Pulse-enhanced electrokinetic remediation of fluorine-contaminated soil

Ming Zhou,Shufa Zhu,Fang Liu,Dongfang Zhou 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.11

The presence of abundant fluorides in soil can pose potential threats to environment and human health. We investigated the effects of pulsed electric field on electrokinetic remediation of fluorine-contaminated soil by varyingthe pulse interval. Although the remediation time was increased, experimental results indicated pulse-enhanced electroki-netic remediation could improve the removal efficiency of fluorine better than the conventional electrokinetic remedia-tion in the same intensity of electric field. The fluorine removal efficiency of the former (30 min, pulse interval) was80.93% and that of normal electrokinetic remediation was 72.40%, because pulsed electric field could reduce the con-centration polarization and increase the electrical current, electroosmotic flow and the electrical voltage part in soilcell. Therefore, in the later phase of electrokinetic remediation, when electrical current and the fluorine removal efficiencydecreased obviously, at this time the pulse-enhanced method would be a considerable choice to eliminate fluorine incontaminated soils.

A Digital Self-Sustained Phase Shift Modulation Control Strategy for Full-Bridge LLC Resonant Converters

Kai Zheng,Dongfang Zhou,Jianbing Li,Li Li,Yujing Zhao 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.3

A digital self-sustained phase shift modulation (DSSPSM) strategy that allows for good soft switching and dynamic response performance in the presence of step variations is presented in this paper. The working principle, soft switching characteristics, and voltage gain formulae of a LLC converter with DSSPSM have been provided separately. Furthermore, the method for realizing DSSPSM is proposed. Specifically, some key components of the proposed DSSPSM are carefully investigated, including a parameter variation analysis, the start-up process, and the zero-crossing capture of the resonant current. The simulation and experiment results verify the feasibility of the proposed control method. It is observed that the zero voltage switching of the switches and the zero current switching of the rectifier diodes can be easily realized in presence of step load variations.

Modeling, Dynamic Analysis and Control Design of Full-Bridge LLC Resonant Converters with Sliding-Mode and PI Control Scheme

Kai Zheng,Guodong Zhang,Dongfang Zhou,Jianbing Li,Shaofeng Yin 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.3

In this paper, a sliding mode and proportional plus integral (SM-PI) control combined with self-sustained phase shift modulation (SSPSM) for LLC resonant converters is presented. The proposed control scheme improves the transient response while preserving good steady-state performance. An averaged large signal model of an LLC converter with the ZVS modulation technique is developed for the SM control design. The sliding surface is obtained based on the input-output linearization concept. A system identification method is adopted to obtain the transform function of the LLC resonant converter, which is used to design the PI control. In order to reduce the inherent chattering problem in the steady state, the combined SM-PI control strategy is derived with fuzzy control, where the SM control is responsive during the transient state while the PI control prevails in the steady state. The combination of SSPSM and the SM-PI control provides ZVS operation, robustness and a fast transient response against step load variations. Simulation and experimental results validate the theoretical analysis and the attractive features of the proposed scheme.

Modeling, Dynamic Analysis and Control Design of Full-Bridge LLC Resonant Converters with Sliding-Mode and PI Control Scheme

Zheng, Kai,Zhang, Guodong,Zhou, Dongfang,Li, Jianbing,Yin, Shaofeng The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.3

In this paper, a sliding mode and proportional plus integral (SM-PI) control combined with self-sustained phase shift modulation (SSPSM) for LLC resonant converters is presented. The proposed control scheme improves the transient response while preserving good steady-state performance. An averaged large signal model of an LLC converter with the ZVS modulation technique is developed for the SM control design. The sliding surface is obtained based on the input-output linearization concept. A system identification method is adopted to obtain the transform function of the LLC resonant converter, which is used to design the PI control. In order to reduce the inherent chattering problem in the steady state, the combined SM-PI control strategy is derived with fuzzy control, where the SM control is responsive during the transient state while the PI control prevails in the steady state. The combination of SSPSM and the SM-PI control provides ZVS operation, robustness and a fast transient response against step load variations. Simulation and experimental results validate the theoretical analysis and the attractive features of the proposed scheme.

