Passivity‑based control strategy for hexagonal converter under unbalanced power grid

Yusheng Lai,Qiming Cheng,Xin Zhang 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.4

When a hexagonal converter (Hexverter) is applied to high-power renewable energy generation such as offshore low-frequencytransmission, using traditional PID control to ensure the stable global operation and strong robustness of the system is difficult due to the random fluctuation of renewable energy, system parameter uptake, its non-linear characteristics, and the possible unbalanced grid situation. This paper proposes a non-linear passivity-based control (PBC) strategy for Hexverter under an unbalanced grid. First, the passivity and stability of Hexverter objects are analyzed based on PBC theory. The unbalanced PBC strategy of Hexverter is then designed and derived. Three control objectives are designed according to different control requirements. Finally, the simulation system of the Hexverter under an unbalanced grid is built on Matlab/ Simulink to verify the effectiveness and superiority of the proposed unbalanced PBC method. The simulation results show that the proposed method has fewer control parameters, faster response, lower harmonic content, and better overall control effect than PID control.

Meta-analysis of randomized controlled trials on the efficacy of daikenchuto on improving intestinal dysfunction after abdominal surgery

Lei Zhang,Yusheng Cheng,Huizi Li,Yufeng Zhou,Bo Sun,Leibo Xu 대한외과학회 2018 Annals of Surgical Treatment and Research(ASRT) Vol.95 No.1

Purpose: Intestinal dysfunction is one of the most common complications in patients after abdominal surgery. Daikenchuto (DKT), a traditional herbal medicine, is recently employed to improve postoperative intestinal dysfunction. The aim of this meta-analysis was to assess the efficacy of DKT in improving intestinal dysfunction after abdominal surgery. Methods: PubMed, Embase, and the Cochrane library were systematically searched to identify randomized controlled trails (RCTs) in adult patients undergoing abdominal surgery, who were randomly distributed to administrate DKT and placebo. The primary outcomes included the time to first postoperative flatus or bowel movement. We used random-effects models to calculate summary mean differences (MDs) with 95% confidence intervals (CIs). Results: Nine RCTs totaling 1,212 patients (618 in DKT, 594 in control group) were included in our study. Compared with control group, DKT can effectively improve postoperative intestinal dysfunction by shortening the time to first postoperative flatus (MD, -0.41; 95% confidence interval [CI], -0.66 to -0.16; P = 0.001) with significant heterogeneity (I<SUP>2</SUP> = 71%, P = 0.004), and bowel movement (MD, -0.65; 95% CI, -0.97 to -0.32; P < 0.001) without significant heterogeneity (I<SUP>2</SUP> = 40%, P = 0.14). Sensitivity analyses by indication of surgery and type of surgery yielded similar results. Conclusion: These data provide limited evidence that DKT shows efficacy on improving intestinal dysfunction after abdominal surgery. However, the results should be interpreted cautiously, due to the heterogeneity of the studies included. Thus, the efficacy of DKT on improving postoperative intestinal dysfunction warrants further investigation.

Toward Low-Overhead Fingerprint-Based Indoor Localization via Transfer Learning: Design, Implementation, and Evaluation

Liu, Kai,Zhang, Hao,Ng, Joseph Kee-Yin,Xia, Yusheng,Feng, Liang,Lee, Victor C. S.,Son, Sang H. IEEE 2018 IEEE TRANSACTIONS ON INDUSTRIAL INFORMATICS - Vol.14 No.3

<P>This work aims at proposing a transfer learning (TL)-based framework to enhance system scalability of fingerprint-based indoor localization by reducing offline training overhead without jeopardizing the localization accuracy. The basic principle is to reshape data distributions in the target domain based on the transferred knowledge from the source domains, so that those data belonging to the same cluster will be logically closer to each other, whereas others will be further apart from each other. Specifically, the TL-based framework consists of two parts, metric learning and metric transfer, which are used to learn the distance metrics from source domains and identify the most suitable metric for the target domain, respectively. Furthermore, this work implements a prototype of the fingerprint-based indoor localization system with the proposed TL-based framework embedded. Finally, extensive real-world experiments are conducted to demonstrate the effectiveness and the generality of the TL-based framework.</P>

Surface Self-Nanocrystallization of α+β Titanium Alloy by Surface Mechanical Grinding Treatment

