Search Results (1,492)

Water-bearing faults pose critical hazards in tunnel excavation due to sudden water inrush, making reliable advance detection essential. This study presents a systematic forward modeling framework that integrates COMSOL Multiphysics and MATLAB to simulate three-dimensional direct current (DC) responses ahead of the tunnel face. A three-dimensional finite-element model was developed to investigate the influence of electrical anisotropy on apparent resistivity under controlled geological conditions. Electrical anisotropy of both surrounding rock and water-bearing faults is incorporated to evaluate its influence on apparent resistivity. Numerical experiments investigate the effects of surrounding-rock and fault anisotropy and reveal the mechanism behind hourglass-shaped low-resistivity anomalies. The results also reveal systematic biases when anisotropy is neglected, including forward-shifted anomaly positions, overestimated lateral extents, and more diffuse anomaly boundaries. When anisotropy is considered in both the surrounding rock and the fault, the simulated anomaly closely matches the preset fault location, demonstrating improved localization accuracy. The modeling results clarify the effects of key parameters on apparent resistivity responses and improve the interpretation of low-resistivity anomalies. They also provide a theoretical basis for enhancing the reliability of DC resistivity-based tunnel advance detection. Full article

With the continuous increase in coal mining depth in China, concealed geological structures—such as collapsed columns and faults—pose a severe threat to mine safety by triggering water inrush accidents. Mine DC resistivity methods exhibit high sensitivity to water-bearing characteristics but suffer from limited resolution, while mine seismic exploration offers superior resolution but weak sensitivity to water-rich bodies. Single-method inversion is inevitably plagued by solution non-uniqueness. This study aims to enhance the detection accuracy of concealed structures by implementing a joint seismic–electric inversion that exploits the complementary strengths of both methods. For the DC resistivity component, a forward model was established using the finite element method with unstructured meshes, and inversion was performed via Occam regularization. For seismic exploration, forward modeling employed curved-ray tracing, and inversion was conducted via the LSQR algorithm. Cross-gradient constraints were incorporated into the joint inversion to establish a structurally coupled framework. The novelty of this study lies in the integration of unstructured mesh discretization, curved-ray seismic tomography, and cross-gradient-constrained joint inversion for mine water detection. Numerical simulation results demonstrate that joint inversion effectively constrains the spatial extent of anomalies, accurately characterizes the morphology of multiple anomalous bodies and water-conducting fault channels, and substantially reduces solution non-uniqueness compared to single-method inversions. This research provides a reliable methodology for the refined detection of concealed hazard-inducing structures, offering considerable practical value for safeguarding coal mine safety. Full article

The increasing penetration of renewable energy sources has increased the need for advanced control strategies capable of maintaining stability under low-inertia, converter-dominated operating conditions. In grid-connected wind energy conversion systems (WECSs), constant power loads (CPLs) exhibit negative incremental impedance characteristics that can amplify DC-link oscillations and complicate the coordination between the electrical and mechanical subsystems. The main contribution of this work is a Soft Actor–Critic (SAC) reinforcement learning algorithm that tunes the outer proportional-integral gains of the machine-side DC-voltage-squared control loop together with the active damping gain, allowing online adaptation of the controller according to the operating condition and disturbance level, thereby improving energy system sustainability. The proposed control framework includes a two-mass shaft model, virtual inertia control, and DC-link load uncertainty in the form of both resistive loads and CPLs. The system is modeled and evaluated using MATLAB/Simulink, and its performance is compared with that of a conventional fixed-gain controller under AC load disturbances and wind speed variations. It has been found that for a 25% load disturbance, the maximum DC-link voltage deviation is reduced by 1.2% under resistive loading and 6.5% under CPL operation. For a 1 m/s reduction in wind speed, the corresponding reductions are 0.8% and 0.9%, respectively. The proposed controller also provides smoother output power and improved damping of the rotor speed and system frequency responses. Full article

