• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권10호
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• pp.3342-3360
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• 2014

In this paper, the capacity and BER performance of downlink distributed antenna systems (DAS) with transmit antenna selection and multiple receive antennas are investigated in MIMO composite channel, where path loss, Rayleigh fading and lognormal shadowing are all considered. Based on the performance analysis, using the probability density function (PDF) of the effective SNR and numerical integrations, tightly-approximate closed-form expressions of ergodic capacity and average BER of DAS are derived, respectively. These expressions have more accuracy than the existing expressions, and can match the simulation well. Besides, the outage capacity of DAS is also analyzed, and a tightly-approximate closed-form expression of outage capacity probability is derived. Moreover, a practical iterative algorithm based on Newton's method for finding the outage capacity is proposed. To avoid iterative calculation, another approximate closed-form outage capacity is also derived by utilizing the Gaussian distribution approximation. With these theoretical expressions, the downlink capacity and BER performance of DAS can be effectively evaluated. Simulation results show that the theoretical analysis is valid, and consistent with the corresponding simulation.

• 한국통신학회논문지
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• 제33권10C호
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• pp.836-843
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• 2008

본 논문에서는 공간 코릴레이션이 존재하는 레일리이 페이딩 환경에서 직교 STBC 알고리즘들의 성능을 이론적으로 유도하고 여러 가지 코릴레이션 조건에서 각 방식의 성능을 비교, 분석한다. 먼저, 채널 코릴레이션 행렬의 고유값 (eigenvalues)을 이용하여 M-ary PSK와 M-ary QAM 변조 방식에 대한 직교 STBC 알고리즘의 비트 에러율을 유도한 다음, $1{\sim}4bps/Hz$의 전송율에 대해 공간 코릴레이션에 의한 성능의 영향을 분석한다. 성능 분석 결과, 공간 코릴레이션이 0.9이상으로 비교적 큰 환경에서는 모든 전송율에 대해 Alamouti 방식이 Tarokh 방식 보다 우수한 성능을 제공함을 알 수 있었다.

• 한국조리학회지
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• 제6권2호
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• pp.5-21
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• 2000

The purpose of this study looks for the directions to improve the performance evaluation of cook by examining the perceptions for performance of cook by supervisors in hotel restaurant. In order for this purpose, this study focuss on two areas: (1) the significant differences of each hotel type on the perceptions of each performance evaluation item, (2) the significant differences of each kitchen type on the perceptions of each performance evaluation item in terms of two different types of hotel. To examine (1) and (2), this study uses Student t test and anova analysis. The findings from this study have both theoretical and practical implications. Implications of these findings are discussed.

• 한국콘텐츠학회논문지
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• 제19권3호
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• pp.539-547
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• 2019

본 연구의 목적은 팀 프로세스의 작은 세상 구조가 팀 성과에 미치는 영향을 탐색적으로 살펴보는 것이다. 관련 문헌을 고찰하여 팀 프로세스의 작은 세상 구조와 팀 성과 사이의 관계를 이론적으로 논의하였으며, 축구팀의 패스 데이터를 이용하여 실증적으로 분석하였다. 2014년 브라질 월드컵 경기의 패스 데이터를 수집하여 128개의 패스 네트워크를 구성하고 작은 세상을 나타내는 구조적 특성을 측정하였다. 이 과정에서 작은 세상의 정도를 측정하는 데 폭넓게 사용된 작은세상지수(small-world index)의 단점을 극복할 수 있는 새로운 지수를 개발하였다. 그리고 작은 세상 구조와 성과 사이의 관계를 밝히기 위하여 상관분석과 회귀분석을 실시하였다. 분석 결과에 의하면, 팀 프로세스의 군집성은 팀 성과와 지수함수의 관계가 있고 팀 프로세스의 연결성은 팀 성과와 로그함수의 관계가 있는 것으로 나타났다. 결과적으로 팀 프로세스의 작은 세상 구조는 팀 성과에 긍정적인 영향을 미치는 것으로 나타났다. 이론적 논의와 실증적 분석을 통해, 본 연구는 팀 프로세스의 작은 세상 구조가 팀원 사이의 업무 조정과 협업을 촉진하는데 효과적으로 작용하여 팀 성과에 긍정적인 영향을 미친다는 것을 밝혀내었다.

