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Constituent Materials (constituent + material)
Selected AbstractsAnalysis of a retrieved Isola spinal system fractured in serviceJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2003E. A. Magnissalis Abstract A 1/4-in.diameter two-column Isola spinal system implanted in a 13-year-old girl suffering from cerebral palsy and a severe neuromuscular scoliosis of 120°, was replaced 22 months after primary implantation. The system was removed due to fracture of the lower left (concave) bar, between its two cross connectors (i.e., the distal bypass connector and a transverse cross link), as a result of a postoperative infection and a subsequently developed pseudarthrosis. The retrieved implants were analyzed with the use of a multitechnique characterization procedure involving macroscopic and microscopic examination, micro-multiple internal reflectance FTIR spectroscopy, X-ray fluorescence (XRF) spectrometry, roughness measurement, and mechanical testing of the constituent material and components. Findings suggest that the spinal system failed due to in vivo loosening of a two-set screw tandem connector and subsequent overloading of the contralateral bar. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 64B: 6,12, 2003 [source] 39Ar- 40Ar chronology of R chondritesMETEORITICS & PLANETARY SCIENCE, Issue 3 2003Eleanor T. DIXON The 39Ar- 40Ar ages were determined on whole-rock samples of four R chondrites: Carlisle Lakes, Rumuruti, Acfer 217, and Pecora Escarpment #91002 (PCA 91002). All samples are breccias except for Carlisle Lakes. The age spectra are complicated by recoil and diffusive loss to various extents. The peak 39Ar- 40Ar ages of the four chondrites are 4.35, ,4.47 ± 0.02, 4.30 ± 0.07 Ga, and 4.37 Ga, respectively. These ages are similar to Ar-Ar ages of relatively unshocked ordinary chondrites (4.52,4.38 Ga) and are older than Ar-Ar ages of most shocked ordinary chondrites («4.2 Ga). Because the meteorites with the oldest (Rumuruti, ,4.47 Ga) and the youngest (Acfer 217, ,4.30 Ga) ages are both breccias, these ages probably do not record slow cooling within an undisrupted asteroidal parent body. Instead, the process of breccia formation may have differentially reset the ages of the constituent material, or the differences in their age spectra may arise from mixtures of material that had different ages. Two end-member type situations may be envisioned to explain the age range observed in the R chondrites. The first is if the impact(s) that reset the ages of Acfer 217 and Rumuruti was very early. In this case, the ,170 Ma maximum age difference between these meteorites may have been produced by much deeper burial of Acfer 217 than Rumuruti within an impact-induced thick regolith layer, or within a rubble pile type parent body following parent body re-assembly. The second, preferred scenario is if the impact that reset the age of Acfer 217 was much later than that which reset Rumuruti, then Acfer 217 may have cooled more rapidly within a much thinner regolith layer. In either scenario, the oldest age obtained here, from Rumuruti, provides evidence for relatively early (,4.47 Ga) impact events and breccia formation on the R chondrite parent body. [source] Magnonic excitations versus three-dimensional structural periodicity in magnetic compositesCRYSTAL RESEARCH AND TECHNOLOGY, Issue 6 2006M. Krawczyk Abstract The study deals with the spin wave spectrum in magnetic macrostructure (composed of two ferromagnetic materials) showing a 3D periodicity; the structure considered consists of spherical ferromagnetic grains disposed in the nodes of a simple cubic crystal lattice and embedded in a matrix with different ferromagnetic properties. It is shown that the magnonic spectrum of this composite structure exhibits frequency regions forbidden for magnon propagation, and the energy gaps are sensitive to the exchange contrast between the constituent materials as well as to the magnetization contrast. The widths of the respective magnonic gaps are studied as functions of parameters characterizing the magnetic structure. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Mathematical modelling of fire development in cable installationsFIRE AND MATERIALS, Issue 4 2001P. Van Hees In 1996 DG XII of the European Commission (Research and Development) approved a 3 year project on the fire performance of electrical cables. Within this FIPEC project, a major part of the work involved correlation and mathematical modelling of flame spread and heat release rate in cable installations. The FIPEC project has developed different levels of testing ranging from a small-scale, cone calorimeter test procedures developed for cables and materials, a full-scale-test procedure based on the IEC 60332-3, but utilizing HRR and SPR measurements, and a real scale test conducted on model cable installations. Links through statistical correlations and mathematical fire modelling between these levels were investigated and the findings are presented in this paper. These links could form the scientific foundations for standards upon which fire performance measurements can be based and for new fire engineering techniques within fire performance based codes. Between each testing level correlation, numerical and mathematical models were performed. All of the models were based on the cone calorimeter test method. The complexity of the models varied from correlation models to advanced physical pyrolysis models which can be used in CFD codes. The results will allow advanced prediction of cable fires in the future. Also a bench mark was established for the prediction of cable performance by means of data obtained from the constituent materials. Copyright © 2002 John Wiley & Sons, Ltd. [source] Computation of the J -integral for large strainsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 12 2008Ágnes Horváth Abstract The phenomenon of failure by catastrophic crack propagation in structural materials poses problems of design and analysis in many fields of engineering. Cracks are present to some degree in all structures. They may exist as basic defects in the constituent materials or they may be induced in construction or during service life. Using the finite element method, a lot of papers deal with the calculation of stress intensity factors for two- and three-dimensional geometries containing cracks of different shapes under various loadings to elastic bodies. In order to increase the accuracy of the results, special elements have been used. They are described together with methods for calculating the stress intensity factors from the computed results. At the vicinity of a crack tip, the strains are not always small, but they may also be large. In