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Extending battery life in CubeSats by charging current control utilizing a long short-term memory network for solar power predictions
No full textRecently, there has been a surge in small satellites and CubeSats. A crucial factor limiting the duration of their missions is the lifespan of their batteries. Typically, batteries are charged immediately when there is sufficient power generated from the solar panels. However, this practice results in additional charging stress and degradation due to unnecessarily high current amplitudes. In this work, a distributed charging strategy based on solar power prediction is proposed to mitigate charging stress and thereby extend battery life, ensuring sufficient charging without jeopardizing spacecraft operation. The proposed method for power generation prediction relies on a Long Short-Term Memory (LSTM) network, trained on GOMX-4A satellite telemetry data. The proposed LSTM method performed an order of magnitude better, with a root mean square error (RMSE) of 0.2274 W, while a baseline prediction utilizing a Seasonal Auto-Regressive Moving Average has an RMSE of 1.2406 W. Using the predicted power generation from the LSTM method, the current is distributed using a proposed charging multiplier control, resulting in 72.0882% reduction in the median charging current. A direct possible impact on lithium-ion batteries was evaluated by employing an electrochemical model from the literature, confirming that the proposed strategy effectively reduces degradation caused by lithium plating. Moreover, the capacity fade in the example scenario at 25 °C was reduced by 0.0849%. The extent of degradation reduction will vary according to the required mission profile, the operational conditions, the specific chemistry, and the type of battery in use. © 2024 Elsevier B.V
Special issue dedicated to Professor Ivo Babuška, the founder of the journal Applications of Mathematics: Editorial
No full textCritical assessment of large-scale rooftop photovoltaics deployment in the global urban environment
No full textIn support of the clean energy transition, rooftop photovoltaics (RTPV) deployment has been globally advocated, enabling citizens as energy prosumers within their localised building environment. However, the effectiveness of RTPV implementation is influenced by diverse bioclimatic conditions. Here, we provide a critical climate-related RTPV characterisation across the globe, consisting of a comprehensive assessment of RTPV performance, taking into account global horizontal irradiation (GHI) and local environmental parameters, including space conditioning requirements in different climatic zones. Additionally, we examine the technological advancements aimed at improving efficiency in RTPV systems.
Within a meta-data analysis, we find that the RTPV systems offer various advantages in terms of building overall energy performance, particularly in moderate and warm climates. We observe that typical or increased insulation values can offset the RTPV effect in uninsulated roofs. This is essential in regions with cold climates and helps to mitigate increased heating requirements during winters or higher cooling demands during summer nights. A relationship between the ratio of building space coverage to PV surface and GHI is proposed for low-energy buildings to calculate the space requirements for achieving net zero buildings, globally. Moreover, in hot climates, cooling the RTPV surfaces can enhance efficiency by up to 20 % and increase power output by up to 15 %. By advancing RTPV efficiency to 30 % with emerging technologies, the decarbonisation of high-rise buildings can be facilitated, alongside energy efficiency and RTPV implementation measures. Striking a balance between thermal insulation needs, we conclude that RTPV offers wide benefits across different climatic condition
Integral micromorphic model reproducing dispersion in 1D continuum
No full textThe paper develops a new integral micromorphic elastic continuum model, which can describe dispersion properties of band-gap metamaterials, i.e., metamaterials that inhibit propagation of waves in a certain frequency range. The enrichment consists in nonlocal treatment of three terms in the expression for the potential energy density of the standard micromorphic continuum. After proper calibration, such a formulation can exactly reproduce two given branches of the dispersion curve (acoustic and optical), even in cases with a band gap. The calibration process exploits Fourier images of the unknown weight functions, which are analytically deduced from the dispersion relation of the material of interest. The weight functions are then reconstructed in the spatial domain by numerical evaluation of the inverse Fourier transform. The presented approach is validated on several examples, including discrete mass–spring chains with alternating masses, for which the dispersion relation has an explicit analytical form and the optical and acoustic branches are separated by a band gap
