Values Of K1 Research Articles

Mass transfer kinetics of ultrasonic- and vacuum-ultrasonic-assisted static brine of chicken breast (Pectoralis major).

The aim of this study was to investigate the effect of different ultrasound treatment (UT) conditions (Control, UT-150, UT-300, UT-450, Vacuum-UT-150, Vacuum-UT-300, Vacuum-UT-450) on the brining kinetics and meat quality of chicken breast. The results showed that vacuum-ultrasonic-assisted treatment greatly accelerated the transfer of moisture and NaCl, and the highest yield was obtained by ultrasonic power of 450W. The mass transfer kinetics (k1 and k2) were significantly related to vacuum pretreatment and ultrasonic power. The values of k1 for total and moisture weight changes decreased with the increase of ultrasonic power, whereas the values of k2 increased with vacuum pretreatment. The application of ultrasound treatment with vacuum improved the NaCl effective diffusion coefficients (De) from 1.189×10-9 to 1.308-1.449×10-9 m2/s, and the highest De was found with Vacuum-UT-450. The treatment of ultrasound and vacuum can reduce shear force and enhance the water-holding capacity (WHC). According to the analysis of water distribution, vacuum and ultrasound could decrease the T23 values, indicating that the mobility of water decreased. The result of microscopic observation further supported that the disruption of myofibrils was related to the tenderness and WHC changes, which was caused by vacuum and ultrasound treatment. Thus, Vacuum-UT brining could be employed as an emerging technology for improving the efficiency of brining and meat quality of other meat. PRACTICAL APPLICATION: Vacuum-ultrasonic-assisted static brine is an effective and feasible treatment to replace tumbling treatment for maintaining the integrity of the muscle bundles and accelerating the brining rate.

Comparative analysis of a novel spectral-domain OCT biometer versus swept-source OCT or OLCR biometer in healthy pediatric ocular biometry

With the advancements in ocular biometric technology, there have been significant improvements in accurately and efficiently measuring ocular parameters. The aim of this study is to compare the reliability of biometric parameters obtained using a new frequency-domain optical coherence tomography (SD-OCT) biometer with the measurements obtained from swept-source OCT (SS-OCT) and optical low coherence reflectometry (OLCR) biometers. This study employed an observational cross-sectional design. Measurements of axial length (AL), flat and steep corneal keratometry (K1 and K2), and central corneal thickness (CCT) obtained using the The Colombo IOL were compared with those obtained with the IOLMaster 700 and SW-9000 devices. The agreement were evaluated using intraclass correlation coefficient (ICC) and Bland–Altman analyses. The differences of the measurements of the three increments were assessed by one-way ANONA. 73 right eyes of 73 healthy pediatric subjects were analyzed. The AL difference measured by Colombo IOL compared with IOLmaster700 and SW-9000 were 0.00 ± 0.02 mm and − 0.07 ± 0.05 mm, respectively (P > 0.05, ANOVA). There was no statistically significant difference in CCT, K1, and K2 among the three instruments (all P > 0.05, ANOVA). The ICC values for AL, K1, K2, and CCT were 0.999, 0.996, 0.995, and 0.998, respectively. The Bland-Altman analysis showed an agreement of AL, K1, K2, and CCT with Colombo IOL and IOLMaster 700 spanned over 0.08 mm, 0.71D, 0.69D, and 12.17 μm, respectively. The agreement of AL, K1, K2, and CCT with Colombo IOL and SW-9000 spanned approximate 0.21 mm, 0.75D, 1.06D, and 14.37 μm, respectively. The new SD-OCT biometer and the SS-OCT biometer showed strong agreement in measuring AL and CCT in healthy pediatric subjects. This supports the reliability of the new SD-OCT biometer as an alternative for assessing these parameters. However, K1 and K2 could not be used interchangeably in clinical practice. Further research is needed to explore their applicability in different clinical settings and patient populations."light" />

Calculation of oxygen distribution coefficients of RF3 (R = La, Gd) fluorides with the tysonite structure during their crystallization from a melt

Using the method of modified cryoscopy, the thermodynamic distribution coefficients of oxygen k0 in LaF3 and α-GdF3 with a tysonite structure (sp. gr. )were calculated from the fusibility diagrams of condensed systems RF3–R2O3 (R = La, Gd). The calculated coefficients k0 are 1.02 and 1.12 for lanthanum and gadolinium trifluorides, respectively. The values of the coefficients k0 satisfy the condition k0 1, which confirms the formation of maxima in the fusibility curves of tysonite solid solutions tys- RF3–2xOx. For LaF3, the proximity of the distribution coefficient to k0 = 1 corresponds to an almost uniform distribution of oxygen in the volume of the crystallized fluoride melt. Knowledge of oxygen distribution coefficients during crystallization from a melt is important for choosing a strategy for crystallophysical purification of trifluorides RF3 from oxygen impurities and obtaining oxofluorides tys-RF3–2xOx with a given impurity distribution.

