Journal articles: 'FFA alumni'

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Perná, Ivana, Tomáš Hanzlíček, Monika Šupová, and Martina Novotná. "Phase Transformations in Fly Ash-Based Solids." Minerals 10, no. 9 (September 11, 2020): 804. http://dx.doi.org/10.3390/min10090804.

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The presented article describes the phase transformations in solid bodies based on fluid fly ash (FFA) over eight years from the initial to the final phases. FFA has been selected as a type of industrial waste whose amount has been growing in recent years. This type of ash has self-hardening properties when watered because of the conditions of its origin. The specific temperature of fluid burning and the addition of calcium carbonate into the burning zone create a mixture of phases which are, even when solidified, ready to form new crystal phases, especially alumina-silicates, relicts of coal clay minerals. For experiments, bricks from the mixture of FFA and quartz sand were industrially produced and left outside. Subsequent mineralogical analyses of samples of various ages confirmed differences in phase compositions. It is supposed that the main role in the presented changes is played by the content of the roentgen-amorphous part of alumina-silicates because they are likely to be transformed into a stable form of feldspar. In addition to that, this article presents the hypothesis of a moving agent, which could explain the transformations in the final bodies.

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Becker, Lillian C., Ivan Boyer, Wilma F. Bergfeld, Donald V. Belsito, Ronald A. Hill, Curtis D. Klaassen, Daniel C. Liebler, et al. "Safety Assessment of Alumina and Aluminum Hydroxide as Used in Cosmetics." International Journal of Toxicology 35, no. 3_suppl (November 2016): 16S—33S. http://dx.doi.org/10.1177/1091581816677948.

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This is a safety assessment of alumina and aluminum hydroxide as used in cosmetics. Alumina functions as an abrasive, absorbent, anticaking agent, bulking agent, and opacifying agent. Aluminum hydroxide functions as a buffering agent, corrosion inhibitor, and pH adjuster. The Food and Drug Administration (FDA) evaluated the safe use of alumina in several medical devices and aluminum hydroxide in over-the-counter drugs, which included a review of human and animal safety data. The Cosmetic Ingredient Review (CIR) Expert Panel considered the FDA evaluations as part of the basis for determining the safety of these ingredients as used in cosmetics. Alumina used in cosmetics is essentially the same as that used in medical devices. This safety assessment does not include metallic or elemental aluminum as a cosmetic ingredient. The CIR Expert Panel concluded that alumina and aluminum hydroxide are safe in the present practices of use and concentration described in this safety assessment.

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Zhou, Hangyu, Guangchuan Wang, Xiao-Feng Li, Yaling Li, Shun-Ya Zhu, Cheng-Feng Qin, and Ruikang Tang. "Alumina-encapsulated vaccine formulation with improved thermostability and immunogenicity." Chemical Communications 52, no. 38 (2016): 6447–50. http://dx.doi.org/10.1039/c6cc02595a.

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Wu, Guoyu, Guihua Liu, Xiaobin Li, Zhihong Peng, Qiusheng Zhou, and Tiangui Qi. "A green approach of preparation of fine active alumina with high specific surface area from sodium aluminate solution." RSC Advances 9, no. 10 (2019): 5628–38. http://dx.doi.org/10.1039/c8ra09853k.

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A green preparation of fine active alumina from saturated sodium aluminate solution by phase evolution is presented. High capillary pressure, numerous mesopores, and the inhibition of aggregation produced FAA with an extremely high specific surface area.

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Begand, Sabine, Thomas Oberbach, and Wilfried Glien. "Mechanical Properties of Hip Joint Heads Made of the Dispersion Ceramic - Alumina Toughened Zirconia." Key Engineering Materials 309-311 (May 2006): 1257–60. http://dx.doi.org/10.4028/www.scientific.net/kem.309-311.1257.

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For orthopaedic applications an Alumina Toughened Zirconia Ceramic was tested regarding its mechanical behaviour. We observed a marked higher strength compared to the requirements according to FDA guidelines and a significantly higher strength compared to alumina ceramic despite of 15 % decreased fatigue burst strength. The wear resistance after ring-on-disc method is significantly improved comparing to standard Al2O3/Al2O3 pairings. It means the application of endoprosthetic components made of ATZ-ceramic offers more safety and reliability.

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Sharma, Dheeraj Kumar, Mainak Bandyopadhyay, Jaydeep Joshi, and Arun K. Chakraborty. "Determination of Residual Stresses in Ceramic-Metal Brazed Joint using Finite Element Analysis (FEA) and Experimental Validation of the Results." SAMRIDDHI : A Journal of Physical Sciences, Engineering and Technology 12, no. 01 (June 30, 2020): 1–7. http://dx.doi.org/10.18090/samriddhi.v12i01.1.

