• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.2
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• pp.301-307
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• 2015

In this paper, we consider wiretap channels in the presence of an eavesdropper assuming spatially correlated MIMO(multiple-input multiple-output) channels, where we analyze a physical layer security performance of orthogonal space-time block code(OSTBC) using one-bit feedback assuming cross polarized antennas at each node. In this paper, we present a method to select a transmit-antenna group for OSTBC using one-bit feedback(O-OSTBC) and compare secrecy outage probabilities of various transmit-antenna grouping methods. Especially, we propose an efficient transmit-antenna grouping method by comparing secrecy outage probabilities of O-OSTBC and conventional OSTBC in highly correlated MIMO channels.

• Journal of the Korean Society of Child Welfare
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• no.59
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• pp.1-23
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• 2017

Using a subsample of 3,409 unmarried smothers and their children from the Fragile Families and Child Wellbeing study, the present study examined the cross-lagged effects of unmarried fathers' involvement on their children's behavior problems. Father involvement was used as a latent variable to measure the frequency of fathers' visits to the child, fathers' instrumental support, and their supportive parenting. Both variables of father involvement and child behavior problems were repeatedly measured at child ages 3, 5, and 9 to estimate their trends over time. The results indicated that fathers' more active engagement in parenting at child ages 3 to 5 reduced behavior problems in children at ages 5 to 9. Further discussions include programs and services to support unmarried fathers through education and training opportunities for effective parenting, relationship skills, and conflict resolutions as well as policy strategies to encourage their continuous involvement in the lives of their children.

• Journal of Technology Innovation
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• v.28 no.4
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• pp.63-93
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• 2020

We suggest a new way of specifying the co-evolution of product and process technologies, and integrating it into one of the well-received technology intelligence tools - a technology radar. Cross impact analysis enables us to identify the core technologies of product-process co-evolution. Combining expert judgment with its results, we can clarify the technological co-evolution trajectory with mainstream as well as emerging core technologies. Reflecting these in the assessment process of a technology radar, we could improve reliance of the technology assessment process and technology portfolio. From the academic perspective, our research provides a point where the co-evolution theory encouners technology intelligence methods. Practically, strategic capability of future-preparedness and strategic management could improve by adopting our method based on our example of co-evolution of semiconductor product and process technologies.

• Communications of Mathematical Education
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• v.18 no.1 s.18
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• pp.111-121
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• 2004

본 발표는 사칙연산과 약수와의 관계, 그리고 소인수 분해와 약수와의 관계를 통한 약수와 공약수, 최대 공약수를 구하는 방법과 약수의 범위 등에 대해서 내용 연구를 하였다. 또한 교차연결고리가 부족한 부분에 스키마식 수업 모델을 제시하여 수학의 연계성과 위계성을 강조함으로써 학생들로 하여금 수학의 구조를 파악하게 하여 수학에 대한 흥미와 필요성을 알게 하고자 한다.

• Communications for Statistical Applications and Methods
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• v.17 no.2
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• pp.241-253
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• 2010

As standard unit root tests are empirically proved to fail to reject the null hypothesis of a unit root for many economic and business time series, it is doubtful that most of those series are informative about the existence of a unit root or that those tests are powerful against relevant alternative hypotheses. This study attempts to perform tests of the null hypothesis of stationarity as well as tests of the null hypothesis of a unit root using the time series data of housing prices in the major metropolitan areas. The results of the additional analyses such as lead-lag, cross-correlation and impulse response for testing the statistical interrelationships between the prices are generally found to be consistent.

• Journal of the Korean Institute of Gas
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• v.13 no.2
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• pp.7-13
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• 2009

In order to make the critical path analysis of gas pipeline located under rigid pipes for interference behavior, FE analysis is performed considering real buried conditions of a drain and a gas pipe according to intersection angle of two pipes. A drain pipe and gas pipe have cover depth respectively 1.0m and 3.39m and this study considers a interference angle in the range of $0{\sim}90^{\circ}$. In this paper, the critical path is analyzed from the result of Ring Deflection and bending stress according to intersection angle. In the event intersection angle of two pipes equal to the critical path of lower pipe. The analysis results show that the critical path of lower gas pipe according to interference behavior has relation to intersection angle of two pipes.

