• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.137-137
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• 2018

이 연구에서는 리튬이온전지용 음극 활물질의 리튬이온 저장 용량을 최적화시키기 위한 새로운 방법이 제안되었다. 그 방법은 솔루션 플라즈마 프로세스를 사용하여 원자 단위의 리튬을 탄소 기반 물질의 내부에 도핑 시키고, 열처리를 통해 그 내부를 재설계하는 것이다. 리튬이온전지용 음극 활물질로 리튬금속 자체를 사용하려는 시도는 있었으나, 이는 충전 및 방전 사이클이 반복됨에 따라 리튬이 수지상으로 석출되어 내부를 단락시키거나, 리튬금속 자체의 폭발성에 의한 취급상의 제약이 있었다. 한편, 원자 단위로 탄소 내부에 도핑 된 리튬은 열처리 과정 동안 탄소 내부에서 확산함으로써 더 많은 리튬이 저장될 수 있는 공간을 만들었고, 사이클이 반복됨에 따라 서서히 충전 및 방전 반응에 참여함으로써 전지의 성능을 개선시켰다. 리튬이 도핑 된 탄소의 전기화학적 테스트 결과를 Fig. 1에 나타내었다. 실험 결과에서 보여진 초기 고용량 및 장기 사이클 특성은 탄소 내부에 도핑 된 리튬이 전지 성능의 향상에 중요한 역할을 한다는 것을 시사한다. 또한, 사이클이 반복됨에 따라 점차 증가하는 용량은 첫 사이클에서 형성된 solid electrolyte interphase의 비가역 용량을 보상할 수 있을 것으로 생각된다. 이상의 결과를 통해, 탄소 내부에 원자단위의 리튬을 도핑시키는 새로운 접근은 리튬이온전지의 성능 개선을 위한 효과적인 방법이 될 수 있을 것으로 보이며, 향후 리튬 이외의 다른 원소들, 즉 소듐과 같은 물질에 대하여 도핑을 시도한다면 새로운 분야에서 이와 같은 접근법이 유용하게 적용될 수 있을 것으로 사료된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.195-195
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• 2012

인공신경망 모형은 복잡하고 비선형의 입력과 출력 관계를 잘 반영할 수 있어서 유출 모델링에 널리 적용되어 왔다. 그러나 인공신경망 모형은 강우나 유역특성의 공간적 분포를 반영하는 것이 어려우며 물리적 개념이 결여되어 있는 단점이 있다. 본 연구에서는 유역특성과 물리적 개념을 반영할 수 있는 물리기반 모형과 인공신경망 모형의 장점들을 조합하여 물리기반 모형의 일 유출량 해석 능력을 향상하기 위하여 SWAT 모형과 인공신경망(ANN)을 연계하였다. SWAT-ANN 연계모형은 두 단계로 구성되어 진다. 첫 번째 단계에서는 관측 자료를 이용하여 SWAT 모형을 보정한다. 두 번째 단계에서는 첫 번째 단계에서 계산한 소유역별 SWAT 모형의 유출결과를 ANN의 입력자료로 이용하여 SWAT-ANN 연계모형을 구축한다. SCE-UA 최적화 방법을 적용하여 SWAT 모형의 매개변수들을 보정하였고, ANN 학습은 3층의 feed-forward 역전파 알고리즘에 기초한 Bayesian Regularization 방법을 적용하였다. ANN 은닉층의 뉴런 및 전달함수는 시행착오를 통하여 적절한 ANN 구조를 설정하여 SWAT-ANN 연계모형의 일유출량을 모의하였다. 여러 가지 통계적 오차기준을 이용하여 보청천 유역에서 SWAT-ANN 연계모형의 결과와 SWAT 단독 모형의 결과를 비교하였다. SWAT-ANN 연계모형이 SWAT 단독 모형보다 더 우수한 결과를 나타내어 일 유출량 해석을 위한 SWAT-ANN 연계모형의 유용성을 확인할 수 있었다.

• Archives of design research
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• v.19 no.5 s.67
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• pp.351-362
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• 2006

Currently, finding one's way in the underground spaces associated with subway stations in large cities is becoming a serious problem, and an environment that facilitates wayfinding is becoming more important. This study investigated interior treatments that function as visual cues in the subway stations of Seoul, Tokyo, and Taipei in order to develop design guidelines that would improve the place-cognition environment. A theoretical study has shown that there are three categories of visual cue for place cognition: marked trails, regional differentiation, and landmarks. The case study showed that marked trails involve treatments like vertical markers, confrontational positioning, and subway color codes. Regional differentiation involves patterns on the floors and walls, and accent colors on the walls and columns. Landmarks include treatments such as super graphics, symbolic features, artistic decoration and special lights. In the cases of Seoul, marked trails and regional differentiation were predominant. In addition, the Olympic symbol 'Hodori' and the ancient Korean character "Hunminjungeum" were used as landmarks. In the cases of Tokyo, regional differentiation predominated over marked trails because of the complexity of the spatial structure and subway line connection system. In the cases of Taipei, simple, unified images predominated, and there was minimal dependence on marked trails and landmarks. The need for regional differentiation was weak, because the stations studied have open structures that guarantee an open field of view. The results of this research could be used as design guidelines, after further experimental verification, that would help to improve the public environment in terms of wayfinding.

