• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.355-355
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• 2018

Natural hydrology systems, including high flow and low flow events, are important for aquatic ecosystem health and are essential for controlling the structure and function of ecological processes in river ecosystems. Ecosystem responses to flow changes have been studied in a variety of ways, but little attention has been given to how episodic typhoons and atmospheric circulation patterns can change these hydrologic regime-ecological response relationships. In this diagnostic study, we use an empirical approach to investigate the salient features of interactions between atmospheric circulation, climate, and runoff in the five major Korean river basins.

• Structural Engineering and Mechanics
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• v.16 no.1
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• pp.47-62
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• 2003

The nonlinear dependence aspect of various conical tool indentation parameters leading to an optimum tool semi angle value for easiest perforation is plotted and discussed explicitly in this work with the conclusion that tool angle has an optimum response towards most of the indentation parameters. Around this optimum angle, the aluminium sheets showed minimum fracture toughness as well as minimum work input to overcome the offered resistance. At the end, the mechanism leading to this phenomenon is presented with the conclusion that plastic flow dominates as the dimple semi cone angle reaches 35 and both pre and post plastic flow perforations lead the tool semi cone angle value towards this dimple cone semi angle of plastic flow initiation for its optimum performance. It is also concluded that specimen material failure is solely under tensile hoop stress and hence results into radial cracks initiation and propagation.

• Transactions of Materials Processing
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• v.15 no.1 s.82
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• pp.15-20
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• 2006

The rapid thermal response (RTR) molding is a novel process developed to raise the temperature of mold surface rapidly to the polymer melt temperature prior to the injection stage and then cool rapidly to the ejection temperature. The resulting filling process is achieved inside a hot mold cavity by prohibiting formation of frozen layer so as to enable thin wall injection molding without filling difficulty. The present work covers flow simulation of thin wall injection molding using the RTR molding process. In order to take into account the effects of thermal boundary conditions of the RTR mold, coupled analysis with transient heat transfer simulation is suggested and compared with conventional isothermal analysis. The proposed coupled simulation approach based on solid elements provides reliable thin wall flow estimation for both the conventional molding and the RTR molding processes.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.7 s.178
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• pp.1753-1762
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• 2000

An inverse method is presented to obtain material's flow properties by using small punch test. This procedure employs, as the objective function of inverse analysis, the balance of measured load-di splacement response and calculated one during deformation. In order to guarantee convergence to global minimum, simulated annealing method was adopted to optimize the current objective function. In addition, artificial neural network was used to predict the load-displacement response under given material parameters which is the most time consuming and limits applications of global optimization methods to these kinds of problems. By implementing the simulated annealing for optimization along with calculating load-displacement curve by neural network, material parameters were identified irrespective of initial values within very short time for simulated test data. We also tested the present method for error-containing experimental data and showed that the flow properties of material were well predicted.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.1053-1057
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• 1996

The purpose of this study is to bring out the optimal design factors which effect on dynamic characteristics in the design of proportional flow control valve with fast response characteristics, and to verify the validity of the design factors In this study, force feedback type flow control valve with nozzle-flapper is studied. And, the influences which fixed orifice, nozzle diameter, and maximum displacement between nozzle and flapper effect on dynamic characteristics are analyzed. We have done simulations using the optimal design factors and simulink(Matlab) as a simulation tool, and verified the validity of our simulations by means of comparison our simulation results with an experimental results of another similar valve.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.09a
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• pp.9-12
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• 2005

The rapid thermal response (RTR) molding is a novel process developed to raise the temperature of mold surface rapidly to the polymer melt temperature prior to the injection stage and then cool rapidly to the ejection temperature. The resulting filling process is achieved inside a hot mold cavity by prohibiting formation of frozen layer so as to enable thin wall injection molding without filing difficulty. The present work covers flow simulation of thin wall injection molding using the RTR molding process. In order to take into account the effects of thermal boundary conditions of the RTR mold, coupled analysis with transient heat transfer simulation is suggested and compared with conventional isothermal analysis. The proposed coupled simulation approach based on solid elements provides reliable thin wall flow estimation fur both the conventional molding and the RTR molding processes

• Tribology and Lubricants
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• v.14 no.4
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• pp.95-99
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• 1998

The electrorheological (ER) behavior of chitosan suspension in the silicone oil was investigated. Chitosan suspension showed a typical ER response, Bingham flow behavior upon application of an electric field due to the polarizability of the branched amino group of the chitosan particles. The shear yield stress exhibited a linear dependence on the volume fraction of particles and the squared electric field. On the basis of the experimental results, chitosan suspension has been correlated with the conduction models for ER response and found to be an ER fluid.

• Journal of Mechanical Science and Technology
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• v.17 no.1
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• pp.40-47
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• 2003

In this paper, we constructed the analytic model of control valve as a function of electric and geometric parameters, and analyzed the influence of the design parameters on the dynamic characteristics. For improving the dynamic characteristics, optimal design is conducted by applying sequential quadratic programming method to the analytic model. This optimal design aims to minimize the response time and maximize force efficiency. By this procedure, control valve can be designed to have fast response in motion.

• Tribology and Lubricants
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• v.17 no.2
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• pp.124-129
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• 2001

The electrical and rheological behaviors of the cellulose phosphate ester suspension in the silicone oil were investigated. Cellulose phosphate ester suspension showed a typical ER response (Bingham flow behavior) upon application of an electric field. The shear stress for the cellulose phosphate ester suspension exhibited a linear dependence on the volume fraction of particles and a square power of the electric field. On the basis of the experimental results, cellulose phosphate ester suspension correlated with the conduction model of Tang et al, and found to be an ER fluid.

• Water for future
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• v.22 no.3
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• pp.289-298
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• 1989

A review is made of transient phenomena ralation to flow in the vadose zone. Reviewed topics include rapid water table response to rainfall, pulsating flow due to pressure perturbations in the vasoes zone, and the wave-like propagation of increased soil moisture caused by intermittent rainfall. As a basis of interpreting these phenomena, zoning of the vadose zone into a residual water zone, an unsaturated capillaty zone, and a saturated capillary zone are proposed. Possible implications with respect to hydrological processes relating to these phenomena are discussed.