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Inference of horizontal velocity fields from the induction equation in the solar atmosphere. I. Analytical and numerical solutions in 2D
No full textSpectroscopic and spectropolarimetric observations, which rely on the Doppler effect, only provide access to the line-of-sight component of the solar plasma velocity (i.e., v_z). However, many dynamic processes in the solar atmosphere involve strong horizontal motions (i.e., in the plane perpendicular to the line of sight: v_x, v_y). Existing methods for estimating horizontal velocities are generally insensitive to variations in height (i.e., the z-coordinate), providing them only on a single plane perpendicular to the line of sight: v_x(x,y), v_y(x,y).
Motivated by the fact that modern analysis techniques (i.e., Stokes inversion) allow us to retrieve the height dependence of v_z and , our goal is to infer also this height dependence for the horizontal velocity field in the solar atmosphere. As a first step, we present, develop, and test a method for the two-dimensional case on the plane so as to show that the z dependence can be successfully retrieved.
The components of the two-dimensional magnetic induction equation are discretized via finite differences, leading to an overdetermined system whose solution provides v_y(y,z). The method assumes that , as well as v_z are known. This is currently possible through modern Stokes inversion techniques applied to spatially and temporally resolved spectropolarimetric observations. its time variation dot B
Using analytically prescribed values and two-dimensional magnetohydrodynamic simulations of the solar surface, we demonstrate that, in these idealized cases, the horizontal velocity component in a two-dimensional domain, v_y(y,z), can be successfully recovered with a mean error of about 1 %. We observe that in the regions where either the modulus of the velocity or its horizontal components are close to zero, its retrieval worsens in comparison to the rest of the domain.
The proposed method successfully retrieves the horizontal velocity field in the plane, thereby establishing the foundation for future extensions to three-dimensional reconstructions of the horizontal velocity field
Phytochemical profile, antioxidant, and antimicrobial activities of
No full textTinospora crispa L. (brotowali) is a traditional medicinal plant used in Southeast Asia to treat fever, diabetes, and infections. This study evaluated the phytochemical composition, antioxidant potential, and antimicrobial activity of its stem fractions. Dried stems of simplicia were extracted with 70% ethanol and fractionated into n-hexane, chloroform, ethyl acetate, and aqueous fractions. Phytochemical screening, total flavonoid, phenolic, and tannin content determination, DPPH radical scavenging assay, antibacterial testing, and Liquid Chromatography–Mass Spectrometry (LC–MS) profiling were performed. The ethyl acetate fraction exhibited the strongest antioxidant activity (IC₅₀ = 24.47 µg/mL), correlating with its highest flavonoid (89.76 mg QE/g), phenolic (41.14 mg GAE/g), and tannin (114.17 mg TAE/g) levels. LC–MS analysis tentatively identified 28 compounds, with siomenine as the major alkaloid. Antibacterial evaluation revealed moderate inhibition zones (4–11 mm) against Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans. However, all tested microorganisms were classified as resistant according to Clinical and Laboratory Standards Institute (CLSI) criteria. Overall, this study demonstrates that polarity-guided fractionation effectively enriches antioxidant constituents in T. crispa L. stems. Further optimization, including MIC/MBC determination and advanced structural confirmation, is required to enhance antibacterial efficacy and substantiate its potential for pharmaceutical or functional applications
Development Of Interactive Website-Based Learning Media Using The PjBL-STEM Laboy-Rush Approach On Thermochemistry Material
No full textThe STEM approach has gained prominence in addressing the demands of 21st-century education, particularly in the complex field of thermochemistry, which poses significant challenges for student understanding due to its abstract nature. Traditional inquiry-based methods, relying on PowerPoint presentations, worksheets, and textbooks, often fail to engage students and promote independent learning. This study introduces ThermoSTEM, an innovative website-based learning platform developed through the Project-Based Learning STEM Laboy-Rush (PjBL-STEM Laboy-Rush) model and the ADDIE instructional framework. The development process included comprehensive stages of analysis, design, and development, followed by rigorous construct and empirical validation. Construct validation by a university lecturer and a high school teacher yielded exceptional validity scores—97.5% for the learning matrix, 91.25% for content validation, 94.38% for the module, 91.25% for instructional materials, 97% for the storyboard, and 96% for the website. Empirical validation involving 30 eleventh-grade students from a senior high school in Malang produced a high readability score of 90.18%, indicating ease of comprehension. These findings confirm that ThermoSTEM is pedagogically sound, user-friendly, and effective for enhancing thermochemistry instruction, ultimately fostering increased engagement, critical thinking, and independent learning among students. In alignment with current educational trends, this innovative platform provides a scalable solution that meets the evolving needs of modern STEM education
