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 's Cover Observations of Old Centaur Rocket from 1966<abstract> <title style='display:none'>Abstract</title> <p>We report the results of radar observations of a near-Earth object discovered on 17 September 2020, with the Pan-STARRS 1 telescope at the Haleakala Observatory in Hawaii. Initially, this object was considered an asteroid and even received the standard provisional designation 2020 SO by the Minor Planet Center. However, its Earth-like orbit and low relative velocity suggested that the object may be of artificial origin, being the Centaur rocket booster from the Surveyor 2 mission that was launched to the Moon on 20 September 1966. In the period from November 2020 to March 2021, this object approached the Earth twice within one lunar distance of the Earth. Radar observations were conducted on 30 November in bistatic mode with the 70-m Goldstone Solar System Radar DSS-14 and 32-m radio telescope RT-32 at the Svetloe Observatory, while the object was in the visibility window of two antennas at about 200 thousand km from the Earth. The main goal of the study was to determine the physical properties of this object using radar astronomy to clarify its origin.</p> </abstract>ARTICLE2022-06-23T00:00:00.000+00:00Magnetic Flux Switching Type Permanent Magnet Generator for Bicycles: Modelling and an Experimental Study<abstract> <title style='display:none'>Abstract</title> <p>The article introduces two new designs of flux switching permanent magnet alternators with a radial and an axial arrangement of the inductor relative to the magnetic flux switch. The study presents the results of 3D magnetic flux modelling along with the outcomes of physical experiments. In the course of laboratory experiments, the results of theoretical estimations are compared with actual physical performance parameters. The results are presented in the form of power and output voltage curves in relation to the frequency and load current. The study proposes the practical application of the alternators based on the magnetic flux switching principle in the development of a bicycle generator. Laboratory test models are made of a laminated steel using a waste-free technology.</p> </abstract>ARTICLE2022-06-23T00:00:00.000+00:00Importance of Spectrum Management in Radio Astronomy<abstract> <title style='display:none'>Abstract</title> <p>The increasing terrestrial and space-borne communications are causing major problems to the radio astronomy observations. Only a minor part of the frequencies is allocated to the passive services, such as Radio Astronomy Services (RAS). There are only a few, relatively narrow frequency bands below 20 GHz, which are still suitable for the radio astronomical observations. In addition, Out-of-Band (OoB) emissions will be a real threat to the observations on these bands. On behalf of all European radio astronomers, the Committee on Radio Astronomy Frequencies (CRAF) of the European Science Foundation (ESF) coordinates activities to keep the frequency bands used by radio astronomy and space sciences free of interference. Along with interference caused by active radio communication services, the local electronic device selection should be considered in the observatories. For instance, more common LED based lamps could cause harmful interference for the observations. Thus, it is very important to perform continuous radio frequency interference (RFI) monitoring locally, in each radio observatory.</p> </abstract>ARTICLE2022-06-23T00:00:00.000+00:00Relationship Between Solar Millimeter and Soft X-Ray Emissions<abstract> <title style='display:none'>Abstract</title> <p>The connection between solar radio and soft X-ray emission has earlier been studied at various radio frequencies. For instance, the intensity peak times during solar flares have been compared between these two wavelength regimes. It has been reported that solar radio emission peaks before soft X-ray emission during a flare. However, opposite results have also been presented. In this study, we compare millimetre (8 mm) solar and soft X-ray emissions (0.5–4 Å and 1–8 Å). The radio observations were made at Metsähovi Radio Observatory of Aalto University in Finland between 2015 and 2019. The soft X-ray data were observed with GOES-15 (Geostationary Operational Environmental Satellite). The data show that the solar millimetre emission can peak either before or after soft X-ray peak emission. In this study, we present two different scenarios, which could explain the peaking time differences and behaviour. The first scenario proposes a tight connection between the millimetre (8 mm) and soft X-ray emissions, the second one is for cases where the emission mechanisms are more separate.