Wide Experimental Range Research Articles

A comprehensively experimental and kinetic modeling investigation of tetrahydropyran pyrolysis and oxidation in a jet-stirred reactor

Tetrahydropyran (THP), a kind of promising green cyclic-ether fuel derived from biomass, exhibits excellent resistance to autoignition characteristics and can be used as an alternative fuel or fuel additive to improve combustion efficiency as well as reduce harmful emissions. To further reveal insights into its high-temperature decomposition and low-and intermediate temperature oxidation behaviors closely related the deflagration to detonation in spark ignition engines, the comprehensive investigation of experiments and detailed kinetic modeling of THP were performed in the present work. The experiments at two equivalence ratios, i.e. ϕ = ∞ (pyrolysis) and ϕ = 1.0, were carried out in a jet-stirred quartz reactor at 1.0 atm and 733–1148 K. More than ten substances were identified and quantified by GC and GC/MS, including small hydrocarbons, oxygenated and stable products. A detailed kinetic model of THP pyrolysis and oxidation was developed by incorporating the O2 additions of fuel radicals and updating the rate constants of key reactions, and validated and showed the slight an improvement for the speciation profiles newly reported in this work and those available in the previous literature over a wide experimental range of 450–1260 K and 1.0–10.0 atm. Rate of production analysis indicated that the H-abstractions by H attacking are the important pathways governing THP reactivity with a minor contribution from C-C and C-O dissociations of ring-opening reactions in high-temperature pyrolysis, whereas the H-abstractions triggered by OH and HO2 largely control fuel consumption in low- and intermediate temperature oxidation. The formed three tetrahydropyranyls, especially α-tetrahydropyranyl, will proceed to decompose into acyclic C5H9O radicals via C-O and C-C β-scissions or C5H9OO2-2 intermediates via O2 addition in THP pyrolysis and oxidation, as the main source of small species. For the unique aromatics detected during the pyrolysis, the combination reactions of C2 + C4 unsaturated hydrocarbons predominantly determinate their generation. This work provides new experimental data and further analyses for understanding the pyrolysis and oxidation chemistry of THP and sheds light on directions for future practical application.

Causal agents of Stemphylium-induced foliar diseases of tomatoes and other Solanaceae hosts in Brazil.

An extensive survey was done to clarify the prevalent Stemphylium species on Solanaceae plants across Brazil, and their host ranges. Eighty nine (89) Stemphylium isolates were obtained from naturally infected tomatoes as well as S. paniculatum, potato, eggplant, scarlet eggplant (Solanum aethiopicum var. gilo), Physalis angulata, and Capsicum species. Phylogenetic analyses encompassing the ITS-5.8S rDNA and glyceraldehyde-3-phosphate dehydrogenase genomic regions placed the isolates into two distinct groupings with either Stemphylium lycopersici or S. solani. Isolates of S. lycopersici (n=81) were obtained infecting tomato, potato, eggplant, S. paniculatum, and P. angulata. Isolates of S. solani (n=8) were detected in natural association with scarlet eggplant and tomato. Two isolates of S. lycopersici displayed a wide experimental host range in greenhouse bioassays, infecting accessions of 12 out of 18 species. Ocimum basilicum (Lamiaceae) was the only experimental host outside the Solanaceae family.

High-throughput thermodynamic analysis of epitaxial growth of β-Ga2O3 by the chemical vapor deposition method from TMGa-H2O system

A comprehensive thermodynamic study of CVD β-Ga2O3 epitaxial films from TMGa-H2O (trimethylgallium-water) system is performed with a wide experimental condition range and high mesh grid number. The high-throughput computational approach was utilized, investigating the effects of temperature (500–1500 K), pressure (0–100,000 Pa) and H2O fraction (0–100%) on equilibrium condensed phase purity and gas speciation. The β-Ga2O3 growth regime expands with increasing temperature and H2O fraction. High purity (>99%) β-Ga2O3 is predicted under high H2O fractions (>80%) and temperatures from 1000–1300 K. And the dominant Ga species are Ga(g), Ga(OH) and Ga2O, while H2O, CO2 and CO carry O. Median temperatures of 1000–1200 K maximize TMGa conversion efficiency while minimizing graphite formation. The computations yield optimal CVD conditions of 1000–1200 K, 2000–10000 Pa, and VI: III> 7 for high quality β-Ga2O3 epitaxial growth, providing useful guidance for further experimental CVD process development.

