• 한국음향학회지
• /
• 제10권2호
• /
• pp.52-60
• /
• 1991

경사해저에서의 음파전달은 해안선에 평행한 방향으로 음파의 궤적이 휘어짐을 보인다. 이 현상에 대한 이론적 해석은 해안선 방향으로 음장구역과 음영구역이 형성됨을 보이고 그 범위는 음원 및 수신기의 위치좌표, 경사각, 주파수에 좌우됨을 보인다. 본 연구에서는 실제 해양의 이 현상에 대한 연구의 일환으로 모형 해저를 이용한 실험으로 기존의 이론해석을 검증하고자 한다. 실험에 사용된 경사해저의 모형은 이상적인 pressure-release 경계조건이었고 경사각은 $22.5{\circ}$였다. 부지향성 음원으로는 단일 주파수신호와 광대역 충격신호 두 종류를 사용하였다. 전자는 해안선에 평행한 방향의 공간적 특성해석, 후자는 특저위치에서 음장의 주파수특성 해석에 사용되었다. 실험결과는 이론적인 해안선 방향의 음영구역및 주파수특성 해석과 좋은 일치를 보였다.

• Coupled systems mechanics
• /
• 제1권1호
• /
• pp.59-78
• /
• 2012

The available analytical methods of analysis for laterally loaded piles in level ground cannot be directly applied to such piles in sloping ground. With the commercially available software, the simulation of the appropriate field condition is a challenging task, and the results are subjective. Therefore, it becomes essential to understand the process of development of a user-framed numerical formulation, which may be used easily as per the specific site conditions without depending on other indirect methods of analysis as well as on the software. In the present study, a detailed three-dimensional finite element formulation is presented for the analysis of laterally loaded piles in sloping ground developing the 18 node triangular prism elements. An application of the numerical formulation has been illustrated for the pile located at the crest of the slope and for the pile located at some edge distance from the crest. The specific examples show that at any given depth, the displacement and bending moment increase with an increase in slope of the ground, whereas they decrease with increasing edge distance.

• 농업과학연구
• /
• 제37권3호
• /
• pp.435-449
• /
• 2010

Soils in the sloping uplands in Korea are subject to intensive land use with high input of agrochemicals and are vulnerable to soil erosion. Development of the environmentally sound land management strategy is essential for a sustainable production system in the sloping upland. This report addresses the status of upland agriculture and the best management practices for the uplands toward the sustainable agriculture. More than 60% of Korean lands are forest and only 21% are cultivating paddy and upland. Uplands are about 7% of the total lands and about 62% of the uplands are in the slopes higher than 7%. Due to the site-specificity of the upland, many managerial and environmental problems are occurring, such as severe erosion, shallow surface soils with rocky fragments, and loadings of non-point source (NPS) contaminants into the watershed. Based on the field trials, most of the sloping uplands were classified as Suitability Class III-V and the major limiting factor was slope and rock fragments. Due to this, soils were over-applied with N fertilizer, even though N rate was the recommendation. This resulted in decreases in yield, degradation of soil quality and increases in N loading to the leachate. Various case studies drew management practices toward sustainable production systems. The suggested BMP on the managerial, vegetative, and structural options were to practice buffer strips along the edges of fields and streams, winter cover crop, contour and mulching farming, detention weir, diversion drains, grassed waterway, and slope arrangement. With these options, conservation effects such as reductions in raindrop impact, flow velocity, runoff and sediment loss, and rill and gully erosion were observed. The proper management practice is a key element of the conservation of the soil and water in the sloping upland.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2010년도 춘계학술대회 논문집
• /
• pp.872-879
• /
• 2010

High rock-fill embankment is relatively flexible, which makes crest of embankment subject to excessive amplification in displacement due to earthquake loading. To overcome problems related with site response in high embankment, it is essential to evaluate shear-wave velocity profile of the embankment with improved accuracy and reliability. In this aspect, an experimental research was performed to answer how to perform surface-wave tests and to analyze measurements at an embankment site with a sloping ground surface. Unlike flat ground surface, sloping ground may hamper and slow down propagation of surface waves due to multiple reflections and refractions in embankment. To figure out this reasoning for the effect of multiple reflections and refractions due to sloping surface, surface wave tests were performed at a reservoir embankment of Chung-Song in North KyeongSang Province. Parameters involved in surface wave tests at non-flat surface, including source directionality, geometry-related constraint and frequency components in source function, were investigated using field measurements.

