• Korean Journal of Agricultural Science
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• v.32 no.1
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• pp.29-42
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• 2005

During a long journey of agricultural products from the production area to markets, the quality of agricultural products was always affected by some degree of vibration. The vibration input during the transportation may cause serious agricultural product injury, and this damage is particularly severe whenever the vegetable inside package is free to bounce, and is vibrated at its resonant frequency. The objectives of this study were to determine the resonant frequency of the oriental melon and to investigate the relationships between resonant frequency and physical properties of the oriental melon such as mass, volume and major and minor axes. In this study vibration testing device was constructed to determine the vibration response of the oriental melon in frequency ranges of 5 to 150 Hz. The computer program for controlling the vibration shaker and the function generator and measuring the vibration characteristics of the oriental melon was developed. The ranges of resonant frequency and peak acceleration at resonance of the oriental melon were 51 to 73 Hz and 1.24 to 1.92 G-rms, respectively. The resonant frequency and the peak acceleration decreased with the increase of the sample mass, volume, major and minor axes of the oriental melon. Multiple regression models for resonant frequency and peak acceleration of the oriental melon as a function of mass, major axis and minor axis of the sample were developed and analyzed.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.4
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• pp.67-75
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• 2004

It is essential to develop a transient analysis model for the turbopump-fed type liquid rocket engine development, especially for deriving the number of test and its parameters. In this study we proposed a mathematical model of turbopump-fed type liquid rocket engine, and inspected transient mode changes of a rocket engine according to variations of thrust control valve opening ratio. To verify the results, we solved the same problem with AnaSyn software from Russia, and concluded that the results of transient code we developed deviated within 2% from AnaSyn results. Also, using the transient engine analysis code we showed the possibility to find out the system level design Parameters of the components. For example, we modeled a pressure stabilizer which is used to control the consistency of mixture ratio in the gas generator as forced damping system, and found the stability range of the natural frequency and the damping ratio with the transient engine system analysis code.

• Geotechnical Engineering
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• v.14 no.1
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• pp.59-70
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• 1998

Samples of silty sands and hydraulic fill ground were investigated by dynamic triaxial teats in order to evaluate the liquefaction strengths. In the tests, (1) undisturbed and disturbed samples were prepared, (2) dynamic shear strengths were measured under isotropic and anisotropic condition, and (3) the test results were compared with the other results which were tested by domestic and foreign researchers. The liquefaction shear strengths under ismtropic test condition were presented in terms of the relative densities. The amount of silt under 30o hardly influenced on the liquefaction strength. In the test results of anisotropically consolidated samples the liquefaction strength was dependent on the magnitude of the effective consolidation ratio. These teat results show that the liquefaction strength of the silty sand in Korea went coast exists within the boundary of the values suggested by Seed and Peacock(1971).

• Magazine of the Korea Concrete Institute
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• v.10 no.4
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• pp.171-182
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• 1998

Vibration-controlled concrete has been developed by using various concrete mixtures, such as latex, rubber powders, plastic resins and polystyrene(styrofoam). As part of the recycling research of obsolete aged tires and plastic materials, various vibration-reducing mixtures are used for 10 concrete panels having above 200 kg/cm$^2$ in uniaxial compressive strength. Plywood box with sand uniformly saturated by the raining device has been used for the analysis of the impact wave, of which data have been transfered by the FFT technique to comparatively investigate damping ratios of 10 concrete panels.According to wave propagation analysis on vibration-controlled concrete for this research, it can be concluded that Latex concrete has relatively larger damping ratios than those for noncontrolled normal concrete in a similar compressive strength

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.5
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• pp.891-901
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• 2016

By comparing test blasting data experimented in three layered-structure polymorphic grounds to a geological profile, influence of blast vibration with respect to uncontrollable ground characteristics was analyzed. Inefficient blast have been performed without sufficient verifications or confirmations because insufficiencies with regard to experiments and data of blasting engineering on the layered structures to be irregularly repeated clinker layer consisted of volcanic clastic zones. It is difficult to quantify N values of clinkers within test blasting region because they have diverse ranges, or coverages. An absolute value of attenuation coefficient N in a field, estimated by blasting vibration predictive equation (SRSD), are lesser than criteria of a design instruction, meaning that vibrations caused by blast can spread far away, and the vibrational characteristics of blasting test No.1, indicating relatively small values, inferred by the geological profile, pressures of gas by the explosion may be lost into a widely distributed clinker layers by penetrating holes resulted from blast into vicinity of clinker layers located in bottom of soft rock layers at the moment of blast. As a result, amounts of spalling rocks are decreased by almost half. Also, ranges of primary frequencies in the fields are identified as similar to those of natural frequency of typical structures.

