• Advances in concrete construction
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• 제13권1호
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• pp.45-69
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• 2022

This paper investigates the shear behavior of reinforced concrete haunched beams (RCHBs) without stirrups. The research objective is to study the effectiveness of the ideal steel fiber (SF) ratio, which is used to resist shear strength, besides the influence of main steel reinforcement, compressive strength, and inclination angles of the haunched beam. The modeling and analysis were carried out by Finite Element Method (FE) based on a software package, called Atena-GiD 3D. The program of this study comprises two-part. One of them consists of nine results of experimental SF RCHBs which are used to identify the accuracy of FE models. The other part comprises 81 FE models, which are divided into three groups. Each group differed from another group by the area of main steel reinforcement (A_s) which are 226, 339, and 509 mm². The other parameters which are considered in each group in the same quantities to study the effectiveness of them, were steel fiber volumetric ratios (0.0, 0.5, and 1.0)%, compressive strength (20.0, 40.0, 60.0) MPa, and the inclination angle of haunched beam (0.0°, 10.0°, and 15.0°). Moreover, the parametric analysis was carried out on SF RCHBs to clarify the effectiveness of each parameter on the mechanical behavior of SF RCHBs. The results show that the correlation coefficient (R²) between shear load capacities of FE proposed models and shear load capacities of experimental SF RCHBs is 0.9793, while the effective inclination angle of the haunched beam is 10° which contributes to resisting shear strength, besides the ideal ratio of steel fibers is 1% when the compressive strength of SF RCHBs is more than 20 MPa.

• Advances in concrete construction
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• 제14권5호
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• pp.299-307
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• 2022

Cement-based matrixes have low tensile strength and negligible ductility. Adding fibres to these matrixes will improve their mechanical properties and make these composites suitable for structural applications. Post-cracking tensile strength of steel fibers-reinforced cementitious composite materials is directly related to the number of transverse fibers passing through the crack width and the pulling-out behavior of each of the fibers. Therefore, the exact recognition of the pullout behavior of single fibers is necessary to understand the uniaxial tensile and bending behavior of steel fiber-reinforced concrete. In this paper, an experimental study has been carried out on the pullout behavior of 3D (steel fibers with totally two hooks at both ends), 4D (steel fibers with a total of four hooks at both ends), and 5D (steel fibers with totally six hooks at both ends) in which the fibers have been located either perpendicular to the crack width or in an inclined manner. The pullout behavior of the mentioned steel fibers at an inclination angle of 0, 15, 30, 45, and 60 degrees and with embedded lengths of 10, 15, 20, 25, and 30 millimetres is studied in order to explore the simultaneous effect of the inclination angle of the fibers relative to the alongside loading and the embedded length of fibers on the pullout response in each case, including the maximal pullout force, the slip of the maximum point of pullout force, pullout energy, fiber rupture, and concrete matrix spalling. The results showed that the maximum pullout energy in 3D, 4D, and 5D steel fibers with different embedded lengths occurs at 0 to 30° inclination angles. In 5D fibers, maximum pullout energy occurs at a 30° angle with a 25 mm embedded length.

• 신재생에너지
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• 제20권2호
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• pp.35-43
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• 2024

A pump turbine is a technically matured option for energy production and storage systems. At the off-design operating range, the pump turbine succumbed to flow instabilities, which correlated with the pump turbine geometry. A low specific speed pump turbine was designed and modified according to the impeller blade angle. Reynolds-Average Navier-Stokes is carried out with a shear stress transport turbulence model to evaluate the detailed flow characteristics in the pump turbine. The impeller blade inlet angle (𝛽₁) and outlet angle (𝛽₂) are used to evaluate hydraulic loss in the pump turbine. When 𝛽₁ changed from low to high value, the maximum efficiency is increased by 4.75% in turbine mode. The S-Curve inclination is reduced by 8% and 42% for changes in 𝛽₁ and 𝛽₂ from low to high values, respectively. At α = 21°, the shock loss coefficient (𝜁_s) is reduced by 16% and 19% with increases of 𝛽₁ and 𝛽₂ from low to high values, respectively. When 𝛽₁ and 𝛽₂ values increased from low to high, the impeller friction coefficient (𝜁_f) increased and decreased by 20% and 8%, respectively. Hence, the high 𝛽₂ effectively reduced the loss coefficient and S-Curve inclination.

