This paper studies the effect of contact areas on the transient response of mechanical structures. Precisely, it investigates replacing the ordinary beam of a structure by two beams of half the thickness, which are joined by bolts. The response of these beams is controlled by adjusting the tightening of the connecting bolts and hence changing the magnitude of the induced frictional force between the two beams which affect the beams damping capacity. A cantilever of two beams joined together by bolts has been investigated numerically and experimentally. The numerical analysis was performed using ANSYS-Workbench version 17.2. A good agreement between the numerical and experimental results has been obtained. In general, results showed that the two beams vibrate independently when the bolts were loosed and the structure stiffness is about 20 N/m and the damping ratio is about 0.008. With increasing the bolts tightening, the stiffness and the damping ratio of the structure were also increased till they reach their maximum values when the tightening force equals to 8330 N, where the structure now has stiffness equals to 88 N/m and the damping ratio is about 0.062. Beyond this force value, increasing the bolts tightening has no effect on stiffness of the structure while the damping ratio is decreased until it returned to 0.008 when the bolts tightening becomes immense and the beams behave as one beam of double thickness.
The research aims to identify the level of educational supervisors' practices of their supervisory duties according to the requirements of comprehensive quality from the viewpoint of teachers in Oman. Moreover, identify the differences between the responses of the sample about these practices, which are attributed to gender, and years of experience. Thus, a questionnaire was administered to teachers, consisting of (48) items distributed on (5) main fields related to the educational supervisor's practices. The sample consisted of (220) teachers who were randomly chosen from the schools in Dhofar region. Data were analyzed using means, standard divisions, T-test, and One Way ANOVA. The research concluded that the level of educational super
... Show MoreThe study aimed to determine the extent of market knowledge in the companies researched, as if market knowledge is qualified to lead the companies researched to achieve marketing performance , for this purpose, formulated hypotheses of the study in three hypotheses, the first major hypothesis "there is a correlation with significance of market knowledge to improve the marketing performance , "while the second major hypothesis, "there is a significant moral influence of market knowledge to improve the marketing performance " these hypotheses targeting to determine the role played by market knowledge in the leadership of companies researched to achieve improvement in marketing perfor
... Show MoreThis study was based on the determination of aphid species that infested Chrysanthemum sp. (Asterales, Asteraceae) in the middle of Iraq; five aphid species belong to subfamily Aphidinae were recorded: Aphis fabae Scopoli, 1763, Aphis gossypii Glover, 1877, Coloradoa rufomaculata (Wilson, 1908), Macrosiphoniella sanborni (Gillette, 1908) and Myzus persicae (Sulzer, 1776). A. gossypii was the most dominant species throughout the study period while M. persicae is the lesser species.
A summary of the main taxonomic characters is presented here and a pictorial key which was designed to separate aphi
... Show MoreThe significance of the study lies in identifying a scientific and objective indicator that clarifies the extent to which key cognitive and visual abilities contribute to skill performance in tennis. This enables coaches and instructors to design scientifically based educational and training units that incorporate these abilities according to their level of contribution, thereby positively impacting technical performance. The abundance of stimuli in tennis and the difficulty of controlling performance, due to the sport's ongoing developments, require a high level of cognitive and visual abilities. The researchers aimed to examine the problem of inadequate organization in educational content, where one aspect is emphasized over other
... Show MoreAryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that regulates T cell function. The aim of this study was to investigate the effects of AhR ligands, 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), and 6-Formylindolo[3,2-b]carbazole (FICZ), on gut-associated microbiota and T cell responses during delayed-type hypersensitivity (DTH) reaction induced by methylated bovine serum albumin (mBSA) in a mouse model. Mice with DTH showed significant changes in gut microbiota including an increased abundance of
The purpose of this research that, the performance budget is the best style of budget styles that can help and contribute in forming preparing federal typical budget in Iraq , By taking advantage of the application of the principles of scientific rules that would ensure optimal allocation and investment of the financial resources of the state and achieve the best performance and the lowest possible cost, both with regard to the administrative and accounting side, reducing the waste of public money, so that can enhance the success , power , and safety of financial activity of managerial system that it focuses on the magnetite and quality of the work done and the objectives wanted to meet. so application of performance budget require
... Show MoreRepresents light a sovereign and importance in cinematography element of what possessed the physical characteristics make it a sharp image detail or opaque, or any other form as he wants the director, Valdu away from the main function, which emerged with the beginnings of cinema, any access to endanger the proper and good, the Alachtgalat dramatic and psychological are deepened performance lighting and functioned in adjacent with the shadows, all the two complement each other, which affects the image details or even the ability to express their personal depths or the social and psychological same place, and this prompted the researcher to determine the search in the following address: (employing lighting to express their personal duplica
... Show Moremany painters tried to mix colors with Music by direct employment through colorful musical pieces or the use of multiple instruments and techniques , or vice versa, including the French artist )Robert Stroben(, he transferred the piece of music to be depicted on the painting and worked on the tones of music (Johann Sebastian Bach) by dropping the color on the lines of the musical scale, for example (the C tone) ranging from brown to red ( Tone La A) from gray to orange, and so on, the presence of links and similarity factors between the world of music and the world of colors facilitated the process of linking musical notes with colors, the most famous of which was presented by the world (Newton) in the circle of basic colors and linking
... Show Morethe mental image is so important in human life as one of the major standers for his trends and behavior, and as the human nature requires to interest in things based on how much it’s close to and how much it effects on his interest, So the neighborhood countries was one of the topics that occupied the attention of the Iraqi individual and pushed him to form perceptions of them based on the cultural heritage and the historical relations of Iraq with these countries as well as the actions of neighboring countries on Iraq and the resulting effects on the course of events. the mental image is so important in human life as one of the major standers for his trends and behavior, and as the human nature requires to interest in things bas
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