Journal of Hunan University Natural Sciences

This study aims to assess the carrying capacity of the Wai Samal and Wai Eti watersheds on Seram Island, Maluku Province, Indonesia, using an integrated multi-criteria approach adapted to small island conditions. A quantitative method was employed using GIS-based land-unit analysis derived from the overlay of topographic, geological, soil, and land-use maps, supported by 31 years of rainfall, hydrological, and socio-economic data. The assessment followed the Indonesian National Watershed Monitoring and Evaluation Framework (Ministerial Regulation No. P.61/Menhut-II/2014), integrating biophysical, hydrological, socio-economic, institutional, water infrastructure, and spatial planning indicators. The results showed that the Wai Samal Watershed achieved a carrying capacity index (DDD) of 78.75 (Good), whereas the Wai Eti Watershed obtained 93.25 (Moderate). The higher carrying capacity of the Wai Samal Watershed was associated with lower critical land extent, lower erosion and flood risk, lower water-use pressure, higher land availability, and stronger institutional performance. In contrast, the Wai Eti Watershed experienced greater environmental and socio-economic pressures, characterized by higher critical land extent, greater land degradation, and less favorable spatial land-use conditions, resulting in lower watershed resilience. These findings demonstrate that the integrated indicator-based assessment provides a scientific basis for identifying watershed-specific management priorities and supports adaptive watershed management and evidence-based spatial planning to enhance long-term sustainability in small island watersheds.

Keywords: watershed carrying capacity; GIS; erosion index; watershed evaluation; small island; integrated watershed management.

DOI https://doi.org/10.55463/issn.1674-2974.53.8.3

This article presents the design and implementation of a cascade control scheme applied to a two degree of freedom (2R) planar robot, focused on trajectory tracking. The system architecture integrates three hierarchical loops: current, speed, and position. The current loop was characterized using the Smith two-point method, while the speed and position loops were tuned using the relay method of Åström and Hägglund, thus enabling the tuning of PI controllers. The actuators are DC motors equipped with incremental encoders for position and speed measurement, along with INA219 sensors for current measurement, programmed through the NUCLEO STM32F746ZG board. In addition, the Raspberry Pi 4 was responsible for supervision, trajectory processing, graphical interface, and neural network execution. Inverse kinematics was solved using an ensemble model of Multilayer Perceptrons (MLP) trained with synthetic data, achieving an RMSE of 0,1046° in θ_1 and 0,0533° in θ_2, outperforming individual models. The motors achieved settling times close to 1 s, overshoots below 3%, and steady-state errors under ±0,12°. The system demonstrated precision in contour tracing, obtained through real-time image processing (e.g., the Windows logo), highlighting the feasibility of integrating cascade control and neural networks into low-cost embedded systems, with applications in education, automation, and robotic prototypes.

Keywords: Artificial intelligence, MLP Neural Network, Robotics, Inverse kinematics, Hierarchical control, Cascade control, Trajectory tracking, Raspberry Pi 4, STM32F746ZG.

DOI https://doi.org/10.55463/issn.1674-2974.53.8.2

Sustainable Public Procurement (SPP) supports Sustainable Development Goal (SDG) target 12.7 by integrating social, economic, and environmental considerations into public procurement policies. Although research on SPP continues to grow, existing studies remain fragmented regarding how drivers, barriers, and implementation strategies operate across diverse national and institutional contexts. This study synthesizes global evidence on the factors facilitating or hindering SPP implementation and identifies strategies to enhance its effectiveness. A systematic literature review following PRISMA protocols and a bibliometric analysis using VOSviewer were conducted on 69 peer-reviewed articles from the Scopus database. The review identified 244 drivers, 121 barriers, and implementation strategies. Drivers were classified into four categories: political will and policy mandates; stakeholder engagement; financial incentives and cost-benefit considerations; and organizational culture and leadership. Barriers were grouped into institutional, technical, and behavioral dimensions, with institutional constraints being the most dominant. Frequently proposed strategies include capacity building, evaluation and accountability mechanisms, institutional and governance reforms, inclusive and socially oriented procurement, and technology-based approaches. Findings also indicate that research on Sustainable Public Procurement (SPP) is concentrated in developed countries, predominantly employs qualitative designs, and focuses primarily on environmental aspects. By integrating bibliometric mapping, thematic synthesis, and cross-contextual comparison, this study presents a comprehensive framework linking the drivers, barriers, and implementation strategies of SPP in both developed and developing nations. Future research needs to expand the evidence base from developing countries, utilize mixed-methods approaches, and examine digital transformation to strengthen SPP implementation.

