Design consideration and conductor selection of a low AC loss HTS REBCO magnet carrying high currents at 20 K and 40 K

AC loss in high temperature superconductor coils have been frequently studied, however, mostly for AC power applications at 77 K, rather than specifically for high current but low frequency AC superconducting magnet at 20–40 K. Due to their easy operation and Helium shortage, more HTS magnet systems employ conduction-cooling with cryocoolers. The HTS magnets are known for high stability and likely tolerate high AC loss, but it is unclear what is the maximum AC frequency assuming that cryocooler has limited capability (a few hundred Watts) for the 20-40 K temperature range. This paper will specifically study AC loss in a simple HTS dipole but with three conductor/cable options using simulations, (1) 12 mm wide tape, (2) two parallel 6 mm wide tapes, and (3) 6/2 (six 2 mm strands) Roebel cables. It has been found that the magnet at 5 Hz generates 200–400 W AC loss at 20 K or 40 K, potentially be cooled by two single stage cryocoolers. The 6/2 Roebel cable based magnet may allow higher frequency (6–8 Hz) due to its transposition and narrower conductor width

Optimizing coil configurations for AC loss reduction in REBCO HTS fast-ramping magnets at cryogenic temperatures

AC loss is one of the critical issues for designing REBCO fast-ramping magnets operating at cryogenic temperatures. There are many ways to reduce AC loss for coil windings. However, it is not clear which method is the most effective way to minimize AC loss in the coil windings for a given Ampere-turns. In this work, we numerically studied coil configurations of several small superconducting magnets constructed from 12 mm SuperPower REBCO coated conductors, for fast-ramping application with the same Ampere-turns to identify the lowest AC loss among them. The HTS magnets have a total turn number of 50 and inner diameter of 30 cm, carrying AC current operating in the temperature range of 20 K – 40 K at 25 Hz. We incorporated several existing loss reduction strategies including spacing between the turns for single pancake coils, grading Ic values for the solenoid configuration, and applying flux diverters to shape the magnetic field around the coil windings. The simulation was implemented using a homogenized H-formulation. Across all studied loss reduction methods, the use of flux diverters has the largest impact in AC loss reduction. The AC loss values in the solenoid winding comprising a stack of five single pancake coils with 0.1 mm turn-to-turn gap with the flux diverters agree well with those in the single pancake coil for 2 mm turn-to-turn gap with the flux diverters. Solenoid type coil configurations with flux diverters generate much smaller AC loss than the single pancake type with flux diverters when they generate the same center magnetic field

Accurately Estimating Rigid Transformations in Registration using a Boosting-Inspired Mechanism

Feature extraction and matching provide the basis of many methods for object registration, modeling, retrieval, and recognition. However, this approach typically introduces false matches, due to lack of features, noise, occlusion, and cluttered backgrounds. In registration, these false matches lead to inaccurate estimation of the underlying transformation that brings the overlapping shapes into best possible alignment. In this paper, we propose a novel boosting-inspired method to tackle this challenging task. It includes three key steps: (i) underlying transformation estimation in the weighted least squares sense, (ii) boosting parameter estimation and regularization via Tsallis entropy, and (iii) weight re-estimation and regularization via Shannon entropy and update with a maximum fusion rule. The process is iterated. The final optimal underlying transformation is estimated as a weighted average of the transformations estimated from the latest iterations, with weights given by the boosting parameters. A comparative study based on real shape data shows that the proposed method outperforms four other state-of-the-art methods for evaluating the established point matches, enabling more accurate and stable estimation of the underlying transformation

Non-uniform ramping losses and thermal optimization with turn-to-turn resistivity grading in a (RE)Ba₂Cu₃O_x magnet consisting of multiple no-insulation pancake coils

This paper presents a study on the ramping losses of a high temperature superconductor (HTS) magnet consisting of multiple no-insulation (NI) (RE)Ba2Cu3Ox coils. The (RE)Ba2Cu3Ox (REBCO) conductor is the second generation HTS thin tape, where RE stands for rare-earth. During a ramping operation of the NI HTS magnet, losses are generated both across turn-to-turn resistances and inside superconducting layers. The former comes with radial current, which is called "turn-to-turn loss;" the latter one is induced by flux creep and jump, called "magnetization loss." The modeling and experimental studies on the ramping losses have been reported on single NI pancake coils in the previous part. In a HTS magnet consisting of multiple NI coils, the electromagnetic coupling between coils has a considerable influence on the distribution of ramping losses. Here, the experimentally validated model is used to investigate a HTS magnet consisting of 14 single pancake REBCO coils. The results show that both the turn-to-turn loss and the magnetization loss present a significant non-uniform distribution among the coils. The highest turn-to-turn loss occurs on the middle coils of the magnet, while the highest magnetization loss happens on the end coils. The non-uniform distribution of ramping losses can result in a considerable temperature difference among coils in the NI HTS magnet. It leads to an additional quench risk on the magnet and requires more attention in design. The distribution of the turn-to-to-turn loss can be optimized by adjusting the turn-to-turn resistivity. A much more uniform turn-to-turn loss distribution among coils is achieved by applying a graded turn-to-turn resistivity on the multiple coils

Soybean root transcriptome profiling reveals a nonhost resistant response during Heterodera glycines infection.

Heterodera glycines (soybean cyst nematode, SCN) is one of the most devastating pathogens of soybean worldwide. The compatible and in compatible interactions between soybean and SCN have well documented. Nevertheless, the molecular mechanism of a nonhost resistant response in soybean against SCN infection remains obscure. Toward this end, a global transcriptional comparison was conducted between susceptible and resistant reactions of soybean roots infected by taking advantage of finding a new pathotype of SCN (SCNT). The soybean cultivar Lee, which exhibits resistant to SCNT and susceptible to HG 1.2.3.4.7 (SCNs) was utilized in the expriments. The results highlighted a nonhost resistant response of soybean. Transcriptome analysis indicated that the number of differentially expressed genes (DEGs) in the resistant interaction (3746) was much larger than that in the susceptible interaction (602). A great number of genes acting as intrinsic component of membrane, integral component of membrane, cell periphery and plasma membrance were remarkably enriched only in the resistant interaction, while the taurine and hypotaurine, phenylpropanoid pathway, plant-pathogen interaction and transcript factors were modulated in both interactions. This is the first study to examine genes expression patterns in a soybean genotype in response to invasion by a virulent and avirulent SCN population at the transcriptional level, which will provide insights into the complicate molecular mechanism of the nonhost resistant interaction

How Much Are Amenities Worth? An Empirical Study on Urban Land and Housing Price Differentials across Chinese Cities

As China is transitioning from a planned economy to a market-based economy, over the past 30 years, China’s economy has experienced the same type of changes that led to amenity-driven housing and land markets in more developed countries. This paper examines the effect of different types of amenities on urban land and housing prices across Chinese cities in 2020. When firms and households value some amenities, the assumption is that the preference for these amenities will be valued and reflected in both land and housing markets. We conduct a cross-sectional analysis of urban land and housing prices in prefecture and higher-level cities in China. We extend the Roback model to explore the extent to which the different land rents and housing prices reflect the compensations for interregional amenity differences across Chinese cities. We include two types of amenities: natural amenities and locally produced amenities. We perform two-stage least squares (2SLS) estimations and compute the implicit prices of various amenities for households and firms. The empirical results show that a range of amenities is valued by both households and firms, resulting in higher housing and industrial prices