• Journal of Advanced Research in Ocean Engineering
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• 제2권1호
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• pp.28-39
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• 2016

This paper provides theoretical and experimental results to verify the crashworthiness of FH32 high-strength steel for arctic marine structures against ice impact. Assuming that side-shell structures of the Korean arctic research vessel, ARAON, with ice-notation PL10, collide with sheet ice, one-third-scale test specimens with a single transverse frame are manufactured. Impact-bending tests were conducted using a rigid steel striker that mimics sheet ice. Drop height was calculated by considering the speed at which sheet ice is rammed. Prior to impact-bending tests, tensile coupon tests were conducted at various temperatures. The impact-bending tests were carried out using test specimens fully fixed to the inside bottom frame of a cold chamber. The drop-weight velocity and test specimen deformation speed were measured using a high-speed camera and digital image correlation analysis (DICA). Numerical simulations were carried out under the same conditions as the impact-bending tests. The simulation results were in agreement with the test results, and strain rate was a key factor for the accuracy of numerical simulations.

• 마이크로전자및패키징학회지
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• 제20권4호
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• pp.69-74
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• 2013

In this paper, the impact of integrating large number of I/O (Input-Output) and Core power Delivery Network (PDN) on a 6 layers Flip-Chip Ball Grid Array (FCBGA) package is investigated. The impact of core induced supply noise on high-speed I/O interfaces, and high-speed I/O interface's supply noise coupling to adjacent high-speed I/O interfaces' jitter impact are studied. Concurrent stress validation software is used to induce SSO noise on each individual I/O interfaces; and at the same time; periodic noise is introduced from Core PDN into the I/O PDN domain. In order to have the maximum coupling impact, a prototype package is designed to merge the I/O and Core PDN as one while impact on jitter on each I/O interfaces are investigated. In order to understand the impact of the Core to I/O and I/O to I/O noise, the on-die noise measurements were measured and results were compared with the original PDN where each I/O and Core PDN are standalone and isolated are used as a benchmark.

• Advanced Composite Materials
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• 제18권4호
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• pp.395-413
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• 2009

Impact tests on high-strength membrane materials under biaxial loads were experimentally conducted in order to evaluate influence of biaxial loads on impact fracture of the membrane materials for the inflated applications. Cruciform specimens of the membrane materials were fabricated for applying biaxial loadings during the impact test. A steel ball was shot using a compressed nitrogen gas gun, and struck the membrane specimen. Impact tests on uniaxial strip specimens were also conducted to obtain the effect of specimen configuration and boundary condition on the impact fracture. The results of the measured crack length and the ultra-high speed photographs indicate the impact fracture properties of the membrane fabrics under biaxial loadings. Crack length due to the impact increased with applied tensile load, and the impact damages of the cruciform membrane materials under biaxial loadings were smaller than those of under uniaxial loadings. Impact fracture of the strip specimen was more severe than that of the cruciform specimen due to the difference of boundary conditions.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.121-121
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• 2000

This paper presents a design of macro-micro system for high-speed mounting of micro-chips. A macro motion device is driven by DC servomotor and ball screw mechanism. To obtain fast response, a micro motion device utilizes a precision elector magnetic actuator In order to reduce peak impact force, We evaluate the design parameters that have an effect on it. And a characteristic of response is simulated using PID controller in velocity and force control.

• 한국분무공학회지
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• 제17권2호
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• pp.86-93
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• 2012

The effects of projectile impact system on the transient spray characteristic which is supersonic liquid tip velocity were studied by experimentally. Supersonic liquid jets were generated by impact of a high speed projectile driven by a Two-stage light gas gun. A high speed camera and schlieren optical system were used to capture the spray structures of the supersonic liquid jets. In a case of nozzle assembly Type-A, expansion gases accelerate a projectile which has a mass of 6 grams from 250 m/s at the exit of the launch tube. Accelerated projectile collides with the liquid storage part, then supersonic liquid jets are injected with instantaneous spray tip velocity from 617.78 m/s to 982.54 m/s with various nozzle L/d. However, In a case of nozzle assembly Type-B which has a heavier projectile (60 grams) and lower impact velocity (182 m/s), an impact pressure was decreased. Thus the liquid jet injected at 210 m/s of the maximum velocity did not penetrate a shock wave and fast break-up was occurred. Pulsed injection of liquid column generated second shock wave and multiple shock wave.

• 한국자동차공학회논문집
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• 제10권2호
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• pp.96-100
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• 2002

The purpose of this paper is presented a rational method of predicting dynamic/impact tensile strength of high tensile steel materials widely used fur structural material of automobiles. It is known that the ultimate strength is related with the loading speed and the Lethargy Coefficient from the tensile test. The Dynamic Lethargy Coefficient is proportional to the disorientation of the molecular structure and indicates the magnitude of defects resulting from the probability of breaking the bonds responsible for its strength. The coefficient is obtained from the simple tensile test such as failure time and stresses at fracture. These factors not only affect the static strength but also have a great influence on the dynamic/impact characteristics of the joist and the adjacent structures. This strength is used to analyze the failure life prediction of mechanical system by virtue of its material fracture. The impact tensile test is performed to evaluate the life parameters due to loading speed with the proposed method. Also the evaluation of the dynamic/impact effect on the material tensile strength characteristics is compared with the result of Campbell-Cooper equation to verify the proposed method.

