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Combined spatial-temporal energy harvesting and relay selection for cognitive wireless powered networks

Digital Communications and Networks 2021年第2期7卷 201-213页

作者： Yuan Gao Haixia He Rongjun Tan junho choi College of IoT Engineering Hohai UniversityChangshou213022China Division of Undeclared Majors Chosun UniversityGwangju61452South Korea

In order to improve the Energy Efficiency(EE)and spectrum utilization of Cognitive Wireless Powered Networks(CWPNs),a combined spatial-temporal Energy Harvesting(EH)and relay selection scheme is *** the proposed scheme,for protecting the Primary User(PU),a two-layer guard zone is set outside the PU based on the outage probability threshold of the ***,to increase the energy of the CWPNs,the EH zone in the two-layer guard zone allows the Secondary Users(SUs)to spatially harvest energy from the Radio Frequency(RF)signals of temporally active *** improve the utilization of the PU spectrum,the guard zone outside the EH zone allows for the constrained power transmission of ***,the relay selection transmission is designed in the transmission zone of the SU to improve the EE of the *** addition to the EE of the CWPNs,the outage probabilities of the SU and PU are *** results reveal that the setting of a two-layer guard zone can effectively reduce the outage probability of the PU and improve the EE of ***,the relay selection transmission decreases the outage probabilities of the SUs.

关键词： Spatial-temporal energy harvesting Cognitive wireless powered networks Guard zone Outage probability Energy efficiency

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Synthesis of N-doped carbon quantumn dots as lubricant additive to enhance the tribological behavioor f MoS_(2)nanofluid

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Friction 2023年第3期11卷 441-459页

作者： Jiaqi HE Jianlin SUN junho choi Chenglong WANG Daoxin SU School of Materials Science and Engineering University of Science and Technology BeijingBeijing 100083China Department of Mechanical Engineering The University of TokyoTokyo 113-8656Japan

In this study,a novel lubricant additive nitrogen-doped carbon quantum dot(N-CQD)nanoparticle was prepared by the solvothermal *** synthesized spherical N-CQD nanoparticles in the diameter of about 10 nm had a graphene oxide(GO)-like structure with various oxygen(O)-and nitrogen(N)-containing functional *** N-CQDs were added to MoS_(2)nanofluid,and the tribological properties for steel/steel friction pairs were evaluated using a pin-on-disk ***-equilibrium molecular dynamics(NEMD)simulations for the friction system with MoS_(2)or MoS_(2)+N-CQD nanoparticles were also *** results showed that friction processes with MoS_(2)+N-CQD nanofluids were under the mixed lubrication *** MoS_(2)nanofluid containing 0.4 wt%N-CQDs could achieve 30.4%and 31.0%reduction in the friction coefficient and wear rate,respectively,compared to those without *** analyzing the worn surface topography and chemical compositions,the excellent lubrication performance resulted from the formation of tribochemistry-induced *** average thickness of tribofilm was about 13.9 nm,and it was composed of amorphous substances,ultrafine crystalline nanoparticles,and self-lubricating FeSO_(4)/Fe2(SO_(4))_(3).NEMD simulation results indicated the interaction between S atoms in MoS_(2)as well as these O-and N-containing functional groups in N-CQDs with steel surfaces enhanced the stability and strength of *** the metal surface was further protected from friction and wear.

关键词： carbon-based quantum dots(CQDs) lubricant nanofluid molecular dynamics(MD) tribofilm

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How Participatory is Participatory Flood Risk Mapping? Voices from the Flood Prone Dharavi Slum in Mumbai

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International Journal of Disaster Risk Science 2022年第2期13卷 230-248页

作者： Subhajyoti Samaddar Ha Si Xinyu Jiang junho choi Hirokazu Tatano Disaster Prevention Research Institute Kyoto UniversityKyoto 6110011Japan School of Management Wuhan University of TechnologyWuhan 430070China Disaster and Safety Management Soongsil UniversitySeoul 06978South Korea

Participatory flood risk mapping(PFRM) is a well-recognized and widely implemented tool for meaningful community involvement in disaster risk reduction(DRR). The effectiveness of PFRM remains anecdotal. The PFRM exercise has rarely been applied identically in two different places by two different organizations, which produces varied and uncertain outcomes. In the absence of any agreed and comprehensive framework for participatory DRR, existing studies struggle to provide a scientific account of how the structure, design, and process of PFRM ensure the effective participation of local *** study, examines what factors and methods make PFRM an effective participatory DRR tool. In this study,we first identified the process-based criteria of participation. Then we briefly introduced a participatory flood risk mapping exercise conducted in a flood-prone informal settlement in Dharavi, Mumbai. The exercise was carefully designed to meet the process criteria of effective participation. Finally, using qualitative research methods, we evaluated the effectiveness of our PFRM from the local community perspective. The findings show that ensuring community livelihood security and true involvement of marginalized groups, preparing an action plan, and incorporating fun and cultural connotations into the facilitation process are critical components that enhance community participation through PFRM in DRR.

