Tom 60 (2023): Zeszyt 1 (February 2023)

Main pipelines as long linear objects are vulnerable to dangerous natural and man-made influences. One of the technogenic sources is large-scale explosions, which cause a sharp fluctuations of soil and cause serious damage to underground pipelines. When calculating the strength of pipeline systems, it is assumed that the damage occurs mainly due to additional axial stretching. However, the destruction and damage of pipelines can occur during seismic impacts directed perpendicular to the longitudinal axis of the pipeline.

To assess the impact of longitudinal and transverse waves on the underground pipeline during seismic action a software-calculation module is developed. It implements a model of dynamic strength analysis, which allows estimating the magnitude of longitudinal and trans-verse seismic loads on the underground pipeline to establish safe parameters of seismic loads and geometric dimensions of the protected object. The final system of equations of motion of N nodes of a discrete system for a single length of the pipeline is presented as a system of 4N equations of the first order.

The efforts on the internal nodes are determined by the strain stresses at the displacement of the nodes of the adjacent rods. The efforts on the nodes of the pipe contour are the diffraction interaction of seismic waves in the soil with the pipe. The system of equations is supplemented by the corresponding initial and boundary conditions.

The dependences of the inflow of longitudinal and transverse pressure of explosive seismic pressure on the pipeline are established. The dependences of stresses in the pipeline of the diameter, thickness and type of soil are researched.

Nowadays autonomous measurement systems are applied for the determination of the cinematic parameters of object motion. The principle of operation of such systems is based on the measurement of the object motion acceleration with the further integration of the accelerometer’s signal. These measurement systems are called inertial systems. Platform-less inertial systems are widely used for these purposes. Their specific property is an installation of the primary information sensors directly on the constructive elements of the object case. The inertial measurement systems have also a negative feature to accumulate constantly the errors of the system.

Green and sustainable hydrogen has a major role in moving towards decarbonization of energy, providing viable solutions in all most challenging sectors of the national economies. It would penetrate practically all sectors of economic activity, such as long-haul transport, steel and chemical industries, power generation and energy storage. Green and sustainable hydrogen cost competitiveness is also closely linked to developments of large-scale renewable energy sources (in case of green hydrogen; hereinafter – RES) and further commercialization of carbon dioxide (in case of sustainable hydrogen produced from natural gas; hereinafter – CO₂) capture and storage (hereinafter – CCS) technologies.

In the European Union (hereinafter – EU), sustainable and especially green hydrogen is gaining strong political and business momentum, emerging as one of major components in governments’ net zero plans within the European Green Deal and beyond. Being extremely versatile both in production and consumption sides, it is light, storable, has high energy content per unit mass and can be readily produced at an industrial scale. The key challenge comes from the fact that hydrogen is the lightest known chemical element and so has a low energy density per unit of volume, making some forms of long-distance transportation and storage complex and costly.

In this paper, green and sustainable hydrogen is reviewed as a vital part of emerging European smart energy framework, which could contribute significantly to economy decarbonization agenda of the EU and Latvia in both in short- and mid-term perspective.

Measures on increasing energy efficiency is a way for ensuring sustainable energy supply, reducing emission of gases causing the greenhouse effect, improving safety of energy supply, decreasing dependence on import of energy and promoting the EU competitiveness. Improvement of energy performance of buildings as a direction of activities is provided in national policy planning documents of major importance such as the National Energy and Climate Plan for 2021–2030 and the Strategy of Latvia for the Achievement of Climate Neutrality by 2050.

Residential buildings form a considerable part of the total Latvian housing stock – 27 % according to the number of buildings and 44 % according to their area. Therefore, the increase of energy performance of residential buildings is very significant for achieving the national energy saving targets, i.e. a cumulative savings of final energy consumption of about 6 PJ by 2030.

The research analyses the sector of residential buildings, their statistical data, the energy consumption and requirements of the energy performance standards. To characterise this sector more comprehensively, information has been evaluated on energy performance certificates of residential buildings issued during the period from 2016 to 2021, allowing the authors to make general conclusions on the energy performance level of residential buildings and to provide proposals for increasing their energy efficiency.

Machining of titanium alloy Ti6Al4V is a challenging task for the industry; however, there are some solutions to overcome these difficulties. One of those is optimizing the machining parameters. Machining of Ti6Al4V made by additive manufacturing is an emerging future and is even more difficult when comparing to standard Ti6Al4V alloy. There is lot of invention on Ti6AL4V 3D printed samples, but influence of machining post-printing is lacking. In additive manufacturing of Ti6Al4V alloy, it is necessary to make a finishing operation to improve the surface quality and to ensure precise geometry tolerances. During this process, it may affect the workpiece properties such as microhardness, microstructure, internal defect distribution, internal stresses. During printing there are lots of stresses created, heat treatment is done to normalize the parts. Machining (using milling machine) also causes internal stresses which can damage the surface and part itself. Optimisation of machining parameters and printing parameters can solve this issue. This study gives an overview of selection of machining parameters by considering all the previous relevant research.

The article presents the results of the analysis of methodological approaches to the development of a mobile space simulator test facility following a low-budget project under the conditional name Metamorphosis. The project was performed at the Institute of Aeronautics of Riga Technical University together with Cryogenic and Vacuum Systems Ltd., a company specializing in the development and production of vacuum and cryogenic equipment, with extensive experience in creating technologies used in space research, and development and exploitation of the space environment simulation. The main aim of the study is to find an inexpensive outer space simulator test facility. The study shows that the liquid helium, hydrogen, and neon are significantly more expensive substances than liquid nitrogen, liquid carbon dioxide, liquid ammonia, and organic refrigerants (as well as equipment for their liquefaction). It is desirable to consider a nitrogen system for cooling the workspace due to the physical properties of nitrogen and cheap refrigerants for a projected low-cost simulator test facility. The description of the systems that should be included in the projected mobile space simulator is provided in the article. A generalized scheme of the simulator based on a cryogenic system is also presented.