The main purpose of this study was to build multivariate classification models using water quality monitoring data for the hydrographic basin of the Gualaxo do Norte River, Minas Gerais state, ...Brazil, which was impacted in 2015 by the rupture of a containment structure for iron ore tailings. A total of 27 points were evaluated, covering areas affected and unaffected by the disaster, with monitoring of chemical, physical, and microbiological variables during the period from July 2016 to June 2017. Multivariate classification techniques were applied to the data, with the aim of developing models to determine when the impacted locations would present characteristics equivalent to those existing prior to the rupture. Classification models constructed using PLS-DA and LDA were able to predict three classes: unaffected main river, affected main river, and tributaries. The first technique was able to clearly differentiate the three classes for the data evaluated, achieving averages corresponding to 90% accuracy. The second method was consistent with the first, identifying the chloride content, conductivity, turbidity, and alkalinity as discriminatory variables, among those monitored, with the relationships among the parameters being coherent with the environmental conditions of the region. The model, with a correct classification rate of 91.67%, enabled identification of the behavior of new samples, using only these easily measured variables. In summary, application of the multivariate statistical tools allowed the development of models capable of providing information about the recovery process of an ecosystem impacted by the greatest environmental disaster to have occurred in Brazil.
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•Assessment of the long-term environmental effects of the Fundão dam failure, Brazil.•Multivariate classification models to assess the profile impacted and non-impacted.•Samples collected in the dry season already showed pre-disaster characteristics.
The growing environmental concerns, governmental regulations, and significant cost savings are the primary motivations for companies to consider the reuse and recovery of products in their inventory ...system. The previous research ignored several realistic features of reusable items inventory systems, such as the presence of multiple products and operational constraints. For the first time, this paper presents a new multiproduct economic order quantity inventory model for an inventory system of reusable products. The goal of the model is to determine the optimal replenishment quantity and reuse quantity of each item so that the system's total cost is minimized. Several operational constraints are considered to provide a more realistic framework, such as the total available budget, warehouse space, and holding cost. Due to the nonlinearity of the presented model, differential evolution (DE) and particle swarm optimization (PSO) algorithms are utilized as two solution approaches. However, these algorithms' performance is highly dependent on their control parameters. Therefore, for the first time, two new variants of these algorithms, called DEQL and PSOQL, are presented in this study, where the control parameters of algorithms are not pre-determined. A powerful reinforcement learning algorithm, Q-learning, adapts these values intelligently. In other words, as a research contribution, this research aims at introducing a new variant of hybrid the DE and PSO algorithms in which a machine learning algorithm controls the value of metaheuristic parameters. The other parameters of the proposed algorithms are tunned employing the Taguchi method. Extensive numerical examples are established in different sizes, and the outputs are discussed in terms of several criteria. Statistical analysis of the results is performed, demonstrating that the proposed reinforcement learning-based parameter adaption has significantly improved algorithms' performance.
This article presents a precise derivation of the prevalent voltage-drop problem in pulsewidth modulation high step-up converters with a transformer-based voltage multiplier. The corresponding ...solution is proposed and analyzed with an isolated interleaved full-bridge high step-up converter as an example. By introducing a resonant capacitor, the improved converter solves the voltage-drop problem caused by the reverse recovery process of the leakage inductor. Meanwhile, the zero-current switching condition is achieved for output diodes due to the resonance between the leakage inductor and the resonant capacitor. Moreover, the proposed solution can be extended to other high step-up converters with voltage-multipliers utilizing transformers or coupled inductors. The voltage-drop problem is analyzed in detail first, followed by the operational principles and steady-state analysis of the improved converter. Experimental results based on a 450-W laboratory prototype at 25-kHz switching frequency verify the validity of the theoretical analysis.