Influence of aqueous foam on gas–liquid flow development of hilly-terrain wet gas pipeline with surfactant injection

This study presents surfactant injection as a replacement technology for mechanical pigging to reduce liquid accumulation for wet gas transmission. The hilly terrain gas/liquid flow development characteristics under surfactant injection were explored in pipelines, and a comprehensive experiment was performed through flow observation and the measurement and analysis of the flow characteristic parameters. The 250 ppm sodium dodecyl sulfate (SDS) surfactant was employed according to the variation characteristics of the flow pattern and pressure drop at different concentrations. Flow observations and liquid holdup characteristics indicate that owing to the formation of aqueous foam, the gas/liquid interface and phase characteristics change significantly, and the liquid holdup decreases by several or even more than ten times and maintains a low value (0.004–0.070), except for the initial gas–liquid flow at low gas flow and high liquid flow rates. The aqueous foam effectively suppresses the slug and pseudo slug initiation, the gas/liquid convection of the slug body, and the large wave rolling of the pseudo-slug body, which induces the dissipation of intermittent flow. The pressure drop under the influence of aqueous foam decreases drastically (60% ∼ 85%) at certain gas and liquid velocities and fluctuates smoothly near zero over a wide experimental range. The surfactant suppression on partially blocked pseudo-slug body induces a significant decrease of pseudo-slug frequency from 0.17 ∼ 0.42 Hz to 0 ∼ 0.06 Hz and transitional velocity from 1.21 ∼ 1.90 m/s to 0 ∼ 1.11 m/s. This research is highly significant for surfactant injection schemes and efficient and sustainable production.

Lipozyme® TL IM Biocatalyst for Castor Oil FAME and Triacetin Production by Interesterification: Activity, Stability, and Kinetics

Global climate change and present geopolitical tensions call for novel, renewable, and, ideally, sustainable resources and processes that, in the end, will be integrated in the natural cycles of carbon and water, progressively replacing non-renewable feedstocks. In this context, the production of biofuels and, in consequence, of biodiesel plays a notable role. This work is focused on the production of fatty acid methyl esters (FAME) from castor oil, an abundant non-edible oil, using a sustainable technology approach based on industrial lipases and methyl acetate as a methylating reagent to reduce biocatalyst inactivation. We have selected a stable industrial enzyme preparation to determine its suitability for FAME production: Lipozyme® TL IM (an inexpensive lipase from Thermomyces lanuginosus immobilized by agglomeration in silica gel). Several operational variables affecting the enzyme activity have been studied: methanol excess (6:1 to 13:1), temperature (from 40 to 60 °C), and enzyme concentration (10 and 30% w/w). At all temperatures and reagent ratios, we have also tested the enzyme stability for six cycles, showing its low to negligible inactivation under operational conditions. Finally, a novel multivariable kinetic model has been proposed and fitted to experimental data obtained in a wide experimental range for the first time, showing that direct and reverse in-series reactions are present. We have estimated the values of the kinetic constants and their standard errors, and goodness-of-fit parameters, observing that the kinetic model fitted very reasonably to all retrieved experimental data at the same time.

High shear cooking extrusion to create fibrous mozzarella cheese from renneted and cultured curd

To understand shearing on cheese curds during high shear extrusion, the controlable parameters of a twin-screw extruder were related with measured and calculated parameters that characterise the extrusion process effects on product properties. Curd properties were correlated with specific mechanical energy SME (23–390 kJ·kg−1), Texit (22–54 °C) and residence time RT (36–507 s); the wide experimental range studied provided new insights regarding extrusion of cheese curds. Longer and finer fibers were produced at low SME (23–27 kJ·kg−1), high Texit (50–54 °C) and short RT (55–60 s). Whereas extruded curds produced at high SME (166–390 kJ·kg−1), low Texit (22–23 °C) and long RT (371–396 s) tend to form a compact structure with less fiber formation. Temperature in the heating section, Th, and temperature of the cooling die, Tc, were found to determine critical curd phase transitions during extrusion, from viscoelastic solid to viscoelastic liquid and vice versa, that are important for the creation of fibrous cheese curd structures. Tc was the most important factor influencing SME, indicating the considerable contribution of the cooling process in increasing the shear forces. Curd composition and textural properties were significantly influenced by Th and Tc, showing that a higher Th enhances curd elasticity and reduces melt strength while a higher Tc induces lower water content and increases melt strength. We concluded that a variety of structured mozzarella products with customized properties can be produced by controlling the extrusion parameters.

