Irregularity in CIECAM02 and its avoidance

Were it not for an algorithm patch, the color‐appearance model CIECAM02 would sometimes be forced to evaluate fractional powers of negative numbers. The artifact arises because the red and green primaries of the initial CAT02 chromatic adaptation lie outside the positive gamut of the Hunt–Pointer–Estévez (HPE) primaries that subsequently convey the color signal in the model. Relocating the chromaticities of the HPE red and green primaries so as to lie on the CAT02 red–green line alleviates the problem, but adds a bit of X and Y to the revised HPE blue. An (x,y) diagram aids in visualizing the CIECAM02 gamut overlaps, with an extension that accommodates the HPE RGB triangle's enclosure of the point at infinity. © 2006 Wiley Periodicals, Inc. Col Res Appl, 31, 142–145, 2006     

Thermal Expansion of Ln6WO12 (Ln = Y,Ho, Er,Yb) and Ln2WO6 (Ln = Gd,Dy, Ho) – an In Situ Synchrotron X‐ray Diffraction Study

The thermal expansion (TE) behavior of cubic and rhombohedral Ln₆WO₁₂ (Ln = Y, Ho, Er, Yb) and monoclinic Ln₂WO₆ (Ln = Gd, Dy, Ho) was investigated by synchrotron X‐ray diffraction from room temperature to approximately 1500°C. The volumetric and lattice parameter expansions were measured for all compositions in both systems, and the respective expansion coefficients were derived and fitted over the observed temperature range with a second‐order polynomial. The relative TE evolution along the unit cell edges in each phase was described from a crystallographic perspective, with the reasons for TE dynamics explained in terms of the fundamental constituent units of the structure. Analysis of the TE ellipsoid of the monoclinic Ln₂WO₆ revealed a continuous change in both its shape and orientation, with the latter effect strongly manifested in the (010) plane. A noticeable reversal of the relative expansion rates between a, and b and c lattice parameters was attributed to the rotation of the ellipsoid cross section in this plane, bringing the larger of the two eigenvectors closer to a, while the smaller one to c. Investigating the structural dynamics of the constituent layers in Ln₂WO₆ suggested that the bridging role of the Ln polyhedron centered on the only general position in the unit cell may be the reason for the rotating TE ellipsoid.     

Graph-Theory Derived Models for the Skeletal Chemical Bonding in Organometallic Metal Carbonyl Clusters

Ideas derived from topology and graph theory can be used to model the skeletal chemical bonding in metal carbonyl clusters as well as boranes and carboranes. In such molecules delocalized skeletal bonding occurs when there is a mismatch between the number of internal orbitals provided by a vertex atom and the number of polyhedral edges meeting at that vertex. Such global delocalization in deltahedral metal clusters may be regarded as a three-dimensional analogue of the aromaticity in planar polygonal molecules such as benzene. Elementary graph-theoretical considerations provide a basis for the 2n+2 skeletal electrons normally observed in n vertex delocalized deltahedral metal clusters lacking tetrahedral chambers. Electron-rich n-vertex metal clusters have more than 2n + 2 skeletal electrons and form polyhedra having at least one face with at least 4 edges. Electron-poor n-vertex metal clusters have less than 2n + 2 skeletal electrons and form deltahedra having at least one tetrahedral chamber. Ideas derived from group theory and graph theory can be used to analyze molecular orbital energy parameters for the most symmetrical deltahedral borane anions B_nH_n²⁻ (particularly n = 6 and 12) computed using either semiempirical extended Hückel methods or ab initio methods based on Gaussian orbitals. Some of the fundamental aspects of the graph-theory derived models for skeletal bonding in delocalized deltahedral metal clusters are closely related to the tensor surface harmonic theory of Stone.     

