1,148 research outputs found
On the Crystallization of Terbium Aluminium Garnet
Attempts to grow terbium aluminium garnet (Tb3Al5O12, TAG) by the Czochralski
method lead to crystals of millimeter scale. Larger crystals could not be
obtained. DTA measurements within the binary system showed that TAG melts
incongruently at 1840 deg. C. The perovskite (TbAlO3, TAP) with a congruent
melting point of 1930 deg. C is the most stable phase in this system. The
region for primary crystallization of TAP covers the chemical composition of
TAG and suppresses the primary crystallization of the terbium aluminium garnet.Comment: 6 pages, 2 figure
Mechanism Design and Non-Cooperative Renegotiation
We characterize decision rules which are implementable in mechanism design settings when, after the play of a mechanism, the uninformed party can propose a new mechanism to the informed party. The necessary and sufficient conditions are, essentially, that the rule be implementable with commitment, that for each type the decision is at least as high as if there were no mechanism, and that the slope of the decision function is not too high. The direct mechanism which implements such a rule with commitment will also implement it in any equilibrium without commitment, so the standard mechanism is robust to renegotiation
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Mechanism Design and Non-Cooperative Renegotiation
We characterize decision rules which are implementable in mechanism design settings when, after the play of a mechanism, the uninformed party can propose a new mechanism to the informed party. The necessary and sufficient conditions are, essentially, that the rule be implementable with commitment, that for each type the decision is at least as high as if there were no mechanism, and that the slope of the decision function is not too high. The direct mechanism which implements such a rule with commitment will also implement it in any equilibrium without commitment, so the standard mechanism is robust to renegotiation
Contract design and non-cooperative renegotiation
We study a contract design setting in which the contracting parties cannot commit not to renegotiate previous contract agreements. In particular, we characterize the outcome functions that are implementable for an uninformed principal and an informed agent if, having observed the agent's contract choice, the principal can offer a new menu of contracts in its place. An outcome function can be implemented in this setting if and only if it is optimal for the principal for some belief over agent types which is more pessimistic, in the sense of the likelihood ratio order, than the prior. Furthermore, the outcome function cannot be too sensitive to variations in the agent's type. We show that the direct revelation mechanism which implements such a function when renegotiation can be prevented will also implement it in any equilibrium when it cannot, so the standard contract is robust to renegotiation
Development of Prototype Pixellated PIN CdZnTe Detectors
We report initial results from the design and evaluation of two pixellated
PIN Cadmium Zinc Telluride detectors and an ASIC-based readout system. The
prototype imaging PIN detectors consist of 4X4 1.5 mm square indium anode
contacts with 0.2 mm spacing and a solid cathode plane on 10X10 mm CdZnTe
substrates of thickness 2 mm and 5 mm. The detector readout system, based on
low noise preamplifier ASICs, allows for parallel readout of all channels upon
cathode trigger. This prototype is under development for use in future
astrophysical hard X-ray imagers with 10-600 keV energy response. Measurements
of the detector uniformity, spatial resolution, and spectral resolution will be
discussed and compared with a similar pixellated MSM detector. Finally, a
prototype design for a large imaging array is outlined.Comment: 10 pages Latex, 9 figures, to appear in Proc. of SPIE Vol. 3446 "Hard
X-ray and Gamma-Ray Detector Physics and Applications
Smith-Purcell Radiation from Rough Surfaces
Radiation of a charged particle moving parallel to a inhomogeneous surface is
considered. Within a single formalism periodic and random gratings are
examined. For the periodically inhomogeneous surface we derive new expressions
for the dispersion relation and the spectral-angular intensity. In particular,
for a given observation direction two wavelengths are emitted instead of one
wavelength of the standard Smith-Purcell effect. For a rough surface we show
that the main contribution to the radiation intensity is given by surface
polaritons induced on the interface between two media. These polaritons are
multiply scattered on the roughness of surface and convert into real photons.
The spectral-angular intensity is calculated and its dependence on different
parameters is revealed.Comment: 6 pages, 2 figures, submitted to Phys. Rev. ST Accel. Beam
Magnetization reversal and local switching fields of ferromagnetic Co/Pd microtubes with radial magnetization
Three-dimensional nanomagnetism is a rapidly growing field of research covering both noncollinear spin textures and curved magnetic geometries including microtubular structures. We spatially resolve the field-induced magnetization reversal of free-standing ferromagnetic microtubes utilizing multifrequency magnetic force microscopy (MFM). The microtubes are composed of Co/Pd multilayer films with perpendicular magnetic anisotropy that translates to an anisotropy with radial easy axis upon rolling-up. Simultaneously mapping the topography and the perpendicular magnetostatic force derivative, the relation between surface angle and local magnetization configuration is evaluated for a large number of locations with slopes exceeding 45 degrees. The angle-dependence of the switching field is concurrent with the Kondorsky model, i.e., the rolled-up nanomembrane behaves like a planar magnetic film with perpendicular anisotropy and a pinning dominated magnetization reversal. Additionally, we discuss methodological challenges when detecting magnetostatic force derivatives near steep surfaces
Investigation of implantation-induced damage in indium phosphide for layer transfer applications
100 keV H+ and He+ ion implantation was performed in 300 µm thick (100) InP substrates at liquid nitrogen temperature with a constant fluence of 1 × 1017 cm–2. The surface morphology of the as-implanted InP samples was studied by optical microscopy. The implantation-induced damage was investigated by cross-sectional TEM, which revealed the formation of damage band in both cases near to the projected range of implanted ions. The formation of hydrogen-induced nanocracks and helium filled nanobubbles was observed in as-implanted InP samples.
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