• The Journal of Korean Institute of Communications and Information Sciences
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• v.14 no.5
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• pp.472-485
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• 1989

This paper represents the occurrence structure of the timing variation of TV horizontal synchronizing pulse(H-sync pulse) in mobile TV reception. Fluttering ghost is caused by timing varations of the H-sync pulse and is due to frequency elective fading in a multipath propagation envoronment. H-sync timing fluctuations, and hence, fluttering ghost are directly correlated with the multipath parameters, i.e., H-sync timing fluctuations reflect well the severity of the multipath environment. The occurrence structure of H-sync timtng fluctuation is analysed theoretically in relation to the multipath environnment. The occurrence structure of H-sync timing fluctuation is analysed theoretically in relation to the multipath parameters, assuming the two-ray propagation model. The H-sync timing fluctuation occurs with the variation in relative phase and /or D/U variation of long-delayed multipath waves.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.46 no.1
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• pp.22-27
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• 2009

Bilateral teleoperation systems, connected to computer networks such as Internet have to deal with the time delay depending on factors such as congestion, bandwidth or distance. And the entire system is easy to become unstable due to irregular time delay. Passivity concept has been using as a framework to solve the stability problem in bilateral control of teleoperation. In this paper, we present a suitable time varying gain inserted in the transmission path that can recover passivity provided a bound on the rate of change of the known delay. Simulation results are presented showing the performance of the resulting control architecture.

• KDI Journal of Economic Policy
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• v.13 no.3
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• pp.55-74
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• 1991

토지문제(土地問題)의 심각성에 대한 사회적(社會的) 합의(合意)에도 불구하고 정부의 개입으로 시정되어야 할 구체적인 정책목표(政策目標)가 무엇인가에 대한 검토(檢討)는 부족한 설정이며, 이를 위해 지가상승(地價上昇)의 원인과 결과에 대한 실증분석(實證分析)을 시도한 예도 찾아보기 힘들다. 본고는 지가상승률(地價上昇率)과 일단의 거시경제변수(巨視經濟變數) 변화율(變化率) 사이에 Granger 개념의 인과관계(因果關係)가 존재하는가를 검증하고 그 현실적인 의미를 살펴보고 있다. 지가상승추세(地價上昇趨勢)를 변화시킬 수 있는 거시변수(巨視變數)는 통화량(通貨量), 민간건설생산(民間建設生産), 주가지수(株價指數)의 변화 등이며, 지가상승이 영향을 미치는 변수(變數)들은 주가지수(株價指數), 실질생산(實質生産) 및 민간건설생산(民間建設生産)의 변화(變化), 사채이자율(私債利子率)로 나타났다. 여기서 포착된 경험적 증거들은 인과관계(因果關係)의 작동경로를 설명하는 이론과 결합되어 발전되어야 할 것이나 우리의 분석결과로부터도 몇가지 정책적(政策的) 시사점(示唆點)을 끌어 낼 수 있다. 무엇보다도, 지가상승(地價上昇)을 거시경제현상(巨視經濟現像)으로 파악하는 것이 필요하며, 거시경제환경이 불안정한 경우 토지조세(土地租稅)와 같은 미시적(微視的) 정책수단(政策手段)이 지가안정 등의 정책목표(政策目標)를 달성하는 데는 뚜렷한 한계가 있다는 것이다. 지가상승(地價上昇)이 물가상승(物價上昇)을 가속화한다는 것도 중요한 점인데 통화긴축(通貨緊縮)과 같은 정책수단이 물가(物價)와 지가(地價)를 모두 안정시킬 수 있다는 점은 다행한 일이다. 또한, 건설생산액(建設生産額) 변화와 지가상승(地價上昇)간의 관계는 적극적인 개발투자(開發投資)가 장기적인 지가안정(地價安定)에도 도움을 준다는 쪽이므로 사회간접자본(社會間接資本)의 확충(擴充), 민간건설(民間建設)의 확대(擴大)가 지속적으로 이루어지도록 해야 할 것이다.

