• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.1
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• pp.20-23
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• 2004

As the integrated circuit device shrinks to the smaller dimension, the chemical mechanical polishing(CMP) process was required for the global planarization of inter-metal dielectric(IMD) layer with free-defect. However, as the IMD layer gets thinner, micro-scratches are becoming as major defects. Chemical-Mechanical polishing(CMP) of conductors is a key process in Damascene patterning of advanced interconnect structure. The effect of alternative commercial slurries pads, and post-CMP cleaning alternatives are discuss, with removal rate, scratch dentisty, surface roughness, dishing, erosion and particulate density used as performance metrics. Electroplated copper deposition is a mature process from a historical point of view, but a very young process from a CMP perspective. While copper electro deposition has been used and studied for decades, its application to Cu damascene wafer processing is only now gaining complete acceptance in the semiconductor industry. The polishing mechanism of Cu-CMP process has been reported as the repeated process of passive layer formation by oxidizer and abrasion action by slurry abrasives. however it is important to understand the effect of oxidizer on copper passivation layer in order to obtain higher removal rate and non-uniformity during Cu-CMP process. In this paper, we investigated the effects of oxidizer on Cu-CMP process regarding the additional volume of oxidizer.

• 한국지형학회지
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• 제23권3호
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• pp.93-104
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• 2016

High school textbooks of world geography show geomorphic featuresin arid environments such as sand dune, yardang and ventifact which are largely created by aeolian processes. Desert pavements, ubiquitous armored surfaces composed of a mosaic of clasts in hot and arid regions, are introduced as a major landform which can be attributed to wind erosion. However, they are formed by a variety of processes including deflation, surface runoff, upward clast migration and dust accretion that cause coarse particles concentration at the surface. The deflation by wind leaving a lag of coarse clasts has been solely regarded at home, even though the classical mechanism of deflation has been evaluated as a relatively unimportant process of pavement formation abroad through empiricalstudies. The accretionary model is gaining wider acceptance, thus implying that desert pavements could be formed through deposition of aeolian material. In addition, sheetflood and upward migration of clasts, irrelevant to the aeolian processes, could also create stone pavements. As a consequence, the deflation process in high school textbooks has to be urgently modified into a range of processes including aeolian mantling. By stressing that desert pavements are an exceptional geomorphic feature in deserts where wind is a predominant geomorphic agent, they can be used as a good example to demonstrate that a landform is not monogenetic.

• Geomechanics and Engineering
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• 제18권5호
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• pp.493-502
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• 2019

Internal stability is an important safety issue for levees, embankments, and other earthen structures. Since a large part of the world's population lives near oceans, lakes and rivers, floods resulting from breaching of dams can lead to devastating disasters with tremendous loss of life and property, especially in densely populated areas. There are some main factors that affect the internal stability of dams, levees and other earthen structures, such as the erodibility of the soil, the water velocity inside the soil mass and the geometry of the earthen structure, etc. Thus, the mechanism of internal erosion and stability of soils is very complicated and it is vital to investigate the assessment methods of internal stability of soils in embankment dams and their foundations. This paper presents an improved support vector machine (SVM) model to predict the internal stability of soils. The grid search algorithm (GSA) is employed to find the optimal parameters of SVM firstly, and then the cross - validation (CV) method is employed to estimate the classification accuracy of the GSA-SVM model. Two examples of internal stability of soils are presented to validate the predictive capability of the proposed GSA-SVM model. In addition to verify the effectiveness of the proposed GSA-SVM model, the predictions from the proposed GSA-SVM model were compared with those from the traditional back propagation neural network (BPNN) model. The results showed that the proposed GSA-SVM model is a feasible and efficient tool for assessing the internal stability of soils with high accuracy.

• 한국재료학회지
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• 제31권6호
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• pp.331-338
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• 2021

Ti-Al-Si target and Cr-Si target are sputtered alternately to develop a multi-layered nitride coating on a steel mold to improve die-casting lifetime. Prior to the multi-layer deposition, a CrN layer is developed as a buffer layer on the mold to suppress the diffusion of reactive elements and enhance the cohesive strength of the multi-layer deposition. Approximately 50 nm CrSiN and TiAlSiN layers are deposited layer by layer, and form about three ㎛-thickness of multi-layered coating. From the observation of the uncoated and coated steel molds after the acceleration experiment of liquid metal injection casting, the uncoated mold is severely eroded by the adhesion of molten metallic glass. On the other hand, the multi-layer coating on the mold prevents element diffusion from the metallic glass and mold erosion during the experiment. The multi-layer structure of the coating transforms the nano-composite structured coating during the acceleration test. Since the nano-composite structure disrupts element diffusion to molten metallic glass, despite microstructure changes, the coating is not eroded by the 1,050 ℃ molten metallic glass.

