• 시스템엔지니어링학술지
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• 제18권1호
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• pp.33-45
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• 2022

This paper relates to the improvement application of operation requirements documents(ORD) on which empirical researches are not sufficient. The application of ORD was drawn up and operated in the acquisition phase, and recently it was decided to apply it in the requirements planning phase. However, the reality is that there are deficiencies in the performance of works, such as the classification of works among related organizations. Therefore, this study analyzed the cases of writing ORD that have been promoted so far, and Its status was enhanced by reflecting it in laws and regulations. In addition, the concept was redefined, and improvement measures such as the level of writing ORD were suggested for each acquisition stages. Above all, it is desirable to incrementally supplement and develop from preliminary conceptual research in the planning stage and drafting at the military level. In addition, the relevant legal system should be supplemented so that such ORD application can be flexibly established in defence acquisition.

• 한국항공운항학회지
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• 제21권2호
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• pp.26-32
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• 2013

The rotorcraft makes lift and control forces by the rotor thrust. At the development phase of the rotorcraft, the operational limitations have to be established. And it shall be demonstrated to operate the rotorcraft safely within the limitations. This paper introduces establishment and evaluation results of operational rotor speed limitations for the medium class utility rotorcraft. And it shows the follow-up activities after design changes of rotor speed indicators and aural warning systems for implementing the rotor speed limitations.

• Applied Microscopy
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• 제45권2호
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• pp.101-105
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• 2015

Numerous digital image analysis techniques have been developed with regard to transmission electron microscopy (TEM) with the help of programming. DigitalMicrograph (DM, Gatan Inc., USA), which is installed on most TEMs as operational software, includes a script language to develop customized software for image analysis. Based on the DM script language, this work provides a script source listing for quantitative strain measurements based on a geometric phase analysis.

• 한국통신학회논문지
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• 제9권1호
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• pp.25-29
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• 1984

연산 증폭기의 능동 보상은 주파수의 증가에 따라 연산 증폭기의 위상천이와 이득의 감소를 보상한 것으로 이 결과를 VCVS와 번전 적분기에 적용하였다. VCVS의 경우 제안된 보상회로의 위상천이는 주파수에 無關하고 보상회로의 궤환저항의 比에 따라서 Soliman에 의해 제안된 보상회로보다 이득특성이 개선되며 Voltage-follower의 경우도 동일한 보상회로로서 주파수에 無關하게 위상이 보상되고 이득특성 또한 개선되었다. 그밖에 반전 적분기에서 Q-factor를 더욱 증가시키는 보상회로도 제시하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.293-296
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• 2008

Injection molding operation consists of filling, packing, and cooling phase. The highest pressure is involved during the packing phase among the operation phases. Cavity pressure depends upon velocity to pressure switchover time and magnitude of packing pressure. The cavity pressure is directly related to stress concentration in the cavity of mold. Thus the observation and control of cavity pressure is very important to prevent mold cracking. In this study, cavity pressures were observed for operational conditions using the commercial CAE software, Moldflow. Operational conditions were velocity to pressure switchover time and packing pressure. Cavity pressures were also measured directly during injection molding. Simulation and experimental results showed good agreement.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2017년도 전력전자학술대회
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• pp.216-218
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• 2017

The imbalance at the 3-phase side at the railway power supply substation has been a well-known issue. Due to the difference in status of loads at each phase at any given moment, it is difficult to maintain the balance in the 2-phase side of the transformer. Consequently, the 3-phase side also presents a certain level of imbalance as well. A co-phase power supply was proposed as a solution. The real application of such system is gradually expanding, proving the effectiveness of the system. In this paper, the application of the single phase D-Q rotating frame theory was applied to the control of the co-phase power supply system. In addition, the power stack of the system was composed of MMC valves, which offers superior operational characteristics. The effectiveness of the system was verified with a real-time simulation, and the results are presented.

• Journal of Electrical Engineering and Technology
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• 제8권5호
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• pp.1107-1115
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• 2013

A new PWM technique for a two-phase BLDC motor fed by a two-phase eight-switch inverter is proposed in this paper. It is well known that a two-phase eight-switch inverter can significantly improve power output compared with a two-phase six-switch inverter in a two-phase motor drive. To drive the two-phase BLDC motor simply and effectively, two normal PWM strategies are investigated to manage speed regulation. However, under the conditions of low speed and light load, especially during the braking process, the current in a short time of one period is near zero, which is a discontinuous waveform every half period. To solve it, a novel PWM technique is investigated to improve the operational performance of normal technique. Using the new PWM scheme, the current continues every half period and the braking performance is improved. The effectiveness of the proposed PWM method is verified through the experiments.

• 한국가스학회지
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• 제10권4호
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• pp.1-5
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• 2006

가스 소비의 급증으로 천연가스의 수송수단인 배관의 역할이 증가하고 있다. 일반적으로 배관으로 가스를 수송할 경우, 주로 컨덴세이트 형성에 기인하는 일부 액체가 관내에 형성되어 가스 산업현장에서 복잡한 조업 상의 문제점을 발생시킨다. 그러므로, 가스 컨덴세이트의 존재가 조업 효율에 미치는 영향을 예측할 수 있는 적절한 방법이 필요하다. 본 연구에서는 통합된 단상/2상 유동개념을 사용하여 가스 컨덴세이트의 발생 시작점과 그 발생량의 영향이 출구 압력에 미치는 영향을 분석할 수 있는 통계 모델을 개발하였다. 또한 컨덴세이트 발생 시작점 이후, 2상 유동지역에서 유동형태의 변화가 출구 압력에 미치는 영향도 분석되었다.

• 전기학회논문지
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• 제65권9호
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• pp.1597-1604
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• 2016

The speed at which the SRM (Switched Reluctance Motor) makes a transition from chopping control to single pulse operation. (i.e., low speed to high speed operation). It is unsatisfied with performance at all operational regimes. In this paper, the operational performance of SRM can be improved by using current hysteresis control method. This method maintains a generally flat current waveform. At the high speed, the current chopping capability is lost due to the development of the back-EMF. Therefore SRM operates in single pulse mode. By using zero-current switching and zero-voltage switching technique, the stress of power switches can be reduce in chopping mode. When the commutation from one phase winding to another phase winding, the current can be zero as fast as possible in this period because several times negative voltage of DC-source voltage produce in phase winding. This paper is compared to performance based on energy efficient C-dump converter topology and the proposed resonant C-dump converter topology. Simulation and experimental results are presented to verify the effectiveness of the proposed circuit.

• Journal of Electrical Engineering and Technology
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• 제12권4호
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• pp.1471-1483
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• 2017

The low-frequency characteristics of four-switch three-phase (FSTP) inverter are investigated in this paper. Firstly, a general space vector pulse width modulation (SVPWM) directly involved the neutral point voltage of DC-link is proposed, where no sector identifications and trigonometric function calculations are needed. Subsequently, to suppress the DC offset in the neutral point voltage, the relationship between the neutral point voltage and the ${\beta}-axis$ component of the load current is derived, and then a new neutral point voltage control scheme is proposed where no low pass filter is adopted. Finally, the relationship between the load power factor and the maximum linear modulation index of the FSTP inverter is revealed. Since the operational region for the FSTP inverter in low frequency is reduced by the enlarged amplitude of the neutral point voltage, a linear modulation range enlargement scheme is proposed. A permanent magnet synchronous motor with preset rotary speed serves as the low-frequency load of the FSTP inverter. Experimental results verify that the new neutral point voltage control scheme is effective in the deviation suppression of the neutral point voltage, and the proposed scheme is able to provide a larger linear operational region in low frequency.