• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.272-278
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• 2018

Traffic volume has been greatly increasing due to urban development and the improvement of living standards, and many complaints are being raised due to the increasing road noise. As a countermeasure against these problems, highly soundproof walls are installed on the sides of roads. However, the ability to bear wind loads is a major design requirement for soundproof walls, which contributes to the exponential increases in construction costs and restricts the height of the walls. The aim of this study is to improve the performance of soundproof walls and to dramatically reduce wind loads while maintaining excellent price competitiveness. Based on Helmholz's resonator theory, a new concept is proposed for a ventilation-type soundproofing plate that can pass through a fluid like air and reduce noise. A full-scale metal soundproofing plate was produced to satisfy the quality standards of highways by conducting a sound-pressure transmission-loss test, wind tunnel test, and material quality test. To verify the reliability, the wall was manufactured and installed, and the sound insulation effect was examined by measuring the noise over time. In the future, ventilated soundproof walls on roads could create a pleasant living environment due to the high noise-insulation effect.

• Journal of Advanced Navigation Technology
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• v.5 no.1
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• pp.62-73
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• 2001

In this paper, performance of DSRC systems is analyzed with considering the real roads and height of vehicles. The channels are modeled as 2-Ray and 4-Ray with a direct wave and reflected waves by a road and buildings in a physical layer because DSRC keeps LOS propagation characteristics, and the pass loss for each model is calculated respectively. Rician factor is obtained through the calculated path loss on two models for DSRC, and the performance of the systems is analyzed in AWGN and Rician fading channels, Impulsive noise and Rician fading channels respectively. As a result, in Rician fading channels with impulsive noise(A=0.2, ${\Gamma}^{\prime}=0.22$), BER is below $10^{-6}$ when the distance is farther than 80[m] and 40[m] in 2-Ray model and 4-Ray model respectively. For performance improvement, BCH coding scheme and MRC diversity scheme are adopted.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.10 no.1
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• pp.74-92
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• 2000

This study was performed to evaluate the working conditions In construction workers through measurements of working environments and to improve the working conditions and to design the appropriate environmental and health management system. The results of measurement for working environments in construction work are as following: 1. The excess rate of noise and dust concentration in express highway construction, road construction, building construction and interior painting was 28.6% and 24.5% respectively. 2. The excess rate of mixed organic solvents concentration in interior painting was 39.3%. 3. The chain type bulldozer has the highest level of vibration; the excess rate was 85.7%, and among the vibration instruments, the level of left hand's vibration of all vibrators exceeded the criterion and in the case of drilling all the level of vibration exceeded the criterion in both hands. On the basis of the results in this research the environmental and health management system for construction workers must be considered. Therefore, it is necessary to be introduced the special medical examination and measurement of working environments in construction industry. In defining "the working place" of Article 39 of Enforcement regulations of industrial safety and health act, the word "indoors" should be deleted. Then the eligible industry for measurement of working environment must be extended. And it is also necessary for construction industry to be performed group health management service by agencies such as other manufacturing industry.

• The Journal of the Korea Contents Association
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• v.14 no.5
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• pp.425-435
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• 2014

The research for extracting man-made features such as building and road from the aerial photograph or satellite imagery has been performed actively. As lately the resolution of digital aerial photographs was improved, unwanted features(noise) would be often detected. An edge detection algorithm is developed to make up for such a noise problem, make boundaries of wanted objects clear and extract only needed features. The algorithm developed in this research performs separating RGB channels, differencing between channels, transforming in to binary images, excluding noises and restoring shapes, and edge extraction in order. The images to be used for edge detection are prepared through bundle adjustment, DTM extraction, orthorectification and mosaicking. The roof edges of small building on preprocessed digital aerial orthophotos were extracted using the algorithm developed in this study. The validity of the algorithms was proved by comparing edge results of small building extracted in this study with those of conventional methods.

• International Journal of Highway Engineering
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• v.16 no.5
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• pp.59-66
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• 2014

PURPOSES : This study is to predict the Sound Pressure Level(SPL) obtained from the Noble Close ProXimity(NCPX) method by using the Extended Kalman Filter Algorithm employing the taylor series and Linear Regression Analysis based on the least square method. The objective of utilizing EKF Algorithm is to consider stochastically the effect of error because the Regression analysis is not the method for the statical approach. METHODS : For measuring the friction noise between the surface and vehicle's tire, NCPX method was used. With NCPX method, SPL can be obtained using the frequency analysis such as Discrete Fourier Transform(DFT), Fast Fourier Transform(FFT) and Constant Percentage Bandwidth(CPB) Analysis. In this research, CPB analysis was only conducted for deriving A-weighted SPL from the sound power level in terms of frequencies. EKF Algorithm and Regression analysis were performed for estimating the SPL regarding the vehicle velocities. RESULTS : The study has shown that the results related to the coefficient of determination and RMSE from EKF Algorithm have been improved by comparing to Regression analysis. CONCLUSIONS : The more the vehicle is fast, the more the SPL must be high. But in the results of EKF Algorithm, SPLs are irregular. The reason of that is the EKF algorithm can be reflected by the error covariance from the measurements.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.4 s.121
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• pp.289-297
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• 2007

