• 대한수학회보
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• 제48권2호
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• pp.377-386
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• 2011

For a smooth algebraic curve C of genus g $\geq$ 4, let $SU_C$(r, d) be the moduli space of semistable bundles of rank r $\geq$ 2 over C with fixed determinant of degree d. When (r,d) = 1, it is known that $SU_C$(r, d) is a smooth Fano variety of Picard number 1, whose rational curves passing through a general point have degree $\geq$ r with respect to the ampl generator of Pic($SU_C$(r, d)). In this paper, we study the locus swept out by the rational curves on $SU_C$(r, d) of degree < r. As a by-product, we present another proof of Torelli theorem on $SU_C$(r, d).

• 대한금속재료학회지
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• 제47권10호
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• pp.613-620
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• 2009

The Kachanov-Rabotnov (K-R) creep model was proposed to accurately model the long-term creep curves above $10^5$ hours of Alloy 617. To this end, a series of creep data was obtained from creep tests conducted under different stress levels at $950^{\circ}C$. Using these data, the creep constants used in the K-R model and the modified K-R model were determined by a nonlinear least square fitting (NLSF) method, respectively. The K-R model yielded poor correspondence with the experimental curves, but the modified K-R model provided good agreement with the curves. Log-log plots of ${\varepsilon}^{\ast}$-stress and ${\varepsilon}^{\ast}$-time to rupture showed good linear relationships. Constants in the modified K-R model were obtained as ${\lambda}$=2.78, and $k=1.24$, and they showed behavior close to stress independency. Using these constants, long-term creep curves above $10^5$ hours obtained from short-term creep data can be modeled by implementing the modified K-R model.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권1호
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• pp.597-600
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• 2007

The address and sustain discharge characteristics in plasma display panels (PDPs) are investigated and compared by the optical emission spectroscopy using the ICCD and Vt close-curve analysis. The observations on the xenon (Xe) emission show that the spatial and temporal evolutions in the first sustain discharge are quite different from those in the address and the other sustain discharges. The striation found in the conventional sustain discharge doesn't occur in the first sustain discharge. These different discharge behaviors are explained by employing the Vt close-curve.

• 소성∙가공
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• 제29권6호
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• pp.316-322
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• 2020

The flow stress curve is usually determined via uniaxial tensile or simple compression test. However, the flow stress curve up to high strain cannot be obtained using these two tests. This study presents a simple method for obtaining the flow stress curve up to high strain via FE analysis, a simple compression test, and an indentation test. In order to draw the flow stress curve up to high strain, the indentation test was carried out with the pre-stained specimen using the simple compression test. The flow stress curve of Al6110 was evaluated up to high strain using the proposed method, and the result was compared with the flow stress curve of the uniaxial tensile test of the initial material.

• 대한기계학회논문집A
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• 제25권5호
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• pp.797-804
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• 2001

To obtain representative fatigue crack growth characteristic curve in residual stress field, fatigue crack growth test was carried out at various stress ratio and fatigue crack growth characteristic curve was represented using crack closure concept. Obtained results are as follows;K(sub)op/K(sub)max was independent of K(sub)max when R was lower than 0.5 and crack closure phenomenon was not observed when R is higher than 0.5. therefore neglecting crack closure behaviour, actual fatigue crack growth rate can be underestimated. Thus, considering crack closure phenomenon, fatigue crack growth characteristics curve of A 106 Gr B Steel weldment can be effectively estimated.

• Asian-Australasian Journal of Animal Sciences
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• 제15권6호
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• pp.890-894
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• 2002

The accuracy of the gamma function to describe lactation curve of Yankasa ewes was investigated using milk production data obtained from 168 ewes with either complete or incomplete 84 day lactation records. Ewes were daily hand milked after over-night separation from lamb and thorough disinfection of the udder. The daily milk yield on the average was estimated from the weekly total yield. The effect of type of birth, parity, season of birth and lactation length on the components of lactation curve (a, b, c and s) were analysed by least-square procedures. All factors except parity significantly (p<0.01) influenced the curve parameters. The goodness of fit of the function did not differ between the two classes of varying duration of lactation; incomplete lactation however, showed a lower persistency and as expected lower level of production. Correlations ($r_p$) between lamb weight gain and milk yield using the weight records from lamb weighed at weekly intervals indicated a high and positive relationship in the early lactation that decreased in intensity as the lactation advanced.

