• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.5 s.110
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• pp.537-543
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• 2006

The impact sound of the golf club is one of the major factors to purchase it. Sound quality metrics has been mostly developed for harmonic sounds. Sound quality evaluation techniques for the impact sound have been contrived in this study. Jury test, one of the typical subjective evaluation scheme, is carried out for evaluating the sound quality of 13 different golf drivers, which classification results are assumed to be correct answers. Conventional objective evaluation methods such as Zwicker loudness sensory pleasantness are calculated. Wavelet analysis and instantaneous loudness are applied in order to evaluate the sound quality of transient sounds, which scheme shows better correlation with the results from jury test.

• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.1
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• pp.47-56
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• 2009

Rock bolts and shotcrete play a crucial role as a main support system in the underground space. Thus, the safety of the underground space may be affected by the defect of rock bolts. In order to evaluate the rock bolt integrity by using non-destructive technique, the transmission method of the guided ultrasonic waves, which are generated by using the piezo disk elements has been successfully performed. The energy generated by the piezo disk elements, however, is not enough for the rock bolts in the field. In addition, the piezo disk elements should be installed at the end of the steel bar during construction of the rock bolts. The purpose of this study is the devolvement of the reflection method, which may generate enough energy, and the application in the field rock bolts. Both laboratory and field tests are carried out. The guided ultrasonic waves with high energy are generated by the hammer impact with the center punch, and the AE sensor is used to measure the reflected guided waves. The received guided waves are analyzed by the wavelet transform. The peak value of the wavelet transform produces the energy velocity, which is used for the evaluation of the rock bolt integrity. The energy velocity increases with an increase in the defect ratio in both laboratory and field rock bolts. This study demonstrates that the hammer-impact reflection method may be a suitable method for the evaluation of the rock bolt in the field.

• Journal of Internet Computing and Services
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• v.24 no.6
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• pp.23-29
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• 2023

As an effort to maximize the immersiveness of user experience in virtual reality, there have been constant efforts to provide a user with tactile sensation by providing haptic feedback. Most of the haptic feedback methods, however, can create only limited or unrealistic haptic sensations since they utilize affordable actuators such as a vibrotactile actuator. When it comes to martial arts training or a game, the limitation of such haptic feedback is apparent due to the significant difference between the physical impact of hitting an object and the sensation departed from a vibrotactile actuator. Noting this, we proposed a haptic impact system that can create a haptic impact when the user hits a virtual object with the fist. The haptic interface uses a quick-return mechanism that can deliver haptic impact feedback to a user's fist. The realism of the haptic impact was evaluated by conducting a human-subject experiment. The results indicate a significant effect of haptic feedback on the realism of the virtual impact.

• Proceedings of the Korean Information Science Society Conference
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• 2000.10a
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• pp.51-53
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• 2000

시공간 추론에 관한 연구는 그 역사가 오래되었으며 지난 수 십년 동안 매우 많은 이론적인 연구 결과를 얻었다. 그러나, 이와 관련된 응용분야의 연구는 거의 진척되지 않았기 때문에 시공간 추론의 이론과 응용 사이의 간격을 줄이고 실제 활용 가능한 시스템 개발을 위해서는 관련 이론을 토대로 한 응용 시스템의 개발이 필요하게 되었다. 따라서, 이 논문에서는 그 동안 연구된 시공간 추론의 이론을 특정 응용 분야인 전장분석에 적용하여 전장분석 및 평가에 중요한 영향을 미치는 미상의 부대, 미확인 부대, 주타격 방향을 추론하고, 부대의 이동 위치 및 이동시간을 추동하는 시공간 추론 시스템을 설계 및 구현하였다.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.183-183
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• 2011

