• Journal of Power Electronics
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• v.15 no.5
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• pp.1358-1366
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• 2015

This study focuses on an advanced second-order sliding mode control strategy for a variable speed wind turbine based on a permanent magnet synchronous generator to maximize wind power extraction while simultaneously reducing the mechanical stress effect. The control design based on a modified version of the super-twisting algorithm with variable gains can be applied to the cascaded system scheme comprising the current control loop and speed control loop. The proposed control inheriting the well-known robustness of the sliding technique successfully deals with the problems of essential nonlinearity of wind turbine systems, the effects of disturbance regarding variation on the parameters, and the random nature of wind speed. In addition, the advantages of the adaptive gains and the smoothness of the control action strongly reduce the chatter signals of wind turbine systems. Finally, with comparison with the traditional super-twisting algorithm, the performance of the system is verified through simulation results under wind speed turbulence and parameter variations.

• Journal of environmental and Sanitary engineering
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• v.8 no.1
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• pp.117-127
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• 1993

When incineration method is utilized as a disposal process of sludge, the treatment generally consists of thickening, dewatering and incineration, implying that sludge dewaterability has a colose relationship with operating condition of a thickener. Dewatering factors should be, therefore investigated for achieving effective sludge treatment. No research on this has been performed in Korea. This study has focused on the evaluation on the effects of thickener operating variables on sludge dewatering, including sludge feed types and retention time. Mixing ratio of the first and the second sludge and operation time were varied in order to observe the change of dewaterability and optimum input of chemical conditioner.

• Proceedings of the Korea Concrete Institute Conference
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• 1993.04a
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• pp.201-206
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• 1993

As the vibration loads are variable and the design criteria are more strict, in this study, the dynamic characteristics of the slab is analyzed and the and the vibration is controlled for the special peculiarity of structures. First, the procedure of dynamic analysis is developed by the finite element method and then examined by using the slab model tests. Second, in order to improve the dynamic characteristics, the effects of the number of supports, material properties, position of exciting force, added mass and dynamic balance on the dynamic behavior of reinforced concrete slabs are analysed. It is concluded that the vibration can be controlled by the change in the natural frequency of system and the use of the high-strength concrete or polymer impregnated concrete (PIC), and the dynamic characteristics can be considerably affected by the arrangement of equipments, added mass, and dynamic balance, etc.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.28 no.3
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• pp.52-60
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• 2020

The purpose of this study was to analyze the effects of Student Majoring in Flight Operation's propensity, safety behavior and aeronautical decision-making. According to the analysis results, First, parents' criticism of perfectionism factor is found to have a negative effect on safety behavior. Second, student pilot's proactive personality has a positive impact on both safety participation behavior and safety compliance behavior. Third, both safety participation behavior and safety compliance behavior are found to have a significant effect on situation awareness, solution generation and solution implementation of decision making stages. Therefore, this study is intended to provide useful basic data that can be applied to studies such as appropriate psychological counseling, optimal training directions and teaching methods in order to cultivate excellent human resources through safe flight training.

• 한국전산유체공학회:학술대회논문집
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• 2004.03a
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• pp.77-82
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• 2004

A new anisotropic mesh refinement method is proposed. The new method is based on a simple second order interpolation error indicator. Therefore, it is methodologically direct and intuitive as compared with traditional anisotropic refinement strategies. Moreover, it does not depend on the mesh type. The error indicator is face-wisely calculated for all faces in a mesh and the cell refinement type is determined by the configuration of face markings with a given threshold. For the sake of simplicity, an application for a poisson equation on a triangle mesh is considered. The error field and resultant mesh refinement pattern are compared and effects of the threshold selection are discussed. Applying anisotropic refinement with various thresholds, we observed higher convergence rates than those in the uniform refinement cases.

