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PDMS-assisted transfer printing has been widely applied in the patterning and device integration process of optoelectronic thin films. However, a traditional transfer method is not suitable for nanomaterials. This is due to the generally low adhesion between nanomaterials and rigid substrates because of the incomplete contact between them caused by the irregular geometric shape of nanomaterials, which is crucial for successful transfer. Here, we introduce a simple and low-cost technique named "ice glue-assisted transfer printing" as a solution to overcome the limitations of the previous method. Benefiting from the ease of reaching the triple point temperature of water, controllable transfer printing of nanomaterials using PDMS stamps can be achieved by utilizing the differences in the mechanical properties of water in different phase states. The transfer characteristics of PDMS stamps to different nanomaterials were investigated, especially in terms of transfer amount and pattern accuracy. The results indicate that, for hydrophobic nanomaterials such as nanocarbon black (NCB), ice-assisted transfer printing can transfer the majority of nanomaterials to the target substrate from the PDMS stamp, whereas, for hydrophilic nanomaterials such as silver nanowires, the complete transfer can be achieved. Most importantly, experimental results also show that water amount and post-processing temperature have a significant impact on the accuracy of transfer printing patterns. Based on this, condensation pretreatment was proposed to introduce an ultra-thin ice layer on the target substrate surface, thereby achieving high-precision patterned transfer printing. Finally, shrinkage transfer printing was proposed to improve the pattern accuracy via prestretching the PDMS stamp, which was successfully applied to the preparation of ultrafine metal wires based on the nanoconductive carbon templated area-selective electroplating method. [ABSTRACT FROM AUTHOR]

One-dimensional copper sulfide (CuS) wires were realized by the acrylamide-assisted hydrothermal process using Cu(NO3)2 and thiourea (NH2CSNH2) as reactants at 100 °C. A copper sulfide/carbon nanotube (CNTs) composite was fabricated as a similar method with the addition of CNTs. The samples are characterized by XRD, SEM, TEM, and Raman scattering spectra, respectively. The influence of reaction temperature and amine on the morphologies of CuS nanocrystals was investigated. As anode materials for sodium-ion batteries, the electrochemical studies show that the CuS/CNT composite electrode delivers a higher reversible capacity of 428.1 mA h g−1 at 0.1 A g−1 for the 100th cycle, because CNTs can be a conductive agent to provide a fast path for electron transportation, compared with the bare CuS wires (280 mAh·g−1 after 100 cycles). The synthesis results indicate that the amine-directed synthesis strategy of copper sulfide could be extended for the preparation of other metal sulfide nanostructures. Further, the incorporation of the CNT matrix into the copper sulfide is an effective approach to enhance the electrochemical performance of CuS. [ABSTRACT FROM AUTHOR]

Yttrium barium copper oxide (YBCO) is used for special applications in linear generators because of its excitation loss, lower weight, and higher efficiency. These qualities enable the compound to operate better than the conventional copper wire coil in the stator unit of the linear generator. However, the continuous use of YBCO in linear generators has a fundamental challenge that affects industrial production and material stability after prolonged use. This paper seeks to sustain the adoption of YBCO by improving its quality for linear generator applications. The yttrium cuprates modification (YBYbCO) was synthesized using the solid-state reaction technique by doping YBCO with ytterbium. The crystalline structure, microstructural pattern, and stability of the new sample were adequately measured and found to be structurally stable to ensure durability. It was reported that applying YBYbCO in the linear generator would lead to a 200% increase in energy generation. The higher number of particles and lower individual particulate resistance enable it to withstand chemical pressure, thereby prolonging the lifespan of the linear generator. [ABSTRACT FROM AUTHOR]

To investigate the problems of overload and excessive thermal insulation associated with building electrical fires caused by wires, a theoretical model of wire heat transfer is established, and the pyrolysis and combustion phenomena of the insulation layer are analyzed. The results showed that the temperature evolution of the wire underwent three stages: constant temperature, insulation heating, and high‐temperature pyrolysis. The insulation layer experiences bulging, exhausting, carbonization, dripping, and burning in sequence, and insulation layer dripping requires at least 160 A of current. As the current increases, the temperature increase rate of the wire increases gradually, and the fusing time of the wire gradually decreases. Under the same current, 160°C is the turning point at which the temperature increases. The temperature increase rate of the copper wire is greater than that of the aluminum alloy wire, and the temperature increase rate of the bare wire is greater than that of the insulated wire. The fusing time of an aluminum alloy wire is less than that of a copper wire, and the fusing time of a bare wire is less than that of an insulated wire. The research results provide theoretical guidance for the prevention and investigation of building electrical fires. [ABSTRACT FROM AUTHOR]

Electrical insulation is a critical component in electrical machines. The performance of the insulation system can be adversely affected by operating conditions that induce aging. Assessing the impact of environmental stresses is essential for predicting the failure of electrical insulation. Predicting maintenance to prevent service interruptions caused by insulation breakdown is a key objective. For type I insulating systems used in low-voltage and low-power rotating electrical machines, it has been demonstrated that partial discharges (PDs) are a contributing factor to electrical insulation breakdown. In fact, these insulating systems are not able to withstand the action of PD activity. The inception and evolution of PD activity is an indication of the poor conditions of the electrical insulating system, and this activity can be produced by the electronic power supply. The progressive reduction in partial discharge inception voltage (PDIV) is attributed to the deterioration of insulation properties induced by operational stresses. This study aims to evaluate and compare the effects of thermal stress on various types of enameled wires by collecting the PDIV values over time. In this paper, the authors analyze some particular effects of thermal stress as an aging factor. During the tests, an electrical stress was applied, which acted as a conditioning stress rather than one capable of producing degradation phenomena, as it was not high enough to initiate PD activity. In this research study, twisted pairs prepared from copper wires were evaluated. These wires were coated with various types of enamel and belonged to the thermal class of 200 °C. The samples were subjected to thermal aging tests at different temperatures. An electrical conditioning stress was also applied during all the tests and pertained to the same voltage, amplitude and frequency. The PDIV value pertaining to each sample was regularly measured to monitor its evolution over time. [ABSTRACT FROM AUTHOR]

