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Angular dependence of second generation (2G) high-temperature superconducting (HTS) tape is a crucial parameter for its industrial applications. Known as soldered-stacked-square (3S) HTS wire, a novel structure of HTS wire has been proposed in our previous research. In this paper, angular dependence of 1 mm HTS tape, 4 mm tape, 1 mm 3S HTS wire, and 1 mm 3S HTS twisted wire were measured in liquid nitrogen bath, respectively. It can be found that the 3S HTS wire would not enhance the critical current density under external magnetic field, while an isotropic angular dependence is obtained when 3S HTS wire is twisted. The test results obtained in this paper provides useful information for the future applications of 3S HTS wire. [ABSTRACT FROM AUTHOR]

This paper focuses on the current distribution and AC loss of BSCCO/REBCO hybrid tapes. Based on their geometry and E-J character of superconductors, a one-dimensional model is established to compute the current distribution and AC loss under an AC operating current in self-magnetic field. The current distributions of hybrid tapes with different number of REBCO tapes and one BSCCO tape are studied. The numerical and experimental results are in good agreement. According to the current distribution characteristics, AC loss of each tape in the hybrid tape is analyzed and calculated. AC losses of 3 kinds of hybrid tapes are measured and discussed. The method proposed in this paper for AC loss simulation is quite effective for hybrid tapes composited by two or more types of superconducting tapes. [ABSTRACT FROM AUTHOR]

This paper proposes a way to represent the anisotropic nonlinear superconducting properties using a discrete model for magnetization with the corresponding critical parameters, equivalent to the Power Law model for currents. This simplified model makes it possible to analyze magnetic systems with superconducting elements in a stationary mode, which reduces the calculation time. Using of proposed model is demonstrated by the calculation of force interactions between high-temperature superconducting (HTS) samples and permanent magnet in zero-field-cooling (ZFC) and field-cooling (FC) modes. HTS bulks in the form of a prism and stack made of HTS tape are considered. The calculation of the electromagnetic field was carried out using the method of integral equations for field sources. The data of calculations are compared with the results of experimental studies. [ABSTRACT FROM AUTHOR]

Short circuit currents show an upward trend in multi-terminal high voltage (MTHV) dc systems. DC resistive type superconducting fault current limiters (SFCLs) can limit short circuit currents to a much lower level to improve the stability of MTHV dc systems. Superconducting tapes used for dc SFCL will quench after a short circuit current attack. Then temperature and voltage of the tapes will increase. The objective of this paper is to obtain the effects of short circuit currents on quench and recovery properties of the superconducting tapes of dc resistive type SFCLs. YBa2Cu3O7-δ (YBCO) tapes was chosen as investigation samples. This paper concluded that for higher short circuit currents, the temperature and the voltage of the tape was higher. The highest temperature was 379.2 K for YBCO tapes when a short circuit current of 10 kA was applied for 50 ms. Recovery time of a short circuit current of 10 kA was 240 ms longer than the recovery time of the short circuit current of 500 A. Quenched resistance curves gotten by experiments and analysis were similar, which proved the accuracy of the analysis. [ABSTRACT FROM AUTHOR]

The main obstacle for the application of the high-temperature superconducting (HTS) coated conductors (CCs) in AC energy applications is the relatively large AC loss. To tackle this, several forms of HTS cables for AC applications have been invented and investigated, such as the HTS Roebel cable, Cable on Round Conductor (CORC), and Twisted Stacked Tape Cable (TSTC). In this paper, the possibility of encapsulating Roebel cables into a single HTS CC is investigated, from which a novel conception of a Roebel tape is proposed. Compared with the existing HTS cables, HTS Roebel tapes are more compact, more capable at carrying large current with minimised AC losses, and easier to manufacture. A 3D finite element method (FEM) model of the Roebel tape is built to optimise the structure and verify the performance. The results show that, compared with normal ReBCO CCs, Roebel tapes with optimum patterns can reduce AC transport losses by 60% through field-cancelling and can reduce magnetisation losses by the factor of the filament number through patterning. With excellent loss reduction performance and high current capability, the Roebel tape shows great potential to become a revolutionary HTS cable for high-current power transmission and AC machine applications. [ABSTRACT FROM AUTHOR]

In the present paper, the possibility of magnetization of HTSC tape by means of pumping by a local magnetic field is considered. Within the framework of the critical state model, the calculation of the density of the induced currents and the magnetization of a square (12 × 12 mm) fragment of a second-generation HTS tape (YBCO) was made. The model considers real dependence of the critical current density on the magnetic field and has been successfully tested previously. In the sample, the currents were induced by the impact of a local magnetic field. The size of the localized area of the external magnetic field to be considered was much smaller than the size of the HTS sample. It is showed that the repeated cyclical impact of the local outer field leads to the accumulation of the total magnetic moment in the sample up to a magnitude of 94% of the theoretical magnetization limit for this sample. The results obtained make it possible to optimize the mode of magnetization of a square fragment of a tape (or a stack of tapes) when implementing a magnetic flux pump. The experimental studies showed results comprisable well with theoretical ones. [ABSTRACT FROM AUTHOR]

Government environment is the main determinant in attracting private investment into public–private partnership (PPP) projects, especially in developing countries. Red tape, an indicator of a government's efficiency, plays a critical role in private investment in PPP projects. Reasonable levels of red tape can enhance government transparency and promote private investment, while excessive red tape usually represents low governance efficiency and imposes further risk on private investors. This article explores how developing countries’ red tape affects private investment in PPP projects by examining the moderating effect of corruption. Analyzing a database of 308 PPP projects in 111 developing countries, the study reveals an inverted U-shaped relationship between red tape and private investment. Corruption weakens the positive relationship between red tape and private investment at low levels of red tape and mitigates their negative relationship at high levels. The study integrates the inconsistent results of previous research that postulated either a positive or negative relationship between red tape and private investment by proposing a nonlinear model. It also theorizes the moderating effect of corruption based on real management practice and illustrates its mechanism in absorbing private investment in PPP projects. [ABSTRACT FROM AUTHOR]

