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Spatio-temporal change in forest cover and carbon storage considering actual and potential forest cover in South Korea

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Science China(Life Sciences) 2015年第7期58卷 713-723页

作者： NAM Kijun LEE Woo-Kyun kim moonil KWAK Doo-Ahn BYUN Woo-Hyuk YU Hangnan KWAK Hanbin KWON Taesung SUNG Joohan CHUNG Dong-Jun LEE Seung-Ho Division of Environmental Science and Ecological Engineering Korea University GIS/RS Center for Environmental Resources Korea University Division of Forest Ecology Korea Forest Research Institute National Forestry Cooperative Federation Division of Forest Economics & Management Korea Forest Research Institute

This study analyzes change in carbon storage by applying forest growth models and final cutting age to actual and potential forest cover for six major tree species in South Korea. Using National Forest Inventory data, the growth models were developed to estimate mean diameter at breast height, tree height, and number of trees for Pinus densiflora, Pinus koraiensis, Pinus rigida, Larix kaempferi, Castanea crenata and Quercus spp. stands. We assumed that actual forest cover in a forest type map will change into potential forest covers according to the Hydrological and Thermal Analogy Groups model. When actual forest cover reaches the final cutting age, forest volume and carbon storage are estimated by changed forest cover and its growth model. Forest volume between 2010 and 2110 would increase from 126.73 to 157.33 m3 hm-2. Our results also show that forest cover, volume, and carbon storage could abruptly change by 2060. This is attributed to the fact that most forests are presumed to reach final cutting age. To avoid such dramatic change, a regeneration and yield control scheme should be prepared and implemented in a way that ensures balance in forest practice and yield.

关键词：森林覆盖率时空变化韩国碳结合森林蓄积量存储采伐年龄森林资源清查

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

Boosted Lithium-Ion Transport Kinetics in n-Type Siloxene Anodes Enabled by Selective Nucleophilic Substitution of Phosphorus

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Nano-Micro Letters 2024年第10期16卷 618-637页

作者： Se In kim Woong-Ju kim Jin Gu Kang Dong-Wan kim School of Civil Environmental and Architectural EngineeringKorea University02841 SeoulSouth Korea Nanophotonics Research Center Korea Institute of Science and Technology02792 SeoulSouth Korea

Doped two-dimensional(2D)materials hold significant promise for advancing many technologies,such as microelectronics,optoelectronics,and energy ***,n-type 2D oxidized Si nanosheets,namely n-type siloxene(n-SX),are employed as Li-ion battery *** thermal evaporation of sodium hypophosphite at 275℃,P atoms are effectively incorporated into siloxene(SX)without compromising its 2D layered morphology and unique Kautsky-type crystal ***,selective nucleophilic substitution occurs,with only Si atoms being replaced by P atoms in the O_(3)≡Si-H *** resulting n-SX possesses two delocalized electrons arising from the presence of two electron donor types:(i)P atoms residing in Si sites and(ii)H *** doping concentrations are varied by controlling the amount of precursors or their mean free *** at 2000 mA g^(-1),the n-SX electrode with the optimized doping concentration(6.7×10^(19) atoms cm^(-3))delivers a capacity of 594 mAh g^(-1) with a 73%capacity retention after 500 *** improvements originate from the enhanced kinetics of charge transport processes,including electronic conduction,charge transfer,and solid-state *** approach proposed herein offers an unprecedented route for engineering SX anodes to boost Li-ion storage.

