• Proceedings of the KSME Conference
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• 2000.04a
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• pp.452-457
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• 2000

This paper presents control response of a semi-active electro-rheological(ER) suspension. After showing dynamic characteristics of the ER damper, 1/4 car model is formulated by incorporating with the time constant of the damping force. $H_{\infty}$ controller compensating mass and time constant uncertainties is then designed in order to suppress vibration level of the suspension. The control responses such as vertical acceleration are presented.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.3 no.3
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• pp.11-16
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• 2004

In this study, the characteristics of signals such as acoustic emission, vibration amplitude and noise level which are derived from the abnormal condition of compressor are investigated. The normal condition, vane stick sound and roller defect condition are chosen to analyze the signal in each cases. From the feature extraction of each signals, the dominant parameters of each signals which can identify the abnormal condition are suggested.

• Journal of KSNVE
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• v.9 no.5
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• pp.949-954
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• 1999

Speed-up and mass reduction of railway vehicle usually causes increased of the interior noise. One of the best ways to control the interior noise is to identify the noise level radiated from each of parts in the cabin. In this paper, we describe the method to estimate the interior noise nad evaluate the noise contribution to each of parts. This method is based that the sound pressure can be calculated by using the frequency response function and acceleration. According to analysis of the noise contribution, we validated that the noise radiated from the floor is the higher in the cabin. We also measured the noise distribution for the side and floor by using the microphone array in order to analyze the effect of the noise flowing into the cabin from the outdoors. Finally, we presented the plan of the interior noise reduction based on the noise levels radiated from each of parts.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.6
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• pp.891-898
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• 2012

The study for the passenger's comfortableness of vehicles and the arousal of car drivers has been done widely. On the other hand, there are few studies for the locomotive engineers. Human error means that the mistakes made by human, recently it receives attention in the field of safety engineering and human engineering. Comparing the operating condition of train with car, because of the simplification of the visual stimulus, the arousal level on the train goes down easily. The arousal level down makes judgement down, the accident risk from human error is getting bigger. In this study, we measured bio-signals(ECG, EDA, PPG, respiration and EEG) from 6 locomotive engineers to evaluate their arousal state while they operated the train. Also we recorded the 3 axes acceleration signal showing the vibration state of train. Also, the existence of tunnels were simultaneously measured. At the station section where the train speed goes down, the size of vector's sum decreases because of reduced vibration. Beta component in EEG tends to increase at the entering point of each station and tunnel. It is due to the arousal reaction and tension growth. The mean SCR(skin conductance response) was more increased in neutral section. As the button control movement (body movement) increases in the neutral section, it is appeared that SCR increase. RR interval tends to gradually increase during train operation for 1 hour 40 minutes. However, It tends to sharply decrease at the stop station because strong concentration needed to stop train on the exact point. The engineer's arousal reaction can be checked through analysing the bio-signal change during train operation. Therefore, if this analysing result is adopted to the sleepiness prevention caution system, it will be useful for the safety train operation.

• Structural Engineering and Mechanics
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• v.45 no.4
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• pp.543-568
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• 2013

This study explores the floor micro-vibrations induced by the automated guided vehicles (AGVs) in liquid-crystal-display (LCD) factories. The relationships between moving loads and both the vehicle weights and speeds were constructed by a modified Kanai-Tajimi (MKT) power spectral density (PSD) function whose best-fitting parameters were obtained through a regression analysis by using experimental acceleration responses of a small-scale three-span continuous beam model obtained in the laboratory. The AGV induced floor micro-vibrations under various AGV weights and speeds were then assessed by the proposed regressional MKT model. Simulation results indicate that the maximum floor micro-vibrations of the target LCD factory fall within the VC-B and VC-C levels when AGV moves at a lower speed of 1.0 m/s, while they may exceed the acceptable VC-B level when AGV moves at a higher speed of 1.5 m/s. The simulated floor micro-vibration levels are comparable to those of typical LCD factories induced by AGVs moving normally at a speed between 1.0 m/s and 2.0 m/s. Therefore, the numerical algorithm that integrates a simplified sub-structural multi-span continuous beam model and a proposed regressional MKT moving force model can provide a satisfactory prediction of AGV-induced floor micro-vibrations in LCD factories, if proper parameters of the MKT moving force model are adopted.

• Journal of the Korean Professional Engineers Association
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• v.16 no.3
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• pp.41-53
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• 1983

