• Journal of Advanced Marine Engineering and Technology
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• v.39 no.5
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• pp.554-562
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• 2015

This paper describes an analysis of an architecture and control system of a firefighting cannon manipulator (FCM) composed of two joint axes and one water-shooting actuator. Because the orienting FCM motion is disturbed by the reaction force from water shooting, the water shooting force has been modeled for robust control. The dynamics model of the manipulator has been set up including the external force of water-shooting reaction on the manipulator. A PD Controller and Sliding Mode Controller have been designed and their performance been tested through simulation to track a desired trajectory under the disturbance of a water-shooting reaction. The simulation shows that the performance of the Sliding Mode Controller is better than that of the PD controller.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.790-794
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• 1995

Differential equations governing dynamic behavior of toroid-shaped ferro-magnetic material having a small gap of uniform width were derived incorporating Maxwell equations of electromagnetic induction relevent to the system and Newtonian equation of motion. Once the external uniform magnetic field was applied within the material through dc-circuit around the toroid, gap begin to change which lead to the abrupt variation of field in the material and gap according to the differential equations already derived. Characteristics of current and electromotive force with respect to time in the circuit consisting of inductance and resistance in series could be predicted from numerical solutions of these equations. As current in the circuit increasesl, magnetic field in the material increases, thus, the gap starts to shrink due to increased attractive force between gap and elastic restoring force in the material. With an appropriate selection of elastic constant of toroidal ferromagnetic material and design of gap structure it is possible to obtain the specified in both linear and nonlinear magnetic characteristics, such as current dependent and independent inductance.

• Journal of the Korean Magnetic Resonance Society
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• v.17 no.1
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• pp.11-18
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• 2013

Rapid advances of computational power and method have made it practical to apply the time-consuming calculations with all-atom force fields and sophisticated potential energies into refining NMR structure. Added to the all-atom force field, generalized-Born implicit solvent model (GBIS) contributes substantially to improving the qualities of the resulting NMR structures. GBIS approximates the effects that explicit solvents bring about even with fairly reduced computational times. Although GBIS is employed in the final stage of NMR structure calculation with experimental restraints, the effects by GBIS on structures have been reported notable. However, the detailed effect is little studied in a quantitative way. In this study, we report GBIS refinements of ubiquitin and GB1 structures by six GBIS models of AMBER package with experimental distance and backbone torsion angle restraints. Of GBIS models tested, the calculations with igb=7 option generated the closest structures to those determined by X-ray both in ubiquitin and GB1 from the viewpoints of root-mean-square deviations. Those with igb=5 yielded the second best results. Our data suggest that the degrees of improvements vary under different GBIS models and the proper selection of GBIS model can lead to better results.

• Journal of the Korean Society of Propulsion Engineers
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• v.5 no.3
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• pp.79-86
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• 2001

The six-components force measurements systems for rocket motors are used to measure multi components force generated by TVC(Thrust Vector Control) motors. This paper suggested the modeling scheme which is used in preliminary design and test analysis procedure and which can be applied to the existing other test stand in operation. The model whose parameters are determined by least square method makes the design engineer build the test stand to satisfy all kinds of requirements such as accuracy, operating condition and structural stability without tradeoff among the requirements. The experimental results shows that the proposed model has better accurate performances than those of other existing model.

• Computers and Concrete
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• v.21 no.2
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• pp.127-137
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• 2018

In this study, the behavior of the number of anchorage bolts on the glass-fiber reinforced polymer (GFRP) plates adhered to the surfaces of reinforcing concrete (RC) T-beams was investigated analytically. The analytical results were compared to the test results in term of shear strength, and midpoint displacement of the beam. The modelling of the beams was conducted in ABAQUS/CAE finite element software. The Concrete Damaged Plasticity (CDP) model was used for concrete material modeling, and Classical Metal Plasticity (CMP) model was used for reinforcement material modelling. Model-1 was the reference specimen with enough sufficient shear reinforcement, and Model-2 was the reference specimen having low shear reinforcement. Model-3, Model-4 and Model-5 were the specimens with lower shear reinforcement. These models consist of a single variable which was the number of anchorage bolts implemented to the GFRP plates. The anchorage bolts of 2, 3, and 4 were mutually mounted on each GFRP plates through the beam surfaces for Model-3, Model-4, and Model-5, respectively. It was found that Model-1, Model-3, Model-4 and Model-5 provided results approximately equal to the test results. The results show that the shear strength of the beams increased with increasing of anchorage numbers. While close results were obtained for Model-1, Model-3, Model-4 and Model-5, in Model-2, the rate of increase of displacement was higher than the increase of load rate. It was seen, finite element based ABAQUS program is inadequate in the modeling of the reinforced concrete specimens under shear force.

