Individual Channel Design-based Modeling and Analysis of Three Phase Grid-tied Inverter with Unbalanced Grid Impedance

Weimin Wu,Yun Li,Jiahao Liu,Frede Blaabjerg 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

Three-phase grid-tied inverters are usually designed to operate in symmetric grid impedance. In actual operations, due to the imbalanced loads, three-phase systems with significant single-phase loads, imbalanced power line impedance or the imbalanced short-circuit impedance of the three grid power transformer, the equivalent three-phase grid impedance is unbalanced. It is, consequently, important to develop an effective model and stability analysis method to address three-phase grid-tied inverter with unbalanced grid impedance. Traditionally, the stability of unbalanced system can be analyzed by harmonic linearization technique, however, the model derivation is complex and the controller parameters need second designing. This paper develops the system model in a multivariable frequency domain, by using the individual channel analysis and design (ICAD), simplifying the stability analysis of the unbalanced system. The detailed study on the three-phase LCL filter-based grid-tied inverter under the unbalanced grid impedance condition is presented. Simulation and experiment analysis are carried out on a 380 V/50 Hz/6 kW grid-tied inverter prototype.

Fracture analysis of a welded front axle tube structure from a mini-truck

Weimin Guo,Ning Ding,Na Xu,Long Liu,Nan Li,Junbo Shi,Chi-Man Lawrence Wu 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.1

The failure (fracture) mechanism of a welded front axle tube structure made of C45E4 steel from a mini truck was analyzed. The fracture occurred on the right side of the right support frame with the fracture surface perpendicular to the tube axis. SEM examination showed that the fracture surface could be divided into three areas: intergranular area, cleavage area and dimple area. Crack initiation site of the failed front axle tube was at the front weld joint fixing the right support frame on the axle tube. The crack propagated in two opposite directions along the circumference of the tube and converged at the dimple area. Intergranular fracture was found to be in heat affected zone (HAZ). With higher magnification, fine dimples, intergranular and trans-granular fracture characteristics were observed in the crack initiation site. By metallurgical examination, Widmanstätten ferrites, which could decrease the toughness and strength of the weld joint, were observed in the columnar grains. The hardness of HAZ coarse grain area (623 VHN) was far higher than HAZ fine grain area (310 VHN) and base metal (225 VHN). As the weld process indicates, neither pre-weld nor post-weld treatment was carried out. A non-uniform temperature distribution around the weld joint could generate large thermal residual tensile stress in HAZ; thus, the material was very unstable. It could fracture for very small or even no external stress. Hydrogen atoms would be released during welding and microstructures with the highest hardness are the most susceptible of hydrogen assisted cracking. It is concluded that the fracture was caused by hydrogen assisted brittleness under the induction of weld residual stress. Post-weld aging treatment (PWAT) is recommended to release the residual stress generated during welding process. In this case, PWAT was carried out on the failed weld joint and Vickers hardness of HAZ coarse grain area, HAZ fine grain area and base metal decreased to 232 VHN, 205 VHN and 125 VHN, respectively. That indicates that the PWAT procedure could effectively soften the material and relieve residual stress.

Chromogenic/Fluorogenic Ensemble Chemosensing Systems

Wu, Jiasheng,Kwon, Bomi,Liu, Weimin,Anslyn, Eric V.,Wang, Pengfei,Kim, Jong Seung American Chemical Society 2015 Chemical reviews Vol.115 No.15

<P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/chreay/2015/chreay.2015.115.issue-15/cr500553d/production/images/medium/cr-2014-00553d_0121.gif'></P>

LncRNA CRNDE Promotes the Progression of B-cell Precursor Acute Lymphoblastic Leukemia by Targeting the miR-345-5p/CREB Axis

Weimin Wang,Feifei Wu,Ping Ma,Silin Gan,Xue Li,Li Chen,Ling Sun,Hui Sun,Zhongxing Jiang,Feng Guo 한국분자세포생물학회 2020 Molecules and cells Vol.43 No.8