Wireless power transfer (WPT) technology offers reliability, safety, and ease of use for low-power charging applications. However, output regulation is difficult when the secondary side is inaccessible, because the magnetic coupling factor $k$ and the equivalent load resistance $R_L$may both be unknown and variable. This work addresses the two unknown parameters problem using only primary-side measurements of the DC-link voltage $V_{DC}$and the primary resonant current $I_1$. An initial calibration stage temporarily connects a known resistance on the receiver side, making it possible to estimate $k$ without a secondary-to-primary communication link. Then, during the charging stage, the previously estimated coupling is used to estimate the equivalent load resistance and to indirectly regulate the charger input voltage through a primary-side pre-regulator. The proposed system is intended for low-power WPT chargers, in which the receiver side must be simple and compact. A resonant DC converter prototype was experimentally implemented using a Class-E inverter, a Series-Series compensation network, a full-bridge rectifier, primary-side voltage/current sensing, and a pre-regulator. The experimental results show a maximum coupling identification error of 3.9% and a maximum load-resistance identification error of 10.67%. The resulting output voltage is not measured directly at the load; instead, it is estimated from primary-side variables and maintained within the 4–6 V input window of the target charger around a 5 V reference, with a maximum relative voltage error of approximately 10%. The work therefore presents a primary-side identification and control proof of concept without secondary-to-primary communication, while explicitly discussing the calibration requirement, equivalent-load validation, efficiency limitations, and the conditions under which recalibration would be required. Full article

This study systematically investigates the effects of varying Ni doping levels (1.0–7.0 wt.%) on the microstructure, static magnetic properties, and high-frequency dynamic magnetic performance of Fe-5.5 wt.% Si soft magnetic composites (SMCs). Toroidal core samples were fabricated using powder metallurgy combined with silicone resin coating and high-temperature annealing. The influence of Ni doping on phase composition, morphology, saturation magnetization, coercivity, effective permeability, quality factor, total core loss and its components, and DC bias characteristics was comprehensively evaluated by XRD, SEM, EDS, hysteresis loop testing, and DC bias measurements. The results indicate that an appropriate Ni content (3.0–5.0 wt.%) promotes the formation of α-Fe(Si,Ni) solid solution and (Fe,Ni)₃Si ordered phases, optimizes grain size and structural ordering, enhances saturation magnetization, and reduces coercivity. In contrast, excessive Ni doping (7.0 wt.%) leads to Ni segregation at grain boundaries, forming strong pinning centers that significantly increase coercivity and hysteresis loss. Within the wide frequency range of 1–100 kHz, Ni doping improves the permeability retention under DC bias but reduces the initial effective permeability. Notably, the sample with 5.0 wt.% Ni exhibits the highest quality factor (Q value) across the entire frequency range, demonstrating the best overall performance. This study provides experimental evidence and theoretical guidance for developing high-saturation-resistance, low-loss soft magnetic composites for medium-to-high-frequency applications. Full article

The degradation of steel used in the oil industry has become a serious problem due to the high costs associated with material loss from corrosion. Applying thin layers of corrosion-resistant material promises to be a viable alternative for extending the service life of pipelines. ERCuAl-A2 electrode claddings were applied to API X70 carbon steel using the MIG brazing process with direct current (DC) and pulsed current (P). The cladding was applied under three conditions: base material (BM) at room temperature, BM preheated to 120 °C, and Ni-buttered BM. Microhardness profiles and Charpy impact tests were performed on the MB and all cladding conditions. The API X70 carbon steel showed a microhardness value of 186.95 ± 11.17 Vickers, while the microhardness profiles of the ERCuAl A2 cladding showed values that differed in the intermetallic zone generated by the welding process. Likewise, the impact behavior of the base material and the applied claddings was ductile, except for conditions C2PF and C3PF, which showed a brittle–ductile behavior. The highest values of absorbed energy obtained from the tests were found in the conditions applied with DC, with values of approximately 50 MJm-3, due to the transfer mode of application of the cladding and/or the position in which the notch was made. Full article

