A pioneering idea for increasing the thermal performance of heat transfer fluids was to use ultrafine solid particles suspended in the base fluid. Nanofluids, synthesized by mixing solid nanometer sized particles at low concentrations with the base fluid, were used as a new heat transfer fluid and developed a remarkable effect on the thermophysical properties and heat transfer coefficient. For any nanofluid to be usable in heat transfer applications, the main concern is its long-term stability. The aim of this research is to investigate the effect of using four different surfactants (sodium dodecyl benzene sulfonate (SDBS), sodium dodecyl sulfate (SDS), cetyl trimethylammonium bromide (CTAB), and gum Arabic (GA)), each with three different concentrations, and five ultrasonication times (15, 30, 60, 90, and 120 min) on the stability of water-based graphene nanoplatelets (GNPs) nanofluids. In addition, the viscosity and thermal conductivity of the highest stability samples were measured at different temperatures. For this aim, nineteen different nanofluids with 0.1 wt% concentration of GNPs were prepared via the two-step method. An ultrasonication probe was utilized to disperse the GNPs in distilled water. UV–vis spectrometry, zeta potential, average particle size, and Transmission Electron Microscopy (TEM) were helpful in evaluating the stability and characterizing the prepared nanofluids. TEM and zeta potential results were in agreement with the UV–vis measurements. The highest nanofluid stability was obtained at 60-min ultrasonication time. The prepared water-based pristine GNPs nanofluids were not stable, and the stability was improved with the addition of surfactants. The presence of SDBS, SDS, and CTAB surfactants in the nanofluids resulted in excessive foam. The best water-based GNPs nanofluid was selected in terms of better stability, higher thermal conductivity, and lower viscosity. From all the samples that were prepared in this research, the (1–1) SDBS–GNPs sample with 60-min ultrasonication showed the highest stability (82% relative concentration after 60 days), the second better enhancement in the thermal conductivity of the base fluid (8.36%), and nearly the lowest viscosity (7.4% higher than distilled water).
The Invar effect in 3D transition metal such as Ni and Mn, were prepared on a series composition of binary Ni1-xMnx system with x=0.3, 0.5, 0.8 by using powder metallurgy technique. In this work, the characterization of structural and thermal properties have been investigated experimentally by X-ray diffraction, thermal expansion coefficient and vibrating sample magnetometer (VSM) techniques. The results show that anonymously negative thermal expansion coefficient are changeable in the structure. The results were explained due to the instability relation between magnetic spins with lattice distortion on some of ferromagnetic metals.
A new hetrocyclic liquid crystal compounds containing 1,3,4-oxadiazole with different substituted in para position (Bromo, Chloro, Nitro and Methyl) were synthesized and characterized by melting points, FTIR Spectroscopy and 1HNMR spectroscopy for [Cl-SR6] and [NO2-SR6] compounds. The liquid crystalline properties of the synthesized compounds were studied by using hot-stage polarizing optical microscopy (POM), so they determined the transition enthalpies and entropies by using differential scanning calorimetery (DSC). All of the compounds show mesomorphic properties. The compounds [Br-SR6], [Cl-SR6] and [NO2SR6] exhibit an enantiotropic dimorphism smectic (Sm) phase, while the compounds [MeSR6] showed nematic (N) phase throw cooli
... Show MoreIn this study, zinc oxide was prepared by pulsed laser ablation method (PLAL), which is an easy-to-use and inexpensive physical method. The optical properties were studied using UV-Vis spectrometers, structure properties by (XRD) to calculate the crystalline size, and particle size determination by Field emission scanning electron microscopy (FE-SEM) and (EDS), transmission electron microscopy (TEM) assays and it was proved that they are within the ideal nanoscale for biological application. These ZnO NPs were employed on the inhibitory activity of different types of Gram-positive and Gram-negative bacteria, as well as on fungi, and it was noted their ability to penetrate the bacterial cell wall and inhibit its action.
This study shows how the structural and dielectric properties of (SnO2)1-x(Mn2O3)x, (where x=0.00, 0.03, 0.05,0.07, and 0.09) prepared using the solid state reaction technique, are affected by the doping of semiconducting metal oxide Mn2O3. Structural analysis of the composites was carried out using information from the composite samples obtained from X-ray diffraction (XRD). The diffraction peak shifting in XRD patterns indicated that Mn ions were successfully incorporated into the SnO2 crystal lattice. Mn ions were successfully doped in the Tin oxide matrix lattice with the subsequent increase of doping levels. The average crystal size evaluated using Scherrer's equation was found to vary from 33 to 37 nm, and the lattice constant
... Show More(Thimma) in Arabic means compact, and immunity. (People of Thimma) are the free non-Muslim people under Muslim rule. This includes Heavenly Religions people, i. e., Christian and Jews).
They have been called (People of Thimma) because they had paid (Jizyah: tribute) so they became safe for their souls, honor, properties at the custody of Muslims.
Islamic law had posed (Jizyah: tribute) upon the Jews and Christians who were living under Muslim rule as a reaction of not embracing Islam Faith against securing their rights and freedom.
Freedoms secured by Islam for the (People of Thimma) had been many, including the right of faith, not coercing them to be Muslim, the right to live, to possess properties, protect and secure them, the
Receipt date:6/3/2021 acceptance date:4/5/2021 Publication date:31/31/2021
This work is licensed under a Creative Commons Attribution 4.0 International License.
The research in the role of variables contact for non-state actors have become more influential in the current of contemporary events, that related with the reality of seeking services and providing all of that in favor of maintaining the social peace, and ensuring its empowerment in order to make peace and stability outcomes as a real fa
... Show MoreIn this article, we developed a new loss function, as the simplification of linear exponential loss function (LINEX) by weighting LINEX function. We derive a scale parameter, reliability and the hazard functions in accordance with upper record values of the Lomax distribution (LD). To study a small sample behavior performance of the proposed loss function using a Monte Carlo simulation, we make a comparison among maximum likelihood estimator, Bayesian estimator by means of LINEX loss function and Bayesian estimator using square error loss (SE) function. The consequences have shown that a modified method is the finest for valuing a scale parameter, reliability and hazard functions.
Abstract
Objective (s): To evaluate reasons for partial compliance and non-compliance to the
routine childhood vaccination schedule in Al-Karkh district
Methodology: Descriptive study , using the evaluation approach, is carried throughout the present study to determine the reasons for the Routine Childhood Vaccination at health care sectors and primary health care centers at Al-Karkh District in Baghdad City, Convenient, non-probability, sample of (90) mother who are recruited from health care sectors at Al-Karkh District in Baghdad City. All mothers, who ha
... Show MoreA series of 4-(methylsulfonyl)aniline derivatives were synthesized in order to obtain new compounds as a potential anti-inflammatory agents with expected selectivity against COX-2 enzyme. In vivo acute anti-inflammatory activity of the final compounds 11–14 was evaluated in rat using an egg-white induced edema model of inflammation in a dose equivalent to 3 mg/Kg of diclofenac sodium. All tested compounds produced significant reduction of paw edema with respect to the effect of propylene glycol 50% v/v (control group). Moreover, the activity of compounds 11 and 14 was significantly higher than that of diclofenac sodium (at 3 mg/Kg) in the 120–300 minute time interval, while compound 12 expressed a comparable effect to that of di
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