Seafloor mapping and vertical deformation monitoring are important for a gas hydrate exploitation. Due to the complexity of the marine environment and the difficulty of the seafloor operation, an in situ seafloor mapping and high-resolution vertical deformation monitoring simultaneously are big challenges. This paper describes an experimental research on an in situ system for a seafloor mapping and vertical deformation monitoring based on an elastic steel tape, along which an array of nine-axis microelectromechanical system (MEMS) sensors is arranged. The tape can measure both the motion of the bend and the twist. The MEMS sensor consists of an accelerometer, a gyroscope, and a magnetometer. The Euler angles obtained from the nine-axis MEMS sensor can be converted to a relative rotation matrix, showing the amount of the bend and the twist, and the curved shape of the tape can be calculated. Based on this concept, multitapes are used for the seafloor mapping and vertical deformation monitoring. To assess the monitoring system, a lab scale experiment in a water tank is carried out. The results demonstrate the feasibility of the proposed system for the seafloor mapping and deformation monitoring. [ABSTRACT FROM AUTHOR]

Accurate peeling off and transferring of microchips play a critical role in LED die sorting technology. Generally, sorting efficiency of more than 36 KUPH, and an alignment deviation less than 1 mil ($25.4~\mu \text{m}$) is required. High precision position control and cooperation of multifactors should be implemented precisely. Among all the factors, the film deformation is an important one. As the sorting proceeds, dies are peeled off from substrates one by one, and the adhesive substrate is penetrated through a hole each time. As the number of stripped chips increases, viscoelastic deformation of tape surface takes place and tiny position shift of die adhered on tape arises. This shift may cause a negative impact on the peeling process. In this paper, linear viscoelastic deformation impact is tested with well-designed experiments. To evaluate the effect of tape deformation accurately for sorting the performance, stochastic Petri net model of the transferring system with dual-independent arms is formulated to analyze the influence of factors. On this basis, strategy on coordinating motion control and scheduling is proposed, rational velocity section is planned, and the active position compensation of supply platform is set, so that the die can be peeled off correctly and efficiently. Finally, to improve sorting performance, methods on active compensation of aligning platform are proposed and proven effective by an experimental validation. [ABSTRACT FROM AUTHOR]

Second-generation high-temperature superconducting (HTS) tapes strongly rely on the substrate material, in many cases Hastelloy C276 (“H-C276”). In order to ameliorate performance (and reduce the price) of superconducting tapes, replacement of H-C276 has been investigated. In this paper, the potential of the readily available austenitic stainless steels X2CrNiMo17-12-2 (“CrNiMo”) and X11CrNiMnN19-8-6 (“CrNiMnN”) as substrates is assessed. It was found that CrNiMnN is not suitable as a replacement for H-C276. Tensile stresses occurring at elevated temperatures during the HTS tape production result in plastic deformation of the CrNiMnN substrate. In the case of CrNiMo, however, plastic deformation was not observed after processing of the HTS tape. Electrical losses as a result of alternating currents beyond those of H-C276 did not occur due to the paramagnetic nature of CrNiMo. It is demonstrated that, for the very same processing parameters, HTS films deposited on electrochemically polished and buffered CrNiMo substrates exhibit similarly high critical current densities as on polished and buffered H-C276 substrates. The application of CrNiMo stainless steel reduces substrate costs considerably. More importantly, tapes processed on CrNiMo substrates withstand higher tension strains with respect to the reduction of the critical current compared to H-C276 substrates. This effect is interpreted to be a result of the matching coefficients of thermal expansion of the HTS layer and CrNiMo, resulting in lower residual tensile stress in the HTS layer after processing. [ABSTRACT FROM AUTHOR]

Quench and recovery characteristics are the most important characteristics of dc resistive type superconducting fault current limiters (SFCLs). In the normal state, the superconducting tapes of SFCLs stay in superconducting state without power loss. However, if there is a thermal disturbance energy impact to the superconducting tapes, the tapes may be quenched, and sometimes even break once their temperature is too high. After the thermal disturbance, the tapes may recover to superconducting state again. A numerical analysis method was proposed to analyze quench propagation and recovery characteristics of the YBa2Cu3O7-δ tapes based on thermal conduction theory. The objective of this paper is to obtain the influencing factors such as magnitude of thermal disturbance, transport current, material of the stabilized layer and cooling on quench, and recovery properties of dc resistive type SFCL. Numerical analysis results show that the temperature and voltage of the tape increased while the transport current through the tape and the magnitude of thermal disturbance increased. The quench propagation velocity was higher and the recovery time was shorter for copper stabilized layers than stainless steel stabilized layers. [ABSTRACT FROM AUTHOR]

