1,721,133 research outputs found
Unified trade-off optimization of quantum harmonic Otto engine and refrigerator
No full textWe investigate quantum Otto engine and refrigeration cycles of a time-dependent harmonic oscillator operating under the conditions of maximum Q function, a trade-off objective function which represents a compromise between energy benefits and losses for a specific job, for both adiabatic and nonadiabatic (sudden) frequency modulations. We derive analytical expressions for the efficiency and coefficient of performance of the Otto cycle. For the case of adiabatic driving, we point out that in the low-temperature regime, the harmonic Otto engine (refrigerator) can be mapped to Feynman's ratchet and pawl model which is a steady-state classical heat engine. For the sudden switch of frequencies, we obtain loop-like behavior of the efficiency-work curve, which is characteristic of irreversible heat engines. Finally, we discuss the behavior of cooling power at maximum Q function.11Nsciescopu
Thermodynamic uncertainty relation in nondegenerate and degenerate maser heat engines
No full textWe investigate the thermodynamic uncertainty relation (TUR), i.e., a tradeoff between entropy production rate and relative power fluctuations, for nondegenerate three-level and degenerate four-level maser heat engines. In the nondegenerate case, we consider two slightly different configurations of the three-level maser heat engine and contrast their degree of violation of the standard TUR. We associate their different TUR-violating properties to the phenomenon of spontaneous emission, which gives rise to an asymmetry between them. Furthermore, in the high-temperature limit, we show that the standard TUR relation is always violated for both configurations. For the degenerate four-level engine, we study the effects of noise-induced coherence on the TUR. We show that, depending on the parametric regime of operation, noise-induced coherence can either suppress or amplify the relative power fluctuations. © 2023 American Physical Society.11Nsciescopu
Lossy Micromaser Battery: Almost Pure States in the Jaynes-Cummings Regime
Get PDFWe consider a micromaser model of a quantum battery, where the battery is a
single mode of the electromagnetic field in a cavity, charged via repeated
interactions with a stream of qubits, all prepared in the same non-equilibrium
state, either incoherent or coherent, with the matter-field interaction modeled
by the Jaynes-Cummings model. We show that the coherent protocol is superior to
the incoherent one, in that an effective pure steady state is achieved for
generic values of the model parameters. Finally, we supplement the above
collision model with cavity losses, described by a Lindblad master equation. We
show that battery performances, in terms of stored energy, charging power, and
steady-state purity, are slightly degraded up to moderated dissipation rate.
Our results show that micromasers are robust and reliable quantum batteries,
thus making them a promising model for experimental implementations.Comment: 15 pages, 7 figure
Micromasers as quantum batteries
No full textWe show that a micromaser is an excellent model of quantum battery. A highly excited, pure, and effectively steady state of the cavity mode, charged by coherent qubits, can be achieved, also in the ultrastrong coupling regime of field-matter interaction. Stability of these appealing features against loss of coherence of the qubits and the effect of counter-rotating terms in the interaction Hamiltonian are also discussed.11Nsciescopu
Understanding Consumer Reactions to Offshore Outsourcing of Customer Services
No full textOffshore outsourcing is a fast-growing aspect of the world economy today and it has drawn attention from policy makers as well as public at large in many developed countries. However, there is hardly any research on how outsourcing of customer services may influence individual consumers, their perceptions, attitudes and behaviors. In this chapter, the authors first review the extant literature in the country-of-origin and services marketing areas to highlight key concepts and theories relevant to this area. Next, they show how offshore outsourcing of customer services may influence consumer perceptions about service quality, brand image and brand loyalty on one hand and impact customer satisfaction, complaint behavior and repurchase intentions on the other. The role of several relevant demographic and psychographic variables is also discussed. Finally, the findings from a survey-based study among customers in three developed countries (U.S., UK and Australia) are reported along with a discussion of managerial implications and future research directions in this area
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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