• 수산해양기술연구
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• 제40권4호
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• pp.247-254
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• 2004

동해안의 연안성 어족인 빨간횟대에 대해 망목크기 등을 달리한 8종류의 장구형 통발을 사용하여, 2003년 6월부터 12월까지 총 6차례에 걸쳐 어선 2척을 용선하여 조업한 어획실험으로부터 망목선택성 곡선을 구하여 합리적인 자원관리에 대한 기초 자료를 구하고자 하였다. 망목 크기가 20mm와 35mm인 두 통발의 빨간횟대 어획물로부터 체장에 따른 어획비율의 차이에 대해 특별한 경향을 발견할 수 없었다. 망목 크기가 20mm와 55mm인 두 통발의 경우에 대해 SELECT방법을 이용하여 equal split model 과 estimated split model을 적용한 결과, AIC 값이 적은 전자가 더 적절한 모델이므로, 빨간횟대의 경우는 이들 두 통발에 대한 입망률의 차이는 없는 것으로 나타났다. 망목 55mm의 통발에서 SELECT 모델로 구한 50% 어획될 빨간횟대의 전장은 22.0cm였다. 망목 크기가 20mm, 35mm, 55mm인 통발의 어획 자료에 Kitahara의 방법으로 logistic식을 적용하여 추정된 선택성 곡선식은 $s(R)\;=\;\frac{1}{1+exp(-0.3545R+2.141)$와 같았고, 현재 규정 망목 크기인 35mm 장구형 통발에 대해 50% 어획될 빨간횟대의 전장은 21.4cm이었다.

• Journal of Information Display
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• 제7권1호
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• pp.25-29
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• 2006

By the voltage threshold (Vt) close-curve measurement method, the changes in the discharge characteristics such as a firing voltage and IR emission among the three electrodes were examined relative to the low or high panel temperature ranging from -10 to $80^{\circ}$. The variation in the panel temperature was found significantly influence the surface discharge between the MgO surfaces rather than the plate gap discharge between the MgO and phosphor layers. Based on this experimental observation, a modified reset waveform that alleviates the surface discharge during a ramp-up and -down period was deeloped. By adopting the proposed reset waveform, a stable address discharge could be obtained irrespective of the panel temperature variation.

• 대한기계학회논문집A
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• 제25권2호
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• pp.296-303
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• 2001

Kachanov-Rabotnov(K-R) creep damage theory was reviewed, and applied to design a creep curve for type 316LN stainless steel. Seven coefficients used in the theory, i.e., A, B, k, m, λ, r, and q were determined, and their physical meanings were analyzed clearly. In order to quantify a damage parameter ($\omega$), cavity amount was measured in the crept specimen taken from interrupted creep test with time variation, and then the amount was reflected into K-R damage equations. Coefficient λ, which is regarded as a creep tolerance feature of a material, increased with creep strain. Mater curve with λ=2.8 was well coincided with an experimental one to the full lifetime. The relationship between damage parameter and life fraction was matched with the theory at exponent ${\gamma}$=24 value. It is concluded that K-R damage equation was reliable as the modelling equation for type 316LN stainless steel. Coefficient data obtained from type 316LN stainless steel can be utilized for life prediction of operating material.

• 한국세라믹학회지
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• 제38권10호
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• pp.936-941
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• 2001

5.31 mol% ${Y_2}{O_3}$-4.45 mo1% ${Nb_2}{O_5}$-90.31 mo1% $ZrO_2$에 ${Al_2}{O_3}$를 첨가한 복합체를 제조하여 알루미나 입도가 복합체의 균열 전파 저항성에 미치는 영향을 조사하였다. $ZrO_2/{Al_2}{O_3}$ 복합체에서는 R-cuve 거동이 관찰되었으며 0.2, $2.8{\mu}m$ ${Al_2}{O_3}$가 20 vol%가 첨가된 복합체의 인성값은 각각 7.9, $8.8MPam^{1/2}$이었다. 파괴인성값의 차이는 ${Al_2}{O_3}$ 입도 크기에 의존하는 $ZrO_2/{Al_2}{O_3}$ 복합체 내의 정방정 $ZrO_2$의 결정립 크기 차이에 의한 것으로 추정된다.