Search

This article investigates the influence of manufacturing tolerances of modular stator core, including radial, circumferential, and axial displacements, on the electromagnetic performance of a modular permanent magnet (PM) machine. First, the analytical analysis of no-load back electromotive force (EMF), circulating current, cogging torque, and unbalanced magnetic force (UMF) is derived. Second, several typical cases are selected to investigate the effects of the three displacement faults. Then, the effects of a single module under the same displacement amplitude fault are compared, and the results reveal the tolerance of electromagnetic performance to different displacements. Finally, references for the design, processing, and manufacturing of modular motors are provided by the analysis results of this article.

In high-temperature superconducting homopolar inductor machine (HTS-HIM), the stationary high-temperature superconducting (HTS) excitation coil is directly exposed to complex external perpendicular alternating field (EPAF). In this situation, the ac loss including dynamic loss and magnetization loss will occur in the HTS coil carrying direct current, which is harmful to the operation of HTS-HIM. To avoid the thermal runaway quench of HTS coil caused by ac loss and ensure the safe and reliable operation of HTS-HIM, the EPAF acting on the HTS coil is investigated and suppressed in this article. First, the characteristics of the EPAF of HTS coil in HTS-HIM are obtained through theoretical and finite element analysis. Then, based on the distribution of EPAF and the special structure of HTS-HIM, a combined suppression method using two sets of U-shaped armature windings and L-shaped flux diverter is proposed and analyzed. The results show that the shielding factors of fundamental and dc components can be reduced to 25% and 31%, respectively.

The electric aircraft propulsion system requires high speed and high power-weight ratio electrical machines. This paper presents a superconducting homopolar inductor machine (HIM) based on HTS REBCO magnets, which could be a promising candidate for high power density electrical machines for future electric aircraft propulsion system. The HTS-HIM has a simple structure, high rotating speed, and huge potential to achieve a high power-weight ratio (kW/kg). This paper presents our design of a 10 kW HTS-HIM with a rotating speed of 3000 rpm. The structure and crucial parameters of HTS-HIM are presented. A 2D-axial pancake coil model for HTS REBCO magnets was built by using COMSOL. Based on this model, HTS REBCO magnets were design and optimized. The loss of REBCO magnets was also calculated. Finally, the output performance of the 10 kW HTS-HIM was simulated. Our work provides preliminary simulation and analysis for future MW-class HTS-HIM.

The electrical machines with fractional slot windings have been widely investigated. The main challenge of this type of machines is that the magnetomotive force (MMF) harmonics of armature winding is rich, which would lead to torque ripple, eddy current loss, and other adverse effects. In this article, multiple three-phase star–delta windings connection for multiphase electrical machine is proposed, which can efficiently reduce the MMF harmonics of armature winding. First, the general principle of harmonic elimination of multiphase electrical machine with multiple star—delta winding connection is deduced. Then, the influence of multiple star–delta windings of machines with different slot/pole combinations on MMF harmonics of armature winding is investigated. To verify the theoretical analyses, the models of permanent magnetic machine with 24-slot and 36-slot are established, and the multiple star–delta windings is compared with the conventional three-phase, star–delta windings and multiple three-phase windings in terms of torque, torque ripple, loss, vibration, and so on, so as to evaluate the superiority of this connection method. Finally, a prototype with 24-slot/10-pole is manufactured and tested. The test results verify the rationality of the theoretical analyses and simulations.

A method for calculating the critical current of high temperature superconducting (HTS) machine using boundary magnetic vector potential constrain and bisection method is proposed in this article. The indirect coupling between superconducting and non-superconducting regions of HTS machine is realized through boundary magnetic vector potential constrain, which avoids the model complexity caused by direct coupling and saves computation time. Taking a 10 kW double-stator HTS machine (DS-HTSM) as an example, the process of calculating critical current through proposed method is given. To verify the correctness and accuracy of proposed method, a direct coupling model of DS-HTSM is established. The results show that there is a high consistency of critical current and magnetic field distribution of direct and indirect coupling models. The calculated results of critical current are in agreement with the experimental in relevant research. The proposed method is quite effective for calculating the critical current of different HTS machines.

