r. seifi

The aim of this work is providing a suitable method based on the theory of critical distance (TCD) to estimate the fatigue life of notched components in the presence of residual stress induced by the overload cycle. Presented method is relied on a virtual stress field to equalize the effects of real stress distribution in the hot spot around the notch root. This method is noted as equivalent virtual stress (EVS) method. The EVS method combined with some versions of the TCD method, such as the point method (PM) and line method (LM), were applied for two types of notched samples. Samples were made with U- and V-notches with axial stress concentration factors as 2.45 and 5.55, respectively. The test material was AA 2024-T3 due to its considerable resistance to fatigue failures. The PM was found more conservative, while LM showed more accuracy, especially when the critical distance parameter locates far from critical regions. A good agreement was observed between experimental and predicted results.

Bovine enzootic leukosis is an important viral disease of cattle with a worldwide distribution. The disease is caused by a virus (Bovine leukemia virus; BLV) of the genus deltaretrovirus within the family Retroviridae. BLV can cause persistent lymphocytosis, malignant lymphoma and leukemia by impairing the proliferation of lymphoid cells. Due to lack of a proper vaccine or treatment, BLV infections cause huge economic losses and costs for the control and eradication programs. Programs to control the BLV infections are based on the screening of animals by serological methods and removing the infected animals. Due to the possibility for transmission of BLV to buffalos, the purpose of this study was to determine the prevalence of BLV infection within the slaughtered buffaloes at Ahvaz abattoir. Therefore, blood samples were collected from a total of 529 buffaloes, including 261 female and 268 male animals and assayed by ELISA. Based on the results, only one animal (0.18%), a female buffalo of 8 years old was found to be positive for BLV specific antibodies. The results of this study are in agreement with the results of other researchers reporting a low prevalence of BLV infections in buffalo.

This paper presents a novel model to simulate the ow-current characteristic curve of an electro-hydraulic servo valve in steady state condition. This characteristic curve has three major zones: dead zone, linear zone and saturation zone. By using the presented approach, we can simulate the behavior of all types of valves including under lapped, critical center (zero lapped) and over lapped valves. A hydraulic tester has been designed and constructed for validation of the results. It can test the performance of ow-current and some other properties of the valve. Comparison of experimental and simulated curves describes that the model has an acceptable accuracy in determining the four important valve characteristics: ow gain, saturation ow, saturation current and dead zone. As a result, the model can be used for other studies such as geometrical sensitivity analysis (the ultimate objective of this modeling) or design optimization. Since this model is presented in a computer based algorithm, it can be easily used to observe and measure the e ects of change in the parameters of interest (particularly geometrical parameters of the valve) on the ow-current curve.