University of Bangka Belitung

Bangka’s mangroves contribute to Indonesia’s species-rich coastal ecosystems, yet they have experienced substantial degradation, largely driven by human activities such as tin mining. Establishing long-term records of mangrove extent is essential for understanding distribution dynamics, assessing impacts, and guiding conservation strategies. In this study, we applied change detection techniques, a random forest classifier, and the LandTrendr algorithm to analyze Landsat time-series data from 1994 to 2023 across Bangka Island. We quantified multi-decadal changes in mangrove extent, periods of disturbance and recovery, and discrepancies between local and global datasets. Mangrove dynamics were spatially heterogeneous, with both expansion and loss observed across regions in landward and seaward settings. Over the 30-year period, total gains reached 4956.39 ha (10.30% of the baseline), yet the net change indicated an overall loss of 1055.85 ha. LandTrendr analysis further revealed sustained mangrove expansion since 1989. Observed changes reflect the combined influence of natural processes, including accretion and erosion, and human pressures, particularly tin mining. Although net area loss aligns with national trends, the drivers in this mining-dominated region differ from those elsewhere, and some mangrove areas remain absent from global datasets. These findings emphasize the need to better capture local gain–loss dynamics to support effective management and conservation.

This journal examines the transformative implications of integrating Living Law into Indonesia's new criminal code within the context of the nation's pluralistic legal framework, encompassing both statutory law and dynamic indigenous legal traditions. The study identifies significant challenges in harmonizing these systems, particularly due to the absence of a comprehensive regulatory framework governing indigenous justice. To address this issue, the establishment of Adat Courts is proposed as a strategic mechanism to preserve and enforce indigenous values without necessitating their formal codification. Employing a qualitative methodology grounded in legal philosophy and regulatory analysis, the research highlights the urgent need to resolve normative conflicts that hinder the effective implementation of Living Law. The findings underscore that Adat Courts serve as a pragmatic and culturally sensitive solution, ensuring the preservation of Indonesia's legal diversity while maintaining the integrity of the national legal order. In conclusion, the integration of Living Law into Indonesia's criminal code signifies a critical juncture in the evolution of the country's legal system. The proposed Adat Courts represent an innovative and harmonious approach to safeguarding indigenous legal principles, fostering cultural authenticity, and mitigating systemic conflicts within the broader framework of legal pluralism.

Accurate stock index prediction is essential for effective investment strategies and economic policymaking. While traditional statistical models often fail to capture the nonlinear dynamics of financial markets, machine learning approaches—particularly Extreme Gradient Boosting (XGBoost)—offer greater flexibility, robustness to overfitting, and computational efficiency. However, the performance of XGBoost strongly depends on hyperparameter tuning, which is difficult to optimize using conventional search methods. To address this, we propose a hybrid framework that integrates XGBoost with Grey Wolf Optimization (GWO) for enhanced hyperparameter selection in stock index forecasting. Using historical data from the Indonesian BBNI stock index (2021–2024) and financial features (price, volume, and temporal), the GWO-optimized XGBoost achieved superior performance, recording the lowest testing MAPE (1.79%), RMSE (108.67), and MAE (84.32). These results surpass classical regressors (Decision Tree, Random Forest, Multilayer Perceptron, Gradient Boosting) by margins of 6–26% and outperform conventional tuning methods (Grid Search, Random Search, Bayesian Optimization) as well as other swarm intelligence approaches (PSO, BA). Moreover, the GWO-based approach reduced error variability and required significantly less optimization time, with the 10-wolf configuration providing the best accuracy–efficiency tradeoff. The scope of this study is limited to a single stock index (BBNI.JK) and financial features, without incorporating macroeconomic indicators, sentiment variables, or cross-market validation. These limitations indicate potential directions for future work to enhance generalizability. Overall, the proposed GWO-XGBoost framework provides a powerful, stable, and time-efficient solution for stock index prediction in volatile market conditions.

Penelitian bertujuan untuk mengevaluasi efektivitas penggunaan substrat buatan dalam meningkatkan jumlah telur cumi yang menempel dan menganalisis tingkat kelulushidupan juvenil cumi. Penelitian dilaksanakan dari bulan September hingga Desember 2025 dengan lokasi pengambilan telur cumi di perairan Pantai Tuing dan penetasannya dilakukan di akuarium di Desa Balunijuk, Kabupaten Bangka. Metode yang digunakan yaitu dengan rancangan percobaan analysis of variance pada 4 substrat yang berbeda yaitu (P0) substrat alami, (P1) atraktor cumi dengan pipa paralon 1”, (P2) atraktor cumi dengan besi cor 6 mm, (P3) tali tambang dan jaring bekas. Hasil menunjukkan bahwa preferensi substrat yang berbeda mempengaruhi jumlah penempelan telur cumi dan survival rate dari juvenil cumi. Tali tambang dan jaring bekas (TTJ = P3) sebagai substrat yang paling optimal dan berbeda sangat nyata (BSN) dibanding substrat lainnya, ditandai dengan banyaknya jumlah gerombol telur cumi pada seluruh periode pengamatan. Karakteristik TTJ yang berserat, berongga, dan fleksibel tampaknya meningkatkan ketertarikan induk cumi untuk bertelur yang mirip dengan habitat alami. Tingkat kelulushidupan juvenil (survival rate) cumi di akuarium dengan rata-rata 39% yang menetas secara bertahap. Keberhasilan penetasan sangat dipengaruhi oleh kondisi telur saat dikumpulkan dari alam. Parameter kualitas air berada dalam kisaran layak bagi perkembangan embrio kecuali kecepatan arus air yang lemah menjadi faktor pembatas sehingga manajemen kualitas air harus diperhatikan. Substrat buatan dan tingkat kelulushidupan juvenil memberikan dasar penting untuk merancang strategi konservasi cumi melalui restocking dan perlindungan habitat.

The increase in coffee production in East Belitung Regency indicates that coffee plants are quite prospective for development and preservation. The development of Robusta coffee cultivation can be done through plant exploration and characterization activities to obtain accessions with superior properties. This study aims to determine the value of variability and kinship relationships of Robusta coffee accessions in East Belitung Regency. The study was conducted from July 2025 to January 2026. This study used an exploration method with a purposive sampling technique on five healthy and vigorous Robusta coffee plant samples at each research location. Morphological characterization was carried out based on coffee descriptors for qualitative and quantitative characters. Analysis of kinship relationships based on qualitative characters used the UPGMA method with NTSYS-pc 2.1 software in the form of a dendogram and analysis of variability on quantitative characters to obtain the phenotypic diversity value of Robusta coffee accessions. The results of Robusta coffee plant exploration in East Belitung Regency found eight Robusta coffee accessions including Mentawak 1, Mentawak 2, Kelubi, Batu Penyu, Limbongan, Dendang, Jangkang and Lintang accessions. The results of data analysis found that Robusta coffee accessions in East Belitung Regency have a close kinship relationship based on qualitative characters with a coefficient of 80%, which are divided into four clusters. Robusta coffee accessions have narrow to wide plant variability. Narrow variability is found in the characters of leaf length, number of flowers per fascicle, fruit diameter, number of petals per flower and seed width. Somewhat narrow variability is found in the characters of leaf width, leaf stalk length, dry weight of 100 fruits and seed length. Quite wide variability is found in the characters of fresh weight of 100 fruits, wet weight of 100 seeds and dry weight of 100 seeds. Wide variability is found in the characters of plant height, number of flowers per node and flower stalk length. Robusta coffee accessions obtained can be useful as genetic resources for further development through plant breeding programs in the future. Key words: East Belitung, Robusta Coffee, Relationship, Variability