• 신재생에너지
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• 제6권4호
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• pp.30-40
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• 2010

Syngas from gasification of coal can be converted to SNG(Synthesis Natural Gas) through gas cleaning, water gas shift, $CO_2$ removal, and methanation. One of the key technologies involved in the production of SNG is the methanation process. In the methanation process, carbon oxide is converted into methane by reaction with hydrogen. Major factors of methanation are hydrogen-carbon oxide ratio, reaction temperature and space velocity. In order to understand the catalytic behavior, temperature programmed surface reaction (TPSR) experiments and reaction in a fixed bed reactor of carbon monoxide have been performed using two commercial catalyst with different Ni contents (Catalyst A, B). In case of catalyst A, CO conversion was over 99% at the temperature range of $350{\sim}420^{\circ}C$ and CO conversions and $CH_4$ selectivity were lower at the space condition over 3000 1/h. In case of catalyst B, CO conversion was 100% at the temperature over $370^{\circ}C$ and CO conversions and $CH_4$ selectivity were lower at the space condition over 4700 1/h. Also, conditions to satisfy $CH_4$ productivity over 500 ml/h.g-cat were over 2000 1/h of space velocity in case of catalyst A and over 2300 1/h of space velocity in case of catalyst B.

• 한국항공우주학회지
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• 제32권1호
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• pp.44-49
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• 2004

• East Asian mathematical journal
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• 제14권1호
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• pp.205-217
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• 1998

We obtain some theorems on nonexistence of certain finite type closed curves on the pseudo-hyperbolic space $H^4(-c^2)$ in the Minkowski spacetime $E^5_1$.

• East Asian mathematical journal
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• 제16권2호
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• pp.169-174
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• 2000

We give an easy proof that ${\phi}(z)=\frac{z^2_1}{1-z^2_2}$ induces the bounded composition operator $C_{\phi}:\mathcal{B}{\rightarrow}{\bigcap}H^p(B_2)$ defined by $C_{\phi}f=f\;o\;{\phi}$.

• Journal of Astronomy and Space Sciences
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• 제33권2호
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• pp.127-135
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• 2016

Inactive space objects are usually rotating and tumbling as a result of internal or external forces. KOREASAT 1 has been inactive since 2005, and its drift trajectory has been monitored with the optical wide-field patrol network (OWL-Net). However, a quantitative analysis of KOREASAT 1 in regard to the attitude evolution has never been performed. Here, two optical tracking systems were used to acquire raw measurements to analyze the rotation period of two inactive satellites. During the optical campaign in 2013, KOREASAT 1 was observed by a 0.6 m class optical telescope operated by the Korea Astronomy and Space Science Institute (KASI). The rotation period of KOREASAT 1 was analyzed with the light curves from the photometry results. The rotation periods of the low Earth orbit (LEO) satellite ASTRO-H after break-up were detected by OWL-Net on April 7, 2016. We analyzed the magnitude variation of each satellite by differential photometry and made comparisons with the star catalog. The illumination effect caused by the phase angle between the Sun and the target satellite was corrected with the system tool kit (STK) and two line element (TLE) technique. Finally, we determined the rotation period of two inactive satellites on LEO and geostationary Earth orbit (GEO) with light curves from the photometry. The main rotation periods were determined to be 5.2 sec for ASTRO-H and 74 sec for KOREASAT 1.

• Journal of Astronomy and Space Sciences
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• 제18권1호
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• pp.7-14
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• 2001

Red giant branch shape and the luminosity of horizontal branch on the (V-I)-V CMD are used to derive the metallicity the globular cluster NGC 5053. The metallicities of NGC 5053 derived by SMR method ([Fe/H]=-2.62$\pm$0.07) and the relation between[Fe/H] and $(V-I)_{0.g}$ ([Fe/H]=-2.50) are in good agreement with previously determined values. This result confirms that the morphologies of RGB and HB on the (V-I)-V CMDs can be good indirect photometric metallicity indicators of galactic globular clusters.

• 천문학회보
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• 제28권1호
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• pp.92-92
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• 2003

• 천문학회보
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• 제28권1호
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• pp.94-94
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• 2003

• 충청수학회지
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• 제34권3호
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• pp.259-269
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• 2021

We shall study the following. Let 𝜙 be an expansive flow on a compact TVS-cone metric space (X, d). First, we give some equivalent ways of defining expansiveness. Second, we show that expansiveness is conjugate invariance. Finally, we prove that lim sup ${\frac{1}{t}}$ log v(t) ≤ h(𝜙), where v(t) denotes the number of closed orbits of 𝜙 with a period 𝜏 ∈ [0, t] and h(𝜙) denotes the topological entropy. Remark that in 1972, R. Bowen and P. Walters had proved this three statements for an expansive flow on a compact metric space [?].

• 대한수학회보
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• 제30권1호
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• pp.65-70
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• 1993

In this paper we will extend some notions of bounded linear operators to some unbounded linear operators. Let H be a complex separable Hilbert space and let B(H) denote the algebra of bounded linear operators. A closed densely defind linear operator S in H, with domain domS, is called subnormal if there is a Hilbert space K containing H and a normal operator N in K(i.e., $N^{*}$N=N $N^*/)such that domS .subeq. domN and Sf=Nf for f .mem. domS. we will show that the Radjavi and Rosenthal theorem holds for some unbounded subnormal operators; if $S_{1}$ and $S_{2}$ are unbounded subnormal operators on H with dom $S_{1}$= dom $S^{*}$$_{1}$ and dom $S_{2}$=dom $S^{*}$$_{2}$ and A .mem. B(H) is injective, has dense range and $S_{1}$A .coneq. A $S^{*}$$_{2}$, then $S_{1}$ and $S_{2}$ are normal and $S_{1}$.iden. $S^{*}$$_{2}$.2}$.X>.