• Journal of the Korean GEO-environmental Society
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• v.5 no.3
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• pp.61-70
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• 2004

N-value by the SPT is one of the key parameter for settlement evaluation. However, if the ground is firm, the usual N-value is not blow count of 30cm depth penetration. In such case, if N-value is more than 50 with 30cm penetration, the N-value 50 is applied for settlement analysis. Therefore, in this study, the modified method of N-value estimation is suggested and compared the settlement by Elastic Theory, and the measured field data by Plate Load Test. As the result of this study, it is shown that the settlement by Elastic Theory with the modified N-value is more accurate than settlement by usual N-value. The application of Elastic Theory for pure sand is also evaluated in this paper.

• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.189-197
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• 2002

The bearing capacity of open-ended piles is affected by the degree of soil plugging, which is quantified by the incremental filling ratio, IFR. There is not at present a design criterion for open-ended piles that explicitly considers the effect of IFR on pile load capacity. In order to investigate this effect, model pile load tests using a calibration chamber were conducted on instrumented open-ended piles. The results of these tests show that the IFR can be estimated from the plug length ratio PLR, which is defined as the ratio of soil plug length to pile penetration depth. The unit base and shaft resistances decrease with increasing IFR. Based on the results of the model pile tests, new design equations for calculating base load capacity and shaft load capacity of open-ended piles are proposed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.1
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• pp.175-183
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• 2014

This study investigates the response of structures to tunnelling-induced ground movements in clay ground, varying tunnel excavation condition (tunnel depth and diameter), tunnel construction condition (ground loss), and tunnel ground condition (soft clay and stiff clay). Four-story block-bearing structures have been used because the structures can easily be characterized of the extent of damages with crack size and distribution. Numerical parametric studies have been used to investigate of the response of structures to varying tunnelling conditions. Numerical analysis has been conducted using Discrete Element Method (DEM) to have real cracks when the shear and tensile stress exceed the maximum shear and tensile strength. The results of structure responses from various parametric studies have been integrated to consider tunnel excavation condition, tunnel construction condition, and tunnel ground condition and provide a relationship chart among them. Using the chart, the response of structures to tunnelling can easily be evaluated in practice in clay ground.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.11
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• pp.2305-2311
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• 2002

The pressure tube is a major component of the CANDU reactor, which supports nuclear fuel bundle and heavy water coolant. Pressure tubes are installed horizontally inside the reactor and only selected samples are periodically examined during in-service inspection. In this respect, a probabilistic safety assessment method is more appropriate fur the assessment of overall pressure tube safety. The failure behavior of CANDU pressure tubes, however, is governed by delayed hydride cracking which is the major difference from pipings and reactor pressure vessels. Since the delayed hydride cracking has more widely distributed governing parameters, it is impossible to apply a general PFM methodology directly. In this paper, a PFM methodology for the safety assessment of CANDU pressure tubes is introduced by applying Monte Carlo simulation in determining failure probability Initial hydrogen concentration, flaw shape and depth, axial and radial crack growth rate and fracture toughness were considered as probabilistic variables. Parametric study has been done under the base of pressure tube dimension and hydride precipitation temperature in calculating failure probability. Unstable fracture and plastic collapse are used for the failure assessment. The estimated failure probability showed about three-order difference with changing dimensions of pressure tube.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.2 no.1
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• pp.29-37
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• 1999

Land cover classification is an essential basic information in natural environment management; however, land cover classification studies in Korea have not yet been proceeded to a sufficient level. At the present, only a limited number of the precedent studies that only cover definite city area has been conducted. Furthermore, there is almost no research conducted on the land cover classification schemes that could accurately classify the Korea's land cover conditions. This study primarily focuses on the land cover classification scheme which carries the most urgent priority in order to classify and to map out the Korean land cover conditions. In order to develop the most suitable land cover classification scheme, many foreign land cover classification cases and projects that are being carried out were reviewed in depth. The land cover classification scheme this study proposes comprises 3 levels : The first level consists of 7 different classes; the second level consists of 22 different classes; and the third level is made up of 50 classes. The land cover classification map will serve many important roles in natural environment management, such as the conjecture of natural habitats and estimation of oxygen production or carbon dioxide absorption capability of a forest. In water pollution modelling, the land cover classification data can be used to estimate and locate non-point sources of water pollution. If applied to a watershed, modelling it will allow to estimate the total amount of pollution from non-point sources of pollution in the water shed. The land cover classification data will also be good as a barometer data that determines defusion of air pollutants in air pollution modelling.

• Journal of Internet Computing and Services
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• v.8 no.5
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• pp.117-123
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• 2007

Catadioptric mirrors are widely used in automatic surveillance system. The major drawback of catadioptric mirror is its unequal image resolution. Equidistance catadioptric mirrir can be the solution to this problem. The exact axial alignment and the exact mount of mirror are the sources that can be avoided but the focal length variation is inevitable. In this paper, the effects of focal length variation on the computation of depth and height of object' point are explained and the effective and simple focal length finding algorithm is presented. First two object's points are selected, and the counterparts on the other stereo image are to be found using MSE criterion. Using four pixel distance from the image center, the assumed focal length is calculated. If the obtained focal length is different from the exact focal length, 24mm, the focal length value is modified by the proposed method. The method is very simple and gives the comparable results with the earlier sophisticated method.

