• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.2
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• pp.253-270
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• 2013

To achieve accurate localization information, complex algorithms that have high computational complexity are usually implemented. In addition, many of these algorithms have been developed to overcome several limitations, e.g., obstruction interference in multi-path and non-line-of-sight (NLOS) environments. However, localization systems those have complex design experience latency when operating multiple mobile nodes occupying various channels and try to compensate for inaccurate distance values. To operate multiple mobile nodes concurrently, we propose a localization system with both low complexity and high accuracy and that is based on a chirp spread spectrum (CSS) radio. The proposed localization system is composed of accurate ranging values that are analyzed by simple linear regression that utilizes a Big-$O(n^2)$ of only a few data points and an algorithm with a self-calibration feature. The performance of the proposed localization system is verified by means of actual experiments. The results show a mean error of about 1 m and multiple mobile node operation in a $100{\times}35m^2$ environment under NLOS condition.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.4
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• pp.1579-1602
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• 2020

In the design of production system, buffer capacity allocation is a major step. Through polymorphism analysis of production capacity and production capability, this paper investigates a buffer allocation optimization problem aiming at the multi-stage production line including unreliable machines, which is concerned with maximizing the system theoretical production rate and minimizing the system state entropy for a certain amount of buffers simultaneously. Stochastic process analysis is employed to establish Markov models for repairable modular machines. Considering the complex structure, an improved vector UGF (Universal Generating Function) technique and composition operators are introduced to construct the system model. Then the measures to assess the system's multi-state reliability and structural complexity are given. Based on system theoretical production rate and system state entropy, mathematical model for buffer capacity optimization is built and optimized by a specific genetic algorithm. The feasibility and effectiveness of the proposed method is verified by an application of an engine head production line.

• Journal of Internet Computing and Services
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• v.21 no.3
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• pp.61-70
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• 2020

The 4th Industrial Revolution is a revolutionary change through intelligence, big fusion and personalization, and the importance of sensor technology that is the basis of core technology is emerging. This study empirically analyzes the derivation of national strategy for R&D of sensor technology, and draws out the effect of technology internalization effort through strategic R&D activities on technical performance and further on national economy. The research and development results are calculated for each type of technology internalization, and the results of the research and development are verified to establish a structure that contributes to the national economic performance. As a national technology internalization strategy, considering its own R&D investment and joint research and development, we examine the impact of each factor on patents and GDP, focusing on causality and ripple effects. For causality analysis, Grandeur causality analysis shows that R&D investment and joint research and development in all countries have mutual causal relationship with GDP. The implications are as follows. First, it is necessary to establish the policy of national economic development through the internalization of technology and knowledge. Second, it is necessary to establish policies according to the type of knowledge internalization. Third, it will be necessary to create an ecosystem environment based on a virtuous relationship between knowledge internalization and national technology and economic development.

• Journal of Educational Research in Mathematics
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• v.24 no.4
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• pp.573-594
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• 2014

Capacity of making assessment items among teacher's assessment competency is essential element in validity and reliability of assessment. Errors in test items on the formal and content aspects can be a big stumbling block to derive a correct evaluation result. Through this assessment, the positive feedback can not be derived. In this study, By analyzing midterm and final 60 exam papers for geometry and vector in 45 high Schools of Seoul GyeonggiIncheon area, We argue error items and improvements on the formal and content aspect the paper-based assessment of mathematics. Through this, Our intention is to improve the skills of teachers for making assessment items.

• Radiation Oncology Journal
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• v.37 no.4
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• pp.249-253
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• 2019

Purpose: We aimed to analyze the trend in intensity-modulated radiation therapy (IMRT) use in Korea from 2011 to 2018. Materials and Methods: We collected data from the Health and Insurance Review and Assessment Service (HIRA) big data based on the National Health Insurance Service claims and reimbursements records using primary treatment planning codes (HD 041) for IMRT from 2011 to 2018. We analyzed the changing patterns in clinical application to specific tumor sites and regional differences in IMRT utilization. Results: The use of IMRT has exhibited an 18-fold steep rise from 1,921 patients in 2011 to 34,759 in 2018. With regard to IMRT in 2018, 70% of patients (24,248/34,759) were treated in metropolitan areas (Seoul, Incheon, and Gyeonggi Province). IMRT was most commonly used to treat breast, lung, and prostate cancers in 2018. Among these, the use of IMRT for breast cancer shows the most remarkable increase from 2016 when the National Health Insurance began to cover IMRT for all solid tumors. Conclusion: The use of IMRT is steadily increasing to treat cancer and is concentrated in metropolitan areas.

