327 research outputs found
Run-time Spatial Mapping of Streaming Applications to Heterogeneous Multi-Processor Systems
In this paper, we define the problem of spatial mapping. We present reasons why performing spatial mappings at run-time is both necessary and desirable. We propose what is—to our knowledge—the first attempt at a formal description of spatial mappings for the embedded real-time streaming application domain. Thereby, we introduce criteria for a qualitative comparison of these spatial mappings. As an illustration of how our formalization relates to practice, we relate our own spatial mapping algorithm to the formal model
Dynamic Resource Allocation
Computer systems are subject to continuously increasing performance demands. However, energy consumption has become a critical issue, both for high-end large-scale parallel systems [12], as well as for portable devices [34]. In other words, more work needs to be done in less time, preferably with the same or smaller energy budget. Future performance and efficiency goals of computer systems can only be reached with large-scale, heterogeneous architectures [6]. Due to their distributed nature, control software is required to coordinate the parallel execution of applications on such platforms. Abstraction, arbitration and multi-objective optimization are only a subset of the tasks this software has to fulfill [6, 31]. The essential problem in all this is the allocation of platform resources to satisfy the needs of an application.\ud
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This work considers the dynamic resource allocation problem, also known as the run-time mapping problem. This problem consists of task assignment to (processing) elements and communication routing through the interconnect between the elements. In mathematical terms, the combined problem is defined as the multi-resource quadratic assignment and routing problem (MRQARP). An integer linear programming formulation is provided, as well as complexity proofs on the N P-hardness of the problem.\ud
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This work builds upon state-of-the-art work of Yagiura et al. [39, 40, 42] on metaheuristics for various generalizations of the generalized assignment problem. Specifically, we focus on the guided local search (GLS) approach for the multi-resource quadratic assignment problem (MRQAP). The quadratic assignment problem defines a cost relation between tasks and between elements. We generalize the multi-resource quadratic assignment problem with the addition of a capacitated interconnect and a communication topology between tasks. Numerical experiments show that the performance of the approach is comparable with commercial solvers. The footprint, the time versus quality trade-off and available metadata make guided local search a suitable candidate for run-time mapping
Enhancing the Mass Sensitivity of Graphene Nanoresonators Via Nonlinear Oscillations: The Effective Strain Mechanism
We perform classical molecular dynamics simulations to investigate the
enhancement of the mass sensitivity and resonant frequency of graphene
nanomechanical resonators that is achieved by driving them into the nonlinear
oscillation regime. The mass sensitivity as measured by the resonant frequency
shift is found to triple if the actuation energy is about 2.5 times the initial
kinetic energy of the nanoresonator. The mechanism underlying the enhanced mass
sensitivity is found to be the effective strain that is induced in the
nanoresonator due to the nonlinear oscillations, where we obtain an analytic
relationship between the induced effective strain and the actuation energy that
is applied to the graphene nanoresonator. An important implication of this work
is that there is no need for experimentalists to apply tensile strain to the
resonators before actuation in order to enhance the mass sensitivity. Instead,
enhanced mass sensitivity can be obtained by the far simpler technique of
actuating nonlinear oscillations of an existing graphene nanoresonator.Comment: published versio
Optimization and Abstraction: A Synergistic Approach for Analyzing Neural Network Robustness
In recent years, the notion of local robustness (or robustness for short) has
emerged as a desirable property of deep neural networks. Intuitively,
robustness means that small perturbations to an input do not cause the network
to perform misclassifications. In this paper, we present a novel algorithm for
verifying robustness properties of neural networks. Our method synergistically
combines gradient-based optimization methods for counterexample search with
abstraction-based proof search to obtain a sound and ({\delta}-)complete
decision procedure. Our method also employs a data-driven approach to learn a
verification policy that guides abstract interpretation during proof search. We
have implemented the proposed approach in a tool called Charon and
experimentally evaluated it on hundreds of benchmarks. Our experiments show
that the proposed approach significantly outperforms three state-of-the-art
tools, namely AI^2 , Reluplex, and Reluval
On T-Duality in Brane Gas Cosmology
In the context of homogeneous and isotropic superstring cosmology, the
T-duality symmetry of string theory has been used to argue that for a
background space-time described by dilaton gravity with strings as matter
sources, the cosmological evolution of the Universe will be nonsingular. In
this Letter we discuss how T-duality extends to brane gas cosmology, an
approximation in which the background space-time is again described by dilaton
gravity with a gas of branes as a matter source. We conclude that the arguments
for nonsingular cosmological evolution remain valid.Comment: 8 pages, Appendix adde
A local and territorial approach to the operation of the culture economy in medium and small cities: case study of the Spanish cities of Merida and Cuenca
The chief objective of this research is to analyze the weight that several factors linked to territory and/or urban society (such as proximity, heritage, image, or infrastructures) exert in the development and operation of cultural clusters in small and medium-sized cities. To this end, a local territorial approach combining quantitative and qualitative methods has been undertaken and applied to the Spanish cities of Merida and Cuenca. The results from this case study show that many parameters observed in the international bibliography that form part of the idiosyncrasy of medium and small cities (''closeness'', possibility of face-to-face contact, quality of life, low production costs) are considered by selected interviewees as essential to understanding the operation of their organizations and the urban cultural economic cluster as a whole. In general, these parameters appear in the international bibliography as contributing to the development of the cultural economy, but their importance in medium and small cities had been tested only rarely
Perturbations on a moving D3-brane and mirage cosmology
We study the evolution of perturbations on a moving probe D3-brane coupled to
a 4-form field in an AdS-Schwarzschild bulk. The unperturbed dynamics are
parametrised by a conserved energy and lead to Friedmann-Robertson-Walker
`mirage' cosmology on the brane with scale factor . The fluctuations
about the unperturbed worldsheet are then described by a scalar field
. We derive an equation of motion for , and find that
in certain regimes of the effective mass squared is negative. On an
expanding BPS brane with E=0 superhorizon modes grow as whilst subhorizon
modes are stable. When the brane contracts, all modes grow. We also briefly
discuss the case when , BPS anti-branes as well as non-BPS branes.