New deviate observer (JF‐DO) obtained from experimental color‐matching functions for small fields of real observers

The CIE established the Standard Deviate Observer (SDO) CIE 1989 for fields of 10°, enabling the evaluation of discrepancies caused by the variability among these observers. This observer could also be applied to smaller fields, depending on the physiological causes of this variability in color‐matching functions (cmf's) among observers. Here, we have obtained a new Deviate Observer (which we call JF‐DO) established from the cmf's for small fields (2°) corresponding to two groups of real observers: JAM, MM and CF; AY, JR, MR, JL, JA and FA. Both groups of cmf's were measured experimentally in our laboratories using one for each of the different experimental methods and devices. All the new cmf's of the 9 real observers were referred to a new, unique system of unreal primaries, which we call X′Y′Z′ (derived in a way similar to that of the CIE 1931 XYZ system of unreal primaries). To establish a new JF‐DO for small fields, we followed a procedure similar to the one used by the CIE to establish the CIE 1989 SDO. A comparative study was also made between the cmf's of the CIE 1989 SDO (established for fields of 10°), the SDO from Stiles‐Burch (which we call Poza‐SDO, developed for small fields), and our JF‐DO. For this comparison, the cmf's of all these deviate observers were referred to the new system of unreal primaries X′Y′Z′. © 2003 Wiley Periodicals, Inc. Col Res Appl, 28, 209–215, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.10146     

Optimal yarn colour combination for full‐colour fabric design and mixed‐colour chromaticity coordinates based on CIE chromaticity diagram analysis

It is challenging for textile designers to achieve full‐colour effects in woven fabric using a limited set of coloured yarns. The common problems encountered during full‐colour fabric design include an insufficient number of colours and a failure to match the fabric colour with the desired colour. Using the theories of primary colours and optical colour mixing, we examine the mixed‐colour distribution of primary colour yarns on the basis of the CIE 1976 chromaticity diagram (CIE u′v′). In our experiment, dope‐dyed polyester filament yarns were selected as raw materials. Eight kinds of gradually varied weave structures and four types of primary colour combination were adopted in order to make different types of full‐colour fabric colour chart. Spectrophotometer and DigiEye colour measurement systems were selected to measure the reflectance and colour value of the fabric samples. By comparing the colour distribution of mixed fabrics in the CIE u′v′ diagram, the relationship between the primary colour combinations and the colour distribution of mixed fabrics is discussed. Of RGB, CMY, NCS, and RGBCMY combinations, only RGBCMY resulted in a relatively complete and large colour gamut. Moreover, the colour positions of mixed fabrics in the CIE u′v′ diagram were almost all distributed on or near the connecting line of the primary colour coordinates. The specific colour position of mixed fabrics in the CIE u′v′ diagram were mainly determined by the proportion of primary colours on the fabric surface. In this way, a new method for computing colour position in the CIE u′v′ diagram is introduced.     

Y5Si2B8: A theoretically predicted new damage‐tolerant MAB phase with layered crystal structure

Layer structured MAB phases (M=transition metal, A=III_A or IV_A group element, B is boron) are promising ternary borides for high and ultrahigh‐temperature applications. Herein, a new MAB phase Y₅Si₂B₈ consisting of alternative stacking of YB₄ and Y₃Si₂ slabs along the [001] direction is investigated. Density functional theory (DFT) calculations on the electronic structure and chemical bonding reveal that this new MAB phase has diverse chemical bonding and properties similar to MAX phases. The strong covalent bonds in the two‐dimensional B network on (001) plane in the YB₄ slab and between Si atoms on (002) plane in the Y₃Si₂‐slab warrant the high stiffness (E_x=288 GPa) of Y₅Si₂B₈ in the ab plane and the weak Y2‐Si and Y1‐B2 bonds that connecting the YB₄ and Y₃Si₂ slabs underpin the low Young's modulus in [001] direction (E_z=200 GPa). The low shear deformation resistance is due to the presence of the metallic bond and the weak bond within the B₆ octahedral. The possible slip systems are {001}< 100> and {110}< 111> . Based on the low shear modulus (G = 104 GPa) and Pugh's ratio G/B, Y₅Si₂B₈ is predicted as a damage tolerant MAB phase. Y₅Si₂B₈ is also predicted electrically conductive and the conductivity is higher in directions parallel to ab plane. In addition, temperature‐dependent phonon and electron heat capacity are predicted based on the electron and phonon density of states analysis.     

