• Advances in materials Research
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• 제13권5호
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• pp.335-353
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• 2024

In the present paper, a simple quasi-3D integral higher-order beam theory (HBT) is presented, in which both shear deformation and thickness stretching effects are included for mechanical analysis of advanced composite beams with simply supported boundary conditions, handling mainly bending, buckling, and free vibration problems. The kinematics is based on a novel displacement field which includes the undetermined integral terms and the parabolic function is used in terms of thickness coordinate to represent the effect of transverse shear deformation. The governing equilibrium equations are drawn from the dynamic version of the principle of virtual work; whereas the solution of the problem is obtained by assuming a Navier technique for simply supported advanced composite beams subjected to sinusoidally and uniformly distributed loads. The correctness of the present computational method is checked by comparing the obtained numerical results with quasi-3D solutions found in the literature and with those provided by other shear deformation beam theories. It can be confirmed that the proposed model, which does not involve any shear correction factor, is not only accurate but also simple and useful in solving the static and dynamic response of advanced composite beams.

• 원예과학기술지
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• 제29권4호
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• pp.298-305
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• 2011

본 연구는 칼슘제의 엽면살포를 이용하여 국내육성 스탠다드 국화 '백마' 의 줄기 경도를 증대함으로써 상품성 향상 및 수송시 줄기가 부러져 절화의 품질이 떨어지는 문제점을 방지하고자 수행하였다. '백마'의 칼슘제 선발시험은 염화칼슘($CaCl_2{\cdot}2H_2O$), 질산칼슘[$Ca(NO_3)_2{\cdot}4H_2O$], OS-Ca(굴껍질에서 추출한 천연 액상 칼슘 화합물)을 사용하였으며 Ca 함량을 기준으로 처리농도는 0, 0.001, 0.01, 0.1, 1.0%로 엽면살포하였다. 모든 칼슘제 1.0% 처리구에서 엽소 현상과 줄기가 휘어지는 심한 약해가 나타났다. OS-Ca는 또한 다른 칼슘제보다 '백마'에 흡수가 가장 잘 되었기 때문에 가장 심한 약해 현상이 나타난 것으로 보인다. 수확 후 최대 줄기경도는 다른 칼슘제 처리구보다 OS-Ca에서 더 높았으며, 특히 0.01% OS-Ca 처리구가 가장 우수하였다. 반면, 탄성강도와 최대굴곡강도에서는 0.001% OS-Ca 처리구가 다른 처리구보다 높게 나타났다. 따라서 OS-Ca 처리시 약해가 발생하지 않았던 농도인 0.005에서 0.05% 사이를 범위로 하여 '백마'의 줄기 강화에 적합한 칼슘제로 OS-Ca을 선정하였다. 다음 실험에서는 OS-Ca의 처리농도를 0, 0.005, 0.01, 0.05%로 세분화하여 처리하였다. OS-Ca 처리 후 생육을 조사한 결과, 0.05% OS-Ca에서 초장, 상 중부 줄기 직경, 엽수 및 부위별 건물중에서 무처리와 다른 처리농도보다 우수하였다. OS-Ca의 농도에 따른 줄기 경도에 있어서는 줄기 내 칼슘 함량, 최대경도, 탄성강도, 최대 굴곡강도에서 0.05% OS-Ca 처리구가 가장 우수하게 나타났고, 무처리구와 OS-Ca 처리구 사이에서 고도의 유의성을 나타내었다. 그러나 줄기횡단면의 총면적, 수조직 면적, 공동 면적, 공동률은 무처리구를 포함하여 모든 처리구 간의 유의성은 없었다. 따라서 '백마'의 줄기 경도와 줄기 공동률 간의 상관관계는 없는 것으로 판단되었다. 결론적으로, 백마의 영양생장기에 가장 적절한 엽면살포 칼슘제와 농도는 0.05% OS-Ca였으며, 수송시 백마의 줄기 경도를 강화시킬 것으로 판단되었다.

