Engineering Science & Technology

Design and Economic Analysis of a Rooftop Photovoltaic Power Generation System for an Educational Institution in Bangladesh

Mingbo Niu — 2026-03-30

The increasing energy demand driven by population growth and urbanization in Bangladesh is primarily met through imported fossil fuels, which raises economic and environmental concerns. Rooftop Photovoltaic (PV) systems provide a sustainable solution to ensure a reliable power supply and reduce disruptions to academic activities caused by frequent power outages. This study offers the design and cost analysis of a rooftop PV power system for Bangladesh's Dhaka High School, with the goal of addressing the school's energy difficulties caused by frequent power outages. The system, which consists of a 4.8 kWp monocrystalline silicon PV array, is intended to meet the school's annual electricity demand of 17,547 kWh. The economic study shows that the installation cost is $ 14,550, which may be reduced to $ 11,640 with a 20% subsidy, lowering energy production costs from $ 0.829/kWh to $ 0.66/kWh. The system has a payback period of 8.5 years and an Return on Investment (ROI) of 86%. The study indicates the viability of incorporating renewable energy solutions into schools, resulting in long-term cost savings and environmental benefits. The findings emphasize the system's potential to reduce reliance on fossil fuels and promote sustainability, serving as a model for other educational institutions in Bangladesh and similar countries.

Toward a Cognitive Model for Group Recommender Systems

Mojdeh Morshedi — 2026-05-25

In the contemporary world, the abundance of data and the growing number of users in virtual environments have led to a focus on classifying data and grouping users to create recommendation lists that enhance user experiences. While existing research has explored various methods in developing group recommender systems, the role of incoming flows and their impacts in the decision-making process of joining a group has been largely overlooked. This study, drawing on cognitive theories, aims to examine user behavior in decision-making and group assignment. Through the mapping of users' interactions in complex dynamic networks, users are categorized based on their incoming interactions. A key feature of this study is its consideration of users belonging to multiple groups simultaneously, with each group’s behavioral profile being delineated accordingly. The proposed method simulates real-world decision-making processes to provide tailored recommendations for each individual. The effectiveness of our approach is assessed using four datasets.

Evaluation of Water Quality by Means of Probabilistic Multi-Objective Optimization

Maosheng Zheng — 2026-02-06

Water quality assessment is a problem in a complex multi-attribute system, and rational approach is still in need for comprehensive evaluation. In this article, a Probabilistic Multi-Objective Optimization (PMOO) evaluation approach for water quality assessment is presented rationally. Firstly, it proposes a quantitative evaluation method of the utility value of each evaluated attribute (indicator), the integration of the utility value with the probabilistic multi-objective optimization is conducted to complete the evaluation and comparison of water quality evaluation comprehensively with a practical example from 7 sampling points of Jinchang city of Gansu province, China, to illuminate the procedure of the approach. Six performance metrics are involved, which include total salinity, total hardness, nitrite, nitrate, phenol, and hexavalent chromium. The evaluated result indicates that the sampling point 1 exhibits the highest total preferable probability and is ranked No. 1 in the comprehensive assessment of quality of water resources by means of PMOO. The proposed approach eliminates the human factors in the previous assessments for comprehensive evaluation with multiple performance metrics.

Direct and Inverse Problems of the Theory of Energy Motion in Hydrodynamics

Sergei Sokolov — 2026-03-31

This paper compares two approaches to implementing the Theory of Energy Motion in a medium such as a liquid. The first approach derives the laws of energy motion from the hydrodynamic equations. The second assumes that the equations of liquid motion can be obtained if the experimentally established characteristics of energy motion are known. An approach for conducting the relevant experiments is proposed. The feasibility arises from observing liquid behavior relative to a state of stable equilibrium. A thought experiment considering the propagation of mechanical energy in an infinite channel was based on an analysis of known experiments. It was found that the energy flow occurred as a wave transfer, and the associated fluid movement occurred as a wave. The conclusions drawn from the two approaches differ regarding the convective form of energy motion. It is suggested that the theoretical existence of convective energy transport is a consequence due to the mathematical structure of the hydrodynamic equations. Based on the analysis of experiments, the observation supports the possibility of describing liquid motion in an alternative manner, not constrained by existing formulations. Several examples are presented to illustrate how Newton's laws may be observed in liquid behavior.

Build Orientation Dependent Dielectric Properties of 3D Printed PUAR/CuO/Graphite Composite Discs