A study of digital camera colorimetric characterization based on polynomial modeling

The digital camera is a powerful tool to capture images for use in image processing and colour communication. However, the RGB signals generated by a digital camera are device‐dependent, i.e., different digital cameras produce different RGB responses for the same scene. Furthermore, they are not colorimetric, i.e., the output RGB signals do not directly correspond to the device‐independent tristimulus values based on the CIE standard colorimetric observer. One approach for deriving a colorimetric mapping between camera RGB signals and CIE tristimulus values uses polynomial modeling and is described here. The least squares fitting technique was used to derive the coefficients of 3 × n polynomial transfer matrices, yielding a modeling accuracy typically averaging 1 ΔE units in CMC(1:1) when a 3 × 11 matrix is used. Experiments were carried out to investigate the repeatability of the digitizing system, characterization performance when different polynomials were used, modeling accuracy when 8‐bit and 12‐bit RGB data were used for characterization, and the number of reference samples needed to achieve a reasonable degree of modeling accuracy. Choice of characterization target and media and their effect on metamerism have been examined. It is demonstrated that a model is dependent upon both media and colorant, and applying a model to other media/colorants can lead to serious eye–camera metamerism problems. © 2001 John Wiley & Sons, Inc. Col Res Appl, 26, 76–84, 2001     

Anisotropic dielectric properties of polyimides consisting of various molar ratios of meta to para diamine with trifluoromethyl group

A series of copolyimides based on pyromellitic dianhydride (PMDA) with various molar fractions of 4,4′‐(hexafluoro‐isopropylidene)dianiline (4,4′‐6F) and 3,3′‐(hexafluoro‐isopropylidene)dianiline (3,3′‐6F) were synthesized by a two‐step method. The five different composition copolyimides in the fozrm of {(PMDA+3,3′?6F)_m/ (PMDA+4,4′?6F)_n were mainly characterized using a dielectric analyzer (DEA) by single surface sensor (in‐plane direction) and thin film parallel plate sensor (out‐of‐plane direction) measurements. DSC, TMA, and XRD were also used to study the structure property. The increasing of molar ratio of para diamine in the copolyimide system up to 35% affected glass transition temperature, coefficient of thermal expansion, in‐plane dielectric constant and out‐of‐plane dielectric constant of copolyimides, correspondingly. The in‐plane dielectric constant was higher than that of the out‐of plane constant for our polyimide films. Anisotropy δε of the dielectric constants was 0.14 for CPI(100/o)a, 0.19 for CPI(85/15)a, 0.11 for CPI(75/25)a, and 0.05 for CPI(65/35)a. The difference in curing history also exhibited an effect on solvent diffusion behavior in our polymer system. Polymers cured at a slower curing rate had smaller CTE than that cured at a faster curing rate, as confirmed by X‐ray diffraction results. Polymers with smaller CTEs had larger dielectric constants at a slower curing rate, and vice versa. The experimental results suggested that CPI(65/35) a with smaller dielectric anisotropy could solve the crosstalk problem and provide equal electrical insulation in microelectronic devices. Therefore, a smaller and faster IC device could, it is hoped, be achieved, with smaller spacing between adjacent metal lines.     

Estimation equations for practical use on lightness-reflectance (L/Y) ratios in the whole chromaticity gamut

A multiple regression analysis is reported to predict L/Y ratios as a function of chromaticity coordinates x, y. the specified variables were selected statistically from the 20 terms of Ψ^mψⁿ. the quantities Ψ, ψ are the transformed values of x, y, respectively, and 1 ≦ m + n ≦ 5. the contour lines of equal L/Y ratios are estimated in the whole chromaticity gamut including spectral colors by using each of the regression equations with 6, 9, and 20 specified variables. the regression equations with 20 specified variables can satisfactorily predict the corresponding experimental results. In case of regression equations with 6 specified variables, the predicted contour lines are significantly different in shape from those of the corresponding experiments. the same defects are found in the Ware-Cowan equation only using 4 specified variables recommended by CIE Division 1 for further tests.     

