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RISS 인기검색어
- 검색키워드
- 저자 : Jianguo Wu (검색결과 19 건)
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Jianguo Lyu,Wenbin Hu,Fuyun Wu,Kai Yao,Junji Wu 전력전자학회 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.5
In order to suppress the low frequency oscillation of the neutral-point voltage for three-level inverters, this paper proposes a new discontinuous pulse width modulation (DPWM) control method. The conventional sinusoidal pulse width modulation (SPWM) control has no effect on balancing the neutral-point voltage. Based on the basic control principle of DPWM, the relationship between the reference space voltage vector and the neutral-point current is analyzed. The proposed method suppresses the low frequency oscillation of the neutral-point voltage by keeping the switches of a certain phase no switching in one carrier cycle. So the operating time of the positive and negative small vectors is equal. Comparing with the conventional SPWM control method, the proposed DPWM control method suppresses the low frequency oscillation of the neutral-point voltage, decreases the output waveform harmonics, and increases both the output waveform quality and the system efficiency. An experiment has been realized by a neutral-point clamped (NPC) three-level inverter prototype based on STM32F407-CPLD. The experimental results verify the correctness of the theoretical analysis and the effectiveness of the proposed DPWM method.
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Jianguo Lyu,Wenbin Hu,Fuyun Wu,Kai Yao,Junji Wu 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.6
Based on the space vector pulse width modulation (SVPWM) theory, this paper realizes an easier SVPWM strategy, which is equivalently implemented by CBSPWM with zero-sequence voltage injection. The traditional SVPWM strategy has no effect on controlling the neutral-point voltage balance. In order to solve the neutral-point voltage unbalance problem for neutral-point-clamped (NPC) three-level inverters, this paper proposes a neutral-point voltage balance controller. The proposed controller realizes controlling the neutral-point voltage balance by dynamically calculating the offset superimposed to the three-phase modulation waves of an equivalent SVPWM strategy. Compared with the traditional SVPWM strategy, the proposed neutral-point voltage balance controller has a strong ability to balance the neutral-point voltage, has good steady-state performance, improves the output waveforms quality and is easy for digital implementation. An experiment has been carried out on a NPC three-level inverter prototype based on a digital signal processor-complex programmable logic device (DSP-CPLD). The obtained experimental results verify the effectiveness of the proposed neutral-point voltage balance controller.
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Lyu, Jianguo,Hu, Wenbin,Wu, Fuyun,Yao, Kai,Wu, Junji The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.6
Based on the space vector pulse width modulation (SVPWM) theory, this paper realizes an easier SVPWM strategy, which is equivalently implemented by CBSPWM with zero-sequence voltage injection. The traditional SVPWM strategy has no effect on controlling the neutral-point voltage balance. In order to solve the neutral-point voltage unbalance problem for neutral-point-clamped (NPC) three-level inverters, this paper proposes a neutral-point voltage balance controller. The proposed controller realizes controlling the neutral-point voltage balance by dynamically calculating the offset superimposed to the three-phase modulation waves of an equivalent SVPWM strategy. Compared with the traditional SVPWM strategy, the proposed neutral-point voltage balance controller has a strong ability to balance the neutral-point voltage, has good steady-state performance, improves the output waveforms quality and is easy for digital implementation. An experiment has been carried out on a NPC three-level inverter prototype based on a digital signal processor-complex programmable logic device (DSP-CPLD). The obtained experimental results verify the effectiveness of the proposed neutral-point voltage balance controller.
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Novel Ceramides from Aerial Parts of Saussurea involucrata Kar. et. Kir.
Wei Wu,Yang Qu,Huiyuan Gao,Jingyu Yang,Jianguo Xu,Lijun Wu 대한약학회 2009 Archives of Pharmacal Research Vol.32 No.9
Novel ceramides, together with nine known compounds were isolated from aerial parts of the Saussurea involucrata Kar. et. Kir. The novel structures were determined by spectroscopic methods and microscale chemical degradation. The ceramides showed appreciable cytotoxicity against three human tumor cell lines including human promyelocytic leukemia (HL-60), human melanoma (A375-S2) and human cervical carcinoma (HeLa) cell lines. The results suggested that this class of ceramides may have potential as an antitumor agent.
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(Ba, Ca)(Ti, Zr)O3-BiFeO3 lead-free piezoelectric ceramics
Jiagang Wu,Wenjuan Wu,Dingquan Xiao,John Wang,Zhenchun Yang,Zhihang Peng,Qiang Chen,Jianguo Zhu 한국물리학회 2012 Current Applied Physics Vol.12 No.2
Effects of BiFeO3 (BFO) content on the microstructure and electrical properties of Ba0.85Ca0.15Ti0.90Zr0.10O3(BCTZ) ceramics prepared by normal sintering in air were investigated. A stable solid solution is formed between BCTZ and BFO. The grain size gradually becomes smaller, and the ceramics become denser with increasing the BFO content. The Curie temperature, dielectric constant, and dielectric loss of BCTZ ceramics decrease simultaneously with the introduction of BFO. Moreover, the remanent polarization reaches a maximum at x ¼ 0.2 mol%, and the coercive field continuously increases with increasing the BFO content due to the introduction of BFO with a higher coercive field. Improved piezoelectric properties (d33 w 405 pC/N and kp w 0.44) are demonstrated for the BCTZ ceramic with x ¼ 0.2 mol%.
