Regular Operation Research Articles

Railway maintenance windows: Discrepancies between planning and practice in Sweden

Efficient and timely maintenance is essential for the robust operation of infrastructure across all types of transport. In the railway sector, track maintenance presents unique challenges. Specifically, some maintenance tasks require track closures, which can disrupt train schedules. Coordinating these closures with regular train operations makes the scheduling process complicated. To ensure sufficient time for maintenance and prevent conflicts with train operations, the Swedish Transport Administration introduced “maintenance windows.” Maintenance windows, ranging from two to six hours, are periods designated for maintenance, with the track free from train operations. They are set before finalizing the annual train timetable. In this study, we examined the practical application of maintenance windows on a railway line in Southern Sweden from 2019 to 2020. Our findings reveal that while 10% of the total line capacity was allocated for maintenance windows, 11% of the capacity was used for maintenance. Alarmingly, 68% of trackwork occurred outside maintenance windows, and only 34% of the reserved maintenance window capacity was utilized. There is a significant discrepancy between the time and location reserved for maintenance windows and their actual utilization. To address this, we propose aligning maintenance windows more closely with contractor needs by 1) incorporating maintenance windows on the weekends, 2) making maintenance windows available closer to the end of the planning horizon, 3) extending the duration of some maintenance windows, and 4) designing and integrating incentives to encourage contractors to operate within planned maintenance windows.

Digital twinning during load tests of railway bridges - case study: the high-speed railway network, Extremadura, Spain

This article presents a case study with various developments of digital twinning of a sample of load tests performed on several railways bridges. The case study is located in Extremadura, South Western Spain and its aim is the generation of a validated, multi-layered information construct in the form of a digital twin as the result of a load test. This result is conceived, not only to verify the assumptions of the design of the bridge but also, to optimize future maintenance plans of the network. This particular case study is framed within a vaster European effort on digitization of the construction sector. Research and Innovation Actions within this demo case are aimed at integrating routine requirements and procedures of load tests with cutting edge digital technologies for the generation of validated virtual replica of these physical bridges. The generated twins during these load tests behaviourally match the obtained response during loading and as such, represent an ideal model for future simulations and behavioural predictions. Different data-gathering techniques and numerical models are integrated within a Common Data Environment (CDE). All efforts related to measurement, simulation, 3D modelling, assessment and validation can be wrapped up systematically for further use during regular operation of the asset.

The cardioprotective potential of melatonin on cardiac hypertrophy: A mechanistic overview

Cardiac hypertrophy (CH) is an increment of muscle mass to maintain the heart regular operations. A physiological cardiac hypertrophy due to exercise or other normal physiological process is characterized by normal contractile function and structural framework of heart tissue. In contrast, pathological hypertrophy occurs in response to increased pressure or volume overload from several cardiovascular diseases including hypertension, valvular diseases, cardiac infarction and heart failure. It is of major concern as it is one of the leading causes of death worldwide. Despite much progress in this field there is a scope for understanding of the molecular mechanisms of this condition. In this review, various types of cardiac hypertrophy and their intricate physio-pathological mechanisms have been discussed. In addition, the genetic mutations in sarcomere genes and oxidative stress are also closely linked to hypertrophic cardiomyopathy. Although several drugs against cardiac hypertrophy have been used, it appears that melatonin, due to its high bioavailability and low side effects, is a better candidate than the conventional medicine for treatment of hypertrophic cardiomyopathy. Melatonin, a hormone and a potent antioxidant, is secreted mainly from the pineal gland, but it is also synthesized from different peripheral tissues including the heart. This molecule can regulate a myriad of cellular functions. It can protect against cardiac hypertrophy via reducing oxidative stress, elevating Cu-Mn SOD via controlling several cell signalling pathways of Akt/mTOR, ROR-α and NLRP3 cascades. Melatonin also mitigates cardiac hypertrophy by suppressing pro-inflammatory cytokines including TNF-α and TGF-β and cardiac hypertrophy markers like β-MHC, ANP, BNP, LDH. This review focuses on the molecular mechanisms of cardiac hypertrophy and the defensive role of melatonin on it. We propose melatoninas a propitious adjunct for the treatment of cardiac hypertrophy.

