• Journal of Electrochemical Science and Technology
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• v.1 no.1
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• pp.31-38
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• 2010

In this study, we have demonstrated the fine structure effect of PdCo electrocatalyst on oxygen reduction reaction activity with different alloy composition and heat-treatment time. In order to identify the intrinsic factors for the electrocatalytic activity, various X-ray analyses were used, including inductively coupled plasma-atomic emission spectrometer, transmission electron microscopy, X-ray diffractometer, and X-ray Absorption Spectroscopy technique. In particular, extended X-ray absorption fine structure was employed to extract the structural parameters required for understanding the atomic distribution and alloying extent, and to identify the corresponding simulated structures by using FEFF8 code and IFEFFIT software. The electrocatalytic activity of PdCo alloy nanoparticles for the oxygen reduction reaction was evaluated by using rotating disk electrode technique and correlated to the change in structural parameters. We have found that Pd-rich surface was formed on the Co core with increasing heating time over 5 hours. Such core shell structure of PdCo/C showed that a superior oxygen reduction reaction activity than pure Pd/C or alloy phase of PdCo/C electrocatalysts, because the adsorption energy of adsorbates was apparently reduced by lowering the dband center of the Pd skin due to a combination of the compressive strain effect and ligand effect.

• Journal of the Korean Ceramic Society
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• v.43 no.12 s.295
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• pp.781-787
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• 2006

NiO-coated YSZ powder was prepared using heterogeneous precipitation of Ni hydroxides on YSZ particle surface and high energy milling. The powders were characterized by TG/DTA, XRD, XPS, and SEM. Amorphous Ni precipitate completely decomposed into NiO at $500^{\circ}C$ and the growth of NiO crystallites was constrained by the core particles. Nanocrystalline NiO-coated YSZ core-shell structure powder could be obtained after calcination at $800^{\circ}C$ for 2 h. A core-shell powder compact, due to high sinterability, showed a near theoretical density at $1350^{\circ}C$. After reduction at $900^{\circ}C$, interpenetrating Ni-YSZ microstructure with very uniformly distributed fine Ni and YSZ grains and pores was observed. In contrast, the mechanically mixed oxide sample showed less uniform distribution of pores and larger discontinuous We particles as compared with the core-shell samples.

• Journal of The Korean Astronomical Society
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• v.48 no.6
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• pp.343-355
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• 2015

There is much observational evidence that active star formation is taking place in the Hii regions Sh 2-255 – 257. We present a photometric study of this star forming region (SFR) using imaging data obtained in passbands from the optical to the mid-infrared, in order to study the star formation process. A total of 218 members were identified using various selection criteria based on their observational properties. The SFR is reddened by at least E(B −V ) = 0.8 mag, and the reddening law toward the region is normal (R_V = 3.1). From the zero-age main sequence fitting method it is confirmed that the SFR is 2.1 ± 0.3 kpc from the Sun. The median age of the identified members is estimated to be about 1.3 Myr from a comparison of the Hertzsprung-Russell diagram (HRD) with stellar evolutionary models. The initial mass function (IMF) is derived from the HRD and the near-infrared (J, J −H) color-magnitude diagram. The slope of the IMF is about Γ = −1.6 ± 0.1, which is slightly steeper than that of the Salpeter/Kroupa IMF. It implies that low-mass star formation is dominant in the SFR. The sum of the masses of all the identified members provides the lower limit of the cluster mass (169M_⊙). We also analyzed the spectral energy distribution (SED) of pre-main sequence stars using the SED fitting tool of Robitaille et al., and confirm that there is a significant discrepancy between stellar mass and age obtained from two different methods based on the SED fitting tool and the HRD.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.1
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• pp.36-41
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• 2000

We studied the exchange anisotropy of Ni-Fe/Co-Fe/Mn-Ir/Cu/buffer/Si multilayers using D.C magnetron sputtering technique. Generally, Ni-Fe/Mn-Ir/buffer(Cu)/Si multilayers cannot pin the ferromagnetic layer for the lower exchange biased field. We got $H_{ex}$ ex/ increased by two times, after using Cu/Ta as buffer layer to get larger grain size of Mn-Ir layer and inserting very thin Co-Fe layer between the Ni-Fe layer and the Mn-Ir layer to get improved grain-to-grain epitaxy relation at the interface between Ni-Fe layer and Mn-Ir layer. The variation of $H_{ex}$ by thickness of Mn-Ir layer in ferromagnete/Mn-Ir/buffer/Si multilayers is different to that in Mn-Ir/ferromagnete/buffer/Si multilayers, because the volume distribution of grain size of Mn-Ir layer and the exchange energy at the interface between the Mn-Ir and the ferromagnetic layers is different for stacking sequence.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.15 no.3
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• pp.120-123
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• 2005

The 5 mol% ZnO doped $LiNbO_3$ film and the 2 mol% MgO doped $LiNbO_3$ film were grown on the $LiNbO_3$ (001) substrate by liquid phase epitaxy (LPE) method with $Li_2CO_3-V_2O_5$ flux system. The crytsallinity and the lattice mismatch between $Zn:LiNbO_3$, film and $Mg:LiNbO_3$, film were analyzed by x-ray rocking curve (XRC). In addition, the ZnO and MgO distribution in the cross-section of the multilayer thin films was observed using electron probe micro analyzer (EPMA).