The imbalance between the proliferation and apoptosis of B-cell precursors is an important contributor to the pathogenesis of B-cell precursor acute lymphoblastic leukemia (BCP-ALL), while its specific regulatory mechanism remains perplexing. This study aimed to expound the underlying mechanism of the proliferation and apoptosis of BCP-ALL cells from the perspective of non-coding RNA. In this study, long non-coding RNA colorectal neoplasia differentially expressed (LncRNA CRNDE) was upregulated in the bone marrow of BCP-ALL patients and BCP-ALL cell lines (NALM-6 and RS4;11). Functionally, LncRNA CRNDE knockdown restrained cell proliferation and boosted cell apoptosis in NALM-6 and RS4;11 cells. The subsequent investigation confirmed that LncRNA CRNDE bound to miR-345-5p and negatively regulated miR-345-5p expression. The overexpression of miR-345-5p suppressed cell proliferation and boosted cell apoptosis in NALM-6 and RS4;11 cells. Further experiments revealed that miR-345-5p downregulated cyclic AMP response element-binding protein (CREB) expression by targeting its mRNA directly. CREB overexpression reversed the effect of miR-345-5p mimic on cell proliferation and apoptosis in NALM-6 and RS4;11 cells. Finally, in vivo experiments showed that LncRNA CRNDE knockdown prolonged the survival of mice xenotransplanted with NALM-6 cells. In conclusion, LncRNA CRNDE upregulated CREB expression by suppressing miR-345-5p, thus promoting cell proliferation and reducing cell apoptosis in BCP-ALL.

The effects of under-ribs convection on enhanced drainage parallel flow field for proton exchange membrane fuel cell

Sida Wu,Weimin Yang,Jin Zhan,Hua Yan,Xianghao Kong,Xiahua Zuo 한국화학공학회 2022 Korean Journal of Chemical Engineering Vol.39 No.8

A new enhanced drainage parallel (EDP) flow field was designed that not only enhances under-rib convectionbut also enables a more uniform distribution of hydrogen and oxygen. Through the optimization of the model, weestablished the influence of the flow field size, relative humidity, and stoichiometric ratio on cell performance. Whenthe rib width is reduced, the maximum power density is improved. Compared with the parallel flow field and serpentineflow field, the maximum power density of the EDP flow field was increased by 69.4% and 7.9%, respectively. Under optimal conditions, the net power of the EDP flow field can reach 0.56 W/cm2. In the single-cell test, the maximumpower density of the EDP flow field can reach 1.19 W/cm2. This implies that the EDP flow field has potentialapplication of proton exchange membrane fuel cells.

Surgical Options for Appropriate Length of J-Pouch Construction for Better Outcomes and Long-term Quality of Life in Patients with Ulcerative Colitis after Ileal Pouch-Anal Anastomosis

Xu Weimin,Tang Wenbo,Ding Wenjun,Hua Zhebin,Wang Yaosheng,Ge Xiaolong,Cui Long,Wu Xiaojian,Zhou Wei,Ding Zhao,Du Peng 거트앤리버 소화기연관학회협의회 2024 Gut and Liver Vol.18 No.1

Background/Aims: Total proctocolectomy with ileal pouch-anal anastomosis (IPAA) is widely accepted as a radical surgery for refractory ulcerative colitis (UC). Definite results on the appropriate pouch length for an evaluation of the risk-to-benefit ratio regarding technical complications and long-term quality of life (QOL) are still scarce. Methods: Data on UC patients who underwent IPAA from 2008 to 2022 in four well-established pouch centers affiliated to China UC Pouch Center Union were collected. Results: A total of 208 patients with a median follow-up time of 6.0 years (interquartile range, 2.3 to 9.0 years) were enrolled. The median lengths of the patients’ short and long pouches were 14.0 cm (interquartile range, 14.0 to 15.0 cm) and 22.0 cm (interquartile range, 20.0 to 24.0 cm), respectively. Patients with a short J pouch configuration were less likely to achieve significantly improved long-term QOL (p=0.015) and were prone to develop late postoperative complications (p=0.042), such as increased defecation frequency (p=0.003) and pouchitis (p=0.035). A short ileal pouch was an independent risk factor for the development of late postoperative complications (odds ratio, 3.100; 95% confidence interval, 1.519 to 6.329; p=0.002) and impaired long-term QOL improvement (odds ratio, 2.221; 95% confidence interval, 1.218 to 4.050, p=0.009). Conclusions: The length of the J pouch was associated with the improvement in long-term QOL and the development of late post-IPAA complications. A long J pouch configuration could be a considerable surgical option for pouch construction.

