects of various treatments on the coloration and mechanical properties of the fabric were compared. This work developed an effective Na2S2O4–H2O2 system for decolorizing waste cotton fabric, with numerous advantages over conventional physicochemical approaches including achieving a CIE whiteness index of 74.1, tensile strength loss of 24.0%, weight loss of 1.2%, decoloration rate of 97.8%, and a degree of polymerization of 735.3. Furthermore, a mechanism was proposed to explain the two-step synergistic decolorization process.

Effect of neutralizers and silicone softeners on phenolic yellowing phenomenon of OBA treated cotton knitted fabric

Phenolic yellowing is a complex physicochemical phenomenon of cotton, especially for white and pastel-colored fabrics. This study tried to analyze the effect of neutralizers and silicone softeners on this. Three types of neutralizers of different chemical characteristics (acetic acid, citric acid, and commercial complex acid) were used to achieve core neutralization whereas two unlike ionic nature of silicone softeners (cationic & non-ionic) for the finishing process used. The acetic acid and nonionic softener treated fabric gives the maximum CIE (International Commission on Illumination) whiteness index value of 151 while citric acid and cationic softener have the least rating of 140.93 with a similar chemical dosage of 1.5 g/l by immediate testing. However, after repeated testing for one-month conditioning in atmospheric conditions, complex acid, and nonionic softener treated samples exhibited the maximum whiteness index of 145.86; on the other hand, citric acid and cationic softener treated one had the least rating of 125.85. Moreover, fabric core pH, reading was found to be 6.68, 6.15 & 5.13 for acetic acid, citric acid, and complex acid through immediate testing. After one month of conditioning, the values were 7.2, 6.61, and 5.25, respectively. Finally, a maximum phenolic yellowing rating of 4–5 was found with complex acid & nonionic softener in contrast poor rating of 2 with acetic acid & cationic softener for immediate testing. Storage of the samples has a significant impact on phenolic yellowing for all types of chemical concentrations. Lightfastness rating was found identical for all samples while bursting strength had a very negligible impact, Fourier transform infrared (FT-IR) spectroscopy also revealed the presence of noticeable chemical functional groups.

An eco-friendly approach to low-temperature and near-neutral bleaching of cotton knitted fabrics using glycerol triacetate as an activator

Near-neutral bleaching of cotton fabrics at low temperature is of great importance for saving energy and ecological friendliness in textile industry. In this work, glycerol triacetate (GT) was investigated as an activator of hydrogen peroxide (H2O2) for low temperature bleaching of cotton knitted fabrics, and satisfactory whiteness was obtained. The bleaching properties of H2O2/GT system for cotton was assessed by the CIE whiteness index (WI), H2O2 decomposition rate, concentration of generated peracetic acid and bursting strength. Possible factors affecting the properties of cotton bleached by H2O2/GT bleaching system were discussed in detail. At 60 °C, adding only 10 mmol/L GT to the hydrogen peroxide solution (60 mmol/L) to bleach cotton knitted fabrics for 60 min, the WI was significantly increased from 52.09 to 68.92. By using benzenepentacarboxylic acid as a fluorescent probe for hydroxyl radical (HO·) detection, it was found that GT could clearly promote HO· generation and its concentration closely related to the WI of cotton fabric. Furthermore, the bleaching mechanism of H2O2/GT system was proposed by exploring the relationship between WI and HO· concentration. GT as a bleach activator has more economical benefits and better water solubility than tetraacetylethylenediamine. The H2O2/GT system may provide a cost-effective and environmentally friendly bleaching approach of cotton as alternative to conventional alkaline high-temperature bleaching.

Established an eco-friendly cotton fabric treating process with enhancing anti-wrinkle performance

This study establishes an eco-friendly anti-wrinkle treating process for cotton fabric. Sodium hydroxide-liquid ammonia pretreatment followed by 6% (w/w) PU100 adding citric acid pad-cure-dry finishing. In this process, citric acid (CA) was used as the fundamental crosslinking agent during finishing because it is a non-formaldehyde based, cost-effective and well wrinkle resistance agent. Environmental-friendly waterborne polyurethane (WPU) was used as an additive to add to the CA finishing solution. Six commercial WPUs were systematically investigated. Fabric properties like wrinkle resistance, tensile strength retention, whiteness, durable press, softness, and wettability were well investigated. Fourier transform infrared spectra and X-ray diffraction spectra were also measured and discussed before and after adding waterborne polyurethane. Tentative mechanism of the interaction among the WPU, CA, and modified cotton fabrics is provided. The effect of cotton fabric pretreatment on fabric performance was also investigated. After the eco-process’s treatment, the fabric wrinkle resistant angle was upgraded to 271 ± 7°, tensile strength retention was maintained at 66.77% ± 3.50% and CIE whiteness was elevated to 52.13 ± 3.21, which are much better than the traditional CA anti-wrinkle finishing based on mercerized cotton fabrics. This study provides useful information for textile researchers and engineers.

