Objective. For autonomous gasification, it is necessary to create river vessels to transport liquefied natural gas and work out the transportation technology. As the most efficient cargo storage system, C-type tanks are selected and operated in a non-drainage mode.

Methods. The existing methodology for determining the level of initial filling of the tank does not consider the storage time of liquefied natural gas, which leads to the forced discharge of the formed liquefied natural gas vapors when the maximum allowable overpressure in the tank is reached. When  upgrading a tanker into a transportation vessel for liquefied natural gas, the authors propose to install two C-type tanks on it. The diameter of the  hemispherical covers is 9 m, the length of the cylindrical part of the tank is 20 m. The maximum permissible overpressure inside the tank is assumed  to be 0.65 MPa. The thickness of the thermal insulation is determined from  the overall dimensions of the hold, considering the condition of ensuring a distance between the hull sidewall and the outer insulation layer of at least
760 mm. The maximum possible thickness of the thermal layer was 1.1 m.

Results. The article proposes a method for determining the optimal tank filling level to achieve a drainless operation mode. The proposed method can achieve the maximum economic efficiency of transportation of liquefied natural gas by eliminating the loss of discharged liquefied natural gas due to long ship crossings and transporting an additional liquefied natural gas  volume for a short changeover. 

Conclusion. As the pressure of liquefied natural gas vapor increases inside the tank, the saturation temperature of the liquid fraction increases, and its density decreases. Thus, the proportion of the liquid volume is constantly increasing, reducing the vapor space of the container. An increase in the mass of liquefied natural gas vapors combined with a decrease in the steam area volume increases the pressure growth rate. When optimizing the initial tank filling level, the amount of liquefied natural gas that will be forced  to be discharged as steam on long legs is determined. Optimization of the operating mode of type C tanks is possible for cases with any thickness of the insulation layer. When performing such calculations, tables  of optimal filling for any range of legs can be created.  

Objective. The use of an absorption lithium bromide refrigerating machine  for cooling the cycle air before the gas turbine unit of a combined-cycle gas  turbine in a hot climate has proven its effectiveness. It is essential to  maintain the design values for which constant monitoring is carried out and  the operation parameters are adjusted. The objective of this work is to  conduct a comprehensive analysis of the absorption lithium bromide  refrigerating machine as part of an energy-saving system.

Methods. As a research method, the method of energy and exergetic  analysis based on the results of a full-scale production experiment was  adopted.

Results. The energy analysis was performed using the ξ-i diagram for a solution of lithium bromide with water. According to the energy analysis results, deviations in the work of the absorption lithium bromide  refrigerating machine were revealed, and the exergetic analysis confirmed these deviations. 

Conclusion. The analysis of the operation of the absorption lithium bromide refrigerating machine allowed identifying deviations in work and their causes.

Objective. The research objective is to develop a mathematical model of a thermoelectric semiconductor system to visualize the temperature fields of objects and study the thermophysical internal processes.

Methods. A thermoelectric semiconductor system was developed for visualizing the temperature fields of flat objects using a liquid crystal film. Its feature is to increase the accuracy of measurements due to a more accurate coupling of the object and the device. A mathematical simulation of  the system was performed based on the solution of a dynamic two- dimensional heat conduction problem with local heat sources and sinks over  the area of a liquid crystal film. 

Results. Dependency graphs were obtained for the dependency of two-dimensional temperature distribution over the surface of the liquid crystal film in the presence of heat sources and sinks, the change in the cooling capacity, the cooling ratio, the supply voltage of the thermoelectric module on the temperature difference between the junctions for different  values of the supply current. 

Conclusion. As a result of calculations, it was found that the color gamut of a liquid crystal film changed significantly in the presence of heat sources and sinks on its surface. During pre-calibration, the system allows visualization  of the object temperature field and determines the value of its temperature at each point. Following the calculated data, it is determined that to ensure  the entire operation of the thermoelectric semiconductor system, a standard thermoelectric module ICE-71 can be used with the following specifications: power range – 16 to 35 W with an average temperature difference between the junctions – 55 K, the supply current – 28 A with a power consumption of 40 to 90 W, the cooling ratio is from 0.38 to 0.43.

Objective. Conduct mathematical modeling of tornado zone structure systems between cyclic flow turbulence stimulators with the surface arrangement of triangular and square cross-sections based on multiblock computational techniques, based on solutions of the factorialized finite- volume procedure of the Reynolds equations (closed through the Menter shear stress transport model) and energy equations (on a multiscale  intersecting structured grid) at high Reynolds criteria Re=106 with an  exhaustive analysis of the relevant current lines.

