Support vector machines (SVMs) have become one of the most popular approaches to learning from examples and have many potential applications in science and engineering However, their applications in fault diagnosis of rotating machinery are rather limited Most of the published papers focus on some special fault diagnoses This study covers the overall diagnosis procedures on most of the faults experienced in rotating machinery and examines the performance of different SVMs strategies The excellent characteristics of SVMs are demonstrated by comparing the results obtained by artificial neural networks (ANNs) using vibration signals of a fault simulator

Fault diagnosis of rotating machinery based on multi-class support vector machines

Wind-induced pressure at external surfaces of a high-rise residential building in Hong Kong

The hemodynamics of the carotid artery was numerically investigated with an approach of fluid-structure interaction (FSI). To predict the blood flow and arterial deformation of carotid artery, a framework for the FSI analysis was developed by coupling computational fluid dynamics and structural analysis. Using this framework, the hemodynamics of the carotid artery was simulated with the patient- specific clinical data of the arterial geometry, pulsatile blood flow, blood rheology and arterial deformation. It is found that the hemody- namic characteristics of the carotid artery are significantly affected by its geometric factors and flow conditions, and relatively low values of the wall shear stress were observed in the post-plaque dilated region of the carotid bifurcated area, which is known to be responsible for the growth of an atherosclerotic plaque. Since the characteristics of the blood flow in a carotid artery are also affected by the hemody- namic factors, the effects of the cardiac output, distal vascular resistance and blood viscosity on hemodynamics were also numerically analyzed.

A fluid-structure interaction analysis on hemodynamics in carotid artery based on patient-specific clinical data

Within this thesis, a methodology for the numerical analysis of the interaction between wind flow and membrane structures is developed. To account for the relevant factors inherent to aeroelastic behavior of light, flexible structures and turbulent air flows, an appropriate combination of physical and numerical disciplines is chosen. The wind-structure interaction is modeled by a surface-coupled fluid-structure interaction (FSI) method. For the numerical simulation of this multiphysics problem, a partitioned solution scheme is selected and implemented in a flexible software environment, which can be applied to various problems of fluid-structure interaction. The potential of the developed software environment is illustrated with the simulation of wind induced, aeroelastic effects on the mobile canopy structure ARIES. The significance of the results obtained is discussed and the method is placed in the framework of wind engineering.

Modeling the Interaction of Wind and Membrane Structures by Numerical Simulation

Exposed-type steel column bases are used widely in low-rise building construction Numerous researchers have examined methods to identify their stiffness and strength, but those studies have heretofore been restricted to in-plane behaviors This paper presents an experimental investigation of inelastic behaviors of square hollow section (SHS) steel column bases under biaxial bending Two types of failure modes are considered anchor bolt yielding and base plate yielding Different pinching effects and interaction surfaces for biaxial bending are observed for these two modes during bi-directional quasi-static cyclic loading tests Differences are elucidated using limit analyses based on a simple analytical model

Evaluation on interaction surface of plastic resistance for exposed-type steel column bases under biaxial bending

Atherosclerosis, which is a degenerative vascular disease, is believed to occur in the blood vessels due to deposition of cholesterol or low density hpoprotein (LDL) Atherosclerotic lumen narrowing causes reduction of blood flow due to hemodynamic features Several hypothetical theories related to the hemodynamic effects have been reported. high shear stress theory, low shear stress theory, high shear stress gradient theory, flow separation and turbulence theory, and high pressure theory However, no one theory clearly explains the causes of atherosclerosis The objective of the present study was to investigate the mechanism of the generation of atherosclerosis In the study, the database of Korean carotid and coronary arteries for geometrical and hemodynamic clinical data was established The atherosclerotic sites were predicted by the computer simulations. The results of the computer simulation were compared with the in vivo experimental results, and then the pathogenesis of atherosclerosis by using the clinical data and several hypothetical theories were investigated From the investigation, it was concluded carefully that the mechanism of the generation of atherosclerosis was related to the hemodynamic effects such as flow separation and oscillatory wall shear stress on the vessel walls

Significance of hemodynamic effects on the generation of atherosclerosis

Application of computational techniques for studies of wind pressure coefficients around an odd-geometrical building

This paper presents the numerical simulations of wind pressure distributions on canopies attached to tall and medium-rise buildings. The most current wind pressure coefficients in wind load codes do not take into account the large scale canopies attached to tall and medium- rise L-shaped buildings. Wind pressure on canopies attached to buildings depends on the building geometry and its features, the location of canopies, surrounding buildings and terrain, as well as canopy sizes and wind directions. Numerical analysis results were compared and investigated using ANSYS CFX 11 codes. Numerical simulation of wind loading on a canopy attached near the base of a tall or medium-height L-shaped building has shown that the downward pressure on the canopy does not grow in proportion to the increase in the height of building-to-canopy ratio. As a result, the downward pressure acting on a canopy attached to a tall L-shaped building is considerably smaller than that of prismatic models used in other researches and we assume that this is due to the shape of the building itself. The results of numerical simulations of L-shaped models differ considerably from those of previous wind tunnel prismatic shape model tests.

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Wind pressure distribution on canopies attached to tall buildings

In large pump station, vortex generation such as free-surface vortex and submerged vortex occurring around pump intake, or at bell-mouth inlet has been an important flow characteristics which should be considered always to keep away the suction of air-entrained or cavitated flow. In this study, a commercial CFD code was used to predict accurately the vortex generation for the specified intake design. These result shows the preliminary result of submerged vortex prediction for the Turbo-machinery Society of Japan Sump Test CFD standard model. At bottom wall, air volume fraction (red color) was found in a large scale to explain the submerged vortex generation at particular operation and configuration condition. And these indicate the free surface formation behind the bell mouth. Particularly, non-uniform approaching flow is a major parameter to govern the occurrence of the free-surface vortex. Futhermore the comparison between turbulence ( & model) mode were executed in this study.

CFD Prediction on Vortex in Sump Intake at Pump Station

Recently, Korean Government is encouraging to propagate the small hydro-electric power in renewable energy development policy as the “Low CO2 Green Growth” policy. However, turbines in the Korea Water Resources Corporation (below K-water) operated at an average of 10% less than well-designed turbines due to the design weakness or the inferior manufacturing techniques for the small hydropower facilities. Thus, maintenance fees increased because the cavitations had excessively occurred on the main parts of turbines such as the runner, guide vane and Stator, the life cycles of turbines were reduced and the frequency breakdowns were increased. In order to improve the efficiency the CFD-based design system is applied to the Francis turbine replacement project with Korea Fluid Machinery Association (below KFMA) and K-water. Therefore, the inversed design technique and the fully turbulent 3-dimensional flow simulations are performed for both the existing and new turbines at design and off design conditions. As a result, the runner is optimized to the greatest extent with a possible minimum cost under the geometrical constraints of the existing machine. The performances of the new design are verified by extensive model tests and the guarantees have all been successfully met.© 2010 ASME

Hyung-Woon Roh

Papers

Significance of hemodynamic effects on the generation of atherosclerosis

Application of computational techniques for studies of wind pressure coefficients around an odd-geometrical building

Wind pressure distribution on canopies attached to tall buildings

CFD Prediction on Vortex in Sump Intake at Pump Station

Development of a High Performance Francis Turbine for Runner Replacement Using a CFD-Based Design System