Improvement in the absorbency of ozone bleached cotton fabric by the addition of surfactant

The combined effect of surfactants with ozone bleaching process on the quality of cotton fabric was examined in this paper. The concentration of surfactants was varied between 0.01- 0.5 g/l in order to evaluate its effect on CIE whiteness, absorbency and strength of cotton fabric bleached by ozone. The maximum improvement in absorbency (1.07 s) and whiteness (WCIE 66.53) was achieved in the presence of anionic surfactant (0.01 g/l) at optimized experimental conditions. The strength properties of cotton fabric bleached by ozone in the presence of surfactant were also improved. Pollution load of ozone bleaching effluent even after adding surfactant was far less than conventional bleaching effluent. Statistically it was confirmed that surfactant addition significantly improved the whiteness and absorbency of ozone bleached cotton fabric.

OCCUPATIONAL AND PUBLIC HEALTH. THE WRINKLE RECOVERY ANGLE (WRA) STUDY OF FABRIC THAT NANO-SILVER TREATED

The constant use of wrinkle-resistant cellulose fabrics in professional and everyday life can negatively affect the health state. This is because formaldehyde vapours, which contribute to allergies, persistent coughing, and irritation of the eyes, nose, and throat, sleep disturbances, headaches, etc., pose a greater danger. In this study an attempt was made to achieve fabric stabilization from wrinkle resistant by formation ionic bonds of as replacement covalent bonds. And this is the main study purpose. Industrially Desized and Bleached 100 % pure cotton fabric with the weight of 110 g/m2, and the chemicals were used. Preparation of cationic glycerine, carboxymethylation of bleached fabric and application of antimicrobial finishes on the ionic cross-linked fabric was provided. Measurements were taken to determine of wrinkle recovery angle (WRA), of absorbency, of whiteness index, of flexural rigidity, of abrasion, of tensile strength. Wrinkle recovery angle was measured by standard method of AATCC 66 (option 2). AATCC Test Method 79-2000 was used to test the absorbency of fabric. The CIE whiteness index was determined using an Xrite Colour Eye 7000A spectrophotometer. Flexural Rigidity was measured through a testing cantilever method ASTM D-1388. Fabric abrasion was checked according to standard method for abrasion resistance of textile fabric ASTM 4966 on Martindale Abrasion Device M235. Mechanical strength of the fabric was measured under the standard method of ASTM D-5034. With the ionic cross-linking, the dry WRA was achieved an optimum of 118º and wet WRA up to 128º with increased fabric strength and whiteness. In addition to ionic cross-linking fabric was treated with Nano silver. Based on the results it was concluded that the fabric can be optimized first with ionic cross-link method and then it can be treated with the antimicrobial making the fabric cleaner and hygienic. This fabric treatment provides the necessary characteristics and is safe for the health of the people who use it.

Whitening citric acid treated cotton fabrics by a TBCC-activated peroxide post-bleaching

Citric acid (CA) is a non-formaldehyde and cost-effective crosslinking agent which can provide cotton fabrics a comparable anti-wrinkle property, however, the CA treated cotton fabrics show serious yellowish appearance which restricts its application. In this study, cotton fabrics treated by CA were whitened using a TBCC-activated peroxide post-bleaching. A response surface methodology based on central composite rotatable design was applied to establish models to investigate how were the CIE whiteness index (WI), wrinkle resistance angle (WRA) and tensile strength retention (TSR) of the CA treated cotton fabrics affected by the post-bleaching variables, namely activator N-[4-(triethylammoniomethyl)benzoyl]caprolactam chloride (TBCC) concentration, temperature and time. For each individual post-bleaching experiment, the molar ratio of TBCC: hydrogen peroxide: sodium bicarbonate was set at 1:1.1:1.2. The analysis of variance results shows that the optimal models for response WI, WRA and TSR were quadratic model, 2-factor interaction model and linear model, respectively. It was possible to obtain CA treated fabrics with enhanced WI, maintainable WRA and improved TSR by a moderate post-bleaching temperature near 60 °C and a TBCC concentration around 30 mmol/L.

