• 한국해안해양공학회지
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• 제6권4호
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• pp.413-420
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• 1994

하천수 플룸(plume)의 퍼짐을 다루는 역학은 플룸의 경계면이 시간과 공간에 따라서 변하기 때문에 자유경계조건의 문제(free boundary problem)로 다루어야 하는 대단히 복잡한 비선형 문제이다. 더욱이 플룸경계를 통한 주변수의 혼합까지 고려할 경우 그 복잡성은 한층 더해진다. 이러한 비선형성과 복잡성을 피하는 기법의 하나가 적분해석법인 바, 본 논문에서는 하천수 플룸의 흐름축에 수직한 횡방향 및 수심방향에 대하여 기본방정식들을 적분함으로 3차원 문제를 1차원 문제로 치환하는 적분해석법을 사용하였다. 다만 이 일이 가능하기 위해서는 유동변수들(유속, 밀도 등)의 횡방향 및 수심방향의 분포함수가 알려져 있음이 전제되어야 하는데 유속의 축방향성분 및 플룸과 주변수 간의 밀도차가 상기 두 방향에 대해서 가우스(Gauss)분포를 갖는다는 잘 검증된 가정을 활용하였다. 그리고 이 가정에서 플룸의 횡방향 유속을 도출해낸 본 연구자들의 기발표된 논문의 결과도 활용하였다. 결과로 얻어진 연행(entrainment)효과까지 포함한 방정식들을 Runge-Kutta 수치해석법을 사용하여 풀었다. 그리하여 하천수 풀룸의 3차원적 해석을 쉽게 수행할 수 있는 수치해석기법을 얻어냈다.

• 한국환경농학회지
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• 제41권4호
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• pp.230-235
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• 2022

BACKGROUND: Ammonia gas emitted from nitrogen fertilizers applied in agricultural land is an environmental pollutant that catalyzes the formation of fine particulate matter (PM2.5). A significant portion (12-18%) of nitrogen fertilizer input for crop cultivation is emitted to the atmosphere as ammonia gas, a loss form of nitrogen fertilizer in agricultural land. The widely practiced method for fertilizer use in agricultural fields involves spraying the fertilizers on the surface of farmlands and mixing those with the soils through such means as rotary work. To test the potential reduction of ammonia emission by nitrogen fertilizers from the soil surface, we have added N, P, and K at 2 g each to the glass greenhouse soil, and the ammonia emission was analyzed. METHODS AND RESULTS: The treatment consisted of non-fertilization, surface spray (conventional fertilization), and soil depth spray at 10, 15, 20, 25, and 30 cm. Ammonia was collected using a self-manufactured vertical wind tunnel chamber, and it was quantified by the indophenol-blue method. As a result of analyzing ammonia emission after fertilizer treatments by soil depth, ammonia was emitted by the surface spray treatment immediately after spraying the fertilizer in the paddy soil, with no ammonia emission occurring at a soil depth of 10 cm to 30 cm. In the upland soil, ammonia was emitted by the surface spray treatment after 2 days of treatment, and there was no ammonia emission at a soil depth of 15 cm to 30 cm. Lettuce and Chinese cabbage treated with fertilizer at depths of 20 cm and 30 cm showed increases of fresh weight and nutrient and potassium contents. CONCLUSION(S): In conclusion, rather than the current fertilization method of spraying and mixing the fertilizers on the soil surface, deep placement of the nitrogen fertilizer in the soil at 10 cm or more in paddy fields and 15 cm or more in upland fields was considered as a better fertilization method to reduce ammonia emission.

• 자원환경지질
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• 제46권2호
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• pp.105-121
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• 2013

본 연구에서는 원격탐사, 전기비저항탐사, 전기전도도탐사(전자기탐사), 시추공 영상촬영법을 융합하여 효과적인 제방의 안정성 및 누수 평가 방법을 서산 A지구 방조제에 적용하여 제시하였다. Landsat ETM+열적외선 밴드를 사용하여 방조제 부근에서 다른 온도의 해수와 담수가 혼합되는 양상을 통해 누수의 존재, 규모 및 기간을 유추하였다. 전기비저항탐사를 방조제를 따라 실시하여 평균비저항 값 83.197 ${\Omega}$-m이하를 보이는 이상대의 수평적 수직적 분포를 확인하였다. 간조와 만조 시의 전기전도도 값의 분석을 통해 배경치의 영향을 최소화한 수평적 이상대 분포를 확인하였다. 시추공영상촬영을 통해 파쇄대의 수직적 분포양상과 기존 탐사법의 정확도를 확인하였다. 그 결과 전체 제방의 연장 중 41.7%에서 세 수평적 이상대 탐사법의 중첩구간이 확인되었으며, 시추공에서 확인된 수직적 파쇄양상을 고려할 때 누수구간이 제방단면의 중심부를 따라 상당부분 수평적으로 연장이 되어 방대한 양의 누수가 존재할 가능성이 높을 것으로 사료된다. 네 탐사법의 융합적 접근은 각 탐사방법이 가지고 있는 장점을 부각하고 단점을 보완하여 수평적 및 수직적인 누수구간과 기간의 확인 및 판별이 가능하고, 시추공에서 확인된 수직적 파쇄양상의 수평적 연장성을 예측하는데 높은 신뢰도를 보인다 할 수 있다.

