• Journal of Labour Economics
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• v.22 no.1
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• pp.1-29
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• 1999

한국은 지난 1960년대 이후 실업률이 추세적으로 하락하여왔기 때문에 실업구조, 직업탐색에 대한 관심이 비교적 적었으나 최근의 고 실업률은 이에 대한 연구의 필요성을 제고시키고 있다. 기존의 연구들은 저 실업률 시기의 자료를 사용한 것이므로 1998년의 고 실업률 자료를 활용한 연구는 다른 연구결과를 가져올 것이다. 이 글은 고 실업률 시기로 진입한 지 1년이 되는 98년 11월말 광주광역시에서 실시된 상시고 실직자에 대한 설문조사자료를 이용하여 고 실업률 시기의 실직자의 직업탐색과 실업기간을 분석하였다. 본 연구결과는 기존의 연구결과와 많은 부분에서 일치하지만 한국에서 대량실업은 처음 겪는 상황이므로 이전의 연구결과와 다르거나 새로 확인된 사실들도 몇 가지 있다. 연구결과를 요약 정리하면 다음과 같다. 첫째, 비자발적 이유에 의한 실직자가 약 70%를 차지하고 구인배율이 아주 낮아 최근의 실업은 수요부족에서 발생한 것이라고 할 수 있다. 따라서 임금을 낮추고 희망하지 않는 직종 산업 종사상 지위로 하향 구직을 하고 있었다. 둘째, 고실업률이 장기화되면서 나타난 현상으로는 구직경로가 다양해졌고, 유보 임금 및 수락임금이 전직임금보다 약 20% 하락함으로써 임금이 신축적임을 보여 주었다. 그러나 고실업 사태를 급작스럽게 맞이하면서 이전임금에 대한 집착이 강하여 하락폭은 충분히 신축적이었다고 보기는 어렵다. 셋째, 실업보험수급자는 유보임금 하락률이 높았고 실업 탈출률도 높았다. 이것은 직업탐색이론과 상반된 결과로 노동수요부족사태를 처음 겪으면서 노동시장에 대한 정보가 모든 실업자에게 동일하지 않고, 실업보험수급자가 보다 완전한 정보를 가지고 있으며, 실업보험지급에 따른 구직독려 때문인 것으로 생각된다. 넷째, 기존 연구들과 마찬가지로 유보임금은 전직 임금에 크게 의존하였으며 실업기간에 대한 해자드 분석에 의하면 유보임금의 대리변수인 전직임금이 낮을수록, 구직을 적극적으로 할수록 탈출률일 높았다. 인적속성으로는 인적자본축적이 많고 다양한 취업정보를 접할 수 있는 고학력자의 탈출률이 높았다. 다른 나라에 대한 기존 연구의 근속기간이 긴 남성 실업자는 실업기간이 길었지만 여기서는 반대의 결과가 나왔다. 그것은 기업의 도산 등에 따른 실직자의 경우 유용한 인적자본 보유자가 많고 축적된 자산으로 자영업으로 탈출할 확률이 높기 때문인 것으로 해석된다.

• Journal of KIISE:Computer Systems and Theory
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• v.26 no.2
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• pp.211-222
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• 1999

본 논문은 위성간 링크를 이용하여 저궤도 위성망을 구성할 때 발생하는 링크할당 문제를 효율적으로 풀기 위한 기법을 제안한다. 제안된 기법은 먼저 위성 궤도운동의 주기성에 기반하여 저궤도 위성망을 유한상태기계로 모델링한 후에, 유한상태기계의 각 상태에서 최적의 링크할당을 구하기 위해서 조합형 최적화 문제에 많이 쓰이는 시뮬레이팅드 어닐리을 이용한다. 제안된 기법의 이점은 저궤도 위성망을 유한상태기계로 모델링함으로써 도적인 움직임을 보이는 저궤도 위성망에서의 링크할당 문제를 고정된 위상을 가지는 망에서의 링크할당 문제로 단순화시키고 이를 토대로 최적화기법을 적용할 수 있다는 것이다. 시뮬레이티드 어닐링에 의하여 최적화된 링크할당의 성능은 정규링크할당과의 비교.분석을 통해서 평가된다. 최적화된 링크할당과 정규링크할당의 성능분석을 위하여 정적경로배정과 동적경로배정 기법이 고려된다. 시뮬레이션을 통한 실험결과는 정적경로배정을 적용한 최적링크할당 기법이 호 봉쇄확률 측면에서 최고의 성능을 가짐을 보여준다. 링크할당기법이 같은 경우에는 정적경로배정이 동적경로배정보다 우수한 성능을 보이는데 이는 동적경로배정의 경우에 상태전이 후에 경로배정 표가 안정화되기 위해서 많은 시간을 필요로 하기 때문이다. 본 논문에서는 제안된 링크할당 기법은 작은 용량의 위성간 링크를 가지고서 많은 호에대한 서비스를 제공하고자 할 때 유용하며, 호의 서비스를 위하여 실제로 필요한 위성간 링크의 용량은 실험결과로부터 유추될 수 있다.