In this study, a technique to estimate the thermal properties of a suspended copper wire using the 3ω method was proposed and its operation was demonstrated. This approach used a digital multimeter with a large measurement buffer to implement a procedure in which an appropriate window function and a discrete Fourier transform (DFT) were applied. This significantly reduces the noise level to a few nV, especially in the lower-frequency regions (less than 1 Hz), even if a longer measurement time is required. The third-harmonic voltage signal containing the thermal properties information for the 3ω method was clearly observed with a high signal-to-noise (S/N) ratio, and the thermal conductivity and diffusivity were estimated from 60 K to 300 K from the current frequency dependence of the third-harmonic voltage. The thermal conductivities of the copper wire were determined to be 423.0 and 385.9 W/mK at 100 and 300 K, respectively. Specific heat was calculated from thermal conductivity and diffusivity, and the Debye temperature was estimated to be 346 K from the temperature dependence of the specific heat. These values were in good agreement with previous research. Measurement of thermal properties using a digital lock-in amplifier with identical configuration resulted in overestimation of thermal conductivity in entire temperature regions owing to a low S/N ratio throughout the analysis of the DFT. The technique based on DFT with a window function is therefore more reliable for detecting the third-harmonic voltage in the low-frequency region of less than 1 Hz because it obtains a high S/N ratio. [ABSTRACT FROM AUTHOR]

This paper presents an innovative experimental method for studying the evolution and energy output characteristics of underwater explosion bubbles. We independently constructed an experimental testing system for underwater electrical wire explosions (UEWE), in which electrodes connected to a metal wire serve as the load, and underwater explosions are initiated through instantaneous high-voltage discharge. By varying the diameter of the metal wire and configuring parallel wire arrays, we analyzed and discussed the explosion characteristic parameters and the current–voltage (I–V) signals under different conditions. The maximum bubble radius of the underwater metal wire explosion was compared with the corresponding equivalent explosive simulation results, and a numerical model for underwater metal wire explosion equivalent to explosive detonation was established. Subsequently, we discussed the characteristics of bubble generation and evolution under various conditions, clarifying the similarities and differences between wire explosions and explosive detonations. On this basis, we explored the propagation laws of shock waves and secondary pulsation waves (SPW) under different conditions. We also calculated and analyzed energy output characteristic parameters, such as shock wave energy and bubble energy. The results indicate that there are significant differences between copper wire and aluminum wire loads in UEWE. For copper wires with a diameter greater than 0.4 mm, the shock wave overpressure peak value significantly decreases, while for aluminum wires with a diameter greater than 0.5 mm, it slightly decreases. Both metals exhibit similar trends in parallel wire arrays, with the shock wave overpressure peak value initially increasing and then decreasing as the number of wires increases. Unlike underwater explosive detonations, the SPW peak value in UEWE may exceed that of the shock wave. For single wires, the SPW peak value of copper wires is generally higher than that of aluminum wires, but in wire arrays, the trend is reversed. The multi-wire parallel connection can improve the energy conversion efficiency of the shock waves. However, for bubble energy, under all conditions, a single aluminum wire with a diameter of 0.5 mm produced the maximum bubble energy, reaching 1023.1 J. These findings provide new insights into the energy features of UEWE. [ABSTRACT FROM AUTHOR]

Copper-based composites with different quality scores for NbC particle reinforcement were prepared by spark plasma sintering. The microstructure of the copper-based composites with different NbC contents was studied, and the influence of NbC content on the density, electrical conductivity and hardness of the copper-based composites was investigated. The results showed that the electrical conductivity of the Cu-4 wt% NbC composite material after spark plasma sintering was 70.4% IACS (IACS is the percentage of the ratio of the conductivity of the sample to a certain standard value. The annealed copper wire with a density of 8.89 g cm−3, a length of 1 m, a weight of 1 g and a resistance of 0.15328 Ohm is used as this certain standard value), and the hardness was 63.4 HV. The strengthening mechanisms of NbC in copper-based composites were dispersion strengthening and fine crystal strengthening. During the spark plasma sintering process, the Zener pinning of NbC particles slowed grain boundary migration, which effectively prevented the pure copper grains from growing and thus enhanced the pure copper. The proportion of NbC in the raw powder was changed to adjust the proportion of fine crystals, and then the mechanical properties of the material were adjusted. Additionally, NbC caused a preferred orientation of pure copper and reduced some of the stress in the material. [ABSTRACT FROM AUTHOR]

Power transmission and transformation are important parts of power distribution, which is increasingly necessary in modern society; this is particularly important due to the green transition. Consequently, increasing the efficiency of power transformers is a priority to improve the economic and environmental aspects of electrical transformation. Lightweight graphene coatings on transformer wire rods represent a valid solution improving thermoelectrical performances. In this work, a graphene coating was applied by electrophoretic deposition to copper wire rods through a sustainable deposition bath, studying the impact of the deposition current density. The morphology of the coated wire rods, the adhesion of the coating to the substrate, and their thermoelectric properties were evaluated. This work demonstrates the application of EPD to coat copper wire rods with graphene, resulting in a 5.58% reduction in electrical resistivity and an 88% enhancement in thermal performance. In addition, relationships between coating performances and deposition parameters were highlighted. An analysis of variation (ANOVA) confirmed the main role of the current density on the examined outputs. [ABSTRACT FROM AUTHOR]

Accurately calculating winding losses has always been a significant challenge in the design of large-capacity medium-frequency transformers. This paper presents an accurate design algorithm for calculating the winding losses of a large-capacity medium-frequency distribution transformer. First, the peculiarities of winding losses in medium-frequency distribution transformers are analyzed. Various commonly used winding conductor types for medium-frequency transformers are introduced. The mechanisms of and differences between AC and DC winding losses in medium-frequency transformers are explained, and an effective analytical method for calculating the AC-to-DC resistance ratio is provided. Finally, the analytical calculation results of different types of winding losses are compared with those obtained through finite element simulations and experimental methods applied to a real transformer prototype. The discrepancies between the analytical results and those obtained using the other two methods were found to be within acceptable error margins, thereby validating the accuracy and effectiveness of the proposed algorithm. [ABSTRACT FROM AUTHOR]