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Ceramic vacuum feedthroughs are an inevitable requirement for any vacuum system which requires electrical feedlines to be inserted into the vacuum environment. These feedthroughs consist of metal-ceramic-metal transition and, therefore, require the brazing process as a joining technique. This process allows joining two base materials, i.e., Alumina and Kovar, for this case, which manifests different thermo-mechanical response. The difference between the coefficient of thermal expansion (CTE) of these materials causes the development of residual stresses during the cooling phase of the brazing process. Such residual stresses, if not addressed properly, can lead to the failure in the brazed joint even before the design limits. The purpose of this study is to assess these stresses by performing the thermo-mechanical analysis of the brazing process of ceramic-metal assembly through finite element analysis (FEA) technique. This study includes the assessment of non-linear behavior (due to temperature-dependent material properties) of Alumina and Kovar assembly. Further, X-ray diffraction (XRD) based residual stress measurement technique has been utilized to validate the FEA results. The paper shall present the FEA methodology (model, boundary condition, and results) followed by the experimental results and their comparison.

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Irez, Alaeddin Burak, Emin Bayraktar, and Ibrahim Miskioglu. "Flexural fatigue damage analyses of recycled rubber- modified epoxy-based composites reinforced with alumina fibres." Fatigue & Fracture of Engineering Materials & Structures 42, no. 4 (January 14, 2019): 959–71. http://dx.doi.org/10.1111/ffe.12964.

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Porto, C. P. S., M. P. L. Parente, R. M. N. Jorge, L. C. Pereira, and S. Griza. "Fracture toughness of the interface between Ni-Cr/ceramic, alumina/ceramic and zirconia/ceramic systems." Fatigue & Fracture of Engineering Materials & Structures 39, no. 7 (February 16, 2016): 817–29. http://dx.doi.org/10.1111/ffe.12394.

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Hattali, M. L., Stéphane Valette, François Ropital, N. Mesrati, and Daniel Treheux. "Fem Calculations and Experimental Determination of Residual Stresses in Alumina/Nickel Alloy Joints. Optimization of Fabrication Parameters." Advanced Materials Research 89-91 (January 2010): 238–43. http://dx.doi.org/10.4028/www.scientific.net/amr.89-91.238.

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The study relates to joints fabricated by solid state bonding between alumina and nickel alloy HAYNESTM214®, using an intermediate nickel metallic foil. Experimentally, damages and cracks often are observed close to the metal/ceramics interface. Consequently, the residual stresses distributions in the specimen were characterized experimentally using X-ray diffraction (XRD) and indentation techniques and predicted by Finite Element Analysis (FEA) calculations using an elastic-plastic-creep model. We demonstrate that a good correlation between FEA calculations and experimental results is obtained. Then, the effect of elaboration and geometrical parameters has been studied in order to minimize the residual stresses in alumina close to the metal-ceramics interface. However, the Al2O3/Ni/HAYNESTM214® system always leads to high residual stresses. To solve this problem, we show that the use of a multi-layer Cu/Ni/Cu joint, associated with the Direct Copper Bonding method (DCB), by pre-oxidation of copper, allows reducing significantly the tensile residual stresses in ceramics.

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Santillán Salgado, Roberto Joaquín, Alejandro Fonseca Ramírez, and Francisco Venegas Martínez. "Impacto de los precios de los metales en la estructura de capital de las empresas minero-metalúrgicas en América Latina (2004-2014)." Contaduría y Administración 63, no. 3 (June 6, 2020): 39. http://dx.doi.org/10.22201/fca.24488410e.2018.837.

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<p>Este trabajo examina los efectos de corto y mediano plazo de las fluctuaciones de los precios internacionales de varios productos minerales (oro, plata, cobre, zinc) y metalúrgicos (aluminio, acero) sobre la estructura de capital de las empresas de la industria minera y metalúrgica listadas en los mercados bursátiles de Argentina, Brasil, México y Perú. Se utilizan datos trimestrales para el periodo 2000-2014. Consistente con la teoría del Orden Selectivo de Preferencia Dinámico “<em>Dynamic Pecking Order</em>”, los resultados del análisis econométrico confirman que la rentabilidad y los precios de los productos se relacionan negativamente con en el apalancamiento financiero de las empresas.</p>

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Elias, Samya, Ademola M. Rabiu, Benjamin I. Okeleye, Vincent Okudoh, and Oluwaseun Oyekola. "Bifunctional Heterogeneous Catalyst for Biodiesel Production from Waste Vegetable Oil." Applied Sciences 10, no. 9 (May 1, 2020): 3153. http://dx.doi.org/10.3390/app10093153.

