Seyed Amirshahi - Academia.edu (original) (raw)

Papers by Seyed Amirshahi

Indices for describing the degree of metamerism are based on either the deviation of the spectra ... more Indices for describing the degree of metamerism are based on either the deviation of the spectra of a metameric pair or the colour difference of the pair under test conditions. The magnitude of illuminant metamerism is commonly evaluated by measuring the colour difference under the test illuminant. The calculated colour differences absolutely vary with the selected test illuminants, so the measured (special) index of metamerism could be considered as a test-illuminant-dependent value. The spectral-based indices of metamerism act as a single-number value, but most of them are criticised for their poor correlation with visual assessment. In this paper, a general metric is developed for evaluating the upper limit of the degree of illuminant metamerism. The suggested approach combines the advantages of general and special indices, avoiding their drawbacks at the same time. The performance of the formula is analysed in a number of numerical experiments, as well as by practical testing.

Damages resulting by micro-organisms on Iranian cotton (Sahel variety) with 65—70% relative humid... more Damages resulting by micro-organisms on Iranian cotton (Sahel variety) with 65—70% relative humidity and 25 °C temperature within four months storage periodare investigated . A number of tests are currently available to identify and quantify such cottons called cavatomic . These tests include pH and reducing sugar determinations, microscopy techniques, staining methods and determination ofphysical changes . Some of these testshavebeenapplied to evaluatepossiblemicrobial damage to cotton ofGonbad-Ghabous spring crop . The effects of the micro-organisms growth on the whiteness and dye- ability of different samples are also determined . Data and observations totally support the slow growth of themicro-organisms in this variety of cottons.

Encyclopedia of Color Science and Technology, 2014

Coloration Technology, 2009

Colorimetric matching is employed under a series of virtual illuminants to produce more controlla... more Colorimetric matching is employed under a series of virtual illuminants to produce more controllable and equalised colour-difference results under multiple illuminants. A method based on weighted principal component analysis of different artificial lights and the weighted mean is used to ...

In order to increase the sorption power of collected fibres, they were powdered by a plain millin... more In order to increase the sorption power of collected fibres, they were powdered by a plain milling machinery to prepare very fine particles with the size of 1 to 5 micron. They provided a very large surface area which speed on the sorption rate. The effects of size of absorbent on depolarization rates of various types of acid dyes as well as the concentration of dyes and the temperature of wastewater were studied by simulation of effluent conditions. The measurement of chemical oxygen demand (COD) and the absorption spectrophotometer technique were used to evaluate the performance of the system. More than 90% of acid dyes were elevated from wastewater with 1g/lit of powdered polyamide.

In this study, two new criteria are suggested to assess the unlevelness of fabrics with different... more In this study, two new criteria are suggested to assess the unlevelness of fabrics with different degrees and patterns of unevennesses by analyzing of data obtained by imagining of fabrics with scanner. The basic statistical properties of matrices of grabbed images, i.e. the singular values extracted by singular value decomposition technique and the two dimensional standard deviations are introduced as the unlevelness indices. The results are compared with those reported by visual assessment of observers as well as numerical outcomes of quantitative method employing the spectral K/S values calculated from reflectance spectra of samples by spectrophotometer.

Optical Review, 2010

The positive basis functions of the reflectance spectra of Munsell color chips are extracted by u... more The positive basis functions of the reflectance spectra of Munsell color chips are extracted by using the classical nonnegative matrix factorization method. Different numbers of basis, i.e., 3 to 5, are determined and used as projection spaces. The spectral reflectances of samples are defined in the desired compact spectral spaces and the performances of the spaces are evaluated through the cost of the ''lost data'' by computing of the root mean square error between the actual and the reconstructed spectra as well as the corresponding color difference values under different viewing conditions. The method is also compared with the most welcomed technique, i.e., principal component analyzing, and its priority is shown to some extent in the three dimensional space. To show the importance of the spectral behaviors of samples in the dataset on the extracted basis and consequently the error of the spectral reconstruction trial, the adaptive non-negative matrix factorization method is introduced and examined in the reconstruction of spectral data from the colorimetric tristimulus values. The suggested method weights the samples in the database proportional to the colorimetric differences between the specimens in the dataset and the sample whose spectral has been aimed, prior to the extraction of all positive bases. The root mean square errors between the actual and the reconstructed spectra as well as the metamerism indices under A and F11 illuminants are calculated and the results show considerable improvement over the classic non-negative matrix factorization method as well as the principal component analyzing technique.

