• Journal of the Korean Society for Precision Engineering
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• v.29 no.11
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• pp.1207-1213
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• 2012

Typically commercial controllers do not give data of the controller gains. Therefore, it is very hard to determine the optimal controller gain even though the dynamic model is derived. In this case, design of experiment (DOE) methodology can be a powerful tool for gain tuning. In this research, gain tuning process is proposed based on the DOE. Micro parallel mechanism platform with 3 degrees-of-freedom (DOF) is used for the experiments. Controller gains are measured indirectly from the voltages of adjustable resistors. The controller gains of three actuators are optimized by two or three steps, respectively. The correlations of the controller gains are also analyzed. The process and methodology can be adopted in gain tuning of other mechanical systems.

• Management Science and Financial Engineering
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• v.22 no.1
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• pp.13-20
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• 2016

We investigate the optimal consumption and investment problem when a working debtor has an option to file for bankruptcy. By applying the duality approach, the closed-form solutions are obtained for the case of CRRA utility function. The optimal bankruptcy time is determined by the first hitting time when the financial wealth hits the wealth threshold derived from the optimal stopping time problem. Moreover, the numerical results show that the investment increases as the wealth approaches the threshold and the value gain from the bankruptcy option is vanished as wealth increases.

• 전기의세계
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• v.26 no.6
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• pp.66-71
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• 1977

In this paper a method is presented for the optimal control of a nuclear reactor at equilibrium state by use of a digital computer. Using the optimal control theory, we formulate the control problem of the reactor as a discrete-time linear regulator problem. A quadratic performance index is defined. The effects of choosing different performance index weighting matrices to the feedback gain matrix and reactor transient responses are studied for the deterministic optimal control with all state variables accessible to measurement.

• 제어로봇시스템학회:학술대회논문집
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• 1986.10a
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• pp.498-502
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• 1986

A generalized singular linear quadratic control technique is developed to design an optimal trajectory tracking system. The output feedback control law is designed using this technique. The feedback gain matrix is synthesized to minimize tracking errors with pole placement capability to satisfy the control activity requirements. An applications to a bank-to-turn missile coordinated autopilot system design is presented.

• Journal of the Semiconductor & Display Technology
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• v.22 no.4
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• pp.142-147
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• 2023

This paper presents a novel design of a differential patch antenna for 60-GHz millimeter-wave applications. The design process of the back-to-back (BTB) patch antenna is based on the conventional single-patch antenna. The initial design of the BTB patch antenna (Type-I) has a patch size of 0.66 × 0.98 mm² and a substrate size of 0.99 × 1.48 mm². It has a gain of 1.83 dBi and an efficiency of 94.4% with an omni-directional radiation pattern. A 0.4 mm-thick high-resistivity silicon (HRS) is employed for the substrate of the BTB patch antenna. The proposed antenna is further analyzed to investigate the effect of substrate size and resistivity. As the substrate resistivity decreases, the gain and efficiency degrade due to the substrate loss. As the substrate (HRS) size decreases approaching the patch size, the resonant frequency increases with a higher gain and efficiency. The BTB patch antenna has optimal performances when the substrate size matches the patch size on the HRS substrate (Type-II). The antenna is redesigned to have a patch size of 0.81 × 1.18 mm² on the HRS substrate in the same size. It has an efficiency of 94.9% and a gain of 1.97 dBi at the resonant frequency of 60 GHz with an omni-directional radiation pattern. Compared to the initial design of the BTB patch antenna (Type-I), the optimal BTB patch antenna (Type-II) has a slightly higher efficiency and gain with a considerable reduction in antenna area by 34.8%.

• Journal of the Korean Geophysical Society
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• v.4 no.4
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• pp.297-311
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• 2001

The gain-clamped EDFA has been developed to eliminate the output power change of WDM surving channels to occur with added or dropped channels, which degrades the performance of WDM optical network. It maintains the constant gain of surviving channels when WDM channels are added or dropped in a network amplifying node. In this paper, the bi-directionally pumped gain-clamped EDFA is implemented to compensate the change of the input power by a lasing. The results show that the lasing of a short wavelength and backward propagation is the optimal condition to minimize the transient response of surviving channels in terms of the overshoot and gain saturation due to the inhomogeneous broadening effect.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.7
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• pp.1003-1011
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• 2009

This study aims at precise control of oil outlet temperature in the oil cooler system of machine tools for enhancement of working speed and processing accuracy. PID control logic is adopted to obtain desired oil outlet temperature of the oil cooler system with hot-gas bypass method. We showed that the gains of PID controller could be easily determined by using gain tuning methods to get the gain of PID controller without any mathematical model. We also investigated various gain tuning methods to design the gains of PID and compared each control performance for selecting the optimal tuning method on the hot gas bypass method through experiments. Moreover, we confirmed excellent control performance with proposed PI controller gain even though disturbances were abruptly added to the experimental system.

• The Journal of Engineering Research
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• v.5 no.1
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• pp.119-133
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• 2004

The gain-clamped EDFA has been developed to eliminate the output power change of WDM surviving channels to occur with added or dropped channels, which degrades the performance of EDM optical network. It maintains the constant gain of surviving channels when WDM channels are added or dropped in a network amplifying node. In this paper, the bi-directionally pumped gain-clamped EDFA is implemented to compensate the change of the input power by a lasing. The results show that the alsing of a short wavelength and backward propagation is the optimal condition to minimize the transient response of surviving channels in terms of the overshoot and gain saturation sue to the inhomogeneous broadening effect.

• Journal of KSNVE
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• v.8 no.3
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• pp.428-434
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• 1998

Optimal design of a piezoelectric smart structure is studied for cabin noise control. A cubic shaped acoustic cavity with a flat plate which covers one side is taken as the problem. The sensor signal is returned to the actuator through a negative gain. The acoustic cavity is modeled using the modal approach which represents the pressure fields in the cavity as a sum of mode shapes of the cavity with unknown coefficients. By using orthogonality of the mode shapes of the cavity, finite element equation for the structure with the influence of the acoustic cavity is derived. The objective function is the average pressure at a certain region, so-called silent zone, in the cavity and the design variables are the locations and sizes of the piezoelectirc actuator and sensor. The optimal design is performed at several frequencies and the results show a remarkable noise reduction. To see the robustness of the optimally designed result, the configuration is used to examine the noise reduction at different frequencies. By adjusting the gain at each frequencies, it is possible to reduce the noise in comparison with the result when the actuator is not activated.

• Journal of the Korean Institute of Intelligent Systems
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• v.10 no.3
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• pp.232-241
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• 2000

This study suggests an integrated method based on concept hierarchies, information gain, and rough set theory for efficient discovery rules from a large amount of data, and implements an optimal rules discovery system. Our approach applies attribute-oriented concept ascension technique to extract generalized knowledge from a database, knowledge reduction technique to remove superfluous attributes and attribute values, and significance of attributes to induce optimal rules. The system first reduces the size of database by removing the duplicate tuples through the condition attributes which have no influences on the decision attributes, and finally induces simplified optimal rules by removing the superfluous attribute values by analyzing the dependency relationships among the attributes. And we induce some decision rules from actual data by using the system and test rules to new data, and evaluate that the rules are well suited to them.