Optimal spectra for double object‐colour solids

Optimal colours for human vision occur on the boundary of a three‐dimensional object‐colour solid, and result from optimal reflectance spectra that take on only the values 0 and 1, with at most two transitions between those values. Different illuminants lead to different solids. If there are two illuminants and a single sensing device, then we can construct a six‐dimensional double object‐colour solid by concatenating colour signals from both illuminants. Colours on the boundary of a double‐object solid, and the spectra that generate them, can also be called optimal. This article shows that, while optimal spectra for double solids take on only the values 0 and 1, there is no maximum number of transitions between those values: given a device, we can always construct two illuminants such that the resulting double object‐colour solid has an optimal reflection spectrum with as many transitions as desired.     

A zonohedral approach to optimal colours

This article demonstrates that the CIE XYZ colour solid is a zonoid. An approximating zonohedral colour solid is constructed explicitly from a set of generating vectors, which are integrals of colour‐matching functions over narrow intervals of the visible spectrum. The zonohedral approach yields an intuitive, constructive proof of the Optimal Colour Theorem: the reflectance function of an optimal colour takes on only the values 0 or 1, with at most two transition wavelengths. In addition, zonohedral techniques can simplify computations: for example, optimal colours can be found without calculating transition wavelengths. Finally, zonohedra provide a simple, unified approach to colour space and eliminate much of the confusion arising from chromaticity diagrams. © 2011 Wiley Periodicals, Inc. Col Res Appl, 2013     

The structure characterization of thermosensitive poly(N‐isopropylacrylamide‐co‐2‐hydroxypropyl methacrylate) hydrogel

The goal of this work was to investigate a possible way of crosslinking polymer chains and the potential formation of intramolecular hydrogen bonds in thermosensitive poly(N‐isopropylacrylamide‐co‐2‐hydroxypropyl methacrylate) (p(NIPAM‐HPMet)) hydrogels obtained by radical polymerization. The chemical structure of the synthesized hydrogels was investigated by Fourier transform infrared (FTIR) spectroscopy and XRD. The FTIR spectrum confirmed the presence of hydrogen bonds formed between the chains in the copolymer. XRD analysis confirmed the amorphous ? crystalline structure of the copolymer. A three‐glass transition and two melting temperatures were detected by DSC. It was found that the addition of HPMet increased the glass transition and melting temperatures of the p(NIPAM‐HPMet) copolymer. The swelling transport mechanism of p(NIPAM‐HPMet) changed from non‐Fickian at 20 °C to case III or zero‐order time‐independent kinetics characterized by a linear mass uptake with time with increasing temperature at 40 °C. © 2013 Society of Chemical Industry     

Individual differences in human colour vision as derived from stiles & Burch 10° colour matching functions

Individual differences between the 49 Stiles & Burch observers have been analyzed using the object‐colour space put forth recently (J of Vision 2009;9:1–23). A set of rectangular reflectance spectra has been used as a common frame of reference for representing object colours for all the observers. Being metameric to one of these rectangular reflectance spectra, every reflectance spectrum can be geometrically represented as a point in the three‐dimentional space. The interindividual differences reveal themselves in that, for various observers, the same reflectance spectrum maps to different points in this space. It has been found that on average such differences do not exceed the differences in object‐colour appearance induced by an illumination shift from daylight to the fluorescent daylight simulator F1. Such small individual variations have been accounted for by the fact that the cone spectral tuning curves have a special form that mitigates the individual differences in cone spectral positioning. © 2012 Wiley Periodicals, Inc. Col Res Appl, 2013     

Fabrication of speedy and super‐water‐absorbing non‐woven cloth with hierarchical three‐dimensional network structure

A novel speedy and super‐water‐absorbing non‐woven cloth with hierarchical three‐dimensional network (3D‐SS‐PET) was fabricated through the induction of UV copolymerization on polyethylene terephthalate (PET) fibers followed by a volume phase transition. The macroscopic three‐dimensional network implied that the PET non‐woven substrates are complicated three‐dimensional fibrous materials including oriented fibers in preferential or random directions. The microscopic three‐dimensional network is poly(acrylic acid‐co‐acrylamide) (poly(AA‐co‐AM)) crosslinked copolymer layers on the fiber surface. The rapid volume phase transition was achieved by immersing the swelled non‐woven poly(AA‐co‐AM) modified PET (PET‐g‐AA‐co‐AM) in ethanol. The above process was an essential step to prepare the copolymer chain; after that the fiber surface was extended to form abundant capillary channels and plenty of space between fibers. The water contact angle decreased remarkably from 130° to 0°, while the absorbing capacity of the saturated water and the average water‐absorbing rate experienced an increasing trend, rising from 300 to 324.6 g g^?1 in 24 h and 18.6 and 222 g (g min)^?1 in 40 s, respectively. It was concluded that surface hydrophilicity and capillaries of the hydrophilic modified macroscopic fibrous structure enhanced the water‐absorbing rate and the swelling process contributed to the higher water absorption capacity. This speedy and super‐water‐absorbing material exhibits great potentiality in diapers, sanitary napkins, wound dressings, surgical pads, and hygroscopic and sweat‐free underwear in extremely cold areas. © 2018 Society of Chemical Industry     

