• Journal of Electrical Engineering and Technology
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• v.9 no.3
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• pp.820-826
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• 2014

It is well known that energy generated by a wind generator (WG) depends on the wind resources at the installation site. In other words, a WG installed in a high wind speed area can produce more energy than that in a low wind speed area. However, a WG installed at a low wind site can produce a similar amount of energy to that produced by a WG installed at a high wind site if the WG is designed with a rated wind speed corresponding to the mean wind speed of the site. In this paper, we investigated the power curve of a WG suitable for Korea's southwestern coast with a low mean wind speed to achieve a high capacity factor (CF). We collected the power curves of the 11 WGs of the 6 WG manufacturers. The probability density function of the wind speed on Korea's southwestern coast was modeled using the Weibull distribution. The annual energy production by the WG was calculated and then the CFs of all of the WGs were estimated and compared. The results indicated that the WG installed on the Korea's southwestern coast could obtain a CF higher than 40 % if it was designed with the lower rated speed corresponding to the mean wind speed at the installation site.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.8
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• pp.1334-1339
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• 2016

In a power grid that has a high wind power penetration, the fast voltage support of a wind power plant (WPP) during the grid fault is required to stabilize the grid voltage. This paper proposes a voltage control scheme of a doubly-fed induction generator (DFIG)-based WPP that can promptly support the voltage of the point of common coupling (PCC) of a WPP during the grid fault. In the proposed scheme, the WPP and DFIG controllers operate in a voltage control mode. The DFIG controller employs two control loops: a maximum voltage dip-dependent reactive current injection loop and a reactive power to voltage loop. The former injects the reactive power in proportion to the maximum voltage dip; the latter injects the reactive power in proportion to the available reactive power capability of a DFIG. The former improves the performance of the conventional voltage control scheme, which uses the latter only, by increasing the reactive power as a function of the maximum voltage dip. The performance of the proposed scheme was investigated for a 100-MW WPP consisting of 20 units of a 5-MW DFIG under various grid fault scenarios using an EMTP-RV simulator. The simulation results indicate that the proposed scheme promptly supports the PCC voltage during the fault under various fault conditions by increasing the reactive current with the maximum voltage dip.

• Journal of Electrical Engineering and Technology
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• v.8 no.5
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• pp.1021-1028
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• 2013

The frequency of a power system should be kept within limits to produce high-quality electricity. For a power system with a high penetration of wind generators (WGs), difficulties might arise in maintaining the frequency, because modern variable speed WGs operate based on the maximum power point tracking control scheme. On the other hand, the wind speed that arrives at a downstream WG is decreased after having passed one WG due to the wake effect. The rotor speed of each WG may be different from others. This paper proposes an algorithm for assigning the droop of each WG in a wind power plant (WPP) based on the rotor speed for the virtual inertial control considering the wake effect. It assumes that each WG in the WPP has two auxiliary loops for the virtual inertial control, i.e. the frequency deviation loop and the rate of change of frequency (ROCOF) loop. To release more kinetic energy, the proposed algorithm assigns the droop of each WG, which is the gain of the frequency deviation loop, depending on the rotor speed of each WG, while the gains for the ROCOF loop of all WGs are set to be equal. The performance of the algorithm is investigated for a model system with five synchronous generators and a WPP, which consists of 15 doubly-fed induction generators, by varying the wind direction as well as the wind speed. The results clearly indicate that the algorithm successfully reduces the frequency nadir as a WG with high wind speed releases more kinetic energy for the virtual inertial control. The algorithm might help maximize the contribution of the WPP to the frequency support.

• Journal of Mushroom
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• v.16 no.3
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• pp.186-191
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• 2018

In order to breed a new Pleurotus eryngii cultivar with a large pileus and convex shape, which are favorite traits of customers from Europe and North America, single crosses between monokaryotic mycelia derived from basidiospores of KNR2555 were performed to yield the new cultivar $2{\times}12$ chosen by cap shape (convex), diameter of pileus (60.7 mm), and quality (4.9) in a preliminary cultivation. The strain was named Gat_aeryni and was cultivated on a large scale for comparison with Kenneutari 2 ho at the GNARES and at mushroom farms. The yield of Gat_aeryni (71.7 g) was not significantly different from that of Kenneutari 2 ho (71.4 g), and the quality of the new cultivar was 6.8, which was not significantly different from that of a reference cultivar (6.5). Days for harvest, length, and diameter of the pileus in the two cultivars were statistically different by an independent t-test (P < 0.001, P < 0.05, P < 0.001 and P < 0.05 respectively). The new and reference cultivars were discriminated by PCR reactions with a primer set (URP1 and URP10) and simultaneous cultivation.

