• Journal of Power Electronics
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• v.18 no.2
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• pp.375-382
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• 2018

A novel active controlled primary current cutting-off zero-voltage and zero-current switching (ZVZCS) PWM three-level dc-dc converter (TLC) is proposed in this paper. The proposed converter has some attractive advantages. The OFF voltage on the primary switches is only Vin/2 due to the series connected structure. The leading-leg switches can obtain zero-voltage switching (ZVS), and the lagging-leg switches can achieve zero-current switching (ZCS) in a wide load range. Two MOSFETs, referred to as cutting-off MOSFETs, with an ultra-low on-state resistance are used as active controlled primary current cutting-off components, and the added conduction loss can be neglected. The added MOSFETs are switched ON and OFF with ZCS that is irrelevant to the load current. Thus, the auxiliary switching loss can be significantly minimized. In addition, these MOSFETs are not series connected in the circuit loop of the dc input bus bar and the primary switches, which results in a low parasitic inductance. The operation principle and some relevant analyses are provided, and a 6-kW laboratory prototype is built to verify the proposed converter.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.3
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• pp.1999-2004
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• 2013

Asian Americans experience disproportionate incidence and mortality rates of certain cancers, compared to other racial/ethnic groups. Primary care physicians are a critical source for cancer screening recommendations and play a significant role in increasing cancer screening of their patients. This study assessed primary care physicians' perceptions of cancer risk in Asians and screening recommendation practices. Primary care physicians practicing in New Jersey and New York City (n=100) completed a 30-question survey on medical practice characteristics, Asian patient communication, cancer screening guidelines, and Asian cancer risk. Liver cancer and stomach cancer were perceived as higher cancer risks among Asian Americans than among the general population, and breast and prostate cancer were perceived as lower risks. Physicians are integral public health liaisons who can be both influential and resourceful toward educating Asian Americans about specific cancer awareness and screening information.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.279-284
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• 2003

A nuclear power plant is composed of a number of primary components. Maintaining the integrity of these components is one of the most critical issues in nuclear industry. In order to maintain the integrity of these primary components, a complicated procedure is required including regular in-service inspection, failure assessment, fracture mechanics analysis, etc. Also, experts in different fields have to co-operate to resolve the integrity issues on the basis of inspection results. This integrity evaluation process usually takes long, and thus, is detrimental for the plant productivity. Therefore, an effective safety evaluation system is essential to manage the integrity issues on a nuclear power plant. In this paper, a web-based fatigue life evaluation system for primary components in nuclear power plant is proposed. This system provides engineering knowledge-based information and concurrent and collaborative working environment through internet, and thus, is expected to raise the efficiency of integrity evaluation procedures on primary components of a nuclear power plant.

• Journal of Korean Elementary Science Education
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• v.19 no.1
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• pp.57-69
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• 2000

The purpose of this study was to seek desirable direction of science teaching and to present meaningful ideas for implementing the science curriculum and teaching materials by measuring the degree of the students' understandings on science and comparing it with those of American students. The researcher comprised 790 primary and middle school students for the study and administered them questionnaires developed by Trowbridge, Bybee, and Sund. The questionnaires were analyzed along with three categories such as science method, science theory, and the achievement of scientists. The researcher used t-test and ANOVA in order to compare the difference of their understandings in accordance with grades and gender, and later compared Korean students' understandings with those of similar aged American students administered by the National Assessment of Educational Progress (NAEP) The research loathed to the overall conclusions as follows; Both primary and middle school students' understandings on science revealed positive and appeared no significant difference in gender. And it is thought that science education was being carried out hopefully to enhancing Korean students' scientific literacy, therefore, science teaching like what is implemented to the classrooms currently should be kept on in future. On the other hand, it is necessary to change primary school children's understandings on attitude and value of scientists while to change middle school students' understandings on scientific processes by experiment. Also primary school children need to understand that scientists are willing to change their ideas when new information becomes known.

• School Mathematics
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• v.2 no.2
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• pp.357-388
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• 2000

This study aims to develop performance assessment tools for mathematics in the primary school. In order to achieve this aim, it reviews the tics in the primary school. In order to achieve this aim, it reviews the meaning and the purpose of mathematics performance assessment, and the characteristics of performance assessment tasks. Then the framework for portfolio developed in this study is introduced. This portfolio is called 'mathematical thinking and applying'. It aims at balanced assessment for improvement of mathematics instruction. It is composed of journal writhing, problem by the student, constructed task, work samples, written test, self assessment, teacher's comment and parents' comment. The criteria of performance tasks is categorized in impact, reasoning, accuracy and communication. The procedures of development of these tasks are as follows: the analysis of mathematics curriculum for the primary school, the design of performance tasks with considering teaching unit goals, designing rubrics, discussing these tasks with teachers in primary school, modifying them when is needed, observing the process of children's task performing, interviewing with teachers and final modifying. After performance assessment tasks are implemented, the answers by the students is analyzed using rubrics. Then anchor papers are selected. Also, the errors of children are analyzed. Through the process, teachers can obtain the information of children for improvement of mathematics instruction. Finally in order to generalize this study, I suggest that we need to cooperate with the field of education and to establish expert assessment groups.

