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Modified analogue forecasting in the hidden Markov frameworkfor meteorological droughts

Science China(Technological Sciences) 2019年第1期62卷 151-162页

作者： CHEN Si CHUNG GunHui kim Byung Sik kim Tae-woong Department of Civil and Environmental Engineering Hanyang University Department of Civil Engineering Hoseo University Department of Urban Environmental Disaster Prevention Engineering Kangwon National University

An analogue method(AM) is a nonparametric approach that has been applied to predict the future states of a dynamic system by following the evolution of the analogues in the historical archive. In this study, we proposed a hidden Markov model(HMM)framework for a modified analogue forecasting(MAF) approach for meteorological droughts in Korea. The unobservable(hidden) state process in the framework aims to model the underlying drought state, while the observation process was formed from the time series of the standardized precipitation index(SPI) as a drought index. Within the framework, the likelihood estimator was used as the measure of similarity between past SPI analogues and current data. The MAF approach was conducted on the selected analogues to make forecasts at lead times of one and three months. The proposed model was applied to five selected stations in Korea using the SPI data from 1973 to 2016. The forecasting performance of the proposed model was tested during the validation period(2003–2016) using several statistical criteria and it was compared to a persistence-based benchmark model. The results showed significant improvement in the forecasting capacity, and satisfactory performance for numerical SPI forecasting and categorical drought forecasting. The results also suggested that the proposed model was able to provide useful information for determining future drought categories for early drought warning with a lead time of up to three months.

关键词： modified analogue forecasting hidden Markov model meteorological drought standardized precipitation index

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The validity of the Reynolds equation in spool valve analysis considering cavitation

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Friction 2016年第3期4卷 266-276页

作者： Sung-Ho HONG Kyung-woong kim School of Mechanical Aerospace & Systems Engineering Korea Advanced Institute of Science and Technology 291 Daehak-ro Yuseong-guDaejeon 305-701 Republic of Korea

The purpose of this research is to investigate the validity of the Reynolds equation in spool valve analysis under cavitation. This study is carried out for a laminar and isothermal flow between a sleeve and spool with grooves. The pressure and lateral force obtained from the Reynolds equation and the Navier-Stokes equation are compared with variations of aspect ratio, cross sectional area, and number of grooves. The cavitation phenomenon is considered by using a cavitation model in the Navier-Stokes equation and the Reynolds cavitation boundary condition in the Reynolds equation. A large difference of more than 20% is found between the equations for a lateral force of spool valve with many grooves. It was found that the Reynolds equation is not suitable for calculation of a lateral force of the spool valve with multiple-grooves of which the width and depth are even larger than the clearance under cavitation.

关键词： validity Reynolds equation Navier-Stokes equation spool valve cavitation

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Ransomware Classification Framework Using the Behavioral Performance Visualization of Execution Objects

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Computers, Materials & Continua 2022年第8期72卷 3401-3424页

作者： Jun-Seob kim Ki-woong Park Department of Computer and Information Security and Convergence Engineering for Intelligent DroneSejong UniversitySeoul05006Korea

A ransomware attack that interrupted the operation of Colonial Pipeline(a large *** pipeline company),showed that security threats by malware have become serious enough to affect industries and social infrastructure rather than individuals *** agents and characteristics of attacks should be identified,and appropriate strategies should be established accordingly in order to respond to such *** this purpose,the first task that must be performed is malware *** creators are well aware of this and apply various concealment and avoidance techniques,making it difficult to classify *** study focuses on new features and classification techniques to overcome these *** propose a behavioral performance visualization method using utilization patterns of system resources,such as the central processing unit,memory,and input/output,that are commonly used in performance analysis or tuning of *** extracted the usage patterns of the system resources for ransomware to performbehavioral performance *** results of the classification performance evaluation using the visualization results indicate an accuracy of at least 98.94%with a 3.69%loss ***,we designed and implemented a framework to perform the entire process—from data extraction to behavioral performance visualization and classification performance measurement—that is expected to contribute to related studies in the future.

关键词： Behavioral performance visualization ransomware malware classification

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Deep Learning Approach for Cosmetic Product Detection and Classification

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Computers, Materials & Continua 2021年第10期69卷 713-725页

作者： Se-Won kim Sang-woong Lee Department of IT Convergence Engineering Gachon UniversitySeongnam13120Korea Department of Software Gachon UniversitySeongnam13120Korea

As the amount of online video content is increasing,consumers are becoming increasingly interested in various product names appearing in videos,particularly in cosmetic-product names in videos related to fashion,beauty,and ***,the identification of such products by using image recognition technology may aid in the identification of current commercial *** this paper,we propose a two-stage deep-learning detection and classification method for cosmetic ***,variants of the YOLO network are used for detection,where the bounding box for each given input product is predicted and subsequently cropped for *** use four state-of-the-art classification networks,namely ResNet,InceptionResNetV2,DenseNet,and EfficientNet,and compare their ***,we employ dilated convolution in these networks to obtain better feature representations and improve *** experiments demonstrate that YOLOv3 and its tiny version achieve higher speed and ***,the dilated networks marginally outperform the base models,or achieve similar performance in the worst *** conclude that the proposed method can effectively detect and classify cosmetic products.

