• 한국ITS학회 논문지
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• 제8권1호
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• pp.102-109
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• 2009

본 논문에서는 타임 슬롯의 사용되지 않는 구간에서 효과적으로 CSMA를 수행하여 Hybrid TDMA/CSMA 프로토콜의 성능을 향상시키는 방법을 제안한다. Hybrid TDMA/CSMA 프로토콜은 디바이스들이 효율적으로 매체를 공유하기 위한 방법으로 TDMA 타임 슬롯의 사용되지 않는 구간을 CSMA 접속 방법을 이용하여 채널의 효율성을 높이고 성능을 개선한다. 그러나 CSMA 구간동안 여러 디바이스들이 경쟁을 벌이기 때문에 지연과 잦은 충돌이 발생하여 네트워크 성능이 낮아진다. 본 논문에서는 이러한 문제점을 개선하기 위하여 타임 슬롯에 따라 여유 구간에서 CSMA를 수행하는 디바이스를 제한하는 방법을 제안한다. 제안된 알고리즘은 CSMA 구간에서 경쟁을 벌이는 디바이스의 수를 줄여 경쟁으로 인한 전송 지연과 충돌 가능성을 감소시킨다. 이러한 지연과 충돌 가능성의 감소는 네트워크의 성능을 향상시킨다. 시뮬레이션을 통하여 본 논문에서 제안한 제한적 CSMA 방법과 기존의 Hybrid TDMA/CSMA 프로토콜의 성능을 비교하여 성능 향상을 검증한다.

• 방송공학회논문지
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• 제22권1호
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• pp.107-117
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• 2017

기존의 방송 단말에서 제공되는 IoT 서비스는 방송과 연계되지 않은 독립형 서비스의 형태로 제공되고 있었으나 최근 하이브리드 방송 관련 기술의 확산으로 방송과 IoT가 유기적으로 연계된 다양한 서비스로의 발전이 기대되고 있다. 하지만 현행 IoT 서비스는 다양한 프로토콜이 혼재된 클라우드 형태로 구성되어 임베디드 어플리케이션인 하이브리드 방송 단말에서의 접근에 많은 제약을 가지고 있다. 이러한 문제를 해결하기 위해, 본 논문에서는 Fog Computing의 개념을 어플리케이션으로 확장한 하이브리드 방송용 Fog Applet 아키텍쳐를 제안한다. Fog Applet 아키텍쳐는 클라우드 기반 IoT 서비스와 방송 단말 어플리케이션 사이에 Fog Applet을 위치시킴으로써 임베디드 어플리케이션의 서비스 접근 요구를 감소시키고 다양한 클라우드 기반 IoT 서비스와 유연한 구성을 제공하는 목적을 가진다. 제안된 아키텍쳐는 하이브리드 방송 기반의 서비스 환경에 대한 구현을 통하여 다종 IoT 서비스의 연동을 지원하는 하이브리드 어플리케이션의 구현을 통하여 그 기능을 검증한다.

• 실내환경 및 냄새 학회지
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• 제17권4호
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• pp.372-380
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• 2018

To abate the problem of odor from restaurants, a hybrid adsorbent consisting of organic and inorganic materials was developed and evaluated using acetaldehyde as a model compound was deveioped and evaluated. Powders of activated carbon, bentonite, and calcium hydroxide were mixed and calcinated to form adsorbent structure. The surface area of the hybrid adsorbent was smaller than that of high-quality activated carbon, but its microscopic image showed that contours and pores were developed on its surface. To determine its adsorption capacity, both batch isotherm and continuous flow column experiments were performed, and these results were compared with those using commercially available activated carbon. The isotherm tests showed that the hybrid adsorbent had a capacity 40 times higher than that of the activated carbon. In addition, the column experiments revealed that breakthrough time of the hybrid adsorbent was 2.5 times longer than that of the activated carbon. These experimental results were fitted to numerical simulations by using a homogeneous surface diffusion model (HSDM); the model estimated that the hybrid adsorbent might be able to remove acetaldehyde at a concentration of 40 ppm for a 5-month period. Since various odor compounds are commonly emitted as a mixture when meat is barbecued, it is necessary to conduct a series of experiments and HSDM simulations under various conditions to obtain design parameters for a full-scale device using the hybrid adsorbent.

