41 results on '"Gu-Yeon Kim"'
Search Results
2. Growth Characteristics of Bolboschoenus planiculmis on the Eulsuk Tidal Flat of the Nakdong River Estuary, Korea
- Author
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Gu Yeon Kim
- Subjects
geography ,Oceanography ,geography.geographical_feature_category ,Environmental science ,Estuary ,Bolboschoenus planiculmis ,Tidal flat - Published
- 2020
3. Effects of regulated dam discharge on plants and migratory waterfowl are mediated by salinity changes in estuaries
- Author
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Ji Yoon Kim and Gu‐Yeon Kim
- Subjects
Salinity ,geography ,geography.geographical_feature_category ,Environmental flow ,Migratory waterfowl ,Ecology ,Freshwater discharge ,Time lag ,Environmental science ,Estuary ,Aquatic Science ,Ecology, Evolution, Behavior and Systematics - Published
- 2020
4. Similarity of zooplankton community structure among reservoirs in Yeongsan-Seomjin River basin
- Author
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Koeuijeong, Joo,Gea-Jae, Gu-Yeon Kim, and Hyun-Woo Kim
- Subjects
Modularity (networks) ,Geography ,geography.geographical_feature_category ,Similarity (network science) ,Ecology ,Eigenvector centrality ,Drainage basin ,Community structure ,Generalist and specialist species ,Zooplankton - Published
- 2019
5. Application of DNA Metabarcoding for Identifying the Diet of Asian Clam (Corbicula fluminea, Müller, 1774)
- Author
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Yu-Ji Heo, Hyunbin Jo, Ji Yoon Kim, Gu-Yeon Kim, Gea-Jae Joo, and Hyun-Woo Kim
- Subjects
Renewable Energy, Sustainability and the Environment ,Geography, Planning and Development ,Building and Construction ,Management, Monitoring, Policy and Law ,next-generation sequencing ,Corbicula fluminea ,gut content ,pseudofeces content ,food source ,Seomjin River ,estuary - Abstract
Corbicula has often been reported as one of the most invasive freshwater species in the world. It plays an important role in the food chains of brackish water zones in Korea, where it is predominant. However, detailed information on the Corbicula diet is still lacking. The purpose of this study was to identify the potential prey of Corbicula fluminea in the Seomjin River using a DNA metabarcoding approach, as very little is known about its feeding selectivity in natural conditions. A survey was conducted at two study sites (1 and 2) in the Seomjin River in November 2021. The two sites were selected based on increasing salinity gradient. The dominant operational taxonomic unit in the pseudofeces and gut content of C. fluminea was Microcyclops varicans (Copepoda) and Oncorhynchus mykiss (Fish), respectively. The alpha diversity at site 1 was higher than that at site 2. More diverse potential prey species were identified at the site with low salinity (i.e., site 1). The utilization of this method is strongly recommended for determining specific predator–prey relationships in complex estuarine ecosystem.
- Published
- 2022
6. The Analysis of the Fish Assemblage Characteristics by Wetland Type (River and lake) of National Wetland Classification System of Wetlands in Gyeongsangnam-do
- Author
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Ju-Duk Yoon, Jeong-Hui Kim, Gu-Yeon Kim, Hyunbin Jo, and Ran-Young Im
- Subjects
Hydrology ,geography ,geography.geographical_feature_category ,biology ,Wetland management ,Freshwater fish ,Environmental science ,Assemblage (archaeology) ,%22">Fish ,Wetland ,Type (model theory) ,biology.organism_classification ,Wetland classification - Abstract
습지 유형에 따른 어류군집 특성을 파악하고 이를 통해 관리 전략을 마련하기 위해 경상남도에 위치한 29개의 습지 (하천형 20개소, 호수형 9개소)를 대상으로 조사를 실시하였다. 조사결과 하천형 습지에서는 평균( ${\pm}SD$ ) $10.3{\pm}4.8$ 종이, 호수형 습지에서는 평균 $9.1{\pm}4.1$ 종이 출현하였으며, 출현...
- Published
- 2018
7. Co-occurrence Patterns of Bird Species in the World
- Author
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Sungwon Hong, Ki Cheol Oh, Joo,Gea-Jae, Young-Min Kim, and Gu-Yeon Kim
- Subjects
Geography ,Group cohesiveness ,Betweenness centrality ,Multinational corporation ,Closeness ,Global network ,Co-occurrence ,Economic geography ,Bird conservation ,Centrality - Abstract
In order to identify key nations and bird species of conservation concern we described multinational collaborations as defined using network analysis linked by birds that are found in all nations in the network. We used network analysis to assess the patterns in bird occurrence for 10,422 bird inventories from 244 countries and territories. Nations that are important in multinational collaborations for bird conservation were assessed using the centrality measures, closeness and betweenness centrality. Countries important for the multinational collaboration of bird conservation were examined based on their centrality measures, which included closeness and betweenness centralities. Comparatively, the co-occurrence network was divided into four groups that reveal different biogeographical structures. A group with higher closeness centrality included countries in southern Africa and had the potential to affect species in many other countries. Birds in countries in Asia, Australia and the South Pacific that are important to the cohesiveness of the global network had a higher score of betweenness centrality. Countries that had higher numbers of bird species and more extensively distributed bird species had higher centrality scores; in these countries, birds may act as excellent indicators of trends in the co-occurrence bird network. For effective bird conservation in the world, much stronger coordination among countries is required. Bird co-occurrence patterns can provide a suitable and powerful framework for understanding the complexity of co-occurrence patterns and consequences for multinational collaborations on bird conservation.
- Published
- 2017
8. Interaction between cathode and anode and its impact on the production of alkyl dicarbonates in lithium ion batteries
- Author
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Gu-Yeon Kim
- Subjects
chemistry.chemical_classification ,020209 energy ,General Chemical Engineering ,Inorganic chemistry ,Diethyl carbonate ,chemistry.chemical_element ,02 engineering and technology ,Electrolyte ,Anode ,chemistry.chemical_compound ,chemistry ,0202 electrical engineering, electronic engineering, information engineering ,Electrochemistry ,Lithium ,Graphite ,Faraday efficiency ,Ethylene carbonate ,Alkyl - Abstract
A new simple storage experiment is introduced to show direct evidence of a cathode-anode interaction. The delithiated positive electrodes and/or the lithiated negative electrodes from Li[Ni 1/3 Mn 1/3 Co 1/3 ]O 2 /graphite and LiCoO 2 /graphite pouch cells are stored in Nalgene bottles (high-density polyethylene) filled with 1.0 M LiPF 6 in an ethylene carbonate: diethyl carbonate (EC:DEC, 1:2 v/v ratio) electrolyte for 2 weeks in an Ar-filled glove box at room temperature. During the storage experiment, the color change of the electrolyte, the formation of alkyl dicarbonates, and the decomposition of LiPF 6 are observed. The most important result of this storage experiment is that these reactions are significantly affected by the cathode-anode interaction. The electrolyte color change comes with slightly larger impedance growth during cycling and the alkyl dicarbonates improve coulombic efficiency. The decomposition of LiPF 6 is suppressed by the negative electrode. The experiment and results shown here will be helpful to those who want to research the cathode-anode interaction and improve the performances of Li-ion batteries.
