• Geophysics and Geophysical Exploration
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• v.5 no.2
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• pp.84-92
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• 2002

In this study, the new modeling scheme has been developed for recently designed and tested electromagnetic survey, which adapts horizontal magnetic dipole with $1\;kHz\~1\;MHz$ frequency range as a source. The 2.5-D secondary field formulation in wavenumber domain was constructed using finite element method and verified through comparing results with layered-earth solutions calculated by integral equations. 2-D conductive- and resistive-block models were constructed for calculating electric field, magnetic field and impedance - the ratio of electric and magnetic fields which are orthogonal each other. This study showed that electric field and impedance are superior in identifying 2-D isolated-body model to magnetic field. In particular, impedance gives more stable results than electric field with similar spatial resolving power, because electric field is divided by magnetic field in impedance. Thus the impedance analysis which uses electric and magnetic fields together would give better result in imaging the shallow anomalies than conventional EM method.

• Geophysics and Geophysical Exploration
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• v.21 no.2
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• pp.125-131
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• 2018

2017 Pohang earthquake (M 5.4) was more disastrous than 2016 Gyeongju earthquake (M 5.8), partly because of its shallow focal depth. However, precise focal depth of Pohang earthquake is still controversial. Close crustal model showed 6 ~ 11.5 km in relocation depth, whereas other models showed almost surface range. Geothermal study indicated temperature of $300^{\circ}C$ at depth of 7.5 km. Related with observations of seismogenic layer, the focal depth of Pohang earthquake seems to be 7 km depth as obtained by close model.

• Geophysics and Geophysical Exploration
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• v.9 no.2
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• pp.163-170
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• 2006

The shortage of proven hydrocarbon reserves has resulted in exploration progressing from the offshore into progressively deeper water of the continental shelf. Despite the success of seismic acquisition at ever greater depths, there are marine geological terrenes in which the interpretation of seismic data is difficult, such regions dominated by scattering or high reflectivity that is characteristic of carbonate reefs, volcanic cover and submarine permafrost. A marine controlled-source electromagnetic (CSEM) method has recently been applied to the oil and gas exploration thanks to its high-resistivity characteristics of the hydrocarbon. In particular, this method produces better results in terms of sensitivity under the deep water environment rather than the shallow water. Only in the last five years has the relevance of CSEM been recognized by oil companies who now use it to help them make exploration drilling decisions. Initial results are most promising and several contractors now offer magnetotelluric and CSEM services.

• Geophysics and Geophysical Exploration
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• v.5 no.4
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• pp.309-315
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• 2002

Conventional electromagnetic (EM) method using small loops as a source and receiver has been used in detection of conductive buried objects like a metal detector or in qualitative estimation of the subsurface conductivity variation. Recently, however, since detection of buried objects and imaging of the subsurface conductivity distribution in a relatively conductive area are in a high demand for environmental and engineering purposes, the quantitative interpretation technique of EM data is actively studied. In this regard, we introduce a brief principle of EM survey and show an example of the detection of buried conductive material and imaging of the subsurface conductivity distribution based on data measured at a test survey area. Through this study, we show that multi-frequency EM surveys using small loops may be a good solution to give quick and detail information of subsurface in a conductive survey area.

• Geophysics and Geophysical Exploration
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• v.5 no.4
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• pp.272-279
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• 2002

During field survey of ground penetrating radar or borehole radar, we often encounter some problems which could be solved easily by modifying structure of the system such as antenna length, shape or array. In addition, it is necessary that the user could easily modify configuration of the radar system na test various array of antennas in order to verify and confirm numerical modeling results concerning radar antennas. We have developed network-analyzer-based, stepped-frequency georadar system. This system had been comprised with coaxial cable to confirm possibility of the system, then we have upgraded the system to use optical cable that is composed of optical/electric transducers, electric/optical transducers, amp, pre-amp and antennas. The software for the aquisition of data has been developed to control the system automatically using PC with GPIB communication and to display the obtained data graphically. We have tested the system in field survey na the results have been compared with those of RAMAC/GPR system.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.37.1-37.1
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• 2019

