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- 저자 : Awwal, Rayhana (검색결과 4 건)
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Awwal Mohammed Arigi,김강민,박주영,김종현 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.1
Since the Fukushima Daiichi accident, there has been an emphasis on the risk resulting from multi-unitaccidents. Human reliability analysis (HRA) is one of the important issues in multi-unit probabilisticsafety assessment (MUPSA). Hence, there is a need to properly identify all the human and organizationalfactors relevant to a multi-unit incident scenario in a nuclear power plant (NPP). This study identifies andcategorizes the human and organizational factors relevant to a multi-unit incident scenario of NPPsbased on a review of relevant literature. These factors are then analyzed to ascertain all possible unit-tounitinteractions that need to be considered in the multi-unit HRA and the pattern of interactions. Thehuman and organizational factors are classified into five categories: organization, work device, task,performance shaping factors, and environmental factors. The identification and classification of thesefactors will significantly contribute to the development of adequate strategies and guidelines for managingmulti-unit accidents. This study is a necessary initial step in developing an effective HRA methodfor multiple NPP units in a site.
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Mohammad Awwal Adeshina,Jonghoo Park,마레디바라쓰쿠마르,강대경,Bongjun Choi 한국센서학회 2019 센서학회지 Vol.28 No.6
Liquid crystal (LC) mesophase materials manifest a variety of phase transitions. The optical properties of LCs are highly dependent upon the phase and orientation of the optical axis with respect to the polarization of incoming light. Studying the LC phase transitions is significantly important for a wide range of scientific and industrial applications. In this study, we demonstrate the propagation velocity of the phase boundary between the nematic and isotropic phase of 4-Cyano-4-pentylbiphenyl (5CB) liquid crystal for different electric fields using a polarized optical microscope. The results demonstrate that the propagation velocity of the phase boundary exhibits a peak value for a specific voltage, attributed to the supercooling of the isotropic phase of the LC. The analysis of the propagation velocity for different electric fields also provides a simple optical platform to measure the thermal anisotropy and voltage dependent thermal properties of the homogeneously aligned LC
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Treatment of human and organizational factors for multi-unit HRA: Application of SPAR-H method
Park, Jooyoung,Arigi, Awwal Mohammed,Kim, Jonghyun Elsevier 2019 Annals of nuclear energy Vol.132 No.-
<P><B>Abstract</B></P> <P>Human reliability analysis (HRA) refers to a method for evaluating human errors and providing human error probabilities for application in probabilistic safety assessments (PSAs). Since the Fukushima accident, HRA has been considered an important issue in multi-unit PSAs. However, existing HRA methods generally focus on the analysis of human errors in single-unit PSAs, while HRA methods for the multi-unit PSA have not been well established. If an accident occurs that influences more than one unit, the human and organizational factors due to the formation of accident management organizations, the use of shared or mobile equipment, and the influence of a severe accident on another unit may have a crucial impact on the plant safety and the result of the PSA. Therefore, issues have been raised regarding the analysis and evaluation of the human and organizational factors in a multi-unit HRA.</P> <P>This study aims to develop an approach to treat the human and organizational factors for a multi-unit HRA on the basis of Standardized Plant Analysis Risk HRA (SPAR-H) method. This approach is applicable to level 1, 2, and 3 PSA. Firstly, six multi-unit task types were considered based on a previous study that identified and categorized human and organizational factors for multi-unit HRA. Secondly, a task analysis considering HRA event tree analysis, suggested by Technique for Human Error Rate Prediction (THERP), and a timeline analysis were performed for six multi-unit task types. Thirdly, to identify the challenges of the existing SPAR-H method for multi-unit task types, an evaluation of the applicability of the existing SPAR-H method was conducted by qualitative and quantitative analyses. In addition, the dependence assessment approach suggested in the existing SPAR-H was also evaluated in terms of multi-unit situations. Lastly, by treating the multi-unit challenges identified in the previous section, methods to 1) analyze six multi-unit task types and 2) evaluate the dependence between the operator actions were suggested with some examples. The study is expected to contribute to the estimation and calculation of human error probabilities for applications in multi-unit PSAs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A multi-unit HRA approach was suggested on the basis of SPAR-H method. </LI> <LI> A wide range of literature and actual practices in emergency response of Korean NPPs have been reviewed. </LI> <LI> Challenges in applying existing SPAR-H to multi-unit HRA were identified. </LI> <LI> A method to analyze multi-unit tasks and dependency between operator’s actions was suggested. </LI> </UL> </P>
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Phase-based direct average strain estimation for elastography
Ara, Sharmin R.,Mohsin, Faisal,Alam, Farzana,Rupa, Sharmin Akhtar,Soo Yeol Lee,Hasan, Md Kamrul,Awwal, Rayhana IEEE 2013 and Frequency Control Vol.60 No.11
<P>In this paper, a phase-based direct average strain estimation method is developed. A mathematical model is presented to calculate axial strain directly from the phase of the zero-lag cross-correlation function between the windowed precompression and stretched post-compression analytic signals. Unlike phase-based conventional strain estimators, for which strain is computed from the displacement field, strain in this paper is computed in one step using the secant algorithm by exploiting the direct phase-strain relationship. To maintain strain continuity, instead of using the instantaneous phase of the interrogative window alone, an average phase function is defined using the phases of the neighboring windows with the assumption that the strain is essentially similar in a close physical proximity to the interrogative window. This method accounts for the effect of lateral shift but without requiring a prior estimate of the applied strain. Moreover, the strain can be computed both in the compression and relaxation phases of the applied pressure. The performance of the proposed strain estimator is analyzed in terms of the quality metrics elastographic signal-to-noise ratio (SNRe), elastographic contrast-to-noise ratio (CNRe), and mean structural similarity (MSSIM), using a finite element modeling simulation phantom. The results reveal that the proposed method performs satisfactorily in terms of all the three indices for up to 2.5% applied strain. Comparative results using simulation and experimental phantom data, and in vivo breast data of benign and malignant masses also demonstrate that the strain image quality of our method is better than the other reported techniques.</P>
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