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Optimization of parameters of integrated optical waveguides based on thin-film Sol-gel structures by using mathematical modelling
摘要： An algorithm for calculating optical waveguide film parameters was proposed, the use of which makes it possible to reduce the time for processing experimental data. The developed algorithm was tested using experimental data of waveguides samples with a wave-guiding layer of zirconium dioxide sol-gel films. A comparison of the developed algorithm and the Wolfram Mathematica program showed a good agreement of the results, as well as the developed method advantage in terms of using ease and timesaving spent on processing the results.
关键词： mathematical modelling,temperature optical coefficient,sol-gel technology,optical waveguide,integrated optics
更新于2025-09-16 10:30:52
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[Laser Institute of America ILSC? 2019: Proceedings of the International Laser Safety Conference - South Kissimmee, Florida, USA (March 18–21, 2019)] International Laser Safety Conference - Probabilistic laser hazard modelling for a fifth-generation low-observable laser designator system
摘要： The advent of so-called “fifth-generation” low-observable strike aircraft with a laser designation capability raises a potentially unique laser hazard. In order to be “stealthy”, the laser designator is likely to be embedded within the aircraft rather than carried externally as a podded system. The difference between an integrated and a pod-based configuration is that the laser exit window in a stealth design is likely to be fixed to the aircraft fuselage, as opposed to being able to move with the laser beam, and it is also likely to be faceted. Unless carefully engineered, a faceted exit window may generate unintended laser beam reflections resulting in stray laser energy (SLE) emissions, as the laser head rotates within the window assembly. High intensity SLE can engender impractically large laser hazard zones using traditional deterministic analysis techniques. The purpose of this paper is to outline the probabilistic modelling of uncontrolled SLE from a hypothetical integrated laser designator system. The discussion will also show the importance of including the aircraft behaviour in the analysis, due to the effect of the aircraft position relative to the target on the SLE scatter patterns.
关键词： probabilistic modelling,fifth-generation aircraft,laser hazard,stray laser energy,laser designator
更新于2025-09-16 10:30:52
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Investigation of spectrally-dependent phonon relaxation mechanism in Yb:YAG gain media and its consequences for thin disk laser performance
摘要： Nonlinear phonon relaxation in Yb:YAG gain media has previously been investigated, and a hypothesis correlating photo-induced free electrons and heat generation in crystals pumped at a wavelength of 940 nm was established (Brandt et al 2011 Appl. Phys. B 102 765–8). Later, we demonstrated efficient suppression of nonlinear phonon relaxation by zero-phonon line (ZPL) pumping of Yb:YAG (969 nm). However, no hypothesis has yet been tested that correlates the heat load and the free electrons in Yb:YAG media. We investigate, both theoretically and experimentally, the behaviour of an Yb:YAG slab pumped by a high-power laser diode at a conventional broadband line (absorption maximum at 941 nm) and a ZPL (absorption maximum at 969 nm), and we compare the generated photocurrent, temperature, and absorbed pump power for those two pump wavelengths. Although the hypothesis established by Brandt et al (2011 Appl. Phys. B 102 765–8) was not confirmed, and the measured photocurrent was identical for the two pump wavelengths, our measurement contributes to the knowledge of the inner processes in Yb:YAG active media. In the following steps we characterized an Yb:YAG thin disk laser, measured the spectrally-resolved absorption and disk surface temperature, and optimised our predictive model of thin disk behaviour. All the experimental and theoretical results are reported.
关键词： numerical modelling,thin disk,thermal effects,Yb:YAG,photocurrent
更新于2025-09-16 10:30:52
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Electrical system architectures for building-integrated photovoltaics: A comparative analysis using a modelling framework in Modelica
摘要： Building integrated photovoltaic (BIPV) systems may be catalyzers of sustainable, near-zero energy buildings. To maximize the benefits of employing BIPV, it is important to integrate them properly into the grid of the building. The discussion on AC versus DC distribution for microgrid and nanogrid backbones is currently revisited as the level of penetration of renewable sources, electric vehicles and DC loads is constantly increasing. This paper tackles this question and provides guidelines using a validated simulation framework. The study compares DC (48 V and 380 V) and AC (230 V/50 Hz) topologies integrated into a ten-story office building with fa?ade-integrated BIPV. Annual simulations are carried out for five locations with different climatic conditions and comparisons are made in terms of system- and component-level efficiency, system losses, self-sufficiency, self-consumption and CO2 emission. The analysis shows that the DC topologies perform better than the AC one, especially for the locations with high solar energy yield compared to the cooling and heating loads. Further, a parametric analysis is performed to determine the optimal sizing of the building grid components, DC and AC alike. Finally, different scenarios of battery energy storage system capacity are examined in order to test the sensitivity of the performed analysis.
