• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.9
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• pp.762-771
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• 2012

In this paper, we propose an adaptive power control scheme employing a self-optimization concept in femtocell systems, in order to improve system capacity, thereby reducing call-drop probability. In the proposed scheme, each femto base station(FBS) controls individual channel's transmission power base on two parameters; the neighboring cell's transmission power for each individual channel which is delivered from a femto-gateway and the received power strength from neighboring cells which is periodically measured by means of a spectrum sensing. Adaptive adjustment of individual channel's transmission power in accordance with femto mobile station(FMS) mobility features can also reduce undesirable handovers and evenly distribute traffic load over all femtocells. In addition, the manipulative control of channel's transmission power is able to keep the system coverage and the call-drop probability within an acceptable range, regardless of density of femtocells. Computer simulation shows that the proposed scheme outperforms existing schemes in terms of the system coverage and the call-drop probability.

• Journal of the Korean association of regional geographers
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• v.8 no.1
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• pp.83-97
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• 2002

In this study we shall compare the differences among Korean tourists' behavioral patterns according to tourists' residences by using statistical techniques on questionnaires for 1,372 tourists around Korea. In conclusion, we found varying degrees of influences among touristic behaviors in relation to residences, We documented 11 out of 14 categories of touristic behaviors in urban/rural areas around Korea. And there were 4 out of 14 categories of those found in provincial areas. Characteristics of urban/rural areas had a significant influence on touristic behaviors compared to provincial areas. Therefore, tour authorities provide for a balanced policy of travel around Korea. As mentioned above, these touristic behaviors had many differences according to urban/rural areas and provinces. We are concerned that these differences are likely to cause psychological disturbances among social classes. I hope that these results will be reflected in the development policies of tourist goods and tour sites.

• Journal of Digital Convergence
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• v.17 no.1
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• pp.179-187
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• 2019

Developing countries, including Africa, are experiencing very little human resources development due to the deprivation of equal educational opportunities, poor educational conditions, and the gap in information technology with developed countries. Developing countries that do not have excellent human resources are lagging behind in globalization competition with developed countries, and the problem of 'human resource development' in developing countries can not be avoided. In developing countries, education budgets are too low to meet education needs and compulsory education, and therefore they are not adequately responding to the increasing demand for education. The lack of education budget is due to the lack of education infrastructure. In this study, the NAS based server is configured to configure functions such as educational content and learning management, and the client area is presented with solutions for various media such as tablet, PC, and beam projector. And to support optimized e-learning services in developing countries by constructing a SCORM-based platform.

• The Korean Journal of Air & Space Law and Policy
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• v.24 no.2
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• pp.47-67
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• 2009

In recent years, greenhouse gas (GHG) reduction has become high priority issue in international aviation. GHG emissions from the aviation sector only accounts for approximately 2 percent of total GHG emissions in the world. However, as with GHG gases in other sectors, it has been pointed out as a contributing factor to global warming and there is an ongoing conversation in the aviation community to establish international framework for emissions reductions. In the case of international aviation, effects of aviation activities of a State go beyond the airports and airspace of that State. This makes compiling of GHG emissions data very difficult. There are also other legal and technical issues, namely the principle of “Common but Differentiated Responsibility (CBDR)” under the United Nations Framework Convention on Climate Change (UNFCCC) and “Fair Opportunity” principle of the Chicago Convention. For all these reason, it is expected that it will not be an easy job to establish an internationally agreed mechanism for reducing emissions in spite of continuing collaboration among States. UN adopted the UNFCCC in 1990 and the Kyoto Protocol in 1997 to impose common but differentiated responsibility on emissions reductions. In international aviation, ICAO has been taking the lead in measures for the aviation sector. In this role, ICAO held the High-level Meeting on International Aviation and Climate Change on 7 to 9 October 2009 at its Headquarters in Montreal and endorsed recommendations on reducing GHG from international aviation which will also be reported to the 15th Meeting of the Conference of the Parties (COP15). Key items include basic principle in global aviation emissions reduction: aspirational goals and implementation options: strategies and measures to achieve goals: means to measure and monitor the implementation; and financial and human resources. It is very likely that the Republic of Korea will be included among the Parties subject to mandatory limitation or reduction of GHG emissions after 2013. Therefore, it is necessary for Korea to thoroughly analyze ICAO measures to develop comprehensive measures for reducing aviation emissions and to take proactive actions to prepare for future discussions on critical issues after COP15.

• Journal of the Korean School Mathematics Society
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• v.6 no.1
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• pp.65-85
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• 2003

The purpose of this research is to increase mathematical problem solving abilities VIa STAD evaluation after completing classes. to which ST AD group study is applied, and promoting the learning accomplishments of students by developing gradual self-leading learning materials about the research project on ' How to use an hour math class efficiently\ulcorner ' For this purpose, the items below were studied. Firstly, gradual self-leading learning materials were developed and applied which were composed of textbook abstracts, basic problems, developing problems and intensive problems rather than existing textbooks. Secondly, the ST AD group study model was selected and applied which invokes competitions among small groups of which learning goals were clear. individual responsibility was important. and successive opportunities were equal. The evaluation using STAD at each end of a chapter was announced instantly using the EXCEL scoring system. Though the results of experimental classes were limited in their size. experimental time, and class selection, there were meaningful changes in the aspect of being able to heighten the accomplishment desire of students by inducing voluntary competitions among small groups without any student omitted. As the result of applying this research to my class, the ST AD group study using gradual self-leading learning materials invoked the interests of students and increased learning accomplishments via increasing problem solving abilities in mathematics. The ST AD group study was easy to use by beginning teachers, and its process was simple. It increased interactions among students and learning motives because its compensation system was open to all students. Among various studying methods for small groups. STAD group study is expected to be widely used for mathematics classes.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.6
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• pp.77-86
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• 2008

