• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.6B
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• pp.517-526
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• 2006

In order to achieve high capacity and reliable link quality in wireless communication, the significant efforts should be concentrated on mitigating interference between cells. To solve the interference problem, the newly introduced concept of a Distributed Wireless Communication System (DWCS) can provide the capability of joint control of the signals at multiple cells. This paper proposes a new concept of virtual cell: the Dual Virtual Cell (DVC), and also proposes DVC employment strategy based on DWCS network. The proposed system manages two kinds of virtual cell. One is the Active Virtual Cell which exists for user's actual data traffic and the other is the Candidate Virtual Cell which contains a set of candidate antennas to protect user's link quality from performance degradation or interruption. The proposed system constructs DVC by using antenna selection method. Also, for multi-user high-rate data transmission, the proposed system introduces multiple antenna technology to get a spatial and temporal diversity gam and exploits space-Time Trellis Codes known as STTC to increase a spectral efficiency.

• Journal of Advanced Navigation Technology
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• v.14 no.5
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• pp.625-631
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• 2010

In this paper, robustness performance of SNUR message is compared with those of existing ones, RTCM(Radio Technical Commission for Maritime Services) v2 MT(Message Type) 18/19 and MT 20/21 under a poor broadcast condition such as temporary data loss or disconnection We defined the temp oral data loss as 2 second delay and reconnection after disconnection as 7 second latency, and then evaluated its robustness for each latency case by double differentiating the observables. Our result shows that SNUR protocol method can reduce the latency error of the existing RTCM messages by 30~60%. Moreover, a rover using SNUR message, whose latency error is bounded within 1/4 L1 wave length, can figure out its own fixed position continuously in spite of 7 second disconnection, while the other using RTCM message, whose error is larger than half wave length, cannot keep its previous fixed solution.

• Korean journal of applied entomology
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• v.49 no.4
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• pp.289-297
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• 2010

The loss of natural habitats and their fragmentation caused by human activities pose a great threat to biodiversity worldwide, reducing animal population to small, fragmented patches of natural habitat. In this paper, a metapopulation dynamics of Sericinus montela koreanus, a species of butterfly, was studied for two years by mark-release-recapture (MRR) techiques in the Musimcheon, Cheongju Korea. 2,749 individuals (males: 2,295, females: 454) were marked and released, with 343 individuals (12.5%) recaptured during the MRR experiment. Capture sex ratio and recapture sex ratios was both consistently male-biased. The Jolly-Seber model was used to estimate daily metapopulation size, survival rates, addition rate, and accidental deaths. We urge conservation biologists to consider the local population dynamics of species for the management of metapopulations in fragmented landscapes. In the case of the S. montela koreanus, continuing site protection is essential.

• Journal of Educational Research in Mathematics
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• v.26 no.2
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• pp.159-172
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• 2016

This study examines the approach of introduction of the real numbers through the infinite decimal, which is suggested by Lee Ji-Hyun(2014; 2015) in the aspect of the overcoming the double discontinuity, and analyses Li(2011), which is the mathematical background of the foregoing Lee's. Also, this study compares these construction methods given by Lee and Li with the traditional method using the nested intervals. As a result of analysis, this study shows that Lee Ji-Hyun(2014; 2015) and Li(2011) face the risk of the circulation logic in making the infinite decimal corresponding each point on the geometrical line, and need the steps not using the 'limit to a real number' in order to compensate the mathematical and educational defect. Accordingly, this study raises the opinion that the traditional method of defining the infinite decimal as a sequence by using the geometrical nested intervals axiom would be a appropriate supplementation.

• Journal of Labour Economics
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• v.36 no.2
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• pp.67-94
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• 2013

Using data from the Economically Active Population Survey: Supplement by Employment Type, This paper examines the effects of the 2007 Act on the Protection of Fixed-term and Part-time Employees on employment levels. Since the Act is applied to only individuals below 55 years of age, we restrict the analysis sample to men whose ages are close to 55 at the time of the survey. For such a sample, the empirical analysis combines regression discontinuity design with a difference-in-differences. The results suggest that the employment effect of the 2007 Act takes a U-shape. The results suggest that the employment effect of the 2007 Act takes a U-shape. The negative effect of the Act was largest around August 2008, a year after it took effect. The negative effects on employment faded away toward August 2009.