• Wind and Structures
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• 제23권6호
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• pp.559-575
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• 2016

In order to investigate the influence of different blade positions on aerodynamic load and wind loads and load-effects of large scale wind turbine tower under the halt state, we take a certain 3 MW large scale horizontal axis three-blade wind turbine as the example for analysis. First of all, numerical simulation was conducted for wind turbine flow field and aerodynamic characteristics under different halt states (8 calculating conditions in total) based on LES (large eddy simulation) method. The influence of different halt states on the average and fluctuating wind pressure coefficients of turbine tower surface, total lift force and resistance coefficient, circular flow and wake flow characteristics was compared and analysed. Then on this basis, the time-domain analysis of wind loads and load-effects was performed for the wind turbine tower structure under different halt states by making use of the finite element method. The main conclusions of this paper are as follows: The halt positions of wind blade could have a big impact on tower circular flow and aerodynamic distribution, in which Condition 5 is the most unfavourable while Condition 1 is the most beneficial condition. The wind loads and load-effects of disturbed region of tower is obviously affected by different halt positions of wind blades, especially the large fluctuating displacement mean square deviation at both windward and leeward sides, among which the maximum response occurs in $350^{\circ}$ to the tower top under Condition 8; the maximum bending moment of tower bottom occurs in $330^{\circ}$ under Condition 2. The extreme displacement of blade top all exceeds 2.5 m under Condition 5, and the maximum value of windward displacement response for the tip of Blade 3 under Condition 8 could reach 3.35 m. All these results indicate that the influence of halt positions of different blades should be taken into consideration carefully when making wind-resistance design for large scale wind turbine tower.

• Earthquakes and Structures
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• 제24권6호
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• pp.455-475
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• 2023

The present study investigates the non-linear soil-pile interaction using three-dimensional (3D) non-linear finite element models. The numerical models were validated by using the results of extensive pile load and shaking table tests. The pile performance in liquefiable and non-liquefiable soil has been studied by analyzing the liquefaction ratio, pile lateral displacement (LD), pile bending moment (BM), and frictional resistance (FR) results. The pile models have been developed for the different ground conditions. The study reveals that the results obtained during the pile load test and shaking cycles have good agreement with the predicted pile and soil response. The soil density, peak ground acceleration (PGA), slenderness ratio (L/D), and soil condition (i.e., dry and saturated) are considered during modeling. Four ground motions are used for the non-linear time history analyses. Consequently, design charts are proposed depended on the analysis results to be used for design practice. Eleven models have been used to validate the capability of these charts to capture the soil-pile response under different seismic intensities. The results of the present study demonstrate that L/D ratio slightly affects the lateral displacement when compared with other parameters. Also, it has been observed that the increasing in PGA and decreasing L/D decreases the excess pore water pressure ratio; i.e., increasing PGA from 0.1 g to 0.82 g of loose sand model, decrease the liquefaction ratio by about 50%, and increasing L/D from 15 to 75 of the similar models (under Kobe earthquake), increase this ratio by about 30%. This study reveals that the lateral displacement increases nonlinearly under both dry and saturated conditions as the PGA increases. Similarly, it is observed that the BM increases under both dry and saturated states as the L/D ratio increases. Regarding the acceleration histories, the pile BM was reduced by reducing the acceleration intensity. Hence, the pile BM decreased to about 31% when the applied ground motion switched from Kobe (PGA=0.82 g) to Ali Algharbi (PGA=0.10 g). This study reveals that the soil conditions affect the relationship pattern between the FR and the PGA. Also, this research could be helpful in understanding the threat of earthquakes in different ground characteristics.

• 고려인삼학회:학술대회논문집
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• 고려인삼학회 1990년도 Proceedings of International Symposium on Korean Ginseng, 1990, Seoul, Korea
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• pp.149-154
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• 1990

Various rates of 2, 4-2 were sprayed on 2 and 3 year old ginseng plants as fouler spray to define the critical concentration. No apparent plant injury was noticeable for those ginseng plants when application concentration of 2, 4-D doubled the recommended dosage (70 mil 10a). Neither abnormal fouler change occurred nor any inhibition in leaf and stem growth was resulted for the plants treated with 2, 4-D concentrated two times of the recommended dosage. When the rates of 2, 4-D application were increased greater than this level, injury ratings increased linearly with the rates of 2, 4-D application and plant growth was inhibited. Ethylene gas was not produced from the ginseng plant treated with 2 times concentrated 2, 4-D, how- ever the ginseng plants produced 0.03 to 0.09 ppd ethylene gas when the rate of application were increased 3 and 4 times, respectively. On the other hand the soybean treated with the recommended amount of 2i-D produced ethylene gas of 10-20 times higher compared with ginseng plants and died. Photosynthesis ability of the ginseng leaf was significantly decreased by 2, 4.D fouler application but it was recovered 4 weeks after 2, 4-D fouler treatment. The herbicide 2, 4-D was appreciated to 2, 3 and 4 years old ginseng plants as fouler spray with the rates of 0.5, 1.0, 1.5 and 2.0 times of the recommended dosage to define the effects of 2, 4-D on the plant growth and root yield of the ginseng, There were no significant differences in the leaf and stem growth between untreated and 2, 4-D treated plant. Berry maturing of 3 and 4 year old ginseng was not influenced by 2, 4-D. The root weight of 4 years old ginseng plant was not reduced b). application of 2, 4-D concentrated 2 times of the recommended dosage. Application time of the herbicide 2, 4-D had no effects on the leaf or stem growth of 2, 3 and 4 year old year old ginseng plants. When the ginseng seedling was treated with 2, 4-D, detrimental phenomena as stem bending and deceleration of seedling leaf margin occurred, but stem bending was recovere d in a few day.

