• International Commerce and Information Review
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• v.16 no.5
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• pp.151-178
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• 2014

The objective of the present case study is to analysis how effectively Hilti, which is a former family firm owned and managed by a family in Liechtenstein as a tiny european country, a land sandwiched between Switzerland and Austria, has made a global market success. Liechtenstein has $160km^2$ land and about 36,000 residents. Despite its small size of country, however, Hilti Corporation doesn't view its location as a liability in its business strategy. Hilti is a global leading provider of professional power tools in building, mining, civil engineering etc. Also, Hilti is a firm with a clear vision to become the leading industry partner for construction professionals and building installations through customer focus, high quality equipment, and tools and systems specially designed for specific jobs. This study considered Hilti as a good case, which verifies that born-conditions, endogenous factors according to Michael Porters diamond model does not decisive role more for international competitiveness of firms. Lessons from Hilti are that in order to obtain and sustain the global competitiveness of small and medium-sized firms in Korean manufacturing sector under high production cost, they have to do actively innovative. Also they can give to customers newer and higher customer-values than competitors in abroad give. The case summarizes that the strategy of Hilti for the global market success is comprised of several factors: Technological and organizational innovation, and a clear customer-value oriented business strategy and its implementation. Innovation and its integration into marketing for the customers value creation is central to Hilti's Success. The present case study is expected to provide insights and implication for many firms in Korea that are seeking to secure global presence and market success.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.1
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• pp.70-79
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• 2003

In this paper, T5 28-watt fluorescent lamp ballast using a piezoelectric transformer is fabricated and its characteristic is investigated. Developed electronic ballast is composed of basic circuits and blocks, such as rectifier part, active power factor corrector part, frequency oscillation part using microcontroller and feedback control, piezoelectric transformer and resonant half bridge inverters. The fabricated ballast uses to variable frequency methode in external so exciting that the frequency of piezoelectric transformer could be generated by voltage control oscillator using microcontroller(AT90S4433). The current of fluorescent lamp is detected by feedback control circuit. The signal of inverter output is received using Piezoelectric transformer, and then its output transmitted to fluorescent lamp. Traditional electromagnetic ballasts operated at 50-60Hz have been suffered from noticeable flicker, high loss, large crest factor and heavy weight. A new electronic ballast is operated at high frequency about 75kHz, and then Input power factor, distortion of total harmonic and lamp current crest factor are measured about 0.9!35, 12H and 1.5, respectively Accordingly, the traditional ballast is by fabricated electronic ballast using piezoelectric transformer and voltage control oscillator because of its lighter weight, high efficiency, economic merit and saving energy.

• Journal of the Korea Convergence Society
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• v.9 no.1
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• pp.419-431
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• 2018

In this paper, we propose a novel method for monitoring mood trend of Twitter users by analyzing their daily tweets for a long period. Then, to more accurately understand their tweets, we analyze all types of content in tweets, i.e., texts and emoticons, and images, thus develop a multimodal sentiment analysis method. In the proposed method, two single-modal analyses first are performed to extract the users' moods hidden in texts and images: a lexicon-based and learning-based text classifier and a learning-based image classifier. Thereafter, the extracted moods from the respective analyses are combined into a tweet mood and aggregated a daily mood. As a result, the proposed method generates a user daily mood flow graph, which allows us for monitoring the mood trend of users more intuitively. For evaluation, we perform two sets of experiment. First, we collect the data sets of 40,447 data. We evaluate our method via comparing the state-of-the-art techniques. In our experiments, we demonstrate that the proposed multimodal analysis method outperforms other baselines and our own methods using text-based tweets or images only. Furthermore, to evaluate the potential of the proposed method in monitoring users' mood trend, we tested the proposed method with 40 depressive users and 40 normal users. It proves that the proposed method can be effectively used in finding depressed users.

