A Mild Strategy to Strengthen Three Dimensional Graphene Aerogel for Supporting Sulfur as a Free‐standing Cathode in Lithium–Sulfur Batteries

Yinglin Yan,Haichao Qin,Yiqi Wei,Rong Yang,Yunhua Xu,Liping Chen,Qiaole Li,Mangmang Shi 대한화학회 2018 Bulletin of the Korean Chemical Society Vol.39 No.5

Recently, three dimensional graphene aerogel (3DGA) supported sulfur microparticles was used as a cathode material for lithium?sulfur batteries, which was considered as one of the most promising next generation rechargeable batteries due to its ultra?high theoretical specific capacity (1675 mAh/g). However, the mechanical strength of 3DGA remains an issue for further application. Herein, a strengthened 3DGA (S3DGA) was achieved by soaking in a low concentration ammonia solution at a relative low temperature. Then the S3DGA loaded sulfur (S3DGA?S) was cut into a round piece and directly used as a cathode without additional binders or conductive additives in Li?S batteries. The mechanical strength, microstructure, and electrochemical properties were investigated by compare with a 3DGA prepared without strengthen. The S3DGA?S presented good mechanical strength, excellent capacity retention, and lower electrochemical impedance.

MMC‑modified sub‑module structure with double reverse blocking IGBTs

Yiqi Liu,Zhaoyu Duan,Qichao Chen,Bingkun Li,Mingfei Ban,Zhenjie Li 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.3

In high-voltage direct current (HVDC) systems, among the voltage source converters (VSCs), the modular multilevel converter (MMC) is a popular choice for power transmission. Unfortunately, the conventional half-bridge sub-module (SM) cannot deal with DC faults by itself. Thus, improved SM topologies enabling DC fault ride-through are significant. With this in mind, an MMC-modified SM structure is presented with double reverse blocking IGBTs (DRBSM). When all of the IGBTs in an MMC are blocked, the DRBSM can insert two capacitors in series to the fault circuit to rapidly overcome the DC fault. First, the DRBSM topology and working principle are analyzed. Second, the DRBSM control strategy is illustrated. Third, the device withstand voltage, DC fault ride-through, cost, and loss performance of the DRBSM are presented in detail. Finally, according to simulation results, the DRBSM fault ride-through speed is shown to be as fast as the full-bridge SM, and faster than the clamp double SM. In addition, experimental results validate the feasibility of the proposed DRBSM structure.

Hybrid DC circuit breaker with current‑limiting capability

Yiqi Liu,Bingkun Li,Laicheng Yin,Junyuan Zheng,Zhaoyu Duan,Zhenjie Li 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.4

Nowadays, traditional DC circuit breakers (DCCBs) are always expensive and lack current-limiting capabilities. Hence, this paper proposes a current limiting and low-cost hybrid DC circuit breaker (HCB). When a fault occurs, the paralleled inductors in the proposed HCB are converted to a series connection due to the cutoff of the converter module, effectively limiting the increase of fault current. Then the cascaded IGBTs undertake the transient interruption voltage. Energy dissipation circuits (EDCs) reduce the fault isolation time (FIT) by bypassing the current-limiting inductor during energy dissipation based on the metal oxide varistors (MOVs). Therefore, the proposed HCB can limit the rate of the fault current increase, reducing the FIT and cost. Finally, the feasibility of the proposed HCB is verified by a single-ended equivalent system and DC grid test systems built in PSCAD/EMTDC. In addition, the proposed HCB FIT is 33.7% quicker, its energy consumption is 87%, and its cost is lower than that of the traditional ABB HCB.

Development of a novel self-validating soft sensor

Yiqi Liu,Daoping Huang,Yan Li,Xuefeng Zhu 한국화학공학회 2012 Korean Journal of Chemical Engineering Vol.29 No.9

A self-validating soft sensor is proposed that not only can perform self-diagnostics and self-reconstruction,but also generate a variety of output data types, including the prediction values, input sensors status of soft sensor and the uncertainty values which represent the credibility of soft sensor’s output. The input sensors are validated before performing a prediction by principal components analysis (PCA) model. These validated data are then employed for subsequent recursive partial least square (RPLS) prediction. Other than input sensor validation and modeling for prediction,a t-statistic confidence interval is created and the status of input sensors is offered. By using this self-validating soft sensor, we can determine the work condition of the soft sensor and take proper actions in real time. The usefulness of the proposed method is demonstrated through a case study of a wastewater treatment process.

