Pattern-Formation During Self-organization in Three-Phase Eutectic Solidification

Eutectic growth is an interesting example for exploring the topic of pattern-formation in multi-phase systems, where the growth of the phases is coupled with the diffusive transport of one or more components in the melt. While in the case of binary alloys, the number of possibilities are limited (lamellae, rods, labyrinth etc.), their number rapidly increases with the number of components and phases. In this paper, we will investigate pattern formation during three-phase eutectic solidification using a state-of-the art phase-field method based on the grand-canonical density formulation. The major aim of the study is to highlight the role of two properties, which are the volume fraction of the solid phases and the solid-liquid interfacial energies, in the self-organization of the solid phases during directional growth. Thereafter, we will show representative phase-field simulations of a micro-structure in a real alloy (Ag-Al-Cu) using an asymmetric phase diagram as well as interfacial properties.

Investigation on the origin of exchange bias in epitaxial, oriented and polycrystalline Fe3O4 thin films

We observe exchange bias (EB) in a single magnetic film Fe3O4 at temperature T < 200 K. Irrespective of crystallographic orientations of grown Fe3O4; they exhibit similar nature of EB for (100) epitaxial, (111) oriented and polycrystalline Fe3O4 thin films. Growth induced defects such as anti-phase boundaries (APBs) in epitaxial Fe3O4 thin film is known to have an influence on the magnetic interaction. But, it is noticed that according to the common consensus of APBs alone cannot explain the origin of EB. If majority of APBs end up with mainly anti-ferromagnetic interactions across these boundaries together with the internal ordering modification in Fe3O4, then EB can emerge at low temperatures. Hence, we propose the idea of directional anti-ferromagnetic APB induced EB in Fe3O4 triggered by internal ordering for T <= 200 K. Similar arguments are extended to (111) oriented as well as polycrystalline Fe3O4 films where the grain boundaries can impart same consequence as that of APBs. (C) 2015 Author(s).

AN INVESTIGATION OF CUTTING MECHANISMS AND STRAIN FIELDS DURING ORTHOGONAL CUTTING IN CFRPs

Fiber-reinforced plastics (FRPs) are typically difficult to machine due to their highly heterogeneous and anisotropic nature and the presence of two phases (fiber and matrix) with vastly different strengths and stiffnesses. Typical machining damage mechanisms in FRPs include series of brittle fractures (especially for thermosets) due to shearing and cracking of matrix material, fiber pull-outs, burring, fuzzing, fiber-matrix debonding, etc. With the aim of understanding the influence of the pronounced heterogeneity and anisotropy observed in FRPs, ``Idealized'' Carbon FRP (I-CFRP) plates were prepared using epoxy resin with embedded equispaced tows of carbon fibers. Orthogonal cutting of these I-CFRPs was carried out, and the chip formation characteristics, cutting force signals and strain distributions obtained during machining were analyzed using the Digital Image Correlation (DIC) technique. In addition, the same procedure was repeated on Uni-Directional CFRPs (UD-CFRPs). Chip formation mechanisms in FRPs were found to depend on the depth of cut and fiber orientation with pure epoxy showing a pronounced ``size effect.'' Experimental results indicate that in-situ full field strain measurements from DIC coupled with force measurements using dynamometry provide an adequate measure of anisotropy and heterogeneity during orthogonal cutting.

Evidence for 3D isotropic long range spin-spin interaction near the ferromagnetic transition in bulk and thin film SrRuO3

In the case of metallic ferromagnets there has always been a controversy, i.e. whether the magnetic interaction is itinerant or localized. For example SrRuO3 is known to be an itinerant ferromagnet where the spin-spin interaction is expected to be mean field in nature. However, it is reported to behave like Ising, Heisenberg or mean field by different groups. Despite several theoretical and experimental studies and the importance of strongly correlated systems, the experimental conclusion regarding the type of spin-spin interaction in SrRuO3 is lacking. To resolve this issue, we have investigated the critical behaviour in the vicinity of the paramagnetic-ferromagnetic phase transition using various techniques on polycrystalline as well as (001) oriented SrRuO3 films. Our analysis reveals that the application of a scaling law in the field-cooled magnetization data extracts the value of the critical exponent only when it is measured at H -> 0. To substantiate the actual nature without any ambiguity, the critical behavior is studied across the phase transition using the modified Arrott plot, Kouvel-Fisher plot and M-H isotherms. The critical analysis yields self-consistent beta, gamma and delta values and the spin interaction follows the long-range mean field model. Further the directional dependence of the critical exponent is studied in thin films and it reveals the isotropic nature. It is elucidated that the different experimental protocols followed by different groups are the reason for the ambiguity in determining the critical exponents in SrRuO3.

