• Korean Journal of Remote Sensing
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• v.7 no.2
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• pp.165-178
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• 1991

A geologic hazard map has been produced in the suburbs of Seoul using GIS technology to analyse the degree of geologic hazard, particularly landslides. Topographic, geologic and soil data were incorporated in a map through GIS, which enable to interpret, analyse and predict the regional geologic hazards. Potential elements causing a landslide are slope geometry, geology, groundwater table, soil property, rainfall and vegetation etc. These elements analysed in the study area were input into GIS system through cartographic simulation to produce the regional geologic hazard map. For this work, ARC/INFO(GIS) and ERDAS(IP) system were used.

• Advances in aircraft and spacecraft science
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• v.10 no.5
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• pp.457-471
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• 2023

The paper evaluates the aerodynamic coefficients on a blunt-nose re-entry capsule with a conical cross-section followed by a cone-flare body. A computer code is developed to solve three-dimensional compressible inviscid equationsfor flow over a Space Recovery Experiment (SRE) configuration at different flare-cone half-angle at Mach 6 and angle of attack up to 5°, at 1° interval. The surface pressure variation is numerically integrated to obtain the aerodynamic forces and pitching moment. The numerical analysis reveals the influence of flare-cone geometry on the flow characteristics and aerodynamic coefficients. The numerical results agree with wind tunnel results. Increase of cone-flare angle from 25° to 35° results in increase of normal force slope, axial forebody drag, base drag and location of centre of pressure by 62.5%, 56.2% and 33.13%, respectively, from the basic configuration ofthe SRE of 25°.

• Ocean and Polar Research
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• v.25 no.4
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• pp.557-567
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• 2003

High-resolution (3.5 kHz) subbottom profiles were analyzed in order to reveal sedimentation pattern of late Quaternary in the northern South Shetland continental margin and the South Scotia Sea, Antarctica. On the basis of clarity, continuity and geometry of surface and subbottom echoes together with seafloor topography, high-resolution echo characters are classified into eight echo types which represent rock basements (echo type III-1), coarse-grained subglacial till or moraine (echo type I-1), slides/slumps (echo type IV), debris-flow deposits (echo types II-3 and III-2), and bottom-current deposits (echo types I-2, II-1 and II-2). Subglacial till or moraine (echo type I-1) is mostly present in the lower continental shelf and upper continental slope of the northern South Shetland continental margin, which changes downslope to slides/slumps (echo type IV) and debris-flow deposits (echo types II-3 and III-2) in the middle to lower continental slope. This distribution suggests that the continental slopes of the northern South Shetland continental margin were mostly affected by downslope gravitational processes. Further downslope, bottom-current sediments (echo type I-2) deposited by the southwestward flowing Antarctic Deep Water (ADW) occur at the South Shetland Trench, reflecting an Interaction between mass flows and bottom currents in the area. In contrast to the northern South Shetland continental margin, the South Scotia Sea is dominated by bottom-current deposits (echo types II-1 and II-2), indicating that the sedimentation was mostly controlled by the westward flowing ADW. Flow intensity of the ADW has increased in the relative topographic highs, forming thin covers of coarse-grained contourites (echo type II-1), whereas it has decreased in the relative topographic lows, depositing thick, fine-grained contourites (echo type II-2). The poor development of wave geometry in the fine-grained bottom-current deposits (echo type II-2) is suggestive of the unsteady nature of the ADW flow.

• Journal of the Korean Geotechnical Society
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• v.33 no.3
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• pp.17-28
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• 2017

We performed laboratory spudcan penetration and extraction tests considering various geometries. Jumunjin sand, representative standard sand in South Korea, and kaolinite were used for uniform sand and clay layers, respectively. The measured vertical bearing and pull-out capacities were compared to empirical equations for shallow foundations. The results showed good agreement between measured and calculated bearing capacity from laboratory test and previous study at shallow depths. The effect of spudcan geometry is shown to depend on site condition. The influence of a sharp spigot is not significant in clays. The slope of the spudcan surface is shown to influence the pull-out capacity. The characteristics of spudcan penetration and extraction behavior considering various geometries can be a useful reference for determining spudcan geometries.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.3
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• pp.231-237
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• 2007

The torque ripple of the hydraulic pumps for the Electro-hydrostatic Actuators can disturb the cylinder position control under slewing speed operation condition. In principle, the periodic change of the reaction torque generated by a piston type pump is highly dependent on the waveform of its cylinder chamber pressure. In case of uni-directional pumps operating at constant speed, the transient overshoot and rising slope of the cylinder pressure can be adjusted by the precompression angle and notch shape of their valve plates. Therefore, the influence of the valve plate geometry on the torque ripple magnitude of a bent-axis type piston pump for EHA application was investigated in this study. The results showed that any improvement of the torque ripple of such a bi-directional pump can not be achieved by modifying the valve plate geometry, regardless of its operation speed.

