• Journal of the Korean Electrochemical Society
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• v.10 no.1
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• pp.7-13
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• 2007

We synthesized and investigated $La_{0.75}Sr_{0.25}FeO_3$ by Glycine Nitrate Process(GNP) method used as cathode materials for SOFC(solid oxide fuel cell). Optimized amount of glycine is 3.17 mol. ICP elemental composition analysis indicated that the stoichiometry of the synthesized powders have nearly nominal values. SEM images and XRD patterns reveal that the synthesized powder has uniform size distribution and high degree of crystallinity. The sample powders were isostatically pressed to form a pellet. The green body was sintered at $1200^{\circ}C$ and the relative density of the sintered specimens were measured by Archimedes mettled. We measured electrochemical performance of LSF by AC impedance spectroscopy. Resistance of LSF shows lower value than that of LSM throughout all temperature region. The anode-supported solid oxide fuel cell showed a performance of $342mW/cm^2(0.7V,\;488mA/cm^2)$ at $750^{\circ}C$. The electrochemical characteristics of the single cell were examined by at impedance method.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.1105-1106
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• 2009

• Journal of Information Technology Applications and Management
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• v.11 no.2
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• pp.29-43
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• 2004

As the development of an information technique, gradually, mobile device is going to be miniaturized and operates at high speed. By such the requirements, the devices using a flash memory as a storage media are increasing. The flash memory consumes low power, is a small size, and has a fast access time like the main memory. But the flash memory must erase for recording and the erase cycle is limited. JFFS is a representative filesystem which reflects the characteristics of the flash memory. JFFS to be consisted of LSF structure, writes new data to the flash memory in sequential, which is not related to a file size. Mounting a filesystem or an error recovery is achieved through the sequential approach. Therefore, the mounting delay time is happened according to the file system size. This paper proposes a MJFFS to use a multi-checkpoint information to manage a mass flash file system efficiently. A MJFFS, which improves JFFS, divides a flash memory into the block for suitable to the block device, and stores file information of a checkpoint structure at fixed interval. Therefore mounting and error recovery processing reduce efficiently a number of filesystem access by collecting a smaller checkpoint information than capacity of actual files. A MJFFS will be suitable to a mobile device owing to accomplish fast mounting and error recovery using advantage of log foundation filesystem and overcoming defect of JFFS.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.11
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• pp.632-638
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• 2003

Modern power systems are very complex and to model them completely is impractical for electromagnetic transient studies. Therefore areas outside the immediate area of interest must be represented by some form of frequency dependent equivalent. The s-domain rational function form of frequency dependent equivalent does not need refitting if the simulation time-step is changed in the electromagnetic transient program. This is because the s-domain rational function coefficients are independent of the simulation time-step, unlike the z-domain rational function coefficients. S-domain rational function fitting techniques for representing frequency dependent equivalents have been developed using Least Squares Fitting(LSF). However it does not suffer the implementation error that exited in this work as it ignored the instantaneous term. This paper Presents the formulation for developing 1 Port Frequency Dependent Network Equivalent(FDNE) with the instantaneous term in S-domain and illustrates its use. This 1 port FDNE have been applied to the CIGRE Benchmark Rectifier test AC system. The electromagnetic transient package PSCAD/EMTDC is used to assess the transient response of the 1 port (FDNE) developed with Thevenin and Norton Equivalent network. The study results have indicated the robustness and accuracy of 1 port FDNE for electromagnetic transient studies.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05c
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• pp.124-130
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• 2003

Zinc Oxide(ZnO) thin films on Si (100) substrate were deposited by RF magnetron sputter with changing sputtering conditions such as argon/oxygen gas ratios, RF power, and substrate temperature, chamber pressure and target-substrate distance. To analyze a crystallographic properties of the films, $\theta/2\theta$ mode X-ray diffraction, SEM, and AFM analyses. C-axis preferred orientation, resistivity. and surface roughness highly depended on $Ar/O_2$ gas ratios. The resistivity of ZnO thin films rapidly increased with increasing oxygen ratio and the resistivity value of $9{\times}10^7{\Omega}cm$ was obtained at a working pressure of 10 mTorr with $Ar/O_2$=50/50. The surface roughness was also improved with increasing oxygen ratio and the ZnO films deposited with $Ar/O_2$=50/50 showed the excellent roughness value of $28.7{\AA}$.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2006.05a
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• pp.65-68
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• 2006

