• 한국항공운항학회지
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• 제20권3호
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• pp.44-50
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• 2012

The noise reduction is important one of considerations in the process of a civil aircraft development program. External noise sources are classified into an air-born source and a structure-born source. Among these noise sources, the most affected noise source into a cabin is the air-born noise source from an engine or propeller. The external noise is transmitted into the cabin through the fuselage structure of airplane which are composed of an fuselage structure, an interior trim panel and an acoustic insulation layer between an fuselage structure and an interior trim panel. Therefore, appropriate fuselage structure and acoustic insulation layer is very important to reduce the internal noise level. In this paper, the vibro-acoustic coupled analysis of the cabin noise of the 80~90 seats regional turboprop aircraft is carried out to validate the acoustic analysis method using Direct BEM and FEM. The sound pressure level onto the fuselage skin is acquired by fan-source noise analysis using BEM, and which sound pressure is used as acoustic noise source in vibro-acoustic noise analysis for cabin noise analysis using FEM.

• 열처리공학회지
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• 제26권3호
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• pp.105-112
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• 2013

The microstructural changes of Fe-20Mn-12Cr-1Cu alloy have been studied during high temperature gas nitriding (HTGN) at the range of $1000^{\circ}C{\sim}1150^{\circ}C$ in an atmosphere of nitrogen gas. The mixed microstructure of austenite and ${\varepsilon}$-martensite of as-received alloy was changed to austenite single phase after HTGN treatment at the nitrogen-permeated surface layer, however the interior region that was not affected nitrogen permeation remained the structure of austenite and ${\varepsilon}$-martensite. With raising the HTGN treatment temperature, the concentration and permeation depth of nitrogen, which is known as the austenite stabilizing element, were increased. Accordingly, the depth of austenite single phase region was increased. The outmost surface of HTGN treated alloy at $1000^{\circ}C$ appeared Cr nitride. And this was in good agreement with the thermodynamically calculated phase diagram. The grain growth was delayed after HTGN treatment temperature ranges of $1000^{\circ}C{\sim}1100^{\circ}C$ due to the grain boundary precipitates. For the HTGN treatment temperature of $1150^{\circ}C$, the fine grain region was shown at the near surface due to the grain boundary precipitates, however, owing to the depletion of grain boundary precipitates, coarse grain was appeared at the depth far from the surface. This depletion may come from the strong affinity between nitrogen and substitutional element of Al and Ti leading the diffusion of these elements from interior to surface. Because of the nitrogen dissolution at the nitrogen-permeated surface layer by HTGN treatment, the surface hardness was increased above 150 Hv compared to the interior region that was consisted with the mixed microstructure of austenite and ${\varepsilon}$-martensite.

• Transactions on Electrical and Electronic Materials
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• 제6권5호
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• pp.229-232
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• 2005

Direct characterization of band alignment at chemical bath deposition $(CBD)-CdS/Cu_{0.93}(In_{1-x}Ga_x)Se_2$ has been carried out by photoemission spectroscopy (PES) and inverse photoemission spectroscopy (IPES). Ar ion beam etching at the condition of the low ion kinetic energy of 400 eV yields a removal of surface contamination as well as successful development of intrinsic feature of each layer and the interfaces. Especially interior regions of the wide gap CIGS layers with a band gap of $1.4\~1.6\;eV$ were successfully exposed. IPES spectra revealed that conduction band offset (CBO) at the interface region over the wide gap CIGS of x = 0.60 and 0.75 was negative, where the conduction band minimum of CdS was lower than that of CIGS. It was also observed that an energy spacing between conduction band minimum (CBM) of CdS layer and valance band maximum (VBM) of $Cu_{0.93}(In_{0.25}Ga_{0.75})Se_2$ layer at interface region was no wider than that of the interface over the $Cu_{0.93}(In_{0.60}Ga_{0.40})Se_2$ layer.

