• Nuclear Engineering and Technology
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• v.49 no.6
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• pp.1157-1164
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• 2017

The Monte Carlo criticality simulation of decoupled systems, as for instance in large reactor cores, has been a challenging issue for a long time. In particular, due to limited computer time resources, the number of neutrons simulated per generation is still many order of magnitudes below realistic statistics, even during the start-up phases of reactors. This limited number of neutrons triggers a strong clustering effect of the neutron population that affects Monte Carlo tallies. Below a certain threshold, not only is the variance affected but also the estimation of the eigenvectors. In this paper we will build a time-dependent diffusion equation that takes into account both spatial correlations and population control (fixed number of neutrons along generations). We will show that its solution obeys a traveling wave dynamic, and we will discuss the mechanism that explains this biasing of local tallies whenever leakage boundary conditions are applied to the system.

• Korean Journal of Materials Research
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• v.15 no.12
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• pp.814-817
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• 2005

In order to enhance energy efficiency in high electric conversion devices such as Power transformers, which need to have high power properties, an alloy design approach in $Pb(Zr,Ti)O_3(PZT)$ base ceramic system was attempted $0.03Pb(Sb_{0.5}Nb_{0.5})O_3-0.03Pb(Mn_{1/3}Nb_{2/3})O_3-(0.94-x)PbTiO_3-xPbZrO_3$[PSN-PMN- PZT] ceramics were synthesized by conventional bulk ceramic processing technique. To improve power properties, the various Zr/Ti ratio was varied ]lear their morphotropic phase boundary (MPB) composition of PSN-PMN-PZT system and their effects on subsequent piezoelectric and dielectric properties for the transformer application at high power were systematically investigated using an impedance analyzer. Microstructure and phase information were characterized using X-ray diffractometer (XRD), a scanning electron microscope (SEM) and others. When the Zr/Ti ratio was 0.415/0.465, the value of $Q_m\;and\;k_p$ were shown to reach to the maximum, indicating that this alloy design can be a feasible composition :or high power transformer.

• Proceedings of the Korea Contents Association Conference
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• 2015.05a
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• pp.33-34
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• 2015

Continuous improvements of network infrastructures and mobile data offloading strategies are among the solutions of cellular providers to cope with the increase in mobile data demand. These options requires a lot of cost and time to implement. Few researches have been conducted to assess the applicability of Pocket Switched Network (PSN) to support mobile data offloading. In this paper, we present a PSN mobile data-offloading scheme that utilizes mobile users with available connectivity to deliver content-aware data to other mobile users. This paper also aims to evaluate the applicability and feasibility of PSN routing schemes to improve the current strategies in mobile data offloading. The simulation results show admirable results in terms of message delivery and latency.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1521-1523
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• 2001

In this paper, High quality factor and fine dielectric loss was resulted on specimen added 0.5wt% $MnO_2$ after compared and analyzed dielectric and piezoelectric properties following that added each 0 $\sim$ 0.9wt% of $Fe_2O_3$, $Nb_2O_5$, and $MnO_2$ on dopant at PSN-PT in two material disposition ceramics with research still is not completed to material investigation to increase high power piezoelectric actuator device efficiency. And, a measuring method and the experimental results of the temperature rise under the high vibrational velocity are also described.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.701-704
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• 2003

In this study, to develop the low temperature sintering ceramics for multilayer piezoelectric transformer, PSN-PNN-PZT system ceramics were manufactured as a function of CuO addition. Its dielectric and piezoelectric characteristics were investigated. With increasing the amount of CuO addition, grain size was increased and density increased until 0.3wt% CuO. Taking into consideration electromechanical coupling factor(kp) of 0.53, mechanical quality factor(Qm) of 423 and ${\epsilon}r$ of 1759, it can be cincluded that the CuO 0.5wt% added composition sintered at $920^{\circ}C$ is suitable for piezoelectric transformer application if Qm is improved.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.656-659
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• 2003

In this study, in order to develop the low temperature sintering ceramics for multilayer piezoelectric transformer, dielectric and piezoelectric properties of PSN-PZT ceramics were investigated according to Zr/Ti ratio. As Zr/Ti ratio is increased, coupling factor(kp) and dielectric constant were increased and then decreased after the ratio of Zr/Ti=50/50. And also, mechanical quality factor were decreased and then increased after the ratio of Zr/Ti=50/50.

• Journal of Sensor Science and Technology
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• v.13 no.2
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• pp.152-156
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• 2004

The dielectric and piezoelectric properties of 0.36Pb($Sc_{1/2}Nb_{1/2}$)$O_{3}$-0.25Pb($Ni_{1/3}Nb_{2/3}$)$O_{3}$-0.39Pb$TiO_{3}$ (hereafter PSNNT) at the morphotropic phase boundary (MPB) composition were investigated with $0{\sim}2.5$ mot% $MnO_{2}$ doping. Bulk density, dielectric loss and tetragonality of crystal structure were all improved with increasing $MnO_{2}$ additive content. With increasing $MnO_{2}$ additive content, the electromechanical coupling factor and quality factor were also increased: Electromechanical coupling $k_{p}$ and quality factor $Q_{m}$ at 2.0 mol% $MnO_{2}$ doping with were showed highest values of 55.6 % and 252, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.256-259
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• 1999

The purpose of this study is to develop the material for multiayer piezoelectric ceramic transformer because multiayer piezoelectric transformer must need low sintering temperature. So that PMN-PSN-PZT family ceramics were added with glass brit(SiO$_2$ $.$ PbO). The dielectric and piezoelectric properties were increased with increasing it until the amounts of additive 0.8wt%. Sintering temperature were low about 100[$^{\circ}C$]. Accordingly, This material could be used to multiayer piezoelectric transformer .

• Journal of the Korean Ceramic Society
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• v.37 no.1
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• pp.63-69
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• 2000

Electrically-induced strain(S) and polarization(P) for Pb(Sc1/2Nb1/2)O3-PbTiO3(1-x)PSN-xPT) crystalline solutions were studied. From the compositional dependence of S and P we could observe two maximum values at x=0.10 and x=0.425. It is considered that PSNT10(x=0.10) composition is the structural phase boundary to indicate the variable order-disorder[VOD] region. PSNT(x=0.425) composition is the morphotropic phase boundary[MPB] to indicate the rhombohedral to tetragonal phase transition. Higher S (0.437%) and P (0.3974$\mu$C/$\textrm{cm}^2$) values were attained by the La substitution (5 wt%) at Pb site in the MPB composition of 57.5PSN-42.5PT.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05c
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• pp.232-235
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• 2003

In this study, in order to develop the low temperature sintering ceramics for multilayer piezoelectric transformer, dielectric and piezoelectric properties of PSN-PZT ceramics were investigated as a function of CuO addition, At the 0.6wt% CuO added specimen sintered at $920^{\circ}C$, the most excellent mechanical quality factor and electromechanical coupling factor were obtained.