Mathematical Model Of Process Research Articles

Hot-Pressing Process of Flat-Pressed Wood-Polymer Composites: Theory and Experiment.

The objective of this research was to develop a mathematical model of the hot-pressing process for making flat-pressed wood-polymer composites (FPWPCs). This model was used to calculate and predict the temperature and time required for FPWPC pressing. The model's performance was analysed using the experimental results of hot pressing FPWPCs. It was found that an increase in the content of wood particles led to a rapid increase in the pressing time. The model and experiment showed that the core temperature of the wood-polymer mat remained nearly constant for the first 20-30 s of the hot-pressing process. After this period, this temperature increased rapidly until it reached 100 °C, after which the rate of increase began to decelerate sharply. This transition was more distinct in FPWPCs with a high wood-particle content, while in those with a high thermoplastic-polymer content, it was smoother. Increasing the pressing temperature contributed to a reduction in the time required to heat the FPWPC, as confirmed by both experimental data and the modelling of the hot-pressing process. A decrease in the predicted density of the FPWPC resulted in a directly proportional increase in the time required to heat the mat. Validation of the mathematical model revealed a mean absolute percentage error (MAPE) of only 2.5%, confirming its high precision and reliability. The developed mathematical model exhibited a high degree of accuracy and can be used for further calculations of the time required for FPWPC pressing, considering variable parameters such as pressing temperature, wood-polymer ratio, mat thickness, and density.

Development of a comprehensive theoretical and experimental methodology for evaluating the parameters of recycling by pyrolysis of plastic based on polycarbonate and polyethylene

The results of thermogravimetric and Fourier transform infrared (FTIR) analysis of polymer composite materials (PCM) based on polyethylene and polycarbonate are presented and compared to the polymers polyethylene and polycarbonate. Empirical data were obtained for mathematical modeling, including the amount of solid residue upon pyrolysis, volatile yield, and ash content of the studied PCMs and polymers. Results of the mathematical modeling of the pyrolysis process at a temperature of 600 °C are presented to quantitatively assess the composition of the pyrolysis gas.

Scientific substantiation of the maximum permissible concentration of the pharmaceutical substance osimertinib mesylate in the air of the working area

Introduction. Osimertinib, a 3rd generation epidermal growth factor receptor tyrosine kinase inhibitor, is currently the only drug registered for the treatment of metastatic non-small cell lung cancer in patients with a positive T790M mutation status. The production of osimertinib mesylate is planned on the territory of the Russian Federation, which necessitates research to substantiate the hygienic standard for the aerosol content of the substance in the air of the working area. Conducting research to substantiate the maximum permissible concentration of a substance requires significant material and time resources, while using the results of preclinical and clinical studies, mathematical modeling of processes, and risk assessment methodology allows for a comprehensive assessment of the substance, while significantly reducing the time and cost of work. The study aims to scientifically substantiate the maximum permissible concentration of the pharmaceutical substance osimertinib mesylate in the air of the working area using data from toxicological studies and mathematical modeling of the effects of the substance on humans in industrial conditions. Materials and methods. The materials used were domestic and international databases, reports, research protocols, scientific articles and monographs containing information on the physico-chemical and toxic properties, pharmacotherapeutic activity of osimertinib. Results. The specialists have conducted hygienic regulation of osimertinib, taking into account data on its toxicity, danger, pharmacotherapeutic activity, side effects, long-term consequences, pharmacokinetic studies and modeling. To substantiate the value of the maximum permissible concentration, the authors used the reference points: an inactive NOEL level of 1 mg/­kg/­day for general toxic effect, established in a 92-day experiment on rats with intragastric administration; the lowest observed level of adverse effects of LOAEL is 0.5 mg/kg/day for general toxic effect, established in a 180-day experiment on dogs with intragastric administration; the level that does not cause adverse effects of NOAEL is 10 mg/kg/day for general toxic effect, established in a 180-day experiment on mice with intragastric administration. Safe concentrations of osimertinib in the air of the work area were evaluated using reference points, including the pharmacological effect and the minimum daily therapeutic dose; toxicokinetic modeling of concentrations of a substance in the human body under production conditions and the level of minimal risk. Limitation. The study is limited to the review of open literature sources describing the toxicological/toxicokinetic characteristics of osimertinib mesylate. Conclusion. The most stringent indicators of safe exposure levels, established on the basis of pharmacological effect and toxicokinetic modeling in dogs, allowed us to recommend 0.005 mg/m3, aerosol, hazard class 1 as the maximum permissible concentration in the air of the working area for osimertinib mesylate. Ethics. This study did not require the conclusion of the Ethics Committee.

