• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.14 no.4
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• pp.195-204
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• 2009

In order to estimate sea surface current fields in the East Sea, we examined characteristics of mean dynamic topography (MDT) fields (or mean surface current field, MSC) generated from three different methods. This preliminary investigation evaluates the accuracy of surface currents estimated from satellite-derived sea level anomaly (SLA) data and three MDT fields in the East Sea. AVISO (Archiving, Validation and Interpretation of Satellite Oceanographic data) provides a MDT field derived from satellite observation and numerical models with $0.25^{\circ}$ horizontal resolution. Steric height field relative to 500 dbar from temperature and salinity profiles in the East Sea supplies another MDT field. Trajectory data of surface drifters (ARGOS) in the East Sea for 14 years provide another MSC field. Absolute dynamic topography (ADT) field is calculated by adding SLA to each MDT. Application of geostrophic equation to three different ADT fields yields three surface geostrophic current fields. Comparisons were made between the estimated surface currents from the three different methods and in-situ current measurements from a ship-mounted ADCP (Acoustic Doppler Current Profiler) in the southwestern East Sea in 2005. For offshore areas more than 50 km away from the land, the correlation coefficients (R) between the estimated versus the measured currents range from 0.58 to 0.73, with 17.1 to $21.7\;cm\;s^{-1}$ root mean square deviation (RMSD). For coastal ocean within 50 km from the land, however, R ranges from 0.06 to 0.46 and RMSD ranges from 15.5 to $28.0\;cm\;s^{-1}$. Results from this study reveal that a new approach in producing MDT and SLA is required to improve the accuracy of surface current estimations for the shallow costal zones of the East Sea.

• The Journal of Engineering Geology
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• v.25 no.1
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• pp.93-102
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• 2015

The characteristics of frozen soils are one of most important factors for foundation design in cold region. The objective of this study is to evaluate the shear strength and stiffness of frozen soils according to the confining conditions during the freezing and shearing phase. A direct shear box is constructed for the frozen specimens and bender elements are mounted on the wall of the shear box to measure shear wave velocities. Specimens are prepared by mixing sand and silt with a silt fraction of 30% in weight and the degree of saturation of 10%, giving a relative density of 60% for all tests. The temperature of the specimens in the freezer is allowed to fall below -5℃, and then direct shear tests are performed. A series of vertical stresses are applied during the freezing and shearing phase. Shear stress, vertical displacement, and shear wave along the horizontal displacement are measured. Experimental results show that in all the tests, shear strength increases with increasing vertical stress applied during the freezing and shearing phases. The magnitude of the increase in shear strength with increasing vertical stress during shearing under fixed vertical stress in the frozen state is smaller than the magnitude of the increase in vertical stress during freezing and shearing. In addition, the change in shear wave velocities varies with the position of the bender elements. In the case of shear waves passing through the shear plane, the shear wave velocities decrease with increasing horizontal displacement. This study provides an evaluation of the properties of shear strength and stiffness of frozen soils under varied confining condition.

• The Journal of the Petrological Society of Korea
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• v.20 no.4
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• pp.173-189
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• 2011

Basic to acidic dykes and systematic joints are observed pervasively in the Jukbyeon-Bugu area, Uljin, east Korea. In order to classify the dykes and joints and to determine the relative chronology, their geometries, kinematics, and cross-cutting relationships, and the petrography and geochemistry of dykes are synthetically analyzed. Based on the orientations and cross-cutting relationships of 144 dykes (137 basic and 7 acidic dykes) and 370 systematic joints, three basic dike swarms (M-10, M-80, and M-100), one acidic dyke group (AD), and four joint sets (J-10, J-40, J-80, and J-150) are classified. Some of the J-150 joints reactivated as dextral strike-slip fault are recognized in the field and named as F-340R. According to petrographic, geochemical, and occurrence features in the field, M-80 and M-100 dykes have originated from a co-magma and intruded under the same stress field, even though they have intruded through different passages, preexisting fractures and new fractures created by magmatic pressure, respectively. And the relative chronology of dyke swarms and joint sets in the study area is determined as follows : ${\rightarrow}$ ${\rightarrow}$ ${\rightarrow}$ ${\rightarrow}$ ${\rightarrow}$ . And the M-80 (M-100) and M-10 dyke swarms intruded under NNE-SSW and NW-SE trending horizontal minimum stress fields, respectively. According to a synthesis of the results of the previous and this studies, the M-80, M-10, and F-340R are interpreted to have been formed about 64-52 Ma, Eocene~Oligocene, and Miocene, respectively.

