rss_2.0Latvian Journal of Physics and Technical Sciences FeedSciendo RSS Feed for Latvian Journal of Physics and Technical Sciences Journal of Physics and Technical Sciences Feed Patterned Growth of ZnO Nanoneedle Arrays<abstract> <title style='display:none'>Abstract</title> <p>Nanostructured coatings are widely used to improve the sensitivity of various types of sensors by increasing the active surface area compared to smooth films. However, for certain applications (in some cases), it may be necessary to achieve selectivity in the coating process to ensure that nanostructures only form in specific areas leaving interelectrode spaces free of nanostructures. This article discusses several methods for creating intricate ZnO nanostructured patterns, including area selective application of Zn acetate seeds followed by hydrothermal growth, selective thermal decomposition of zinc acetate via laser irradiation followed by hydrothermal growth, and the electrochemical deposition method. These methods enable ZnO nanostructures to grow onto designated surface areas with customised, patterned shapes, and they are rapid, cost-effective, and environmentally benign.</p> <p>The article examines the process of producing a nanostructured coating with a complex shape and discusses several factors that can impact the quality of the final product. These include the influence of the thermocapillary flows and the “coffee stain” effect on the deposition of a seed layer of zinc oxide from an ethanol solution of zinc acetate. Additionally, the study found that using a protective screen during the growth of nanostructures can reduce the occurrence of unintended parasitic structures in areas lacking a seed layer. Overall, the article presents various techniques and strategies to improve the quality of nanostructured coatings.</p> <p>We have proven that the use of laser radiation to create a seed layer does not impact the final morphology of the resulting nanostructures. However, when combined with computer-controlled technology, this approach allows for the creation of intricate patterns made up of micrometre-sized lines which cannot be achieved by using other methods.</p> <p>The article also demonstrates an electrochemical technique for obtaining zinc oxide nano-structures that can selectively coat metal electrodes without requiring a seed layer.</p> </abstract>ARTICLEtrue Modelling of a Turbine Flow Meter Used as Part of the Hydrogen Compressor System<abstract> <title style='display:none'>Abstract</title> <p>This study analyses a turbine flow meter in the context of a hydrogen compressor system. Basic concepts of turbine flow meter, accuracy and linearity, as well as calibration are described. Physical experimental testing scheme is presented in the paper. The viscosity of the fluid is one of the major factors that affects the performance of turbine flow meters. Numerical modelling experiments for different fluids with different viscosities are performed. Performed numerical modelling experiments give a possibility to continue research into the hydrogen compression system.</p> </abstract>ARTICLEtrue Distribution System of Latvia and its Transitional Challenges<abstract> <title style='display:none'>Abstract</title> <p>The future of the European Union’s (EU) gas sector and gas distribution systems in particular is under review as a necessity to move away from conventional natural gas is strictly outlined in its strategical energy framework. The main questions of future gas sector layout are largely related to gas decarbonization paths – whether they will include simultaneous transportation, distribution and storage of methane-based and non-methane based renewable gases or not. In general, this question is left for different Member States to decide, because as alternatives to it there are two options – decommissioning of all gas distribution and partially gas transportation and storage systems on the one hand and total replacement of existing gas transportation system with brand new hydrogen transportation and distribution system on the other. The first option leaves only liquified renewable gases (including, hydrogen) that are transported via truck and the second – pipeline transportation and distribution only for hydrogen, limiting methane-based renewable gases to road transportation solutions only.