Evidence for 3D isotropic long range spin-spin interaction near the ferromagnetic transition in bulk and thin film SrRuO3

In the case of metallic ferromagnets there has always been a controversy, i.e. whether the magnetic interaction is itinerant or localized. For example SrRuO3 is known to be an itinerant ferromagnet where the spin-spin interaction is expected to be mean field in nature. However, it is reported to behave like Ising, Heisenberg or mean field by different groups. Despite several theoretical and experimental studies and the importance of strongly correlated systems, the experimental conclusion regarding the type of spin-spin interaction in SrRuO3 is lacking. To resolve this issue, we have investigated the critical behaviour in the vicinity of the paramagnetic-ferromagnetic phase transition using various techniques on polycrystalline as well as (001) oriented SrRuO3 films. Our analysis reveals that the application of a scaling law in the field-cooled magnetization data extracts the value of the critical exponent only when it is measured at H -> 0. To substantiate the actual nature without any ambiguity, the critical behavior is studied across the phase transition using the modified Arrott plot, Kouvel-Fisher plot and M-H isotherms. The critical analysis yields self-consistent beta, gamma and delta values and the spin interaction follows the long-range mean field model. Further the directional dependence of the critical exponent is studied in thin films and it reveals the isotropic nature. It is elucidated that the different experimental protocols followed by different groups are the reason for the ambiguity in determining the critical exponents in SrRuO3.

Multiphase technique improves mud-pulse velocity calculations

Measurement while drilling (MWD) has become a popular survey technology to monitor directional data, drilling data, formation evaluation data and safety data in the world. And closed loop drilling shows promise in recent years. Obviously, the method of tr

Influence of the Processing Conditions on the Characteristics of the Clad Layers Produced with Laminar Plasma Technology

Laminar plasma technology was used to produce ceramic hardened layers of Al2O3-40% mass Ni composite powders on stainless steel substrates. In order to investigate the influences of processing conditions on the morphologies of the surface modified layers, two different powder-feeding methods were tested, one with carrier gas called the powder injection method, and the other without carrier gas called powder transfers method. The microscopic investigations demonstrate that the cross-section of the clad layers consists of two distinct microstructural regions, in which the Al2O3 phases exhibit different growth mechanisms. When the powder transfers method is adopted, the number density and volume fraction of the Al2O3 particles increase considerably and their distributions exhibit zonal periodical characteristics. When the powder-feeding rate increases, the microstructure of the Al2O3 phases changes from a small globular to a long needle shape. Finite element simulations show that the transient thermo-physical features of the pool substances, such as solidification rate and cooling rate, influence strongly the mechanisms of the nucleation and the directional growth of the Al2O3 phases in the thermal processing.

Numerical approximation improves well survey calculation

It is now possible to improve the precision of well survey calculations by order of magnitude with numerical approximation.

Although the most precise method of simulating and calculating a wellbore trajectory generally requires more calculation than other, less-accurate methods, the wider use of computers in oil fields now eliminates this as an obstacle.

The results of various calculations show that there is a deviation of more than 10 m among the different methods of calculation for a directional well of 3,000 m.¹ Consequently, it is important to improve the precision and reliability of survey calculation-the fundamental, necessary work of quantitatively monitoring and controlling wellbore trajectories.

Study Of The Damage-Induced Anisotropy Of Quasi-Brittle Materials Using The Component Assembling Model

Damage-induced anisotropy of quasi-brittle materials is investigated using component assembling model in this study. Damage-induced anisotropy is one significant character of quasi-brittle materials coupled with nonlinearity and strain softening. Formulation of such complicated phenomena is a difficult problem till now. The present model is based on the component assembling concept, where constitutive equations of materials are formed by means of assembling two kinds of components' response functions. These two kinds of components, orientational and volumetric ones, are abstracted based on pair-functional potentials and the Cauchy - Born rule. Moreover, macroscopic damage of quasi-brittle materials can be reflected by stiffness changing of orientational components, which represent grouped atomic bonds along discrete directions. Simultaneously, anisotropic characters are captured by the naturally directional property of the orientational component. Initial damage surface in the axial-shear stress space is calculated and analyzed. Furthermore, the anisotropic quasi-brittle damage behaviors of concrete under uniaxial, proportional, and nonproportional combined loading are analyzed to elucidate the utility and limitations of the present damage model. The numerical results show good agreement with the experimental data and predicted results of the classical anisotropic damage models.

