• Tribology and Lubricants
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• 제20권5호
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• pp.237-244
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• 2004

Micro/nano tribological characteristics of PTFE coating films were experimentally studied. PTFE (polytetrafluoroethylene) modified polyethylene and low molecular weight PTFE were used as a coating materials. These films were deposited on Si-wafer (100) by IBAD (ion beam assisted deposition) method. The Ar ion beam sputtering was performed to change the surface topography of films using a hollow cathode ion gun under different Ar ion dose conditions in a vacuum chamber. Micro/nano tribological characteristics, water wetting angles and roughness were measured with a micro tribotester, SPM (scanning probe microscope), contact anglemeter and profilometer, respectively. The durability of the films were measured with macro tribotester. Results showed that the PTFE coating surfaces were converted to hydrophobic. The water contact angle of coated surfaces and surface roughness increased with the coating thickness. Adhesion and friction in micro and nano scale were governed by magnitude of normal load in soft material such as PTFE films. As the increase of sputtering time on low molecular weight PTFE films, the surface roughness was increased and nano adhesion and friction were decreased. The nano tribological characteristics of surfaces are mainly improved by chemical modification such as PTFE coating and given a synergy effect by the physical modification such as topographic modification.

• Asian Journal of Atmospheric Environment
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• 제10권2호
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• pp.80-89
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• 2016

In the complex terrain where local wind systems are formed, accurate understanding of regional wind variability is required for wind resource assessment. In this paper, cluster analysis based on the similarity of time-series wind vector was applied to classify wind regions with similar wind characteristics and the meteorological validity of regionalization method was evaluated. Wind regions in Jeju Island and Busan were classified using the wind resource map of Korea created by a mesoscale numerical weather prediction modeling. The evaluation was performed by comparing wind speed, wind direction, and wind variability of each wind region. Wind characteristics, such as mean wind speed and prevailing wind direction, in the same wind region were similar and wind characteristics in different wind regions were meteor-statistically distinct. It was able to identify a singular wind region at the top area of Mt. Halla using the inconsistency of wind direction variability. Furthermore, it was found that the regionalization results correspond with the topographic features of Jeju Island and Busan, showing the validity.

• 한국소음진동공학회논문집
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• 제14권6호
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• pp.495-502
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• 2004

This paper presents the vibration analysis and the performance evaluation of cantilevers with probing tips for non-contact scanning probe microscopy. One of the current issues of the scanning probe microscopy technology is to increase the measurement speed, which is closely tied with the dynamic characteristics of cantilevers. The primary concern in this research is to investigate the relation between the maximum possible speed of non-contact scanning probe microscopy and the dynamic characteristics of cantilevers. First, the finite element analysis is made for the vibration characteristics of various cantilevers in use. The computed natural frequencies of the cantilevers are in good agreement with measured ones. Then, each cantilever is tested with topographic measurement for a standard sample with the scanning speed changed. The performances of cantilevers are analyzed along with the natural frequencies of cantilevers. Experiments are also performed to test the effects of how to attach cantilevers in the piezo-electric actuator. Finally, measurement sensitivity has been analyzed to enhance the performance of scanning probe microscopy.

• 한국조경학회지
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• 제27권2호
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• pp.41-50
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• 1999

The purpose of this study is to find out the changes in geomorphic characteristics of a small watershed when a golf course is constructed. The research site is a set of seven small watersheds including an 18-hole golf course that were randomly selected. The size, shape, and drainage network of watersheds were measured by using planimeter, watershed eccentricity, and stream order, respectively. In addition, a 25m$\times$25m mesh was used on topographic maps and grading plans in order to obtain the slope, elevation, and aspect of the watersheds. The major results of this research, while investigating of the changes in geomorphic characteristics of watersheds when a golf course is constructed, are as follows: 1. The size of watersheds is increased in accordance to the difference in elevation between the golf course site and the small watershed. 2. The watershed eccentricities are in general similar except for a few low-valued cases. 3. The changes in the average altitude and the gradient are more drastic with their bigger original values. 4. The aspects are changed more with decreasing elevation. 5. The stream order decreases in the case of a low watershed eccentricity. 6. The surface modification has a closer relationship to the slope rather than the size of effective use area. 7. With a steeper gradient and an excessively low gradient, the height of cutting/filling is increased.

