• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.553-556
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• 2003

In this paper was studied the improvements and increasements of the data transmission rate in UWB (Ultra wideband) systems. so Considered that previous UWB systems of code structure and proposed the New constructure that was synthesized the PPM and Bi-Phase Modulation structure, may increase the data transmission rate of multiple channel structure using Time-slots. This proposed structure was modeled suitable at Home Networking conditions and was simulated. and so measure the performance of coding construction, and compare that New synthesized structure with early structure. so we can verify the superiority of New experiment.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.11
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• pp.1029-1034
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• 2003

The Bi$_2$Sr$_2$Ca$_{n}$Cu$_{n+1}$ O$_{x}$, superconducting thin films arc fabricated by using the sputtering and evaporation method. Because we confirmed the sticking ratio of Bi element in the Bi$_2$Sr$_2$Ca$_{n}$Cu$_{n+1}$ O$_{x}$ superconducting thin film fabricated by using the sputtering method was much lower than the expected value, to get the enough number of the flakes of Bi, faraday cup was used to evaporate Bi clement. As a result of the fabrication, Bi 2201 and Bi 2212 single phases could be made by the optima of deposition condition. And we confirmed the sticking coefficient of Bi element was clearly related to the temperature change of the substrate and the generation of Bi22l2 phase

• Journal of the Korean Ceramic Society
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• v.38 no.4
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• pp.360-364
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• 2001

고상반응법(solid-state reaction)으로 산화물 초전도체 Bi$_{2+x}$ Sr$_{1.8}$ $CaCu_2$$O_{8+\delta}$(-0.2$\leq$x$\leq$0.2)을 제조하여 조성변화에 따른 산소량과 Bi 이온의 하전가(valence)가 구조변조의 주기에 미치는 영향을 조사하였다. 2212상의 단일상 고용한계는 -0.1$\leq$x$\leq$0.1 영역이었다. 이 영역에서 x의 증가에 따라 격자상수 c는 감소를 보이며, 온셋 임계온도 Tc$^{on}$ 과 산소량은 증가하는 경향을 보였다. 또한, Bi 이온의 하전기와 구조변조의 주기는 단일상 고용한계 영역 내에서 x의 증가에 따라 감소하는 경향을 보이고 있다. 구조변조의 주기는 산소량이 증가함에 따라 감소하고 Bi 이온의 하전가 증가에 따라 증가함을 보였다. 즉, 산소의 절대량과 Bi 이온의 하전가에 따라 구조변조의 주기가 변화하는 것을 알 수 있었다.

• Electrical & Electronic Materials
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• v.10 no.9
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• pp.869-875
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• 1997

Bi based superconducting thin films were fabricated by 4-target RF magnetron sputtering using the method of controlling the on-off time. These thin films showed better crystal structures. The ratio of Cu/Bi decreased but the critical temperature increased with increasing the temperature of the substrate. High temperature phase low temperature of the substrate. High temperature phase low temperature phase and semiconducting phase can be formed by controlling the on-off time of the shutter respectively.

• Progress in Superconductivity and Cryogenics
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• v.5 no.1
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• pp.40-43
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• 2003

The phase transformation, variation of secondary phase, and critical current density $(J_c) for (Bi,Pb)_2Sr_2Ca_2Cu_3O_10 (2223)$ tapes have been studied through the thermal slide heat treatment (TSHT) process. This process consists of a multiple variations of oxygen partial pressures and temperatures at the initial heat treatment During the initial heat treatment some secondary phase such as $(Ca,Sr)_2CuO_3(2/1 AEC), (Ca,Sr)_{14}Cu_{24}O_{41} (14/24 AEC), and (Bi,Pb)_2Sr_2CuO_y$(2201, amorphous phase) farm in Bi-2223 tapes, especially at the 2223 grain boundaries. These secondary phases are detrimental to the phase transformation and final properties. In order to control the secondary phase in Bi-2223 tapes the amount and size of secondary phases among the TSHT process were observed. The results indicate that the amount and particle size of AEC particles were smaller when the TSHT process was used than when the normal process at the initial heat treatment was used which results in the improved $J_c$ properties after the final process.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.1
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• pp.15-22
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• 2014

