Search Results (675)

In recent years, significant attention has been directed toward the development of coating materials capable of tailoring surface properties for various functional applications. Transition metal nitrides, in particular, have garnered interest due to their superior physical and chemical properties, including high hardness, excellent wear resistance, and strong corrosion resistance. In this study, a fabrication process for CrN-based thin films was developed by combining reactive direct current magnetron sputtering (dcMS) with post-deposition annealing in air. CrN coatings were deposited by reactive dcMS using different argon-nitrogen (Ar:N₂) gas ratios (4:1, 3:1, 2:1, and 1:1), followed by annealing at 550 °C for 1.5 h in ambient air. XRD and EDS analysis revealed that this treatment results in the formation of a composite phase comprising CrN and Cr₂O₃. The resulting coating exhibited favorable mechanical and tribological properties, including a maximum hardness of 12 GPa, a low wear coefficient of 0.254 and a specific wear rate of 7.05 × 10⁻⁶ mm³/N·m, making it a strong candidate for advanced protective coating applications. Full article

The improvement of environmental conditions has become a priority for governments and legislators. New electrified mobility systems are increasingly present in our environment, as they enable the reduction of polluting emissions. Electric vehicles (EVs) are one of the fastest-growing alternatives to date, with exponential growth expected over the next few years. In this article, the various charging modes for EVs are explored, and the risks associated with charging technologies are analysed, particularly for charging systems in high-power DC with Lithium battery energy storage, given their long market deployment and characteristic behaviour. In particular, the Arc Flash (AF) risk present in high-power DC chargers will be studied, involving numerous simulations of the charging process. Subsequently, the Incident Energy (IE) analysis is carried out at different specific points of a commercial high-power ‘Mode 4’ charger. For this purpose, different analysis methods of recognised prestige, such as Doan, Paukert, or Stokes and Oppenlander, are applied, using the latest version of the ETAP^® simulation tool version 22.5.0. This study focuses on quantifying the potential severity (consequences) of an AF event, assuming its occurrence, rather than performing a probabilistic risk assessment according to standard methodologies. The primary objective of this research is to comprehensively quantify the potential consequences for workers involved in the operation, maintenance, repair, and execution of tasks related to EV charging systems. This analysis makes it possible to provide safe working conditions and to choose the appropriate and necessary personal protective equipment (PPE) for each type of operation. It is essential to develop this novel process to quantify the consequences of AF and to protect the end users of EV charging systems. Full article

A quantitative analysis of the fault transient is critical for system resilience assessment and protection coordination. Focusing on hybrid modular multilevel converter (MMC)-based HVDC architecture with enhanced fault ride-through (FRT) capability, this study develops a mathematical calculation framework to quantify how controller configurations influence fault current profiles. Unlike conventional static topologies (e.g., RLC or fixed-voltage RL circuits), the proposed model integrates an RL network with a time-variant controlled voltage source, which can emulate closed-loop control response during the FRT transient. Then, the quantitative relationship is established to map the parameters of DC controllers to the fault current across diverse FRT strategies, including scenarios where control saturation dominates the transient response. Simulation studies conducted on a two-terminal MMC-HVDC architecture substantiate the efficacy and precision of the developed methodology. The proposed method enables the evaluation of DC fault behavior for hybrid MMCs, concurrently appraising FRT control strategies. Full article

Enhancing the resilience of renewable energy systems in ultra-weak grids is crucial for promoting sustainable energy adoption and ensuring a reliable power supply during disturbances. Ultra-weak grids characterized by a very low Short-Circuit Ratio, less than 2, and high grid impedance significantly impair voltage and frequency stability, imposing challenging conditions for Inverter-Based Resources. To address these challenges, this paper considers a 110 KVA, three-phase, two-level Voltage Source Converter, interfacing a 700 V DC link to a 415 V AC ultra-weak grid. X/R = 1 is controlled using Sinusoidal Pulse Width Modulation, where the Grid-Connected Converter operates in Grid-Forming Mode to maintain voltage and frequency stability under a steady state. During symmetrical and asymmetrical faults, the converter transitions to Grid-Following mode with current control to safely limit fault currents and protect the system integrity. After fault clearance, the system seamlessly reverts to Grid-Forming Mode to resume voltage regulation. This paper proposes an improved control strategy that integrates voltage feedforward reactive power support and virtual capacitor-based virtual inertia using Active Disturbance Rejection Control, a robust, model-independent controller, which rapidly rejects disturbances by regulating d and q-axes currents. To test the practicality of the proposed system, real-time implementation is carried out using the OPAL-RT OP4610 platform, and the results are experimentally validated. The results demonstrate improved fault current limitation and enhanced DC link voltage stability compared to a conventional PI controller, validating the system’s robust Fault Ride-Through performance under ultra-weak grid conditions. Full article

