bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Study on the Effect of Geometrical Parameter on the Thermal-Hydraulic Performance of the Metal Foam Heat Exchanger
Authors: Jasim Noor M , Fayyadh Ekhlas M , Hasan Moayed Razoki 
Published: March 2021

Abstract
A numerical study was conducted to examine the heat transfer and pressure drop of the metal foam-wrapped array heat exchanger. Effects of geometrical parameters, including arrangement of metal foam heat exchanger (two arrangement: fully-filled of metal foam while other have a gap between metal foam and the chamber walls), porosity, and the pore density on the thermal hydraulic performance of copper metal foam heat exchanger are examined. Numerical modelling was done considering the thermal non-equilibrium energy model and the Darcy-Forchheimer flow model for metal foam heat exchangers in the Star-CCM+ program version 2019. Four types of metal foams at fixed dimensional thickness of 0.91 with variable properties were adopted, where the pores density was 5PPI & 20PPI and the porosity was 89% and 95%. The heat exchanger system is simulated over a range of Reynolds number, based on tube diameter, from 1333 to 6555 with tubes heated at a constant wall temperature. The layout and geometry of the foam heat exchangers were compared with bare tube heat exchanger. It was found that At low porosity 89%, the configuration of metal foam heat exchanger that have pores density of 5PPI gives higher thermal performance (higher area goodness factor ratio) than 20 PPI. Also, decreasing porosity from 95% to 89% enhancement in the thermal performance was achieved. However, the metal foam heat exchanger that has a gap between metal foam and the chamber walls gave better thermal performance as compared with fully-filled foam heat exchanger.
Prediction of Indoor Airflow and Contaminant Transport in Office with Coupled Displacement Ventilation and Ceiling Radiant Cooling Panel
Authors: Shoky Mays Ahyab , Lafta Ali , Hussein Hasanen M 
Published: March 2021

Abstract
In this research, an experimental and numerical analysis have been conducted to predict the temperature, velocity distribution, and contaminant concentration in indoor spaces conditioned with corrugated ceiling radiant cooling panel (RCP) and Displacement Ventilation. The experiments were done on a model room with dimensions of (1.6m×1.2m×0.8m) built according to a suitable scale factor (1/5) to simulate the temperature, velocity distribution, and CO2 concentration by 36 measuring devices in an array scheme in three different zones and heights. Two cases were considered in this work, the first was with chilled ceiling panels only (without ventilation) and the second was with displacement ventilation. The experiments primary variable was the mean panel temperature (Tmp) with values of (15, 16, and 17oC). The second experimental cases were taken with an air inlet temperature of 24oC and a velocity of 0.7m/s with a range of outdoor air temperatures of (36 to 42oC). A computational fluid dynamics (CFD) program was built up to simulate air distribution in an enclosed environment with the DV-PCB system, which was then validated by the measured data. The validated CFD model was employed to analyze thermal comfort and indoor air quality in the enclosed environment with the DV-PCB coupled system using four indices: vertical temperature gradient, draft rate, normalized contaminant concentration, and age of air. The results indicate that CRCP is quite effective in reducing the temperature gradient created by DV. The results show that there is an enhancement in the total cooling capacity. Most of the computed results were presented as temperature contours and velocity vectors diagrams compared with the experimental work. The comparisons show a reasonably good agreement. Both experimental and numerical studies assist RCP for cooling purposes in the Iraqi climate for its ease, simplicity, and good comfort performance.
Mechanical Properties of Acrylic Laminations Resin (PMMA) Reinforced by Natural Nanoparticles and Hemp Fibers
Authors: Ahmed S H , Salih W M 
Published: March 2021

AbstractThe current research uses the chopped hemp fibers (HF) with a length of 0.5mm at a various mass fraction (0.0, 0.3, 0.6, and 0.9 wt%) to acrylic resin (PMMA) reinforced with 0.3% of walnut shell nanoparticles (WSP) for building up the properties of PMMA to be utilized in attachment prosthetics. Some mechanical and physical properties were studied. The results indicated that all properties were improved when the hemp fibers reached the most extreme value at 0.9% mass fraction of HF to polymer nanocomposite (PMMA: 0.3% walnut shell nanoparticle (WSP)) test. Therefore, this hybrid composite might be used for accomplishing the required properties for the prosthetic application.
Influence of Adding Nano Coating Layers on the Hardness and Impact strength Properties for Low Carbon Steel
Authors: Kareem Layth Zbbal Abd UL , Alithari Ali Sadiq , AL-Zurfi Nabeel 
Published: March 2021

