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Seeing the potentialities at the intersection: A reflection on performativity and processuality mindsets
© 2019 M@n@gement. In this paper, we propose to approach performativity and processuality as mindsets. We suggest that researchers interested by or pursuing performative studies should recognize more explicitly the inherent processuality of performativity. After offering broad overviews on performativity and process thinking, we highlight that both mindsets rest on a similar view of reality as processual, and both share a strong commitment to qualitative empirical work. In spite of the differences that exist between the two mindsets-such as their treatment of agency, the place of socio-materiality and their approach to continuity and change-we contend that acknowledging and engaging more directly with processuality benefits performative studies, as it helps these studies to deal with some of the challenges they often face. In doing so, performative studies could refine their analyses of managerial and organizational phenomena and would also increase their contribution to our field
Internet's Critical Path Horizon
Internet is known to display a highly heterogeneous structure and complex
fluctuations in its traffic dynamics. Congestion seems to be an inevitable
result of user's behavior coupled to the network dynamics and it effects should
be minimized by choosing appropriate routing strategies. But what are the
requirements of routing depth in order to optimize the traffic flow? In this
paper we analyse the behavior of Internet traffic with a topologically
realistic spatial structure as described in a previous study (S-H. Yook et al.
,Proc. Natl Acad. Sci. USA, {\bf 99} (2002) 13382). The model involves
self-regulation of packet generation and different levels of routing depth. It
is shown that it reproduces the relevant key, statistical features of
Internet's traffic. Moreover, we also report the existence of a critical path
horizon defining a transition from low-efficient traffic to highly efficient
flow. This transition is actually a direct consequence of the web's small world
architecture exploited by the routing algorithm. Once routing tables reach the
network diameter, the traffic experiences a sudden transition from a
low-efficient to a highly-efficient behavior. It is conjectured that routing
policies might have spontaneously reached such a compromise in a distributed
manner. Internet would thus be operating close to such critical path horizon.Comment: 8 pages, 8 figures. To appear in European Journal of Physics B (2004
Linear Quantum Entropy and Non-Hermitian Hamiltonians
We consider the description of open quantum systems with probability sinks
(or sources) in terms of general non-Hermitian Hamiltonians.~Within such a
framework, we study novel possible definitions of the quantum linear entropy as
an indicator of the flow of information during the dynamics. Such linear
entropy functionals are necessary in the case of a partially Wigner-transformed
non-Hermitian Hamiltonian (which is typically useful within a mixed
quantum-classical representation). Both the case of a system represented by a
pure non-Hermitian Hamiltonian as well as that of the case of non-Hermitian
dynamics in a classical bath are explicitly considered.Comment: Entropy, Special Issue "Entropy in Quantum Systems and Quantum Field
Theory (QFT)
Deterministic constant-temperature dynamics for dissipative quantum systems
A novel method is introduced in order to treat the dissipative dynamics of
quantum systems interacting with a bath of classical degrees of freedom. The
method is based upon an extension of the Nos\`e-Hoover chain (constant
temperature) dynamics to quantum-classical systems. Both adiabatic and
nonadiabatic numerical calculations on the relaxation dynamics of the
spin-boson model show that the quantum-classical Nos\`e-Hoover chain dynamics
represents the thermal noise of the bath in an accurate and simple way.
Numerical comparisons, both with the constant energy calculation and with the
quantum-classical Brownian motion treatment of the bath, show that the
quantum-classical Nos\`e-Hoover Chain dynamics can be used to introduce
dissipation in the evolution of a quantum subsystem even with just one degree
of freedom for the bath. The algorithm can be computationally advantageous in
modeling, within computer simulation, the dynamics of a quantum subsystem
interacting with complex molecular environments.Comment: Revised versio
On the Geometry and Entropy of Non-Hamiltonian Phase Space
We analyze the equilibrium statistical mechanics of canonical, non-canonical
and non-Hamiltonian equations of motion by throwing light into the peculiar
geometric structure of phase space. Some fundamental issues regarding time
translation and phase space measure are clarified. In particular, we emphasize
that a phase space measure should be defined by means of the Jacobian of the
transformation between different types of coordinates since such a determinant
is different from zero in the non-canonical case even if the phase space
compressibility is null. Instead, the Jacobian determinant associated with
phase space flows is unity whenever non-canonical coordinates lead to a
vanishing compressibility, so that its use in order to define a measure may not
be always correct. To better illustrate this point, we derive a mathematical
condition for defining non-Hamiltonian phase space flows with zero
compressibility. The Jacobian determinant associated with time evolution in
phase space is altogether useful for analyzing time translation invariance. The
proper definition of a phase space measure is particularly important when
defining the entropy functional in the canonical, non-canonical, and
non-Hamiltonian cases. We show how the use of relative entropies can circumvent
some subtle problems that are encountered when dealing with continuous
probability distributions and phase space measures. Finally, a maximum
(relative) entropy principle is formulated for non-canonical and
non-Hamiltonian phase space flows.Comment: revised introductio
Investigation on edge joints of Inconel 625 sheets processed with laser welding
Abstract Laser welding of Inconel 625 edge joint beads in square groove configuration was investigated. The use of different weld geometries in new aerospace solutions explains research on edge joints. A structured plan was carried out in order to characterize the process defining the influence of laser power and welding speed and to study possible interactions among the governing factors. As weld pool protection is crucial in order to obtain sound joints when processing superalloys, a special glove box for gas supply was designed to upgrade the welding head. Welded joints were characterized referring to bead profile, microstructure and X-rays. It was found that heat input plays an important role as it affects welding stability, porosity content and bead shape. Results suggest operating with low values of heat input to reduce porosity and guarantee stable bead conformation. Furthermore, a decrease in the grain size has been observed as a consequence of decreasing heat input
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