• 한국통신학회논문지
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• 제21권9호
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• pp.2433-2443
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• 1996

In this paper, a new technique is proposed for obtaining the error probabilities of the VSB(vestigial sideband modulation) signal in the presence of the cochannel interference and frequency-selective fading channel. For the receivers, a suboptimal matched filter receiver and the MLSE(maximum likelihood sequence estimation) receiver, which is known to be optimal on the fading channel, are considered. First, for the matched filter receiver, the distributions of the random variables, which determine the SER(symbol error rate) are obtained by decomposing the multi-path fading channel into Rayleigh distributed main path and Gaussian distributed remained path channels. the random variables mean the energy of the main path and subpath respecitively, and SER can be calculated from the distribution of them. Next, for the case of the MLSE receover, it is found that the random variables are expressed as a function of integrals. In order to obtain the distribution for the random variables, we expanded each element of integrals with the KL(Karhunen-Loeve) transformation. And it is derived that the distributions for the transformed random variables are given by a sum of chi-square distributions. Finally, we calculated the error rate derived formula on the two-ray fading channel, which is one of widely used models for the frequency-selective fading channel. From the numerical results, it is found that for the matched filer receiver, performance degradation is significant, while the performance degradation at the MLSE receiver is insignificant on the frequency-selective fading channel. However, in case of cochannel interference environment, the error rateis found to increase significantly both at the matched filter and at the MLSE receiver.

• 대한교통학회지
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• 제33권2호
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• pp.192-203
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• 2015

보행자는 일반적인 보행로뿐만 아니라 건물을 통과하거나 넓은 공간을 가로지르는 등의 비정형적인 보행 경로를 통해 다양한 방식으로 이동한다. 본 연구는 이러한 보행 경로를 social path로 정의하여 보행 네트워크의 범주 안에 포함시켜 정의하였다. 기존의 보행 접근성 연구에서는 이러한 보행 경로를 고려하지 못해 대상지의 공간적 위계 수준과 각 가로의 연결성을 올바르게 평가하지 못하였다. 이를 개선하기 위해 본 연구는 대중교통의 요지임과 동시에 상업 시설이 밀집된 서울의 주요 대상지를 선정하여 social path의 효과 분석을 수행하였다. 이를 위해서는 네트워크 공간 분석에서 활용되는 space syntax 기법의 공간 통합도(Integration)를 평가 지표로 설정하였다. 분석 결과, social path로 인해 각 가로의 연결성이 변화됨과 동시에 보행자의 최적 경로가 합리적으로 바뀌는 것으로 나타났다. 특히, 대상지 내부의 주요 가로와 social path의 개선효과가 두드러졌다. 이러한 점을 통해 social path의 연결성이 뛰어나고 보행자의 최적 경로를 보다 현실적으로 구현할 수 있다는 점을 증명하였다.

• 한국군사과학기술학회지
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• 제13권5호
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• pp.824-830
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• 2010

It is not easy job to find a underwater target using sonar system in the ASW operations. Many researchers have tried to solve anti-submarine search problem aiming to maximize the probability of detection under limited searching conditions. The classical 'Search Theory' deals with search allocation problem and search path problem. In both problems, the main issue is to prioritize the searching cells in a searching area. The number of possible searching path that is combination of the consecutive searching cells increases rapidly by exponential function in the case that the number of searching cells or searchers increases. The more searching path we consider, the longer time we calculate. In this study, an effective algorithm that can maximize the probability of detection in shorter computation time is presented. We show the presented algorithm is quicker method than previous algorithms to solve search problem through the comparison of the CPU computation time.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 추계학술대회논문집
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• pp.208-214
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• 2000

Reduction of structure-borne noise of the compartment in a car is an important task in automotive engineering. Transfer path analysis using vibroacoustic reciprocity technique or multiple path decomposition method has generally been used for structure-borne noise path analysis. These methods are useful in solving particular problem but do not quantify the effectiveness of vibration isolation of each isolator of a vehicle. To quantify the effectiveness of vibration isolation, the vibrational power flow has been used for a simple isolation system or a laboratory based isolation system. It is often difficult to apply the vibrational power flow technique to the complex isolation system like a car. In this paper, a simple equation is derived for calculation of the vibrational power flow of an isolation system with multiple isolators such as a car. It is successfully applied to not only quantifying the relative contributions of eighteen isolators but also reducing structure-borne noise of a passenger car. According to the results, the main contributor of eighteen isolators is the rear roll mount of an engine. The reduced structure-borne noise level is about 5dBA.

• 한국콘텐츠학회논문지
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• 제14권10호
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• pp.562-569
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• 2014

본 연구의 목적은 응급실을 경유한 정신 및 행동장애 중 기분[정동]장애만을 주상병으로 하는 입원환자와 정신 및 행동장애를 부상병으로 동반한 기분[정동]장애 입원환자의 총진료비에 미치는 영향 요인을 알아보고자 한다. 본 연구는 건강보험심사평가원 2009년 표본자료에서 응급실 경유 입원환자가 '정신 및 행동장애'(F00-F99)중에서 주상병 코드가 기분[정동] 장애(F30-F39)인 환자와 부상병 코드가 '정신 및 행동장애'(F00-F99)를 가진 환자를 추출하여 753명을 분석 대상으로 사용하였다. 본 연구에서 수집된 자료는 통계 프로그램 SPSS 18(Statistical Package for the Science)을 이용하여 빈도분석, t-test, ANOVA, 다중회귀분석을 실시하였다. 연구결과는 주상병의 경우, 총진료비에 영향을 미치는 변수들은 연령을 제외한 모든 성별(p<.01), 응급실 도착경로(p<.001), 진료 결과(p<.001), 입원일수(p<.001) 변수들이 통계적으로 유의한 것으로 나타났다. 또한 부상병의 경우, 총진료비에 영향을 미치는 변수들은 살펴보면, 모든 변수 즉 성별(p<.01), 연령(p<.001), 응급실 도착경로(p<.001), 진료 결과(p<.001), 입원일수(p<.001) 등이 통계적으로 유의한 것으로 나타났다. 앞으로 정부는 장기적이고 지속적으로 국민의 정신건강을 위해 효율적인 방안을 마련하고 효과적인 예방 및 관리, 정신건강 중재 프로그램 개발, 정신건강관련 진료지침, 맞춤형 치료 및 상담서비스 등 사전 사후 체계적인 정신건강증진 종합대책을 추진해야 할 것이다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.183-188
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• 2003

