• Proceedings of the Korea Information Processing Society Conference
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• 2000.10b
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• pp.1405-1408
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• 2000

소프트웨어의 사용자층이 확대되면서 소프트웨어는 갈수록 많은 기능을 가진 복잡한 시스템이 되고 있다. 사용자의 요구 사항에 부응할 수 있도록 소프트웨어가 대형화되고 복잡해졌으며 이로 인해 품질의 중요성이 더욱 높아지게 되었다. 그러나 다수의 소프트웨어들이 품질관리의 미흡으로 인해 발견되지 못한 오류들을 지닌 채 상품화되고 있는 것이 현실이다. 소프트웨어의 오류를 최소화하기 위해 일반적으로 소프트웨어에 대한 시험 사례를 통해 검증하게 되며 구현 이후, 시험 단계에서 이루어지는 경우가 대부분이다. 그러나 소프트웨어의 오류는 생명주기 전단계에 걸쳐 발생될 수 있으므로 생명주기 전단계에 걸친 적절한 시험을 통해 문제점을 점검하는 것이 고품질의 소프트웨어를 개발하는 최선의 방법이 될 수 있을 것이다. 본 연구에서는 생명주기 단계 중 소프트웨어 구현 단계의 테스트를 위한 시험 측정 항목을 개발하였다.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.3
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• pp.143-152
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• 2002

Frequency is regarded as one of most important indices for the operating power systems. Several digital techniques for measuring frequency have been presented in the last decades. This paper proposes a design and implementation an adaptive scheme using phase angle difference calculation fort frequency measuring in power system. The advantages of the proposed technique are demonstrated by fault signals from EMTP simulation and user defined arbitrary signals by Excel program. The proposed technique is compared with the conventional methods. Performance teat results indicate that the proposed technique provides accurate measures in pretence of noise and harmonics and in case faults and is suitable for measurement near-nominal, nominal. and off-nominal frequencies. We can see that It will be useful in microprocessor based relays and digital metiers that need to measure power system frequency.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.527-533
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• 1998

An optimized PWM switching strategy for an induction motor voltage control is developed and demonstrated. Space vector modulation in voltage source inverter offers improved DC-bus utilization and reduced commutation losses, and has been therefor recognizedas the perfered PWM method, especially in the case of digital implementation. Three-phase invertor voltage control by space vector modulation consists of switching between the two active and one zero voltage vector by using the proposed optimal PWM algorithm. The prefered switching sequence is defined as a function of the modulation index and period of a carrier wave. The sequence is selected by suing the inverter switching losses and the current ripple as the criteria. For low and medium power application, the experimental results indicate that good dynamic response and reduced harmonic distortion can be achieved by increasing switching frequency.

• Proceedings of the KIEE Conference
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• 2005.10a
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• pp.145-149
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• 2005

Frequency is an important operating parameter of a power system. Electric power systems sustain transient frequency swings whenever the balance between generation and load does not no longer hold. To cope with this Constraints, it requires an accurate and high speedy frequency deviation estimation technique and suitable adjustment to obtain the power system energy balance. This paper describes the design, computational aspects and implementation of an iterative technique for measuring power system. The rate change of the phase angle is used for estimation. To confirm the validity of the proposed algorithm, the simulation studies carried out on a typical 154[KV] double T/L system by using EMTP software. Some test results are presented in the paper.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.5
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• pp.575-582
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• 2007

In this paper, a 100 Watt high power amplifier has been implemented and performed evaluation, which is operating at UHF band ($470\;{\sim}\;806\;MHz$) for Digital TV repeater. To achieve increase of bandwidth and high power capability, 3-way power combiner and divider of Wilkinson type was adopted. In order to measure the fabricated 100 Watt power amplifier, the estimation technique function which makes equivalent mask was used. As a result of the measurement, the existence of pilot signal is confirmed and the signal transmitted at the rated output power 100 Watt is brought out the flat feature through 6 MHz bandwidth. and it resulted that its value was less than -47 dB at the edge of radiation channel and less than -110 dB at more than 6 MHz position from channel edge.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.10a
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• pp.141-146
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• 2002

Real-time monitoring and control of the cutting force is essential for unmanned cutting process. Although the cutting force can be measured directly using tool dynamometers, their implementation is not feasible in industry due to high cost. Alternative approach is the cutting force estimation based on spindle drive models, but it requires the knowledge of their characteristics with the spindle speed variation. This paper investigates the power-factor and frictional characteristics of three-phase induction motors and determines its characteristics below and above the base speed, respectively. In order to realize the proposed cutting force monitoring system, a stand-alone DSP board was utilized. Its monitoring and control performance is evaluated in a CNC lathe.