Magnetization loss is an important parameter in the design of high-temperature superconducting (HTS) power devices. It is produced under the external alternating magnetic fields. In previous work, for the purpose of reducing the loss, our group proposed and fabricated a novel soldered-stacked-square (3S) HTS wire with a cross-section of 1 mm × 1 mm. In this paper, the magnetization losses of the 3S wire are investigated numerically. First, numerical and theoretical losses in single HTS tapes are compared and their consistence proves the reliability of the numerical model. Also, the losses in tapes of different widths are evaluated, which shows the 1-mm tapes have less magnetization losses under perpendicular field. Moreover, the numerical model for estimating losses in 3S wires has also been built. According to a series of calculation and comparison, the 1-mm stacked wires have less losses than those wider stacked wires under perpendicular field. Besides, considering the practical application of HTS power devices, angular dependence of the loss in 3S wires containing one HTS tape is studied as well. The results indicate the loss increases with the increase of the angle with respect to the wire surface. [ABSTRACT FROM AUTHOR]

This paper studies the current limiting behavior based on an air-core high-temperature superconducting transformer (HTST) and a group of inductor–capacitor series resonant limiters. The air-core HTST is composed of four same double-pancake type high-temperature superconducting coils made up of Bi-2333/Ag tape, and both of primary and secondary windings include two series superconducting coils. It plays the roles of inductive fault current limiting and transformation impedance; in addition, the magnetic flux saturation can also be avoided. Meanwhile, the inductor and capacitor series with the secondary winding of the air-core HTST in series resonance state are the conventional devices. The influence of them on the circuit can almost be ignored, because they are in series resonant state in normal operation. While the fault current appeared in the primary circuit, it will be limited by the impedance of the air-core HTST and the inductor without quench (the inductor and capacitor would quit the series resonant state). According to the preliminary experiment carried out in our laboratory, this superconducting current limiting module can operate as expected, and its behavior is satisfactory. [ABSTRACT FROM AUTHOR]

This paper presents an experimental method for investigating the dependence of critical current on the applied magnetic-field intensity and the angular orientation in high-temperature superconductor (HTS) tapes and cables. Comparisons between critical-current measured and simulated data are presented as a function of field angular orientation. The obtained relation can be used as input data for numerical calculations or simulations for designing application devices that utilize HTS tapes and cables. [ABSTRACT FROM AUTHOR]

The mechanism of the passive intermodulation (PIM) distortion caused by the loose contact in coaxial connectors is of great importance in wireless communication systems. This paper focuses on the effect of the additional impedance on PIM levels in coaxial connectors. First, the additional impedance and PIM levels of the loose contact coaxial connectors are measured. Then, the S-parameters and the additional impedance with three different loose contact cases are simulated. Finally, a modified coaxial connector with different values of conductive tapes is designed to verify the additional impedance impacts on the PIM level. It is shown that the increase of the additional impedance of the metal–metal loose contact will lead to the deterioration of PIM levels in the coaxial connector. [ABSTRACT FROM AUTHOR]

Striated YBCO-coated conductor is a variant structure of the second-generation high-temperature superconducting (HTS) tapes. The ac loss is reduced owing to the YBCO layer of the striated YBCO tape is divided into filaments by laser scribing. Hence, it is promising for practical HTS electrical application, such as HTS transformer and cable. However, when the superconducting apparatuses are operated in the power grid, it will possibly experience the lightning impulse current in some extreme working condition. Thus, the performance of striated YBCO tapes suffering from exposure to lightning current is important to be studied. In this paper, a numerical model based on the electromagnetic–thermal coupling is built to analyze the lightning current performance of the striated YBCO tapes. The influence of structural changes on the thermal stability is discussed. The standard lightning current waveform is chosen, i.e., 8/20 μs. The simulated results show that cutting the copper edges of striated YBCO tapes will significantly degrade the lightning current withstand capacity. Instead, the degradation effect of grooves is not so obvious. [ABSTRACT FROM AUTHOR]

A key factor concerning the superconducting application of HTS tapes is the volume of current they can carry. The resistivity of the HTS tape is theoretically zero if lower than the critical temperature, but it cannot carry an infinitely large current. Therefore, the critical current of different HTS tapes must be evaluated to determine their maximum current carrying capacity. First, this study proposed an experimental structure based on controllable dc current ramp rate (R-value) and the critical current of three kinds of tapes were measured, respectively. Finally, this research provides new insight into the understanding of HTS tapes with the magnetic substrates and the nonmagnetic substrates. [ABSTRACT FROM AUTHOR]

Critical current density is an important parameter reflecting power transmission capacity of HTS cable. Based on the superconducting energy pipeline, a tightly wound cable structure along arc of the pipeline is studied in this paper. Critical current density of electromagnetic thermal coupling is calculated and optimized superconducting cable structure is evaluated. Experimental results are useful to the design of high-temperature superconducting (HTS) cable in energy pipelines. [ABSTRACT FROM AUTHOR]

The performance of High Temperature Superconducting (HTS) tapes is strongly affected by the mechanical loadings they experience during manufacturing, cooldown and operation. Therefore, the development of HTS-based applications requires thorough investigations on the impact of these loadings on the critical current. In this work, a measurement procedure is applied to determine the critical current of a (Re)BCO tape at 77 K, after double bending at room temperature around a cylindrical mandrel. In this procedure, the tape is cooled down to cryogenic temperature, and the critical current is first measured on the straight sample. After warming the tape up to room temperature, a double bending around a cylindrical mandrel is applied in two opposite directions and the critical current is measured at the following cooldown. This analysis is repeated for different mandrel diameters in order to identify to study the impact of the curvature radius on the performance degradation. The application of one single bending at room temperature is compared to the results of the double bending procedure. The influence on the performance degradation of applying a known force to the tape during the double bending at room temperature is also experimentally analyzed. [ABSTRACT FROM AUTHOR]