• 한국토양비료학회지
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• 제40권4호
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• pp.262-268
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• 2007

농업 비점오염원으로부터의 수질 보전이나 수자원 관리는 농업적 관리뿐만 아니라 수질관리 및 수자원 관리를 위해서도 유역단위 특히, 소유역의 토양특성을 포괄하는 단위로 체계적으로 분류할 필요성이 있다. 우리나라의 남서쪽에 위치한 영산강유역의 50개 소유역을 대상으로 토양도, 지형도, 하천도 및 유역도를 이용하여 만곡도, 산림의 비율, 평탄지의 비율, 다른 소유역으로부터의 유입 여부 등 토양학적으로 중요한 4개의 특성을 이용하여 군집분석을 수행하였다. 그 결과 5개의 군으로 구분할 수 있었으며, 이 구분의 적합도를 검정하기 위하여 Mantel test를 한 결과 r = 0.83으로 나타나 적합하다는 결론을 얻었다. 이와 같이 토양과 지형특성을 포괄하는 소유역의 분류 및 유사성에 따른 그룹화는 농업에서의 최적영농관리나 오염물질에 따른 수질관리, 수문모형의 적용성 확대 및 수자원 관리에 합리적 유용성을 제공할 것이며 체계적 관리의 밑바탕이 될 것이다.

• 한국환경보건학회지
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• 제47권3호
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• pp.267-278
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• 2021

Objectives: Using atmospheric dispersion representative models (AERMOD and CALPUFF), the emissions characteristics of each model were compared and analyzed in ready-mixed concrete manufacturing facilities that generate a large amount of particulate matter (PM-10, PM-2.5). Methods: The target facilities were the ready-mixed concrete manufacturing facilities (Siheung RMC, Goyang RMC, Ganggin RMC) and modeling for each facility was performed by dividing it into construction and operation times. The predicted points for each target facility were selected as 8-12ea (Siheung RMC 10, Goyang RMC 8, and Gangjin RMC 12ea) based on an area within a two-kilometer radius of each project district. The terrain input data was SRTM-3 (January-December 2019). The meteorological input data was divided into surface weather and upper layer weather data, and weather data near the same facility as the target facility was used. The predicted results were presented as a 24-hour average concentration and an annual average concentration. Results: First, overall, CALPUFF showed a tendency to predict higher concentrations than AERMOD. Second, there was almost no difference in the concentration between the two models in non-complex terrain such as in mountainous areas, but in complex terrain, CALPUFF predicted higher concentrations than AERMOD. This is believed to be because CALPUFF better reflected topographic characteristics. Third, both CALPUFF and AERMOD predicted lower concentrations during operation (85.2-99.7%) than during construction, and annual average concentrations (76.4-99.9%) lower than those at 24 hours. Fourth, in the ready-mixed concrete manufacturing facility, PM-10 concentration (about 40 ㎍/m³) was predicted to be higher than PM-2.5 (about 24 ㎍/m³). Conclusions: In complex terrain such as mountainous areas, CALPUFF predicted higher concentrations than AERMOD, which is thought to be because CALPUFF better reflected topographic characteristics. In the future, it is recommended that CALPUFF be used in complex terrain and AERMOD be used in other areas to save modeling time. In a ready-mixed concrete facility, PM-10, which has a relatively large particle size, is generated more than PM-2.5 due to the raw materials used and manufacturing characteristics.

• 대한토목학회논문집
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• 제26권6D호
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• pp.1019-1023
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• 2006

DEM에 기초한 경사정보는 도시계획, 조경, 도로설계분야는 물론 강우유출 및 토사유실평가와 같은 수자원분야에서도 매우 유용하게 활용된다. DEM에서 추출한 경사도의 해상도는 응용분야 및 모델링의 종류에 따라 다양하게 결정될 수 있으며, 특히 해상도가 낮아질수록 수평거리가 증가하기 때문에 경사도는 감소하는 특징을 갖는다. 본 연구에서는 해상도에 따른 경사정보의 손실을 개선하고자 유량공식과 Manning의 유속공식을 조합한 경사도 평가기법을 제안하였으며, 토사유실모델의 지형인자를 계산하는데 활용하였다. 적용결과 기존의 경사도 평가기법을 이용한 지형인자는 34.8%의 오차를 나타낸 반면, 조합방법에 의한 경사도를 활용한 경우에는 12.6%로 비교적 낮은 오차특성을 확보할 수 있었다. 또한 지형특성에 따른 영향을 평가하기 위해, 유역내 상 중 하류 지역을 선정하여 조합방법에 의한 효용성을 평가한 결과, 조합방법이 기존방법에 비해 개선된 결과를 보였다. 따라서 조합방법에 의한 경사도 평가기법은 강우유출모델과 같은 수자원분야에서 해상도 변화에 따른 경사정보의 손실을 효과적으로 개선할 수 있을 있으리라 판단된다.

