Renewal Process Research Articles

System-level Probabilistic Remaining Useful Life Prognostics and Predictive Inspection Planning for Wind Turbines

Wind energy plays a crucial role in the energy transition. However, it is often seen as an unreliable source of energy, with many production peaks and lows. Some of the drivers of uncertainty in energy production are the unexpected wind turbine (WT) failures and associated unscheduled maintenance. To support an effective health management and maintenance planning of WTs, we propose an integrated data-driven framework for Remaining Useful Life (RUL) prognostics and inspection planning of WTs. We propose a Long-short term memory (LSTM) neural network with Monte Carlo dropout to estimate the distribution of the RUL of WTs, i.e. we develop probabilistic prognostics. Different from existing studies focused on prognostics for single components, we consider the simultaneous health-monitoring of multiple components of the WTs, thus seeing the turbine as an integrated system. The obtained prognostics are further included into a stochastic planning model which determines optimal moments for inspections. For this, we pose the problem of WT inspections as a renewal reward process. We illustrate our framework for four offshore WTs which are continuously monitored by Supervisory Control and Data Acquisition (SCADA) systems. The results show that LSTMs are able to estimate well the RUL of the WTs, even in the early phase of their usage. We also show that the prognostics are informative for maintenance planning and are conducive to conservative inspections.

Некоторые особенности биологии редкого эндемичного вида Arafoe aromatica Pimenov & Lavrova на территории Рицинского реликтового национального парка (Республика Абхазия)

For the first time, the features of rare endemic species of Caucasus Arafoe aromatica biology in the Ritsa Strict Nature Reserve (Republic of Abkhazia) were studied. The age, vitality structure of coenopopulations (CP) and the variability of morphometric parameters were determined. The study was carried out using standard methods of population biology. The variability of morphometric parameters was studied on 25 middle-aged plants in each CP. The CP density is low (1–2.6 ind./m2). According to the delta-omega classification, one CP is transitional, and one is mature. Most of the morphological features are characterized by a normal degree of variation (14.7–37.0%). Vitality analysis showed that one CP is prosperous, the other is depressed. The state of the studied A. aromatica coenopopulations is satisfactory. Anthropogenic disturbances lead to a decrease in the number and seed productivity, worsening conditions for seed germination and renewal processes. To preserve the rare species, it is necessary to limit the anthropogenic load in the places of growth, prohibit the collection of plants by the population, monitor and control the CP state.

Maxima over random time intervals for heavy-tailed compound renewal and Lévy processes

We derive subexponential tail asymptotics for the distribution of the maximum of a compound renewal process with linear component and of a Lévy process, both with negative drift, over random time horizon τ that does not depend on the future increments of the process. Our asymptotic results are uniform over the whole class of such random times. Particular examples are given by stopping times and by τ independent of the processes. We link our results with random walk theory.

Perspectives for and obstacles to energy democracy in renewable energy transition processes

The paper is an attempt to show both opportunities and limitations for energy democracy, which also multiplies the ambiguity of this concept, arising from the lack of coherent legal regulations. This means that, the perspectives that energy democracy opens can simultaneously be the barriers to its development. This results in a different social perception of this phenomenon, which affects legislation and effectiveness of forms of democratic participation in energy policy.

Personalised education in current pedagogical renewal centers

Pedagogical renewal is a concept loaded with a historical-pedagogical trajectory linked to reflection, social justice, educational improvement, teacher commitment and the questioning of the educational model, with personalised education being a key aspect. The aim of this paper is to analyse how learning is personalised in primary education centres that promote processes of pedagogical renewal. A qualitative methodology is used, based on a case study. Two schools with a high intensity of pedagogical renewal were selected and in-depth interviews were conducted with the management team and teachers, focus groups with families and students, and participant observation. The information derived is analysed with the ATLAS.Ti 22 programme, after coding and categorisation. The results reveal a number of common elements and processes of personalisation of learning which are structured in three dimensions. In the first dimension, school characteristics, the following stand out: student autonomy, individualisation of learning and freedom of choice of learning pathways. As for the second dimension, educational project, the following elements stand out: flexible curricular organisation, active methodology where group work is a key element, organisation of timetables without previously established patterns, the role of accompanying teachers, student focus and active participation of families in daily school life. Finally, from the third dimension, inclusion, the following can be extracted: daily educational work where diversity is not a limitation, but a source of learning of great didactic value.

