rss_2.0Sciendo RSS Feed for Latvian Journal of Physics and Technical Scienceshttps://sciendo.com/journal/LPTShttps://www.sciendo.comhttps://sciendo-parsed.s3.eu-central-1.amazonaws.com/66995f27244b564e1b9fbbee/cover-image.jpghttps://sciendo.com/journal/LPTS140216https://sciendo.com/article/10.2478/lpts-2024-0028<abstract> <title style='display:none'>Abstract</title> <p>A prototype solar trigeneration system was built in a new private single-family residential house for experimental purposes. The prototype system was designed to supply the building with the required thermal energy and cooling to a full extent. In addition, one of the conditions is that the thermal and the electrical energy generated by the solar systems should be used for the needs of the building to a maximum extent. The prototype system provides an opportunity to recover thermal energy both during the heating and the cooling season.</p> <p>This article describes the prototype configuration, the first results of testing, analysis of the results obtained, and the operational features and shortcomings of the open system, as well as the possibilities for its improvement.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/lpts-2024-00282024-07-18T00:00:00.000+00:00https://sciendo.com/article/10.2478/lpts-2024-0026<abstract> <title style='display:none'>Abstract</title> <p>The current study introduces porous ceramic materials fabricated from cenospheres through spark plasma sintering. The investigation delves into the impact of sintering temperature, mould diameter (20 and 30 mm), and cenosphere size on the resulting material properties. Notably, sample shrinkage initiates at 900 °C and demonstrates an upward trend with temperature escalation, while a larger mould diameter contributes to sample shrinkage. Elevated sintering temperature leads to increased apparent density across various sample series, such as CS 63–150 µm in a 20 mm mould (0.97 to 2.3 g/cm³ at 1050–1300 °C), CS 150–250 µm in a 20 mm mould (0.93 to 1.96 g/cm³ at 1050–1200 °C), and others in different mould sizes. Total porosity decreases from 61.5 % to 3.9 % with a rising sintering temperature (1050 to 1250 °C), while open porosity starts decreasing at lower temperatures. Closed porosity peaks in samples sintered at 1150 °C. Furthermore, an increase in sintering temperature from 1050 to 1300 °C boosts the compressive strength of CS 63–150 samples in a 20 mm mould from 11 MPa to 312 MPa. These findings align with the Rice model, illustrating an exponential relationship between compressive strength, material porosity, and fully dense material compressive strength.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/lpts-2024-00262024-07-18T00:00:00.000+00:00https://sciendo.com/article/10.2478/lpts-2024-0024<abstract> <title style='display:none'>Abstract</title> <p>The study focuses on the development and evaluation of a motion control system for the Large Range Robotic Motion Simulator (LaRRMoS), which is based on a serial manipulator with 6 degrees-of-freedom. Two motion cueing algorithms (MCAs) – Classical Washout Filter (CWF) and Classical Washout Filter with Cylindrical coordinates (CYL) – are implemented and tested for simulation fidelity and LaRRMoS workspace utilization. CWF and CYL motion cueing performance gets assessed in two use cases: car simulation and luge sports simulation. The car case is a typical driving simulator application. The luge sports case is chosen for its high dynamics to assess the limits of the robot and motion cueing. Though this study uses a pre-recorded set of motion data and runs simulations in non-interactive mode, it aims for real-time interactive simulation for LaRRMoS in the future, so only MCAs capable of real-time operation are inspected. Conducted tests show that the CYL algorithm provides superior performance in highly dynamic motion replication, particularly in lateral accelerations.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/lpts-2024-00242024-07-18T00:00:00.000+00:00https://sciendo.com/article/10.2478/lpts-2024-0029<abstract> <title style='display:none'>Abstract</title> <p>This study focuses on overview and general economic viability evaluation of four types of portable electric generators: diesel and petrol internal combustion engines, batteries/accumulators and inverter systems (especially lithium polymer and lithium-ion battery systems), hydrogen fuel cell systems and combination (hybrid) of the latter. It does not include the rarely used, inefficient forms of energy conversion, such as steam turbines, as well as energy generators that are difficult to adjust with consumption and supply variations (variable forms of RES like wind and solar energy). The main targets of the study are battery/inverter systems, hydrogen fuel cell systems, and hybrid battery/inverter and hydrogen fuel cell systems, with hydrogen fuel cell systems being the thematic core.