A model and properties of a thermodynamically reversible logic gate

Requirements for a completely reversible (in thermodynamic terms) binary logic gate in which the computing energy returns to the system and is used in subsequent computations are put forward. A set of elements of the reversible gate is considered, and conditions necessary for its operation are formulated. A mechanical and an electronic design of the completely reversible gate, as well as the configurations of reversible logic units of arbitrary complexity, are suggested. Difficulties in implementing a reversible power supply are discussed. Results of computer-aided simulation of CMIS reversible logic devices are presented.     

Understanding the unique properties of SPD-induced microstructures

Refining microstructure by severe plastic deformation to a nanometer range changes fundamental properties, such as the Curie and Debye temperatures, and engineering properties of pragmatic significance, such as strength and ductility. These enhancements originate in the combination of very small grain sizes coupled with specific defect structures. Ongoing research is rapidly advancing the understanding of severe plastic deformation-induced microstructures, leading toward the commercialization of these materials. For more information, contact T.C. Lowe, Los Alamos National Laboratory, Materials Science and Technology Division, MD G754, Los Alamos, New Mexico 87545; (505) 665-1131; fax (505) 665-4584; e-mail tlowe@lanl.gov. Authors’ Note: All compositions are given in weight per cent.     

Pseudopartial wetting of grain boundaries in severely deformed Al-Zn alloys

After severe plastic deformation by the high-pressure torsion, Al-Zn alloys have three various classes of Al/Al grain boundaries (GBs) wetted with a second zinc-rich phase. Completely wetted Al/Al GBs are coated with the layer of a zinc-rich phase more than 30 nm thick. Partially (incompletely) wetted Al/Al GBs contact particles of the zinc-rich phase with a contact angle >60°, but contain no measurable zinc concentration. Pseudopartially wetted Al/Al GBs also contact Zn particles with a contact angle >60°. However, they have a thin interlayer of the zinc-rich phase with a uniform thickness of 2–4 nm, the presence of which explains the unusually high ductility of Al-Zn alloys after high-pressure torsion.     

Creation of submicrocrystalline structure and improvement of functional properties of shape memory alloys of the Ti-Ni-Fe system with the help of ECAP

The structure and mechanical and functional properties of shape memory alloys of the Ti-Ni-Fe system are studied by methods of x-ray diffraction analysis, transmission electron microscopy, and mechanical and thermomechanical testing. The alloys are subjected to high-temperature thermomechanical treatment (HTMT) and equichannel angular pressing (ECAP). The tested objects are thermomechanical clutches from a Ti-Ni-Fe alloy subjected to ECAP and to control treatment (for comparison). The bearing capacity and the low-temperature stability of thermomechanical joints of such clutches were studied. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 2, pp. 8–13, February, 2007.     

Superplasticity of nanostructured metallic materials obtained by methods of severe plastic deformation

A review of primarily the authors’ own works on the effect of nano-and submicrocrystalline structure obtained by methods of severe plastic deformation, such as equal channel angular pressing and severe plastic deformation by torsion, on the superplasticity of alloys at relatively low temperature and/or high deformation rate is presented. Special features of the microstructure (grain size, grain-boundary angles, phase composition) required for manifestation of the effect of enhanced superplasticity in ultrafine-grained metals are considered. Special attention is devoted to the effect of grain refinement and development of grain boundary sliding in low-temperature and high-temperature superplasticity. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 2, pp. 5–10, February, 2006.     

Schmidt modes and entanglement in continuous-variable quantum systems

The extraction of Schmidt modes for continuous-variable systems is considered. An algorithm based on the singular-value decomposition of a matrix is proposed. It is applied to the entanglement in (i) an atom—photon system with spontaneous emission and (ii) a system of biphotons with spontaneous parametric downconversion (SPDC) of type II. For the atom—photon system, the evolution of entangled states is found to be governed by a parameter approximately equal to the fine-structure constant times the atom-to-electron mass ratio. An analysis is made of the dynamics of atom—photon entanglement on the assumption that the system’s evolution is determined by the superposition of an initial and a final state. It is shown that in the course of emission the entanglement entropy first rises on a timescale of order the excited-state lifetime and then falls, approaching asymptotically a residual level due to the initial energy spread of the atomic packet (momentum spread squared). SPDC of type II is analyzed by means of the polarization density matrix and a newly introduced coherence parameter for two spatially separated modes. The loss of intermodal coherence is addressed that results from the difference in behavior between ordinary-and extraordinary-ray photons in a nonlinear crystal. The degree of intermodal coherence is investigated as a function of the product of crystal length and pump bandwidth.     

Systems of agents controlled by logical programs: Complexity of verification

The complexity of the verification problem for the behavior (dynamical properties) of systems of interacting intelligent agents is considered. This paper is a continuation of our publications [1–3], in which this problem was mainly considered as applied to deterministic and nondeterministic systems, and largely focuses on asynchronous systems.     

Microhardness measurements and the Hall-Petch relationship in an Al---Mg alloy with submicrometer grain size

An Al-3% Mg solid solution alloy was subjected to intense plastic deformation, using either equal-channel angular (ECA) pressing or torsion straining, to produce grain sizes in the submicrometer range. Static annealing at elevated temperatures led to grain growth and average grain sizes of up to > 100 μm. As-fabricated and statically annealed specimens were used to determine the variation in microhardness with grain size, and results confirm that the Hall-Petch relationship persists down to at least the finest grain size examined experimentally (90 nm). The results provide no evidence to support the claims of a negative Hall-Petch slope when the average grain size is very small, but there is evidence of a decrease in the slope of the Hall-Petch plot at the very finest grain sizes (< 150 nm); this is attributed to the increased participation of mobile extrinsic dislocations in the boundary regions when taking the hardness measurements.     

Structure and deformaton behaviour of Armco iron subjected to severe plastic deformation

Structural evolutions in an Armco iron subjected to severe plastic deformation by torsion under high pressure are anlysed with conventional and high resolution electron microscopes. The substructure observed at low strains appears to shrink with increasing deformation and transforms at very high strains into grain boundaries. The resulting grain size decreases down to a constant submicrometric value. Meanwhile, the material strength, as revealed by micro hardness measurements, levels out. Dislocation densities and internal stress levels are used to discuss the structural transformations. Hydrostatic pressure and deformation temperature are believed to modify the steady-state stress level and structural size by impeding the recovery processes involving diffusion.     

Cavity distribution pattern in a superplastically deformed aluminum alloy

Cavitation in superplastically formed AA7475 aluminum alloy by gas pressure has been investigated. Two systems of cavity stringers on the diametrical section of the pressure-formed domes were observed by using optical microscopy under normal light, polarized light, and dark field. Qualitative analyses have shown that the cavity stringers are oriented 35 ∼ 60 deg to the midplane of the sheet, and the spacing of the cavity stringers decreases with increasing strain. The explanation of this new observation of cavity morphology is given from a viewpoint of cooperative grain boundary sliding (CGBS). Formerly Associate Professor with the Department of Materials Science, Ufa Aviation Institute