• 한국자동차공학회논문집
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• 제24권6호
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• pp.694-701
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• 2016

According to revolutionary developments in automobile technologies, eco-friendly advanced vehicles (hybrid vehicle, hydrogen fuel-cell vehicle, electric vehicle, etc.) are rapidly increasing. The electromagnetic compatibility is getting more important for development of a vehicle because those advanced vehicles are driven by electric energy and equipped with more electric systems. In general, electromagnetic compatibility tests consist of an electromagnetic interference(EMI) test and an electromagnetic susceptibility(EMS) test. EMI test of the electric vehicles are needed not only in driving mode but also in charging mode because they must be recharged by much electric energy for driving. Depending on vehicle manufacturers, the charging device type and the location of charging device inlet in electric vehicles are various. In this paper, in order to investigate EMI of electric vehicles in charging mode in consideration of the direction of measuring antenna and the location of charging device inlet, a series of electromagnetic emission tests are conducted using three electric vehicles (neighborhood electric vehicle, electric vehicle and electric vehicle-bus). The test results show that electromagnetic emission measurements in charging mode are dependent on the direction of measuring antenna and the location of charging device inlet.

• 한국광학회:학술대회논문집
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• 한국광학회 2009년도 동계학술발표회 논문집
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• pp.495-496
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• 2009

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 춘계학술대회 논문집
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• pp.204-205
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• 2013

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 추계학술대회 논문집
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• pp.167-168
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• 2012

• 한국지반환경공학회 논문집
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• 제7권1호
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• pp.67-80
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• 2006

본 논문에서는 지반 하이브리드-온라인 시뮬레이션의 방법을 압밀 해석에 적용하기 위한 시도를 수행하였다. 일반적인 수치해석법이 실내시험을 통해 얻어진 흙의 구성모델을 이상화시켜 사용하는 것과 달리, 이 방법에서는 흙의 거동을 요소시험체로부터 직접 도입해가면서 해석을 수행한다. 그러므로 복잡한 파라미터의 평가과정이 생략될 수 있게 되며 인위적 이상화에 의한 해석 오차를 경감할 수 있게 된다. 본 논문에서는 실험장치의 물리적 성능을 검증하기 위하여 단계압밀시험과 투수시험(CONPERM test)을 수행하여 제어와 계측의 결과를 고찰하였으며, 시스템으로부터 얻은 데이터의 건전성을 평가하기 위하여 검증해석을 수행하였다. 결과적으로, 본 연구를 통해 개발된 하이브리드-온라인 압밀해석 시스템은 재성형된 카오리나이트의 압밀거동을 모순없이 재현하고 있음을 알 수 있었다.

• Earthquakes and Structures
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• 제15권3호
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• pp.227-241
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• 2018

The present paper deals with the optimum performance of the passive hybrid control system for the benchmark highway bridge under the six earthquakes ground motion. The investigation is carried out on a simplified finite element model of the 91/5 highway overcrossing located in Southern California. A viscous fluid damper (known as VFD) or non-linear fluid viscous spring damper has been used as a passive supplement device associated with polynomial friction pendulum isolator (known as PFPI) to form a passive hybrid control system. A parametric study is considered to find out the optimum parameters of the PFPI system for the optimal response of the bridge. The effect of the velocity exponent of the VFD and non-linear FV spring damper on the response of the bridge is carried out by considering different values of velocity exponent. Further, the influences of damping coefficient and vibration period of the dampers are also examined on the response of the bridge. To study the effectiveness of the passive hybrid system on the response of the isolated bridge, it is compared with the corresponding PFPI isolated bridges. The investigation showed that passive supplement damper such as VFD or non-linear FV spring damper associated with PFPI system is significantly reducing the seismic response of the benchmark highway bridge. Further, it is also observed that non-linear FV spring damper hybrid system is a more promising strategy in reducing the response of the bridge compared to the VFD associated hybrid system.

• 한국태양에너지학회 논문집
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• 제32권5호
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• pp.59-67
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• 2012

In this study,the compact type solar thermal and ground coupled heat pump hybrid system for space heating/cooling and hot water supply has been developed. This hybrid system was installed in Zero Energy Solar House(ZeSH) in KIER for the demonstration. The thermal performance and operational characteristics of this hybrid system were analysed especially. The results are as follows. (1) This hybrid system was designed in order to address the existing disadvantages of solar thermal/ground coupled heat pump system. For this design, all parts except solar collector and ground coupled heat pump were integrated into a single product in a factory. The compact type unit includes two buffer tanks, an expansion tank, pumps, valves, a controller, etc. This system has an advantage of easy installation with simple plumbing work even in narrow space. (2) The thermal charging and discharging time of the buffer tanks and its characteristics by ground coupled heat pump, and heat pump COP according to geo-source temperature and buffer storage temperature have been studied. This system was found to meet well to the heat load without any other auxiliary heating equipment. (3) The operating hours of the ground coupled heat pump as a backup device of solar thermal can be reduced significantly by using solar heat. It was also found that the minimum heating water supply setting temperature and maximum cooling water supply setting temperature make an influence on the heat pump COP. The lower heating water and the higher cooling water temperature, the higher COP. In this respect, the hybrid system's performance can be improved in ZeSH than conventional house.