• Journal of Biosystems Engineering
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• v.34 no.5
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• pp.305-314
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• 2009

The purpose of this paper was to design an effective control system of 1-axis exciter for a seat vibration test of agricultural tractors using MATLAB simulation. The developed simulation model was composed with a hydraulic pump, a hydraulic servo valve, a hydraulic cylinder and load system. Also it was verified by comparing the simulation results with experimental results of actual control system in order to optimize the control performance. And in order to improve its control performance, the designed PID controller in this research was tuned using Ziegler-Nichols 2nd law and zero's moving method of PID controller's transfer function. As the result of these research, the developed position control system was able to control the system's position accurately within 5% errors.

• Journal of the Korean Geosynthetics Society
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• v.21 no.4
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• pp.41-53
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• 2022

In the excavation work like blasting/excavator work bordering on the urban railway, the dynamic safety of railway structures like tunnel, open-cut box structure and elevated bridge was investigated by numerical analysis in this study. The practically presented criteria on influential zones at the blasting work in the construction industry was numerically checked in cases of the precise vibration-controlled blasting (type II) and the small scale vibration-controlled blasting (type III) and it was shown that the criteria on blasting work methods needed to be supplemented through continuous field tests and numerical analyses. The influence of excavation vibration by mechanical excavators was especially investigated in case of earth auger and breaker. The numerical analysis of tunnel shows that the criteria on vibration velocities from the regression analysis of field test values was conservative. The amplification phenomenon of excavating vibration velocity was shown passing through the backfilling soil between the earth auger and the open-cut box structure. It was shown that the added-vibration on the superstructure of elevated bridge was occurred at the bottom of pile like earthquake when the excavator vibration was arriving at the pile toe. The systematic and continuous research on the vibration effect from excavating works was needed for the safety of urban railway structures and nearby facilities.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.3 s.108
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• pp.283-290
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• 2006

This study is concerned with static and sinusoidal disturbance rejection for a single periodic input disturbance with known period. In the area of active elimination of a disturbance force, the control input should have two different kinds of gains: one is to deliver a stable control and the other is a force component to cancel the external disturbance force. In this paper we employ a simple state feedback control law to make the balance beam stable and employ a linear observer to estimate the states which represent the external disturbance force components. Simulation results verify our proposed control method to reject a static and sinusoidal disturbance force.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.131-131
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• 2012

압전재료는 그 특성상 항공우주분야에서 활용범위가 넓어지고 있는데, 특히 진동제어 분야에 널리 이용되고 있다. 최근에는 위성카메라의 영상 품질개선을 위한 구동기(actuator) 연구도 진행 중이다. 그러나 위성체가 작동하는 우주환경인 고진공상태에서는 각 부품에서 발생할 수 있는 outgassing으로 인해 위성체가 오염되어 위성임무 실패를 초래할 수도 있다. 따라서 지상에서 위성체 부품에 대해 고온($60^{\circ}C$)과 고진공(5.0 E-03 Pa 이하)의 상태를 모사하여 오염물질을 제거함으로써 outgassing 발생을 막고, 오염근원을 검출할 수 있는 bacuum bake-out 시험이 필요수적이다. 압전체의 위성부품 활용성 연구를 위하여 bake-out 챔버를 이용하여 오염측정에 관한 연구를 수행하였다. Vacuum bake-out 시험시에는 TQCM을 사용하여 발생하는 오염물질의 방출률을 측정한다. 아울러, 압전체에 대한 시험 전후의 압전특성을 비교 분석하여 진공 및 온도 환경하에서의 특성 변화를 관찰하였다.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1324-1325
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• 2008

근래 선진 중전기 메이커에서는 차단기, GIS 등의 전통적인 단품 위주에서 탈피하여 전력 IT 기술을 접목한 전력기기/변전소 자동화를 강력하게 추진하고 있다. 특히 전체 변전소를 감시, 제어, 계측, 보호할 수 있도록 전력 IT 기술을 기반으로 한 IEC 61850 적용 변전소 종합 자동화 시스템 개발에 역량을 집중하고 있다. 본 논문에서는 당사에서 개발한 최신 IT 기술을 적용한 IEC 61850 기반 170㎸ GIS용 Bay Controller 관련 구성, 기능, 성능시험 결과에 대해 기술하며, 변전소 내 노이즈로 인해 유발될 수 있는 전자장치 오동작 등을 보증하기 위해 실시한 전자파 장해시험 결과와 GIS와 동일한 환경에 설치되므로 온/습도, 진동/충격시험을 관련 국제규격인 IEC 60255-6, IEC 60255-21-1, 2, 3에 의거하여 실시한 내용을 기술하도록 한다.