• Earthquakes and Structures
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• v.27 no.4
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• pp.251-262
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• 2024

To improve the seismic behavior of composite column with high strength concrete-filled steel tubular in bridge engineering, four column specimens, including one specimen with vertical prestressing force and three specimens with tri-directional prestressing force, were conducted under low cyclic loading. Test parameters including axial compression ratio, degree of vertical prestressing and existence of prestressed steel strips were emphatically analyzed. Experimental results revealed that applying tri-directional prestressing force to column with high strength concrete-filled steel tubular produced more beneficial behavior in terms of ductility, energy-dissipation and self-centering capacity over that of specimens only with vertical prestress. Moreover, ultimate bearing capacity of composite column was improved with increase of degree of vertical prestress and external axial force, while ductility would be reduced. External axial force showed slight influence on the self-centering behavior. Finally, a calculation equation for predicting the shear capacity of the tri-directional prestressed composite column was proposed and the accuracy of the calculated results validated by experimental data.

• Journal of Sensor Science and Technology
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• v.25 no.1
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• pp.27-34
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• 2016

This paper describes the development of a rehabilitation robot that can provide wrist bending exercise to a severe stroke patient staying in a bed ward or at home. The developed rehabilitation robot has a three-axis force sensor which detects three directional force Fx, Fy, and Fz. The sensor measures a bending force (Fz) exerted on the wrist and the signal force (Fx and Fy) which can be used for the safety purpose. The robot was designed for severe stroke patients in bed, and the robot program was developed to perform a wrist bending rehabilitation exercise. In our tests including a nine-day experimental exercise, the developed force sensor-based robot operated effectively and safely.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.137.4-137
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• 2001

Omni-directional mobile robots have been employed popularly in several application areas. However, the optimal design has not been considered yet. This paper introduces an optimal design methodology for omni-directional mobile robots. Optimal design parameters such as the offset distance and the wheel radius are identified with respect to isotropy. Furthermore, the force transmission ratio and actuator sizing problem are treated. Conclusivel, three cases are compared minimum actuation, two active caster wheel, and three active caster wheel, we claim that the redundantly actuated mobile robot with three active caster wheel has the best performance.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.04a
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• pp.353-360
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• 2001

An analysis procedure of 2-dimensional bridge dynamics has been developed by using force-deformation model, which simulates the pier motion under biaxial bending due to the bi-directional input seismic excitations. A three-dimensional mechanical model is utilized, which can consider the other major phenomena such as pounding, rotation of the superstructure, abutment stiffness degradation, and motions of the foundation motions. The bi-directional dynamic behaviors of the bridge are then examined by investigating the relative displacements of each oscillator to the ground. It is found that the nonlinearity of the pier due to biaxial bending affects the pier motions, but the global bridge behaviors are greatly governed by the pounding phenomena and stiffness degradation of the abutment-backfill system. Especially, the relative displacement of the abutment system (A2) with movable supports to the ground is increased about 30% due to the abutment stiffness degradation.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.539-539
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• 2000

This paper shows how to implement force reflection for a needle insertion problem. The target is a needle spine biopsy simulator for tumor inspection by needle insertion. Simulated force is calculated from the relationship of volume graphic data and the orientation and Position of the needle, and it is generated using PHANTOM$^{TM}$. To generate realistic force reflection, the directional force of the needle has been generated by tissue model. The other rotational force is generated using a pivot to keep the needle in the initial inserted direction after puncturing the skin. Since the used haptic device has limitation for generating high stiffness and large damping, scale downed model and digital filter are used to stabilize the system.m.

• Journal of Drive and Control
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• v.17 no.2
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• pp.55-62
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• 2020

There are two types of IMV for MCV, the spool type and the poppet type. The spool type is used in the existing excavator MCV and easily meets large-capacity flow conditions, but has a flow force problem which affects the spool control. The poppet type stably blocks the flow and has excellent rapid response. However, the larger the capacity, the larger the diameter of the poppet needed, requiring a strong spring to withstand the oil pressure. In this study, a bi-directional three-stage IMV for MCV that can be used in medium and large hydraulic excavators was proposed. This is a poppet type, enabling bi-directional flow control and resolves the problem of proportional solenoid suction force limitation. To investigate the validity of the proposed valve, the system was mathematically modeled and the static and dynamic characteristics were investigated through the simulation using commercial software. It has been concluded that the reverse flow is possible in a regeneration circuit and that the proposed IMV can be used to perform various excavation modes.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.1071-1074
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• 1995

This paper proposes two directional bending actator using three link, two shape memory alloys(SMA) of coil-type springs and two guide wires. By the heating of two SMA springs sequentially, the bending and stretching of the actuator is possible. Bending angle, force and repeated bending motion of actuator were measured and characterized. The performance of the actuator has been characterized for the possible application for catheter.

• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.36-37
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• 2003

Three-dimensional numerical analysis of the flow around rectangular cylinders with various side ratios, D/H, from 0.2 to 2.0 is carried out for Reynolds number of 1000 by using multi-directional finite difference method in multi-grid. The predicted results are well compared with the experimental data. It is found that fluid dynamics characteristics alternate between high pressure mode. and low pressure mode of the base pressure for rectangular cylinder of D/H=0.2-0.6.

• Korean Journal of Applied Biomechanics
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• v.17 no.3
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• pp.125-131
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• 2007

The purpose of this study was to evaluate the difference in grip force and angular kinematic variables between elite (handicap${\leq}2$) and novice golfers. Three-dimensional motion analysis system with synchronized grip force measurement system was used. The participants consisted of two groups based on their playing ability: 10 elite golfers and 10 novice golfers. Each subject performed 5 putting strokes at the distance of 1, 3, and 5m with randomly selected order. During entire putting phase, elite group showed relatively constant grip force but novice group showed continuously increasing grip force pattern. There existed a clear difference in the trajectory of shoulder line between two groups. As for novice group the rotational center did not converge into one point, for elite group the rotational center converged into precise single point. And there was a clear difference pattern in anterior-posterior directional movement at shoulder between two groups. These difference might be helpful for improving consistent putting skills.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.10a
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• pp.144-149
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• 2001

The failure at the head section of rubble-mound detached breakwaters is more important than other failure modes. because this initial failures will occur the failure of the trunk section and lead to the instability of the structure. The three-dimensional failure modes are discussed using the experimental data with multi-directional waves considering the failure modes occurring around the head of the rubble-mound detached breakwater. The spacial characteristics of failure mode around the rubble-mound structures can be summarized as follows: 1) It was clarified that the failure modes at the round head of a detached breakwater are classified as failure by plunging breaker on the slope, failure by direct incident wave force and failure by scouring at the toe of the detached breakwater. 2) The failure mode was found in the lower wave height than the design wave by the breaker depth effects. It is clarified that the structure monitored was safely designed for the design wave but the failure was occurred by the reason of breaker waves and scouring processes at the toe 3) It was observed that scouring at the toe developed in the region where steady stream due to vorticity was generated and the spatial variation of scour at the toe of the round head was predominated by incident wave direction.