1,537 research outputs found
Complexity of waves in nonlinear disordered media
The statistical properties of the phases of several modes nonlinearly coupled
in a random system are investigated by means of a Hamiltonian model with
disordered couplings. The regime in which the modes have a stationary
distribution of their energies and the phases are coupled is studied for
arbitrary degrees of randomness and energy. The complexity versus temperature
and strength of nonlinearity is calculated. A phase diagram is derived in terms
of the stored energy and amount of disorder. Implications in random lasing,
nonlinear wave propagation and finite temperature Bose-Einstein condensation
are discussed.Comment: 20 pages, 11 Figure
From approximating to interpolatory non-stationary subdivision schemes with the same generation properties
In this paper we describe a general, computationally feasible strategy to
deduce a family of interpolatory non-stationary subdivision schemes from a
symmetric non-stationary, non-interpolatory one satisfying quite mild
assumptions. To achieve this result we extend our previous work [C.Conti,
L.Gemignani, L.Romani, Linear Algebra Appl. 431 (2009), no. 10, 1971-1987] to
full generality by removing additional assumptions on the input symbols. For
the so obtained interpolatory schemes we prove that they are capable of
reproducing the same exponential polynomial space as the one generated by the
original approximating scheme. Moreover, we specialize the computational
methods for the case of symbols obtained by shifted non-stationary affine
combinations of exponential B-splines, that are at the basis of most
non-stationary subdivision schemes. In this case we find that the associated
family of interpolatory symbols can be determined to satisfy a suitable set of
generalized interpolating conditions at the set of the zeros (with reversed
signs) of the input symbol. Finally, we discuss some computational examples by
showing that the proposed approach can yield novel smooth non-stationary
interpolatory subdivision schemes possessing very interesting reproduction
properties
Exponential Splines and Pseudo-Splines: Generation versus reproduction of exponential polynomials
Subdivision schemes are iterative methods for the design of smooth curves and
surfaces. Any linear subdivision scheme can be identified by a sequence of
Laurent polynomials, also called subdivision symbols, which describe the linear
rules determining successive refinements of coarse initial meshes. One
important property of subdivision schemes is their capability of exactly
reproducing in the limit specific types of functions from which the data is
sampled. Indeed, this property is linked to the approximation order of the
scheme and to its regularity. When the capability of reproducing polynomials is
required, it is possible to define a family of subdivision schemes that allows
to meet various demands for balancing approximation order, regularity and
support size. The members of this family are known in the literature with the
name of pseudo-splines. In case reproduction of exponential polynomials instead
of polynomials is requested, the resulting family turns out to be the
non-stationary counterpart of the one of pseudo-splines, that we here call the
family of exponential pseudo-splines. The goal of this work is to derive the
explicit expressions of the subdivision symbols of exponential pseudo-splines
and to study their symmetry properties as well as their convergence and
regularity.Comment: 25 page
XNOR Neural Engine: a Hardware Accelerator IP for 21.6 fJ/op Binary Neural Network Inference
Binary Neural Networks (BNNs) are promising to deliver accuracy comparable to
conventional deep neural networks at a fraction of the cost in terms of memory
and energy. In this paper, we introduce the XNOR Neural Engine (XNE), a fully
digital configurable hardware accelerator IP for BNNs, integrated within a
microcontroller unit (MCU) equipped with an autonomous I/O subsystem and hybrid
SRAM / standard cell memory. The XNE is able to fully compute convolutional and
dense layers in autonomy or in cooperation with the core in the MCU to realize
more complex behaviors. We show post-synthesis results in 65nm and 22nm
technology for the XNE IP and post-layout results in 22nm for the full MCU
indicating that this system can drop the energy cost per binary operation to
21.6fJ per operation at 0.4V, and at the same time is flexible and performant
enough to execute state-of-the-art BNN topologies such as ResNet-34 in less
than 2.2mJ per frame at 8.9 fps.Comment: 11 pages, 8 figures, 2 tables, 3 listings. Accepted for presentation
at CODES'18 and for publication in IEEE Transactions on Computer-Aided Design
of Circuits and Systems (TCAD) as part of the ESWEEK-TCAD special issu
Studio di un Riscaldatore per Catodi Neutralizzatori per Applicazioni Spaziali
Il presente lavoro di tesi descrive lo studio di un riscaldatore per catodi neutralizzatori, con l’obiettivo di fornire le linee guida per la progettazione del sistema di riscaldamento inteso come riscaldatore, isolamento elettrico e termico
Finding a reflexive voice : -- researching the problems of implementing new learning practices within a New Zealand manufacturing organisation : a 100pt thesis presented in partial fulfilment of the requirements for the degree of Master of Management in Human Resources Management at Massey University
This study explored the social forces mediating manager's participation in a new reflexive participative learning practice designed to improve profitability within a New Zealand manufacturing organisation. Despite a large theoretical and managerial body of literature on organisational learning there has been little empirical investigation of how people experience and engage their reflexivity towards challenging the status-quo to create high level learning and new knowledge. Power was identified as a potential moderator of the reflexive learning experience and the variable relations of power and learning were constructed from a review of literature and these relationships were explored and investigated within the case study. Two prevailing discourses were identified as powerful moderators of public reflexivity, the traditionalist discourse which constructed managers actions and conversations towards insularism and survivalist concerns and the productionist discourse in which institutionalised production practices encircled and mediated managers actions and what constituted legitimacy in conversations. This study used a critical action research method to place the reflexive experience of managers and the researcher at the centre of the study and provide data representative of the social discourses that constructed variable freedoms and constraints upon the reflexive voice
Your Attack Is Too DUMB: Formalizing Attacker Scenarios for Adversarial Transferability
Evasion attacks are a threat to machine learning models, where adversaries
attempt to affect classifiers by injecting malicious samples. An alarming
side-effect of evasion attacks is their ability to transfer among different
models: this property is called transferability. Therefore, an attacker can
produce adversarial samples on a custom model (surrogate) to conduct the attack
on a victim's organization later. Although literature widely discusses how
adversaries can transfer their attacks, their experimental settings are limited
and far from reality. For instance, many experiments consider both attacker and
defender sharing the same dataset, balance level (i.e., how the ground truth is
distributed), and model architecture.
In this work, we propose the DUMB attacker model. This framework allows
analyzing if evasion attacks fail to transfer when the training conditions of
surrogate and victim models differ. DUMB considers the following conditions:
Dataset soUrces, Model architecture, and the Balance of the ground truth. We
then propose a novel testbed to evaluate many state-of-the-art evasion attacks
with DUMB; the testbed consists of three computer vision tasks with two
distinct datasets each, four types of balance levels, and three model
architectures. Our analysis, which generated 13K tests over 14 distinct
attacks, led to numerous novel findings in the scope of transferable attacks
with surrogate models. In particular, mismatches between attackers and victims
in terms of dataset source, balance levels, and model architecture lead to
non-negligible loss of attack performance.Comment: Accepted at RAID 202
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