- Published
- 2016
9. Above-ground biomass estimation of tuberous bulrush (Bolboschoenus planiculmis) in mudflats using remotely sensed multispectral image
- Author
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Gea-Jae Joo, Ran-Young Im, Ji Yoon Kim, Gu-Yeon Kim, and Yuno Do
- Subjects
0106 biological sciences ,Biomass (ecology) ,Multivariate statistics ,010504 meteorology & atmospheric sciences ,biology ,010604 marine biology & hydrobiology ,Multispectral image ,Spectral bands ,Bulrush ,Oceanography ,Spatial distribution ,biology.organism_classification ,01 natural sciences ,Pearson product-moment correlation coefficient ,symbols.namesake ,symbols ,Environmental science ,Satellite imagery ,0105 earth and related environmental sciences ,Remote sensing - Abstract
We present a multivariate regression approach for mapping the spatial distribution of above-ground biomass (AGB) of B. planiculmis using field data and coincident moderate spatial resolution satellite imagery. A total of 232 ground sample plots were used to estimate the biomass distribution in the Nakdong River estuary. Field data were overlain and correlated with digital values from an atmospherically corrected multispectral image (Landsat 8). The AGB distribution was derived using empirical models trained with field-measured AGB data. The final regression model for AGB estimation was composed using the OLI3, OLI4, and OLI7 spectral bands. The Pearson correlation between the observed and predicted biomass was significant (R = 0.84, p 200 kg DW/900 m2) constituted approximately 23.91% of the total vegetated area. Our findings suggest the expandability of remotely sensed products to understand the distribution pattern of estuarine plant productivity at the landscape level.
- Published
- 2016
10. Changes of fish assemblages after construction of an estuary barrage in the lower Nakdong River, South Korea
- Author
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Kwang-Seok Jeong, Gu-Yeon Kim, Hyunbin Jo, Min-Ho Jang, Ju-Duk Yoon, and Gea-Jae Joo
- Subjects
0106 biological sciences ,Hydrology ,geography ,geography.geographical_feature_category ,Ecology ,biology ,010604 marine biology & hydrobiology ,Fish species ,Estuary ,Aquatic Science ,biology.organism_classification ,010603 evolutionary biology ,01 natural sciences ,Tide level ,Fishery ,Monitoring data ,Freshwater fish ,%22">Fish ,Environmental science ,Seawater ,Ecosystem ,Water Science and Technology - Abstract
In the Nakdong River, an estuary barrage was constructed in 1987, and it divided the freshwater and the seawater, resulting in a change in the ecosystem. To estimate the impact of barrage construction on fish assemblages, we evaluated 20 years of monitoring data before and after the construction of the estuary barrage, and evaluated the role of fishways. The barrage construction generated entire changes of fish assemblages. After construction, the number of fish species dropped sharply, and 36 species disappeared. Conversely, 18 species appeared at this site, including eight freshwater species, seven of which were exotic or translocated species. Barrage construction affected freshwater fish more severely than it did estuarine and marine species because of the existence of an estuarine environment below the barrage. We did not detect any evidence of recovery of fish assemblages. A total of 31 species were collected at fishways, and the number of individuals collected at each fishway was positively correlated with the amount of discharge from the estuary barrage, mean daily tide level, and water temperature. Migratory fish using a fishway had obvious occurrence periods. Therefore, the efficiency of fishway use can be increased if an appropriate management plan is prepared and implemented.
- Published
- 2016
11. A scientometric study of the limnological societies: inferences of research collaboration and core topics based on publication networks
- Author
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Yuno Do, Gu-Yeon Kim, Ji Yoon Kim, Hyun-Woo Kim, and Gea-Jae Joo
- Subjects
Citation network ,Research groups ,Ecology ,Limnology ,05 social sciences ,010501 environmental sciences ,Aquatic Science ,Monsoon ,01 natural sciences ,Bibliographic coupling ,Geography ,Regional science ,East Asia ,0509 other social sciences ,050904 information & library sciences ,Citation ,Centrality ,0105 earth and related environmental sciences ,Water Science and Technology - Abstract
Scientometric analysis of limnological societies and related publications revealed complex relationships among research topics and research collaborations. We applied scientometric analysis, word networks, bibliographic coupling, and author networks analysis, to 34 777 publications related to limnology and monsoon research. We analyzed usage frequencies of limnology-related words in a Google corpus and found that usage frequencies of most limnological terms peaked during the 1980s. Social interest in the term “limnology” showed a gradually decreasing trend after the late 1990s. Monsoon research was focused in the Asian–Indian region but not in the European, African, and American regions. Word networks of limnological studies related to monsoons were mainly grouped into 3 clusters (Indian monsoons, East Asian monsoons, and monsoon assessment clusters). In the citation network of limnology journals, water quality, plankton, and invertebrate research groups generally showed strong internal citation networks. An author connection map of the limnological societies revealed strong modulators in the international societies, whereas research collaboration was rather limited to small groups within the entire network. This retrospective analysis will provide meaningful information to further develop and enhance international collaboration within limnological studies.