• 동아시아경상학회지
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• 제5권4호
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• pp.39-49
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• 2017

Purpose - This study is to propose a creative idea for constant business growth and development by examining characteristics of business outcomes by phase, which are "growth" and "erosion and stagnation," respectively. Research design, data, methodology - It is necessary to identify an occurrence of crisis and its diffusion with a dynamic model in order to identify a success and failure of businesses in an organic way, not on a binary structure. The static perspective is to understand a crisis as a simply one-time event or as a linear causation. Thus, it has a limited understanding of the overall situation and has limits to investigating a foundational cause and developing long-term countermeasures. On the contrary, the dynamic perspective is to understand the crisis as circulation process of the overall system. Thus, it divides elements of the crisis as external and internal ones to understand it as the causal relationship of each element. Results - During the growth period of Burger King, the company promoted its brand very successfully with aggressive and creative marketing activities. However, due to the founder's disposal of management rights and the following changes in the management, the company had no choice but to lose focus on its business philosophy and brand management, and eventually it had to face the big crisis (resonance) which was delisting from the stock market because of the external threat; well-being trend. However, Burger King resumed lifting on the stock exchange by making great efforts to clearly identify the current issues and seek solutions. Under the spirit of "perseverance" and its slogan "Have it your way" the company is now going head to head with McDonald's in the North American region and emerging countries. Conclusions - Then, what is the most crucial factor in the success and failure of businesses? Answers may vary, however, as learned from the case study of Burger King, corporations should inspect the present and focus on developing a long-term strategy for the future and actively fulfill the actions. McDonald's may not be able to innovate by itself in the future as it may become routinized to the growth. There will be chances of winning if we change conditions of individuals or organizations to an organic system in terms of being creative. There is a hopeful message here that an individual or small business may have more advantages in the era of the idea and innovation.

• 한국지역지리학회지
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• 제7권2호
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• pp.71-81
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• 2001

하안단구는 지반운동이나 기후변화에 따른 하천력/저항력 관계의 변화로 평형상태를 유지하던 전(前) 하천시스템의 하도 일부가 남은 것이다. 우리나라의 대부분의 하천 주변에는 비교적 최근에 형성된 저위 하안단구가 널리 분포한다. 그러나 저위 하안단구의 형성 메커니즘은 잘 알려져 있지 않다. 본 연구에서는 낙동강 유역에 분포하는 저위 하안단구를 형성한 요인과 형성시기를 고찰하였다. 저위 하안단구는 지난 최종 빙기시의 해수면 하강과 냉량습윤한 기후에 따른 하천침식력 증가 때문에 형성되었다. 저위하안단구는 지난 최종 빙기시에 해수면이 하강함으로써 하천의 하방침식력이 증대되었고, 냉량습윤한 환경에서 하천력이 저항력을 초과함으로써 하상(河床)이 깊게 파이면서 형성되기 시작하였다. 이 시기에는 곡류하천이 많이 절단되기도 하였다. 하지만 상대적으로 빙기가 짧았기 때문에 하천이 전 구간에서 평형을 이루지 못한 상태에서 해수면이 상승하기 시작하였다. 두부침식은 곡류의 절단에 힘입어 하계폭포까지 그대로 유지되었으며, 하류의 깊게 파인 곡과 절단된 구하도는 메워지게 되었다. 따라서 최상류 구간은 최종 간빙기, 상류 구간은 최종 빙기, 중 하류 구간은 후빙기의 하천종단곡선을 각각 나타낸다. 따라서 저위 하안단구는 '최종 빙기에서 현재에 이르는 침식강화기'에 만들어지고 있다.

• 한국해안·해양공학회논문집
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• 제33권6호
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• pp.308-320
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• 2021

해안침식의 근본적 대책으로서 감소한 공급 토사량 회복을 포함한 종합 토사관리 대책이 유효하지만, 계획에 있어서는 하천에서 바다로 유출된 토사 가운데 어느 정도의 양이 어느 정도의 속도로 해안에 다시 공급되는 토사량의 평가와 이를 위해서는 하천과 바다의 결절점인 하구지역에서 발생하는 토사의 이동 메커니즘 분석이 매우 중요하다. 하지만 지금까지 홍수 시의 하구사주 붕괴(flushing) 과정을 해석하는 수치모델에 관한 연구는 진행되고 있지만 하구사주의 형성 및 발달 과정을 해석하는 수치모델은 아직 확립되어 있지 않은 것이 현재의 연구 진행상태이다. 본 연구에서는 종합토사관리를 위해 유출된 토사가 회복되는 토사량의 평가를 위해 파랑변형, 유황계산 및 지형변화 모델을 구축하여 하구사주의 생성과정을 수치해석을 통한 재현을 목적으로 한다. 하구사주의 생성과정을 모의하였으며 에너지 파랑 및 작용 시간의 개념을 도입하여 장기간 표사이동의 예측을 실시하였다. 계산에 필요한 외력조건은 하구사주가 지배적으로 발달하는 동계시 작용하는 파랑조건과 하천의 유량을 고려하였으며 초기지형은 홍수시 마읍천의 하구사주가 붕괴(flushing)된 직후의 지형정보를 초기조건으로 설정하였다. 그 결과 입사파향에 따라 해빈류에 의해 하구사주의 발달과 생성과정을 재현하였으며 초기지형으로부터 약 66시간 경과 후 맹방하구 사주의 형태로 발달되는 것으로 나타났다.

