• Journal of Information Technology Applications and Management
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• 제12권4호
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• pp.133-155
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• 2005

This Paper makes an attempt to suggest a process of automatically generating application software based on the Entity-Relationship model 1. The designer develops an E-R model of an real-world system. 2. The designer inputs the entity and relationship types, and attributes shown in the E-R model, and also the basic operations of the application system to the software generator. 3. The application generator produces database schema and link information between application programs, and then automatically generates a stereo-type application system. In order for the automated application generator to build the application system in a systematic way, four basic program generation rules have been suggested. A set of computer programs have been developed in order to show the applicability of the automated software generation process suggested in this paper. By following each rule with the generator, the designer can build an application in an efficient manner compared with traditional (manual programming) approaches. It has been demonstrated from the case study that the idea of applying an automated generator in systems development based upon the E-R model is feasible.

• Journal of Power Electronics
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• 제18권5호
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• pp.1577-1584
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• 2018

The content of harmonic current increases with an increase in the number of power electronic devices in power grid. When a generator is directly connected to the power grid through a step-up transformer, the influence of the harmonic currents on the generator is inevitable. To study the influences of harmonics on generators, a 24-MW bulb tubular turbine generator is taken as an example in this paper. A 2-D transient electromagnetic field model is established. Through a comparative analysis of the data of experiments and simulations, the correctness of the model is verified. The values of the air gap magnetic density, torque and losses of the generator under various conditions are calculated using the finite element method. Taking the rated condition as a reference, the influence of the harmonic currents on the magnetic flux density is analyzed. It is confirmed that the time harmonic is a key factor affecting the generator performance. At the same time, the effects of harmonic currents on the torque ripple, average torque and eddy current loss of the generator are studied, and the mechanism of the variation of the eddy current loss is also discussed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.250-255
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• 2007

Steam generator tubes play an important role in safety because they constitute one of the primary barriers between the radioactive and non-radioactive sides of the nuclear power plant. For this reason, the integrity of the tubes is essential in minimizing the leakage possibility of radioactive water. The integrity of the tubes is evaluated based on NDE (non-destructive evaluation) inspection results. Especially ECT (eddy current test) method is usually used for detecting the flaws in steam generator tubes. However, detection capacity of the NDE is not perfect and all of the "real flaws" which actually existing in steam generator tunes is not known by NDE results. Therefore reliability of NDE system is one of the essential parts in assessing the integrity of steam generators. In this study POD (probability of detection) of ECT system for ODSCC in steam generator tubes is evaluated using multivariate logistic regression. The cracked tube specimens are made using the withdrawn steam generator tubes. Therefore the cracks are not artificial but real. Using the multivariate logistic regression method, continuous POD surfaces are evaluated from hit (detection) and miss (no detection) binary data obtained from destructive and non-destructive evaluation of the cracked tubes. Length and depth of cracks are considered in multivariate logistic regression and their effects on detection capacity are evaluated.

• 한국지진공학회논문집
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• 제7권2호
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• pp.85-92
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• 2003

본 논문에서는 교량의 건전도 감시용 자립형 계측유닛을 위한 교량의 상시진동을 이용한 진동발전시스템을 제시하였다. 본 연구에서는 전기자 반작용의 영향을 최소화한 새로운 구조의 진동발전기를 제안하고, 기계적 및 전기적인 설계식을 유도한 다음, 시험용 진동발전기를 제작하였다. 또한, 매우 작은 발전 전류의 축전시스템에 대하여 고찰하고 개선점을 도출하였다. 축전시스템에 대한 고찰 결과, 정류기에 사용된 다이오드 특성이 충전과정에서 지배적임을 밝혔다. 마지막으로, 진동발전시스템 모델에 실측 남해대교 가속도 데이터를 적용한 시뮬레이션과 실내 실험을 수행하였고, 제작된 시험용 진동발전기의 적용성과 효용성을 확인할 수 있었다.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2007년도 추계학술대회 논문집
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• pp.199-201
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• 2007

This paper presents the installation of measuring system for the transient behaviors of grounding system impedances using portable impulse current generator. The measuring system is controller, with controller, power supply, impulse current generator and data aquisition system. In the evaluation of the impulse response in a ground electrode, the step response is calculated based on the ratio of the voltage and current observed.

• 전기학회논문지
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• 제58권4호
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• pp.688-693
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• 2009

The response characteristics of power system frequency are determined by generator droop characteristics and load damping properties. The characteristics of governor droops are termed by generators constant, while those of load damping by load constant. In this paper, the generator constant and the load constant are assessed by measured data at the event of generator trips.

• Journal of Mechanical Science and Technology
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• 제14권6호
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• pp.590-596
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• 2000

Cause of excessive vibration with twice the rotational speed of a two-pole generator rotor for the fossil power plants was investigated. The two-pole generator rotor, treated as a typically asymmetric rotor in vibration analysis, produces asynchronous vibration with twice the rotational speed, sub-harmonic critical speeds, and potentially unstable operating zones due to its own inertia and/or stiffness asymmetry. This paper introduces a practical balancing procedure, and presents the results of the investigation on sources of the excessive vibration based on the experimental vibration data of the asymmetric two-pole rotor in balancing.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1989년도 하계종합학술대회 논문집
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• pp.221-225
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• 1989

Direct calculation algorithm for the elements of A matrix in multimachine power systems with constant impedance loads has been suggested. Generator's rotor parameters need not be determined from the manufacturer's data. We can identify the elements of A matrix into two categories: One is related to only generator parameters, and the other is related to generator parameters, initial values, and $Z_{Bus}$ matrix.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 추계종합학술대회 논문집
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• pp.693-696
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• 1999

This paper presents an analysis of the chaotic behavior in the discrete-time chaotic generator fabricated by CMOS technology. An approximated empirical equation is extracted from the measurement data of a nonlinear function block. Then the bifurcation diagram and Lyapunov exponent and time waveforms and frequency responses of the chaotic generator are calculated and simulated. And results of experiments in the chaotic circuit with the $\pm$2.5V power supply and clock rate of 10KHz are shown, and analysed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.2050-2051
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• 2007

As a fundamental investigation to develop a sensor which is able to detect shorted turn phenomenon of generator rotor, we have experimented with self-made sensor using flux generator and high-resolution oscilloscope. We have recorded sensor-induced voltage according to the different condition, such as variations of turn, diameter and length of sensor. Based on the acquired data, we analyzed and simulated under similar circumstances of actual spot to maximize reliability. We have a plan to invest more resources to supply power plants with the developed sensor for ourselves.