The first studies on shocks and vibrations were carried out at the beginning of the 1930s to improve the behavior of buildings during earthquakes. Vibration tests on aircraft were developed from 1940 to verify the resistance of parts and equipments prior to their first use. Flutter is a well-known example of dynamic aero elasticity, where when oscillation of structure interacted with unsteady aerodynamic forces the flutter will occur. Vibration on any structure without damping means that self-harmonic oscillation will occur, and in most cases the oscillation may start to increase until structural failure. This behavior is very similar to resonance phenomena if only the oscillation is being studied as a vibration case. In vibration suppression, the active vibration control is one of the more effective technique which is used for attenuating bad effects of disturbances on structure. In this work, two different composite wings have been used; one of them is made of Glass-fiber random matt and the other is made of woven ({0/90} Glass-fiber). The proportional-integral-derivative (PID) control is employed here for studying the suppression of active vibration wing affected by wind velocity flow through wind tunnel in the laboratory of mechanical engineering department at the university of Baghdad. Piezoelectric (PZT (transducers are used as sensors and actuators in vibration control systems. The attack angle was 10 degrees and three different velocities (15, 20, 35 m/s) have been taken to show their effect on the wings vibrations suppression. Is noticed that the suppression of the wing amplitude is reduced when the wind velocity increases for both woven and random composite wing matt. This is happened due to the vortex which has became more violent increase in wind velocity. It is concluded that the composite woven wing has high resistance more than the composite random wing. Also, the maximum control amplitude of woven matt is 1.9 cm and the damping is about 33% at 25 m/s wind velocity while the amplitude is 2.22 cm and the damping is about 53% at 10 m/s wind velocity for random wing.
This research aims at investigating pupils’ ability in using discourse markers which are identified in the English textbooks of secondary schools. Four texts are chosen from third intermediate class. The four texts are short stories of different topics.
This research hypothesizes that there are no statistical significant differences among Iraqi intermediate pupils’ ability in using textual
... Show MoreThe present research aims at identifying the educational problems and psychological problems of distinguished students at the intermediate level. The research sample consists of (246) students who are randomly selected from four distinguished schools (2) in the Karkh\1 and (2) in the Rusafa\2.
The researcher has constructed two scales for measuring the educational and psychological problems. She ensures the psychometric characteristics of the two scales. Alph-Cronbach and test-retest methodsare used to ensure reliability. Some statistical treatments are used to find out the aims of research. These treatments include the one-sample T-test, two independent samples T-test, and the Pearson correlation coefficient. The results show th
... Show MoreArabian Political Regimes: Problems of Policies and Rule; An Introduction to Interpreting (The Arabian Spring) The Arab Region witnessed, since 2011, critical changes overthrew a group of Arab regimes in some of its countries, and the reaction of these changes are still going on up to now. These changes were given lots of justifications and interpretations. The current study tries to concentrate on the most important problems which were due to what was known as (The Arab Spring). The study proposes that the crisis which the countries of the area are exposed to is not spontaneous in many of its aspects. It is totally a crisis of rule and policies. Because it is a reflection of the nature of authority in the Arabian regimes on the one hand
... Show MoreThis study aims to explain the role of green target costing technique in improving the relationship with suppliers in a sample of industrial companies listed on the Iraq Stock Exchange. The descriptive analytical approach was used, where a questionnaire was designed that included a set of questions that were directed to a sample of 84 individuals including production managers, finance managers, quality managers, and purchasing managers in these companies. The study uses some statistical analyzes such as correlation analysis and regression analysis to analyze the questionnaires. The study finds a positive impact of the green target costing technique on improving the relationship with suppliers. The results indicate that the relation
... Show MoreThe results showed the spread of disease blight leaves caused by injury fungus Alternaria in different areas of cultivation in the city of Baghdad where he was recording the highest rate and the severity of the disease of 100% and 80%, respectively, in the Abu Ghraib area and the least of 20% and 12% respectively in the Amiriya district results showed test pathogenicity of the fungus pathogen emergence of symptoms of the disease superficial discoloration Authority of black paper when wound areas and yellowing of leaves about race as centrist and leaky latest country clear ????? on Central race after 48 hours ....
This research deals with the study of the obstacles to peaceful coexistence in Iraq. Therefore, our hypothesis is that these obstacles are not attributed to one reason or to one source. Therefore, peaceful coexistence among the components of Iraqi society remains fragile and vulnerable to collapse and threat at any moment. This society, which is already in need of social relations, needs more than ever to coexist and consolidate it. Through the exercise of democracy in Iraq in a manner that guarantees rights and duties for all, to restore mutual trust between the components of this community in a way that feels they are citizens of the state.
The type of groundwater in the studied area is slightly brackish. In general, the dominant water type is calcium-sulfate. The reasons behind these different chemical groundwater types can be referred to the active ion exchange between the groundwater of the Dammam aquifer and Rus Formation. The groundwater of the Dammam unconfined aquifer is not suitable for human drinking in all the parameters properties. The groundwater class is fair in the Qasir Al-Ukhaider area, while the Shebcha area and Al-Salman area are poor class except the eastern part of Al-Salman area is very poor.
Logic in the philosophy of ethical behavior in business organizations