• Honam Mathematical Journal
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• v.38 no.2
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• pp.305-316
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• 2016

In this paper we study general rotational surfaces in the 4-dimensional Euclidean space $\mathbb{E}^4$ and give a characterization of flat general rotational surface with pointwise 1-type Gauss map. Also, we show that a flat general rotational surface with pointwise 1-type Gauss map is a Lie group if and only if it is a Clifford torus.

• Communications of the Korean Mathematical Society
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• v.28 no.3
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• pp.425-432
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• 2013

Let S be a minimal surface of general type with $p_g(S)=q(S)=0$ having an involution ${\sigma}$ over the field of complex numbers. It is well known that if the bicanonical map ${\varphi}$ of S is composed with ${\sigma}$, then the minimal resolution W of the quotient $S/{\sigma}$ is rational or birational to an Enriques surface. In this paper we prove that the surface W of S with $K^2_S=5,6,7,8$ having an involution ${\sigma}$ with which the bicanonical map ${\varphi}$ of S is composed is rational. This result applies in part to surfaces S with $K^2_S=5$ for which ${\varphi}$ has degree 4 and is composed with an involution ${\sigma}$. Also we list the examples available in the literature for the given $K^2_S$ and the degree of ${\varphi}$.

• Bulletin of the Korean Mathematical Society
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• v.47 no.6
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• pp.1269-1274
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• 2010

As the sequel to our previous work [4], we construct a minimal complex surface of general type with $p_g=0$, $K^2=3$ and $H_1$ = $\mathbb{Z}/2\mathbb{Z}$ by using a rational blow-down surgery and $\mathbb{Q}$-Gorenstein smoothing the-ory.

• Communications of the Korean Mathematical Society
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• v.32 no.3
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• pp.479-494
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• 2017

We construct various examples of simply connected minimal complex surfaces of general type with $p_g=0$ and $K^2=1,2$ using ${\mathbb{Q}}$-Gorenstein smoothing method.

• Journal of the Korean Mathematical Society
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• v.50 no.3
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• pp.493-507
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• 2013

We construct a new family of simply connected minimal complex surfaces of general type with $p_g$ = 1, $q$ = 0, and $K^2$ = 3, 4, 5, 6, 8 using a $\mathbb{Q}$-Gorenstein smoothing theory.

• Journal of the Korean Home Economics Association
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• v.11 no.4
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• pp.363-373
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• 1973

The Sewability was tested with the seam strength and Puckering Grade by a general sewing machine according to some properties of simulated Leather, yarn tensile strength needle and stitches. The main results tested are as follows ; 1. The thick and uncomfortable leather is unable to be sewed by a general sewing machine, but the thin and soft one is able to. 2. The interval between stitches depends on type of leather used, and the variance in accordance with type of leather varies much more in the case of narrower interval. 3. When the sewability of leather-surface is not so good, is desirable to pour oil on the surface for the purpose of better efficiency. 4. The seam strength is directly proportional to interval of stitch and tensile strength of yarn and leather used, and needle No. 14 is more effective than No.1l. 5. The more the soft and thin leather is, the lower the Puckering Grade becomes. Type of yarn and interval of stitches do not seem to effect the Puckering Grade.

• Bulletin of the Korean Chemical Society
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• v.33 no.3
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• pp.775-778
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• 2012

The potential energy surfaces of ammonia molecule adsorptions on the symmetrically chlorinated Si(100)-$2{\times}1$ surface were explored with SIMOMM:MP2/6-31G(d). It was found that the initial nucleophilic attack by ammonia nitrogen to the surface Si forms a $S_N2$ type transition state, which eventually leads to an HCl molecular desorption. The second ammonia molecule adsorption requires much less reaction barrier, which can be rationalized by the surface cooperative effect. In general, it was shown that the surface Si-Cl bonds can be easily subjected to the substitution reactions by ammonia molecules yielding symmetric surface Si-$NH_2$ bonds, which can be a good initial template for subsequent surface chemical modifications. The ammonia adsorptions are in general more facile than the corresponding water adsorption, since ammonia is better nucleophile.

• Journal of The Korean Society of Agricultural Engineers
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• v.46 no.4
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• pp.39-46
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• 2004

This experiment was carried out to study on the effect of surface coating on thermal insulation of farm structures to improve thermal resistance and reflective effect of solar radiation. Nine different types of experimental specimen were compared in the temperature variations of inside and outside; A, B, C, D. E and F types are box container and G, H and I types are drum container. The size of these containers is $1,500{\times}2,000{\times}2,500$ mm and ${\varphi}$ $280{\times}330$ mm, respectively. Specimen of 3-type box(A, B, C) is galvanized steel sheet of thickness 0.45 mm. D, E and F types are sandwich panel of the thickness 50 mm inserted with urethane, glass wool and polystyrene form, respectively. G, H and I types are paint pot using in general. The surface of A. D, E, F and I types didn't any treatment, B, C and G types were treated with thermal insulation coating on the outside surface(B, G) or the inside and outside surface(C). And H type was treated with water paint coating on the only outside surface. In general, the experimental results showed the following tendencies; In case of A, B and C types. it was found that the thermal insulation effect of types coated with thermal insulation coating was improved remarkably than that of no treatment. And the thermal insulation effect between steel sheet and sandwich panel type was nearly similar There was not a significant difference of thermal insulation effect between thermal insulation coating and water paint coating. In time of drum container filled with rough rice, The difference of heat transfer tendency and temperature variation among surface treatments was nearly similar that of box types of galvanized steel sheet. And there was time lag about 6 hours between the temperature of middle part of rice and that of inside or outside surface.

• Communications of the Korean Mathematical Society
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• v.27 no.1
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• pp.37-46
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• 2012

It is well known that plurigenus does not vanish for a sufficiently large multiple on a canonical threefold over $\mathbb{C}$. There is Reid Fletcher formula for plurigenus. But, unlike in the case of surface of general type, it is not easy to compute plurigenus. In this paper, we in-duce a different version of Reid-Fletcher formula and show that the constant term in the induced formula has periodic properties. Using these properties we have an application to nonvanishing of plurigenus.

• Journal of the Korean Mathematical Society
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• v.53 no.4
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• pp.869-893
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• 2016

We construct the extension of a hyperelliptic K3 surface to a Fano 6-fold with extraordinary properties in moduli. This leads us to a family of surfaces of general type with $p_g=1$, q = 0, $K^2=2$ and hyperelliptic canonical curve, each of which is a weighted complete inter-section inside a Fano 6-fold. Finally, we use these hyperelliptic surfaces to determine an 8-parameter family of Godeaux surfaces with ${\pi}_1={\mathbb{Z}}/2$.