• Bulletin of the Korean Chemical Society
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• v.31 no.9
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• pp.2565-2570
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• 2010

The orthorhombic $MgB_2C_2$ structure contains well-separated parallel graphite-like $B_2C_2^{2-}$ layers which extend infinitely in two dimensions. Three possible ways to distribute B and C atoms in the hexagonal sublattice sites are adopted. Band structures for the hypothetical distribution patterns are examined to assess the electronic stability of these phases and to account for the observed arrangement by means of extended Huckel tight-binding calculations. The preferred choice is the layer with B and C alternating strictly so that B is nearest neighbor to C and vice versa. A rationale for this is given. Due to the alternation of B and C within the honeycomb layers, $MgB_2C_2$ is a band insulator, which through partial substitution of Mg with Li, is predicted to turn metallic with holes in the $\sigma$ bands at the Fermi level.

• Journal of the Korean Magnetics Society
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• v.3 no.2
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• pp.94-100
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• 1993

Electronic and magnetic properties of the novel rare-earth permanent magnet, $Sm_{2}Fe_{17}N_{3}$, are investigated by performing self-consistent local density functional electronic structure calculations. Employing the LMTO(Linearized Muffin-Tin Orbital) band method, we have obtained the electronic band structures for both paramag-netic and ferromagnetic phases of $Sm_{2}Fe_{17}N_{3}$. Based on the energy band structures, we have studied bonding ef-fects among Sm, Fe, and N atom as well as electronic and magnetic structures. It is found that the N atom sub-stantially reduces the magnetic moment of neighboring Fe atoms through the hybridization interaction and also plays a role in stabilizing the structure. the average magnetic moment of Fe atoms in the ferromagnetic phase of $Sm_{2}Fe_{17}N_{3}$ is estimated to be $2.33{\mu}_B$, which is ~8% larger than the magnetic moment of $Sm_{2}Fe_{17}$, $2.16{\mu}_B$. The Fe I (c) atom, which is located farthest from the N atom and surrounded by 12 Fe nearest neighbors, has the largest magnetic moment ($2.65{\mu}_B$), while the Fe III (f), whose hybridization interaction with N atom is very strong, has the smallest magnetic moment($1.96{\mu}_B$).

• Proceedings of the Korean Magnestics Society Conference
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• 2007.05a
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• pp.13.2-13.2
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• 2007

• Interaction and multiscale mechanics
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• v.2 no.2
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• pp.109-128
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• 2009

Multiscale analysis is a stepwise procedure to obtain macro-scale material laws, directly amenable to structural analysis, based on information from finer scales. An essential ingredient of this mode of analysis is mathematical homogenization of heterogeneous materials at these scales. The purpose of this paper is to demonstrate the potential of multiscale analysis in civil engineering. The materials considered in this work are wood, shotcrete, and asphalt.

• IE interfaces
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• v.20 no.1
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• pp.79-86
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• 2007

In B2B e-commerce environments, many initiatives for process modeling have made efforts to design business processes correctly. Especially, Petri nets have been widely used as a good theory to design and verify process models. Therefore, we propose the process modeling method for the B2B e-commerce based on Petri nets. First of all, a B2B process model based on BPSS is represented by the UML activity diagram. Second, the activity diagram is transformed to a Petri net model. For the transformation, well-behaved building blocks/control structures and the modeling rules for inter-organizational workflow processes are proposed. Third, the process is partitioned into sharable processes for individual business partners. Finally, according to needs of individual business partners, the sharable processes are modified by well-structured refinement rules. The whole procedure is explained with the purchase process of an e-bookstore.

