A comparative study of finite element methodologies for the prediction of torsional response of bladed rotors

R. Scheepers,P. S. Heyns 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.9

The prevention of torsional vibration-induced fatigue damage to turbo-generators requires determining natural frequencies by either field testing or mathematical modelling. Torsional excitation methods, measurement techniques and mathematical modelling are active fields of research. However, these aspects are mostly considered in isolation and often without experimental verification. The objective of this work is to compare one dimensional (1D), full three dimensional (3D) and 3D cyclic symmetric (3DCS) Finite element (FE) methodologies for torsional vibration response. Results are compared to experimental results for a small-scale test rotor. It is concluded that 3D approaches are feasible given the current computing technology and require less simplification with potentially increased accuracy. Accuracy of 1D models may be reduced due to simplifications but faster solution times are obtained. For high levels of accuracy model updating using field test results is recommended.

Impeller fault detection under variable flow conditions based on three feature extraction methods and artificial neural networks

A. Jami,P. S. Heyns 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.9

Nonstationary flow conditions can introduce complexities and nonlinear characteristics to pumping systems. This paper presents comparative studies of impeller fault detection techniques combined with artificial neural networks (ANNs) to propose the most appropriate diagnosis system. An experimental study, including seven impeller conditions, is performed to further explore the phenomena. Statistical parameters, frequency peaks, and wavelet packet energy present data feature sets, and a three-layer back-propagation ANN is used for fault recognition. The verification of the results proves that the detectability of the wavelet packet transform (WPT)-ANN model is considerably improved by using the energy of the decomposed vibration from WPT. This model can save computational time and provide superior diagnostic information. This study provides two key contributions. First, the feasibility and effectiveness of common monitoring techniques are compared. Second, the results demonstrate the accuracy of the proposed models for impellers operating under variable working conditions, which has not been previously addressed in the literature.

Fault detection in roller bearing operating at low speed and varying loads using Bayesian robust new hidden Markov model

Henry Ogbemudia Omoregbee,P. Stephan Heyns 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.9

This paper uses Bayesian robust new hidden Markov modeling (BRNHMM) for bearing fault detection and diagnosis based on its acoustic emission signal. A variational Bayesian approach is used that simultaneously approximates the distribution over the hidden states and parameters with simpler distribution hence using Bayesian inference for the estimation of the posterior HMM hyperparameters. This allows for online detection as small data sets can be used. Also, the Kullback-Leibler (KL) divergence is effectively used to access the divergence of the probability function of the BRNHMM, to find its lower bound approximation and by applying a linear transform to the maximum output probability parameter generation (MOPPG). The training set result obtained from BRNHMM is then compared to the result from artificial neural network (ANN) fault detection for same complex system of low speed and varying load conditions which are difficult from a diagnostic perspective, as found in rolling mills.

Study of the Reliability Impact of Chlorine Precursor Residues in Thin Atomic-Layer-Deposited <tex> $\hbox{HfO}_{2}$</tex> Layers

Cho, Moonju,Degraeve, Robin,Pourtois, Geoffrey,Delabie, Annelies,Ragnarsson, Lars-ke,Kauerauf, Thomas,Groeseneken, Guido,De Gendt, Stefan,Heyns, Marc,Hwang, Cheol Seong IEEE 2007 IEEE transactions on electron devices Vol.54 No.4

<P>Atomic layer deposition (ALD) with HfCl<SUB>4</SUB> as a precursor is widely used for HfO<SUB>2</SUB> fabrication. Due to the nature of the precursor under study, i.e., HfCl<SUB>4</SUB> and H<SUB>2</SUB>O, the presence of chlorine residues in the film due to insufficient hydrolysis is eminent. Obviously, the chlorine residue in the HfO<SUB>2</SUB> film is suspected to affect the quality of the HfO<SUB>2</SUB> film. In this paper, The authors reduced the concentration of chlorine residues by increasing the H<SUB>2</SUB>O oxidant pulse time in between the deposition cycles from 0.3 to 10 and 90 s. Time-of-flight secondary ion mass spectrometry analysis shows that this decreases the chlorine concentration in the HfO<SUB>2</SUB> film by more than one order of magnitude. However, time-dependent dielectric breakdown analysis shows that the lifetime remains quasi unaffected (within identical error bars) for the different injection cycles. Charge pumping analysis was done by varying both pulse frequency and amplitude to investigate the creation of defects, but negligible differences were observed. Therefore, the presence of chlorine residues has no significant impact on the trap generation and reliability of ALD HfO<SUB>2</SUB> layers, and this result corresponded with the mobility result. The experimental picture is confirmed with first-principle calculations that show that the presence of chlorine residues does not induce defect levels in the bandgap of HfO<SUB>2</SUB></P>