• The korean journal of orthodontics
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• v.32 no.1 s.90
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• pp.9-18
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• 2002

The present study hypothesized that the double keyhole looped archwire plays a positive role for the sake of translatory movement and/or controlled tipping of upper 6 anteriors, and secures anchorage control as well. The purposes of the study were to evaluate the changes in lateral cephalograms during orthodontic treatment with DKHLs and to compare the skeletal & dental changes before- & after-treatment. The materials of this study were lateral cephalograms of 20 adult patients with upper dentoalveolar protrusion both in class I and in class II Division1 malocclusion. Lateral cephalograms were taken before and after orthodontic treatment with upper 1st bicuspid extraction and DKHLs. The results were obtained as follows : 1. There were no statistically significant differences in skeletal measurement except SNB and PTFH between before- & after-treatment. The major changes were in dentoalveolar region. 2. After treatment, there were statistically significant decrease in dental measurement except interincisal angle. 3. Both upper & lower lip protrusion was decreased. 4. There were statistically differences in upper anterior crown horizontal & root vertical dimension(7.08 ${\pm}$ 2.14 mm, 2.38 ${\pm}$ 1.15 mm, p<0.01). 5. There were statistically differences in upper posterior dental(both crown & root) horizontal dimension(2.48 ${\pm}$ 0.99 mm, 2.05 ${\pm}$ 0.91 mm, p<0.01).

• The Journal of the Petrological Society of Korea
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• v.18 no.1
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• pp.19-30
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• 2009

The main fault of Yangsan Fault Zone (YFZ) and Quaternary fault were found in a trench section with NW-SE direction at an entrance of the Sinheung village in the northern Eonyang, Ulsan, Korea. We interpreted the movement history of the southern part of the YFZ from the geometric and kinematic characteristics of basement rock's fault of the YFZ (Sinheung Fault) and Quaternary fault (Quaternary Sinheung Fault) investigated at the trench section. The trench outcrop consists mainly of Cretaceous sedimentary rocks of Hayang Group and volcanic rocks of Yucheon Group which lie in fault contact and Quaternary deposits which unconformably overlie these basement rocks. This study suggests that the movement history of the southern part of the YFZ can be explained at least by two different strike-slip movements, named as D1 and D2 events, and then two different dip-slip movements, named as D3 and D4 events. (1) D1 event: a sinistral strike-slip movement which caused the bedding of sedimentary rocks to be high-angled toward the main fault of the YFZ. (2) D2 event: a dextral strike-slip movement slipped along the high-angled beddings as fault surfaces. The main characteristic structural elements are predominant sub-horizontal slickenlines and sub-vertical fault foliations which show a NNE trend. The event formed the main fault rocks of the YFZ. (3) D3 event: a conjugate reverse-slip movement slipped along fault surfaces which trend (E)NE and moderately dip (S)SE or (N)NW. The slickenlines, which plunge in the dip direction of fault surfaces, overprint the previous sub-horizontal slickenlines. The fault is characterized by S-C fabrics superimposed on the D2 fault gouges, fault surfaces showing ramp and flat geometry, asymmetric and drag folds and collapse structures accompanied with it. The event dispersed the orientation of the main fault surface of the YFZ. (4) D4 event: a Quaternary reverse-slip movement showing a displacement of several centimeters with S-C fabrics on the Quternary deposits. The D4 fault surfaces are developed along the extensions of the D3 fault surfaces of basement rocks, like the other Quaternary faults within the YFZ. This indicates that these faults were formed under the same compression of (N)NW-(S)SE direction.

• Economic and Environmental Geology
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• v.47 no.4
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• pp.381-393
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• 2014

Seismic reflection data are integrated with fieldwork data in order to understand startigraphy, structural geology and hydrocarbon potentials of Cretaceous strata in the Mesopotamian basin, Northeastern Iraq. Cretaceous strata in the basin divided into the Qamchuqa, Kometan, Bekhme and Shiranish formations, which are composed of carbonates deposited in shallow marine environment. The geological structures in these formations are mainly recognized as thrusts, detachment folds, fault propagation folds and fault bend folds. As well, NW-SE trending fractures are regularly developed, and are horizontal or perpendicular to the structures. The distribution and frequency of fractures are related to the development of the thrusts. In terms of hydrocarbon potentials, Cretaceous strata in the basin have limited capacities for source rocks and seal rocks due to the lack of organic carbon content and the well-developed fractures, respectively. Although these carbonates have limited primary porosity, however, development of the secondary porosity derived from the fractures contributes to enhance the reservoir quality. Most important factor for the reservoir quality of Cretaceous strata seems to be the frequency and connectivity of fractures relative to locations of folds and faults. The results delineated in this study will use as reference for recognizing stratigraphy and structures of Cretaceous strata and will provide useful information on hydrocarbon potentials of Cretaceous strata in the Mesopotamian basin, NE Iraq.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.2
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• pp.347-353
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• 2018

