A Parameter Selection Method for Multi-Element Resonant Converters with a Resonant Zero Point

Yifeng Wang,Liang Yang,Guodong Li,Shijie Tu 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.2

This paper proposes a parameter design method for multi-element resonant converters (MERCs) with a unique resonant zero point (RZP). This method is mainly composed of four steps. These steps include program filtration, loss comparison, 3D figure fine-tuning and priority compromise. It features easy implementation, effectiveness and universal applicability for almost all of the existing RZP-MERCs. Meanwhile, other design methods are always exclusive for a specific topology. In addition, a novel dual-CTL converter is also proposed here. It belongs to the RZP-MERC family and is designed in detail to explain the process of parameter selection. The performance of the proposed method is verified experimentally on a 500W prototype. The obtained results indicate that with the selected parameters, an extensive dc voltage gain is obtained. It also possesses over-current protection and minimal switching loss. The designed converter achieves high efficiencies among wide load ranges, and the peak efficiency reaches 96.9%.

A High-Reliability Soft-Start Igniter for HPS Lamps

Wang Yifeng,Xu Dianguo,Wang Yijie,Zhang Xiangjun 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5

In this paper, the analysis and design of a new igniter based on half bridge inverter is presented. The proposed igniters can tolerant of the leakage inductance and the parasitic capacitor influence inherent in the transformer. the location of the ignition pulses is near the edge of the square wave automatically. Meanwhile there are enough ignition pulses during a switching period that can ignite high-pressure-sodium (HPS) lamps without any voltage shock. The parameters are given by theoretical calculation, and then verified by PSpice simulation results. At last experimental results of the igniter are presented. Due to the location of ignition pulses, the optimized waveform and high frequency of pulse voltage, the proposed igniter can reliably start most of the 1㎾ HPS lamps without voltage or current surge.

Design of miniaturized and lightweight coupling inductors for interleaved parallel DC/DC converters

Wang, Yifeng,Cheng, Pengyu,Ma, Xiaoyong,Tao, Long,Zhao, Danfeng The Korean Institute of Power Electronics 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.10

At present, coupled inductance is an effective method for the development of the interleaved parallel converters in terms of high efficiency, miniaturization, and light weight. In view of the difficulty in designing coupling inductors in multiphase interleaved parallel converters, a general coupling inductor design criterion is proposed in this paper. First, the equivalent steady-state inductance and equivalent transient inductance expressions of a converter are obtained according to the modal transformation law of a two-phase interleaved parallel buck converter circuit. In addition, the volume modeling and weight modeling of the core are established, and expressions of the self-inductance and coupling coefficient are obtained. Then, the self-inductance and coupling coefficients are derived with the constraints of the steady-state current ripple and transient response speed as well as the objective function of the volume modeling and weight modeling. It is ensured that the designed coupled inductor successfully achieves its purposes of reducing the volume, weight, and inductor current ripple of the converter while improving the system response speed. Finally, the correctness of the theoretical analysis and the accuracy of the design method were verified on a 40 kW experimental platform based on a SiC MOSFET.

A Parameter Selection Method for Multi-Element Resonant Converters with a Resonant Zero Point

Wang, Yifeng,Yang, Liang,Li, Guodong,Tu, Shijie The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.2

This paper proposes a parameter design method for multi-element resonant converters (MERCs) with a unique resonant zero point (RZP). This method is mainly composed of four steps. These steps include program filtration, loss comparison, 3D figure fine-tuning and priority compromise. It features easy implementation, effectiveness and universal applicability for almost all of the existing RZP-MERCs. Meanwhile, other design methods are always exclusive for a specific topology. In addition, a novel dual-CTL converter is also proposed here. It belongs to the RZP-MERC family and is designed in detail to explain the process of parameter selection. The performance of the proposed method is verified experimentally on a 500W prototype. The obtained results indicate that with the selected parameters, an extensive dc voltage gain is obtained. It also possesses over-current protection and minimal switching loss. The designed converter achieves high efficiencies among wide load ranges, and the peak efficiency reaches 96.9%.

