Search Results (58)

Iron-based superconductors have strong potential for magnet applications through their very high upper critical field, low anisotropy and manufacturability through the powder-in-tube (PIT) route. The engineering critical current density (J_e) is a key parameter for measuring the maximum current density that superconducting materials can withstand in practical applications. It serves as a bridge between theoretical research and practical applications of superconductors and has great significance in promoting the development and application of superconducting technology. In this study, Ag sheathed Ba_0.6K_0.4Fe₂As₂ (Ba-122) iron-based superconducting tapes were prepared by using the process of drawing, flat rolling and heat treatment by hot pressing (HP). For the first time, the filling factor of the tapes increased to about 40%, leading to a reduction in the volume fraction of Ag, consequently lowering the overall cost. The optimal parameters for achieving high transport J_e were obtained by comparing the effects of different HP pressures on the properties and micro-morphology of the tapes. The prepared mono-filament tapes are capable of carrying the transport J_e of 4.1 × 10⁴ A/cm² (I_c = 350 A) at 4.2 K, 10 T, marking the highest J_e reported for Ba-122 wires and tapes to date. Our results show that high transport J_e can be obtained in Ba-122 superconducting tapes, and iron-based superconductors have a promising future in practical applications. Full article

This paper presents the findings of the research aimed at developing computer models to determine the operating conditions in electric power systems (EPSs) feeding DC and AC railway substations. The object of the research is an EPS with a predominant traction load whose high-voltage power lines are connected to transformer and converter substations with 3 kV and 27.5 kV traction networks. The supply network includes 110 kV and 220 kV power lines. The EPS operating parameters are calculated based on the decomposition of the system into alternating and direct current segments. Calculations are performed for the fundamental frequency and high harmonic frequencies. The modeling technique is universal and can be used to determine the operating parameters and power quality indices for any configuration of an EPS and various designs of traction networks. With this technique, one can solve numerous additional problems, such as calculating the processes of ice melting in traction networks and power lines, determining electromagnetic field strengths, and assessing the heating of power line wires and catenary suspensions. The results obtained show that the voltages on the current collectors are within acceptable limits for all AC and DC electric locomotives. The levels of asymmetry on the 110 and 220 kV tires of traction substations (TP) do not exceed the normally permissible values. The values of the asymmetry coefficients for DC TP are tenths of a percent. With an increase in the size of traffic and in post-emergency conditions caused by the disconnection of communication between one of the support substations and the EPS, the asymmetry indicators on the 220 kV buses of AC substations may exceed the permissible limits. Phase-controlled reactive power sources can be used to reduce them. The analysis of the results of the determination of non-sinusoidal modes allows us to formulate the conclusion that the values of harmonic distortion go beyond the normative limits. Passive and active filters of higher harmonics can be used to normalize them. Calculations of thermal modes of traction transformers show that the temperatures of the most heated points do not exceed acceptable values. Full article

High systolic blood pressure and increased blood pressure variability after the onset of ischemic stroke are associated with poor clinical outcomes. One of the key determinants of blood pressure is arteriolar size, determined by vascular smooth muscle tone and vasodilatory and vasoconstrictor substances that are released by the endothelium. The aim of this study is to outline alterations in vasomotor function in isolated peripheral arteries following ischemic stroke. The reactivity of thoracic aortic segments from male C57BL/6 mice to dilators and constrictors was quantified using wire myography. Acetylcholine-induced endothelium-dependent vasodilation was impaired after ischemic stroke (LogIC50 Sham = −7.499, LogIC50 Stroke = −7.350, p = 0.0132, n = 19, 31 respectively). The vasodilatory responses to SNP were identical in the isolated aortas in the sham and stroke groups. Phenylephrine-induced vasoconstriction was impaired in the aortas isolated from the stroke animals in comparison to their sham treatment counterparts (Sham LogEC50= −6.652 vs. Stroke LogEC50 = −6.475, p < 0.001). Our study demonstrates that 24 h post-ischemic stroke, peripheral vascular responses are impaired in remote arteries. The aortas from the stroke animals exhibited reduced vasoconstrictor and endothelium-dependent vasodilator responses, while the endothelium-independent vasodilatory responses were preserved. Since both the vasodilatory and vasoconstrictor responses of peripheral arteries are impaired following ischemic stroke, our findings might explain increased blood pressure variability following ischemic stroke. Full article

In this paper, a new method involving a wear-resistant and reusable template is proposed for the preparation of high-mechanical-strength superhydrophobic polymer film based on wire electrical discharge machining (WEDM). A solid−liquid-contact-angle simulation model was established to obtain surface-texture types and sizes that may achieve superhydrophobicity. The experimental results from template preparation show that there is good agreement between the simulation and experimental results for the contact angle. The maximum contact angle on the template can reach 155.3° given the appropriate triangular surface texture and WEDM rough machining. Besides, the prepared superhydrophobic template exhibits good wear resistance and reusability. PDMS superhydrophobic polymer films were prepared by the template method, and their properties were tested. The experimental results from the preparation of superhydrophobic polymer films show that the maximum contact angle of the polymer films can be up to 154.8° and that these films have good self-cleaning and anti-icing properties, wear resistance, bending resistance, and ductility. Full article