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Bifunctional solid catalysts facilitate the esterification of free fatty acids (FFA) into alkyl esters alongside the transesterification reaction, which allows for the use of waste vegetable oils with high water and FFA contents for biodiesel production. This makes the process economically viable and greener, as the waste fats and oils are readily available. The concurrent esterification and transesterification of waste palm oil (WPO) and waste sunflower oil (WSO) with methanol was investigated in the presence of calcium oxide on alumina catalyst in a conventional batch process. The catalyst characterization showed the existence of calcium oxide aluminates (calcined at 750 °C), which exhibited crystalline phases with porous/spongy-like particles. The high concentration of CaO in CaO/Al2O3 was a favorable support material in the heterogeneously-catalyzed transesterification reactions. The optimum catalyst parameters for the production of fatty acid methyl esters (FAMEs) were observed at 65 °C for 4 h with a methanol-to-oil ratio of 9:1, 60% (waste palm oil, or WPO) and 80% (waste sunflower oil, or WSO), CaO/Al2O3 (% wt/wt) catalyst ratio as well as 4% CaO/Al2O3 concentration (% wt.) for WSO and WPO. The simultaneous esterification/transesterification reactions at optimum conditions on WPO and WSO led to high yield of FAMEs of 89, 61 and 55% for WPO and 54, 75 and 98% for WSO at catalyst ratios (wt %) of 60, 70 and 80% respectively. The use of bifunctional heterogeneous catalyst (CaO/Al2O3) with waste vegetable oil can result in high performance and the upscaling of biodiesel production.

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Karbasi, Ali, Ali Hadjikhani, and W. Kinzy Jones. "Effect of platinum metallization in cofired platinum / alumina microsystems for implantable medical applications." Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2013, CICMT (September 1, 2013): 000177–82. http://dx.doi.org/10.4071/cicmt-wp34.

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Typically, hermetic feedthroughs for implantable devices, such as pacemakers, use an alumina ceramic insulator brazed to a platinum wire pin. This material combination has a long history in implantable devices and is the desired structure due to the acceptance by the FDA for implantable hermetic feedthroughs. The growing demand for increased input/output (I/O) hermetic feedthroughs for implantable neural stimulator applications can be addresses by developing a new, co-fired platinum/alumina multilayer ceramic technology in a configuration that supports 300 plus I/Os, which is not commercially available. Different densification rate of platinum and alumina is the major issue in developing a high-density feedthrough. This difference in densification rate could create delamination and crack in feedthrough structure and decrease the reliability and degree of the hermeticty of the final assembly. In this paper different metallization were evaluated to minimize this difference. Additionaly the firing atmosphere and the firing profiles were evaluated to minimize this difference. FIB nano-machining and SEM with EDS were used for the analysis of these conditions.

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Sadowski, Tomasz, and Błażej Pankowski. "Peridynamical Modelling of Nanoindentation in Ceramic Composites." Solid State Phenomena 254 (August 2016): 55–59. http://dx.doi.org/10.4028/www.scientific.net/ssp.254.55.

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Indentation in brittle solids involves many complex phenomena related to cleavage and contact, as well as intrinsic stress singularities, which are almost impossible to capture with traditional continuum approach and FEA at mesoscale. In case of a two-phase ceramic composite [1–3] the number of unknown material and interfacial constants, that have to be calibrated experimentally, increases rapidly [4, 5]. In this paper, nanoindentation in zirconia-toughened alumina (ZTA) is modelled using discrete (peridynamical) approach

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Moris, Izabela C. M., Carolina Alves Moscardini, Luana Kelle Batista Moura, Yara Teresinha Corrêa Silva-Sousa, and Erica Alves Gomes. "Evaluation of Stress Distribution in Endodontically Weakened Teeth Restored with Different Crown Materials: 3D-FEA Analysis." Brazilian Dental Journal 28, no. 6 (December 2017): 715–19. http://dx.doi.org/10.1590/0103-6440201701829.

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Abstract This study evaluated the stress distribution in endodontically treated teeth, weakened (W) or not weakened (NW), restored with different materials of prosthetic crown using 3D-FEA. Models of a maxillary canine were constructed based on micro-CT images and divided into the groups: G1 (control) - sound tooth; G2 to G7 - endodontically treated teeth restored with glass fiber post (GFP); which G2 to G4 simulated NW root and G5 to G7 simulated W root. For crown material the teeth were restored with: G2 and G5: metallic coping and ceramic veneering, G3 and G6: zirconia coping and ceramic veneering, G4 and G7: alumina coping and ceramic veneering. Load of 180 N was applied at the incisal third of lingual surface at 45º. Models were supported by the periodontal ligament (x=y=z=0). The von Mises stress (VMS) values were calculated. The W teeth presented higher VMS at coping when compared to NW teeth and group G1 showed lower VMS value. For crown material, for both W or NW teeth, increasing VMS was found at metallic, zirconia and alumina coping, respectively. Metallic coping showed a better performance despite its unfavorable esthetics, suggesting as an appropriate material for prosthetic restoration of endodontically treated teeth.

