• International Journal of Automotive Technology
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• v.7 no.1
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• pp.83-90
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• 2006

The purpose of this paper is to describe the design and implementation of an unmanned ground vehicle, called the TailGator at CIMAR (Center for Intelligent Machines and Robotics) of the University of Florida. The TailGator is a gas powered, four-wheeled vehicle that was designed for the AUVSI Intelligent Ground Vehicle Competition and has been tested in the contest for 2 years. The vehicle control model and design of the sensory systems are described. The competition is comprised of two events called the Autonomous Challenge and the Navigation Challenge: For the autonomous challenge, line following, obstacle avoidance, and detection are required. Line following is accomplished with a camera system. Obstacle avoidance and detection are accomplished with a laser scanner. For the navigation challenge, waypoint following and obstacle detection are required. The waypoint navigation is implemented with a global positioning system. The TailGator has provided an educational test bed for not only the contest requirements but also other studies in developing artificial intelligence algorithms such as adaptive control, creative control, automatic calibration, and internet-base control. The significance of this effort is in helping engineering and technology students understand the transition from theory to practice.

• Journal of the Korean Geotechnical Society
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• v.18 no.2
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• pp.23-37
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• 2002

Failure of the cut slope is triggered by combination of internal and extemal failure factors. Internal failure factors are related to geological and geometrical conditions of slope itself, and natural and/or artificial loadings on slope can be the external failure factors. Influences of these failure factors show different intensity according to the ground condition and are controlled by behavior characters of the slope. In this study, the soil depth ratio(SR), block size ratio(BR) and rock strength are used as the criteria to divide ground condition based on behavior characteristics. Ground condition of the slope is divided into discontinuous jointed rock mass and continuos soil-like mass, highly fractured rock mass and massive rock mass by the criteria(SR and BR). The SFi-system is a rating system to determine the slope failure index(SFi) by analyzing internal and external factors based on classification of the ground condition. The results of the SFi-system application to the real cut slopes show close relationship between the SFi value and potential or dimension of the failure. Therefore, the SFi-system can be used as a useful tool to predict and analyze the characteristic of the slope failure.

• Journal of the Korean GEO-environmental Society
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• v.24 no.5
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• pp.13-20
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• 2023

The Gangneung region has an environment suitable for the formation of organic soil, and there is an alluvial layer in which sedimentary sand layers are distributed on the upper and lower parts of the organic soil. In order to evaluate the seismic safety of the railway roadbed passing through the Gangneung area, a railway roadbed and ground model considering the similarity ratio was fabricated, a shaking table test was conducted, and the seismic stability was evaluated by comparing the effective stress analysis results. The applied seismic waves were artificial seismic waves, Gyeongju seismic waves, Borah seismic waves, Nahanni seismic waves, and Tabas seismic waves. It became. Due to the ground reinforcement effect by jet grouting applied to the lower ground of the new roadbed, the displacement of the new roadbed was found to be reduced from a minimum of 33.7% to a maximum of 56.7% compared to the existing roadbed. The shaking table test results were verified by effective stress analysis using the Finn model of the Flac program, and showed a similar trend to the shaking table test values.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2020.11a
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• pp.54-55
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• 2020

In 4th Industrial Revolution, technologies such as artificial intelligence, Internet of Things, and Big data are closely related to the maritime industry, which led to the birth of autonomous vessels. Due to the technical characteristics of the current vessel, the speed cannot be suddenly lowered, so complex communication such as the help of a tug boat, boarding of a pilot, and control of the vessel at the onshore control center is required to berth at the port. In this study, clustering analysis was used to resolve how to establish control criteria for vessels to enter port when autonomous vessels are operating. K-Means clustering was used to quantitatively stage the arrival pattern based on the accumulated AIS(Automatic Identification System) data of the incoming vessel, and the arrival phase using SOG(Speed over Ground), COG(Course over Ground), and ROT(Rate of Turn) Was divided into six phase.

