This research introduces a developed analytical method to determine the nominal and maximum tensile stress and investigate the stress concentration factor. The required tooth fillets parametric equations and gears dimensions have been reformulated to take into account the asymmetric fillets radiuses, asymmetric pressure angle, and profile shifting non-standard modifications. An analytical technique has been developed for the determination of tooth weakest section location for standard, asymmetric fillet radiuses, asymmetric pressure angle and profile shifted involute helical and spur gears. Moreover, an analytical equation to evaluate gear tooth-loading angle at any radial distance on the involute profile of spur and helical gears, (taking into account the effect of profile shift factor) has been derived. In addition, numerical solution for the evaluation of the maximum fillet tensile stress and the combined tensile stress concentration factor for the verification of the analytical method using computer-aided engineering software (ANSYS Version 18.1). The analytical and FE result have been compared and found to be very close. The most effective method for reducing the stress concentration factor have been found by applying negative profile shifting on asymmetric tooth with lower unloaded pressure angle and high loaded pressure angle and fillet radius, which can lead to an enhancement percentage of (20%) when using a (35o/20o) asymmetric spur gear of a (24) teeth number with a shift factor of (-0.3mo) compared with standard (20o) one.
This paper aimed to investigate the relationship between work stress and cognitive failures among administrators of university professors and included a sample by searching from (474) teachers’ administrators and those who obtaining master degree or doctorate. Work stress scale was used, which is prepared by Amina Boashiri supporting by that, a measure of cognitive failures has also been used which is prepared by Khamis Shaeal Al Badri. In order to obtain the results statistical methods were used including (one-sample t-test, Pearson correlation coefficient) results indicated a high level of stress Work stress and high level of cognitive failures among professors as administrators, and also there is a positive correlation, as well as stat
... Show MoreShear lag is the phenomenon that occurs when a supported slender member undergoes deformation from lateral loading, causing in-plane non-uniform distribution of stresses that results in reducing the member’s minimum strength capacity. This paper investigates the behaviour of shear distribution in steel I-section and box girders when subjected to both static and impact loadings. Three-dimensional finite element analysis models were prepared in Strand7 and validated against experimental results providing a basis for further comparison research into shear lagging effects. A parametric study was conducted comparing the effects of impact loading through certain specified velocities at the midspan of restrained ends. It provided new ins
... Show MoreAlgae have been considered a sources task of biofuels, which is a future alternative to fossil fuels, and this lead the environmental studies concerned with the lifting of curves or growth rates and time of replication of different kinds of algae, as well as algae cells in response to different environmental conditions, whether chemical or physical, to assess their impact on the composition of these cells and the extent of affected components that make up the living, especially fatty acid ,total fats, proteins and carbohydrates, Gbrha. Green Chlorococcum humicola showed a different response when treated with an average of agriculture Chu-10 and Chu-13 which used as control media,Compared with the degree of its response when exposed to e
... Show MoreBackground. The use of modern aids and technology has contributed greatly to football development, the goalkeeper is the most important position in the team, and the use of devices gave objective readings about the goalkeeper's ability in terms of skill and physical aspects. Objectives. The research aimed to prepare exercises using an electronic device to measure the knee bending angle because of its great importance in developing the skill of catching and dimensions of the high ball for football goalkeepers. Methods. The researchers used the experimental method, and the sample consisted of (4) male goalkeepers under 15 years of age, one of the research procedures was to determine the biomechanical variables affecting the development of the
... Show MoreAdversity and psychosocial stress are involved in aging through the following pathways. psychological stress enhances the nerve system to secrete endocrine mediators (hormones). Mitochondrial respiration mediates energy production stimulated by binding to these hormones to their receptors. Energy produced by mitochondria accelerates metabolism and, in its turn, leads to increases in reactive oxygen species (ROS) of free radicals. Cellular stress and accumulation of damage can result from an excess of ROS. Accumulation of damage comprises damages in telomeric and nontelomeric DNA, in addition to mitochondrial DNA. Mitochondrial DNA damage plays an important role in increasing the pathway of p53/p21. The expression of the PGC-1α gene is inhi
... Show MoreThe aim of the study was comparative between oxidative stress in diabetes mellitus using the measurement of some biophysical and biochemical parameters on two groups of diabetic patients, were conducted in the Al-Yarmuk Teaching Hospital,30 patients insulin dependent diabetes mellitus (IDDM) or type 1 ,their ages ranged between (15-45) and30 patients non- insulin dependent diabetes mellitus (NIDDM) or type 2,their ages ranged between (42-65).This study has been compared with 30 healthy subjects. The present study was demonstrated to evaluate the alteration in oxidative stress as measured by plasma and red blood cells Malondialdehyde (MDA) andchanges in antioxidant mechanism as measured by plasma and red blood cells Glutathione (GSH)
... Show MoreThis is a descriptive study that used the survey method, it’s aimed to identify the topics and frameworks of diplomatic and political issues covered by the news of the website of the Iraqi Ministry of Foreign Affairs, through the content analysis method applied on a sample selected in a systematic random manner for news published in the year 2021. The sample included (191) news equivalent to (20%) of the total study population of (942). The study reached some results, the most important of which were as follows: The political issue, in its general sense, grabbed the most prominent attention among the various issues and events focused on by Iraqi diplomacy: "international cooperation", "bilateral cooperation", and then "regional politic
... Show More