KTU Open Journal Systems (Kaunas University of technology)
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Experimental Investigation of Mortars with Diverse Sand Types
No full textFine aggregates, particularly river sand (NS) and crushed sand (CS), play a key role in concrete production. However, the excessive extraction of river sand has become a serious environmental concern, encouraging the search for sustainable alternatives. This study investigates the feasibility of incorporating recycled sand (RS), obtained by crushing and grinding standard concrete cylinders (16 × 32 cm), as a partial replacement for NS and CS in ternary mortar mixtures, with substitution levels ranging from 20 % to 100 %. Mortars were prepared with a fixed water-to-cement ratio, and their fresh and hardened properties were evaluated in terms of workability, bulk density, water absorption (immersion and capillarity), and compressive strength at 3, 14, and 28 days. The results show that mortars containing up to 40 % RS maintain mechanical and physical performances comparable to those prepared with natural sand. Beyond this threshold, compressive strength decreases and water absorption increases. A strong correlation (R² = 0.98) was observed between dry density and water absorption, confirming the consistency of the results. Overall, the findings demonstrate that recycled sand produced from laboratory concrete specimens can be effectively used as a sustainable alternative in mortar production, contributing to resource conservation and reducing the environmental footprint of the construction sector
World Heritage Potential: the Role of Heritage Sites on the Development of Hilla’s City Center
No full textCultural heritage areas (World Heritage Sites) have long stood as prominent symbols of historical and cultural civilizations in their respective environments and today serve as a strong incentive for attracting both local and international tourists. However, the urban expansion driven by rapid population growth has led to challenges, including the differentiation of their urban fabric. This highlights an urgent need to develop these cultural and tourist urban nodes and integrate them into the urban development trends of the city. Sustainable development has become a pressing agenda for such cities to protect and revitalize cultural areas and enhance accessibility to them. The study aims to evaluate the spatial configuration of the city of Babylon (within the center of Al-Hillah city, including the World Heritage Site of Babylon) over a twenty-year period (2004-2024). The research addresses a knowledge gap: The absence of precise quantitative analysis of the study area within both local and global studies, which provides a true impression of the urban development trajectory experienced by the city over the past two decades and assesses the effectiveness of the World Heritage Site as a dynamic urban node within the city. The study applied the method of space syntax and conducted axial and segment analyses based on the city\u27s street network data for the years 2004 and 2024, measuring Depthmap X 0.8.0 program indicators related to the research vocabularies (choice, connectivity, integration, intelligibility, synergy). The analysis results indicated that the current spatial configuration of the city achieved higher values in the choice and connectivity indicators. However, the integration indicator recorded a higher value in the past, due to the significant expansion that the center of Al-Hillah city witnessed towards the south of the historic city, while the eastern and western directions achieved medium values. This underscores the development axes that should be focused on to activate and enhance land use in the areas surrounding and adjacent to the historical site
Optimisation of Heating System Powered by Air Heat Pump and Gas Condensing Boiler Hybrid Unit
No full textGas condensing boiler and air to water heat pump hybrid unit is an optimal way to introduce renewable energy resources in existing buildings. Two energy sources (gas & electricity) give hybrid unit higher flexibility in comparison to typical air to water heat pump. In hybrid solution air heat pump can be used in locations with low temperature heating seasons. Hybrid unit can output higher heat carrier temperatures, because of this, it can be used in combination with older radiator heating systems.
There are many parameters that can influence the performance of hybrid heating unit. This paper investigates heat terminal type, heat carrier temperature, and outdoor switchover temperature setting (outdoor temperature at which hybrid unit switches from electricity to fossil fuel) influence on air to water heat pump and gas condensing boiler hybrid heating unit performance parameters (total efficiency - ηhybrid and primary energy factor - PEFhhp). Hybrid heating units performance is evaluated by using a computer model created in program IDA ice 4.8. The created computer model represents a real building, located in Latvia, that uses the previously mentioned hybrid heating unit. The model is verified by comparing its results with energy meter data from the real building, for time period from 01.03.2022 to 28.02.2023.The verified model is used to simulate how hybrid heating units performance is influenced by changes in heating terminal type, heat carrier temperature and outdoor switchover temperature setting.
