• Journal of the Korean Geotechnical Society
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• v.34 no.1
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• pp.5-16
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• 2018

In this study, seismic performance of geotechnical seismic isolation system capable of primary seismic isolation in the ground was evaluated. 1-G shaking table test was used to assess the performance of Teflon or steel slag as geotechnical seismic isolation systems installed beneath superstructure foundation. Response acceleration and response spectra were analyzed considering different input motions. The results were compared with those of fixed foundation structure without seismic isolation system. The steel slag-type seismic isolation system showed significant reduction in acceleration. The teflon-type seismic isolation system did not show significant effects on acceleration reduction in low-to-moderate seismicity condition, but it did show better effects in case of strong seismic condition. As input motion was transferred to the upper mass, the response spectrum of the fixed foundation structure was amplified in the short period range. In contrast, the response spectrum of the structure with seismic isolation using teflon or steel slag amplified in the long period range. It is found that the change of periodicity and the friction characteristics between isolation materials and foundations affected acceleration reduction.

• KIPS Transactions on Computer and Communication Systems
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• v.2 no.10
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• pp.427-436
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• 2013

In this paper, a method of moving path control of an automatic guided vehicle in an indoor environment through recognition of marker images using vision sensors is presented. The existing AGV moving control system using infrared-ray sensors and landmarks have faced at two critical problems. Since there are many windows in a crematorium, they are going to let in too much sunlight in the main hall which is the moving area of AGVs. Sunlight affects the correct recognition of landmarks due to refraction and/or reflection of sunlight. The second one is that a crematorium has a narrow indoor environment compared to typical industrial fields. Particularly when an AVG changes its direction to enter the designated furnace the information provided by guided sensors cannot be utilized to estimate its location because the rotating space is too narrow to get them. To resolve the occurrences of such circumstances that cannot access sensing data in a WSN environment, a relative distance from marker to an AGV will be used as fingerprinting used for location estimation. Compared to the existing fingerprinting method which uses RSS, our proposed method may result in a higher reliable estimation of location. Our experimental results show that the proposed method proves the correctness and applicability. In addition, our proposed approach will be applied to the AGV system in the crematorium so that it can transport a dead body safely from the loading place to its rightful destination.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.6
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• pp.615-624
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• 2014

It has been well known the sloshing pressure has complex shape and various patterns. The pattern of sloshing pressure is variously characterized by the pressure amplitude, duration time and skewness. The structural response induced by the sloshing pressure is also affected by the pattern of sloshing pressure and the type of structural members. In order to understand the structural response by the perspective view of categorized pattern, it is more efficient to make simple sloshing pressure pattern than to reflect the complex pressure history. In this study, the sloshing pressures obtained by the small scale model test are simplified with respect to their duration and skewness. Dynamic analyses of Mark-III LNG CCS are then parametrically performed with the consideration of various types of sloshing impact. Meanwhile, the failure pressures given the duration and skewness are investigated after parametric calculations are conducted to investigate the effect of pressure parameters on the structural response.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.3D
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• pp.363-373
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• 2011

With rapid economic development, general demand and interest in surroundings that consist of our lives have grown gradually. In addition, as there has been increased social interest in creating landscape of roads, which considers all important factors from the user's view including accessibility, safety, and psychological stability, efforts to improve quality of roads are required. Therefore it is needed to establish standards on safe and comfort road design based on sensibility satisfaction of road users rather than based on standardized road design guidance from the engineering perspective. To this end, research was carried out to analyze sensibility satisfaction of users about road landscape focused on elements of road cross section in a city. It identified relation between sensibility satisfaction and the elements by using principal and cluster analysis, and the multiple regression models. It also found that user's satisfaction about roads and a road landscape is high with road width (3~5 meters), clear zone (2.2~3.9 meters), road central garden (1.05~1.9 meters), shoulder (0.55~1.43 meters), median (0.65~1.625 meters), the number of travel lanes (2~5), height of trees at the central garden (6.4~15 meters) and height of buildings surrounding roads (18~44 meters or 6~15 floors).

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.9
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• pp.756-761
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• 2016

The objective of this study is to design and manufacture a fuel pump with the plunger diameter of 4 mm and stroke of 7 mm that can be mounted in a small single-cylinder four-stroke agricultural diesel engine, and to investigate the performance characteristics of the pump. The combustion pressure in a cylinder was reproduced by forming the back pressure of 1, 6, 11, 16 and 21 bar with a nitrogen gas in the home-manufactured modeling cylinder. In the experiment, the discharge pressure was measured at the spot of 1 cm away from the discharge port of a developed fuel pump. The delivery pressure and delivery flow rate were measured at the spot of 30 cm away from the discharge port of the pump, and the pump efficiency was calculated. The pump motor speed was changed from 600 to 800, 1000, 1200 and 1400 rpm. It is found that the delivery feed rate of fuel pump is increased as the rotational speed is raised, and is decreased as the back pressure, compression pressure in the cylinder, is increased. Also, the pump efficiency is reduced as the rotational speed and back pressure are increased.