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/lpts-2024-00292024-07-18T00:00:00.000+00:00https://sciendo.com/article/10.2478/lpts-2024-0030<abstract> <title style='display:none'>Abstract</title> <p>Electromagnetic levitation (EML) is a promising technique allowing to melt various materials, including refractive metals, while avoiding physical contact between the molten material and components of the melting system, thus avoiding contamination of the molten material. EML coils act both as a container and a heating source for a conductive sample placed within it. EML systems are difficult to optimize for specific tasks and computational simulations are often used to aid the process. Development of simulations of EML processes is an ongoing field of research. Obtaining precise experimental measurement data of EML processes is important for development and verification of computational simulations. This study aims to provide experimental data of simultaneous measurements for magnetic field, Joule heating and lift force in different conical EML coils with a counterturn.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/lpts-2024-00302024-07-18T00:00:00.000+00:00https://sciendo.com/article/10.2478/lpts-2024-0031<abstract> <title style='display:none'>Abstract</title> <p>The utility of polymers in the fabrication of nanofibres via electrospinning is well established. Paramount to their application is understanding of their thermal properties, as these dictate not only their processability but also their mechanical robustness, stability under elevated temperatures, and suitability for intended applications. The electrospinning process, which involves heating polymers and subjecting them to high voltage, inherently modifies their thermal characteristics. This study attempts to elucidate these alterations, particularly by focusing on polyacrylonitrile (PAN) nanofibres. Employing techniques such as thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC), the study compares the thermal properties of electrospun PAN nanofibre mats with those of their virgin counterparts. The PAN nanofibres were synthesised by electrospinning the PAN polymer solution and collecting the resultant mat on a flat plate collector. For a comparative analysis, virgin PAN, from which nanofibres were derived, underwent identical thermal testing. The findings reveal a reduction in the glass transition temperature of PAN nanofibres by approximately 3–5 % compared to virgin PAN. In addition, a significant reduction in heat capacity of about 42 % was observed in the nanofibres. Additionally, the TGA results indicated solvent evaporation at approximately 110 °C. Therefore, this investigation sheds light on the nuanced alterations in the thermal characteristics of PAN nanofibre mats as a result of the electrospinning process, providing vital insights for their application in various thermal management scenarios.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/lpts-2024-00312024-07-18T00:00:00.000+00:00https://sciendo.com/article/10.2478/lpts-2024-0025<abstract> <title style='display:none'>Abstract</title> <p>Standards are critically important for smartening the grid because they affect the interoper-ability, compatibility, efficiency, and realisation of new technologies and services. In this paper we assess the contribution of EU funded Horizon 2020 projects to adapting or initiating new Smart Grid standards. We provide a comprehensive overview of the Smart Grid standardisation ecosystem and identify opportunities for researchers and innovators to participate in stan-dardisation activities. We identify 225 Horizon 2020 Smart Grid projects and explore which have contributed to the creation or revision of Smart Grid standards. We identify the type of standardisation activities undertaken and explore the factors that influence engagement. We have found that 21 % of EU Horizon 2020 Smart Grid projects engage in some level of standardisation activities. Of these projects the majority (60 %) are involved in understanding standards, 31 % actively engage in influencing standards, while 8 % successfully participate in elaborating new standards. Our study demonstrates that despite the complexity of the Smart Grid Standardisation ecosystem, EU funded researchers and innovators play an important role in the standardisation process.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/lpts-2024-00252024-07-18T00:00:00.000+00:00https://sciendo.com/article/10.2478/lpts-2024-0027<abstract> <title style='display:none'>Abstract</title> <p>The hybrid photodetector (HPD) is a photomultiplier tube combined with the semiconductor device within the vacuum. The photoelectrons emitted from the photocathode directly hit the semiconductor enabling efficient electron multiplication with low noise and symmetric output pulse. These properties make a hybrid photodetector a good solution for photon-counting applications. At the Satellite Laser Ranging Station of the Institute of Astronomy at the University of Latvia, the hybrid photodetector characteristics were evaluated for SLR applications, including multiphoton mode and time-walk compensation.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/lpts-2024-00272024-07-18T00:00:00.000+00:00https://sciendo.com/article/10.2478/lpts-2024-0020<abstract> <title style='display:none'>Abstract</title> <p>In accordance with the goal approved by the Council of the European Union, a European climate-neutrality must be achieved by 2050. Namely, the European Union must significantly reduce greenhouse gas emissions and find ways to compensate for the remaining and unavoidable ones. Within the framework of the European Green Deal, which is a set of policy initiatives to achieve climate neutrality goals, energy communities are considered in the context of two initiatives: a just transition and clean and safe energy at an affordable price. Within the latter, energy community is seen as citizen-led actions in the energy sector that will help pave the way for the transition to clean energy.