전 국토의 65%가 산악지형으로 이루어져 있는 우리나라는 도로개설 및 산업기지 건설, 대규모 주택단지 개발 등으로 자연사면을 변형시키는 규모나 빈도가 증가하고 있고, 최근에는 기상이변에 의한 집중호우가 빈번히 발생하여 절토사면에서 낙석이 발생할 위험이 점점 높아지고 있는 실정이다. 낙석방지를 위한 대책공법으로는 낙석방지 망, 낙석방지 울타리 등이 있으며 이중에서 낙석방지 울타리는 국내의 국도 낙석방지 대책공법 중 70% 이상을 차지하고 있다. 그러나 국내 설계지침에는 낙석방지 울타리에 대한 다양한 성능등급과 성능평가를 위한 표준화된 시험방법이 제시되어 있지 않아 현장여건을 고려하여 적절한 낙석방지 울타리를 선정하고 낙석방지 울타리들의 성능을 비교검토하기에 어려움이 있다. 유럽의 경우 유럽연합 출범이후 낙석방지 시설에 대한 통합기준의 필요성이 대두되어 유럽 여러 나라의 성능평가 방법과 스위스의 설계지침을 고려하여 2008년에 유럽 통합 지침인 ETAG 27을 제정하였다. ETAG 27에는 낙석방지 울타리의 성능등급이 100kJ~4,500kJ이상 9등급으로 분류되어 있고 성능등급 별로 Service Energy Level과 Maximum Energy Level에 대하여 실물시험을 통한 성능평가 시험과 구성요소에 대한 검증시험을 수행하도록 되어있다. 실물시험은 낙석에너지의 산정과 낙석질량의 타격위치를 정확하게 결정할 수 있는 방법을 이용하여 수행토록 규정되어 있다. 미국의 경우에는 주별로 상이한 설계기준으로 인하여 발생하는 문제를 해소하기 위하여 2003년에 스위스의 설계지침을 준용하여 통합기준인 NCHRP Report 20-07을 결정하였다. NCHRP Report 20-07에는 낙석방지 울타리의 성능등급이 100kJ~5,000kJ까지 9등급으로 분류되어 있고 성능등급 별 낙석질량이 규정되어 있으며 등급별 낙석에너지의 50%와 100%에 대하여 실물시험을 통한 성능평가 시험을 수행하도록 되어 있다. 실물시험은 낙석에너지의 산정과 낙석질량의 타격위치를 정확하게 결정할 수 있는 방법을 이용하여 수행토록 규정되어 있다. 낙석방지 울타리에 대한 국내 설계지침과 유럽과 미국의 설계지침을 비교분석하고 국내에서 수행된 실물실험을 통한 성능평가 연구결과를 검토하였다. 또한 구성요소의 역학적 특성변화가 전체 시스템의 성능에 미치는 영향을 조사하기 위해서 국내 설계 지침에 제시된 낙석방지 울타리에 대하여 컴퓨터 시뮬레이션을 이용한 성능평가를 수행하였다. 이러한 연구결과에 근거하여 국내 설계지침은 현장여건에 따라 적절한 낙석방지 울타리를 선정할 수 있도록 다양한 성능등급을 규정하고, 낙석방지 울타리의 성능을 합리적으로 비교검토 할 수 있게 하는 표준화 성능평가 시험방법과 평가기준을 정립하며, 구성요소의 품질에 대한 신뢰성을 확인하는 구성요소의 검증시험을 포함하는 방향으로 개선될 필요가 있는 것으로 조사되었다.

• Convergence Security Journal
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• v.17 no.2
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• pp.159-164
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• 2017

The international community recognizes North Korea's nuclear and missile provocation as a real threat. This is due to the analysis and evaluation that has developed nuclear electro magnetic pulse of domestic and overseas North Korea experts, intelligence agencies related to electro magnetic pulse. Electro magnetic pulse experts are concerned about North Korea's nuclear electro magnetic pulse in the following aspects. First, industrial, military, medical, and living facilities in modern society are constructed with electrical and electronic systems. So, All electrical and electronic appliances will become neutralization if North Korea's nuclear electro magnetic pulse was set off over the world(i.e. Korean Peninsula, United States etc). Second, North Korea will judge that possibility of criticism by the international community is low from the point of view of an attacker. Because nuclear electro magnetic pulse aim to destroy only the electronic equipment of the opposite nation and cause damage rather than taking life. Finally, nuclear electro magnetic pulse is more threatening than weapons like mass destruction because it does not need to hit targets accurately and can strike a wide area with nuclear weapon of the low technology levels. In this respect, we will analyze and evaluate nuclear and missile development and make a prospects about nuclear electro magnetic pulse developed by North Korea.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.708-712
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• 2013

