• Earthquakes and Structures
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• v.17 no.5
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• pp.435-445
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• 2019

The collapses of curved bridges are mainly caused by the damaged columns, subjected to the combined loadings of axial load, shear force, flexural moment and torsional moment, under earthquakes. However, these combined loadings have not been fully investigated. This paper firstly investigated the mechanical characteristics of the bending-torsion coupling effects, based on the seismic response spectrum analysis of 24 curved bridge models. And then 9 reinforced concrete (RC) and circular column specimens were tested, by changing the bending-tortion ratio (M/T), axial compression ratio, longitudinal reinforcement ratio and spiral reinforcement ratio, respectively. The results show that the bending-torsion coupling effects of piers are more significant, along with the decrease of girder curvature and the increase of pier height. The M/T ratio ranges from 6 to 15 for common cases, and influences the crack distribution, plastic zone and hysteretic curve of piers. And these seismic characteristics are also influenced by the compression ratio, longitudinal reinforcement ratio and spiral reinforcement ratios of piers.

• Proceedings of the ESK Conference
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• 1992.10a
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• pp.46-53
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• 1992

Finger movements in the sagittal plane mainly consist of flexion and extension about the metacarpophalangeal(MCP) and proximal interphalangeal(PIP) joints. A kinematic finger model was developed with the assumption of constant tendon moment arms. Equations of static equilibrium were derived for the finger model using the principle of virtual work. Equations of static equilibrium for the finger model were indeterminate since only three equations were available for five unknown variables(forces). The number of variables was reduced based on information on muscular activities in finger movements. Then the amounts of forces which muscles exerted to maintain static equilibrium against external loads were computed from the equilibrium equations. The muscular forces were expressed mathematically as functions of finger positions, tendon moment arms, lengths of phalanges, and the magnitude and direction of external load. The external finger strength were computed using the equations of muscular forces and anatomical data. Experiments were performed to measure finger strengths. Measurements were taken in combinations of four finger positions and four directions of force exertions. Validation of the finger models and of procedure to estimate finger strengths was done by comparing the results of computations and experiments. Significang differences were found between the predicted and measured finger strengths. However, the trends of finger strengths with respect to finger positions were similar inboth the predicted and measured. These findings indicate that the finger model and the procedure to predict finger strengths were correctly developed.

• Tribology and Lubricants
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• v.14 no.2
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• pp.26-34
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• 1998

This paper presents a high-speed performance analysis of ball bearings with ceramic balls under thrust loads. The sliding velocity profiles between a ball and raceways were obtained by the 3-D quasi-dynamic equations of motion including both centrifugal force and gyroscopic moment derived by vector matrix algebra. The friction at the contact areas was obtained by the Bair-Winer's non-Newtonian rheological model and the Hamrock-Dowson's central film thickness in EHL analysis. The nonlinear equations were solved by the Newton-Raphson method and the underrelaxation iterative method. The friction torques and ball behaviors with various loads, ball materials, and contact angles were predicted by this model. It was shown that the friction torque was sensitive to thrust load and contact angle, and that the friction torque and the pitch angle of the bearing with ceramic balls are smaller than those of the bearing with steel balls.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.3
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• pp.315-323
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• 2016

This paper deals with experimental investigation of active flow control via synthetic jets using an unmanned combat air vehicle (UCAV) planform. Fourteen arrays of synthetic jets, mounted along both leading edges, were fully or partially activated to increase aerodynamic efficiency and reduce pitch-up moment. The measurements were carried out using a six-component external balance, a pressure scanner, and tuft flow visualization. It was observed that aerodynamic efficiency (L/D) and pitching moment were clearly affected by the location of jets. In particular, inboard and outboard actuation could effectively increase L/D. Moreover, inboard actuation showed a reduction in the pitch-up, even more than that generated by the full actuation. These results suggest that inboard actuation not only effectively increases L/D but also reduces the pitch-up using only a few actuators.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.564-568
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• 2006

Smooth picture module is operated by vibration to tilt the light from the DMD (digital micro mirror device) of DLP projection TV, which makes the screen of the TV smoother and DMD chip cost lower. To satisfy the vibration characteristics of smooth picture module, it is designed by optimizing moment of inertia, spring constant and damping coefficient, using structural and fluid dynamic simulation that showed a good agreement with experimental data. To reduce the material cost and moment of inertia, engineering plastic is used and the reliability is estimated. A VCM (voice coil motor) type actuator for smooth picture has to satisfy performance requirements such as higher driving force, lower power consumption, and lower cost. The initial design and optimization for VCM was performed using FE analysis. It allowed us to optimize the design of magnetic circuit of the proposed actuator to obtain higher force while maintaining a lower cost.

