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    46940 research outputs found

    Versatile AHU Fault Detection – Design, Field Validation and Practical Application

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    This paper describes a new tool developed for the detection of operating faults in ventilation units with heat recovery. In principle, the tool is based on the APAR (Air Handling Unit Performance Assessment Rules) method. By following the semantic data description in accordance with the BrickSchema and Project Haystack initiatives, the tool is portable. The executive part of the fault detection system consists of several dozen detection rules, which simultaneously seeks to estimate wasted energy, the threat to user comfort, or the risk of reduced device lifespan, so that the detected faults can be sorted according to their severity. The developed detection tool was validated on real devices incorporated in a pilot plant. For validation purposes, the method of fault induction on real HVAC (Heating, Ventilation and Air Conditioning system) units was used, with subsequent inspection of whether the faults were revealed or not. The results revealed a 90% detection rate. The data set created as a result of this pilot plant is published as an annex to this article. In addition, the ability of the detection tool to reveal faults was also verified on the basis of data sets of measurements taken during the standard operation of several dozen HVAC units. The elimination of the identified operating faults generated energy savings of several thousands of dollars per year

    Experimental development of the plate shower heat exchanger to reduce the domestic hot water energy demand

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    The article describes an experimental development of a new prototype of the horizontal plate shower exchanger for wastewater heat recovery. The prototype is designed so that while achieving the highest possible value of efficiency, it also respects the requirements of the spatial arrangement of the heat exchanger casing and, thus, allows an appropriate flow of wastewater on both sides of the heat transfer surface. At the same time, emphasis is placed on the smallest possible height of the heat exchanger casing with regard to the minimisation of the built-up space and the expected wastewater flow during the shower cycle. Experimental testing was performed according to the conditions meeting the certification criteria of the Passive House Institute, while for a given heat exchanger, the investigated flows and water temperatures, as well as the heat transfer efficiency of the new prototype was determined, reaching peak values ​​of up to 62%. An energy analysis and derivation of the equation was also performed, according to which it is possible to determine the achieved heat savings in the preparation of domestic hot water from the heat transfer efficiency of the exchanger, including all heat losses of the system. With new prototype, heat savings more than 21% are achieved

    Pressurized axisymmetric membrane deforming into a prescribed shape

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    This paper presents a new approach to the optimal design of an axisymmetric membrane with variable thickness, which has potential applications in the development of active optical elements (liquid lenses). The governing equations are based on the Saint Venant-Kirchhoff material law, which postulates a linear relation between the Green-Lagrange strains and the second Piola-Kirchoff stresses, combined with the exact description of geometric nonlinearity, without any simplifying assumptions. It is shown that the membrane thickness can be designed such that the prestressed membrane subjected to a given uniform liquid pressure deforms into a prescribed rotationally symmetric shape, e.g., a spherical or parabolic cap. For the special but important case of a spherical cap, a closed-form solution is derived. A numerical procedure is developed for the general case, and its high accuracy and efficiency is demonstrated by examples. The sensitivity of the optimal design to material parameters and prestressing displacement is assessed

    Hydrological and thermal regime of a thin green roof system evaluated by physically-based model

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    Green roofs, as an element of the green infrastructure, contribute to the urban heat island effect mitigation and the urban drainage outflow reduction. To achieve the desired functions, it is essential to understand the role of the individual roof layers and ensure their proper design.A physically-based model was used to assess the hydrological and thermal regime of two experimental green roof test beds containing distinct soil substrates (a local Technosol and a more permeable commercial substrate “Optigreen”). The test beds together with a meteorological station were built on the building green roof. Each test bed has an effective area of one square meter and is equipped with a soil temperature sensor and an outflow gauge; one of the test beds is continuously weighed. The observed conditions were simulated using one-dimensional numerical model describing the water flow in variably saturated porous medium by Richards’ equation and the heat transport by the advection-conduction equation.The model was able to satisfactorily reproduce the measured outflow and soil temperature. The water-potential-gradient based root water uptake module effectively captured the water storage depletion between the rainfall events. The difference between the two soil substrates tested is demonstrated by the contrasting ability of the soil layers to retain water. Model representation of the thermal conditions within the green roof soils was achieved using independently evaluated thermal properties of the soils and drainage board. The model was also used to analyze the effects of the substrate depth and type of vegetation cover on the transpiration and soil water regime of the green roofs. Increasing the substrate depth causes a rise of root water uptake and induces a significant reduction of the maximal temperature. The thinner soil profiles are more sensitive to the plant species selection

