• 열처리공학회지
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• 제7권3호
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• pp.155-159
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• 1994

As Cr-Mo-V steels have excellent mechanical and creep properties at elevated temperatures, they are extensively used in power plants. However, the steam turbine components are supposed to have suffered material degradation during long-term service at elevated tenperatures. Many efforts have been made to assess the safety and residual life of these components by means of non-destructive methods such as plastic replication, hardness and electric resistance techniques. Recently, a parameter correlating hardness changes during long-term heating to those during creep was introduced and it was named 'G parameter'. The electric resistivity as well as hardness are affected by damage accumulation, but there have been no efforts to correlate G parameter to resistivity changes. In this study, relationship between G parameter and changes in electric resistivity was investigated using artificially aged Cr-Mo-V steel. It is well understood that G parameter can be applied to electric: resistance techmique.

• 전기전자학회논문지
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• 제25권4호
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• pp.689-696
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• 2021

본 논문에서는 고장예측진단 및 건전성 관리 기법(Prognostics and Health Management, PHM)을 적용하기 위해 해당 시스템 혹은 회로 내부에서 결함특성을 감지하고 예측할 수 있는 회로 구조를 제안하였다. 기존 연구에서 회로 결함의 진행에 따라, S-parameter 크기 최소값의 주파수가 변화하는 것을 확인하였다. 이러한 특성을 기존에는 네트워크 분석기(Network Analyzer)를 활용하여 측정하였으나, 본 연구에서는 같은 결함검출기법을 활용하더라도 큰 계측장비 없이 결함의 진행상황 및 잔여 수명, 결함발생 여부를 확인할 수 있는 소형화된 회로를 설계하였다. 본 연구에서는 S-parameter의 변화를 야기하는 임피던스의 변화를 감지할 수 있도록 회로를 설계하였으며, Bond-wire의 온도반복에 따른 S-parameter 변화 측정결과를 제안하는 회로에 적용하였다. 이를 통해 해당 회로가 Bond-wire의 결함을 감지할 수 있다는 것을 성공적으로 검증하였다.

• Journal of Mechanical Science and Technology
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• 제18권12호
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• pp.2158-2173
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• 2004

In this paper, the higher order terms in the crack tip stress fields are investigated macroscopically for more realistic assessment of structural material behaviors. For reactor pressure vessel material of A533B ferritic steel, effects of crack size and temperature have been evaluated using 3-point SENB specimens through a series of finite element analyses, tensile tests and fracture toughness tests. The T-stress, Q-parameter and q-parameter as well as the K and J-integral are calculated and mutual relationships are investigated also. Based on the evaluation, it has proven that the effect of crack size from standard length (a/W=0.53) to shallow length (a/W=0.11) is remarkable whilst the effect of temperature from -20$^{\circ}C$ to -60$^{\circ}C$ is negligible. Finally, the cleavage fracture toughness loci as a function of the promising Q-parameter or q-parameter are developed using specific test results as well as finite element analysis results, which can be applicable for structural integrity evaluation considering constraint effects.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.222-227
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• 2001

Nonlinear acoustic effect has been considered as an effective tool for the evaluation of material degradation. In this paper, the applicability of nonlinear acoustic effect to the evaluation of degradation of 2.25Cr-1Mo steel is investigated. Firstly, a number of 2.25Cr-1Mo steel samples were heat-treated, and their damage mechanism was examined. Secondly, Ultrasonic nonlinear parameter was measured. Nonlinear acoustic parameter was found to be clearly sensitive to the material degradation.

• Journal of Mechanical Science and Technology
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• 제18권1호
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• pp.55-64
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• 2004

Many researchers have made a lot of progress in studying the evaluation of fracture probability of brittle materials. However, studies of fracture probability for elastic-plasticity have not been made yet. An evaluation method for fracture probability which is grafted onto a 2-parameter criterion and statistical probability analysis is not only introduced in this study, but also applied to the simple 2-dimensional model and carbon steel piping to vealuate the effect of statistical variables.

