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Recommender systems are crucial for filtering vast amounts of digital content and providing personalized recommendations; however, their effectiveness is often hindered by data sparsity, where limited user-item interactions lead to reduced prediction accuracy. This study introduces a novel hybrid model, Optimization Hybrid Weighted Switching Filtering (OHWSF), to overcome this challenge by integrating two complementary strategies: Hybrid Weighted Filtering (HWF), which linearly combines predictions from SVD and SVD++ using a weighting parameter (α), and Hybrid Switching Filtering (HSF), which dynamically selects predictions based on a threshold rating (θ). The OHWSF framework introduces a tunable optimization mechanism governed by the parameter σ₁ to adaptively balance weighting and switching decisions based on actual rating deviations. Unlike existing static or manually tuned hybrid methods, the proposed model combines dynamic switching with weight optimization to minimize prediction error effectively. Extensive experiments on four benchmark datasets (ML-100K, ML-1M, Amazon Cell Phones Reviews, and GoodBooks-10K) demonstrate that OHWSF consistently outperforms traditional collaborative filtering (UBCF, IBCF), matrix factorization techniques (SVD, SVD++), and standalone hybrid models across all evaluation metrics (MAE, MSE, RMSE). The model achieves optimal performance within the range of α = 0.6–0.9 and θ = 1.0–1.5, demonstrating robustness across varying sparsity levels. Notably, OHWSF achieves up to 742.16% MAE improvement over the UBCF model, with significantly reduced training time compared to SVD++. These findings confirm that OHWSF significantly improves prediction accuracy, scalability, and adaptability in sparse data environments. This research contributes a flexible, interpretable, and efficient hybrid recommendation framework suitable for real-world applications.

Mangrove Sari Tourism Village is an ecotourism community located in Brebes Regency, Central Java, Indonesia. The establishment of this tourist village originated from the collective effort of the Pandansari Hamlet community to combat coastal erosion by planting mangrove, eventually transforming the area into the tourist destination. The objective of this study was to assess the capacity of the local community in developing community-based ecotourism and leveraging the ecosystem services of the mangrove forest. To achieve this objective, a qualitative descriptive method was employed, encompassing various research techniques such as observation, semi-structured interviews, documentation, and literature review. The study’s finding revealed the following key point: (1) The local community exhibited significant potential (with a score of 34) for the development of Mangrove Sari ecotourism, as assessed based on the parameters of attractions, activities, accessibility, and amenities. (2) The resident of Kaliwlingi Village has actively embraced the concept of community-based ecotourism in managing Mangrove Sari, emphasizing the involvement and participation of the local community. (3) The existence of the mangrove forest ecosystem in Pandansari Hamlet has provided both physical and social environmental services to the community, falling into four categories: service provisioning, regulating, cultural, and supporting services.

An increase in the operating temperature of photovoltaic (PV) panels caused by high levels of solar irradiation can affect the efficiency and lifespan of PV panels. This study uses numerical and experimental analyses to investigate the reduction in the operating temperature of PV panels with an air-cooled heat sink. The proposed heat sink was designed as an aluminum plate with perforated fins that is attached to the back of the PV panel. A comprehensive computational fluid dynamics (CFD) simulation was conducted using the software ANSYS Fluent to ensure that the heat sink model worked properly. The influence of heat sinks on the heat transfer between a PV panel and the circulating ambient air was investigated. The results showed a substantial decrease in the operating temperature of the PV panel and an increase in its electrical performance. The CFD analysis in the heat sink model with an air flow velocity of 1.5 m/s and temperature of 35°C under a heat flux of 1000 W/m2 showed a decrease in the PV panel’s average temperature from 85.3°C to 72.8°C. As a consequence of decreasing its temperature, the heat sink increased the open-circuit photovoltage (VOC) and maximum power point (PMPP) of the PV panel by 10% and 18.67%, respectively. Therefore, the use of aluminum heat sinks could provide a potential solution to prevent PV panels from overheating and may indirectly lead to a reduction in CO2 emissions due to the increased electricity production from the PV system.

Land management, especially land that is not in accordance with the rules can cause damage/change in soil properties which in turn impacts the disruption of biomass production. The lack of available data regarding soil degradation, especially in Tanjungpinang City, has resulted in less than optimal supervision and control over land management. Mapping the condition of soil degradation is necessary to exercise control over land management. The purpose of this research is to assess soil degradation in Tanjungpinang City, Riau Archipelago for biomass production. Soil degradation can be modeled by scoring and overlaying four parameters, namely land use, slope, soil type, and rainfall, producing a tentative map of potential soil degradation. Next, a tentative map of soil degradation is corrected using a field survey. Field surveys are used to measure the standard criteria for soil degradation according to Government Regulation No. 150 of 2000. The results show that the criteria for soil degradation in Tanjungpinang City are light damage and moderate damage. The criteria for moderate damage have the largest area spread over Dompak Sub-District, Batu Sembilan, Melayu City Plate, Bukit Cermin, West Tanjungpinang, East Tanjungpinang, Kampung Baru, and Tanjung Ayun Sakti. The main limiting factors that limit land use in Tanjungpinang City are permeability, surface rocks, and redox.

DKI Jakarta, the capital city of Indonesia, as the center of growth and development has a high population. The high population has an impact on land use change in an effort to fulfill housing which directly impacts the increase in building density or Normalized Diffrence Built-up Index (NDBI). The purpose of this research is to analyze the rate of land subsidence in DKI Jakarta and analyze the effect of building density on land subsidence. The impact of high growth rates creates the potential for natural and anthropogenic disasters. This research uses the Differential Inferometry Synthetic Aperarure Radar (DinSAR) method, in observing land subsidence with accuracy reaching cm units. The data used in this research is Sentinel 1A image with observation time in 2018, 2020, and 2023. The results showed that land subsidence in DKI Jakarta was dominated in the North Jakarta area, the highest land subsidence value reached -26.08 cm/year. The fastest land subsidence occurs in densely populated areas prone to flooding. The correlation results show that there is no relationship between the high level of building density and land subsidence.

