• Journal of Powder Materials
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• v.20 no.1
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• pp.13-18
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• 2013

In the present study, we systematically investigated the effect of Mn addition on nitrogenation behavior and magnetic properties of Sm-Fe powders produced by reduction-diffusion process. Alloy powders with only $Sm_2(Fe,Mn)_{17}$ single phase were successfully produced by the reduction-diffusion process. The coercivity of $Sm_2(Fe,Mn)_{17}$ powder rapidly increased during nitrogenation and reached the maximum of 637 Oe after 16 hours. After further nitrogenation, it decreased. In contrast, the coercivity of $Sm_2Fe_{17}$ powder gradually increased during nitrogenation for 24 hours. The coercivity of $Sm_2(Fe,Mn)_{17}$ powder was higher than that of $Sm_2Fe_{17}$ powder at the same condition of nitrogenation. It was considered that the Mn addition facilitates the nitrogenation of $Sm_2Fe_{17}$ powder and enhances the coercivity.

• Korean Journal of Materials Research
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• v.14 no.10
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• pp.696-700
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• 2004

The reduction behavior of $Al_{2}O_3/CuO$ powder mixtures, prepared from $Al_{2}O_3/CuO$ or $Al_{2}O_3/Cu-nitrate$, was investigated by using thermogravimetry and hygrometry. The powder characteristics were examined by BET, XRD and TEM. Also, the influence of powder characteristics on the microstructure and properties of hot-pressed composites was analyzed. The formation mechanism of nano-sized Cu dispersions was explained based on the powder characteristics and reduction kinetics of oxide powders. In addition, the dependence of the microstructure and mechanical properties of hot-pressed composites on powder characteristics is discussed in terms of the initial size and distribution of Cu particles. The practical implication of these results is that an optimum processing condition for the design of homogeneous microstructure and required properties can be established.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.838-845
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• 2006

Recently construction work in Korea, demands of favorable condition ground had been increased with industrialization acceleration and economic growth. However, because of limited land space, it was so hard to ensure favorable condition grounds that construction work proceeds until soft ground area on plans of road, railroad and industrial complex. In this case, soft ground improvement was required such as a stone column method. Stone column method, making a compaction pile using crushed stone, is a soft ground improvement method. However, stone column method is difficult to apply to the ground which is not mobilized enough lateral confine pressure because no bulging failure resistance. Hence, in present study, evaluates the stone columns reinforced by geogrid for settlement reduction and wide range of application of stone columns. Triaxial compression tests were conducted for evaluation which is about behavior characteristics of stone column on replacement rate. Then, 3-dimensional numerical analysis were conducted for application of stone column reinforced by geogrid as evaluate behavior characteristics and settlement reduction effect of stone column reinforced by geogrid on reinforcing depth change of geogrid.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.476-479
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• 2008

Understanding the dynamics of proteins is essential to gain insight into biological functions of proteins. The protein dynamics is delineated by conformational fluctuation (i.e. thermal vibration), and thus, thermal vibration of proteins has to be understood. In this paper, a simple mechanical model was considered for understanding protein's dynamics. Specifically, a mechanical vibration model was developed for understanding the large protein dynamics related to biological functions. The mechanical model for large proteins was constructed based on simple elastic model (i.e. Tirion's elastic model) and model reduction methods (dynamic model condensation). The large protein structure was described by minimal degrees of freedom on the basis of model reduction method that allows one to transform the refined structure into the coarse-grained structure. In this model, it is shown that a simple reduced model is able to reproduce the thermal fluctuation behavior of proteins qualitatively comparable to original molecular model. Moreover, the protein's dynamic behavior such as collective dynamics is well depicted by a simple reduced mechanical model. This sheds light on that the model reduction may provide the information about large protein dynamics, and consequently, the biological functions of large proteins.

• Bulletin of the Korean Chemical Society
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• v.28 no.11
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• pp.1996-2002
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• 2007

The redox behavior of a [Ni6(μ3-Se)2(μ4-Se)3(Fe(η 5-C5H4P-Ph2)2)3] (= [Ni-Se-dppf], dppf = 1,1-bis(diphenylphosphino) ferrocene) cluster was studied using platinum (Pt) and glassy carbon electrodes (GCE) in nonaqueous media. The cluster showed electrochemical activity at the potential range between +1.6 and ?1.6 V. In the negative region (0 to ?1.6 V), the cluster exhibited two-step reductions. The first step was one-electron reversible, while the second step was a five-electron quasi-reversible process. On the other hand, in the positive region (0 to +1.6 V), the first step involved one-electron quasi-reversible process. The applicability of the cluster was found towards the electrocatalytic reduction of CO2 and was evaluated by experiments using rotating ring disc electrode (RRDE). RRDE experiments demonstrated that two electrons were involved in the electrocatalytic reduction of CO2 to CO at the Se-Ni-dppf-modified electrode.

