• 환경위생공학
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• 제13권2호
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• pp.14-25
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• 1998

To investigate the behavior of reaction products with the reactor heights by the change of upflow velocity, a typical real height USAB reactor was built and experiment was conducted. The flow in the reactor by the upflow velocity was flug flow at low upflow velocity but the flow was completely mixed flow at high upflow velocity. Therefore, the concentration of pH, alkalinity and volatile acid was not so different with reactor heights at high upflow velocity. And comparing with low upflow velocity, the distribution of microorganisms with reactor heights did not show big different at high upflow velocity. The removal efficiency of organic compounds depended on the distribution of microorganisms and it was low at high upflow velocity. It is concluded that the operation of reactor with proper upflow velocity to improve contact with organic compounds and microorganisms is recommended.

• 한국항공우주학회지
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• 제50권7호
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• pp.465-470
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• 2022

본 논문은 알루미늄 6061의 고속 충격 해석과 고속 충격 시험 결과를 비교 검증하여 금속 재료의 고속 충격에 의한 거동 특성을 연구하였다. 고속 충격 해석을 위해 만능재료시험기를 이용한 준정적 시험과 Hopkinson bar를 이용한 동적 시험을 통해 Huh-Kang 모델과 Johnson-Cook 파손 모델의 계수를 구했다. LS-DYNA 프로그램 해석을 이용하여 관통 속도와 형상을 결과로 예측했고 고속 충격 시험기를 이용한 시험 결과와 비교하였다. 이를 바탕으로 항공기 가스터빈 엔진 블레이드 컨테인먼트 평가 연구에 적용하고자 한다.

• 지구물리와물리탐사
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• 제16권4호
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• pp.225-233
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• 2013

효율적이고 객관적인 NMO 속도분석을 위해 사용되는 자동 속도분석의 정확성은 속도 빛띠의 속도 해상도에 많은 영향을 받는다. 본 연구에서는 고해상도 BDS (high-resolution Bootstrapped Differential Semblance)를 이용하여 속도 빛띠를 구성하고, 이를 이용하여 공통 중간점 모음 별로 병렬적으로 자동 속도분석을 수행하는 모듈을 개발하였다. 또한 이 고해상도 BDS를 이용하는 자동 속도분석 모듈의 속도분석 결과를 BDS (Bootstrapped Differential Semblance)를 이용한 자동 속도분석의 결과와 비교하였다. 수평층을 포함한 속도모델로부터 얻은 합성 탄성파 탐사자료를 생성하고 이를 이용하여 개발된 모듈을 검증한 결과 본 연구를 통해 개발된 모듈이 좀 더 정확한 속도를 추정하는 것을 확인하였다. 또한 현장자료에 개발된 모듈을 적용하여 이벤트의 연속성이 향상된 공통 중간점 겹쌓기 단면을 구할 수 있는 NMO 속도를 추정하였다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2001년도 제23회 KOSCO SYMPOSIUM 논문집
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• pp.104-110
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• 2001

Characteristics of lifted flame for highly diluted propane with nitrogen in high temperature coflowing air have been experimentally investigated, and the stabilization mechanism of lifted flame in high temperature air coflow have been proposed. As the coflow temperature increases, the liftoff height of flame decreased due to the increase of stoichiometry laminar burning velocity. At same coflow temperature, the difference of liftoff height between the fuel mole fractions has been disappeared by scaling the liftoff velocity with stoichiometry laminar burning velocity. It has been found that lifted flame can be stabilized for even smaller fuel velocity than stoichiometry laminar burning velocity. This can be attributed to buoyancy effect and the liftoff velocity characteristics for coflow temperature support it.

• International Journal of Aeronautical and Space Sciences
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• 제14권2호
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• pp.140-145
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• 2013

The development of high performance fabrics have advanced body armor technology and improved ballistic performance while maintaining flexibility. Utilization of the shear thickening phenomenon exhibited by Shear Thickening Fluids (STF) has allowed further enhancement without hindering flexibility of the fabric through a process of impregnation. The effect of STF impregnation on the ballistic performance of fabrics has been studied for impact velocities below 700 m/s. Studies of STF-impregnated fabrics for high velocity impacts, which would provide a transition to significantly higher velocity ranges, are lacking. This study aims to investigate the effect of STF impregnation on the high velocity impact characteristics of Kevlar fabric by effectively dispersing silica nanoparticles in a suspension, impregnating Kevlar fabrics, and performing high velocity impact experiments with projectile velocities in the range of 1 km/s to compare the post impact characteristics between neat Kevlar and impregnated Kevlar fabrics. 100 nm diameter silica nanoparticles were dispersed using a homogenizer and sonicator in a solution of polyethylene glycol (PEG) and diluted with methanol for effective impregnation to Kevlar fabric, and the methanol was evaporated in a heat oven. High velocity impact of STF-impregnated Kevlar fabric revealed differences in the post impact rear formation compared to neat Kevlar.