SAFRS is the system designed to reproduce the harmonic sound into the space according to the environmental factors. Here the harmonic sound means the sound which judged by the subjective tests, and the methods were suggested in the former studies. In this research, SAFRS was applied into the Square of D University to evaluate and verify the effectiveness of the system and a few evaluations were carried out as follows; 1) sound perception, frequency, volume and harmony with the space, 2) images of the square and acoustic environment and 3) acoustic environment with existing sounds, fountain sound, produced sound by SAFRS, and both of them respectively. The results can be summarized as follows; 1) According to the evaluation on acoustic environment, no relationships were shown between the cognition of sounds produced by SAFRS and the frequency or volume, but inverse proportion was shown between the volume and special harmony. 2) As the result of image evaluation. the relationship between space and sound image was shown proportional only except the evaluation on main road at night time, it means that the sound proposal with the visual contents matching with the sounds would be more effective than the proposal of sound only. 3) Results of evaluation on acoustic environment showed that the cognition effect at night time was shown higher than that of day time when only the acoustic element was given and the effect was increased when the visual elements matches with the acoustic elements if both of them were given. It confirmed the harmony between visual and acoustic elements was very important.

• International Journal of Highway Engineering
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• v.13 no.1
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• pp.223-228
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• 2011

The initial joint width design of the terminal joint between post-tensioned concrete pavement (PTCP) and jointed concrete pavement (JCP) was studied in this research. The joint width between PTCP and JCP directly affects noise and ride quality. If the initial joint width is very large, noise increases and ride quality decreases. If the initial joint width is very small, on the other hand, under high temperatures, PTCP slabs can blow up, or failures near the joint can occur due to excessive compressive stresses. The terminal joint width behavior between PTCP and JCP near Jumunjin at Donghae expressway under temperature changes was measured in August and November 2010 and the data was analyzed. From this study, the design methodology of the optimal initial terminal joint width was proposed.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.10
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• pp.52-60
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• 2010

It is generally important to get a precise position information for autonomous unmanned vehicle(AUV) to run safely. For getting the position of AUV, the GPS has been using to navigation in a vehicle. Though it is useful to finding a position, it is difficult to precisely control a trajectory of the AUV due to large measuring error which may reach over 10 meters. Therefore to apply AUV it needs to compensate for the error. This paper proposes a method to more precisely localize AUV using three low-cost differential global positioning systems (DGPS). The distance errors between each DGPS are minimized as using the least square method (LSM) and the Kalman filter to eliminate a Gaussian white noise. The selected DGPS is cheaper and easier to set up than the RTK-GPS. It is also more precise than the general GPS. The proposed method can compensate the relatively position error according to stationary and moving distance of the AUV. For evaluating the algorithm by simulation, the DGPS signal with the Gaussian white noise to any points is generated by the AR model and compared with the measurement signal. It is confirmed that the proposed method can effectively compensate the position error as comparing with the measurement signal. The compensated position signal can be used to localize and control the AUV in the road.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.12 s.105
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• pp.1389-1397
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• 2005

Since blast-induced vibration may cause serious problem to the rock mass as well as the nearby structures, the prediction of blast-induced nitration and the stability evaluation must be performed before blasting activities. Dynamic analysis has been increased recently in order to analyze the effect of the blast-Induced vibration. Most of the previous studies, however, were based on the continuum analysis unable to consider rock joints which significantly affect the wave propagation and attenuation characteristics. They also adopted pressure corves estimated tv theoretical or empirical equations as input detonation load, thus there were very difficult to reflect the characteristics of propagating media. In this study, therefore, we suggested a dynamic distinct element analysis technique which uses velocity waveform obtained from a test blast as an input detonation load. A distinct element program, UDEC was used to consider the effect of rock joints. In order to verify the validity of proposed method, the test blast was simulated. The predicted results from the proposed method showed a good agreement with the measured vibration data from the test blast. Through the dynamic numerical modelling on the planned road tunnel and slope, we evaluated the effect of blast-induced nitration and the stability of rock slope.

• Journal of the Ergonomics Society of Korea
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• v.30 no.1
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• pp.237-250
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• 2011

The train transportation has a lot of advantages-energy efficiency is high, it is eco-friendly, safety is better than normal roads and it is possible for people to arrive on time. In these days, the valuation of ride comfort, which is only limited to road transportation, is newly recognized in order to having competitiveness from other transportation. Especially, in the development of the Korean high-speed railroad business, the ride comfort enhancement of train is very important problem to be solved. Currently, there are international standards of ride comfort such as UIC13, ISO2631. In Korea case, although it has own standard like KS R9216, it mainly depends on the physical parameter such as vibration and noise. So recently, in the valuation of ride comfort, the movements of living parameter technique introduction are increasing on the base of Japan and many developed countries of Europe techniques. Presently, the method of train ride comfort is mainly based of vibration, that is, mechanical parameter adding selection of variable acceleration and noise. This paper would like to show biological parameter; heart rate and blood pressure variation. This method is more direct, based on human body response, than mechanical parameter method. In this experiment, the variability of heart rate and blood pressure of passengers according to tilting angle change of Train, the Korean tilting train, we are supposed to know that the extent of tilting on the simulation has influence on variability of heart rate and blood pressure, which are living parameter of heart's blood.