According to simulation data, at constant heat carrier temperature, heat terminal type has no influence on hybrid heating unit’s performance parameters. It has been found that increased heating system volume can reduce hybrid heating unit’s run time. In this case replacing panel radiators with floor heating, there is a 33% reduction in unit’s annual running time. In simulated scenarios, heat carrier temperature reduction by 15°C, increases ηhybrid by 8.7% and decreases PEFhhp by 17.5 % (at temperature graph 40/35°C). Switch over temperature increase from -7 to 3°C decreases ηhybrid by 47% and increases PEFhhp 7 %. Switch over temperature increase also reduces ηhybrid and PEFhhp change magnitude, when changing heat carrier temperature graphs. When changing the temperature graph from 40/35 to 55/50 °C the changes are as follows: at switchover temperature setting of -7°C, drops by 14,33 %, but PEFhhp increases by 23,42%; at switchover temperature setting of -2°C (actual setting), drops by 8,7 %, but PEFhhp increases by 17,51%; at switchover temperature setting of +3°C, drops by 1,74 %, but PEFhhp increases by 6,45%
Vertical Farming: a Catalyst for Integrating Biophilic Design into Built Environment
No full textCould integrating vertical farming into buildings be a catalyst for promoting biophilic design? Answering this question is the aim of this study. Biophilic design (BD) focuses on human-nature connection (HNC) in the built environment (BE), and vertical farming (VF) systems provide an innovative way to integrate green spaces, natural elements, and activities related to vertical farming systems into buildings in a way that supports the goals of BD. Therefore, the study conducted a literature review on BD as an approach to HNC and extracted the goals of BD, application strategies, and elements of nature relevant to its goals. The study then addressed the concept of vertical farming and its systems, in addition to extracting the most important elements of nature that affect each system, based on the components of each system and its method of operation, in addition to comparing several vertical farming projects integrated into buildings, with a focus on the BD goals that each project seeks to achieve. Hence the term "Vertical Farming (VF) -Based Biophilic Buildings" was coined and the study then presented a SWOT analysis of this proposed term. The study concluded that integrating VF into urban buildings creates harmonious environments where nature and the BE coexist. Thus, we can create (VF) -Based Biophilic Buildings that can encourage residents’ participation in natural processes, and promote health, social, and well-being goals, along with economic, environmental, and sustainability goals
A Comprehensive Study of Space Efficiency in Tall Buildings: the Australian Perspective
No full textSpatial efficiency in Australian towers is shaped by a multifaceted interaction of many parameters such as architectural and structural considerations. However, there are no comprehensive studies available on space utilization in Australian high-rise towers. The article addresses this gap by investigating 32 case studies. This study aims to investigate how contemporary Australian tall buildings achieve spatial efficiency by analyzing the relationship between architectural and structural parameters and internal usable area ratios. Key findings: residential function, centrally-located core layouts, and prismatic arrangements are the most widespread trends; concrete is the favored construction material, with the shear-walled frame system being the most commonly used structural system; average space efficiency is 82%, with a core-to-GFA ratio of 16%. The paper offers valuable understandings for construction experts to inform design decisions in high-rise construction projects within the Australian context
Zur Übersetzung von Fachwörtern im Sprachenpaar Deutsch-Litauisch am Beispiel des Bildungswesens als Herausforderung in der Fachkommunikation
No full textIm Hinblick auf die Diskussion um die Übersetzung von Fachbegriffen aus dem Deutschen ins Litauische sind die Kategorien der Fachkommunikation von besonderer Relevanz. Die Fachsprachen als Varietäten der Standardsprache bieten dem Übersetzer keine allzu großen Probleme. Die Übersetzung von Fachwörtern, Termini und Fachbegriffen ist dagegen nicht unproblematisch und bedarf einer besonderen Herangehensweise.
Fachbegriffe im Bereich Bildungswesen sind zwar von kodifizierten Termini einerseits und kulturspezifischen Realien andererseits abzugrenzen, bereiten bei der Urkundenübersetzung erhebliche Schwierigkeiten, die mittels bestimmter Verfahren bewältigt werden können. Wörtliche Übersetzung und die Lehnübersetzung als analoge Entsprechungen sind nur in einem gewissen Maße einsetzbar. Vielmehr dominieren Verfahren zur Schließung von wörtlichen und begrifflichen Lücken. Solche Verfahren sind meistens zielsprachenorientiert und werden bei der Übersetzung von fachspezifischen Begriffsformulierung, bei Berufsbezeichnungen und Abschlussbezeichnungen herangezogen. Diese Erkenntnisse korrespondieren zum Teil mit den Ergebnissen der stichprobenartigen Fragebogenerhebung, die vor allem terminologische und technologische Schwierigkeiten hervorhebt. Die Ergebnisse der Korpusanalyse haben gezeigt, dass Bezeichnungen von Studiengängen, Lehr- und Studienformen sich sowohl zielsprachlich-adaptierend als auch ausgangssprachlich-erhaltend übersetzen lassen und dass keine universellen Regeln angewendet werden können.
