• Solar Energy
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• v.20 no.1
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• pp.1-9
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• 2000

Wind turbine system converts wind energy into electric energy. Since the velocity of wind is random in nature, control of the angular velocity of the blade is necessary in order to generate high quality electric power. The control of a blade can be divided into a stall regulation and a pitch control types. The stall regulation type which is based on the characteristics of an aerodynamic stall of the blades is simple and cheap, but it suffers from fluctuation of the resulting power. Or the contrary, pitch control type is based on the fact that the torque of the blade can be changed by varying the pitch angle of the blade. It is mechanically and mathematically complicated, but the control performance is better than that of the stall regulation type. This paper suggests a method of denying a mathematical modeling of the wind turbine system, and develops a speed control algorithm by pitch control. The validity of the algorithm is demonstrated with the results produced through sets of simulation.

• Phonetics and Speech Sciences
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• v.11 no.2
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• pp.15-21
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• 2019

Korean and English are both known to show on-focus pitch range expansion and post-focus pitch range compression (PFC). But it is not clear if this prosodic similarity would make it easy for Korean speakers to learn English focus prosody. In the present study, we conducted a production experiment using phone number strings to examine whether Korean learners of English produce a native-like focus prosody. Korean learners of English were classified into three groups (advanced, intermediate and low) according to their English proficiency and were compared to native speakers. Results show that intermediate and low groups of speakers did not increase duration, intensity, and pitch in the focus positions, nor did they compress those cues in the post-focus positions. Advanced speakers noticeably increased the acoustic cues in the focus positions to a similar extent as native speakers. However, their performance in post-focus positions was quite far from that of native speakers in terms of pitch and excursion size. These results thus demonstrate a lack of positive transfer of focus prosody from Korean to English in L2 learning, and learners may have to relearn it from scratch, which is consistent with a previous finding. More importantly, the results provide further support for the view proposed in other works that acoustic properties of PFC were not easily transferred from one language to another.

• Phonetics and Speech Sciences
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• v.12 no.1
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• pp.75-83
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• 2020

The purpose of this study was to examine how a singing program using self-voice monitoring for children with cochlear implants (CI) influences on the intonation and the accuracy of pitch production. To verify and estimate the effectiveness, a program was conducted with participants of 7 prelingual CI users, whose aged between 4 years and 7 years. The program adopted three stages from the self-voice monitoring: Listen, Explore, and Reproduce (LER stage). All participants received 8 singing sessions over 8 weeks, including pre-test, intervention, and post-test. For the pre and post-test, participants' singing of an excerpt of a song "happy birthday" and speaking three assertive sentences and three interrogative sentences were recorded and analyzed in terms of the intonation slopes at the end of the sentences and the melodic contour. From the sentence speeches, we found that the intonation slopes of the interrogative sentences significantly improved as they showed similar patterns with that of the average normal hearing group. Also, in regard to singing, we observed that the melody contour had progressed, as well as the range of pitch production had extended. The positive result from the intervention indicates that the singing program was effective for children with CI to develop the intonation skill and accuracy of pitch production.

• Korean Journal of Computational Design and Engineering
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• v.10 no.3
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• pp.199-209
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• 2005

In this paper, a digital simulation model for an automotive assembly line is constructed by adapting a digital manufacturing methodology. Applied methodology is a simulation for a plant level of the assembly production line. The first significance of this methodology is a validation of the production planning based on various scenarios. The second is pre-verification for the new production plan or production method. The third is a visualization of the production process. Several models were implemented and those models were verified. Then, it was possible to find a most efficient production scenario and production method.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.7
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• pp.28-35
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• 2010