    Comparison of two UHPFRC premixes blast resistance with commonly used concrete based on the failure mode prediction

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    Abstrakt. Tento článek popisuje výsledky z rozsáhlého experimentálního programu, který byl proveden ve spolupráci s LAFARGE Centre de Recherche, Univerzitou Pardubice a technického v Praze. Během experimentu byly dvě patentované směsi UHPFRC testovány na výbuchovou odolnost při kontaktním a blízkém výbuchu. Během experimentu bylo vyzkoušeno celkem dvacet osm čtvercových desek o rozměru 1000 x 1000 mm a třech různých tloušťkách 100, 150 a 200 mm. Odlišných zatěžovacích podmínek bylo dosaženo pomocí změny hmotnosti nálože (100 – 1000 g) a vzdálenosti nálože od horního povrchu vzorku (0 – 100 mm). Na všech vzorcích bylo měřeno výsledné poškození vzorků, typ porušení a byly sledovány vzniklé trhliny. Následně byly získané výsledky vyhodnoceny z hlediska typu porušení a porovnány s výsledky dostupnými v literatuře. Tyto výsledky jsou v článku zastoupeny dvěma empirickými přístupy běžně používanými pro stanovení typu porušení a rozsahu poškození. Ze získaných výsledků je patrné, že zkoumané UHPFRC směsi vykazují lepší výbuchovou odolnost než běžně používané betony. V článku jsou následně tyto rozdíly a možnosti úprav empirických metod pro odhad poškození UHPFRC popsány. Na závěr jsou uvedeny i získané poznatky ze samotného porovnání obou zkoušených materiálů.Abstract. This paper presents results of the extensive experimental programme which was performed in cooperation with the LAFARGE Centre de Recherche, University of Pardubice. Two proprietary UHPFRC composite materials were tested for their blast (contact and close-in) resistance. In total, twenty-eight slabs with dimensions of 1000 x 1000 mm and thicknesses of 100, 150 and 200 mm were tested. Specimens were loaded with explosive charge of weight of 100 - 1000 g in various distances from the specimens top surface. All specimens were visually evaluated for the damage extend, failure mode and crack pattern. Results from the experiment were compared with the results for normal strength reinforced concrete available in literature. These results are covered by two empirical approaches commonly used for the estimation of the type of failure and damage extend. Results showed that both tested premixes performed better than ordinary mixtures in terms of blast resistance. Differences between tested materials and commonly used mixtures were described as well. Finally, both materials were compared from the material properties point of view as well as by their blast resistance performance

    Risk of a Brittle Failure of the Concrete Members with the Minimum Shear and Torsional Reinforcement

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    V oblastech železobetonových konstrukčních prvků, kde nevzniknou trhliny od posouvající síly a/nebo krouticího momentu, není dle ČSN EN 1992 třeba počítat smykovou výztuž a postačuje provést pouze minimální (konstrukční) vyztužení. Na základě parametrické studie a nelineárních numerických modelů předložený článek ukazuje, že pro běžné čtvercové, obdélníkové a kruhové průřezy může toto doporučení normy snadno vést k návrhu nedostatečně únosné výztuže. V případě vzniku jediné trhliny poté hrozí riziko náhlého křehkého porušení celého prvku, které může nastat například i pro malé obdélníkové průřezy od velikosti 100×300 mm.According to the ČSN EN 1992, a shear reinforcement of the concrete member does not need to be checked when no cracks occur due to the shear force and/or the torsional moment. Then only the minimum shear reinforcement is required. Presented parametric study and nonlinear numerical models show that the recommendation of the Eurocode 2 may easily lead to the design of the insufficient reinforcement for the common rectangular and circular cross-section. Subsequently, if a single shear crack occurs a sudden brittle failure of the whole member may follow, for example even for the small cross section with dimensions 100×300 mm

