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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]

All different Steiner systems S(2, 4, 3) of order 2 and rank 2 − m − 1 + s over $$\mathbb{F}_2$$, where 0 ≤ s ≤ m − 1, are constructed. The number of different systems S(2, 4, 3) whose incident matrices are orthogonal to a fixed code is obtained. A connection between the number of different Steiner systems and of different Latin cubes is described. [ABSTRACT FROM AUTHOR]

The structure of all different Steiner triple systems S(2−1, 3, 2) of rank 2− m+2 over $\mathbb{F}_2 $ is described. This induces a natural recurrent method for constructing Steiner triple systems of any rank. In particular, the method gives all different such systems of order 2 − 1 and rank ≤ 2 − m + 2. The number of such different systems of order 2 − 1 and rank less than or equal to 2 − m + 2 which are orthogonal to a given code is found. It is shown that all different triple Steiner systems of order 2 − 1 and rank ≤ 2 − m + 2 are derivative and Hamming. Furthermore, all such triples are embedded in quadruple systems of the same rank and in perfect binary nonlinear codes of the same rank. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article "Steiner Triple Systems S(2m - 1, 3, 2) of Rank 2m -m + 1 over F2" published in a 2012 issue.

Steiner systems S(2 − 1, 3, 2) of rank 2 − m+1 over the field $$\mathbb{F}_2$$ are considered. A new recursive method for constructing Steiner triple systems of an arbitrary rank is proposed. The number of all Steiner systems of rank 2 − m+1 is obtained. Moreover, it is shown that all Steiner triple systems S(2 − 1, 3, 2) of rank r ≤ 2 − m+1 are derived, i.e., can be completed to Steiner quadruple systems S(2, 4, 3). It is also proved that all such Steiner triple systems are Hamming; i.e., any Steiner triple system S(2 − 1, 3, 2) of rank r ≤ 2 − m + 1 over the field $$\mathbb{F}_2$$ occurs as the set of words of weight 3 of a binary nonlinear perfect code of length 2−1. [ABSTRACT FROM AUTHOR]

For an arbitrary Steiner system S( v, k, t), we introduce the concept of a component as a subset of a system which can be transformed (changed by another subset) without losing the property for the resulting system to be a Steiner system S( v, k, t). Thus, a component allows one to build new Steiner systems with the same parameters as an initial system. For an arbitrary Steiner system S( v, k, k − 1), we provide two recursive construction methods for infinite families of components (for both a fixed and growing k). Examples of such components are considered for Steiner triple systems S( v, 3, 2) and Steiner quadruple systems S( v, 4, 3). For such systems and for a special type of so-called normal components, we find a necessary and sufficient condition for the 2-rank of a system (i.e., its rank over $\mathbb{F}_2$) to grow under switching of a component. It is proved that for k ≥ 5 arbitrary Steiner systems S( v, k, k − 1) and S( v, k, k − 2) have maximum possible 2-ranks. [ABSTRACT FROM AUTHOR]

Focuses on the design of a rapid single-flux-quantum switching cryonetwork for petaflops-scale computing. Backpressure and buffering; Throughput and latency of banyan and mesh networks; Modeling and simulation results.

Objective: The current study longitudinally examines college student Twitter patterns throughout initial phases of the COVID-19 pandemic. This study aims to better understand psychological impact and online personal communication during the pandemic., Participants: A dataset consisting of ∼720,000 tweets posted by students from universities throughout the United States during the 2020 spring semester was analyzed according to structural and sentimental analysis., Methods: Using a data-driven approach, three time periods emerged which reflected the transition to online learning., Results: Significant changes in structure and sentiment of tweets were observed across phases., Conclusions: Changes in Twitter patterns revealed important features of this unprecedented transition to online learning for college students.