5,616 research outputs found
On Eigenvalue spacings for the 1-D Anderson model with singular site distribution
We study eigenvalue spacings and local eigenvalue statistics for 1D lattice
Schrodinger operators with Holder regular potential, obtaining a version of
Minami's inequality and Poisson statistics for the local eigenvalue spacings.
The main additional new input are regular properties of the Furstenberg
measures and the density of states obtained in some of the author's earlier
work.Comment: 13 page
Where is the warm H2 ? A search for H2 emission from disks around Herbig Ae/Be stars
Mid-IR emission lines of H2 are useful probes to determine the mass of warm
gas present in the surface layers of disks. Numerous observations of Herbig
Ae/Be stars (HAeBes) have been performed, but only 2 detections of mid-IR H2
toward HD97048 and AB Aur have been reported. We aim at tracing the warm gas in
the disks of 5 HAeBes with gas-rich environments and physical characteristics
close to those of AB Aur and HD97048, to discuss whether the detections toward
these 2 objects are suggestive of peculiar conditions for the gas. We search
for the H2 S(1) emission line at 17.035 \mu\m with VISIR, and complemented by
CH molecule observations with UVES. We gather the H2 measurements from the
literature to put the new results in context and search for a correlation with
some disk properties. None of the 5 VISIR targets shows evidence for H2
emission. From the 3sigma upper limits on the integrated line fluxes we
constrain the amount of optically thin warm gas to be less than 1.4 M_Jup in
the disk surface layers. There are now 20 HAeBes observed with VISIR and TEXES
instruments to search for warm H2, but only two detections (HD97048 and AB Aur)
were made so far. We find that the two stars with detected warm H2 show at the
same time high 30/13 \mu\m flux ratios and large PAH line fluxes at 8.6 and
11.3 \mu\m compared to the bulk of observed HAeBes and have emission CO lines
detected at 4.7 \mu\m. We detect the CH 4300.3A absorption line toward both
HD97048 and AB Aur with UVES. The CH to H2 abundance ratios that this would
imply if it were to arise from the same component as well as the radial
velocity of the CH lines both suggest that CH arises from a surrounding
envelope, while the detected H2 would reside in the disk. The two detections of
the S(1) line in the disks of HD97048 and AB Aur suggest either peculiar
physical conditions or a particular stage of evolution.Comment: accepted for publication in A&A : 10 pages, 6 figure
Adaptation “in the Wild”: Ontology-Based Personalization of Open-Corpus Learning Material
Abstract. Teacher and students can use WWW as a limitless source of learning material for nearly any subject. Yet, such abundance of content comes with the problem of finding the right piece at the right time. Conventional adaptive educational systems cannot support personalized access to open-corpus learning material as they rely on manually constructed content models. This paper presents an approach to this problem that does not require intervention from a human expert. The approach has been implemented in an adaptive system that recommends students supplementary reading material and adaptively annotates it. The results of the evaluation experiment have demonstrated several significant effects of using the system on students ’ learning
Adaptation “in the Wild”: Ontology-Based Personalization of Open-Corpus Learning Material
Teacher and students can use WWW as a limitless source of learning material for nearly any subject. Yet, such abundance of content comes with the problem of finding the right piece at the right time. Conventional adaptive educational systems cannot support personalized access to open-corpus learning material as they rely on manually constructed content models. This paper presents an approach to this problem that does not require intervention from a human expert. The approach has been implemented in an adaptive system that recommends students supplementary reading material and adaptively annotates it. The results of the evaluation experiment have demonstrated several significant effects of using the system on students’ learning.\u
Analysing the Moodle e-learning platform through subgroup discovery algorithms based on evolutionary fuzzy systems
Nowadays, there is a increasing in the use of learning management systems
from the universities. This type of systems are also known under other
di erent terms as course management systems or learning content management
systems. Speci cally, these systems are e-learning platforms o ering
di erent facilities for information sharing and communication between the
participants in the e-learning process.
This contribution presents an experimental study with several subgroup
discovery algorithms based on evolutionary fuzzy systems using data from a
web-based education system. The main objective of this contribution is to
extract unusual subgroups to describe possible relationships between the use
of the e-learning platform and marks obtained by the students. The results
obtained by the best performing algorithm, NMEEF-SD, are also presented.
The most representative results obtained by this algorithm are summarised in
order to obtain knowledge that can allow teachers to take actions to improve student performance
Subgroup Discovery: Real-World Applications
Subgroup discovery is a data mining technique which extracts interesting rules with respect
to a target variable. An important characteristic of this task is the combination of predictive
and descriptive induction. In this paper, an overview about subgroup discovery is performed.
In addition, di erent real-world applications solved through evolutionary algorithms where the
suitability and potential of this type of algorithms for the development of subgroup discovery
algorithms are presented
Subgroup Discovery trhough Evolutionary Fuzzy Systems applied to Bioinformatic problems
Subgroup discovery is a descriptive data mining technique using supervised learning. This
paper presents a summary about the main properties and elements about subgroup discovery task.
In addition, we will focus on the suitability and potential of the search performed by evolutionary
algorithms in order to apply in the development of subgroup discovery algorithms, and in the use
of fuzzy logic which is a soft computing technique very close to the human reasoning. The
hybridisation of both techniques are well known as evolutionary fuzzy system.
The most relevant applications of evolutionary fuzzy systems for subgroup discovery in the
bioinformatics domains are outlined in this work. Specifically, these algorithms are applied to a
problem based on the Influenza A virus and the accute sore throat problem
Analysing inter-relationships among water, governance, human development variables in developing countries
The "Integrated Water Resources Management" principle was formally laid down at the International Conference on Water and Sustainable development in Dublin 1992. One of the main results of this conference is that improving Water and Sanitation Services (WSS), being a complex and interdisciplinary issue, passes through collaboration and coordination of different sectors (environment, health, economic activities, governance, and international cooperation). These sectors influence or are influenced by the access to WSS. The understanding of these interrelations appears as crucial for decision makers in the water sector. In this framework, the Joint Research Centre (JRC) of the European Commission (EC) has developed a new database (WatSan4Dev database) containing 42 indicators (called variables in this paper) from environmental, socio-economic, governance and financial aid flows data in developing countries. This paper describes the development of the WatSan4Dev dataset, the statistical processes needed to improve the data quality, and finally, the analysis to verify the database coherence is presented. Based on 25 relevant variables, the relationships between variables are described and organised into five factors (HDP – Human Development against Poverty, AP – Human Activity Pressure on water resources, WR – Water Resources, ODA – Official Development Aid, CEC – Country Environmental Concern). Linear regression methods are used to identify key variables having influence on water supply and sanitation. First analysis indicates that the informal urbanisation development is an important factor negatively influencing the percentage of the population having access to WSS. Health, and in particular children's health, benefits from the improvement of WSS. Irrigation is also enhancing Water Supply service thanks to multi-purpose infrastructure. Five country profiles are also created to deeper understand and synthetize the amount of information gathered. This new classification of countries is useful in identifying countries with a less advanced position and weaknesses to be tackled. The relevance of indicators gathered to represent environmental and water resources state is questioned in the discussion section. The paper concludes with the necessity to increase the reliability of current indicators and calls for further research on specific indicators, in particular on water quality at national scale, in order to better include environmental state in analysis to WSS
- …