• Geophysics and Geophysical Exploration
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• v.11 no.2
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• pp.116-126
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• 2008

In gas hydrate survey, seismic amplitude and frequency characteristics play a very important role in determining whether gas hydrate exists. According to the variation of source frequency and scatterer size, we study seismic amplitude characteristics using elastic modeling applied at staggered grids. Generally speaking, scattering occurs in proportion to the square of source frequency and the scatterer volume, which has an effect on seismic amplitude. The higher source frequency is, the more scattering occurs in gas hydrate bearing zone. Therefore, BSR is hardly observed in high frequencies. On the other side, amplitude blanking zone and BSR is clearly observed in lower frequencies although the resolution is poor as a whole. Seismic reflections traveling through free-gas layer below gas hydrate bearing zone decay so severely a high frequency component that a low frequency term is dominant. Amplitude anomaly of BSR result from high acoustic impedance contrast due to free-gas, which is a very crucial factor to estimate gas hydrate bearing zone. Seismic frequency analysis is carried out using wavelet transform method that frequency component could be decomposed with time variation. In application of wavelet transform to the seismic physical experiments data, we can observe that reflections traveling through air layer, which corresponds to the free-gas layer, decay a high frequency component.

• Journal of Convergence Society for SMB
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• v.3 no.2
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• pp.1-8
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• 2013

This study examine the relation between small and medium firm's stability and tax avoidance. We use some financial data of small and medium IT firms in KOSDAQ during 2001 to 2009. Following previous research(Desai and Dhamapala 2006), we estimate corporate tax avoidance. And we use quick ratio and current ratio as a short-term stability and equity ratio as a long-term stability. Empirical results follows as. First, It was not significant statistically between short-term stability and corporate tax avoidance. Second, it was significant statistically between the long-term stability and corporate. As corporate tax avoidance increases, the long-term stability(equity ratio) was low. Our analysis provides the empirical evidence between long-term stability and tax avoidance. It offers implications of corporate tax avoidance to small and medium IT firms in KOSDAQ. But this results is difficult generalization because of sample limits.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.13 no.1
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• pp.117-127
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• 1991

When open reduction of maxilla fractures is postponed due to concurrent life-threatening injuries, delayed union may result with malunion or nonunion. If delayed malunion is occurred, significant facial deformity may result, including a dished-out face, irregular retromaxillism with Angle's class III malocclusion, open anterior bite, nasal collapse, telecanthus and malar flattening. The treatment planning for this problem includes cephalometric evaluation anterior and lateral tomograms, dental casts, orthodontic planning, dental planning and use of impression tray to rupture the fibrous tissue casts, orthodontic planning, dental planning and use of impression tray to rupture the fibrous tissue attachment at the fracture site. In this paper, one case presented a 58-year-old female patient with maxilla retrusion after comminuted fracture, who was treated with orthodontic methods of maxillary protraction headgear and Plaster headcap, whereas the other two cases were about male patients who were treated principally with surgically open reduction or Le Fort I-controlled transverse osteotomy with iliac bone graft.

• Journal of the Korean Magnetics Society
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• v.14 no.6
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• pp.219-223
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• 2004

L $i_{0.5}$F $e_{2.5-{\chi}}$R $h_{\chi}$ $O_4$ ($\chi$ = 0.25, 0.50, 0.75, 1.00) has been prepared by solid state reaction. Crystallographic and magnetic properties were investigated by Mossbauer spectroscopy, SQUID magnetometry, and x-ray diffraction. The crystal structure is found to be a cubic spinel structure with space group Fd3m for all the samples. The lattice constant $a_{0}$ increases from 8.3365 $\AA$ to 8.3932 $\AA$ with increasing Rh concentration $\chi$. The migration of Li ion has been confirmed by x-ray patterns and the results of applied field Mossbauer analysis. The temperature dependence of the absorption area of each site was analyzed with the Debye model for the recoil-free fraction. The Debye temperature for the octahedral sites is almost as large as for the tetrahedral sites, thereby suggesting similar inter-atomic binding forces for the octahedral and the tetrahedral sites. The saturated magnetic moment and the Mossbauer spectra taken at 4.2 K under the applied field (6 T) show that the spin structure of L $i_{0.5}$F $e_{2.5-{\chi}}$R $h_{\chi}$ $O_4$ is compatible with the collinear Neel Model.

• Journal of the Earthquake Engineering Society of Korea
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• v.16 no.4
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• pp.19-26
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• 2012

For a seismic design or performance evaluation of a structure, an experimental investigation on a scale model of the structure or numerical analysis based on the finite element model is considered. Regarding the numerical analysis, a three-dimensional finite element analysis is performed if a high accuracy of the results is required, while a sensitivity or fragility analysis which uses huge seismic ground motions leads to the use of a lumped-mass stick model. The conventional modeling technique to build the lumped-mass stick model calculates the amount of the lumped mass by considering the geometric shape of the structure, like a tributary area. However, the eigenvalues of the conventional model obtained through such a calculation are normally not the same as those of the actual structure. In order to overcome such a deficiency, in this study, a new lumped mass stick model is proposed. The model is named the "frequency adaptive-lumped-mass stick model." It provides the same eigenvalues and similar dynamic responses as the actual structure. A non-prismatic column is considered as an example, and its natural frequencies as well as the dynamic performance of the new lumped model are compared to those of the full-finite element model. To investigate the damping effect on the new model, 1% to 5% of the critical damping ratio is applied to the model and the corresponding results are also compared to those of the finite element model.