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Silica Fume Modified Cement-Based Mortar Exposed to High Temperatures: Residual Strengths and Microstructure
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Several previous investigations and studies utilized silica fume (SF) or (micro silica) particles as supplementary cementitious material added as a substitute to cement-based mortars and their effect on the overall properties, especially on physical properties, strength properties, and mechanical properties. This study investigated the impact of the inclusion of silica fume (SF) particles on the residual compressive strengths and microstructure properties of cement-based mortars exposed to severe conditions of elevated temperatures. The prepared specimens were tested and subjected to 25, 250, 450, 600, and 900 °C. Their residual compressive strengths and microstructure were evaluated and compared with control samples (CS) subjected to similar conditions (the same temperature category). The outcomes indicated that including silica fume particles in mortar mixtures lowered the amount and width of microcracks, upgraded the mass-loss performance, lowered crystalline calcium hydroxide, and reinforced the cement paste, which explained the improvement in residual mechanical strengths.

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Publication Date
Tue Mar 01 2016
Journal Name
Journal Of Engineering
Analytical and Numerical Tooth Contact Analysis (TCA) of Standard and Modified Involute Profile Spur Gear
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Among all the common mechanical transmission elements, gears still playing the most dominant role especially in the heavy duty works offering extraordinary performance under extreme conditions and that the cause behind the extensive researches concentrating on the enhancement of its durability to do its job as well as possible. Contact stress distribution within the teeth domain is considered as one of the most effective parameters characterizing gear life, performance, efficiency, and application so that it has been well sought for formal gear profiles and paid a lot of attention for moderate tooth shapes. The aim of this work is to investigate the effect of pressure angle, speed ratio, and correction factor on the maxi

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Publication Date
Wed Dec 01 2021
Journal Name
Journal Of Engineering
Laboratory Study on the Effect of Water-Cement Ratio on Strength Characteristics of Jet Grouting Columns
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Jet grouting is one of the most widely applied soil improvement techniques. It is suitable for most geotechnical problems, including improving bearing capacity, decreasing settlement, forming seals, and stabilizing slopes. One of the difficulties faced by designers is determining the strength and geometry of elements created using this method. Jet grouted soil-cement columns in soil are a complicated issue because they are dependent on a number of parameters such as soil type, grout and water flow rate, rotation and lifting speed of monitor, nozzle jetting force, and water to cement ratio of slurry. This paper discusses the effect of the water-cement ratio on the physical and mechanical characteristics of soilcrete. In t

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Publication Date
Tue Jul 09 2024
Journal Name
Modeling Earth Systems And Environment
Genesis Geological Model of Intracontinental Volcanism Contribution in Polymorphic Silica Geodes Formation, Northern Arabian Plate 
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Publication Date
Sun Nov 01 2020
Journal Name
Iop Conference Series: Materials Science And Engineering
Assessment of some mechanical properties of PMMA/silica/zirconia nanocomposite as a denture base material
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Abstract<p>In this research, nanocomposites of poly(methyl methacrylate) (PMMA) and a mixture of nano silica (SiO<sub>2</sub>) and nano zirconia (ZrO<sub>2</sub>) were prepared in different weight percentages of the nano fillers to improve some of the properties of PMMA resin to be used as a denture base material. The nano filles were surface modified with a coupling agent and added to the PMMA in different amounts. Impact strength, transverse strength, hardness and roughness were tested for both control and experimental groups. The results indicate that PMMA/silica/zirconia nanocomposites, prepared with 5% by weight of both types of fillers, had a slight increase in impact s</p> ... Show More
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Publication Date
Wed Dec 30 2009
Journal Name
Iraqi Journal Of Chemical And Petroleum Engineering
Differences Between Sodium Metasilicate and Silicic Acid as Silica Source for Zeolite Y Nano particles Synthesis by Sol- Gel Method
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Zeolite Y nanoparticles were synthesized by sol - gel method. Dffirent samples using two silica sources were prepared.
Sodium metasilicate (Na2SiO3) (48% silica) and silicic acid silica (H2SiO3) (75% silica) were employed as silica
source and aluminum nitrate (Al(NO3)3.9H2O) was the aluminum source with tetrapropylammonium hydroxide
(TPAOH) as templating agent.
The synihesized-samples were characterized by X-ray diffraction, showed the requirement of diffirent aging time for
complete crystallization to be achieved. Transmission Electronic Microscope (TEM) images, showed the particles were
in the same range of 30 - 75 nm. FT-IR spectroscory, showed the synthesized samples having the zeolite Y crystal
properties. The i