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Kulkarni, S. G., Achchhe Lal, and J. V. Menghani. "Effect of reinforcement type and porosity on strength of metal matrix composite." International Journal of Computational Materials Science and Engineering 05, no. 01 (March 2016): 1650006. http://dx.doi.org/10.1142/s2047684116500068.

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In the present work, experimental investigation and the numerical analysis are carried out for strength analysis of A356 alloy matrix composites reinforced with alumina, fly ash and hybrid particle composites. The combined strengthening effect of load bearing, Hall–Petch, Orowan, coefficient of thermal expansion mismatch and elastic modulus mismatch is studied for predicting accurate uniaxial stress–strain behavior of A356 based alloy matrix composite. The unit cell micromechanical approach and nine noded isoparametric finite element analysis (FEA) is used to investigate the yield failure load by considering material defect of porosity as fabrication errors in particulate composite. The Ramberg–Osgood approach is considered for the linear and nonlinear relationship between stress and strain of A356 based metal matrix composites containing different amounts of fly ash and alumina reinforcing particles. A numerical analysis of material porosity on the stress strain behavior of the composite is performed. The literature and experimental results exhibit the validity of this model and confirm the importance of the fly ash as the cheapest and low density reinforcement obtained as a waste by product in thermal power plants.

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Bayata, Fatma, and Cengiz Yildiz. "The Mechanical Behaviors of Various Dental Implant Materials under Fatigue." Advances in Materials Science and Engineering 2018 (2018): 1–10. http://dx.doi.org/10.1155/2018/5047319.

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The selection of materials has a considerable role on long-term stability of implants. The materials having high resistance to fatigue are required for dental implant applications since these implants are subjected to cyclic loads during chewing. This study evaluates the performance of different types of materials (AISI 316L stainless steel, alumina and its porous state, CoCr alloys, yttrium-stabilized zirconia (YSZ), zirconia-toughened alumina (ZTA), and cp Ti with the nanotubular TiO2 surface) by finite element analysis (FEA) under real cyclic biting loads and researches the optimum material for implant applications. For the analysis, the implant design generated by our group was utilized. The mechanical behavior and the life of the implant under biting loads were estimated based on the material and surface properties. According to the condition based on ISO 14801, the FEA results showed that the equivalent von Mises stress values were in the range of 226.95 MPa and 239.05 MPa. The penetration analysis was also performed, and the calculated penetration of the models onto the bone structure ranged between 0.0037389 mm and 0.013626 mm. L-605 CoCr alloy-assigned implant model showed the least penetration, while cp Ti with the nanotubular TiO2 surface led to the most one. However, the difference was about 0.01 mm, and it may not be evaluated as a distinct difference. As the final numerical evaluation item, the fatigue life was executed, and the results were achieved in the range of 4 × 105 and 1 × 109 cycles. These results indicated that different materials showed good performance for each evaluation component, but considering the overall mechanical performance and the treatment process (implant adsorption) by means of surface properties, cp Ti with the nanotubular TiO2 surface material was evaluated as the suitable one, and it may also be implied that it displayed enough performance in the designed dental implant model.

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Uribe, Juliana, Jérôme Hausselle, Jean Geringer, and Bernard Forest. "Finite Element Modelling of Shock-Induced Damages on Ceramic Hip Prostheses." ISRN Materials Science 2011 (September 6, 2011): 1–14. http://dx.doi.org/10.5402/2011/121486.

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The aim of this work was to simulate the behaviour of hip prostheses under mechanical shocks. When hip joint is replaced by prosthesis, during the swing phase of the leg, a microseparation between the prosthetic head and the cup could occur. Two different sizes of femoral heads were studied: 28 and 32 mm diameter, made, respectively, in alumina and zirconia. The shock-induced stress was determined numerically using finite element analysis (FEA), Abaqus software. The influence of inclination, force, material, and microseparation was studied. In addition, an algorithm was developed from a probabilistic model, Todinov's approach, to predict lifetime of head and cup. Simulations showed maximum tensile stresses were reached on the cup's surfaces near to rim. The worst case was the cup-head mounted at 30°. All simulations and tests showed bulk zirconia had a greater resistance to shocks than bulk alumina. The probability of failure could be bigger than 0.9 when a porosity greater than 0.7% vol. is present in the material. Simulating results showed good agreement with experimental results. The tests and simulations are promising for predicting the lifetime of ceramic prostheses.