• Transactions of the Korean Society of Automotive Engineers
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• v.1 no.3
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• pp.1-11
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• 1993

An experimental study was carried out to evaluate the characteristics of transient performance of carburettered gasoline engine under rapid accelerating transient driving conditions. In order to evaluate the characteristics of transient performance quantitatively, the concept of dead time $t_d$ response delay time $t_r$ are introduced. Performance parameters such as air mass fiowrate Gat, engine speed N, manifold boost pressure Pb, and output torque T are measured simultaneously during the rapid opening of the throttle valve by the stepping motor. During the rapid opening of the throttle valve, air mass fiowrate Gat is increased immediately without delay time, but response of engine revolution N, and output torque T are delayed. Therefore hesitation, and stumble phenomena are occurred. Dead time $t_d$ and response delay time $t_r$ of engine revolution N, which is extremely delayed comparing to other performance parameters, are respectively 0.2-0.3sec., 3.0-4.6sec., and dead time rate $t_d/{\Delta}t$ and response delay time rate $t_r/{\Delta}t$ are linearly increased with the throttle valve opening rate ${\theta}$ during the acceleration from 12 degree to 20 degree at 1250rpm.

• Journal of Korean language education
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• v.25 no.1
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• pp.1-27
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• 2014

This study investigates how common English hedge expressions such as 'I think' and 'I guess' appear in Korean, with the aim of providing explicit explanation for English-speaking leaners of Korean. Based on a contrastive analysis of spoken English and Korean corpus, this study argues three points: Firstly, 'I guess' appears with a wider variety of modalities in Korean than 'I think'. Secondly, this study has found that Korean textbooks contain inappropriate use of registers regarding the English translations of '-geot -gat-': although these markers are used in spoken Korean, they were translated into written English. Therefore, this study suggests that '-geot -gat-' be translated into 'I think' in spoken English, and into 'it seems' in the case of written English and narratives. Lastly, the contrastive analysis has shown that when 'I think' is used with deontic modalities such as 'I think I have to', Korean use '-a-ya-get-': the use of hedge marker 'I think' with 'I have to', which shows obligation or speaker's volition turns the deontic modalities into expressions of speaker's opinion.

• Journal of the Korean Society of Food Science and Nutrition
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• v.45 no.12
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• pp.1808-1815
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• 2016

In this study, quality characteristics of three different kinds of Gat Kimchi, added with Cheonnyuncho fruit (C-fruit) water extract, Cheonnyuncho cladodes (C-cladodes) water extract, and without Cheonnyuncho water extract (control group), were investigated during storage for 80 days at $5{\pm}1^{\circ}C$. In terms of mineral content of Gat Kimchi, C-fruit group showed higher calcium and zinc contents than the control group, whereas Cheonnyuncho groups showed higher iron content, and C-cladodes showed higher potassium content than the control group. The pH was mostly higher in Cheonnyuncho groups than in the control group until 40 days of storage, whereas the pH of the C-cladodes group significantly decreased after 60 days. On the other hand, titratable acidity showed the reverse tendency during storage. Hunter's color L, a, and b values all increased during the storage period. The hardness value was significantly higher in Cheonnyuncho groups than in the control group after 40 days of storage, and hardness value of the C-fruit group was significantly higher than those of the other groups after 80 days of storage. In terms of sensory evaluation, there was no significant difference between the control group and Cheonnyuncho group during fermentation. As a result, the study suggests that addition of C-fruit extracts increase nutrition and function of Gat Kimchi during storage.

