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Advanced Energy Detector with Correlated Multiple Antennas
( Sungtae Kim ),( Sungmook Lim ) 한국인터넷정보학회 2021 KSII Transactions on Internet and Information Syst Vol.15 No.12
In cognitive radio networks where unlicensed secondary users opportunistically access to licensed spectrum unused by licensed primary users, spectrum sensing is one of the key issues in order to effectively use the frequency resource. For enhancing the sensing performance in energy detection-based spectrum sensing, spatial diversity based on multiple antennas is utilized. However, the sensing performance can be degraded when antennas are spatially correlated, resulting in inducing the harmful interference to primary users. To overcome this problem, in this paper, an advanced energy detector is proposed. In the proposed sensing method, a weight matrix based on the eigenvalues of the spatial channels without any prior information on the primary signals is defined and utilized. In numerical simulations, it is shown that the proposed detector outperforms the conventional detector with regard to false-alarm and detection probabilities when antenna are spatially correlated.
Sound Quality Enhancement by using the Single Core Exciter in OLED Panel
( Sungtae Lee ),( Kwanho Park ),( Hyungwoo Park ) 한국인터넷정보학회 2020 KSII Transactions on Internet and Information Syst Vol.14 No.2
With the development of display engineering and technology, the screen and sound quality of information devices such as TVs are improving. The screen used LEDs via LCD and PDP and a large flat panel in the early CRT to create super-high resolution. The sound is improved by directly vibrating a thin and simple panel, such as an OLED. In our previous study, the exciter speaker was attached to the rear of the OLED panel to be used as the diaphragm of the speaker, and the sound quality was as good as that of the TV using the existing dynamic speaker. This method supplied the viewer with the direct sound coming from the panel, delivering clear sound, and the sound and image came from the same location, thus giving the viewer high immersion and maximizing the effect of information transfer. OLED exciter speakers, however, have a special directivity, which tends to slightly attenuate the tone at the very center of the screen. This study improves the sound quality by improving the structure of the exciter speaker and the radiated sound of the flat panel display. A 2-in-1 Exciter is made into a single core to improve the speaker's radiation pattern.
Design and Assessment of Phase-Shifting Algorithms in Optical Interferometer
Sungtae Kim,Jurim Jeon,Yangjin Kim,Naohiko Sugita,Mamoru Mitsuishi 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.10 No.2
Silicon wafers and transparent glass plates are major components in the semiconductor industry. In semiconductor devices, the surface shape and optical thickness of the wafers and glass plates are the key parameters for the optimal performance of the devices. Phase-shifting interferometry has been widely used to achieve precision measurements of these parameters. The phase-shifting algorithm significantly affects the interferometric measurement results with phase-shifting interferometry. In this review, we introduce the design and assessment of phase-shifting algorithms in the Fizeau interferometer. Section 2 categorized the phase-shifting algorithms designed by several methods in terms of their error compensation ability. Then, the optical setup of the Fizeau interferometer used for surface and thickness measurement is explained in Sect. 3. In addition, Sect. 4 explained the principle of phase extraction using phase-shifting interferometry and discussed its error sources. Moreover, design methods for the phase-shifting algorithm to eliminate error sources are introduced in Sect. 5. Finally, the error compensation abilities of designed algorithms are estimated by several methods in Sect. 6.
