Pseudo-fermions in an electronic loss-gain circuit

In some recent papers a loss-gain electronic circuit has been introduced and analyzed within the context of PT-quantum mechanics. In this paper we show that this circuit can be analyzed using the formalism of the so-called pseudo-fermions. In particular we discuss the time behavior of the circuit, and we construct two biorthogonal bases associated to the Liouville matrix \Lc used in the treatment of the dynamics. We relate these bases to \Lc and \Lc^\dagger, and we also show that a self-adjoint Liouville-like operator could be introduced in the game. Finally, we describe the time evolution of the circuit in an {\em Heisenberg-like} representation, driven by a non self-adjoint hamiltonian.Comment: International Journal of Theoretical Physics, in pres

Expander selection for an on board ORC energy recovery system

This paper deals with the comparison between volumetric expanders (screw, scroll and rotary vane) and an Inlet Forward Radial (IFR) micro turbine for the exploitation of an on board Organic Rankine Cycle (ORC) energy recovery system. The sensible heat recovered from a common bus engine (typically 8000cc) feeds the energy recovery system that can generate sufficient extra power to sustain the air-conditioning system and part of the auxiliaries. The concept is suitable for all kind of thermally propelled vehicles, but the application considered here is specific for an urban bus. The ORC cycle performance is calculated by a Process Simulator (CAMEL Pro) and the results are discussed. A preliminary design of the considered expanders is proposed using ad-hoc made models implemented in MATLAB; the technical constraints inherent to each machine are listed in order to perform the optimal choice of the expander based on efficiency, reliability and power density. Last step will be the selection of the expander that suites the specific technical and design requests. The final choice relapsed on the screw motor, for it is the best compromise in terms of efficiency, lubrication and reliability

On the dynamics of the collapse of a diffusion-flame hole

The collapse dynamics of a diffusion-flame hole in the presence of a counterflow are studied. We construct unsteady solutions of the one-dimensional edge-flame model of Buckmaster (1996), in which heat and mass transverse losses are algebraic. The flame structure is determined in the classical limit of large activation energy. Solutions for both planar and axisymmetric strain geometry are considered for the particular case of unity Lewis number. It is shown that the final stage of the edge-flame collapse is determined by a dominant balance between the time rate of change of the mass fractions (and temperature) and diffusion, giving a self-similar structure in which the size of the edge-flame hole approaches zero, to leading (zeroth) order, as a 1/2-power of time. This solution suggests an expansion of the full model equations in 1/2-powers of time that allows detailed analysis of the effects of side losses and flow distribution in the edge-flame collapse process. It is found that side loss effects are apparent at the first order, whereas convection by the counterflow is first felt during collapse at the second order in the fractional-time expansion. Numerical integrations of the governing equations are found to verify the analytic results

COLLISIONAL VERSUS COLLISIONLESS MATTER: A ONE-DIMENSIONAL ANALYSIS OF GRAVITATIONAL CLUSTERING

We present the results of a series of one-dimensional N-body and hydrodynamical simulations which have been used for testing the different clustering properties of baryonic and dark matter in an expanding background. Initial Gaussian random density perturbations with a power-law spectrum $P(k) \propto k^n$ are assumed. We analyse the distribution of density fluctuations and thermodynamical quantities for different spectral indices $n$ and discuss the statistical properties of clustering in the corresponding simulations. At large scales the final distribution of the two components is very similar while at small scales the dark matter presents a lumpiness which is not found in the baryonic matter. The amplitude of density fluctuations in each component depends on the spectral index $n$ and only for $n=-1$ the amplitude of baryonic density fluctuations is larger than that in the dark component. This result is also confirmed by the behaviour of the bias factor, defined as the ratio between the r.m.s of baryonic and dark matter fluctuations at different scales: while for $n=1,\ 3$ it is always less than unity except at very large scales where it tends to one, for $n=-1$ it is above 1.4 at all scales. All simulations show also that there is not an exact correspondence between the positions of largest peaks in dark and baryonic components, as confirmed by a cross-correlation analysis. The final temperatures depend on the initial spectral index: the highest values are obtained for $n=-1$ and are in proximity of high density regions.Comment: 7 pages Latex (MN style) + 10 figures in postscript files, uuencoded submitted to MNRA

Dynamics of Silent Universes

We investigate the local non--linear dynamics of irrotational dust with vanishing magnetic part of the Weyl tensor, $H_{ab}$. Once coded in the initial conditions, this dynamical restriction is respected by the relativistic evolution equations. Thus, the outcome of the latter are {\it exact solutions} for special initial conditions with $H_{ab}=0$, but with no symmetries: they describe inhomogeneous triaxial dynamics generalizing that of a fluid element in a Tolman--Bondi, Kantowski--Sachs or Szekeres geometry. A subset of these solutions may be seen as (special) perturbations of Friedmann models, in the sense that there are trajectories in phase--space that pass arbitrarily close to the isotropic ones. We find that the final fate of ever--expanding configurations is a spherical void, locally corresponding to a Milne universe. For collapsing configurations we find a whole family of triaxial attractors, with vanishing local density parameter $\Omega$. These attractors locally correspond to Kasner vacuum solutions: there is a single physical configuration collapsing to a degenerate {\it pancake}, while the generic configuration collapses to a triaxial {\it spindle} singularity. These {\it silent universe} models may provide a fair representation of the universe on super horizon scales. Moreover, one might conjecture that the non--local information carried by $H_{ab}$ becomes negligible during the late highly non--linear stages of collapse, so that the attractors we find may give all of the relevant expansion or collapse configurations of irrotational dust.Comment: 40 pages with 4 figures, compressed and uuencoded PostScript file, submitted to ApJ, SISSA preprint Ref. 85/94/

Benefits and risks associated with time choice of innovating in retail settings

Purpose- The innovation success requires a deep understanding of risks and benefits of the process, as well as of the best moment for innovating. The aim of this paper is to explore the current retailers’ choice of innovating in terms of being the first innovator imitating competitors’ innovations, by declining the benefits and risks associated with the both strategies. Design/Methodology/Approach- Building on qualitative data from retail industry, with emphasis on fashion (including clothes, jewellery, and accessories), our investigation provides an empirical contribution to the emerging area on innovation management in retailing through its in-depth investigation of the strategies of eight case retailers who introduced technological innovations in the last three years, and by mapping the patterns between strategy and outcomes. Findings - Our analysis revealed how pioneers and followers acted their strategies for achieving benefits and reducing the encountered risks. In particular, findings identify to what extend pioneers act according the technology push and followers according to the demand pull. Originality/value- The research starts from the definition of the time choice of innovating, and the subsequent choice of being the first innovation adopter or the imitator. Our insights support scholarly exploration of innovation management by offering a new marketing management perspective, and providing practitioners with a better understanding on the time choice for innovating in retailing and also in broader empirical settings

Engaging consumer through the storefront: evidences from integrating interactive technologies

Although previous studies identified the importance of storefront windows on consumer’s entry decision, there is still a lack of research on engaging consumers at the storefront through the integration with interactive technologies. The purpose of this study is to carry out an exploratory investigation into the consumers preference for a certain store based on the storefront windows (in terms of entry decision), with emphasis on the current most attractive interactive technologies. Thus, we examine the extent to which an exploratory sample of consumers is influenced by storefront interactive technologies. Emotional aspects emerge as the most influencing ones in the case of traditional storefronts, while both emotional and functional aspects emerge as the most influencing factors while considering the integration of interactive technologies. In particular, our results shed light on the way these elements can be managed for the design of future attractive storefront windows, by providing important insights for scholars and practitioners