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Publication Date
Tue Dec 01 2020
Journal Name
Journal Of Economics And Administrative Sciences
The interactive role of high performance work systems in the relationship between high Involvement management practices and strategic Entrepreneurship / case study at Diyala State Company
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The research aims to form a clear theoretical philosophy and perceptions about strategic Entrepreneurship through the relationship between high Involvement management practices, the basis in creating that leadership and high-performance work systems as a support tool in achieving them according to the proposals (Hitt et al, 2011), in an attempt to generalize theoretical philosophy and put forward how to apply it within The Iraqi environment, and on this basis the problem of the current research was launched to bridge the knowledge gap between the previous proposals and the possibility of their application, aiming to identify the practices of high Involvement management and the possibility of high-performance work systems and thei

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Publication Date
Mon Sep 01 2025
Journal Name
Journal Of Oral Biology And Craniofacial Research
Morphological &amp; chemo mechanical analysis of exposed cervical dentin treated with three different desensitizing pastes (comparative in vitro study)
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Background Obstructing dentinal tubules is a valuable approach for managing dentin hypersensitivity. Although various agents promote dentin remineralization, direct comparisons between theobromine, bioactive glass (BAG), and nano-hydroxyapatite (Nano-HAP) under simulated oral conditions remain limited. To fill this gap, this in vitro study aimed to evaluate and compare the effectiveness of these three treatments on exposed cervical dentin. The assessment focused on their chemical, morphological, and mechanical effects on dentin. Materials and methods Forty-eight human dentin slabs were obtained from the cervical portions of twelve sound premolar teeth. Baseline Raman spectroscopy and VMH tests were done to exclude outliers. All specimens we

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Publication Date
Sun Feb 10 2019
Journal Name
Iraqi Journal Of Physics
A study of the effect of silica particles addition on some physical properties of PVC as a packaging material
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In this work, varying compositions of SiO2 micro filler were added
with the Polyvinyl Chloride (PVC) and samples have been prepared
using film casting technique. The results have been analyzed and
compared for PVC samples with (1 wt%, 3 wt%, 5 wt% and 10 wt%)
SiO2 micro filler. Mechanical characteristics such as tensile strength,
elongation at break and Young`s modulus were measured for all the
samples, where the tensile strength was increased from 8.39 Mpa for
purified PVC to 16 Mpa for 3% SiO2/PVC composite. Also, thermal
conductivity measurement values illustrated that composite materials
have a good thermal insulation at 10 wt. %, thermal conductivity was
decreased from 0.1684 W/m.

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Publication Date
Mon Apr 01 2019
Journal Name
Journal Of Educational And Psychological Researches
The Teaching Practices of Faculty Members in Northern Border University According to the Brain-Based Learning Theory
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The present study aims to identify the most and the least common teaching practices among faculty members in Northern Border University according to brain-based learning theory, as well as to identify the effect of sex, qualifications, faculty type, and years of experiences in teaching practices. The study sample consisted of (199) participants divided into 100 males and 99 females. The study results revealed that the most teaching practice among the study sample was ‘I am trying to create an Environment of encouragement and support within the classroom which found to be (4.4623). As for the least teaching practice was ‘I use a natural musical sounds to create student's mood to learn’ found to be (2.2965). The study results also in

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Publication Date
Mon Feb 14 2022
Journal Name
Journal Of Educational And Psychological Researches
Developing and Applying the Unrealistic Optimism Scale among Junior High School Students
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The present study aims to develop and apply the unrealistic optimism scale among high school students. The researcher has designed a scale of (38) paragraphs to measure the unrealistic optimism. A sample of (200) male and female students were chosen randomly to collect the needed data. The study found that the unrealistic scale of optimism has good psychometric characteristics. The research sample has a high level of التفاؤل غير الواقعي لدى عينة البحث unrealistic optimism. There is a statistically significant difference between male and female in the unrealistic optimism in favor of the male students. Finally, there is a statistically significant difference between students in the fourth and sixth gra

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