• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.12
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• pp.1659-1665
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• 2015

In general, AT(Auto-transformer) is used to improve voltage sag and inductive interference in power lines and communication lines in AC electrical railway feeding system. Especially, Korean AT feeding system has different composition compared to other countries like Japan or France, so that it has some special characteristics. However, relays imported from other countries have been used in Korea, and settings of these relays should be modified and reflect distinct characteristics of Korean AT feeding system. Therefore, study about fault analysis based on modeled AT feeding system is important. In this paper, we modeled a single track AT feeding system by using PSCAD and analyzed fault current flow in case of trolley-rail short circuit fault. Finally, we presented current magnitude of each branch expressed by boosting current of AT.

• Journal of Power Electronics
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• v.17 no.3
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• pp.695-703
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• 2017

In order to satisfy the urgent requirements for the overheating protection of induction motors, an approach that can be used to identify motor temperature has been proposed based on the rotor slots harmonic (RSH) in this paper. One method to accomplish this is to improve the calculation efficiency of the RSH by predicting the stator winding distribution harmonic order by analyzing the harmonics spectrum. Another approach is to increase the identification accuracy of the RSH by suppressing the influence of voltage flashes or current surges during temperature estimation based on model predictive control (MPC). First, an analytical expression of the stator inductance is extracted from a steady-state positive sequence motor equivalent circuit model developed from the rotor flux field orientation. Then a procedure that applies MPC for reducing the identification error of the rotor temperature caused by voltage sag or swell of the power system is given. Due to this work, the efficiency and accuracy of the RSH have been significantly improved and validated our experiments. This work can serves as a reference for the on-line temperature monitoring and overheating protection of an induction motor.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.64 no.2
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• pp.79-84
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• 2015

Voltage sags are considered the dominant disturbances affecting power quality. Dynamic voltage restorers(DVRs) are mainly used to protect sensitive loads from the electrical network voltage disturbances such as sags or swells and could be used to reduce harmonic distortion of ac voltages. The typical DVR topology essentially contains a PWM inverter with LC Filter, an injection transformer connected between the ac voltage line and the sensitive load, and a DC energy storage device. For injecting series voltage, the PWM inverter is used and the passive filter consist of inductor(L) and capacitor(C) for harmonics elimination of the inverter. However there are voltage pulsation responses by the characteristic of the LC passive filter that eliminate the harmonics of the PWM output waveform of the inverter. Therefore, this paper presented design and feedback performance of LC filter used in the DVRs. The voltage control by LC filter should be connected in the line side since this feedback method allows a relatively faster dynamic response, enabling the elimination of voltage notches or spikes in the beginning and in the end of sags and strong load voltage THD reduction. Illustrative examples are also included.

• The Journal of Information Technology
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• v.8 no.3
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• pp.105-115
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• 2005

The CMA and MMA blind equalization algorithm has the inevitable large residual error caused by mismatching between the symbol constellation at a steady state after convergence. Stop-and-Go algorithm has a very superior residual error characteristics at a steady state but a relatively slow convergence characteristics. In this paper, we propose a SAG-Flagged MMA as a new adaptive blind equalization algorithm with a Stop-and-Go flag which follows a flagged MMA in update scheme of tap weights as appling the flag obtaining from Stop-and-Go algorithm to MMA. Using computer simulation, it is confirmed that the proposed algorithm has an enhancing performance from the viewpoint of residual ISI, residual error and convergence speed in comparison with MMA and Stop-and-Go algorithm. Algorithm has a new error function using the decided original constellation instead of the reduced constellation. By computer simulation, it is confirmed that the proposed algorithm has the performance superiority in terms of residual ISI and convergence speed compared with the adaptive blind equalization algorithm of CMA family, Constant Modulus Algorithm with Carrier Phase Recovery and Modified CMA(MCMA).

• Biotechnology and Bioprocess Engineering:BBE
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• v.6 no.6
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• pp.376-385
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• 2001

Considerable attention has been focused in recent years upon the field of biosorption for the removal of metal ions from aqeous effluents. Compared to other technologies, the advan-tages of biosortption are the high purity of the treated waste water and the cheap raw material. Really, the first major challenge for the biosorption field is to select the most promising types of biomass. Abundant biomass types either generated as a waste by-product of large-scale industrial fermentations particularly fungi or certain metal-binding seaweeds have gained importance in re-cent years due to their natural occurrence, low cost and, of course good performance in metal biosorption. Industrial solutions commonly contain multimetal systems or several organic and in organic substances that form complexes with metals at relatively high stability forming a very complex environment. When several components are present, interference and competition phe-nomena for sorption sites occur and lead to a more complex mathematical formulation of the process. The most optimal configuration for continuous flow-biosorption seems to the packed-bed column which gets gradually from the feed to the solution exit end. Owing to the com-petitive ion exchange taking place in the column, one or more of the metals present even at trace levels may overshot the acceptable limit in the column effluent before the breakthrough point of the trargeted metal. Occurrence of 'overshoot's and impact on havey metal removal has not been analyzed enough. New trends in biosorption are discussed in this review.

