Dragline Field Testing

Draglines are the most expensive pieces of equipment used in coal mines at a cost of $50 M to$100M each. Improving their productivity will produce major benefits to the coal mining industry. The dynamic behaviour of the dragline structure has a significant effect on the fatigue life of the main components of a dragline and related maintenance costs. This paper describes the field tests conducted on the dragline DRE23 at the Peak Down coal mine, Queensland, Australia. Sixteen accelerometers were installed on the dragline boom and mast. Three different excitation methods were used in the test: 5.4-kg impact hammer, dragline bucket impulse and ambient excitations produced during normal operation. The aim of the modal testing was set to explore the six global modes for the dragline boom structure. The results showed that the impact hammer excitation was not adequate to excite any of the global modes. The excitation produced by bucket impulse was powerful but was difficult to control. The output-only identification using the response to the ambient excitation was promising but it was difficult to identify all targeted global modes

Electrocardiographic Abnormalities Among Arsenic-exposed Persons Through Groundwater in Bangladesh

This study was carried out among arsenic-exposed and non-exposed people of Bangladesh to assess and compare their cardiac status based on electrocardiographic (ECG) findings. For the purpose of the study, participants were included in three groups: arsenic-exposed persons with arsenicosis (arsenicosis group), arsenic-exposed persons without arsenicosis (non-arsenicosis group), and persons not exposed to arsenic (non-exposed group). Each group included 50 respondents. In this study, no significant difference in heart rate, rhythm, axis, and pulse rate interval was detected among the arsenicosis, non-arsenicosis and non-exposed groups. A significant difference in corrected QT interval between the arsenicosis and the non-exposed group (p<0.05) was observed. On the contrary, no statistically significant difference in corr-ected QT interval between the non-arsenicosis and the non-exposed group was found. Abnormal QRS complex was found among 14%, 8%, and 2% of the arsenicosis, non-arsenicosis, and non-exposed groups respectively. ECG findings, indicative of left ventricular hypertrophy, ischaemic heart disease, andright bundle branch block, were high among the arsenicosis group. Overall, abnormal ECG findings were high (58%) among the respondents of the arsenicosis group and were highly significant (p<0.001). The findings revealed that there was a significant association between ECG abnormalities and arsenic exposure

A numerical study on the effects of axis and blockage ratios on the fluid flow over a cylinder.

The fluid flow over a circular cylinder has been studied extensively. On the other hand, literature on the flow over an elliptical cylinder, particularly at low Reynolds number, is limited. Intending to bridge the gap, the effects of axis ratio (0.3 ≤ AR ≤ 1) and blockage ratio (0 ≤ BR ≤ 0.12) were studied by implementing the computational fluid dynamics code FLUENT, using the control volume approach at a Reynolds number of 40 based on hydraulic diameter. For unbounded flow, a circular computational domain having a radius of 40 times the diameter (d) of the circular cylinder was considered. The front half of the circumference of the computational domain was treated as a uniform velocity inlet while the rear half was considered as a pressure outlet. In the case of bounded flow, the cylinder was placed between two streamwise symmetrical flat plates (walls) with a uniform velocity inlet at 15d upstream and pressure outlet at 20 d downstream from the centre of the cylinder. A no-slip boundary condition was applied on the cylinder surface, on the top and bottom walls (in the case of bounded flow) of the computational domain. (Abstract shortened by UMI.)Dept. of Mechanical, Automotive, and Materials Engineering. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2005 .F37. Source: Masters Abstracts International, Volume: 44-03, page: 1487. Thesis (M.A.Sc.)--University of Windsor (Canada), 2005

Confinement effects on air cross-flow over an elliptical cylinder

Cylinders in cross-flow encountered in engineering applications and in nature may or may not have confinement influence due to the presence and proximity of neighboring structures. On the other hand, fluid-structure experiments conducted in wind and water tunnels are typically restricted and affected by confinement. The confinement is usually expressed in terms of the blockage ratio, which is the cylinder/tunnel cross sectional area ratio. Therefore, a good understanding of the role of blockage is critical in further advancing the knowledge of fluid-structure interactions. The effect of blockage ratio on the fluid flow over a circular cylinder has been addressed by some authors, but, literature on elliptical cylinders is limited. In this study, fluid flow over an elliptical cylinder with axis ratios (minor to major axis ratio) of 1 (circular cylinder), 0.5 and 0.4 were investigated numerically, using control volume approach in FLUENT, at a Reynolds number (based on the hydraulic diameter) of 40. The flow was considered to be uniform at the entrance (40d and 15d upstream from the center of the cylinder for unbounded and bounded flow respectively) of the two dimensional computational domain, steady and parallel to the major axis of the cylinder. Blockage ratios of 0 (un-confined scenario), 0.07 and 0.12 were studied because of the availability of experimental data at these blockage ratios for the circular cylinder case. From the simulation output, the velocity distributions were analyzed in detail. The increase of blockage ratio increases the drag coefficient and reduces the wake size of the circular cylinder. On the other hand, the increase in blockage ratio increases the wake length of elliptical cylinders with (minor/major) axis ratios of 0.5 and 0.4. These results agree well with the available data in the literature. Copyright © 2005 by ASME

