Fault Analysis and Application Based on Improved Phase-Coordinates Fixed-Point Iterative Method in Three-Phase Power Systems

Mingrui Mo,Naishan Hang 대한전기학회 2019 Journal of Electrical Engineering & Technology Vol.14 No.4

This paper proposes an improved version of the Fixed-point iterative method to solve the fault problems in three-phase power systems by phase-coordinates. The proposed method has non-expansive characteristic using for fault analysis and calculation, when the injected currents of the loads are with non-increasing functions about voltages. Based on the decoupling method, the network topologies enable to obtain the connections models for the system’s equipment and faults by adjusting the values of connected admittances, which makes the fault power systems easy to integrate into the proposed method rather than the multi-port Thevenin’s theory or the compensation method. And the matched version of the Fixed-point iterative method is designed and developed that can be used directly to calculate and analyze all kinds of simple faults and complicated faults both in the power systems and in the power system of multiple parallel lines. The validity and eff ectiveness of the proposed method can be demonstrated by the numerical test systems.

Performance of DF Protocol for Distributed Cooperative Spectrum Sensing in Cognitive Radio

Mingrui Zou(추명예),Sangjun Bae(배상준),Kyungsup Kwak(곽경섭) 한국통신학회 2009 韓國通信學會論文誌 Vol.34 No.2A

Cognitive radio has been proposed to mitigate the spectrum scarcity problem by allowing the secondary users to access the under-utilized frequency bands and opportunistically transmit. Spectrum sensing, as a key technology in cognitive radio, is required to reliably detect the presence of primary users to avoid the harmful interference. However, it would be very hard to reliably detect the presence of primary users due to the channel fading, shadowing. In this paper, we proposed a distributed cooperative spectrum sensing scheme based on conventional DF (decode-and-forward) cooperative diversity protocol. We first consider the cooperation between two secondary users to illustrate that cooperation among secondary users can obviously increase the detection performance. We then compare the performance of DF based scheme with another conventional AF (amplify-and-forward) protocol based scheme. And it is found that the proposed scheme based on DF has a better detection performance than the one based on AF. After that, we extend the number of cooperative secondary users, and demonstrate that increasing the cooperation number can significantly improve the detection performance.

Cooperative Spectrum Sensing in Cognitive Radio Based on DF Diversity Protocol

Mingrui Zou,Chengshi Zhao,Kyungsup Kwak 한국통신학회 2008 한국통신학회 학술대회논문집 Vol.2008 No.7

Crashworthiness of Thermoplastic Woven Glass Fabric Reinforced Composite Tubes Manufactured by Pultrusion

Mingrui Liu,Biao Yan,Xiongqi Peng,Fujun Peng,Lidong Wang 한국섬유공학회 2020 Fibers and polymers Vol.21 No.2

In this paper, crashworthiness of thermoplastic woven fabric reinforced composite tubes were investigated. Thermoplastic composite tubes with various length (40 mm and 80 mm) and fiber yarn orientation with respective tolengthwise (0 o/90 o, 15 o/75 o, 30 o/60 o and 45 o/45 o) were manufactured by pultrusion and welding from home-made woven glass fabric/PP prepreg sheets. Quasi-static axial compressive tests of the composite tubes were performed under various temperatures (298 K, 358 K, 398 K and 453 K). Three crushing modes were observed: progressive folding, splaying and weld seam cracking. The influence of fiber orientation, tube length-diameter ratio and testing temperature on the peak load, mean load, specific energy absorption and crush efficiency were investigated. The results show that the peak load is controlled by fiber orientation and testing temperature. The mean force, specific energy absorption and crush efficiency are related to the three mentioned factors. Both fiber orientation and testing temperature have obviously influence on crushing modes of thermoplastic composite tubes. Length-to-diameter ratio also plays a role in crushing modes when the testing temperature is higher than the melting point of the resin.

Effect of pre-annealing on the Ge-alloyed Cu₂SnS₃ (CTGS) Thin film solar cells

Mingrui He,In Young Kim(김인영),Jin HyeoK Kim(김진혁) 한국신재생에너지학회 2017 한국신재생에너지학회 학술대회논문집 Vol.2017 No.5

Improved performance of sputtered Cu₂(Sn,Ge)S₃ thin film for photovoltaic application via controlled Ge doping

He, Mingrui,Kim, Jihun,Suryawanshi, M.P.,Ghorpade, U.V.,Gang, Myengil,Suryawanshi, U.P.,Kim, Jin Hyeok Elsevier 2018 Materials letters Vol.211 No.-