This paper presents a novel method for estimating the capacitance of DC-link capacitors in frequency converters. The proposed approach leverages the characteristic changes in the DC-link voltage slope induced by capacitor aging, specifically degradation in capacitance and equivalent series resistance (ESR). The estimation algorithm extracts the 100 Hz and 300 Hz voltage ripple harmonics at the rectifier output to determine the ripple amplitude. The applicability of this method is inherently limited to topologies utilizing front-end diode rectifiers. The proposed estimation method allows for very small errors, ranging from 0.5% to 9%, even with very large capacity changes. Simulation models were validated using a comprehensive experimental dataset acquired from a dedicated laboratory setup. Furthermore, the robustness of the capacitance estimation process was evaluated under various grid and load disturbances. Full article

Nimotuzumab is a humanized anti-EGFR monoclonal antibody with a unique pharmacodynamic profile characterized by intermediate affinity and bivalent binding dependence, enabling density-selective tumor targeting while sparing normal tissues from the severe skin rash and other toxicities common to EGFR inhibitors. Since its first approval in 2002, nimotuzumab has been registered for eight cancer indications. Unlike conventional fixed-dose schedules, emerging evidence supports prolonged administration beyond initial combination therapy. This review summarizes clinical data from pancreatic cancer, esophageal cancer, high-grade glioma, pediatric diffuse intrinsic pontine glioma, head and neck squamous cell carcinoma, nasopharyngeal cancer and other solid tumors, showing that extended nimotuzumab exposure, often as maintenance monotherapy, may prolong overall survival, progression-free survival, and disease control compared to limited cycles. Despite heterogeneity in tumor types and treatment regimens, maintenance nimotuzumab was consistently associated with better results, particularly in terms of overall survival. Notably, significant survival benefits were observed in locally advanced SCCHN (24.9 vs. 12.5 months) and esophageal cancer (15.9 vs. 8.1 months) across independent clinical trials. Mechanistically, nimotuzumab exerts direct cytostatic effects via G1 arrest, potent anti-angiogenic activity through VEGF downregulation, indirect pro-apoptotic effects, and broad immunomodulation including ADCC, NK-DC cross-talk, EGFR-specific CD8+ T cell priming, upregulation of HLA class I, and favorable regulation of regulatory T cells. Its density-selective binding reduces selective pressure for acquired resistance. Future research priorities should include prospective randomized trials specifically evaluating maintenance strategies, biomarker-driven patient selection, the molecular characterization of resistance mechanisms, integration with immunotherapy and modern combination regimens, and the development of next-generation platforms, including antibody–drug conjugates and multi-specific constructs. Full article

The reuse of small-capacity lithium-ion cells recovered from disposable e-cigarettes is limited by the lack of rapid and low-cost screening methods. This study evaluates a low-complexity 3-30-3 pre-sorting methodology based on a 30 s DC load pulse and a 3 min rest period applied to series connected cells under identical current conditions. Generic 13350-type cells with a nominal capacity of approximately 850 mAh were tested, and cell suitability was assessed from voltage drop, effective direct-current resistance, and stability over repeated load cycles. In the tested batch, the coefficient of variation of the effective resistance reached 28–35%, indicating substantial cell-to-cell variation within this pilot sample. Repeated loading improved discrimination between stable and degraded cells and enabled selection of a compatible subset for assembly into a 3S3P battery pack. The assembled pack operated successfully as a power source for a FläktWoods 227VM pressure controller in biomass drying monitoring. The proposed method does not replace full battery diagnostics, but it provides a practical first-stage filter that can reduce testing time by more than 90% and improve the safety of second-life cell grouping. Full article