Wire icing events pose a significant threat to the southern power grid’s transmission lines in China. Fifteen such events were identified from 2018 to 2020 on the Guilin-Haiyang Mountain transmission line. Hourly measurements of ice thickness and concurrent meteorological data were analyzed using the Makkonen model’s freezing rate formula to categorize the events into distinct growth patterns: dry and wet. The relationship between wire icing and meteorological factors across different micro-topography (windward slope, leeward slope, and pass) was further explored. Several key conclusions can be drawn. First, the altitude is positively correlated to the icing thickness, but relatively independent of the icing rate; however, such independence between the icing rate and altitude cannot be interpreted by the negative correlation of altitude with temperature and the positive relationship between wind speed and liquid water content. Second, a pronounced connection of the icing rate with meteorological factors is not shown until the wet and dry patterns are separated. Notably, the correlations differ between these two patterns, with icing rate being negatively correlated with temperature for the wet growth process, but positively correlated with wind speed and liquid water content for the dry growth process. Third, both wet and dry growth processes exist across the icing events. A shift from wet to dry growth was evident with increasing altitude. At the mountain’s base, wet growth predominates, with the icing rate determined by the temperature close to the freezing point, whereas the higher temperature and lower liquid water flux account for the shorter wire icing duration, lower icing rate, and thus the thinner icing thickness at the leeward slope compared to the windward slope at a similar altitude. This study sheds light on the variations in icing rates under different micro-topographies and the underlying physical mechanisms governing icing growth patterns and provides a much-needed understanding of these distinct growth processes on the development of a more sophisticated predictive model for conductor icing. Full article

Melt pond is one of the most significant and important features of Arctic sea ice in the summer and can dramatically reduce the albedo of ice, promoting more energy into the upper ocean. The observation of the seasonal evolution of melt pond can improve our fundamental understanding of the role and sensitivity of sea ice in the context of global climate change. In this study, an ice-tethered observation system is developed for melt pond evolution with vision and temperature profile measurements. The system composition, structure of the ice-tethered buoy, freeze-resistant camera, and thermistor chain are analyzed. A sealed shell and electric heating wires are used to increase the temperature to around the camera in low-temperature environments. The ice thickness and depth of melt pond can be inverted using a specific interface recognition algorithm. A low-light image enhancement strategy is proposed to improve the quality of images under the low lighting conditions in polar regions. The proposed system was tested in the second reservoir of Fen River, Yellow River, from 15 January to 27 January 2021. An artificial freshwater pond was used as the location for thermistor chain deployment and observation. The differences in mean square error (MSE), peak signal-to-noise ratio (PSNR), and feature similarity index (FSIM) between the original and enhanced images indicate that the proposed algorithm is suitable for low-light image enhancement. The research on the ice-tethered observation system will provide a new framework and technical support for the seasonal observation for melt pond. Full article

The issue of aircraft icing poses a substantial threat to flight safety. In order to investigate more efficient anti-icing and de-icing technologies, a comparative analysis was conducted on the de-icing characteristics of three types of actuator materials under varying conditions. Initially, experimental research was undertaken to analyze the temperature traits of three actuators under ice-free conditions. Three power densities were chosen for the experiment: 0.170 W/cm², 0.727 W/cm², and 1.427 W/cm². The research findings revealed distinct characteristics: plasma actuators and resistance wire actuators exhibited a strip-like high-temperature region during operation, with well-defined boundaries between the high-temperature and low-temperature zones, whereas ceramic-based semiconductor actuators showcased a uniform high-temperature region. As energy consumption rose, the thermal equilibrium temperatures of all three types tended to converge, with resistance wire actuators operating at 1.427 W/cm², showing the highest temperature rise rate at that power density. Subsequently, experimental research was carried out on the de-icing performance of three actuators under icing conditions at a specific power density. Following 120 s of de-icing, the ice layer covering the surface of the plasma actuator completely melted, forming a cavity. Conversely, the ice layer on the ceramic-based semiconductor actuator remained partially intact in a strip shape. Ice deposits were still visible on the surface of the resistance wire actuator. This observation highlights the remarkable de-icing speed of the plasma actuator. The propulsive force of plasma generated on the fluid inside the ice layer enhances heat transfer efficiency, thereby accelerating the de-icing process of the plasma actuator at the same power density. The analysis of the de-icing performance of these three novel types of actuators establishes a robust groundwork for exploring more effective aircraft de-icing methods. Furthermore, it furnishes theoretical underpinning for the advancement of composite anti-icing and de-icing strategies. Full article