- Published
- 2016
12. The Effect of Some Nitriles as Electrolyte Additives in Li-Ion Batteries
- Author
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Gu-Yeon Kim and J. R. Dahn
- Subjects
Materials science ,Renewable Energy, Sustainability and the Environment ,Inorganic chemistry ,Materials Chemistry ,Electrochemistry ,Electrolyte ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Ion - Published
- 2015
13. Use of large web-based data to identify public interest and trends related to endangered species
- Author
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Gu-Yeon Kim, Gea-Jae Joo, Yuno Do, Ran-Young Im, and Ji Yoon Kim
- Subjects
Ecology ,business.industry ,Biodiversity ,Endangered species ,Biology ,Public interest ,Taxon ,Negative relationship ,Web application ,The Internet ,Common name ,business ,Ecology, Evolution, Behavior and Systematics ,Nature and Landscape Conservation - Abstract
Use of the Internet by an increasing number of people to search for information related to varying disciplines has led to more precise data on societal views and trends. We used web search log data from a 6-year period and examined characteristics related to public interest in endangered species. Web search data for 246 endangered species as determined by the Ministry of Environment of Korea were evaluated. Relative search volumes for species were correlated with the status of conservation practices, and a self-organizing map (SOM) was used to analyze the relationship among selected variables. The relative search volume for higher taxa, including mammals, birds, amphibians and reptiles, were ten times higher than those for other taxa. SOM clusters were mainly divided according to the rank designation of the endangered species and the existence of a conservation facility dedicated to the species. The relative search volume and amount of web materials were the highest for the most highly ranked species. A positive relationship between the relative search volume and number of printed media articles (β 2.68; R 2 0.45; p
- Published
- 2014
14. Effects of Monsoon on Topography, Soil Variables, and Coastal Plants
- Author
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Yuno Do, Gu-Yeon Kim, Gea-Jae Joo, and Ji Yoon Kim
- Subjects
geography ,geography.geographical_feature_category ,Ecology ,biology ,Climate change ,Estuary ,Edaphic ,Vegetation ,Aquatic Science ,Cynodon dactylon ,Monsoon ,biology.organism_classification ,Phragmites ,Canonical correspondence analysis ,Environmental science ,Physical geography ,Ecology, Evolution, Behavior and Systematics - Abstract
Coastal dunes are highly vulnerable to disturbances. We characterized changes in the plant distribution, soil properties, and topology of a coastal dune field during the monsoon period. We selected a 600 × 300 m rectangular area of Dadaepo in the Nakdong River estuary and measured variables at 40 sampling points. A field survey was performed over two periods (pre- and post-monsoon) in 2009. Soil, topological features, and vegetation were surveyed at each point, and canonical correspondence analysis was used to identify relationships among the variables during the monsoon. The volumetric net change in the study site was 33,104 m3 during the monsoon. When topographic and edaphic variables were compared, topological variables were found to be the dominant factors in dune vegetation zonation; however, their influence on vegetation change during the monsoon was less prominent than that of edaphic variables. Inland exotic species (Oenothera odorata and Conyza canadensis) and Cynodon dactylon replaced most of the Carex pumila distribution (54 % decrease) after the monsoon. Phragmites australis expanded its distribution and replaced the adjacent community after the monsoon. The area of Suaeda japonica decreased by more than 85 %, and this area was also replaced by P. australis. This knowledge of the dynamics of dune vegetation and environmental variables will be important for predicting the impacts of climate change, such as sea level rise and increased rainfall frequency.
- Published
- 2014
15. Standing Crop Distribution of Aquatic Plants in the West Nakdong River and Riparian Wetlands in the Nakdong River
- Author
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Ji Yoon Kim and Gu-Yeon Kim
- Subjects
geography ,geography.geographical_feature_category ,Standing crop ,business.industry ,Ecology ,Aquatic plant ,Environmental science ,Distribution (economics) ,Vegetation ,Riparian wetland ,business ,Riparian zone - Published
- 2014
16. Effects of Succinonitrile (SN) as an Electrolyte Additive on the Impedance of LiCoO2/Graphite Pouch Cells during Cycling
- Author
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J. R. Dahn, Gu-Yeon Kim, and Remi Petibon
- Subjects
Materials science ,Renewable Energy, Sustainability and the Environment ,Inorganic chemistry ,Electrolyte ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Succinonitrile ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Materials Chemistry ,Electrochemistry ,Graphite ,Pouch ,Cycling ,Electrical impedance - Published
- 2014
17. ARC Studies of the Effects of Electrolyte Additives on the Reactivity of Delithiated Li1-x[Ni1/3Mn1/3Co1/3]O2and Li1-x[Ni0.8Co0.15Al0.05]O2Positive Electrode Materials with Electrolyte
- Author
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Gu-Yeon Kim and J. R. Dahn
- Subjects
Arc (geometry) ,Electrode material ,Renewable Energy, Sustainability and the Environment ,Chemistry ,Inorganic chemistry ,Materials Chemistry ,Electrochemistry ,Reactivity (chemistry) ,Electrolyte ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials - Published
- 2014
18. Combinations of Ethylene Sulfite (ES) and Vinylene Carbonate (VC) as Electrolyte Additives in Li(Ni1/3Mn1/3Co1/3)O2/Graphite Pouch Cells
- Author
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C. P. Aiken, J. R. Dahn, Liuping Chen, Gu-Yeon Kim, J. C. Burns, Jian Xia, and Lin Ma
- Subjects
Ethylene ,Materials science ,Vinylene carbonate ,Renewable Energy, Sustainability and the Environment ,Inorganic chemistry ,Electrolyte ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,chemistry ,Sulfite ,Materials Chemistry ,Electrochemistry ,Graphite ,Pouch - Published
- 2014
19. Correlation Analysis between Phenology of Salix spp. and Meteorological Factors
- Author
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Seong-Bo Kim, Ji Yoon Kim, Ran-Young Im, Yuno Do, Hee-Sun Park, Gea-Jae Joo, and Gu-Yeon Kim
- Subjects
Horticulture ,biology ,Phenology ,Botany ,Correlation analysis ,Precipitation ,biology.organism_classification ,Salix chaenomeloides ,Salix subfragilis - Abstract
The objective of this study was to analyze correlation between phenological characteristics of Salix spp. and meteorological factors in the Upo wetlands. Phenology of Salix subfragilis Andersson and Salix chaenomeloides Kimura was monitored from 2007 to 2012. Meteorological variables were monitored by Korea Meteorological Administration (Hap-chon). Average date of flowering, fruiting, seed dispersion was 86, 113, 136 days for S. subfragilis and 112, 140, 164 days for S. chaenomeloides as Julian days. Flowering of S. subfragilis and S. chaenomeloides were correlated with daily mean air temp. in March (r=-0.92, r=-0.85, p
- Published
- 2013
20. Study of Methylene Methanedisulfonate as an Additive for Li-Ion Cells
- Author
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J. R. Dahn, N. N. Sinha, Jian Xia, Gu-Yeon Kim, Deijun Xiong, and Liuping Chen
- Subjects
chemistry.chemical_compound ,Materials science ,chemistry ,Renewable Energy, Sustainability and the Environment ,Materials Chemistry ,Electrochemistry ,Methylene ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Nuclear chemistry ,Ion - Published
- 2013
21. Acid–base interaction between carbon black and polyurethane molecules with different amine values: Dispersion stability of carbon black suspension for use in lithium ion battery cathodes
- Author
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Myung Duk Lim, Jin-Uk Lee, Ungyu Paik, Chae Woong Cho, Gu Yeon Kim, Kyung Min Jeong, Ki-jun Kim, and Ki Chun Kil
- Subjects
Materials science ,Adsorption ,Chemical engineering ,General Chemical Engineering ,Dispersion stability ,Electrochemistry ,Organic chemistry ,Amine gas treating ,Carbon black ,Dispersion (chemistry) ,Dispersant ,Lithium-ion battery - Abstract
The dispersion properties of carbon black (CB) slurries as well as the accompanying electrochemical properties of Li(Ni 1/3 Co 1/3 Mn 1/3 )O 2 (NCM) electrodes were investigated by controlling the amine value of polyurethane-based dispersants. The increase in amine value of dispersants leads to an increase in adsorption level on CB surface due to a strong acid/base interaction between dispersants and CB particles, providing the improvement of steric repulsion between particles at the solid–liquid interface. This results in the enhancement of the dispersion stability of CB and the related microstructure of the electrodes. Electrochemical experiments indicated that the rate capabilities and cycle performance of the electrodes are in good agreement with dispersion properties of CB slurries. However, it was found that the excessive addition of the dispersant was deleterious to electrochemical properties because the non-adsorbed dispersants act as an electronic conduction barrier between solid phases. Therefore, it is suggested that the amine value of dispersant and tailored amount of dispersant addition can be key roles for obtaining the optimized dispersion stability of CB and the corresponding excellent electrochemical properties of the cathode.