• International Journal of Reliability and Applications
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• v.2 no.4
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• pp.269-280
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• 2001

The objective of this paper is to provide a model for effective implementation of costing RAM management in the design and procurement of production facility considering the system cost-performance trade-off. This research proposes a two-step approach of costing RAM design and test of system RAM for production facility. In Step 1, a static model is proposed to find an initial system configuration to meet the required performance based on system RAM and LCC and analyzes the trade-off relationships between various factors of RAM and LCC. In the second Step, we developed time and failure truncated models for system reliability test and analysis. For the computational purpose, we developed computer programs and have shown the sample results. By the sample test run, the proposed model has shown the possibilities to provide a good method to analyze system performance evaluation for both design and operational phase, This model can be applied to a wide variety of systems not only for costing RAM of the production facilities but also for the other kinds of equipment.

• Proceedings of the KSR Conference
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• 2005.11a
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• pp.258-263
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• 2005

The purpose of this research is to present a practical method for efficiently monitoring a reliability growth process using AMSAA(Army Materiel Systems Analysis Activity) reliability growth model. The presented method is viable for identifying failure modes, incorporating design changes and monitoring reliability progress on an on-going basis during the early stages of a product development program. According to the Application Guide for EN 50126(RAM part for Rolling Stock), reliability growth monitoring is essential part of the main tasks of design phase in RAM growth monitoring. Implementation of reliability growth management program will provide very useful information on concept selection, product/process reliability, and cost effectiveness without too much time, money and engineering effort being spent on the development of failure suspect parts.

• Proceedings of the IEEK Conference
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• 2001.06e
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• pp.165-168
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• 2001

In this W the complexity of implementation is reduced by the reduction into half of the number of the multiplier in filter structure of the conventional carrier recovery loop, and as the drawback of NCO of the conventional carrier recovery loop wastes a amount of power for the structure of lookup table, We designed the structure of combinational logic without the lookup table. In the comparison with dynamic power of the proposed NCO, the power of NCO with the lookup table is 175${\mu}$W, NCO with the proposed of structure is 24,65${\mu}$W. As if result, it is recognized that about one eight of loss power is reduced In the simulation of carrier recovery loop designed QPSK demodulator, it is known that the carrier phase is compensated.

• The Journal of the Acoustical Society of Korea
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• v.17 no.8
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• pp.103-109
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• 1998

디지털신호의 변조에는 기본적으로 진폭 편이 변조(ASK: Amplitude-Shift Keying), 주파수 편이 변조(FSK: Frequency-Shift Keying), 위상 편이 변조(PSK: Phase-Shift Keying) 등의 세 가지 방법이 있다. 본 논문에서는 표본클록 합성계수 방식에 관한 이론을 고찰하고, 클록초기치 누적방식의 DDFS를 이용하여 위에서 언급한 변조방법을 실현할 수 있는 주파수 도약 대역 확산 통신에 적합한 변조기를 구현하였다. 또한, 합성된 출력주파수 의 정현파형에 대한 스펙트럼 분석과 PN(Pseudo Noise) 부호를 사용한 순시적인 주파수 도 약 상태, 위상제어의 가능성 등을 확인한 결과 실험으로부터 다음과 같은 결과를 얻었다. 첫 째, 합성된 출력주파수는 주파수 Index에 따라 기준주파수에 정확히 정수배가 되며, 둘째, 합성된 정현파형의 스펙트럼으로 기본파와 여러 고조파의 크기를 비교하여 본 결과 50[dB] 이상의 차이가 남으로서 고조파 성분들이 상당히 감소되었음을 확인하였고, 셋째, PN 코드 를 사용하여 순시적인 주파수 도약 상태를 확인하여 본 결과 스위칭 시간이 빠르기 때문에 주파수 도약 특성이 뛰어남을 알 수 있었으며 또한, 누산기의 set/reset 상태를 변화시킴에 따라 위상이 제어됨을 입증하였다.