scholarly journals Electrocatalysis Beyond 2020 – How to Tune Preexponential Frequency Factor?

2021 ◽  
Author(s):  
Praveen Narangoda ◽  
Ioannis Spanos ◽  
Justus Masa ◽  
Robert Schlögl ◽  
Aleksandar Zeradjanin
Keyword(s):  
Frequency Factor

Some Statistical Properties of Short-Duration Rainfall

1984 ◽  
Vol 16 (8-9) ◽  
pp. 93-100
Author(s):  
D M Hershfield
Keyword(s):  
Short Duration ◽  
Time Distribution ◽  
Distribution Curve ◽  
Frequency Factor ◽  
Design Criteria ◽  
Annual Maximum ◽  
Maximum Rainfall ◽  
Small Areas ◽  
Drainage Design ◽  
Time Distribution Curve

Storm data and climatological quantities from both dense raingage networks and individual stations are used to elucidate some of the important problems in developing drainage design criteria for small areas. Examples are presented displaying the variability of rainfall rates for very short durations of time over very small areas. An “average” time distribution curve is presented along with relationships between rainfall amounts for durations from 2- to 60-min. One example outlines a procedure for estimating and comparing six quantities from series of annual maximum rainfalls for several short durations. The quantities include a frequency factor, 100-yr value, the probable maximum rainfall, and the observed world maximum rainfalls.

Electroreduction of Cr(VI) from solutions of bifunctional alcohols

1989 ◽  
Vol 54 (10) ◽  
pp. 2638-2643
Author(s):  
David I. Balanchivadze ◽  
Tamara R. Chelidze ◽  
Jondo J. Japaridze
Keyword(s):  
Activation Energy ◽  
Ethylene Glycol ◽  
Electrode Surface ◽  
Frequency Factor ◽  
Limiting Current ◽  
Factor Log ◽  
Standard Rate ◽  
Standard Rate Constant ◽  
Chromate Ion ◽  
Activation Energy Of Diffusion

The effect of bifunctional alcohols ethylene glycol (EG) and 1,2-propylene glycol (1,2 PG) on the kinetic parameters for the irreversible chromate ion reduction were investigated by polarographic and coulometric methods of analysis. The electroreduction of chromate ion in neutral bifunctional alcohol solutions proceeds according to the scheme: Cr(VI)–Cr(III)–Cr(II) and the values of the standard rate constant k*0 decrease in the order H2O > EG > 1,2 PG. The values of real activation energy, Q, activation energy of diffusion, QD, and frequency factor log A° have been calculated. The obtained values of QD as well as Q proved the diffusion nature of limiting current. The values of the frequency factor log A° decrease in the order H2O > EG > 1,2 PG, which points to a less favourable orientation of the electroactive ions at the electrode surface in glycols.

The Urbach Rule for the Sodium- and Potassium-Halides

1974 ◽  
Vol 29 (1) ◽  
pp. 145-157 ◽  
Author(s):  
Tetsuhiko Tomiki ◽  
Takeo Miyata ◽  
Hirokazu Tsukamoto
Keyword(s):  
Temperature Dependence ◽  
Acoustic Phonon ◽  
Frequency Factor ◽  
Host Lattice ◽  
Exciton Peak ◽  
Urbach Rule ◽  
Temperature Dependences ◽  
Hole Band ◽  
Sodium And Potassium ◽  
Potassium Halides

Phenomenological and physical aspects of the intrinsic tail spectra of the alkalihalides are studied referring to the new results on the intrinsic tail spectra of KBr and KI and to the temperature dependences of the lowest-energy Γ-exciton peak of the sodium- and potassium-halides. Systematically analysing the temperature dependence of the steepness parameter σs (T) of the Urbach rule for these halides, it is found that the frequency factor has the value nearly equal to the acoustic phonon energy at X or L of each host lattice and the steepness constant σs0 becomes larger in passing from fluoride to iodide. This halogen dependence of σs0 is discussed in terms of the hole band-mass of the Γ8-level.

