• The Transactions of the Korean Institute of Power Electronics
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• v.28 no.1
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• pp.68-75
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• 2023

This paper proposes a three-phase single-stage AC-DC converter for the small wind generation system. Input power factor improvement and insulated output can be implemented with the proposed three-phase single-stage AC-DC converter under the wide power generation voltage (80-260 V_ac) and frequency (10-42 Hz) in a small wind power generation (WPG) system. The proposed converter is also capable of zero-voltage switching in the primary-side switches and zero-current switching in the secondary-side diodes by phase-shift control at a fixed switching frequency. In addition, it is possible to control a wide output voltage (V_o: 39 V_DC-60 V_DC) by varying the link voltage and improving the input power factor (PF) and the total harmonic distortion factor (THD_i). Simulation and experimental results verified the validity of the proposed converter.

• The Plant Pathology Journal
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• v.39 no.6
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• pp.566-574
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• 2023

The aim of this study was to investigate the regulation of lantipeptide production in Streptomyces globisporus SP6C4, which produces the novel antifungal lantipeptides conprimycin and grisin, and to identify the role of cytochrome P450 (P450) in tis regulation. To investigate the regulation of lantipeptide production, we created gene deletion mutants, including ΔP450, ΔtsrD, ΔlanM, ΔP450ΔtsrD, and ΔP450ΔlanM. These mutants were characterized in terms of their morphology, sporulation, attachment, and antifungal activity against Fusarium oxysporum. The gene deletion mutants showed distinct characteristics compared to the wild-type strain. Among them, the ΔP450ΔlanM double mutant exhibited a recovery of antifungal activity against F. oxysporum, indicating that P450 plays a significant role in regulating lantipeptide production in S. globisporus SP6C4. Our findings highlight the significant role of P450 in the regulation of lantipeptide production and morphological processes in S. globisporus. The results suggest a potential link between P450-mediated metabolic pathways and the regulation of growth and secondary metabolism in SP6C4, thereby highlighting P450 as a putative target for the development of new antifungal agents.

• International Journal of Computer Science & Network Security
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• v.23 no.4
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• pp.55-68
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• 2023

In recent years, the Television White Space (TVWS) has attracted the interest of many researchers due to its propagation characteristics obtainable between 470MHz and 790MHz spectrum bands. The plenty of unused channels in the TV spectrum allows the secondary users (SUs) to use the channels for broadband services especially in rural areas. However, when the number of SUs increases in the TVWS wireless network the aggregate interference also increases. Aggregate interferences are the combined harmful interferences that can include both co-channel and adjacent interferences. The aggregate interference on the side of Primary Users (PUs) has been extensively scrutinized. Therefore, resource allocation (power and spectrum) is crucial when designing the TVWS network to avoid interferences from Secondary Users (SUs) to PUs and among SUs themselves. This paper proposes a model to improve the resource allocation for reducing the aggregate interface among SUs for broadband services in rural areas. The proposed model uses joint power and spectrum hybrid Firefly algorithm (FA), Genetic algorithm (GA), and Particle Swarm Optimization algorithm (PSO) which is considered the Co-channel interference (CCI) and Adjacent Channel Interference (ACI). The algorithm is integrated with the admission control algorithm so that; there is a possibility to remove some of the SUs in the TVWS network whenever the SINR threshold for SUs and PU are not met. We considered the infeasible system whereby all SUs and PU may not be supported simultaneously. Therefore, we proposed a joint spectrum and power allocation with an admission control algorithm whose better complexity and performance than the ones which have been proposed in the existing algorithms in the literature. The performance of the proposed algorithm is compared using the metrics such as sum throughput, PU SINR, algorithm running time and SU SINR less than threshold and the results show that the PSOFAGA with ELGR admission control algorithm has best performance compared to GA, PSO, FA, and FAGAPSO algorithms.