Analisis Implementasi Pembelajaran Active Learning di Kelas 4 SDN Blumbungan 3 Pamekasan

Learning will, of course, undergo a process of renewal in order to adapt to the demands of current developments, such as the curriculum update carried out by the government in recent years, namely the Merdeka Curriculum. In the Merdeka curriculum, students are required to always be active in the learning process and give teachers the freedom to use any model or method according to the needs of each student. When conducting research. The aim of this research is to find out whether there is an implementation of active learning in class 4 of SDN Blumbungan 3 Pamekasan. This research uses a descriptive qualitative method, which is an approach that states certain social situations by describing reality correctly in the form of words based on data collection and analysis techniques. relevant information obtained from natural situations involving teachers and students. The descriptive method is a method that examines a group of people, objects, conditions, thought systems, or current events. The descriptive qualitative research technique analyzes the implementation of active learning, namely by conducting observations, interviews, and documentation. The results found in class 4 at SDN Blumbungan 3 did not implement active learning because the teacher still used a lecture, discussion, and question-and-answer system in the learning process.

Counting jumps: does the counting process count?

In this paper, we develop a ‘jump diffusion type’ financial model based on renewal processes for the discontinuous part of the risk driver, and study its ability to price options and accurately reproduce the corresponding implied volatility surfaces. In this model, the log-returns process displays finite mean and variance, and non-vanishing skewness and excess kurtosis over a long period. The proposed construction is parsimonious, and it allows for a simple and intuitive pricing formula for European vanilla options; furthermore, it offers an efficient Monte Carlo sample path generator for the pricing of exotic options. We illustrate the performance of the proposed framework using observed market data, and we study the features of the best fitting model specifications.

Quenched large deviations in renewal theory

In this paper we introduce and study renewal–reward processes in random environments where each renewal involves a reward taking values in a Banach space. We derive quenched large deviation principles and identify the associated rate functions in terms of variational formulas involving correctors. We illustrate the theory with three examples: compound Poisson processes in random environments, pinning of polymers at interfaces with disorder, and returns of Markov chains in dynamic random environments.

Union strategies in conflict: A comparative study of strike fund institutionalisation and infrastructural resources

AbstractThis article unveils the establishment or rejection of strike funds as a tangible organisational tool towards union renewal. Despite strike funds being a necessary and recurring instrument in the organisation of strikes, they have seldom been theorised as a distinct (infrastructural) power resource fundamental to understanding unions’ readiness and preparation for industrial conflict. Institutionalised strike funds, supported by union dues, provide economic support to strikers, reinforce their collective identity, legitimise a more confrontational position towards collective bargaining and may garner support from the broader community. Additionally, strike funds may serve as tools to attract members and shape narratives that can influence corporate positions and public opinion during labour disputes. Through a comparative analysis of 10 confederal unions in Spain, we illustrate the different strategic views that unions may hold with respect to them. Crucially, we find that the presence or absence of strike funds reflects the specific political position a union adopts concerning industrial conflict and how they may possibly articulate them with other power resources. Hence, the institutionalisation of strike funds involves a complex union renewal process, which is also influenced by a comparative learning process between unions. Finally, we also explain the flourishing of different strike funds during the last decades that derive from a spillover effect between counterpower and radical unions.

The Robust Classical MTBF Test

For the reliability demonstration of a repairable system, testers expediently assume that the rate of occurrence of failures (ROCOF) can be modeled by a homogenous Poisson process (HPP), also called an ordinary renewal process (ORP), and therefore the times between failure, or interarrival times, are exponentially distributed with a constant mean time between failures (MTBF). This often-used test is colloquially called the “classical MTBF test” because it has been widely used by both government and industry for the past 50 years. The test is simple; operate a system for a period and the sample estimate for MTBF is the operating time divided by the number of failures. A confidence interval is applied to the sample estimate to determine the test result. This paper considers the validity of the test result if the repairable system has an increasing or decreasing MTBF, that is, a nonhomogeneous Poisson process (NHPP). Specifically, the change in consumer’s risk is analyzed if the repairable system has a decreasing MTBF (increasing ROCOF). A simple risk mitigation strategy consisting of a burn-in period equal to the threshold MTBF is also considered and found to be effective. The classical MTBF test is shown to be a robust test and a burn-in period prior to testing makes the classical MTBF test even more robust.

Process of Renewal of PC&PNDT License of a Large Tertiary Care Teaching Hospital of North India: How One Needs to Plan for It?

Background The Pre-Conception and Pre-Natal Diagnostic Techniques (Prohibition of Sex Selection) Act (PC&PNDT Act), 1994 was enacted to prevent sex determination and female feticide. As a mandatory statutory requirement, All India Institute of Medical Sciences, New Delhi, India has to renew its PC&PNDT license after every 5 years. Aim The current study was undertaken with an objective to delineate in detail, the process of PC&PNDT license renewal, and the challenges dealt with while submitting the renewal application. Methods and Material An observational descriptive study was conducted from February to July 2022. The renewal process was categorized into preapplication, application, and postapplication phases. The requisite documents and data were collected from the Hospital Establishment Section and Medical Records Department. Results The preapplication phase involved obtaining details from 24 departments, with 20 responding initially. Challenges included incomplete documents and deficient details. The application phase required consolidation, affidavits, form filling, and fee payment. Postapplication, an inspection was conducted, and the renewal certification was obtained. Conclusion The study highlights the complexities of renewal of PC&PNDT license of a large multispecialty tertiary care teaching hospital. Planning leads obtained during various phases could serve as a guiding template for other similar teaching hospitals. The study suggests the need for digitalization and streamlining of documentation process to ease out the renewal process and hence contribute to better patient care at large.

