• Proceedings of the Safety Management and Science Conference
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• 2011.11a
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• pp.93-99
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• 2011

안전모는 낙하, 비례물에 대한 두부를 보호하는 보호구로 낙하물의 충격을 일부 흡수하여 완화시켜주는 기능을 하고 있다. 안전모 충격 흡수 성능으로 최고전달충격력이 있으나 낮을수록 성능이 좋은 것으로 나타나지만 안전모 제조과정에서 얼마 만큼의 충격이 흡수되는지는 알 수 없었다. 이로 인하여 성능 향상을 위한 충격력의 명확한 제어 가능한 성능 향상의 기준을 잡는데 어려움이 있었다. 본 연구에서는 충격량과 연관된 반발계수로 충격흡수 성능의 정도를 찾고자 하였다. 연구 대상은 시중에서 주로 착용되고 있는 ABS 재질의 안전인증 합격품을 대상으로 선정 하였다. 연구 방법으로는 운동량과 충격량의 이론으로 안전모 충격흡수성능 시험장치를 활용하여 인두에 전달된 충격량을 활용하여 충격흡수시의 반발계수를 구하고, 충격을 흡수치 않을 때를 가정하여 추정 충격력 곡선을 유도하고 충격흡수 전의 추정 최고 전달충격력과 반발계수를 구하여 충격흡수의 성능을 나타내었다. 연구결과 국내 안전인증 H사의 안전모의 최고전달충격력은 4100 N 이였고, 충격흡수 성능은 400 N 으로 약 9 %를 흡수되는 것으로 나타났다.

• Journal of Korean Society of Transportation
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• v.29 no.3
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• pp.123-137
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• 2011

In general, flow propagation has been explained using the shock wave theory which is expressed as a function of variations in volume and density. However, the theory has certain limitation in portraying heterogeneous flow, e.g., flow propagation between lanes. Motivated by this fact, this study seeks a new measure for analyzing the propagation characteristics of traffic flow at three sections of highway (i.e., merging area, weaving section, and basic section) from temporal and spatial perspectives, and then develops a model for estimating the measure for the flow propagation. The "shock wave speed" which is the measure widely adopted in literature, was first applied to describe the propagation characteristics, but it was hard to find distinct characteristics in the propagation. This finding inspires to develop a new measure named "Impulse Volume". It is shown that the measure better explains the propagation characteristics at the three study sections of highway. In addition, several models are also developed by performing multi-regression analyses to explain the flow propagation between lanes. The models proposed in this paper can be distinguished in three sections and the lane placement.

• Journal of Korean Society of Transportation
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• v.26 no.2
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• pp.167-176
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• 2008

Although a rate of car accident death is on the decrease, internal rate of median encroachment accident is still high. In order to reduce the median encroachment accident, government use median barriers but there are no exact criteria of them. Particularly, current impulse measurement method has adopted the uniformly operating speed and encroachment angle. At reality, however, there are various conditions depends on driver's characters. In that reason, this study calculates reasonable impulse quantity through encroachment angle and operating speed. It will be necessary to prevent overuse treasury and car accidents.

• Composites Research
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• v.29 no.3
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• pp.91-97
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• 2016

In this paper, impulse-momentum theory was coupled to a constitutive equation both for implementing quasi-static and impact characteristics of EPP (Expanded polypropylene). Also, parameters which have physical meanings were expressed as functions of relative density. Simultaneous nonlinear Newton-Raphson method was applied to find the proper values for parameters in the constitutive equation along with quasi-static test data. Results from the impulse-momentum theory coupled constitutive equation showed good agreement with experimental data and the potential to be applied to different material type polymeric foam.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 2000.11a
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• pp.353-356
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• 2000

두 물체의 충격운동량-충격 및 탄성파 발생의 순으로 작용하도록 하면 계 내에서 충돌 후 생기는 운동량의 관성 속도와 충돌기간동안 발생하는 탄성파의 충격에너지 전달속도가 다른 경우가 있다. 이것은 충돌기간동안 총 운동량은 보존되나 선 운동량이 비 보존되는 경우가 있어서 충돌기간동안 비 보존된 내부 운동량의 시간 적분만큼 충돌을 가한 질량중심이 이동했다는 의미이다. 충돌기간동안 충격파는 탄성파에 근사시키고 그것은 군속도에 근사시켜 이론적 근거를 만들고 실험에 의해 확인했다. 폐쇄된 계 내에서 내부에너지를 이용하여 특별한 두 물체의 충돌기간동안 비 보존되는 운동량 때문에 질량중심이 이동되는 것에 대해 해석한다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.191-195
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• 2003

