117,049 research outputs found
Mobile object location discovery in unpredictable environments
Emerging mobile and ubiquitous computing environments present hard challenges to software engineering. The use of mobile code has been suggested as a natural fit for simplifing software development for these environments. However, the task of discovering mobile code location becomes a problem in unpredictable environments when using existing strategies, designed with fixed and relatively stable networks in mind. This paper introduces AMOS, a mobile code platform augmented with a structured overlay network. We demonstrate how the location discovery strategy of AMOS has better reliability and scalability properties than existing approaches, with minimal communication overhead. Finally, we demonstrate how AMOS can provide autonomous distribution of effort fairly throughout a network using probabilistic methods that requires no global knowledge of host capabilities
An instance of the MIKADO migration model
In this document, we briefly describe the main contribution to the deliverable on experimenting with the implementation of most of the calculi considered in the project. First, we describe how two well known calculi for mobile processes KLAIM and DÏ have been implemented on the top of IMC. We then describe the implementation of the MiKO programming language, an instance of the parametric calculus introduced in the WP1 with the TyCO calculus as the content of the membrane itself. After this, we outline the description of the implementation of the abstract machine for an instance of the Kell Calculus that dedicates particular attention to the proof of its correctness. Our presentation ends with a discussion of the problem of implementing security membranes on the top of an execution platform
Process Management in Distributed Operating Systems
As part of designing and building the Amoeba distributed operating system, we have come up with a simple set of mechanisms for process management that allows downloading process migration, checkpointing, remote debugging and emulation of alien operating system interfaces.\ud
The basic process management facilities are realized by the Amoeba Kernel and can be augmented by user-space services: Debug Service, Load-Balancing Service, Unix-Emulation Service, Checkpoint Service, etc.\ud
The Amoeba Kernel can produce a representation of the state of a process which can be given to another Kernel where it is accepted for continued execution. This state consists of the memory contents in the form of a collection of segments, and a Process Descriptor which contains the additional state, program counters, stack pointers, system call state, etc.\ud
Careful separation of mechanism and policy has resulted in a compact set of Kernel operations for process creation and management. A collection of user-space services provides process management policies and a simple interface for application programs.\ud
In this paper we shall describe the mechanisms as they are being implemented in the Amoeba Distributed System at the Centre for Mathematics and Computer Science in Amsterdam. We believe that the mechanisms described here can also apply to other distributed systems
RAFDA: A Policy-Aware Middleware Supporting the Flexible Separation of Application Logic from Distribution
Middleware technologies often limit the way in which object classes may be
used in distributed applications due to the fixed distribution policies that
they impose. These policies permeate applications developed using existing
middleware systems and force an unnatural encoding of application level
semantics. For example, the application programmer has no direct control over
inter-address-space parameter passing semantics. Semantics are fixed by the
distribution topology of the application, which is dictated early in the design
cycle. This creates applications that are brittle with respect to changes in
distribution. This paper explores technology that provides control over the
extent to which inter-address-space communication is exposed to programmers, in
order to aid the creation, maintenance and evolution of distributed
applications. The described system permits arbitrary objects in an application
to be dynamically exposed for remote access, allowing applications to be
written without concern for distribution. Programmers can conceal or expose the
distributed nature of applications as required, permitting object placement and
distribution boundaries to be decided late in the design cycle and even
dynamically. Inter-address-space parameter passing semantics may also be
decided independently of object implementation and at varying times in the
design cycle, again possibly as late as run-time. Furthermore, transmission
policy may be defined on a per-class, per-method or per-parameter basis,
maximizing plasticity. This flexibility is of utility in the development of new
distributed applications, and the creation of management and monitoring
infrastructures for existing applications.Comment: Submitted to EuroSys 200
Generative Model with Coordinate Metric Learning for Object Recognition Based on 3D Models
Given large amount of real photos for training, Convolutional neural network
shows excellent performance on object recognition tasks. However, the process
of collecting data is so tedious and the background are also limited which
makes it hard to establish a perfect database. In this paper, our generative
model trained with synthetic images rendered from 3D models reduces the
workload of data collection and limitation of conditions. Our structure is
composed of two sub-networks: semantic foreground object reconstruction network
based on Bayesian inference and classification network based on multi-triplet
cost function for avoiding over-fitting problem on monotone surface and fully
utilizing pose information by establishing sphere-like distribution of
descriptors in each category which is helpful for recognition on regular photos
according to poses, lighting condition, background and category information of
rendered images. Firstly, our conjugate structure called generative model with
metric learning utilizing additional foreground object channels generated from
Bayesian rendering as the joint of two sub-networks. Multi-triplet cost
function based on poses for object recognition are used for metric learning
which makes it possible training a category classifier purely based on
synthetic data. Secondly, we design a coordinate training strategy with the
help of adaptive noises acting as corruption on input images to help both
sub-networks benefit from each other and avoid inharmonious parameter tuning
due to different convergence speed of two sub-networks. Our structure achieves
the state of the art accuracy of over 50\% on ShapeNet database with data
migration obstacle from synthetic images to real photos. This pipeline makes it
applicable to do recognition on real images only based on 3D models.Comment: 14 page
On the orbital evolution and growth of protoplanets embedded in a gaseous disc
We present a new computation of the linear tidal interaction of a
protoplanetary core with a thin gaseous disc in which it is fully embedded. For
the first time a discussion of the orbital evolution of cores with eccentricity
(e) significantly larger than the gas-disc scale height to radius ratio (H/r)
is given. We find that the direction of orbital migration reverses for
e>1.1H/r. This occurs as a result of the orbital crossing of resonances in the
disc that do not overlap the orbit when the eccentricity is very small. Simple
expressions giving approximate fits to the eccentricity damping rate and the
orbital migration rate are presented. We go on to calculate the rate of
increase of the mean eccentricity for a system of protoplanetary cores due to
dynamical relaxation. By equating the eccentricity damping time-scale with the
dynamical relaxation time-scale we deduce that an equilibrium between
eccentricity damping and excitation through scattering is attained on a 10^3 to
10^4 yr time-scale, at 1au. The equilibrium thickness of the protoplanet
distribution is such that it is generally well confined within the gas disc. By
use of a three dimensional N-body code we simulate the evolution of a system of
protoplanetary cores, incorporating our eccentricity damping and migration
rates. Assuming that collisions lead to agglomeration, we find that the
vertical confinement of the protoplanet distribution permits cores to build up
from 0.1 to 1 earth mass in only ~10^4 yr, within 1au. The time-scale required
to achieve this is comparable to the migration time-scale. We deduce that it is
not possible to build up a massive enough core to form a gas giant planet
before orbital migration ultimately results in the preferential delivery of all
such bodies to the neighbourhood of the central star. [Abridged]Comment: Latex in MNRAS style, 13 pages with 6 figures, also available from
http://www.maths.qmw.ac.uk/~jdl
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Survey of partitioning techniques in silicon compilation
In the silicon compilation design process, partitioning is usually the first problem to be investigated because partitioning algorithms form the backbone of many algorithms including: system synthesis, processor synthesis, floorplanning, and placement. In this survey, several partitioning techniques will be examined. In addition, this paper will review the partitioning algorithms used by synthesis systems at different design levels
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