• Korean Journal of Weed Science
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• v.6 no.1
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• pp.1-6
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• 1986

The growth, development, and morphological characteristics of Echinochtoa colons (L.) Link were determined through one life cycle. E. colons emerged 2 to 3 days after seeding (DAS) and reached the two leaf stage by 8 DAS. During the early growth stages, root length was greater than plant height, but the relationship was reversed from 4 weeks after seeding (WAS). Tillering started from the third leaf of the main culm as the sixth leaf on the main calm emerged. The unfolding of the leaves and tillering followed a regular pattern during the vegetative growth period. This resulted in the production of 19 tillers (5 primary, 12 secondary, 1 tertiary, and I nodal) at the 14-leaf stage. Shoot-root weight ratio was highest just before panicle initiation. The second spike from the top of the panicle was the shortest and produced the fewest seeds. Thereafter, spike length and the number of seeds per spike generally increased, the lower the position of the spike on the panicle. Seeds on the lower spikes weighed less and had lower germination ability than those from the upper spikes. Adventitious roots arose from the leaf sheath bases of a flowering stalk. The ability to produce adventitious roots was greater in a younger stalls than in an older stalk.

• Journal of Korean Medical classics
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• v.25 no.1
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• pp.1-16
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• 2012

"Yixuerumen" is a comprehensive medical text published in the Ming-dynasty by Li Chan(李梴). In this text, Sanghan(傷寒, cold damage) is categorized among external contraction(外感) with much emphasis. The subject of this study is the verse "The Principal and secondary aspects must first be decided." and its annotations in the in the Sanghan chapter of "Yixuerumen". The complex theoretical structure of this verse was firstly analyzed, together with the historical background of how and why Li Chan adopted this concept. The Pyo-Bon concept is the contrast between phenomena(標) and its underlying source of motivation(本). The methodology for this study was to compare and analyze this main verse with contents on Sanghan and Un-gi(運氣) within the text, while reviewing historical theories explaining the physiology and pathology of the human body in terms of the Pyo-bon(標本) concept. As a result, we discovered that the Pyo-bon(標本) concept used in the aforementioned verse of "Yixuerumen" matches the Three Eum Three Yang(三陰三陽)-標本中氣(pyo-bon-jung gi)-gi transformation(氣化) theory of Un-gi(運氣). Li Chan created the connecting link in understanding the Three Eum Three Yang diagnosis system through the viscera/bowels theory(臟腑論) by adopting the Three Eum Three Yang(三陰三陽)-標本中氣(pyo-bon-jung gi)-gi transformation(氣化) theory from Un-gi. Li's work lead to several changes in the field of Sanghan. First, Li understood the disease pattern of Sanghan by using the accumulated knowledge of the viscera/bowel theory during the Jin-Yuan dynasty, and developed a medical perspective that observes the disease pattern based on the body's essence gi(精氣). Second, he set the category of the Sanghan-Three Eum Three Yang disease pattern, establishing a separate guideline. Third, by adding knowledge of herbs to the accumulated knowledge of the viscera/bowel theory, the process of diagnosis and herbal application were made explicable. On the other hand, in the process of interpreting the 三陰三陽 diagnosis system with viscera/bowels theory, theoretical inconsistencies appeared, of which Li tried to mend by several means. The results of the research on "Yixuerumen(醫學入門) the Sanghan chapter(傷寒篇)" calls for further studies, as it has effected both "Dongeuibogam(東醫寶鑑) the Sanghan part(寒門)" and "Dongeuisoosebowon(東醫壽世保元)" as well.

• Journal of Science Education
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• v.45 no.3
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• pp.336-348
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• 2021

The goal of this study is to investigate the current status of implementation of convergence education in elementary, middle, and high schools. A survey was conducted on 871 in-service teachers nationwide, and frequency analysis was conducted by school level. Key findings are as follows: first, 449 (51.5%) are found to practice convergence education. Second, the reason for implementing convergence education is the voluntary effort of teachers and the educational necessity for the future society. Third, it was found that convergence education is being implemented centered on science, arts, and social studies as a link between subjects in regular curriculum hours. Fourth, 270 (64%) of teachers who implemented convergence education in response to COVID-19 performed online convergence education, and experienced difficulties in creating class materials and communicating with students. Fifth, the excessive work of teachers, insufficient support for teacher training and research group activities, and lack of various convergence education programs are suggested as reasons for not implementing convergence education. This study hopes to provide implications for policy and implementation for revitalizing convergence education.