• 한국환경생태학회지
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• 제2권1호
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• pp.19-36
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• 1988

치악산국립공원의 주연부 식생구조 및 출현수종을 밝히기 위해 1988년 7월-9월 사이에 현지조사를 한 결과는 다음과 같다. 수관선형, 수간선형 및 전진형 주연부식생이 나타나고 있었으며, 주연부에서 삼림내부로의 거리에 따른 출현수종들이 수관층위별 상대우점치 변화가 방위와 기존 상층우점수종별로 달랐다. 특히, 남사면의 소나무림 내부에서 주연부 양수들이 우세하게 출현하고 있었으며, 북사면 계류 주연부에서는 호습성수종들이 양수들과 함께 우세하게 출현하였다. 삼림주연부로부터 삼림내부로의 거리가 증가할 수록 수관층위별 종수 및 개체수, 종다양도 및 상이도는 감소하는 경향을 나타냈으며, 주연부깊이는 15-20m로 나타났다. 환경유형별 관목층과 임상층의 주연부우점수종은 고도와 지형적 위치 즉, 계곡부, 능선, 정상부에 따라 달랐으며 특히, 정상부의 주연부 우점수종은 독특하였다. 그리고 고도, 지형적 위치 및 방위가 주연부식생간의 유사도에 영향을 미치는 것으로 나타났다. 고도, 방위 및 지형적위치에 따라 주연부 수종들의 출현빈도계급이 달랐으며, 병꽃나무는 전지역에서 높은 출현빈도를 나타냈으며 병꽃나무, 신갈나무, 물푸레나무, 다래, 산딸기, 소나무, 생강나무, 노린재나무, 두릅나무는 대체적으로 전지역에서 주연부 수종으로 출현했다.

• 한국도로학회논문집
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• 제2권1호
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• pp.135-145
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• 2000

최근 포장도로의 역학적 상태를 평가하는 방법으로 비파괴 시험인 FWD(Falling Weight Deflectometer)와 탄성파시험이 많이 이용되고 있다. 그러나 기존의 방법들은 공용중인 도로에서 차량을 통제시킨 후 시험을 실시해야 하는 제한이 있다. 그러므로 실제 주행하중 통과시 아스팔트 콘크리트 포장구조체의 물성을 추정하여 잔존수명 예측 및 이동하중에 대한 포장체 거동을 분석하는 경우에는 FWD와 같이 표면처짐으로부터 아스팔트 콘크리트 포장구조체 각 층의 물성을 추정하는 방법의 사용이 곤란하다. 이런 경우에 MDD (Multi-Depth Deflectometer)를 통해 얻어진 깊이별 처짐을 사용하여 아스팔트 콘크리트 포장구조체 각 층의 물성을 역산 추정하고자 본 연구에서는 다층 탄성이론의 반복적인 역산과 충격하중의 영향을 고려하여 깊이별 처짐으로부터 아스팔트 콘크리트 포장구조체 각층의 물성을 추정할 수 있는 역산반복기법을 개발한 후 이를 수치검증하였다. 수치모델을 통하여 검증한 결과, 역산추정된 탄성계수와 실제탄성계수 사이의 오차는 최대 0.114%로 신뢰성 있는 결과를 얻었다. 또한 본 연구에서는 주행하중의 속도에 따른 아스팔트 콘크리트 포장구조체의 동적특성을 파악하여 실제적인 포장구조체의 거동을 분석하고자 수도권 외곽 순환고속도로 김포구간에서 실제 트럭주행을 통한 현장시험을 실시하였다. 주행하중에 대한 아스팔트 콘크리트 포장구조체의 거동을 깊이별 처짐 측정장비인 MDD를 이용하여 깊이별 상대처짐을 측정하고, 주행속도에 따라 포장구조체의 거동을 해석하여 차량의 속도와 포장체 거동을 역학적으로 분석하였고, 주행속도별 층별 동적물성을 개발된 역해석 프로그램으로부터 산정하였다. 주행속도별 동적특성 분석결과, 차량의 주행속도가 증가할수록 깊이별 상대처짐은 감소하였고, 실측된 깊이별 처짐으로부터 포장구조체의 층별 물성을 역해석한 결과 속도가 증가할수록 탄성계수가 증가하였다. 따라서 주행속도가 줄어들수록 포장체의 구조적 능력 저하에 크게 영향을 주는 것을 알 수 있었다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2003년도 봄 학술발표회 논문집
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• pp.131-136
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• 2003

Landslide is a natural disaster frequently noticed In korea during monsoon season in flicting nationwise damages on human lives, properties, transportation networks, construction sites, etc. This study is about landslide characteristic in rainfall. This study selects seven sites that occured in 2001 and 2002. So elect areas divide and studied special quality by carcinoma by igneous rock, metamorphic rock, sedimentary rock. According to study finding, because igneous rock area is very thin into 1m interior and exterior soil layer, failures happened much rock and soil interface. There was place that depth of soil layer becomes about 2∼3m being area that receive serious weathering case of metamorphic rock. Therefore, at collapse much debriflow occurrence expect. Case that sedimentary rock area is broken through stratification looked. When see such results, it may become many helps to study characteristics of landslide occurrence area grasping collapse special quality by rock type.