• 한국결정성장학회지
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• 제8권4호
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• pp.532-538
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• 1998

한국산 천연베릴을 잉요하여 온도구배융제환류법에 의해 에메랄드($3BeO{\cdot}Al_2O_3{\cdot}6SiO_2:Cr^{3+}$) 단결정이 성장되었다. 리튬-몰리브데늄-바나디움 산화물계 융제는 $(MoO_3+V_2O_5)/Li_2O$, 와 $V_2O_5-Li_2O$를 서로 다르게 용융한 2종류의 융제를 혼합하여 제조하였다. 융제의 최적 조성은 산화몰리브데늄.바나디움에 대한 산화리튬의 몰비($(MoO_3+V_2O_5)/Li_2O$)가 3몰이었고 융제첨가제는 Li2O량에 대하여 $K_2O$ 또는 $Na_2O$를 0.2mole% 이내로 치환하였다. 베릴원료의 용융 농도는 융제량에 대하여 3~10% 함량이었고, $Cr_2O_3$ 발색제는 베릴량에 대하여 1%이었다. 융액은 용융, 성장, 회수 블록으로 나뉘어진 3지대 온도구배 결정성장로에서, $1100^{\circ}C$와 $1000^{\circ}C$ 사이의 안정상태에서 연속적으로 순환되도록 하였다. 에메랄드 단결정은 성장지대에서 950~$1000^{\circ}C$ 구간에서 1일 1회 2시간동안 열진동 처리하였을 때 미소핵의 생성이 억제된 대형 단결정을 성장시킬 수 있었다. 육각주상 에메랄드 단결정의 우선성장방향은 c(0001) 바닥면이었고, m(1010) 기둥면에 수직이었다.

• 한국공작기계학회논문집
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• 제18권2호
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• pp.194-200
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• 2009

The extruder type is classified as screw type and non-screw type in terms of the extrusion method. The screw type extruder, which is the most frequently used, is classified as the single screw extruder and the multi-screw extruder. They are classified as vertical type and horizontal type in terms of structure; and those for compounding and for forming in terms of function. The single screw extruder is a universal extruder, most of which is suitable for the extrusion forming of thermoplastic resin. The multi-screw(two-screw, three-screw and four-screw) extruder can increase the extrusion power using the engagement of the screw flank. The single screw extruder does not have a good mixing ratio of the raw material and stable extrusion power, while it has low construction cost and operation cost. In this study, the single screw extruder, which has many weak points compared with the multi-screw extruder, was studied. There have been many studies on the single screw extruder, and they led to its significant development. The existing study method, however, had complex analysis processes and required much time. In this study, the CFD was applied to the performance test and analysis of the extruder, and the optimal design condition of the extrusion power for the screw and die of the single screw extruder was found by comparing the analysis results with the actual performance measurement of the single screw extruder.

• 한국전기전자재료학회논문지
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• 제28권1호
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• pp.51-56
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• 2015

The object of this study is to obtain the optimum mix proportion of halogen free compound with flame resistance and, for the purpose, thermal/electrical characteristics test are conducted using compatibilizing agents, flame resistance agents, hydroxide aluminum, sunscreen, antioxidant and silicon oil on the base resin of linear low density polyethylene (LLDPE), Ethylene vinyl acetate copolymer (EVA). Existing compound method accompanies many requirements to be satisfied including a lot of addition of flame resistance agents, prohibition of impact on mixing capability with base and property and etc. In this study, different from the existing method, the optimum mix proportion is determined and experimented by adding nano clay. Oxygen index test shows no difference between specimens while T-6, T-9 shows oxygen index of 29[%] and 26[%], respectively. This is concluded that hydroxide aluminum, which is a flame resistance agent, leads low oxygen index. From UL94-V vertical flame resistance test, the combustion behavior is determined as V-0, Fail based on UL94-V decision criteria. Viscometry shows low measurements in specimens with separate addition of compatibilizing agents or nano clay. Volume resistivity test shows low measurement mainly in specimens without compatibilizing agents. Therefore, with the flame resistance compound shows better performance for thermal/electrical property and the optimum mix proportion are achieved among many existing materials.