Redox kinetics of multi-electron transfer reactions of polyoxometalates (POMs) relevant to electrochemical devices

The formal equilibrium potential (E0′) and heterogeneous rate constant (k0) are characteristics of any electron-transfer reaction. The estimation of these characteristics for very fast multiple electron-transfer reactions of polyoxometalates (POMs) relevant to various applications including redox flow batteries, hydrogen storage materials, and electrocatalysis is highly challenging by the conventional electrochemical methods. Therefore, E0′and k0 (k0∼10–2 cm sec‑1) of such reactions (for e.g., that of tungstosilicic acid (SiW12) and phosphotungstic acid (PW12)) separated by small potential windows are estimated from the background current free higher harmonic response of large-amplitude AC voltammetry. For SiW12/PW12 redox species, the E0′ values of processes 1, 2, and 3 estimated from the minima of second harmonic response are -0.326/-0.127, -0.530/-0.380 and -0.691/-0.701 (V vs. Ag/AgCl), respectively. The k0 values of the first redox process (P1) of SiW12 (SiW12/ SiW12-,4.8 × 10–2 cm sec‑1) and PW12 (PW12/PW12-,5.2 × 10–2 cm sec‑1) estimated from the large-amplitude AC voltammetry are further validated through the impedance measurement (2.1 × 10–2 and 2.4 × 10–2 cm sec‑1). The uniqueness of large-amplitude AC voltammetry over conventional DC techniques and impedance spectroscopy is illustrated. The relevance of k0 values in the context of electrocatalytic processes and RFBs system is also presented.

Establishing reference ranges of serum vitamin K in healthy children

Objective: To establish and validate reference intervals of serum vitamin K for healthy children in China. Methods: A cross-sectional study was conducted from January 2020 to May 2023, involving 807 healthy children aged 0 to 14 years, selected by stratified random sampling based on the population distribution of children in eastern, central, western, and northeastern China. Sample collection was carried out in 16 hospitals across 12 provinces, autonomous regions, and municipalities. Basic information of the children was collected using a standardized self-design questionnaire. Serum levels of vitamin K1 and vitamin K2 (menaquinone-4 (MK-4), menaquinone-7 (MK-7)) were measured using liquid chromatography-tandem mass spectrometry. The reference intervals was established by direct approach. The children were divided into different groups by age. Inter-group comparisons were conducted using the Kruskal-Wallis non-parametric test, and the reference intervals (P2.5-P97.5) were determined using non-parametric methods. Screening 40 healthy children for small sample validation based on age groups within the reference range(25 from eastern, 10 from central, and 5 from western regions). Results: The age of the 807 children was 5.00 (2.00, 9.81) years, and 495 (61.3%) were males and 312 (38.7%) females. Reference intervals were established for 795 children, of whom 303 children were aged 1 month to 3 years and 492 were aged 4 to 14 years. The reference intervals for serum vitamin K1 were 0.09-4.54 μg/L for children aged 1 month to 3 years, and 0.10-1.73 μg/L for 4-14 years. For MK-7, the intervals were 0.07-1.42 μg/L for 1 month to 3 years and 0.19-2.03 μg/L for 4-14 years. The reference intervals for MK-4 in children aged 1 month to 14 years were 0-0.42 μg/L. The measured values of serum vitamin K1, MK-4, and MK-7 in the validation samples did not exceed the reference limit in more than 2 samples. Conclusion: Reference intervals for vitamin K1, MK-4, and MK-7 in healthy children aged 1 month to 14 years have been established and validated, and can be used to assess vitamin K nutritional status in children.

