• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.864-868
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• 2005

This paper develops an analysis model of a piezoelectric transducer. The transducer considered in this paper is a bolt-clamped Langevin-type transducer, which consists of a couple of piezoelectric discs, a couple of metal blocks for added mass effect, and a bolt to tighten them. A new analytical model for the transducer has been developed by taking into account the contact area between the piezoelectric ceramic and the metal block. The analysis model is verified by calculating the variations of the resonance frequency due to the contact area and comparing them with reported experimental results.

• IEMEK Journal of Embedded Systems and Applications
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• v.14 no.3
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• pp.123-131
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• 2019

In recent years, a non-contact respiration and heart rates monitoring via IR-UWB radar has been paid much attention to in various applications - patient monitoring, occupancy detection, survivor exploring in disaster area, etc. In this paper, we address a novel approach of real time heart rate estimation using IR-UWB radar. We apply sine fitting and peak detection method for estimating respiration rate and heart rate, respectively. We also deploy two techniques to mitigate the error caused by wrong estimation of respiration rate: a moving average filter and finding the frequency of the highest occurrence. Experimental results show that the algorithm can estimate heart rate in real time when respiration rate is presumed to be estimated accurately.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2000.06a
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• pp.134-141
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• 2000

The real area of contacts, average film thickness, mean real pressure, and mean hydrodynamic pressure are investigated numerically in this study, especially for the parallel thrust bearing. Model surface is generated numerically with given autocorrelation function and some surface profile parameters. Then the average Reynolds equation contained flow factors and contact factor is applied to predict the effects of surface roughness in mixed lubrication regimes. In this equation, flow factors are defined as correction terms to smooth out high frequency surface roughness and contact factor is introduced to relieve from obtaining the average film thickness. Therefore the computation time to obtain h can be reduced.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.3
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• pp.155-162
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• 2004

This paper presents the fabrication procedure and the experiments for the 3-axis fine positioning stage proposed in［1］. First, the dynamic characteristics of the actuator and the stage are tested with the preload changed in order to validate the stage design specifications. Secondly, the performance of the stage is also evaluated on the accuracy associated with linear positioning, angular error, and straightness error. Experimental results show that the developed stage is accurate enough to be used for nanometer positioning. Through the analysis and experiment, the developed fine positioning stage are found to have a long stroke due to the magnetically preloaded PZT actuators, the minimum motion crosstalk due to the use of a ball contact mechanism and the compact design.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.630-635
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• 2002

This work is concerned with the damage size estimation by using propagating bending wave signals in a beam. For the accurate estimation, we apply the continuous wavelet transforms to the incident waves and the reflected waves from a small damage in a long cylindrical beam. In particular, we propose to use the ratio of the magnitude of the incident and reflected waves along the ridges in the wavelet-transformed time-frequency plane. This technique is applied to the signals measured by non-contact magnetostrictive sensors. Experimental results indicate that the present method using the magnetostrictive sensor can be quite effective for accurate damage size estimation with simple measurements.

• Child Health Nursing Research
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• v.8 no.1
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• pp.77-85
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• 2002

Recently in Korea, the adolescents' sexual problems including sexual violence have increased, and those phenomena have escalated to be one of the major social issues. This study was conducted to identify the variables related to the sexual harassments of the Korean adolescents. The variables to which the subjects belong were gender, school grade, religion, extracurricular activity, amount of pocket money, school performance traffic mean to school, ownership of PC, internet contact frequency and place, contact to pornography, heterosexual friend, drinking, and smoking. The period of survey was from July 2000 to Dec. 2000. The subjects were 475 middle and high-schoolers in Busan and Kyung-Nam. The instrument to measure sexual harassments of the subjects was questionnaire. That was gained by modifying the three patterns(physical, verbal and visual) in the manual provide by the Ministry of Labor(1999). The degree of sexual harassments was measured by 4-point Likert scale. The collected data was analyzed with t-test and ANOVA by SPSS win(10.0). The findings were as follows ;1. The variables related to the physical harassment were gender, age, pocket money, perceived school performance, traffic means, contact to pornography, having heterosexual friend, experience of drinking and smoking.2. The variables related to the visual harassments were gender, age, perceived school performance, traffic mean, internet contact, contact to pornography, having heterosexual friend, experience of drinking & smoking.3. The variables related to the verbal harassments were gender, age, pocket money, perceived school performance, traffic mean, internet contact, contact to pornography, having heterosexual friend, and experience of drinking & smoking.

• Korean Journal of Culture and Social Issue
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• v.19 no.3
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• pp.435-456
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• 2013

This study examined the factors influencing aging anxiety among college students. 336 college students from universities in Seoul and Gyeonggi-Do were participated in the survey. Regression analyses confirmed that variables influencing 4 dimensions of aging anxiety are different. Quality of contact and attitude toward elderly predicted 'Fear of Old People' dimension. As for 'Psychological Concerns', death anxiety, attitude toward elderly and Quality of contact were influencing factors. Death anxiety, Quality of contact and sex was significant factors predicting. 'Physical/Appearance anxiety'. As for Fear of Losses, Death anxiety and attitude toward elderly affect. On the whole college students' aging anxiety tended to increase as having lower death anxiety, positive quality of contact, positive attitude towards elderly. And female has higher Physical/ Appearance anxiety than male. whereas results have not found a correlation between either knowledge of aging and frequency of contact with aging anxiety. Discussion focuses on the importance of the findings, limitations and future directions.

• The Journal of the Acoustical Society of Korea
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• v.37 no.2
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• pp.92-98
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• 2018

This paper is a study on the generation mechanism of propeller singing based on the cavitation tunnel test, underwater impact test, finite element analysis and computational flow analysis for the model propeller. A wire screen mesh, a propeller and a rudder were installed to simulate ship stern flow, and occurrence and disappearance of propeller singing phenomenon were measured by hydrophone and accelerometer. The natural frequencies of propeller blades were predicted through finite element analysis and verified by contact and non-contact impact tests. The flow velocity and effective angle of attack for each section of the propeller blades were calculated using RANS (Reynolds Averaged Navier-Stokes) equation-based computational fluid analysis. Using the high resolution analysis based on detached eddy simulation, the vortex shedding frequency calculation was performed. The numerical predicted vortex shedding frequency was confirmed to be consistent with the singing frequency and blade natural frequency measured by the model test.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.273-274
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• 2002

In order to evaluate the flying characteristics of slider, the acoustic emission (AE) as well as friction signals are typically utilized. In this work the frequency spectrum analysis is performed using the AE signal obtained during the head/disk interaction such as load/unload mechanism using ramp, impact situation in the presence of a bump on disk surface and other contact phenomena including particle interaction. It was shown that the influence of impact can be characterized effectively in the AE frequency spectrum. As a result of this work, frequency spectrum analysis will be utilized with better understanding for studying the head/disk interface (HDI) characteristics and monitoring the particle interaction in HDI effectively.

• KSTLE International Journal
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• v.5 no.1
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• pp.28-31
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• 2004

The object of the present work is the natural frequency analysis of subambient pressure tri-pad and pico sliders. Head/disk interaction during start/stop and constant speed were detected by using the acoustic emission (AE) test system. The frequency spectrum analysis is performed using the AE signal obtained during the head/disk interaction. The FFT (Fast Fourier Transform) analysis of the AE signals is used to understand the interaction between the AE signal and the state of contact. Natural frequency analysis was performed using the Ansys program. The results indicate acceptable accordance of finite element calculation results with the experimental results.