• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.4
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• pp.25-33
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• 1999

Leaky wave radiation and surface wave launching problems in a dielectrically covered and periodically slitted parallel-plate waveguide(PPW) are considered for the TEM wave incidence case. Both the infinite and finite periodic geometries are analyzed by use of the method of moments. Some numerical results for the reflected and transmitted powers in the PPW, radiation efficiency into the free space, surface wave launching efficiency into the slab, antenna gain, and radiation patterns against dielectric thickness are presented to show the effect of the dielectric cover on the performances of the slitted leaky wave antenna. In addition, the method for improving surface wave launching efficiency using the proposed periodic geometry is described and maximum launching efficiency of 97.5% is obtained theoretically. So this structure is thought to be promising as an efficient feeder of dielectric grating antenna as well as image guide.

• Journal of Korean society of Dental Hygiene
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• v.12 no.3
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• pp.585-595
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• 2012

Objectives : The study enquires into OHB and its importance of preschooler mothers, based on perceived experiences of OHE. It also investigates mothers' sense of responsibility for children's oral health. The purpose is to enhance the effectiveness of OHE and its orientation. Methods : From April 20th to June 15th, 2011, 14 nurseries or preschools were randomly selected from childcare facilities of one gu(borough) in Busan. The objects of study are mothers of four to seven-year-old children. The collected survey data were analyzed using SPSS 12.0 for Windows. Results : 1. There is a statistically significant difference(p<0.01) in relations between the mothers' working status and perceived experiences on OHE. 2. On the survey about OHB practices, there are significant differences(p<0.001) in toothbrushing before breakfast, after meals, in three minutes and after refreshments Significant differences(p<0.01) are also shown in toothbrushing after eating fruits. 3. On the survey about the importance of OHB, there are statistical significances(p<0.001) in toothbrushing manner-rather than the number of it-toothbrushing in three minutes after meals and following the correct way of toothbrushing. There are also significant differences(p<0.05) in brushing teeth for more than three minutes. 4. There are significant differences(p<0.001) in mothers' periodic dental examination, children's periodic dental examination and training experience on children's toothbrushing. 5. On the survey about the sense of responsibility for children's OHE based on experiences of OHE, there is a significant difference(p<0.05) in that many replied OHEis "much-needed" regardless of their experiences on it. Conclusions : The results show that of infants' mothers, those with experience on OHE, have an accurate knowledge about toothbrushing, due to the effectiveness of the education. Both groups, however, replied that children's OHE is much needed, suggesting problems about the accessibility of the OHE.

• Journal of Korean Association for Spatial Structures
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• v.12 no.2
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• pp.109-118
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• 2012

Few paper deal with the dynamic bucking under the load with periodic characteristics, and the behavior under periodic excitation is expected the different behavior against STEP excitation. A space frame structure has high stiffness with a structure resisting external forces in steric conformation. According to many structural conditions, structural stability problems in the space frame are determined and considered very important. This study seeks to understand the space frame collapse mechanism using the 2-free nodes truss model in order to examine static structural instability characteristics of the latticed dome. According to geometrical shape, the star dome, parallel lamella dome and three way grid dome were selected as models. The models were examined for characteristics of instability behavior according to rise-span ratio(${\mu}$) and shape imperfection.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.3
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• pp.173-178
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• 2019

To analyze the diffraction properties of optical signals by periodic blazed 2D diffraction gratings, Toeplitz dielectric tensor is first defined and formulated by 2D spatial Fourier expansions associated with asymmetric blazed grating profile. The characteristic modes in each layer is then based on eigenvalue problem, and the complete solution is found rigorously in terms of modal transmission-line theory (MTLT) to address the pertinent boundary-value problems. Toeplitz matrix of symmetric and sawtooth profiles is derived from that of asymmetric blazed grating profile, and the diffraction properties for each profile are numerically simulated. The numerical results reveal that the asymmetric and symmetric profiles behave as anti-reflection GMR filter while the sawtooth profile works better as anti-transmission one rather than anti-reflection filter.

• Safety and Health at Work
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• v.6 no.2
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• pp.85-89
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• 2015

Background: The study was designed to assess the changes in working conditions through a comparative analysis of the characteristics of working conditions in 2006 and 2010. Methods: We performed a comparative analysis of the data related to the first Korean Working Conditions Survey (KWCS) and the second KWCS in the categories of demographic characteristics, quality of labor, exposure to hazards, and health problems. Results: From our analysis of the demographic characteristics, we saw an increase in labor force participation rate of women and elderly people. As a result of the investigation with regards to working hours, the ratio of employees who worked for ${\geq}49$ hours per week was decreased and the ratio of employees who worked for ${\geq}40h/wk$ increased. As for exposure to hazards, exposure to tobacco smoke notably decreased in 2010 compared with 2006. With regards to health problems, there was a sharp increase in the number of people who complained of muscle pain in their arms and legs. Conclusion: KWCS data included many aspects of working conditions as a nationwide sample. In addition, because this is a periodic nationwide survey, the labor force, working hours, harmful factor exposure, and the change in health problems characteristics according to the flow of time could be investigated. The information comparing the main results of the first survey conducted in 2006 and the second survey conducted in 2010 obtained through this study can be used as an important base material for the establishment of the national policy.

