Effect of Zr content on phase stability, deformation behavior, and Young's modulus in Ti-Nb-Zr alloys

Ti alloys have attracted continuing research attention as promising biomaterials due to their superior corrosion resistance and biocompatibility and excellent mechanical properties. Metastable beta-type Ti alloys also provide several unique properties such as low Young's modulus, shape memory effect, and superelasticity. Such unique properties are predominantly attributed to the phase stability and reversible martensitic transformation. In this study, the effects of the Nb and Zr contents on phase constitution, transformation temperature, deformation behavior, and Young's modulus were investigated. Ti-Nb and Ti-Nb-Zr alloys over a wide composition range, i.e., Ti-(18-40)Nb, Ti-(15-40)Nb-4Zr, Ti-(16-40)Nb-8Zr, Ti-(15-40)Nb-12Zr, Ti-(12-17)Nb-18Zr, were fabricated and their properties were characterized. The phase boundary between the beta phase and the alpha '' martensite phase was clarified. The lower limit content of Nb to suppress the martensitic transformation and to obtain a single beta phase at room temperature decreased with increasing Zr content. The Ti-25Nb, Ti-22Nb-4Zr, Ti-19Nb-8Zr, Ti-17Nb-12Zr and Ti-14Nb-18Zr alloys exhibit the lowest Young's modulus among Ti-Nb-Zr alloys with Zr content of 0, 4, 8, 12, and 18 at.%, respectively. Particularly, the Ti-14Nb-18Zr alloy exhibits a very low Young's modulus less than 40 GPa. Correlation among alloy composition, phase stability, and Young's modulus was discussed.Web of Science132art. no. 47

Basic iron (III) alkanoate complexes

Much information appears in the literature concerning the preparation, properties and structure of the basic iron (III) acetates...This study was initiated to prepare a number of the basic trinuclear iron (III) alkanoate complexes and to investigate the possibility of a common structure for all of these as suggested by the work of Orgel. The structural investigation was done on the basis of stoichiometric relationships, infrared spectra and magnetic moments --Abstract, pages ii-iii

Open quantum dots modeled with microwave cavities

In this work, open microwave resonators have been investigated as a model system of a quantum dot. Since quantum dots are micrometer-sized, measurements in quantum dots are still very difficult except for transport measurement, but relatively simple in a microwave resonator. We fabricated a flat resonator and a resonator with soft-wall potential so that the shape corresponded to a quantum dot which has been investigated in the laboratory of J.P. Bird. For a flat resonator, i.e. a resonator with a hard-wall potential, periodically occurring scarred wave function families are analyzed, and the associated orbits are identified. For complicated wave function families, we use a Fourier spectroscopy. Influence of an absorber center is investigated using Fourier transform of transmission between the input and output leads. The Fourier map is analyzed to identify scar families. The calculated orbits lengths and the experimentally obtained values show very good agreement. By varying the height of the resonator, potentials can be simulated, using the correspondence between quantum mechanics and electrodynamics. Using this relation, a resonator with soft-wall potential was fabricated. The shape of the potential corresponds to the above mentioned quantum dot. The measured eigenfrequencies for the periodic bouncing-ball scar families agree very well with the theoretical values from a WKB approximation . The wave function family of an X-like cross bouncing ball is used to obtain evidence of dynamical tunneling. By phase difference analysis and transport behavior, the presence of dynamical tunneling is proven. In the last part of this work, the statistical properties of the wave functions of an asymmetric open flat resonator are discussed. Opening to the outside world of billiard makes the wave function complex, since there is transport. This cross-over regime, from real to imaginary of wave functions is investigated opening of the billiard by frequency increasing. The phase rigidity distribution which give the ratio between the real and imaginary parts of the wave function, the long-range correlation of intensity and the current density are compared with the theoretical values calculated from the random superposition of plane waves theory. For all investigated quantities, a very good agreement between experiment and theory is found

Effects of Using Online Forum for Problem-Solving Skills and Collaborative Construction of Knowledge in Student Teaching

The purpose of the study was to seek a way to strengthen student teachers’ understanding of the complex nature of teaching and increase their competence in solving problems. To accomplish our goal, we embarked upon a study to explore on a computer-mediated conferencing group model enriched with constructivist principles and features of a community of learners. The study is guided by two major models: Problem Solving Approach Model and Interaction Analysis Model (IAM) for Computer-Mediated Communication rooted in social constructivist theory. This study also is aimed at assessing the quality of interaction by means of IAM for examining social construction of knowledge, and of learning experiences of student teachers during computer conferencing while learning problem-solving skills. Implications and suggestions for teacher educators will be offered