Third order interactions shift the critical coupling in multidimensional Kuramoto models

The study of higher order interactions in the dynamics of Kuramoto oscillators has been a topic of intense research. Previous works have demonstrated that such interactions can give rise to interesting new phenomena such as multi-stability and synchronization even if the interaction between oscillators is repulsive. Here we consider higher order interactions in the multidimensional Kuramoto model where pairs (1-simplex), triplets (2-simplex) and quadruples (3-simplex) of oscillators interact simultaneously with different coupling strengths, k1, k2 and k3, respectively. For the types of asymmetric interactions considered, we show that three body terms shift the critical coupling for synchronization towards higher values, except in 2 dimensions where a cancellation occurs. However, after the transition, three and four body interactions combine to facilitate synchronization. We also show that, for fixed values of k2 and k3, and fully connected networks, the behavior of the order parameter r(k1) is described by a universal curve given by its value at k2=k3=0, shifted along the k1 axis. Similar to the 2-dimensional case with asymmetric interactions, bi-stability and hysteresis develop for large enough higher order interactions. Multi-stability, typical of symmetric higher order interactions, is not found. We show simulations in three and four dimensions to illustrate the dynamics.

Change of ectropion surgery on astigmatic vector and ocular biometry

Aim: To evaluate corneal astigmatism change and intraocular lens (IOL) power values following ectropion surgery. Materials and Methods: This comparative prospective research included patients with involutional ectropion who were divided using the snap-back test. The severity of ectropion increased progressively to reach the highest levels in Group 4. Patients underwent lateral tarsal strip procedures, and preoperative and 3-month postoperative biometry measurements were performed. Results: While the mean flattest keratometry (K1), steepest keratometry (K2), and mean keratometry (Km) values exhibited nonsignificant increases at 3 months after surgery in Groups 1 and 2 (p>0.05 for all), the mean values of K1, K2, and Km were increased with statistical significance in Groups 3 and 4 at 3 months postoperatively (p<0.05 for all). Conclusion: According to the snap-back test, ectropion in advanced stages will affect topographic values and IOL power calculations. If surgeons are going to perform cataract or refractive surgery after ectropion repair, they may consider changing the lens power selection accordingly.

Calculation of the Rate Constants of Vacuum Residue Hydrogenation Reactions in the Presence of a Chrysotile/NiTi Nanocatalyst

The paper presents the results of an investigation into the kinetics of catalytic hydrogenation of vacuum residue at temperatures of 380, 400 and 420 °C and different durations, ranging from 30 to 70 min, using a nanocatalyst containing the active metals nickel and titanium supported on chrysotile. It was found that the yield of oils from 30 to 50 wt.% and tars from 12 to 18 wt.% increased with increasing temperatures and reaction times. A slight increase in the proportion of solids in the range of 2.0 to 6.0 wt.% is explained by the activity of the nanocatalyst used. In the study of the kinetics of vacuum residue hydrogenation, using the nanocatalyst developed by the authors, we were able to achieve a low yield of solids with a short contact time as well as a high yield of low-molecular-weight compounds such as oils and tars. To determine the kinetic parameters (rate constants and activation energies), Simpson’s integral method and a random search engine optimization method were used. High values of rate constants are characteristic of reactions in the formation of oils k1, tars k2 and asphaltenes k3 in the temperature range of 380–420 °C. The high values of the rate constants k1, k2 and k3 in the catalytic hydrogenation of the vacuum residue indicate the high reaction rate and activity of the nanocatalyst used. With an increase in temperature from 380 to 420 °C, the rate constant of the formation of gas products from vacuum residue and the conversion of asphaltenes into oils significantly increase, which indicates the accumulation of low-molecular-weight compounds in oils. The activation energy for reactions leading to the formation of oils, tars, asphaltenes, gas and solid products was 75.7, 124.8, 40.7, 205.4 and 57.2 kJ/mol, respectively. These data indicate that the processes of vacuum residue hydrogenation with the formation of oils and asphaltenes require the lowest energy inputs. Reducing the process temperature to increase the selectivity of the vacuum residue hydrogenation process when using the prepared nanocatalyst is recommended. The formation of oils at the initial stage plays a key role in the technology of the heavy hydrocarbon feedstock (HHF) hydrogenation process. Perhaps the resulting oils can serve as an additional solvent for high-molecular-weight products such as asphaltenes, as evidenced by the low activation energy of the process.

