An application of the Error-in-Variables Model—parameter estimation from Van Ness-type vapour-liquid equilibrium experiments

The Error-in-Variables Model (EVM) provides a means for estimating parameter values in mathematical models where there is error in every measured variable. This is a distinct improvement over the Method of Least Squares in most situations because the latter requires that there be error in measuring only one of the variables. As an example of the use of EVM, a method is presented for estimating Wilson equation parameters in binary and ternary vapour-liquid equilibrium where the data are obtained using the Van Ness experimental technique. The application presents unusual difficulties in that the compositions of the phases are not measured directly and the total quantity of one component is only measured as the sum of a series of increments. Data for the ternary system n-heptane/n-propanol/1-chlorobutane and the binary system n-heptane/1-chlorobutane are analysed by the proposed method, and the results are compared with the empirical results of Sayegh et al. (1979). The results of the EVM analysis are considerably more accurate. Analysis of the residuals obtained by the EVM procedure suggest serious deficiencies in the thermodynamic model.     

Temperature-dependent vapor–liquid equilibria and solvation free energy estimation from minimal data

We present a new strategy to estimate the temperature-dependent vapor–liquid equilibria and solvation free energies of dilute neutral molecules based on only their estimated solvation energy and enthalpy at 298 K. These two pieces of information coupled with matching conditions between the functional forms developed by Japas and Levelt Sengers for near critical conditions and by Harvey for low and moderate temperature conditions allow the fitting of a piecewise function that predicts the temperature-dependent solvation energy for dilute solutes up to the critical temperature of the solvent. If the Abraham and Mintz parameters for the solvent and solute are available or can be estimated from group contributions, this method requires no experimental data and can still provide accurate estimates with an error of about 1.6 kJ/mol. This strategy, which requires minimal computational resources, is shown to compare well with other methods of temperature-dependent solvation free energy prediction.     

Early bird gets the network: The relative importance of reactivity ratios, Ψ parameter,and crosslinker level on gel formation in FRP

Network topology is manipulated in free-radical copolymerization via proper selection of crosslinker type and its respective properties when paired with specific monomers. Our prior work has focused on the impact of the reduced reactivity parameter Ψ applied to a pendent vinyl, characteristic for each monomer/crosslinker pair, yet here we assess the relative importance of the comonomer reactivity ratios to see whether one factor can counterbalance the other. The traditional reactivity ratio determines when the crosslinker molecule is incorporated into the polymer backbone, while the reduced reactivity Ψ parameter relates to the efficiency of the resulting pendent side chain vinyl being utilized to form a crosslink node at some later point during the polymerization. Both factors are then contrasted with simply the overall loading of crosslinker. Either n-butyl methacrylate (n-BMA) or styrene (STY) was chosen as a primary backbone monomer to copolymerize with one of three crosslinkers: 1,4-butanediol dimethacylate (BDDMA), 1,4-butanediol diacrylate (BDDA), or divinylbenzene (DVB). Both kinetics and gel can be most dramatically boosted when a crosslinker is applied having a reactivity ratio favouring early insertion. This in turn leads to an earlier onset of gel formation, which ultimately results in greater final gel content. This amplification of both kinetics and gel can overcome an otherwise small Ψ due to crosslinker or main monomer choice. This reactivity ratio effect was further confirmed by Monte Carlo simulations. By whatever mechanism (higher Ψ, lower r_A, or higher crosslinker level), earlier onset of gelation produces more gel overall and a tighter network topology.     

Nanofiltration for textile dye–water treatment: Experimental and parameter estimation studies using a spiral wound module and validation of the Spiegler–Kedem-based model

The present work deals with the study of the nanofiltration process for textile dye wastewater treatment. Effects of feed pressure, dye concentration, and feed flow rate on dye rejection and recovery for the spiral wound nanofiltration module were studied. The permeate characteristics were predicted by using the Spiegler–Kedem (SK)-based model. A finite difference numerical technique is used to discretize the transport equations and an optimization technique was used for estimation of unknown parameters (B, σ, k_a, and k_b) in the SK-based model. The model and the estimated parameter values were validated with experimental results for the spiral wound nanofiltration (NF) membrane module.     