On DC-Side Impedance Frequency Characteristics Analysis and DC Voltage Ripple Prediction under Unbalanced Conditions for MMC-HVDC System Based on Maximum Modulation Index

Yiqi Liu,Qichao Chen,Ningning Li,Bing Xie,Jianze Wang,Yanchao Ji 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.1

In this study, we first briefly introduce the effect of circulating current control on the modulation signal of a modular multilevel converter (MMC). The maximum modulation index is also theoretically derived. According to the optimal modulation index analysis and the model in the continuous domain, different DC-side output impedance equivalent models of MMC with/without compensating component are derived. The DC-side impedance of MMC inverter station can be regarded as a series xR + yL + zC branch in both cases. The compensating component of the maximum modulation index is also related to the DC equivalent impedance with circulating current control. The frequency characteristic of impedance for MMC, which is observed from its DC side, is analyzed. Finally, this study investigates the prediction of the DC voltage ripple transfer between two-terminal MMC high-voltage direct current systems under unbalanced conditions. The rationality and accuracy of the impedance model are verified through MATLAB/Simulink simulations and experimental results.

A Decentralized Optimal Load Current Sharing Method for Power Line Loss Minimization in MT-HVDC Systems

Yiqi Liu,Wenlong Song,Ningning Li,Linquan Bai,Yanchao Ji 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.6

This paper discusses the elimination of DC voltage deviation and the enhancement of load current sharing accuracy in multi-terminal high voltage direct current (MT-HVDC) systems. In order to minimize the power line losses in different parallel network topologies and to insure the stable operation of systems, a decentralized control method based on a modified droop control is presented in this paper. Averaging the DC output voltage and averaging the output current of two neighboring converters are employed to reduce the congestion of the communication network in a control system, and the decentralized control method is implemented. By minimizing the power loss of the cable, the optimal load current sharing proportion is derived in order to achieve rational current sharing among different converters. The validity of the proposed method using a low bandwidth communication (LBC) network for different topologies is verified. The influence of the parameters of the power cable on the control system stability is analyzed in detail. Finally, transient response simulations and experiments are performed to demonstrate the feasibility of the proposed control strategy for a MT-HVDC system.

On DC-Side Impedance Frequency Characteristics Analysis and DC Voltage Ripple Prediction under Unbalanced Conditions for MMC-HVDC System Based on Maximum Modulation Index

Liu, Yiqi,Chen, Qichao,Li, Ningning,Xie, Bing,Wang, Jianze,Ji, Yanchao The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.1

In this study, we first briefly introduce the effect of circulating current control on the modulation signal of a modular multilevel converter (MMC). The maximum modulation index is also theoretically derived. According to the optimal modulation index analysis and the model in the continuous domain, different DC-side output impedance equivalent models of MMC with/without compensating component are derived. The DC-side impedance of MMC inverter station can be regarded as a series xR + yL + zC branch in both cases. The compensating component of the maximum modulation index is also related to the DC equivalent impedance with circulating current control. The frequency characteristic of impedance for MMC, which is observed from its DC side, is analyzed. Finally, this study investigates the prediction of the DC voltage ripple transfer between two-terminal MMC high-voltage direct current systems under unbalanced conditions. The rationality and accuracy of the impedance model are verified through MATLAB/Simulink simulations and experimental results.