• Steel and Composite Structures
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• v.29 no.6
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• pp.771-783
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• 2018

In this paper, topology optimization (TO) is applied to find a new configuration for the perforated steel plate shear wall (PSPSW) based on the maximization of reaction forces as the objective function. An infill steel plate is introduced based on an experimental model for TO. The TO is conducted using the sensitivity analysis, the method of moving asymptotes and SIMP method. TO is done using a nonlinear analysis (geometry and material) considering the buckling. The final area of the optimized plate is equal to 50% of the infill plate. Three plate thicknesses and three length-to-height ratios are defined and their effects are investigated in the TO. It indicates the plate thickness has no significant impact on the optimization results. The nonlinear behavior of optimized plates under cyclic loading is studied and the strength, energy and fracture tendency of them are investigated. Also, four steel plates including infill plate, a plate with a central circle and two types of the multi-circle plate are introduced with equal plate volume for comparing with the results of the optimized plate.

• The korean journal of orthodontics
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• v.36 no.1 s.114
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• pp.30-44
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• 2006

This study was performed to investigate the location of the ideal bracket positioning plane in lingual orthodontics using the three-dimensional finite element method. Displacement of the anterior teeth were evaluated according to the vertical and the angular movements of the bracket positioning plane. To achieve the ideal movement of anterior teeth in the lingual central plane, the location of the force application point and the amount of the moment applied to the four incisors were evaluated. As the bracket positioning plane was moved parallel toward the incisal edge, uncontrolled tipping and extrusion of the maxillary and the mandibular incisors were increased. But lingual tipping of the crown was decreased in the maxillary and the mandibular canines. As the bracket positioning plane was inclined toward the incisal edge, lingual tipping was increased in the 6 anterior teeth and extrusion of incisors and intrusion of the canine was also increased. As the retraction hook of the canine bracket was elongated, lingual tipping and extrusion of the central incisor and mesial movement and extrusion of the lateral incisor were increased. In the canine, mesial and labial movements of the crown were increased. When the moment was applied to the 4 incisors of the maxillary and the mandibular arch in the lingual central plane, 280 gf-mm in the maxillary central incisor, 500 gf-mm in the maxillary lateral incisor, 170 gf-mm in the mandibular central incisor and 370 gf-mm in the mandibular lateral incisor produced bodily movement of the individual tooth.

• Journal of the Society of Naval Architects of Korea
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• v.37 no.1
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• pp.1-9
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• 2000

The roll damping characteristics of the three models of a 3 ton class fishing vessel such as the bare hull, hull with bilge keels, and hull with bilge keels and a central wing are investigated by the free roll tests in calm water in a towing tank with the variations of the forward speed, initial angle and OG. The experimental results are compared with the numerical results of mathematical modellings by the energy method for these three models and the energy dissipation patterns are also compared.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.1
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• pp.1-7
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• 2016

The influence of boundary condition of the bodies with gas flows is one of the most important problems in high-altitude aerodynamics. In this paper presents the results of the calculation of aerodynamic characteristics of aerospace vehicle using Monte-Carlo method based on three different gas-surface interaction models - Maxwell model, Cercignani-Lampis-Lord (CLL) model and Lennard-Jones (LJ) potential. These models are very sensitive for force and moment coefficients of aerospace vehicle in the hypersonic free molecular flow. The models, method and results can be used for new generation aerospace vehicle design.

• Bulletin of the Korean Mathematical Society
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• v.47 no.6
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• pp.1139-1153
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• 2010

Let {$X_j,\;j\geq1$} be a strictly stationary $\phi$-mixing sequence of non-degenerate random variables with $EX_1$ = 0. In this paper, we establish a self-normalized weak invariance principle and a central limit theorem for the sequence {$X_j$} under the condition that L(x) := $EX_1^2I{|X_1|{\leq}x}$ is a slowly varying function at $\infty$, without any higher moment conditions.