• International Journal of Highway Engineering
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• v.9 no.4
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• pp.117-127
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• 2007

The exposed aggregate PCC(EAP) pavements have been successfully used in Europe and Japan as low-noise pavements. Coarse aggregate are exposed on the pavement surface texture of EAP by removing mortar of surface. The pavement surface texture should maintain not only low-noise characteristic but also adequate skid resistance level during the performance period. Skid resistance decreased with wearing and polishing of tire and pavement surface due to the repetition of tire-pavement contact. Since the tires mainly contact the exposed coarse aggregate, the shape and rock type of coarse aggregate significantly influence wearing and polishing of EAP pavements. The test for resistance to abrasion coarse aggregate by use of the Los Angeles machine(KS F 2508) and the method of test for resistance to abrasion coarse aggregate by use of the Accelerated Polishing Machine(ASTM D 3319-90) are generally used to evaluate polishing characteristics of aggregate. In this study, polishing of coarse aggregate of different five rock types were evaluated by KS F 2508(LA abrasion test) and ASTM D 3319-90(PSV method). The results of LA abrasion test and PSV method were contrary to each other. Since LA abrasion test is estimated the quantity of abrasion by the impact of aggregate, it may not be adequate to evaluate the polishing of aggregate by the repetition of tire. In the case of PSV method, the resistance of polishing is estimated the skid resistance variation of polished aggregate after repetition of tire. The PSV method is adequate for the evaluation on polishing of coarse aggregate. From the test results of PSV method, it was founded that rock type, specific gravity, coarse aggregate angularity, flat or elongated particles in coarse aggregate are significant to the resistance characteristic of coarse aggregate.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2011.11a
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• pp.46-48
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• 2011

선원들은 '배'라는 한정된 생활공간에서 공동생활을 하면서 선원만의 특수한 생활형태를 형성하고 있다. 즉 선원근로자들은 선상작업을 통하여 통일적이고 협동적인 과업수행을 요구 받으며, 바다라는 고립적 환경에서 장기간 단조로운 집단생활로 인하여 상당한 스트레스에 노출되어 있을 것으로 예상된다. 또한 선내의 환경은 운항에 따른 높은 수준의 소음과 선체의 동요, 한랭과 폭염, 습도 등에 노출되어 있으며, 장시간 격리된 채 바다에서 생활함으로써 가족, 친구 등과의 교류의 기회가 제약됨으로써 이러한 요인들 또한 스트레스로 작용할 가능성이 높은 직업군이다. 본 연구에서는 선상환경에서 선원들의 스트레스 요인과 그 대처방안을 모색하고자 그 기초조사로써 예부선 선원근로자의 직무스트레스와 직무만족도 조사를 실시하였다.

• Journal of the korean academy of Pediatric Dentistry
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• v.48 no.2
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• pp.209-220
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• 2021

The noise is defined as unwanted sound that causes discomfort and physical changes. This study was conducted to evaluate intensity of noise in the pediatric dental clinic and to investigate noise environment of a pediatric dentist. Human ear shaped microphone and mobile noise level meter were used for recording noise and calculating intensity of noise. By recording according to the method specified by Korea Occupational Safety and Health Agency (KOSHA) of Korea Ministry of labor and employment, the following results were obtained. For 16 experimental days, 8 hour time weighted average (8hr-TWA) was 49.33 dBA (A-weighted deci-Bell) on daily average with maximum 58.54 dBA and minimum 33.97 dBA. And Dose was 0.49% on daily average with maximum 1.28%, minimum 0.04%. These values are less than criteria of KOSHA standard (85 dBA, 100%). Comparing the highest noise level for each patient, pulp therapy group and Frankel grade I group were the highest. The intensity of dental noise of pediatric dental clinic didn't meet standard of KOSHA. It is necessary to re-evaluate noise environment by establishing new standards considering environment of pediatric dental clinic.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.69-74
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• 1998