• 천문학회지
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• 제4권1호
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• pp.1-8
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• 1971

The average velocity, 330km/sec. of the high velocity stars with respect to the galactic center is obtained from the data used by Fricke on the assumption that the rotational velocity of the Local Standard of Rest is 250km/sec. Comparing this value with the escape velocity, 380km/sec, at the solar neighborhood which is calculated from Mestel's model of the Galaxy, it is shown that most of the high velocity stars are bound to the Galaxy and that their average apogalacticon is about 40 kpc from the galactic center. And the fact that stars with radial velocities larger than 63km/sec are missing in the direction of galactic rotation of L.S.R. is interpreted as the result partly of the random distribution of the directions of motion of the high velocity stars and partly of the observational errors.

• 한국해양공학회지
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• 제17권1호
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• pp.55-60
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• 2003

The effect of size and volume fraction of ceramic particles, with sliding velocity on the wear properties were investigated for the metal matrix composites fabricated by the pressureless infiltration process. The metal matrix composites exhibited about 5.5 - 6 times the wear resistance compared with AC8A alloy at high sliding velocity, and by increasing the particle size and decreasing the volume fraction, the wear resistance was improved. The wear resistance of metal matrix composites and AC8A alloy exhibited different aspects. Wear loss of AC8A alloy increased with sliding velocity, linearly : whereas, metal matrix composites indicated more wear loss than AC8A alloy at the slow velocity region. However, a transition point of wear loss was found at the middle velocity region, which shows the minimum wear loss. Further, wear loss at the high velocity region exhibited nearly the same value as the slow velocity region. In terms of wear mechanism, the metal matrix composites generally exhibited abrasive wear at slow to high sliding velocity； however, AC8A alloy showed abrasive wear at low sliding velocity and adhesive and melt wear at high sliding velocity.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 추계학술대회 논문집
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• pp.379-384
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• 2002

The effect of size and volume fraction of ceramic particles with sliding velocity on the wear properties were investigated for the metal matrix composites fabricated by pressureless infiltration process. The particulate metal matrix composites exhibited about 5.5 - 6 times of excellent wear resistance compared with AC8A alloy at high sliding velocity, and as increasing the particle size and decreasing the volume fraction the wear resistance was improved. The wear resistance of metal matrix composites and AC8A alloy exhibited different aspects. Wear loss of AC8A alloy increased with sliding velocity linearly. whereas metal matrix composites indicated more wear loss than AC8A alloy at slow velocity region, however a transition point of wear loss was found at middle velocity region which show the minimum wear loss, and wear loss at high velocity region exhibited nearly same value with slow velocity region. In terms of wear mechanism, the metal matrix composites exhibited the abrasive wear at slow to high sliding velocity generally, however AC8A alloy showed abrasive wear at low sliding velocity and adhesive and melt wear at high sliding velocity.

• 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.

• 전기학회논문지
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• 제67권1호
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• pp.131-136
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• 2018

Reliable velocity estimation technology for trains is one of technologies used to operate trains safely and effectively. Various sensors such as tachometers, doppler radars, and global positioning systems are used to estimate velocity of a train. Tachometer is widely used to estimate velocity of a trains due to its simplicity, small volume, cost-effectiveness, continuously measurement at high speed, and robustness against noise. Accuracy in the velocity calculation using a tachometer depends on quantization error, measurement error of wheel radius or diameter, and tachometer's imperfection from manufacturing or installation process. In this paper, we present an accurate velocity estimation method using a low-resolution tachometer, which is commonly installed on a high-speed train. Baseline estimation method is proposed to accurately calculate the velocity of the high-speed train from tachometer's pulses. HEMU-430x test train is used for the experiment and verification of the proposed method. Experimental results with several routes show that the proposed method is more accurate than a conventional method.