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Improved Switching Ripple Suppression Strategy for Multi-Paralleled Grid-Connected Inverters System
Wu Cao,Haotian Kang,Kangli Liu,Shunyu Wang,Jianfeng Zhao,Xiaochun Ji,Jun Zhao 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
The switching operations of inverters in the distributed system inevitably introduce high-frequency harmonics into grid, which may make influences on electrical devices. To address it, this paper proposes a ripple suppression strategy based on active cancellation combined with passive filtering. The active cancellation is realized by carrier-phase-shift (CPS) technique and the passive filtering is achieved by filters. Furthermore, two component-shared LCL-type filters improved by traditional LCL filters are studied from the points of resonance and accuracy of gridinjected current. To valid the effectiveness of the proposed strategy, simulations and experimental test are carried out. The results show that the proposed strategy can effectively suppress high-frequency harmonics and two componentshared LCL-type filters can become promising filters for the multi-paralleled grid-connected inverters.
Wu Cao,Kangli Liu,Sheng Xu,Haotian Kang,Jianfeng Zhao 대한전기학회 2019 Journal of Electrical Engineering & Technology Vol.14 No.3
The frequent starting of large capacity lifting machines and other surge ship electrical loads will result in severe impacts on a shipboard power network, such as voltage and frequency fl uctuations. Therefore, a novel stabilization control strategy for shore power systems based on virtual synchronous generator is proposed in this paper, so as to improve the power quality and enhance the stability and reliability of shipboard power networks. In this strategy, a reactive power inertia component is embedded into the virtual synchronous generator aiming at shipboard surge reactive powers. On this basis, a voltage and frequency stability control method is presented to improve the static performances of shore power systems. In addition, a d-q decoupling control scheme in synchronous reference frame for the voltage and current double closed-loop control system is designed, and moreover, the infl uence of diff erent feedback voltages on the output characteristics of shore power supplies is studied. The theoretical analysis, simulation and experiment results show that, the proposed control strategy can eff ectively attenuate the frequency and voltage fl uctuations, eliminate the frequency and voltage steady-state errors, as well as realize the power distribution evenly for modular shore power supplies.
Cao, Hua-Lian,Kang, Moon-Ho,Lee, Jin-Yong,Park, Won-Jong,Choung, Han-Wool,Choung, Pill-Hoon Korean Association of Maxillofacial Plastic and Re 2020 Maxillofacial Plastic Reconstructive Surgery Vol.42 No.-
Background: To evaluate the facial asymmetry, three-dimensional computed tomography (3D-CT) has been used widely. This study proposed a method to quantify facial asymmetry based on 3D-CT. Methods: The normal standard group consisted of twenty-five male subjects who had a balanced face and normal occlusion. Five anatomical landmarks were selected as reference points and ten anatomical landmarks were selected as measurement points to evaluate facial asymmetry. The formula of facial asymmetry index was designed by using the distances between the landmarks. The index value on a specific landmark indicated zero when the landmarks were located on the three-dimensional symmetric position. As the asymmetry of landmarks increased, the value of facial asymmetry index increased. For ten anatomical landmarks, the mean value of facial asymmetry index on each landmark was obtained in the normal standard group. Facial asymmetry index was applied to the patients who had undergone orthognathic surgery. Preoperative facial asymmetry and postoperative improvement were evaluated. Results: The reference facial asymmetry index on each landmark in the normal standard group was from 1.77 to 3.38. A polygonal chart was drawn to visualize the degree of asymmetry. In three patients who had undergone orthognathic surgery, it was checked that the method of facial asymmetry index showed the preoperative facial asymmetry and the postoperative improvement well. Conclusions: The current new facial asymmetry index could efficiently quantify the degree of facial asymmetry from 3D-CT. This method could be used as an evaluation standard for facial asymmetry analysis.