Kinetic studies on esterification of acetic acid with isopropyl alcohol in presence of novel solid catalyst

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Mallaiah Mekala
Keyword(s):  
Acetic Acid ◽  
Kinetic Model ◽  
Isopropyl Alcohol ◽  
Frequency Factor ◽  
Activation Energies ◽  
Catalyst Loading ◽  
Solid Catalyst ◽  
Heat Of Reaction ◽  
Resin Catalyst ◽  
Isopropyl Acetate

AbstractThe reaction of isopropyl alcohol with acetic acid was carried out in an isothermal batch reactor in presence of solid resin catalyst to produce isopropyl acetate and water. A novel solid resin catalyst Indion 140 was used in the present study. The temperature of reaction mixture was maintained in the range of 333.15 – 363.15 K. The effects of reaction temperature, catalyst loading, mole ratio, size of catalyst, agitation speed were investigated on acetic acid conversion. Further, pseudo-homogeneous kinetic model was developed for the catalyzed reaction. The forward reaction rate constants and activation energies were determined from the Arrhenius plot. The forward and backward activation energies are found to 53,459 J/mol and 54,748 J/mol, respectively. The heat of reaction is −1.289 kJ/mol with Indion 140 catalyst. The mathematical equation was developed for frequency factor as function of the catalyst loading and found that it follows a linear relationship between frequency factor and catalyst loading. The simulations were performed for pseudo homogeneous kinetic model and found that the model is able to predict the experimental data very well. The developed kinetic equation is useful for the simulation of a reactive distillation column for the synthesis of isopropyl acetate.

Dynamic Behavior of an Orthotropic Material Containing a Central Crack

1989 ◽  
Vol 111 (2) ◽  
pp. 172-176 ◽  
Author(s):  
Y. M. Tsai
Keyword(s):  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Orthotropic Material ◽  
Crack Surface ◽  
Frequency Factor ◽  
Wave Frequency ◽  
Intensity Factors ◽  
Central Crack ◽  
Material Constants ◽  
Principal Axes

The dynamic response of a central crack in an orthotropic material is investigated. The crack is situated along one of the principal axes of the material. The load is harmonic in time and normally applied to the crack surface. The Fourier transform is used to solve the dynamic fracture problem, and the results are simplified through a complete contour integration. The dynamic stress intensity factor is obtained in an exact expression in terms of the frequency factor and the material constants. The frequency factor is defined as the product of the wave frequency and the half-crack length, divided by the shear wave speed. Glass/epoxy and graphite/epoxy composite materials are used as example materials in calculating the numerical values of the stress intensity factors. The maximum values of the stress intensity factors are shown to be dependent on the value of the nondimensional frequency factor and the material anisotropy. The motion of the crack surface is also investigated. The crack surface distortion from the associated static crack shape also depends on the wave frequency and the orthotropic material constants.

scholarly journals Thin film bi-epitaxy and transition characteristics of TiO2/TiN buffered VO2 on Si(100) substrates

MRS Advances ◽  
2016 ◽  
Vol 1 (37) ◽  
pp. 2635-2640 ◽  
Author(s):  
Adele Moatti ◽  
Reza Bayati ◽  
Srinivasa Rao Singamaneni ◽  
Jagdish Narayan
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Magnetic Properties ◽  
Frequency Factor ◽  
Misfit Strain ◽  
Buffer Layers ◽  
Intrinsic Defects ◽  
Domain Matching Epitaxy ◽  
Out Of Plane