• Journal of The Korean Association of Information Education
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• v.14 no.2
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• pp.251-259
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• 2010

According to the school autonomy plan on April 15, 2008, schools have a responsibility for ICT in education policy. Because of this plan, A guideline for governmental action for ICT education was repealed, on the contrary, responsibilities for ICT education in school level has increased. The radical exchange of education policy has a big impact on decision-making about ICT in education policy in school level. Consequently, the digital divide is generated between students, teachers and schools. So, this paper is intended as an investigation of decision-making types and awareness of teachers about ICT in education policy in elementary school. And this paper presents new ideas for decision-making of ICT policy in elementary schools.

• Korean Institute of Interior Design Journal
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• v.19 no.4
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• pp.22-30
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• 2010

Light has primary function to enlighten the darkness. However, as development and progresses in media has caused big change in our life, the range of usage and application of light is broadened. And these days, light is actively used as a communication tool in a space. This thesis is based on an idea that a new prospect of light is required and at the same time the theoretical foundation should be established to take active advantage of light. In Chapter two, analysis criteria are established to verify study hypothesis. The applied methodology is to analysis the contents based on literature review. Key words related light in space design are extracted and the frequency of those key words are quantitatively measured. Taking advantage of the result, the characteristics of light are divided into three categories, 'light as symbolic information', 'light as communication medium' and 'light as topological form'. In chapter three, analysis of cases is performed. The cases are selected based on space analyzing criteria established in Chapter two. Qualitative analysis is performed on the cases categorized into natural light and artificial light. Basic analysis elements are evaluated for each case. And each case is allocated to one of three categories, 'light as symbolic information', 'light as communication medium' and 'light as topological form'. Through this analysis, it is found that light in space has prevailing characteristics of 'light as symbolic information' and 'light as communication medium'.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.4
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• pp.609-613
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• 2016

A hybrid charging method with serial and parallel architecture has been developed to resolve the unbalanced charge problem among battery cells for Electric Vehicles. In this method, the major charging is performed with serial part and the balancing is carried out with the parallel part, where the serial part is big and heavy but the parallel part is smaller and lighter than serial part. A sensor array to detect the individual battery cell voltage, duty rate control incorporated IGBTs, and battery management system are employed as the core parts of the proposed system.

• Korean Institute of Interior Design Journal
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• v.15 no.5 s.58
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• pp.298-305
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• 2006

The purpose of this study is to figure out the profiles of eco-friendly finishing materials and intoner products through content analysis on the advertisements of three domestic interior design magazines, which have been published for 4 years since 2002. The amount of advertisements has been continuously increasing due to the public concerns on well-being. Finishing material types absolutely took the greatest proportion (92.8%), while products such as furniture and household equipments were only 7.2% among the advertisements. Charcoal, natural jade, yellow soil and nano-silver were the frequently mentioned health-related components in the finishing material. Only 35.7% of the finishing materials hold certification on indoor air quality. Among the interior products, phytonchid in air cleaner was the only advertised component related to health. In conclusion, controlling pollutants of indoor air quality, such as HCHO, VOC, seems to be the big issue in both materials and products due to the concern of Sick Building Syndrome. However, more scientific and objective guidelines are necessary for consumers to live in healthy interior environment.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.9
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• pp.1334-1340
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• 2017

In this paper, a tie-plate shape is optimized by using the numerical technique to reduce the stray load loss of the tie-plate which is a mechanical structure for assembling and supporting of the transformer core. The eddy current loss of the structure is calculated by an electromagnetic field FEM program and the results are compared with 4 different shapes of tie-plates. Since the thickness of the tie-plate is very thin, and the skin depth is very small, the number of FE elements for 3-D transformer model is too big to solve. So, the surface impedance boundary condition (SIBC) is used to reduce the system matrix size and its computing time. To verify the method a 2.5 MVA 22,900/380V distribution transformer is simulated using one objective function and three design variables with some constraints. The final optimized tie-plate has three slots of 6 mm width and 23 mm gap, and the loss is reduced by 75 %. Consequently, the proposed algorithm seems to be considerably applicable to electric machinery as well as power transformer.