Characterizing short-range vs. long-range spatial correlations in dislocation distributions

Hard X-ray diffraction experiments have provided evidence of a strongly heterogeneous distribution of dislocation densities along the axis of cylindrical ice single crystals oriented for basal slip in torsion creep. The dislocation arrangements showed a complex scale-invariant character, which was analyzed by means of statistical and multifractal techniques. A trend to decreasing autocorrelation of the dislocation distribution was observed as deformation proceeds. At low strain levels, long-range spatial correlations control the distribution, but short-range correlations in relation with cross-slip progressively prevail when strain increases. This trend was reproduced by a model based on field dislocation dynamics, a theory accounting for both long-range elastic interactions and short-range interactions through transport of dislocation densities.     

Picosecond photonics

The basic principles of new ultrafast all-optical processing devices are experimentally demonstrated. One type of device relies on the interaction between an input signal and two colliding spatial solitons of a different wavelength in a planar waveguide with third order nonlinearity. The devices which belong to the second type are based on second order nonlinear interactions (degenerate difference frequency mixing) and operate as ultrafast sampling gate or as deflector or as phase conjugator. We report in a second part the design and performances of a laser that could be used to trigger the above mentionned systems. The laser cavity has two arms and two separate diode-pumped laser crystals (Nd/YAG). The two laser beams are coherently recombined inside the resonator into a single Gaussian beam. Picosecond pulses emission is ensured by passive mode-locking thanks to a nonlinear mirror set-up.     

Diagnosis Method Using ΔIDDQ Probabilistic Signatures: Theory and Results

This paper presents a diagnostic method based on differential I_DDQprobabilistic signatures, inspired by telecommunications systems. The method and its unique features are described. Then, results from an IC monitor containing controllable faults show the capability of the method to diagnose actual activated faults, despite a strong experimental current standard variation. These results validate previous simulation procedures, which are applied to quantify effects not covered by the monitor experiment, that is, the effect of the load of a bridged node and the effect of the bridge resistance value. These experimental and simulation results reveal the robustness of the proposed diagnosis method, that has identified and located every single fault considered so far.     

Transmission non linéaire dans les fibres optiques monomodes faiblement biréfringentes

The authors report the existence of large modulations in the signal transmitted by a monomode and weakly biréfringent optical fiber. These modulations are related to the intensity and the polarization of the input light. They show that this phenomenon can occur at a weak intensity level and in short fiber lengths. They make use of the Poincaré sphere representation to illustrate all the implied linear and non linear effects.     

Building a global clock for observing computations in distributed memory parallel computers

A common time reference (i.e. global clock) is needed for observing the behavior of a distributed algorithm on a distributed computing system. The paper presents a pragmatic algorithm to build a global clock on any distributed system, which is optimal for homogeneous distributed memory parallel computers (DMPCs). In order to observe and sort concurrent events in common DMPCs, we need a global clock with a resolution finer than the message transfer time variance, which is better than what deterministic and fault-tolerant algorithms can obtain. Thus a statistical method is chosen as a building block to derive an original algorithm valid for any topology. Its main originality over related approaches is to cope with the problem of clock granularity in computing frequency offsets between local clocks to achieve a resolution comparable with the resolution of the physical clocks. This algorithm is particularly well suited for debugging distributed algorithms by means of trace recordings because after its acquisition step it does not induce message overhead: the perturbation induced on the execution remains as small as possible. It has been implemented on various DMPCs: Intel iPSC/2 hypercube and Paragon XP/S, Transputer-based networks and Sun networks, so we can provide some data about its behavior and performances on these DMPCs.     

Influence of water addition on structural and electrochemical behaviour of liquid ammoniates: A study of LiClO4·4NH 3 ammoniate/H2O mixtures

The ammoniates of lithium perchlorate (LiClO₄•xNH₃) can be used as liquid or solid electrolytes in lithium batteries. The compounds possess a very low ammonia pressure and a large electroactivity range at room temperature. The presence of water in the electrolyte is one of the main problems for the lithium anode. From calorimetric measurements on the water-ammoniate system and an X-ray powder diffraction study on crystalline compounds that appear on lithium dipped in the electrolyte, a maximum water content, x = 0.2, can be derived. Above this limit, the thermodynamic properties of the compounds change and the lithium reacts dramatically with the electrolyte. Electrochemical stability ranges behave, over all the water molar fractions studied, in accordance with structural features.     

Is congruity due to encoding?

Theories that ascribe the congruity effect in mental comparisons to an encoding stage predict an interaction of congruity with stimulus quality. In Experiments 1–7, stimuli were degraded by being combined with dot masks of varying densities. Experiments 1, 6, and 7 examined potential effects of attentional load on degraded and intact finite-set stimuli; Experiments 2–5 examined attentional load and stimulus quality effects in an infinite-set paradigm. Experiment 8 allowed a comparison of dot with luminosity degradation to assess potential cascade-model interpretations of additivity of dot degradation with congruity. Effective manipulations of stimulus quality in these experiments were additive with congruity, regardless of attentional load. Thus, within the framework of either a cascade model or a discrete stage model, congruity appears to involve processes separate from encoding. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Phase Stability,Magnetic Properties,and Martensitic Transformation of Ni2−xMn1+x+ySn1−y Heusler Alloy with Excess Mn by First-Principles Calculations

The phase stability, magnetic properties, martensitic transformation, and electronic properties of the Ni_2−xMn_1+x+ySn_1−y system with excess Mn have been systematically investigated by the first-principles calculations. Results indicate that the excess Mn atoms will directly occupy the sublattices of Ni (Mn_Ni) or Sn (Mn_Sn). The formation energy (E_f) of the austenite has a relationship with the Mn content: E_f = 135.27(1 + x + y) − 293.01, that is, the phase stability of the austenite decreases gradually with the increase in Mn content. According to the results of the formation energy of austenite, there is an antiparallel arrangement of the magnetic moment between the excess and normal Mn atoms in the Ni_2−xMn_1+x+ySn_1−y (x = 0 or y = 0) system, while the magnetic moment direction of the normal Mn atoms arranges antiparallel to that of Mn_Ni atoms and parallel to that of Mn_Sn atoms in the Ni_2−xMn_1+x+ySn_1−y (x, y ≠ 0) system. The martensitic transformation occurs in some Ni_2−xMn_1+x+ySn_1−y (x, y ≠ 0) alloys with large magnetic moments of ferrimagnetic austenite. Besides, the valence electrons tend to distribute around the Ni or Mn_Ni atoms and mainly bond with the normal Mn atoms. The results of this work can lay a theoretical foundation for further development of the Ni_2−xMn_1+x+ySn_1−y system as the potential ferromagnetic shape memory alloys.