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Dezhi, S,Sheng, C,Chung, JS,Xiaodong, D,Zhibin, Z Pergamon Press 2005 Photochemistry and photobiology Vol.81 No.2
A novel continuous-flow photocatalytic reactor was designed to decompose toluene by using porous nickel sheets that were coated with a Fe-doped TiO<SUB>2</SUB> catalyst. While locating the UV lamp at the central axis, the catalyst sheets were located along the inner wall and positioned vertically with an equal space of 50 mm along the reactor. This geometry ensures better use of UV light, and a zigzag flow pattern of gas between the vertically located sheets provides for better mass transfer. The X-ray diffraction, scanning electron microscope and electric field-induced surface photovoltage spectra characterizations showed that Fe<SUP>3+</SUP> ions were embedded effectively and distributed evenly throughout the TiO<SUB>2</SUB> crystal lattice and an optimum molar ratio of Fe:Ti was 0.007. The reactor was used to investigate the factors that affect toluene degradation. The results showed that inlet toluene concentration, relative humidity and gas flow rate significantly affect toluene decomposition. The conversion decreases as inlet concentration increases. Degradation efficiencies of more than 95% can be achieved provided that the toluene concentration is kept below 3200 mg/m<SUP>3</SUP>. The conversion is affected little when oxygen content exceeds 21%. The optimal relative humidity is 25%. From the experimental data, a rate constant k of 131 mg/(m<SUP>3</SUP>.min) and Langmuir adsorption coefficient K of 0.0175 m<SUP>3</SUP>/mg were obtained.
A Novel Cost-Effective Two-Level Inverter with Combined Use of Thyristors and IGBTs
Dezhi Chen,Wenliang Zhao,Byung-il Kwon 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.1
In this paper, a novel topology of two-level voltage-type inverter is proposed. The proposed inverter has three bridge arms while each bridge is made up of two thyristors, one IGBT and four diodes. Thyristors complete the phase positioning of the inverter, IGBT completes the modulation of different modulation modes such as SPWM, SVPWM, and SHPWM, and the diodes complete the commutation of the bridge arms. Compared to the traditional voltage-type inverter with six IGBTs, the proposed voltage-type inverter using three IGBTs can achieve the same function with highly reduced cost. The principle of the proposed two-level inverter is explained in detail. The simulation and experiment results demonstrate the performance and effectiveness of the proposed inverter-type inverter.
Synthesis and Optical Characteristics of PAM/HgS Nanocomposites
Dezhi Qin,Guangrui Yang,Li Zhang,Xian Du,Yabo Wang 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.4
Polyacrylamide (PAM) -HgS nanocomposites were successfully prepared in polyacrylamide (PAM) matrix. From TEM and XRD characterizations, the synthesized HgS nanocrystals were chain-like spherical in shape with a diameter of about 40-60 nm and high crystalline quality. The quantum-confined effect of HgS nanocrystals was confirmed by UV-vis diffuse reflection spectra. The optical properties of products were investigated by using photoluminescence (PL) spectra, which showed that HgS nanocrystals exhibited good optical properties with maximum emission peak at about 640 and 650 nm at different reaction temperatures. The interaction of HgS nanocrystals with PAM was studied through FT-IR spectroscopy and TG analysis, which suggested that Hg2+ could interact with functional groups of PAM. The experimental results indicated that PAM not only induced nucleation, but also inhibited further growth of HgS crystals and play an important role in the formation of PAM/HgS nanocomposites. In addition, the possible mechanism of HgS nanoparticles growth in PAM solution was also discussed.
Dezhi Chen,Byung-il Kwon,Baodong Bai 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
This paper proposes a novel analytical approach for accurate calculation of IGBT losses in rectifier and inverter, aiming to improve the appropriate selection process of IGBTs and the design of power electronic radiator devices. A 1140V/75kW variable frequency speed control system is investigated and the IGBTs selection is performed considering the effects of gate drive resistance and DC bus voltage on losses. These effects are further analyzed in detail and an analytical approach for conduction, total switching losses, efficiency, temperature difference and junction temperature of the inverter and IGBTs is provided. Based upon the interaction between IGBT losses and junction temperature, an IGBT junction temperature curve is obtained. Accordingly, an IGBT selection is decided and a water cooling radiator is designed. The experimental result of temperature is used to verify the accuracy of the proposed analytical approach for IGBT loss calculation and selection as well as the radiator design.
