• Journal of Power Electronics
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• v.16 no.3
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• pp.960-969
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• 2016

High-power three-level voltage-source converters are widely utilized in high-performance AC drive systems. In several ultra-power instances, the harmonics on the grid side should be reduced through multiple rectifications. A combined harmonic elimination method that includes a dual primary-side series-connected winding transformer and selective harmonic elimination pulse-width modulation is proposed to eliminate low-order current harmonics on the primary and secondary sides of transformers. Through an analysis of the harmonic influence caused by dead time and DC magnetic bias, a synthetic compensation control strategy is presented to minimize the grid-side harmonics in the dual primary side series-connected winding transformer application. Both simulation and experimental results demonstrate that the proposed control strategy can significantly reduce the converter input current harmonics and eliminates the DC magnetic bias in the transformer.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.5
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• pp.1286-1302
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• 2012

In this paper, the resource allocation problem with proportional fairness rate in cognitive OFDM-based wireless network is studied. It aims to maximize the total system throughput subject to constraints that include total transmit power for secondary users, maximum tolerable interferences of primary users, bit error rate, and proportional fairness rate among secondary users. It is a nonlinear optimization problem, for which obtaining the optimal solution is known to be NP-hard. An efficient bio-inspired suboptimal algorithm called immune clonal optimization is proposed to solve the resource allocation problem in two steps. That is, subcarriers are firstly allocated to secondary users assuming equal power assignment and then the power allocation is performed with an improved immune clonal algorithm. Suitable immune operators such as matrix encoding and adaptive mutation are designed for resource allocation problem. Simulation results show that the proposed algorithm achieves near-optimal throughput and more satisfying proportional fairness rate among secondary users with lower computational complexity.

• Korean Journal of Ecology and Environment
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• v.43 no.2
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• pp.298-306
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• 2010

We estimated aboveground primary productivity of Salix nipponica based on biomass using allometry and basal area at Janghang wetland in Han River estuary. In addition, we estimated secondary production of sesarmine crab (Sesarma dehaani) living under the Salix community to interpret relationships between Salix nipponica and Sesarma dehaani. Salix nipponica showed primary productivity of 4,777 g DW $m^{-2}yr^{-1}$, which appear to be the highest primary productivity in South Korea. The estimated amount of autochthonous organic matter from S. nipponica and allochthonous organic matter from the Han River into sediment was 359 g C $m^{-2}yr^{-1}$ and 347 g C $m^{-2}yr^{-1}$, respectively. The secondary productivity of Sesarma dehaani was 100.2 g FW $m^{-2}yr^{-1}$, which was 2.1% of the primary productivity of S. nipponica. The biomass of Sesarma dehanni was average 140 g FW $m^{-2}$, which consumed their prey of approximately 2,140 g FW $yr^{-1}$, which is equivalent to approximately 208 g C $m^{-2}yr^{-1}$.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.2
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• pp.45-49
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• 2015

In this paper, we proposed not specturm sensing but also save energy without consume energy of secondary network that spectrum sensing of cognitive applied energy harvesting scheme. Algorithms of sensing and harvesting is determine active or idle of primary network, compares the amount of energy that is harvested by energy harvesting scheme with the threshold. If secondary network to send a message and primary network is active, by changing frequency to use the spectrum. Further, if secondary network have no message, continues energy harvest. Therefore, spectrum sensing applied energy harvesting scheme, energy of secondary network is remove waste and charge energy, efficiency and utilization of cognitive network can be increase.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.3
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• pp.73-76
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• 2015

In this paper, we propose energy harvesting apply to spectrum sensing. In this case, we can be spectrum sensing without consume energy. Algorithms of sensing and harvesting are determine active or idle of primary network, Compares with the threshold energy and the amount of energy that is harvested by energy harvesting scheme. If the secondary network want to send a message while the primary network is active, secondary users will change frequency to use the spectrum. Further, if the secondary network has not message, it will continues harvest energy. Therefore, spectrum sensing applied the energy harvesting method, energy of secondary network is remove waste and charge energy. So, efficiency and utilization of cognitive network can be increase.

