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.
A series of coumarin derivatives linked to amino acid ester side chains were synthesized and evaluated of their antibacterial and antifungal activity. The coumarin derivatives was alkylated by the ethyl bromoacetate and then using potassium carbonate to get alkylated hymecromone. Conventional solution method for amide bond formation was used as a coupling method between the carboxy-protected amino acids with acetic acid side chain of coumarin derivatives. The DCC/ HOBt coupling reagents were used for peptide bond formation. The proposed analogues were successfully synthesized and their structural formulas were consistent with the proposed struct
... Show MoreThis research aims to study the important of the effect of analysis of covariance manner for one of important of design for multifactor experiments, which called split-blocks experiments design (SBED) to deal the problem of extended measurements for a covariate variable or independent variable (X) with data of response variable or dependent variable Y in agricultural experiments that contribute to mislead the result when analyze data of Y only. Although analysis of covariance with discussed in experiments with common deign, but it is not found information that it is discussed with split-Blocks experiments design (SBED) to get rid of the impact a covariance variable. As part application actual field experiment conducted, begun at
... Show MoreSupport vector machines (SVMs) are supervised learning models that analyze data for classification or regression. For classification, SVM is widely used by selecting an optimal hyperplane that separates two classes. SVM has very good accuracy and extremally robust comparing with some other classification methods such as logistics linear regression, random forest, k-nearest neighbor and naïve model. However, working with large datasets can cause many problems such as time-consuming and inefficient results. In this paper, the SVM has been modified by using a stochastic Gradient descent process. The modified method, stochastic gradient descent SVM (SGD-SVM), checked by using two simulation datasets. Since the classification of different ca
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يعد البيت المكان الاجتماعي الأول الذي تبنى فيه الصحة النفسية لدى الفرد منذ بداية حياته كطفل في ظل أسرته ، إلا أن الروضة تمتلك على الرغم من ذلك أثراً تكوينياً مهماٌ في حياة الطفل وعلى شخصيته ، والتي لا يمكن ان يقلُّ عن أثر الايجابي للبيت ؛ ذلك أن المفهوم الجديد لدور الروضة لا يقتصر بمجرد كونها مكانًا تقوم فيها المعلمة بتزويد الاطفال بالمعر
... Show MoreVillages in most rural areas of the developing world, including Iraq, suffer from a deterioration in the urban structure in its various aspects, both in the lack of internal planning in terms of residential unit design which is not commensurate with the sustainable health life, in addition to the lack of infrastructure and community services networks As well as road networks linking them to neighboring urban centers, which was accompanied by the emergence of other problems, including the desire of the population to migrate to neighboring cities and the deterioration of economic activities due to lack of activation of economic development plans (Rural villages suffer from a lack of interest in urban development within the regional spatial
... Show MoreRecently, gallbladder stones have been contained bile salt saturated a proximal 70 % cholesterol. This led us to investigate how can use transformer Streptococcus salivarius with plasmid pMG36bsh to fragment cholesterol of gallstones in vitro. Total mRNA of S. salivarius was produced using easy-spinTM, total RNA extraction kit and PCR cDNA-RT to observe the change after percent pMG36bsh vector and prepare S. salivarius have two copies from bsh genes (cgh, bsh) to fragment gallstone in bacterial culture. Our data shows increase bacterial bsh expression help to reduce gallstones concentration in culture when bile salt presented as stimulating agent for the association bsh genes were 77% compare with wild type has the reducing concentration ra
... Show MoreSince 1990 internal combustion engines and variable systems has been considered as emission. Noise can be defined as undesirable sound, and in high levels it can be considered ahealth hazard. Large internal combustion engines produce high levels of noise. In many countries there are laws restricting the noise levels in large engine rooms and fixed applications. Locomotives engines have the minimum emission influence because of noise control techniques capability.
In this paper study on a single cylinder internal combustion engine was conducted. The engine works by adding ethanol to gasoline, at variable speeds, without adding ethanol, and with adding 10 and 20% ethanol in volumetric ratio. Using one sound insulator or two or with
... Show MoreStudies on the flexural behavior of post-tensioned beams subjected to strand damage and strengthened with near-surface mounted (NSM) technique using carbon fiber-reinforced polymer (CFRP) are limited and fail to examine the effect of CFRP laminates on strand strain and strengthening efficiency systematically. Furthermore, a design approach for UPC structures in existing design guidelines for FRP strengthening techniques is lacking. Hence, the behavior of post-tensioned beams strengthened with NSM-CFRP laminates after partial strand damage is investigated in this study. The testing program consists of seven post-tensioned beams strengthened by NSM-CFRP laminates with three partial strand damage ratios (14.3% symmetrical damage, 14.3%
... Show MoreThe effectiveness of (200 m) of the events of extreme intensity and this is characterized by training in the anaerobic energy system prevailing in the result of this privacy as these are based on the physical abilities and functional indicators identified in this direction and hence the importance of research in the evaluation of training programs on the basis of physical abilities and some indicators of the functionality of the hostile 200 m . The study aimed to: 1. Evaluation of training programs according to physical abilities and some functional indicators of hostile men.The researchers used the descriptive analytical method to suit the nature of the research. The researchers selected them research sample by the deliberate method of the
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