</p> <p>The Latvian gas distribution system is also facing imminent transformation in foreseeable future; thus, at the moment its sustainability priority is the maintenance of the existing system in a safe and secure manner by improving it in accordance with technical necessities and immediate customer requests. The current research shows two sides of gas distribution system priorities in Latvia – its maintenance and development trends prior to fundamental transformations of gaseous fuel transition and general transitional challenges laying ahead.</p> </abstract>ARTICLEtrue CoO Nanostructure-Based Electrochemical Sensor for HO Detection<abstract> <title style='display:none'>Abstract</title> <p>This article describes the synthesis of nanostructured cobalt oxide on iron wires and its application for the detection of hydrogen peroxide as working electrode for non-enzymatic electrochemical sensor. Cobalt oxide was obtained by the hydrothermal synthesis method using chloride and acetate anions. The resulting nanostructured coating obtained from the chloride precursor is a uniform homogeneous porous network of long nanofibers assembled into regular honeyсomb-like formations. In the case of an acetate precursor, instead of nanofibers, petal-like nanostructures assembled into honeycomb agglomerates are observed. The structure, surface, and composition of the obtained samples were studied using field-emission scanning electron microscopy along with energy-dispersive spectroscopy and X-ray diffractometry.</p> <p>The resultant nanostructured specimens were utilized to detect H<sub>2</sub>O<sub>2</sub> electrochemically through cyclic voltammetry, differential pulse voltammetry, and i-t measurements. A comparative research has demonstrated that the nanostructures produced from the chloride precursor exhibit greater sensitivity to H<sub>2</sub>O<sub>2</sub> and have a more appropriate morphology for designing a nanostructured sensor. A substantial linear correlation between the peak current and H<sub>2</sub>O<sub>2</sub> concentration within the 20 to 1300 μM range was established. The Co<sub>3</sub>O<sub>4</sub> electrode obtained exhibits a sensitivity of 505.11 μA·mM<sup>−1</sup>, and the electroactive surface area is calculated to be 4.684 cm<sup>2</sup>. Assuming a signal-to-noise ratio of 3, the calculated limit of detection is 1.05 μM. According to the interference study, the prevalent interfering agents, such as ascorbic acid, uric acid, NaCl, and glucose, do not influence the electrochemical reaction. The obtained results confirm that this sensor is suitable for working with complex analytes.The actual sample assessment demonstrated a recovery rate exceeding 95 %.</p> </abstract>ARTICLEtrue Partial Solar Eclipse for the 14-Metre Radio Telescope Calibration<abstract> <title style='display:none'>Abstract</title> <p>A partial solar eclipse occurred on 25 October 2022, in the central and northern parts of Europe. The partial solar eclipse was observed at Aalto University Metsähovi Radio Observatory, Finland at the radio wavelength of 8 mm (37 GHz). In Finland, the magnitude of the partial solar eclipse was 62.7 %. Solar radio maps at the time cadence of about 9 minutes were observed over the whole eclipse. The solar eclipse observations could be used for instrument calibration purposes. This paper investigates the solar brightness temperature, the limb brightening effect, the height of the chromosphere and the location of radio brightening using the aforementioned partial solar eclipse observations.</p> <p>We got the confirmation that our earlier results are consistent, e.g., the solar brightness temperature matches with 8100 K ± 300 K. It was also possible to detect limb brightening effect. However, the prevailing solar activity might have distorted the final conclusions. The Moon should operate as a focusing element and the location of radio brightenings could be defined more carefully than in the normal conditions. We investigated this feature. Our results are in some parts unexpected and need further investigations.</p> </abstract>ARTICLEtrue to Decentralized Renewable Energy in Latvia: A Comprehensive Payback Analysis<abstract> <title style='display:none'>Abstract</title> <p>It is believed that the transition to renewable decentralized energy supply solutions (e.g., solar panels, storage of electricity in batteries) will help promote the decarbonization of the energy system. At the same time, it is expected to happen only when society is convinced of the environmental benefits and when there are enough economic incentives for it. This study analyses the economic feasibility of transitioning to decentralized renewable energy solutions, including solar panels and electricity storage, in Latvia. Our research explores potential savings of these solutions under various scenarios based on different factors, such as national NETO billing system, financial support scheme, electricity pricing, distribution network tariffs, energy storage options, as well as the impact of the battery energy storage system (BESS) discharging strategy. The results show that the potential savings can vary depending on these factors that are changing over time. Nevertheless, the rise in small-scale power generation at households shows that there is an increasingly rapid transition from centralized electricity supply to a decentralized supply system, which might indicate that society supports energy transition.