AbstractNanotechnology is one of the great techniques that helping to considerably improve many technologies and industry sectors such as information technology, homeland security, medicine, transportation, energy, food safety, and environmental science. Low carbon steel is widely used in many applications because it is cheap and it has high workability. However, low surface hardness and impact toughness are its main disadvantages. In this work, the nanocoating of tungsten carbide (WC) has been added to the low carbon steel surface with a thickness of 30, 40, and 50μm by using the thermal spray process with the HVOF technique. The present work aims to investigate the coating layer influence on the hardness and impact toughness. The results showed a significant improvement in the hardness, reaching 94.7%, while the impact toughness improved by 36% for a sample coated with a 50μm comparing with uncoated samples. The improvement in the hardness and impact toughness is due to the good adhesion of nano coat with the steel surface and the high hardness of tungsten Carbide as well as the good toughness of tungsten. The thickness of the coating layer is detected by using the scanning electron microscope images for each spray time. The results show that the coating with a layer of a thickness of more than 50μm will cause flaking and removing the coating layers.
Graphene-Reinforced the Structure and Mechanical Properties of New PMMA-PVA Hybrid Nanocomposites
Authors: Abdullah Salah Shadhan , kadhim Mohammed Abdul , Al-Bermany Ehssan 
Published: March 2021

Abstract
Graphene challenges the logic with its behavior and properties because of its multiple uses, so scientists and researchers paid great attention to it. In this study, newly fabricated nanocomposites consist of polymethyl methacrylate and polyvinyl alcohol using Dimethylformamide-co-distilled water and Dimethylformamide solvent with various loading ratios (0.09, 0.18, and 0.27 wt.%) of graphene oxide nanosheets, applying a developed solution casting method. The microstructure, some physical and mechanical properties of the polymethyl methacrylate - polyvinyl alcohol/graphene oxide nanocomposites, such as density, viscosity, ultrasonic velocity, coefficient of ultrasonic absorption, compressibility and bulk modulus, etc. were measured. The method exhibited the successful synthesis of these nanocomposites for the first time with good homogeneity and good desperation as existing clearly in the images of the optical microscopy. Additionally, strong interfacial interaction was formed between the polymers and nano-graphene sheets as exhibited in Fourier-transform infrared spectra with the most functional group of polymer and graphene oxide in the nanocomposites. The scanning electron microscope images also confirmed this finding. These images illustrated the smooth and homogeneous fracture surface with good dispersion of the nanosheets of graphene oxide into the polymer mixture. The low loading ratio of graphene oxide in the matrix from 0.09 to 0.27 wt.% exhibited significant improvement of the viscosity of ultrasonic velocity, bulk modulus, and coefficient of absorption of the mechanical waves up to 79%, 63 %, 225%, and 127%, respectively, with the blended polymers. These findings could help to realize these new nanocomposites as promising materials for wide applications, such as car glass and backlight and ultraviolet filters applications.
Optimization of Manufacturing Titanium-Magnesium alloy for Biomaterial Applications using Grey Relational Analyses
Authors: Al-Ethari Haydar , Abbas Sundus , Zamel Ekhlas Khalid 
Published: March 2021

Abstract
The present paper is focusing on improving the performance of titanium-magnesium alloys prepared by the powder metallurgy technique. These alloys show good biocompatibility and bioactivity, but there is still a demand to study their manufacturing factors. Optimizing the manufacturing process of Ti-Mg alloys increases its expected life. The response selected to evaluate the produced alloys are the hardness, the compressive strength, and the porosity, while the affecting manufacturing parameters are the compacting pressure, sintering time, and magnesium content. Three levels of these parameters were selected to design the experiments based on a standard L9 orthogonal array of the Taguchi method. A Grey relational analysis method was performed to optimize the responses. The obtained experimental results were analyzed using Minitab 16 software at a confidence level of 0.5%. The results indicated that the selected parameters significantly influence the responses of the alloy samples. The optimum level of the affecting parameters was found in a compacting pressure of 760MPa, sintering time of 6hours, and 15wt% of magnesium content.
Fabrication and Study Properties of ZnO/SiC Quantum Dots
Authors: Al-Ali Entesar SJ , Abdalwahid KR , Al-Sultani Kadhim F 
Published: March 2021

