Yazar "Ozdemir, L" seçeneğine göre listele

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    Effect of angle of wrap on cutting performance of drum shearers and continuous miners
    (Taylor & Francis Ltd, 2004) Hekimoglu, OZ; Ozdemir, L
    The significance of angle of wrap in tool-lacing has, to date, been investigated in detail on the loading efficiency of shearer drums only; no comprehensive work on the cutting efficiency has, however, been found. This paper is concerned with the effects of angle of wrap on the cutting performance of rock and coal cutting picks fitted on drum shearers and continuous miners. A series of laboratory trials was carried out at full-scale, to simulate the actual cutting position of the picks in a cutting sequence at varying angular positions, which correspond to the angle of wrap. The results showed that the tool forces varied remarkably with the changes in the angular position, in such a way that all exhibited a minimum at 10degrees angle, being more pronounced for the sideways force components. It was also inferred that cutting drums, which operate at higher advance per revolutions, might experience poor performance due to higher tool forces if greater angle of wraps are employed.
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    Relation between coronary artery disease, risk factors and intima-media thickness of carotid artery, arterial distensibility, and stiffness index
    (Westminster Publ Inc, 2003) Alan, S; Ulgen, MS; Ozturk, O; Alan, B; Ozdemir, L; Toprak, N
    Atherosclerosis is a diffuse process that involves vessel structures. In recent years, the relation of noninvasive parameters such as intima-media thickening (IMT), arterial distensibility (AD), and stiffness index (SI) to cardiovascular diseases has been researched. However, we have not found any study that has included all these parameters. The aim of this study is to examine the relation between the presence of coronary artery disease (CAD) and its risk factors to AD, SI, and IMT, which are the noninvasive predictors of atherosclerotic process in the carotid artery. Included in the study were 180 patients who were diagnosed as having CAD by coronary angiography (those with at least; greater than or equal to 30% stenosis in the coronary arteries) and, as a control group, 53 persons who had normal appearing coronary angiographies. IMT, AD, and SI values of all the patients in the study were measured by echo-Doppler imaging (AD formula = 2 x (AoS-AoD)/PP x AoD, SI formula = (SBP/DBP)/([AoS - AoD]/AoD). Significantly increased IMT (0.82 +/-0.1, 0.57 +/-0.1, p<0.05), decreased AD (0.25 +/-0.9, 0.37 +/-0.1, p<0.05), and increased SI (13 +/-4, 8 +/-3, p<0.05) values were detected in the CAD group compared to the control group. A significant correlation was found between IMT and presence of diabetes mellitus (DM), systolic blood pressure, total cholesterol, and presence of plaque in carotids, and age. In the coronary artery disease group there was a significant correlation between AD and age, systolic blood pressure, and HDL cholesterol levels, while there was no significant correlation with plaque development. A significant correlation was also found between stiffness index and systolic blood pressure and age; however, there was no relation between number of involved vessels and IMT, AD, and SI. We found sensitivity, specificity, and positive predictive and negative predictive values for CAD diagnosis to be 70%, 75%, 77%, and 66%, respectively. In CAD cases, according to data in this study, IMT and SI increased while AD decreased, and this was detected by carotid artery Doppler ultrasonography. Therefore, it was concluded that these cheaper, noninvasive, and easily available parameters could be used in early diagnosis of CAD.