In the display industry, COG bonding method is being applied to production of LCD panels that are used for mobile phones and monitors, and is one of the mounting methods optimized to compete with the trend of ultra small, ultra thin and low cost of display. In COG bonding process, electrical characteristics such as contact resistance, insulation property, etc and mechanical characteristics such as bonding strength, etc depend on properties of conductive particles and epoxy resin along with ACF materials used for COG by manufacturers. As the properties of such materials have close relation to optimization of bonding conditions such as temperature, pressure, time, etc in COG bonding process, it is requested to carry out an in-depth study on characteristics of COG bonding, based on which development of bonding process equipment shall be processed. In this study were analyzed the characteristics of COG bonding process, performed the analysis and reliability evaluation on electrical and mechanical characteristics of COG bonding using ACF to find optimum bonding conditions for ACF, and performed the experiment on bonding characteristics regarding fine pitch to understand the affection on finer pitch in COG bonding. It was found that it is difficult to find optimum conditions because it is more difficult to perform alignment as the pitch becomes finer, but only if alignment has been made, it becomes similar to optimum conditions in general COG bonding regardless of pitch intervals.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.52 no.1
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• pp.56-64
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• 2016

This study analyzed characteristics of officers' watch-keeping during fishing operation at the fisheries training ship KAYA (GT: 1,737 tons, Pukyong National University). It observed fishing works of three officers in wheel house of KAYA. The observations were carried out at the fishing ground 45 miles away from east of Jeju from 7 to 8 January 2010. The works and movements of the officers were recorded with three common video cameras and a 4-channel MPEG-4 Triplex DVR. Recorded data of the working circulation was analyzed by using the post-processing method. As a result of the traffic lines, the average (${\pm}S.D$) of working hour (min) and moving frequency (times), distance (m) and speed (m/min) during setting the net was 11.8 (0.9), 43.7 (8.1), 133.9 (35.8) and 10.5 (0.6), respectively. During trawling the net, it was 100, 241 (39.8), 615.7 (194.6) and 5.2 (1.6), respectively. During hauling the net, it was 17.6 (1.4), 41.0 (7.2), 196.9 (37.6) and 10.7 (0.8), respectively. In addition, it has a different tendency of the instrument usage frequency by the fishing works. During setting, the usage priority was CCTV, ECDIS, RPM and pitch controller, net monitor, GPS plotter, chart room, X-band radar, fish finder and public addressor. During trawling, it was CCTV, ECDIS, fish finder, X-band radar, net monitor, chart room, GPS plotter, RPM and pitch controller, auto pilot and steering, interphone, wind speed and direction indicator, No.1. VHF, navigation light control panel and public addressor. During hauling, it was CCTV, RPM and pitch controller, GPS plotter, public addressor, chart room, net monitor, X-band radar, auto pilot and steering and fish finder.

• Speech Sciences
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• v.11 no.3
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• pp.111-128
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• 2004

In English, a focused word with new information receives a pitch accent. This paper examines how English native speakers and Korean speakers produce and perceive focus in English yes-no questions. The production experiments show that native speakers realize an appropriate intonation of yes-no questions, in which a focused word has a low pitch accent followed by a high phrasal accent and a high boundary tone. However, Korean speakers usually give a high tone to a focused word. In a like manner, the perception experiments show that English native speakers judge a word with a low tone to be focused, while Korean speakers have difficulty in comprehending a focused word realized as a low tone. And it is found that Korean speakers tend to perceive low tones on sentence initial and final focused words better than those on sentence medial focused words, and they often perceive a word with a relatively high fundamental frequency or a sharp rise of fundamental frequency as a focused word. This paper shows that Korean speakers have trouble to produce and perceive an appropriate tonal pattern of a focused yes-no question, and that can cause confusion in a conversation with native speakers.