关键词： Cosmetic product detection cosmetic product classification deep learning

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Hyperreflective photonic crystals created by shearing colloidal dispersions at ultrahigh volume fraction

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Microsystems & Nanoengineering 2024年第1期10卷 161-173页

作者： Minji kim Jong bin kim Shin-Hyun kim Department of Chemical and Biomolecular Engineering Korea Advanced Institute of Science and Technology(KAIST)Daejeon 34141Republic of Korea

Colloidal crystallization serves as one of the most economic and scalable production methods for photonic ***,insufficient optical performance,nonuniformity and low reproducibility remain challenges for advanced high-value *** this study,we optimally formulate a photocurable dispersion of silica particles and apply shear flow to unify the orientation of the colloidal crystals,ensuring high optical performance and *** silica particles experience strong repulsion at ultrahigh volume fractions of 50%but demonstrate low mobility,leading to polycrystalline *** shear flow to the dispersions allows the silica particles to rearrange into larger crystalline domains with a unidirectional orientation along the *** shear-induced structural change produces absolute reflectivity at the stopband as high as 90%and a high transparency of 90%at off-resonant wavelengths with minimal diffusive ***,the strong interparticle repulsion ensures a uniform volume fraction of particles throughout the dispersion,reducing deviations in the optical *** intricately micropattern the photocurable dispersions using ***,the photonic films and patterns can be stacked to form multiple layers,displaying mixed structural colors and multiple reflectance peaks without sacrificing *** superior photonic materials hold promise for various optical applications,including optical components and anticounterfeiting patches.

关键词： properties. dispersion reflectivity

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Vertical Nanowire Array-Based Light Emitting Diodes

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Nano Research 2008年第2期1卷 123-128页

作者： Elaine Lai woong kim Peidong Yang Department of Chemistry University of CaliforniaBerkeleyCA 94720USA Molecular Foundry Material Sciences DivisionLawrence Berkeley National LaboratoryBerkeleyCA 94720USA

Electroluminescence from a nanowire array-based light emitting diode is *** junction consists of a p-type GaN thin fi lm grown by metal organic chemical vapor deposition(MOCVD)and a vertical n-type ZnO nanowire array grown epitaxially from the thin fi lm through a simple low temperature solution *** fabricated devices exhibit diode like currentvoltage *** is visible to the human eye at a forward bias of 10 V and spectroscopy reveals that emission is dominated by acceptor to band transitions in the p-GaN thin fi *** is suggested that the vertical nanowire architecture of the device leads to waveguided emission from the thin fi lm through the nanowire array.

关键词： ZnO nanowire electroluminescence LED waveguiding

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Half-Covered 'Glitter-Cake' AM@SE Composite:A Novel Electrode Design for High Energy Density All-Solid-State Batteries

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Nano-Micro Letters 2025年第05期 471-486页

作者： Min Ji kim Jin-Sung Park Jin woong Lee Sung Eun Wang Dowoong Yoon Jong Deok Lee Jung Hyun kim Taeseup Song Ju Li Yun Chan Kang Dae Soo Jung Energy and Environmental Division Korea Institute of Ceramic Engineering and Technology Department of Materials Science and Engineering Korea University Department of Nuclear Science and Engineering Massachusetts Institute of Technology Department of Materials Science and Engineering Ajou University Department of Energy Systems Research Ajou University Department of Energy Engineering Hanyang University Department of Materials Science and Engineering Massachusetts Institute of Technology

All-solid-state batteries（ASSBs） are pursued due to their potential for better safety and high energy density. However, the energy density of the cathode for ASSBs does not seem to be satisfactory due to the low utilization of active materials（AMs） at high loading. With small amount of solid electrolyte（SE） powder in the cathode, poor electrochemical performance is often observed due to contact loss and non-homogeneous distribution of AMs and SEs, leading to high tortuosity and limitation of lithium and electron transport pathways. Here, we propose a novel cathode design that can achieve high volumetric energy density of 1258 Wh L-1at high AM content of 85 wt% by synergizing the merits of AM@SE core–shell composite particles with conformally coated thin SE shell prepared from mechanofusion process and small SE particles. The core–shell structure with an intimate and thin SE shell guarantees high ionic conduction pathway while unharming the electronic conduction. In addition, small SE particles play the role of a filler that reduces the packing porosity in the cathode composite electrode as well as between the cathode and the SE separator layer. The systematic demonstration of the optimization process may provide understanding and guidance on the design of electrodes for ASSBs with high electrode density, capacity, and ultimately energy density.