A New Phenolic Glycoside from Mussaenda pubescens

Zhao, Weimin,Xu, Rensheng,Qin, Guowei,Wu, Houming,Jiang, Shaokai,Yang, Genjin The Korean Society of Pharmacognosy 1996 Natural Product Sciences Vol.2 No.1

A new phenolic glycoside named mussaendoside L (1), along with four known iridoidal glycosides $(2{\sim}5)$ were isolated from the aerial parts of Mussaenda pubescens Ait.f. Their structures were elucidated on the basis of chemical and spectroscopic evidence.

AN ULTRA-LUMINOUS QUASAR AT <i>z</i> = 5.363 WITH A TEN BILLION SOLAR MASS BLACK HOLE AND A METAL-RICH DLA AT <i>z</i> ∼ 5

Wang, Feige,Wu, Xue-Bing,Fan, Xiaohui,Yang, Jinyi,Cai, Zheng,Yi, Weimin,Zuo, Wenwen,Wang, Ran,McGreer, Ian D.,Ho, Luis C.,Kim, Minjin,Yang, Qian,Bian, Fuyan,Jiang, Linhua IOP Publishing 2015 ASTROPHYSICAL JOURNAL LETTERS - Vol.807 No.1

<P>We report the discovery of an ultra-luminous quasar J030642.51+185315.8 (hereafter J0306+1853) at redshift 5.363, which hosts a supermassive black hole with M-BH = (1.07 +/- 0.27) x 10(10) M-circle dot. With an absolute magnitude M-1450 = -28.92 and a bolometric luminosity L-bol similar to 3.4 x 10(14) L-circle dot, J0306+1853 is one of the most luminous objects in the early universe. It is not likely to be a beamed source based on its small flux variability, low radio loudness, and normal broad emission lines. In addition, a z = 4.986 damped Ly alpha system (DLA) with [M/H] = -1.3 +/- 0.1, among the most metal-rich DLAs at z greater than or similar to 5, is detected in the absorption spectrum of this quasar. This ultra-luminous quasar puts strong constraints on the bright end of the quasar luminosity function and massive end of the black hole mass function. It will provide a unique laboratory for the study of BH growth and the co-evolution between a BH and the host galaxy with multi-wavelength follow-up observations. The future high-resolution spectra will give more insight into the DLA and other absorption systems along the line of sight of J0306+1853.</P>

Device-to-Device assisted user clustering for Multiple Access in MIMO WLAN

( Zhao Hongyi ),( Wu Weimin ),( Lu Li ),( Liu Yingzhuang ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.7

WLAN is the best choice in the place where complex network is hard to set up. Intelligent terminals are more and more assembled in some areas now. However, according to IEEE 802.11n/802.11ac, the access-point (AP) can only serve one user at a single frequency channel. The spectrum efficiency urgently needs to be improved. In theory, AP with multi-antenna can serve multiple users if these users do not interfere with each other. In this paper, we propose a user clustering scheme that could achieve multi-user selection through the mutual cooperation among users. We focus on two points, one is to achieve multi-user communication with multiple antennas technique at a single frequency channel, and the other one is to use a way of distributed users` collaboration to determine the multi-user selection for user clustering. Firstly, we use the CSMA/CA protocol to select the first user, and then we set this user as a source node using users` cooperation to search other proper users. With the help of the users` broadcast cooperation, we can search and select other appropriate user (while the number of access users is limited by the number of antennas in AP) to access AP with the first user simultaneously. In the network node searching, we propose a maximum degree energy routing searching algorithm, which uses the shortest time and traverses as many users as possible. We carried out the necessary analysis and simulation to prove the feasibility of the scheme. We hope this work may provide a new idea for the solution of the multiple access problem.

Parameters Design Strategy of PBC Controller for LCL-Filtered Grid-Tied Inverter Based on Limited Steady-State Error

Jinpin Zhao,Weimin Wu,Zhikang Shuai,An Luo,Henry Chung,Frede Blaabjerg 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

Nowadays, the passivity-based control (PBC) as a nonlinear control method with much superiority has been studied more and more frequently, where it has been successfully used in Grid-Tied Inverters (GTI). Due to the high order characteristics of a LCL-filtered GTI, the PBC control law tends to be complicated, resulting in a difficult selection on control parameters. In this paper, a novel PBC parameters design strategy based on the expectant limited steady-state error is proposed. Simulation platform was built in MATLAB/Simulink and a 3-kW experimental device was carried out with DS1202 to verify the correctness and effectiveness of the proposed strategy.