• 한국정밀공학회지
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• 제11권4호
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• pp.126-137
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• 1994

Performance management of computer networks is intended to improve a given network performance in order for more efficient information exchange between subsystems of an integrated large-scale system. Importance of perfomance management is growing as many functions of the large- scale system depend on the quality of communication services provided by the network. The role of performance management is to manipulate the adjustable protocol parameters on line so that the network can adapt itself to a dynamic environment. This can be divided into two subtasks : performance evaluation to find how changes in protocol parameters affect the network performance and decision making to determine the magnitude and direction of parameter adjustment. This paper is the first part of the two papers focusing on conceptual design, development, and evaluation of performance management for token bus networks. This paper specifically deals with the task of performance evaluation which utilizes the principle of perturbation analysis of discrete event dynamic systems. The developed algorithm can estimate the network performance under a perturbed protocol parameter setting from observations of the network operations under a nominal parameter setting.

• 한국CDE학회논문집
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• 제20권1호
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• pp.11-21
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• 2015

Currently, the United States, the United Kingdom, Australia etc. are actively utilizing energy simulation for efficiency evaluation of building energy. However, domestic energy efficiency assessment system doesn't use energy simulation system properly at present: parameters based architecture plans and Ashrae Standard are inputted for the evaluation, because the input parameters for the simulation haven't been established yet. This fact causes poor reliability during energy simulation, as the values of the two standards are different from each other. Therefore, the aim of the study is to set domestic standard parameter for BIM-based energy performance evaluation, focusing on possession area per person of occupants at government office in Korea. We found that the difference among the result values occurred approximately 3% in the energy simulation. As a result of the analysis, possession area per person of occupants in Government office is $31.87m^2$. Other input parameters may be set based on this. This will increase the reliability of energy simulation through a domestic standard parameter.

• 대한전기학회논문지:시스템및제어부문D
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• 제52권12호
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• pp.702-707
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• 2003

This study describes a new technique for human sensibility evaluation using electroencephalogram(EEG). Production of EEG is assumed to be linear. The linear predictor coefficients and the linear cepstral coefficients of EEG are used as the feature parameters of sensibility and pattern classification performances of them are compared. Using the better parameter, a human sensibility evaluation algorithm is designed. The obtained results are as follows. The linear predictor coefficients showed the better performance in pattern classification than the linear cepstral coefficients. Then, using the linear predictor coefficients as the feature parameter, a human sensibility evaluation algorithm is developed at the base of a multi-layer neural network. This algorithm showed 90% of accuracy in comfortableness evaluation in spite of fluctuations in statistics of EEG signal.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2005년도 학술발표회 논문집
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• pp.292-299
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• 2005

This paper presents evaluation of seismic design code for AASHTO, Eurocode 8, NZS 3101, and ATC-32 and influence of parameter such as confinement steel ratio, axial force ratio, aspect ratio and longitudinal steel ratio. These seismic design code prescribe confinement steel ratio for appropriate seismic performance which is considered various design parameter. But there is doubt that these parameters are considered rationally in seismic design code. The object of this research is rational evaluation of seismic performance by analysis of existing related experimental research. According to this research, most influence parameter of seismic performance is axial force ratio.

• International Journal of Computer Science & Network Security
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• 제21권7호
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• pp.93-102
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• 2021

This study aimed to test method on the accuracy of estimating the items parameters and ability, using the Three Parameter Logistic. To achieve the objectives of the study, an achievement test in chemistry was constructed for third-year secondary school students in the course of "natural sciences". A descriptive approach was employed to conduct the study. The test was applied to a sample of (507) students of the third year of secondary school in the "Natural Sciences Course". The study's results revealed that the (EAP) method showed a higher degree of accuracy in the estimation of the difficulty parameter and the abilities of persons higher than the MML method. There were no statistically significant differences in the accuracy of the parameter estimation of discrimination and guessing regarding the difference of the two methods: (MML) and (EAP).