Methods. The calculations were carried out on a mathematical foundation based on the solution of the factorized finite-volume procedure of the Reynolds equations, which are closed using the low-Reynolds Menter shear stress transport model, and the energy equations on a multiscale  intersecting structured grid (factorized finite-volume procedure).

Results. Mathematical simulations of the heat exchange process in straight
and round horizontal pipes with turbulence stimulators with d/D=0.95...0.90 and t/D=0.25...1.00 of triangular and square transverse profiles with large Reynolds numbers (Re=106) on a foundation with multiblock computing technologies, which are based on solutions of factorized and finite-volume Reynolds equations and energy equations, were conducted. It was found that the relative intensification of heat transfer [(Nu/NuGL)|Re=106]/[(Nu/NuGL)|Re=105] in round pipes with square air turbulence stimulators for large Reynolds numbers (Re=106), which may be relevant in the channels used in heat exchangers, could be higher with a large-scale increment of hydraulic resistance than for slightly smaller numbers (Re=105), for relatively high flow turbulence stimulators d/D=0.90 for the entire range under consideration for the parameter of the relative step between them t/D=0.25...1.00 a little more than 3%; for triangular turbulence stimulators, the crosssection profiles have similar  values. For lower square turbulence stimulators with d/D=0.95, this increase  in relative heat transfer for large Reynolds numbers (Re=106) compared to smaller numbers (Re=105) does not exceed 6%; for triangular cross-section turbulence stimulators, similar indicators are slightly more  than 4%. 

Conclusion. The calculated results based on the developed model can optimize the intensification by turbulence stimulators and control the processes of heat transfer intensification. It is shown that for higher square  turbulence stimulators and higher Reynolds numbers, a limited increase in  the relative Nusselt criterion Nu/NuGL is accompanied by a significant increase in the relative hydro resistance due to the very significant influence  of return currents, which can flow directly on the turbulence stimulator to  the greater extent, the higher the Reynolds number; for triangular  turbulence stimulators, the above trend persists and even deepens.

Objective. Flow metering and the evaluation of cryogenic product losses at production and consumption facilities involve determining the mass of the vapor-liquid medium in the tank equipment.

Methods. The calculation of the mass of the cryogenic vapor-liquid medium is associated with the determination of the density of the vapor and liquid phases. The densities of media, in turn, depend on their component  composition, pressure, and temperature, which, in general, cannot be  determined reliably without direct measurements. However, for the estimation of mass in tanks, the state of the medium in which is accepted as equilibrium, the problem can be significantly simplified, and the missing information recovered based on indirect methods. This type of system includes cryogenic onboard fuel systems and, in particular, cryogenic fuel tanks, since the movement of the vehicle leads to mixing of the stored product, and an assumption can be made about the equilibrium of the  vapor-liquid medium. Similarly, the methodology can be extended to  transport tanks and multimodal reservoirs. 

Results. A review and comparison of the applied methods for calculating the density of the vapor-liquid medium and equilibrium compositions for hydrocarbon liquefied natural gas type mixtures in the cryogenic temperature range are presented. The existing methods for calculating the  density and phase composition of cryogenic multicomponent media are  complex in practical engineering and cannot be recommended for estimating the consumption of liquefied natural gas in the production tasks of fuel flow  metering and quantity control. An easy-to-use simplified calculation device  for determining the state of a vapor-liquid medium in cryogenic tanks based on approximation dependencies is proposed.

Conclusion. The simplified method is approximate in nature but is based on strict physical dependencies, and therefore does not lead to a significant increase in the error when varying the initial conditions. The liquefied natural gas composition, which can be obtained from the product data sheet, and the pressure of the vapor-liquid medium are transmitted to  the methodology as initial data. 

Objective. Integrating the numerical solution module of the kinetic equation for the droplet size distribution function in a CFD package. Application of the module to volumetric condensation at the supersonic flow of a vapor-gas  mixture through a nozzle in a two-dimensional formulation, comparison of  the results with experimental data of third-party authors.

Methods. In this  paper, the problem of volume condensation in the supersonic flow of a vapor-gas mixture through a nozzle is solved by finite element methods in a two-dimensional formulation using user-defined functions.

Results. A module for the numerical solution of the kinetic equation for the droplet size distribution function is presented as a user-defined function integrated into the calculated CFD package.

