• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.12 no.1
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• pp.21-25
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• 2006

Measurements of accelerometer levels transmitted from the floor in commercials truck shipments were carried out transportation of 300 Kg-load from Gyungbu Highway(Waegouan-Seoul) to 88 Highway(Gwangju-Daegu). Different characteristics were observed the values measured the vibration levels with directions in the two Highway's as a function of road condition and truck speed. The results showed that the vibration levels of the Gyungbu Highway is much higher than those of the 88 Highway. A following analysis on the obtained values was used to get the acceleration spectral density (ASD) and power spectral density (PSD). For the entire transit route, the results showed that the level of vibration to vertical direction was significant effects for damaging the products carried compared to other directions such as longitudinal and transverse. This paper provides an updated history of measured characteristics of vibration levels for highways using mainly in domestic area.

• Journal of electromagnetic engineering and science
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• v.5 no.4
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• pp.197-203
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• 2005

This paper evaluates the impacts for interference from UWB system, and determines the tolerable UWB power spectral density(PSD) to the new deploying system, which is called a portable internet service in Korea. It also proposes the interference analysis scheme that can evaluate the characteristics of the performance degradation for portable internet service according to the emission power of UWB systems at the specified frequency bands. The proposed scheme includes a multi-rate and data service environments to deal with interference to portable internet service. It is obtained from simulation results that the transmission PSD of UWB systems should be rigidly restricted by less approximately 10 ${\~}$ 20 dB than FCC provisional limit for coexistence between UWB and portable internet service already allocated at 2.3 GHz frequency bands in Korea.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.675-679
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• 2005

This paper deals with the problem of gust load alleviation in active control for the case that aeroelasticity takes place due to interaction between wing structure and aerodynamics on wing when aircraft meets gust during flight. Aeroservoelasticity model includes wing structure modeled in FEM, unsteady aerodynamics in minimum state approximate method, and models of actuator and sensors in state space. Based on this augmented model, digitally redesigned gust load alleviation system is designed in sampled-data control technique. From numerical simulation, this digital control system is effective to gust load on aircraft wing, which is shown in transient responses and PSD analysis to random gust inputs.

• JSTS:Journal of Semiconductor Technology and Science
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• v.5 no.3
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• pp.187-194
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• 2005

An analysis of the 1/f or flicker noise in FD n-channel Double Gate SOI MOSFET is proposed. In this paper, the variation of power spectral density (PSD) of the equivalent noise voltage and noise current with respect to frequency, channel length and gate-to-source voltage at various temperatures and exponent $C(i.e\;1/f^c$ is reported. The temperature is varied 125 K from to room temperature. The variation of PSD with respect to channel length down to $0.1{\mu}m$ technology is considered. It is analyzed that l/f noise in FD n-channel Double Gate SOI MOSFET is due to both carrierdensity fluctuations and mobility-fluctuations. But controversy still exits to its origin.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.508-512
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• 2004

An aerospace vehicle in flight can be exposed to random gust which may cause critical structural failure. In this paper, the failure analysis is conducted for composite wing subjected to random gust. For this, the profile of random gust is idealized as a stationary Gaussian random process and the power spectral density (PSD) of wing bending moment induced by gust is obtained. The PSD function is converted to probabilistic distributions and the failure probability during total flight time is calculated by Monte Carlo simulation.

• Aerospace Engineering and Technology
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• v.7 no.1
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• pp.177-182
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• 2008

In this article, a mathematical modeling which is composed of linearized transfer functions on POGO suppression device was executed. The main parameters of PSD model can not be easily determined from the analysis due to the nonlinearity of the parameters. This article deals a method to get the values of the main parameters from the experimental results.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.3
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• pp.353-362
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• 2015

Platform screen door (PSD) installed at underground subway station has reduced the safety accident, but it may cause poor air ventilation condition due to the isolated exhaust duct in the subway tunnel area. In this study, the additional ventilation system was suggested, which can be installed at a void space (i.e., storage room under stairs) of platform in order to improve efficiency of air ventilation rate. Exhausted air from platform was directed to underneath of platform and joined with existing ventilation duct of train exhaust system (TES). One subway station in Seoul city was selected to predict the effectiveness of the suggested lower exhaust system by using the computational fluid dynamics (CFD) analysis. The predicted mean age of air was decreased by 16.5% which proves the improvement of air ventilation efficiency when the suggested lower exhaust system was applied.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.561-566
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• 2013

This study aims to develop the control system of vehicle height and apply this developed system to common passenger car. The vibration characteristics to affect ride comfort are examined through driving tests. The hydraulic control system of vehicle height is designed by Macpherson type used most commonly at current passenger car. Tests in this study are operated by the vehicle installed with genuine suspension system of Macpherson type, tuning suspension system and hydraulic control system of vehicle height. As vibration characteristics transmitted to vehicle become random types values of PSD(Power Spectrum Density) are compared.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.04a
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• pp.216-216
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• 2014

과거 유체 유발 진동(FIV : Fluid Induced Vibration)은 배관계 설계 하중에 고려되지 않은 설계 하중이었다. 하지만, 원자력 발전소 또는 화력 발전소의 배관형상이 복잡하고 고온수가 배관 내부에서 유동하는 배관계에서 육안으로 관측이 가능한 배관진동이 발생하였다. 이에 배관 진동에 대하여 원인 분석과 배관 구조 건전성 평가에 관심을 가지게 되었다. 배관 진동은 배관 형상에 따라 배관 내부 난류 유동에 대한 압력 변동이 하나의 원인이며, 고온수가 유동하는 배관일수록 압력 변동에 대한 배관 진동이 크게 나타나는 것으로 분석되었다. 배관 내부 난류 유동에 대한 압력 변동을 불규칙 수력하중이라고 한다. 본 연구에서는 배관 내부에서 난류 유동으로 발생하는 불규칙 수력하중을 유동해석을 이용하여 PSD(Power Spectral Density)로 산출하고, PSD 하중을 이용하여 불규칙 구조 응답 해석을 수행하여 배관계 응력 분포에 대하여 연구하였다. 배관 내부 난류 유동에 대한 불규칙 수력하중은 DES 난류 모델을 사용하여 시간에 대한 배관 내부 표면의 유체 속도를 유동 해석으로 산출하였으며, 유체 속도를 동압으로 계산한 후 FFT(Fast Fourier Transform)를 수행하여 PSD 하중으로 산출하였다. 그리고 불규칙 구조 응답 해석에서 배관 내부 유체 영향에 대한 진동 감쇠를 표현하기 위하여 유체 질량을 산출하고, 배관 구조 해석 모델 표면에 질량을 입력하는 방법으로 배관 고유진동수 및 불규칙 구조 응답 해석을 수행하였다.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.1
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• pp.34-43
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• 2007

As a method to improve the poor torque capacity on the continuously variable transmission(CVT), power splitted devices(PSD) reducing the power entering into the transmission has been considered. But this kind of PSD requires for the variator to be a large coverage of the speed ratio (CSR) Since the CSRs of the well-known push belt or the toroidal ones are not enough large, the power splitted CVTs (PSCVTs) using them should be made with multiple modes. inevitably adding the do9 clutches and the associated accessories. In this paper a PSCVT with single mode is conceptually designed A new continuously variable unit (CVU) consisting of the paired inner and outer spherical rotors is used. The CVU has large CSR and excellent compactness. As a PSD. a variable bridge (VB) using the Planetary gear units (PGUs) is considered because it has an upper bound on the power ratio. An optimal design to minimize the effective efficiency of the PSCVT is carried out. Through the performance analysis on the designed model, good expectation on the practicability in the heavy vehicle system is shown.