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Search Results: 1 - 10 of 4794 matches for " composite "
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In Vitro Evaluation of Polyurethane-Chitosan Scaffolds for Tissue Engineering  [PDF]
Imelda Olivas-Armendariz, Perla García-Casillas, Adriana Martel Estrada, Alberto Martínez-Villafa?e, Laura A. A. de la Rosa, Carlos A. Martínez-Pérez
Journal of Biomaterials and Nanobiotechnology (JBNB) , 2012, DOI: 10.4236/jbnb.2012.34044
Abstract: In this work the use of Polyurethane (PU)-Chitosan(CH) scaffolds prepared by thermal induced phase separation (TIPS) for osteoblast proliferation and bone mineralization is described. Primary rat calvaria osteoblasts were seeded in the scaffolds and it was shown that supported cell adhesion and growth. The behavior osteoblast cells growing in the scaffold in function of the different ratio of PU and CH is presented. The results showed that TIPS is an appropriate technique for the production of PU-CH scaffolds with high potential for application as cell scaffolds in bone tissue engineering.
Microleakage of Nanofilled Composite Resin Restorative Material  [PDF]
Ibrahim Hamouda, Hagag abd Elkader, Manal F. Badawi
Journal of Biomaterials and Nanobiotechnology (JBNB) , 2011, DOI: 10.4236/jbnb.2011.23040
Abstract: The role of nanofillers in reducing the microleakage of dental composite resins has not been previously investigated. So this study was designed to evaluate microleakage of nanofilled composite resin in comparison to the conventional hybrid composite. Twenty extracted sound molars were selected. Class II cavities were prepared. All cavities were etched (enamel and dentin) with 37% phosphoric acid. Dentin bonding agents were applied to etched tooth surfaces and restored with nanofilled and hybrid composite restorative materials. The restored teeth were thermocycled. Specimens were immersed in 2% methylene blue dye, sectioned along the mesio-distal direction; dye penetration of occlusal and gingival margins of each section was evaluated using a stereo-microscope. No significant difference was found between the microleakage of nanofilled and hybrid composite restorations at occlusal / enamel and at gingival / dentin margins. Also, there were no significant differences for nanofilled composite restorations at occlusal / enamel margins and gingival / dentin margins. On the other hand, there were a significant differences for hybrid composite restorations at occlusal / enamel margins and gingival / dentin margins.
In Vitro Screening and Selection of Probiotic Lactic Acid Bacteria Isolated from Spontaneously Fermenting Kunu-Zaki  [PDF]
Solakunmi Omotunde Oluwajoba, Felix Akinsola Akinyosoye, Victor Olusegun Oyetayo
Advances in Microbiology (AiM) , 2013, DOI: 10.4236/aim.2013.34044

The present study was conducted to determine the pro-biotic properties in vitro of the lactic acid bacteria isolated from spontaneously fermenting kunu-zaki. Kunu-zaki was processed using composite, non composite, germinated and ungerminated Digitaria exilis (Fonio), Sorghum bicolor (Sorghum) and Pennisetum americanum (Millet) cereals. A total of 150 LAB isolates were obtained from all the fermenting slurries. These 150 LAB isolates were screened for their ability to grow at pH 3.0, resistance against bile salt and ability to inhibit reference test pathogens. Out of these 150 LAB isolates; 21 exhibited good probiotic properties. All the 21 isolates were further identified to specie and subspecies level using standard API50CHL system with all 21 showing good survival (P < 0.05) in a pH 3.0 buffered medium and subsequent resistance to 0.3% bile. The LAB isolates which survived these conditions consisted of 18 Lactobacillus species, 2 Pediococcus species and 1 Lactococcus specie. These LAB species were further examined for antimicrobial activity against the growth of reference pathogens Staphylococcus aureus 25923, Escherichia coli 25922, Pseudomonas aeruginosa 27853 and Enterococcus faecalis 29212. All 21 LAB species exhibited good inhibition of all test reference pathogens except Lactobacillus fructivorans, Lactococcus lactis sp lactis and L. fermentum which however, showed no zone of inhibition against the growth of E. faecalis. Kunu-zaki made from composite un-germinated Sorghum bicolor (Sorghum) and Pennisetum americanum (Millet) cereal grains contained the highest percentage (52%) of LAB species which showed good probiotic criteria in vitro. Non composite ungerminated cereals accounted for 33% of the total probiotic LAB isolates whilst the germinated non composite and composite cereals recorded the lowest percentage (10%) and (5%) of probiotic LAB respectively. The results of this research study showed that the LAB species isolated from wild fermentation of kunu-zaki beverage fulfilled the criteria for in vitro screening of probiotic characteristics. These LAB species possed potential for further use as probiotic in human preparations and suggested the use of kunu-zaki made from ungerminated composite sorghum and millet grains as a natural probiotic drink.

Review of Recent Literature on Static Analyses of Composite Shells: 2000-2010  [PDF]
Mohammad S. Qatu, Ebrahim Asadi, Wenchao Wang
Open Journal of Composite Materials (OJCM) , 2012, DOI: 10.4236/ojcm.2012.23009
Abstract: Laminated composite shells are frequently used in various engineering applications including aerospace, mechanical, marine, and automotive engineering. This article reviews the recent literature on the static analysis of composite shells. It follows up with the previous work published by the first author [1-4] and it is a continuation of another recent article that focused on the dynamics of composite shells [3]. This paper reviews most of the research done in recent years (2000-2010) on the static and buckling behavior (including postbuckling) of composite shells. This review is conducted with an emphasis on the analysis performed (static, buckling, postbuckling, and others), complicating effects in both material (e.g. piezoelectric) and structure (e.g. stiffened shells), and the various shell geometries (cylindrical, conical, spherical and others). Attention is also given to the theory being applied (thin, thick, 3D, nonlinear …). However, more details regarding the theories have been described in previous work [1,3].
Modeling Fiber Composites during the Cure Process for Piezoelectric Actuation  [PDF]
Darryl V. Murray, Oliver J. Myers
World Journal of Mechanics (WJM) , 2013, DOI: 10.4236/wjm.2013.31002