ABSTRACTBi-epitaxial VO2 thin films with [011] out-of-plane orientation were integrated with Si(100) substrates through TiO2/TiN buffer layers. At the first step, TiN is grown epitaxially on Si(100), where a cube-on-cube epitaxy is achieved. Then, TiN was oxidized in-situ ending up having epitaxial r-TiO2. Finally, VO2 was deposited on top of TiO2. The alignment across the interfaces was stablished as VO2(011)║TiO2(110)║TiN(100)║Si(100) and VO2(110) /VO2(010)║TiO2(011)║TiN(112)║Si(112). The inter-planar spacing of VO2(010) and TiO2(011) equal to 2.26 and 2.50 Å, respectively. This results in a 9.78% tensile misfit strain in VO2(010) lattice which relaxes through 9/10 alteration domains with a frequency factor of 0.5, according to the domain matching epitaxy paradigm. Also, the inter-planar spacing of VO2(011) and TiO2(011) equals to 3.19 and 2.50 Å, respectively. This results in a 27.6% compressive misfit strain in VO2(011) lattice which relaxes through 3/4 alteration domains with a frequency factor of 0.57. We studied semiconductor to metal transition characteristics of VO2/TiO2/TiN/Si heterostructures and established a correlation between intrinsic defects and magnetic properties.

Harmonic Resonance Frequency Factor of Spur Gear System and Oscillation Reduction Approaches

2007 ◽  
Author(s):  
Jianping Wang ◽  
Pengfei Li ◽  
Ziying Wu ◽  
Minghong Zhang
Keyword(s):  
Parametric Excitation ◽  
Linear Time ◽  
Primary Resonance ◽  
Frequency Factor ◽  
Multiple Scale ◽  
Transmission Error ◽  
Spur Gear ◽  
High Order ◽  
Time Varying ◽  
Harmonic Resonance

In this study, a non-linear time-varying dynamic model of a spur gear pair system is used to investigate the dynamic behavior of the system by means of multiple scale approach. Both time-varying stiffness, transmission error and tooth backlash clearance of the system are taken into account in the model. The mesh stiffness fluctuation is developed as high order Fourier series and tooth backlash clearance is fitted by high order polynomial function. The frequency factors of the system are investigated and the frequency-response equations at the case of internal and external excitation, parametric excitation and combined excitation are obtained. The peak value of the amplitude of the primary resonance, super and sub harmonic resonance and combination harmonic under internal, external and parametric excitation are researched. The approaches of vibration reduction are investigated. Finally an example is investigated using the presented process and the results indicate the sensitivity and correctness of the presented analysis approaches.

Meyer-Neldel Rule on thermal stability parameters (trap depth and frequency factor) of luminescence signals in quartz

2021 ◽  
Author(s):  
Zuzanna Kabacińska ◽  
Alida Timar-Gabor ◽  
Benny Guralnik
Keyword(s):  
Activation Energy ◽  
Thermal Stability ◽  
Hydrogen Diffusion ◽  
Dose Range ◽  
Accurate Determination ◽  
Frequency Factor ◽  
Proton Conduction ◽  
High Dose ◽  
Compensation Law ◽  
Thermal Stability Of

