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Self assembly of biomimetic hydroxyapatite on the surface of different polymer thin films
M. Petrovic 한양대학교 세라믹연구소 2012 Journal of Ceramic Processing Research Vol.13 No.4
The role of the process of designing a scaffold in bone tissue engineering is to provide optimal conditions for new bone tissue growth. The primary concern of such engineering is to create an adequate nanotopology of the scaffold inner walls, which can initiate the growth and activity of bone cells. Here, we present a completely new scaffold designing process based on a biomimetic approach in order to improve the nanostructure of pore walls of previously-made calcium hydroxyapatite (CHA) porous scaffolds. CHA porous scaffolds were covered with different polymer thin films (alginate, cellulose and PLGA) and exposed to simulated body fluid (SBF) for 42 days. SBF induced in situ formation of “bone-like” apatite phases on the surface of CHA/polymer composites. Fourier Transformed Infrared (FTIR) spectroscopy showed that the biomimetically-assembled phase is CHA of slightly shifted stoichiometry. X-ray diffraction confirmed that CHA is self-assembled on the surface of all investigated thin films. The calculation of crystallite sizes showed small differences in the degree of crystallinity between different samples. Scanning electron microscopy revealed a dominant blow-ball morphology of CHA particles (size 1 - 5 µm) with nano-sized branches on their surfaces.
Evaluation of the Composition and Morphology of a WTi/Si System Processed by a Picosecond Laser
Suzana Petrovic,D. Peruško,I. Radovi-Bogdanovic,G. Brankovic,M. Cˇekada,B. Gakovic,M. Jakšic,M. Trtica,Milosavljevic 대한금속·재료학회 2012 METALS AND MATERIALS International Vol.18 No.3
In this work we studied the influence of laser radiation on the composition, structure and morphology of WTi thin films deposited on n-type (100) silicon wafers. The films were deposited by d.c. sputtering from a 70:30 at% W-Ti target, using Ar ions, to a thickness of ~190 nm. Irradiation was performed with a pulsed Nd:YAG laser operating at 1064 nm, whereas the pulse duration was 150 ps. Laser fluences of 3.2and 5.9 J/cm2were found to be sufficient for modification of the WTi/silicon target system. The results show: (i) ablation of WTi thin film and a Si substrate in the central zone of spots, (ii) appearance of hydrodynamic features like resolidified material, (iii) partial ablation of the WTi thin film at the periphery and (iv) appearance of thin film cracks at the far periphery. On the non-ablated areas, the laser modifica-tion induced changes in composition, such as inter-mixing of components at the WTi/Si interface with for-mation of silicides in both metals. Surface oxidation was the dominant process in the ablated areas, which is demonstrated by the presence of a SiO2 phase.
Magnetic resonance in bilayers of ferrite and functionally graded piezoelectric
Bichurin, M.I.,Petrov, R.V.,Petrov, V.M.,Saplev, A.F.,Tatarenko, A.S.,Kovalenko, D.V.,Melnichuk, D.G.,Yang, Su-Chul Elsevier 2017 Materials research bulletin Vol.96 No.3
<P><B>Abstract</B></P> <P>The particular purpose of this paper is theoretical modeling of magnetoelectric interactions at the ferromagnetic resonance in a layered structure of a ferrite and a piezoelectric with through-thickness graded polarization. We show that using the functionally graded piezoelectric with through-thickness variation of polarization can lead to an electric field induced broadening of ferromagnetic resonance line. As an example, we consider the laminate based on the yttrium iron garnet layer which is placed between two lead zirconate titanate layers with different poling direction. The maximal ferromagnetic resonance line broadening of 9.3Oe is obtained for the yttrium iron garnet to lead zirconate titanate layer thickness ratio of 1.7 at 9.3GHz for E equal to 10kV/cm.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ferromagnetic resonance in a ferrite-piezoelectric laminate is studied. </LI> <LI> An electric field induced FMR line broadening results from bending the sample. </LI> <LI> Ferrite layer between the two piezoelectric layers shows a large line broadening. </LI> </UL> </P>
Impact of molybdenum cross sections on FHR analysis
Kyle M. Ramey,Marat Margulis,Nathaniel Read,Eugene Shwageraus,Bojan Petrovic 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.3
A recent benchmarking effort, under the auspices of the Organization for Economic Cooperation andDevelopment (OECD) Nuclear Energy Agency (NEA), has been made to evaluate the current state ofmodeling and simulation tools available to model fluoride salt-cooled high temperature reactors (FHRs). The FHR benchmarking effort considered in this work consists of several cases evaluating the neutronicparameters of a 2D prismatic FHR fuel assembly model using the participants’ choice of simulation tools. Benchmark participants blindly submitted results for comparison with overall good agreement, exceptfor some which significantly differed on cases utilizing a molybdenum-bearing control rod. Participantsutilizing more recently updated explicit isotopic cross sections had consistent results, whereas thoseusing elemental molybdenum cross sections observed reactivity differences on the order of thousands ofpcm relative to their peers. Through a series of supporting tests, the authors attribute the differences asbeing nuclear data driven from using older legacy elemental molybdenum cross sections. Quantitativeanalysis is conducted on the control rod to identify spectral, reaction rate, and cross section phenomenaresponsible for the observed differences. Results confirm the observed differences are attributable to theuse of elemental cross sections which overestimate the reaction rates in strong resonance channels.
Experiments to separate the effect of texture on anisotropy of pipeline steel
Joo, M.S.,Suh, D.-W.,Bae, J.H.,Sanchez Mourino, N.,Petrov, R.,Kestens, L.A.I.,Bhadeshia, H.K.D.H. Elsevier Sequoia 2012 Materials science & engineering. properties, micro Vol.556 No.-
Many linepipe steels exhibit a variation in mechanical properties as a function of the orientation of the test sample relative to the rolling and transverse directions of the steel plate. Such anisotropy limits the optimum design and exploitation of the steel, and its occurrence has been attributed to effects such as microstructural banding and the associated delamination during fracture, and unfavourably oriented ferrite cleavage planes. It is often difficult to separate the factors, but an experiment has been designed and implemented to study the role of crystallographic texture in isolation. It is demonstrated that the texture plays a major role in influencing the anisotropy of the Charpy test energy.
“Lomonosov” Satellite—Space Observatory to Study Extreme Phenomena in Space
Sadovnichii, V. A.,Panasyuk, M. I.,Amelyushkin, A. M.,Bogomolov, V. V.,Benghin, V. V.,Garipov, G. K.,Kalegaev, V. V.,Klimov, P. A.,Khrenov, B. A.,Petrov, V. L. Springer Science + Business Media 2017 Space science reviews Vol.212 No.3
<P>This paper is directed towards the general description of both scientific goals of the project and scientific equipment on board the satellite. The following papers of this issue are devoted to detailed descriptions of scientific instruments.</P>
The TUS Detector of Extreme Energy Cosmic Rays on Board the Lomonosov Satellite
Klimov, P. A.,Panasyuk, M. I.,Khrenov, B. A.,Garipov, G. K.,Kalmykov, N. N.,Petrov, V. L.,Sharakin, S. A.,Shirokov, A. V.,Yashin, I. V.,Zotov, M. Y.,Biktemerova, S. V.,Grinyuk, A. A.,Grebenyuk, V. M. Springer-Verlag 2017 Space science reviews Vol.212 No.3
<P>It will also be able to register slower atmospheric transient events: atmospheric fluorescence in electrical discharges of various types including precipitating electrons escaping the magnetosphere and from the radiation of meteors passing through the atmosphere. We describe the design of the TUS detector and present results of different ground-based tests and simulations.</P>