Thermal decomposition of alkenes: role of allylic C-C bond cleavage

Thermal decomposition of alkenes is critical in many chemical processes. In the alkene moiety, allylic CC bonds are significantly weaker than alkylic and vinylic CC bonds. To address literature discrepancies in the rate of allylic CC bond cleavage, the current work investigates the thermal decomposition of two prototype molecules, namely 1-hexene (k1) and 4-methyl-1-pentene (k2). The formation of product allyl radicals is tracked using a highly sensitive UV laser diagnostic to determine the rate coefficients of k1 and k2 over 1178–1359 K in a shock tube. Both reactions exhibit a positive Arrhenius temperature dependence, with the decomposition of 4-methyl-1-pentene occurring 1.5–3 times faster than that of 1-hexene. Values of k1 adopted in literature models vary by an order of magnitude.By integrating our previous measurements of 1-butene and 1-pentene decomposition (Zhou et al., 2024), this work establishes a comprehensive set of rate rules that encompasses the decomposition of allylic-primary (P), allylic-secondary (S21 and S22), and allylic-tertiary (T) CC bonds. At 1200 K, the decomposition of a tertiary allylic CC bond (kT) occurs 42 times faster than that of the primary CC bond (kP). Notably, our established rate rules caution against commonly adopted analogies between the rate coefficients of the thermal decomposition of 1-butene and 1-pentene, as kS21 proceeds 3–7 times faster than kP.The implementation of these rate rules in various kinetic models of alkenes and biofuels greatly enhances the accuracy of their predictions. This work thus contributes to a deeper understanding of the mechanisms underlying soot formation during from the combustion of unsaturated fuels.

Comparison of axial length and anterior segment parameters of patients with myopia measured using 2 fourier-domain optical coherent biometry devices

BackgroundThis study assessed the agreement of ocular parameters of patients with myopia measured using Colombo intraocular lens (IOL) 2 and IOLMaster 700.MethodsEighty patients (male, 22; average age, 29.14 ± 7.36 years) with myopia (159 eyes) were included in this study in May 2023. The participants’ axial length (AXL), central corneal thickness (CCT), lens thickness (LT), white-to-white distance (WTW), front flat (K1), steep (K2), mean (Km) corneal keratometry, astigmatism (Astig), J0 vector, and J45 vector were measured using the IOLMaster 700 and Colombo IOL 2. The measurements from both devices were compared using the generalized estimating equation, correlation analysis, and Bland-Altman plots.ResultsWith the Colombo IOL 2, lower values for K2 and J0 (odds ratio [OR] = 0.587, p = 0.033; OR = 0.779, p < 0.0001, respectively), and larger values for WTW, Astig, and J45 (OR = 1.277, OR = 1.482, OR = 1.1, all p < 0.0001) were obtained. All ocular measurements by both instruments showed positive correlations, with AXL demonstrating the strongest correlation (r = 0.9996, p < 0.0001). The intraclass correlation coefficients for AXL and CCT measured by both instruments was 0.999 and 0.988 (both p < 0.0001), and Bland-Altman plot showed 95% limits of agreement (LoA) of -0.078 to 0.11 mm and − 9.989 to 13.486 μm, respectively. The maximum absolute 95% LoA for LT, WTW, K1, K2, and J0 were relatively high, achieving 0.829 mm, 0.717 mm, 0.983 D, 0.948 D, and 0.632 D, respectively.ConclusionsIn young patients with myopia, CCT and AXL measurements obtained with the Colombo IOL 2 and IOLMaster 700 were comparable. However, WTW, LT, corneal refractive power, and astigmatism values could not be used interchangeably in clinical practice.

Corneal topography findings among patients with thyroid dysfunction

Background Hormonal dysregulation impacts the metabolism of the cornea and could be linked to keratoconus. Previous research has suggested an association between keratoconus and autoimmune thyroid disorders. Aim The aim of this study was to compare the topographic corneal changes in patients with thyroid dysfunction. Patients and methods This is a cross-sectional study of 200 patients with thyroid dysfunction attending the Endocrinology Clinic at the Faculty of Medicine, Alexandria University. The corneal topography of patients was examined with TMS. Serum levels of thyroid-stimulating hormone, free thyroxine, and free triiodothyronine were measured. Results Two hundred patients with thyroid dysfunction were enrolled in the study. Of them, 129 were hypothyroid patients and 71 were hyperthyroid patients. The study included 137 females and 63 males with a mean age of 32.4 ± 8.2 years. Corneal keratometry readings, including K1, K2, and K max readings, were measured. The mean value of K1 was 45.86 ± 4.69 D, mean K2 was 47.89 ± 5.08 D and the mean corneal thickness was 475 ± 0.36 µm, no relation was found between any of these parameters and serum thyroid-stimulating hormone, free triiodothyronine, or free thyroxine levels. Conclusion In our study, more topographic changes in favor of a thin cornea and steep cornea rather than a true keratoconus were detected in patients with thyroid dysfunction, making cautious analysis of corneal topography important, especially before refractive surgery.

