The heat exchanger is a device used to transfer heat energy between two fluids, hot and cold. In this work, an output feedback adaptive sliding mode controller is designed to control the temperature of the outlet cold water for plate heat exchanger. The measurement of the outlet cold temperature is the only information required. Hence, a sliding mode differentiator was designed to estimate the time derivative of outlet hot water temperature, which it is needed for constructing a sliding variable. The discontinuous gain value of the sliding mode controller is adapted according to a certain adaptation law. Two constraints which imposed on the volumetric flow rate of outlet cold (control input) were considered within the rules of the proposed adaptation law in this work. These are the control input is a positive quantity, and it limited by a maximum value. The maximum allowable desired outlet cold water has been estimated as function of heat exchanger parameters and maximum control input. The simulation results demonstrate the performance of the proposed adaptive sliding mode control where the outlet cold water was forced to follow desired temperature equal to 45𝑜 . Additionally, the robustness of the proposed controller was tested for the case where the cold water inlet temperature is not constant, and also for the case of heat exchanger parameters uncertainty. The results were revealed the robustness of the proposed controller.
The deficit of the federal budget and the structural imbalances suffered by the Iraqi economy has affected the direction of research towards suggesting steps and mechanisms can be relied upon in the near term to form a broader base of non-oil revenues aimed at achieving a balanced budget, and to proceed to reform the financial situation, In reducing their financial dictates, whether capital or operational, which lead to significant financial and economic consequences. This also requires that the Iraqi political elite have the real will, strategic vision and full awareness that the implementation of these reforms has potential social and economic effects, with long-term measures to be taken. The aim is not only to reform the finan
... Show MoreGlobally, Sustainability is very quickly becoming a fundamental requirement of the construction industry as it delivers its projects; whether buildings or infrastructures. Throughout more than two decades, many modeling schemes, evaluation tools, and rating systems have been introduced en route to realizing sustainable construction. Many of these, however, lack consensus on evaluation criteria, a robust scientific model that captures the logic behind their sustainability performance evaluation, and therefore experience discrepancies between rated results and actual performance. Moreover, very few of the evaluation tools available satisfactorily address infrastructure projects. The res

The current research aims to identify measure classroom flexibility for kindergartens children, identify the correlation between the classroom flexibility of kindergartens children and the gender of the child, and identify the correlation between the classroom flexibility of kindergartens children and their classroom. The current research sample consisted of (200) boys and girls selected randomly from the governmental Riyadh affiliated with the six directorates of education of Baghdad on both sides (al-karkh - al-rasafa). in order to achieve the objectives of the current research, this required including two tools, one is the scale of classroom flexibility for the kindergartens' children, which was constructed by the researcher based on
... Show MoreThe following list comprises sixty-one species and subspecies of coccine¬llid beetles belonging to twenty-two genera distributed among six tribes in three subfamilies. All the species and subspecies have been recorded for Iraq. The categories have been arranged systematically according to Korschefsky's (1931) catalogue.
Many critics suggest that Beckett’s early plays are comic because they focus their analyses on the use comic elements. Waiting for Godot is one of Beckett’s early plays, and it has been heavily analyzed and read as a comic text partly because its subtitle is “a tragicomedy in two acts” and also because of the comic techniques used in the play. The present paper, however, attempts to read the play as a piece in which comedy fails to produce any effects on the characters who remain apparently very desperate and frustrated throughout the play. The characters perform different comic acts, but they do not really feel amused or entertained. The paper suggests that the acts these characters put on stage are only means to pass t
... Show MoreCognitive radios have the potential to greatly improve spectral efficiency in wireless networks. Cognitive radios are considered lower priority or secondary users of spectrum allocated to a primary user. Their fundamental requirement is to avoid interference to potential primary users in their vicinity. Spectrum sensing has been identified as a key enabling functionality to ensure that cognitive radios would not interfere with primary users, by reliably detecting primary user signals. In addition, reliable sensing creates spectrum opportunities for capacity increase of cognitive networks. One of the key challenges in spectrum sensing is the robust detection of primary signals in highly negative signal-to-noise regimes (SNR).In this paper ,
... Show More