Electrochemical treatment by means of direct current (DC) is usually used as a measure for steel rebar corrosion protection, e.g., cathodic protection (CP), electrochemical chloride extraction (ECE), and re-alkalization (RA). However, the passage of an electrical charge through the pore system of concrete or mortar, coupled with the migration of ions, concentration changes, and resulting phase changes, may alter its chloride penetration resistance and, subsequently, the time until rebar corrosion activation. Porosity changes in hardened Portland cement mortar were studied by means of mercury intrusion porosimetry (MIP) and electrochemical impedance spectroscopy (EIS), and alterations in the mortar surface phase composition were observed by means of X-ray diffraction (XRD). In order to innovatively investigate the impact of DC treatment on the properties of the mortar–electrolyte interface, the cathode-facing mortar surface and the anode-facing mortar surface were analyzed separately. The corrosion of steel coupons embedded in DC-treated hardened mortar was monitored by means of the free corrosion potential (E_oc) and polarization resistance (R_p). The results showed that the DC treatment affected the surface porosity of the hardened Portland cement mortar at the nanoscale. Up to two-thirds of the small pores (0.001–0.01 µm) were replaced by medium-sized pores (0.01–0.06 µm), which may be significant for chloride ingress. Although the porosity and phase composition alterations were confirmed using other techniques (EIS and XRD), corrosion tests revealed that they did not significantly affect the time until the corrosion activation of the steel coupons in the mortar. Full article

This study presents a novel spatio-temporal detection framework for identifying False Data Injection (FDI) attacks in DC microgrid systems from the perspective of cyber–physical symmetry. While modern DC microgrids benefit from increasingly sophisticated cyber–physical symmetry network integration, this interconnected architecture simultaneously introduces significant cybersecurity vulnerabilities. Notably, FDI attacks can effectively bypass conventional Chi-square detector-based protection mechanisms through malicious manipulation of communication layer data. To address this critical security challenge, we propose a hybrid deep learning framework that synergistically combines: Convolutional Neural Networks (CNN) for robust spatial feature extraction from power system measurements; Long Short-Term Memory (LSTM) networks for capturing complex temporal dependencies; and an attention mechanism that dynamically weights the most discriminative features. The framework operates through a hierarchical feature extraction process: First-level spatial analysis identifies local measurement patterns; second-level temporal analysis detects sequential anomalies; attention-based feature refinement focuses on the most attack-relevant signatures. Comprehensive simulation studies demonstrate the superior performance of our CNN-LSTM-Attention framework compared to conventional detection approaches (CNN-SVM and MLP), with significant improvements across all key metrics. Namely, the accuracy, precision, F1-score, and recall could be improved by at least 7.17%, 6.59%, 2.72% and 6.55%. Full article

Stainless steel (SS) is one of the materials most commonly utilized for fabrication of medical implants and its properties are often improved by deposition of protective coatings. This study investigates certain physico-chemical and biological properties of SS substrate coated with multilayer thin film consisting of titanium nitride and silver layers (TiN-Ag film). TiN-Ag films were deposited on the surface of AISI 316 SS substrate by a combination of cathodic arc evaporation and DC magnetron sputtering. SS substrate was analyzed by TEM, while deposited coatings were analyzed by SEM, EDS and wettability measurements. Also, mitochondrial activity assay, and osteogenic and chondrogenic differentiation were performed on dental pulp stem cells (DPSCs). SEM and EDS revealed excellent adhesion between coatings’ layers, with the top layer predominantly composed of Ag, which is responsible for antibacterial properties. TiN-Ag film exhibited moderately hydrophilic behaviour which is desirable for orthopedic implant applications. Biological assays revealed significantly higher mitochondrial activity and enhanced osteogenic and chondrogenic differentiation of DPSC on TiN-Ag films compared to TiN films. The newly designed TiN-Ag coatings showed a great potential for the surface modification of SS implants, and further detailed investigations will explore their suitability for application in clinical practice. Full article