Alternative green application areas for olive pomace catalytic pyrolysis biochar obtained via marble sludge catalyst

Evaluating industrial wastes in the system with minimum preprocessing and generation economically valuable products from them have critical importance. In this regard, especially cheap, wieldy, and readily available catalysts have been researched to increase variety of useful products in pyrolysis systems, to reduce process time, and to increase quality and diversity of products. Therefore, in this study, marble sludge (named K1) was evaluated as catalyst at different dosages (10%, 20%, 30%, 50%) and pyrolysis temperatures (300, 500, 700 °C) in olive pomace (OP) pyrolysis and; the potential green applications of produced new biochars at new usage areas with different purposes based on characteristics were investigated. ANOVA test results showed that temperature and catalysts ratio had significant effect on pyrolysis product yields since significance value for K1 and temperature was lower than 0.05 for pyrolysis products. OP-K1 biochars had alkaline properties and high earth metal quantities. Moreover, increment in K1 ratio and temperature resulted in decrement of the biochar surface acidity. Therefore, it can be indicated that these biochars can have a potential usage for anaerobic digestion processes, lithium-ion batteries, and direct carbon solid oxide fuel cell (DC-SOFC) but further electrochemical property test should be performed. Moreover, produced biochars can be alternative fuels in some processes instead of coal since they have low S content and high heat values. Consequently, it is foreseen that produced biochars will have an important place in the development of potential usage areas with a new and environmentally friendly approach in different areas apart from the conventional uses of catalytic pyrolysis chars.Graphical abstract

On characteristics of K0 value and shear behaviour of loess using triaxial test

Compared with conventional soils, such as sand and clay, little knowledge on the coefficient of lateral earth pressure at-rest (K0) has been established for loess in the current literature. This paper presents an experimental investigation on K0 of compacted loess and the associated impacts on undrained shear behaviour. By adopting a K0 consolidation module in the triaxial system, the K0 stress state for loess samples was achieved through a unique feedback control. During the K0 consolidation, the deviatoric stress (q) increases progressively with the premise that the volumetric strain (εv) of the sample equals to the axial strain (εa). The results show that the K0 value of compacted loess is in a range of 0.28 to 0.53, which is dependent on the packing density and the clay content. A distinguishable decrease of K0 was found in the course of K0 consolidation for the loosely compacted loess sample, whereas a similar trend was not observed in the dense sample. In the undrained shear stage, all loess specimens revealed contractive response in the stress path (q-p’) diagram, which can be quantified by a modified collapsibility index (Ic). The index is consistently higher for the K0 consolidated loess samples than for the isotropic ones. The experimental results indicate a strong impact of the initial stress state on the shear behaviour of compacted loess.

Raman spectra soft modeling of the biodiesel oxidation through evolving factor analysis & multivariate curve resolution

The oxidative stability of biodiesel is defined by its relative resistance to the action of oxygen at room temperature. Its determination is an essential reference to the quality of biofuel and a significant parameter to be determined. This parameter concerns the quality of the biodiesel to be supplied to the consumer, and its determination is fundamental to maintaining the engine's proper functioning. Raman spectroscopy allows the rapid obtaining of structural information regarding biodiesel quality and, when aided by multivariate analysis methods, allows a quantitative determination of specific properties. This work uses Raman spectroscopy, Multivariate Curve Resolution with Alternative Least Squares (MCR-ALS) method, and Evolving Factor Analysis (EFA) to study biodiesel's oxidation kinetics. Also, the vibrational modes C = C, CH2, and CH3 were identified as the main structural groups involved in this process, corroborating previous studies. The MCR-ALS & EFA combination allowed modeling of the degradation kinetics following an A → B → C mechanism, where A corresponds to the biodiesel (starting material), B is related to the hydroperoxide mixture, and C is the final product. The results also suggested that this process follows a first-order reaction, with kinetic constant values of k1 = 0.0056 min−1 and k2 = 0.0031 min−1.