ПІДВИЩЕННЯ ГАЛЬМІВНОЇ ЗДАТНОСТІ ЛОКОМОТИВА ПРОМИСЛО-ВОГО ТРАНСПОРТУ З УРАХУВАННЯМ ЗУСИЛЬ У ЙОГО ЗЧІПНИХ ПРИСТРОЯХ

Objective: substantiation the rational concept of increasing the braking capacity of the industrial locomotive in transient modes of train movement, taking into account the force factor in its coupling device. Methodology of the work: theoretical studies of the energy from the deformation of the coupling devices of the industrial locomotive in the transient modes of train movement; theoretical studies of excessive coupling of locomotive wheels with rails in the presence of force on the locomotive's coupling device; determination of kinematic and dynamic parameters of the transient mode of train movement. A mathematical model of the train motion transitory process has been developed, it using the example of locomotive braking process, which allows determining the current values of train element velocities, as well as coupling forces, and has a low average discrepancy with the data of the technological calculation of industrial locomotive. Fixed: the force on the coupling device of the locomotive changes with a high frequency. The braking process is conventionally divided into 3 stages, which are characterized by oscillations, stabilization and a drop in clutch force; the energy corresponding to the change in force in the clutch during braking falls on 90.5% of the first and second stages. Taking into account the obtained results, the conceptual adjustment of the force of the coupling of the wheel pairs of the locomotive with the rails at the level of the maximum forces in the coupling device of the locomotive, determined by the simulation results, is adopted. Scientific novelty: improvement of the method of determining the required force of the traction the wheels of locomotive with the rails by taking into account the energy corresponding to the change in the effort in the coupling device of the locomotive during the braking time of the train. Practical value: the development of an improved concept by regulating the force the traction of locomotive wheel pairs with rails in transient modes of train movement, taking into account the energy assessment of the effort in the locomotive's coupling device.

Time scale analysis of enzymatic reduction of uric acid in a microfluidic biomedical device

Time Scale Analysis (TSA) is an investigative tool used in engineering design to identify locations in processes that should be a focus of Process Intensification (PI). Furthermore, TSA points to process variables and parameters that could be used to advance and measure PI improvement. However, TSA cannot suggest any specific design solution to intensify process performance. Instead, design engineers should use their fundamental knowledge and creative intelligence to specify detailed design transformations. TSA will then provide a specific quantitative measure of the improvement. TSA implementation improves an explicitly defined process performance, thus helping achieve process intensification goals. TSA is based on first principles, and it utilizes Characteristic Times (CT) such as diffusion, mean residence, and reaction times to improve an existing process. In this study, we specifically consider microfluidic biomedical devices. To illustrate the genesis of CT and TSA, we start by developing a mathematical model of an enzymatic degradation process in a biomedical device called iCore based on mass, momentum, and kinetic equations. After introducing user-defined scaling parameters, we extract CTs pertinent to the enzymatic degradation of uric acid in this microfluidic biomedical device. Diffusion coefficients, microchannel architectural characteristics, enzyme loading, hydrogel thickness, and characteristic parameters of enzyme kinetics are the parameters and process variables incorporated in this analysis. Finally, we compared the extracted CTs with a COMSOL Multiphysics parametric study to demonstrate how time scale analysis as a design tool and adjusting design parameters, such as diffusion coefficient, hydrogel layer thickness, substrate concentration, and enzyme concentration, can enhance the enzymatic reaction process without a need for complex computational modeling. It is crucial to recognize that pertinent CTs can be determined by understanding the type and nature of the observed process, previous experience, published data, and other foundational engineering design work. There is no need for mathematical modeling and numerical simulations to identify and acknowledge the CTs relevant and essential to the observed process; in this work, we only illustrate the principal origin of CTs via a detailed mathematical model of the process, as previously reported by Jovanovic et al. Therefore, in a routine application of TSA, it is important to remember that mathematical modeling and detailed numerical simulations are not necessary. This is a very comforting fact when TSA is deployed as a tool in higher-level process design functions. The investigations on how best to apply TSA in these higher level design functions such as Process Intensification, scale-up/numbering-up, change of device architecture, change of operating conditions, change of process feed characteristics, change of material physical and chemical properties, parametric optimization of the system for various objective functions, and techno-economic analysis, are yet to be studied and reported.