</p> </abstract>ARTICLE2022-06-23T00:00:00.000+00:00Microwave Observations of the Sun with Virac RT-32 Radio Telescope: The Expansion of Possibilities<abstract> <title style='display:none'>Abstract</title> <p>Nowadays there is increasing interest in narrowing coronal areas with reduced brightness temperatures (LTR – Low Temperature Regions) associated with local open magnetic fields (S-web, “coronal partings”, “dark coronal corridors”) as one of the eventual sources of slow solar wind. Ventspils International Radio Astronomy Centre (VIRAC) performs routine spectral polarimetric observations of the Sun with RT-32 radio telescope equipped with the multi-channel (16 frequency channels) spectral polarimeter for the wave length range of 3.2–4.7 cm (6.3–9.3 GHz) and both circular polarizations simultaneously. The analysis of relevant tasks of clear and reliable observations and detections of LTR shows the necessity to improve noise parameters, dynamic range and stability of the actual solar spectral polarimeter and to expand its wavelength range. Taking into account these requirements, the low noise and thermally stabilized solar spectral polarimeter was developed. The new multi-channel spectral polarimeter is expected to observe right and left circular polarization of the solar emission in the wavelength range of 2.1–7.5 cm (4.1–14.3 GHz) divided into 12 frequency bands. The dynamic range was expanded to &gt;36 db and the signal/noise ratio (referred to as quiet Sun brightness temperatures) was enhanced to &gt; 22–24 db.</p> <p>The paper deals with some test observations of the newly developed solar spectral polar-imeter and its feature analysis. Some eventual problems of solar physics which could be solved with the spectral polarimeter are also discussed.</p> </abstract>ARTICLE2022-06-23T00:00:00.000+00:00Observations of Weak Galactic OH Masers in 1.6 GHz Frequency Band Using Irbene RT-32 Radio Telescope<abstract> <title style='display:none'>Abstract</title> <p>Ventspils International Radio Astronomy Centre (Ventspils University of Applied Sciences) is implementing the scientific project “Complex Investigations of the Small Bodies in the Solar System” (lzp-2018/1-0401) related to the research of the small bodies in the Solar system (mainly, focusing on asteroids and comets) using methods of radio astronomy and signal processing. One of the research activities is weak hydroxyl (OH) radical observation in the radio range – single antenna observations using Irbene RT-32 radio telescope. To detect weak (0.1 Jy) OH masers of astronomical objects using radio methods, a research group in Ventspils adapted the Irbene RT-32 radio telescope working at 1665.402 and 1667.359 MHz frequencies. Spectral analysis using Fourier transform and continuous wavelet transform was applied to radio astronomical data from multiple observations related to weak OH maser detection. Multiple observation sessions of OH maser objects (R LMi, RU Ari, V524 Cas, OH 138.0+7.2, U Aur, etc) were carried out in 2020–2021.</p> </abstract>ARTICLE2022-06-23T00:00:00.000+00:00Artificial Intelligence Meets Radio Astronomy<abstract> <title style='display:none'>Abstract</title> <p>Artificial intelligence is widely spreading in all modern technologies. Such a very powerful methodology can have important applications in radio astronomy technology, for instance, in the new DBBC4 VLBI backend development project and in the low frequency array AntArr under development on the Etna slopes in Italy.</p> <p>In the present paper, we describe the method currently adopted for those projects and some possible applications, which could provide substantial new features in this decade to the radio astronomy science and technology.</p> </abstract>ARTICLE2022-06-23T00:00:00.000+00:00Hydrogen Hydraulic Compression System for Refuelling Stations<abstract> <title style='display:none'>Abstract</title> <p>The article investigates the properties and potential of compressed hydrogen as one of the most promising energy carriers in order to facilitate the development of energy storage capabilities and lay down a stable foundation for the future of a sustainable energy sector. The study considers the use of hydrogen, compressed at high pressure from 50 MPa to 100 MPa, at refuelling stations to supply electric cars. The technical properties of modern hydraulic compressors used for hydrogen accumulation in high pressure buffer containers are considered. The study shows that the design of hydraulic compressors in terms of their technical characteristics optimally corresponds to the primary requirements for their use as booster compressors at refuelling stations. The authors conclude with the proposal of an enhanced design of the hydraulic compressor with the use of fluid flow counters in a control system of a hydrogen compression cycle. The proposed technical solution provides for continuous monitoring of the hydrogen compression process that increases the reliability of control system operation.