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Lyu, Jianguo,Hu, Wenbin,Wu, Fuyun,Yao, Kai,Wu, Junji The Korean Institute of Power Electronics 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.5
In order to suppress the low frequency oscillation of the neutral-point voltage for three-level inverters, this paper proposes a new discontinuous pulse width modulation (DPWM) control method. The conventional sinusoidal pulse width modulation (SPWM) control has no effect on balancing the neutral-point voltage. Based on the basic control principle of DPWM, the relationship between the reference space voltage vector and the neutral-point current is analyzed. The proposed method suppresses the low frequency oscillation of the neutral-point voltage by keeping the switches of a certain phase no switching in one carrier cycle. So the operating time of the positive and negative small vectors is equal. Comparing with the conventional SPWM control method, the proposed DPWM control method suppresses the low frequency oscillation of the neutral-point voltage, decreases the output waveform harmonics, and increases both the output waveform quality and the system efficiency. An experiment has been realized by a neutral-point clamped (NPC) three-level inverter prototype based on STM32F407-CPLD. The experimental results verify the correctness of the theoretical analysis and the effectiveness of the proposed DPWM method.
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Xiaoyu Chen,Jiagang Wu,Xiaojing Cheng,Bo Wu,Wenjuan Wu,Dingquan Xiao,Jianguo Zhu 한국물리학회 2012 Current Applied Physics Vol.12 No.3
[Li0.03(K0.48Na0.52)0.97](Nb0.97Sb0.03)O3-(Ba0.85Ca0.15)(Ti0.90Zr0.10)O3 [(1-x)LKNNS-xBCTZ] lead-free piezoelectric ceramics were prepared by the conventional solid state method, and effects of BCTZ content on the piezoelectric properties of LKNNS ceramics were mainly investigated. A stable solid solution has been formed between LKNNS and BCTZ, and a morphotropic phase boundary of (1-x)LKNNS-xBCTZ ceramics is identified in the range of 0 < x ≤ 0.02. The Curie temperature of (1-x)LKNNS-xBCTZ ceramics decreases with increasing BCTZ content. A higher εr value and a lower tan d value are demonstrated for the (1-x)LKNNS-xBCTZ ceramic with x = 0.02. The (1-x)LKNNS-xBCTZ ceramic with x = 0.02 has an enhanced electrical behavior of d33w237 pC/N, kpw 48.6%, 3 rw1451, tan d w0.037, and Tcw335 ℃. As a result, (1-x)LKNNS-xBCTZ ceramics are promising candidate materials for the field of lead-free piezoelectric materials.
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Use of Long-chain Alcohol in Extraction and Purification of Lincomycin from Fermentation Broth
Wu, Bin,Zhu, Jiawen,Chen, Kui,Ji, Lijun,Guo, Jianguo,Zhao, Jianxi 한국화학공학회 2003 Korean Journal of Chemical Engineering Vol.20 No.2
Low selectivity for lincomycin in butanol extraction process leads to relatively higher content of impurities. A novel process for extraction of lincomycin from fermentation broth was studied in this work. Mixture of n-octanol and n-decanol is used as extractant to replace n-butanol in extraction of lincomycin. Oprimal operation conditions for the process have been studied. Due to higher extraction selectivity for lincomycin A by long-chain alcohol, content of impurity(lincomycin B) in the final product is much lower than that in product by butanol process. Furthemore, the practicability for combination of long-chain alcohol and butanol in purification of linecomycin was investigated.
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Experimental investigations of machining characteristics of SiC in high speed plunge grinding
Chongjun Wu,Beizhi Li,Jianguo Yang,Steven Y. Liang 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.3
Grinding is widely used as a productive technique for finishing ceramic components in the manufacturing industry. However,it is still difficult to achieve a satisfying finishing quality for scarce of comprehensive engineering investigations of damage-freeand economical techniques of advanced ceramics. This paper will utilize a high speed grinder to develop the grinding forces,temperature, grinding surface and subsurface features in high speed plunge grinding of SiC. The ductile grinding of SiC undera relatively high grinding speed will be investigated. A set of detecting equipment, including a rotating dynamometer and agrindable thermocouple, will be used to measure the online grinding forces and temperature. Besides, the subsurface damage,chips and ground surface will be examined by SEM micrographs. It has been found that ductile grinding of SiC can beachieved through a combination of the increase of the wheel speed and the control of grinding parameters. Via causing lowerforce and thermal effects, the critical value for ductile grinding of SiC can be greatly improved under high speed grindingcomparing to conventional speed grinding. Moreover, the grinding subsurface integrity will not be adversely effected thoughimproving material removal volumes under high speed grinding.
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Absorption of SO<sub>2</sub> at High Temperatures by Ionic Liquids and the Absorption Mechanism
Tian, Shidong,Hou, Yucui,Wu, Weize,Ren, Shuhang,Qian, Jianguo Korean Chemical Society 2014 Bulletin of the Korean Chemical Society Vol.35 No.9
The capture of $SO_2$ at or close to the temperatures of real flue gas is much more attractive in application. In this work, two kinds of ionic liquids (ILs) based on lactate anion were used to absorb $SO_2$ at high temperatures from 100 to $120^{\circ}C$. The ILs show high absorption capacities of over one mol $SO_2$ per mol IL at $110^{\circ}C$. The absorption of $SO_2$ by the ILs based on lactate anion is reversible and the ILs can be reused for the capture of $SO_2$ at high temperatures with high absorption capacity and thermal stability. Furthermore, the absorption mechanism of $SO_2$ by the ILs was studied by FT-IR, $^1H$ NMR and $^{13}C$ NMR spectra. It has been found that there are strong chemical interactions between the ILs and $SO_2$. Also the absorption mechanism is different when there is water present in ILs compared to when there is not.
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