Electrical and physical failure analyses have played a key role in the yield enhancement of large-scale integrated circuits. However, the growing cost of product wafers has progressively hindered their use for analysis, depending on the shrinkage of device dimensions. To overcome these difficulties, we propose a new analytical style that uses the remaining dies on a sawn wafer after all the good dies have been picked and taken for assembly. We call the resulting structure a “skeleton-wafer”. In the present study, we have developed a testing system that can handle a skeleton-wafer in the same manner as a conventional wafer. Basically, skeleton-wafer testing is performed at room temperature, given that commonly used dicing tapes have low heat-resistance. We have also developed a sophisticated method that enables analytical testing on the remaining dies at high temperature. A case example achieves high throughput and good contact characteristics, enabling the developed system to be of practical use in high-volume electrical failure analysis. We illustrate how our analytical testing system has improved cost-effectiveness and time-efficiency in yield enhancement activity. [ABSTRACT FROM AUTHOR]

A simplified two-dimensional (2D) model, which takes the helical structure of the conductor on round core (CORC) cable into consideration, is utilized to analyze the electromagnetic and thermal properties of the cable. The model couples multi-physical fields through the JcBT(B,T) properties of the superconducting tape. We first introduced the modeling strategy and verified the validity of the 2D model. Then, considering the influence of thermal on the critical current of the tape, the cable loss under different conditions has been calculated. By changing the relative positions of the inner and outer conductor layers of the 2D model, the influence of the magnetic field on CORC cable loss can be obtained, and it can be extended to the periodic three-dimensional (3D) structure. [ABSTRACT FROM AUTHOR]

Second-generation high-temperature superconductors, being brittle, need to be deposited on a substrate and converted to tapes with additional reinforcement layers. These tapes are wound on a core to make superconducting wires and cables. The mechanical loads during bending, twisting, winding, etc., can degrade the superconductor. It is necessary to determine the strain-induced during these processes. Variations in induced strain with bending of superconductors have been investigated analytically and numerically for various configurations of Rare-Earth Barium Copper Oxide (REBCO) tape. The numerical simulation has been carried out using COMSOL Multiphysics software; the analytical examination of the effect has been performed applying the Flexure formula. The geometrical configuration of the superconducting tape is varied in terms of the bending radius, the thickness of constituting layers made of Hastelloy and copper. The results showed that the variation in the thickness of the substrate has a large influence on the induced strain. Electrical performance analysis is also carried out using the power law of strain dependence and the 5% critical current degradation point is noted. Results of these numerical and analytical investigations are expected to help in finding out critical parameters to avoid degradation while being in use. [ABSTRACT FROM AUTHOR]

Internet-of-Things (IoT) innovations produce interesting opportunities, impact ethical and social aspects toward human society, and influence operational and technical solutions toward the structural systems. This article discusses the impact of some relevant characteristics of the IoT innovations. Significant debated aspects are the product discontinuity in the global market, their durability, the upcoming “social” virtual systems, new “socialized” equipment, the promotion of electrical microsystems, the human competence in the digital age, the safety, operability, and security of IoT. These innovations require an advancement of the technical culture and open new frontiers for electroforensic engineering. In the next future, forensic engineering can promote an international reference organization as a mediator between social, technical, and regulatory aspects. Innovations and efficient sustainability need adequate global regulatory changes to favor the spreading of advantages, with more cert success if old businesses are transferred into new businesses. [ABSTRACT FROM AUTHOR]

In this article, a novel approach for the versatile wrinkle-free application of (curved) precut adhesive tapes on freeform 3-D surfaces is presented. Straight and curved tape application paths are mapped onto the 3-D object as geodesics and as lines with imposed geodesic curvature, respectively. The proposed surface-based path following control concept extends the classical path following control by a novel parallel contact frame and a parallel projection operator. Using a static state feedback, the robotic system is transformed into a system with linear input-output behavior in the path coordinates. This allows to traverse a path on a 3-D object with a draping roll without turning around the surface normal vector. The latter prevents distortions and wrinkles of the applied tape. Experimental results with a Kuka LBR iiwa 14 R820 demonstrate the feasibility of the proposed approach. [ABSTRACT FROM AUTHOR]

The second-generation high-temperature superconducting tapes (2G-HTS) such as the REBCO coated conductors are known for their strong mechanical properties and high current carrying capacity with low ac losses compared with first-generation HTS tapes as well as low-temperature superconductors. Therefore, they seem to be good candidates to assemble coils for superconducting rotating electric machines (SuREMs). In this article, to investigate the influence of a soft magnetic composite (SMC) material on the dc and ac HTS coil performances at cryogenic temperatures, GdBCO- and YBCO-based commercial tapes from different manufactures were used to assemble ten HTS coils in double-pancake configuration. These tapes were wound using two different core structures, i.e., fixed and movable cores, having the same circular shape but different diameters as well as materials, i.e., fiberglass and SMC. Critical currents and ac transport current losses of these coils were measured using the electrical method. To evaluate the parallel and perpendicular components of the profile of magnetic flux density for each assembled HTS coil, a finite element model has been developed using Maxwell 2D. Eventually, the performance of different coils for SuREM application was discussed. [ABSTRACT FROM AUTHOR]

Modeling high temperature superconductor (HTS) motors remains challenging mainly due to the high aspect ratio of these conductors but also because of the properties of the magnetic materials. This article presents a 2-D time dependent model to assess the ac losses of superconducting motors based on the new T–A-formulation, which by using the finite-element method, allows its implementation in commercial software. The T–A-formulation computes the magnetic flux density with different Maxwell's equations depending on the areas of the motor and makes it possible to use the thin strip approximation i.e., the HTS tapes are modeled as infinitely thin lines. The model is then expected to tackle the high aspect ratio of the HTS as well as decreasing both the mesh complexity and the computing time. The first objective of the article is to validate the method in 2-D by evaluating the ac losses of a specific synchronous motor called superconducting torque motor; the computed results are compared with good agreements to those assessed with the minimum electromagnetic entropy production method, already validated. In a second part, the same losses are computed, taking into account the field anisotropy of Jc with the implementation of a dataset based on experimentally measured Ic at 65 and 77 K. With the model proposed in this article, it is possible to calculate the magnetic field of a whole electrical machine cross section and compute the ac losses in the individual tapes of its windings within the same numerical model. [ABSTRACT FROM AUTHOR]

