723 research outputs found
Fluctuation of the Solute Concentration in Al Rich Al-Zn Alloys
Several Al-Zn alloys containing 0.041-4.4 at % Zn were studied by means of measurements of electrical resistivity. The results obtained are as follows : (1) The electrical resistivity increases when the specimen is annealed at temperatures higher than the solvus temperature of the G.P. zones. The increase of the resistivity is due to the formation of fluctuation. (2) The electrical resistivity of the specimen containing fluctuation is dependent upon annealing temperature only and independent of quenching temperature. (3) The fluctuation is formed in very dilute alloys as 0.041 at % Zn at temperatures higher than the solvus temperature of the G.P. zones. (4) The formation energy of vacancy and the migration energy of the Zn atom in the alloys determined by the formation process of fluctuation are in good agreement with those by the formation process of G.P. zones. (5) In spite of the result (4), it seems that the
fluctuation is not the same as the small G.P. zones which are observed in the early stage of aging
Building Secure and Anonymous Communication Channel: Formal Model and its Prototype Implementation
Various techniques need to be combined to realize anonymously authenticated
communication. Cryptographic tools enable anonymous user authentication while
anonymous communication protocols hide users' IP addresses from service
providers. One simple approach for realizing anonymously authenticated
communication is their simple combination, but this gives rise to another
issue; how to build a secure channel. The current public key infrastructure
cannot be used since the user's public key identifies the user. To cope with
this issue, we propose a protocol that uses identity-based encryption for
packet encryption without sacrificing anonymity, and group signature for
anonymous user authentication. Communications in the protocol take place
through proxy entities that conceal users' IP addresses from service providers.
The underlying group signature is customized to meet our objective and improve
its efficiency. We also introduce a proof-of-concept implementation to
demonstrate the protocol's feasibility. We compare its performance to SSL
communication and demonstrate its practicality, and conclude that the protocol
realizes secure, anonymous, and authenticated communication between users and
service providers with practical performance.Comment: This is a preprint version of our paper presented in SAC'14, March
24-28, 2014, Gyeongju, Korea. ACMSAC 201
On the Apparent Activation Energy for Clustering in Dilute Al-Zn Alloys
The clustering phenomenon was observed when dilute Al-Zn alloys were annealed at temperatures higher than the solvus of the G.P.zones. In this report the apparent activation energy for clustering is estimated and compared with the experimental results. The estimated value of the apparent activation energy for clustering in several Al-Zn alloys comes to 0.51 eV, which is larger than the effective migration energy 0.43 eV of Zn atoms in Al-Zn alloys
SAXS from the GP Zones in Al-4mass % Cu Alloy at Initial Stages of Ageing
A series of small-angle X-ray scattering photographs with monochromated and point focussed copper Ka(1) radiation was taken of a single crystal of an Al-4mass % Cu alloy at the as-quenched state from 823K and at successive stages of ageing at 313K. The crystal was so oriented that the incident direction of the radiation was along [001] axis, and was cooled with liquid nitrogen during the exposure.
The pattern of the as-quenched state was homogeneous, but
each of the patterns of the aged states consisted of streaks along [100] and [010] directions and a quasi-ring around the trace of the incident beam on the film (even at the shortest ageing time. l6sec). The most intense regions were found in [100], [010] , [100] and [010] directions on the ring. With the progress of the ageing the streaks and the ring became more intense and narrower. The results can be interpreted from points of view of the formation of the GP zones parallel to {100} planes ab initio, the effect of the inter-particle interference on scattering of X-rays, and the growth of the GP zones with the ageing. Guinier
radius of the GP zones at each stage can be obtained from intensity change along [110], and the values are reasonably consistent with those obtained from the cross section of the streak. The presence of multi-layer zones, besides the one-layer ones, is suggested from the humps found on several intensity curves along [100] at later stages
Experimental characterization of the electronic structure of anatase TiO2: Thermopower modulation
Thermopower (S) for anatase TiO2 epitaxial films (n3D: 1E17-1E21 /cm3) and
the gate voltage (Vg) dependence of S for thin film transistors (TFTs) based on
TiO2 films were investigated to clarify the electronic density of states (DOS)
around the conduction band bottom. The slope of the |S|-log n3D plots was -20
{\mu}V/K, which is an order magnitude smaller than that of semiconductors (-198
{\mu}V/K), and the |S| values for the TFTs increased with Vg in the low Vg
region, suggesting that the extra tail states are hybridized with the original
conduction band bottom.Comment: 11 pages, 4 figure
SAXS Intensity Measurements by Photographic Methods
Photographic method for measurement of small-angl X-ray scattering (SAXS) is improved. Intense pointfocussing incident beam is obtained by using doubly bent crystal monochromator made of aluminium single crystal. Microphotometry and the subsequent calculation to obtain profiles, Guinier and Porod radii, integrated intensities, and so on are facilitated by using microcomputer. Integrated SAXS intensities measured from an Al-Zn alloy which has been treated under the same heat treatment conditions are coincident with one another with probable errors less than ±6 % . Ratio of the integrated intensities obtained from two Al-Zn alloys of different composition is reasonable compared with the quasi-equilibrium phase diagram
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