Learning fluid physics from highly turbulent data using sparse physics-informed discovery of empirical relations (SPIDER)

We show how a complete mathematical model of a physical process can be learned directly from data via a hybrid approach combining three simple and general ingredients: physical assumptions of smoothness, locality and symmetry, a weak formulation of differential equations and sparse regression. To illustrate this, we extract a complete system of governing equations of fluid dynamics – the Navier–Stokes equation, the continuity equation and the boundary conditions – as well as the pressure-Poisson and energy equations, from numerical data describing a highly turbulent channel flow in three dimensions. Whether they represent known or unknown physics, relations discovered using this approach take the familiar form of partial differential equations, which are easily interpretable and readily provide information about the relative importance of different physical effects. The proposed approach offers insight into the quality of the data, serving as a useful diagnostic tool. It is also remarkably robust, yielding accurate results for very high noise levels, and should thus be well suited for analysis of experimental data.

Towards a Systemic Concept of the Brain Ishemia Stroke: Monte Carlo Driven in silico Model.

The work proposes a new mathematical model of dynamic processes of a typical spatially heterogeneous biological system, and sets and solves a mathematical problem of modeling the dynamics of the system of neurovascular units of the brain in conditions of ischemic stroke. There is a description of only a small number of mathematical models of stroke in the literature. This model is being studied and a numerical and software implementation of the corresponding mathematical problem is proposed. This work is the first attempt ever aiming to employ a Monte Carlo computational approach for In Silico simulation of the most critical parameters in molecular and cellular pathogenesis of the brain ischemic stroke. In this work, a new mathematical model of the development of ischemic stroke is proposed in the form of a discrete model based on neurovascular units (NVU) as elements. As a result of testing the program with the assignment of empirically selected coefficients, data were obtained on the evolution of the states of the lattice of the cellular automaton of the model for the spread of stroke in a region of the brain tissue. A resulting new theoretical model of the particular pathologically altered biosystem might be taken as a promising tool for further studies in neurology; general pathology and cell biology. For the first time, a mathematical model has been constructed that allows us to represent the spatial dynamics of the development of the affected area in ischemic stroke of the brain, taking into account neurovascular units as single morphofunctional structures.

Research on the process of heat transfer between mobile variable temperature heat source and thermoacoustic plate

The purpose of this paper is to analyze the effects of several easy-to-operate parameters (operating frequency, plate stack length, plate stack position, and amplitude) on the refrigeration performance, to explore the optimization path of thermoacoustic refrigerator, and to provide a design basis for further cost reductions. The heat transfer process between the air mass and the plate was investigated as an object, and the physical and mathematical models of the heat transfer process were established. The gas microcluster moving heat and plate stack temperature difference were taken as the response. Operating frequency, plate position, plate length and gas vibration displacement amplitude were the design factors. The change relationship of the system response under the interaction of factors was analyzed by using the central composite experimental design and the response surface method, and experimental verification was carried out. The results show that the deviation of the predicted model from the experimental data is less than 5.9 % when the operating frequency is in the range of 0 Hz–12 Hz, and that the location of the plate stack is 0.45 from the pressure belly point of the sound field, where the heat of the air mass transfer is the largest.