• Journal of the Korean Society of Marine Environment & Safety
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• v.5 no.2
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• pp.15-26
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• 1999

The marine structures with sea water cooling system always expose to the oceanic atmosphere. Therefore, the protection of the equipments is very important. To investigate the effectiveness of advanced composite materials for the application in offshore environments, the tensile test, hardness test, undercutting property test, permeance test and the friction and wear test were carried out by using various applicable coating materials. The main results obtained can be summarized as follows; 1. The micro-hardness of the Archcoat 502B showed the highest value. 2. The coefficient of friction of the Rigspray coating at the speed of 2.21m/sec showed the lowest value, and that of the Archcoat 502B coating at 1.08m/sec and 0.18m/sec indicated the lowest values. 3. The wear mass at the speed of 0.18m/sec and 1.08m/sec in dry condition showed the smallest values. 4. The Archcoat 502B coating is fitted to the dynamic instruments in the range of low speed and middle speed. Rigspray coating is fitted to the dynamic instruments in the range of high speed. 5. The wear mass of five kinds of coating materials at the range of low speed was very small, and those of the Archcoat S02B, Archcoat 402B and Rigspray coating at high speed range were quitely smaller than those of the Modified Epoxy and Tar Epoxy.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.7 s.250
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• pp.692-699
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• 2006

In this work, $TiO_2$ nanoparticles were synthesized using $N_2-diluted$ and Oxygen-enriched co-flow hydrogen diffusion flames. The effect of flame temperature on the crystalline structure of the formed $TiO_2$ nanoparticles was investigated. The measured maximum centerline temperature of the flame ranged from 2,103k for oxygen-enriched flame to 1,339K for $N_2-diluted$ flame. The visible flame length and the height of the main reaction zone were characterized by direct photographs. The crystalline structures of $TiO_2$ nanoparticles were analyzed by XRD. From the XRD analysis, it was evident that the crystalline structures of the formed nanoparticles were divided into two sorts. In the higher temperature region, over the 1,700K, the fraction of formed $TiO_2$ nanoparticles having anatase-phase crystalline structure increased with increasing the flame temperature. On the contrary, in the lower temperature region, below the 1,600K, the fraction of anatase-phase nanoparticles increased with decreasing the flame temperature.

• Journal of the Korean Institute of Landscape Architecture International Edition
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• no.2
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• pp.109-113
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• 2004

It is important to consider urban parks and greenery not only from the viewpoint of amenity or aesthetics but also from the viewpoint of biodiversity. In this study, we focused on bryophytes (mosses), and analyzed how existence of artificial structures in urban greeney, such as concrete curbs and stone walls, affect species diversity of bryophytes. Kyoto Gyoen in Kyoto City, western Japan, was selected as the study site. In consideration of kinds of substrates on which bryophytes grow, microhabitats of Kyoto Gyoen were divided into ten types including concrete curbs and stone walls. In each type of microhabitats, we selected the area where bryophyte diversity was highest, and established a quadrat for bryophyte flora survey. Our results showed that the number of bryophyte species and growth forms and the value of diversity indices on concrete curbs or stone walls were higher than the averages of those. The bryophyte species were divided into the four groups by TWINSPAN as follows: Group A (epiphyte species), Group B (rocky species), Group C (roadsides, grassland or forest species), and Group D (waterside species). Bryophytes classified into Group B (rocky species) were mainly recorded on concrete curbs or stone walls. It was considered that the existence of artificial structures (concrete curbs and stone walls) provided favorite habitats for the bryophytes classified into Group B (rocky species), which mainly grows on concrete or rocks, and enhanced species diversity of bryophytes in Kyoto Gyoen.

• Bulletin of the Korean Mathematical Society
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• v.55 no.6
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• pp.1727-1748
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• 2018

In this paper, we characterize the graded post-Lie algebra structures on the W-algebra W(2, 2). Furthermore, as applications, the homogeneous Rota-Baxter operators on W(2, 2) and solutions of the formal classical Yang-Baxter equation on $W(2,2){\ltimes}_{ad^*} W(2,2)^*$ are studied.

• Proceedings of the Korean Magnestics Society Conference
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• 2007.05a
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• pp.237.2-237.2
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• 2007