Electromagnet coil is mainly composed of enameled wire which wound on the coil skeleton, and the function is to convert the electrical signal into a magnetic signal, which is a very important electric‐magnetic conversion element. When designing the electromagnet coil, usually only the total winding turns and winding inner diameter can be calculated, and the specific design parameters such as the diameter of copper wire, paint layer thickness, and winding turns of each layer can only be selected through experience, indicating that the design method should be improved. In addition, the unreasonable design parameters will seriously affect the power consumption and cost of coil, so it is highly necessary to improve the optimization design method. In order to solve the above problems, an optimization design method for DC electromagnet coil is proposed in this paper. This method simultaneously takes into account both power consumption and manufacturing cost, and can achieve the optimal matching of design parameters. In this paper, the structure of electromagnet coil is introduced, and the theoretical calculation model of resistance is improved first. Then, according to the expected requirements of electromagnet coil for steady current, the optimization design method is proposed and the optimal design parameters are obtained. Finally, the effectiveness of the proposed optimization design method is verified by the test platform of electromagnet coil. The results show that the electromagnet coil designed by the optimization design method fully meets the expected requirements. The relevant research results can provide reference for the optimization design of electromagnet coil, which has a certain engineering practical value. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Expendable Bathythermographs (XBTs) are oceanographic instruments that fall through the ocean's water column and measure ocean temperature with depth. In many instances, however, XBTs continue to record temperature after they impact the seabed. Here we show evidence that XBTs produce unique temperature responses when they impact the seabed that depend directly on seabed physical properties. Specifically, standard‐use XBTs (e.g., T‐4s and T‐5s), when deployed above a mud‐rich seabed, require significant time (tens of minutes) to equilibrate to steady‐state seafloor temperatures after seabed impact. In contrast, XBTs deployed above sand‐rich sediments equilibrate to seabed temperatures rapidly (<5 min) after seafloor impact. One explanation for this difference in temperature response is that XBTs deployed above mud‐rich sediment penetrate into low permeability marine muds that jacket the XBT, where diffusive heat flow dominates. Both observations and numerical modeling results support the hypothesis that XBTs impacting muddy seafloors exhibit slow, diffusion‐dominated heat flow, while XBTs impacting harder, sand‐rich seabed sites exhibit rapid seafloor temperature equilibration, consistent with advection‐driven heat flow and little if any XBT seabed penetration. Given that >644k XBT measurements exist publicly (via the National Oceanographic and Atmospheric Administration website), and >74,000 XBTs record temperatures post seabed impact, we suggest that XBT data represents a large, low‐cost, and currently untapped data set for characterizing seabed physical properties globally. Plain Language Summary: Expendable Bathythermographs (XBTs) are hand‐deployable torpedo‐shaped single‐use thermistors that measure ocean temperature with depth by being dropped from a ship and transmitting temperature values along a thin copper wire that unspools from the XBT as it falls. When the XBT impacts the seabed, it often continues recording temperature, however, researchers focused on ocean temperature‐depth measurements typically ignore these data. Here, we take a first‐look at XBT temperature response after seabed impact for two different seabed settings: (a) a soft muddy seabed where XBTs may penetrate the seafloor, and (b) a hard, sandy seabed where the XBT likely fails to penetrate. We find that XBTs that impact a soft, muddy seabed show significantly slower rates of change in temperature after impact compared to XBTs that impact hard sandy sediment, consistent with numerical modeling temperature predictions for XBTs impacting and penetrating mud but failing to penetrate sand. XBT temperature response after seabed impact may therefore provide a crude but efficient tool for rapidly assessing seabed physical properties (such as seabed hardness). With more than 74,000 publicly available XBT seabed temperature measurements available in every ocean, XBTs may provide a useful tool for roughly characterizing seabed properties globally. Key Points: XBT temperature response after seabed impact varies depending on seabed physical propertiesXBT rates of temperature change after seabed impact are nearly an order of magnitude lower in mud versus sand due to XBT burial in mudXBTs may provide a crude but useful, rapid tool for assessing seabed physical properties globally [ABSTRACT FROM AUTHOR]

Nanocrystalline NiFe thin films of 11 μm thickness have been deposited on Cu wire using an electrochemical technique in galvanostatic mode with a sodium gluconate (SG) additive in the plating solution. The SG concentration is systematically varied from 0 g/L to 80 g/L, which results in a substantial enhancement in the soft magnetic characteristics and magnetoimpedance (MI) ratio of the plated wire across a broad frequency spectrum, specifically attributed to the optimal inclusion of SG at 55 g/L. The observed improvements in magnetic softness and MI ratio are linked to the reduction in crystalline size and surface roughness and modifications in the microstructure influenced by the SG additive in the electroplating bath. Furthermore, an equivalence between experimental impedance data and the theoretical framework based on the analytical model of circumferential permeability is outlined to extract the material parameters of the permalloy magnetic films. These extracted parameters play a pivotal role, enabling a comprehensive understanding of the variation in the MI ratio as well as circumferential permeability of the thin films as a function of the SG additive concentration in the plating bath. The intricate association observed between the MI ratio and circumferential permeability suggests that the amplification of the MI ratio resulting from the inclusion of SG is linked primarily to enhancements in circumferential permeability and the incorporation of magnetic softness. Thus, the present work offers both a theoretical and experimental framework for future research in advanced MI-based devices for magnetic sensing applications. [ABSTRACT FROM AUTHOR]