Semiconductor pixel detectors for nuclear physics and quantum astrometry
Full text linkTato práce představuje výsledky dvou různých projektů zaměřených na testování polovodičových detektorů ve dvou různých oblastech fyziky. V prvním projektu bylo cílem otestovat detektor založený na vyčítacím čipu Timepix3 na tokamaku COMPASS, a to při studiu ubíhajících elektronů, což jsou vysoce energetické částice, které mohou poškodit vakuovou komoru tokamaku, pokud nejsou včas detekovány. Druhý projekt se zaměřil na testování nového detektoru založeného na jednofotonových lavinových diodách, LinoSPAD2, pro intenzitní interferometrii.This work presents results from two different projects on testing semiconducto
Anchor test and long-term monitoring of grouted anchors instrumented with Fiber Bragg Grating sensing technology
Full text linkGeotechnical monitoring of anchors provides fundamental data for analysis and evaluation to ensure safe environment. The use of optic fiber sensing technology, especially Fiber Bragg Gratings, brings many advantages of optic fiber sensors, such as high measurement accuracy, real-time continualmonitoring of deformation, on-line access to data and resistance against electromagnetic interferences. This article deals with anchor tests instrumented with FBG deformation gauges of the root and the tendon of the pre-stressed strand anchor in a test field in the Central Bohemian Region. First, the anchor with three optic cables with FBG sensors for measurement of axial deformation was subjected to six loading stages of the anchor test. Most of the sensors measured values of axial deformation less than 200 με and the root mobilisation was observed. Then, the measurement continued by 26-day long-term monitoring and a trend of a small increase of deformations occurred
Implementing Systemic Approach to Safety Investigation for a Biz Jet Operator
Full text linkLetecká doprava klade vysoký důraz na bezpečnost a efektivní interní šetření událostí je zásadní pro identifikaci příčin a implementaci nápravných opatření, která mohou předejít opakování událostí. Tato diplomová práce se zaměřuje na zavedení systémového přístupu k šetření událostí v letecké organizaci, která provozuje a udržuje letadla typu business jet. Cílem je implementovat komplexnější systémový přístup k bezpečnosti, který nahradí současný model založený na metodě Root Cause Analysis, jež se zaměřuje na identifikaci jedné hlavní příčiny události. Nový návrh využívá metodu Causal Analysis based on System Theory, která umožňuje provádět analýzu událostí v širším systémovém kontextu a identifikuje všechny přispívající faktory. Na základě tří vybraných případů z různých oblastí provozu organizace je v práci vytvořen nový návrh interního šetření, který reflektuje současné poznatky z oblasti bezpečnostního inženýrství. Tento přístup přináší podrobný a systematický pohled na události včetně konkrétních doporučení pro zlepšení bezpečnostní kultury, optimalizaci procesů a zefektivnění budoucího šetření událostí. Navržený systémový přístup může výrazně přispět k prevenci opakování událostí a dlouhodobě ke zvýšení bezpečnosti provozu v letectví.The air transport places a high emphasis on safety, and effective internal event investigations are crucial for identifying causes and implementing corrective measures that can prevent event recurrence. This thesis focuses on the implementation of a systemic approach to event investigations within an aviation organization that operates and maintains business jet aircraft. The aim is to implement a more comprehensive systemic approach to safety, replacing the current model based on the Root Cause Analysis (RCA) method, which focuses on identifying a single primary cause of an event. The new approach employs the Causal Analysis based on System Theory (CAST) methodology, enabling the analysis of events within a broader systemic context and identifying all contributing factors. Based on three selected cases from different operational areas of the organization, the thesis develops a new internal investigation framework that reflects current knowledge in safety engineering. This approach provides a detailed and systematic perspective on events, including specific recommendations for improving safety culture, optimizing processes, and enhancing the efficiency of future investigations. The proposed systemic approach can significantly contribute to preventing event recurrence and, in the long term, improving operational safety in aviation