Precipitation of calcium and magnesium from seawater using CO2——Effect of temperature and salinity

对CO2法脱除海水中钙离子和镁离子进行研究,控制海水的pH值恒为8,考察温度、盐度对脱钙率和脱镁率的影响。结果表明,盐度35‰的海水,30～50 ℃时脱钙率由90%增长至95%,与此同时脱镁率由0增长至42%;脱钙率、脱镁率随温度升高而升高。在温度为30 ℃时,盐度35‰～105‰的海水脱钙率可由90%增长到97%,与此同时脱镁率由0增长到67%;脱钙率、脱镁率随盐度升高而升高。将得到的固体进行XRD检测可知,产物固相组成随温度、盐度的变化而变化。由此可知,海水盐度为35‰、pH值为8、温度为30 ℃是CO2法高效脱钙的最佳工艺条件。     

Estimating the parameters of γ-models for binary mixtures from surface tension data

An approach based on the conception that the surface layer of a surfactant solution is a phase with a finite thickness is suggested for estimating the parameters of γ-models of binary mixtures from their surface tension data. Experimental surface tension data are presented for the acetone-water, methanol-water, ethanol-water, and isopropanol-water systems over the entire concentration ranges. The parameters of the Margules model have been determined for these solutions.     

Effect of temperature and addition of α-tocopherol on the oxidation of trilinolein model systems

The effects of temperature and addition of α-tocopherol were evaluated in trilinolein model systems through quantification of oxidized TAG monomers, dimers, and polymers following oxidation at different temperatures. Samples of trilinolein without and with 250 and 500 mg/kg α-tocopherol added were stored at 25, 60, and 100°C. Quantification of oxidized monomers, dimers, and polymers by a combination of adsorption and exclusion chromatography provided a useful measurement for studying the evolution of oxidation. Results showed that the amounts of primary oxidation compounds (trilinolein oxidized monomers) that accumulated during the induction period decreased as the temperature increased, indicating that the slope of the initial linear stage of oxidation depended on temperature. The end of the induction period was marked by a sharp increase in the levels of total oxidation compounds, the initiation of polymerization, and the loss of α-tocopherol. Addition of α-tocopherol did not prevent, but rather delayed, formation of trilinolein oxidized monomers and the initiation of polymerization.     

Influence of the temperature dependence of the thermophysical properties of coal–water fuel on the conditions and characteristics of ignition

The results of an experimental study and mathematical simulation of the ignition of coal–water fuel (CWF) particles, the main thermophysical characteristics of which (thermal conductivity (λ), heat capacity (C), and density (ρ)) depend on temperature, are reported. Based on the results of the numerical study, the influence of changes in the thermophysical properties upon the heating of the main bed of fuel on the conditions and characteristics of its ignition was analyzed. The ignition delay times (t _i) of CWF particles were determined under the typical furnace conditions of boiler aggregates. As a result of the mathematical simulation of the process of CWF ignition, it was established that the temperature dependence of thermophysical characteristics can exert a considerable effect on the characteristics and conditions of ignition. In this case, it was found that the ignition of coal–water drops is possible under the conditions of their incomplete dehydration. A good agreement of the theoretical ignition delay times of the CWF particles and the experimental values of t _i was established.     

Supported Ziegler–Natta catalyst for ethylene polymerization: Novel data on the effect of polymerization temperature on the number of active centers and propagation rate constant

The number of active centers at ethylene polymerization over highly active supported catalyst TiCl₄/MgCl₂ + AlEt₃ was determined at various polymerization temperatures. It was found that the increase in polymerization temperature in the range of 40–80 °C increases the number of active centers. The data on reversible changes in the polymerization rate with temperature in a single experiment give grounds for supposing that alteration of the number of active centers with temperature is a reversible process. The propagation rate constants and the activation energy of the propagation reaction (4.0 kcal mol^− 1) were calculated; the latter value being considerably lower than the effective activation energy of polymerization (16.5 kcal mol^− 1) due to the increase in C_P with rising temperature.     

Polymerization temperature effects on the properties of l-lactide and ε-caprolactone copolymers

Summary The large difference in reactivity of L-lactide and -caprolactone in ring opening polymerization with stannous octoate, leads to the formation of copolymers with blocky structures. By varying the polymerization temperature, copolymers with different average sequence lengths and molecular weights can be synthesized. It is shown that the average monomer sequence length has a large effect on the thermal and mechanical properties of these copolymers.     

Structure of the O-Antigen and the Lipid A from the Lipopolysaccharide of Fusobacterium nucleatum ATCC 51191

Fusobacterium nucleatum is a common member of the oral microbiota. However, this symbiont has been found to play an active role in disease development. As a Gram-negative bacterium, F. nucleatum has a protective outer membrane layer whose external leaflet is mainly composed of lipopolysaccharides (LPSs). LPSs play a crucial role in the interaction between bacteria and the host immune system. Here, we characterised the structure of the O-antigen and lipid A from F. nucleatum ssp. animalis ATCC 51191 by using a combination of GC-MS, MALDI and NMR techniques. The results revealed a novel repeat of the O-antigen structure of the LPS, [→4)-β-d -GlcpNAcA-(1→4)-β-d -GlcpNAc3NAlaA-(1→3)-α-d -FucpNAc4NR-(1→], (R=acetylated 60 %), and a bis-phosphorylated hexa-acylated lipid A moiety. Taken together these data showed that F. nucleatum ATCC 51191 has a distinct LPS which might differentially influence recognition by immune cells.     

