• 전기전자학회논문지
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• 제15권1호
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• pp.1-9
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• 2011

현재 유선방송 기술기준 상에서 CDMA 이동통신시스템에 대한 간섭을 고려하여 강화된 824~849MHz대역의 누설전자파 기준이 $3{\mu}V$/m(10m 거리)인데, 이를 실제 옥외에서 일반적인 측정방법으로 측정하여 적합여부를 판정하기 어렵다. 본 논문은 이러한 문제점을 이론적으로 규명하고, 이를 해결하기 위해 스펙트럼분석기, 저잡음증폭기(LNA), 안테나를 이용한 측정모델을 제안하였다. 또한, 실제 옥외에서 실험을 통해 측정한 결과를 분석하여 그 유용성을 입증하였고, 적합 여부를 판정하는 프로세스를 수립하였다.

• 한국자동차공학회논문집
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• 제20권3호
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• pp.83-87
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• 2012

Computational Fluid Dynamics (CFD) method has been used to investigate the axial force of automotive water pump. As the excessive axial force can make some unexpected problems like impeller interference and coolant leakage we have focused on finding the cause of axial force and its reduction in this paper. First, we have tested the closed type water pump with and without balance hole by the calculation methods. By examining the pressure contour around the impeller, we have found that the axial force arises not only from the pressure difference around shroud but also from the pressure difference around hub. So we have tested two impellers - one is normal open type impeller and the other is open type impeller with modified hub. The results show that the axial force reduction is about 150~200N for normal one and 700N@3000RPM for modified impeller. And the hydraulic efficiency which is important in aspect of engine fuel efficiency is reduced about 6.5% for normal one but increased 4%@3000RPM for modified impeller.

• 대한정형외과스포츠의학회지
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• 제11권1호
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• pp.57-61
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• 2012

전방십자인대 재건술 후에 발생한 커다란 크기의 경골 근위부 낭종은 드문 합병증이다. 경골 전방의 낭종은 생분해성간접나사의 분해로 인한 이물반응으로 발생하나 이 외에도 여러 가지 원인들로 인해 발생하게 된다. 저자들은 38세 남자환자에서 전방십자인대 재건술을 시행한지 2년 후 발생한 경골 전방의 커다란 크기의 낭종 1예를 관찰하였기에 동종골을 이용한 골 이식을 시행하고 예상되는 발생 원인을 문헌 고찰과 함께 보고하고자 한다.

• 한국재난정보학회 논문집
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• 제4권2호
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• pp.138-154
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• 2008

The conventional non-dig underground structure building method which made an appearance to reduce the social and environmental costs and maximize the efficiency of the social overhead capital facilities could not help being uneconomical because of many problems such as unnecessary excessive excavation, water leakage, obstacle interference, difficulty of curvilinear application and connection complexity between propelled and injected bodies due to indiscriminate application of small and large circular steel pipes without consideration of the site conditions. The T.S.T.M, in which a protruded square tube is applied as a propulsion and injection body in a design that considered site conditions such as ground condition, depth of soil and live load, was able to be economical as it solved the problems of water resistance, minimization of obstacle interference and curvilinearity, and we can see that it can be applied to all grounds by utilizing or complementing the target ground in terms of engineering. Also in configuring the transverse section, it is possible to not only secure excellent structural safety but also implement all of the above engineering characteristics not only in the square cross section but also in the arch cross section, so it was possible to build structures on any section or ground, and we could confirm the LCC reduction effect and the VE effect.

• Journal of Communications and Networks
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• 제13권4호
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• pp.327-338
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• 2011

With the incitation to reduce power consumption and the aggressive reuse of spectral resources, there is an inevitable trend towards the deployment of small-cell networks by decomposing a traditional single-tier network into a multi-tier network with very high throughput per network area. However, this cell size reduction increases the complexity of network operation and the severity of cross-tier interference. In this paper, we consider a downlink two-tier network comprising of a multiple-antenna macrocell base station and a single femtocell access point, each serving multiples users with a single antenna. In this scenario, we treat the following beamforming optimization problems: i) Total transmit power minimization problem; ii) mean-square error balancing problem; and iii) interference power minimization problem. In the presence of perfect channel state information (CSI), we formulate the optimization algorithms in a centralized manner and determine the optimal beamformers using standard convex optimization techniques. In addition, we propose semi-decentralized algorithms to overcome the drawback of centralized design by introducing the signal-to-leakage plus noise ratio criteria. Taking into account imperfect CSI for both centralized and semi-decentralized approaches, we also propose robust algorithms tailored by the worst-case design to mitigate the effect of channel uncertainty. Finally, numerical results are presented to validate our proposed algorithms.