Integration of Modernized application of smart Bus Pass.

The Android Smart Bus Pass System and the proposed digitalization initiative for the traditional bus transportation system converge to redefine and elevate the public transportation experience. The Android Smart Bus Pass System, designed to leverage mobile technology, streamlines fare management, and enhances user convenience. It eliminates physical tickets through mobile ticketing, supports contactless payments, and provides real-time pass updates, route information, and robust security features. In alignment with this, the proposed digitalization initiative aims to revolutionize the current manual processes associated with bus pass applications and renewals. The goal is to establish a user-friendly online platform, liberating citizens, especially students, from the constraints of physical documents and inconvenient counter transactions. The integration of modern digital solutions seeks to break free from traditional practices, allowing users to apply for and renew passes effortlessly at their convenience. This collaborative effort represents a transformative shift towards a technologically advanced and user-centric public transportation network. By digitizing the bus pass application and renewal process, the initiative aligns with the Android Smart Bus Pass System's goal of simplifying ticketing processes, reducing queues, and improving overall transportation efficiency. Together, these innovations aim to create a seamless and accessible public transportation experience for citizens, ultimately shaping the future of bus transportation services.

The bioaccumulation and ecotoxicity of co-exposure of per(poly)fluoroalkyl substances and polystyrene microplastics to Eichhornia crassipes

Gen X and F-53B have been popularized as alternatives to PFOA and PFOS, respectively. These per(poly)fluoroalkyl substances pervasively coexist with microplastics (MPs) in aquatic environments. However, there are knowledge gaps regarding their potential eco-environmental risks. In this study, a typical free-floating macrophyte, Eichhornia crassipes (E. crassipes), was selected for hydroponic simulation of a single exposure to PFOA, PFOS, Gen X, and F-53B, and co-exposure with polystyrene (PS) microspheres. F-53B exhibited the highest bioaccumulation followed by Gen X, PFOA, and PFOS. In the presence of PS MPs, the bioavailabilities of the four PFASs shifted and the whole plant bioconcentration factors improved. All four PFASs induced severe lipid peroxidation, which was exacerbated by PS MPs. The highest integrated biomarker response (IBR) was observed for E. crassipes (IBR of shoot: 30.01, IBR of root: 22.79, and IBR of whole plant: 34.96) co-exposed to PS MPs and F-53B. The effect addition index (EAI) model revealed that PS MPs showed antagonistic toxicity with PFOA and PFOS (EAI < 0) and synergistic toxicity with Gen X and F-53B (EAI > 0). These results are helpful to compare the eco-environmental impacts of legacy and alternative PFASs for renewal process of PFAS consumption and provide toxicological, botanical, and ecoengineering insights under co-contamination with MPs.

Effect of globalization on the technological changes tendencies

Methods. The following scientific methods are the methodological basis of the research: analytical – when distinguishing positive and negative aspects of the globalization process; concrete and abstract – when generalizing the nature of the impact of globalization processes on technological development; analysis and synthesis – when clarifying the cyclic patterns of technological changes. Results. The cyclic patterns of technological changes under the influence of globalization processes are analyzed. The contradictory nature of the processes of globalization in modern conditions, which led to the regionalization of world economic relations and affected the nature of international competition, was highlighted. On the basis of the theories of long-term fluctuations, the cyclic patterns of technological changes are considered. It is emphasized that different approaches to studying the regularities of long-term economic dynamics and processes of periodic renewal of technological methods of production complement each other. The nature of structural crises as a phase of long-term economic fluctuations is revealed. It is noted that in modern conditions, the nature of technological changes is determined by the mutual influence of globalization processes, scientific and technological progress, and economic policy. Novelty. It has been established that the nature of technological changes, as an objective process of periodic renewal of technological methods of production, in modern conditions is significantly modified by the contradictory processes of globalization. Practical value. The results of the study can be used by scientists, representatives of the state authorities in the process of research and development of mechanisms of technological modernization of the national economy of Ukraine.