• Laser Solutions
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• v.5 no.1
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• pp.23-31
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• 2002

The uniform metal droplet generation using Nd-YAG laser was studied and experiment was carried out. The shape and volume of developed droplet was measured and the Young-Laplace equation and equilibrium condition of force were applied this model. The differential equation predicting shape of droplet using equilibrium condition of force instead of Navier-stokes equation was induced and numerical solution of differential equation compared with experimentation data. The differential equation was solved by Runge-Kutta method. Surface tension coefficient of droplet was determined with numerical solution relate to experimental result under the statical condition. In case of dynamic vibration, metal droplet shape and detaching critical volume are predicted by recalculating proposed model. The result revealed that this model could reasonably describe the behavior of molten metal droplet on vibration.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.5
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• pp.96-103
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• 2001

The quality requirements for thickness accuracy in cold rolling continue to become more stringent, particularly in response to exacting design specification from automotive customers. One of the major impacts from the tighter tolerance level is more unusable product on the head end and tail end of tandem mill coils when the mill is in transition to or from steady state rolling condition. A strip thickness control system for a tandem cold steel rolling mills is composed with blocked non-interacting controller and controllers for strip thickness and tension control of each rolling stands. An intelligent mathematical model included an elastic deformation of strip has been developed and applied to the field in order to predict the rolling force. The simulated results showed that the effect of elastic recovery should be included the model, even if the effect of elastic compression was not important.

• Korean Chemical Engineering Research
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• v.55 no.2
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• pp.201-213
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• 2017

Water is removed from crude oil containing water by using oil separator. This study aims to develop a three-dimensional (3D) Eulerian computational fluid dynamics (CFD) model to predict the separation efficiency of air-water-oil separator. In the incompressible, isothermal and unsteady-state CFD model, air is defined as continuous phase, and water and oil are given as dispersed phase. The momentum equation includes the drag force, lift force and resistance force of porous media. The standard k-${\varepsilon}$ model is used for turbulence flow. The exit pressures of water and oil play an important role in determining the liquid level of the oil separator. The exit pressures were identified to be 6.3 kPa and 5.1 kPa for water and oil, respectively, to keep a liquid level of 25 cm at a normal operating condition. The time evolution of volume fractions of air, water and oil was investigated. The settling velocities of water and oil along the longitudinal separator distance were analyzed, when the oil separator reached a steady-state. The oil separation efficiency obtained from the CFD model was 99.85%, which agreed well with experimental data. The relatively simple CFD model can be used for the modification of oil separator structure and finding optimal operating conditions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5A
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• pp.887-899
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• 2006

The aim of this study is to investigate a correlation between fundamental data on aerodynamic characteristics of bridge girder cross-sections, such as aerodynamic force coefficients and flutter derivatives, and their aerodynamic behaviour. The section model tests were carried out in three stages. In the first stage, seven deck configurations were studied, namely; Six 2-edge girders and one box girder. In this stage, changes in aerodynamic force coefficients due to geometrical shape of girders, incidence angle of flow, wind directions and turbulence intensities were studied by static section model tests. In the second stage, the dynamic section model tests were carried out to investigate the relativity of static coefficients to dynamic responses. And finally, the two-dimensional (lift-torsion) aerodynamic derivatives of three bridge deck configurations were investigated by dynamic section model tests. The aerodynamic derivatives can be best described as a representation of the aerodynamic damping and the aerodynamic stiffness provided by the wind for a given deck geometry. The method employed here to extract these unsteady aerodynamic properties is known as the initial displacement technique. It involves the measurement of the decay in amplitude with time of an initial displacement of the deck in heave and torsion, for various wind speeds, in smooth flow. It is suggested that the proposed aerodynamic force coefficients and flutter derivatives of bridge girder sections will be potentially useful for the aeroelastic analysis and buffeting analysis.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.50 no.5
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• pp.211-217
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• 2001

In this paper, we have developed the 6 DOF force display system to be based on the single PC. The system is composed of the force display device, the force reflecting rendering algorithm and the high-speed controller. The previous systems had a problem, that must adopt high performance workstation or 2-PC in order to control the graphics speedily and stably. In this paper, it is possible to improve the problem as to develop its exclusive controller and new rendering algorithm. The proposed new rendering algorithm is based on the Proxy algorithm, which can convert information of the position, the velocity, and the haptic information into the force-data. Especially, as to use the proxy algorithm, we can construct dynamical virtual-environment with the elasticity, the viscosity, the mass, and the friction force. As the result of the experiment, we found that our system has much superior characteristics than some other haptic interfaces, because it can control of 30,000 polygon model constructed virtual object with 1[kHz] haptic interrupt cycle and 20[Hz] graphic interrupt cycle in the single PC based system.