• 한국전자통신학회논문지
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• 제18권6호
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• pp.1049-1056
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• 2023

대기경계층 고도는 지면의 가열로 인해 발생한 난류가 경계층 내의 열, 수증기 등을 혼합하면서 생성되는 꼭대기로 일반적으로 열역학적 방법을 통해 결정한다. 윈드프로파일러는 대기 중으로 보낸 신호의 산란 정보로 대기의 정보를 산출한다. 윈드프로파일러 관측으로 대기경계층 깊이를 결정하기 위해 난류 성분의 스펙트럼 및 난류운동에너지 소산율, 굴절지수구조계수를 산출하는 방법을 제시하였다. 라디오존데 자료를 기반으로 산출한 온위와 비습의 연직 분포 특징과 비교하여 윈드프로파일러 산출물 기반의 대기경계층 고도 결정 방법이 매우 유용한 것으로 평가되었다.

• 대한건축학회논문집:계획계
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• 제34권11호
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• pp.113-123
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• 2018

First of all, the multi-story Housing applying resident's participation in europe was classified by the menu selection method, the two-step supply method and the cooperative method. And then I analyzed flexible unit plan of cases for deriving the planning methode and the characteristics of flexibility. First, I analyzed the area and form of the unit plan, structure and Installation, fixed and variable elements to derive the planning method. The area of units are distributed from a minimum of $35m^2$ to a maximum of $150m^2$, and many of the unit planes have a narrow front and a deep depth. The structure is a long-span wall-structure or a skeleton structure, and is designed without any columns and bearing walls in the interior space for flexibility in spatial composition. The vertical shafts are located in the center of the unit in a box-form or in the corner at the unit dividing wall for free placement of interior wall. Fixed elements are framework and facility systems. Most of the future residents in the two-steps supply method and the cooperative method were able to freely design the internal space within the zoning concept proposed by the architect and change the location of the facade element within module system proposed by the architect. Second, the characteristics of the flexibility applied to the unit plan were divided in integrated flexibility, functional flexibility, construction flexibility, and supply flexibility. The integrated flexibility enables residents to give the variable space combination based on the complex structure of the inner space for providing various living experiences. Regarding functional flexibility, the three-dimensional spatial structure with neutral space has multi-functionality according to the needs of residents and easily accepts mixing of hybrid programs such as work and residence. Constructive flexibility allows residents to create identity by freely planning interior space and changing the size or location of facade components in a determined system of architects. Finally, various types of size and space composition are proposed and realized in the whole building applying menu selection method, so that flexibility in the offer can accommodate and integrate various types of living.

• 대기
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• 제28권4호
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• pp.369-382
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• 2018

Planetary boundary layer height (PBLH), produced by the Local Data Assimilation and Prediction System (LDAPS), was verified using RawinSonde (RS) data obtained from observation at Daegwallyeong (DGW) and Sokcho (SCW) during the International Collaborative Experiments for Pyeongchang 2018 Olympic and Paralympic winter games (ICE-POP 2018). The PBLH was calculated using RS data by applying the bulk Richardson number and the parcel method. This calculated PBLH was then compared to the values produced by LDAPS. The PBLH simulations for DGW and SCW were generally underestimation. However, the PBLH was an overestimation from surface to 200 m and 450 m at DGW and SCW, respectively; this result of model's failure to correctly simulate the Surface Boundary Layer (SBL) and the Mixing Layer (ML) as the PBLH. When the accuracy of the PBLH simulation is low, large errors are seen in the mid- and low-level humidity. The highest frequencies of Planetary boundary layer (PBL) types, calculated by the LDAPS at DGW and SCW, were presented as types Ι and II, respectively. Analysis of meteorological factors according to the PBL types indicate that the PBLH of the existing stratocumulus were overestimated when the mid- and low-level humidity errors were large. If the instabilities of the surface and vertical mixing into clouds are considered important factors affecting the estimation of PBLH into model, then mid- and low-level humidity should also be considered important factors influencing PBLH simulation performance.

• 한국환경과학회지
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• 제23권2호
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• pp.249-259
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• 2014

This paper investigates the characteristics of high $PM_{2.5}$ episodes occurred at Anmyeondo area in spring time, 2009. The monthly mean $PM_{2.5}$ concentration during April was the highest in the year and especially, high levels of $PM_{2.5}$ exceeding standard regulation level were sustained consecutively during 5 to 13 April. To analyze more detailed $PM_{2.5}$ characteristics, numerical simulations were carried out using CMAQ(Community Multi-scale Air Quality) with IPR(Integrated Process Rate) and DDM-3D(Decoupled Direct Method). $PM_{2.5}$ level was lower in daytime than that in nighttime due to vigorous vertical mixing during daytime. The chemical composition was showed that ratio of primary ion components such as sulfate($SO_4{^{2-}}$), nitrate($NO_3{^-}$) and ammonium($NH_4{^+}$) were nearly half of total amount of $PM_{2.5}$. Aerosol and transport process dominantly contributed to $PM_{2.5}$ concentration in Anmyeondo area and contribution rate of local emissions was nearly zero since Anmyeondo area has rare anthropogenic PM emission sources. DDM-3D analysis result showed that $PM_{2.5}$ in Anmyeondo area was influenced by emissions from Shanghai and Shandong region of China.