• Bulletin of the Korean Chemical Society
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• v.31 no.4
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• pp.781-788
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• 2010

Experimental and theoretical studies show that all covalent azides possess a nonlinear azide group. They also rationalize this remarkable structural feature. We have seen that the most important non-covalent contributions in the covalently bound azides system (X-N1-N2-N3) are the $\pi$-delocalization over the entire molecule and a strong negative hyperconjugation which donates electron density from the filled $\sigma$ (X-N1) orbital into the unfilled, antibonding $\pi^*$ (N2-N3) orbital. For transition metal azide complexes, a bent configuration and a small difference between the N-N bond lengths, generally the longer one being adjacent to the transition metal, were observed.

• Journal of the Korean Magnetic Resonance Society
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• v.27 no.4
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• pp.28-34
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• 2023

We study the linear-nonlinear quantum transport theory of Wannier-Landau transition system in the confinement of electrons by a square well confinement potential. We use the projected Liouville equation method with the ensemble density projection technique. We select the dynamic value under a linearly oscillatory external field. We derive the dynamic value formula and the memory factor functions in three electron phonon coupling systems and electron impurity coupling systems of two transition types, the intra-band transitions and inter-band transitions. We obtain results that can be applied directly to numerical analyses. For simple example of application, we analyze the absorption power and line-widths of ZnO, through the numerical calculation of the theoretical result in the Landau system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.1
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• pp.44-51
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• 1998

In order to develop the evaluation methods of degradation for the Ni-Cr-Mo-V steel, which is in use for turbine rotor in nuclear power plant, the degraded materials were prepared by simulated degradation methods. The result of impact test and fatigue crack growth test shows that the FATT(Fracture Appearance Transition Temperature) and fatigue crack growth rate increased with the increase of degradation. And the result of new electrochemical polarization test method was suggested for the evaluating FATT, fatigue crack growth exponent and coefficient C values based on the results of relationship between corrosion current density(Icorr) & FATT, and the m & C and Icorr.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.6
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• pp.814-822
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• 1986

Flow patterns and its transitions in vertical two phase flow of air-water isothermal flow are identified objectively by void output signals and moments computed from the Probability Density Function which is associated with the statistical measurement for time average local void fractions using conductance probe. It has been shown that the probe output signals, PDF distributions and its moments are deterministic criteria of flow pattern and transition classification.

• Journal of the Korean Vacuum Society
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• v.5 no.1
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• pp.48-53
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• 1996

We present a microscopic description for generation of 1/f noise in interfaces between cobalt thin film and silicon substrate. Along with surface resistance measurements and transmission electron diffraction observations. 1/f noise power spectral density has been measured for the interfacial structures at the liquid nitrogen temperature . The cobalt films have been deposited by the electron-beam evaporation technique onto p-type (100) silicon in the high vacuum condition. The measured noise power spectral density shows highest magnitude near the structural transition and metallization transition region. The noise magnitude rapidly decreased after the cobalt silicide nucleation. The noise parameter is concluded to be originated form the structural fluctuations.

• ALGAE
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• v.30 no.2
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• pp.139-146
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• 2015

Urchin barrens have been a major issue of rocky coastal ecosystems in temperate regions. In South Korea, the east coast and Jeju Island have especially been a focus because the area of barren ground increases in spite of continual efforts to install artificial reefs. This study approached the urchin barrens issue in South Korea, by focusing on a correlational analysis of urchin and macroalgal abundance. Urchin density and algal species coverage were obtained using a quadrat image analysis. Subtidal sites were then classified into three groups according to the average densities of urchins to evaluate the characterization of the macroalgal community: no urchin (NU) zone; transition (TR) zone, $4inds.\;m^{-2};$ and urchin (UR) zone, ${\geq}8inds.\;m^{-2}$. The average urchin density in the study site was $4.7inds.\;m^{-2}$ and 57 macroalgal species were found in the study site. From the NU zone to UR zone, total species number, species diversity index and evenness gradually decreased, whereas the dominance index increased. The algae species with negative correlations were Grateloupia divaricata, Polysiphonia morrowii, Chondracanthus intermedius, Delesseria violacea, Desmarestia viridis; and those with positive correlations were the crustose corallines, Sargassum horneri. Other species were not significantly correlated with urchin density. The significant correlations indicate that the abundance of some macroalgal species is proportionally regulated by sea urchin density. This study also shows how macroalgal vegetation changes in response to an urchin's density gradient in a natural condition; and there is a TR zone that existed with respect to an intermediate level of algal abundance.

• Bulletin of the Korean Chemical Society
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• v.17 no.11
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• pp.1074-1077
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• 1996

• Journal of the Korean housing association
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• v.26 no.2
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• pp.21-28
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• 2015

The purpose of this paper is to estimate and deduct appropriate Hanok type within Suwon Hwaseong Fortress in which formula Hanok type has not remained. To do so, urban change according to chronology is analyzed and architectural aspect of transition is collected. By using geographic information in Suwon Hwaseong Fortress, present urban structural density, status of architecture and chronological aspect of transition in one-story buildings is surveyed. Through these data, appropriate Hanok form and density to the area is suggested. As a result, Hanok with two or more stories is economically suitable because its average plottage is excessively narrow. And back trowelling is desirable to construct walls in some concentrated areas with Hanok through arrangement of construction. Also in the other building sites, Hanoks are formed by a standard for separation to the property line. However it is necessary that exist standard about separation of property line is institutionally alleviated.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.26-26
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• 2003

Lithium storage electrodes for rechargeable batteries require mixed electronic-ionic conduction at the particle scale in order to deliver desired energy density and power density characteristics at the device level. Recently, lithium transition metal phosphates of olivine and Nasicon structure type have become of great interest as storage cathodes for rechargeable lithium batteries due to their high energy density, low raw materials cost, environmental friendliness, and safety. However, the transport properties of this family of compounds, and especially the electronic conductivity, have not generally been adequate for practical applications. Recent work in the model olivine LiFePO$_4$, showed that control of cation stoichiometry and aliovalent doping results in electronic conductivity exceeding 10$^{-2}$ S/cm, in contrast to ~10$^{-9}$ S/cm for high purity undoped LiFePO$_4$. The increase in conductivity combined with particle size refinement upon doping allows current rates of >6 A/g to be utilized while retaining a majority of the ion storage capacity. These properties are of much practical interest for high power applications such as hybrid electric vehicles. The defect mechanism controlling electronic conductivity, and understanding of the microscopic mechanism of lithiation and delithiation obtained from combined electrochemical and microanalytical techniques, will be discussed

• Carbon letters
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• v.28
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• pp.55-59
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• 2018

Transition-metal-embedded carbon nanotubes (CNTs) have been accepted as a novel type of sensing material due to the combined advantage of the transition metal, which possesses good catalytic behavior for gas interaction, and CNTs, with large effective surface areas that present good adsorption ability towards gas molecules. In this work, we simulate the adsorption of $O_2$ and $O_3$ onto Rh-doped CNT in an effort to understand the adsorbing behavior of such a surface. Results indicate that the proposed material presents good adsorbing ability and capacities for these two gases, especially $O_3$ molecules, as a result of the relatively large conductivity changes. The frontier molecular orbital theory reveals that the conductivity of Rh-CNT would undergo a decrease after the adsorption of two such oxidizing gases due to the lower electron activity and density of this media. Our calculations are meaningful as they can supply experimentalists with potential sensing material prospects with which to exploit chemical sensors.