Theoretical Analysis Of Process Research Articles

An adaptive‐impedance fault current limiter for accelerating fault current suppression in MMC‐HVDC systems

DC fault clearance is one of the critical issues for the modular-multilevel-converter-based high voltage direct current (MMC-HVDC) systems. Employing a hybrid DC circuit breaker (H-DCCB) to isolate the faulty line is a typical method to achieve fast fault clearance. However, the H-DCCB has to interrupt the fault current and absorb the energy up to tens of megawatts in several milliseconds. Through theoretical analysis of the interruption process using the H-DCCB, reducing the equivalent inductance of the fault circuit during the fault falling stage is recommended to accelerate the fault current suppression for the H-DCCBs. This paper proposes a novel adaptive-impedance fault current limiter (AFCL), which contains two coupled DC reactors and an energy absorption branch (EAB). The proposed AFCL can automatically limit the fault current during the current rising stage and works as a DC reactor with a fixed equivalent inductance through a two-state model analysis. Meanwhile, the AFCL contributes to accelerating the decline of the current by adaptively reducing the inductance of the discharge circuit. Consequently, the fault current suppression time and the energy absorbed by the H-DCCB are reduced. Simulation case studies and hardware experiments are carried out to verify the performance and practicality of the proposed AFCL.

Decision support architectures for the recovery of interdependent infrastructure with large‐scale damage and socially vulnerable populations

AbstractInfrastructure damage has household‐level consequences after a major disaster. Losses are experienced due to factors such as unavailable services and impaired mobility. Socially vulnerable residents, in particular, have few resources with which to adapt. Decision support tools for making justifiable, transparent, repeatable decisions that center the needs of users during recovery are currently nonexistent. In part, this is because infrastructure recovery is a complex process, often involving the coordination of multiple entities. The recovery problem can be rendered more tractable by applying tools suitable for modeling complex systems and processes. System theoretic process analysis (STPA) can be used for goalsetting in a complex, dynamic system such as community civil infrastructure. STPA is used here to devise a decision support tool architecture suitable for coordinated multiagency recovery efforts. The example application is a long‐term recovery process with widespread infrastructure damage, population displacement, and other disruptions in system use due to a major disaster. In the example, losses and hazards are defined to reflect recovery challenges commonly faced by vulnerable populations experiencing partial or total displacement. This extension of STPA then reverses these hazards, starting with the most hazardous system states and progressing sequentially to less hazardous states until recovery is complete.

A systems theoretic process analysis (STPA) approach for analyzing the governance structure of fecal sludge management in Japan

Fecal sludge management (FSM) stakeholders have hitherto been unable to benefit from analytical approaches based on systems thinking principles, as studies utilizing theoretical frameworks to analyze governance structures remain in a nascent stage. One such prominent framework is the Systems Theoretic Process Analysis (STPA), which has no FSM-related applications in the literature. Relying on official documents such as ministerial ordinances, this study conducts a multistage STPA for a well-established and sustainable FSM system, that is, the Johkasou system in Japan. The analysis maps the key stakeholders and their interactions to comprehensively identify potential risks and corresponding novel indicators to help manage risks within the Johkasou system. The features of governance structure thus obtained also highlight the steps necessary to address governance issues for Japan and other countries attempting to establish sustainable FSM. The study extends the STPA literature by providing a substantial validity of STPA’s capability for analyzing the FSM governance structure against robust and independent criteria that define the objectives of a “good” governance structure, that is, efficiency, accountability, and legitimacy. The STPA results identify novel leading indicators to guide Japanese policymakers to improve FSM management. The results from STPA also effectively provide valuable insights for other countries by highlighting the various features contributing to an effective governance structure of the Johkasou, such as centralized decision-making in a combination of a hierarchy of goals to establish a clear division of responsibility across various actors. The study also notes potential challenges for field implementation of STPA and discusses directions that future work could explore.

