• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2001.11a
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• pp.132-135
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• 2001

본 논문에서는 SAR를 저감시킬 수 있는 IMT-2000 단말기용 PIFA의 설계에 대한 내용을 다루었다. 안테나의 설계 파라미터에 따른 공진 특성을 분석하고, PIFA와 동일한 공진 주파수를 갖는 모노폴 안테나와 Side-mounted PIFA를 설계하여 공진 특성과 SAR를 비교\ulcorner분석하였다. 그 결과 중심주파수에서 PIFA의 대역폭은 213MHz로 Side-mounted PIFA보다 50MHz로 증가하였고, 모노폴 안테나와 비교시에는 87MHz정도 감소하였다. 또한, 1g 및 10g SAR 평균 첨두치는 PIFA가 0.9869, 0.453 으로 Side-mounted PIFA, 모노폴 안테나에 비해 각각 10.3 %, 50% 감소하였다.

• Proceedings of the KAIS Fall Conference
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• 2009.05a
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• pp.902-905
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• 2009

축사 또는 쓰레기장에서 에서 발생되는 있는 물질인 암모니아, 아민, 메탄, 탄화수소류 등에 대한 처리를 위한 촉매 개발을 수행하였다. 암모니아를 금속산화물형태의 촉매를 사용하여 산화하였을 경우 $N_2$, NO, $NO_2$, $N_2O$가 일정 비율로 생성되게 된다. 이때의 NO, $NO_2$는 악취는 발생하지 않으나 유독성 가스이므로 이에 대한 선택성이 낮은 촉매를 선별하고 온도에 따른 활성능을 시험하여 최적의 촉매조성을 도출하였다. 다양한 산화가를 지닌 망간을 대상으로 각종 조촉매의 혼합에 따른 실험을 수행하여 최적 조성을 도출 하였다. 촉매 선별작업에서는 충전층을 사용하고, 선별된 촉매에 대하여 모노리스에 코팅하여 사용할 수 있는 모노리스형태의 반응기를 장착하여 모노리스 형태 촉매의 반응성 및 피독특성을 실험하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.3
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• pp.250-256
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• 2002

In this paper, a broadband sleeve monopole antenna using a loading coil in sleeve is proposed. The center frequency of the proposed antenna is 1,990MHz. The antenna of the proposed structure has the same of the single sleeve monopole antenna, except for using the coil instead of the inner conductor in sleeve. As a result, it is found that the bandwidth is 1.239~2.154 GHz(above 53.9 %) for $S_{11}=-10\;d B$(VSWR<2), and the antenna impedance is good for a communication system and feeder which the impedance has 50 Ω.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.159-161
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• 2005

본 논문은 회전형 대용량의 진단 X-선 발생장치를 모노 블록 형태로 설계, 병원의 모바일 진단장치나, 산업용 X-선 장치로의 적용이 가능한 16kw급 X-선 발생장치에 관한 연구이다. 본 장치는 X-선 발생을 위한 고전압 발생부에 회전형 Anode 형의 X-선관을 사용하였고, X-선관의 로터를 구동할 수 있는 로터 구동회로를 추가 하였다. 고주파 고전압용 인버터에는 IGBT(600/300A)를 100kHz로 고주파 스위칭 함으로서 고전압 변압기를 비롯한 고전압 발생부의 크기와 무게를 최소화하였다. 또한, 기존의 16kw급 대용량 진단 X-선 발생장치를 X-선관과 고전압부를 일체화한 모노블록 형태로 설계, 제작하여 부하변동에 따른 X-선 관전압과 관전류의 동작특성을 실험을 통하여 입증하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.1
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• pp.89-95
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• 2004

In this paper, we proposed a multiple meander strip monopole antenna. Using meander strip structure, we could broaden the impedance bandwidth and reduce the antenna height. The proposed antenna has broad bandwidth, from 2.9 ㎓ to 10.85 ㎓, for VSWR $\leq$ 2 and has vertically polarized omnidirectional conical beam radiation pattern, which is suitable for UWB wireless systems.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.2
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• pp.31-38
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• 2022

Recently, the development of offshore wind farms based on past technical experiences from onshore wind turbine installations has become a worldwide issue. This study investigated the technical issues related to offshore wind farms and large-diameter monopiles from an economic perspective. In particular, the monopile foundation system (MFS), which is the most important part of the proposed fast construction system, is applied for the first time in Korea, and structural verification is essential because it supports large-diameter monopiles and is in charge of excavation. Therefore, in this study, a rapid construction system for large offshore wind power generators was introduced, and stability verification was performed through the structural analysis of the MFS.