• Korean Journal of Ecology and Environment
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• v.44 no.2
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• pp.226-238
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• 2011

Ichthyological fauna and community structure were surveyed in the Naeseong Stream around the planed Yeongju Dam, Yeongju City, Gyeongsangbuk-do from April 2007 to October 2009, During the survey period, 27 species (25 genera, 10 families) were collected. Cyprinid fish comprised 63.0% (17 species) and cobitid fish comprised 7.4% (2 species). Ten of the 27 species (37.0%) were endemic species. The dominant and subdominant species based on the number of individuals was Zacco platypus (43.2%) and Zacco koreanus (15.8%), respectively. Introduced from the other native rivers and exotic fish were Opsariichthys uncirostris amurensis, Leiocassis ussuriensis, and Micropterus salmoides (11.1%). The declining population density of Zacco koreanus and its subdominant status represents a change, since, up until the mid 1990's, it was widely distributed throughout the area and was the dominant species. The distribution area of Zacco koreanus decreased in size; by 2009, it no longer inhabited the lower reaches of the Naeseong Stream. On the other hand, Zacco platypus remained the dominant species throughout the area, except for the upper-reaches of the water-course. Gobiobotia naktongensis inhabited all areas of Naeseong Stream, which mainly has a sandy bottom. Analyses of the fish community revealed species diversity, even-ness and dominant indices were 0.881, 0.615, and 0.230 respectively. These results showed that the main river, in which the water width and flow are abundant and which has various habitats, has a higher species diversity (0.829) than the tributary (0.735).

• Journal of Convergence for Information Technology
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• v.10 no.11
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• pp.156-167
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• 2020

The purpose of this study is to analyze the influence of the mindset on stress and job performance. For the analysis, a questionnaire is conducted for cabin crew members in K airlines, and a total of 266 copies are used for the final analysis. To verify the hypotheses of the study, frequency analysis, exploratory factor analysis, reliability analysis, confirmatory factor analysis, measurement model analysis, validation of the measuremen model, and structural equation model analysis are used based on the questionnaire. First, it is confirmed that the mindset had a negative (-) effect on the cabin crew's role stress, reward stress and relationship stress. Second, it is found that cabin crew's reward stress have a negative (-) effect on job performance. On the other hand, relationship stress is found to have a positive influence on job performance and there is no significant result in effect with role stress. Third, the mindset showes a significant positive impact relationship on job performance. As a result, it is necessary to introduce a mindset intervention program so that it can be applied in practical work. These research results confirm the positive effects of mindsets and show that they contribute to organizational performance. In addition, it is necessary to prepare a program to change the mindset of airline cabin crew and to be applied in actual work.

• Korean Journal of Ichthyology
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• v.35 no.4
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• pp.285-293
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• 2023

This study conducted to investigate the temporal and spatial variations in the fish community structure in the Seomjin River estuary (ES1~ES3) and Gwangyang Bay (ES4~ES8). Surveys were conducted at eight points between May and September from 2020 to 2021. A total of 5,111 fish were collected, representing 42 families, 68 genera, and 78 species. The dominant species collected during the survey period were Pennahia argentata, with 2,370 individuals and a relative abundance of 46.4%. Also, as a subdominant species, Nuchequula nuchalis, 1643 individuals were caught, accounting for 32.1% relative abundance. According to Bray-Curtis similarities, observations were divided into three groups based on the fish community composition, and they were further categorized into brackish water areas, coastal areas, inner areas, and outer areas. Group 1 mainly consisted of fish inhabiting freshwater and brackish water areas, while group 3 exclusively contained fish living in marine waters. ANOSIM (Analysis of Similarity) analysis revealed a significant difference (ANOSIM R=0.783, p=0.001) between Group 2 and Group 3, and the species contributing to these clusters were P. argentata and Muraenesox cinereus. The study demonstrated spatial changes in the fish community structure from the Seomjin River estuary to the outer coast. The findings highlight the importance of long-term monitoring of major species that exhibit spatial variations, serving as essential foundational data for the conservation and management of economically significant fish species.

