An Improved Model Predictive Direct Torque Control for Induction Machine Drives

Wenxiang Song,Shengkang Le,Xiaoxin Wu,Yi Ruan 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.3

The conventional model predictive direct torque control (MPDTC) method uses all of the voltage vectors available from a two level voltage source inverter for the prediction of the stator flux and stator current, which leads to a heavy computational burden. This paper proposes an improved model predictive direct torque control method. The stator flux predictive controller is obtained from an analysis of the relationship between the stator flux and the torque, which can be used to calculate the desired voltage vector based on the stator flux and torque reference. Then this method only needs to evaluate three voltage vectors in the sector of the desired voltage vector. As a result, the computational burden of the conventional MPDTC is effectively reduced. The time delay introduced by the computational time causes the stator current to oscillate around its reference. It also increases the current and torque ripples. To address this problem, a delay compensation method is adopted in this paper. Furthermore, the switching frequency of the inverter is significantly reduced by introducing the constraint of the power semiconductor switching number to the cost function of the MPDTC. Both simulation and experimental results are presented to verify the validity and feasibility of the proposed method.

Interesting Rules Mining with Deductive Method

Wenxiang Dou,Jinglu Hu,Gengfeng Wu 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8

In this paper, we propose a novel rule deductive method to mine the real demanded association rules for any given user. This method does not like the most existing methods that mine frequent itemsets starting from candidate two-itemsets to candidate (n-1)-itemsets with inductive method and produce huge rough rules on these frequent itemsets. On the contrary, it avoids producing huge amounts of frequent itemsets contained by their upper long frequent itemsets and can interact with users by making them pick up their interested items to deduce the final interesting association rules. Moreover, it can do dynamic response to users in any time when users want to check whether their interested frequent itemsets have been founded. Its several dynamic response strategies have been proposed. These dynamic response algorithms can find most long frequent itemsets in initial time. Therefore, users can find their interested rules in short time with high probability. So, our method also can be used applied in online data mining.

Detection of LSB Matching Revisited Using Pixel Difference Feature

( Wenxiang Li ),( Tao Zhang ),( Zhenhao Zhu ),( Yan Zhang ),( Xin Ping ) 한국인터넷정보학회 2013 KSII Transactions on Internet and Information Syst Vol.7 No.10

This paper presents a detection method for least significant bit matching revisited (LSBMR) steganography. Previous research shows that the adjacent pixels of natural images are highly correlated and the value 0 appears most frequently in pixel difference. Considering that the message embedding process of LSBMR steganography has a weighted-smoothing effect on the distribution of pixel difference, the frequency of the occurrence of value 0 in pixel difference changes most significantly whereas other values approximately remain unchanged during message embedding. By analyzing the effect of LSBMR steganography on pixel difference distribution, an equation is deduced to estimate the frequency of difference value 0 using the frequencies of difference values 1 and 2. The sum of the ratio of the estimated value to the actual value as well as the ratio of the frequency of difference value 1 to difference value 0 is used as the steganalytic detector. Experimental results show that the proposed method can effectively detect LSBMR steganography and can outperform previous proposed methods.

Geochemical record of rapid climate change and chemical weathering in a semi-arid area, northeastern Tibetan Plateau

Wenxiang Zhang,Hucai Zhang,Jie Niu,Guoliang Lei,Fengqin Chang 한국지질과학협의회 2020 Geosciences Journal Vol.24 No.6

Lacustrine deposits can provide insight into chemical weathering and climate change. Based on the analysis of the element concentrations and parameters of the acid-leaching residual fractions (AR) in the lacustrine deposits of the Qaidam Basin (QB), chemical weathering and paleoclimate changes in the northeastern Tibetan Plateau (NETP) have been studied. The results show that the characteristics of trace element concentrations exhibit two kinds of patterns by normalized element arbitrary units (a.u.). The rare earth element (REE) distribution patterns are moderately rich in light rare earth elements (LREEs) with slightly right-tilting and negative Eu anomalies. Triangular plots of the REEs and (La/Yb)n-ΣREE suggest that the sediments have a similar source. The geochemical records of climate proxies indicated warm-wet climate stages during 45.1–31.6 cal. ka BP., further proving that a megalake stage existed in the semi-arid area in marine isotope stage (MIS) 3. Strong evaporation resulted in a high paleolake level history in the northeastern Tibetan Plateau after the late period of MIS 3. Meanwhile, the geochemical records of the Qaidam Basin are synchronous with the global records.