Molecular simulation of the glass transition and proton conductivity of 2,2′‐benzidinedisulfonic acid and 4,4′‐diaminodiphenylether‐2,2′‐disulfonic acid‐based copolyimides as polyelectrolytes for fuel cell applications

The glass transition temperatures (T_gs) and proton conductivities of polyimides synthesized from naphthalene‐1,4,5,8‐tetracarboxylic dianhydride (NTDA), 2,2′‐benzidinedisulfonic acid (BDSA), 4,4′‐diaminodiphenylether‐2,2′‐disulfonic acid (ODADS), and non‐sulfonated diamine monomers have been predicted using molecular dynamics simulations. The specific volumes for two dry and four hydrated NTDA‐based polyimides were plotted versus temperatures above and below T_gs to obtain the glass transition temperatures. The simulation results suggest that the ODADS‐based polyimide membranes exhibit lower T_gs and thus better mechanical properties than the BDSA‐based polyimides, which may be attributed to the high mobility of backbones of ODADS as supported by the vectorial autocorrelation function (VACF) results of this study. In addition, comparison of the simulated T_gs for the dry and hydrated ODADS‐based polyimides has shown that water content in polyimides can affect their T_gs. The proton conductivities of a representative polyimide in both dry and hydrated conditions have been obtained from molecular dynamics simulations of the proton and hydronium ion diffusion. The simulated conductivity for the hydrated NTDA‐ODADS/BAPB cell is in reasonable agreement with the experimental value obtained from the AC impedance method. The relationship between the chemical composition, chain flexibility, and the glass transition and proton conduction of these NTDA‐based polyimides was explored on the basis of VACF and pair correlation function analysis. Copyright © 2006 Society of Chemical Industry     

DOPO‐Based Phosphorus‐Containing Methacrylic (Co)Polymers: Glass Transition Temperature Investigation

A two‐step synthetic procedure is designed for preparing new flame‐retardant methacrylic monomers containing 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) as a substituent side group. DOPO and methacrylate moieties are linked by linear aliphatic hydrocarbon spacers (3 to 11 carbon atoms). Copolymerization with methyl methacrylate is carried out leading to copolymers containing between 2 and 10 wt% phosphorus. All homo‐ and copolymers exhibit a unique glass transition temperature (T_g ). A new group contribution for DOPO‐based substituent is extracted that leads to reasonable estimations of T_g s of other published polymers. The Fox equation provides a good estimation of T_g s for most copolymers and for physical blends of poly(methyl methacrylate) (PMMA) and DOPO. When using monomers having three and four carbon atoms in the hydrocarbon spacer, the T_g of copolymers remains close to that of PMMA over a wide range of composition.     

Investigations on the polyimides derived from unfunctionalized symmetric cyclopentyl‐containing alicyclic cardo‐type dianhydride

This study presents an investigation on polyimides derived from a unfunctionalized symmetric cyclopentyl‐containing alicyclic cardo‐type dianhydride with ester linkage 1,1‐bis(4‐(3,4‐dicarboxylbenzoyloxy)phenyl)cyclopentylene dianhydride (BDPCP) that was readily accessed starting from cyclopentanone through two steps in high yield. Two series of polyimides, Cardo‐type series (CPI‐x) and analogous aromatic series (ArPI‐x) were prepared from condensation of BDPCP and aromatic 3,3′,4,4′‐Oxydiphthalic dianhydride with four aromatic diamines, respectively. Comparative studies revealed that CPI polymers show more favorable properties including better solubility in organic solvents, higher transparency with lower cut‐off wavelength (λ₀) ranging in 395–375 nm than 425–405 nm, lower water absorption ranging in 0.66–1.14% and surface energy 23.71–32.77 mN/m than 1.01–1.28% and 29.52–41.99 mN/m of ArPI analogs. Meanwhile, CPI series exhibit considerable mechanical properties with tensile strengths ranging in 87.6–102.9 MPa, elongations at break 6.6–8.9%. Owing to the moderate strain in cyclopentyl ring, CPI series retain good thermal properties with the glass transition temperature (T_g) in the range of 217–271°C. Dynamic dielectric measurement revealed that Cardo‐type dianhydride BDPCP endows CPI‐4 film with lower dielectric constant (ε′) 3.34 at 1 MHz and 25°C and dielectric loss (ε′′) 0.0064 at 1 kHz and 25°C than 3.49 and 0.013 for ArPI‐4 film. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42670.     