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Lombardi, Adolph V., Keith R. Berend, Brian E. Seng, Ian C. Clarke, and Joanne B. Adams. "Delta Ceramic-on-Alumina Ceramic Articulation in Primary THA: Prospective, Randomized FDA-IDE Study and Retrieval Analysis." Clinical Orthopaedics and Related Research® 468, no. 2 (November 3, 2009): 367–74. http://dx.doi.org/10.1007/s11999-009-1143-9.

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HYNES, N. RAJESH JESUDOSS, P. NAGARAJ, and R. MEBY SELVARAJ. "FINITE ELEMENT BASED THERMAL MODELING OF FRICTION WELDING OF DISSIMILAR MATERIALS." International Journal of Modern Physics: Conference Series 22 (January 2013): 196–202. http://dx.doi.org/10.1142/s201019451301012x.

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Friction welding is a solid state joining process of joining either similar or dissimilar materials. Joining of ceramic/metal joints by friction welding has opened up new possibilities in many engineering applications. In the present work, thermal modeling of friction welding process has been carried out. Using Finite Element Approach (FEA), analytical solutions were arrived for different ceramic/metal combinations. The temperature distributions of cylindrical surfaces of the alumina and the metals are found by means of 1D heat transfer assumption considering the effect of convection. In the thermal analysis, interfacial temperature and thermal conductivity of the material play a significant role. Based on the obtained temperature distribution the graphs are plotted between the length of the joint and the temperatures. Thus the knowledge of the temperature joint distribution could be helpful in predicting the thermal cycle of the process, microstructure evolution and residual stress formation. Thus the obtained graph helps to study and predict the temperature distribution of both the materials.

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Johnson, A. C., F. M. Zhao, S. A. Hayes, and F. R. Jones. "Influence of a matrix crack on stress transfer to an α-alumina fibre in epoxy resin using FEA and photoelasticity." Composites Science and Technology 66, no. 13 (October 2006): 2023–29. http://dx.doi.org/10.1016/j.compscitech.2005.12.027.

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JESUDOSS HYNES, N. RAJESH, P. NAGARAJ, and S. JOSHUA BASIL. "NUMERICAL SIMULATION ON JOINING OF CERAMICS WITH METAL BY FRICTION WELDING TECHNIQUE." International Journal of Modern Physics: Conference Series 22 (January 2013): 190–95. http://dx.doi.org/10.1142/s2010194513010118.

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The joining of ceramic and metals can be done by different techniques such as ultrasonic joining, brazing, transient liquid phase diffusion bonding, and friction welding. Friction Welding is a solid state joining process that generates heat through mechanical friction between a moving workpiece and a stationary component. In this article, numerical simulation on thermal analysis of friction welded ceramic/metal joint has been carried out by using Finite Element Analysis (FEA) software. The finite element analysis helps in better understanding of the friction welding process of joining ceramics with metals and it is important to calculate temperature and stress fields during the welding process. Based on the obtained temperature distribution the graphs were plotted between the lengths of the joint corresponding to the temperatures. To increase the wettability, aluminium sheet was used as an interlayer. Hence, numerical simulation of friction welding process is done by varying the interlayer sheet thickness. Transient thermal analysis had been carried out for each cases and temperature distribution was studied. From the simulation studies, it is found that the increase in interlayer thickness reduces the heat affected zone and eventually improves the joint efficiency of alumina/aluminum alloy joints.

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Ramesh, C. S., and C. Shashishekar. "The Effect of Flexion Angle and Sagittal Radius on Femorotibial Contact Stresses." Advanced Materials Research 421 (December 2011): 388–91. http://dx.doi.org/10.4028/www.scientific.net/amr.421.388.

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The artificial knee joint need to satisfy and meet certain design requirements in addition to being biocompatible. These being the design of the flexion angle and sagittal radius of the prosthetic knee for specific activities such as walking and exercising. Day to day physical activities do result in generating frequent contacts between the femur and tibia leading to stresses at the interface of the femorotibial joint. These stresses on exceeding certain limit do result in damage of the tibia which acts as bearing surface carrying loads during each of the knee activity. Hence, prediction and minimization of the stresses at the knee interfaces is the key issue to ensure high performance knee joints. In the light of the above, the stresses at the knee interfaces are computed using commercially available FEA software (ANSYS 10). The three dimensional model was developed using PRO E software for sagittal radius of 40, 50 and 60 mm. The flexion angles considered are 0, 20 and 40 degrees. A load of 500N was considered. It is observed that the stress intensity increases with increase in flexion angle and sagittal radius for all the material combinations of the prosthetic knee joint. Further, alumina ceramic femur and polyethylene chopped carbon fiber composite tibia exhibits the least stress levels at all the studied sagittal radius and flexion angles.