Keywords: sustainable public procurement; public procurement; sustainable development goals; systematic literature review; drivers; barriers; VOSviewer; PRISMA.

DOI https://doi.org/10.55463/issn.1674-2974.53.8.1

Seawater intrusion represents a major threat to groundwater sustainability in rapidly urbanizing coastal areas, particularly where groundwater abstraction and land-use changes are intensifying. This study aimed to evaluate the spatial distribution, intensity, and controlling factors of seawater intrusion into shallow aquifers in the coastal area of Belawan, North Sumatra, Indonesia. Thirty shallow groundwater samples were collected from wells located at approximately 2-km intervals and analyzed for chloride (Cl⁻), bicarbonate (HCO₃⁻), carbonate (CO₃²⁻), and electrical conductivity (EC). Seawater intrusion was evaluated using the chloride-to-bicarbonate ratio (CBR), while groundwater was classified according to chloride concentration and electrical conductivity. Chloride concentrations ranged from 2 to 31,160 mg/L, whereas EC values ranged from 186 to 26,400 µS/cm. Among the 30 sampled wells, 20 were classified as freshwater, three as brackish water, and seven as saline water. Based on the CBR classification, three wells exhibited low seawater intrusion and five showed high seawater intrusion. Spatial analysis revealed that seawater intrusion was predominantly concentrated in densely populated coastal zones characterized by permeable sandy-gravel aquifers and intensive land development. The results provide updated hydrochemical evidence on the extent of seawater intrusion in the Belawan coastal area and may support groundwater monitoring, coastal land-use planning, and sustainable groundwater management.

Keywords: seawater intrusion; coastal aquifer; groundwater salinization; chloride-to-bicarbonate ratio; electrical conductivity; hydrochemistry.

DOI https://doi.org/10.55463/issn.1674-2974.53.7.14

Port terminals are subject to converging normative demands spanning quality, environmental, and occupational health and safety management, driving the widespread parallel adoption of ISO 9001, ISO 14001, and ISO 45001 certifications. Despite the growing prevalence of co-certification in the port sector, the mechanisms through which these three standards interact, and the organizational conditions under which such interactions produce additive, synergistic, or compensatory performance effects, remain theoretically underdeveloped. This article presents a conceptual modeling study that constructs an integrated analytical framework for mapping the cross-impacts of ISO 9001, ISO 14001, and ISO 45001 on the operational, environmental, organizational, and social performance dimensions of port terminals. The methodology combines a structured literature synthesis, a contextual analysis of Moroccan port terminals drawing on secondary sources and official documentation, and a theoretical triangulation grounded in the Resource-Based View, stakeholder theory, and neo-institutionalism. The conceptual findings identify three interaction regimes, addition, synergy, and compensation, whose activation is moderated by integration maturity, governance structure, technological capability, institutional pressure, and cultural absorption capacity. Applied to six major Moroccan port terminals spanning from Optimization-level (Tanger Med) to Correspondence-level (Agadir) integration configurations, the model illuminates differentiated certification trajectories and their performance implications. Six testable research propositions are derived to guide empirical validation. This study contributes to the Integrated Management Systems (IMS) literature by operationalizing cross-certification dynamics within a port-specific and institutionally embedded North African context, while providing port managers with a structured decision framework for optimizing certification integration strategies.

Keywords: Integrated management systems; ISO certifications; Port terminal performance; Cross-effects; Organizational performance; Managerial synergies; Moroccan port context.

DOI https://doi.org/10.55463/issn.1674-2974.53.7.13