Modeling of heat transfer during the desublimation of substances into refrigerated containers

This paper presents the results of the theoretical and computational analysis of the thermal processes during the desublimation of uranium hexafluoride and hydrogen fluoride in refrigerated containers. The technological scheme of the hydrogen fluoride desublimation in the containers refrigerated by the cold air is presented. We have substantiated the desublimation method of the uranium hexafluoride residues and hydrogen fluoride from the process stream into one container. The paper also provides the estimation of the maximum container loading, when the pressure of the saturated vapors above the surface of the desublimated mixture reaches the limiting value.

Impact of superhydrophobic sphere onto a pool covered by oil layer

We experimentally investigate the impact of a millimetric superhydrophobic sphere on a water pool covered by a thin oil layer, with the aim of seeking the critical conditions for sphere entrapment at the interfaces. The interfacial tension and viscosity of the thin oil layer are found to have a significant effect on the fate of the impacting spheres that are denser than the liquids: sinking or floating. For the oil layer of low viscosity, the impact dynamic is dominated by the capillary force, and the sphere experiences more or less uniform acceleration after the impact, which is similar to a sphere impacting onto a pure water pool. For the oil layer of relatively high viscosity, the viscous dissipation inside the thin oil layer greatly hinders the descending of the sphere, and thus, it is the viscosity of the oil layer that dictates the acceleration process of the spheres at the early stage of impact. At the late stage, the sphere moves very slowly under water (particularly at the onset of sinking), and the competition between the oil–water interfacial tension and buoyancy determines whether the sphere would eventually sink or float. We then conduct the theoretical analysis of the dynamic processes of the impacting sphere and give the theoretical predictions of the respective critical conditions, which agree well with the experimental observations.

Application of Systems Theoretic Process Analysis and Failure Modes and Effects Analysis to Process Reliability and Occupational Safety and Health in Construction Projects

Construction, a leading industry in many countries, contributes greatly to gross domestic product (GDP). In a construction project, several processes must be performed with high reliability and quality, while maintaining the occupational safety and health (OSH) of workers. This paper explores the process reliability and OSH related analysis of the subsystem related to epoxy resin application on concrete structure, using systems theoretic process analysis (STPA), and failure modes and effects analysis (FMEA). The STPA focuses on the hierarchical control structures of a system/subsystem, their unsafe control actions (UCAs), and the causes of the UCAs. Meanwhile, the FMEA emphasizes the potential failures in a system/subsystem, as well as their modes, effects, causes, and ranking. On the subsystem related to epoxy resin application, the two approaches yield complementary results, which can be used in the industry to improve process reliability and OSH.

System-Theoretic Process Analysis Based on SysML/MARTE and NuSMV

Systems Theoretical Accident Model and Process (STAMP), which considers system safety as an emergent property of the system, is a more effective accident/loss causality model for modern complex systems. Based on STAMP, System Theoretical Process Analysis (STPA) has attracted increasing attention as a new approach to hazard analysis, and relevant international standards are being developed. However, STPA is mainly performed manually, leading to inefficiencies, and constructs models in non-standard language, hindering the integration with existing systems engineering. STPA-SN (STPA based on SysML/MARTE and NuSMV) is proposed to build model in SysML, describing the timing with MARTE (Modeling and Analysis of Real-Time and Embedded Systems), transform SysML model into NuSMV model and output loss scenarios automatically with model checker. An application example of STPA-SN is provided to demonstrate potentials for higher efficiency of analysis and for collaboration with SysML-based systems engineering.

Effect of Contact Preference among Heterogeneous Individuals on Social Contagions

In social networks, individual heterogeneity is widely existed, and an individual often tends to contact more frequently with friends of similar status or opinion. It is worth noting that the contact preference characteristic among heterogeneous individuals will have a significant effect on social contagions. Thus, we propose a social contagion model which takes the heterogeneity of individual influence and contact preference into account, and make a theoretical analysis of the social spreading process by developing an edge-based compartmental theory. We find that the competition between simple contagion and complex contagion leads to the emergence of crossover phase transition phenomena when the influence of ordinary individuals is low: it changes from being hybrid to continuous, then to hybrid, and eventually to continuous phase transition with the increase of the contact probability of homogeneous individuals. However, it changes from being first-order to continuous phase transition when the influence strength of ordinary individuals is relatively high. In addition, there is an optimal value or range of contact probability of homogeneous individuals which maximizes the spreading size, and the optimal value or lower bound of the optimal range decreases with the increase of transmission probability. Our theoretical prediction results are in good agreement with the simulation results.