차량에서 인체가 노출되는 진동환경으로서 좌석과 바닥에서의 진동사이에 위상차가 존재하는 경우에 대한 인체의 반응을 주관평가 실험을 통해 분석하였다. 인체가 진동에 민감하게 반응할 뿐만 아니라 인체와 좌석으로 구성되는 진동시스템의 공진주파수와 관련된 2.5, 3.15, 4, 5, 6.3 Hz의 주파수에서, 진동의 크기를 각각 0.25, 0.4, 0.63, 1.0, 1.6m/s$^{2}$로 변화시켜 가며 위상차가 인체의 안락성에 어떻게 영향을 미치는 지를 분석하였다. 두 진동간의 위상차는 진동량이 적을수록, 또 주파수가 낮을수록 인체의 안락성에 악영향을 미쳤다. 진동의 진폭이 0.25m/s$^{2}$ 일 때 위상차가 180.deg.인 경우의 불편함은 0.deg.인 경우보다 2.5배 정도 큰 것으로 나타났다. 특히 현가장치가 장착된 의자의 경우에는 좌석과 바닥진동의 위상차이가 안락성에 미치는 영향을 정량적으로 파악하여 인체-좌석 시스템의 공진주파수를 선정해야 함을 알 수 있다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.455-458
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• 2001

In this paper, ISO2631-1(1997) was used to assess the vibration and shock transmitted by train seat with respect to possible effects on human health. Evaluations have been performed on the seat acceleration measured in two type of train, Saemaulho and Mugunghwaho. For each train, limiting daily exposure durations were estimated by comparing the frequency weighted root mean square(i.e., r.m.s) acceleration and the vibration dose values(i.e., VDV), calculated according to ISO2631-1(1997) with exposure limits, health guidance caution zones.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.228-232
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• 2004

This paper is to identify the position of random disturbance on flexible dynamic system, and the position of the piezo ceramic actuator 0 minimize tip response. Correlation of the output signals from each parts on flexible system is used to identify the position of random disturbance. Except the correlation with an output signal from the position of random disturbance, other correlations have time delay. This is a base idea to identify the position on this study.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.1032-1037
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• 2003

This work measured the hand-transmitted vibration due to shipyard worker's grinding and assessed the vibration exposure for predicted 10% prevalence of vibration-induced white finger in a group of exposed persons according to test procedure of ISO 5349-1. And also the transmissibility performance of resilient material, mainly applied to anti-vibration gloves in present market was measured on the basis of ISO 13753 and confirmed that the material would Probably not provide greater attenuation below 30㎐, the dominant frequency range of hand-transmitted vibration due to grinder.

• Journal of KSNVE
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• v.5 no.2
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• pp.247-256
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• 1995

In this paper, double exposure holographic interferometry using ruby pulse laser is formed in order to investigate the propagation of transient waves. The vibration characteristics according to the change of impact load direction, i.e., impacted in the shear direction and in the normal direction are analyzed. It was observed that the macroscopic trends of transient wave generation and propagation in the assembly of precipitator plates were almost similar regardless of the change of impact load direction. But the propagation and mixing of transient wave was advanced relatively slowly when impacted in the normal direction.

• Explosives and Blasting
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• v.11 no.2
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• pp.60-68
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• 1993

The noise and vibration generated by the subway rolling stocks operated along the Seoul Subway Line No.1, 2, 3, and 4 lead to a controversy of pollution problem especially in residential areas. However, there is no data or guide to define the damage or provide adequate protection against such pollutions. The field measurements were made to characterize the noise attenuation due to distance, noise level distribution around the subway track of the aboveground and underground parts of each Line. The assessment criteria and methods are considered in addition to the practical available noise control methods. The noise level measured at Line No. 1 and 3 are less than 60 dB(A) with no pollution problem. Only a part of the aboveground section of Line No.2 and 4 indicates severe noise pollution. The effective boundary of these areas exposed to 70dB (A) noise are within 50m from the track centerline of No.2 line and 25m of No.4 line. The residents file a strong complaints whenever the noise level exceeds the 80dB (A) , and an occasional complaints between 70 to 80 dB(A). The distribution of high level noise of 80 dB(A) occurs within 25m from the track centerline of the overbridge, 12.5m of the short steel bridge, and about loom of the long steel bridge such as Dangsan Bridge. The intermediate noise level of 70 to 80 dB(A) is recorded within 50m from the overbridge, U-type retaining structure, and short steel structure, and 280m from the long steel bridge. The results presented in this paper can be used to understand the characteristics of the noise pollution along the Seoul Subway now In operation, and used as a guide to improve the existing noise pollution problems.

• 대한예방의학회:학술대회논문집
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• 2001.10a
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• pp.452-452
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• 2001