The watershed has many functions related to ecosystem protection. The existence of vegetation in the watershed can absorb some carbon from the atmosphere through photosynthesis. In fact, this carbon sequestration potential is declining due to vegetated land conversion phenomena. Therefore, monitoring carbon sequestration in this area needs to be done. However, it faces a problem due to the large size of the watershed area in a tropical region, so carbon sequestration cannot be measured by field-measurement. By combining RS and GIS, the carbon sequestration in a large watershed can be measured frequently to solve the problem. This research aims to analyze the dynamic change of carbon sequestration in Upper Bengawan Solo from 2000 until 2020. In this research, carbon sequestration was modelled using the Net Primary Productivity (NPP). NPP was measured by using the CASA method used Landsat Imagery and Meteorological Data from Meteorological Agency of Indonesia (BMKG). The results show that the carbon sequestration in Upper Bengawan Solo over 20 years decreased. The most significant decrease happens in the sub-urban area surrounding the urban area in Surakarta city. It indicates an environmental change in this watershed due to physical or human interference during this period. Meanwhile, by using RS and GIS, the spatial distribution of carbon sequestration change can be known, so it can be used to pinpoint the location which needs prior attention based on the higher level of these changes. This research implies that combining RS and GIS can help carbon sequestration monitoring be quicker and cost-limited.

The research documented here aims to clarify the transport and fate of carbon species that evolved in a typical conical karst system in Gunungsewu. Special interest is attributed to the estimate of carbon flux by considering the conical karst as a whole system. It includes carbon input to karst area, soil respiration, SOC, soil CO2, particulate-dissolved and organic carbon, as well as dissolved organic carbon. The research was conducted between 2012 and 2015. Two study sites were selected to represent different morphological and hydrogeological settings. Carbon input was collected for one year round on the basis of conical hill topo-sequence. Carbon input included in this research was litter fall, plant residue, and organic fertilizer. Incorporated with field measurement, soil samples were also collected for SOC estimation. DIC and DOC were estimated from the underground river of Gilap. The results show that carbon flux in the Gunungsewu karst is favored by the agricultural land uses and practices. Accordingly, the organic carbon input to the karst area is governed by spatial distribution of agricultural land uses and practices. Organic carbon input tends to be in the order of organic fertilizer > litter input > and plant residue. Soil CO2 varies in depth and season. Soil organic carbon also varies seasonally, of which the higher content occurs in the rainy season. Most of the carbon is stored as SOC, 20 % is emitted to the atmosphere through soil respiration, and 9 % is transferred to the deeper zone through a hydrological cycle in the form of dissolved organic carbon and particulate-dissolved organic carbon. The results suggest that carbon sink in the karst area is ten order higher than that previously estimated from DIC.Key words: soil organic carbon, carbon flux, Gunungsewu, Java, karst carbon sink.

In practice, there is mixed data which is a combination of continuous and discrete variables. [...]to simplify the study it is assumed that all variables are discrete in order to solve practical problems in the implementation of theory. Since the sixteenth century [1], probability theory has been used to measure uncertainty and to assist in decision making. The data in this study consist of continuous variables (E, P, and F) and discrete variables (C, S, L, and D). Since we use the assumption that all discrete variables, we will discretize data on all continuous variables by means of the K-Means clustering method. First Edition.

Biduk-Biduk Karst Region has great potential to absorb and store organic carbon in vegetation and soil as well as to absorb inorganic carbon through the process of dissolution. The area has important economic value in supporting the REDD Program in Berau District. The purpose of this study is (1) to identify the amount of carbon stocks in various ecosystems; and (2) to identify the amount of carbon uptake in various ecosystems in the study area. Carbon stocks are computed based on four carbon sinks, i.e., above ground biomass, underground biomass, litter, and soil organic matter using the standard measurement method of SNI 7724: 2011. Carbon sequestration is calculated based on the input of carbon from the atmosphere to ecosystems through litter fall and karstification process and the output of carbon from the ecosystem to the atmosphere through soil respiration. Litter fall is measured using the litter trap method. Karstification is measured with standard limestone tablet method. Soil respiration is calculated with the closed chamber method. The results show that the ecosystems in the Biduk-Biduk Karst Region have a potential carbon stock of 4,800.92 tons/ha with the largest value in the secondary tropical forest of 732.6 tons/ha and the lowest value in the teak forest plantation of 358.2 tons/ha. Ecosystems in the Biduk-Biduk Karst Region have a potential carbon sequestration of 37.33 tons/ha/year with the largest contribution in the primary tropical forest of 7,63 tons/ha/year.

The Darrieus H-Rotor turbine is a vertical-axis wind turbine designed to capture wind from various directions. This research aims to enhance the performance of the Darrieus H-Rotor turbine by adding passive control devices, specifically Vortex Generators (VGs). Computational Fluid Dynamics (CFD) methodology, using the ANSYS Fluent, is employed to calculate and analyze airflow contours in the turbine area. The turbine’s performance is assessed by it’s power coefficient (Cp). Using a trapezoid counter-rotating configuration, VGs are applied at 10%, 15%, and 20% chord length variations from each blade’s leading edge. The research findings indicate that the optimal position for the VGs is at 15% chord length, which results in the highest Cp value of 0.230 at a Tip Speed Ratio (TSR) of 1.25. Additionally, the average Cp is increased by 17% compared to the averages calculated at TSR values at 0.5, 0.75, 1.0, 1.25, and 1.5, with a variation of 10% variation.