Three‐dimensional dielectric characterization of polymer films

Polymer films are widely used in electronic packaging applications due to their low dielectric constant and ease of fabrication. These films often exhibit anisotropic electrical and thermomechanical properties, due to orientation of polymer chains, which need to be evaluated for performance and reliability modeling of electronic packages. This article presents a dual‐capacitor technique to measure the anisotropic dielectric permittivities of such films. Results are reported for in situ measurements for several spin‐coated polymeric films, some of which exhibit different permittivities in the in‐plane (x and y) and the through‐plane (z) directions (transversely isotropic), and free‐standing liquid crystalline Vectran films which exhibit orthotropic permittivities. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2328–2334, 2001     

Evaluation of the derivatives of the strain energy function with respect to strain invariants for carbon black–filled EPDM

The experimental and theoretical investigation of the mechanical properties of an ethylene‐propylene‐diene terpolymer (EPDM) elastomer reinforced with carbon black was examined. The material constants of the testing material were determined by plotting the stress‐strain experimental curve in a reduced stress versus the inverse stretch diagram. The Ogden equation was used for the strain energy function to fit uniaxial experimental stress‐strain curves. The characterization of the material was examined using the contour maps of ?W/?I₁ and ?W/?I₂, i.e., of the derivatives of strain energy function with respect to strain invariants I₁ and I₂.     

Measuring thermal conductivities of anisotropic synthetic graphite–liquid crystal polymer composites

In this study, synthetic graphite particles were added to a liquid crystal polymer and the resulting composites were tested for both the through‐plane thermal conductivity k_thru and the in‐plane thermal conductivity k_in using the transient plane source method. The end use application for these composites is in fuel cell bipolar plate fabrication. The goal of this work was to expand upon a previously developed simple empirical model for the in‐plane thermal conductivity, which is easily measured with the transient plane source method. The results show that the square root of the product of the through‐plane and in‐plane thermal conductivities is an exponential function of the volume percent of filler, ϕ. As the through‐plane thermal conductivity of these composites is accurately predicted with a modified Nielsen model, this empirical relationship can be used to estimate in‐plane thermal conductivities for a range of applications. POLYM. COMPOS., 27:388–394, 2006. © 2006 Society of Plastics Engineers     

Two nucleophilic mutants of the Micromonospora viridifaciens sialidase operate with retention of configuration by two different mechanisms

Mutants of the Micromonospora viridifaciens sialidase, Y370E and Y370F, are catalytically active retaining enzymes that operate by different mechanisms. Previous substitutions with smaller amino acids, including Y370D, yielded inverting sialidases. At least one water molecule can fit into the active‐site cavity of this mutant and act as a nucleophile from the face opposite the leaving group (Biochemistry 2003 , 42, 12 682). Thus, addition of a CH₂ unit (Asp versus Glu) changes the mechanism from inversion back to retention of configuration. Based on Brønsted β_lg values, it is proposed that the Y370E mutant reacts by a double‐displacement mechanism (β_lg on k_cat/K_m ?0.36±0.04) with Glu370 acting as the nucleophile. However, the Y370F mutant (β_lg on k_cat/K_m ?0.79±0.12) reacts via a dissociative transition state. The crystal structure of the Y370F mutant complexed with 2‐deoxy‐2,3‐dehydro‐N‐acetylneuraminic acid shows no significant active‐site perturbation relative to the wild‐type enzyme.     

