Highly Efficient Ge-Rich Ge<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Pb<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Te Thermoelectric Alloys

The search for alternative energy sources is presently at the forefront of applied research. In this context, thermoelectricity for direct energy conversion from thermal to electrical energy plays an important role. This paper is concerned with the development of highly efficient p-type Ge _x Pb_1−x Te alloys for thermoelectric applications, using spark plasma sintering. The carrier concentration of GeTe was varied by alloying of PbTe and/or by Bi₂Te₃ doping. Very high ZT values up to ~1.8 at 500°C were obtained by doping Pb_0.13Ge_0.87Te with 3 mol% Bi₂Te₃.     

Structural Evolution Following Spinodal Decomposition of the Pseudoternary Compound (Pb0.3Sn0.1Ge0.6)Te

Pseudoternary (Ge,Sn,Pb)Te compounds display favorable thermoelectric properties. Spinodal decomposition in the quasiternary (Ge,Sn,Pb)Te system is at the origin of a wide solubility gap at low Sn concentrations. The structural evolution of the spinodal decomposition was investigated as a function of aging time at 500°C, using x-ray diffraction, electron microscopy, and scanning electron microscopy. The evolution of the structure at 500°C consists initially of a short diffusion-controlled demixing stage into Pb- and Ge-rich coherent areas, with compositions corresponding to the inflection points of the free-energy curve. The Pb-rich areas adopt configurations associated with the directions of the soft elastic moduli of the cubic compound. Both the Pb- and Ge-rich areas are supersaturated and undergo in a second stage a nucleation and growth process and give rise to a biphased structure with equilibrium compositions corresponding to the boundaries of the miscibility gap. The resulting Pb-rich areas display a relatively stable microstructure suggesting the presence of long-range interactions between the Pb-rich precipitates in the Ge-rich matrix.     

Understanding metaphorical comparisons: Beyond similarity.

Traditionally, metaphors such as "my job is a jail" have been treated as implicit similes (i.e., this metaphor would be treated as if it were a comparison statement, "my job is like a jail"). A. Tversky's (1977) account of similarity is applied to such nonliteral similarity expressions, and is shown to apply as readily to nonliteral comparisons as to literal comparisons. But treating metaphors as comparison statements fails to account for certain important phenomena, including metaphoricity itself (the judgment that a comparison statement is nonliteral). We argue that metaphors are exactly what they appear to be: class-inclusion assertions, in which the topic of the metaphor (e.g., "my job") is assigned to a diagnostic category (e.g., entities that confine one against one's will, are unpleasant, are difficult to escape from). In such assertions, the metaphor vehicle (e.g., "jail") refers to that category, and at the same time is a prototypical exemplar of that category. This account of metaphor provides a basis for a theory of metaphor comprehension, and also clarifies why people use metaphors instead of similes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A note on efficient aggregate queries in sensor networks

We consider a scenario where nodes in a sensor network hold numeric items, and the task is to evaluate simple functions of the distributed data. In this note we present distributed protocols for computing the median with sublinear space and communication complexity per node. Specifically, we give a deterministic protocol for computing median with polylog complexity and a randomized protocol that computes an approximate median with polyloglog communication complexity per node. On the negative side, we observe that any deterministic protocol that counts the number of distinct data items must have linear complexity in the worst case.     

Synchronized manufacturing as in OPT: from practice to theory

Synchronized manufacturing as in the OPT system (Optimized Production Technology, by Creative Output Inc.) is a relatively new concept for production management.

This paper analyses the nine OPT rules, the OPT concepts and OPT philosophy in order to establish an analytical, theoretical basis for the OPT system. The analysis is based on systems theory concepts, mathematical programming theory and techniques, as well as queuing theory, the Pareto rule, and the Japanese production experience.

It is shown that the OPT rules reflect substantial integration of well established MS/OR techniques with the whole OPT philosophy. The paper analyzes the OPT classification of VAT plants and the Drum-Buffer-Rope concept used in OPT.

Our analysis makes a clear distinction between BIG OPT (the management system) and its subsystem SMALL OPT (the scheduler). The paper suggests that while the BIG OPT concepts may be applied in all types of processes, job shop processes and very complex assembly lines are the most suitable ones for the SMALL OPT scheduling system. The paper then shows the management by constraints methodology as a natural enhancement of the OPT concepts.     

Effects of automatic associative activation on explicit and implicit memory tests.

Ss made either a graphemic or a semantic decision concerning word pairs during a study phase. Pair relatedness effects were observed in behavioral measures for the semantic task only, but a physiological measure (event-related potential) showed relatedness effects for both study tasks. Relatedness at study helped subsequent memory for tests involving word generation (fragment completion and cued recall). These effects were independent of those of the level of processing on memory. The results support P. Graf and G. Mandler's (1984) 2-process model of implicit and explicit remembering and demonstrate that automatically activated associations can have significant effects on both types of remembering. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

SOME ASYMPTOTIC PROPERTIES OF THE SAMPLE COVARIANCES OF GAUSSIAN AUTOREGRESSIVE MOVING-AVERAGE PROCESSES

Abstract. The paper deals with the asymptotic variances of the sample covariances of autoregressive moving average processes. Using state-space representations and some matrix Lyapunov equation theory, closed-form expressions are derived for the asymptotic variances of the sample covariances and for the Cramer-Rao bounds on the process covariances. The main results obtained from these expressions are as follows: For ARMA ( p, q ) processes with p ≥ q , the sample covariance of order n is asymptotically efficient if and only if 0 ≤ n ≤ p – q .
For ARMA ( p, q ) processes with p < q , none of the sample covariances is asymptotically efficient.     

Ortho Effects. I. The Mechanisms of the H3O and CH3O2 Elimination from the Molecular Ion of N-Methyl Ortho-Nitro-Para-Toluidine

The molecular ion of the N-methyl ortho-nitro-para-toluidine (I) readily eliminates H₃O. The sources of the H atoms lost were proved by deuterium labeling to be an HNCH₃ group as well as, probably, the C-methyl group of the aromatic ring. The interaction between the N-methyl and nitro groups in I also leads to the expulsion of CH₃O₂ from the molecular ion.     

Nacre in Mollusk Shells as a Multilayered Structure with Strain Gradient

How do living organisms attain the complicated shapes of grown bio‐composites? This question is answered when studying the mechanics of the nacre layer in the bivalve mollusk shells. In this study, the internal strains/stresses across the shell thickness are profiled as a function of depth by strain gauge measurements during controlled etching in the selected areas. Measurements of stress release under etching provide clear evidence that the investigated shells, in fact, are strained multilayered structures, which are elastically bent due to the forces evolving at the organic/inorganic interfaces. The stresses are mostly concentrated in the “fresh” nacre sub‐layers near the inner surface of the shell adjacent to the mollusk mantle. This analysis unexpectedly shows that the elastic bending of the nacre layer is due to strain gradients which are originated in the gradual in‐depth changes of the thickness of ceramic lamellae. The changes mentioned were directly observed by scanning electron microscopy. By this sophisticated design of the ultra‐structure of the nacre layer, the bowed shape of the bivalve shells is apparently achieved.