TY - JOUR AU - Hosszú, Gábor László TI - Validation of graph sequence clusters through multivariate analysis: application to Rovash scripts JF - HERITAGE SCIENCE J2 - HERIT SCI VL - 12 PY - 2024 IS - 1 PG - 18 SN - 2050-7445 DO - 10.1186/s40494-024-01211-7 UR - https://m2.mtmt.hu/api/publication/34773845 ID - 34773845 N1 - Export Date: 12 April 2024 Correspondence Address: Hosszú, G.; Department of Electron Devices, Hungary; email: hosszu.gabor@vik.bme.hu AB - This paper introduces the concept of pattern systems that evolve, with a focus on scripts, a specific type of pattern system. The study analyses the development of different script systems, known as scriptinformatics, with a focus on the historical Rovash scripts used in the Eurasian steppe. The aim is to assess the traditional classification of historical inscriptions, referred to as script relics, into distinct Rovash scripts. Clustering and ordination techniques were used to perform multivariate analyses on Rovash scripts and inscriptions. The study presents two new measures, the script-specific holophyletic index and the joint holophyletic index, for evaluating trees produced by hierarchical clustering. The results indicate that holophyletic indices can validate the traditional assignment of inscriptions to scripts through phylogenetic tree evaluation. This method can be extended to include pattern systems with evolutionary properties and graph sequences derived from them, as well as additional scripts and inscriptions. LA - English DB - MTMT ER - TY - JOUR AU - Harsányi, Gábor AU - Poppe, András AU - Hegedüs, János AU - Hantos, Gusztáv AU - Bojta, Péter AU - Kovacs, Robert TI - Climatically Accelerated Material Processes Determining the Long-Term Reliability of Light-Emitting Diodes JF - MATERIALS J2 - MATERIALS VL - 17 PY - 2024 IS - 7 SP - 1643 SN - 1996-1944 DO - 10.3390/ma17071643 UR - https://m2.mtmt.hu/api/publication/34767534 ID - 34767534 AB - LEDs (Light-Emitting Diodes) are widely applied not only in decorative illumination but also in everyday lighting in buildings, flats, public areas, and automotive fields. These application areas often mean harsh environments, for example, regarding the humidity content of the surrounding air: besides outdoor and automotive illumination, even the household use cases (kitchen, bathroom, cellar) may represent extreme temperature and humidity variations (often reaching relative humidity levels close to 100%) for these devices; thus, their reliability behaviour in such circumstances should be better understood. Thermally activated processes were studied in several previous publications, but less information is available regarding high-humidity environmental tests. Moisture and temperature ageing tests with appropriate environmental parameter settings were performed as accelerated lifetime tests to investigate not only the effect of temperature but also that of humidity on the ageing and reliability of LED packages containing RGB (red green blue) chips and phosphor-converted white (pcW) LEDs. The ageing was followed not only through monitoring optical/electrical/spectral parameters but also with material analysis. Moisture–material interaction models were proposed and set up. It was found that humidity-accelerated ageing processes are more severe than expected from previous assumptions. RGB and pcW LEDs showed strongly different behaviour. LA - English DB - MTMT ER - TY - JOUR AU - Darwish, Mahmoud Ibrahim Azmi AU - Pohl, László TI - Insulator Metal Transition-Based Selector in Crossbar Memory Arrays JF - ELECTRONIC MATERIALS J2 - ELECTRON MATER VL - 5 PY - 2024 IS - 1 SP - 17 EP - 29 PG - 13 SN - 2673-3978 DO - 10.3390/electronicmat5010002 UR - https://m2.mtmt.hu/api/publication/34681240 ID - 34681240 N1 - Export Date: 5 April 2024 Correspondence Address: Pohl, L.; Department of Electron Devices, Hungary; email: pohl.laszlo@vik.bme.hu AB - This article investigates resistive random access memory (ReRAM) crossbar memory arrays, which is a notable development in non-volatile memory technology. We highlight ReRAM’s competitive edge over NAND, NOR Flash, and phase-change memory (PCM), particularly in terms of endurance, speed, and energy efficiency. This paper focuses on the architecture of crossbar arrays, where memristive devices are positioned at intersecting metal wires. We emphasize the unique resistive switching mechanisms of memristors and the challenges of sneak path currents and delve into the roles and configurations of selectors, particularly focusing on the one-selector one-resistor (1S1R) architecture with an insulator–metal transition (IMT) based selector. We use SPICE simulations based on defined models to examine a 3 × 3 1S1R ReRAM array with vanadium dioxide selectors and titanium dioxide film memristors, assessing the impact of ambient temperature and critical IMT temperatures on array