23,959 research outputs found
CSP methods for identifying atomic actions in the design of fault tolerant concurrent systems
Limiting the extent of error propagation when faults occur and localizing the subsequent error recovery are common concerns in the design of fault tolerant parallel processing systems, Both activities are made easier if the designer associates fault tolerance mechanisms with the underlying atomic actions of the system, With this in mind, this paper has investigated two methods for the identification of atomic actions in parallel processing systems described using CSP, Explicit trace evaluation forms the basis of the first algorithm, which enables a designer to analyze interprocess communications and thereby locate atomic action boundaries in a hierarchical fashion, The second method takes CSP descriptions of the parallel processes and uses structural arguments to infer the atomic action boundaries. This method avoids the difficulties involved with producing full trace sets, but does incur the penalty of a more complex algorithm
Session Types with Runtime Adaptation: Overview and Examples
In recent work, we have developed a session types discipline for a calculus
that features the usual constructs for session establishment and communication,
but also two novel constructs that enable communicating processes to be
stopped, duplicated, or discarded at runtime. The aim is to understand whether
known techniques for the static analysis of structured communications scale up
to the challenging context of context-aware, adaptable distributed systems, in
which disciplined interaction and runtime adaptation are intertwined concerns.
In this short note, we summarize the main features of our session-typed
framework with runtime adaptation, and recall its basic correctness properties.
We illustrate our framework by means of examples. In particular, we present a
session representation of supervision trees, a mechanism for enforcing
fault-tolerant applications in the Erlang language.Comment: In Proceedings PLACES 2013, arXiv:1312.221
Online Visual Robot Tracking and Identification using Deep LSTM Networks
Collaborative robots working on a common task are necessary for many
applications. One of the challenges for achieving collaboration in a team of
robots is mutual tracking and identification. We present a novel pipeline for
online visionbased detection, tracking and identification of robots with a
known and identical appearance. Our method runs in realtime on the limited
hardware of the observer robot. Unlike previous works addressing robot tracking
and identification, we use a data-driven approach based on recurrent neural
networks to learn relations between sequential inputs and outputs. We formulate
the data association problem as multiple classification problems. A deep LSTM
network was trained on a simulated dataset and fine-tuned on small set of real
data. Experiments on two challenging datasets, one synthetic and one real,
which include long-term occlusions, show promising results.Comment: IEEE/RSJ International Conference on Intelligent Robots and Systems
(IROS), Vancouver, Canada, 2017. IROS RoboCup Best Paper Awar
Online Multi-Object Tracking Using CNN-based Single Object Tracker with Spatial-Temporal Attention Mechanism
In this paper, we propose a CNN-based framework for online MOT. This
framework utilizes the merits of single object trackers in adapting appearance
models and searching for target in the next frame. Simply applying single
object tracker for MOT will encounter the problem in computational efficiency
and drifted results caused by occlusion. Our framework achieves computational
efficiency by sharing features and using ROI-Pooling to obtain individual
features for each target. Some online learned target-specific CNN layers are
used for adapting the appearance model for each target. In the framework, we
introduce spatial-temporal attention mechanism (STAM) to handle the drift
caused by occlusion and interaction among targets. The visibility map of the
target is learned and used for inferring the spatial attention map. The spatial
attention map is then applied to weight the features. Besides, the occlusion
status can be estimated from the visibility map, which controls the online
updating process via weighted loss on training samples with different occlusion
statuses in different frames. It can be considered as temporal attention
mechanism. The proposed algorithm achieves 34.3% and 46.0% in MOTA on
challenging MOT15 and MOT16 benchmark dataset respectively.Comment: Accepted at International Conference on Computer Vision (ICCV) 201
Hierarchies, relational contracts and new forms of outsourcing.
We observe that economic restructuring is significantly changing organizational governance. On the one hand, we witness an increase in mergers & acquisitions, which substitutes markets for hierarchies and, on the other hand, we see an increase in outsourcing and subcontracting activities, appearing to replace hierarchies by markets. However, there is evidence that an increasing part of outsourcing activities mix hierarchies with market forms of governance. The key argument of this paper is that firms have established governance structures based on markets, hierarchies and self-enforcing relational contracts so that they are able to keep a substantial amount of control despite of sourcing out labour. Furthermore, we argue that such hierarchical forms of outsourcing produce dependency. Using empirical evidence of the Austrian insurance industry, it is demonstrated that dependency is created, firstly, by the contractual restriction of alternative uses of resources, secondly, by support measures that bind the upstream party closely to the downstream party, thirdly, by relationship-specific investments made by the upstream party, and fourthly, by authority elements.
Conformational Dynamics of Supramolecular Protein Assemblies in the EMDB
The Electron Microscopy Data Bank (EMDB) is a rapidly growing repository for
the dissemination of structural data from single-particle reconstructions of
supramolecular protein assemblies including motors, chaperones, cytoskeletal
assemblies, and viral capsids. While the static structure of these assemblies
provides essential insight into their biological function, their conformational
dynamics and mechanics provide additional important information regarding the
mechanism of their biological function. Here, we present an unsupervised
computational framework to analyze and store for public access the
conformational dynamics of supramolecular protein assemblies deposited in the
EMDB. Conformational dynamics are analyzed using normal mode analysis in the
finite element framework, which is used to compute equilibrium thermal
fluctuations, cross-correlations in molecular motions, and strain energy
distributions for 452 of the 681 entries stored in the EMDB at present. Results
for the viral capsid of hepatitis B, ribosome-bound termination factor RF2, and
GroEL are presented in detail and validated with all-atom based models. The
conformational dynamics of protein assemblies in the EMDB may be useful in the
interpretation of their biological function, as well as in the classification
and refinement of EM-based structures.Comment: Associated online data bank available at:
http://lcbb.mit.edu/~em-nmdb
Authority inside the firm: multiple mechanisms of coordination
In the last twenty years, through a growing awareness of contractual incompleteness, the concept of authority has regained primacy in the analysis of the employment relationship. This article pursues two goals. First, we assess the famous controversy between Coase and Alchian and Demsetz via an analysis of the foundations of intra-firm authority. Second, we argue that intra-firm authority cannot hinge on a single variable and, to the contrary, rests on multiple mechanisms. The employer's authority over the employee is therefore not binary âinfinite or null â and should be understood in terms of degree.authority; firm; incomplete contracts; law and economics
A Supervisory Control Algorithm Based on Property-Directed Reachability
We present an algorithm for synthesising a controller (supervisor) for a
discrete event system (DES) based on the property-directed reachability (PDR)
model checking algorithm. The discrete event systems framework is useful in
both software, automation and manufacturing, as problems from those domains can
be modelled as discrete supervisory control problems. As a formal framework,
DES is also similar to domains for which the field of formal methods for
computer science has developed techniques and tools. In this paper, we attempt
to marry the two by adapting PDR to the problem of controller synthesis. The
resulting algorithm takes as input a transition system with forbidden states
and uncontrollable transitions, and synthesises a safe and
minimally-restrictive controller, correct-by-design. We also present an
implementation along with experimental results, showing that the algorithm has
potential as a part of the solution to the greater effort of formal supervisory
controller synthesis and verification.Comment: 16 pages; presented at Haifa Verification Conference 2017, the final
publication is available at Springer via
https://doi.org/10.1007/978-3-319-70389-3_
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