Confinement effects on air cross-flow over an elliptical cylinder

Cylinders in cross-flow encountered in engineering applications and in nature may or may not have confinement influence due to the presence and proximity of neighboring structures. On the other hand, fluid-structure experiments conducted in wind and water tunnels are typically restricted and affected by confinement. The confinement is usually expressed in terms of the blockage ratio, which is the cylinder/tunnel cross sectional area ratio. Therefore, a good understanding of the role of blockage is critical in further advancing the knowledge of fluid-structure interactions. The effect of blockage ratio on the fluid flow over a circular cylinder has been addressed by some authors, but, literature on elliptical cylinders is limited. In this study, fluid flow over an elliptical cylinder with axis ratios (minor to major axis ratio) of 1 (circular cylinder), 0.5 and 0.4 were investigated numerically, using control volume approach in FLUENT, at a Reynolds number (based on the hydraulic diameter) of 40. The flow was considered to be uniform at the entrance (40d and 15d upstream from the center of the cylinder for unbounded and bounded flow respectively) of the two dimensional computational domain, steady and parallel to the major axis of the cylinder. Blockage ratios of 0 (un-confmed scenario), 0.07 and 0.12 were studied because of the availability of experimental data at these blockage ratios for the circular cylinder case. From the simulation output, the velocity distributions were analyzed in detail. The increase of blockage ratio increases the drag coefficient and reduces the wake size of the circular cylinder. On the other hand, the increase in blockage ratio increases the wake length of elliptical cylinders with (minor/major) axis ratios of 0.5 and 0.4. These results agree well with the available data in the literature. Copyright © 2005 by ASME

The effects of axis ratio on laminar fluid flow around an elliptical cylinder

An elliptical cylinder is a generic shape which represents a flat plate at its minor to major axis ratio (AR) limits of zero and infinity, and a circular cylinder at AR of unity. While incompressible flows over a streamwise flat plate (AR = 0), a cross-stream flat plate (AR = ∞), and a circular cylinder have been studied extensively, the role of AR on the detailed flow structure is still not well understood. Therefore, a numerical study was conducted to examine the flow field around an elliptical cylinder over a range of ARs from 0.3 to 1, with the major axis parallel to the free-stream, at a Reynolds number of 40 based on the hydraulic diameter. The control volume approach of FLUENT was used to solve the fluid flow equations, assuming the flow over the cylinder is unbounded, steady, incompressible and two-dimensional. It has been found that a pair of steady vortices forms when AR reaches a critical value of 0.34; below this value no vortices are formed behind the elliptical cylinder. Various wake parameters, drag coefficient, pressure and velocity distributions, have been characterized as functions of AR. The wake size and the drag coefficient are found to increase with the increase of AR. Quadratic correlations have been obtained to describe the relations of wake length and drag coefficient with axis ratio. © 2006 Elsevier Inc. All rights reserved

Electrocardiographic Abnormalities Among Arsenic-exposed Persons Through Groundwater in Bangladesh

This study was carried out among arsenic-exposed and non-exposed people of Bangladesh to assess and compare their cardiac status based on electrocardiographic (ECG) findings. For the purpose of the study, participants were included in three groups: arsenic-exposed persons with arsenicosis (arsenicosis group), arsenic-exposed persons without arsenicosis (non-arsenicosis group), and persons not exposed to arsenic (non-exposed group). Each group included 50 respondents. In this study, no significant difference in heart rate, rhythm, axis, and pulse rate interval was detected among the arsenicosis, non-arsenicosis and non-exposed groups. A significant difference in corrected QT interval between the arsenicosis and the non-exposed group (p<0.05) was observed. On the contrary, no statistically significant difference in corr-ected QT interval between the non-arsenicosis and the non-exposed group was found. Abnormal QRS complex was found among 14%, 8%, and 2% of the arsenicosis, non-arsenicosis, and non-exposed groups respectively. ECG findings, indicative of left ventricular hypertrophy, ischaemic heart disease, andright bundle branch block, were high among the arsenicosis group. Overall, abnormal ECG findings were high (58%) among the respondents of the arsenicosis group and were highly significant (p<0.001). The findings revealed that there was a significant association between ECG abnormalities and arsenic exposure