关键词： Li-ion battery Two-dimensional N-type siloxene Doping mechanism Kinetics

Radial growth response of Pinus densiflora and Quercus *** topographic and climatic factors in South Korea

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Journal of Plant Ecology 2013年第5期6卷 380-392页

作者： Jae Gyun Byun Woo Kyun Lee moonil kim Doo Ahn Kwak Hanbin Kwak Taejin Park Woo Hyuk Byun Yowhan Son Jung Kee Choi Young Jin Lee Joachim Saborowski Dong Jun Chung Jin Hyun Jung Institute for Environmental Research(Biology V) RWTH Aachen UniversityWorringerweg 152074 AachenGermany Division of Environmental Science and Ecological Engineering Korea UniversitySeoul136-701Korea GIS/RS Center for Environmental Resources Korea UniversitySeoul 136-173Korea Department of Forest Management Kangwon National UniversityChunchon 200-701Korea Department of Forest Resources Kongju National UniversityKongju 341-701Korea Institute of Forest Biometry and Informatics Georg-August-University Gottingen37077 GottingenGermany National Forestry Cooperative Federation Daejeon 306-808Korea

Aims This study aimed to develop radial growth models and to predict the potential spatial distribution of Pinus densiflora(Japanese red pine)and Quercus spp.(Oaks)in South Korea,considering topographic and climatic *** We used a dataset of diameter at breast height and radial growth estimates of individual trees,topographic and climatic factors in systematic sample plots distributed over the whole of South *** the basis that radial growth is attributed primarily to tree age,we developed a radial growth model employing tree age as an explanatory *** estimated standard growth(SG),defined as radial growth of the tree at age 30,to eliminate the influence of tree age on radial *** addition,SG estimates including the Topographic Wetness Index,temperature and precipitation were calculated by the Generalized Additive *** Findings As a result of variogram analysis of SG,we found spatial autocorrelation between SG,topographic and climatic *** temperature had negative impacts on radial growth of *** and positive impacts on that of Quercus *** was associated with positive effects on both tree *** on the model,we found that radial growth of *** would be more vulnerable than that of Quercus *** climatic *** simulation with the radial growth model,it was predicted that *** stands would be gradually replaced with Quercus *** in eastern coastal and southern regions of South Korea in the *** models developed in this study will be helpful for understanding the impact of climatic factors on tree growth and for predicting changes in distribution of *** and Quercus *** to climate change in South Korea.

关键词： standard radial growth general additive model climatic factors climate change forest-cover change

Investigation of operation and degradation mechanisms in ZnTeSe blue quantum-dot light-emitting diodes by identifying recombination zone

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Nano Research 2024年第7期17卷 6527-6533页

作者： Oul Cho Sujin Park Hogeun Chang Jiwhan kim Jaekwon kim Sungwoo kim Taehyung kim Jeonghun Kwak Department of Electrical and Computer Engineering Inter-university Semiconductor Research Centerand Soft Foundry InstituteSeoul National UniversitySeoul 08826Republic of Korea Material Research Center Samsung Advanced Institute of TechnologySuwonGyeonggi-do 16419Republic of Korea

ZnTeSe quantum dots(QDs),recognized as promising eco-friendly blue electroluminescent emitters,remain under-explored in light-emitting diode(LED)***,to elucidate the operation and degradation mechanisms of ZnTeSe blue QD-LEDs,stacked ZnTeSe QD layers with discernable luminescence are designed by varying Te doping concentrations,and the recombination zones(RZs)of the blue QD-LEDs are *** RZs are identified near the hole-transport layer(HTL),confirmed by angular-dependent electroluminescence measurements and optical *** addition,in order to investigate carrier dynamics in the process of recombination,the transient electroluminescence(tr-EL)signals of the dichromatic QD-LEDs are *** a result,it is inferred that the RZ initially formed near the electron-transport layer(ETL)due to the high injection barriers of ***,due to the fast electron mobility,the RZ shifts toward the HTL as the operating current *** the device lifetime tests,the RZ remains stationary while the photoluminescence(PL)corresponding to the RZ undergoes a substantial decrease,indicating that the degradation is accelerated by the concentrated *** this study contributes to a deeper understanding of the operational mechanisms of ZnTeSe blue QD-LEDs.