Monitoring of bridge overlay using shrinkage-modified high performance concrete based on strain and moisture evolution

Yifeng Ling,Gilson Lomboy,Zhi Ge,Kejin Wang Techno-Press 2023 Structural monitoring and maintenance Vol.10 No.2

High performance concrete (HPC) has been extensively used in thin overlay for repair purpose due to its excellent strength and durability. This paper presents an experiment, where the sensor-instrumented HPC overlays have been followed by dynamic strain and moisture content monitoring for 1 year, under normal traffic. The vibrating wire and soil moisture sensors were embedded in overlay before construction. Four given HPC mixes (2 original mixes and their shrinkage-modified mixes) were used for overlays to contrast the strain and moisture results. A calibration method to accurately measure the moisture content for a given concrete mixture using soil moisture sensor was established. The monitoring results indicated that the modified mixes performed much better than the original mixes in shrinkage cracking control. Weather condition and concrete maturity at early age greatly affected the strain in concrete. The strain in HPC overlay was primarily in longitudinal direction, leading to transverse cracks. Additionally, the most moisture loss in concrete occurred at early age. Its rate was very dependent on weather. After one year, cracking survey was carried out by vision to verify the strain direction and no cracks observed in shrinkage modified mixes.

Diffusion-Weighted MR Imaging of Unicystic Odontogenic Tumors for Differentiation of Unicystic Ameloblastomas from Keratocystic Odontogenic Tumors

Yifeng Han,Xindong Fan,Lixin Su,Zhenfeng Wang 대한영상의학회 2018 Korean Journal of Radiology Vol.19 No.1

Objective: Differentiating unicystic ameloblastomas from keratocystic odontogenic tumors (KCOT) is necessary for the planning of different treatment strategies; however, it is difficult based on conventional CT and MR sequences alone. The purpose of this study was to investigate the utility of diffusion-weighted imaging (DWI) and apparent diffusion coefficients (ADCs) in the differentiation of the two tumors. Materials and Methods: We prospectively studied 40 patients with odontogenic cysts and tumors of the maxillomandibular region using conventional MR imaging and DWI. ADCs were measured using 2 b factors (500 and 1000). Results: Unicystic ameloblastomas (n = 11) showed free diffusion on DWI and a mean ADC value of 2.309 ± 0.17 x 10-3 mm2/s. KCOT (n = 15) showed restricted diffusion on DWI with a mean ADC value of 0.923 ± 0.20 x 10-3 mm2/s. The ADC values of unicystic ameloblastomas were significantly higher than those of KCOT (p < 0.001, Mann-Whitney U-test). An ADC cut-off value of 2.0 x 10-3 mm2/s to differentiate KCOT and unicystic ameloblastomas resulted in a 100% sensitivity and 100% specificity. Dentigerous cysts (n = 3) showed restricted diffusion on DWI and similar ADC values (1.257 ± 0.05 x 10-3 mm2/s) to those of KCOT. Conclusion: Diffusion-weighted imaging and ADC determination can be used as an adjuvant tool to differentiate between unicystic ameloblastomas and KCOT, although the ADC values of dentigerous cysts overlap with those of KCOT.

On Block-decoupling of Boolean Control Networks

Lei Wang,Jiandong Zhu,Yifeng Li 제어·로봇·시스템학회 2023 International Journal of Control, Automation, and Vol.21 No.1

In this paper, two block-decoupling problems of Boolean control networks (BCNs), one of which is related to system decomposition and the other is not, are investigated by using the method of the semi-tensor product of matrices. Necessary and sufficient graphic conditions for block-decoupling of BCNs in the two cases are obtained. Moreover, a logical coordinate transformation is constructed to achieve block-decoupling related to system decomposition when the corresponding graphic conditions are satisfied. Finally, two illustrative examples are provided to illustrate the theoretical results.