Describing Political Candidates : News Media's Intermedia Agenda Setting Effects
Sungtae Ha 한국소통학회 2013 한국소통학보 Vol.21 No.-
본 연구는 뉴스미디어의 미디어 간 의제설정 기능을 2008년 미국 민주당 대선후보 경선에 대한 뉴스보도를 중심으로 국제적 수준에서 살펴보았다. 특히 교차지연상관관계 분석기법을 통하여 미디어 간 의제의 유사성에 대한 검토와 더불어 의제설정영향의 인과적 방향성을 규명하려는 데 초점을 맞추었다. 결론을 살펴보면, 미디어 간 의제설정효과에 대한 분석결과는 권위적 미디어의 리더십에 대한 강력한 지지를 보여 주었다. 이슈의제 수준에서 경선후보들에 대한 장기간의 뉴스보도에 대한 양적인 분석을 통해 미국과 한국의 미디어 간 밀접한 보도 양태를 관찰할 수 있었으며, 속성의제에 대한 일련의 교차상관관계분석은 경선후보에 대한 미국 유수언론의 보도가 국내미디어 보도에 유의미한 영향을 미쳤음을 또한 보여 주고 있다. 무엇보다 본 연구는 교차지연분석을 통해 그러한 미디어 간 영향의 방향성에 대한 하나의 경험적 자료를 제시하고 있다는 점에서 국제적 수준에서의 미디어 간 의제설정연구의 필요성을 제기하고 있다. This study examines news media’s intermedia agenda-setting role at an international level in the news coverage of candidates for the 2008 U.S. Democratic presidential nomination. By employing a cross-lagged correlation analysis, we clarified the causal direction of the intermedia influence between the U.S. news media and the online news media of Korea as well as the similarity of their news coverage. In results, such intermedia influence at an international level appeared to have a strong implication for an elite media leadership. First, at the issue level of intermedia agenda-setting, a longitudinal examination of news stories about the political candidates demonstrated a close association in political news coverage between U.S. and Korean news media. In addition, at the attribute level, a series of cross-lagged correlation analyses found significant influence from U.S. to Korean news media. By determining the direction of influence, these time-lag analyses provided a nice evidence of U.S. media’s leadership over Korean media concerning the U.S. political news coverage.
Conceptual design of an offshore LNG bunkering terminal
Sungtae Yun(윤성태),Jiheon Ryu(유지헌),Suwon Seo(서수원),Sangick Lee(이상익),Hyun Chung(정현),Yutaek Seo(서유택),Daejun Chang(장대준) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
This study proposes the conceptual design of an offshore LNG bunkering terminal that would play a critical role in the LNG supply chain for LNG-fuelled ship propulsion. The principal functions of the LNG bunkering terminal include importing LNG from LNG carriers, storing it temporarily, and exporting the stored LNG to LNG bunkering shuttles or LNG-fuelled ships. One of the critical issues facing cargo operation from a safety point of view is the treatment of boiloff gas (BOG) generated from several sources in the storage systems of the bunkering terminal. Several methods of handling BOG seem feasible. The employment of a pressure vessel with a re-liquefaction system is considered the most effective and safe alternative.
Low bias frequency domain SNR estimator using DCT in mobile fading channels
Sungtae Kim,Hyunkyu Yu,Jemin Lee,Daesik Hong IEEE 2009 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.8 No.1
<P>The authors analyze the cause of bias in a fast Fourier transform (FFT)-based frequency domain signal-to-noise ratio (SNR) estimator by deriving the upper bound of the bias. The analysis is then used to propose a new frequency domain estimator using discrete cosine transform (DCT), which has lower bias. In addition, a criterion is proposed for use when maximum Doppler frequency information is available; it is based on the derived upper bound and can be used to improve the mean squared error (MSE) performance of the proposed DCT-based estimator. Simulation results show that the proposed estimator reduces the MSE remarkably by diminishing the bias..</P>
Evaluation Model of Defense Information Systems Use
Sungtae Kim,Hanjun Lee,Hyukjin Kwon,Sangho Lee 한국정보기술융합학회 2015 JoC Vol.6 No.1
The Republic of Korea’s Ministry of National Defense (ROK-MND) has developed various defense information systems, and most of the projects for the development of such information systems are now in their completion or maintenance stage. Because information system (IS) use is a precondition to get the benefit and it can show what IS should be improved, measuring IS use is important. In this study, we benchmarked ISO/IEC 25010 and a guideline of Korean government for operational performance of information systems. We proposed the framework that can measure the degree of IS use with three perspectives such as task support, relevant information provision, and user convenience from the viewpoint of users, and conducted an evaluation of defense information systems with it. Moreover, we classified the defense information systems into four groups by two dimensions such as the status of use and the frequency of maintenance demand, and then made suggestions for better management of IS in each classification.