• Journal of the Korean Electrochemical Society
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• v.6 no.1
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• pp.53-58
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• 2003

It is well known that the anode substrate of anode-supported type SOFC should have high electrical conductivity and high gas permeability to minimize the polarization loss of the cell performance during operation. In this study, we made anode substrates of SOFC with two different methods, which gave different anode microstructures, especially different pore structures with each other. We performed electrical and microstructural characterization of Ni/YSZ cermet anode via extensive measurements of its electrical conductivity and gas permeability combined with adequate image analysis based on quantitative stereological theory

• Progress in Superconductivity
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• v.2 no.2
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• pp.92-96
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• 2001

We have fabricated a modified hairpin-type YBa$_2$Cu$_3$O$_{7-{\delta}}$ (YBCO) 2-pole microstrip bandpass filter with the center frequency of 5.8 GHz. We designed a hairpin-type filter with interdigital-coupled inner poles to improve the filter performance. Compared to a typical hairpin-type filter of the same size, the center frequency, the bandwidth and the insertion loss appeared smaller by 14.5% ,29.6%, and 0.55 dB, respectively. The dimensions of the filter were 13.7mm ${\times}$3.3 mm. YBCO films deposited on r-cut sapphire buffered with a CeO$_2$thin layer were used fur making the filter.

• Journal of Korean Society of Steel Construction
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• v.12 no.2 s.45
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• pp.143-150
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• 2000

Depending upon the combination of tolerances specified in the standards on bolt, nut and washer for high tension bolt sets, there arises center-to-center deviation between bolt and washer. This deviation nay cause loss of effective contact area between nut- and washer-faces, which leads to some dispersion of the torque coefficient K. By adapting circular arc surface instead of flat surface for the nut, it is shown through numerical analyses that the dispersion of the torque coefficient can be minimized. In this way, optimum radius of curvature of the nut bearing surface is proposed.

• Tribology and Lubricants
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• v.24 no.6
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• pp.315-319
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• 2008

This paper presents the interface bonding characteristics between a phosphor bronze and a steel plate for pin-bush bearings. The pin-bush bearing is an important component in which is used to reduce a friction loss and a wear against the piston pin. The pin-bush bearing is manufactured by hot-pressing a phosphor bronze and a back metal of a steel plate. This paper investigated the bonding interface characteristics in which is manufactured by melting a copper based bronze and a steel plate. The hardness from the inner surface of a bronze to the outer one of steel has been measured using a Vickers hardness tester. The experimental results show that the hardness of a bronze is superior to that of the conventional bronze and the transient hardness of pin-bush bearings is gradually increasing to the hardness of the steel back metal. This means that the bonding interface zone of pin-bush bearings may be fabricated by defusing a bronze to the steel plate due to a density difference between two materials.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.3
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• pp.214-218
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• 2009

The occlusal force of the tooth leads to loss of tooth tissue owing to attrition and abrasion, and may cause abfraction and pathological change of the dentin. Thus, we developed finite element models, examined them by applying ordinary occlusal force, and analyzed the stress distribution. Specimens used were mandibular first premolars from 15 Korean males and 13 females and were made into finite element models from medical images that were obtained using a Micro-CT. We have found that the irregular feature of the tooth is not only useful to masticating and pronouncing as well known, but it is also suitable for protecting inner tissue by dispersing stress and delivering proper pressure to periodontal tissue to continue a physiological action. Also, image analysis could let us know the factor that is the cause of a disorder due to stress concentration in the cervical line. These results are expected to support the field of dental treatment planning, operating procedure and clinical trial, and the advance of technical expertise to develop implants and dentures.

