• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.3
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• pp.240-248
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• 2013

Torsional vibrations, such as the gear rattle of the manual transmission in vehicle systems, are correlated with the firing stroke from the engine. These vibro-impacts can be examined based upon linear time-invariant analysis. In order to understand the gear dynamics, a specific manual transmission with a front-engine front-wheel drive configuration is investigated. A method to reduce the degrees of freedom is suggested based upon the eigensolutions and frequency response functions, which will lead to the development of an efficient matrix size. The dynamic characteristics of single- and dual-mass flywheels are then compared. The effect of the dual-mass flywheel is investigated based upon the mobility analysis, which will lead to understanding of the concepts for avoiding vibro-impacts. A linear time-invariant system model is examined by employing the effective clutch stiffness from a two-stage clutch damper. Thus, the relationship between the dynamic characteristics and the clutch damper can be predicted by assuming a combination of different stage stiffness levels.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.13 no.2
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• pp.89-99
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• 2001

In the present paper, Helmholtz resonator, which is widely used as a sound-amplification device, is applied to the development of seawater-exchanging breakwater. The incident waves can induce a large response in the resonator when incident wave frequency is close to one of natural modes of the resonator. Largely amplified potential energy due to the resonance supplies clean seawater into the harbor side throughout the channel. Flow supplied by the resonator circulates the seawater of harbor and helps to improve water quality. Within the framework of linear potential theory, matched asymptotic expansion method is employed to analyze the wave responses in a resonator. The semi-circular shape of the resonator has been chosen as an analytic model for mathematical simplicity. The wave responses of both single and arrays of Helmholtz resonator are investi¬gated. To validate an analytic solution, model test is conducted at 2-dimensional wave tanle Wave hcights in the resonator and velocity at the channel are measured for the state of valve-on and valve-off.

• The Korean Journal of Physiology and Pharmacology
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• v.12 no.6
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• pp.299-306
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• 2008

Sometimes, spinal cord injury (SCI) results in various chronic neuropathic pain syndromes that occur diffusely below the level of the injury. It has been reported that behavioral signs of neuropathic pain are expressed in the animal models of contusive SCI. However, the observation period is relatively short considering the natural course of pain in human SCI patients. Therefore, this study was undertaken to examine the time course of mechanical and cold allodynia in the hindpaw after a spinal cord contusion in rats for a long period of time (30 weeks). The hindpaw withdrawal threshold to mechanical stimulation was applied to the plantar surface of the hindpaw, and the withdrawal frequency to the application of acetone was measured before and after a spinal contusion. The spinal cord contusion was produced by dropping a 10 g weight from a 6.25 and 12.5 mm height using a NYU impactor. After the injury, rats showed a decreased withdrawal threshold to von Frey stimulation, indicating the development of mechanical allodynia which persisted for 30 weeks. The withdrawal threshold between the two experimental groups was similar. The response frequencies to acetone increased after the SCI, but they were developed slowly. Cold allodynia persisted for 30 weeks in 12.5 mm group. The sham animals did not show any significant behavioral changes. These results provide behavioral evidence to indicate that the below-level pain was well developed and maintained in the contusion model for a long time, suggesting a model suitable for pain research, especially in the late stage of SCI or for long term effects of analgesic intervention.

• Journal of Technologic Dentistry
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• v.39 no.3
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• pp.197-204
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• 2017

Purpose: This study aims to discover the degree of department of dental technology students' oral health recognition and to find out the differences of oral health beliefs depending on oral health behaviors. Method: The subjects in this study were the students who attended department of dental technology in Daejon, Daegu, Iksan. After a survey was conducted, the collected data were analyzed with SPSS 23.0. An analysis of frequency, independent t-test, one-way ANOVA, correlation was used. Result: Among the general things related to oral health behaviors was the statistical significant differences(p<0.05) in the area of oral health belief depending on the opportunity of oral health education, attendance of oral health course, self-aware of oral health, the number of times of teeth brushing, teeth brushing status, experience and the degree of smoking. There was a positive correlation between the degree of susceptibility and that of response to severity, barrier, salience and benefit. Severity also showed the positive correlation with barrier. Higher barrier susceptibility meant higher salience and higher benefit. So was the correlation between benefit and salience. Conclusion: This study showed that college education should focus on the students' possible behaviors in order to convey the effective oral health knowledge.

• Journal of the Korea Fashion and Costume Design Association
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• v.17 no.4
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• pp.67-76
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• 2015

The purpose of this study is to set a direction for the development of men's underwear after analyzing current applications for patent regarding men's special-purpose underwear. In terms of a research method, the disclosed patents and utility models were investigated using the patent information database provided by Korea Institute of Patent Information (KIPRIS, http://www.kipris.or.kr). For this, the patents applied from 1990 to October 2015 were targeted. The keywords used for patent search were 'men's underwear' and 'men's special-purpose underwear.' When searched by the keywords above, a total of 1,089 cases were found. Except for expired or cancelled ones, 243 cases were investigated. Then, annual application trends, current registrations on literature records, classification of utility model right holders and contents by topic were analyzed. In terms of data analysis, frequency analysis, crosstabulation analysis and multiple response analysis were conducted, using SPSS 18.0. The results found the followings: In terms of annual application trends, the number of applications for patent started to gradually increase since 2007. Since 2011, it has rapidly increased. In terms of the number of patent registrations, literature registration was far higher than utility model registration. In terms of application rights, 'individually registered (58.8%)' was higher than 'registered by the organization (41.2%).' Among 243 cases, 'underwear (58%)' was the highest, followed by 'men's underwear-related items (29.2%)' and 'thermals (8.2%).' According to analysis on the details of the patent applied for men's underwear, 'penis-scrotum separation' was most focused, followed by 'disposable product' 'airy features,' 'scrotum protection' and 'structure of underwear.'