The appearance of the Korean bell is exceptional comparing to that of other bells. The sound of the Korean bell is also distinguishable because of its remarkable appearance. The sound of the Korean bell is composed of striking sound and residue sound. This study focuses mainly on the striking sound of the Korean bell. The primary purpose of this study is to suggest a proper sound quality evaluation method for Korean bell. To implement this study, examine the formerly established methods which are method using rating method and method using generally used Psychoacoustics metrics. Also, subjective Sound Quality evaluation was conducted to compare the results of method using rating method and the method using psychoacoustics metrics.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.88-88
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• 2018

기후변화와 기후변동으로 인해 태풍과 홍수 등의 자연재난 발생빈도가 증가하고 있으며, 이로 인해 심각한 인적 경제적 피해가 발생하고 있다. 피해 정도와 규모는 각 지역의 사회 경제적 요소에 따라 큰 차이를 보이고 있지만, 일반적으로 특정 지역에서 발생한 피해는 연속적으로 타 지역에 영향을 미치고 궁극적으로 국가 경제에 심각한 타격을 주는 경향이 있다. 따라서 본 연구에서는 산업연관모형을 이용하여 태풍 '차바'로 인해 울산지역에 발생한 피해가 국가 경제에 미치는 영향을 평가하였다. 본 연구결과는 특정 지역에서 발생한 피해가 타지역 및 국가 경제에 어떤 영향을 미치는지 정량적으로 평가하였고, 효율적인 재난관리의 기초자료로 사용될 수 있을 것으로 기대된다.

• The Journal of the Acoustical Society of Korea
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• v.25 no.2
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• pp.49-55
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• 2006

Measurement of impact sound insulation of floor, by current Korean Standard KS F 2810-2. is to be made with peak levels over 4 point in a receiving room. But it is often the case that there is inconsistency in results at various receiving points in the receiving room. Such variations obviously have effects on the repeatability and reproducibility of measured data. The result shows that there are even 10 dB deviations in 63Hz octave band frequency range and relatively less variations are occurred in other low frequency ranges. Such variations seems to be coming from modal overlaps of the receiving room. According to current rating method of floor impact sound. KS F 2863-2, that may affect on the single number latins scheme. From the result of tests in this study, there are 2dB to 6dB differences in the sin91e number with the combination of measurement points. This means that the reduction of measurement variations from the microphone positions is needed for a better credibility of measurement results.

• Journal of the Korean Geotechnical Society
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• v.37 no.11
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• pp.51-60
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• 2021

River scour erodes the soil around the pier, reducing the lateral bearing capacity of the pier and lowering the stability of the structure. In this study, in order to examine the effect of scouring on the stability of the structure, an experiment was performed to measure the natural frequency of the pier according to the excavation of the surrounding ground. Impact vibration test was conducted on the pier with the caisson foundation of the Mangyeonggang Bridge, which is scheduled to be demolished. Accelerometers were attached to the top, center, and bottom of the pier and the acceleration responses were measured by hitting those three points. The experimental results showed that the top hit showed consistent and reasonable results of the acceleration responses according to the hitting position. The measured accelerations were converted to the frequency domain through Fast Fourier Transform (FFT), and then the natural frequency was determined. In addition, to analyze the scour effect on the natural frequency of the pier, the ground around the pier was excavated and the natural frequency change was analyzed. As a result, the natural frequency showed the decreasing tendency according to the excavation depth, but the decrease was small due to the large stiffness of the caisson foundation.