In order to improve the preparation efficiency, quality stability, and large-area preparation of superhydrophobic thin films, a roll-to-roll continuous micro–nano imprinting method for the efficient preparation of superhydrophobic polymer films is proposed. A wear-resistant mold roller with hierarchical microstructure is prepared by wire electrical discharge machining (WEDM). The rheological filling model is constructed for revealing the forming mechanism of superhydrophobic polymer films during continuous micro/nano imprinting. The effects of imprinting temperature, rolling speed and the surface texture size of the template on the surface texture formation rate of polymer films are analyzed. The experimental results show that, compared with other process methods, the template processed by WEDM shows excellent wear resistance. Moreover, the optimal micro/nano imprinting parameters are the mold temperature of 190 °C (corresponding film temperature of 85 ± 5 °C), rolling speed of 3 rpm and roller gap of 0.1 mm. The maximum contact angle of the polymer film is 154°. In addition, the superhydrophobic polymer thin film has been proven to have good self-cleaning and anti-icing performance. Full article

The contactless interrogation of an inductive sensor (IS) for conductive target detection is presented. The IS comprises a solenoidal coil of copper wire wrapped around a plastic pipe which is connected to a series capacitor to form an LC circuit resonating at the frequency f_r. A conductive target placed at different positions inside the pipe modifies the inductance of the coil, and in turn, f_r. An external interrogation coil (IC) electromagnetically coupled to the IS allows the f_r to be read through a contactless interrogation technique. The approach has been tested by varying both the position of a lead sphere adopted as the target and the interrogation distance d between the IS and IC. Without the sphere, the LC circuit has f_r0 = 2.51 MHz. The target sphere has been detected at up to |x| = 7.5 mm from the center of the IS coil with a frequency variation ∆ f_r = 180 kHz at x = 0. Full article

A digital twin is recognized as a pivotal technology in a new type of power system monitoring as it provides an effective method for monitoring the vibration caused by ice shedding in overhead transmission lines. The digital twin model differs from traditional models in that it has the characteristics of precise mapping and real-time simulation. These emerging characteristics lead to urgent updating of the existing modeling approaches. Therefore, the current study proposes a dynamic digital twin modeling method for transmission line ice-shedding systems. In this approach, an analytical solution for conductor deicing oscillation is proposed to describe the span and tension unchanged in any time period and then segmented and iteratively corrected with measured time-varying parameters to implement real-time simulation functionality. A dynamic geometric model for transmission lines is proposed based on the Unity3D platform. In addition, a human-computer interaction visualization platform is proposed to display twin data, with the objective of realizing precise mapping of real transmission lines. Finally, an application of this systematic approach to continuous three-span wire demonstrates the feasibility and effectiveness of the proposed approach. Full article

Wire icing is a prevalent challenge in both industrial and scientific domains, and it is widely acknowledged that terrain and water vapor are significant contributing factors in the formation of wire icing. Consequently, the identification of terrains that are prone to inducing water vapor uplift serves as the scientific foundation for predicting ice accumulation on power lines. Yunnan Province, a mountainous province in China, features a large elevation difference. In winter, this region is prone to wire, pole and tower icing, which can affect power transmission and cause economic and property losses. Therefore, it is necessary to conduct research on the identification of typical terrain patterns in this region. In previous terrain studies, more attention has been focused on slope and aspect, watershed analysis and terrain profile analysis. When the purpose of the terrain identification is to analyze which terrains are more prone to collecting water vapor, we hope to obtain slightly larger terrain blocks and analyze the water vapor sources for different terrains in order to identify typical terrains that are conducive to icing formation. A new technology for identifying terrain patterns based on the K-means clustering method is proposed in this study to explore the typical terrain in Yunnan province. Additionally, the influences of different terrain patterns on water vapor movement are also analyzed. The results indicate that the typical terrains in Yunnan are “Valley-Air Channel”, “Topographic Uplifting”, “Ravine”, “Mountain Pass” and “Alpine Divide” patterns. The results show that the identified typical terrain is consistent with observations from satellite images, which verifies the effectiveness of this identification method. Among these five typical terrains, the “Valley-Air Channel”, the “Topographic Uplifting” and the “Mountain Pass” terrains are prone to collecting water vapor and forming ice cover. The “Alpine Divide” terrain is also prone to accumulating water vapor on both sides to form ice cover. The identified typical terrain demonstrates that typical terrain patterns near water bodies are more prone to the occurrence of wire, pole and tower icing because these areas are abundant in water vapor, and the extensive water vapor is easily condensed under the effects of terrain uplifting and cooling. In these key areas, existing wires and towers, as well as those to be constructed in the future, deserve our special attention. Full article