Heat Loss Analysis of Flow Boiling Experiments Onboard International Space Station with Unclear Thermal Environmental Conditions (1st Report: Subcooled Liquid Flow Conditions at Test Section Inlet)

Two series of flow boiling experiments have been conducted onboard the International Space Station (ISS) as a part of the TPF (Two-Phase Flow) experiment promoted by JAXA during July 2017–March 2018, February 2019–July 2019. Microgravity data on two-phase flow and heat transfer in flow boiling of n-Perfluorohexane (FC-72) have been obtained by a copper heated test tube and a transparent glass heated tube in a wide experimental range of mass velocity, liquid subcooling, vapor quality and heat flux. Furthermore, detailed two-phase flow behaviors have been observed by using high frame rate camera in the unheated observation section. In order to elucidate the accurate influence of gravity on flow boiling, it is essential to compare the heat transfer data and two-phase flow behaviors obtained under normal (terrestrial) gravity and microgravity environments at the same flow and heating conditions. However, both experiments cannot be performed by using the same experimental apparatus and under the same thermal environmental conditions. In addition, the heat loss cannot be negligible due to the forced avionics air flow inside the experimental apparatus in ISS. Therefore, exact evaluation of the fluid conditions at the inlet of the heated test tube requires the heat loss model with high-accuracy. In the present paper, the heat loss models for evaluating the degree of liquid subcooling at the inlet of the heated test tube and net heat flux from the heated tube to test fluid has been developed by using the results of preliminary heat loss experiments conducted onboard ISS. The correction of the degree of liquid subcooling by the proposed heat loss models is not negligible for the accurate analysis of gravity effects. The accuracy of the heat loss models has been verified through the evaluation of heat transfer coefficients for single-phase turbulent forced convection obtained from the heating experiments onboard ISS.

Correction factor development for the 2006 Groeneveld CHF look-up table for rectangular channels under low pressure

Similar to commercial nuclear reactors, research reactors are recommended to be designed with sufficient safety margins for thermalhydraulic issues such as critical heat flux (CHF) in both normal and accident conditions. In the MARS-KS system code, developed based on RELAP5, the 2006 Groeneveld CHF look-up table (Groeneveld et al., 2007) is adopted to predict CHF for plate-type fuel. The applicability of this table to CHF in rectangular channels for high pressure conditions of over 40 bar has been confirmed (Choi et al., 2015); however, its applicability to pressure conditions under 40 bar has yet to be clarified. While Sudo and Kaminaga previously suggested a rectangular CHF model for a wide experimental range, some notifications have indicated the inclusion of flow excursion data in their model. In this paper, a rectangular channel CHF database was constructed for wide experimental ranges and used to assess the 2006 Groeneveld CHF look-up table and Sudo-Kaminaga correlation to confirm their applicability to rectangular channels under low pressure. Then, with several parameters selected by the Random Forest method in the R package (Reynolds number, quality, aspect ratio, diameter ratio, and length over diameter), a new correction factor was suggested by applying a non-linear regression method from a statistical software package to correct the CHF values in the CHF look-up table for rectangular channels. Results confirmed that the CHF LUT with the newly suggested correction factor is capable to predict CHF in rectangular channels.

Sorption of radionuclides onto minerals: Experiments and modelling

Sorption of various radionuclides such as Cs(I), Eu(III)/Am(III), Np(V), U(VI) and others onto iron oxide (goethite, hematite) and clay minerals (montmorillonite, kaolinite) was studied at wide experimental range (pH ionic strength, total radionuclides concentrations). In all case athermodynamic model for describing sorption onto studied minerals was built and successfully applied for all experiments. The required constants were calculated or verified from published data. For modelling sorption in mineral assemblages Component Additivity (CA) approach was successfully applied.

