• Journal of the Korean GEO-environmental Society
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• v.13 no.2
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• pp.27-39
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• 2012

This research is to propose the reinforcing method and design code for the lateral behaviors of the abutment displacement induced from the rainfall infiltration on high landfill slope. First, to make the proper numerical analysis, in-situ soil (weathered granite soil) was taken, and the variance of strength parameters according to water content variance was examined by undrained direct shear test, furthermore, other soil parameters were calculated from the standard penetration test such as elastic modulus and Poisson's ratio etc,. Those parameters were used to calculate the lateral behavior of abutment by finite element method and the member force of pile in high landfill slope according to rainfall infiltration . From the results, the shoe displacement on abutment was calculated as 8.98cm, which is 3 times bigger than the allowable displacement, 3cm. To reinforce it, several reinforcing methods were selected and analyzed such as reinforced retaining wall, soil surcharge, pile reinforcing (5m enlargement, 3-line arrangement, 5m enlargement and 3-line arrangement). In case of 5m enlarged and 3-line arrangement piles, the lateral behavior of shoe showed lower value(2.26 cm) than allowable displacement.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.5 no.6
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• pp.72-85
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• 2002

This study was conducted to investigate the germination rates and ground coverage rates of the 16 native wild flower, herbaceous, shrub and woody plants according to temperature and seeding timing for the revegetation and rehabilitation of the roadside slopes. Also, this study was conducted to suggest design criteria to select revegetation plants and to decide proper seed mixture for ecological restoration of the disturbed manmade slopes as a environmentally friendly construction. The results are summarized as follows. 1. Most of the plants germinated after 10~14 days. Woody plants germinated more slowly than wild flowers and herbaceous plants because of the hard seed. 2. Most of the plants showed the highest percentage of the germination rates under $15/25^{\circ}C$ temperature. The next was in order of under the $20/30^{\circ}C$ temperature, normal temperature(October) and $25/35^{\circ}C$ temperature. 3. At the chamber experiment, the Sorbaria sorbifolia var. stellipila showed the highest germination rates. Most of the native wild flowers germinated well and showed high germination rates under the various temperature. 4. As the field germination experiments, the seeding at August shows higher germination rates than that of the seeding at September, but showed lower surviving percentage of the germinated seedlings and lower ground coverage percentage than those of the seeding at September. After one year, Chionanthus retusus, Acer palmatum, Albizzia julibrissin are germinated and showed 10% coverage rates. So, they can be used as revegetation plants for the restoration works. 5. As seed mixture experiment, it was not effective only to increase the proportion of the ratio of the tree seeds, relatively high price, for making woody vegetation. It would be more successful to make vegetation structure by natural competition among wild flowers, shrubs and trees. 6. The excessive dominance of trees in revegetation works may destroy the lower layer of vegetation and it will be undesirable on the species diversity. It is more important to recover the species diversity of the plant community by seed mixture with the considering the germination, the growth characteristics and the correlation effect among revegetation plants. 7. To recover the manmade slopes quickly, increasing the ratio of the wild flower was recommended.

• Journal of Wetlands Research
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• v.17 no.3
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• pp.303-310
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• 2015

Recently the water quality management policy gives priority to management the point source. Point pollution sources have definite emission points and are discharged to one point through a pipe. But Nonpoint pollution source (NPS) has uncertain pathway, pollutant load and runoff characteristics unlike point pollution sources, making them difficult to manage. Thus, the Korea government plans to develop and equip facilities that help reduce NPS so as to manage them more easily. But removal efficiency of Best Management Practice (BMPs) is in influenced by rainfall, hydrologic condition like natural phenomenon, so factors of removal efficiency are difficult. Thus there is a need for multilateral research about many factors that affect removal efficiency for removal facility design of proper non-point pollution. In this research, mapping, vegetation coverage and retention time were investigated in the case of factors that affect removal efficiency in grassed swale, a nature-type non-point removal facility. Grassed swale obtained changed of coverage using Braun-Blanquet within swale and retention time was obtained from point that rainfall effluent enters into swale to the time that first outflow starts. Besides, correlation analysis was obtained using pearson correlation analysis method. As a result, it was shown that removal efficiency increases as retention time is longer in grassed swale and that retention time increases as vegetation coverage is higher.

• International Journal of Highway Engineering
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• v.13 no.3
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• pp.93-102
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• 2011

The Korean government recently has focused on variety of policies to promote the use of bikes to control the emission of carbon. However, bike facilities with no regard to the safety and comfort of bike drivers has made inefficient bike roads. Also, the accidents related to bikes have increased rapidly. This study proposes the proper types of the bike roads considering land use and bike driver characteristics. The elements classifying the bike driver characteristics are driven through oneway ANOVA and cluster analysis. It is found that the types of the bike roads can be classified by the ratio of child and elderly bikers and the ratio of heavy trucks. Also, the each type is characterized by the land use types such ad residential, commercial and industrial areas through cluster analysis. According to the results of the cluster analysis, installation of bike roads in residential area needs to consider convenience and safety simultaneously. It is also found that convenience should be the most considerable factor in commercial area. Lastly, safety should be considered in industrial area. Recommended methodology and bike road type based on the land use and bike driver's characteristics can be useful to develop bike-friendly environments and increase mode share of bikes.