• Ocean and Polar Research
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• v.27 no.3
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• pp.335-339
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• 2005

The underwater positioning system is important in interpreting data that are acquired from towing vehicles such as the deep-sea camera (DSC) system. Currently, several acoustic positioning systems such as long baseline (LBL), short baseline (SBL), and ultra short baseline (USBL), are used for underwater positioning. The accurate position of DSC, however, could not be determined in a R/V Onnuri unequipped with any of these underwater positioning systems. As an alternative, the DSC position was estimated based on the topography of towing track and cable length in the cruises before 1999. The great uncertainties, however, were found in the areas of flat bottom topography. In the 2003 and 2004 cruises these uncertainties were reduced by calculating the position of DSC with the cable length and seafloor depth below the vessel. The Japanese cruises for Mn-nodule used a similar estimation method for the DSC positioning system with a CTD sensor. Although the latter can provide better information for the position of DSC, the USBL underwater positioning system is strongly recommended for establishing better positioning of DSC and other towing devices.

• Journal of Ocean Engineering and Technology
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• v.17 no.2
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• pp.34-39
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• 2003

Recent deepwater offshore structures in the Gulf of Mexico utilize butt welded tubular joints. Application of a welded tubular joint includes tendons, production risers, and steel catenary risers. Fatigue life assessment of these joints becomes more critical, as the structures to which they are attached are allowed to undergo cyclic and sometimes large displacements around an anchored position. Estimation of the fatigue behavior of these tubular members in the design stage is generally condrcted by using S-N curves, as specified in the codeds and standards. Applying the stress concentration factor of the welded structure to the S-N approach often results in a very conservative assessment, because the stress field acting on the tubular has a non-uniform distribution through the thickness. Fatigue life analysis using fracture mechanics has been applied in the design of the catenary risers. This technology enables the engineer to establish proper requirements on weld quality and inspection acceptance criteria to assure satisfactory structural integrity during its design life. It also provides guidance on proper design curves and a methodology for accounting for the effects of non-uniform stress distribution through the wall thickness. Still, there is inconsistency when designing tubular joints using a conventional S-N approach and when specifying weld flaw acceptance criteria using fracture mechanics approach. This study developed fatigue curves that are consistent with both the S-N approach and the fracture mechanics approach. Accounting for non-uniform stress distribution and threshold stress intensity factor were key parameters in relating both approaches. A series of S-N curves, generated from the fracture mechanics approach, were compared to the existing S-N curves. For flat plate butt joint, the S-N curve generated from fracture mechanics matches with the IIW class 100 curve when initial crack depth was 0.5 mm (0.02 ). The new curves for tubular joint agree very well with the experimental results. The comparison also indicated the degree of conservatism built into the API X design curve.

• Journal of Communications and Networks
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• v.18 no.5
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• pp.837-845
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• 2016

Providing a customer with tailored location-based services (LBSs) is a fundamental problem. For location-estimation techniques with radio-based measurements, LBS applications are widely available for mobile devices (MDs), such as smartphones, enabling users to run multi-task applications. LBS information not only enables obtaining the current location of an MD but also provides real-time push-pull communication service. For indoor environments, localization technologies based on radio frequency (RF) pattern-matching approaches are accurate and commonly used. However, to survey radio information for pattern-matching approaches, a considerable amount of time and work is spent in indoor environments. Consequently, in order to reduce the system-deployment cost and computing complexity, this article proposes an indoor positioning approach, which involves using Asus Xtion to facilitate capturing RF signals during an offline site survey. The depth information obtained using Asus Xtion is utilized to estimate the locations and predict the received signal strength (RF information) at uncertain locations. The proposed approach effectively reduces not only the time and work costs but also the computing complexity involved in determining the orientation and RF during the online positioning phase by estimating the user's location by using a smartphone. The experimental results demonstrated that more than 78% of time was saved, and the number of samples acquired using the proposed method during the offline phase was twice as much as that acquired using the conventional method. For the online phase, the location estimates have error distances of less than 2.67 m. Therefore, the proposed approach is beneficial for use in various LBS applications.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.2
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• pp.152-162
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• 2001

Laser-generated ultrasonic technique which is one of the reliable nondestructive evaluation techniques has been applied to evaluate the integrity of structures by analyzing the characteristics of signal obtained from surface crack. Therefore, the signal analysis of the laser-generated ultrasonics is absolutely necessary for the accurate and quantitative estimation of the surface defects. In this study, one-sided measurement by laser-generated ultrasonic has been applied to evaluate the depth of the surface-breaking crack in the materials. However, since the ultrasonic waveform excited by pulse laser is very difficult to distinguish the defect signals, it is necessary to consider the signal analyses of the transient waveform. Wavelet Transform(WT) is a powerful tool for processing transient signals with temporally varying spectra that helps to resolve high and low frequency transient components effectively. In this paper, the analyses of the surface-breaking crack of the ultrasonic signal excited by pulse laser are presented by employing the WT analyses.