Husni Husin

This study investigates how adding silica fume (SF) influences the microstructure and strength of rice husk ash (RHA)-based geopolymer mortar. The experiment was conducted by preparing and mixing five geopolymer mortar specimens with 0, 5, 10, 15, and 20% SF additions. Subsequently, compressive strength (CS) and flexural strength (FS) tests were conducted on specimens at 3, 7, 28, 56, 90, and 120 days, while X-Ray Diffraction (XRD), Fourier Transform Infrared (FTIR) Spectroscopy, and Scanning Electron Microscopy – Energy Dispersive Spectroscopy (SEM-EDS) analyses were performed only on specimens at 120 days. The results indicated that the strength of the geopolymer mortar improved as the SF content increased and with the specimens’ age. Among the mixtures, the addition of 15% SF was identified as the optimal content, providing the best balance between strength and durability performance. SEM-EDS results showed that SF addition produced a denser and more compact microstructure with a lower Si/Al ratio. Based on FTIR spectra, strong absorption bands were observed in the 1000–450 cm⁻¹ region, showing Si-O and Si-O-Si stretching vibrations, which were characteristic of the silicate structure in geopolymer materials. In line with XRD patterns, the cristobalite and quartz peaks decreased with rising SF, showing that SF reduced the crystalline phase in geopolymer mortar and increased the amorphous phase, thereby improving strength. The aluminosilicate hydrate and the amorphous phase of geopolymer were clearly visible in all specimens. To predict the CS and FS of geopolymer mortar due to SF addition and increasing age, Artificial Neural Network Backpropagation (ANN-B) and Response Surface Methodology (RSM) analyses were carried out. The ANN-B model accurately predicted CS and FS, with coefficient of determination (R2) values of 0.95 for both. Meanwhile, RSM results showed that the second-order regression model could predict the CS and FS of geopolymer mortar, with R2 values of 0.95 and 0.96, respectively.

This study aims to develop a composite hydrogel based on biochar derived from pineapple crown waste and polyacrylamide, and to analyze its physicochemical and mechanical characteristics. Biochar was produced through three main stages: (1) pretreatment, during which the pineapple crown was cleaned, washed, and dried; (2) pyrolysis, carried out at 500 °C for 2 hours; and (3) activation, performed using 35% NaOH for 24 hours, followed by drying at 105 °C. After these processes, the activated biochar was mixed with polyacrylamide and methylenebisacrylamide (MBA) to form the composite hydrogel. FTIR analysis identified interactions between polyacrylamide and biochar through characteristic peaks associated with functional groups such as –OH, –NH, and C=O, contributing to the hydrogel’s mechanical stability. BET analysis revealed a high specific surface area (846.923 m²/g for 1 g biochar), indicating excellent potential for solvent and water absorption. SEM–EDS analysis confirmed a porous structure and successful incorporation of biochar through the presence of carbon, nitrogen, and oxygen. Shore A durometer testing showed that the composite hydrogel exhibited low hardness (9 ± 1 at 1 s), suggesting good elasticity. Overall, the results demonstrate that the pineapple crown biochar–polyacrylamide composite hydrogel has significant potential for use as an environmentally friendly and sustainable absorbent material and active substance delivery system.

The escalating accumulation of single-use plastic waste represents a significant environmental challenge, encouraging the exploration of thermochemical strategies such as pyrolysis to convert plastics into valuable liquid fuels. This research examines the catalytic performance of a Pt/Nb ₂ O ₅ system in the pyrolysis of post-consumer plastic straws. The catalyst was prepared through direct impregnation with Nb ₂ O ₅ loadings between 1–9 wt% and characterized using FTIR and SEM analyses. FTIR spectra confirmed the presence of active surface groups (–OH, Nb–O–Nb, and Nb=O), while SEM images revealed rough, porous aggregates that favor improved diffusion and surface reactivity. Pyrolysis was carried out at 500 °C, and catalytic pyrolysis at 400 °C using a Pt/Nb ₂ O ₅ catalyst containing 3 wt% Pt under a nitrogen atmosphere. The optimal Nb ₂ O ₅ composition of 5 wt% yielded the highest liquid fraction (69.11%), whereas further loading increases (≥7 wt%) led to decreased yield due to the formation of NbO _x layers and strong metal–support interactions. GC–MS analysis identified medium-chain hydrocarbons (C ₇ –C ₁₃ ) as the main products, with 2,4-dimethyl-1-heptene and 2-undecene prevailing within the gasoline range. Overall, the Pt/Nb ₂ O ₅ catalyst exhibited bifunctional activity, effectively enhancing both conversion efficiency and selectivity toward high-quality fuel precursors from plastic waste.

Marine pollution caused by ship-generated waste remains a critical environmental challenge, particularly on training vessels that operate continuously with high waste variability. This study aims to develop and validate an incinerator-based onboard waste management model that enhances waste processing efficiency while ensuring compliance with MARPOL 73/78 regulations. A mixed-method approach was applied, integrating quantitative waste characterization and regression-based estimation of waste generation with qualitative operational analysis across six Indonesian training ships. The regression outputs were used to parameterize incinerator capacity and combustion load, while system integration, thermal simulation, and operational validation were conducted to evaluate performance under representative shipboard conditions. The findings demonstrate that the engineered incinerator significantly improves feeding capacity, combustion efficiency, and energy utilization, while reducing residual ash and carbon monoxide emissions by approximately 15–20 ppm compared to standard systems. Thermal simulations confirmed stable combustion at 950–1050°C and effective exhaust gas treatment through water spray cooling and activated carbon filtration. The proposed model offers a system-level improvement over existing studies by explicitly integrating regulatory requirements, engineering design, emission control, and crew-operational workflows within the spatial and functional constraints of training vessels. This integrated and vessel-specific approach constitutes the main novelty of the study, providing a practical, compliant, and environmentally sustainable solution for shipboard waste management and marine pollution mitigation.

