Impedance Characteristics Analysis of Modular Multilevel Converter with Direct Modulation and Compensated Modulation

Jing Lyu,Jinshui Dai,Chen Zhang,Jianwen Zhang,Xu Cai 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

This paper presents a comparative analysis of impedance characteristics of modular multilevel converter (MMC) with direct modulation and compensated modulation. The analytical derivations of the ac-side impedances of the MMC with these two modulation modes are provided, respectively, which are then validated by the measured impedances in the time-domain simulation model. Subsequently, a case study is carried out to show the impact of the two modulation modes on the stability of the MMCbased interconnected system using the impedance-based analysis method. The findings could provide a reference for controller design of MMC-based power electronic systems from a stability perspective.

Research on Cross-Regional Environmental Governance Cooperation between China and Korea

Jing, Qiwei,Lyu, Lin,Chen, Yuting 한국콘텐츠산업학회 2023 콘텐츠와 산업 Vol.5 No.2

The current environmental issues have attracted worldwide attention due to their cross-border, public, global, and long-term nature, making it difficult for any one country to address them independently. The shared environmental challenges faced by human society and the common need for international environmental governance compel countries to break down the barriers of national borders, social systems, policies, culture, and religious beliefs. Sovereign governments and non-governmental organizations must actively coordinate and participate in joint governance, and cross-regional environmental governance cooperation has become an important form of international environmental governance. Based on a systematic description of the severe challenges of cross-regional environmental pollution faced by the Republic of Korea and China, this study explores and summarizes the international experience of cross-regional environmental governance cooperation in regions such as Europe, North America, and ASEAN in recent years. Additionally, this study analyzes the necessity of cross-regional environmental governance cooperation between China and the Republic of Korea from the perspective of game theory and economics. Building upon previous research, this study explores the framework and system for cross-regional environmental governance cooperation between China and the Republic of Korea. It designs the direction of regional environmental governance mechanisms and examines the implementation of specific measures in areas such as interest linkage, institutional guarantees, cooperation institutions, public participation, funding sources, and talent teams. The goal of this study is to provide strategic suggestions for promoting global cross-regional environmental governance cooperation.

火 및 火病의 意義에 관한 文獻的 考察

박진성,류영수 대한한방신경정신과학회 1997 동의신경정신과학회지 Vol.8 No.1

I got the following result from the bibliographic study about the meaning of Hwa(火) and Hwa- byung(火病) at the concept and the aspect of pathological and etiological factors. The results are as follows. 1. The pathological characteristics of Hwa(火) mean the inflammed state, the excited mental condition and perinervous hyperfunction caused by exopathy produced by any of the six extermal etiological factors(外感六淫) and Hwa caused by interior injury(內傷火熱). 2. Hwa caused by the fire emotions(五志之火); anger, gladness, contemplation, sadress, fear by menta complications brings to Hwa caused by the five viscera(五?之火) and Hwa caused by the stagnation of the liver - energy(肝鬱之火) is the rpresentive Hwa caused by the five viscera and the six hollow organs(贓?之火). 3. A symptom caused by a pathogenic Hwa(화증) is understood in a pathological sense involved an inflammed disease and is considered as a pathological state of excess syndrome(實證) caused by exterior Hwa( 外火). 4. The pathologic process of Hwa-byung(火病) as the mental disease is based upon our people's emotion; Han(恨) to be pathologized without being overcome and can be considered as the process of Hwa caused by long-term(鬱久而火化). 5. Hwa-byung(火病) means a psychosomatic disorder resulting from stress reaction caused by personal relations in the climacterium. Form the above mentioned study, the meaning of Hwa(火) and Hwa-byung(火病) is set theoretically and it also needs to be maintained reserching and studying about Hwa-byung(火病) consistantly.

MRU-Net: A remote sensing image segmentation network for enhanced edge contour Detection

Jing Han,Weiyu Wang,Yuqi Lin,Xueqiang LYU 한국인터넷정보학회 2023 KSII Transactions on Internet and Information Syst Vol.17 No.12

Remote sensing image segmentation plays an important role in realizing intelligent city construction. The current mainstream segmentation networks effectively improve the segmentation effect of remote sensing images by deeply mining the rich texture and semantic features of images. But there are still some problems such as rough results of small target region segmentation and poor edge contour segmentation. To overcome these three challenges, we propose an improved semantic segmentation model, referred to as MRU-Net, which adopts the U-Net architecture as its backbone. Firstly, the convolutional layer is replaced by BasicBlock structure in U-Net network to extract features, then the activation function is replaced to reduce the computational load of model in the network. Secondly, a hybrid multi-scale recognition module is added in the encoder to improve the accuracy of image segmentation of small targets and edge parts. Finally, test on Massachusetts Buildings Dataset and WHU Dataset the experimental results show that compared with the original network the ACC、mIoU and F1 value are improved, and the imposed network shows good robustness and portability in different datasets.