Modeling the thermodynamic behavior of cryo-compressed hydrogen tanks for trucks

The novel set of differential-algebraic equations models the thermodynamic behavior of a cryo-compressed hydrogen on board tank system. The internal energy U is used in the energy balance to be independent of the hydrogen phases in all relevant tank scenarios: refueling, discharge, and dormancy. The occurring phase changes in the tank during refueling from gaseous hydrogen through the two-phase region to fully liquid and finally, supercritical hydrogen can be described rigorously without changing the set of the model equations. The comparison of car and truck tanks shows that smaller car tanks have an at least 40% lower loss-free dormancy time than high volume heavy duty truck tanks with the same insulation. A rapid cool-down of the tank from ambient temperature without loss of hydrogen is shown during regular truck operation. For the cyclic-periodic driving and refueling cycle, an optimal stop density ϱstopopt is found where the refueling shall start such that a maximized usable density Δϱuse of 72.7 g/L is reached.

Sources of variation in nutrient loads collected through street sweeping in the Minneapolis-St. Paul Metropolitan Area, Minnesota, USA

Excess non-point nutrient loading continues to impair urban surface waters. Because of the potential contribution of tree litterfall to nutrient pollution in stormwater, street sweeping is a promising management tool for reducing eutrophication in urban and suburban regions. However, nutrient concentrations and loads of material removed through street sweeping have not been well characterized, impeding the development of pollution reduction credits and improvement of models for stormwater management. We evaluated the role of canopy cover over streets, street sweeper type, season, and sweeping frequency in contributing to variation in concentrations and loads of nitrogen (N), phosphorus (P), and solids recovered in street sweepings, using analyses of samples collected during regular street sweeping operations in five cities in the Minneapolis-St. Paul Metropolitan Area, Minnesota, USA. We expected that nutrient concentrations and loads would be highest in seasons and places of higher tree litterfall. We also expected that regenerative-air sweepers would recover higher loads compared to mechanical broom sweepers. Total N and P concentrations in sweepings increased most strongly with canopy cover in June, October, and November. Total N and P recovered in street sweepings similarly increased with canopy cover in June, October, and November, and peaked in early summer and autumn, times of high litterfall. In contrast, total dry mass in sweepings was greatest in early spring, following winter snowmelt. However, nutrient loads and concentrations did not differ between sweeper types. Our results add to growing evidence of the importance of street trees in contributing nutrient pollution to urban surface waters. Street sweeping focused on high-canopy streets during early summer and autumn is likely an effective management tool for stormwater nutrient pollution.

Order continuity of Arens extensions of regular multilinear operators

First we give a counterexample showing that recent results on separate order continuity of Arens extensions of multilinear operators cannot be improved to get separate order continuity on the product of the whole of the biduals. Then we establish conditions on the operators and/or on the underlying Riesz spaces/Banach lattices so that the extensions are order continuous on the product of the whole biduals. We also prove that all Arens extensions of any regular multilinear operator are order continuous in at least one variable and we study when Arens extensions of regular homogeneous polynomials on a Banach lattice $E$ are order continuous on $E^{**}$ .

Using age compositions derived from spatio-temporal models and acoustic data collected by uncrewed surface vessels to estimate Pacific hake (Merluccius productus) biomass-at-age

