• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.8
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• pp.711-717
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• 2012

During the conceptual design phase of a light sport aircraft, the wind tunnel tests were conducted to investigate the static stability of newly-designed configuration. The 1/5 scale-down wind tunnel model consisted of fuselage, main wing, vertical tail and horizontal tail. The main wing and tails were able to be attached or detached from the fuselage. The aerodynamic forces and moments acting on the 6 different configurations compounding each component were measured by using the internal balance system and their static stability derivatives were derived. With these experimental data, the baseline lift and drag characteristics as well as the effects of each component to the longitudinal, directional and lateral static stability were quantitatively analyzed.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.3
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• pp.43-49
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• 2008

The objective of this research was to test a hypothesis that sprawl increases congestion, and so the estimated evacuation time become longer. For this, sprawl was thought to be poor accessibility so that vehicle miles of travel become longer. This research shows that the daily vehicle miles per lane mile that are thought to be an accessibility index had a strong and statistically significant relationship to the estimated evacuation time, while urban population density has no statistically significant relationship to the evacuation time. The result of this research recommends that we should consider sustainable land use patterns that decrease traffic demand by providing good accessibility.

• Journal of the Korean Society for Library and Information Science
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• v.39 no.2
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• pp.123-146
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• 2005

This study aims to find consistent strategies for feature selection and feature weighting methods, which can improve the effectiveness and efficiency of kNN text classifier. Feature selection criteria and feature weighting methods are as important factor as classification algorithms to achieve good performance of text categorization systems. Most of the former studies chose conflicting strategies for feature selection criteria and weighting methods. In this study, the performance of several feature selection criteria are measured considering the storage space for inverted index records and the classification time. The classification experiments in this study are conducted to examine the performance of IDF as feature selection criteria and the performance of conventional feature selection criteria, e.g. mutual information, as feature weighting methods. The results of these experiments suggest that using those measures which prefer low-frequency features as feature selection criterion and also as feature weighting method. we can increase the classification speed up to three or five times without loosing classification accuracy.

• Journal of Life Science
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• v.24 no.1
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• pp.98-103
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• 2014

NAD(P)H quinone oxidoreductase 1 (NQO1) is a flavoprotein that catalyzes the two electron reduction of diverse substrates, including quinones. It uses NADH or NADPH as a cofactor for enzymatic machinery. In the metabolism of quinones, NQO1 has two conflicting functions because of the different stability of converted hydroquinones. The stable form of hydroquinone is excreted from cells by conjugation with glutathione or glucuronic acid. The unstable form of hydroquinone induces cell death by induction of oxidative stress and DNA damage. Certain quinones known as bio-reductive agents have a cytotoxic function following reduction by NQO1. Bio-reductive agents, such as ${\beta}$-lapachone or mitomycin C, induce the depletion of NAD(P)H and the generation of oxidative stress in an NQO1-dependent manner. NQO1 is highly expressed in several cancer tissues. Therefore, NQO1 is a good therapeutic target for cancer treatment with bio-reductive agents.

• Journal of the Korean Institute of Gas
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• v.21 no.6
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• pp.61-69
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• 2017

In case of plant accident, the most important measures that field operators, control-room operators and fire fighters must take are the escape from and going into the accident sites. These two different actions are reverse directional moving actions. By training operators and fire fighters with counter-accident path taking measurements, we can prevent the small accidents from becoming large-scale accidents, and can take efficient measurements in case of actual plant accidents. Out of necessities of path-taking training, in this research, we developed the escape and rescue path-taking method for plant accident response training. We can calculate the escape and rescue routes from a operator or fire fighter's current location as of accident happening and provide route data which in turn can be used as the safety training scenario. We expect this path-taking method can enhance the effectiveness and reality of escape and rescue training scenarios.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.4
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• pp.432-436
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• 2015

This study computationally explored the thermal performance of passively-cooled polymer heat sinks utilizing seawater. Polymer heat sinks are proposed as cooling modules of the cold sides of thermoelectric generators for waste heat recovery. 3-D Computational Fluid Dynamics (CFD) modelling was conducted for a detailed numerical study. Polyphenylene sulfide (PPS) and pyrolytic graphite (PG) were selected for the base materials of polymer heat sinks. The computational study evaluated the performance of the PPS and PG heat sinks at various fin numbers and fin thicknesses. Their performances were compared with those of aluminum (Al) and titanium (Ti) heat sinks. The study results showed that the thermal performance of the PG heat sink was 3~4 times better than that of the Ti heat sink. This might be due mainly to the better heat spreading of the PG heat sink than the Ti heat sink. The effect of the number of fins on the performance of the PG heat sink was dissimilar to the cases of the PPS and Ti heat sinks. This result can be explained by the interrelationships among heat spreading, surface area enhancement, and fluidic resistance incorporating with an increase in the number of fins.

