Reduced Model Design of Multilayer Ceramic Capacitor for Vibration Analysis

YIQI WANG,Byung-Han Ko(고병한),No-cheol Park(박노철),Yonug-Pil Park(박영필) 한국소음진동공학회 2014 한국소음진동공학회 학술대회논문집 Vol.2014 No.4

On DC-Side Impedance Frequency Characteristics Analysis and DC Voltage Ripple Prediction under Unbalanced Conditions for MMC-HVDC System Based on Maximum Modulation Index

Yiqi Liu,Qichao Chen,Ningning Li,Bing Xie,Jianze Wang,Yanchao Ji 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.1

In this study, we first briefly introduce the effect of circulating current control on the modulation signal of a modular multilevel converter (MMC). The maximum modulation index is also theoretically derived. According to the optimal modulation index analysis and the model in the continuous domain, different DC-side output impedance equivalent models of MMC with/without compensating component are derived. The DC-side impedance of MMC inverter station can be regarded as a series xR + yL + zC branch in both cases. The compensating component of the maximum modulation index is also related to the DC equivalent impedance with circulating current control. The frequency characteristic of impedance for MMC, which is observed from its DC side, is analyzed. Finally, this study investigates the prediction of the DC voltage ripple transfer between two-terminal MMC high-voltage direct current systems under unbalanced conditions. The rationality and accuracy of the impedance model are verified through MATLAB/Simulink simulations and experimental results.

Synergy of ionic liquid and confinement in the design of supported palladium catalyst for efficient selective hydrogenation of acetylene

Qingtao Wang,Yiqi Xu,Jing Zhou,Longyu Xu,Lu Yu,Dahao Jianga,Chunshan Lu,Zhiyan Pan,Qunfeng Zhang,Xiaonian Li 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.93 No.-

We present here a novel fabrication of highly effective supported Pd catalysts (Pd@S-1@IL) derived fromPd@S-1 core–shell material coated with ionic liquids (ILs), [Prmim][Cl], for the selective hydrogenation ofacetylene. Catalytic testing on Pd@S-1@IL catalyst illustrated a remarkable selectivity towards semihydrogenation(over 90% for ethylene, irrespective of conversion level). Moreover, no indications ofdeactivation were observed after 800 h on stream even under relatively severe conditions. Detailedcharacterization indicated that the selectivity enhancement was ascribed to thefilter effect along withelectronic effect on the adsorption/desorption processes arising from the ionic liquids layer. The stability,which has ranked the top reported values over advanced Pd-based catalysts, is attributed to theconfinement effect of Pd NPs within the supports thus restricting the migration of metals. The fabricationof core–shell architecture combined with the advantages of ionic liquid layer offers a promising guidelinefor efficient catalytic transfer of chemical resource.

On DC-Side Impedance Frequency Characteristics Analysis and DC Voltage Ripple Prediction under Unbalanced Conditions for MMC-HVDC System Based on Maximum Modulation Index

Liu, Yiqi,Chen, Qichao,Li, Ningning,Xie, Bing,Wang, Jianze,Ji, Yanchao The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.1

In this study, we first briefly introduce the effect of circulating current control on the modulation signal of a modular multilevel converter (MMC). The maximum modulation index is also theoretically derived. According to the optimal modulation index analysis and the model in the continuous domain, different DC-side output impedance equivalent models of MMC with/without compensating component are derived. The DC-side impedance of MMC inverter station can be regarded as a series xR + yL + zC branch in both cases. The compensating component of the maximum modulation index is also related to the DC equivalent impedance with circulating current control. The frequency characteristic of impedance for MMC, which is observed from its DC side, is analyzed. Finally, this study investigates the prediction of the DC voltage ripple transfer between two-terminal MMC high-voltage direct current systems under unbalanced conditions. The rationality and accuracy of the impedance model are verified through MATLAB/Simulink simulations and experimental results.

The Impact of Chinese SMEs' Financial Structure on Innovation Efficiency

왕의기,심재연,Wang, Yiqi,Sim, Jae-Yeon Industrial Promotion Institute 2022 산업진흥연구 Vol.7 No.4

본 논문은 2010년부터 2020년까지 중국 중소기업협회에 등재된 중소기업의 패널 데이터를 연구 표본으로 하고, 계량경제학 모형을 이용하여 금융구조가 중소기업의 혁신효율성에 미치는 영향을 살펴보았다. 확률 변경 분석법(SFA)에 의해 측정된 중소기업의 혁신효율성을 측정하고, Tobit 모형으로 중소기업의 자금조달구조와 혁신효율성의 관계를 살펴보고, 이에 상응하는 이질성 분석을 하였다. 마지막으로, 모델의 견고성을 테스트하였다. 부채와 주식금융이 혁신의 양적 효율성에 미치는 영향은 비선형적이고, 주로 반전된 "U"자형 관계를 나타낸다는 결론이 나왔다. 혁신의 질적 효율성을 위한 채권재무는 긍정적으로 기여한 반면에 주식재무는 부정적으로 나타났다. This paper examined the impact of financing structure on the innovation efficiency of SMEs by constructing an econometric model using panel data of SMEs listed on the SME board from 2010 to 2020 as the research sample. The innovation efficiency of SMEs was measured by the Stochastic Frontier Analysis (SFA), the relationship between financing structure and innovation efficiency of SMEs was examined with the help of the Tobit model, and the corresponding heterogeneity analysis was conducted. Finally, the robustness of the model was tested. It was concluded that the effects of debt and equity financing on the quantitative efficiency of innovation were non-linear and mainly showed an inverted "U" shaped relationship. For innovation quality efficiency, bond financing could positively contribute, while equity financing negatively inhibits. Finally, the corresponding advice was given.

