• Journal of the Computational Structural Engineering Institute of Korea
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• v.37 no.4
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• pp.225-232
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• 2024

This study focuses on the determination of the fracture mode in composite laminates using deep learning. With the increase in the use of laminated composites in numerous engineering applications, the insurance of their integrity and performance is of paramount importance. However, owing to the complex nature of these materials, the identification of fracture modes is often a tedious and time-consuming task that requires critical domain knowledge. Therefore, to alleviate these issues, this study aims to utilize modern artificial intelligence technology to automate the fractographic analysis of laminated composites. To accomplish this goal, scanning electron microscopy (SEM) images of fractured tensile test specimens are obtained from laminated composites to showcase various fracture modes. These SEM images are then categorized based on numerous fracture modes, including fiber breakage, fiber pull-out, mix-mode fracture, matrix brittle fracture, and matrix ductile fracture. Next, the collective data for all classes are divided into train, test, and validation datasets. Two state-of-the-art, deep learning-based pre-trained models, namely, DenseNet and GoogleNet, are trained to learn the discriminative features for each fracture mode. The DenseNet models shows training and testing accuracies of 94.01% and 75.49%, respectively, whereas those of the GoogleNet model are 84.55% and 54.48%, respectively. The trained deep learning models are then validated on unseen validation datasets. This validation demonstrates that the DenseNet model, owing to its deeper architecture, can extract high-quality features, resulting in 84.44% validation accuracy. This value is 36.84% higher than that of the GoogleNet model. Hence, these results affirm that the DenseNet model is effective in performing fractographic analyses of laminated composites by predicting fracture modes with high precision.

• KIPS Transactions on Software and Data Engineering
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• v.5 no.5
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• pp.203-208
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• 2016

Information system audit is the requirement to configure the information system successfully. However, there is a problem with reduction of efficiency in the audit work when the system capacity is growing up. In the subsidiary field of information system audit, there is the same problem. In this paper, we will focus on the database audit, and implement an SQL audit tool in order to improve the performance of a database. During the designing phase of the SQL audit tool which aim to improve the performance of a database, we have analyzed the requirements of SQL audit work. Based on the aforementioned them, the process of the SQL audit tool has been designed with SQL audit features in accordance with information audit process. During the implementation phase, we have implemented 3 main function modules according to the output of the design phase. The main modules we implemented are the audit job definition module, audit job executing module and result reporting module. With the implemented tool, it applied to an Electric Power Corporation project in China and compared with other tools that are able to use SQL audit. In this paper, the implemented SQL audit tool is able to perform the general SQL audit work and to reduce the cost of the audit work for database performance and to raise the accuracy of result and to apply the extended inspection rule which need to use SQL parsing.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.12
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• pp.43-53
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• 2007

We have analyzed low current operation characteristics of a VCSEL transmitter operating at fixed Current over wide temperature range. Used 850 nm oxide VCSEL has low temperature dependence of the threshold current and $d^2I_{th}/dT^2$ is approximately $1.346\times10^{-4}mA/^{\circ}C^2$. We fixed on-current so that output power from the chip is 1 mW at $20^{\circ}C$ and investigated the turn-on, turn-off characteristics and eye-diagram of the 850 nm oxide VCSEL transmitter with varying ambient temperature and off-current. We measured rise time, fall time, extinction ratio and timing jitter by changing tile ambient temperature and off-current. With the fixed off-current of around $0.1\sim0.2mA$ lower than the lowest threshold current the transmitter successfully operated at 1.25 Gbps over a wide temperature range from $-20^{\circ}C$ to $80^{\circ}C$.

• Membrane Journal
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• v.20 no.1
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• pp.29-39
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• 2010

This study focuses on the modeling of DMFC to predict the characteristics and to improve its performance. This modeling requires deep understanding of the design and operating parameters that influence on the cell potential. Furthermore, the knowledge with reference to electrochemistry, transport phenomena and fluid dynamics should be employed for the duration of mathematical description of the given process. Considering the fact that MEA is the nucleus of DMFC, special attention was made to the development of mathematical model of MEA. Multiscale modeling is comprised of process modeling as well as a computational fluid dynamics (CFD) modeling. The CFD packages and process simulation tools are used in simulating the steady-state process. The process simulation tool calculates theelectrochemical kinetics as well as the change of fractions, and at the same time, CFD calculates various balance equations. The integrated simulation with multiscal modeling explains experimental observations of transparent DMFC.

• Korean Journal of Remote Sensing
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• v.34 no.2_1
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• pp.203-211
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• 2018

Dam discharge is carried out for the management of rivers and area around rivers due to rainy season or drought. Dam discharge should be based on an accurate understanding of the flow rate that can be accommodated in the river. Therefore, understanding the allowable storage capacity of river is an important factor in the management of the environment around the river. However, the methods using water level meters and images, which are currently used to determine the allowable flow rate of rivers, show limitations in terms of accuracy and efficiency. In order to solve these problems, this paper proposes a method to automatically calculate the allowable storage capacity of river based on the images taken by drone. In the first step, we create a 3D model of the river by using the drone images. This generation process consists of tiepoint extraction, image orientation, and image matching. In the second step, the allowable storage capacity is calculated by cross section analysis of the river using the generated river 3D model and the road and river layers in the target area. In this step, we determine the maximum water level of the river, extract the cross-sectional profile along the river, and use the 3D model to calculate the allowable storage capacity for the area. To prove our method, we used Bukhan river's data and as a result, the allowable storage volume was automatically extracted. It is expected that the proposed method will be useful for real - time management of rivers and surrounding areas and 3D models using drone.