• 콘크리트학회논문집
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• 제24권6호
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• pp.633-641
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• 2012

이 논문에서는 비탄성 시간이력해석을 통해 보-기둥 접합부 비탄성 전단거동이 구조물 거동에 미치는 영향을 알아보기 위해 지반조건 $S_B$ 내진설계범주 C에 대해서 5층 철근콘크리트 보통모멘트골조를 KBC2009에 맞게 구조설계 하였다. 보 및 기둥 부재의 휨모멘트-곡률 관계는 fiber model로 확인하였으며 보-기둥 접합부 모멘트-회전각 관계는 simple and unified joint shear behavior model과 보-기둥 접합부 모멘트 평형관계를 이용하여 확인하였다. 이력거동은 IDARC 프로그램의 three-parameter model을 활용하여 나타내었다. 2400년 재현주기 수준의 최대지반가속도에 대한 비탄성 시간이력해석 결과 비탄성 보-기둥 접합부를 고려하는 경우 최대밑면전단력은 감소하나 최대지붕층변위, 최대층간변위는 차이가 없었으며 발생한 최대층간변위도 KBC2009의 허용층간변위를 만족하여 구조설계 과정에서 보-기둥 접합부의 비탄성 전단거동을 고려하지 않아도 문제가 없을 것으로 판단된다.

• Journal of Ginseng Research
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• 제14권2호
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• pp.291-296
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• 1990

Various rates of 2,4-D were sprayed on 2 and 3 year old ginseng plants as foliar spray to define the critical concentration. No apparent plant injury was noticable for those ginseng plants when application concentration of 2,4-D doubled the recommended dosage (70 ml/10a). Neither abnormal foliar change occurred nor any inhibition in leaf and stem growth was resulted for the plants treated with 2,4-D concentrated two times of the recommended dosage. When the rates of 2,4-D application were increased greater than this level, injury ratings increased linearly with the rates of 2,4-D application and plant you was inhibited. Ethylene gas was not produced from the ginseng plant treated with 2 times concentrated 2,4-D, however the ginseng plants produced 0.03 to 0.09 ppm ethylene gas when the rate of application were increased 3 and 4 times, respectively. On the other hand the soybean treated with the recommended amount of 21-D produced ethylene gas of 10-20 times higher compared with ginseng plants and died. Photosynthesis ability of the ginseng leaf was significantly decreased by 2,4-D foliar application but it was recovered 4 weeks after 2,4-D foliar treatment. The herbicide 2,4-D was applicated to 2,3 and 4 years old ginseng plants as foliar spray with the rates of 0.5, 1.0, 1.5 and 2.0 times of the recommended dosage to define the effects of 2,4-D on the plant growth and root yield of the ginseng. There were no significant differences in the leaf and stem growth between untreated and 2,4-D treated plant. Berry maturing of 3 and 4 year old ginseng was not influenced by 2,4-D. The root weight of 4 years old ginseng plant was not reduced by application of 2,4-D concenrated 2 times of the recommended dosage, Application time of the herbicide 2,4-D had no effects on the leaf or stem growth of 2,3 and 4 year old year old ginseng plants. When the ginseng seedling was treated with 2,4-D, detrimental phenomena as stem bending and docoration of seedling leaf margin occurred, but stem bending was recovered in a few day s. Keywords Panax ginseng C.A. Meyer, 2,4-D , herbicide.

