Applications Analysis of Big Data Analysis in the Medical Industry

Zhendong Ji 보안공학연구지원센터 2015 International Journal of Database Theory and Appli Vol.8 No.4

With the promoting of big data analysis in every industry, the medical industry is also being widely used big data analysis as the tools, medical industry accumulated a large amount of data because of the wide ranging, it’s has an important role in creating new business value for the medical industry and enhancing healthcare industry by performing the analysis of big data,. This paper focuses on the analysis of big data applications in the medical industry, and discussed the potential of its commercial value for the healthcare industry.

Fault-Tolerant Control of Cascaded H-Bridge Converters Using Double Zero-Sequence Voltage Injection and DC Voltage Optimization

Zhendong Ji,Jianfeng Zhao,Yichao Sun,Xiaojun Yao,Zean Zhu 전력전자학회 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.5

Cascaded H-Bridge (CHB) converters can be directly connected to medium-voltage grids without using transformers and they possess the advantages of large capacity and low harmonics. They are significant tools for providing grid connections in large-capacity renewable energy systems. However, the reliability of a grid-connected CHB converter can be seriously influenced by the number of power switching devices that exist in the structure. This paper proposes a fault-tolerant control strategy based on double zero-sequence voltage injection and DC voltage optimization to improve the reliability of star-connected CHB converters after one or more power units have been bypassed. By injecting double zero-sequence voltages into each phase cluster, the DC voltages of the healthy units can be rapidly balanced after the faulty units are bypassed. In addition, optimizing the DC voltage increases the number of faulty units that can be tolerated and improves the reliability of the converter. Simulations and experimental results are shown for a seven-level three-phase CHB converter to validate the efficiency and feasibility of this strategy.

Framework and Key Technology Review of Big Data Analysis in the Social Network Background

Zhendong Ji 보안공학연구지원센터 2016 International Journal of Database Theory and Appli Vol.9 No.6

As the network promoting in people's lives, more and more people use the social networks and other network platform, the concepts of big data have been gradually reference to the network data analysis, researching big data analysis framework and technology can improve enterprise management level. This paper analyzes the framework and its key technology of big data analysis in the context of social network, in order to be able to provide the corresponding theoretical support and reference for analysis of social network data.

Fault-Tolerant Control of Cascaded H-Bridge Converters Using Double Zero-Sequence Voltage Injection and DC Voltage Optimization

Ji, Zhendong,Zhao, Jianfeng,Sun, Yichao,Yao, Xiaojun,Zhu, Zean The Korean Institute of Power Electronics 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.5

Cascaded H-Bridge (CHB) converters can be directly connected to medium-voltage grids without using transformers and they possess the advantages of large capacity and low harmonics. They are significant tools for providing grid connections in large-capacity renewable energy systems. However, the reliability of a grid-connected CHB converter can be seriously influenced by the number of power switching devices that exist in the structure. This paper proposes a fault-tolerant control strategy based on double zero-sequence voltage injection and DC voltage optimization to improve the reliability of star-connected CHB converters after one or more power units have been bypassed. By injecting double zero-sequence voltages into each phase cluster, the DC voltages of the healthy units can be rapidly balanced after the faulty units are bypassed. In addition, optimizing the DC voltage increases the number of faulty units that can be tolerated and improves the reliability of the converter. Simulations and experimental results are shown for a seven-level three-phase CHB converter to validate the efficiency and feasibility of this strategy.

Gecko's Ground Reaction Forces on Level/Vertical/Inverted Surfaces

Aihong Ji(지아홍),Zhendong Dai(대젠동),Zhouyi Wang(왕주이),Jintong Wang(왕진통) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5

Geckos can run even on an inverted surfaces with exceptional speed, strength and agility for their size, representing in many respects an ideal model system for the study of terrestrial locomotion. By measuring the ground reaction force(GRF)s generated by animals when walking upright, climbing vertically or walking on an. inverted surface, we can understand animals adhesion mechanism and locomotion dynamics. We used a sensors array to measure the GRFs. When geckos walked on vertical and inverted surfaces, the lateral force and the fore-aft force play an important role.

