Spatial Magnetic-Field Description Method Aimed at 2 × 25 kV Auto-Transformer Power Supply System in High-Speed Railway

Complete and accurate spatial magnetic field description is the premise of effectively assessing the power supply capability of a high-speed railway (HSR). Its evaluation indicators are the current distributions and the integrated impedance of traction network. This paper proposes a spatial magnetic-field description method for the auto-transformer (AT) power supply system. Due to the limitations of previous approaches, all the real loop circuits of the AT system are considered for structuring a loop circuit matrix. At first, different description processes are divided, respectively, into those for the right side and the left side of the load. Then, considering that two types of return conductors exist in an AT system, a certain current ratio deduced in existing studies is introduced. As the introduced current ratio of the left side of the load is approximate, an iterative scheme is adopted. By constantly adjusting current ratio to satisfy a constraint condition of circuit voltages, accurate traction network impedance is obtained. Last, in order to verify the effectiveness of the proposed description method, two real-life experiments in a Chinese HSR line are performed, which indicate that the proposed method can not only directly reflect complete and accurate current distribution, but also deduce the exact traction network integrated impedance

A Vibration Model of Ball Bearings with a Localized Defect Based on the Hertzian Contact Stress Distribution

To study the vibration mechanism of ball bearings with localized defects, a vibration model of a ball bearing based on the Hertzian contact stress distribution is proposed to predict the contact force and vibration response caused by a localized defect. The calculation of the ball-raceway contact force when the ball passes over the defect is key to establishing a defect vibration model. Hertzian contact theory indicates that the contact area between the ball and the raceway is an elliptical contact surface; therefore, a new approach is used to calculate the ball-raceway contact force in the defect area based on the stress distribution and the contact area. The relative motion between the inner ring, the outer ring, and the balls is considered in the proposed model, and the Runge-Kutta algorithm is used to solve the vibration equations. In addition, vibration experiments of a bearing with an outer ring defect under different loads are performed. The numerical signals and experimental signals are compared in the time and frequency domains, and good correspondence between the numerical and experimental results is observed. Comparisons between the traditional model and the proposed model reveal that the proposed model provides more reasonable results

A Vibration Model of Ball Bearings with a Localized Defect Based on the Hertzian Contact Stress Distribution

To study the vibration mechanism of ball bearings with localized defects, a vibration model of a ball bearing based on the Hertzian contact stress distribution is proposed to predict the contact force and vibration response caused by a localized defect. The calculation of the ball-raceway contact force when the ball passes over the defect is key to establishing a defect vibration model. Hertzian contact theory indicates that the contact area between the ball and the raceway is an elliptical contact surface; therefore, a new approach is used to calculate the ball-raceway contact force in the defect area based on the stress distribution and the contact area. The relative motion between the inner ring, the outer ring, and the balls is considered in the proposed model, and the Runge-Kutta algorithm is used to solve the vibration equations. In addition, vibration experiments of a bearing with an outer ring defect under different loads are performed. The numerical signals and experimental signals are compared in the time and frequency domains, and good correspondence between the numerical and experimental results is observed. Comparisons between the traditional model and the proposed model reveal that the proposed model provides more reasonable results

Slab Breakoff of the Neo-Tethys Ocean in the Lhasa Terrane Inferred From Contemporaneous Melting of the Mantle and Crust

Oceanic slab breakoff significantly affects the thermal regime of the lithosphere during continental collision. This often triggers extension-related mafic magmatism and crustal melting. It is generally accepted that the Neo-Tethyan lithosphere subducted beneath the southern Lhasa Subterrane, resulting in the formation of the Gangdese magmatic arc. However, the timing of slab breakoff is still disputed, due to a lack of evidence for extension-related mafic magmatism. In this study, we provide comprehensive age, element and Sr-Nd-Hf isotopic data of mafic dikes, felsic intrusions, and enclaves from the Daju area, southern Lhasa Subterrane. The timing of mafic dikes and granitoids are contemporaneous at circa 57 Ma. The mafic dikes are characterized by high Th/U, and Zr/Y ratios, their geochemistry indicates an intraplate affinity rather than arc magmas. Furthermore, the mafic dikes show strongly variable igneous zircon (Hf)(t), and lower whole-rock (Nd)(t) than granitoids. This evidence suggests that the mafic dikes represent asthenosphere-derived melts contaminated by various degrees of ancient lithosphere. However, the granitoids were directly derived from the juvenile lower crust. Given the abrupt decrease in the convergence rate between India and Asia, and the surface uplift and sedimentation cessation in the southern Lhasa Subterrane in the early Cenozoic, the occurrence of synchronous mafic dikes and granitoids is best explained by a slab breakoff model. The occurrence of intraplate-type magmas likely corresponds to the magmatic expression of the initial stage of Neo-Tethyan slab breakoff. The slab breakoff concept also explains the onset of the magmatic flare-up and crustal growth after 57 Ma

