Optimal mission abort policy for systems subject to random shocks based on virtual age process

For safety-critical systems such as aircrafts and submarines, mission abort is commonly deployed to enhance system survivability at the cost of reducing mission success probability. In addition to mission abort, protective device can also mitigate the failure risk of safety-critical systems by reducing the magnitude of external shocks. Considering the effect of protective device on system failure behavior, this article proposes a condition-based mission abort policy where a mission is terminated and rescue procedure starts immediately if the state of system is worse than a control limit. Based on the developed mission abort policy, mission reliability and system survivability are evaluated to analyze the risk of mission failure and system failure. The optimal mission abort threshold balancing the tradeoff between mission reliability and system survivability is investigated. Furthermore, the joint optimization of mission abort and protective device selection policies is explored by simultaneously optimizing the defensive factor and abort threshold. A numerical example on a hydraulic system is presented to illustrate the applicability of the proposedpolicies.

Reliability modeling for balanced systems considering mission abort policies

Phased-mission systems are widely utilized in aerospace, defense fields, and production processes. These systems are characterized by missions consisting of multiple consecutive phases, each with distinct objectives and operating conditions. Due to complex operational environments and internal degradation, such systems face high failure risks, potentially re- sulting in irreversible economic losses and safety hazards. Therefore, designing a rational mission abort policy during mission execution to balance mission reliability and system survivability is of significant practical importance. This paper addresses the specific charac- teristics of phased-mission systems and proposes a mission abort policy based on the degra- dation process. A multi-phase Wiener process with phase-specific parameters is employed to depict system degradation behavior in different phases. A dynamic decision-making frame- work is developed to determine whether to continue or abort the mission by minimizing the expected total cost. A dynamic programing algorithm is used to find the optimal mission abort policy. The structural properties of the optimal policy are examined. The mission success probability is derived recursively using a matrix method. The practical value of the proposed model is validated through numerical analysis and comparative studies.

The balanced system often performs key missions in many fields, such as aerospace, new energy storage, and the military. However, the failure of the system can cause major losses. Therefore, the mission needs to be aborted when the risk of system failure is higher. In this paper, the optimal mission abort policy for a k‐out‐of‐n: F balanced system is studied. The system with a restricted mechanism consists of m sectors and there are n components in each sector, in which the components fail due to two situations: internal failure or external shocks. If the number of working components in m sectors is the same, the system is balanced. If one component fails, the system will force down or resume a component with a probability to keep balance. The model of the mentioned system is established, and the Markov process imbedding approach is used for deriving the reliability indices. Two optimization models are established according to two competitive abort criteria. Finally, an unmanned aerial vehicle performing a mission is discussed to illustrate the proposed mission abort policy.

The delay time concept is widely adopted in literature to model the two‐stage failure process of most industrial systems which can be divided into normal stage (from new to an initial point of a defect) and defective stage (from defect arrival point to failure). Most existing delay time models assume that the normal and defective stages are independent. A generalized delay time model is proposed in this paper by considering the dependence between the normal and defective stages which is reflected in the fact that they share the same external shock process. According to the definition of shot‐noise process, external shocks will incur random hazard rate increments in the two stages. The failure state is self‐announcing, whereas the defective state can only be detected by block‐based inspection or opportunistic inspection offered by unexpected shutdown due to unavoidable external factors. The system is correctively replaced upon the occurrence of a system failure or preventively replaced at the detection of a defective state. Based on the stochastic failure model and maintenance policy, this paper evaluates system reliability performance and average long‐run cost rate via a Markov‐chain based approach. Finally, a case study on a steel convertor plant is given to demonstrate the applicability of the proposed model.

Optimal loading of repairable system with perfect product storage

The paper contains a series of complex analyses on the study of typologies of economic crises and can bring a significant contribution to the literature in determining the effects of external factors on economic growth, taking into account the distinct characteristics of the periods of decline. The work includes Hodrick-Prescott filtering techniques for characterizing business cycles in three Central and Eastern European countries and the Structural Vector Autoregression (SVAR) technique is used to analyze the impact of external shocks on economic growth over two distinct time-horizons. External shocks such as external debt, external interest rate, external output, producer price index and real interest rate were taken into account. For each economy analyzed, the impact of the two types of economic crisis was observed, namely financial crisis and health crisis, and two time-horizons were defined for each complete economic cycle. Over these two time-horizons, the impact of external shocks on economic growth has been assessed. There has been a general decrease in the effects of shocks in the second time-horizon, in which the most severe values of economic growth are associated with the health crisis, compared to the time-horizon associated with the financial crisis. It has also been observed that, in the case of both Hungary and Romania, the responses of economic growth to external shocks are faster compared to the Czech economy. Moreover, external production is the factor that explains most of the variance in the economic growth rate in the first time-horizon, while in the second, one of the most influential indicators is the external production price index, which has been severely affected by the slowdown in the global production process.

