TEMPERATURE MEASUREMENT ERROR BY RADIAL INSERTION OF THERMOCOUPLE IN THERMAL CONDUCTIVITY MEASURING DEVICE

To measure the temperature of the inner part of a material, an axially inserted thermocouple is often used. But, when the measurement by an axially inserted thermocouple is difficult, we must insert the thermocouple radially. In the case of radial insertion, a measuring error usually exists. To know the true temperature by the method of radial insertion of a thermocouple, we must conduct numerical calculations.

In this report, numerical calculations have been conducted for the temperature measuring error by radial insertion of thermocouple in a gas thermal conductivity measuring device.^2-5     

Regio- and stereochemistry of the first insertion step in the 1,3-butadiene polymerization catalyzed by CpTiCl3-MAO

CpTiCl₃-MAO (methylaluminoxane) catalytic system promotes the butadiene polymerization leading to 85% of 4,1-cis polymer. The generally well accepted homopolymerization mechanism involves a diene insertion on a π-allylic terminal growing chain. In α-olefin-diene copolymerizations, diene monomer can also insert on a σ carbon-metal bond.In order to simulate an insertion of a conjugated diene on a σ chain, experimental and theoretical studies, relative to the first insertion step, are reported. Unexpectedly 56% of 1,2-primary and 44% of 4,1-trans first inserted units were obtained, by using as catalyst CpTiCl₃/MAO/Al(¹³CH₃)₃. The experimental results were rationalized by DFT (Density Functional Theory) calculations, by including a solvent molecule coordinated to the catalytic site during the first insertion step.     

The Influence of the Variation of Combustion Chamber Volume under pressure load on the determinational of thermodynamic characteristics of solid propellants in pressure bombs

Detailed combustion studies in high-pressure bombs show that the measured maximum gas pressures are always lower than theoretically calculated values and that these differences increase more than proportionally with rising loading densities. By means of experiments and calculations we show that a considerable part of the pressure difference is brought about by the expansion of the combustion chamber during pressure load. The expansion of the combustion chamber is responsible for pressure measurements that are about 5% too low at currently used pressures of 500 MPa. Furthermore the covolume yields an error of about 12% if the constants of the Abel state equation are determined using the standardized method for loading densities of 0.20 g/cm³ and 0.22 g/cm³. The error of the force constant remains under 1%. As the values determined from pressure bomb measurements are to be introduced into further calculations, they must be corrected according to the combustion chamber expansion, or new measuring methods will be necessary.     

Temperature-Dependent Re-alignment of the Short Multifunctional Peptide BP100 in Membranes Revealed by Solid-State NMR Spectroscopy and Molecular Dynamics Simulations

BP100 is a cationic undecamer peptide with antimicrobial and cell-penetrating activities. The orientation of this amphiphilic α-helix in lipid bilayers was examined under numerous conditions using solid-state ¹⁹F, ¹⁵N and ²H NMR. At high temperatures in saturated phosphatidylcholine lipids, BP100 lies flat on the membrane surface, as expected. Upon lowering the temperature towards the lipid phase transition, the helix is found to flip into an upright transmembrane orientation. In thin bilayers, this inserted state was stable at low peptide concentration, but thicker membranes required higher peptide concentrations. In the presence of lysolipids, the inserted state prevailed even at high temperature. Molecular dynamics simulations suggest that BP100 monomer insertion can be stabilized by snorkeling lysine side chains. These results demonstrate that even a very short helix like BP100 can span (and thereby penetrate through) a cellular membrane under suitable conditions.     

Laminar mixed convection in the thermal entrance region of horizontal rectangular channels with uniform heat input axially and uniform wall temperature circumferentially

This paper presents a numerical study on laminar mixed convection in the thermal entrance region of horizontal rectangular channels with uniform heat input axially and uniform wall temperature circumferentially. A relatively novel numerical method of solution is developed to obtain the developing velocity and temperature fields. The values of Prandtl number are 0.7 and 7.2, corresponding to air and water, respectively. The values of Rayleigh number are 0, 10⁴, 3 × 10⁴ and 10⁵. The channel aspect ratios considered are 0.2, 0.5, 1, 2 and 5. Variations in local friction factor ratios and local Nusselt numbers are presented. It is found that the circumferential boundary condition of uniform wall temperature significantly increases the value of local Nusselt number as compared to that found in earlier works under the boundary condition of uniform wall heat flux. But the boundary condition effect on the friction factor is shown to be comparatively minor. The asymptotic solutions at z → are compared to the existing numerical data with good agreement.     