Mapping and Candidate Gene Analysis of the Low-Temperature-Sensitive Albino Gene <i>OsLTSA8</i> in Rice Seedlings

Chloroplasts are organelles responsible for photosynthesis in plants, providing energy for growth and development. However, the genetic regulatory mechanisms underlying early chloroplast development in rice remain incompletely understood. In this study, we identified a rice seedling thermosensitive chlorophyll-deficient mutant, osltsa8, and the genetic analysis of two F2 populations suggested that this trait may be controlled by more than one pair of alleles. Through reciprocal F2 populations and QTL-seq technology, OsLTSA8 was mapped to the interval of 24,280,402–25,920,942 bp on rice chromosome 8, representing a novel albino gene in rice. Within the candidate gene region of OsLTSA8, there were 258 predicted genes, among which LOC_Os08g39050, LOC_Os08g39130, and LOC_Os08g40870 encode pentatricopeptide repeat (PPR) proteins. RNA-seq identified 18 DEGs (differentially expressed genes) within the candidate interval, with LOC_Os08g39420 showing homology to the pigment biosynthesis-related genes Zm00001d017656 and Sb01g000470; LOC_Os08g39430 and LOC_Os08g39850 were implicated in chlorophyll precursor synthesis. RT-qPCR was employed to assess the expression levels of LOC_Os08g39050, LOC_Os08g39130, LOC_Os08g40870, LOC_Os08g39420, LOC_Os08g39430, and LOC_Os08g39850 in the wild-type and mutant plants. Among them, the differences in the expression levels of LOC_Os08g39050 and LOC_Os08g39430 were the most significant. This study will contribute to further elucidating the molecular mechanisms of rice chloroplast development

Tuning the Activities of Cu2O Nanostructures via the Oxide-Metal Interaction

Despite tremendous importance in catalysis, the design and improvement of the oxide- metal interface has been hampered by the limited understanding on the nature of interfacial sites, as well as the oxide-metal interaction (OMI). Through the construction of well-defined Cu2O-Pt, Cu2O-Ag, Cu2O-Au interfaces, we found that Cu2O Nanostructures (NSs) on Pt exhibit much lower thermal stability than on Ag and Au, although they show the same surface and edge structures, as identified by element-specific scanning tunneling microscopy (ES-STM) images. The activities of the Cu2O-Pt and Cu2O-Au interfaces for CO oxidation were further compared at the atomic scale and showed in general that the interface with Cu2O NSs could annihilate the CO-poisoning problem suffered by Pt group metals and enhance the interaction with O2, which is a limiting step for CO oxidation catalysis on group IB metals. While both interfaces could react with CO at room temperature, the OMI was found to determine the reactivity of supported Cu2O NSs by 1) tuning the activity of interfacial oxygen atoms and 2) stabilizing oxygen vacancies or vice versa, the dissociated oxygen atoms at the interface. Our study provides new insight for OMI and for the development of Cu-based catalysts for low temperature oxidation reactions

PECSS: Pulmonary Embolism Comprehensive Screening Score to safely rule out pulmonary embolism among suspected patients presenting to emergency department

Abstract Background Pulmonary embolism is a severe cardiovascular disease and can be life-threatening if left untreated. However, the detection rate of pulmonary embolism using existing pretest probability scores remained relatively low and clinical rule out often relied on excessive use of computed tomographic pulmonary angiography. Methods We retrospectively collected data from pulmonary embolism suspected patients in Zhongshan Hospital from July 2018 to October 2022. Pulmonary embolism diagnosis and severity grades were confirmed by computed tomographic pulmonary angiography. Patients were randomly divided into derivation and validation set. To construct the Pulmonary Embolism Comprehensive Screening Score (PECSS), we first screened for candidate clinical predictors using univariate logistic regression models. These predictors were then included in a searching algorithm with indicators of Wells score, where a series of points were assigned to each predictor. Optimal D-Dimer cutoff values were investigated and incorporated with PECSS to rule out pulmonary embolism. Results In addition to Wells score, PECSS identified seven clinical predictors (anhelation, abnormal blood pressure, in critical condition when admitted, age > 65 years and high levels of pro-BNP, CRP and UA,) strongly associated with pulmonary embolism. Patients can be safely ruled out of pulmonary embolism if PECSS ≤ 4, or if 4 < PECSS ≤ 6 and D-Dimer ≤ 2.5 mg/L. Comparing with Wells approach, PECSS achieved lower failure rates across all pulmonary embolism severity grades. These findings were validated in the held-out validation set. Conclusions Compared to Wells score, PECSS approaches achieved lower failure rates and better compromise between sensitivity and specificity. Calculation of PECSS is easy and all predictors are readily available upon emergency department admission, making it widely applicable in clinical settings. Trail registration The study was retrospectively registered (No. CJ0647) and approved by Human Genetic Resources in China in April 2022. Ethical approval was received from the Medical Ethics Committee of Zhongshan Hospital (NO.B2021-839R)