• Korean Journal of Environment and Ecology
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• v.34 no.4
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• pp.282-293
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• 2020

This study investigated a long-term variation trend of water quality, fish compositions, and ecological health conditions in the Gwanpyeong stream located in the nearby Daejeon metropolitan city to understand the impact of urban development projects on the aquatic ecosystem. The sampling was made in four surveys (2009, 2010, 2016, 2019) before and after urbanization. The urban development was conducted in 2008, resulting in the stream's ecological disturbance, and the stream restoration was conducted in 2012. Thus, stream monitoring was conducted to analyze the ecological trends before and after the restoration. The multi-metric models for Fish Assessment Index(FAI) and necropsy-based Health Assessment Index(HAI) were applied in the fish community and organ-level, respectively, to assess the ecological health of the stream. Minimum turbidity and chlorophyll-a(Chl-a) occurred in the mid-stream(St. 2), and this was probably due to rapid current velocity in the riffle zone. We collected 18 fish species, and the dominant species was Zacco platypus (40.6%). In 2016 immediately after the stream restoration, the relative proportions of sensitive species and insectivore species were the highest along with highest values in the species diversity and species richness index, resulting in the best condition in the ecological health, based on FAI model values. However, the ecological health, based on the FAI, became worse in the latest survey conducted in 2019. The analysis of the HAI model based on the organ-level approach showed skin erosion in the fish of upper stream, kidney defects in downstream, and the liver and gill defects observed in all sites, indicating that the anatomical health was also affected.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.3
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• pp.29-45
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• 2017

Ad hoc sensor network is characterized by decentralized structure and ad hoc deployment. Sensor networks have all basic features of ad hoc network except different degrees such as lower mobility and more stringent energy requirements. Existing protocols provide different tradeoffs among some desirable characteristics such as fault tolerance, distributed computation, robustness, scalability and reliability. wireless protocols suggested so far are very limited, generally focusing on communication to a single base station or on aggregating sensor data. The main reason having such restrictions is due to maximum lifetime to maintain network activities. The network lifetime is an important design metric in ad hoc networks. Since every node does a router role, it is not possible for other nodes to communicate with each other if some nodes do not work due to energy lack. In this paper, we suggest an experimental ad-hoc on-demand distance vector routing protocol to optimize the communication of energy of the network nodes.The load distribution avoids the choice of exhausted nodes at the route selection phase, thus balances the use of energy among nodes and maximizing the network lifetime. In transmission control phase, there is a balance between the choice of a high transmission power that lead to increase in the range of signal transmission thus reducing the number of hops and lower power levels that reduces the interference on the expense of network connectivity.

• Journal of the Korea Society of Computer and Information
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• v.25 no.11
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• pp.27-40
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• 2020

In this paper, we investigate the correlation between the amount of English sentences that Korean English learners (L2ers) are exposed to and their sentence processing patterns by examining what Long Short-Term Memory (LSTM) language models (LMs) can learn about implicit syntactic relationship: that is, the filler-gap dependency. The filler-gap dependency refers to a relationship between a (wh-)filler, which is a wh-phrase like 'what' or 'who' overtly in clause-peripheral position, and its gap in clause-internal position, which is an invisible, empty syntactic position to be filled by the (wh-)filler for proper interpretation. Here to implement L2ers' English learning, we build LSTM LMs that in turn learn a subset of the known restrictions on the filler-gap dependency from English sentences in the L2 corpus that L2ers can potentially encounter in their English learning. Examining LSTM LMs' behaviors on controlled sentences designed with the filler-gap dependency, we show the characteristics of L2ers' sentence processing using the information-theoretic metric of surprisal that quantifies violations of the filler-gap dependency or wh-licensing interaction effects. Furthermore, comparing L2ers' LMs with native speakers' LM in light of processing the filler-gap dependency, we not only note that in their sentence processing both L2ers' LM and native speakers' LM can track abstract syntactic structures involved in the filler-gap dependency, but also show using linear mixed-effects regression models that there exist significant differences between them in processing such a dependency.

• Tunnel and Underground Space
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• v.24 no.4
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• pp.255-274
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• 2014

The target of this study is large scale rock slope collapsed by around 7 pm on August, 2012, which is located at ${\bigcirc}{\bigcirc}$ limestone quarries of Gangneung city, Gangwondo. The slope prior to the collapse is formed as the height of about 200 m and the average inclination of $45^{\circ}$. The estimated amount of the collapse is about $1,500,000m^3$ with respect to the slope after the collapse. Geotechnical and field investigations such as boring, geophysical prospecting, surface geological survey, geological lineaments, borehole imaging, metric 3D imaging, experimental and field test, mining work by year, and daily rainfall were performed to find the cause of rock slope failure. Various analyzes using slope mass rating, stereonet projection, limit equilibrium method, continuum and non-continuum model were conducted to check of the stability of the slope. It is expected that the cause of slope failure from the results of various analysis and survey is due to the combined factors such as topography, rainfall, rock type and quality, discontinuities, geo-structural characteristics as the limestone cavity and fault zones, but the failure of slope in case of the analysis without the limestone cavity is not occurred. Safe factor of 0.66 was obtained from continuum analysis of the slope considering the limestone cavity, so the ultimate causes of slope failure is considered to be due to the influence of limestone cavity developed along fault zone.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.6
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• pp.171-178
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• 2010