Generating biomass-at-age indices for fisheries stock assessments with acoustic data collected by uncrewed surface vessels (USVs) has been hampered by the need to resolve acoustic backscatter with contemporaneous biological (e.g., age) composition data. To address this limitation, Pacific hake (Merluccius productus; “hake”) acoustic data were gathered from a USV survey (in 2019) and acoustic-trawl survey (ATS; 2019 and eight previous years), and biological data were gathered from fishery-dependent and non-target (i.e., not specifically targeting hake) fishery-independent sources (2019 and eight previous years). To overcome the lack of contemporaneous biological sampling in the USV survey, age class compositions were estimated from a generalized linear mixed spatio-temporal model (STM) fit to the fishery-dependent and non-target fishery-independent data. The validity of the STM age composition estimation procedure was assessed by comparing estimates to age compositions from the ATS in each year. Hake biomass-at-age was estimated from all combinations of acoustics (USV or ATS in 2019, ATS only in other years) and age composition information (STM or ATS in all years). Across the survey area, proportional age class compositions derived from the best STM differed from ATS observations by 0.09 on average in 2019 (median relative error (MRE): 19.45%) and 0.14 across all years (MRE: 79.03%). In data-rich areas (i.e., areas with regular fishery operations), proportional age class compositions from the STM differed from ATS observations by 0.03 on average in 2019 (MRE: 11.46%) and 0.09 across years (MRE: 54.96%). On average, total biomass estimates derived using STM age compositions differed from ATS age composition-based estimates by approximately 7% across the study period (~ 3% in 2019) given the same source of acoustic data. When biomass estimates from different sources of acoustic data (USV or ATS) were compared given the same source of age composition data, differences were nearly ten-fold greater (22% or 27%, depending on if ATS or STM age compositions were used). STMs fit to non-contemporaneous data may provide suitable information for assigning population structure to acoustic backscatter in data-rich areas, but advancements in acoustic data processing (e.g., automated echo classification) may be needed to generate viable USV-based estimates of biomass-at-age.

Historical Progress in Electromagnetic Interference Shielding Effectiveness of Conventional Mg Alloys Leading to Mg‐Li‐Based Alloys: A Review

Magnesium alloy (Mg alloy) materials have attracted considerable attention recently due to their potential applications in electronics, communication, computers, aerospace, and defense regarding electromagnetic interference (EMI) shielding, where high performance and reliability are required, and the unwanted electromagnetic fields are prevented from interfering with the regular operation of electronic devices and systems. Material's EMI shielding effectiveness (SE) depends on several factors: conductivity, magnetic permeability, reflectivity, absorption, and multiple scattering. Mg alloys also have high conductivity, magnetic permeability, high stiffness, high specific strength, and high damping properties. This makes them a better SE material than other shielding materials, such as Al alloys, for practical purposes. Various methods, such as alloying, heat treatment, deformation, surface treatment, and composite fabrication, can be used to modify Mg alloys to improve their SE and other properties. This review summarizes the recent progress and challenges in developing Mg alloy materials for EMI shielding applications. The effects of different factors on Mg alloys' SE, such as composition, microstructure, frequency, and thickness, are discussed. Also, the importance of Mg‐Li alloys and why they are better electromagnetic shielding materials than conventional Mg alloys is discussed. Finally, some perspectives and suggestions for future research directions are provided.

What Drives the Morphological Traits of Stress-Tolerant Plant Cynodon dactylon in a Riparian Zone of the Three Gorges Reservoir, China

The cyclical process of water storage and recession in the regular operation of the Three Gorges Reservoir creates a unique habitat stress that alters the structural and functional attributes of vegetation ecology within the riparian zone. The stress-tolerant plant Cynodon dactylon (L.) Pers is the dominant plant species in the riparian zone of the Three Gorges Reservoir. In this study, the riparian zone of the Daning River, a tributary located in the center of the Three Gorges Reservoir, was selected as our study area. To identify the drivers of the morphological traits of C. dactylon in the riparian zone of Daning River, we examined plant biomass and plant characteristics across different elevation gradients, with reference to abiotic factors to determine the distribution patterns of plant morphological traits. Results indicated that in the two main soil types of the riparian zone, plant biomass showed a consistent trend along the elevation gradient, with a “middle-height expansion” pattern; biomass increased and then decreased with rising water levels. Plant biomass positively correlated with soil total nitrogen and negatively correlated with soil pH, electrical conductivity, and total phosphorus. C. dactylon adapted to prolonged flooding in the riparian zone by having a significant negative correlation between plant height and erect stem length with soil moisture content to facilitate root respiration.

