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Aeroengine performance degradation prediction method considering operating conditions
Bang-Cheng Zhang,Shuo Gao,Zhong Zheng,Guanyu Hu 한국인터넷정보학회 2023 KSII Transactions on Internet and Information Syst Vol.17 No.9
It is significant to predict the performance degradation of complex electromechanical systems. Among the existing performance degradation prediction models, belief rule base (BRB) is a model that deal with quantitative data and qualitative information with uncertainty. However, when analyzing dynamic systems where observable indicators change frequently over time and working conditions, the traditional belief rule base (BRB) can not adapt to frequent changes in working conditions, such as the prediction of aeroengine performance degradation considering working condition. For the sake of settling this problem, this paper puts forward a new hidden belief rule base (HBRB) prediction method, in which the performance of aeroengines is regarded as hidden behavior, and operating conditions are used as observable indicators of the HBRB model to describe the hidden behavior to solve the problem of performance degradation prediction under different times and operating conditions. The performance degradation prediction case study of turbofan aeroengine simulation experiments proves the advantages of HBRB model, and the results testify the effectiveness and practicability of this method. Furthermore, it is compared with other advanced forecasting methods. The results testify this model can generate better predictions in aspects of accuracy and interpretability.
Network Intrusion Detection Based on Directed Acyclic Graph and Belief Rule Base
Bang-Cheng Zhang,Guan-Yu Hu,Zhi-Jie Zhou,You-Min Zhang,Pei-Li Qiao,Lei-Lei Chang 한국전자통신연구원 2017 ETRI Journal Vol.39 No.4
Intrusion detection is very important for network situation awareness. While a few methods have been proposed to detect network intrusion, they cannot directly and effectively utilize semi-quantitative information consisting of expert knowledge and quantitative data. Hence, this paper proposes a new detection model based on a directed acyclic graph (DAG) and a belief rule base (BRB). In the proposed model, called DAG-BRB, the DAG is employed to construct a multi-layered BRB model that can avoid explosion of combinations of rule number because of a large number of types of intrusion. To obtain the optimal parameters of the DAG-BRB model, an improved constraint covariance matrix adaption evolution strategy (CMA-ES) is developed that can effectively solve the constraint problem in the BRB. A case study was used to test the efficiency of the proposed DAG-BRB. The results showed that compared with other detection models, the DAG-BRB model has a higher detection rate and can be used in real networks.
Study of processing adsorption mechanism of amphoteric polyelectrolyte in BaTiO3 colloids suspension
Wen-Cheng J. Wei,Bang-Ying Yu,Kung-Chung Hsu 한양대학교 세라믹연구소 2004 Journal of Ceramic Processing Research Vol.5 No.2
An amphoteric dispersant, copolymer (α-N,N-dimethyl-N-acryloyloxyethyl) ammonium ethanateacrylamide (PAAM/DAAE), was used for the dispersion of BaTiO3 (BT) colloids in an aqueous solution, and compared to a commercial acrylic- based polymeric dispersant, ammonium salt of polymethylacrylic acid (PMAA-NH4). Several properties, including surface potential, sedimentation height ratio, green density, and Ba2+ dissolution from the particle surface were studied. Due to the branch structure of PAAM/DAAE and more importantly the amphoteric functional groups of PAAM/DAAE, the macromolecules adsorbed on BT in much higher concentration (up to 7 mg/g) and limited the dissolution of Ba2+ ions from the BT surface. Strong steric repulsion between BT particles with PAAM/DAAE resulted in a good dispersion of fine particles and greater packing density in the green state than that of PMAA-NH4. The adsorption mechanism and interactions among BT, dispersants, and H2O are reported.