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Cowan, Robert. "ACDC Agency: Food and Politics with Community College Students at Vassar." Radical Teacher 107 (February 2, 2017): 45–51. http://dx.doi.org/10.5195/rt.2017.189.

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The food at the All-College Dining Commons (ACDC) at Vassar College stinks. Not that is literally smells foul; it just isn’t very good. The high-achieving community college students in the Exploring Transfer Program (ET) eat breakfast and dinner there for the five weeks that they are studying at Vassar. Ironically, the course I co-taught in ET for two summers, with the Chair of Environmental Studies, is entitled Feast or Famine: Food, Society, Environment. This course is a survey of issues concerning food systems, such as industrial farming, the role of agricultural lobbyists in Washington, overfishing, food sovereignty in developing countries, food stamps, food deserts, the USDA, FDA, WTO, IMF, etc. And yet, with all of the knowledge the students are gleaning from authors like Marion Nestle, Michael Pollan, Wendell Berry and myriad others, they have to eat the crappy food at ACDC. We have had students in this course from Argentina, Bosnia, Bourkina Faso, China, El Salvador, Ghana, Guyana, Haiti, Italy, Mexico, Pakistan, Poland, the Philippines, Sweden, Uzbekistan, and Vietnam. They come from community colleges mostly in the New York area, but also from as far away as Boston, Maine, Los Angeles, and Diné Community College, which is on a Navajo reservation in Northern Arizona. This program—over 30 years old and with over 1,000 alumni—is a sort of academic boot camp for community college students who hope to transfer to an elite liberal arts college, a Research 1 university, or an Ivy League school. It’s a full scholarship program during which they take two courses in five weeks, each team-taught by a community college professor and a Vassar professor. “AC/DC” seems an apt metaphor for the ET program; not for its pop-metal connotations but because of the fact that it demands that students that are accustomed to operating in one current suddenly adjust to quite another. The question that arises out of the experience of eating ACDC, though—of being low-income, immigrant, first-generation college students, studying at one of the whitest and most expensive schools in the country and yet being forced to eat poor food—is “how do they develop a sense of personal agency,” since that is what the transition through community college and onto a school like Vassar requires.

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Tateiwa, Toshiyuki, Elia Marin, Alfredo Rondinella, Marco Ciniglio, Wenliang Zhu, Saverio Affatato, Giuseppe Pezzotti, et al. "Burst Strength of BIOLOX®delta Femoral Heads and Its Dependence on Low-Temperature Environmental Degradation." Materials 13, no. 2 (January 12, 2020): 350. http://dx.doi.org/10.3390/ma13020350.

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Zirconia-toughened alumina (ZTA) currently represents the bioceramic gold standard for load-bearing components in artificial hip joints. ZTA is long known for its high flexural strength and fracture toughness, both properties arising from a microscopic crack-tip shielding mechanism due to the stress-induced tetragonal-to-monoclinic (t→m) polymorphic transformation of zirconia. However, there have been concerns over the years regarding the long-term structural performance of ZTA since the t→m transformation also spontaneously occurs at the material’s surface under low-temperature environmental conditions with a concomitant degradation of mechanical properties. Spontaneous surface degradation has been extensively studied in vitro, but predictive algorithms have underestimated the extent of in vivo degradation observed in retrievals. The present research focused on burst-strength assessments of Ø28 mm ZTA femoral before and after long-term in vitro hydrothermal ageing according to ISO 7206-10. An average burst strength of 52 kN was measured for pristine femoral heads. This value was ~36% lower than results obtained under the same standard conditions by other authors. A further loss of burst strength (~13% in ultimate load) was observed after hydrothermal ageing, with increased surface monoclinic content ranging from ~6% to >50%. Nevertheless, the repetitively stressed and hydrothermally treated ZTA heads exceeded the minimum burst strength stipulated by the US Food and Drug Administration (FDA) despite severe test conditions. Lastly, Raman spectroscopic assessments of phase transformation and residual stresses on the fracture surface of the femoral heads were used to clarify burst-strength fluctuations and the effect of hydrothermal ageing on the material’s overall strength degradation.