Carbon fiber heating technology has been widely used in pavement surfaces in practical engineering projects as an environmentally friendly, efficient, and safe ice melting technique. However, the current design of carbon fiber-heated pavement focuses primarily on the ice melting effect while neglecting the crucial mechanical performance evaluation. Therefore, this study aims to investigate the temperature and thermal strain distributions of concrete pavement through model tests and develop a corresponding three-dimensional numerical model to analyze the temperature stress field distribution of carbon fiber-heated pavement. The accuracy of the numerical model is verified by comparing the model test results with the numerical analysis results. The numerical model test results indicate that the maximum compressive stress near the carbon fiber wire is 4 MPa, while the maximum tensile stress between the two carbon fiber wires is 1 MPa. According to the design standard for highway cement concrete pavement, the temperature stress induced by temperature change is significantly lower than the design value of the material’s inherent strength. In addition, a linear relationship between the depth and temperature gradient affecting temperature stress is observed after establishing a correlation between the temperature gradient and temperature stress. The findings of this study can provide valuable insight into the design of carbon fiber-heated concrete pavements. Full article

In integrated circuit (IC) design for advanced manufacturing processes, iterative improvement processes are an approach commonly used for improving design quality, particularly for low-energy, high-frequency circuits. Layout-dependent effects (LDEs) affect IC design and fabrication, resulting in differences in circuit functionality and performance in presimulation versus postsimulation. These differences can greatly increase the length of design iteration cycles. Foundries have attempted to accelerate the iterative design process by providing process design kit libraries to IC designers. However, these kits can neither fully mitigate the negative affect of LDEs on design for manufacturability (DFM) nor eliminate the difference between presimulation and postsimulation results. To address this problem, this study proposed a novel algorithm-based design process in which an IC designer can use layout parasitic extraction to extract the DFM parameters of all components in a circuit prior to the routing process; these parameters include netlists that describe the internal connectivity of components as well as their interconnectivity with other components. Accordingly, the IC designer can determine the effects of DFM parameters on the circuit and modify them in advance if necessary. When the LDEs generated by device placement have been confirmed to not affect circuit properties, physical verification of the routing of metal wires in the IC layout can be performed. In this verification, postsimulations only need to focus on problems regarding the wire loading and timing effects of metal routing. The proposed design process is useful for mitigating LDEs in IC design and considerably reduces the time required for iterative improvement processes. Specifically, this study provides a method of enhancing design iteration cycles and provides guidelines for analyzing factors that hinder IC device functionality and performance. In sum, various problems can be resolved by separately extracting the DFM parameters associated with LDEs and parasitic parameters associated with routing. Full article

The superconducting joints of superconducting in situ MgB₂ wires have been of great interest since the first MgB₂ wires were manufactured. The necessity of joining fully reacted wires in applications such as NMR brings complexity to the methodology of connecting already reacted wires sintered under optimised conditions via a mixture of Mg + 2B and subsequential second heat treatment to establish fully superconducting MgB₂ joints. Some of the data in the literature resolved such a procedure by applying high cold pressure and sintering at a low temperature. A topical review publication did not address in depth the question of whether cold sintering is a potential solution, suggesting that hot pressing is the way forward. In this paper, we discuss the potential joint interfacial requirements, suggesting a thermo-mechanical procedure to successfully form a superconductive connection of two in situ reacted wires in the presence of Mg + 2B flux. The critical current at 25 K of the researched junction achieved 50% I_c for an individual in situ wire. Full article

Brillouin optical time domain reflectometry (BOTDR) detects fiber temperature and strain data and represents one of the most critical ways of identifying abnormal conditions such as ice coverage and lightning strikes on optical fiber composite overhead ground wire (OPGW) cable. Existing BOTDR extracts brillouin frequency shift (BFS) features with cumulative averaging and curve fitting. BFS feature extraction is slow for long-distance measurements, making realizing real-time measurements on fiber optic cables challenging. We propose a fast feature extraction method for block matching and 3D filtering (BM3D) + Sobel brillouin scattering spectroscopy (BGS). BM3D takes the advantage of non-local means (NLM) and wavelet denoising (WD) and utilizes the spatial-domain non-local principle to enhance the denoising in the transform domain. The global filtering capability of BM3D is utilized to filter out the low cumulative average BGS noise and the BFS feature extraction is completed using Sobel edge detection. Simulation verifies the feasibility of the algorithm, and the proposed method is embedded in BOTDR to measure 30 km of actual OPGW line. The experimental results show that under the same conditions, the processing time of this method is reduced by 37 times compared to that with the 50,000-time cumulative averaging + levenberg marquardt (LM) algorithm without severe distortion of the reference resolution. The method improves the sensor demodulation speed by using image processing technology without changing the existing hardware equipment, which is expected to be widely used in the new generation of BOTDR. Full article