This study aims to assess the compatibility of various e-thermal fluids for immersion cooling in battery electric vehicles through a copper wire resistance corrosion test. The tested fluids include a polyalphaolefin, diester, mineral oil API G-III, transformer oil, and a fully formulated dielectric coolant. The test was conducted at 130 °C for 336 h, and the resistance of the copper wires was monitored in vapor and oil phases. By comparing the resistance variation and analyzing portions of the wires through scanning electron microscopy, it was found that the vapor phase of PAO and diester in one of the tests exhibited significant corrosion, while the dielectric coolant showed minimal corrosive effects, implying better compatibility. These results provide insights into the corrosion behavior and compatibility of the fluids with copper, which are essential for selecting suitable dielectric fluids for immersion cooling applications in electric vehicles. [ABSTRACT FROM AUTHOR]

Vortex flow characteristics in a reservoir and horizontal water intake have been predicted by using regression models in this numerical research. In this paper, three standalone machine learning models - Random Forest (RF), K-nearest neighbours (KNN), Gradient Boosting (GB) - and a proposed hybrid model based on Lévy Jaya Algorithm (LJA) and GB (LJA-GB) are employed to estimate the effect of trash racks on flow properties at power intakes. The experimental data which are prepared for the proposed study in this paper were obtained through a rectangular laboratory tank 8.3m³ with various submergence depths and Froude numbers on nine trash racks with 63.7%-84.1% opening, made out of 2, 2.5, 4, and 6 mm thick copper wire. The outcomes revealed that the proposed LJA-GB model shows the best overall performance among the four models used for estimation. Thus, the LJA-GB model has the lowest mean absolute error (MAE) (0.3344), mean squared error (MSE) (0.1784), and root mean squared error (RMSE) (0.4223) values and highest R-squared (R²) (0.9899) and Willmott's index (WI) values (0.9508) in the testing stage metrics for Vxy/Vi estimation and MAE (0.0061), MSE (0.0001), RMSE (0.0073), R² (0.9971), WI (0.9727) for Nt estimation. Whereas the RF and KNN models exhibited poor performance in both stages of estimation. [ABSTRACT FROM AUTHOR]

Purpose: A previously published method for MRI‐based transfer function assessment makes use of the so‐called transceive phase assumption (TPA). This limits its applicability to shorter leads and/or lower field strengths. A new method is presented where the background electric field is determined from both B1+$$ {\mathrm{B}}_1^{+} $$‐ and B1−$$ {\mathrm{B}}_1^{-} $$‐field distributions, avoiding the TPA and making it more generally applicable. Theory and Methods: These B1$$ {\mathrm{B}}_1 $$‐distributions are determined from a spoiled gradient echo multiflip angle acquisition. From the separated B1$$ {\mathrm{B}}_1 $$‐components the background electrical field and the induced current are computed. Further improvement is achieved by recasting the B1$$ {\mathrm{B}}_1 $$‐field model as a "magnitude squared least squares" problem. The proposed reconstruction method is used to determine transfer functions of various copper wire lengths up to 40 cm inside an elliptical ASTM phantom. The method is first tested on EM‐simulated data and subsequently phantom and bench measurements are used to determine transfer functions experimentally. Results: In silica reconstructions demonstrate the validity of the proposed B1$$ {\mathrm{B}}_1 $$‐field model resulting in highly accurate reconstructed B1$$ {\mathrm{B}}_1 $$‐fields, currents, incident electric fields and transfer functions. The experimental results show slight deviations in the field model, however, resulting transfer functions are accurately determined with high similarity to simulations and comparable to bench measurements. Conclusion: A more generally applicable method for MRI‐based transfer function assessment is presented. The proposed method circumvents phase assumptions making it applicable for longer objects and/or higher field strengths. Additional improvements are implemented in the B1$$ {\mathrm{B}}_1 $$‐mapping method and the solution algorithm. [ABSTRACT FROM AUTHOR]

Aquasols produced by exploding copper wires represent complex systems in which identifying individual colloidal components poses challenges due to broad and multimodal size distributions and varying shares among oxidation states. To evaluate the reproducibility of copper wire explosion, the size distribution of metallic and oxidized colloidal components within the 10–300 nm diameter range was assessed. Classification of each individual particle into bins according to size and chemical composition was accomplished by reconstructing the recorded optical extinction spectra of three sols produced under identical conditions as the weighted sum of the extinction spectra of individual copper and copper-oxide particles, computed using Mie theory. Our spectrophotometry-based component analysis revealed differences in particle number concentrations of the mainly oxidized nanoparticles, corresponding to deviations observed in the ultraviolet portion of the extinction spectra. Notable uniformity was observed, however, in the number of metallic fine particles, consistent with agreement in spectral features in the visible range. Regarding mass concentration, practically no differences were observed among the three samples, with nano-to-fine ratios of copper particles agreeing within 0.45%. Despite the complex processes during explosion leading to limited reproducibility in the ratio of different copper oxidation states, very good reproducibility (54.2 ± 0.7%) was found when comparing the total copper content of the samples to the mass of the exploded copper wire. [ABSTRACT FROM AUTHOR]

A proton exchange membrane increases the electrical performance of a microbial fuel cell (MFC). New inexpensive materials should be sought, especially in a constructed wetland microbial fuel cell (CW-MFC). Here, in a laboratory-scale system of five CW-MFCs, wet clay, wet earth or mud, and non-woven cloth were used as inexpensive separators with long-term stability. The five CW-MFCs were planted with Typha latifolia, fed with synthetic wastewater, and packed with natural porous material. Graphite felt was used as electrodes and the experimental system had a hydraulic residence time of 3 days, operating under shade and natural conditions of temperature and light. Electrodes were connected to current collectors (copper wire) and to an external resistance, with a change every 20 days, starting in open-circuit and following with 20000, 18000, 15000, 10000, 5600, 1000, 560, and 10 Ω. These laboratory-scale CW-MFCs reduced concentrations of nitrates, ammonium ion, and sulfates without inhibiting electricity production. Microbiological analyses indicated that anaerobic, facultative, aerobic, and denitrifying bacteria may have caused these reductions. The reactor with the live plant and with the wet earth or mud separator achieved the highest production of electricity (22.6 mW/m2), and may be worth further attention. [ABSTRACT FROM AUTHOR]