PERIODIC ATEB-FUNCTIONS AND THE VAN DER POL METHOD FOR CONSTRUCTING SOLUTIONS OF TWO-DIMENSIONAL NONLINEAR OSCILLATIONS MODELS OF ELASTIC BODIES

In the process of operation, the simplest elements (hereinafter elastic bodies) of machines and mechanisms under the influence of external and internal factors carry out complex oscillations ‒ a combination of longitudinal, bending and torsion combinations in various combinations. In general, mathematical models of the process of such complex phenomena in elastic bodies, even for one-dimensional calculation models, are boundary value problems for systems of partial differential equations. A two-dimensional mathematical model of oscillatory processes in a nonlinear elastic body is considered. A method of constructing an analytical solution of the corresponding boundary-value problems for nonlinear partial differential equations is proposed, which is based on the use of Ateba functions, the Van der Pol method, ideas of asymptotic integration, and the principle of single-frequency oscillations. For "undisturbed" analogues of the model equations, single-frequency solutions were obtained in an explicit form, and for "perturbed" ‒ analytical dependences of the basic parameters of the oscillation process on a small perturbation. The dependence of the main frequency of oscillations on the amplitude and non-linearity parameter of elastic properties in the case of single-frequency oscillations of "unperturbed motion" is established. An asymptotic approximation of the solution of the autonomous "perturbed" problem is constructed. Graphs of changes in amplitude and frequency of oscillations depending on the values of the system parameters are given.

Mathematical modeling of pollution of underground aquifers due to mining of minerals

Purpose. The research aims to create a mathematical model of salt contamination spreading through underground aquifers in the event of depressurization of the hydrocarbon production well crater for further assessment of environmental and economic damage from these processes. Methods. To predict the environmental and economic damage from salt contamination, the distribution of concentrations of harmful substances was investigated, taking into account the number of supply sources and their intensity over time, based on situ studies at the Rybalske Oil Field, Okhtyrskyi District of Sumska Oblast in Ukraine, where there were technological failures wells, accompanied by open fountains with the release of large amounts of highly mineralized water and the formation of craters. Mathematical modelling methods were used to process the data from the study of accidental technogenic pollution of underground aquifers. Findings. Based on real data from the study of the processes of potential salt contamination spread in fresh aquifers as a result of accidents at hydrocarbon production facilities, a mathematical model of salt contamination spreading in drinking groundwater in the event of depressurization of an oil field well crater has been developed. Potential economic losses in case of possible groundwater contamination with highly mineralized solution, which can into drinking groundwater aquifers, are substantiated. It has been established that in connection with the occurrence of an emergency situation due to the release of formation water to the surface in the territory of oil and gas fields, the formation of technogenic meromictic reservoirs is possible, which is confirmed by the example of the Rybalske Oil Field. It is proved that the total mineralization of crater water increases linearly with depth of the reservoir occurrence, and a similar dependence is characteristic of the chloride ion content. Originality. For the first time, a multicomponent mathematical model of mineral salt migration processes in underground freshwater aquifers in the case of depressurization of a meromictic reservoir has been developed. Practical implications. The research results obtained using numerical methods make it possible to predict the processes of spreading harmful substances in drinking underground aquifers as a result of emergencies at oil and gas fields, taking into account the number of sources of pollutants penetrating the study area, the heterogeneity of properties of the environment into which the harmful substance enters, and to assess the dynamics of changes in the concentration of these substances and time with further assessment of environmental and economic damage from these processes.