• Journal of the Korean Operations Research and Management Science Society
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• v.31 no.1
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• pp.91-103
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• 2006

Given a bill of materials (BOM) tree T labeled by the breadth first search (BFS) order from node 0 to node n and a general network ${\Im}=(V,A)$, where V={1,2,...,m} is the set of production facilities and A is the set of arcs representing transportation links between any of two facilities, we assume that each node of T stands for not only a component. but also a production stage which is a possible stocking point and operates under a periodic review base-stock policy, We also assume that the random demand which can be achieved by a suitable service level only occurs at the root node 0 of T and has a normal distribution $N({\mu},{\sigma}^2)$. Then our integrated model of facility location problems and safety stock optimization problem (FLP&SSOP) is to identify both the facility locations at which partitioned subtrees of T are produced and the optimal assignment of safety stocks so that the sum of production cost, inventory holding cost, and transportation cost is minimized while meeting the pre-specified service level for the final product. In this paper, we first formulate (FLP&SSOP) as a nonlinear integer programming model and show that it can be reformulated as a 0-1 linear integer programming model with an exponential number of decision variables. We then show that the linear programming relaxation of the reformulated model has an integrality property which guarantees that it can be optimally solved by a column generation method.

• Journal of the Korean Society of School Health
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• v.13 no.2
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• pp.331-340
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• 2000

Primary school is regarded as an important period when many health-related behaviors and life-styles begin to be formed. Acquiring them through school heath education has a strong influence on the health promotion of not only the family but also the community. The objectives of this study were to evaluate current oral health care of elementary schools in Chungnam province and to provide information for further development in elementary school oral health. We performed a questionnaire survey to 280 health teachers and among them, 155 teachers answered. The result of this study were as follows: 1. Sixty five percent of the health teachers had little interest in oral health. Major information sources for teaching oral health were books in 58.1% of the 155 teachers and 83.2% of teachers spent 30 minutes to 1hour per day in oral health care practice for the students. 2. Contents of the oral health education were composed of regular and special curriculums, and an average of education time during a semester was 2.6 hours in 3rd grade, and 1.3 hours in first and second grade. 60.6% of the teachers made the children practice the proper method of tooth brushing during the education time. 3. Major problems in oral health education were insufficient time, lack of equipment and difficulty in teaching method. The educational media were tooth models among 91.0% and OHP among 85.2% of the teachers. The tooth model was usually used in first to fourth grades and OHP in fifth to sixth grades. But 63.9% health teachers need to develop stronger educational methods using multimedia. 4. Meanwhile the most important strategy of oral health in urban schools was health education, that of rural schools was fluoride mouth-rinsing programme. Fluoride mouth-rinsing programmes were performed by 60.0% of the elementary school. Periodic dental examination was performed in all elementary schools. 98.2% of the schools sent the results home through school notification letters, but post-examination management was performed in only 67.1% of them 64.5% of the health teachers do follow-ups on the oral disease of the children after the examination. Only 0.7% of the schools have oral health education plans for the students' parents. Considering these major strategies for elementary school oral health care were health education, practicing proper methods of tooth brushing, periodic dental examinations, and fluoride mouth-rinsing programmes. But health teachers need more time for oral health education, practicing and management, and developing education materials. With regard to the high demand for oral health education and poor follow-up after periodic examination, the oral health education in elementary school should be considered as a formal educational course for more proper management of oral health, including application of major strategies to the children in earlier grades and efforts for increasing recognition and participation of the parents.

• Journal of Korean Society of Transportation
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• v.28 no.5
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• pp.91-106
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• 2010

Recently, interest in supply chain management is rising along with the increasing oil prices and traffic congestion. In particular, people started studying the issue, but realized that advantageous strategies for suppliers and retailers are not always advantageous to a carrier. Therefore, in this study the atuhors set up a simulation scenario to understand delivery vehicle routing problems under various inventory policies, namely Economic Order Quantity (EOQ) and Periodic Order Quantity (POQ) and network configurations. First, the authors made a virtual supply chain. Then they analyzed characteristics of delivery vehicle routing under various inventory policies (EOQ and POQ) and network configurations. As a result, the POQ inventory policy decreases the number of vehicles, the number of drivers, and the service time of vehicles. Also, the centralized network increases the load factor of vehicles and decreases the service time of vehicles. In other words, the centralized network and the POQ inventory policy are better for the carrier. These results show a savings of 15,556,806 won ($13,389.10) in a month: a reduction of 17%.

• The Journal of the Korea Contents Association
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• v.18 no.8
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• pp.102-108
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• 2018

The existing data transmission technology applied between the non-secure external internet and the secure internal business network has various problems when applied to the building facility management SCADA system control network. Traditional inter-network data transfer technologies involve high complexity and high costs because blacklist-based security techniques are applied to all data. However, whitelist-based security techniques can be applied to data distributed in Building Facility Management SCADA control systems because a small number of structured control data are repeatable and periodic. This simplifies the security technology applied to inter-network data transmission, enabling building facility management SCADA system control network deployment at low cost. In this paper, we proposed building control networks specialized in building facility management SCADA control systems by providing solutions to address and address these problems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.2
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• pp.77-85
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• 2014

Recently, utilization of MIMO(Multi-Input Multi-Output) system using array antennas is evaluated significantly according to the extension of high-capacity and high-speed communication services. However, MIMO system has disadvantages such as high-complexity and high-power-consumption, because RF(Radio Frequency) chain is required as antenna number, and several array antenna is used in conventional MIMO system. In order to solve these problems, research about beamspace MIMO system using ESPAR(Electronically Steerable Parasitic Array Radiator) antenna that has single RF chain by using one active antenna and several parasitic elements has been studied actively. Beamspace MIMO system using ESPAR antenna is possible to solve the problems of conventional MIMO system, because this system is composed by single RF chain. In this paper, in order to improve the system security, chaos communication algorithm that has characteristics such as non-periodic, non-predictability, easy implementation and initial condition is applied to QPSK (Quadrature Phase Shift Keying) modulated beamspace MIMO system. We design the chaos QPSK modulated beamspace MIMO system, and evaluate SER performance of this system.