• 자원환경지질
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• 제37권4호
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• pp.425-436
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• 2004

본 연구의 목적은 2002년 태풍 루사로 인해 강릉지역에서 발생한 산사태와 관련 요인들 간의 공간적 관계를 분석하는 것이다. 산사태 위치는 위성영상 및 현지조사를 실시하여 탐지하였다. 지형도, 토양도, 임상도, 지질도, 토지피복도 등을 GIS를 이용하여 공간 데이터베이스로 구축되었고, 이러한 데이터베이스로부터, 경사, 경사방향, 곡률, 수계, 지형 종류, 토질, 토앙모재, 토앙배수, 유효토심, 임상종류, 임상경급, 임상영급, 임상밀도, 암상, 토지피복도, 선구조도 등이 산사태 발생요인으로 이용되었다. 빈도비 모델을 이용하여 산사태와 발생 요인 간의 공간적 관계를 추출하였다. 그 결과인 공간적 상관관계는 2002년 루사로 인한 산사테의 특성을 설명하고, 산사태 취약성도를 작성하는데 이용될 수 있다.

• Journal of Welding and Joining
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• 제33권2호
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• pp.8-13
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• 2015

This study was carried out to evaluate mechanical properties of the jointed Al6061/HT590 alloys by friction stir welding (FSW). FSW was conducted under the conditions with tool rotating speed of 500 RPM and traveling speed of 300 mm/min., where Ar gas was introduced to prevent the materials from corrosion during the welding process. Electron back-scattering diffraction (EBSD) was used to characterize microstructures such as grain size, misorientation angle and crystal orientation. Evolution of intermetallic compounds in Al6061 during the process were examined in terms of morphology, size and aspect ratio at three distinct zones Al base material, heat affected zone and stir zone, where transmission electron microscope (TEM) was used. It was revealed that FSW gave rise to refinement of grains as well as growth of intermetallic compounds in Al6061. The morphological changes of intermetallic compounds exerted an influence on mechanical properties, resulting in occurrence of fracture in the part of the base material instead of the jointed parts (heat affected zone and stir zone). This study systematically evaluated the microstructural evolutions during the FSW for joining Al6061 with HT590 and their effect on mechanical properties.

• 한국농공학회논문집
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• 제60권2호
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• pp.121-132
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• 2018

Along with climate change, it is reported that the extreme climate events such as severe drought could cause difficulties of agricultural water supply. To minimize such damages, it is necessary to secure the agricultural water resources by using or saving the amount of irrigation water efficiently. The objectives of this study were to develop paddy water management scenarios and to evaluate their effectiveness on water saving. Three water management scenarios (a) deep irrigation with ponding depth of 20~80 mm (control, CT), (b) no/intermittent irrigation until paddy cracks (water management A, WM-A), and (c) intermittent irrigation with ponding depth under 20 mm (water management B, WM-B) were developed. Water saving effects were analyzed using monitored data from experimental paddy fields, and agricultural water supply was analyzed on a reservoir-scale using MASA model. The observed irrigation amounts were reduced by 21 % and 17 % for WM-A and WM-B compared to CT, respectively, and mainly occurred by the increase of effective rainfall. The simulation results showed that water management scenarios could reduce irrigation by 21~51 % and total inflow by 10~24 % compared to CT. The long-term simulated water level change of agricultural reservoir resulted in the decrease of dead level occurrence for WM-A and WM-B. The study results showed that WT-A and WT-B have more benefit than CT in the aspect of agricultural reservoir water supply.

• 농촌계획
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• 제21권3호
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• pp.145-154
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• 2015

