• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(2)
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• pp.713-717
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• 2004

This is a thesis that a quarter-brick size of 100W class open-frame type on board power module comprising telecommunication application is reported. The input voltage is established between 36 and 75 in range in order for power module to be utilized for the telecommunication application, and output were set at 3.3V and 30A. A number of parts used for transformer, inductor, and hit sink are composed of PCB in order for DC-DC converter to be lowered below 8 mm. A constant current control circuit was annexed to the system as well as basic protection prototypes such as over-voltage, over-current, and over-temperature were well considered to enhance more credibility, and were tested. As a result, high circuit performance and credibility turned out to be significant.

• Korean Journal of Mathematics
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• 제16권3호
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• pp.355-362
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• 2008

We prove the existence of a unique positive solution for a class of systems of the following nonlinear suspension bridge equation with Dirichlet boundary conditions and periodic conditions $$\{{u_{tt}+u_{xxxx}+\frac{1}{4}u_{ttxx}+av^+={\phi}_{00}+{\epsilon}_1h_1(x,t)\;\;in\;(-\frac{\pi}{2},\frac{\pi}{2}){\times}R,\\{v_{tt}+v_{xxxx}+\frac{1}{4}u_{ttxx}+bu^+={\phi}_{00}+{\epsilon}_2h_2(x,t)\;\;in\;(-\frac{\pi}{2},\frac{\pi}{2}){\times}R,$$ where $u^+={\max}\{u,0\},\;{\epsilon}_1,\;{\epsilon}_2$ are small number and $h_1(x,t)$, $h_2(x,t)$ are bounded, ${\pi}$-periodic in t and even in x and t and ${\parallel} h_1{\parallel}={\parallel} h_2{\parallel}=1$. We first show that the system has a positive solution, and then prove the uniqueness by the contraction mapping principle on a Banach space

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 하계종합학술대회논문집
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• pp.70-73
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• 1998

This paper present a new priority control mechanism which is to balance the cell loss rate by measuring, in real time, the number of discarded cells in the queuing system with a different loss priority for each class of service such that each class of service meets its cell loss rate requirements. And, to reduce the delay rates we modified existing cell scheduling scheme. Throughout the computer simulation, the existing methods and proposed scheme is compared with respect to cell loss rate and average delay time. In the result of simulation, the proposed scheme have more improved performance than the other schemes with respect to cell loss rate and average delay time.

• 한국환경보건학회지
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• 제20권4호
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• pp.10-16
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• 1994

A Study was performed in order to measure mixed organic solvent concentrations in air of painting operations during January 5-28, 1991. The mixed organic solvent concentrations were analyzed by the gas chromatography. The results were as follows: 1. The detection of organic solvent was highest in aromatic hydrocarbon(68%), and followed by aliphatic hydrocarbon (18%), and ketone (14%). 2. The detection of organic solvent by component category was highest in the grid class solvent (79.4%), and followed by the 3rd class solvent (20.6%). 3. Number of cases exceeding TLVS of mixed solvent level in air was highest on dipping operation (44%), and followed by spray operation (40%), dry and washing operation (33%), and adhensive operation (12%).

• 호남수학학술지
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• 제28권2호
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• pp.185-196
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• 2006

A scheme based on the cryptography for enforcing multilevel security in a system where hierarchy is represented by a partially ordered set was first introduced by Akl et al. But the key generation algorithm of Akl et al. is infeasible when there is a large number of users. In 1985, MacKinnon et al. proposed a paper containing a condition which prevents cooperative attacks and optimizes the assignment in order to overcome this shortage. In 2005, Kim et al. proposed key management systems for multilevel security using one-way hash function, RSA algorithm, Poset dimension and Clifford semigroup in the context of modern cryptography. In particular, the key management system using Clifford semigroup of imaginary quadratic non-maximal orders is based on the fact that the computation of a key ideal $K_0$ from an ideal $EK_0$ seems to be difficult unless E is equivalent to O. We, in this paper, show that computing preimages under the bonding homomorphism is not difficult, and that the multilevel cryptosystem based on the Clifford semigroup is insecure and improper to the key management system.

