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Jinfeng Zhang,Guanyi Chen,Qin Zhang,Yi Luo,Chunsong Wu,Songyan Qin 대한환경공학회 2022 Environmental Engineering Research Vol.27 No.3
Tetracycline antibiotic wastewater with high chemical oxygen demand (COD) concentration and containing bio-refractory compounds was investigated in a lab-scale up-flow anaerobic sludge blanket (UASB) and anoxic-oxic (A/O) reactor. Specific methanogenic activity (SMA) was determined to reveal the inhibition levels of methane production and volatile fatty acid (VFA) accumulation. The results showed that microorganisms can adapt to tetracycline or oxytetracycline when the concentration of antibiotics is less than 400 mg/L. Acetic acid, propanoic acid, and n-butyric acid accounted for more than 90% of VFA with increasing antibiotic concentration from 50 mg/L to 600 mg/L. During the 215 d of operation, the concentration of tetracycline antibiotic increased from 0 to 95 mg/L, and the COD concentration from 3,500 to 6,500 mg/L. The average COD and tetracycline antibiotic removal rates of the reactors were maintained above 90%. The methane production of the UASB reactor achieved 0.32 L/g COD. VFA accumulation was observed when tetracycline antibiotic concentration increased to 47.5 mg/L. The sludge granule diameter increased from 0–300 μm to 300–1,500 μm during the operation. Rod-shaped and coccus-shaped organisms with pores and internal channels on the granule surface were observed using scanning electron microscopy. In the internal space, methanogenic filamentous bacteria constitute a rock-steady structure.
Jinfeng Zhang,Guanyi Chen,Yanning Ma,Miao Xu,Songyan Qin,Xiaoliang Liu,Haijun Feng,Lian Hou 대한환경공학회 2022 Environmental Engineering Research Vol.27 No.1
A new technique for treating pickling wastewater discharged from the steel industry using membrane filters was developed and membrane fouling was characterized in a full scale membrane filter. The morphological and chemical properties were examined through scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS) and inductively coupled plasma optical emission spectroscopy (ICP-OES) etc. The results showed that inorganic elements such as phosphates, chlorides, and sulfates were severely blocked in membrane surfaces and pores. The porosity, permeability, hydrophilic contact angle, and surface charge capacity of fouled membranes were all lower than those of new membranes, while the optimal neutralization reaction pH region for fouled membranes shifted and narrowed. Charge neutralization is a critical reason to membrane fouling. By increasing the Zeta potential of the pickling wastewater, the membrane fouling could be controlled. This method is proven to effectively improve the separation property of precipitates after pickling wastewater was neutralized. Moreover, Neutralization helped to reduce the unit number of treatment processes. This investigation could assist in obtaining a better understanding of the fouling properties and behavior in the full-scale membrane filters in the pickling wastewater treatment.
Fangfang Zhang,Jinfeng Gao,Huanshui Zhang,Cheng Tan,Wei Wang 제어·로봇·시스템학회 2017 International Journal of Control, Automation, and Vol.15 No.6
In this paper, the distributed control of the LQR problem for continuous-time multi-agent systems isconsidered. Based on the centralized optimal control, we prove that the solution of the algebraic Riccati equationis the maximal solution of the algebraic Riccati inequality. The algebraic relations of the solutions of the algebraicRiccati equations for different weighted matrices are shown and two distributed controllers are designed: the fullydistributed one and the interconnected distributed one. They can provide an upper bounds and a lower bounds ofthe centralized optimal cost function. The optimal closed-loop feedback control systems for the two distributedcontrollers are also asymptotically stable. Some examples are given to show the correctness of the proposed results.
Jinfeng Liu,Yu Zhang,Xudong Wang,Herbert Ho-Ching IU 대한전기학회 2017 Journal of Electrical Engineering & Technology Vol.12 No.4
This paper presents a synchronous generator with a distributed system of multiple parallel three-phase power cells. This generator can immediately output high DC. Each power cell comprises three-phase windings and a three-phase synchronous rectification bridge with a deadbeat control of load power feedforward, which can improve the characteristics of dynamic response and reflect the load variance in real time. Furthermore, each power cell works well independently and modularly using the method of automatic maximum current sharing. The simulation and experimental results for the distributed controller of multiple power cells demonstrate that the deadbeat control method can respond quickly and optimize the quality of the energy. Meanwhile, automatic maximum current sharing can realize the validity of current sharing among power cells.