</p> </abstract>ARTICLEtrue Formation at the Junctions of the Polycrystal Intergranular Boundary Under Plastic Deformation<abstract> <title style='display:none'>Abstract</title> <p>The article is devoted to the study of the mechanism of nanopore formation in the junctions of polycrystal grains under the plastic deformation of a polycrystal due to the conservative sliding of lattice dislocations. A mechanism for the formation of a stress concentrator at the junction of the polycrystal grain boundaries is proposed. The possibility of relaxation of the stress state due to the formation of a junction nanopore is considered in the paper.</p> </abstract>ARTICLEtrue Manufacturing of Ti-6Al-4V with Carbon Nanotube Composite Material<abstract> <title style='display:none'>Abstract</title> <p>This research is dedicated to investigating whether mechanical properties of Ti-6Al-4V (Titanium Grade 5) base material for additive manufacturing processes can be improved by addition of carbon nanotubes in the base material. Based on other research results with other materials, the assumption was made that reinforcing Ti-6Al-4V material with carbon nano-tubes should improve mechanical properties of the base material by 15–20 % in the additive manufacturing process. The research was divided in two steps, the first one was to investigate pure Ti-6Al-4V material and find optimal additive manufacturing processing parameters, which could maintain necessary quality standards and achieve material density levels higher than 98 % and tensile strength higher than 1000 MPa. The second part was to mix base powder with carbon nanotubes and using previously obtained processing parameters print test samples to investigate how a carbon nanotube concentration in a base powder would influence mechanical properties of the base material.</p> </abstract>ARTICLEtrue of Calcium Aluminate Doped with Mn and Cr in Optical Thermometry<abstract> <title style='display:none'>Abstract</title> <p>Optical thermometers are advantageous for temperature measurement in electromagnetic fields and aggressive environments; however, their composition mostly relies on materials doped with expensive and resource-limited rare earth ions.</p> <p>In this article, we describe the application of calcium aluminate doped with transition metal ions (Mn<sup>2+</sup> and Cr3+) in optical thermometry, employing optical fibres for signal transmission. Upon excitation with 450 nm laser diode radiation, changes in the luminescence of Mn<sup>2+</sup> ions in the 500–550 nm band are followed along with changes in the Cr<sup>3+</sup> band at 750–800 nm.</p> <p>The application has been tested in the temperature range from 20 °C to 800 °C. The temperature dependence of Cr<sup>3+</sup> luminescence encompasses the high-temperature range, whereas the luminescence band of Mn<sup>2+</sup> ions gives an increase in the total intensity and provides a more consistent change in the range from 400 °C to 550 °C.</p> </abstract>ARTICLEtrue Design and Performance of Internally Cooled Cutting Tools for Turning: A Literature Review<abstract> <title style='display:none'>Abstract</title> <p>Near–dry machining and dry machining lead to increased temperature of the cutting tools. To reduce tool wear and extend the tool lifetime, and, eventually, to keep the accuracy of manufactured parts within acceptable limits as long as possible, a sustainable cooling technique is required. The technology of internal cooling of the cutting tool appears to be the most promising, because it allows eliminating the presence of the coolant on the manufacturing part and delivers the heat–transferring fluid to the very cutting area of the tool. This paper provides a literature review on the closed–loop internally cooled cutting tools (CLICCT) for turning. The current level of knowledge and experimental machining with prototypes has proven that CLICCT can utilize the benefits of dry cooling, having a longer tool life.