Conclusion. The module application to volumetric condensation for a vapor-gas mixture flow through the nozzle gave a qualitative agreement in all areas and a quantitative agreement in the area of intense condensation with  measurement data. The distributions of temperatures, pressures, and  the degree of supersaturation are presented both along the central axis and  on the plane bounded by the contour of the computational domain. It is shown that the module does not depend on the solver type (stationary or non-stationary).

Objective. The objective of the study is to develop a model of a geoinformation system functioning in destabilization, as well as indicators that assess the ability of a geoinformation system to perform its functions in destabilization.

Methods. Geographic information systems are becoming an integral part of almost all information and decision-making systems. The research methods are based on a deterministic or stochastic model of destabilization, but the geographic information system is characterized by a non-stochastic model.

Results. It is shown that any task exists in the geoinformation system in the form of consumption of four types of performance: computers, storage devices, communication channels, input/output devices. Based on this, a model of the geoinformation system (FIST – Full Infrastructure of Sources Toolkit) was developed, which allows evaluating the "margin of safety" of the geoinformation system, expressed in the available performance of all four  types. The model considers elements of different degrees of mobility and performance and is suitable for describing classical, cloud, and fog  geoinformation systems. An example of the model operation in  destabilization is given. A theorem on the independence of events of solving  problems for any directed graph is formulated and proved. Based on the model, integral and differential efficiency indicators are proposed. The  integrated indicator characterizes the share of tasks solved over a time  interval; the differential indicator characterizes the "performance margin." 

Conclusion. The developed model and performance indicators can be used to design new and evaluate existing geographic information systems.

Objective. The article is devoted to solving the practical problem of evaluating the operational indicator of the quality characteristics of the information security system usability.

Methods. Evaluation of the operational characteristics of software systems can be performed theoretically and by measurement. Since the theoretical  assessment of operational characteristics has some disadvantages and  limitations, an experimental assessment is advisable. Simultaneously, it is  advisable to use the "Complexity" indicator of a typical operation performed by a security administrator, which expresses the average time of its  execution as the primary indicator of the quality of the functioning of the information security system usability. Measurement evaluation of the  operational characteristics of the information security system was carried out using the eye and mouse movement tracking methods.

Results. The article provides an assessment of the "Complexity" indicator of all typical operations performed by the security administrator during the  Sentinel NT 3.0 ISS operation following the program documentation.

Conclusion. The obtained values of the "Complexity" indicator can be used in the formation of a work plan for the operation and maintenance of  protected automated systems, in particular, with the installed information security system, when evaluating the timeliness of the performance of the  listed works, as well as when justifying the structure of the units responsible  for information protection and their quantity.  

Objective. Investigation of the problems of zonal disintegration of rocks around deep underground workings in extremely small sampling, arising in geomechanical phenomena and processes in rock mass during mining.

Methods. The primary tool used is numerical resampling methods, namely randomization, bootstrap, and Monte Carlo methods, which allow increasing the sample size, according to the available field data, to the required size for conducting a statistically sound analysis.

Results. The problem of zonal fracture of rocks around deep underground workings is solved, for which the analytical dependence of the periodicity parameter of the defect function on the rock strength limit is estimated. The primary indicator of the statistical significance of the constructed model in work is the determination factor, based on which the type of analytical dependence under study is selected. Its deviation in the final model does not exceed 0.5% for any bootstrap sample volume, while in the other models considered in this paper, this value is achieved at n>200.

Conclusion. The obtained interval estimates using bootstrap methods have a significant advantage over traditional approaches, increasing the reliability of the result in extremely small data samples without losing the level of significance.

Objective. Develop a principle of constructing tools and procedures for optimal routing of targets by an autonomous uncrewed aerial vehicle, which have an acceptable complexity for implementation on an onboard computer.

Methods. The rules for optimizing the terrain map with the located targets, creating a penalty matrix that considers the disturbing factors of the  unstable air environment in the planning process, and building a reference  tree for finding the minimum route for the accepted cost of flying around the targets.

Results. A principle is proposed to develop effective procedures for planning minimum cost-effective routes to fly around targets in an unstable air  environment. The basis for behavior planning is the optimization of the formal description of a given terrain map, which leads to a significant reduction in the number of alternatives compared in the process of searching  for a minimum route to fly around targets. This, in turn, makes it  possible to implement planning procedures on the onboard computer system of an autonomous uncrewed aerial vehicle. A statement is proved to justify the existence of a minimum route for the accepted cost of overflying targets  in the formal description of the terrain map obtained as a result of  converting its original representation based on the developed optimization rules.