Exploration of the Infrared Sensitivity for a ZnSe Electrode of an IR Image Converter

Significant improvement has been carried out in the field of the II–VI group semiconductor device technology. Semiconductors based on the II–VI group are attractive due to their alternative uses for thermal imaging systems and photonic applications. This study focuses on experimental work on the optical, electrical and structural characterization of an infrared (IR) photodetector zinc selenide (ZnSe). In addition, the IR sensitivity of the ZnSe has primarily been investigated by exploiting the IR responses of the material for various gas pressures, p, and interelectrode distances, d, in the IR converter. The experimental findings include the results of plasma current and plasma discharge emission under various illumination conditions in the IR region. The electron density distributions inside the gas discharge gap have also been simulated in two-dimensional media. Experimentally, the current–voltage, current–time, and discharge light emission plots are produced for a wide experimental parameter range. Consequently, the structural and optical properties have been studied through atomic force microscopy and Fourier-transform infrared spectroscopy techniques to obtain a comprehensive knowledge of the material.

Generating quantum correlated twin beams by four-wave mixing in hot cesium vapor

Using a nondegenerate four-wave mixing process based on a double-$\Lambda$ scheme in hot cesium vapor, we generate quantum correlated twin beams with a maximum intensity-difference squeezing of 6.5 dB. The substantially improved squeezing can be mainly attributed to very good frequency and phase-difference stability between the pump and probe beams in our experiment. Intensity-difference squeezing can be observed within a wide experimental parameter range, which guarantees its robust generation. Since this scheme produces multi-spatial-mode twin beams at the Cs $D_{1}$ line, it is of interest for experiments involving quantum imaging and coherent interfaces between atomic and solid-state systems.

Highlighting the role of surface groups in the gasification of carbonized raw materials of different natures with steam and supercritical water at pressures ranging from 1 to 1000 bar

This manuscript describes a kinetic and mechanistic study of the gasification with water of two carbonized materials originating from a phenolic textile fiber and holm oak wood at 540–650 °C and 1–1000 bar. The wide experimental range studied causes the number of hydrogen bonds to strongly vary with the gasifying conditions, which generates important changes in the structure and properties of water. The solvent–solvent and solvent–solute interactions are significantly affected, with pressure favoring the formation of clusters. The concentration of the gas produced and the kinetics and pathways of gasification show a strong dependence on pressure. The study reveals the importance of the oxygen surface groups in gasification. These groups take part in some pathways of the gasification and control the gasification rate and the concentration of the gases. The formation of clusters of water molecules on the oxygen surface groups at high pressures enables a new pathway that accelerates the gasification and guides it toward the direct formation of CO2. Although gasification is accelerated by pressure, increasing amounts of the H2 produced are readsorbed onto the active sites of the solid, disabling them from being gasified (auto-inhibition phenomenon). Consequently, a pressure within this range yields the highest gasification rate.

Voltage relaxation and impedance spectroscopy as in-operando methods for the detection of lithium plating on graphitic anodes in commercial lithium-ion cells

In this study, voltage relaxation and impedance spectroscopy are introduced as in-operando methods for detecting lithium plating in commercial lithium-ion cells with graphitic anodes. Voltage relaxation is monitored subsequent to defined charge steps of variable amplitudes, charge throughputs, termination criteria and at different ambient temperatures yielding dependencies over a wide experimental parameter range. An adapted differential voltage analysis is presented to resolve the characteristic mixed potential evolving in case of plating. Impedance spectroscopy is applied in parallel to the relaxation phase to trace a possible alteration of the cell's impedance due to the concurrent depletion of reversibly deposited lithium. The introduced voltage differentials are shown to resolve the mixed potential with restrictions only for little charge throughputs. The comparison of voltage relaxation and already established stripping discharge reveals similarities of the underlying physicochemical processes and allows an estimate of the amount of deposited lithium in case of relaxation. In the evolution of the cell's impedance, a reversible shrinkage of the high frequency intersection resistance and the arc representing the anodic charge transfer process are identified as indicators towards plating. The presented methods solely rely on non-destructive measurement quantities and thus are fully suitable for the application in battery management systems.