</p> </abstract>ARTICLEtrue Role of Decentralized Electrode Boiler in Ancillary Services and District Heating: a Feasibility Assessment<abstract> <title style='display:none'>Abstract</title> <p>This article evaluates the feasibility of using electrode boiler in grid ancillary services and district heating scenarios. Electrode boilers in the context of electricity grid management can be considered as a relatively new technology. This study assesses the technical and economic viability of electrode boiler by considering various factors such as energy demand, technical feasibility, economic viability, and regulatory market conditions. The simplified mathematical model has been developed for simulation of electrode boiler use for grid services and heat production. The results have shown that electrode boiler have the potential to be a cost-effective solution for heating and grid balancing services in certain scenarios. However, it may not be applicable or economically viable in all situations or regions; thus, further research and development is needed to fully realize their potential.</p> </abstract>ARTICLEtrue Hydrogen With Natural Gas/Biomethane and Transportation in Existing Gas Networks<abstract> <title style='display:none'>Abstract</title> <p>The existing European Union (EU) natural gas network provides large capacity to integrate renewable (RGs) and low-carbon gases. Today, hydrogen contributes only a few percent to Europe’s energy consumption and is almost exclusively produced from fossil fuels and used in the industry. Nevertheless, hydrogen has a significant role to play in emission reduction in hard-to-decarbonize sectors, in particular, as a fuel in transport applications and as a fuel or feedstock in certain industrial processes (steel, refining or chemical industries, the production of “green fertilizers”). Carbon dioxide (CO<sub>2</sub>) in reaction with hydrogen can also be further processed into synthetic fuels, such as synthetic kerosene in aviation. In addition, hydrogen brings other environmental co-benefits when used as fuel, such as the lack of air pollutant emissions.</p> <p>However, in transitional phase from fossil to RG, namely, renewable or green hydrogen, natural gas/biomethane and hydrogen blends, are needed to gradually replace natural in existing gas transmission and distribution networks. The gas networks are believed to be able to use natural gas/biomethane and hydrogen blends with 5–20 % of hydrogen by volume. Most systems and applications are able to handle it without a need for major infrastructure upgrades or end-use appliance retrofits or replacements. The promotion of hydrogen network such as European Hydrogen backbone (EHB) is gaining momentum in Europe. To decarbonize the natural gas grids, the threshold of hydrogen in the existing grid systems must be increased, which can be done by means of wider natural gas/biomethane and hydrogen blending and simultaneous transportation in currently operational gas networks.</p> </abstract>ARTICLEtrue and Implementation of Energy Efficiency Measures in Multi-Apartment Buildings in Latvia<abstract> <title style='display:none'>Abstract</title> <p>A simplified life cycle of any product or service consists of three main stages – manufacturing, including obtaining, transformation, combination of raw materials; transportation, as well as packaging; consumption from purchase up to actual use. Energy is not an exception, it is also an item offered by the market in different forms, and everyone in need of it has the right to buy it in case the price is acceptable. Heat power is one of the energy types required by households and important for proper maintenance. Without heating, as well as electricity, modern houses cannot function appropriately, are not attractive to their inhabitants, do not provide comfort and safety. Nevertheless, heat power often is considered as a by-product of electricity production, nowadays a swift price increase for both types of energy is inevitable.</p> <p>Energy efficiency is the level of appropriate usage of energy resources, which can be determined as the relation between final product type, quality, quantity and consumption of energy necessary to create this product [<xref ref-type="bibr" rid="j_lpts-2023-0031_ref_001">1</xref>].</p> <p>Indirectly energy efficiency impacts health of the society in general and each individual in particular. Renovated energy efficient apartment buildings have a better ventilation system and microclimate. The problem of moisture and mold is at least partly solved, comfort is reached by consuming less energy, especially, heat power [<xref ref-type="bibr" rid="j_lpts-2023-0031_ref_002">2</xref>].