• Journal of Educational Research in Mathematics
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• v.25 no.3
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• pp.263-279
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• 2015

The introduction of real numbers is one of the most difficult steps in the teaching of school mathematics since the mathematical justification of the extension from rational to real numbers requires the completeness property. The author elucidated what questions about real numbers can be unanswered as the "institutional didactic void" in school mathematics defining real numbers as the union of the rational and irrational numbers. The pre-service teachers' explanations on the extension from rational to real numbers and the raison d'$\hat{e}$tre of arbitrary non-recurring decimals showed the superficial and fragmentary understanding of real numbers. Connecting school mathematics to university mathematics via the didactic void, the author discussed how pre-service teachers could break the illusion of transparency about the real number.

• Journal of the Korean School Mathematics Society
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• v.9 no.1
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• pp.57-76
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• 2006

In this paper, we generalized number partion problems in elementary situations to number partition models that provide some mathematical problem situations for experiencing mathematising of secondary pre-service teachers. We designed substantial teaching units entitled 'the inquiry intof number partition models' through 4 steps: (1) key problems, (2) integration from the view of partition, (3) defining partition (4) a real practice of inquiry into models. This teaching unit can contribute to secondary pre-service teacher education as follows: first, This teaching unit have pre-service teachers experience mathemtising. second, This teaching unit have pre-service teachers see the connection between school mathematics and academic mathematics. third, This teaching unit have pre-service teachers foster their mathematical creativity.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.7
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• pp.423-442
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• 2018

This study observes the psychological changes of unemployed people according to their unemployment period. With this what psychological changes they face according to their unemployment period and what psychological characteristics they show, whether if psychological changes and job hunting activities are in relation, and whether if psychological changes affect job hunting activities. The study subjects received unemployment wage and were divided according to before employment, 1~3 months unemployed, and 4 months or more unemployed. An in-depth research of 8 people was conducted within the period of 2017.05~08. The psychological characteristics of people, in the period from when they first sense unemployment possibilities until three months of unemployment, are anger, anxiety, fear, which is a mixed characteristic that does not disappear but continues deepening. In study there was no significant difference in depression, anxiety, anger, social phobia, alcohol, religion factors, low self-esteem, and low self-efficacy in before employment, 1~3 months unemployed, and 4 months or more unemployed. However, the average levels of anger anxiety, depression, and social phobia were higher when the unemployment period was longer and the results of low self-esteem and low self-efficacy support further research.

• Archives of design research
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• v.18 no.4 s.62
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• pp.237-246
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• 2005

This study was intended to enlighten two-faced desires of the Bauhaus, revealing that it is closely related with the child education rooted in Frobel. The Bauhaus declared to disconnect with the traditional education standing for Academies and asked students to go bad to such 'innocence' as children had. The faculty of Bauhaus tried to understand of the essence of the world through primary geometrical forms as 'purity' without any inessential things as $Fr{\ddot{o}}bel$ did. Their attempts not to admit any nonessential things, however, and dinging to purity was rather a sort of neurosis. The modernism is not different from the child art hiding sadistic and dictatorial elements behind the myth of 'innocence'. Considering the child education was born and grown with nutrition from the bourgeois development, it was not compatible with democratic ideals of the Bauhaus. While the new types of schools for children provided an excellent preparation for the Bauhaus to initiate a new design education, people of the Bauhaus were going toward a different direction from aspiration of the bourgeois, strong supporters of the new schools.

• Journal of Advanced Navigation Technology
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• v.21 no.1
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• pp.12-20
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• 2017

A maritime DGPS in Korea offers pseudo-range correction information and monitors integrity of correction data by using multiple GNSS receivers. The maritime DGPS reference station and integrity monitor service sets alarm threshold value about integrity monitoring parameters for preventing service interruption status. However there is no way to avoid system interruption according to malfunction of backup systems and outside factors. Therefore, in this paper, warning threshold values were proposed for maritime DGPS operator can be counteract in advance. And Markov analysis method was carried out for selection of these warning threshold values.