Выдавливание замкового блока при строительстве транспортных тоннелей большого диаметра

Purpose: to consider the problem of the key-segment extrusion that occurs during the construction of subway tunnels in St. Petersburg using prefabricated high-precision reinforced concrete linings with increased water resistance with a diameter of 10.3 m. To analyze the possible processes leading to this phenomenon and methods of solving the problem in construction conditions. To determine the consequences of the currently used solutions to the problem. To develop an analytical methodology for determining the magnitude of the friction force acting on the radial joints planes of contacting segments based on classical structural mechanics methods (displacement method). To carry out mathematical modeling of the extrusion process by the finite element method and compare its results with those obtained analytically. To develop recommendations for the elimination of block extrusion, which can be both applied in construction conditions and taken into account when designing lining structures. To analyze the effectiveness of the proposed recommendations. Methods: full-scale data from constructed objects, analytical calculations and mathematical modeling by the finite element method were used. Results: an analytical method is proposed for determining the magnitude of the pushing force of the key-segment and the friction force in the radial segment joints. The results of mathematical modeling showed high convergence of the results obtained by the two methods. Recommendations have been developed to eliminate the phenomenon of extrusion, and their effectiveness has been evaluated. Practical importance: the results of the study can be used at the design stage of prefabricated reinforced concrete linings with increased water resistance for large-diameter tunnels, as well as in construction conditions at the time of installation of the key segment.

Hyperbolic Balance Laws: Interplay between Scales and Randomness

Hyperbolic balance laws are fundamental in the mathematical modeling of transport-dominated processes in natural, socio-economic and engineering sciences. The aim of the workshop was to discuss open questions in the area of nonlinear hyperbolic conservation and balance laws. We have focused on a delicate interplay between scale hierarchies and random/stochastic effects and discuss them from analytical, numerical and modeling point of view. This leads to questions of admissibility criteria connecting to ill-posedness of weak entropy solutions, hyperbolic problems with non-local terms, mean field theory, multiscale and structure preserving numerical methods, random solutions and uncertainty quantification methods, as well as data-based methods.

Mathematical Modeling of the Global Engineering Process for Optimizing Product Quality in the Aerospace Industry

The aerospace industry faces the challenge of maintaining product excellence amidst intricate processes and demands for cost and time efficiency. Mathematical modeling emerges as a valuable tool for optimizing the engineering process and enhancing quality, with potential applications extending beyond aerospace to other sectors with high quality and safety standards. This study develops and validates a mathematical model specific to the aerospace industry, aiming to assess the impact of human resource expertise on product quality. Through a case study within an aerospace organization, an IDEF0-methodology-based mathematical model, coupled with weighted averages, was constructed to depict the comprehensive engineering process and quantify knowledge’s impact on deliverable quality. Simulation data, gathered through human resource knowledge assessments and non-conformity analyses, revealed a direct correlation between technical knowledge levels and deliverable quality, consequently impacting final product quality. The proposed model serves as a tool for estimating potential deliverable error rates and pinpointing critical areas within the process that necessitate refinement. The research underscores the significance of knowledge investment and effective knowledge management strategies in upholding quality and competitiveness across industries with stringent quality requirements.

Model of the non-stationary thermal processes in the ground heat pump system

One of the main directions for improving heat supply systems is the tendency to switch to low-temperature heating systems by using heat pump units is the tendency of implementation the low-temperature heating systems based on the use of heat pump units. In the work, the main attention is focused on the improvement of thermal parameters and circuit design features of elements of the heat pump system of heat supply using soil energy. For this purpose, the toolkit of mathematical modelling of processes in ground heat pumps is applied, taking into account the climatic conditions of Ukraine. The paper proves the technical possibility of creating an autonomous system of alternative heat supply for energy-saving technologies with the possibility of using ground energy, taking into account environmental requirements. It is substantiated that the use of the proposed systems is a promising direction for Ukraine, which is experiencing a shortage of its own energy resources, because it provides an opportunity to increase the share of organic fuel substitution and reduce the volume of heat emissions into the environment. A mathematical model of heat processes in the elements of the heat exchange equipment of the heat pump system based on renewable energy (soil energy) and secondary energy (wastewater) was developed, taking into account environmental requirements (preventing hypothermia of the soil during the operation of soil pipes and damage to vegetation, respectively), which allows choosing a rational mode of operation of the system under seasonal climatic changes and technological conditions. Numerical modelling of heat processes in elements of the heat exchange equipment of the heat pump system using groundwater and waste water was performed, and the energy and environmental efficiency of the system under variable climatic and technological factors was determined. Analysis and generalization of the calculation results of the heat pump heat supply systems using alternative energy based on the proposed mathematical model, taking into account environmental requirements (preventing thermal relaxation of the soil) allows to take into account the change in the temperature gradient around the soil heat exchanger and more accurately determine the heat flow from each section of the heat exchanger. It has been established that for heat pumps with soil heat exchangers, the maximum substitution ratio of the traditional fuel is 75 %, and the economically feasible quantity of soil heat exchangers is 9 units. Heat pumps using waste water can completely replace traditional heat supply systems. For individual consumers, it is possible to recommend heat pump units with soil heat exchangers, at the same time, it is necessary to provide a backup source of energy to increase the reliability of heat supply.