• 한국관개배수논문집
• /
• 제10권2호
• /
• pp.62-70
• /
• 2003

강원도의 고랭지 감자밭에 3개의 침사구를 2002년도에 설치하고 유출수와 함께 배출되는 유사의 제거효과를 평가하였다. 연구유역의 토성은 사질토로 침투능이 매우 커서 강우량과 강우강도가 컸을 때만 5회의 유출현상이 발생하였다. 침사구의 유사제거 효과는 3개의 침사구에서 모두 98$\%$이상으로 측정되었다. 유사제거 효과가 매우 큰 원인중의 하나는 토성이 사질토로 유출수의 유속이 침사구에서 감소하면서 다량의 유사가 침전하였기 때문으로 분

• 한국농공학회지
• /
• 제38권5호
• /
• pp.55-63
• /
• 1996

The situation and cause of bund collapse in steep sloping paddy area by a heavy rainfall of Chungbuk Province were investigated by field surveys. Shapes of paddy plots are irregular and average size of them is 12.6a. Surface, groundwater and plot-to-plot irrigations are being carried out in the study plots. The type of bund collapse can be divided as follows: overflow type and inundation type. The overflow type generally occurs at the bund with slope lacking the design standard. The inundation type damages paddy plots more seriously than the overflow type. It induces continuous bund collapse from a inflow-plot to a outflow-plot and includes lots of type (inside paddy) collapse, which results in much subsoil erosion. The installation of mountain stream weir and maintenance of mountain stream are proposed to prevent the inundation type collapse.

• Advances in robotics research
• /
• 제1권1호
• /
• pp.21-39
• /
• 2014

Due to the rapid progress in the field of robotics, it is a high time to concentrate on the development of a robot that can manoeuvre in all type of landscapes, ascend and descend stairs and sloping surfaces autonomously. This paper presents details of a prototype robot which can navigate in very rough terrain, ascend and descend staircase as well as sloping surface and cross ditches. The robot is made up of six differentially steered wheels and some passive mechanism, making it suitable to cross long ditches and landscape undulation. Static stability of the developed robot have been carried out analytically and navigation capability of the robot is observed through simulation in different environment, separately. Description of embedded system of the robot has also been presented and experimental validation has been made along with some details on obstacle avoidance. Finally the limitations of the robot have been explored with their possible reasons.

• 한국토양비료학회지
• /
• 제49권2호
• /
• pp.157-167
• /
• 2016

The interspecific estimation for tolerance capacities of upland crop species to excessive soil water stress in paddy field is significant in agricultural practices. Most of upland crops can be damaged by either excessive soil water or capillary rise of the water table during rainy season in paddy fields. The major objective of this study was to evaluate water stress of upland crops under different drainage classes in converted paddy field. This experiment was carried out in poorly drained soil (PDS) and imperfectly drained soil (IDS) of alluvial sloping area located at Toero-ri, Bubuk-myeon, Miryang-si, Gyeongsangnam-do. The soil was Gagog series, which was a member of the fine silty, mixed, nonacid, mesic family of Aeric Endoaquepts (Low Humic-Gley soils). Two drainage methods, namely under Open ditch drainage methods (ODM) and, Closed pipe drainage methods (PDM) were installed within 1-m position at the lower edge of the upper paddy fields. The results showed that sum of excess water days ($SWD_{30}$), which was used to represent the moisture stress index, was 42 days (the lowest) in the PDM compared with 110 days in the ODM. Most of upland crops were more susceptible to excessive soil water during panicle initial stage on more PDS than on IDS. Yield of upland crops in the PDM was continuously increased by the rate of 15.1% on sorghum, 15.4% foxtail millet, 53.6% proso millet, 49.6% soybean and 47.9% adzuki bean as compared in the ODM. The capacity for tolerance by excessive soil water based on yield of each upland crop in the poorly drained sloping paddy fields was the order of sorghum, soybean, foxtail millet, proso millet and adzuki bean. Therefore, Sorghum is relatively tolerant to excessive soil water conditions and, may be grown successfully in converted paddy field.