Suppressed atmospheric chemical aging of cooking organic aerosol particles in wintertime conditions

Abstract. Cooking organic aerosol (COA) is one of the major constituents of particulate matter in urban areas. COA is oxidized by atmospheric oxidants such as ozone, changing its physical, chemical and toxicological properties. However, atmospheric chemical lifetimes of COA and its tracers such as oleic acid are typically longer than those that have been estimated by laboratory studies. We tackled the issue by considering temperature. Namely, we hypothesize that increased viscosity of COA at ambient temperature accounts for its prolonged atmospheric chemical lifetimes in wintertime. Laboratory-generated COA particles from cooking oil were exposed to ozone in an aerosol flow tube reactor for the temperature range of −20 to 35 °C. The pseudo-second-order chemical reaction rate constants (k2) were estimated from the experimental data by assuming a constant ozone concentration in the flow tube. The estimated values of k2 decreased by orders of magnitude for lower temperatures. The temperature dependence in k2 was fit well by considering the diffusion-limited chemical reaction mechanism. The result suggested that increased viscosity was likely the key factor to account for the decrease in chemical reactivity at the reduced temperature range, though the idea will still need to be verified by temperature-dependent viscosity data in the future. In combination with the observed global surface temperature, the atmospheric chemical lifetimes of COA were estimated to be much longer in wintertime (&gt; 1 h) than in summertime (a few minutes) for temperate and boreal regions. Our present study demonstrates that the oxidation lifetimes of COA particles will need to be parameterized as a function of temperature in the future for estimating environmental impacts and fates of this category of particulate matter.

Enhancing CO2 Capture via Metal-Ligand Cooperativity: Tuning Ligand Basicity and Zn(II) Lewis Acidity.

A series of thiosemicarbazonato-hydrazinatopyridine zinc(II) complexes were evaluated as direct air CO2 capture agents. The complexes sequester CO2 in a methanol solution as a metal-coordinated methylcarbonate. The reaction is reversible upon sparging of solutions with an inert gas (N2 or Ar). The capture process involves metal-ligand cooperativity with the noncoordinating nitrogen of the hydrazinatopyridine functional group serving as a Brønsted-Lowry base and the zinc acting as a Lewis acid. In this study, the pendent amine of the thiosemicarbazonato group was varied to include 4-phenyl (ZnL5), 4-(trifluoromethyl)phenyl (ZnL6), 4-cyanophenyl (ZnL7), 4-tolyl (ZnL8), and 4-naphthyl (ZnL9). Hyperconjugation between the pendent group and the ligand core resulted in modulation of the metal ion acidity, as quantified by ligand exchange equilibrium constants (K3 = 193-511) and ligand basicity (pKa,MeOH = 11.09-11.94). Variations in electronic structure that decreased ligand basicity were more than offset by increases in Lewis acidity. The equilibrium constant (K1) for CO2 capture varied from 46300 to 73700. Overall, the value of K1 was directly related to the relative Lewis acidity of the complexes (K3). Notably, there was an overall inverse relationship between K1 and the ligand basicity. The results provide insights into ligand design to further improve CO2 capture.

Entropy optimization of lid-driven micropolar hybrid nanofluid flow in a partially porous hexagonal-shaped cavity with relevance to energy efficient storage processes

Hydromagnetically associated heat convection can greatly enhance the performance of high-efficiency thermal appliances and renewable energy sources through an optimized design. This investigation examines the production of thermodynamic irreversibility and heat convection for a double lid-driven flow within a partially porous stratified hexagonal enclosure. The top and bottom-wall are moving in the opposite direction with an equal velocity U0. The top-wall and the bottom-wall are kept at temperature Tc and Th (Th >\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$>$$\\end{document} Tc) while the slanted walls are assumed to be thermally insulated. A constant magnetic field is employed in the horizontal x-direction. The hexagonal cavity was filled with a micropolar hybrid nanofluid Ag-MgO/water. The system of dimensionless equations was solved by the finite difference method (FDM) associated with successive over-relaxation (SOR), successive under-relaxation (SUR), and Gauss–Seidel iteration tactics and required results are computed with problem specific program in MATLAB code. The results indicate that the Ra and the thickness of the porous layer (Xp) significantly influences heat convection and thermal irreversibility processes. The Nuavg and STotal rises 6.299% and 3.373% as ‘ϕhnf\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\upphi }_{{\ ext{hnf}}}$$\\end{document}’ enhances from 0 to 4%, respectively. Furthermore, as the values of Ra, Ha, K0, and ϕhnf\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\upphi }_{{\ ext{hnf}}}$$\\end{document} increase, Beavg experiences a decline of 53.73%, 11.04%, 38.36%, and 0.09% respectively. Also, movement of wall has a significant impact on heat transfer rates and entropy production. The present study may be extended in numerous areas to mimic the problems like—(1) onset of thermo-mechanical process for solid–fluid interaction in a conduit. (2) Thermos-chemical process with extraction of ions in two-phase fluid for double layer plating on a continuously moving sheet, as region of porous stratum saturated with a class of fluid and region without porous medium occupied with other fluid.