On the Release and Renewal of Freshwater in the Beaufort Gyre of the Arctic Ocean

Abstract The Arctic Beaufort Gyre plays a critical role in climate and marine ecosystems. This study investigates the response of the liquid freshwater in the Beaufort Gyre to various wind perturbations using numerical simulations. A new diagnostic called “freshwater renewal” is introduced, which quantifies the amount of freshwater that has entered the Beaufort Gyre since a specific point in time. The findings reveal that the process of freshwater renewal is persistently efficient in the Beaufort Gyre region, occurring irrespective of the gyre’s status. The spatial distribution of freshwater renewal varies, influenced by factors such as wind forcing and gyre circulation patterns. Cyclonic wind perturbation associated with a negative Beaufort high sea level pressure anomaly triggers freshwater release from the Beaufort Gyre, with freshwater export and renewal dependent on wind-perturbation locations and time scales. While some released Beaufort Gyre freshwater exits the Arctic Ocean through the Davis and Fram Straits, a considerable portion could remain within the Arctic Ocean for many years under specific conditions. Wind perturbation associated with the positive Arctic Oscillation enhances the Arctic export of Beaufort Gyre freshwater, mainly through the Fram Strait. The Arctic export of total freshwater and the Arctic export of the portion originating from the Beaufort Gyre have different time scales and magnitudes. Hence, it is essential to collectively examine different freshwater components in order to assess the role of Arctic export in the climate system.

Energy Transition: The Impact of Increasing Energy Production from Renewable Sources on the Commercial Optimization Process of Conventional Power Generation Assets

Abstract Changing the way electricity is produced, as part of the energy transition process, brings new challenges to the energy industry and in particular to the power generation practices. The switch from energy systems based on fossil fuels to generation technologies based on renewable sources is proving to be much more complex than expected. Multiple recent studies have shown that the intermittency in renewable production processes is putting pressure on the system and increasing balancing and maintenance costs of the grid, calling for an efficient management of the electricity produced. Therefore, a complete phase-out of conventional power generation units (e.g. coal, gas and nuclear) is still difficult to imagine in practice, mainly because of their role in balancing the system during the hours when renewables are not available (e.g. no wind, no sun or reduced hydraulicity). From the perspective of technical and commercial management aspects, the operation of conventional assets involves the consideration of multiple constraints (such as a longer operating time before they are shut down, or a longer preparation time before they can be restarted) in order to avoid financial loss and further damages. Therefore, the aim of this is to: 1. study the impact brought by the large installed capacity of renewable assets on the energy system; 2. analyse the options for gradual phase-out of conventional assets, from the perspective of system stability; 3. draw conclusions on how the commercial optimization of the production assets should develop as the energy transition advances. The novelty of this paper lies in the fact that it makes a business study of this transition process, which does not really exist yet, and case and simulation studies, along with statistical and time series analysis were used as a methodological approach for the research.

Asymptotic Expansions for the Stationary Moments of a Modified Renewal-Reward Process with Dependent Components

Asymptotic Expansions for the Stationary Moments of a Modified Renewal-Reward Process with Dependent Components

Why Your Friends Are More Popular Than You: The inspection paradox makes mathematical sense of social networks, long train wait times and always-busy call centers.

Why Your Friends Are More Popular Than You: The inspection paradox makes mathematical sense of social networks, long train wait times and always-busy call centers.

Investigations on transport behaviours of rotating packed bed for CO2 capture by chemical absorption using CFD simulation

A rotating packed bed (RPB) has been proposed to overcome the limitations of high operating and capital costs involved in conventional columns which are used for chemical absorption-based carbon dioxide (CO2) capture. The design of large-scale RPBs depends on their transport characteristics. Owing to the difficulties in predicting the transport characteristics of RPBs experimentally, Computational Fluid Dynamics (CFD) simulation has been implemented. In this study, a two-dimensional (2D) volume of fluid (VOF) simulation is conducted to predict transport characteristics of RPB including, hydrodynamics, and physical and reactive mass transfers. To predict hydrodynamics of RPBs accurately, the liquid holdup by CFD simulation is compared against experimental prediction, showing a strong agreement between simulation and experimentation. Various liquid phase flow patterns within RPB are observed and these are cross-referenced with findings in the existing literature. Additionally, the impacts of rotational motion and flow rate are further assessed in the study. For the mass transfer performance, the prediction of the volumetric mass transfer coefficient, kLae of the air-water system from CFD simulation is studied. Two different mass transfer theories such as surface renewal theory and penetration theory are studied to predict kLae. It is observed that the kLae from the penetration theory closely follows the trend of the experimental data. Finally, a 2D simulation of the reactive absorption of CO2 by diethylenetriamine (DETA) in RPB is developed and compared with the existing available data in the literature. The present model underpredicts CO2 capture efficiency in RPB, which needs further improvement in reaction kinetics. In general, the present CFD model has the capability of predicting the transport characteristics of RPB.

Methodology for the Ensemble Synthesis of Stochastic Seismic Event Sets Satisfying the Renewal Process for Local Strong Earthquakes

Methodology for the Ensemble Synthesis of Stochastic Seismic Event Sets Satisfying the Renewal Process for Local Strong Earthquakes