Temporal Variation and Comparison of Particulate Matter Levels Before, During, and After the COVID-19 Pandemic in Dhaka City, Bangladesh: Analysis of Historic Data and Current Trend

This study analyzes the temporal and seasonal variations in particulate matter (PM2.5 and PM10) levels in Dhaka, Bangladesh, with a focus on the periods before, during, and after the COVID-19 pandemic. Secondary data (2017-2023) from two Continuous Air Monitoring Stations (CAMS) located at Farmgate and Darussalam were analyzed alongside recent primary data (November 2024-January 2025) obtained through a portable air quality monitoring device. Findings demonstrated persistently high PM concentrations, especially during winter, regularly exceeding Bangladesh’s National Ambient Air Quality Standards. The initial phase of the COVID-19 lockdown led to a temporary reduction in PM2.5 (by 38.5%) and PM10 (by 21.9%), but levels rebounded post-lockdown, with recent data indicating even higher pollution levels. Seasonal analysis revealed winter peaks and monsoon-related declines. Strong correlations exist between PM2.5 and PM10, and the higher PM2.5/PM10 ratio demonstrated a predominance of pollution from finer particles. Comparative analyses with other global megacities highlighted a similar trend in particulate pollution during the COVID-19 lockdown. The study recommends urgent policy interventions, including emission controls and sustainable urban development, to improve air quality and protect public health in Dhaka, with broader relevance for rapidly urbanizing cities in the Global South

Enhancing Traditional Trade Through a Market Basket Analysis-Based Recommendation System

Traditional trade businesses in Thailand are increasingly challenged by the rapid growth of modern e-commerce. This study aims to strengthen the competitiveness of wholesalers and retailers in traditional trade by developing and implementing a market basket analysis-based recommendation system. The system applies association rule mining to generate tailored product suggestions based on purchasing patterns, rather than relying on top-selling products. It was integrated into an existing B2B e-commerce platform serving 1,168 retailers and 45 wholesalers. The system’s performance was evaluated using key business metrics, including order behavior, product diversity, sales value, and retailer satisfaction, and the association rules were generated from transaction data collected between January 2021 and March 2022. After implementation, the proportion of orders containing recommended products increased by 64%, and the diversity of recommended products rose by 1,060%, showing that the system broadened exposure to items that were previously rarely purchased. The total value of recommended product purchases grew by 34%. Additionally, a Net Promoter Score of 55% indicated strong user satisfaction. These results demonstrate that a data-driven recommendation system can significantly enhance engagement, product exposure, and revenue in traditional trade environments. The findings underscore the potential for association rule mining to support digital transformation in sectors with limited access to advanced analytics

Improving The Resolution of The Sumatran Fault Structure Using A Fusion Processing on Multi-Source Gravity Data

The Great Sumatran Fault (GSF) extends approximately 1900 km from Lampung in Sumatra to Andaman Inlands and is divided into several segments on the island of Sumatra. The high-resolution fault map of Sumatra remains very limited, especially in the northern part of the region, making it very challenging to accurately assess earthquake risk mitigation. This research aims to improve the resolution of the Sumatra Fault structures, particularly in areas where seismic activities have not been significantly released, such as the Aceh and Seulimum segments, which are characterized by relatively low historical seismic releases, by applying the fusion processing approach on multi-source gravity data, such as EGM2008 (9 km), WGM2012 (2.5 km), and TOPEX/Poseidon (1.8 km), and integrating using normalization and fusion methods to construct a high-resolution Bouguer anomaly model for mapping the GSF fault. The fused Bouguer anomaly clearly delineates the Aceh and Seulimum fault segments trending SE–NW, characterized by anomaly amplitudes of 20 to 60 mGal. High-pass filtering enhances shorter-wavelength anomalies associated with local fault structures, while the vertical and horizontal derivatives further sharpen the fault boundaries. The integrated gravity data obtained using the fusion technique have increased the resolution of regional and local fault-structure mapping, providing insight into fault structure for earthquake risk assessment

Facile Alkali Treatment of Commercial and Synthesized ZSM-5 Zeolites at Different NaOH Concentrations and Plasma-Catalytic Reforming Activities

This work aims to modify the pore structure of commercial (purchased) and synthesized ZSM-5 zeolites by a facile alkali treatment, and presents the first demonstration of pore-modified commercial ZSM-5 zeolite catalyst in a nonthermal plasma reactor for methane reforming with CO2. The ZSM-5 zeolites were alkali-treated at different concentrations of NaOH aqueous solution. Their textural properties were characterized by XRD, N2 adsorption-desorption, SEM-EDS, and PSD techniques. The changes in relative crystallinity, chemical composition, meso-micropore porosity, surface morphology, and particle size distribution of ZSM-5 zeolites before/after alkali treatment were clarified. The surface area and pore volume of mesopores had the increment at the increasing NaOH concentration. The ZSM-5 zeolite treated in 0.5 M NaOH solution acquired the pore structure containing totally mesopores. In the plasma-assisted methane reforming with CO2, the result interestingly revealed the modified commercial ZSM-5 zeolite catalyst had a synergistic influence on the overall performance in terms of improving conversion rate, consumed energy, and syngas yield. The commercial ZSM-5 zeolite catalyst treated in 0.5 M NaOH solution (CZ-0.5M) performed the best result, demonstrating the controlled mesoporosity development and surface acidity adjustment could enhance the plasma-catalytic reforming performance