• Journal of the Korea Fashion and Costume Design Association
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• v.10 no.1
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• pp.99-116
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• 2008

This study reviewed pertinent literature and examined relics of manggon(a headband worn to hold a man's topknot hair in place), donggot(a topknot pin), and chigwan(a topknot cover). Before the modernized short hair style, wearing a gat was an important custom. Therefore, manggon, which was used to hold a man's hair in place under the gat, was considered an essential part of the man's official dress code. Donggot is a pin that held the topknot hair in place. It was a must have for a married man, like the binyeo, a lod-like hairpin, for a married woman. Unlike gwanja, it had nothing to do with official rank, but materials were of a variety of materials, including jade and gold. The structure of the donggot was studied in three parts-head, neck and body. Major forms for the head include the mushroom, bean and ball. Bullet and half-cut bullet forms were also found. Forms for the neck include straight-neck and curved-neck. A neck with a belt around a double chin was also found. Forms for the body include the tetrahedron, octahedron and cylinder. The most popular form for silver and white bronze donggot heads was the mushroom, followed by bean and pile forms. Chigwan is also called chipogwan, chichoal, choalgyesogwan, noingwan and sangtugwan. In poetry it was called chichoal, and it used to be called taegogwan in the past as well. Chigwan was so small that it managed to hold a topknot. According to confucian custom in the Joseon period, by wearing chigwan, men didn't display their bare topknot even when they didn't dress up. When they went out, they wore another official hat over the chigwan.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.1363-1369
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• 2015

The frequency of a power system should be maintained within the allowed limits for stable operation. When a disturbance such as generator tripping occurs in a power system, the frequency is recovered to the nominal value through the inertial, primary, and secondary responses of the operating synchronous generators (SGs). However, for a power system with high wind penetration, the system inertia will decrease significantly because wind generators (WGs) are operating decoupled from the power system. This paper proposes a dynamic droop-based inertial control for a WG. The proposed inertial control determines the dynamic droop depending on the rate of change of frequency (ROCOF). At the initial period of a disturbance, where the ROCOF is large, the droop is set to be small to release a large amount of the kinetic energy (KE) and thus the frequency nadir can be increased significantly. However, as times goes on, the ROCOF will decrease and thus the droop is set to be large to prevent over-deceleration of the rotor speed of a WG. The performance of the proposed inertial control was investigated in a model system, which includes a 200 MW wind power plant (WPP) and five SGs using an EMTP-RV simulator. The test results indicate that the proposed scheme improves the frequency nadir significantly by releasing a large amount of the KE during the initial period of a disturbance.

• Journal of the Korean Society of Costume
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• v.56 no.6 s.105
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• pp.72-86
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• 2006

The study aimed to materialize the meaning of the names through analyzing names that have synonyms and ambiguous words. The subjects of the study are seven foreign language study books such as $\ll$譯語類解 Yeokeoyuhae $\gg$ $\ll$譯語類解補編 Yeokeoyuhae - supplementary book$\gg$, $\ll$同文類解 Dongmunyuhae$\ggl$, $\ll$象語類解 Mongeoyuhae$\gg$, $\ll$象語類解補編 Mongeoyuhae- supplementary book$\gg$, $\ll$俊語類解 Oaeeoyuhae$\gg$ and $\ll$方름類釋 Bangeonyuseok$\gg$. The study selected vocabularies related with headgear, socks, clothing from those vocabulary books. The results are as follows: 1. The result focusing on the same Chinese terms in multiple forms has shown that '帽子(Moja), 斗逢(Dubong), 頭面(Dumyen), 襪(Mal), 木?(Mokgeuk), 　據子(Nanmalja), 樓子(Oja), 小樓子(Sooja), 養衣(Saui), 團領(Danlyeng), 掛子(Goija), 齊肩掛(Jegyengae), 彩兒(Sama), 單補(Dango)' have differences in Korean annotations, and it has been found that these differences are spelt as synonyms in general. 2. The result focusing on the same Korean terms in multiple forms has shown that Gamto, Gat, Satgat, Bolkki, Gatmo, Neoneol, Gatdongot, Ddambatgijeoksam, Nuyeok, Tyeollik, Goui, Baji, Gatdongot, Hatot, Dongdoljji, Yusam, Chima and ete. have 2 or more Chinese spellings. Among these, Neoneol, Ddambatgijeoksam, Nuyeok, Tyeollik, and etc. seem to have used similar Chinese spellings, and Gat, Dongdoljji, and etc. seem to have used Chinese spellings according to the multiple forms in each country. 3. There have also been records of terms seldom used at present such as Dalogi, Neoneol, and etc., and it has been found that Mahulae, Doljji, Dunja, and etc. are the terms have been geographically influenced by the northern race as they have been left as a dialect in North Korea currently. 4. Mahulae, Kulimae, Neolku, and etc. may be inferred as they have originated from Manchu language through pronunciation of each country spelt in translated books.