With the rapid change of rural communities and increasing desire for social welfare, the demand for the quality of public spaces and facilities is increasing. However, inefficient location of rural public space and facility has caused problems such as economic inefficiency, inconvenient accessibility, environmental pollution, unsustainable energy use, and disturbance of visual landscape. This study aims to evaluate suitability of public spaces and facilities in three types of rural village: rural downtown village, rural clustered village, and individual village. As a way to measure the suitability of public spaces and facilities, we assessed indicators of suitability in terms of accessibility, usability, biophysical environment, and sustainable management. To evaluate the accessibility, we applied indicators such as distance from residential areas, public transit, market and public facilities. For the evaluation of biophysical environment, we applied indicators such as slope, elevation, aspect, and occurrence of natural disasters. We analyzed digital maps representing the indicators listed above using GIS. We also conducted a survey and face-to-face interviews to evaluate usability and sustainability of management which are not possible to understand through maps. As a result, we identified that suitability of public spaces and facilities in downtown villages is higher than clustered and individual villages. In particular, suitability of infrastructure facilities, social welfare facilities, and income generation facilities in downtown village are higher than those in clustered and individual villages. The suitability of tourism facilities is generally lower than other types of public facility across the three types of villages. Tourism facilities in clustered village have been identified especially unsuitable compared to other types of villages. We expect the outcome of the research is helpful to improve allocation of public spaces and facilities in rural villages.

• Journal of Welding and Joining
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• 제33권6호
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• pp.27-35
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• 2015

Laser welding sector in the automotive industry has been widely recognized as one of the most important bonding processes, such as parts welding. Efforts to improve productivity and weld quality have been progressing steadily. In addition, laser welding is suitable for welding process that can produce high-quality welds suitable for flexible production and small quantity batch productions. In order to ensure the rigidity of the material, high strength material are applied to more than 1 GPa class body parts and automotive bumper beams. However, not only the situation is that the trend of domestic research, but also development is based on product molding considering freedom of shape where reinforcement is applied to meet the safety regulations and high-speed crash performance, despite the use of high strength materials. The tendency for heat-affected zone (HAZ) softening phenomenon common in areas of laser welded high tensile steel welding confirmed the occurrence of weld softening effect according to the process parameters. Based on this, range of process parameters could be selected for ensuring weld quality.

• 동력기계공학회지
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• 제20권6호
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• pp.40-45
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• 2016

The manufacturing process of large scaled Al 7050 alloy is difficult for the occurrence of solidification crack during casting. The aims of this study are the evaluations of microstructure and mechanical properties of extruded Al 7050 billet and ring forged one with large scale. Large scaled Al 7050 billet was casted by direct-chill casting process. The extruded and ring forged specimens were prepared from the casted ingot after residual stress relief and homogenization heat treatment, respectively. Microstructures, hardness and tensile test of the surface, middle and center part of each specimen were performed at room temperature. Sheared and elongated type grains were observed at the edge parts of surface and center area and its aspect ratios of grains were low and similar as 0.21 while that of middle area was closed to 0.92 value in ring forged Al 7050 alloy. The mechanical properties of extruded Al 7050 alloy were superior than those of ring forged one. The hardness values of surface and center part were slightly higher than that of middle part in ring forged Al 7050 alloy.

• 한국지반공학회논문집
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• 제21권9호
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• pp.77-86
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• 2005

집중강우로 인한 철도연변 사면의 활동 및 선로의 유실은 철도 운행에 있어 불안정성을 유발하는 요인으로서 이에 대한 적절한 평가기법이 요구된다. 현장조사 결과 강우로 인한 사면의 활동은 사면내 흙의 특성, 강우강도, 사면의 3차원상 형상과 지층의 지질학적 조건과 상관이 있는 것으로 관측되었다. 본 연구에서는 사면의 활동패턴 중 사면내 요부에서 주변 수계로부터 흘러 들어온 표면유출수로 인하여 발생하는 사면의 활동을 대상으로 하고 있다. 표면유출수의 발생은 Philip 공식에서 계산된 침투율과 강우강도의 비교를 통해서 판정되었다. 표면유출수의 심도를 계산하기 위하여 합리식과 Manning 공식을 적용하였으며, 심도별 사면의 안전율을 구하기 위하여 Iverson 모텔을 수정하여 적용하였다. 수정된 Iverson 모델의 적용에 있어 표면 유출수의 심도를 고려하므로 최대 동수경사가 1 이상의 경우를 고려하였다.

