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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
Fri Aug 01 2014
Journal Name
Journal Of Economics And Administrative Sciences
The role of intellectual capital in promoting financial performance an applied study on a sample of the companies listed in Iraq stock exchange
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The interest in the intellectual capital and its development is a civilized necessity imposed by the requirements of the times and cannot imagine an advanced society in its potential productivity in poor efficiency of human capital, and features the work environment change permanently, putting the management of financial companies against a constant challenge toward coping with new developments in this changing environment and this is not taken unless owned by these companies qualified human resources and the provision of Culture organizers have, which manifested itself with the research problem by the following two questions:

  1. Did the intellectual capital value specific financial and

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Publication Date
Mon Jun 15 2020
Journal Name
Journal Of Baghdad College Of Dentistry
Evaluation of dental enamel color after fixed orthodontic therapy using two types of protectors to prevent white spot lesions (A prospective clinical study)
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Background: The aim of this study is to evaluate the color change ∆E of the dental enamel following treatment with 2 kinds of protector (icon infiltrant, clinpro varnish) before fixed orthodontic treatment to avoid the possible white spot lesions. Materials and Methods: Fifty four subjects treated with fixed appliances were divided into 3 groups: the 1st group was control, while the 2nd and 3rd groups were treated with icon infiltrant and clinpro varnish before bonding procedure, respectively. Color parameters (L,a,b) were recorded for the middle and gingival thirds before and after bonding procedure to get the ∆E of each group. Results: One-way ANOVA test showed a non-significant difference in ∆E between the 3 groups a

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Publication Date
Wed Jan 30 2019
Journal Name
Journal Of The College Of Education For Women
Forced displacement in Iraq its causes and its effects on displaced families (A field study of displaced families to the city of Baghdad)
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After a temporary halt to forced thghebr in different cities of Iraq this methodlogy
opeations returned directiy in the areas of political conflict on the ground which are translated
operations and forced displacement violence es they operations aimed at completing the
forced displacement that occurred after the occupation in(2003)which took an upward curve
publicly after these events and some of which are aimed at the liquidation of some provinces
than any demographic diversity of religious or sectarian or alhens and others aimed at
redemographic distribution within the province itself to produce a net sectarian zones as is the
case in Diyala Nineveh and Babylon Baghdad has the epicenter of sectarian violence and th

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Publication Date
Sun Aug 30 2020
Journal Name
Journal Of Economics And Administrative Sciences
Measuring the impact of corporate governance mechanisms on social responsibility reports for a sample of Iraqi companies listed on the Iraq Stock Exchange
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The study aims to indicate the role of the mechanisms and principles of corporate governance in the activation of social responsibility reports, and increase disclosure, to achieve sustainability, legitimacy, and integrity of the business. Through the presentation of the conceptual framework for corporate governance and social responsibility, identify the key dimensions of social responsibility and the statement of the relationship between the mechanisms of governance and social responsibility reports in accordance with these dimensions. To prove the hypothesis research has selected a sample of listed companies in the Iraqi market for securities,

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Publication Date
Wed May 01 2024
Journal Name
Journal Of Studies In Humanities And Educational Sciences
Unlocking the Language of the Heart: A Stylistic Analysis of EmotiveTechniques in Paulo Coelho's By the River Piedra I Sat Down and Wept
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This paper presents an in-depth stylistic analysis of the linguistic artistry andliterary techniques employed by Paulo Coelho in his novel By the River Piedra ISat Down and Wept. A close reading approach guided by stylistics and linguisticsframeworks reveals Coelho's extensive incorporation of imaginative metaphors,vivid imagery, poetic diction, and resonant symbols across the narrative. Analysisspecifically elucidates how Coelho adeptly manipulates various stylistic features toconvey thematic content, shape characterization, and produce aesthetic impacts.Findings provide critical insights into Coelho’s linguistic mastery and contribute toresearch in stylistics and literary linguistics through rigorous examination of anentire contemporary