Chuang Li,Wenfang Cui,Yusheng Zhang 대한금속·재료학회 2017 METALS AND MATERIALS International Vol.23 No.3

In this work, the heavy deformation was performed on Ti6Al4V alloy by using surface mechanical grindingtreatment (SMGT) in order to obtain surface nanocrystalline layer. The phase structure and microstructuresin the deformation zones were characterized by XRD, SEM and TEM. The nanocrystallization mechanisms ofα and α phase were clarified. The results show that a gradient structure including nano grain, quasi nanograinand micro-grains was achieved within the depth of 500 μm below the surface. The depth of nanocrystallineslayer was at least 20 μm. From the non deformation zone in the center to the heavy deformation zone close totreated surface, dislocation densities gradually increased. The original coarse grains gradually evolved intodislocation cell structures and subgrains through dislocation movement. In the depth of about 20 μm belowthe treated surface, the subgrains began to split into nano-scale grains with high angle grain boundaries bylattice rotation and tilting mechanisms. During SMGT, β phase deformed and refined prior to α phase, andinhibited the generation of twinning in α grain. The coordinated deformation between a and β phase promotedthe formation of nanocrystallines.

Recent advances in cobalt-based Fischer-Tropsch synthesis catalysts

Yujun Suo,Yali Yao,Yusheng Zhang,Sijia Xing,Zhong-Yong Yuan 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.115 No.-

Fischer-Tropsch synthesis (FTS) is a promising technology for converting renewable energy sources tosynthetic liquid fuels, olefins or oxygenates. As one of the metal-based FTS catalysts with excellent intrinsicactivity, supported Co-based catalysts have attracted much attention. Their properties depend on theirgeometric morphology, surface composition and metal-support interaction (MSI). This paper reviews thelatest research progress of the supported Co-based catalysts for FTS, including recently-developed functionalmodification strategies to adjust the cobalt phase, crystallite size, metal dispersion, site density andmetal-support interaction to optimize the performance of cobalt-based catalysts. The effects of importantmaterials (including cobalt precursors, supports and promoters) on catalytic performance are discussedand compared. A summary is provided of the modifications made to catalysts with a unique and controllablestructure, in order to improve the catalytic activity and focus the product distribution on targetedwax, gasoline, diesel, olefins and oxygenate products. Guidance is provided regarding controlling thestructure and functions of Co-based catalysts. Opportunities and perspectives on future research intomodification strategies used for Co-based FTS catalyst are also noted.

Simultaneous Single-Position Oblique Lateral Interbody Fusion Combined With Unilateral Percutaneous Pedicle Screw Fixation for Single-Level Lumbar Tuberculosis: A 3-Year Retrospective Comparative Study

Jinyue He,Jiezhong Deng,Yusheng Yang,Tingting Zheng,Fei Luo,Jianzhong Xu,Zehua Zhang 대한척추신경외과학회 2023 Neurospine Vol.20 No.4

Objective: To illustrate a simultaneous single-position oblique lateral interbody fusion (SPOLIF) combined with unilateral percutaneous pedicle screw fixation in treating single-level lumbar tuberculosis, compared with posterior-only approach in clinical and radiographic evaluations. Methods: Consecutive patients who had undergone surgeries for single-level lumbar tuberculosis from January 2018 to December 2020 were retrospectively reviewed. The patients included were divided into SP-OLIF and posterior-only groups according to surgical methods applied, with follow-up for at least 36 months. Outcomes included estimated blood loss, operative time, and complications for safety evaluation; visual analogue scale (VAS), Oswestry Disability Index (ODI) for efficacy evaluation; erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) for evaluating tuberculosis activity; x-ray and computed tomography scan were used for radiographic evaluation. Results: A total of 136 patients had been enrolled in the study (60 for SP-OLIF and 76 for Posterior-only). The median operative time, blood loss, and hospital stay in SP-OLIF group were significantly less, with a lower complication rate. Meanwhile, the SP-OLIF group showed substantially lower VAS in 1 and 7 days and decreased ODI in the first month postoperatively, without significant difference afterward. Similarly, the median CRP and ESR in SP-OLIF group were significantly lower in 3 and 7 days postoperatively. All indicators had reduced to normal after 3 months. No recurrence had been reported throughout the whole follow-up. Conclusion: SP-OLIF was an efficient minimally invasive protocol for single-level lumbar tuberculosis, facilitating earlier clinical improvement, with decreased blood loss, operative time and hospital stay compared with posterior-only approach.

