• 지질공학
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• 제22권1호
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• pp.113-121
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• 2012

본 연구에서는 부산시 금정구 금정산 일대에서 채취한 단층비지대의 공학적 특성을 여러 형태의 절리모형실험을 통하여 파악하였다. 이 지역은 양산단층과 동래단층과 같은 주요 대규모 단층과 부수적인 소규모 단층이 다수 분포하고 있어, 이 지역의 시추공 중 이러한 단층을 관통한 시추공에서 단층비지 및 흑운모 화강암 절리 시료를 추출하여 실내 실험에 사용하였다. 우선 단층비지대의 광물학적 특성을 파악하기 위한 XRD 및 SEM 분석에서는 단층비지대가 수분 함유에 따른 급격한 전단강도 감소를 예측할 수 있는 판상구조의 점토광물인 kaolinite, montmorillonite, illite, sericite으로 이루어져 있는 것으로 파악되었다. 단층비지에 대한 전단강도 특성은 비지 자체의 전단강도 측정과 단층비지를 충전한 여러 형태의 자연 및 인공절리면에 대한 절리면의 전단강도 측정으로 구하였다. 실험 결과, 단층비지가 충전된 절리면은 충전물질이 없는 절리면보다 급격한 전단강도의 감소가 발생하였으며, 단층비지의 내부 마찰각보다 절리면 사이에 충전된 단층비지의 마찰각이 더욱 낮게 측정되었다. 이러한 실험 결과는 암반과 접하고 있는 단층비지의 전단 특성은 단층비지 자체가 가진 전단강도보다 더욱 작은 값을 가지기 때문에 암반 구조물의 안정성을 저해하는 요소로 작용할 수 있다는 것을 보여주고 있다.

• 한국정밀공학회지
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• 제12권9호
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• pp.115-125
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• 1995

부품가공에 있어서 생산성향상을 위하여 버제거를 위한 고도의 기술이 더욱 중요하게 되었다. 특히 CIM 체제에서는 버제거의 자동화를 위하여 가공중에 발생하는 버형성과 파단현상을 정량적으로 예측할 필요성이 더욱 커졌다. 이미 연구된 2차원절삭에서의 버형성 모델을 실제적인 3차원절삭에 적용하기 위하여 기존의 모델을 수정하는 작업이 이루어졌다. 3차원 절삭모델로는 절삭인선에 수직한 면에서의 칩과 공구의 상대운동에 의해서 결정된다고 하는 Rubenstein의 가정이 사용되었다. 본연구에서 다루에되는 롤오버(roll-over) 버는 항상 공구진행방향으로 발생하기 때문에 3차원절삭에서의 버형성을 공구진행방향의 평면내에서의 2차원 절삭의 집합 으로 가정하였다. 공구의 기울림각(inclination angle)이 커질수록 버형성의 크기나 파단면의 크기가 감소하였다. 두종류의 파단이 버형성중에 관찰되었다. 하나는 가공물 끝면에 평행하게 파단면이 발생하였으며 다른 하나는 이에대하여 기울어진 파단이 일어났다. 가공물 끝면에 평행한 경우는 수정된 모델로부터 등가초기공구위치( equivalent initial tool distance)로부터 예측이 가능하며 기울어진 경우는 이결과와 공구의 기울림각으로부터 파단위치를 예측할 수 있다.

• Composites Research
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• 제13권6호
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• pp.9-22
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• 2000

한 방향으로 상자형 단면을 갖는 보강재로 보강된 복합재료 사각판에 대한 고유진동수 및 한 방향 압축, 양방향압축, 양 또는 음의 전단하중에 대한 임계좌굴하중에 대한 이론적 해석을 위해 에너지법을 기초로 한 Rayleigh-Ritz 과정이 이용되었다. 해석과정에서 판 구조물에서의 보강재에 의한 보강효과를 표현하기 위해 이산보강이론이 도입되었다. 해의 정확도를 검증하기 위해 수렴성 검토가 이루어졌으며, 몇 가지 예에 대해 진동 및 좌굴모드형상의 contour plot이 제시되었다. 보강재의 수, 위치, 형상비와 판의 적층각, 형상비 등과 같은 변수에 따른 영향을 중점적으로 설명하였다.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 추계학술대회 논문집
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• pp.192-197
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• 2002