• Phonetics and Speech Sciences
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• v.6 no.3
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• pp.81-89
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• 2014

Korean English learners tend to have difficulty perceiving and producing English vowels. The purpose of this study is to examine a link between perceived and produced vowel spaces of Korean learners of English. Sixteen Korean male and female participants perceived two sets of English synthetic vowels on a computer monitor and rated their naturalness. The same participants produced English vowels in a carrier sentence with high and low pitch variation in a clear speaking mode. The author compared the perceived and produced vowel spaces in terms of the pitch and gender variables. Results showed that the perceived vowel spaces were not significantly different in either variables. Korean learners perceived the vowels similarly. They did not differentiate the tense-lax vowel pairs nor the low vowels. Secondly, the produced vowel spaces of the male and female groups showed a 25% difference which may have come from their physiological differences in the vocal tract length. Thirdly, the comparison of the perceived and produced vowel spaces revealed that although the vowel space patterns of the Korean male and female learners appeared similar, which may lead to a relative link between perception and production, statistical differences existed in some vowels because of the acoustical properties of the synthetic vowels, which may lead to an independent link. The author concluded that any comparison between the perceived and produced vowel space of nonnative speakers should be made cautiously. Further studies would be desirable to examine how Koreans would perceive different sets of synthetic vowels.

• Journal of the Korean Wood Science and Technology
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• v.18 no.3
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• pp.53-68
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• 1990

This research has been executed for maximization of lumber yield and more efficient use of small diameter logs. Sample logs from thinnings carne from densed artificial stands at the Kwangnung Experimental Forests situated in the central region of Korean peninsula. Species of sample logs were obtained to execute sawing and strength test for larch, and lumber strength test in full size for pitch pine and Korean pine. A survey on sawmills consuming domestic logs was carried out to know sawmill production, costs and utilization structure of lumber as a guide to business analysis. Results showed that sawing pattern from small logs less than 15cm in diameter was necessary to cut 9cm by 9cm square per one log in order to obtain high lumber recovery and provide for wide market needs. The total lumber yield of squares plus side boards was 56 percent to 58 percent from small logs and the yield for log sweep in 30 percent decreased by 24.5 percent in sawing production, compared to yield for straight logs. In sawing efficiency, production of lumber by twin band saw could be improved 238 percent higher than lumber of the same species produced by conventional sawmilling methods, and sawing accuracy with twin band saw was much higher at the lumber production than band saw. Lumber from the small larch logs has shown 70 knots per $m^2$ on its faces and also lumber showed lots of face checkings by air drying on the yard, compared to other species. MOR in bending of lumber in full size from small logs of larch was found ranging from 380kg/$cm^2$ to 460kg/$cm^2$, resulting in 40 percent less than the strength from clear small specimens. In lumber containing knots, cross grain, etc, longitudinal stress wave speed was delayed about 48 percent by defects in lumber from both larch and pitch pine logs. The surveyed sample sawmills consumed the domestic logs at the rate of 54 percent to 84 percent in the total timber consumption, showing high consumption at mills located in the mountains.

• Journal of Ecology and Environment
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• v.41 no.9
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• pp.265-270
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• 2017

Background: Over the years, pine pollens have been excluded as an allergen due to its relatively large size, low protein content, and waxy hydrophobic layer, despite their abundance. However, recent studies suggest the possibilities of pine pollens being allergens, and it has been reported that allergy symptoms were highly prevalent in areas with considerably large pine forests and high possibility of exposure to the pollen. Therefore, we conducted a comparative analysis of the allergenicities of the pollens from the dominant species of Korean pines, red pine (Pinus densiflora), black pine (Pinus thunbergii), and pitch pine (Pinus rigida), in mice. Methods: The protein composition of the pollens from the three pine species was compared via sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The pine pollens and proteins extracted from the pollens were introduced to BALB/c mice by nasal inhalation and application to exposed skin and the IgE produced by the mice were extracted from blood and analyzed via ELISA. Results: SDS-PAGE showed differing protein compositions of the pollens of the three pine species. Analysis of blood IgE compositions showed a similar amount of IgE produced when pollens were applied to skin. In contrast, when mice inhaled the pollens, P. densiflora was shown to induce significantly more IgE production than those of the other two species. Conclusions: The experimental results demonstrate that the pollens of all three South Korean pine species induce IgE production, and this production was more pronounced when the pollens were inhaled than when they were applied to the skin. Of the three species, the pollen of P. densiflora was found to induce the highest level of IgE production.