• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.3
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• pp.285-290
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• 2008

Pyrotechnic shock or pyroshock is characterized as a transient vibration phenomena which shows large acceleration and high frequency range up to 10kHz during the operation of separation devices where explosives are used. During the flight of a launch vehicle, pyro-shock is mainly generated at several events such as satellite separation, fairing separation and stage separation. In this paper, characteristics of pyroshock are introduced briefly, and PEEK washer shock absorber is applied for the reduction of pyroshock in the high frequency range. With some electronic devices, reduction characteristic of pyroshock using washer type shock absorber are studied. Random vibration tests are also performed for the verification of vibrational characteristics.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.9
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• pp.923-928
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• 2008

Pyrotechnic shock or pyroshock is characterized as a transient vibration phenomenon which shows large acceleration and high frequency range up to 10kHz during the operation of separation devices where explosives are used. During the flight of a launch vehicle, pyroshock is mainly generated at several events such as satellite separation, fairing separation and stage separation. In this paper, wiremesh isolators are introduced and several types of isolators are manufactured for the performance tests. For the investigation of typical characteristics of wiremesh isolators, compressive loading tests are basically performed and pyroshock tests are accomplished to confirm pyroshock isolation ability of each wiremesh isolator by using 4Kg dummy mass.

• Journal of Convergence for Information Technology
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• v.11 no.3
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• pp.132-139
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• 2021

The response characteristics of the forced vibration generated when the high-damped vehicle pass the bumped barrier was studied, and in particular, the response behavior of displacement, velocity and acceleration was analyzed for the forced vibration model. In addition, in order to obtain responses such as displacement, velocity, and acceleration, a numerical analysis technique of the Runge-Kutta-Gill method was performed in time domain. The response was successfully obtained in detail under several high damping conditions. As a numerical analysis result, the response of the vehicle was obtained by considering the vehicle body to which the impulse impact was applied. Also, the analysis result was compared with the experimental result in order to verify the validity of vehicle model. The amplitude and natural frequency of the vehicle were considered and analyzed. The Nyquist diagram of the vehicle model was also obtained and the relationship could be analyzed. And the vibration response was analyzed on different mass, damping and stiffness.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.2
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• pp.187-192
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• 2013

Thin metallic sandwich plate with pyramidal metallic inner structures is manufactured from a continuous projection welding between face sheets and inner structures. Due to the welding pressure, imperfections of inner structures induced by the deformation of the inner structures occur. The imperfections affect the response of the thin metallic sandwich plate subjected to low-velocity impact loading. The goal of this paper is to obtain a proper dominant imperfection mode of the thin metallic sandwich plate with pyramidal metallic inner structures. The variation of impact responses of the thin metallic sandwich plate for different imperfection modes are investigated by finite element analysis. The results of the FE analysis are compared to those of drop impact experiments. From the results of the comparison, it has been shown that the dominant imperfection mode of the thin metallic sandwich plate with pyramidal metallic inner structures is all type of symmetric imperfection mode with symmetrical imperfections of four struts.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1A
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• pp.45-52
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• 2010

This study pointed on the dynamic impact of AGT (Automated Guide-way Transit) bridge, due to concrete rail prominence. An experiment was done with 30 m P.S.C. bridge in AGT test line in Kyungsan. An artificial prominence with 10 mm hight, was installed at the mid span of concrete rail. And computer simulation was executed for the artificial prominence. As an experiment result, in the case of with prominence, bridge acceleration responses are increased 50% at the speed range of 20 km/h-60 km/h, and bridge displacement responses increased slightly. With these results, the prominence of concrete rail can be induce excess impact and vibration. And the computer program simulated much the same as experiments. So this program can be used for AGT bridge design and formulate the standard of concrete rail management.

• Journal of the Society of Naval Architects of Korea
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• v.57 no.5
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• pp.305-311
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• 2020

This study presents a probabilistic time series forecast of ship structural response using Bayesian inference combined with Volterra linear model. The structural response of a ship exposed to irregular wave excitation was represented by a linear Volterra model and unknown uncertainties were taken care by probability distribution of time series. To achieve the goal, Volterra series of first order was expanded to a linear combination of Laguerre functions and the probability distribution of Laguerre coefficients is estimated using the prepared data by treating Laguerre coefficients as random variables. In order to check the validity of the proposed methodology, it was applied to a linear oscillator model containing damping uncertainties, and also applied to model test data obtained by segmented hull model of 400,000 DWT VLOC as a practical problem.

• Journal of Ocean Engineering and Technology
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• v.31 no.5
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• pp.357-363
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• 2017

The sloshing pressure acting on a membrane-type LNG CCS is a typical irregular impact load, and the structural response of a tank system induced by sloshing also shows very complex behavior, including fluid structure interaction. Therefore, it is not easy to accurately estimate the sloshing impact pressures and resulting structural response. Moreover, a huge time consuming process to deal with the enormous pressure data obtained during a model tank test and the following structural analysis would be inevitable. To reduce the computation time for structural analysis, in this study, a rational structural modeling strategy was considered, and a simplified scheme to analyze the dynamic structural responses of an LNG CCS was introduced, which was based on the concept of the linear combination of the triangular response functions obtained by a transient response analysis of structures under unit triangular impact pressure. A structural analysis of a real Mark III membrane type insulation system under the sloshing impact pressure time histories obtained by model tests was performed using the various proposed structural models and simplified analysis scheme. The results were investigated in detail, including the elastic support effects of the hull structure.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.317-322
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• 2002

There are many researches to identify the rigid body properties from the mass-line obtained by impact hammer testing. The correct rigid body properties of the structure may be estimated if the mass-line of the structure could be obtained exactly. When the structure is mounted by elastic materials, the mass-line cannot be read correctly from the impulse response spectrum. The reason is due to the effects of rigid body modes of mounted structure. In this paper, the effects of rigid body modes of mounted structure to the mass-line are discussed and the method to remove these effects is also presented.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.336.2-336
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• 2002

There are many researches to identify the rigid body properties from the mass-line obtained by impact hammer testing. The correct rigid body properties of the structure may be estimated if the mass-line of the structure could be obtained exactly. When the structure is mounted by elastic materials, the mass-line cannot be read correctly from the impulse response spectrum. The reason is due to the effects of rigid body modes of mounted structure. (omitted)

• Annual Conference of KIPS
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• 2016.10a
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• pp.685-686
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• 2016

엑스선 투시촬영장치와 같은 의료용 동영상의 잡음 제거에 있어서 시공간 잡음제거 알고리즘을 제안한다. 제안된 알고리즘에서는 무한 충격 응답 기반 시간 영역 잡음 제거 얄고리즘을 도입하여 움직임이 적은 영역에서는 자연스러운 잡음 제거가 가능하며 움직임이 많은 영역에서는 연산량 측면에서 효율성을 고려하여 지역적 평균 필터 기반 공간 잡음 제거 알고리즘을 적용하여 움직임에 의한 흐려짐 열화 현상을 최소화 하면서 잡음 제거를 수행하였다.