- Published
- 2013
22. Impact of over-wintering waterfowl on tuberous bulrush (Bolboschoenus planiculmis) in tidal flats
- Author
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George G. Ganf, Chan-Woo Lee, Gea-Jae Joo, Ji Yoon Kim, and Gu-Yeon Kim
- Subjects
Biomass (ecology) ,biology ,Range (biology) ,Ecology ,Sediment ,Plant Science ,Bulrush ,Aquatic Science ,biology.organism_classification ,Grazing pressure ,Agronomy ,Grazing ,Waterfowl ,Bolboschoenus planiculmis - Abstract
We investigated the effects of grazing by over-wintering waterfowl on tuberous bulrush (Bolboschoenus planiculmis) biomass in tidal flats. Our aim was to address the influence of the grazing pressure of different waterfowl groups during winter on tuber burial depth. An enclosure experiment was conducted to estimate the level of grazing, and individual numbers of waterfowl were monitored. Plant biomass rapidly decreased following the arrival of over-wintering waterfowl in October. Tuber biomass accounted for more than 69.2% of the total belowground biomass and was mainly used by waterfowl. Tuber biomass was highest at depths of 20–40 cm and lowest at depths >40 cm. After the arrival of migratory waterfowl, tuber biomass decreased relative to its depth range because of different shoveling abilities among ducks, geese, and swans. Ducks and geese grazed mainly on stems and tubers from surficial layers. Swans grazed deeper than geese; this correlated with biomass loss from deeper sediment layers (r: 0.78, P
- Published
- 2013
23. Effects of Electrode Density on the Safety of NCA Positive Electrode for Li-Ion Batteries
- Author
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Gu-Yeon Kim and J. R. Dahn
- Subjects
Materials science ,Renewable Energy, Sustainability and the Environment ,Inorganic chemistry ,Electrode ,Materials Chemistry ,Electrochemistry ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Ion - Published
- 2013
24. Enhanced Electrochemical Properties of LiFePO4 Electrodes with Carboxylated Poly(vinyl difluoride) in Lithium-Ion Batteries: Experimental and Theoretical Analysis
- Author
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Maeng-Eun Lee, Gu Yeon Kim, Geunbae Kim, Chae-Woong Cho, Ki Chun Kil, Ki-jun Kim, and Ungyu Paik
- Subjects
chemistry.chemical_classification ,Materials science ,Difluoride ,Analytical chemistry ,chemistry.chemical_element ,Polymer ,Adhesion ,Internal resistance ,Electrochemistry ,Cathode ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,General Energy ,Chemical engineering ,chemistry ,law ,Electrode ,Lithium ,Physical and Theoretical Chemistry - Abstract
The adhesion strengths between LiFePO4 cathodes and aluminum (Al) current collectors as well as the corresponding electrochemical properties of electrodes with carboxylated poly(vinyl difluoride) (C-PVdF) were experimentally and theoretically investigated. The adhesion strength of LiFePO4 cathodes with C-PVdF on Al current collectors were increased, compared with that of as-received PVdF, resulting in the reduction of the internal resistance of the electrode. These results were supported by theoretical simulations based on the Metropolis Monte Carlo method. Electrochemical experiments indicated that the cyclability and rate capabilities of the cathode were improved as the weight fraction of C-PVdF in the electrode increased up to 70% of the polymer binders. In addition, 18 650-sized full cells employing the electrodes with C-PVdF showed promising performance in terms of rate capability as well as long-term cyclability, which suggests that this strategy can be beneficial for the realization of high power s...
- Published
- 2011
25. Korea National Long-Term Ecological Research: provision against climate change and environmental pollution (Review)
- Author
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Chang-Seok Lee, Gea-Jae Joo, Yuno Do, Myung Jin Kim, Gu-Yeon Kim, Byeong Gug Yang, and Ji Yoon Kim
- Subjects
Ecology ,business.industry ,Multidisciplinary approach ,Animal ecology ,Political science ,Environmental resource management ,Climate change ,Environmental pollution ,Christian ministry ,business ,Ecology, Evolution, Behavior and Systematics ,Term (time) - Abstract
The Korea National Long-Term Ecological Research (KNLTER) was initiated in 2004 by the Korean Ministry of Environment. This project entered its third and final phase in 2010. Committee members have suggested that the project needs to be assessed in terms of its achievement and advised regarding its refinement. In this review, we recapitulated the last 7 years of KNLTER progress for developing further program improvements. We reviewed ecological research before the existing LTER, project initiation, the increase in the number of research sites, and research topics. Then, we briefly exam ine the status of KNLTER and discuss areas for improvement and avenues for further research. The KNLTER established 20 research sites covering 80 topics related to terrestrial, freshwater, coastal, and animal ecology. To strengthen its role in LTER research, KNLTER participants need to confirm standard protocols and data formats for an efficient interaction with other LTER programs. All participants should enhance communication at both the domestic and international levels to reach out and collaborate on research and multidisciplinary studies. Climate change and environmental pollution issues will be solved with a global research network and long-term research projects focusing on this issue.