• The Journal of Engineering Geology
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• v.7 no.2
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• pp.101-112
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• 1997

Gravity and electrical resistivity surveys were carried out across the Kwangju fault in the downstream area of the Jangsung Lake, to investigate the location and geometrical feature of the fault. In the resistivity survey, dipole - dipole array method was adopted for 3 survey lines of which length and electrode spacing are 500m and 25m, respectively. Resistivity data are interpreted with aid of computer program "RESIS" which is widely used in resistivity data analysis and two dimensional resistivity profiles are obtained for 3 survey lines. Two large fracture zones relevant to the Kwangju fault are identified in the resistivity profiles. The total of 80 gravity data are observed with the mean spacing of 40 m and the exact leveling is accompanied to obtain more precise gravity anomalies. The subterranean density discontinuities calculated from the inverse method are appeared at the depths of 650rn and 120m. It is considered that the deep discontinuity indicates boundary between Jurassic granites and oveflying Cretaceous tuff formation. while, the shallow discontinuity is interpreted to be a boundary between alluvial deposits and basements. The subsurface geological structure to satisfy the observed Bouguer anomaly is determined from the iterative forward method in which results from existing surface geological informations, the inverse method, and from the resistivity interpretations are employed as an iuitial model. In conclusion, Kwangju fault is appeared to be a high angle normal fault mainly formed in tension stress filed.

• The KIPS Transactions:PartA
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• v.17A no.5
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• pp.229-236
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• 2010

With an increasing number of documents in the Internet or enterprises, it becomes crucial to efficiently support users' queries on those documents. In that situation, the full-text search technique is accepted in general, because it can answer uncontrolled ad-hoc queries by automatically indexing all the keywords found in the documents. The size of index files made for full-text searches grows with the increasing number of indexed documents, and thus the disk cost may be too large to process multi-keyword queries against those enlarged index files. To solve the problem, we propose both of the index file structure and its management scheme suitable to the processing of multi-keyword queries against a large volume of index files. For this, we adopt the structure of inverted-files, which are widely used in the multi-keyword searches, as a basic index structure and modify it to a hierarchical structure for join operations and ranking operations performed during the query processing. In order to save disk costs based on that index structure, we dynamically store in the main memory the results of join operations between two keywords, if they are highly expected to be entered in users' queries. We also do performance comparisons using a cost model of the disk to show the performance advantage of the proposed scheme.

• Journal of Korea Water Resources Association
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• v.41 no.10
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• pp.983-993
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• 2008

In recent times, sea level increasing caused by abnormal weather and global warming, sea-sand dredging and complex development causes various kind of erosion damages onto the coastal area in the world. The various types of erosion control and protection methods are applied but there are no signs of fruitful effectiveness. The PC concrete protection block for shore protection structure is practically installed in globally but most of structures in the present day became villainous because of bad accessability. In this study, hydrophilic revetments for control and protection of coastline erosion will be developed in order to make up for a faculty of the shore erosion protection block with better accessibility and excellent protection ability. Experimental measurements were researched to insure for the capacity and facility on reflection coefficient, overtopping volume, and overtopping height characteristics of newly developed shore erosion protection block in model tests. As the result, hydraulic model tests show much excellent than the general step block. Field tests were carried out also to verify through vegetative test on an affinity and construction work test of control-protection on coastline erosion with actual utilization. In the latter case, deposition of sand accumulation occurred in fairly short time at the established reaches and then we can be confirmed to utilize for newly developed block as the revetments for control and protection of coastline erosion.

• Journal of Life Science
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• v.17 no.6 s.86
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• pp.783-790
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• 2007

G protein coupled receptors (GPCRs) transmit various extracellular signals into the cells. Upon binding of the ligands, conformational changes in the extracellular and/or transmembrane (TM) domains of CPCRs were propagated into the cytoplasmic (CP) domain of the molecule leading to the activation of their cognate heterotrimeric C proteins and kinases. Constitutively active GPCR mutants causing the activation of C Protein signaling even in the absence of ligand binding are of interest for the study of activation mechanism of GPCRs. Two classes of constitutively active mutations, categorized by their effects on the salt bridge between Ell3 and K296, were found in the TM domain of rhodopsin. Opsin mutants containing combinations of the mutations were constructed to study the conformational changes required for the activation of rhodopsin. Rhodopsin chromophore regenerated with 11-cis-retinal showed a thermal stability inversely correlated with its constitutive activity. In contrast, rhodopsin mutants exhibited a binding affinity to an agonist, all-trans-retinal, in a constitutive activity-dependent manner. In order to test whether the conformational changes responsible for the activation of trans-ducin (Gt) are the same as the conformation required for the recognition of rhodopsin kinase, analysis of the mutants were carried out with phosphorylation by rhodopsin kinase. Rhodopsin mutants containing combinations of different classes of the mutations showed a strong synergistic effect on the phosphorylation of the mutants in the dark as similar to that of Gt activation. The results suggest that at least two or three kinds of segmental and independent conformational changes are required for the activation of rhodopsin and the conformational changes responsible for activating rhodopsin kinase and Gt are similar to each other.