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A review of ultra-high temperature materials for thermal protection system
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Abstract<p>Ultra-High Temperature Materials (UHTMs) are at the base of entire aerospace industry; these high stable materials at temperatures exceeding 1600 °C are used to manage the heat shielding to protect vehicles and probes during the hypersonic flight through reentry trajectory against aerodynamic heating and reducing plasma surface interaction. Those materials are also recognized as Thermal Protection System Materials (TPSMs). The structural materials used during the high-temperature oxidizing environment are mainly limited to SiC, oxide ceramics, and composites. In addition to that, silicon-based ceramic has a maximum-use at 1700 °C approximately; as it is an active oxidation process over low temperature and water vapor environment condition. However, a great emphasis is required for developing structural materials in oxidation and rapid heating environment where the temperature is greater than 1700 °C. This review covers briefly all main types of Thermal Protection Systems (TPSs) and all the materials are used to fabricate them with the maximum operational temperatures. Also, it covers the promised UHTMs (SiC, ZrB<sub>2</sub>, HfB<sub>2</sub>, SiB<sub>6</sub> and B<sub>4</sub>C) which are currently using for several aerospace applications, especially for TPS. Besides, it discusses the oxidation of SiC, B<sub>4</sub>C, SiB<sub>6</sub>, ZrB<sub>2</sub> and HfB<sub>2</sub>. Therefore, the carbides and borides of the transition metals, Zr and Hf have a high-melting temperature and good stability in forming high-melting temperature oxides.</p>
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Publication Date
Sun Nov 01 2020
Journal Name
Solid State Technology
Access Control Security Review: Concepts and Models
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Publication Date
Mon Apr 01 2024
Journal Name
Al-qadisiyah Journal Of Veterinary Medicine Sciences
Mycoplasma gallisepticum Infection in Poultry: Article Review
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Publication Date
Tue Dec 19 2023
Journal Name
Journal Of Madenat Alelem College
Review Article: Amygdalin as Anti-Cancer Agent
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Amygdalin (d-Mandelonitrile 6-O-β-d-glucosido-β-d-glucoside) and its semi synthetic product is Laetrile ( also called vitamin B17): a natural cyanogenic glycoside occurring in the seeds of some edible plants, such as bitter almonds and peaches. Early in the 19th century, Amygdalin was first isolated in 1830 by two French chemists, Robiquet and Boutron-Charlard, as active components in various fruit pits and raw nuts. However, the systematized study of vitamin B17 started when chemist Bohn (1802) discovered that a hydrocyanic acid is released during distillation of the water from bitter almonds. The various pharmacological effects of Laetrile include antiatherogenic, activity in renal fibrosis, pulmonary fibrosis, immune regulation, ant

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Publication Date
Wed Apr 03 2019
Journal Name
Al-kindy College Medical Journal
Low Back Pain and Obesity (Review Article)
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Low back pain a major causes of morbidity throughout the world and it is a most debilitating condition ,and can lead to decreased physical function ,compromised quality of life, and psychological distress.

Obesity is nowadays a pandemic condition. Obese subjects are commonly characterized by musculoskeletal disorders and particularly by non-specific LBP. However, the relationship between obesity and LBP remain to date unsupported by objective measurements of mechanical behavior of spine and it is morphology in obese subjects.                                   &nb

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Publication Date
Thu May 20 2021
Journal Name
International Journal Of Research In Social Sciences And Humanities
SUBJECT REVIEW: ACCULTURATION AND SECOND LANGUAGE ACQUISITION
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This paper aims to give an overview of acculturation in the literature by means of its explicit definitions, main characteristics, and categorical process. It also foreshadows the significance of acquiring novice culture with particular connection to second language acquisition. Schumann and John Berry underscored acculturation each with its own model of acculturation. In the case of this review, you will realize that Schumann's two main aspects are firmly rooted in berry's model of acculturation as an exclusive description in relation to second language acquisition. Steven Krashen outlined acquiring language from the intellectual and linguistic view of learning, whereas Micheal Long demanded for communication in social perspective. It has

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Publication Date
Sun Feb 28 2021
Journal Name
Jurnal Teknologi
HEAT TRANSFER ENHANCEMENT USING PASSIVE TECHNIQUE: REVIEW
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Preserving and saving energy have never been more important, thus the requirement for more effective and efficient heat exchangers has never been more important. However, in order to pave the way for the proposal of a truly efficient technique, there is a need to understand the shortcomings and strengths of various aspects of heat transfer techniques. This review aims to systematically identify these characteristics two of the most popular passive heat transfer techniques: nanofluids and helically coiled tubes. The review indicated that nanoparticles improve thermal conductivity of base fluid and that the nanoparticle size, as well as the concentrations of the nanoparticles plays a major role in the effectiveness of the nanofluids.

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Publication Date
Sun Nov 01 2020
Journal Name
Solid State Technology
Access Control Security Review: Concepts and Models
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HS Saeed, SS Abdul-Jabbar, SG Mohammed, EA Abed, HS Ibrahem, Solid State Technology, 2020

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Publication Date
Wed May 22 2024
Journal Name
Journal Of Biotechnology Research Center
Review Article: DNA Methylation in Cancer Immunity
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Background: The transcriptional control of various cell types, especially in the development or functioning of immune system cells involved in either promoting or inhibiting the immune response against cancer, is significantly influenced by DNA or RNA methylation. Multifaceted interconnections exist between immunological or cancer cell populations in the tumor's microenvironment (TME). TME alters the fluctuating DNA (as well as RNA) methylation sequences in these immunological cells to change their development into pro- or anti-cancer cell categories (such as T cells, which are regulatory, for instance). Objective: This review highlights the impact of DNA and RNA methylation on myeloid and lymphoid cells, unraveling their intricate

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Publication Date
Thu Dec 01 2011
Journal Name
Iraqi Journal Of Physics
Structural and D.C. conductivity investigation of the ternary alloy System a-AlXGa1-x As:H films prepared by new deposition method
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In this paper Alx Ga1-x As:H films have been prepared by using new deposition method based on combination of flash- thermal evaporation technique. The thickness of our samples was about 300nm. The Al concentration was altered within the 0 x 40.
The results of X- ray diffraction analysis (XRD) confirmed the amorphous structure of all AlXGa1-x As:H films with x  40 and annealing temperature (Ta)<200°C. the temperature dependence of the DC conductivity GDC with various Al content has been measured for AlXGa1-x As:H films.
We have found that the thermal activation energy Ea depends of Al content and Ta, thus the value of Ea were approximately equal to half the value of optical gap.

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Publication Date
Tue Jun 11 2024
Journal Name
International Journal Of Civil Engineering
Strength Evaluation of CFRP-Strengthened RC Slab-Beams System by Load Test to Satisfy the Safety Requirements: A Case Study
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The primary goal of in-situ load testing is to evaluate the safety and performance of a structural system under particular loading conditions. Advancements in building techniques, analytical tools, and monitoring instruments are prompting the evaluation of the appropriate loading value, loading process, and examination criteria. The procedure for testing reinforced concrete (RC) structures on-site, as outlined in the ACI Building Code, involves conducting a 24-h load test and applying specific evaluation criteria. This article detailed a retrofitting project for an RC slab-beams system by utilizing carbon fiber-reinforced polymer (CFRP) sheets to strengthen the structure following a fire incident. The RC structure showed indicators of deter

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