265 research outputs found
Influence of Strain on the Kinetics of Phase Transitions in Solids
We consider a sharp interface kinetic model of phase transitions accompanied
by elastic strain, together with its phase-field realization. Quantitative
results for the steady-state growth of a new phase in a strip geometry are
obtained and different pattern formation processes in this system are
investigated
Evaluation of vacuum bonded GaAs/Si spin-valve transistors
In this article a new type of spin-valve transistor, a hybrid GaAs/Si device, is presented. In this device the Si emitter is replaced by a GaAs emitter launcher structure. The integration of the GaAs with the Si was done by means of a room temperature vacuum bonding technique. By using a soft NiFe/Au/Co spin-valve structure as metal base, a 63% change in collector current is obtained at room temperature for a saturation field of 30 Oe. The corresponding in-plane magnetoresistance is only 1%
Stereo vision enhances the learning of a catching skill
The aim of this study was to investigate the contribution of stereo vision to the acquisition of a natural interception task. Poor catchers with good (N = 8; Stereo+) and weak (N = 6; Stereo-) stereo vision participated in an intensive training program spread over 2 weeks, during which they caught over 1,400 tennis balls in a pre-post-retention design. While the Stereo+ group improved from a catching percentage of 18% to 59%, catchers in the Stereo- group did not significantly improve (from 10 to 31%), this progress being indifferent from a control group (N = 9) that did not practice at all. These results indicate that the development and use of of compensatory cues for depth perception in people with weak stereopsis is insufficient to successfully deal with interceptions under high temporal constraints, and that this disadvantage cannot be fully attenuated by specific and intensive training. © 2007 Springer-Verlag
Droplet Fluctuations in the Morphology and Kinetics of Martensites
We derive a coarse grained, free-energy functional which describes droplet
configurations arising on nucleation of a product crystal within a parent. This
involves a new `slow' vacancy mode that lives at the parent-product interface.
A mode-coupling theory suggests that a {\it slow} quench from the parent phase
produces an equilibrium product, while a {\it fast} quench produces a
metastable martensite. In two dimensions, the martensite nuclei grow as
`lens-shaped' strips having alternating twin domains, with well-defined front
velocities. Several empirically known structural and kinetic relations drop out
naturally from our theory.Comment: 4 pages, REVTEX, and 3 .eps figures, compressed and uuencoded,
Submitted to Phys. Rev. Let
Magnetic phase separation in ordered alloys
We present a lattice model to study the equilibrium phase diagram of ordered
alloys with one magnetic component that exhibits a low temperature phase
separation between paramagnetic and ferromagnetic phases. The model is
constructed from the experimental facts observed in CuAlMn and it
includes coupling between configurational and magnetic degrees of freedom which
are appropriated for reproducing the low temperature miscibility gap. The
essential ingredient for the occurrence of such a coexistence region is the
development of ferromagnetic order induced by the long-range atomic order of
the magnetic component. A comparative study of both mean-field and Monte Carlo
solutions is presented. Moreover, the model may enable the study of the
structure of the ferromagnetic domains embedded in the non-magnetic matrix.
This is relevant in relation to phenomena such as magnetoresistance and
paramagnetism.Comment: 12 pages, 11 figures, accepted in Phys. Rev.
Delayed Appearance of High Altitude Retinal Hemorrhages
When closely examined, a very large amount of climbers exhibit retinal hemorrhages during exposure to high altitudes. The incidence of retinal hemorrhages may be greater than previously appreciated as a definite time lag was observed between highest altitude reached and development of retinal bleeding. Retinal hemorrhages should not be considered warning signs of impending severe altitude illness due to their delayed appearance
Analysis of the transformations temperatures of helicoidal Ti-Ni actuators using computational numerical methods
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