• Journal of the Korean Society for Railway
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• v.16 no.5
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• pp.386-393
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• 2013

In this study, the so-called repeated plate load bearing test (RPBT) used to get $E_{v2}$ values in order to check the degree of compaction of subgrade, and to get design parameters for determining the thickness of the trackbed foundation, is investigated. The test procedure of the RPBT method is scrutinized in detail. $E_{v2}$ values obtained from the field were verified in order to check the reliability of the test data. The $E_{v2}$ values obtained from high-speed rail construction sites were compared to converted modulus values obtained from resonant column (RC) test results. For these tests, medium-size samples composed of the same soils from the field were used after analyzing stress and strain levels existing in the soil below the repeated loading plates. Finite element analyses, using the PLAXIS and ABAQUS programs, were performed in order to investigate the impact of the strain influence coefficient. This was done by getting newly computed $I_z$ to get the precise strain level predicted on the subgrade surface in the full track structure; under wheel loading. It was verified that it is necessary to use precise loading steps to construct nonlinear load-settlement curves from RPBT in order to get correct $E_{v2}$ values at the proper strain levels.

• Journal of Digital Convergence
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• v.10 no.10
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• pp.215-220
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• 2012

This paper proposes a ontology of tree structure approach for adaptive object recognition in a situation-variant environment. In this paper, we introduce a new concept, ontology of tree structure ontology, for context sensitivity, as we found that many developed systems work in a context-invariant environment. Due to the effects of illumination on a supreme obstinate designing context-sensitive recognition system, we have focused on designing such a context-variant system using ontology of tree structure. Ontology can be defined as an explicit specification of conceptualization of a domain typically captured in an abstract model of how people think about things in the domain. People produce ontologies to understand and explain underlying principles and environmental factors. In this research, we have proposed context ontology, context modeling, context adaptation, and context categorization to design ontology of tree structure based on illumination criteria. After selecting the proper light-ontology domain, we benefit from selecting a set of actions that produces better performance on that domain. We have carried out extensive experiments on these concepts in the area of object recognition in a dynamic changing environment, and we have achieved enormous success, which will enable us to proceed on our basic concepts.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.9
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• pp.251-258
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• 2012

Recently, NAND Flash memory structure is evolving from SDR (Single Data Rate) to high speed DDR(Double Data Rate) to fulfill the high performance requirement of SSD and SSS. Accordingly, the proper ways of transferring data that latches valid data stably and minimizing data skew between pins by using PHY(Physical layer) circuit techniques have became new issues. Also, rapid growth of speed in NAND flash increases the operating frequency and power consumption of NAND flash controller. Internal voltage variation margin of NAND flash controller will be narrowed through the smaller geometry and lower internal operating voltage below 1.5V. Therefore, the increase of power budge deviation limits the normal operation range of internal circuit. Affection of OCV(On Chip Variation) deteriorates the voltage variation problem and thus causes internal logic errors. In this case, it is too hard to debug, because it is not functional faults. In this paper, we propose new architecture that maintains the valid timing window in cost effective way under sudden power fluctuation cases. Simulation results show that the proposed technique minimizes the data skew by 379% with reduced area by 20% compared to using PHY circuits.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.4
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• pp.49-60
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• 2010

Semiconductor packages are increasingly moving toward miniaturization, lighter and high performance. Futhermore, packages become thinner. Thin packages will generate serious reliability problems such as warpage, crack and other failures. Reliability problems are mainly caused by the CTE mismatch of various package materials. Therefore, proper selection of the package materials and geometrical optimization is very important for controlling the warpage and the stress of the package. In this study, we investigated the characteristics of the warpage and the stress of several packages currently used in mobile devices such as CABGA, fcSCP, SCSP, and MCP. Warpage and stress distribution are analyzed by the finite element simulation. Key material properties which affect the warpage of package are investigated such as the elastic moduli, CTEs of EMC molding and the substrate. Geometrical effects are also investigated including the thickness or size of EMC molding, silicon die and substrate. The simulation results indicate that the most influential factors on warpage are EMC molding thickness, CTE of EMC, elastic modulus of the substrate. Simulation results show that warpage is the largest for SCSP. In order to reduce the warpage, DOE optimization is performed, and the optimization results show that warpage of SCSP becomes $10{\mu}m$.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.40 no.1
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• pp.1-11
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• 2020

Medium to large post structures installed along the roadside without proper protection can lead to serious vehicle damage and occupant injury at the impact. In North America and Europe, splitting systems such as slip base or breakaway device are used to reduce impacts. But the system has the risk of secondary accident when the splitted post falls down to the traffic or pedestrian. Sliding Post have been proposed as a way to solve this problem. By studying the crash test results of the 1.3ton and 0.9ton vehicle with 60 km/h and 80 km/h to a Rigidly Fixed Post (RFP) and Sliding Post (SP), danger of the conventional RFP and crashworthiness of the SP have been proven. While collision analysis only from the acceleration measured at the center of the vehicle assumes the motion of the post is the same as that of the vehicle, in this paper, by adding high speed film data to the analysis with vehicle acceleration could have separate the post motion from the vehicle motion. It gives better explanations on the movement of post and vehicle in each distinctive time step and provides basics to the crashworthy post design.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.10 no.4
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• pp.287-294
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• 2016

Based on upper limb torque by different angles of a back, distance between crank axis and chest and angles of hand-grips, this research is to develop variable hand bikes. By doing so, it is to offer guidance for its design. For this research three normal persons took part in the experiment. Results are as follows. First, upper limb torque was found to be the highest at 50 degree of a back and muscle endurance was shown to be the highest at 80 degree of a back. It means that as a back of a chair gets lower the speed and efficiency becomes better, which contradicts the subjective fact that K-type hand bikes would show the highest speed. Second, among types of grips of hand bikes 45 degree ones have been shown to be the ones with the highest torque. This is due to proper distribution of power of joints in arms, elbows, and shoulders. Third, in case of distance of 45cm between crank axis and chest, it has shown the most efficient torque. This is because of the effect of gravity and exhaustion when handling.