• Korean Journal of Optics and Photonics
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• v.11 no.2
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• pp.73-79
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• 2000

We measure a beam diameter of scan and sub-scan direction of LSD (Laser Scanning Urnt) which uses $fheta$ lens produced by injecLion molding method as a scanning lens. While the measured beam diameter in scan direction, which is $62muextrm{m}$ to $68\mu\textrm{m}$, shows similar size comparing to the design beam diameter, the sub-scan beam diameter shows sIzable beam diameter deviation as much as 37 11m ranging from $78\mu\textrm{m}$ to $115\mu\textrm{m}$. Injection molding lens has the surface figure error due to the shrinkage III the cooling time and the internal distortion (birefringence) due to the uneven cooling conditIOn so that these bring about wavefront aberration (i.e., the enlargement of beam size), and are eventually expre~sed as the deterioration of the pdnting image. In this paper. we first measure and analyze beam diameter, birefringence (polanzation ratio), and asphedcal figure error of mIens in order to know the principle cause of the beam diameter deviation in sub-scan directIOn. And Lhen. through the analysis of a designed depth of focus and a calculated field curvature (imaging position of the optical axis directIon) using the above figure elTor data, we know Lhat the birefringence IS the main factor of sizable beam diameter deVIation in sub-scan direction. ction.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.7
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• pp.305-314
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• 2018

The steel-plate concrete composite beam is composed of a steel plate, concrete and a shear connector to combine the two inhomogeneous materials. In general, the steel plate is assembled by welding an existing composite beam. In this study, a new steel-plate concrete composite (SPCC) beam was developed to reduce the size of the shear connector and improve its workability. The SPCC beam was composed of folded steel plates and concrete, without any shear connector. The folded steel plate was assembled with high strength bolts instead of welding. To improve the workability in field construction, a hat-shaped cap was attached in the junction with the slab. Monotonic two-point load testing was conducted under displacement control mode. The flexural strength of the SPCC beam specimen was calculated to be 76% of that of the complete composite beam by using the plastic stress distribution method and strain compatibility method. The cap acted as the stud and accessory. The synthesis rate could be increased by controlling the gap of the cap, and the bending performance could be evaluated by using the strain fitting method considering the synthesis rate of the SPCC beam.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.4_1
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• pp.129-136
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• 1992

A precedure for recovering surface displacement from a time series of pressure measured by a pressure gage in a shallow water (that is, FFTM, LCM. IWM) is investigated with respect to a proper cut-off-frequency of a frequency response function for the accurate recovery of wave height and period. The authors examined the applicability of above mentioned three transformation procedures through field observations and laboratory experiments and the following results are obtained. i) The cut-off-frequency of the frequency response function used in FFTM is deeply depend on both the frequency response of the pressure sensor and the water depth at the sensor. In this study, a relatively accurate surface displacement can be recovered when the frequency response function is cut off at the frequency corresponding to kh=3.0 where k is a wave number at the depth of h. The frequency response function in the region higher than the cut-off-frequency is set constant to be the value at the cut-off-frequency. ii) The transformed surface displacements by LCM are affected by the small waves of short periods included in the measured pressure. It is found that pressure variation whose local frequency is higher than kh=1.5 has to be neglected to recover surface displacement sufficiently. iii) In IWM, the linear pressure response function is usually utilized by multiplying a coefficient N which is a function of the frequency (or kh) and takes a value around unity. However, in this study, a constant value of N(=1.0) gives a relatively accurate recovery of surface displacements.

• Economic and Environmental Geology
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• v.37 no.2
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• pp.207-223
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• 2004

The purpose of this study is to reveal spatial relationships between landslide and geospatial data set, to map the landslide susceptibility using the relationship and to verify the landslide susceptibility using the landslide occurrence data in Boun area in 1998. Landslide locations were detected from aerial photography and field survey, and then topography, soil, forest, and land cover data set were constructed as a spatial database using GIS. Various spatial parameters were used as the landslide occurrence factors. They are slope, aspect, curvature and type of topography, texture, material, drainage and effective thickness of soil. type, age, diameter and density of wood, lithology, distance from lineament and land cover. To calculate the relationship between landslides and geospatial database, Bayesian probability methods, weight of evidence. were applied and the contrast value that is >$W^{+}$->$W^{-}$ were calculated. The landslide susceptibility index was calculated by summation of the contrast value and the landslide susceptibility maps were generated using the index. The landslide susceptibility map can be used to reduce associated hazards, and to plan land cover and construction.

