• Journal of Preventive Medicine and Public Health
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• v.28 no.4 s.51
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• pp.765-771
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• 1995

This study was performed to investigate the possibility of temporary threshold shift (TTS) of vibration sense could induced by exposure to high-frequency vibration or by work position taking by dentists in drilling or polishing. The vibratory perception thresholds (VPT) of 28 healthy men were measured on the index fingertip pulp of dominant hand at 250 Hz. The vibrating tool used in test was a low-speed handpiece of 34,000 rpm. For the TTS test, the dominant hand was exposed to high-frequency vibration and to work position for five minutes, respectively. The VPTs before and after vibratory exposure were $23.5{\pm}3.5dB,\;30.8{\pm}4.2dB$, respectively and VPT after work position was $23.7{\pm}4.6dB$. The difference between before and after vibartory exposure was statistically significant (p<0.001). The correlation of height, weight and BMI with baseline VPTs was not statistically significant. Also, there was no difference of VPTs by smoking. These results suggest that high-frequency vibration from dental handpieces might cause the impairment of vibration sensation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.205-205
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• 2009

태양광 발전은 다른 발전방식과는 달리 연료비가 불필요하고 대기오염이나 폐기물 발생이 없으며 부위가 반도체 소자이고 제어부가 전자제품이므로 기계적인 진동과 소음 등의 공해가 전혀 없는 에너지원이다. 그러나 태양광 발전은 에너지 밀도가 낮아 일사량, 온도, 계절 등 기상조건의 작은 변화에도 발전량의 편차가 심하고 출력이 불안정하여 상용전원과의 연계나 별도의 축전설비 또는 발전설비 없이 독립적으로 사용하기에는 다소 무리가 있다는 단점이 있다. 따라서 본 논문에서는 이러한 문제점을 해결하기 위해서 1년 동안 실증운전을 통한 종합적인 운전특성 데이터, 태양전지 어레이 출력의 전압 전류, 교류 전력 및 전력량, 일사량 및 모듈의 온도, 외기온도 등 분석기간 동안 수집된 운전 데이터를 이용하여 태양이 태양전지 모듈에 입사되는 각과 발전량 즉 태양 전지 어레이 형태와 발전량과의 상관관계를 정량적으로 규명하여 태양광 발전시스템의 설계 및 시공의 최적화가 이루어질 수 있도록 하였다.

• Journal of the Korean Geotechnical Society
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• v.29 no.4
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• pp.5-11
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• 2013

In close to downtown construction, the main problem is complaints caused by blasting vibration and noise. To reduce blasting vibration and noise, deck-charge blasting method using electronic detonator can be more secure because there is no cut-off problem. And in this method it is possible to blast in horizontal direction. In this study, the efficiency of horizontal direction deck-charge blasting method using electronic detonator is compared to that of the existing blasting method. And the possibility of applying the construction site is evaluated. As a result, the reduction of blasting vibration, noise and secondary breaking has been determined, as well as large-scale blasting in the vibration criterion can be regulated by the overall increase in blasting efficiency.

• Explosives and Blasting
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• v.23 no.2
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• pp.15-21
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• 2005

Already, VARI-STEM, CAS-BAG, POWER DECK etc. are used by various blasting methods to take the advantage of air decking technology in abroad. This study analyzed the application and the effect of Air ball blasting method in domestic blasting area. It is shown that blasting vibration was showed decrease about $30\~40\%$ and quantities of explosives was shown decrease about $20\~25\%$. Also, in the case of using air ball blasting method, it is found for airblast to be lower than common blasting method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11b
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• pp.129-133
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• 2005

Vibration transmitted through rolling tire is a major source of road noise in vehicle interior noise on the range of low frequency.($0{\sim}500Hz$) Among various road noises, tire cavity noise has very peak on $200{\sim}250Hz$. And generally it is generated by cavity resonance of tire. In this paper, tire cut-sample is used to calculate the tire cavity frequency. Cavity resonance frequency of tire is measured through vertical/tangential forces at load cell of axle using drum cleat impact. This method is useful to find cavity peak because measured forces do not have complex peaks. And changing the test conditions (air inflation, loads), tire cavity resonance characteristics are identified. Finally, vehicle interior noise is measured as tire/vehicle are changing. As difference of tire vertical force is bigger, interior noise level is higher at cavity frequency. Also we can assume that vehicle sensitivity is important factor at tire cavity noise.