Atık Selülozik Karışımı Kaynaklardan Üretilen Alçı Esaslı Levhalar: 2. Bölüm. Kimyasal ve Teknolojik Özellikler

En yüksek toplam renk farkı (∆E) benzer üretim şartlarında atık kağıt ve eski oluklu muykavvalardan üretilmiş levhalarda (A4: 6.09; B4: 5.79) gözlemlenmiştir. Bu levhalara aynı zamanda en düşük CIE whiteness değerleri göstermiştir (A4: -33.19; B4: -28.44). FTIR tekniği yarımıyla levhaların yüzeylerindeki kimyasal gruplar incelenmiştir. A ve C tipi levhaların diagramları benzerlik göstermekle birlikte B tipi levhaların TGA diyagramları oldukça farklı olduğu anlaşılmıştır. Özellikle başlangış sıcaklık değerlerinde (100-120 0C) B tipi levhaalrın ağırlık kaybı diğer A ve C tipi levhadan daha yüksektir. Bu durum muhtemelern atık oluklu mukavva (B tipi levha) yapısında selülozik liflerden ayrı olarak daha yüksek oranda nişasta, silika, lignin bulunmasından ileri gelmesindir. Deneme levhalarının yüzeyine uygulanan alevin, tüm levhalar için kritik eşik değer olan 150 mm seviyesine gelmediği gözlemlenmiştir. Alev uzaklaştırıldıktan sonra dahi, yüzeydeki yayılma kritik sınır değerine ulaşmamıştır. Buradan üretilen deneme levhalarının TS EN-ISO 11925-2 standardına göre yanma malzeme sınıfına dahil edilebilir. Deneme levhalarının ısı yalıtım özellikleri incelendiğinde, alçı yapısına lignoselüloik hammaddenin ekllenmesinin olumlu katkı yaptığı anlaşılmıştır. Levha yapısında %10 dan daha yüksek atık kağıt eklenmesinin (A3-A6 levhalar) aynı üretim şartlarındaki atık oluklu mukavva (B tipi) ve sekonder lif esaslı (C tipi) deneme levhalarından daha yüksek ısı yalıtımı sağladığı anlaşılmıştır. Genel olarak ısı transfer ortalama değerleri kontrol örneğine göre daha iyi olduğu görülmüştür. İlginç olarak en yüksek ısı izolasyonu sağlayan örnek aynı zamanda en yüksek kütle kaybı göstermiştir. En yüksek kütle kaybı A tipi levhadalarda %3,52 (A6), B tipi levhalarda 3.46% (B6) ve C tipi levhalarda 3.28% (C8) olarak ölçülmüştür.

High‐performance printable paper‐like composites derived from plastic flexible film wastes

AbstractOwing to lack of proper recycling methods, plastic flexible film wastes are usually directly discarded or incinerated, which brings about severe environmental pollution. Therefore, converting plastic wastes into value‐added products has received more and more attention in recent years. In this work, paper‐like composites derived from plastic flexible film wastes were prepared via the thermally induced phase separation method by adding polyethylene‐graft‐maleic anhydride (PE‐g‐MAH) as a compatibilizer and fumed silica as an additive. The resulting paper‐like composites were characterized by SEM and infrared spectroscopy. Other properties such as mechanical properties, thermal properties, whiteness, printability and adsorption performance were also tested in detail. It was found that remarkable enhancements in mechanical, thermal and printable properties of the paper‐like composites were obtained when nano‐SiO2 loading was 2.5–3 wt%. Uniformly distributed holes that can endow good printability by providing space for ink or other functional molecules were observed by using SEM. Furthermore, the CIE whiteness value of the resulting composites can reach 91.6%–96.7% on adding nano‐SiO2. Additionally, the paper‐like composites integrating nano‐SiO2 and PE‐g‐MAH exhibited good solid ink affinity and high water or oil adsorption capacity. Thus, according to this research, high‐performance printable paper‐like composites used as major components of multifunctional papers can be prepared based on plastic flexible film wastes. © 2019 Society of Chemical Industry

New Metrics for Evaluating Whiteness of Fluorescent Samples

A magnitude estimation experiment was carried out to scale the extent of whiteness from a set of near white textile samples including fluorescent white agent. Each was assessed under 4 different CCTs, each having a high and a low level of UV energy. The results were used to test various existing whiteness formulae. Finally, by fitting to the present data, two new metrics were developed. One is based on CIECAM02, and the other is based on the present CIE whiteness formula by transforming the data to D65 chromaticity from the other white sources via CAT02 chromatic adaption transform with a proper incomplete adaptation factor (D). It was also tested using an independent set of data. Both formulae gave accurate prediction to the data. The former metric is proposed because it is based on a colour appearance model.