Measuring lead scandium tantalate phase transition entropy by infrared camera

Using an infrared camera, we measured the latent heat of the first order phase transition in lead scandium tantalate at different applied electric fields. The entropy change value of 3.4 J kg⁻¹ K⁻¹ is consistent with differential scanning calorimetry measurements. The advantage of such an approach stems from the possibility to obtain both adiabatic temperature change and latent heat of the phase transition material only with an infrared camera or a thermocouple. This may prove useful for a systemic characterization of first order electrocaloric materials.     

The effect of quantum vibrations on electrochemical outer sphere redox reactions

The influence of an inner sphere vibration with a frequency in the region 10¹³ s^?1 ≤ ω ≤ 4 × 10¹⁴ s^?1 on simple electrochemical redox reactions is examined. The numerical calculations, based on first order perturbation theory and the Frank—Condon approximation, exhibit the following effects: the energy of activation decreases with temperature due to an increase in tunnel transitions of the system; the transfer coefficient is temperature dependent; the curvature of Tafel lines is greater at lower temperatures. All of these effects are of a quantum mechanical nature, and disappear both for very high and very low frequencies. These results are compared with classical and semi-classical approximations. At high overpotentials, the calculations predict limiting currents corresponding to activationless transfer. The magnitude of the limiting current is determined by the electronic matrix element and is independent of the model Hamiltonian for the solvation sphere.     

聚丙烯保压注射成型冷却过程温度场的研究

采用数值模拟结合实验验证的方法,对聚丙稀（PP）注射成型（保压和不保压）冷却过程实验和数值模拟进行分析。用数据采集器对不同共混物注射冷却过程中的温度变化进行数据采集,并将采集所得温度的实验值与根据改进焓法用Matlab软件对聚丙烯冷却过程中温度分布进行数值模拟计算所得的值进行了比较分析,结果表明聚丙烯在液体冷却段温度分布的实验值与理论值几乎完全吻合,在结晶段和固体冷却段实验值略有不同。     

Polymer bilayers with enhanced dielectric permittivity and low dielectric losses by Maxwell–Wagner–Sillars interfacial polarization: Characteristic frequencies and scaling laws

An efficient approach to obtain polymeric materials with high permittivity values and low dielectric losses is presented in the current study. For this purpose, dielectric measurements by means of broadband dielectric spectroscopy, numerical simulations, and analytical calculations have been carried out for bilayer structures consisting in an insulating and a conductive polymer layer. Polyethyleneterephtalate and polytetrafluoroethylene have been used as insulating layers while, as conductive materials, blends of polyvinyl acetate with an ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate. The dielectric properties of the samples have been investigated in a broad frequency (from 10⁻¹ to 10⁷ Hz) and temperature range in order to determine, through the analysis of the scaling laws governing the interfacial polarization effects, the characteristic frequency ranges and the amplitude of the enhanced permittivity. An excellent agreement is found between the experimental results, the numerical simulations, and the analytical calculations. Finally, we show that bilayer polymeric materials with permittivity values as high as ε′ = 556 and with low dielectric losses (tan(δ) = 0.001) can be readily obtained by the current approach. This could have multiple applications, especially in the field of organic electronics. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47551.     

Synthesis and electrode performance of layered nickel dioxide containing alkaline ions

Several polymorphs of layered nickel dioxide were prepared by using the chemical insertion of alkaline ions into Li_0.10NiO₂. We used aqueous AOH (A = Li, Na, K) solutions as reducing agents. Sodium and potassium insertion resulted in hydrated layered compounds that can be classified as γ-NiOOH with high crystallinity, while lithium insertion occurred without hydration. We discuss the coordination environment around the A⁺ ions for these inserted compounds. The thermal behavior, analyzed using high temperature (HT) X-ray diffraction (XRD) and thermogravimetric (TG) measurements, indicated that heating the hydrate at 150 °C yielded its dehydrate. The electrode performance of the nickelate was studied in lithium cells. We discuss the effect of interlayer water on cell rechargeability and the similarity between these nickelate and hydrated manganese dioxide (birnessite).     