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Effect of an extraction solvent on the antioxidant quality of Pinus densiflora needle extract

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Journal of Pharmaceutical Analysis 2019年第3期9卷 193-200页

作者： Thamizhiniyan Venkatesan Young-woong Choi Young-Kyoon kim Department of Forest Products and Biotechnology College of Science and TechnologyKookmin University

Pinus densiflora needle extract (PDNE) is widely reported to have many pharmacological activities including antioxidant potential. However, the solvent system used for extraction greatly affects its antioxidant quality. Hence, in the present study, we investigated the effect of a different ratio (vol/vol) of ethanol to water (0-100%) in the extraction of PDNE with potent antioxidant capacity. The chemical assays, 2,2-diphenyl-1 picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), were conducted to assess the antioxidant potential of PDNE. Subsequently, the cytoprotective effect of PDNE was determined using tert-butyl hydroperoxide (TBHP)-challenged HepG2 cellular model. The needle extracts from 40% ethanol (PDNE-40) showed greater radical scavenging activity followed by 60%, 20%, 80%, 0% and 100% ethanol extracts. EC50 value of the most active extract, PDNE-40, was 8.56 ± 0.51 μg/mL, relative to 1.34 ± 0.28 μg/mL of the standard trolox (for ABTS radical), and 75.96 ± 11.60 μg/mL, relative to 4.83 ± 0.26 μg/mL of the standard trolox (for DPPH radical). Either PDNE-20 or PDNE-40 pretreatment remarkably decreased the levels of reactive oxygen species (ROS), lipid peroxides and protein carbonyls in TBHP-challenged HepG2 cells. In addition, both PDNE-20 and PDNE-40 significantly reversed the decreased ratio of reduced (GSH) to oxidized (GSSG) glutathione. Moreover, these two extracts showed a significant inhibitory effect on TBHP-induced nuclear damage and loss of cell viability. In summary, the inclusion of 40% ethanol in water for extraction of Pinus densiflora needle greatly increases the antioxidant quality of the extract.

关键词： Pinus densiflora needle extract Oxidative stress Cytoprotective Natural antioxidant

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2D reduced graphene oxide-titania nanocomposites synthesized under different hydrothermal conditions for treatment of hazardous organic pollutants

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Particuology 2018年第1期16卷 165-173页

作者： Migyeong kim Won-Hwa Hong woong kim Sung Hyuk Park Wan-Kuen Jo Department of Environmental Engineering Kyungpook National University Daegu 702-701 Republic of Korea School of Architecture Kyungpook National University Daegu 702-701 Republic of Korea Department of Materials Science and Metallurgical Engineering Kyungpook National University Daegu 702-701 Republic of Korea

Two-dimensional reduced graphene oxide-titania （RGO-TiO2） composites were prepared using a single- step hydrothermal method under various hydrothermal reaction conditions. The morphological and surface characteristics of the RGO-TiO2 composites and reference materials were determined. The RGO-TiO2 composites showed photocatalytic activity for the decomposition of two target pollutants that was superior to both pure TiO2 and RGO under fluorescent daylight lamp illumination. The photo- catalytic activity of the RGO-TiO2 composite increased as the hydrothermal treatment time increased from 1 to 24 h, but then it decreased as the time increased to 36 h, which indicated the presence of an optimal treatment time. RGO-TiO2 composites activated by violet light-emitting diodes （LEDs） displayed lower decomposition efficiency than those activated by a daylight lamp, likely because of the lower light intensity of violet LEDs （0.2 mW/cm2） when compared with that of the daylight lamp （1.4mW/cm2）. However, the photocatalytic decomposition of the target pollutants using the RGO-TiO2 composite was more energy-efficient using the violet LEDs. The photocatalytic reaction rates increased as the residence time decreased, whereas the reverse was true for the decomposition efficiency.

关键词： TiO2 composite Continuous-flow mode Hydrothermal time VioletLight emitting diode

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Green Nanocomposites Made With Polyvinyl Alcohol and Cellulose Nanofibers Isolated From Recycled Paper

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Journal of Renewable Materials 2019年第7期7卷 621-629页

作者： Le Van Hai Lindong Zhai Hyun Chan kim Jung woong kim Jaehwan kim Creative Research Center for Nanocellulose Future Composites Inha UniversityIncheonRepublic of Korea Department of Pulp and Paper Technology Phutho College of Industry and TradePhuthoVietnam

This paper reports green nanocomposites made by blending polyvinyl alcohol(PVA)with cellulose nanofiber(CNF)isolated from recycled deinked copy/printing paper(DIP).The reinforcement effect of DIPCNF in the nanocomposites is compared with other CNFs isolated from native cotton and hardwood by means of *** prepared PVA-CNF nanocomposites are characterized in terms of morphology,chemical interaction,structural,thermal and mechanical properties.X-ray diffraction and Fourier transform infrared spectroscopy confirm the reinforcing ability of cellulose nanofibers into *** blending CNFs into PVA matrix,the thermal stability of the nanocomposites is improved and DIPCNF shows similar enhancement effect with COCNF and *** prepared nanocomposites exhibit 50%Young’s modulus improvement by adding 6%of CNF and DIPCNF exhibits similar enhancement of the mechanical properties to COCNF and HWCNF in the *** indicates that the use of DIPCNF is beneficial for environment protection,resource retaining and save energy in comparison with COCNF and HWCNF.

关键词： Green nanocomposite cellulose TEMPO-oxidation recycled paper,polyvinyl alcohol

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