• Explosives and Blasting
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• v.34 no.1
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• pp.11-18
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• 2016

It is necessary to minimize ground vibration and noise due to blasting work in urban environment. The blast induced ground vibration and noise are generally generated by a portion of detonation energy, where most of the energy is utilized for rock breakage and movement of rock mass. Recently a blast method utilizing U-shaped steel charge holder was suggested to reduce the ground vibration without decreasing destructive power toward the free surface. In this study, single hole blasting utilizing U-shaped steel charge holder were simulated and the stress waves caused by the detonation of explosives were monitored using AUTODYN software. In order to examine the fragmentation efficiency of the U-shaped steel charge holder, one free face blasting models which adapt the blast induced stress waves were simulated by dynamic fracture process analysis (DFPA) code. In addition, the general blasting models were also simulated to investigate the fragmentation effectiveness of the U-shaped steel charge holder in rock blasting.

• Journal of the Korean Geotechnical Society
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• v.20 no.6
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• pp.41-49
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• 2004

In general, open trenches or in-filled trenches have been used to isolate transmitting of vibration. Recently alternative methods, in which various materials are used for wall barriers have been proposed and performed in several sites. Although the effects of these methods are verified, resonable and qualitative evaluation methods have not yet been conducted. It may be because many factors, such as the characteristics of vibration sources, ground condition, and parameters of wall barrier are coupled complicatedly. In this study, a series of centrifugal modelings were conducted in order to examine the evaluation method of a vibration wall barrier when point load transmits to the surface. The experiments were performed with different stiffness of wall barriers and different depths of installations. Using the results obtained from tests, effects of those variables on the efficiency of vibration barrier were analyzed. Through this investigation we observed vibration transmission of under ground, and verified the applicability of ball dropping system which was developed in this study.

• Journal of Navigation and Port Research
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• v.26 no.1
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• pp.43-49
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• 2002

In this Paper, the mechanical behavior of two reかangular plates spot-welded under free vibration is investigated in detail. The focus of the analysis is to evaluate the effect of thickness of reinforced plates with equivalent thickness. The results of this the investigation are compared with detailed finite element analysis end experiments of the plates spot-welded for various parameters, such as aspect ratio, arm ratio, and distance ratio of spot-welding Points. The conclusion obtained are as followed. 1. The effect thickness due to spot-weld is very large, such as 55% in comparison with area ratio of spot-welding joint is just 4.52%. 2 The effect of thickness with respect to the distance ratio is maximized when the distance ratio is 0.4.

• Journal of the Korea Convergence Society
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• v.11 no.9
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• pp.31-37
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• 2020

The purpose of this study was to investigate the Effect of transcranial direct current stimulation convergence task-oriented training combined with vibration stimulation on hand dexterity and upper limb function in stroke patients. One time 30 minutes 5 times a week for 4 weeks. experimental group of transcranial direct current stimulation convergence task-oriented training combined with vibration stimulation and control group of the task-oriented training combined with vibration stimulation were divided into 10 members. Hand dexterity and upper limb recovery were measured. The experimental group and the control group showed significant improvement in hand dexterity and grasping(p<.05), grasping, and gross movement(p<.05). The experimental group showed a significant improvement in hand dexterity and grasp and grip than the control group. Effect size showed more than small effect in all evaluation items. Based on the results of this study, it is considered that more effective and efficient rehabilitation treatment can be performed in the clinic.

• Magazine of the Korea Concrete Institute
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• v.8 no.5
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• pp.123-133
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• 1996

Recently, the construction of infrastructures has been booming and accelerating to keep up with rapid economic growth. Construction activities and operation of transportation facilities cause unfavorable effects such as civil petitions associated with vibration-induced damages or nuisances. Accordingly, the objective of this study is to develop vibration-controlled concrete using various vibration-controlled mixtures, and also to recycle obsolete materials in part. As the first step to achieve this research, preliminary mix designs have been carried out to obtain an appropriate mix proportion above 200kg/$\textrm{cm}^2$ in uniaxial compressive strength. Test specimen based on the mix proportion selected have been actuated by the impact hammer to investigate their dynamic characteristics. Vibration-controlled mixtures are foam, latex, rubber powder and plastic resin, which have been determined to reduce a vibration by and large. KS F2437 and travel time method have been used to figure out 1st natural frequency and dynamic elastic moduli. Damping ratios have been computed by adopting the polynomial curvefitting method and the geometric analysis method on the frequency response spectrum curve. of which results have been compared and analyzed hereon.