Pipeline structure is one of core underground infrastructure which transports primary sources. Since the almost pipeline structures are placed underground and connected each other complexly, it is difficult to monitor their structural health condition continuously. In order to overcome this limitation of recent monitoring technique, recently, a Ubiquitous Sensor Network (USN) system based on on-line and real-time monitoring system is being developed by the authors' research group. In this study, real-time pipeline health monitoring (PHM) methodology is presented based on electromechanical impedance methods using USN. Two types of damages including loosened bolts and notches are artificially inflicted on the pipeline structures, PZT and MFC sensors that have piezoelectric characteristics are employed to detect these damages. For objective evaluation of pipeline conditions, Damage metric such as Root Mean Square Deviation (RMSD) value was computed from the impedance signals to quantify the level of the damage. Optimal threshold levels for decision making are estimated by generalized extreme value(GEV) based statistical method. Throughout a series of experimental studies, it was reviewed the effectiveness and robustness of proposed PHM system.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.26 no.3
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• pp.167-182
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• 2021

This study was carried out to investigate temporal and spatial distribution of macrobenthic community and elucidate effects of environmental factors on change of community structure in an intertidal flat, Hakseong-ri, Boryeong, Korea. Field surveys were seasonally conducted to collect samples of sediment and macrobenthos using can core in triplicate at nine stations in 2016 and 2017. Our results showed that sediment had high mud content (above 60%) in most samples and mean content of loss on ignition was 2.3% in 2016. A total of 79 species was collected in the study site during the study period. Mean density and biomass were 611 ind./m² and 64.1 gWWt/m², respectively. Heteromastus filiformis was the dominant species (48.6%, 297 ind./m²) followed by Macrophthalmus japonicus (10.1%, 62 ind./m²) and Upogebia major (6.9%, 42 ind./m²). Three assembly groups resulted from cluster analysis were more distinguished by interaction between organisms and frequency of dominant species than by physical and chemical environment characteristics. In addition, macrobenthic community in the Hakseong intertidal flat showed seasonal changes based on non metric multidimensional scaling using species abundance.

• Korean Journal of Ecology and Environment
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• v.54 no.2
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• pp.87-95
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• 2021

Macroinvertebrates in forest streams affect the overall health of other streams in the same water system. In this study, we compared differences in the benthic macroinvertebrate community at two headwater streams located at different latitudes in the southern and northern parts of South Korea. We calculated the community temperature index (CTI), which represents the thermal preferences of the benthic communities. Hierarchical cluster analyses (HCA) were conducted to compare the similarities among sampling sites. In addition, we analyzed the relationship between community composition and environmental and community characteristics using non-metric multidimensional scaling (NMDS). Our results showed that CTI was significantly different between the two regions, indicating that these benthic macroinvertebrate communities have different thermal preferences. These two regions were clearly distinguished from each other in the HCA; furthermore, seasonal differences in benthic community composition were observed within each region. The functional feeding groups present in the benthic macroinvertebrate communities were different even though their habitat was similar.

• KIPS Transactions on Software and Data Engineering
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• v.12 no.12
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• pp.505-518
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• 2023

3D point cloud semantic segmentation is a computer vision task that involves dividing the point cloud into different objects and regions by predicting the class label of each point. Existing 3D semantic segmentation models have some limitations in performing sufficient fusion of multi-modal features while ensuring both characteristics of 2D visual features extracted from RGB images and 3D geometric features extracted from point cloud. Therefore, in this paper, we propose MMCA-Net, a novel 3D semantic segmentation model using 2D-3D multi-modal features. The proposed model effectively fuses two heterogeneous 2D visual features and 3D geometric features by using an intermediate fusion strategy and a multi-modal cross attention-based fusion operation. Also, the proposed model extracts context-rich 3D geometric features from input point cloud consisting of irregularly distributed points by adopting PTv2 as 3D geometric encoder. In this paper, we conducted both quantitative and qualitative experiments with the benchmark dataset, ScanNetv2 in order to analyze the performance of the proposed model. In terms of the metric mIoU, the proposed model showed a 9.2% performance improvement over the PTv2 model using only 3D geometric features, and a 12.12% performance improvement over the MVPNet model using 2D-3D multi-modal features. As a result, we proved the effectiveness and usefulness of the proposed model.

• 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.

• Korean Journal of Ecology and Environment
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• v.43 no.3
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• pp.428-436
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• 2010

This study was to evaluate water quality characteristics and ecological health using a mulimetric fish model in Taehwa-River watershed during May~September 2009. The ecological health assessments were based on the Index of Biological Integrity (IBI) using fish community and the multimetric model of Qualitative Habitat Evaluation Index (QHEI). For the study, the models of IBI and QHEI were modified as 8 and 11 metric attributes, respectively. We also analyzed spatial patterns of chemical water quality over the period of 2000~2009, using the water chemistry dataset, obtained from the Ministry of Environment, Korea. Values of BOD and COD averaged $1.7\;mg\;L^{-1}$ (scope: $0.1{\sim}31.8\;mg\;L^{-1}$) and $3.6\;mg\;L^{-1}$ (scope: $0.4{\sim}33\;mg\;L^{-1}$), respectively during the study. Total nitrogen (TN) and total phosphorus (TP) averaged $2.8\;mg\;L^{-1}$ and $96.8\;{\mu}g\;L^{-1}$, respectively, indicating an eutrophic-hypertrophic state. Also, TN and TP showed longitudinal increases toward the downriver reach. In the watershed, QHEI values varied from 67.5 (fair condition) to 164.5 (good condition) by the criteria of US EPA (1993). There was a abruptly decreasing tendency from T9 site in the QHEI values. According to 1st and 2nd surveys of Taewha River, multimetric model values of IBI was averaged 26.1 (n=14) with "good" condition (B) and the spatial variation was evident. Our results suggest that the mainstream sites was getting worse health condition along the river gradient due to inputs of the point and non-point sources from the urban (Ulsan city). Overall, dataset of IBI, QHEI, and water chemistry indicated that the ecological river health showed a downriver decline and the pattern was closely associated with habitat degradations and chemical pollutions as the waters pass through the urban region.