An improved design for virtual synchronous generator control loop based on synergy theory

Virtual synchronous generator (VSG) technology has achieved some results in distributed generation networks and enhanced system stability. For problems that may occur in the system due to ignoring parameter linkages, this paper designs a synergistic controller that establishes the connection between the active frequency and the reactive voltage control loop based on synergy theory. As the output of the synergetic controller, the derived control law u is added to the power frequency control in the form of negative feedback. Two disturbance forms, a step disturbance, and a three-phase short-circuit fault, are set up. The conventional droop control and synergetic droop control results are compared using a MATLAB simulation system. Then, the system parameter variations were studied and analyzed, and the sensitivity of the control system with different values of parameters K1, K2, and K3 in the case of a three-phase short circuit was analyzed, which provides a reference guide for selecting parameters in later control optimization. Finally, the control effectiveness of a multi-machine VSG system was tested. The simulation results show that the proposed method has a pronounced effect on making the system stabilize quickly, which illustrates the effectiveness of this technique.

Self-characterization of irradiation facility using synthetic multi-element standard for determination of k0-factors of seven radionuclides of interest

In this study, the k0 factors of 7 short and medium-lived radionuclides (i.e. 66Cu, 52V, 38Cl, 134mCs, 128I, 140La and 56Mn) were experimentally determined at the Dalat nuclear research reactor (DNRR). The synthetic multi-element standard (SMELS) samples were irradiated at Channel 7-1 installed at the DNRR. SMELS Type III contains Au and Zr, thus also allowing the self-characterization of the irradiation facility (i.e. the direct determination of f and a with only this material). The k0 factors of 7 short and medium-lived radionuclides obtained in this work are a good agreement with the reference k0 factors. The ratio values between the experimental and reference k0 values were 66Cu of 1.004, 52V of 1.004, 38Cl of 0.961 and 0.976 (1642.7 keV and 2167.4keV, respectively), 134mCs of 0.831, 128I of 1.022, 140La of 0.936, 0.955 and 0.955 (328.8 keV, 487.0 keV and 1596.2keV, respectively), 56Mn of 0.985 and 0.973 (846.8 keV and 1810.7keV, respectively). The radionuclides range of uncertainty values were lower than 7%. The present result indicates that the k0 factors can be determined by using synthetic multi-element standards (SMELS).

Comparison of Different Electrochemical Methodologies for Electrode Reactions: A Case Study of Paracetamol

Understanding electrochemical reactions at the surface of electrodes requires the accurate calculation of key parameters—the transfer coefficient (α), diffusion coefficient (D0), and heterogeneous electron transfer rate constant (k0). The choice of method to calculate these parameters requires careful consideration based on the nature of the electrochemical reaction. In this study, we conducted the cyclic voltammetry of paracetamol to calculate the values of these parameters using different methods and present a comparative analysis. Our results demonstrate that the Ep − Ep/2 equation for α and the modified Randles–Ševčík equation for D0 is particularly effective for the calculations of these two parameters. The Kochi and Gileadi methods are reliable alternatives for the calculation of k0. Nicholson and Shain’s method using the equation k0 = Ψ(πnD0Fν/RT)1/2 gives the overestimated values of k0. However, the value of k0 calculated using the plot of ν−1/2 versus Ψ (from the Nicholson and Shain equation, where ν is scan rate) agrees well with the values calculated from the Kochi and Gilaedi methods. This study not only identifies optimal methodologies for quasi-reversible reactions but also contributes to a deeper understanding of electrochemical reactions involving complex electron transfer and coupled chemical reactions, which can be broadly applicable in various electrochemical studies.