• The Journal of the Korean dental association
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• v.9 no.10
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• pp.617-622
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• 1971

In order to establish a more concrete dental health education and control program with the investigation of the knowledge levels concerning the dental health and the control of the dental health, twelve questionaires concerning the dental health were given to 263 inhabitants in the farm villages, 105 primary school teachers and 78 school health nurses. The results obtained from the information were as follows: 1. The knowledge levels of the primary school teachers and school health nurses as well as the inhabitants in the farm villages concerning the dental health were very low. 2. Most Korean population have not control ed their oral health in the right method using the toothbrushes and the dentifrices. 3. Most primary school teachers and school health nurses have not the ability to educate the primary school childen for the good dental health. 4. In Korea, the policies of the education and the control concerning the dental health must be reestablished. 5. Many Korean population complained the economic limitation and the over duties in their social life for the good dental health control. 6. It seems the complete medical and dental insurance system to be established for the good dental health control of most Korean population.

• Proceedings of the National Institute of Ecology of the Republic of Korea
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• v.4 no.1
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• pp.16-27
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• 2023

Primary succession on bare rocks is a challenge for invaders, including one of which was plants. The invasion of bare rock by exotic species raises the question of whether their presence hinders or facilitates succession. This study aimed to determine the role of exotic species in primary succession in six overburden (OB) coal mines using a chronosequence approach. Vegetation analysis was undertaken using line transects. Measurements were carried out on the absolute and relative coverage of each species. Native and exotic species were identified and grouped using information from local communities, identification books, and websites. The relationship between time and number of species, time, and relative dominance of exotic and native species was analyzed using Pearson's correlation. Species number and dominance data were analyzed descriptively. The number of native species from the six OB heaps was higher (57) than that from exotic heaps (50). Neither the number of species nor the coverage showed a significant relationship with time. Exotic species predominated throughout the age of the embankment but tended to decrease over time. Temporary dominance by exotic species plays a role in assisting primary succession in the OB. This process might be prolonged without the temporary dominance of exotic species during early primary succession.

• Journal of Korea Society of Industrial Information Systems
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• v.23 no.5
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• pp.103-118
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• 2018

This study compared the production inducement effects of primary industries between Korea, China, and Japan for the period from 2000 to 2014, by examining the forward and backward linkage effects using the World Input-Output Tables. Although research on the industrial effect of primary industries has been conducted actively, this study is contributive since it compares the differences in industrial linkage effects between Korea, China, and Japan. According to Fisher(1939)'s and Clark(1957)'s classifications of primary industries, this study classified agriculture, forestry, fishing, and mining industries as primary industries. The analysis methodology of this study is to use the World Input-Output Tables to create the industry linkage model between Korea, China, and Japan, and then conduct a comparative analysis. According to the results of this study, the forward and backward linkage effects of agriculture industry between Korea, China, and Japan are significantly different, while the forward and backward linkage effects of forestry and fishing industries between Korea, China, and Japan are partially different. By comparing the changes in industrial dependencies of primary industries due to the 4th Industrial revolution between the three countries, this study suggested the future development direction of primary industries.

• Journal of the korean academy of Pediatric Dentistry
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• v.50 no.1
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• pp.24-34
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• 2023

The aim of this study was to retrospectively analyze the effects of pulp treatment on exfoliation of primary teeth and its related factors. In this study, 167 teeth of 97 patients aged 6 months to 12 years who were treated with pulp treatment at Dankook Dental Hospital were selected, and information related to pulp treatment and tooth loss was collected. The included subjects were 72 primary anterior teeth (43.1%) and 95 primary posterior teeth (56.9%), of which 56 were males (57.7%) and 41 females (42.3%). The mean follow-up period was 106.1 ± 38.7 months, and the mean age at pulp treatment was 34.8 ± 15.4 months for primary anterior teeth and 69.1 ± 25.1 months for primary posterior teeth. Unilaterally pulpectomized teeth were significantly exfoliated earlier than the same tooth on the opposite side (p < 0.05). Also, in the case of teeth with periapical lesions, despite pulp treatment, the probability of extraction due to infection has been increased on primary anterior teeth (p < 0.05), but not on posterior teeth (p > 0.05). Pulpectomized teeth were lost earlier, an average of 7.8 months for primary anterior teeth and 8.5 months for primary posterior teeth. Early loss of the primary tooth can lead to space loss and premature eruption of the successor, so this can be considered when planning or performing treatment of the primary tooth.

• Proceedings of the Korea Information Processing Society Conference
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• 2006.05a
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• pp.1041-1044
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• 2006

This paper proposes a dynamic IP address configuration (DAC) scheme for mSCTP handover, which exploits the information from the link layer to support SCTP handover between heterogeneous access networks. The proposed DAC scheme enables a mobile terminal to automatically add a new IP address in the newly visited region, change the primary path, and delete the old IP address so as to support the mSCTP handover. For experimental analysis of mSCTP handover, we consider the handover scenarios for 3G-BWA and 3G-WLAN over Linux platforms. From experimental results, it is shown that the throughput and handover latency of the mSCTP handover would be affected by the timing of primary-change and the overlapping period.