Pb2+ as a Substrate and a Cofactor of a Porphyrin Metalation DNAzyme

We herein report a DNAzyme named T30695 (sequence: (G₃T)₄) that can catalyze Zn²⁺ insertion into three different porphyrins in the presence of Pb²⁺ as a cofactor. Meanwhile, T30695 with Pb²⁺ alone was found to cause a shift in both the fluorescence and UV-vis spectra of protoporphyrin IX (PPIX), thus suggesting that metalation of Pb²⁺ was also achieved at room temperature. From kinetic measurements, the reaction required two Pb²⁺ ions; this is consistent with one being a cofactor and the other being a substrate. No previous reports inserted Pb²⁺ into porphyrins by using DNAzymes or protein-based enzymes. This reaction was most significantly inhibited in the presence of K⁺ followed by Na⁺ and Li⁺, suggesting the importance of the Pb²⁺-stabilized G-quadruplex. When Pb²⁺ is inserted into PPIX, its emission blue shifts from 635 to 590 nm, thus allowing simple ratiometric fluorescent sensing with a detection limit of 1.2 nM Pb²⁺.     

A study on the mixing of flour in a motionless Sulzer (Koch) mixer using a radioactive tracer

This work was concerned with the evaluation of the motionless Sulzer (Koch) mixer for radial mixing of flour. A radioactive tracer technique was employed. The tracer employed, mainly radiosotope ⁵⁶Mn, was created by neutron activation with a neutron flux of 1.44 × 10¹² n/cm² sec. The method has a high degree of accuracy and the advantage that no physical differences exist between the bulk and tracer materials. The concentration distribution in the radial direction was measured, and the resulting degrees of mixedness of the mixture after passing through the mixer for 1, 2, 3, 5 and 10 passes were determined. The degress of mixedness in the radial direction increased with the number of passes. The experimental results were compared to the same mixture passing through an empty column without mixing elements inserted. The comparison indicated that the mixing elements enhanced the mixing process in a predictable way. Finally, a mechanistic model was developed and verified by the experimental results.     

Note on Nonisothermal Flow in Field-Flow Fractionation

Abstract

Myers et al. (1) derived an expression for the velocity profile of a fluid flowing under an applied pressure gradient between parallel flat plates separated by a small distance h. The coefficient of viscosity (μ) was allowed to vary between the plates, say, as the result of a (linear) temperature gradient established by controlling the temperature on each plate to a different value. In this note an error in their hydrodynamic analysis is corrected, and sample calculations are given to demonstrate the possible quantitative effect of this error on the fluid velocity profile.     

Precise Temperature Measurement in Debye-Scherrer Specimens at Elevated Temperatures

A general method was developed for precisely measuring the temperature of a Debye-Scherrer specimen at elevated temperatures. The method consists of measuring the lattice parameters versus temperature of a primary standard which forms one leg of a calibrated thermocouple, with both specimen and thermocouple junction in the X-ray beam, and then mixing the internal standard in powdered form with the powdered Debye-Scherrer specimen so that the lattice parameters of the internal standard directly indicate temperature. Gold was used as the primary standard, platinum as the other thermocouple leg, and magnesium oxide as the Debye-Scherrer specimen. The platinum/gold thermocouple was calibrated from 0° to 1000°C by the National Bureau of Standards. The lattice parameters (in angstroms; corrected for refraction in Ni Kα radiation) versus temperature are expressed by the equations: Gold (25° to 1000°C)

Magnesium oxide (25° to 932°C)

The temperature precision attained with the gold standard was estimated to be 1.5°C.     

Probing and Manipulating the Lateral Pressure Profile in Lipid Bilayers Using Membrane-Active Peptides—A Solid-State 19F NMR Study

The lateral pressure profile constitutes an important physical property of lipid bilayers, influencing the binding, insertion, and function of membrane-active peptides, such as antimicrobial peptides. In this study, we demonstrate that the lateral pressure profile can be manipulated using the peptides residing in different regions of the bilayer. A ¹⁹F-labeled analogue of the amphiphilic peptide PGLa was used to probe the lateral pressure at different depths in the membrane. To evaluate the lateral pressure profile, we measured the orientation of this helical peptide with respect to the membrane using solid-state ¹⁹F-NMR, which is indicative of its degree of insertion into the bilayer. Using this experimental approach, we observed that the depth of insertion of the probe peptide changed in the presence of additional peptides and, furthermore, correlated with their location in the membrane. In this way, we obtained a tool to manipulate, as well as to probe, the lateral pressure profile in membranes.     

