• 대한교통학회지
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• 제34권4호
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• pp.354-372
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• 2016

공사구간에서는 교통류의 안전한 합류 및 통과를 위해 속도관리와 차로차단을 통한 체계적인 교통관리가 요구된다. 본 연구에서는 공사구간 교통관리특성을 교통안전분석에 반영하기 위해서 사고자료, 차량검기지에서 추출된 속도 및 교통자료, 공사 시 종점, 페쇄 차로 등의 정보가 포함된 공사장 이력자료를 활용하였다. 2010년부터 2014년까지 발생한 고속도로 공사구간 사고자료 중 총 231건의 사고에 대해 교통상황자료 및 공사장 이력자료를 매칭시킨 분석 대상 자료셋을 구축하고, 순서형 프로빗 모형을 적용하여 사고 심각도 영향 요인을 도출하였다. 분석결과, 속도, 차로 폐쇄에 따른 용량 감소량, 주의구간 내 사고 위치, 공사 작업 유형의 변수들이 공사구간 사고 심각도에 영향을 미치는 것으로 분석되었다. 분석결과를 바탕으로 6가지 공사구간 안전성 증진 방안을 수립하였다. 안전성 증진방안으로는 차로 합류 및 차단 방안, 주의구간 내 정보 제공 방안, 공사구간 속도 관리 방안, 공사구간 경고 정보 제공 방안, 공사구간 교통안전시설 도입, 공사구간 안전성 효과분석 및 모니터링 방안을 제시하였다.

• 한국ITS학회 논문지
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• 제17권3호
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• pp.1-17
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• 2018

렌터카 차량의 교통사고 발생건수 및 사망자 수는 꾸준히 증가하는 추세를 보이며, 사고로 인한 사망률 또한 일반 승용차 및 영업용 택시보다 높다. 본 연구는 전국을 대상으로 2010년부터 2014년까지 발생한 렌터카 사고 데이터를 분석하여 사고 심각도에 영향을 미치는 요인들을 도출하였다. 사고 심각도와 관련된 17개 변수를 렌터카 사고 데이터로부터 추출하였으며 이를 4가지(인적, 차량, 도로 및 환경) 요인으로 구분한 후 순서형 로짓 모델을 적용하여 통계적으로 분석하였다. 분석 결과, 운전자 연령, 교차로 형태, 사고 발생 요일을 제외한 나머지 14개 변수가 렌터카 사고 심각도에 영향을 미치는 요인으로 통계적 유의성이 있는 것으로 분석되었다. 연구결과는 다음과 같이 요약될 수 있다. 첫째, 거주 지역이 아닌 곳에서 발생한 렌터카 사고의 심각도가 더 큰 것으로 나타났다. 둘째, 일반 도로 대비 고속도로 렌터카 사고, 과속 및 11대 중과실 위반 등 법규 위반 관련 렌터카 사고의 경우 사고 심각도가 더 큰 것으로 나타났다. 셋째, 지리적으로 익숙하지 않은 렌터카 운전자 특성상 도로 기하구조가 복잡하며, 운전자의 시야가 분산되는 커브구간 등에서의 사고 심각도가 높게 나타났다. 넷째, 지역별로 렌터카 사고 심각도에 차이가 있으나, 2010년 이후 사고 심각도는 전반적으로 감소하고 있는 것으로 나타났다. 본 연구의 결과는 향후 렌터카 사고 심각도를 줄이기 위한 기초자료로 활용될 수 있을 것으로 생각한다.

• 대한가정학회지
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• 제44권12호
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• pp.155-165
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• 2006

The purpose of this study was to analyse the factor of the variables that contributed to the ego-identity of middle-aged women. The subjects were 751 middle-aged women whose age was from 40 to 60 years old. The instruments used in the study were the assessments of ego-identity, self-differentiation, and internal systems. The data were analysed by using pearson correlation and hierarchical multiple regression. The findings were as follows; (1) In the result of the analysis about relationships with ego-identity, the ego-identity was positively correlated with self-differentiation and the self of internal systems and negatively correlated with the parts of internal systems; (2) Predictors of ego-identity of the middle-aged women ordered occupation type, the level of education, cognitive-emotional function, self integration, family projection process, self, pleasing/abandoned part, and self-harming part. Based on these results, the recommendations for the future research in this area were discussed.

• 한국통신학회논문지
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• 제30권5C호
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• pp.338-343
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• 2005

다중 송수신 안테나(Multiple Input Multiple Output : MIMO) 시스템은 높은 데이터율 뿐만 아니라 효율적인 주파수 자원의 활용을 필요로 하는 차세대 이동 통신 시스템에 가장 적합한 시스템 중 하나로 주목받고 있다. 그에 따라 MIMO 전송 데이터율을 높이기 위해 2개의 송신 안테나를 기본으로 하는 STTC 부호화 그룹을 다수 형성하여 전송하고 수신단에서 다른 그룹의 간섭을 제거하는 BLAST-STTC 기법이 제안되었다. 본 논문에서는 모든 그룹이 최대 다이버시티 이득을 얻는 동시에 간섭 제거 기법의 성능을 향상시킬 수 있는 역순서화된 반복 복호화 기법을 제안한다. 그리고 모의실험을 통해 제안된 기법과 기존 기법의 프레임 오류확률(Frame Error Rate : FER) 성능을 비교한다.