Data-driven Sliding Mode Control for MIMO systems and Its Application on Linear Induction Motors
Dezhi Xu,Xiaoqi Song,Bin Jiang,Weilin Yang,Wenxu Yan 제어·로봇·시스템학회 2019 International Journal of Control, Automation, and Vol.17 No.7
In this paper, a model free adaptive integral sliding mode constrained control (MFAISMCC) is proposedto maintain the flux linkage of a linear induction motor (LIM) while tracking the speed reference. Firstly, themathematica model of a LIM is given after the electrical analysis. In order to linearize the motor system, thetechnology of compact form dynamic linearzation (CFDL) is applied. Then, the MFAISMCC is proposed basedon the analysed linear model. Furthermore, a novel anti-windup compensator for MIMO systems is proposed incase the actuator is within saturation. The whole closed-system stability is proven by Lyapunov stability method. Finally, some simulation results are given to testify the effectiveness of the proposed method compared with thePID controllers.
Effects of Diosgenin on Cell Proliferation Induced by IGF-1 in Primary Human Thyrocytes
Dezhi Bian,Zhiwei Li,Hongyan Ma,Sumin Mu,Chunyan Ma,Bin Cui,Ling Gao,Jiajun Zhao 대한약학회 2011 Archives of Pharmacal Research Vol.34 No.6
Others and our previous studies showed that the increase of IGF-1 was involved in the formation of goiter. Our aim here was to evaluate the possible effects of diosgenin on cell proliferation induced by IGF-1 in primary human thyroid cells. The cells were treated with or without different concentrations of diosgenin in the present or absent of IGF-1 for 24, 48 and 72 h, respectively. Cell viability was determined by MTT, and cell proliferation was tested by EdU assay, and cell cycle analysis was performed by FACS. In addition, Cyclin D1 and B1 protein expression was tested by Western Blotting, respectively. We found that IGF-1 promoted cell cycle progression to S phase and increased the primary human thyroid cells proliferation. Diosgenin decreased the protein expression of cyclin D1 and resulted in cell G_0 /G_1 arrest. Importantly, when the human thyrocytes were exposed to diosgenin in the present of IGF-1,the IGF-1 inducing proliferation was significantly decreased and the proportion of the cells in G_0 /G_1 phase was increased, while that of S phase was decreased. This study shows that diosgenin inhibited cell proliferation, caused G_0 /G_1 arrest, and could inhibit cell proliferation induced by IGF-1 in primary human thyroid cells.
Dezhi Chen,Zhiyu Feng,Wenliang Zhao,Baodong Bai 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
This paper introduces the mathematical model of a double boost circuit for the condition that the short circuit to ground happens to one phase of inverters, taking into account the impact of leakage inductance of power transformers. The corresponding energy transmission modes are analyzed, mainly focusing on the reason that the rectifier diode reverses voltage and the DC bus voltage rises. Then a novel method for rectifier determination, considering the short circuit to ground in one phase of inverters, is proposed. The effectiveness of the proposed method is verified by both simulation and experiment.
Dezhi Hao,Xianwen Gao,Wenhai Qi 제어·로봇·시스템학회 2022 International Journal of Control, Automation, and Vol.20 No.11
In this paper, a novel data augmentation method is proposed for imbalanced fault diagnosis in the sucker rod pumping system (SRPS) based on the improved generative adversarial network (GAN). The dynamometer cards (DCs) of minority fault classes are expanded steadily through learning the data distribution of the original imbalanced training data. The generalization ability and accuracy of the different fault diagnosis models are improved with the expanded DCs. Firstly, benefit from introducing the auxiliary conditional information to the Wasserstein GAN with gradient penalty (WGAN-GP), a stable and practical framework is constructed to generate specific categories of DCs. Secondly, the traditional random noise is replaced by the Gaussian mixture noise to guarantee the diversity of the generated DCs with few training samples. Moreover, problematic training, such as unstable training and mode collapse, is effectively avoided with the presented optimization strategy, training structure and data processing method. Eventually, generated data evaluation and comparative experiments are conducted using practical DCs collected from several oil wells with similar working conditions in the northeastern of China. The results verify the validity of the proposed data augmentation method.