5,242 research outputs found
Drastic disorded-induced reduction of signal amplification in scale-free networks
Understanding information transmission across a network is a fundamental task
for controlling and manipulating both biological and man-made information
processing systems. Here, we show how topological resonant-like amplification
effects in scale-free networks of signaling devices are drastically reduced
when phase disorder in the external signals is considered. This is demonstrated
theoretically by means of a star-like network of overdamped bistable systems,
and confirmed numerically by simulations of scale-free networks of such
systems. The taming effect of the phase disorder is found to be sensitive to
the amplification's strength, while the topology-induced amplification
mechanism is robust against this kind of quenched disorder in the sense that it
does not significantly change the values of the coupling strength where
amplification is maximum in its absence.Comment: 5 pages, 4 (double) figure
Which quantum states are dual to classical spacetimes?
It is commonly accepted that states in a conformal field theory correspond to
classical spacetimes with Anti-de-Sitter asymptotics. In this work we give a
prescription for the CFT states with a dual classical spacetime and, using
basic holographic rules, show that they are holographically connected to
coherent states in the large-N limit, or by considering linearized
perturbations. We also point out implications in the spacetime emergence
mechanism, for instance, the (entangled) state dual to the black hole should be
properly described as a quantum superposition of products of these states. This
also complements the quantum interpretation of the Hawking-Page transition.Comment: 14 pages, 8 figure
Impact of Gamma Radiation on Dynamic RDSON Characteristics in AlGaN/GaN Power HEMTs
GaN high-electron-mobility transistors (HEMTs) are promising next-generation devices in the power electronics field which can coexist with silicon semiconductors, mainly in some radiation-intensive environments, such as power space converters, where high frequencies and voltages are also needed. Its wide band gap (WBG), large breakdown electric field, and thermal stability improve actual silicon performances. However, at the moment, GaN HEMT technology suffers from some reliability issues, one of the more relevant of which is the dynamic on-state resistance (RON_dyn) regarding power switching converter applications. In this study, we focused on the drain-to-source on-resistance (RDSON) characteristics under 60Co gamma radiation of two different commercial power GaN HEMT structures. Different bias conditions were applied to both structures during irradiation and some static measurements, such as threshold voltage and leakage currents, were performed. Additionally, dynamic resistance was measured to obtain practical information about device trapping under radiation during switching mode, and how trapping in the device is affected by gamma radiation. The experimental results showed a high dependence on the HEMT structure and the bias condition applied during irradiation. Specifically, a free current collapse structure showed great stability until 3.7 Mrad(Si), unlike the other structure tested, which showed high degradation of the parameters measured. The changes were demonstrated to be due to trapping effects generated or enhanced by gamma radiation. These new results obtained about RON_dyn will help elucidate trap behaviors in switching transistors
Homogenization of a Dirichlet semilinear elliptic problem with a strong singularity at in a domain with many small holes
We perform the homogenization of the semilinear elliptic problem
\begin{equation*} \begin{cases} u^\varepsilon \geq 0 & \mbox{in} \;
\Omega^\varepsilon,\\ \displaystyle - div \,A(x) D u^\varepsilon =
F(x,u^\varepsilon) & \mbox{in} \; \Omega^\varepsilon,\\ u^\varepsilon = 0 &
\mbox{on} \; \partial \Omega^\varepsilon.\\ \end{cases} \end{equation*} In this
problem is a Carath\'eodory function such that a.e. for every , with in some
and a function such that and for every . On the other hand the open sets
are obtained by removing many small holes from a fixed
open set in such a way that a "strange term" appears in the
limit equation in the case where the function depends only on .
We already treated this problem in the case of a "mild singularity", namely
in the case where the function satisfies . In this case the solution to the problem
belongs to and its definition is a "natural" and
rather usual one.
In the general case where exhibits a "strong singularity" at , which is the purpose of the present paper, the solution to
the problem only belongs to but in
general does not belongs to any more, even if
vanishes on in some sense.
Therefore we introduced a new notion of solution (in the spirit of the
solutions defined by transposition) for problems with a strong singularity.
This definition allowed us to obtain existence, stability and uniqueness
results
A semilinear elliptic equation with a mild singularity at : existence and homogenization
In this paper we consider semilinear elliptic equations with singularities,
whose prototype is the following \begin{equation*} \begin{cases} \displaystyle
- div \,A(x) D u = f(x)g(u)+l(x)& \mbox{in} \; \Omega,\\ u = 0 & \mbox{on} \;
\partial \Omega,\\ \end{cases} \end{equation*} where is an open
bounded set of ,
is a coercive matrix, is continuous, and
, with
and , if , if ,
if , a.e. .
We prove the existence of at least one nonnegative solution and a stability
result; moreover uniqueness is also proved if is nonincreasing or
"almost nonincreasing".
Finally, we study the homogenization of these equations posed in a sequence
of domains obtained by removing many small holes from a fixed
domain
How do market imperfections affect working capital management?
This paper examines whether Working Capital Management (WCM) is sensitive to market imperfections such as asymmetric information, agency conflicts or financial distress. We find that firms have a target investment in working capital and that they take decisions in order to achieve this. In addition, the results appear to support the hypothesis that the working capital competes with investment in fixed assets for the funds of the firms when they have financial constraints. Finally, we also find that WCM depends on bargaining power and other financial factors such as the availability of internal finance, cost of financing and access to capital markets. Este artÃculo analiza si la gestión del capital circulante está afectada por las imperfecciones de mercado tales como la asimetrÃa informativa, los conflictos de agencia o las dificultades financieras. Los resultados muestran que las empresas tienen un nivel de inversión en capital circulante objetivo y toman decisiones con el fin de alcanzarlo. Además, los resultados parecen apoyar la hipótesis de que el capital circulante compite con los activos fijos por los fondos de las empresas cuando éstas tienen restricciones financieras. Finalmente, la gestión del capital circulante depende del poder de negociación y otros factores financieros tales como la disponibilidad de financiación interna, el coste de financiación y el acceso a los mercados de capitales.ciclo de efectivo, gestión del capital circulante, imperfecciones de mercado, datos de panel net trade cycle, working capital management, market imperfections, panel data
Determinants of working capital management
This paper analyzes the determinants of working capital management (WCM) for a sample of Spanish firms during the period 1997-2004. We find that firms have a target investment in working capital and that they take decisions in order to achieve this. The results appear to support the hypothesis that the working capital competes with investment in fixed assets for the funds of the firms when they have financial constraints. Finally, we also find that WCM depends on bargaining power and other financial factors such as the availability of internal finance, cost of financing and financial constraints.Research Agency of the Spanish Government ECO2008-06179/ECO
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