The main objective of this article is to establish which of the many dicing tapes used in the semiconductor industry would be most suitable for use in plasma dicing. Tape design over the past 40 years has continually evolved through advancements in both dicing technologies and the incessant revision of integrated circuit packaging. Die singulation has traditionally been accomplished using a diamond saw, laser-based technology, or a combination of both. The stress on dicing tape was, therefore, limited to fatigue through the physical nature of saw dicing or heat energies induced during laser dicing. These processes do not expose dicing tape to either a high vacuum or a variety of plasma chemistries. This investigative work is a continuation of studies examining the dicing tape behavior when used in plasma dicing. Results show that polyolefin (PO) UV tape with low-to-medium adhesion strength exhibits the greatest resilience under harsh plasma etch conditions and that efficient photoinitiated cross linking (or curing) of the adhesive is triggered if directly exposed to the photonic energies present in a pure SF6 plasma or full plasma dicing process. However, the postplasma dice, post-UV cure adhesive strength can still be minimized if the tape manufacturers recommended time limitations between which the tape mount, plasma dice, and die pickup process are adhered to. [ABSTRACT FROM AUTHOR]

The ultrathin integrated circuit (IC) chip ejecting and pick-up process plays an important role in advanced packages since the success ratio and productivity are determined by the delamination of chips from the adhesive tape substrate. As thinning of the IC chip occurs, chip cracking between the adhesive tape and ultrathin IC chip increases due to the low strength of the ultrathin IC chip in the die pick-up process. In this paper, the interfacial adhesion strength and energy release rate between an ultrathin IC chip and base tape were measured by a 90° peel test as a function of the peeling velocity. Also, an index was defined to characterize the competing fracture behavior between the delamination of the chip from the adhesive tape and chip cracking. Finite-element analysis of the die pick-up process with a virtual crack-closure technique was performed to predict stable peeling off of the chip with respect to the velocity of the chip holder as well as the pressure of the blown air considering the interfacial energy release rate and chip strength. The results show that the velocity of the chip holder and the pressure of the blown air should be lower than 50 mm/min and 90 kPa, respectively. [ABSTRACT FROM AUTHOR]

High critical current density is desired for cables adopted in fusion or accelerator applications. The bending diameter of REBCO tapes is very important for the preparation of such cables. The bending diameter of REBCO tape is related to many factors. It is necessary to identify the most important factors determining the bending diameter by experiments. In this article, a new measurement method for bending diameter is developed. Short samples are taken from individual tapes in a large batch and connected in series into one long piece for bending diameter measurement. This way, a large batch of tapes can be efficiently assessed in one go. The samples prepared by Shanghai Superconducting Technology Co., Ltd. (SST) have been tested. It is concluded that the critical bending diameter of the tapes, which we define that the critical current attenuation is less than 10%, is closely related to its thickness, stiffness, superconducting layer thickness, and copper plating thickness. The composition of the superconducting layer has little effect on it. By testing the tapes prepared by SST in large quantity, it is found that when the REBCO faces inward during bending, tapes plated with 5 and 10 μm copper on one side only have smaller critical bending diameter than tapes plated with copper on both sides. The current has no attenuation when the bending diameter is 2.6 mm. When REBCO faces outward, copper plating has little effect on the critical bending diameter, which varies between 6 and 14 mm. [ABSTRACT FROM AUTHOR]

This article presents an integral modeling approach for computing ac losses in high-temperature superconductors near magnetic materials. The current density and magnetic field distributions are calculated by solving Maxwell's equations in integral form in the active parts. Equivalent surface and interface current densities are considered in the magnetic material to take into account its magnetic field-dependent relative permeability. The proposed approach is applied to compute ac losses in a second-generation high-temperature superconducting tape with a magnetic substrate. The obtained results are compared with the finite element method using H formulation to check the validity and performances of the proposed integral approach. [ABSTRACT FROM AUTHOR]

A split-core technique is proposed to mitigate the gap losses in high-frequency nanocrystalline cores, which enables significant size reductions in thermally limited designs. Finite element analysis is used to examine the gap loss dependence on core width D revealing a nonlinear relationship of the form loss ∝ $D^{\alpha }$. α is approximately constant for frequencies of 10–200 kHz over the range of core widths typically used in power electronics, but α increases with gap length. Splitting the core into a number of subcores can therefore provide significant reductions in gap loss, especially with larger gap lengths. The results from a 300-A (peak), 200-A (continuous) inductor show that with three subcores and a gap length of 4 mm, the gap losses are reduced by 50%, and the hot-spot temperature is reduced by 24.5 °C. Using the technique it is estimated that the original inductor weight could be reduced by 40% with four split cores, making a significant impact on converter power density. [ABSTRACT FROM AUTHOR]