An effective approach to high-sensitivity magnetic field detection under low-frequency excitation by soft magnetic ribbons and a rectangular solenoid is proposed and certificated. The solenoid wound by nonmagnetic copper wire is located at the geometric center region of the soft magnetic ribbons that act as the magnetic core. The proposed magnetic sensor utilizes the nonlinear magnetization of soft magnetic ribbons and the magneto-inductive effect and proximity effect of the solenoid, exhibiting significant impedance variation at a relatively low frequency. The impedance ratio and impedance sensitivity of the prototype reaches the maximum value of 5630% and 570% Oe−1 at 500 kHz, which is far superior to the conventional giant magneto-impedance (GMI) magnetic sensor and planar coil laminated GMI magnetic sensor. The investigation indicates the fabricated magnetic sensor with optimal dimension parameters can provide a sensitivity of 3329 mV Oe−1 at 500 kHz. More importantly, the proposed prototype is particularly suitable for micromachining, providing the possibility for manufacturing high-sensitivity micro-magnetic sensors. [ABSTRACT FROM AUTHOR]

The thermal characterization of power devices is an inevitable task in the industry. Thermal transient testing is one of the major tools for this characterization, as it is not only capable of giving information about the actual thermal parameters but may also reveal the root cause of potential device failures. The testing may occur on single packages or modules on a dedicated standard test bench, or "in situ", in an actual assembly. The testing process itself is very fast in both cases, on the order of seconds, but the transient measurement needs to be preceded by a calibration step to determine the temperature dependence of a temperature-sensitive parameter (TSP) of the semiconductor device. This may require a long time, as the device has to be measured at many stabilized temperatures, which in the case of power devices may take hours. It also has to be considered that, especially in "in situ" measurements, reaching the highest device temperatures of power devices may even damage other parts of the surrounding electronics. Moreover, the temperature distribution inside a module will be different at calibration time than during operation with the same junction temperature, as bond wires and copper traces do not reach the chip temperature in the latter case. This paper presents a methodology that can be used to replace the lengthy measurement of one parameter at many temperatures with a fast single I–V characteristics measurement at room temperature. Physics-based calculations assign a unique temperature-sensitive parameter to each item of interest in the system. After the presentation of the theoretical background, the usability of the method is demonstrated by verifying measurements on silicon power devices. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) of copper through laser‐based processes poses challenges, primarily attributed to the high thermal conductivity and low laser absorptivity of copper powder or wire as the feedstock. Although the use of copper salts in vat photopolymerization‐based AM techniques has garnered recent attention, achieving micro‐architected copper with high conductivity and density has remained elusive. In this study, we present a facile and efficient process to create complex 3D micro‐architected copper structures with superior electrical conductivity and hardness. The process entails the formulation of an ion‐exchangeable photoresin, followed by the utilization of digital light processing (DLP) printing to sculpt 3D hydrogel scaffolds, which were transformed into Cu2+‐chelated polymer frameworks (Cu‐CPFs) with a high loading of Cu2+ ions through ion exchange, followed by debinding and sintering, results in the transformation of Cu‐CPFs into miniaturized copper architectures. This methodology represents an efficient pathway for the creation of intricate micro‐architected 3D metal structures. [ABSTRACT FROM AUTHOR]

A wearable microstrip UWB antenna employing jeans textile material as a substrate is proposed and analyzed. Two variants of conducting material comprising copper tape and copper wire of thickness of 0.1mm are utilized as patch and ground. The overall antenna volume is 50 × 50 × 1 mm3 with an impedance bandwidth of 24.13 GHz (0.87 to 25 GHz) and a peak gain of 10.93 dB at 14.80 GHz. The design comprising an annular ring structure with connecting feed at the optimized location has been analyzed and optimized using FEM based ANSYS High-Frequency Structural Simulator. The low values of Specific Absorption Rate (SAR) 1.23W/kg, 1.26W/kg, and 0.64W/kg averaged over 1-g of tissue for arm, leg, and head respectively at 2.45 GHz validate the antenna design for wearable telemetry applications. The proposed design is also analyzed under different bent radii for wearable applications. Measured results for both prototypes agree well with the simulated results. [ABSTRACT FROM AUTHOR]

A severe Covid lockdown in South Africa may have changed burn patterns due to the downturn of the economy and stay-at-home policies. We describe the volume and type of burn admitted to a tertiary hospital before and during the Covid lockdown. This was a retrospective study from before (April 2019-March 2020) and during (April 2020-March 2021) the Covid pandemic. Patient demographics, burn etiology, and clinical outcomes were described. Logistic regression was used to model associations between burn etiology and the Covid period. Of 544 burns, 254 (46.7%) occurred before and 290 (53.3%, p = 0.051) during Covid. The proportion of electrical burns doubled during Covid n = 20, 32.3% vs n = 42, 67.7%, (p = 0.053) periods. At least half were associated with suspected cable or copper theft. On multivariate analysis, flame burns (OR=2.42, p < 0.001), electrical burns (OR=4.88, p < 0.001), and paying patients (OR=4.21, p < 0.001) were more likely to be associated with the Covid period. Electrical burns doubled during Covid, potentially related to an increase in cable and copper wire theft, a phenomenon described during hard economic times in other settings. More studies to understand this potential relationship are indicated to prepare burn centers during future pandemics and/or economic hardship. • In South Africa the electrical burns doubled during the Covid lockdown. • Cable and copper wire theft may have resulted in the higher electrocution rates. • More research to reduce the risk of electrocution are needed. [ABSTRACT FROM AUTHOR]