• Asian Pacific Journal of Cancer Prevention
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• 제14권6호
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• pp.3491-3497
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• 2013

Background: Gastric and esophageal cancers are among the most lethal human malignancies worldwide. Of all malignancies estimated in Iran (47,100), gastric and esophageal cancers were responsible for 7,800 and 3,500 deaths in 2008 respectively. The present study aimed to provide an image of patho-epidemiological characteristics with their trends during two past decades with emphasis on topographic, morphologic, and some demographic features. Materials and Methods: In a hospital-based retrospective study in 2009, all pathological reports from esophageal endoscopies and gastric biopsies through a 20 years period (1989-2008) were collected and analyzed in four interval periods(five years each). Also, all eligible samples in hospital archives were enrolled for further testing. Besides, demography, topography and morphology of all samples were determined and analyzed by statistical software. Results: No significant statistical difference was seen in frequency of espohageal and gastric tumors throughout the study. Esophageal cancer cases were older than gastric. Sex ratio was 2.33/1 and men had a higher rate of both esophageal and gastric tumors. Stomach cancer included 64.3% of all cases. Inferior third and end of esophagus were common locations for esophageal tumors whereas proximal stomach was common for gastric tumors. Squamous cell carcinoma and adenocarcinoma were common morphological types of tumors in esophagus and stomach respectively. Conclusions: Morphological trends showed an increase of esophageal adenocarcinoma and diffuse/intestinal ratio in stomach cancers. Trends in incidence from gastric cancer decreased based on topographic studies but we could not find a topographical trend toward cadia.

• 대한지리학회지
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• 제43권6호
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• pp.1002-1015
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• 2008

이 논문에서는 기상관측소의 기온 및 강수 관측치를 이용한 공간적 분포도 작성에 수치표고모델(DEM)과 다변량 크리깅의 적용 가능성을 검토하였다. 기온 및 강수와 상관성을 가지면서 연구지역의 모든 지점에서 값을 제공하는 고도자료를 분포도 작성에 이용함으로써, 미관측 지점에서의 정보 부재 효과를 완화하면서 지형효과를 잘 반영하는 분포도를 작성하고자 하였다. 제주도 지역의 2005년 1월, 4월, 8월 및 10월의 월평균기온 및 월강수량 분포도 작성 사례 연구를 통해, 고도자료를 공동 크리깅에 의해 통합하였을 때 평활화 효과를 완화하면서 지형효과를 잘 반영하는 기온 및 강수 분포도 작성이 가능하였다. 또한 단변량 지구통계 기법인 정규 크리깅과 비교하였을 때, 보다 향상된 예측 능력을 나타내었다. 부가적으로 고도자료와의 상관성이 높을수록, 상대적 너겟 효과가 적을수록 예측 능력이 향상됨을 확인할 수 있었다.

• 한국습지학회지
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• 제18권1호
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• pp.45-57
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• 2016

실무에서 사용되고 있는 제방의 안전도 평가는 여러 가지 붕괴원인 중 하나의 요인에 대해서만 평가를 하거나 주로 제방의 물리적인 특성을 이용한 1차원 수리분석을 통한 평가에 국한되어 왔다. 하지만 이러한 평가기법들은 제방의 다양한 붕괴원인을 동시에 고려할 수 없으며, 정확한 지형정보를 필요로 하는 곳에서 신뢰도가 떨어지는 문제점을 안고 있다. 따라서 본 논문에서는 정확한 지형정보를 반영한 2차원 수리해석을 결과를 이용하여 제방의 다양한 붕괴원인인 월류, 침투, 침식위험도를 동시에 고려한 제방 위험도 지수를 제안하였다. 낙동강 유역의 주요 합류부에 대해 하천준설사업 전 후의 지형 변화를 고려하여 2차원 수리모형을 이용한 수리해석을 실시하고 그 결과를 통해 제방 위험도를 평가하였다. 본 연구는 정확한 하천의 형상을 반영한 수리해석 결과를 이용한 객관적이고 신뢰도 높은 제방위험도 평가에 기여할 수 있을 것으로 기대된다.