An Improved Model Predictive Direct Torque Control for Induction Machine Drives

Song, Wenxiang,Le, Shengkang,Wu, Xiaoxin,Ruan, Yi The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.3

The conventional model predictive direct torque control (MPDTC) method uses all of the voltage vectors available from a two level voltage source inverter for the prediction of the stator flux and stator current, which leads to a heavy computational burden. This paper proposes an improved model predictive direct torque control method. The stator flux predictive controller is obtained from an analysis of the relationship between the stator flux and the torque, which can be used to calculate the desired voltage vector based on the stator flux and torque reference. Then this method only needs to evaluate three voltage vectors in the sector of the desired voltage vector. As a result, the computational burden of the conventional MPDTC is effectively reduced. The time delay introduced by the computational time causes the stator current to oscillate around its reference. It also increases the current and torque ripples. To address this problem, a delay compensation method is adopted in this paper. Furthermore, the switching frequency of the inverter is significantly reduced by introducing the constraint of the power semiconductor switching number to the cost function of the MPDTC. Both simulation and experimental results are presented to verify the validity and feasibility of the proposed method.

BIBLIOMETRIC ANALYSIS OF IOT APPLICATION IN MEDICAL FIELD

Cui Wenxiang,Liu Yi 한국엔터테인먼트산업학회 2018 한국엔터테인먼트산업학회 학술대회 논문집 Vol.2018 No.7

Applying bibliometric method and visualization software, the paper analyzed the articles which subject matter for the internet of things in medical field from 1999 to 2018,including periodicals distribution, the status of current researches, the frequency of keywords, and in order to provide readers a better understanding about the hot spot of domestic internet of things in medical field. This study reveals the development trend in the future and put forward suggestions.

Two-color field for the generation of an isolated attosecond pulse in water-window region.

Chen, Wenxiang,Chen, Guanglong,Kim, Dong Eon Optical Society of America 2011 Optics express Vol.19 No.21

<P>For the investigation of various ultrafast electron dynamics, an isolated attosecond pulse in a broad spectral range is necessary. The generation of isolated attosecond pulses demands the manipulation of the electric field of a laser. We propose a two-color field scheme for generating an isolated attosecond pulse in the water-window region. Two-color fields are generated by mixing two equally-strong pulsed color fields. The investigation shows that an isolated attosecond pulse with a photon energy of near 500 eV and a pulse duration of 125 - 188 attoseconds can be generated using 10 - 15 fs FWHM laser fields.</P>

對外漢語敎學中的構式語塊敎學模式初探

?文香(Qi Wenxiang) 중국어문학연구회 2012 중국어문학논집 Vol.0 No.75

The Construction-Chunk Approach in teaching Chinese as a foreign language is popular in recent years .According to the Constructionist theory and the Chunk theory,the linear combinations of the language is cutted into the Chunks, which consistent with the principles of language acquisition and the menial lexical, has achieved a good result in the applications. Textbook compilation should also follow the Construction-Chunk Approach, increase the chunk content, improve the teaching efficiency, raises the student language sense, language expression capability enhancement. This paper could be an exploration to the Construction-Chunk Approach, which makes detail analysis and deep study to the chunk structure of the audio visual teaching material “Growing Pains”.

중국 포양호 주변의 농경지 현황 및 수질 오염 부하량

이종식,정구복,윤순강,정광용,Chuanji Yu,Wenxiang Liu 한국국제농업개발학회 2002 韓國國際農業開發學會誌 Vol.14 No.4

Model-free kinetics applied to an oxidation mechanism of a biomorphic carbon template derived from pine

Pengzhao Gao,Wenxiang Wang,Weiei Gong 한양대학교 세라믹연구소 2010 Journal of Ceramic Processing Research Vol.11 No.4

A biomorphic carbon template (BCT) was developed by carbonizing pine under vacuum. Structural and oxidation properties of BCT were evaluated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA). Experimental results show that BCT has a topologically uniform interconnected porous network microstructure, and is typical non-graphitizable carbon containing C =C bonds, C–O–C bonds and a C–H structure. The non-isothermal oxidation properties of BCT exhibit a partially self-accelerating characteristic; the oxidation process of BCT is firstly controlled by a chemical reaction, and then controlled by a chemical reaction and gas diffusion together, which is obtained from a Vyazovkin model-free method, and the corresponding activation energy (E a) is also calculated.