• Journal of Power Electronics
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• 제17권6호
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• pp.1445-1453
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• 2017

In this study, a new zero-voltage transition (ZVT) buck converter with coupled inductor using a synchronous rectifier and a lossless clamp circuit is proposed. The regular buck converter with tapped inductor has extended duty cycle for high step-down applications. However, the leakage inductance of the coupled inductor produced considerable voltage spikes across the switch. A lossless clamp circuit is used in the proposed converter to overcome this problem. The freewheeling diode was replaced with a synchronous rectifier to reduce conduction losses in the proposed converter. ZVT conditions at turn-on and turn-off instants were provided for the main switch. The synchronous rectifier switch turned on under zero-voltage switching, and the auxiliary switch turn-on and turn-off were under zero-current condition. Experimental results of a 100 W-100 kHz prototype are provided to justify the validity of the theoretical analysis. Moreover, the conducted electromagnetic interference of the proposed converter is measured and compared with its hard-switching counterpart.

• 대한전자공학회논문지TC
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• 제41권11호
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• pp.17-23
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• 2004

본 논문에서는 전 디지털 모뎀의 기저 대역 전송 신호를 IF 출력 신호로 주파수 변환하는 모듈에서 발생하는 국부발진 누설 신호를 역 위상 기법을 사용하여 제거하고, aperture 개방형 루프 공진기로 구성되는 광대역 필터를 구성하여 낮은 군지연과 높은 대역 제한 특성을 갖는 광대역 IF 인터페이스 모듈을 설계하고 제작하였다. 45 Mbps 및 155 Mbps 전 디지털 모뎀을 위한 광대역 IFIU는 전송 대역과 밀접하여 간섭 신호로 작용하는 국부발진 신호의 누설 신호를 -60 dBc 이하로 억압하였으며, 각각의 전송율에 대한 IFIU의 군 지연은 15 ns와 8 ns의 낮은 특성으로 구현하였다. L-대역 중심 주파수와 150 MHz 대역통과 특성을 갖는 모듈의 이득 평탄도는 2 dB 이내의 특성으로 광대역 위성통신 시스템 전송에 필요한 요구 조건을 만족하였다.

• 한국정보기술학회논문지
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• 제17권10호
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• pp.49-55
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• 2019

본 논문은 다중 사용자 다중 입력 단일 출력 (MISO) 간섭 채널에서 복수의 도청자가 존재하는 경우에, 보안 채널 수율을 향상시키기 위한 간단한 프리코딩 벡터 설계 기법을 제안한다. 제안하는 기법에서는 보안 채널 수율을 최적화하는 문제에 대해 다루었으며, 수학식으로 주어지는 분석해를 구하는 것을 목표로 하였다. 이를 위해서 신호대 누수 잡음비 (SLNR) 기반으로 프리코딩 벡터를 설계하는 방법을 제시한다. 구체적으로는, 도청자가 정보 신호를 전혀 검출할 수 없도록 도청 채널 수율을 완전히 제거하면서, 송신단-수신단 링크 간의 채널 수율을 최대화시키도록 프리코딩 벡터를 설계한다. 성능 검증을 위하여 모의실험을 수행하였으며, 송신 안테나 개수, 송신단-수신단 링크 개수, 도청자 수 간에 특별한 조건식을 만족하지 않는 환경에서는, 제안하는 기법이 모든 신호대 잡음비 범위에서 기존 기법보다 더 우수한 보안 채널 수율을 나타낸다는 것을 제시한다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2016년도 전력전자학술대회 논문집
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• pp.105-106
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• 2016

In low-power grid-connected photovoltaic(PV) system, Single-phase transformerless full-bridge inverter is commonly used. However in transformerless photovoltaic application, the ground parasitic capacitance created by grounding between PV panels and ground. This ground parasitic capacitance inject additional current into the inverter, these currents cause electromagnetic interference problem, safety problem and harmonics problem in PV applications. In order to eliminate the ground current, This paper propose various inverter topologies in PV applications. These proposed inverter topologies are verified through simulation using PSIM.

• Journal of electromagnetic engineering and science
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• 제3권1호
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• pp.7-11
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• 2003

CDMA(code division multiple access) has very large peak to average power ratio(PAR) and behave as noise-like wide band digital signals with 1.2288 Mbps transmission rate. For signals with high PAR like CDMA, it is reasonable to prescribe occupied bandwidth(OBW) as average occupied bandwidth. Bandwidth measurements of CDMA signals at remote site are affected by co-channel and adjacent channel interference from adjacent CDMA base station, distortion of signal by fading effect, spurious emission and environment noises. In this study, we have compared OBW measurements in an on-air environment with those measured in a base station using adjacent channel leakage ratio(ACLR) as a reference measurement factor. As results of analysis, the OBW at ACLR$\geq$35 ㏈ shows nearly same statistical characteristics regardless of the measurement locations and environments.