• 한국작물학회지
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• 제34권4호
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• pp.422-427
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• 1989

제초제 2, 4-D의 처리가 인삼의 생육 및 근수량에 미치는 영향을 구명하기 위하여 2, 4-D 제초제량 (유제 :70ml/100$\ell$/10a, 수화제 : 250g/100$\ell$/10a)의 0.5, 1.0, 2.0 배액을 2년, 3년 및 4년생 인삼에 대하여 출아후 40일에 각각 엽면처리아여 경엽의 상육과 장과의 착생 및 근수량의 변이를 조사하고 무처리대조구와 비교 분석하였던 바 그 결과를 요약하면 다음과 같다. 1. 2년, 3년 및 4년생 인삼에 2, 4-D를 일반제초약량의 2배로 경엽산포하여도 지상부의 전체적인 생육상은 무처리구와 차이가 없었으며 특별한 약해현장도 나타나지 않았다. 2. 2년, 3년 및 4년생 인삼에 있어 무처리구와 2, 4-D 유제 및 수화제 처리 농도간에 엽장, 여폭, 경장 및 경직경 등 유의차가 인정되지 않았다. 3. 3년생 및 4년생 인삼의 장과착생수는 2, 4-D 유제를 일반체초제의 2배로 처리한 구에서도 무처리구와의 유의차는 인정되지 않았으며 외관상의 형태에도 전혀 이상이 없었다. 4. 4년생 인삼에 있어 무처리구와 2, 4-D 유제 및 수화제의 처리농도간에 근장, 근식경, 지근수 및 근주의 차이는 인정되지 않았다. 5. 묘삼에 2, 4-D 유제 및 수화제의 일반제초제량을 경엽처리할 경우 줄기가 연화되어 구부러졌으며 특히 수화제 처리시는 잎의 끝이 백화고사되는 약해현장을 나타내었고 구부러진 줄기는 2~3일 후 다시 상향으로 회복되기는 하였으나 이상신장된 결과를 보였다.

• 콘크리트학회논문집
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• 제14권6호
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• pp.892-899
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• 2002

콘크리트 휨 부재의 내하능력을 개선하는 방법들 중에서, 최근에 와서, 기존의 철근콘크리트 부재에서 사용하는 철근을 대신하여 섬유보강폴리머(FRP) 복합재료 층으로 보강한 콘크리트 부재에 관한 연구가 이루어지고 있다. 본 연구는 휨을 받는 원형단면 FRP 콘크리트 부재의 거동을 예측하기 위한 해석모델에 중점을 두고 있다. FRP층과 내부에 충진된 콘크리트로 이루어진 부재의 응력 및 변형을 예측하기 위하여 층분할 단면해석 모델이 제시되었다. 콘크리트의 압축거동이 횡방향 팽창에 의존한다는 가정과 다축 압축 응력상태의 구성관계에 기초하여 FRP 층으로 둘러 쌓인 콘크리트의 응력변형률 관계를 정식화하였다. 고전적 적층이론에서, FRP 층의 거동은 2차원 적층의 면내거동의 응력-변형률 관계에 기초한 등 가직교재료특성에 기초하여 정식화하였다. 소개된 해석모델의 검증을 위하여 원형단면 FRP 콘크리트 휨 부재의 4점 실험과 비교한 결과, 본 모델은 부재의 모멘트-곡률 관계, 단면에서의 축방향 변형률뿐만 아니라 횡방향 변형률, 그리고 FRP 층으로 인한 콘크리트의 구속효과의 증진에 관한 거동 특성들을 잘 예측해 주었다.

• 대한기계학회논문집A
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• 제37권7호
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• pp.841-849
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• 2013

본 연구에서는, 핵연료 지지격자 딤플 굴곡부에 성형결함을 줄이고자, 1차 스탬핑 금형이 추가된 2-step 스탬핑모델을 제시한다. 우선 순수굽힘 변형률과의 비교로, 딤플 굴곡부 변형률의 특성을 조사한다. 이어 2 차원 1-step 기준 스탬핑 유한요소모델을 정하고 이에 상응하는 최대변형률을 구한다. 1 차 스탬핑 금형의 설계변수들을 각각 변화시켜 변형률에 대한 목적함수를 구하고, 반응표면법을 이용해 1차 스탬핑 금형의 최적 변수값을 선정한다. 다음으로 이를 3차원 모델에 적용해 2-step 스탬핑 모델의 향상된 성형성을 확인한다.