The response of the combustor’s liner to the air-flow that passes through it is the key reason for the combustion chambers noise, hence the instabilities of those chambers that decreases the mechanical efficiency of such sections, by increased its mechanical vibrations, which increases the failure rate created during originating of the cracks spreading by the shakes producing by the series of high-level frequencies. Accordingly, any work debating the impact of the context of liners in the combustion chamber can provide grasping for the combustion noise generated by the undesirable vibrations, and benefits the industrial firms to design an ideal production procedure which increases the lifespan of the combustor. The goal of this work is to examine the influence of the acoustic treatment using a double layers cylindrical perforated liner on the acoustic transmission loss of gas turbines. The liners layout influences on this acoustic parameter was examined using an experimental data gained by the insertion of a full scale single and double patterns of perforated liners into the unique large scale acoustic wind tunnel at the acoustic research center at Hull University. The experimental tests under-designed acoustic signals were established firstly using 0m/s air cross-flow velocity, then by changed velocities with interval 5m/s ranging between 10m/s to 25m/s. MATLAB script was used to simulate, analyze, and figure out the data collected the insertion of single and double layer patterns of the perforated liner. The experiments demonstrated that, if the perforation acoustic treatments are applied, the acoustic transmission loss will decrease, particularly obvious at higher level frequencies. Further, the results exposed that the air tunnel with the insertion of the liner with double layers reveals an improved perforation acoustic treatment.
Writing in English language demands both mental skills and a suitable level of language proficiency. Some studies showed that writing anxiety has an impact on the acquisition of language learning. This study; however, teaches the cognitive strategies (PLAY & WRITE) as a writing strategy, so as to decrease students’ use of it when experiencing writing anxiety at the academic writing level. The sample has been (100) second-stage Department of English learners at the College of Education (Ibn –Rushd), in the University of Baghdad-Iraq. They have been randomly selected and divided into experimental and control groups; (50) students in each group. To achieve the objective of the study, SLWAI questionnaire has been distributed to the e
... Show MoreThe study seeks to investigate the effect of Dunn Dunn learning style model on students’ achievement. Besides, the way of developing students’ deductive thinking by testing the null hypothesis: there is no significant difference between experimental group who takes Dunn Dunn model as style in studying geography and control group that follows a traditional method in studying geography at the level of (0,05). Additionally, there is no significant difference between experimental group who takes Dunn Dunn model as style in studying geography and control group that follows a traditional method in studying geography at the level of (0,05) on testing developing deductive thinking skills. The researcher adopted a quasi-experimental posttest
... Show MoreThe study aimed to determine the effect of the flipped learning model in improving the acquisition of the overhand serve skill in volleyball among second-year students at the College of Physical Education and Sport Sciences, University of Baghdad, for the academic year 2024/2025. The study used an experimental design with a control group and pre-post testing, on a purposive sample consisting of 12 students. The model relied on watching short videos before class via the SGS application, and practical application in class at a rate of three sessions per week. The results showed a significant improvement in performance, as the calculated value (t = 5.356) exceeded the tabulated value (2.042) at a significance level of 0.05. The percentage of s
... Show MoreWhile many educators are highly focused on state test, it is important to consider that
over the course of a year, instructors can build in many opportunities to assess how learners
are learning. Therefore, assessment techniques are considered a good method to get benefit
for both instructors and learners in the process of teaching and learning. The sample consists
of 27 learners who participated in TOEFL training course in the Development and Continuous
Education Centre. Validity and reliability were verified.
To fulfill the aims and verify the hypothesis which reads as follows” It is hypothesized
that the TOEFL learners' scores will not be increased after TOEFL course training.” T-test
for two dependent samp
In this paper, the effect of wear in the fluid film journal bearings on the dynamic behavior of rotor bearing system has been studied depending on the analytical driven of dynamic stiffness and damping coefficients of worn journal bearing. The finite element method was used to modeling rotor bearing system. The unbalance response, critical speed and natural frequency of rotor bearing system have been studied to determine the changes in these parameters due to wear. MATLAB software was used to find the analytical values of dynamic coefficients of journal bearing. The results of rotor mounted on fluid film journal bearings showed that the wear in journal bearing increases the amplitude of unbalance response and decrease critical speed, sta
... Show MoreIn this work an approach has been developed to investigate the influence of surface roughness on thermohydrodynamic performance in aligned and misaligned journal bearings by considering an average flow model and deriving the shear flow factor for various roughness configurations, similar to the pressure flow factor. An average Reynolds equation for rough surfaces is defined in term of pressure and shear flow factors, which can be obtained by numerical flow simulation, though the use of measured or numerically generated rough surfaces. Reynolds, heat conduction and energy equations are solved simultaneously by using a suitable numerical technique (Finite Difference Method) to obtain the pressure and temperature di
... Show Moreالهدف من الدراسة هو معرفة أثر استراتيجيات التفكير البصري (VTS) على تحصيل طلاب الكلية في مهارات الاتصال باللغة الإنكليزية. ولتحقيق هدف الدراسة تم استخدام التصميم البعدي التجريبي. وتمثلت العينة بـ (70) من طلاب المرحلة الثانية بقسم اللغة الإنجليزية بكلية التربية. وقد تم اختيارهم عشوائياً وتقسيمهم إلى مجموعتين: المجموعة التجريبية والضابطة (35) طالباً في كل مجموعة. ولتحقيق هدف الدراسة تم بناء اختبار تحصيلي لمهارا
... Show MoreWriting in English language demands both mental skills and a suitable level of language proficiency. Some studies showed that writing anxiety has an impact on the acquisition of language learning. This study; however, teaches the cognitive strategies (PLAY & WRITE) as a writing strategy, so as to decrease students’ use of it when experiencing writing anxiety at the academic writing level. The sample has been (100) second-stage Department of English learners at the College of Education (Ibn –Rushd), in the University of Baghdad-Iraq. They have been randomly selected and divided into experimental and control groups; (50) students in each group. To achieve the objective of the study, SLWAI questionnaire has been distributed to
... Show MoreUnderstanding energy metabolism and intracellular energy transmission requires knowledge of the function and structure of the mitochondria. Issues with mitochondrial morphology, structure, and function are the most prevalent symptoms. They can damage organs such as the heart, brain, and muscle due to a variety of factors, such as oxidative damage, incorrect metabolism of energy, or genetic conditions. The control of cell metabolism and physiology depends on functional connections between mitochondrial and biological surroundings. Therefore, it is essential to research mitochondria in situ or in vivo without isolating them from their surrounding biological environment. Finding and spotting abnormal alterations in mitochondria is the
... Show More