Fracture behavior and thermal durability of lanthanum zirconate-based thermal barrier coatings with buffer layer in thermally graded mechanical fatigue environments

Lyu, Guanlin,Kim, Bong Gu,Lee, Seoung-Soo,Jung, Yeon-Gil,Zhang, Jing,Choi, Baig-Gyu,Kim, In-Soo Elsevier 2017 Surface & coatings technology Vol.332 No.-

<P><B>Abstract</B></P> <P>The effects of buffer layer on the fracture behavior and lifetime performance of lanthanum zirconate (La<SUB>2</SUB>Zr<SUB>2</SUB>O<SUB>7</SUB>; LZO)-based thermal barrier coatings (TBCs) were investigated through thermally graded mechanical fatigue (TGMF) tests, which are designed to simulate the operating conditions of rotating parts in gas turbines. To improve the thermal durability of LZO-based TBCs, composite coats consisting of two feedstock powders of LZO and 8wt% yttria-doped stabilized zirconia (8YSZ) were prepared by mixing different volume ratios (50:50 and 25:75, respectively). The composite coat of 50:50 volume ratio was employed as the top coat, and two types of buffer layers were introduced (25:75 volume ratio in LZO and 8YSZ, and 8YSZ only). These TBC systems were compared with a reference TBC system of 8YSZ. The TGMF tests with a tensile load of 60MPa were performed for 1000cycles, at a surface temperature of 1100°C and a dwell time of 10min, and then the samples were cooled at room temperature for 10min in each cycle. For the single-layer TBCs, the composite top coat showed similar results as for the reference TBC system. The triple-layer coating (TLC) showed the best thermal cycle performance among all samples, suggesting that the buffer layer was efficient in improving lifetime performance. Failure modes were different for the TBC systems. Delamination and/or cracks were created at the interface between the bond and top coats or above the interface in the single-layer TBCs, but the TBCs with the buffer layer were delaminated and/or cracked at the interface between the buffer layer and the top coat, independent of buffer layer species. This study allows further understanding of the LZO-based TBC failure mechanisms in operating conditions, especially in combined thermal and mechanical environments, in order to design reliable TBC systems.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Multilayered LZO-based TBCs were well prepared using composite powders. </LI> <LI> The lifetime performance of LZO-based TBCs was investigated through TGMF test. </LI> <LI> TBC with triple-layered top coat showed the most outstanding thermal durability. </LI> <LI> Crack initiation and its growth behavior were affected by the direction of applied load. </LI> </UL> </P>

Sintering behavior and phase transformation of YSZ-LZ composite coatings

Lyu, Guanlin,Kim, In-Soo,Song, Dowon,Park, Hyeon-Myeong,Kim, Jun Seong,Song, Taeseup,Myoung, Sangwon,Jung, Yeon-Gil,Zhang, Jing Elsevier 2020 CERAMICS INTERNATIONAL Vol.46 No.2

<P><B>Abstract</B></P> <P>Sintering behavior and phase transformations in yttria-stabilized zirconia (YSZ)-based thermal barrier coatings (TBCs) control their applications in gas turbines operated at high working temperatures required for improved fuel efficiency. In this work, to control the sintering behavior and reduce phase transformations in YSZ-based TBCs, lanthanum zirconate (LZ) powder was blended with the YSZ feedstock powder, and YSZ-LZ composite coatings were fabricated using the air plasma spraying method. The influence of mixture weight ratio of YSZ to LZ (75:25, 50:50, and 25:75) on the sintering behavior and phase stability of the composite coatings was investigated through the isothermal exposure test at 1100, 1300, and 1400 °C. The as-coated composites showed the pyrochlore and tetragonal phases, indicating that the phases are LZ and YSZ, respectively. As the exposure temperature was increased, the phase transformation of YSZ from the tetragonal phase to the monoclinic phase was accelerated. The content of monoclinic phase was changed with the increasing LZ content after thermal exposure at 1300 and 1400 °C. In addition, the composites showed different sintering and bridging behaviors at the adjacent splats with the LZ content. The composites prepared with the blended feedstock powders of LZ and YSZ produced an obvious effect on the phase stability and mechanical properties.</P>

New Type of Cycloid Planetary Reducer for Precision Transmission

Jing Zhang(장정),Bingkui Chen(첸빙구아이),Qi Zhang(장기),Jaejun Koo(구재준),Sungki Lyu(류성기) 한국정밀공학회 2009 한국정밀공학회 학술발표대회 논문집 Vol.2009 No.6월

Pharmacological blockade of cholesterol trafficking by cepharanthine in endothelial cells suppresses angiogenesis and tumor growth

Lyu, Junfang,Yang, Eun Ju,Head, Sarah A.,Ai, Nana,Zhang, Baoyuan,Wu, Changjie,Li, Ruo-Jing,Liu, Yifan,Yang, Chen,Dang, Yongjun,Kwon, Ho Jeong,Ge, Wei,Liu, Jun O.,Shim, Joong Sup Elsevier 2017 Cancer letters Vol.409 No.-