A Novel Counter Sheet-Flow Sandwich Cell Culture Device For Mammalian Cell Growth In Space

Cell culture and growth in space is crucial to understand the cellular responses under microgravity. The effects of microgravity were coupled with such environment restrictions as medium perfusion, in which the underlying mechanism has been poorly understood. In the present work, a customer-made counter sheet-flow sandwich cell culture device was developed upon a biomechanical concept from fish gill breathing. The sandwich culture unit consists of two side chambers where the medium flow is counter-directional, a central chamber where the cells are cultured, and two porous polycarbonate membranes between side and central chambers. Flow dynamics analysis revealed the symmetrical velocity profile and uniform low shear rate distribution of flowing medium inside the central culture chamber, which promotes sufficient mass transport and nutrient supply for mammalian cell growth. An on-orbit experiment performed on a recovery satellite was used to validate the availability of the device.

On crack path stability in a layered material

Crack paths in an elastic layer on top of a substrate are considered. Crack growth is initiated from an edge crack in the layer. The plane of the initially straight crack forms an angle to the free surface. The load consists of a pair of forces applied at the crack mouth and parallel to the interface. Crack paths are calculated using a boundary element method. Crack growth is assumed to proceed along a path for which the mode II stress intensity factor vanishes. The inclination and the length of the initial crack are varied. The effect of two different substrates on the crack path evolution is demonstrated. A crack path initially leading perpendicularly to the interface is shown to be directionally unstable for a rigid substrate. Irrespective of its initial angle, the crack does not reach the interface, but reaches the free surface if the layer is infinitely long. At finite layer length the crack reaches the upper free surface if the initial crack inclination to the surface is small enough. For an inextendable flexible substrate, on the other hand, the crack reaches the interface if its initial inclination is large enough. For the flexible substrate an unstable path parallel with the sides of an infinitely long layer is identified. The results are compared with experimental results and discussed in view of characterisation of directionally unstable crack paths. The energy release rate for an inclined edge crack is determined analytically.

El desarrollo profesional de los trabajadores como ventaja competitiva de las empresas

[ES] En este trabajo se hace una revisión de la literatura sobre el concepto de profesión y a continuación se propone un modelo de desarrollo profesional en el que se destacan los retos profesionales de los trabajadores y la posibilidad de las empresas de ayudarles a afrontarlos. También se analizan los sistemas de desarrollo profesional y los roles que en ellos juegan empleados, directores y empresas. Para finalizar, se exponen varias cuestiones de actualidad relativas al desarrollo profesional: incorporación y orientación, estabilización, obsolescencia de las habilidades, doble trayectoria profesional, conflictos trabajo-familia, pérdida del puesto de trabajo y jubilación.

Study of the damage-induced anisotropy of quasi-brittle materials using the component assembling model

Damage-induced anisotropy of quasi-brittle materials is investigated using component assembling model in this study. Damage-induced anisotropy is one significant character of quasi-brittle materials coupled with nonlinearity and strain softening. Formulation of such complicated phenomena is a difficult problem till now. The present model is based on the component assembling concept, where constitutive equations of materials are formed by means of assembling two kinds of components' response functions. These two kinds of components, orientational and volumetric ones, are abstracted based on pair-functional potentials and the Cauchy - Born rule. Moreover, macroscopic damage of quasi-brittle materials can be reflected by stiffness changing of orientational components, which represent grouped atomic bonds along discrete directions. Simultaneously, anisotropic characters are captured by the naturally directional property of the orientational component. Initial damage surface in the axial-shear stress space is calculated and analyzed. Furthermore, the anisotropic quasi-brittle damage behaviors of concrete under uniaxial, proportional, and nonproportional combined loading are analyzed to elucidate the utility and limitations of the present damage model. The numerical results show good agreement with the experimental data and predicted results of the classical anisotropic damage models.