- Published
- 2011
26. Electrochemical behaviors of Li[Li(1−x)/3Mn(2−x)/3Nix/3Cox/3]O2 cathode series (0<x<1) synthesized by sucrose combustion process for high capacity lithium ion batteries
- Author
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Seung-Beob Yi, Gu-Yeon Kim, Ho Gi Kim, and Yong Joon Park
- Subjects
chemistry.chemical_classification ,Sucrose ,Chemistry ,Mechanical Engineering ,Inorganic chemistry ,High capacity ,Condensed Matter Physics ,Electrochemistry ,XANES ,Cathode ,Ion ,law.invention ,Divalent ,chemistry.chemical_compound ,Mechanics of Materials ,Oxidation state ,law ,General Materials Science - Abstract
A mixed cathode material between Li2MnO3 and Li[Mn1/3Ni1/3Co1/3]O2 for high capacity lithium secondary batteries was introduced in this study. It was prepared using the sucrose combustion process because this is a simple process. The oxidation states of Mn, Co and Ni ions in the pristine Li[Li(1−x)/3Mn(2−x)/3Nix/3Cox/3]O2 compounds were confirmed to be tetravalent, trivalent and divalent, respectively, via XANES measurements. Electrochemical charge/discharge studies showed that the highest first discharge capacity of 224 mAh/g was obtained in composition of x = 0.5 at a 0.2 C rate. The oxidation state of the Co and Ni ions in the Li[Li1/6Mn1/2Ni1/6Co1/6]O2 changed to higher oxidation states, but that of the Mn ions did not change.
- Published
- 2008
27. High-rate, high capacity ZrO2 coated Li[Li1/6Mn1/2Co1/6Ni1/6]O2 for lithium secondary batteries
- Author
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Ho Gi Kim, Gu-Yeon Kim, Dae-Jin Yang, Ju Wook Lee, Kwang Hee Jung, and Yong Joon Park
- Subjects
Materials science ,General Chemical Engineering ,chemistry.chemical_element ,High capacity ,Electrolyte ,engineering.material ,Electrochemistry ,Cathode ,Dielectric spectroscopy ,law.invention ,Coating ,chemistry ,Chemical engineering ,law ,Electrode ,Materials Chemistry ,engineering ,Lithium - Abstract
Recently, there have been many reports on efforts to improve the rate capability and discharge capacity of lithium secondary batteries in order to facilitate their use for hybrid electric vehicles and electric power tools. In the present work, we present a ZrO2-coated Li[Li1/6Mn1/2Co1/6Ni1/6]O2. The bare Li[Li1/6Mn1/2Co1/6Ni1/6]O2 shows a high initial discharge capacity of 224 mAh g−1 at a 0.2 C rate. Owing to the stability of ZrO2, it was possible to enhance the rate capability and cyclability. After 1 wt% ZrO2 coating, the ZrO2-coated Li[Li1/6Mn1/2Co1/6Ni1/6]O2 showed a high discharge capacity of 115 mAh g−1 after 50 cycles under a 6 C rate, whereas the bare Li[Li1/6Mn1/2Co1/6Ni1/6]O2 showed a discharge capacity of only 40 mAh g−1 and very poor cyclability under the same conditions. Based on results of XRD and EIS measurements, it was found that the ZrO2 suppressed impedance growth at the interface between the electrodes and electrolyte and prevented collapse of the layered hexagonal structure.
- Published
- 2008
28. Evaluation of Winter Barley Fields as Feeding Habitat for Waterfowl in the Dongup Reservoir System, Korea
- Author
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Joo,Gea-Jae and Gu-Yeon Kim
- Subjects
Biomass (ecology) ,Ecology ,biology ,biology.organism_classification ,Goose ,Agronomy ,Habitat ,biology.animal ,Grazing ,Shoot ,Exclosure ,Waterfowl ,Ecology, Evolution, Behavior and Systematics ,Anser - Abstract
As a Biodiversity Management Plan in S. Korea, barley fields are being prepared for the wintering migratory birds. However, the effectiveness of barley fields as a feeding habitat has not been evaluated. In 2003/04 wintering period, we installed exclosures in the barley fields to evaluate the waterfowl grazing effectiveness. Approximately 8,000 waterfowls used the Dongup Reservoir System and utilized the barley fields during the daytime. The white-fronted goose Anser albifrons occupied more than 90% of the all barley-feeding waterfowls. Waterfowls significantly impacted to the shoot density and biomass of barley. In the closed plot, barley shoot density gradually increased to 267±27/m 2 in January, 2004. Shoot density in open plots (site 1) declined sharply from 15 December (189±18/m 2 ) to 5 January 2004 (25±11/m 2 ). However, barley shoot density in open plots (site 2) was stable in January 2004 because of human disturbances. The changes in barley biomass and shoot density showed similar trend in both open and closed plot. From the exclosure experiment, it was clear that barley fields were important feeding habitat for wintering waterfowls in this area. Further, human disturbances such as noise from traffic and other human activities (farming and hiking) had significant impact on waterfowls’ grazing activity. Collectively, winter barley fields were effective for waterfowl feeding, but the location of barley fields should be carefully selected for the maximum utilization of the barley feeding.
- Published
- 2006
29. Changes of Distribution of Vascular Hydrophytes in the Nakdong River Estuary and Growth Dynamics of Schenoplectus triqueter, Waterfowl Food Plant
- Author
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Gu-Yeon Kim, Hae-Soon Yoon, Chan-Woo Lee, and Gea-Jae Joo
- Subjects
Eichhornia crassipes ,geography ,geography.geographical_feature_category ,Myriophyllum ,biology ,Brackish water ,Ecology ,Aquatic plant ,Waterfowl ,Estuary ,Wetland ,Zostera ,biology.organism_classification - Abstract
A study on changes on the distribution of vascular hydrophytes and the growth pattern of Schenoplectus triqueter (Scirpus triqueter) was undertaken at the Nakdong River estuary from 2002 to 2004. The change was due to physical alteration of the estuary for the past 25 years. These plant species are the major food sources for winter waterfowl. A total of 32 species of vascular hydrophytes from 17 families were found in the West Nakdong River (freshwater), the main channel of Nakdong River (freshwater) and the Nakdong River Estuary (brackish water). After the construction of the barrage on the estuary in 1987, the number of hydrophytes has remarkably increased to 17 species (5 species in 1985) in the main channel of the River. In particular, a community of Eurale ferox was found at the backwater wetland of the Daejeo side of the main channel. The introduced species of Eichhornia crassipes and Pistia stratiotes that were epidemic in 2001 at West Nakdong River was not found any more. The other species such as Nymphoides indica, Myriophyllum spicatum, Ruppia spp. were rediscovered. The large area (about 1,300ha) of Zostera spp. was the main sources of food for swans, but disappeared because of direct and indirect impacts of reclamation in the River estuary. Currently, there remains a small patch of Zostera spp. and about 250ha of S. triqueter. Schenoplectus triqueter grew mostly between April-September and tuber formed, between September-October. The growth of S. triqueter up to in length was observed in 5 sites out of the 7 sites in brackish area. Tubers of S. triqueter were eaten by waterfowls such as swans as winter food. In five sites, tubers took of total biomass in October. Tubers were found in deep layers; (9%), (28%), (55%), below 40cm . The distribution of vascular hydrophytes has remarkably changed in the Nakdong River Estuary due to the reclamation of the area. In order to determine the extent of changes of the distribution of these plants and the carrying capacity of the area for waterfowl, an intensive research is urgently needed.
