• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.247-248
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• 2008

A recent dynamic increase in demand for wireless multimedia services has greatly accelerated the research on dynamic channel adaptation of high quality video applications. In this paper, we explore a theoretical approach to cross-layer optimization between multimedia and wireless networks by means of a quality criterion termed "visual throughput" for downlink video transmission using a layered coding algorithm. We obtain the optimal loading ratio of orthogonal frequency division multiple access (OFDMA) subcarriers through an optimization problem balancing the trade-off relationship between inter-cell interference (ICI) and channel throughput. In the simulation, we show that the visual throughput gain at the cell boundary is increased by about 32%.

• 한국생산제조학회지
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• 제20권5호
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• pp.605-611
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• 2011

In this study, based on previous studies, the thrust generated by using flapping tandem wings is examined. We studied on the relationship between the parameters for characterizing oscillatory tandem wings (namely, the Strouhal number and Reynolds number) for thrust generation in micro flow regime. At each Reynolds number, Strouhal number, heaving amplitude, distance between tandem wings, and phase difference are varied and the flapping motions of tandem mode are calculated to find the optimum conditions for generating thrust. As a result, comparing with a single flapping mode, we found that the minimum Strouhal number for generating thrust is shifted down up to approximately 25% when the tandem flapping mode is applied.

• Bulletin of the Korean Chemical Society
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• 제32권2호
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• pp.411-416
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• 2011

Steric and electronic parameters of 4'-substituents play significant roles in steering the conformation of nucleoside analogues. In order to investigate the relationship of 4'-group with antiviral enhancement, novel 4'-hydroxymethyl-5'-norcarbocyclic adenosine phosphonic acid analogues were designed and synthesized from 2,2-dimethyl-1,3-dioxolane-4-ethanol (5) using reiterative Grignard addition and ring-closing metathesis (RCM) as key reactions. The synthesized adenosine phosphonic acids analogues (22) and (23) were subjected to antiviral screening against HIV-1. Compound (23) exhibited moderate anti-HIV activity ($EC_50$ = 8.61 ${\mu}M$) in the CEM cell line.

• Archives of Pharmacal Research
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• 제25권3호
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• pp.240-249
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• 2002

Dibenzyl-g-butyrolactone and 1,2,3,4-tetrahydro-2-naphthoic acid $\gamma$-lactone (TNL) derivatives were synthesized and evaluated for cytotoxic activity against some cancer cell lines. It was found that TNL derivatives with a shorter distance between C-4 in ring A and C'-2 in ring C were more cytotoxic, while dibenzyl-${\gamma}$-butyrolactones with a longer one were nearly inactive. In TNL series, presence of 3,4-dioxy group in ring A and 2-methoxy group in ring C was essential for the enhancement of the activity.

• 설비공학논문집
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• 제16권4호
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• pp.318-323
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• 2004

When a strong electric field is applied between a sharply curved electrode and a blunt surface, the corona may result in a gas movement in the electrode gap which is directed toward the blunt surface. That is called the corona wind. It enhances heat and mass transfer between the surface and the surrounding gas. Moreover such enhancement causes no noise or vibration, which can be applied in complex, isolated geometries, and allows simple control of surface temperatures. This paper examines the relationship between the corona wind and the relative humidity. The facility consists of high voltage power supply thin tungsten wire, plate electrode, multimeter, microammeter and flow meter. Gas velocity is a linear function of voltage, relative humidity and is proportional to the square root of the current. The maximum velocities for the positive and negative corona discharge are 1.9 m/s (2.74 CMM/m), 1.5 m/s(2.15 CMM/m), respectively.

• Transactions on Electrical and Electronic Materials
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• 제16권1호
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• pp.20-24
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• 2015

We studied the relationship between the surface smoothness of the internal Cu ribbon and the morphology of the Sn-Pb plating layer for solar cell modules. A bumpy surface was observed on the surface of the solar ribbon, which caused irregular reflection of light. Large, Pb-rich, primary ${\alpha}$-phases were found below the convex surface of the solar ribbon, passing from the surface of the internal Cu ribbon to the surface of the plating layer. The primary ${\alpha}$-phases heterogeneously nucleated on the convex surface of the Cu ribbon, and then largely grew to the convex surface of the plating layer. The restriction of the primary ${\alpha}$-phase's formation was enabled by enhancing the smoothness of the Cu ribbon's surface; it was also possible to increase the adhesive strength and decrease contact resistance. We confirmed that the solar ribbon's surface smoothness depends on the internal Cu ribbon's surface smoothness.

• 대한가정학회지
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• 제41권11호
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• pp.201-214
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• 2003

The purpose of this research was to develop the education program for post-divorce adjustment and to evaluate effectiveness of the program. This program was consisted of eight sessions and applied to divorced parents. It was focused for the understanding of grief processes for adults, recovery by forgiveness, children's responses and coping strategies to divorce, open minded relationship between parents and children, and enhancement of self-esteem to be healthy single parent. Results of paired t-test showed that there were significant differences between pre-test and post-test, and the effectiveness remained until follow-up. In conclusion, this program was thought to be effective for improving self-esteem, divorce coping competency and minimizing of the depressions. Continual education is thought to be necessary for maintaining of the effectiveness to the divorced parents.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 ICEIC The International Conference on Electronics Informations and Communications
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• pp.52-56
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• 2004

Computing today is becoming ubiquitous. In such ubiquitous computing environments, entities expect to access resources and services at any time from anywhere. Therefore, the question rises of how to establish trust relationship in previously unknown devices or resources with such environment. After reviewing a model to delegate trust to communicating entities in ubiquitous environment and its security problems, we present a new model for secure delegation over communication entities. We adopt two-party signature scheme as cryptographic primitives. Additionally, we apply threshold cryptosystems to our model for more secure enhancement.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(4)
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• pp.191-194
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• 2002

The final purpose of this paper is the enhancement of speech recognition rate under the matched telephone environment between training data and test data. To analyze the effect by the distortion of the changing telephone channel on every call, MFCC is used as the feature parameter and CMN, RTCN, and RASTA are used as channel compensation techniques. For each case, the variation of feature parameters of all phones is analyzed. And, we find recognition rates according to each compensation method using the continuous HMM recognizer, and examine the relationship between variation and recognition rate.

• 지역사회간호학회지
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• 제24권3호
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• pp.255-263
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• 2013

Purpose: This study examined the fitness of a path model for the relationship among daily life stress, problem of life, social support, depression, and suicidal ideation in adolescents. Methods: The subjects consisted of 247 adolescents. Data were collected through self-report questionnaires. The data were analyzed by the SPSS and AMOS programs. Results: Daily life stress, problem of life, social support, and depression showed direct effects on suicidal ideation in adolescents, while daily life stress and problem of life showed indirect effects on suicidal ideation in adolescents. Daily life stress and problem of life showed direct effects on social support and depression in adolescents. The hypothetical path model of adolescents' suicidal ideation was proven correct. Conclusion: Based on the outcomes of this study, it is necessary to design an intervention program that emphasizes the reduction of daily life stress, problem of life, depression and enhancement social support in order to prevention adolescents' suicidal ideation.