Novel Switched-Inductor Quasi-Z-source Inverter

Deng, Kai,Zheng, Jianyong,Mei, Jun The Korean Institute of Power Electronics 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.1

A novel switched-inductor quasi-Z-source inverter is proposed in this study. Compared with classic topologies, the boost ability of the proposed topology is strengthened. The voltage stress of the capacitors, diodes, and power devices are reduced, and the current ripple of the DC voltage source is suppressed. Conversion efficiency is also improved. The operation principle of the proposed topology is analyzed in detail and compared with that of similar topologies. The feasibility of the proposed topology is verified by simulations and experiments on a laboratory prototype.

Novel Switched-Inductor Quasi-Z-source Inverter

Kai Deng,Jianyong Zheng,Jun Mei 전력전자학회 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.1

A novel switched-inductor quasi-Z-source inverter is proposed in this study. Compared with classic topologies, the boost ability of the proposed topology is strengthened. The voltage stress of the capacitors, diodes, and power devices are reduced, and the current ripple of the DC voltage source is suppressed. Conversion efficiency is also improved. The operation principle of the proposed topology is analyzed in detail and compared with that of similar topologies. The feasibility of the proposed topology is verified by simulations and experiments on a laboratory prototype.

Performance Analysis for Distributed-Antenna OFDM Systems with Multiple CFOs Using Zero-Forcing Detection

Kai Deng,Wanzhi Ma 보안공학연구지원센터 2016 International Journal of Future Generation Communi Vol.9 No.7

This paper theoretically analyzes the performance of distributed-antenna orthogonal frequency division multiplexing (OFDM) systems with multiple carrier frequency offsets (CFO) using zero-forcing (ZF) detection. Considering both the large-scale fading and the multipath fading of the wireless channel, we derive the average power of the inter-carrier interference (ICI) due to the CFOs and thus obtain the expression for the signal to interference and noise ratio (SINR). By analyzing the underlying characteristics of the ZF detection, we address the reason for the inaccuracy of the conventional SINR expression and propose a novel modified SINR expression with better precision, and hence obtain a closed-form expression for the bit error rate (BER) performance with the presence of multiple CFOs. It is shown by the analytical and simulation results that the analytical SINR obtained by the conventional expression appears lower than actually while the analytical SINR and BER obtained by the expressions presented in this paper are more accurate and closer to the corresponding simulation results.

An Extended Switched-inductor Quasi-Z-source Inverter

Kai Deng,Fei Mei,Jun Mei,Jianyong Zheng,Guangxu Fu 대한전기학회 2014 Journal of Electrical Engineering & Technology Vol.9 No.2

In this paper, an extended switched-inductor quasi-Z-source inverter (ESL-qZSI) with high boost voltage inversion ability is presented, which combines the SL-qZSI with the traditional boost converter, as well as improves the switched-inductor cell. Compared with the classic qZSI topologies, the proposed topology reduces the voltage stresses of capacitors, power devices and diodes for the same input and output voltage. Furthermore, the conversion efficiency is improved. The operation principle of the proposed topology is analyzed in details, which is followed by the comparison between the three topologies. In addition, the performance of the proposed topology is verified by simulations and experiments.

An Extended Switched-inductor Quasi-Z-source Inverter

Deng, Kai,Mei, Fei,Mei, Jun,Zheng, Jianyong,Fu, Guangxu The Korean Institute of Electrical Engineers 2014 Journal of Electrical Engineering & Technology Vol.9 No.2

In this paper, an extended switched-inductor quasi-Z-source inverter (ESL-qZSI) with high boost voltage inversion ability is presented, which combines the SL-qZSI with the traditional boost converter, as well as improves the switched-inductor cell. Compared with the classic qZSI topologies, the proposed topology reduces the voltage stresses of capacitors, power devices and diodes for the same input and output voltage. Furthermore, the conversion efficiency is improved. The operation principle of the proposed topology is analyzed in details, which is followed by the comparison between the three topologies. In addition, the performance of the proposed topology is verified by simulations and experiments.