• Journal of the Korean association of regional geographers
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• v.15 no.2
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• pp.307-315
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• 2009

The purpose of map generalization is a method of map making to transmit the concise cartographic representation and geographic meaning. New generalization algorithm has been developed to be applied in the digital environments by the development of computer cartography. This study aims to look into possibilities of the multiscale mapping by generalization in application with the coordinate transformation and LoD(level of detail) in the web cartography. A method of the coordinate transformation is to improve a transmission of spatial data. Lod is a method which is making web map with selection spatial data by zoom level of users. Layers for test constructed contour line, stream network, the name of a place, a summit of mountain, and administrative office. The generalization was applied to zoom levels by scale for the linear and polygonal features using XML-Based scalable vector graphics(SVG). Resultantly, storage capacity of data was minimized 41% from 9.76mb to 4.08mb in SVG. Generalization of LoD was applied to map elements by stages of the zoom level. In the first stages of zoom level, the main name of places and administrative office, higher order of stream channels, main summit of mountain was represented, and become increase numbers of map elements in the higher levels. Results of this study can help to improve esthetic map and data minimization in web cartography, and also need to make an efforts to research an algorithm on the map generalization over the web.

• Journal of the Korean Association of Geographic Information Studies
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• v.20 no.2
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• pp.32-46
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• 2017

Recent rapid urban expansion and crowding of various industrial facilities has affected the features of a significant part of downtown area, resulting in areas having buildings with a wide range of height and the foothills. To compute a velocity pressure exposure coefficient, namely the design wind speed factor, this study defines ground surface roughness by utilizing concentration analysis for the height of each building. After obtaining spatial data by extracting a building layer from digital maps, the study area was partitioned for the concentration analysis and to allow investigation of the frequency distribution of building heights. Concentration analysis by building height was determined with the Variation-to-Means Ratio (VMR) and Poisson distribution analysis using a buildings distribution chart, with statistical significance determined using Chi-square verification. Applying geographic information systems (GIS) with the architectural information made it possible to estimate a velocity pressure exposure coefficient factor more quantitatively and objectively, by including geographic features, as compared to current methods. Thus, this method is expected to eliminate inaccuracies that arise when building designers calculate the velocity pressure exposure coefficient in subjective way, and to help increase the wind resistance of buildings in a more logical and cost-effective way.

• Journal of Korean Society for Geospatial Information Science
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• v.20 no.2
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• pp.63-71
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• 2012

Recently, web portals have been offering georeferenced SLI(Street-Level Imagery) services, such as Google Streetview. The SLI has a distinctive strength over aerial images or vector maps because it gives us the same view as we see the real world on the street. Based on the characteristic, applicability of the SLI can be increased substantially through conflation with other spatial datasets. However, spatial inconsistency between different datasets is the main reason to decrease the quality of conflation when conflating them. Therefore, this research aims to remove the spatial inconsistency to conflate an SLI with a widely used 2D vector map. The removal of the spatial inconsistency is conducted through three sub-processes of (1) road intersection matching between the SLI trace and the road layer of the vector map for detecting CPPs(Control Point Pairs), (2) inaccurate CPPs filtering by analyzing the trend of the CPPs, and (3) local alignment using accurate CPPs. In addition, we propose an evaluation method suitable for conflation result including an SLI, and verify the effect of the removal of the spatial inconsistency.

• Journal of Korean Society of Forest Science
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• v.96 no.1
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• pp.7-13
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• 2007

This study was done to develop PDA based application system for forest geographic information with GPS. The major results obtained in this study were as follows. A PDA based application program was developed to work on $Microsoft^{TM}$ PocketPC 2002 and 2003 operating system. The screen of PDA displays a 1:25,000 digital topographical map adopted DXF format converted from PC, and the map data with 1:2,500 to 1:30,000 on PDA can be zoomed in or out to five levels. Current position and navigating path received from GPS can be displayed on the screen and be saved in PDA. Information selected among layers of digital topographic map in DXF format can be converted into binary files which can be used on forest geographic information software. This can compress DXF files to 90% in size, and the processing speed of PDA was improved. The forest geographic information management system can be used to manage sample plots on which forest inventory is done, with the help of the sub-menus and grid index values with position information received from GPS. Forest workers can in quire forest geographic information such as forest type, location, forest roads, soil erosion control dams using forest geographic information management system in the field. The forest geographic information management system can provide current position and mobile path information to people who enjoy forest related activities like mountain-climbing, sightseeing, and visiting to historic spots.

• Membrane Journal
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• v.24 no.1
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• pp.63-68
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• 2014

Manufacturing facility for non-alcoholic drink, the parts of the food industry, disposes wastewater which includes high organic concentration and low nitrogen, phosphorus concentration. For this kind of wastewater, the treatment plant consists mainly of aerobic reactor and chemical coagulation process. And sand-filter or activated carbon process is normally installed further. However, aerobic reactor must have long HRT to treat high concentration of organic contaminant included in this wastewater, so the large site area is required. And settling tank which is normally applied for wastewater treatment facility has some problems such as water quality degradation caused by the sludge spill. To solve these problems, we applied MBR system for the wastewater. And the MBR pilot plant was installed nearby the wastewater treatment facility of W food factory and operated during long term to evaluate treatment efficiency. This plant was operated about 3 months and than the result was 97% of organic removal rate on conditions of flow rate $20m^3/day$, HRT 29 hr, recycle 4Q. However, contaminant removal ratio of bio-reactor decreased and TMP of membrane increased rapidly on more conditions.