Broadband luminescent ferroelectric biocompatible Er:(Na,K)NbO3 nanofibers

Dense homogeneous fabric composed from continuous bead‐free erbium‐doped sodium potassium niobate (Er:NKN) 100 μm long and 100‐200 nm in diameter nanofibers was sintered by sol‐gel calcination assisted electrospinning technique. X‐ray diffraction revealed preferential cube‐on‐cube [001]‐directional growth of fibers containing predominantly monoclinic Na_0.35K_0.65NbO₃‐type phase and significantly less of tetragonal NbO₂, cubic Er₂O₃, and monoclinic ErNbO₄ phases. Er doping with the concentration of 2 at.% provides readily detectable room‐temperature broad‐band photoluminescence (PL) centered at λ_PL = 0.55 and 0.98 μm being pumped, respectively, with 532 and 785 nm lasers. Impedance spectroscopy and static electrical tests revealed ferroelectric properties, electric field induced resistance switching and strong rectification effect in nanoporous sandwich Au/Er:NKN/Pt capacitive cell. Memristor‐type current‐voltage (I‐V) characteristics originate from the electrochemical migration of oxygen vacancies at the n‐type NKN oxide/high work function Pt cathode junction interface.     

Quantitative evaluation of rate‐determining steps in polymer complexation

A quantitative method to find the rate determining steps in the ion‐adsorption kinetics of polymer complexation agents is theoretically formulated and experimentally established. The degree of film‐diffusion control and particle‐diffusion control is simultaneously evaluated based on the law of addition of kinetic resistances combined with Einstein's viscosity expression. The change in the initial rate with respect to the resin concentration was scrutinized by plotting the effective rate constant versus the initial rate, and the film mass transfer coefficient was calculated. This is a concise and practical procedure to analyze the rate determining steps of polymer complexation kinetics. The validity of the method was confirmed by studying the adsorption of Cu(II) ion on crosslinked chitosans. In these materials, the importance of film diffusion was found both in adsorption and desorption processes. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44738.     

A Study on CO2 Absorption Kinetics by Aqueous Solutions of N,N‐Diethylethanolamine and N‐Ethylethanolamine

N‐Ethylethanolamine (EEA) and N,N‐diethylethanolamine (DEEA) represent promising candidate alkanolamines for CO₂ removal from gaseous streams, as they can be prepared from renewable resources. In this work, the reaction rate constant for the reaction between CO₂ and EEA was determined from the absorption rate measurements of CO₂ in a blend comprising DEEA, EEA and H₂O. A stirred‐cell reactor with a plane, horizontal gas‐liquid interface was used for the absorption studies. While the DEEA concentration in the formulated solution was varied in the range of 1.5–2.5 kmol/m³, the initial EEA concentration was 0.1 kmol/m³. A zwitterion mechanism for EEA and a base‐catalyzed hydration mechanism for DEEA were used to describe the reaction kinetics. At 303 K, the second‐order reaction rate constant for the CO₂ reaction with EEA was found to be 8041 m³/(kmol s). The liquid‐side mass transfer coefficient was also estimated, and its value (0.004 cm/s) is in line with those typical of stirred‐cell reactors.     

Use of regression methods for determining the relation between theoretical–linear and spectrophotometrical colour values of bicolour woven structures

In this paper, new approaches for evaluating the entire colour effect of optical mixing of bicolour woven structures are presented. Simple woven structures with constant colour in the warp direction and different colours in the weft direction were prepared and analysed. The constructional parameters of these woven fabrics were systematically changed, which resulted in the variations of the fractions of colour components and, consequently, also in the changes of colour properties (lightness, hue, chroma) of bicolour optical mixtures. The position of colours of the bicolour structures and the approximate direction (linear) of colour changes in CIELAB colour space were theoretically determined with a simple geometrical model and additive method. Furthermore, the bicolour optical effects were determined spectrophotometrically. The differences between the linear–theoretical and the spectrophotometrical colour values of bicolour woven fabrics were mathematically analysed with linear and non‐linear regression methods to determine the positions of colour coordinates L*, a* and b* of bicolour woven fabrics in the a*b* plane by increasing or reducing the cover factors of warp and weft threads (addition or reduction of colour components). The results present, on the one hand, the strong influence of original colours of warp and weft threads and, on the other hand, the minor influence of constructional parameters on the form of linear/non‐linear behaviour of colours of bicolour compositions. When the characteristics of a specific colour combination are taken into account, the spectrophotometrical colour values of bicolour woven fabrics can be also mathematically determined with additive–theoretical colour values and, to some extent, with predictable colour deviations.     