Preliminary Application of High-Definition CT Gemstone Spectral Imaging in Hand and Foot Tendons

Kai Deng,Cheng-Qi Zhang,Wei Li,Jun-Jun Wang,Xin-Yi Wang,Tao Pang,Guang-Li Wang,Cheng Liu 대한영상의학회 2012 Korean Journal of Radiology Vol.13 No.6

Objective: To assess the feasibility of visualizing hand and foot tendon anatomy and disorders by Gemstone Spectral Imaging (GSI) high-definition CT (HDCT). Materials and Methods: Thirty-five patients who suffered from hand or foot pain were scanned with GSI mode HDCT and MRI. Spectrum analysis was used to select the monochromatic images that provide the optimal contrast-to-noise ratio (CNR) for tendons. The image quality at the best selected monochromatic level and the conventional polychromatic images were compared. Tendon anatomy and disease were also analyzed at GSI and MRI. Results: The monochromatic images at about 65 keV (mean 65.09 ± 2.98) provided the optimal CNR for hand and foot tendons. The image quality at the optimal selected monochromatic level was superior to conventional polychromatic images (p = 0.005, p < 0.05). GSI was useful in visualizing hand and foot tendon anatomy and disorders. There were no statistical differences between GSI and MRI with regard to tendon thickening (χ2 = 0, p > 0.05), compression (χ2 = 0.5, p > 0.05), absence (χ2 = 0, p > 0.05) and rupture (χ2 = 0, p > 0.05). GSI was significantly less sensitive than MRI in displaying tendon adhesion (χ2 = 4.17, p < 0.05), degeneration (χ2 = 4.17, p < 0.05), and tendinous sheath disease (χ2 = 10.08, p < 0.05). Conclusion: GSI with monochromatic images at 65 keV displays clearly the most hand and foot tendon anatomy and disorders with image quality improved, as compared with conventional polychromatic images. It may be used solely or combined with MRI in clinical work, depending on individual patient disease condition. Objective: To assess the feasibility of visualizing hand and foot tendon anatomy and disorders by Gemstone Spectral Imaging (GSI) high-definition CT (HDCT). Materials and Methods: Thirty-five patients who suffered from hand or foot pain were scanned with GSI mode HDCT and MRI. Spectrum analysis was used to select the monochromatic images that provide the optimal contrast-to-noise ratio (CNR) for tendons. The image quality at the best selected monochromatic level and the conventional polychromatic images were compared. Tendon anatomy and disease were also analyzed at GSI and MRI. Results: The monochromatic images at about 65 keV (mean 65.09 ± 2.98) provided the optimal CNR for hand and foot tendons. The image quality at the optimal selected monochromatic level was superior to conventional polychromatic images (p = 0.005, p < 0.05). GSI was useful in visualizing hand and foot tendon anatomy and disorders. There were no statistical differences between GSI and MRI with regard to tendon thickening (χ2 = 0, p > 0.05), compression (χ2 = 0.5, p > 0.05), absence (χ2 = 0, p > 0.05) and rupture (χ2 = 0, p > 0.05). GSI was significantly less sensitive than MRI in displaying tendon adhesion (χ2 = 4.17, p < 0.05), degeneration (χ2 = 4.17, p < 0.05), and tendinous sheath disease (χ2 = 10.08, p < 0.05). Conclusion: GSI with monochromatic images at 65 keV displays clearly the most hand and foot tendon anatomy and disorders with image quality improved, as compared with conventional polychromatic images. It may be used solely or combined with MRI in clinical work, depending on individual patient disease condition.

Bioactivity of essential oil of Litsea cubeba from China and its main compounds against two stored product insects

Kai Yang,Cheng FangWang,Chun Xue You,Zhu Feng Geng,Rui Qi Sun,Shan Shan Guo,Shu Shan Du,Zhi Long Liu,Zhi Wei Deng 한국응용곤충학회 2014 Journal of Asia-Pacific Entomology Vol.17 No.3

During our screening program for agrochemicals from Chinese medicinal herbs and wild plants, the essential oilof Litsea cubeba fruits was found to possess strong contact toxicity against the cigarette beetle Lasiodermaserricorne adults and the booklouse Liposcelis bostrychophila, with LD50 values of 27.33 μg/adult and71.56 μg/cm2, respectively, and also showed strong fumigant toxicity against the two stored product insectswith LC50 values of 22.97 and 0.73 mg/L, respectively. The essential oil obtained by hydrodistillation wasinvestigated by GC MS. The main components of the essential oil were identified to be E-citral (geranial)(27.49%), Z-citral (neral) (23.57%) and D-limonene (18.82%) followed by β-thujene (3.34%), β-pinene (2.85%), α-pinene (2.57%), 6-methyl-5-hepten-2-one (2.40%) and linalool (2.36%). Citral (Z/E-citral), D-limonene, β-pinene,α-pinene and linalool were separated and purified by silica gel column chromatography and preparative thinlayer chromatography, and further identified by means of physicochemical and spectrometric analysis. Citral andlinalool showed strong contact toxicity against L. serricorne and L. bostrychophila (LD50 = 11.76, 12.74 μg/adultand 20.15, 99.97 μg/cm2, respectively) and fumigant toxicity against L. serricorne and L. bostrychophila (16.54,18.04 mg/L air and 0.14, 0.71 mg/L air, respectively). Otherwise, citral, D-limonene and linalool were strongly repellentagainst the cigarette beetle L. serricorne as the essential oil whereas β-pinene and α-pinene exhibited weakerrepellency against the cigarette beetle compared with the positive control, DEET. Moreover, except α-pinene andlinalool, the other three compounds as well as the essential oil exhibited comparable repellency against thebooklouse relative to DEET.