The faint quasars with M1450 > -24 mag are known to hold the key to the determination of the ultraviolet emissivity for the cosmic reionization. But only a few have been identified so far because of the limitations on the survey data. Here we present the first results of the z ~ 5 faint quasar survey with the Infrared Medium-deep Survey (IMS), which covers ${\sim}100deg^2$ areas in J band to the depths of $J_{AB}$ ~ 23 mag. To improve selection methods, the medium-band follow-up imaging has been carried out using the SED camera for QUasars in Early uNiverse (SQUEAN) on the Otto Struve 2.1 m Telescope. The optical spectra of the candidates were obtained with 8 m class telescopes. We newly discovered 10 quasars with -25 < $M_{1450}$ < -23 at z ~ 5, among which three have been missed in a previous survey using the same optical data over the same area, implying the necessity for improvements in high-redshift faint quasar selection. We derived photometric redshifts from the medium-band data and found that they have high accuracies of ${\langle}{\mid}{\Delta}z{\mid}/(1+z){\rangle}=0.016$. The medium-band-based approach allows us to rule out many of the interlopers that contaminate ${\geq}20%$ of the broadband-selected quasar candidates. These results suggest that the medium-band-based approach is a powerful way to identify z ~ 5 quasars and measure their redshifts at high accuracy (1%-2%). It is also a cost-effective way to understand the contribution of quasars to the cosmic reionization history.

• Advances in pediatric surgery
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• v.13 no.1
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• pp.30-36
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• 2007

Intestinal malrotation is usually asymptomatic and most often is found during abdominal exploration for other surgical diseases. However, a serious complication of intestinal malrotation, midgut volvulus is a true surgical emergency of childhood. The clinical findings, diagnostic procedures, treatment, and prognosis of midgut volvulus were reviewed by a retrospective study. Between 1980 and 2005, 29 patients with midgut volvulus ranging in age from 1 day and 15 years were treated at HanYang University Hospital. Seventy-nine percent of the patients presented before 1 month of age. Midgut volvulus occurred 2 times more frequently in male. The clinical findings were bilious vomiting (96.6 %), irritability (34.5 %), abdominal distention (13.8 %), abdominal pain (10.3 %), and palpable abdominal mass (6.9 %). The diagnosis was made by abdominal simple x-ray (17.2 %), upper gastro-intestinal contrast study (37.9 %), abdominal sonogram (20.7 %), abdominal CT (3.4 %), and abdominal exploration (20.7 %). Among the 29 patients, 5 patients developed gangrene of small intestine due to strangulation and underwent resection of bowel. Two patients died due to sepsis.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.5
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• pp.413-418
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• 2012

This paper presents a multi-robot path planner for environment exploration and monitoring. Robotics systems are being widely used as data measurement tools, especially in dangerous environment. For large scale environment monitoring, multiple robots are required in order to save time. The path planner should not only consider the collision avoidance but efficient coordination of robots for optimal measurements. Nonlinear spring force based planning algorithm is integrated with the spatial gradient following path planner. Perturbation/Correlation based estimation of spatial gradient is applied. An algorithm of tuning the stiffness for robot coordination is presented. The performance of the proposed algorithm is discussed with simulation results.

• Journal of Community Nutrition
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• v.8 no.4
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• pp.165-170
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• 2006

This study was conducted to develop and apply a computer-based multimedia nutrition education program for preschoolers based on the Dick and Carey model of instructional design. The Dick and Carey model included 4 phases: analysis, design, development, and evaluation. The program's instructional goals, objectives, assessment instruments, content, examples, and practice questions with feedback were written in the design phase. To be familiar with the 5 food groups, 'Nutrition exploration' were programmed using Hyperstudio. 'Nutrition exploration' was designed as a five-session, interactive multimedia game, with each session taking about 5 minutes to complete. Nineteen preschoolers, aged 6, volunteered to participate formative evaluation. The effectiveness of the program was examined using a pre-post test design. Participants were recruited by personal contact at the individual preschool education center. The application was carried out during 4 weeks. The results showed that intervention participants significantly increased knowledge between pre-test and post-test. The results support using IMM (interactive multimedia) to disseminate nutrition education to the target population. This research provides the basis for continuing development of computer-based nutrition education materials.

• Geophysics and Geophysical Exploration
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• v.5 no.1
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• pp.1-5
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• 2002

We developed a modeling and visualization software that can analyze 3-dimensional spatial information in the ArcView environment. The software constructs and visualizes an object in 3 dimensional space from the input data given a number of horizontal cross-sections. The software can generate and visualize the cross-sections of the object in any azimuth and inclination. Utilizing the program users can modify the 3-D shape of the object by interactively editing the cross-sections.