</p> <p>The aim of the paper is to research the impact of different energy efficiency increasing measures on heat consumption in multi-apartment buildings.</p> </abstract>ARTICLEtrue of NaYF:Yb, Tm Nanocrystals Via the Thermal Decomposition Method Using Refined Sunflower Oil<abstract> <title style='display:none'>Abstract</title> <p>In recent years, up-conversion luminescence nanoparticles have attracted significant attention from researchers in fields such as analytical chemistry (for example qualitative and quantitative analysis of metal and non-metal ions) and biomedicine (cancer imaging, drug delivery, treatment, etc.) due to their high rate of emission efficiency, easy surface functionalization, great chemical and thermal and photostability and other favorable properties. NaYF<sub>4</sub> in particular has attracted interest of researchers as a host material due to its low phonon energy, thus increasing the efficiency of emission. In this study, the synthesis of NaYF<sub>4</sub>:Yb<sup>3+</sup>,Tm<sup>3+</sup> nanocrystals using the hydrothermal method was successfully carried out. Refined sunflower oil containing oleic acid was used as a solvent instead of analytical grade oleic acid and octadecene-1, reducing the cost of the synthesis. Using semi-quantitative XRD measurement analysis, it was determined that 25.3 % hexagonal β-NaYF<sub>4</sub>:Yb<sup>3+</sup>,Tm<sup>3+</sup> as well as 23.8 % cubic α-NaYF<sub>4</sub> nanocrystal crystalline phases were found in the synthesized sample. The sample showed mainly luminescent characteristics typical of hexagonal NaYF<sub>4</sub>:Yb<sup>3+</sup>,Tm<sup>3+</sup> lattice nanoparticles.</p> </abstract>ARTICLEtrue Fault Locator for High-Voltage Transmission Lines Based on the Estimation of Power System Model Parameters<abstract> <title style='display:none'>Abstract</title> <p>This paper presents an adaptive transmission line fault location method, which incorporates fault location devices at both line ends and utilises data import from a supervisory control and data acquisition system without strictly requiring data synchronisation. The developed method aims at achieving a higher degree of robustness, adaptiveness and accuracy. The adaptiveness is achieved by dynamic updating of mathematical models used on the basis of network-wide information, such as data on the state of circuit-breakers and apparent power at load and generation nodes. The robustness and accuracy are enhanced by incorporating two stages of identification of model parameters with the goal of reducing the decision variable space for the stage identifying fault parameters. Furthermore, in addition to utilisation of all measurements available at a particular substation, the developed method partially employs the measurements from the other end of the line by means of result cross-checks, but does not require a full data set, unlike deterministic-model-based methods. An optimisation-based approach, redundancy on the basis of extended measurement set, and cross-checks reduce the risk of fault location errors due to measurement errors or “voids” in the data available. Testing of the developed method demonstrates its accuracy and robustness in a wide range of pre-fault and fault regime scenarios, even when considering various pre-fault contingencies.</p> </abstract>ARTICLEtrue Influence of the Thermal Effect on the Stress-Strain State of the Soil<abstract> <title style='display:none'>Abstract</title> <p>The present paper provides the dependence of the temperature change on time and the depth of the soil massif based on numerical calculations. Mathematical modelling of the one-dimensional soil temperature field via an algorithm and a PC program is carried out without taking into account the influence of the phase transition of moisture in the soil pores during seasonal freezing and thawing using the finite difference method. The amplitude of fluctuations in the temperature regime is obtained as that decreases with depth from the soil surface. It is established that over time heat spreads from the pipeline to the surface of the soil, and over time more intense heating occurs both near the pipeline and in the body of the soil massif.