충격음 저감재의 동탄성계수와 감쇠계수는 차단성능을 평가하는데 있어 중요한 물성치가 된다. 저감재의 동탄성계수는 뜬바닥구조의 고유진동수를 결정짓게 되며, 저감재의 동탄성계수가 높을수록, 즉 고유진동수가 높아짐에 따라 실험실 경량충격음레벨 저감량은 지수함수적으로 감소됨을 실험을 통해 알 수 있다. 또한, 저감재를 포함한 뜬바닥구조를 1자유도 진동계로 가정한 이론값과 실험실 경량충격음레벨 저감량의 결과가 비교적 잘 일치하는 것으로 나타났으며, 이 때 감쇠계수의 영향은 반드시 고려되어야 한다.

• Explosives and Blasting
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• v.26 no.1
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• pp.15-21
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• 2008

In case of estimating the shocking vibration during the blasting demolitions, the weight and falling height of the structure, that is a potential energy, had been considered. But, this study presented a new equation which used the impulse concerning a falling weight instead of potential energy as a method of predicting the shock vibration. In this experiment, the data of the impulse were compared with the data of the potential energy by performing the free-fall, and all data were comparatively analyzed by the regression analysis method. Also, the method of the superposition theory, which is calculated by the diminution ratio according to distance, the free-fall difference according to height, and the time giving the shock to the ground according to the breakdown pattern, was compared with the previous vibration data occurring from the blasting demolitions in the same conditions. As a result, this study suggests that the impulse and the method of superposition theory be applied as a method of predicting the shocking vibration. Therefore, these results could be expected to estimate the shocking vibration more accurately than the previous method.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.546-550
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• 2007

수중보는 하천, 하수관 또는 인공수로에 건기시 유지수량을 확보할 목적으로 설치되며 보통 10년 주기 내외의 평균 강우량에 맞추어 그 용량을 결정한다. 수처리를 위한 장치의 규모는 적정한 재현기간에 맞추어 설계하고, 재현기간을 초과하여 강우가 발생할 경우 강우 유입을 우회시켜 경제성을 확보할 수 있어야 한다. 따라서 완충회전수문은 초과하는 수량을 우회 또는 통과시킬 목적으로 개발되었으며 기존 연구에서 실내 및 현장 실험 모형을 제작하여 여러 차례 실험을 토대로 한계수심 및 충격량을 이론적으로 산정하고 현장 적용성을 검증한 바 있다. 본 연구에서는 수문의 개 폐시 원형실린더에 부착되어 있는 날개의 길이 및 개수 변이에 따른 항력의 영향으로 충격량을 측정하여 현장에 보다 적합한 완충회전수문의 최적설계방안을 제시하고자 한다.

• Tunnel and Underground Space
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• v.31 no.6
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• pp.578-592
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• 2021

This study performed to investigate the propagation characteristics of overpressure, impulse, vibration in underwater blasting. The difference between air blasting and underwater blasting is that noise and vibration propagate through water as a medium. In some cases, the noise and vibration propagates through various media (rock, water, air, etc.). In this study, the underwater blasting was simulated using AUTODYN, and the propagation characteristics of overpressure, impulse and vibration induced by blasting were analyzed. We mainly focused on the effect of mesh size on the overpressure, impulse and peak particle velocity from the underwater blasting simulation. The numerical results indicated that the overpressure and peak particle velocity tended to decrease as the mesh size increased, while the impulse increased with the mesh size. The results also indicated that the mesh dependence varied depending on the explosive charge and scaled distance.

• Explosives and Blasting
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• v.34 no.4
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• pp.28-34
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• 2016

Empirical model, phenomenological model, and CFD model have been used to evaluate the blast effects produced by explosion of explosives, flammable gas and liquid or dust. TNT equivalence method which is one of empirical models has been widely used as it is simple. In this study, new peak overpressure-scaled distance and scaled impulse-scaled distance equations are induced through fitting data from the curves given by TNT equivalence method. If the TNT equivalent mass is calculated, it is possible to estimate the peak overpressure and impulse using the regression equations. Differences of peak overpressure with yield factor which is a component of TNT equivalence method are found to be great in near-by distances from explosion source where the increase in overpressure is very steep, but the differences are getting smaller as the distances increase.