Illuminance dependency of L/Y (lightness/luminance-factor)-ratio effect

Using a modified model for predicting the perceived lightness of chromatic object colors for various adapting illuminances, the following two kinds of predictions were done for seven illuminance levels from 2 to 3000 lx on the basis of the Wysecki data. One concerned the contour lines of equal L/Y (lightness/luminance-factor) ratios in the whole chromaticity gamut, and the other the values of L/Y ratios for spectral colors. All the colors predicted have tristimulus value Y = 20. The computed results confirmed that the difference of L/Y-ratio effect found between the Wysecki and the Sanders-Wyszecki experiment was caused by the difference of the test adapting illuminance between them.     

On the solution of population balance equations (PBE) with accurate front tracking methods in practical crystallization processes

The PBE (population balance equation) containing birth, growth, agglomeration and breakage kinetics is described by a conservation law with a moving source term. For the solution of the PBE, we compare two accurate front tracking methods such as a modified method of characteristics (MOC) and a finite difference method with the weighted essentially non-oscillatory (WENO) scheme. Both methods are applied to a potassium sulfate crystallization problem (K₂SO₄-H₂O system) with a discontinuous initial condition. Parameters of agglomeration and breakage kinetics are estimated on the basis of the experimental data of the K₂SO₄-H₂O system.Owing to moving axis along a crystal growth rate (i.e. elimination of the growth term), the modified MOC is able to provide a highly accurate solution even at discontinuous points without numerical diffusion error. However, in the case of stiff nucleation which can commonly appear in practical crystallization processes, it is necessary to adaptively determine time levels to add a mesh of the nuclei size. For solving PBEs involving agglomeration and breakage terms, the MOC can take more long computational time than the spatial discretization methods like the WENO scheme. It is pointed out that the MOC is not available to solve more than two coupled PBEs in general.WENO schemes for spatial discretization are firstly addressed in this study for the dynamic simulation of batch crystallization processes. The WENO schemes show improvements of accuracy and stability over conventional discretization methods (e.g., backward, central or common upwinding schemes). However the WENO schemes on fixed meshes show, to some extent, the numerical diffusion error near discontinuities or steep moving fronts like other finite difference methods. Hence, they require spatially-adaptive mesh techniques in order to track more accurately the moving fronts. Even though the WENO schemes are less accurate than the MOC, they are of practical use for solving complex PBEs owing to a short computational time and little limitation to use.     

Liquid Precursor Route for Hetero-epitaxy of Zr(Y)O2 Thin Films on (001) Cubic Zirconia

ZrO₂–3 mol% Y₂O₃„single-crystal” thin films with multiple variants were epitaxially formed on (100) cubic zirconia substrates. The films were prepared by spin-coating an aqueous zirconium acetate/yttrium nitrate solution onto the cubic zirconia substrates and subsequently heat-treated at temperatures between 1100° and 1400°C. Electron diffraction and dark-field TEM observations showed that the film has tetragonal symmetry and consists of 50–100 nm variants with their c-axes aligned with one of the three substrate cube axes. Unrelaxed strain energy estimates indicate that the two variants with their c ₁-axis parallel to the substrate/thin film interface are energetically favorable.     

Y/composite titania-silica (CTS) supported catalyst for hydrotreating coker gas oil

Y/composite titania-silica (CTS) support was prepared by the in situ growth of CTS on HY zeolite. The effects of HY zeolite pretreatment and Y/CTS modification with P and F for adjusting the acidity of the support were studied. The results showed that the structure of Y/CTS was in the form of CTS as shell and HY zeolite particles as core. The content of HY zeolite affected the acidity, acidity distribution and pore structure of Y/CTS. The density of strong acid sites on the HY zeolite surface could be partly reduced by dealumination with citric acid. This reduced the CTS coverage on the outer surface of the HY zeolite, leading to the increased acidity of Y/CTS. The acidity distribution of the support could also be adjusted by P and F modification. Hydrotreating catalysts were prepared with Y/CTS as support. The catalysts were tested using the hydrotreating reaction of a coker gas oil (CGO). The experimental results showed that the catalyst hydrodenitrogenation (HDN) performance could be remarkably improved by adjusting the acidity of the catalyst support via HY zeolite pretreatment and P and F modification. The catalysts with proper Brönsted (B) acidity and Lewis (L) acidity behaved well in hydrodesulfurization (HDS) and HDN performances.     

Effect of ionic strength on the reactivity ratios of acrylamide/acrylic acid (sodium acrylate) copolymerization

The ionic strength (IS) of polyelectrolyte solutions plays an important role in influencing reaction kinetics. The largely unstudied effect of IS on monomer reactivity ratios and copolymerization rates of acrylamide (AAm) and acrylic acid (AAc), in the form of sodium acrylate (NaAc), is investigated. Salt addition affects the nature of overall charges of the polyelectrolyte solution and diminishes the electrostatic repulsions between reacting chains. Therefore, changing the IS of the solution by incorporating salts affect not only the point estimates of the monomer reactivity ratios but also the overall behavior of the copolymerization (with a transition to azeotropic behavior). Experimental results on copolymerization rates confirm the observed trends in reactivity ratio behavior. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40949.     