Conclusion. The considered approach effectively solves various types of issues reduced to the traveling salesman problem, including planning the  minimum route of flying around targets by an autonomous uncrewed aerial vehicle in an unstable air environment under uncertainty conditions.  

Objective. The most important task of the theory and practice of ensuring the information security of automated systems during their operation in a secure version at the objects of computerization of internal affairs bodies is to analyze the functioning process of systems for protecting confidential information resources from unauthorized access in case of network attacks, which involves modeling the process of their implementation and the development of graph models of the implementation dynamics of the main types of network attacks.

Methods. The method for solving this problem is a mathematical simulation of implementing network attacks in protected automated systems of internal affairs bodies by constructing and describing graph models of typical network attacks on a confidential information resource in the dynamics of  their implementation.

Results. Based on the analysis of typical network attacks on the information resource of modern automated systems operated in a secure version at the objects of computerization of internal affairs bodies, graph models of these attacks in the dynamics of their implementation were developed, with the allocation of key elements and functional components of models identical to real network attacks. The developed graph models allow visualizing the process of implementing the main malicious functions of the considered  network attacks and consider the attacker's alleged actions.

Conclusion. The conducted research results can be used to develop simulation models of typical network attacks on a confidential information resource to obtain probabilistic-temporal characteristics in the form of the execution times of each attack of malicious functions for a quantitative risk  assessment of their implementation. This can become the basis for forming  a specific model of actual attacks for a specific automated system and  substantiating quantitative requirements for promising software and  information security systems at the computerization facilities of the internal affairs bodies following the current regulatory documentation requirements.

Objective. Every year, environmental issues are becoming more and more critical. Experts predict no more than ten years of reaching the point of no return when environmental problems will move into a phase of uncontrolled chaos. Most often, catastrophic changes are associated with climate warming due to greenhouse gas emissions from industry and transport. However, the root cause of everything, as established in the research by Slesarev et al., is the construction industry as the primary source of environmental problems. The problem of environmental safety especially concerns cities and large settlements. The conducted research has established that environmental safety is determined as the sum of the impacts of construction projects on a unit area of residential territory. For an objective assessment of environmental safety, environmental pollution, the impact of various factors, and the resulting effect of the indirect impact of construction projects on the environment were considered.

Methods. New conceptual approaches and principles were applied in assessing the environmental safety of construction sites and territories, taking into account the current environmental status of the built-up areas, which makes the problem of environmental safety manageable, and provides  modern and future generations with health, a comfortable environment, and health.

Results. As a result of process modeling, the "real estate concentration degree" ratio was adopted as an integrating concept of environmental safety
of the area, and the concepts of "environmental reserve," "environmental safety threshold," and "sustainable state range" were introduced. The stability ratio concept (rstab) is introduced, a method for calculating this  ratio is developed to assess the range of the sustainable environment state – the magnitude of the variation in the size of the ecological reserve depending on climatic conditions, time of day, week, year. As a result, the numerical values of the above-mentioned indicators for the studied areas are obtained. As the main document reflecting the state of the environmental safety of the construction object, the development of the environmental  facility certificate and the environmental area certificate is proposed. To create an environmental certificate, the structure of environmental safety  has been developed and justified, which includes four main blocks: external  environmental safety, internal environmental safety, energy efficiency, and  autonomy of the facility (area).

Conclusion. The proposed approach to the assessment of environmental safety makes it possible to reliably assess the possibilities of areas for the placement of construction projects with various industry-related potential, plan measures to ensure a range of sustainable conditions of the  areas, which ultimately ensures the quality of life and health of the population, a comfortable and safe environment of residential areas, as well as the wildlife preservation.

Objective. Based on the theoretical results obtained in the article [17], the analysis of the influence of various design parameters on the sole weight  and cost of the metal of a single-strutframed beam is carried out. Various  tables have been compiled that show the efficiency of the strutframed beam with optimal characteristics.

Methods. Many numerical examples were carried out, and a pilot design of strut-framed beams with different design characteristics was carried out. The corresponding tables were compiled.

Results. The constructed tables allow concluding about the effectiveness of the optimal parameters of single-strut-framed beams.

Conclusion. The proposed method and algorithm indicate the effectiveness of the design. Steel savings and a reduction in the metal cost of single-strut-framed beams compared to conventional beams reach up to 40%.