</p> </abstract>ARTICLE2022-06-23T00:00:00.000+00:00The Study of Properties of an Axial Flux Switching Permanent Magnet Alternator with Open Magnetic Cores<abstract> <title style='display:none'>Abstract</title> <p>The article studies magnetic field distribution in the alternator inductors with an axial arrangement of open magnetic cores (OMC) and an external closure of the magnetic flux. The study compares the efficiency of magnetic flux utilization for four models with different modifications of the geometry of the magnetic circuit of inductors. The analysis of the density distribution of magnetic flux in OMC is carried out by 3D modelling of the magnetic field using EMWorks software. Based on the experimental study of the properties of the base model, the influence of the configuration of the magnetic circuit of the inductor on the efficiency of the alternator is shown. The results are presented in the form of tables and diagrams characterising changes in magnetic fluxes and electromotive force (EMF) in relative units. The results provide the grounds for assessing the potential and possible limits of optimization with respect to the size of air gaps and dimensions of the magnetic flux toggle switches. The study indicates that the proposed alternator can be adapted for various load requirements and optimized for various applications, such as charging power banks and powering bicycle electronics. The study also demonstrates that for such generators, OMC can be manufactured using a waste-free strip production technology.</p> </abstract>ARTICLE2022-06-23T00:00:00.000+00:00Axial Flux Switching Permanent Magnet Alternator with External Magnetic Cores<abstract> <title style='display:none'>Abstract</title> <p>The article introduces the results of studying the magnetic field distribution in the alternator inductor with an axial arrangement of open magnetic cores (OMC) and external closure of magnetic fluxes. The study compares the efficiency of using magnetic fluxes from permanent magnets (PM) on the example of two model variants of inductors with OMC developed by the authors. The analysis of the density distribution of magnetic fluxes in OMC was carried out by 3D modelling of the magnetic field using EMWorks software. It has been shown that such generators can be manufactured using a waste-free technology for strip of OMC. This technology significantly reduces the production costs of OMC. By modelling the distribution of magnetic fluxes in the OMC of the inductor, the results of experimental studies and analysis of the created device show that the capacity of generator can be varied by changing its dimensions and the number of the toggle switches on the rotor. This allows the alternator to be adapted to the load requirements – power banks and bicycle electronics.</p> </abstract>ARTICLE2022-06-23T00:00:00.000+00:00Technological Assurance of Ti-6Al-4V Parts Produced by Additive Manufacturing Using Selective Metal Laser Sintering<abstract> <title style='display:none'>Abstract</title> <p>The research relates to a technological assurance of Ti6-Al-4V parts produced by additive manufacturing (AM) by means of a metal laser sintering, especially by a fibre laser 3D printer. The influence of technological parameters such as layer thickness, hatch spacing, laser travel speed and laser power have been analysed as well as the influence of thermal treatment as a post processing method has been studied. Technological parameters in combination with a thermal treatment present a challenge in order to manufacture satisfactory products in terms of mechanical properties. The research guides through different phases of experiments to distinguish the best technological parameters. The following research may be used for further investigation of technological assurance for additive manufacturable parts as well as forms the springboard for further research in development of new titanium composites using additive manufacturing methods.</p> </abstract>ARTICLE2022-06-23T00:00:00.000+00:00Specifics of Power Losses in Power Lines Including Parallel Lines<abstract> <title style='display:none'>Abstract</title> <p>Reducing power losses is invested in the trend of combating climate warming. It is necessary to know what parameters of power transmission lines affect the losses in them. In short and medium lines with accounted lumped parameters, the role and influence of the line parameters on losses are visible. In the lines with distributed parameters, at least with one series parameter and one parallel parameter, the role played by them, computing losses in ordinary way as difference between power at line sending and receiving end, is hidden. This is pronounced when considering parallel lines. In two parallel lines the losses can be greater than in a single line. This may occur when the current at the end of the lines is less than the boundary value: the value when two parallel lines and a single line have the same losses. The longer the line and the higher the rated voltage, the stronger the effect. In view of this aspect, it is necessary to know the boundary current. This current can be determined in ordinary way by a series of calculations changing the load value. In some cases, boundary current is affected not only by modulus of the current at the end of the line but also by its angle. It is better to calculate the boundary current by a formula, while studying the role of each parameter.