• Structural Engineering and Mechanics
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• 제89권4호
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• pp.411-420
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• 2024

The purpose of this research was to investigate the cyclic behavior of the D-shaped dampers (DSD). Similarly, at first, the numerical model was calibrated using the experimental sample. Then, parametric studies were conducted in order to investigate the effect of the radius and thickness of the damper on energy dissipation, effective and elastic stiffness, ultimate strength, and equivalent viscous damping ratio (EVDR). An analytical equation for the elastic stiffness of the DSD was also proposed, which showed good agreement with experimental results. Additionally, approximate equations were introduced to calculate the elastic and effective stiffness, ultimate strength, and energy dissipation. These equations were presented according to the curve fitting technique and based on numerical results. The results indicated that reducing the radius and increasing the thickness led to increased energy dissipation, effective stiffness, and ultimate strength of the damper. On the other hand, increasing the radius and thickness resulted in an increase in EVDR. Moreover, the ratio of effective stiffness to elastic stiffness also played a crucial role in increasing the EVDR. The thickness and radius of the damper were evaluated as the most effective dimensions for reducing energy dissipation and EVDR.

• 식물병연구
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• 제20권2호
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• pp.95-100
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• 2014

본 연구는 에스필과 수산화동의 혼용에 의한 오이, 토마토, 고추의 흰가루병에 대한 방제 효과를 구명하고자 수행하였다. 오이 흰가루병에서 에스필과 수산화동의 혼용 처리는 4 : 1 혼용처리구에서 발병엽률 18.9%와 방제효과 69.9%, 8 : 1 혼용 처리구에서 발병엽률 18.1%와 방제효과 71.1%로 가장 효과적이었다. 토마토 흰가루병에서 에스필과 수산화동의 혼용 처리는 4 : 1 혼용 처리구에서 발병엽률 12.4%와 방제효과 85.3%, 8 : 1 혼용 처리구에서 발병엽률 14.3%와 방제효과 83.0%로 가장 효과적이었다. 고추 흰가루병에서 에스필과 수산화동의 혼용 처리는 4 : 1 혼용 처리구에서 발병엽률 17.7%와 방제효과 76.4%로 가장 효과적이었다. 이상의 결과를 종합할 때 에스필과 수산화동 혼용처리에 의한 오이와 토마토 흰가루병에 대한 방제 효과는 4 : 1 혹은 8 : 1 혼용 처리가 가장 효과적이고, 고추 흰가루병에서는 4 : 1 혼용 처리가 가장 효과적인 방제 방법으로 구명되었다.

• 한국물환경학회지
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• 제23권5호
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• pp.650-658
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• 2007

The Universal Soil Loss Equation (USLE) has been used in over 100 countries to estimate potential long-term soil erosion from the field. However, the USLE estimated soil erosion cannot be used to estimate the sediment delivered to the stream networks. For an effective erosion control, it is necessary to compute sediment delivery ratio (SDR) for watershed and sediment yield at watershed outlet. Thus, the Sediment Assessment Tool for Effective Erosion Control (SATEEC) was developed to compute the sediment yield at any point in watershed. In this study, the SATEEC was applied to the Sudong watershed, Chuncheon Gangwon to compare the sediment yield using area-based sediment delivery ratio (SDRA) and slope-based sediment delivery ratio (SDRS) at watershed outlet. The sediment yield using the SDRA by Vanoni, SYA and the sediment yield using the SDRS by Willams and Berndt, SYS were compared for the same sized watersheds. The 19 subwatersheds was 2.19 ha in size, the soil loss and sediment yield were estimated for each subwatershed. Average slope of main stream was about 0.86~3.17%. Soil loss and sediment yield using SDRA and SDRS were distinguished depending on topography, especially in steep and flat areas. The SDRA for all subwatersheds was 0.762, however the SDRS were estimated in the range of 0.553~0.999. The difference between SYA and SYS was -79.74~27.45%. Thus site specific slope-based SDR is more effective in sediment yield estimation than area-based SDR. However it is recommended that watershed characteristic need to be considered in estimating yield behaviors.

• 콘크리트학회논문집
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• 제28권3호
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• pp.267-278
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• 2016

이 논문에서는 저자가 제안한 전단경간비가 3 이하인 철근콘크리트 보의 부정정 스트럿-타이 모델 및 하중분배율을 이용하여 파괴실험이 수행된 335개 철근콘크리트 보의 극한강도를 평가하였다. 또한 이들 보의 극한강도를 실험 전단강도모델에 기초한 설계기준, 이론 전단강도모델에 기초한 설계기준, 그리고 현행 스트럿-타이 모델 설계기준 등으로 평가하였다. 각 설계기준 및 이 연구의 방법에 의한 극한강도 평가결과를 비교분석하여 저자가 제안한 부정정 스트럿-타이 모델 및 하중분배율의 타당성을 검증하였다.

• The Journal of Korean Physical Therapy
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• 제13권1호
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• pp.161-174
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• 2001

The purpose of this study was to reduce the spasticity of plantarflexion. the subjects of this study were 30 hemiplegic patients with stroke who received of physical therapy in JinJu o o hospital from May to July 2000. the subjects were divided into three groups(FES groups 10, FES + tilt table-wedge board standing groups 10, & tilt table-wedge board standing groups 10). The result were as follow 1. FES therapy was a effective method to reduce the spasticity of plantarflexor. there was a significant difference in modified Ashworth scale(p<.01). there was a significant difference in weight bearing ratio between nonparetic and paretic side(p<.01). 2. Tilt table-wedge board standing therapy was a effective method to reduce the spasticity of plantarflexor to a degree but there was a no significant difference in modified Ashworth scale(p<.05). there was a significant difference in weight bearing ratio between nonparetic and paretic side(p<.01). 3. Tilt table-wedge board standing therapy + FES therapy was a effective method to reduce the spasticity of plantarflexor. there was a significant difference in modified Ashworth scale(p<.01). there was a significant difference in weight bearing ratio between nonparetic and paretic side(p<.01) 4. There was a significant difference in weight bearing ratio between nonparetic and paretic side according to the grade spasticity(p<.01). 5. For normal persons vs hemiplegic patients, there was a significant different in weight bearing ratio between nonparetic and paretic side(experimental subjects 1 p<.01, experimental subjects 2 p<.01, control subjects p<.05).