• Journal of the Korean Society for Railway
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• v.16 no.4
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• pp.286-297
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• 2013

In this paper we evaluated dynamic stability, considering the effects of modeling and analysis methods on moving load analysis, for which a sophisticated 3 dimensional model of a PSC-I type girder bridge was used. For this purpose, we suggested a reasonable modeling method and the physical properties of the concrete and ballasted track system involved. We also analyzed the response characteristics according to: 1) the type of track system; 2) whether or not the track was modeled; 3) whether or not the distance between the girder center and the bearing were considered; 4) the analysis method (i.e., direct integral and modal analysis); 5) whether or not the frequency was filtered.

• Smart Structures and Systems
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• v.4 no.6
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• pp.727-740
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• 2008

A down hole vertical seismic array is a sequence of instruments installed at various depths in the earth to record the ground motion at multiple points during an earthquake. Numerous studies demonstrate the unique utility of vertical seismic arrays for studying in situ site response and soil behavior. Examples are given of analyses made at two sites to show the value of data from vertical seismic arrays. The sites examined are the Lotung, Taiwan SMART1 array and a new site installed at Jingliao, Taiwan. Details of the installation of the Jingliao array are given. ARX models are theoretically the correct process models for vertical wave propagation in the layered earth, and are used to linearly map deeper sensor input signals to shallower sensor output signals. An example of Event 16 at the Lotung array is given. This same data, when examined in detail with a Bayesian inference model, can also be explained by nonlinear filters yielding commonly accepted soil degradation curves. Results from applying an ARMAX model to data from the Jingliao vertical seismic array are presented. Estimates of inter-transducer soil increment resonant frequency, shear modulus, and damping ratio are presented. The shear modulus varied from 50 to 150 MPa, and damping ratio between 8% and 15%. A new hardware monitoring system - TerraScope - is an affordable 4-D down-hole seismic monitoring system based on independent, microprocessor-controlled sensor Pods. The Pods are nominally 50 mm in diameter, and about 120 mm long. An internal 16-bit micro-controller oversees all aspects of instrumentation, eight programmable gain amplifiers, and local signal storage.

• Journal of Ocean Engineering and Technology
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• v.27 no.5
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• pp.63-69
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• 2013

The mooring lines of a floating type offshore plant are known to show wide banded and bimodal responses. These phenomena come from a combination of low and high frequency random load components, which are derived from the drift-restoring motion characteristic and wind- sea, respectively. In this study, fatigue models were applied to predict the fatigue damage of mooring lines under those loads, and the result were compared. For this purpose, seven different fatigue damage prediction models were reviewed, including mathematical formula. A FPSO (floating, production, storage, and offloading) with a $4{\times}4$ spread catenary mooring system was selected as a numerical model, which was already installed at an offshore area of West Africa. Four load cases with different combinations of wave and wind spectra were considered, and the fatigue damage to each mooring line was estimated. The rain flow fatigue damage for the time process of the mooring tension response was compared with the results estimated by all the fatigue damage prediction models. The results showed that both Benasciutti-Tovo and JB models could most accurately predict wide banded bimodal fatigue damage to a mooring system.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.3
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• pp.75-89
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• 1993

The present paper describes an application of UA(Uncertainty Analysis) to seakeeping model test, basically according to the Performance Test Code of ASME(American Society of Mechanical Engineers), in which all the possible error sources involved in the preparation of test, calibration of instruments, data acquisition and analysis are quantified, and summed up with error propagation coefficients to the final uncertainties. The differences between the static test such as resistance and propulsion test and the dynamic test like seakeeping test are clearly identified during all the procedures of UA and asymmetric bias errors are considered. The DRE(data reduction equation) subject to present UA are the heave and pitch response amplitude operator and nondimensionalized absolute frequency. The usefulness of UA in seakeeping test were confirmed not only for quantifying errors and improving measurement accuracy but also for the validation of various seakeeping analysis tools.

• Earthquakes and Structures
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• v.17 no.2
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• pp.175-189
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• 2019

The aim of the study is to show the results of complex shaking table experimental investigation focused on the response of two models of cylindrical steel tanks under mining tremors and moderate earthquakes, including the aspects of diagnosis of structural damage. Firstly, the impact and the sweep-sine tests have been carried out, so as to determine the dynamic properties of models filled with different levels of liquid. Then, the models have been subjected to seismic and paraseismic excitations. Finally, one fully filled structure has been tested after introducing two different types of damages, so as to verify the method of damage diagnosis. The results of the impact and the sweep-sine tests show that filling the models with liquid leads to substantial reduction in natural frequencies, due to gradually increasing overall mass. Moreover, the results of sweep-sine tests clearly indicate that the increase in the liquid level results in significant increase in the damping structural ratio, which is the effect of damping properties of liquid due to its sloshing. The results of seismic and paraseismic tests indicate that filling the tank with liquid leads initially to considerable reduction in values of acceleration (damping effect of liquid sloshing); however, beyond a certain level of water filling, this regularity is inverted and acceleration values increase (effect of increasing total mass of the structure). Moreover, comparison of the responses under mining tremors and moderate earthquakes indicate that the power amplification factor of the mining tremors may be larger than the seismic power amplification factor. Finally, the results of damage diagnosis of fully filled steel tank model indicate that the forms of the Fourier spectra, together with the frequency and power spectral density values, can be directly related to the specific type of structural damage. They show a decrease in the natural frequencies for the model with unscrewed support bolts (global type of damage), while cutting the welds (local type of damage) has resulted in significant increase in values of the power spectral density for higher vibration modes.