• Journal of the Korean Geographical Society
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• v.32 no.4
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• pp.421-434
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• 1997

Flume experiments are conducted to describe channel adjustments at stream confluences and to examine some factors to which changes in channel characteristics are subject. There are different factors controlling channel size and shape; shereas the fomer is primarily controlled by water discharge alone, the latter including channel slope is influenced by sediment load as well as water discharge. The morphometric adjustments of confluent tributaries can be consequently classified into three types based upon changes in sediment concentration which are associated with the relative increasing rates of water discharge and sediment load at these sites. Flow is accelerated at stream confluences due to the convergence of confluent flows, causing an sharp increase in velocity. It restrains an increase in channel capacity, and furthers a decrease in channel slope, of a receiving stream. As a result, effects of slight increases in sediment concentration hardly appear on changes in channel characterisitics at stream confluences.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.2
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• pp.94-102
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• 2013

In this study, numerical modeling was performed to investigate influence of the apron shape on the discharge performance of the sluice for tidal power plant. The numerical modeling was carried out for comparison of the difference in the discharge coefficient when the apron width, slope, and the length of the horizontal section were different, without considering change in the shape of the sluice caisson itself. The modeling result showed that significant discrepancy in terms of the overall discharge performance appeared according to the apron geometry. In order to achieve maximum discharge performance of the sluice caisson, it is desirable to make the design by putting a space equivalent to the width of the sluice caisson on its both sides, by making the apron slope be 1:5, and by keeping length of the horizontal section to be 50 m that is corresponding to the streamwise length of the sluice caisson.

• Journal of the Optical Society of Korea
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• v.18 no.3
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• pp.207-216
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• 2014

In this work, we report detailed numerical analysis of the near-elliptic core index-guiding triangular-lattice and square-lattice photonic crystal fiber (PCFs); where we numerically characterize the birefringence, single mode, cut-off behavior and group velocity dispersion and effective area properties. By varying geometry and examining the modal field profile we find that for the same relative values of $d/{\Lambda}$, triangular-lattice PCFs show higher birefringence whereas the square-lattice PCFs show a wider range of single-mode operation. Square-lattice PCF was found to be endlessly single-mode for higher air-filling fraction ($d/{\Lambda}$). Dispersion comparison between the two structures reveal that we need smaller lengths of triangular-lattice PCF for dispersion compensation whereas PCFs with square-lattice with nearer relative dispersion slope (RDS) can better compensate the broadband dispersion. Square-lattice PCFs show zero dispersion wavelength (ZDW) red-shifted, making it preferable for mid-IR supercontinuum generation (SCG) with highly non-linear chalcogenide material. Square-lattice PCFs show higher dispersion slope that leads to compression of the broadband, thus accumulating more power in the pulse. On the other hand, triangular-lattice PCF with flat dispersion profile can generate broader SCG. Square-lattice PCF with low Group Velocity Dispersion (GVD) at the anomalous dispersion corresponds to higher dispersion length ($L_D$) and higher degree of solitonic interaction. The effective area of square-lattice PCF is always greater than its triangular-lattice counterpart making it better suited for high power applications. We have also performed a comparison of the dispersion properties of between the symmetric-core and asymmetric-core triangular-lattice PCF. While we need smaller length of symmetric-core PCF for dispersion compensation, broadband dispersion compensation can be performed with asymmetric-core PCF. Mid-Infrared (IR) SCG can be better performed with asymmetric core PCF with compressed and high power pulse, while wider range of SCG can be performed with symmetric core PCF. Thus, this study will be extremely useful for designing/realizing fiber towards a custom application around these characteristics.

• The Journal of Engineering Geology
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• v.19 no.3
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• pp.331-344
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• 2009

Large landslides occurred since 1990 on natural terrain, Korea were reviewed with the existing data to characterize them in terms of the condition of rainfall, geology and geometry. Ten landslide areas over the nationwide are selected for this study. Among them, five areas consist of granite basement, four areas of granite and metamorphic rocks and the remaining an area of gabbro. The basement lithology on which landslides most dominantly occurred is granite, on which 58% of landslides among the total 3,435 are taken place, the next dominant one is metamorphic rocks where 24% of landslides are occurred, and the remaining 18% are on the areas of volcanic and sedimentary rocks which are partly distributed in some areas. The landslide occurrences may depend on the rainfall intensities rather than durations. We applied the theories of Caine's threshold and Olivier's final response coefficient to the Korean cases. The rainfall conditions at the landslide areas were all satisfied enough with the landslide triggering conditions suggested by Caine and Olivier. The triggering mechanism and type of landslides may largely depend on the weathering and geomorphic characteristics of basement lithology. The granite areas are characterized by being relatively shallow but consistent weathering profiles and almost no outcrop, and therefore, shallow translational slides are dominant. Whereas metamorphic areas are characterized by consisting of steep slope, weathered outcrops on ridges and partly on flanks and irregular weathering profiles, and relatively large debris flows are dominant.

• Korean Journal of Environment and Ecology
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• v.18 no.1
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• pp.92-102
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• 2004

In this study, landscape changes were examined by periods through the analysis of visual quantity on the landscape components of national road including the mountains, the sky, road pavements, street trees, paddy fields and dry fields, billboard, telegraph pole, building, structure, slope, guard fence, soundproof wall, and median strip etc. For this, subject national road in suburb arreas was selected to grasp its landscape characteristics, and divisional criteria of landscape type of the national road were suggested to look into the trend of landscape changes by periods. Findings of this study are as follows：1.Divisional criteria of landscape type of the national road include location and geometry, structure, land use, perspective, and surrounding buildings of the national road. 2.The highest visual quantity was found in road pavements by periods among landscape components of the national road. It was found that this result has a thread of connection with previous study emphasizing the importance of road geometry as one of landscape components, and road geometry shall be regarded as a visually significant component in analyzing and evaluating landscape of the national road. 3.Most distinguished factors of landscape changes of the national road by periods were median strip(F＝33.296) and street tree(F＝32.881), and then the sky(F＝24.735) and mountain(F＝23.477) showed similar level of statistically significant difference. However, statistically significance difference was not found in buildings and structures. 4.It was shown that natural elements decreased gradually but structural landscape made of artificial elements became the main in construction of the national road. This result implies that although the scenic and ecological soundness is recognized in construction of the national road, it is not out of the limitation of functionalities that is, access and mobility.