• ETRI Journal
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• v.27 no.3
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• pp.243-249
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• 2005

A mobile antenna for multimedia communications with Ku-band geostationary satellite KOREASAT-3 and JSAT-2A is presented. The forward link of the satellite communication is 11.7 to 12.75 GHz, and the return link is 14.0 to 14.5 GHz. The mobile antenna is designed to be a stair structure using 24 active phased array elements in order to provide a low profile, and to be at a non-periodic array distance using the genetic algorithm. Also, the designed antenna uses the double beam forming method for stable satellite tracking. The fabricated mobile antenna is examined using various experiments to confirm its capability for practical application. From the measured results, the fabricated mobile antenna system is confirmed to have a good performance.

• Proceedings of the IEEK Conference
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• 2002.07a
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• pp.110-112
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• 2002

In this paper, a new technique for Thai isolated speech phoneme segmentation is proposed. Based on Thai speech feature, the isolated speech is first divided into low and high frequency components by using the technique of wavelet decomposition. Then the energy contour of each decomposed signal is computed and employed to locate phoneme boundary. To verity the proposed scheme, some experiments have been performed using 1,000 syllables data recorded from 10 speakers. The accuracy rates are 96.0, 89.9, 92.7 and 98.9% for initial consonant, vowel, final consonant and silence, respectively.

• ETRI Journal
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• v.36 no.3
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• pp.343-351
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• 2014

For the fine-pitch application of flip-chip bonding with semiconductor packaging, fluxing and hybrid underfills were developed. A micro-encapsulated catalyst was adopted to control the chemical reaction at room and processing temperatures. From the experiments with a differential scanning calorimetry and viscometer, the chemical reaction and viscosity changes were quantitatively characterized, and the optimum type and amount of micro-encapsulated catalyst were determined to obtain the best pot life from a commercial viewpoint. It is expected that fluxing and hybrid underfills will be applied to fine-pitch flip-chip bonding processes and be highly reliable.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.373-382
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• 1993

A non-contact sensor for detecting distance from field surface to a predetermined location of a tractor will be useful to control precise height of implements such as tillage machinery, mowers etc.. An optical and an ultrasonic sensors were designed and fabricated . The indoor and outdoor experiments were conducted to obtain the static and dynamic characteristics of the two sensors at several moisture levels of four soils and on the soil surface with a designed shape. The results revealed that the optical sensor is unsuitable for soils with high moisture content but showed better detecting accuracy on the irregularity of soil surface.

• The Journal of the Acoustical Society of Korea
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• v.16 no.2E
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• pp.32-37
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• 1997

This paper proposes a isolated speech recognition method of Korean digits using a TDNN(Time Delay Neural Network) which is able to recognizc time-varying speech properties. We also make an investigation of effect on network parameter of TDNN ; hidden layers and time-delays. TDNNs in our experiments consist of 2 and 3 hidden layers and have several time-delays. From experiment result, TDNN structure which has 2 hidden-layers, gives a good result for speech recognition of Korean digits. Mis-recognition by time-delays can be improved by changing TDNN structures and mis-recognition separated from time-delays can be improved by changing input patterns.

• Particle and aerosol research
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• v.12 no.3
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• pp.103-107
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• 2016

We conducted experiments on mask filters. We measured filtering efficiencies of several new mask filters which were manufactured by disassembling and reassembling of one type of mask filter. New filter (A+C: combination of the first layer and the third layer of the tested mask filter) showed the highest efficiency (97.7%) with the respiratory resistance of 98 pa.

• The Journal of the Acoustical Society of Korea
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• v.23 no.2E
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• pp.44-50
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• 2004

A theoretical formula that is based on the geometrical theory of diffraction (GTD) is proposed for computing sound diffraction by multiple wedges, barriers, and polygonal-like shapes. The formula can treat both convex and concave edges, where edges mayor may not be inter-connected. Comparisons of theoretical predictions with other results done by the BEM or experiments for scaled model confirm the accuracy of the present formula. Numerical examples such as double wedges and doubly inclined barrier show that when there exist several diffraction paths for given source and receiver positions, the insertion loss is dominated by the diffraction associated with the shortest propagation path.

• Bulletin of the Korean Chemical Society
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• v.26 no.3
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• pp.423-427
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• 2005

The bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex-272) and sodium diethyl- dithiocarbamate (NaDDC) ligands were used to extract of metal ions ($Cd^{2+},\;Co^{2+},\;Cu^{2+},\;Pb^{2+},\;Zn^{2+}$) in supercritical $CO_2$. Experiments showed a strong synergistic effect and better extraction efficiency if the two ligands were used together. In-situ UV-visible observation indicates that NaDDC in the water/supercritical $CO_2$ started to decompose slowly. The synergistic effect seems to come from the deprotonation of the organophosphorus ligand by amines from the decomposed NaDDC. The enhancing role of amines was confirmed using the mixture of Cyanex-272 and diethylamine(DEA) in the metal extraction.

• Elastomers and Composites
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• v.2 no.1
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• pp.31-36
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• 1967

As a series of the studies of thin rubber coated fabrics, the experiments were concentrated on the investigation of the physical properties of the surface and back coated fabrics with natural and synthetic rubber. Cotton poplin and nine other cotton shootings were used as a base fabric and both sides of fabric, face and back, were coated by means of topping or spreading process. The physical properties of finished material were broadly investigated especially in view of the quality requirements of the poncho.

• ETRI Journal
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• v.33 no.3
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• pp.466-469
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• 2011

As a fine-grained power gating method for achieving greater power savings, our approach takes advantage of the finite state machine with a datapath (FSMD) characteristic which shows sequential idleness among subcircuits. In an FSMD-based power gating, while only an active subcircuit is expected to be turned on, more subcircuits should be activated due to the power overhead. To reduce the number of missed opportunities for power savings, we deactivated some of the turned-on subcircuits by slowing the FSMD down and predicting its behavior. Our microprocessor experiments showed that the power savings are close to the upper bound.