    Estimating the limits of renewable energy from phytomass

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    The energy production from phytomass on agricultural and forest lands can be calculated on the basis of the annual production of hydrocarbons (cellulose, starch, sugar, etc.), without needing to take into account the type of phytomass and the mean-weighted specific power production per unit of land area. Land with a mostly uniform climate and soil class produces similar specific power per unit of land area. It was proved in the case of the Czech Republic, where the meanweighted value of specific power production has been calculated as 3.16 kW/ha. Biomass energy can be released in three ways in which conversion takes place. i) direct phytomass combustion, ii) conversion to methane (biogas), iii) conversion to bioethanol. Conclusions about the effectiveness of different conversion methods were obtained by executing the enthalpy balances of the individual transfer processes. The method using methane (raw gas) seems to be the most energetically advantageous. The close connection between the circulation of CO2, H2O, and O2 has been quantified. The same amount of water as CO2 is produced and remains int in the atmosphere, and it significantly reflects radiation away from the ground. Cooling heat flux can be lowered about 1.6 times, thus contributing to climate change

    Automatic intron detection in metagenomes using neural networks.

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    Tato práce se zabývá detekcí intronů v metagenomech hub pomocí hlubokých neuronových sítí. Přesné biologické mechanizmy rozpoznávání a vyřezávání intronů nejsou zatím plně známy a jejich strojová detekce není považovaná za vyřešený problém. Rozpoznávání a vyřezávání intronů z DNA sekvencí je důležité pro identifikaci genů v metagenomech a hledání jejich homologií mezi známými DNA sekvencemi,které jsou dostupné ve veřejných databázích. Rozpoznání genů a nalezení jejich případných homologů umožňuje identifikaci jak již známých tak i nových druhů a jejich taxonomické zařazení. V rámci práce vznikly dva modely neuronových sítí, které detekují začátky a konce intronů, takzvaná donorová a akceptorová místa sestřihu. Detekovaná místa sestřihu jsou následně zkombinována do kandidátních intronů. Překrývající se kandidátní introny jsou poté odstraněny pomocí jednoduchého skórovacího algoritmu. Práce navazuje na existující řešení, které využívá metody podpůrných vektorů (SVM). Výsledné neuronové sítě dosahují lepších výsledků než SVM a to při více než desetinásobně nižším výpočetním čase na zpracování stejně obsáhlého genomu.This work is concerned with the detection of introns in metagenomes with deep neural networks. Exact biological mechanisms of intron recognition and splicing are not fully known yet and their automated detection has remained unresolved. Detection and removal of introns from DNA sequences is important for the identification of genes in metagenomes and for searching for homologs among the known DNA sequences available in public databases. Gene prediction and the discovery of their homologs allows the identification of known and new species and their taxonomic classification. Two neural network models were developed as part of this thesis. The models' aim is the detection of intron starts and ends with the so-called donor and acceptor splice sites. The splice sites are later combined into candidate introns which are further filtered by a simple score-based overlap resolving algorithm. The work relates to an existing solution based on support vector machines (SVM). The resulting neural networks achieve better results than SVM and require more than order of magnitude less computational resources in order to process equally large genome

    The Development of a New AdsorptionDesorption Device

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    The aim of this work was to construct a new adsorption-desorption device based on the principle of separation of volatile organic compounds, e.g., ethanol. As an adsorbent, it is possible to use granulated activated carbon (GAC) in the adsorption and desorption process. In this study, two kinds of GACs were used and marked as GAC1 and GAC2. A particle size distribution and water vapour sorption for the selected GACs were measured. An experiment with distilled water was performed as a preliminary study of the new device’s functionality. After the determination of the time necessary for the adsorption and desorption, the experiments were carried out with a model mixture (5% v/v ethanol-water mixture), which resulted in a product with the ethanol content of 39.6 %. The main advantage of this device would be the potential competition of conventional distillation

    Ventilation of a Multifunctional Building in Zábřeh

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    Diplomová práce se zaměřuje na větrání multifukčního objektu v Zábřehu z hlediska výběru optimální varianty způsobu větrání. V textové části se budu věnovat možným způsobům větrání bytových jednotek a komerčních prostorů. V praktické části vypracuji projekt větrání multifukčního domu dle zvoleného nejvhodnějšího řešení.The diploma thesis focuses on the vetilation of a multifunctional building in Zábřeh in terms of selecting suitable variants of ventilation. In the text part, we will focus on the possible way of ventilation of housing units and commercial premises. In the practical part I will work out a project of ventilation of a multifunctional house according to the chosen most suitable solution


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