Energy harvesting is a promising strategy utilizing renewable energy to power low-power-consumption electronics, such as wireless sensor network (WSN) nodes and wearable electronics. In this article, a tape-like vibrational energy harvester, using flexible fluorinated polyethylene propylene (FEP) piezoelectret films as transduction material, is reported. Due to a specific air-filled parallel tunnel structure, the FEP piezoelectret films in this study exhibit both significant longitudinal and transverse piezoelectric effects and could be made into tape-like flexible transduction devices. The results show that the experimental data are consistent with the theoretical prediction and the finite-element method (FEM) calculation. For a device with an effective area of 18 mm $\times25$ mm and a seismic mass of 0.195 g on one edge, the output power at a resonant frequency of 16 Hz amounts to 3.1 $\mu \text{W}$ for an acceleration of 1 ${g}$. Owing to the tape-like and flexible transduction elements, the power generated by the device can be enhanced readily by either enlarging area of the transduction elements or multiplying a few transduction elements in series or parallel to meet the power requirement of electronic devices, which makes the practical application flexible. [ABSTRACT FROM AUTHOR]

The efficient pick-up of thin/ultrathin integrated circuit chip from the wafer is one of the key techniques in advanced microelectronic packaging, whose success rates are determined by the peeling-off of chip from the adhesive tapes. Analytical models for estimating the effects on process parameters represent important design tools. Here, solutions for adhesive stresses and mixed-mode peeling are presented in chip-adhesive-substrate structure based on mixed boundary conditions, in which the geometrical dimensions and material properties of this three-layer system are included. Analytical expressions are defined in terms of structural parameters and several integration constants, which can be obtained by a given system of linear equations. These models agree well with finite element models with virtual crack-closure technique. In particular, the mechanism of tunable mode peeling is uncovered, and the technological limit of normal single ejecting needle is discussed. [ABSTRACT FROM PUBLISHER]

In this work, we experimentally investigate the current carrying capacity of single REBCO tapes and stacks made 5 12 mm REBCO tapes with a 25 μm copper stabilizer in liquid helium in comparison with those made of bare tapes with no stabilizer at current ramp rates up to 55 kA/s. The motivation for the research was checking the usability of REBCO stacks as basic sub-elements for high current superconducting cables operating in fast cycling modes at 4.2 K. An original experimental technique was employed to induce the extremely high ramp rates. During the tests, one or 5-folded stacks curled into rings 95 mm dia with different types of joints were charged in the external magnetic field generated by an outer solenoid at ramp rates up to 1.6 T/s. The curled REBCO stacks were either soft-soldered over their entire length or contained local joints only. The maximum screening current induced in the samples during the outer solenoid charging Imax was registered. Our experiments showed that the current carrying capacity of the REBCO tapes and stacks was strongly affected by the absence or presence of the copper stabilizer as well as the type of the joint. The reasons for the Imax limitation for the copper stabilized and bare samples are also briefly discussed. [ABSTRACT FROM AUTHOR]

In this article, to accurately analyze the magnetic properties of high-temperature superconductor (HTS), a superconductor hysteresis model is proposed. Based on the physical mechanism, the hysteresis loop of HTS can be decomposed into an antimagnetic curve and a paramagnetic loop. The calculated and measured results of silver-sheathed Bi2223 superconducting tape samples under an external magnetic field are compared to show the effectiveness and accuracy of the presented method. [ABSTRACT FROM AUTHOR]

Superconducting coils may suffer from electromagnetic vibration due to changing electromagnetic fields under AC conditions. In the long term, this vibration may cause performance degradation of superconducting tapes. In order to study the influence of electromagnetic vibration between superconducting tapes on their performance, the study can be started from the simplest form of electromagnetic vibration, that is, the electromagnetic vibration between two superconducting tapes. The degree of electromagnetic vibration under different AC currents were analyzed by simulation, and the variation of critical current (Ic) and the n-value of Y-Ba-Cu-O (YBCO) tapes after undergoing long-term electromagnetic vibration through experiments were measured. The results show that two YBCO tapes does not show obvious performance degradation under tens of hours the electromagnetic vibration caused by the AC current amplitude of 1.2 to 1.4 times Ic. [ABSTRACT FROM AUTHOR]

A quench detection method using a low-temperature superconducting quench detector (QD) has been proposed to protect rare-earth barium copper oxide (REBCO) coils at temperatures below 20 K in magnetic fields. In this study, we first conducted an experiment at 4.2 K in 0–9 T using a locally- degraded REBCO tape and Nb–Ti QDs (Nb–Ti/Cu, Nb–Ti/Cu–Ni). Quick quench detection before thermal runaway of the REBCO tape was demonstrated by the Nb–Ti/Cu–Ni QD in 0–9 T, whereas Nb–Ti/Cu QD exhibited quick quench detection only at 9 T. Furthermore, we numerically evaluated the quench detection time of Nb–Ti QDs attached to a REBCO tape with local degradation at 4.2 K in 0–9 T. The simulation reproduced the experimental results. Moreover, the contact resistance between the REBCO tape and QD should be lower than 1.0 × 10−3 m2K/W for quick quench detection. [ABSTRACT FROM AUTHOR]

The superconducting joint between Bi2223 tapes has been developed with a method of joint by incongruent melting (JIM) in our Laboratory. The multi-junction method used to increase the contact area yielded a demonstrated increase in critical current. In previous studies, a simple boundary shape with lap-joint was chosen to connect several filaments in the tape, and this method is not suitable for connecting all about 100 filaments. Of course, more filaments are necessary to be joined with superconducting boundary, in order to increase the critical current of joint. However, due to the thin tape structure, there is difficult to use of butt joint between two cross-sections of tapes. In this study, we proposed a multi-junction method by using multiple boundaries with stepped structure. In experiments, joint samples with increasing of junction number to three from one were prepared, and the critical current for each unction number were measured at 77 K (self-magnetic field). In result, the critical current is increased with increasing of the junction number, and a highest critical current of 51.8 A was obtained in three-junction sample. in particular, the critical current at first junction (end of tapes) is highest, indicating that critical current at the end is important in total critical current of joint. Therefore, single junction at end of tapes was prepared and evaluated by using X-ray diffraction and critical current measurement. From X-ray diffraction patterns, the joint area is estimated to be about 1 cm. The critical current was 36.5 A at 77 K. [ABSTRACT FROM AUTHOR]