Numerical simulation of CO oxidation using a Pt/Al
No full textCarbon monoxide (CO) oxidation is a key reaction for controlling vehicle emissions and serves as a model for studying catalytic behavior. Fixed-bed reactor simulations are highly sensitive to kinetic parameters, where modulation of flow rate and feed concentration can influence conversion. However, comparative unsteady-state simulations of these modulations are still limited. This study numerically simulates high-temperature CO oxidation over a Pt/Al2O3 catalyst using FlexPDE 8.0 Lite under steady and unsteady conditions in a one-dimensional pseudo-homogeneous fixed-bed model. The effects of inlet CO concentration (0.020–0.125 mol/m3), gas velocity (0.48–0.90 m/s), and switch time (10– 30 s) were investigated at 900 K to eliminate light-off effects. As predicted by the Langmuir–Hinshelwood mechanism, steady-state conversion dropped sharply with increasing CO concentration, falling below 10% above 0.05 mol/m3. Unsteady-state operation enhanced conversion, with single-parameter modulation outperforming simultaneous modulation. Concentration modulation at a 15 s switch time achieved up to 35.24% conversion—twice that of steady state—while flow rate modulation at 10 s also doubled conversion (7.24% to 15.70%). Longer switch times reduced improvement. In simultaneous modulation, the best result occurred with a positive phase shift in CO concentration and a negative phase shift in velocity. These findings support future development of unsteady-state catalytic reactor models
Synthesis and characterization of HAp/MgPO
No full textThis study aimed to synthesis and characterization material HAp/MgPO4 as an adsorbent for wastewater analysis using the precipitation method on green mussel shell waste (biogenic Ca source) and characterized by XRD, FTIR, SEM-EDX, UV-Vis and AAS. Calcination at 800-1000 °C yielded a pure HAp phase (COD 9011091) with increasing crystallinity at higher temperature (95.86 %). FTIR confirmed HAp characteristic bands (PO 3-, OH⁻) and some carbonate inclusion, indicating successful HAp formation. SEM-EDX revealed porous aggregates (4-100 nm) with a dominant Ca, P, Mg, O composition. XRF of raw shells showed Ca 96.3 %, rising to 98.6 % CaO after calcination. AAS measurements of filtrate showed Ca2+ release of 56.7, 154.1, and 50.1 ppm for samples calcined at 800, 900, and 1000 °C (highest at 900 °C). The results of UV-Vis measurements showed that the absorbance (A) and concentration (ppm) values changed with increasing temperature. At 800°C, the highest absorbance value was 1.28 with a concentration of 0.332 ppm, while at 900°C the absorbance value decreased to 1.11 with a concentration of 0.287 ppm. At 1000 °C, the absorbance value increased slightly to 1.12 with a concentration of 0.290 ppm. These structural features suggest effective adsorption of Fe2+/Ni2+. Green mussel-derived HAp/MgPO4 thus offers an eco-friendly, high-purity adsorbent
A hybrid PSO-LSTM-based electricity prediction and optimization technique for home appliances
No full textWith population growth and technological advancements, electricity demand in residential buildings has increased sharply. Accurate energy consumption forecasting allows building owners and operators to understand and predict the energy usage patterns of their buildings. However, the prevailing forecasting techniques have certain limitations that must be addressed for improved energy optimization. This paper proposes a three-stage energy optimization technique for individual home appliances. The first stage performs season-wise cluster analysis using a hierarchical clustering algorithm. Secondly, an electricity prediction approach has been designed and implemented using an adaptive long short-term memory (LSTM) model. The third stage deploys particle swarm optimization (PSO) to determine optimal hyperparameters. The proposed hybrid technique has been rigorously evaluated using a benchmark energy consumption dataset of individual home appliances. The comparative analysis with pevious state-of-the-art prediction models reveals the superiority of the proposed work. This technique can significantly contribute to achieving sustainable and optimal energy management in residential buildings