Analytical, numerical, and experimental modeling methods are presented to predict deformation after the cure process of thin unsymmetric laminates for piezoelectric actuation. During fabrication, laminates deform to several post-cure room temperature shapes. Thin cross-ply laminates deform to a circular cylindrical post-cure shape while thicker laminates deform to a saddle shape. Post-cure shapes are dependent on ply orientation, thickness, and material properties. Because, CLT alone does not always predict the correct post-cure room temperature shape of the thin composite laminates, an extension of CLT with the Rayleigh-Ritz technique and potential energies are used to better predict these shapes. Finite element models are used to predict the post-cure room temperature shapes. Thin composite laminates are modeled coupling heat transfer and structural mechanics, which are necessary for modeling the cure process. Modeling the fabrication process captured important data such as residual stresses from the cure process, room temperature shapes, and bi-stability of the composite laminates. To validate these analytical and numerical results, experiments were con- ducted using macro-fiber composite (MFC) patches for morphing the laminates. The experimental piezoelectric morph- ing results relate well to analytical and numerical results.

The Structure of Modified Fe-Ni Bioxide Composite Nanoparticles Using Fe(NO3)3  [PDF]
Yueqiang Lin, Jian Li, Lihua Lin, Xiaodong Liu, Longlong Chen, Decai Li
Advances in Nanoparticles (ANP) , 2013, DOI: 10.4236/anp.2013.24040

Composite nanoparticles containing a γ-Fe2O3 core, Ni2O3 external shell and FeCl3·6H2O outermost layer can be synthesized by chemically induced transition in FeCl2 solution. These may be modified by treatment with Fe(NO3)3 to obtain particles for the preparation of ionic ferrofluids. Vibrating sample magnetometer (VSM) measurements and transmission electron microscopy (TEM) observations show that after Fe(NO3)3 treatment, the specific magnetization becomes weaker and the size becomes larger for treated particles compared with the untreated particles. Using energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), the structure of the particles before and after the treatment is revealed. The experimental results show that the γ-Fe2O3

The Uniformal Metallization of the AlSiC Metal Matrix Composite Material Surface  [PDF]
Nikolai Vladimirovich Sevostyanov, Konstantin Nikolaevich Nishchev, Mikhail Il’ich Novopoltsev
Journal of Surface Engineered Materials and Advanced Technology (JSEMAT) , 2014, DOI: 10.4236/jsemat.2014.44026

The surface of the AlSiC composite material consists of aluminum and silicon carbide areas. The uniformal metallization by nickel is necessary in order to provide solderability and high thermal conductivity of the surface. The process of chemical deposition of nickel coatings elaborated in the research center VIAM yields the uniformal highly adhesive metallization. The kinetics of the deposition process has been studied and the estimation of the coatings quality has been made in comparison with commercially available samples produced elsewhere.

To Improve Mixed-Mode Interlaminar Fracture Toughness of Composite Sub-Structures  [PDF]
Hessam Ghasemnejad, Hossein Mirzaii
Open Journal of Composite Materials (OJCM) , 2014, DOI: 10.4236/ojcm.2014.41004

The present paper investigates the influence of stitching on delamination resistance of laminated composite structures. The mixed-mode interlaminar fracture toughness, GI/IIC, of the stitched hybrid laminated composites is studied in order to investigate the resistance of the 3D-composites to the crack propagation in delaminated composite structures. To that end, the mixed-mode interlaminar fracture toughness was measured using the asymmetric double cantilever beam (ADCB) test method. The hybrid ADCB and stitched hybrid ADCB composite beams were laid-up in order to study the effect of stitching on the interlaminar fracture toughness. The test results showed that the resistance of stitched fibres against the crack propagation in stitched hybrid composites can significantly improve the mixed-mode interlaminar fracture toughness.

Wear Characteristics in Al-SiC Particulate Composites and the  [PDF]
Z. Hasan, R. K. Pandey, D.K. Sehgal
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2011, DOI: 10.4236/jmmce.2011.1014104
Abstract: The Al-Si alloy with near eutectic composition has been conventionally used as a piston material for automobile applications. It is required to possess high abrasive wear resistance for enhanced life of the engine. The alloy is known to have fairly good wear resistance due to increased percentage of silicon present in fine form. In the present investigation, Al-SiC particulate composites have been studied for their wear resistance against emery paper (400 grit SiC particles) counterface and a comparison has been made with existing piston alloy i.e. Al-Si alloy. The Al-SiC composites have been prepared using Liquid Metallurgy technique employing 2124 Al alloy as the base material with 10 and 20 % SiC particulates by weight. The abrasive wear study has been conducted on a Pin on Disc machine. The wear rate in terms of weight loss per unit sliding distance as well as the volumetric wear rate have been obtained for the Al-SiC composites. The characteristics of worn surface were investigated using SEM. The composites are found to possess very high wear resistance as compared to Al-Si piston alloy. The results have been discussed and important conclusions are outlined.
The Pattern of Prime Numbers  [PDF]
José William Porras Ferreira
Applied Mathematics (AM) , 2017, DOI: 10.4236/am.2017.82015
Abstract: The prime numbers P≥5 obey a pattern that can be described by two forms or geometric progressions \"\" or \"\" that facilitates obtaining them sequentially, being possible also to calculate the quantity of primes that are in the geometric progressions \"\" as it is described in this document.
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