• Journal of Electrical Engineering and Technology
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• v.5 no.4
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• pp.614-622
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• 2010

This paper presents a control method, which reduces the pulsating torque and DC voltage problems of a doubly fed induction generator (DFIG)-based wind turbine system. To reduce the torque and power ripple, a current control scheme consisting of a proportional integral (PI) controller is presented in a positive synchronously rotating reference frame, which is capable of providing precise current control for a rotor-side converter with separated positive and negative components. The power theory can reduce the oscillation of the DC-link voltage in the grid-side converter. In this paper, the generator model is examined, and simulation results are obtained with a 3 kW DFIG-based wind turbine system to verify the proposed control strategy.

• Journal of the korean society of oceanography
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• v.31 no.3
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• pp.107-116
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• 1996

A shallow water numerical model is established to investigate the response of coastal water in the Korea Strait to typhoons that pass nearby the Korea Strait. Atmospheric pressure and wind by Fujita's formula (1952) and Miyazaki et al. (1961), respectively are used in the model. The model results show an agreement fair with the observation partially, but poor with the amplitude of the sea level variation. In particular, the discrepancy is larger in a typhoon passing through right side than that through left side of the Korea Strait. The model showes that the disagreement between the model and the observation can be caused by numerically unrealistic distributions of armospheric pressure and wind around the strait. In the Korea Strait the isostatic effects in the model were underestimated, whereas the wind fields were overestimated.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.10
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• pp.528-534
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• 2003

A grid connection algorithm is proposed for the doubly-fed induction generator (DFIG) which is widely adopted in high power variable speed wind turbine. Before the stator of DFIG is connected to grid, rotor-side converter is used to control the induced stator voltage. As a result, the stator transient current is limited below the rate value during the connection by the proposed synchronization of the stator voltage to the grid voltage. A wind power generation simulator using DC motor and wound-rotor induction generator is built and the dynamic characteristics of proposed algorithm is verified experimentally.

• Journal of Haehwa Medicine
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• v.8 no.2
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• pp.171-189
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• 2000

By Literatural studying on migraine, The results were obtained as fallow : 1. A different name on migraine were called hemicrania(頭偏痛, 邊頭痛, 偏頭風). 2. In the cause of a disease in migraine, the cases were clasified into the fallowing kind : internal cause were a decline in energy and blood(氣血具虛), external cause were outside evil(外邪) in wind cold heat wetness(風寒暑濕), non internal, external cause were exhaustion. The right side migraine were concerned phlegm heat, the right side migraine were concerned wind decline in blood. 3. Migraine is appeared on the side, For the reason, liver function in excess of normal limits(肝陽上亢), a sudden of liver fire(肝火) is becomeed of invasion upon soyangkuong(少陽經) in internal external cause 4. Usage method of medicines is appeared that order underclothes theraphy(內服法), to pump out in nose theraphy, to join head theraphy(頭點法), heating smoke theraphy(熏煙法) 5. CNIDII RHIZOMA(川芎) is in mostly general use for migraine, in that order LEDEBOURIELLAE RADIX(防風) ANGELICAE DAHURICAE RADIX(白芷) ASARI HERBA CUM RADICE(細辛) NOTOPTERYGII RHIZOMA(羌活) GLYCYRRHIZAE RADIX(甘草) CHRYSANTHEMI FLOS(菊花) BUPLEURI RADIX(柴胡) SCUTELLARIAE RADIX(黃芩) ANGELICAE GIGANTIS RADIX(當歸) GYPSUM FIBROSUM(石膏) MENTHAE HERBA(薄荷) GLYCYRRHIZAE RADIX(炙甘草) VITICIS FRUCTUS(蔓荊子), nature is in mostly general hot warm(辛溫), bitter cold(苦寒), guikuong(歸經) is in mostly general liver gall kuong(肝膽經), efficacy is in mostly general to remove wind pain (祛風止痛) and to down fire(瀉火).

• Journal of Power Electronics
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• v.17 no.1
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• pp.212-221
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• 2017

Permanent-Magnet Synchronous Generators (PMSGs) are used widely in Wind Power Generation Systems (WPGSs), and the Vienna rectifier was recently proposed to be used as the generator-side converter to rectify the AC output voltage in PMSG-based WPGS. Compared to conventional six-switch two-level PWM (2L-PWM) converters, the Vienna rectifier has several advantages, such as higher efficiency, improved total harmonic distortion, etc. The motivation behind this paper is to verify the performance of direct-driven PMSG wind turbine system based-Vienna rectifier by using a simulated direct-driven PMSG WPGS. In addition, for the purpose of reducing the reactive power loss of PMSGs, this paper proposes an induced voltage sensing scheme which can make the stator current maintain accurate synchronization with the induced voltage. Meanwhile, considering the Neutral-Point Voltage (NPV) variation in the DC-side of the Vienna rectifier, a NPV balancing control strategy is added to the control system. In addition, both the effectiveness of the proposed method and the performance of the direct-driven PMSG based-Vienna rectifier are verified by simulation and experimental results.

