• Journal of Advanced Marine Engineering and Technology
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• 제23권2호
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• pp.150-158
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• 1999

The process of designing protective circuits against damage by transient overvoltages requires much work and expensive equipment. However computer simulation using PSpice can overcome these problems. In this paper a gas tube and a ZnO varistor Pspice-model considering the steepness of the wave-front were presented. The effects of various waveforms on the transient behaviors and firing volt-ages of a gas tube were modeled by controlled voltage source E controlled current source G and TABLE function of PSpice. And the nonlinear characteristics of a ZnO varistor were modeled by controlled voltage source E and H. To estimate the characteristics of the models proposed various waveforms specified in IEC Std. 1000310-4-5 were used in the simulation and the actual tests. The simulation results were compared with test results and showed good agreement.

• 한국농공학회논문집
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• 제61권1호
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• pp.75-83
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• 2019

Fruit bagging is a traditional way to produce high-quality fruit and to prevent damage from insects and diseases. Growing pears by non-bagging is concerned about the damage from insect, it can be controlled by installing a insect net facility. Wind load should be considered to design the insect net facility because it has the risk of collapse due to the strong wind. So we carried out wind tunnel test for measurement of drag force, where the insect net with porosity about 65% is selected as an experimental subject. As a result of the test, drag force was measured to be 244.14 N when insect net area and wind speed are $1m^2$ and 22.7 m/s respectively. And, drag coefficients for the insect net were found to be about 0.55~0.57, which may be used as the preliminary data to design the insect net facilities at the orchard.

• 터널과지하공간
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• 제19권6호
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• pp.545-557
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• 2009

단계별 손상에 따른 취성재료의 동적손상메커니즘을 파악하고자 국내암석을 대상으로 스플릿 홉킨슨 압력바 시스템을 이용한 단계적 충격하중실험을 수행하였다. 실험시료 내 동적손상을 평가하기 위하여 고해상도 X-ray 단층촬영 시스템을 적용하였다. 그 결과 낮은 충격하중에서는 시료 내 전반적으로 축방향 균열 즉 수직균열이 발생하지만, 충격속도가 증가함에 따라 시료와 입사바 또는 전달바와의 접촉면에 구속효과가 발생하여 입사바와의 접촉면 중심부에 균열이 사라지는 경향을 보였다. 그러나 구속력을 적게 받는 시료의 원주표면 부근에서는 박리균열을 보였다.

• 한국강구조학회 논문집
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• 제25권1호
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• pp.103-114
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• 2013

최근 지진동과 같은 강한 수평력 작용시 골조에 작용하는 대부분의 손상을 댐퍼부에 집중시키며 주부재의 재사용을 가능하게 하는 지속가능형 접합부 시스템에 관한 관심이 커지고 있다. 본 연구에서는 이러한 개념을 적용한 새로운 형태의 손상제어형 접합부 시스템을 제안하고 실물대 반복이력실험 및 비선형 유한요소해석을 통하여 제안 시스템의 주요 구조성능을 분석하였다. 분석결과를 통하여 주부재의 손상을 극소화하면서 보의 전소성모멘트 이상을 만족하는 최적의 댐퍼/보 내력비를 도출하였으며 내진접합상세로서의 적용가능성을 확인하였다.

• 대한기계학회논문집A
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• 제27권1호
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• pp.167-174
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• 2003

Fatigue damage of 2.2Ni-1Cr-0.5Mo steel used fir high strength pressure tubes and vessels was evaluated using uniaxial specimens subjected to strain-controlled fatigue loading. Based on the fatigue test results from different strain ratios of -2. -i 0, 0.5, 0.75, the fatigue damage of the steel was represented by using a cyclic strain energy density. Mean stress relaxation depended on the magnitude of the applied strain amplitude. The high pressure vessel steel exhibited the cyclic softening behavior. Total strain energy density consisting of the plastic strain energy density and the elastic tensile strain energy density described fairly well the fatigue life of the steel, taking the mean stress effects into account. Compared to other fatigue damage parameters, fatigue life prediction by the cyclic strain energy density showed a good correlation with the experimental fatigue lift within a factor of 3.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2003년도 학술발표논문집
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• pp.335-338
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• 2003

The Self-Controlled Screen which removed canal underwear garbage in order to prevent the damage of the arable land that increased by a typhoon and a concentration precipitation was developed. A method to remove garbage let communicate the force that a water mill was run by water pressure in the canal, and occurred in a water mill to Rake, and to have walked on a screen was adopted. As a result of was designed by structure calculation, and was made, and having installed in an experimental laboratory, operation was able to know that was become smoothly well. Afterwards, It is going to test for model development of a water mill to be able to more very generate an influence and force to reach to a canal.