• 한국생산제조학회지
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• 제8권1호
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• pp.21-27
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• 1999

In this study, stress intensity factors KI, KII, KIII are existing at the same time to a hollow cylindrical bar of three dimension inclination crack. In order to investigate by experimentally the effect of the inclination angle $\psi$ of crack, artificial inclination cracks in the circumferential direction are put in the surface of a hollow cylindrical bar made by the epoxy-resin. Experimentally, stress analysis methods of stress intensity factors were proposed. But, suitable method are the caustic method and the photoelastic stress freezing method. The mixed mode of KI, and KII, were determined by the photoelastic method of the classical approach method and the FORTRAN language program of the used smallest square method.

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2018년도 공동국제학술발표회
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• pp.145-145
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• 2018

• 대한기계학회논문집B
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• 제36권6호
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• pp.571-578
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• 2012

본 연구에서는 등온 가열 조건 하에서 플레이트-휜을 가지는 자연대류 히트싱크의 열성능을 측정하기 위한 실험적 연구를 수행하였다. 실험은 자연대류 히트싱크의 열입력량, 휜 간격 및 높이를 변화시키면서 수행하였다. 특히, 경사각 변화가 자연대류 히트싱크의 열성능에 미치는 영향에 대해 연구하였다. 기존 연구자들이 제시한 열저항 상관식과 본 연구에서 수행한 실험결과의 비교를 통해 실험결과의 타당성을 검증하였다. 또한 실험결과를 바탕으로 자연대류 히트싱크의 열입력량, 휜 간격 및 높이, 그리고 경사각에 대하여 기존 연구자들이 제시한 상관식의 적용가능 범위를 평가하였다.

• 한국운동역학회지
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• 제21권5호
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• pp.653-660
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• 2011

The purpose of this study was to compare selected kinematic variables between male medalists and a Korean male javelin thrower at the IAAF World Championships, Daegu 2011. The three medalists and one Korean javelin thrower that participated in the Championships were videotaped using three high-speed cameras (300 frames/s, EX-F1 Exilim, Casio, Japan). The results showed that the release and attitude angles of the Korean male javelin thrower (KMJT) were greater than that of the medalists, whereas the attack angle of the KMJT was smaller than that of the medalists. This study also found that the KMJT clearly had a lower release height than the medalists. As a possible adaptation of his physique to the skill, the KMJT used a small trunk inclination angle and produced greater inclination angles at his upper extremities. These results may be linked to an increase in the release angle of the KMJT. There were some difference between the KMJT and the medalists in terms of the length and duration of the delivery phase. In harmony with the shorter length of the delivery phase, its duration was shorter for the KMJT in comparison to the medalists. Because the delivery stride is considered to be a primary generator of endpoint speed, this decrease in the delivery phase time would decrease the javelin velocity at release. The amount of time taken in the delivery phase may be a critical factor to enhance a javelin thrower's performance. Thus, rhythmic movement training specifically designed for the KMJT will help him attain an optimal throwing position.