Design and research of high misalignment tolerant magnetic couplers for dynamic wireless charging systems

Zhenjie Li,Xuezhi Yang,Jun Ma,Mingfei Ban,Yiqi Liu 전력전자학회 2024 JOURNAL OF POWER ELECTRONICS Vol.24 No.3

This paper proposes a main-auxiliary cooperative receiving coil (MA-coil) with a lower space occupation rate and a simple control based on the time-sharing working principle, which can effectively improve the anti-misalignment capability of a dynamic wireless charging (DWC) system. First, the structure and circuit topology of the MA-coil are designed. The two auxiliary coils (A-coil) are connected in reverse series and symmetrically placed on both sides of the main coil (M-coil). Second, the output performance of the MA-coil in the y-direction is calculated based on the time-sharing working principle. The A-coil works by itself and enhances the output power when side shift occurs. Third, the most suitable ratio of coil width w M and w A is determined. The anti-misalignment performance and the effective side shift range are compared through simulation between the MA-coil in this case and the square coil. Finally, an experimental prototype is built to verify the feasibility of the proposed structure, and experimental results obtained from the prototype are basically consistent with the theoretical analysis. The anti-misalignment capability of the MA-coil is more than 20% higher than that of the square coil.

A Dual Functional Ti-Ga Alloy: Inhibiting Biofilm Formation and Osteoclastogenesis Differentiation via Disturbing Iron Metabolism

Fupeng Li,Kai Huang,Jinbing Wang,Kai Yuan,Yiqi Yang,Yihao Liu,Xianhao Zhou,Keyu Kong,Tao Yang,Jian He,Chunjie Liu,Haiyong Ao,Fengxiang Liu,Qian Liu,Tingting Tang,Shengbing Yang 한국생체재료학회 2023 생체재료학회지 Vol.27 No.00

Background Although biomedical implants have been widely used in orthopedic treatments, two major clinical challenges remain to be solved, one is the bacterial infection resulting in biofilm formation, and the other is aseptic loosening during implantation due to over-activated osteoclastogenesis. These factors can cause many clinical issues and even lead to implant failure. Thus, it is necessary to endow implants with antibiofilm and aseptic looseningprevention properties, to facilitate the integration between implants and bone tissues for successful implantation. To achieve this goal, this study aimed to develop a biocompatible titanium alloy with antibiofilm and anti-aseptic loosening dual function by utilizing gallium (Ga) as a component. Methods A series of Ti-Ga alloys were prepared. We examined the Ga content, Ga distribution, hardness, tensile strength, biocompatibility, and anti-biofilm performance in vitro and in vivo. We also explored how Ga3+ ions inhibited the biofilm formation of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) and osteoclast differentiation. Results The alloy exhibited outstanding antibiofilm properties against both S. aureus and E. coli in vitro and decent antibiofilm performance against S. aureus in vivo. The proteomics results demonstrated that Ga3+ ions could disturb the bacterial Fe metabolism of both S. aureus and E. coli, inhibiting bacterial biofilm formation. In addition, Ti-Ga alloys could inhibit receptor activator of nuclear factor-κB ligand (RANKL)-dependent osteoclast differentiation and function by targeting iron metabolism, then suppressing the activation of the NF-κB signaling pathway, thus, showing their potential to prevent aseptic loosening. Conclusion This study provides an advanced Ti-Ga alloy that can be used as a promising orthopedic implant raw material for various clinical scenarios. This work also revealed that iron metabolism is the common target of Ga3+ ions to inhibit biofilm formation and osteoclast differentiation.

Combining Differential Evolution with Particle Filtering for Articulated Hand Tracking from Single Depth Images

Dongnian Li,Yiqi Zhou 보안공학연구지원센터 2015 International Journal of Signal Processing, Image Vol.8 No.4

Tracking articulated hand motion from visual observations is challenging mainly due to the high dimensionality of the state space. Dense sampling is difficult to be performed in such high-dimensional space, so the traditional particle filtering can’t track articulated motion well. In this paper, we propose a new algorithm by combining differential evolution with a particle filter, to track the articulated motion of a hand from single depth images captured by a Kinect sensor. Through the optimization procedure of differential evolution, the particles are moved to the regions with a high likelihood. Only single depth information is used as the input, so our method is immune to illumination and background changes. The tracking system is developed with OpenSceneGraph (OSG). Experiments based on both synthetic and real image sequences demonstrate that the proposed method is capable of tracking articulated hand motion accurately and robustly.