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/lpts-2024-00202024-05-30T00:00:00.000+00:00https://sciendo.com/article/10.2478/lpts-2024-0016<abstract> <title style='display:none'>Abstract</title> <p>The paper investigates the process of phase separation and morphology of organic-inorganic interpenetrating polymer networks (OI IPNs) based on the cross-linked polyurethane (PU), poly(hydroxyethyl methacrylate) (PHEMA) and poly(titanium oxide) (–TiO₂–)_n obtained by solgel method in the presence of poly(oxypropylene glycol) (POPG) at various molar ratio of titanium (IV) isopropoxide (Ti(OPrⁱ)₄) and water. It has been established that the phase separation in OI IPNs depends on the kinetics of PHEMA-component formation and it occurs through the mechanism of the spinodal decomposition. It has been shown that by varying the ratio of IPNs components, content of inorganic component and Ti(OPrⁱ)₄/H₂O molar ratio it is possible to control the phase separation process and obtain OI IPNs with a different phase structure.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/lpts-2024-00162024-05-30T00:00:00.000+00:00https://sciendo.com/article/10.2478/lpts-2024-0017<abstract> <title style='display:none'>Abstract</title> <p>Holograms recorded by focused light beams have several advantages over usual plane wave holograms such as reduced size, white light readout possibility and others. Focused polarization grating recording in an azobenzene-based molecular glasy film 5,5,5-triphenylpentyl 4-((4-(2-(4-bis(2-hydroxyethyl)amino)phenyl)-1-cyanovinyl)phenyl)dyazenyl)benzoate (which we shortly denoted as B11) is experimentally studied and compared with such grating recording in other materials. It has been determined that focusing manifests itself differently than in other materials, e.g., as in a-As₂S₃ and a-As-S-Se chalcogenide films. Thus, it reduces the holographic grating recording efficiency independently of recording and readout beam polarizations. It has also been found that recording efficiency with circularly and orthogonally <italic>L-R</italic> polarized beams is higher than with linearly polarized <italic>p-p</italic> beams. The highest diffraction eficiency of 26% is achieved with <italic>L-R</italic> polarized unfocused beams.</p> <p>Recording efficiency grating period dependences for unfocused beams at 200 J/cm² exposure and at 1000 J/cm² exposure are different with a maxima at 2 μm and 6 μm, respectively. In contrast, recording efficiency grating period dependences for focused beams at 200 J/cm² exposure and at 1000 J/cm² exposure are the same with the maximum at 6 μm.</p> <p>The obtained results are discussed in terms of <italic>trans-cis-trans</italic> photoisomerization followed by mass transfer and their light intensity dependence, light electric field gradient force, the photoinduced light scattering and photoelastic forces.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/lpts-2024-00172024-05-30T00:00:00.000+00:00https://sciendo.com/article/10.2478/lpts-2024-0023<abstract> <title style='display:none'>Abstract</title> <p>The accumulation of plutonium produced by LWR operations causes public concern related to its radiotoxicity and proliferation issue. Therefore, there is some interest in developing various methods for consuming plutonium through plutonium incineration i.e., by utilising thorium-based nuclear fuel. Thorium-plutonium mixed oxide fuel (Thorium MOX) is an attractive option considered for plutonium incineration. The aim of the study is to investigate the neutronic characteristics of Thorium MOX fuel in VVER-1000 nuclear reactor fuel assemblies. The VVER-1000 Benchmark model was utilised in the present study. A series of calculations were performed with the MCNP6 code and the ENDF/B-VII library. The calculation results show that a proper increase in Pu content could increase <italic>k</italic>_inf of ThMOX fuel, so it could have almost the same <italic>k</italic>_inf with MOX fuel or increase Pu content when needed. It was also shown that Thorium MOX fuel assembly had more negative Doppler reactivity due to neutron capture by thorium (²³²Th). The moderator temperature coefficient was found to be more negative than the Doppler coefficient, and it could be concluded that replacing uranium with thorium could reduce the amount of plutonium produced while increasing plutonium consumption.