Technical University of Sofia

Performance Boundaries of Hybrid Photovoltaic–Battery Inverters Under Dynamic, Unbalanced, and Grid Disturbance Conditions

Hybrid photovoltaic (PV)–battery inverters are increasingly required to provide functions extending beyond conventional energy conversion, including zero-export operation, battery coordination, grid support, and backup supply. However, rated power and peak efficiency alone do not...

Validation of Commercial Wearables for Driver Monitoring: Assessing Heart Rate Accuracy and Reliability for Early Detection of Sudden Illnesses

Sudden medical illnesses (SMI), including myocardial infarctions and occult arrhythmias, represent a primary etiology of catastrophic motor vehicle collisions. Although consumer wearable technologies provide a non-invasive modality for continuous driver monitoring, their measurem...

Physics-Informed Explainable Machine Learning for Hybrid State of Health and Remaining Useful Life Estimation of Lithium-Ion Batteries

Accurate health assessment is essential for the reliable and cost-effective operation of lithium-ion battery energy storage systems. This study presents a physics-informed explainable machine-learning framework for hybrid State-of-Health (SoH) estimation and Remaining Useful Life...

Extraction dataset, risk-of-bias assessments and analysis code for Incremental value of integrating histopathology with omics for prediction in non-small-cell lung cancer: a systematic review and meta-analysis

This record contains the data and code supporting the systematic review and meta-analysis "Incremental value of integrating histopathology with omics for prediction in non-small-cell lung cancer: a systematic review and meta-analysis" (submitted to Briefings in Bioinformatics). T...

From ESG Commitment to Sustainable Construction Practices: Evidence from an Emerging European Market

This study examines the relationship between ESG integration and sustainable construction practices in the Bulgarian construction sector. The analysis is based on 143 valid responses from representatives of construction companies operating in Bulgaria. The study employed descript...

Digital Twins for Nuclear Reactor Monitoring and Operational Intelligence: A Systematic Scoping Review

Digital twins (DTs) are increasingly proposed for nuclear-reactor monitoring, diagnosis, prediction, control, and decision support, but the maturity of reported systems is difficult to compare because DT realization, physical anchoring, synchronization, adaptation, validation, re...

A Two-Stage Framework for Sports Betting Asset Construction: Probabilistic Prediction and Risk-Aware Portfolio Allocation

This manuscript presents a two-stage framework that treats sports betting markets as an alternative asset class, coupling probabilistic prediction with risk-aware portfolio allocation. The first stage produces calibrated probabilistic forecasts of match outcomes using heterogeneo...

Evidence-Grounded Runtime Assurance for AI-Assisted Power-Electronics Design: Three-State Constraint Semantics and Deterministic Validation

AI-assisted engineering workflows can assign stronger validity claims than their evidence supports. This study develops an executable evidence contract for preliminary power-electronics design by instantiating established multi-valued monitoring. A deterministic monitor checks in...

Effect of Ethanol Extract of Propolis on Paper Packaging Material

Propolis is a natural, accessible, and valuable bee product belonging to the group of so-called bioproducts. Its composition varies significantly depending on a number of factors, resulting in a wide range of data. The aim of this work is to investigate the antimicrobial effect o...

LEADI: Operating-Mode-Aware Machine Condition Monitoring for Leak-Related Energy Anomalies—A Before-and-After Maintenance Study of a Single Production Asset

Compressed-air leaks create persistent parasitic demand, but machine-level condition monitoring is difficult because air consumption changes strongly with operating mode. LEADI (Leak Energy Anomaly Detection Index) was developed as an operating-mode-aware procedure that evaluates...

Surface Roughness Estimation from Internal Spindle Torque During Side Milling of Invar 36

Surface roughness is a key quality characteristic in machining Invar 36 components used in dimensionally stable applications. This study evaluates the effects of cutting parameters on surface roughness and internal spindle torque during peripheral side milling of annealed Invar 3...

Structure–Property Relationships of Tungsten Nitride Coatings on Copper Substrates Prepared by Reactive Direct Current Magnetron Sputtering

Tungsten nitride (WN) coatings were deposited on copper substrates by reactive direct current magnetron sputtering using deposition times of 15, 30, 45, and 60 min. The influence of deposition time on the structural, morphological, and electrical properties of the coatings was sy...

Intelligent Forecasting of Smart Home Energy Consumption and Generation Based on Weather Variables

The growing adoption of artificial intelligence (AI) aims to improve global standards of living. However, this trend is accompanied by an increasing demand for energy. AI is rapidly integrating into home energy management systems (HEMS). While numerous artificial neural network (...

Experimental Study and Simplified Modelling of 1 kW Proton Exchange Membrane Fuel Cell for Mobile and Stationary Hybrid Systems Optimization

The conversion of hydrogen into electricity is a subject of intense interest. Various technologies are available at laboratory level, but in industrial applications, the most established of them is the proton exchange membrane-based fuel cell. This increased interest, combined wi...

Heat Pumps in Green Hydrogen Production Systems: A Technical Review

Green hydrogen production through water electrolysis is a key pathway to the decarbonization of future energy systems. However, part of the electrical input is transformed into waste heat. In this study, alkaline, proton-exchange membrane, anion-exchange membrane, and solid oxide...

Symmetry-Aware Simulation and Modeling of Noise-Robust Electric Load Forecasting Using Hybrid MMPF-NARX and GA/PSO

Reliable electric load forecasting is an important engineering problem for power-system planning, grid stability, and mission-critical energy management. This paper presents a symmetry-aware simulation and modeling framework for medium-range electric load forecasting under noisy...

Performance Analysis of Q-Learning; DQN-Enhanced PID Controllers for Aircraft Trajectory Tracking Under Wind Disturbances

Traditional fixed-gain proportional–integral–derivative (PID) controllers often exhibit limited adaptability when regulating the longitudinal motion of passenger aircraft under varying flight conditions and external disturbances. This study proposes an adaptive control framework...

Reimagining digital literacy and virtual identity in the Age of AI” - Special Collection Editorial

This special collection reflects on the need to reimagine teaching and learning spaces in the age of artificial intelligence (AI). Understanding digital literacy and virtual identity is essential to engaging with our contemporary society, which is defined by the fast pace of soci...

Non-Compensatory Security and Utility Gates for Blockchain Lifecycle Assessment: Framework Development and an Operational-Energy Application to the Ethereum Merge

Environmental comparisons of blockchain systems are often reduced to electricity per transaction, although operational services also depend on validators, cloud gateways, storage, monitoring, key management, recovery, and hardware replacement. This study develops a lifecycle asse...

Taylor Recurrences and Coulomb-Corrected Asymptotics for the Schrödinger–Newton Ground State

We study the positive, radial ground-state profile of the stationary Schrödinger–Newton system in the fixed-energy normalization μ=1 with V(∞)=0. Using regularity and radial symmetry of solutions, we derive convergent even Taylor expansions for the wave function and Newtonian pot...