Verification of Design Forces Used in Seismic Design of Buildings By The Equivalent Lateral Force Method

The equivalent lateral force (ELF) method is widely accepted and deemed safe for seismic design of regular buildings; however, dynamic analysis methods such as the Response Spectrum Analysis (RSA) are expected to yield more accurate results as it can explicitly consider the effects of higher modes of vibration. The Thai seismic design standard (DPT 1301/1302-61) and ASCE 7-22 permit the use of the ELF method for analysis and design of all buildings in seismic design category (SDC) C regardless of building heights and irregularities. There is doubt whether dynamic analysis should be required when the building is tall or irregular. This research therefore aims to evaluate adequacy of the ELF method when it is applied to regular tall buildings, and torsionally irregular buildings in SDC C located in Bangkok and tall regular buildings in SDC D located in Chiang Mai. A total of 21 buildings were studied: 7 regular and 7 torsionally irregular buildings in Bangkok, and 7 regular buildings in Chiang Mai, ranging from 6 to 42 stories. All buildings employ special reinforced concrete shear wall systems. The study further investigates whether shear force demands for design of structural walls amplified by factors in ACI 318-19 are adequate when compared to the nonlinear response history analysis (NLRHA) results. The results show that ELF tends to slightly overestimate floor displacements and story drifts.  ELF becomes inadequate in estimating story shear forces in tall buildings in Chaing Mai near the base and top of buildings, and in torsionally irregular buildings in Bangkok, particularly at core wall farthest from center of mass. RSA can provide a more reliable estimation of structural responses when compared to those from NLRHA. Furthermore, the ELF method can not well capture the variation of force demands along the building height

Sustainable Stabilization of Fine-Grained Soils using Lime, Rice Husk Ash, Bottom Ash, and Coir Fiber: A Comprehensive Review

Fine-grained soils are particularly problematic due to their poor strength, high swelling potential, high compressibility, and low permeability, which compromise their ability to support structural loads without prior treatment. Although cement has traditionally been effectively used to improve the engineering properties of fine-grained soils, its production emits substantial amounts of carbon dioxide, contributing to environmental challenges. The incorporation of waste materials such as rice husk ash (RHA), bottom ash (BA), and coir fiber (CF), in combination with alternative cementitious binders like lime, not only reduces reliance on conventional stabilizers but also promotes effective waste utilization. This review provides a comprehensive synthesis of previous studies on the stabilization of fine-grained soils using lime, RHA, BA, and CF, and evaluates their impact on engineering properties, including compressive strength, compaction, plasticity, compressibility, and permeability. Findings of this review indicate that RHA, BA, and CF, when used alongside lime, provide optimal performance within the ranges of 10%–20%, 15%–20%, and 0.5%–1.0%, respectively, when evaluated in terms of compressive strength improvement, plasticity reduction, permeability enhancement, and compressibility reduction. This study highlights the potential and limitations of these sustainable materials to improve geotechnical performance while supporting effective waste utilization and cost-effectiveness for infrastructure developments

Virtual Reality Rehabilitation Platform for Mild Cognitive Impairment: A Metaverse Approach

Mild Cognitive Impairment (MCI) is increasingly prevalent among elderly populations, necessitating new approaches that support cognitive engagement, social interaction, and remote monitoring. This study presents a Virtual Reality Rehabilitation Platform designed within a metaverse-based framework to enhance usability and accessibility for elderly individuals with cognitive impairment. Unlike conventional VR rehabilitation systems, the proposed platform integrates three key innovations: (1) a metaverse-oriented, multi-user environment that enables avatar-based social interaction, co-presence with therapists, and persistent shared game spaces; (2) an MQTT-based real-time monitoring and control channel that allows therapists to observe gameplay events, adjust sessions, and supervise users remotely with low latency; and (3) deployment and preliminary usability validation with elderly individuals with MCI in a real-world clinical context, demonstrating its feasibility for remote, home-based rehabilitation via high-speed wireless networks, including 5G-ready infrastructure. A total of 18 elderly participants engaged with the platform over a five-week period, using Oculus Quest 2 devices to perform memory, spatial awareness, and interaction-based VR tasks. This study intentionally focuses on evaluating usability, acceptance, and user experience rather than clinical cognitive outcomes; as such, no pre-/post-intervention cognitive assessments were conducted. Quantitative satisfaction surveys, game evaluations, and qualitative focus group findings revealed generally positive user engagement, clear task comprehension, and moderate-to-high satisfaction across VR interaction elements, while also identifying areas for improvement such as device comfort and motion smoothness. The results highlight the potential of metaverse-supported VR rehabilitation as an accessible and socially engaging tool for elderly individuals with cognitive impairment, and they establish a foundation for future studies evaluating clinical efficacy and long-term cognitive benefits