In the present paper, we studied the interaction of microwave radiation with conductive indium tin oxide (ITO) coatings deposited on a borosilicate glass. The experiments were carried out with the ITO films, the thickness of which varied in the range from 85 to 607 nm. The transmittance and reflectivity of the ITO film/K108 glass structures were measured in the frequency region from 3 to 23 GHz. Theoretical modeling of the spectra was performed by means of the transfer matrix method. It was shown that for a given thickness of the glass substrate, the transmission and reflection spectra of the ITO film/K108 glass structures were fully determined by only one parameter of the ITO film, namely, its DC sheet resistivity. The considered model predicts an increase in maximum microwave shielding effectiveness up to 45.6 dB with a decrease in DC sheet resistivity to 1 Ohm/sq. ITO coatings with DC sheet resistivities down to 2.3 Ohm/sq have been experimentally investigated. The model microwave transmittance and reflectivity spectra were in good agreement with the experimental ones. In particular, the coefficient of determination for the transmittance spectra was rather high: R² > 0.93. It was experimentally demonstrated that applying antireflective coatings on both sides of the ITO film/K108 glass microwave shielding filter significantly improved its transparency in the operating optical range. A filter has been created that provides microwave shielding effectiveness of 38.7 dB with an average transmission coefficient of 0.81 in the visible range. Full article

Glutathione peroxidase 4 (GPX4) is canonically viewed as the primary suppressor of ferroptosis, yet its role in the tumor microenvironment (TME) extends far beyond antioxidant catalysis to encompass immuno-metabolic regulation. In this review, we synthesize recent advances in enzymology, immunology, and cancer metabolism to propose a “lipid peroxidation threshold” framework, wherein GPX4 sets cell-type-specific thresholds that determine susceptibility to ferroptosis across tumor cells, CD8⁺ T cells, dendritic cells (DCs), and myeloid populations. We discuss how these thresholds are dynamically adjusted by post-translational modifications, nutrient competition and intercellular feedback loops, resulting in significant spatial heterogeneity between the tumor core and the tumor invasive front. There is a current selectivity paradox in GPX4 inhibitors, as well as resistance through nuclear factor erythroid 2-related factor 2 (Nrf2) and ferroptosis suppressor protein 1 (FSP1) that restricts the efficacy of GPX4 inhibitors as monotherapy. We focus on rational combination approaches: GPX4 modulation with immune checkpoint blockade (ICB), chemotherapy, and targeting myeloid-derived suppressor cells (MDSCs); and the pressing need for predictive biomarkers and single-cell spatial profiling. We conclude that successful clinical translation requires moving beyond indiscriminate GPX4 inhibition toward precision “threshold engineering” that selectively lowers tumor lipid peroxidation thresholds while sparing immune cells. Full article

Electrical resistance measurements can provide supplementary information for the characterization of carbon steels, since resistivity is influenced by composition, microstructure, geometry, processing history, and temperature. This work presents an experimental methodology for the electrical resistance-based characterization of AISI 1045 carbon steel specimens using controlled current injection and parameter estimation. The proposed system integrates a DC-modulated excitation stage, a four-terminal measurement configuration, voltage, current, and temperature acquisition, signal preprocessing, and offline resistance estimation using Python 3 scripts. Ten cylindrical specimens were evaluated through 10 repeated characterization experiments per sample, yielding 100 characterization records, each containing 100,000 voltage, current, and temperature measurements. The sample resistance is estimated using a least-squares formulation based on synchronized voltage–current data and is compared with a mean-based estimator derived from instantaneous resistance values. The results show that the least-squares estimator produced repeatable resistance values concentrated within a narrow interval, from approximately $443.43\mathrm{\mu }\mathrm{\Omega }$ to $445.55\mathrm{\mu }\mathrm{\Omega }$, with interquartile ranges below $4.46\mathrm{\mu }\mathrm{\Omega }$ for all specimens. In contrast, the mean-based estimator exhibited larger resistance values and substantially higher dispersion. The least-squares resistance-derived resistivity values ranged from $1.823\times {10}^{-7}$ to $2.263\times {10}^{-7}\mathrm{\Omega }·$m, which is consistent with the expected order of magnitude for AISI 1045 steel when compared with temperature-dependent theoretical reference values. The corresponding relative differences ranged from 1.94% to 11.00%, with most specimens remaining below 6%. These findings indicate that controlled current injection, combined with four-terminal sensing, signal preprocessing, and least-squares estimation, provides a reproducible framework for the low-resistance characterization of carbon steel specimens. Although the present study focuses on AISI 1045 steel, the methodology may be adapted to other metallic specimens, steel grades, heat-treated samples, or controlled thermal-cycle experiments, provided that geometry, temperature, calibration, and material-specific reference conditions are properly considered. Full article