- Published
- 2005
30. Synthesis of LiFePO4 with fine particle by co-precipitation method
- Author
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YJ Park, Gu-Yeon Kim, Sung Bo Lee, KS Park, KT Kang, and Ho Gi Kim
- Subjects
Aqueous solution ,Coprecipitation ,Mechanical Engineering ,Inorganic chemistry ,chemistry.chemical_element ,Condensed Matter Physics ,Electrochemistry ,Cathode ,law.invention ,chemistry ,Mechanics of Materials ,law ,Particle ,General Materials Science ,Lithium ,Reactivity (chemistry) ,Carbon - Abstract
LiFePO{sub 4} is a potential candidate for the cathode material of the lithium secondary batteries. A co-precipitation method was adopted to prepare LiFePO{sub 4} because it is simple and cheap. Nitrogen gas was needed to prevent oxidation of Fe{sup 2+} in the aqueous solution. The co-precipitated precursor shows the high reactivity with the reductive gas, and the single phase of LiFePO{sub 4} is successfully synthesized with the aid of carbon under less reductive conditions. LiFePO{sub 4} fine powder prepared by co-precipitation method shows high rate capability, impressive specific capacity and cycle property.
- Published
- 2004
31. Relative importance of hydrological variables in predicting the habitat suitability of Euryale ferox Salisb.
- Author
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Ji Yoon Kim, Gu-Yeon Kim, Yuno Do, Hee-Sun Park, and Gea-Jae Joo
- Subjects
NYMPHAEACEAE ,PLANT habitats ,BIODIVERSITY conservation ,HYDROLOGY ,REMOTE sensing - Abstract
Aims: Aquatic ecosystems are a priority for conservation as they have become rapidly degraded with land-use changes. Predicting the habitat range of an endangered species provides crucial information for biodiversity conservation in such rapidly changing environments. However, the complex network structure of aquatic ecosystems restricts spatial prediction variables and has hitherto limited the use of habitat models to predict species occurrence in aquatic ecosystems. We used the maximum entropy model to evaluate the potential distribution of an endangered aquatic species, Euryale ferox Salisb. We tested the relative influence of (i) climatic variables, (ii) topographic variables, and (iii) hydrological variables derived from remote sensing data to improve the prediction of occurrence of aquatic plant species. Methods: We considered the southern part of the Korean Peninsula as the modeling extent for the potential distribution of E. ferox. Occurrence records for E. ferox were collected from the literature and field surveys. We applied maximum entropy modeling using remotely sensed environmental variables and evaluated their relative importance as prediction variables with variation partitioning. Important Findings: The species distribution model predicted potential habitats of E. ferox that matched the actual distribution well. Floodplain wetlands and shallow reservoirs were the favored habitats of E. ferox. Quantitative loss and fragmentation of wetland habitats appeared to be a major reason for the decrease of E. ferox populations. Our results also imply that hydrological variables (i.e. normalized difference water index) derived from remote sensing data greatly increased model prediction (relative contribution: 10.5–37.0%) in the aquatic ecosystem. However, interspecific competition within a similar niche environment should be considered to increase the accuracy of the distribution model. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
32. Relative importance of hydrological variables in predicting the habitat suitability ofEuryale feroxSalisb
- Author
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Ji Yoon Kim, Hee-Sun Park, Gu-Yeon Kim, Yuno Do, and Gea-Jae Joo
- Subjects
0106 biological sciences ,geography ,geography.geographical_feature_category ,Ecology ,biology ,Range (biology) ,010604 marine biology & hydrobiology ,Aquatic ecosystem ,Species distribution ,Endangered species ,Wetland ,Plant Science ,biology.organism_classification ,010603 evolutionary biology ,01 natural sciences ,Habitat ,Aquatic plant ,Environmental science ,Ecology, Evolution, Behavior and Systematics ,Euryale ferox - Abstract
Aquatic ecosystems are a priority for conservation as they have become rapidly degraded with land-use changes. Predicting the habitat range of an endangered species provides crucial information for biodiversity conservation in such rapidly changing environments. However, the complex network structure of aquatic ecosystems restricts spatial prediction variables and has hitherto limited the use of habitat models to predict species occurrence in aquatic ecosystems. We used the maximum entropy model to evaluate the potential distribution of an endangered aquatic species, Euryale ferox Salisb. We tested the relative influence of (i) climatic variables, (ii) topographic variables, and (iii) hydrological variables derived from remote sensing data to improve the prediction of occurrence of aquatic plant species. We considered the southern part of the Korean Peninsula as the modeling extent for the potential distribution of E. ferox. Occurrence records for E. ferox were collected from the literature and field surveys. We applied maximum entropy modeling using remotely sensed environmental variables and evaluated their relative importance as prediction variables with variation partitioning. The species distribution model predicted potential habitats of E. ferox that matched the actual distribution well. Floodplain wetlands and shallow reservoirs were the favored habitats of E. ferox. Quantitative loss and fragmentation of wetland habitats appeared to be a major reason for the decrease of E. ferox populations. Our results also imply that hydrological variables (i.e. normalized difference water index) derived from remote sensing data greatly increased model prediction (relative contribution: 10.5–37.0%) in the aquatic ecosystem. However, interspecific competition within a similar niche environment should be considered to increase the accuracy of the distribution model.