The Dangri Crushed Stone Quarry is located in Dangridong, Busan City, and around the estuary of the Nagdong River. The quarry is considered to be a very promised one in the urban area from the standpoints of the assessment of the aggregate rank, the environmental impacts and the transportation distance. The crushed stones for aggregate of the quarry marks the higher rank in the gravity, the absorption ratio, the abrasion ratio, and the stability in comparison with the JISA 5005. The basement vibrations of the residential section in the vicinity of the quarry, which are arised by the millisecond blasting at the quarry site using the gelatin dynamites less than 39kg in weight, are measured to assess the vibration nuisance. The values of acceleration and the magnitudes are less than eight gals and O on the Richter scale respectively, the vibration nuisance thus can be ignored in such scales of the experiments. The traffic vibrations of the residential section are slightly susceptible. In the experiments, the traffic vibrations appears to be sensibler to the basement than the explosion vibration. The explosion noises in the experiments are not checked not only on the RION Sound Level Meter but also to our ears. The values of traffic noises also are in the safety values of the noise nuisance. The crush dust suspends in the air toward the upper valley in the opposite side of the residential area because of the influences of the sea breeze and the valley wind in the daytime, and the monsoon and the topographic disposition. the dust nuisance thus would not be remained in problem. The quarry is operated in the daytime only. The traffic dust in the residential area will be reduced by the faultless pavement and the careful driving. The elaborate survey on the ridges and peaks surrounded the quarry is recommended to prevent in advance the accidents of the rock slide. Moreover, it is required to make an advisory committee to develop the industry and to save the techniques. The most important matter is the accomodation between the attitude of the enterprising man for the social responsibility to the public nuisance and the cooperative spirit of the inhabitants for the industry.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.4
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• pp.47-55
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• 2009

The purpose of this study is to verify the transfer function of input acceleration and output control force by linearizing a velocity-dependent damping term of Liquid Column Vibration Absorber (LCVA). Analytical and experimental research is conducted to identify natural frequency, damping ratio and participated mass ratio of LCVA with various section ratios of vertical and horizontal areas. Findings obtained experimentally by the shaking table test are compared with analytical findings using optimization technique with constraints. The results indicate that the level of liquid and section ratio of LCVA affect the characteristics of damping ratio and mass ratio. Damping and mass ratio increase as the section of vertical column of LCVA decreases, due to turbulence in the elbow of LCVA.

• Safety and Health at Work
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• v.6 no.4
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• pp.268-278
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• 2015

Background: This study aimed to assess the whole-body vibration (WBV) exposure among large blast hole drill machine operators with regard to the International Organization for Standardization (ISO) recommended threshold values and its association with machine- and rock-related factors and workers' individual characteristics. Methods: The study population included 28 drill machine operators who had worked in four opencast iron ore mines in eastern India. The study protocol comprised the following: measurements of WBV exposure [frequency weighted root mean square (RMS) acceleration ($m/s^2$)], machine-related data (manufacturer of machine, age of machine, seat height, thickness, and rest height) collected from mine management offices, measurements of rock hardness, uniaxial compressive strength and density, and workers' characteristics via face-to-face interviews. Results: More than 90% of the operators were exposed to a higher level WBV than the ISO upper limit and only 3.6% between the lower and upper limits, mainly in the vertical axis. Bivariate correlations revealed that potential predictors of total WBV exposure were: machine manufacturer (r = 0.453, p = 0.015), age of drill (r = 0.533, p = 0.003), and hardness of rock (r = 0.561, p = 0.002). The stepwise multiple regression model revealed that the potential predictors are age of operator (regression coefficient ${\beta}=-0.052$, standard error SE = 0.023), manufacturer (${\beta}=1.093$, SE = 0.227), rock hardness (${\beta}=0.045$, SE = 0.018), uniaxial compressive strength (${\beta}=0.027$, SE = 0.009), and density (${\beta}=-1.135$, SE = 0.235). Conclusion: Prevention should include using appropriate machines to handle rock hardness, rock uniaxial compressive strength and density, and seat improvement using ergonomic approaches such as including a suspension system.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.6
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• pp.469-477
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• 2017

In this paper, the floor vibration of an example concert hall building was measured and floor safety criteria were analytically checked through comparison between experimental and analytical results. The floor bottom plate model was constructed considering the composite effect and the analytical model was modified to have the natural frequency identical to the measured one. Also, time history analysis was conducted using the dynamic loads induced by human rhythmic movement during a musical performance, and the analytically calculated floor accelerations were similar to the measured one. Based on this model, the floor vibration level due to the group activities of about 400 persons, maximum available persons for the concert hall, was estimated. It was confirmed that the human induced dynamic loads applied to the column and beam would be much lower than the design strength. In addition, the horizontal acceleration level is just 2% of the design seismic load, so the concert hall is safe in both vertical and horizontal excitations by human rhythmic movements.

• Journal of the Korea Concrete Institute
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• v.16 no.2 s.80
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• pp.221-228
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• 2004

In recent years building floors become larger and more spacious due to the development of new design methods and high strength and light weight materials. However, such long span floor systems may provide smaller amount of damping and have a longer period so that they may be more vulnerable to the floor vertical vibration. In Korea when floors are to be checked against the floor vertical vibration, the provisions developed in foreign countries have been used. However these guidelines have been developed based on human perception, which may vary from country to country. Also, Korea have particular floor systems, such as flat plate floor system of apartment building. This study attempts to evaluate the vibration performance of the floors in typical apartment buildings. Two different floors with the area of $28 m^2$ and $32 m^2$ were investigated. The criteria provided by ATC-1(1999), AISC-11(1997), AIJ(1991) and the local criteria developed in the previous study(Han, 2003) was used to check the acceptability of the floor vertical vibration.