• 대한기계학회논문집A
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• 제40권10호
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• pp.857-864
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• 2016

항공산업의 발달로 하늘에는 많은 비행기, UAV, 드론이 비행하고 있다. 비행기와 UAV는 빠른 속도로 비행하며 드론의 프로펠러는 빠른 속도로 회전하고 있다. 이렇게 빠른 속도의 비행체간의 충돌은 비행기 운항과 승객의 안전성을 위협하고, 지상에 있는 인명과 재산에 피해를 줄 수 있다. 비행체의 운항속도는 음속(340m/s) 내외이며, 프로펠러의 회전 속도는 그 보다 작은 속도 영역이다. 현재까지의 충돌 실험은 공기의 힘을 이용한 방식으로 충돌 속도를 얻었고, 공기 팽창에 따른 넓은 공간을 필요로 한다. 하지만 전자기력 발사장치는 그보다 작은 공간에서 충분한 속도를 얻을 수 있다.(~500m/s) 본 논문에서는 전자기력 발사장치의 설계와 이에 따른 제작에 관한 방법을 제시하고자 한다.

• Nuclear Engineering and Technology
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• 제54권10호
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• pp.3745-3765
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• 2022

The concrete structures related to nuclear safety are threatened by accidental impact loadings, mainly including the low-velocity drop-weight impact (e.g., spent fuel cask and assembly, etc. with the velocity less than 20 m/s) and high-speed projectile impact (e.g., steel pipe, valve, turbine bucket, etc. with the velocity higher than 20 m/s), while the existing studies are still limited in the impact resistant design of nuclear power plant (NPP), especially the primary RC slab. This paper aims to propose the numerical simulation and theoretical approaches to assist the impact-resistant design of RC slab in NPP. Firstly, the continuous surface cap (CSC) model parameters for concrete with the compressive strength of 20-70 MPa are fully calibrated and verified, and the refined numerical simulation approach is proposed. Secondly, the two-degree freedom (TDOF) model with considering the mutual effect of flexural and shear resistance of RC slab are developed. Furthermore, based on the low-velocity drop hammer tests and high-speed soft/hard projectile impact tests on RC slabs, the adopted numerical simulation and TDOF model approaches are fully validated by the flexural and punching shear damage, deflection, and impact force time-histories of RC slabs. Finally, as for the two low-velocity impact scenarios, the design procedure of RC slab based on TDOF model is validated and recommended. Meanwhile, as for the four actual high-speed impact scenarios, the impact-resistant design specification in Chinese code NB/T 20012-2019 is evaluated, the over conservation of which is found, and the proposed numerical approach is recommended. The present work could beneficially guide the impact-resistant design and safety assessment of NPPs against the accidental impact loadings.

• 콘크리트학회논문집
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• 제22권6호
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• pp.797-803
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• 2010

경부 고속철의 PSC 박스거더 교량의 동적응답에 대하여 보다 우수한 평가를 얻기 위한 동적거동해석방법을 개발하였다. 특히, 고속철 차량, 교량 그리고 궤도구조물간의 구조적 상호작용을 고려한 3차원 수치해석모델을 개발하여 고속철 속도에 의하여 발생되는 PSC 교량의 동적응답을 정확하게 해석하고 심도깊은 영향평가를 수행하였다. PSC 박스거더 교량은 40 m 경간의 단순교를 뼈대요소를 사용하여 3차원 프레임 모형화 하였다. K-TGV 고속철 차량은 동력차를 포함하여 다련 38자유도 모형으로 개발하고 차체와 대차의 연직변위, 횡변위, 종변위 및 피칭, 롤링, 요잉을 모두 고려하였다. 동적충격계수는 정적해석결과와 Runge-Kutta 기법으로 산출된 동적해석 결과를 비교 산출하였으며, 고속철 차량 속도에 따른 그 차이를 회귀분석을 통하여 추정실험식으로 제안하였다.

• 대기
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• 제31권2호
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• pp.157-170
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• 2021

To investigate the effect of snowfall on the traffic of general roads in Gangwon-do, case analysis was performed in Gangneung, Pyeongchang, and Chuncheon using ASOS (Automated Synoptic Observing System) snowfall data and VDS (Vehicle Detector System) traffic data. First, we analyzed how much the traffic volume and speed decrease in snowfall cases on regional roads compared to non-snow cases, and the characteristics of monthly reduction due to snowfall were investigated. In addition, Pearson correlation analysis and regression analysis were performed to quantitatively grasp the effect of snowfall on traffic volume and speed, and sensitivity tests for snowfall intensity and cumulative snowfall were performed. The results showed that the amount of snowfall caused decrease both in the traffic volume and speed from usual (non-snowfall) condition. However, the trend was different by region: The decrease rate in traffic volume was in the order of Gangneung (17~22%), Chuncheon (14~17%), and Pyeongchang (11~14%). The decrease rate in traffic speed was in the order of Chuncheon (9~10%), Gangneung (8~9%), Pyeongchang (5~6%). No significant results were found in the monthly decrease rate analysis. In all regions, traffic volume and speed showed a negative correlation with snowfall. It was confirmed that the greater the amount of traffic entering the road, the greater the slope of the trend line indicating the change in snowfall due to the traffic volume. As a result of the sensitivity test for snowfall intensity and cumulative snowfall, the snowfall information at intervals of 6-hours was the most significant.