• 천문학회보
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• 제38권2호
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• pp.56.1-56.1
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• 2013

Supernovae type Ia (SNe Ia) cosmology is providing the only direct evidence for the presence of dark energy. This result is based on the assumption that the look-back time evolution of SNe Ia luminosity, after light-curve shape correction, would be negligible. However, the most recent compilation of SNe Ia data shows systematic difference in the Hubble residual (HR) between the E and Sd/Irr galaxies, indicating that the light-curve fitters used by the SNe Ia community cannot quite correct for a large portion of the population age effect. In order to investigate this possibility more directly, we have obtained low-resolution spectra for 30 nearby early-type host galaxies. This data set is used to estimate the luminosity-weighted mean ages and metallicities of host galaxies by employing the population synthesis models. We found an interesting trend between the host galaxy age and HR, in the sense that younger galaxies have positive residuals (i.e., light-curve corrected SNe Ia luminosity is fainter). This result is rather independent of the choice of the population synthesis models employed. Taken at face value, this age (evolution) effect can mimic a large fraction of the HR used in the discovery of the dark energy. This result is significant at 1.4 - 3 sigma levels, depending on the light curve fitters adopted, and further observations and analyses are certainly required to confirm the trend reported here.

• 한방재활의학과학회지
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• 제25권4호
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• pp.83-92
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• 2015

Objectives To measure and analyze the curvature of the cervical spine for university students. Methods This study carried out on 132 students. The cervical spine curvature was measured by six measuring methods. The type and numeric value of cervical spine curvature was analyzed by Angle of cervical curve (C1~C7), Angle of cervical curve (C2~C7), Jackson's angle, Ishihara Index, Depth of cervical curve and Method of Jochumsen. Cervical spine curvatures between male and female are compared by Mann-Whitney test. Rate of type of cervical curvature between male and female are compared by linear by linear association. Results 1. The average of angle of cervical curve (C1~C7) is $33.78{\pm}9.85^{\circ}$, angle of cervical curve (C2~C7) is $10.28{\pm}8.12^{\circ}$. The average of Jackson's angle is $14.02{\pm}10.01^{\circ}$, average of Ishihara Index is $8.46{\pm}10.58%$. The average of Depth of cervical curve is $5.15{\pm}4.72mm$ and average of Method of Jochumsen is $0.94{\pm}3.83mm$. 2. More than half of student's cervical curvature showed hypolordosis except Ishihara index. 3. There was significant difference in numeric value of cervical curvature between male and female both groups in terms of Ishihara index. 4. There were insignificant differences between male and female in terms of type of cervical curvature. Conclusions According to above results, we found out average of student's cervical curve. And the results suggest that most of the student's cervical curvature decrease.

• 한국의류산업학회지
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• 제17권2호
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• pp.227-236
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• 2015

This study analyzed the lower body type of 30's Korean men to develop a slim-fit pants pattern. As the analysis data, direct measurement data of anthropometric measured value in the 6th Size Korea(KATS, 2010) was used as basic data with 481 men in 30's as analysis objects. The result are as follows. First, the result of analyzing factors for the lower body type classification indicated five factors. Second, the result of executing group analysis (with the independent variable of 5 clusters extracted from the factor analysis)classified the following three types. Type 1(36.8%) displayed a medium height of lower body type, small waist and hip, slim and fit body type with a slim shape between the knee and ankle. The shape between the waist and hip had characteristics of a slight curve and short length. Type 2(35.6%) displayed lowest height of a lower body type that was large and thick between the waist and the hip. The drop value of the waist and the hip was small; therefore, the body type was flat with a minimal curve. The underpart type (below the knee) was the thickest and the length was short. Type 3(27.7%) displayed the highest lower body type, a medium level waist size, flat and narrow waist and belly. This body type had a curve with big drop value of the waist and the hip, lower part from the hip to the ankle (including the knee) and a thick calf with along leg.

• 천문학회보
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• 제45권1호
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• pp.36.1-36.1
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• 2020

The progenitor of Type Ia supernovae (SNe Ia) is mainly believed to be a carbon/oxygen white dwarf (WD) with non-degenerate (single degenerate) or another WD companion (double degenerate). However, there is little observational evidence of their progenitor system. Recent studies suggest that shock-breakout cooling emission after the explosion can constrain the size of the progenitor system. To do so, we obtained a optical/Near-IR light curve of SN 2019ein, a normal but slightly sub-luminous type Ia supernova, from the very early phase using our high-cadence observation of Intensive Monitoring Survey of Nearby Galaxies (IMSNG). Assuming the expanding fireball model, the simple power-law fitting of the early part of the light curve gives power indices of 1.91 (B) and 2.09 (R) implying radioactive decay of 56Ni is the dominant energy source. By comparison with the expected light curve of the cooling emission, the early observation provides us an upper limit of the companion size of R∗≤1R⊙. This result suggests that we can exclude a large companion such as red giants, which is consistent with the previous study.