Theoretical and Numerical Analysis of Nonlinear Processes in Amperometric Enzyme Electrodes with Cyclic Substrate Conversion

A theoretical model of amperometric enzyme electrodes has been developed in which chemical amplification occurs in a single enzyme membrane via cyclic substrate conversion. The system is based on non-stationary diffusion equations with a nonlinear factor related to the Michaelis–Menten kinetics of the enzymatic reaction. By solving the nonlinear equations using the AGM technique, simple analytical expressions of concentration substrate, product, and amperometric current response are derived. Further, biosensor sensitivity, resistance, and gain are obtained from the current. MATLAB programming was used to carry out the digital simulation. The analytical results are validated with the numerical results. The effect of substrate concentration, maximum enzymatic rate, and membrane thickness on biosensor response was evaluated.

Effect of high-frequency phase shift on metal transfer and weld formation in aluminum alloy double-wire DP-GMAW

This paper presents a double-wire gas metal arc welding (GMAW) system for investigating the effects of high-frequency phase shift of the double pulse on metal transfer and bead formation. First, a theoretical analysis of the double-wire metal transfer process was carried out and a mathematical model of droplet impact was established. The metal transfer processes of different phase shifts were then photographed using a high-speed camera, the droplet velocity and impact on the weld pool at different phase shifts were calculated, and geometries of the weld beads were analyzed. Penetration of the longitudinal section fluctuated due to the modulated double pulse and the penetration depth increased with increasing phase shift; however, the weld reinforcement was irregular. The weld width increased with decreasing phase shift due to the temperature gradient. Moreover, since a reduction in double arc interference reduced the size and number of pores, porosity of the weld decreased with higher phase shifts. Stirring induced by the double pulse promoted floating and precipitation of pores. The experimental results show that a 180° phase shift leads to the most stable welding process resulting in a sound weld and an obvious fish-scale appearance. No undercut, hump, or spatter defects were observed. In addition, the deepest penetration with a uniform and smooth penetration fluctuation curve and the lowest porosity were also achieved with a phase shift of 180°.

Optimization of the polishing process on a polishing machine with horizontal overarm

Understanding the basic principles of polishing on machines with autorotating swing kinematics is important for the description and understanding of more advanced polishing technologies. The article deals with the theoretical and numerical analysis of the polishing process and its comparison with the experiment performed during the real process on the machine. The dependence of the mutual position of the tool and workpiece axes on the removal distribution within the polished surface was described and demonstrated

ГЕОДИНАМИЧЕСКИЕ ПРОЦЕССЫ В СКЛОНЕ ПОДНЯТИЯ

The flow for the uplift slope is considered in the viscous liquid model. The relevance of the study is justified by the need for experimental and theoretical analysis of the geodynamic processes occurring in the slopes of rises. The object of the study is the slopes of rises, formed by mantle thermochemical plumes which have not come to the surface. The objectives of the study are to present the velocity profile of the viscous flow of the uplift slope and to determine the friction coefficient for it; to find out the effect of the dynamic viscosity coefficient of the slope on the appearance of compressive and tensile stresses; on the basis of laboratory and theoretical simulations to find out the hydrodynamics of the flow when the liquid flows from a rectangular vessel and using the results of geodynamic simulations to determine the flow parameters in the area of the uplift slope fault formation. The flow occurring in a viscous liquid at a constant inclination angle of the free surface of the elevation slope is considered. In a highly viscous liquid at low flow velocities, the inertial terms in the equation of motion can be neglected. For this case, the solution of the equation of motion in a layer with an inclined free surface at a constant horizontal pressure gradient is obtained. The flow velocity profile in such a layer and the relation for the maximum flow velocity are obtained. The tangential stress on the sole of the layer is determined. The tangential stress does not depend on the viscosity, but depends on the layer thickness. With a constant viscosity of the layer, the elevation slope is under conditions of compressive stresses. Strain conditions for the uplift slope are possible when the viscosity of the layer decreases with distance from the main ridge. Discontinuities occur on the elevation slopes due to changes in viscosity along the slope and changes in the velocity. Under the influence of gravitational forces caused by the density difference at the rupture boundary, flow occurs and the resulting free volume is filled. The motion in a highly viscous liquid during the formation of a free vertical surface has been studied experimentally when liquid flows out of a transparent rectangular vessel. Photographs of the free surface were obtained. A linear dependence of the relative height of the free surface location on the relative horizontal coordinate is observed. Expressions are obtained for the average velocity and expiration time of a viscous liquid from a rectangular vessel. Estimates of the average velocity and outflow time for the specified slope parameters are presented

