1. Numerical solving of dynamic thermography inverse problem for skin cancer diagnosis based on non-Fourier bioheat modelIvan Dominik Horvat, Jurij Iljaž, 2025, izvirni znanstveni članek Opis: This paper presents numerical solving of the inverse bioheat problem to estimate four skin cancer parameters; diameter, thickness, blood perfusion rate and thermal relaxation time, based on the thermal response on the skin surface obtained by dynamic thermography and numerical skin cancer model, which can greatly enhance dynamic thermography diagnostics. To describe the heat transfer inside biological tissue and thermal behavior during the dynamic thermography process as realistic as possible, the non-Fourier dual-phase-lag bioheat model was used, as well as skin cancer model has been composed of multilayered healthy skin, embedded skin tumor and subcutaneous fat and muscle. Boundary element method has been used to solve a complex non-Fourier bioheat model to simulate dynamic thermography based on the skin cancer model and guessed searched parameters to obtain the thermal response on the skin surface during the cooling and rewarming phase using a cold air jet provocation, which is needed for the solution of the inverse bioheat problem. The inverse problem has been solved by optimization approach using the hybrid Levenberg-Marquardt optimization method, while the measurement data has been generated numerically with known exact tumor parameters and added noise, to evaluate the accuracy and sensitivity of the solution. Inverse problem solution has been tested for two different thermal responses; absolute temperature and temperature difference response, as well as for two different tumor stages; early stage or Clark II and later stage or Clark IV tumor. All important tumor parameters were successfully retrieved, especially the diameter and relaxation time, even for the high level of noise, while the accuracy of obtained parameters is slightly better using absolute temperature response. The results demonstrate the robustness of the method and a promising way for early diagnosis. The findings contribute to improving bioheat modeling in biological tissues, solving inverse bioheat problems and advancing dynamic thermography as a non-invasive tool for early skin cancer diagnosis.
Ključne besede: numerical modeling, dynamic thermography, inverse problem, non-Fourier bioheat transfer, dual-phase-lag model, boundary element method, Levenberg-Marquardt optimization
Objavljeno v DKUM: 09.12.2025; Ogledov: 0; Prenosov: 7
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2. Dynamic modeling and experimental validation of the photovoltaic/thermal systemKlemen Sredenšek, Eva Simonič, Klemen Deželak, Marko Bizjak, Niko Lukač, Sebastijan Seme, 2025, izvirni znanstveni članek Opis: The aim of this paper is to present a novel and comprehensive methodology for the dynamic modeling and experimental validation of a photovoltaic/thermal system. The dynamic model is divided into thermal and electrical subsystems, encompassing the photovoltaic/ thermal module and the thermal energy storage. The thermal subsystem of both the photovoltaic/thermal module and the thermal energy storage is described by a one-dimensional dynamic model of heat transfer mechanisms and optical losses, while the electrical subsystem is presented as an electrical equivalent circuit of double diode solar cell. Model validation was conducted on a modern experimental photovoltaic/thermal system over an extended operational period at a five-minute resolution, with validation days classified as sunny, cloudy, or overcast based on weather conditions, thereby demonstrating an applied approach. The results demonstrate the lowest deviation values reported to date, confirmed using six quantitative indicators. The added value of the proposed methodology, not previously addressed in the literature, lies in the following contributions: (i) comprehensive modeling of the entire photovoltaic/thermal system, (ii) accurate consideration of optical losses in the photovoltaic/thermal module, and (iii) long-term experimental validation. Overall, the proposed methodology provides a reliable and efficient framework for PV/T system design, optimization, and long-term performance assessment.
Ključne besede: photovoltaic/thermal system, thermal energy storage, dynamic modeling, experimental validation, heat transfer mechanism, temperature, electrical power
Objavljeno v DKUM: 10.11.2025; Ogledov: 0; Prenosov: 13
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3. Numerical modeling of non-Fourier bioheat transfer in multilayer biological tissue using BEM to simulate dynamic thermography in skin tumor diagnosticsIvan Dominik Horvat, Jurij Iljaž, 2025, izvirni znanstveni članek Opis: This paper presents a novel approach for modeling non-Fourier dual-phase-lag bioheat transfer in multilayer biological tissue, aimed at simulating dynamic thermography for the early detection of skin tumors at Clark II and IV stages. The proposed algorithm, based on the boundary element method, enables the assignment of distinct thermophysical properties and non-Fourier relaxation time parameters to each tissue layer, thereby enhancing the realism of bioheat transfer modeling. Results show that accounting for non-Fourier effects significantly impacts the transient thermal contrast between tumor and healthy skin, particularly in Clark IV tumors and at higher relaxation times. These findings support the development of more accurate and physiologically realistic models of heat transfer in complex biological structures, and advance the application of dynamic thermography in early skin tumor detection and the diagnosis of other dermatological conditions.