Im Bereich Bildungswesen gibt es hinsichtlich des Sprachenpaars Deutsch-Litauisch nur vereinzelte Forschungsarbeiten. Im litauischen Raum liegt eine kleine Anzahl erklärender Glossare vor. Daher wird im vorliegenden Beitrag ein Überblick über ein umfassendes Instrumentarium gegeben, das den Übersetzenden behilflich sein kann
Circular Economy in Agriculture: The Case for Bioactive Compounds from Sea Buckthorn By-products
No full textThe implementation of closed-loop manufacturing models in berry farming represents a transformative approach to sustainable agriculture, enhancing both environmental sustainability and economic resilience. By integrating waste materials back into the production cycle, these models minimize environmental impact while maximizing resource efficiency. In the context of sea buckthorn (Hippophae rhamnoides L.), a crop with significant nutritional and medicinal properties, utilizing by-products such as fruit residues pomace, leaves and twigs offers a practical solution to waste management challenges while creating high-value products for the food, cosmetic, and pharmaceutical industries. Food Institute of Kaunas University of Technology has implemented the project “Circular manufacturing model for producing biologically active materials”, validating the soundness of closed-loop manufacturing systems for berries by demonstrating sustainable practices for the extraction and utilization of bioactive compounds from sea buckthorn by-products. The project results emphasize the feasibility of integrating eco-friendly extraction methods while addressing environmental and economic challenges
Furtherance of Multilevel Inverter and Evolution of a Packed Inverter Unit for Dynamic Loads
No full textMultilevel inverters (MLIs) provide a solution for high-power applications due to the production of a high-quality output voltage with low harmonic distortion. This technology is gaining popularity in the power industry for applications such as renewable energy systems, motor drives, and electric vehicles. MLIs are categorised on the basis of the number of levels in their output waveform. This article includes a discussion of two, three, and higher-level inverters with respect to design aspects and their application in the power industry, contributing to the development of sustainable and efficient systems. In addition, a packed inverter unit (PIU) with 11 IGBT switches and three uneven DC voltages is used to generate 11 voltage steps. From the suggested axioms, the amplitude of the DC sources is chosen to generate larger voltage steps with the fewest possible circuit components. Additionally, an 11-level inverter is simulated for fixed and variable R/RL loads. A comparison analysis of the circuit components between the developed circuit and existing MLIs is carried out. Finally, 11-level inverters are evaluated in real time for constant, fluctuating R/RL loads, and various performance metrics are noticed
BSPR-Net: Dual-Branch Feature Extraction Network for LiDAR Place Recognition in Unstructured Environments
No full textLiDAR point cloud-based place recognition (LPR) in unstructured natural environments remains an open challenge with limited existing research. To address the limitations of unstructured environments, such as sparse structural features, uneven point cloud density, and significant viewpoint variations, we present BSPR-Net, a dual-branch point cloud feature extraction approach for point cloud place recognition, which consists of a BEV - projection rotation - invariant convolution branch and a point cloud sparse convolution branch. This design enhances the representation capability of geometric structural features while aggregating rotation-invariant characteristics of point clouds, thereby better addressing the challenge of large viewpoint disparities in reverse-revisited unstructured environments. The proposed network was tested on multiple reverse-revisited sequences of the Wild-Places data set, a benchmark for unstructured natural environment place recognition. It achieved a maximum F1 score of 85.46 %, exceeding other classical methods by more than 4 %. The ablation experiments further confirmed the effectiveness of each module in improving place recognition performance
Numerical Investigation of Yield Stress and Damping Force for a Modeled Damper Using Different MR Fluids
No full textThis article presents the yield stress, shear damping force, viscous damping force, and total damping force generated in a modeled damper using various magnetorheological (MR) fluids. The values of the generated magnetic field intensity in a modeled damper have been obtained by performing a magnetostatic analysis using ANSYS Maxwell v.16 software. All the used MR fluids exhibit growth in yield stress and damping force on increasing the input current. The magnetic field intensity values are fitted into yield stress-magnetic field intensity quadratic equations which are developed for all the used MR fluids using the least square techniques in order to compute the yield stress. The estimated yield stress is maximum for AMT RHEOTEC+ fluid and lowest for MRF-122EG for all input current values. The computed yield stress of in-house prepared optimal MR fluid exhibits good agreement with the commercially available MR fluids. The results exhibit that the MRF-140CG owns the largest viscous damping force (90.72 N) while MRF-122EG owns the lowest viscous damping force (13.61 N) for the modeled damper. AMT RHEOTEC+ fluid possesses the largest shear damping force (controllable force) as well as total damping force while MRF-122 EG is the one that exhibits the lowest value for shear as well as total damping forc