4,398 research outputs found
KR: An Architecture for Knowledge Representation and Reasoning in Robotics
This paper describes an architecture that combines the complementary
strengths of declarative programming and probabilistic graphical models to
enable robots to represent, reason with, and learn from, qualitative and
quantitative descriptions of uncertainty and knowledge. An action language is
used for the low-level (LL) and high-level (HL) system descriptions in the
architecture, and the definition of recorded histories in the HL is expanded to
allow prioritized defaults. For any given goal, tentative plans created in the
HL using default knowledge and commonsense reasoning are implemented in the LL
using probabilistic algorithms, with the corresponding observations used to
update the HL history. Tight coupling between the two levels enables automatic
selection of relevant variables and generation of suitable action policies in
the LL for each HL action, and supports reasoning with violation of defaults,
noisy observations and unreliable actions in large and complex domains. The
architecture is evaluated in simulation and on physical robots transporting
objects in indoor domains; the benefit on robots is a reduction in task
execution time of 39% compared with a purely probabilistic, but still
hierarchical, approach.Comment: The paper appears in the Proceedings of the 15th International
Workshop on Non-Monotonic Reasoning (NMR 2014
REBA: A Refinement-Based Architecture for Knowledge Representation and Reasoning in Robotics
This paper describes an architecture for robots that combines the
complementary strengths of probabilistic graphical models and declarative
programming to represent and reason with logic-based and probabilistic
descriptions of uncertainty and domain knowledge. An action language is
extended to support non-boolean fluents and non-deterministic causal laws. This
action language is used to describe tightly-coupled transition diagrams at two
levels of granularity, with a fine-resolution transition diagram defined as a
refinement of a coarse-resolution transition diagram of the domain. The
coarse-resolution system description, and a history that includes (prioritized)
defaults, are translated into an Answer Set Prolog (ASP) program. For any given
goal, inference in the ASP program provides a plan of abstract actions. To
implement each such abstract action, the robot automatically zooms to the part
of the fine-resolution transition diagram relevant to this action. A
probabilistic representation of the uncertainty in sensing and actuation is
then included in this zoomed fine-resolution system description, and used to
construct a partially observable Markov decision process (POMDP). The policy
obtained by solving the POMDP is invoked repeatedly to implement the abstract
action as a sequence of concrete actions, with the corresponding observations
being recorded in the coarse-resolution history and used for subsequent
reasoning. The architecture is evaluated in simulation and on a mobile robot
moving objects in an indoor domain, to show that it supports reasoning with
violation of defaults, noisy observations and unreliable actions, in complex
domains.Comment: 72 pages, 14 figure
High-Velocity Features in Type Ia Supernova Spectra
We use a sample of 58 low-redshift (z <= 0.03) Type Ia supernovae (SNe Ia)
having well-sampled light curves and spectra near maximum light to examine the
behaviour of high-velocity features (HVFs) in SN Ia spectra. We take advantage
of the fact that Si II 6355 is free of HVFs at maximum light in all SNe Ia,
allowing us to quantify the strength of HVFs by comparing the structure of
these two lines. We find that the average HVF strength increases with
decreasing light-curve decline rate, and rapidly declining SNe Ia (dm_15(B) >=
1.4 mag) show no HVFs in their maximum-light spectra. Comparison of HVF
strength to the light-curve colour of the SNe Ia in our sample shows no
evidence of correlation. We find a correlation of HVF strength with the
velocity of Si II 6355 at maximum light (v_Si), such that SNe Ia with lower
v_Si have stronger HVFs, while those SNe Ia firmly in the "high-velocity"
(i.e., v_Si >= 12,000 km/s) subclass exhibit no HVFs in their maximum-light
spectra. While v_Si and dm_15(B) show no correlation in the full sample of SNe
Ia, we find a significant correlation between these quantities in the subset of
SNe Ia having weak HVFs. In general, we find that slowly declining (low
dm_15(B)) SNe Ia, which are more luminous and more energetic than average SNe
Ia, tend to produce either high photospheric ejecta velocities (i.e., high
v_Si) or strong HVFs at maximum light, but not both. Finally, we examine the
evolution of HVF strength for a sample of SNe Ia having extensive pre-maximum
spectroscopic coverage and find significant diversity of the pre-maximum HVF
behaviour.Comment: Version accepted by MNRA
Development of high resolution simulations of the atmospheric environment using the MASS model
Numerical simulations were performed with a very high resolution (7.25 km) version of the MASS model (Version 4.0) in an effort to diagnose the vertical wind shear and static stability structure during the Shuttle Challenger disaster which occurred on 28 January 1986. These meso-beta scale simulations reveal that the strongest vertical wind shears were concentrated in the 200 to 150 mb layer at 1630 GMT, i.e., at about the time of the disaster. These simulated vertical shears were the result of two primary dynamical processes. The juxtaposition of both of these processes produced a shallow (30 mb deep) region of strong vertical wind shear, and hence, low Richardson number values during the launch time period. Comparisons with the Cape Canaveral (XMR) rawinsonde indicates that the high resolution MASS 4.0 simulation more closely emulated nature than did previous simulations of the same event with the GMASS model
A Survey of Search-Based Refactoring for Software Maintenance
Abstract This survey reviews published materials related to the specific area of Search-Based Software Engineering that concerns software maintenance and, in particular, refactoring. The survey aims to give a comprehensive review of the use of search-based refactoring to maintain software. Fifty different papers have been selected from online databases to analyze and review the use of search-based refactoring in software engineering. The current state of the research is analyzed and patterns in the studies are investigated in order to assess gaps in the area and suggest opportunities for future research. The papers reviewed are tabulated in order to aid researchers in quickly referencing studies. The literature addresses different methods using search-based refactoring for software maintenance, as well as studies that investigate the optimization process and discuss components of the search. There are studies that analyze different software metrics, experiment with multi-objective techniques and propose refactoring tools for use. Analysis of the literature has indicated some opportunities for future research in the area. More experimentation of the techniques in an industrial environment and feedback from software developers is needed to support the approaches. Also, recent work with multi-objective techniques has shown that there are exciting possibilities for future research using these techniques with refactoring. This survey is beneficial as an introduction for any researchers aiming to work in the area of Search-Based Software Engineering with respect to software maintenance and will allow them to gain an understanding of the current landscape of the research and the insights gathered
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Improving Workflovf In Home Healthcare Industry: A Case Study
Home healthcare industry is facing increasing pressure to change business processes and manage information flow electronically. With the help of a case example, this paper describes how a webbased system could improve the workflow communication problems in home healthcare companies. Every department of the case company has its own software to assist in everyday operations but is unable to communicate with one another electronically. All documents necessary in the coordination of care have to move physically between departments. The proposed solution is a web-based electronic form management system that would improve regulatory compliance and operating efficiency
Recommended from our members
Improving Workflow in Home Healthcare Industry: A Case Study
Home healthcare industry is facing increasing pressure to change business processes and manage information flow electronically. With the help of a case example, this paper describes how a web- based system could improve the workflow communication problems in home healthcare companies. Every department of the case company has its own software to assist in everyday operations but is unable to communicate with one another electronically. All documents necessary in the coordination of care have to move physically between departments. The proposed solution is a web-based electronic form management system that would improve regulatory compliance and operating efficiency
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