• Journal of the Korean Chemical Society
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• v.50 no.3
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• pp.237-242
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• 2006

Nowadays, LEDs has been applied to the luminescent devices of various fields because of the invention of high efficient blue chip. Recently, especially, the white LEDs composed of InGaN blue chips and a yellow phosphor (YAG:Ce3+) have been investigated extensively. With the exception of YAG:Ce3+ phosphor, however, there are no reports on yellow phosphor that has significant emission in the 450~470 nm excitation range and this LED system is the rather low color rendering index due to their using two wavelength. Hence, we have attempted to synthesize thiogallate phosphors that efficiently under the long wavelength excitation range in the present case. Among those phosphors, we have synthesized Sr2Ga2S5:Eu2+ phosphor by change the host material of SrGa2S4:Eu2+ which is well known phosphor and we investigated the luminescent properties. In order to obtain the harmlessness and simplification of the synthesis process, sulfide materials and mixture gas of 5 % H2/95 % N2 were used instead of the CS2 or H2S gas. The prepared phosphor shows the yellow color peaking at the 550 nm wavelength and it possible to emit efficiently under the broad excitation band in the range of 300~500 nm. And this phosphor shows high luminescent intensity more than 110 % in comparison with commercial YAG:Ce3+ phosphor and it can be applied for UV LED due to excitation property in UV region.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.351-351
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• 2011

최근 지구온난화와 더불어 이상기후가 대두됨에 따라 기상 예측이 더욱더 중요시되고 있다. 또한 이전부터 가뭄 및 홍수와 같은 기상현상으로 인한 피해 사례가 빈번하였으며, 이로 인하여 물 관리의 어려움을 겪고 있다. 한 예로 이상기후가 유난히 잦았던 2010년 여름철 경우 평년보다 발달한 북태평양고기압의 영향으로 여름철 92일 가운데 81일의 전국 평균기온이 평년보다 높게 나타났다. 또한 강우 일수가 평년에 비해 7.4일 많은 44.2일을 기록하였으며, 국지성 집중호우 사례가 빈번하였다. 또한 8월 9일 발생한 태풍 `뎬무'를 포함해서 한 달 동안 3개의 태풍이 한반도에 영향을 끼치는 이례적인 사례가 발생하였다. 따라서 본 연구는 이러한 기상재해에 따른 물 관리를 장기적으로 대비하고자 고해상도 전지구 모델 GME를 이용하여 2010년 여름철 강수 예측을 실시하였다. 강수 예측에 사용된 전지구 모델 GME는 기존의 카테시안 격자체계를 가진 모델과 달리 전구를 삼각형으로 구성된 20면체로 격자화 한 Icosahedral-hexagonal grid 격자체계로 구성되어 있어, 해상도 증가에 용이할 뿐만 아니라, HPC(High Performance Computing)환경에서 효율성이 높은 장점을 가지고 있다. 본 계절 예측을 수행함에 있어 발생하는 잡음을 최소화하고자, Time-lag 기법을 이용하여 5개의 앙상블 멤버로 구성되어있으며, 이를 비교 분석하기위해 Climatology를 이용하여 총 10개의 앙상블 멤버로 규준실험을 수행하였다. 선행 연구에 따르면 1개월 이상의 장기 적분의 경우 초기조건보다 외부 강제력이 더 중요한 역할을 한다고 연구된 바 있다. (Yang et al., 1998) 특히 계절 변동성의 경우 대기-해양간의 상호작용에 의해 지배되며, 이를 고려하여 본 연구는 해수면 온도를 경계 자료로 사용하여 계절 예측을 수행하였다. 앞서 말한 실험 계획을 바탕으로 하여 나온 결과를 통해 동아시아지역 및 한반도 도별 강수 및 온도 변수에 대해 순별 및 월별 카테고리맵 분석을 실시하여 한눈에 보기 쉽게 나타냈다. 또한 주요 도시별 강수량 및 온도의 시계열 분석을 실시하여 시간이 지남에 따라 나타나는 변동성을 확인하였다. 계절 예측 결과에서 온도의 경우 평년보다 높게 나타났으며, 이는 실제 온도 예측과도 유사한 패턴을 가졌다, 강수의 경우 7월부터 8월 중순까지 평년보다 다소 적게 모의되었으며, 8월 하순경 회복하는 것으로 예측하였다. 따라서 본 계절 강수 예측은 다소 역학 모델이 가지는 한계를 가지고 있으나, 실제와 비교하여 어느 정도의 경향성이나 패턴에 있어 유사성을 보임을 확인하였으며, 이를 장기적 차원의 물관리를 함에 있어 참고 및 활용 가능할 것으로 예상한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.608-613
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• 2019

