Defect diagnostics of gas turbine engine using hybrid SVM-ANN with module system in off-design condition

A hybrid method of an artificial neural network (ANN) and a support vector machine (SVM) has been used for a health monitoring algorithm of a gas turbine engine. The method has the advantage of reducing learning data and converging time without any loss of estimation accuracy, because the SVM classifies the defect location and reduces the learning data range. In off-design condition, however, the operation region of the engine becomes wide and the nonlinearity of learning data increases considerably. Therefore, an improved hybrid method with the module system and the advanced SVM has been suggested to solve the problems. The module system divides the whole operating region into reasonably small-sized sections, and the advanced SVM has two steps of the classification. The proposed algorithm has been proven to reliably and effectively diagnose the simultaneous defects of the triple components as well as the defects of the single and dual components of the gas turbine engine in off-design condition. This paper was recommended for publication in revised form by Associate Editor Tong Seop Kim Tae-Seong Roh received his B.S. and M.S. degrees in Aeronautical Engineering from Seoul National University in 1984 and 1986. He then went on to receive his Ph.D. degree from Pennsylvania State University in 1995. Dr. Roh is currently a Professor at the department of Aerospace Engi-neering at Inha University in Incheon, Korea. His research interests are in the area of combustion instabilities, rocket and jet propulsions, interior ballistics, and gas turbine engine defect diagnostics. Dong-Whan Choi received his B.S. degree in Aeronautical Engineering from Seoul National University in 1974. He then went on to receive his M.S. and Ph.D. degrees from University of Washington in 1978 and 1983. Dr. Choi served three years as a President of Korea Aerospace Research Institute from 1999. He is currently a professor at the department of Aerospace Engineering at Inha University in Incheon, Korea. His research interests are in the area of turbulence, jet propulsions, and gas turbine defect diagnostics.     

Micro-capacitors based on electrochemically grown vertical arrays of gold nanowires as electrodes

This paper describes the development of micro-capacitors with electrodes based on electrochemically grown vertical gold nanowire arrays. A high aspect-ratio anodized aluminum oxide template integrated on silicon dioxide/silicon substrates was exploited for fabricating a vertical array of nanowires with a high surface to volume ratio. Bismuth ferric oxide thin films were deposited to create high dielectric material between the electrodes using room temperature electrodeposition. This nanofabrication process may be compatible with a complementary metal-oxide-semiconductor (CMOS) process, therefore, this capacitor can be used for protecting and regulating the surge voltage biased to the CMOS circuits. This capacitor achieved a high density capacitance of 3.1 μF/m² at 1 MHz, which was measured using a parallel plate set-up.     

Investigating the reliability of second-order formative measurement in information systems research

Recently, a few studies empirically explored the stability of first-order formative measurement, and raised concerns with its estimation reliability. Interpretational confounding, the disparity in the nominal and empirical meaning of a formatively measured construct, is at the center stage of the concern. Our study examines the issue in the context of the higher-order abstraction, focusing on the formatively defined relationship between the second-order construct and its indicators (i.e., first-order latent variables). Although the second-order formative abstraction is a widely accepted practice in structural equation modeling, the estimation results have been given a blind faith with no attempt to evaluate their integrity. Our empirical test, therefore, constitutes an attempt to fill the void. This study observed moderations of the theoretical relationship between reflectively designed first-order constructs and formatively defined second-order constructs when there is a change of endogenous variables. For this, two different formatively defined second-order constructs (i.e., IT management capabilities and IT personnel expertise) are utilized for the empirical testing. The estimation reveals that, while there was a considerable moderation of weights between IT management capabilities and its first-order constructs, those between IT personnel expertise and its first-order constructs remained relatively stable. These results demonstrate that the formatively defined relationship between the first- and second-order constructs can be precarious depending on the choice of the dependent variables. The analysis, therefore, revealed a significant presence of interpretational confounding and a higher chance of Type 1 error in model estimation. This implies that it becomes difficult to retain the construct validity and external validity of a formatively defined second-order construct. Thus, researchers are encouraged to exercise caution in mobilizing the formatively defined second-order measurement.     