• The Journal of the Acoustical Society of Korea
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• v.39 no.5
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• pp.379-389
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• 2020

In this study, the flow and noise performances of high-speed fan motor unit for cordless vacuum cleaner is improved by optimizing the impeller which drives the suction air through flow passage of the cordless vacuum cleaner. Firstly, the unsteady incompressible Reynolds averaged Navier-Stokes (RANS) equations are solved to investigate the flow through the fan motor unit using the computational fluid dynamics techniques. Based on flow field results, the Ffowcs-Williams and Hawkings (FW-H) integral equation is used to predict flow noise radiated from the impeller. Predicted results are compared to the measured ones, which confirms the validity of the numerical method used. It is found that the strong vortex is formed around the mid-chord region of the main blades where the blade curvature change rapidly. Given that vortex acts as a loss for flow and a noise source for noise, impeller blade is redesigned to suppress the identified vortex. The response surface method using two factors is employed to determine the optimum inlet and outlet sweep angles for maximum flow rate and minimum noise. Further analysis of finally selected design confirms the improved flow and noise performance.

• Economic and Environmental Geology
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• v.55 no.6
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• pp.633-648
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• 2022

Gravity data were analyzed to identify the cause of clustered seismicity that occurred intensively in Yeoncheon, located in the central part of the Korean Peninsula. Our analysis suggests that the En echelon faults developed in the northwest-southeast direction. In addition, in the eastern part of the Dongducheon Fault, it was interpreted that high-density lower bedrock intermittently lifts close to the surface due to vertical tectonic movement accompanied by a flower structure. The fracture zone of the Dongducheon Fault is estimated that the width is about 200 m, the depth is at least 5 km, and the density is about 15% lower than the adjacent rocks. It is analyzed that the shallow earthquakes that occurred within 5 km depth was concentrated along the low-density En echelon fault fracture zone developed between the high-density rocks intruding close to the surface. Therefore, the earthquakes can be interpreted as the result that the north-south stress caused by the dextral tectonic movement of the Dongducheon Fault activated the En echelon fault in the northwest-southeast direction.

• Spatial Information Research
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• v.8 no.1
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• pp.141-153
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• 2000

The purpose of this study is to develop and apply spatial landslide information system using Geographic information system (GIS) in concerned with spatial data. Landslide locations detected from interpretation of aerial photo and field survey, and topographic , soil , forest , and geological maps of the study area, Yongin were collected and constructed into spatial database using GIS. As landslide occurrence factors, slope, aspect and curvature of topography were calculated from the topographic database. Texture, material, drainage and effective thickness of soil were extracted from the soil database, and type, age, diameter and density of wood were extracted from the forest database. Lithology was extracted from the geological database, and land use was classified from the Landsat TM satellite image. In addition, landslide damageable objects such as building, road, rail and other facility were extracted from the topographic database. Landslide susceptibility was analyzed using the landslide occurrence factors by probability, logistic regression and neural network methods. The spatial landslide information system was developed to retrieve the constructed GIS database and landslide susceptibility . The system was developed using Arc View script language(Avenue), and consisted of pull-down and icon menus for easy use. Also, the constructed database can be retrieved through Internet World Wide Web (WWW) using Internet GIS technology.

• Economic and Environmental Geology
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• v.52 no.3
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• pp.251-258
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• 2019

During the detailed geological survey around the southern Yangsan Fault, we newly found a Quaternary fault outcrop, which cuts unconsolidated sediments. The fault named the Sinwoo site, located in the Sinwoo pasture, Miho-ri, Duseo-myeon, Ulsan metropolitan city, is the first discovered Quaternary fault near the western part of the south Yangsan Fault. In this study, we provide information on characteristics of fault geometry and unconsolidated sediment at Sinwoo site based on the analysis data of topography, drainage, and lineament around the study site. The fault site is situated at pediment slope, but fan-shaped middle terrace, as well as thick sediment exposed at low terrace, indicates that the unconsolidated sediments have been deposited in the alluvial fan environment. The drainage develops to the third-order drainage system, and the first and the second drainage system meet at right angles to each other and form a radial drainage pattern. In addition, the NE-SW direction lineaments can be identified on the basis of the curvature of the river and the step of the topographic relief, running over the Sinwoo site. The fault of $N30-35^{\circ}E/79-82^{\circ}SE$ shows ~ 5.8 m apparent vertical offset and dominantly reverse-slip sense based on slickenline, rotation of pebbles, and drag folding at footwall. However, some discontinuous sediments observed in the footwall are interpreted as fissure-filling materials due to the strike-slip movement. Now, we are under multidisciplinary investigations of additional field survey and age dating in order to determine the evolution of Sinwoo site fault during the Quaternary.