- Published
- 2016
33. Reversible Nature of Impedance on LiCoO2/Graphite and Li[Ni0.42Mn0.42Co0.16]O2/Graphite Pouch Cells Cycled to High Voltages
- Author
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David Yaohui Wang, Gu-Yeon Kim, and Jeff Dahn
- Abstract
Introduction Development of high voltage Li-ion cells is critical for the improvement of energy density of Li-ion cells [1]. Electrolyte additives are used to improve the properties and performance of Li-ion cells [2]. However, the way that electrolyte additives function and the impedance changed that occurs with voltage in Li-ion cells have not been well-explained in the literature. A Maccor 4000 series charger, combined with a frequency response analyzer (Maccor FRA 0356), was used to investigate the effects of electrolyte additives on cell impedance changes with voltage in Li[Ni0.42Mn0.42Co0.16]O2 (NMC)/graphite and LiCoO2(LCO)/graphite pouch cells. Experimental Machine-made Li[Ni1/3Mn1/3Co1/3]O2/graphite and LiCoO2/graphite dry pouch cells (402030 size, 220 mAh) were supplied by reputable manufacturers and were filled and sealed at Dalhousie University. Cells were filled with 1 M LiPF6in ethylene carbonate (EC):ethylmethyl carbonate (EMC) (3:7 by weigh, BASF) as control electrolyte. Vinylene carbonate (VC, BASF, 99.97%) was used as an electrolyte additive. After electrolyte filling and vacuum sealing (MTI Corporation, MSK-115A) in an argon-filled glove box, a 24 h hold at 40.0 ± 0.1°C and 1.5 V was used to ensure complete wetting of the cell coil. The first charge cycle (called the formation process here) consisted of charging at 11 mA (corresponding to C/20 current) to 3.5 V. Then cells were degassed in the glove box and vacuum sealed again. Subsequently, cells were charged to 4.5V using the same current, followed by degassing and vacuum sealing in the glove box. The cells were cycled using a Maccor 4000 series charger between 2.8 and 4.7 V at 40.0 ± 0.1°C using currents corresponding to C/20 while the cell impedance was measured at every 0.1 V interval between 3.6 and 4.7 V with a Maccor frequency response analyzer (FRA 0356). The FRA unit and cells during testing were in temperature controlled environments (21°C for NMC/graphite pouch cells, and 30°C for LCO/graphite pouch cells) with variations in temperature of an amplitude less than 2°C. AC impedance spectra were collected from 10 kHz – 10 mHz with an amplitude of 2 mV. Ten data points per decade were measured. Results and discussion Figure 1 shows selected Nyquist plots for NMC cells containing 2 % VC during the first charge and the first discharge. The charge transfer resistance (Rct) was marked in Figure 1a and taken to be the diameters of overlapping semicircles from the Nyquist plots [3]. Cells with a small Rct are much more desirable. Figure 2 shows summary of Rctversus voltage for NMC/graphite and LCO/graphite pouch cells with 2 % VC. The impedance of NMC/graphite cells increases a lot as the cells are charged above 4.3 V. This impedance change is almost reversible over one cycle but the impedance slowly increases cycle by cycle. By contrast the LCO materials do not show any real impedance increase after charging to 4.4V. There are many interesting things to note which will be discussed in the lecture. References [1] M. Hu, X. Pang and Z. Zhou, J. Power Sources, 237, 229 (2013). [2] S.S. Zhang, J. Power Sources, 162,1379 (2006). [3] D.Y. Wang, N.N. Sinha, R. Petibon, J.C. Burns, and J.R. Dahn, J. Power Sources, 251, 311 (2014).
- Published
- 2014
34. Combinations of Ethylene Sulfite (ES) and Vinylene Carbonate (VC) As Electrolyte Additives in Li(Ni1/3Mn1/3Co1/3)O2/Graphite Pouch Cells
- Author
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Jian Xia, Connor Aiken, Lin Ma, Gu-Yeon Kim, John Chris Burns, and Jeff Dahn
- Abstract
Introduction Electrolyte additives can be used to improve the lifetime of a Li-ion cell [1]. Electrolyte additives are believed to function by forming or modifying a solid electrolyte interface (SEI) layer on the surface of the positive or negative electrode thus impacting the cycle life, calendar life and safety of Li-ion cells. Ethylene sulfite (ES) has been widely studied by many researchers and has been regarded as an effective SEI-forming additive, especially in PC based electrolytes. Wrodnigg et al. [2] found the introduction of 5 vol % ES to a PC-based electrolyte could suppress or even prevent PC co-intercalation into graphite. Ota et al [3] suggested that when ES was used as an electrolyte additive, the SEI film on the graphite anode contained both inorganic materials like Li2SO3 and organic materials like ROSO2Li. The bulk of the studies on ES have focused upon its effect on the carbon electrode. In this presentation, a detailed study of ES and/or VC as electrolyte additives for Li[Ni1/3Mn1/3Co1/3]O2/graphite pouch cells was investigated using UHPC [4] and a precision storage system at Dalhousie University [5]. Gas evolution during formation and cycling, coulombic efficiency (CE) and charge endpoint capacity slippage during cycling as well as charge transfer resistance before and after cycling were examined and compared. Experimental Dry Li[Ni1/3Mn1/3Co1/3]O2 (NMC)/graphite pouch cells (225 mAh) were obtained from Whenergy (Shandong, China). Before electrolyte filling, the cells were cut just below the heat seal and dried at 80°C under vacuum for 14 h to remove any residual water. Then the cells were transferred immediately to an argon-filled glove box for filling and vacuum sealing. Cells cycled using the UHPC were tested between 2.8 and 4.2 V at 40.0 ± 0.05 °C using currents corresponding to C/20 for 15 cycles where comparisons were made. Electrochemical impedance spectroscopy (EIS) measurements were conducted on NMC/graphite pouch cells before and after cycling on the UHPC. Results and discussion Figure 1 shows data collected from the UHPC during cycling. Figure 1 shows cells containing 2% VC + ES (1 % or 2 %) can provide similar performance in delta V, coulombic efficiency and charge endpoint capacity slippage to cells containing 2% VC. Figure 2 shows the Nyquist plots for NMC/graphite pouch cells with different amounts of ES and/or VC after formation and after UHPC cycling measured at 3.80 V and 10°C. Figure 2 shows that cells containing only ES show obvious impedance growth during cycling. When ES (1% or 2%) is used in combination with VC, the impedance was dramatically decreased both before and after cycling. Cells with 2% VC + 2% ES have the lowest impedance after cycling, only half of that of cells with 2% VC. Therefore, there appear to be significant benefits of the combination of VC and ES for high power cells. References 1. S. S. Zhang, J. Power Sources, 162, 1379 (2006). 2. G. H. Wrodnigg, J. O. Besenhard and M. Winter, J. Electrochem. Soc., 146, 470 (1999). 3. H. Ota, T. Akai, H. Namita, S. Yamaguchi and M. Nomura, J. Power Sources, 119-121, 567 (2011). 4. T. M. Bond, J.C. Burns, D.A. Stevens, H.M. Dahn, and J.R. Dahn, J. Electrochem. Soc., 160 , A521 (2013). 5. N. N. Sinha, T. H. Marks, H. M. Dahn, A. J. Smith, D. J. Coyle, J. J. Dahn and J. R. Dahn, J. Electrochem. Soc., 159, A1672 (2012).