• International Journal of Control, Automation, and Systems
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• 제1권4호
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• pp.412-430
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• 2003

In many practical problems in signal processing and control, the signal values are often restricted to belong to a finite number of levels. These questions are generally referred to as "finite alphabet" problems. There are many applications of this class of problems including: on-off control, optimal audio quantization, design of finite impulse response filters having quantized coefficients, equalization of digital communication channels subject to intersymbol interference, and control over networked communication channels. This paper will explain how this diverse class of problems can be formulated as optimization problems having finite alphabet constraints. Methods for solving these problems will be described and it will be shown that a semi-closed form solution exists. Special cases of the result include well known practical algorithms such as optimal noise shaping quantizers in audio signal processing and decision feedback equalizers in digital communication. Associated stability questions will also be addressed and several real world applications will be presented.

• 충청수학회지
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• 제22권1호
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• pp.17-23
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• 2009

Let F be a finite real abelian extension of a global function field k with G = Gal(F/k). Assume that F is an extension field of the Hilbert class field $K_e$ of k and is contained in a cyclotomic function field $K_n$. Let $\ell$ be any prime number not dividing $ph_k{\mid}G{\mid}$. In this paper, we show that if $\theta{\in}\mathbb{Z}[G]$ annihilates the Sylow $\ell$-subgroup of ${\mathcal{O}}^{\times}_F/{\mathcal{C}}_F$, then (q-1)$\theta$ annihilates the Sylow $\ell$-subgroup of ${\mathcal{Cl}}_F$.

• 아동학회지
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• 제20권2호
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• pp.3-19
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• 1999

The Revised Classroom Play(RCP) scale was validated for Korean 4th grade students. 104 boys and 80 girls took the translated RCP. Test-retest reliability was established with 41 children after 2 months, and test of criterion-related validation was established by the Social Behavior Scale administered to 71 children. All raw scores were standardized by classroom and sex to adjust for differences in the number of nominators and nominatees. The structure of the RCP resulted in 3 factors, 'sociability-disruptive' and 'shy-isolated', with 28 items similar to the original RCP 3 factors. For criterion-related validity, the correlations between the 3 factors of the RCP and the 3 factors of the Social Behavior Scale were positive. For internal consistencies, Cronbach's ${\alpha}$ of the RCP factors ranged from .77 to .94. Test-retest reliability coefficients ranged from .33 to .51. Analyses of variance revealed good item discrepancies for all 28 items. These results confirm the RCP as a valid and reliable measure of the quality of peer relations.

• 한국환경과학회지
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• 제17권8호
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• pp.879-889
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• 2008

Community structure of benthic macroinvertebrates was investigated from Gigye stream, Pohang, Korea from May to November, 2007. As results, total of 108 species of macroinvertebrates under 49 families, 15 orders, 5 classes in 3 phyla were identified. The number of species was the most abundantly revealed in aquatic insects (class Insecta) with 86 species (82.6%) under 7 orders. The phylum Mollusca (10 species, 9.2%) and the phylum Annelida (6 species, 5.6%) were followed in order. In the class Crustacea, 6 species (5.6%) were distributed. In aquatic insects, the order Odonata was the most abundant taxon (20 species, 23.3%). Seventeen species (19.8%) of the order Ephemeroptera and 16 species (18.6%) of the Coleoptera were followed. The primary dominant species in the stream was Cloeon dipterum of Ephemeroptera. For community analysis, the values of diversity index (H'), evenness index (J'), dominance index (DI) and richness index (RI) were studied and the average values of them were 5.65, 0.84, 0.13, and 13.18, respectively.

• 한국실내디자인학회:학술대회논문집
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• 한국실내디자인학회 1999년도 춘계학술발표대회 논문집
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• pp.114-117
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• 1999

The purpose of this study was to compare with the characteristics of Wumul-maru components in upper class Chosun dynasty. Physical trace method was used for this study. The samples were taken from the Sarang-taechong of 6 traditional Korean houses, Yunkyungdang, the ancient Chusa estate, Sunkyojand, Chunghyodang, Yangjindang, Unjoru. The major findings were summarized as follows; 1) Regarding to the scale characteristics, the number of changguit'ul(long board) was 1, chungguit'ul(middle-length board) 5, tongguit'ul(center board) 8m and maruno. 98, and the size of changguit'ul was 253$\times$4478mm, chungguit'ul 182$\times$2396mm, tongguit'ul 179$\times$2310mm, and marunol 247$\times$574mm. 2) Regarding to the proportion characteristics, the proportion of changguit'ul was 1:18.2, chungguit'ul 1:16.7, tongguit'ul 1:12.9, and marunol 1:2.62 and the proportion of components was 1:3:4:17.