Finally, the perturbed brane embedding gives rise to scalar perturbations in
the FRW universe. We show that is proportional to the gauge invariant
Bardeen potentials on the brane.Comment: 26 pages, 5 figures, to appear in Phys.Rev.D, comments and minor
corrections adde
Chronic cochlear implantation with and without electric stimulation in a mouse model induces robust cochlear influx of CX3CR1+/GFP macrophages
BACKGROUND: Cochlear implantation is an effective auditory rehabilitation strategy for those with profound hearing loss, including those with residual low frequency hearing through use of hybrid cochlear implantation techniques. Post-mortem studies demonstrate the nearly ubiquitous presence of intracochlear fibrosis and neo-ossification following cochlear implantation. Current evidence suggests post-implantation intracochlear fibrosis is associated with delayed loss of residual acoustic hearing in hybrid cochlear implant (CI) recipients and may also negatively influence outcomes in traditional CI recipients. This study examined the contributions of surgical trauma, foreign body response and electric stimulation to intracochlear fibrosis and the innate immune response to cochlear implantation and the hierarchy of these contributions.
METHODS: Normal hearing CX3CR1
RESULTS: A ST peri-implant cellular infiltrate and fibrosis occurred exclusively in the chronically implanted groups starting on day 7 with a concurrent infiltration of CX3CR1+ macrophages not seen in the other groups. CX3CR1+ macrophage infiltration was seen in the LW and RC in all experimental groups within the first week, being most prominent in the 3 chronically implanted groups during the second and third week.
CONCLUSIONS: The cochlear immune response was most prominent in the presence of chronic cochlear implantation, regardless of electric stimulation level. Further, the development of intracochlear ST fibrosis was dependent on the presence of the indwelling CI foreign body. An innate immune response was evoked by surgical trauma alone (sham and acute CI groups) to a lesser degree. These data suggest that cochlear inflammation and intrascalar fibrosis after cochlear implantation are largely dependent on the presence of a chronic indwelling foreign body and are not critically dependent on electrical stimulation. Also, these data support a role for surgical trauma in inciting the initial innate immune response
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The validation of a computer-based food record for older adults: the Novel Assessment of Nutrition and Ageing (NANA) method
Dietary assessment in older adults can be challenging. The Novel Assessment of Nutrition and Ageing (NANA) method is a touch-screen
computer-based food record that enables older adults to record their dietary intakes. The objective of the present study was to assess
the relative validity of the NANA method for dietary assessment in older adults. For this purpose, three studies were conducted in which a
total of ninety-four older adults (aged 65–89 years) used the NANA method of dietary assessment. On a separate occasion, participants
completed a 4 d estimated food diary. Blood and 24 h urine samples were also collected from seventy-six of the volunteers for the analysis
of biomarkers of nutrient intake. The results from all the three studies were combined, and nutrient intake data collected using the NANA
method were compared against the 4 d estimated food diary and biomarkers of nutrient intake. Bland–Altman analysis showed
a reasonable agreement between the dietary assessment methods for energy and macronutrient intake; however, there were small, but
significant, differences for energy and protein intake, reflecting the tendency for the NANA method to record marginally lower energy intakes.
Significant positive correlations were observed between urinary urea and dietary protein intake using both the NANA and the 4 d estimated
food diary methods, and between plasma ascorbic acid and dietary vitamin C intake using the NANA method. The results demonstrate the
feasibility of computer-based dietary assessment in older adults, and suggest that the NANA method is comparable to the 4 d estimated
food diary, and could be used as an alternative to the food diary for the short-term assessment of an individual’s dietary intake
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