• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.1365-1371
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• 2009

A new s-wave probe, called "MudFork", has been recently developed and is used in accurate measurements of shear wave velocities of soft soils. In previous researches, some instrumental defects of the probe have been reported. Bending deformation of probe is caused by small section modulus of blades, and open-ended bender elements are vulnerable to damage during penetration. Herein, we improved the MudFork to solve these problems. Field tests at Sinan, Jeollanamdo using the improved MudFork were conducted. Results from MPT are compared with the results from CPT.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1629-1633
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• 2004

Liquid is commonly introduced as transversal jets in venturi scrubber which is one of the gas cleaning equipments. The jet dynamics such as penetration and breakup is of fundamental importance to the dust-collection efficiency. We have developed a model that can numerically simulate the breakup of the liquid jet in crossflow. This simulation consists of models on liquid column, jet surface breakup, column fracture and secondary droplet breakup. These models have been embedded in the KIVA3-V code. We have calculated such parameters as the jet penetration, jet trajectory, droplet size, velocity field and the volume flux distribution. The results are compared with the experimental data in this paper.

• 한국군사과학기술학회지
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• 제7권1호
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• pp.59-65
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• 2004

Survivability of the general purpose warhead during the target impact was studied. We first simulated the penetration phenomena and temporarily defined the survivability of the warhead at the impact situation. Next we launched the warhead projectiles by using Counter Mass Gun(CMG) system against the simulated specific steel target. The recovered warheads were carefully investigated and the penetration behaviors were analyzed. As a result the warhead can be hardened efficiently to enhance the survivability with the help of CMG test ＆ analysis.

• 한국정밀공학회지
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• 제18권10호
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• pp.116-126
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• 2001

This paper suggests a numerical method to find optimal geometric path and minimum-time motion for a spatial 6-link manipulator arm (PUMA 560 type). To find a minimum-time motion, the optimal geometric paths minimizing 2 different dynamic performance indices are searched first, and the minimum-time motions are searched on these optimal paths. In the algorithm to find optimal geometric paths, the objective functions (performance indices) are selected to minimize joint velocities, actuator forces or the combinations of them as well as to avoid one static obstacle. In the minimum-time algorithm the traveling time is expressed by the power series including 21 terms. The coefficients of the series are obtained using nonlinear programming to minimize the total traveling time subject to the constraints of velocity-dependent actuator forces.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.233-236
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• 2002

The high-pressurized spray nozzle is used f3r special washing and cutting with strong impact force. The performance of this nozzle, which focused on spray penetration and radial dispersion, was mainly investigated to maximize the momentum and minimize the flow loss. Hence, our experimental research was conducted by changing the aspect ratio ranging from 0 to 3 with nozzle outlet of 1.1. The spray trajectory far high-pressurized water was experimentally investigated using PDPA diagnostics, which was available at spray downstream region. As the spray at upstream near the nozzle exit did not show the improved disintegration. The results showed empirical correlation with regard to non-dimensional axial velocity distribution, spray penetration, and radial spreading rate with photographic visualization.

• Composites Research
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• 제26권1호
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• pp.21-28
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• 2013

본 논문에서는 유효 면적의 제한이 있는 복합재 적층판의 탄도한계속도를 예측하였다. 탄도한계속도를 예측하기 위해 정적압입 관통실험과 고속충격 실험 그리고 준실험식을 이용하였다. 정적압입 관통실험을 통해 하중-변위 데이터를 취득하고 이를 이용해서 관통에너지를 측정하였다. 고속충격 실험을 통해 실제 관통 속도 및 관통 에너지를 측정하였다. 정적압입 관통실험과 고속충격 실험을 통해 구한 에너지를 이용해 준실험식을 만들고, 준실험식과 고속충돌 실험결과와 비교해 보았다. 위 방법을 이용해 탄도한계속도를 예측하였고 정적압입 관통 실험과 준실험식에 의한 탄도한계속도 예측의 타당성을 확인하였다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2017년도 춘계 학술논문 발표대회
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• pp.254-255
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• 2017