Combining Non-Contrast CT Signs With Onset-to-Imaging Time to Predict the Evolution of Intracerebral Hemorrhage

Song Lei,Qiu Xiaoming,Zhang Cun,Zhou Hang,Guo Wenmin,Ye Yu,Wang Rujia,Xiong Hui,Zhang Ji,Tang Dongfang,Zou Liwei,Wang Longsheng,Yu Yongqiang,Guo Tingting 대한영상의학회 2024 Korean Journal of Radiology Vol.25 No.2

Objective: This study aimed to determine the predictive performance of non-contrast CT (NCCT) signs for hemorrhagic growth after intracerebral hemorrhage (ICH) when stratified by onset-to-imaging time (OIT). Materials and Methods: 1488 supratentorial ICH within 6 h of onset were consecutively recruited from six centers between January 2018 and August 2022. NCCT signs were classified according to density (hypodensities, swirl sign, black hole sign, blend sign, fluid level, and heterogeneous density) and shape (island sign, satellite sign, and irregular shape) features. Multivariable logistic regression was used to evaluate the association between NCCT signs and three types of hemorrhagic growth: hematoma expansion (HE), intraventricular hemorrhage growth (IVHG), and revised HE (RHE). The performance of the NCCT signs was evaluated using the positive predictive value (PPV) stratified by OIT. Results: Multivariable analysis showed that hypodensities were an independent predictor of HE (adjusted odds ratio [95% confidence interval] of 7.99 [4.87–13.40]), IVHG (3.64 [2.15–6.24]), and RHE (7.90 [4.93–12.90]). Similarly, OIT (for a 1-h increase) was an independent inverse predictor of HE (0.59 [0.52–0.66]), IVHG (0.72 [0.64–0.81]), and RHE (0.61 [0.54– 0.67]). Blend and island signs were independently associated with HE and RHE (10.60 [7.36–15.30] and 10.10 [7.10–14.60], respectively, for the blend sign and 2.75 [1.64–4.67] and 2.62 [1.60–4.30], respectively, for the island sign). Hypodensities demonstrated low PPVs of 0.41 (110/269) or lower for IVHG when stratified by OIT. When OIT was ≤ 2 h, the PPVs of hypodensities, blend sign, and island sign for RHE were 0.80 (215/269), 0.90 (142/157), and 0.83 (103/124), respectively. Conclusion: Hypodensities, blend sign, and island sign were the best NCCT predictors of RHE when OIT was ≤ 2 h. NCCT signs may assist in earlier recognition of the risk of hemorrhagic growth and guide early intervention to prevent neurological deterioration resulting from hemorrhagic growth.

Dynamic Multi-peak MPPT for Photovoltaic Power Generation Under Local Shadows Based on Improved Mayfly Optimization

Yi Lingzhi,Shi Hao,Liu Jiangyong,Zhou Dongfang,Liu Ximeng,Zhu Jiang 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.1

The P-U curves of PV array panels under partial shading shows multi-peaked characteristics, therefore, conventional Maximum Power Point Tracking (MPPT) methods may fail or not be accurate enough. In this paper, a Chaos Mayfl y Optimization with Lévy Flight and Adaptive Algorithm (CMOFA) is proposed to track the maximum power points of PV arrays under partial shading. Firstly, sin chaos is used to initialize the population, then adaptive adjustment of inertia weights is introduced and the learning factor is changed to enhance the local search ability of the algorithm. Later in the operation of the algorithm, when the search falls into the local optimum, Lévy fl ight with induced variable step length is used to make the algorithm jump out of the local optimum and improve the local optimum avoidance ability of the mayfl y algorithm. The simulation results show that CMOFA is not only able to avoid local shading and dynamic shading changes, but also has a signifi cant improvement in convergence speed and search accuracy compared with conventional intelligent algorithms.