• Journal of Navigation and Port Research
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• v.34 no.6
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• pp.441-445
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• 2010

The ouput power of wave energy system in buoy is determined according to the inner diameter of oscillating water column and flow resistance. The increase of adhered shellfish inside the water column leads to decrease the inner diameter of wave energy converter. Influx loss of seawater reduces the efficiency of output power in the wave generation system. In this paper, the test result of AFS characteristic is described for preventing the deposition with shellfish and etc. The current of anode is controlled by buck converter, and the control algorithm developed for AFS in buoy. The experimental results is shown excellent preventing capapbility of AFS in buoy.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.1
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• pp.44-48
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• 2002

In this paper, we demonstrated the simultaneous measurment of triple parameters such as strain, temperature, and vibration using single FBG/EFPI hybrid sensor. The FBG/EFPI sensor system for the strain and temperature measurement and the EFPI sensor system for the the vibration measurement were combined by a wavelength division multiplexer. The optical source of FBG/ EFPI sensor system is a wavelength-swept fiber laser(WSFL) and that of an EFPI sensor system is a laser diode. We performed the simultaneous measurement of thermal strain, temperature, and vibration of a aluminum beam placed in a thermal chamber and validated the efficiency of the constructed measurment system.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.7
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• pp.631-639
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• 2013

Virtual seat method(VSM) which is an evaluation method combined objective and subjective process is used in this study in order to determine seat comfort index of idle vibration of passenger vehicle. The VSM is implemented by two steps which are for objective index in the first step and for subjective estimation in the second step. In the study, two seats mounted on passenger vehicle was compared in terms of dynamic seat comfort by six subjects employed for the VSM method as well as SEAT value which is a conventional objective method. It is concluded that the dynamic comfort index by the VSM is more reliable than the SEAT value thanks to adding subjective evaluation on top of the objective result.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.3
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• pp.59-64
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• 1994

A study was conducted to investigate the propeller singing place of an 86, 000 ton Deadweight Crude Oil Tanker. In preliminary study, proper use of finite element analysis was verified by comparing with the result of hammering test in the air. Then the finite element analysis was carried out for the blade in the water and compared with the noise measurement during sea trial, which enabled to confirm the local resonances of blade structure. Result of the study showed that the singing occurred most probably at trailing edges on the blade tip over 95% of propeller diameter. Owing to edge cutting of a successfoul remdial action, the singing excitation forces seemed to be reduced whereas the vibration characteristics of the blade was not changed.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.6
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• pp.882-889
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• 2022

In this study, to understand the factors influencing the flow change the Tsushima Warm Current (TWC), the correlation between the volume transport the TWC, El Niño Southern Oscillation (ENSO), and Pacific Decadal Oscillation (PDO) was analyzed. A calculation of the monthly volume transport of TWC for 25 years (1993-2018) revealed that the seasonal fluctuation cycle was the largest in summer and smallest in winter. Power spectrum analysis to determine the periodicity of the TWC volume transport, Oceanic Niño Undex (ONI), and PDO indicated that the TWC volume transport peaked at a one year cycle, but ONI and PDO showed no clear cycle. Further, to understand the correlation between the TWC transport volume and ONI and PDO, the coherence estimation method was used for analysis. The coherence of ONI and PDO had a high mutual contribution in long-period fluctuations of three years or more but had low mutual contribution in short-period fluctuations within one year. However, the coherence value between the two factors of the TWC volume transport and PDO was 0.7 in the 0.8-1.2 year cycle, which had a high mutual contribution. Meanwhile, the TWC volume transport and PDO have an inverse correlation between period I (1993-2002) and period III (2010-2018). When the TWC maximum transport volume (2.2 Sv or more) was high, the PDO index showed a negative value below -1.0, and the PDO index showed a positive value when the TWC maximum transport volume was (below 2.2 Sv). Therefore, using long-term PDO index data, changes in the TWC transport volume and water temperature in the East Sea coastal area could be predicted.