A Novel Curved-Coil Transmitter for Quasiomnidirectional Wireless Power Transfer

Guo Bochao,Zhao Yubo,Chen Wei,Guo Ni,Tian Zijian 한국전자파학회 2023 Journal of Electromagnetic Engineering and Science Vol.23 No.2

Achieving stable power transfer by merely relying on quasi-omnidirectional couplers is challenging. In this paper, we propose a quasi-omnidirectional wireless power transfer (QWPT) system with a novel curved-coil transmitter to achieve steady transmission performance. A single power source is used to drive the transmitter's current without using a phase and current control methodology. Power is transmitted to the receiver through magnetic resonant coupling at a distance of 50 mm. Moreover, an equivalent circuit model of the curved-coil system is derived and mathematically analyzed. The mutual inductance of the proposed QWPT system is evaluated through analysis and experiments. The experimental results for the resonant coupling system confirm the theoretical analysis of the performance of the curved-coil transmitter and quasi-omnidirectional power transfer.

Enhancement Method of Weak Transmission Area for Omnidirectional Wireless Power Transfer System

Guo Bochao,Zhao Yubo,Chen Wei,Pan Shan,Tian Zijian 대한전기학회 2024 Journal of Electrical Engineering & Technology Vol.19 No.3

Reducing the weak transmission area (WTA) of omnidirectional transmitter in wireless power transfer is a challenge. In this paper, we propose a method to enhance the WTA with nonorthogonal coils, and two types of transmitters are made, the 90° sandglass Tx and the 20° sandglass Tx. Specifcally, a single power source is utilized to drive the current of Tx without phase and current control methodology. Power is transmitted to the receiver through magnetic resonant coupling in 50 mm. In addition, an equivalent circuit model of the sandglass Tx system is derived and mathematically analyzed. The magnetic induction density of the sandglass Tx system is evaluated via analysis and experiments. Finally, practical experimental results from the resonant coupling system confrm the theoretical analysis.

Aerodynamic analysis on the step types of a railway tunnel with non-uniform cross-section

Wenhui Li,Tanghong Liu,Xiaoshuai Huo,Zijian Guo,Yutao Xia 한국풍공학회 2022 Wind and Structures, An International Journal (WAS Vol.35 No.4

The pressure-mitigating effects of a high-speed train passing through a tunnel with a partially reduced cross-section are investigated via the numerical approach. A compressible, three-dimensional RNG k-ε turbulence model and a hybrid mesh strategy are adopted to reproduce that event, which is validated by the moving model test. Three step-like tunnel forms and two additional transitions at the tunnel junction are proposed and their aerodynamic performance is compared and scrutinized with a constant cross-sectional tunnel as the benchmark. The results show that the tunnel step is unrelated to the pressure mitigation effects since the case of a double-step tunnel has no advantage in comparison to a single-step tunnel, but the excavated volume is an essential matter. The pressure peaks are reduced at different levels along with the increase of the excavated earth volume and the peaks are either fitted with power or logarithmic function relationships. In addition, the Arc and Oblique-transitions have very limited gaps, and their pressure curves are identical to each other, whereas the Rec-transition leads to relatively lower pressure peaks in CP max, CP min, and ΔCP, with 5.2%, 4.0%, and 4.1% relieved compared with Oblique-transition. This study could provide guidance for the design of the novel railway tunnel.

Yaw effects on train aerodynamics on a double-track viaduct: A wind tunnel study

Wenhui Li,Tanghong Liu,Pedro Martinez-Vazquez,Zhengwei Chen,Xiaoshuai Huo,Zijian Guo,Yutao Xia 한국풍공학회 2021 Wind and Structures, An International Journal (WAS Vol.33 No.3

The aerodynamic performance of a scaled high-speed train model mounted on a double-track viaduct was studied through a wind tunnel test. The pressure distribution of different loops and the centerline on the streamlined nose region, as well as the aerodynamic load coefficients of the leading car were explored under yaw effects ranging from β=-30° to β=30°. Results showed that Reynolds effects became independent when the wind speed surpassed 40 m/s, the corresponding Re of which equals 6.51 × 105 . The pressures recorded along the centerline of train nose for the upstream scenario, was more sensitive to the yaw effects as the largest pressure difference gradually broadened against yaw angles. In addition, the pressure coefficients along the centerline and symmetrical taps of the loops, approximately fit a quadratic relationship with respect to yaw angles. The presence of the tracks and viaduct decks somehow mitigated the intensity of the airflow at downstream side. The experimental test also revealed that, the upstream configuration provided higher mean side force, yawing, and rolling moments up to β=20° whereas over that angle the force and moments exhibited the opposite performance.