• Economic and Environmental Geology
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• v.57 no.1
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• pp.17-23
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• 2024

Ground penetrating radar (GPR) survey is a geophysical method that utilizes electromagnetic waves reflecting from a boundary where the electromagnetic property changes. As the frequency of the antenna is about 25 MHz ~ 1 GHz, it is effective to acquire high resolution images of underground pipe, artificial structure, underground cavity, and underground structure. In this study, we analyzed the change of signals reflected from the same underground objects according to the arrangement of transceiver antennas used in ground penetrating radar survey. The antenna used in the experiment was 200 MHz, and the survey was performed in the vertical direction across the sewer and the parallel direction along the sewer to the sewer buried under the road, respectively. A total of five antenna array methods were applied to the survey. The most used arrangement is when the transmitting and receiving antennas are all perpendicular to the survey line (PR-BD). The PR-BD arrangement is effective when the object underground is a horizontal reflector with an angle of less than 30°, such as the sewer under investigation. In this case study, it was confirmed that the transmitter and receiver antennas perpendicular to the survey line (PR-BD) are the most effective way to show the underground structure. In addition, in the case where the transmitting and receiving antennas are orthogonal to each other (XPOL), no specific reflected wave was observed in both experiments measured across or parallel to the sewer. Therefore, in the case of detecting undiscovered objects in the underground, the PR-BD array method in which the transmitting and receiving antennas are aligned in the direction perpendicular to the survey line taken as a reference and the XPOL method in which the transmitting and receiving antennas are orthogonal to each other are all used, it can be effective to apply both of the above arrangements after setting the direction to 45° and 135°.

• Journal of Korean Society of Forest Science
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• v.78 no.2
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• pp.209-217
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• 1989

Seedlings of 6 tree species were treated with artificial acid rain and acid mist (pH 5.0, 4.0, 3.0) and ground water (pH 6.5), to select $SO_2$-resistant tree species. The growth variable, leaf injury rate and chlorophyll content were measured and compared among the various pH levels. Seedling height of Rosy multiflora decreased with deceasing pH levels of artificial acid rain and was tallest at control plot, but that of Ailanthus altissima was tallest at pH 5.0 plot. For the seedlings of Robinia pseudoacacia, Magnolia obovata and Wistaria floribunda, top and root dry weights per seedling at pH 5.0 plot were higher than those at control plot. Leaf injury rate(injured leaf area and injured leaf rate) increased with decreasing pH levels of artificial acid rain, the changes of leaf chlorophyll content was slightly different among tree species. Leaf chlorophyll content of Rosa multiflora, measured during the period July to September, decreased with decreasing pH levels of artificial acid rain. Leaf chlorophyll content of Magnolia obovata increased on July, but decreased severely on September, with decreasing pH levels, of artificial acid rain.

• Journal of the Korean Institute of Landscape Architecture
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• v.37 no.5
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• pp.98-108
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• 2009

The purpose of this study is to analyze the characteristics of limited methods, economics and breeding appropriateness of native and imported ground cover plants in the methodology of a shallow soil rooftop garden. The new shallow soil rooftop gardening method uses a total of 13cm in soil thickness, including 4.5cm of top soil on a 7.5cm rock-wool-mat stacked onto a 1cm roll-type-draining plate. The total construction cost for each method of soil level within the design price standard for SEDUM BLOCK is 89,433won/$m^2$, and for DAKU is 92,550won/$m^2$. By comparing those two methods, the construction cost of the shallow soil artificial foundation methodology is 45,000won/$m^2$; this shows the new method is 50% less expensive than the existing method of shallow soil rooftop gardening. The experiment was executed on the rooftop of the Korean National Housing Corporation to ensure validity of the shallow soil artificial foundation planting, and the sample plants which were imported and grown now in native covering. A list investigating the growing plants was made of the cover rate in each plant class, both while alive and the dry plant weight. The native ground cover plants, Sedum kamtschaticum, Sedum middendorffianum, Allium senescens, Sedum sarmentosum, Aquilegia buergariana, and Caryopteris incana increased the cover rate, live weight and dry weight in the shallow soil artificial foundation method. Among the imported cover plants, Sedum sprium and Sedum reflexum, the cover rate increased and growth conditions improved. However, some species needed weed maintenance. After examination with the less expensive shallow soil artificial foundation method and growth analysis, it was found that rooftop gardens are a low-cost option and the growth of plants is great. This result shows the new method can contribute to the proliferation of rooftop gardens in urban settings.

• Journal of the Korean Geosynthetics Society
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• v.20 no.4
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• pp.85-93
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• 2021