• Korean Journal of Materials Research
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• v.27 no.10
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• pp.513-517
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• 2017

An optimum route to fabricate a hybrid-structured W powder composed of nano and micro size powders was investigated. The mixture of nano and micro W powders was prepared by a ball milling and hydrogen reduction process for $WO_3$ and W powders. Microstructural observation for the ball-milled powder mixtures revealed that the nano-sized $WO_3$ particles were homogeneously distributed on the surface of large W powders. The reduction behavior of $WO_3$ powder was analyzed by a temperature programmed reduction method with different heating rates in Ar-10% $H_2$ atmosphere. The activation energies for the reduction of $WO_3$, estimated by the slope of the Kissinger plot from the amount of reaction peak shift with heating rates, were measured as 117.4 kJ/mol and 94.6 kJ/mol depending on reduction steps from $WO_3$ to $WO_2$ and from $WO_2$ to W, respectively. SEM and XRD analysis for the hydrogen-reduced powder mixture showed that the nano-sized W particles were well distributed on the surface of the micro-sized W powders.

• Journal of applied mathematics & informatics
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• v.32 no.5_6
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• pp.807-816
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• 2014

The asymptotic behavior of solutions of Lyapunov type matrix Volterra integro differential equation, in which the coefficient matrices are not stable, is studied by the method of reduction.

• Korean Journal of Human Ecology
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• v.11 no.3
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• pp.249-262
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• 2002

This paper was written to find the tendency of pro-environmental consumer behavior and environmentally conscious citizen behavior of university students. The difference between two behavioral tendencies were existed and variables influenced on those tendencies each other. The results were as follows: 1. The pro-environmental consumer behavior of university students was consisted of five tendencies, such as practice in life, environment preservation, environment consideration, patience in uncomfortableness and diversity in circumstances. 2. The environmentally conscious citizen behavior of University students were consisted of four tendencies, such as environment contamination, self-centered, resource economy, pollution reduction. 3. The pro-environmental consumer behavior tendencies of university students were inconsistent with those of environmentally conscious citizen behavior. 4. The variables influenced on those tendencies were sex, concern in environment problem and living condition.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.324-329
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• 1993

A reduction method of GSPN (generalized stochastic Petri net) is proposed. A GSPN is basically a SPN (stochastic Petri net) with transition a that are either timed or immediate. Then the proposed method is defined on the basis of the dynamic behavior and the structure of the net. The reduction preserves the properties such as liveness, boundedness, and allows easy analysis of the GSPN.

• Korean Journal of Human Ecology
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• v.16 no.4
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• pp.837-848
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• 2007

The literature suggested that a small reduction in overall blood pressure can have a large effect on overall prevalence of hypertension, and therefore, the affect of taste preferences of the population on salt intake should be considered for long-term blood pressure intervention programs. The purpose of this study is to investigate the influence of salt taste preference and salt taste sensitivity on salt intake behavior as risk factors for high blood pressure. We collected information on blood pressure, diet and lifestyle behaviors, salt taste preference and salt taste sensitivity from 540 respondents from Suseo-dong, Seoul. Salt taste sensitivity was assessed by administering a 1% NaCl solution to the subject's tongue and measuring the perceived intensity on 10 level scale. Salt intake behavior was classified into 3 categories: frequency of high-sodium foods, practice of salt-reducing behavior and frequency of vegetable and fruit intake. Salt taste preference showed a significant relation to the subjects' blood pressure, i.e. subjects with a higher salt preference had higher blood pressure. Salt taste sensitivity did not show a significant relation to blood pressure. However, there was a positive correlation between salt taste preference and salt taste sensitivity. Among the 3 indicators used to measure salt intake behavior, the practice of salt-reducing behavior remained significantly correlated to blood pressure. Moreover, salt-reducing behavior and salt taste preference showed a significant correlation, i.e. people who do not like salty foods tend to practice more salt-reducing behavior, leading to reduced levels in blood pressure. In a population, a small reduction in overall blood pressure can have large effects in overall prevalence of hypertension, in contrast to clinical studies where achievement of an individual's normal blood pressure is emphasized. Therefore, taste preference of the population should be considered for long-term blood pressure intervention programs.