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Thermoelectric properties of nanostructured Sb2Te3/graphite composites are investigated both experimentally and theoretically and the contribution of graphite to heat transport mechanism is addressed. XRD results indicate the solid state insolubility of the graphite phase in Sb2Te3 as no shift is observed in the diffraction peaks corresponding to Sb2Te3 in the composite samples. Raman spectroscopic analysis confirms the presence of graphite in the nanostructured composite samples. Temperature dependence of carrier concentration nH, thermal conductivity κ, Seebeck coefficient S, resistivity ρ, and, hence, the thermoelectric figure of merit ZT is reported. Graphite incorporation leads to around 40% decrease of κ, essentially due to the decrease of lattice thermal conductivity, κL. A low κL value of 0.8 Wm−1 K−1 is reported, which mostly arises due to enhanced phonon scattering at the heterointerfaces created by the addition of graphite. S increases in Sb2Te3/graphite nanocomposites. Calculation reveals that reported large S value is related with the low hole concentration. Theoretical simulation in the frame of Boltzmann equation approach shows satisfactory agreement of nH, S, and ρ with experimental data, and based on the modification of the density of states and its derivative near Fermi energy with graphite addition, a plausible explanation is provided. [ABSTRACT FROM AUTHOR]

We enumerate all -ary additive (in particular, linear) block codes of length and cardinality with exactly two distances: and . For arbitrary codes of length with distances and , we obtain upper bounds on the cardinality via linear programming and using relationships to 2-distance sets on a Euclidean sphere. [ABSTRACT FROM AUTHOR]

A study of rapid single flux quantum circuits is presented with emphasis on their reliability. The bit error rate and pulse jitter of these circuits were examined in two experiments and analysed.

The 1991 version of the Personal Superconductor Circuit Analyzer software was improved for rapid single-flux-quantum circuit simulation and optimization. Improvements involve the verification of the correct circuit behavior and the numerical simulation algorithm. The new version exhibited enhanced simulation speed and optimization time for Josephson junction circuits.

Several new Rapid Single-Flux-Quantum (RSFQ) circuits for digital applications are presented. The circuits, which belong to the family of Josephson junction digital devices, were tested via numerical simulations and experimental measurements. The rate errors in these circuits were also evaluated. Results show that the RSFQ circuits have wide parameter margins, thereby, ensuring a very low probability of digital errors.

We consider a generalized concatenated construction for error-correcting codes over the q-ary alphabet in the modulus metric L1 and Lee metric L. Resulting codes have arbitrary length, arbitrary distance (independently of the alphabet size), and can correct both independent errors and error bursts in both metrics. In particular, for any length 2m we construct codes over with Lee distance 4 which under the Gray mapping yield extended binary perfect codes of length 2m+1 (with code distance 4). We construct codes over of length n with Lee distance n which under the Gray mapping yield Hadamard matrices of order 2n (under the additional condition that an Hadamard matrix of order n exists). The constructed new codes in the Lee metric are often better in their parameters than previously known ones; in particular, they are essentially better than previously constructed Astola codes. [ABSTRACT FROM AUTHOR]

Antimony-telluride-based nanocomposite samples containing different weight fractions of graphite (Sb2Te3 + x% graphite, where x = 0.0, 0.5, 1.0, and 2.5%) are synthesized and studied. The samples are produced by a solid-state reaction with the use of a ball mill. X-ray diffraction measurements show that the Sb2Te3 phase is present in the nanocomposites. All of the diffraction peaks are identified as corresponding to the rhombohedral structure of symmetry . No additional peaks related to graphite are observed because of its low content. Moreover, the X-ray data show the insolubility of graphite in Sb2Te3: the peaks related to Sb2Te3 remain unchanged upon the addition of graphite. The thermal conductivity, thermoelectric power, and resistivity of the samples are studied in the temperature range 80 K ≤ T ≤ 320 K. The thermal conductivity k of the nanocomposite decreases several times compared to the thermal conductivity of single-crystal Sb2Te3 and reaches k ≈ 0.95 W m–1 K–1 at x = 0.5%. The parameter k unsteadily depends on the content of graphite. The thermoelectric power of the nanocomposites with graphite at x = 1.0% is higher compared to that of nanostructured Sb2Te3. [ABSTRACT FROM AUTHOR]