关键词： Dharavi Evaluation Mumbai flood Participatory disaster risk reduction Participatory flood risk mapping Process-based criteria of participation

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对卡尔曼滤波器应用到雷达跟踪问题的评论

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现代防御技术 1989年第4期 31-37页

作者： junho choi 姜东波

本文的主要目的是阐明标准卡尔曼滤波器和卡尔曼预测器之间的差别。为此,发表了标准卡尔曼滤波器和卡尔曼预测器在雷达跟踪问题中的应用。为了获得跟踪目标的较好的位置和速度精度,这两种标法已被广泛地用在边搜索边跟踪的雷达系统中。... 详细信息

本文的主要目的是阐明标准卡尔曼滤波器和卡尔曼预测器之间的差别。为此,发表了标准卡尔曼滤波器和卡尔曼预测器在雷达跟踪问题中的应用。为了获得跟踪目标的较好的位置和速度精度,这两种标法已被广泛地用在边搜索边跟踪的雷达系统中。两种方法间的性能分析和比较与实际卫星跟踪数据一起已被发表。结果表明对于大机动目标,标准卡尔曼滤波器优于卡尔曼预测器。

关键词：卡尔曼滤波器坐标位置预报值 Kalman滤波器数字滤波器协方差矩阵残差平方和方程卡尔曼预测器修正协方差雷达跟踪无线电跟踪状态估计器

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Cartesian Grid Method with Cut Cell in the Mold Filling Simulation

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Journal of Materials Science & Technology 2008年第3期24卷 379-382页

作者： Youngsim choi junho Hong Hoyoung Hwang Jeongkil choi Center-for e-Design KITECH7-47-Songdo-DongYeonsu-Ku

In this paper, a Cartesian grid method with cut cell has been developed to simulate mold filling of casting process. Cut cells at the cast-mold interface are generated on the Cartesian grid. With the boundary cut cells, a special treatment is necessary. That is Cartesian grid method with cut cell. A simple shape was tested and the cut cell method was compared with the traditional one on Cartesian grids. And, a developed method was applied to the real casting product simulation. Cartesian grid system causes momentum loss and unsound fluid flow patterns because of inaccurate generation of meshes. These problems have been improved by using cut cell method.

关键词： Cartesian grids Cut cell Momentum loss

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Multiple-patterning colloidal lithography-implemented scalable manufacturing of heat-tolerant titanium nitride broadband absorbers in the visible to near-infrared

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Microsystems & Nanoengineering 2021年第2期7卷 51-58页

作者： Dasol Lee Myeongcheol Go Minkyung Kim junho Jang Chungryong choi Jin Kon Kim Junsuk Rho Department of Mechanical Engineering Pohang University of Science and Technology(POSTECH)Pohang37673Republic of Korea Department of Chemical Engineering Pohang University of Science and Technology(POSTECH)Pohang37673Republic of Korea National Institute of Nanomaterials Technology(NINT) Pohang37673Republic of Korea

Broadband perfect absorbers have been intensively researched for decades because of their near-perfect absorption optical property that can be applied to diverse applications. Unfortunately, achieving large-scale and heat-tolerant absorbers has been remained challenging work because of costly and time-consuming lithography methods and thermolability of materials, respectively. Here, we demonstrate a thermally robust titanium nitride broadband absorber with >95% absorption efficiency in the visible and near-infrared region (400–900 nm). A relatively large-scale (2.5 cm × 2.5 cm) absorber device is fabricated by using a fabrication technique of multiple-patterning colloidal lithography. The optical properties of the absorber are still maintained even after heating at the temperatures >600 ∘C. Such a large-scale, heat-tolerant, and broadband near-perfect absorber will provide further useful applications in solar thermophotovoltaics, stealth, and absorption controlling in high-temperature conditions.

关键词： absorber titanium absorption

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