This paper proposes an Active Gate Driver (AGD) for a DC–DC boost converter based on Silicon Carbide (SiC) power devices, in which surge voltage and ringing arise from their fast-switching characteristics. In this work, a practical and simple 4-bit logic AGD was proposed to adjust the gate resistance during the Miller interval of the SiC MOSFET. This helps suppress these effects and lowers the surge voltage and ringing stress on the power device. Experimental results demonstrate that the voltage overshoot decreases from 52 V to 22 V, corresponding to a reduction from 52% to 22% under a 100 V output condition, while the peak drain–source voltage decreases from 152 V to 122 V. The turn-off energy increases from 60.2 µJ to 76.9 µJ due to the slightly reduced switching speed. This trade-off represents the improvement in the comparison between transient suppression and switching loss. In addition, the voltage ringing is significantly attenuated. Although the modified switching strategy slightly increases switching loss, it effectively improves waveform quality and reduces voltage stress. These results confirm that the proposed AGD provides a simple and effective solution for improving the switching robustness and reliability of SiC-based DC–DC boost converters. Full article

This study investigates the effect of low-temperature pulsed DC plasma nitriding on the surface properties of AISI 304 stainless steel for homogenizer valve-seat components. Plasma nitriding was performed in an ammonia atmosphere at 400, 440 and 480 °C for 8 h. The treatment led to the formation of expanded austenite at 400 °C, while higher temperatures promoted the formation of Fe-N and CrN-containing phases. The thickness of the modified layer increased from approximately 36 μm at 400 °C to 65 μm at 480 °C. Surface microhardness increased from 203 HV0.1 for the untreated steel to 652.6, 806.0 and 961.8 HV0.1 after nitriding at 400, 440 and 480 °C, respectively. The wear rate decreased markedly, reaching 1.92 × 10⁻⁵ mm³/(N·m) for DCPN480 compared with 30.65 × 10⁻⁵ mm³/(N·m) for the untreated sample. Among the nitrided samples, DCPN440 showed the most favorable corrosion behavior in 3.5 wt.% NaCl solution, indicating a balance between surface hardening and preservation of corrosion resistance. Numerical modeling confirmed that the strengthened surface layer can withstand equivalent homogenizer valve-seat loading without local plastic deformation. The results demonstrate that pulsed DC plasma nitriding can significantly improve the hardness and wear resistance of AISI 304 stainless steel while maintaining acceptable corrosion performance under optimized treatment conditions. Full article

Existing single-ended protection schemes for flexible DC transmission lines are negatively affected by traveling wave (TW) refraction and reflection interference and nonlinear overfitting under low-resistance faults. To address this, in this study, line-mode voltage reverse TWs are mathematically analyzed, revealing that internal faults and forward external faults exhibit single- and double-exponential attenuation, respectively. An adaptive constant-value flattening method is proposed to suppress subsequent TW refraction and reflection. Additionally, a composite fitting strategy utilizing Levenberg–Marquardt (LM) and Moore–Penrose pseudoinverse (PINV) algorithms is proposed to fit the measured waveforms, solving the problem of low-resistance overfitting and amplifying residual differences between internal and external faults. Based on these principles, a novel single-ended protection scheme is proposed. Simulations verify that this scheme exhibits a high operating speed and strong robustness against different fault distances, different fault resistances, and noise. Full article