• Applied Chemistry for Engineering
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• v.10 no.2
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• pp.177-182
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• 1999

The electrolyte was brought into contact with air and potassium carbonate concentration was measured with various contact time in order to check the effect of carbon dioxide in the air on zinc-air cell. The relationship between potassium carbonate concentration in electrolyte and battery capacity was also studied. The potassium carbonate concentration increased due to carbon dioxide absorption with increasing contact time with air, but the cell capacity linearly decreased with increasing potassium carbonate concentration in the electrolyte. The rate of carbon dioxide absorption was mainly affected by the pore size of hydrophobic membrane. Our study showed that adapting the pore of hydrophobic membrane decreased the loss of cell discharge performance due to the presence of carbon dioxide or water vapor in the atmosphere.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.2
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• pp.670-683
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• 2016

Network coding, as a new technique to improve the throughput, is studied combined with multi-relay model in this paper to address the challenges of long distance and power limit in deep space communication. First, an amplify-and-forward relaying approach based on analog network coding (AFNC) is proposed in multi-relay network to improve the capacity for deep space communication system, where multiple relays are introduced to overcome the long distance link loss. The design of amplification coefficients is mathematically formulated as the optimization problem of maximizing SNR under sum-power constraint over relays. Then for a dual-hop relay network with a single source, the optimal amplification coefficients are derived when the multiple relays introduce non-coherent noise. Through theoretic analysis and simulation, it is shown that our approach can achieve the maximum transmission rate and perform better over single link transmission for deep space communication.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.8
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• pp.1860-1875
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• 2013

In this paper, we present a comparative performance evaluation of the sampling frequency synchronization method that eliminates the initial sampling frequency offset (SFO) to reduce the overall synchronization time in Digital Radio Mondiale (DRM) receivers. To satisfy the advanced synchronization performance requirements of DRM receivers, we introduce the conventional DRM synchronization method (Method 1) and another method (Method 2), which does not perform the initial sampling frequency synchronization in the conventional synchronization method (both methods are mentioned later in this paper). To demonstrate the effectiveness of the performance evaluation, analytical expressions for frame detection are derived and simulations are provided. Based on the simulations and numerical analysis, our result shows that Method 2, with a negligible performance loss, is robust to the effects of the initial sampling frequency synchronization even if SFO is present in the DRM signal. In addition, we verify that the inter-cell differential correlation used between reference cells is robust to the effect of the initial SFO.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.2
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• pp.237-246
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• 1999

A miniaturized waveguide bandpass filter is designed by combining a corrugated lowpass structure and a highpass configuration based on the cut-off effect of waveguides. It is smaller than the conventional waveguide bandpass filter composed of half-wavelength resonators and has wider spurious free characteristics. Optimized design data for a seven-order waveguide bandpass filter with the symmetrical structure are given at the center frequency of 10 GHz with 800 MHz bandwidth. Measured bandwidth of the center frequency of 9.97 GHz is 840 MHz and measured insertion loss is 0.97dB, The length of the bandpass filter is 64.38mm. The first spurious response is produced at 26.1 GHz.

• Journal of the Korean Chemical Society
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• v.62 no.6
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• pp.427-432
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• 2018

The reaction of [$[Ni(L)]Cl_2{\cdot}2H_2O$ (L = 3,14-dimethyl-2,6,13,17-tetraazatricyclo[$14,4,0^{1.18},0^{7.12}$]docosane) with 1,1-cyclohexanediacetic acid ($H_2cda$) yields mononuclear nickel(II) complex, [$Ni(L)(Hcda^-)_2$] (1). This complex has been characterized by X-ray crystallography, electronic absorption, cyclic voltammetry and thermogravimetric analyzer. The crystal structure of 1 exhibits a distorted octahedral geometry with four nitrogen atoms of the macrocycle and two 1,1-cyclohexanediacetate ligands. It crystallizes in the triclinic system P-1 with a = 11.3918(7), b = 12.6196(8), $c=12.8700(8){\AA}$, $V=1579.9(2){\AA}^3$, Z = 2. Electronic spectrum of 1 also reveals a high-spin octahedral environment. Cyclic voltammetry of 1 undergoes one wave of a one-electron transfer corresponding to $Ni^{II}/Ni^{III}$ process. TGA curve for 1 shows three-step weight loss. The electronic spectra, electrochemical and TGA behavior of the complex are significantly affected by the nature of the axial $Hcda^-$ ligand.