Evaluation of colorimetric indices for the assessment of tooth whiteness

ObjectivesTo evaluate the performance of existing equations that measure perceptual whiteness of teeth. MethodsThree new psychophysical experiments were conducted and combined with two previously published experiments to form a large set of data to test performance of whiteness indices. Three whiteness indices (WIC, WIO, WID,) were compared with regard to their ability to measure perceived whiteness. Coefficient of determination (r2) and ‘% wrong decisions’ were used as measures of performance. One of the new experiments involved 500 participants across five different countries to explore the effect of gender, age and culture on whiteness perception. ResultsEquations (WIO and WID) that have been optimized for use with tooth whiteness better correlated with visual perceptions of changes in tooth whiteness than the more general CIE whiteness index (WIC). The best performance was given by WIO (in terms of both r2 and % wrong decisions). No effect of age, gender or culture was found on whiteness perception. ConclusionsWIO is a robust method for assessing whiteness of human teeth.

Development of a whiteness formula for surface colors under an arbitrary light source.

The whiteness specification is critically important in surface color industry, especially when fluorescent whitening agents (FWAs) are added to objects. The CIE whiteness formula, the most widely used whiteness formula, only characterizes the whiteness under CIE standard D65, which ignores the change of whiteness under different light sources due to the spectral content of the light sources. Though the adoption of a Chromatic Adaptation Transform (CAT02) in the CIE whiteness formula was found effective in recent studies, it failed to allow a comparison across different correlated color temperatures (CCTs). In this study, a haploscopic viewing condition was employed, with a D65 simulator in the left booth, for evaluating the whiteness of eight samples under different light sources in the right booth. The whiteness of the four samples under the D65 simulator was employed as a whiteness scale to aid the evaluation. Based on the experiment results, the characterization of whiteness for a surface under an arbitrary light source is proposed to use the CIE whiteness formula with the sample chromaticities being transformed using CAT02 and an adjusted degree of chromatic adaptation factor D.

Judgment of White Appearance for Surface Colors under Individual and Simultaneous Observations

ABSTRACT The weakness of the CIE whiteness formula, the most widely used formula to characterize the whiteness of surface colors, has been well documented. It cannot characterize the whiteness under the illuminants other than CIE standard D65 and has a small whiteness boundary. A psychophysical experiment was carried out to investigate the whiteness boundary toward the blue-tint direction under 3000 and 6500 K illuminants with high violet radiations to excite the fluorescent whitening agents (FWAs) and to cover a wide range of whiteness appearance. Sixty samples (that is, 30 paper and 30 fabric samples) were individually and simultaneously evaluated for whether the samples appeared white or not by the same group of human observers. The judgments made by the observers were significantly different between the two evaluations. When the samples were simultaneously evaluated, the samples needed to have higher whiteness values to be judged as white and there were large interobserver variations, which was speculated to be due to the variation in chromatic adaptation among the observers. Such a variation was likely caused by the wide range of whiteness appearance included in this experiment and each observer was adapted to the color of the whitest sample selected by him or her during the simultaneous evaluations.

Synthesis of novel 4,4'-bis(2,4-pyrimidinyl)-diaminostilbene-2,2'-disulfonic acid derivatives and their whitening effect on cotton fiber as fluorescent whitening agents

Some novel 4,4'-bis(2,4-pyrimidinyl)-diamino stilbene-2,2'-disulfonic acid derivatives 4a-d were designed and synthesized. Their structures were confirmed by proton nuclear magnetic resonance, elemental analysis and ultraviolet absorption spectra. All newly synthesized compounds were interrogated on their whitening effect on cotton fiber as fluorescent whitening agents. Their optical properties were evaluated by the degree of whiteness, color index, light fastness, wet rubbing fastness and dry rubbing fastness. The results indicated that compounds 4a-d showed an obvious whitening effect on cotton fiber and higher fastness than that of C186. The reflectivity of cotton fiber treated with compounds 4a-d at the critical concentration was up to 120.76%. In contrast, the reflectivity of untreated cotton fiber was only 87.23%. The ultraviolet absorption properties of compound 4d were tested under diverse pH values. The results showed that the ultraviolet absorption intensity of compound 4d decreased significantly and the absorption curve had blue shift under acidic conditions. Compound 4d was found to be the most effective molecule as a fluorescent whitening agent with a higher degree of whiteness (CIE Whiteness 135.04) compared to untreated cotton fiber (CIE Whiteness 73.02) at the critical concentration (0.1%).

