• Journal of applied mathematics & informatics
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• 제27권5_6호
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• pp.1435-1446
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• 2009

In this paper we investigate the blow up properties of the positive solutions to a semi linear parabolic system with coupled nonlocal sources $u_t={\Delta}u+k_1{\int}_{\Omega}u^{\alpha}(y,t)v^p(y,t)dy,\;v_t={\Delta}_v+k_2{\int}_{\Omega}u^q(y,t)v^{\beta}(y,t)dy$ with non local Dirichlet boundary conditions. We establish the conditions for global and non-global solutions respectively and obtain its blow up set.

• 대한수학회지
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• 제56권3호
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• pp.579-594
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• 2019

A colored space is a pair (X, r) of a set X and a function r whose domain is $\(^X_2\)$. Let (X, r) be a finite colored space and $Y,\;Z{\subseteq}X$. We shall write $Y{\simeq}_rZ$ if there exists a bijection $f:Y{\rightarrow}Z$ such that r(U) = r(f(U)) for each $U{\in}\({^Y_2}\)$ where $f(U)=\{f(u){\mid}u{\in}U\}$. We denote the numbers of equivalence classes with respect to ${\simeq}_r$ contained in $\(^X_i\)$ by $a_i(r)$. In this paper we prove that $a_2(r){\leq}a_3(r)$ when $5{\leq}{\mid}X{\mid}$, and show what happens when equality holds.

• 전기학회논문지
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• 제59권4호
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• pp.768-773
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• 2010

In this paper, we study on an optimal design of a triple-band PIFA (Planar Inverted-F Antenna) of 433 MHz, 912 MHz and 2.45 GHz by using evolution strategy. Generally, the resonant frequency of the PIFA is determined by the width and length of a U-type slot used. However the resonant frequencies of the multiple U slots are varied by the mutual effect of the slots. Thus the optimal width and length of U-type slots are determined by using an optimal design program based on the evolution strategy. To achieve this, an interface program between a commercial EM analysis tool and the optimal design program is constructed for implementing the evolution strategy technique that seeks a global optimum of the objective function through the iterative design process consisting of variation and reproduction. The resonant frequencies of initial model are 439.5 MHz, 981.5 MHz and 2.563 GHz. However, the resonant frequencies of the triple-band PIFA yielded by the optimal design program are 430.5 MHz, 907 MHz and 2.4515 GHz. Measured resonant frequencies are 433.5 MHz, 905.5 MHz and 2.454GHz, which show a good agreement with the simulation results.

• 대한전자공학회논문지TC
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• 제49권6호
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• pp.63-70
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• 2012

UWB 주파수대역의 안테나로써 CPW 급전의 U-자형 평면 패치 안테나모델의 지향성이득 향상 방법을 검토하였다. 지향성 이득 향상을 위해 CPW 급전의 U-자형 패치 안테나 모델에 개구슬롯 반사면을 부가하여 마이크로스트립 구조로 재구성하였다. 재구성한 안테나는 특성 임피던스 $50.08{\Omega}$에 대해 반사계수는 -6.5dB(VSWR < 3.3)이하이며 지향성이득은 7.8 dBi ~ 9.6 dBi, 전후방비는 17.8dB ~ 28.7dB 그리고 ${\theta}=0^{\circ}$의 주방사 방향에 대해 -3dB 방사각의 범위가 ${\pm}30^{\circ}$의 방사지향성의 패턴을 나타내 보였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.495-498
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• 2008

In this paper applicable range of U-Channel Bridge (UCB) that has recently been introduced as a new bridge type was studied. For structural analysis models used with the frame and plate elements was proposed, and verification of the models were performed. Using these structural models structural analysis of models with span length of 20m-45m and inner width of 5m-13m were performed. As a result for U-shape sections were applicable in the range of 20m span and 35m span, slab was applicable in the range of 5m inner width and 12m inner width. To increase applicable range of UCB H-shape sections and slab with rib were proposed. As a result UCB were applicable in the range of 20m span and 45m span, in the range of 5m inner width and 13m inner width.

• 기술사
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• 제14권2호
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• pp.5-11
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• 1981

This analysis has been conducted for 8 chemical plants built in Korea during 1975-1976 and the results have been compared with those in U.S.A. observed by Kenneth M. Guthrie. Equipment and materials supplied by domestic makers are limited in activity field and occupy only 12% of all equipment and material cost. However, unit costs of most materials supplied by home such as cement, steel, cables and carbon steel pipes, etc. being relatively cheaper than those of abroad, their effects on material-to-equipment ratios are apparent. There is a deep difference in labor wage rates between Korea and U.S.A. as much as 16 times. However, the labor productivity observed in these model projects is in the range of 1.1-1.4 to the Gulf Coast, U.S.A. during the same period. And this low wage rate and relatively high productivity have the greatest influence on deviation of Korean cost structure from that of U.S.A. In these model projects, engineering and construction management was conducted by foreign contractors (mostly U.S.A.), and the resulting project indirect cost amounts to 7.5 times as high as most cases executed by Korean contractors alone. Weighted percentage of each component and L/M-ratio by activities of direct field cost derived from this analysis are shown in detail in Tables 2 and 5 to provide a basis for futher study and comparison.