</p> </abstract>ARTICLE2022-06-23T00:00:00.000+00:00Scenario-Based Modelling of Residential Sector Consumption: A Case Study in Latvia<abstract> <title style='display:none'>Abstract</title> <p>Promoting the development of energy communities is one of the planned development areas mentioned in the Latvian National Energy and Climate Plan (NECP). Even though energy communities do not yet exist in Latvia, they could improve the quality of the environment and stimulate the local economy. In any case, it is expected that the structure of household energy consumption in Latvia will change as households start to adopt new technologies such as electric cars and heat pumps, as well as participate in energy production and demand response.</p> <p>Often the starting point for the development of an energy community is the geographic location of consumers. Therefore, for this study, a microdistrict was chosen in one of the most developed suburbs of Riga in Latvia, in which 76 households are located. The study identified five milestones on the path from mere neighborhood to the energy community. The resLoadSIM Residential Load Simulation tool was chosen to simulate realistic energy consumption with a 1-minute time resolution, as well as to model the future solar energy consumption and generation in the community on its way to becoming an energy community and meeting these goals. The network constraints associated with the transformer and lines are taken into account and it is assumed that the district will not invest in the development and expansion of the network.</p> <p>Based on the results of the modelling, an analysis was made of the impact of the development of the energy community in Latvia and how each stage of development will affect energy consumption, the amount of renewable energy, the energy sent to the grid, the power consumed directly, and the share of solar energy in energy consumption.</p> </abstract>ARTICLE2022-06-23T00:00:00.000+00:00Multifocal Near-Eye Display: Timing of Optical Diffuser Elements and Synchronization to DLP-Based Projection Microunit<abstract> <title style='display:none'>Abstract</title> <p>The paper present the key technical details of a multifocal near-eye display concept. Along with an overview of the basic architecture, a particular implementation that utilises a digital light processing (DLP<sup>®</sup>) based spatial light modulator as the image source is provided in the study. The investigated approach involves the utilisation of a small-scale volumetric screen formed by a stack of fast-switching optical diffuser elements based on liquid crystal technology. The volumetric screen is illuminated by a rear image projector. To make the whole system functional and small, the challenge lies within the development of integrated control board for the projection modules as well as the synchronization of the DLP<sup>®</sup> projector image output to the optical diffuser element switching-cycle.</p> <p>The main difficulty of the development process is accounting for the peculiarities of in-house developed diffuser elements and the off-the-shelf DLP<sup>®</sup>, which is the main focus of this paper. There is no direct control over the full set of DLP<sup>®</sup> operational parameters, an indirect method for adjusting frame dead time is proposed, showing that an increase in dead time close to 0.3 ms (from 0.3 ms to 0.6 ms in the particular setup) can be achieved without significantly sacrificing image colour depth or quality. Tuneable dead time mitigates the limitations set by the non-instantaneous switching of liquid crystal diffuser elements as longer dead times allow for the removal of image bleeding between frames.</p> </abstract>ARTICLE2022-06-23T00:00:00.000+00:00On the Issue of Collision of Balls in an Auto-Balancing Device<abstract> <title style='display:none'>Abstract</title> <p>The paper considers a model of a vertical double pendulum, which includes two balls suspended on rigid non-deformable threads to one centre of the suspension. For the proposed system of pendulums, differential equations of motion and conditions for collision of balls have been recorded. When simulating the motion of the pendulums, the central collision of the balls has been considered for various options of the motion of the suspension point: the suspension point is motionless; the suspension point oscillates in the vertical direction; the suspension point makes rotational motions in the vertical plane. Meanwhile, various conditions for the central collision between the balls have been considered: a perfectly inelastic collision; a perfectly elastic collision; a collision with transformation of collision energy (partially elastic collision). The results of numerical simulation are consistent with the behaviour of pendulums in real physical models, which makes it possible to simulate an elastic collision between balls when studying their acceleration in auto-balancing devices.