• Journal of KIISE:Information Networking
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• v.29 no.5
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• pp.553-561
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• 2002

We present a novel service discipline, called linear service discipline, to serve multiple QoS queues sharing a resource and analyze its properties. The linear server makes the output traffic and the queueing dynamics of individual queues as a linear function of its input traffic. In particular, if input traffic is Gaussian, the distributions of queue length and output traffic are also Gaussian with their mean and variance being a function of input mean and input power spectrum (equivalently, autocorrelation function of input). Important QoS measures including buffer overflow probability and queueing delay distribution are also expressed as a function of input mean and input power spectrum. This study explores a new direction for network-wide traffic management based on linear system theories by letting us view the queueing process at each node as a linear filter.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.5
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• pp.302-307
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• 2017

Draft ice in polar regions is formed due to sea level changes and various environmental factors cause damage due to collision with offshore plants and ships for resource development. Drift ice in polar regions is a potential source of accidents for offshore plants that perform long-term operations in one place, as well as on the ship. To prevent accidents with drift ice, offshore plants and ships in polar regions use satellite image information and detection radar to detect drift ice. However, the inability to use visible satellite images at night significantly lowers the detection probability by radar for small drift ice. In this study, we used a thermal imaging system which can be operated day and night for the detection of drift ice, and carried out an experimental study on the detection characteristics of drift ice. To examine the night operation of the thermal imaging system, the experimental condition was set and the thermal image was measured according to the measurement angle change. Under this condition, the correlation was analyzed by theoretical calculating the radiant energy of the drift ice and the sea water.

• International Journal of Highway Engineering
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• v.13 no.4
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• pp.71-79
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• 2011

Korean national highway has been increased 2 times more for the past ten years because of many highway geometric improvements and new routes since 2000. According to the reasons, maintenance cost has been increased continuously. Deterioration of concrete bridge decks caused by asphalt pavement deformation occupies a high proportion of overall bridge management budget. The number of current highway bridges has reached over 7,800 in 2011, and It is difficult to determine to some future budget. This study predicted the remaining life of concrete bridge decks using the reliability analysis based on Weibull distribution. and The expected future maintenance cost was estimated.

• Tunnel and Underground Space
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• v.28 no.4
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• pp.343-357
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• 2018

Algorithm which can analyze the slope failure behavior utilizing the comprehensive information of the dense point of joint poles and the joint set orientations, both of which are obtained statistically, and the defect pattern of pole distribution has been developed. This method overcomes the potential incorrectness of the hemispheric projection method utilizing the joint set orientations only and also enhances the reliability of slope failure analysis. To this end a method capable of calculating the joint dispersion index directly from the joint pole distribution, instead of contour map, has been devised. The representative orientations for the slope failure analysis has been determined by considering the number and orientations of cone angle-dependent joint sets as well as the joint dispersion index. By engaging these representative orientations to the hemispheric projection analysis more reliable slope failure examination has been carried out. Sensitivity analysis for the potentially unstable slope of plane failure mode has been performed. Significance of joint strength index and the external seismic loading on the slope stability has been fully analyzed.

• The Korean Journal of Applied Statistics
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• v.6 no.1
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• pp.125-143
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• 1993

The primary objective of the paper is to review the development of approximations of the null distribution of a scan statistic and to show how these approximations were improved. Let $X_1, \cdots, X_N$ be a sequence of independent uniform random variables on an interval (0, t]. A can statistic is defined to be the maximum number of observations in a subinterval of length t $\leq$ T, when we continuously (or discretely) move the subinterval from 0 to T. A scan statistic is used to test whether certain events occur in a cluster aganist a null hypothesis of the uniformity. It is difficult to calculate the exact null distribution of a scan statistic. Several authors have suggested approximations of the null distribution of a scan statistic since Naus(1966). We conceive that a scan statistic can be used for detecting a "hot region" is defined to be a region at which the frequencies of mutations are relatively high. A "hot region" may be regarded as a generalized version of a hot spot. We leave it for a further study the concrete formulation of deteciton a "hot region" in a mutational spectrum.uot; in a mutational spectrum.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.8C
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• pp.645-654
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• 2012

In this paper, we consider a two-way relay (TWR) system, where two user nodes exchange their information within two transmission phases, by the help of a relay node adopting physical layer network coding. In the system, two users transmit their binary phase shift keying symbols simultaneously in the first phase, and the relay node decodes the XORed version of two user data and broadcasts it back to two users in the second phase. The performance of the system is analyzed in terms of the average end-to-end symbol error probability in Nakagami-m fading channels, for which a tight upper bound is derived in a closed form to provide an accurate and handy estimate on the performance. The results show that our upper bounds are almost indistinguishable from simulation results for various channel and system configurations. In addition, the optimal relay location and power allocation for various conditions can be obtained quickly with our analysis.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.4
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• pp.10-16
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• 2007

This paper analyzes the output signal-to-interference-plus-noise ratio (SINR) for a multiple-input-multiple-output (MIMO) multicarrier code division multiple access (MC-CDMA) system with minium mean square error receivers. A previous work of a single antenna MC-CDMA system cannot directly applied to a MIMO MC-CDMA system because some assumptions for single antenna do not match the case of multiple antenna. Therefore this paper expands the concept of freeness to MIMO system by using the Marcenko Pastur law. The analysis shows that the output SINR asymptotically converges to a deterministic value and finds the value on the assumption of freeness. From the analysis, it is easy to calculate bit error rate and the calculation is verified by simulations.

• Journal of the Korea Society for Simulation
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• v.17 no.3
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• pp.35-44
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• 2008

Facility location problem is an important subject in many areas of modern business environment. In this paper, we deal with uncapacitated and multi-period facility location problem where the object is a maximization of total profit within predetermined cost. We assume that all demand have to be met. Particularly, we represent various types of customer based on four well-known urban spatial structures to represent a spread of customers. Those are concentric zone model, sector model, multiple nuclei model and star model respectively. We apply to the genetic algorithm to simulate a large scaled problem and develop simulator. We analyze both optimal numbers and locations of facilities for each urban structure. Furthermore, we examine the appropriate time to further expansion of the facilities in the planning horizon. The experimental results show that the developed algorithm can be applied effectively to the facility location problem in the various types of urban area.