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.
In the current study, new derivatives were synthesized by reaction of N-hydroxyphthalimide with chloro acetyl chloride in the presence of Et3N as a base to form 1,3-dioxoisoindolin-2-yl 2-chloroacetate (B1), which in turn enters several reactions with different amines where it interacts with primary amines to give 1,3-dioxoisoindolin-2-yl acetate derivatives (B2-B4) in basic medium, in the same way it interacts with these amines but with adding KNCS to form thiourea derivatives (B5-B7). It also reacts with diamines to give bis(azanediyl) derivatives (compounds B8-B10). The prepared derivatives were diagnosed using infrared FTIR and 1HNMR,13CNMR for some derivatives. Compounds B4, B5 and B9 were measured as corrosion inhibitors the inhibitio
... Show MoreIn this investigation, the mechanical properties and microstructure of Metal Matrix Composites (MMCs) of Al.6061 alloy reinforced by ceramic materials SiC and Al2O3 with different additive percentages 2.5, 5, 7.5, and 10 wt.% for the particle size of 53 µm are studied. Metal matrix composites were prepared by stir casting using vortex technique and then treated thermally by solution heat treatment at 530 0C for 1 hr. and followed by aging at 175 0C with different periods. Mechanical tests were done for the samples before and after heat treatment, such as impact test, hardness test, and tensile test. Also, the microstructure of the metal matrix composites was examine
... Show MoreBackground: The accuracy of fitness of any dental casting is imperative for the success of any prosthodontic treatment. From the time that dental casting was first introduced, efforts have been made to produce more accurate and better fitted castings with minimal marginal discrepancy. The aim of this in vitro study was to evaluate the effects of three different investing and burnout techniques on the vertical marginal discrepancies ofceramometalcopings invested with two types of phosphate- bonded investments. Materials and methods: Sixty wax patterns were fabricated on a standardized prepared brass die representing an upper central incisor by the aid of a custom-made split mold. Three different investing and burnout techniques were applied
... Show MoreThe current study aims at the extent of determining the interest of the Ministry of Higher Education and Scientific Research and its various departments in the process of strategic foresight, and whether this interest is reflected in its strategic decisions if the study relies on an exploratory and analytical approach and has targeted managers in the higher management within this ministry, and the questionnaire has also been used as a basic tool for collecting For data, the study population was (94), (89) questionnaires were distributed, (86) questionnaires were retrieved, and usable questionnaires amounted to (83). The sub-variable had the highest impact on strategic decision-making (intuition), as this research demonstrated the
... Show MoreBackground Median sternotomy is the gold standard incision for most cardiac operations. However, with the advent of minimal invasive surgery, a new approach emerged in cardiac surgery named mini-sternotomy and has been successfully used to perform a variety of operations.
The aim of this paper is to present our experience of using mini-sternotomy to harvest the left internal mammary artery (LIMA) for off-pump revascularization of the left anterior descending artery (LAD)
Methodology Over a 2-year period (October 2012-October 2014), 100 patients underwent coronary artery bypass grafting (CABG) via conventional median sternotomy (CMS) (n=80) and mini-sternotomy (MS) (n=20). The
... Show MoreThis study aims to examine the technologies of education and their importance, shedding light on their reality and status in Sudan especially in the secondary stage. It has become necessary to invest these technologies and include them in different aspects of the technical education curricula. Such a step helps cope with the innovative scientific development in the advanced countries, qualify professors and technicians, develop the factories and workshops, and create an attractive technical educational environment to the pupils. Thus, the researcher has adopted a descriptive analytical approach that is based on conducting pilot visits to certain technical schools in Al-Khartoum state. Different aspects of such schools were examined
... Show MoreThe study aims to build a model that enhances trust-building for public and private banks to compare and determine the significant differences between public and private banks, by testing the impact of governance mechanisms (transparency, accountability, justice, independence, and social responsibility) (Agere, 2000) on trust-building strategies (trust and trust building, people management, work relations, training and development, leadership practices, and communications) (Ngalo, 2011; Stone et al., 2005), to indicate the level of employees’ awareness of the theoretical contents of the two variables and their importance to banking work, with the aim of improving performance. The main question is the role of governance mechanisms
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