The recovery of Ukraine will require the involvement of as many actors and resources as possible. Higher education institutions will play a significant role in the recovery of the country and its ...regions and communities. Educational institutions can participate in the recovery process both by training the required personnel and by directly participating in the development of relevant policies, programmes and strategic documents, analysing the needs and capabilities of local communities, providing advice and expert assistance in their areas of expertise, etc. There are already scientific publications and case studies that demonstrate the role of higher education institutions in recovery processes. Moreover, special attention is paid to displaced higher education institutions as those with specific experience and knowledge. The purpose of the article is to determine the role of displaced higher education institutions in the recovery and restoration of the country and its regions using the example of the twice displaced Volodymyr Dahl East Ukrainian National University. For this purpose, the article uses such methods as observation, analysis and synthesis. In addition, a survey was conducted among the staff and students of Volodymyr Dahl East Ukrainian National University regarding the role of the displaced higher education institution in the recovery process, the results of which are summarised in the article. Ukraine has experience in relocating higher education institutions, some of which were relocated twice in 2014 and 2022. The article examines the case of the Volodymyr Dahl EUNU and reveals the main activities and projects implemented by the university after the first and second relocations aimed at recovery and development of territorial communities. In particular, the institutionalised practices of participation of Volodymyr Dahl EUNU in the recovery processes are presented. The survey of academic staff and students of the university showed the distribution of opinions on the role of higher education institutions in the recovery of the community, the region and the country as a whole, and also identified the specific role of displaced HEIs in such processes. The study revealed the willingness and existence of active practices of participation of the academic staff and students in the recovery of socio-economic systems of various levels, as well as their readiness and conditions for joining such activities. The results of the survey conducted among the academic staff and students of the Volodymyr Dahl East Ukrainian National University show that the respondents are aware of the role of educational institutions in the recovery and restoration of communities, regions and the country as a whole, as well as their readiness to return to the liberated territories to restore them together with the university.
Following a radiological or nuclear emergency, workers, responders and the public may be internally contaminated with radionuclides. Screening, monitoring and assessing any internal contamination and ...providing necessary medical treatment, especially when a large number of individuals are involved, is challenging. Experience gained and lessons learned from the management of previous incidents would help to identify gaps in knowledge and capabilities on preparedness for and response to radiation emergencies. In this paper, eight largescale and five workplace radiological and nuclear incidents are reviewed cross 14 technical areas, under the broader topics of emergency preparedness, emergency response and recovery processes. The review findings suggest that 1) new strategies, algorithms and technologies are explored for rapid screening of large populations; 2) exposure assessment and dose estimation in emergency response and dose reconstruction in recovery process are supported by complementary sources of information, including ‘citizen science’; 3) surge capacity for monitoring and dose assessment is coordinated through national and international laboratory networks; 4) evidence-based guidelines for medical management and follow-up of internal contamination are urgently needed; 5) mechanisms for international and regional access to medical countermeasures are investigated and implemented; 6) long-term health and medical follow up programs are designed and justified; and 7) capabilities and capacity developed for emergency response are sustained through adequate resource allocation, routine nonemergency use of technical skills in regular exercises, training, and continuous improvement.
Due to the strong interdependence of cyber systems and physical systems, cyber-physical systems (CPS) often face serious coupling faults in case of extreme natural disasters. To improve the ability ...of the distribution CPS to withstand extreme events and rapidly resume normal operation, it is critical to consider effective recovery processes and formulate the collaborative resilience enhancement strategy of CPS. In this paper, a sequential multi-stage collaborative recovery strategy from CPS faults caused by natural disasters is proposed, considering the interdependence of the cyber system and physical system at the layers of facilities, topologies and functions, and the coupling relationship of power grid integration in the recovery process. In the implementation of this strategy, on the cyber side, based on the demand of power grid integration recovery, the communication optical fiber aims to be repaired as quickly as possible to control the power grid Remote Controlled Switches (RCS). On the physical side, the power grid is restored with the objective to reduce loss of load, considering the whole process of degradation, response and recovery during fault handling in coordination. Resilience metrics based on the proposed method are introduced to evaluate the resilience level, as the absorption rate, adaptation rate and energy supply rate. IEEE-33 system is used as an example to show that compared with the traditional recovery strategy that considers only the power grid, the proposed strategy can significantly improve the system's ability to face disasters at the early stage, maintain power supply after the disaster, and speed up the overall load recovery.