• 한국토양비료학회지
• /
• 제45권5호
• /
• pp.704-710
• /
• 2012

경사지 배수불량 논에서 밭작물의 안정적인 재배를 위한 배수개선 방법을 개발하기 위하여 논둑아래 기저부에 1열로 명거 (겉도랑 배수), 비닐차단막, 암거 (속도랑 배수), 관다발 등 네 가지 종류의 배수시설을 설치하여 배수개선 방법에 따른 토양의 물리적 특성변화를 비교 분석한 결과 다음과 같은 결론을 얻었다. 배수방법별 토양의 용적밀도는 배수방법 간에 큰 차이가 없었으나 집적층 (B층)의 투수력은 암거배수구가 $2.67cm\;hr^{-1}$로 가장 높았고 다음은 관다발배수 $1.53cm\;hr^{-1}$이었으며, 명거배수, 비닐차단막은 $0.8cm\;hr^{-1}$내외로 낮은 경향을 보였다. 경작층 (Ap)의 액상은 명거배수, 비닐차단막 처리구가 35% 내외로 높은 경향을 보였으나 암거배수구에서는 수분함량이 크게 감소되었다. 또한 암거배수구의 기상은 32 ~ 35% 내외로 명거배수, 비닐차단막, 관다발 처리구 17 ~ 20% 보다 상대적으로 높아 공극률이 증가하는 것으로 나타났다. 명거배수 처리구의 토색은 수분과다와 높은 지하수위로 환원작용이 일어나 회색을 보인 반면 암거배수구에서는 투수성 및 통기성이 증가하여 회색층의 토색이 명갈색을 변화되었고 환원층의 출현 깊이가 깊어지고 점차 층위분화가 진행됨을 확인할 수 있었다. 강우 후 토양 깊이별 수분함량 변화를 분석한 결과 명거배수 처리구의 표토에서는 7일이 경과하여야 토양수분이 30 mm이하로 감소되었으나 20 cm 이하의 깊이에서는 항상 수분이 과잉된 상태로 지속되는 경향을 보였다. 반면 암거 배수 처리구에서는 강우 후 5 일이 경과 후에 토양 30 cm 깊이까지 수분함량이 30 mm 이하로 감소되어 배수개선 효과가 가장 높았다. 따라서 "배수불량"인 경사지 논에서 논둑 밑 1열의 암거배수 시설 설치가 명거배수, 비닐차단막, 관다발 배수방법에 비해 토양의 물리성 개선효과가 높아 밭작물의 안정적인 생산과 농지자원의 이용전환 즉 논을 밭으로 이용해야 하는 범용농지 기반 조성을 위한 저비용의 실용적인 배수개선 방법으로 이용성이 높은 것으로 판단되었다.

• 한국농공학회지
• /
• 제45권6호
• /
• pp.83-95
• /
• 2003

In this study, a new concept in a paddy consolidation project is introduced in that curved parallel terracing with contour-lined layout is adopted in sloping areas instead of conventional rectangular terracing. The contoured layout reduces earth-moving considerably compared to rectangular methods in consolidation projects. The objective of the paper is to develop a combinatorial optimization model using the network theory for the design of contour-lined plots which minimizes the volume of earth moving. The results showed that as the length of short side of plot is longer or the land slope is steeper, the volume of earth moving for land leveling increases. The developed optimization model is applied for three consolidated districts and the resulting optimal earth moving is compared with the volume of earth from the conventional method. The shorter is the minimum length of short side of a polt with increases the number of plots, the less is the volume of earth. As the minimum length of short side is 20 m for efficient field works by farm machinery, the volume of earth moving of optimal plot is less by 21.0∼27.1 % than that of the conventional consolidated plots.