• 한국방재학회 논문집
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• 제8권1호
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• pp.89-96
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• 2008

본 연구는 되 메움 된 굴착 양측 벽이 비대칭으로 경사진 경우에 대하여 벽체간의 폭, 벽면경사각, 상대밀도, 벽면마찰각의 크기를 변화시켜 Kellogg의 이론과 이를 보완한 수정식으로 토압을 산정하고 또한, 벽면마찰반력을 고려한 토압 식을 제안하여 상호간 거동을 구명하였다. 이들 결과로부터 구한 지중 토압을 검증하기 위하여 총 62종류의 모형실험을 수행한 결과를 이론식에 의한 거동과 비교, 검토하였다. 본 연구결과 양측 벽이 비대칭으로 경사진 경우, 되 메움 토압에 가장 큰 영향을 미치는 요소는 벽체경사각의 크기였으며, 또한 되 메움 공간이 협소할수록 그리고 수평면과 이루는 벽체의 경사각이 클수록 벽 마찰의 영향이 크게 나타났다. 한편, 실측토압과 가장 근소한 차이를 나타낸 것은 벽면마찰반력을 고려한 제안 식으로 구한 경우였으며 또한, 벽면사이의 폭이 좁은 경우 아칭효과가 크게 나타나 실측토압 및 제안된 이론토압모두 지중 토압과 가장 근소한 차이를 나타내었다.

• The Journal of Korean Physical Therapy
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• 제18권1호
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• pp.95-106
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• 2006

Purpose: The aim of this study was to investigate the kinematics of young adults during ramp climbing at different inclinations. Methods: Twenty-three subjects ascended and descended four steps at four different inclinations(level, $8^{\circ},\;16^{\circ},\;24^{\circ}$). Temporal-spatial parameters were measured by GaitRite system(standard mat). Groups difference was analysed with on-way ANOVA and Student-Newman-Keuls test. Results: The different kinematics of ramp ascent and descent were analysed and compared to level walking patterns. In ascending ramps, step length and stride length decreased with $24^{\circ}$ inclination (p<.000). Stance duration increased with $24^{\circ}$, but swing duration decreased with $24^{\circ}$ inclination (p<.000). Step time and velocity decreased with $16^{\circ}C,\;24^{\circ}$ inclination (p<.000). Cadence decreased with all inclination($8^{\circ},\;16^{\circ},\;24^{\circ}$)(p<.000). In descending ramps, step length and stride length, velocity decreased with all inclination($8^{\circ},\;16^{\circ},\;-24^{\circ}$)(p<.000). Stance duration increased with all inclination($8^{\circ},\;-16^{\circ},\;-24^{\circ}$) and swing duration decreased with all inclination($-8^{\circ},\;-16^{\circ},\;-24^{\circ}$)(p<.000). But Step time was not differentiated with different inclinations. Cadence decreased with only. $8^{\circ}$ inclination(p<.05). Conclusion: These results suggest that there is a certain inclination angle or angular range where subjects do switch between level walking and ramp walking gait pattern. This shows their motor control strategy between level and ramp walking. Further studies are necessary to confirm and detect the ascent and descent ramp gait patterns.

• 대한치과교정학회지
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• 제17권1호
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• pp.63-72
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• 1987

This is to investigate the difference between craniofacial correlation of Angle's class III malocclusion and that of normal occlusion. For this investigation, 28 adult males and famales, who have class III malocclusion, and 35 adult males and 46 adult famals., who have normal occlusion were selected to measure actual dimension of cranial base and to investigate ratio of various parts of maxillofacial skeleton against cranial base. Class III malocclusion were, also , classified based on SNA and SNB angle in normal range. Results were as follows. 1. In class III malocclusion, actual dimension of cranial base were appeared to be less than normal occlusion in both sex. 2. In class III malocclusion, values were less than normal occlusion in BN/ptm-A in both sex, but had no significance between two. 3. In class III malocclusion, ramal inclination, mandible inclination, BN/Go-Pog, lower genial angle were appeared to be greater. Thus, characteristic mandibular protrusive appearance of class III malocclusion was due to relative ratio and morphologic characteristic of mandibular body dimension against cranial base. 4. In class III malocclusion, upper incisors were labially tilted and lower incisors were lingually tilted compared to normal occlusion. 5. In typing of class III malocclusion, the most common type was found to be one which maxillas were in normal range, while mandibles were in protrusive tendency.