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.4
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• pp.23-30
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• 2000

Cogeneration systems are seen as a significant innovation for dispersed energy generation since they are both environmentally friendly and has comparatively high degrees of efficiency. It is especially suited for the decentralized provision of electricity and heat. However, it causes operational problems such as voltage regulation, voltage variation, protection and safety. Especially, it is expected that the interconnection/disconnection operation of cogeneration system has an effect on distribution voltage regulation and variation. Recently, with the increased use of customer-owned computers and other sensitive electronic equipment, electric power quality has become an important concerns. Therefore, the voltage quality problems with cogeneration system should be investigated because the voltage quality is an important part of electrical power quality. In this paper, the momentary voltage dips associated with the interconnection/disconnection operation of cogeneration system are analyzed, including restraint solutions at the customer level. In addition, the unit capacity of cogeneration systems per feeder are evaluated from the view point of momentary voltage variations. The results of this paper are useful analysis data for interconnection standards/guidelines of cogeneration systems and dispersed generation (DG)

• Korean Chemical Engineering Research
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• v.46 no.4
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• pp.701-706
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• 2008

Nano-sized nickel powders were prepared by evaporating the bulk nickel metarial using transferred arc thermal plasma. Nitrogen gases are easily dissociated to atomic nitrogen in thermal plasma and they are quickly dissolved in molten nickel. Super-saturated atomic nitrogen in molten nickel is recombined to nitrogen gas because of the relatively low temperature of nickel surface. Generally, the recombine reaction of atomic nitrogen is exothermic, so bulk nickel is quickly evaporated to nickel vapor due to the thermal energy of recombine reaction. The particle size of nickel powder was controlled by $N_2$ used as the diluting gas. It was observed that as the diluting gas flow rate was increase, the particle size was decreased and the particle size distribution was narrowed. The average particle size at 250 l/min of the diluting gas was 202 nm analyzed by means of the particle size analyzer (PSA).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.10
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• pp.2090-2101
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• 2015

We propose a robust tracking method that combines the merits of ACM(active contour model) and the color-based PF(particle filter), effectively. In the proposed method, PF and ACM track the color distribution and the contour of the target, respectively, and Decision part merges the estimate results from the two trackers to determine the position and scale of the target and to update the target model. By controlling the internal energy of ACM based on the estimate of the position and scale from PF tracker, we can prevent the snake pointers from falsely converging to the background clutters. We appled the proposed method to track the head of person in video and have conducted computer experiments to analyze the errors of the estimated position and scale.

• Bulletin of the Korean Chemical Society
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• v.35 no.4
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• pp.1182-1190
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• 2014

$Cd_{1-x}Zn_xS$-sensitized $K_4Nb_6O_{17}$ composite photocatalysts (designated $Cd_{1-x}Zn_xS/K_4Nb_6O_{17}$) were prepared via a simple deposition-precipitation method. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDS), $N_2$ sorption, ultraviolet-visible light diffuse reflectance spectroscopy (UV-Vis DRS), photoluminescence measurements (PL), and X-ray photoelectron spectroscopy (XPS). The $Cd_{0.8}Zn_{0.2}S$ particles were scattered on the surface of $K_4Nb_6O_{17}$, and had a relatively uniform size distribution around 50 nm. The absorption edge of $K_4Nb_6O_{17}$ was shifted to the visible light region and the recombination of photo-generated electrons and holes suppressed after $Cd_{0.8}Zn_{0.2}S$ loading. The $Cd_{0.8}Zn_{0.2}S$(25 wt %)/$K_4Nb_6O_{17}$ composite possessed the highest photocatalytic activity for hydrogen production under visible light irradiation, evolving 8.278 mmol/g in 3 h. Recyclability tests were performed, and the composite photocatalysts were found to be fairly stable. The mechanism of charge separation between the photogenerated electrons and holes at the $Cd_{0.8}Zn_{0.2}S/K_4Nb_6O_{17}$ composite was discussed.

• Journal of Digital Convergence
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• v.12 no.3
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• pp.237-242
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• 2014

Recently, wind energy is expanding to combination of computing to forecast of wind power generation as well as intelligent of wind powerturbine. Wind power is rise and fall depending on weather conditions and difficult to predict the output for efficient power production. Wind power is need to reliably linked technology in order to efficient power generation. In this paper, distributed power generation forecasts to enhance the predicted and actual power generation in order to minimize the difference between the power of distributed power short-term prediction model is designed. The proposed model for prediction of short-term combining the physical models and statistical models were produced in a physical model of the predicted value predicted by the lattice points within the branch prediction to extract the value of a physical model by applying the estimated value of a statistical model for estimating power generation final gas phase produces a predicted value. Also, the proposed model in real-time National Weather Service forecast for medium-term and real-time observations used as input data to perform the short-term prediction models.