人間敎育硏究와 開發을 爲한 大學硏究컴퓨터實習室體制에 關한 硏究

金憲洙,孫忠基,李相基 圓光大學校 敎育問題硏究所 1986 敎育硏究 Vol.- No.5

The main purpose of this study is to formulate the new conceptual prototype on the university computer laboratory and practice room system for human education research and development. This study focused its effort on clarifing the value and function of modern scientific and technological devices, such as LAUTOGS, AUTOMAWS, AUTONEWS, TUTOS and LAUSHERDS. 1. LAUTOGS is an integrated dynamic system consisting of hardware, software, and manuals. 2. AUTOMAWS is a sub-system supported by LAUTOGS designed to generate educational manuscripts automatically for use in printed form or on a computer. 3. AUTONEWS is an integrated, multi-purpose personal computer network system which can be utilized conveniently with a little simple training and practice. 4. TUTOS is a means to be used by a student who is ready to engage in learning for mastery by selecting learning tasks suitable for him or her, on the P.C. or E level. 5. LAUSHERDS is a system designed for use in a laboratory for educational research, development and field study. The primary role of this laboratory would be improve LAUTOGS, AUTOMAWS, AUTONEWS, and TUTOS creatively and continuously. In short, they mean an approach which helps learners learn and develop to their utmost and teachers perform their work at their best, in their given situations favorable or unfavorable. The expected results of this study are: 1. To improve the educational environment of teachers and learners by reducing the burdens in performing their work through the use of low cost personal computer systems which have been developed by SSHE in Korea. 2. To contribute to the improvement of research and development in the production and utilization of various educational resources using indigenous personnel and materials. 3. To equalize excellence in education starting with primary mathematics.

서서히 진행하는 치매와 뇌위축을 주소로 내원한 원발성 항인지질 항체 증후군 2예

이창선,김현각,이재홍 대한치매학회 2002 Dementia and Neurocognitive Disorders Vol.1 No.1

Primary antiphospholipid syndrome (PAPS) is a complication of autoimmune antiphospholipid antibodies with lack of serologic and clinical features of systemic lupus erythematosus or other collagen vascular disorders We have observed progressive dementia. One patient is 31-year-old female who presented with progressive cognitive impairment of 2 years′ duration and decreased hand dexterity. Her Mini-Mental State Exam(MMSE) score was 20. Livedo reticularis was noted on both forearms and knees. She was tested positive for VDRL, lupus anticoagulant and anti-cardiolipin antibody. FTA-ABS and all other antibodies for collagen vascular disease were negative. Brain MRI showed mild to moderatrate cortical atrophy with no definite parenchymal lesion Her dementia deteriorated despite corticosteroid therapy and follow-up MRI revealed marked brain atrophy with ventricular dilatation The other patient, a 36-year-old male, presented with a one-year history of memory impairment and mental slowing Laboratory tests were significant only for lgG anti-cardiolipin antibody His MMSE score was 26. Brain MRI showed mild brain atrophy with some small T2 signal intensities in the centrum serriovale Cerebral angiogram was unrevealing We suggest that PAPS may produce progressive dementia mainly by causing cortical atrophy PAPS should be suspected in the differential diagnosis of young adult dementia.

[AMSTERDAM] Iconic Pedestrian Bridge

Velorose,Heyne Tillett Steel 현대건축사 2012 월간 CONCEPT Vol.- No.157

Lactoferrin Stimulates Mouse Macrophage to Express BAFF via Smad3 Pathway

Chang, Heyn-Keyung,Jin, Bo-Ra,Jang, Young-Saeng,Kim, Woan-Sub,Kim, Pyeung-Hyeun The Korean Association of Immunobiologists 2012 Immune Network Vol.12 No.3

B cell-activating factor belonging to the TNF family (BAFF) is primarily expressed by macrophages and stimulates B cell proliferation, differentiation, survival, and Ig production. In this study, we explored the effect of lactoferrin (LF) on BAFF expression by murine macrophages. We determined the level of BAFF expression at the transcriptional and protein levels using RT-PCR and ELISA, respectively. LF markedly enhanced BAFF expression in mouse macrophages at both the transcriptional and protein levels. Overexpression of Smad3/4 further increased LF-induced BAFF transcription while DN-Smad3 abolished the LF-induced BAFF expression. These results demonstrate that LF can enhance BAFF expression through Smad3/4 pathway.

A large scale simulation of floe-ice fractures and validation against full-scale scenario

Lu, Wenjun,Heyn, Hans-Martin,Lubbad, Raed,Loset, Sveinung The Society of Naval Architects of Korea 2018 International Journal of Naval Architecture and Oc Vol.10 No.3

While interacting with a sloping structure, an ice floe may fracture in different patterns. For example, it can be local bending failure or global splitting failure depending on the contact properties, geometry and confinement of the ice floe. Modelling these different fracture patterns as a natural outcome of numerical simulations is rather challenging. This is mainly because the effects of crack propagation, crack branching, multi fracturing modes and eventual fragmentation within a solid material are still questions to be answered by the on-going research in the Computational Mechanic community. In order to simulate the fracturing of ice floes with arbitrary geometries and confinement; and also to simulate the fracturing events at such a large scale yet with sufficient efficiency, we propose a semi-analytical/empirical and semi-numerical approach; but with focus on the global splitting failure mode in this paper. The simulation method is validated against data we collected during the Oden Arctic Technology Research Cruise 2015 (OATRC2015). The data include: 1) camera images based on which we specify the exact geometry of ice floes before and after an impact and fracturing event; 2) IMU data based on which the global dynamic force encountered by the icebreaker is extracted for the impact event. It was found that this method presents reasonably accurate results and realistic fracturing patterns upon given ice floes.

소동파(蘇東坡)의 산문이론(散文理論) 연구

박노현 ( Ro Heyn Park ) 한국한문고전학회(구.성신한문학회) 2003 漢文古典硏究 Vol.7 No.-