关键词： quantum dots light-emitting diodes degradation recombination zones carrier dynamics

Dragonfly Interaction Algorithm for Optimization of Queuing Delay in Industrial Wireless Networks

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Journal of Bionic Engineering 2024年第1期21卷 447-485页

作者： Sanjay Bhardwaj Da-Hye kim Dong-Seong kim Department of IT Convergence Engineering ICT Convergence Research CenterKumoh National Institute of TechnologyGumiSouth Korea

In industrial wireless networks,data transmitted from source to destination are highly *** often leads to the queuing of the data,and poor management of the queued data results in excessive delays,increased energy consumption,and packet ***,a nature-inspired-based Dragonfly Interaction Optimization Algorithm(DMOA)is proposed for optimization of the queue delay in industrial wireless *** term“interaction”herein used is the characterization of the“flying movement”of the dragonfly towards damselflies(female dragonflies)for *** a result,interaction is represented as the flow of transmitted data packets,or traffic,from the source to the base *** includes each and every feature of dragonfly movement as well as awareness of the rival dragonflies,predators,and damselflies for the desired optimization of the queue *** features are juxtaposed as noise and interference,which are further used in the calculation of industrial wireless metrics:latency,error rate(reliability),throughput,energy efficiency,and fairness for the optimization of the queue *** analysis,convergence analysis,the Wilcoxon test,the Friedman test,and the classical as well as the 2014 IEEE Congress of Evolutionary Computation(CEC)on the benchmark functions are also used for the evaluation of DMOA in terms of its robustness and *** results demonstrate the robustness of the proposed algorithm for both classical and benchmarking functions of the IEEE CEC ***,the accuracy and efficacy of DMOA were demonstrated by means of the convergence rate,Wilcoxon testing,and ***,fairness using Jain’s index in queue delay optimization in terms of throughput and latency,along with computational complexity,is also evaluated and compared with other *** results show that DMOA exceeds other bio-inspired optimization algorithms in terms of fairness in queue delay management and average packet *** proposed a

关键词： Dragonfly Damselfly Interaction Queuing delay Optimization Industrial wireless networks

Ag-GST/HfO_(x)-based unidirectional threshold switching selector with low leakage current and threshold voltage distribution for high-density cross-point arrays

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Rare Metals 2024年第1期43卷 280-288页

作者： Kyoung-Joung Yoo Dae-Yun Kang Nahyun kim Ho-Jin Lee Ta-Hyeong kim Taeho kim Tae Geun kim School of Electrical Engineering Korea UniversitySeoul 02841Republic of Korea

The use of electrochemical-metallization-based volatile threshold switching selectors in cross-point arrays has been widely explored owing to their high on-off ratios and simple ***,these devices are unsuitable for cross-point architectures because of the difficulty in controlling the random filament formation that results in large fluctuations in the threshold voltage during *** this study,we investigated the unidirectional threshold transition characteristics associated with an Ag/GST/HfO_(x)/Pt-based bilayer selector and demonstrated the occurrence of a low leakage current(<1×10^(-11) A) and low distribution of the threshold voltage(Δ0.11 V).The bilayer structure could control the filament formation in the intermediate state through the insertion of an HfO_(x) tunneling *** stacking a bilayer selector with NiO_(x)based resistive random-access memory,the leakage and programming currents of the device could be significantly *** the crossbar array configuration,we performed equivalent circuit analysis of a one-selector oneresistor(1S1R) devices and estimated the optimal array size to demonstrate the applicability of the proposed *** maximum acceptable crossbar array size of the 1S1R device with the Ag/GST/HfO_(x)/Pt/Ti/NiO_(x)/Pt structure was 5.29×10^(14)(N^(2),N=2.3×10^(7)).