</p> </abstract>ARTICLEtrue of Mathematical Modeling of Acoustic Emission Method for Diagnosis of Fatigue Cracks in the Elements of Marine Power Plants<abstract> <title style='display:none'>Abstract</title> <p>This article analyses the main characteristics of marine power plants, which include internal combustion engines (ICE) and gas turbine engines (GTE). At the same time, gas turbines are considered in comparison with aircraft engines. The study considers the possibility of using the acoustic emission (AE) method to evaluate the fatigue resistance of critical elements of ICE and GTE, based on the valve block in the ICE and turbine rotor blades. AE criteria for determining the growth of fatigue cracks are analysed, a method for evaluating individual durability and a method for calculating crack length are proposed.</p> </abstract>ARTICLEtrue of a Hydraulic Hydrogen Compression System for Refuelling Stations<abstract> <title style='display:none'>Abstract</title> <p>The article presents a hydraulic hydrogen compression solution designed to serve as a booster compressor. It can be adapted to changing parameters of the inlet pressure of hydrogen and allows stabilising the hydrogen accumulation process in the high-pressure storage.</p> <p>The main results of this study were obtained using a numerical model developed to explore the thermodynamic processes that occur during the hydraulic compression of hydrogen. The modelling was carried out using COMSOL Multiphysics® 6.0 software with the CFD and heat transfer modules. The compression chamber in the form of a cylinder with a volume of 1.14 <italic>l</italic> and wall thickness of 5 mm was used in the computational model. The aim of these simulations was to investigate the temperature change limits of hydrogen, cylinder walls and working fluid, as well as to estimate the actual value of pressure inside the cylinder. The considered process of pressure increase in the cylinder chamber was modelled as a continuous change of volume filled with working fluid with discrete time step of 0.01 <italic>s</italic>, taking into account the increase of temperature inside the cylinder. The derived modelling results for different durations of compression stroke t<sub>s</sub> from 0.5 to 20.0 <italic>s</italic> were presented. The curves of energy consumption and temperature rise during the compression process were calculated for initial hydrogen pressures P<sub>1</sub> = 3.0, 10.0, 15.0 and 20.0 <italic>MPa</italic> and compression ratio Kc = 5.0.</p> <p>The results of simulation of thermodynamic processes and their analysis allowed estimating energy consumption in the system of hydraulic compression and determining conditions which would lead to the increase in efficiency of hydrogen compression operation systems under consideration.</p> </abstract>ARTICLEtrue of FWM-Based OFC for DWDM Optical Communication System with Embedded FBG Sensor Network<abstract> <title style='display:none'>Abstract</title> <p>Four-wave mixing optical frequency comb fibre-based setups (FWM-OFCs) have the potential to improve the combined dense wavelength division multiplexed passive optical network (DWDM-PON) and fibre Bragg grating (FBG) temperature sensors network providing easier application, broader technological opportunities for network development, and energy efficiency by substituting a power-demanding laser array.</p> <p>In this research, OFCs are generated for the purpose of combined network application of DWDM-PON and FBG optical sensors. The paper also investigates compatibility scenarios with OFCs in such systems. The mathematical simulation model has been developed and the performance of FWM-OFC based 8-channel 50 GHz spaced non-return-to-zero on-off keying (NRZ-OOK) modulated DWDM-PON transmission system, operating at 50 km single-mode fibre (SMF) with a bit rate of at least 10 Gbps embedded with 7 FBG optical temperature sensors, has been studied. As it is shown, FWM application results in OFC source that has fluctuations of the individual comb tones of less than 3 dB in power, and with an extinction ratio of about 33 dB for operation range of 192.9–193.25 THz, acting as a unified light source for all the data transmission channels. Embedded FBG optical sensors network causes negligible 0.3 dB power penalty.</p> </abstract>ARTICLEtrue Emission Method as a Means of Quality Control in Multilayer Welding of Thick-Walled Welded Joints<abstract> <title style='display:none'>Abstract</title> <p>The article reviews the capacities of the acoustic emission method usage to assess the technical condition and integrity of thick-walled welded structures, the quality control of welded joints in multilayer welding. As a result of the analysis of AE control data, the authors propose a set of informative parameters of the AE method, which form a criterion space for separating the reflected signals from defects and signals from interference.</p> </abstract>ARTICLEtrue