• 한국산림과학회지
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• 제97권3호
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• pp.332-339
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• 2008

경상북도 23개 시․군 산사태 발생지 172개소를 대상지로 선정하여 산사태 발생 특성을 다양한 요인별로 조사 분석하여 산사태 발생 위험 예측을 위한 판정기준표를 작성하였다. 산사태 위험 판정기준표는 수량화 I류를 이용하여 분석하였으며, 산사태 발생량에 영향을 많이 주는 요인은 경사위치, 경사길이, 모암, 방위, 임분경급, 종단명형, 경사도의 순으로 나타났다. 산사태 발생 위험 예측을 위한 산사태 붕괴 위험도 판정기준표를 작성한 결과, 107점 미만 : 안정(IV등급), 107~176점 : 위험도 소(III등급), 177~246점 : 위험도 중(II등급), 247점 이상 : 위험도 대(I등급)로 붕괴 위험도가 구분되었다.

• 한국작물학회지
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• 제44권1호
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• pp.32-37
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• 1999

The experiment was conducted to investigate emergence response of lowland weeds at different soil moisture contents, burying depths and upon changes in soil moisture. Rice germination was over 50% at all burying depths under aerobic condition, but the emergence rate of the soil surface placed seeds in saturated and flooded conditions decreased by 19% and 29%, respectively, as compared with that of aerobic condition. Rice seeds at burying depth of over 3 cm did not emerge at all. The emergence rate of Echinochloa crus­galli (L.) Beauv. in aerobic condition was lower than 30%, but the emergence pattern of E. crus galli (L.) Beauv. at different soil moisture contents and seeding depths was similar to that of rice. Emergence behavior of lschaemum rugosum Salisb., Ludwigia octovalvis (Jacq.) Raven and Sphenoclea zeylanica Gaertn. which are dominant lowland weed species in the Philippines also differed depending on soil moisture conditions and burying depths. lschaemum rugosum Salisb. emerged at all burying depths under aerobic condition, whereasLudwigia octovalvis (Jacq.) Raven emerged only at 0 cm deep under saturated and aerobic condition and Sphenoclea zeylanica Gaertn. at 0 cm deep under flooding condition. Weed seeds planted at 1, 3, and 5 cm deep in continuous flooded and saturated condition did not emerge at all, but upon a change of soil moisture condition from saturated to drainage (S$\rightarrow$D) and flooded to drainage (F$\rightarrow$D), grass weeds began to germinate again and the average emergence rate in S$\rightarrow$D and F$\rightarrow$D were 26% and 5% forE. crus­galIi (L.) Beauv., 9% and 8% forI. rugosum SaIisb., respectively. Weed seeds buried in soil in the pot showed great emergence at S$\rightarrow$D but did not emerge under continuous flooded condition. The diversity index accounting for dominance degree and occurrence aspect of weed, was the lowest at F$\rightarrow$D.

• 한국정밀공학회지
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• 제6권1호
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• pp.45-51
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• 1989

In metal cutting various types of chips are produced in consequence of cutting conditions. According to the type of chips the cutting mechanism is to be changed. Most of the cutting theory is based on the continuous chip because of its convenient analysis, but the occurrence of the saw-toothed chip depends upon the workpiece and/or the cutting conditions, one of which is titanium alloy used widely. Nowadays titanium alloys are used widely with the rapid development of aerospace structural engineering application, whereas the theory of cutting mechanism has not been established yet, and the formatting process has not been understood satisfactorily, either. Unfortunately several misconceptions, conflicting statements and statements needing further clarifi- cation are also found. In this paper an attempt is made to clarify the formation process of saw-toothed chips which are to be produced during the orthogonal cutting process of titanium alloys. They were machined at low speed to avoid the rapid tool wear. We observed the SEM-photographs of chips taken at the quick-st- opping device. It is hoped that a rational model of the mechanics of cyclic chip formation can be developed. The results obtained are as follows. 1. When a saw- toothed chip is formed, the shear band begins at the primary shear zone and trans- fers to the free surface, so that a segment is produced and it is completed by upsetting between the formatting segment and the formatted segment. 2. As the rake angle or the clearance angle increases in the machining of the titanium alloy, the chip approaches to that of the continous type. 3. When the rake angle and the clearance angle are increased the shear energy and the unit friction energy decrease, which shows the same aspect as that of the continuous chip.