• Korean Journal of Family Social Work
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• no.55
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• pp.31-58
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• 2017

This study aims to explore the longitudinal reciprocal relationship between family conflict and depression level of household head. Using the Korean Welfare Panel study (KOWEPS) of 2006-2009, the study applied multiple regression analysis and autoregressive cross-lagged model to test the hypothesis. Results of multiple regression analysis indicate that single direction of the impact of family conflict on a head of household's levels of depression and the vise versa were statistically significant. That is, higher level of family conflict in 2006 caused an increased levels of depression of household head in 2009, controlling gender, age and depression level in 2006. Also, the higher level of depression of household head in 2006 increased the level of family conflict in 2009 fixed with same control variables. The autoregressive and cross-lagged coefficients of family conflict and a head of household's levels of depression were statistically significant during the 4 years. The findings support the family system theory, indicating that there are reciprocal causal relationships between the whole family conflict and individual depression level. The strategies of social welfare practice and policy should thus aim to decrease individual's levels of depression and improve positive family function simultaneously to break the vicious circle.

• Korean Journal of Remote Sensing
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• v.38 no.5_1
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• pp.587-596
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• 2022

Sea levels are rising as a result of climate change, and low-lying areas along the coast are at risk of flooding. Therefore, we tried to investigate the relationship between sea level change and climate indices using satellite altimeter data (Topex/Poseidon, Jason-1/2/3) and southern oscillation index (SOI) and the Pacific decadal oscillation (PDO) data. If time domain data were converted to frequency domain, the original data can be analyzed in terms of the periodic components. Fourier transform and Wavelet transform are representative periodic analysis methods. Fourier transform can provide only the periodic signals, whereas wavelet transform can obtain both the periodic signals and their corresponding time location. The cross-wavelet transformation and the wavelet coherence are ideal for analyzing the common periods, correlation and phase difference for two time domain datasets. Our cross-wavelet transform analysis shows that two climate indices (SOI, PDO) and sea level height was a significant in 1-year period. PDO and sea level height were anti-phase. Also, our wavelet coherence analysis reveals when sea level height and climate indices were correlated in short (less than one year) and long periods, which did not appear in the cross wavelet transform. The two wavelet analyses provide the frequency domains of two different time domain datasets but also characterize the periodic components and relative phase difference. Therefore, our research results demonstrates that the wavelet analyses are useful to analyze the periodic component of climatic data and monitor the various oceanic phenomena that are difficult to find in time series analysis.

• Proceedings of the Korea Contents Association Conference
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• 2014.11a
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• pp.377-378
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• 2014

본 연구의 목적은 청소년기의 사회적 위축과 또래관계, 그리고 우울 간에 어떠한 종단적 관계가 있는지 검증하고자 하는 것이다. 이를 위하여 본 연구에서는 한국아동 청소년패널조사(KCYPS) 중학교 1학년 2, 3차년도 자료에 대하여 자기회귀 교차지연모형을 구성하고 이에 대하여 구조방정식을 이용하여 실증적 검증을 실시하였다. 분석 결과, 2차년도의 사회적 위축, 또래관계, 우울은 각각 3차년도의 동일한 변인에 대하여 유의한 영향을 미치는 것으로 나타났으며, 2차년도의 또래관계는 3차년도의 사회적 위축과 우울에 모두 유의한 영향을 미치는 반면, 2차년도의 사회적 위축과 우울은 각각 3차년도의 또래관계에만 유의한 영향을 미치는 것으로 확인되었다. 이상에서 도출된 연구 결과에 근거하여 사회적 위축과 또래관계, 그리고 우울을 경험하고 있는 청소년들에 대한 예방 및 개입과 관련된 함의가 제시되었다.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.22 no.4
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• pp.14-34
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• 2023

The purpose of this study was to calculate the appropriate yellow-signal time for intersections, to find out the relationship between the approach speed and intersection width when calculating the time, and to secure safety by minimizing conflicts and dilemma sections in intersections that change according to the signal operation. For this purpose, 6,824 data points from 5 intersections were collected and analyzed. The main results of the study are as follows. First, the approach speed of individual vehicles in different lanes was analyzed, and the width of an intersection was defined by considering the conflict in each direction. Second, we developed a multiple regression model based on the approach speed and conflict points, which compensated for the problems of an existing formula. Third, a standard table is presented for applying the appropriate yellow-signal time according to the approach speed and intersection width based on a development formula. A method is also presented to determine the safety of the length of the dilemma according to the change in the yellow-light time by presenting a calculation table that can cross-analyze the yellow-signal time and a dilemma section using the relationship.