• 대한건축학회논문집:구조계
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• 제34권3호
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• pp.19-28
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• 2018

Key factors that ensure competitiveness of modular unit include consistent high quality and connection condition that ensures high structural performance while minimizing the overall scale of the on-site process. However, it is difficult to evaluate the structural performance of the connection of modular unit, and its structural analysis and design method can be different depending on the connection to its development, which affects the seismic performance of its final design. In particular, securing the seismic performance is the key to designing modular systems of mid-to-high-rise structure. In this paper, therefore, the seismic performance of the modular system with bracket-typed fully restrained moment connections according to stiffness and the shapes of various connection members was evaluated through experimental and analytical methods. To verify the seismic performance, a cyclic loading test of the connection joint of the proposed modular system was conducted. As a result of this study, theoretical values and experimental results were compared with the initial stiffness, hysteresis behavior and maximum bending moment of the modular system. Also, the connection joint was modeled, using the commercial program ANSYS, which was then followed by finite element analysis of the system. According to the results of the experiment, the maximum resisting force of the proposed connection exceeded the theoretical parameters, which indicated that a rigid joint structural performance could be secured. These results almost satisfied the criteria for connection bending strength of special moment frame listed on KBC2016.

• Earthquakes and Structures
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• 제24권1호
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• pp.11-20
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• 2023

"Performance-based design (PBD)" is based on designing a structure with choosing a performance target under design criteria to increase the structure's resistance against earthquake effect. The plastic hinge formation is determined as one of the fundamental data in finite elements nonlinear analysis to distinguish the condition of the structure where more significant potential damage could occur. If the number of plastic hinges in the structure is increased, the total horizontal load capability of the structure is increased, also. Theoretically, when the number of plastic hinges of the plane frame structure reaches "the degree of hyperstaticity plus one", the structure will reach the capability of the largest ultimate horizontal load. As the number of plastic hinges to be formed in the structure increases towards the theoretical plastic hinge number (TPHN), the total horizontal load capability of the structure increases, proportionally. In the previous studies of the authors, the features of examining the new performance criteria were revealed and it was formulated as follows "Increase the total number of plastic hinges to be formed in the structure to the number of theoretical plastic hinges as much as possible and keep the structure below its targeted performance with related codes". With this new performance criterion, it has been shown that the total lateral load capability of the building is higher than the total lateral load capability obtained with the traditional PBD method by the FEMA 440 and FEMA 356 design guides. In this study, PBD analysis results of structures with frame carrier systems are presented in the light of the Turkey Building Earthquake Code 2019. As a result of this study, it has been shown that the load capability of the structure in the examples of structures with frame carrier system increases by using this new performance criterion presented, compared to the results of the examination with the traditional PBD method in TBEC 2019.

• 벤처창업연구
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• 제14권5호
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• pp.13-24
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• 2019

본 연구의 목적은 기업의 성공과 실패를 좌우하는 결정요인으로 제시되고 있는 창업가 역량과 기업성과 간의 관계를 고찰한 기존의 실증연구들을 체계적으로 통합하여 향후 연구에 이론적 기초를 제공하는 데 있다. 본 연구에서는 선행연구에서 창업가 역량과 기업성과 간의 관계를 고찰한 실증분석 결과가 혼재되어 있음에 따라, 메타분석 방법론을 통해 개별 연구에서 도출된 상이한 결과를 표준화된 통계치로 도출하고자 하였다. 이를 위해 본 연구에서는 선행연구의 이론적 고찰을 통해 기업성과에 영향을 미치는 주요 창업가 역량으로 기회인식 역량, 관리적 역량, 기술적 역량, 전략적 역량, 그리고 관계 역량을 선정하고 가설을 설정하였다. 다음으로 메타분석 수행 절차에 따라 15개의 연구를 최종 분석 데이터로 선정하고, 오픈소스 기반의 통계 프로그램인 R을 활용하여 메타분석을 실시하였다. 분석 결과를 요약하면 다음과 같다. 창업가의 기회인식 역량, 관리적 역량, 기술적 역량, 전략적 역량, 그리고 관계 역량은 기업성과를 유의하게 향상시키는 요인임이 확인되었다. 또한, 각 역량요인들은 기업성과에 모두 중간정도의 효과크기를 갖는 것으로 나타났다. 이들 변수 중 기업성과에 대한 효과크기가 가장 큰 역량은 전략적 역량이며, 그 다음으로 기회인식 역량, 관리적 역량, 기술적 역량, 그리고 관계 역량순으로 효과크기가 큰 것으로 분석되었다. 아직까지 창업가 역량과 기업성과 간의 관계를 메타분석을 통해 살펴본 연구는 국내에 부재한 실정으로, 본 연구의 결과를 통해 향후 연구의 이론적 기초를 발전시키는데 있어서 시사점을 제공할 수 있을 것으로 기대한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권10호
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• pp.2493-2508
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• 2012