Design of thermal imprinting system with uniform residual thickness

A new thermal imprinting system for the printed circuit boards (PCBs) with both large areas and fine conducting lines was developed adopting hot airs with a high pressure. Several small nickel stamps were used to cover the large area, and the stamps were replicated from an electroforming process, in addition, a vacuum jig was utilized to avoid bubbles captured in resins or imprinted interfaces. Stefan’s equation was used to estimate residual thicknesses of the imprinted resins, and effects of imprinting conditions on the residual thickness were investigated from numerical analyses to confirm process profiles and specifications of the developed equipment. The results show that the developed imprinting system can remarkably improve the uniformity of the residual thickness after imprinting, as compared with those of the conventional press, in spite of the thickness difference between the used stamps.     

Numerical and experimental studies on characteristic surface temperature variations of aluminum plates facing different directions

This paper is a part of the work in developing a software that predicts IR signatures from objects in the scene by considering the direct and diffuse solar irradiations, the atmospheric convection and the conduction within objects. The thermal information of the objects and their background is essential for understanding the IR signature characteristics from the scene. The thermal contrast between the objects and the background is then used to obtain their infrared radiation contrast which is the important signal in identifying the objects. We considered the composite heat transfer modes including conduction, convection and spectral solar irradiation on the objects within a scene to calculate the surface temperature distribution. The radiative energy components included in the thermal analyses are consisted of the direct and diffuse solar irradiances and sky thermal irradiation, while the thermal conduction within the object is approximated as one-dimensional heat transfer into the depth. The measured diurnal surface temperature variations on the three different test plates facing east, south and west respectively are fairly well compared with the modeled results obtained from the software developed in this study and a commercial software. A complete set of measured data including the plate temperature together with the detailed weather information and the irradiation data can be valuable reference for future study.     

In-vivo human brain molecular imaging with a brain-dedicated PET/MRI system

Advances in the new-generation of ultra-high-resolution, brain-dedicated positron emission tomography-magnetic resonance imaging (PET/MRI) systems have begun to provide many interesting insights into the molecular dynamics of the brain. First, the finely delineated structural information from ultra-high-field MRI can help us to identify accurate landmark structures, thereby making it easier to locate PET activation sites that are anatomically well-correlated with metabolic or ligand-specific organs in the neural structures in the brain. This synergistic potential of PET/MRI imaging is discussed in terms of neuroscience and neurological research from both translational and basic research perspectives. Experimental results from the hippocampus, thalamus, and brainstem obtained with ¹⁸F-fluorodeoxyglucose and ¹¹C-3-amino-4-(2-dimethylaminomethylphenylsulfanyl)benzonitrile are used to demonstrate the potential of this new brain PET/MRI system.     

Preparation of Pt-loaded TiO2 nanofibers by electrospinning and their application for WGS reactions

Preparation of Pt-loaded TiO₂ nanofibers and their catalytic performance for water gas shift (WGS) reactions have been explained in this work. The Pt-loaded TiO₂ nanofibers were obtained by electrospinning poly-ethylene oxide (PEO) aqueous solutions containing Ti(OH)_n slurry and Pt nanoparticles at room temperature, followed by calcination at 773 K for 4 h. The calcined nanofibers were rougher than the nanofibers of PEO/Ti(OH)_n/Pt due to the PEO degradation and oxidation of Ti(OH)_n to TiO₂. Diameters of the Pt-loaded TiO₂ nanofibers ranged between 200 and 900 nm. Catalytic activity of the Pt-loaded TiO₂ nanofibers for water gas shift (WGS) reactions was evaluated and it was observed that their activity was 5–7 times higher than that of a bulk catalyst. Such improvement is attributed to the larger surface area of the nanofiber catalyst compared to that of the bulk catalyst. To the best of our knowledge, this is the first demonstration of a synthesis of Pt-loaded TiO₂ nanofibers from a Ti(OH)_n nanoparticle slurry using electrospinning and its application to WGS reactions.     

用于低成本高效率离线LED驱动器的视级端调节技术

随着照明行业的不断创新和迅速发展，加之节能和环保日益重要，高亮度（HB）LED已从简单的指示灯演变为超越传统光源的重要照明源。相比其他照明解决方案，HBLED具有数项显著的优势，例如能耗低、寿命长和照明质量高。不过，HBLED要想成功取代普通白炽灯进入大批量市场，其驱动电子装置的成本必须降至最低。