Easterner, Vol. 66, No. 26, May 6, 2015

The issue of the Easterner contains articles about the Investiture Ceremony for president Mary Cullinan, women distance runners on the track team, a book talk by Jared Diamond in Spokane, an earthquake outside Hayden, Idaho, Jake Rodgers selection by the Atlanta Falcons in the NFL draft, and the track and field team\u27s performance in Corvallis, Oregon.https://dc.ewu.edu/student_newspapers/1889/thumbnail.jp

New Mexico Lobo, Volume 028, No 6, 10/26/1925

New Mexico Lobo, Volume 028, No 6, 10/26/1925https://digitalrepository.unm.edu/daily_lobo_1925/1024/thumbnail.jp

Ferroelectric and dielectric characterization studies on relaxor- and ferroelectric-like strontium-barium niobates

Ferroelectric domain structure evolution induced by an external electric field was investigated by means of nematic liquid crystal (NLC) method in two strontium-barium niobate single crystals of nominal composition: Sr_{0.70}Ba_{0.30}Nb_{2}O_{6} (SBN:70 - relaxor) and Sr_{0.26}Ba_{0.74}Nb_{2}O_{6} (SBN:26 - ferroelectric). Our results provide evidence that the broad phase transition and frequency dispersion that are exhibited in SBN:70 crystal have a strong link to the configuration of ferroelectric microdomains. The large leakage current revealed in SBN:26 may compensate internal charges acting as pinning centers for domain walls, which gives rise to a less restricted domain growth similar to that observed in classical ferroelectrics. Microscale studies of a switching process in conjunction with electrical measurements allowed us to establish a relationship between local properties of the domain dynamics and macroscopic response i.e., polarization hysteresis loop and dielectric properties.Comment: 10 pages, 7 figure

Digital imaging: A unified topological framework

International audienceIn this article, a tractable modus operandi is proposed to model a (binary) digital image (i.e., an image defined on Z^n and equipped with a standard pair of adjacencies) as an image defined in the space of cubical complexes (F^n). In particular, it is shown that all the standard pairs of adjacencies (namely the (4, 8) and (8, 4)-adjacencies in Z^2, the (6, 18), (18, 6), (6, 26), and (26, 6)-adjacencies in Z^3 , and more generally the (2n, 3n−1) and (3n−1, 2n)-adjacencies in Z^n) can then be correctly modelled in F^n . Moreover, it is established that the digital fundamental group of a digital image in Z^n is isomorphic to the fundamental group of its corresponding image in F^n , thus proving the topological correctness of the proposed approach. From these results, it becomes possible to establish links between topology-oriented methods developed either in classical digital spaces (Z^n) or cubical complexes (F^n), and to potentially unify some of them

Characterization of the mechanical properties of thermal barrier coatings by 3 points bending tests and modified small punch tests

Issu de : ICMCTF 2017 - 44th International Conference on Metallurgical Coatings and Thin Films, San Diego, UNITED STATES, April 24-28, 2017International audienceThe Atmospheric Plasma Sprayed Thermal Barrier Coatings (APS TBCs) is commonly used to insulate hot sections in gas turbines. Cyclic oxidation failure usually results from the spallation of the ceramic top coat. In order to predict such spalling phenomena, understanding the mechanisms for cracks initiation and propagation in thermal barriers is a major issue for engine-makers. Failure of the TBC is strongly related to the thermal and mechanical properties of each component of the multi-materials system (substrate, bond coat and ceramic) but also to the response of the TBC as a whole. The purpose of the present work is to assess the mechanical behavior of a complete TBC using comparative experimental (uniaxial and biaxial loading) and Digital Images Correlation (DIC) analysis approaches for classical TBC microstructures obtained through APS coatings.The experimental characterization of the mechanical behavior of the TBC systems was studied on as deposited specimens. Three Points Bending (3PB) tests were performed at room temperature, with the ceramic coating either under tension or compression. Additionally, in situ observations during 3PB tests by a camera, associated to a DIC analysis, allow determining the evolution of the strain field of surface sample correlated with the damage evolution. Location of crack initiation and crack propagation paths up to macroscopic failure were investigated. These tests highlighted the strong differences in mechanical behavior and fracture mode depending on the tension or compression stress state in ceramic coating. Small Punch Tests (SPT) were also performed at room temperature using both geometries (tension/compression). This allows pointing out the similarities of failure modes between uniaxial solicitation and biaxial flexure. Tests performed at 850 °C in the SPT ring show that when temperature varies, different mechanical properties can be observed

Effects of a nonadiabatic wall on supersonic shock/boundary-layer interactions

Direct numerical simulations are employed to investigate a shock wave impinging on a turbulent boundary layer at free-stream Mach number M=2.28 with different wall thermal conditions, including adiabatic, cooled, and heated, for a wide range of deflection angles. It is found that the thermal boundary condition at the wall has a large effect on the size of the interaction region and on the level of pressure fluctuations. The distribution of the Stanton number shows a good agreement with prior experimental studies and confirms the strong heat transfer and complex pattern within the interaction region. An effort was also made to describe the unsteady features of the flow by means of wall pressure and heat flux spectra. Numerical results indicate that the changes in the interaction length due to the wall thermal condition are mainly linked to the incoming boundary layer, which is in agreement with previous experimental studies