Correlation between crystallinity and resistive switching behavior of sputtered WO3 thin films
Thi Bang Tam Dao,Kim Ngoc Pham,Yi-Lung Cheng,김상섭,Bach Thang Phan 한국물리학회 2014 Current Applied Physics Vol.14 No.12
The as-depositedWO3 thin films were post-annealed at different temperatures (300 C and 600 C) in air to investigate a correlation between crystallinity and switching behavior of WO3 thin films. Associating the results of XRD, FTIR, XPS and FESEM measurements, the annealing-caused crystallinity change contributes to the variation of the switching behaviors of theWO3 thin films. The as-depositedWO3 films with low crystalline structure are preferred for random Ag conducting path, resulting in large switching ratio but fluctuating IeV hysteresis, whereas the annealedWO3 films with crystallized compact structure limits Ag conducting path, favoring the stable IeV hysteresis but small switching ratio. It is therefore concluded that electrochemical redox reaction-controlled resistance switching depends not only on electrode materials (inert and reactive electrodes) but also on crystallinity of host oxide.
Colloidal processing of Pb(Zr,Ti)O3, Part I-Pb dissolution
Wen-Cheng J. Wei,Wen-Ting Hsu,Bang-Ying Yu 한양대학교 세라믹연구소 2006 Journal of Ceramic Processing Research Vol.7 No.3
The dissolution behavior of aqueous Pb(Zr,Ti) O3(PZT) suspensions were studied by Atomic Adsorption (AA) and Inductively Coupling Plasma (ICP) spectroscopies, specially emphasizing the change of solution acidity within pH 2 to 12, the effects of polymeric dispersant, and comparing with the dissolution behavior of PbO. The iso-electric-point (IEP) of a 2.0 wt % PZT solution was measured and compared to the minimal dissolution case (less than 10 ppm) to be in the range of pH 7 to 10. The effects of one dispersants, poly (α-N,N-dimethyl-N-acryloxyethyl) ammonium ethnate acrylamide (PMAA/DAAE) was investigated in comparison with a commercial anionic dispersant, an ammonium salt of polymethylacrylic acid (PMAAN). A possible dissolution model and the thickness of the Pb depletion zone on PZT particles are proposed based on the experimental observation. The dissolution behavior of aqueous Pb(Zr,Ti) O3(PZT) suspensions were studied by Atomic Adsorption (AA) and Inductively Coupling Plasma (ICP) spectroscopies, specially emphasizing the change of solution acidity within pH 2 to 12, the effects of polymeric dispersant, and comparing with the dissolution behavior of PbO. The iso-electric-point (IEP) of a 2.0 wt % PZT solution was measured and compared to the minimal dissolution case (less than 10 ppm) to be in the range of pH 7 to 10. The effects of one dispersants, poly (α-N,N-dimethyl-N-acryloxyethyl) ammonium ethnate acrylamide (PMAA/DAAE) was investigated in comparison with a commercial anionic dispersant, an ammonium salt of polymethylacrylic acid (PMAAN). A possible dissolution model and the thickness of the Pb depletion zone on PZT particles are proposed based on the experimental observation.
A Comment on GMM Estimation in IS Research
Ningning Cheng,Youngsok Bang 한국경영정보학회 2019 한국경영정보학회 학술대회논문집 Vol.2019 No.5
As a quick econometric solution to handle potential endogeneity issues in panel data models, the Generalized Method of Moments (GMM) estimator is gaining popularity in IS research. Despite the sensitivity of this estimator to model specifications and estimation strategies, a noticeable number of IS studies employing this method fail to report the detailed model specifications, robustness check results with different model specifications and estimation strategies, or test statistics, which render their empirical results less credible. We demonstrate, based on the dataset used by Arellano and Bond (1991), that passing the commonly required tests such as the m2 test and the Sargan-Hansen test does not guarantee validity of the estimate, because the size and the statistical significance of the estimate can largely depend on the choice of estimation procedure and possible moment restrictions that pass such required tests. We urge researchers not only to report the results of significant focal variables, but also to be explicit about the model specifications and estimation strategies, and to provide robustness checks with different model specifications, along with their complete test results.