Facile synthesis and catalytic activity of well‐defined amphiphilic block copolymers based on N‐vinylimidazolium

Well‐defined amphiphilic block copolymers, poly(styrene)‐b‐poly(N‐vinylimidazole) (PS‐b‐PVim), were successfully synthesized by macromolecular design via interchange of the xanthates/reversible addition–fragmentation chain transfer (RAFT) polymerization. The structure of the copolymer based on Vim can be well controlled, and the molecular weight distribution was relatively narrow (PDI = 1.24). The size and morphology of the aggregates of the amphiphilic copolymers were investigated by dynamic light scattering and transmission electron microscope, the results implied that the uniform spheroidal micelles consisting of PS core and PVim corona were assembled, and the catalytic activities of PS‐b‐PVim for the hydrolysis of p‐nitrophenyl acetate at different temperatures were also investigated by high‐performance liquid chromatograph (HPLC); the catalytic activities of diblock copolymers were prominently improved compared with that of PVim homopolymers. Moreover, the catalytic activities of the copolymers followed the Arrhenius behavior in the wide experimental temperature range. Copyright © 2013 John Wiley & Sons, Ltd.

Characterization of Friction Modified Processing – A Novel Tool for Enhancing Surface Properties in Cast Aluminium Alloys

Friction Modified Processing (FMP) is a novel solid state processing technique which can be used for microstructural modification of surface layers in metallic materials. The paper deals with the investigation of the influence of process parameters on the microstructure in the surface layer of a cast aluminum alloy. The FMP was conducted on a constructed welding machine equipped with appropriate devices (LOWSTIR and TermSTIR). The measurements of temperature in the stir zone were compared with a numerical model. Another model was developed to determine the quantitative relationships between mass of modified material and processing speeds over a wide experimental range. An exponential formula has been found to describe the relationship between mass of modified material and rotational speed. The evaluation of the traveling speed affecting the mass of the modified material was successfully approximated by linear functions.

Coulombic Free Energy of Polymeric Nucleic Acid: Low- and High-Salt Analytical Approximations for the Cylindrical Poisson−Boltzmann Model

An accurate analytical expression for the Coulombic free energy of DNA as a function of salt concentration ([salt]) is essential in applications to nucleic acid (NA) processes. The cylindrical model of DNA and the nonlinear Poisson-Boltzmann (NLPB) equation for ions in solution are among the simplest approaches capable of describing Coulombic interactions of NA and salt ions and of providing analytical expressions for thermodynamic quantities. Three approximations for Coulombic free energy G(u,infinity)(coul) of a polymeric nucleic acid are derived and compared with the numerical solution in a wide experimental range of 1:1 [salt] from 0.01 to 2 M. Two are obtained from the two asymptotic solutions of the cylindrical NLPB equation in the high-[salt] and low-[salt] limits: these are sufficient to determine G(u,infinity)(coul) of double-stranded (ds) DNA with 1% and of single-stranded (ss) DNA with 3% accuracy at any [salt]. The third approximation is experimentally motivated Taylor series up to the quadratic term in ln[salt] in the vicinity of the reference [salt] 0.15 M. This expression with three numerical coefficients (Coulombic free energy and its first and second derivatives at 0.15 M) predicts dependence of G(u,infinity)(coul) on [salt] within 2% of the numerical solution from 0.01 to 1 M for ss (a = 7 A, b = 3.4 A) and ds (a = 10 A, b = 1.7 A) DNA. Comparison of cylindrical free energy with that calculated for the all-atom structural model of linear B-DNA shows that the cylindrical model is completely sufficient above 0.01 M of 1:1 [salt]. The choice of two cylindrical parameters, the distance of closest approach of ion to cylinder axis (radius) a and the average axial charge separation b, is discussed in application to all-atom numerical calculations and analysis of experiment. Further development of analytical expression for Coulombic free energy with thermodynamic approaches accounting for ionic correlations and specific effects is suggested.

