• Korean Management Science Review
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• v.32 no.4
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• pp.19-28
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• 2015

This study presents a mathematical programming model to develop production planning in the manufacturing processes for photovoltaic silicon ingots and wafers. The model is formulated as a linear programming model that maximizes total growth margin, which is composed of production cost, inventory cost, shortage cost, and sales profit while considering the constraints associated with the production environments of photovoltaic materials. In order to demonstrate the utility of the model for production planning, we run operations for a planning horizon of a year for a case study. When the primary results of this mathematical programming are compared with the historical records, the model could have resulted in the considerable increase of the total growth margin by effectively reducing inventory cost if a decision maker had employed the model as a decision support system with perfect information for sales demand.

• Journal of the Korean Graphic Arts Communication Society
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• v.22 no.1
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• pp.65-74
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• 2004

This study analyzed the main bodies, sizes of litters, spaces between letters, Words, lines, length of lines, sizes of main body and margin, Position of the main bodies of PDF(Portable Document Format) in high schools and "the criteria of reading system for the textbooks" which was suggested by the Department of Education and Provided some suggestions for the improvement. First, it is judged that spaces of the main body of textbooks should be shrunken to make the ratio of 50:50 between the main body and space margin. Second, it is judged that the main body should be placed in the center of text page. Third, the results of the above findings showed that it would be difficult to deal with the task of deciding space and position or the main body and marginal space in a form of single project, because there are many variables involved and psychologically complicated elements which can not be measured objectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.5
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• pp.509-520
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• 1992

AIGaAs /GaAs HBT OR /NOR gate. which can be used for high speed digital system was designed. Equivalent circuit parameters of HBT were obtained from Gummel-Poon's model and direct extraction method. Simulation results with PSPI CE showed that propagation delay time and cutoff toggle frequency of designed gate were 25ps and 200Hz, respectively. the designed gate exhibited superior properties to the recently reported HBT ECL and MESFET SCFL when considering the fan-out characteristics and noise margin.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.161-167
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• 1993

This paper presents robustness properties of the Kalman Filter ad the associated LQG/LTR method for linear time-invariant systems having delays in both the state and output. A circle condition relating to the return difference matrix associated with the Kalman filter is derived. Using this circle condition, it is shown that the Kalman filter guarantees(1/2, .inf.) gain margin and .+-.60.deg. phase margin, which are the same as those for nondelay systems. However, it is shown that, even for minimum phase plants, the LQG/LTR method can not recover the target loop transfer function. Instead, an upper bound on the recovery error is obtained using an upper bound of the solution of the Kalman filter Riccati equations. Finally, some dual properties between output-delated system and input-delayed systems are exploited.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.05a
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• pp.225-226
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• 2010

ISO 22266-1 issued in May 2009 provides guidelines for applying shaft torsional vibration criteria, under normal operating conditions, for the coupled shaft system and long blades of a turbine generator set. In case that a turbine generator vendor do not meet the separation margin of torsional natural frequencies in the technical specifications of the purchaser, this standard can present the reasonable and objective criteria about torsional vibration which both purchaser and supplier can agree on, while ensuring the integrity of turbine generator. This paper describes the application case of ISO 22266-1 for the establishment of torsinal vibration criteria under retrofitting the turbine generator of 'U' nuclear power plant.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.7
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• pp.1123-1128
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• 2008

The necessity of online dynamic security assessment is getting apparent under Electricity Market environments, as operation of power system is exposed to more various operating conditions. For on-line dynamic security assessment, fast transient stability analysis tool is required for contingency selection. The TEF(Transient Energy Function) method is a good candidate for this purpose. The clustering of critical generators is crucial for the precise and fast calculation of energy margin. In this paper, we propose a new method for fast decision of mode of instability by using stability indices and energy margin. The method is a new version of our previous paper.[1] Case studies are showing very promising results.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.9
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• pp.1618-1623
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• 2008

In this paper, a new design method for IMC-PID that adds a phase scaling factor of system identifications to the standard IMC-PID controller as a control parameter is proposed. Based on analytically derived frequency properties such as gain and phase margins, this tuning rule is an optimal control method determining the optimum values of controlling factors to minimize the cost function, integral error criterion of the step response in time domain, in the constraints of design parameters to guarantee qualified frequency design specifications. The proposed controller improves existing single-parameter design methods of IMC-PID in the inflexibility problem to be able to consider various design specifications. Its effectiveness is examined by a simulation example, where a comparison of the performances obtained with the proposed tuning rule and with other common tuning rules is shown.

• Korean Journal of Optics and Photonics
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• v.10 no.2
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• pp.169-173
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• 1999

We have experimentally investigated the eye margin characteristics of intensity modulated 10Gb/s NRZ signals in optically amplified systems depending on optical signal-to-noise ratio and chromatic dispersion. For the practical system application, the minimum optical signal-to-noise ratio was 25 dB. We utilized the negative chirped transmitter and a dispersion compensation fiber to compensate the chromatic dispersion in single mode fiber. We found the optimum eye opening and receiver sensitivity in case of the residual dispersion of 0~+935 ps/nm.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.770-774
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• 2003

We propose the re-design method of modal parameters to depress the 2nd resonance peak of the ultra-slim-height optical pick-up actuator. With the addition of tile counter mode near the 2nd resonance frequency, we can achieve the gain margin which is sufficient to meet the system requirement. It would alleviate the burden of the additional filter for a high-speed drive.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.4
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• pp.176-181
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• 2001

As the data rate between chip-to-chip gets high, the skin effect and load of pins deteriorate noise margin. With these, noise disturbances on the bus channel make it difficult for receiver circuits to read the data signal. This paper has proposed a new pre-emphasis driver circuit which achieves wide noise margin by enlarging the signal voltage range during data transition. When data is transferred from a memory chip to a controller, the output boltage of the driver circuit reaches the final values through the intermediate voltage level. The proposed driver supplies more currents applicable to a packet-based memory system, because it needs no additional control signal and realizes very small area. The circuit has been designed in a 0.18 ${\mu}m$ CMOS process, and HSPICE simulation results have shown that the data rate of 1.32 Gbps be achieved. Due to its result, the proposed driver can achieved higher speed than conventional driver by 10%.