Domain adaptive networks with limited data for rotating machinery fault diagnosis: a case of study of gears

Rotating machinery is one of the most common components in the industry. Therefore, timely and accurate fault diagnosis of rotating machinery is essential for the regular operation of equipment. At present, some achievements have been made in rotating machinery fault diagnosis based on a large number of marked fault data. However, most of the machines are in a normal state in actuality. Especially, the machines run under different loads, so it is costly to collect a large number of labeled fault data under different load distributions. To solve rotating machinery fault diagnosis in different load conditions with limited samples, a domain adaptive group convolutional neural network is proposed. Firstly, the least squares generative adversarial networks were used to expand the limited target sample data. By changing the objective function, the two defects of the low quality of the vibration signal generated by the traditional generative adversarial networks and the unstable training process are optimized. Secondly, the raw vibration signals in the source domain are pre-trained by the group convolutional neural network, and the group training network effectively reduces network parameters. Finally, the source domain signals and target domain signals were trained in domain adversarial networks to diagnose different distributed data in target domains. The proposed method is validated by collecting the raw vibration signals of gears under different loads and different health states, and the effectiveness of the proposed method is proved. Experimental validation shows that the method proposed in this paper achieves an average accuracy improvement of more than 12% compared to other existing methods.

FEATURES OF DIAGNOSING ROLLING BEARINGS BY THE ENVELOPE METHOD

The article is devoted to the work on identifying defects of the surface crack type by the vibrodiagnostic method of non-destructive testing using the envelope method on the example of a rolling bearing. Used in the work rolling bearings with a set of various surface defects: a roller crack and an outer ring crack along the rolling surfaces. The rolling bearing was installed in a test bench, which simulated its regular operation, with a fixed outer ring and internal ring rotated at a constant frequency. The features of the detection of the following specific defects are established: a roller crack, a crack in the outer ring, etc., as well as the correspondence of the calculated frequencies of the bearing elements to the actual ones obtained during the research. The norm/rejection criteria were obtained in a numerical value in relation to specific types of defects, namely: weak, strong defects of the rolling elements and the outer ring of the rolling bearing. The features of detecting specific defects by the envelope method, that depends on the pressure on the outer ring and its spatial location relative to the defect, are experimentally established.

Dynamic CFD modeling of calcination in a rotary lime kiln with an external dryer

Mid-kiln ring formation is a problem in lime kilns that may be related to fluctuations in the start location of calcination. To calculate fluctuations in bed and gas temperature profiles within a lime kiln with an external dryer, a dynamic two-dimensional (2D) axisymmetric computational fluid dynamics (CFD) gas model with a methane burner implemented in ANSYS Fluent, coupled by mass and heat balances to a one-dimensional (1D) bed model, was developed. The dynamic model was used to calculate changes in the location where calcination starts with fluctuations in operational conditions using pulp mill data. This model simulates radiative, convective, and conductive heat transfer between the gas, wall, and bed to determine the axial bed temperature in the kiln. The calcination reaction is described using a shrinking core model that allows for the prediction of the location at which calcination begins and the degree of calcination achieved. The solid motion within the kiln is modeled using Kramer’s equation modified for transient response. Steady-state and dynamic simulation results were compared to data from an industrial dry lime kiln, and good agreement was found. A sensitivity analysis was also performed to provide insight on how operating conditions and model variables impact the calcination location and degree of calcination. Of the variables examined, the fuel rate and the feed temperature had the largest impact on both the calcination location and degree of calcination in the kiln. Model predictions of a period of ring formation in the industrial kiln showed that the start location of calcination fluctuated by more than 2 m on either side of the mean of regular operation, warranting further investigation of the importance of these fluctuations on mid-kiln ring formation.