Effect of spinning temperature and blend ratios on electrospun chitosan/poly(acrylamide) blends fibers

We report the formation of non-woven fibers without bead defects by electrospinning blend solutions of chitosan and polyacrylamide (PAAm) with blend ratios varying from 75 wt% to 90 wt% chitosan using a modified electrospinning unit wherein polymer solutions can be spun at temperatures greater than ambient up to 100 °C. Electrospinning at elevated temperature leads to further expansion of the processing window, by producing fibers with fewer defects at higher chitosan weight percentage in the blends. Effects of varying blend ratios, spinning temperatures, and molecular weights on fiber formation were studied and optimum conditions for formation of uniform non-woven fiber mats with potential applications for air and water filtration were obtained. Uniform bead-less fiber mats with fiber diameter as low as 307 ± 67 nm were formed by spinning 90% chitosan in blend solutions at 70 °C.     

Estimation of the impact in the air quality by the use of clean fuels (fuel oil versus natural gas)

The extended use of fuels with high sulfur content (fuel oil) in the electric power industry represents one of the biggest concerns on air quality currently in Mexico. The organic sulfur compounds in the fuel oil are oxidized as SO_x during combustion, causing high concentration at the surface level near the releasing point. Shifting towards cleaner energy is crucial, however natural gas (NG) production is currently scarce and substantial investment is required to assure the NG supply to replace the fuel oil. Large investments should be made by the public and private sectors to replace heavy fuel oil use by NG. In order to support decision takers, this work assess the air quality impact due to cleaner energy use and determine the optimal NG and fuel oil mixture required to reduce substantially the SO₂ concentration. The dispersion model was applied to compare, against a base case, a set of artificial emissions scenarios with different fuel oil and NG mixtures. The model was previously validated against SO₂ field measurements performed at an Industrial Corridor, Mexico. The results show that increasing 40% the NG consumption, the SO₂, concentration in the air is reduced in 90%, therefore not further NG increasing is needed.     

Estimation of Parameters in the NLAR(p) Model

Abstract. In this article, we study a new Laplace autoregressive model of order p– NLAR(p). Conditional least squares, weighted conditional least squares and maximum quasi‐likelihood are used to estimate the model parameters. Comparisons among these estimates of the NLAR(2) model are given via simulation studies.     

Novel method for the preparation of Cs-containing FAU(Y) catalysts for aniline methylation

Cs-containing FAU(Y)-type zeolite catalysts were prepared by conventional and novel ion exchange procedures followed by incipient wetness impregnation with CsOH. The novel ion exchange procedure involved hydrothermal treatment of NaY zeolite in aqueous solution of CsCl at 140–200 °C for 6–24 h. The samples were characterized by low-temperature nitrogen adsorption, X-ray fluorescence analysis, X-ray powder diffraction, scanning electron microscopy, ²³Na, ²⁷Al and ¹³³Cs magic angle spinning nuclear magnetic resonance, CO₂ and NH₃-Temperature programmed desorption. The results show that hydrothermal treatment at 200 °C allows to obtain higher degrees of ion-exchange (up to 83%) with respect to conventional method giving maximum 66%–69%. Catalytic properties of Cs-containing FAU(Y) were studied in aniline methylation. The yield of N-methylaniline is shown to correlate with catalyst’s basicity. The best catalyst performance was achieved over the catalyst with the highest ion-exchange degree impregnated with CsOH. The selectivity to N-methylaniline over this catalyst reached 96.4%.

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Loading (L) Factors for the Biaxial Flexure Test

The dependence of the loading ( L ) factor on the Weibull modulus ( m ) was derived for the biaxial flexure test assuming a 2-parameter Weibull stress function and noninteracting orthogonal stresses. The specimen and test fiture dimensions influence the dependence significantly, whereas little difference is found between a 3-point or ring specimen support. The L factors are more strongly influenced by the Weibull modulus than in a 3-point bend test.     

Poly(3-hexylthiophene) wrapped carbon nanotube/poly(dimethylsiloxane) composites for use in finger-sensing piezoresistive pressure sensors

We fabricated a piezoresistive composite using multi-walled carbon nanotubes (MWCNTs) as a conductive filler and polydimethylsiloxane (PDMS) as a polymer matrix, which operated in the extremely small pressure range required for finger-sensing. To achieve a homogeneous dispersion of MWCNTs in PDMS, the MWCNTs were modified by a polymer wrapping method using poly(3-hexylthiophene) (P3HT). The percolation threshold of the composites was significantly lowered by the presence of P3HT. The electrical conductivity and piezoresistive sensitivity of the composite were found to strongly depend on the P3HT concentration. The well-dispersed P3HT-MWCNT/PDMS composite showed good piezoresistive characteristics in the 0–0.12 MPa pressure range.     