• Geotechnical Engineering
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• v.13 no.4
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• pp.121-134
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• 1997

Vibrations induced by traffic loading and construction activities are extremely important due to their potential to cause damage to adjacent structures and toy complaints to the neighbors. Vibration induced damage to the built environment may be caused by the direct transmission of vibrations as well as by the, vibration induced differential settlement. In order to effectively control the vibration related problems, the accurate in-situ vibration monitoring is essential. In this paper, a calibration technique of a geophone which is widely used in practice was described. Once the frequency characteristics of individual geophones were calibrated, the 3fomponent geophone was developed for the in-depth vibration measurement, and the dot ailed calibration and application techniques of the 3fomponent geophone were described. Vibrations caused by blasting, train loading, and pile driving were measured and the applicability of the 3fomponent geophone was assessed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.3
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• pp.19-28
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• 1990

The main purpose of this paper is to present both fundamental and some higher natural frequencies of catenary arcs. The differential equations governing planar free vibrations for these arcs are derived, in which the rotatory inertia is included, as non-dimensional forms and solved numerically to obtain frequencies and mode shapes. The hinged-hinged and clamped-clamped end constraints are applied in numerical examples. The lowest four natural frequencies are reported as the functions of non -dimensional system parameters; the slenderness ratio and the rise to span length ratio. The effects of rotatory inertia on natural frequencies are reported and some typical mode shapes are also presented.

• Journal of Korean Society of Steel Construction
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• v.13 no.6
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• pp.651-659
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• 2001

The main purpose of this paper is to present an analytical method for free vibration of stepped horizontally curved members on two-parameter elastic foundation. The ordinary differential equations governing the free vibration of such beams are derived as non-dimensional forms including the effects of rotatory inertia and shear deformation. The governing equations are solved numerically for the circular, parabolic, sinusoidal and elliptic curved beams with hinged-hinged, hinged-clamped and clamped-clamped end constraints. As the numerical results, the lowest four natural frequency parameters are presented as the functions of various non-dimensional system parameters. Also the typical mode shapes are presented.

• Proceedings of the KIPE Conference
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• 2010.11a
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• pp.15-16
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• 2010

본 논문에서는 최소의 진동/소음을 가지는 SRM을 설계하기 위하여 고정자와 회전자의 Skew에 따른 단상 6/6 SRM의 소음/진동 특성을 비교, 분석하였다. SRM(Switched Reluctance Motor)에 발생하는 소음/진동의 주 원인은 모터 구동 시 Yoke 에 발생하는 방사방향 힘의 변화라고 할 수 있다. Yoke에 작용하는 힘은 돌극이 위치한 곳에 집중되므로 더욱 큰 진동을 유발하지만 회전자와 고정자에 동일한 Skew를 적용시키면 힘을 받는 Yoke의 면적은 늘어나게 되고, 따라서 방사방향의 힘을 요크 전체로 분산 시킬 수 있다. 이에 따라 스위치 온, 오프시 요크에 인가되는 방사방향의 힘의 최대치는 감소하게 되어 진동/소음이 현저히 줄어들게 된다. 본 논문에서는 최소의 진동/소음을 가지는 SRM을 설계하기 위하여 시뮬레이션을 통하여 회전자와 고정자의 스큐 각도에 따른 힘의 분포를 분석하였다. 시뮬레이션 결과를 바탕으로 하여 대표적인 특성을 가진 $0^{\circ}$, $18^{\circ}$의 SRM을 설계하여 소음/진동을 측정한 결과 제안한 방식이 소음/진동을 현저하게 감소시키는 효과를 가짐을 입증하였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.04a
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• pp.223-230
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• 1995

본 연구에서는 선박소음해석을 수행하기 위한 기초작업으로서 실선 선박모델을 크게 3가지 경우로 구분하여 모델링 하였으며, SEA법을 적용하여 고체소음의 전달손실을 이론적으로 예측할 수 있는 방법을 제시하였으며, 또한 STL을 도입하여 각 요소간의 에너지 흐름 및 구성판요소의 재료별 방진효과를 알아보았다. 이 방법의 결과 다음과 같은 결론을 얻을 수 있었다. 1) 내장판의 종류에 따른 전달특성은 고주파 대역에서는 plywood, 저주파 대 역에서는 rockwool이 높은 손실값을 보였으며, glasswool은 전 주파수 대역에서 고른 손실값을 가짐을 확인하였다. 2) 기진원으로부터의 거리가 멀어짐에 따라 내장판의 효과가 크게 나타나며, 기진원의 근방 요소에서는 내장판의 효과보다는 강판의 두께의 영향이 두드 러짐을 알 수 있었다. 3) 내장판 요소중 plywood의 방진효과가 가장 크게 나타남을 알 수 있었다. 4) 본 SEA법에 의한 연구에서는 구성 판요소의 재질과 두께에 따른 고쳇음 의 전달특성을 이론적으로 해석하였으며, 차후 실험을 통한 검증이 요구되어 진다.