Anharmonicity of thermal vibrations and grüneisen parameter of chalcogenide glasses in the Ge-As-S system within the approximation of the free volume concept

The Grüneisen parameter and the ultimate strain of “bond breaking” at the ultimate elongation of interparticle bonds have been calculated. The Grüneisen parameters determined from different formulas are compared. It is demonstrated that the volume deformation required to form a microvoid in the glass network only slightly depends on glass composition. The microvoid volume is determined primarily by the ultimate strain of the interatomic bond. In chalcogenide glasses, the ultimate strain of the interatomic bond is governed by the limiting displacement of a bridging chalcogen atom, which varies in inverse proportion to the lattice Grüneisen parameter. The role of the Grüneisen parameter in the fluctuation free volume and soft configuration models is discussed.     

Influence of temperature on the bending stiffness and tensile-shear strength of composite–metal joints

The temperature effect on bending and shear strength of single lap joints, composed by metal–composite substrates with fixed geometry, was evaluated in this paper. The tests provide analysis associated with a system frequently used in the oil and gas industry, characterized by the use of polymeric composite materials with adhesives for repairing and reinforcing pipelines. The results revealed that the tensile behavior of the composite is highly affected by temperature and can be predicted by a linear function with good agreement. The bending stiffness and tensile-shear strength of composite–metal single lap joints are also dependent of the test temperature. The first can be represented by a linear equation and the second by a power law, both with good agreement.     

Spherical nanoparticle effects on the lower critical solution temperature phase behavior of poly(ε-caprolactone)/poly(styrene-co-acrylonitrile) blends: Separation of thermodynamic aspects from kinetics

The effects of spherical nanosilica particles on the lower critical solution temperature (LCST) phase diagram of poly(ε-caprolactone) (PCL)/poly(styrene-co-acrylonitrile) (SAN) blends are investigated by using isochronal dynamic temperature sweep tests at different cooling rates. A stronger dependency of the rheologically determined phase-transition points on the cooling rate is observed in the presence of nanoparticles, which results from the large contribution of entropic surface tension of chains in the Gibbs free energy of mixing and much slower rate of PCL/SAN phase dissolution. By alleviating the effects of kinetic factors, it is found that the drop in the LCST-type phase boundary of PCL/SAN blends by adding nanofiller is more apparent than real. However, the closest LCST phase diagram to the real steady-state thermodynamic diagram shows an unexpected shift to lower temperatures by adding nanosilica. The migration of nanosilica particles to the SAN domains especially at lower cooling rates in the dynamic measurements is the most likely explanation of these observations. The findings that prove the profound impact of kinetic factors in dynamic temperature measurements are reached in a hybrid system, wherein the SAN chains are preferentially absorbed on the surface of a nanofiller having very small primary particle size. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48679.     

Shock-wave data as evidence of the presence of carbon in the earth’s core and lower mantle

The standard density and average atomic weights of hypothetical materials contained in the inner layers of the Earth are calculated from results of shock-wave studies using a previously proposed method for determining the velocity of sound in materials at high pressures and density, and from seismic data. These data turned out to be sufficient to refine the elemental composition of the Earth’s interior. It is shown that the iron-nickel core of the Earth should contain ≈10% (by weight) carbon, partly in the diamond phase. According to the calculations, the lower mantle can contain up to 20% carbon, which probably comes from the core. Translated fromFizika Goreniya i Vzryva, Vol. 36, No. 4, pp. 108–114, July–August, 2000. The results of the work can be supported by measurements of velocities of sound in magnetically oriented, diamond-containing mixtures, measurements of velocities of sound behind SW fronts in diamond-containing iron nickel alloys, iron carbides, and other materials, and comparison of the results with seismic data.     

Effect of activation temperature on the surface copper particles and catalytic properties of Cu–Ni–Mg–Al oxides from hydrotalcite-like precursors

The Cu–Ni–Mg–Al oxides catalysts for furfural hydrogenation were prepared from the hydrotalcite-like precursors, and the effect of activation temperature on the Cu⁰ particles and catalytic properties of the catalyst was thoroughly investigated. The catalyst activated by H₂ at 300 °C was found to exhibit the best catalytic activity, due to the presence of the smallest Cu⁰ particles with a high dispersion. Moreover, the bigger Cu⁰ particles were active for furfuralcohol hydrogenolysis to 2-methylfuran in the liquid-phase (ethanolic solution), and the hydrogenation of the furan ring of furfuralcohol and 2-methylfuran on Cu⁰ particles was easily achieved in the vapour-phase.