this case, the J -integral can also be applied to characterize the cracks in elastic or elastic,plastic bodies. This paper describes the computation of the two-dimensional J -integral for large strains to elastic and elastic,plastic bodies and represents some numerical examples. Copyright © 2007 John Wiley & Sons, Ltd. [source] Molecular dynamics and multiscale homogenization analysis of seepage/diffusion problem in bentonite clayINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 12 2002Y. Ichikawa Abstract A scheme combining a molecular behaviour and macro-continuum phenomenon is presented for bentonite clay, which is a key component of a barrier system for disposal and containment of hazardous wastes. On designing a disposal facility we use a macro-phenomenological model. However the existing model is not sufficiently effective. Bentonite is a microinhomogeneous material. Properties of the saturated bentonite are characterized by montmorillonite and water, called montmorillonite hydrate. Since the crystalline structure of montmorillonite determines the fundamental properties of the montmorillonite hydrate, we analyse its molecular behaviour by applying a molecular dynamics simulation to enquire into the physicochemical properties of the montmorillonite hydrate such as diffusivity of chemical species. For extending the microscopic characteristics of constituent materials to a macroscopic diffusion behaviour of the microinhomogeneous material we apply a multiscale homogenization analysis, especially in order to treat micro-level of adsorption behaviour. Copyright © 2002 John Wiley & Sons, Ltd. [source] A directive dual-band and dual-polarized antenna with zero index metamaterialMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 11 2008Zi-Bin Weng Abstract A novel directive dual-band and dual-polarized microstrip antenna with ZIM is presented. An averaging effect over constituent materials of the metamaterial structure yields an effective permittivity that approaches zero at dual band with different polarizations, and then it results in a metamaterial with zero index of refraction and the radiation energy of this antenna is congregated. The experimental results show that this method is effective, and this structure can greatly increase the gain at dual frequencies. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2902,2904, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23855 [source] Nanoclay-reinforced syntactic foams: Flexure and thermal behaviorPOLYMER COMPOSITES, Issue 8 2010Mrinal C. Saha Syntactic foams containing 60 vol% of hollow glass microballoons in epoxy matrix are modified with untreated nanoclays using combined mechanical and ultrasonication methods. Effects of nanoclays on flexure and thermal behavior of syntactic foams are investigated by adding different amount of nanoclays in the range of 1,3% by weight. Microscopic examinations and physical property characterization are performed to determine the interactions among constituent materials and the void formation during fabrication. It is found that the syntactic foams with 2 wt% nanoclays show the highest improvement in flexural properties (,42% strength and ,18% modulus) and dynamic mechanical properties (,30% storage modulus and ,28% loss modulus) properties. Thermal decomposition temperature is found to be unaffected by the addition of nanoclays, whereas a continuous reduction in the coefficient of thermal expansion (CTE) is observed. An examination of failure surface indicates that the failure is initiated on the tension side of the flexure sample due to fracturing of microballoons. POLYM. COMPOS., 31:1332,1342, 2010. © 2009 Society of Plastics Engineers [source] Structure,properties relations in titanium-based thermoplastic fiber,metal laminatesPOLYMER COMPOSITES, Issue 3 2006P. Cortés This paper investigates the interfacial, tensile, and fatigue properties of a titanium alloy fiber,metal laminate (Ti-FML) based on woven glass-fiber-reinforced polyetherimide (GF/PEI). Initial tests, using the single cantilever beam (SCB) geometry have shown that it is not necessary to surface treat the titanium alloy in order to achieve a high value of metal,composite interfacial fracture toughness. Tensile tests have shown that the mechanical properties of the FML lie between those offered by its constituent materials. Tension,tension fatigue tests have shown that the fatigue lives of these laminates are superior to those offered by the plain titanium alloy. The mechanical properties of this glass fiber/PEI FML have also been compared with those offered by an FML based on a unidirectional carbon-fiber-reinforced polyetheretherketone (CF/PEEK) composite. Here, it has been shown that although the fatigue properties of this woven GF/PEI composite are inferior to those of the CF/PEEK FML, they do offer a higher temperature capability due to the higher glass transition temperature of the PEI matrix. Polym. Compos. 27:264,270, 2006. © 2006 Society of Plastics Engineers. [source] Third generation photovoltaics: Ultra-high conversion efficiency at low costPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 2 2001Martin A. GreenArticle first published online: 5 APR 200 Since the early days of terrestrial photovoltaics, a common perception has been that ,first generation' silicon wafer-based solar cells eventually would be replaced by a ,second generation' of lower cost thin-film technology, probably also involving a different semiconductor. Historically, cadmium sulphide, amorphous silicon, copper indium diselenide, cadmium telluride and now thin-film polycrystalline silicon have been regarded as key thin-film candidates. Any mature solar cell technology seems likely to evolve to the stage where costs are dominated by those of the constituent materials, be they silicon wafers or glass sheet. It is argued, therefore, that photovoltaics is likely to evolve, in its most mature form, to a ,third generation' of high-efficiency thin-film technology. By high efficiency, what is meant is energy conversion values double or triple the 15,20% range presently targeted, closer to the thermodynamic limit of 93%. Tandem cells are the best known of such high-efficiency approaches, where efficiency can be increased merely by adding more cells of different bandgap to a cell stack, at the expense of increased complexity and spectral sensitivity. However, a range of other more ,paralleled' approaches offer similar efficiency to an infinite stack of tandem cells. These options are reviewed together with possible approaches for practical implementation, likely to become more feasible with the evolution of materials technology over the next two decades. Copyright © 2001 John Wiley & Sons, Ltd. [source] | ||||||||||||||||