In order to accurately grasp the operational state of DC protection devices in converter stations, a DC protection device state assessment method based on the variable weight theory and correlation degree analysis is proposed. Constructing condition assessment indicators for DC protection device of converter stations containing overhaul in-formation, operation information and defect information, when the actual value of the indicator exceeds the specified range of values, the DC protection device is directly judged to be in ‘alarm’ status; when the actual value of the indicator is within the specified range of values, Analytic Hierarchy Process (AHP) and variable weight theory are combined to adjust variable weights of assessment indicators in real time. At the same time, the correlation between the indicators and each state level is calculated, and the correlation of the indicators and their corresponding weights are weighted and summed to obtain the comprehensive correlation of each state level of the DC protection device, and the correlation of each state level of the DC protection device is calculated, using the principle of maximum correlation, the DC protection device status is obtained. Example analyses show that the method is simple and easy to implement and can accurately assess the operational state of the DC protection device in converter stations. Full article

Microgrids (MGs) technologies, with their advanced control techniques and real-time monitoring systems, provide users with attractive benefits including enhanced power quality, stability, sustainability, and environmentally friendly energy. As a result of continuous technological development, Internet of Things (IoT) architectures and technologies are becoming more and more important to the future smart grid’s creation, control, monitoring, and protection of microgrids. Since microgrids are made up of several components that can function in network distribution mode using AC, DC, and hybrid systems, an appropriate control strategy and monitoring system is necessary to ensure that the power from microgrids is delivered to sensitive loads and the main grid effectively. As a result, this article thoroughly assesses MGs’ control systems and groups them based on their degree of protection, energy conversion, integration, advantages, and disadvantages. The functions of IoT and monitoring systems for MGs’ data analytics, energy transactions, and security threats are also demonstrated in this article. This study also identifies several factors, challenges, and concerns about the long-term advancement of MGs’ control technology. This work can serve as a guide for all upcoming energy management and microgrid monitoring systems. Full article

With the increasing deployment of DC power systems, particularly in DC distribution systems, there is a growing demand for rapid and effective fault current limiting solutions. Conventional fault current limiters (FCLs) often suffer from limitations in terms of response time, size, and operational complexity. As a solution to these challenges, this paper proposes a hybrid FCL based on a pyro conductor switch (PCS), which combines passive limiting elements with an active switching mechanism. The proposed PCS FCL consists of a pyro fuse, an IGBT switch, a limiting inductor, and a damping resistor. Upon fault detection, the IGBT switch is first turned off to initiate current transfer into the limiting branch. Subsequently, the pyro fuse operates by explosively severing the embedded conductor using a pyrotechnic charge, thereby providing galvanic isolation and reinforcing current commutation into a high-impedance path. This operational characteristic enables effective fault current suppression without requiring complex control or real-time sensing. A detailed analysis using PSCAD/EMTDC simulations was conducted to evaluate the current limiting characteristics under fault conditions, and a prototype was subsequently developed to validate its performance. The simulation results were verified through experimental testing, indicating the limiter’s ability to reduce peak fault current. Furthermore, the results demonstrated that the degree of current limitation can be effectively designed through the selection of appropriate current limiting parameters. This demonstrates that the proposed PCS-based FCL provides a practical and scalable solution for improving protection in DC power distribution systems. Full article

GaN flying-capacitor-multi-level (FCML) Totem-Pole power-factor-correctors (PFCs) have been demonstrated with very high density and efficiency in the literature. However, there is still a lack of detailed discussion about flying capacitor voltage precharge during the start-up for GaN FCML Totem-Pole PFCs. To enhance the reliability during start-up, we propose a multi-path and multi-step flying capacitor precharge method. In our proposed method, the bulky DC link capacitor is precharged through the path of the auxiliary line-frequency Si diode half-bridge and the body-diodes of the Si MOSFET half-bridge. The flying capacitors which have much smaller capacitances are precharged through the path of the GaN devices and the body-diodes of the Si half-bridge. The DC link capacitor is more than 100 times higher than the flying capacitor in this topology. Therefore, by splitting the total precharging current into two paths, the precharging current through the GaN devices is almost 100 times lower than that through the body-diodes of Si MOSFETs. As a result, this method protects expensive GaN devices from high inrush current and significantly improves the reliability of the GaN devices during the voltage precharge. Detailed operation principles and experimental verifications are presented in this paper. Full article