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/lpts-2024-00232024-05-30T00:00:00.000+00:00https://sciendo.com/article/10.2478/lpts-2024-0021<abstract> <title style='display:none'>Abstract</title> <p>The paper proposes a method of simultaneous reconstruction of the electrical conductivity and magnetic permeability profiles of planar metal research objects based on the results of single measurements by eddy current probes using surrogate optimization techniques in a reduced compact subspace design and accumulating the full amount of the most important a priori information about the modes of electromagnetic objects. In addition to the information on the response of probe signals to changes in electrophysical parameters, a priori information includes the data on multifrequency sensing and changes in the lift-off between metal research objects and eddy current probes. All the main stages for the implementation of the method of solving the inverse problem are demonstrated, namely, creating a uniform computer quasi-design of the experiment with improved 2D-projections based on LP_τ-Sobol’s sequences; creating surrogate models on fully connected deep neural networks; reducing the dimensionality of the full design space using the principal components method of PCA; reconstructing profiles as a result of surrogate optimisation in a compact subspace. Numerical examples of the method are also presented in the paper.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/lpts-2024-00212024-05-30T00:00:00.000+00:00https://sciendo.com/article/10.2478/lpts-2024-0022<abstract> <title style='display:none'>Abstract</title> <p>At the end of 2019, the EC presented the European Green Deal – a set of policy initiatives with the ultimate goal of making Europe climate-neutral by 2050. This means that all EU member states must reach climate neutrality. Emissions in all sectors shall be substantially reduced to achieve this goal. Most of the energy is produced using fossil fuels, which contributes to climate change, water and air pollution, as well as the depletion of natural resources. Individual and district heating systems, which supply residential buildings with heat and hot water, are responsible for a part of global emissions.</p> <p>Electricity generation also produces emissions. The EU recognises the mitigation of climate change as one of the main challenges that must be overcome to ensure sustainable development of the European Union, which is why it has defined ambitious goals to promote decarbonisation and is deliberately moving towards the implementation of renewable energy.</p> <p>This article aims at analysing the opportunity of using renewable energy resources in multi-apartment residential buildings in the context of sustainability.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/lpts-2024-00222024-05-30T00:00:00.000+00:00https://sciendo.com/article/10.2478/lpts-2024-0018<abstract> <title style='display:none'>Abstract</title> <p>This study explores the recent legislative changes allowing prosumers and consumers in Latvia to form energy communities (EnCs). In spite of legal advancements, the absence of supporting regulations and potential barriers, such as the lack of tailored support schemes and forecasting tools, pose challenges. International experiences highlight additional hurdles, including weak stakeholder dialogue and limited EnC modelling tools. To address these issues, the study proposes a prosumer and consumer EnC business model aligned with Latvia’s legislation, emphasising a peer-to-peer (P2P) trading approach. The model incorporates state aid, electricity trader responsibilities, and reinvestment of EnC profits, eliminating the need for a dedicated trading platform. The study introduces a user-friendly planning tool in MS Excel, evaluating economic viability through case studies and scenarios. Findings emphasise the optimisation of EnC effectiveness by adjusting tariffs, minimising initial investment costs, securing external funding, and managing loan durations. The planning tool serves as a universal instrument, offering insights into individual EnC economic indicators based on their unique characteristics. The research provides valuable guidance to stakeholders and policymakers in Latvia’s evolving energy landscape.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/lpts-2024-00182024-05-30T00:00:00.000+00:00https://sciendo.com/article/10.2478/lpts-2024-0019<abstract> <title style='display:none'>Abstract</title> <p>The paper demonstrates a spectrum slicing technique applied to PAM-4 modulated signal spectrum at 40 Gbaud baudrate for optical access networks. The spectrum slicing is shown in VPIphotonics simulation environment, where characteristics of key components are measured in the laboratory and loaded into the corresponding elements of the simulation setup. The spectrum of electrical baseband signal is sliced in four slices introducing an additional degree of freedom – higher data rate signals can be transmitted by re-using already-existing lower bandwidth transceiver components in an optical access network. This tackles the electronic bottleneck enabling the on-demand variable bandwidth allocation and extends the life span of opto-electrical components during network upgrades. Furthermore, the use of the proposed spectrum slicing technique has a positive side-effect when it comes to security concerns, as the signal spectrum is divided into slices. All slices are necessary to obtain the reconstructed signal and even if an eavesdropper gets most of the slices it is still not enough. The simulation results show that the proposed spectrum slicing and stitching approach is a viable solution to overcome the problem of limited frequency bandwidth of electrical components.