performance. We highlight the operational regions of low resistive state (LRS) and high resistive state (HRS), providing insights into the electrical behavior of these components under various conditions. Lastly, we demonstrate the impact of selector presence on sneak path currents. This research contributes to the overall understanding of ReRAM crossbar arrays integrated with IMT material-based selectors. LA - English DB - MTMT ER - TY - CHAP AU - Khafajy, Osama Ali Salman AU - Hosszú, Gábor László TI - Using distance-based methods to calculate optimal and suboptimal parsimony trees T2 - Proceedings of the Workshop on the Advances of Information Technology 2024 PB - BME Irányítástechnika és Informatika Tanszék CY - Budapest SN - 9789634219422 PY - 2024 SP - 79 EP - 84 PG - 6 UR - https://m2.mtmt.hu/api/publication/34572693 ID - 34572693 LA - English DB - MTMT ER - TY - JOUR AU - Hantos, Gusztáv TI - Karakterizáló és élettartamvizsgáló mérőkörnyezet LED-ek számára JF - ELEKTROTECHNIKA J2 - ELEKTROTECHNIKA VL - 116. PY - 2024 IS - 2023/11-12 SP - 35 EP - 39 PG - 5 SN - 0367-0708 UR - https://m2.mtmt.hu/api/publication/34551019 ID - 34551019 LA - Hungarian DB - MTMT ER - TY - CHAP AU - Poppe, András AU - Hantos, Gusztáv AU - Hegedüs, János AU - Ender, Ferenc TI - IMPLEMENTATION OF A HIGH-SPEED LED CHARACTERISATION SYSTEM T2 - CIE x050:2023 Proceedings of the 30th Session of the CIE, Ljubljana, Slovenia, September 15 – 23, 2023, Volume 1 PB - International Commission on Illumination, CIE SN - 9783902842770 PY - 2023 SP - 1060 EP - 1069 PG - 10 DO - 10.25039/x50.2023.PO057 UR - https://m2.mtmt.hu/api/publication/34689425 ID - 34689425 AB - The purpose of this paper is to provide an overview on the realization of the concept aimed at high throughput LED testing. The target was to achieve at least one order of magnitude decrease in the overall testing time spent on a single LED package. The main goal of the improved throughput of laboratory testing of LEDs facilitate that Delph4LED-style LED modelling becomes an industrial reality. The second overall objective is to assure, that isothermal IVL characterization of the LED packages being aged becomes a feasible option, thus making it possible to create the elapsed lifetime dependent multi-domain circuit simulation model of LEDs. LA - English DB - MTMT ER - TY - CHAP AU - Lipák, G. AU - Takács, D. AU - Hegedüs, János AU - Hantos, Gusztáv TI - MODELLING THE SPECTRAL POWER DISTRIBUTION OF MONOCHROMATIC AND PHOSPHOR-CONVERTED POWER LEDS T2 - CIE x050:2023 Proceedings of the 30th Session of the CIE, Ljubljana, Slovenia, September 15 – 23, 2023, Volume 1 PB - International Commission on Illumination, CIE SN - 9783902842770 PY - 2023 SP - 1168 EP - 1177 PG - 10 DO - 10.25039/x50.2023.PO103 UR - https://m2.mtmt.hu/api/publication/34689398 ID - 34689398 AB - The goal of our work is to prepare a generally usable spectral power distribution model that can be directly applied to the measurement results of LEDs. As a first step, the distribution functions found in the literature were examined based on our measurement results, and the suitable functions for further work were determined. Temperature and forward current-dependent models are then created with the help of polynomial regression, for the parameters established during fitting. In the field of phosphor modelling, a new aging test based on samples with a distant phosphor arrangement was launched, the details of which are discussed in the paper. LA - English DB - MTMT ER - TY - CHAP AU - Hegedüs, János AU - Hantos, Gusztáv AU - Poppe, András AU - Kovács, R. AU - Bojta, Péter AU - Harsányi, Gábor TI - LED LIFETIME TESTS FOR CIRCUIT SIMULATION MODELLING T2 - CIE x050:2023 Proceedings of the 30th Session of the CIE, Ljubljana, Slovenia, September 15 – 23, 2023, Volume 1 PB - International Commission on Illumination, CIE SN - 9783902842770 PY - 2023 SP - 803 EP - 812 PG - 10 DO - 10.25039/x50.2023.PP010 UR - https://m2.mtmt.hu/api/publication/34689374 ID - 34689374 AB - Lifetime testing and modelling studies of LEDs play an increasingly important role in the implementation of design solutions with an Industry 4.0 approach. This article presents the work carried out in two departments of the Budapest University of Technology and Economics, during which the frequency-dependent aging of high-power LEDs in pulsed mode (at the Department of Electron Devices) and the temperature- and relative humidity-dependent aging of low-power LEDs (at the Department of Electronics Technology) were investigated. LA - English DB - MTMT ER - TY - CHAP AU - Alshahmani, Ahmad Halal AU - Plesz, Balázs ED - Poppe, András TI - Thermal Behavior of Crystalline Silicon Bottom Cell in a Monolithic Perovskite/Si Tandem Solar Cells T2 - 2023 29th International Workshop on Thermal Investigations of ICs and Systems (THERMINIC) PB - IEEE CY - Budapest SN - 