• Journal of applied mathematics & informatics
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• 제9권1호
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• pp.101-124
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• 2002

The convergence rate of a numerical procedure barred on Schwarz Alternating Method (SAM) for solving elliptic boundary value problems (BVP's) depends on the selection of the interface conditions applied on the interior boundaries of the overlapping subdomains. It hee been observed that the Robin condition(mixed interface condition), controlled by a parameter, can optimize SAM's convergence rate. Since the convergence rate is very sensitive to the parameter, Tang[17] suggested another interface condition called over-determined interface condition. Based on the over-determined interface condition, we formulate the two-layer multi-parameterized SAM. For the SAM and the one-dimensional elliptic model BVP's, we determine analytically the optimal values of the parameters. For the two-dimensional elliptic BVP's , we also formulate the two-layer multi-parameterized SAM and suggest a choice of multi-parameter to produce good convergence rate .

• 한국수산과학회지
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• 제22권6호
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• pp.415-423
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• 1990

In a laboratory model the response of the boundary layer flow over topography is studied in a rotating sliced cylinder by employing the source-sink analogy with Ekman layer dynamics. The boundary layer flow is produced by two different fluid. In the first experiment homogeneous fluid is used both for the source and the working fluid of the container. In the second experiment a denser fluid is used for the source with the same working fluid. For the homogeneous western boundary layer flow both the northward and the southward flow were affected by the topography(ridge) to produce a cyclonic motion near the ridge. When woughward moving heavy boundary flow of slower speed and the northward moving faster flow were present at the same time, the splitting of southward flow and the separating of the northward flow were observed with a cyclonic motion at the ridge. The most important factor that influence production of the cyclonic motion has been turned out to be the presence of the topography in the western boundary layer. In particular the role of the southward moving heavy flow over the interior flow pattern was found to be very significant.

• 대한치과보철학회지
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• 제17권1호
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• pp.35-46
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• 1979

A number of experimental studies have been carried out in order to clarify the question as to how temporomandibular joint adapt to the changes of mandibular movement and occlusal equilibration. Recently, the studies on the interrelations between anatomical structure of temporomandibular joint and the state of occlusion have been actively performed in dentistry particularly in prosthodontic field. Author performed extraction of unilateral mandibular molars in 30 mature male rats, and observed histological changes of temporomandibular joint through the light microscope. Following results were obtained. 1. The loss of unilateral teeth gave rise to the changes in the location of condylar head, that is, interior displacement of condylar head in the extraction side and upper displacement in the non-extraction side. 2. Articular disk was compressed by the interior surface of condylar head, resulting in its extension below the condylar neck in the extraction side, and the histological arrangement of the compressed area showed irregular feature. 3. The extension of articular disk below the condylar neck was accompanied with the contraction of muscle fibers which were originated from the articular disk. 4. The cartilage layer of articular fossa to the exterior of the extraction side showed hypertropy. 5. Early in the experiment, the inernal extremity of condylar head of extract ion side showed bone resorption, and cartilage layer of condylar head showed hypertropy. At 12 weeks after experiment, the condylar surface showed flattened, and the cartilage layer of condylar head was replaced by the compact bone. 6. The articular disk showed the formation of pannus in the extraction side as well as in the non-extraction side. 7. The occlusal disturbance due to unilateral missing teeth has brought about the non-inflammatory retrogressive change and osteoarthrotic change late in the experiment.

• 대한기계학회논문집A
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• 제34권12호
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• pp.1821-1828
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• 2010

레이저 샥 피닝(LSP)은 금속재료 표면처리를 위한 획기적인 기술로서 금속 부품의 피로성능 개선을 위해 최근에 널리 적용되고 있다. 널리 알려진 바와 같이 금속재료의 피로 균열은 재료의 응력 상태가 인장(Tension)하에서만 발생되고, 압축(Compression)상태에서는 발생하지 않는다. 따라서 피로수명 개선을 위해 전통적인 샷 피닝(SP)과 함께 다양한 분야에 응용되고 있으며, 특히 LSP 는 금속재료의 표면과 깊이방향에 대해 높은 압축잔류응력을 생성시켜 준다. 본 논문에서는 유한요소 해석기법을 이용하여 LSP 에 의해 발생되는 압축잔류응력 생성과정을 모사하고, 압축잔류응력에 영향을 미치는 다양한 변수에 대해 민감도 해석을 수행하였다.