A mild,rapid, and efficient method of lipid extraction for use in determining vitamin E/lipid ratios

A new, general method for lipid extraction and measurement of vitamin E/total lipid ratios in tissue and cell samples has been developed. The new extraction procedure use a combination of sodium dodecylsulfate, ethanol andn-heptane, and is mild, clean, convenient, efficient and rapid (≤5 min). The efficiency of the new method has been confirmed for human plasma, red blood cells and rat liver homogenate by the comparison of the yields of vitamin E, O-acyl lipid and cholesterol with the yields obtained following conventional extraction procedures. Extraction efficiency also has been confirmed for multilamenllar vesicles composed of known quantities of vitamin E, egg lecithin and cholesterol. N.R.C.C. No. 23769.     

Biodegradable polymers for use in surgery—poly(ethylene oxide) poly(ethylene terephthalate) (PEO/PET) copolymers: 1

The requirement for a biodegradable material in surgery is discussed. The synthesis of a series of biodegradable polymers based on the copolymers of polyethylene oxide (PEO) and polyethylene terephthalate (PET) are described. The synthesis of copolymers in the range 50–70 wt % PEO was followed by time sampling techniques with subsequent characterization of the samples being undertaken by gel permeation chromatography (g.p.c.), ¹³C nuclear magnetic resonance spectroscopy (n.m.r.) and infra-red spectroscopy (i.r.). Details of the g.p.c., n.m.r. and i.r. analysis are described. The morphology of the copolymers as a function of composition was studied by differential scanning calorimetry (d.s.c.) and X-ray crystallography. Tensile properties as a function of composition are reported and compared with current materials used in surgery.     

Morphology of Tetragonal ZrO2 in a Ternary (Mg,Y)-PSZ

The precipitation of tetragonal ( t ) ZrO₂ in a ternary (Mg,Y)-PSZ has been studied. Nucleation of t -ZrO₂ occurs homogeneously, as in other PSZ's, and coarsened precipitates are multivariant and have an unusual tetrahedral morphology.     

A recoverable catalyst Co(salen) in zeolite Y for the synthesis of methyl N-phenylcarbamate by oxidative carbonylation of aniline

A green process for the synthesis of methyl N-phenylcarbamate (MPC) by the oxidative carbonylation of aniline was studied. In this process, Co(salen) complexes were successfully encapsulated in zeolite Y by a flexible ligand method. The heterogeneous catalysts were characterized by AAS, BET, IR, TGA, XRD and XPS. The catalytic activities of the encapsulated catalysts and their homogeneous analogues were examined in the oxidative carbonylation of aniline to MPC. Under the conditions of aniline (11 mmol), encapsulated catalyst (0.5 g), KI (0.365 g), CO/O₂ ratio 9:1, 4 MPa, 170 °C, 3 h, Co(salophen)(OH)₂–Y catalyst shows the highest activity with the conversion of 67.1% and the selectivity of 77.3%. Co(salophen)(OH)₂–Y could be recycled at least five times and no significant loss of catalytic activity was observed.     

Color-Discrimination Thresholds Translated from the CIE (x,y, Y) Space to the CIE 1976 (L*,a*,b*)

Departures from exact ellipticity when color-discrimination ellipsoids or ellipses are translated to CIELAB have been numerically analyzed. The greatest distortions for ellipses were around 5% at the most saturated orange-red centers. The distortions for ellipsoids were of the same order as those of the ellipses at the five CIE centers. These small distortions are well covered by the interobserver variability and could be ignored in most cases, but an appropriate method must be used for the translation of color-threshold results to CIELAB. Experimental results published by Luo and Rigg for 132 chromaticity-discrimination ellipses are expressed in CIELAB. These results may be useful in checking the performance of new color-difference Jormulas.     

Citrate-Gel Syntheses in the Y(O)–Ba(O)–Cu(O) System

A synthetic procedure has been developed for the yttrium-barium-copper oxides, in terms of a liquid-mixed citrate precursor and the use of yttrium oxide, barium carbonate, and basic copper carbonate as starting materials. The stability of the citrate gels against phase separation is investigated as a function of the content of metal oxides in the gels, and critical concentrations for the individual metals are derived in terms of the maximum metal-to-citric acid ratio across the Y(O)–Ba(O)–Cu(O) phase diagram. Sintering properties and compositions of the products are investigated as functions of the thermal treatment of the citrate precursor. The present citrate-gel procedure does not make use of internal oxidants like nitrates and polymerization agents like glycol. This approach decreases the incineration temperature and leads to a nanodispersed precursor (except submicrometer Cu), which, e.g., yields virtually phase-pure (< 1% of impurities) YBa₂Cu₃O₇ already after the first firing at 900°C in pure O₂.