</p> </abstract>ARTICLE2022-06-23T00:00:00.000+00:00Development of the District Heating System on the Left Bank of the Daugava River in Riga<abstract> <title style='display:none'>Abstract</title> <p>In Latvia, heat supply is provided in three different ways: using district heating (<italic>hereinafter –</italic> DH), local heating and individual heating systems. Heat energy consumption consists of heat energy consumption for heating, hot water and heat energy technological processes. The structure of DH consumers has not changed in recent years and the largest consumers of heat are households <italic>–</italic> 70 % of the total energy consumption. The district heating system accounts for approximately 29 % of the total consumption. There is also the so-called tertiary sector, which is made of municipal and state buildings with a minor total heat consumption of about 1 %.</p> <p>It should be noted that 65<italic>–</italic>70 % of energy is used for heating needs, and 30<italic>–</italic>35% for hot water preparation. In Latvia, heat of DH consumers is produced both in boiler houses (<italic>hereinafter –</italic> BHs) and cogeneration plants (<italic>hereinafter –</italic> CHPs). The latter also produce electricity. Over the past 10 years, the distribution of heat produced in BHs and CHPs has changed significantly. The heat supply of the Latvian energy sector is a system consisting of three main elements <italic>–</italic> heat source, transmission and distribution networks, and end consumer. Low efficiency of heat supply system elements creates risks to security of heat supply, resource sustainability and competitiveness. Increasing energy efficiency in the system as a whole, or in individual elements of the system, will promote the enhancement of the heat supply sector, while promoting economic growth as well. The research attempts to evaluate the energy efficiency of DH systems in the so-called left bank (<italic>hereinafter –</italic> LB) DH area (located on the left bank of the Daugava River in Riga).</p> </abstract>ARTICLE2022-06-23T00:00:00.000+00:00Study on Potential Role and Benefits of Liquified Natural Gas Import Terminal in Latvia<abstract> <title style='display:none'>Abstract</title> <p>Natural gas is relatively clean energy source, which emits less greenhouse gases (hereinafter – GHG), compared to other fossil fuels, such as hard and brown coal, and therefore it may be the most feasible resource to ensure smooth energy transition towards Europe’s climate neutrality by 2050. Traditional natural gas can be easily transported and used in liquefied (hereinafter – LNG) or compressed form. As for biomethane, in future it also can be used in liquefied (hereinafter – bioLNG) and compressed form, as well as transported by means of the current natural gas infrastructure. It can also significantly enhance regional and national energy security and independence, which has been challenging for the European Union (hereinafter – EU) over at least several decades.</p> <p>Issue on energy independence, security of supply, alternative natural gas sources has been in a hotspot of the Baltic energy policy makers as well. Now, considering Russia’s invasion in Ukraine, since late February 2022, a problem of the EU natural gas dependency on the Russian Federation has escalated again and with force never before experienced. The European natural gas prices also hit records, as the natural gas prices in the Netherlands Title Transfer Facility reached 345 euros per megawatt-hour (hereinafter – EUR/MWh) in March 2022.</p> <p>Therefore, LNG import terminal is the only viable option to reduce national dependency of the so-called pipe gas which in some cases, due to the insufficient interconnections, may be delivered from very limited number of sources. The European policy makers and relevant institutions are currently working towards radical EU natural gas supply diversification, where LNG deliveries coming from outside of Russia will certainly take a central stage.</p> <p>In case of Latvia, the potential benefits of the LNG terminal development in Skulte were evaluated in order to reduce energy independence of the Russian natural gas deliveries in the Baltic region and to introduce new ways and sources of the natural gas flows to the Baltics. LNG terminal in Skulte could ensure significant capital investment cost reduction comparing to other projects proposed for Latvia in different periods, due to already existing natural gas transmission infrastructure and the relative closeness to the Incukalns underground gas storage (hereinafter – UGS). Various aspects, such as technical, political and economic ones, were analysed to assure that Skulte LNG terminal would be a real asset not only to customers of Latvia, but also to those of the whole Baltic region, where in future it would be possible to use biomethane for efficient utilisation of existing and developing natural gas infrastructure.