关键词： Modelica,Building-Integrated Photovoltaics (BIPV),Electrical configuration,Modelling,Building energy simulation
更新于2025-09-16 10:30:52
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Preserving the Knowledge of the Past Through Virtual Visits: From 3D Laser Scanning to Virtual Reality Visualisation at the Istanbul ??atalca ?°nce??iz Caves
摘要： Cultural landscapes are those that are shaped through the combined forces of cultural and natural activity, typically over a long period that may reach back to historic and prehistoric times. Amongst these, the documenting, modelling and visualisation of cave landscapes have always been particularly important for scientific communities such as speleology. In the current state of the art, terrestrial laser scanning provides a level of documentation of objects whose accuracy cannot be achieved by conventional methods. In addition to the highly accurate metric and geometric information, visual information brings incredible richness to the presentation of data. Virtual reality (VR) allows individuals to immerse themselves within virtual environments to explore monuments and other cultural heritage sites up close. More and more, VR systems are available at lower prices and are not only limited to VR labs. In this paper, we present research on the generation of a virtual 3D model of the ?nce?iz caves, located at the ?atalca district of Istanbul, Turkey, and its integration within the Unity 3D game engine. This project, carried out as a collaboration between B?MTA?, a company of the Greater Municipality of Istanbul, Turkey and the Photogrammetry & Laser Scanning Lab of the HafenCity University Hamburg, Germany, aimed at developing an immersive and interactive VR visualisation of the cave for the HTC Vive Pro VR system. The entire workflow, from data acquisition to VR visualisation, is described here in detail with particular emphasis given to the 3D modelling of the cave and its integration within a VR environment.
关键词： HTC Vive Pro,Cave,3D,Modelling,Virtual reality,Digital reconstruction
更新于2025-09-16 10:30:52
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Thermo-fluid-metallurgical modelling of the selective laser melting process chain
摘要： The entire process chain of selective laser melting of Ti-6Al-4V is analysed. First, a thermo-fluid dynamical model is used to investigate the temperature profile during the process and estimate the size and shape of the melt pool. The inclusion of the Marangoni effect improves upon previous work by showing the liquid velocity in the melt pool. Next, this information allows us to estimate the morphology of the grains of a part produced by selective laser melting. Finally, a cellular automata is used to model the microstructural evolution during a uniform heat treatment at the beta transus temperature. It is shown that the model shows good agreement with earlier experimental results.
关键词： selective laser melting,Ti6Al4V,computational fluid dynamics,thermal modelling,microstructural modelling
更新于2025-09-12 10:27:22
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Circuit Model of LED Light Bulb suitable for typical voltage THD on LV distribution networks
摘要： In lighting system design, the LED light bulb technology is gaining more and more advantages in comparison to other previous solutions. On the other hand, the designers of lighting systems have to face the specific problems created by this technology in terms of deterioration of the power quality on the mains. The knowledge of lamp electrical models is a key point for the optimal design of the lighting systems but such models are not provided by the manufactures. Moreover, the voltage on the mains may vary along the day due to the load fluctuation as well as due to the variation of the power generated by distributed renewable resources. Consequently, suitable electrical models have to be able at emulating the lamp behavior according to the voltage variability. The paper proposes an equivalent electrical circuit of LED light bulb. The components of the model are identified by means of simple electrical measurements. In particular, the circuit enables to emulate the current waveform in the case of network voltage variability. The validation has highlighted that the simulated currents waveforms have a good matching with the experimental data obtained in presence of distorted voltage on the mains (provided that the voltage THD is compliant with IEEE-Std-519). The validation has been performed also at voltage values different from the ones used for the components identification.