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This study investigates the behavior of recycled Reactive Powder Concrete (RPC), made from finely ground recycled raw materials and containing a certain percentage of recycled copper (electrical waste copper wire) and steel fibers. This concrete has a relatively low water-to-binder ratio and is composed of cement, fine aggregate, and ultrafine powders, such as quartz powder and silica fume. The properties of Fiber-Reinforced Reactive Powder Concrete (FR-RPC) containing micro-steel fibers, recycled copper fibers, and a mixture of steel-recycled and copper fibers were investigated. A micro-steel fiber RPC (MF1) was used as a reference mix, having 1% steel fibers by volume with 13 mm length and 0.2 mm diameter. Recycled copper fiber RPC (MF2) was prepared utilizing 1% recycled copper fibers by volume, with a diameter of 0.2 mm and a length of 10 mm. In addition, Hybrid FR-RPC (HFR-RPC) samples were prepared by mixing micro steel fibers and recycled copper fibers in proportions of 0.5-0.5% (MF3), 0.4-0.6% (MF4), and 0.3-0.7% (MF5), respectively. The compressive strength, flexural strength, and splitting tensile strength of these FR-RPC mixes were studied. The results displayed that MF3 achieved slightly lower compressive strength, flexural strength, and splitting tensile strength than MF1 and higher than MF2, MF4, and MF5. Although the mechanical strengths of MF3 were marginally lower than those of MF1, compressive strength, flexural strength, and splitting tensile strength were almost the same. Therefore, copper wire waste fibers can be employed along with steel fibers with excellent results. [ABSTRACT FROM AUTHOR]

In this paper, we focus on the development of a machine for manufacturing needle probes used in the electrical testing of printed circuit board (PCB) in-circuit-test fixtures. Currently, the manufacturing process for needle probes involves manual tasks such as wire threading, soldering, heat shrink tubing application, heat shrink tubing heating, and placing cylindrical terminals into a needle disc. Owing to the time-consuming nature of this production process, automation is proposed for improvement. The system development involves programmable logic controller (PLC) control and pneumatic cylinder mechanisms to replicate the manual wire threading process. Pneumatic grippers are used to position cylindrical terminals and heat shrink tubing. Two stepper motors drive plastic rollers for copper wire extension by a rolling process along V-shaped groove straightening guides, reaching the wire insertion holes on the PCB. A YZ-axis servo stage with clamping fixtures secures the PCB and moves it to the wire insertion holes. Once the copper wire extends through the cylindrical terminal, the threading action for that PCB hole is completed. Subsequently, laser welding joins the cylindrical terminal with the copper wire, and a hot air blower fuses the heat shrink tubing with the cylindrical terminal. Pneumatic grippers grasp the threaded cylindrical terminals. Simultaneously, an XY-axis servo stage with clamping fixtures places the disc into the clamping fixture, moves it beneath the pneumatic grippers, and inserts the cylindrical terminals into the disc. After completion, a few centimeters of copper wire in front of the rollers are cut, marking the completion of the needle placement for that hole on the disc. The combination of PCB hole wire threading and disc hole needle placement constitutes one cycle of the wire threading fixture. The machine repeats this automated sequence until the entire needle probe fixture is produced. [ABSTRACT FROM AUTHOR]

The results of measurements of the frequency dependence of the active resistance of a circular cross-section of aluminum and copper conductors with a various diameter in a wide frequency range from 20 Hz to 2 MHz are presented. Using the skin effect simulation we show that for all types of wires an increased active resistance observed, compared to the theoretical values in the frequency range above 200 kHz, where the skin layer thickness becomes less than 200 μm. This phenomenon may be associated with the manufacturing process of a metal wire by drawing through a die, when defects are formed in the near-surface layer, leading to its increased resistivity. [ABSTRACT FROM AUTHOR]

This study examines the characteristics of the low-voltage MIMO-PLC electric power line channel, which operates within the 2-100 MHz frequency range. The research involved measurements in four different Setups using 2.5 mm copper wires, including phase, neutral, and protective earth wires. These wires were transposed within a conduit, measured in pairs, with variations in the number and lengths of branches, assuming a deterministic modeling behavior of the electric power line. Throughout the experimentation process, essential parameters such as the magnitude of the S21 scattering parameters and VSWR identify frequency ranges suitable for efficient data transmission. The findings suggest remarkable prospects for enhancing PLC communication across MIMO channels. Depending on the combination of cable lines, over 70% of the bandwidth remains available. Additionally, the overall average impedance measured at 77.14 Ω is vital for impedance matching in PLC coupling circuit designs. [ABSTRACT FROM AUTHOR]

AbstractIn this article, we report the design and fabrication of a ‘do-it-yourself’ microfluidic channel with a circular cross-section, created outside a cleanroom facility. In this approach, the fabrication of the channel do not require any chemical etching or lithography steps, making it safe and suitable for small research groups. The channel is fabricated using the soft-lithography method in polydimethylsiloxane (Sylgard® 184). A copper wire with a diameter of 240 µm is used as a mold, and the channel is created using the wire pull-out method. This work also addresses the optimal use of polydimethylsiloxane in channel fabrication, as well as the challenges faced when connecting the microchannel to the outside world via tubing and techniques to overcome them. All simulations were conducted using COMSOL Multiphysics 6.0. The analytical, simulation, and test results, show a good match.

This study explores the design and optimization of thermomagnetic generators with a primary emphasis on enhancing energy efficiency. The core objectives revolve around improving power generation and efficient heat dissipation. We conducted an extensive investigation, systematically varying parameters such as dimensions, coil turns, and material properties, including temperatures and magnetization. At the heart of this research lies the utilization of the variable magnetic susceptibility of ferromagnetic–paramagnetic materials within distinct temperature zones. Gadolinium (Gd) was selected due to its unique Curie temperature (TC) closely aligned with room temperature. The Gd disk's motion serves a dual purpose—acting as a heat conveyor from source to sink and inducing voltages. The synergy between a copper wire coiled around the Gd disk and the magnetic field generated by a permanent magnet (PM) facilitates voltage induction. The dynamic motion of the Gd disk, driven by changes in net forces (permanent magnet force, gravity force, and spring force), powers this energy conversion process. This versatile technique holds promise across various applications, especially in scenarios characterized by significant waste heat, such as engines and solar panels. Our multifaceted optimization approach not only enhances our understanding of thermomagnetic generators but also underscores their potential as sustainable and efficient contributors to energy solutions. [ABSTRACT FROM AUTHOR]