<P><B>Abstract</B></P> <P>Cu<SUB>2</SUB>SnS<SUB>3</SUB> (CTS) thin films have been investigated extensively as an absorber layer for photovoltaic applications owing to the use of low-cost and earth-abundant materials. However, the performance of CTS solar cells still suffers from voltage deficit, resulting in a low value of open-circuit voltage (<I>V</I> <SUB>oc</SUB>). In this study, we introduce a Ge layer into CTS materials using Ge metal target asa doping source. Subsequently, the sputtered Cu/Ge/Sn precursors are sulfurized under sulfur vapor ambient to form a Cu<SUB>2</SUB>(Sn,Ge)S<SUB>3</SUB> (CTGS) thin film. Meanwhile, we also fabricate a CTS solar cell under the same experimental conditions as compared with CTGS solar cell. The Ge layer of thickness approximately 20nm enhanced the efficiency from 0.45% (CTS) to 3.05% (CTGS), whereas the improvement in performance was limited for Ge layer of thickness more than 20nm.</P> <P><B>Highlights</B></P> <P> <UL> <LI> CTGS thin film solar cell exhibited the highest efficiency of 3.05%. </LI> <LI> The Ge layer of thickness approximately 20nm is optimized doping concentration for CTGS thin film solar cell. </LI> <LI> Ge doping approach can boost the value of <I>V</I> <SUB>oc</SUB> significantly. </LI> </UL> </P>

전통복식 요소가 현대 패션디자인과 문화 전파에 미친 영향

( Zhao Mingrui ),( Ko Jeong Hoon ) 한국상품문화디자인학회 2023 상품문화디자인학연구 Vol.72 No.-

민족 전통문화의 디자인적 요소를 파악하는 것은 디자이너에게 있어 중요한 과제이다. 디자인을 통해 저마다 깊은 뿌리를 가지고 있는 민족 문화를 나타내는 것은 민족정신을 보여주는 효과적인 실천 방법이 될 수 있으며, 특히 패션디자인 분야에서 적극적인 활용이 가능하다. 본문은 사례 분석을 통해, 문헌법을 연구 방법으로 하였다. 본 논문은 의상이라는 매개체를 통해 전통 복식의 예술적 특징과 시대에 따라 반영되는 시대적 특성을 분석 정리한 것, 현대 민족복식을 형상화하여 중국 전통복식의 요소를 파악하여 패션디자인에 적용한다. 이러한 디자인 이념이 현대 패션디자인에 미치는 영향에 대해 전통 복식문화의 깊은 문화적 가치와 현대화복(華服) 디자인의 특징 논의함과 동시에 민족 문화를 담고 있는 패션디자인이 국제무대에 진출함으로써 갖는 민족 문화 전파 촉진의 의미와 영향에 대해 연구한다. For designers how to extract elements that can be used for design from traditional national culture is a crucial topic. Every national culture has its profound foundation. Displaying culture from design is a way to demonstrate national spirit in actuality. At least, it can come true in the field of fashion design. With costumes as the carrier, this paper explores how to extract Chinese traditional costume elements and apply them to fashion design and how the displayed design concepts affect contemporary fashion design. At the same time, it discusses the significance and influence of promoting the spread of national culture by taking fashion design as the carrier and pushing national culture to the international stage. Due to the cultural differences in different periods, regions and nationalities, this paper focuses on how to create contemporary Chinese national costumes how to draw nutrients from traditional costumes and apply them to contemporary Huafu(華服) design and how design itself affects the development of costumes and cultural communication. Designers should spread and develop the cultural concepts in our traditional national costumes while meeting people’s aesthetic demand for costumes. By collecting and sorting out the relevant materials of ancient costumes, this paper analyzes and summarizes the artistic features of traditional costumes and the characteristics of the times reflected in different times and designs modern costumes by combining modern science and technology with traditional techniques. By shaping modern national costumes, it aims to demonstrate the deep cultural value of traditional costume culture and characteristics in modern Huafu(華服) design.