• The Journal of Internal Korean Medicine
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• v.12 no.1
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• pp.166-182
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• 1991

This study has been carried out to investigate the cause and symptom of Hae su (咳嗽) cause by a cold referring to 25 literature. 1. Cause : wind (風), cold (寒), heat (署), moisture (濕), dryness (燥), fire (火). It appears to cause double and above. 2. Symptoms : PunghanHaeSu (風寒咳嗽) ; HaeSu (咳嗽), Balyul (發熱), DamHueSaegBaeg (痰稀色白), Hu Yang Sung Tag (喉痒聲濁), BiSaegYuChe (鼻塞流涕), OhPungHan (要風寒), DooShinTong (頭身痛), TaeBaqBaeg (笞薄白), Maeg Bu Gin (脈浮緊). PungYeulHaeSu (風熱咳嗽) ; HaeSu (咳嗽), DamJo (痰稠), SaegHwang (色黃), KaegChulBulSang (喀出不痰), KuKallnTong (口瀉咽痛), BalYeul (發熱), OhPungYuHan (要風有肝), HogYuDuTong (或有頭痛), TaeBagHwang (笞薄黃), Maegbusag (脈浮數). JoYeulHaeSu (燥熱咳嗽) ; KunHaeMuDarn (乾咳無痰), HogDamJungDaeHyulSa (或痰中帶血絲), HaelnHungTong (咳引胸痛), BiJolnKun (鼻燥咽乾), pliogyuOhPungBalYeul (或要風發熱), TaeBagHqangIKun (笞薄黃而乾), MaegSeSag (脈細數). 3. Treatment ; PungHanHaeSu ; SoPungSanHan (疏風散寒), Sun PaeJiHae (宣肺止咳), PungYeulHaeSu ; SoPungchungYeul (疏風淸熱), SunPaeJiHae (宣肺止咳), JoYeulHaeSu; CheongPoeYunJo (淸肺潤燥), SaengJinJiHae (生津止咳). Basing on the literature research, I found that Hae Su (咳嗽) caused by a cold belong to category of YugEum(六淫).

• Journal of Gifted/Talented Education
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• v.12 no.2
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• pp.17-29
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• 2002

The purpose of this study was to examine the sex role identity of children who are gifted in mathematics and sciences. In order to investigate the sex role identity types, Korean Sex Role Inventory was administered to 192 gifted and 128 normal children in elementary schools. The research findings are the followings: 1. There was no statistically significant difference in the sex role identity types between gifted boys and gifted girls. 2. There were statistically significant differences between gifted and normal groups. The gifted children are more androgynous and less undifferentiated than normal group. 3. Gifted boys were higher in androgyny and masculinity than the normal group. Gifted girls showed the same pattern.

• Journal of the Korean Society of Food Science and Nutrition
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• v.27 no.5
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• pp.833-839
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• 1998

Hwangkeum Kong was stored at 5$^{\circ}C$, $25^{\circ}C$ and 35$^{\circ}C$ for 8 months to investigate the changes of the suitability for Tofu processing. The properties of Tofu prepared with the soybeans stored at 5$^{\circ}C$ for 8 months showed no significant differences from the non-stored control soybeans. However, soybeans stored under high temperatures showed low yield, water holding capacity and Sag value of Tofu Compared with the soybeans stored at 5$^{\circ}C$ for 8 months, fracturability in the texture of Tofu significantly increased when the soybeans had been stored at $25^{\circ}C$ and 35$^{\circ}C$ for 8 months, while hardness, cohesiveness, adhesiveness, elasticity, gumminess and chewiness decreased. The color of Tofu changed from pale yellow to brown depending on high temperature and long-term of storage. The Tofu prepared with the soybeans stored under high temperatures was significantly different in sensory evaluations from the non-stored soybeans as well as from the soybeans stored at 5$^{\circ}C$ for 8 months in color(p<0.01), texture(p<0.05) and taste(p<0.05).

• Journal of Welding and Joining
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• v.30 no.3
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• pp.38-43
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• 2012

In this study, active metal brazing methods for $ZrO_2$ and Ti alloy were discussed. To get a successful metal-ceramic bonding, various factors (melting temperature, corrosion, sag resistance, thermal expansion coefficient etc. of base materilas and filler metal) should be considered. Moreover, in order to clarify bonding between the metal and ceramic, the mechanism of the interfacial structure of the joints should be identified. The driving force for the formation of metal and ceramic interfaces is the reduction of the free energy which occurs when their contact becomes complete. Interfacial bonding depends on the material combinations and the bonding processes. This study describes the bonding between ceramic and metal in an active metal brazing.

• Journal of Power Electronics
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• v.19 no.5
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• pp.1270-1277
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• 2019

A problem with virtual synchronous generator (VSG) systems is that they are difficult to operate stably with photovoltaic (PV) power as the DC side. With this problem in mind, a PV-VSG control strategy considering the dynamic characteristics of the DC side is proposed after an in-depth analysis of the dynamic characteristics of photovoltaic power with a parallel energy-storage capacitor. The proposed PV-VSG automatically introduces DC side voltage control for the VSG when the PV enters into an unstable working interval, which avoids the phenomenon where an inverter fails to work due to a DC voltage sag. The stability of the original VSG and the proposed PV-VSG were compared by a root locus analysis. It is found that the stability of the PV-VSG is more sensitive to the inertia coefficient J than the VSG, and that a serious power oscillation may occur. According to this, a new rotor model is designed to make the inertial coefficient automatically change to adapt to the operating state. Experimental results show that the PV-VSG control strategy can achieve stable operation and maximum power output when the PV output power is insufficient.