This study compared the Au-Pd-coated copper (CPA) with the micro-alloyed copper wires (MAC) without a coating layer. Results have shown that heat treatment can improve the electrical properties of the wire, but excessive heating can lead to a deterioration in hardness and electrothermal fatigue. In addition, the surface temperature of the wire can be inferred from the Joule heating relationship. The formula derived from the study, T = IV 2.7227 × 10 - 3 + 25 , can be utilized to assess the heating behavior during electrification at room temperature and standard pressure. To validate the accuracy of this formula, this research also compared the oxidation morphology of copper at high temperatures with other reports in the literature. It was found that the Au-Pd-coated copper (CPA) wire begins to dissolve at 0.38 A (370°C) and completely dissolves at 0.42 A (550°C). This phenomenon increases the wire resistance but decreases the fusing current. In comparison, Cu-Ti (CT) micro-alloyed wires showed no deterioration at 0.43 A. In addition, the electrothermal effect causes diffusion in the CPA wire's coating layer and results in poor fatigue life. In conclusion, the CT wire has a longer electrothermal fatigue life and better stability, making it a promising candidate for future copper-based wires. [ABSTRACT FROM AUTHOR]

This paper reports the influence of hydrolytic aging on the rupture voltage of copper wire enameled with polyestermide reinforced by a polyamide imide layer. A large population of samples was put in a climatic chamber regulated at 40°C and 93% relative humidity. The wet aging was carried out until 15000h. Every time of 500h, 80 samples were taken from the climatic chamber and submitted to AC breakdown test. A statistic investigation of breakdown voltage values was done using Weibull model. Scale parameter, shape parameter and confidence intervals are presented. The breakdown voltage changes in function of aging time. The raise is ascribed to the arrangement in the structure of the polymer. While its lowering is assigned to the diminution in the viscosity causing a raise of mean free path of charge carriers. The shape parameter changes versus aging time. The shortening is due to the increase in the size of defects. Whereas its raise is allotted to the arrangement in the structure. TGA shows a variation of the onset temperature and the residue during the aging. The FTIR tests show a weak modification of the spectra. There is no degradation of the insulation, however a change in molecular conformation occurs. The results are analyzed and discussed. [ABSTRACT FROM AUTHOR]

Traditional microstrip antennas have problems with heavy weight and poor gain. In order to reduce the weight of the antenna itself and improve its gain, the preforms of the 3-D woven rectangular hollow structure conformal bearing microstrip antenna (3DWRHS-CB-MA)with different heights were woven from ultra-high molecular weight polyethylene (UHMWPE) filament yarns and copper wires on a common loom through reasonable design. The preform was used as the reinforcement and epoxy resin was used as the matrix, four different heights (2, 4, 6, and 8mm) of 3DWRHS-CB-MA were prepared by vacuum-assisted resin transfer molding (VARTM) process. Finally, the electromagnetic performance was analyzed by high-frequency structure simulator (HFSS) and experimental testing. The results showed that the frequency deviation of the 2 mm height microstrip antenna was minimal; while the 4 mm height microstrip antenna had better gain efficiency and directional diagram compared to others. The 4 mm height microstrip antenna has good radiation performance with a weight of only 35 g which shows that 3DWRHS-CB-MA are potential candidates for future intelligent textile materials and wireless communication fields. Highlights • Weaving with UHMWPE filament yarns and copper wires on common looms. • The preform was used as the reinforcement, and epoxy resin was used as the matrix. • Simulation of electromagnetic characteristics of antennas using HFSS software. • Proving the effectiveness of the electromagnetic simulation model. • Revealing the electromagnetic radiation mechanisms. [ABSTRACT FROM AUTHOR]

This study aims to illustrate the design, fabrication, and optimisation of an ultrasonic welding (UW) machine to join copper wires with non-woven PVC textiles as smart textiles. The study explicitly evaluates UW parameters' impact on heat generation, joint strength, and electrical properties, with a comprehensive understanding of the process dynamics and developing a predictive model applicable to smart textiles. The methodological approach involved designing and manufacturing an ultrasonic piezoelectric transducer using ABAQUS finite element analyses (FEA) software and constructing a UW machine for the current purpose. The full factorial design (FFD) approach was employed in experiments to systematically assess the influence of welding time, welding pressure, and copper wire diameter on the produced joints. Experimental data were meticulously collected, and a backpropagation neural network (BPNN) model was constructed based on the analysis of these results. The results of the experimental investigation provided valuable insights into the UW process, elucidating the intricate relationship between welding parameters and heat generation, joint strength, and post-welding electrical properties of the copper wires. This dataset served as the basis for developing a neural network model, showcasing a high level of accuracy in predicting welding outcomes compared to the FFD model. The neural network model provides a valuable tool for controlling and optimising the UW process in the realm of smart textile production. [ABSTRACT FROM AUTHOR]

Copper powder and copper wire mesh were used as raw materials, and porous copper powder/mesh plates were prepared by pressing, rolling, and vacuum sintering. The plate morphology was observed by scanning electron microscopy. The air permeability of the porous plates was tested according to Darcy's law, and uniaxial tensile tests were carried out on the porous plates to determine the influence of raw material mesh number and powder content on the porous plates' permeability and tensile mechanical properties. The porous plate was fabricated into a restrictor of an aerostatic thrust bearing, and the static bearing performance of the bearing was tested on a bearing capacity testing platform. The results showed that the copper powder/mesh porous plate had a uniform pore distribution and a porosity range of 10% to 30%; the higher the porosity and lower the powder concentration, the better the performance was in terms of gas permeability. Tensile mechanical properties improved with decreasing porosity and increasing powder content. At a gas film thickness of 10 μm, the prepared gas hydrostatic thrust bearing could support a maximum load of 381.1 N. [ABSTRACT FROM AUTHOR]