Mechanical induced electrical failure of shock compressed PZT95/5 ferroelectric ceramics

Hengchang Nie,Jia Yang,Xuefeng Chen,Fuping Zhang,Yin Yu,Genshui Wang,Yusheng Liu,Hongliang He,Xianlin Dong 한국물리학회 2017 Current Applied Physics Vol.17 No.4

A comparative experimental study of shock compressed Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3 (hereafter referred to as PZT95/5) ferroelectric ceramics within different insulation materials were performed in this study. It was found that the insulating materials play a significant role in the electrical failure behavior of PZT95/5 ferroelectric ceramic. The electrical breakdown behavior of PZT95/5 ferroelectric ceramics within epoxy resin was observed to aggravate at low temperature 55 C. Porous PZT95/5 ferroelectric ceramic was found to exhibit lower failure probability than its dense counterpart. Electrical failure of PZT95/5 ferroelectric ceramics under shock wave was found to be an extrinsic behavior and a tentative explanation was proposed based on the mechanical compressive stress-induced cracks initiation by epoxy resin.

Research Progress in SiC-Based Ceramic Matrix Composites

Shaoming Dong,Zhen Wang,Haijun Zhou,Yan-Mei Kan,Xiangyu Zhang,Yusheng Ding,Le Gao,Bin Wu,Jianbao Hu 한국세라믹학회 2012 한국세라믹학회지 Vol.49 No.4

SiC-based ceramic matrix composites show many advantages over their monolithic ceramic counterparts, which makes them potential candidates for applications in various fields. Depending strongly on the chemical composition and microstructure of the fiber reinforcement, matrix as well as the fiber/matrix interphase in the material, the properties of ceramic matrix composites(CMCs) are highly tailorable. In this paper, the latest progresses in the interphase design, matrix modification and fiber reinforcement decoration of CMCs are reviewed, their effects on the properties of the CMCs are introduced.

Research Progress in SiC-Based Ceramic Matrix Composites

Dong, Shaoming,Wang, Zhen,Zhou, Haijun,Kan, Yan-Mei,Zhang, Xiangyu,Ding, Yusheng,Gao, Le,Wu, Bin,Hu, Jianbao The Korean Ceramic Society 2012 한국세라믹학회지 Vol.49 No.4

SiC-based ceramic matrix composites show many advantages over their monolithic ceramic counterparts, which makes them potential candidates for applications in various fields. Depending strongly on the chemical composition and microstructure of the fiber reinforcement, matrix as well as the fiber/matrix interphase in the material, the properties of ceramic matrix composites(CMCs) are highly tailorable. In this paper, the latest progresses in the interphase design, matrix modification and fiber reinforcement decoration of CMCs are reviewed, their effects on the properties of the CMCs are introduced.

R3: A Lightweight Reactive Ring based Routing Protocol for Wireless Sensor Networks with Mobile Sinks

Yu, Sheng,Zhang, Baoxian,Yao, Zheng,Li, Cheng Korean Society for Internet Information 2016 KSII Transactions on Internet and Information Syst Vol.10 No.12

Designing efficient routing protocols for a wireless sensor network with mobile sinks (mWSN) is a challenging task since the network topology and data paths change frequently as sink nodes move. In this paper, we design a novel lightweight reactive ring based routing protocol called R3, which removes the need of proactively maintaining data paths to mobile sinks as they move in the network. To achieve high packet delivery ratio and low transmission cost, R3 combines ring based forwarding and trail based forwarding together. To support efficient ring based forwarding, we build a ring based structure for a network in a way such that each node in the network can easily obtain its ring ID and virtual angle information. For this purpose, we artificially create a virtual hole in the central area of the network and accordingly find a shortest cycled path enclosing the hole, which serves as base ring and is used for generating the remaining ring based structure. We accordingly present the detailed design description for R3, which only requires each node to keep very limited routing information. We derive the communication overhead by ring based forwarding. Extensive simulation results show that R3 can achieve high routing performance as compared with existing work.