• Proceedings of the KWS Conference
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• 2000.10a
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• pp.192-195
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• 2000

This paper describes a fundamental investigation of the friction welding condition for pure copper/pure titanium and the effect of friction time, upset pressure on the mechanical and metallurgical properties of friction welding. Under the constant upset pressure, the tensile strength make a little difference with an increase in friction time. At the constant friction time, the tensile strength increased with an increase in upset pressure. The tensile fracture of Cu to Ti joint occurred in Cu base material near interface.

• Journal of the Korean Institute of Telematics and Electronics
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• v.11 no.3
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• pp.27-31
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• 1974

The maximum principle of Pontryagin provides the celebrated method to obtain the optimum control switching time and switching points on the nuclear reactor. The control trajectories transfered from its initial state to the target state are optimized based on time optioptimal control method with the given reactor parameters and the piecewise constant input values.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.03b
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• pp.11-11
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• 2010

Recently, annual usage of energy is dramatically increasing by industrialization is going faster and more electricity is needed due to various electronic devices. This paper present relationships between the Vmax, $V_T$, load and time constant of solar cell charge and discharge curve. Charging and discharging recording where the external resistance will become larger Vmax, $V_T$ is decrease and the time increases and decreases there is a possibility of knowing.

• Journal of Powder Materials
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• v.21 no.2
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• pp.114-118
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• 2014

In this study, an aluminum oxide layer for sealing treatment of nano-diamond powder was synthesized by anodizing under constant current. The produced pore size and oxide thickness were investigated using scanning electron microscopy. The pore size increased as the treatment time increased, current density increased, sulfuric acid concentration decreased, which is different from the results under constant voltage, due to a dissolution of the oxide layers. The oxide layer thickness by the anodizing increased as temperature, time, and current density increased. The results of this study can be applied to optimize the sealing treatment process of nano-diamond particles of 4-10 nm to enhance the resistances of corrosion and wear of the matrix.

• Journal of Advanced Marine Engineering and Technology
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• v.19 no.2
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• pp.81-91
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• 1995

A miniature size electrostatic induction motor has been fabricated and studied with emphasis on the role of the surface resistivity, the relative dielectric constant of the rotor surface materials and the rotor liner materials, which control the charge induction and relaxation on the rotor surface and the field intensity between the rotor and the stator. It is found that the higher resitivity and/or the higher relative dielectric constant, concurrently the longer relaxation time constant of the rotor surface materials make the motor speed get higher speed. In case of discrete coated rotor surface it is found that the motor speed was increased logarithmically as narrow as width of the discrete coated Ti. And the degree of width of discrete coated Ti to the axial direction of the rotor was $60^{\circ}$ and $150^{\circ}$, the motor has got a 125% higher than that at the degree of $0^{\circ}$.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10a
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• pp.941-946
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• 1992

Three different reflux policies are compared for a batch distillation process in which a fixed recovery with a given average purity of the distillate is required ; the first, for the constant distillate purity ; the second, for the constant reflux ratio ; finally, for the optimal reflux policy which gives the minimum operation time. The optimal reflux policy was obtained using pontryagin's maximum principle. Througy the numerical simulations for the three different binary mixtures, it was found that the time advantage of the optimal reflux operation over the constant overhead composition operation varies form 10.0 to 22.4% and the advantage over the constant reflux operation varies from 1106 to 36.6% in the three cases considered.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.32B no.1
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• pp.180-188
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• 1995

A modified Kohonen's self-organizing feature map (SOFM) algorithm which has binary reinforcement function and a constant learning rate is proposed. In contrast to the time-varing adaptaion gain of the original Kohonen's SOFM algorithm, the proposed algorithm uses a constant adaptation gain, and adds a binary reinforcement function in order to compensate for the lowered learning ability of SOFM due to the constant learning rate. Since the proposed algorithm does not have the complicated multiplication, it's digital hardware implementation is much easier than that of the original SOFM.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.8
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• pp.1058-1063
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• 2020

This paper presents a new insulation resistance calculation technique to prevent electric shock and fire accidents due to the dielectric breakdown in the primary insulation section of the IT ground system. The solar power generation market is growing rapidly due to the recent expansion of renewable energy and energy storage systems, but as the insulation is destroyed and fire accidents frequently occur, a device for monitoring the insulation resistance state is indispensable to the IT grounding method. Compared to the conventional algorithm that use a method of multiplying a time constant to a fixed coefficient, the proposed insulation resistance calculation method has a fast response time and high accuracy over a wide insulation resistance range by applying a different coefficient according to the values of the insulation impedance. The proposed dynamic time constant based insulation resistance calculation technique reduces the response time by up to 39.29 seconds and improves the error rate by 20.11%, compared to the conventional method.

• Journal of Korea Foundry Society
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• v.42 no.1
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• pp.61-66
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• 2022

Hydraulic units are important components of agricultural and construction machinery, and thus require high-quality castings. However, gas defects occurring inside the sand cores of the castings due to the resin used is a problem. This study therefore aimed to develop a casting simulation method that can clarify the gas defect positions. Gas defects are thought to be caused by gas generated after the molten metal fills up the mold cavity. The gas constant is the most effective factor for simulating this gas generated from sand cores. It is calculated by gas generating temperature and analysis of composition in the inert gas atmosphere modified according to the mold filling conditions of molten metal. It is assumed that gases generated from the inside of castings remain if the following formula is established. [Time of occurrence of gas generation] + [Time of occurrence of gas floating] > [Time of occurrence of casting surface solidification] The possibility of gas defects is evaluated by the time of occurrence of gas generation and gas floating calculated using the gas constant. The residual position of generated gases is decided by the closed loops indicating the final solidification location in the casting simulation. The above procedure enables us to suggest suitable casting designs with zero gas defects, without the need to repeat casting tests.

• Proceedings of the Korean Geotechical Society Conference
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• 1997.10a
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• pp.123-132
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• 1997