The increasing attention to medium-voltage direct current (MVDC) distribution networks is motivated by the need to efficiently connect renewable energy sources and DC loads. However, fast and reliable protection strategies remain a key challenge due to the rapid rise and high magnitude of DC fault currents. This paper proposes a protection strategy for MVDC distribution networks considering network reconfiguration. The strategy integrates a fault-detection scheme based on the product of the rate of change in current and voltage (ROCOC × ROCOV) and a fault-identification scheme based on the ratio of the magnitudes of the positive and negative pole voltages. In a radial topology, the sign of ROCOC × ROCOV provides selectivity between internal and external faults. In multi-terminal topologies under network reconfiguration, external faults can present characteristics similar to those of internal faults. To ensure selectivity, communication is introduced between protective relays that share the same protection zone. Thresholds were set without large-scale simulations. The protection strategy was implemented in PSCAD/EMTDC and evaluated in a 37.4 kV MVDC distribution network. The strategy was validated under various fault conditions in radial and multi-terminal MVDC distribution networks, demonstrating fast, sensitive, and selective performance. The proposed strategy can contribute to the stable operation of MVDC distribution networks. Full article

Cancer continues to pose a significant challenge to global health, resulting in millions of deaths annually despite advancements in treatments like surgery, chemotherapy, and radiotherapy. A key factor complicating successful outcomes is the presence of cancer stem cells (CSCs), which possess distinctive features that facilitate tumor initiation and progression as well as resistance to therapies. These cells are adept at evading conventional treatments and can hinder the effectiveness of immunotherapy, often manipulating the tumor microenvironment to suppress immune responses. This review delves into the complex interplay between CSCs and immune cells, emphasizing their contributions to tumor heterogeneity and therapeutic resistance. By investigating the CSC niche in which these cells thrive and their complex interactions with the immune system, we aim to reveal new therapeutic avenues that could enhance patient outcomes and minimize the risk of recurrence. CSCs are characterized by remarkable self-renewal and plasticity, allowing them to transition between stem-like and differentiated states in response to various stimuli. Their existence within the CSC niche confers immune protection and maintains stem-like properties while promoting immune evasion. Activating key signaling pathways and specific surface markers is crucial in developing CSC traits, pointing to potential strategies for effective tumor eradication. Conventional therapies often fail to eliminate CSCs, which can lead to tumor recurrence. Therefore, innovative immunotherapeutic strategies such as dendritic cell vaccines (DC vaccines), chimeric antigen receptor (CAR) engineered T cells, and immune checkpoint inhibitors (ICIs) are under examination. This review sheds light on CSC’s roles across different malignancies, highlighting the necessity for innovative targeted approaches in cancer treatment. Full article

This study investigated the effects of alternating current (AC) interference on pipeline steel under cathodic protection (CP). In a simulated solution, real-time electrochemical measurements and corrosion rate analysis were conducted on two steel types (C1018 and X60) under various levels of AC interference with CP. Due to the complexity of AC-induced corrosion, relying on the shift in DC potential alone cannot accurately demonstrate the corrosion behavior in the presence of AC interference. In fact, such an approach may mislead the predictions of corrosion performance. It is observed that AC interference reduced the effectiveness of CP and increased the corrosion rate of the steel, both in weight loss and Tafel Extrapolation (Tafel) measurements. The study concluded that conventional CP standards used in the field were inadequate in the presence of high AC-level interference. Furthermore, this study found that a more negative CP current density (−0.75 A/m²) could reduce the effect of AC interference by 46–93%. This is particularly shown in the case of low-level AC interference, where the reduction can reach up to 93%. Utilizing the experimental data obtained by the two measurement methods, probabilistic models to predict the corrosion rate were developed with consideration of the uncertainty in the measurements. The sensitivity analysis showed how AC interference impacts the corrosion rate for a given CP level. Full article

The rhizome of Atractylodes lancea (Thunb.) DC. is a traditional Chinese medicine used extensively owing to its antimicrobial properties. It is utilized to treat nyctalopia and problems related to the gastrointestinal tract. However, its yield is limited because of its endangered status, long growth period, and restricted reproductive ability. Ancillary approaches have not been established to ensure sustainable resource utilization by applying efficient plant regeneration technologies and producing bioactive metabolites via genome editing. This study reports the effects of explants, hormones, and culture conditions on embryogenic callus induction, plant regeneration, adventitious and hairy root cultivation, and essential oil production. Embryogenic calli were successfully induced in MS and 2.0 mg/L 2,4-D and 1.0 mg/L NAA and 1/2MS medium supplemented with 4.0 mg/L 6-BA and 0.4 mg/L NAA, which were optimal for callus differentiation. Maximum proliferation (12-fold) of cluster buds was observed with a select combination of hormones [NAA (0.2 mg/L) and 6-BA (2.0 mg/L)]. “Efficient plant regeneration and bioactive metabolite production” can provide technical support for the protection and sustainable utilization of A. lancea germplasm resources in terms of resource preservation and new variety breeding, natural product production, and industrial breeding of medicinal plants. Full article