Experimental and numerical investigations on effect of reverse flow on transient from forced circulation to natural circulation

Li, Mingrui,Chen, Wenzhen,Hao, Jianli,Li, Weitong Korean Nuclear Society 2020 Nuclear Engineering and Technology Vol.52 No.9

In a sudden shutdown of primary pump or coolant loss accident in a marine nuclear power plant, the primary flow decreases rapidly in a transition process from forced circulation (FC) to natural circulation (NC), and the lower flow enters the steam generator (SG) causing reverse flow in the U-tube. This can significantly compromise the safety of nuclear power plants. Based on the marine natural circulation steam generator (NCSG), an experimental loop is constructed to study the characteristics of reverse flow under middle-temperature and middle-pressure conditions. The transition from FC to NC is simulated experimentally, and the characteristics of SG reverse flow are studied. On this basis, the experimental loop is numerically modeled using RELAP5/MOD3.3 code for system analysis, and the accuracy of the model is verified according to the experimental data. The influence of the flow variation rate on the reverse flow phenomenon and flow distribution is investigated. The experimental and numerical results show that in comparison with the case of adjusting the mass flow discontinuously, the number of reverse flow tubes increases significantly during the transition from FC to NC, and the reverse flow has a more severe impact on the operating characteristics of the SG. With the increase of flow variation rate, the reverse flow is less likely to occur. The mass flow in the reverse flow U-tubes increases at first and then decreases. When the system is approximately stable, the reverse flow is slightly lower than obverse flow in the same U-tube, while the flow in the obverse flow U-tube increases.

Spatiotemporal dynamics of perfusion and oximetry during ictal discharges in the rat neocortex.

Zhao, Mingrui,Ma, Hongtao,Suh, Minah,Schwartz, Theodore H The Society 2009 The Journal of neuroscience Vol.29 No.9

<P>Epileptic events elicit a large focal increase in cerebral blood flow (CBF) to perfuse metabolically active neurons in the focus. Conflicting data exists, however, on whether hemoglobin saturation increases or decreases in the focus and surrounding cortex, and whether CBF increases globally or is decreased in adjacent areas. How these hemodynamic events correlate with actual changes in tissue oxygenation is also not known. Using laser Doppler flowmetry, oxygen microsensors and intrinsic optical imaging spectroscopy, we demonstrate that the dip in hemoglobin in the focus correlates with a profound but temporary decrease in tissue oxygenation despite a large increase in CBF. Furthermore, CBF simultaneously decreases in the cortex immediately adjacent to the focus. These events are then replaced with a longer duration, less focal increase in CBF, cerebral blood volume, and hyperoxygenation, the duration of which correlates with the duration of the seizure. These findings raise the question of whether transient focal hypoxia and vascular steal might contribute to progressive deleterious effects of chronic epilepsy on the adult and developing brain. Possible mechanisms based on recent astrocyte-based models of neurovascular coupling are discussed.</P>

Fabrication of sputtered deposited Cu₂SnS₃ (CTS) thin film solar cell with power conversion efficiency of 2.39 %

He, Mingrui,Lokhande, A.C.,Kim, In Young,Ghorpade, U.V.,Suryawanshi, M.P.,Kim, Jin Hyeok ELSEVIER SCIENCE 2017 JOURNAL OF ALLOYS AND COMPOUNDS Vol.701 No.-

<P><B>Abstract</B></P> <P>Cu<SUB>2</SUB>SnS<SUB>3</SUB> (CTS) thin film solar cell with power conversion efficiency (PCE) of 2.39% is fabricated using sputtered metallic Cu/Sn stacked precursors subjected to sulfurization. The crystal structure, phase purity, atomic composition, oxidation state, external quantum efficiency, optical and electrical properties of the thin films are characterized in detail using X-ray diffraction (XRD), Raman spectroscopy, X-ray fluorescence (XRF) spectroscopy, X-ray photoelectron spectroscopy (XPS), a quantum efficiency study, UV–visible and a hall measurement system, respectively. The influence of various Cu deposition time on the structural, compositional and microstructural properties as well as on the device performance of CTS thin films are evaluated. It is found that the properties of CTS thin films are strongly dependent on the Cu deposition time during the sputtering process. The Cu deposition time is varied from 2812 s to 3212 s, and the film deposited at 2812 s showed the highest power conversion efficiency (PCE) of 2.39% with an open circuit voltage (V<SUB>oc</SUB>) of 208 mV, a short circuit current density (J<SUB>sc</SUB>) of 28.92 mA/cm<SUP>2</SUP> and a fill factor (FF) of 39.7%.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Cu<SUB>2</SUB>SnS<SUB>3</SUB> (CTS) thin films have been successfully fabricated using radio frequency sputtered Cu-Sn metallic precursors. </LI> <LI> Influence of Cu deposition time on properties of CTS thin films is studied. </LI> <LI> It is found that the properties of CTS thin films are strongly dependent on the copper content. </LI> <LI> CTS thin film with Cu deposition time of 2812 s exhibited the highest efficiency of 2.39%. </LI> </UL> </P>