• 한국안광학회지
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• 제15권1호
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• pp.61-66
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• 2010

목적: 주시시차 카드를 이용하여 수직주시시차를 측정하였다. 이 연구의 목적은 Wesson 주기시차카드를 이용한 주시시차 검사법에 의해 수직주시시차의 분포를 조사하고, 진단과 처방에 응용하는데 있다. 방법: Wesson 주시시차 카드를 이용하여 52명을 대상으로 수직주시시차를 측정하였다. 주시시차곡선은 추가한 프리즘량과 주시시차량에 대한 함수이며, 주시시차 곡선에서 진단과 처방에 사용되는 값은 x-절편, y-절편, 기울기, 곡선 타입이다. 결과: Wesson 주시시차 카드를 이용한 두시시차 측정 결과 여러 가지 type의 수직주시시차 곡선을 얻을 수 있었다. 결론: 수직주시시차 곡선을 진단과 처방에 이용할 수 있다.

• 천문학회보
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• 제45권1호
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• pp.48.4-49
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• 2020

We reconstruct the expansion history of the universe using type Ia supernovae (SN Ia) in a manner independent of any cosmological model assumptions. To do so, we implement a nonparametric iterative smoothing method on the Joint Light-curve Analysis (JLA) data while exploring the SN Ia light-curve hyperparameter space by Markov Chain Monte Carlo (MCMC) sampling. We test to see how the posteriors of these hyperparameters depend on cosmology, whether using different dark energy models or reconstructions shift these posteriors. Our constraints on the SN Ia light-curve hyperparameters from our model-independent analysis are very consistent with the constraints from using different parameterizations of the equation of state of dark energy, namely the flat ΛCDM cosmology, the Chevallier-Polarski-Linder model, and the Phenomenologically Emergent Dark Energy (PEDE) model. This implies that the distance moduli constructed from the JLA data are mostly independent of the cosmological models. We also studied that the possibility the light-curve parameters evolve with redshift and our results show consistency with no evolution. The reconstructed expansion history of the universe and dark energy properties also seem to be in good agreement with the expectations of the standard ΛCDM model. However, our results also indicate that the data still allow for considerable flexibility in the expansion history of the universe. This work is published in ApJ.

• 대한수학회지
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• 제57권1호
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• pp.89-111
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• 2020

In the present paper, we give some characterization of the L₂ maximal estimate for the operator P^t_a,γf(Γ(x, t)) along curve with complex time, which is defined by $$P^t_{a,{\gamma}}f({\Gamma}(x,t))={\displaystyle\smashmargin{2}{\int\nolimits_{\mathbb{R}}}}\;e^{i{\Gamma}(x,t){\xi}}e^{it{\mid}{\xi}{\mid}^a}e^{-t^{\gamma}{\mid}{\xi}{\mid}^a}{\hat{f}}({\xi})d{\xi}$$, where t, γ > 0 and a ≥ 2, curve Γ is a function such that Γ : ℝ×[0, 1] → ℝ, and satisfies Hölder's condition of order σ and bilipschitz conditions. The authors extend the results of the Schrödinger type with complex time of Bailey [1] and Cho, Lee and Vargas [3] to Schrödinger operators along the curves.

• 대한수학회지
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• 제55권4호
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• pp.923-938
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• 2018

In this paper, we handle the Gauss map of a tubular surface which is constructed according to the parallel transport frame of its spine curve. We show that there is no tubular surface having harmonic Gauss map. Moreover, we give a complete classification of this kind of tubular surface having pointwise 1-type Gauss map in Euclidean 4-space ${\mathbb{E}}^4$.

• Journal of Mechanical Science and Technology
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• 제18권1호
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• pp.106-113
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• 2004

Recently, a new issue in designing spot welded structures such as automobile and train car bodies is to predict an economical fatigue design criterion. One of the most typical and traditional methods is to use a ΔP-N$\sub$f/ curve. However, since the fatigue data on the ΔP-N$\sub$f/ curve vary according to the welding conditions, materials, geometry of joint and fatigue loading conditions, it is necessary to perform the additional fatigue tests for determining a new fatigue design criterion of spot-welded lap joint having specific dimension and geometry. In this study, the stress distributions around spot welds of various spot welded lap joints such as in-plane bending type (IB type), tension shea. type (TS type) and cross tension type (CT type) were numerically analyzed. Using these results, the ΔP-N$\sub$f/ curves Previously obtained from the fatigue tests for each type were rearranged into the Δ$\sigma$-N$\sub$f/ relations with the maximum stresses at the nugget edge of the spot weld.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1996년도 특별강연 및 춘계학술발표 개요집
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• pp.96-98
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• 1996

Welding of corner area across the edge is a difficult problem in robotized arc welding system, especially when continuously-welded leakage-proof product is required. This paper presents the methodology of cooperation plan of an arc welding robot and 1 or 2 axis welding manipulators for corner area welding. Welding trajectory for the robot is generated using clothoid curves; symmetrical double clothoid curve or unsymmetrical clothoid curve depending on the nature of the workpiece. The clothoid curve is first formulated for the case of linear type positioning table and then applied to the case of rotary type manipulator. The methodology is then illustrated for practical downhand welding situations.