Wave Sensor Technologies, St Petersburg, Florida, March 7-9, 2007: workshop proceedings

The Alliance for Coastal Technologies (ACT) convened a workshop on "Wave Sensor Technologies" in St. Petersburg, Florida on March 7-9, 2007, hosted by the University of South Florida (USF) College of Marine Science, an ACT partner institution. The primary objectives of this workshop were to: 1) define the present state of wave measurement technologies, 2) identify the major impediments to their advancement, and 3) make strategic recommendations for future development and on the necessary steps to integrate wave measurement sensors into operational coastal ocean observing systems. The participants were from various sectors, including research scientists, technology developers and industry providers, and technology users, such as operational coastal managers and coastal decision makers. Waves consistently are ranked as a critical variable for numerous coastal issues, from maritime transportation to beach erosion to habitat restoration. For the purposes of this workshop, the participants focused on measuring "wind waves" (i.e., waves on the water surface, generated by the wind, restored by gravity and existing between approximately 3 and 30-second periods), although it was recognized that a wide range of both forced and free waves exist on and in the oceans. Also, whereas the workshop put emphasis on the nearshore coastal component of wave measurements, the participants also stressed the importance of open ocean surface waves measurement. Wave sensor technologies that are presently available for both environments include bottom-mounted pressure gauges, surface following buoys, wave staffs, acoustic Doppler current profilers, and shore-based remote sensing radar instruments. One of the recurring themes of workshop discussions was the dichotomous nature of wave data users. The two separate groups, open ocean wave data users and the nearshore/coastal wave data users, have different requirements. Generally, the user requirements increase both in spatial/temporal resolution and precision as one moves closer to shore. Most ocean going mariners are adequately satisfied with measurements of wave period and height and a wave general direction. However, most coastal and nearshore users require at least the first five Fourier parameters ("First 5"): wave energy and the first four directional Fourier coefficients. Furthermore, wave research scientists would like sensors capable of providing measurements beyond the first four Fourier coefficients. It was debated whether or not high precision wave observations in one location can take the place of a less precise measurement at a different location. This could be accomplished by advancing wave models and using wave models to extend data to nearby areas. However, the consensus was that models are no substitution for in situ wave data.[PDF contains 26 pages]

Migrations of yellowfin tuna in the Eastern Pacific Ocean as determined from tagging experiments initiated during 1968-1974

ENGLISH: Data from tagging experiments initiated during 1968-1974 in the eastern Pacific Ocean were used to study the migrations of yellowfin tuna in that area. The map method, the parallel-area method, and the Jones method were employed in the analyses. The map method gives a useful impression of the distances and directions traveled, but does not express these parameters in quantitative terms. The parallel-area method is particularly useful for determining whether or not there is net movement in particular directions, i.e. inshore-offshore, east-west, or north-south. The first of these is of particular interest, as the incidence of smaller fish is much higher in the catches made inshore than in those made offshore, and it is desirable to know whether this is due to relatively greater abundance or to relatively greater vulnerability of the smaller fish in the inshore areas. If the former were the case an offshore movement of the fish as they grew older would probably be detected. Such a movement was not detected, however, so it appears likely that the differences in the catches of smaller fish in the inshore and offshore areas are due mainly to differences in vulnerability. Few or no east-west or north-south tendencies in the movements of the fish were detected. The Jones method indicates that the movement is not random, but reveals no pronounced directional tendencies. SPANISH: Se emplearon los datos de los experimentos de marcado, iniciados en el Océano Pacífico oriental durante 1968-1974 para estudiar los desplazamientos del atún aleta amarilla en esa zona. En los análisis se emplearon los métodos cartográficos, de las zonas paralelas y de Jones. El método cartográfico ofrece una idea útil sobre la distancia y dirección de los desplazamientos, pero no expresa estos parámetros en términos cuantitativos. El método de las zonas paralelas es particularmente conveniente para determinar si existe o nó un desplazamiento neto en una dirección especial, es decir, hacia la costa-fuera de la costa, este-oeste o norte-sur. El primero de éstos tiene un interés especial, ya que la incidencia de peces más pequeños es muy superior en las capturas realizadas cerca de la costa que en las de mar afuera, y se desea conocer si ésto se debe a la abundancia relativamente superior o a las vulnerabilidad relativamente mayor de los pequeños peces en las zonas costeras. Si el caso fuera el primero, se podría descubrir probablemente un movimiento de los peces mar afuera a medida que crecen. Sin embargo, no se ha descubierto tal movimiento, así que es probable que las diferencias en las capturas de peces pequeños en las zonas costeras y mar afuera se deban principalmente a diferencias en la vulnerabilidad. Se descubrió poca o ninguna tendencia en los peces a desplazarse este-oeste o norte-sur. El método de Jones indica que el movimiento no es aleatorio, pero no revela una tendencia pronunciada a orientarse direccionalmente.