A Longitude-Purification Mechanism for Tunable Fiber Laser Based on Distributed Feedback

Advanced applications in optical frequency metrology demand improved tunable lasers with high coherence. Herein, a tunable single-frequency fiber laser based on the longitude-purification induced by the distributed feedback has been demonstrated. The key device in the proposed laser structure is a distributed self-injection feedback structure (DSIFS) which function as a mode selector to have a robust frequency-domain mode suppression and wavelength adaptability. Our work is distinctly focused on the theoretical analysis of the formation process of single-longitudinal-mode (SLM) laser output and the wavelength adaptive characteristics in the DSIFS. In this experiment, the side mode suppression of the resonant longitudinal modes can be achieved in a fiber ring laser without any accurate control of the main cavity. The fiber laser obtained a compressed laser linewidth of 855 Hz, enhanced side mode suppression ratio (SMSR) of ∼67 dB, and frequency noise suppression of 40 dB. Furthermore, the fiber laser can be tuned over the entire flat gain region. The measured output power, wavelength and SMSR variations of the proposed laser over a long-term observation are less than 0.034 mW, 0.028 nm and 2.53 dB, respectively. In addition, the SLM operation of the laser can also be obtained at different pump power for every wavelength channel. Moreover, this method is applicable to any other gain-type lasers, indicating that the longitude-purification mechanism has a broad application prospect in other highly coherent tunable lasers.

Інституційні перешкоди для інвестиційно-інноваційного розвитку фірми в кланово-олігархічній економічній системі

The purpose of the article, taking into account mainly the normative nature of most domestic studies of the problems of investment-innovation development of the national economy, as well as the latest foreign studies of the firm theory, and based on the institutional methodology, is to carry out a positive analysis of this problem, which, on the one hand, will bring the theoretical analysis of innovative processes in the Ukrainian economy closer to modern realities, and on the other hand, will be aimed at developing more adequate ways to solve existing problems. As result of the study, it is concluded that systemic institutional obstacles to the innovative development of the Ukrainian economy are present. During the years of independence, a powerful system of informal institutions of influence on all aspects of public life was formed in the country. In fact, the lion’s share of property and power is concentrated in the hands of a small number of the most influential families of both former and current politicians, placed in key positions of law enforcement officials and the judiciary in close contact with criminal circles. The real motivation of the activities of oligarchic circles fits into the feudal-mafia mental model of thinking, making and implementing managerial decisions. Promising directions of further research on this issue are the search for conditions and factors for dismantling the clan-oligarchic system, including the following components: demonopolization of political life and balanced political representation of the main social strata; real support on the part of the State for small and medium-sized businesses on the basis of maximum deregulation; priority development of health care, education and science on the basis of at least 10 years of allocation of 5% of GDP for these needs; proper reform of the law enforcement and judicial systems

