• Journal of Korean Society of Transportation
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• v.11 no.2
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• pp.45-62
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• 1993

The major objective of this study is to analyze the differences between operating costs of teleconferencing and alternative transportation modes for the conference in major compaines. Alternative transportation modes include road, rail, and air transportation mode. A case study is conducted using the data gathered for Pohang Steel Coperations. The main results are: (1) the operating cost of the teleconferencing is cheaper than operating cost of transportation modes when the number of teleconferencing are over 12 frequencs, and the number of person are over 15. Results reveal that teleconferencing turns out to be effective means of conference. (2) the amount of differences of operating costs on teleconsferencing and transportation modes gets higher according to the time elapsed. In particular, when teleconferencing cost is compared to operating cost of road transportation, it is found that the cost saving of 2.75 billion won in year 2001 can be realized.

• Nuclear Engineering and Technology
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• v.54 no.4
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• pp.1336-1342
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• 2022

Risk-informed safety classification of structures, systems and components (SSCs) is very important for ensuring the safety and economic efficiency of nuclear power plants (NPPs). However, previous methods for safety classification of SSCs do not take the plant operating modes or the operational process of SSCs into consideration, thus cannot concentrate on the safety and economic efficiency accurately. In this contribution, a new method for safety classification of SSCs based on the categorization of plant operating modes is proposed, which considers the NPPs operating history to improve the economic efficiencies while maintaining the safety. According to the time duration of plant configurations in plant operating modes, average importances of SSCs are accessed for an NPP considering the operational process, and then safety classification of SSCs is performed for plant operating modes. The correctness and effectiveness of the proposed method is demonstrated by application in an NPP's safety classification of SSCs.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.4
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• pp.694-699
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• 2009

Combined cycle plants which feature distinct advantages for power generation such as fast response, high efficiency, environmental friendliness, fuel flexiblity represent the majority of new generating plant installations across the globe. Combined cycle plants have different operating modes where the operating parameters can differ greatly depending which mode is operating at the time. This paper addresses the bidding strategy model of combined cycle plants in a competitive electricity market by using a characteristic of multiple operating modes of combined cycle plants. Simulation results of case studies show that an operating mode among multiple ones is selected strategically in generation bidding for more profit of generation company.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.46 no.4
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• pp.281-293
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• 2023

This study addresses the optimal design methodology for switching between active electronically scanned array (AESA) radar operating modes to easily select the necessary information to reduce pilots' cognitive load and physical workload in situations where diverse and complex information is continuously provided. This study presents a procedure for defining a hidden Markov chain model (HMM) for modeling operating mode changes based on time series data on the operating modes of the AESA radar used by pilots while performing mission scenarios with inherent uncertainty. Furthermore, based on a transition probability matrix (TPM) of the HMM, this study presents a mathematical programming model for proposing the optimal structural design of AESA radar operating modes considering the manipulation method of a hands on throttle-and-stick (HOTAS). Fighter pilots select and activate the menu key for an AESA radar operation mode by manipulating the HOTAS's rotary and toggle controllers. Therefore, this study presents an optimization problem to propose the optimal structural design of the menu keys so that the pilot can easily change the menu keys to suit the operational environment.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.7
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• pp.903-909
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• 2014

As a direct drive type washing machine requires two operating modes, washing and spinning modes, a design of the motor with high efficiency in each mode is not applicable to a conventional procedure. To achieve the requirements, a multi-pole outer rotor type switched reluctance motors are considered. To select a suitable motor type for the application, a static toque is compared based on the FEM analysis. The selected type is obtained for high and wide toque than other types of the motor. Further, the pole shape and arc are optimized to meet the required torque and torque ripple. To verify the proposed structure, the prototype is designed and manufactured. And the simulation and experimental results verify the validity of the proposed structure.

• Journal of Power Electronics
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• v.15 no.4
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• pp.1035-1046
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• 2015

This study presents a practical implementation of a multi-mode two-phase interleaved boost converter for fuel cell electric vehicle application. The main operating modes, which include two continuous conducting modes and four discontinuous conducting modes, are discussed. The boundaries and transitions among these modes are analyzed with consideration of the inductor parasitic resistance. The safe operational area is analyzed through a comparison of the different operating modes. The output voltage and power characteristics with open-loop or closed-loop operation are also discussed. Key performance parameters, including the DC voltage gain, input ripple current, output ripple voltage, and switch stresses, are presented and supported by simulation and experimental results.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.9
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• pp.2744-2751
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• 1996

In case of limited power supply, a rotating shaft system may not reach its operating speed that is greater than its critical speed, but the speed oscillates with small ampllitude near critical speed. As a result, it is considered that the operating mode plays an important role in the smooth start of machines. In order to investigate the dynamic behaviors of the rotating shaft system at the beginning stage, one has derived the equations of motion whose degrees of freedom is three, two translations and one rotation. The simultaneous differential equations are numerically solved by using runge-Kutta method, and thus the small time step length could be required corresponding to the stability of solution. Three types of operating modes dependent upon the driving torque rate have been numerically investigated according to the maximum displacement of shaft center. The first type of relation is linear, the second type is composed of two linear curves recommended by machine manufacturer, and the last one is the proposed torque curve reflecting the frequency response curve of one degree of freedom system. For the second type of modes, it is found that the optimal range of intermediate speed to the critical speed lies between 0.8 and 0.9. In addition to that, the maximum displacement can be reduced more if the third type of mode is utilized.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.903-908
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• 1998

This paper aims at investigating the characteristics of the operating modes of two-module Thyristor Controlled Series Compensator (TCSC) in a power transmission system. The operating modes of two-module TCSC are defined, analyzed and compared to those of single-module TCSC are defined, analyzed and compared to those of single-module TCSC. The load flow program, the stability calculation program and Electro Magnetic Transient Program (EMTP) simulation of a TCSC power transmission system are developed for the performance evaluation of two-module TCSC as a power flow controller. In the process of the simulation study, the potential problem areas of the TCSC power transmission system are identified.

• Aerospace Engineering and Technology
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• v.3 no.1
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• pp.65-78
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• 2004

This research was conducted for an acquisition of the ramjet engine test facility design technique which are concerned about freejet type test facility. In this research, we concentrated on the design technique and the construction technique of the vitiation air heater(VAH), test section, diffuser and ejector. Based on the operating modes of the basic test facility, ten operating modes in coordinates "Altitude-Mach number" was regenerated from Mach 2, Altitude 0km to Mach 5, Altitude 15km. In this operating modes, we calculated a design parameter of the supersonic nozzle, VAH, diffuser and ejector and acquired a technique for the ramjet test facility operating and repairing.

• Journal of Electrical Engineering and Technology
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• v.11 no.3
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• pp.543-550
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• 2016

The Active Superconducting Current Controller (ASCC) is a new type of Superconducting Fault Current Limiters (SFCL) which can limit the fault current in different modes. It also has the particular abilities of compensating active and reactive powers for electrical networks. In this paper, it is confirmed that the performance of ASCC in different operating modes introduces a limiting impedance in series with the network which can even degrade the transient stability and the operation of the Over-Current Relays (OCR) employed in a power system. In addition, the model of a three-phase ASCC is simulated, and the effect of descriptive modes on the current limiting level is investigated. For the transient stability analysis, a single machine-infinite bus system is tested, and the effect of operation modes is studied based on an equal area criterion obtaining the critical time and the critical angle. Modifying the setting parameters of OCR such as time dial and pick-up current, the protective coordination is also studied in different operating modes.