Abstract
In this research, heterojunction was developed by using SiC quantum dots. High-quality n-ZnO film on commercial p-SiC quantum dots has been prepared based on utilizing pulse laser deposition technique and spin coating under the pressure of 10−5 mbar, deposited at room temperature on a substrate of glass at various values of the thickness (113.3 and 160) nm, respectively. Then, annealed for two hours at 450 °C. ZnO/SiC QDs were described by the estimation of XRD and FE-SEM. XRD estimation uncovered that the SiC QDs prepared by spin coating with dye were hexagonal structure. The pulse laser deposition PLD method used to make ready ZnO thin film was hexagonal wurtzite with high-quality polycrystalline. UV-Visible spectrophotometer utilized in the range of (200-800) nm to determine spectral absorbance, transmittance, and energy gap of heterojunction. The optical properties results showed that the transmittance was (98 and 87)% for ZnO film and SiC, respectively. The pure ZnO thin film allowed a direct energy gap (Eg) that was 3.8 eV, while SiC QDs were 2.65 eV direct energy gap.
Investigation of the Polyol Types and Isocyanate Concentrations on the Rheological, Morphological and Mechanical Properties of Polyurethane Foams
Authors: Mohamed Dhey Jawad , Hadi Nizar Jawad , Alobad Zoalfokkar Kareem 
Published: March 2021

AbstractThis research studies the preparation and characterization of polyurethane foams, which are produced from the reaction of isocyanate Methylene Diphenyl Diisocyante “MDI” and polyol with water being used as a chemical blowing agent. The effect of isocyanate concentration on the cross-linking formation of polyurethane samples and its influence on the final properties of the foams were investigated. Each type of polyols (Local commercial market polyester, Quickmast120 and Quickmast110 polyether) were mixed with the isocyanate at equivalent ratio of (isocyanate: polyol) (0.5:1, 1:1, 2:1 and 3:1) to prepare polyurethane foam using one shot method. Rheological tests were performed for the polyols and isocyanate to find out their effect on the formability processes. The morphology and structure were performed using FTIR and digital microscopy. The tensile strength, compression strength and the hardness were conducted to show the effect of isocyanate concentrations on the mechanical properties of samples. The result display the Quickmast 120 polyol was unsuitable due to the large cells, unstable rheological properties and high hardness, which leads to a loss of flexibility of the polyurethane foams. The ratio of (1:1) (polyol/isocyanate) was the best in terms of the formability of the foam giving the smaller cells size and the best mechanical characteristics as compared to other concentrations of isocyanate.
Effects of Titanium Dioxide Nanoparticles on the Mechanical Strength of Epoxy Hybrid Composite Materials Reinforced with Unidirectional Carbon and Glass Fibers.
Authors: Abass Basim A , Hunain Mustafa B , Khudair Jaafar M A 
Published: March 2021

Abstract
The present work describes the development of hybrid epoxy composite reinforced with unidirectional carbon, glass fibers and nano-TiO2 powder in order to study some of its mechanical properties. Titanium dioxide (TiO2) were dispersed in epoxy with different weight fractions (1, 3, and 5 wt. %) using sonication. Composite materials under study have been prepared by reinforcing the resulted nanocomposite by three different layers of unidirectional carbon fibers and glass bidirectional fibers using hand lay-up technique. Tensile and hardness tests as well as the surface roughness test have been performed during the experimental work. It has been observed that the tensile strengths of the fiber-reinforced polymer composites increase with fiber content, and TiO2 nanoparticles up to a maximum value of 3 wt % after which it decreases. The value, modulus of elasticity, tension resistance, and hardness of the fiber-reinforced polymer composites increase with increasing fiber loading. The results obtained in this work show that the addition of TiO2 nanoparticles at up to 3%wt to the epoxy composite reinforced with unidirectional carbon and glass fibers enhances the mechanical strength of such material.
Laser Treatment Influence on Estimated Fatigue Life of AA2017
Authors: Al-Helli Ali H , Hamza Assad Kh 
Published: March 2021