Cogging torque (CT) would cause the vibration and noise of the permanent magnet homopolar inductor machine (PMHIM), which should be suppressed. However, the unipolar air-gap flux density and the dual-segment stator and rotor cores of PMHIM make the characteristics of CT unclear, which leads to a lack of theoretical basis for suppressing the CT. Addressing this issue, the CT of PMHIM is investigated and suppressed. First, the model of CT of PMHIM with integer and fractional slot configurations is developed, and the factors affecting the CT are revealed. Then, the methods for suppressing the CT are proposed based on changing rotor parameters. The influences of different rotor parameters on electromagnetic performance, including back electromagnetic force (EMF), output torque, current, and efficiency are fully analyzed. In addition, the characteristics of the proposed method are highlighted by comparing the performance of the method proposed in this article with the global optimization method in terms of CT suppression. Finally, the theoretical analyzes are validated by experiments. The results show that the CT of PMHIM can be effectively suppressed by the proposed method in this work.

The high temperature superconducting homopolar inductor machine (HTS-HIM) is identified as a promising candidate for the high-speed field of superconducting machine. The reliability and performance of HTS-HIM is closely related to the critical current of its HTS excitation coil. However, the critical current is limited by the turn with the highest risk of quench, which means that not all the turns of HTS coil can achieve the best performance. Targeting ensures the reliability of HTS-HIM and enhance the utilization rate of HTS tape, the HTS coil is designed considering the critical current reduction of local turn in this paper. Firstly, the operation principle of HTS-HIM is illustrated, and the design process is given. Then, the feasibility of calculating critical current using constant sweep rate method is described, and the HTS coil of a 10 kW HTS-HIM is designed utilizing the MAX criterion. Thirdly, the external field of the HTS coil is analyzed based on the simplified model of HTS-HIM. According to the external field distribution, an easily installed L-shaped flux diverter is proposed to suppress critical current reduction of local turn of HTS coil. The results show that the current safety margin is increased by 24% at the cost of very little extra loss and weight through the proposed method.

The armature winding of slotless motor is directly exposed to the air-gap magnetic field. During high-speed operation, the effective part of the armature winding cuts the flux lines directly, which would inevitably cause large ac copper loss. Moreover, when the rotor is eccentric, appreciable distortions would be appeared in the air-gap flux density. The additional flux density would aggravate the ac copper loss. In this article, the mechanism of ac copper loss of high-speed slotless motors is explained first. Then, the influence of eccentricity on ac copper loss is evaluated. Finally, the difference in the effect of dynamic and static eccentricity on ac copper loss is compared.

In this paper, a practical process to synthesize the key intermediate R-tetrahydropapaverine of cisatracurium besylate was proposed. First, tetrahydropapaverine hydrochloride (1.HCl) was prepared from inexpensive and commercially available 2-(3,4-dimethoxyphenyl)ethanamine (2) and 3,4-dimethoxybenzeneacetic acid (3) through a one-pot process. The yield and purity of the product were up to 85.4 and 98.1% on a 150 g scale, respectively. Then, a new resolution process was developed to prepare R-tetrahydropapaverine by using a half equivalent of N-acetyl-d-phenylalanine, and the obtained R-tetrahydropapaverine had a yield of 28.1% and 98.0% eeon a 120 g scale. Furthermore, the S-isomer was racemized to 1.HCl in the one-pot process with 77.7% isolated yield and 99.0% purity.