•A coupling fault location method is proposed;•A CPS collaborative recovery strategy is proposed;•Appropriate metrics are used to evaluate network resilience.
After service failure situations, firms often carry out transactional activities to achieve customer recovery (CR), using corrective actions to restore the exchange (e.g., economic and social ...compensations). Furthermore, during the service recovery process, firms can encourage activities of co-creation (CC) to prevent similar future failures. This paper discusses the importance of CC and service recovery process communication (RPC), in which customers are informed of the adoption of solutions to address the cause of the failure, so as to avoid the same problem happening again. Experimental studies investigate the impact, individually and together, of CR, CC, and RPC on satisfaction, repurchase intentions, and word of mouth. The results indicate that CC and RPC improve customer’s satisfaction, repurchase intentions, and word of mouth. Firms that want to maximize the return on their efforts to prevent service failures, should encourage CC, develop solutions to prevent future failure recurrence, and implement strategies of RPC. Firms must decide how to promote CC and which media to use for RPC.
The resilience of power systems against extreme events has become a growing concern in recent years. In view of the fact that the resilience of a distribution system depends on its system function ...throughout the entire multi-stage recovery process after extreme events, and to comprehensively improve the abilities of distribution systems in resisting and rapidly recovering from extreme events, it is necessary to consider this multi-stage recovery process. In this paper, a novel resilience enhancement method is proposed, where proactive islanding and RCS (remote-controlled switch)-based fast fault isolation and service restoration are comprehensively considered to improve the abilities of distribution systems in resisting and rapidly recovering from extreme events. The multi-stage recovery process is modeled in detail, including the topological and operational constraints of each stage in the multi-stage recovery process, as well as the coupling relationship among the stages. The model is formulated as a mixed-integer linear programming problem and applies to scenarios where the network topology varies. Resilience metrics based on the proposed method are introduced to evaluate the resilience level. Case studies on the IEEE 33-bus system and the real-world 94-bus system show that the proposed method is effective at resilience enhancement.
We considered the problem of forecasting the degradation recovery process of civil structures for prognosis and health management. In this process, structural health degrades over time but recovers ...when a maintenance intervention is performed. Maintenance interventions are typically recorded in terms of date and type. Such records can be represented as binary time series. Using binary maintenance intervention records, we forecast the process by using Long Short-Term Memory (LSTM). In this study, we experimentally examined how to feed binary time series data into LSTM. To this end, we compared the concatenation and reinitialization methods. The former is used to concatenate maintenance intervention records and health data and feed them into LSTM. The latter is used to reinitialize the LSTM internal memory when maintenance intervention is performed. The experimental results with the synthetic data revealed that the concatenation method outperformed the reinitialization method.
In the HVdc circuit breaker testing process, a thyristor is used to generate high current for the testing purpose. However, the reverse recovery process (RRP) of a thyristor can induce a significant ...overvoltage problem, which jeopardizes the reliable operation. It is important to model the RRP of a thyristor. The existing modeling methods usually omit the stray inductances in the circuit, which cannot describe the hard-switching process accurately. Therefore, this article proposes a novel method to model the RRP, considering the stray inductances. There are mainly three original contributions. First, the physical mechanism of the RRP is analyzed, describing the internal charge behavior and dividing the RRP into two stages. Second, this article provides a novel trigonometric exponential (TE) model of the thyristor voltage and current with analytical equations. Third, the extraction method of model parameters is also provided based on external circuit parameters and thyristor characteristics. In order to verify the proposed modeling method, a 1 kV/830 A IGBT-based circuit breaker is implemented with a thyristor to initialize the current. The experimental results show that the negative peak voltage induced by the RRP is as high as 4.26 kV, and the proposed TE model can precisely predict the overvoltage with a relative error of 7.51%.