Ključne besede: numerical modeling, non-Fourier heat transfer, bioheat transfer, dual-phase-lag model, boundary element method, dynamic thermography
Objavljeno v DKUM: 03.11.2025; Ogledov: 0; Prenosov: 7
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4. Experimental validation of a dynamic photovoltaic/thermal collector model in combination with a thermal energy storage tankKlemen Sredenšek, Sebastijan Seme, Bojan Štumberger, Miralem Hadžiselimović, Amor Chowdhury, Zdravko Praunseis, 2021, izvirni znanstveni članek Opis: The primary objective of this paper is to present a dynamic photovoltaic/thermal collector model in combination with a thermal energy storage tank. The added value of the proposed model is the use and integration of existing dynamic models for describing the entire photovoltaic/thermal system. The presented model was validated using measurements on the experimental system located at the Institute of Energy Technology, Faculty of Energy Technology, University of Maribor. The validation was carried out based on three different weather conditions—sunny, cloudy, and overcast. The validation results were evaluated using the normalized root mean square error and mean absolute percentage error for the temperature and output power of the photovoltaic/thermal collector and the temperature of the thermal energy storage tank. The model results concurred with the measurements, as the average mean absolute percentage error values for the temperature and output power of the photovoltaic/thermal collector and thermal energy storage tank temperature were 5.82%, 1.51%, and 7.58% respectively.
Ključne besede: photovoltaic/thermal collector, thermal energy storage tank, dynamic modeling, temperature distribution, output power
Objavljeno v DKUM: 13.11.2023; Ogledov: 318; Prenosov: 42
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5. Experimental validation of a thermo-electric model of the photovoltaic module under outdoor conditionsKlemen Sredenšek, Bojan Štumberger, Miralem Hadžiselimović, Sebastijan Seme, Klemen Deželak, 2021, izvirni znanstveni članek Opis: An operating temperature of the photovoltaic (PV) module greatly affects performance and its lifetime. Therefore, it is essential to evaluate operating temperature of the photovoltaic module in different weather conditions and how it affects its performance. The primary objective of this paper is to present a dynamic thermo-electric model for determining the temperature and output power of the photovoltaic module. The presented model is validated with field measurement at the Institute of Energy Technology, Faculty of Energy Technology, University of Maribor, Slovenia. The presented model was compared with other models in different weather conditions, such as clear, cloudy and overcast. The evaluation was performed for the operating temperature and output power of the photovoltaic module using Root-Mean-Square-Error (RMSE) and Mean-Absolute-Error (MAE). The average RMSE and MAE values are 1.75C and 1.14C for the thermal part and 20.34 W and 10.97 W for the electrical part.
Ključne besede: dynamic modeling, thermo-electric model, accuracy, measuring device, temperature, output power, PV module
Objavljeno v DKUM: 13.11.2023; Ogledov: 380; Prenosov: 464
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6. Understanding the structural complexity of induced travel demand in decision-making : a system dynamics approachJuan Angarita-Zapata, Jorge Parra-Valencia, Hugo Andrade-Sosa, 2016, izvirni znanstveni članek Opis: Background and purpose: Induced travel demand (ITD) is a phenomenon where road construction increases vehicles’ kilometers traveled. It has been approached with econometric models that use elasticities as measure to estimate how much travel demand can be induced by new roads. However, there is a lack of “white-box” models with causal hypotheses that explain the structural complexity underlying this phenomenon. We propose a system dynamics model based on a feedback mechanism to explain structurally ITD.
Methodology: A system dynamics methodology was selected to model and simulate ITD. First, a causal loop diagram is proposed to describe the ITD structure in terms of feedback loops. Then a stock-flows diagram is formulated to allow computer simulation. Finally, simulations are run to show the quantitative temporal evolution of the model built.
Results: The simulation results show how new roads in the short term induce more kilometers traveled by vehicles already in use; meanwhile, in the medium-term, new traffic is generated. These new car drivers appear when better flow conditions coming from new roads increase attractiveness of car use. More cars added to vehicles already in use produce new traffic congestion, and high travel speeds provided by roads built are absorbed by ITD effects.
Conclusion: We concluded that approaching ITD with a systemic perspective allows for identifying leverage points that contribute to design comprehensive policies aimed to cope with ITD. In this sense, the model supports decision- making processes in urban contexts wherein it is still necessary for road construction to guarantee connectivity, such as the case of developing countries.
Ključne besede: induced travel demand, system dynamics, decision-making, dynamic modeling
Objavljeno v DKUM: 23.01.2018; Ogledov: 1477; Prenosov: 212
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