Simulation of recrystallization of cold-rolled automotive sheet depending on the degree of deformation, annealing temperature and chemical composition

The article presents the results of modeling the recrystallization of a cold-rolled sheet of 10 grades of automotive steels of various chemical composition. Mathematical models of recrystallization processes in cold-rolled sheets of the studied steels have been developed, which describe with satisfactory accuracy both the kinetics of the process during isothermal annealing and the grain size of recrystallized ferrite. The developed recrystallization model predicts with sufficient accuracy the kinetics of crystallization under conditions of heating at an arbitrary rate and subsequent isothermal exposure, which are used in annealing cold-rolled sheets on industrial production lines. The developed recrystallization model adequately takes into account both the influence of the carbon content and the main alloying elements of substitution (Mn, Si, Nb, Ti) on the kinetics of the process

Efficient control scheme development for a highly integrated multi-component distillation process

This research aims to address intricate control challenges in a highly integrated multi-component distillation process within a polyolefin elastomers plant. The studied process incorporates various process intensification techniques into a unified unit, resulting in strong interactivity and presenting unique control challenges. To tackle these challenges, a rigorous mathematical model of the distillation process is established, and index reduction is employed to handle the high-index DAE system. Various control structures and algorithms are utilized to comprehensively assess their feasibility and effectiveness in disturbance rejection, setpoint tracking, and handling inaccurate measurements. The control structures include temperature inferential control, temperature-composition hybrid control, and composition control. The control algorithms encompass PI control, linear model predictive control (LMPC), and nonlinear model predictive control (NMPC). Results indicate that both temperature-composition hybrid control and composition control exhibit comparable and superior performance. This suggests that temperature-composition hybrid control is an effective and cost-efficient configuration for complex distillation systems. The dynamic responses of MPC outperform those of PI control, as evidenced by a reduction in the integral of the absolute error. NMPC exhibits the most outstanding performance in all scenarios, showcasing the smallest maximum deviations and shortest settling times.

Thermal Energy Resource Potentials of the Kara-Bogaz-Gol Gulf as a “Solar Pond”

Introduction. The use of environmentally-friendly engineering systems including solar energy technologies makes it possible to reduce energy costs and therefore to lower production costs and anthropogenic stress on the environment.Aim of the Study. The authors used innovative techniques to assess the thermal resource potential of solar radiation, to analyze the salt deposits of the Kara-Bogaz-Gol Gulf as thermal accumulators for the development, introduction and use of solar thermal technologies and to justify the technical and economic feasibility of their use in engineering systems in the Kara-Bogaz-Gol Gulf (Caspian region).Meterials and Methods. The study design is based on systematic theoretical calculations of the gross, technical, economic and ecological potentials of solar radiation taking into account environmental conditions. For calculating there were used the methods of mathematical modeling of heat and mass transfer processes in active solar energy systems when converting solar energy into thermal energy in the salty reservoir of the Kara-Bogaz-Gol Gulf as a “solar pond”.Results. There have been assessed the solar energy characteristics for the introduction of various engineering storage systems and technologies. There have been determined the results of energy storage on the reservoir salt surface during the day: in winter – 1 009.0 W/m2 per day, in summer – 1 574.7 W/m2 per day. It has been proven that the potential of solar energy conversion into thermal energy varies from 40 to 70% depending on the season. Aaccording to theoretical calculations, the solar pond efficiency in winter is 11.4% and in summer – 14.6%. In summer, there was measured the average temperature on the salt surface of the reservoir bottom, it ranges from 55.04 to 79.8 ºC, in winter from 20.0 to 25.6 ºC.Discussion and Conclusion. The results obtained can be used for strengthening energy security, developing energy systems and producing autonomous thermal power devices based on solar energy that will reduce the energy consumption of fossil fuels and improve the environmental situation in the region. The materials of the article can be used in preparing design estimates and feasibility study for developing various solar energy systems and technologies in the Caspian region.

