• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.3
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• pp.77-86
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• 2008

A database program is constructed by collecting all information related to shallow foundations such as measured load-settlement data, foundation shapes and sizes, properties of soils under the foundation and various measured data obtained from field investigation methods including CPT, PMT and SPT etc.. Based on the database program, a special program module is developed for performing statistical analyses of reliability and accuracy of predicting equations used for calculation of settlement of the shallow foundations. Special interests are focused not only on the settlement, but also on the settlement to width ratio (s/B). Results of the reliability and accuracy analyses on five available settlement equations are provided. Conclusions based on the provided results can be confirmed by extending number of related reliable data about the shallow foundations and can be adapted as guidelines for design of the shallow foundations.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.9 no.1
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• pp.83-96
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• 1991

The use of SPOT Imagery is a growing trend in the field of small and middle scale mapping, as well as in establishing topographic database. This study is about 3-D positioning using the SPOT Imagery, where the accuracy and the gemetric characteristics of SPOT photos are analysed according to the preprocessing level (level 1AP,1B). As a result of this study the following could be determined, i. e 1) the geometric characteristics of SPOT Imagery according to the preprocessing level, 2) the optimal polynomial type for exterior orientations of each preprocessing level, and 3) the type of significant additional parameters. It was found that both the geometric precision and accuracy of level 1AP is higher than those of level 1B, which implies that level 1AP is more suitable for precise 3-D positioning and map production.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.40 no.5
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• pp.403-412
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• 2022

As the 4th industrial revolution is in full swing and next-generation ICT(Information & Communications Technology) convergence technology is being developed, various smart construction technologies are being rapidly introduced in the construction field to respond to technological changes. In particular, since the earth-volume calculation process for site design accounts for a large part of the design cost at the construction site, related researches are being actively conducted to improve the efficiency of the process and accurately calculate the earth-volume. The purpose of this study is to present a method for quickly constructing the topography of a construction site in 3D and efficiently calculating earth-volume using the results. For this purpose, the construction site was constructed as a 3D realistic model using large-scale aerial photos obtained from UAV(Unmanned Aerial Vehicle). At this time, since the constructed 3D realistic model has a surface model structure in which volume calculation is impossible, the structure was converted into a 3D solid model to enable volume calculation. And we devised a methodology to calculate earth-volume based on CAD(Computer-Aided Design and Drafting) using the converted solid model. Automatically calculating earth-volume from the solid model by applying the method. As a result, It was possible to confirm a relative deviation of 1.52% from the calculated earth-volume from the existing survey results. In addition, as a result of comparative analysis of the process time required for each method, it was confirmed that the time required is reduced of 60%. The technique presented in this study is expected to be utilized as a technology for smart construction management, such as periodic site monitoring throughout the entire construction process, as well as cost reduction for earth-volume calculation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.5
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• pp.517-524
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• 2011

A vortex tube is a device that can separate small particles from a compressed gas or separate a compressed gas into hot and cold flows. We experimentally analyzed the energy-separation characteristics of a vortex tube with a diameter of 10 mm. We measured the energy-separation characteristics of the vortex tube for different inlet air pressures, orifice diameters, and tube lengths. The orifice diameter and inlet pressure are important for the vortex tube design and operation. The tube length has a small effect on the energy-separation performance. Maximum energy separation occurs for a vortex tube with Dc = 0.7 D and L = 16 D.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.39 no.3
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• pp.239-248
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• 2003

This paper was conducted as an attempt in order to construct the data bank of target strength for acoustic estimation of fish length in the coastal waters of Korea. The fish length dependence of acoustic target strength for 13 large yellow croakers (Pseudosciaena crocea) at 75 kHz was investigated and the prediction of the target strength by using the Kirchhoff-Ray Mode model (KRM model) was compared with target strength measurements. The results obtained are summarized as follows; 1. In the averaged target strength pattern for 13 large yellow croakers the maximum target strength was -35.13 dB at $-13.35^{\circ}$ on a tilted angle. 2. The relationship between fork length(L, cm) and averaged target strength(TS, dB) was expressed as follows; TS=23. 76log (L) -73.45 (r=0.47) TS=20log(L) -67.35 From this result, the conversion coefficient was -73.45 dB and 6.1 dB lower than the coefficient -67.35 dB where the value of the slope of the regression equation is forced to be 20. 3. Averaged target strength and a length conversion coefficient derived from a target strength histogram for 13 large yellow croakers of mean length 25.59 cm were -41.23 dB, -69.72 dB, respectively. 4. In the range of $$2;{\ll} L (fish length /{\lambda}(wave length);{\ll}40$$, the prediction of the averaged target strength by the KRM model increased gradually with the increasing of $L/{\lambda}$ and was lower than the measured target strength.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.9
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• pp.25-30
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• 2004

