• Journal of the Optical Society of Korea
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• v.11 no.3
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• pp.108-112
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• 2007

Spectroscopic ellipsometry (SE) has become an important tool in scatterometry based nano-structure 3D profiling. In this paper, we propose a novel 3D nano object recognition method by use of phase sensitive scatterometry. We claims that only phase sensitive scatterometry can provide a reasonable 3D nano-object recognition capability since phase data gives much higher sensitive 3D information than amplitude data. To show the validity of this approach, first we generate various $0^{th}$ order SE spectrum data ($\psi$ and ${\Delta}$) which can be calculated through rigorous coupled-wave analysis (RCWA) algorithm and then we calculate correlation values between a reference spectrum and an object spectrum which is varied for several different object 3D shape.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.276-279
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• 2005

This paper presents a novel cylindrical capacitive sensor (CCS) for both radial and axial motion measurements. Although the new CCS has almost the same geometric configuration as the conventional CCS, the unused axial area of the CCS is utilized to measure the axial motion of the rotor, which can affords more compact design and reduction of the system complexity. First, a theoretical model of the proposed CCS is derived. Based on the derived theoretical model, compensation methods to decouple the radial and axial motion measurements are proposed. In addition, error analysis is performed and a design rule is proposed to guarantee the same accuracy in measuring both radial and axial motions. Finally, a test rig and electronics for the proposed CCS are built and the effectiveness of the proposed CCS is verified with experiments and simulations.

• Wind and Structures
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• v.21 no.5
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• pp.523-536
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• 2015

To study the vibration frequency of super high-rise buildings in the process of vortex induced vibration (VIV), wind tunnel tests of multi-degree-of-freedom (MDOF) aero-elastic models were carried out to measure the vibration frequency of the system directly. The effects of structural damping, wind field category, mass density, reduced wind velocity ($V_r$), as well as VIV displacement on the VIV frequency were investigated systematically. It was found that the frequency drift phenomenon cannot be ignored when the building is very high and flexible. When $V_r$ is less than 8, the drift magnitude of the frequency is typically positive. When $V_r$ is close to the critical wind velocity of resonance, the frequency drift magnitude becomes negative and reaches a minimum at the critical wind velocity. When $V_r$ is larger than12, the frequency drift magnitude almost maintains a stable value that is slightly smaller than the fundamental frequency of the aero-elastic model. Furthermore, the vibration frequency does not lock in the vortex shedding frequency completely, and it can even be significantly modified by the vortex shedding frequency when the reduced wind velocity is close to 10.5.

• Computational Structural Engineering
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• v.20 no.1 s.75
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• pp.11-18
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• 2007

• Journal of the Society of Disaster Information
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• v.17 no.4
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• pp.890-896
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• 2021

Purpose: The called Aero System is important to find the well detected place in the livingroom or bedroom so, it needs to the confirmation through the Fire Dynamics Simulation Method: A fire simulation of a residential space of 59 m² was performed, and in order to find the point where the fire environment was exposed quickly, measuring points were installed at 0.6 m and 1.5 m in height for each bedroom and living room, and the point where the fire was quickly detected was confirmed. Result: It was confirmed that the temperature and carbon monoxide sensor set at a point of 1.5 m was quickly detected at the reference value. Conclusion: The Fire detection would be relatively quick if the product in which the fire extinguishing module and the AQI module were separated was installed on the wall.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.8
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• pp.767-773
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• 2010

In the present work, vibration control performance of piezoactuator-based active mount system for unmanned aero vehicle(UAV) equipment is evaluated via hardware in the loop simulation(HILS). At first, the vibration level of UAV is measured and from this vibration data, the proper piezostack actuator is selected. Then, the dynamic model of active mount system including four active mounts and UAV camera equipment is derived. In order to evaluate vibration control performance, the HILS system is constructed. The proposed mount is prepared as hardware part and the other mounts are considered in software part. A sliding mode controller is designed and implemented to the HILS system. Effective vibration control results are presented in both time and frequency domains.