• 한국초지조사료학회지
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• 제25권1호
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• pp.65-70
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• 2005

This study was conducted to investigate the effect of combine crawler attaching slurry spreader on soil and growth of rye. The performance test at actual field was conducted to test for possibility of practical use. Field test of the slurry spreader was operated in upland and paddy field. Experiments was conducted to compare the effects of the soil damage and crop productivity incorporating Pig slurry by two different types of slurry spreader. In this experiment a slurry spreader using crawler of combine have been designed and developed to enhance the operation in small field and reduce e damage of soil structure. but it was not suitable for transference in long distance. Conventional tractor mounted vacuum is not suitable for $71.6\%$ water condition in the small areas of paddy land. But the slurry spreader using crawler could be controlled the working point and moving by crawler in paddy land of small area. The wheels depths of soil in the supplementary application in the rye field was 4.9 m in tractor mounted spreader. but the wheels depth of crawler attaching spreader was 1.6cm. The dry matter yield of rye was reduced by $12\%$ in supplementary application of slurry due to mechanical damage from passage of the tires. This is particularly noticeable at high soil moisture condition in paddy land. It was concluded that the slurry spreader developed in this study could be successfully used for basal and supplementary application of slurry in rye paddy field.

• 조명전기설비학회논문지
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• 제27권2호
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• pp.84-94
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• 2013

In case when the existing TRIAC phase controlled dimmer is drove for the LED lighting equipments, there are many problems such as the LED flicker in low phase-angles, the acoustic noise and elements damage by increase of the peak voltage in the input filter capacitor, mulfunction by insufficiency of the TRIAC holding current, and the abnormal oscillation by LC resonant. In this paper, we proposes the single-stage quasi-resonant PSR(Primary Side Regulation) PWM converter, and the design, the simulation and experiment are performed. As a result, it could confirm that the proposed PWM converter is the lighting equipments for LED drive which can alternate the existing 60W class incandescent bulbs and it has the high drive performance of the efficiency 80% and over, the power factor 0.95 and over under the normal voltage 220V. Finally, total harmonic distortion(THD) is gratified with a standard[1] of the lighting equipments and the durability is evaluated as the high reliablilty of 150,000 hours and over.

• 대한기계학회논문집A
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• 제41권6호
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• pp.567-573
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• 2017

자동차 부품 중 드라이브 샤프트는 엔진에서 발생하는 토크를 바퀴에 전달하는 동력 전달장치의 핵심 부품이다. 엔진에서 입력되는 비틀림 하중과 주행 중 발생하는 실동하중에 의한 부품의 파손을 방지하기 위해, 고주파 열처리로 강도 및 피로수명이 개선되고 있다. 본 연구에서는 고주파 열처리에 따른 드라이브 샤프트의 피로수명을 정량적으로 평가할 수 있는 피로수명 평가기법을 구축하였다. 드라이브 샤프트의 소재인 SAE10B38M2 강재로 모재 및 경화깊이가 서로 다른 고주파 열처리 시편 두 종을 제작하여 비틀림 하중 하에서의 전단 변형률 제어 피로시험을 진행하였고, 변형률-수명 피로수명 평가에 필요한 피로 물성값을 구하였다. 얻어진 피로 물성값을 이용하여 드라이브 샤프트의 변형률 기반 피로해석을 진행하였으며, 얻어진 피로수명 결과를 시제품 피로시험 결과와 비교하여 해석기법의 타당성을 검증하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2006년도 추계학술대회 논문집
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• pp.538-544
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• 2006

This paper is to investigate the dynamic characteristics of prestressed concrete (PSC) girder that has been spliced with precast box segments. A 20 m long full-scale spliced precast concrete box railway girder was fabricated and tested to identify its dynamic properties against a monolithic girder. The monolithic girder has the same geometric and material properties with respect to the spliced girder. Dynamic parameters including natural frequency, mode shape, and damping ratio were identified using the a digitally controlled exciter. Modal analyses were performed based on three-dimensional finite element models, and the calculated modal parameters were compared with test results. Finally, the characteristic decrease of natural frequency due to damage for each girder has been examined after the load test.