• Journal of Electrical Engineering and Technology
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• v.9 no.5
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• pp.1569-1576
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• 2014

This paper mainly proposes a direct torque control strategy to minimize torque ripple in brushless DC (BLDC) motor. BLDC motor has large current and torque ripple when one voltage vector applied in one cycle due to its low inductance. Hence, this paper proposed a hysteresis torque control with PWM mode to control the resultant torque. Moreover, when the direct torque control system is operating during the two-phase half-bridge $120^{\circ}$ conduction mode, large torque ripple in commutation area appears every 120 electrical degree. Based on analyzing the root of torque ripple in detail, lookup tables of switching devices states for new half-bridge modulation mode in the positive and negative reference torque put forwarded. Finally, simulations by MATLAB software and experiment results from DSP are presented to verify the feasibility and effectiveness of the proposed strategy operating in four-quadrant operation.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.2
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• pp.103-110
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• 2020

In this study, the design and operating strategy of DC home grid with PV, battery, and ultracapacitor have been discussed, The proposed sizing method can find the optimum size of the battery and PV which can reduce yearly utility energy consumption, whereas the control scheme can maintain the DC-bus voltage level of the DC home grid under different operating conditions, where day or night time operation, load and PV power levels, and the maximum current and state-of-charge of batter are considered. In addition, a supervisory power management strategy has been suggested, and its validity has been verified by HILS (hardware in-the-loop simulation) results.

• Korean Journal of Cognitive Science
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• v.16 no.4
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• pp.271-285
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• 2005

An experiment was conducted to investigate the effect of three types of prior knowledge (domain related knowledge, summary-writing strategy knowledge, and neutral unrelated knowledge) and two types (analytic and wholistic) of cognitive styles on the quality of the summary writing of a descriptive text. The results showed that learning domain-related knowledge and summary-writing-strategy knowledge increased the level of understanding of the target text and the quality of the summary; the former operating mainly at the understanding phase, and the latter operating mainly during the summary planning and producing phases. The effect of the types of cognitive style was found somewhat limited but mainly operating In the process of planing the summary. Other features of time course in writing a summary were further discussed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.5
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• pp.233-240
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• 2015

This paper discusses compressors operating number control strategy using cooperative logic to cope with variable partial load for high efficiency of a centrifugal water chiller. The cooperative logic is composed of a speed-up and speed-down controller, enabling smooth operation of compressors and equivalent distribution of thermal load in each compressor. This centrifugal water chiller design can be operated with high efficiency without incurring excessive energy waste and large transient phenomena at partial load states. Simulations in MATLAB and experiments in a real chiller system were conducted and verified the high efficiency control of a centrifugal water chiller achieved by the suggested strategy.

• Knowledge Management Research
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• v.14 no.3
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• pp.37-54
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• 2013

Technology standards have gained importance as global market becomes more competitive. Since a technology acknowledged as a standard brings significant benefits to the developer firm, firms in the IT industry tend to pursue standardization for the technology, being it proprietary or open. However, the paths or strategic implications are seldom discussed in academia. Therefore, our study uses iPhone of Apple, one of the proprietary standards successes, to further understand corporate strategies over two standard choices. Our case study suggests that iPhone's entry timing was optimal for creating a new mobile environment. Design excellence and user-friendly interface increased networking effects and switching costs among consumers. Apple developed independent mobile operating system (iOS) through improvement on the existing operating system. During the process, Apple chose proprietary standard and, by installing the same UX on its sibling products such as iPod Touch or iPad, overcame the subsequent problems that might arise from the limited use of iOS. Based on the capability of concurrently developing both hardware and software, Apple connected operating system, machine, and contents, which deems to contribute to its proprietary standards success. We argue that this strategy should be considered for firms which plan proprietary standard strategy.

• KSBB Journal
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• v.13 no.3
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• pp.259-267
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• 1998

Optimal feeding strategies in bioreactor operation of Scutellaria baicalensis G. plant cell culture were investigated to maximize the production of flavone glycosides by using a structured kinetic model which can predict culture growth and flavone glycosides synthesis in a rigorous, quantitative manner. For the production of baicalin and wogonin-7-0-GA, the strategies for glucose feeding into Scutellaria baicalensis G. plant cell culture were proposed based on the model, which are a periodic fed-batch operation with maintenance of cell viability and of specific production rate respectively, and a perfusion operation with maintenance of specific production rate for baicalin and wogonin-7-0-GA. Simulation results showed that the highest volumetric concentration of flavone glycosides was obtained in a periodic fed-batch operation with maintenance of cell viability among all the suggested strategies. In the periodic fed-batch operations, the higher volumetric production of flavone glycosides was achieved compared with that in the perfusion operation. It can be concluded that a periodic fed-batch operation with maintenance of cell viability would be the optimal and practical operating strategy of Scutellaris baicalensis G. plant cell culture for the production of flavone glycosides.

• International Journal of Automotive Technology
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• v.7 no.7
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• pp.785-793
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• 2006

The topic of this study is the control strategy of a mild hybrid electric vehicle (HEV) equipped with a continuously variable transmission (CVT). A brief powertrain and vehicle configuration is introduced followed by the control strategy of the HEV with emphasis on two key parts. One of them is an ideal operating surface (IOS) that operates the CVT powertrain optimally from the viewpoint of the tank-to-wheel efficiency. The other is a charge sustaining energy management to maintain the battery state of charge (SOC) within an appropriate level. The fuel economy simulation results of the HEV over standard driving cycles were compared with those of the baseline vehicle. Depending on the driving cycle, 1.3-20% fuel saving potential is predicted by the mild hybridisation using an integrated starter alternator (ISA). The detailed energy flow analysis shows that the majority of the improvement comes from the idle stop function and the benefits for electrical accessories. Additionally, the differences between the initial and the final SOC are in the range $-1.0{\sim}+3.8%$ in the examined cycle.

• Transportation Technology and Policy
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• v.12 no.4
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• pp.32-39
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• 2015

• Proceedings of the Korean Nuclear Society Conference
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• 2001.10a
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• pp.163.2-163
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• 2001

• Proceedings of the Korean Nuclear Society Conference
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• 2002.10a
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• pp.180.1-180
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• 2002