• Journal of The Korean Association For Science Education
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• v.29 no.6
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• pp.593-610
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• 2009

The purpose of this study was to investigate students' views on the value of school science lessons and the aspects of science lessons that appeal to students. For the investigation, semi-structured in-depth interviews with 16 secondary school students were conducted. The results showed that about half of the participants thought that science lessons are important, but not all students have to learn science. And they considered only intrinsic interest and career hopes as critical elements in judging the necessity of science education for all. To appeal to students: first, science lessons should have relevance to students' career hopes, interest, curiosity, abilities, real life, experiences, and test scores. Second, they should acquire students' understanding. Third, they should include more experiments. Finally, they should be related to real life, reflect students' interest and concerns, and link new things with what students already know in terms of contexts and contents. Students thought that science lessons are not suitable for students who don't desire to pursue a science-related career. This suggests that present science curriculum perceived by students doesn't match well with the idea of science education for all. To overcome this problem, students need to be included in the debate about the relevance of science curriculum.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.12
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• pp.2372-2380
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• 2015

In this paper, we propose frequency allocation and path selection scheme in underlay cognitive radio (CR) networks using network coding. In the proposed scheme, we choose the path with consideration of network coding and interference temperature in underlay CR networks and propose an optimization problem to maximize the system throughput of secondary users (SUs). Then, we represent the proposed optimization problem as the multi-dimensional multiple-choice knapsack problem and give the theoretical upper bound for the system throughput of SUs by using linear programming. Finally, we compute the system throughput of SUs by using brute-force search (BFS) and link quality first (LQF) scheme in underlay CR networks. Simulation results show that the system throughput of SUs with BFS is higher than that with LQF in underlay CR networks with and without application of network coding, respectively.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.295-300
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• 2001

A variety of high voltage DC power supplies employing the high frequency inverter are difficult to achieve soft switching considering a quick response and no overshoot response under the wide load variation ranges which are used in medical-use x-ray high voltage generator from 20kV to 150kV in the output voltage and from 0.5mA to 1250mA, respectively. The authors develops soft switching high voltage DC power supply designed for x-ray power generator applications, which uses series resonant inverter circuit topology with a multistage voltage multiplier instead of a conventional high voltage diode rectifier connected to the second-side of a high-voltage transformer with a large turn ratio. A constant on-time dual mode frequency control scheme operating under a principle of zero-current soft switching commutation is described. Introducing the multistage voltage multiplier, the secondary transformer turn-numbers and stray capacitance of high-voltage transformer is effective to be greatly reduced. It is proved that the proposed high-voltage converter topology with dual mode frequency modulation mode control scheme is able to be the transient response and steady-state performance in high-voltage x-ray tube load. The effectiveness of this high voltage converter is evaluated and discussed on the basis of simulation analysis and observed data in experiment.

• Journal of Electrical Engineering and Technology
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• v.9 no.6
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• pp.2224-2236
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• 2014

The performance of an isolated high voltage full bridge converter is improved using a voltage doubler. In a conventional high voltage full bridge converter, the diode of the transformer secondary voltage undergoes a voltage spike due to the leakage inductance of the transformer and the resonance occurring with the parasitic capacitance of the diode. In addition, in the phase shift control, conduction loss largely increases from the freewheeling mode because of the circulating current. The efficiency of the converter is thus reduced. However, in the proposed converter, the high voltage dual converter consists of a voltage doubler because the circulating current of the converter is reduced to increase efficiency. On the other hand, in the proposed converter, an input current is distributed when using parallel input / serial output and the output voltage can be doubled. However, the voltages in the 2 serial DC links might be unbalanced due to line impedance, passive and active components impedance, and sensor error. Considering these problems, DC injection is performed due to the complementary operations of half bridge inverters as well as the disadvantage of the unbalance in the DC link. Therefore, the serial output of the converter needs to control the balance of the algorithm. In this paper, the performance of the conventional converter is improved and a balance control algorithm is proposed for the proposed converter. Also, the system of the 1.5[kW] PCS is verified through an experiment examining the operation and stability.