• School Mathematics
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• v.18 no.3
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• pp.441-455
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• 2016

The position as saying that the math learning needs to begin from what diversely presents concrete object or familiar situation is well known as a name dubbed CSA(Concrete-Semiconcrete-Abstract). Compared to this, a recent research by Kaminski, et al. asserts that learning an abstract concept first may be more effective in the aspect of knowledge transfer than learning a mathematical concept with concrete object of having various contexts. The purpose of this study was to analyze a class, which differently applied a guidance sequence of concrete object, semi-concrete object, and abstract concept in consideration of this conflicting perspective, and to confirm its educational implication. As a result of research, a class with the application of a concept starting from the concrete object showed what made it have positive attitude toward mathematics, but wasn't continued its effect, and didn't indicate significant difference even in achievement. Even a case of showing error was observed rather owing to the excessive concreteness that the concrete object has. This error wasn't found in a class that adopted a concept as semi-concrete object. This suggests that the semi-concrete object, which was thought a non-essential element, can be efficiently used in learning an abstract concept.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.8 no.2
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• pp.137-145
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• 1996

Effects of nonlinear terms on the generation of M$_2$ tide residual elevation and M$_4$ tide in the Yellow Sea and the East China Sea are investigated using a depth-integrated two-dimensional nonlinear M$_2$tidal model. The model domain (117$^{\circ}$E-130$^{\circ}$E, 24$^{\circ}$N-41$^{\circ}$N) covers the whole region of the Yellow Sea and the East China Sea with grid resolution of 1/6$^{\circ}$ in longitude and 1/8$^{\circ}$in latitude. A radiational boundary condition is used along the open boundaries. Calculations show that advection terms yield negative residual elevation, while shallow-water terms in continuity equation yield positive residual elevation. The contribution of both advection terms and shallow-water terms to tile generation of the M$_4$ constituent is more than 90 percents, but that of quadratic bottom friction terms to the M$_4$ constituent is comparatively small.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2003.11a
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• pp.61-64
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• 2003

무손실 이미지 압축은 (Lossless Image Compression)은 손실이미지 압축(Lossy Image Compression)에 비해, 압축률(compression ratio)은 떨어지지만, 반면 원이미지와 복원이미지가 완전히 일치하므로, 원인이미지의 품질을 그대로 유지학 수 있다. 따라서, 이미지의 품질(Quality)과 압축효율(compression ratio)은 서로 상반된 관계에 있으며, 지금도 좀 더 놀은 압축효과를 얻으려는 여러 무손실 압축 방법이 발표되고 있다. 무손실 이미지 압축은 이미지의 정확성과 정밀성이 요구되는, 의료영양분야에서 가장 널리 쓰이고 있으며, 그밖에, 원본이미지를 기본으로 다른 이미지프로세싱이 필요한 경우, 압축 복원을 반복적으로 수행할 필요가 있을 때, 기타 사진 예술분야, 원격 영상 등 정밀성이 요구되는 분양에서 쓰이고 있다. [7]. 무손실 이미지 압축의 가장 대표적인 CALIC[3]과 JPEG_LS[2]를 들 수 있다. CALIC은 비교적 높은 압축률을 나타내지만, 3-PASS의 과정을 거치는 복잡도가 지적되고 있다. 반면 JPEG-LS는 압축률은 CALIC에 미치지 못하지만 빠른 코딩/디코딩 속도를 보인다. 본 논문에서는 여거 가지의 예측 모드를 두어, 블록단위별로 주변 CONTEXT에 따라, 최상의 예측 모드를 판단하여, 이를 적용, 픽셀의 여러 값을 최소화하였다. 그 후 적응산술 부호기(Adaptive arithmetc coder)를 이용하여, 인코딩을 하였다. 이때 최대 에러값은 64를 넘지 않게 했으며, 또한 8*8블록별로 에러의 최대값을 측정하여 그 값을 $0\~7$까지의 8개의 대표값으로 양자화하는 방법을 통하여 그에 따라 8개의 보호화 심볼 모델중 알맞은 모델에 적용하였다. 이를 통해, 그 소화값의 확률 구간을 대폭 넓힘으로써, 에러 이미지가 가지고 있는 엔트로피에 좀 근접하게 코딩을 할 수 있게 되었다. 이 방법은 실제로 Arithmetic Coder를 이용하는 다른 압축 방법에 그리고 적용할 수 있다. 실험 결과 압축효율은 JPEG-LS보다 약 $5\%$의 압축 성능 개선이 있었으며, CALIC과는 대등한 압축률을 보이며, 부호화/복호화 속도는 CALIC보다 우수한 것으로 나타났다.

• Information Systems Review
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• v.5 no.2
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• pp.1-21
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• 2003

In this paper, we investigate industrial product intermediary's transformation strategy by exploiting advantages afforded by web based information technologies. Our motivation for this research stems from exploring intermediary's responding strategy to cope with supplier's threatening to disintermediation. From transaction cost perspective, internet can induce both the vertical quasi-integration (electronic hierarchy) and outsourcing (electronic market). Our rationale on directing one of these bi-directional movements is specified on intermediary's value adding on the supply chain. As such, we investigated supply chain performance, IT effects on customer's requirement of channel functions, and channel power structure. Propositions to suggest contingent e-transforming strategic alternatives are logically derived from dyadic nature of supply chain characteristics such as efficiency versus customer services, and supplier dominant versus easy replaceability of suppliers. The contingent e-transformation framework developed from intermediary's perspective is reviewed through longitudinal industry case analysis. Implications from the industry case analysis give us insights for the effectiveness of the framework to combine supply chain characteristics with intermediary's e-transformation.