Exploling the Scientific Model for Constructing a Platform for the International Communication of PingJiang Opera

Purpose: Considerable changes have occurred in many areas of science and technology as a result of the current information technologies' quick development and use. Specifically, new theories in mathematics have surfaced; they may be used to construct and refine current mathematical models of different processes and objects. Method: Regulatory and permitting decision-makers are worried about the ambiguity surrounding the possible environmental consequences arising from the introduction of these innovative devices in coastal and riverine ecosystems as research and testing of maritime energy devices progress. The Triton Initiative conducts studies and makes suggestions for environmental monitoring techniques and technology to give industry stakeholders with the information required to approve maritime energy system testing. Results: The efficient distribution of research findings is crucial in enhancing data accessibility for stakeholders who might use the information to make informed policy choices. Nevertheless, there are few frameworks available for carrying out scientific communications related to marine energy projects. Using the Triton Initiative's pilot scientific communication program as a case study, we discuss methods, resources, and strategies for creating a science communication framework for marine energy projects or other related fields of research in this article. Conclusion: This article uses the historic Pingjiang Road in Suzhou, China, as a case study to investigate how, in the era of globalization and digital media, urban spaces that have been revitalized for historic and cultural consumption may demonstrate the publicness or potential capacity for publicity.

Large Debris Removal: Using Features of Attitude Motion for Load Factor Regulation during Re-Entry

This paper focuses on the active removal of spent upper stages from LEO using de-orbiting devices. It proposes a method of regulating aerodynamic loads on the target during its re-entry by utilizing the features of spatial attitude motion. A mathematical model of the re-entry process is developed, and numerical simulations are conducted, demonstrating that the nature of the attitude motion during the descent influences the load factors and, thus, the breakup altitude. It is shown that the respective de-orbiting devices should control both the initial tumbling and spin of the target to achieve different mission outcomes, such as minimizing the debris footprint size or maximizing the breakup altitude.

Mathematical modeling of nonequilibrium combustion processes in a liquid rocket engine

The key problems of safety for Space missions begin with safety, reliability and effectiveness of rocket engines of different types used at different launch stages and orbit corrections. Today, the possibilities for improving chemical rocket engines of traditional types are almost completely exhausted and are limited to minor improvements in energy-mass characteristics. A qualitative leap in the development of engine building can only be achieved through the development and implementation of new types of engines. As unburned fuel in the combustion chamber is a loss of thrust for the engine, the study of droplet combustion and evaporation, in particular, the droplet lifetime, is of fundamental importance in the creation of combustion chambers using atomized liquid fuel in their operation.In this paper a quasi-stationary model, which describes the evaporation of a single droplet in a gaseous atmosphere, is presented. Since in the numerical implementation the mass flow from the liquid phase to the gas and the heat flux from the droplet to the gas are calculated based on the Peclet number and the droplet surface temperature obtained from the quasi-stationary problem, approximation formulas for these parameters are developed in this paper. As an example, the problems of evaporation of a liquid oxygen droplet in an atmosphere of gaseous hydrogen and a droplet of liquid n-decane in an atmosphere of gaseous oxygen are considered. Formulas for calculation of mass flow and heat flux from liquid phase to gas based on the solution of the droplet evaporation problem are presented. Estimates of droplets lifetime in engine are provided based on developed droplet evaporation models.