Performance Prediction and Flow Field Calculation for Airfoil Fan with Impeller Inlet Clearance
Kang, Shin-Hyoung,Cao, Renjing,Zhang, Yangjun The Korean Society of Mechanical Engineers 2000 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.14 No.2
The performance prediction of an airfoil fan using a commerical code, STAR/CD, is verified by comparing the calculated results with measured performance data and velocity fields of an airfoil fan. The effects of inlet tip clearance on performance are investigated. The calculations overestimate the pressure rise performance by about 10-25 percent. However, the performance reduction due to tip clearance is well predicted by numerical simulations. Main source of performance decrease is not only the slip factor but also impeller efficiency. The reduction in performance is 12-16 percent for 1 percent gap of the diameter. The calculated reductions in impeller efficiency and slip factor are also linearly proportional to the gap size. The span-wise distributions of phase averaged velocity and pressure at the impeller exit are strongly influenced by the radial gap size. The radial component of velocity and the flow angle increase over the passsage as the gap increases. The slip factor decreases and the loss increases with the gap size. The high velocity of leakage jet affects the impeller inlet and passage flows. With a larger clearance, the main stream moves to the impeller hub side and high loss region extends from the shroud to the hub.
Analysis of succinate dehydrogenase subunit B gene alterations in gastric cancers
Cao, Zhang,Song, Jae Hwi,Kang, Young Whi,Yoon, Jung Hwan,Nam, Suk Woo,Lee, Jung Young,Park, Won Sang Blackwell Publishing Asia 2010 Pathology international Vol.60 No.8
<P>Recently, the succinate dehydrogenase subunit B gene, <I>SDHB</I>, has emerged as a novel tumor suppressor. In this study, we have examined the genetic and epigenetic alterations of the <I>SDHB</I> gene in sporadic gastric adenocarcinomas in order to investigate if the <I>SDHB</I> gene is involved in gastric carcinogenesis. The expression of <I>SDHB</I> proteins was also examined with immunohistochemistry and Western blot in 184 and eight gastric cancers, respectively. There was loss or reduced expression of <I>SDHB</I> in 45 (24.5%) of the 184 gastric cancers. Statistically, altered expression of <I>SDHB</I> was not associated with clinicopathological parameters, including tumor differentiation, location, depth of invasion, and lymph node metastasis (<I>P</I> > 0.05). Western blot analysis showed a reduced expression of <I>SDHB</I> in four (50.0%) of the eight paired gastric cancer tissues. Genetic analysis showed one missense mutation, GCC → ACC (Ala → Thr) at codon 29. In addition, promoter hypermethylation was not detected in the gastric cancer samples. This is the first investigation of the genetic and protein expression analysis of the <I>SDHB</I> gene in gastric cancers. Our results suggest that genetic, epigenetic, and protein expression pattern alterations of the <I>SDHB</I> gene might play a minor role in the development or progression of gastric cancers.</P>
Kang, Dae Gill,Cao, Li Hua,Lee, Jun Kyoung,Choi, Deok Ho,Kim, Seung Ju,Lee, Hyuck,Kim, Jin Sook,Lee, Ho Sub Institute for Advanced Research in Asian Science a 2006 The American journal of Chinese medicine Vol.34 No.4
<P>The butanol extract of Phellinus igniarius (BPI) induced relaxation of the phenylephrin e-precontracted rat aorta in a dose-dependent manner, and its effect was abolished by the removal of functional endothelium. Pretreatment of the aortic tissues with N(G)-nitro-L-arginine methyl ester (L-NAME), methylene blue, or 1H-[1,2,4]-oxadiazole-[4,3-alpha]-quinoxalin1-one (ODQ) inhibited the vascular relaxation induced by BPI. BPI-induced vascular relaxations were also markedly attenuated by the addition of verapamil or diltiazem, while the relaxant effect of BPI was not blocked by pretreatment with indomethacine, glibenclamide, tetraethylammonium (TEA), atropine, or propranolol. Incubation of endothelium-intact rat aorta with BPI increased the production of cGMP in a dose-dependent manner. These results suggest that BPI dilates vascular smooth muscle via endothelium-dependent nitric oxide-cGMP signaling pathway, with the possible involvement of L-type Ca(2+) channels.</P>