• Title/Summary/Keyword: Topographic Characteristics

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Micro/Nano Adhesion and Friction Characteristics of PTFE Coating Film Deposited by IBAD Method (IBAD 방법으로 코팅된 PTFE 박막의 마이크로/나노 응착 및 마찰 특성)

  • 윤의성;오현진;한흥구;공호성;장경영
    • Tribology and Lubricants
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    • v.20 no.5
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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.

Surface Wind Regionalization Based on Similarity of Time-series Wind Vectors

  • Kim, Jinsol;Kim, Hyun-Goo;Park, Hyeong-Dong
    • Asian Journal of Atmospheric Environment
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    • v.10 no.2
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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.

Vibration Characteristics and Performance of Cantilever for Non-contact Atomic Force Microscopy (비접촉 원자간력 현미경의 탐침 캔틸레버 진동 특성 및 측정 성능 평가)

  • 박준기;권현규;홍성욱
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.14 no.6
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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.

The Effects of Golf Course Construction on the Geomorphic Characteristics of a Small Watershed (골프장 조성이 소유역의 지형적 특성에 미치는 영향 분석)

    • Journal of the Korean Institute of Landscape Architecture
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    • v.27 no.2
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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.

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Morphological Classification of Unit Basin based on Soil & Geo-morphological Characteristics in the yeongsangang Basin (토양 및 지형학적 특성에 따른 영산강유역의 소유역 분류)

  • Sonn, Yeon-Kyu;Hyun, Byung-Keun;Jung, Suk-Jae;Hur, Seong-Oh;Jung, Kang-Ho;Seo, Myung-Chul;Ha, Sang-Keun
    • Korean Journal of Soil Science and Fertilizer
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    • v.40 no.4
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    • pp.262-268
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    • 2007
  • To characterize morphological classification of the basins, four major basin characteristics of the unit basins, including sinuosity, ratio of forest, ratio of flat area, and tributary existence were selected for cluster analysis. The analysis was carried out using soil map, topographic map, water course map, and basin map of the fifty unit basins in the Yeongsangang Basin. The unit basins could be categorized to five basin groups. The fitness by the Mantel test showed good fit of which r was 0.830. These grouping based on comprehensive soil and topographic characteristics provides best management practices, water quality management according to pollutants, increased water related model application and reasonable availability of water management. For agricultural management of water resources and conservation of water quality from agricultural non-point pollutants, therefore, comprehensive systematic classification of soil characteristics on unit basin might be an useful tool.

Comparative Analysis of the CALPUFF and AERMOD Atmospheric Dispersion Models for Ready-Mixed Concrete Manufacturing Facilities Generating Particulate Matter (미세먼지 발생 레미콘시설에서의 대기확산모델 CALPUFF와 AERMOD 비교 분석)

  • Han, Jin-hee;Kim, Younghee
    • Journal of Environmental Health Sciences
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    • v.47 no.3
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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.

Suggestion of Slope Evaluation by DEM-based Aggregation Method (DEM 기반 조합방법에 의한 경사도 평가기법의 제안)

  • Lee, Geun Sang;Choi, Yun Woong;Cho, Gi-Sung
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.26 no.6D
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    • pp.1019-1023
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    • 2006
  • The slope information based on DEM is very useful for urban planning, landscape, road design and water resource areas such as rainfall-runoff and soil erosion estimation. The resolution of slope, which is from DEM, can be variously decided by an application fields and the kinds of modeling method. In particular, the more decreased resolution makes the more decreased slope value because of the increased horizontal distance. This study presents slope evaluation method by aggregation method based on discharge and Manning's velocity equation to advance the loss of slope information in according to the resolution, and then applied it to calculate topographic factors of soil erosion model. As a result, conventional method shows 34.8% errors but aggregation method shows 12.6% errors. This study selected up-, middle-, and downstream region in watershed and analyzed the capability of aggregation method in order to estimate the influence of topographic characteristics. As a result of estimation, aggregation method shows more advanced results than conventional method. Therefore, the slope evaluation method by aggregation method can improve efficiently the loss of slope information in according to the variation of resolution in water resource area such as rainfall-runoff model.

Patho-epidemiological Features of Esophageal and Gastric Cancers in an Endemic Region: a 20-year Retrospective Study

  • Hajmanoochehri, Fatemeh;Mohammadi, Navid;Nasirian, Neda;Hosseinkhani, Mohsen
    • Asian Pacific Journal of Cancer Prevention
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    • v.14 no.6
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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.

Mapping of Temperature and Rainfall Using DEM and Multivariate Kriging (수치표고모델과 다변량 크리깅을 이용한 기온 및 강수 분포도 작성)

  • Park, No-Wook;Jang, Dong-Ho
    • Journal of the Korean Geographical Society
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    • v.43 no.6
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    • pp.1002-1015
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    • 2008
  • We investigate the potential of digital elevation model and multivariate geostatistical kriging in mapping of temperature and rainfall based on sparse weather station observations. By using elevation data which have reasonable correlation with temperature and rainfall, and are exhaustively sampled in the study area, we try to generate spatial distributions of temperature and rainfall which well reflect topographic effects and have less smoothing effects. To illustrate the applicability of this approach, we carried out a case study of Jeju island using observation data acquired in January, April, August, and October, 2005. From the case study results, accounting for elevation via colocated cokriging could reflect detailed topographic characteristics in the study area with less smoothing effects. Colocated cokriging also showed much improved prediction capability, compared to that of traditional univariate ordinary kriging. According to the increase of the magnitude of correlation between temperature or rainfall and elevation, much improved prediction capability could be obtained. The decrease of relative nugget effects also resulted in the improvement of prediction capability.

Hazard Evaluation of Levee by Two-Dimensional Hydraulic Analysis (2차원 수리해석에 의한 하천 제방 위험도 평가분석)

  • Park, Jun Hyung;Kim, Tae Hyung;Han, Kun Yeun
    • Journal of Wetlands Research
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    • v.18 no.1
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    • pp.45-57
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    • 2016
  • Levee safety is being evaluated using one of the several failure causes including overtopping, infiltration and erosion or 1D hydraulic analysis considering physical characteristics of levee in practical engineering works. However, mentioned evaluation methods are not able to consider various failure causes of levee at the same time and to get reliable results where requires the accurate topographic information. This study proposed the flood hazard index which is able to consider several hazard factors involving overtopping, infiltration and erosion risk simultaneously. The index was generated from results of 2D hydraulic analysis reflecting accurate topographic information. The study areas are the confluences of the Nakdong River and two streams(Gamcheon and Hoecheon). Levee safety was evaluated using results based on 2D hydraulic analysis considering riverbed changes of before and after dredging work in the study area. This study will contribute to estimate the reliable safety evaluation of levee where may have hazards during extreme flood events.