РЕЗОНАНСНИЙ ПІДСИЛЮВАЧ АКТИВНОЇ ЕЛЕКТРИЧНОЇ ПОТУЖНОСТІ. ПРОПОЗИЦІЯ, АНАЛІЗ, ЧИСЛОВІ ОЦІНКИ

The purpose of this work is to substantiate the real effectiveness of the proposed active electric power resonant amplifier circuit, represented by a sequence of four inductively coupled active-reactive circuits. The first of them is the input with a source of a harmonic signal to be amplified. The second one generates amplified reactive power in the voltage resonance mode. The third one carries out theoutput of power from the second circuit without the reverse influence of the amplification processes with an additional third-party voltage source in the current resonance mode. The fourth circuit inductively connected to the third circuit contains an output load -a resistor that simulates the release of amplified active power. The analysis and numerical assessments of the characteristics of the processes in the proposed scheme of the resonant amplifier of active electric powermade it possible to substantiate its fundamental capability. Quantitative estimates for the experimental model made it possible to give recommendations on the choice of the parameters of the circuit elements of the resonant amplifier, which has sufficiently high efficiency indicators for low-resistance output active loads.The results obtained are based on the conclusions of a generalized theoretical analysis of electromagnetic processes and numerical estimates for its experimental implementation.The proposed scheme for the resonantamplification of active electric power, the rationale for its fundamental effectiveness, the theory and numerical assessments of the characteristics of the ongoing processes are of practical interest for further experimental studies, as well as for formulating recommendations for the manufacture of operating samples of this proposal are very promising directions. The results of the conducted research are seen as a theoretical search for the conditions for the highest efficiency and an experimental study ofelectromagnetic processes in the proposed circuit of a resonant amplifier of active electric power.

A High-Level Risk Management Framework as Part of an Overall Asset Management Process for the Assessment of Industry 4.0 and Its Corollary Industry 5.0 Related New Emerging Technological Risks in Socio-Technical Systems

Suffice to say that long-established businesses have their own challenges. Furthermore, accurate systematic methods and tools for managing risks in the context of industry 4.0 are lacking or less efficient, spreading unrealistic awareness of risk (or situational awareness) in various domains where risk management is needed. Conventional methods have their own limits and might not identify all aspects that influence system safety. Once traditional industry challenges are combined with emerging risks along with new systemic and organizational risks as well as cognitive and motivational biases in human logic, there will be the necessity of building thorough Asset Management and Decision Support approaches accounting both for conventional and emerging risk safety management. Hence, innovative, and efficient approaches that can investigate issues from a broad systemic perspective to support asset management practitioners to deal with those threats associated with the complexity of socio-technical systems are of interest. On these grounds, this paper focuses on identifying and analyzing components of risk management approaches especially for new emerging safety risks within industry 4.0 (emerging technology-related risks), as well as the rising of extreme, rare, and disruptive events, at a time of continued uncertainty in the global economy, in conjunction with the highly insecure political situation caused by recent armed conflicts (for e.g., Russia vs Ukraine), and the coronavirus disease pandemic (COVID-19) that might create fatal disturbance of the performance of organizations. We opt for the relatively new methods that have been developed based on system theories, viz. the Functional Resonance Analysis Method (FRAM), the System-Theoretic Accident Model and Processes (STAMP, System Theoretic Process Analysis (STPA)) and the global risk-informed decision-making approach (RIDM) in asset management as the best suited approach for this research. We first discuss the benefits of these methods then outline the possibility of combining them to conduct high-level risk management and decision-making framework. Further research would validate their efficiency and practicality. Therefore, future research initiatives will be devoted to conducting case studies in order to obtain more accurate data.

Situational Risk Assessment Design for Autonomous Mobile Robots

The emerging autonomous mobile robots promise a new level of efficiency and flexibility. However, because these types of systems operate in the same space as humans, mobile robots must cope with dynamic changes and heterogeneously structured environments. To ensure safety, new approaches are needed that model risk at runtime. This risk depends on the situation and is therefore a situational risk. In this paper, we propose a new methodology to model situational risk based on multi-agent adversarial reinforcement learning. In this methodology, two competing groups of reinforcement learning agents, namely the protagonists and the adversaries, fight against each other in the simulation. The adversaries represent the disruptive and destabilizing factors, while the protagonists try to compensate for them. The situational risk is then derived from the outcome of the simulated struggle. At this point, the system’s Digital Twin provides up-to-date and relevant models for simulation and synchronizes the simulation with the real asset. Our risk modeling differentiates the four steps of intelligent information processing: sense, analyze, process, and execute. To find the appropriate adversaries and actors for each of these steps, this methodology builds on Systems Theoretic Process Analysis (STPA). Using STPA, we identify critical signals that lead to losses when a disturbance under certain conditions or in certain situations occurs. At this point, the challenge of managing the complexity arises. We face this issue using training effort as a metric to evaluate it. Through statistical analysis of the identified signals, we derive a procedure for defining action spaces and rewards for the agents in question. We validate the methodology using the example of a Robotino 3 Premium from Festo, an autonomous mobile robot.