• Journal of Ocean Engineering and Technology
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• v.37 no.4
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• pp.164-171
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• 2023

Vibration and noise must be considered to maximize the efficiency of a yaw system and reduce the fatigue load acting on a wind turbine. This study investigated a method for analyzing yaw-system vibration based on the change in the load-duration distribution (LDD). A substructure synthesis method was combined with a planetary gear train rotational vibration model and finite element models of the housing and carriers. For the vibration excitation sources, the mass imbalance, gear mesh frequency, and bearing defect frequency were considered, and a critical speed analysis was performed. The analysis results showed that the critical speed did not occur within the operating speed range, but a defect occurred in the bearing of the first-stage planetary gear system. It was found that the bearing stiffness and first natural frequency increased with the LDD load. In addition, no vibration occurred in the operating speed range under any of the LDD loads. Because the rolling bearing stiffness changed with the LDD, it was necessary to consider the LDD when analyzing the wind turbine vibration.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5A
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• pp.467-475
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• 2009

Existing studies have suggested Universal Curve only for supplemental damping by damper. Therefore net damping has been determined by means of arithmetic summation between intrinsic, aero-damping of cable and supplemental damping of damper. However linear combination approach by means of the arithmetic summation is not enough theoretical background. So validity of this approach should be verified in order to design adequate cable-damper system by engineers. This study establishes governing differential equation which can consider intrinsic, aero-damping and supplemental damping as well. And also analysis method is solved by combination of muller method and successive iteration method. Consequently, this study succeeds in verification for validity of linear combination approach. As a result of this study, linear combination approach is limitedly effective in case of low stiffness and optimum damping coefficient of damper, short distance from support to damper, lower vibration mode, low aero-damping, and normal windy environment. Whereas this study will be effective in case of opposite conditions, and existing studies or linear combination approach occur to further error. Meaning of this study presents exact solution for net damping of cable-damper system, and verifies linear combination approach by means of the analysis method. In the future, if monitoring of optimum damping coefficient of a damper against aero-damping is feasible on time, algorithm of this study will be available for control of cable and semi-active damper system such as magneto-rheological damper.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.5
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• pp.846-855
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• 1987

The experimental study was carried out to investigate the performance characteristics of the aero-valved pulsating combustor designed to increase the practical applications of the system. The geometric effect on the stable condition and the dynamic behavior of the system is identified. The equivalence ratio, the inflammability limit, the operating frequency, and thrust were also measured when the system oscillated stably. It is found that while the operating condition is sensitive to the diameter of the inlet pipe and the length of the tailpipe, the maximum value of the turn down ratio was obtained up to 3.2. The measured air flow rate shows that the equivalence ratio increases monotonously with the increasing fuel flow rate and decreasing air inlet diameter and tailpipe length. The measured operating frequency can be approximated by the simple linear equation and the discrepancy is within five percent. The system produced the maximum total thrust of 14N and the minimum specific fuel consumption of 0.155 Nm$^{3}$/h.N when the total thrust was 13N.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.2
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• pp.328-337
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• 1988

Experimental study was carried out to investigate the combustion characteristics of the hero-valved pulsating combustor with maximum operating capacity of 56kW. The pressure, the ion current, and the temperature fluctuations were simultaneously measured and statistically analyzed to identify the combustion process, the reignition and the mixing process of the reactants. It was found that the pulse combustion process was intermittent and the reignition of the reactants was caused by a direct contact and rapid mixing with the previous hot residuals. The analysis of the measured data indicated that the combustion process consisted of there stages in the combustion chamber; the preheating of the reactants in the vicinity of the air inlet pipe, the explosive combustion in the central region and the afterburning in the vicinity of the tailpipe. Wile the inflow of the fresh air occurred during the negative period of the pressure in the mechanical valved system, it occurred during the rising period of the pressure in the aero-valved system.