Synthesis of Valuable Chiral Intermediates by Isolated Ketoreductases: Application in the Synthesis of α‐Alkyl‐β‐hydroxy Ketones and 1,3‐Diols

Regio‐ and stereoselective reductions of α‐substituted 1,3‐diketones to the corresponding β‐keto alcohols or 1,3‐diols by using commercially available ketoreductases (KREDs) are described. A number of α‐monoalkyl‐ or dialkyl‐substituted symmetrical as well as non‐symmetrical diketones were reduced in high optical purities and chemical yields, in one or two enzymatic reduction steps. In most cases, two or even three out of the four possible diastereomers of α‐alkyl‐β‐keto alcohols were synthesized by using different enzymes, and in two examples both ketones were reduced to the 1,3‐diol. By replacing the α‐alkyl substituent with the OAc group, 1‐keto‐2,3‐diols, as well as 1,2,3‐triols were synthesized in high optical purities. These enzymatic reactions provide a simple, highly stereoselective and quantitative method for the synthesis of different diastereomers of valuable chiral synthons from non‐chiral, easily accessible 1,3‐diketones.     

AB‐ and ABC‐type di‐ and triblock copolymers of poly[styrene‐block‐(ε‐caprolactone)] and poly[styrene‐block‐(ε‐caprolactone)‐block‐lactide]: synthesis,characterization and thermal studies

Polystyrene terminated with benzyl alcohol units was employed as a macroinitiator for ring‐opening polymerization of ε‐caprolactone and L ‐lactide to yield AB‐ and ABC‐type block copolymers. Even though there are many reports on the diblock copolymers of poly(styrene‐block‐lactide) and poly(styrene‐block‐lactone), this is the first report on the poly(styrene‐block‐lactone‐block‐lactide) triblock copolymer consisting of two semicrystalline and degradable segments. The triblock copolymers exhibited twin melting behavior in differential scanning calorimetry (DSC) analysis with thermal transitions corresponding to each of the lactone and lactide blocks. The block derived from ε‐caprolactone also showed crystallization transitions upon cooling from the melt. In the DSC analysis, one of the triblock copolymers showed an exothermic transition well above the melting temperature upon cooling. Thermogravimetric analysis of these block copolymers showed a two‐step degradation curve for the diblock copolymer and a three‐step degradation for the triblock copolymer with each of the degradation steps associated with each segment of the block copolymers. The present study shows that it is possible to make pure triblock copolymers with two semicrystalline segments which also consist of degradable blocks. Copyright © 2009 Society of Chemical Industry     

Molecular mobility in comb‐like copolymethacrylates with chalcone‐containing side‐chains

The molecular mobility of comb‐like copolymers of amyl methacrylate with N‐methacryloyl‐(4‐amino‐4′‐bromochalcone) with various concentrations (20, 30, 40, 50 and 60 mol%) of chalcone‐containing comonomer was studied using dielectric spectroscopy. It was found that chalcone chromophores participate in two forms of molecular mobility: cooperative motion in the rubbery state (δ‐relaxation) and local motion in the glassy state (β‐relaxation). In addition, α‐, β₁‐ and γ‐processes, being related to cooperative segmental mobility, to local motion of ester groups adjacent to the backbone and to local motion of terminal side‐groups, respectively, were evident. The molecular mobility of the β₁‐, β‐ and γ‐processes changed slightly with the concentration of chromophore groups. For the δ‐ and α‐processes, the glass transition temperatures, T_δ and T_g, increased with the molar fraction of chalcone groups, the difference between them remaining nearly constant (ca 55 °C). The T_δ values obtained should be considered as optimal temperatures for the corona‐poling of the chromophore‐containing polymers for the preparation of second‐order nonlinear optical polymer films with non‐centrosymmetric arrangement of chromophore groups. Copyright © 2011 Society of Chemical Industry     