• Journal of the Korean Home Economics Association
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• v.44 no.5 s.219
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• pp.99-107
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• 2006

The purposes of this study are to identify the types of teacher efficacy, to present a theoretical base for teacher efficacy among Home Economics teachers and subsequently, to improve the quality in the practices of home economics education. To achieve these purposes, 263 secondary school home economics teachers were surveyed by the prime investigator. The three research questions of this study were: 1. What are the individual characteristics, the environmental characteristics and the trends of teacher efficacy among secondary school home economics teachers? 2. What is the factor in teacher efficacy among secondary school home economics teachers? 3. What are the types of teacher efficacy among secondary school home economics teachers? For these research questions, factor analysis and cluster analysis were conducted. The factor analysis on teacher efficacy with a survey of secondary school home economics teachers produced 5 factors of efficacy: classroom management, needs assistance, instructional strategies, environmental assistance and teaming assistance. The teacher efficacy had a mean of 3.58 and the home economics teachers showed a slightly higher level in teacher efficacy. Of the 5 efficacy factors, classroom management showed the highest level (M=3.89), followed by learning assistance (M=3.81), instrumental strategies (M=3.57), environmental assistance (M=3.42) and needs assistance (M=3.19). Overall, the teachers had positive feeling in teacher efficacy. Three types of teachers were found in the types of teacher efficacy: the supreme, the average and the efforts-needy. Those types were identified based on the mean scores of the five sub-domains from the factor analysis. To enhance the teacher efficacy, the needs assessments for the students and behavioral adjustment issues should be reflected in the curriculum of teacher education and workshops. The primary investigator suggested that continuous and long-term plans for teacher education need to be developed because short-term plans may not be effective in changing attitudes such as teacher efficacy.

• Education of Primary School Mathematics
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• v.16 no.3
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• pp.251-266
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• 2013

With elementary school students who have learned the primary concepts of the four arithmetic operations as its subjects, this study has investigated in depth how schema and transformed schema are composed by recognition of the correct concepts and connection of concepts, that is to say, what schema learners form along with transformed schema with the primary concepts of the four arithmetic operations to understand the secondary concepts when power and mixed calculations are taken into contents. It has also investigated how the subjects use the schema they have formed for themselves and the transformed schema to approach problem solving, and how their composition of concepts and schema in problem solving ability achieve transformations. As a result, we can tell that the recognition of precise primary concepts and transformed schema work as important factors in the development from the primary to the secondary concepts. Here, we can also see learn that the formation of the schema created due to the connection among the primary concepts and the recognition of them and of the transformed schema play more important roles in the development toward the secondary concepts and the solution of arithmetic problems than any other factors.

• Hwankyungkyoyuk
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• v.19 no.2 s.30
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• pp.133-146
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• 2006

The purpose of this study was to examine how environmental education teachers think about environmental teaching materials of their use in primary and secondary schools. For this purpose, six primary and secondary school teachers were selected for focus group discussion on October 17th, 2005. The discussion of focus group was recorded both on video and audio tapes. Teachers' discussion could be analyzed in the perspectives of two big ideas, 'content selection' and 'content organization and presentation'. The big ideas were categorized into several areas: 1) The idea of 'content selection' was classified into 4 areas such as integration, difficulty level, locality, and timeliness, 2) The idea of 'content organization and presentation' was classified into 4 areas such as learning motivation, teaching and teaming strategy, evaluation method, application of teaching materials. This study provided meaningful ideas, which can be used in developing environmental education materials as well as effective teaching and teaming strategies for school environmental educators.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.173.2-173.2
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• 2016

A two-step oxidation method was applied on Al6061 to debate the growth mechanism of plasma electrolytic oxidation (PEO) coating. The specimens were first oxidized in the primary electrolyte solution {$Na_3PO_4$ (8g/l), NaOH (2g/l), consequently, the specimens were transferred into a different electrolyte {$K_2ZrF_6$ (8g/l), NaOH (2g/l), $Na_2SiF_6$ (0.5g/l)} for further oxidation. The processes was conducted for various processing times. It was found the second step electrolyte component were reached to inner layers, in contrast to the primary step components which were thrustle to the outer layer. The presence of the secondary component in the inner layers were significantly varied with processing time which suggest the change in growth properties with processing time. further more the inside growth of the secondary component confirmed the increasing trend in the downward growth of the coating layer. The corrosion and hardness properties of the coatings were found highly improved with change in growth features with increasing the processing time.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.5
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• pp.1638-1653
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• 2014

A sequential optimization algorithm (SOA) for resource allocation in a cyclic-prefixed single-carrier cognitive relay system is proposed in this study. Both subcarrier pairing (SP) and power allocation are performed subject to a primary user interference constraint to minimize the mean squared error of frequency-domain equalization at the secondary destination receiver. Under uniform power allocation at the secondary source and optimal power allocation at the secondary relay, the ordered SP is proven to be asymptotically optimal in maximizing the matched filter bound on the signal-to-interference-plus-noise ratio. SOA implements the ordered SP before power allocation optimization by decoupling the ordered SP from the power allocation. Simulation results show that SOA can optimize resource allocation efficiently by significantly reducing complexity.