• 해양환경안전학회지
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• 제18권4호
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• pp.365-370
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• 2012

최근 소형선박 국제표준규격(ISO-12215)이 제정되면서 소형선박-선체구조 및 치수-제5장 부속서 B에 의하여 길이 2.5미터 이상 6미터 미만 소형선박의 낙하시험에 의한 강도시험 기준을 적용할 수 있게 되었으나, 육안검사로 실시되는 현재의 방법으로는 선체 강도 평가의 객관적인 평가가 어려운 문제점이 있다. 본 연구에서는 레저선박의 낙하시험의 정량적 평가가 가능한 평가시스템을 개발하기 위하여 레저선박의 낙하시험에 대한 국내 외 규정을 기반으로 한 낙하시험 평가시스템을 설계하였으며, 5미터급 알루미늄선박의 낙하시험을 통하여 시스템의 적용가능성을 검토하고 낙하 시 선박의 상태 및 낙하자세에 따라 발생되는 문제점을 확인하였다.

• Journal of Mechanical Science and Technology
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• 제18권12호
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• pp.2294-2302
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• 2004

The objective of this study is to obtain detailed information for the micro fabrication of lead frames by applying spray technology to wet etching process. Wet etching experiments were performed with different etching parameters such as injection pressure, distance from nozzle tip to etched substrate, nozzle pitch and etchant temperature. The characteristics of single and twin spray were measured to investigate the correlation between the spray characteristics and the etching characteristics. Drop size and velocity were measured by Phase-Doppler Anemometer (PDA). Four liquids of different viscosity were used to reveal the effects of viscosity on the spray characteristics. The results indicated that the shorter the distance from nozzle tip and the nozzle pitch, the larger etching factor became. The average etching factor had good positive correlation with average axial velocity and impact force. It was found that the etching characteristics depended strongly on the spray characteristics.

• Journal of Korea Trade
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• 제25권3호
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• pp.48-64
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• 2021

Purpose - This study examined the effect of tariff cuts on productivity in Korea's manufacturing industries and the effect of initial productivity level before tariff cuts on productivity improvement after tariff cuts. We also attempted to identify whether import-driven or export-driven factors are more important for productivity improvement, especially in low productivity industries. Design/methodology - Since tariff reduction is a policy decision that can affect cross-industry, its impact is spread across all industries beyond the scope of a single firm through the input and output network of industry structure. Accordingly, we proposed a new method to measure the change in productivity to reflect the impact of tariff cuts across industries. Through an Armington CGE analysis, changes in endogenous variables can be directly measured after the exogenous shock of tariff reduction, and the amount of movements in productivity triggered by tariff cuts can also be calculated. We can thus assess the effectiveness of exogenous policy, such as tariff cuts, through the difference between the benchmark and counterfactual values of endogenous variables. Findings - This study confirmed that tariff reduction positively affected productivity improvement in Korea's manufacturing industries. It also confirmed that productivity gains occur in Korea's leading export industries. Finally, greater productivity gains were recorded in the group with additional high-export-share or high-import-share conditions for low productivity industries. These results are, in a limited sense, consistent with the existing studies that emphasize the importance of exports and imports on productivity improvement, especially for low productivity industries. Originality/value - The results of our experiments are different from those of non-CGE studies, which measure the industry-level change in productivity with dummy coefficients, in terms of directly calculating the amount of change in productivity. In addition, we propose that the Armington CGE model is more appropriate than the Melitz CGE model to directly measure the productivity after tariff cuts. This is because the Melitz CGE model assumes the given specific productivity density, which does not change after an overall drop of tariffs. To the best of our knowledge, this approach to directly calculating productivity by reflecting the impact of tariff reduction across industries through CGE analysis, is unprecedented in this literature.

• 한국자동차공학회논문집
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• 제19권5호
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• pp.76-81
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• 2011

Exhaust gas recirculation is the well-known and widely used NOx reduction technology for diesel engines. More effective EGR cooler has been developed and applied to diesel engines to meet the reinforced emission regulation. However, the contaminated EGR cooler by diesel exhaust gas reduces the performance of the engine and NOx reduction rate. The buildup of deposits in EGR coolers cause significant degradation in heat transfer performance, often on the order of 20~30%. Deposits also increase pressure drop across coolers and thus may degrade engine efficiency under some operation conditions. In this study, as a solution for this problem, DOC assisted EGR cooler is designed and then investigated to reduce fouling and its impact on cooler performance. A single channel EGR cooler fouling test apparatus and soot particle generator were developed to represent the real EGR cooler and exhaust gas of diesel engine. EGR cooler effectiveness of the case with catalyst of pt 30g/ft3 decreased just up to 5%. This value was 45% less compared to the case without catalyst which decreased up to 9% after 10hours experiments.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.171-171
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• 2009

We have investigated the impact of coffee ring effect on the inkjet-printed $Al_2O_3$ thick films. In a single solvent system such as Dimethylformamide, the coffee-ring-pattern has appeared on the edge of sessile drop after evaporation. The peak-to-valley height difference in $Al_2O_3$ coffee ring is over 2um. This non-uniform deposition of $Al_2O_3$ over the surface leads to sever surface roughness of the inkjet-printed films. However, we have manipulated our printing parameters to improve the surface roughness and the packing density of the printed $Al_2O_3$ films. Our inkjet-printed $Al_2O_3$ films show 10 times smoother surface than the initially printed sample's surface. Also the packing density of the printed Ah03 film becomes 70% of high packed $Al_2O_3$. In this presentation, we would like to present the key process parameters of the inkjet printing process to overcome the genetic coffee ring problem.