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Santos-Filho, Paulo César de Freitas, Crisnicaw Verissimo, Cristhiane Leão Queiroz, Rebeca Carniello Saltarelo, Carlos José Soares, and Bruno de Castro Ferreira Barreto. "The effect of type post, crown, and ferrule presence on stress distribution of maxillary central incisors with weakened roots: Finite Element Analysis." Journal of Research in Dentistry 1, no. 2 (August 2, 2013): 154. http://dx.doi.org/10.19177/jrd.v1e22013154-164.

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The aim of this study was to evaluate the biomechanical behavior, by means FEA, of maxillary central incisor with weakened roots restored with different posts, crowns and ferrule presence. A digital image of an intact maxillary central incisor section plane around the alveolar bone was obtained in order to build the model of sound tooth. A sound tooth and eight two-dimensional numerical models were generated from the protocol of image processing. The studied factors were: crown type - metal-ceramic crown (MC) and alumina-reinforced ceramic (CC); post type - glass fiber post (GFP) and cast post and core (CPC); and ferrule - absence of ferrule (AFE) and 2,0 mm ferrule (FE2). A 2N static and oblique load with a 135° inclination to the tooth longitudinal axis was applied at the level of palatal surface of the crown. The displacement was restricted and stress of tensile and compression within the tooth structure was recorded. Cast post and core models concentrated stresses in post dentin interface and glass fiber post models had homogeneous stresses distribution within the root dentin similar to sound tooth. The restorative complex GFP-CC concentrated higher stress in coping than GFP-MC, both models with or without ferrule. The ferrule presence improved the stress distribution regardless of the crown and post types. Therefore, cast post-and-cores concentrate too much stresses within a root dentin and post interface; glass fiber post has more homogeneous stress distribution in dentin than cast post-and-cores; the presence of 2 mm ferrule improves the mechanical behavior.

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Pineda, Alfredo, Moreica B. Pabbruwe, Alan M. Kop, Philip Vlaskovsky, and Mark Hurworth. "The effect of implant modification." Bone & Joint Journal 101-B, no. 10 (October 2019): 1248–55. http://dx.doi.org/10.1302/0301-620x.101b10.bjj-2019-0135.r2.

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Aims The aim of this study was to conduct the largest low contact stress (LCS) retrieval study to elucidate the failure mechanisms of the Porocoat and Duofix femoral component. The latter design was voluntarily recalled by the manufacturer. Materials and Methods Uncemented LCS explants were divided into three groups: Duofix, Porocoat, and mixed. Demographics, polyethylene wear, tissue ingrowth, and metallurgical analyses were performed. Results In 104 implants, a decrease in the odds of loosening and an increase in metallosis and tissue staining in the Duofix group relative to Porocoat group was detected (p = 0.028). There was an increased presence of embedded metallic debris in the Duofix group (p < 0.001). Decreased tissue ingrowth was associated with the Duofix surface (p < 0.001). The attached beads had reduced microhardness, indicative of adverse thermal processing, which resulted in bead shedding, particulate debris, and metallosis. Conclusion Hydroxyapatite coating of the LCS femoral component produced unexpected results and led to its recall. The root cause was likely a combination of retained alumina grit and a reduction in bead microhardness (mechanical strength) resulting in increased particle debris, metallosis, and early revision. The Duofix LCS femoral component was not equivalent to the Porocoat version despite its approval through the Food and Drug Administration (FDA) 510(k) equivalance approval process. Regulation of the introduction of modified existing devices needs to be improved and the Duofix LCS should have been considered to be a new device for which equivalence had not been demonstrated at the point of introduction. Cite this article: Bone Joint J 2019;101-B:1248–1255

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"Evaluation of Mechanical Properties of AA7075 /Al2O3/Mg Hybrid Composites." International Journal of Engineering and Advanced Technology 8, no. 6 (August 30, 2019): 5044–46. http://dx.doi.org/10.35940/ijeat.f9547.088619.

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The present work was planned to evaluate the mechanical properties of alumina reinforced aluminium alloy such hardness and compression behavior of al2o3 /aa7075 alloy metal matrix composites. Both, experimental and finite element analyses were carried out to establish tensile behaviour of the composites with different weight percentage of al2o3 fabricated by the stir casting process. The results concluded that addition of alumina to the aa7075 improves the mechanical properties of the composite. Further the results of FEA simulation of the composites are close to the actual results which shows that cost and time can be reduced if FEA is performed

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Casa Nova, Silvia Pereira de Castro. "IMPACTS OF SPECIAL ACCOUNTING MASTER PROGRAMS IN ITS ALUMNI TRAJECTORY:." Revista Contabilidade e Controladoria 4, no. 3 (December 20, 2012). http://dx.doi.org/10.5380/rcc.v4i3.29952.