The aim of this study is to investigate the impact resistant performance of steel short fiber-reinforced cement based composites (SFRCCs) containing 1.0, 1.5, 2.0 and 3.0% volume fraction of steel short fibers subjected to high velocity impact of steel projectile (the diameter of 19.05mm and the mass of 28.13g). The gunpowder impact facility was used for impact tests, and the impact velocity was from about 350 to 700m/s. The specimens were damaged in various failure modes, which are penetration, scabbing, and perforation. Comparing with Plain specimen, SFRCCs have superior capacity on the scabbing limit, and slightly bulged in the back side under the impact velocity of 700m/s. In addition, the impact resistant performance of SFRCCs improved with increase of steel short fiber volume ratio. The fibers play an important role in controlling the local damage of SFRCCs.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.142-152
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• 2008

SPT-Uphole method was introduced for the evaluation of near subsurface shear wave velocity (Vs) profile. In SPT-Uphole method, SPT (Standard Penetration Test) which is common in geotechnical site investigation was used as a source and several surface geophones in line were used as receivers. 1D shearwave velocity profile can be obtained in the manner of downhole method, Vs distribution map which is the triangular shape around the boring point can be developed by tomography inversion. To obtain the exact travel time information of shear wave component, a procedure using the magnitude summation of vertical and horizontal components was used based on the evaluation of particle motion at the surface. It was verified that proposed method could give reliable Vs distribution map through the numerical study using the FEM (Finite Element Method) model. Finally, SPT-Uphole method was performed and the feasibility of proposed method was verified in the field.

• 콘크리트학회논문집
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• 제14권6호
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• pp.973-981
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• 2002

최근 들어, 고강도 콘크리트의 사용이 증가하고 있으나 응결과 같은 초기 성질에 관한 연구는 미흡한 실정이다. 콘크리트의 초결과 종결 시간을 결정하기 위해 널리 사용되어 온 관입 저항 시험 방법(KS F 2436)은 점성이 커서 콘크리트로부터 모르타르를 얻기 어려운 고강도 콘크리트에는 적용하는 데에 어려움이 따른다. 따라서, 콘크리트의 응결 거동을 조사하기 위해 본 연구에서는 관입 저항 방법 대신에 초음파 속도 모니터링 시스템을 이용하여, 다양한 물-결합재 비(W/B)와 플라이 애쉬의 사용량에 따른 모르타르와 콘크리트에 대해 배합 직후부터 처음 24시간 동안 초음파 속도를 연속적으로 측정하였다. 실험 결과, 콘크리트의 초음파 속도가 동일한 W/B을 갖는 모르타르보다 빨리 발현되었으며, 일반 콘크리트의 초음파 속도 발현이 플라이애쉬 콘크리트보다 빠른 것으로 나타났다. 또한, 세 가지의 규준, 즉 (1) 관입 저항 시험, (2) 초음파 속도가 증가하기 시작하는 시점, (3) 초음파 속도의 증가율이 최대가 되는 시점 등에 근거하여 초결과 종결에 해당하는 초음파 속도 값을 제시하였다. 본 연구에서 사용한 초음파 속도 모니터링 장치와 응결 추정 방법은 콘크리트 현장에서 특히, 고강도 콘크리트의 응결 평가에 유용하게 적용될 수 있을 것으로 사료된다.

• 한국지반공학회논문집
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• 제37권6호
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• pp.29-37
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• 2021

화강 풍화대 지반은 지반구조물의 주요 지지층으로 활용되고 있으므로 화강 풍화대의 지반특성을 평가하는 것은 중요하다. 특히, 내진설계의 중요성이 부각되고 있음에 따라 지반분류 및 지반 최대 전단 탄성계수(G_max) 평가에 활용되는 전단파 속도(V_S)의 합리적인 평가의 중요성이 증가하고 있다. 본 연구에서는 국내 화강 풍화대 지층을 대상으로 표준관입시험(SPT: Standard penetration test) N₆₀ 및 채취한 시료의 화학적 풍화지수를 바탕으로 비선형 다변량 회귀분석을 수행하여 전단파 속도(V_S) 추정식을 제안하였고, 기존 관련 연구결과와 비교하였다. 화학적 풍화지수를 추가적인 독립변수로 고려하여 풍화도를 고려한 경우 N₆₀만을 사용하여 수행한 단순 회귀분석 결과에 비해 결정계수가 증가하여 전단파 속도 추정식의 정확도가 향상됨을 확인하였다.