Formation of galacto‐oligosaccharides during lactose hydrolysis by a novel β‐galactosidase from the moderately thermophilic fungusTalaromyces thermophilus

Discontinuous and continuous processes of lactose hydrolysis and concomitant galacto-oligosaccharide (GalOS) formation were studied. To this end a wide experimental range of the main variables was evaluated, including the initial lactose concentration, the degree of lactose conversion, the pH value and the temperature for discontinuous transformations, while the initial lactose concentration and the feed rate were varied for the continuous process. For both processes a high-initial lactose concentration proved to be advantageous for the formation of GalOS. The maximum amount of GalOS (100 g/L, corresponding to a yield of approximately 50% based on the initially employed lactose) was obtained after 8 h of incubation when using 200 g/L lactose as substrate and 90% lactose hydrolysis was observed. GalOS productivity in the continuous process (g/L.h) was enhanced by an increase of the flow rate. The maximum GalOS productivity of 70 g/L.h was obtained at a flow rate of 24 mL/h when using a reactor with a total working volume of 21 mL. As was evident from these experiments, this beta-galactosidase from a moderately thermophilic fungus showed a strong transgalactosylation activity and can be used for the formation of GalOS, sugars that are of considerable interest for functional food applications because of their presumed healthpromoting effects.

Critical Heat Flux of Steady Boiling for Subcooled Water Jet Impingement on the Flat Stagnation Zone

An experimental investigation was carried out for predicting the critical heat flux (CHF) of steady boiling for a round subcooled water jet impingement on the flat stagnation zone. The experimental data were measured in a steady nucleate boiling state. Three main influencing parameters, i.e., subcooling, impact velocity and jet nozzle size were widely changed and their effects on the critical heat flux were systemically studied. An empirical correlation was obtained using the experimental data over a wide experimental range for predicting the critical heat flux of steady boiling for a round subcooled water jet impingement on the flat stagnation zone.

Experimental design and modelling in the investigation of PECVD parameters effects on the structural and gas transport properties of plasma polysiloxane membranes

The experimental design method was used to investigate the PECVD parameters effects on the properties of plasma polysiloxane membranes synthesized using octamethylcyclotetrasiloxane or hexamethyldisiloxane as monomers. On a wide experimental range and with a minimum number of experiments, the use of such a statistical tool enabled us to set up complete and reliable correlations, in the form of polynomial models connecting the gas transport properties (H 2 permeability coefficient, H 2/N 2 ideal selectivity) and the structural properties (growth rate, density, organic/inorganic nature) of synthesized films with the two most influent synthesis parameters of the PECVD process: the input power (represented by the input voltage) and the monomer flux. The polynomial models enabled us not only to statistically confirm the effects of the PECVD parameters displayed by previous classical experimental studies, but also to model, in the mathematical sense, the evolution of each property of materials taking into account the first and second orders effects of both PECVD synthesis parameters. By the use of a performing statistical tool, we managed to improve the knowledge of relations between synthesis parameters/structure/properties relative to our process.

Linear and nonlinear viscoelasticity of carbon black filled elastomers: Use of complementary rheological characterizations

AbstractThe viscoelastic properties of filled elastomers (uncured styrene–butadiene rubber filled with carbon black) were investigated with two shear rheometers specially designed for the characterization of complex polymer systems. A torsional strain‐controlled rheometer [i.e., a rubber process analyzer (RPA)] was used in dynamic and relaxation modes for measuring the storage and loss moduli and the relaxation modulus. A stress‐controlled sliding cylinder rheometer (SCR) was operated for the measurement of the creep compliance. Both devices could be operated on a large scale of imposed strains or stresses ranging from the linear viscoelastic regime to the nonlinear viscoelastic regime, and they were complementary in supporting the original viscoelastic behavior of filled elastomers for a wide experimental time range. Moreover, when the measuring ranges of the two apparatus overlapped, a cross‐check of the material functions obtained with the RPA or SCR could be successfully carried out. This validation of the data was performed not only in the linear domain of viscoelasticity, with the classical approach of a generalized Maxwell model, but also in the nonlinear domain, with a viscoelastic integral model of type K‐BKZ. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 31–41, 2003