• The Journal of the Acoustical Society of Korea
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• v.30 no.4
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• pp.181-189
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• 2011

According to developments of digital signal processing, 3D sound come into focus on multimedia systems. Many studies on 3d sound have proposed lots of clues to create realistic sounds. But these clues are only focused on binaural systems which two ears are normal. If we make the 3d sound using those clues at monaural systems, the performance goes down dramatically. In order to use the clues for monaural systems, we have studies algorithms such as duplex theory. In duplex theory, the sounds that we listen are affected by human's body, pinna and shoulder. So, we can enhance sound localization performances using its characteristics. In this paper, we propose a new method to use psychoacoustic theory that creates realistic 3D audio at monaural systems. To improve 3d sound, we calculate the excitation energy rates of each symmetric HRTF and extract the weights in each bark range. Finally, they are applied to emphasize the characteristics related to each direction. Informal listening tests show that the proposed method improves sound localization performances much better than the conventional methods.

• Journal of Korean Society of Steel Construction
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• v.25 no.4
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• pp.421-430
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• 2013

To predict behaviors of offshore wind turbines which are highly laterally loaded structures and to design them rationally, evaluating the soil-foundation interaction is important. Nowadays, there are many soil modeling methods for structural analysis of general structures subjected to vertical loads, but using the methods without any consideration for design of a monopile foundation is eschewed because it might cause wrong structural design due to the deferent loading state. In this paper, we identify the differences of the member forces and displacements by design methods. The results show that fixed end method is barely suitable for monopile design in terms of checking the serviceability because it underestimate the lateral displacement. Fixed end method and stiffness matrix method underestimate the member forces, whereas virtual fixed end method overestimates them. The results of p-y curve method and coefficient of subgrade reaction method are similar to the results of 3D soil modeling method, and 2D soil modeling method overestimates the displacement and member forces as compared with other methods.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.5
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• pp.35-43
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• 2014

In this paper, we propose a performance enhancement method of the target tracking system for communication signal using the monopulse and the ${\alpha}{\beta}$ filter to keep the connection of the communication system between the airplane and the ground. We suggest the minimum distance measurement method for tracking error angle of the monopulse signal instead of the generally used method of MR(Monopulse Ratio) curve, and the ${\alpha}{\beta}$ filter with variable gain for enhancement of the tracking accuracy and the probability of re-tracking the monopulse signal under the disconnection of link. We show the performance enhancement of the proposed method of monopulse system using the measured MR Curve results of the prototype system. And also, the comparison of simulation results between the ${\alpha}{\beta}$ filter with variable gain and the ${\alpha}{\beta}$ filter with fixed gain shows the performance enhancement of the proposed ${\alpha}{\beta}$ filter. Using the proposed methods, we expect the enhanced performance of the existing target tracking system for communication signal only by changing the algorithm without hardware changes.

• Journal of the Korean GEO-environmental Society
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• v.13 no.6
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• pp.91-100
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• 2012

Wireless monitoring system for the structural health evaluation has a limit to the reliability of measured response. The objective of this study is to evaluate an effective measurement range of the wireless monitoring system on the analyzed data. For the wireless monitoring system, Bluetooth and Wi-Fi are applied to datalogger-receiver and receiver-personal computer, respectively. For the model of the monopile structure response, a laboratory-scale monopile is manufactured with Mono Cast Nylon and a lateral loading is applied by hammer impacting. Strain gauges attached on the model monopile are connected with the datalogger. The distances of datalogger-receiver and receiver-personal computer are changed for the evaluation of the measurement range. Experimental results show that the receiving rates of the response remain almost constant within limited distance, while the receiving rates dramatically decrease out of effective range. In addition, the receiving rates affect on the measured natural frequencies of the model monopile. This study suggests that the effective range evaluation of the wireless monitoring system may be used for the determination of a monitoring distance to the monopile installed in the offshore wind farm.