<p>Thermally activated processes can be described mathematically by the Arrhenius equation. The Meyer-Neldel Rule (MNR), or compensation law, linearly relates the pre-exponent term to the logarithm of the excitation enthalpy for processes that are thermally driven in an Arrhenian manner. This empirical rule was observed in many areas of materials science, in physics, chemistry, and biology. In geosciences it was found to uphold in hydrogen diffusion (Jones 2014a) and proton conduction (Jones 2014b) in minerals.</p><p>Trapped charge dating methods that use electron spin resonance (ESR) or optically or thermally stimulated luminescence (OSL and TL) are based on the dose-dependent accumulation of defects in minerals such as quartz and feldspar. The thermal stability of these defects in the age range investigated is a major prerequisite for accurate dating, while the accurate determination of the values of the trap depths and frequency factors play a major role in thermochronometry applications. </p><p>The correlation of kinetic parameters for diffusion has been very recently established for irradiated oxides (Kotomin et al. 2018). A correlation between the activation energy and the frequency factor that satisfied the Meyer–Neldel rule was reported when the thermal stability of [AlO<sub>4</sub>/h<sup>+</sup>]<sup>0</sup> and [TiO<sub>4</sub>/M<sup>+</sup>]<sup>0</sup> ESR signals in quartz was studied as function of dose (Benzid and Timar-Gabor 2020). Here we compiled the optically stimulated luminescence (OSL) data published so far in this regard, and investigated experimentally the thermal stability of OSL signals for doses ranging from 10 to 10000 Gy in sedimentary quartz samples. We report a linear relationship between the natural logarithm of the preexponent term (the frequency factor) and the activation energy E, corresponding to a Meyer-Neldel energy of 45 meV, and a deviation from first order kinetics in the high dose range accompanied by an apparent decrease in thermal stability. The implications of these observations and the atomic and physical mechanisms are currently studied.</p><p> </p><p><strong>References</strong></p><p>Benzid, K., Timar Gabor, A. 2020. The compensation effect (Meyer–Neldel rule) on [AlO<sub>4</sub>/h<sup>+</sup>]<sup>0</sup> and [TiO<sub>4</sub>/M<sup>+</sup>]<sup>0</sup> paramagnetic centers in irradiated sedimentary quartz. <em>AIP Advance</em>s 10, 075114.</p><p>Kotomin, E., Kuzovkov, V., Popov, A. I., Maier, J., and Vila, R. 2018. Anomalous kinetics of diffusion-controlled defect annealing in irradiated ionic solids. <em>J. Phys. Chem. A</em> 122(1), 28–32</p><p>Jones, A. G. (2014a), Compensation of the Meyer-Neldel Compensation Law for H diffusion in minerals, <em>Geochem. Geophys. Geosyst.</em>, 15, 2616–2631</p><p>Jones, A. G. (2014b), Reconciling different equations for proton conduction using the Meyer-Neldel compensation rule, <em>Geochem. Geophys. Geosyst</em>., 15, 337–349</p>

The C—Br bond dissociation energy in halogenated bromomethanes

1951 ◽  
Vol 209 (1096) ◽  
pp. 110-131 ◽  
Keyword(s):  
Bond Dissociation Energy ◽  
Dissociation Energy ◽  
Methyl Bromide ◽  
Frequency Factor ◽  
Unimolecular Dissociation ◽  
Bond Dissociation Energies ◽  
Kcal Mole ◽  
Fast Reaction ◽  
Bond Dissociation ◽  
Dissociation Energies

The pyrolyses of methyl bromide and of the halogenated bromomethanes, CH 2 CI. Br, CH 2 Br 2 , CHCl 2 .Br, CHBr 3 , CF 3 Br, CCI 3 . Br and CBr 4 , have been investigated by the ‘toluene-carrier' technique. It has been shown that all these decompositions were initiated by the unimolecular process R Br → R + Br. (1) Since all these decompositions were carried out in the presence of an excess of toluene, the bromine atoms produced in process (1) were readily removed by the fast reaction C 6 H 5 .CH 3 + Br → C 6 H 5 . CH 2 • + HBr. Hence, the rate of the unimolecular process (1) has been measured by the rate of formation of HBr. The C—Br bond dissociation energies were assumed to be equal to the activation energies of the relevant unimolecular dissociation processes. These were calculated by using the expression k ═ 2 x 10 13 exp (- D/RT ). The reason for choosing this particular value of 2 x 10 13 sec. -1 for the frequency factor of these reactions is discussed. The values obtained for the C—Br bond dissociation energies in the investigated bromomethanes are: D (C—Br) D (C—Br) compound (kcal./mole) compound (kcal./mole) CH 3 Br (67.5) CHBr 3 55.5 CH 2 CIBr 61.0 CF 3 Br 64.5 CH 2 Br 2 62.5 CCI 3 Br 49.0 CHCl 2 Br 53.5 CBr 4 49.0 The possible factors responsible for the variation of the C—Br bond dissociation energy in these compounds have been pointed out.

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