Three Dimensional Ground Reaction Forces of Eerthesina fullo on Level and Vertical Surfaces

Aihong Ji,Huabing Yan,Hui Shen,Zhendong Dai 한국응용곤충학회 2005 한국응용곤충학회 학술대회논문집 Vol.2005 No.05

A Study of the SPWM High-Frequency Harmonic Circulating Currents in Modular Inverters

Sheng Xu,Zhendong Ji 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.6

Due to detection and control errors, some high-frequency harmonics with voltage-source characteristics cause circulating currents in modular inverters. Moreover, the circulating currents are usually affected by the output filters (OF) of each module due to their filter and resonance properties. The interaction among the circulating currents in the modules increase the power loss and reduce system stability and control precision. Therefore, this paper reports the results of a study on the SPWM high-frequency harmonics circulating currents for a double-module VSI. In the paper, an analysis of the circulating-current circuits is briefly described. Next, a mathematic model of the single-module output voltage based on the carrier frequency of SPWM is built. On this basis, through mathematic modeling of high-frequency harmonic circulating currents, the formation mechanism and distribution characteristics of circular currents and their influences are studied in detail. Finally, the influences of the OF on the circulating currents are studied by mainly taking an LC-type filter as an example. A theoretical analysis and experimental results demonstrate some important characteristics. First, the carrier phase shifting of the SPWM for each module is the major cause of the SPWM harmonic circulating currents, and the circulating currents are in an odd distribution around n-times the carrier frequency nωs, where n = 1, 2, 3, …. Second, the harmonic circular currents do not flow into the parallel system. Third, the OF can effectively suppress the non-circulating part of the high-frequency harmonic currents but is ineffective for the circulation part, and actually reduces system stability.

A Study of the SPWM High-Frequency Harmonic Circulating Currents in Modular Inverters

Xu, Sheng,Ji, Zhendong The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.6

Due to detection and control errors, some high-frequency harmonics with voltage-source characteristics cause circulating currents in modular inverters. Moreover, the circulating currents are usually affected by the output filters (OF) of each module due to their filter and resonance properties. The interaction among the circulating currents in the modules increase the power loss and reduce system stability and control precision. Therefore, this paper reports the results of a study on the SPWM high-frequency harmonics circulating currents for a double-module VSI. In the paper, an analysis of the circulating-current circuits is briefly described. Next, a mathematic model of the single-module output voltage based on the carrier frequency of SPWM is built. On this basis, through mathematic modeling of high-frequency harmonic circulating currents, the formation mechanism and distribution characteristics of circular currents and their influences are studied in detail. Finally, the influences of the OF on the circulating currents are studied by mainly taking an LC-type filter as an example. A theoretical analysis and experimental results demonstrate some important characteristics. First, the carrier phase shifting of the SPWM for each module is the major cause of the SPWM harmonic circulating currents, and the circulating currents are in an odd distribution around n-times the carrier frequency $n{\omega}_s$, where n = 1, 2, 3, ${\ldots}$. Second, the harmonic circular currents do not flow into the parallel system. Third, the OF can effectively suppress the non-circulating part of the high-frequency harmonic currents but is ineffective for the circulation part, and actually reduces system stability.

Study on the Regulation and Motor Control of the Gecko’s Foot

Guo Ce,Dai Zhendong,Ji Aihong,Wang Weiying,Sun Jiurong 한국응용곤충학회 2005 한국응용곤충학회 학술대회논문집 Vol.2005 No.05

A Modifed Finite Control Set Model Predictive Control for 3L−NPC Grid−Connected Inverters Using Virtual Voltage Vectors

Jianguo Lyu,Binghui Ma,Han Yan,Zhendong Ji,Jinyong Ding 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.1

In order to improve the performance of a 3−level neutral point clamped (3L−NPC) grid−connected inverter with fnite control set model predictive control (FCS−MPC), this paper proposes a modifed FCS−MPC algorithm based on the rearranged control set (MFCS−MPC). By adding synthetic virtual voltage vectors to rearrange the fnite control set (FCS) of the 3L−NPC inverter, the frequency spectrum of output leg voltage becomes concentrated, which is benefted for decreasing total harmonic distortion (THD) of grid currents and makes it easier to design output flters for the grid−connected inverter. Moreover, based on switching state sequences of virtual voltage vectors, the modifed predictive model of the proposed method is established considering capacitor voltage diference. Besides, according to the location of the reference output voltage vector, a preselection step is incorporated into MFCS−MPC to narrow the control set for predictions, which avoids evaluating all candidate voltage vectors in the control set, and hence, the online computational burden is signifcantly reduced. A prototype of 3L−NPC grid−connected inverter is established to validate the proposed MFCS−MPC method and the experimental results show that this method has excellent static and dynamic performance, with a low THD for a wide range of modulation indexes.