• Korean Journal of Social Welfare
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• v.62 no.4
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• pp.377-402
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• 2010

This study examines the effects and process of housing poverty on children's physical health, internalizing problems and academic achievement using the first Korea Welfare Panel Study. The results show that sub-minimum standard housing condition and housing expenditures have increased the housing instability, non-study activities, while harming parent's health and decreasing non-housing expenditures. And this process negatively affects children's internalizing problems and academic achievement. The findings of this study have value for controlling the confounding factors as income poverty, neighborhood poverty and characters of household. This research is significant in that it develops the theoretical model of housing poverty and suggests the necessity of interventions to alleviate housing poverty.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.3
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• pp.397-408
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• 1988

The study is concerned with the theoretical and experimental investigation of the elliptical bulge test. The elliptical bulge test is analyzed by using a rigid-plastic finite element method incorporating large deformation and normal anisotropy. Thin elliptical diaphragms of mild steel are bulged for three aspect ratios. The contact problem the die round and the sheet is successfully solved by using a skew boundary condition. It is shown that the proper consideration of die radius and normal anisotropy is very significant. The relation between bulging pressure and deformation is obtained. It has been found that the pole is nearly under proportional straining during deformation. The instability criterion by maximum load condition enables the effective prediction of instability pressure. The computional results are in good agreement with experimental results and to be very useful for a better understanding of the elliptical bulge test.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.6
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• pp.591-598
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• 1984

The results of measurements showing normal vibrations and rubbing noise generated during unlubricated smooth sliding between metal surfaces are presented. The measurements were made on pin-on-disc type apparatus instrumented with piezoelectric acceleration transducers and microphones. Spectral analysis of the both signals up to frequency of 10kHz indicates that they are closely correlated. The major components of both signals in this frequency range are primarily associated with the normal contact vibrations which are excited by surface irregularities being swept through the contact region during sliding. As an approximation to the seismic input of surface irregularities, an effective surface wavenumber spectrum was assumed in the form of an inverse vibration and noise measurements for a number of surface finishes and mean loads. The predominant frequency component of which levels of the normal vibration and noise are close to overall levels of the both signals is induced by contact resonance between the two bodies and its frequency can be calculated from the Hertzian theory.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.1
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• pp.96-104
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• 1989

The behaviors of acoustic emission emitted in the tests of the fracture toughness and fracture stability are observed by using the specimens of aluminum 2024-T351 and 7039-T6 alloys. The empirical eqution of J-R curve is derived. It is demonstrated from the comparison of the fracture toughness obtained from J-R curve with that from ASTM standard E813-81 that the latter is larger than the former. The discontinuous point in the log-log graph of J-integral vs. total acoustic emission count is observed in between the two offset lines referred from ASTM standard E813-81, but it's physical meaning is uncretain. An empirical material tearing modulus is derived in terms of the total acoustic emission count and proved to be valid in fracture instability test.

• Journal of the Society of Disaster Information
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• v.11 no.4
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• pp.527-533
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• 2015

A simplified method for the calculation of dynamic characteristics of initially stressed antisymmetric cross-ply laminated shells is presented in this paper using the natural frequencies under unloading state. The equation of motion of laminated shell with two opposite edges simply supported is investigated on the basis of Rayleigh-Ritz method and Mindlin shell theory with effect of the curvature term. The relationships of the non-dimensional natural frequencies with initial stresses the coeffcients of critical buckling and the boundaries of te dynamic principal instability region can be characterized by the non-dimensional natureal frequencies under unloading state. Numerical examples are presented t verify the simplified equations and to illustrate potential applications of the analysis.

• Journal of the Korean BIBLIA Society for library and Information Science
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• v.25 no.4
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• pp.59-78
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• 2014

Since 2010, the itinerant librarian project has aimed to support small libraries and to establish cooperative systems between public libraries and small libraries. However, the project has been criticized for several issues, although there are some positive evaluations. In this context this study aims to analyze various issues of the project and to provide alternative strategies. Based on analyzing previous studies the study discusses the concept and social background of itinerant librarians. Furthermore, it explores the issues of the project, including low awareness and employment instability of itinerant librarians through the interviews with participants of the project. As a result, the study provides six alternative strategies to improve the project.

• Journal of Ocean Engineering and Technology
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• v.7 no.1
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• pp.13-24
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• 1993

The dispersion in the oscillatory flow generated by gravitational waves above the spatially periodic repples is studied. The steady parts of equations describing the orbit of the passive particle in a two dimensional field are assumed to be simply trigonometric functions. From the view point of nonlinear dynamics, the motion of the particle is chaotic under externally time-periodic perturbations which come from the wave motion. Two cases considered here are; (i) shallow water, and (ii) deep water approximation.