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Publication Date
Tue Mar 01 2022
Journal Name
Academy Of Accounting And Financial Studies Journal
Impact of Digital Audit on Improving performance Quality and Reduce Costs An applied research in a sample of private auditing firms and offices
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Publication Date
Sun Jul 01 2018
Journal Name
Journal Of Global Pharma Technology
Preparation, Characterization and Biological Activity of New Derivatives of 3-Cyclic Oxazepine, 3-Cyclic Lactam and 3- Aminomethyl Imidazo (1, 2-a) Benzthiazol
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In this work a series of fourteen new compounds were synthesized. Compound [1] was formed from the reaction of 2-aminobenzothiazole and p-bromophenacyl bromide. Aldehyde group [2] was obtained from the reaction of compound [1] with pocl3 in presence of DMF and CHCl3 .After that shiff bases have been synthesized from the reaction of compound [2] with different aromatic amine to give new shiff bases [3- 5]. These new shiff bases have been reduced to their corresponding amine [6-8] by means of sodium borohydride. Then reaction of shiff bases [3-5] with phenyl isocyanate gives 3-cyclic lactam derivatives [9-11]. 3-cyclic Oxazepine derivatives [12-14] were obtained by reaction of shiff bases [3-5] with succinic anhydride. These new formed co

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Publication Date
Wed Nov 26 2025
Journal Name
Journal Of Baghdad College Of Dentistry
Early and delayed effect of 2% chlorhexidine on the shear bond strength of composite restorative material to dentin using a total etch adhesive
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Background: Lack of durability of the bond of the dental adhesive systems to tooth structure is one of the most important problems in tooth colored restorative work. This in vitro study was performed to evaluate the effect of 2% chlorhexidine gluconate(CHX) on dentin bond strength by using total etch adhesive system at twenty-four hours and three months of water storage. Material and methods:A flat dentin surface was prepared for forty sound human maxillary premolar teeth which were acid etched with 36% phosphoric acid gel after being divided randomly into four groups of ten teeth each according to storage time and CHX application, theCHX was applied for 60 seconds before adhesive application for groups I and III which were tested after twe

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Publication Date
Wed Oct 26 2022
Journal Name
Membranes
Classification of Nanomaterials and the Effect of Graphene Oxide (GO) and Recently Developed Nanoparticles on the Ultrafiltration Membrane and Their Applications: A Review
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The emergence of mixed matrix membranes (MMMs) or nanocomposite membranes embedded with inorganic nanoparticles (NPs) has opened up a possibility for developing different polymeric membranes with improved physicochemical properties, mechanical properties and performance for resolving environmental and energy-effective water purification. This paper presents an overview of the effects of different hydrophilic nanomaterials, including mineral nanomaterials (e.g., silicon dioxide (SiO2) and zeolite), metals oxide (e.g., copper oxide (CuO), zirconium dioxide (ZrO2), zinc oxide (ZnO), antimony tin oxide (ATO), iron (III) oxide (Fe2O3) and tungsten oxide (WOX)), two-dimensional transition (e.g., MXene), metal–organic framework (MOFs), c

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Publication Date
Sun Apr 30 2023
Journal Name
Al-kindy College Medical Journal
Influence of Vitamin D Deficiency on the Level of Salivary cathelicidin LL-37 in relation to Dental Caries Experience: A Case-Control Study
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Background: Vitamin D improves innate immunity by enhancing the expression of antimicrobial peptides. The antimicrobial action of cathelicidin is widespread and effective against cariogenic bacteria. This research aimed to investigate the effect of vitamin D deficiency on the level of salivary cathelicidin concerning dental caries experience.

Subjects and Methods: A case-control study was carried out, and the sample was composed of 80 females; the study group involved 40 females with a serum vitamin D concentration of less than 10 ng/ml. In addition to the control group involving 40 females wh

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