Integration of STPA and TOPSIS fuzzy methods for risk analysis in aerospace projects

There are several types of risks in organisations and projects, including technological, financial, environmental, legal, and operational. This article focuses on a risk analysis framework for complex aerospace research projects, some of which are innovations in the area and do not have a history of data from previous activities. The objective of this study is to analyse the feasibility of integrating the systems theoretic process analysis (STPA) method for systemic assessment of safety and fuzzy technique for order preference by similarity to ideal solution (TOPSIS) for prioritising unsafe control actions (UCAs). The proposed integration method was applied to the Laboratory of Injection Systems for Liquid Propellants at the Aeronautics Institute of Technology (ITA). The results obtained were the need for an emergency response plan, signalling, access control, and safety training for laboratory technicians. Therefore, risk analysis is essential to support the decision-making process, to identify and reduce hazards and losses.

Analysis of aesthetic minimalism: a view at the creative process in minimalist Brand Design

The search for a more sustainable and at the same time clean and elegant style is increasingly present in people's lives in order to have greater sustainability, freedom from excess for the awareness of what really matters which reflects in the aesthetic standards in the area of Design . The creative process starts to reflect also through society's behaviors. In this case, more specifically in the construction of Brand Design. So, aesthetic minimalism is also increasingly present in brand design projects, reflecting consumer behavior. This article aims to address the definitions of aesthetic minimalism present in brand design projects in their creative process. To understand all these aspects, a theoretical foundation, relevant discussions and analysis of the creative process of a minimalist brand were made. The methodology used for this article was qualitative exploratory research. Finally, final considerations are presented, addressing the impact and importance that these changes can have within design styles in the creative process for professionals in the field.

MODELING OF TECHNOLOGICAL PROCESSES OF FILLING THE GEOMETRIC STRUCTURES OF THE WORKING BODIES OF A BUNKER TYPE OF AGRICULTURAL MACHINES WITH MATERIALS OF A SPHERICAL SHAPE

Optimization of geometric parameters of bunkers, feeders of agricultural machines depends on the type of process, mechanical and technological properties of materials, production technologies. Modern containers can be metal, plastic or glass. Growing requirements in a competitive market environment necessitate the constant improvement of existing and the creation of new machines with optimal parameters of the working bodies. Various agricultural materials, such as sandy soils, grain, fertilizers, tubers, fruits have different properties of flowability and mutual movement of particles in the form of spherical bodies. The article presents improved theoretical principles of practical orientation of optimal filling of containers with agricultural materials. As a result of research on modeling of technological processes of filling geometric structures with working materials of spherical shape, using a fundamental analytical and mathematical apparatus, an algorithmic model that describes the optimal filling of space typical for seed boxes, harvesters or seeders has been developed. The maximum filling of a given flat and three-dimensional geometric figure by a set of balls of the same radius have been calculated, namely, the quantitative component of such optimal filling is described, and the criterion for estimating such filling is formed. Such processes occur during the production operation of seeders and planters, machines for harvesting and post-harvest processing of grain, root crops, fruits, etc. The use of an algorithm for mathematical analysis and calculation of technological processes and technical systems provides the creation of the necessary conditions to prevent injury to seeds. In addition, innovative methods of theoretical analysis and calculation of processes, as well as phenomena characteristic of agro-industrial production have been proposed. These methods can be effectively applied in the educational process when preparing specialists for project activities.