829,653 research outputs found
Towards open CSCW systems
Applications designed to support the work of groups will becoming increasingly important to future distributed systems. This paper considers the role of distributed systems within the development of cooperative systems. In particular, we focus on the need to provide Open CSCW systems and their impact on distributed systems. The work currently being undertoken in Open Distributed Systems (ODP) is used to highlight significant trends for future open CSCW systems. It will be shown that the
CSCW and ODP community share mutual interests and have complementary aims and goals developed from different perspectives.
Within the paper we provide a brief introduction to CSCW highlighting the requirements CSCW places on distributed systems. The development of an environment
to support open CSCW systems is introduced and briefly described. Finally, the relationships between requirements and models for Open CSCW systems and the Basic
Reference Model of ODP are discussed.Peer ReviewedPostprint (published version
A Tutorial on Distributed Optimization for Cooperative Robotics: from Setups and Algorithms to Toolboxes and Research Directions
Several interesting problems in multi-robot systems can be cast in the
framework of distributed optimization. Examples include multi-robot task
allocation, vehicle routing, target protection and surveillance. While the
theoretical analysis of distributed optimization algorithms has received
significant attention, its application to cooperative robotics has not been
investigated in detail. In this paper, we show how notable scenarios in
cooperative robotics can be addressed by suitable distributed optimization
setups. Specifically, after a brief introduction on the widely investigated
consensus optimization (most suited for data analytics) and on the
partition-based setup (matching the graph structure in the optimization), we
focus on two distributed settings modeling several scenarios in cooperative
robotics, i.e., the so-called constraint-coupled and aggregative optimization
frameworks. For each one, we consider use-case applications, and we discuss
tailored distributed algorithms with their convergence properties. Then, we
revise state-of-the-art toolboxes allowing for the implementation of
distributed schemes on real networks of robots without central coordinators.
For each use case, we discuss their implementation in these toolboxes and
provide simulations and real experiments on networks of heterogeneous robots
Random Walks in Random Environments
Random walks provide a simple conventional model to describe various
transport processes, for example propagation of heat or diffusion of matter
through a medium. However, in many practical cases the medium is highly
irregular due to defects, impurities, fluctuations etc., and it is natural to
model this as random environment. In the random walks context, such models are
referred to as Random Walks in Random Environments (RWRE). This is a relatively
new chapter in applied probability and physics of disordered systems, initiated
in the 1970s. Early interest was motivated by some problems in biology,
crystallography and metal physics, but later applications have spread through
numerous areas. After 30 years of extensive work, RWRE remain a very active
area of research, which has already led to many surprising discoveries. The
goal of this article is to give a brief introduction to the beautiful area of
RWRE. The principal model to be discussed is a random walk with
nearest-neighbor jumps in independent identically distributed (i.i.d.) random
environment in one dimension, although we shall also comment on some extensions
and generalizations. The focus is on rigorous results; however, heuristics is
used freely to motivate the ideas and explain the approaches and proofs. In a
few cases, sketches of the proofs have been included, which should help the
reader to appreciate the flavor of results and methods.Comment: A review article in the Encyclopedia of Mathematical Physics
(Elsevier, 2006).
http://www.elsevier.com/wps/find/bookdescription.cws_home/705128/descriptio
Simulation System for the Wendelstein 7-X Safety Control System
The Wendelstein 7-X (W7-X) Safety Instrumented System (SIS) ensures personal
safety and investment protection. The development and implementation of the SIS
are based on the international safety standard for the process industry sector,
IEC 61511. The SIS exhibits a distributed and hierarchical organized
architecture consisting of a central Safety System (cSS) on the top and many
local Safety Systems (lSS) at the bottom. Each technical component or
diagnostic system potentially hazardous for the staff or for the device is
equipped with an lSS. The cSS is part of the central control system of W7-X.
Whereas the lSSs are responsible for the safety of each individual component,
the cSS ensures safety of the whole W7-X device. For every operation phase of
the W7-X experiment hard- and software updates for the SIS are mandatory. New
components with additional lSS functionality and additional safety signals have
to be integrated. Already established safety functions must be adapted and new
safety functions have to be integrated into the cSS. Finally, the safety
programs of the central and local safety systems have to be verified for every
development stage and validated against the safety requirement specification.
This contribution focuses on the application of a model based simulation system
for the whole SIS of W7-X. A brief introduction into the development process of
the SIS and its technical realization will be give followed by a description of
the design and implementation of the SIS simulation system using the framework
SIMIT (Siemens). Finally, first application experiences of this simulation
system for the preparation of the SIS for the upcoming operation phase OP 1.2b
of W7-X will be discussed
Studies of CMS data access patterns with machine learning techniques
This thesis presents a study of the Grid data access patterns in distributed analysis in
the CMS experiment at the LHC accelerator.
This study ranges from the deep analysis of the historical patterns of access to the
most relevant data types in CMS, to the exploitation of a supervised Machine Learning classification system to set-up a machinery able to eventually predict future data access patterns - i.e. the so-called dataset “popularity” of the CMS datasets on the Grid - with focus on specific data types. All the CMS workflows run on the Worldwide LHC Computing Grid (WCG) computing centers (Tiers), and in particular the distributed analysis systems sustains hundreds of users and applications submitted every day. These applications (or “jobs”) access different data types hosted on disk storage systems at a large set of WLCG Tiers. The detailed study of how this data is accessed, in terms of data types, hosting Tiers, and different time periods, allows to gain precious insight on storage occupancy over time and different access patterns, and ultimately to extract suggested actions based on this information (e.g. targetted disk clean-up and/or data replication). In this sense, the application of Machine Learning techniques allows to learn from past data and to gain predictability potential for the future CMS data access patterns.
Chapter 1 provides an introduction to High Energy Physics at the LHC.
Chapter 2 describes the CMS Computing Model, with special focus on the data management sector, also discussing the concept of dataset popularity.
Chapter 3 describes the study of CMS data access patterns with different depth levels.
Chapter 4 offers a brief introduction to basic machine learning concepts and gives an introduction to its application in CMS and discuss the results obtained by using this approach in the context of this thesis
OpTiX-II: A Software Environment for MCDM based on Distributed and Parallel Computing
The intention of the paper is to give an introduction to the OpTiX-II Software Environment, which supports the parallel and distributed solution of decision problems which can be represented as mathematical nonlinear programming tasks. First, a brief summary of nonsequential solution concepts for this class of decision problems on multiprocessor systems will be given. The focus of attention will be put on coarse-grained parallelization and its implementation on multi-computer clusters. The conceptual design objectives for the OpTiX-II Software Environment will be presented as well as the implementation on a workstation cluster, a transputer system and a multiprocessor workstation (shared memory). The OpTiX-II system supports the steps from the formulation of decision problems to their solution on networks of (parallel) computers. In order to demonstrate the use of OpTiX-II, the solution of a decision problem from the field of structural design is discussed and some numerical test results are supplied
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