Accurate shipboard waste prediction is essential for MARPOL compliance, yet maritime research has predominantly relied on fleet-wide aggregated models that may obscure vessel-specific patterns. The occurrence of statistical paradoxes in hierarchical maritime data has not been systematically examined. This study provides the first systematic documentation of Simpson's Paradox in maritime operational environmental data, using shipboard waste generation as a case study. By analyzing engine running hours and waste generation from six Indonesian training ships, we demonstrate the risks of data aggregation in maritime predictive analytics. We compared fleetwide Generalized Linear Models with individual vessel regression approaches using 66 observations over 11 days. Simpson's Paradox emerged in Auxiliary Engine data: strong individual-level correlations (r = 0.993) were masked by weak fleet-wide correlation (r = 0.416), demonstrating how aggregation can fundamentally misrepresent underlying relationships. Individual ship models achieved substantially higher predictive performance (97.38% and 98.60%) than fleet-wide models (89.5% and 17.3%), with cross-validation (CV) confirming robustness. The findings reveal that fleet-wide aggregation can produce misleading predictions with significant operational consequences for waste storage planning and regulatory compliance. This study establishes the necessity of vessel-specific modeling in maritime environmental management and provides methodological guidance for analyzing hierarchical operational data.

Land surface temperature (LST) is an important indicator of ecosystem sustainability and climate change resilience, particularly in highland watersheds characterized by fast land use and land cover (LULC) changes. In this research, the LST dynamics of the Laut Tawar Sub-watershed, Central Aceh, Indonesia, were investigated, based on Landsat 9 OLI/TIRS 2024 imagery. Supervised classification identified eight land cover categories, and their thermal contrasts were evident: built-up and plantation zones exhibited the highest LST values (25–32 °C), while water bodies and forests acted as natural coolers (9.5–17 °C), with elevation further modulating these patterns by creating cooler microclimates at higher altitudes (>2000 m), highlighting the impact of topography in generating microclimatic diversity. Intermediate values were shown for the moderate and sparse forest areas, which thus worked as transition zones with low cooling capabilities. Natural land covers contributed to thermal regulation, whereas built-up and agricultural expansion exacerbated surface heat and possible urban heat island (UHI) effects. This research highlights the importance of protecting forests and water bodies, controlling land conversion, and applying targeted green infrastructure informed by the thermal disparities and land cover dynamics observed.

Change of land use and intensification of human activity significantly influence the sur-face temperature of the land, which is a basic parameter in climate change and balance of ecosystems. This study uses Landsat-9 data to analyze spatial and temporal distribution in Laut Tawar Sub watershed Surface Temperature Patterns and discuss major factors influencing surface temperature patterns. Integration of remote sensing data with geospatial analyses leads this study to establish that variations in LST are strongly controlled by topography, vegetation cover, degree of urbanization, and agricultural land conversion. The mapped results show that densely vegetated and water areas are relatively cool with temperature ranging from 9.5–17°C, whereas urbanized and converted areas demonstrate an obvious temperature increase as high as 25–32°C, supporting an important role of elevation, slope aspect, and vegetation in mitigating heat accumulation. The present study has implications for UHI mitigation measures, nature-based spatial planning and sustainable water resources management. Landsat-9 thermal data has a good potential to quantify the thermal pattern in detail, and this shall provide a great contribution to the climate adaptation strategies, including the local and regional habitat conservation efforts.

To achieve sustainability with limited global energy resources, minimizing energy consumption and utilizing local materials are essential. In Aceh, Indonesia, traditional houses have evolved over centuries, integrating passive design features that enhance thermal comfort. This study analyzes the...

Refugee tents are essential temporary shelters in disaster-prone regions like Aceh, Indonesia, which experiences a warm and humid tropical climate. Ensuring thermal comfort in these shelters is crucial for the well-being and recovery of displaced individuals. This study evaluates the thermal comfort of refugee tents deployed in Aceh through a combination of field measurements and computational simulations using Ansys Fluent 19.2 (CFD software). Field measurements captured real-time environmental data, including temperature, humidity, and airflow inside and around the tents. Thermal comfort was assessed using the Indonesian National Standard (SNI 03-6572-2001) through Effective Temperature (ET), and the ASHRAE 55 through Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD). This study also analyzed the thermal performance of alternative tent configurations designed to improve thermal comfort in tropical climates. Two new tent designs were proposed: one with rooftop openings to release trapped hot air and another with both upper ventilation and a double-layer outer skin with a 10 cm air gap. The results show that the tent with upper ventilation reduces the air temperature by approximately 0.5 K and increases air speed by around 0.18 m/s. The design combining upper ventilation and a double skin achieves a greater temperature reduction of 2.9 K compared to the outside environment, with a faster airflow than ventilation alone. These findings highlight the importance of advanced ventilation strategies and thermal insulation in improving indoor environments, offering valuable insights for future refugee tent designs aimed at enhancing thermal comfort.