<P><B>Abstract</B></P> <P>Cholesterol is an important modulator of membrane protein function and signaling in endothelial cells, thus making it an emerging target for anti-angiogenic agents. In this study, we employed a phenotypic screen that detects intracellular cholesterol distribution in endothelial cells (HUVEC) and identified 13 existing drugs as cholesterol trafficking inhibitors. Cepharanthine, an approved drug for anti-inflammatory and cancer management use, was amongst the candidates, which was selected for in-depth mechanistic studies to link cholesterol trafficking and angiogenesis. Cepharanthine inhibited the endolysosomal trafficking of free-cholesterol and low-density lipoprotein in HUVEC by binding to Niemann-Pick disease, type C1 (NPC1) protein and increasing the lysosomal pH. The blockade of cholesterol trafficking led to a cholesterol-dependent dissociation of mTOR from the lysosomes and inhibition of its downstream signaling. Cepharanthine inhibited angiogenesis in HUVEC and in zebrafish in a cholesterol-dependent manner. Furthermore, cepharanthine suppressed tumor growth in vivo by inhibiting angiogenesis and it enhanced the antitumor activity of the standard chemotherapy cisplatin in lung and breast cancer xenografts in mice. Altogether, these results strongly support the idea that cholesterol trafficking is a viable drug target for anti-angiogenesis and that the inhibitors identified among existing drugs, such as cepharanthine, could be potential anti-angiogenic and antitumor agents.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A phenotypic screen identified 13 existing drugs, including cepharanthine, as cholesterol trafficking inhibitors. </LI> <LI> Cepharanthine inhibited lysosomal cholesterol trafficking by binding to NPC1 protein and increasing the lysosomal pH. </LI> <LI> The blockade of cholesterol trafficking led to a cholesterol-dependent dissociation of mTOR from the lysosomes. </LI> <LI> Cepharanthine inhibited angiogenesis in HUVEC and in zebrafish in a cholesterol-dependent manner. </LI> <LI> Cepharanthine treatment enhanced the antitumor activity of cisplatin in lung and breast cancer xenografts in mice. </LI> </UL> </P>

Effect of thermal cycling frequency on the durability of Yb-Gd-Y-based thermal barrier coatings

Lyu, Guanlin,Choi, Baig-Gyu,Lu, Zhe,Park, Hyeon-Myeong,Jung, Yeon-Gil,Zhang, Jing Elsevier 2019 Surface & coatings technology Vol.364 No.-

<P><B>Abstract</B></P> <P>The effects of thermal cycling frequency and buffer layer on the crack generation and thermal fatigue behaviors of Yb–Gd–Y-stabilized zirconia (YGYZ)-based thermal barrier coatings (TBCs) were investigated through thermally graded mechanical fatigue (TGMF) test. TGMF tests with low- (period of 10 min) and high-frequency (period of 2 min) cycling were performed at 1100 °C with a 60 MPa tensile load. Different cycling frequencies in TGMF test generate two kinds of crack propagation modes. The sample with low-frequency cycling condition shows penetration cracks in the YGYZ top coat, and multiple narrow vertical cracks are generated in high-frequency cycling. To enhance the thermomechanical properties, different buffer layers were introduced into the TBC systems, which were deposited with the regular (RP) or high-purity 8 wt% yttria stabilized zirconia (HP-YSZ) feedstock. The purity of the feedstock powder used for preparing the buffer layer affected the fracture behavior, showing a better thermal durability for the TBCs with the HP-YSZ in both frequency test conditions. A finite element model is developed, which takes creep effect into account due to thermal cycling. The model shows the high stresses at the interfaces between different layers due to differential thermal expansion. The failure mechanisms of YGYZ-based TBCs in TGMF test are also proposed. The vertical cracks are preferentially created, and then the vertical and horizontal cracks will be propagated when the vertical cracks are impeded by pores and micro-cracks.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Yb-Gd-Y-stabilized zirconia (YGYZ) based TBCs with buffer layer was well prepared. </LI> <LI> Thermal cycling frequency caused different crack growth behavior in TGMF test. </LI> <LI> HP-YSZ buffer layer showed a better thermal durability in low-frequency TGMF test. </LI> <LI> A finite element model showed the high stresses at the interfaces between different layers. </LI> <LI> The failure mechanisms of YGYZ-based TBCs in TGMF test were proposed. </LI> </UL> </P>

Static Load Analysis of Twin-screw Kneaders

Jing Wei,Guang-Hui Zhang,Qi Zhang,Junseong Kim,SungKi Lyu 한국정밀공학회 2008 International Journal of Precision Engineering and Vol.9 No.3

A static load analysis of twin-screw kneaders is required not only for the dynamic analysis, but also because it is the basis of the stiffness and strength calculations that are essential for the design of bearings. In this paper, the static loads of twin-screw kneaders are analyzed, and a mathematical model of the force and torque moments is presented using a numerical integration method based on differential geometry theory. The calculations of the force and torque moments of the twin-screw kneader are given. The results show that the Mx and My components of the fluid resistance torque of the rotors change periodically in each rotation cycle, but the Mz component remains constant. The axis forces Fz in the female and male rotors are also constant. The static load calculated by the proposed method tends to be conservative compared to traditional methods. The proposed method not only meets the static load analysis requirements for twin-screw kneaders, but can also be used as a static load analysis method for screw pumps and screw compressors.