Ephemeral gullies are widely distributed in the hilly and gully region of the Loess Plateau and play a unique role in the slope gully erosion system. Rapid and accurate identification of ephemeral gullies impacts the distribution law and development trend of soil erosion on the Loess Plateau. Deep learning algorithms can quickly and accurately process large data samples that recognize ephemeral gullies from remote sensing images. Here, we investigated ephemeral gullies in the Zhoutungou watershed in the hilly and gully region of the Loess Plateau in China using satellite and unmanned aerial vehicle images and combined a deep learning image semantic segmentation model to realize automatic recognition and feature extraction. Using Accuracy, Precision, Recall, F1value, and AUC, we compared the ephemeral gully recognition results and accuracy evaluation of U-Net, R2U-Net, and SegNet image semantic segmentation models. The SegNet model was ranked first, followed by the R2U-Net and U-Net models, for ephemeral gully recognition in the hilly and gully region of the Loess Plateau. The ephemeral gully length and width between predicted and measured values had RMSE values of 6.78 m and 0.50 m, respectively, indicating that the model has an excellent recognition effect. This study identified a fast and accurate method for ephemeral gully recognition in the hilly and gully region of the Loess Plateau based on remote sensing images to provide an academic reference and practical guidance for soil erosion monitoring and slope and gully management in the Loess Plateau region.

[Display omitted]

CRISPR-Cas9 is a common tool for gene editing, and appropriate sgRNAs are the key factor for successful editing. In this study, the effect of sgRNA length and number on editing efficiency was analyzed in rice using CYP81A6as the target gene. A series of CRISPR-Cas9 plant expression vectors containing single sgRNAs with different lengths (17, 18, 19, 20, 21, 22, 23 nt) or two sgRNAs were constructed and introduced into rice cultivar Zhonghua11 by Agrobacterium-mediated transformation. Analysis of the editing status of 1283 transgenic rice plants showed that 371 were successfully edited with base preference. Single A or T insertions were the most frequent among the six edited types. The editing efficiency of transgenic rice with two sgRNAs was higher than that with a single sgRNA. Editing efficiency and sgRNA length showed a normal distribution with 20 nt sgRNA (25%) being the most efficient. The editing efficiency decreased slightly with decreases of 1–2 bases (19 nt 20%, 18 nt 21%), but decreased significantly with a decrease of 3 bases (17 nt 4.5%). Editing efficiency was significantly reduced by adding 1 to 3 bases (21 nt 16.8%, 22 nt 13%, 23 nt 13%) to the sgRNA. These results provide data for successful gene editing or rice by CRISPR-Cas9.

The irrational or excessive use of antibiotics causes the emergence of bacterial resistance, making antibiotics less effective or ineffective. As the number of resistant antibiotics increases, it is crucial to develop new strategies and innovative approaches to potentiate the efficacy of existing antibiotics. In this paper, we report that some existing antibiotics can produce reactive oxygen species (ROS) directly under light irradiation. Thus, a novel antibacterial photodynamic therapy (PDT) strategy is proposed by using existing antibiotics for which the activities are potentiated via light-activation. This antibiotic-based PDT strategy can achieve efficient bacteria killing with a low dosage of antibiotics, indicating that bacterial killing can be enhanced by the light-irradiated antibiotics. Moreover, the specific types of ROS produced by different antibiotics under light irradiation were studied for better elucidation of the antibacterial mechanism. The findings can extend the application of existing antibiotics and provide a promising strategy for treatment of bacterial infections and even cancers.

Hollow mesoporous carbon submicrospheres (HMCNs) have been successfully synthesized via a facile silica-assisted sol–gel strategy, which were further treated with KOH or/and HNO3to obtain four adsorbents with different structures and surface properties for the removal of dibenzothiophene (DBT). KOH activation can effectively adjust the micro/mesoporous structure by increasing the number of micropores, and HNO3oxidation can modify the surface properties by introducing oxygen-containing functional groups. HMCNs treated with KOH first and then HNO3are the best for DBT removal with the adsorption capacity of 33.20 mg S·g–1, which is nearly 45% higher than that of activated carbon with the same treatment. Notably, the adsorption equilibrium can be achieved within only 5 min, much faster than active carbon owing to the existence of abundant mesopores favorable to the diffusion of DBT. The negative ΔG° from thermodynamics result suggests it is a favorable and spontaneous adsorption process.