9798350318623 PY - 2023 PG - 6 DO - 10.1109/THERMINIC60375.2023.10325899 UR - https://m2.mtmt.hu/api/publication/34448284 ID - 34448284 N1 - Conference code: 194796 Export Date: 22 December 2023 Funding Agency and Grant Number: Stipendium Hungaricum Scholarship Program of the Hungarian Government [2020 1.1.2-PIACI-KFI-2021-00242]; National Research, Development and Innovation Office (NKFIH) Funding text: This research is supported by the Stipendium Hungaricum Scholarship Program of the Hungarian Government and project number 2020 1.1.2-PIACI-KFI-2021-00242 of the National Research, Development and Innovation Office (NKFIH). AB - Monolithic Perovskite/Si tandem solar cells represent a promising direction in photovoltaic technology. However, understanding the temperature coefficient is essential for predicting performance and improving the temperature adaptability of these devices under varying weather conditions. This paper conducts a detailed analysis of the thermal behavior of c-Si as a bottom cell in a monolithic Perovskite/Si tandem arrangement, exploring how its behavior differs from standalone configurations. This investigation is carried out through a numerical simulation using SCAPS software. The simulation considers the temperature-dependent bandgap and absorption for both c-Si and perovskite, as well as the temperature effects on series and shunt resistances. Four simulation scenarios were analyzed, 1) as a standalone c-Si solar cell, 2) c-Si bottom cell in perovskite/Si tandem structure with spectrum split at the perovskite bandgap, 3) c-Si bottom cell, considering perovskite temperature-dependent bandgap, and 4) c-Si bottom cell, considering perovskite layer thickness, absorption and its temperature-dependent bandgap. The results reveal that c-Si solar cells in tandem structures experience notable differences in temperature coefficients, especially in the short-circuit and MPP current densities, compared to standalone configurations. This difference is mainly attributed to the spectrum splitting and temperature-dependent perovskite absorption. Splitting the spectrum leads to an increase in the temperature coefficient of JSC from 0.0944% °C-1 to 0.2539% °C-1; this temperature coefficient reached 0.983% °C-1 when the top cell layer thickness and perovskite's temperature-dependent bandgap and absorption were incorporated into the analysis. Nevertheless, only a minor variation was observed in the voltage temperature coefficient, for both in standalone c-Si cells and those incorporated as bottom cells in the tandem structure. © 2023 IEEE. LA - English DB - MTMT ER - TY - CHAP AU - ALNAHHAL, AHMED I M AU - Plesz, Balázs ED - Poppe, András TI - Performance Analysis of Stacked Photovoltaic-Thermoelectric Generator Using Mathematical Thermal-Electrical Model T2 - 2023 29th International Workshop on Thermal Investigations of ICs and Systems (THERMINIC) PB - IEEE CY - Budapest SN - 9798350318623 PY - 2023 PG - 5 DO - 10.1109/THERMINIC60375.2023.10325680 UR - https://m2.mtmt.hu/api/publication/34448283 ID - 34448283 N1 - Conference code: 194796 Export Date: 22 December 2023 Correspondence Address: Alnahhal, A.I.; Budapest University of Technology and Economics, Hungary; email: aalnahhal@edu.bme.hu Funding Agency and Grant Number: Stipendium Hungaricum Scholarship Program; National Research, Development, and Innovation Office (NKFIH) [2020-1.1.2-PIACI-KFI-2021-00242] Funding text: The research is supported by the Stipendium Hungaricum Scholarship Program and the project number 2020-1.1.2-PIACI-KFI-2021-00242 of the National Research, Development, and Innovation Office (NKFIH). AB - This paper proposes an electrical-thermal model to evaluate the performance of often proposed PV-TEG stacked systems where the thermoelectric generator device is mounted on the back side of the PV cell. This way, the heat generated by the PV cell is collected by the surface area of the heat collector. The heat sink has been settled at the bottom of the thermoelectric generator device. Investigations were performed at different light concentration levels of 1, 2, 3, 4 and 5 suns. The efficiency of the thermoelectric generator increases with the light concentration due to the increasing in the temperature difference across its terminals. The results showed that the stacked system efficiency is decreasing with the increase of light concentration level and still lower than the efficiency of standalone illuminated PV cell. This is due to the high junction temperature which results in a decrease in the solar cell efficiency where the TEG device is still not able to compensate the decrease in the efficiency of the PV cell. It can be concluded that thermal coupling between the two devices has to be avoided to enable both devices to operate efficiently at their respective optimal operational temperatures. © 2023 IEEE. LA - English DB - MTMT ER -