• 한국항공우주학회지
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• 제47권1호
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• pp.26-34
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• 2019

본 논문에서는 이산요소법을 이용하여 성긴 달토양 수치해석모델을 생성하고 그 정확도를 실제 달토양의 물리적 특성과 비교 및 검증한다. 실제 달의 표면은 다수의 분화구와 바위로 구성되어 있고 매우 미세한 건조토양으로 덮여있으므로 달토양 특성은 달착륙선의 착륙안정성을 결정짓는 중요한 인자이다. 따라서 달토양특성을 고려하기 위해 이산요소법을 이용하여 달토양의 수치해석모델을 생성하고 검증한다. 달토양 압입시험 및 직접전단시험을 해석적으로 구현하여 해석용 달토양이 실제 달토양과 유사한 물리적 특성(압입깊이, 점착력, 내부마찰각 등)을 갖는 것을 확인한다. 이렇게 생성한 달토양 모델 위에 single-leg 착륙장치 유한요소모델을 낙하시키는 해석을 통해 착륙장치 스트럿에 가해지는 충격하중을 예측하고 시험결과와 비교하여 제안된 방법의 적절성을 검토한다.

• Geomechanics and Engineering
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• 제29권5호
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• pp.567-582
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• 2022

In the present study, a series of physical experiments and numerical simulations were conducted to investigate the effects of mode I and mixed-mode I/II cracks on the fracture modes and stability of roadway tunnel models. The experiments and simulations incorporated different inclination angle flaws under both static and dynamic loads. The quasi-static and dynamic testing were conducted by using an electro-hydraulic servo control device and drop weight impact system (DWIS), and the failure process was simulated by using rock failure process analysis (RFPA) and AUTODYN software. The stress intensity factor was also calculated to evaluate the stability of the flawed roadway tunnel models by using ABAQUS software. According to comparisons between the test and numerical results, it is observed that for flawed roadways with a single radical crack and inclination angle of 45°, the static and dynamic stability are the lowest relative to other angles of fractured rock masses. For mixed-mode I/II cracks in flawed roadway tunnel models under dynamic loading, a wing crack is produced and the pre-existing cracks increase the stress concentration factor in the right part of the specimen, but this factor will not be larger than the maximum principal stress region in the roadway tunnel models. Additionally, damage to the sidewalls will be involved in the flawed roadway tunnel models under static loads.

• 한국의학물리학회지:의학물리
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• 제23권4호
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• pp.269-278
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• 2012

두경부암 방사선치료 시 공동 경계면 및 주변 치료 부위의 선량 균일도 향상을 위하여 조직 등가의 thermoplastic 구강 보상체를 개발하였다. Thermoplastic의 유용성 평가를 위해, 기존에 사용해 오던 치과용 인상재료인 paraffin, alginate, 그리고 putty로 제작한 각 구강 보상체의 물성 및 선량 분포 향상도를 비교하였다. 물성 평가에는 강도 평가(압축 실험, 낙하 실험)와 자연변형도(시간에 따른 체적 변화) 평가를 수행하였으며, 개발한 선량 검증용 팬톰에 삽입한 유리선량계와 Gafchromic EBT2 필름을 이용하여 표면선량, 공동 경계면 선량 및 빔 측면도를 측정하여 전달 선량을 평가하였다. 두 달간 각 구강 보상체의 자연변형도 평가하였을 때, alginate는 수분증발로 최대 80% 체적 변화를 보였으나, thermoplastic을 포함한 나머지 조직 등가 물질은 체적 변화가 3% 미만으로 나타났다. 강도 평가 중 5회 반복한 1.5 m 높이의 자유 낙하실험에서 paraffin은 충격에 의하여 파손이 발생되었으나, thermoplastic은 낙하에 의한 파손이 발생되지 않았으며, 압축 강도 실험에서도 paraffin에 비하여 8배 이상의 높은 힘에서도 파손되지 않았다. 유리선량계를 이용한 선량 검증 결과, 1문 조사 시 조직등가[약 80 HU (Hounsfield Unit)]의 thermoplastic은 동일한 처방 선량 전달 시 약 1,000 HU 이상의 값을 나타내는 putty에 비해 4% 낮은 출력계수(monitor unit) 전달로 약 4.9%의 낮은 표면 선량을 전달하였다. 또한 빔 입사 방향을 기준으로 할 때, 구강 통과 후 경계면의 빔 측면도에서 선량 균일도 평가를 위해 측정한 조사영역 편평도는 air, thermoplastic, putty에서 각각 11.41, 3.98, 4.30으로 나타났다. Thermoplastic 구강 보상체는 조직 등가 물질로 기존에 사용해오던 구강 보상체에 비하여 강도가 높고 물질 변형 확률이 적으며, 구강을 포함을 경계면 및 주변 부위에 균일한 선량 분포를 형성할 수 있으므로 균일한 처방 선량 전달 및 피부 선량 감소가 가능하다.