현재 전력설비에 사용되고 있는 $SF_6$ 가스는 절연 및 소호성능이 우수하고 회복특성이 뛰어나기 때문에 각종 전력기기의 절연매체로서 널리 사용되고 있다. 하지만 산업사회의 발달로 인하여 도시의 공간 활용의 효율성 측면에서 전력기기들의 소형화, 지중화 및 고 신뢰화가 시도되고 있으며, 또한 온실가스에 대한 규제로서 '도쿄 의정서'가 정식 발효됨에 따라 환경문제로 인하여 전력설비의 $SF_6$ 가스의 유출 최소화, 대체 절연물질 개발 등의 친환경 재료의 개발이 새롭게 대두되고 있다. 따라서, 본 연구에서는 $SF_6$를 액화시켜 기존의 $SF_6$ 가스와 액체 $SF_6(LSF_6)$의 절연파괴특성을 측정/분석하여 $SF_6$의 대체물질로 $LSF_6$의 가능성을 검토하고, 혹한 지역에서 운용되고 있는 $SF_6$ 이용 전력설비의 온도저하에 따른 문제점을 구명하였다.

• Journal of Korea Water Resources Association
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• v.48 no.6
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• pp.491-500
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• 2015

In order to improve the runoff estimation accuracy of the Natural Resources Conservation Service (NRCS) curve number (CN) model, this study incorporated rainfall and maximum potential retention as contributors for initial abstraction. The modification was proposed based on 658 rank-order data of rainfall and subsequent runoff from 15 watersheds. The NRCS-CN model (M1), one of its inspired modified model (M2), and the proposed model (M3) were analyzed employing different CN approaches. Using tabulated, calculated and least squares fitted CNs ($CN_T$, $CN_C$, $CN_{LSF}$, respectively), the models' performances were evaluated based on Root Mean Square Error (RMSE), Nash-Sutcliffe Efficiency (NSE), and Percent Bias (PBIAS). Applications of model M1, M2, and M3, respectively exhibited watershed cumulative mean [RMSE (23.60, 18.12, 16.04), NSE (0.54, 0.73, 0.79), and PBIAS (36.54, 20.25, 12.00)]. Similarly, using CNC (for M1 and M2 model) and $CN_{LSF}$ (for M3 model), the performance of three models respectively were assessed based on watershed cumulative mean [RMSE (17.17, 15.88, 13.82), NSE (0.76, 0.80, 0.85), and PBIAS (3.06, 4.47, 0.11)]. The proposed model (M3) that linked all of the NRCS-CN variants showed more statistically significant agreement between the observed and estimated data.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.08a
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• pp.131-135
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• 1998

5.6kbps 의 전송율에서 fixed codebook 으로 ISPP의 dynamic sparse algebraic codebook을 이용한 ACELP 알고리즘을 제안한다. 저전송율에서 음질에 중대한 영향을 미치는 대수적 방식의 고정코드북이 가지는 문제점을 최소화하여 음질의 증진을 꾀하였다. 또한 추가 계산량이 필요없는 U/V 분리기를 도입하여 LSF 보간시 발생하는 천이구간에서의 지연을 최소화하였다. 구현된 5.6 kbps ACELP 는 전화선상의 음질을 시료로 하여 주관적 음질면에서 6.3 kbps MP-MLQ와 동등하였으며 MNRU 15dB에서 약간 낮았다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.10
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• pp.2261-2268
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• 2010

The information captured by imaging devices such as CCD or CIS may contain external noises through the processes of passing signals or storing images. In this paper, we propose a Modified Sigma Filter (MSF) algorithm to reduce such noises. In experiment, we verified that our MSF algorithm showed better performance in PSNR and 1D plot of simulation results compared with Gaussian Filter (GF), Local Sigma Filter (LSF). Tested images include random Gaussian Noises.

• Resources Recycling
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• v.13 no.3
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• pp.19-26
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• 2004

In order to use the mine tailing which was generated in the flotation process of scheelite ore into the raw material of ordinary portland cement, the characteristics of the prepared cement clinker was investigated. Scheelite mine tailing is composed of 68.8% of $SiO_2$, 8.6% of $Al_2$$O_3$, 10.8% of $Fe_2$$O_3$, 5.0% of CaO, respectively. It exists as $\alpha$-quartz, muscovite, clinochlore and has 8.0% of 88 $\mu\textrm{m}$ residue. When LSF, SM, and IM of the raw materials (such as limestone, convertor slag, fly ash, and mine tailing) are 91.0, 2.60, and 1.60, respectively, the burnability index of the raw materials is 50.7, the crystal size of $C_3$S and $\beta$-C$_2$S in the prepared clinker is 15∼35$\mu\textrm{m}$, and about 3.8% of scheelite mine tailing can be used as raw material.