AbstractThis paper deals with improving the fatigue strength of AA2017-T0 aluminium alloy by using laser surface treatment. A set of rotating fatigue specimens were machined and prepared for this rezone. Half number of them was surface-treated using 1 Joule laser machine. The fatigue tests for the treater and as reserved specimens were used for different loads to draw the S-N curves. It was shown that the laser treatment was improving the fatigue strength for the alloy. The effect of varying the stress amplitude through-loading life was studied. It was shown that the (high-low) loading types give a longer life than the (low-high) loading types. The results show that the thermal laser treatment of the surface of the aluminium alloy AA2017 gives higher hardness and generates compression residual stresses that improving the mechanical properties of the alloy. Comparing experimental and numerical finite element results gives a good agreement with maximum error not exceeding (9.68%).
Effect of Different Multi-Walled Carbon Nanotubes MWCNTs on Mechanical and Physical Properties of Epoxy Nanocomposites
Authors: Mahmood Olfat A , Jameel Zainab N , Abdullah Hind W 
Published: March 2021

Abstract
Different types of long and short multiwalled carbon nanotubes (MWCNTs) were used as structural support in epoxy resin with a percentage of weight (0.1,0.2,0.5,1.0,1.5,2.0,2.5,3.0,3.5,4.0,4.5,&5) wt. percent, Utilization of direct mixing processes to prepare Nano-Composites (Epoxy/MWCNTs). The ultrasonic mixing method has been used to disperse the nanotubes into the epoxy resin system. SEM was used to demonstrate the dispersion in the epoxy polymer matrix of different MWCNT concentrations. The findings show that electrical conductivity properties boost effect, thermal conductivity coefficient, and A.C with percentage enhancement of less than 2 percent, and then raising with further raise in the content of MWCNTs.
Design and Construction of Device for Rubber Material Fatigue Test
Authors: Al-Raheem Saddam K , Jweeg Muhsin J , Hassan Abdul kareem F 
Published: March 2021

Abstract
Due to the wide use of rubber components in different engineering applications such as vibration isolators, engine mounts, car tires, and bridge bearing pads, etc., this rubber component is mostly subjected to repeated loads continuously. As a result, these loads will initiate cracks on the outside surface of a component and then, these cracks will grow over time, and then, the growth of the cracks increase leading to a failure of the rubber component. Many researchers have studied the behavior of fatigue under the action of many factors by utilizing many devices. These devices produce repeated loading on the sample made of rubber material, initiating cracks and, then crack growth, which leads to failure. Therefore, in this paper, a modern test device has been developed and constructed to perform laboratory rubber fatigue testing. This device has been proven to be accurate and with the ability of repeatability.
Synthesis and Characterization of Low-Cost Adsorbent and used for Alizarin Yellow GG and Alizarin Red S Dyes Removal from Aqueous Solutions
Authors: Al-Salihi K J , Alfatlawi W R 
Published: March 2021