Various strand concept for high-temperature superconductor (HTS) flat tapes have been developed in the past few years for fusion magnet applications. We developed a round HTS strand with soldered multilayer copper tapes as filler and support called SaMiT following the technic path of twisted stacked-tape cable. DC tests performed under bending and twisting condition demonstrated that the proposed design of the HTS strand is promising in the high current cable and magnet application, but the study on electromechanical properties against the transverse and cyclic load is still needed. A press device was designed to measure the critical current of SaMiT sample at 77 K and self-field as a function of transverse and cyclic load to simulate the electromagnetic force load during the magnet operation. Transverse load amplitudes have been applied up to 40 MPa and cyclic load up to 1000 cycles at certain load amplitude. The experimental results are presented and structural optimization suggestions are discussed with visual inspection and analysis. [ABSTRACT FROM AUTHOR]

The local thermal disturbance will produce a joule heat. When the joule heat is larger than the minimum quench energy (MQE), it will lead to the phenomenon of a quench. The same problem exists in stacked superconducting tapes. In this article, the defects in REBCO tapes were created using the bending method. The voltage and temperature traces were measured during the quench process. The quench characteristics of the MQE and normal zone propagation velocity (NZPV) of the stacked REBCO tapes were investigated of different stacked REBCO tapes in the following configurations: two defects-free tapes; one defect-free tape and one tape with a defect; and both tapes with defects. The MQE of the stacked tapes with the defect is smaller than that of the tapes without defects, while the NZPV of the stacked tapes with the defect is larger than that of the tapes without defects. [ABSTRACT FROM AUTHOR]

This article intends to explore the optimal electrical characteristics of different winding processes for future high-field accelerator magnet insert. In the study, five double-pancake (DPC) racetrack ReBCO coils were wound by dry winding with no insulation (NI) process, dry winding with Kapton insulation (KI) process, wet winding with KI process, wet winding with NI process, and dry winding cowound with stainless steel tape process, respectively. The five DPC racetrack coils were fabricated and tested at 77 K in the Institute of High Energy Physics, Chinese Academy of Sciences. The article mainly presented the two winding processes, dry winding with NI and cowind with 304 stainless steel tape insulation since their special self-protect character during quench and delay effects during excitation and demagnetization. Through the experiments, we studied the characteristics of different winding processes and quench protection methods, which are important for the future application of High-temperature superconducting (HTS) insert coils. [ABSTRACT FROM AUTHOR]

Trapped-flux magnets made of stacks of superconducting tapes are an interesting and important alternative to the application of rare-earth permanent magnets and trapping flux in bulk superconductors. Many applications, such as electric motors, can require the complex shapes of magnetic elements to combat issues such as demagnetization during the operation. Therefore, a reliable production technique of high temperature superconductor (HTS) stacks with different geometries is required to meet the needs of industry. In this article, a method of shaping the epoxy-glued stacks of superconducting tapes is proposed and investigated. The application of hot press allows to easily change the shape of the stack. The influence of shaping the stack on the density of trapped magnetic flux as well as critical current are presented. Experimental and numerical analyses are performed and their results are matched to find the change in the superconducting properties of the tapes. They show that with the proper process parameters the stacks can be shaped with only minor decrease of performance. However, strong degradation is observed if the applied force is too high. The observed problems are discussed and the possible solutions are proposed. [ABSTRACT FROM AUTHOR]

A new modular configuration of resistive superconducting fault current limiter (SFCL) unit is developed to study the temperature and resistance profile on copper laminated 2G high-temperature superconductor (HTS) tape during fault and recovery at 77 K using a lab-scale resistive modular SFCL unit. The thermal characteristics and their transition behavior, i.e., the resistance profile on the HTS tape are investigated using five cycles of the fault of peak currents 1.8, 2.2, and 4 kA. The temperature of the HTS tape is measured during fault and recovery under load. The fault limiting characteristics are analyzed for various output voltages (20, 40, and 60 Vrms) across the modular SFCL unit. The resistance profile on the HTS tape is estimated analytically, which is compared with the experimental measurement of resistance. The recovery time is measured and it is correlated with the peak temperature on the HTS tape and the associated heat transfer in the liquid nitrogen bath. The study will be useful for developing a higher rating of SFCL using this modular configuration. [ABSTRACT FROM AUTHOR]

Continuous cardiac monitoring using electrocardiograms (ECG) provides a range of patient information, essential for making clinical decisions, to healthcare providers. Unfortunately, the clinical standard of ECG recording requires the use of rigid metal electrodes, conductive gels, and wired electronic devices, which often cause skin injuries and health risks for pediatric patients with underdeveloped, fragile skin. Here, we introduce a wireless, soft, comfortable electronic system that obviates the need for skin preparation, electrolyte gels, or aggressive tapes. The low-profile device incorporates a thin-film circuit and nanomembrane sensors, encapsulated in a hyperelastic elastomer. The soft elastomeric membrane offers an optimized adhesion that ensures a conformal lamination of stretchable electrodes on the skin for recording of high-fidelity biopotentials. The combined set of on-board Bluetooth module, front-end amplifier, and voltage regulator enables a real-time, long-range, wireless monitoring of physiological data, including ECG, heart rate (HR) and respiratory rate (RR). A pilot study with pediatric patients demonstrates the clinical feasibility of the device as a comfortable, reliable biopotential monitor, suggesting a new standard for safe and effective pediatric care. [ABSTRACT FROM AUTHOR]