Over the past few years the South African economy experienced strong exchange rate movements as well as shocks to oil prices and import prices. Thorough knowledge of the pass-through of these external factors to domestic inflation is of particular importance for monetary policy. This paper makes use of a VAR of a distribution chain to provide empirical evidence on the pass-through of three external shocks (oil price shocks, exchange rate shocks and non-oil import price shocks) on inflation in South Africa at different price stages. Including prices along a distribution chain is of great interest for price analysis as it reveals how external shocks are propagated from one price stage to the next. The study highlights the relative importance of different external shocks, as well as their combined importance in explaining domestic inflation in South Africa.

This study is aim to find out the contribution of intensive margin and extensive margin of Chinese aquatic products export. We construct a measure of the export margin and exploit export data of Chinese firms to analyze it, the result imply that intensive margin affect the export growth significantly, while the role of extensive margin is much important than intensive margin facing external shocks. We also find heterogeneity of markets and firms influence contribution of intensive margin and extensive margin differently: (i) intensive margin plays a positive and steady role in export growth which is imported by developing economies, while external shocks affect intensive margin negatively which is exported to developed economies; (ii) intensive margin and extensive margin of state-owned enterprises negatively impact exports in most years, while the contribution of intensive margin compared with extensive margin more pronounced on both private and foreign firms. However, the impact of external shock on intensive margin of foreign companies is more significantly.

Optimizing time-varying performance and mission aborting policy in resource constrained missions

The purpose of this study is to develop approaches for assessing the effectiveness of monetary transmission in Ukraine as a systemic indicator of the ability of monetary policy to achieve its declared goals under conditions of extreme uncertainty. Special emphasis is placed on the need to adapt traditional analytical methods to new challenges associated with profound structural transformations of the economy, the impact of external shocks, and the evolving role of central banks in unstable environments.The research methodology includes a critical review of scientific literature, systems analysis of the transmission mechanism structure, modeling of an adaptive effectiveness metric, and elements of comparative analysis. The approach considers both the objectives and outcomes of monetary policy, accounting for delay factors, institutional inertia, sensitivity of transmission channels, and their interactions.The main outcome of the research is the development of a conceptual approach to evaluating monetary policy effectiveness, based on the perception of the financial and economic system as a filtering mechanism designed to smooth internal and external shocks, within which the monetary regulator and transmission mechanism operate (referred to as the “managed shock filtering” concept). The proposed coefficient, through time-varying weights, allows adapting to modifications in monetary goals and principles by operating the sets of monetary instruments and targets, while penalizing the dispersion of instruments to ensure a minimum necessary and predictable policy approach.The practical application of the results lies in the use of the proposed approaches for analyzing the policies of the National Bank of Ukraine and other central banks under crisis or extreme uncertainty, particularly for developing adaptive monetary rules, communication strategies, and more resilient models for forecasting the impact of monetary impulses.The study summarizes the directions for improving the proposed framework, including the application of structural economic models and benchmarking approaches. It is also emphasized that the prerequisites for changing transmission efficiency may lie both within and beyond the scope of macro-financial regulation.

Purpose Seasonal data are characterized by multiple complex features such as seasonal fluctuations and stage differences, which presents challenges for the scientifically sound construction of its predictive models. This article proposes a novel seasonal grey prediction model with a weighted fractional order accumulation operator for accurate prediction of China’s natural gas production. The grey models proposed in this article optimize the accumulation method of the traditional grey model, and flexibly adjust the generation sequence through the two parameters introduced, so as to explore the internal law of the data information at a deeper level, and achieve the purpose of improving the model accuracy. Design/methodology/approach Firstly, based on the seasonal fluctuations of the raw data, the raw data is divided into four seasonal groups. Secondly, when an external disturbance affects the system, the classic average weakening buffer operator is used to weaken its effects. Then, the new information accumulation parameters ? and the fractional-order cumulative generating operator parameter r, are optimized using the particle swarm optimization (PSO) technique. Findings The experimental results show that the new grey prediction model (DGGM(1,1,λ,r)and DGGM(1,N,λ,r)) perform better than other models. This model is more suitable for solving the prediction problem of seasonal fluctuation systems with external disturbances. Practical implications The seasonal grey model proposed in this article is suitable for predicting data sequences with seasonal changes while considering the impact of external shock. Two models proposed in this article are used in two cases, i.e. estimating China’s natural gas production and predicting total electricity consumption in Nanjing city. Accurately predicting to provide a decision-making basis for the Chinese government to formulate energy policies, plan energy layouts, and adjust industrial structures. Originality/value Simultaneously considering seasonal changes and external shock disturbances, the data grouping approach is used to identify seasonal changes. This article proposes a new weighted fractional order accumulation operator that combines the new information accumulation operator and the fractional order accumulation operator. A novel seasonal grey prediction model with external impacts is proposed to improve the predictive performance of the system. The PSO algorithm is used to solve the parameter optimization problem of the model.