Traditional cluster-based routing method is a representative method for increasing the energy efficiencies. In these cluster-based routing methods, the selected cluster head collect/aggregate the information and send the aggregated information to the base station. But they have to solve the unnecessary energy dissipation of frequent information exchange between the cluster head and whole member nodes in cluster. In this paper, we minimize the frequency of the information exchange for reducing the unnecessary transmit/receive frequencies as calculate the overlapped area or number of overlapped member nodes between the selected cluster head and previous cluster head in the setup phase. And besides, we consider the direction of super cluster head for optimal cluster formation. So, we propose the modified cluster selection scheme that optimizes the energy dissipation in the setup phase and reuses the saved energy in the steady phase efficiently that prolongs the whole wireless sensor network lifetime by uniformly selecting the cluster head.

• Education of Primary School Mathematics
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• v.14 no.1
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• pp.81-95
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• 2011

In order to raise people with mathematical power and positive attitude toward mathematics fit for the 21st century, individual students should be provided with equal learning opportunities according to their ability and level, and the need of such mathematics education is even stronger for underachievers. As textbooks were considered the optimal learning materials at each stage, this study purposed to examine changes in students' mathematical learning abilities and mathematical tendency brought by the activities of analyzing and reviewing the textbooks of the previous grades. The subjects of this study were 5 mathematics underachievers from 3 fifth grade classes at D Elementary School. They were sampled from those who were selected based on the results of diagnostic assessment and the records at the end of April and gave their consent to participation in this study. For the sampled children, their current state was surveyed first, and then the experimental classes were given twice a week and a total of 32 sessions. The children judged their mathematical abilities through reviewing the textbooks from the 1st grade to the 4th grade, and studied the textbook of each stage by themselves. After the self study, they had the textbook contents review activity that extracted 10 problems considered important per semester, and the textbook analysis activity that grouped units in each stage according to relevancy, identified similarities and differences, and examined hierarchy. From the results of this study was found that the mathematics underachiever teaching method using the textbooks of the previous grades gives mathematics underachievers confidence in their abilities, strengthens mathematical connection, and develops the habits of exploring key contents through self study.

• Journal of the Korean Association of Geographic Information Studies
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• v.14 no.2
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• pp.53-68
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• 2011

A selection of viewpoint is a first priority for landscape evaluation. However, it has been artificially carried out by a subjective method without of criterion. Therefore, this study proposed the objective and quantitative viewpoint selection methods using space syntax and GIS. For this, the study area on samduk3 residential improvement district located at Daegu city was divided into 24 sectors of visibility zone by distance and direction. After that, the preliminary viewpoints equally distributed in space were selected by axial map analysis of space syntax and viewshed-frequency analysis of GIS. According to the result of selection of the final viewpoints using the VEI(Viewpoint Evaluation Index), all the final viewpoints were placed in the National Debt Repayment Movement; VEI value of VP-2 was 112.63 in the foreground, VP-10 was 18.31 in the middleground and VP-18 was 5.55 in the background. Selected viewpoints were verified as a big changing of landscape variation and high chance of view such as the public area, the park and the high-density residential area. Thus, VEI will be used as a quantitative method of selecting viewpoints and it is expected to be able to use as the objective indicator.

• The KIPS Transactions:PartA
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• v.16A no.5
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• pp.395-402
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• 2009

Since 2005, Cyber home learning systems(CHLS) have been run with the purpose of clearing up the regional disparity and reducing the private education cost. At this point, it is necessary to have the analysis on the satisfaction and effectiveness awareness of the CHLS. The goal of this paper is to suggest an evaluation model for satisfaction and pedagogical effectiveness of CHLS and to support the management of satisfaction and effectiveness awareness of the CHLS for the low-income bracket children. Our major contributions can be summarized as follows: First, we present an evaluation model of satisfaction and effectiveness awareness of the CHLS for the low-income bracket children. Second, we survey the satisfaction, effectiveness awareness and improvement facts from the students who divided according to their sex, residence area and classes and compare with suggesting evaluation models. This paper is to find the measurement of the satisfaction and effectiveness awareness of the CHLS for the low-income bracket children. Furthermore, we can use this model as a material to balance the education opportunity, which is the purpose of CHLS, and abolish the education differentials.

• Journal of Internet Computing and Services
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• v.17 no.6
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• pp.17-23
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• 2016

In the future network such as Internet of Things (IoT), the number of computing devices are expected to grow exponentially, and each of the things communicates with the others and acquires information by itself. Due to the growing interest in IoT applications, the broadcasting in Opportunistic ad-hoc networks such as Machine-to-Machine (M2M) is very important transmission strategy which allows fast data dissemination. In distributed networks for IoT, the energy efficiency of the nodes is a key factor in the network performance. In this paper, we propose a fuzzy logic based probabilistic multi-hop broadcast (FPMCAST) algorithm which statistically disseminates data accordingly to the remaining energy rate, the replication density rate of sending node, and the distance rate between sending and receiving nodes. In proposed FPMCAST, the inference engine is based the fuzzy rule base which is consists of 27 if-then rules. It maps input and output parameters to membership functions of input and output. The output of fuzzy system defines the fuzzy sets for rebroadcasting probability, and defuzzification is used to extract a numeric result from the fuzzy set. Here Center of Gravity (COG) method is used to defuzzify the fuzzy set. Then, the performance of FPMCAST is evaluated through a simulation study. From the simulation, we demonstrate that the proposed FPMCAST algorithm significantly outperforms flooding and gossiping algorithms. Specially, the FPMCAST algorithm has longer network lifetime because the residual energy of each node consumes evenly.