This study is to make the fundamentals of sound quality evaluation in regard of acoustical characteristics of passenger compartment. The deviation of frequency response function level within audible frequency is evaluated at receiving point in the research of room acoustics. In this study, frequency response function is the one between speaker and driver's ear positions. The positions of driver and audio speakers are optimized by analysis of acoustic mode of acoustic cavity. The main reflection planes are determined by analysis sound ray path diffused at optimized speaker positions. Finally, designer selects acoustical material by analysis of absorption effect of acoustical materials on the main reflection planes in order to avoid to distortion and fluctuation of frequency response function..

• 경영과학
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• 제27권2호
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• pp.1-20
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• 2010

Many firms are trying to acquire innovative technologies and relative knowledge by offshoring R&D work. Although research to date has focused on the multinational corporations' motivations of R&D offshoring, such as cost reduction and market expansion, little is known about external or environmental factors influencing the performance of global R&D activities. We investigated the relationship between the offshore R&D performance and the technical capabilities of the parent company, the host country and the home country as enhancers from outside R&D facilities. The analysis uses European patent data and EU R&D scoreboard of 134 overseas R&D labs from 46 multinational corporations in 2005. Also, we calculated total patent number of each country for this. Results from path analysis supported our main hypothesis that the technological capabilities of the parent company and the host country positively affect the overseas R&D performances. By multi-group analysis, we also found that the relationships among the variables are different for each industry.

• 한국정보전자통신기술학회논문지
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• 제12권3호
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• pp.201-210
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• 2019

본 논문에서는 농장의 위성 사진 혹은 드론 사진을 이용하여 농장을 구분하고 농장 드론과 트랙터의 자율주행 및 행동을 제어하는 'AMCS(Agricultural Machine Control System)'를 제안한다. AMCS는 드론과 트랙터의 센서 데이터 및 비디오 영상 데이터로부터 농장 경계를 구분하고, 메인 서버에서 원격 제어 명령어를 읽어 들인 후 드론 및 트랙터 스프링클러와의 연동을 통해, 관리지역 내의 원격 제어 명령을 전달하는 'LSM(Local Server Module)'과 드론과 트랙터가 농장 밖에서 농장으로 이동하는 경로와 농장 안에서 저비용, 고효율로 일을 처리할 수 있는 경로를 설정하는 'PSM(Path Setting Module)'으로 구성된다. 본 논문에서 제안하는 AMCS의 성능분석 결과 AMCS의 PSM은 외부 출발점에서 농장까지 도달하는 경로를 설정할 때 다익스트라 알고리즘보다 약 100% 향상된 성능을 보였으며, 농장 내부 작업 경로를 설정할 때 기존 경로보다 약 13% 높은 작업 효율을 보였고 36% 낮은 작업 거리를 설정했다. 따라서 PSM은 기존 방식보다 더 효율적으로 트랙터와 드론을 제어할 수 있다.

• International Journal of Automotive Technology
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• 제4권1호
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• pp.21-30
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• 2003

In this paper a systematic test procedure for evaluation of road-induced noise of a vehicle and guidelines for each test are presented. Also, a practical application of the test procedure to a small SUV is presented. According to the test procedure, all the tests were performed to evaluate road-induced booming noise that is in low frequency range. First of all the information on characteristics of road-induced noise was obtained through baseline test. Coupling effects between body structure and acoustic cavity of a compartment were obtained by means of modal tests for a structure and an acoustic cavity. Local stiffness of joint areas between chassis system and car-body was determined by test for measurement of input point inertance. Noise sensitivities of body joints to operational forces were obtained through test for measurement of noise transfer functions. Operational deflection shapes made us analyze behaviors of chassis system under running condition and then find sources of noise due to resonance of the chassis system. Finally, Principal Component Analysis and Transfer Path Analysis were utilized to investigate main paths of road-induced noise. In order to evaluate road-induced booming noise exactly, all of tests mentioned above should be performed systematically.

• 한국IT서비스학회지
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• 제17권4호
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• pp.37-52
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• 2018

With the increasing severity of the shortage of highly-skilled IT personnel, more and more attention is being paid to the professional career path and systematic career management of IT employees. Although some studies have been conducted to describe the current status of IT personnel, limited attempts have been made to analyze the career paths or career patterns of IT professionals from a longitudinal perspective. In this context, this study explored the job career patterns of IT professionals in Korea and examined their relationship with subjective and objective career success. To identify job career patterns over time, detailed information about jobs and positions were used and an optimal matching analysis (OMA) was conducted to calculate the dissimilarity matrix between employees' career sequences, while a cluster analysis was used to categorize the meaningful groups based on this dissimilarity data. This analysis revealed that career patterns among Korean IT personnel are more varied than previously thought. These career types have a significant relationship with individual profiles, such as age, education, industry and company size, and account for significant variations in the three main career success variables, i.e. quality of life, assessment of software quality, and wage level. It is expected that the findings of this study will contribute to refining the Korean career path so as to retain IT personnel, and raise the need to improve the low quality of life and poor SW work environment of IT personnel.