• 통합자연과학논문집
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• 제14권2호
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• pp.50-56
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• 2021

Due to the recent increase in the mobile streaming market, mobile traffic is increasing exponentially. IMT-2020, named as the next generation mobile communication standard by ITU, is called the 5th generation mobile communication (5G), and is a technology that satisfies the data traffic capacity, low latency, high energy efficiency, and economic efficiency compared to the existing LTE (Long Term Evolution) system. 5G implements this technology by utilizing a high frequency band, but there is a problem of path loss due to the use of a high frequency band, which is greatly affected by system performance. In this paper, small cell technology was presented as a solution to the high frequency utilization of 5G mobile communication system, and furthermore, the system performance was improved by applying machine learning technology to macro communication and small cell communication method decision. It was found that the system performance was improved due to the technical application and the application of machine learning techniques.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 추계학술발표대회 논문집
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• pp.74-78
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• 2001

In this study, out-of-plane properties and CTEs were predicted for 8-harness satin weave textile composites. The properties were calculated by unit cell analysis for configurations with varied waviness ratio and phase shifts. Macro elements were employed to reduce the computer resource requirement. It was found that the out-of-plane properties and CTEs were varied as the phase shift changed. However the dependency was much weaker than the in-plane properties.

• 한국컴퓨터정보학회:학술대회논문집
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• 한국컴퓨터정보학회 2016년도 제53차 동계학술대회논문집 24권1호
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• pp.275-277
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• 2016

이동통신망에서 광대역 멀티미디어 서비스를 위한 무선 자원 확보를 위해서는 매크로셀/마이크로/피코셀(macro/micro/pico cell) 구조를 통해 무선 자원을 효과적으로 재사용할 필요가 있다. 이런 구조에서는 작은 셀 반경으로 인하여 빈번히 핸드오버가 발생하게 되고 이동성 또한 시간과 장소에 따라서 다양하게 나타난다. 본 논문에서는 차세대 이동통신망의 핸드오버 상황에서, 다양한 고속 멀티미디어 서비스에 일정한 수준의 QoS (Quality of Services)를 보장하기 위한 자원할당 시의 부하 제어 방안을 제안한다.

• 한국콘텐츠학회논문지
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• 제7권1호
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• pp.40-47
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• 2007

단백질 매크로 어레이 영상에서 단백질 칩 각각의 특징을 규명하는 것은 중요한 것이다. 사람의 시각에 의한 판단은 많은 단백질 칩 영상을 실험할 경우, 장시간의 관찰과 그로 인한 오류가 발생할 수 있다. 따라서 시뮬레이터를 통한 특성 파악이 필요하게 되고, 매크로 어레이 스캔 영상에 대해 특성 분석을 할 경우 효율을 극대화할 수 있다. 형광 스캔 영상에 있어서, 각 셀의 반응도는 컬러 영상의 R, G, B 분포에 의존하여 왔다. 그러나 중첩되는 영상의 경우는 한쪽으로 구분하여 분류하기가 어렵다. 본 논문은 이러한 단점을 극복하기 위해 사용자가 원하는 색상에 대한 퍼지 측도 값을 적용한 퍼지 적분 값으로서 단백질 칩의 반응색상을 구분 지었다. Scan Array 5000에 의해 구성된 매크로 어레이 형광 영상들에 대해 실험한 결과, 퍼지 적분을 사용한 제안 방법이 모호한 색상에 대해 결정을 내릴 수 있는 요소가 됨을 보여 주었다.

• 한국통신학회논문지
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• 제36권3A호
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• pp.240-249
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• 2011

본 논문은 펨토셀시스템(femtocell system)의 단말(mobile station)이 핸드오버(handover)하기 전에 이웃한 기지국(neighbor station)의 정보를 공유하는 셀 관리(cell management) 기법과 핸드오버 방법에 대해 제안한다. 펨토셀시스템에서는 셀관리를 위해 수많은 펨토셀의 정보를 MOB_NBR-ADV메시지에 포함하여 방송하는데, 단말과 기지국에서 MOB_NBR-ADV메시지를 처리할 때 일시적인 부하가 발생된다. 따라서 효율적인 동작과 핸드오버 성공률 개선을 위해 MOB_NBR-ADV메시지의 구성 및 전송방법을 제안한다. 또한, 셀 간 중첩된 영역에서 핸드오버의 핑퐁(ping-pong) 현상을 막기 위해 히스테리시스 범위(hysteresis margin)를 이용한다. 그러나 수많은 펨토셀이 도입된 경우 기존의 히스테리시스범위 만으로 핑퐁현상을 막을 수 없다. 본 논문에서는 중첩된 셀의 개수가 증가하는 경우 히스테리시스범위가 커지는 방법과, 차등적으로 셀을 관리하여 불필요한 핸드오버의 횟수를 최소화하는 방법 등을 제안하였다. 컴퓨터 모의실험을 통해 성능 검증한 결과, 제안한 방식이 기존의 펨토셀 시스템의 셀 관리 및 핸드오버 방식에 비해 성능을 개선시키는 것을 확인하였다.

