• 한국산학기술학회논문지
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• 제10권10호
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• pp.2733-2740
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• 2009

최근 All-IP 네트워크 환경이 구축되면서 다양한 형태의 트래픽이 송수신되고 있으며, 이와 더불어 악의적 공격이 급증하고 있어 이에 대한 능동적 대응 방안이 제시되어야 한다. 기존 연구로는 SPIE 시스템을 통해 일방향 해쉬함수와 Bloom Filter 방식을 적용한 라우터 중심 패킷 경로 추적 기법이 제시되었으나, DDoS 공격이 발생할 경우 이를 능동적으로 차단하면서 공격 근원지를 효율적으로 추적하기에는 문제점이 있다. 따라서 본 연구에서는 기존 SPIE 및 Sinkhole 기반 라우터 기법의 장단점에 대한 분석을 통해 두 방식의 장점을 결합하여 All-IP 네트워크 환경에 적합한 IP 추적 방식을 설계하고 이를 구현하였다. 본 연구에서 제시한 기법은 기존의 Sinkhole 방식과 유사하게 공격 패킷에 대한 수집/모니터링 기능을 제공하면서도 추적 패킷 Manager 시스템을 기반으로 공격 패킷에 대한 판단 및 수집/제어기능을 제공하여 성능 향상과 함께 DDoS 공격에 대한 능동적 대응이 가능하였다.

• Bulletin of the Korean Chemical Society
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• 제34권8호
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• pp.2325-2329
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• 2013

Second-order rate constants $k_N$ have been measured for reactions of benzyl 2-pyridyl thionocarbonate (4b) and t-butyl 2-pyridyl thionocarbonate (5b) with a series of cyclic secondary amines in MeCN at $25.0{\pm}0.1^{\circ}C$. The $k_N$ values for the reactions of 4b and 5b have been compared with those reported previously for the corresponding reactions of benzyl 2-pyridyl carbonate (4a) and t-butyl 2-pyridyl carbonate (5a) to investigate the effect of changing the electrophilic center from C=O to C=S on reactivity and reaction mechanism. The thiono compound 4b is more reactive than its oxygen analogue 4a. The Br${\o}$nsted-type plots for the reactions of 4a and 4b are linear with ${\beta}_{nuc}=0.57$ and 0.37, respectively. The reactions of 4a were previously reported to proceed through a concerted mechanism, while those of 4b in this study have been concluded to proceed through a stepwise mechanism with formation of an intermediate being the rate-determining step on the basis of the ${\beta}_{nuc}$ value of 0.37. Enhanced polarizability upon changing the C=O in 4a by C=S has been suggested to be responsible for the reactivity order and the contrasting reaction mechanisms. In contrast, the reactivity of 5a and 5b is similar, but they are much less reactive than 4a and 4b. Furthermore, the reactions of 5a and 5b have been concluded to proceed through the same mechanism (i.e., a concerted mechanism) on the basis of linear Bronsted-type plots with ${\beta}_{nuc}=0.45$ or 0.47. It has been concluded that the strong steric hindrance exerted by the t-Bu in 5a and 5b causes a decrease in their reactivity and forces the reactions to proceed through a concerted mechanism.

• 대한기계학회논문집B
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• 제35권1호
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• pp.75-82
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• 2011

디젤의 대체연료인 디메틸 에테르의 반응기구 축소에 관한 수치해석을 수행하였다. 상세반응기구(79 개의 화학종과 351 개의 반응단계)를 기초로, 최대몰농도 해석과 민감도 해석을 균질 반응기 모델에 적용하였다. 축소반응기구는 상세반응기구의 착화지연기간과 비교하여 구축하였는데, 기준값으로 $7.5{\times}10^{-5}$을 적용했을 때 44 개의 화학종과 166 개의 반응단계로 구성된다. 축소반응기구의 계산 정확도를 검증하기 위하여 두 반응기구를 단일영역 균일예혼합 압축착화 엔진모델에 적용하였고, 축소반응기구의 계산결과는 상세반응기구의 결과와 일치하였다. 따라서 본 연구의 축소반응기구는 계산의 정확도의 손실 없이 DME 를 연료로 사용하는 압축착화엔진의 착화 및 연소 과정을 모사하는데 이용될 수 있다.

• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 1997년도 춘계학술대회
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• pp.119-119
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• 1997

Valacyclovir is a L-valyl ester prodrug of acyclovir which is a highly effective and selective antiviral agent in the treatment of herpes virus diseases. Valacyclovir is rapidly and almost completely converted to acyclovir and increases the oral bioavailability of acyclovir three to five fold. However, the intestinal absorption mechanism of valacyclovir is not clear. If the improved absorption mechanism of valacyclovir is fully understood, it will provide a rationale of designing the amino acid ester prodrugs of polar drugs containing hydroxyl group. The main objective of our present study is to characterize the membrane transport mechanism of valacyclovir. Methods : Intestinal absorption of valacyclovir was investigated by using in-situ rat perfusion study and its wall permeability was estimated by modified boundary layer model. The membrane transport mechanism was also investigated through the uptake study in Caco-2 cells and in CHO-hPepTl cells. Results : In the rat perfusion study, the wall permeability of valacyclovir was ten times higher than acyclovir and showed concentration dependency, Valacyclovir also demonstrated a D,L stereo-selectivity with L-isomer having an approximately five-fold higher permeability than D-isomer. Mixed dipeptides and cephalexin, which are transported by dipeptide carriers, strongly competed with valacyclovir for the intestinal absorption, while L-valine did not show any competition with valacyclovir. This indicated that the intestinal absorption of valacyclovir could be dipeptide carrier-mediated. In addition, the competitive uptake study in Caco-2 cells presented that dipeptides reduced the valacyclovir uptake but valine did not. Also, in IC$\sub$50/ study, valacyclovir showed strong inhibition on the $^3$H-gly-sar uptake in CHO-hPepTl cells over-expressing a human intestinal peptide transporter. Taken together, the result from our present study indicated that valacyclovir utilized the peptide transporter for the intestinal absorption.

