1,095 research outputs found
On Calculation of Thermal Conductivity from Einstein Relation in Equilibrium MD
In equilibrium molecular dynamics, Einstein relation can be used to calculate
the thermal conductivity. This method is equivalent to Green-Kubo relation and
it does not require a derivation of an analytical form for the heat current.
However, it is not commonly used as Green-Kubo relationship. Its wide use is
hindered by the lack of a proper definition for integrated heat current (energy
moment) under periodic boundary conditions. In this paper, we developed an
appropriate definition for integrated heat current to calculate thermal
conductivity of solids under periodic conditions. We applied this method to
solid argon and silicon based systems; compared and contrasted with the
Green-Kubo approach.Comment: We updated this manuscript from second version by changing the title
and abstract. This paper is submitted to J. Chem. Phy
Грамматические тенденции как отражение категориальной связи двух сторон языкового знака
Статья из специализированного выпуска научного журнала "Культура народов Причерноморья", материалы которого объединены общей темой "Язык и Мир" и посвящены общим вопросам Языкознания и приурочены к 80-летию со дня рождения Николая Александровича Рудякова.Статья из специализированного выпуска научного журнала "Культура народов Причерноморья", материалы которого объединены общей темой "Язык и Мир" и посвящены общим вопросам Языкознания и приурочены к 80-летию со дня рождения Николая Александровича Рудякова
Electrical transport measurements in the superconducting state of Bi2212 and Tl2201
Precise measurements of the in-plane microwave surface impedance of
high-quality single crystals of Bi2212 and Tl2201 are used to probe the
relaxation time of nodal quasiparticles in the d-wave superconducting state
through a two-fluid analysis of the microwave conductivity. While this analysis
requires us to posit a form for the frequency-dependent quasiparticle
conductivity, we clearly demonstrate that the extraction of the relaxation rate
is quite insensitive to the assumed shape of the quasiparticle spectrum. The
robustness of the analysis is rooted in the oscillator-strength sum rule and
the fact that we simultaneously measure the real and imaginary parts of the
conductivity. In both Bi2212 and Tl2201 we infer a linear temperature
dependence of the transport relaxation rate 1/tau and a small but finite
zero-temperature intercept. The linear temperature dependence of 1/tau is in
accord with expectations for weak elastic scattering in an unconventional
superconductor with line nodes and a small residual density of states. The same
analysis reveals an onset of inelastic scattering at higher temperatures
similar to that seen in the YBCO superconductors. Finally we extrapolate the
two-fluid model over a range of frequencies up to five times the measurement
frequency, where the extrapolation predicts behaviour that is qualitatively
similar to terahertz conductivity data on Bi2212 thin films. While relaxation
rates in Bi2212 and Tl2201 are substantially higher than in YBCO there are
qualitative similarities between all three materials, and the differences can
likely be attributed to varying levels of static disorder. We therefore
conclude that a universal picture of quasiparticle scattering in the cuprates
is emerging.Comment: 10 pages, 9 figure
Apache Mahout: Machine Learning on Distributed Dataflow Systems
Apache Mahout is a library for scalable machine learning (ML) on distributed dataflow systems, offering various implementations of classification, clustering, dimensionality reduction and recommendation algorithms. Mahout was a pioneer in large-scale machine learning in 2008, when it started and targeted MapReduce, which was the predominant abstraction for scalable computing in industry at that time. Mahout has been widely used by leading web companies and is part of several commercial cloud offerings. In recent years, Mahout migrated to a general framework enabling a mix of dataflow programming and linear algebraic computations on backends such as Apache Spark and Apache Flink. This design allows users to execute data preprocessing and model training in a single, unified dataflow system, instead of requiring a complex integration of several specialized systems. Mahout is maintained as a community-driven open source project at the Apache Software Foundation, and is available under https://mahout.apache.org
Group medical appointments for people with physical illness
This is the protocol for a review and there is no abstract. The objectives are as follows: To assess the effects of group medical appointments (GMAs) on the health status and well-being of patients with a primary physical illness as compared to one-to-one patient-clinician appointments
Discriminative value of frailty screening instruments in end-stage renal disease
Background: Numerous frailty screening instruments are available, but their applicability for identifying frailty in patients with end-stage renal disease (ESRD) is unknown. We aimed to investigate the diagnostic accuracy of three instruments used for frailty screening in an ESRD population. Methods: The study was conducted in 2013 in a teaching hospital in The Netherlands and included patients receiving haemodialysis, peritoneal dialysis and pre-dialysis care. We determined the sensitivity and specificity of three screening instruments: the Groningen Frailty Indicator (GFI), the Identification of Seniors at Risk-Hospitalized Patients (ISAR-HP) and the Veiligheidsmanagementsysteem (VMS), which is a safety management system for vulnerable elderly patients. The Frailty Index was the gold standard used. Results: The prevalence of frailty was 37% in a total of 95 participants with ESRD [mean age 65.2 years (SD 12.0), 57% male]. Frailty prevalence in participants ?65 years of age and <65 years of age was 44% and 28%, respectively (P = 0.11). Sensitivity and specificity for frailty of the GFI were 89% and 57%, respectively; ISAR-HP 83% and 77%, respectively; and VMS 77% and 67%, respectively. Conclusions: Although the GFI showed the highest sensitivity, it is not yet possible to propose a firm choice for one of these screening instruments or specific items due to the small scale of the study. Since there is a high prevalence of frailty in ESRD patients, translation and testing of the effectiveness of screening using the GFI in the prognostication and prevention of development or deterioration of frailty in this population should be the next step
Heat exchanger/reactors (HEX reactors): Concepts, technologies: State-of-the-art
Process intensification is a chemical engineering field which has truly emerged in the past few years and is currently rapidly growing. It consists in looking for safer operating conditions, lower waste in terms of costs and energy and higher productivity; and away to reach such objectives is to develop multifunctional devices such as heat exchanger/reactors for instance. This review is focused on the latter and makes a point on heat exchanger/reactors. After a brief presentation of requirements due to transposition from batch to continuous apparatuses, heat exchangers/reactors at industrial or pilot scales and their applications are described
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