NOx (Nitrogen oxide) in the exhaust gas from vehicle engines is considered one of the most harmful substances in air pollution problems. NOx is made when combustion occurs under high temperature conditions and EGR (exhaust gas recirculation) is normally used to lower the combustion temperature. As the EGR ratio increases, the NOx level becomes low, but a high EGR ratio makes the combustion unstable and causes further air pollution problems, such as CO and unburned hydrocarbon level increase. This study showed that fuel droplets could move more freely by the radiation of sonic wave for the stable combustion. In addition, the engine performance improved with increasing EGR ratio. As a basic study, the effect of sonic wave radiation on the velocity of fuel droplets was studied using CFD software. The results showed that the velocity of small droplets increased more under high frequency sonic wave conditions and the velocity of the large droplets increased at low frequency sonic wave conditions. In addition, an engine analysis model was used to study the effects of the increased combustion stability. These results showed that a 15% increase in EGR ratio in combustion resulted in a 45% decrease in NOx and a 10% increase in thermal efficiency.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.17-25
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• 2017

Owing to recent climate change, the scale of rainfall tends to increase gradually and the risk of flooding has increased. Therefore, the importance of improving the levee management and disaster response is increasing. Levee management in Korea is carried out at the level of damage recovery after the occurrence of damage. Therefore, it is necessary to develop a technology for predicting and managing the levee safety with proactive river management. In this study, a method to estimate the safety against erosion and overflow was suggested. A map of levee safety that can be used as basic data is presented by displaying the levee safety on the map. The levee erosion safety was calculated as the ratio of the internal and external force for each shore type. The levee overflow safety was calculated as the ratio of the maximum conveyance and design flood. The maximum conveyance was a discharge when the level of the river was equal to the level of the levee crown. The levee safety was classified into 5 grades: very safe, safe, normal, dangerous, and very dangerous. As a research area from downstream of Nam River Dam to Nakdong River Junction, the levee safety against erosion and overflow was estimated for all levees and all cross-sections of the river. The levee safety was displayed on a map using GIS. Through the levee safety map as a result of this study, the levee safety can be observed intuitively. Using the levee safety map, a maintenance plan for a river can be easy to build. This levee safety map can be used to help determine the priority of investment for efficient budget used.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.113-113
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• 2017

최근 많은 산업의 발전으로 인해 환경오염을 유발시키는 폐수가 다량으로 배출되고 있으며, 이러한 폐수 속에는 유기용매, 고분자 물질 및 각종 염 등의 난분해성 물질들이 다량으로 함유되어 있다. 이런 물질들을 분해시키기 위해 물리적, 생물학적 수처리 방법이 많이 이용되고 있지만 이 방법들은 각각 운전비용과 처리비용이 고가인 단점이 있다. 따라서 비용과 효율 측면에서 효과적인 폐수처리를 위해서 전기화학적 폐수처리 방법이 많이 사용되고 있다. 물리적, 생물학적 처리 방법에 비해 비용이 적게 들고, 처리 후 잔류물이 남지 않으며, 독성을 띄는 산화제의 첨가 없이도 높은 폐수처리 능력을 보이기 때문에 친환경적이므로, 전기화학적 폐수산화 처리에 사용되는 불용성 전극에 대한 연구가 많이 진행되어져 오고 있다. 그 중 BDD(Boron-doped diamond) 전극은 표면에서 강력한 산화제인 수산화 라디칼의 높은 발생량으로 인해 뛰어난 폐수처리 능력을 보이므로 불용성 전극 분야에서 활발한 연구가 진행 중이다. 그러나 기존에 BDD 전극의 기판 모재로 이용되던 Si, W, Pb등은 모두 기계적 강도, 폐수처리 능력 및 독성 문제로 인해 한계가 있었고, 특히 Nb기판 위에 형성시킨 BDD 전극은 뛰어난 폐수처리 능력에도 불구하고 비싼 모재 원가로 인해 상용화가 힘든 실정이다. 이런 문제점을 해결하기 위해 높은 기계적 강도와 전기화학적 안정성을 가진 Ti 기판을 사용한 BDD 전극에 대한 연구가 보고되고 있다. 그러나 BDD와 Ti 간의 lattice mismatch, BDD층 형성을 위한 고온 공정시 탄소의 확산으로 인한 기판 표면에서의 TiC층 형성으로 인해 접착력이 감소하여 박리가 생기는 문제점이 있다. BDD와 Ti의 접착력을 향상시키기 위해 융점이 높고, 전기전도성이 우수한 TiN을 diffusion barrier layer로 삽입하면 탄소 확산에 의한 TiC층의 생성을 억제하여, 내부응력에 기인한 접착력 감소를 방지할 수 있다. 또 하나의 방법으로 Ti 기판의 전처리를 통해 BDD층의 접착력을 향상 시킬 수 있다. Sanding과 etching을 통해 기판 표면의 물리, 화학적인 표면조도를 부여하고, seeding을 통해 diamond 결정 성장에 도움을 주는 seed 입자를 분포시킴으로써, 중간층과 BDD층의 접착력을 향상시키고, BDD 결정핵 성장을 촉진시켜 고품질의 BDD박막 증착이 가능하다. 본 연구에서는 기존 Si, Nb 등의 기판 모재를 Ti로 대체함으로써 제조원가를 절감시키고, TiN 중간층을 삽입하여 접착력을 향상 시킴으로써 기존의 BDD 전극과 동등한 수준의 물성 및 수처리 특성을 가진 BDD전극 제작을 목표로 하였다. $25{\times}25mm$의 Ti 기판위에 TiN 중간층을 DC magnetron sputtering을 이용하여 증착 후, BDD 전극 층을 HFCVD로 증착하였다. 전처리를 진행한 기판과 중간층 및 BDD층의 미세구조를 XRD로 분석하였고, 표면 형상을 SEM으로 확인하였다. BDD전극의 접착력 분석을 통해 TiN 중간층의 최적 조성을 도출하고, 최종적으로 BDD/TiN/Ti 전극의 CV특성과 가폐수의 COD분해능력 및 축산폐수, 선박평형수 등의 실제 폐수 처리 능력을 BDD/Si, BDD/Nb 전극과 비교 검토할 것이다.