• 한국통신학회논문지
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• 제39B권2호
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• pp.61-74
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• 2014

In recent years, development of femtocells are receiving considerable attention towards increasing the network coverage, capacity, and improvement in the quality of service for users. In 3GPP LTE-Advanced (LTE-A) system, to efficiently utilize the bandwidth, femtocell and macro cell uses the same frequency band, but this deployment poses a technical challenge of cross-tier interference to macro users. In this paper, the novel quality of service based fractional power control (QoS-FPC) scheme under the heterogeneous networks environment is proposed, which considers the users priority and QoS-requirements during the power allocation. The proposed QoS-FPC scheme has two focal points: firs, it protects the macrocell users uplink communication by limiting the cross-tier interference at eNB below a given threshold, and second, it ensures the optimization of femtocell users power allocation at each power adjustment phase. Performance gain is demonstrated with extensive system-level simulations to show that the proposed QoS-FPC scheme significantly decreases the cross-tier intereference and improves the overall users throughput.

• Journal of Electrochemical Science and Technology
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• 제7권3호
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• pp.218-227
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• 2016

The light harvesting efficiency is counted as an important factor in the power conversion efficiency of DSSCs. There are two measures to improve this parameter, including enhancing the dye-loading capacity and increasing the light trapping in the photoanode structure. In this paper, these tasks are addressed by introducing a macro-porous silicon (PSi) substrate as photoanode. The effects of the novel photoanode structure on the DSSC performance have been investigated by using energy dispersive X-ray spectroscopy, photocurrent-voltage, UV-visible spectroscopy, reflectance spectroscopy, and electrochemical impedance spectroscopy measurements. The results indicated that bigger porosity percentage of the PSi structure improved the both anti-reflective/light-trapping and dye-loading capacity properties. PSi based DSSCs own higher power conversion efficiency due to its remarkable higher photocurrent, open circuit voltage, and fill factor. Percent porosity of 64%, PSi(III), resulted in nearly 50 percent increment in power conversion efficiency compared with conventional DSSC. This paper showed that PSi can be a good candidate for the improvement of light harvesting efficiency in DSSCs. Furthermore, this study can be considered a valuable reference for more investigations in the design of multifunctional devices which will profit from integrated on-chip solar power.

• 한국통신학회논문지
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• 제39B권11호
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• pp.771-778
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• 2014

본 논문에서는 이종네트워크에서 펨토셀의 전력제어 기법을 게임이론을 이용해 정의한다. 저전력으로 고품질의 통신환경을 제공하는 펨토셀은 여러 장점으로 인해 최근 이슈화 되고 있지만 다수의 펨토셀 사용은 매크로셀과의 같은 채널을 사용함으로 인한 많은 량의 간섭으로 작용한다. 게임이론의 적용을 위해 셀룰러 네트워크의 기지국 및 사용자를 게임을 하는 플레이어로 설정하고 서로에게 미치는 간섭 영향을 전력 효용함수로 모델링 하였다. 또한 최적의 전력을 사용하여 시뮬레이션을 통한 저전력 사용, 간섭량 감소 그리고 시스템 전체 성능 향상을 확인하였다.

• ETRI Journal
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• 제37권5호
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• pp.856-866
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• 2015

A heterogeneous network (HetNet) is a network topology composed by deploying multiple HetNets under the coverage of macro cells (MCs). It can improve network throughput, extend cell coverage, and offload network traffic; for example, the network traffic of a 5G mobile communications network. A HetNet involves a mix of radio technologies and various cell types working together seamlessly. In a HetNet, coordination between MCs and small cells (SCs) has a positive impact on the performance of the networks contained within, and consequently on the overall user experience. Therefore, to improve user-perceived service quality, HetNets require high-efficiency network protocols and enhanced radio technologies. In this paper, we introduce a 5G HetNet comprised of MCs and both fixed and mobile SCs (mSCs). The featured mSCs can be mounted on a car, bus, or train and have different characteristics to fixed SCs (fSCs). In this paper, we address the technical challenges related to mSCs. In addition, we analyze the network performance under two HetNet scenarios-MCs and fSCs, and MCs and mSCs.

• 한국주조공학회지
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• 제33권1호
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• pp.13-21
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• 2013

The effects of rare earth element (R.E.) and cooling rate on the eutectic reaction of flake graphite cast irons were studied by combined analysis of macro/micro-structure and cooling curve data. The correlation between eutectic reaction parameter and macro/micro-structure was systematically investigated. Two sets of chemical compositions with the different addition of R.E. were designed to cast. Three types of molds for cylindrical specimens with the different diameters were prepared to analyze cooling rate effect. The difference between undercooling temperature and cementite eutectic temperature (${\Delta}T_1=T_{U}-T_{E,C}$), which is increased by adding R.E. and decreased by increasing cooling rate, is considered to be a suitable eutectic reaction parameter for predicting graphite morphology. According to the criterion, A-type graphite is mainly suggested to form for ${\Delta}T_1$ over $20^{\circ}C$. Eutectic reaction time (${\Delta}t$), which is decreased by adding R.E. or increasing cooling rate, is a suitable eutectic reaction parameter for predicting eutectic cell size. Eutectic cell size is found to decrease in a proportion to the decrease of ${\Delta}t$.