• 대한토목학회논문집
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• 제37권2호
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• pp.333-342
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• 2017

사질해안의 폭풍 및 평상파 단면사이의 지형변화 특성을 이해하기 위해 2차원 이동상 수리실험을 수행하였다. 폭풍 및 평상파 단면을 발달시키는 입사파 파라미터를 조건으로, 연속적으로 단면 지형변화와 수면변위를 계측하였다. 두 입사파 조건을 번갈아 각각의 평형 상태에 도달하기까지의 변화를 쇄파대에서 관측하였다. 폭풍파 조건에서 붕괴(plunging) 쇄파로 사주가 발달하고 포말대의 경사가 급해짐을 보였으며, 평상파 조건에서는 말림(spilling) 쇄파에 의해 사주가 소멸함을 보였다. 단면 지형변화 관측을 통하여 폭풍파 조건에서 표사가 외해로 유출되고, 평상파조건에서 내해로 표사가 유입됨을 알 수 있었다. 폭풍파 조건에서 외해방향으로의 표사이송에 지배적인 역할을 하는 강한 역저류(undertow)가 발달하였고, 평상파 조건에서는 약한 역저류가 발달하였다. 그리고 두 조건에서 모두 해안방향으로의 표사이송에 지배적 역할을 하는 비선형 파동에 의한 왜도(skewness)와 비대칭성(asymmetry)이 관측되었다.

• Biomolecules & Therapeutics
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• 제7권4호
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• pp.362-370
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• 1999

Propolis, a natural resinous compound collected from honey bees, contains many biochemical constituents(wax, flavonoids, phenolic compounds, etc.) and has been used in traditional medicines as early as 300 B.C. It was been demonstrated that ethanol, acetylsalicylic acid, ischemia reperfusion, non-steroidal antiin-flammatory drugs and stress induce gastric lesions by promoting the generation of reactive oxygen metabolites. Therefore, some drugs that are capable of scavenging or inhibiting the generation of reactive oxygen radicals might be expected to prevent the gastric mucosal injury. The aim of this study was 1) to examine the antiulcer effect of propolis, 2) to investigate the mechanism of action by determining gastric acid secretion, lipid per-oxidation, mucus content and proton pump ($H^+$/$K^+$-ATPase) activity on gastric mucus in varios experimental models, and finally, 3) to isolate and identify the pure compounds that exert antiulcer activity. Step 2-1 and 2-3 sub-sub fraction shoed a significant reduction of severity of gastirc damage at the dose of 25 mg/kg in various experimental models. We isolated 4 sub-sub-sub fractions by flash column chromatography of Step 2-1 sub-sub fraction and one sub-sub-sub fraction by recrystalization of Step 2-3 sub-sub fraction. The protective effects of propolis sub-sub-sub fraction manifested sifnificant effects in HCl-ethanol induced gastric erosion model and aspirin induced gastric ulcer model. These results showed that the gastric mucosal protective effect of propolis might result from the increase of mucus secretion, free radical scavenging effect as well as the reduction of acid secretion in accordance with the reduction of $H^+$/$K^+$-ATPase activitv. Three compounds were isolated and identified from sub-sub fraction of propolis which showed antiulcer effects. Subsequently, these compounds were identified as a flavonoid, namely, 2-acetoxy-5,7,-dihydroxy-flavanone, galangin and chrysin.

• 한국지반신소재학회논문집
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• 제14권2호
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• pp.11-21
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• 2015

2002년 피해조사 결과에 따르면, 하천제방 관련 홍수피해는 월류, 침식, 제체불안정(파이핑, 부적절한 축제재료선정, 다짐불량 등), 구조물에 의한 파괴 등으로, 월류에 의한 제방붕괴는 39.5 %로서 주요 요인인 것으로 평가되었다. 한편, 제방붕괴각(${\theta}$), 제방붕괴율(k) 등 관련 월류제방 붕괴특성은 침수모델링 해석 시 침수속도 및 면적 등에 영향을 미치나 국내 관련 연구 실적이 미진한 실정에 있다. 본 논문에서는 프루드(Froude) 상사(${\lambda}_{Fr}=1$)를 가정한 제방고(0.20 m, 0.25 m, 0.30 m, 0.40 m)에 따른 제방붕괴모형실험을 수행하여 제방고 변화(H)에 따른 제방붕괴 메카니즘, 붕괴연장, 제방붕괴각(${\theta}$), 제방붕괴율(k) 등을 제시하였다.