• International Journal of Contents
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• 제8권1호
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• pp.10-15
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• 2012

Since MegaStudy started e-learning business for Korean high school students, the Korean e-learning industry began to expand and steadily gain attention. This paper focused on the analysis of the development of the Korean e-learning business for teens and the growth of MegaStudy. The three institutional mechanisms were used to examine the factors that aided the development of the business. The regulatory mechanism was the government policy to prevent the expansion of the offline private education sector, which greatly aided the growth of the e-learning business. The mimetic mechanism was the notion to mimic the characteristics of the Korean e-business initiatives. The normative mechanism involved the widespread social norm suggesting that every student should be given an equal opportunity of private education. This paper also examined the case of MegaStudy as a successful case of the e-learning companies. It analyzed the business model of MegaStudy, which is based on its advantage as the front-runner and its high-quality contents and services.

• 품질경영학회지
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• 제29권3호
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• pp.138-150
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• 2001

Recently, industrial environments have been drastically changed. Customers require cheaper, better, stronger products more than ever. Thus companies have to satisfy the requirements of customers to be survived in this kind of industrial environments. To cope with these requirements from customers, engineers in industries must accept new paradigm and use some special tools for developing new product. This study has applied a Concurrent Engineering which would be good for shortening of product development period in developing of Full Logic Deck mechanism using in car audio. In this paper, a real case of systematic approach and successful story of Concurrent Engineering application in developing Full Logic Deck mechanism is illustrated.

• 한국의상디자인학회지
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• 제11권3호
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• pp.17-25
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• 2009

The purpose of this study is to help understanding of abstract patterns and to play a guideline's role in the development of designs and the prediction of trends for present and future fashion designers and textile designers. The summary of this study's results is like followings. Formative characteristics of abstract pattern in 2000's fashion are Impromptu, Anti-mechanism, Superimposing, Disorder. First, Impromptu is rebounce against uniformity, mechanism, man-created beauty Second, Anti-mechanism represents unfinishing, unbalance, inaccuracy and relates with each traditional of nation or ethnic group. Third, Presupposing transparency Superimposing offsets each patterns. So Their images are ambiguity, ununiformity, unequality, incompletion, uncertainty and so on. Fourth, Disorder breaks and ignores physical balance, rule, order and so on. These images represent uncertainty, freedom, naturality. From this result, I can interpret that these images are representing of humanism reacting about uniformity, mechanism, man-created beauty, completeness of modernism since the Industrial Revolution.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.703-707
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• 2000

This paper studied on the lateral motion of the gantry crane which is used for the automated container terminal. Though several problems are occurred in driving of gantry crane, they are solved by the motion by the operator. But, if the gantry crane is unmanned, it is automatically controlled without any human operation. Especially, the collision between wheel-flange and rail is a very critical problem in driving of unmanned gantry crane. To bring a solution to these problems, the lateral and yaw dynamic equations of the driving mechanism of gantry crane are derived. And this study used PD(Proportional-Derivative) Controller to control the lateral displacement and the yaw angle. The simulation result of the driving mechanism using the Runge-Kutta method is presented in this paper.

• 디지털산업정보학회논문지
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• 제6권4호
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• pp.251-265
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• 2010

Recently, with increasing interest in the subject of interfirm relationship mechanism, some information systems researchers point out that existing outsourcing theories are limited in explaining the choice of governance mechanisms in interfirm relational exchanges. Recognizing the importance of trust-commitment, this study focuses on the relationship of between control mechanism and commitment. Especially the role of trust as mediator is mainly researched. A mediation model was suggested on the basis of theoretical linkages from prior relevant studies. The research model was empirically tested with 73 IS outsourcing projects. The findings have significant impactions for further research and practice. Findings are as follows: First, outcome control, process control, social control had positive effects on trust and commitment. Second, inter-organizational trust played as a partial mediator on the relationship between control mechanisms and commitment. Based on these findings, the implication and the limitation of the study were presented including some directions for future studies.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.872-876
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• 1996

Most studies of rotary machinery design have been performed to establsih a new mechanism or a dramatic combination of machine elements for the power transmission. Although the rotary machine is worked very efficiently, that still has a major work to better performance which is the optimization of the selected mechanism for the mechanical efficiency, low vibration and noise, or customer interest. This work presents a practical approach used for washer's efficiency and machinery vibration and noise reduction along with a systematic procedure. Also for the confirming the study, a computer simulation program and a real working mock-up are developed and used to show very good agreement with the analytical result.