关键词： Selector device Tunneling barrier Threshold switching Sputtering 1S1R Cross-point array

Anomaly Detection in Imbalanced Encrypted Traffic with Few Packet Metadata-Based Feature Extraction

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Computer Modeling in Engineering & Sciences 2024年第10期141卷 585-607页

作者： Min-Gyu kim Hwankuk kim Department of Financial Information Security Kookmin UniversitySeoul02707Republic of Korea Department of Information Security Cryptography Mathematics Kookmin UniversitySeoul02707Republic of Korea

In the IoT(Internet of Things)domain,the increased use of encryption protocols such as SSL/TLS,VPN(Virtual Private Network),and Tor has led to a rise in attacks leveraging encrypted *** research on anomaly detection using AI(Artificial Intelligence)is actively progressing,the encrypted nature of the data poses challenges for labeling,resulting in data imbalance and biased feature extraction toward specific *** study proposes a reconstruction error-based anomaly detection method using an autoencoder(AE)that utilizes packet metadata excluding specific node *** proposed method omits biased packet metadata such as IP and Port and trains the detection model using only normal data,leveraging a small amount of packet *** makes it well-suited for direct application in IoT environments due to its low resource *** experiments comparing feature extraction methods for AE-based anomaly detection,we found that using flowbased features significantly improves accuracy,precision,F1 score,and AUC(Area Under the Receiver Operating Characteristic Curve)score compared to packet-based ***,for flow-based features,the proposed method showed a 30.17%increase in F1 score and improved false positive rates compared to Isolation Forest and ***,the proposedmethod demonstrated a 32.43%higherAUCwhen using packet features and a 111.39%higher AUC when using flow features,compared to previously proposed oversampling *** study highlights the impact of feature extraction methods on attack detection in imbalanced,encrypted traffic environments and emphasizes that the one-class method using AE is more effective for attack detection and reducing false positives compared to traditional oversampling methods.

关键词： One-class anomaly detection feature extraction auto-encoder encrypted traffic CICIoT2023

Trend of Developing Aqueous Liquid and Gel Electrolytes for Sustainable,Safe,and High‑Performance Li‑Ion Batteries

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Nano-Micro Letters 2024年第1期16卷 17-34页

作者： Donghwan Ji Jaeyun kim School of Chemical Engineering Sungkyunkwan University(SKKU)Suwon 16419Republic of Korea Department of Health Sciences and Technology Samsung Advanced Institute for Health Sciences&Technology(SAIHST)Sungkyunkwan University(SKKU)Suwon 16419Republic of Korea Biomedical Institute for Convergence at SKKU(BICS) Sungkyunkwan University(SKKU)Suwon 16419Republic of Korea Institute of Quantum Biophysics(IQB) Sungkyunkwan University(SKKU)Suwon 16419Republic of Korea Present Address:Department of NanoEngineering University of California San DiegoLa JollaSan DiegoCA 92093USA

Current lithium-ion batteries(LIBs)rely on organic liquid electrolytes that pose significant risks due to their flammability and *** potential for environmental pollution and explosions resulting from battery damage or fracture is a critical ***-based(aqueous)electrolytes have been receiving attention as an alternative to organic ***,a narrow electrochemicalstability window,water decomposition,and the consequent low battery operating voltage and energy density hinder the practical use of aqueous ***,developing novel aqueous electrolytes for sustainable,safe,high-performance LIBs remains *** Review first commences by summarizing the roles and requirements of electrolytes–separators and then delineates the progression of aqueous electrolytes for LIBs,encompassing aqueous liquid and gel electrolyte development trends along with detailed principles of the *** aqueous electrolytes are progressed based on strategies using superconcentrated salts,concentrated diluents,polymer additives,polymer networks,and artificial passivation layers,which are used for suppressing water decomposition and widening the electrochemical stability window of water of the *** addition,this Review discusses potential strategies for the implementation of aqueous Li-metal batteries with improved electrolyte–electrode interfaces.A comprehensive understanding of each strategy in the aqueous system will assist in the design of an aqueous electrolyte and the development of sustainable and safe high-performance batteries.

关键词： Lithium-ion battery(LIB) Aqueous electrolyte Gel electrolyte Electrochemical stability window Li dendrite