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A presença feminina na academia no Brasil é pequena e o tema de pesquisa tem sido relativamente pouco explorado. A identificação da presença de fenômenos como critical mass, role model, glass ceiling ou pipeline (explorados na literatura internacional) é primeiro passo para contribuir com a modificação do quadro por meio da conscientização e da instituição de políticas de apoio. Considerando a Universidade de São Paulo (USP), uma das principais instituições de ensino e pesquisa no país, apenas em 1995, foi eleita pela primeira vez uma mulher como vice-reitora; a primeira professora titular da Escola Politécnica, também da USP, data de 2000; a primeira mulher a ocupar a diretoria da Faculdade de Direito o fez em 1998 (Plonski & Saidel, 2001). A primeira reitora da USP foi eleita apenas em 2005. Na Faculdade de Economia, Administração e Contabilidade, em dados de 2010, dentre os 184 docentes, 30 eram mulheres. Essa relação varia entre as unidades, conforme a área de conhecimento, sendo que em Enfermagem (84/81) e Educação (104/68), as mulheres superam os homens. Em termos do país, quando depurados os dados da Relação Anual das Informações Sociais (RAIS, 2010), dentre os professores do ensino superior de ciências econômicas, administrativas e contábeis no país, constatamos que maior percentual das mulheres recebiam até 3 salários mínimos e na faixa dos que recebiam mais de 10 salários mínimos, os homens tem maior participação. A proposta de pesquisa pretende endereçar-se a esse tema, especificamente na área de ensino e pesquisa em Ciências Contábeis visa analisar a trajetória acadêmica de egressos do Programa de Pós-Graduação em Controladoria e Contabilidade, do Departamento de Contabilidade e Atuária da Faculdade de Economia, Administração e Contabilidade da Universidade de São Paulo (PPGCC-EAC-FEA/USP). Esse programa de pós-graduação tem uma situação sui generis na área e no país. Durante muito tempo foi um dos poucos mestrados em Contabilidade e até 2008 ainda era o único a oferecer o Doutorado em Contabilidade. Manteve programas especiais para formação de mestres em diferentes formatos, com apoio da Capes (Mestrado Interinstitucional) e do Conselho Federal de Contabilidade (CFC), órgão de representação profissional (Mestrado Especial para Professores de Universidades Públicas e Mestrado Especial em convênio com o CFC), formando em cada uma das iniciativas, cinco turmas de professores e profissionais. Assim, o objetivo central da pesquisa consiste em examinar a trajetória dos egressos desses programas especiais, analisando o impacto que o programa possa ter tido em sua evolução e avaliando especialmente os possíveis efeitos que o desenho distinto dos programas possa ter tido em termos da participação e permanência de mulheres. As análises, de caráter exploratório, indicam que o programa especial de Mestrado em Contabilidade do CFC, em formato semi-presencial, permitiu uma maior participação das mulheres, tendo em vista a possibilidade de maior conciliação com a vida familiar e pessoal.

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Lakshmi Sankar, S., G. Arun Kumar, and A. Venkata Suresh. "Design and Analysis of Wishbones in Double Wishbone Suspension System: Technical Note." International Journal of Vehicle Structures and Systems 10, no. 4 (November 1, 2018). http://dx.doi.org/10.4273/ijvss.10.4.06.

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This paper details the design and analysis of the wishbones in double wishbone suspension system. Initially Pugh’s matrix approach is used to score the conventional materials and light weight metal matrix composites for the wishbone design. Based on the scores, an Alumina matrix composite has been found as the preferred material. Then, the designed wishbones were analysed using ANSYS finite element analysis software using AISI 1040 and metal matrix composite materials. Based on the FEA results, it has been concluded that the metal matrix composite yielded a better durability and strength than conventional metal.

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Wong, Boon, and David C. Sandkulla. "A Methodology for Reliability Assessment of Non-Ductile Encapsulants." MRS Proceedings 226 (1991). http://dx.doi.org/10.1557/proc-226-97.

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AbstractThis paper presents a probabilistic fracture-mechanics based methodology for the reliability assessment of non-ductile encapsulants. The study used an alumina-epoxy encapsulant as a working example and assessed the reliability in terms of (1) fast fracture and (2) delayed failure behavior of the material.Applying the Weibull probabilistic model to flexural strength data, survival probabilities and strength requirements against fast fracture of the encapsulant under various stress states were quantified. Unifying the probabilistic concept and linear elastic fracture mechanics (LEFM), the probabilistic lifetime of the encapsulant was predicted as a function of stress magnitude, stress state, and material size. Merging the results obtained from this study with the mechanical response results independently acquired from finite element analysis (FEA) one may then establish conservative design margins for the encapsulant used in various electronic assemblies.

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Journal articles on the topic 'FFA alumni'

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