AbstractThe effective use of a synthetic clay as ionic solid adsorbent for the removal of alizarin yellow GG and alizarin red S from aqueous solutions was investigated as low-cost adsorbent. Anionic clay of layered double hydroxide (LDH) was prepared from the salts of magnesium-aluminium nitrate in a ratio of (5:1) by co-precipitation method, characterized by X-ray diffraction (XRD), FT-IR spectroscopy and thermogravimetric analysis (TGA) to confirm the presence of LDH. The effect of various experimental parameters like contact time, initial and concentrations were investigated. The experiments were carried out in a batch system to optimize operation variables. The Langmuir and Freundlich isotherm equations applied to the data and the isotherm analysis indicated that the equilibrium was fitted to both of Freundlich and Langmuir. The models showed physio – chemical sorption for both of Alizarine yellow GG and Alizarin Red S on LDH surface. Kinetics study was made using lagergreen equations and the results show that the sorption of Alizarine Yellow GG and Red dye uptake on layered double hydroxide (LDH) were fitted with both pseudo-first order until the adsorption reach equilibrium, then, they fellow pseudo second order where the adsorption rates depend on the amount of adsorbent and concentration of adsorbate. The partition coefficient Kd for the sorption of alizarine yellow GG and alizarin red S on LDH were also determined and it was indicated that the value of Kd increases with time until equilibrium is reached and becomes constant because of the extra unoccupied sites until the adsorption reaches equilibrium.
Assembly of large hBN nanocrystal arrays for quantum light emission
Authors: Preuß Johann A , Rudi Eduard , Kern Johannes , Schmidt Robert , Bratschitsch Rudolf , Michaelis de Vasconcellos Steffen 
Published: March 2021

Abstract
We fabricate rectangular arrays of hexagonal boron nitride (hBN) nanoplatelet clusters extending over hundreds of microns. Positioning is achieved by capillary assembly of suspended hBN particles into submicron polymer holes, patterned by electron-beam lithography. After removal of the patterned polymer from the SiO2/Si surface, average positioning yields of 74% at the desired locations are routinely achieved. At 10% of the locations, single-photon emitters (SPEs) are found. Thermal post-annealing of the prepared samples at 850 °C increases the number of SPEs by 50%. Our work paves the way for the production of wafer-scale SPE arrays based on commercially available hBN nanocrystals for a systematic statistical analysis of individually addressable SPEs, as well as for deterministic coupling of many emitters to a large number of photonic structures on photonic chips.
TIGER: inferring DNA replication timing from whole-genome sequence data
Authors: Koren Amnon , Massey Dashiell J , Bracci Alexa N 
Published: March 2021

Abstract

Motivation
Genomic DNA replicates according to a reproducible spatiotemporal program, with some loci replicating early in S phase while others replicate late. Despite being a central cellular process, DNA replication timing studies have been limited in scale due to technical challenges.

Results
We present TIGER (Timing Inferred from Genome Replication), a computational approach for extracting DNA replication timing information from whole genome sequence data obtained from proliferating cell samples. The presence of replicating cells in a biological specimen leads to non-uniform representation of genomic DNA that depends on the timing of replication of different genomic loci. Replication dynamics can hence be observed in genome sequence data by analyzing DNA copy number along chromosomes while accounting for other sources of sequence coverage variation. TIGER is applicable to any species with a contiguous genome assembly and rivals the quality of experimental measurements of DNA replication timing. It provides a straightforward approach for measuring replication timing and can readily be applied at scale.

Availability and implementation
TIGER is available at https://github.com/TheKorenLab/TIGER.

Supplementary information
Supplementary data are available at Bioinformatics online.
The computational neurology of movement under active inference
Authors: Parr Thomas , Limanowski Jakub , Rawji Vishal , Friston Karl 
Published: March 2021

Abstract
We propose a computational neurology of movement based on the convergence of theoretical neurobiology and clinical neurology. A significant development in the former is the idea that we can frame brain function as a process of (active) inference, in which the nervous system makes predictions about its sensory data. These predictions depend upon an implicit predictive (generative) model used by the brain. This means neural dynamics can be framed as generating actions to ensure sensations are consistent with these predictions—and adjusting predictions when they are not. We illustrate the significance of this formulation for clinical neurology by simulating a clinical examination of the motor system using an upper limb coordination task. Specifically, we show how tendon reflexes emerge naturally under the right kind of generative model. Through simulated perturbations, pertaining to prior probabilities of this model’s variables, we illustrate the emergence of hyperreflexia and pendular reflexes, reminiscent of neurological lesions in the corticospinal tract and cerebellum. We then turn to the computational lesions causing hypokinesia and deficits of coordination. This in silico lesion-deficit analysis provides an opportunity to revisit classic neurological dichotomies (e.g. pyramidal versus extrapyramidal systems) from the perspective of modern approaches to theoretical neurobiology—and our understanding of the neurocomputational architecture of movement control based on first principles.