Fibers and Polymers, 2013

ABSTRACT A new method for determining the dye distribution in the cross section of polyamide rods... more ABSTRACT A new method for determining the dye distribution in the cross section of polyamide rods from the scanner data is presented. Three commercial disperse dyes are used for dyeing purposes and two series of dyed samples are prepared. The first set is the samples with the full diffusion of dyes within the cross section of rods that used as the reference samples while the second set includes samples with different depths of penetrations, hence they benefit from non homogenous dye distribution in their cross sections. A conventional scanner is characterized with the ColorChecker SG and the transformation matrix is computed to convert the RGB values of samples to the CIEXYZ data. The spectral reflectances as well as the RGB values of the cross sections of the full diffused dyed samples are measured and the classical version and the weighted version of principal component analysis technique are employed to estimate the spectral behaviors of homogenous dyed samples from the CIEXYZ values obtained from the corresponding RGB data. Finally, the well known Kubelka Munk equation is employed to estimate the concentration of dyes in the cross sections of samples. The work is extended to non homogenous dyed samples to find the spatial distributions of dyes over the cross sections of rods. Similar to full diffused dyed samples, the spatial reflectance spectra of the cross sections are firstly estimated from the measured RGB values and then the spatial concentrations are computed. The plotted concentration-distance profiles confirm the classical variations of dye concentrations over the cross sections of dyed rods similar to those that are obtainable by conventional methods such as multiple membranes and Boltzmann-Matano as well as laser scanning confocal microscopy methods.

Fibers and Polymers, 2010

Fibers and Polymers, 2008

The reflectance factors of the polyamide rods which were dyed with different concentrations of th... more The reflectance factors of the polyamide rods which were dyed with different concentrations of three commercial yellow, red, and blue disperse dyes are recovered from their RGB data obtained from scanning of the cross sections of rods with the desktop scanner. The RGB data are converted to device independent XYZ tristimulus values by simple polynomial regression technique. Then, the principal component analysis (abbreviated by PCA) technique is employed for the recovery of reflectance spectra from the tristimulus values by using three different datasets, i.e. using the reflectance factors of Munsell chips, MacBeth ColorChecker SG, and a dynamic dataset prepared from the reflectance factors of dyed rods samples. The first three eigenvectors of each dataset are extracted and employed in the reconstruction process of spectral reflectance from XYZ colorimetric data. Finally, the well known Kubelka-Munk function is implemented for estimation of concentration of dye from the recovered spectral reflectance. The root mean square (RMS) errors between the reconstructed and the actual reflectance data over the visible spectrum are calculated. According to results, the RMS errors for the reflectance recovery are within the acceptable range. Error of estimation of dye concentration in the rods varies for different hues as well as concentrations and changes with applied dataset.

Coloration Technology, 2011

The spectral dependence of the colorimetric characterisation of a typical scanner was investigate... more The spectral dependence of the colorimetric characterisation of a typical scanner was investigated. Different colour sets, including ColorChecker SG, Kodak Q-60 colour input target, a set of plain woven coloured fabrics with a large colour gamut, and randomly selected samples of the Munsell Book of Color were used as training and testing sets in the colorimetric characterisation of a scanner by employing a non-linear regression method. The coefficient matrices were optimised for each particular media in the training stage and ...