The seventy percentage of Korean Peninsular is covered by the mountainous area, and the depth of west sea and south sea is relatively shallow. Therefore, a large scale land reclamation from the sea has been implemented for the construction of industrial complex, residental area, and port and airport facilities. The common problem of reclaimed land is consisted of soft ground, and hence it has low load bearing capacity as well as excessive settlement upon loading on the ground surface. The hollow concrete block has been used to reinforce the loose and soft foundation soil where the medium-high apartment or one-story industrial building is being planned to be built. Recently the earthquakes with the magnitude of 4.0~5.0 have been occurred in the west coastal and southeast coastal areas. Lee (2019) reported the advantages of hollow concrete block reinforced shallow foundation through the static laboratory bearing capacity tests. In this study, the dynamic behavior of hollow concrete block reinforced sandy ground with filling the crushed stone in the hollow space has been investigated by the means of shaking table test with the size of shaking table 1000 mm × 1000 mm. Three types of seismic wave, that is, Ofunato, Hachinohe, Artificial, and two different accelerations (0.154 g, 0.22 g) were applied in the shaking table tests. The horizontal displacement of structure which is situated right above the hollow concrete block reinforced ground was measured by using the LVDT. The relative density of soil ground are varied with 45%, 65%, and 85%, respectively, to investigate the effectiveness of reinforcement by hollow block and measured the magnitude of lateral movement, and compared with the limit value of 0.015h (Building Earthquake Code, 2019). Based on the results of shaking table test for hollow concrete block reinforced sandy ground, honeycell type hollow block gives a large interlocking force due to the filling of crushed stone in the hollow space as well as a great interface friction force by the confining pressure and punching resistance along the inside and outside of hollow concrete block. All these factors are contributed to reduce the great amount of horizontal displacement during the shaking table test. Finally, hollow concrete block reinforced sandy ground for shallow foundation is provided an outstanding reinforced method for medium-high building irrespective of seismic wave and moderate accelerations.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.2 no.2
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• pp.24-32
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• 1999

To develope appropriate soil base for planting on the artificial ground, 9 kinds of soil types(varying the components and mixing ratios) and 3 levels of soil depths(10cm, 15cm, 20cm) were chosen. And their plant growing effects were tested and analysed from the test plant Zoysia japonica. The results of the research are as follows. 1. Among the 9 type of soil mixtures, the "sandy loam" soil type gave the worst effects on germination, disease contamination and ground covering. 2. The soil types like VSH(vermiculite20%+sand70%+humus sawdust10%), VSS(vermiculite 40%+sand 50%+humus sawdust 10%) and VS(vermiculite 70%+sand 30%), where vermiculite and sand were added to, show better germination effect promoted from the better condition of aeration and saturation. 3. The plant growing effects(leaf length and ground covering ratio) was evident under the soil types like VSH(vermiculite20%+sand70%+humus sawdust10%) and VSS(vermiculite40%+sand50%+humus sawdust10%), where organic matters were added to. 4. Vermiculite added soil types effect fast leaf decolorization on the tested Zoysia japonica plant, on the contrary to organic matter mixed soil types including SCS(sandy loam 50%+carbonized rice husk30%+sand20%) and SHS(sandy loam 50%+humus sawdust30%+sand20%) with which green leaves subsist longer. S. Soil depth effect to plant growth was found. And a favorable covering rate was accomplished even at the soil depth of 15cm - the limit soil depth for grass survival - from the soil types where organic matters were mixed to. From this result, the soil depth limit for plant survival could be said to be shall owed if appropriate soil type were based.

• Geophysics and Geophysical Exploration
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• v.10 no.3
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• pp.191-202
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• 2007

To identify the detailed attenuation structure in the southern Korean Peninsula, a numerical test was conducted for the Q tomography inversion to be applied to the accumulated dataset until 2005. In particular, the stochastic pointsource ground-motion model (STGM model; Boore, 2003) was adopted for the 2D Q tomography inversion for direct application to simulating the strong ground-motion. Simultaneous inversion of the STGM model parameters with a regional single Q model was performed to evaluate the source and site effects which were necessary to generate an artificial dataset for the numerical test. The artificial dataset consists of simulated Fourier spectra that resemble the real data in the magnitude-distance-frequency-error distribution except replacement of the regional single Q model with a checkerboard type of high and low values of laterally varying Q models. The total number of Q blocks used for the checkerboard test was 75 (grid size of $35{\times}44km^2$ for Q blocks); Q functional form of $Q_0f^{\eta}$ ($Q_0$=100 or 500, 0.0 < ${\eta}$ < 1.0) was assigned to each Q block for the checkerboard test. The checkerboard test has been implemented in three steps. At the first step, the initial values of Q-values for 75 blocks were estimated. At the second step, the site amplification function was estimated by using the initial guess of A(f) which is the mean site amplification functions (Yun and Suh, 2007) for the site class. The last step is to invert the tomographic Q-values of 75 blocks based on the results of the first and second steps. As a result of the checkerboard test, it was demonstrated that Q-values could be robustly estimated by using the 2D Q tomography inversion method even in the presence of perturbed source and site effects from the true input model.