Recently, parallel operation of dc-dc converters has been widely used in distributed power systems. In this paper, a control method to achieve parallel operation of three-phase bi-directional isolated interleaved dc-dc converters is discussed for the battery charging and discharging system which consists of the 32 battery charger/dischargers and two three-phase bi-directional isolated interleaved dc-dc converters. In the boost mode, the battery energy is delivered to the grid, whereas the grid energy is transferred to the battery in the buck mode operation. The average current sharing control method is employed to obtain an equal conducting of each phase current in the three-phase dc-dc converter. By using the proposed method, the imbalance factor is gratefully reduced from 8 percent to 1 percent. Two 2.5kW three-phase bi-directional dc-dc converter prototype have been built and the proposed method has been verified through experiments.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.198-203
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• 2000

This paper investigated the effects of doping elements on the Bi-Sr-Ca-Cu-O ceramics. The doping elements can be classified into four groups depending on their superconducting characteristics in the Bi-Sr-Ca-Cu-O structure. The first group of doping elements(Co, Fe, Ni and Zn) substitute into the copper site and can reduce the critical temperatures of the 2223 and 2212 phases. The second group of doping elements(Y and La) substitute into the Ca site and cause the disappearance of the 2223 phase and increase the critical temperatures in the 2212 phase. The third group of doping elements(P and K) have a tendency to decompose the superconducting phase and reduce the optimal sintering temperature. The fourth group of doping elements(B, Si, Sn and Ba) almost unaffected the superconductivity of the 2223 and 2212 phase.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.217-220
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• 1999

We investigated the effects of doping elements on the Bi-Sr-Ca-Cu-0 ceramics. The doping elements can be classified into groups depending on their supeconducting characteristics in the Bi -Sr-Ca-Cu -O structure. The first group of doping elements(Co, Fe, Ni and Zn) substitute into the copper site and can reduce the critical temperatures of the 2223 and 2212 phases. The second group of doping elements(Y and La) substitute into the Ca site and cause the disappearance of the 2223 phase and increase the critical temperatures in the 2212 phase.

• Bulletin of the Korean Chemical Society
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• v.15 no.2
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• pp.115-118
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• 1994

Samples of ($Bi_{2-x}Sb_x)PbSr_2Ca_2Cu_3O_y$, compositions with x=0.0, 0.1, and 0.2 were prepared by solid-state reaction. The solubility of Sb into the 2223 phase is lower than 0.05 for the ratio of Sb/Bi. The lack of stability of the Sb-substituted $Bi_2O_2$ double layers is likely to cause the solubility low. There is no great dependence of lattice parameters on the Sb-content, and bonds around the square-pyramidal Cu atom are not affected by the $Sb^{3+}$ ion substituted. The superconducting transition temperature of this system is decreased gradually with increase of Sb, which is tentatively attributable to the perturbation of the Bi 6p-O 2p band and/or to the low volume fraction of the 2223 phase.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.8
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• pp.222-227
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• 2020

Pb(Zr,Ti)O₃(denoted as PZT) in the perovskite phase is used as a dielectric, piezoelectric, and super appetizer material owing to its ferroelectric properties. A PZT film was formed by an RF magnetron sputtering process by preparing a target composed of Pb_1.3(Zr_0.52Ti_0.48)O₃. The PZT film was formed by dividing the material into a mono-layer PZT produced continuously with the same sputtering power and a bi-layer PZT produced with two-stage sputtering power. The bi-layer PZT consisted of a lower layer produced under low-power sputtering conditions and an upper layer produced under the same conditions as the mono-layer PZT. XRD revealed small amounts of pyrochlore phase in the mono-layer PZT, but only the perovskite phase was detected in the bi-layer PZT. SEM and AFM revealed the upper part of the bi-layer PZT to be more compact and smooth. Moreover, the bi-layered PZT showed superior symmetry polarization and a significantly reduced leakage current of less than 1×10-5 A/cm². This phenomenon observed in bi-layer PZT was attributed to the induction of growth into a pure perovskite phase by suppressing the formation of a pyrochlore phase in the upper PZT layer where the densely formed lower PZT layer was produced sequentially.