• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.1985-1990
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• 2008

1970년대 이후의 고도경제성장기에 치수대책과 동시에 건설골재로서 하상이 굴착된 하천이 많으며, 국가하천 지정구간외에서는 평균하상고가 1.0m 이상 저하한 하천구간도 많다. 또한 국가하천은 상류의 사방공사나 댐건설에 의한 영향이 복합적으로 하도에 나타나고 있어 하상굴착이 하도특성에 어떤 영향을 미치는가를 실증적(實證的)으로 검증하는 것은 어려운 과제이다. 하천에서의 골재채취는 제방부의 침식에 의한 호안파괴, 하상저하에 따른 교량이나 취수보 등 구조물의 기초 노출이 치수적인 문제를 야기할 뿐만 아니라, 단시간내에 하도의 지형구조를 급격하게 변화시켜 여울 소의 하상구조 교란이나 수중 및 하천변의 서식처 파괴 등으로 하천의 물리적 환경에 큰 영향을 미침으로써 생태계를 교란하거나 파괴하는 결과를 초래하게 된다. 본 연구에서는 골재채취로 인하여 교란된 하천의 복원 및 적응관리 계획수립의 전단계에 필요한 교란평가기법을 개발하기 위하여 황강, 남강 및 감천을 대상으로 하여 대조구간과 교란구간을 선정하고 조사 분석하였다. 하천골재 채취가 없거나 경미한 대조구간에서는 홍수량이 변하지 않으면 terrace 모양의 하안부 재료가 하상재료와 거의 같기 때문에 홍수가 있으면 침식된 원래의 하폭으로 회복되는 방향으로 변하지는 않는 경향이 나타났다. 반면에 골재채취가 많은 경우 큰 홍수시의 저수로부의 수심을 증가시키기 때문에 수충부 등의 최심하상고가 크게 되는 경향이 있었으며, 고수부는 침수되는 빈도와 수심이 감소하기 때문에 토사의 퇴적속도(고수부의 상승속도)의 감소, 퇴적물의 세립화 경향이 나타나서 모래, 실트가 퇴적하지 않는 고수부상에 모래, 실트가 퇴적되는 경우가 있고, 반대로 고수부의 퇴적속도가 상승하는 경우도 있었다. 골재채취로 횡단방향의 평탄화가 초래되어 여울 소의 하상구조가 교란됨과 동시에 구간별로 종단경사가 완만해지며, 대부분 교량부에 하상유지공을 설치해야 할 정도로 하상경사가 급변하는 구간이 다수 조사되었다. 또한 선행연구에서 개발된 하상서식환경, 하상재료, 유속/수심상황, 유사퇴적, 하도흐름상태, 하도개수, 여울출현 빈도, 하안 안정성, 식생피복 및 하반림 등 10개의 교란평가항목을 적용하여 대조구간과 비교 평가하였다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.3
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• pp.115-119
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• 2001

Hydroxyapatite-yttria stabilized zirconia bioceramics containing fine zirconia particles were prepared as 3-layered functionally graded materials (FGMs) using a spark plasma sintering (SPS) and hot pressing (HP) apparatuses. The pretreatment of the raw hydroxyapatite promoted the sinterability of hydroxyapatite. The maximum density of pretreated FGM composites could be obtained at lower temperature than that for he untreated FGM samples. No decomposition from hydroxyapatite to three calcium phosphate (TCP) was observed in FGMs of HAp-$ZrO_2$ sintered below $1200^{\circ}C$ for 8 min under 10 MPa by SPS. However, the transformation of the tetragonal zirconia to the cubic modification had occurred in FGMs at this temperature. The presence of zirconia i.e. stress induced transformation of zirconia may be expected to enhance the mechanical properties of HAp-$ZrO_2$ FGM. The SPS is concluded as a better method to fabricated the FGM with dense and high strength compared with HP process.

• Journal of Korean Society for Geospatial Information Science
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• v.13 no.4 s.34
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• pp.27-32
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• 2005

DEM is needed for urban modeling, forecasting of floods and the analysis of slope and aspect. It has been generated using digital maps, aerial photos or satellite imageries. Recently, however, many studies on DEM generation from LiDAR data has been conducted because of its efficiency and accuracy. Filtering is said to be the process of making DEM by eliminating non-ground points from LiDAR data. In most researches, some input parameters such as the size of filter are required. The purpose of this investigation is to automatically obtain DEM by eliminating objects of various sizes without the knowledge of the objects' sizes. The experimental results show that most of objects on steep terrain are eliminated by the proposed method.

• Applied Chemistry for Engineering
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• v.7 no.1
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• pp.18-25
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• 1996

Power input in stirred vessel is especially important in the design of mixers, as well as the evaluation of mixing processes. A type of baffles in mechanically agitated vessels and power employed are major factors that determine the stirring efficiency in a large scale, multi-step processes. In the present study, power input in the totally baffled agitated vesseles was compared systematically in connection with several previous studies and adequate power input correlation was found to be : $Np_{(pitch)}=({\theta}/90^{\circ})Np_{(90^{\circ})}$ Power number correlation was dependent upon the distance of among the impeller in the agitated vesseles, as follows : $$Np=7.09(n_p)^{0.7}(\frac{b_(double)}{d})(\frac{H}{D})^{0.18}$$, $${n_p}^{0.7}(\frac{b_{(double)}}d)$$<2 $$Np=8.73\{(n_p)^{0.7}(\frac{b_{(double)}}{d})\}^{0.7}(\frac{H}{D})^{0.18}$$, $${n_p}^{0.7}(\frac{b_{(double)}}d)$$>2.