A great progress in the electrical performance of high-temperature superconductor (HTS) REBCO tapes allows for a much increased transport current capability in cables especially at high magnet fields. This is of interest to future fusion magnet applications. A variant type of twisted stacked-tape cable called quasi-round twisted stacked-tapes conductor (QisTac) is proposed and developed for the superconducting conductor of the China fusion engineering test reactor. The stack of the twisted HTS tapes is wrapped by a tight spiral made with copper wires. The stack with the copper wire is, then, soldered to form the solid round conductor, which is reliable and easy to manufacture in long lengths. A QisTac sample with four REBCO tapes was prepared and measured at 77 K and in the self-field condition. The measurement result shows the expected critical current calculated from the individual tapes considering the self-field effect. The bending characteristic of the sample was also tested under different bending radii. The critical current is reduced by roughly 5% at 0.54% bending strain. Some residual bending strain is maintained when the maximal bending force is released. This result is promising, but reproducibility testing and tests at high field and current are needed for future high field application. [ABSTRACT FROM AUTHOR]

This article presents a simple approach for high-accuracy assembly of multiple ultrathin chips on flexible foil substrates. The chips are placed initially in the cavities on a chip carrier substrate and transferred onto a thermally releasable adhesive tape. After application of the epoxy-based adhesive onto the chip surface, the chips are transferred onto the foil substrate. Finally, the epoxy adhesive is cured and the adhesive tape is removed. It was found that a wafer dicing tape with a releasing temperature of 90 °C as thermally releasable adhesive tape and a two-component epoxy adhesive with a curing temperature of 65 °C is suitable for the process. High placement accuracy of the chips of less than $30~\mu \text{m}$ in the ${x}$ - and ${y}$ -orientation as well as rotational misalignment lower than 0.2° were obtained. The process is demonstrated on a polyimide foil with a resulting chip flatness of $\pm 5~\mu \text{m}$. [ABSTRACT FROM AUTHOR]

Polyglass banding tapes consist of parallel, non-woven, twisted and high tensile strength glass yarns that are pre-impregnated with a special thermosetting resin; the resin employed permits long self life in the semi cured tapes. The tape has replaced steel rope in large dc rotor, commutator banding and transformer leg locking to minimize eddy current, over-heating and flashover etc. The thermosetting resin has an important role in the performance of polyglass banding tapes. A new polyglass banding tape was developed with a very special thermosetting polyester resin modified with organic silicone compound. The mechanical and electrical properties of the cured banding tape were thoroughly evaluated. Special test rings were fabricated from this tape to measure the moisture resistance by the effects of immersion in boiling water on tensile strength. The accelerated thermal aging test on the flexural strength of the tape was done and the Arrhenius type plot of logarithm of time vs. inverse of absolute temperature to 20000 hours line gave its temperature class. It was observed that the new polyglass banding tape had very high thermal stability (over 220 °C) as well as an excellent humidity resistance. The cured structure was a homogenous laminate with smooth, resin rich surface that offered excellent track and arc resistance. The silicone modified polyester based glass banding tape is expected to be suitable for motor and transformer operating in a tropical environment as evidenced from the sufficient resistance to moisture. [ABSTRACT FROM AUTHOR]

Developing a flexible and adaptable sensor for the detection of ethanol vapor is important for many healthcare and environmental applications. Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate has shown excellent electrical properties and is easily processed. Adhesive tapes are used widely in many applications due to their excellent adaptability to various environments. Here, we show, for the first time, the development of a flexible adhesive tape-based sensor for the detection of ethanol vapor. The sensor shows a detection range of 5%–60% of saturated ethanol vapor and a rapid measuring time of about 15 s with an excellent linear correlation to the commercial available sensor. It is expected that these results could open exciting opportunities for fundamental studies of construction of new types of flexible sensors as well as serve in various healthcare, environmental, and defense applications. [ABSTRACT FROM AUTHOR]

An all polyimide system made by plain and adhesive coated tapes has been adopted for the insulation of the LHC coils. In this analysis we put in evidence how different parameters in the curing cycles could affect the final bonding quality. Data for two different glue compositions are compared showing how the conjoint efforts of CERN and tape supplier Kaneka High-Tech Materials has helped to enlarge the window in which this material provides outstanding gluing, making easier to keep under control bonding quality throughout the mass production in a real industrial environment. [ABSTRACT FROM AUTHOR]

The development of new bioelectronic platforms could provide exciting new opportunities for clinical analysis, environmental monitoring, and defense. Wearable adhesive tapes could adhere to skin to be in close contact with sweat that consists of many healthcare-related proteins, small molecules, and ions, and thus could function as unique platforms for the sensor construction. Here, we show for the first time the construction of wearable adhesive tape-based smart biosensing systems, and their determinations of lactate and glucose. The sensor is built by printing carbon graphite and Ag/AgCl inks on an adhesive tape to function as the working, reference, and counter electrodes, followed by the immobilization of lactate oxidase or glucose oxidase on the working electrode. The sensor shows a sensitive and broad detection range from micromolar to millimolar, and a quick measuring time of within 5 min for the determination of lactate or glucose. It is expected that these results could open up exciting new avenues for the development of novel wearable sensors, and toward advanced sweat-sensor applications. [ABSTRACT FROM AUTHOR]