• 말소리와 음성과학
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• 제5권3호
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• pp.39-46
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• 2013

This study examined the perception of two Korean vowels using F1/F2 manipulated synthetic vowels. Previous studies indicated that there is an overlap between the acoustic spaces of Korean /o/ and /u/ in terms of the first two formants. A continuum of eleven synthetic vowels were used as stimuli. The experiment consisted of three tasks: an /o/ identification task (Yes-no), an /u/ identification task (Yes-no), and a forced choice identification task (/o/-/u/). ROC(Receiver Operating Characteristic) analysis and logistic regression were performed to calculate the boundary criterion of the two vowels along the stimulus continuum, and to predict the perceptual judgment on F1 and F2. The result indicated that the location between stimulus no.5 (F1 = 342Hz, F2 = 691Hz) and no.6 (F1 = 336Hz, F2 = 700Hz) was estimated as a perceptual boundary region between /o/ and /u/, while stimulus no.0 (F1=405Hz, F2=666Hz) and no.10 (F1=321Hz, F2=743Hz) were at opposite ends of the continuum. The influence of F2 was predominant over F1 on the perception of the vowel categories.

• Journal of Radiation Protection and Research
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• 제10권2호
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• pp.144-147
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• 1985

고체비적검출기(固體飛跡檢出器)인 운모(雲母)를 $^{238}UO_2$ 박판(箔板)에 약(約) 5년간(年間) 밀착(密着)시켜 두었다가 운모(雲母)만을 꺼내어 불산(弗酸)속에서 부식(腐蝕)시킨후, 광학현미경(光學顯微鏡)으로 그 속에 생긴 핵분열파편(核分裂破片)의 비적(飛跡)을 관측(觀測)하여 $^{238}U$의 자발핵분열률(自發核分裂率)을 결정(決定)하였다. 이 실험(實驗)에서 얻은 $^{238}U$의 자발핵분열률(自發核分裂率)은 $5.21{\pm}0.33$ fissions/g-sec이었다.

• 한국강구조학회 논문집
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• 제26권5호
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• pp.419-430
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• 2014

연구대상인 강바닥판교의 U-리브와 가로리브를 교차하는 접합부에 대한 연구는 지속적으로 이루어지고 있으나 아직까지는 현재 적용되고 있는 스캘럽 자체 또는 내부의 다이아프램 형상을 개발 이용하고 있는 정도이다. 근본적으로 문제가 되고 있는 교차부 U-리브 하단 부위의 피로손상을 줄이기 위해, 본 연구를 통하여 제시된 SRH, 즉, U-리브가 교차하는 가로리브의 적절한 위치에 적합한 크기의 원형의 구멍을 두는 방안에 대하여 검토하였다. 최종적으로 원형 SRH가 강바닥판교의 U-리브와 가로리브 교차부 응력집중을 충분히 완화시킬 수 있음을 확인하였고, 이 부위의 구조상세의 피로손상을 방지할 수 있는 방안 중 하나로 SRH를 제안할 수 있었다.

• 한국수산과학회지
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• 제34권6호
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• pp.577-583
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• 2001

황복의 소화효소의 변화과정을 부화직후부터 부화 후 65일까지 측정 하였다. 발육단계에 따른 소화효소의 발현과 활성의 변화에서 $\alpha-amylase$ 비활성은 전장 10mm에서 0.0493U/mg의 최소값을 나타낸 후, 전장 19mm를 전후하여 0.1480 U/mg의 최대값을 나타냈다. Trypsin과 pepsin 비활성은 전장 16mm에서 각각 0.0264U/mg, 0.0258U/mg 와 전장 24mm에서 0.0178U/mg, 0.0201 U/mg의 값을 가지는 두 번의 peak를 보였고, 이 시기에 황복 자치어의 성장률도 증가하는 경향을 보였다. 또한, trypsin과 pepsin의 비활성을 비교하여 보면, 자어기인 전장 $4\~5mm$와 치어 II기인 전장 $19\~24mm$에서는 pepsin이 높았고, 치어 I 기인 전장 $11\~16mm$와 유어기인 전장27 mm 이후에서는 trypsin이 높았다.