• Journal of the Korean Geophysical Society
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• v.9 no.4
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• pp.311-320
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• 2006

Digital filters designed using wavelet theory are applied to bathymetry data acquired from KR5 area of Korea Deepsea Mining Area. The filters used in this study are the linear B-spline wavelet filter and derivative of a Cubic B-spline filter. With proper tuning of the digital filters, we can identify the location and orientation of the abyssal hill and abyssal trough in bathymetry. These features obtained from the digital filters are well correlated with bathymetric image. This quantitative information, which can be used to understand the underlying geophysical processes, can be further processed to obtain the spacing, orientation and distribution of the abyssal hill. This wavelet analysis of bathymetry provides good data to select the mining site.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.13 no.6
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• pp.480-489
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• 1988

Although CDP stacking of common depth gathering is used to get the zero-offset-section, the exploding reflector concept is examined for the modeling of zero source to receiver offset sections in this paper. The acoustic wave equation is compared with a one way wave equation which represents the upgoing wave field only. The one way wave equation used is not derived through an expansion and, therefore, can represent dips up do 90b degrees and may not lost the signals by the dipping angles. There is apparently no simple counterpart of this equation is the space domain and it can be conveniently implemented only by a Fourier method. This paper compares their modeling technique with ray tracing and wave method for over thrust structure which is one of the geological structures are dificult to process and interpret. As a result of modeling much clean and accurate signals, especially, diffractions form the corner and dipping angles can be gathered.

• Journal of the Korean Association of Geographic Information Studies
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• v.11 no.4
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• pp.193-202
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• 2008

The objectives of this study are to analyze the spatial site characteristics of existing tombs and the change in the pattern of spatial distributions of tombs over time. The spatial distributions of tombs located in Honam province along the Honam expressway were investigated by interpreting digital aerial photographs taken in two different points of time; 1990 and 2000. According to the results of the study, the tombs newly observed in 2000 photos were located closer to roads and villages than those found in the photos of 1990. This is a finding indicating that the accessibility of tombs has been more important consideration in determining the location of tomb sites. Also found were the gentle slopes of southern aspects to be favored as tomb sites. Based on the data sets of tombs locations and their topographic site characteristics, the probability function of tombs appearance in the study area was derived using the logistic regression analysis technique. As a result, tomb sites were classified as 74.7% by logistic regression. All of six input factors (elevation, slope, aspect, distance from the roads, the town and the stream, respectively) affected the probability of tombs appearance significantly.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.3 no.4
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• pp.228-233
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• 1998

This study presents a close-range photogrammetry that is applicable to beach profile estimation using a non-metric camera. Based on the analysis of oblique video image in which the video camera was installed on a horizontal plane and the field of view was fixed, a new equation to analyze a photograph was developed considering the following aspects: (1) camera is allowed to be rotated about its optical axis and (2) a simple error model is adopted to correct lens distortion and other systematic errors associated with the non-metric camera, which improves accuracy of non-metric imageries. To test the modified technique, photographs of the beach were taken near the Donghae City in February, 1998. In addition, beach profiles were surveyed with conventional dumpy level and surveying staff. RMS error between the estimated and measured beach profiles is less than 10 cm in elevation.

• Fire Science and Engineering
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• v.28 no.6
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• pp.22-27
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• 2014

In this study a Fuel bed where surface fire spreads through is made to measure the data such as the flame height, radiation, spread rate and temperature distribution of Fuel bed. As experimental variables species of trees, wind velocities and slop are chosen. Fallen leaves of Quercus Variabilis (Q.V.) and Pinus Densiflora (P.D.) are used as fuel. Wind velocity is controlled by simply designed wind turnnel from 1 to 5 m/s. Slope of fuel bed is changed from $0^{\circ}$ to $30^{\circ}$. For the measurements of temperature distribution and spread rate total 35 of K-type 1.6 mm thermocouples are positioned as a lattice design. Radiant heat flow meters are used besides video camera and thermovision camera.

• Journal of Korean Society of Transportation
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• v.24 no.2 s.88
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• pp.79-89
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• 2006

The purpose of this study is to propose a new method using the GPS-INS integrated system which measures the superelevation of a curved yoad rapidly and safely Also, using the CPS-INS integrated system. this Paper is to analyze the expected accuracy of the superelevation on the roads which are already opened for traffic. The superelevation of the roads which are already opened for traffic often changes by roads rehabilitation work such as resurfacing of Pavement and rutting However, it is difficult to measure 1,he changes of road geometry because or the high cost and the safety problem. If the measurement of superelevation using GPS-INS integrated system is used instead of existing conventional surveying method, the superelevation of road is expected to be measured accurately(under 0.4% RMSE) just by driving without interfering the traffic Therefore, the application of the GPS-INS integrated system is expected to be useful tool for measuring the superelevation of the roads.