Approach to the study of AUV control algorithms in the event of faults in its equipment

The stand for modeling the functioning of subsystems of an autonomous underwater vehicle and its control system is considered, the possibility of testing algorithms in the event of malfunctions in the equipment is analyzed - with-out interfering with the regular operation of algorithms placed in the form of programs on the standard hardware. An approach is proposed for conducting research related to the occurrence of malfunctions in the equipment of the subsystems of the apparatus and aimed at testing the operation of the algorithms for the functioning of the subsys-tems of the apparatus and its control system. The approach is based on the formation of a database of possible faults for each subsystem of the device and the device as a whole, the development of an algorithm for the ran-dom occurrence of faults of one of the types from the database of faults. An operator's workstation has been de-veloped with an interface for the fault setting program, which provides for the fault setting both by the operator and by the probabilistic program at random times. The interface allows you to visually display service information about the current consumption, energy consumption and heat generation of each of the subsystems, transfer this data to the software simulator of the power generation and distribution subsystem to assess the load of the power supply system and power sources. Protocols for setting simulation modes have been developed that do not affect the ex-change of information using standard protocols for information and technical interaction. The behavior of the ap-paratus in the event of malfunctions has been studied. The results of testing the developed fault simulation algo-rithms and protocols for setting simulation modes showed the correctness of the proposed approach; the results were implemented in the existing stand for modeling the functioning of the apparatus. The developed algorithms and protocols for setting simulation modes, their implementation in the form of software made it possible to carry out large-scale numerical experiments on the bench for simulating the operation of the apparatus to develop algo-rithms and programs not only in normal modes of their operation, but also in the event of malfunctions.

Employment of Some Aquatic Plants for Removal of Cadmium, Lead, and Copper from the River Water

The world’s most valuable resource is water in addition to being essential to life, freshwater is also used in many other processes, including those that involve agriculture, industry, and human consumption due to interference with its quality, it continues to be a limited resource. Fresh potable water supply, particularly in urban areas, has been severely impacted by population increase, urbanization, and consumption. Therefore, the aim of this study was to understand the behavior of some heavy metals in the river waters via aquatic life represented by some aqua plants to achieve this three tanks of river water made from glass were prepared and injected with three heavy metals each which they are (copper, lead, and cadmium). The first tank represents the control (without any plants) while the second tank contains lentil plants moreover, the third tank contains the ceratophllum. The removal of heavy metals from river waters is enhanced by the presence of these plants using lentil plants and Ceratophyllum plants, respectively, led to removals of roughly 77% and 73% of the copper (Cu) content compared to the regular operation (control tank). For lead (Pb) removal, the Ceratophyllum removed about 72.6%, and the presence of lentil plant removes 52% of the Pb and only around 20% of the substance has been removed in the control tank. With ceratophullum present, there was a higher removal percentage of cadmium (45.9%)compared to tanks without aqua plants or lentil plants, which had removal rates of 21% and 42.3%, respectively. In general, necessary action to minimize the impact of discharging polluted wastewater must be taken to save aquatic life and the environment.

Robust Mechanical Fault Diagnosis With Noisy Label Based on Multistage True Label Distribution Learning

Fault diagnosis is an essential means to ensure the regular operation of mechanical systems. The existing data-driven algorithms are developed based on the assumption that the given label is entirely correct. However, mislabeling is common, which often occurs in industrial applications. These methods will overfit these mislabeled samples, resulting in inferior generalization. To this end, this article proposes a novel multistage true label distribution learning algorithm. Specifically, based on the training characteristics of data-driven algorithms on noisy datasets, a novel multistage adversarial loss function (MSA-Loss) is proposed. MSA-Loss can make the model construct the true label distribution from noisy datasets, prevent the model from overfitting the noisy samples, and finally keep the model with good generalization. The proposed method can be easily applied to any existing data-driven algorithm to improve its performance on noisy datasets. Our method is verified on high-speed aeronautical bearing and motor datasets, which prove that MSA-Loss has an excellent performance in noisy label scenarios. It can significantly improve the potential of existing diagnostic models in practical industrial applications.

