1,721,017 research outputs found
A non-linear approach to Kalecki's investment cycle
No full textIn this paper, looking at some new contributions to the Kalecki business cycle theory, we re-examine his 1935 model concerning the gestation period between orders and deliveries of capital goods. The model gives rise to a delay differential equation (DDE) with delay dependent coefficients depending on the time delay. The model has only one equilibrium point. Proved that a unique stability switch exists, we study the emergence of the Hopf bifurcation and the direction, stability and period of the bifurcating periodic solutions. We derive an explicit formula for determining the properties of the Hopf bifurcation by using the first Lyapunov coefficient. To confirm our analytic results, we consider two types of non-linear functions, all consistent with Kalecki's hypotheses: two S-shaped functions and one fractional function. Some comments dealing with the economic implications of our analysis are also included
Internazionalizzazione, Mercato del Lavoro e Capitale Umano in Italia
Full text linkIn the case of Italy, the effect of international trade on the relative labor demand may be assessed appropriately by examining territorial differences. Given the characteristics of trade flows and labor markets in Italy, the results of analysis presented here show how the effects of crowding-out induced by trade with less advanced countries on the relative unqualified labor demand mainly operate in Northern Italy. In the period 1990-2002, while upgrading of the training level of the labor force was a phenomenon general to all areas of Italy, the development of the factorial content of trade flows was regionally differentiated, with upgrading emerging only in Northern Italy
Electrochemical Synthesis and Analytical Characterization of Hybrid Zinc/Calcium Antimicrobial Nano-Oxides for Cultural Heritage Applications
No full textThe present study proposes the one-step synthesis of Zn/Ca hybrid nano-oxides combining an electrochemical route to ZnO nanostructures (NSs) with the wet chemical production of Ca(OH)2 NSs. ZnO is a known antimicrobial and Ca(OH)2 has consolidating properties, both appealing for stone artwork preservation in the field of cultural heritage. Two concentrations of the electrolytic bath (NaOH 0.1 and 0.4 M) were studied resulting in distinct final nanomaterials (Zn−Ca0.1 and Zn−Ca0.4). Fourier transform infrared, X-ray photoelectron spectroscopies, and transmission electron microscopy demonstrated that Zn−Ca0.1 consisted of lamellar calcium hydroxyzincate NSs, whereas Zn−Ca0.4 showed hexagonal Ca(OH)2 (∼500 nm) and ZnO (∼50 nm) NSs. Nanocoatings prepared with Zn−Ca0.1 exhibited a Zn2+ release increasing up to 1 μmol cm−2 in 24 h. Instead, Zn−Ca0.4-based nanocoatings released a constant value of about 0.35 μmol/cm2. Both types of nanocoatings showed good antimicrobial activity against Bacillus subtilis after 48 h and hydrophilic behavior over 28 days
Green Synthesis and Analytical Characterization of Core-Shell Copper Sub-Microparticles
No full textThis study demonstrates a simple and reproducible approach to synthesize green core-shell copper sub-microparticles stabilized by poly(n-vinyl)pyrrolidone (PVP). Cu@PVP colloids were here prepared using copper sulfate pentahydrate as precursor and glucose as reducing agent. The presence of PVP in the synthetic medium eliminates the need for an inert atmosphere during the process, thus simplifying the whole method. Both the morphology and the spectroscopic properties of Cu@PVP colloids were investigated by transmission electron microscopy, and infrared, UV-Vis and X-ray photoelectron spectroscopies. Size distributions and average shell thickness were obtained by statistical analysis on TEM micrographs, and spectroscopies demonstrated the formation of a PVP layer around the copper core. The produced colloids were employed in composite thin films for potential antimicrobial application, in association with a highly-recyclable polymer: polycarbonate (4,4’-(1-methylethylidene)bis(phenol))
Stability and direction of Hopf bifurcations of a cyclical growth model with two-time delays and one-delay dependent coefficients
No full textThis paper deals with the impact of two discrete-time delays on the basic Goodwin growth cycle model.
The former concerns the existence of a finite time delay for building capital goods as suggested by
Kalecki. The latter pertains to the wage lag hypothesis. This is because, taking the current change of the
employment rate into account, workers and capitalists bargain new wage periodically. There are no examples
in the literature on the Goodwin model of the use of both those lags in order to explore the GDP
dynamics. From the analytical point-of-view, what we obtain is a delayed differential equation system
with discrete-time delays and delay-dependent coefficients depending only on one of the time delays.
Having chosen the time delays as bifurcation parameters, we study the stability-switching properties of
the transcendental characteristic equation resulting from the stability analysis and the direction of the
Hopf bifurcations. Although the system with no lag displays a stable focus, the introduction of the two
lags preserves the stable solution only for particular combinations of parameters and length of the lags.
In any other case, instability prevails and regular cycles or chaotic fluctuations emerge. Finally, we provide
the analytical results with the necessary economic interpretations.
© 2020 Elsevie
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
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