In this study, examined the cutting characteristics of alumuminum alloy AC8A-T6 that is used to present car piston materials. And in been holding materials machining empirically escape as result that experiment comparison changing the cutting speed and feed on various condition to choose efficient machining condition. The following results can be summarized from this research. 1. As the cutting speed decreased, principal cutting force and thrust cutting force is increased, and reason that cutting force interacts greatly in the low cutting speed is thought by result by BUE's stabilization. 2. The feed speed and cutting speed increase, friction factor is decrescent and the cause appeared the thrust cutting force is fallen than cutting force relatively because chip flow according to increase of the feed rate is constraint. 3. Though specific cutting resistance grows cutting area and the feed rate are few, the cause was expose that shear angle decreases by rake face of tool gets into negative angle remarkably as wear of a cutting tool or defect part of workpiece is cut. 4. Cutting speed do greatly depth of cut is slow, surface roughness examined closely through an experiment that becomes bad, and know that it can get good surface that process cutting speed because do feed rate by 0.1mm/rev low more than 250m/min to get good surface roughness can.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 춘계학술대회논문집
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• pp.183-190
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• 2009

The objective of this study is to get simulation data about pulsatile flow around an interior solid body inside a bifurcated tube. All the processes were based on CFD method, with a commercial FVM code, SC/Tetra ver. 6.0 for solving, and with CATIA R16 for generating geometries. The bifurcated tube models were drawn with the bifurcated angle of 45 degrees, considering Murray's law about the diameter ratio. With various locations of the object, the effects of flow on the drag were considered. For the pulsating flow condition, the velocity wave profile was given as the inlet boundary condition. To validate all the result, the simulation was compared with the existing data of the other papers first. Overall flow field of both data were similar, but there was some difference at a zero velocity. Therefore the next simulation was continued with the sine wave profiles where there is no negative flow, and then the data was compared with one of the pulmonary artery velocity where there is negative flow. The final process was to calculate flow variables such as the wall shear stress (WSS) and to compute the drag of the solid object.

• Computers and Concrete
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• 제31권3호
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• pp.207-221
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• 2023

In this investigation, the interaction between opening space and neighboring joint has been examined by experimental test and Particle flow code in two dimension (PFC2D) simulation. Since, firs of all PFC was calibrated using Brazilian experimental test and uniaxial compression test. Secondly, diverse configurations of opening and neighboring joint were provided and tested by uniaxial test. 12 rectangular sample with dimension of 10 cm*10 cm was prepared from gypsum mixture. One quarter of tunnel and one and or two joint were drilled into the sample. Tunnel diameter was 5.5 cm. The angularities of joint in physical test were 0°, 45° and 90°. The angularities of joint in numerical simulation were 0°, 30°, 60°, -30°, -45°, -60° and its length were 2cm and 4cm. Loading rate was 0.016 m/s. Tensile strength of material was 4.5 MPa. Results shows that dominant type of crack which took place in the model was tensile cracks and or several shear bands develop within the model. The Final stress is minimum in the cases where oriented angle is negative. The failure stress decrease by decreasing the joint angle from 30° to 60°. In addition, the failure stress decrease by incrementing the joint angle from -30° to -60°. The failure stress was incremented by decreasing the number of notches. The failure stress was incremented by decreasing the joint length. The failure stress was incremented by decreasing the number of notches. Comparing experimental results and numerical one, showed that the failure stress is approximately identical in both conditions.

• 한국농공학회지
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• 제31권2호
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• pp.43-53
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• 1989

In this research programs, a series test was conducted to show the effects of freeze/thaw process on the various soil properties. The tests were carried out taken from the west sea shore of Korean peninsular and the west sea shore of Scotland, and their results are as follows; 1. There was a positive total heave in a freezing run, although water may he expelled for the sample initially. The water flow must he reverse' from expulsion to intake. 2. The confining pressure had an overriding influence on the heave and frost penetration, a sudden change of the axial strain at failure with strain rate was observed occuring at a strain rate between 10-5 and 10-6, and the initial friction angle of frozen clay was appeared zero. 3. There was shown a significant decrease in liquid limit of soil which was subjected to freeze/thaw process for the initial value of about 20% because of soil particles aggregation. 4. The cyclic freeze/thaw caused a sinificant reduction in shear strength and its thixotropic regain. The frozen/thawed soil exibited negative strength regain, particularly at high freeze/thaw cycles. 5. The freezing temperature greatly influenced on the failure strength of soils and this. Trend was more pronounced the lower the freezing temperature and shown the ductile failure with indistinct peaks.