Mobility Data for a Safer and Greener Transport

Traffic network operators are using several channels to share their traffic related data, on one hand because of legal obligation, on the other hand to ensure a higher level of service for their customers. Of course, the value chain, and the provided content will change a lot with the emerge of connected and automated driving, or with the spread of Mobility-as-a-Service solutions and Alternative Fuel Infrastructure Regulation (AFIR) related data sharing in the near future. This paper gives a comprehensive overview of the current practice in Hungary, introducing the ways of distributing multimodal traffic related information, some existing services that were implemented based on these automatic data channels. The paper also gives an overview on the ongoing transition towards automatic data provision and how the regular road operators’ role change to digital road operators, furthermore the European harmonisation process that was started in the framework of the Napcore project.

Experimental Evaluation of SOFC System Exposed to Marine Inclination Conditions

To comply with future emission regulations, the marine industry needs to reduce emissions. Marine actors are showing an increased interest in the application of Solid Oxide Fuel Cells (SOFCs) for ocean going ships, because of their high conversion efficiency, low pollutant emissions, and fuel flexibility. However, operation in ships is fundamentally different from stationary applications, since the installation rooms accelerate and incline due to wave-induced ship motions. This could lead to pressure variations in the fuel streams or detrimental mechanical stresses. So far it has not been extensively investigated what the consequences of inclinations and motions are on the operation of SOFCs. The goal of this research is to evaluate the influence of marine conditions in terms of static and dynamic inclinations on the operation, safety, and lifetime of SOFC systems. Ship motions are simulated with a one-axial oscillation platform. The inclination conditions the SOFC system is exposed to are derived from ship motion studies and marine regulations. The test campaign consists of two phases. In this paper, the results of the first test phase will be explained in detail. Moreover, the learned lessons and their implementation into the plan of the second test phase will also be shared.In the first phase of the test campaign, a 1.5kW SOFC system is inclined around two horizontal axes of rotation while producing power at nominal conditions. During the static experiments, the SOFC system is operated at fixed inclinations from -30 degrees to 30 degrees with steps of 5 degrees. In the dynamic experiment, the system is oscillated up to an angle of 30 degrees with frequencies of 0.025, 0.033, 0.05, and 0.1 Hz. The experiment showed no gas leakages or other significant safety risks during the experiment. However, for slow oscillations, relatively large deviations in several system parameters (e.g., fuel flow, stack voltage, and fuel utilisation) were found compared with the non-inclined operation. This indicates the natural frequency behaviour of particular components in the system. Although the deviations were much larger than in regular operation, the early stage indication was that these deviations do not result in safety issues or decreased system lifetime.The second phase of the test campaign was focused on including a larger range of possible ship motions and increasing test durations. An additional aim was to find the physical cause of the deviations in system parameters during oscillations. Additionally, a 100h test on one oscillation condition is included to evaluate whether the ship motions could cause increased cell degradation. Furthermore, several part-load conditions are included in the experiment.The results of the experiments are used to propose design improvements for SOFC systems that require to be inclined or accelerated. These proposals contribute to the marinization of SOFC systems. Furthermore, the results will be used to help class societies defining proper regulations for SOFC implementation in seagoing vessels. Figure 1

Investigating the Effects of Cascading Accelerated Stress Tests (ASTs) on the Localized Electrochemical Performance Degradation in Polymer Electrolyte Fuel Cells (PEFCs)