Purpose– The purpose of this study is to elucidate the determinants of economic resilience at various levels of analysis. While the economic benefits of regional clustering are well-documented, the impact of external shocks on regional clusters has only recently gained attention. This study explores the antecedents of economic resilience, defined as sustained employment growth, prior to and during the global financial crisis within the German biotechnology industry.Design/methodology/approach– This study combines multilevel linear regression analysis with egocentric network analysis. This allows us to distinguish micro- and context-level effects in the analysis of economic resilience.Findings– The findings of this study indicate that while specialization at the network and context-level is conducive to firm growth prior to the crisis, these configurations seem to be particularly susceptible to external shocks. Conversely, diversity (diversified regional agglomerations and diverse networks) seems to be associated with economic resilience during the crisis. Moreover, we find that economic resilience is connected to adaptive capability at the micro-level, that is, the ability to expand and diversify a firms’ portfolio of network ties in the face of an external shock. Finally, we show that these adaptive processes are facilitated by geographical proximity among collaborating organizations.Originality/value– This study contributes to the existing literature by showing that the antecedents of economic resilience are located at multiple levels of analysis. An important implication of this study is that the examination of the resilience of regional clusters may thus be significantly enhanced by disentangling effects at the firm, network and regional (i.e. context) level.

The European energy crisis not only led to an increase in energy prices but also to a recession in the Moldovan economy. After the end of the energy crisis, stagnation was registered in Moldova. The recession and subsequent stagnation led to an increase in the number of people living below the poverty line, as well as to the rise in energy poverty. Thus, in these circumstances, the study of energy vulnerability and its impact on the quality of life has become especially relevant. Therefore, the main research problem in this article is to analyze energy vulnerability as a risk factor for the decline in the quality of life in Moldova. The aim of the research is to assess the relationship between energy vulnerability and quality of life in Moldova. The main objectives of this study are to analyze the theoretical aspects of the concept of energy vulnerability, identify and analyze the determinants of energy vulnerability, and conduct an empirical assessment of the impact of energy vulnerability on households in Moldova. The object of the study is energy vulnerability and its impact on the quality of life. The article examines the theoretical aspects of the concept of energy vulnerability, as well as the determinants of energy vulnerability. Research methods: abstract logical method, comparative analysis method, statistical and economic methods. The central hypothesis: Moldova’s energy vulnerability at the macro level is transformed into a decline in the quality of life and into deprivation of households at the micro level. The statement of basic materials: The conducted empirical analysis showed that Moldova is vulnerable to external energy shocks, as it mainly imports energy resources. Domestic primary energy production covered 22.2% of total energy consumption, while domestic electricity production covered 11.3% of total electricity consumption in 2023. The primary sources of electricity are the CHP (Combined Heat and Power) plants in Chisinau and Balti, as well as the growing green energy. But, unfortunately, the share of renewable energy is still small. Moldova is pursuing a strategy of energy resource diversification to strengthen energy security. To this end, the synchronization of Moldovan power grids with the European ENTSO-E (European Network of Transmission System Operators for Electricity) network and the construction of the Iasi-Ungheni-Chisinau gas pipeline were carried out. However, the implementation of these projects has not yet yielded tangible results. The main reason is the increase in the price of energy resources, which has negatively affected the competitiveness of goods, as their prices have also risen due to the rise in energy costs. As a result, there is a decline in production and an increase in the number of unemployed, which negatively affects the quality of life. At the same time, the increase in tariffs for energy resources has led to a rise in the share of energy expenditure above 10% of total consumer spending, which indicates both energy poverty and a decrease in the quality of life of the population. The originality and practical significance of the study: This study contributes to the scientific literature by presenting the results of an empirical analysis using the example of a country with a high dependence on energy imports. In this paper, the authors examine how the impact of external shocks on energy vulnerability is manifested in the quality of life of the population. Conclusions and prospects for further research: The results of the study revealed that energy vulnerability is a persistent issue in Moldova. It is leading to energy poverty and limiting the basic opportunities of the population to access quality food, to purchase clothes and shoes, since, within the available budget, households are forced to reduce other expenditure items to cover the costs of heating, hot water, and electricity. The transition to lower-quality nutrition leads to health problems. Thus, energy vulnerability will lead to a decrease in the quality of life and is an obstacle to a decent life.

In recent years, system of systems resilience has been widely studied. System of systems has obvious resilience properties when considering dynamic reconfiguration in the following four parts: avoidance, survival, adaption and recovery. System of systems can be downgraded and recovered by reconfiguring resources to keep the performance output enough to satisfy the threshold under internal failure or external shocks. In other words, because of dynamic reconfiguration, system of systems has obvious characteristics of resilience. In this study, first, a new resilience model for systems and system of systems based on the performance threshold is proposed. Second, military system of systems is decomposed hierarchically, including system of systems–level, platform-level and system-level top-down, respectively. Third, a radar network of military system of systems is taken as a typical case. A performance model for a radar network under internal or external shocks is established based on the linear-Gauss-Poisson process in system of systems, and its parameters are discussed in detail. Finally, a typical 5-node radar network of formation air defense military system of systems is taken as an example to demonstrate proposed models and methods. The reliability and resilience loss are achieved by considering internal failure or external shocks, which can serve as a reference for evaluating and improving the effectiveness of system of systems.