European Journal of Sustainable Development Research

K-Nearest Neighbors as a Transparent Baseline for Automated EEG Sleep Staging

Ahmet Sertol Köksal — 2025-12-31

Sleep staging plays a key role in evaluating sleep health, but manually annotating polysomnography data is both time-consuming and prone to inconsistencies. This study presents the first comprehensive baseline evaluation of the K-Nearest Neighbors algorithm for EEG-based sleep staging, using a nested subject-wise cross-validation approach. We assessed 24 configurations combining six data scalers and four distance metrics on the ISRUC dataset. Overall, KNN delivered stable performance, with macro-F1 scores between 0.59 and 0.62 and Cohen’s κ ranging from 0.55 to 0.57. Among scalers, the Normalizer consistently performed the worst (macro-F1≈0.52), while Power transform, Standard, and Quantile scalers produced more reliable outcomes. The choice of distance metric had a relatively minor impact, but Euclidean distance offered the best trade-off—slightly improving accuracy while delivering runtimes up to five times faster than Cosine. Hyperparameter tuning consistently favored k ≈ 30 with distance weighting, indicating that extensive parameter searches may not be necessary. At the individual class level, Wake (F1≈0.79) and N3 (F1≈0.82) stages were identified with high accuracy, whereas N2 (F1≈0.68) was moderately accurate. REM (F1≈0.56) and particularly N1 (F1≈0.27) remained difficult to classify, though some setups improved performance by up to 8%. In summary, while KNN does not match deep learning in raw accuracy, it provides valuable benefits in terms of transparency, reproducibility, and interpretability. We recommend using Euclidean distance, k≈30 with distance weighting, and avoiding the Normalizer as a practical and interpretable baseline for future EEG-based sleep analysis.

Proposal for a World Energy Stock Balance Sheet

Michael Bosch — 2025-12-31

Considering the sharp increase in global energy demand, the question arises whether worldwide energy resources will be sufficient to cover humankind's future energy requirements (including energy for food requirements). In addition to the urgent built up of renewable energy systems, energy-intensive processes to prevent greenhouse gases from being released into the atmosphere (Carbon Capture and Storage, CCS) or removed from there (Carbon Dioxide Removal, CDR, in particular Direct Air Capture, DAC) are required to meet the climate targets. On the basis of a comprehensive analysis of existing Systems of Environmental Economic Accounting (SEEA) and the International Recommendations for Energy Statistics (IRES), a proposal for a World Energy Stock Balance Sheet (WESBS) consistent with these systems was developed. The principle of prudent valuation, borrowed from business accounting, was also applied, which requires the inclusion of energy consumption for CCS and DAC. The assets side of the WESBS shows all fossil and renewable primary, secondary and final energy sources at the balance sheet date prudently valued with the energy unit Peta Joule (PJ). Provisions for the energy losses in PJ that would arise when the capitalized primary, secondary and final energy stocks are converted into useful energy are shown on the liability side of the WESBS, as well as provisions for the energy consumption for CCS and DAC. The respective energy consumption is calculated by first applying Life Cycle Assessment (LCA) emission factors to calculate the greenhouse gas emissions and thereafter using LCA energy consumption factors of CCS or DAC. The difference between energy assets and energy liabilities results in the energy equity in PJ, which is available for the future useful energy demand of humankind under the precondition that the climate targets are met. This paper explains the items of the proposed WESBS and the developed valuation methods in appropriate detail.

Enhancing Thermal Efficiency of Panel Radiators Through Turbulence-Inducing Modifications in Water Channels

Umut Ucak — 2025-12-31

This study aims to improve the thermal efficiency of panel radiators, which are widely used in building heating systems. By promoting turbulent flow inside the water channels, heat transfer can be increased without raising energy use. In the modified design, small 90° rectangular blocks (5 mm wide and 10 mm long) are added inside the vertical channels to create turbulence. This design distinguishes itself from other methods by creating turbulence through indentations in the sheet metal that forms the channel, rather than using additional turbulators such as twisted tape inserts or wire coil inserts. This unique strategy not only boosts heat transfer performance but also leads to energy savings, reduced emissions, and more efficient heating in both residential and commercial buildings. With the modified design, due to increased friction, the pressure rise shows a 1.36% increase compared to the current design. Meanwhile, the temperature of the water circulating in the panel radiator channels has decreased further compared to the current design, resulting in a 1.21% increase in ΔT. This indicates that the modified design transfers more heat from the water to the environment, causing the water's outlet temperature to drop more significantly. Additionally, with the modified design, the water contact surface area has decreased by 0.64 m², while the water heat flux has increased by approximately 25% compared to the current design. The higher heat flux achieved with a smaller water contact surface area demonstrates the efficiency of the system compared to the existing design.

Comparative Analysis of Energy Footprints of Traditional and Green Building Materials: Towards the Net Zero Construction Goal

Ayse Arici — 2025-12-31

Globally, the construction sector is one of the most critical industries regarding environmental sustainability due to its high energy consumption and resulting carbon emissions. This study aims to reveal the energy footprint differences between traditional and green building materials, in line with the goal of "net-zero construction," by examining building materials' embodied energy and operational energy components throughout their life cycle, from production to end-of-use.

The research collected data on production, procurement, and application processes through a Likert-type survey administered to 180 construction material manufacturers and suppliers operating in Turkey. The data were evaluated using factor analysis and multivariate regression models, and a life cycle assessment (LCA) was also conducted for three material categories: conventional binders, sustainable alternatives, and hybrid systems.

The results show that green materials consume an average of 28% less total energy during production than conventional systems. Bio-based binders, in particular, reduce maintenance requirements, resulting in long-term energy savings. However, high production costs and limited supply infrastructure slow down the transition to sustainable materials. The research demonstrates that the widespread adoption of green materials depends on technological innovation, policy incentives, standardization, and cross-sector collaboration.

Microstructural Strength Properties and Energy Efficiency of Concrete Elements Produced with 3D Printing Technology

Ayse Arici — 2025-12-31

This study comprehensively examines the effects of three-dimensional (3D) concrete printing systems, one of the most innovative applications of digital manufacturing technologies in the construction industry, on the material's microstructural strength properties and energy efficiency. The study compared laboratory-scale 3D-printed concrete samples with control groups prepared using the traditional mold casting method, and analyzed the effects of printing direction (0°, 45°, 90°), nozzle speed, and layer thickness on microporosity, density, compressive strength, and thermal conductivity.

The data obtained revealed that concrete produced with 3D printing exhibited compressive strength changes of 12–20% depending on the layer orientation and increased energy efficiency by up to 18%. SEM (Scanning Electron Microscopy) and Micro-CT (Micro-Computed Tomography) analyses demonstrated that the oriented pore structure between layers improves thermal insulation performance by reducing the material's heat transfer coefficient. Furthermore, printing direction and nozzle speed were determined to influence microcrack formation and pore continuity.

In conclusion, the interaction between microstructure and energy efficiency in concrete elements produced with 3D printing technology demonstrates that digital manufacturing represents a formal and material-based revolution in sustainable building production. This technology offers a new paradigm focused on material optimization and energy savings in future structural engineering.