Color Research & Application, 2009

Berns' method for the synthesis of spectral reflectance curve from the tristimulus color coordina... more Berns' method for the synthesis of spectral reflectance curve from the tristimulus color coordinates is modified. Firstly, the Gaussian bell shape red primary is replaced with a sigmoidal one to solve the dissimilarity between the spectral curves at the end region of spectrum. Secondly, three predetermined Gaussian primaries used in the original Berns' method are replaced by the adaptive ones which their half-height bandwidths vary with the tristimulus values of the desired color. The mentioned modifications are applied for the recovery of the reflectance curves of 1409 surface colors (including 1269 Munsell color chips and 140 samples of Colorchecker SG) and also 204 textile samples. Results of recovery are evaluated by the mean and the maximum color difference values under other standard light sources. The mean as well as the maximum of root mean squares between the reconstructed and the actual spectra are also calculated. The modifications are compared with the common principal component analysis (PCA) as well as Hawkyard's methods for recovery of reflectance factor. Although the PCA leads to the best results, the modifications significantly improve the recovery outcomes in comparison with the original Berns method.

D yeing behaviour of chitosan pretreated cotton fabric with reactive dyes is the subject of this ... more D yeing behaviour of chitosan pretreated cotton fabric with reactive dyes is the subject of this study. Cotton fabric is treated with chitosan using five different techniques, consisting of exhaustion, pad-dry, pad-batch, pad-steam and pad-drysteam methods. To find the influence of concentration of chitosan on the dyeability behaviour, different amounts of chitosan were used and the suitable concentration was determined. It is observed that chitosan pretreatment increases the exhaustion of reactive dyes and the highest dye up-take is achieved for pad-dry method. The effect of the period of storage of chitosan treated sample before dyeing process on dyeability of fabrics is examined by comparison of samples which was dyed immediately after treatment with the one which was kept for 48 h after treatment. The results show that dyeing immediately after treatment leads to higher dyeability and the effect of treatment decreases for the samples which were pkept for 48 h before dyeing process. The light and wash fastnesses of treated samples are measured and some reduction in light and wash fastnesses were observed.

Research Journal of Textile and Apparel, 2006

Analytical Sciences the International Journal of the Japan Society For Analytical Chemistry, 2010

where Si(λ) is the spectral sensitivity of each channel i (i = 1,...,P), E(λ) and R(λ) refers to ... more where Si(λ) is the spectral sensitivity of each channel i (i = 1,...,P), E(λ) and R(λ) refers to the spectral power of the light 2010

Large multi-spectral datasets such as those created by multi-spectral images require a lot of dat... more Large multi-spectral datasets such as those created by multi-spectral images require a lot of data storage. Compression of these data is therefore an important problem. A common approach is to use principal components analysis (PCA) as a way of reducing the data requirements as part of a lossy compression strategy. In this paper, we employ the fast MCD (Minimum Covariance Determinant) algorithm, as a highly robust estimator of multivariate mean and covariance, to detect outlier spectra in a multi-spectral image. We then show that by removing the outliers from the main dataset, the performance of PCA in spectral compression significantly increases. However, since outlier spectra are a part of the image, they cannot simply be ignored. Our strategy is to cluster the outliers into a small number of groups and then compress each group separately using its own cluster-specific PCAderived bases. Overall, we show that significantly better compression can be achieved with this approach.

In this work, new method was used for prediction the concentration of binary mixture of textile d... more In this work, new method was used for prediction the concentration of binary mixture of textile dyes by using spectrophotometric data. New method is based on ratio derivative spectra of dyes mixtures solution. The obtained results by this method have been compared with usual spectroscopy methods. In special mixture with overlap spectra such as red and yellow mixtures, the derivative method was better than normal spectroscopy method.

An adaptive dataset technique is employed in this study to recover the spectral behavior of acryl... more An adaptive dataset technique is employed in this study to recover the spectral behavior of acrylic paints from their tristimulus values under a given observing-illumination condition. Related to the color specifications of proposed sample, the suitable dataset was built from proper samples which were selected from the 2802 acrylic paints. Then, the basis functions of the each collected dataset were determined. Finally, the spectral reflectance of proposed sample was reconstructed by usual linear model. So, different datasets were formed and implemented for determination of basis functions, adaptive to the color specifications of proposed samples and adjusted criterion.