SVPWM Overmodulation Region II Control Method Based on the Chaos Ant Colony Algorithm
Zhang Siyan,Wang Xudong,Gao Junshan,Wu Xiaogang,Liu Jinfeng 대한전기학회 2021 Journal of Electrical Engineering & Technology Vol.16 No.4
The control method of space vector pulse width modulation (SVPWM) overmodulation region II has the disadvantages of a complicated process and large harmonic content. To solve these problems, this paper proposes an SVPWM overmodulation region II control method based on the chaos ant colony algorithm. Since the multiple control of the rotation angle ( θ ) in the SVPWM algorithm will bring about diff erent implementation eff ects, this paper uses the chaotic ant colony algorithm to optimize the control process of θ in overmodulation region II and summarizes the θ equations in each sector to achieve the goal of suppressing the total harmonic distortion ( THD ) in the output voltage vector. Simulation and experimental results demonstrate that this method makes the amplitude of the output voltage vector relatively continuous, thereby avoiding the harmonic content caused by the voltage jump of the traditional algorithm in overmodulation region II.
Synthesis, Characterization and Photocatalytic Activity of Reduced Graphene Oxide-Ce/ZnO Composites
( Wenjun Zhang ),( Jinfeng Zhao ),( Xuefeng Zou ) 한국화학공학회 2016 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.54 No.1
A series of Ce-doped ZnO (Ce/ZnO) nanostructures were fabricated using the co-precipitation method, then a simply nontoxic hydrothermal approach was proposed for preparation of reduced graphene oxide (rGO)-Ce/ZnO composites. The synthesized composites were investigated by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), photoluminescence spectroscopy (PL), electrochemical impedance spectroscopy (EIS), UV-vis diffuse reflectance spectroscopy (DRS) techniques and Raman pattern. The as-synthesized rGO-Ce/ZnO composites showed high photodecomposition efficiency in comparison with the rGO-ZnO, Ce/ZnO, pure ZnO under UV, visible-light and sunlight irradiation. The degradation of methylene blue (MB) (10 mg/L, 100ml) by 95.8% within 60 min by using rGO-2 (10 mg) under sunlight irradiation was observed. The repeated use of the rGO-2 was investigated, and the results showed almost no decay in the catalytic activity.
Siyan Zhang,Xudong Wang,Kai Zhou,Xuan Shao,Jinfeng Liu 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.11
To solve the problem where the space vector pulse width modulation (SVPWM) of a three-phase inverter produces large harmonic components near the switching frequency (fs) and its doubling frequency, a frequency-optimized random switching frequency SVPWM (FORSF-SVPWM) control strategy is proposed in this paper. In this strategy, the basic principle of the chaotic ant colony algorithm in path optimization is used to determine the optimized scheme of the switching frequency distribution in the FORSF-SVPWM. Research shows that the frequency sample formed by the sigmoid function curve in the switching frequency range can cause the energy that was originally concentrated on the switching frequency and its doubling frequency to be more evenly distributed in the whole frequency range. Moreover, the amplitude of each harmonic wave is shown to be suppressed. The proposed strategy reduces the high-frequency noise and conducted electromagnetic interference (EMI) existing in power switching circuits. Thus, this strategy is obviously better than the traditional random switching frequency SVPWM (RSF-SVPWM) algorithm with its approximately uniform frequency distribution. Simulation and experimental results show that this strategy can work well in the hardware platform of a three-phase inverter without changing the topology of the main circuit of the system. In addition, this strategy is easy to implement.
Modified Slip Surface Stress Method for Potential Slip Mass Stability Analysis
Haitao Zhang,Xianqi Luo,Jinfeng Bi,Zijing Guo 대한토목학회 2019 KSCE Journal of Civil Engineering Vol.23 No.1
A modified slip surface stress method is proposed with the concept of vector sum and rigorous force analysis. Theoretically, the proposed method could degenerate into the existing methods by adding the corresponding assumptions. Through five typical slope cases, comparisons are made among the Factor of Safety (FoS) calculated by the proposed method and others. Results show that the proposed method could evaluate slopes at the limit state. Moreover, the proposed method is capable to calculate the FoS of the potential slip mass for both homogeneous and heterogeneous cases with regular or irregular slip surface in both two- and three-dimension spaces. Also, the proposed method could give the potential slip direction of a slope, which is useful for the design of measures to reinforce the slope.