1,871 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
General phase-diagram of multimodal ordered and disordered lasers in closed and open cavities
We present a unified approach to the theory of multimodal laser cavities
including a variable amount of structural disorder. A general mean-field theory
is studied for waves in media with variable non-linearity and randomness. Phase
diagrams are reported in terms of optical power, degree of disorder and degree
of non-linearity, tuning between closed and open cavity scenario's. In the
thermodynamic limit of infinitely many modes the theory predicts four distinct
regimes: a continuous wave behavior for low power, a standard mode-locking
laser regime for high power and weak disorder, a random laser for high pumped
power and large disorder and an intermediate regime of phase locking occurring
in presence of disorder below the lasing threshold.Comment: 9 pages, 3 figure
Chipmunk: A Systolically Scalable 0.9 mm, 3.08 Gop/s/mW @ 1.2 mW Accelerator for Near-Sensor Recurrent Neural Network Inference
Recurrent neural networks (RNNs) are state-of-the-art in voice
awareness/understanding and speech recognition. On-device computation of RNNs
on low-power mobile and wearable devices would be key to applications such as
zero-latency voice-based human-machine interfaces. Here we present Chipmunk, a
small (<1 mm) hardware accelerator for Long-Short Term Memory RNNs in UMC
65 nm technology capable to operate at a measured peak efficiency up to 3.08
Gop/s/mW at 1.24 mW peak power. To implement big RNN models without incurring
in huge memory transfer overhead, multiple Chipmunk engines can cooperate to
form a single systolic array. In this way, the Chipmunk architecture in a 75
tiles configuration can achieve real-time phoneme extraction on a demanding RNN
topology proposed by Graves et al., consuming less than 13 mW of average power
Time-resolved dynamics of granular matter by random laser emission
Because of the huge commercial importance of granular systems, the
second-most used material in industry after water, intersecting the industry in
multiple trades, like pharmacy and agriculture, fundamental research on
grain-like materials has received an increasing amount of attention in the last
decades. In photonics, the applications of granular materials have been only
marginally investigated. We report the first phase-diagram of a granular as
obtained by laser emission. The dynamics of vertically-oscillated granular in a
liquid solution in a three-dimensional container is investigated by employing
its random laser emission. The granular motion is function of the frequency and
amplitude of the mechanical solicitation, we show how the laser emission allows
to distinguish two phases in the granular and analyze its spectral
distribution. This constitutes a fundamental step in the field of granulars and
gives a clear evidence of the possible control on light-matter interaction
achievable in grain-like system.Comment: 16 pages, 7 figure
A 64mW DNN-based Visual Navigation Engine for Autonomous Nano-Drones
Fully-autonomous miniaturized robots (e.g., drones), with artificial
intelligence (AI) based visual navigation capabilities are extremely
challenging drivers of Internet-of-Things edge intelligence capabilities.
Visual navigation based on AI approaches, such as deep neural networks (DNNs)
are becoming pervasive for standard-size drones, but are considered out of
reach for nanodrones with size of a few cm. In this work, we
present the first (to the best of our knowledge) demonstration of a navigation
engine for autonomous nano-drones capable of closed-loop end-to-end DNN-based
visual navigation. To achieve this goal we developed a complete methodology for
parallel execution of complex DNNs directly on-bard of resource-constrained
milliwatt-scale nodes. Our system is based on GAP8, a novel parallel
ultra-low-power computing platform, and a 27 g commercial, open-source
CrazyFlie 2.0 nano-quadrotor. As part of our general methodology we discuss the
software mapping techniques that enable the state-of-the-art deep convolutional
neural network presented in [1] to be fully executed on-board within a strict 6
fps real-time constraint with no compromise in terms of flight results, while
all processing is done with only 64 mW on average. Our navigation engine is
flexible and can be used to span a wide performance range: at its peak
performance corner it achieves 18 fps while still consuming on average just
3.5% of the power envelope of the deployed nano-aircraft.Comment: 15 pages, 13 figures, 5 tables, 2 listings, accepted for publication
in the IEEE Internet of Things Journal (IEEE IOTJ
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
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