• Macromolecular Research
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• 제17권10호
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• pp.797-806
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• 2009

The mechanical and thermal behaviors of polyamide-6/clay nanocomposites were studied using the continuum-based, micromechanical models such as Mori-Tanaka, Halpin-Tsai and shear lag. Mechanic-based model prediction provides a better understanding regarding the dependence of the nanocomposites' reinforcement efficiency on conventional filler structural parameters such as filler aspect ratio ($\alpha$), filler orientation (S), filler weight fraction (${\Psi}_f$), and filler/matrix stiffness ratio ($E_f/E_m$). For an intercalated and exfoliated nanocomposite, an effective, filler-based, micromechanical model that includes effective filler structural parameters, the number of platelets per stack (n) and the silicate inter-layer spacing ($d_{001}$), is proposed to describe the mesoscopic intercalated filler and the nanoscopic exfoliated filler. The proposed model nicely captures the experimental modulus behaviors for both intercalated and exfoliated nanocomposites. In addition, the model prediction of the heat distortion temperature is examined for nanocomposites with different filler aspect ratio. The predicted heat distortion temperature appears to be reasonable compared to the heat distortion temperature obtained by experimental tests. Based on both the experimental results and model prediction, the reinforcement efficiency and heat resistance of the polyamide-6/clay nanocomposites definitely depend on both conventional (${\alpha},\;S,\;{\Psi}_f,\;E_f/E_m$) and effective (n, $d_{001}$) filler structural parameters.

• 한국환경복원기술학회지
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• 제9권6호
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• pp.38-51
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• 2006

This study was carried out to improve rehabilitation effect by hydro-seeding methods on denuded slopes. Lespedeza cyrtobotrya, Indigofera pseudotinctoria, Arudinella hirta, Poa pratensis, and Lolium perenne were used in this study. The results of the germination and growth characteristics by seed coating, slope control and soil mulching treatments are summarized here. Seed coating of those plants had an effect on germination ratio, germination force, $LD_{50}$, and seedling growth of stem, leaf and root. The seed coating effect was highest for I. pseudotinctoria while the seedling growth was best for L. cyrtobotrya. Vermiculite+Talcum was the best coating material for germination and seedling growth of the plants. As the slopes were steeper, germination ratio was lower and seedling growth of stem and root decreased. Lots of seeds and soils were swept away when the slope was steep. Soil mulching was effective for germination, seedling growth of stem and root, and soil stabilization. It was more effective when the slope was steeper. Coir net was the most effective soil mulching material n this study.

• 대한기계학회논문집
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• 제10권2호
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• pp.208-214
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• 1986

본 연구에서는 균열 닫힘에 관한 연구의 일환으로 5083-O 알루미늄합금을 사용하고 소규모강복조건하에서 일정진폭하중피로시험을 시행하여 이 재료의 피로균열 진전속도와 균열닫힘에 관하여 검토하였다.

• Structural Engineering and Mechanics
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• 제45권6호
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• pp.741-758
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• 2013

In this study, inelastic displacement ratios are investigated for existing systems with known lateral strength considering soil structure interaction. For this purpose, SDOF systems for period range of 0.1-3.0 s with different hysteretic behaviors are considered for a number of 18 earthquake motions recorded on soft soil. The effect of stiffness degradation on inelastic displacement ratios is investigated. The Modified Clough model is used to represent structures that exhibit significant stiffness degradation when subjected to reverse cyclic loading and the elastoplastic model is used to represent non-degrading structures. Soil structure interaction analyses are conducted by means of equivalent fixed base model effective period, effective damping and effective ductility values differing from fixed-base case. For inelastic time history analyses, Newmark method for step by step time integration was adapted in an in-house computer program. A new equation is proposed for inelastic displacement ratio of system with SSI with elastoplastic or degrading behavior as a function of structural period ($\tilde{T}$), strength reduction factor (R) and period lengthening ratio ($\tilde{T}$/T). The proposed equation for $\tilde{C}_R$ which takes the soil-structure interaction into account should be useful in estimating the inelastic deformation of existing structures with known lateral strength.

• Earthquakes and Structures
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• 제7권3호
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• pp.295-315
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• 2014

This paper presents the results of an analytical study on seismic reliability of viscoelastically damped frame systems in comparison with that of conventional moment resisting frame systems. In order to exhibit the reliability of the frame systems with viscoelastic dampers, seismic reliability analyses were carried out for steel framed buildings, 5 and 12 storeys in height, designed as: (a) Case 1: Conventional moment resisting frame, (b) Case 2: Frame with viscoelastic dampers providing supplemental effective damping ratio of 10%, and (c) Case 3: Frame with viscoelastic dampers providing supplemental effective damping ratio of 20%. Nonlinear time history analyses were utilized to develop seismic fragility curves whilst monitoring various performance objectives. To obtain robust estimators of the seismic reliability, a database including 15 natural earthquake ground motion records with markedly different characteristics was employed in the fragility analysis. The results indicate that depending upon the supplemental effective damping ratio, frames designed with viscoelastic dampers have considerably lower annual probability of exceedance of performance limit states for structural components, showing up to a five-fold reduction in comparison to conventionally designed moment resisting frame system.