In this Paper, the 0.1 w InGaAs/InAlAs/GaAs Metamorphic HEMT, which is applicable to MIMIC, and a 100 GHz MIMIC amplifier were designed and fabricated. The DC characteristics of MHEMT are 640 mA/mm of drain current density, 653 mS/mm of maximum transconductance. The current gain cut-off frequency(fT) is 173 GHz and the maximum oscillation frequency(fmax) is 271 GHz. A 100 GHz amplifier was designed using 0.1${\mu}{\textrm}{m}$ MHEMT and CPW technology. The measured results from the 100 GHz MIMIC amplifiers show good S21 gain of 10.1 dB and 12.74 dB at 100 GHz and 97.8 GHz, respectively.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.8
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• pp.48-53
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• 2008

In this paper, we developed the MMIC low noise amplifier using 100 nm metamorphic HEMTs technology in combination with coplanar circuit topology for 94 GHz applications. The $100nm\times60{\mu}m$ MHEMT devices for the MMIC LNA exhibited DC characteristics with a drain current density of 655 mA/mm, an extrinsic transconductance of 720 mS/mm. The current gain cutoff frequency $(f_T)$ and maximum oscillation frequency $(f_{max})$ were 195 GHz and 305 GHz, respectively. The realized MMIC LNA represented $S_{21}$ gain of 14.8 dB and noise figure of 4.6 dB at 94 GHz with an over-all chip size of $1.8mm\times1.48mm$.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.3
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• pp.180-190
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• 2017

This paper describes the application of Multi-frame based super-resolution method to enhance resolution of image information from the UAV, and the improvement of UAV's ground target recognition ability. To verify this algorithm, we designed a flight/ground control system, and the UAV, and then the algorithm was validated using the UAV system with ground target. As a result of the comparison between the pre-applied image and post-applied one shows that the RMSE is from 0.0677 to 0.0315, NRMSE is from 7.4030% to 3.5726%, PSNR is from 23.3885dB to 30.0036dB, and SSIM is from 0.6996 to 0.8948. Through these results, we validate this study can enhance the resolution of UAV's image using Multi-frame based super-resolution algorithm.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.4
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• pp.378-383
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• 2004

The Korean Performance Demonstration(KPD) System for the ultrasonic testing personnel, equipments and procedures applicable to the Class 1 and 2 piping examination for nuclear power plant in Korea has been established. A round robin test was conducted in order to compare the examination results by the method of Performance Demonstration(PD) with the traditional dB-drop method. The round robin test shows that the reliability of the PD method is better than that of the dB-drop method. As a result, adoption of the PD method to the in-service inspection of the nuclear power plants will improve the reliability of the ultrasonic test results.

• Journal of the Korean Geotechnical Society
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• v.25 no.12
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• pp.69-85
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• 2009

It is very important to measure reliable dynamic properties of each zone in dam for seismic design. However, the Vs values of core and rock-fill zone are seldom determined by field test. Consequently, seismic design in dam is performed using Vs values assumed or empirically determined. So, it is required that reliable Vs has to be evaluated by in-situ test. In this study, surface wave method, which is nondestructive, was applied to dam to evaluate Vs profiles of core and rock-fill zone in dam. In 6 dams, using SASW and HWAW methods, Vs profiles were evaluated reliably. D/B of Vs profiles of each zone with depth and relationship between confining pressure and Vs profiles of rock-fill zone were constructed including existing results of other dams. The evaluated D/B and proposed relationship were compared with the frequently used empirical method by Sawada and Takahashi.