• Korean Journal of Biological Psychiatry
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• v.23 no.2
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• pp.41-47
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• 2016

Dementia with Lewy bodies (DLB) is the second most common causes of dementia. It can exhibit a variety of clinical symptoms including cognitive decline, cognitive fluctuation, visual hallucinations, parkinsonism, REM sleep behavior disorder, hypersensitivity to neuroleptics and autonomic dysfunctions. Despite more well-known criteria for DLB, there are often misdiagnosis and inappropriate treatment. It gives a lot of clinical burden to the clinician as well as to patients and families. When reducing the misdiagnosis, the burden of all will be reduced. The special concern and solicitation are needed in order not to miss the diagnosis when the cardinal features of DLB may not be volunteered by patients and the caregivers. To control the symptoms, clinicians must find and reduce drugs that can have the negative effects on DLB symptoms. There is limited evidence about specific interventions but available data suggest cholinesterase inhibitors improve the cognitive and behavioral symptoms and menmantine slightly improves the global impression.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.04a
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• pp.207-210
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• 2014

This paper is concerned with the prediction of lift-off acoustic loads for a launch vehicle. Intense acoustic load is generated when a launch vehicle is lifted off, and it can induce vibrations of a launch vehicle which cause damage or malfunction of a launch vehicle and a satellite. Lift-off acoustic loads of NARO are predicted by the modified Eldred's second method and the result is compared with the measured data in flight test. The prediction shows similar peak and shape of spectrum to the test data, but some discrepancy can be observed due to the predicted margin. In order to reduce such discrepancy, the sound pressure levels with four source distribution assumptions are calculated. Also, the surface diffraction effects are considered in the predict ion of lift-off acoustic loads, and the predicted result is more similar to the test data.

• Structural Engineering and Mechanics
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• v.51 no.1
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• pp.111-130
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• 2014

The aim of this study is to investigate the effects of the beam aspect ratio(L/h), hole diameter, hole location and stacking layer sequence ($[0/45/-45/90]_s$, $[45/0/-45/90]_s$ and $[90/45/-45/0]_s$) on natural frequencies of glass/epoxy perforated beams under room and high (40, 60, 80, and $100^{\circ}C$) temperatures for the common clamped-free boundary conditions (cantilever beam). The first three out of plane bending free vibration of symmetric laminated beams is studied by Timoshenko's first order shear deformation theory. For the numerical analyses, ANSYS 13.0 software package is utilized. The results show that the hole diameter, stacking layer sequence and hole location have important effect especially on the second and third mode natural frequency values for the short beams and the high temperatures affects the natural frequency values significantly. The results are presented in tabular and graphical form.

• Journal of the Korea Computer Industry Society
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• v.5 no.3
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• pp.355-362
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• 2004

This paper presents the common and different results between the galloping cable and torsional oscillations in suspension bridge. Numerical results of the galloping cable and torsional oscillations in suspension bridge are presented by using the second-order Runge Kutta method under the initial conditions. This paper shows that large amplitude solution can coexist with the small amplitude one as the frequency and amplitude of the oscillation change. The differences in symmetry and transient effects are presented.

• The Journal of Asian Finance, Economics and Business
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• v.2 no.3
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• pp.17-22
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• 2015

This paper examines the effect of impulsiveness of euro on Indian stock market. In order to examine the problem, we select rupee-euro exchange rates and S&P CNX NIFTY and BSE30 SENSEX to represent stock price. We select euro as it considered as second most widely used currency at the international level after dollar. The data are collected a daily basis over a period of 3-Apr-2007 to 30-Mar-2012. The statistical and time series properties of each and every variable have examined using the conventional unit root such as ADF and PP test. Adopting a generalized autoregressive conditional heteroskedasticity (GARCH) and exponential GARCH (EGARCH) model, the study suggests a negative relationship between exchange rate and stock prices in India. Even though India is a major trade partner of European Union, the study couldn't find any significant statistical effect of fluctuations in Euro-rupee exchange rates on stock prices. The study also reveals that shocks to exchange rate have symmetric effect on stock prices and exchange rate fluctuations have permanent effects on stock price volatility in India.