</p> </abstract>ARTICLE2022-04-22T00:00:00.000+00:00Study on Mass and Linear Attenuation Coefficients of PMMA as Human Tissue-Equivalent Material<abstract> <title style='display:none'>Abstract</title> <p>To research the improvements of clinical imaging of human tissues, tissue-equivalent materials are one of the reasonable strategies for evaluating the impact of radiation dosages on human tissues. Hence, considering mass and linear attenuation coefficients is a promising method to foresee the appropriate tissue-identical material. In this examination, we utilise the built-up estimations of elemental compositions (mass portion of every component) of PMMA material by numerous analyses in literature. XCOM program was utilised to figure estimations of mass attenuation coefficients of PMMA for various photon energies (0.015–2.0) MeV. The outcomes reveal that the estimations of mass and linear attenuation coefficients are high as the energies begin to decrease and diminish gradually with an expansion in photon energies. Making a sensible coordinating between mass and linear attenuation coefficients of PMMA as human tissue-equivalent material with mass and linear attenuation coefficients of lung, brain, muscle and blood human tissues has demonstrated a phenomenal match.</p> </abstract>ARTICLE2022-04-22T00:00:00.000+00:00Lattice Dynamics Calculations for MgZnO Solid Solutions<abstract> <title style='display:none'>Abstract</title> <p>In this study, Mg<sub>1-x</sub>Zn<sub>x</sub>O solid solutions are studied by modelling lattice dynamics, using the methods of classical molecular dynamics. These time-efficient methods are of great interest since they allow using large crystallic structures, which reduce artificial defect periodicity. The main program used is General Utility Lattice Program (<italic>GULP</italic>). The Buckingham potential is used for modelling interatomic forces. The parameters for this potential are found for different effective ionic charges by using lattice parameters and vibrational frequencies obtained from <italic>ab initio</italic> calculations performed in the program <italic>CRYSTAL14</italic>. With these potentials, the dispersion relations and densities of states have been calculated for MgO, ZnO and Mg<sub>1-x</sub>Zn<sub>x</sub>O. Calculations have been made for different Mg and Zn contents in the wurtzite and cubic phase solid solutions, respectively, using the supercell method and a large number of Brillouin zone sampling points.</p> <p>New interatomic potentials for interactions Mg-O, O-O, Zn-O have been obtained. These potential parameters have been verified and the phonon dispersion curves and DOS for MgO and ZnO utilising these potential parameters have been compared to other studies, both experimental and theoretical. By adding more Zn in the cubic phase (c-MgO) solution, no local vibrational modes are observed; however, there is a clear spectral widening and a noticeable change in the low frequency region (100–300 cm<sup>−1</sup>) of the DOS. Adding more Mg in wurtzite phase (w-ZnO) solution, on the other hand, results in local vibrational modes in the mid (350 cm<sup>−1</sup>) and high frequency (650 cm<sup>−1</sup>) regions.</p> </abstract>ARTICLE2022-04-22T00:00:00.000+00:00Maximum Shannon Information Delivered in a Lecture<abstract> <title style='display:none'>Abstract</title> <p>The aim of our paper is to evaluate the maximum Shannon (syntactic) information carried through a video lecture. To achieve the aim, we have considered a natural lecture delivered by a lecturer as a signal transmitted over the physical communication channel consisting of a sound sub-channel and light sub-channel. Receivers are eyes and ears of listeners whose physical characteristics are taken into account. The physiological, neurological and cognitive aspects of the problem are neglected in calculations. The method has been developed to calculate the absolute maximum values of Shannon information characteristics of a natural lecture basing on the capacity formula of continuous communication channel and physical considerations taken into account for the first time, to our knowledge. Maximum Shannon information characteristics (entropies of sound and light frames, amounts of total acoustical and optical information, capacities of sound and light sub-channels, total amount of information and total capacity) of a natural lecture perceived by the audience have been calculated. These values are the upper bounds of a video lecture. The obtained results are discussed in the paper. After some modification, the proposed method can be practically applied for the optimization of both natural and video lectures because there is some correlation between syntactic and semantic information characteristics.</p> </abstract>ARTICLE2022-04-22T00:00:00.000+00:00en-us-1