In this paper, we studied a design method for a band-pass waveguide filter with a modified H-type resonant iris (RI) placed in a thin transverse wall of a rectangular waveguide. The horizontal straight gap at the center of a conventional H-shaped iris is modified to a U-shaped one to increase the equivalent capacitance, and the equivalent inductance is improved by changing the vertical two straight slots into C-shaped ones. From some simulation results for the frequency response of the proposed RI, it was observed that the proposed iris was advantageous for reducing its size and having better cutoff, compared to typical H-shaped one. Equivalent inductance, capacitance, and quality factor of the proposed RI were extracted to analyze its performance. A third-order band pass filter using the proposed modified H-shaped iris was designed and, it was observed that the filter operated in the frequency range of 9.18-9.84 GHz with its insertion loss of 0.3 dB and return loss of 14 dB.

• Journal of The Korean Association For Science Education
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• v.38 no.3
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• pp.343-354
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• 2018

In this study, the first experience of the whole research process of a novice scientist (student A) who participated in the Undergraduate Research Program (URP) was analyzed. The data were collected through observation, interviews, and document analysis with the cultural historical activity theory being used as a theoretical lens. At the beginning of novice's research, the mentor guided him in setting a research goal and provided mediating artifacts. Student A formed a research team based on the vertical relationship without a shared mental model. Two major contradictions occurred and they were the sources of changes of student A's activity system. The first contradiction was between the mentor's educational philosophy and the mentee's educational needs, which was resolved in a way that student A asked and used the mentor's network to obtain his needs about task-specific details. The second contradiction arose because the team members wanted horizontal relationship while student A wanted to stick to the vertical relationship. After student A accepted the opinions of the team members, they cooperatively changed the division of labor in the activity system. Student A decided to become a scientist and not a physics teacher, even if his major is physics education after finishing his URP research process. His URP experience also created and expanded his network in the academic field, and his negative attitude toward collaboration changed positively. Through the analysis of the structure and changes in the activity system of URP research, implications for instructional method and support system of the apprenticeship can be obtained.

• The Journal of Engineering Geology
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• v.19 no.2
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• pp.191-203
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• 2009

The effect of stabilizing piles on cut slopes is checked and the behavior of slope soil and piles are observed throughout the year by field measurements on the large-scale cut slopes. First of all, the behavior of the slope soil was measured by inclinometers during slope modification. Landslides occurred in this area due to the soil cutting for slope modification. The horizontal deformations of slope soil are gradually increased and rapidly decreased at depth of sliding surface. As the result of measuring deformation, the depth of sliding surface below the ground surface can be known. Based on the measuring the depth of the sliding surface, some earth retention system including stabilizing piles were designed and constructed in this slope. To check the stability of the reinforced slope using stabilizing piles, an instrumentation system was installed. As the result of instrumentation, the maximum deflection of piles is measured at the pile head. It is noted that the piles deform like deflection on a cantilever beam. The maximum bending stress of piles is measured at the soil layer. The pile above the soil layer is subjected to lateral earth pressure due to driving force of the slope, while pile below soil layer is subjected to subgrade reaction against pile deflection. The deflection of piles is increased during cutting slope in front of piles for the construction of soil nailing. As a result of research, the effect and applicability of stabilizing piles in large-scale cut slopes could be confirmed sufficiently.

• Geophysics and Geophysical Exploration
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• v.13 no.3
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• pp.249-255
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• 2010

Since the 1990's, a number of ULF geomagnetic disturbance associated with earthquake occurrences have actively been reported, and polarization analysis of geomagnetic fields becomes one of potential candidates to be capable of predicting short-term earthquake. This study develops the modified polarization analysis method based on the previous studies, and analyzes three-component geomagnetic fields obtained at Cheongyang geomagnetic observatory using the developed method. A daily polarization value (the ratio of spectral power of horizontal and vertical geomagnetic field) is calculated with a focus on the 0.01 Hz band, which is known to be the most sensitive to seismogenic ULF radiation. We analyze a total of 10 months of geomagnetic data obtained at Cheongyang observatory, and compare the polarization values with the Kp index and the earthquake occurred in the analysis period. The results show that there is little correlation between the temporal variations of polarization values and Kp index, but remarkable increases in polarization values are identified which are associated with two earthquakes. Comparison the polarization values obtained at Cheongyang and Kanoya observatory indicates that the increases of polarization values at Cheongyang might be due to not global geomagnetic induction but the locally occurred earthquakes. Furthermore, these features are clearly shown in normalized polarization values, which take account in the statistical characteristics of each geomagnetic field. On the basis of these results, polarization analysis can be used as promising tool for monitoring the earthquake-precursory phenomenon.