Comparison study of the effect of bridge-tunnel transition on train aerodynamic performance with or without crosswind

Lei Zhou,Tanghong Liu,Zhengwei Chen,Wenhui Li,Zijian Guo,Xuhui He,You-Wu Wang 한국풍공학회 2021 Wind and Structures, An International Journal (WAS Vol.32 No.6

This paper studied the case of high-speed train running from flat ground to bridges and into/out of tunnels, with or without crosswind based on the Computational Fluid Dynamics (CFD) method. First, the flow structure was analyzed to explain the influence mechanisms of different infrastructures on the aerodynamic characteristics of the train. Then, the evolution of aerodynamic forces of the train during the entire process was analyzed and compared. Additionally, the pressure variation on the train body and the tunnel wall was examined in detail. The results showed that the pressure coefficient and the flow structure on both sides of the high-speed train were symmetrical for no crosswind case. By contrast, under crosswind, there was a tremendous and immediate change in the pressure mapping and flow structure when the train passing through the bridge-tunnel section. The influence of the ground-bridge transition on the aerodynamic forces was much smaller than that of the bridge-tunnel section. Moreover, the variation of aerodynamic load during the process of entering and exiting the bridge-tunnel sections was both significant. In addition, in the case without crosswind, the change in the pressure change in the tunnel conformed to the law of pressure wave propagation, while under crosswind, the variation in pressure was comprehensively affected by both the train and crosswind in the tunnel.

Subgingival microbiome in periodontitis and type 2 diabetes mellitus: an exploratory study using metagenomic sequencing

Xianjun Lu,Tingjun Liu,Jiani Zhou,Jia Liu,Zijian Yuan,Lihong Guo 대한치주과학회 2022 Journal of Periodontal & Implant Science Vol.52 No.4

Purpose: To explore differences in the subgingival microbiome according to the presence of periodontitis and/or type 2 diabetes mellitus (T2D), a metagenomic sequencing analysis of the subgingival microbiome was performed. Methods: Twelve participants were divided into 4 groups based on their health conditions (periodontitis, T2D, T2D complicated with periodontitis, and generally healthy). Subgingival plaque was collected for metagenomic sequencing, and gingival crevicular fluids were collected to analyze the concentrations of short-chain fatty acids. Results: The shifts in the subgingival flora from the healthy to periodontitis states were less prominent in T2D subjects than in subjects without T2D. The pentose and glucuronate interconversion, fructose and mannose metabolism, and galactose metabolism pathways were enriched in the periodontitis state, while the phosphotransferase system, lipopolysaccharide (LPS) and peptidoglycan biosynthesis, bacterial secretion system, sulfur metabolism, and glycolysis pathways were enriched in the T2D state. Multiple genes whose expression was upregulated from the red and orange complex bacterial genomes were associated with bacterial biofilm formation and pathogenicity. The concentrations of propionic acid and butyric acid were significantly higher in subjects with periodontitis, with or without T2D, than in healthy subjects. Conclusions: T2D patients are more susceptible to the presence of periodontal pathogens and have a higher risk of developing periodontitis. The pentose and glucuronate interconversion, fructose and mannose metabolism, galactose metabolism, and glycolysis pathways may represent the potential microbial functional association between periodontitis and T2D, and butyric acid may play an important role in the interaction between these 2 diseases. The enrichment of the LPS and peptidoglycan biosynthesis, bacterial secretion system, and sulfur metabolism pathways may cause T2D patients to be more susceptible to periodontitis.