The manganese dioxide electrode Part XII: Gibbs free energy of H insertion compounds and a planar model

Experimental values for the Gibbs free energy of mixing of solid solutions produced by electrochemical H insertion into a commercial synthetic -Mn0₂ have been derived from published electrode potential measurements carried out in Leclanche electrolyte. Calculated values are based on the reasonable assumption that the solid solutions are thermodynamically ideal so that the Gibbs free energy of mixing can be estimated from the positional entropy of the inserted species. Comparison of the two sets of values provides strong evidence that the inserted H is present as two thermodynamically independent species H⁺ and e at least up to 40% fill. Additional insight is provided by a planar random insertion model. The model shows the development of microdomains of fully H inserted material at the higher levels of insertion but prior to complete insertion as is required to explain published experimental phenomena. The model also allows the calculation of the Gibbs free energy of mixing to be refined to take into account either the stabilisation of certain We pair types or restriction in the movement of the H⁺ and e species of pairs caused by adjacent pairs blocking pathways. The latter refinement gives very good agreement with the experimental data using one adjustable parameter namely a blocking efficiency of 50%.     

Swirling flow of natural gas in supersonic separators

The supersonic swirling separator is a new apparatus for offshore and subsea natural gas separation, due to its lightweight and the viability of unmanned operation. A new supersonic swirling separator was designed for the numerical calculation, in which a central body was inserted based on the principle of conservation of angular momentum. Axial and radial distribution of the main parameters of natural gas flow was investigated with RNG K-? turbulence model. The effects of the shock waves on the natural gas flow fields were analyzed in the supersonic separator. The results show that water and heavy hydrocarbons can be separated from natural gas due to the low temperature and high centrifugal field. The non-uniformity of radial distribution of the gas dynamic parameters significantly affects the gas/liquid separation. The position of the shock wave determines the distribution of the temperature, which has a great influence on the re-evaporation of liquid droplets.     

Studies on the modeling of a molten carbonate fuel cell (MCFC) 5 kW class stack

A mathematical model was developed to simulate the performance of a molten carbonate fuel cell (MCFC) 5 kW class stack. In the modeling calculations, the average current densities of each cell were adjusted to be same for all cells in the stack. In this procedure the operating voltages of each cell were decided. Temperatures of matrixes with an electrolyte increased to a maximum value at the 7 ^th cell. Because the temperatures of the 1 ^st and 9 ^th cells were lower than those of the other cells, the operating voltage of these cells was lower than those of the other cells. Compared to the measured temperature distributions, the calculated results were quite low near the gas entrance. The measured data of the temperature of the matrixes with an electrolyte and the power were estimated well with the modeling calculations. The current density distributions in all cells from the model calculations were similar.     

Mass Transfer of Diffusive Species with Nonconstant In-Flight Formation and Removal in Laminar Tube Flow. Application to Unattached Short-Lived Radon Daughters

This article deals with convective-diffusive aerosol transport with in-flight formation and removal and is applied to the unattached fraction of short-lived radon decay products. Two novel contributions to previous studies are given in this numerical and experimental work: on the one hand, we solve the mass-transport equations for all the short-lived radon daughters; on the other hand, we include the ²¹⁸Po neutralization into the mass-transport equation of the first radon decay product. Concerning the mass-transfer of all short-lived radon daughters, numerical calculations lead to the development of simple correlations for the ²¹⁴Pb and ²¹⁴Bi penetration fractions. Those correlations can be used to determine the diffusion coefficient of ²¹⁴Pb and ²¹⁴Bi using the 2-filter method. In our experiments, a diffusion coefficient equal to 5 X 10^-6 m² s^-1 is found for the ²¹⁴Pb. Concerning the ²¹⁸Po neutralization, better agreement is observed between our numerical and experimental results when ²¹⁸Po neutralization is taken into account. These results confirm the neutralization rates found by Howard and Strange (1994).