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/lpts-2024-00192024-05-30T00:00:00.000+00:00https://sciendo.com/article/10.2478/lpts-2024-0010<abstract><title style='display:none'>Abstract</title> <p>Laser-induced breakdown spectroscopy (LIBS) provides a rapid, cost-effective, and extra-sensitive analysis of geological samples to make preliminary conclusions about the presence of valuable elements up to the trace levels in the ore. We present the first results of a highly sensitive qualitative analysis of the core samples of geological ore from two boreholes in Latvia (Staicele 1, from a depth range of 794–802 m, and Garsene (Subate) 2A, from a depth range of 1102–1103 m) using LIBS. Our measurements using this technique confirmed the high iron content and indicated traces of rare and high in-demand metals (such as Ti, V, Co, Sm, etc.) in the sample from Staicele, renewing interest in studying boreholes across Latvia. The presented pilot studies demonstrated effectiveness and unique possibility in performing a very sensitive and time-saving qualitative analysis of the composition of samples of ores from the old but still valuable borehole cores by using the LIBS method. We compare these measurements with other methods of sample analysis.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/lpts-2024-00102024-03-30T00:00:00.000+00:00https://sciendo.com/article/10.2478/lpts-2024-0014<abstract><title style='display:none'>Abstract</title> <p>The aim of the study is to analyse energy consumption for heating in set of the school buildings. Data analysis includes three data sets – predictions from energy performance certificates (EPC), measured data from heat meters and measured climate corrected data. Data sets were statistically checked and processed and represented graphically. The actual energy consumption differs from the one stated in the EPCs in all cases, which means that schools consume on average 15 % more energy than it is stated in the EPC. Overall, the data reveal that the actual energy consumption differs from the theoretical consumption, with all schools having higher actual consumption than the theoretical values. The differences in the data sets are discussed, and possible improvements are suggested taking into account strong relation between energy consumption and indoor air quality.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/lpts-2024-00142024-03-30T00:00:00.000+00:00https://sciendo.com/article/10.2478/lpts-2024-0012<abstract><title style='display:none'>Abstract</title> <p>During the pandemic and periods of martial law, educational institutions in Ukraine implemented various forms of organising the educational process, combining in-person and remote classes. As a result, there has been a decrease in the level of use of building premises. The analysis of the characteristics of energy consumption in these conditions requires additional attention. In this study, a dynamic energy model of the building was created using the educational building of Igor Sikorsky Kyiv Polytechnic Institute as an example. Energy consumption for heating needs was determined for normal operating conditions and quarantine conditions in Ukraine (only a specific part of the premises is being operated, ensuring that the standard temperature value is maintained while people are present). Based on the results of the study, the features of the energy consumption of the building during quarantine/martial law restrictions, subject to the partial use of the building, were analysed, and the main disadvantages of such a mode were identified. For the educational building of the university, the total energy consumption for heating needs depends on the number of rooms that are actively used, and the modes of regulation of heating and ventilation; the consumption can decrease depending on the chosen scenario by 61 %, 56 %, and 34 % in quarantine mode. The findings indicate that the efficiency of regulation modes can decrease by more than four times when compared to normal mode due to internal heat exchange with unoccupied rooms.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/lpts-2024-00122024-03-30T00:00:00.000+00:00https://sciendo.com/article/10.2478/lpts-2024-0009<abstract><title style='display:none'>Abstract</title> <p>Transition metal dichalcogenides (TMDs), specifically those involving V and Ti, possess fascinating material properties, making them interesting candidates for scientific studies. The existing growth methods of these materials are typically limited by scalability – either low yield or high cost. Here, we propose an alternative 2-step method valid for scalable production. In the first step, precursor films of Ti / V are deposited using magnetron sputtering, followed by the second step of selenization of these samples using elemental Se in a vacuum-sealed quartz ampoule for conversion to their respective diselenide material. Synthesized films are char-acterised using scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and X-ray photoelectron (XPS). The method demonstrated here can be used to increase the active surface area of TiSe₂ and VSe2 for their potential catalytic and HER applications using nanostructured substrates, while also providing an opportunity for scalable synthesis of films that can be extended to synthesize other TMDs as well.</p> </abstract>ARTICLEtruehttps://sciendo.com/article/10.2478/lpts-2024-00092024-03-30T00:00:00.000+00:00en-us-1