Highly Ordered Mesoporous Crystalline MoSe₂ Material with Efficient Visible‐Light‐Driven Photocatalytic Activity and Enhanced Lithium Storage Performance

Shi, Yifeng,Hua, Chunxiu,Li, Bin,Fang, Xiangpeng,Yao, Chaohua,Zhang, Yichi,Hu, Yong‐,Sheng,Wang, Zhaoxiang,Chen, Liquan,Zhao, Dongyuan,Stucky, Galen D. WILEY‐VCH Verlag 2013 Advanced functional materials Vol.23 No.14

<P><B>Abstract</B></P><P>Highly ordered mesoporous crystalline MoSe<SUB>2</SUB> is synthesized using mesoporous silica SBA‐15 as a hard template via a nanocasting strategy. Selenium powder and phosphomolybdic acid (H<SUB>3</SUB>PMo<SUB>12</SUB>O<SUB>40</SUB>) are used as Se and Mo sources, respectively. The obtained products have a highly ordered hexagonal mesostructure and a rod‐like particle morphology, analogous to the mother template SBA‐15. The UV‐vis‐NIR spectrum of the material shows a strong light absorption throughout the entire visible wavelength region. The direct bandgap is estimated to be 1.37 eV. The high surface area MoSe<SUB>2</SUB> mesostructure shows remarkable photocatalytic activity for the degradation of rhodamine B, a model organic dye, in aqueous solution under visible light irradiation. In addition, the synthesized mesoporous MoSe<SUB>2</SUB> possess a reversible lithium storage capacity of 630 mAh g<SUP>−1</SUP> for at least 35 cycles without any notable decrease. The rate performance of mesoporous MoSe<SUB>2</SUB> is much better than that of analogously synthesized mesoporous MoS<SUB>2</SUB>, making it a promising anode for the lithium ion battery.</P>

Average Consensus Seeking of High-order Continuous-time Multi-agent Systems with Multiple Time-varying Communication Delays

Qingjie Zhang,Yifeng Niu,Lin Wang,Lincheng Shen,Huayong Zhu 제어·로봇·시스템학회 2011 International Journal of Control, Automation, and Vol.9 No.6

The average consensus problem of high-order multi-agent systems with multiple time-varying communication delays is investigated in this paper. By using the idea of state decomposition, the condition for guaranteeing average consensus is converted into verifying the stability of zero equi-librium of disagreement system. Considering multiple time-varying communication delays, Lyapunov-Krasovskii approach in time-domain is employed to analyze the stability of zero equilibrium. With the help of Free-weighting Matrices (FWM) approach, the tolerant upper bounds on communication delays can be obtained through solving feasible linear matrix inequalities (LMIs). Delay-dependent stability criteria for both strongly-connected fixed and switching topologies are provided in the main results. Further, the conclusion is extended to the case of jointly-connected switching topologies. Numerical examples and simulation results are given to demonstrate the effectiveness and the benefit on reducing conservativeness of the proposed method.

Synthesis of N-doped Carbon Spheres Using Extended Stöber Method for SO2 Adsorption

Yunqian Li,Yifeng Yu,Lei Liu,Hongliang Zhang,Guoxu Wang,Aibing Chen 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2017 NANO Vol.12 No.1

SO2 is one of the major pollutants in the atmosphere. N-doped microporous carbon spheres (NCS) have been demonstrated to be effective for SO2 adsorption. Here we report the synthesis of monodispersed NCS by the extended Stöber method with urea resorcinol-formaldehyde resins as carbon source, urea as nitrogen source and ammonia as catalyst in an ethanol-water mixed solvent. The obtained carbon spheres show a uniform diameter of around 550 nm, specific surface area of 476 m2 g-1, micropores pore volume of 0.20 cm3 g-1 and nitrogen doping. The NCS manifest special performance for SO2 capture with capability of 75.34 mg g-1 and good cycling stability, due to the large surface area, abundant micropores and nitrogen functionality.