- Published
- 2014
35. Effects of Electrode Density On the Safety of NCA Positive Electrode for High Capacity Li-Ion Batteries
- Author
-
Gu-Yeon Kim and Jeff Dahn
- Abstract
not Available.
- Published
- 2013
36. Improved Electrochemical Behavior of the LiFePO4 Electrode with the Functionalized Poly(vinyldifluoride) in the Lithium-Ion Rechargeable Batteries: Theoretical and Experimental Analysis
- Author
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Jeong Hyun Kim, Chae-Woong Cho, Maeng Eun Lee, Gu Yeon Kim, Won-Seok Kim, Woon Suk Jang, and Ungyu Paik
- Abstract
not Available.
- Published
- 2010
37. Sugar Combustion Synthesis for Cathode Materials of the Lithium Secondary Battery
- Author
-
Seung-Beob Yi, Gu-Yeon Kim, Jin-Seong Yoo, Hoon-Taek Chung, and Ho-Gi Kim
- Abstract
not Available.
- Published
- 2006
38. ARC Studies of the Effects of Electrolyte Additives on the Reactivity of Delithiated Li1-x[Ni1/3Mn1/3Co1/3]O2 and Li1-x[Ni0.8Co0.15Al0.05]O2...
- Author
-
Gu-Yeon Kim and Dahn, J. R.
- Subjects
ELECTROLYTES ,CALORIMETRY ,LITHIUM ,BATTERY additives ,ELECTROCHEMISTRY - Abstract
Using accelerating rate calorimetry (ARC), the effect of lithium bis(oxalato)borate (LiBOB), vinylene carbonate (VC) and succinonitrile (SN) electrolyte additives and LiPF
6 salt on the reactivity between electrolyte and charged positive electrode material has been investigated. The ARC samples were made with varying concentrations of LiBOB, VC and SN as electrolyte additives and delithiated Li1-x [Ni1/3 Mn1/3 Co1/3 ]O2 (NMC) and Li1-x [Ni0.8 Co0.15 Al0.05 ]O2 (NCA) charged to 4.2 V as positive electrode materials. The thermal stability of NMC decreases slightly with the addition of the electrolyte additives but the thermal stability of NCA increases with the addition of the electrolyte additives except in the case of VC. The thermal stability of NMC decreases as the concentration of LiPF6 increases while the thermal stability of NCA increases as the concentration of LiPF6 increases. The ARC results shown here suggest that additives and LiPF6 salt can play a different role in thermal stability depending on the positive electrode material. Therefore careful considerations about safety are required to incorporate new electrolyte additives in Li-ion cells. [ABSTRACT FROM AUTHOR]- Published
- 2014
- Full Text
- View/download PDF
39. ARC Studies of the Effects of Electrolyte Additives on the Reactivity of Delithiated Li1-x[Ni1/3Mn1/3Co1/3]O2 and Li1-x[Ni0.8Co0.15Al0.05]O2 Positive Electrode Materials with Electrolyte.
- Author
-
Gu-Yeon Kim and Dahn, J. R.
- Published
- 2014
- Full Text
- View/download PDF
40. Effects of Succinonitrile (SN) as an Electrolyte Additive on the Impedance of LiCoO2/Graphite Pouch Cells during Cycling.
- Author
-
Gu-Yeon Kim, Petibon, R., and Dahn, J. R.
- Subjects
ELECTRODES ,SUCCINONITRILE ,ELECTROLYTES ,ELECTRIC impedance ,ADDITIVES ,LITHIUM compounds - Abstract
LiCoO
2 /graphite pouch cells with 1.0M LiPF6 in EC:DEC (1:2 v/v) electrolyte were used to study the effect of succinonitrile (SN) as an electrolyte additive on the cell impedance during cycling. Pouch cells containing no additives, 2 wt% vinylene carbonate (VC), 2 wt% SN and 2 wt% VC + 2 wt% SN were studied for comparison. In order to investigate which electrode contributed to impedance changes during charge and discharge cycling, positive and negative electrode symmetric cells, fabricated using electrodes extracted from the parent pouch cells, were studied using electrochemical impedance spectroscopy (EIS). Two wt% VC added to the electrolyte suppressed impedance growth of the positive electrode during cycling, while the addition of 2 wt% SN greatly increased the impedance growth of the positive electrode during cycling. The addition of both 2 wt% VC and 2 wt% SN leads to intermediate behavior. In all cases, the negative electrode impedance decreased during cycling when VC, SN or VC+SN additives were present. The dominant contribution to the impedance growth of pouch cells containing SN during cycling comes from the positive electrode. [ABSTRACT FROM AUTHOR]- Published
- 2014
- Full Text
- View/download PDF
41. Importance of closed landfills as green space in urbanized areas: ecological assessment using carabid beetles
- Author
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Ji Yoon Kim, Gea-Jae Joo, Yuno Do, and Gu-Yeon Kim
- Subjects
Habitat ,Ecology ,Biodiversity ,Environmental science ,Plant cover ,Ecological assessment ,Context (language use) ,Species richness ,Vegetation ,Landscape ecology ,Management, Monitoring, Policy and Law ,Nature and Landscape Conservation - Abstract
In a closed landfill, we investigated the diversity and ecological characters of carabid beetles to understand the ecological importance of closed landfills that have the potential as a multi-functional habitat for improving biodiversity in urbanized areas. In addition, we studied the influence of environmental factors (vegetation structure, soil) on distribution and diversity of carabid beetles. A total of 92,495 individuals representing 15 carabid species were collected from the closed landfill. Although the species richness of carabid beetles recorded in the closed landfill was not higher than the other green spaces in the city, the closed landfill could sufficiently provides a stable habitat as a semi-natural area for carabid beetles. Soil pH, Na, and tall grass plant cover influenced carabid assemblage in the closed landfill. However, other environmental variables (e.g., K+, Na+, Mg2+, bare land cover, weedy cover, and tree cover) were not correlated with carabid species composition. It is implied that in the closed landfill, which is a highly modified engineered environment, other abiotic environmental (e.g., drainage, soil texture, leachate, and landscape context, etc.) and biotic factors (e.g., intra- and interspecific competition) may have affected carabid assemblage. Although artificial drainages are essential facilities for landfill management, they are a critical factor that affects the species inhabiting the landfill. However, carabid beetles seemed to randomly fall into the artificial drainage. For successful management of closed landfills, it is very important that minimize the intervention and that develop the ecological sensitively management method.
- Full Text
- View/download PDF
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