Multi‐wavelength excitation method for measuring FWA‐treated paper

Colorimetric properties of fluorescent materials depend on the SPD of the illumination. That is why most standards for evaluating them specify the illuminations, which are often hard‐to‐realize daylight illuminants. The presented method using commercially available LEDs enables accurate enough colorimetric measurements of FWA‐treated papers or prints on them illuminated by the specified illuminant. The total spectral radiance factor of a fluorescent specimen, from which most colorimetric values are derived, consists of the luminescent spectral radiance factor and the spectral reflectance factor. This method separately estimates those of FWA‐treated paper to add up to the total spectral radiance factor. The luminescent spectral radiance factor is obtained by estimating the SPD of luminescence excited by the specified illuminant as the weighted sum of the multiple SPDs of luminescence excited by the respective narrow band LED emissions at different wavelengths. The LEDs and their weights are determined optimally for generally used papers. The spectral reflectance factor is derived from the estimated SPD of the radiation with fluorescence excluded from the paper illuminated by visible illumination. The method was applied with five different illumination systems each using two or three narrow band LEDs in the excitation range. They were evaluated by measuring the total spectral radiance factors by D50 of seven FWA‐treated papers and CMYK prints on four papers. The derived colorimetric values were compared to the respective references by the ideal D50.     

Interrelation of Flooding and Complete Dispersion in Agitated Gas‐Liquid Contactors

Despite the fact that the complete dispersion characteristics in agitated gas‐liquid contactors are operationally important, the flooding‐loading transition is widely used as a design criterion, due to its experimental convenience and accuracy. Moreover, limited data are available in the literature on the interrelation of the flooding‐loading and the loading‐complete dispersion transitions, although several investigators have worked on these two transition stages. Thus, knowledge of the interrelation between these two stages would be of theoretical and practical importance. In this work, the dependence of the stirrer speed at complete dispersion, n_CD, on the stirrer speed at flooding, n_F, was experimentally studied, in coalescing and non‐coalescing systems, using Rushton turbines of two different diameters. The experimental results, having an accuracy of < 5 %, are given in the form of a dimensionless correlation.     

Analytic Model of Laminar‐Turbulent Transition for Bingham Plastics

It is often desirable to operate industrial pipelines transporting non‐Newtonian materials near the transition from laminar to turbulent flow. For the commonly used Bingham plastic model, the Hedström technique overestimates turbulent flow friction losses because it does not take account of viscous‐layer thickening. In the present paper, the Wilson‐Thomas model is applied to predict the transition point for Bingham plastics. Laminar and turbulent friction losses are calculated to show that conditions at transition depend only on the Hedström number. The results are approximated by simplified fit functions. Comparison with existing empirical correlations and experimental data from various sources shows satisfactory agreement.     

Between‐phase calibration modeling and transition analysis for phase‐based quality interpretation and prediction

The quality‐concerned between‐phase transition analysis is performed and an improved calibration modeling strategy is designed for quality prediction and interpretation in multiphase batch processes. From the between‐phase viewpoint, the quality‐related phase behaviors are decomposed and two subspaces are separated. In common subspace, the underlying quality‐relevant variation stays invariable between the neighboring phases, showing the common contribution to quality. The other part changes with the alternation of phases and has the different influences on quality interpretation, termed specific subspace here. Based on subspace separation, between‐phase transition regions are distinguished from steady phases. Different models are developed in steady phases and transition regions respectively for online quality prediction. Offline quality analyses are also conducted in two subspaces to explore the time cumulative effects. The proposed method gives an interesting insight into the phase behaviors and between‐phase transitions for quality prediction. The feasibility and performance of the proposed method are illustrated with a typical multiphase batch process. © 2012 American Institute of Chemical Engineers AIChE J, 59: 108–119, 2013     

Triple‐shape‐memory polymer films created by forced‐assembly multilayer coextrusion

Triple‐shape‐memory polymers are capable of memorizing two temporary shapes and sequentially recovering from the first temporary shape to the second temporary shape and eventually to the permanent shape upon exposure to a stimulus. In this study, unique three‐component, multilayered films with an ATBTA configuration [where A is polyurethane (PU), B is ethylene vinyl acetate (EVA), and T is poly(vinyl acetate) (PVAc)] were produced as a triple‐shape‐memory material via a forced‐assembly multilayer film coextrusion process from PU, EVA, and PVAc. The two well‐separated thermal transitions of the PU–EVA–PVAc film, the melting temperature of EVA and the glass‐transition temperature of PVAc, allow for the fixing of the two temporary shapes. The cyclic thermomechanical testing results confirm that the 257‐layered PU–EVA–PVAc films possessed outstanding triple‐shape‐memory performance in terms of the shape fixity and shape‐recovery ratios. This approach allowed greater design flexibility and simultaneous adjustment of the mechanical and shape‐memory properties. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44405.     

