2,712 research outputs found
S-DIMM+ height characterization of day-time seeing using solar granulation
To evaluate site quality and to develop multi-conjugative adaptive optics
systems for future large solar telescopes, characterization of contributions to
seeing from heights up to at least 12 km above the telescope is needed. We
describe a method for evaluating contributions to seeing from different layers
along the line-of-sight to the Sun. The method is based on Shack Hartmann
wavefront sensor data recorded over a large field-of-view with solar
granulation and uses only measurements of differential image displacements from
individual exposures, such that the measurements are not degraded by residual
tip-tilt errors. We conclude that the proposed method allows good measurements
when Fried's parameter r_0 is larger than about 7.5 cm for the ground layer and
that these measurements should provide valuable information for site selection
and multi-conjugate development for the future European Solar Telescope. A
major limitation is the large field of view presently used for wavefront
sensing, leading to uncomfortably large uncertainties in r_0 at 30 km distance.Comment: Accepted by AA 22/01/2010 (12 pages, 11 figures
GBG++: A Fast and Stable Granular Ball Generation Method for Classification
Granular ball computing (GBC), as an efficient, robust, and scalable learning
method, has become a popular research topic of granular computing. GBC includes
two stages: granular ball generation (GBG) and multi-granularity learning based
on the granular ball (GB). However, the stability and efficiency of existing
GBG methods need to be further improved due to their strong dependence on
-means or -division. In addition, GB-based classifiers only unilaterally
consider the GB's geometric characteristics to construct classification rules,
but the GB's quality is ignored. Therefore, in this paper, based on the
attention mechanism, a fast and stable GBG (GBG++) method is proposed first.
Specifically, the proposed GBG++ method only needs to calculate the distances
from the data-driven center to the undivided samples when splitting each GB
instead of randomly selecting the center and calculating the distances between
it and all samples. Moreover, an outlier detection method is introduced to
identify local outliers. Consequently, the GBG++ method can significantly
improve effectiveness, robustness, and efficiency while being absolutely
stable. Second, considering the influence of the sample size within the GB on
the GB's quality, based on the GBG++ method, an improved GB-based -nearest
neighbors algorithm (GBNN++) is presented, which can reduce
misclassification at the class boundary. Finally, the experimental results
indicate that the proposed method outperforms several existing GB-based
classifiers and classical machine learning classifiers on public benchmark
datasets
Using Granule to Search Privacy Preserving Voice in Home IoT Systems
The Home IoT Voice System (HIVS) such as Amazon Alexa or Apple Siri can provide voice-based interfaces for people to conduct the search tasks using their voice. However, how to protect privacy is a big challenge. This paper proposes a novel personalized search scheme of encrypting voice with privacy-preserving by the granule computing technique. Firstly, Mel-Frequency Cepstrum Coefficients (MFCC) are used to extract voice features. These features are obfuscated by obfuscation function to protect them from being disclosed the server. Secondly, a series of definitions are presented, including fuzzy granule, fuzzy granule vector, ciphertext granule, operators and metrics. Thirdly, the AES method is used to encrypt voices. A scheme of searchable encrypted voice is designed by creating the fuzzy granule of obfuscation features of voices and the ciphertext granule of the voice. The experiments are conducted on corpus including English, Chinese and Arabic. The results show the feasibility and good performance of the proposed scheme
Granular computing, rough entropy and object extraction
The problem of image object extraction in the framework of rough sets and granular computing is addressed. A measure called "rough entropy of image" is defined based on the concept of image granules. Its maximization results in minimization of roughness in both object and background regions; thereby determining the threshold of partitioning. Methods of selecting the appropriate granule size and efficient computation of rough entropy are described
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Hierarchical wireless framework for real-time collaborative generation and distribution of telemetry data
This project introduces a novel multidisciplinary approach combining Vehicular Ad Hoc Networks and Granular Computing, to the data processing and information generation problem in large urban traffic systems. It addresses the challenge of realtime information generation and dissemination in such systems by designing and investigating a hierarchical real-time information framework. The research work is complemented by designing and developing a simulator for such a system, which provides a simulation environment for the model developed. The proposed multidisciplinary hierarchical real-time information processing and dissemination system framework utilises results from two different areas of study, which are Vehicular Ad Hoc Networks (VANETS) and Granular Computing concepts. Furthermore, a new geographically constrained VANET topology for information generation is proposed, simulated and investigated
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