Structure and Binding of Peptide‐Dendrimer Ligands to Vitamin B12

The third‐generation peptide‐dendrimer B1 (AcES)₈(BEA)₄(K‐Amb‐Y)₂BCD‐NH₂ (B=branching (S)‐2,3‐diaminopropanoic acid, K=branching lysine, Amb=4‐aminomethyl‐benzoic acid) is the first synthetic model for cobalamin‐binding proteins and binds cobalamin strongly (K_a=5.0×10⁶ M ^?1) and rapidly (k₂=346 M ^?1 s^?1) by coordination of cobalt to the cysteine residue at the dendrimer core. A structure–activity relationship study is reported concerning the role of negative charges in binding. Substituting glutamates (E) for glutamines (Q) in the outer branches of B1 to form N3 (AcQS)₈(BQA)₄(B‐Amb‐Y)₂BCD‐NH₂ leads to stronger (K_a=12.0×10⁶ M ^?1) but slower (k₂=67 M ^?1 s^?1) cobalamin binding. CD and FTIR spectra show that the dendrimers and their cobalamin complexes exist as random‐coil structures without aggregation in solution. The hydrodynamic radii of the dendrimers determined by diffusion NMR either remains constant or slightly decreases upon binding to cobalamin; this indicates the formation of compact, presumably hydrophobically collapsed complexes.     

The properties of multiple CMF determinations using alternative primary sets Part II: A data unification methodology

The spectral power values representing Thornton's “alternative primary” PC, NP, and AP colour matching functions (CMF) are compared with the power values representing the 49‐observer Stiles–Burch average definition. The Thornton measurements are first converted by matrix transformation into a data set expressed in terms of spectral power at the Stiles–Burch primary wavelengths. Graphs and power ratios are used to compare the definitions for two alternative matches to the same visual stimulus. A triplet of n:n spectral‐power ratios (one in each dimension, R, G, and B) is used to quantify the differences between the alternative matches. The relationship between the Thornton PC and Stiles–Burch match‐definitions is then found to deviate from the expected power‐ratio of 1:1 after matrix transformation. The revealed relationship is an internally consistent and smooth function of matched wavelength, which has a different nonlinear characteristic in each R, G, and B dimension relative to the Stiles–Burch reference model. The “Thornton bow‐tie” phenomenon is also demonstrated between a pair of maximum saturation CMF definitions made with alternative primaries. The implicit differences in neutral axis definition represented by the bow‐tie diagram are linked to differences in trichromatic unit (T‐unit) definition. In this case, the conventional CMF normalization process is postulated to be inaccurate at the wavelengths concerned, resulting in incompatibility between the T‐unit definitions of the two primary sets being compared. The conventional N→3 T‐unit definition of visual neutrality equating Illuminant S_E to a single R:G:B power ratio is extended, by adding an extra N→N mapping to the definition. The resulting N→N→3 mapping is in principle a fully determined redefinition of three‐dimensional T‐unit equivalence, in which many R:G:B ratios for a comprehensive set of visually neutral metamers can be mapped by N→N transformation onto the conventional single ratio. The effect of N→N mapping is to transform spectral power distributions (SPDs) into spectral effect distributions (SEDs) expressed in T‐units. The SPD/SED transform, thus defined, is proposed as a method for unifying CMF determinations made with alternative primaries. The expected outcome is that after transforming SPDs by N→N mapping into SEDs the definitions for all visually matching metamers will be demonstrably interconvertible by matrix product. © 2004 Wiley Periodicals, Inc. Col Res Appl, 29, 438–450, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20069