Hyperspectral Instrumentation for Close-up Biomedical Imaging
Full text linkTato diplomová práce se zaměřuje na využití hyperspektrální zobrazovací technologie v biologii a medicíně, zejména na možnost jejího rozšíření pro detailní (makro) zobrazování. Na základě přehledu současného stavu bylo identifikováno potenciální využití HS systému v těchto oborech. Dále byla provedena detailní analýza možností úpravy komerčně dostupného hyperspektrálního systému Specim PFD4K-65-V10E pro účely makro zobrazování. Byly navrženy a aplikovány dvě úpravy a jejich výsledky byly porovnány. S cílem optimalizace systému byly navrženy a realizovány testovací postupy pro měření klíčových optických parametrů. Následně byly na základě získaných dat stanoveny optimální snímací parametry pro daný systém a vybranou techniku makro zobrazování. Pro ověření funkčnosti upraveného systému byly provedeny experimenty na reálných biologických vzorcích.This thesis focuses on the use of hyperspectral imaging technology in biology and medicine, especially the possibility of its extension for detailed (macro) imaging. Based on a review of the state-of-the-art, the potential use of the HS system in these fields was identified. Furthermore, a detailed analysis of the possibilities of modifying the commercially available Specim PFD4K-65-V10E hyperspectral system for macro imaging purposes was performed. Two modifications were proposed and applied and their results were compared. In order to optimize the system, test procedures for measuring key optical parameters were designed and implemented. Subsequently, the optimal sensing parameters for the system and the selected macro imaging technique were determined based on the acquired data. To verify the functionality of the modified system, experiments were performed on real biological samples
Dual Circularly Polarized Waveguide Antenna
Full text linkTato diplomová práce popisuje návrh, simulaci, výrobu a měření duální kruhově polarizované antény pracující v pásmu 4.7 GHz až 5.7 GHz. Systém se skládá ze čtvercového vlnovodného polarizátoru se zkosenými rohy, dvojitého koaxiálního napájení a kuželové antény. Polarizátor generuje pravotočivou a levotočivou kruhovou polarizaci selektivně buzené jedním ze dvou základních módů čtvercového vlnovodu. Potřebné buzení zajišťuje duální koaxiální napájení. Kuželová anténa navržená pomocí programu Antenna Magus a přizpůsobená polarizátoru dosahuje cílového zisku. Pro elektromagnetické simulace byla použit software CST Studio Suite, zatímco Python s použitím knihovny SciPy umožnil dynamickou optimalizaci pro vynucení geometrických omezení. Naměřený výkon zhotovené antény se přesně shoduje se simulacemi a vykazuje osový poměr pod 5 dB a zisk přibližně 14 dBi v celém pásmu. Tato práce přináší kompaktní, vyrobitelnou konstrukci duální kruhově polarizované antény s potenciálním využitím v satelitní komunikaci, radarové technice a dalších bezdrátových systémech.This thesis details the design, simulation, fabrication, and measurement of a novel dual circularly polarized antenna operating in the 4.7 GHz to 5.7 GHz band. The system comprises a square waveguide polarizer with chamfered corners, a dual-coaxial feed, and a conical horn antenna. The polarizer generates right-hand and left-hand circular polarization by selectively exciting one of the two fundamental modes of the square waveguide. The dual coaxial feed provides the necessary excitation. The conical horn, designed using Antenna Magus and adapted to the polarizer, achieves target gain. CST Studio Suite was used for electromagnetic simulations, while Python with SciPy enabled dynamic optimization for enforcing geometric constraints. The fabricated antenna's measured performance closely aligns with simulations, demonstrating an axial ratio below 5 dB and a gain of approximately 14 dBi across the band. This work contributes to a compact, manufacturable, dual circularly polarized antenna design with potential applications in satellite communications, radar, and other wireless systems
Optimization of CMP Stream Storage Performance
No full textTato práce se zabývá návrhem a implementací datového úložiště pro zpracování vysokorychlostního síťového toku s protokolem CMP (Capture Module Protocol). Práce se zaměřuje na optimalizaci přijímání dat skrz ethernet a jejich ukládání.This thesis deals with the design and implementation of a data storage system for processing high-speed network traffic with the Capture Module Protocol (CMP). The work focuses on the optimization of data reception through Ethernet and its storage