With a recent shift in focus from light-duty to heavy-duty vehicle applications, the durability and performance targets for polymer electrolyte fuel cells (PEFCs) have become even more stringent and challenging to achieve; for example, a net power output of 2.5 kW/g-PGM (1.07 A/cm2 current density) at 0.7 V is required after 25,000 hour-equivalent accelerated stress test (AST) [1]. Generally, different ASTs are designed to evaluate Pt electrocatalyst and support durability; for example, a square-wave (SW) AST with H2/N2 between 0.6 V to 0.95 V vs. reversible hydrogen electrode (RHE) targets Pt catalyst and a separate triangular-wave (TW) AST with a higher potential range (1 – 1.5 V vs. RHE) assesses the durability of carbon-based supports [2]. Recently, many studies [3]–[7] have revealed the heterogeneous nature of cathode catalyst layer degradation under different ASTs. Fuel cell electric vehicles are typically subjected to an enormous number of load/unload and start/stop cycles during regular operation. Though there is a considerable body of literature discussing the isolated effects of load/unload and start/stop cycles on durability and performance, there is a dearth of studies exploring the effects of cascading load/unload and start/stop cycles, a scenario more relevant to actual automotive conditions. In the present study, a segmented cell along with ex-situ Pt particle size mapping (through micro-X-ray diffraction) is used to understand the effects of cascading a DoE square-wave AST (0.6 V to 0.95 V vs. RHE) and a triangular-wave (1 – 1.5 V vs. RHE) on the durability and performance of a PEFC.The membrane electrode assemblies (MEAs) are subjected to two cascade ASTs. The first one involves 15k cycles of SW AST followed by 2.5k cycles of TW AST (referred to as Pt-followed-by-carbon, PtfCC, AST) and the other one involves 2.5k cycles of TW AST followed by 15k cycles of SW AST (referred to as Carbon-followed-by-Pt, CCfPt, AST). Multiple in-situ and post-mortem ex-situ techniques are used to obtain particle size distribution and spatial degradation profiles. Preliminary results indicate that the performance losses at the end-of-life (EOL) depend on the cascade order; PtfCC AST leads to higher losses compared to CCfPt AST in wet polarization conditions. The local current distributions are also strongly impacted by the cascade order during the aging process. Figure 1 shows the polarization performance of the samples at the beginning, middle (following the first AST), and the end-of-life of cascade ASTs.

Decentralized Control Strategy for Participation of Electric Vehicles in Distribution Voltage Control

With the accelerating transportation electrification, increasing numbers of electric vehicles (EVs) are connected to distribution networks via electric vehicle charging stations (EVCSs). Due to the uncertain charging behaviors of EV users, concentrated high-power EV charging during peak hours can result in significant undervoltage issues, affecting the regular operation of distribution networks and having detrimental effects on regular EV charging. Conventional EV charging scheduling methods are conducted in a centralized way, requiring extensive investment in communication infrastructure and intensive computing power. Accordingly, this paper proposes a novel decentralized voltage control scheme with the participation of EVs and EVCSs. The proposed control scheme first divides the distribution network into clusters based on a modified modularity index. Then, it applies the rolling optimization-based control of the EVs and EVCSs within each cluster to solve the regional voltage problems. The optimization window length is self-adapted based on the monitored states of the grid-connected EVs and EVCSs. Case studies show that the proposed decentralized voltage control strategy could effectively address the undervoltage violation issues and alleviate the pressure on peak shaving during peak hours, while satisfying the charging requirements of EV users.

Abrasive Wear Properties Evaluation of the Thixoformed A380/NbC Composite

Composite materials are increasingly being used in several areas, especially in the automotive and aerospace industries, however, during regular operation their wear is one of the main causes of failure. Consequently, developing and researching new composite materials is essential to increase and improve service life. In addition, thixoforming is claimed to exhibit superior properties by reducing typical defects in casting like shrinkage and porosity. Therefore, the main objective of this study is to produce and analyze abrasion wear properties of the thixoformed aluminum matrix composite reinforced with NbC, obtained by the stir-casting method. Three different composites with 5 wt.%, 10 wt.%, and 15 wt.% of NbC were manufactured with the stir-casting method, compared with A380 alloy. The procedure involves an A380 aluminum alloy that was molten at 750 °C. In sequence, niobium carbide powder was added by mechanical stirring for 10 min; Mg was added to improve the wettability between the reinforcement and matrix. Chemical grain refinement by Al-5Ti-1B master alloy was used for non-dendritic feedstock production. Hence, the induction furnace was used for the thixoforming process, to achieve a mushy of 60 % solid fraction at 562 °C, determined by Differential Scanning Calorimetry (DSC) analysis. The holding time applied was 90s. Optical microscopy (OM) and scanning electron microscope (SEM) analyses allowed the microstructural characterization. Abrasive wear tests, according to the ASTM G65 standard, showed an improvement of the composites’ abrasion wear resistance after the thixoforming process, with a higher amount of NbC, potentially increasing the range of use of this technology and materials.