Eliminating material dependency in spectra measurement via non‐neighbouring band regression

A multispectral imaging system, after necessary calibration, can measure the spectral reflectances of colour samples accurately at a high spatial resolution. A limitation is that agreement of its measurements with those of a reference spectrophotometer is affected by the reflective characteristics of sample materials. The state‐of‐the‐art methods aim to improve interinstrument agreement using the spectral values of neighbouring bands. However, it is observed that non‐neighbouring bands are more effective in modelling interinstrument agreement. Inspired by this observation, the present paper proposes a method for eliminating material dependency by least‐squares regression among non‐neighbouring spectral bands. The fundamental issue of band selection is solved using a binary differential evolution algorithm. Experimental results confirm that the proposed method is effective in reflectance correction in terms of both spectral and colorimetric accuracy. The method is of practical application to multispectral imaging systems when measuring the spectral reflectances of colour samples with different materials.     

Magnetic‐induced coil‐globule transition for polyelectrolytes

The effects of an applied magnetic field on the system composed of polyelectrolytes (PEs) and magnetic nanoparticles oppositely charged are studied by means of Monte Carlo method within the framework of “single‐site bond fluctuation model.” For a certain concentration of chains, the coil‐globule transition can be induced by the applied magnetic field. The mean‐square end‐to‐end distance and gyration radius as well as the shape factor of PE chains are used to characterize the conformational transitions. The statistical analysis of the system energy demonstrates this significant physical process. The role of entropy‐energy balance is well‐understood for different chain lengths, and a typical phase‐transition anomaly concerned with specific heat curve is observed. Under a certain magnetic field, the PE chains will regularly collapse due to the enough adsorption of magnetic particles. The magnetic particles exhibit peculiar spatial distribution at high magnetic fields: the string‐like arrangement along the magnetic field and the square lattice‐like arrangement perpendicular to the magnetic field. The applied magnetic field has a great influence on the length of string‐like structures formed by nanoparticles. This investigation may cast light on the collapse of PEs and provide a promising method for producing new nanocomposites. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of N‐methylimidazole and 3,5‐dimethylpyrazole ligands on the polymerization of di(2,6‐dichlorophenolato) Cu(II)/Co(II) complexes in the solid state

The polymerization of 2,6‐dichlorophenol (DCPH) was achieved through the thermal decomposition of copper complexes of DCPH with N‐methylimidazole (NMIz) and 3,5‐dimethylpyrazole (DMPz) ligands. Fourier transform infrared (FTIR), differential scanning calorimetry (DSC), mass spectrometry, ultraviolet–visible spectroscopy, diffuse reflectance spectroscopy, magnetic susceptibility balance, electron spin resonance, X‐ray analysis, and elemental analysis were used to characterize the complexes. The polymerization was achieved either in the solid state or in the melt. The structural analyses were performed with FTIR and NMR spectroscopy analyses. The glass‐transition temperatures were determined by DSC, and the intrinsic viscosities were determined by viscosimetry. The effects of the temperature and time on the conversion percentage and viscosity of the polymers were examined. Varying the decomposition temperature during a 3‐h scan showed that the DMPz complex of Cu decomposed at lower temperatures than the NMIz complex, whereas the NMIz complex yielded a higher conversion to the polymer. Complexes of DCPH with NMIz and DMPz ligands produced 1,2‐ and 1,4‐addition products, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3797–3805, 2004     

Impact of gravity on the bubble‐to‐pulse transition in packed beds

A model based on two‐phase volume‐averaged equations of motion is proposed to examine the gravity dependence of the bubble‐to‐pulse transition in gas‐liquid cocurrent down‐flow through packed beds. As input, the model uses experimental correlations for the frictional pressure drop under both normal gravity conditions and in the limit of vanishing gravity, as well as correlations for the liquid‐gas interfacial area per unit volume of bed in normal gravity. In accordance with experimental observations, the model shows that, for a given liquid flow, the transition to the pulse regime occurs at lower gas‐flow rates as the gravity level or the Bond number is decreased. Predicted transition boundaries agree reasonably well with observations under both reduced and normal gravity. The model also predicts a decrease in frictional pressure drop and an increase in total liquid holdup with decreasing gravity levels. © 2013 American Institute of Chemical Engineers AIChE J 60: 778–793, 2014