Sam Ratulangi University

Multi-Criteria Decision Making (MCDM) methods are widely used to address complex decision problems involving multiple alternatives and criteria with different characteristics. However, ranking outcomes may be sensitive to normalization mechanisms, criterion weights, and aggregation processes, particularly when benefit and cost criteria are evaluated simultaneously. This study proposes the Enhanced Root Assessment Method (ERAM), an improved root-based MCDM framework designed to provide a more structured and balanced evaluation of alternative performance while improving ranking stability. ERAM integrates modified normalization, weighted normalization, positive and negative aggregation, Relative Benefit–Penalty Balance, and an Enhanced Root Assessment Index to construct the final preference measure. The proposed method is evaluated using a new store location selection dataset comprising eight alternatives and six criteria. Its performance is examined through comparative analysis with SAW, WASPAS, GRA, and MOORA, together with sensitivity analysis using ±0.05 changes in criterion weights. The results show that ERAM maintains a stable ranking structure under weight variations and achieves a strong Spearman correlation of 0.9286 with the reference ranking, exceeding WASPAS (0.9048) and SAW, GRA, and MOORA (0.8810). These findings demonstrate that ERAM can produce consistent rankings while maintaining robustness against moderate changes in criterion importance. Therefore, ERAM provides a structured and robust framework for multi-criteria ranking problems involving heterogeneous criteria and uncertain decision preferences.

This study investigates the fuel properties of ethanol-butanol-gasoline emulsions prepared with varying ethanol concentrations (80, 90, and 96%) to develop stable and efficient alternative fuels. fuel density, specific gravity (SG), distillation characteristics, and copper strip corrosion resistance, with an emphasis on stability and performance at temperatures between 15 and 30 degrees C. The results indicate that these fuel blends exhibit high octane ratings, with RON values ranging from 91.8 to 94.1, demonstrating strong anti-knock characteristics suitable for high-performance engines. The RVP increases from 41 to 50 kPa as ethanol content rises, supporting stability under diverse environmental conditions. Fuel density decreases from 0.798 to 0.759 g cm-3, while SG ranges from 0.770 to 0.715, reflecting the influence of ethanol content on fuel mass and volume. Copper strip corrosion tests conducted in accordance with American Society for Testing and Materials, ASTM D130 standards confirmed that all blends are non-corrosive, achieving a "Class 1" corrosion rating and ensuring compatibility with engines containing copper or other metallic components. Distillation tests revealed initial boiling points (IBP) between 41 and 45 degrees C and final boiling points (FBP) from 122 to 177 degrees C. Overall, these findings suggest that ethanol-butanol-gasoline emulsions offer notable benefits for enhancing engine performance, reducing emissions, and improving fuel stability.

Indonesia possesses abundant biomass resources with great potential for value-added applications. Siam weed (Chromolaena odorata L.), an invasive plant species, is widely distributed and underutilized. In this study, nitrogen self-doped hydrochar (NSD-HC) was synthesized from Siam weed leaves via hydrothermal carbonization, followed by KOH treatment, producing a pore-like structure with abundant surface functionalities. The NSD-HC was analyzed using FTIR, SEM, EDS, XRD, Raman, XPS, and UV-vis spectrometry to elucidate its characteristics. Its adsorption performance was evaluated against various synthetic dyes, including crystal violet (CV), under different adsorption conditions (contact time, CV concentration, and NSD-HC weight). The data indicated that the adsorption kinetics fitted with the PSO model, while the equilibrium data followed the Langmuir isotherm model. The NSD-HC exhibited rapid adsorption kinetics with a maximum adsorption capacity of 37.47 mg g-1. The adsorption efficiency was associated with electrostatic interactions, hydrogen bonding, and pi-pi interactions between NSD-HC's active sites and CV molecules. This study demonstrates a sustainable and cost-effective method for valorizing invasive biomass into a good adsorbent, enabling efficient treatment of dye-laden wastewater while mitigating the ecological impact of invasive species.

Background Biotic diversification in ancient lakes is shaped by complex geological histories and genetic exchange among populations. The Malili Lake system on Sulawesi Island represents a classic natural laboratory for studying freshwater fish evolution and harbors multiple endemic Oryzias species that diversified under repeated hydrological reorganizations. Previous genomic analyses inferred that two sympatric species in Lake Towuti (O. profundicola and O. loxolepis) experienced a single ancient introgression event from a "ghost lineage" derived from O. marmoratus inhabiting another lake. However, recent taxonomic re-evaluation has revealed the presence of an extant O. marmoratus population within Lake Towuti itself. This finding suggests that the putative ghost lineage may in fact represent a living population co-occurring in the lake, calling for a re-examination of the introgression history and speciation mode in Lake Towuti. Results By incorporating newly generated ddRAD-seq data from the true O. marmoratus in Lake Towuti, we reanalyzed phylogenetic relationships and population genetic structure among Malili Lake Oryzias. Previously reported major phylogenetic relationships and inter-lake introgression patterns were largely reproduced. In contrast, TreeMix and f(4)-statistic analyses revealed that introgression signals previously attributed to a "ghost lineage" into O. profundicola and O. loxolepis instead originated from the extant O. marmoratus population coexisting within Lake Towuti. Demographic model comparisons explicitly incorporating within-lake gene flow further supported a scenario in which O. profundicola and O. loxolepis diverged in allopatry, subsequently came into secondary contact within Lake Towuti, and later experienced additional gene flow following secondary contact with O. marmoratus that entered the lake. Conclusion Our results demonstrate that introgression from the O. marmoratus lineage into O. profundicola and O. loxolepis was not a single ancient event, but rather a more sustained process.This finding highlights the critical importance of taxonomic resolution for accurately inferring introgression and divergence history. Comparative studies across other ancient lakes on Sulawesi will be valuable for understanding how the timing and nature of gene flow from third lineages influence patterns of population divergence and the strength of reproductive isolation.

Synthetic dyes are highly dangerous if not managed properly. Many studies have reported the use of economical materials and methods. In this study, GO/CS/ZnO composites were synthesized by immobilizing graphene oxide (GO) into chitosan (CS)/ZnO. The steps carried out were corncob carbonization, graphite formation, GO preparation, and finally, GO/CS/ZnO composite synthesis. The composites were evaluated as adsorbents for the methylene blue (MB) dye. The final yield achieved during the composite synthesis stage was 96.9%. This figure represents a significantly higher product recovery than that obtained in the preceding synthesis steps for both the graphite and the GO. XRD and FTIR data supported the presence of components in the composite material, as confirmed by EDS analysis, which showed elemental compositions of 55.8%, 10.9%, and 32.4% for C, O, and Zn, respectively. The morphology of each material was different; GO showed a smoother surface compared to other materials, while the composite showed agglomeration due to the combination of GO, CS, and ZnO. The adsorption activity test showed that the composite had better adsorption efficiency compared to its raw materials, with efficiencies of 89.2%, 96.6%, and 98.0% for contact time, pH, and MB concentration, respectively. The adsorption equilibrium model of the composite followed the Freundlich model. Therefore, this composite holds great promise for development as an adsorbent for synthetic dyes or other substances.