• ETRI Journal
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• 제39권1호
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• pp.13-20
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• 2017

A method is proposed for scheduling sensor accesses to the shared network in a networked control system. The proposed method determines the access order in which the sensors are granted medium access through minimization of the state estimation error covariance. Solving the problem by evaluating the error covariance for each possible ordered set of sensors is not practical for large systems. Therefore, a convex optimization problem is proposed, which yields approximate yet acceptable results. A state estimator is designed for the augmented system resulting from the incorporation of the optimally chosen communication sequence in the plant dynamics. A car suspension system simulation is conducted to test the proposed method. The results show promising improvement in the state estimation performance by reducing the estimation error norm compared to round-robin scheduling.

• 산업공학
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• 제16권spc호
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• pp.33-38
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• 2003

In this paper we study the delivery policy of internet bookstores and recommend the improved policy to increase customer satisfaction and sales revenue. We classify customers into two, the price-sensitive and the delivery time-sensitive, and develop a new shipping method, the unhurried shipping, for the price-sensitive who are reluctant to pay shipping fee for the small purchase but willing to wait extra time for the ordered goods. The customers could get discount on shipping fee by the unhurried shipping but have to accept the longer delivery lead-time. We investigate the possible ways to reduce costs with the prolonged delivery time and show that some costs regarding shipmentand inventory could be saved in order to make up for additional shipping costs for the price-sensitive.

• 품질경영학회지
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• 제35권1호
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• pp.20-23
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• 2007

A generalized spare ordering policy is treated in this paper. If the operating unit fails before a scheduled ordering time an expedited order is placed at the failure time instant, otherwise a regular order for a spare is placed at the scheduled time. The original unit is replaced when the ordered spare is delivered. The lifetime, regular and expedited lead times have general distributions. The problem is to find the optimum ordering time which minimizes the expected cost rate including the observation, ordering, uptime and down-time costs. Some properties regarding the optimal policy are derived. To explain the spare ordering policy a numerical example is also included.

• Bulletin of the Korean Chemical Society
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• 제31권1호
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• pp.100-103
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• 2010

In this study, NO reduction behaviors of copper-loaded mesoporous molecular sieves (Cu/MCM-41) have been investigated. The Cu loading on MCM-41 surfaces was accomplished by a chemical reduction method with different Cu contents (5, 10, 20, and 40%). $N_2/77$ K adsorption isotherm characteristics, including the specific surface area and pore volume, were studied by BET's equation. NO reduction behaviors were confirmed by a gas chromatography. From the experimental results, the Cu loading amount on MCM-41 led to the increase of NO reduction efficiency in spite of decreasing the specific surface area of catalysts. This result indicates that highly ordered porous structure in the MCM-41 and the presence of active metal particles lead the synergistical NO reduction reactions due to the increase in adsorption energy of MCM-41 surfaces by the Cu particles.

• Bulletin of the Korean Chemical Society
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• 제15권1호
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• pp.64-74
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• 1994

The nonstoichiometric chalcogenides with NaCl-type structure were prepared and the physical and structural properties were studied. The homogeneous range and the structural change were studied based on X-ray powder diffractions using Rietveld-type full-profile fitting technique. Wide homogeneous ranges were observed in Y-S and Y-Se systems, and relatively narrow homogeneous ranges were observed in Yb-S and Yb-Se systems. Both in $Yb_{1-x}S\;and\;Yb_{1-x}Se$, a vacancy ordering transition occurred in (111) plane direction. The ordered superstructure had cubic symmetry(Fm$\bar{3}m) with doubled unit cell "a" parameter compared to the original NaCl-type. The superlattice developed in a continuous second-order transitiion was characterized by the reduced waved vector k= $(a^*+b^*+c^*)/2$. Y-S system had metallic, and YSe, YbSe system had semiconducting properties in their homogeneous ranges. It was observed that the change of electronic transport properties in extended homogeneous range did not depend on the relativeratio of metal to nonmetal, but on the quantities of vacancies.

• ETRI Journal
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• 제43권2호
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• pp.197-208
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• 2021

Single-carrier frequency division multiple access (SC-FDMA) is currently being used in long-term evolution uplink communications owing to its low peak-to-average power ratio (PAPR). This study proposes a new transceiver design for an SC-FDMA system based on Walsh-Hadamard transform (WHT). The proposed WHT-based SC-FDMA system has low-PAPR and better bit-error rate (BER) performance compared with the conventional SC-FDMA system. The WHT-based SC-FDMA transmitter has the same complexity as that of discrete Fourier transform (DFT)-based transmitter, while the receiver's complexity is higher than that of the DFT-based receiver. The exponential companding technique is used to reduce its PAPR without degrading its BER. Moreover, the performances of different ordered WHT systems have been studied in additive white Gaussian noise and multipath fading environments. The proposed system has been verified experimentally by considering a real-time channel with the help of wireless open-access research platform hardware. The supremacy of the proposed transceiver is demonstrated based on simulated and experimental results.