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Absorption Coefficient of a Double-Layer Inhomogeneous Micro-perforated Panel Backed with Multiple Cavity Depths
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Double-layer micro-perforated panels (MPPs) have been studied extensively as sound absorption systems to increase the absorption performance of single-layer MPPs. However, existing proposed models indicate that there is still room for improvement regarding the frequency bands of absorption for the double-layer MPP. This study presents a double-layer MPP formed with two single MPPs with inhomogeneous perforation backed by multiple cavities of varying depths. The theoretical formulation is developed using the electrical equivalent circuit method to calculate the absorption coefficient under a normal incident sound. The simulation results show that the proposed model can produce absorption coefficient with wider absorption bandwidth compared with the conventional double- and even triple-layer MPPs. The bandwidth can be increased to higher frequency by decreasing the cavity depth behind a sub-MPP with small hole diameter and a high perforation ratio, and to lower frequency by increasing the cavity depth behind a sub-MPP with large hole diameter and a small perforation ratio. The experimental data, measured by impedance tube, are in good agreement with the predicted results.

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Publication Date
Sun Aug 03 2025
Journal Name
Journal Of Physical Education
The Effect of Electric Stimulation Using Proposed Apparatus on Static Balance Through Hamstring Muscle Rehabilitating in Athletes Suffering from Mild Muscle Tear
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Publication Date
Thu Aug 06 2009
Journal Name
Dirasat
Geneses of the zinc-lead – barite deposits in the Northern Iraq: ore mineralogy, geochemistry, fluid inclusions, lead isotopes and sulfur isotopes implicatiuons
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Publication Date
Sat Jun 18 2022
Journal Name
Sciencescholar Publication
Logical reasoning skills according to Piaget's model for chemistry students in the college of education for pure sciences Ibn al-Haytham in
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Abstract---The aim of the current research is to identify the level of logical reasoning skills in chemistry students at the Faculty of Education for Pure Sciences/ Ibn Al-Haytham for the academic year (2021-2022). The differences in their level of skills according to the gender variable (males and females) and the academic stages (first- second - third - fourth). The descriptive approach was adopted because it corresponds to the nature of the research objectives. The research sample consisted of (400 )students selected in a relatively random stratified way. The researcher constructed a logical reasoning test, which includes (6) sub-skills , which is (proportional - probabilistic- synthetic- deductive- logic- variable adjustment). The psych

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Publication Date
Sun Mar 28 2021
Journal Name
Journal Of The College Of Education For Women
Argumentative Communication in RawdatAl-MuhebbenwaNozhattAl-Mushtaqeen’s Book by Ibn Al-Qayyem: The Foundations and Mechanisms of its Functioning: مريم إبراهيم علي غبان
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This research seeks to unravel the components of the argumentative discourse in the Book ofʻRawdat al-MuhebbeenwaNozhatt al-Mushtaqeenʼ - The Garden of Lovers and the Promenade of Longing People – by Ibn Al-Qayyem Al-Jawziyah. This is because this book has a moderate discourse with a sound Islamic thought that is characterized by its sustainability, popularity, realism, and interaction with the successive developments of the new age. This reflects the intellectual maturity the composing process has reached in the philosophy of love and its educational bases in every place and time. To explore the componets, properties, and the working mechanisms of an argumentative discourse in Ibn Qayyem’s book, the present work has been conducted

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Publication Date
Mon Aug 19 2024
Journal Name
Chemical Papers
In vitro and in silico evaluation of 4'-hydroxy-[1,1'-biphenyl]-4-carbohydrazide Schiff base and oxadiazole derivatives targeting EGFR allosteric site
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Publication Date
Sun Aug 03 2025
Journal Name
Iraqi Journal Of Science
Synthesis, Characterization and Quantum Mechanical Study of Some New 2-benzylidenehydrazinecarbothioamide Derivatives as Corrosion Inhibitors for Carbon/mild Steel in Acidic Medium.
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In this work, some of new 2-benzylidenehydrazinecarbothioamide derivatives have been prepared by condensation of thiosemicarbazide and different substituted aromatic benzaldehydes in presence of glacial acetic acid to give compounds (1-6), these compounds have characterized by its physical properties and spectroscopic methods. This work also included theoretical study to prove the ability of these compounds as corrosion inhibitors; The program package of Gaussian 09W with its graphical user interface GaussView 5.0 had used for this purpose; the methods of Density Functional Theory (DFT) with basis set of 6-311G (d,p) / hybrid function of B3LYP and semiempirical method of PM3 have been used, the study included theoretical simulation

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Publication Date
Sun Dec 15 2019
Journal Name
Journal Of Baghdad College Of Dentistry
Evaluation of Crestal Bone Resorption around Dental Implants in Flapped and Flapless Surgical Techniques Depending on Cone Beam CT Scan (Comparative Study)
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Background: The long term survival of dental implants is evaluated by the amount of crestal bone loss around the implants. Some initial loss of bone around dental implants is generally expected. There is reason to believe that reflecting a mucoperiosteal flap promotes crestal bone loss in the initial phase after an implant has been inserted. The surgical placement of a dental implant fixture is constantly changing and in recent years, there has been some interest in developing techniques that minimize the invasive nature of the procedure, with flapless implant surgery being advocated. The purpose of this study was to compare the radiographic level of the peri- implant bone after implant placement between traditional flapped surgery and f

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Publication Date
Mon Sep 23 2024
Journal Name
Journal Of Inorganic And Organometallic Polymers And Materials
Quaternary Biocomposite of Chitosan-Polyvinyl Alcohol/Food Grade Algae/ Montmorillonite Clay for Cationic Methyl Violet 2B Dye Removal: Optimization and Desirability Functions
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Publication Date
Wed May 19 2010
Journal Name
College Of Science – University Of Babylon
Synthesis and Characterisation of Cu(II) ,Co(II) ,Ni(II) and Zn(II) Complexes Derived from Acetylacetone and P–Amino benzoic acid
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Publication Date
Tue Aug 02 2022
Journal Name
Muthanna Journal For Admisrative And Economic Sciences
MEASURING AND ANALYSING THE CAUSAL RELATIONSHIP BETWEEN AGRICULTURAL TERMS OF TRADE AND SOME AGRICULTURAL VARIABLES IN IRAQ FOR THE PERIOD 1990-2019
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The research aims to investigate the existence of a direct causal relationship between selected agricultural variables: agricultural output (as a representative of growth in the agricultural sector), agricultural terms of trade as a completely new variable in agricultural studies in recent years, agricultural labour which is an important part in the total workforce for Iraq, and finally, agricultural investment because of its importance and vital role in the production process, creating job opportunities, and then raising the level of employment, then it's role to achieving agricultural growth and development. For this purpose, the researchers used the Toda-Yamamoto causality methodology for a time series covering from 1990 to 2019. The res

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