Degradation Mechanisms of Chloride Contaminated Cast-in-Situ Concrete Partially Exposed to Magnesium-Sulfate Combined Environment

Gaowen Zhao,Yiqi Hu,Shaomin Li,Zhuo Wang,Mengzhen Guo,Fangzhou Han,Haoran Wang 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.2

Cast-in-situ concrete suffers complicated working conditions in sulfate-rich saline soil areas. Sulfate-magnesium combined attack can be encountered in heavy saline or salty lake areas. This study investigated the degradation process and corresponding mechanisms of cast-in-situconcrete, contaminated by chlorides, partially exposed to sulfate-magnesium combined corrosiveenvironments. Concrete samples were cast and partially immersed in the pre-prepareddistilled water, sulfate or sulfate-magnesium mixed solutions for 12 months. Physical andmechanical properties of concrete samples were continuously measured and recorded duringthe immersion. Sulfate concentration in different depths were measured by chemical titration. SEM, XRD, TG/DTG tests were conducted to analyze the microstructural and mineral propertychanges after corrosion for concrete suffered different corrosion conditions. Results show thatpartially immersed concrete encounters both chemical and physical degradation induced bycorrosive sources. Concrete contaminated by chlorides obviously shows weaker resistanceagainst sulfate attack and the strength development is also negatively affected. Magnesium inthe environments reduces the early strength of partially immersed cast-in-situ concrete whileenhancing the sulfate resistance ability in the later corrosion stage. Magnesium limits thenegative effect of contaminated chlorides on the partially immersed cast-in-situ concrete. Performance of cast-in-situ concrete is different from precast concrete when encounteringdifferent corrosive sources, and thus more attention should be paid on the degradation ofcast-in-situ concrete structures induce by aggressive environments.

A Dual Functional Ti-Ga Alloy: Inhibiting Biofilm Formation and Osteoclastogenesis Differentiation via Disturbing Iron Metabolism

Fupeng Li,Kai Huang,Jinbing Wang,Kai Yuan,Yiqi Yang,Yihao Liu,Xianhao Zhou,Keyu Kong,Tao Yang,Jian He,Chunjie Liu,Haiyong Ao,Fengxiang Liu,Qian Liu,Tingting Tang,Shengbing Yang 한국생체재료학회 2023 생체재료학회지 Vol.27 No.00

Background Although biomedical implants have been widely used in orthopedic treatments, two major clinical challenges remain to be solved, one is the bacterial infection resulting in biofilm formation, and the other is aseptic loosening during implantation due to over-activated osteoclastogenesis. These factors can cause many clinical issues and even lead to implant failure. Thus, it is necessary to endow implants with antibiofilm and aseptic looseningprevention properties, to facilitate the integration between implants and bone tissues for successful implantation. To achieve this goal, this study aimed to develop a biocompatible titanium alloy with antibiofilm and anti-aseptic loosening dual function by utilizing gallium (Ga) as a component. Methods A series of Ti-Ga alloys were prepared. We examined the Ga content, Ga distribution, hardness, tensile strength, biocompatibility, and anti-biofilm performance in vitro and in vivo. We also explored how Ga3+ ions inhibited the biofilm formation of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) and osteoclast differentiation. Results The alloy exhibited outstanding antibiofilm properties against both S. aureus and E. coli in vitro and decent antibiofilm performance against S. aureus in vivo. The proteomics results demonstrated that Ga3+ ions could disturb the bacterial Fe metabolism of both S. aureus and E. coli, inhibiting bacterial biofilm formation. In addition, Ti-Ga alloys could inhibit receptor activator of nuclear factor-κB ligand (RANKL)-dependent osteoclast differentiation and function by targeting iron metabolism, then suppressing the activation of the NF-κB signaling pathway, thus, showing their potential to prevent aseptic loosening. Conclusion This study provides an advanced Ti-Ga alloy that can be used as a promising orthopedic implant raw material for various clinical scenarios. This work also revealed that iron metabolism is the common target of Ga3+ ions to inhibit biofilm formation and osteoclast differentiation.

Borassus 섬유/PP 복합재료의 기계적 및 열적 물성

혜지붕(Zhipeng-Hui),수다카라(Sudhakara),왕일기(YiQi-Wang),이동우(Lee Dong Woo),송정일(Jung-il Song) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.5-3

The design of new composites based on made an attempt to fabricate new borassus fruit fiber/Polypropylene (BFF/PP) composites by injecter-molded; Fibers were chemically modified by alkali treatment and a maleic acid anhydride grafted PP(MAPP) were used as coupling agent to improve the adhesion between fibers and matrix. The overall fiber contain was 5%. The effect of alkali treatment as well as MAPP on thermal, mechanical and morphological properties were explored by thermo gravimetric analysis (TAG), differential scanning calorimetry (DSC), universal testing machine (UTM) and scanning electron microscopy (SEM), respectively. Thermal stability of the composites was slightly enhanced on alkali treatment and addition of MAPP. The tensile strength and modulus, flexural strength and modulus, impact strength were increased for alkali treated/MAPP compatibilized composites by 4.5%, 17%, 17.2%, 9% and 10% respectively. SEM studies on tensile fractured specimens of unmodified composites reveal the poor fiber-matrix interaction, whereas in case of modified fiber composites, the fiber-matrix interaction is strong with enhanced mechanical properties. Overall the physical and mechanical properties are comparable with those of other important natural fiber composites.