The performance of a MIMO system with adaptive modulation (AM) and space-time coding over Ricean fading channels for perfect and imperfect channel state information (CSI) is presented. The fading gain value is partitioned into a number of regions by which the modulation is adapted according to the region the fading gain falls in. Under a target bit error rate (BER) constraint, the switching thresholds for AM are given. Based on these results, we derive the calculation formulae of the theoretical spectrum efficiency (SE) and average BER. As a result, closed-form SE expression and accurate BER expression are respectively obtained. Besides, using the approximation of complementary error function, a tightly closed-form approximation of average BER is also derived to simplify the calculation of accurate theoretical BER. Computer simulation shows that the theoretical SE and BER are in good agreement with the corresponding simulation, and the approximate BER is also close to the accurate one. The results show that the AM scheme in Ricean fading channel provides better SE than that in Rayleigh fading channel due to the direct-path propagation, and has performance degradation in SE and BER for imperfect CSI.

• 복식
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• 제43권
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• pp.125-142
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• 1999

This research was aimed to present a model of clothing products evaluation nd to classify the effect of extrinsic cues on clothing products evaluation. In order to accomplish following subjects were established. First it is to find the effect of extrinsic cues -price brand store - on perceived quality perceived risk perceived value and purchase intention of clothing products. Second it is to formulate a model of clothing products evaluation and find the relation among the variables such as extrinsic cues perceived quality perceived risk perceived value and purchase intention. This research was mainly divided into theoretical and empirical part. In the theoretical part previous theories and studies on clothing products cues clothing products evaluation perceived quality perceived risk and perceived value were examined to establish a research model and to present a theoretical frame for clothing products evaluation. In the empirical research a questionnaire was developed and statistical data were collected from during July 1997. The subjects were 862 women in the age of 20-35 living in Seoul and kyungki region. SAS and LISREL were used to analyze the collected data. frequency percentage factor analysis ANOVA duncan test correlation analysis regression analysis and LISREL were applied. The results of this research are as follows: First perceived quality consists of performance quality external quality and utility quality in a form of multi dimensional structural. Perceived risk is structured by social/resultant risk financial/fashionable risk and performance/management risk. Second this research proved that extrinsic cues are influenced by each individual variable and extrinsic cues interact with each other through the variable. The perceived quality is influenced most by price Among the perceived risk social/resultant risk by brand financial/fashionable risk by price and performance/management risk by store. respectively. Perceived value is inflenced by price and brand. Third in evaluating process consumer use extrinsic cues to first formulate perceived quality and perceived risk of clothing products and then formulate perceived value ot decide on purchase intention.

• 한국추진공학회지
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• 제19권3호
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• pp.47-53
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• 2015

이론성능해석을 통하여 메탄/산소 이원추진제 소형로켓엔진의 형상설계에 필요한 설계인자들을 도출하였다. 로켓엔진의 이론성능 분석을 위해 CEA를 이용하였고, 추력실 내부의 화학반응을 화학평형 상태로 가정하여 엔진의 형상설계에 필요한 최적의 추진제 혼합비, 특성길이, 최적 팽창비 등을 도출하였다. 인젝터의 경우, 미립화 성능이 우수하고, 다른 인젝터 형상에 비해 연소효율이 높은 스월 동축 인젝터를 설계하였다. 노즐형상은 80%의 길이를 갖는 벨형 노즐을 설계하였고, 추력실 내부압력 1.72 MPa, 총 추진제 질량유량 0.18 kg/s, O/F ratio 2.7일 때의 지상연소시험용 로켓엔진의 형상설계 결과를 제시한다.