An Experimental Study on Thermal Stability, Char Morphology, and Antioxidant Activity for Enhancing Fire Resistance of Intumescent Coatings with Rice Husk Ash

The mechanical and thermal properties of intumescent fire-retardant coatings (IFRC) are essential. At temperatures higher than 550°C, structural steel loses its qualities. The coating creates a carbon layer that shields the steel basis from heat fire. The amount of rice husk ash (RHA)was altered from 0 to 10 wt. % in different IFRC substrates. As per American society for testing materials (ASTM), standard test method E119 applied for one hour. No fractures were visible on the coal surface. In comparison to the control formula coating (IFRC-1), the lowest backside temperatures were attained IFRC-3 (229°C) and IFRC-4 (225°C), which decreased the backside temperatures to 89°C and 93°C. For carbon analysis, all coatings were baked at 500°C in a muffle furnace. The maximum swelling coefficient value of 6.14 was found in IFRC-3 with the formulation of Ammonium polyphosphate(APP) 6%, Expandable graphite(EG) 6%,Zinc borate(ZB) 2.5%, Melamine(MEL) 10%, Kaolin clay(KC) 4.5%,Epoxy resin(ER) 48.4%, Epoxy hardener (EH) 12.1%, Titanium dioxide(TiO2) 3.5%, RHA7%). As the amount of rice husk ash increased, so did the residual coal yield. At 800 °C, IFRC-4 (RHA=10%) had a residual coal weight of 22.79%, which was 31.99% greater than that of the control coating. The char morphology is dense, compact, and has a porous surface structure of integrated char with an increasing proportion of RHA, according to scanning electronic microscope (SEM). Energy dispersive spectrometer (EDX) analysis results indicated that IFRC-4 had the highest antioxidant activity, measuring 1.69. The formation of pertinent functional groups and a more stable structure demonstrated by fourier transform infrared spectroscopy (FTIR)

Structural and Geometric Enhancements of Microperforated Panel Absorbers: A Systematic Literature Review

This systematic review analyses sixty-one recent studies on structural and geometric enhancements of microperforated panel (MPP) absorbers, consolidating them into two primary categories: cavity structural strategies and panel modifications. Cavity-related approaches include multilayer, multi-depth, folded, and partitioned designs, while panel-related strategies address perforation geometry, distribution, and surface profiling. Hybrid designs that integrate both approaches are acknowledged but not the focus of this study. Comparative analysis indicates that cavity-related enhancements are particularly effective in extending sound absorption into low frequencies, whereas panel modifications provide greater flexibility for tuning absorption peaks and achieving compact broadband performance. Cross-category comparisons reveal performance trade-offs and clarify the structural solutions most suitable for engineering applications such as built environments, transportation systems, and enclosed technological spaces. The review establishes a structured overview of MPP absorber design strategies, highlighting current trends, limitations, and opportunities for future development. The synthesis not only provides design guidance for absorbers with improved low-frequency and broadband performance but also situates MPPs within the broader landscape of acoustic materials and engineering technologies

Full-Scale Bi-Directional Static Load Testing of Large-Diameter Hand-Dug Caissons Using Distributed Fibre Optic Sensing

In response to the increasing demand for high-resolution evaluation of deep foundations under extreme axial loading, this study presents an integrated application of bi-directional static load testing (BDSLT) and distributed fibre optic sensing (DFOS) on large-diameter hand-dug caissons. Although widely used in urban and access-constrained sites, caisson performance is often under-investigated due to the limitations of conventional load testing and point-based instrumentation. This study addresses this gap through full-scale testing of two caissons: one socketed into moderately weathered granite and the other terminating in residual soil, both constructed in Pahang, Malaysia, with diameters ranging from 2800 mm to 4000 mm. Each pile was instrumented with four DFOS cables for continuous axial strain profiling and tested up to 200% of the working load. The socketed pile mobilised peak shaft friction of 2586 kN/m², while the non-socketed caisson reached 516.8 kN/m². End-bearing remained linear, indicating that capacity was not fully mobilised. Settlements at peak load were 13.8 mm (socketed) and 25 mm (non-socketed), confirming the rock socket's role in enhancing foundation stiffness. DFOS enabled high-resolution detection of strain anomalies and load transfer patterns beyond the reach of discrete sensors. The results confirm the performance benefits of granite socketing and establish DFOS as a transformative tool for pile testing and deep foundation verification in complex geology