• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.3
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• pp.233-238
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• 2013

In this paper, a novel diversity and directivity mode-switchable planar antenna array is proposed. For the diversity mode, four elements are unfolded on the plane and high isolation can be achieved. On the other hand, the antenna function is changed to the directivity mode when they are folded and stacked. Each element works such as a stacked Yagi-Uda antenna with high directivity. Especially, the curved feed line as well as the hybrid feeding method is used to improve performances. The simulation results agree well with measurement results and it is successfully demonstrated that two modes are properly working at 2.4 GHz.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.17 no.1
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• pp.10-16
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• 2024

Microstrip directional couplers using microstrip lines do not have good directivity characteristics because the dielectric constant of the substrate is different from that of air. To solve this problem, a compensation capacitor is sometimes attached between the coupling lines to improve directivity. This paper proposes a directional coupler with high directivity using interdigital capacitors implemented with transmission lines instead of lumped capacitors. The directional coupler designed and fabricated using the proposed method showed a coupling factor of 20 dB and a directivity of higher than 30 dB at 2.14 GHz. This directional coupler can be used as two directional couplers because it has two coupling ports and two isolated ports.

• The Journal of the Korea Contents Association
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• v.13 no.6
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• pp.212-226
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• 2013

In this paper, I tried to analyze objectively the structural relation among market directivity, study directivity, and achievement of organization which are intended to equip competitive power of social welfare organization on the social service market centrally formed by the voucher business. Data collection objectives is consist of 7 metropolitan cities social welfare organizations, performing voucher businesses of the Ministry of Health and Welfare, and data is secured from 203 institutions. Some basic technological statistics and regression analysis employing structural equation was used for analysing data. Analyzed result, the structural relation among market directivity and study directivity and organizational performance is appeared meaningfully according to the fact that goodness of fit coefficients is TLI = .86, CFI = .89, RMSEA = .02. With respect to achievement of organization, market directivity and study directivity are all confirmed as positively influenced. The results of analysis about whether market directivity and study directivity for achievement of organization is direct effect or indirect effect shows that market directivity and study directivity are all influenced both directly to organizational performance, and as parameter. By the results of this research, social welfare organizations performing voucher business are to have practical implication requiring organization learning needed collecting and sharing the relevant information and organizational response toward voucher social service market.

• Geophysics and Geophysical Exploration
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• v.11 no.2
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• pp.137-147
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• 2008

Fault rupture directivity of the Odaesan earthquake, which was inferred to be the main cause of the high PGAvalue (> 0.1 g) unusually observed at the near-source region, was analyzed by using the data from the nearby (R < 100 km) dense seismic stations. The Boatwright's method (2007) was adopted for this purpose in which the azimuth and takeoff angle of the unilateral rupture directivity function could be estimated based on the relative peak ground-motions of seismic stations resulting from the nature of the rupture directivity. In this study, the approximate values of the relative peak ground-motions was derived from the difference between the log residuals of the point-source spectral model (Boore, 2003) for the main and secondary events based on the Random Vibration Theory. In this derivation, the spectral difference for a frequency range between the source corner frequencies of main and secondary events was considered to reflect only the effect of the fault directivity. The inversion result of the model parameters for the fault directivity function showed that the fault-plane of NWW-SEE direction dipping steeply to the North with high rupture velocity near upward in SE direction is responsible for the observed high level of ground-motion at the near-source region.

• Journal of Digital Convergence
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• v.11 no.12
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• pp.829-834
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• 2013

This study intended to find out an efficient teaching-learning method by identifying the effect of achievement goal directivity and self-regulated learning strategy on the level of learning achievement in class. This study analyzed the relationship between the achievement goal directivity and the average and standard deviation of self-regulated learning strategy as well as the relationship between the achievement goal directivity and the learning achievement of self-regulated learning strategy and also analyzed the effect of achievement goal directivity and self-regulated learning strategy on the level of learning achievement, based on the result of survey targeting 133 university students attending the Department of Social Welfare. The findings show that the higher the tendency of achievement goal directivity and self-regulated learning ability, the higher the academic performance, which means that it is necessary to resolve any anxiety through motivation control training and mentoring learning for academic achievement of students and inducing their proactive participation in class.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.9
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• pp.63-69
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• 2007

The directivity of crossed waveguide directional coupler is generally decreased according as coupling coefficient of it increase. In this paper, the geomertical parameters of crossed slot pair for directivity improvement is modified and the formulas for design of it are proposed. The crossed waveguide directional coupler designed upon the formulas is fabricated with the WR42 waveguide in K-band. The measured results show that the coupling coefficient is 21.5 dB and directivity is minimum 23.9 dB over the operating frequency from 18GHz to 26.5GHz.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.4 no.3
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• pp.197-201
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• 2011

The use of gestures provides an attractive alternate to cumbersome interfaces for human-computer devices interaction. This has motivated a very active research area concerned with computer vision-based recognition of hand gestures. The most important issues in hand gesture recognition is to recognize the directivity of finger. The primitive elements extracted to a hand gesture include in very important information on the directivity of finger. In this paper, we propose the recognition algorithm of finger directivity by using the cross points of circle and sub-primitive element. The radius of circle is increased from minimum radius including main-primitive element to it including sub-primitive elements. Through the experiment, we demonstrated the efficiency of proposed algorithm.

• The Journal of the Acoustical Society of Korea
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• v.22 no.8
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• pp.629-636
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• 2003

It will be very convenient if the directivity characteristics of ultrasonic transducer array are controllable by the purpose of use in the fields of sonar system or ultrasonic diagnostic system, In this paper, a control method of the directivity characteristics was suggested. The transducer array was consisted of two-layered piezoelectric vibrators. Efficiency of each vibrator is controlled in 2nd harmonic mode by electrical capacitance. Therefore, the beam width of the transducer array can be controlled by changing the capacitance. The directivity characteristics of the array were analyzed experimentally and theoretically. As the results, it is confirmed that -3 dB beam width of main lobe can be controlled in the range of 7.6°∼16.2°.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.12
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• pp.1321-1328
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• 2003

In this paper, we demonstrate that the directivity of the CPW(Coplanar Waveguide) directional coupler with finite-extent backed conductor is enhanced by eliminating center region of backed conductor appropriately. If the backed conductor is removed at center region of couplers, the couplers have two backed conductors. If effective odd mode dielectric constant is decreased at center region, the electrical length for odd mode is changed and phase velocity is same at the directional couplers. Hence, directivity is improved. The eliminated length is solved by an odd and even mode analysis. The designed moderate CPW directional coupler with the proposed compensation structure has excellent directivity and matching characteristic at center frequency in simulation and measurement.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.4
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• pp.368-378
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• 2004

In this paper, we proposed the compensation structures for the enhanced directivity of CPW(Coplanar waveguide) directional couplers with finite-extent backed conductor. The proposed compensation structures are. realized by expanding the slot width between signal line and ground plane in center region of couplers. The CPW couplers with expanded slot have the same phase velocity for even and odd mode because of added inductance and changed capacitance appropriately, so the enhanced directivity is accomplished. The designed CPW directional couplers have good directivity and matching characteristic at center frequency in simulation and measurement.