Bleaching of cotton fabric with tetraacetylhydrazine as bleach activator for H2O2

Tetraacetylhydrazine (TH) as bleach activator for H2O2 cotton bleaching was synthesized and characterized by 1H NMR, 13C NMR and MS spectra. TH has better solubility than that of TAED. The CIE whiteness index (WI), H2O2 decomposition rate and bursting strength were employed to investigate the performance of H2O2/TH bleaching system. By addition of TH, WI and H2O2 decomposition rate increased significantly at 70 °C. Bleaching temperature, NaHCO3 concentration and bleaching time were also discussed in detail and the loss of bursting strength is not clear. By using benzenepentacarboxylic acid (BA) as a fluorescent probe for hydroxyl radical detection, the bleaching process of H2O2/TH system was investigated. Acetylhydrazine and diacetylhydrazine were also utilized to further confirm the process. In addition, bimolecular decomposition was investigated by using 9,10-dimethylanthracene (DMA) as fluorescent probe of 1O2. Based on these experimental results, the bleaching mechanism of H2O2/TH system was proposed.

Development of o-phthalic anhydride as a low-temperature activator in H2O2 bleaching system for cotton fabric

O-phthalic anhydride (PA) was developed as a low-temperature activator in the H2O2 bleaching system for cotton fabric. The performance of the H2O2/PA bleaching system was investigated by measuring the CIE whiteness index (WI) of the bleached cotton fabric, H2O2 decomposition rate and bursting strength, respectively. The effects of experimental conditions, including PA dosage, bleaching time, bleaching temperature and NaOH concentration, were discussed in the H2O2/PA bleaching system. Upon addition of PA, the WI and H2O2 decomposition rate increased significantly at 70 °C. The results showed that the bleaching system had a promising application prospect. Compared with the H2O2 system, the H2O2/PA system significantly promoted 1O2 generation under the same alkali condition by using 9,10-dimethylanthracene as a fluorescent probe for 1O2. And the generation of large amount of 1O2 did not obviously affect the bleaching performance in the H2O2/PA system. By using benzenepentacarboxylic acid as a fluorescent probe for HO· detection, it was found that the fluorescence intensity was enhanced 14 folds in the presence of PA, indicating that PA could strongly promote HO· generation. By using dimethyl sulfoxide as a scavenger to control HO· concentration, it was found that the WI of the fabric was closely related to the HO· concentration, revealing that the HO· could play an important role in the bleaching process. Phthalic acid was also added to the H2O2 bleaching system to investigate potential bleaching route of the H2O2/PA system. Based on these experimental results, a possible bleaching mechanism of the H2O2/PA system was proposed.

Chromaticity and characterization of whiteness for surface colors

Whiteness is an important colorimetric characteristic for surface colors. The CIE whiteness formula, the most widely used formula, only characterizes the whiteness of a surface color under CIE standard D65 and requires a sample to be within a small chromaticity region. In this study, 20 observers evaluated the whiteness appearance of 88 samples under four light settings at different CCT levels (i.e., 3000, 4000, 5000, and 6500 K). The 88 samples were carefully selected and the spectral power distributions of the light settings were carefully designed using a spectrally tunable LED device, so that the chromaticities of the samples under each light settings uniformly covered a wide range along the yellow/blue direction in a color space, which had never been realized before. The results, together with the two recent studies, allowed the derivation of ellipsoids for classifying the whiteness appearance for surface colors. For the samples within the derived ellipsoids, though the Uchida whiteness formula with CAT02 (WUchida,CAT02) had a higher correlation to the perceived whiteness than the CIE whiteness formula with CAT02 (WCIE,CAT02), samples that were perceived as white and had a high chroma with a hue angle of blue due to the high violet/ultraviolet radiation in the illumination may had a negative WUchida,CAT02 value. A comprehensive whiteness formula that can accurately characterize the whiteness appearance for surface colors under an arbitrary light source by considering different conditions is still necessary and the work is undergoing.