• Applied Chemistry for Engineering
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• v.10 no.3
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• pp.400-406
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• 1999

In an effort to obtain high efficiency in gas fired absorption chillers, a new working fluid has been developed with thc addition of the component of $LiNO_3$, LiCl and LiI to the conventional solution of $LiBr-H_2O$. The solubility and vapor pressure of the 4 component working fluid developed in this work were measured and compared to the results of $LiBr-H_2O$ solution. It was observed that there exists an optimal mole ratio of the inorganic salts in terms of solubility. The mole ratio of LiBr, $LiNO_3$ and LiCl was found to be around 5:1:1~2 in the $LiBr-LiNO_3-LiCl-H_2O$ mixture, and in the case of $LiBr-LiO_3-Lil-H_2O$ and $LiBr-Lil-LiCl-H_2O$ mixtures, the mole ratio of LiBr, $LiNO_3$ and Lil/ LiBr, LiI and LiCl were found to be around 5:1:1 and 5:1:0.5~1 respectively. The vapor pressure of the 4 component working fluid of the optimal mole ratio was increascd with adding the component of $LiNO_3$, LiCl and LiI except for $LiBr-LiNO_3-LiCl-H_2O$ mixture. The absorption capacity of $LiBr-LiNO_3-LiCl-H_2O$ mixture was obtained higher than that of $LiBr-H_2O$ mixture.

• Applied Biological Chemistry
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• v.46 no.3
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• pp.183-188
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• 2003

Storage stabilities of soybean curds using cuttle bone powder treated with acetic acid (ATC-soybean curd) and calcium chloride (calcium chloride-soybean curd) as a coagulants were examined. The pH, turbidity of soaking solution, titratable acidity, and viable cell counts of calcium chloride-soybean curd did not change up to 6 days of storage, then decreased rapidly in pH and turbidity and increased rapidly in titratable acidity and viable cell counts, whereas those of ATC-soybean curd did not change up to 9 days of storage, then decreased slowly in pH and turbidity and increased slowly in titratable acidity and viable cell counts. Regardless of coagulants and storage period, white index of soybean curds did not change during cold storage. Hardness and brittleness of calcium chloride-soybean curd decreased rapidly up to 3 days in of storage, remained stable from 3 days to 6 days, then decreased rapidly. Hardness and brittleness of ATC-soybean curd also decreased rapidly up to 3 days in of storage and remained stable from 3 to 9 days, but then decreased slowly. Regardless of coagulants, results of sensory evaluation were similar to those of physicochemical tests. Judging from the above results, shelf-lives were determined as 9 and 6 days for ATC- and calcium chloride-soybean curds, respectively.