Bhanu Prakash Bisht — 2026-06-17

Polyurethane acrylate resin discs with Copper Oxide (CuO) and Graphite fillers of different growth orientations from 0° to 90° are fabricated using Digital Light Processing (DLP) 3D printing technique to study their dielectric properties. Three different composites, Polyurethane Acrylate Resin (PUAR)/CuO (PUA-1), PUAR/CuO/ Graphite (PUA-2), and PUAR/Graphite (PUA-3), with 1 wt% total filler concentration, are prepared for the present study. X-Ray Diffraction (XRD) analysis of composites shows peaks, 2θ ~ 20.4° (PUAR), 35.4° and 38.6° (CuO), and 26.4° (graphite). Fourier Transform Infrared (FTIR) analysis reveals intensity reduction of C=O and C=C peaks, while the Raman spectrum shows a shift by 20 ± 5 cm^-1 in PUA-1, 2, and 3, confirming filler interaction with PUAR and phase modification due to polymer-filler interface. Thermo-gravimetric analysis indicates a strong interaction between the filler and the resin, especially for PUA-3, with degradation in two stages at 320 °C and 430 °C due to hard-and soft segment decomposition. Capacitance measurements at 100 kHz and 1 MHz indicate a higher dielectric constant for PUA-3 than for PUA-0, which decreases with increasing build orientation and reaches a minimum at 45°. Anisotropy due to the build and filler orientation is studied using space-charge polarization. The equivalent circuit for dependence on build orientation is understood in terms of capacitances due to fillers, represented by a Constant Phase Element (CPE), with both perpendicular and parallel components contributing to the composite disc's capacitance. With an increase in build orientation angle, the interfacial polarization decreases and so capacitance, CPE₀ >> CPE_x > CPE₉₀. Finite Element Analysis (FEA) further examines build orientation-dependent filler-resin interaction, and dielectric properties show dependence on both filler morphology and build angle. FEA highlights the role of orientation-dependent space charge distribution and Maxwell-Wagner-Sillars interfacial polarization, driven by filler morphology and alignment, in governing dielectric anisotropy. FEA corroborates the experimental observations, showing that space-charge accumulation at filler-matrix interfaces is maximal for 0° build orientation, where graphite flakes are perpendicular to the electric field, and minimal for 45°-90°.

Sustainable Swimming Pool Management Under Climate Stress: A Structured Review of Water-Energy Strategies in Europe

Athena Deligianni — 2026-04-16

The accelerating impacts of climate change-including intensifying heatwaves, recurrent droughts, and growing water scarcity-are placing increasing pressure on urban infrastructure, including recreational facilities such as swimming pools. The review considers both public and private swimming pool facilities, with particular relevance to urban and tourism-oriented pools that face increasing resource pressures under climate stress. While pools provide important public-health benefits by offering spaces for exercise, social interaction, and thermal relief, they are also highly water-and energy-intensive. This paper develops a conceptual framework for sustainable swimming pool management under climate stress, integrating the water-energy nexus, climate-resilient infrastructure, and sustainability transitions. A structured review of peer-reviewed literature published primarily between 2017 and 2026 (Google Scholar, GreenFILE, and PubMed) synthesizes technical, environmental, and policy evidence on water use, energy demand, and mitigation options in pool operations. The review predominantly draws on European case studies and policy contexts, reflecting climatic, regulatory, and infrastructural conditions common in Southern and Central Europe. The analysis shows that energy use-dominated by pool heating-represents the largest source of environmental impact, making renewable heating technologies such as solar thermal systems, photovoltaic-thermal collectors, and ground-source heat pumps among the most effective climate-mitigation measures. On the water side, backwash water recovery and reuse systems emerge as the single most powerful intervention, capable of reducing freshwater demand by up to 96% in well-designed systems, while low-cost efficiency devices provide essential baseline savings. By reframing swimming pools as adaptive urban infrastructures rather than discretionary amenities, the paper demonstrates how recreational water facilities can function as testbeds for integrated water-energy solutions, contributing to climate adaptation, resource efficiency, and long-term public-health resilience.

BIM Applications in Transportation Infrastructure: A Bibliometric and Systematic Literature Review

Khanh-Giang Le — 2026-04-24

This study presents a comprehensive bibliometric analysis combined with a Systematic Literature Review (SLR) to examine the global research landscape of Building Information Modeling (BIM) applications in transportation infrastructure. The motivation of this study arises from the increasing complexity of modern infrastructure systems, including railways, tunnels, bridges, roads, and airports, which require advanced digital solutions to address challenges related to interoperability, lifecycle management, and data integration. A total of 1,615 peer-reviewed articles published between 2010 and July 2025 were retrieved from the Scopus database. Bibliometric techniques, including keyword co-occurrence and citation analysis, were applied using Visualization of Similarities viewer (VOSviewer), followed by an in-depth systematic review of the most influential publications. The results indicate a substantial increase in research activity after 2018, with railway infrastructure emerging as a major application domain. Five principal thematic clusters are identified: Geographic Information Systems (GIS) integration, Digital Twins (DT), tunnel and bridge engineering, lifecycle sustainability, and smart monitoring technologies. Keyword evolution analysis further reveals a transition from design-oriented studies prior to 2020 toward asset management and digital intelligence after 2022. The study also identifies leading journals and key technologies shaping current research trends, while recent publications in 2025 demonstrate increasing attention to immersive DT, robotic manufacturing, and multi-criteria decision-making frameworks. This study contributes by systematically mapping the development of BIM knowledge in transportation infrastructure and identifying underexplored areas, particularly in operation and maintenance applications and regional disparities in research output. Limitations include the reliance on Scopus-indexed, English-language publications and the use of citation-based selection criteria, which may introduce bias toward older, highly cited studies. Despite these limitations, the findings provide valuable insights for researchers, practitioners, and policymakers seeking to align future efforts with ongoing digital transformation in transportation infrastructure.