The emergence of drug-resistant bacteria severely challenges the antimicrobial agents and antibacterial strategy. Here, we demonstrate a novel, simple, and highly efficient combination therapy strategy by direct combinations of cationic conjugated polymers (CCPs) with polypeptide antibiotics against Gram-negative and Gram-positive bacteria based on a synergistic antibacterial effect. The combination therapy method enhances the antibacterial efficacy with a significantly reduced antibiotic dosage. Also, the highly efficient and synergistic killing of drug-resistant bacteria is realized. Using combinations of CCPs and antibiotics to show increased antibacterial activity, this strategy will provide a much wider scope of the discovery of efficient antibacterial systems than that of antibiotic–antibiotic combinations. The proposed combination therapy method provides a universal and powerful platform for the treatment of pathogens, in particular, the drug-resistant bacteria, and also opens a new way for the development of efficient antibacterial systems.

With the widespread cultivation of transgenic crops, there is increasing concern about unintended effects of these crops on soil environmental quality. In this study, we used the Biolog method and ELISA to evaluate the possible effects of OsrHSA transgenic rice on soil microbial utilization of carbon substrates under field conditions. There were no significant differences in average well-color development (AWCD) values, Shannon–Wiener diversity index (H), Simpson dominance indices (D) and Shannon–Wiener evenness indices (E) of microbial communities in rhizosphere soils at eight samplings between OsrHSA transgenic rice and its non-transgenic counterpart. The main carbon sources utilized by soil microbes were carbohydrates, carboxylic acids, amino acids and polymers. The types, capacities and patterns of carbon source utilization by microbial communities in rhizosphere soils were similar throughout the detection period. We detected no OsrHSA protein in the roots of OsrHSA transgenic rice. We concluded that OsrHSA transgenic rice and the rHSA protein it produced did not alter the functional diversity of microbial communities in the rhizosphere.

To establish a model for nerve grafts and determine the anatomic characteristics of the brachial plexus in rhesus monkeys. Ten specimens of the brachial plexus were obtained from five rhesus monkey cadavers. Anatomic dissection of the brachial plexus was systemically performed. The length of each root, trunk, and each division was measured using a Vernier caliper proximodistally. The anatomic distributions of the suprascapular, axillary, and musculocutaneous nerve were documented. The brachial plexus of rhesus monkeys included the spinal nerves or roots of C5, C6, C7, C8, and T1 (80, 810), with a small contribution from the C4 root (20, 210) occasionally. The upper trunk was not measurable because of their irregular structures. The lower trunk had a mean length of 1.62 (range, 0.96–2.1 mm) and a mean diameter of 2.29 (range, 1.9–2.94 mm). For the upper trunk, the C5 and C6 roots either divided into two very short divisions or sent out very long divisions before they joined together. For the middle trunk, the C7 root had a straight course after leaving the foramen and blended imperceptibly into the middle trunk before dividing into the anterior and posterior divisions. The lower trunk was noted in almost all the specimens (80, 810), which was formed by C8 and T1. The brachial plexus in rhesus monkeys varies from that of humans, and defects can be made at the level of C5 and C6 roots and the C7 root should also be cut off and ligated.

The catalytic hydrogenation of petroleum resin (PR) is an efficient process to produce high-value-added hydrogenated PR with improved performance and wide applications. Herein, a hierarchical flower-like NiCu/SiO2bimetallic catalyst has been successfully prepared by reducing the hierarchically structured NiCu silicate precursor ((Ni,Cu)3Si2O5(OH)4) and applied for PR hydrogenation. The generated bimetallic NiCu alloy nanoparticles are anchored on the surface of the intercrossed silica nanoplatelets, constructing a unique multilevel NiCu/SiO2superstructure. Moreover, the addition of Cu could not only lower the reduction temperature of Ni species but also provide electrons to Ni to form electron-rich active sites. The NiCu/SiO2bimetallic catalyst exhibited enhanced catalytic activity and stability for PR hydrogenation. The hydrogenation degrees for C5PR and C9PR could reach up to 94.9 and 96.3%, respectively, which are much higher than those catalyzed by the catalyst prepared via an impregnation method (85.9 and 88.7%). Such notably enhanced performances could be ascribed to the synergistic effect between Ni–Cu bimetals and the highly porous superstructure. Our findings provide guidance for the design and synthesis of efficient and stable bimetallic nanocatalysts for PR hydrogenation.