A new all-solid-state ion selective electrode (ASS-ISE) was developed for the determination of thulium trivalent cation. The potentiometric sensor was made by depositing a thin PVC membrane containing N'-[(2-hydroxyphenyl)methylidene]-2-furohydrazide (L) as a selectophore on a conducting solid-state electrode. The solid-state electrode was a thin copper wire coated by a mixture of multi-walled carbon nanotubes (MWCNTs) and an epoxy resin. The optimal composition of the PVC membrane was 25%wt. of PVC powder, 68% wt. of benzyl acetate, 2% wt. of sodium tetraphenyl borate (NaTPB)), and 5% wt. of L. The sensor showed good selectivity for Tm3+ ion with a Nernstian calibration plot slope of 19.6±0.4 mV/decade in Tm3+ ion solutions with concentrations ranging from 1.0×10-8 M to 1.0×10-3 M, and its limit of detection was as low as 6.3×10-9 M. The proposed sensor was able to detect Tm3+ cations in the wastewater matrix. [ABSTRACT FROM AUTHOR]

This work studies evolution of copper microstructure during a combined deformation process. The essence of this process is in deformation of copper wire in a rotating equal-channel stepped matrix with subsequent drawing. Deformed wire is examined using transmission electron microscopy and EBSD analysis. After three cycles of deformation, an ultrafine-grained gradient microstructure with a high component of high-angle grain boundaries is obtained. [ABSTRACT FROM AUTHOR]

Numerous studies have been made to design broadband frequency selective rasorber (FSR). However, it is still a challenge to realize optically transparent FSR, due to the difficulty in realizing high transparency, high-quality factor(Q) parallel resonance, and low-Q series resonance simultaneously. Here, we propose a new method to design transparent FSR for the first time. To break through the technical barrier, a thin copper wire with a different configuration method is utilized to design lossy layer, which can realize high transparency, in-band transmission, and out-of-band absorption concurrently. The proposed FSR is configured by cascading a transparent lossy layer above a transparent frequency selective layer with an air space to separate them. We adopt the equivalent circuit model, electric field distribution, and loss distribution to reveal the physical mechanism of the FSR. The simulation results show that the transmission loss is 1 dB at 8.3 GHz, and the reflection amplitude is less than −10 dB in 2.7–8.9 GHz. The FSR can achieve 96.3% optical transparency theoretically. A prototype is fabricated and measured to validate the proposed design. The measured results achieve good agreement with the simulated results. The proposed FSR can act as a stealth radome for transparent components of ships and aircrafts. The application scenarios can be extended to communication and imaging systems. [ABSTRACT FROM AUTHOR]

Steam reforming of methanol is an effective way to provide an on-line hydrogen source for fuel cells. However, due to the poor utilization of the performance of the catalyst, the traditional reformer has the problems of slow start-up, low hydrogen production. Therefore, it is urgent to develop new catalyst loading methods to make full use of the performance of the catalyst. In this paper, a foamed metal with nano copper wire is used for methanol-reformer. The relevant experiments were carried out to investigate the hydrogen production performance of the foam copper reformer based on nano copper wire and the traditional impregnation method. The results showed that compared with the metal foam autocatalysis, the hydrogen concentration in the product of the nano-copper wire reformer could be increased by more than 8 times. What's more, the concentration of hydrogen in the product is twice that of the current widely used impregnation method. Furthermore, this method reduced the start-up time of the reformer. Meanwhile, the best working parameters of nano copper wire methanol-reformer were obtained through experiments. [Display omitted] • An efficient methanol reforming reactor catalyzed by nano copper wire was developed. • The concentration of hydrogen in the product of copper nanofiber foam was increased by more than two times. • Nano structured copper foam can greatly shorten the start-up time of the reformer. • There is an optimum working condition of nano copper wire reformer. [ABSTRACT FROM AUTHOR]

Flexible and stretchable electronic yarn containing electronic components (i.e., hybrid electronic yarn) are essential for manufacturing smart textile garments or fabrics. Due to their low stretchability and easy interconnection fracture, previously reported hybrid electronic sensing yarns have poor mechanical durability and washability. In order to address this issue, a stretchable hybrid electronic yarn for body temperature monitoring was designed and prepared using a spandex filament as the core yarn and a thin enameled copper wire connected with a thermal resistor as the wrapping fiber. The temperature sensing performance of different hybrid electronic yarn samples was evaluated using the following three types of interconnection methods: conductive adhesive bonding, melt soldering, and hot pressure bonding. The optimal interconnection method with good sensing performance was determined. Furthermore, in order to improve the mechanical durability of the hybrid electronic yarn made using the optimal interconnection method, the interconnection area was encapsulated with polymers, and the effect of polymer materials and structures on the temperature-sensing properties was evaluated. The results show that traditional wrapping combined with hot pressing interconnection followed by tube encapsulating technology is beneficial for achieving high stretchability and good temperature-sensing performance of hybrid electronic yarn. [ABSTRACT FROM AUTHOR]

In this paper, a series of comparative experiments were performed to study the upward flame spread over single and adjacent twin polyethylene-insulated copper wires from horizontal (0°) to vertical (90°). The flame morphology and flame spreading rate of single and twin wires were compared at different inclination angles, which show a larger flame size, but a lower overall flame spread rate over twin wires. As the inclination angle increases, the flame characteristic length, and flame spread rate increase with the inclination angle for both wire arrangements. The flame spreads steadily to the end of the sample without molten dripping or sliding for single-wire conditions. However, molten dripping or sliding behaviors were found during flame spreading for twin-wire conditions, and the averaged dripping or sliding frequency increases with the inclination angle. Correspondingly, the periodical variation of flame characteristic length, flame height, and flame spread rate for twin-wire conditions have been investigated in detail compared with single-wire conditions. Finally, a simplified heat transfer analysis is carried out to quantitatively study the flame spread rate for both wire arrangements, and the effects of molten dripping/sliding and overlapped area on the heat transfer and flame spread rate are qualitatively discussed. [ABSTRACT FROM AUTHOR]