• 한국전산유체공학회:학술대회논문집
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• 2007.04a
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• pp.64-67
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• 2007

In the present study, the wind pressure transients on platform screen door in side platforms caused by passing trains have been investigated numerically. The transient compressible 3-D full Navier-Stokes solution is obtained with actual operational condition of subway train and the moving mesh technique is adopted considering the train movement. To achieve more accurate analysis, the entrance and exit tunnel of platform are included in a computational domain and detailed shape of train is also modeled Numerical analyses were conducted on five operational condition which are different velocity variation of subway train, existence of stationary train and passing each other trains. The results show that pressure load on platform screen door is maximized when the two trains are passing each other. It is also seen from the computational results that the maximum pressure variation was found to be satisfactory to various foreign standards.

• Journal of Environmental Impact Assessment
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• v.19 no.6
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• pp.583-590
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• 2010

To determine nocturnal inversion characteristics at the leeward side of high-rise building, air temperature data were observed at 10 minute interval from February 22, 2010 to April 15, 2010. The observed data were compared, analyzed and examined to illustrate air temperature differences between the roof (XAR) and surface (XAG) of X apartment. The wind speed, wind direction and precipitation data were also observed at XAR and YJL (Yangjae Stream) sites at the same time. After the analysis, the maximum nocturnal inversion was observed by $4.0^{\circ}C$ at 3:40, 3:50, 4:10 on February 24th 2010, at that time the weather condition was clear and weak wind. Air temperature inversions at the leeward side of high-rise building were observed on whole day in wintertime and air temperature inversion intensity was also higher than other nearby area (SMG).

• Journal of computational fluids engineering
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• v.12 no.4
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• pp.1-6
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• 2007

In the present study, the wind pressure transients on platform screen door in side platforms caused by passing trains have been investigated numerically. The transient compressible 3-D full Navier-Stokes solution is used with actual operational condition of subway train by adopting the moving mesh technique considering the train movement. To achieve more accurate analysis, the entrance and exit tunnel connecting the stations are included in a computational domain with modeling the detailed shape of the train. Numerical analyses are conducted on five operational conditions which include the variation of the train speed, case with or without the train stopped in the other track, and case for two trains passing each other inside the station. The results show that pressure load on platform screen door is maximized when the two trains are passing each other. It is also seen from the computational results that the maximum pressure variation for the cases considered in the present study is found to be satisfactory to various foreign standards.

• Wind and Structures
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• v.34 no.1
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• pp.101-113
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• 2022

We experimentally investigate the high-Reynolds flow around a rectangular cylinder of aspect ratio 5:1. This configuration is the object of the international BARC benchmark. Wind tunnel tests have been carried out for the flow at zero angle of attack and a Reynolds number, based on the crossflow cylinder length and on the freestream velocity, equal, to 40 000. Velocity measurements are obtained by using hot-wire anemometry along 50 different cross-flow traverses on the cylinder side and in the near wake. Differential pressure measurements are acquired on multiple streamwise sections of the model. The obtained measurements are in a good agreement with the state-of-the-art experiments. For the first time among the several contributions to the BARC benchmark, detailed flow measurements are acquired in the region near the cylinder side and in the near-wake flow. The edges and the thickness of the shear layers detaching from the upstream edges are derived from velocity measurements. Furthermore, we compute the flow frequencies characterizing the roll-up of the shear layers, the evolution of vortical structures near the cylinder side and the vortex shedding in the wake.

• Wind and Structures
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• v.27 no.1
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• pp.29-40
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• 2018

To investigate the characteristics of the combined wind field produced by the natural wind field and the train-induced wind field on the bridge, the aerodynamic models of train and bridge are established and the overset mesh technology is applied to simulate the movement of high-speed train. Based on ten study cases with various crosswind velocities of 0~20 m/s and train speeds of 200~350 km/h, the distributions of combined wind velocities at monitoring points around the train and the pressure on the car-body surface are analyzed. Meanwhile, the difference between the train-induced wind fields calculated by static train model and moving train model is compared. The results show that under non-crosswind condition, the train-induced wind velocity increases with the train speed while decreases with the distance to the train. Under the crosswind, the combined wind velocity is mainly controlled by the crosswind, and slightly increases with the train speed. In the combined wind field, the peak pressure zone on the headstock surface moves from the nose area to the windward side with the increase of wind velocity. The moving train model ismore applicable in analyzing the train induced wind field.