关键词： Current harmonics,power conversion,optimal design,modelling,power quality,lighting,equivalent circuits
更新于2025-09-12 10:27:22
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[IEEE 2019 21st European Conference on Power Electronics and Applications (EPE '19 ECCE Europe) - Genova, Italy (2019.9.3-2019.9.5)] 2019 21st European Conference on Power Electronics and Applications (EPE '19 ECCE Europe) - A Single-Phase dc-ac Dual-Active-Bridge Based Resonant Converter For Grid-Connected Photovoltaic (PV) Applications
摘要： This paper presents the topology, modelling and control strategy for a single-phase grid-connected converter for photovoltaic (PV) applications based on the series-resonant dual active bridge (DAB). A state-space large-signal model is derived for phase-shift based modulations, and a linearized model is presented for control design. A multi-loop control strategy is presented where a current-control loop regulates the current that the converter injects in-phase with the grid voltage, while a slower loop regulates the PV array voltage for MPPT. To verify the model and control strategy, simulation and experimental results are presented.
关键词： Power Converter,ZVS converters,Photovoltaic,Hardware,Converter circuit,DC-AC,Converter control,Microinverter,Modelling,High frequency power converter,Dual active bridge,Resonant converter
更新于2025-09-12 10:27:22
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AIP Conference Proceedings [AIP Publishing PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS: ICAM 2019 - Kerala, India (12–14 June 2019)] PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS: ICAM 2019 - A review on computational modelling of individual device components and interfaces of perovskite solar cells using DFT
摘要： Perovskite structures with the same crystal structure as CaTiO3, are of importance in the field of Materials Science right from the discovery of ceramic high-temperature superconductors to the organic–inorganic semiconductors for high-efficiency photovoltaics. Owing to their unique crystal structure, perovskites display a variety of interesting properties like ferroelectricity, superconductivity, magnetoresistance, birefringence, piezoelectricity etc. Moreover, the efficiency of perovskite solar cells has increased from 3.1% in 2009 to 22.1% in 2017. Since a large number of elements can be combined to form perovskite structures, one can selectively design and optimize perovskite’s physical, optical and electrical characteristics. Through theoretical and computational modelling, it is possible to access the hitherto unknown atomistic properties, opto-electronic properties and operational mechanisms of these materials with high accuracy. This paper aims at explaining some of the potentialities of DFT hybrid functionals to analyze the electronic, structural and optical properties of compounds constituting various layers of a perovskite solar cell with the help of software packages like VASP, Wien 2k. Gaussian 09 etc. This paper also reviews the effect of doping on the electronic properties of various layers of perovskite solar cells including the band gap, visible light absorption, relaxation time of holes and electrons using DFT, which in turn determines the optimum charge separation. The effect of introduction of an Intermediate Band Gap in the perovskite structure using DFT methods based on G0W0+SOC approach is also discussed here. A study on the effect of various intrinsic defects present in perovskite structures using DFT calculations with VASP package is also discussed. The relevance of modelling the interfaces of various layers of perovskite solar cells with DFT packages is discussed with the help of selected examples of materials and representative interfaces.
关键词： optical properties,DFT,computational modelling,electronic properties,interfaces,Perovskite solar cells
更新于2025-09-12 10:27:22
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A Detailed Optimisation of Solar Photovoltaic/Thermal Systems and its Application.
摘要： There have been various studies and experimental results analysing the operational behaviour of PVT, most of which has been done at steady state or quasi-state. Variable factors can be controlled to optimise the PVT output such as mass flow rate, irradiation falling on the PVT through tracking or incidence angles in a day and fixed factors that depend on the design of the chosen PVT system as well as location parameters such as ambient temperature, wind speed, Transport Fluid used, Difference in Structure, Packing Density, Nominal operating temperature, stagnation temperatures, Fill Factor, Thickness of each layer, Location and Latitude and Heat removal factor (harp or serpentine design). The aim of this research is to validate and predict the dynamic behaviour of PVT systems while accurately describing the factor responsible for the loss of efficiency at any point in time under various weather constraints. A commercial system was considered (Solar Angel PVT system) here and is simulated for an entire year. The system was modelled in MATLAB and solved in implicit RK-4 method. The research question finds out to establish the basis for a standard testing protocol for assessing PV-T performance throughout various differences. It also analyses the long-term dynamic performance of PV/T technology by providing evidential data analysis (solar irradiance, heat and electricity, ambient temperature, operational temperatures, flow rates and thermal storage capacity) while completing an assessment of PVT behaviour with respect to an equivalent PV under different weather conditions. The flow rates, heat removal factor and the location affect the thermal behaviour of the PV/T to a greater extent than nominal temperatures and stagnation temperatures.
关键词： Electric and Thermal Energy,Solar Photovoltaic thermal systems,Optimising,Solar Energy,Dynamic Modelling,Optimal operation of PVT,PVT systems with storage
更新于2025-09-12 10:27:22