• Applied Biological Chemistry
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• 제48권4호
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• pp.404-410
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• 2005

Sopoongsan is an oriental medicinal composition including 12 medicinal herbs. Sopoongsan is known to have anti-inflammatory, antimicrobial, anti-allergic, and anticancer effects on human skin. The results of stability test showed that the creams containing Sopoongsan extracts were very stable at both accelerated temperature conditions and sun-light. And pH and viscosity of each cream did not change greatly for 56 days. From the particle size and rheological measurements, it can be known that when the amount of the Sopoongsan extracts increases, the mean value of particle size decreases, and the value of the complex modulus and loss angle increases, which means the Sopoongsan extracts help stabilize the emulsion. From the result of human patch test to assess the safety of cream containing Sopoongsan extracts, there was no stimulus of negative reaction on skin. In result of the user tests, it can be known that the higher concentration of the Sopoongsan was preferred by customers.

• Wind and Structures
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• 제11권1호
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• pp.1-18
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• 2008

Interference effects in five square tall buildings arranged in an L- or T-shaped pattern are investigated in the wind tunnel. Mean and fluctuating shear forces, overturning moments and torsional moment are measured on each building with a force balance mounted at its base. Results are obtained at two values of clear separation between adjacent buildings, at half and a quarter building breadth. It is found that strong interference effect exists on all member buildings, resulting in significant modifications of wind loads as compared with the isolated single building case. Sheltering effect is observed on wind loads acting along the direction of an arm of the "L" or "T" on the inner buildings. However, increase in these wind loads from the isolated single building case is found on the most upwind edge building in the arm when wind blows at a slight oblique angle to the arm. The corner formed by two arms of buildings results in some wind catchment effect leading to increased wind pressure on windward building faces. Interesting interference phenomena such as negative drag force are reported. Interference effects on wind load fluctuations, load spectra and dynamic building responses are also studied and discussed.

• 한국산림과학회지
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• 제66권1호
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• pp.16-36
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• 1984

화강암질풍화토(花崗岩質風化土)의 미교란(未攪亂) 시료(試料)를 사용하여 일면(一面) 직접(直接) 전단시험(剪斷試驗)으로 측정(測定)한 전단강도(剪斷强度)와 함수비(含水比), 간극비(間隙比), 건조밀도(乾燥密度), 비중(比重)과의 관계(關係)를 통계(統計) 분석(分析)하였고, 화강암질풍화토(花崗岩質風化土)의 사방시공지(砂防施工地)에 식재(植栽)된 리기다소나무림(林)과 리기테-다소나무림(林)에서 토양단면(土壤斷面)을 만들어 산중식토양경도계(山中式土壤硬度計)로 토양(土壤)의 견밀도(堅密度)를 측정(測定)하고 수근분포(樹根分布)를 조사(調査)하여 통계(統計) 분석(分析)한 결과(結果) 다음과 같다. 1) 함수비(含水比), 간극비(間隙比)와 전단강도(剪斷强度) 간(間)에는 유의적(有意的)인 부(負)의 상관(相關)이며 직접적(直接的)인 관계(關係)에 있었다. 2) 건조밀도(乾燥密度)와 전단강도(剪斷强度) 사이에는 정(正)의 상관(相關)이며 직접적(直接的)인 관계(關係)에 있었다. 3) 비중(比重)과 전단강도(剪斷强度) 간(間)에는 유의적(有意的)인 상관관계(相關關係)를 인정(認定)할 수 없었다. 4) 전단강도(剪斷强度)에 영향(影響)을 미치는 영향요소(影響要素)의 직접효과(直接效果)의 크기는 함수비(含水比)>간극비(間隙比)>건조밀도(乾燥密度)의 순위(順位)이다. 5) 다중선형(多重線型) 회귀방정식(回歸方程式)의 분산분석결과(分散分析結果) 함수비(含水比)만이 회귀성(回歸性)이 인정(認定)되므로 함수비(含水比)를 독립변수(獨立變數)로 하여 전단강도(剪斷强度)를 추정(推定)하기 위한 회귀방정식(回歸方程式)은 제한(制限)된 건조밀도(乾燥密度)의 범위내(範圍內)에서 적합도(適合度)가 매우 높게 평가(評價)되었다. 6) 토양(土壤)의 견밀도(堅密度)는 토심(土深)이 깊어짐에 따라 높아진다. 7) 토양(土壤)의 지표경도(指標硬度)와 수근수(樹根數) 간(間)에는 유의적(有意的)인 부(負)의 상관(相關)이며 직접적(直接的)인 관계(關係)에 있었다. 8) 리기다소나무와 리기테-다소나무의 수근(樹根)은 토심(土深) 20cm까지에 대부분 분포(分布)하고 있었다. 9) 리기다소나무림(林)과 리기테-다소나무림(林)에서 측정(測定)한 토양(土壤)의 지표경도(指標硬度)를 독립변수(獨立變數)로한 회귀방정식(回歸方程式)으로 수근수(樹根數)를 추정(推定)할 수 있었으나 낮은 적합도(適合度)를 나타내었다.