Oxygen vacancy engineering of TiO2-x nanostructures for photocatalytic CO2 reduction

Deng Hexia,Zhu Xueteng,Chen Zhangjing,Zhao kai,Cheng Gang 한국탄소학회 2022 Carbon Letters Vol.32 No.7

The conversion of CO2 into solar fuels by photocatalysis is a promising way to deal with the energy crisis and the greenhouse effect. The introduction of oxygen vacancy into semiconductor has been proved to be an effective strategy for enhancing CO2 photoreduction performance. Herein, TiO2-x nanostructures have been prepared by a simple solvothermal method and engineered by the reaction time. With the prolonging of reaction time, the oxygen vacancy signal gradually increases while the band gap becomes narrow for the as-synthesized TiO2-x nanostructures. The results show that the TiO2-x-6 h, TiO2-x-24 h, and TiO2-x-48 h samples have the main product of CH4 (more) and CO (less) for CO2 photoreduction. Among the three oxygen vacancy photocatalysts, the TiO2-x-24 h sample shows the highest CH4 generation rate of 41.8 μmol g−1 h−1. On the basis of photo/electrochemical measurements, the TiO2-x-24 h sample exhibits efficient electron–hole separation and charge transfer capabilities, thus allows much more electrons to participate in the reaction and finally promotes the photocatalytic CO2 reduction reaction. It further confirms that the optimization of oxygen vacancy concentration could facilitate the photoinduced charge separation and accordingly improve photocatalytic CO2 conversion.

Design and homogenization of metal sandwich tubes with prismatic cores

Kai Zhang,Zichen Deng,Huajiang Ouyang,Jiaxi Zhou 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.45 No.4

Hollow cylindrical tubes with a prismatic sandwich lining designed to replace the solid cross-sections are studied in this paper. The sections are divided by a number of revolving periodic unit cells and three topologies of unit cells (Square, Triangle and Kagome) are proposed. Some types of multiple-topology designed materials are also studied. The feasibility and accuracy of a homogenization method for obtaining the equivalent parameters are investigated. As the curved elements of a unit cell are represented by straight elements in the method and the ratios of the lengths of the curved elements to the lengths of the straight elements vary with the changing number of unit cells, some errors may be introduced. The frequencies of the first five modes and responses of the complete and equivalent models under an internal static pressure and an internal step pressure are compared for investigating the scope of applications of the method. The lower bounds and upper bounds of the number of Square, Triangular and Kagome cells in the sections are obtained. It is shown that treating the multiple-topology designed materials as a separate-layer structure is more accurate than treating the structure as a whole.

New Strategy for Eliminating Zero-sequence Circulating Current between Parallel Operating Three-level NPC Voltage Source Inverters

Kai Li,Zhenhua Dong,Xiaodong Wang,Chao Peng,Fujin Deng,Josep M. Guerrero,Juan Vasquez 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.1

A novel strategy based on a zero common mode voltage pulse-width modulation (ZCMV-PWM) technique and zero-sequence circulating current (ZSCC) feedback control is proposed in this study to eliminate ZSCCs between three-level neutral point clamped (NPC) voltage source inverters, with common AC and DC buses, that are operating in parallel. First, an equivalent model of ZSCC in a three-phase three-level NPC inverter paralleled system is developed. Second, on the basis of the analysis of the excitation source of ZSCCs, i.e., the difference in common mode voltages (CMVs) between paralleled inverters, the ZCMV-PWM method is presented to reduce CMVs, and a simple electric circuit is adopted to control ZSCCs and neutral point potential. Finally, simulation and experiment are conducted to illustrate effectiveness of the proposed strategy. Results show that ZSCCs between paralleled inverters can be eliminated effectively under steady and dynamic states. Moreover, the proposed strategy exhibits the advantage of not requiring carrier synchronization. It can be utilized in inverters with different types of filter.